WorldWideScience

Sample records for annual carbon dynamics

  1. Reconstruction of annual carbon dynamics and balance for an oligotrophic pine fen

    Energy Technology Data Exchange (ETDEWEB)

    Alm, J.; Silvola, J.; Aaltonen, H. [Joensuu Univ. (Finland). Dept. of Biology; Talanov, A.; Ikkonen, E. [Karelian Research Centre of Russian Academy of Sciences (Russian Federation). Inst. of Biology; Nykaenen, H.; Martikainen, P.J. [National Public Health Inst. Kuopio (Finland). Dept. of Environmental Microbiology

    1996-12-31

    Atmospheric carbon dioxide (CO{sub 2}) is bound by mire vegetation in photosynthesis during the growing season, and is re-released by respiration of plants, soil animals and microorganisms consuming dead organic matter. A small proportion of annual primary production may fall below the water table to anoxic conditions and thus escapes the oxidative decomposition. Also from anoxic peat, carbon is released with clear seasonal and spatial variation as methane (CH{sub 4}.). The rate of carbon accumulation in peat depends on the annual inbalance of plant production and litter decomposition. Exchange of CO{sub 2} and CH{sub 4} between peat, vegetation and the atmosphere thus reflects the dynamics of carbon flows in the ecosystem. Net ecosystem CO{sub 2} exchange (PN), total CO{sub 2} release (RTOT) and CH{sub 4} release (D) from different treeless surfaces of low-sedge Sphagnum papillosum pine fen was studied in eastern Finland. (8 refs.)

  2. The impact of roots on soil organic carbon dynamics in annual and perennial agricultural systems

    Science.gov (United States)

    Beniston, J.; Dupont, T.; Glover, J.; Lal, R.

    2012-12-01

    Identifying and developing agricultural systems capable of transferring large quantities of carbon (C) to the soil and sustaining ecosystem processes and services is a priority for ecological researchers and land managers. Temperate grasslands have extensive root systems and transfer large quantities of C to the soil organic C (SOC) pool, which has lead to widespread interest in utilizing perennial grasses as both bioenergy crops and as a model for perennial grains. This study examined five sites in north central Kansas (U.S.A.) that contain the unique land use pairing of tall grass prairie meadows (PM) that have been harvested annually for hay for the past 75 years and annual grain (wheat) production fields (AG) that have been cultivated for a similar length of time, all on deep alluvial soils. Specific research objectives included: 1) To quantify below-ground biomass pools and root C contributions in the two systems; 2) To analyze and compare SOC pools and SOC concentration in primary particle size fractions in the two systems; 3) To utilize natural abundance δ13C signatures to determine the source and turnover of SOC in the soils of the AG sites; and 4) To elucidate the relationship of roots to both SOC pools and nematode food webs. Soil core samples were collected to a depth of 1 m in May and June 2008. Soil samples were analyzed for SOC, microbial biomass C (MBC), nematodes, and a particle size fractionation of SOC in coarse (>250 μm), particulate organic matter (POM) (53-250 μm), silt (2-53 μm), and clay (food web dynamics at these sites. Collectively, the data presented in this study demonstrate the potential of production systems based on perennial grasses to transfer greater quantities of C to SOC pools than annual crops, through larger C allocations to root and microbial pools.

  3. A novel method for diagnosing seasonal to inter-annual surface ocean carbon dynamics from bottle data using neural networks

    Directory of Open Access Journals (Sweden)

    T. P. Sasse

    2013-06-01

    Full Text Available The ocean's role in modulating the observed 1–7 Pg C yr−1 inter-annual variability in atmospheric CO2 growth rate is an important, but poorly constrained process due to current spatio-temporal limitations in ocean carbon measurements. Here, we investigate and develop a non-linear empirical approach to predict inorganic CO2 concentrations (total carbon dioxide (CT and total alkalinity (AT in the global ocean mixed layer from hydrographic properties (temperature, salinity, dissolved oxygen and nutrients. The benefit of this approach is that once the empirical relationship is established, it can be applied to hydrographic datasets that have better spatio-temporal coverage, and therefore provide an additional constraint to diagnose ocean carbon dynamics globally. Previous empirical approaches have employed multiple linear regressions (MLR and relied on ad hoc geographic and temporal partitioning of carbon data to constrain complex global carbon dynamics in the mixed layer. Synthesizing a new global CT/AT carbon bottle dataset consisting of ~33 000 measurements in the open ocean mixed layer, we develop a neural network based approach to better constrain the non-linear carbon system. The approach classifies features in the global biogeochemical dataset based on their similarity and homogeneity in a self-organizing map (SOM; Kohonen, 1988. After the initial SOM analysis, which includes geographic constraints, we apply a local linear optimizer to the neural network, which considerably enhances the predictive skill of the new approach. We call this new approach SOMLO, or self-organizing multiple linear output. Using independent bottle carbon data, we compare a traditional MLR analysis to our SOMLO approach to capture the spatial CT and AT distributions. We find the SOMLO approach improves predictive skill globally by 19% for CT, with a global capacity to predict CT to within 10.9 μmol kg−1 (9.2 μmol kg−1 for AT. The non-linear SOMLO approach is

  4. Carbon and nitrogen dynamics in agricultural soils

    OpenAIRE

    Karlsson, Thord

    2012-01-01

    An understanding of soil organic carbon (C) and nitrogen (N) dynamics is essential for efficient and environmentally sustainable agricultural production. This thesis includes model studies of C mineralization at regional/national level with annual time steps, N balances at field level with annual time steps, and N dynamics at 34 locations within a single field with daily time steps. The same model family (ICBM) was used in all studies. Generally, carbon stocks in mineral soils increased from ...

  5. The dynamic of the annual carbon allocation to wood in European tree species is consistent with a combined source-sink limitation of growth: implications for modelling

    Science.gov (United States)

    Guillemot, J.; Martin-StPaul, N. K.; Dufrene, E.; Francois, C.; Soudani, K.; Ourcival, J. M.; Delpierre, N.

    2015-05-01

    The extent to which wood growth is limited by carbon (C) supply (i.e. source control) or by cambial activity (i.e. sink control) will strongly determine the responses of trees to global changes. Nevertheless, the physiological processes that are responsible for limiting forest growth are still a matter of debate. The aim of this study was to evaluate the key determinants of the annual C allocation to wood along large soil and climate regional gradients over France. The study was conducted for five tree species representative of the main European forest biomes (Fagus sylvatica, Quercus petraea, Quercus ilex, Quercus robur and Picea abies). The drivers of stand biomass growth were assessed on both inter-site and inter-annual scales. Our data set comprised field measurements performed at 49 sites (931 site-years) that included biometric measurements and a variety of stand characteristics (e.g. soil water holding capacity, leaf area index). It was complemented with process-based simulations when possible explanatory variables could not be directly measured (e.g. annual and seasonal tree C balance, bioclimatic water stress indices). Specifically, the relative influences of tree C balance (source control), direct environmental control (water and temperature controls of sink activity) and allocation adjustments related to age, past climate conditions, competition intensity and soil nutrient availability on growth were quantified. The inter-site variability in the stand C allocation to wood was predominantly driven by age-related decline. The direct effects of temperature and water stress on sink activity (i.e. effects independent from their effects on the C supply) exerted a strong influence on the annual stand wood growth in all of the species considered, including deciduous temperate species. The lagged effect of the past environmental conditions (e.g. the previous year's water stress and low C uptake) significantly affected the annual C allocation to wood. The C supply

  6. Deforestation in Amazonia impacts riverine carbon dynamics

    Science.gov (United States)

    Langerwisch, F.; Walz, A.; Rammig, A.; Tietjen, B.; Thonicke, K.; Cramer, W.

    2015-10-01

    Fluxes of organic and inorganic carbon within the Amazon basin are considerably controlled by annual flooding, which triggers the export of terrigenous organic material to the river and ultimately to the Atlantic Ocean. The amount of carbon imported to the river and the further conversion, transport and export of it, depend on terrestrial productivity and discharge, as well as temperature and atmospheric CO2. Both terrestrial productivity and discharge are influenced by climate and land use change. To assess the impact of these changes on the riverine carbon dynamics, the coupled model system of LPJmL and RivCM (Langerwisch et al., 2015) has been used. Vegetation dynamics (in LPJmL) as well as export and conversion of terrigenous carbon to and within the river (RivCM) are included. The model system has been applied for the years 1901 to 2099 under two deforestation scenarios and with climate forcing of three SRES emission scenarios, each for five climate models. The results suggest that, following deforestation, riverine particulate and dissolved organic carbon will strongly decrease by up to 90 % until the end of the current century. In parallel, discharge increases, leading to roughly unchanged net carbon transport during the first decades of the century, as long as a sufficient area is still forested. During the following decades the amount of transported carbon will decrease drastically. In contrast to the riverine organic carbon, the amount of riverine inorganic carbon is only determined by climate change forcing, namely increased temperature and atmospheric CO2 concentration. Mainly due to the higher atmospheric CO2 it leads to an increase in riverine inorganic carbon by up to 20 % (SRES A2). The changes in riverine carbon fluxes have direct effects on the export of carbon, either to the atmosphere via outgassing, or to the Atlantic Ocean via discharge. Basin-wide the outgassed carbon will increase slightly, but can be regionally reduced by up to 60 % due to

  7. Annual Report 2000. Chemical Structure and Dynamics

    Energy Technology Data Exchange (ETDEWEB)

    Colson, Steven D.; McDowell, Robin S.

    2001-04-15

    This annual report describes the research and accomplishments of the Chemical Structure and Dynamics Program in the year 2000, one of six research programs at the William R. Wiley Environmental Molecular Sciences Laboratory (EMSL) - a multidisciplinary, national scientific user facility and research organization. The Chemical Structure and Dynamics (CS&D) program is meeting the need for a fundamental, molecular-level understanding by 1) extending the experimental characterization and theoretical description of chemical reactions to encompass the effects of condensed media and interfaces; 2) developing a multidisciplinary capability for describing interfacial chemical processes relevant to environmental chemistry; and 3) developing state-of-the-art research and analytical methods for characterizing complex materials of the types found in natural and contaminated systems.

  8. Carbon dioxide and methane dynamics in Russian tundra

    DEFF Research Database (Denmark)

    Johansson, Paul Torbjörn; Kiepe, Isabell; Herbst, Mathias;

    interactions and the annual carbon dynamics. Here we present eddy correlation measurements of CO2 and CH4 exchange during the period from early spring to late autumn, covering the full growing season, i.e., mid June to mid September. We present preliminary seasonal budgets of carbon, greenhouse gas exchange......, and discuss possible implications of climatic change on this lowland tundra ecosystem. This study have been conducted as a part of the CARBO-North project (2006-2010), a project within the EU 6th framework programme, aiming at quantifying the carbon budget in Northern Russia across temporal and...

  9. Annual Report 1999 Environmental Dynamics and Simulation

    Energy Technology Data Exchange (ETDEWEB)

    NS Foster-Mills

    2000-06-28

    This annual report describes selected 1999 research accomplishments for the Environmental Dynamics and Simulation (ED and S) directorate, one of six research organizations in the William R. Wiley Environmental Molecular Sciences Laboratory (EMSL). These accomplishments are representative of the different lines of research underway in the ED and S directorate. EMSL is one of US Department of Energy's (DOE) national scientific user facilities and is the centerpiece of DOE's commitment to providing world-class experimental, theoretical, and computational capabilities for solving the nation's environmental problems. Capabilities in the EMSL include over 100 major instrument systems for use by the resident research staff, their collaborators, and users of the EMSL. These capabilities are used to address the fundamental science that will be the basis for finding solutions to national environmental issues such as cleaning up contamianted areas at DOE sites across the country and developing green technologies that will reduce or eliminate future pollution production. The capabilities are also used to further the understanding of global climate change and environmental issues relevant to energy production and use and health effects resulting from exposure to contaminated environments.

  10. Azure Dynamics Corporation annual report 2004

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2005-07-01

    Azure Dynamics Corporation is an international leader in the development of proprietary hybrid electric vehicles (HEV) and electric powertrains. In 2004, the company moved its Canadian operations to Vancouver where it can develop and test its technology. Azure has developed HEV technology for the light to medium duty commercial vehicle category. In particular, its main business is the commercialization of HEV and electric vehicle (EV) control and powertrain systems for commercial vehicles (ACS Technology). In 2004, Azure announced an agreement with British-based Leyland Product Development, Zebra Batteries and Renault Trucks to produce a master electric delivery van. It also introduced the first hybrid electric taxi in London and delivered 30 vehicles in the initial phase of an agreement with Purolator that could see delivery of up to 2,000 vehicles. Azure also acquired Solectria Corporation in the United States and is currently developing a powertrain platform for vehicles in the medium-duty weight range of 7,500 to 14,000 pounds gross vehicle weight, and another powertrain for vehicles in the light-duty weight range of 5,000 to 7,5000 pounds gross vehicle weight. Commercial sales of its product is targeted for 2005. This annual report includes information on the company's net earnings and investor profiles, and includes consolidated financial statements and common share information such as assets, liabilities, revenues, expenses and cash flows. tabs., figs.

  11. Azure Dynamics Corporation annual report 2004

    International Nuclear Information System (INIS)

    Azure Dynamics Corporation is an international leader in the development of proprietary hybrid electric vehicles (HEV) and electric powertrains. In 2004, the company moved its Canadian operations to Vancouver where it can develop and test its technology. Azure has developed HEV technology for the light to medium duty commercial vehicle category. In particular, its main business is the commercialization of HEV and electric vehicle (EV) control and powertrain systems for commercial vehicles (ACS Technology). In 2004, Azure announced an agreement with British-based Leyland Product Development, Zebra Batteries and Renault Trucks to produce a master electric delivery van. It also introduced the first hybrid electric taxi in London and delivered 30 vehicles in the initial phase of an agreement with Purolator that could see delivery of up to 2,000 vehicles. Azure also acquired Solectria Corporation in the United States and is currently developing a powertrain platform for vehicles in the medium-duty weight range of 7,500 to 14,000 pounds gross vehicle weight, and another powertrain for vehicles in the light-duty weight range of 5,000 to 7,5000 pounds gross vehicle weight. Commercial sales of its product is targeted for 2005. This annual report includes information on the company's net earnings and investor profiles, and includes consolidated financial statements and common share information such as assets, liabilities, revenues, expenses and cash flows. tabs., figs

  12. Annual carbon balance of a peatland 10 yr following restoration

    Directory of Open Access Journals (Sweden)

    M. Strack

    2013-05-01

    Full Text Available Undisturbed peatlands represent long-term net sinks of carbon; however, peat extraction converts these systems into large and persistent sources of greenhouse gases. Although rewetting and restoration following peat extraction have taken place over the last several decades, very few studies have investigated the longer term impact of this restoration on peatland carbon balance. We determined the annual carbon balance of a former horticulturally-extracted peatland restored 10 yr prior to the study and compared these values to the carbon balance measured at neighboring unrestored and natural sites. Carbon dioxide (CO2 and methane (CH4 fluxes were measured using the chamber technique biweekly during the growing season from May to October 2010 and three times over the winter period. Dissolved organic carbon (DOC export was measured from remnant ditches in the unrestored and restored sites. During the growing season the restored site had greater uptake of CO2 than the natural site when photon flux density was greater than 1000 μmol m−2 s−1, while the unrestored site remained a source of CO2. Ecosystem respiration was similar between natural and restored sites, which were both significantly lower than the unrestored site. Methane flux remained low at the restored site except from open water pools, created as part of restoration, and remnant ditches. Export of DOC during the growing season was 5.0 and 28.8 g m−2 from the restored and unrestored sites, respectively. Due to dry conditions during the study year all sites acted as net carbon sources with annual balance of the natural, restored and unrestored sites of 250.7, 148.0 and 546.6 g C m−2, respectively. Although hydrological conditions and vegetation community at the restored site remained intermediate between natural and unrestored conditions, peatland restoration resulted in a large reduction in annual carbon loss from the system resulting in a carbon balance more similar to a natural

  13. Annual Report: Carbon Capture (30 September 2012)

    Energy Technology Data Exchange (ETDEWEB)

    Luebke, David; Morreale, Bryan; Richards, George; Syamlal, Madhava

    2014-04-16

    Capture of carbon dioxide (CO{sub 2}) is a critical component in reducing greenhouse gas emissions from fossil fuel-based processes. The Carbon Capture research to be performed is aimed at accelerating the development of efficient, cost-effective technologies which meet the post-combustion programmatic goal of capture of 90% of the CO{sub 2} produced from an existing coal-fired power plant with less than a 35% increase in the cost of electricity (COE), and the pre-combustion goal of 90% CO{sub 2} capture with less than a 10% increase in COE. The specific objective of this work is to develop innovative materials and approaches for the economic and efficient capture of CO{sub 2} from coal-based processes, and ultimately assess the performance of promising technologies at conditions representative of field application (i.e., slip stream evaluation). The Carbon Capture research includes seven core technical research areas: post-combustion solvents, sorbents, and membranes; pre-combustion solvents, sorbents, and membranes; and oxygen (O{sub 2}) production. The goal of each of these tasks is to develop advanced materials and processes that are able to reduce the energy penalty and cost of CO{sub 2} (or O{sub 2}) separation over conventional technologies. In the first year of development, materials will be examined by molecular modeling, and then synthesized and experimentally characterized at lab scale. In the second year, they will be tested further under ideal conditions. In the third year, they will be tested under realistic conditions. The most promising materials will be tested at the National Carbon Capture Center (NCCC) using actual flue or fuel gas. Systems analyses will be used to determine whether or not materials developed are likely to meet the Department of Energy (DOE) COE targets. Materials which perform well and appear likely to improve in performance will be licensed for further development outside of the National Energy Technology Laboratory (NETL

  14. Terahertz Dynamics in Carbon Nanomaterials

    Science.gov (United States)

    Kono, Junichiro

    2012-02-01

    This NSF Partnerships for International Research and Education (PIRE) project supports a unique interdisciplinary and international partnership investigating terahertz (THz) dynamics in nanostructures. The 0.1 to 10 THz frequency range of the electromagnetic spectrum is where electrical transport and optical transitions merge, offering exciting opportunities to study a variety of novel physical phenomena in condensed matter. By combining THz technology and nanotechnology, we can advance our understanding of THz physics while improving and developing THz devices. Specifically, this PIRE research explores THz dynamics of electrons in carbon nanomaterials, namely, nanotubes and graphene --- low-dimensional, sp^2-bonded carbon systems with unique finite-frequency properties. Japan and the U.S. are global leaders in both THz research and carbon research, and stimulating cooperation is critical to further advance THz science and to commercialize products developed in the lab. However, obstacles exist for international collaboration --- primarily linguistic and cultural barriers --- and this PIRE project aims to address these barriers through the integration of our research and education programs. Our strong educational portfolio endeavours to cultivate interest in nanotechnology amongst young U.S. undergraduate students and encourage them to pursue graduate study and academic research in the physical sciences, especially those from underrepresented groups. Our award-winning International Research Experience for Undergraduates Program, NanoJapan, provides structured research internships in Japanese university laboratories with Japanese mentors --- recognized as a model international education program for science and engineering students. The project builds the skill sets of nanoscience researchers and students by cultivating international and inter-cultural awareness, research expertise, and specific academic interests in nanotechnology. U.S. project partners include Rice

  15. Deforestation in Amazonia impacts riverine carbon dynamics

    OpenAIRE

    F. Langerwisch; Walz, A; A. Rammig; Tietjen, B.; Thonicke, K.; Cramer, W.

    2015-01-01

    Fluxes of organic and inorganic carbon within the Amazon basin are considerably controlled by annual flooding, which triggers the export of terrigenous organic material to the river and ultimately to the Atlantic Ocean. The amount of carbon imported to the river and the further conversion, transport and export of it, depend on terrestrial productivity and discharge, as well as temperature and atmospheric CO2. Both terrestrial productivity and discharge are influenced by climate and l...

  16. Unravelling carbon allocation dynamics in an evergreen temperate forest

    Science.gov (United States)

    Griebel, Anne; Bennett, Lauren T.; Arndt, Stefan K.

    2015-04-01

    Eucalypt trees have the potential to sequester carbon from the atmosphere year-round by maintaining evergreen leaves with a prolonged multi-year lifetime. Unlike deciduous trees, eucalypts are generally known to grow opportunistic resulting in a lack of defined growth rings and no distinct seasonal crown turnover events. Stem expansion has been successfully measured with micro-dendrometers, however, it remains challenging to monitor crown dynamics at a similarly high temporal resolution. Hence, carbon allocation dynamics and seasonal variations of carbon distribution between stem and crown biomass remain largely unknown for evergreen species. Ecosystem scale observations of net ecosystem exchange (NEE) from a flux tower located in a predominantly temperature and moisture regulated environment in south-eastern Australia have demonstrated that the ecosystem is a constant terrestrial sink for carbon. Intra-annual variations in temperature and moisture and prolonged heat waves and dry spells result in a wide range of annual sums (e.g. 2013: NEE~4 t C ha-1yr-1, 2012: NEE~12 t C ha-1yr-1). Newly developed low-cost terrestrial lidar sensors (VEGNET) now allow for automated daily monitoring of crown dynamics, enabling more detailed observations on the duration of crown biomass changes. In addition to leaf area index (LAI), VEGNET sensors define the location within the crown strata of the gains and losses in plant volume across the vertical forest structure. With the development of VEGNET sensors, combined with ecosystem carbon fluxes from eddy covariance measurements and with micro-dendrometers, we are able to quantify the dynamics of carbon allocation to above ground biomass pools. Our results demonstrate that stem growth dominates in spring and in autumn, and is strongly associated with water availability. Leaf turnover predominantly takes place in summer and is initiated by prolonged heat stress and isolated storm events, yet crown biomass remains stable throughout the

  17. Simulating long-term carbon and water dynamics in northern peatlands (Invited)

    Science.gov (United States)

    Frolking, S. E.; Roulet, N. T.; Quillet, A.; Tuittila, E.; Bubier, J. L.

    2009-12-01

    We present a new model that simulates coupled carbon and water dynamics of northern peatlands at an annual time step over time scales of decades to millennia. The Holocene Peatland Model (HPM) simulates peatland carbon and water dynamics as the net consequence of several interacting processes: (1) above- and below-ground vegetation NPP and litter production for bryophytes and vascular plants; (2) aerobic and anaerobic litter/peat decomposition down the peat profile; (3) the dependence of peat physical and hydraulic properties on peat humification; and (4) peatland annual water balance, water table depth, and unsaturated zone water content. The model generates time series of vegetation, carbon and water dynamics over a 5000-10000 year simulation, and a ‘final state’ peat core that can be compared to contemporary peat core data. The sensitivities of peatland carbon and water dynamics to climate and climate variability and to succession rate are evaluated.

  18. Carbon Management Response curves: estimates of temporal soil carbon dynamics.

    Science.gov (United States)

    West, Tristram O; Marland, Gregg; King, Anthony W; Post, Wilfred M; Jain, Atul K; Andrasko, Kenneth

    2004-04-01

    Measurement of the change in soil carbon that accompanies a change in land use (e.g., forest to agriculture) or management (e.g., conventional tillage to no-till) can be complex and expensive, may require reference plots, and is subject to the variability of statistical sampling and short-term variability in weather. In this paper, we develop Carbon Management Response (CMR) curves that could be used as an alternative to in situ measurements. The CMR curves developed here are based on quantitative reviews of existing global analyses and field observations of changes in soil carbon. The curves show mean annual rates of soil carbon change, estimated time to maximum rates of change, and estimated time to a new soil carbon steady state following the initial change in management. We illustrate how CMR curves could be used in a carbon accounting framework while effectively addressing a number of potential policy issues commonly associated with carbon accounting. We find that CMR curves provide a transparent means to account for changes in soil carbon accumulation and loss rates over time, and also provide empirical relationships that might be used in the development or validation of ecological or Earth systems models. PMID:15453404

  19. Chemical structure and dynamics: Annual report 1993

    Energy Technology Data Exchange (ETDEWEB)

    Colson, S.D.

    1994-07-01

    The Chemical Structure and Dynamics program responds to the need for a fundamental, molecular-level understanding of chemistry at the wide variety of environmentally-important interfaces. The research program is built around the established relationship between structure, thermodynamics, and kinetics. This research effort continues to evolve into a program of rigorous studies of fundamental molecular processes in model systems (e.g., well-characterized surfaces, single-component solutions, clusters, and biological molecules), and studies of complex systems found in the environment. Experimental studies of molecular and supramolecular structures and thermodynamics are key to understanding the nature of matter, and lead to direct comparison with computational results. Kinetic and mechanistic measurements, combined with real-time dynamics measurements of atomic and molecular motions during chemical reactions, provide for a molecular-level description of chemical reactions. The anticipated results of this work are the achievement of a quantitative understanding of chemical processes at complex interfaces, the development of new techniques for the detection and measurement of species at such interfaces, and the interpretation and extrapolation of the observations in terms of models of interfacial chemistry. The Chemical Structure and Dynamics research program includes five areas described in detail in this report: Reaction mechanisms at solid interfaces; Solution and solution interfaces; Structure and dynamics of biological systems; Analytical methods development; and atmospheric chemistry. Extended abstracts are presented for 23 studies.

  20. Chemical structure and dynamics: Annual report 1996

    Energy Technology Data Exchange (ETDEWEB)

    Colson, S.D.; McDowell, R.S.

    1997-03-01

    The Chemical Structure and Dynamics (CS&D) program is a major component of the William R. Wiley Environmental Molecular Sciences Laboratory (EMSL) developed by Pacific Northwest National Laboratory (PNNL) to provide a state-of-the-art collaborative facility for studies of chemical structure and dynamics. We respond to the need for a fundamental, molecular-level understanding of chemistry at a wide variety of environmentally important interfaces by (1) extending the experimental characterization and theoretical description of chemical reactions to encompass the effects of condensed media and interfaces; (2) developing a multidisciplinary capability for describing interfacial chemical processes within which the new knowledge generated can be brought to bear on complex phenomena in environmental chemistry and in nuclear waste processing and storage; and (3) developing state-of-the-art analytical methods for characterizing waste tanks and pollutant distributions, and for detecting and monitoring trace atmospheric species.

  1. Chemical structure and dynamics: Annual report 1996

    International Nuclear Information System (INIS)

    The Chemical Structure and Dynamics (CS ampersand D) program is a major component of the William R. Wiley Environmental Molecular Sciences Laboratory (EMSL) developed by Pacific Northwest National Laboratory (PNNL) to provide a state-of-the-art collaborative facility for studies of chemical structure and dynamics. We respond to the need for a fundamental, molecular-level understanding of chemistry at a wide variety of environmentally important interfaces by (1) extending the experimental characterization and theoretical description of chemical reactions to encompass the effects of condensed media and interfaces; (2) developing a multidisciplinary capability for describing interfacial chemical processes within which the new knowledge generated can be brought to bear on complex phenomena in environmental chemistry and in nuclear waste processing and storage; and (3) developing state-of-the-art analytical methods for characterizing waste tanks and pollutant distributions, and for detecting and monitoring trace atmospheric species

  2. Chemical structure and dynamics. Annual report 1995

    Energy Technology Data Exchange (ETDEWEB)

    Colson, S.D.; McDowell, R.S.

    1996-05-01

    The Chemical Structure and Dynamics program is a major component of Pacific Northwest National Laboratory`s Environmental Molecular Sciences Laboratory (EMSL), providing a state-of-the-art collaborative facility for studies of chemical structure and dynamics. We respond to the need for a fundamental, molecular-level understanding of chemistry at a wide variety of environmentally important interfaces by (1) extending the experimental characterization and theoretical description of chemical reactions to encompass the effects of condensed media and interfaces; (2) developing a multidisciplinary capability for describing interfacial chemical processes within which the new knowledge generated can be brought to bear on complex phenomena in environmental chemistry and in nuclear waste processing and storage; and (3) developing state-of-the-art analytical methods for the characterization of waste tanks and pollutant distributions, and for detection and monitoring of trace atmospheric species.

  3. Proceses in the Southern Ocean carbon cycle: Dissolution of carbonate sediments and inter-annual variability of carbon fluxes

    OpenAIRE

    Hauck, Judith

    2012-01-01

    The Southern Ocean (SO) carbon cycle is and will be undergoing various changes in a high-CO2 world. This thesis analyzes two key processes: dissolution of carbonate sediments on Antarctic shelves and inter-annual variability of upper ocean carbon fluxes. In the first part of the thesis, the main question is whether dissolution of carbonate sediments from Antarctic shelves can be a negative feedback to ocean acidification. Patterns in the CaCO3 distribution are related to primary production in...

  4. Chemical Structure and Dynamics annual report 1997

    International Nuclear Information System (INIS)

    The Chemical Structure and Dynamics (CS and D) program is a major component of the William R. Wiley Environmental Molecular Sciences Laboratory (EMSL), developed by Pacific Northwest National Laboratory (PNNL) to provide a state-of-the-art collaborative facility for studies of chemical structure and dynamics. The authors respond to the need for a fundamental, molecular level understanding of chemistry at a wide variety of environmentally important interfaces by: (1) extending the experimental characterization and theoretical description of chemical reactions to encompass the effects of condensed media and interfaces; (2) developing a multidisciplinary capability for describing interfacial chemical processes within which the new knowledge generated can be brought to bear on complex phenomena in environmental chemistry and in nuclear waste processing and storage; and (3) developing state-of-the-art analytical methods for characterizing complex materials of the types found in stored wastes and contaminated soils, and for detecting and monitoring trace atmospheric species. The focus of the research is defined primarily by DOE's environmental problems: fate and transport of contaminants in the subsurface environment, processing and storage of waste materials, cellular effects of chemical and radiological insult, and atmospheric chemistry as it relates to air quality and global change. Twenty-seven projects are described under the following topical sections: Reaction mechanisms at interfaces; High-energy processes at environmental interfaces; Cluster models of the condensed phase; and Miscellaneous

  5. Chemical Structure and Dynamics annual report 1997

    Energy Technology Data Exchange (ETDEWEB)

    Colson, S.D.; McDowell, R.S.

    1998-03-01

    The Chemical Structure and Dynamics (CS and D) program is a major component of the William R. Wiley Environmental Molecular Sciences Laboratory (EMSL), developed by Pacific Northwest National Laboratory (PNNL) to provide a state-of-the-art collaborative facility for studies of chemical structure and dynamics. The authors respond to the need for a fundamental, molecular level understanding of chemistry at a wide variety of environmentally important interfaces by: (1) extending the experimental characterization and theoretical description of chemical reactions to encompass the effects of condensed media and interfaces; (2) developing a multidisciplinary capability for describing interfacial chemical processes within which the new knowledge generated can be brought to bear on complex phenomena in environmental chemistry and in nuclear waste processing and storage; and (3) developing state-of-the-art analytical methods for characterizing complex materials of the types found in stored wastes and contaminated soils, and for detecting and monitoring trace atmospheric species. The focus of the research is defined primarily by DOE`s environmental problems: fate and transport of contaminants in the subsurface environment, processing and storage of waste materials, cellular effects of chemical and radiological insult, and atmospheric chemistry as it relates to air quality and global change. Twenty-seven projects are described under the following topical sections: Reaction mechanisms at interfaces; High-energy processes at environmental interfaces; Cluster models of the condensed phase; and Miscellaneous.

  6. Dynamic carbon allocation significantly changed land carbon sink and carbon pool sizes

    Science.gov (United States)

    Xia, J.; Yuan, W.

    2015-12-01

    The allocation of photosynthate among the plant components (e.g., leaves, stems, and roots) plays an important role in regulating plant growth, competition, and terrestrial carbon cycle. However, the carbon allocation process is still a weak part in the earth system models (ESMs). In this study, the Integrated BIosphere Simulator (IBIS) model coupled with a dynamic carbon allocation model (IBISAL) is used to explore the impact of carbon allocation on the terrestrial carbon cycle. This dynamic carbon allocation model suggests that plants should allocate the largest part of carbon to the plant components which need to capture the most limiting resources, such as light, water and nitrogen. In comparison to the results of original IBIS model using fixed allocation ratios, the net ecosystem productivity, global biomass and soil organic carbon simulated by IBISAL model decreased by13.4% , 9.9% and 20.8%, respectively . The dynamic allocation scheme tends to benefit roots allocation. Because roots had short turnover times, high roots allocation led to the decreases of global carbon sink and carbon pool sizes. The observations showed that the carbon allocation ratios changed with temperature and precipitation. The dynamic carbon allocation model could reproduce this phenomenon correctly. The results show that the dynamic carbon allocation ratios of boreal evergreen forests and C3 grasses are consistent well with the observations. However, the IBISAL, and another three ESMs (i.e., CESM1-BGC, IPSL-CM5A-MR and NorESM1-ME models) adopting dynamic allocation scheme overestimated the stems allocation of tropical forests. This study shows the substantial influences of carbon allocation on the carbon sink and carbon pool sizes. Therefore, improving estimations of carbon allocation by ESMs are an important and effective path to reduce uncertainties in the global carbon cycle simulation and climate change prediction.

  7. Chemical structure and dynamics. Annual report 1994

    Energy Technology Data Exchange (ETDEWEB)

    Colson, S.D.

    1995-07-01

    The Chemical Structure and Dynamics program was organized as a major component of Pacific Northwest Laboratory`s Environmental and Molecular Sciences Laboratory (EMSL), a state-of-the-art collaborative facility for studies of chemical structure and dynamics. Our program responds to the need for a fundamental, molecular-level understanding of chemistry at the wide variety of environmentally important interfaces by (1) extending the experimental characterization and theoretical description of chemical reactions to encompass the effects of condensed media and interfaces, and (2) developing a multidisciplinary capability for describing interfacial chemical processes within which the new knowledge generated can be brought to bear on complex phenomena in environmental chemistry and in nuclear waste processing and storage. This research effort was initiated in 1989 and will continue to evolve over the next few years into a program of rigorous studies of fundamental molecular processes in model systems, such as well-characterized surfaces, single-component solutions, clusters, and biological molecules; and studies of complex systems found in the environment (multispecies, multiphase solutions; solid/liquid, liquid/liquid, and gas/surface interfaces; colloidal dispersions; ultrafine aerosols; and functioning biological systems). The success of this program will result in the achievement of a quantitative understanding of chemical reactions at interfaces, and more generally in condensed media, that is comparable to that currently available for gas-phase reactions. This understanding will form the basis for the development of a priori theories for predictions of macroscopic chemical behavior in condensed and heterogeneous media, adding significantly to the value of field-scale environmental models, the prediction of short- and long-term nuclear waste storage stabilities, and other problems related to the primary missions of the DOE.

  8. Annual Report 1998: Chemical Structure and Dynamics

    Energy Technology Data Exchange (ETDEWEB)

    SD Colson; RS McDowell

    1999-05-10

    The Chemical Structure and Dynamics (CS&D) program is a major component of the William R. Wiley Environmental Molecular Sciences Labo- ratory (EMSL), developed by Pacific Northwest National Laboratory (PNNL) to provide a state-of- the-art collaborative facility for studies of chemical structure and dynamics. We respond to the need for a fundamental, molecular-level understanding of chemistry at a wide variety of environmentally important interfaces by (1) extending the experimental characterization and theoretical description of chemical reactions to encompass the effects of condensed media and interfaces; (2) developing a multidisciplinary capability for describing interracial chemical processes within which the new knowledge generated can be brought to bear on complex phenomena in envi- ronmental chemistry and in nuclear waste proc- essing and storage; and (3) developing state-of- the-art analytical methods for characterizing com- plex materials of the types found in stored wastes and contaminated soils, and for detecting and monitoring trace atmospheric species. Our program aims at achieving a quantitative understanding of chemical reactions at interfaces and, more generally, in condensed media, compa- rable to that currently available for gas-phase reactions. This understanding will form the basis for the development of a priori theories for pre- dicting macroscopic chemical behavior in con- densed and heterogeneous media, which will add significantly to the value of field-scale envi- ronmental models, predictions of short- and long- term nuclear waste storage stabilities, and other areas related to the primary missions of the U.S. Department of Energy (DOE).

  9. Dynamics models of soil organic carbon

    Institute of Scientific and Technical Information of China (English)

    YANGLi-xia; PANJian-jun

    2003-01-01

    As the largest pool of terrestrial organic carbon, soils interact strongly with atmosphere composition, climate, and land change. Soil organic carbon dynamics in ecosystem plays a great role in global carbon cycle and global change. With development of mathematical models that simulate changes in soil organic carbon, there have been considerable advances in understanding soil organic carbon dynamics. This paper mainly reviewed the composition of soil organic matter and its influenced factors, and recommended some soil organic matter models worldwide. Based on the analyses of the developed results at home and abroad, it is suggested that future soil organic matter models should be developed toward based-process models, and not always empirical ones. The models are able to reveal their interaction between soil carbon systems, climate and land cover by technique and methods of GIS (Geographical Information System) and RS (Remote Sensing). These models should be developed at a global scale, in dynamically describing the spatial and temporal changes of soil organic matter cycle. Meanwhile, the further researches on models should be strengthen for providing theory basis and foundation in making policy of green house gas emission in China.

  10. Methane in carbon nanotube - molecular dynamics simulation

    OpenAIRE

    Bartuś, Katarzyna; Bródka, Aleksander

    2011-01-01

    Abstract The behaviour of methane molecules inside carbon nanotube at room temperature is studied using classical molecular dynamics simulations. A methane molecule is represented either by a shapeless super-atom or by rigid set of 5 interaction centres localised on atoms. Different loadings of methane molecules ranging from the dense gas density to the liquid density, and the influence of flexibility of the CNT on structural and dynamics properties of confined molecules are consid...

  11. A new model of long-term, coupled dynamics of carbon and water in northern peatlands

    Science.gov (United States)

    Frolking, S.; Roulet, N.

    2008-12-01

    We present a new model that simulates coupled carbon and water dynamics of northern peatlands at an annual time step over time scales of decades to millennia. The Holocene Peatland Model (HPM) simulates peatland carbon and water dynamics as the net consequence of several interacting processes: (1) above- and below-ground vegetation NPP and litter production for bryophytes, woody and herbaceous plants; (2) aerobic and anaerobic litter/peat decomposition down the peat profile; (3) the dependence of peat physical and hydraulic properties on peat composition and degree of humification; and (4) peatland annual water balance, water table depth, and unsaturated zone water content. In this initial analysis, a simulation of long- term peat accumulation is compared against peat core data from a northern peatland in North America. The sensitivity of peatland carbon and water dynamics to climate variability are explored.

  12. Regional carbon dynamics in monsoon Asia and its implications for the global carbon cycle

    Science.gov (United States)

    Tian, H.; Melillo, J.M.; Kicklighter, D.W.; Pan, S.; Liu, J.; McGuire, A.D.; Moore, B., III

    2003-01-01

    Data on three major determinants of the carbon storage in terrestrial ecosystems are used with the process-based Terrestrial Ecosystem Model (TEM) to simulate the combined effect of climate variability, increasing atmospheric CO2 concentration, and cropland establishment and abandonment on the exchange of CO2 between the atmosphere and monsoon Asian ecosystems. During 1860-1990, modeled results suggest that monsoon Asia as a whole released 29.0 Pg C, which represents 50% of the global carbon release for this period. Carbon release varied across three subregions: East Asia (4.3 Pg C), South Asia (6.6 Pg C), and Southeast Asia (18.1 Pg C). For the entire region, the simulations indicate that land-use change alone has led to a loss of 42.6 Pg C. However, increasing CO2 and climate variability have added carbon to terrestrial ecosystems to compensate for 23% and 8% of the losses due to land-use change, respectively. During 1980-1989, monsoon Asia as a whole acted as a source of carbon to the atmosphere, releasing an average of 0.158 Pg C per year. Two of the subregions acted as net carbon source and one acted as a net carbon sink. Southeast Asia and South Asia were sources of 0.288 and 0.02 Pg C per year, respectively, while East Asia was a sink of 0.149 Pg C per year. Substantial interannual and decadal variations occur in the annual net carbon storage estimated by TEM due to comparable variations in summer precipitation and its effect on net primary production (NPP). At longer time scales, land-use change appears to be the important control on carbon dynamics in this region. ?? 2003 Elsevier Science B.V. All rights reserved.

  13. Dynamic adsorption of radon on activated carbon

    International Nuclear Information System (INIS)

    The adsorption of 222Rn from air onto activated carbon was studied over the range 0 to 550C. A sharp pulse of radon was injected into an air stream that flowed through a bed of activated carbon. The radon concentration in the exit from the column was continuously monitored using a zinc sulfide α-scintillation flow cell. Elution curves were analyzed to determine the dynamic adsorption coefficient and the number of theoretical stages. Five types of activated carbon were tested and the dynamic adsorption coefficient was found to increase linearly with surface area in the range 1000 to 1300 m2g-1. The adsorptive capacity of activated carbon was reduced by up to 30% if the entering gas was saturated with water vapor and the bed was initially dry. If the bed was allowed to equilibrate with saturated air, the adsorptive capacity was too low to be of practical use. The minimum height equivalent to a theoretical stage (HETS) was about four times the particle diameter and occurred at superficial velocities within the range 0.002 to 0.02 m s-1. For superficial velocities above 0.05 m s-1, the HETS was determined by the rate of mass transfer. The application of these results to the design of activated carbon systems for radon retention is discussed

  14. Annual variation of carbon flux and impact factors in the tropical seasonal rain forest of Xishuangbanna, SW China

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    <正>Two years of eddy covariance measurements of above- and below-canopy carbon fluxes and static opaque chamber and gas chromatography technique measurements of soil respiration for three treatments (bare soil, soil+litterfall, soil+litterfall+seedling) were carried out in a tropical seasonal rain forest. In addition, data of photosynthesis of dominant tree species and seedlings, leaf area index, litter production and decomposing speed, soil moisture, soil temperature and photosynthetic photon flux density within the forest were all measured concurrently. Data from January 2003 to December 2004 are used to present annual variability of carbon flux and relationships between carbon flux and impact factors. The results show that carbon flux of this forest presented unusual tendency of annual variation; above-canopy carbon fluxes were negative in the dry season (November-April) and mainly positive in the rainy season, but overall the forest is a carbon sink. Carbon flux has obviously diurnal variation in this tropical seasonal rain forest. Above-canopy carbon fluxes were negative in the daytime and absolute values were larger in the dry season than that in the rainy season, causing the forest to act as a carbon sink; at night, carbon fluxes were mainly positive, causing the forest to act as a carbon source. Dominant tree species have greater photosynthesis capability than that of seedlings, which have a great effect on above-canopy carbon flux. There was a significant correlation between above-canopy carbon flux and rate of photosynthesis of tree species. There was also a significant correlation between above-canopy carbon flux and rate of photosynthesis of seedlings; however, the below-canopy carbon flux was only significantly correlated with rate of photosynthesis of seedlings during the hot-dry season. Soil respiration of the three treatments displayed a markedly seasonal dynamic; in addition, above-canopy carbon fluxes correlated well with soil respiration

  15. Seasonal changes in stable carbon isotope ratios within annual growth rings of Pinus radiata

    International Nuclear Information System (INIS)

    The stable isotope composition of photosynthetically assimilated carbon (δ13C) is determined by the ratio of the leaf internal CO2 concentration (ci) to that of the ambient air (ca), and so reflects the contribution of both stomatal conductance (gs) and the rate of photosynthesis (A). Assimilated carbon which is subsequently laid down as wood in annual growth rings may therefore represent a time integrated record of physiological responses by the whole tree to seasonal changes in the environmental variables regulating growth. We analysed the stable carbon isotope composition of Pinus radiata wood collected from two plantation forest sites in New Zealand which differ markedly in temperature, rainfall and soil characteristics. For both sites, discs were cut from the stem of several trees near ground level and whole wood samples were taken from within individual annual growth rings over a number of years. At one site, diameter bands were installed over the 1994 - 1996 growing seasons in order to date precisely the formation of wood during that time. Trees at each site consistently showed a seasonal pattern in the stable isotope composition of wood within individual growth rings. The amplitude of seasonal δ13C variation at the wet and dry sites were 1-2 per thousand and 4 per thousand respectively. Mean δ13C values from the wet site were 3 per thousand more 13C depleted than those from the dry site implying lower water-use efficiency (carbon assimilation per unit transpiration). A process-based, model of stomatal conductance and CO2 assimilation was combined with a soil-water balance model to estimate the average daily leaf-level intercellular CO2 concentration (ci). Over two growing seasons at each site there was generally good agreement between mean canopy-level ci derived from the tree-ring δ13C data and modelled leaf-level ci levels. Further, the ratio of annual CO2 assimilation to transpiration estimated by the model for each site correlated with the

  16. Vegetation and carbon cycle dynamics in Holocene

    Science.gov (United States)

    Rachmayani, R.; Prange, M.; Schulz, M.

    2009-04-01

    Holocene climate has been relatively well investigated with global climate models. Ruddiman suggested that the growth of atmospheric carbon dioxide during the Holocene recorded in the Taylor Dome ice core is a result of profound human impact on climate due to slash-and-burn agricultural practice during the Neolithic period. A series of numerical time slice experiments using the comprehensive global climate model CCSM3 (Community Climate System Model, version 3) has been carried out to study orbitally driven climate variability during the Holocene. The importance of biogeophysical feedbacks between vegetation and climate as well as the role of terrestrial carbon storage in atmospheric carbon dioxide dynamics will be analyzed. The results will be compared to other climate models in order to address some aspects of the Ruddiman hypothesis on exceptional long-term atmospheric carbon dioxide increase during the Holocene. To this end, the land model component of CCSM3 has been improved. The improvements lead to a better simulation of global forest cover and net primary production. Key words Climate, CCSM3, Holocene, Vegetation

  17. Annual Report: Carbon Capture Simulation Initiative (CCSI) (30 September 2013)

    Energy Technology Data Exchange (ETDEWEB)

    Miller, David C. [National Energy Technology Lab. (NETL), Morgantown, WV (United States); Syamlal, Madhava [National Energy Technology Lab. (NETL), Morgantown, WV (United States); Cottrell, Roger [URS Corporation. (URS), San Francisco, CA (United States); National Energy Technology Lab. (NETL), Morgantown, WV (United States); Kress, Joel D. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Sundaresan, S. [Princeton Univ., NJ (United States); Sun, Xin [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Storlie, C. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Bhattacharyya, D. [West Virginia Univ., Morgantown, WV (United States); National Energy Technology Lab. (NETL), Morgantown, WV (United States); Tong, Charles [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Zitney, Stephen E [National Energy Technology Lab. (NETL), Morgantown, WV (United States); Dale, Crystal [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Engel, Dave [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Agarwal, Deb [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Calafiura, Paolo [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Shinn, John [SynPatEco, Pleasant Hill, CA (United States)

    2014-03-05

    -ANOVA-UQ) for calibration and validation of CFD models. 8. A new basic data submodel in Aspen Plus format for a representative high viscosity capture solvent, 2-MPZ system. 9. An updated RM tool for CFD (REVEAL) that can create a RM from MFIX. A new lightweight, stand-alone version will be available in late 2013. 10. An updated RM integration tool to convert the RM from REVEAL into a CAPE-OPEN or ACM model for use in a process simulator. 11. An updated suite of unified steady-state and dynamic process models for solid sorbent carbon capture included bubbling fluidized bed and moving bed reactors. 12. An updated and unified set of compressor models including steady-state design point model and dynamic model with surge detection. 13. A new framework for the synthesis and optimization of coal oxycombustion power plants using advanced optimization algorithms. This release focuses on modeling and optimization of a cryogenic air separation unit (ASU). 14. A new technical risk model in spreadsheet format. 15. An updated version of the sorbent kinetic/equilibrium model for parameter estimation for the 1st generation sorbent model. 16. An updated process synthesis superstructure model to determine optimal process configurations utilizing surrogate models from ALAMO for adsorption and regeneration in a solid sorbent process. 17. Validation models for NETL Carbon Capture Unit utilizing sorbent AX. Additional validation models will be available for sorbent 32D in 2014. 18. An updated hollow fiber membrane model and system example for carbon capture. 19. An updated reference power plant model in Thermoflex that includes additional steam extraction and reinjection points to enable heat integration module. 20. An updated financial risk model in spreadsheet format.

  18. 4D Dynamic RNP Annual Interim Report-Year 1

    Science.gov (United States)

    Finkelsztein, Daniel M.; Sturdy, James L.; Alaverdi, Omeed; Chung, William W.; Salvano, Daniel; Klooster, Joel; Hochwarth, Joachim K.

    2010-01-01

    This Annual Interim Report summarizes the activities led by Raytheon, in collaboration with GE Aviation and SAIC, and presents the results obtained during the first year of this research effort to expand the RNP concept to 4 dimensions relative to a dynamic frame of reference. Joint Program Development Office (JPDO)Concepts of Operations for the Next Generation Air Transportation System (NextGen) considers 4 Dimension Trajectory (4DT) procedures a key enabler to Trajectory Based Operations (TBO). The JPDO defines 4DT as a precise description of an aircraft path in space and time . While NextGen assumes that this path is defined within an Earth-reference frame, many 4DT procedure implementations will require an aircraft to precisely navigate relative to a moving reference such as another aircraft to form aggregate flows or a weather cell to allow for flows to shift. Current methods of implementing routes and flight paths rely on aircraft meeting a Required Navigation Performance (RNP) specification and being equipped with a monitoring and alerting capability to annunciate when the aircraft system is unable to meet the performance specification required for the operation. Since all aircraft today operate within the NAS relative to fixed reference points, the current RNP definition is deemed satisfactory. However, it is not well understood how the current RNP construct will support NextGen 4DT procedures where aircraft operate relative to each other or to other dynamic frames of reference. The objective of this research effort is to analyze candidate 4DT procedures from both an Air Navigation Service Provider (ANSP) and aircraft perspective, to identify their specific navigational requirements, assess the shortcomings of the current RNP construct to meet these requirements, to propose an extended 4 Dimensional Dynamic RNP (4D Dynamic RNP) construct that accounts for the dynamic spatial and temporal nature of the selected 4DT procedures, and finally, to design an

  19. Carbon dynamics in corn-soybean sequences as estimated from natural carbon-13 abundance

    International Nuclear Information System (INIS)

    Carbon flow in terrestrial ecosystems regulates partitioning between soil organic C (SOC) and atmospheric CO2. Our objectives were to assess SOC dynamics using natural 13C abundance in corn (Zea mays L., a C4 species)-soybean [Glycine max (L.) Merr., a C3 species] sequences. Fifteen treatments of continuous corn, continuous soybean, various sequences of corn and soybean, and fallow were initiated in 1981 at Lamberton, MN, on a Webster clay loam (fine-loamy, mixed, mesic Typic Haplaquoll). In 1991, soil and aboveground shoot samples from all treatments were analyzed for total organic C and delta 13C. Carbon inputs, delta 13C, and SOC were integrated into a two-pool model to evaluate C dynamics of corn and soybean. Total SOC was similar across all treatments after 10 yr; however, differences in soil delta 13C occurred between continuous corn (delta 13C = -17.2 per thous and) and continuous soybean (delta 13C = -18.2 per thousand). Modeled C dynamics showed SOC decay rates of 0.011 yr-1 for C4-derived C and 0.007 yr-1 for C3-derived C, and humification rates of 0.16 yr-1 for corn and 0.11 yr-1 for soybean. Decay and humification rates were slightly lower than those found in other Corn Belt studies. Levels of SOC were predicted to decline an additional 7 to 18% with current C inputs from either corn or soybean, respectively. Annual C additions required for SOC maintenance averaged 5.6 Mg C ha-1, 1.4 to 2.1 times greater than previously reported estimates. Controlled variation in natural 13C abundance in corn-soybean rotations during a 10-yr period adequately traced C dynamics

  20. Dynamics in storage-discharge relations on annual and seasonal scale in a large sub-Arctic catchment.

    Science.gov (United States)

    Ploum, Stefan; van der Velde, Ype; Teuling, Ryan; Lyon, Steve

    2015-04-01

    Warming of the Arctic and sub-Arctic environment can affect the global carbon budget because tundra systems have the potential to develop from a carbon sink into a major carbon source. The transport of carbon on catchment scale is tightly related to hydrology: stream water DOC (dissolved organic carbon) and DIC (dissolved inorganic carbon) concentrations are affected by water flow paths and travel times, and these are again sensitive to shifts in temperature. In this study we investigate the effects of soil temperature and snow levels on streamflow recessions in Abiskojokken, a large sub-Arctic catchment in northern Sweden (566 km2). During a large part of the year the storage depends on the presence of soil frost and snow accumulation, which both vary annually. This means that combining hydrological groundwater theory and temperature records could learn us how sensitive storage-discharge relations are to temperature change. Because a large part of the yearly discharge occurs in spring and summer, we focused on the comparison of recessions during these seasons. We expected that soil frost early in the spring generates surface runoff and thus causes a fast catchment response. However, our results indicate that recessions in spring melt are slower than recessions in the summer. We did a second analysis on years which experienced extremities in winter duration, soil temperatures or snow level. Under certain conditions (long winters, low soil temperatures and both high and low snow levels), the recession behaviour in the spring again becomes similar to summer recessions. These results indicate recession behaviour in spring is influenced by winter conditions and that the storage-discharge relation in a sub-Arctic setting are dynamic on seasonal and annual scale. We conclude that the spatial elapse of snowmelt over the large catchment and the soil frost state are important for this dynamic storage-discharge relation. For accurate carbon export rates, it is of interest to

  1. Microbial carbon recycling: an underestimated process controlling soil carbon dynamics

    Science.gov (United States)

    Basler, A.; Dippold, M.; Helfrich, M.; Dyckmans, J.

    2015-07-01

    The mean residence times (MRT) of different compound classes of soil organic matter (SOM) do not match their inherent recalcitrance to decomposition. One reason for this is the stabilisation within the soil matrix, but recycling, i.e. the reuse of "old" organic material to form new biomass may also play a role as it uncouples the residence times of organic matter from the lifetime of discrete molecules in soil. We analysed soil sugar dynamics in a natural 30 years old labelling experiment after a~wheat-maize vegetation change to determine the extent of recycling and stabilisation in plant and microbial derived sugars: while plant derived sugars are only affected by stabilisation processes, microbial sugars may be subject to both, stabilisation and recycling. To disentangle the dynamics of soil sugars, we separated different density fractions (free particulate organic matter (fPOM), light occluded particulate organic matter (≤1.6 g cm-3; oPOM1.6), dense occluded particulate organic matter (≤2 g cm-3; oPOM2) and mineral-associated organic matter (>2 g cm-3; Mineral)) of a~silty loam under long term wheat and maize cultivation. The isotopic signature of sugars was measured by high pressure liquid chromatography coupled to isotope ratio mass spectrometry (HPLC/IRMS), after hydrolysis with 4 M Trifluoroacetic acid (TFA). While apparent mean residence times (MRT) of sugars were comparable to total organic carbon in the bulk soil and mineral fraction, the apparent MRT of sugars in the oPOM fractions were considerably lower than those of the total carbon of these fractions. This indicates that oPOM formation was fuelled by microbial activity feeding on new plant input. In the bulk soil, mean residence times of the mainly plant derived xylose (xyl) were significantly lower than those of mainly microbial derived sugars like galactose (gal), rhamnose (rha), fucose (fuc), indicating that recycling of organic matter is an important factor regulating organic matter dynamics

  2. Control factors and scale analysis of annual river water, sediments and carbon transport in China

    OpenAIRE

    Chunlin Song; Genxu Wang; Xiangyang Sun; Ruiying Chang; Tianxu Mao

    2016-01-01

    Under the context of dramatic human disturbances on river system, the processes that control the transport of water, sediment, and carbon from river basins to coastal seas are not completely understood. Here we performed a quantitative synthesis for 121 sites across China to find control factors of annual river exports (Rc: runoff coefficient; TSSC: total suspended sediment concentration; TSSL: total suspended sediment loads; TOCL: total organic carbon loads) at different spatial scales. The ...

  3. [Forest biomass carbon storage and its dynamics in Tanjiang River basin].

    Science.gov (United States)

    Yang, Kun; Guan, Dongsheng; Zhou, Chunhua

    2006-09-01

    Based on an improved estimation method of forest carbon storage and the inventory of forest resources, this paper estimated the forest carbon storage and its dynamic changes in Tanjiang River basin, and analyzed the relationships of the carbon storage and its density with the increase of population density and GDP during the urbanization in 1990-2001. The results showed that the forest carbon storage in Tanjiang River basin increased from 5.906 x 10(6) t in 1990 to 7.852 x 10(6) t in 2001, with an annual average accumulation amount of 0.18 x 10(6) t or an annual average accumulation rate of 3.05%, and playing a role of carbon sink. The rapid increase of population density and GDP didn't influence the increase of forest carbon storage and density, but the development of forestry was far lower than that of economy. To have a better service function of forest ecosystem in the process of urbanization, and to promote the sustainable development of regional ecological environment, the key point is the reasonable coordination of forestry management with the development of economy. PMID:17147160

  4. Dynamic damage in carbon-fibre composites.

    Science.gov (United States)

    Bourne, N K; Parry, S; Townsend, D; Withers, P J; Soutis, C; Frias, C

    2016-07-13

    The Taylor test is used to determine damage evolution in carbon-fibre composites across a range of strain rates. The hierarchy of damage across the scales is key in determining the suite of operating mechanisms and high-speed diagnostics are used to determine states during dynamic loading. Experiments record the test response as a function of the orientation of the cylinder cut from the engineered multi-ply composite with high-speed photography and post-mortem target examination. The ensuing damage occurs during the shock compression phase but three other tensile loading modes operate during the test and these are explored. Experiment has shown that ply orientations respond to two components of release; longitudinal and radial as well as the hoop stresses generated in inelastic flow at the impact surface. The test is a discriminant not only of damage thresholds but of local failure modes and their kinetics. This article is part of the themed issue 'Multiscale modelling of the structural integrity of composite materials'. PMID:27242311

  5. RIVERINE INORGANIC CARBON DYNAMICS: OVERVIEW AND PERSPECTIVE

    Institute of Scientific and Technical Information of China (English)

    YAO Guan-rong; GAO Quan-zhou

    2006-01-01

    Inorganic carbon, the great part of the riverine carbon exported to the ocean, plays an important role in the global carbon cycle and ultimately impacts the coupled carbon-climate system. An overview was made on both methods and results of the riverine inorganic carbon researches. In addition to routine in situ survey, measurement and calculation,the direct precipitation method and the gas evolution technique were commonly used to analyze dissolved inorganic carbon in natural water samples. Soil CO2, carbonate minerals and atmospheric CO2 incorporated into riverine inorganic carbon pool via different means, with bicarbonate ion being the dominant component. The concentration of inorganic carbon, the composition of carbon isotopes (δ13C and △14C), and their temporal or spatial variations in the streams were controlled by carbon input, output and changes of carbon biogeochemistry within the riverine system. More accurate flux estimation, better understanding of different influential processes, and quantitative determination of various inputs or outputs need to be well researched in future.

  6. Modeling carbon dynamics and social drivers of bioenergy agroecosystems

    Science.gov (United States)

    Hunt, Natalie D.

    Meeting society's energy needs through bioenergy feedstock production presents a significant and urgent challenge, as it can aid in achieving energy independence goals and mitigating climate change. With federal biofuel production standards to be met within the next decade, and with no commercial scale production or markets currently in place, many questions regarding the sustainability and social feasibility of bioenergy still persist. Clarifying these uncertainties requires the incorporation of biogeochemical, biophysical, and socioeconomic modeling tools. Chapter 2 validated the biogeochemical cycling model AGRO-BGC by comparing model estimates with empirical observations from corn and perennial C4 grass systems across Wisconsin and Illinois. AGRO-BGC, in its first application to an annual cropping system, was found to be a robust model for simulating carbon dynamics of an annual cropping system. Chapter 3 investigated the long-term implications of bioenergy feedstock harvest on soil productivity and erosion in annual corn and perennial switchgrass agroecosystems using AGRO-BGC and the soil erosion model RUSLE2. Modeling environments included biophysical landscape characteristics and management practices of bioenergy feedstock production systems. This study found that intensifying aboveground residue harvest reduces soil productivity over time, and the magnitude of these losses is greater in corn than in switchgrass systems. Results of this study will aid in the design of sustainable bioenergy feedstock management practices. Chapter 4 provided evidence that combining biophysical crop canopy characteristics with satellite-derived vegetation indices offers suitable estimates of crop canopy phenology for corn and soybeans in Southwest Wisconsin farms. LANDSAT based vegetation indices, when combined with a light use efficiency model, provide yield estimates in agreement with farmer reports, providing an efficient and accurate means of estimating crop yields from

  7. Forest structure and carbon dynamics in Amazonian tropical rain forests.

    Science.gov (United States)

    Vieira, Simone; de Camargo, Plinio Barbosa; Selhorst, Diogo; da Silva, Roseana; Hutyra, Lucy; Chambers, Jeffrey Q; Brown, I Foster; Higuchi, Niro; dos Santos, Joaquim; Wofsy, Steven C; Trumbore, Susan E; Martinelli, Luiz Antonio

    2004-08-01

    Living trees constitute one of the major stocks of carbon in tropical forests. A better understanding of variations in the dynamics and structure of tropical forests is necessary for predicting the potential for these ecosystems to lose or store carbon, and for understanding how they recover from disturbance. Amazonian tropical forests occur over a vast area that encompasses differences in topography, climate, and geologic substrate. We observed large differences in forest structure, biomass, and tree growth rates in permanent plots situated in the eastern (near Santarém, Pará), central (near Manaus, Amazonas) and southwestern (near Rio Branco, Acre) Amazon, which differed in dry season length, as well as other factors. Forests at the two sites experiencing longer dry seasons, near Rio Branco and Santarém, had lower stem frequencies (460 and 466 ha(-1) respectively), less biodiversity (Shannon-Wiener diversity index), and smaller aboveground C stocks (140.6 and 122.1 Mg C ha(-1)) than the Manaus site (626 trees ha(-1), 180.1 Mg C ha(-1)), which had less seasonal variation in rainfall. The forests experiencing longer dry seasons also stored a greater proportion of the total biomass in trees with >50 cm diameter (41-45 vs 30% in Manaus). Rates of annual addition of C to living trees calculated from monthly dendrometer band measurements were 1.9 (Manaus), 2.8 (Santarém), and 2.6 (Rio Branco) Mg C ha(-1) year(-1). At all sites, trees in the 10-30 cm diameter class accounted for the highest proportion of annual growth (38, 55 and 56% in Manaus, Rio Branco and Santarém, respectively). Growth showed marked seasonality, with largest stem diameter increment in the wet season and smallest in the dry season, though this may be confounded by seasonal variation in wood water content. Year-to-year variations in C allocated to stem growth ranged from nearly zero in Rio Branco, to 0.8 Mg C ha(-1) year(-1) in Manaus (40% of annual mean) and 0.9 Mg C ha(-1) year(-1) (33% of

  8. Modeling the dynamics of carbon emission performance in China: A parametric Malmquist index approach

    International Nuclear Information System (INIS)

    This paper contributes to the existing literature on the methodology of modeling the dynamic of carbon emission performance. Based on the analytical framework of Zhou et al. (Energy Economics, 32, 194–201, 2010), we develop a parametric Malmquist index approach that takes into account statistical noises. Moreover, the fixed-effect panel stochastic frontier model is employed to deal with regional heterogeneity. The proposed approach is applied to analyze the dynamics of carbon emission performance in 30 Chinese provinces during the period of 2000–2010. The main findings are as follows. First, the carbon emission performances of 30 provinces as a whole improved by 4.1% annually during the sample period, which was mainly driven by efficiency change component. Second, the east area shows the best performance with an average Malmquist CO2 emissions performance index (MCPI) of 1.108, followed by the central area (1.039). Unlike the east and central areas, the west area experienced deterioration in carbon emission performance. More effective environmental policies should be implemented to change the situation. Third, compared with the proposed approach, the nonparametric approach tends to underestimate China's MCPI and gives rise to volatile results. - Highlights: • This paper analyzes the dynamics of carbon emission performance in China. • A parametric Malmquist index approach is presented. • China's carbon emission performance annually improved by 4.1% during the period 2000–2010. • Efficiency change is the major contributor to the improvement of China's MCPI

  9. An eddy covariance derived annual carbon budget for an arctic terrestrial ecosystem (Disko, Greenland)

    Science.gov (United States)

    McConnell, Alistair; Lund, Magnus; Friborg, Thomas

    2016-04-01

    Ecosystems with underlying permafrost cover nearly 25% of the ice-free land area in the northern hemisphere and store almost half of the global soil carbon. Future climate changes are predicted to have the most pronounced effect in northern latitudes. These Arctic ecosystems are therefore subject to dramatic changes following thawing of permafrost, glacial retreat, and coastal erosion. The most dramatic effect of permafrost thawing is the accelerated decomposition and potential mobilization of organic matter stored in the permafrost. This will impact global climate through the mobilization of carbon and nitrogen accompanied by release of greenhouses gases, including carbon dioxide. This study presents the initial findings and first full annual carbon (CO2) budget, derived from eddy covariance measurements, for an Arctic landscape in West Greenland. The study site, a terrestrial Arctic maritime climate, is located at Østerlien, near Qeqertarsuaq, on the southern coast of Disko Island in central West Greenland (69° 15' N, 53° 34' W) within the transition zone from continuous to discontinuous permafrost. The mean annual air temperature is -5 C and the annual precipitation as rain is 150-200 mm. Arctic ecosystem feedback mechanisms and processes interact on micro, local and regional scales. This is further complicated by several potential feedback mechanisms likely to occur in permafrost-affected ecosystems, involving the interactions of microorganisms, vegetation and soil. The eddy covariance method allows us to interrogate the processes and drivers of land-atmosphere carbon exchange at extremely high temporary frequency (10 Hz), providing landscape-scale measurements of CO2, H2O and heat fluxes for the site, which are processed to derive daily, monthly and now, annual carbon fluxes. We discuss the scientific methodology, challenges, and analysis, as well as the practical and logistic challenges of working in the Arctic, and present an annual carbon budget

  10. The Effects of Nitrogen Enrichment and a Simulated Rainfall Event on Soil Carbon Dioxide Efflux in an Annual California Grassland

    Science.gov (United States)

    Johnson, T. P.; Strong, A. L.; Chiariello, N.; Field, C. B.

    2013-12-01

    Soils contain the largest pool of carbon in terrestrial ecosystems and play a critical role in the global carbon cycle. Previous studies have shown that enhanced precipitation (projected by climate models) and human activities (such as increased fertilizer use) may alter this cycle by enhancing soil microbial activity, although effects are often variable. Soils in semi-arid grasslands play a vital role in the global carbon cycle and may be responsive to environmental perturbations. Previous studies have demonstrated that wet-up treatments positively influence soil carbon dioxide efflux rates, which are otherwise low during dry summers. A preliminary study performed in a semi-arid annual grassland has shown that long-term nitrogen enrichment (equivalent to 70kg N per hectare) positively influences soil carbon dioxide efflux during peak biomass in the wet season. However, the combined effect and seasonal dynamics of these environmental changes is poorly understood. In order to assess this interaction, we explore the short-term response of soil carbon dioxide efflux rates in a semi-arid grassland to a combination of long-term nitrogen enrichment and a simulated 20-mm rainfall event in the Jasper Ridge Global Change Experiment (JRCGE), a long-term, multi-factorial experiment in a semi-arid annual grassland located in the foothills of the Santa Cruz mountains in central California. We measured soil carbon dioxide efflux rates from pre-installed soil respiration collars for forty-eight hours after a simulated rainfall event (20mm) during the dry season in late July 2013. Both the enhanced and non-enhanced nitrogen treatments had an immediate pronounced response to the wet-up stimulation in which efflux rates increased by an average of more than six-fold. In contrast with previous studies of soil carbon dioxide efflux at JRGCE during the wet season in which N enrichment elevated efflux rates relative to controls, however, the soil carbon dioxide efflux rates in response

  11. [Carbon isotope fractionation in plants]: Annual technical progress report

    International Nuclear Information System (INIS)

    Plants fractionate carbon isotopes during photosynthesis in ways which reflect photosynthetic pathway and environment. The fractionation is product of contributions from diffusion, carboxylation and other factors which can be understood using models which have been developed in our work. The object of our work is to use this fractionation to learn about the factors which control the efficiency of photosynthesis. Unlike previous studies, we do not rely principally on combustion methods, but instead develop more specific methods with substantially higher resolving power. We have recently developed a new short-term method for studying carbon isotope fractionation which promises to provide a level of detail about temperature, species, and light intensity effects on photosynthesis which has not been available until now. We are studying the isotopic compositions of metabolites (particularly aspartic acid) in C3 plants in order to determine the role of phosphoenolpyruvate carboxylase in C3 photosynthesis. We are studying the relative roles of diffusion and carboxylation in nocturnal CO2 fixation in CAM plants. We are studying the use of isotopic content as an index of water-use efficiency in C3 plants. We are developing new methods for studying carbon metabolism in plants. 3 refs

  12. Annual Carbon Emissions from Deforestation in the Amazon Basin between 2000 and 2010.

    Directory of Open Access Journals (Sweden)

    Xiao-Peng Song

    Full Text Available Reducing emissions from deforestation and forest degradation (REDD+ is considered one of the most cost-effective strategies for mitigating climate change. However, historical deforestation and emission rates-critical inputs for setting reference emission levels for REDD+-are poorly understood. Here we use multi-source, time-series satellite data to quantify carbon emissions from deforestation in the Amazon basin on a year-to-year basis between 2000 and 2010. We first derive annual deforestation indicators by using the Moderate Resolution Imaging Spectroradiometer Vegetation Continuous Fields (MODIS VCF product. MODIS indicators are calibrated by using a large sample of Landsat data to generate accurate deforestation rates, which are subsequently combined with a spatially explicit biomass dataset to calculate committed annual carbon emissions. Across the study area, the average deforestation and associated carbon emissions were estimated to be 1.59 ± 0.25 M ha•yr(-1 and 0.18 ± 0.07 Pg C•yr(-1 respectively, with substantially different trends and inter-annual variability in different regions. Deforestation in the Brazilian Amazon increased between 2001 and 2004 and declined substantially afterwards, whereas deforestation in the Bolivian Amazon, the Colombian Amazon, and the Peruvian Amazon increased over the study period. The average carbon density of lost forests after 2005 was 130 Mg C•ha(-1, ~11% lower than the average carbon density of remaining forests in year 2010 (144 Mg C•ha(-1. Moreover, the average carbon density of cleared forests increased at a rate of 7 Mg C•ha(-1•yr(-1 from 2005 to 2010, suggesting that deforestation has been progressively encroaching into high-biomass lands in the Amazon basin. Spatially explicit, annual deforestation and emission estimates like the ones derived in this study are useful for setting baselines for REDD+ and other emission mitigation programs, and for evaluating the performance of such

  13. Annual Carbon Emissions from Deforestation in the Amazon Basin between 2000 and 2010.

    Science.gov (United States)

    Song, Xiao-Peng; Huang, Chengquan; Saatchi, Sassan S; Hansen, Matthew C; Townshend, John R

    2015-01-01

    Reducing emissions from deforestation and forest degradation (REDD+) is considered one of the most cost-effective strategies for mitigating climate change. However, historical deforestation and emission rates-critical inputs for setting reference emission levels for REDD+-are poorly understood. Here we use multi-source, time-series satellite data to quantify carbon emissions from deforestation in the Amazon basin on a year-to-year basis between 2000 and 2010. We first derive annual deforestation indicators by using the Moderate Resolution Imaging Spectroradiometer Vegetation Continuous Fields (MODIS VCF) product. MODIS indicators are calibrated by using a large sample of Landsat data to generate accurate deforestation rates, which are subsequently combined with a spatially explicit biomass dataset to calculate committed annual carbon emissions. Across the study area, the average deforestation and associated carbon emissions were estimated to be 1.59 ± 0.25 M ha•yr(-1) and 0.18 ± 0.07 Pg C•yr(-1) respectively, with substantially different trends and inter-annual variability in different regions. Deforestation in the Brazilian Amazon increased between 2001 and 2004 and declined substantially afterwards, whereas deforestation in the Bolivian Amazon, the Colombian Amazon, and the Peruvian Amazon increased over the study period. The average carbon density of lost forests after 2005 was 130 Mg C•ha(-1), ~11% lower than the average carbon density of remaining forests in year 2010 (144 Mg C•ha(-1)). Moreover, the average carbon density of cleared forests increased at a rate of 7 Mg C•ha(-1)•yr(-1) from 2005 to 2010, suggesting that deforestation has been progressively encroaching into high-biomass lands in the Amazon basin. Spatially explicit, annual deforestation and emission estimates like the ones derived in this study are useful for setting baselines for REDD+ and other emission mitigation programs, and for evaluating the performance of such efforts. PMID

  14. Dynamic friction force in a carbon peapod oscillator

    OpenAIRE

    Su, Haibin; Goddard, William A.; Zhao, Yang

    2006-01-01

    We investigate a new generation of fullerene nano-oscillators: a single-walled carbon nanotube with one buckyball inside with an operating frequency in the tens-of-gigahertz range. A quantitative characterization of energy dissipation channels in the peapod pair has been performed via molecular dynamics simulation. Edge effects are found to be the dominant cause of dynamic friction in the carbon-peapod oscillators. A comparative study on the energy dissipation also reveals the significant imp...

  15. Can heterotrophic uptake of dissolved organic carbon and zooplankton mitigate carbon budget deficits in annually bleached corals?

    Science.gov (United States)

    Levas, Stephen; Grottoli, Andréa G.; Schoepf, Verena; Aschaffenburg, Matthew; Baumann, Justin; Bauer, James E.; Warner, Mark E.

    2016-06-01

    Annual coral bleaching events due to increasing sea surface temperatures are predicted to occur globally by the mid-century and as early as 2025 in the Caribbean, and severely impact coral reefs. We hypothesize that heterotrophic carbon (C) in the form of zooplankton and dissolved organic carbon (DOC) is a significant source of C to bleached corals. Thus, the ability to utilize multiple pools of fixed carbon and/or increase the amount of fixed carbon acquired from one or more pools of fixed carbon (defined here as heterotrophic plasticity) could underlie coral acclimatization and persistence under future ocean-warming scenarios. Here, three species of Caribbean coral— Porites divaricata, P. astreoides, and Orbicella faveolata—were experimentally bleached for 2.5 weeks in two successive years and allowed to recover in the field. Zooplankton feeding was assessed after single and repeat bleaching, while DOC fluxes and the contribution of DOC to the total C budget were determined after single bleaching, 11 months on the reef, and repeat bleaching. Zooplankton was a large C source for P. astreoides, but only following single bleaching. DOC was a source of C for single-bleached corals and accounted for 11-36 % of daily metabolic demand (CHARDOC), but represented a net loss of C in repeat-bleached corals. In repeat-bleached corals, DOC loss exacerbated the negative C budgets in all three species. Thus, the capacity for heterotrophic plasticity in corals is compromised under annual bleaching, and heterotrophic uptake of DOC and zooplankton does not mitigate C budget deficits in annually bleached corals. Overall, these findings suggest that some Caribbean corals may be more susceptible to repeat bleaching than to single bleaching due to a lack of heterotrophic plasticity, and coral persistence under increasing bleaching frequency may ultimately depend on other factors such as energy reserves and symbiont shuffling.

  16. Annual Report: Carbon Capture Simulation Initiative (CCSI) (30 September 2012)

    Energy Technology Data Exchange (ETDEWEB)

    Miller, David C. [National Energy Technology Lab. (NETL), Morgantown, WV (United States); Syamlal, Madhava [National Energy Technology Lab. (NETL), Morgantown, WV (United States); Cottrell, Roger [URS Corporation. (URS), San Francisco, CA (United States); National Energy Technology Lab. (NETL), Morgantown, WV (United States); Kress, Joel D. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Sun, Xin [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Sundaresan, S. [Princeton Univ., NJ (United States); Sahinidis, Nikolaos V. [Carnegie Mellon Univ., Pittsburgh, PA (United States); National Energy Technology Lab. (NETL), Morgantown, WV (United States); Zitney, Stephen E. [NETL; Bhattacharyya, D. [West Virginia Univ., Morgantown, WV (United States); National Energy Technology Lab. (NETL), Morgantown, WV (United States); Agarwal, Deb [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Tong, Charles [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Lin, Guang [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Dale, Crystal [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Engel, Dave [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Calafiura, Paolo [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Beattie, Keith [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Shinn, John [SynPatEco. Pleasant Hill, CA (United States)

    2012-09-30

    The Carbon Capture Simulation Initiative (CCSI) is a partnership among national laboratories, industry and academic institutions that is developing and deploying state-of-the-art computational modeling and simulation tools to accelerate the commercialization of carbon capture technologies from discovery to development, demonstration, and ultimately the widespread deployment to hundreds of power plants. The CCSI Toolset will provide end users in industry with a comprehensive, integrated suite of scientifically validated models, with uncertainty quantification (UQ), optimization, risk analysis and decision making capabilities. The CCSI Toolset incorporates commercial and open-source software currently in use by industry and is also developing new software tools as necessary to fill technology gaps identified during execution of the project. Ultimately, the CCSI Toolset will (1) enable promising concepts to be more quickly identified through rapid computational screening of devices and processes; (2) reduce the time to design and troubleshoot new devices and processes; (3) quantify the technical risk in taking technology from laboratory-scale to commercial-scale; and (4) stabilize deployment costs more quickly by replacing some of the physical operational tests with virtual power plant simulations. CCSI is organized into 8 technical elements that fall under two focus areas. The first focus area (Physicochemical Models and Data) addresses the steps necessary to model and simulate the various technologies and processes needed to bring a new Carbon Capture and Storage (CCS) technology into production. The second focus area (Analysis & Software) is developing the software infrastructure to integrate the various components and implement the tools that are needed to make quantifiable decisions regarding the viability of new CCS technologies. CCSI also has an Industry Advisory Board (IAB). By working closely with industry from the inception of the project to identify

  17. Optics and Fluid Dynamics Department annual progress report for 2001

    DEFF Research Database (Denmark)

    Bindslev, H.; Hanson, Steen Grüner; Lynov, Jens-Peter;

    2002-01-01

    The Optics and Fluid Dynamics Department performs basic and applied research within three scientific programmes: (1) laser systems and optical materials, (2) optical diagnostics and information processing and (3) plasma and fluid dynamics. The departmenthas core competences in: optical sensors...

  18. Optics and Fluid Dynamics Department annual progress report for 2002

    DEFF Research Database (Denmark)

    Bindslev, H.; Hanson, Steen Grüner; Lynov, Jens-Peter;

    2003-01-01

    The Optics and Fluid Dynamics Department performs basic and applied research within three scientific programmes: (1) laser systems and optical materials (2) optical diagnostics and information processing and (3) plasma and fluid dynamics. The departmenthas core competences in: optical sensors...

  19. Patterns of Forest Disturbance and Recovery Dynamics on Structure and Carbon Fluxes in New England Forests

    Science.gov (United States)

    Dolan, K.; Hurtt, G. C.; Huang, C.; Dubayah, R.; Fisk, J. P.; Duncanson, L.; Masek, J. G.

    2012-12-01

    Forest disturbance and recovery strongly influence forest structure, function and services. Forest disturbance and recovery are critical mechanisms for transferring carbon between the land surface and the atmosphere, yet the role of forest disturbance within the terrestrial carbon cycle still remains uncertain and only recently have these events been accounted for within regional-scale and global carbon models. Adding ecological disturbance into biogeochemical models is noted as critical to estimating current and future carbon stocks and fluxes. This study used satellite-based observations of forest change, lidar derived structure data and a height structured ecosystem model to improve knowledge of disturbances role in carbon cycle by quantifying how forest disturbance and recovery vary at different spatial and temporal scales. Annual forest change maps from 1984-2010 were produced using the highly automated Vegetation Change Tracker (VCT) algorithm (Huang et al 2009). Mapped forest change was further broken down into land conversion (forest to non forest), severe disturbance (stand replacing), and non severe (partial clearing/ thinning). Areas of forest change were aggregated at different spatial scales and temporal scales and integrated into the Ecosystem Demography model (ED), a mechanistic model of forest ecosystem dynamics, to calculate changes in biomass and carbon fluxes. Forest structural data derived from NASA's Laser Vegetation Imaging Sensor (LVIS) was used to assess regrowth of forests and compare to ED's height and structure properties. Results in the New England Region show both spatial and temporal variation in area disturbed. The northern region encompassing Northern New Hampshire showed higher and more variable rates with an average annual rate of disturbance of approximately 0.5% (range 0.2- 08%) conversion/ non regeneration forest clearing range 0.02 -0.08%. While the southern averaged annual disturbance of 0.3% (ranged 0.2 - 0.5%) it had a much

  20. Carbon dynamics in an almond orchard soil amended with raw and treated pig slurry

    Science.gov (United States)

    Domínguez, Sara G.; Zornoza, Raúl; Faz, Ángel

    2010-05-01

    In SE Spain, intensive farming is very common which supposes the generation of great amounts of pig slurries. These residues cause many storage problems due to their pollution capacity. A good management of them is necessary to avoid damages to the environment. The use of this effluent as fertilizer is a usual practice that in the correct dose is a good amend and important for sustainable development, but in excess can be a risk of polluting and damaging soil, water and crop conditions. Pig slurry is a source of many nutrients and specially rich in organic matter. The main objective of this study is to determine changes in soil organic carbon dynamics resulting from raw and treated slurry amendments applied in different doses. The experimental area is an almond orchard located in Cartagena (SE Spain). The climate of the area is semiarid Mediterranean with mean annual temperature of 18°C and mean annual rainfall of 275 mm. A total of 10 plots (12 m x 30 m) were designed, one of them being the control without fertilizer. Surface soil samples (0-25 cm) were collected in September 2009. Three different treatments were applied, raw slurry, the effluent obtained after solid-liquid separation and solid manure, all of them in three doses being the first one of 170 kg N/ha, (maximum permitted in nitrates directive 91/676/CEE), and the others two and three times the first one. Soil biochemical parameters are rapid indicators of changes in soil quality. According to this, total organic carbon, soil microbial biomass carbon, soluble carbon, and β-glucosidase, β-galactosidase and arylesterase activities were measured in order to assess some soil biochemical conditions and carbon dynamics in terms of the different treatments. As we expected, the use of these organic fertilizers rich in organic matter, had an effect on soil carbon and soil microbial activity resulting in an increase in most of the parameters; total organic carbon and β-galactosidase activity showed the

  1. Discerning the cows from the pasture when determining annual NEE and carbon budget

    Science.gov (United States)

    Ammann, Christof; Felber, Raphael; Neftel, Albrecht

    2015-04-01

    The CO2 exchange of ecosystems and the resulting annual net ecosystem exchange (NEE) and total carbon budget (soil carbon sequestration) is commonly investigated using the eddy covariance (EC) technique. For the carbon budget of managed ecosystems also the import and export of organic carbon has to be taken into account. Grazed pasture systems represent a special challenge because their respiration can considerably contribute to the measured CO2 flux, but this contribution depends on the spatial distribution of the cows relative to the footprint and thus is variable in time. This has implications for the gap filling of CO2 flux time series necessary to determine annual NEE. In few existing studies two procedures have been suggested to determine the NEE of grazed pasture: (a) discarding all cases with cows in the footprint and gap-filling the remaining dataset; (b) treating the cow respiration as part of total ecosystem respiration and gap fill the entire flux dataset including cow contributions. Both approaches rely on idealized assumptions and have limitations. In our study we evaluated and compared the two approaches (for the first time to our knowledge) for a grazed pasture in Switzerland. For this purpose, the grazing cows were equipped with GPS sensors to monitor their position relative to the flux footprint. We found that the resulting annual NEE strongly depends on the flux data selection (e.g. u* filtering) and the applied gap filling procedure. Using an optimized procedure, the annual NEE with approach (b) was several times larger than the result of approach (a), but the difference agreed fairly well with independent estimates of cow respiration. Necessary assumptions and requirements of the two approaches for the determination of the pasture carbon budget will be discussed.

  2. The dynamic response of carbon fiber-filled polymer composites

    OpenAIRE

    Patterson B.; Orler E.B.; Furmanski J.; Rigg P.A.; Scharff R.J.; Stahl D.B.; Sheffield S.A.; Gustavsen R.L.; Dattelbaum D.M.; Coe J.D.

    2012-01-01

    The dynamic (shock) responses of two carbon fiber-filled polymer composites have been quantified using gas gun-driven plate impact experimentation. The first composite is a filament-wound, highly unidirectional carbon fiber-filled epoxy with a high degree of porosity. The second composite is a chopped carbon fiber- and graphite-filled phenolic resin with little-to-no porosity. Hugoniot data are presented for the carbon fiber-epoxy (CE) composite to 18.6 GPa in the through-thickness direction,...

  3. Fluvial carbon dynamics in degraded peatland catchments

    OpenAIRE

    Stimson, Andrew Graham

    2016-01-01

    Inland waters including streams, rivers, reservoirs and lakes are regarded as a significant site of Organic Carbon (OC) cycling, and greenhouse gas production. As a result, there has been significant recent interest in the rates and fate of fluvial carbon exported from organic soils, such as peatlands. Additionally, peatlands can be subject to substantial degradation resulting in high rates of fluvial OC export, and this has led to efforts to repair degraded peatlands through restoration pr...

  4. Integrating microbial diversity in soil carbon dynamic models parameters

    Science.gov (United States)

    Louis, Benjamin; Menasseri-Aubry, Safya; Leterme, Philippe; Maron, Pierre-Alain; Viaud, Valérie

    2015-04-01

    Faced with the numerous concerns about soil carbon dynamic, a large quantity of carbon dynamic models has been developed during the last century. These models are mainly in the form of deterministic compartment models with carbon fluxes between compartments represented by ordinary differential equations. Nowadays, lots of them consider the microbial biomass as a compartment of the soil organic matter (carbon quantity). But the amount of microbial carbon is rarely used in the differential equations of the models as a limiting factor. Additionally, microbial diversity and community composition are mostly missing, although last advances in soil microbial analytical methods during the two past decades have shown that these characteristics play also a significant role in soil carbon dynamic. As soil microorganisms are essential drivers of soil carbon dynamic, the question about explicitly integrating their role have become a key issue in soil carbon dynamic models development. Some interesting attempts can be found and are dominated by the incorporation of several compartments of different groups of microbial biomass in terms of functional traits and/or biogeochemical compositions to integrate microbial diversity. However, these models are basically heuristic models in the sense that they are used to test hypotheses through simulations. They have rarely been confronted to real data and thus cannot be used to predict realistic situations. The objective of this work was to empirically integrate microbial diversity in a simple model of carbon dynamic through statistical modelling of the model parameters. This work is based on available experimental results coming from a French National Research Agency program called DIMIMOS. Briefly, 13C-labelled wheat residue has been incorporated into soils with different pedological characteristics and land use history. Then, the soils have been incubated during 104 days and labelled and non-labelled CO2 fluxes have been measured at ten

  5. Dynamic simulation of the carbon-in-pulp and carbon-in-leach processes

    Directory of Open Access Journals (Sweden)

    L. R. P. de Andrade Lima

    2007-12-01

    Full Text Available Carbon-in-leach and carbon-in-pulp are continuous processes that use activated carbon in a cascade of large agitated tanks, which have been widely used to recover or concentrate precious metals in gold extraction plants. In the carbon-in-pulp process adsorption occurs after the leaching cascade section of the plant, and in the carbon-in-leach process leaching and adsorption occur simultaneously. In both processes the activated carbon is moved from one tank to another in countercurrent with the ore pulp until the recovery of the loaded carbon in the first tank. This paper presents a dynamic model that describes, with minor changes, the carbon-in-leach, the carbon-in-pulp, and the gold leaching processes. The model is numerically solved and calibrated with experimental data from a plant and used to perform a study of the effect of the activated carbon transfer strategy on the performance of the adsorption section of the plant. Based on the calculated values of the gold loss in the liquid and of the gold recovered in the loaded activated carbon that leaves the circuit, the results indicate that strategies in which a significant amount of activated carbon is held in the first tank and the contact time between the carbon and the pulp is longer are the best carbon transfer strategies for these processes.

  6. Optics and Fluid Dynamics Department annual progress report for 1995

    Energy Technology Data Exchange (ETDEWEB)

    Hanson, S.G.; Lading, L.; Lynov, J.P.; Skaarup, B. [eds.

    1996-01-01

    Research in the Optics and Fluid Dynamics Department has been performed within the following two programme areas: (1) optical diagnostics and information processing and (2) plasma and fluid dynamics. The optical activities are concentrated on optical materials, diagnostics and sensors. The plasma and fluid dynamics activities are concentrated on nonlinear dynamics in fluids, plasmas and optics as well as on plasma and fluid diagnostics. Scientific computing is an integral part of the work. The activities are supported by several EU programmes, including EURATOM, by research councils and by industry. A summary of the activities in 1995 is presented. (au) 36 ills., 166 refs.

  7. Optics and Fluid Dynamics Department annual progress report for 1995

    International Nuclear Information System (INIS)

    Research in the Optics and Fluid Dynamics Department has been performed within the following two programme areas: (1) optical diagnostics and information processing and (2) plasma and fluid dynamics. The optical activities are concentrated on optical materials, diagnostics and sensors. The plasma and fluid dynamics activities are concentrated on nonlinear dynamics in fluids, plasmas and optics as well as on plasma and fluid diagnostics. Scientific computing is an integral part of the work. The activities are supported by several EU programmes, including EURATOM, by research councils and by industry. A summary of the activities in 1995 is presented. (au) 36 ills., 166 refs

  8. Carbon dynamics and their link to dissolved organic matter quality across contrasting stream ecosystems.

    Science.gov (United States)

    Bodmer, Pascal; Heinz, Marlen; Pusch, Martin; Singer, Gabriel; Premke, Katrin

    2016-05-15

    Streams represent active components of the carbon cycle as emitters of carbon dioxide (CO2) and methane to the atmosphere at a global scale. However, the mechanisms and governing factors of these emissions are still largely unknown, especially concerning the effect of land use. We compared dissolved and gaseous carbon dynamics in streams bordered by contrasting types of land use, specifically agriculture and forest. Carbon dioxide and methane partial pressures (pCO2 and pCH4, respectively) in the water body and carbon emissions via both gases were studied for 24h during four field expeditions. pCH4 did not differ between the two system types. pCO2 was constantly oversaturated in all streams and significantly higher in agricultural streams (annual mean 4282ppm) compared to forest streams (annual mean 2189ppm) during all seasons. However, emissions of CO2 were not significantly different between the stream types due to significantly higher gas transfer velocity in forest compared to agricultural streams. pCO2 was significantly positively correlated to the concentrations of dissolved organic carbon, dissolved nitrogen and soluble reactive phosphorus in the water. Furthermore, pCO2 was correlated to optical parameters of dissolved organic matter (DOM) quality, e.g., it increased with indicators of molecular size and an allochthonous fluorescent component identified by Parallel Factor Analysis (PARAFAC). This study demonstrates that different forms of land use may trigger a cascade of effects on the carbon production and emission of streams linked to changes in DOM quality. PMID:26938320

  9. Annual report of the Dynamic Meteorology Laboratory, 1986

    International Nuclear Information System (INIS)

    Research on climate simulation; data assimilation and forecasting; nonlinear dynamics and atmospheric turbulence; wave dynamics in the middle atmosphere; African and tropical meteorology and climatology; spectroscopy and modeling of atmospheric radiation; satellite meteorology and climatology; and active lidar remote sensing is presented

  10. Annual report of the Dynamic Meteorology Laboratory, 1985

    International Nuclear Information System (INIS)

    Research on climate simulation; data assimilation and forecasting; nonlinear dynamics and atmospheric turbulence; wave dynamics in the middle atmosphere; African and tropical meteorology and climatology; spectroscopy and modeling of atmospheric radiation; satellite meteorology and climatology; and active lidar remote sensing is presented

  11. Optics and Fluid Dynamics Department annual progress report for 1999

    DEFF Research Database (Denmark)

    Hanson, Steen Grüner; Johansen, Per Michael; Lynov, Jens-Peter;

    2000-01-01

    The Optics and Fluid Dynamics Department performs basic and applied research within the three programmes: (1) optical materials, (2) optical diagnostics and information processing and (3) plasma and fluid dynamics. The department has core competences in:optical sensors, optical materials, biooptics...

  12. Optics and Fluid Dynamics Department annual progress report for 2000

    International Nuclear Information System (INIS)

    The Optics and Fluid Dynamics Department performs basic and applied research within three scientific programmes: (1) optical materials, (2) optical diagnostics and information processing and (3) plasma and fluid dynamics. The department has core competence in: optical sensors, optical materials, optical storage, bio-optics, numerical modelling and information processing, non-linear dynamics and fusion plasma physics. The research is supported by several EU programmes, including EURATOM, by Danish research councils and by industry. A summary of the activities in 2000 is presented. (au)

  13. Optics and Fluid Dynamics Department. Annual progress report for 2003

    Energy Technology Data Exchange (ETDEWEB)

    Bindslev, H.; Hanson, S.G.; Lynov, J.P.; Petersen, P.M.; Skaarup, B. (eds.)

    2004-05-01

    The Optics and Fluid Dynamics Department performs basic and applied research within three scientific programmes: (1 laser systems and optical materials, (2 optical diagnostics and information processing and (3 plasma and fluid dynamics. The department has core competences in: optical sensors, optical materials, optical storage, biophotonics, numerical modelling and information processing, non-linear dynamics, fusion plasma physics and plasma technology. The research is supported by several EU programmes, including EURATOM, by Danish research councils and by industry. A summary of the activities in 2003 is presented. (au)

  14. Optics and Fluid Dynamics Department. Annual progress report for 2001

    International Nuclear Information System (INIS)

    The Optics and Fluid Dynamics Department performs basic and applied research within three scientific programmes: 1) laser systems and optical materials, 2) optical diagnostics and information processing and 3) plasma and fluid dynamics. The department has core competence in: optical sensors, optical materials, optical storage, bio-optics, numerical modelling and information processing, non-linear dynamics and fusion plasma physics. The research is supported by several EU programmes, including EURATOM, by Danish research councils and by industry. A summary of the activities in 2001 is presented. (au)

  15. Optics and Fluid Dynamics Department. Annual Progress Report for 2002

    International Nuclear Information System (INIS)

    The Optics and Fluid Dynamics Department performs basic and applied research within three scientific programmes: (1 Laser systems and optical materials (2 Optical diagnostics and information processing and (3 Plasma and fluid dynamics. The department has core competences in: optical sensors, optical materials, optical storage, biophotonics, numerical modelling and information processing, non-linear dynamics and fusion plasma physics. The research is supported by several EU programmes, including EURATOM, by Danish research councils and by industry. A summary of the activities in 2002 is presented. (au)

  16. Optics and Fluid Dynamics Department. Annual progress report for 2001

    Energy Technology Data Exchange (ETDEWEB)

    Bindslev, H.; Hanson, S.G.; Lynov, J.P.; Petersen, P.M.; Skaarup, B. (eds.)

    2002-03-01

    The Optics and Fluid Dynamics Department performs basic and applied research within three scientific programmes: 1) laser systems and optical materials, 2) optical diagnostics and information processing and 3) plasma and fluid dynamics. The department has core competence in: optical sensors, optical materials, optical storage, bio-optics, numerical modelling and information processing, non-linear dynamics and fusion plasma physics. The research is supported by several EU programmes, including EURATOM, by Danish research councils and by industry. A summary of the activities in 2001 is presented. (au)

  17. Optics and Fluid Dynamics Department. Annual Progress Report for 2002

    Energy Technology Data Exchange (ETDEWEB)

    Bindslev, H.; Hanson, S.G.; Lynov, J.P.; Petersen, P.M.; Skaarup, B

    2003-05-01

    The Optics and Fluid Dynamics Department performs basic and applied research within three scientific programmes: (1) Laser systems and optical materials (2) Optical diagnostics and information processing and (3) Plasma and fluid dynamics. The department has core competences in: optical sensors, optical materials, optical storage, biophotonics, numerical modelling and information processing, non-linear dynamics and fusion plasma physics. The research is supported by several EU programmes, including EURATOM, by Danish research councils and by industry. A summary of the activities in 2002 is presented. (au)

  18. Optics and Fluid Dynamics Department. Annual progress report for 2003

    International Nuclear Information System (INIS)

    The Optics and Fluid Dynamics Department performs basic and applied research within three scientific programmes: (1 laser systems and optical materials, (2 optical diagnostics and information processing and (3 plasma and fluid dynamics. The department has core competences in: optical sensors, optical materials, optical storage, biophotonics, numerical modelling and information processing, non-linear dynamics, fusion plasma physics and plasma technology. The research is supported by several EU programmes, including EURATOM, by Danish research councils and by industry. A summary of the activities in 2003 is presented. (au)

  19. Optics and Fluid Dynamics Department annual progress report for 2000

    Energy Technology Data Exchange (ETDEWEB)

    Hanson, S.G.; Johansen, P.M.; Lynov, J.P.; Skaarup, B. (eds.)

    2001-05-01

    The Optics and Fluid Dynamics Department performs basic and applied research within three scientific programmes: (1) optical materials, (2) optical diagnostics and information processing and (3) plasma and fluid dynamics. The department has core competence in: optical sensors, optical materials, optical storage, bio-optics, numerical modelling and information processing, non-linear dynamics and fusion plasma physics. The research is supported by several EU programmes, including EURATOM, by Danish research councils and by industry. A summary of the activities in 2000 is presented. (au)

  20. Comparative carbon cycle dynamics of the present and last interglacial

    Science.gov (United States)

    Brovkin, Victor; Brücher, Tim; Kleinen, Thomas; Zaehle, Sönke; Joos, Fortunat; Roth, Raphael; Spahni, Renato; Schmitt, Jochen; Fischer, Hubertus; Leuenberger, Markus; Stone, Emma J.; Ridgwell, Andy; Chappellaz, Jérôme; Kehrwald, Natalie; Barbante, Carlo; Blunier, Thomas; Dahl Jensen, Dorthe

    2016-04-01

    Changes in temperature and carbon dioxide during glacial cycles recorded in Antarctic ice cores are tightly coupled. However, this relationship does not hold for interglacials. While climate cooled towards the end of both the last (Eemian) and present (Holocene) interglacials, CO2 remained stable during the Eemian while rising in the Holocene. We identify and review twelve biogeochemical mechanisms of terrestrial (vegetation dynamics and CO2 fertilization, land use, wildfire, accumulation of peat, changes in permafrost carbon, subaerial volcanic outgassing) and marine origin (changes in sea surface temperature, carbonate compensation to deglaciation and terrestrial biosphere regrowth, shallow-water carbonate sedimentation, changes in the soft tissue pump, and methane hydrates), which potentially may have contributed to the CO2 dynamics during interglacials but which remain not well quantified. We use three Earth System Models (ESMs) of intermediate complexity to compare effects of selected mechanisms on the interglacial CO2 and δ13CO2 changes, focusing on those with substantial potential impacts: namely carbonate sedimentation in shallow waters, peat growth, and (in the case of the Holocene) human land use. A set of specified carbon cycle forcings could qualitatively explain atmospheric CO2 dynamics from 8 ka BP to the pre-industrial. However, when applied to Eemian boundary conditions from 126 to 115 ka BP, the same set of forcings led to disagreement with the observed direction of CO2 changes after 122 ka BP. This failure to simulate late-Eemian CO2 dynamics could be a result of the imposed forcings such as prescribed CaCO3 accumulation and/or an incorrect response of simulated terrestrial carbon to the surface cooling at the end of the interglacial. These experiments also reveal that key natural processes of interglacial CO2 dynamics - shallow water CaCO3 accumulation, peat and permafrost carbon dynamics - are not well represented in the current ESMs. Global

  1. Modeling the dynamics of continental shelf carbon.

    Science.gov (United States)

    Hofmann, Eileen E; Cahill, Bronwyn; Fennel, Katja; Friedrichs, Marjorie A M; Hyde, Kimberly; Lee, Cindy; Mannino, Antonio; Najjar, Raymond G; O'Reilly, John E; Wilkin, John; Xue, Jianhong

    2011-01-01

    Continental margin systems are important contributors to global nutrient and carbon budgets. Effort is needed to quantify this contribution and how it will be modified under changing patterns of climate and land use. Coupled models will be used to provide projections of future states of continental margin systems. Thus, it is appropriate to consider the limitations that impede the development of realistic models. Here, we provide an overview of the current state of modeling carbon cycling on continental margins as well as the processes and issues that provide the next challenges to such models. Our overview is done within the context of a coupled circulation-biogeochemical model developed for the northeastern North American continental shelf region. Particular choices of forcing and initial fields and process parameterizations are used to illustrate the consequences for simulated distributions, as revealed by comparisons to observations using quantitative statistical metrics. PMID:21329200

  2. Dynamic response of porous calcium carbonate minerals

    International Nuclear Information System (INIS)

    A theoretical study of the shock-loaded response of calcium carbonate materials is presented in which both dry and water-saturated samples with porosities up to 50 percent are considered. Data are presented for the unloading response from 15.0 and 18.5 GPa, and calculations from a mixture model using a Mie-Grueneisen equation of state with volume-dependent parameters are compared to both the Hugoniot and the isentropic unloading response

  3. Molecular Dynamics Simulations of Laser Powered Carbon Nanotube Gears

    Science.gov (United States)

    Srivastava, Deepak; Globus, Al; Han, Jie; Chancellor, Marisa K. (Technical Monitor)

    1997-01-01

    Dynamics of laser powered carbon nanotube gears is investigated by molecular dynamics simulations with Brenner's hydrocarbon potential. We find that when the frequency of the laser electric field is much less than the intrinsic frequency of the carbon nanotube, the tube exhibits an oscillatory pendulam behavior. However, a unidirectional rotation of the gear with oscillating frequency is observed under conditions of resonance between the laser field and intrinsic gear frequencies. The operating conditions for stable rotations of the nanotube gears, powered by laser electric fields are explored, in these simulations.

  4. Hydrological niche separation explains seasonal and inter-annual variations of vegetation dynamics in seasonally dry tropical forests

    Science.gov (United States)

    Xu, X.; Medvigy, D.; Powers, J. S.; Becknell, J. M.; Guan, K.

    2015-12-01

    Despite ample water supply, vegetation dynamics are subject to seasonal water stress in large fraction of tropical forests. These seasonally dry tropical forests (SDTFs) account for over 40% of tropical forests, harbor high biodiversity, have large potential carbon sink due to forest recovery from human disturbance and also play a critical role in global carbon budget and inter-annual variations. Plants in this biome display notably diverse responses to seasonal and inter-annual variations of water availability, especially inter-specific variations in canopy seasonality and biomass growth. Current process-based dynamic vegetation models cannot represent these diversities and are shown to perform poorly on simulating drought responses of tropical forests, calling into question of their ability to accurately simulate future changes in SDTFs. Accumulated field observations, suggest that hydrological niche separation driven by coordinated plant functional traits is associated with plants' performance under drought. Yet, it remains not clear whether the physiology-level hydrological niche separation can explain the ecosystem-level diversity observed in SDTFs. Here, we test the theory with a model-data fusion approach. We implemented a new plant hydrodynamic module that is able to track leaf water potential at sub-daily scale in ED2 model. We further incorporated a hydrological niche separation scheme based on a meta-data analysis of key functional traits in SDTFs. Simulated ecological patterns with and without hydrological niche separation were then compared with remote-sensing and long-term field observations from an SDTF site in Palo Verde, Costa Rica. Using several numerical experiments, we specifically examine the following questions: (i) Whether hydrological niche separation can explain the diversity in canopy seasonality and biomass growth? (ii) How important are the yet uncertain belowground functional traits, especially root profile in determining canopy

  5. Carbon dynamics of contrasting agricultural practices

    Science.gov (United States)

    Ghee, Claire; Hallett, Paul; Neilson, Roy; Robinson, David; Paterson, Eric

    2013-04-01

    Application of organic amendments can improve soil quality and provide crop nutrients. To optimise these agricultural benefits from organic applications, the capacity of microbe-driven nutrient and carbon cycling must be understood and exploited. Consideration is therefore required of the complex interactions between the rhizosphere, microbial biomass and organic amendment. We hypothesise that the labile C present in root exudates of plants increases the mineralisation of organic matter in soil, constituting a mechanism to promote nutrient acquisition. This mechanism is known as the 'priming effect', but is poorly understood in the context of agricultural carbon and nutrient management. Field data from the Centre of Sustainable Cropping (CSC) research platform (Dundee, Scotland, UK) are utilised to build an understanding of soil C and N fluxes between contrasting agricultural practices. The field site uses a split-plot design to compare (i) compost amended soils with reduced tillage and chemical inputs and (ii) conventionally managed soils, reflective of current UK commercial arable practice. Significant differences (p= conventionally managed soils at field-scale with respect to soil microbial biomass (SMB), total organic carbon (TOC) and mineral nitrogen. Investigation into the priming effect within compost amended soils was subsequently undertaken under laboratory conditions. Stable isotope analysis and measurements of soil biotic parameters were used to quantify priming resulting from Spring Barley (Hordeum vulgare cv. Optic) cultivation for (i) unamended and (ii) municipal compost incorporated soils. Compost treatments comprised amendments of 25, 50 and 150 t/Ha and planted soils were compared with unplanted controls. Soil mesocosms were maintained under controlled environmental conditions within labelling chambers supplied continuously with 13C-depleted CO2. Throughout a 41-day incubation period, soil CO2 efflux and dissolved organic carbon (DOC) was collected

  6. Optics and fluid dynamics department annual progress report for 1994

    International Nuclear Information System (INIS)

    Research in the Optics and Fluid Dynamics Department is performed within the following two programme areas: optics and continuum physics. In optics the activities are within (a) optical materials and electromagnetic propagation, (b) diagnostics and sensors, and (c) information processing. In continuum physics the activities are (a) nonlinear dynamics and (b) computer physics. The activities are supported by several EU programmes, including EURATOM, by research councils, and by industry. A special activity is the implementation of pellet injectors for fusion research. A summary of activities in 1994 is presented. (au) (27 ills., 44 refs.)

  7. Optics and fluid dynamics department annual progress report for 1994

    Energy Technology Data Exchange (ETDEWEB)

    Hanson, S.G.; Lading, L.; Lynov, J.P.; Michelsen, P.

    1995-01-01

    Research in the Optics and Fluid Dynamics Department is performed within the following two programme areas: optics and continuum physics. In optics the activities are within (a) optical materials and electromagnetic propagation, (b) diagnostics and sensors, and (c) information processing. In continuum physics the activities are (a) nonlinear dynamics and (b) computer physics. The activities are supported by several EU programmes, including EURATOM, by research councils, and by industry. A special activity is the implementation of pellet injectors for fusion research. A summary of activities in 1994 is presented. (au) (27 ills., 44 refs.).

  8. Optics and fluid dynamics department annual progress report for 1992

    International Nuclear Information System (INIS)

    Research in the Optics and FLuid Dynamics Department is performed within two sections. The Optics Section has activities within (a) optical materials, (b) quasielastic light scattering and diagnostics in solids, fluids and plasmas, and (c) optical and electronic information processing. The Continuum Physics Section performs (a) studies of nonlinear dynamical processes in continuum systems, (b) investigations of other problems in fusion plasma physics, and (c) develops pellet injectors for fusion experiments. Most of these activities are done in connection with the Euratom Association. A summary of activities in 1992 is presented. (au) (25 ills., 36 refs.)

  9. Does carbon availability control temporal dynamics of radial growth in Norway spruce (Picea abies)?

    Science.gov (United States)

    Oberhuber, Walter; Gruber, Andreas; Swidrak, Irene

    2015-04-01

    Intra-annual dynamics of cambial activity and wood formation of coniferous species exposed to soil dryness revealed early culmination of maximum growth in late spring prior to occurrence of more favourable environmental conditions, i.e., repeated high rainfall events during summer (Oberhuber et al. 2014). Because it is well known that plants can adjust carbon allocation patterns to optimize resource uptake under prevailing environmental constraints, we hypothesize that early decrease in radial stem growth is an adaptation to cope with drought stress, which might require an early switch of carbon allocation to belowground organs. Physical blockage of carbon transport in the phloem through girdling causes accumulation and depletion of carbohydrates above and below the girdle, respectively, making this method quite appropriate to investigate carbon relationships in trees. Hence, in a common garden experiment we will manipulate the carbon status of Norway spruce (Picea abies) saplings by phloem blockage at different phenological stages during the growing season. We will present the methodological approach and first results of the study aiming to test the hypothesis that carbon status of the tree affects temporal dynamics of cambial activity and wood formation in conifers under drought. Acknowledgment The research is funded by the Austrian Science Fund (FWF): P25643-B16 "Carbon allocation and growth of Scots pine". Reference Oberhuber W, A Gruber, W Kofler, I Swidrak (2014) Radial stem growth in response to microclimate and soil moisture in a drought-prone mixed coniferous forest at an inner Alpine site. Eur J For Res 133:467-479.

  10. Non-native plant litter enhances soil carbon dioxide emissions in an invaded annual grassland.

    Science.gov (United States)

    Zhang, Ling; Wang, Hong; Zou, Jianwen; Rogers, William E; Siemann, Evan

    2014-01-01

    Litter decomposition is a fundamental ecosystem process in which breakdown and decay of plant detritus releases carbon and nutrients. Invasive exotic plants may produce litter that differs from native plant litter in quality and quantity. Such differences may impact litter decomposition and soil respiration in ways that depend on whether exotic and native plant litters decompose in mixtures. However, few field experiments have examined how exotic plants affect soil respiration via litter decomposition. Here, we conducted an in situ study of litter decomposition of an annual native grass (Eragrostis pilosa), a perennial exotic forb (Alternanthera philoxeroides), and their mixtures in an annual grassland in China to examine potential invasion effects on soil respiration. Alternanthera litter decomposed faster than Eragrostis litter when each was incubated separately. Mass loss in litter mixes was more rapid than predicted from rates in single species bags (only 35% of predicted mass remained at 8 months) showing synergistic effects. Notably, exotic plant litter decomposition rate was unchanged but native plant litter decomposition rate was accelerated in mixtures (decay constant k = 0.20 month(-1)) compared to in isolation (k = 0.10 month(-1)). On average, every litter type increased soil respiration compared to bare soil from which litter was removed. However, the increases were larger for mixed litter (1.82 times) than for Alternanthera litter (1.58 times) or Eragrostis litter (1.30 times). Carbon released as CO2 relative to litter carbon input was also higher for mixed litter (3.34) than for Alternathera litter (2.29) or Eragrostis litter (1.19). Our results indicated that exotic Alternanthera produces rapidly decomposing litter which also accelerates the decomposition of native plant litter in litter mixtures and enhances soil respiration rates. Thus, this exotic invasive plant species will likely accelerate carbon cycling and increase soil respiration

  11. Optics and Fluid Dynamics Department annual progress report for 2003

    DEFF Research Database (Denmark)

    Bindslev, H.; Hanson, Steen Grüner; Lynov, Jens-Peter;

    2004-01-01

    , optical materials, optical storage, biophotonics, numerical modelling and information processing, non-linear dynamics, fusion plasma physics and plasma technology. The research is supported by several EUprogrammes, including EURATOM, by Danish research councils and by industry. A summary of the activities...

  12. Autonomous Sensing of Particulate Inorganic Carbon Dynamics

    Science.gov (United States)

    Weiss, G. A.; Bishop, J. K.; Strubhar, W. D.; Wood, T.

    2011-12-01

    Particulate inorganic carbon (PIC) is produced by coccolithophore phytoplankton and shelled foraminifera and pterpod microzooplankton. These calcite and aragonite particles contribute to excess density of aggregate particles enabling carbon export from surface waters; they are sensitive to the effects of ocean acidification. Concentrations in surface waters range from below 100 nM in oligotrophic waters to 40 uM in the North Atlantic. Very limited ship observations in the Oyashio and subarctic NE Pacific show short term PIC variability of more than one order of magitude over 10 days and 3 months, respectively. At depth concentrations can drop to near zero in waters deeper than the carbonate saturation horizon. Seasonal variations of a factor of two or more at 1000 m depth have been observed. Near surface variability is impossible to follow from ships. We are working on the development of a robust PIC sensor capable of deployment on platforms ranging from CTD's to floats and thus address the gap in observations. The sensor, which uses cross polarized optics, detects the photons that have interacted with birefringent minerals (of which calcite dominates) in the water column. The detection of this very weak signal - which can be 10-6 of the primary beam energy is a daunting task. Here we report results from incomparison deployments of a 'next gen' and prototype sensor during recent expeditions to California coastal and offshore waters (NE Pacific Gyre, Santa Barbara Basin (June 2009); Santa Catalina Basin (October 2010), Santa Cruz Basin (May 2011), California Current and Coastal Waters (July 2011; September 2011). In addition we report calibrations the sensors based on particulate samples filtered from 1L samples and analyzed by HR-ICP-MS.

  13. Dry-season length and runoff control annual variability in stream DOC dynamics in a small, shallow groundwater-dominated agricultural watershed

    Science.gov (United States)

    Humbert, G.; Jaffrezic, A.; Fovet, O.; Gruau, G.; Durand, P.

    2015-10-01

    As a phenomenon integrating climate conditions and hydrological control of the connection between streams and terrestrial dissolved organic carbon (DOC) sources, groundwater dynamics control patterns of stream DOC characteristics (concentrations and fluxes). Influence of intra-annual variations in groundwater level, discharge and climatic factors on DOC concentrations and fluxes were assessed over 13 years at the headwater watershed of Kervidy-Naizin (5 km2) in western France. Four seasonal periods were delineated within each year according to groundwater fluctuations (A: rewetting, B: high flow, C: recession, and D: drought). Annual and seasonal base flow versus stormflow DOC concentrations were defined based on daily hydrograph readings. High interannual variability of annual DOC fluxes (5.4-39.5 kg ha-1 yr-1) indicates that several years of data are required to encompass variations in water flux to evaluate the actual DOC export capacity of a watershed. Interannual variability of mean annual DOC concentrations was much lower (4.9-7.5 mg C L-1), with concentrations decreasing within each year from ca. 9.2 mg C L-1 in A to ca. 3.0 mg C L-1 in C. This indicates an intra-annual pattern of stream DOC concentrations controlled by DOC source characteristics and groundwater dynamics very similar across years. Partial least squares regressions combined with multiple linear regressions showed that the dry season characteristics (length and drawdown) determine the mean annual DOC concentration while annual runoff determines the annual flux. Antagonistic mechanisms of production-accumulation and dilution-depletion combined with an unlimited DOC supply from riparian wetland soils can mitigate the response of stream concentrations to global changes and climatic variations.

  14. Optics and Fluid Dynamics Department annual progress report for 1996

    International Nuclear Information System (INIS)

    Research in the Optics and Fluid Dynamics Department has been performed within the following three programme areas: (1) optical materials, (2) optical diagnostics and information processing and (3) plasma and fluid dynamics. The work is concentrated on combinations of systems, structures and materials. The systems work is focused on sensors, information processing an storage; the structures work is concentrated on pattern formation and diffractive elements; the materials work is centred on the understanding and utilisation of nonlinear phenomena. Scientific computing is an integral part of the work. The activities are supported by several EU programmes, including EURATOM, by research councils and by industry. A summary of the activities in 1996 is presented. (au) 53 ills., 232 refs

  15. Optics and Fluid Dynamics Department annual progress report for 1997

    Energy Technology Data Exchange (ETDEWEB)

    Hanson, S.G.; Johansen, P.M.; Lading, L.; Lynov, J.P.; Skaarup, B. [eds.

    1998-04-01

    Research in the Optics and Fluid Dynamics Department has been performed within the following three programme areas: (1) optical materials, (2) optical diagnostics and information processing and (3) plasma and fluid dynamics. The work is concentrated on combinations of systems, structures and materials. The systems work is focused on sensors, information processing and storage; the structures work is concentrated on pattern formation and diffractive elements; the materials work is centred on the understanding and utilisation of nonlinear phenomena for optical components and systems. Scientific computing is an integral part of the work. Biomedical optics is a new activity and the work on polymer optics is enhanced considerably. The activities are supported by several EU programmes, including EURATOM, by research councils and by industry. A summary of the activities in 1997 is presented. (au) 1 tab., 63 ills., 249 refs.

  16. Optics and Fluid Dynamics Department annual progress report for 1993

    International Nuclear Information System (INIS)

    Research in the Optics and Fluid Dynamics Department is performed within the following two programme areas: optics and continuum physics. In optics the activities are within (a) optical materials, (b) quasi-elastic light scattering and diagnostics in solids, fluids, and plasmas, and (c) optical and electronic information processing. Within continuum physics the activities are within (a) studies of non-linear dynamical processes in continuum systems, (b) investigations of problems with relevance to fusion plasma physics. The injection of pellets in fusion experiments has been investigated and pellet injectors to European fusion experiments are manufactured. The department is also responsible for the EURATOM collaboration within fusion plasma physics. A summary of activities in 1993 is presented. (au) (27 ills., 24 refs.)

  17. Optics and Fluid Dynamics Department annual progress report for 1997

    International Nuclear Information System (INIS)

    Research in the Optics and Fluid Dynamics Department has been performed within the following three programme areas: (1) optical materials, (2) optical diagnostics and information processing and (3) plasma and fluid dynamics. The work is concentrated on combinations of systems, structures and materials. The systems work is focused on sensors, information processing and storage; the structures work is concentrated on pattern formation and diffractive elements; the materials work is centred on the understanding and utilisation of nonlinear phenomena for optical components and systems. Scientific computing is an integral part of the work. Biomedical optics is a new activity and the work on polymer optics is enhanced considerably. The activities are supported by several EU programmes, including EURATOM, by research councils and by industry. A summary of the activities in 1997 is presented. (au)

  18. Optics and Fluid Dynamics Department annual progress report for 1996

    Energy Technology Data Exchange (ETDEWEB)

    Hanson, S.G.; Johansen, P.M.; Lading, L.; Lynov, J.P.; Skaarup, B. [eds.

    1997-01-01

    Research in the Optics and Fluid Dynamics Department has been performed within the following three programme areas: (1) optical materials, (2) optical diagnostics and information processing and (3) plasma and fluid dynamics. The work is concentrated on combinations of systems, structures and materials. The systems work is focused on sensors, information processing an storage; the structures work is concentrated on pattern formation and diffractive elements; the materials work is centred on the understanding and utilisation of nonlinear phenomena. Scientific computing is an integral part of the work. The activities are supported by several EU programmes, including EURATOM, by research councils and by industry. A summary of the activities in 1996 is presented. (au) 53 ills., 232 refs.

  19. Carbon dynamics and changing winter conditions: a review of current understanding and future research directions

    Science.gov (United States)

    Haei, M.; Laudon, H.

    2015-09-01

    Despite the important role of winters for northern ecosystems, it remains the least understood of all the seasons. Here, we summarize existing empirical studies on winter climate and carbon dynamics and highlight some important future research directions. The existing studies include field-scale snow-cover manipulation experiments representing extreme soil climate conditions, laboratory soil incubations studying the influential factors, and time-series of climate and carbon data showing long-term natural variations and existing trends. Most of the field and laboratory experiments indicate an increased soil organic carbon loss due to soil frost. Long-term data demonstrate temporal changes in winter CO2 efflux and its important contribution to the annual fluxes. A number of research priorities to improve our understanding of winter conditions include (i) ecosystem processes in the fall-winter and winter-spring shoulder seasons, (ii) extreme events, (iii) partitioning into organic- and inorganic carbon, (iv) carry-over effects of winter and growing season on each other, (v) long-term cumulative impacts, and (vi) improved winter process modelling. These areas of research would enable an improved understanding of the role of the snow covered period for carbon cycling, and provide a basis for more realistic models that include winter processes.

  20. Dynamics of carbon in deep soils inferred from carbon stable isotopes signatures : a worldwide meta-analysis

    Science.gov (United States)

    Balesdent, Jérôme; Basile-Doelsch, Isabelle; Chadoeuf, Joël; Cornu, Sophie; Derrien, Delphine; Fekiacova, Zuzana; Hatté, Christine

    2014-05-01

    to the 30-100 cm layer was estimated to 0.3 times (with 1 S.D. = 0.2 times) that to the topsoil 0-30 cm, whereas the corresponding ratio for total carbon stocks is close to 1. A multivariate analysis confirmed that the turnover rate in the topsoil is dependent on land use and mean annual temperature, and related to a lesser extent to aridity index and clay content. The relative proportion of carbon input to the subsoil is higher in croplands than in forests or grasslands, in probable accordance with the exportation of plant aerial parts as crops. We derive from this study quantitative constraints on depth-dependent mechanisms that drive carbon dynamics, such as decreasing decay rates down the depth and the magnitude of priming effects, the rate and intensity of carbon transport downwards, or the occurrence of stable C throughout the profiles. We also propose simplified expressions for the parameterization of models of carbon exchanges between deep soil organic carbon and the atmosphere.

  1. Accounting for forest carbon pool dynamics in product carbon footprints: Challenges and opportunities

    International Nuclear Information System (INIS)

    Modification and loss of forests due to natural and anthropogenic disturbance contribute an estimated 20% of annual greenhouse gas (GHG) emissions worldwide. Although forest carbon pool modeling rarely suggests a ‘carbon neutral’ flux profile, the life cycle assessment community and associated product carbon footprint protocols have struggled to account for the GHG emissions associated with forestry, specifically, and land use generally. Principally, this is due to underdeveloped linkages between life cycle inventory (LCI) modeling for wood and forest carbon modeling for a full range of forest types and harvest practices, as well as a lack of transparency in globalized forest supply chains. In this paper, through a comparative study of U.S. and Chinese coated freesheet paper, we develop the initial foundations for a methodology that rescales IPCC methods from the national to the product level, with reference to the approaches in three international product carbon footprint protocols. Due to differences in geographic origin of the wood fiber, the results for two scenarios are highly divergent. This suggests that both wood LCI models and the protocols need further development to capture the range of spatial and temporal dimensions for supply chains (and the associated land use change and modification) for specific product systems. The paper concludes by outlining opportunities to measure and reduce uncertainty in accounting for net emissions of biogenic carbon from forestland, where timber is harvested for consumer products. - Highlights: ► Typical life cycle assessment practice for consumer products often excludes significant land use change emissions when estimating carbon footprints. ► The article provides a methodology to rescale IPCC guidelines for product-level carbon footprints. ► Life cycle inventories and product carbon footprint protocols need more comprehensive land use-related accounting. ► Interdisciplinary collaboration linking the LCA and

  2. Annual litterfall dynamics and nutrient deposition depending on elevation and land use at Mt. Kilimanjaro

    Directory of Open Access Journals (Sweden)

    J. Becker

    2015-07-01

    Full Text Available Litterfall is one of the major pathways connecting above- and belowground processes. The effects of climate and land-use change on carbon (C and nutrient inputs by litterfall are poorly known. We quantified and analyzed annual patterns of C and nutrient deposition via litterfall in natural forests and agroforestry systems along the unique elevation gradient of Mt. Kilimanjaro. Tree litter in three natural (lower montane, Ocotea and Podocarpus forests, two sustainably used (homegardens and one intensively managed (shaded coffee plantation was collected on a biweekly basis from May 2012 to July 2013. Leaves, branches and remaining residues were separated and analyzed for C and nutrient contents. The annual pattern of litterfall was closely related to rainfall seasonality, exhibiting a large peak towards the end of the dry season (August–October. This peak decreased at higher elevations with decreasing rainfall seasonality. Macronutrients (N, P, K in leaf litter increased at mid elevation (2100 m a.s.l. and with land-use intensity. Carbon content and micronutrients (Al, Fe, Mn, Na however, were unaffected or decreased with land-use intensity. On the southern slope of Mt. Kilimanjaro, the annual pattern of litterfall depends on seasonal climatic conditions. While leaf litterfall decreased with elevation, total annual input was independent of climate. Compared to natural forests, the nutrient cycles in agroforestry ecosystems were accelerated by fertilization and the associated changes in dominant tree species.

  3. Annual litterfall dynamics and nutrient deposition depending on elevation and land use at Mt. Kilimanjaro

    OpenAIRE

    Becker, J.; Pabst, H.; Mnyonga, J.; Kuzyakov, Y

    2015-01-01

    Litterfall is one of the major pathways connecting above- and belowground processes. The effects of climate and land-use change on carbon (C) and nutrient inputs by litterfall are poorly known. We quantified and analyzed annual patterns of C and nutrient deposition via litterfall in natural forests and agroforestry systems along the unique elevation gradient of Mt. Kilimanjaro. Tree litter in three natural (lower montane, Ocotea and Podocarpus forests)...

  4. Annual litterfall dynamics and nutrient deposition depending on elevation and land use at Mt. Kilimanjaro

    OpenAIRE

    Becker, J.; Pabst, H.; Mnyonga, J.; Kuzyakov, Y

    2015-01-01

    Litterfall is one of the major pathways connecting above- and below-ground processes. The effects of climate and land-use change on carbon (C) and nutrient inputs by litterfall are poorly known. We quantified and analyzed annual patterns of C and nutrient deposition via litterfall in natural forests and agroforestry systems along the unique elevation gradient of Mt. Kilimanjaro. Tree litter in three natural (lower montane, Ocotea and Podocarpus forests), two sustainab...

  5. Molecular Dynamics Simulations of Carbon Nanotubes in Water

    Science.gov (United States)

    Walther, J. H.; Jaffe, R.; Halicioglu, T.; Koumoutsakos, P.

    2000-01-01

    We study the hydrophobic/hydrophilic behavior of carbon nanotubes using molecular dynamics simulations. The energetics of the carbon-water interface are mainly dispersive but in the present study augmented with a carbon quadrupole term acting on the charge sites of the water. The simulations indicate that this contribution is negligible in terms of modifying the structural properties of water at the interface. Simulations of two carbon nanotubes in water display a wetting and drying of the interface between the nanotubes depending on their initial spacing. Thus, initial tube spacings of 7 and 8 A resulted in a drying of the interface whereas spacing of > 9 A remain wet during the course of the simulation. Finally, we present a novel particle-particle-particle-mesh algorithm for long range potentials which allows for general (curvilinear) meshes and "black-box" fast solvers by adopting an influence matrix technique.

  6. Growing up with stress - carbon sequestration and allocation dynamics of a broadleaf evergreen forest

    Science.gov (United States)

    Griebel, Anne; Bennett, Lauren T.; Arndt, Stefan K.

    2016-04-01

    Evergreen forests have the potential to sequester carbon year-round due to the presence of leaves with a multi-year lifespan. Eucalypt forests occur in warmer climates where temperature and radiation are not imposing a strong seasonality. Thus, unlike deciduous or many coniferous trees, many eucalypts grow opportunistically as conditions allow. As such, many eucalypts do not produce distinct growth rings, which present challenges to the implementation of standard methods and data interpretation approaches for monitoring and explaining carbon allocation dynamics in response to climatic stress. As a consequence, there is a lack of detailed understanding of seasonal growth dynamics of evergreen forests as a whole, and, in particular, of the influence of climatic drivers on carbon allocation to the various biomass pools. We used a multi-instrument approach in a mixed species eucalypt forest to investigate the influence of climatic drivers on the seasonal growth dynamics of a predominantly temperate and moisture-regulated environment in south-eastern Australia. Ecosystem scale observations of net ecosystem exchange (NEE) from a flux tower in the Wombat forest near Melbourne indicated that the ecosystem is a year-round carbon sink, but that intra-annual variations in temperature and moisture along with prolonged heat waves and dry spells resulted in a wide range of annual sums over the past three years (NEE ranging from ~4 to 12 t C ha-1 yr-1). Dendrometers were used to monitor stem increments of the three dominant eucalypt species. Stem expansion was generally opportunistic with the greatest increments under warm but moist conditions (often in spring and autumn), and the strongest indicators of stem growth dynamics being radiation, vapour pressure deficit and a combined heat-moisture index. Differences in the seasonality of stem increments between species were largely due to differences in the canopy position of sampled individuals. The greatest stem increments were

  7. Modelling carbon dynamics from urban land conversion: fundamental model of city in relation to a local carbon cycle

    Directory of Open Access Journals (Sweden)

    Schellnhuber Hans-Joachim

    2006-08-01

    Full Text Available Abstract Background The main task is to estimate the qualitative and quantitative contribution of urban territories and precisely of the process of urbanization to the Global Carbon Cycle (GCC. Note that, on the contrary to many investigations that have considered direct anthropogenic emission of CO2(urbanized territories produce ca. 96–98% of it, we are interested in more subtle, and up until the present time, weaker processes associated with the conversion of the surrounding natural ecosystems and landscapes into urban lands. Such conversion inevitably takes place when cities are sprawling and additional "natural" lands are becoming "urbanized". Results In order to fulfil this task, we first develop a fundamental model of urban space, since the type of land cover within a city makes a difference for a local carbon cycle. Hence, a city is sub-divided by built-up, „green" (parks, etc. and informal settlements (favelas fractions. Another aspect is a sub-division of the additional two regions, which makes the total number reaching eight regions, while the UN divides the world by six. Next, the basic model of the local carbon cycle for urbanized territories is built. We consider two processes: carbon emissions as a result of conversion of natural lands caused by urbanization; and the transformation of carbon flows by "urbanized" ecosystems; when carbon, accumulated by urban vegetation, is exported to the neighbouring territories. The total carbon flow in the model depends, in general, on two groups of parameters. The first includes the NPP, and the sum of living biomass and dead organic matter of ecosystems involved in the process of urbanization, and namely them we calculate here, using a new more realistic approach and taking into account the difference in regional cities' evolution. Conclusion There is also another group of parameters, dealing with the areas of urban territories, and their annual increments. A method of dynamic forecasting

  8. Innovation with carbon materials---A report on the annual world conference on carbon, Carbon 2015%炭材料的革新--记Carbon 2015国际炭会议

    Institute of Scientific and Technical Information of China (English)

    张强

    2015-01-01

    The annual world conference on carbon, Carbon 2015, was held in Dresden, Germany, and was hosted by the German Carbon Group and German Ceramic Society, during July 12~17, 2015. About 582 attendees from 40 countries participated in the conference, and 540 papers were accepted for discussion, including 4 plenary lectures, 256 oral presentations, and 280 posters in-volved in 12 topics, namely, activated carbon, biomass derived carbon, carbon black, carbon fiber and composites, granular/nucle-ar carbon, natural graphite, nanoforms, industrial, conversion process, physical &chemical properties, environmental &medical, and energy storage. Carbon fiber, graphite, carbon black, and carbon alloy were the subjects of the plenary lectures. The innovation of the traditional carbon materials and new nanocarbon, the critical role of carbon in energy, environment, and healthcare applica-tion, as well as the new insights on the relationship of structure and properties at the molecular scale were strongly considered in this event. Carbon materials required continuous innovation to meet the rising requirement of sustainable society.

  9. Dynamic topography and the Cenozoic carbonate compensation depth

    Science.gov (United States)

    Campbell, S. M.; Moucha, R.; Raymo, M. E.; Derry, L. A.

    2015-12-01

    The carbonate compensation depth (CCD), the ocean depth at which the calcium carbonate accumulation rate goes to zero, can provide valuable insight into climatic and weathering conditions over the Cenozoic. The paleoposition of the CCD can be inferred from sediment core data. As the carbonate accumulation rate decreases linearly with depth between the lysocline and CCD, the CCD can be calculated using a linear regression on multiple sediment cores with known carbonate accumulation rates and paleodepths. It is therefore vital to have well-constrained estimates of paleodepths. Paleodepths are typically calculated using models of thermal subsidence and sediment loading and compaction. However, viscous convection-related stresses in the mantle can warp the ocean floor by hundreds of meters over broad regions and can also vary significantly over millions of years. This contribution to paleobathymetry, termed dynamic topography, can be calculated by modeling mantle flow backwards in time. Herein, we demonstrate the effect dynamic topography has on the inference of the late Cenozoic CCD with an example from the equatorial Pacific, considering sites from IODP Expeditions 320/321. The equatorial Pacific, given its large size and high productivity, is closely tied to the global carbon cycle. Accordingly, long-term changes in the equatorial Pacific CCD can be considered to reflect global changes in weathering fluxes and the carbon cycle, in addition to more regional changes in productivity and thermohaline circulation. We find that, when the dynamic topography contribution to bathymetry is accounted for, the equatorial Pacific CCD is calculated to be appreciably shallower at 30 Ma than previous estimates would suggest, implying a greater deepening of the Pacific CCD over the late Cenozoic.

  10. Molecular dynamics analysis on impact behavior of carbon nanotubes

    International Nuclear Information System (INIS)

    Graphical abstract: - Highlights: • We present an analytical solution of impact based on two degree of freedom model. • The accuracy is verified by Molecular dynamics simulations. • The effects of the small-size effects on the dynamic deflections are investigated. • The relative motion is also accounted that is due to local indentation. - Abstract: Dynamic analysis of impact of a nanoparticle on carbon nanotubes is investigated based on two degree of freedom model. The accuracy and stability of the present methods are verified by molecular dynamics (MD) simulations. The effect of different types of boundary condition on the maximum dynamic deflections is studied for zigzag and armchair SWCNTs with various aspect ratios (length/diameter). Besides, the influences of velocity of impactor on the dynamic deflections are studied. It is shown that the dynamic behavior on the armchair and zigzag single-walled carbon nanotubes are almost similar. Finally, by making use of the above MD simulation and theoretical results some insight has been obtained about the dynamic characteristics of the impact problems of nanobeam structures. Nonlocal Timoshenko beam models TBT2 should be employed for an accurate prediction of the dynamic deflection rather than nonlocal Euler–Bernoulli beam models EBT2 which ignores the effects of transverse shear deformation and rotary inertia that is especially significant for short beams. The results from nonlocal EBT2 and TBT2 models demonstrated good agreement with MD simulation. The EBT2 and TBT2 models also account for the relative motion between the nanoparticle and the nanobeam that is due to local indentation as can be seen in MD simulation

  11. Molecular dynamics analysis on impact behavior of carbon nanotubes

    Energy Technology Data Exchange (ETDEWEB)

    Seifoori, Sajjad, E-mail: sajjad.seifoori@vru.ac.ir

    2015-01-30

    Graphical abstract: - Highlights: • We present an analytical solution of impact based on two degree of freedom model. • The accuracy is verified by Molecular dynamics simulations. • The effects of the small-size effects on the dynamic deflections are investigated. • The relative motion is also accounted that is due to local indentation. - Abstract: Dynamic analysis of impact of a nanoparticle on carbon nanotubes is investigated based on two degree of freedom model. The accuracy and stability of the present methods are verified by molecular dynamics (MD) simulations. The effect of different types of boundary condition on the maximum dynamic deflections is studied for zigzag and armchair SWCNTs with various aspect ratios (length/diameter). Besides, the influences of velocity of impactor on the dynamic deflections are studied. It is shown that the dynamic behavior on the armchair and zigzag single-walled carbon nanotubes are almost similar. Finally, by making use of the above MD simulation and theoretical results some insight has been obtained about the dynamic characteristics of the impact problems of nanobeam structures. Nonlocal Timoshenko beam models TBT2 should be employed for an accurate prediction of the dynamic deflection rather than nonlocal Euler–Bernoulli beam models EBT2 which ignores the effects of transverse shear deformation and rotary inertia that is especially significant for short beams. The results from nonlocal EBT2 and TBT2 models demonstrated good agreement with MD simulation. The EBT2 and TBT2 models also account for the relative motion between the nanoparticle and the nanobeam that is due to local indentation as can be seen in MD simulation.

  12. Carbon dioxide and methane emission dynamics in central London (UK)

    Science.gov (United States)

    Helfter, Carole; Nemitz, Eiko; Barlow, Janet F.; Wood, Curtis R.

    2013-04-01

    London, with a population of 8.2 million, is the largest city in Europe. It is heavily built-up (typically 8% vegetation cover within the central boroughs) and boasts some of the busiest arteries in Europe despite efforts to reduce traffic in the city centre with the introduction of a congestion charging scheme in 2007. We report on two substantial pollution monitoring efforts in the heart of London between October 2006 and present. Fluxes of carbon dioxide (CO2) and water (H2O) were measured continuously by eddy-covariance in central London from October 2006 until May 2008 from a 190 m telecommunication tower (BT tower; 51° 31' 17.4'' N 0° 8' 20.04'' W). The eddy-covariance system consisted of a Gill R3-50 ultrasonic anemometer operated at 20 Hz and a LI-COR 6262 infrared gas analyser. Air was sampled 0.3 m below the sensor head of the ultrasonic anemometer - which was itself mounted on a 3 m mast to the top of a 15 m lattice tower situated on the roof of the tower (instrument head at 190 m above street level) - and pulled down 45 m of 12.7 mm OD Teflon tubing. In addition, meteorological variables (temperature, relative humidity, pressure, precipitation, wind speed and direction) were also measured with a multi-sensor (Weather Transmitter WXT510, Vaisala). Eddy-covariance measurements at the BT tower location were reinstated in July 2011 and include methane (CH4), CO2 and H2O concentrations measured by a Picarro fast methane analyser (G2301-f). CO2 emissions were found to be mainly controlled by fossil fuel combustion (e.g. traffic, commercial and domestic heating). Diurnal averages of CO2 fluxes were found to be highly correlated to traffic. However changes in heating-related natural gas consumption and, to a lesser extent, photosynthetic activity in two large city centre green spaces (Hyde Park and Regent's Park) explained the seasonal variability. Annual estimates of net exchange of CO2 obtained by eddy-covariance agreed well with up-scaled data from the UK

  13. Control factors and scale analysis of annual river water, sediments and carbon transport in China

    Science.gov (United States)

    Song, Chunlin; Wang, Genxu; Sun, Xiangyang; Chang, Ruiying; Mao, Tianxu

    2016-05-01

    Under the context of dramatic human disturbances on river system, the processes that control the transport of water, sediment, and carbon from river basins to coastal seas are not completely understood. Here we performed a quantitative synthesis for 121 sites across China to find control factors of annual river exports (Rc: runoff coefficient; TSSC: total suspended sediment concentration; TSSL: total suspended sediment loads; TOCL: total organic carbon loads) at different spatial scales. The results indicated that human activities such as dam construction and vegetation restoration might have a greater influence than climate on the transport of river sediment and carbon, although climate was a major driver of Rc. Multiple spatial scale analyses indicated that Rc increased from the small to medium scale by 20% and then decreased at the sizable scale by 20%. TSSC decreased from the small to sizeable scale but increase from the sizeable to large scales; however, TSSL significantly decreased from small (768 g·m‑2·a‑1) to medium spatial scale basins (258 g·m‑2·a‑1), and TOCL decreased from the medium to large scale. Our results will improve the understanding of water, sediment and carbon transport processes and contribute better water and land resources management strategies from different spatial scales.

  14. Dynamics of carbon, biomass, and structure in two Amazonian forests

    Science.gov (United States)

    Pyle, Elizabeth Hammond; Santoni, Gregory W.; Nascimento, Henrique E. M.; Hutyra, Lucy R.; Vieira, Simone; Curran, Daniel J.; van Haren, Joost; Saleska, Scott R.; Chow, V. Y.; Carmago, Plinio B.; Laurance, William F.; Wofsy, Steven C.

    2008-11-01

    Amazon forests are potentially globally significant sources or sinks for atmospheric carbon dioxide. In this study, we characterize the spatial trends in carbon storage and fluxes in both live and dead biomass (necromass) in two Amazonian forests, the Biological Dynamic of Forest Fragments Project (BDFFP), near Manaus, Amazonas, and the Tapajós National Forest (TNF) near Santarém, Pará. We assessed coarse woody debris (CWD) stocks, tree growth, mortality, and recruitment in ground-based plots distributed across the terra firme forest at both sites. Carbon dynamics were similar within each site, but differed significantly between the sites. The BDFFP and the TNF held comparable live biomass (167 +/- 7.6 MgC.ha-1 versus 149 +/- 6.0 MgC.ha-1, respectively), but stocks of CWD were 2.5 times larger at TNF (16.2 +/- 1.5 MgC.ha-1 at BDFFP, versus 40.1 +/- 3.9 MgC.ha-1 at TNF). A model of current forest dynamics suggests that the BDFFP was close to carbon balance, and its size class structure approximated a steady state. The TNF, by contrast, showed rapid carbon accrual to live biomass (3.24 +/- 0.22 MgC.ha-1.a-1 in TNF, 2.59 +/- 0.16 MgC.ha-1.a-1 in BDFFP), which was more than offset by losses from large stocks of CWD, as well as ongoing shifts of biomass among size classes. This pattern in the TNF suggests recovery from a significant disturbance. The net loss of carbon from the TNF will likely last 10-15 years after the initial disturbance (controlled by the rate of decay of coarse woody debris), followed by uptake of carbon as the forest size class structure and composition continue to shift. The frequency and longevity of forests showing such disequilibruim dynamics within the larger matrix of the Amazon remains an essential question to understanding Amazonian carbon balance.

  15. Carbon dynamics in topsoil and subsoil along a cultivated toposequence

    DEFF Research Database (Denmark)

    Chirinda, Ngoni; Elsgaard, Lars; Thomsen, Ingrid Kaag; Heckrath, Goswin Johann; Olesen, Jørgen E

    2014-01-01

    Topography-induced spatial heterogeneity influences soil organic carbon (SOC) stocks and microbial degradation (respiration) both in topsoil and subsoil compartments. However, the interaction between topographic position and soil horizons has rarely been assessed. This study aimed to investigate...... SOC dynamics in topsoil (5 cm) and subsoil horizons (40 and 80 cm) at shoulderslope and footslope positions in a toposequence in a Danish winter wheat field. In addition, SOC was quantified for 20-cm depth intervals to 100 cm depths. Over a 1 year period, gas samples for carbon dioxide (CO2) and...

  16. Dynamic Behavior of Sand: Annual Report FY 11

    Energy Technology Data Exchange (ETDEWEB)

    Antoun, T; Herbold, E; Johnson, S

    2012-03-15

    Currently, design of earth-penetrating munitions relies heavily on empirical relationships to estimate behavior, making it difficult to design novel munitions or address novel target situations without expensive and time-consuming full-scale testing with relevant system and target characteristics. Enhancing design through numerical studies and modeling could help reduce the extent and duration of full-scale testing if the models have enough fidelity to capture all of the relevant parameters. This can be separated into three distinct problems: that of the penetrator structural and component response, that of the target response, and that of the coupling between the two. This project focuses on enhancing understanding of the target response, specifically granular geomaterials, where the temporal and spatial multi-scale nature of the material controls its response. As part of the overarching goal of developing computational capabilities to predict the performance of conventional earth-penetrating weapons, this project focuses specifically on developing new models and numerical capabilities for modeling sand response in ALE3D. There is general recognition that granular materials behave in a manner that defies conventional continuum approaches which rely on response locality and which degrade in the presence of strong response nonlinearities, localization, and phase gradients. There are many numerical tools available to address parts of the problem. However, to enhance modeling capability, this project is pursuing a bottom-up approach of building constitutive models from higher fidelity, smaller spatial scale simulations (rather than from macro-scale observations of physical behavior as is traditionally employed) that are being augmented to address the unique challenges of mesoscale modeling of dynamically loaded granular materials. Through understanding response and sensitivity at the grain-scale, it is expected that better reduced order representations of response can

  17. Comparison of soil microbial respiration and carbon turnover under perennial and annual biofuel crops in two agricultural soils

    Science.gov (United States)

    Szymanski, L. M.; Marin-Spiotta, E.; Sanford, G. R.; Jackson, R. D.; Heckman, K. A.

    2015-12-01

    Bioenergy crops have the potential to provide a low carbon-intensive alternative to fossil fuels. More than a century of agricultural research has shown that conventional cropping systems can reduce soil organic matter (SOM) reservoirs, which cause long-term soil nutrient loss and C release to the atmosphere. In the face of climate change and other human disruptions to biogeochemical cycles, identifying biofuel crops that can maintain or enhance soil resources is desirable for the sustainable production of bioenergy. The objective of our study was to compare the effects of four biofuel crop treatments on SOM dynamics in two agricultural soils: Mollisols at Arlington Agricultural Research Station in Wisconsin and Alfisols at Kellogg Biological Station in Michigan, USA. We used fresh soils collected in 2013 and archived soils from 2008 to measure the effects of five years of crop management. Using a one-year long laboratory soil incubation coupled with a regression model and radiocarbon measurements, we separated soils into three SOM pools and their corresponding C turnover times. We found that the active pool, or biologically available C, was more sensitive to management and is an earlier indicator of changes to soil C dynamics than bulk soil C measurements. There was no effect of treatment on the active pool size at either site; however, the percent C in the active pool decreased, regardless of crop type, in surface soils with high clay content. At depth, the response of the slow pool differed between annual and perennial cropping systems. The distribution of C among SOM fractions varied between the two soil types, with greater C content associated with the active fraction in the coarser textured-soil and greater C content associated with the slow-cycling fraction in the soils with high clay content. These results suggest that the effects of bioenergy crops on soil resources will vary geographically, with implications for the carbon-cost of biocrop production.

  18. Soil respiration and organic carbon dynamics with grassland conversions to woodlands in temperate china.

    Science.gov (United States)

    Wang, Wei; Zeng, Wenjing; Chen, Weile; Zeng, Hui; Fang, Jingyun

    2013-01-01

    Soils are the largest terrestrial carbon store and soil respiration is the second-largest flux in ecosystem carbon cycling. Across China's temperate region, climatic changes and human activities have frequently caused the transformation of grasslands to woodlands. However, the effect of this transition on soil respiration and soil organic carbon (SOC) dynamics remains uncertain in this area. In this study, we measured in situ soil respiration and SOC storage over a two-year period (Jan. 2007-Dec. 2008) from five characteristic vegetation types in a forest-steppe ecotone of temperate China, including grassland (GR), shrubland (SH), as well as in evergreen coniferous (EC), deciduous coniferous (DC) and deciduous broadleaved forest (DB), to evaluate the changes of soil respiration and SOC storage with grassland conversions to diverse types of woodlands. Annual soil respiration increased by 3%, 6%, 14%, and 22% after the conversion from GR to EC, SH, DC, and DB, respectively. The variation in soil respiration among different vegetation types could be well explained by SOC and soil total nitrogen content. Despite higher soil respiration in woodlands, SOC storage and residence time increased in the upper 20 cm of soil. Our results suggest that the differences in soil environmental conditions, especially soil substrate availability, influenced the level of annual soil respiration produced by different vegetation types. Moreover, shifts from grassland to woody plant dominance resulted in increased SOC storage. Given the widespread increase in woody plant abundance caused by climate change and large-scale afforestation programs, the soils are expected to accumulate and store increased amounts of organic carbon in temperate areas of China. PMID:24058408

  19. Soil respiration and organic carbon dynamics with grassland conversions to woodlands in temperate china.

    Directory of Open Access Journals (Sweden)

    Wei Wang

    Full Text Available Soils are the largest terrestrial carbon store and soil respiration is the second-largest flux in ecosystem carbon cycling. Across China's temperate region, climatic changes and human activities have frequently caused the transformation of grasslands to woodlands. However, the effect of this transition on soil respiration and soil organic carbon (SOC dynamics remains uncertain in this area. In this study, we measured in situ soil respiration and SOC storage over a two-year period (Jan. 2007-Dec. 2008 from five characteristic vegetation types in a forest-steppe ecotone of temperate China, including grassland (GR, shrubland (SH, as well as in evergreen coniferous (EC, deciduous coniferous (DC and deciduous broadleaved forest (DB, to evaluate the changes of soil respiration and SOC storage with grassland conversions to diverse types of woodlands. Annual soil respiration increased by 3%, 6%, 14%, and 22% after the conversion from GR to EC, SH, DC, and DB, respectively. The variation in soil respiration among different vegetation types could be well explained by SOC and soil total nitrogen content. Despite higher soil respiration in woodlands, SOC storage and residence time increased in the upper 20 cm of soil. Our results suggest that the differences in soil environmental conditions, especially soil substrate availability, influenced the level of annual soil respiration produced by different vegetation types. Moreover, shifts from grassland to woody plant dominance resulted in increased SOC storage. Given the widespread increase in woody plant abundance caused by climate change and large-scale afforestation programs, the soils are expected to accumulate and store increased amounts of organic carbon in temperate areas of China.

  20. Northern peatland carbon stocks and dynamics: a review

    Directory of Open Access Journals (Sweden)

    Z. C. Yu

    2012-10-01

    Full Text Available Peatlands contain a large belowground carbon (C stock in the biosphere, and their dynamics have important implications for the global carbon cycle. However, there are still large uncertainties in C stock estimates and poor understanding of C dynamics across timescales. Here I review different approaches and associated uncertainties of C stock estimates in the literature, and on the basis of the literature review my best estimate of C stocks and uncertainty is 500 ± 100 (approximate range gigatons of C (Gt C in northern peatlands. The greatest source of uncertainty for all the approaches is the lack or insufficient representation of data, including depth, bulk density and carbon accumulation data, especially from the world's large peatlands. Several ways to improve estimates of peat carbon stocks are also discussed in this paper, including the estimates of C stocks by regions and further utilizations of widely available basal peat ages.

    Changes in peatland carbon stocks over time, estimated using Sphagnum (peat moss spore data and down-core peat accumulation records, show different patterns during the Holocene, and I argue that spore-based approach underestimates the abundance of peatlands in their early histories. Considering long-term peat decomposition using peat accumulation data allows estimates of net carbon sequestration rates by peatlands, or net (ecosystem carbon balance (NECB, which indicates more than half of peat carbon (> 270 Gt C was sequestrated before 7000 yr ago during the Holocene. Contemporary carbon flux studies at 5 peatland sites show much larger NECB during the last decade (32 ± 7.8 (S.E. g C m−2 yr–1 than during the last 7000 yr (∼ 11 g C m−2 yr–1, as modeled from peat records across northern peatlands. This discrepancy highlights the urgent need for carbon accumulation data and process understanding, especially at decadal and centennial timescales

  1. Austrian Carbon Calculator (ACC) - modelling soil carbon dynamics in Austrian soils

    Science.gov (United States)

    Sedy, Katrin; Freudenschuss, Alexandra; Zethner, Gehard; Spiegel, Heide; Franko, Uwe; Gründling, Ralf; Xaver Hölzl, Franz; Preinstorfer, Claudia; Haslmayr, Hans Peter; Formayer, Herbert

    2014-05-01

    Austrian Carbon Calculator (ACC) - modelling soil carbon dynamics in Austrian soils. The project funded by the Klima- und Energiefonds, Austrian Climate Research Programme, 4th call Authors: Katrin Sedy, Alexandra Freudenschuss, Gerhard Zethner (Environment Agency Austria), Heide Spiegel (Austrian Agency for Health and Food Safety), Uwe Franko, Ralf Gründling (Helmholtz Centre for Environmental Research) Climate change will affect plant productivity due to weather extremes. However, adverse effects could be diminished and satisfying production levels may be maintained with proper soil conditions. To sustain and optimize the potential of agricultural land for plant productivity it will be necessary to focus on preserving and increasing soil organic carbon (SOC). Carbon sequestration in agricultural soils is strongly influenced by management practice. The present management is affected by management practices that tend to speed up carbon loss. Crop rotation, soil cultivation and the management of crop residues are very important measures to influence carbon dynamics and soil fertility. For the future it will be crucial to focus on practical measures to optimize SOC and to improve soil structure. To predict SOC turnover the existing humus balance model the application of the "Carbon Candy Balance" was verified by results from Austrian long term field experiments and field data of selected farms. Thus the main aim of the project is to generate a carbon balancing tool box that can be applied in different agricultural production regions to assess humus dynamics due to agricultural management practices. The toolbox will allow the selection of specific regional input parameters for calculating the C-balance at field level. However farmers or other interested user can also apply their own field data to receive the result of C-dynamics under certain management practises within the next 100 years. At regional level the impact of predefined changes in agricultural management

  2. Fluid dynamic lateral slicing of high tensile strength carbon nanotubes

    Science.gov (United States)

    Vimalanathan, Kasturi; Gascooke, Jason R.; Suarez-Martinez, Irene; Marks, Nigel A.; Kumari, Harshita; Garvey, Christopher J.; Atwood, Jerry L.; Lawrance, Warren D.; Raston, Colin L.

    2016-03-01

    Lateral slicing of micron length carbon nanotubes (CNTs) is effective on laser irradiation of the materials suspended within dynamic liquid thin films in a microfluidic vortex fluidic device (VFD). The method produces sliced CNTs with minimal defects in the absence of any chemical stabilizers, having broad length distributions centred at ca 190, 160 nm and 171 nm for single, double and multi walled CNTs respectively, as established using atomic force microscopy and supported by small angle neutron scattering solution data. Molecular dynamics simulations on a bent single walled carbon nanotube (SWCNT) with a radius of curvature of order 10 nm results in tearing across the tube upon heating, highlighting the role of shear forces which bend the tube forming strained bonds which are ruptured by the laser irradiation. CNT slicing occurs with the VFD operating in both the confined mode for a finite volume of liquid and continuous flow for scalability purposes.

  3. Dislocation dynamics in multiwalled carbon nanotubes at high temperatures.

    Science.gov (United States)

    Huang, J Y; Ding, F; Yakobson, B I

    2008-01-25

    Dislocation dynamics dictate the mechanical behavior of materials. Dislocations in periodic crystalline materials have been well documented. On the contrary, dislocations in cylindrical carbon nanotubes, particularly in multiwalled carbon nanotubes (MWCNTs), remain almost unexplored. Here we report that a room temperature 1/2 sessile dislocation in a MWCNT becomes highly mobile, as characterized by its glide, climb, and the glide-climb interactions, at temperatures of about 2000 degrees C. The dislocation glide leads to the cross-linking of different shells; dislocation climb creates nanocracks; and the interaction of two 1/2 dislocations creates kinks. We found that dislocation loops act as channels for mass transport. These dislocation dynamics are drastically different from that in conventional periodic crystalline materials due to the cylindrical, highly anisotropic structures of MWCNTs. PMID:18232998

  4. Soil organic matter dynamics and the global carbon cycle

    International Nuclear Information System (INIS)

    The large size and potentially long residence time of the soil organic matter pool make it an important component of the global carbon cycle. Net terrestrial primary production of about 60 Pg C·yr-1 is, over a several-year period of time, balanced by an equivalent flux of litter production and subsequent decomposition of detritus and soil organic matter. We will review many of the major factors that influence soil organic matter dynamics that need to be explicitly considered in development of global estimates of carbon turnover in the world's soils. We will also discuss current decomposition models that are general enough to be used to develop a representation of global soil organic matter dynamics

  5. Fluid dynamic lateral slicing of high tensile strength carbon nanotubes.

    Science.gov (United States)

    Vimalanathan, Kasturi; Gascooke, Jason R; Suarez-Martinez, Irene; Marks, Nigel A; Kumari, Harshita; Garvey, Christopher J; Atwood, Jerry L; Lawrance, Warren D; Raston, Colin L

    2016-01-01

    Lateral slicing of micron length carbon nanotubes (CNTs) is effective on laser irradiation of the materials suspended within dynamic liquid thin films in a microfluidic vortex fluidic device (VFD). The method produces sliced CNTs with minimal defects in the absence of any chemical stabilizers, having broad length distributions centred at ca 190, 160 nm and 171 nm for single, double and multi walled CNTs respectively, as established using atomic force microscopy and supported by small angle neutron scattering solution data. Molecular dynamics simulations on a bent single walled carbon nanotube (SWCNT) with a radius of curvature of order 10 nm results in tearing across the tube upon heating, highlighting the role of shear forces which bend the tube forming strained bonds which are ruptured by the laser irradiation. CNT slicing occurs with the VFD operating in both the confined mode for a finite volume of liquid and continuous flow for scalability purposes. PMID:26965728

  6. Molecular dynamics simulations of a lithium/sodium carbonate mixture.

    Science.gov (United States)

    Ottochian, Alistar; Ricca, Chiara; Labat, Frederic; Adamo, Carlo

    2016-03-01

    The diffusion and ionic conductivity of Li x Na1-x CO3 salt mixtures were studied by means of Molecular Dynamics (MD) simulations, using the Janssen and Tissen model (Janssen and Tissen, Mol Simul 5:83-98; 1990). These salts have received particular attention due to their central role in fuel cells technology, and reliable numerical methods that could perform as important interpretative tool of experimental data are thus required but still lacking. The chosen computational model nicely reproduces the main structural behaviour of the pure Li2CO3, Na2CO3 and K2CO3 carbonates, but also of their Li/K and Li/Na mixtures. However, it fails to accurately describe dynamic properties such as activation energies of diffusion and conduction processes, outlining the need to develop more accurate models for the simulation of molten salt carbonates. PMID:26897519

  7. Molecular Dynamics Modeling of Carbon Nanotubes and Their Composites

    Science.gov (United States)

    Jensen, Lars R.; Pyrz, Ryszard

    2004-06-01

    The tensile modulus of individual nanotubes and nanotube-polypropylene composites has been determined using molecular dynamics simulations. Simulations of individual single-walled carbon nanotubes showed that their tensile modulus was dependent on the tube structure and the diameter if the diameter was below 1,6 nm. The tensile modulus was determined for an infinite single-walled carbon nanotube embedded in an amorphous polypropylene matrix and for a finite and capped single-walled carbon nanotube embedded in a polypropylene matrix. For the infinite nanotube-polypropylene system the modulus was found to correspond to the one given by the Voigt approximation. For the finite nanotube-polypropylene system the reinforcing effect of the nanotube was not very pronounced. A pull out simulation showed that the length of the nanotube in the simulation was much smaller than the critical length and hence no load transfer between the nanotube and the matrix existed.

  8. Exciton decay dynamics in individual carbon nanotubes at room temperature

    OpenAIRE

    Gokus, Tobias; Hartschuh, Achim; Harutyunyan, Hayk; Allegrini, Maria; Hennrich, Frank; Kappes, Manfred; Green, Alexander A.; Hersam, Mark C.; Araujo, Paulo T.; Jorio, Ado

    2008-01-01

    We studied the exciton decay dynamics of individual semiconducting single-walled carbon nanotubes at room temperature using time-resolved photoluminescence spectroscopy. The photoluminescence decay from nanotubes of the same (n,m) type follows a single exponential decay function, however, with lifetimes varying between about 1 and 40 ps from nanotube to nanotube. A correlation between broad photoluminescence spectra and short lifetimes was found and explained by defects promoting both nonradi...

  9. Annual litterfall dynamics and nutrient deposition depending on elevation and land use at Mt. Kilimanjaro

    Science.gov (United States)

    Becker, J.; Pabst, H.; Mnyonga, J.; Kuzyakov, Y.

    2015-10-01

    Litterfall is one of the major pathways connecting above- and below-ground processes. The effects of climate and land-use change on carbon (C) and nutrient inputs by litterfall are poorly known. We quantified and analyzed annual patterns of C and nutrient deposition via litterfall in natural forests and agroforestry systems along the unique elevation gradient of Mt. Kilimanjaro. Tree litter in three natural (lower montane, Ocotea and Podocarpus forests), two sustainably used (homegardens) and one intensively managed (shaded coffee plantation) ecosystems was collected on a biweekly basis from May 2012 to July 2013. Leaves, branches and remaining residues were separated and analyzed for C and nutrient contents. The annual pattern of litterfall was closely related to rainfall seasonality, exhibiting a large peak towards the end of the dry season (August-October). This peak decreased at higher elevations with decreasing rainfall seasonality. Macronutrients (N, P, K) in leaf litter increased at mid elevation (2100 m a.s.l.) and with land-use intensity. Carbon content and micronutrients (Al, Fe, Mn, Na) however, were unaffected or decreased with land-use intensity. While leaf litterfall decreased with elevation, total annual input was independent of climate. Compared to natural forests, the nutrient cycles in agroforestry ecosystems were accelerated by fertilization and the associated changes in dominant tree species.

  10. Simulated impacts of insect defoliation on forest carbon dynamics

    International Nuclear Information System (INIS)

    Many temperate and boreal forests are subject to insect epidemics. In the eastern US, over 41 million meters squared of tree basal area are thought to be at risk of gypsy moth defoliation. However, the decadal-to-century scale implications of defoliation events for ecosystem carbon dynamics are not well understood. In this study, the effects of defoliation intensity, periodicity and spatial pattern on the carbon cycle are investigated in a set of idealized model simulations. A mechanistic terrestrial biosphere model, ecosystem demography model 2, is driven with observations from a xeric oak–pine forest located in the New Jersey Pine Barrens. Simulations indicate that net ecosystem productivity (equal to photosynthesis minus respiration) decreases linearly with increasing defoliation intensity. However, because of interactions between defoliation and drought effects, aboveground biomass exhibits a nonlinear decrease with increasing defoliation intensity. The ecosystem responds strongly with both reduced productivity and biomass loss when defoliation periodicity varies from 5 to 15 yr, but exhibits a relatively weak response when defoliation periodicity varies from 15 to 60 yr. Simulations of spatially heterogeneous defoliation resulted in markedly smaller carbon stocks than simulations with spatially homogeneous defoliation. These results show that gypsy moth defoliation has a large effect on oak–pine forest biomass dynamics, functioning and its capacity to act as a carbon sink. (letter)

  11. The importance of a surface organic layer in simulating permafrost thermal and carbon dynamics

    Science.gov (United States)

    Jafarov, Elchin; Schaefer, Kevin

    2016-03-01

    Permafrost-affected soils contain twice as much carbon as currently exists in the atmosphere. Studies show that warming of the perennially frozen ground could initiate significant release of the frozen soil carbon into the atmosphere. Initializing the frozen permafrost carbon with the observed soil carbon distribution from the Northern Circumpolar Soil Carbon Database reduces the uncertainty associated with the modeling of the permafrost carbon feedback. To improve permafrost thermal and carbon dynamics we implemented a dynamic surface organic layer with vertical carbon redistribution, and introduced dynamic root growth controlled by active layer thickness, which improved soil carbon exchange between frozen and thawed pools. These changes increased the initial amount of simulated frozen carbon from 313 to 560 Gt C, consistent with observed frozen carbon stocks, and increased the spatial correlation of the simulated and observed distribution of frozen carbon from 0.12 to 0.63.

  12. Exploring the options for carbon dioxide mitigation in Turkish electric power industry: System dynamics approach

    International Nuclear Information System (INIS)

    Electric power industry has a huge carbon mitigation potential, fundamentally because there are large carbon-free, renewable resource options. In Turkey, with growing demand in electricity consumption and incentives offered for natural gas fired electricity generation, CO2 emissions sourced from electric power industry had tripled over the last two decades. Current governmental strategy focuses on energy security and resource diversity in a growing economy and does not articulate sufficient mitigation targets and appropriate regulations. In this research, an original dynamic simulation model is built, validated and analyzed to explore the options for carbon mitigation in Turkish electric power industry. Model structure represents the investment, dispatch and pricing heuristics as well as the natural resource base of electricity generation in Turkey. It operates on annual basis over 30 years to simulate installed capacities and generations of power plants with alternative resources and their resulting CO2 emissions. The analysis presented in this paper reveals that there are mitigation options below 50% of business as usual growth, with common policy options such as feed-in-tariffs, investment subsidies and carbon taxes. The model can serve as an experimental platform for further analysis of problems related to carbon mitigation in Turkish electricity sector. - Highlights: • An original computer model is created to investigate carbon mitigation. • It is holistic and comprises investment, generation, dispatch, and resources. • The model's structure, information base and foresights are specific to Turkey. • Direct and indirect strategies are explored and integrated. • Dramatic reductions are possible only with supply side strategies

  13. The role of stream water carbon dynamics and export in the carbon balance of a tropical seasonal rainforest, southwest China.

    Directory of Open Access Journals (Sweden)

    Wen-Jun Zhou

    Full Text Available A two-year study (2009 ~ 2010 was carried out to investigate the dynamics of different carbon (C forms, and the role of stream export in the C balance of a 23.4-ha headwater catchment in a tropical seasonal rainforest at Xishuangbanna (XSBN, southwest China. The seasonal volumetric weighted mean (VWM concentrations of total inorganic C (TIC and dissolved inorganic C (DIC were higher, and particulate inorganic C (PIC and organic C (POC were lower, in the dry season than the rainy season, while the VWM concentrations of total organic C (TOC and dissolved organic C (DOC were similar between seasons. With increased monthly stream discharge and stream water temperature (SWT, only TIC and DIC concentrations decreased significantly. The most important C form in stream export was DIC, accounting for 51.8% of the total C (TC export; DOC, POC, and PIC accounted for 21.8%, 14.9%, and 11.5% of the TC export, respectively. Dynamics of C flux were closely related to stream discharge, with the greatest export during the rainy season. C export in the headwater stream was 47.1 kg C ha(-1 yr(-1, about 2.85% of the annual net ecosystem exchange. This finding indicates that stream export represented a minor contribution to the C balance in this tropical seasonal rainforest.

  14. Importance of vegetation dynamics for future terrestrial carbon cycling

    International Nuclear Information System (INIS)

    Terrestrial ecosystems currently sequester about one third of anthropogenic CO2 emissions each year, an important ecosystem service that dampens climate change. The future fate of this net uptake of CO2 by land based ecosystems is highly uncertain. Most ecosystem models used to predict the future terrestrial carbon cycle share a common architecture, whereby carbon that enters the system as net primary production (NPP) is distributed to plant compartments, transferred to litter and soil through vegetation turnover and then re-emitted to the atmosphere in conjunction with soil decomposition. However, while all models represent the processes of NPP and soil decomposition, they vary greatly in their representations of vegetation turnover and the associated processes governing mortality, disturbance and biome shifts. Here we used a detailed second generation dynamic global vegetation model with advanced representation of vegetation growth and mortality, and the associated turnover. We apply an emulator that describes the carbon flows and pools exactly as in simulations with the full model. The emulator simulates ecosystem dynamics in response to 13 different climate or Earth system model simulations from the Coupled Model Intercomparison Project Phase 5 ensemble under RCP8.5 radiative forcing. By exchanging carbon cycle processes between these 13 simulations we quantified the relative roles of three main driving processes of the carbon cycle; (I) NPP, (II) vegetation dynamics and turnover and (III) soil decomposition, in terms of their contribution to future carbon (C) uptake uncertainties among the ensemble of climate change scenarios. We found that NPP, vegetation turnover (including structural shifts, wild fires and mortality) and soil decomposition rates explained 49%, 17% and 33%, respectively, of uncertainties in modelled global C-uptake. Uncertainty due to vegetation turnover was further partitioned into stand-clearing disturbances (16%), wild fires (0%), stand

  15. Importance of vegetation dynamics for future terrestrial carbon cycling

    Science.gov (United States)

    Ahlström, Anders; Xia, Jianyang; Arneth, Almut; Luo, Yiqi; Smith, Benjamin

    2015-05-01

    Terrestrial ecosystems currently sequester about one third of anthropogenic CO2 emissions each year, an important ecosystem service that dampens climate change. The future fate of this net uptake of CO2 by land based ecosystems is highly uncertain. Most ecosystem models used to predict the future terrestrial carbon cycle share a common architecture, whereby carbon that enters the system as net primary production (NPP) is distributed to plant compartments, transferred to litter and soil through vegetation turnover and then re-emitted to the atmosphere in conjunction with soil decomposition. However, while all models represent the processes of NPP and soil decomposition, they vary greatly in their representations of vegetation turnover and the associated processes governing mortality, disturbance and biome shifts. Here we used a detailed second generation dynamic global vegetation model with advanced representation of vegetation growth and mortality, and the associated turnover. We apply an emulator that describes the carbon flows and pools exactly as in simulations with the full model. The emulator simulates ecosystem dynamics in response to 13 different climate or Earth system model simulations from the Coupled Model Intercomparison Project Phase 5 ensemble under RCP8.5 radiative forcing. By exchanging carbon cycle processes between these 13 simulations we quantified the relative roles of three main driving processes of the carbon cycle; (I) NPP, (II) vegetation dynamics and turnover and (III) soil decomposition, in terms of their contribution to future carbon (C) uptake uncertainties among the ensemble of climate change scenarios. We found that NPP, vegetation turnover (including structural shifts, wild fires and mortality) and soil decomposition rates explained 49%, 17% and 33%, respectively, of uncertainties in modelled global C-uptake. Uncertainty due to vegetation turnover was further partitioned into stand-clearing disturbances (16%), wild fires (0%), stand

  16. Multi-annual fluxes of carbon dioxide from an intensively cultivated temperate peatland

    Science.gov (United States)

    Cumming, Alex; Balzter, Heiko; Evans, Chris; Kaduk, Joerg; Morrison, Ross; Page, Susan

    2016-04-01

    East Anglia contains the largest continuous area of lowland fen peatlands in the United Kingdom (UK) which store vast quantities of terrestrial carbon (C) that have accrued over millennia. These long term C stores have largely been drained and converted for agricultural land use over the last 400 years due to their high agricultural production potential. Initial drainage of these peatlands leads to surface lowering and peat wastage. Prolonged exposure of carbon dense peat soils to oxygen through continued agricultural management results in sustained losses of carbon dioxide (CO₂) to the atmosphere. An increasing population in the UK has the potential to put further stress on these productive but rapidly diminishing Grade 1 agricultural land. Improving our understanding of land management impacts on CO₂ emissions from these soils is crucial to improving their longevity as an important store of C and as an economic resource. Our measurements at an intensively cultivated lowland peatland in Norfolk, UK, are the first multi-annual record using the micrometeorological eddy covariance (EC) technique to measure CO₂ fluxes associated with the production of horticultural salad crops. Three full years of flux measurements over leek (2013), lettuce (2014) and celery (2015) cropping systems found that the site was a net annual source of CO₂ with a net ecosystem exchange (NEE) of 6.59, 7.84 and 7.71 t C-CO₂ ha-1 a-1 respectively. The leek crop, with its longer growing period, had a lower annual NEE due to its long growth period from early spring through to late autumn, whereas the shorter growing periods of lettuce and celery meant their peak growth (CO₂ uptake, Gross Primary Productivity, GPP) took place during early/mid-summer with post-harvest weeds exploiting the later growing season but exhibited lower CO₂ assimilation than the leek crop. Periods of high CO₂ emissions from the soil to the atmosphere were measured during mechanical disruptions to the soils

  17. The dynamic response of carbon fiber-filled polymer composites

    Directory of Open Access Journals (Sweden)

    Patterson B.

    2012-08-01

    Full Text Available The dynamic (shock responses of two carbon fiber-filled polymer composites have been quantified using gas gun-driven plate impact experimentation. The first composite is a filament-wound, highly unidirectional carbon fiber-filled epoxy with a high degree of porosity. The second composite is a chopped carbon fiber- and graphite-filled phenolic resin with little-to-no porosity. Hugoniot data are presented for the carbon fiber-epoxy (CE composite to 18.6 GPa in the through-thickness direction, in which the shock propagates normal to the fibers. The data are best represented by a linear Rankine-Hugoniot fit: Us = 2.87 + 1.17 ×up(ρ0 = 1.536g/cm3. The shock wave structures were found to be highly heterogeneous, both due to the anisotropic nature of the fiber-epoxy microstructure, and the high degree of void volume. Plate impact experiments were also performed on a carbon fiber-filled phenolic (CP composite to much higher shock input pressures, exceeding the reactants-to-products transition common to polymers. The CP was found to be stiffer than the filament-wound CE in the unreacted Hugoniot regime, and transformed to products near the shock-driven reaction threshold on the principal Hugoniot previously shown for the phenolic binder itself. [19] On-going research is focused on interrogating the direction-dependent dyanamic response and dynamic failure strength (spall for the CE composite in the TT and 0∘ (fiber directions.

  18. Current-induced dynamics in carbon atomic contacts

    Directory of Open Access Journals (Sweden)

    Jing-Tao Lü

    2011-12-01

    Full Text Available Background: The effect of electric current on the motion of atoms still poses many questions, and several mechanisms are at play. Recently there has been focus on the importance of the current-induced nonconservative forces (NC and Berry-phase derived forces (BP with respect to the stability of molecular-scale contacts. Systems based on molecules bridging electrically gated graphene electrodes may offer an interesting test-bed for these effects.Results: We employ a semi-classical Langevin approach in combination with DFT calculations to study the current-induced vibrational dynamics of an atomic carbon chain connecting electrically gated graphene electrodes. This illustrates how the device stability can be predicted solely from the modes obtained from the Langevin equation, including the current-induced forces. We point out that the gate offers control of the current, independent of the bias voltage, which can be used to explore current-induced vibrational instabilities due the NC/BP forces. Furthermore, using tight-binding and the Brenner potential we illustrate how Langevin-type molecular-dynamics calculations including the Joule heating effect for the carbon-chain systems can be performed. Molecular dynamics including current-induced forces enables an energy redistribution mechanism among the modes, mediated by anharmonic interactions, which is found to be vital in the description of the electrical heating.Conclusion: We have developed a semiclassical Langevin equation approach that can be used to explore current-induced dynamics and instabilities. We find instabilities at experimentally relevant bias and gate voltages for the carbon-chain system.

  19. Inter-annual variability of the carbon dioxide oceanic sink south of Tasmania

    Directory of Open Access Journals (Sweden)

    A. V. Borges

    2008-02-01

    Full Text Available We compiled a large data-set from 22 cruises spanning from 1991 to 2003, of the partial pressure of CO2 (pCO2 in surface waters over the continental shelf (CS and adjacent open ocean (43° to 46° S; 145° to 150° E, south of Tasmania. Climatological seasonal cycles of pCO2 in the CS, the subtropical zone (STZ and the subAntarctic zone (SAZ are described and used to determine monthly pCO2 anomalies. These are used in combination with monthly anomalies of sea surface temperature (SST to investigate inter-annual variations of SST and pCO2. Monthly anomalies of SST (as intense as 2°C are apparent in the CS, STZ and SAZ, and are indicative of strong inter-annual variability that seems to be related to large-scale coupled atmosphere-ocean oscillations. Anomalies of pCO2 normalized to a constant temperature are negatively related to SST anomalies. A reduced winter-time vertical input of dissolved inorganic carbon (DIC during phases of positive SST anomalies, related to a poleward shift of westerly winds, and a concomitant local decrease in wind stress is the likely cause of the negative relationship between pCO2 and SST anomalies. The observed pattern is an increase of the sink for atmospheric CO2 associated with positive SST anomalies, although strongly modulated by inter-annual variability of wind speed. Assuming that phases of positive SST anomalies are indicative of the future evolution of regional ocean biogeochemistry under global warming, we show using a purely observational based approach that some provinces of the Southern Ocean could provide a potential negative feedback on increasing atmospheric CO2.

  20. Climate impacts on China's terrestrial carbon cycle : an assessment with the dynamic land ecosystem model

    International Nuclear Information System (INIS)

    Studies have suggested that China's rate of climate change is significantly more accelerated than rates observed in other countries. This study used climate data analysis and a dynamic land ecosystem model (DLEM) to investigate temporal and spatial climate change patterns in China in relation to net primary production (NPP) and net carbon exchange (NCE) in terrestrial ecosystems. The study also examined the influence of monsoon and El Nino events on NPP and NCE. Data from 740 weather stations were interpolated with resolution maps. China was divided into 5 climate zones to address climate change patterns in different regions. Other input data included a digital elevation map; land use histories; pH values; soil depths; and atmospheric concentrations of carbon dioxide (CO2). The DLEM was used to simulate the effects of changing climate patterns by coupling carbon (C), nitrogen (N) and water to estimate fluxes. The model was also able to estimate emissions of multiple trace gases. Two scenarios were used: (1) climate change only; and a climate change scenario with changes in ozone, CO2 and land uses. Results showed that air temperature increased by 0.2 degrees C per decade in China from 1961 to 2000, while precipitation increased 5.88 mm per decade. Global average precipitation increased by 0.05 to 1.0 per cent, while average temperatures increased by 0.1 degrees C. Annual NCE and NPP in China showed substantial spatial variations. Most areas of China were CO2 sources. The highest NPP was located in northeastern China. Results also showed that annual NCE increased greatly with increasing monsoon intensity. However, changes in NPP were not significant. 26 refs., 1 tab., 8 figs

  1. Spatiotemporal dynamics of forest fragmentation and its potential implications for carbon dynamics in the Brazilian Amazon between 2001 and 2010

    Science.gov (United States)

    Numata, I.; Cochrane, M.

    2012-12-01

    Vast tracts of Amazonian tropical rain forest have been converted to human land uses in recent decades as regional development proceeds. Large losses of forest cover are exacerbated because remaining forests are fragmented into smaller habitats. The current basin-wide status and implications of forest fragmentation on remnant forests and regional carbon dynamics are not well known. We performed a regional forest fragmentation analysis for the entire Brazilian Amazon between 2001 and 2010 using INPE PRODES data. During the past decade, the number of forest fragments doubled, nearly 125,000 fragments were formed, with more than 50% being smaller than 10 ha. Forest edges increased by 36,335 km/year on average over the study period. However, the rate was much greater from 2001-2005 (50,046 km/year) than 2006-2010 (25,365 km/year) when deforestation rates dropped drastically. In 2010, 55% of basin-wide forest edges were Amazon. Edge-released carbon accounted for 2.6-4.5% of deforestation-related carbon emissions. However, the relative importance of carbon emissions from forest fragmentation varied according to annual deforestation rates and increased from 1.7-3.0% to 3.3-5.6% of the respective deforestation emissions in 2001-2005 and 2006-2010, respectively. As of 2010, 17% of Amazonian forests are within 1km of forest edges, making them easily accessible and vulnerable to degradation. On the other hand, 51% of remaining forests across the basin are within protected areas and only 1.5% has been deforested within 1 km of a forest edge, while, unprotected forests, 1km-edge forests averaged 34% deforestation. The state of Rondônia, where 95% of unprotected forests are within 1km of edges in 2010, emits the largest amount of carbon unit area of forest edge (4.7Mg/km2), while overall edge-related carbon across the Amazon is 2.7 Mg/km2. Our results indicate that the Brazilian Amazon now largely consists of two contrasting forest conditions: protected areas with vast

  2. Classical molecular dynamics investigations of biphenyl-based carbon nanomembranes

    Directory of Open Access Journals (Sweden)

    Andreas Mrugalla

    2014-06-01

    Full Text Available Background: Free-standing carbon nanomembranes (CNM with molecular thickness and macroscopic size are fascinating objects both for fundamental reasons and for applications in nanotechnology. Although being made from simple and identical precursors their internal structure is not fully known and hard to simulate due to the large system size that is necessary to draw definite conclusions.Results: We performed large-scale classical molecular dynamics investigations of biphenyl-based carbon nanomembranes. We show that one-dimensional graphene-like stripes constitute a highly symmetric quasi one-dimensional energetically favorable ground state. This state does not cross-link. Instead cross-linked structures are formed from highly excited precursors with a sufficient amount of broken phenyls.Conclusion: The internal structure of the CNM is very likely described by a disordered metastable state which is formed in the energetic initial process of electron irradiation and depends on the process of relaxation into the sheet phase.

  3. Dipolar dissociation dynamics in electron collisions with carbon monoxide

    CERN Document Server

    Chakraborty, Dipayan; Nandi, Dhananjay

    2016-01-01

    Dipolar dissociation processes in the electron collisions with carbon monoxide have been studied using time of flight (TOF) mass spectroscopy in combination with the highly differential velocity slice imaging (VSI) technique. Probing ion-pair states both positive and/or negative ions may be detected. The ion yield curve of negative ions provides the threshold energy for the ion-pair production. On the other hand, the kinetic energy distributions and angular distributions of the fragment anion provide detailed dynamics of the dipolar dissociation process. Two ion-pair states have been identified based on angular distribution measurements using VSI technique.

  4. Model Establishment for Simulating Soil Organic Carbon Dynamics

    Institute of Scientific and Technical Information of China (English)

    HUANG Yao; LIU Shi-liang; SHEN Qi-rong; ZONG Liang-gang

    2002-01-01

    Assuming that decomposition of organic matter in soils follows the first-order kinetics reaction,a computer model was developed to simulate soil organic matter dynamics. Organic matter in soils is divided up into two parts that include incorporated organic carbon from crop residues or other organic fertilizer and soil intrinsic carbon. The incorporated organic carbon was assumed to consist of two components, labile-C and resistant-C. The model was represented by a differential equation of dCi/dt = Ki× fT × fw × fs × Ci ( i = l,r, S ) and an integral equation of Cit = Cio × EXP ( Ki X fT X fw X fs X t ). Effect of soil parameters of temperature, moisture and texture on the decomposition was functioned by the fT, fw and fs, respectively.Data from laboratory incubation experiments were used to determine the first-order decay rate Ki and the fraction of labile-C of crop residues by employing a nonlinear method. The values of K for the components of labile-C and resistant-C and the soil intrinsic carbon were evaluated to be 0. 025,0. 080 × 10-2 and 0. 065 ×10-3d-1, respectively. The labile-C fraction of wheat straw, wheat roots, rice straw and rice roots were0.50, 0.25, 0.40 and 0.20, respectively. These values are related to the initial residue carbon-to-nitrogen ratio ( C/N) and lignin content.

  5. A Molecular Dynamics Study on the Confinement of Carbon Dioxide Molecules in Carbon Nanotubes

    Science.gov (United States)

    Lazor, Meagan; Rende, Deniz; Baysal, Nihat; Ozisik, Rahmi

    2012-02-01

    The influence of atmospheric carbon dioxide (CO2) concentration on global warming is considered as one of the primary environmental issues of the past two decades. The main source of CO2 emission is human activity, such as the use of fossil fuels in transportation and industrial plants. Following the release of Kyoto Protocol in 1997, effective ways of controlling CO2 emissions received much attention. As a result, various materials such as activated carbon, zeolites, and carbon nanotubes (CNTs) were investigated for their CO2 adsorbing properties. CNTs were reported to have CO2 adsorption capability twice that of activated carbon, hence they received the most attention. In the current study, single walled carbon nanotubes (SWNTs) were used as one dimensional nanoporous materials and their CO2 adsorption capacity was analyzed with Molecular Dynamics simulations. Results indicated that SWNTs are excellent CO2 adsorbers and their effectiveness increase at low CO2 concentrations. In addition, we showed that by varying temperature, CO2 can be removed from the SWNTs, providing a simple method to reuse SWNTs.

  6. Variation in forest structure and carbon dynamics in tropical rain forests of Amazonia

    Science.gov (United States)

    Vieira, S.; Selhorst, D.; Hutyra, L.; da Silva, R.; Camargo, P.; Chambers, J. Q.; Brown, I. F.; Higuchi, N.; Dos Santos, J.; Martinelli, L. A.; Trumbore, S.

    2002-12-01

    A better understanding of the variations in the dynamics and structure of trees in tropical forests is necessary for predicting the potential for these ecosystems to lose or store carbon. Data from forest inventory plotsshow large differences in forest structure, biomass, and tree growth rates among plots in three location. The number of stems (g.t. 10cm diameter)per hectare is higher in the Manaus site (626 ha-1) than in the Rio Branco (466 ha-1) or Santrem (460 ha-1) sites. Stocks of C in above-ground biomass in the three areas were 180.1 (Manaus), 122.1 (Rio Branco), and 140.6 (Santarem) MgC ha-1. Estimates of mean annual accumulation of C in living trees based on monthly dendrometer band measurements ranged from 1.6 (Manaus), 2.5 (Rio Branco), to 2.8 (Santarem) MgC ha-1 yr-1. Our results showed marked seasonality to growth, with highest growth rates in the wet and lowest rates in the dry season. This effect was most pronounced for trees with diameter g. t. 50cm. Comparing the three areas investigated suggests that forests experiencing a longer dry season have larger annual diameter growth increments for individual trees, and more of the forest biomass in the largest trees.

  7. NONLINEAR DYNAMICS OF CARBON NANOTUBES UNDER LARGE ELECTROSTATIC FORCE

    KAUST Repository

    Xu, Tiantian

    2015-06-01

    Because of the inherent nonlinearities involving the behavior of CNTs when excited by electrostatic forces, modeling and simulating their behavior is challenging. The complicated form of the electrostatic force describing the interaction of their cylindrical shape, forming upper electrodes, to lower electrodes poises serious computational challenges. This presents an obstacle against applying and using several nonlinear dynamics tools typically used to analyze the behavior of complicated nonlinear systems undergoing large motion, such as shooting, continuation, and integrity analysis techniques. This works presents an attempt to resolve this issue. We present an investigation of the nonlinear dynamics of carbon nanotubes when actuated by large electrostatic forces. We study expanding the complicated form of the electrostatic force into enough number of terms of the Taylor series. Then, we utilize this form along with an Euler-Bernoulli beam model to study for the first time the dynamic behavior of CNTs when excited by large electrostatic force. The geometric nonlinearity and the nonlinear electrostatic force are considered. An efficient reduced-order model (ROM) based on the Galerkin method is developed and utilized to simulate the static and dynamic responses of the CNTs. Several results are generated demonstrating softening and hardening behavior of the CNTs near their primary and secondary resonances. The effects of the DC and AC voltage loads on the behavior have been studied. The impacts of the initial slack level and CNT diameter are also demonstrated.

  8. The role of snow cover and soil freeze/thaw cycles affecting boreal-arctic soil carbon dynamics

    Directory of Open Access Journals (Sweden)

    Y. Yi

    2015-07-01

    Full Text Available Northern Hemisphere permafrost affected land areas contain about twice as much carbon as the global atmosphere. This vast carbon pool is vulnerable to accelerated losses through mobilization and decomposition under projected global warming. Satellite data records spanning the past 3 decades indicate widespread reductions (∼ 0.8–1.3 days decade−1 in the mean annual snow cover extent and frozen season duration across the pan-Arctic domain, coincident with regional climate warming trends. How the soil carbon pool responds to these changes will have a large impact on regional and global climate. Here, we developed a coupled terrestrial carbon and hydrology model framework with detailed 1-D soil heat transfer representation to investigate the sensitivity of soil organic carbon stocks and soil decomposition to changes in snow cover and soil freeze/thaw processes in the Pan-Arctic region over the past three decades (1982–2010. Our results indicate widespread soil active layer deepening across the pan-Arctic, with a mean decadal trend of 6.6 ± 12.0 (SD cm, corresponding with widespread warming and lengthening non-frozen season. Warming promotes vegetation growth and soil heterotrophic respiration, particularly within surface soil layers (≤ 0.2 m. The model simulations also show that seasonal snow cover has a large impact on soil temperatures, whereby increases in snow cover promote deeper (≥ 0.5 m soil layer warming and soil respiration, while inhibiting soil decomposition from surface (≤ 0.2 m soil layers, especially in colder climate zones (mean annual T ≤ −10 °C. Our results demonstrate the important control of snow cover in affecting northern soil freeze/thaw and soil carbon decomposition processes, and the necessity of considering both warming, and changing precipitation and snow cover regimes in characterizing permafrost soil carbon dynamics.

  9. Land use change and carbon stock dynamics in Sub-Saharan Africa - Case study of Western Africa - Ghana

    Science.gov (United States)

    Grieco, E.; Chiti, T.; Valentini, R.

    2012-04-01

    Among different regions of the world, Africa and particularly sub-Saharan Africa (SSA) has contributed less than any other to the greenhouse gas emissions, but it is also the region most vulnerable and the least well equipped to the consequences. In SSA the role of land use change in controlling CO2 emissions may be more critical than in any other regions and perhaps the most uncertain component of the global carbon cycle. The most typical example of incomplete estimates will arise from the lack of reliable data for carbon pools. Three factors account for much of the rest of the uncertainty: (1) initial stocks of carbon in ecosystems affected by land-use change, (2) per hectare changes in carbon stocks in response to different types of land-use change, and (3) legacy effects; that is, the time it takes for carbon stocks to equilibrate following a change in land use. Considering the source of uncertainty and the lack of field data for SSA, the study has been located in Ghana (Jomoro district, Western Region) where forest is the only source of wood for domestic uses and deforestation annual rate was 2.2% for the period 2005-2010. This study analyze the above mentioned gaps by assessing: 1) initial carbon stocks (tropical rain forest), 2) per hectare changes in carbon stocks as consequence of deforestation followed by six different main land uses [tree plantations (rubber, coconut, cocoa, oil palm, mixed plantations) and a secondary forest], 3) dynamics of soil carbon stocks through the time considering chronosequences. When accounting changes in carbon stocks in the UNFCCC framework, it is required to consider 5 carbon pools that are: aboveground biomass, belowground biomass, litter, dead wood and soil. Within REDD+ mechanism it is clear that only aboveground pool has to be always considered, belowground biomass is recommended and the others are facultative. Evidence from official UNFCCC reports suggests that only a very small fraction of developing countries

  10. Annual benthic metabolism and organic carbon fluxes in a semi-enclosed Mediterranean bay dominated by the macroalgae Caulerpa prolifera

    OpenAIRE

    Ruiz-Halpern, Sergio; Vaquer-Sunyer, Raquel; Duarte, Carlos M.

    2014-01-01

    Coastal areas play an important role on carbon cycling. Elucidating the dynamics on the production, transport, and fate of organic carbon (OC) is relevant to gain a better understanding on the role coastal areas play in the global carbon budget. Here, we assess the metabolic status and associated OC fluxes of a semi-enclosed Mediterranean bay supporting a meadow of Caulerpa prolifera. We test whether the EDOC pool is a significant component of the OC pool and associated fluxes in this ecosyst...

  11. Economic Growth And Carbon Emission: A Dynamic Panel Data Analysis

    Directory of Open Access Journals (Sweden)

    Ibrahim BAKIRTAS

    2014-10-01

    Full Text Available The relationship between carbon dioxide emission (CO2 and economic growth is one of the crucial topics in environmental economics. This study is aimed to investigatethat problem. In this study, depending on the theory of Environmental Kuznets Curves (EKC, the impact of income in carbon dioxide emission has measured for 34 OECD and5 BRICS countries with using Dynamic Panel Data Analysis. In this regard OECD countries are classified by income groups due to the average per capita income rate ofOECD to solve the homogeneity problem among OECD countries. On the other hand EKC hypothesis analysed by short and long run income elasticity which will be using foran evident that a country reduces CO2 emissions with the income increase in this study. According to the findings of the study, % 36 of the country sample coherent with theEKC hypothesis. The main encouragement for testing this relationship between economic growth and CO2 emission is leading politicians to reconsider the environmental impactswhich are arising from income increase when they are taking a decision to maximizes the economic growth.Keywords: EKC; OECD; Dynamic Panel Data

  12. Aggregate and soil organic carbon dynamics in South Chilean Andisols

    Science.gov (United States)

    Huygens, D.; Boeckx, P.; Van Cleemput, O.; Oyarzún, C.; Godoy, R.

    2005-06-01

    Extreme sensitivity of soil organic carbon (SOC) to climate and land use change warrants further research in different terrestrial ecosystems. The aim of this study was to investigate the link between aggregate and SOC dynamics in a chronosequence of three different land uses of a south Chilean Andisol: a second growth Nothofagus obliqua forest (SGFOR), a grassland (GRASS) and a Pinus radiata plantation (PINUS). Total carbon content of the 0-10cm soil layer was higher for GRASS (6.7 kg C m-2) than for PINUS (4.3 kg C m-2, while TC content of SGFOR (5.8 kg C m-2) was not significantly different from either one. High extractable oxalate and pyrophosphate Al concentrations (varying from 20.3-24.4 g kg-1, and 3.9-11.1 g kg-1, respectively) were found in all sites. In this study, SOC and aggregate dynamics were studied using size and density fractionation experiments of the SOC, δ13C and total carbon analysis of the different SOC fractions, and C mineralization experiments. The results showed that electrostatic sorption between and among amorphous Al components and clay minerals is mainly responsible for the formation of metal-humus-clay complexes and the stabilization of soil aggregates. The process of ligand exchange between SOC and Al would be of minor importance resulting in the absence of aggregate hierarchy in this soil type. Whole soil C mineralization rate constants were highest for SGFOR and PINUS, followed by GRASS (respectively 0.495, 0.266 and 0.196 g CO2-Cm-2d-1 for the top soil layer). In contrast, incubation experiments of isolated macro organic matter fractions gave opposite results, showing that the recalcitrance of the SOC decreased in another order: PINUS>SGFOR>GRASS. We deduced that electrostatic sorption processes and physical protection of SOC in soil aggregates were the main processes determining SOC stabilization. As a result, high aggregate carbon concentrations, varying from 148 till 48 g kg-1, were encountered for all land use sites. Al

  13. Aggregate and soil organic carbon dynamics in South Chilean Andisols

    Directory of Open Access Journals (Sweden)

    D. Huygens

    2005-01-01

    Full Text Available Extreme sensitivity of soil organic carbon (SOC to climate and land use change warrants further research in different terrestrial ecosystems. The aim of this study was to investigate the link between aggregate and SOC dynamics in a chronosequence of three different land uses of a south Chilean Andisol: a second growth Nothofagus obliqua forest (SGFOR, a grassland (GRASS and a Pinus radiata plantation (PINUS. Total carbon content of the 0-10cm soil layer was higher for GRASS (6.7 kg C m-2 than for PINUS (4.3 kg C m-2, while TC content of SGFOR (5.8 kg C m-2 was not significantly different from either one. High extractable oxalate and pyrophosphate Al concentrations (varying from 20.3-24.4 g kg-1, and 3.9-11.1 g kg-1, respectively were found in all sites. In this study, SOC and aggregate dynamics were studied using size and density fractionation experiments of the SOC, δ13C and total carbon analysis of the different SOC fractions, and C mineralization experiments. The results showed that electrostatic sorption between and among amorphous Al components and clay minerals is mainly responsible for the formation of metal-humus-clay complexes and the stabilization of soil aggregates. The process of ligand exchange between SOC and Al would be of minor importance resulting in the absence of aggregate hierarchy in this soil type. Whole soil C mineralization rate constants were highest for SGFOR and PINUS, followed by GRASS (respectively 0.495, 0.266 and 0.196 g CO2-Cm-2d-1 for the top soil layer. In contrast, incubation experiments of isolated macro organic matter fractions gave opposite results, showing that the recalcitrance of the SOC decreased in another order: PINUS>SGFOR>GRASS. We deduced that electrostatic sorption processes and physical protection of SOC in soil aggregates were the main processes determining SOC stabilization. As a result, high aggregate carbon concentrations, varying from 148 till 48 g kg-1, were encountered for all land use

  14. DRAINMOD-FOREST: Integrated Modeling of Hydrology, Soil Carbon and Nitrogen Dynamics, and Plant Growth for Drained Forests.

    Science.gov (United States)

    Tian, Shiying; Youssef, Mohamed A; Skaggs, R Wayne; Amatya, Devendra M; Chescheir, G M

    2012-01-01

    We present a hybrid and stand-level forest ecosystem model, DRAINMOD-FOREST, for simulating the hydrology, carbon (C) and nitrogen (N) dynamics, and tree growth for drained forest lands under common silvicultural practices. The model was developed by linking DRAINMOD, the hydrological model, and DRAINMOD-N II, the soil C and N dynamics model, to a forest growth model, which was adapted mainly from the 3-PG model. The forest growth model estimates net primary production, C allocation, and litterfall using physiology-based methods regulated by air temperature, water deficit, stand age, and soil N conditions. The performance of the newly developed DRAINMOD-FOREST model was evaluated using a long-term (21-yr) data set collected from an artificially drained loblolly pine ( L.) plantation in eastern North Carolina, USA. Results indicated that the DRAINMOD-FOREST accurately predicted annual, monthly, and daily drainage, as indicated by Nash-Sutcliffe coefficients of 0.93, 0.87, and 0.75, respectively. The model also predicted annual net primary productivity and dynamics of leaf area index reasonably well. Predicted temporal changes in the organic matter pool on the forest floor and in forest soil were reasonable compared to published literature. Both predicted annual and monthly nitrate export were in good agreement with field measurements, as indicated by Nash-Sutcliffe coefficients above 0.89 and 0.79 for annual and monthly predictions, respectively. This application of DRAINMOD-FOREST demonstrated its capability for predicting hydrology and C and N dynamics in drained forests under limited silvicultural practices. PMID:22565258

  15. Dynamics and Disequilibrium Carbon Chemistry in HD 209458b's Atmosphere

    CERN Document Server

    Cooper, C S; Cooper, Curtis S.; Showman, Adam P.

    2006-01-01

    Chemical equilibrium considerations suggest that, assuming solar elemental abundances, carbon on HD 209458b is sequestered primarily as carbon monoxide (CO) and methane (CH4). The relative mole fractions of CO(g) and CH4(g) in chemical equilibrium are expected to vary greatly according to variations in local temperature and pressure. We show, however, that in the p = 1--1000 mbar range, chemical equilibrium does not hold. To explore disequilibrium effects, we couple the chemical kinetics of CO and CH4 to a three-dimensional numerical model of HD 209458b's atmospheric circulation. These simulations show that vigorous dynamics caused by uneven heating of this tidally locked planet homogenize the CO and CH4 concentrations at p < 1 bar, even in the presence of lateral temperature variations of ~500--1000 K. In the 1--1000 mbar pressure range, we find that over 98% of the carbon is in CO. This is true even in cool regions where CH4 is much more stable thermodynamically. Our work shows furthermore that planets 3...

  16. Drought during canopy development has lasting effect on annual carbon balance in a deciduous temperate forest.

    Science.gov (United States)

    Noormets, Asko; McNulty, Steve G; DeForest, Jared L; Sun, Ge; Li, Qinglin; Chen, Jiquan

    2008-01-01

    * Climate change projections predict an intensifying hydrologic cycle and an increasing frequency of droughts, yet quantitative understanding of the effects on ecosystem carbon exchange remains limited. * Here, the effect of contrasting precipitation and soil moisture dynamics were evaluated on forest carbon exchange using 2 yr of eddy covariance and microclimate data from a 50-yr-old mixed oak woodland in northern Ohio, USA. * The stand accumulated 40% less carbon in a year with drought between bud-break and full leaf expansion (354 +/- 81 g C m(-2) yr(-1) in 2004 and 252 +/- 45 g C m(-2) yr(-1) in 2005). This was caused by greater suppression of gross ecosystem productivity (GEP; 16% = 200 g) than of ecosystem respiration (ER; 11% = 100 g) by drought. Suppressed GEP was traced to lower leaf area, lower apparent quantum yield and lower canopy conductance. The moisture sensitivity of ER may have been mediated by GEP. * The results highlight the vulnerability of the ecosystem to even a moderate drought, when it affects a critical aspect of development. Although the drought was preceded by rain, the storage capacity of the soil seemed limited to 1-2 wk, and therefore droughts longer than this are likely to impair productivity in the region. PMID:18537894

  17. Human impacts on soil carbon dynamics of deep-rooted Amazonian forests

    Science.gov (United States)

    Nepstad, Daniel C.; Stone, Thomas A.; Davidson, Eric A.

    1994-01-01

    Deforestation and logging degrade more forest in eastern and southern Amazonia than in any other region of the world. This forest alteration affects regional hydrology and the global carbon cycle, but our current understanding of these effects is limited by incomplete knowledge of tropical forest ecosystems. It is widely agreed that roots are concentrated near the soil surface in moist tropical forests, but this generalization incorrectly implies that deep roots are unimportant in water and C budgets. Our results indicate that half of the closed-canopy forests of Brazilian Amazonic occur where rainfall is highly seasonal, and these forests rely on deeply penetrating roots to extract soil water. Pasture vegetation extracts less water from deep soil than the forest it replaces, thus increasing rates of drainage and decreasing rates of evapotranspiration. Deep roots are also a source of modern carbon deep in the soil. The soils of the eastern Amazon contain more carbon below 1 m depth than is present in above-ground biomass. As much as 25 percent of this deep soil C could have annual to decadal turnover times and may be lost to the atmosphere following deforestation. We compared the importance of deep roots in a mature, evergreen forest with an adjacent man-made pasture, the most common type of vegetation on deforested land in Amazonia. The study site is near the town of Paragominas, in the Brazilian state of Para, with a seasonal rainfall pattern and deeply-weathered, kaolinitic soils that are typical for large portions of Amazonia. Root distribution, soil water extraction, and soil carbon dynamics were studied using deep auger holes and shafts in each ecosystem, and the phenology and water status of the leaf canopies were measured. We estimated the geographical distribution of deeply-rooting forests using satellite imagery, rainfall data, and field measurements.

  18. Impacts of natural and human-induced disturbances on carbon dynamics in Northern Eurasia

    Science.gov (United States)

    Shvidenko, A.; Shchepashchenko, D.

    2012-12-01

    Disturbance regimes (DR) of vegetation ecosystems of Northern Eurasia (NE, limited to Russian territories) are represented by complicated and interacting sets of natural and human-induced disturbances (D). We present a unified classification of D and DR in major land cover classes of Northern Eurasia (forests, agriculture, wetlands, shrubs & grasses), their connections to succession regularities, and minimal informative set of indicators, which are able to describe both specifics of individual types of D and their impacts on annual carbon budget. The assessment of extent, severity and consequences of D was done based on an Integrated Land Information System for Russia, which accumulated all relevant spatially distributed information including multi-sensor and multi-temporal remote sensing concept, in situ measurements and ground data from diverse inventories and surveys. Major emissions caused by D are produced by consumption of plant products (agriculture and forestry), wild fire, and biotic D (basically insect outbreaks). For example, the annual flux due to human consumption of plant products is estimated at 170 Tg C yr-1. Wild fire in 1998-2010 enveloped 106.9 x 106 ha-1, on average 8.23 x 106 ha-1 yr-1, with variation from 4.2 to 17.3 x 106 ha-1 yr-1. Average direct carbon emissions due to wildfire were estimated to be at 121.0 Tg C yr-1, including 84.6% as C-CO2, 8.2% C-CO, C-CH4 - 1.1%, C-NMHC - 1.2%, organic carbon - 1.2% and black carbon - 0.1%, particulate matter 3.5%, of which PM2.5 - 1.2%. About 2/3 of burnt area and carbon emissions were on forest land. While the area of fire on wetlands was only 7.3%, this land class delivered 15.2% of the total fire emissions. Emissions caused by biotic D (accounted for forests only) is estimated at 50.8 Tg C yr-1. Overall, direct emissions due to D amounted at about 350 Tg C yr-1, or ~7% of annual Net Primary Production of terrestrial ecosystems of Russia. These data do not include long-term consequences of D, which

  19. Multiwalled carbon nanotubes as masks against carbon and argon irradiation. A molecular dynamics study

    Science.gov (United States)

    Denton, Cristian D.; Moreno-Marín, Juan Carlos; Heredia-Avalos, Santiago

    2016-04-01

    Experiments showed that multiwalled carbon nanotubes (MWCNT) can be used as masks against irradiation to create metallic nanowires in a substrate. In order to understand the limitations of this application, it is interesting to know the energy and number of carbon atoms emerging from the MWCNT after the irradiation and how the structure of the MWCNT is modified. Using a molecular dynamics code that we have previously developed, we have simulated the continuous irradiation of MWCNT with carbon and argon projectiles. We have obtained that the use of carbon instead of argon to irradiate the MWCNT increases de effectiveness of the MWCNTs as masks, due to the ability of the carbon projectiles to be part of the MWCNT structure and partially mend the damage produced during irradiation. We have analyzed the number, energy, and spatial distribution of the recoils generated during irradiation and the change of the MWCNT structure as a function of the incident energy (100 and 500 eV), fluence (up to 4.5 ·1015ions /cm2), and number of shells (up to 5-shells) of the MWCNT. These results determine the effectiveness of MWCNT as a mask, being useful to understand whether the atoms emerging from the MWCNT produce damage in the substrate or not. We find that for carbon projectiles the efficiency of MWCNT as masks does not depend much on the fluence, but on the number of nanotube shells and projectile incident energy. On the other hand, for a given nanotube and fluence, we observe a threshold incident energy below which the nanotube acts as a perfect mask.

  20. Estimating national forest carbon stocks and dynamics: combining models and remotely sensed information

    Science.gov (United States)

    Smallman, Luke; Williams, Mathew

    2016-04-01

    Forests are a critical component of the global carbon cycle, storing significant amounts of carbon, split between living biomass and dead organic matter. The carbon budget of forests is the most uncertain component of the global carbon cycle - it is currently impossible to quantify accurately the carbon source/sink strength of forest biomes due to their heterogeneity and complex dynamics. It has been a major challenge to generate robust carbon budgets across landscapes due to data scarcity. Models have been used but outputs have lacked an assessment of uncertainty, making a robust assessment of their reliability and accuracy challenging. Here a Metropolis Hastings - Markov Chain Monte Carlo (MH-MCMC) data assimilation framework has been used to combine remotely sensed leaf area index (MODIS), biomass (where available) and deforestation estimates, in addition to forest planting and clear-felling information from the UK's national forest inventory, an estimate of soil carbon from the Harmonized World Database (HWSD) and plant trait information with a process model (DALEC) to produce a constrained analysis with a robust estimate of uncertainty of the UK forestry carbon budget between 2000 and 2010. Our analysis estimates the mean annual UK forest carbon sink at -3.9 MgC ha‑1yr‑1 with a 95 % confidence interval between -4.0 and -3.1 MgC ha‑1 yr‑1. The UK national forest inventory (NFI) estimates the mean UK forest carbon sink to be between -1.4 and -5.5 MgC ha‑1 yr‑1. The analysis estimate for total forest biomass stock in 2010 is estimated at 229 (177/232) TgC, while the NFI an estimated total forest biomass carbon stock of 216 TgC. Leaf carbon area (LCA) is a key plant trait which we are able to estimate using our analysis. Comparison of median estimates for LCA retrieved from the analysis and a UK land cover map show higher and lower values for LCA are estimated areas dominated by needle leaf and broad leaf forests forest respectively, consistent with

  1. Collision dynamics of laser produced carbon plasma plumes

    Science.gov (United States)

    Favre, M.; Ruiz, H. M.; Cortés, D.; Merello, F.; Bhuyan, H.; Veloso, F.; Wyndham, E.

    2016-05-01

    We present preliminary experimental observations of the collision processes between two orthogonal laser produced plasmas in a low pressure neutral gas background. A Nd:YAG laser, 340 mJ, 3.5 ns, at 1.06 μm, operating at 10 Hz, is used in the experiments. The main laser beam is divided in two beams by a 50% beam splitter, and then focused over two rotating graphite targets, with characteristic fluence 3.5 J/cm2. Experiments are conducted in a range from a base pressure of 0.3 mTorr, up to 50 mTorr argon. The dynamics of the laser plasmas is characterized by time resolved and time integrated optical emission spectroscopy (OES), with 20 ns and 10 ms time resolution, and 50 ns time resolved plasma imaging of visible plasma emission. Clear effects of the neutral gas background on the postcollision plasma dynamics are identified. The overall dynamics of the post-collision plasma is found to be consistent with high collisionality of the carbon plasma plumes, which results in full stagnation on collisioning.

  2. Austenite decomposition in carbon steel under dynamic deformation conditions

    Directory of Open Access Journals (Sweden)

    A. Nowotnik

    2007-01-01

    Full Text Available Purpose: The main purpose of this paper was to estimate the effect of the dynamic conditions resulting fromdeformation process on the austenite decomposition into ferrite and pearlite (A→F+P in the commercial carbon steel.Design/methodology/approach: In the paper flow stress curves and microstructure of deformed steel within therange of discontinuous (austenite to pearlite and austenite to ferrite transformation at different strain rates andcooling rates were presented. The microstructure of hot deformed samples was tested by means of an opticaland electron microscopy.Findings: It was shown that the flow localization during hot deformation and preferred growth of the pearlitecolonies at shear bands was very limited. The most characteristic feature of the microstructure observed for hotdeformed samples was the development of carbides that nucleated along elongated ferrite grains.Research limitations/implications: In spite of intense strain hardening due to deformation and phasetransformation overlapping, microstructural observation of deformed samples did not reveal significant flowlocalization effects or heterogeneous distribution of the eutectoid components. Therefore, complementary testsshould be carried out on the steel with higher strain above the 0.5 value.Originality/value: There was no data referred to particular features of the dynamic processes, such as dynamicrecrystallization and recovery, dynamic precipitation, that can occur during austenite decomposition into ferrite,and especially during discontinuous transformation of austenite to pearlite.

  3. Dynamics of carbon nanotube alignment by electric fields

    International Nuclear Information System (INIS)

    The dynamics of multiwall carbon nanotube (MWCNT) alignment inside viscous media using electric fields is investigated. Electrical current measurements were performed in situ during the application of an electric field to liquid solutions of deionized water or dissolved polymer containing MWCNTs. The variation of electrical current over time was associated to the dynamics of the MWCNT network formation. The influence of the electric field magnitude and frequency on the MWCNT network formation was studied. MWCNT migration towards the negative electrode was observed when a direct current electric field was applied, whereas formation of an aligned MWCNT network was achieved for an alternating current electric field. The increase of the electric field frequency promotes a faster formation of an aligned MWCNT network and thinner MWCNT bundles. A higher viscosity of the liquid medium yields slower MWCNT alignment evidenced by a slower change of electrical current through the viscous system. An analytical model based on the dielectrophoresis-induced torque, which considers the viscosity of the medium, is also proposed to explain the dynamics of MWCNT alignment. Furthermore, aligned MWCNT/polysulfone solid composites were fabricated and electrically characterized. The solid composites presented anisotropic electrical conductivity, which was more evident for low MWCNT concentrations (0.1–0.2 wt%). (paper)

  4. Estimating annual soil carbon loss in agricultural peatland soils using a nitrogen budget approach.

    Directory of Open Access Journals (Sweden)

    Emilie R Kirk

    Full Text Available Around the world, peatland degradation and soil subsidence is occurring where these soils have been converted to agriculture. Since initial drainage in the mid-1800s, continuous farming of such soils in the California Sacramento-San Joaquin Delta (the Delta has led to subsidence of up to 8 meters in places, primarily due to soil organic matter (SOM oxidation and physical compaction. Rice (Oryza sativa production has been proposed as an alternative cropping system to limit SOM oxidation. Preliminary research on these soils revealed high N uptake by rice in N fertilizer omission plots, which we hypothesized was the result of SOM oxidation releasing N. Testing this hypothesis, we developed a novel N budgeting approach to assess annual soil C and N loss based on plant N uptake and fallow season N mineralization. Through field experiments examining N dynamics during growing season and winter fallow periods, a complete annual N budget was developed. Soil C loss was calculated from SOM-N mineralization using the soil C:N ratio. Surface water and crop residue were negligible in the total N uptake budget (3 - 4 % combined. Shallow groundwater contributed 24 - 33 %, likely representing subsurface SOM-N mineralization. Assuming 6 and 25 kg N ha-1 from atmospheric deposition and biological N2 fixation, respectively, our results suggest 77 - 81 % of plant N uptake (129 - 149 kg N ha-1 was supplied by SOM mineralization. Considering a range of N uptake efficiency from 50 - 70 %, estimated net C loss ranged from 1149 - 2473 kg C ha-1. These findings suggest that rice systems, as currently managed, reduce the rate of C loss from organic delta soils relative to other agricultural practices.

  5. Dynamics of planktonic prokaryotes and dissolved carbon in a subtropical coastal lake

    Directory of Open Access Journals (Sweden)

    Maria Luiza eSchmitz Fontes

    2013-04-01

    Full Text Available To understand the dynamics of planktonic prokaryotes in a subtropical lake and its relationship with carbon, we conducted water sampling through four 48 h periods in Peri Lake for one year. Planktonic prokaryotes were characterized by the abundance and biomass of heterotrophic bacteria and of cyanobacteria (coccoid and filamentous cells. During all experiments, we measured wind speed, water temperature (WT, pH, dissolved oxygen (DO, precipitation, dissolved organic carbon (DOC, dissolved inorganic carbon (DIC, and carbon dioxide (CO2. DOC was higher in the summer experiment (average = 465 μM - WT = 27°C and lower in the winter experiment (average = 235 μM – WT = 17°C, with no significant variability throughout the daily cycles. CO2 concentrations presented a different pattern, with a minimum in the warm waters of the summer period (8.31 μM and a maximum in the spring (37.13 μM. Daily trends were observed for pH, DO, WT, and CO2. At an annual scale, both biological and physical-chemical controls were important regulators of CO2. Heterotrophic bacteria abundance and biomass were higher in the winter experiment (5.60 x 109 cells L-1 and 20.83 μmol C L-1 and lower in the summer (1.87 x 109 cells L-1 and 3.95 μmol C L-1. Filamentous cyanobacteria (0.23 x 108 – 0.68 x 108 filaments L-1 produced up to 167.16 μmol C L-1 as biomass (during the warmer period, whereas coccoid cyanobacteria contributed only 0.38 μmol C L-1. Precipitation, temperature, and the biomass of heterotrophic bacteria were the main regulators of CO2 concentrations. Temperature had a negative effect on the concentration of CO2, which may be indirectly attributed to high heterotroph activity in the autumn and winter periods. DOC was positively correlated with the abundance of total cyanobacteria and negatively with heterotrophic bacteria. Thus, planktonic prokaryotes have played an important role in the dynamics of both dissolved inorganic and organic carbon in the lake.

  6. Dynamics of planktonic prokaryotes and dissolved carbon in a subtropical coastal lake.

    Science.gov (United States)

    Fontes, Maria Luiza S; Tonetta, Denise; Dalpaz, Larissa; Antônio, Regina V; Petrucio, Maurício M

    2013-01-01

    To understand the dynamics of planktonic prokaryotes in a subtropical lake and its relationship with carbon, we conducted water sampling through four 48-h periods in Peri Lake for 1 year. Planktonic prokaryotes were characterized by the abundance and biomass of heterotrophic bacteria (HB) and of cyanobacteria (coccoid and filamentous cells). During all samplings, we measured wind speed, water temperature (WT), pH, dissolved oxygen (DO), precipitation, dissolved organic carbon (DOC), dissolved inorganic carbon (DIC), and carbon dioxide (CO2). DOC was higher in the summer (average = 465 μM - WT = 27°C) and lower in the winter (average = 235 μM - WT = 17°C), with no significant variability throughout the daily cycles. CO2 concentrations presented a different pattern, with a minimum in the warm waters of the summer period (8.31 μM) and a maximum in the spring (37.13 μM). Daily trends were observed for pH, DO, WT, and CO2. At an annual scale, both biological and physical-chemical controls were important regulators of CO2. HB abundance and biomass were higher in the winter sampling (5.60 × 10(9) cells L(-1) and 20.83 μmol C L(-1)) and lower in the summer (1.87 × 10(9) cells L(-1) and 3.95 μmol C L(-1)). Filamentous cyanobacteria (0.23 × 10(8)-0.68 × 10(8) filaments L(-1)) produced up to 167.16 μmol C L(-1) as biomass (during the warmer period), whereas coccoid cyanobacteria contributed only 0.38 μmol C L(-1). Precipitation, temperature, and the biomass of HB were the main regulators of CO2 concentrations. Temperature had a negative effect on the concentration of CO2, which may be indirectly attributed to high heterotroph activity in the autumn and winter periods. DOC was positively correlated with the abundance of total cyanobacteria and negatively with HB. Thus, planktonic prokaryotes have played an important role in the dynamics of both dissolved inorganic and organic carbon in

  7. Causes and consequences of complex population dynamics in an annual plant, Cardamine pensylvanica

    Energy Technology Data Exchange (ETDEWEB)

    Crone, E.E.

    1995-11-08

    The relative importance of density-dependent and density-independent factors in determining the population dynamics of plants has been widely debated with little resolution. In this thesis, the author explores the effects of density-dependent population regulation on population dynamics in Cardamine pensylvanica, an annual plant. In the first chapter, she shows that experimental populations of C. pensylvanica cycled from high to low density in controlled constant-environment conditions. These cycles could not be explained by external environmental changes or simple models of direct density dependence (N{sub t+1} = f[N{sub t}]), but they could be explained by delayed density dependence (N{sub t+1} = f[N{sub t}, N{sub t+1}]). In the second chapter, she shows that the difference in the stability properties of population growth models with and without delayed density dependence is due to the presence of Hopf as well as slip bifurcations from stable to chaotic population dynamics. She also measures delayed density dependence due to effects of parental density on offspring quality in C. pensylvanica and shows that this is large enough to be the cause of the population dynamics observed in C. pensylvanica. In the third chapter, the author extends her analyses of density-dependent population growth models to include interactions between competing species. In the final chapter, she compares the effects of fixed spatial environmental variation and variation in population size on the evolutionary response of C. pensylvanica populations.

  8. Carbon dioxide in an ionic liquid: Structural and rotational dynamics

    Science.gov (United States)

    Giammanco, Chiara H.; Kramer, Patrick L.; Yamada, Steven A.; Nishida, Jun; Tamimi, Amr; Fayer, Michael D.

    2016-03-01

    Ionic liquids (ILs), which have widely tunable structural motifs and intermolecular interactions with solutes, have been proposed as possible carbon capture media. To inform the choice of an optimal ionic liquid system, it can be useful to understand the details of dynamics and interactions on fundamental time scales (femtoseconds to picoseconds) of dissolved gases, particularly carbon dioxide (CO2), within the complex solvation structures present in these uniquely organized materials. The rotational and local structural fluctuation dynamics of CO2 in the room temperature ionic liquid 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (EmimNTf2) were investigated by using ultrafast infrared spectroscopy to interrogate the CO2 asymmetric stretch. Polarization-selective pump probe measurements yielded the orientational correlation function of the CO2 vibrational transition dipole. It was found that reorientation of the carbon dioxide occurs on 3 time scales: 0.91 ± 0.03, 8.3 ± 0.1, 54 ± 1 ps. The initial two are attributed to restricted wobbling motions originating from a gating of CO2 motions by the IL cations and anions. The final (slowest) decay corresponds to complete orientational randomization. Two-dimensional infrared vibrational echo (2D IR) spectroscopy provided information on structural rearrangements, which cause spectral diffusion, through the time dependence of the 2D line shape. Analysis of the time-dependent 2D IR spectra yields the frequency-frequency correlation function (FFCF). Polarization-selective 2D IR experiments conducted on the CO2 asymmetric stretch in the parallel- and perpendicular-pumped geometries yield significantly different FFCFs due to a phenomenon known as reorientation-induced spectral diffusion (RISD), revealing strong vector interactions with the liquid structures that evolve slowly on the (independently measured) rotation time scales. To separate the RISD contribution to the FFCF from the structural spectral

  9. Inter-annual variation of carbon uptake by a plantation oak woodland in south-eastern England

    Directory of Open Access Journals (Sweden)

    M. Wilkinson

    2012-12-01

    Full Text Available The carbon balance of an 80-yr-old deciduous oak plantation in the temperate oceanic climate of the south-east of Great Britain was measured by eddy covariance over 12 yr (1999–2010. The mean annual net ecosystem productivity (NEP was 486 g C m−2 yr−1 (95% CI of ±73 g C m−2 yr−1, and this was partitioned into a gross primary productivity (GPP of 2034 ± 145 g C m−2 yr−1, over a 165 (±6 day growing season, and an annual loss of carbon through respiration and decomposition (ecosystem respiration, Reco of 1548 ± 122 g C m−2 yr−1. Although the maximum variation of NEP between years was large (333 g C m−2 yr−1, the ratio of Reco/GPP remained relatively constant (0.76 ± 0.02 CI. Some anomalies in the annual patterns of the carbon balance could be linked to particular weather events, such as low summer solar radiation and low soil moisture content (values below 30% by volume. The European-wide heat wave and drought of 2003 did not reduce the NEP of this woodland because of good water supply from the surface-water gley soil. The inter-annual variation in estimated intercepted radiation only accounted for ~ 47% of the variation in GPP, although a significant relationship (p < 0.001 was found between peak leaf area index and annual GPP, which modified the efficiency with which incident radiation was used in net CO2 uptake. Whilst the spring start and late autumn end of the net CO2 uptake period varied substantially (range of 24 and 27 days respectively, annual GPP was not related to growing season length. Severe outbreaks of defoliating moth caterpillars, mostly Tortrix viridana L. and Operophtera brumata L., caused considerable damage to the forest canopy in 2009 and 2010, resulting in reduced GPP in these two years. Inter-annual variation in

  10. Using Ecosystem Functional Types in land-surface modeling to characterize and monitor the spatial and inter-annual variability of vegetation dynamics

    Science.gov (United States)

    Alcaraz-Segura, D.; Paruelo, J.; Epstein, H. E.; Berbery, E. H.; Kalnay, E.; Cabello, J.; Jobbagy, E. G.

    2009-12-01

    Including the inter-annual variability of vegetation dynamics into land-surface models is necessary to account for land use/cover change effects on Global Climate Models. However, land-surface models use land-cover classifications dictated by structural attributes of vegetation that have little sensitivity to environmental change and are difficult to update and result in a delayed response. This rigid representation of vegetation reduces the ability of models to represent rapid changes including land-use shifts, fires, floods, droughts, and insect outbreaks. Functional attributes of vegetation describing its energy and matter exchange with the atmosphere, have a shorter response to environmental changes and are relatively easy to monitor with satellite data. We applied the concept of Ecosystem Functional Types (EFTs; patches of the land-surface with similar carbon gain dynamics) to characterize the spatial and inter-annual variability of vegetation dynamics across natural and agricultural systems in the La Plata Basin of South America. Three descriptors of carbon gain dynamics were derived from seasonal curves of Normalized Difference Vegetation Index (NDVI) and used to identify EFTs based on annual mean (surrogate of primary production), seasonal coefficient of variation (indicator of seasonality), and date of maximum NDVI (descriptor of phenology). Results from two NDVI datasets were compared (AVHRR-LTDR version 2, 1982-1999, 15-day and 5 km resolution; and MOD13A2 MODIS, 2000-2006, 16-day and 1 km resolution). Both datasets showed greater spatial and inter-annual variability of the EFT composition in agricultural areas compared to natural areas. During 1982-1999, the percentage of the La Plata Basin occupied by EFTs with low productivity, high seasonality, and spring and fall NDVI maxima tended to decrease, while EFTs with high productivity, low seasonality, and summer maxima tended to increase. We speculate that these trends may be due to a positive trend in

  11. Dynamics of Soil Organic Carbon and Microbial Biomass Carbon in Relation to Water Erosion and Tillage Erosion

    OpenAIRE

    Xiaojun, Nie; Jianhui, Zhang; Zhengan, Su

    2013-01-01

    Dynamics of soil organic carbon (SOC) are associated with soil erosion, yet there is a shortage of research concerning the relationship between soil erosion, SOC, and especially microbial biomass carbon (MBC). In this paper, we selected two typical slope landscapes including gentle and steep slopes from the Sichuan Basin, China, and used the 137Cs technique to determine the effects of water erosion and tillage erosion on the dynamics of SOC and MBC. Soil samples for the determination of 137Cs...

  12. Soil carbon dynamics inferred from carbon isotope compositions of soil organic matter and soil respiration

    International Nuclear Information System (INIS)

    To better understand 14C cycling in terrestrial ecosystems, 14C abundances were evaluated for fractionated soil organic matter (SOM) and soil respiration in an urban forest. In 2001 soil profile, Δ 14C values of litter and bulk SOM increased rapidly from litter surface (62.7 per mille) to uppermost mineral soil layer (244.9 per mille), and then decreased sharply to 6 cm depth of mineral soil (125.0 per mille). Carbon enriched in 14C by atmospheric nuclear weapons testing had penetrated to at least 16 cm depth of mineral soil. The average Δ 14C in atmospheric CO2 was 58.8 per mille in August 2001, suggesting recent carbon input to the topmost litter layer. Although a similar depth distribution was observed for Δ 14C values of residual SOM after acid hydrolysis, the Δ 14C values were slightly lower than those in bulk SOM. This indicates input of 'bomb' C into this organic fraction and higher 14C abundance in acid-soluble SOM. The most of CO2 may be derived from the microbial decomposition of the acid-soluble, or labile, SOM. Therefore, the labile SOM may become most influential pool for soil carbon cycling. In contrast, carbon in base-insoluble SOM remained considerably low in 14C abundance at all depths, suggesting no or little incorporation of 'bomb' C to this fraction. Values of Δ 14C in soil respiration ranged from 91.9 to 146.4 per mille in August 2001, showing a significant contribution from decomposition of SOM fixed over past 2-40 years. These results indicate that the use of bulk SOM as a representative of soil carbon pool would lead to severe misunderstand of the soil C dynamics on decadal and shorter time scales. (author)

  13. Molecular dynamics of a water jet from a carbon nanotube.

    Science.gov (United States)

    Hanasaki, Itsuo; Yonebayashi, Toru; Kawano, Satoyuki

    2009-04-01

    A carbon nanotube (CNT) can be viewed as a molecular nozzle. It has a cylindrical shape of atomistic regularity, and the diameter can be even less than 1 nm. We have conducted molecular-dynamics simulations of water jet from a (6,6) CNT that confines water in a form of single-file molecular chain. The results show that the water forms nanoscale clusters at the outlet and they are released intermittently. The jet breakup is dominated by the thermal fluctuations, which leads to the strong dependence on the temperature. The cluster size n decreases and the release frequency f increases at higher temperatures. The f roughly follows the reaction kinetics by the transition state theory. The speed of a cluster is proportional to the 1/sqrt[n] because of the central limit theorem. These properties make great contrast with the macroscopic liquid jets. PMID:19518333

  14. Dynamic simulation of a direct carbonate fuel cell power plant

    Energy Technology Data Exchange (ETDEWEB)

    Ernest, J.B. [Fluor Daniel, Inc., Irvine, CA (United States); Ghezel-Ayagh, H.; Kush, A.K. [Fuel Cell Engineering, Danbury, CT (United States)

    1996-12-31

    Fuel Cell Engineering Corporation (FCE) is commercializing a 2.85 MW Direct carbonate Fuel Cell (DFC) power plant. The commercialization sequence has already progressed through construction and operation of the first commercial-scale DFC power plant on a U.S. electric utility, the 2 MW Santa Clara Demonstration Project (SCDP), and the completion of the early phases of a Commercial Plant design. A 400 kW fuel cell stack Test Facility is being built at Energy Research Corporation (ERC), FCE`s parent company, which will be capable of testing commercial-sized fuel cell stacks in an integrated plant configuration. Fluor Daniel, Inc. provided engineering, procurement, and construction services for SCDP and has jointly developed the Commercial Plant design with FCE, focusing on the balance-of-plant (BOP) equipment outside of the fuel cell modules. This paper provides a brief orientation to the dynamic simulation of a fuel cell power plant and the benefits offered.

  15. High dynamic orientation of protons, deuterons and carbon-13 nuclei

    International Nuclear Information System (INIS)

    The behaviour of hydrogen, deuterium, and carbon-13 nuclear spin systems have been studied in partially deuterated diols, doped with paramagnetic Crsup(V) complexes, between 0.1 and 0.5 K. Experimental evidence is given that the dynamic polarization in such samples comes from a cooling of the electron spin-spin interaction reservoir by off-resonance microwave irradiation; a strong thermal coupling between this reservoir and the nuclear Zeeman reservoirs cools these too, thus changing the polarizations. In a 25 kG magnetic field at a lattice temperature of 0.37 K we reached a common spin temperature for the nuclear Zeeman reservoirs of 1.1 mK in 1,2-propanediol-D6, which corresponds to a proton polarization of 98%, a deuteron polarization of 44%, and a carbon-13 polarization of 52%. A new way of dynamic orientation of the deuteron spin system was found. It allows one to vary the deuteron tensor polarization or alignment independently of its vector polarization. This can be done by slightly off-resonance RF irradiation of the polarized proton system, which cools the proton spin-spin interaction reservoir. It appeared that at the same time the RF field provides a thermal contract between this reservoir and the deuteron quadrupole interaction reservoir, which caused the observed alignment. Values around 60% were reached for some parts of the deuteron spin system, corresponding to a deuteron quadrupole spin temperature of 7 uK. The dependence of the alignment on RF frequency and initial proton polarization as well as thermal mixing rates are in good agreement with quantitative estimates from spin temperature theory. (author)

  16. Threshold Dynamics in Soil Carbon Storage for Bioenergy Crops

    Science.gov (United States)

    Woo, D.; Quijano, J.; Kumar, P.; Chaoka, S.; Bernacchi, C.

    2014-12-01

    Due to increasing demands for bioenergy, a considerable amount of land in the Midwestern United States could be devoted to the cultivation of second-generation bioenergy crops, such as switchgrass and miscanthus. In this study, we attempt to explore and analyze how different amounts of above-ground biomass returned to the soil at harvest affect the below-ground dynamics of carbon and nitrogen as a comparative study between miscanthus, swichgrass, and corn-corn-soybean rotation. The simulation results show that there is a threshold effect in the amount of above-ground litter input in the soil after harvest that will reach a critical organic matter C:N ratio in the soil, triggering a reduction of the soil microbial population, with significant consequences in other microbe-related processes such as decomposition and mineralization. These thresholds are approximately 25% and 15% of above-ground biomass for switchgrass and miscanthus, respectively. However, we do not observe such threshold effects for corn-corn-soybean rotation. These results suggest that values above these thresholds could result in a significant reduction of decomposition and mineralization, which in turn would enhance the sequestration of atmospheric carbon dioxide in the topsoil and reduce inorganic nitrogen losses when compared with a corn-corn-soybean rotation.

  17. Inter-annual dynamics of abyssal polychaete communities in the North East Pacific and North East Atlantic—A family-level study

    Science.gov (United States)

    Laguionie-Marchais, C.; Billett, D. S. M.; Paterson, G. L. D.; Ruhl, H. A.; Soto, E. H.; Smith, K. L., Jr.; Thatje, S.

    2013-05-01

    Characterising how deep-sea communities change on contemporary time-scales and understanding underlying ecosystem processes has become important under changing climate and the rise in the exploitation of deep-sea resources. However, little is known about these dynamics and processes. Long-term observations from which inter-annual variations can be detected are scarce in the deep sea. This study examines inter-annual changes in density, family richness and evenness, family and functional group rank abundance distributions of infaunal polychaetes at two abyssal stations in the North East Pacific (Station M, 1991 to 2005) and in the North East Atlantic (Porcupine Abyssal Plain, 1991 to 1999). The two long-term data sets were used to investigate not only if polychaete community structure and composition varied at inter-annual scales in terms of diversity and rank abundance distributions but also if any changes were related to previous observations in megafauna and environmental factors at each locality. The polychaete community structure at each locality was analysed using univariate statistics as well as multivariate ordination techniques based on Bray-Curtis similarity of the yearly family density. Sub-surface deposit feeders, such as Paraonidae, dominated the North East Pacific, whereas surface deposit feeders, such as Cirratulidae, dominated the North East Atlantic. Both stations showed inter-annual variations in density, family evenness and rank abundance distributions. The greatest changes occurred in 1998 in both time series when polychaete densities peaked, and switches in the rank abundance of the most abundant families and functional groups took place. Inter-annual variations in the polychaete community were correlated with a limited number of holothurian species changes, but no correlation was found with particulate organic matter flux or climate indices. Ecological and environmental factors behind the family-level changes remain elusive. Overall, changes in

  18. Proximate and ultimate controls on carbon and nutrient dynamics of small agricultural catchments

    Science.gov (United States)

    Thomas, Z.; Abbott, B. W.; Troccaz, O.; Baudry, J.; Pinay, G.

    2015-09-01

    Direct and indirect effects from agriculture, urbanization, and resource extraction have dramatically increased nutrient loading to aquatic inland and estuarine ecosystems. The capacity of a watershed to remove or retain nutrients is a function of biotic and abiotic conditions across the terrestrial-aquatic gradient including soil, groundwater, riparian zone, and surface water. The goal of this study was to identify proximate and ultimate controls on dissolved organic carbon and nutrient dynamics in small agricultural catchments. We analysed a five-year, high frequency water chemistry dataset from 3 catchments ranging from 2.3 to 10.8 km2 in northwestern France. Catchments differed in the relationship between hydrology and solute concentrations, associated with catchment characteristics such as hedgerow density, agricultural activity, and geology. The catchment with thicker soil and higher surface roughness appeared to have greater transient storage and residence time, buffering the catchment to fluctuations in water chemistry, reflected in relatively invariant carbon and nutrient chemistry across hydrologic conditions. Conversely, the catchments with smoother, thinner soils responded to both intra- and inter-annual hydrologic variation with high concentrations of PO43- and NH4+ during low flow conditions and strong increases in DOC, sediment, and particulate organic matter during high flows. Despite contrasting agricultural activity between catchments, the physical context (geology, topography, and land use) appeared to be the most important determinant of catchment solute dynamics based on principle components analysis. The influence of geology and accompanying topographic and geomorphological factors on elemental fluxes is both direct and indirect because the distribution of agricultural activity in these catchments is largely a consequence of the geologic and topographic context. This link between inherent catchment buffering capacity and probability of human

  19. Multiclass relevance vector machine classification to explore annual and seasonal dynamics of an Invasive reed

    Science.gov (United States)

    Zaman, B.; Torres, A.; McKee, M.

    2014-12-01

    Phragmites Australis forms dense stands which shade native vegetation and alter the ecosystem. Information on annual and seasonal dynamics of this plant contributes to the decision support system of wetland management. The study area is the Bear River Migratory bird refuge (BRMBR) which encompasses the Bear river and its delta where it flows into the northern part of theGreat Salt Lake, Utah. Seasonal change detection was carried out between the months of June 2010 and September 2010. The imagery from June 2011 and July 2011 were used for annual change detection. The remote sensing data was acquired by AggieAir, an unmanned aerial vehicle (UAV) platform, flown autonomously via pre-programmed flight plans at low altitudes to limit atmospheric effects. This UAV acquires high resolution multispectral images in the visible, near-infrared and thermal bands and has a flight interval of about 30 minutes. The reflectance values of the classes in wavebands 550, 650 and 850 nm were used to train the Multiclass relevance vector machine (MCRVM) model developed to classify the imagery of study area. There were a total of 5 classes: water, phragmites australis, marshy land, mixed vegetation and salt flats and three attributes. The multiclass classification accuracy achieved for June 2010, September 2010 and July 2011 were 95.2%, 95% and 98.7% respectively. The seasonal change detection indicated an average increase of 17% in area of phragmites and annual change detection results indicated an average increase of 110% from June 2010 to July 2011. It's astonishing rate of increase in distribution and abundance was alarming.

  20. Molecular Dynamics Simulation of Carbon Nanotube Based Gears

    Science.gov (United States)

    Han, Jie; Globus, Al; Jaffe, Richard; Deardorff, Glenn; Chancellor, Marisa K. (Technical Monitor)

    1996-01-01

    We used molecular dynamics to investigate the properties and design space of molecular gears fashioned from carbon nanotubes with teeth added via a benzyne reaction known to occur with C60. A modified, parallelized version of Brenner's potential was used to model interatomic forces within each molecule. A Leonard-Jones 6-12 potential was used for forces between molecules. One gear was powered by forcing the atoms near the end of the buckytube to rotate, and a second gear was allowed.to rotate by keeping the atoms near the end of its buckytube on a cylinder. The meshing aromatic gear teeth transfer angular momentum from the powered gear to the driven gear. A number of gear and gear/shaft configurations were simulated. Cases in vacuum and with an inert atmosphere were examined. In an extension to molecular dynamics technology, some simulations used a thermostat on the atmosphere while the hydrocarbon gear's temperature was allowed to fluctuate. This models cooling the gears with an atmosphere. Results suggest that these gears can operate at up to 50-100 gigahertz in a vacuum or inert atmosphere at room temperature. The failure mode involves tooth slip, not bond breaking, so failed gears can be returned to operation by lowering temperature and/or rotation rate. Videos and atomic trajectory files in xyz format are presented.

  1. Carbon Nanotube Liquid Crystals: Nematic Droplets and Coarsening Dynamics

    Science.gov (United States)

    Behabtu, Natnael; Senyuk, Bohdan; Smalyukh, Ivan; Pasquali, Matteo

    2012-02-01

    On a fundamental basis, carbon nanotubes (CNTs) offer a new model molecule to explore the dynamics and phases of rigid rods and test theories. Their large aspect ratio (100 to 100,000) and persistence length (˜ 100 microns) allow exploring the physics of nematic phases with high Frank elastic constant. Moreover, understanding of CNT liquid crystals is key to their rational processing into ordered materials such as fibers. Here we report the formation of elongated nematic droplets of CNTs in chlorosulfonic acid. In nematic droplets, a continuous transition from a homogeneous to bipolar nematic director field is expected theoretically, as a function of droplet volume; yet, experimental determination of such transition has been elusive. We show that CNT nematic droplets display such transition. We study the coarsening dynamics of positive and negative nematic droplets and observe that two or more droplets merge by matching their nematic director. Merging scenarios that lead to defect formation are not observed. Negative tactoids (isotropic phase in liquid crystalline continuum) merge through attractive forces induced by the nematic director distortion with quadrupolar symmetry.

  2. Dating Cactus: Annual and Sub-annual Variations of Oxygen-18, Carbon-13 and Radiocarbon in Spines of a Columnar Cactus, Carnegiea gigantea.

    Science.gov (United States)

    Dettman, D. L.; English, N. B.; Sandquist, D. R.; Williams, D. G.

    2006-12-01

    We measured δ18O, δ13C and F14C of spines from a long-lived columnar cactus, Carnegiea gigantea (saguaro), to resolve a record of plant physiological responses to annual and sub-annual climate variation in the eastern Sonoran Desert. Spines grow from the apex of the cactus and are arranged serially along the side of the cactus oldest at the base, youngest at the apex. To establish the age of the spine series, we measured F14C of spines collected at 8 different heights from the apex (3.77 m) to the base of a naturally occurring saguaro. These spines yielded fractions of modern carbon (F14C) from 0.9679 and 1.5537, indicating the presence of carbon in spine tissue derived from atmospheric nuclear testing. We used the F14C of spine tissue to calculate the year of spine emergence for each of the 11 spines, assuming minimal re-allocation of stored carbon to growing spines. At the same 8 heights, we interpolated the date of spine emergence from observed height measurements made between 1964 and 2002. A very strong positive correlation (linear regression, r2 = 0.99, P saguaro (between 1.77 and 3.50 m) and representing ~15 years of growth, yielded δ18O variations in spine bulk organic material from 38° to 50° (VSMOW) and in δ13C from ° to 11.5° (VPDB). The δ18O and δ13C values were positively correlated over the entire record (linear regression, r2 = 0.22, P saguaro 30 km distant. Temporal isotopic records from saguaro and potentially other long-lived succulent plants may provide useful high-frequency records of ecological responses to climate variation in desert environments where other such records are lacking.

  3. Extreme late-summer drought causes neutral annual carbon balance in southwestern ponderosa pine forests and grasslands

    International Nuclear Information System (INIS)

    We assessed the impacts of extreme late-summer drought on carbon balance in a semi-arid forest region in Arizona. To understand drought impacts over extremes of forest cover, we measured net ecosystem production (NEP), gross primary production (GPP), and total ecosystem respiration (TER) with eddy covariance over five years (2006–10) at an undisturbed ponderosa pine (Pinus ponderosa) forest and at a former forest converted to grassland by intense burning. Drought shifted annual NEP from a weak source of carbon to the atmosphere to a neutral carbon balance at the burned site and from a carbon sink to neutral at the undisturbed site. Carbon fluxes were particularly sensitive to drought in August. Drought shifted August NEP at the undisturbed site from sink to source because the reduction of GPP (70%) exceeded the reduction of TER (35%). At the burned site drought shifted August NEP from weak source to neutral because the reduction of TER (40%) exceeded the reduction of GPP (20%). These results show that the lack of forest recovery after burning and the exposure of undisturbed forests to late-summer drought reduce carbon sink strength and illustrate the high vulnerability of forest carbon sink strength in the southwest US to predicted increases in intense burning and precipitation variability. (letter)

  4. Inter-annual variation of carbon uptake by a plantation oak woodland in south-eastern England

    Directory of Open Access Journals (Sweden)

    M. Wilkinson

    2012-07-01

    Full Text Available The carbon balance of an 80 yr old deciduous oak plantation in the temperate oceanic climate of the south-east of Britain was measured by eddy covariance over 12 yr (1999–2010. The mean annual net ecosystem productivity (NEP was 486 g C m−2 y−1 (95% CI of ±73 g C m−2 y−1, and this was partitioned into a Gross Primary Productivity (GPP of 2034 ± 145 g C m−2 y−1, over a 165 (±6 day growing season, and an annual loss of carbon through respiration and decomposition (ecosystem respiration, Reco of 1548 ± 122 g C m−2 y−1. The interannual variation of NEP was large (coefficient of variation (CV 23%, although the variation for GPP and Reco was smaller (12% and the ratio of Reco/GPP was relatively constant (0.76 ± 0.02 CI. Some anomalies in the annual patterns of the carbon balance could be linked to particular combinations of anomalous weather events, such as high summer air temperature and low soil moisture content. The Europe-wide heat-wave and drought of 2003 had little effect on the C balance of this woodland on a surface water gley soil. Annual variation in precipitation (CV 18% was not a main factor in the variation in NEP. The inter-annual variation in estimated intercepted radiation only accounted for ~ 47% of the variation in GPP, although a significant relationship (p<0.001 was found between peak leaf area index and annual GPP which in turn played an important role in modifying the efficiency with which incident radiation was used in net CO2 uptake. Whilst the spring start and late autumn end of the net CO2 uptake period varied substantially (range of 24 and 27 days, respectively, annual GPP was not related to growing season length. Severe outbreaks of defoliating moth caterpillars, mostly Tortrix viridana L. and Operophtera brumata L

  5. Dynamics of formation of particles of the condensed carbon phase at shock compression of organic materials

    CERN Document Server

    Fedotov, M G; Luckjanchikov, L A; Lyakhov, N Z; Sharafutdinov, M R; Sheromov, M A; Ten, K A; Titov, V M; Tolochko, B P; Zubkov, P I

    2001-01-01

    Results of the SR study of the density behavior and dynamics of formation of condensed carbon particles at expansion of shock waves in organic materials and some low-sensitive explosives as well as at shock loading of ultra-dispersed diamonds are presented. Appearance of particles of the condensed carbon phase was observed in carbon-rich organic materials.

  6. Fluid Dynamics of Carbon Dioxide Disposal into Saline Aquifers

    Energy Technology Data Exchange (ETDEWEB)

    Garcia, Julio Enrique

    2003-12-18

    Injection of carbon dioxide (CO{sub 2}) into saline aquifers has been proposed as a means to reduce greenhouse gas emissions (geological carbon sequestration). Large-scale injection of CO{sub 2} will induce a variety of coupled physical and chemical processes, including multiphase fluid flow, fluid pressurization and changes in effective stress, solute transport, and chemical reactions between fluids and formation minerals. This work addresses some of these issues with special emphasis given to the physics of fluid flow in brine formations. An investigation of the thermophysical properties of pure carbon dioxide, water and aqueous solutions of CO{sub 2} and NaCl has been conducted. As a result, accurate representations and models for predicting the overall thermophysical behavior of the system CO{sub 2}-H{sub 2}O-NaCl are proposed and incorporated into the numerical simulator TOUGH2/ECO{sub 2}. The basic problem of CO{sub 2} injection into a radially symmetric brine aquifer is used to validate the results of TOUGH2/ECO2. The numerical simulator has been applied to more complex flow problem including the CO{sub 2} injection project at the Sleipner Vest Field in the Norwegian sector of the North Sea and the evaluation of fluid flow dynamics effects of CO{sub 2} injection into aquifers. Numerical simulation results show that the transport at Sleipner is dominated by buoyancy effects and that shale layers control vertical migration of CO{sub 2}. These results are in good qualitative agreement with time lapse surveys performed at the site. High-resolution numerical simulation experiments have been conducted to study the onset of instabilities (viscous fingering) during injection of CO{sub 2} into saline aquifers. The injection process can be classified as immiscible displacement of an aqueous phase by a less dense and less viscous gas phase. Under disposal conditions (supercritical CO{sub 2}) the viscosity of carbon dioxide can be less than the viscosity of the aqueous

  7. The topology of non-linear global carbon dynamics: from tipping points to planetary boundaries

    International Nuclear Information System (INIS)

    We present a minimal model of land use and carbon cycle dynamics and use it to explore the relationship between non-linear dynamics and planetary boundaries. Only the most basic interactions between land cover and terrestrial, atmospheric, and marine carbon stocks are considered in the model. Our goal is not to predict global carbon dynamics as it occurs in the actual Earth System. Rather, we construct a conceptually reasonable heuristic model of a feedback system between different carbon stocks that captures the qualitative features of the actual Earth System and use it to explore the topology of the boundaries of what can be called a ‘safe operating space’ for humans. The model analysis illustrates the existence of dynamic, non-linear tipping points in carbon cycle dynamics and the potential complexity of planetary boundaries. Finally, we use the model to illustrate some challenges associated with navigating planetary boundaries. (letter)

  8. Carbon nanotubes as nanodelivery systems an insight through molecular dynamics simulations

    CERN Document Server

    Lim, Melvin Choon Giap

    2013-01-01

    This book showcases the application of carbon nanotubes as nanodelivery systems for copper atoms, using molecular dynamics simulations as a means of investigation. The nanodelivery system of the carbon nanotube presents the possible usage of the carbon structure in many areas in the future. This book is comprehensive and informative, and serves as a guide for any reader who wishes to perform a molecular dynamics simulation of his own and to conduct an analytical study of a molecular system.

  9. Dynamic carbon caps. Splitting the bill: A fairer solution post-Kyoto?

    International Nuclear Information System (INIS)

    A dynamic carbon cap scheme is described and illustrated using a future growth scenario. This scheme, called a 'bill-splitting dynamic carbon cap', uses national carbon caps that change in a manner designed to distribute burden equitably, and at the same time to encourage and feed off economic growth. This is achieved by distributing emission-reduction obligations away from the growers, and onto the emitters. The global emission-reduction response is thereby pegged to global growth.

  10. Optical properties of carbon grains: Influence on dynamical models of AGB stars

    OpenAIRE

    Andersen, Anja C.; Loidl, Rita; Hofner, Susanne

    1999-01-01

    For amorphous carbon several laboratory extinction data are available, which show quite a wide range of differences due to the structural complexity of this material. We have calculated self-consistent dynamic models of circumstellar dust-shells around carbon-rich asymptotic giant branch stars, based on a number of these data sets. The structure and the wind properties of the dynamical models are directly influenced by the different types of amorphous carbon. In our test models the mass loss ...

  11. Seasonal and annual variation of carbon fluxes in a young Siberian larch (Larix sibirica plantation in Iceland

    Directory of Open Access Journals (Sweden)

    B. D. Sigurdsson

    2009-07-01

    Full Text Available This study reports 3-year measurements (2004–2006 of net ecosystem exchange (NEE over a 12–14 year old Siberian larch forest in Iceland established on previously grazed heath land pasture that had been site-prepared prior to planting. The study evaluated interannual and seasonal variation of NEE and its component fluxes, gross primary production (GPP and ecosystem respiration (Re, with the aim to clarify how climatic factors controlled the site's carbon balance. The young plantation acted as a relatively strong sink for CO2 during all of the three years, with a net sequestration of −375, −566 and −245 g CO2 m−2 for years 2004, 2005 and 2006, respectively. The annual carbon balance was strongly influenced by climatic factors leading to a high inter-annual variability in NEE. This variation was more related to variation in carbon efflux (Re than carbon uptake (GPP. The abiotic factors that showed the strongest correlation to Re were air temperature during the growing season and soil water potential. The GPP mostly followed the seasonal pattern in irradiance, except in 2005, when the plantation experienced severe spring frost damage that set the GPP back to zero. It was not expected that the rather slow-growing Siberian larch plantation would be such a strong sink for atmospheric CO2 only twelve years after site preparation and afforestation.

  12. Insights into soil carbon dynamics across climatic and geologic gradients from time-series and fraction-specific radiocarbon analysis

    Science.gov (United States)

    van der Voort, Tessa Sophia; Hagedorn, Frank; Zell, Claudia; McIntyre, Cameron; Eglinton, Tim

    2016-04-01

    Understanding the interaction between soil organic matter (SOM) and climatic, geologic and ecological factors is essential for the understanding of potential susceptibility and vulnerability to climate and land use change. Radiocarbon constitutes a powerful tool for unraveling SOM dynamics and is increasingly used in studies of carbon turnover. The complex and inherently heterogeneous nature of SOM renders it challenging to assess the processes that govern SOM stability by solely looking at the bulk signature on a plot-scale level. This project combines bulk radiocarbon measurements on a regional-scale spanning wide climatic and geologic gradients with a more in-depth approach for a subset of locations. For this subset, time-series and carbon pool-specific radiocarbon data has been acquired for both topsoil and deeper soils. These well-studied sites are part of the Long-Term Forest Ecosystem Research (LWF) program of the Swiss Federal Institute for Forest, Snow and Landscape research (WSL). Statistical analysis was performed to examine relationships of radiocarbon signatures with variables such as temperature, precipitation and elevation. Bomb-curve modeling was applied determine carbon turnover using time-series data. Results indicate that (1) there is no significant correlation between Δ14C signature and environmental conditions except a weak positive correlation with mean annual temperature, (2) vertical gradients in Δ14C signatures in surface and deeper soils are highly similar despite covering disparate soil-types and climatic systems, and (3) radiocarbon signatures vary significantly between time-series samples and carbon pools. Overall, this study provides a uniquely comprehensive dataset that allows for a better understanding of links between carbon dynamics and environmental settings, as well as for pool-specific and long-term trends in carbon (de)stabilization.

  13. Estimating forest carbon dynamics in South Korea from 1954 to 2050 - coupling global forestry model and forest soil carbon model

    Science.gov (United States)

    Lee, Jongyeol; Kim, Moonil; Lakyda, Ivan; Pietsch, Stephan; Shvidenko, Anatoly; Kraxner, Florian; Forsell, Nicklas; Son, Yowhan

    2016-04-01

    There have been demands on reporting national forest carbon (C) inventories to mitigate global climate change. Global forestry models estimate growth of stem volume and C at various spatial and temporal scales but they do not consider dead organic matter (DOM) C. In this study, we simulated national forest C dynamics in South Korea with a calibrated global forestry model (G4M model) and a module of DOM C dynamics in Korean forest C model (FBDC model). 3890 simulation units (1-16 km2) were established in entire South Korea. Growth functions of stem for major tree species (Pinus densiflora, P. rigida, Larix kaempferi, Quercus variabilis, Q. mongolica, and Q. acutissima) were estimated by internal mechanism of G4M model and Korean yield tables. C dynamics in DOMs were determined by balance between input and output (decomposition) of DOMs in the FBDC model. Annual input of DOM was estimated by multiplying C stock of biomass compartment with turnover rate. Decomposition of DOM was estimated by C stock of DOM, mean air temperature, and decay rate. C stock in each C pool was initialized by spin-up process with consideration of severe deforestation by Japanese exploitation and Korean War. No disturbance was included in the simulation process. Total forest C stock (Tg C) and mean C density (Mg C ha‑1) decreased from 657.9 and 112.1 in 1954 to 607.2 and 103.4 in 1973. Especially, C stock in mineral soil decreased at a rate of 0.5 Mg C ha‑1 yr‑1 during the period due to suppression of regeneration. However, total forest C stock (Tg C) and mean C density (Mg C ha‑1) gradually increased from 607.0 and 103.4 in 1974 to 1240.7 and 211.3 in 2015 due to the national reforestation program since 1973. After the reforestation program, Korean forests became C sinks. Model estimates were also verified by comparison of these estimates and national forest inventory data (2006-2010). High similarity between the model estimates and the inventory data showed a reliability of down

  14. Dielectric constants of binary mixtures of propylene carbonate with dimethyl carbonate and ethylene carbonate from molecular dynamics simulation: comparison between non-polarizable and polarizable force fields

    Science.gov (United States)

    Lee, Sanghun; Park, Sung Soo

    2013-01-01

    Using non-polarizable and polarizable molecular dynamics simulations, binary mixtures of propylene carbonate + dimethyl carbonate and propylene carbonate + ethylene carbonate with various compositions were investigated. The polarizable model produces more reasonable estimation of dielectric constants than the non-polarizable model; however, combining the electronic continuum model with the non-polarizable MD improves the comparison between the two models. Fair agreement was found between the results from these simulations and available experimental data. In addition, for a better understanding of the mixing behaviour, the excess dielectric constants over the entire composition were calculated. By comparison of the two mixtures in various mole fractions, distinctive mixing behaviours of propylene carbonate + dimethyl carbonate (poorly symmetric mixture) and propylene carbonate + ethylene carbonate (highly symmetric mixture) were observed.

  15. Adaptive dynamic resource allocation in annual eusocial insects: environmental variation will not necessarily promote graded control

    Directory of Open Access Journals (Sweden)

    Strohm Erhard

    2007-12-01

    Full Text Available Abstract Background According to the classical model of Macevicz and Oster, annual eusocial insects should show a clear dichotomous "bang-bang" strategy of resource allocation; colony fitness is maximised when a period of pure colony growth (exclusive production of workers is followed by a single reproductive period characterised by the exclusive production of sexuals. However, in several species graded investment strategies with a simultaneous production of workers and sexuals have been observed. Such deviations from the "bang-bang" strategy are usually interpreted as an adaptive (bet-hedging response to environmental fluctuations such as variation in season length or food availability. To generate predictions about the optimal investment pattern of insect colonies in fluctuating environments, we slightly modified Macevicz and Oster's classical model of annual colony dynamics and used a dynamic programming approach nested into a recurrence procedure for the solution of the stochastic optimal control problem. Results 1 The optimal switching time between pure colony growth and the exclusive production of sexuals decreases with increasing environmental variance. 2 Yet, for reasonable levels of environmental fluctuations no deviation from the typical bang-bang strategy is predicted. 3 Model calculations for the halictid bee Lasioglossum malachurum reveal that bet-hedging is not likely to be the reason for the graded allocation into sexuals versus workers observed in this species. 4 When environmental variance reaches a critical level our model predicts an abrupt change from dichotomous behaviour to graded allocation strategies, but the transition between colony growth and production of sexuals is not necessarily monotonic. Both, the critical level of environmental variance as well as the characteristic pattern of resource allocation strongly depend on the type of function used to describe environmental fluctuations. Conclusion Up to now bet

  16. Uncertainties and novel prospects in the study of the soil carbon dynamics

    International Nuclear Information System (INIS)

    Establishment of the Kyoto Protocol has resulted in an effort to look towards living biomass and soils for carbon sequestration. In order for carbon credits to be meaningful, sustained carbon sequestration for decades or longer is required. It has been speculated that improved land management could result in sequestration of a substantial amount of carbon in soils within several decades and therefore can be an important option in reducing atmospheric CO2 concentration. However, evaluation of soil carbon sources and sinks is difficult because the dynamics of soil carbon storage and release is complex and still not well understood. There has been rapid development of quantitative techniques over the past two decades for measuring the component fluxes of the global carbon cycle and for studying the soil carbon cycle. Most significant development in the soil carbon cycle study is the application of accelerator mass spectrometry (AMS) in radiocarbon measurements. This has made it possible to unravel rates of carbon cycling in soils, by studying natural levels of radiocarbon in soil organic matter and soil CO2. Despite the advances in the study of the soil carbon cycle in the recent decades, tremendous uncertainties exist in the sizes and turnover times of soil carbon pools. The uncertainties result from lack of standard methods and incomplete understanding of soil organic carbon dynamics, compounded by natural variability in soil carbon and carbon isotopic content even within the same ecosystem. Many fundamental questions concerning the dynamics of the soil carbon cycle have yet to be answered. This paper reviews and synthesizes the isotopic approaches to the study of the soil carbon cycle. We will focus on uncertainties and limitations associated with these approaches and point out areas where more research is needed to improve our understanding of this important component of the global carbon cycle. (author)

  17. Quantifying terrestrial ecosystem carbon dynamics in the Jinsha watershed, upper Yangtze, China from 1975 to 2000.

    Science.gov (United States)

    Zhao, Shuqing; Liu, Shuguang; Yin, Runsheng; Li, Zhengpeng; Deng, Yulin; Tan, Kun; Deng, Xiangzheng; Rothstein, David; Qi, Jiaguo

    2010-03-01

    Quantifying the spatial and temporal dynamics of carbon stocks in terrestrial ecosystems and carbon fluxes between the terrestrial biosphere and the atmosphere is critical to our understanding of regional patterns of carbon budgets. Here we use the General Ensemble biogeochemical Modeling System to simulate the terrestrial ecosystem carbon dynamics in the Jinsha watershed of China's upper Yangtze basin from 1975 to 2000, based on unique combinations of spatial and temporal dynamics of major driving forces, such as climate, soil properties, nitrogen deposition, and land use and land cover changes. Our analysis demonstrates that the Jinsha watershed ecosystems acted as a carbon sink during the period of 1975-2000, with an average rate of 0.36 Mg/ha/yr, primarily resulting from regional climate variation and local land use and land cover change. Vegetation biomass accumulation accounted for 90.6% of the sink, while soil organic carbon loss before 1992 led to a lower net gain of carbon in the watershed, and after that soils became a small sink. Ecosystem carbon sink/source patterns showed a high degree of spatial heterogeneity. Carbon sinks were associated with forest areas without disturbances, whereas carbon sources were primarily caused by stand-replacing disturbances. It is critical to adequately represent the detailed fast-changing dynamics of land use activities in regional biogeochemical models to determine the spatial and temporal evolution of regional carbon sink/source patterns. PMID:19296154

  18. Comparison of carbon dynamics in tropical and temperate soils using radiocarbon measurements

    OpenAIRE

    Trumbore, S.

    1993-01-01

    The magnitude and timing of the response of the soil carbon reservoir to changes in land use or climate is a large source of uncertainty in global carbon cycle models. One method of assessing soil carbon dynamics, based on modeling the observed increase of C-14 in organic matter pools during the 30 years since atmospheric weapons testing ended, is described in this paper. Differences in the inventory and residence time of carbon are observed in organic matter from soils representing tropical ...

  19. Dynamic polarization effects on the angular distributions of protons channeled through carbon nanotubes in dielectric media

    OpenAIRE

    Borka, D.; Mowbray, D. J.; Mišković, Z. L.; Petrović, S.; Nešković, N.

    2008-01-01

    The best level of ordering and straightening of carbon nanotube arrays is often achieved when they are grown in a dielectric matrix, so such structures present the most suitable candidates for future channeling experiments with carbon nanotubes. Consequently, we investigate here how the dynamic polarization of carbon valence electrons in the presence of various surrounding dielectric media affects the angular distributions of protons channeled through (11,~9) single-wall carbon nanotubes. Pro...

  20. Carbon Dioxide Information Analysis Center and World Data Center for Atmospheric Trace Gases Fiscal Year 2000 Annual Report; ANNUAL

    International Nuclear Information System (INIS)

    The Carbon Dioxide Information Analysis Center (CDIAC), which includes the World Data Center (WDC) for Atmospheric Trace Gases, is the primary global change data and information analysis center of the U.S. Department of Energy (DOE). More than just an archive of data sets and publications, CDIAC has, since its inception in 1982, enhanced the value of its holdings through intensive quality assurance, documentation, and integration. Whereas many traditional data centers are discipline-based (for example, meteorology or oceanography), CDIAC's scope includes potentially anything and everything that would be of value to users concerned with the greenhouse effect and global climate change, including concentrations of carbon dioxide (CO(sub 2)) and other radiatively active gases in the atmosphere; the role of the terrestrial biosphere and the oceans in the biogeochemical cycles of greenhouse gases; emissions of CO(sub 2) and other trace gases to the atmosphere; long-term climate trends; the effects of elevated CO(sub 2) on vegetation; and the vulnerability of coastal areas to rising sea levels

  1. Scenario Analysis of Tillage, Residue and Fertilization Management Effects on Soil Organic Carbon Dynamics

    Institute of Scientific and Technical Information of China (English)

    WANG Xiao-Bin; CAI Dian-Xiong; W.B.HOOGMOED; O.OENEMA; U.D.PERDOK

    2005-01-01

    Based on data from 10-year field experiments on residue/fertilizer management in the dryland farming region of northern China, Century model was used to simulate the site-specific ecosystem dynamics through adjustment of the model's parameters, and the applicability of the model to propose soil organic carbon (SOC) management temporally and spatially, in cases such as of tillage/residue/fertilization management options, was identified via scenario analysis.Results between simulations and actual measurements were in close agreement when appropriate applications of stover,manure and inorganic fertilizer were combined. Simulations of extreme C/N ratios with added organic materials tended to underestimate the measured effects. Scenarios of changed tillage methods, residue practices and fertilization options showed potential to maintain and enhance SOC in the long run, while increasing inorganic N slowed down the SOC turnover rate but did not create a net C sink without any organic C input. The Century model simulation showed a good relationship between annual C inputs to the soil and the rate of C sequestration in the top 20 cm layer and provided quantitative estimations of changes in parameters crucial for sustainable land use and management. Conservation tillage practices for sustainable land use should be integrated with residue management and appreciable organic and inorganic fertilizer application, adapted according to the local residue resource, soil fertility and production conditions. At least 50%residue return into the soil was needed annually for maintenance of SOC balance, and manure amendment was important for enhancement of SOC in small crop-livestock systems in which crop residue land application was limited.

  2. Evaluation of atmospheric aerosol and tropospheric ozone effects on global terrestrial ecosystem carbon dynamics

    Science.gov (United States)

    Chen, Min

    period of 2003-2010. Ecosystem heterotrophic respiration (RH) was negatively affected by the aerosol loading. These results support previous conclusions of the advantage of aerosol light scattering effect on plant productions in other studies but suggest there is strong spatial variation. This study finds indirect aerosol effects on terrestrial ecosystem carbon dynamics through affecting plant phenology, thermal and hydrological environments. All these evidences suggested that the aerosol direct radiative effect on global terrestrial ecosystem carbon dynamics should be considered to better understand the global carbon cycle and climate change. An ozone sub-model is developed in this dissertation and fully coupled with iTem. The coupled model, named iTemO3 considers the processes of ozone stomatal deposition, plant defense to ozone influx, ozone damage and plant repairing mechanism. By using a global atmospheric chemical transport model (GACTM) estimated ground-level ozone concentration data, the model estimated global annual stomatal ozone deposition is 234.0 Tg O3 yr-1 and indicates which regions have high ozone damage risk. Different plant functional types, sunlit and shaded leaves are shown to have different responses to ozone. The model predictions suggest that ozone has caused considerable change on global terrestrial ecosystem carbon storage and carbon exchanges over the study period 2004-2008. The study suggests that uncertainty of the key parameters in iTemO3 could result in large errors in model predictions. Thus more experimental data for better model parameterization is highly needed.

  3. Annual sums of carbon dioxide exchange over a heterogeneous urban landscape through machine learning based gap-filling

    Science.gov (United States)

    Menzer, Olaf; Meiring, Wendy; Kyriakidis, Phaedon C.; McFadden, Joseph P.

    2015-01-01

    A small, but growing, number of flux towers in urban environments measure surface-atmospheric exchanges of carbon dioxide by the eddy covariance method. As in all eddy covariance studies, obtaining annual sums of urban CO2 exchange requires imputation of data gaps due to low turbulence and non-stationary conditions, adverse weather, and instrument failures. Gap-filling approaches that are widely used for measurements from towers in natural vegetation are based on light and temperature response models. However, they do not account for key features of the urban environment including tower footprint heterogeneity and localized CO2 sources. Here, we present a novel gap-filling modeling framework that uses machine learning to select explanatory variables, such as continuous traffic counts and temporal variables, and then constrains models separately for spatially classified subsets of the data. We applied the modeling framework to a three year time series of measurements from a tall broadcast tower in a suburban neighborhood of Minneapolis-Saint Paul, Minnesota, USA. The gap-filling performance was similar to that reported for natural measurement sites, explaining 64% to 88% of the variability in the fluxes. Simulated carbon budgets were in good agreement with an ecophysiological bottom-up study at the same site. Total annual carbon dioxide flux sums for the tower site ranged from 1064 to 1382 g C m-2 yr-1, across different years and different gap-filling methods. Bias errors of annual sums resulting from gap-filling did not exceed 18 g C m-2 yr-1 and random uncertainties did not exceed ±44 g C m-2 yr-1 (or ±3.8% of the annual flux). Regardless of the gap-filling method used, the year-to-year differences in carbon exchange at this site were small. In contrast, the modeled annual sums of CO2 exchange differed by a factor of two depending on wind direction. This indicated that the modeled time series captured the spatial variability in both the biogenic and

  4. INVESTIGATION OF THE DYNAMIC BUCKLING OF DOUBLEWALLED CARBON NANOTUBE SUBJECTED TO AXIAL PERIODIC DISTURBING FORCES

    Institute of Scientific and Technical Information of China (English)

    SHA Feng-huan; ZHAO Long-mao; YANG Gui-tong

    2005-01-01

    The dynamic response of a double-walled carbon nanotube embedded in elastic medium subjected to periodic disturbing forces is investigated. Investigation of the dynamic buckling of a double-walled carbon nanotube develops continuum model. The effect of the van der Waals forces between two tubes and the surrounding elastic medium for axial dynamic buckling are considered. The buckling model subjected to periodic disturbing forces and the critical axial strain and the critical frequencies are given. It is found that the critical axial strain of the embedded multi-walled carbon nanotube due to the intertube van der Waals forces is lower than that of an embedded single-walled carbon nanotube. The van der Waals forces and the surrounding elastic medium affect region of dynamic instability. The van der Waals forces increase the critical frequencies of a double-walled carbon nanotube. The effect of the surrounding elastic medium for the critical frequencies is small.

  5. Dynamic adsorption properties of xenon on activated carbons and their structure characterization

    International Nuclear Information System (INIS)

    Background: In recent years, adsorption of radioactive xenon by activated carbon has been increasingly applied to the treatment of off-gas in nuclear power project. Though pore structure of activated carbon has a great impact on its dynamic adsorption coefficients for xenon, the concerned research is rare. Purpose: It is very necessary to figure out the relationship between the pore structure and the dynamic adsorption coefficients for the purpose of the selection and development of activated carbon. Methods: In this study, the dynamic adsorption coefficients of xenon on four kinds of activated carbons were measured on a dynamic adsorption platform under the condition of 25℃, OMPa (gauge pressure). And these four kinds of activated carbons were characterized by nitrogen adsorption and SEM. Results: The results show that the activated carbon of JH12-16 with the specific surface area of 991.9 m2·g-1 has the largest xenon dynamic adsorption coefficient among these activated carbons. Conclusions: The dynamic adsorption coefficient of xenon on activated carbon doesn't increase with the specific surface area or the pore volume. The mesopore and macropore only play the role of passageway for xenon adsorption. The most suitable pore for xenon adsorption is the pore with the pore size ranged from 0.55 to 0.6 nm. (authors)

  6. Dynamic interaction between localized magnetic moments in carbon nanotubes

    Energy Technology Data Exchange (ETDEWEB)

    Costa, A T; Muniz, R B [Instituto de FIsica, Universidade Federal Fluminense, 24210-346 Niteroi, RJ (Brazil); Ferreira, M S [School of Physics, Trinity College Dublin, Dublin 2 (Ireland)], E-mail: antc@if.uff.br, E-mail: bechara@if.uff.br, E-mail: ferreirm@tcd.ie

    2008-06-15

    Magnetic moments dilutely dispersed in a metallic host tend to be coupled through the conduction electrons of the metal. This indirect exchange coupling (IEC), known to occur for a variety of magnetic materials embedded in several different metallic structures, is of rather long range, especially for low-dimensional structures like carbon nanotubes. Motivated by recent claims that the indirect coupling between magnetic moments in precessional motion has a much longer range than its static counterpart, we consider here how magnetic atoms adsorbed to the walls of a metallic nanotube respond to a time-dependent perturbation that induces their magnetic moments to precess. By calculating the frequency-dependent spin susceptibility, we are able to identify resonant peaks whose respective widths provide information about the dynamic aspect of the IEC. We show that by departing from a purely static representation to another in which the moments are allowed to precess, we change from what is already considered a long-range interaction to another whose range is far superior. In other words, localized magnetic moments embedded in a metallic structure can feel each other's presence more easily when they are set in precessional motion. We argue that such an effect can have useful applications leading to large-scale spintronics devices.

  7. Dynamic interaction between localized magnetic moments in carbon nanotubes

    International Nuclear Information System (INIS)

    Magnetic moments dilutely dispersed in a metallic host tend to be coupled through the conduction electrons of the metal. This indirect exchange coupling (IEC), known to occur for a variety of magnetic materials embedded in several different metallic structures, is of rather long range, especially for low-dimensional structures like carbon nanotubes. Motivated by recent claims that the indirect coupling between magnetic moments in precessional motion has a much longer range than its static counterpart, we consider here how magnetic atoms adsorbed to the walls of a metallic nanotube respond to a time-dependent perturbation that induces their magnetic moments to precess. By calculating the frequency-dependent spin susceptibility, we are able to identify resonant peaks whose respective widths provide information about the dynamic aspect of the IEC. We show that by departing from a purely static representation to another in which the moments are allowed to precess, we change from what is already considered a long-range interaction to another whose range is far superior. In other words, localized magnetic moments embedded in a metallic structure can feel each other's presence more easily when they are set in precessional motion. We argue that such an effect can have useful applications leading to large-scale spintronics devices

  8. An overview of observations and assessment of forest carbon dynamics following disturbance in North America

    Science.gov (United States)

    Goetz, S. J.; Bond-Lamberty, B. P.

    2012-12-01

    Disturbance processes of various types substantially modify ecosystem carbon dynamics both temporally and spatially, and constitute a fundamental part of larger landscape-level dynamics. Forests typically lose carbon for several years to several decades following severe disturbance, but our understanding of the duration and dynamics of post-disturbance forest carbon fluxes remains limited. We capitalize on a recent North American Carbon Program disturbance synthesis to discuss techniques and future work needed to better understand carbon dynamics after forest disturbance. Specifically, we address three topics: (1) the history, spatial distribution, and characteristics of different types of disturbance (in particular fire, insects, and harvest) in North America; (2) the integrated measurements and experimental designs required to quantify forest carbon dynamics in the years and decades after disturbance, as presented in a series of case studies; and (3) a synthesis of the greatest uncertainties spanning these studies, as well as the utility of multiple types of observations in understanding their dynamics. The case studies - in the southeast U.S., central boreal Canada, U.S. Rocky Mountains, and Pacific Northwest - explore how different measurements can be used to constrain and understand carbon dynamics in regrowing forests, with the most important measurements summarized for each disturbance type. We identify disturbance severity and history as key but highly uncertain factors driving post-disturbance carbon source-sink dynamics across all disturbance types. We suggest integrative analyses using multiple lines of evidence, increased measurement capabilities, shared models and online data sets, and innovative numerical algorithms hold promise for improved understanding and prediction of carbon dynamics in disturbance-prone forests.

  9. Forest carbon in North America: annual storage and emissions from British Columbia’s harvest, 1965–2065

    Directory of Open Access Journals (Sweden)

    Dymond Caren C

    2012-07-01

    Full Text Available Abstract Background The default international accounting rules estimate the carbon emissions from forest products by assuming all harvest is immediately emitted to the atmosphere. This makes it difficult to assess the greenhouse gas (GHG consequences of different forest management or manufacturing activities that maintain the storage of carbon. The Intergovernmental Panel on Climate Change (IPCC addresses this issue by allowing other accounting methods. The objective of this paper is to provide a new model for estimating annual stock changes of carbon in harvested wood products (HWP. Results The model, British Columbia Harvested Wood Products version 1 (BC-HWPv1, estimates carbon stocks and fluxes for wood harvested in BC from 1965 to 2065, based on new parameters on local manufacturing, updated and new information for North America on consumption and disposal of wood and paper products, and updated parameters on methane management at landfills in the USA. Based on model results, reporting on emissions as they occur would substantially lower BC’s greenhouse gas inventory in 2010 from 48 Mt CO2 to 26 Mt CO2 because of the long-term forest carbon storage in-use and in the non-degradable material in landfills. In addition, if offset projects created under BC’s protocol reported 100 year cumulative emissions using the BC-HWPv1 the emissions would be lower by about 11%. Conclusions This research showed that the IPCC default methods overestimate the emissions North America wood products. Future IPCC GHG accounting methods could include a lower emissions factor (e.g. 0.52 multiplied by the annual harvest, rather than the current multiplier of 1.0. The simulations demonstrated that the primary opportunities for climate change mitigation are in shifting from burning mill waste to using the wood for longer-lived products.

  10. Soil Organic Carbon dynamics in agricultural soils of Veneto Region

    Science.gov (United States)

    Bampa, F. B.; Morari, F. M.; Hiederer, R. H.; Toth, G. T.; Giandon, P. G.; Vinci, I. V.; Montanarella, L. M.; Nocita, M.

    2012-04-01

    One of the eight soil threats expressed in the European Commission's Thematic Strategy for Soil Protection (COM (2006)231 final) it's the decline in Soil Organic Matter (SOM). His preservation is recognized as with the objective to ensure that the soils of Europe remain healthy and capable of supporting human activities and ecosystems. One of the key goals of the strategy is to maintain and improve Soil Organic Carbon (SOC) levels. As climate change is identified as a common element in many of the soil threats, the European Commission (EC) intends to assess the actual contribution of the soil protection to climate change mitigation and the effects of climate change on the possible depletion of SOM. A substantial proportion of European land is occupied by agriculture, and consequently plays a crucial role in maintaining natural resources. Organic carbon preservation and sequestration in the EU's agricultural soils could have some potential to mitigate the effects of climate change, particularly linked to preventing certain land use changes and maintaining SOC stocks. The objective of this study is to assess the SOC dynamics in agricultural soils (cropland and grassland) at regional scale, focusing on changes due to land use. A sub-objective would be the evaluation of the most used land management practices and their effect on SOC content. This assessment aims to determine the geographical distribution of the potential GHG mitigation options, focusing on hot spots in the EU, where mitigation actions would be particularly efficient and is linked with the on-going work in the JRC SOIL Action. The pilot area is Veneto Region. The data available are coming from different sources, timing and involve different variables as: soil texture, climate, soil disturbance, managements and nutrients. The first source of data is the LUCAS project (Land Use/Land Cover Area Frame statistical Survey). Started in 2001, the LUCAS project aims to monitor changes in land cover/use and

  11. Bacterioplankton and organic carbon dynamics in the lower mesohaline chesapeake bay.

    Science.gov (United States)

    Jonas, R B; Tuttle, J H

    1990-03-01

    The mesohaline portion of the Chesapeake Bay is subject to annual summertime hypoxia and anoxia in waters beneath the pycnocline. This dissolved oxygen deficit is directly related to salinity-based stratification of the water column in combination with high levels of autochthonously produced organic matter and a very high abundance of metabolically active bacteria. Throughout the water column in the lower, mesohaline part of the bay, between the Potomac and Rappahannock rivers, near the southern limit of the mainstem anoxia, bacterial abundance often exceeded 10 x 10 cells per ml and bacterial production exceeded 7 x 10 cells per liter per day during summer. Bacterial biomass averaged 34% (range, 16 to 126%) of the phytoplankton biomass in summer. These values are equal to or greater than those found farther north in the bay, where the oxygen deficit is more severe. Seasonal variations in bacterial abundance and production were correlated with phytoplankton biomass (lag time, 7 to 14 days), particulate organic carbon and nitrogen, and particulate biochemical oxygen demand in spring; but during summer, they were significantly correlated only with dissolved biochemical oxygen demand. During summer, dissolved biochemical oxygen demand can account for 50 to 60% of the total biochemical oxygen demand throughout the water column and 80% in the bottom waters. There is a clear spring-summer seasonal shift in the production of organic matter and in the coupling of bacteria and autochthonous organic matter. The measurement of dissolved, microbially labile organic matter concentrations is crucial in understanding the trophic dynamics of the lower mesohaline part of the bay. The absolute levels of organic matter in the water column and the bacterial-organic carbon relationships suggest that a lower bay source of organic matter fuels the upper mesohaline bay oxygen deficits. PMID:16348148

  12. Modeling Potential Distribution and Carbon Dynamics of Natural Terrestrial Ecosystems: A Case Study of Turkey

    Directory of Open Access Journals (Sweden)

    Can Ertekin

    2007-10-01

    Full Text Available We derived a simple model that relates the classification of biogeoclimatezones, (coexistence and fractional coverage of plant functional types (PFTs, and patternsof ecosystem carbon (C stocks to long-term average values of biogeoclimatic indices in atime- and space-varying fashion from climate–vegetation equilibrium models. ProposedDynamic Ecosystem Classification and Productivity (DECP model is based on the spatialinterpolation of annual biogeoclimatic variables through multiple linear regression (MLRmodels and inverse distance weighting (IDW and was applied to the entire Turkey of780,595 km2 on a 500 m x 500 m grid resolution. Estimated total net primary production(TNPP values of mutually exclusive PFTs ranged from 108 26 to 891 207 Tg C yr-1under the optimal conditions and from 16 7 to 58 23 Tg C yr-1 under the growth-limiting conditions for all the natural ecosystems in Turkey. Total NPP values ofcoexisting PFTs ranged from 178 36 to 1231 253 Tg C yr-1 under the optimalconditions and from 23 8 to 92 31 Tg C yr-1 under the growth-limiting conditions. Thenational steady state soil organic carbon (SOC storage in the surface one meter of soil wasestimated to range from 7.5 1.8 to 36.7 7.8 Pg C yr-1 under the optimal conditions andfrom 1.3 0.7 to 5.8 2.6 Pg C yr-1 under the limiting conditions, with the national range of 1.3 to 36.7 Pg C elucidating 0.1% and 2.8% of the global SOC value (1272.4 Pg C, respectively. Our comparisons with literature compilations indicate that estimated patterns of biogeoclimate zones, PFTs, TNPP and SOC storage by the DECP model agree reasonably well with measurements from field and remotely sensed data.

  13. Modeling Potential Distribution and Carbon Dynamics of Natural Terrestrial Ecosystems: A Case Study of Turkey

    Science.gov (United States)

    Evrendilek, Fatih; Berberoglu, Suha; Gulbeyaz, Onder; Ertekin, Can

    2007-01-01

    We derived a simple model that relates the classification of biogeoclimate zones, (co)existence and fractional coverage of plant functional types (PFTs), and patterns of ecosystem carbon (C) stocks to long-term average values of biogeoclimatic indices in a time- and space-varying fashion from climate–vegetation equilibrium models. Proposed Dynamic Ecosystem Classification and Productivity (DECP) model is based on the spatial interpolation of annual biogeoclimatic variables through multiple linear regression (MLR) models and inverse distance weighting (IDW) and was applied to the entire Turkey of 780,595 km2 on a 500 m × 500 m grid resolution. Estimated total net primary production (TNPP) values of mutually exclusive PFTs ranged from 108 ± 26 to 891 ± 207 Tg C yr-1 under the optimal conditions and from 16 ± 7 to 58 ± 23 Tg C yr-1 under the growth-limiting conditions for all the natural ecosystems in Turkey. Total NPP values of coexisting PFTs ranged from 178 ± 36 to 1231 ± 253 Tg C yr-1 under the optimal conditions and from 23 ± 8 to 92 ± 31 Tg C yr-1 under the growth-limiting conditions. The national steady state soil organic carbon (SOC) storage in the surface one meter of soil was estimated to range from 7.5 ± 1.8 to 36.7 ± 7.8 Pg C yr-1 under the optimal conditions and from 1.3 ± 0.7 to 5.8 ± 2.6 Pg C yr-1 under the limiting conditions, with the national range of 1.3 to 36.7 Pg C elucidating 0.1% and 2.8% of the global SOC value (1272.4 Pg C), respectively. Our comparisons with literature compilations indicate that estimated patterns of biogeoclimate zones, PFTs, TNPP and SOC storage by the DECP model agree reasonably well with measurements from field and remotely sensed data.

  14. Carbon and nitrogen dynamics in a soil profile: Model development

    Science.gov (United States)

    Batlle-Aguilar, Jordi; Brovelli, Alessandro; Barry, D. Andrew

    2010-05-01

    In order to meet demands for crops, pasture and firewood, the rate of land use change from forested to agricultural uses has steadily increased over several decades, resulting in an increased release of nutrients towards groundwater and surface water bodies. In parallel, the degradation of riparian zones has diminished their capacity to provide critical ecosystem functions, such as the ability to control and buffer nutrient cycles. In recent years, however, the key environmental importance of natural, healthy ecosystems has been progressively recognized and restoration of degraded lands towards their former natural state has become an area of active research worldwide. Land use changes and restoration practices are known to affect both soil nutrient dynamics and their transport to neighbouring areas. To this end, in order to interpret field experiments and elucidate the different mechanisms taking place, numerical tools are beneficial. Microbiological transformations of the soil organic matter, including decomposition and nutrient turnover are controlled to a large extent by soil water content, influenced in turn by climatic and environmental conditions such as precipitation and evapotranspiration. The work presented here is part of the Swiss RECORD project (http://www.cces.ethz.ch/projects/nature/Record), a large collaborative research effort undertaken to monitor the changes in ecosystem functioning in riparian areas undergoing restoration. In this context we have developed a numerical model to simulate carbon and nitrogen transport and turnover in a one-dimensional variably saturated soil profile. The model is based on the zero-dimensional mechanistic batch model of Porporato et al. (Adv. Water Res., 26: 45-58, 2003), but extends its capabilities to simulate (i) the transport of the mobile components towards deeper horizons, and (ii) the vertical evolution of the profile and the subsequent distribution of the organic matter. The soil is divided in four

  15. Long-term Black Carbon Dynamics in Cultivated Soil

    Energy Technology Data Exchange (ETDEWEB)

    Nguyen, Binh T; Lehmann, Johannes C; Kinyangi, James; Smernik, Ron; Riha, Susan J; Engelhard, Mark H

    2008-07-01

    Black carbon (BC) is a quantitatively important C pool in the global carbon cycle due to its relative recalcitrance against decay compared with other C pools. However, how rapidly BC is oxidized and in what way the molecular structure changes during decomposition over decadal time scales, is largely unknown. In the present study, the long-term dynamics in quality and quantity of BC were investigated in cultivated soil using X-ray Photoelectron Spectroscopy (XPS), Fourier-Transform Infrared (FTIR) and Nuclear Magnetic Resonance (NMR) techniques. BC particles, obtained from soil samples at 8 conversion ages stretching over 100 years and from a forest soil sample from Kenya, were manually picked under a light microscope for characterization and quantification. BC contents rapidly decreased from 12.7 to 3.8 mg C g⁻¹ soil during the first 30 years since conversion, after which they slowly decreased to a steady state at 3.51 mg C g ⁻¹soil. BC-derived C losses over 100 years were estimated at 6000 kg C ha⁻¹ to a depth of 0.1 m. The initial rapid changes in BC stocks resulted in a mean residence time of only around 8.3 years, which was likely a function of both decomposition as well as transport processes. The molecular properties of BC changed more rapidly on surfaces than in the interior of BC particles and more rapidly during the first 30 years than during the following 70 years. The Oc/C ratios (Oc is O bound to C) and carbonyl groups (C=O) increased over time by 133 and 192 %, respectively, indicating oxidation was an important degradation process controlling BC quality. Al, Si, polysaccharides, and to a lesser extent Fe were rapidly adsorbed on BC particle surfaces within the first few years after BC deposition to soil. The protection by physical and chemical stabilization was apparently sufficient to not only minimize decomposition below detection between 30 and 100 years after deposition, but also physical export by erosion and vertical transport below 0

  16. Spatial and seasonal dynamics of riverine carbon fluxes of the Brantas catchment in East Java

    Science.gov (United States)

    Aldrian, Edvin; Chen, Chen-Tung Arthur; Adi, Seno; Prihartanto, null; Sudiana, Nana; Nugroho, Sutopo Purwo

    2008-09-01

    Dissolved and particulate organic and inorganic carbon concentrations and flux were measured from July 2005 to June 2006 in the Brantas River basin, a midsized tropical mountainous river and the second largest in Java. There were large seasonal differences in carbon fluxes. Dissolved inorganic carbon (DIC) fluxes were 9.3 times greater and dissolved organic carbon (DOC) fluxes were 532 times greater in the wet season (October to April) than in the dry season. These large contrasts in concentration lead to large differences in load between dry and wet months. In the wet season between January and April, DIC and DOC fluxes are 66% and 87%, respectively, of the total annual fluxes. Most of the annual fluxes of total suspended solids (2.7 × 106 t a-1), total dissolved solids (2.3 × 106 t a-1), DIC (0.26 × 106 t a-1), and DOC (0.2 × 106 t a-1) are transported into the Madura Strait. Accordingly, the Brantas River ranks number 17 among the top 20 rivers that originate at elevations above 3000 m. The concentration of DIC is consistently high all yearlong due to carbonate weathering in the river basin, except in the middle part of the basin, whereas the concentration of DOC is highly seasonal because of variations in biological activities. The total inorganic carbon concentration substantially exceeded the total organic carbon concentration, but the differences decreased from January to April when DOC increased sharply. The carbon budget indicates that the upstream river is a carbon source, and the middle sections of the river are a carbon sink. No carbon trapping was observed by the several impoundments over the basin while sediment trapping was obvious.

  17. Management Impacts on Carbon Dynamics in a Sierra Nevada Mixed Conifer Forest.

    Science.gov (United States)

    Dore, Sabina; Fry, Danny L; Collins, Brandon M; Vargas, Rodrigo; York, Robert A; Stephens, Scott L

    2016-01-01

    Forest ecosystems can act as sinks of carbon and thus mitigate anthropogenic carbon emissions. When forests are actively managed, treatments can alter forests carbon dynamics, reducing their sink strength and switching them from sinks to sources of carbon. These effects are generally characterized by fast temporal dynamics. Hence this study monitored for over a decade the impacts of management practices commonly used to reduce fire hazards on the carbon dynamics of mixed-conifer forests in the Sierra Nevada, California, USA. Soil CO2 efflux, carbon pools (i.e. soil carbon, litter, fine roots, tree biomass), and radial tree growth were compared among un-manipulated controls, prescribed fire, thinning, thinning followed by fire, and two clear-cut harvested sites. Soil CO2 efflux was reduced by both fire and harvesting (ca. 15%). Soil carbon content (upper 15 cm) was not significantly changed by harvest or fire treatments. Fine root biomass was reduced by clear-cut harvest (60-70%) but not by fire, and the litter layer was reduced 80% by clear-cut harvest and 40% by fire. Thinning effects on tree growth and biomass were concentrated in the first year after treatments, whereas fire effects persisted over the seven-year post-treatment period. Over this period, tree radial growth was increased (25%) by thinning and reduced (12%) by fire. After seven years, tree biomass returned to pre-treatment levels in both fire and thinning treatments; however, biomass and productivity decreased 30%-40% compared to controls when thinning was combined with fire. The clear-cut treatment had the strongest impact, reducing ecosystem carbon stocks and delaying the capacity for carbon uptake. We conclude that post-treatment carbon dynamics and ecosystem recovery time varied with intensity and type of treatments. Consequently, management practices can be selected to minimize ecosystem carbon losses while increasing future carbon uptake, resilience to high severity fire, and climate related

  18. Molecular dynamics simulation on mechanical property of carbon nanotube torsional deformation

    Institute of Scientific and Technical Information of China (English)

    Chen Ming-Jun; Liang Ying-Chun; Li Hong-Zhu; Li Dan

    2006-01-01

    In this paper torsional deformation of the carbon nanotubes is simulated by molecular dynamics method. The Brenner potential is used to set up the simulation system. Simulation results show that the carbon nanotubes can bear larger torsional deformation, for the armchair type (10,10) single wall carbon nanotubes, with a yielding phenomenon taking place when the torsional angle is up to 63°(1.1rad). The influence of carbon nanotube helicity in torsional deformation is very small. The shear modulus of single wall carbon nanotubes should be several hundred GPa, not 1 GPa as others reports.

  19. Annual dynamics of wild bee densities: attractiveness and productivity effects of oilseed rape.

    Science.gov (United States)

    Riedinger, Verena; Mitesser, Oliver; Hovestadt, Thomas; Steffan-Dewenter, Ingolf; Holzschuh, Andrea

    2015-05-01

    Mass-flowering crops may affect long-term population dynamics, but effects on pollinators have never been studied across several years. We monitored wild bees in oilseed rape fields in 16 landscapes in Germany in two consecutive years. Effects on bee densities of landscape oilseed rape cover in the years of monitoring and in the previous years were evaluated with landscape data from three consecutive years. We fit empirical data to a mechanistic model to provide estimates for oilseed rape attractiveness and its effect on bee productivity in comparison to the rest of the landscape, and we evaluated consequences for pollinator densities in consecutive years. Our results show that high oilseed rape cover in the previous year enhances current densities of wild bees (except for bumble bees). Moreover, we show a strong attractiveness of and dilution on (i.e., decreasing bee densities with increasing landscape oilseed rape cover) oilseed rape for bees during flowering in the current year, modifying the effect of the previous year's oilseed rape cover in the case of wild bees (excluding Bombus). As long as other factors such as nesting sites or natural enemies do not limit bee reproduction, our findings suggest long-term positive effects of mass-flowering crops on bee populations, at least for non-Bombus generalists, which possibly help to maintain crop pollination services even when crop area increases. Similar effects are conceivable for other organisms providing ecosystem services in annual crops and should be considered in future studies. PMID:26236848

  20. Annual dynamics of North Sea bacterioplankton: seasonal variability superimposes short-term variation.

    Science.gov (United States)

    Lucas, Judith; Wichels, Antje; Teeling, Hanno; Chafee, Meghan; Scharfe, Mirco; Gerdts, Gunnar

    2015-09-01

    The dynamics of coastal marine microbial communities are driven by seasonally changing abiotic and biotic factors as well as by rapidly occurring short-term changes such as river fresh water influxes or phytoplankton blooms. We examined the variability of the free-living bacterioplankton at Helgoland Roads (German Bight, North Sea) over a period of one year with high temporal and taxonomic resolution to reveal variation patterns and main influencing factors. 16S rRNA gene tag sequencing of the bacterioplankton community hints at annual recurrence and resilience of few main taxa belonging to Alphaproteobacteria, Betaproteobacteria, Flavobacteriia, Acidimicrobiia and Thermoplasmata. Multiple regression analyses with various environmental factors revealed changes in water current patterns and resulting phytoplankton blooms as the main driving factors for short-term variation and temperature as the overlying factor for seasonal variation. Comparison of bacterioplankton successions during spring and summer phytoplankton blooms revealed the same dominating Flavobacteriia operational taxonomic units (OTUs) but shifts in Roseobacter related OTUs (Alphaproteobacteria) and SAR92 clade members (Gammaproteobacteria). Network analysis suggests that during spring and summer phytoplankton blooms temperature-dependent guilds are formed. In conclusion, our data imply that short-term bacterioplankton successions in response to phytoplankton blooms are indirectly affected by temperature, which is a major niche-defining factor in the German Bight. PMID:26298013

  1. Organic carbon dynamics in mangrove ecosystems: a review

    OpenAIRE

    Kristensen, E.; BOUILLON, S; Dittmar, T.; Marchand, C

    2008-01-01

    Our current knowledge on production, composition, transport, pathways and transformations of organic carbon in tropical mangrove environments is reviewed and discussed. Organic carbon entering mangrove foodwebs is either produced autochthonously or imported by tides and/or rivers. Mangrove litter and benthic microalgae are usually the most important autochthonous carbon sources. Depending on local conditions, phytoplankton and seagrass detritus imported with tides may represent a significant ...

  2. The dynamics simulation of Ne atom injected into single-wall carbon nanotube

    International Nuclear Information System (INIS)

    The dynamical processes of Ne atom injected into single-wall carbon nanotube (SWCNT) are modeled with molecular dynamics simulations. The threshold energies to encapsulate rare-gas atoms in SWCNT are presented. The range of tube radius for stable oscillation is revealed, which is independent of the type of carbon nanotubes. And the oscillatory frequency is sensitive to the change in the diameter, the length and chirality of the tube

  3. Two novel low-power and high-speed dynamic carbon nanotube full-adder cells

    OpenAIRE

    Eshghi Mohammad; Bagherizadeh Mehdi

    2011-01-01

    Abstract In this paper, two novel low-power and high-speed carbon nanotube full-adder cells in dynamic logic style are presented. Carbon nanotube field-effect transistors (CNFETs) are efficient in designing a high performance circuit. To design our full-adder cells, CNFETs with three different threshold voltages (low threshold, normal threshold, and high threshold) are used. First design generates SUM and COUT through separate transistors, and second design is a multi-output dynamic full adde...

  4. Spatial dynamics of carbon storage: a case study from Turkey.

    Science.gov (United States)

    Sivrikaya, Fatih; Baskent, Emin Zeki; Bozali, Nuri

    2013-11-01

    Forest ecosystems have an important role in carbon cycle at both regional and global scales as an important carbon sink. Forest degradation and land cover changes, caused by deforestation and conversion to non-forest area, have a strong impact on carbon storage. The carbon storage of forest biomass and its changes over time in the Hartlap planning unit of the southeastern part of Turkey have been estimated using the biomass expansion factor method based on field measurements of forests plots with forest inventory data between 1991 and 2002. The amount of carbon storage associated with land use and land cover changes were also analyzed. The results showed that the total forested area of the Hartlap planning unit slightly increased by 2.1%, from 27,978.7 ha to 28,282.6 ha during the 11-year period, and carbon storage increased by 9.6%, from 390,367.6 to 427,826.9 tons. Carbon storage of conifer and mixed forests accounted for about 70.6% of carbon storage in 1991, and 67.8% in 2002 which increased by 14,274.6 tons. Land use change and increasing forest area have a strong influence on increasing biomass and carbon storage. PMID:23771281

  5. Dynamics of Intracellular Polymers in Enhanced Biological Phosphorus Removal Processes under Different Organic Carbon Concentrations

    OpenAIRE

    Lizhen Xing; Li Ren; Bo Tang,; Guangxue Wu; Yuntao Guan

    2013-01-01

    Enhanced biological phosphorus removal (EBPR) may deteriorate or fail during low organic carbon loading periods. Polyphosphate accumulating organisms (PAOs) in EBPR were acclimated under both high and low organic carbon conditions, and then dynamics of polymers in typical cycles, anaerobic conditions with excess organic carbons, and endogenous respiration conditions were examined. After long-term acclimation, it was found that organic loading rates did not affect the yield of PAOs and the app...

  6. Impact of Environmental Factors on the Carbon Dynamics at Hooghly Estuarine Region

    OpenAIRE

    Joyita Mukherjee; Moitreyee Banerjee; Arnab Banerjee; Madhumita Roy; Phani Bhusan Ghosh; Santanu Ray

    2014-01-01

    Degradation of litter from mangrove forests adjacent to the creeks at Sagar Island of the Hooghly-Matla estuarine ecosystem is one of the principal sources of nutrient to the estuary. This system receives a major load of carbon from adjacent mangrove forest in the form of litterfall throughout the year. Keeping in view, the effect of environmental factor on the dynamics of carbon is studied through multivariate statistics. Essential environmental variables like soil carbon,...

  7. Responses of Carbon Dynamics to Nitrogen Deposition in Typical Freshwater Wetland of Sanjiang Plain

    OpenAIRE

    2014-01-01

    The effects of nitrogen deposition (N-deposition) on the carbon dynamics in typical Calamagrostis angustifolia wetland of Sanjiang Plain were studied by a pot-culture experiment during two continuous plant growing seasons. Elevated atmospheric N-deposition caused significant increases in the aboveground net primary production and root biomass; moreover, a preferential partition of carbon to root was also observed. Different soil carbon fractions gained due to elevated N-deposition and their r...

  8. Impact of Environmental Factors on the Carbon Dynamics at Hooghly Estuarine Region

    Directory of Open Access Journals (Sweden)

    Joyita Mukherjee

    2014-01-01

    Full Text Available Degradation of litter from mangrove forests adjacent to the creeks at Sagar Island of the Hooghly-Matla estuarine ecosystem is one of the principal sources of nutrient to the estuary. This system receives a major load of carbon from adjacent mangrove forest in the form of litterfall throughout the year. Keeping in view, the effect of environmental factor on the dynamics of carbon is studied through multivariate statistics. Essential environmental variables like soil carbon, dissolved carbon, temperature, salinity, pH, and dissolved oxygen are analyzed following standard protocol. Multivariate statistical analyses like correlation, regression, and centered PCA ordination are done in order to know the impact of environmental variables on carbon dynamics. The results reflect a close intercorrelation among the studied environmental variables and carbon. It also emphasizes the fact that soil and water temperature, and dissolved oxygen affect soil carbon dynamics, whereas salinity and pH of soil and water greatly regulate dissolved carbon dynamics. The variance pattern of these studied variables through seasons is also enumerated by PCA ordination studies.

  9. Effect of Initial Principal Stress Direction on the Dynamic Characteristics of Carbonate Sand

    Institute of Scientific and Technical Information of China (English)

    Yu Haizhen; Zhao Wenguang; Wang Ren; Li Jianguo; He Yang

    2005-01-01

    The dynamic characteristics of carbonate sand under wave loads are very important for constructions on the ocean floor. The initial principal stress direction has been known to exert some influence on the dynamic characteristics of sand during cyclic loading. In an effort to investigate this aspect of the problem, several series of cyclic undrained tests were carried out on a saturated and loose sample of carbonate sand using a geotechnical static and dynamic universal triaxial shear apparatus. In this test apparatus, a hollow cylindrical sand specimen is subjected to a simultaneous application of both triaxial and torsional modes of shear stresses, which brings about the continuous rotation of principal stress axes. The test results indicated that the initial principal stress direction has a considerable influence on the dynamic strength of loose carbonate sand and with the increase of initial orientation of principal stress, dynamic strength will be reduced, the cyclic pore pressure increased, but the residual pore pressure reduced.

  10. Organic carbon dynamics in mangrove ecosystems: a review

    NARCIS (Netherlands)

    Kristensen, E.; Bouillon, S.; Dittmar, T.; Marchand, C.

    2008-01-01

    Our current knowledge on production, composition, transport, pathways and transformations of organic carbon in tropical mangrove environments is reviewed and discussed. Organic carbon entering mangrove foodwebs is either produced autochthonously or imported by tides and/or rivers. Mangrove litter an

  11. Molecular DYNAmics of Soil Organic carbon (DYNAMOS ): a project focusing on soils and carbon through data and modeling

    Science.gov (United States)

    Mendez-Millan, Mercedes

    2010-05-01

    Here we present the first results of the DynaMOS project whose main issue is the build-up of a new generation of soil carbon model. The modeling will describe together soil organic geochemistry and soil carbon dynamics in a generalized, quantitative representation. The carbon dynamics time scale envisaged here will cover the 1 to 1000 yr range and describe molecule behaviours (i.e.)carbohydrate, peptide, amino acid, lignin, lipids, their products of biodegradation and uncharacterized carbonaceous species of biological origin. Three main characteristics define DYNAMOS model originalities: it will consider organic matter at the molecular scale, integrate back to global scale and account for component vertical movements. In a first step, specific data acquisition will concern the production, fate and age of carbon of individual organic compounds. Dynamic parameters will be acquired by compound-specific carbon isotope analysis of both 13C and 14C, by GC/C/IR-MS and AMS. Sites for data acquisition, model calibration and model validation will be chosen on the base of their isotopic history and environmental constraints: 13C natural labeling (with and without C3/C4 vegetation changes), 13C/15N-labelled litter application in both forest and cropland. They include some long-term experiments owned by the partners themselves plus a worldwide panel of sites. In a second step the depth distribution of organic species, isotopes and ages in soils (1D representation) will be modeled by coupling carbon dynamics and vertical movement. Besides the main objective of providing a robust soil carbon dynamics model, DYNAMOS will assess and model the alteration of the isotopic signature of molecules throughout decay and create a shared database of both already published and new data of compound specific information. Issues of the project will concern different scientific fields: global geochemical cycles by refining the description of the terrestrial carbon cycle and entering the chemical

  12. Population dynamics of Agriophyllum squarrosum, a pioneer annual plant endemic to mobile sand dunes, in response to global climate change

    OpenAIRE

    Qian, Chaoju; Yin, Hengxia; Shi, Yong; Zhao, Jiecai; Yin, Chengliang; Luo, Wanyin; Dong, Zhibao; Chen, Guoxiong; Yan, Xia; Wang, Xiao-Ru; Ma, Xiao-Fei

    2016-01-01

    Climate change plays an important role in the transition of ecosystems. Stratigraphic investigations have suggested that the Asian interior experienced frequent transitions between grassland and desert ecosystems as a consequence of global climate change. Using maternally and bi-parentally inherited markers, we investigated the population dynamics of Agriophyllum squarrosum (Chenopodiaceae), an annual pioneer plant endemic to mobile sand dunes. Phylogeographic analysis revealed that A. squarr...

  13. Northern peatland carbon stocks and dynamics: a review

    Directory of Open Access Journals (Sweden)

    Z. Yu

    2012-04-01

    Full Text Available Here I review different approaches and associated uncertainties of estimates in the literature of carbon stocks and found that there is most likely 500 (± 100 range gigatons of carbon (Gt C in northern peatlands. The greatest uncertainty for all the approaches is the lack or insufficient representation of data, including depth, bulk density and carbon accumulation data, especially from the world's large peatlands. Several ways to improve estimates of peat carbon stocks were also discussed in this paper. Changes in peatland carbon stocks over time, estimated using Sphagnum (peat moss spore data and down-core peat accumulation records, show different patterns during the Holocene. Considering long-term peat decomposition using peat accumulation data allows estimates of net carbon sequestration rates by peatlands, or net ecosystem carbon balance (NECB, which indicates more than half of peat carbon (> 270 Gt C was sequestrated before 7000 yr ago during the Holocene. Contemporary carbon flux studies at 5 peatland sites show much larger NECB during the last decade (32 ± 7.8 (S.E. g C m−2 yr−1 than during the last 7000 yr (~ 11 g C m−2 yr−1 as modeled from peat records across northern peatlands. This discrepancy highlights the urgent need for carbon accumulation data and process understanding, especially at decadal and centennial timescales, that would bridge current knowledge gaps and facilitate comparisons of NECB across all timescales.

  14. Patterns and predictability in the intra-annual organic carbon variability across the boreal and hemiboreal landscape.

    Science.gov (United States)

    Hytteborn, Julia K; Temnerud, Johan; Alexander, Richard B; Boyer, Elizabeth W; Futter, Martyn N; Fröberg, Mats; Dahné, Joel; Bishop, Kevin H

    2015-07-01

    Factors affecting total organic carbon (TOC) concentrations in 215 watercourses across Sweden were investigated using parameter parsimonious regression approaches to explain spatial and temporal variabilities of the TOC water quality responses. We systematically quantified the effects of discharge, seasonality, and long-term trend as factors controlling intra-annual (among year) and inter-annual (within year) variabilities of TOC by evaluating the spatial variability in model coefficients and catchment characteristics (e.g. land cover, retention time, soil type). Catchment area (0.18-47,000 km2) and land cover types (forests, agriculture and alpine terrain) are typical for the boreal and hemiboreal zones across Fennoscandia. Watercourses had at least 6 years of monthly water quality observations between 1990 and 2010. Statistically significant models (pstreamflow were identified in 209 of 215 watercourses with a mean Nash-Sutcliffe efficiency index of 0.44. Increasing long-term trends were observed in 149 (70%) of the watercourses, and intra-annual variation in TOC far exceeded inter-annual variation. The average influences of the discharge and seasonality terms on intra-annual variations in daily TOC concentration were 1.4 and 1.3 mg l(-1) (13 and 12% of the mean annual TOC), respectively. The average increase in TOC was 0.17 mg l(-1)year(-1) (1.6% year(-1)). Multivariate regression with over 90 different catchment characteristics explained 21% of the spatial variation in the linear trend coefficient, less than 20% of the variation in the discharge coefficient and 73% of the spatial variation in mean TOC. Specific discharge, water residence time, the variance of daily precipitation, and lake area, explained 45% of the spatial variation in the amplitude of the TOC seasonality. Because the main drivers of temporal variability in TOC are seasonality and discharge, first-order estimates of the influences of climatic variability and change on TOC concentration should

  15. Carbonate chemistry dynamics and biological processes along a river-sea gradient (Gulf of Trieste, northern Adriatic Sea)

    Science.gov (United States)

    Ingrosso, Gianmarco; Giani, Michele; Cibic, Tamara; Karuza, Ana; Kralj, Martina; Del Negro, Paola

    2016-03-01

    In this paper we investigated, for two years and with a bi-monthly frequency, how physical, chemical, and biological processes affect the marine carbonate system in a coastal area characterized by high alkalinity riverine discharge (Gulf of Trieste, northern Adriatic Sea, Mediterranean Sea). By combining synoptic measurements of the carbonate system with in situ determinations of the primary production (14C incorporation technique) and secondary prokaryotic carbon production (3H-leucine incorporation) along a river-sea gradient, we showed that the conservative mixing between river endmember and off-shore waters was the main driver of the dissolved inorganic carbon (DIC) distribution and seasonal variation. However, during spring and summer seasons also the influence of biological uptake and release of DIC was significant. In the surface water of June 2012, the spreading and persistence of nutrient-rich freshwater stimulated the primary production (3.21 μg C L- 1 h- 1) and net biological DIC decrease (- 100 μmol kg- 1), reducing the dissolved CO2 concentration and increasing the pHT. Below the pycnocline of August 2012, instead, an elevated bacterial carbon production rate (0.92 μg C L- 1 h- 1) was related with net DIC increase (92 μmol kg- 1), low dissolved oxygen concentration, and strong pHT reduction, suggesting the predominance of bacterial heterotrophic respiration over primary production. The flux of carbon dioxide estimated at the air-sea interface exerted a low influence on the seasonal variation of the carbonate system. A complex temporal and spatial dynamic of the air-sea CO2 exchange was also detected, due to the combined effects of seawater temperature, river discharge, and water circulation. On annual scale the system was a sink of atmospheric CO2. However, in summer and during elevated riverine discharges, the area close to the river's mouth acted as a source of carbon dioxide. Also the wind speed was crucial in controlling the air-sea CO2

  16. Seasonal dynamics of carbon and nutrients from two contrasting tropical floodplain systems in the Zambezi River Basin

    Directory of Open Access Journals (Sweden)

    A. L. Zuijdgeest

    2015-07-01

    Full Text Available Floodplains are important biogeochemical reactors during fluvial transport of carbon and nutrient species towards the oceans. In the tropics and subtropics pronounced rainfall seasonality results in highly dynamic floodplain biogeochemistry. Massive construction of hydropower dams, however, has significantly altered the hydrography and chemical characteristics of many (subtropical rivers. In this study, we compare organic matter and nutrient biogeochemistry of two large, contrasting floodplains in the Zambezi River Basin in Southern Africa, the Barotse Plains and the Kafue Flats. Both systems are of comparable size, but differ in anthropogenic influence: while the Barotse Plains are still relatively pristine, the Kafue Flats are bordered by two hydropower dams. While the Barotse Plains retain particles during the wet season, annual yields of particulate organic carbon and nitrogen are higher than previously reported for the Zambezi and other tropical rivers. Enhanced wet-season runoff adds soil-derived dissolved organic carbon and nitrogen to the Zambezi River, with a corresponding increase in the Barotse Plains. Soil-derived organic matter dominates the particulate phase year-round in the Barotse Plains, and a varying influence of C3- and C4-plant vegetation can be observed throughout the year. In contrast to the Barotse Plains, net export of particulate matter from the Kafue Flats has been observed during the wet season, but over an annual cycle, the Kafue Flats are effectively accumulating dissolved carbon and nutrients. In the Kafue Flats, the runoff-induced increase in dissolved organic carbon and nitrogen concentrations is delayed by the upstream dam operation. The dam reservoir also causes a shift in the source of the particulate organic matter – from soil-derived during the dry season to aquatically produced in the wet season – in the downstream Kafue Flats. Spatial zonation in vegetation and temporal flooding dynamics in the Kafue

  17. Plant-soil interactions and soil carbon dynamics under climate extremes

    Science.gov (United States)

    Bahn, Michael

    2016-04-01

    Climate extremes have been suggested to increase significantly in intensity and frequency in the coming decades, and may influence ecosystem processes and the carbon cycle more profoundly than gradual climate warming. While there is a growing understanding of plant-soil interactions in extreme environments and from lab experiments, we still know very little about how such interactions affect soil carbon dynamics in real-world ecosystems exposed to climate extremes. In this talk I will give a brief overview of the topic and will present evidence from in-situ experiments on plant-soil interactions and their consequences for soil carbon dynamics under severe drought.

  18. Using city-wide mobile noise assessments to estimate bicycle trip annual exposure to Black Carbon.

    Science.gov (United States)

    Dekoninck, Luc; Botteldooren, Dick; Int Panis, Luc

    2015-10-01

    Several studies have shown that a significant amount of daily air pollution exposure, in particular Black Carbon (BC), is inhaled during bicycle trips. Previously, the instantaneous BC exposure of cyclists was modeled as the sum of a background concentration and a local traffic related component based on a local assessment of traffic noise. We present a fast and low cost methodology to achieve a city-wide assessment of yearly average BC exposure of cyclists along their trips, based on a city-wide mobile noise sensing campaign. The methodology requires participatory sensing measurements of noise, partially combined with BC and/or other air pollutants sensitive to local traffic variations. The combined measurements cover the spatial and meteorological variability and provide the data for an instantaneous exposure model. The mobile noise-only measurements map the full city; and yearly meteorology statistics are used to extrapolate the instantaneous exposure model to a yearly average map of in-traffic air pollution exposure. Less than four passages at each segment along the network with mobile noise equipment are necessary to reach a standard error of 500 ng/m(3) for the yearly average BC exposure. A strong seasonal effect due to the BC background concentration is detected. The background contributes only 25% to the total trip exposure during spring and summer. During winter the background component increases to 50-60%. Engine related traffic noise along the bicyclist's route is a valid indicator of the BC exposure along the route, independent of the seasonal background. Low exposure route selection results in an exposure reduction of 35% in winter and 60% in summer, sensitive to the weather conditions, specific trip attributes and the available alternatives. The methodology is relevant for further research into the local effects of air pollution on health. Mobile noise mapping adds local traffic data including traffic dynamics into the air pollution exposure

  19. Dynamic powder compaction of rapidly solidified Path A alloy with increased carbon and titanium content

    International Nuclear Information System (INIS)

    The objective of this study is to show the potential of the dynamic powder compaction technique to consolidate rapidly solidified Path A alloys and to develop microstructures with improved irradiation performance in the fusion environment. Samples of rapidly solidified and dynamically compacted Path A alloy with increased carbon and titanium content have been included in alloy development irradiation experiments

  20. Carbon allocation to biomass production of leaves, fruits and woody organs at seasonal and annual scale in a deciduous- and evergreen temperate forest

    Directory of Open Access Journals (Sweden)

    M. Campioli

    2010-10-01

    Full Text Available Carbon taken up by the forest canopy is allocated to tree organs for biomass production and respiration. Because tree organs have different life span and decomposition rate, the tree C allocation determines the residence time of C in the ecosystem and its C cycling rate. The study of the carbon-use efficiency, or ratio between net primary production (NPP and gross primary production (GPP, represents a convenient way to analyse the C allocation at the stand level. Previous studies mostly focused on comparison of the annual NPP-GPP ratio among forests of different functional types, biomes and age. In this study, we extend the current knowledge by assessing (i the annual NPP-GPP ratio and its interannual variability (for five years for five tree organs (leaves, fruits, branches, stem and coarse roots, and (ii the seasonal dynamic of NPP-GPP ratio of leaves and stems, for two stands dominated by European beech and Scots pine.

    The average NPP-GPP ratio for the beech stand (38% was similar to previous estimates for temperate deciduous forests, whereas the NPP-GPP ratio for the pine stand (17% is the lowest recorded till now in the literature. The proportion of GPP allocated to leaf NPP was similar for both species, whereas beech allocated a remarkable larger proportion of GPP to wood NPP than pine (29% vs. 6%, respectively. The interannual variability of the NPP-GPP ratio for wood was substantially larger than the interannual variability of the NPP-GPP ratio for leaves, fruits and overall stand and it is likely to be controlled by previous year air temperature (both species, previous year drought intensity (beech and thinning (pine. Seasonal pattern of NPP-GPP ratio greatly differed between beech and pine, with beech presenting the largest ratio in early season, and pine a more uniform ratio along the season. For beech, NPP-GPP ratio of leaves and stems peaked during the same period in the early season, whereas they peaked in opposite periods

  1. Annual benthic metabolism and organic carbon fluxes in a semi-enclosed Mediterranean bay dominated by the macroalgae Caulerpa prolifera.

    Directory of Open Access Journals (Sweden)

    Sergio eRuiz-Halpern

    2014-12-01

    Full Text Available Coastal areas play an important role on carbon cycling. Elucidating the dynamics on the production, transport and fate of organic carbon is relevant to gain a better understanding of the role coastal areas play in the global carbon budget. Here, we assess the metabolic status and associated organic carbon fluxes of a semi-enclosed Mediterranean bay supporting a meadow of Caulerpa prolifera. We test whether the EDOC pool is a significant component of the organic carbon pool and associated fluxes in this ecosystem. The Bay of Portocolom was in net metabolic balance on a yearly basis, but heterotrophic during the summer months. Community respiration (CR was positively correlated to C. prolifera biomass, while net community production (NCP had a negative correlation. The benthic compartment represented, on average, 72.6 ± 5.2 % of CR and 86.8 ± 4.5 % of gross primary production (GPP. Dissolved organic carbon (DOC production peaked in summer and was always positive, with the incubations performed in the dark almost doubling the flux of those performed in the light. Exchangeable dissolved organic carbon (EDOC, however, oscillated between production and uptake, being completely recycled within the system and representing around 14% of the DOC flux. The pools of bottom and surface DOC were high for an oligotrophic environment, and were positively correlated to the pool of EDOC. Thus, despite being in metabolic balance, this ecosystem acted as a conduit for organic carbon (OC, as it is able to export OC to adjacent areas derived from allochtonous inputs during heterotrophic conditions. These inputs likely come from groundwater discharge, human activity in the watershed, delivered to the sediments through the high capacity of C. prolifera to remove particles from the water column, and from the air-water exchange of EDOC, demonstrating that these communities are a major contributor to the cycling of OC in coastal embayments.

  2. Responses of Carbon Dynamics to Nitrogen Deposition in Typical Freshwater Wetland of Sanjiang Plain

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    Yang Wang

    2014-01-01

    Full Text Available The effects of nitrogen deposition (N-deposition on the carbon dynamics in typical Calamagrostis angustifolia wetland of Sanjiang Plain were studied by a pot-culture experiment during two continuous plant growing seasons. Elevated atmospheric N-deposition caused significant increases in the aboveground net primary production and root biomass; moreover, a preferential partition of carbon to root was also observed. Different soil carbon fractions gained due to elevated N-deposition and their response intensities followed the sequence of labile carbon > dissolved organic carbon > microbial biomass carbon, and the interaction between N-deposition and flooded condition facilitated the release of different carbon fractions. Positive correlations were found between CO2 and CH4 fluxes and liable carbon contents with N-deposition, and flooded condition also tended to facilitate CH4 fluxes and to inhibit the CO2 fluxes with N-deposition. The increases in soil carbon fractions occurring in the nitrogen treatments were significantly correlated with increases in root, aboveground parts, total biomass, and their carbon uptake. Our results suggested that N-deposition could enhance the contents of active carbon fractions in soil system and carbon accumulation in plant of the freshwater wetlands.

  3. Convergence of Phenological and Physiological Control on Annual Terrestrial Carbon Dioxide Uptake

    Science.gov (United States)

    Xia, J.; Luo, Y.; Niu, S.; Hui, D.; Dong, J.; Chen, J.; Weng, E.; Li, J.

    2013-12-01

    Despite enormous variations in vegetation type, climate, and soil from tropics to tundra, we found terrestrial gross primary production (GPP) is fundamentally under a joint control of the length of CO2 uptake period (CUP) and seasonal physiological maximal capacity of CO2 uptake (GPPmax). Across 213 globally distributed sites of eddy covariance, the ratio (ɛ) of terrestrial annual GPP to the product of CUP and GPPmax converges to a quite narrow range (90% values in 0.61-0.83). In North America, the satellite-based ɛ converges to 0.60-0.70 in most regions ranging from the Arctic down to the middle of the U.S., and gradually increases toward 1.0 in the tropical regions in the west coast of Mexico and the Caribbean region. The changes in averaged annual GPP across North America from 2000 to 2010 cannot be explained by either GPPmax or CUP alone, but is well interpreted by their combination. We further detected the recent increasing trends in annual GPP in North America is more contributed by CUP in northwestern Canada but by GPPmax in most other regions. In most biomes and regions, GPPmax is more important than CUP in regulating the spatiotemporal variability of terrestrial annual GPP. Although the causes for the converged ɛ remain unclear, it may be largely determined by the co-variation between the lengths of CUP and the stable phase of GPPmax. Our findings provide significant insights into the underlying mechanism of variations in terrestrial annual GPP, which can improve our understanding of the intricate GPP responses to the ongoing multiple-factor environmental changes and the large uncertainty in predicted future land CO2 uptake among different terrestrial biosphere models.

  4. Annual variation of strato-mesospheric carbon monoxide measured by ground-based Fourier transform infrared spectrometry

    Directory of Open Access Journals (Sweden)

    V. Velazco

    2007-01-01

    Full Text Available We present long-term time-series of strato-mesospheric CO vertical columns measured from stations located in Antarctica, mid-latitudes and the Arctic, covering the period from 1997–2005. The instrument and the measurement technique allows the separation of tropospheric and strato-mesospheric contributions to the CO column, therefore providing information on the chemistry and dynamics both at low and high altitudes. Data from polar stations show a similar annual variability of strato-mesospheric CO with a strong maximum in late winter and spring. A small enhancement in late summer for some stations, which we call the "summer bulge", can be seen occasionally. Generally, the mid-latitude stations show no significant annual variability of strato-mesospheric CO columns. Measurements were compared with a two-dimensional chemistry-transport model of the middle atmosphere. The annual and latitudinal variations of CO are reproduced well by a model run including thermospheric CO. Comparison with two model scenarios show that the polar winter maximum is due solely to downward transport of thermospheric CO, while CHOx chemistry in the stratosphere could probably contribute to the summer maximum.

  5. Single-Wall Carbon Nanotube Growth from Graphite Layers-a Tight Binding Molecular Dynamics Simulation

    Institute of Scientific and Technical Information of China (English)

    Yuntuan FANG; Min ZHU; Yongshun WANG

    2003-01-01

    The growth of single-wall carbon nanotube from graphite layers is studied by tight binding molecular dynamics simulation. Given temperature of 2500 K or 3500 K and an interval of 0.25 nm for the two layers of graphite, a single-wall carbon nanotube with a zigzag shell will be produced. On the other conditions the carbon nanotube cannot grow or grows with too many defects. All carbon nanotube ends have pentagons which play an important role during the tube ends closing.

  6. Comparison of carbon dynamics in tropical and temperate soils using radiocarbon measurements

    OpenAIRE

    Trumbore, Susan E.

    1993-01-01

    The magnitude and timing of the response of the soil carbon reservoir to changes in land use or climate is a large source of uncertainty in global carbon cycle models. One method of assessing soil carbon dynamics, based on modeling the observed increase of 14C in organic matter pools during the 30 years since atmospheric weapons testing ended, is described in this paper. Differences in the inventory and residence time of carbon are observed in organic matter from soils representing tropical (...

  7. 5.04 - Carbon Dioxide and Methane Dynamics in Estuaries

    OpenAIRE

    Borges, Alberto; Abril, Gwenaël

    2011-01-01

    Estuaries profoundly transform the large amounts of carbon delivered from rivers before their transfer to the adjacent coastal zone. As a consequence of the complex biogeochemical reworking of allochthonous carbon in the sediments and the water column, CO2 and CH4 are emitted into the atmosphere. We attempt to synthesize available knowledge on biogeochemical cycling of CO2 and CH4 in estuarine environments, with a particular emphasis on the exchange with the atmosphere. Unlike CH4, the global...

  8. WIMP detection and slow ion dynamics in carbon nanotube arrays

    OpenAIRE

    Cavoto, G.; Cirillo, E. N. M.; Cocina, F.; Ferretti, J.; Polosa, A.D.

    2016-01-01

    Large arrays of aligned carbon nanotubes (CNTs), open at one end, could be used as target material for the directional detection of weakly interacting dark matter particles (WIMPs). As a result of a WIMP elastic scattering on a CNT, a carbon ion might be injected in the body of the array and propagate through multiple collisions within the lattice. The ion may eventually emerge from the surface with open end CNTs, provided that its longitudinal momentum is large enough to compensate energy lo...

  9. Moss and soil contributions to the annual net carbon flux of a maturing boreal forest

    Science.gov (United States)

    Harden, J.W.; O'Neill, K. P.; Trumbore, S.E.; Veldhuis, H.; Stocks, B.J.

    1997-01-01

    We used input and decomposition data from 14C studies of soils to determine rates of vertical accumulation of moss combined with carbon storage inventories on a sequence of burns to model how carbon accumulates in soils and moss after a stand-killing fire. We used soil drainage - moss associations and soil drainage maps of the old black spruce (OBS) site at the BOREAS northern study area (NSA) to areally weight the contributions of each moderately well drained, feathermoss areas; poorly drained sphagnum - feathermoss areas; and very poorly drained brown moss areas to the carbon storage and flux at the OBS NSA site. On this very old (117 years) complex of black spruce, sphagnum bog veneer, and fen systems we conclude that these systems are likely sequestering 0.01-0.03 kg C m-2 yr-' at OBS-NSA today. Soil drainage in boreal forests near Thompson, Manitoba, controls carbon storage and flux by controlling moss input and decomposition rates and by controlling through fire the amount and quality of carbon left after burning. On poorly drained soils rich in sphagnum moss, net accumulation and long-term storage of carbon is higher than on better drained soils colonized by feathermosses. The carbon flux of these contrasting ecosystems is best characterized by soil drainage class and stand age, where stands recently burned are net sources of CO2, and maturing stands become increasingly stronger sinks of atmospheric CO2. This approach to measuring carbon storage and flux presents a method of scaling to larger areas using soil drainage, moss cover, and stand age information.

  10. Carbon dynamics in subtropical forest soil. Effects of atmospheric carbon dioxide enrichment and nitrogen addition

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Juxiu X.; Zhou, Guoyi Y.; Zhang, Deqiang Q.; Duan, Honglang L.; Deng, Qi; Zhao, Liang [Chinese Academy of Sciences, Guangzhou (China). South China Botanical Garden; Xu, Zhihong H. [Griffith Univ., Nathan, Queensland (Australia). Environmental Futures Centre and School of Biomolecular and Physical Sciences

    2010-06-15

    The levels of atmospheric carbon dioxide concentration ([CO{sub 2}]) are rapidly increasing. Understanding carbon (C) dynamics in soil is important for assessing the soil C sequestration potential under elevated [CO{sub 2}]. Nitrogen (N) is often regarded as a limiting factor in the soil C sequestration under future CO{sub 2} enrichment environment. However, few studies have been carried out to examine what would happen in the subtropical or tropical areas where the ambient N deposition is high. In this study, we used open-top chambers to study the effect of elevated atmospheric [CO{sub 2}] alone and together with N addition on the soil C dynamics in the first 4 years of the treatments applied in southern China. Materials and methods Above- and below-ground C input (tree biomass) into soil, soil respiration, soil organic C, and total N as well as dissolved organic C (DOC) were measured periodically in each of the open-top chambers. Soil samples were collected randomly in each chamber from each of the soil layers (0-20, 20-40, and 40-60 cm) using a standard soil sampling tube (2.5-cm inside diameter). Soil leachates were collected at the bottom of the chamber below-ground walls in stainless steel boxes. Results and discussion The highest above- and below-ground C input into soil was found in the high CO{sub 2} and high N treatment (CN), followed by the only high N treatment (N+), the only high CO{sub 2} treatment (C+), and then the control (CK) without any CO{sub 2} enrichment or N addition. DOC in the leachates was small for all the treatments. Export of DOC played a minor role in C cycling in our experiment. Generally, soil respiration rate in the chambers followed the order: CN treatment > C + treatment > N + treatment > the control. Except for the C+ treatment, there were no significant differences in soil total N among the CN treatment, N + treatment, and the control. Overall, soil organic C (SOC) was significantly affected by the treatments (p < 0.0001). SOC

  11. Inter-annual variability of carbon exchange and extreme events at the Loobos pine forest

    Science.gov (United States)

    Elbers, Jan; Moors, Eddy; Hutjes, Ronald; Jacobs, Cor; Jans, Wilma; Kruijt, Bart; Stolk, Petra; ter Maat, Herbert; Vermeulen, Marleen; Abreu, Pedro

    2013-04-01

    Introduction At the seasonal to inter-annual time scale large variations in net uptake exist as a result of changing weather conditions. It is therefore important to investigate the inter-annual variability of the uptake of forests as accurately as possible and relate it to physiological and physical constraints of the biosphere-atmosphere system. Present model concepts on NEE are well capable to reproduce average conditions, however they fail to reproduce short term variations. If we are able to explain these variations this will help to improve explaining inter-annual variability. We analysed the impact of extremes on inter-annual variation observed in measurements of eddy-covariance fluxes over the years 1997-2012 over a mid-latitude pine forest in The Netherlands. To improve our understanding of these variations, we tried to quantify and make a distinction between variations caused by environmental conditions by means of ecosystem response curves for real and maximum response. We analysed the remaining variation by looking at changes in site conditions, such as aging and nitrogen availability and disturbances caused by abrupt events such as storms, frost, harvest, fire etc. Results Based on annual totals, the inter-annual variability in NEE is the result of variations in Reco and, to a lesser extent, GPP. There is no evidence that annual meteorological averages are the main drivers for inter-annual variation in observed NEE. Response functions However at a monthly time step there is a strong correlation between GPP and radiation and to a lesser extend with temperature and maximum vapour pressure deficit. The correlation with VPDmax reflects the strong control VPD has on the stomatal closure of this eco-system. Reco correlates best with air temperature, marginally better than with superficial soil temperature. Including superficial soil moisture in the function slightly increases the correlation. Fitted response curves show that non-stressed ecosystem

  12. Effect of carbonation on the linear and nonlinear dynamic properties of cement-based materials

    Science.gov (United States)

    Eiras, Jesus N.; Kundu, Tribikram; Popovics, John S.; Monzó, José; Borrachero, María V.; Payá, Jordi

    2016-01-01

    Carbonation causes a physicochemical alteration of cement-based materials, leading to a decrease of porosity and an increase of material hardness and strength. However, carbonation will decrease the pH of the internal pore water solution, which may depassivate the internal reinforcing steel, giving rise to structural durability concerns. Therefore, the proper selection of materials informed by parameters sensitive to the carbonation process is crucial to ensure the durability of concrete structures. The authors investigate the feasibility of using linear and nonlinear dynamic vibration response data to monitor the progression of the carbonation process in cement-based materials. Mortar samples with dimensions of 40×40×160 mm were subjected to an accelerated carbonation process through a carbonation chamber with 55% relative humidity and >95% of CO2 atmosphere. The progress of carbonation in the material was monitored using data obtained with the test setup of the standard resonant frequency test (ASTM C215-14), from a pristine state until an almost fully carbonated state. Linear dynamic modulus, quality factor, and a material nonlinear response, evaluated through the upward resonant frequency shift during the signal ring-down, were investigated. The compressive strength and the depth of carbonation were also measured. Carbonation resulted in a modest increase in the dynamic modulus, but a substantive increase in the quality factor (inverse attenuation) and a decrease in the material nonlinearity parameter. The combined measurement of the vibration quality factor and nonlinear parameter shows potential as a sensitive measure of material changes brought about by carbonation.

  13. Ignoring detailed fast-changing dynamics of land use overestimates regional terrestrial carbon sequestration

    Directory of Open Access Journals (Sweden)

    S. Zhao

    2009-03-01

    Full Text Available Land use change is critical in determining the distribution, magnitude and mechanisms of terrestrial carbon budgets at the local to global scales. To date, almost all regional to global carbon cycle studies are driven by a static land use map or land use change statistics with decadal time intervals. The biases in quantifying carbon exchange between the terrestrial ecosystems and the atmosphere caused by using such land use change information have not been investigated. Here, we used the General Ensemble biogeochemical Modeling System (GEMS, along with consistent and spatially explicit land use change scenarios with different intervals (1 yr, 5 yrs, 10 yrs and static, respectively, to evaluate the impacts of land use change data frequency on estimating regional carbon sequestration in the southeastern United States. Our results indicate that ignoring the detailed fast-changing dynamics of land use can lead to a significant overestimation of carbon uptake by the terrestrial ecosystem. Regional carbon sequestration increased from 0.27 to 0.69, 0.80 and 0.97 Mg C ha−1 yr−1 when land use change data frequency shifting from 1 year to 5 years, 10 years interval and static land use information, respectively. Carbon removal by forest harvesting and prolonged cumulative impacts of historical land use change on carbon cycle accounted for the differences in carbon sequestration between static and dynamic land use change scenarios. The results suggest that it is critical to incorporate the detailed dynamics of land use change into local to global carbon cycle studies. Otherwise, it is impossible to accurately quantify the geographic distributions, magnitudes, and mechanisms of terrestrial carbon sequestration at local to global scales.

  14. Ignoring detailed fast-changing dynamics of land use overestimates regional terrestrial carbon sequestration

    Directory of Open Access Journals (Sweden)

    S. Q. Zhao

    2009-08-01

    Full Text Available Land use change is critical in determining the distribution, magnitude and mechanisms of terrestrial carbon budgets at the local to global scales. To date, almost all regional to global carbon cycle studies are driven by a static land use map or land use change statistics with decadal time intervals. The biases in quantifying carbon exchange between the terrestrial ecosystems and the atmosphere caused by using such land use change information have not been investigated. Here, we used the General Ensemble biogeochemical Modeling System (GEMS, along with consistent and spatially explicit land use change scenarios with different intervals (1 yr, 5 yrs, 10 yrs and static, respectively, to evaluate the impacts of land use change data frequency on estimating regional carbon sequestration in the southeastern United States. Our results indicate that ignoring the detailed fast-changing dynamics of land use can lead to a significant overestimation of carbon uptake by the terrestrial ecosystem. Regional carbon sequestration increased from 0.27 to 0.69, 0.80 and 0.97 Mg C ha−1 yr−1 when land use change data frequency shifting from 1 year to 5 years, 10 years interval and static land use information, respectively. Carbon removal by forest harvesting and prolonged cumulative impacts of historical land use change on carbon cycle accounted for the differences in carbon sequestration between static and dynamic land use change scenarios. The results suggest that it is critical to incorporate the detailed dynamics of land use change into local to global carbon cycle studies. Otherwise, it is impossible to accurately quantify the geographic distributions, magnitudes, and mechanisms of terrestrial carbon sequestration at the local to global scales.

  15. Projecting pest population dynamics under global warming: the combined effect of inter- and intra-annual variations.

    Science.gov (United States)

    Zidon, Royi; Tsueda, Hirotsugu; Morin, Efrat; Morin, Shai

    2016-06-01

    The typical short generation length of insects makes their population dynamics highly sensitive not only to mean annual temperatures but also to their intra-annual variations. To consider the combined effect of both thermal factors under global warming, we propose a modeling framework that links general circulation models (GCMs) with a stochastic weather generator and population dynamics models to predict species population responses to inter- and intra-annual temperature changes. This framework was utilized to explore future changes in populations of Bemisia tabaci, an invasive insect pest-species that affects multiple agricultural systems in the Mediterranean region. We considered three locations representing different pest status and climatic conditions: Montpellier (France), Seville (Spain), and Beit-Jamal (Israel). We produced ensembles of local daily temperature realizations representing current and future (mid-21st century) climatic conditions under two emission scenarios for the three locations. Our simulations predicted a significant increase in the average number of annual generations and in population size, and a significant lengthening of the growing season in all three locations. A negative effect was found only in Seville for the summer season, where future temperatures lead to a reduction in population size. High variability in population size was observed between years with similar annual mean temperatures, suggesting a strong effect of intra-annual temperature variation. Critical periods were from late spring to late summer in Montpellier and from late winter to early summer in Seville and Beit-Jamal. Although our analysis suggested that earlier seasonal activity does not necessarily lead to increased populations load unless an additional generation is produced, it is highly likely that the insect will become a significant pest of open-fields at Mediterranean latitudes above 40° during the next 50 years. Our simulations also implied that current

  16. Carbon dynamics in highly heterotrophic subarctic thaw ponds

    Directory of Open Access Journals (Sweden)

    T. Roiha

    2015-07-01

    Full Text Available Global warming has accelerated the formation of permafrost thaw ponds in several subarctic and arctic regions. These ponds are net heterotrophic as evidenced by their greenhouse gas (GHG supersaturation levels (CO2 and CH4, and generally receive large terrestrial carbon inputs from the thawing and eroding permafrost. We measured seasonal and vertical variations in the concentration and type of dissolved organic matter (DOM in five subarctic thaw (thermokarst ponds in northern Quebec, and explored how environmental gradients influenced heterotrophic and phototrophic biomass and productivity. Late winter DOM had low aromaticity indicating reduced inputs of terrestrial carbon, while the high concentration of dissolved organic carbon (DOC suggests that some production of non-chromophoric dissolved compounds by the microbial food web took place under the ice cover. Summer DOM had a strong terrestrial signature, but was also characterized with significant inputs of algal-derived carbon, especially at the pond surface. During late winter, bacterial production was low (maximum of 0.8 mg C m−3 d−1 and was largely based on free-living bacterioplankton (58 %. Bacterial production in summer was high (up to 58 mg C m−3 d−1, dominated by particle-attached bacteria (67 %, and strongly correlated to the amount of terrestrial carbon. Primary production was restricted to summer surface waters due to strong light limitation deeper in the water column or in winter. The phototrophic biomass was equal to the heterotrophic biomass, but as the algae were mostly composed of mixotrophic species, most probably they used bacteria rather than solar energy in such shaded ponds. According to the δ13C analyses, non-algal carbon supported 51 % of winter and 37 % of summer biomass of the phantom midge larvae, Chaoborus sp., that are at the top of the trophic chain. Our results point to a strong heterotrophic energy pathway in these thaw pond ecosystems, where

  17. Carbon dynamics in highly heterotrophic subarctic thaw ponds

    Science.gov (United States)

    Roiha, T.; Laurion, I.; Rautio, M.

    2015-07-01

    Global warming has accelerated the formation of permafrost thaw ponds in several subarctic and arctic regions. These ponds are net heterotrophic as evidenced by their greenhouse gas (GHG) supersaturation levels (CO2 and CH4), and generally receive large terrestrial carbon inputs from the thawing and eroding permafrost. We measured seasonal and vertical variations in the concentration and type of dissolved organic matter (DOM) in five subarctic thaw (thermokarst) ponds in northern Quebec, and explored how environmental gradients influenced heterotrophic and phototrophic biomass and productivity. Late winter DOM had low aromaticity indicating reduced inputs of terrestrial carbon, while the high concentration of dissolved organic carbon (DOC) suggests that some production of non-chromophoric dissolved compounds by the microbial food web took place under the ice cover. Summer DOM had a strong terrestrial signature, but was also characterized with significant inputs of algal-derived carbon, especially at the pond surface. During late winter, bacterial production was low (maximum of 0.8 mg C m-3 d-1) and was largely based on free-living bacterioplankton (58 %). Bacterial production in summer was high (up to 58 mg C m-3 d-1), dominated by particle-attached bacteria (67 %), and strongly correlated to the amount of terrestrial carbon. Primary production was restricted to summer surface waters due to strong light limitation deeper in the water column or in winter. The phototrophic biomass was equal to the heterotrophic biomass, but as the algae were mostly composed of mixotrophic species, most probably they used bacteria rather than solar energy in such shaded ponds. According to the δ13C analyses, non-algal carbon supported 51 % of winter and 37 % of summer biomass of the phantom midge larvae, Chaoborus sp., that are at the top of the trophic chain. Our results point to a strong heterotrophic energy pathway in these thaw pond ecosystems, where bacterioplankton dominates

  18. Carbon dioxide and methane annual emissions from two boreal reservoirs and nearby lakes in Quebec, Canada

    Directory of Open Access Journals (Sweden)

    M. Demarty

    2009-03-01

    Full Text Available The results of dissolved GHG (CO2 and CH4 measurement campaigns carried out in Quebec (Canada during the open-water periods and under-ice in a newly created reservoir (Eastmain 1, a 25 year old reservoir (Robert-Bourassa and in three reference lakes are presented. While CO2 partial pressures varied with season with a net increase under the ice cover, CH4 partial pressures did not. We were able to extrapolate the highest CO2 partial pressures reached in the different studied systems just before ice break-up with high spring emission period. We then estimated the springtime CO2 fluxes and compared them to annual CO2 fluxes and GHG fluxes. Thus we clearly demonstrated that in our systems CH4 fluxes was of minor importance in the GHG emissions, CO2 fluxes representing around 90% of the annual fluxes. We also pointed out the importance of springtime emissions in the annual budget.

  19. Molecular Dynamics Simulation of Formaldehyde Adsorption and Diffusion in Single-Wall Carbon Nanotube

    Institute of Scientific and Technical Information of China (English)

    Pin Lv; Zhenan Tang; Jun Yu; Yanbing Xue

    2006-01-01

    For gas sensor application, adsorption and diffusion of formaldehyde gas in single-wall carbon nanotube were investigated by using molecular dynamics simulation. The conformations of formaldehyde molecule adsorbed in carbon nanotube were optimized according to principle of minimum energy. The axis of conformatiot is parallel to the axis of carbon nanotube and about 0.3 nm~0.4 nm away from carbon nanotube wall. The conformation, which is different from that of the formaldehyde molecule in the gas-phase, rotates around carbon nanotube axis. The adsorption energy and diffusivity of formaldehyde molecule in single-wall carbon nanotube is of-56.2 kJ/mol and of 0.2× 10-4 cm2/s, respectively.

  20. Aggregate structure and stability linked to carbon dynamics in a south Chilean Andisol

    Science.gov (United States)

    Huygens, D.; Boeckx, P.; van Cleemput, O.; Godoy, R.; Oyarzún, C.

    2005-02-01

    The extreme vulnerability of soil organic carbon to climate and land use change emphasizes the need for further research in different terrestrial ecosystems. We have studied the aggregate stability and carbon dynamics in a chronosequence of three different land uses in a south Chilean Andisols: a second growth Nothofagus obliqua forest (SGFOR), a grassland (GRASS) and a Pinus radiata plantation (PINUS). The aim of this study was to investigate the role of Al as soil organic matter stabilizing agent in this Andisol. In a case study, we linked differences in carbon dynamics between the three land use treatments to physical protection and recalcitrance of the soil organic matter (SOM). In this study, C aggregate stability and dynamics were studied using size and density fractionation experiments of the SOM, δ13C and total carbon analysis of the different SOM fractions, and mineralization measurements. The results showed that electrostatic attractions between and among Al-oxides and clay minerals are mainly responsible for the stabilization of soil aggregates and the physical protection of the enclosed soil organic carbon. Whole soil C mineralization rate constants were highest for SGFOR and PINUS, followed by GRASS. In contrast, incubation experiments of isolated macro organic matter fractions showed that the recalcitrance of the SOM decreased in another order: PINUS > SGFOR > GRASS. We concluded that physical protection of soil aggregates was the main process determining whole soil C mineralization. Land use changes affected soil organic carbon dynamics in this south Chilean Andisol by altering soil pH and consequently available Al.

  1. Gasification of disordered carbons (chars). Annual Progress Report for Period August 1, 1979-October 31, 1980

    Energy Technology Data Exchange (ETDEWEB)

    Walker, P.L. Jr.; Jenkins, R.G.

    1980-06-01

    It has been shown that rates of gasification of chars derived from coals vary widely with the rank of coal and the gasification medium used. Variation in rates is thought to be attributable to: (i) variation in active surface area and (ii) extent to which gasification is catalyzed by inorganic impurities present. It is the main objective of this research to confirm this hypothesis for carbons of different morphologies, including disordered carbons (chars). Initially studies are being performed on the carbon-oxygen reaction. This report covers progress in research in three areas: (i) measurement of rate constants for the adsorption step in the reaction of O/sub 2/ with a high purity char at low pressures, (ii) design and construction of a high pressure reactor to be used to measure rate constants for the desorption step in the reaction of O/sub 2/ with carbons, and (iii) development of small angle x-ray scattering (SAXS) to characterize both dispersion of catalysts supported on carbon and the micropore system of chars.

  2. Instituto Nacional del Carbon (INCAR) Consejo Superior de Investigaciones Cientificas (CSIC) annual report 2007; Instituto Nacional del Carbon (INCAR), Consejo Superior de Investigaciones Cientificas (CSIC) memoria de actividades 2007

    Energy Technology Data Exchange (ETDEWEB)

    Concha Prieto Alas (ed.)

    2008-07-01

    The annual report gives facts and figures about INCAR and outlines research lines in organic petrology, coke quality, carbon capture and control, coal utilisation, hydrogen generation, coal carbon materials, materials for generation and purification of hydrogen and energy storage, adsorbents, carbon-carbon composites, synthesis of nanostructured raw materials and valorisation of different residues. The next section gives details of the organisation and structure of INCAR. This is followed by a listing of scientific activities, a record of the organisation's output (publications, lectures, meetings etc.) and details of its national and international scientific corporation, teaching programme (courses and seminars), and research awards.

  3. Estimating Forest Carbon Stock Dynamics from Forest Inventories, Disturbance Data and Simulation Models: An Integrated Analysis for British Columbia

    Science.gov (United States)

    Kurz, W. A.; Beukema, S. J.; Robinson, D. C.; Apps, M. J.

    2001-12-01

    Forest inventories and growth and yield projection systems are an integral part of modern forest management. This information is commonly used for the long-term planning of annual allowable cuts and timber supply analysis. A strategy for the use of such information in a comprehensive, regional carbon budget model was developed and implemented for British Columbia, Canada. Data readily accessible from forest information systems include the area, stratification and attributes (including merchantable volume) of forests. Growth and yield tables or empirical models provide the required information on stand dynamics. Disturbance statistics (harvest, fire, insects) describe the dynamics of the forest area. Temporary and permanent sample plots provide millions of tree measurements that were used in the conversion of volume to biomass estimates. Methods previously developed for the Carbon Budget Model of the Canadian Forest Sector (CBM-CFS2) were used to calculate belowground biomass and to establish the various dead organic matter pools. Inventory data are nearly complete, except for a small portion of the total forest area. Land-use change statistics are available for forest roads, but not yet for other causes of land-use change. A modified version of the CBM-CFS2 was used to calculate C stocks and stock changes for the period 2000 to 2032. Results indicate that ecosystem C stocks in the timber harvest land base are changing very little, with between-year variability of - 20 to + 20 Tg C / year. In contrast, ecosystem C stocks in the non-timber harvest land base are increasing at a rate of about 100 Tg C / year, largely because of the absence of harvesting and the assumed rates of future fire and insect disturbances, which could be the result of protection efforts. Actual disturbance rates, observed in future years, could have large impacts on C stock changes. Annual changes in C stocks will also be influenced by climate variability. Growth and yield models predict

  4. Carbon dynamics and ecosystem diversity of Amazonian peatlands

    Energy Technology Data Exchange (ETDEWEB)

    Laehteenoja, O.

    2011-07-01

    The overall aim was to initiate peatland research in Amazonia, which has been referred to as 'one of the large white spots on the global peatland map'. Specifically, the study was to clarify how common peat accumulation is on Amazonian floodplains, and how extensive and thick peat deposits can be encountered. Secondly, the intention was to study how rapidly Amazonian peatlands sequester carbon, and how much carbon they store and thirdly, to gain some understanding of the diversity of peatland ecosystem types and of the processes forming these ecosystems

  5. The changing global carbon cycle: Linking plant-soil carbon dynamics to global consequences

    Science.gov (United States)

    Chapin, F. S., III; McFarland, J.; McGuire, David A.; Euskirchen, E.S.; Ruess, R.W.; Kielland, K.

    2009-01-01

    Most current climate-carbon cycle models that include the terrestrial carbon (C) cycle are based on a model developed 40 years ago by Woodwell & Whittaker (1968) and omit advances in biogeochemical understanding since that time. Their model treats net C emissions from ecosystems as the balance between net primary production (NPP) and heterotrophic respiration (HR, i.e. primarily decomposition).

  6. Dynamic analysis of the urban-based low-carbon policy using system dynamics: Focused on housing and green space

    International Nuclear Information System (INIS)

    To systematically manage the energy consumption of existing buildings, the government has to enforce greenhouse gas reduction policies. However, most of the policies are not properly executed because they do not consider various factors from the urban level perspective. Therefore, this study aimed to conduct a dynamic analysis of an urban-based low-carbon policy using system dynamics, with a specific focus on housing and green space. This study was conducted in the following steps: (i) establishing the variables of urban-based greenhouse gases (GHGs) emissions; (ii) creating a stock/flow diagram of urban-based GHGs emissions; (iii) conducting an information analysis using the system dynamics; and (iv) proposing the urban-based low-carbon policy. If a combined energy policy that uses the housing sector (30%) and the green space sector (30%) at the same time is implemented, 2020 CO2 emissions will be 7.23 million tons (i.e., 30.48% below 2020 business-as-usual), achieving the national carbon emissions reduction target (26.9%). The results of this study could contribute to managing and improving the fundamentals of the urban-based low-carbon policies to reduce greenhouse gas emissions

  7. Dynamic analysis of the urban-based low-carbon policy using system dynamics: Focused on housing and green space

    Science.gov (United States)

    Hong, Taehoon; Kim, Jimin; Koo, Choongwan; Jeong, Kwangbok

    2015-02-01

    To systematically manage the energy consumption of existing buildings, the government has to enforce greenhouse gas reduction policies. However, most of the policies are not properly executed because they do not consider various factors from the urban level perspective. Therefore, this study aimed to conduct a dynamic analysis of an urban-based low-carbon policy using system dynamics, with a specific focus on housing and green space. This study was conducted in the following steps: (i) establishing the variables of urban-based greenhouse gases (GHGs) emissions; (ii) creating a stock/flow diagram of urban-based GHGs emissions; (iii) conducting an information analysis using the system dynamics; and (iv) proposing the urban-based low-carbon policy. If a combined energy policy that uses the housing sector (30%) and the green space sector (30%) at the same time is implemented, 2020 CO2 emissions will be 7.23 million tons (i.e., 30.48% below 2020 business-as-usual), achieving the national carbon emissions reduction target (26.9%). The results of this study could contribute to managing and improving the fundamentals of the urban-based low-carbon policies to reduce greenhouse gas emissions.

  8. ANNUAL REPORT. THE INFLUENCE OF CALCIUM CARBONATE GRAIN COATINGS ON CONTAMINANT REACTIVITY IN VADOSE ZONE SEDIMENTS

    Science.gov (United States)

    The primary objective of this project is to investigate the role of calcium carbonate grain coatings on adsorption and heterogeneous reduction reactions of key chemical and radioactive contaminants in sediments on the Hanford Site. Research will ascertain whether these coatings p...

  9. Physicochemical characteristics and droplet impact dynamics of superhydrophobic carbon nanotube arrays.

    Science.gov (United States)

    Aria, Adrianus I; Gharib, Morteza

    2014-06-17

    The physicochemical and droplet impact dynamics of superhydrophobic carbon nanotube arrays are investigated. These superhydrophobic arrays are fabricated simply by exposing the as-grown carbon nanotube arrays to a vacuum annealing treatment at a moderate temperature. This treatment, which allows a significant removal of oxygen adsorbates, leads to a dramatic change in wettability of the arrays, from mildly hydrophobic to superhydrophobic. Such change in wettability is also accompanied by a substantial change in surface charge and electrochemical properties. Here, the droplet impact dynamics are characterized in terms of critical Weber number, coefficient of restitution, spreading factor, and contact time. Based on these characteristics, it is found that superhydrophobic carbon nanotube arrays are among the best water-repellent surfaces ever reported. The results presented herein may pave a way for the utilization of superhydrophobic carbon nanotube arrays in numerous industrial and practical applications, including inkjet printing, direct injection engines, steam turbines, and microelectronic fabrication. PMID:24866696

  10. Impact of water table level on annual carbon and greenhouse gas balances of a restored peat extraction area

    Directory of Open Access Journals (Sweden)

    J. Järveoja

    2015-10-01

    Full Text Available Peatland restoration may provide a potential after-use option to mitigate the negative climate impact of abandoned peat extraction areas; currently, however, knowledge about restoration effects on the annual balances of carbon (C and greenhouse gas (GHG exchanges is still limited. The aim of this study was to investigate the impact of contrasting water table levels (WTL on the annual C and GHG balances of restoration treatments with high (Res-H and low (Res-L WTL relative to an unrestored bare peat (BP site. Measurements of carbon dioxide (CO2, methane (CH4 and nitrous oxide (N2O fluxes were conducted over a full year using the closed chamber method and complemented by measurements of abiotic controls and vegetation cover. Three years following restoration, the difference in the mean WTL resulted in higher bryophyte and lower vascular plant cover in Res-H relative to Res-L. Consequently, greater gross primary production and autotrophic respiration associated with greater vascular plant cover were observed in Res-L compared to Res-H. However, the means of the measured net ecosystem CO2 exchanges (NEE were not significantly different between Res-H and Res-L. Similarly, no significant differences were observed in the respective means of CH4 and N2O exchanges in Res-H and Res-L, respectively. In comparison to the two restored sites, greater net CO2, similar CH4 and greater N2O emissions occurred in BP. On the annual scale, Res-H, Res-L and BP were C sources of 111, 103 and 268 g C m−2 yr−1 and had positive GHG balances of 4.1, 3.8 and 10.2 t CO2 eq ha−1 yr−1, respectively. Thus, the different WTLs had a limited impact on the C and GHG balances in the two restored treatments three years following restoration. However, the C and GHG balances in Res-H and Res-L were considerably lower than in BP owing to the large reduction in CO2 emissions. This study therefore suggests that restoration may serve as an effective method to mitigate the negative

  11. Impact of water table level on annual carbon and greenhouse gas balances of a restored peat extraction area

    Science.gov (United States)

    Järveoja, Järvi; Peichl, Matthias; Maddison, Martin; Soosaar, Kaido; Vellak, Kai; Karofeld, Edgar; Teemusk, Alar; Mander, Ülo

    2016-05-01

    Peatland restoration may provide a potential after-use option to mitigate the negative climate impact of abandoned peat extraction areas; currently, however, knowledge about restoration effects on the annual balances of carbon (C) and greenhouse gas (GHG) exchanges is still limited. The aim of this study was to investigate the impact of contrasting mean water table levels (WTLs) on the annual C and GHG balances of restoration treatments with high (ResH) and low (ResL) WTL relative to an unrestored bare peat (BP) site. Measurements of carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) fluxes were conducted over a full year using the closed chamber method and complemented by measurements of abiotic controls and vegetation cover. Three years following restoration, the difference in the mean WTL resulted in higher bryophyte and lower vascular plant cover in ResH relative to ResL. Consequently, greater gross primary production and autotrophic respiration associated with greater vascular plant cover were observed in ResL compared to ResH. However, the means of the measured net ecosystem CO2 exchanges (NEE) were not significantly different between ResH and ResL. Similarly, no significant differences were observed in the respective means of CH4 and N2O exchanges. In comparison to the two restored sites, greater net CO2, similar CH4 and greater N2O emissions occurred in BP. On the annual scale, ResH, ResL and BP were C sources of 111, 103 and 268 g C m-2 yr-1 and had positive GHG balances of 4.1, 3.8 and 10.2 t CO2 eq ha-1 yr-1, respectively. Thus, the different WTLs had a limited impact on the C and GHG balances in the two restored treatments 3 years following restoration. However, the C and GHG balances in ResH and ResL were considerably lower than in BP due to the large reduction in CO2 emissions. This study therefore suggests that restoration may serve as an effective method to mitigate the negative climate impacts of abandoned peat extraction areas.

  12. Dynamic elastic modulus of single-walled carbon nanotubes in different thermal environments

    International Nuclear Information System (INIS)

    This Letter reports the result of investigation on the effect of loading rate (strain rate) on mechanical properties of armchair and zigzag nanotubes in different thermal environments, based on the molecular structural mechanics model in which the primary bonds between two nearest-neighboring carbon atoms are treaded as dimensional 2-node Euler-Bernoulli beam considering the effect of environmental temperature on force constant values of the bonds stretching, bonds angle bending and torsional resistance. Nanoscale finite element simulations of the dynamic Young's modulus of single-walled carbon nanotubes under different strain rates and environmental temperatures reveal that the dynamic Young's modulus of the single-walled carbon nanotubes increases with the increase of strain rate, and decreases significantly with the increase of environment temperature. It is significant that the dynamic Young's modulus of zigzag nanotubes is more sensitive to strain rate and environmental temperature due to the tube chirality

  13. Single-particle and collective dynamics of methanol confined in carbon nanotubes: a computer simulation study

    International Nuclear Information System (INIS)

    We present the results of computer simulations of methanol confined in carbon nanotubes. Different levels of confinement were identified as a function of the nanotube radius and characterized using a pair-distribution function adapted to the cylindrical geometry of these systems. Dynamical properties of methanol were also analysed as a function of the nanotube size, both at the level of single-particle and collective properties. We found that confinement in narrow carbon nanotubes strongly affects the dynamical properties of methanol with respect to the bulk phase, due to the strong interaction with the carbon nanotube. In the other cases, confined methanol shows properties quite similar to those of the bulk phase. These phenomena are related to the peculiar hydrogen bonded network of methanol and are compared to the behaviour of water confined in similar conditions. The effect of nanotube flexibility on the dynamical properties of confined methanol is also discussed.

  14. A dynamic mathematical model for packed columns in carbon capture plants

    DEFF Research Database (Denmark)

    Gaspar, Jozsef; Jørgensen, John Bagterp; Fosbøl, Philip Loldrup

    2015-01-01

    In this paper, we present a dynamic mathematical model for the absorption and desorption columns in a carbon capture plant. Carbon capture plants must be operated in synchronization with the operation of thermal power plants. Dynamic and flexible operation of the carbon capture plant is important...... is suitable for gas-liquid packed columns, e.g. for CO2 absorption and desorption. The model is based on rigorous thermodynamic and conservation principles and it is set up to preserve these properties upon numerical integration in time. The developed model is applied for CO2 absorption and desorption...... process. The response of the model is shown in terms of capture efficiency and purity of the CO2 product stream. The model is aimed for rigorous dynamic simulation in the context of optimization and control strategy development....

  15. Endotoxemia reduces cerebral perfusion but enhances dynamic cerebrovascular autoregulation at reduced arterial carbon dioxide tension*

    DEFF Research Database (Denmark)

    Brassard, Patrice; Kim, Yu-Sok; van Lieshout, Johannes;

    2012-01-01

    OBJECTIVE:: The administration of endotoxin to healthy humans reduces cerebral blood flow but its influence on dynamic cerebral autoregulation remains unknown. We considered that a reduction in arterial carbon dioxide tension would attenuate cerebral perfusion and improve dynamic cerebral...... in arterial carbon dioxide tension explains the improved dynamic cerebral autoregulation and the reduced cerebral perfusion encountered in healthy subjects during endotoxemia.......-104] mm Hg; p = .75), but increased cardiac output (8.3 [6.1-9.5] L·min vs. 6.0 [4.5-8.2] L·min; p = .02) through an elevation in heart rate (82 ± 9 beats·min vs. 63 ± 10 beats·min; p <.001), whereas arterial carbon dioxide tension (37 ± 5 mm Hg vs. 41 ± 2 mm Hg; p <.05) and middle cerebral artery mean...

  16. Effects of carbon substrate lability on carbon mineralization dynamics of tropical peat

    Science.gov (United States)

    Jauhiainen, Jyrki; Silvennoinen, Hanna; Könönen, Mari; Limin, Suwido; Vasander, Harri

    2016-04-01

    Extensive draining at tropical ombrotrophic peatlands in Southeast Asia has made them global 'hot spots' for greenhouse gas emissions. Management practises and fires have led to changed substrate status, which affects microbial processes. Here, we present the first data on how management practises affect carbon (C) mineralization processes at these soils. We compared the carbon mineralization potentials of pristine forest soils to those of drained fire affected soils at various depths, with and without additional labile substrates (glucose, glutamate and NO3-N) and in oxic and anoxic conditions by dedicated ex situ experiments. Carbon mineralization (CO2 and CH4 production) rates were higher in the pristine site peat, which contains more labile carbon due to higher input via vegetation. Production rates decreased with depth together with decreasing availability of labile carbon. Consequently, the increase in production rates after labile substrate addition was relatively modest from pristine site as compared to the managed site and from the top layers as compared to deeper layers. Methanogenesis had little importance in total carbon mineralization. Adding labile C and N enhanced heterotrophic CO2 production more than the sole addition of N. Surprisingly, oxygen availability was not an ultimate requirement for substantial CO2 production rates, but anoxic respiration yielded comparable rates, especially at the pristine soils. Flooding of these sites will therefore reduce, but not completely cease, peat carbon loss. Reintroduced substantial vegetation and fertilization in degraded peatlands can enrich recalcitrant peat with simple C and N compounds and thus increase microbiological activity.

  17. Dynamics of Planktonic Prokaryotes and Dissolved Carbon in a Subtropical Coastal Lake

    OpenAIRE

    Maria Luiza eSchmitz Fontes; Larissa eDalpaz; Denise eTonetta; Regina Vasconcellos Antônio; Maurício ePetrucio

    2013-01-01

    To understand the dynamics of planktonic prokaryotes in a subtropical lake and its relationship with carbon, we conducted water sampling through four 48 h periods in Peri Lake for one year. Planktonic prokaryotes were characterized by the abundance and biomass of heterotrophic bacteria and of cyanobacteria (coccoid and filamentous cells). During all experiments, we measured wind speed, water temperature (WT), pH, dissolved oxygen (DO), precipitation, dissolved organic carbon (DOC), dissolved ...

  18. Thermal rectification of a single-wall carbon nanotube: a molecular dynamics study

    OpenAIRE

    Foulaadvand, M. Ebrahim; Saeedi, Azadeh; Yousefi, Farrokh; Khadesadr, Saeed

    2014-01-01

    We have investigated the thermal rectification phenomenon in a single-wall mass graded carbon nanotube by molecular dynamics simulation. Second generation Brenner potential has been used to model the inter atomic carbon interaction. Fixed boundary condition has been taken into account. We compare our findings to a previous study by Alaghemandi et al which has been done with a different potential and boundary condition. The dependence of the rectification factor $R$ on temperature, nanotube di...

  19. Aggregate structure and stability linked to carbon dynamics in a south Chilean Andisol

    OpenAIRE

    C. Oyarzún; Godoy, R.; O. Van Cleemput; P. Boeckx; Huygens, D.

    2005-01-01

    International audience The extreme vulnerability of soil organic carbon to climate and land use change emphasizes the need for further research in different terrestrial ecosystems. We have studied the aggregate stability and carbon dynamics in a chronosequence of three different land uses in a south Chilean Andisols: a second growth Nothofagus obliqua forest (SGFOR), a grassland (GRASS) and a Pinus radiata plantation (PINUS). The aim of this study was to investigate the role of Al as soil ...

  20. Physicochemical Characteristics and Droplet Impact Dynamics of Superhydrophobic Carbon Nanotube Arrays

    OpenAIRE

    Aria, Adrianus I.; Gharib, Morteza

    2014-01-01

    The physicochemical and droplet impact dynamics of superhydrophobic carbon nanotube arrays are investigated. These superhydrophobic arrays are fabricated simply by exposing the as-grown carbon nanotube arrays to a vacuum annealing treatment at a moderate temperature. This treatment, which allows a significant removal of oxygen adsorbates, leads to a dramatic change in wettability of the arrays, from mildly hydrophobic to superhydrophobic. Such change in wettability is also accompanied by a su...

  1. Static and Dynamic Moduli of Malm Carbonate: A Poroelastic Correlation

    Science.gov (United States)

    Hassanzadegan, Alireza; Guérizec, Romain; Reinsch, Thomas; Blöcher, Guido; Zimmermann, Günter; Milsch, Harald

    2016-06-01

    The static and poroelastic moduli of a porous rock, e.g., the drained bulk modulus, can be derived from stress-strain curves in rock mechanical tests, and the dynamic moduli, e.g., dynamic Poisson's ratio, can be determined by acoustic velocity and bulk density measurements. As static and dynamic elastic moduli are different, a correlation is often required to populate geomechanical models. A novel poroelastic approach is introduced to correlate static and dynamic bulk moduli of outcrop analogues samples, representative of Upper-Malm reservoir rock in the Molasse basin, southwestern Germany. Drained and unjacketed poroelastic experiments were performed at two different temperature levels (30 and 60°). For correlating the static and dynamic elastic moduli, a drained acoustic velocity ratio is introduced, corresponding to the drained Poisson's ratio in poroelasticity. The strength of poroelastic coupling, i.e., the product of Biot and Skempton coefficients here, was the key parameter. The value of this parameter decreased with increasing effective pressure by about 56 ~% from 0.51 at 3 MPa to 0.22 at 73 MPa. In contrast, the maximum change in P- and S-wave velocities was only 3 % in this pressure range. This correlation approach can be used in characterizing underground reservoirs, and can be employed to relate seismicity and geomechanics (seismo-mechanics).

  2. Beyond annual budgets: carbon flux at different temporal scales in fire-prone Siberian Scots pine forests

    International Nuclear Information System (INIS)

    accumulation as a function of time since the last surface fire, but ignores carbon dynamics in the mineral soil. In burned mature lichen type stands, NEPS was 6.2 ± 2.6 mol C/m2/yr (74 ± 31 g C/m2/yr) and thus five times higher than NEPC at the respective age (1.2 ± 0.6 mol C/m2/yr or 14 ± 7 g C/m2/yr). Comparing NEPS and NEPC of mature stands, we estimate that 48% of NPP are consumed by heterotrophic respiration and additional 35% are consumed by recurrent surface fires. As expected, in unburned stands NEPC and NEPS were of similar magnitude. Exploring a site specific model of CWD production and decomposition we estimated that fire reduces the carbon pool of newly produced CWD by 70%. Direct observation revealed that surface fire events consume 50% of the soil organic layer carbon pool (excluding CWD). We conclude that surface fires strongly reduced NEPC. In ecosystems with frequent fire events direct flux measurements using eddy covariance are likely to record high rates of carbon uptake, since they describe the behaviour of ecosystems recovering from fire without capturing the sporadic but substantial fire-related carbon losses

  3. Carbon Budget and its Dynamics over Northern Eurasia Forest Ecosystems

    Science.gov (United States)

    Shvidenko, Anatoly; Schepaschenko, Dmitry; Kraxner, Florian; Maksyutov, Shamil

    2016-04-01

    The presentation contains an overview of recent findings and results of assessment of carbon cycling of forest ecosystems of Northern Eurasia. From a methodological point of view, there is a clear tendency in understanding a need of a Full and Verified Carbon Account (FCA), i.e. in reliable assessment of uncertainties for all modules and all stages of FCA. FCA is considered as a fuzzy (underspecified) system that supposes a system integration of major methods of carbon cycling study (land-ecosystem approach, LEA; process-based models; eddy covariance; and inverse modelling). Landscape-ecosystem approach 1) serves for accumulation of all relevant knowledge of landscape and ecosystems; 2) for strict systems designing the account, 3) contains all relevant spatially distributed empirical and semi-empirical data and models, and 4) is presented in form of an Integrated Land Information System (ILIS). The ILIS includes a hybrid land cover in a spatially and temporarily explicit way and corresponding attributive databases. The forest mask is provided by utilizing multi-sensor remote sensing data, geographically weighed regression and validation within GEO-wiki platform. By-pixel parametrization of forest cover is based on a special optimization algorithms using all available knowledge and information sources (data of forest inventory and different surveys, observations in situ, official statistics of forest management etc.). Major carbon fluxes within the LEA (NPP, HR, disturbances etc.) are estimated based on fusion of empirical data and aggregations with process-based elements by sets of regionally distributed models. Uncertainties within LEA are assessed for each module and at each step of the account. Within method results of LEA and corresponding uncertainties are harmonized and mutually constrained with independent outputs received by other methods based on the Bayesian approach. The above methodology have been applied to carbon account of Russian forests for 2000

  4. Carbon Dynamics in Heathlands in Response to a Changing Climate

    DEFF Research Database (Denmark)

    Nielsen, Pia Lund

    Climate is changing, and more adverse changes are expected in the future. Changes, caused by continuously rising atmospheric concentrations of greenhouse gasses as CO2, will affect ecosystem processes and functions in the future and hence the cycling of carbon. The vaste amount of studies have...... focused on effects of climate change on aboveground biomass, less have been conducted on belowground biomass, and the thesis is one of few studies comprising both above- and belowground biomass and take interactions of climate change factors into account. To follow the fate of carbon in the ecosystem we...... persistent changes over the years. Responses of aboveground and belowground biomass were coupled, and Deschampsia flexuosa showed high ability to adapt to treatments. As the major response was observed belowground, I further studied decomposition of fine roots. Fine roots of Deschampsia flexuosa from deep...

  5. Workshop highlights iron dynamics in ocean carbon cycle

    OpenAIRE

    Johnson, Kenneth S.; Moore, J. Keith; Smith, Walker O

    2002-01-01

    The role of iron in regulating the flux of carbon through the surface layer of the ocean has become increasingly apparent during the past 15 years. Before that time, the analytical challenges of measuring trace (parts per trillion) iron concentrations from iron ships using gear suspended on an iron wire precluded oceanographers from making accurate measurements. Laboratory experiments were invariably conducted with samples that were seriously contaminated with elevated iron concentrations. We...

  6. Ecosystem carbon dynamics in logged forest of Malaysian Borneo

    OpenAIRE

    Saner, P G

    2009-01-01

    The tropical rainforest of Borneo is heavily disturbed by logging, to date less than half of the original forest cover remains. To counteract such development logged forest is rehabilitated to regenerate its natural protective function. In this thesis we consider the carbon budget of logged forest and the ecology of the trees that are planted for rehabilitation. We show that the logged forest under study differs from unlogged forest due to the lack of the dominant trees and hence the organic ...

  7. WIMP detection and slow ion dynamics in carbon nanotube arrays

    CERN Document Server

    Cavoto, G; Cocina, F; Ferretti, J; Polosa, A D

    2016-01-01

    Large arrays of aligned carbon nanotubes (CNTs), open at one end, could be used as target material for the directional detection of weakly interacting dark matter particles (WIMPs). As a result of a WIMP elastic scattering on a CNT, a carbon ion might be injected in the body of the array and propagate through multiple collisions within the lattice. The ion may eventually emerge from the surface with open end CNTs, provided that its longitudinal momentum is large enough to compensate energy losses and its transverse momentum approaches the channeling conditions in a single CNT. Therefore, the angle formed between the WIMP wind apparent orientation and the direction of parallel carbon nanotube axes must be properly chosen. We focus on very low ion recoil kinetic energies, related to low mass WIMPs (~ 10 GeV) where most of the existing experiments have low sensitivity. Relying on some exact results on two-dimensional lattices of circular obstacles, we study the low energy ion motion in the transverse plane with ...

  8. WIMP detection and slow ion dynamics in carbon nanotube arrays

    Science.gov (United States)

    Cavoto, G.; Cirillo, E. N. M.; Cocina, F.; Ferretti, J.; Polosa, A. D.

    2016-06-01

    Large arrays of aligned carbon nanotubes (CNTs), open at one end, could be used as target material for the directional detection of weakly interacting dark matter particles (WIMPs). As a result of a WIMP elastic scattering on a CNT, a carbon ion might be injected in the body of the array and propagate through multiple collisions within the lattice. The ion may eventually emerge from the surface with open end CNTs, provided that its longitudinal momentum is large enough to compensate energy losses and its transverse momentum approaches the channeling conditions in a single CNT. Therefore, the angle formed between the WIMP wind apparent orientation and the direction of parallel carbon nanotube axes must be properly chosen. We focus on very low ion recoil kinetic energies, related to low mass WIMPs (≈ 11 GeV) where most of the existing experiments have low sensitivity. Relying on some exact results on two-dimensional lattices of circular obstacles, we study the low energy ion motion in the transverse plane with respect to CNT directions. New constraints are obtained on how to devise the CNT arrays to maximize the target channeling efficiency.

  9. Olefin metathesis for effective polymer healing via dynamic exchange of strong carbon-carbon bonds

    Science.gov (United States)

    Guan, Zhibin; Lu, Yixuan

    2015-09-15

    A method of preparing a malleable and/or self-healing polymeric or composite material is provided. The method includes providing a polymeric or composite material comprising at least one alkene-containing polymer, combining the polymer with at least one homogeneous or heterogeneous transition metal olefin metathesis catalyst to form a polymeric or composite material, and performing an olefin metathesis reaction on the polymer so as to form reversible carbon-carbon double bonds in the polymer. Also provided is a method of healing a fractured surface of a polymeric material. The method includes bringing a fractured surface of a first polymeric material into contact with a second polymeric material, and performing an olefin metathesis reaction in the presence of a transition metal olefin metathesis catalyst such that the first polymeric material forms reversible carbon-carbon double bonds with the second polymeric material. Compositions comprising malleable and/or self-healing polymeric or composite material are also provided.

  10. Non-Native Plant Litter Enhances Soil Carbon Dioxide Emissions in an Invaded Annual Grassland

    OpenAIRE

    Zhang, Ling; Wang, Hong; Zou, Jianwen; Rogers, William E; Siemann, Evan

    2014-01-01

    Litter decomposition is a fundamental ecosystem process in which breakdown and decay of plant detritus releases carbon and nutrients. Invasive exotic plants may produce litter that differs from native plant litter in quality and quantity. Such differences may impact litter decomposition and soil respiration in ways that depend on whether exotic and native plant litters decompose in mixtures. However, few field experiments have examined how exotic plants affect soil respiration via litter deco...

  11. Dynamic response of a carbon nanotube-based rotary nano device with different carbon-hydrogen bonding layout

    Science.gov (United States)

    Yin, Hang; Cai, Kun; Wan, Jing; Gao, Zhaoliang; Chen, Zhen

    2016-03-01

    In a nano rotational transmission system (RTS) which consists of a single walled carbon nanotube (SWCNT) as the motor and a coaxially arranged double walled carbon nanotube (DWCNT) as a bearing, the interaction between the motor and the rotor in bearing, which has great effects on the response of the RTS, is determined by their adjacent edges. Using molecular dynamics (MD) simulation, the interaction is analyzed when the adjacent edges have different carbon-hydrogen (Csbnd H) bonding layouts. In the computational models, the rotor in bearing and the motor with a specific input rotational speed are made from the same armchair SWCNT. Simulation results demonstrate that a perfect rotational transmission could happen when the motor and rotor have the same Csbnd H bonding layout on their adjacent ends. If only half or less of the carbon atoms on the adjacent ends are bonded with hydrogen atoms, the strong attraction between the lower speed (100 GHz) motor and rotor leads to a synchronous rotational transmission. If only the motor or the rotor has Csbnd H bonds on their adjacent ends, no rotational transmission happens due to weak interaction between the bonded hydrogen atoms on one end with the sp1 bonded carbon atoms on the other end.

  12. Molecular dynamics simulations of the morphology transformations in unzipped carbon nanotubes

    Science.gov (United States)

    Xu, Jiafang; Zhang, Yingnan; Wang, Tao; Zheng, Xin; Li, Wen; Dong, Zihan; Wang, Wensen

    2016-08-01

    Tuning the assembly of carbon nanomaterials to obtain a kaleidoscope of carbon nanostructures is very important and challenging for the development of nanotechnology. Using molecular dynamics simulations method, we studied the morphology transformations of unzipped CNTs with different unzipping patterns. By modulating the unzipping patterns, the CNTs could self-assemble forming graphene nanoribbons and carbon nanoscrolls. From the energy analyzation, we find that the van der Waals interactions are responsible for the assembly of the unzipped CNTs. This unusual self-assembling method for CNTs could provide clues for further studies on the design of novel nanostructures.

  13. Wetting of Liquid Iron in Carbon Nanotubes and on Graphene Sheets: A Molecular Dynamics Study

    Institute of Scientific and Technical Information of China (English)

    GAO Yu-Feng; YANG Yang; SUN De-Yan

    2011-01-01

    Using molecular dynamics simulations, we study the wetting of liquid iron in a carbon nanotube and on a graphene sheet. It is found that the contact angle of a droplet in a carbon nanotube increases linearly with the increase of wall curvature but is independent of the length of the filled liquid. The contact angle for a droplet on a graphene sheet decreases with the increasing droplet size. The line tension of a droplet on a graphene sheet is also obtained.Detailed studies show that liquid iron near the carbon walls exhibits the ordering tendencies in both the normal and tangential directions.

  14. Molecular dynamics study of the stability of a carbon nanotube atop a catalytic nanoparticle

    OpenAIRE

    Verkhovtsev, Alexey V.; Schramm, Stefan; Solov'yov, Andrey V.

    2014-01-01

    The stability of a single-walled carbon nanotube placed on top of a catalytic nickel nanoparticle is investigated by means of molecular dynamics simulations. As a case study, we consider the $(12,0)$ nanotube consisting of 720 carbon atoms and the icosahedral Ni$_{309}$ cluster. An explicit set of constant-temperature simulations is performed in order to cover a broad temperature range from 400 to 1200 K, at which a successful growth of carbon nanotubes has been achieved experimentally by mea...

  15. Gas dynamic effects on formation of carbon dimers in laser-produced plasmas

    Science.gov (United States)

    Al-Shboul, K. F.; Harilal, S. S.; Hassanein, A.

    2011-09-01

    We investigated the effect of helium and nitrogen pressures on the dynamics of molecular species formation during laser ablation of carbon. For producing plasmas, planar carbon targets were irradiated with 1064 nm, 6 ns pulses from an Nd:yttrium aluminum garnet laser. The emission from excited C2 and CN molecules was studied using space resolved optical time-of-flight emission spectroscopy and spectrally resolved fast imaging. The intensity oscillations in C2 and CN monochromatic fast imaging and their emission space-time contours suggest that recombination is the major mechanism of C2 formation within the laser ablation carbon plumes in the presence of ambient gas.

  16. Dynamics of Intracellular Polymers in Enhanced Biological Phosphorus Removal Processes under Different Organic Carbon Concentrations

    Directory of Open Access Journals (Sweden)

    Lizhen Xing

    2013-01-01

    Full Text Available Enhanced biological phosphorus removal (EBPR may deteriorate or fail during low organic carbon loading periods. Polyphosphate accumulating organisms (PAOs in EBPR were acclimated under both high and low organic carbon conditions, and then dynamics of polymers in typical cycles, anaerobic conditions with excess organic carbons, and endogenous respiration conditions were examined. After long-term acclimation, it was found that organic loading rates did not affect the yield of PAOs and the applied low organic carbon concentrations were advantageous for the enrichment of PAOs. A low influent organic carbon concentration induced a high production of extracellular carbohydrate. During both anaerobic and aerobic endogenous respirations, when glycogen decreased to around 80 ± 10 mg C per gram of volatile suspended solids, PAOs began to utilize polyphosphate significantly. Regressed by the first-order reaction model, glycogen possessed the highest degradation rate and then was followed by polyphosphate, while biomass decay had the lowest degradation rate.

  17. Simulating the effects of climate change and climate variability on carbon dynamics in Arctic tundra

    Science.gov (United States)

    Stieglitz, Marc; Giblin, Anne; Hobbie, John; Williams, Matthew; Kling, George

    2000-12-01

    Through a simple modeling exercise, three mechanisms have been identified, each operating at a different timescale, that may govern carbon dynamics in Arctic tundra regions and partially explain observed CO2 flux variability. At short timescales the biosphere reacts to meteorological forcing. Drier conditions are associated with aerobic soil decomposition, a large CO2efflux, and a net ecosystem loss of carbon. Cooler and moister conditions favor slower anaerobic decomposition in soils, good growing conditions, and terrestrial carbon sequestration. At intermediate timescales, periods of terrestrial carbon loss are directly linked to periods of carbon sequestration by the ability of the ecosystem to retain labile nitrogen. Labile nitrogen released to the soil during periods when the tundra is a source of carbon (soil respiration > net primary productivity) is retained within the ecosystem and accessed during periods when carbon sequestration is favored (net primary productivity > soil respiration). Finally, the ability of vegetation to respond to long-term changes in soil nutrient status via changes in leaf nitrogen and leaf area index modulates this dynamic at intermediate to long timescales.

  18. Complex forest dynamics indicate potential for slowing carbon accumulation in the southeastern United States

    OpenAIRE

    John W. Coulston; Wear, David N.; Vose, James M.

    2015-01-01

    Over the past century forest regrowth in Europe and North America expanded forest carbon (C) sinks and offset C emissions but future C accumulation is uncertain. Policy makers need insights into forest C dynamics as they anticipate emissions futures and goals. We used land use and forest inventory data to estimate how forest C dynamics have changed in the southeastern United States and attribute changes to land use, management, and disturbance causes. From 2007-2012, forests yielded a net sin...

  19. Pulse-induced nonequilibrium dynamics of acetylene inside carbon nanotube studied by an ab initio approach

    OpenAIRE

    Y. Miyamoto; Zhang, H.; Rubio, A.

    2012-01-01

    Nanoscale molecular confinement substantially modifies the functionality and electronic properties of encapsulated molecules. Many works have approached this problem from the perspective of quantifying ground-state molecular changes, but little is known about the nonequilibrium dynamics of encapsulated molecular system. In this letter, we report an analysis of the nonequilibrium dynamics of acetylene (C2H2) inside a semiconducting carbon nanotube (CNT). An ultrashort high-intense laser pulse ...

  20. Diameter-dependent bending dynamics of single-walled carbon nanotubes in liquids

    OpenAIRE

    Fakhri, Nikta; Tsyboulski, Dmitri A.; Cognet, Laurent; Weisman, R. Bruce; Pasquali, Matteo

    2009-01-01

    By relating nanotechnology to soft condensed matter, understanding the mechanics and dynamics of single-walled carbon nanotubes (SWCNTs) in fluids is crucial for both fundamental and applied science. Here, we study the Brownian bending dynamics of individual chirality-assigned SWCNTs in water by fluorescence microscopy. The bending stiffness scales as the cube of the nanotube diameter and the shape relaxation times agree with the semiflexible chain model. This suggests that SWCNTs may be the ...

  1. Incorporating microbial dormancy dynamics into soil decomposition models to improve quantification of soil carbon dynamics of northern temperate forests

    Science.gov (United States)

    He, Yujie; Yang, Jinyan; Zhuang, Qianlai; Harden, Jennifer W.; McGuire, Anthony; Liu, Yaling; Wang, Gangsheng; Gu, Lianhong

    2015-01-01

    Soil carbon dynamics of terrestrial ecosystems play a significant role in the global carbon cycle. Microbial-based decomposition models have seen much growth recently for quantifying this role, yet dormancy as a common strategy used by microorganisms has not usually been represented and tested in these models against field observations. Here we developed an explicit microbial-enzyme decomposition model and examined model performance with and without representation of microbial dormancy at six temperate forest sites of different forest types. We then extrapolated the model to global temperate forest ecosystems to investigate biogeochemical controls on soil heterotrophic respiration and microbial dormancy dynamics at different temporal-spatial scales. The dormancy model consistently produced better match with field-observed heterotrophic soil CO2 efflux (RH) than the no dormancy model. Our regional modeling results further indicated that models with dormancy were able to produce more realistic magnitude of microbial biomass (soil organic carbon) and soil RH (7.5 ± 2.4 Pg C yr−1). Spatial correlation analysis showed that soil organic carbon content was the dominating factor (correlation coefficient = 0.4–0.6) in the simulated spatial pattern of soil RHwith both models. In contrast to strong temporal and local controls of soil temperature and moisture on microbial dormancy, our modeling results showed that soil carbon-to-nitrogen ratio (C:N) was a major regulating factor at regional scales (correlation coefficient = −0.43 to −0.58), indicating scale-dependent biogeochemical controls on microbial dynamics. Our findings suggest that incorporating microbial dormancy could improve the realism of microbial-based decomposition models and enhance the integration of soil experiments and mechanistically based modeling.

  2. Dynamics of dissolved organic carbon in the northwestern Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    DileepKumar, M.; Rajendran, A.; Somasundar, K.; Haake, B.; Jenisch, A.; Shuo, Z.; Ittekkot, V.; Desai, B.N.

    stream_size 42710 stream_content_type text/plain stream_name Mar_Chem_31_299.pdf.txt stream_source_info Mar_Chem_31_299.pdf.txt Content-Encoding UTF-8 Content-Type text/plain; charset=UTF-8 Marine Chemistry, 31 (1990... in the conversion of detrital 0304-4203/90/$03.50 © 1990 -- Elsevier Science Publishers B.V. 300 M. DILEEP KUMAR ET AL. matter into inorganic carbon dioxide and plays a pivotal role in food chain processes by becoming a substrate for micro-organisms. The nature...

  3. Graphene and carbon nanotubes ultrafast relaxation dynamics and optics

    CERN Document Server

    Malic, Ermin

    2013-01-01

    The book introduces the reader into the ultrafast nanoworld of graphene and carbon nanotubes, including their microscopic tracks and unique optical finger prints. The author reviews the recent progress in this field by combining theoretical and experimental achievements. He offers a clear theoretical foundation by presenting transparently derived equations. Recent experimental breakthroughs are reviewed. By combining both theory and experiment as well as main results and detailed theoretical derivations, the book turns into an inevitable source for a wider audience from graduate students to researchers in physics, materials science, and electrical engineering who work on optoelectronic devices, renewable energies, or in the semiconductor industry.

  4. The effect of cyclic and dynamic loads on carbon steel pipe

    International Nuclear Information System (INIS)

    This report presents the results of four 152-mm (6-inch) diameter, unpressurized, circumferential through-wall-cracked, dynamic pipe experiments fabricated from STS410 carbon steel pipe manufactured in Japan. For three of these experiments, the through-wall crack was in the base metal. The displacement histories applied to these experiments were a quasi-static monotonic, dynamic monotonic, and dynamic, cyclic (R = -1) history. The through-wall crack for the third experiment was in a tungsten-inert-gas weld, fabricated in Japan, joining two lengths of STS410 pipe. The displacement history for this experiment was the same history applied to the dynamic, cyclic base metal experiment. The test temperature for each experiment was 300 C (572 F). The objective of these experiments was to compare a Japanese carbon steel pipe material with US pipe material, to ascertain whether this Japanese steel was as sensitive to dynamic and cyclic effects as US carbon steel pipe. In support of these pipe experiments, quasi-static and dynamic, tensile and fracture toughness tests were conducted. An analysis effort was performed that involved comparing experimental crack initiation and maximum moments with predictions based on available fracture prediction models, and calculating J-R curves for the pipe experiments using the η-factor method

  5. Dynamics and Friction in Double Walled Carbon Nanotubes

    CERN Document Server

    Servantie, J

    2006-01-01

    The goal of this PhD thesis was to characterize the properties of friction in nanotubes and from a more general point of view the understanding of the microscopic origin of friction. Indeed, the relative simplicity of the system allows us to interpret more easily the physical phenomenon observed than in larger systems. In order to achieve this goal, non-equilibrium statistical mechanics permitted first to develop models based on Langevin equations describing the dynamics of rotation and translation in double walled nanotubes. The molecular dynamics simulations then permitted to validate these analytical models, and thus to study general properties of friction such as the dependence on area of contact, temperature and the geometry of the nanotubes. The results obtained shows that friction increases linearly with the sliding velocity or the angular velocity until very high values beyond which non-linearities appear enhancing dissipation. In the linear regime, it is shown that the proportionality factor between ...

  6. Spatiotemporal visualization of subcellular dynamics of carbon nanotubes

    KAUST Repository

    Bayoumi, Maged Fouad

    2012-12-12

    To date, there is no consensus on the relationship between the physicochemical characteristics of carbon nanotubes (CNTs) and their biological behavior; however, there is growing evidence that the versatile characteristics make their biological fate largely unpredictable and remain an issue of limited knowledge. Here we introduce an experimental methodology for tracking and visualization of postuptake behavior and the intracellular fate of CNTs based on the spatial distribution of diffusion values throughout the plant cell. By using raster scan image correlation spectroscopy (RICS), we were able to generate highly quantitative spatial maps of CNTs diffusion in different cell compartments. The spatial map of diffusion values revealed that the uptake of CNTs is associated with important subcellular events such as carrier-mediated vacuolar transport and autophagy. These results show that RICS is a useful methodology to elucidate the intracellular behavior mechanisms of carbon nanotubes and potentially other fluorescently labeled nanoparticles, which is of relevance for the important issues related to the environmental impact and health hazards. © 2012 American Chemical Society.

  7. Spatiotemporal visualization of subcellular dynamics of carbon nanotubes.

    Science.gov (United States)

    Serag, Maged F; Braeckmans, Kevin; Habuchi, Satoshi; Kaji, Noritada; Bianco, Alberto; Baba, Yoshinobu

    2012-12-12

    To date, there is no consensus on the relationship between the physicochemical characteristics of carbon nanotubes (CNTs) and their biological behavior; however, there is growing evidence that the versatile characteristics make their biological fate largely unpredictable and remain an issue of limited knowledge. Here we introduce an experimental methodology for tracking and visualization of postuptake behavior and the intracellular fate of CNTs based on the spatial distribution of diffusion values throughout the plant cell. By using raster scan image correlation spectroscopy (RICS), we were able to generate highly quantitative spatial maps of CNTs diffusion in different cell compartments. The spatial map of diffusion values revealed that the uptake of CNTs is associated with important subcellular events such as carrier-mediated vacuolar transport and autophagy. These results show that RICS is a useful methodology to elucidate the intracellular behavior mechanisms of carbon nanotubes and potentially other fluorescently labeled nanoparticles, which is of relevance for the important issues related to the environmental impact and health hazards. PMID:23170917

  8. Carbon Dynamics of Pinus palustris Ecosystems Following Drought

    Directory of Open Access Journals (Sweden)

    Gregory Starr

    2016-04-01

    Full Text Available Drought can affect forest structure and function at various spatial and temporal scales. Forest response and recovery from drought may be a result of position within landscape. Longleaf pine forests in the United States have been observed to reduce their carbon sequestration capacity during drought. We collected eddy covariance data at the ends of an edaphic longleaf pine gradient (xeric and mesic sites over seven years; two years of normal rainfall were followed by 2.5 years of drought, then 2.5 years of normal or slightly above-average rainfall. Drought played a significant role in reducing the physiological capacity of the sites and was compounded when prescribed fire occurred during the same periods. The mesic site has a 40% greater basal area then the xeric site, which accounts for its larger sequestration capacity; however, both sites show the same range of variance in fluxes over the course of the study. Following drought, both sites became carbon sinks. However, the xeric site had a longer carry-over effect and never returned to pre-drought function. Although this study encompassed seven years, we argue that longer studies with greater spatial variance must be undertaken to develop a more comprehensive understanding of forest response to changing climate.

  9. Climate policies between carbon prices, oil rents and urban dynamics

    International Nuclear Information System (INIS)

    This thesis investigates the effects of constraints imposed on economic interactions by limitations due to natural resources, among which oil and urban land play a crucial role in the context of climate change. These dimensions, often neglected in existing analyses, have an ambiguous effect since they suggest both the risk of enhanced costs if carbon limitations reinforce the sub-optimalities caused by pre-existing constraints, but also, conversely, the possibility of co-benefits if the climate policy helps to correct some pre-existing imperfections of socio-economic trajectories. To investigate this issue, an innovative modeling framework of the energy-economy interactions is elaborated that embarks the specificities of the deployment of oil production capacities and the issues related to the spatial organization in urban areas. We demonstrate that, beyond the carbon price, the costs of climate policy essentially depend on the sequencing of complementary measures, with a crucial role of spatial policy designed to control transport-related emissions through mobility. (author)

  10. Simulating Field-Scale Soil Organic Carbon Dynamics Using EPIC

    Energy Technology Data Exchange (ETDEWEB)

    Causarano, Hector J.; Shaw, Joey N.; Franzluebbers, A. J.; reeves, D. W.; Raper, Randy L.; Balkcom, Kipling S.; Norfleet, M. L.; Izaurralde, R Cesar

    2007-07-01

    Simulation models integrate our knowledge of soil organic C (SOC) dynamics and are useful tools for evaluating impacts of crop management on soil C sequestration; yet, they require local calibration. Our objectives were to calibrate the Environmental Policy Integrated Climate (EPIC) model, and evaluate its performance for simulating SOC fractions as affected by soil landscape and management. An automated parameter optimization procedure was used to calibrate the model for a site-specific experiment in the Coastal Plain of central Alabama. The ability of EPIC to predict corn (Zea mays L.) and cotton (Gossypium hirsutum L.) yields and SOC dynamics on different soil landscape positions (summit, sideslope and drainageway) during the initial period of conservation tillage adoption (5 years) was evaluated using regression and mean squared deviations. Simulated yield explained 88% of measured yield variation, with greatest disagreement on the sideslope position and highest agreement in the drainageway. Simulations explained approximately 1, 34 and 40% of the total variation in microbial biomass C (MBC), particulate organic C (POC) and total organic C (TOC), respectively. Lowest errors on TOC simulations (0-20 cm) were found on the sideslope and summit. We conclude that the automated parameterization was generally successful, although further work is needed to refine the MBC and POC fractions, and to improve EPIC predictions of SOC dynamics with depth. Overall, EPIC was sensitive to spatial differences in C fractions that resulted from differing soil landscape positions. The model needs additional refinement for accurate simulations of field-scale SOC dynamics affected by short-term management decisions.

  11. Holocene carbon dynamics and radiative forcing of three different types of peatlands in Finland

    Science.gov (United States)

    Mathijssen, Paul; Väliranta, Minna; Lohila, Annalea; Minkkinen, Kari; Tuittila, Eeva-Stiina; Tuovinen, Juha-Pekka; Korrensalo, Aino

    2016-04-01

    Peatlands contain approximately a third of all soil carbon globally and as they exchange carbon dioxide (CO2) and methane (CH4) copiously with the atmosphere, changes in peatland carbon budgets have a large impact on the global carbon balance and the concentration of greenhouse gasses in the atmosphere. There has been a growing interest in reconstructing and linking peatland carbon dynamics to past climate variations, because quantitative reconstructions can be used as a basis for future carbon balance predictions. In order to increase our understanding on peatland development and response patterns we quantitatively reconstructed Holocene carbon dynamics of three different peatlands in Finland: a subarctic fen, a boreal peatland complex and a boreal managed pine bog. Several cores from each peatland were investigated. The peatlands showed distinct successional pathways, which were sometimes triggered by fires. Successional stages were partly reflected in carbon accumulation patterns. Sometimes variations in carbon accumulation rates coincided with autogenic changes in peat type and vegetation, but accumulation rates were also related to the large-scale Holocene climate phases. However, Holocene climate changes as such did not seem to result in changes in the peat plant species composition. The mid-Holocene warm and dry climate conditions reduced the carbon accumulation in the subarctic fen and in the fen part of the boreal peatland complex, but when the peatland was in bog phase this effect was not visible. Some bog cores showed a clear increase in carbon accumulation after fen-bog transition, but the pattern was not unanimous. In addition to carbon accumulation, we estimated past CH4 emissions for each peatland respectively by applying different methods and by utilising the established current vegetation-CH4 emission relationship. The reconstructions showed that CH4 emissions always decreased during bog stages, but that the CH4 emissions played a major role in the

  12. Historical analysis and modeling of the forest carbon dynamics using the Carbon Budget Model: an example for the Trento Province (NE, Italy

    Directory of Open Access Journals (Sweden)

    Pilli R

    2014-02-01

    Full Text Available Historical analysis and modeling of the forest carbon dynamics using the Carbon Budget Model: an example for the Trento Province (NE, Italy. The Carbon Budget Model (CBM-CFS3 developed by the Canadian Forest Service was applied to data collected by the last Italian National Forest Inventory (INFC for the Trento Province (NE, Italy. CBM was modified and adapted to the different management types (i.e., even-aged high forests, uneven-aged high forests and coppices and silvicultural systems (including clear cuts, single tree selection systems and thinning applied in this province. The aim of this study was to provide an example of down-scaling of this model from a national to a regional scale, providing (i an historical analysis, from 1995 to 2011, and (ii a projection, from 2012 to 2020, of the forest biomass and the carbon stock evolution. The analysis was based on the harvest rate reported by the Italian National Institute of Statistics (from 1995 to 2011, corrected according to the last INFC data and distinguished between timber and fuel woods and between conifers and broadleaves. Since 2012, we applied a constant harvest rate, equal to about 1300 Mm3 yr-1, estimated from the average harvest rate for the period 2006-2011. Model results were consistent with similar data reported in the literature. The average biomass C stock was 90 Mg C ha-1 and the biomass C stock change was 0.97 Mg C ha-1 yr-1 and 0.87 Mg C ha-1 yr-1, for the period 1995 -2011 and 2012-2020, respectively. The C stock cumulated by the timber products since 1995 was 96 Gg C yr-1, i.e., about 28% of the average annual C stock change of the forests, equal to 345 Gg C yr-1. CBM also provided estimates on the evolution of the age class distribution of the even-aged forests and on the C stock of the DOM forest pools (litter, dead wood and soil. This study demonstrates the utility of CBM to provide estimates at a regional or local scale, using not only the data provided by the forest

  13. Carbon dynamics of Oregon and Northern California forests and potential land-based carbon storage.

    Science.gov (United States)

    Hudiburg, Tara; Law, Beverly; Turner, David P; Campbell, John; Donato, Dan; Duane, Maureen

    2009-01-01

    Net uptake of carbon from the atmosphere (net ecosystem production, NEP) is dependent on climate, disturbance history, management practices, forest age, and forest type. To improve understanding of the influence of these factors on forest carbon stocks and flux in the western United States, federal inventory data and supplemental field measurements at additional plots were used to estimate several important components of the carbon balance in forests in Oregon and Northern California during the 1990s. Species- and ecoregion-specific allometric equations were used to estimate live and dead biomass stores, net primary productivity (NPP), and mortality. In the semiarid East Cascades and mesic Coast Range, mean total biomass was 8 and 24 kg C/m2, and mean NPP was 0.30 and 0.78 kg C.m(-2).yr(-1), respectively. Maximum NPP and dead biomass stores were most influenced by climate, whereas maximum live biomass stores and mortality were most influenced by forest type. Within ecoregions, mean live and dead biomass were usually higher on public lands, primarily because of the younger age class distribution on private lands. Decrease in NPP with age was not general across ecoregions, with no marked decline in old stands (>200 years old) in some ecoregions. In the absence of stand-replacing disturbance, total landscape carbon stocks could theoretically increase from 3.2 +/- 0.34 Pg C to 5.9 +/- 1.34 Pg C (a 46% increase) if forests were managed for maximum carbon storage. Although the theoretical limit is probably unattainable, given the timber-based economy and fire regimes in some ecoregions, there is still potential to significantly increase the land-based carbon storage by increasing rotation age and reducing harvest rates. PMID:19323181

  14. Determination of Water Diffusion Coefficients and Dynamics in Adhesive/ Carbon Fiber Reinforced Epoxy Resin Composite Joints

    Institute of Scientific and Technical Information of China (English)

    WANG Chao; WANG Zhi; WANG Jing; SU Tao

    2007-01-01

    To determinate the water diffusion coefficients and dynamics in adhesive/carbon fiber reinforced epoxy resin composite joints, energy dispersive X-ray spectroscopy analysis(EDX) is used to establish the content change of oxygen in the adhesive in adhesive/carbon fiber reinforced epoxy resin composite joints. As water is made up of oxygen and hydrogen, the water diffusion coefficients and dynamics in adhesive/carbon fiber reinforced epoxy resin composite joints can be obtained from the change in the content of oxygen in the adhesive during humidity aging, via EDX analysis. The authors have calculated the water diffusion coefficients and dynamics in the adhesive/carbon fiber reinforced epoxy resin composite joints with the aid of both energy dispersive X-ray spectroscopy and elemental analysis. The determined results with EDX analysis are almost the same as those determined with elemental analysis and the results also show that the durability of the adhesive/carbon fiber reinforced epoxy resin composite joints subjected to silane coupling agent treatment is better than those subjected to sand paper burnishing treatment and chemical oxidation treatment.

  15. Carbon respiration and nitrogen dynamics in Corsican pine litter amended with aluminium and tannins

    NARCIS (Netherlands)

    P. Kraal; K.G.J. Nierop; J. Kaal; A. Tietema

    2009-01-01

    We investigated the carbon (C) mineralisation and nitrogen (N) dynamics in litter from a Corsican pine forest in response to individual and combined additions of aluminium (M), condensed tannin (extracted from fresh Corsican pine needles) and hydrolysable tannin (commercial tannic acid). Production

  16. Molecular dynamics simulation study on capacitive nano-accelerometers based on telescoping carbon nanotubes

    International Nuclear Information System (INIS)

    We investigated the characteristics of a capacitive nano-accelerometer based on a telescoping carbon nanotube by means of classical molecular dynamics simulations. The position of the telescoping nanotube was controlled by an externally applied force, and feedback sensing was based on the capacitance change. The capacitance variations, which were almost linearly proportional to the applied acceleration, were monitored within an error tolerance

  17. Mechanisms of oxygen reduction reactions for carbon alloy catalysts via first principles molecular dynamics

    International Nuclear Information System (INIS)

    Carbon alloy catalysts (CACs) are one of promising candidates for platinum-substitute cathode catalysts for polymer electrolyte fuel cells. We have investigated possible mechanisms of oxygen reduction reactions (ORRs) for CACs via first-principles-based molecular dynamics simulations. In this contribution, we review possible ORRs at likely catalytic sites of CACs suggested from our simulations. (author)

  18. Dynamic surface rearrangement and thermal stability of nitrogen functional groups on carbon nanotubes

    OpenAIRE

    R. Arrigo; Hävecker, M.; Schlögl, R.; Su, D.

    2008-01-01

    Dynamic surface rearrangement and thermal stability of N-functional groups on carbon nanotubes (CNTs), obtained by functionalization of pristine CNTs with NH3, were studied by temperature-programmed XPS and MS: a link between the stability of the functional group and decomposition temperature have been established and a conversion into graphitic nitrogen was observed.

  19. Effects of harvest on carbon and nitrogen dynamics in a Pacific Northwest forest catchment

    Science.gov (United States)

    We used a new ecohydrological model, Visualizing Ecosystems for Land Management Assessments (VELMA), to analyze the effects of forest harvest on catchment carbon and nitrogen dynamics. We applied the model to a 10 ha headwater catchment in the western Oregon Cascade Range where t...

  20. Dynamic mechanical and dielectric properties of ethylene vinyl acetate/carbon nanotube composites

    Czech Academy of Sciences Publication Activity Database

    Valentová, H.; Ilčíková, M.; Czaniková, K.; Špitalský, Z.; Šlouf, Miroslav; Nedbal, J.; Omastová, M.

    2014-01-01

    Roč. 53, č. 3 (2014), s. 496-512. ISSN 0022-2348 R&D Projects: GA TA ČR TE01020118 Institutional support: RVO:61389013 Keywords : carbon nanotubes * dielectric relaxation spectroscopy * dynamic mechanical analysis Subject RIV: JA - Electronics ; Optoelectronics, Electrical Engineering Impact factor: 0.740, year: 2014

  1. Winter spring dynamics in sea-ice carbon cycling in the coastal Arctic Ocean

    Science.gov (United States)

    Riedel, Andrea; Michel, Christine; Gosselin, Michel; LeBlanc, Bernard

    2008-12-01

    An understanding of microbial interactions in first-year sea ice on Arctic shelves is essential for identifying potential responses of the Arctic Ocean carbon cycle to changing sea-ice conditions. This study assessed dissolved and particulate organic carbon (DOC, POC), exopolymeric substances (EPS), chlorophyll a, bacteria and protists, in a seasonal (24 February to 20 June 2004) investigation of first-year sea ice and associated surface waters on the Mackenzie Shelf. The dynamics of and relationships between different sea-ice carbon pools were investigated for the periods prior to, during and following the sea-ice-algal bloom, under high and low snow cover. A predominantly heterotrophic sea-ice community was observed prior to the ice-algal bloom under high snow cover only. However, the heterotrophic community persisted throughout the study with bacteria accounting for, on average, 44% of the non-diatom particulate carbon biomass overall the study period. There was an extensive accumulation of sea-ice organic carbon following the onset of the ice-algal bloom, with diatoms driving seasonal and spatial trends in particulate sea-ice biomass. DOC and EPS were also significant sea-ice carbon contributors such that sea-ice DOC concentrations were higher than, or equivalent to, sea-ice-algal carbon concentrations prior to and following the algal bloom, respectively. Sea-ice-algal carbon, DOC and EPS-carbon concentrations were significantly interrelated under high and low snow cover during the algal bloom ( r values ≥ 0.74, p algae are primarily responsible for the large pools of DOC and EPS-carbon and that similar stressors and/or processes could be involved in regulating their release. This study demonstrates that DOC can play a major role in organic carbon cycling on Arctic shelves.

  2. Femtosecond Dynamics in Single Wall Carbon Nanotube/Poly(3-Hexylthiophene Composites

    Directory of Open Access Journals (Sweden)

    Alexandrou Ioannis

    2008-01-01

    Full Text Available AbstractFemtosecond transient absorption measurements on single wall carbon nanotube/poly(3-hexylthiophene composites are used to investigate the relaxation dynamics of this blended material. The influence of the addition of nanotubes in polymer matrix on the ultrashort relaxation dynamics is examined in detail. The introduction of nanotube/polymer heterojunctions enhances the exciton dissociation and quenches the radiative recombination of composites. The relaxation dynamics of these composites are compared with the fullerene derivative-polymer composites with the same matrix. These results provide explanation to the observed photovoltaic performance of two types of composites.

  3. Dynamic Recrystallization and Grain Growth Behavior of 20SiMn Low Carbon Alloy Steel

    Institute of Scientific and Technical Information of China (English)

    DONG Lanfeng; ZHONG Yuexian; MA Qingxian; YUAN Chaolong; MA Lishen

    2008-01-01

    A senes of thermodynamics experiments were used to optimize the hot forging process of 20SiMn low-carbon alloy steel.A dynamic recrystallization and grain growth model was developed for the 20SiMn steel for common production conditions of heavy forgings by doing a nonlinear curve fit of the expenment data.Optimized forging parameters were developed based on the control of the dynamic recrystallization and the MnS secondary phase.The data shows that the initial grain size and the MnS secondary phase all affect the behavior of the 20SiMn dynamic recrystallization and grain growth.

  4. Carbon Nanotube Based Molecular Electronics and Motors: A View from Classical and Quantum Dynamics Simulations

    Science.gov (United States)

    Srivastava, Deepak; Saini, Subhash (Technical Monitor)

    1998-01-01

    The tubular forms of fullerenes popularly known as carbon nanotubes are experimentally produced as single-, multiwall, and rope configurations. The nanotubes and nanoropes have shown to exhibit unusual mechanical and electronic properties. The single wall nanotubes exhibit both semiconducting and metallic behavior. In short undefected lengths they are the known strongest fibers which are unbreakable even when bent in half. Grown in ropes their tensile strength is approximately 100 times greater than steel at only one sixth the weight. Employing large scale classical and quantum molecular dynamics simulations we will explore the use of carbon nanotubes and carbon nanotube junctions in 2-, 3-, and 4-point molecular electronic device components, dynamic strength characterization for compressive, bending and torsional strains, and chemical functionalization for possible use in a nanoscale molecular motor. The above is an unclassified material produced for non-competitive basic research in the nanotechnology area.

  5. Radius dependence of the melting temperature of single-walled carbon nanotubes: molecular-dynamics simulations

    International Nuclear Information System (INIS)

    We have investigated the radius dependence of the melting temperature of single-walled carbon nanotubes (SWCNTs) by classical molecular-dynamics (MD) simulations using the environment-dependent interatomic potential (EDIP) proposed by Marks. Here we define the 'melting temperature' as a temperature at which there occurs a thermal instability of SWCNTs. We have carried out molecular-dynamics simulations at several temperatures for carbon nanotubes with various radii and estimated the 'melting temperature' based on the temperature dependence of the radial distribution functions, mean-square displacements and atomic configurations. It is shown that the 'melting temperature' of SWCNTs decreases with decreasing radius. The origin of this radius dependence of the melting temperature of SWCNTs is discussed in relation to the stability of SWCNTs energetically based on the strain energy of carbon nanotubes

  6. Dynamics in carbon exchange fluxes for a grazed semi-arid savanna ecosystem in West Africa

    DEFF Research Database (Denmark)

    Tagesson, Torbern; Fensholt, Rasmus; Cropley, Ford;

    2015-01-01

    The main aim of this paper is to study land-atmosphere exchange of carbon dioxide (CO2) for semi-arid savanna ecosystems of the Sahel region and its response to climatic and environmental change. A subsidiary aim is to study and quantify the seasonal dynamics in light use efficiency (ε) being a key...... variable in scaling carbon fluxes from ground observations using earth observation data. The net ecosystem exchange of carbon dioxide (NEE) 2010-2013 was measured using the eddy covariance technique at a grazed semi-arid savanna site in Senegal, West Africa. Night-time NEE was not related to temperature...... (C) MJ-1 for the dry season and 2.27gCMJ-1 for the peak of the rainy season, and its seasonal dynamics was governed by vegetation phenology, photosynthetically active radiation, soil moisture and vapor pressure deficit (VPD). The CO2 exchange fluxes were very high in comparison to other semi...

  7. Optical properties of carbon grains Influence on dynamical models of AGB stars

    CERN Document Server

    Andersen, A C; Höfner, S; Andersen, Anja C.; Loidl, Rita; Hofner, Susanne

    1999-01-01

    For amorphous carbon several laboratory extinction data are available, which show quite a wide range of differences due to the structural complexity of this material. We have calculated self-consistent dynamic models of circumstellar dust-shells around carbon-rich asymptotic giant branch stars, based on a number of these data sets. The structure and the wind properties of the dynamical models are directly influenced by the different types of amorphous carbon. In our test models the mass loss is not severely dependent on the difference in the optical properties of the dust, but the influence on the degree of condensation and the final outflow velocity is considerable. Furthermore, the spectral energy distributions and colours resulting from the different data show a much wider spread than the variations within the models due to the variability of the star. Silicon carbide was also considered in the radiative transfer calculations to test its influence on the spectral energy distribution.

  8. Single, competitive, and dynamic adsorption on activated carbon of compounds used as plasticizers and herbicides.

    Science.gov (United States)

    Abdel daiem, Mahmoud M; Rivera-Utrilla, José; Sánchez-Polo, Manuel; Ocampo-Pérez, Raúl

    2015-12-15

    The main aim of this study was to investigate the single, competitive, and dynamic adsorption of phthalic acid (PA), bisphenol A (BPA), diphenolic acid (DPA), 2,4-dichlorophenoxy-acetic acid (2,4-D), and 4-chloro-2-methylphenoxyacetic acid (MCPA) on two activated carbons with different chemical natures and similar textural characteristics. The adsorption mechanism was also elucidated by analyzing the influence of solution pH and ionic strength. The activated carbons demonstrated high adsorption capacity to remove all micropollutants due to the presence of active sites on their surfaces, which increase dispersive interactions between the activated carbon graphene layers and the aromatic ring of pollutants. The adsorption capacity of the activated carbons increased in the order: DPAdynamic regime, the amount of pollutant adsorbed was much higher for PA, followed by DPA, and was approximately similar for BPA, 2,4-D, and MCPA. Finally, the amount of BPA and DPA adsorbed on activated carbon decreased by around 50% and 70% in the presence of DPA and BPA, respectively, indicating that both compounds are adsorbed on the same adsorption sites of the activated carbon. PMID:26282767

  9. Nitrogen Deposition Effects on Soil Carbon Dynamics in Temperate Forests

    DEFF Research Database (Denmark)

    Ginzburg Ozeri, Shimon

    Soils contain the largest fraction of terrestrial carbon (C). Understanding the factors regulating the decomposition and storage of soil organic matter (SOM) is essential for predictions of the C sink strength of the terrestrial environment in the light of global change. Elevated long-term nitrogen...... (N) deposition into forest ecosystems has been increasing globally and was hypothesized to raise soil organic C (SOC) stocks by increasing forest productivity and by reducing SOM decomposition. Yet, these effects of N deposition on forest SOC stocks are uncertain and largely based on observations...... edges were used to study the effects of varying N deposition load on SOC stocks and fluxes as well as on the temperature sensitivity of SOM respiration. In a third study, the effects of 20 years of continuous experimental N addition (35 kg N ha-1 year-1) on soil C budget were investigated. Our general...

  10. The carbon cycle and biogeochemical dynamics in lake sediments

    Science.gov (United States)

    Dean, W.E.

    1999-01-01

    The concentrations of organic carbon (OC) and CaCO3 in lake sediments are often inversely related. This relation occurs in surface sediments from different locations in the same lake, surface sediments from different lakes, and with depth in Holocene sediments. Where data on accumulation rates are available, the relation holds for organic carbon and CaCO3 accumulation rates as well. An increase of several percent OC is accompanied by a decrease of several tens of percent CaCO3 indicating that the inverse relation is not due to simple dilution of one component by another. It appears from core data that once the OC concentration in the sediments becomes greater than about 12%, the CO2 produced by decomposition of that OC and production of organic acids lowers the pH of anoxic pore waters enough to dissolve any CaCO3 that reaches the sediment-water interface. In a lake with a seasonally anoxic hypolimnion, processes in the water column also can produce an inverse relation between OC and CaCO3 over time. If productivity of the lake increases, the rain rate of OC from the epilimnion increases. Biogenic removal of CO2 and accompanying increase in pH also may increase the production of CaCO3. However, the decomposition of organic matter in the hypolimnion will decrease the pH of the hypolimnion causing greater dissolution of CaCO3 and therefore a decrease in the rain rate of CaCO3 to the sediment-water interface.

  11. Molecular dynamics study of radiation damage and microstructure evolution of zigzag single-walled carbon nanotubes under carbon ion incidence

    Science.gov (United States)

    Li, Huan; Tang, Xiaobin; Chen, Feida; Huang, Hai; Liu, Jian; Chen, Da

    2016-07-01

    The radiation damage and microstructure evolution of different zigzag single-walled carbon nanotubes (SWCNTs) were investigated under incident carbon ion by molecular dynamics (MD) simulations. The radiation damage of SWCNTs under incident carbon ion with energy ranging from 25 eV to 1 keV at 300 K showed many differences at different incident sites, and the defect production increased to the maximum value with the increase in incident ion energy, and slightly decreased but stayed fairly stable within the majority of the energy range. The maximum damage of SWCNTs appeared when the incident ion energy reached 200 eV and the level of damage was directly proportional to incident ion fluence. The radiation damage was also studied at 100 K and 700 K and the defect production decreased distinctly with rising temperature because radiation-induced defects would anneal and recombine by saturating dangling bonds and reconstructing carbon network at the higher temperature. Furthermore, the stability of a large-diameter tube surpassed that of a thin one under the same radiation environments.

  12. Photocatalytic and chemical oxidation of organic compounds in supercritical carbon dioxide. 1998 annual progress report

    International Nuclear Information System (INIS)

    'This report summarizes the results of work done during the first 1.3 years of a three year project. During the first nine months effort focussed on the design, construction and testing of a closed recirculating system that can be used to study photochemistry in supercritical carbon dioxide at pressures up to 5,000 psi and temperatures up to about 50 C. This was followed by a period of work in which the photocatalytic oxidation of benzene and acetone in supercritical, liquid, and gaseous carbon dioxide containing dissolved oxygen was demonstrated. The photocatalyst was titanium dioxide supported on glass spheres. This was the first time it was possible to observe photocatalytic oxidation in a supercritical fluid and to compare reaction in the three fluid phases of a solvent. This also demonstrated that it is possible to purify supercritical and liquid carbon dioxide using photochemical oxidation with no chemical additions other than oxygen. The oxidation of benzene produced no intermediates detectable using on line spectroscopic analysis or by gas chromatographic analysis of samples taken from the flow system. The catalyst surface did darken as the reaction proceeded indicating that oxidation products were accumulating on the surface. This is analogous to the behavior of aromatic compounds in air phase photocatalytic oxidation. The reaction of acetone under similar conditions resulted in the formation of low levels of by-products. Two were identified as products of the reaction of acetone with itself (4-methyl-3-penten-2-one and 4-hydroxy-4-methyl-2-pentanone) using gas chromatography with a mass spectrometer detector. Two other by-products also appear to be from the self-reaction of acetone. By-products of this type had not been observed in prior studies of the gas-phase photocatalytic oxidation of acetone. The by-products that have been observed can also be oxidized under the treatment conditions. The above results establish that photocatalytic oxidation of

  13. Decadal and annual changes in biogenic opal and carbonate fluxes to the deep Sargasso Sea

    Science.gov (United States)

    Deuser, W.G.; Jickells, T.D.; Commeau, Judith A.

    1995-01-01

    Analyses of samples from a 14-year series of sediment-trap deployments in the deep Sargasso Sea reveal a significant trend in the ratio of the sinking fluxes of biogenic calcium carbonate and silica. Although there are pronounced seasonal cycles for both flux components, the overall opal/CaCO3 ratio changed by 50% from 1978 to 1991 (largely due to a decrease of opal flux), while total flux had no significant trend. These results suggest that plankton communities respond rapidly to subtle climate change, such as is evident in regional variations of wind speed, precipitation, wintertime ventilation and midwater temperatures. If the trends we observe in the makeup of sinking particulate matter occur on a large scale, they may in turn modify climate by modulating ocean-atmosphere CO2 exchange and albedo over the ocean.

  14. Improved recovery demonstration for Williston Basin carbonates. Annual report, June 10, 1995--June 9, 1996

    Energy Technology Data Exchange (ETDEWEB)

    Carrell, L.A.; Sippel, M.A.

    1996-09-01

    The purpose of this project is to demonstrate targeted infill and extension drilling opportunities, better determinations of oil-in-place, methods for improved completion efficiency and the suitability of waterflooding in Red River and Ratcliffe shallow-shelf carbonate reservoirs in the Williston Basin, Montana, North Dakota and South Dakota. Improved reservoir characterization utilizing three-dimensional and multi-component seismic are being investigated for identification of structural and stratigraphic reservoir compartments. These seismic characterization tools are integrated with geological and engineering studies. Improved completion efficiency is being tested with extended-reach jetting lance and other ultra-short-radius lateral technologies. Improved completion efficiency, additional wells at closer spacing and better estimates of oil in place will result in additional oil recovery by primary and enhanced recovery processes.

  15. Aggregate structure and stability linked to carbon dynamics in a south Chilean Andisol

    Directory of Open Access Journals (Sweden)

    C. Oyarzún

    2005-02-01

    Full Text Available The extreme vulnerability of soil organic carbon to climate and land use change emphasizes the need for further research in different terrestrial ecosystems. We have studied the aggregate stability and carbon dynamics in a chronosequence of three different land uses in a south Chilean Andisols: a second growth Nothofagus obliqua forest (SGFOR, a grassland (GRASS and a Pinus radiata plantation (PINUS. The aim of this study was to investigate the role of Al as soil organic matter stabilizing agent in this Andisol. In a case study, we linked differences in carbon dynamics between the three land use treatments to physical protection and recalcitrance of the soil organic matter (SOM. In this study, C aggregate stability and dynamics were studied using size and density fractionation experiments of the SOM, δ13C and total carbon analysis of the different SOM fractions, and mineralization measurements. The results showed that electrostatic attractions between and among Al-oxides and clay minerals are mainly responsible for the stabilization of soil aggregates and the physical protection of the enclosed soil organic carbon. Whole soil C mineralization rate constants were highest for SGFOR and PINUS, followed by GRASS. In contrast, incubation experiments of isolated macro organic matter fractions showed that the recalcitrance of the SOM decreased in another order: PINUS > SGFOR > GRASS. We concluded that physical protection of soil aggregates was the main process determining whole soil C mineralization. Land use changes affected soil organic carbon dynamics in this south Chilean Andisol by altering soil pH and consequently available Al.

  16. Carbon value dynamics for France: A key driver to support mitigation pledges at country scale

    International Nuclear Information System (INIS)

    The climate agenda in France and several other countries is a complex combination of unilateral commitments with regional and international objectives. When analyzing national policies, the findings of worldwide analyses are of limited accuracy and the large aggregates on which they are built level out most local specificities and inertia. Specific assessments are hence needed. This paper quantifies the dynamic evolution of carbon values for French climate and energy policy. Its time dependency over successive periods and the effects of setting intermediate targets are evaluated using a long-term optimization model. Addressing critical issues for France, we produce consistent energy, emissions and carbon value estimates with a 5-year time step. Our results are situated above the upper range of carbon value estimates of world models with an overlapping zone. We show that the official policy guideline value is only consistent with an optimistic combination of assumptions. The central estimates are 4 times greater than the guideline carbon value for 2050 and up to 14 times greater in 2020 because of short-term inertia that are costly to move. We also find that with intermediate objectives, the carbon value's dynamic is more than a simple upward curve and that its variability is itself time dependent. - Highlights: → We quantify the dynamic evolution of carbon values for France. → We use a long-term optimization energy model from the MARKAL family. → We compute consistent energy balances for different climate and energy policy. → We show that the official guideline is only consistent with optimistic assumptions. → The dynamic is not a simple upward curve and influencing parameters are analyzed.

  17. Modeling carbon dynamics in vegetation and soil under the impact of soil erosion and deposition

    Science.gov (United States)

    Liu, S.; Bliss, N.; Sundquist, E.; Huntington, T.G.

    2003-01-01

    Soil erosion and deposition may play important roles in balancing the global atmospheric carbon budget through their impacts on the net exchange of carbon between terrestrial ecosystem and the atmosphere. Few models and studies have been designed to assess these impacts. In this study, we developed a general ecosystem model, Erosion-Deposition-Carbon-Model (EDCM), to dynamically simulate the influences of rainfall-induced soil erosion and deposition on soil organic carbon (SOC) dynamics in soil profiles. EDCM was applied to several landscape positions in the Nelson Farm watershed in Mississippi, including ridge top (without erosion or deposition), eroding hillslopes, and depositional sites that had been converted from native forests to croplands in 1870. Erosion reduced the SOC storage at the eroding sites and deposition increased the SOC storage at the depositional areas compared with the site without erosion or deposition. Results indicated that soils were consistently carbon sources to the atmosphere at all landscape positions from 1870 to 1950, with lowest source strength at the eroding sites (13 to 24 gC m-2 yr-1), intermediate at the ridge top (34 gC m-2 yr-1), and highest at the depositional sites (42 to 49 gC m-2 yr-1). During this period, erosion reduced carbon emissions via dynamically replacing surface soil with subsurface soil that had lower SOC contents (quantity change) and higher passive SOC fractions (quality change). Soils at all landscape positions became carbon sinks from 1950 to 1997 due to changes in management practices (e.g., intensification of fertilization and crop genetic improvement). The sink strengths were highest at the eroding sites (42 to 44 gC m-2 yr-1 , intermediate at the ridge top (35 gC m-2 yr-1), and lowest at the depositional sites (26 to 29 gC m-2 yr-1). During this period, erosion enhanced carbon uptake at the eroding sites by continuously taking away a fraction of SOC that can be replenished with enhanced plant residue

  18. Carbon and nitrogen dynamics in soils: Effects of residue quality and localization

    International Nuclear Information System (INIS)

    During the years 1999-2005 a series of incubation experiments were conducted under controlled conditions to investigate the effect of plant litter quality and residue location (surface vs. incorporated) on residue decomposition, C storage and N dynamics in soils. Comparisons between decomposition of roots and other plant parts (leaves and stems) were emphasized in order to better evaluate the contribution of root systems to nutrient release and soil C sequestration. The second aspect investigated was the decomposition of residues from forest, grassland and annual crops. The aim was to assess the relative effects of soil past history and residue quality on short term biodegradation. During the initial phase of decomposition, the principal factor determining decomposition kinetics was the nature of the added carbon, which strongly affected the nature and activity of the decomposing microbial biomass. Initial C mineralization (after 3 d of incubation) was significantly related to the percentage of soluble compounds in the residue, while after 142 d, a linear relationship was observed between cumulative C mineralization and the percentage of the lignin-like fraction. The amount of N mineralized was strongly related to the initial N content of the residues. No specific interaction with the origin of the residues (agro-, pasture or forest ecosystem) was observed, indicating that concepts for describing crop residue decomposition may be generalized for the decomposition of grass roots and tree leaves, and therefore for mixed residues in agroforestry systems. The C and N mineralization of leaf and stem residues from four tropical species were related to their biochemical composition and could be predicted from their N content, thus indicating a similar behaviour for a range of temperate crop residues. C mineralized from roots was 20 to 30% less than for leaves and stems, and this was assumed to be related to the presence of a high lignin-suberin content. The lower

  19. Human impacts on soil carbon dynamics of deep-rooted Amazonian forests and effect of land use change on the carbon cycle in Amazon soils

    Science.gov (United States)

    Nepstad, Daniel; Stone, Thomas; Davidson, Eric; Trumbore, Susan E.

    1992-01-01

    The main objective of these NASA-funded projects is to improve our understanding of land-use impacts on soil carbon dynamics in the Amazon Basin. Soil contains approximately one half of tropical forest carbon stocks, yet the fate of this carbon following forest impoverishment is poorly studied. Our mechanistics approach draws on numerous techniques for measuring soil carbon outputs, inputs, and turnover time in the soils of adjacent forest and pasture ecosystems at our research site in Paragominas, state of Para, Brazil. We are scaling up from this site-specific work by analyzing Basin-wide patterns in rooting depth and rainfall seasonality, the two factors that we believe should explain much of the variation in tropical soil carbons dynamics. In this report, we summarize ongoing measurements at our Paragominas study site, progress in employing new field data to understand soil C dynamics, and some surprising results from our regional, scale-up work.

  20. Self-healing in defective carbon nanotubes: a molecular dynamics study

    International Nuclear Information System (INIS)

    The self-healing phenomenon of defective single-walled carbon nanotubes (SWCNTs) is observed at the atomic level from a molecular dynamics (MD) simulation test. The ideal network of carbon nanotubes is unable to avoid damage under destabilizing loads at high temperature, leading to unforeseen patterns in bond breakages and vacancy defects on the wall. We observe that (10, 10) and (17, 0) carbon nanotubes containing such vacancies are energetically unstable. In the situation of unloading or increasing temperature, the local structures around the vacancies reconstruct through dangling bond saturation, forming non-hexagonal rings, 5-7-7-5 defects or an ideal graphite network. We find that a defective carbon nanotube with large vacancies is re-mendable, and the Stone-Wales (SW) construction is energetically preferred in self-healing processes

  1. Mechanical property of carbon nanotubes with intramolecular junctions: Molecular dynamics simulations

    International Nuclear Information System (INIS)

    Intramolecular junctions (IMJs) of carbon nanotubes hold a promise of potential applications in nano-electromechanical systems. However, their structure-property relation is still unclear. Using the revised second-generation Tersoff-Brenner potential, molecular dynamics simulations were performed to study the mechanical properties of single-walled to four-walled carbon nanotubes with IMJs under uniaxial tension. The dependence of deformation and failure behaviors of IMJs on the geometric parameters was examined. It was found that the rupture strength of a junction is close to that of its thinner carbon nanotube segment, and the rupture strain and Young's modulus show a significant dependence on its geometry. The simulations also revealed that the damage and rupture of multi-walled carbon nanotube junctions take place first in the innermost layer and then propagate consecutively to the outer layers. This study is helpful for optimal design and safety evaluation of IMJ-based nanoelectronics

  2. Trends in nanoscale mechanics mechanics of carbon nanotubes, graphene, nanocomposites and molecular dynamics

    CERN Document Server

    2014-01-01

    This book contains a collection of the state-of-the-art reviews written by the leading researchers in the areas of nanoscale mechanics, molecular dynamics, nanoscale modeling of nanocomposites and mechanics of carbon nanotubes. No other book has reviews of the recent discoveries such as a nanoscale analog of the Pauli’s principle, i.e., effect of the spatial exclusion of electrons or the SEE effect, a new Registry Matrix Analysis for the nanoscale interfacial sliding and new data on the effective viscosity of interfacial electrons in nanoscale stiction at the interfaces. This volume is also an exceptional resource on the well tested nanoscale modeling of carbon nanotubes and nanocomposites, new nanoscale effects, unique evaluations of the effective thickness of carbon nanotubes under different loads, new data on which size of carbon nanotubes is safer and many other topics. Extensive bibliography concerning all these topics is included along with the lucid short reviews. Numerous illustrations are provided...

  3. Simulation of Young's modulus of single-walled carbon nanotubes by molecular dynamics

    International Nuclear Information System (INIS)

    Based on molecular dynamics (MD) simulation, the Young's moduli of carbon nanotubes are studied. The inter-atomic short-range interaction and long-range interaction of carbon nanotubes are represented by a second generation reactive empirical bond order (REBO) potential and Lennard-Jones (LJ) potential, respectively. The obtained potential expression is used to calculate the total potential energies of carbon nanotubes. Three types of single-walled carbon nanotubes (SWCNTs), armchair, zigzag and chiral tubules, are calculated, respectively. The computational results show that the Young's moduli of SWCNTs are in the range of 929.8±11.5 GPa. From the simulation, the Young's moduli of SWCNTs are weakly affected by the tube chirality and tube radius. The numeric results are in good agreement with the existing experimental results

  4. Carbon mineralization and oxygen dynamics in sediments with deep oxygen penetration, Lake Superior

    DEFF Research Database (Denmark)

    Li, Jiying; Crowe, Sean Andrew; Miklesh, David;

    2012-01-01

    To understand carbon and oxygen dynamics in sediments with deep oxygen penetration, we investigated eight locations (160–318-m depth) throughout Lake Superior. Despite the 2–4 weight percent organic carbon content, oxygen penetrated into the sediment by 3.5 to > 12 cm at all locations. Such deep......, suggesting that temporal variability in deeply oxygenated sediments may be greater than previously acknowledged. The oxygen uptake rates (4.4–7.7 mmol m−2 d−1, average 6.1 mmol m−2 d−1) and carbon mineralization efficiency (∼ 90% of deposited carbon) were similar to those in marine hemipelagic and pelagic...... penetration is explained by low sedimentation rates (0.01–0.04 cm yr−1), high solubility of oxygen in freshwater, and a shallow (∼ 2 cm) bioturbation zone. In response mainly to oxygen variations in the bottom waters, the sediment oxygen penetration varied seasonally by as much as several centimeters...

  5. Dynamic powder compaction of rapidly solidified Path A alloy with increased carbon and titanium content

    International Nuclear Information System (INIS)

    Different techniques for consolidation of rapidly solidified alloys which are available or are under study at the present time include conventional consolidation techniques (hot extrusion, HIP,...), high velociy consolidation of atomized partially solidified particulates and dynamic powder compaction (DPC). This report describes the results of dynamic compaction of Path A alloy with increased carbon and titanium content. The microstructure of the as-compated alloy is highly complex, evidencing an extreme degree of deformation. TEM revealed very high dislocation and twin density reflecting high hardness of the as-compacted alloy. Annealing studies revealed that recovery and recrystallization processes in dynamically compacted alloy are slower than in conventionally treated materials. High dislocation density appears to be an intrinsic property of the dynamic compaction process and it may be potentially useful in developing materials for irradiation performance. Other potential applications of dynamic compaction include preparation of graded materials and ceramic materials

  6. Vegetation Dynamics and Carbon-Nitrogen Cycles in NCAR CLM4-CNDV Under Changing Climate

    Science.gov (United States)

    Sakaguchi, K.; Zeng, X.; Shao, P.

    2012-12-01

    The global biogeochemical cycle has become a major component of climate change studies. There are numerous important aspects in the biogeochemical feedbacks to the externally forced climate, and two of them are vegetation dynamics and coupling of carbon-nitrogen cycles. It is well established that evolution of vegetation cover substantially influences biogeophysical interactions with the atmosphere. More recently several studies suggest that the nitrogen cycle can significantly change the feedback of the land biosphere to the warming climate (commonly noted as γ) and to the increase of CO2 (β) compared to the models considering only the carbon cycle. The number of such studies is still small, however, particularly with dynamic vegetation models. Here we report several characteristics of a global land model NCAR CLM4-CNDV, which simulates the interactions between the vegetation dynamics and carbon-nitrogen cycles (but not the anthropogenic land use and land cover changes). A series of global off-line simulations are run with reanalysis-based atmospheric data as well as the model output from one member of the fully coupled CCSM4 simulations contributing to phase five of the Coupled Model Intercomparison Project (CMIP5). They cover pre-industrial conditions, the historical period, and future projection under RCP8.5 scenario in CMIP5. The topics will include the diagnosis of the simulated vegetation distribution, global-scale quantities (total carbon storage, average albedo, etc), and the sensitivity of the land carbon pool to warming climate and CO2 (γ, β). For the vegetation dynamics, grid-level evolution in time from the initial conditions to quasi-equilibrium and the regional change over the tropics and Arctic regions in the future will be summarized. The other results will be compared to previous studies on carbon-nitrogen coupling within NCAR CLM to augment them by dynamic vegetation and/or transient simulations extending to the future. The results will be

  7. Carbon Fiber Strand Tensile Failure Dynamic Event Characterization

    Science.gov (United States)

    Johnson, Kenneth L.; Reeder, James

    2016-01-01

    There are few if any clear, visual, and detailed images of carbon fiber strand failures under tension useful for determining mechanisms, sequences of events, different types of failure modes, etc. available to researchers. This makes discussion of physics of failure difficult. It was also desired to find out whether the test article-to-test rig interface (grip) played a part in some failures. These failures have nothing to do with stress rupture failure, thus representing a source of waste for the larger 13-00912 investigation into that specific failure type. Being able to identify or mitigate any competing failure modes would improve the value of the 13-00912 test data. The beginnings of the solution to these problems lay in obtaining images of strand failures useful for understanding physics of failure and the events leading up to failure. Necessary steps include identifying imaging techniques that result in useful data, using those techniques to home in on where in a strand and when in the sequence of events one should obtain imaging data.

  8. CaTMAS : A multi-agent model for simulating the dynamics of carbon resources of West African villages

    OpenAIRE

    Belem, Mahamadou; Manlay, R. J.; Muller, J.P.; Chotte, Jean-Luc

    2011-01-01

    Carbon is an important determinant of the sustainability of West African farming systems and of the atmospheric greenhouse effect. Given the complexity of C dynamics, various simulation models have been developed. Few include socioeconomic factors or handle system heterogeneity. This study proposes a generic, multi-agent model for the analysis of C dynamics at village level. It assumes that a better analysis of carbon dynamics at village level requires account to be taken of social, economic,...

  9. Impacts of Invasive Pests on Forest Carbon and Nitrogen Dynamics

    Science.gov (United States)

    Lovett, G. M.; Crowley, K. F.

    2014-12-01

    Forests of the U.S. have been subject to repeated invasions of destructive insects and diseases imported from other continents. Like other disturbances, these pests can produce short-term ecosystem effects due to tree mortality, but unlike other disturbances, they often target individual species and therefore can cause long-term species change in the forest. Because tree species vary in their influence on carbon (C) and nitrogen (N) cycles, pest-induced species change can radically alter the biogeochemistry of a forest. In this paper we use both data and modeling to examine how pest-induced species change may alter the C and N cycling in forests of the eastern U.S. We describe a new forest ecosystem model that distinguishes individual tree species and allows species composition to shift over the course of the model run. Results indicate that the mortality of eastern hemlock (Tsuga canadensis) by hemlock woolly adelgid and its replacement by faster-growing species such as black birch (Betula lenta) will reduce forest floor C stocks but increase productivity as the birch become established. Decline of American beech (Fagus grandifolia) from beech bark disease and its replacement by sugar maple (Acer saccharum) is likely to decrease soil C storage and increase N leaching from the ecosystem. Responses to other invasive pests will also be discussed. The magnitude of these species-specific effects on C and N cycling is in many cases larger than direct effects expected from changes in climate and atmospheric N deposition, indicating that species change should be included in models that predict forest ecosystem function under future environmental conditions.

  10. Optics and Fluid Dynamics Department. Annual progress report 1 January - 31 December 1990

    International Nuclear Information System (INIS)

    Research in the Optics and Fluid Dynamics Department covers plasma physics, fluid dynamics, optics, and neural networks. Plasma physics is concentrated on basic investigations with relevance to fusion plasmas. Both theoretical and experimental work has been performed. Pellet injection systems have been developed. Within the area of fluid dynamics spectral models for studying the dynamcis of coherent structures have been developed. Optical diagnostic methods based on quasi-elastic light scattering have been developed. Beam propagation in random and nonlinear media has been investigated. Spatial and temporal processing schemes, especially for pattern recognition, have been investigated. (author)

  11. Epiphyte dynamics and carbon metabolism in a nutrient enriched Mediterranean seagrass ( Posidonia oceanica ) ecosystem

    Science.gov (United States)

    Apostolaki, Eugenia T.; Holmer, Marianne; Marbà, Núria; Karakassis, Ioannis

    2011-08-01

    The study aimed at examining the relationship between epiphyte dynamics and carbon metabolism in seagrass ecosystems under nutrient enrichment. Temporal variability of epiphytes and factors controlling their dynamics (i.e. environmental conditions, substratum availability, substratum stability and herbivore pressure) were assessed in a fish farm impacted and an unaffected Mediterranean seagrass ( Posidonia oceanica) meadow in the Aegean Sea (Greece). The factors controlling epiphyte dynamics responded differently to nutrient enrichment and partly interacted, rendering their cumulative effect on epiphyte load difficult to elucidate. Yet epiphytes accumulated on seagrass leaves near to the fish farm throughout the year, contributing 2 times more in above-ground biomass at cages than the control station. Reduction in substratum availability (i.e. decrease in leaf biomass) and increase in herbivore pressure affected epiphyte load, albeit their effects were not strong enough to counterbalance the effect of nutrient input from fish farm effluents. Moderate yet continuous nutrient input possibly stimulated epiphyte growth in excess of herbivory, shifting the control of epiphytes from top-down to bottom-up. Epiphyte accumulation affected carbon metabolism in the seagrass ecosystem by contributing to enhanced dissolved organic carbon (DOC) release, but seagrass loss was so acute that increased epiphyte cover could not counterbalance the decrease in community carbon production which was mainly driven by seagrass decline.

  12. Response of tundra ecosystems to elevated atmospheric carbon dioxide. [Annual report

    Energy Technology Data Exchange (ETDEWEB)

    Oechel, W.C.; Grulke, N.E.

    1988-12-31

    Our past research shows that arctic tussock tundra responds to elevated atmospheric CO{sub 2} with marked increases in net ecosystem carbon flux and photosynthetic rates. However, at ambient temperatures and nutrient availabilities, homeostatic adjustments result in net ecosystem flux rates dropping to those found a contemporary CO{sub 2} levels within three years. Evidence for ecosystem-level acclimation in the first season of elevated CO{sub 2} exposure was found in 1987. Photosynthetic rates of Eriophorum vaginatum, the dominant species, adjusts to elevated CO{sub 2} within three weeks. Past research also indicates other changes potentially important to ecosystem structure and function. Elevated CO{sub 2} treatment apparently delays senescence and increases the period of positive photosynthetic activity. Recent results from the 1987 field season verify the results obtained in the 1983--1986 field seasons: Elevated CO{sub 2} resulted in increased ecosystem-level flux rates. Regressions fitted to the seasonal flux rates indicate an apparent 10 d extension of positive CO{sub 2} uptake reflecting a delay of the onset of plant dormancy. This delay in senescence could increase the frost sensitivity of the system. Major end points proposed for this research include the effects of elevated CO{sub 2} and the interaction of elevated atmospheric CO{sub 2} with elevated soil temperature and increased nutrient availability on: (1) Net ecosystem CO{sub 2} flux; (2) Net photosynthetic rates; (3) Patterns and resource controls on homeostatic adjustment in the above processes to elevated CO{sub 2}; (4) Plant-nutrient status, litter quality, and forage quality; (5) Soil-nutrient status; (6) Plant-growth pattern and shoot demography.

  13. Theoretical studies of zirconium and carbon clusters with molecular dynamics simulations

    International Nuclear Information System (INIS)

    In this dissertation, we will present a systematic study of structures of fullerenes ranging from C20 to C100 by introducing a novel scheme. Using our new scheme, we not only reproduce all known fullerene structures but also successfully predicted several other fullerene structures which were confirmed by experiments. By utilizing the tight-binding molecular-dynamic (TBMD) simulation, we also studied the dynamical behavior of fullerenes: Vibrations, thermal disintegration of individual clusters as well as collisions between fullerenes. If the beauty of carbon fullerene is not enough, people found that carbon can also form tubules and even speculated that they can form three-dimensional graphite-like networks. By extending our fullerene structure searching scheme, we performed a search for the ground-state structure of three dimensional carbon network. We found the most stable structure people ever proposed for simple cubic based networks. From the difference of this new form of carbon and graphite in the electronic and vibrational properties, we propose an experimental probe to identify these novel three-dimensional carbon networks

  14. Characterizing the dynamics of soil organic carbon in grasslands on the Qinghai-Tibetan Plateau

    Institute of Scientific and Technical Information of China (English)

    ZHANG YongQiang; TANG YanHong; JIANG Jie; YANG YongHui

    2007-01-01

    Carbon dynamics of grasslands on the Qinghai-Tibetan Plateau may play an important role in regional and global carbon cycles. The CENTURY model (Version 4.5) is used to examine temporal and spatial variations of soil organic carbon (SOC) in grasslands on the Plateau for the period from 1960 to 2002. The model successfully simulates the dynamics of aboveground carbon and soil surface SOC at the soil depth of 0-20 cm and the simulated results agree well to the measurements. Examination of SOC for eight typical grasslands shows different patterns of temporal variation in different ecosystems in 1960-2002. The extent of temporal variation increases with the increase of SOC of ecosystem. SOC increases first and decreases quickly then during the period from 1990 to 2000. Spatially, SOC density obtained for the equilibrium condition declines gradually from the southeast to the northwest on the plateau and showed a high heterogeneity in the eastern plateau. The results suggest that (i) SOC density in the alpine grasslands shows remarkable response to climate change during the 42 years, and (ii) the net carbon exchange rate between the alpine grassland ecosystems and the atmosphere increases from 1990 to 2000 as compared with that before 1990.

  15. Characterizing the dynamics of soil organic carbon in grasslands on the Qinghai-Tibetan Plateau

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Carbon dynamics of grasslands on the Qinghai-Tibetan Plateau may play an important role in regional and global carbon cycles. The CENTURY model (Version 4.5) is used to examine temporal and spatial variations of soil organic carbon (SOC) in grasslands on the Plateau for the period from 1960 to 2002. The model successfully simulates the dynamics of aboveground carbon and soil surface SOC at the soil depth of 0-20 cm and the simulated results agree well to the measurements. Examination of SOC for eight typical grasslands shows different patterns of temporal variation in different ecosystems in 1960-2002. The extent of temporal variation increases with the increase of SOC of ecosystem. SOC increases first and decreases quickly then during the period from 1990 to 2000. Spatially, SOC density obtained for the equilibrium condition declines gradually from the southeast to the northwest on the plateau and showed a high heterogeneity in the eastern plateau. The results suggest that (i) SOC den-sity in the alpine grasslands shows remarkable response to climate change during the 42 years, and (ii) the net carbon exchange rate between the alpine grassland ecosystems and the atmosphere increases from 1990 to 2000 as compared with that before 1990.

  16. Deforestation, floodplain dynamics, and carbon biogeochemistry in the Amazon Basin

    Science.gov (United States)

    Bryan, M. L.; Dunne, T.; Richey, J.; Melack, J.; Simonett, D. S.; Woodwell, G.

    1984-01-01

    Three aspects of the physical geographic environment of the Amazon Basin are considered: (1) deforestation and reforestation, (2) floodplain dynamics, and (3) fluvial geomorphology. Three independent projects are coupled in this experiment to improve the in-place research and to ensure that the Shuttle Imaging Radar-B (SIR-B) experiment stands on a secure base of ongoing work. Major benefits to be obtained center on: (1) areal and locational information, (2) data from various depression angles, and (3) digital radar signatures. Analysis will be conducted for selected sites to define how well SIR-B data can be used for: (1) definition of extent and location of deforestation in a tropical moist forest, (2) definition and quantification of the nature of the vegetation and edaphic conditions on the (floodplain) of the Amazon River, and (3) quantification of the accuracy with which the geometry and channel shifting of the Amazon River may be mapped using SIR-B imagery in conjunction with other remote sensing data.

  17. Implications of altered phenology on the carbon dynamics of deciduous oak woodland

    Science.gov (United States)

    Wilkinson, Matthew; Eaton, Edward; Pinnington, Ewan; Morison, James

    2016-04-01

    The widely observed advance in spring budburst across a range of temperate forest species due to climatic warming has received considerable attention. Such changes in phenology have important implications not only for the choice of species and provenances currently being planted, which need to be suited to both current and future climatic conditions, but also for the carbon dynamics of forest ecosystems. Using a combination of phenology observations and carbon balance modelling, this study examines the influence of tree phenology and growing season length on carbon sequestration. Tree phenology and seasonal carbon dynamics were measured using phenocam images and Eddy Covariance (EC) at a deciduous oak plantation in the south-east of England (Alice Holt, Hampshire, UK). Manual phenology observations of spring budburst were also recorded in a range of European oak provenances over seven years (2004 - 2009 and again in 2013) at a trial site nearby. The EC and manual observation sites were exposed to very similar meteorological conditions. At the manual observation site there was a strong correlation between mean spring air temperature and the date of budburst in all provenances. The order in which budburst occurred was largely conserved between years and was strongly linked to source latitude, provenances that originated from southerly locations consistently reached budburst prior to those from more northerly locations. The timing of budburst in the local provenance at the manual observation site was synchronous with budburst at the EC site. The Data Assimilation Linked Ecosystem Carbon (DALEC) model was optimised for the Alice Holt site. By altering the timing of budburst within the model to reflect the observed variation in the European provenances, we assessed the implications of altered phenology on the carbon dynamics of deciduous oak in southern England.

  18. Dynamics of Soil Organic Carbon Under Uncertain Climate Change and Elevated Atmospheric CO2

    Institute of Scientific and Technical Information of China (English)

    LIN Zhong-Bing; ZHANG Ren-Duo

    2012-01-01

    Climate change and elevated atmospheric CO2 should affect the dynamics of soil organic carbon (SOC).SOC dynamics under uncertain patterns of climate warming and elevated atmospheric CO2 as well as with different soil erosion extents at Nelson Farm during 1998-2100 were simulated using stochastic modelling.Results based on numerous simulations showed that SOC decreased with elevated atmospheric temperature but increased with atmospheric CO2 concentration.Therefore,there was a counteract effect on SOC dynamics between climate warming and elevated CO2.For different soil erosion extents,warming 1 ℃ and elevated atmospheric CO2 resulted in SOC increase at least 15%,while warming 5 ℃ and elevated CO2 resulted in SOC decrease more than 29%.SOCpredictions with uncertainty assessment were conducted for different scenarios of soil erosion,climate change,and elevated CO2.Statistically,SOC decreased linearly with the probability.SOC also decreased with time and the degree of soil erosion.For example,in 2100 with a probability of 50%,SOC was 1617,1 167,and 892 g m-2,respectively,for no,minimum,and maximum soil erosion.Under climate warming 5 ℃ and elevated CO2,the soil carbon pools became a carbon source to the atmosphere (P > 95%).The results suggested that stochastic modelling could be a useful tool to predict future SOC dynamics under uncertain climate change and elevated CO2.

  19. Peatland Carbon Dynamics in Alaska During Past Warm Climates

    Science.gov (United States)

    Yu, Z.; Cleary, K.; Massa, C.; Hunt, S. J.; Klein, E. S.; Loisel, J.

    2013-12-01

    Peatlands represent a large belowground carbon (C) pool in the biosphere. However, how peatland C sequestration capacity varies with changes in climate and climate-induced disturbance is still poorly understood and debated. Here we summarize results from Alaskan peatlands to document how peat C accumulation has responded to past warm climate intervals. We find that the greatest C accumulation rates at sites from the Kenai Peninsula to the North Slope occurred during the Holocene thermal maximum (HTM) in the early Holocene. This time period also corresponds with explosive formation and expansion of new peatlands on the landscape across Alaska. In addition, we note that many peatlands that existed during the earlier Holocene on the North Slope have disappeared and are presently covered by mineral soils under tundra or sandy deposits. During the Medieval Climate Anomaly (MCA) around 1000-500 years ago, several peatlands in Alaska show high rates of C accumulation when compared to the period before the MCA during the Neoglacial or the following Little Ice Age period. Altogether, our results indicate that the Alaskan landscape was very different during the last 10,000 years and that peatlands can rapidly accumulate C under warm climatic conditions. We speculate that warmth-stimulated increase in plant production surpasses increase in peat decomposition during the early Holocene, and potentially also during the MCA. Other factors that might have contributed to rapid peat accumulation during the early Holocene include increased summer sunlight, lowered sea levels, and decreased sea-ice cover/duration. Summer insolation was ca. 8% higher than today during the early Holocene due to orbital variations, which likely promoted plant productivity by increasing growing seasons sunlight. Furthermore, lower sea levels and exposed shallow continental shelves in the Beaufort Sea (Arctic Ocean) would have made the present-day Arctic Coastal Plain more continental, with warmer summers

  20. Influence of soil texture on carbon dynamics and storage potential in tropical forest soils of Amazonia

    OpenAIRE

    Telles, Everaldo de Carvalho Conceicao; Camargo, Plinio Barbosa; Luiz A Martinelli; Trumbore, Susan E.; da Costa, Enir Salazar; Santos, Joaquim; Higuchi, Niro; de Oliveira, Raimundo Cosme

    2003-01-01

    Stable and radiocarbon isotopes were used to investigate the role of soil clay content in the storage and dynamics of soil carbon in tropical forest soils. Organic matter in clay-rich Oxisols and Ultisols contains at least two distinct components: (1) material with light δ13C signatures and turnover times of decades or less; and (2) clay-associated, 13C-enriched, carbon with turnover times of decades at the surface to millennia at depths >20 cm. Soil texture, in this case clay content, exerts...

  1. Influence of soil texture on carbon dynamics and storage potential in tropical forest soils of Amazonia

    OpenAIRE

    Telles, E.; de Camargo, P.; Martinelli, L.; Trumbore, S.; Da Costa, E; Santos, J.; N. Higuchi; de Oliveira, R.

    2003-01-01

    [1] Stable and radiocarbon isotopes were used to investigate the role of soil clay content in the storage and dynamics of soil carbon in tropical forest soils. Organic matter in clay-rich Oxisols and Ultisols contains at least two distinct components: ( 1) material with light delta(13)C signatures and turnover times of decades or less; and ( 2) clay-associated, C-13-enriched, carbon with turnover times of decades at the surface to millennia at depths > 20 cm. Soil texture, in this case clay c...

  2. Ab initio molecular dynamics simulation study of successive hydrogenation reactions of carbon monoxide producing methanol

    Science.gov (United States)

    Pham, Thi Nu; Ono, Shota; Ohno, Kaoru

    2016-04-01

    Doing ab initio molecular dynamics simulations, we demonstrate a possibility of hydrogenation of carbon monoxide producing methanol step by step. At first, the hydrogen atom reacts with the carbon monoxide molecule at the excited state forming the formyl radical. Formaldehyde was formed after adding one more hydrogen atom to the system. Finally, absorption of two hydrogen atoms to formaldehyde produces methanol molecule. This study is performed by using the all-electron mixed basis approach based on the time dependent density functional theory within the adiabatic local density approximation for an electronic ground-state configuration and the one-shot GW approximation for an electronic excited state configuration.

  3. Dynamic balancing of isoprene carbon sources reflects photosynthetic and photorespiratory responses to temperature stress.

    Science.gov (United States)

    Jardine, Kolby; Chambers, Jeffrey; Alves, Eliane G; Teixeira, Andrea; Garcia, Sabrina; Holm, Jennifer; Higuchi, Niro; Manzi, Antonio; Abrell, Leif; Fuentes, Jose D; Nielsen, Lars K; Torn, Margaret S; Vickers, Claudia E

    2014-12-01

    The volatile gas isoprene is emitted in teragrams per annum quantities from the terrestrial biosphere and exerts a large effect on atmospheric chemistry. Isoprene is made primarily from recently fixed photosynthate; however, alternate carbon sources play an important role, particularly when photosynthate is limiting. We examined the relative contribution of these alternate carbon sources under changes in light and temperature, the two environmental conditions that have the strongest influence over isoprene emission. Using a novel real-time analytical approach that allowed us to examine dynamic changes in carbon sources, we observed that relative contributions do not change as a function of light intensity. We found that the classical uncoupling of isoprene emission from net photosynthesis at elevated leaf temperatures is associated with an increased contribution of alternate carbon. We also observed a rapid compensatory response where alternate carbon sources compensated for transient decreases in recently fixed carbon during thermal ramping, thereby maintaining overall increases in isoprene production rates at high temperatures. Photorespiration is known to contribute to the decline in net photosynthesis at high leaf temperatures. A reduction in the temperature at which the contribution of alternate carbon sources increased was observed under photorespiratory conditions, while photosynthetic conditions increased this temperature. Feeding [2-(13)C]glycine (a photorespiratory intermediate) stimulated emissions of [(13)C1-5]isoprene and (13)CO2, supporting the possibility that photorespiration can provide an alternate source of carbon for isoprene synthesis. Our observations have important implications for establishing improved mechanistic predictions of isoprene emissions and primary carbon metabolism, particularly under the predicted increases in future global temperatures. PMID:25318937

  4. Effects of high CO2 levels on dynamic photosynthesis: carbon gain, mechanisms, and environmental interactions.

    Science.gov (United States)

    Tomimatsu, Hajime; Tang, Yanhong

    2016-05-01

    Understanding the photosynthetic responses of terrestrial plants to environments with high levels of CO2 is essential to address the ecological effects of elevated atmospheric CO2. Most photosynthetic models used for global carbon issues are based on steady-state photosynthesis, whereby photosynthesis is measured under constant environmental conditions; however, terrestrial plant photosynthesis under natural conditions is highly dynamic, and photosynthetic rates change in response to rapid changes in environmental factors. To predict future contributions of photosynthesis to the global carbon cycle, it is necessary to understand the dynamic nature of photosynthesis in relation to high CO2 levels. In this review, we summarize the current body of knowledge on the photosynthetic response to changes in light intensity under experimentally elevated CO2 conditions. We found that short-term exposure to high CO2 enhances photosynthetic rate, reduces photosynthetic induction time, and reduces post-illumination CO2 burst, resulting in increased leaf carbon gain during dynamic photosynthesis. However, long-term exposure to high CO2 during plant growth has varying effects on dynamic photosynthesis. High levels of CO2 increase the carbon gain in photosynthetic induction in some species, but have no significant effects in other species. Some studies have shown that high CO2 levels reduce the biochemical limitation on RuBP regeneration and Rubisco activation during photosynthetic induction, whereas the effects of high levels of CO2 on stomatal conductance differ among species. Few studies have examined the influence of environmental factors on effects of high levels of CO2 on dynamic photosynthesis. We identified several knowledge gaps that should be addressed to aid future predictions of photosynthesis in high-CO2 environments. PMID:27094437

  5. Carbon monoxide and disequilibrium dynamics in Saturn and Jupiter

    International Nuclear Information System (INIS)

    High resolution (ξ/Δξ ∼ 30,000) spectra of Jupiter and Saturn were obtained in order to study the composition and dynamics of Jupiter and Saturn. The shapes of CO absorption lines in Jupiter are broad, consistent with line formation at P ∼ 2-9 bars. This is strong evidence in favor of internal mixing as the source of CO in Jupiter. Further, we find that the O abundance at 1100 K must be nearly solar. No variations in CO abundance were found between the North Equatorial Belt, the North Tropical Zone, and the Great Red Spot. Because CO is very sensitive to variations in the rate of mixing, we conclude that there are no gross variations in mixing with location on Jupiter. We observed CO in Saturn for the first time. The source of CO in Saturn is uncertain, although theoretical arguments favor an external source to an internal one. If Saturn's rings are the source of the oxygen that eventually leads to CO in Saturn, the rate of influx required imposes an upper limit to the lifetime of the rings of t 4 in the atmosphere of Saturn. Absorption lines in the P and R branch of GeH4 are observed although no evidence of the stronger Q branch is found. We postulate that scattered solar radiation may be responsible for altering the thermal spectrum in regions of very low flux such as the Q branch region. The abundance of GeH4 is consistent with the expected disequilibration from internal mixing in Saturn. Finally, we found more acetylene in the stratosphere of Saturn as compared to Jupiter, indicating possibly faster mixing in Saturn's upper atmosphere

  6. Improved risk estimated from carbon tetrachloride. Annual progress report, October 1, 1996--September 30, 1997

    Energy Technology Data Exchange (ETDEWEB)

    Benson, J.M.

    1997-10-27

    'Carbon tetrachloride (CCl{sub 4}) has been used extensively within the Department of Energy (DOE) nuclear weapons facilities. Rocky Flats was formerly the largest volume user of CCl{sub 4} in the US, with 5,000 gallons used there in 1977 alone. At the Hanford site, several hundred thousand gallons of CCl{sub 4} were discharged between 1955 and 1973 into underground cribs for storage. Levels of CCl{sub 4} in groundwater at highly contaminated sites at the Hanford. facility have exceeded the drinking water standard of 5 ppb by several orders of magnitude. High levels of CCl{sub 4} at these facilities represent a potential health hazard for workers conducting cleanup operations and for surrounding communities. The level of CCl{sub 4} cleanup required at these sites and associated costs are driven by current human health risk estimates which assume that CCl{sub 4} is a genotoxic carcinogen. The overall purpose of these studies is to improve the scientific basis for assessing the health risk associated with human exposure to CCl{sub 4}. Specifically, the authors will determine the toxicokinetics of inhaled and ingested CCl{sub 4} in F344/Crl rats, B6C3F1 mice, and Syrian hamsters. They will also evaluate species differences in the metabolism of CCl{sub 4} by rats, mice, hamsters, and man. Dose-response relationships will be determined in all these studies. This information will be used to improve the physiologically based pharmacokinetic (PBPK) model for CCl4 originally developed by Paustenbach et al. (1988) and more recently revised by Thrall and Kenny (1996). They will also provide scientific evidence that CCl{sub 4} , like chloroform, is a hepatocarcinogen only when exposure results in cell damage, cell killing, and regenerative cell proliferation. In combination, the studies outlined in this proposal will provide the exact types of information needed to enable refined cancer risk estimates for CCl{sub 4} under the new guidelines for risk assessment proposed by

  7. Land-use changes reinforce the impacts of climate change on annual runoff dynamics in a southeast China coastal watershed

    Directory of Open Access Journals (Sweden)

    A. Ervinia

    2015-06-01

    Full Text Available Study on runoff dynamics across different physiographic regions is fundamentally important to formulate the sound strategies for water resource management especially in the coastal watershed where peoples heavily concentrated and relied on water resources. The L−R diagram, a conceptual model by which the land-changes evapotranspiration (ΔL was estimated as the difference between actual and climate evapotranspiration to identify the specific impact of land-use changes on annual runoff changes (ΔR, was developed using the 53-year hydro-climatic data of Jiulong River Watershed, a typical medium-sized subtropical coastal watershed in China. This study found that land-use changes have reinforced the impact of climatic changes on runoff changes where nearly all points were scattered in II and IV quadrant. Deforestation and expansion of built up area has diminished the water retention capacity in a catchment as well as evapotranspiration thus produce extra runoff accounting for 12–183 % of total runoff increase. In contrast, reforestation makes the significant contribution to decreasing annual runoff for about 21–82 % of total runoff loss. This study revealed the river runoff has become more vulnerable to intensive anthropogenic disturbances under the context of climate changes in a coastal watershed.

  8. Population dynamics of Agriophyllum squarrosum, a pioneer annual plant endemic to mobile sand dunes, in response to global climate change.

    Science.gov (United States)

    Qian, Chaoju; Yin, Hengxia; Shi, Yong; Zhao, Jiecai; Yin, Chengliang; Luo, Wanyin; Dong, Zhibao; Chen, Guoxiong; Yan, Xia; Wang, Xiao-Ru; Ma, Xiao-Fei

    2016-01-01

    Climate change plays an important role in the transition of ecosystems. Stratigraphic investigations have suggested that the Asian interior experienced frequent transitions between grassland and desert ecosystems as a consequence of global climate change. Using maternally and bi-parentally inherited markers, we investigated the population dynamics of Agriophyllum squarrosum (Chenopodiaceae), an annual pioneer plant endemic to mobile sand dunes. Phylogeographic analysis revealed that A. squarrosum could originate from Gurbantunggut desert since ~1.6 Ma, and subsequently underwent three waves of colonisation into other deserts and sandy lands corresponding to several glaciations. The rapid population expansion and distribution range shifts of A. squarrosum from monsoonal climate zones suggested that the development of the monsoonal climate significantly enhanced the population growth and gene flow of A. squarrosum. These data also suggested that desertification of the fragile grassland ecosystems in the Qinghai-Tibetan Plateau was more ancient than previously suggested and will be aggravated under global warming in the future. This study provides new molecular phylogeographic insights into how pioneer annual plant species in desert ecosystems respond to global climate change, and facilitates evaluation of the ecological potential and genetic resources of future crops for non-arable dry lands to mitigate climate change. PMID:27210568

  9. A Radiocarbon Database for Improving Understanding of Global Soil Carbon Dynamics: Part I

    Science.gov (United States)

    Torn, M. S.; Trumbore, S.; Smith, L. J.; Nave, L. E.; Sierra, C. A.; Harden, J. W.; Agarwal, D.; van Ingen, C.; Radiocarbon Database Workshop 2011

    2011-12-01

    Soils play a large role in the global carbon cycle, but soil carbon stocks and dynamics remain highly uncertain. Radiocarbon (14C) observations from soils and soil respiration provide one of the only ways to infer terrestrial carbon turnover times or to test ecosystem carbon models. Although a wealth of such observations exists, they are scattered in small data sets held by individual researchers, and have not been compiled in a form easy to use for multi-site analysis, global assessments, or model testing. Here we introduce a new, global radiocarbon database that will synthesize datasets from multiple contributors to facilitate research on three broad questions: (1) What are current patterns of soil carbon dynamics, and what factors influence these patterns? (2) What is the sequestration capacity of different soils? (3) What are likely impacts of global change on the soil resource? (4) How well do models represent important carbon cycle processes, and how can they be improved? In addition to assembling data in a common format for analyses, this database will offer query capabilities and the ability to combine data with gridded global products, such as temporally resolved temperature and precipitation, NPP and GPP, and a climate-based decomposition index. Some of the near-term synthesis goals include analyzing depth profiles of 14C for across gradients in ecosystem state factors (climate, organisms, relief, parent material, time, and human influence) and soil orders; mapping surface-soil 14C values on soil temperature and moisture; and comparing soil carbon turnover times to NPP and soil carbon stocks. We are currently incorporating data from 18 contributors and six continents, with 14C measurements from soils representing nine soil orders, plant and microbial tissues, and respiration fluxes. Our intention is to grow the database and make it available to a wide community of scientists. For example, observations for different disturbance, experimental treatment, or

  10. Effects of climate change and land management on soil organic carbon dynamics and carbon leaching in northwestern Europe

    Science.gov (United States)

    Stergiadi, Maria; van der Perk, Marcel; de Nijs, Ton C. M.; Bierkens, Marc F. P.

    2016-03-01

    Climate change and land management practices are projected to significantly affect soil organic carbon (SOC) dynamics and dissolved organic carbon (DOC) leaching from soils. In this modelling study, we adopted the Century model to simulate past (1906-2012), present, and future (2013-2100) SOC and DOC levels for sandy and loamy soils typical of northwestern European conditions under three land use types (forest, grassland, and arable land) and several future scenarios addressing climate change and land management change. To our knowledge, this is the first time that the Century model has been applied to assess the effects of climate change and land management on DOC concentrations and leaching rates, which, in combination with SOC, play a major role in metal transport through soil. The simulated current SOC levels were generally in line with the observed values for the different kinds of soil and land use types. The climate change scenarios result in a decrease in both SOC and DOC for the agricultural systems, whereas for the forest systems, SOC is projected to slightly increase and DOC to decrease. An analysis of the sole effects of changes in temperature and changes in precipitation showed that, for SOC, the temperature effect predominates over the precipitation effect, whereas for DOC the precipitation effect is more prominent. A reduction in the application rates of fertilisers under the land management scenario leads to a decrease in the SOC stocks and the DOC leaching rates for the arable land systems, but it has a negligible effect on SOC and DOC levels for the grassland systems. Our study demonstrated the ability of the Century model to simulate climate change and agricultural management effects on SOC dynamics and DOC leaching, providing a robust tool for the assessment of carbon sequestration and the implications for contaminant transport in soils.

  11. Use of carbon isotopes as tracer to estimate carbon dynamics in forest

    International Nuclear Information System (INIS)

    Soil respiration is the sum of heterotrophic respiration (decomposition of soil organic matter and litter) and root respiration. These CO2 sources may respond differently to the variation in environmental change. Hence, the production of CO2 from each source needs to be estimated individually. In this study, we use radiocarbon signatures to partition soil respiration in a cool-temperate deciduous forest in Japan by means of an isotope mass balance approach. Monthly measurements of Δ14C in soil respiration were conducted using the closed chamber method. The Δ14C in root respiration was assumed to be the value equivalent to the present atmospheric CO2 and the Δ14C in heterotrophic respiration was estimated from the depth profile of Δ14C in soil organic matter. The results showed the seasonal variation in each source; the contribution of root respiration increased in July, while the contribution of heterotrophic respiration increased with the rise in soil temperature in August. The annual CO2 flux was calculated using temperature-CO2 flux model and the hourly soil temperature data in the site. Based on the results, the contribution ratios of CO2 sources to soil respiration were estimated as: 34% from litter decomposition, 31% from soil organic matter decomposition and 35% from root respiration. (author)

  12. The effect of empirical potential functions on modeling of amorphous carbon using molecular dynamics method

    International Nuclear Information System (INIS)

    Empirical potentials have a strong effect on the hybridization and structure of amorphous carbon and are of great importance in molecular dynamics (MD) simulations. In this work, amorphous carbon at densities ranging from 2.0 to 3.2 g/cm3 was modeled by a liquid quenching method using Tersoff, 2nd REBO, and ReaxFF empirical potentials. The hybridization, structure and radial distribution function G(r) of carbon atoms were analyzed as a function of the three potentials mentioned above. The ReaxFF potential is capable to model the change of the structure of amorphous carbon and MD results are in a good agreement with experimental results and density function theory (DFT) at low density of 2.6 g/cm3 and below. The 2nd REBO potential can be used when amorphous carbon has a very low density of 2.4 g/cm3 and below. Considering the computational efficiency, the Tersoff potential is recommended to model amorphous carbon at a high density of 2.6 g/cm3 and above. In addition, the influence of the quenching time on the hybridization content obtained with the three potentials is discussed.

  13. Dynamic Mechanism of Single-Stranded DNA Encapsulated into Single-Wall Carbon Nanotubes: A Molecular Dynamics Simulation Study

    Science.gov (United States)

    Xing, Yan-Fei; Yang, Chuan-Lu; Mo, Yong-Fang; Wang, Mei-Shan; Ma, Xiao-Guang

    2014-02-01

    Hybrids of single-walled carbon nanotubes (SWCNTs) and biological molecules have been utilized for numerous applications in sensing, imaging, and drug delivery. By molecular dynamics simulation, we investigate the encapsulation of single-strand DNA (ssDNA) containing eight adenine bases with (17,17)-(12,12) SWCNTs. The effects of the diameter and length of SWCNTs on the encapsulation process are explored with the calculated curves of the center-of-mass distance, the van der Waals interaction between the ssDNA and SWCNT, the root-mean-square deviation of the ssDNA, and the radius of gyration of the ssDNA. The free energy of the encapsulated ssDNA for each SWCNT is also obtained via steered molecular dynamics simulation. The most suitable SWCNT for encapsulating the ssDNA is also suggested.

  14. Microbial carbon recycling - an underestimated process controlling soil carbon dynamics - Part 1: A long-term laboratory incubation experiment

    Science.gov (United States)

    Basler, A.; Dippold, M.; Helfrich, M.; Dyckmans, J.

    2015-10-01

    Independent of its chemical structure carbon (C) persists in soil for several decades, controlled by stabilization and recycling. To disentangle the importance of the two factors on the turnover dynamics of soil sugars, an important compound of soil organic matter (SOM), a 3-year incubation experiment was conducted on a silty loam soil under different types of land use (arable land, grassland and forest) by adding 13C-labelled glucose. The compound-specific isotope analysis of soil sugars was used to examine the dynamics of different sugars during incubation. Sugar dynamics were dominated by a pool of high mean residence times (MRT) indicating that recycling plays an important role for sugars. However, this was not substantially affected by soil C content. Six months after label addition the contribution of the label was much higher for microbial biomass than for CO2 production for all examined land use types, corroborating that substrate recycling was very effective within the microbial biomass. Two different patterns of tracer dynamics could be identified for different sugars: while fucose and mannose showed highest label contribution at the beginning of the incubation with a subsequent slow decline, galactose and rhamnose were characterized by slow label incorporation with subsequently constant levels, which indicates that recycling is dominating the dynamics of these sugars. This may correspond to (a) different microbial growing strategies (r and K-strategist) or (b) location within or outside the cell membrane (lipopolysaccharides vs. exopolysaccharides) and thus be subject of different re-use within the microbial food web. Our results show how the microbial community recycles substrate very effectively and that high losses of substrate only occur during initial stages after substrate addition. This study indicates that recycling is one of the major processes explaining the high MRT observed for many SOM fractions and thus is crucial for understanding the

  15. Optics and Fluid Dynamics Department. Annual progress report 1 January - 31 December 1991

    International Nuclear Information System (INIS)

    Research in the Optics and Fluid Dynamics Department covers quasi-elastic light scattering, optical and electronic information processing, continuum physics and activities in connection with the Euratom fusion association. A summary of activities in 1991 is presented. Optical diagnostic methods based on quasielastic light scattering have been developed. Beam propagation in random and nonlinear media has been investigated. Spatial and temporal processing schemes, especially for pattern recognition, have been investigated. Within the area of fluid dynamics spectral models for studying the dynamics of coherent structures have been developed. Coherent structures have been investigated in a plasma and are now also investigated in a rotating fluid. Fusion relevant work performed under the Euratom association includes investigations of turbulent transport and the development of diagnostic methods. A special activity is concentrated on the development of pellet injection systems for fusion research. (au) (1 tab., 20 ills., 37 refs.)

  16. Improving Terrestrial Carbon and Water Simulations with Dynamic Root Distribution over the Amazon Basin

    Science.gov (United States)

    Wang, Y.; Xie, Z.; Jia, B.

    2015-12-01

    Realistic representation of roots and their behavior are important in hydrological, ecological and climate modeling. However, land surface models currently prescribe rooting profiles as a function of only the plant functional types, with no consideration of the dynamic rooting strategies in response to the changing environments. In this study, a new dynamic rooting scheme which taking the controlling effects of soil water and nitrogen on rooting strategies into account was incorporated into the version 4.5 of the Community Land Model with carbon-nitrogen interactions (CLM4.5-CN). Two pairs of experiments were conducted to study the effects of dynamic root distribution on eco-hydrological modeling for the Tapajos National Forest km83 (BRSa3) site and the Amazon Basin. For site-level comparisons, the dynamic rooting scheme can improve the carbon and water cycle modeling by reducing the root-mean-square error (RMSE) in gross primary production (GPP) by 0.4 g C m-2 day-1, net ecosystem exchange (NEE) by 1.96 g C m-2 day-1, latent heat (LE) by 5.0 W m-2, soil moisture (SM) by 0.03 m3 m-3. In the Amazon basin, the vegetation responses (including GPP and LE) to seasonal drought and server 2005 drought are also better captured with dynamic root distribution incorporated.

  17. Annual dynamics of impervious surface in the Pearl River Delta, China, from 1988 to 2013, using time series Landsat imagery

    Science.gov (United States)

    Zhang, Lei; Weng, Qihao

    2016-03-01

    Information on impervious surface distribution and dynamics is useful for understanding urbanization and its impacts on hydrological cycle, water management, surface energy balances, urban heat island, and biodiversity. Numerous methods have been developed and successfully applied to estimate impervious surfaces. Previous methods of impervious surface estimation mainly focused on the spectral differences between impervious surfaces and other land covers. Moreover, the accuracy of estimation from single or multi-temporal images was often limited by the mixed pixel problem in coarse- or medium-resolution imagery or by the intra-class spectral variability problem in high resolution imagery. Time series satellite imagery provides potential to resolve the above problems as well as the spectral confusion with similar surface characteristics due to phenological change, inter-annual climatic variability, and long-term changes of vegetation. Since Landsat time series has a long record with an effective spatial resolution, this study aimed at estimating and mapping impervious surfaces by analyzing temporal spectral differences between impervious and pervious surfaces that were extracted from dense time series Landsat imagery. Specifically, this study developed an efficient method to extract annual impervious surfaces from time series Landsat data and applied it to the Pearl River Delta, southern China, from 1988 to 2013. The annual classification accuracy yielded from 71% to 91% for all classes, while the mapping accuracy of impervious surfaces ranged from 80.5% to 94.5%. Furthermore, it is found that the use of more than 50% of Scan Line Corrector (SLC)-off images after 2003 did not substantially reduced annual classification accuracy, which ranged from 78% to 91%. It is also worthy to note that more than 80% of classification accuracies were achieved in both 2002 and 2010 despite of more than 40% of cloud cover detected in these two years. These results suggested that the

  18. Diameter-dependent bending dynamics of single-walled carbon nanotubes in liquids

    Science.gov (United States)

    Fakhri, Nikta; Tsyboulski, Dmitri A.; Cognet, Laurent; Weisman, R. Bruce; Pasquali, Matteo

    2009-01-01

    By relating nanotechnology to soft condensed matter, understanding the mechanics and dynamics of single-walled carbon nanotubes (SWCNTs) in fluids is crucial for both fundamental and applied science. Here, we study the Brownian bending dynamics of individual chirality-assigned SWCNTs in water by fluorescence microscopy. The bending stiffness scales as the cube of the nanotube diameter and the shape relaxation times agree with the semiflexible chain model. This suggests that SWCNTs may be the archetypal semiflexible filaments, highly suited to act as nanoprobes in complex fluids or biological systems. PMID:19706503

  19. Selective optical switching of interface-coupled relaxation dynamics in carbon nanotube-Si heterojunctions

    KAUST Repository

    Ponzoni, Stefano

    2014-10-16

    By properly tuning the photon energy of a femtosecond laser pump, we disentangle, in carbon nanotube-Si (CNT/Si) heterojunctions, the fast relaxation dynamics occurring in CNT from the slow repopulation dynamics due to hole charge transfer at the junction. In this way we are able to track the transfer of the photogenerated holes from the Si depletion layer to the CNT layer, under the action of the built-in heterojunction potential. This also clarifies that CNT play an active role in the junction and do not act only as channels for charge collection and transport.

  20. Dynamics of the Oxygen, Carbon Dioxide, and Water Interaction across the Insect Spiracle

    Directory of Open Access Journals (Sweden)

    S. M. Simelane

    2014-01-01

    Full Text Available This paper explores the dynamics of respiratory gases interactions which are accompanied by the loss of water through an insect’s spiracle. Here we investigate and analyze this interaction by deriving a system of ordinary differential equations for oxygen, carbon dioxide, and water vapor. The analysis is carried out in continuous time. The purpose of the research is to determine bounds for the gas volumes and to discuss the complexity and stability of the equilibria. Numerical simulations also demonstrate the dynamics of our model utilizing the new conditions for stability and instability.

  1. Dynamic characteristics of multi-walled carbon nanotubes under a transverse magnetic field

    Indian Academy of Sciences (India)

    S Li; H J Xie; X Wang

    2011-02-01

    This paper reports the results of an investigation into the effect of transverse magnetic fields on dynamic characteristics of multi-walled carbon nanotubes (MWNTs). Couple dynamic equations of MWNTs subjected to a transverse magnetic field are derived and solved by considering the Lorentz magnetic forces induced by a transverse magnetic field exerted on MWCNTs. Results show that the transverse magnetic field exerted on MWNTs makes the lowest frequency of the MWNTs nonlinearly decrease and the highest frequency, changeless. When the strength of applied transverse magnetic fields is larger than a given value the two walls of MWNTs appear in the radial and axial coaxial vibration phenomena.

  2. STUDY OF DYNAMIC RECRYSTALLIZATION OF LOW CARBON STEEL IN THIN SLAB CONTINUOUS ROLLING PROCESS

    Institute of Scientific and Technical Information of China (English)

    X.K. Liang; X.J. Sun; Q.Y. Liu; H. Dong

    2006-01-01

    Combined with the technological characteristics of thin slab continuous rolling process (TSCR),dynamic recrystallization of an extremely coarse austenite of low carbon steel is studied by Thermecmaster-Z hot simulator. By the analysis of true stress-strain curves and the observation of microstructures at different deformation stages, the critical stress and critical strain are determined under different deformation conditions. The effect of Z parameter on dynamic recrystallization of coarse austenite is studied. The microstructure evolution in real production is also discussed.

  3. Collision dynamics of polyatomic molecules containing carbon rings at low temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Li, Zhiying; Heller, Eric J. [Department of Physics, Harvard University, Cambridge, Massachusetts 02138 (United States); Krems, Roman V. [Department of Chemistry, The University of British Columbia, Vancouver, British Columbia V6T 1Z1 (Canada)

    2014-09-14

    We explore the collision dynamics of complex hydrocarbon molecules (benzene, coronene, adamantane, and anthracene) containing carbon rings in a cold buffer gas of {sup 3}He. For benzene, we present a comparative analysis of the fully classical and fully quantum calculations of elastic and inelastic scattering cross sections at collision energies between 1 and 10 cm{sup −1}. The quantum calculations are performed using the time-independent coupled channel approach and the coupled-states approximation. We show that the coupled-states approximation is accurate at collision energies between 1 and 20 cm{sup −1}. For the classical dynamics calculations, we develop an approach exploiting the rigidity of the carbon rings and including low-energy vibrational modes without holonomic constraints. Our results illustrate the effect of the molecular shape and the vibrational degrees of freedom on the formation of long-lived resonance states that lead to low-temperature clustering.

  4. Two novel low-power and high-speed dynamic carbon nanotube full-adder cells

    Directory of Open Access Journals (Sweden)

    Eshghi Mohammad

    2011-01-01

    Full Text Available Abstract In this paper, two novel low-power and high-speed carbon nanotube full-adder cells in dynamic logic style are presented. Carbon nanotube field-effect transistors (CNFETs are efficient in designing a high performance circuit. To design our full-adder cells, CNFETs with three different threshold voltages (low threshold, normal threshold, and high threshold are used. First design generates SUM and COUT through separate transistors, and second design is a multi-output dynamic full adder. Proposed full adders are simulated using HSPICE based on CNFET model with 0.9 V supply voltages. Simulation result shows that the proposed designs consume less power and have low power-delay product compared to other CNFET-based full-adder cells.

  5. Molecular dynamics simulation of thermal conductivity of single-wall carbon nanotubes

    International Nuclear Information System (INIS)

    Based on equilibrium molecular dynamics (EMD) simulation method, the thermal conductivity of single-wall carbon nanotubes (SWNTs) dependent on tube length and temperature is investigated. Nonequilibrium molecular dynamics (NEMD) simulations are also carried out as comparison at 1000 K. Through extrapolation to an infinite system size, the data from the NEMD method are in the same order of the simulated results calculated from the EMD model. The effects of isotopic atom and vacancy on the thermal conductivity of carbon nanotubes (CNTs) are also investigated from EMD simulation results. It is demonstrated that the vacancy scattering on phonons is stronger than the isotopic atom doing at the same concentration, which causes more reduction on lattice thermal conductivity of CNTs

  6. Ultrafast carrier dynamics in tetrahedral amorphous carbon: carrier trapping versus electron-hole recombination

    International Nuclear Information System (INIS)

    We report the investigation of the ultrafast carrier dynamics in thin tetrahedral amorphous carbon films by means of femtosecond time-resolved reflectivity. We estimated the electron-phonon relaxation time of a few hundred femtoseconds and we observed that under low optical excitation photo-generated carriers decay according to two distinct mechanisms attributed to trapping by defect states and direct electron-hole recombination. With high excitation, when photo-carrier and trap densities are comparable, a unique temporal evolution develops, as the time dependence of the trapping process becomes degenerate with the electron-hole recombination. This experimental evidence highlights the role of defects in the ultrafast electronic dynamics and is not specific to this particular form of carbon, but has general validity for amorphous and disordered semiconductors

  7. Annual plankton dynamics in a coupled physical-biological model of the Strait of Georgia, British Columbia

    Science.gov (United States)

    Peña, M. Angelica; Masson, Diane; Callendar, Wendy

    2016-08-01

    A three-dimensional coupled biophysical model was developed to study the dynamics of the plankton ecosystem in the Strait of Georgia (SoG) estuary. The ocean circulation component is an implementation of the Regional Ocean Modeling System (ROMS) and the lower trophic level ecosystem is a nine-compartment Nutrient-Phytoplankton-Zooplankton-Detritus (NPZD) model that includes two types of phytoplankton and of zooplankton. A three year hindcast (2007-2009) is used to examine the mean annual seasonal cycle of the local plankton dynamics. For realistic values of irradiance, wind forcing and fresh water fluxes, the model predicts a seasonal cycle of salinity, nutrients and plankton in reasonable agreement with observations. In particular, the model reproduces the main features of the estuarine circulation, the marked increase in phytoplankton biomass during spring followed by intermittent less intense blooms during summer and fall, as well as the seasonal pattern of zooplankton biomass. Model results show that primary production fluctuates between low values in January and high values in April, with an annual production of 270 ± 33 (gC m-2) in the SoG. Most primary production is fueled by nitrate (f-ratio of about 0.7). Upwelling is the main source of nitrate into the upper layer, while most of the nitrate entering the Strait is exported out by horizontal advection. Physical processes, such as freshwater inflow, wind events, tidal mixing, and horizontal transports are important in maintaining the high spatio-temporal variability of the local phytoplankton biomass and production. Horizontal variability is high during the growing season (March to September). In summer, phytoplankton concentrates near the surface, in the shallow mixed layer, resulting in sporadic nutrient limitation of phytoplankton growth. In the northern portion of the strait, weaker summer winds and tidal currents lead to increased near-surface stratification which restricts nutrient fluxes and limit

  8. Carbon Dioxide Information Analysis Center and World Data Center for Atmospheric Trace Gases Fiscal Year 2001 Annual Report

    Energy Technology Data Exchange (ETDEWEB)

    Cushman, R.M.

    2002-10-15

    The Carbon Dioxide Information Analysis Center (CDIAC), which includes the World Data Center (WDC) for Atmospheric Trace Gases, is the primary global change data and information analysis center of the U.S. Department of Energy (DOE). More than just an archive of data sets and publications, CDIAC has, since its inception in 1982, enhanced the value of its holdings through intensive quality assurance, documentation, and integration. Whereas many traditional data centers are discipline-based (for example, meteorology or oceanography), CDIAC's scope includes potentially anything and everything that would be of value to users concerned with the greenhouse effect and global climate change, including concentrations of carbon dioxide (CO{sub 2}) and other radiatively active gases in the atmosphere; the role of the terrestrial biosphere and the oceans in the biogeochemical cycles of greenhouse gases; emissions of CO{sub 2} and other trace gases to the atmosphere; long-term climate trends; the effects of elevated CO{sub 2} on vegetation; and the vulnerability of coastal areas to rising sea levels. CDIAC is located within the Environmental Sciences Division (ESD) at Oak Ridge National Laboratory (ORNL) in Oak Ridge, Tennessee. CDIAC is co-located with ESD researchers investigating global-change topics, such as the global carbon cycle and the effects of carbon dioxide on climate and vegetation. CDIAC staff are also connected with current ORNL research on related topics, such as renewable energy and supercomputing technologies. CDIAC is supported by the Environmental Sciences Division (Jerry Elwood, Director) of DOE's Office of Biological and Environmental Research. CDIAC represents DOE in the multi-agency Global Change Data and Information System (GCDIS). Wanda Ferrell is DOE's Program Manager with overall responsibility for CDIAC. Roger Dahlman is responsible for CDIAC's AmeriFlux tasks, and Anna Palmisano for CDIAC's Ocean Data tasks. CDIAC is made

  9. Temporal dynamics of soil organic carbon after land-use change in the temperate zone – carbon response functions as a model approach

    DEFF Research Database (Denmark)

    Poeplau, Christopher; Don, Axel; Vesterdal, Lars; Leifeld, Jens; van Wesemaels, Bas; Schumacher, Jens; Gensior, Andreas

    2011-01-01

    Land-use change (LUC) is a major driving factor for the balance of soil organic carbon (SOC) stocks and the global carbon cycle. The temporal dynamic of SOC after LUC is especially important in temperate systems with a long reaction time. On the basis of 95 compiled studies covering 322 sites in...... the temperate zone, carbon response functions (CRFs) were derived to model the temporal dynamic of SOC after five different LUC types (mean soil depth of 30±6 cm). Grassland establishment caused a long lasting carbon sink with a relative stock change of 128±23% and afforestation on former cropland a...... sink of 116±54%, 100 years after LUC (mean±95% confidence interval). No new equilibrium was reached within 120 years. In contrast, there was no SOC sink following afforestation of grasslands and 75% of all observations showed SOC losses, even after 100 years. Only in the forest floor, there was carbon...

  10. Contributions of secondary forest and nitrogen dynamics to terrestrial carbon uptake

    Directory of Open Access Journals (Sweden)

    X. Yang

    2010-10-01

    Full Text Available We use a terrestrial carbon-nitrogen cycle component of the Integrated Science Assessment Model (ISAM to investigate the impacts of nitrogen dynamics on regrowing secondary forests over the 20th century. We further examine what the impacts of nitrogen deposition and land use change history are on terrestrial carbon uptake since preindustrial time. Our results suggest that global total net land use emissions for the 1990s associated with changes in cropland, pastureland, and wood harvest are 1.22 GtC/yr. Without considering the secondary forest regrowth, the estimated net global total land use emissions are 1.58 GtC/yr or about 0.36 GtC/yr higher than if secondary forest regrowth is considered. Results also show that without considering the nitrogen dynamics and deposition, the estimated global total secondary forest sink for the 1990s is 0.90 GtC/yr or about 0.54 GtC/yr higher than estimates that include the impacts of nitrogen dynamics and deposition. Nitrogen deposition alone is responsible for about 0.13 GtC/yr of the total secondary forest sink. While nitrogen is not a limiting nutrient in the intact primary forests in tropical regions, our study suggests that nitrogen becomes a limiting nutrient for regrowing secondary forests of the tropical regions, in particular Latin America and Tropical Africa. This is because land use change activities, especially wood harvest, removes large amounts of nitrogen from the system when slash is burnt or wood is removed for harvest. However, our model results show that carbon uptake is enhanced in the tropical secondary forests of the Indian region. We argue that this may be due to enhanced nitrogen mineralization and increased nitrogen availability following land use change in the Indian tropical forest ecosystems. Results also demonstrate that there is a significant amount of carbon accumulating in the Northern Hemisphere where most land use changes and forest regrowth has occurred in recent decades

  11. Contributions of secondary forest and nitrogen dynamics to terrestrial carbon uptake

    Directory of Open Access Journals (Sweden)

    X. Yang

    2010-04-01

    Full Text Available We use a terrestrial carbon-nitrogen cycle component of the Integrated Science Assessment Model (ISAM to investigate the impacts of nitrogen dynamics on regrowing secondary forests over the 20th century. We further examine what the impacts of nitrogen deposition and land use change history are on terrestrial carbon uptake since preindustrial time. Our results suggest that global total net land use emissions for the 1990s associated with changes in cropland, pastureland, and wood harvest are 1.22 GtC/yr. Without considering the secondary forest regrowth, the estimated net global total land use emissions are 1.58 GtC/yr or about 0.36 GtC/yr higher than if secondary forest regrowth is considered. Results also show that without considering the nitrogen dynamics and deposition, the estimated global total secondary forest sink for the 1990s is 0.90 GtC/yr or about 0.54 GtC/yr higher than estimates that include the impacts of nitrogen dynamics and deposition. Nitrogen deposition alone is responsible for about 0.13 GtC/yr of the total secondary forest sink. While nitrogen is not a limiting nutrient in the intact primary forests in tropical regions, our study suggests that nitrogen becomes a limiting nutrient for regrowing secondary forests of the tropical regions, in particular Latin America and Tropical Africa. This is because land use change activities, especially wood harvest, removes large amounts of nitrogen from the system when slash is burnt or wood is removed for harvest. However, our model results show that carbon uptake is enhanced in the tropical secondary forests of the Indian region. We argue that this may be due to enhanced nitrogen mineralization and increased nitrogen availability following land use change in the Indian tropical forest ecosystems. Results also demonstrate that there is a significant amount of carbon accumulating in the Northern Hemisphere where most land use changes and forest regrowth has occurred in recent decades

  12. Contributions of secondary forest and nitrogen dynamics to terrestrial carbon uptake

    Science.gov (United States)

    Yang, X.; Richardson, T. K.; Jain, A. K.

    2010-10-01

    We use a terrestrial carbon-nitrogen cycle component of the Integrated Science Assessment Model (ISAM) to investigate the impacts of nitrogen dynamics on regrowing secondary forests over the 20th century. We further examine what the impacts of nitrogen deposition and land use change history are on terrestrial carbon uptake since preindustrial time. Our results suggest that global total net land use emissions for the 1990s associated with changes in cropland, pastureland, and wood harvest are 1.22 GtC/yr. Without considering the secondary forest regrowth, the estimated net global total land use emissions are 1.58 GtC/yr or about 0.36 GtC/yr higher than if secondary forest regrowth is considered. Results also show that without considering the nitrogen dynamics and deposition, the estimated global total secondary forest sink for the 1990s is 0.90 GtC/yr or about 0.54 GtC/yr higher than estimates that include the impacts of nitrogen dynamics and deposition. Nitrogen deposition alone is responsible for about 0.13 GtC/yr of the total secondary forest sink. While nitrogen is not a limiting nutrient in the intact primary forests in tropical regions, our study suggests that nitrogen becomes a limiting nutrient for regrowing secondary forests of the tropical regions, in particular Latin America and Tropical Africa. This is because land use change activities, especially wood harvest, removes large amounts of nitrogen from the system when slash is burnt or wood is removed for harvest. However, our model results show that carbon uptake is enhanced in the tropical secondary forests of the Indian region. We argue that this may be due to enhanced nitrogen mineralization and increased nitrogen availability following land use change in the Indian tropical forest ecosystems. Results also demonstrate that there is a significant amount of carbon accumulating in the Northern Hemisphere where most land use changes and forest regrowth has occurred in recent decades. This study indicates

  13. Dynamical and biogeochemical control on the decadal variability of ocean carbon fluxes

    Directory of Open Access Journals (Sweden)

    R. Séférian

    2013-04-01

    Full Text Available Several recent observation-based studies suggest that ocean anthropogenic carbon uptake has slowed down due to the impact of anthropogenic forced climate change. However, it remains unclear whether detected changes over the recent time period can be attributed to anthropogenic climate change or rather to natural climate variability (internal plus naturally forced variability alone. One large uncertainty arises from the lack of knowledge on ocean carbon flux natural variability at the decadal time scales. To gain more insights into decadal time scales, we have examined the internal variability of ocean carbon fluxes in a 1000 yr long preindustrial simulation performed with the Earth System Model IPSL-CM5A-LR. Our analysis shows that ocean carbon fluxes exhibit low-frequency oscillations that emerge from their year-to-year variability in the North Atlantic, the North Pacific, and the Southern Ocean. In our model, a 20 yr mode of variability in the North Atlantic air-sea carbon flux is driven by sea surface temperature variability and accounts for ~40% of the interannual regional variance. The North Pacific and the Southern Ocean carbon fluxes are also characterised by decadal to multi-decadal modes of variability (10 to 50 yr that account for 20–40% of the interannual regional variance. These modes are driven by the vertical supply of dissolved inorganic carbon through the variability of Ekman-induced upwelling and deep-mixing events. Differences in drivers of regional modes of variability stem from the coupling between ocean dynamics variability and the ocean carbon distribution, which is set by large-scale secular ocean circulation.

  14. Spatial and Temporal Dynamics of Carbonate Chemistry in the Northwestern Hawaiian Islands

    Science.gov (United States)

    Coughlin, C.; Winn, C. D.; Kahng, S.

    2014-12-01

    The rapid increase in atmospheric and surface ocean CO2 concentrations has the potential to drastically alter the metabolic processes particularly in nearshore ecosystems. However, much of what is known about carbonate chemistry is based on observations and analysis of surface waters of the open ocean where spatial and temporal variability is far less dynamic than in nearshore coral reef ecosystems. Carbon system dynamics data from four consecutive years has been examined in the coastal and nearshore waters of the Papahānaumokuākea Marine National Monument in the Northwest Hawaiian Islands. This data has been collected for the purpose of improving our understanding of the carbon system dynamics in this unique and pristine environment. The data collected includes continuous CTD data and discrete bottle samples, as well as continuous underway measurements. In addition to standard hydrographic profile data, water column alkalinity and pH have been measured on discrete water samples, and continuous underway measurements of pCO2 and pH have been obtained. This data is used to investigate the impact of NWHI coral reef ecosystems on the carbon system in and surrounding the archipelago. The data demonstrates that a significant "island mass effect" with respect to the oceanographic carbon system exists around the islands within the archipelago. In addition, spatial and temporal variability of several oceanographic features that exhibit a radial, latitudinal, or longitudinal gradient in the nearshore waters of the NWHI islands, islets, and atolls will be described. Finally, a shallow pH maximum coincident with the shallow oxygen maximum is observed, which suggests an open ocean feature substantially influenced by turbulence surrounding the islands within the monument. The data analysis and coral reef ecosystem monitoring will aid in developing a long-term plan to assist in the sustainability of Papahānaumokuākea Marine National Monument.

  15. Evaluating the effectiveness of carbon tax for total emission control of carbon dioxide. Systems analysis of a dynamic environmental-economic model

    International Nuclear Information System (INIS)

    This paper deals with how to evaluate the effectiveness of carbon tax (environmental tax) for regulating the carbon dioxide emissions. For this purpose we mainly deal with a primal problem and its dual problem of dynamic linear programming model. The primal problem is formulated by using Leontief type input-output model and the basic idea of commodity stocks. It represents the balance of materials. The dual problem is obtained and interpreted as cash balance. It is clarified in this paper whether the carbon tax is effective to decrease the total amount of carbon dioxide emissions. (author)

  16. The role of tropical deforestation in the global carbon cycle: Spatial and temporal dynamics

    Science.gov (United States)

    Houghton, R. A.; Skole, David; Moore, Berrien; Melillo, Jerry; Steudler, Paul

    1995-01-01

    'The Role of Tropical Deforestation in the Global Carbon cycle: Spatial and Temporal Dynamics', was a joint project involving the University of New Hampshire, the Marine Biological Laboratory, and the Woods Hole Research Center. The contribution of the Woods Hole Research Center consisted of three tasks: (1) assist University of New Hampshire in determining the net flux of carbon between the Brazilian Amazon and the atmosphere by means of a terrestrial carbon model; (2) address the spatial distribution of biomass across the Amazon Basin; and (3) assist NASA Headquarters in development of a science plan for the Terrestrial Ecology component of the NASA-Brazilian field campaign (anticipated for 1997-2001). Progress on these three tasks is briefly described.

  17. Visualizing the growth dynamics of individual single-wall carbon nanotubes

    DEFF Research Database (Denmark)

    Wagner, Jakob Birkedal; Zhang, Lili; He, Maoshuai;

    In order to meet the increasing demand of faster and more flexible electronics and optical devices and at the same time decrease the use of the critical metals, carbon based devices are in fast development. Single walled carbon nanotube (SWCNT) based electronics is a way of addressing the...... environment friendly approach of faster and better electronics. In order to exploit the potential of SWCNTs in the electronic industry fully, selective growth of either conducting or semiconducting tubes is of high importance. Understanding the mechanism for growth of SWCNTs is of great importance for...... around the studied sample at elevated temperature gives a unique way of monitoring gas-solid interactions such as CNT growth. Here we show the direct experimental evidence on the growth dynamics of SW-CNTs from Co/MgO catalysts using CO as carbon source inside the environmental TEM. The evolution of the...

  18. Molecular Dynamics Study of Carbon Nanotubes/Polyamide Reverse Osmosis Membranes: Polymerization, Structure, and Hydration.

    Science.gov (United States)

    Araki, Takumi; Cruz-Silva, Rodolfo; Tejima, Syogo; Takeuchi, Kenji; Hayashi, Takuya; Inukai, Shigeki; Noguchi, Toru; Tanioka, Akihiko; Kawaguchi, Takeyuki; Terrones, Mauricio; Endo, Morinobu

    2015-11-11

    Carbon nanotubes/polyamide (PA) nanocomposite thin films have become very attractive as reverse osmosis (RO) membranes. In this work, we used molecular dynamics to simulate the influence of single walled carbon nanotubes (SWCNTs) in the polyamide molecular structure as a model case of a carbon nanotubes/polyamide nanocomposite RO membrane. It was found that the addition of SWCNTs decreases the pore size of the composite membrane and increases the Na and Cl ion rejection. Analysis of the radial distribution function of water confined in the pores of the membranes shows that SWCNT+PA nanocomposite membranes also exhibit smaller clusters of water molecules within the membrane, thus suggesting a dense membrane structure (SWCNT+PA composite membranes were 3.9% denser than bare PA). The results provide new insights into the fabrication of novel membranes reinforced with tubular structures for enhanced desalination performance. PMID:26505521

  19. Molecular dynamics simulations of defect production in graphene by carbon irradiation

    International Nuclear Information System (INIS)

    We present molecular dynamics simulations with empirical potentials to study the type of defects produced when irradiating graphene with low energy carbon ions (100 eV and 200 eV) and different dose rates. Simulations show the formation of very stable structures such as dimers, single chains of carbons and double chains of carbons. These structures are similar to those described in the literature, observed experimentally when irradiating graphene. For high doses or dose rates, the formation of nanopores is observed, similar to previous results by other authors for higher energies of the implanted ions. These simulations show how tunning the different parameters of irradiation conditions can be used to selectively create defects in graphene

  20. Molecular dynamics simulations of defect production in graphene by carbon irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Martinez-Asencio, J.; Caturla, M.J., E-mail: mj.caturla@ua.es

    2015-06-01

    We present molecular dynamics simulations with empirical potentials to study the type of defects produced when irradiating graphene with low energy carbon ions (100 eV and 200 eV) and different dose rates. Simulations show the formation of very stable structures such as dimers, single chains of carbons and double chains of carbons. These structures are similar to those described in the literature, observed experimentally when irradiating graphene. For high doses or dose rates, the formation of nanopores is observed, similar to previous results by other authors for higher energies of the implanted ions. These simulations show how tunning the different parameters of irradiation conditions can be used to selectively create defects in graphene.

  1. Carbon dynamics, food web structure and reclamation strategies in Athabasca oil sands wetlands (CRFAW)

    International Nuclear Information System (INIS)

    This abstract provided details of the Carbon Dynamics, Food Web Structure and Reclamation Strategies in Athabasca Oil Sands Wetlands (CFRAW) program, a collaboration between oil sands industry partners and university laboratories. CFRAW researchers are investigating the effects of mine tailings and process waters on the development, health, and function of wetland communities in post-mining landscapes. The aim of the program is to accurately predict how quickly the reclaimed wetlands will approach conditions seen in reference wetland systems. The program is also examining the effects of hydrocarbons as a surrogate source of carbon after they are metabolized by bacteria. The biological uptake, pathways, and movement through the food web of materials used by the biota in constructed wetlands are also being studied. Flux estimates will be used to determine if wetlands amended with peat will maintain their productivity. A conceptual model of carbon pathways and budgets is also being developed.

  2. Statics and dynamics of carbon fibre reinforcement composites on steel orthotropic decks

    Czech Academy of Sciences Publication Activity Database

    Frýba, Ladislav; Pirner, Miroš; Urushadze, Shota

    Southampton : WIT Press, 2009 - (Carlomagno, G.; Brebbia, C.), s. 117-123 ISBN 978-1-84564-187-0. [International Conference Computational Methods and Experimental Measurements /14./. Algarve (PT), 10.06.2009-12.06.2009] Grant ostatní: GA ČR(CZ) GA103/08/1340 Institutional research plan: CEZ:AV0Z20710524 Keywords : carbon fibre reinforced composite * orthotropic deck * fatigue life * dynamic load * crack propagation Subject RIV: JM - Building Engineering

  3. Molecular Dynamics Simulation Study on the Carbon Nanotube Interacting with a Polymer

    International Nuclear Information System (INIS)

    Using molecular dynamics simulation method, we studied the carbon nanotube (CNT) non-covalently interacting with a polymer. As the polymer coiled around the CNT, the diameter of CNT deformed by more than 40% of its original value within 50 ps. By considering three different polymers, we conclude that the interaction between the CNT and polymer is governed by the number of repeating units in the polymer, not by the molecular weight of polymer

  4. Interfacial Characteristics of Carbon Nanotube-Polyethylene Composites Using Molecular Dynamics Simulations

    OpenAIRE

    Zhang, Z. Q.; Ward, D. K.; Y. Xue; Zhang, H. W.; Horstemeyer, M. F.

    2011-01-01

    The rate-dependent interfacial behavior between a carbon nanotube (CNT) and a polyethylene (PE) matrix is investigated using molecular dynamics (MD) simulations. Various MD simulations were set up to determine the “size” effects on the interfacial properties, such as the molecular weight, or the length of the polymer, the diameter of the CNT, and the simulation model size. The interfacial rate-dependency was probed by applying various relative sliding velocities between the CNT and the polyme...

  5. Molecular Dynamics Simulation Study of Carbon-Nanotube Oscillator in Graphene Nanoribbon Trench

    OpenAIRE

    Lee, Eunae; Kang, Jeong Won; Kim, Ki-Sub; Kwon, Oh-Kuen

    2016-01-01

    Graphene/carbon-nanotube (CNT) hybrid material can be useful in energy storage and nanoelectronic technologies. Here we address the CNT-oscillator encapsulated in a graphene-nanoribbon (GNR) trench as a novel design, and investigate its properties via classical molecular dynamics simulations. Since the energy barrier was very low while the CNT was encapsulated in the GNR trench, the CNT absorbed on the GNR surface could easily be encapsulated in the GNR trench. MD simulations showed that the ...

  6. Quantification and Physiology of Carbon Dynamics in Intensively Managed Loblolly Pine (Pinus taeda L.)

    OpenAIRE

    Gough, Christopher Michael

    2003-01-01

    Loblolly pine (Pinus taeda L.) occupies 13 million hectares in the United States and represents a critical component of the global carbon (C) cycle. Forest management alters C dynamics, affecting the C sequestration capacity of a site. Identifying drivers that influence C cycling, quantifying C fluxes, and determining how management alters processes involved in C cycling will allow for an understanding of C sequestration capacity in managed forests. Objectives of the first study included (...

  7. Carbon Dynamics and Land-use Choices: Building a Regional-scale Multidisciplinary Model

    OpenAIRE

    2003-01-01

    Policy enabling tropical forests to approach their potential contribution to global-climate-change mitigation requires forecasts of land use and carbon storage on a large scale over long periods. In this paper, we present an integrated modeling methodology that addresses these needs. We model the dynamics of the human land-use system and of C pools contained in each ecosystem, as well as their interactions. The model is national scale, and is currently applied in a preliminary way to Costa Ri...

  8. Landscape-scale modelling of soil carbon dynamics under land use and climate change

    OpenAIRE

    Lacoste, Marine; VIAUD, Valérie; Michot, Didier,; Walter, Christian

    2013-01-01

    Soil organic carbon (SOC) sequestration is highly linked to soil use and farming practices, but also to soil redistribution, soil properties, and climate. In a global change context, landscape, farming practice and climate changes are expected; and they will most probably impact SOC dynamics. To assess their respective impacts, we modelled the SOC contents and stocks evolution at the scale of an agricultural landscape, by taking into account the soil redistribution by tillage and water proces...

  9. Numerical Simulation of Dynamic Performance of the Molten Carbonate Fuel Cell

    Institute of Scientific and Technical Information of China (English)

    于立军; 袁俊琪; 曾广益; 姜秀民

    2004-01-01

    A three dimension of dynamic mathematical model of the molten carbonate fuel cell is established,in which the heat generation, mass transfer and electrochemical characteristics are described. The performance of the fuel cell including the distributions of the temperature and the velocity is predicted numerically. Then the experimental data including the output performance of the fuel cell generation system and the temperature distributions are compared. The numerical results are in agreement with the experiment results.

  10. [Development and testing of theories of population dynamics]. First annual report

    Energy Technology Data Exchange (ETDEWEB)

    Murdoch, W.W.; Bence, J.R.; McCauley, E.; Nisbet, R.M.

    1990-03-15

    We report new analyses to test competing models of the Daphnia/algal interaction. Our model is good at predicting equilibrium algal densities, and if our new insights can account for stability in this system across a wide range of natural environments, this may contribute to understanding predator-prey dynamics in general.

  11. Annual progress report FY 1976. [Numerical methods for time-dependent reactor dynamics

    Energy Technology Data Exchange (ETDEWEB)

    Hansen, K.F.; Henry, A.F.

    1976-03-01

    This project is directed toward development of numerical methods suitable for the computer solution of problems in reactor dynamics and safety. Specific areas of research include methods of integration of the time-dependent diffusion equations by finite difference and finite element methods; representation of reactor properties by various homogenization procedures; application of synthesis methods; and development of response matrix techniques.

  12. Transpiration efficiency over an annual cycle, leaf gas exchange and wood carbon isotope ratio of three tropical tree species.

    Science.gov (United States)

    Cernusak, Lucas A; Winter, Klaus; Aranda, Jorge; Virgo, Aurelio; Garcia, Milton

    2009-09-01

    Variation in transpiration efficiency (TE) and its relationship with the stable carbon isotope ratio of wood was investigated in the saplings of three tropical tree species. Five individuals each of Platymiscium pinnatum (Jacq.) Dugand, Swietenia macrophylla King and Tectona grandis Linn. f. were grown individually in large (760 l) pots over 16 months in the Republic of Panama. Cumulative transpiration was determined by repeatedly weighing the pots with a pallet truck scale. Dry matter production was determined by destructive harvest. The TE, expressed as experiment-long dry matter production divided by cumulative water use, averaged 4.1, 4.3 and 2.9 g dry matter kg(-1) water for P. pinnatum, S. macrophylla and T. grandis, respectively. The TE of T. grandis was significantly lower than that of the other two species. Instantaneous measurements of the ratio of intercellular to ambient CO(2) partial pressures (c(i)/c(a)), taken near the end of the experiment, explained 66% of variation in TE. Stomatal conductance was lower in S. macrophylla than in T. grandis, whereas P. pinnatum had similar stomatal conductance to T. grandis, but with a higher photosynthetic rate. Thus, c(i)/c(a) and TE appeared to vary in response to both stomatal conductance and photosynthetic capacity. Stem-wood delta(13)C varied over a relatively narrow range of just 2.2 per thousand, but still explained 28% of variation in TE. The results suggest that leaf-level processes largely determined variation among the three tropical tree species in whole-plant water-use efficiency integrated over a full annual cycle. PMID:19661136

  13. Impacts of Changing Climate and Land Cover on Water and Carbon Dynamics in Northern Eurasia

    Science.gov (United States)

    Liu, Y.; Zhuang, Q.; Kicklighter, D. W.; Tchebakova, N.; Chen, J.; Melillo, J. M.

    2014-12-01

    The ecosystems in Northern Eurasia (NE) play an important role in the global climate system due to their vast land coverage, higher-than-global average rate of warming, and the potential feedbacks to the global climate. Water and carbon fluxes interact with each other and vary with climate change and land cover change (LUC). To understand the coupled effects of climate change and LUC on water and carbon dynamics in NE, we modified the algorithms for evapotranspiration (ET), incorporated the effects of forest stand age and fires on these dynamics, and assimilated forest inventory data and eddy covariance observations into the Terrestrial Ecosystem Model (TEM) to better estimate water and carbon fluxes. With consideration of ET from uplands and wetlands, evaporation from water bodies, and snow sublimation, TEM substantially improves its estimation of ET and runoff. Estimated regional ET varies between 263.5-369.3 mm yr-1 during 1979-2008 depending on the choice of forcing data. With the most accurate available forcing data, modification to TEM results in a decrease of root mean square error from 527.74 km3 yr-1 to 126.23 km3 yr-1 for the total discharge estimates of the six largest watersheds in NE. Site-level experiments show that with/without consideration of forest stand age and fires leads to 12.8-53.5% differences in ET estimates, and shifts NE ecosystems between carbon sink and source activities depending on fire severities. Consequently, consideration of these impacts at regional scales may result in large differences in estimates of water and carbon fluxes across NE. Our study highlights the role of snow in the hydrometeorology of NE, and suggests that the quality of forcing data remains a major challenge for accurate quantification of regional water balance, and urges consideration of forest stand age and fires in estimation of water and carbon fluxes in NE.

  14. Dynamic polarization effects on the angular distributions of protons channeled through carbon nanotubes in dielectric media

    CERN Document Server

    Borka, D; Mišković, Z L; Petrović, S; Nešković, N

    2008-01-01

    The best level of ordering and straightening of carbon nanotube arrays is often achieved when they are grown in a dielectric matrix, so such structures present the most suitable candidates for future channeling experiments with carbon nanotubes. Consequently, we investigate here how the dynamic polarization of carbon valence electrons in the presence of various surrounding dielectric media affects the angular distributions of protons channeled through (11,~9) single-wall carbon nanotubes. Proton speeds between 3 and 10 a.u., corresponding to energies of 0.223 and 2.49 MeV, are chosen with the nanotube's length varied between 0.1 and 1 $\\mu$m. We describe the repulsive interaction between a proton and the nanotube's atoms in a continuum-potential approximation based on the Doyle-Turner potential, whereas the attractive image force on a proton is calculated using a two-dimensional hydrodynamic model for the dynamic response of the nanotube valence electrons, while assigning to the surrounding medium an appropri...

  15. Dynamics of the Particulate Organic Carbon in the southern Baltic Sea.

    Science.gov (United States)

    Dzierzbicka-Glowacka, L.; Maciejewska, A.; Kuliński, K.; Pempkowiak, J.

    2009-04-01

    This paper presents a one-dimensional Particulate Organic Carbon Dynamic Model 1D-POCD. The particulate organic carbon concentration is determined as the sum of phytoplankton, zooplankton and dead organic matter (detritus) concentrations. Mathematically, the pelagic variables of 1D-POCD model are described by a second-order partial differential equation of the diffusion type with biogeochemical sources and sinks. The temporal changes in the phytoplankton biomass are caused by primary production, respiration, mortality, grazing by zooplankton and sinking. The zooplankton biomass is affected by ingestion, excretion, respiration, fecal production, mortality, and carnivorous grazing. The changes in the pelagic detritus concentration are determined by input of: dead phytoplankton and zooplankton, natural mortality of predators, fecal pellets, and sinks: sedimentation, zooplankton grazing and decomposition. The 1D-POCD model was used to simulate the seasonal dynamics of particulate organic carbon fluxes in the southern Baltic Sea (Gdańsk Deep, Bornholm Deep and Gotland Deep). The results of the simulations were compared with the mean concentrations of particulate organic carbon recorded in situ at station situated at the Gdańsk Deep. Generally good agreement between the measured and modeled POC concentration was obtained.

  16. Molecular dynamics study of the stability of a carbon nanotube atop a catalytic nanoparticle

    Science.gov (United States)

    Verkhovtsev, Alexey V.; Schramm, Stefan; Solov'yov, Andrey V.

    2014-09-01

    The stability of a single-walled carbon nanotube placed on top of a catalytic nickel nanoparticle is investigated by means of molecular dynamics simulations. As a case study, we consider the (12,0) nanotube consisting of 720 carbon atoms and the icosahedral Ni309 cluster. An explicit set of constant-temperature simulations is performed in order to cover a broad temperature range from 400 to 1200 K, at which a successful growth of carbon nanotubes has been achieved experimentally by means of chemical vapor deposition. The stability of the system depending on parameters of the involved interatomic interactions is analyzed. It is demonstrated that different scenarios of the nanotube dynamics atop the nanoparticle are possible depending on the parameters of the Ni-C potential. When the interaction is weak the nanotube is stable and resembles its highly symmetric structure, while an increase of the interaction energy leads to the abrupt collapse of the nanotube in the initial stage of simulation. In order to validate the parameters of the Ni-C interaction utilized in the simulations, DFT calculations of the potential energy surface for carbon-nickel compounds are performed. The calculated dissociation energy of the Ni-C bond is in good agreement with the values, which correspond to the case of a stable and not deformed nanotube simulated within the MD approach.

  17. Inter-annual variability of the atmospheric carbon dioxide concentrations as simulated with global terrestrial biosphere models and an atmospheric transport model

    International Nuclear Information System (INIS)

    Seasonal and inter-annual variations of atmospheric CO2 for the period from 1961 to 1997 have been simulated using a global tracer transport model driven by a new version of the Biome BioGeochemical Cycle model (Biome-BGC). Biome-BGC was forced by daily temperature and precipitation from the NCEP reanalysis dataset, and the calculated monthly-averaged CO2 fluxes were used as input to the global transport model. Results from an inter-comparison with the Carnegie-Ames-Stanford Approach model (CASA) and the Simulation model of Carbon CYCLE in Land Ecosystems (Sim-CYCLE) model are also reported. The phase of the seasonal cycle in the Northern Hemisphere was reproduced generally well by Biome-BGC, although the amplitude was smaller compared to the observations and to the other biosphere models. The CO2 time series simulated by Biome-BGC were compared to the global CO2 concentration anomalies from the observations at Mauna Loa and the South Pole. The modeled concentration anomalies matched the phase of the inter-annual variations in the atmospheric CO2 observations; however, the modeled amplitude was lower than the observed value in several cases. The result suggests that a significant part of the inter-annual variability in the global carbon cycle can be accounted for by the terrestrial biosphere models. Simulations performed with another climate-based model, Sim-CYCLE, produced a larger amplitude of inter-annual variability in atmospheric CO2, making the amplitude closer to the observed range, but with a more visible phase mismatch in a number of time periods. This may indicate the need to increase the Biome-BGC model sensitivity to seasonal and inter-annual changes in temperature and precipitation

  18. The impact of oxalogenic plants on soil carbon dynamics: formation of a millennium carbon storage as calcium carbonate

    OpenAIRE

    Ferro, Katia Imeria; Verrecchia, Eric

    2013-01-01

    Au sud du Burkina Faso, des milliers d’années de pédogénèse ont produit des «Plinthic Ferralsols Arenic» (suivant la WRB). Il a toutefois été observé que sous l’influence d’arbres oxalogènes tels que Milicia excelsa, Afzelia africana et Bombax costatum, les sols évoluent vers des «Ferralic Calcisols Arenic» (selon la WRB) en quelques décennies. Il est admis que le moteur de cette accumulation carbonatée est l’oxalotrophie bactérienne, qui crée une pompe à carbone entre l’atmosphère et les sol...

  19. Stable and radioactive carbon in forest soils of Chhattisgarh, Central India: Implications for tropical soil carbon dynamics and stable carbon isotope evolution

    Science.gov (United States)

    Laskar, A. H.; Yadava, M. G.; Ramesh, R.

    2016-06-01

    Soils from two sites viz. Kotumsar and Tirathgarh, located ∼5 km apart in a tropical reserve forest (18°52‧N, 81°56‧E) in central India, have been explored for soil organic carbon (SOC) content, its mean residence time (MRT) and the evolution of stable carbon isotopic composition (δ13C). SOC stocks in the upper 30 cm of soil layers are ∼5.3 kg/m2 and ∼3.0 kg/m2; in the upper 110 m are ∼10.7 kg/m2 and ∼7.8 kg/m2 at Kotumsar and Tirathgarh, respectively. SOC decreases with increasing depth. Bomb carbon signature is observed in the upper ∼10 cm. Organic matters in the top soil layers (0-10 cm) have MRTs of the order of a century which increases gradually with depths, reaching 3500-5000 yrs at ∼100 cm. δ13C values of SOC increase with depth, the carbon isotopic fractionation is obtained to be -1.2‰ and -3‰ for soils at Kotumsar and Tirathgarh, respectively, confirmed using Rayleigh isotopic fractionation model. The evolution of δ13C in soils was also studied using a modified Rayleigh fractionation model incorporating a continuous input into the reservoir: the depth profiles of δ13C for SOC show that the input organic matter from surface into the deeper soil layers is either insignificant or highly labile and decomposes quite fast in the top layers, thus making little contribution to the residual biomasses of the deeper layers. This is an attempt to understand the distillation processes that take place in SOC, assess the extent of decomposition by microbes and effect of percolation of fresh organic matter into dipper soil layers which are important for stable isotope based paleoclimate and paleovegetation reconstruction and understanding the dynamics of organic carbon in soils.

  20. Carbon balance and crop residue management in dynamic equilibrium under a no-till system in Campos Gerais

    Directory of Open Access Journals (Sweden)

    Ademir de Oliveira Ferreira

    2012-11-01

    Full Text Available The adoption of no-tillage systems (NT and the maintenance of crop residues on the soil surface result in the long-term increase of carbon (C in the system, promoting C sequestration and reducing C-CO2 emissions to the atmosphere. The purpose of this study was to evaluate the C sequestration rate and the minimum amount of crop residues required to maintain the dynamic C equilibrium (dC/dt = 0 of two soils (Typic Hapludox with different textural classes. The experiment was arranged in a 2 x 2 x 2 randomized block factorial design. The following factors were analyzed: (a two soil types: Typic Hapludox (Oxisol with medium texture (LVTM and Oxisol with clay texture (LVTA, (b two sampling layers (0-5 and 5-20 cm, and (c two sampling periods (P1 - October 2007; P2 - September 2008. Samples were collected from fields under a long-term (20 years NT system with the following crop rotations: wheat/soybean/black oat + vetch/maize (LVTM and wheat/maize/black oat + vetch/soybean (LVTA. The annual C sequestration rates were 0.83 and 0.76 Mg ha-1 for LVTM and LVTA, respectively. The estimates of the minimum amount of crop residues required to maintain a dynamic equilibrium (dC/dt = 0 were 7.13 and 6.53 Mg ha-1 year-1 for LVTM and LVTA, respectively. The C conversion rate in both studied soils was lower than that reported in other studies in the region, resulting in a greater amount of crop residues left on the soil surface.

  1. Dynamics of Phenanthrenequinone on Carbon Nano-Onion Surfaces Probed by Quasielastic Neutron Scattering

    International Nuclear Information System (INIS)

    We used quasielastic neutron scattering (QENS) to study the dynamics of phenanthrenequinone (PQ) on the surface of onion-like carbon (OLC), or so called carbon onions, as a function of surface coverage and temperature. For both the high- and low-coverage samples, we observed two diffusion processes; a faster process and nearly an order of magnitude slower process. On the high-coverage surface, the slow diffusion process is of long-range translational character, whereas the fast diffusion process is spatially localized on the length scale of ∼ 4.7. On the low-coverage surface, both diffusion processes are spatially localized; on the same length scale of ∼ 4.7 for the fast diffusion and a somewhat larger length scale for the slow diffusion. Arrhenius temperature dependence is observed except for the long-range diffusion on the high-coverage surface. We attribute the fast diffusion process to the generic localized in-cage dynamics of PQ molecules, and the slow diffusion process to the long-range translational dynamics of PQ molecules, which, depending on the coverage, may be either spatially restricted, or long-range. On the low-coverage surface, uniform surface coverage is not attained, and the PQ molecules experience the effect of spatial constraints on their long-range translational dynamics. Unexpectedly, the dynamics of PQ molecules on OLC as a function of temperature and surface coverage bears qualitative resemblance to the dynamics of water molecules on oxide surfaces, including practically temperature-independent residence times for the low-coverage surface. The dynamics features that we observed may be universal across different classes of surface adsorbates.

  2. The influence of compliant chassis components on motorcycle dynamics: an historical overview and the potential future impact of carbon fibre

    Science.gov (United States)

    Lake, Kelvin; Thomas, Richard; Williams, Owen

    2012-07-01

    This paper details the influence of compliant chassis components on motorcycle dynamics. Initially, research which has previously been carried out in terms of motorcycle dynamics and in particular the impact of compliant chassis components on motorcycle dynamics is discussed. This paper then considers the consequences of these findings with regard to the use of modern materials such as carbon fibre reinforced plastics and the impact they will potentially have on motorcycle dynamics and its simulation.

  3. Monte Carlo and molecular dynamics simulations of screw dislocation locking by Cottrell atmospheres in low carbon Fe–C alloys

    International Nuclear Information System (INIS)

    On-lattice Monte Carlo shows strong carbon segregation at a screw dislocation in bcc iron for carbon contents that vary from 20 to 500 ppm, typical in ultra low and low carbon steels. Molecular dynamics simulations are then carried out using the atomic coordinates of equilibrated Cottrell atmospheres. The stresses required to make the screw dislocation break free of the carbon cloud are very high compared to carbon in solid solution; the locking time is also much longer. All simulations are performed at 300 K

  4. Molecular dynamics simulation for arrangement of nickel atoms filled in carbon nanotubes

    International Nuclear Information System (INIS)

    Carbon Nanotubes (CNTs) filled with metals can be used in capacitors, sensors, rechargeable batteries, and so on. Atomic arrangement of the metals has an important role in the function of the composites. The tips of CNTs were opened, and then nickel was filled by means of hydrothermal oxidation/ultrasonic vibration method. The tests of TEM, HREM, and EDX (energy-dispersive X-ray spectroscopy) analysis showed that Ni was filled in CNTs successfully. The atomic arrangement of nickel filled into single wall carbon nanotubes was investigated by molecular dynamics simulation. The radial distribution function and bond orientation order were established to analyze the atomic arrangement of nickel filled in carbon nanotubes during the cooling process. The results show that nickel atoms became in order gradually and preferably crystallized on the inner wall of carbon nanotubes when the temperature decreased from 1600 K. After it cooled to 100 K, the arrangement of nickel atoms in outermost circle was regular and dense, but there were many defects far from the wall of CNTs. According to the calculation of bond orientation order parameters Q6 and its visualization, the structure of nickel is Face-centered cube (f.c.c). (1,1,1)Ni was close on the inner surface of carbon nanotubes. Radial direction of CNTs was [1,1,1] crystal orientation. Axial direction of CNTs, namely, filling direction, was [1¯, 1¯,2] crystal orientation

  5. Process of Energetic Carbon Atom Deposition on Si (001) Substrate by Molecular Dynamics Simulation

    Institute of Scientific and Technical Information of China (English)

    于威; 滕晓云; 李晓苇; 傅广生

    2002-01-01

    The process of energetic C atom deposition on Si (001)-(2×1) is studied by the molecular dynamics method using the semi-empirical many-bond Tersoff potential. It is found that the incident energy of the carbon atom has an important effect on the collision process and its diffusion process on the substrate. Most of the incident energy of the carbon atom is transferred to the substrate atoms within the initial two vibration periods of substrate atoms and its value increases with the incident energy. The spreading distance and penetration depth of the incident atom increasing with the incident energy are also identified. The simulated results imply that an important effect of energy of incident carbon on the film growth at Iow substrate temperature provides activation energy for silicon carbide formation through the vibration enhancement of local substrate atoms. In addition, suppressing carbon atom inhomogeneous collection and dispensing with the silicon diffusion process may be effectively promoted by the spreading and penetration of the energetic carbon atom in the silicon substrate.

  6. Land use and carbon dynamics in the southeastern United States from 1992 to 2050

    International Nuclear Information System (INIS)

    Land use and land cover change (LUCC) plays an important role in determining the spatial distribution, magnitude, and temporal change of terrestrial carbon sources and sinks. However, the impacts of LUCC are not well understood and quantified over large areas. The goal of this study was to quantify the spatial and temporal patterns of carbon dynamics in various terrestrial ecosystems in the southeastern United States from 1992 to 2050 using a process-based modeling system and then to investigate the impacts of LUCC. Spatial LUCC information was reconstructed and projected using the FOREcasting SCEnarios of future land cover (FORE-SCE) model according to information derived from Landsat observations and other sources. Results indicated that urban expansion (from 3.7% in 1992 to 9.2% in 2050) was expected to be the primary driver for other land cover changes in the region, leading to various declines in forest, cropland, and hay/pasture. The region was projected to be a carbon sink of 60.4 gC m−2 yr−1 on average during the study period, primarily due to the legacy impacts of large-scale conversion of cropland to forest that happened since the 1950s. Nevertheless, the regional carbon sequestration rate was expected to decline because of the slowing down of carbon accumulation in aging forests and the decline of forest area. (letter)

  7. Faunal Influences on Fracture-Induced Carbon Flux Dynamics in Dryland Soils

    Science.gov (United States)

    DeCarlo, K. F.; Caylor, K. K.

    2015-12-01

    Organismal activity, in addition to its role in ecological feedbacks, ha the potential to serve as instigators or enhancers of atmospheric and hydrologic fluxes via alterations in soil structural regimes. We investigated the effect of faunally-induced crack morphology on soil carbon dynamics in three dryland soil systems in central Kenya: bioturbated soils, biocompacted soils, and undisturbed soils. Carbon fluxes were characterized using a closed-system respiration chamber, with CO2 concentration differences measured using an infrared gas analyzer. Results show that faunal influenes play a divergent biomechanical role in bulk soil cracking morphology and topology: macrofauna-induced bioturbation creates shallow, large, well-connected networks relative to those from megaherbivore-induced biocompaction, with the latter showing a "memory" of past drying events through a crack layering effect. These morphologies may further drive differences in soil carbon flux: under dry conditions, bioturbated and control soils show a persistently high and low mean carbon flux, respectively - biocompacted soils suggest a diurnal trend, with daytime lows and nighttime highs comparable to the control and bioturbated soils, respectively. Overall fluxes under wet conditions are considerably higher, but also more variable, though higher mean carbon fluxes are observed in the biocompacted and bioturbated soils. Our results suggest that fracture morphology induced in biocompacted soils may enhance diffusive fluxes that are typical in undisturbed soils to levels that are as high as those from macrofaunal respiration, but that particular physical conditions in fracture morphology and topology may be necessary as a prerequisite.

  8. Evaluate Habitat Use and Population Dynamics of Lampreys in Cedar Creek, Annual Report 2002.

    Energy Technology Data Exchange (ETDEWEB)

    Pirtle, Jodi; Stone, Jennifer; Barndt, Scott

    2003-03-01

    Pacific lamprey (Lampetra tridentata) in the Columbia River basin have declined to a remnant of their pre-1940s populations and the status of the western brook lamprey (L. richardsoni) and river lamprey (L. ayresi) is unknown. Identifying the biological and ecological factors limiting lamprey populations is critical to their recovery, but little research has been conducted on these species within the Columbia River basin. This ongoing, multi-year study examines lamprey populations in Cedar Creek, Washington, a third-order tributary to the Lewis River. This annual report describes the activities and results of the third year of this project. Adult (n = 62), metamorphosed (n = 76), transforming (n = 4), and ammocoete (n = 315) stages of Pacific and western brook lamprey were examined in 2002. Lampreys were captured using adult fish ladders, lamprey pots, rotary screw traps, and lamprey electrofishers. In addition, fifty-four spawning ground surveys were conducted during which 124 Pacific lamprey and 13 western brook lamprey nests were identified. Stream gradient of spawning grounds were surveyed to better understand spawning habitat requirements.

  9. A neural network-based estimate of the seasonal to inter-annual variability of the Atlantic Ocean carbon sink

    Directory of Open Access Journals (Sweden)

    P. Landschützer

    2013-05-01

    carbon sink north of the equator (–0.007 Pg C yr–1 decade–1. Surface ocean pCO2 was also increasing less than that of the atmosphere over most of the Atlantic south of the equator, leading to a substantial trend toward a stronger CO2 sink for the entire South Atlantic (–0.14 Pg C yr–1 decade–1. The Atlantic carbon sink varies relatively little on inter-annual time-scales (±0.04 Pg C yr–1; 1σ.

  10. A neural network-based estimate of the seasonal to inter-annual variability of the Atlantic Ocean carbon sink

    Science.gov (United States)

    Landschützer, P.; Gruber, N.; Bakker, D. C. E.; Schuster, U.; Nakaoka, S.; Payne, M. R.; Sasse, T. P.; Zeng, J.

    2013-11-01

    , while in other regions of the North Atlantic the sea surface pCO2 increased at a slower rate, resulting in a barely changing Atlantic carbon sink north of the Equator (-0.01 ± 0.02 Pg C yr-1 decade-1). Surface ocean pCO2 increased at a slower rate relative to atmospheric CO2 over most of the Atlantic south of the Equator, leading to a substantial trend toward a stronger CO2 sink for the entire South Atlantic (-0.14 ± 0.02 Pg C yr-1 decade-1). In contrast to the 10 yr trends, the Atlantic Ocean carbon sink varies relatively little on inter-annual timescales (±0.04 Pg C yr-1; 1 σ).

  11. Temporal dynamics of carbon dioxide and carbon monoxide in the Salt Lake Valley urban ecosystem of northern Utah, USA

    Science.gov (United States)

    Bush, S. E.; Ehleringer, J. R.; Hopkins, F. M.; Randerson, J. T.; Lai, C.

    2013-12-01

    Urban ecosystems are a significant source of greenhouse gas emissions. Existing data obtained from surface based measurements of carbon dioxide (CO2) and carbon monoxide (CO) are largely limited to static monitoring stations and show a high degree of temporal and spatial variability both within and across urban areas. Finer scale spatial resolution data of surface measurements were collected to obtain a more comprehensive view of trace gas dynamics at the whole-ecosystem scale, to integrate across space among existing stationary measurement locations, and to provide data for the development and validation of modeled emissions estimates. We utilized a mobile laboratory to obtain high precision measurements of CO2 and CO in the highly urbanized and urbanizing areas across the Salt Lake Valley of northern Utah, USA. Continuous measurements of CO2, CO, and geospatial position data were obtained at a 5-second frequency along a transect route representative of major urban land use types. Data collection across the transect route was repeated thrice daily (morning, afternoon and evening) through all seasons of the year. Preliminary results show significant spatial structure in CO2, CO, and the ratio of CO to CO2 across both diurnal and seasonal time scales. In general, we found higher concentrations of both trace gases as well as the ratio of CO to CO2 in the morning and evening periods compared to the afternoon time periods. In addition, we found higher concentrations of both trace gases and the ratio of CO to CO2 in winter than summer time periods. Our results provide a foundation for the information needed to improve our understanding of whole-ecosystem scale temporal dynamics of CO2 and CO in urban regions.

  12. Hybrid Dynamic Modeling and Control of Molten Carbonate Fuel Cell Stack Shutdown

    Institute of Scientific and Technical Information of China (English)

    LI Yong; CAO Guang-yi; ZHU Xin-jian

    2007-01-01

    A hybrid automaton modeling approach that incorporates state space partitioning, phase dynamic modeling and control law synthesis by control strategy is utilized to develop a hybrid automaton model of molten carbonate fuel cell (MCFC) stack shutdown. The shutdown operation is divided into several phases and their boundaries are decided according to a control strategy, which is a set of specifications about the dynamics of MCFC stack during shutdown. According to the control strategy, the specification of increasing stack temperature is satisfied in a phase that can be modeled accurately. The model for phase that has complex dynamic is approximated. The duration of this kind of phase is decreased to minimize the error caused by model approximation.

  13. Molecular dynamics investigation of carbon nanotube junctions in non-aqueous solutions

    KAUST Repository

    Gkionis, Konstantinos

    2014-07-23

    The properties of liquids in a confined environment are known to differ from those in the bulk. Extending this knowledge to geometries defined by two metallic layers in contact with the ends of a carbon nanotube is important for describing a large class of nanodevices that operate in non-aqueous environments. Here we report a series of classical molecular dynamics simulations for gold-electrode junctions in acetone, cyclohexane and N,N-dimethylformamide solutions and analyze the structure and the dynamics of the solvents in different regions of the nanojunction. The presence of the nanotube has little effect on the ordering of the solvents along its axis, while in the transversal direction deviations are observed. Importantly, the orientational dynamics of the solvents at the electrode-nanotube interface differ dramatically from that found when only the electrodes are present.

  14. Nitrifying and heterotrophic population dynamics in biofilm reactors : effects of hydraulic retention time and the presence of organic carbon

    OpenAIRE

    Regina Nogueira; Melo, Luis F.; Ulrike Pulrkhold; Stefan Wuertz; Michael Wagner

    2002-01-01

    Two biofilmreactors operated with hydraulic retention times of 0.8 and 5.0 h were used to study the links between population dynamics and reactor operation performance during a shift in process operation from pure nitrification to combined nitrification and organic carbon removal. The ammonium and the organic carbon loads were identical for both reactors. The composition and dynamics of the microbial consortia were quantified by fluorescence in situ hybridization (FISH) with rRNA-...

  15. An Integrated Model of Market-Driven Dynamics of Carbon in Exurban Landscapes

    Science.gov (United States)

    Brown, D. G.; Sun, S.; Currie, W.; Nassauer, J. I.; Page, S. E.; Parker, D. C.; Riolo, R. L.; Robinson, D. T.

    2012-12-01

    As coupled human-environment system, exurban land-use systems and their ecological and social outcomes are driven by interactions between the human actors and natural processes at play. Carbon storage in exurban land-use systems is driven by interactions among market forces driving land-use change, developer and resident decisions about land cover and land management, and ecosystem processes affecting ecosystem function. Whether or not vegetation in these landscapes contribute to carbon sinks that mitigate global change, and their future trajectory, depends on dynamics in both human and biophysical processes. Understanding these interactions in a coupled human and natural system might best be advanced by iterating between data collection efforts on various aspects of the system (including the states and changes in the social and natural aspects of the system) and modeling in ways that explicitly represents social and natural processes and their interactions. A challenge is to build models that are both explicable based on existing process knowledge and supportable by existing or newly collected data. We coupled an agent-based model of developer and resident decision making about landscape structure and management with a biogeochemical model of carbon flux and storage to evaluate the drivers of and possible mechanisms to achieve increased carbon storage. Model-based experiments demonstrate the (a) effects of various residential land management strategies on carbon storage, suggesting that removals of litter have a larger effect on overall carbon storage than additions of fertilizer and irrigation; (b) effects of subsidies or payments for increased carbon storage paid to developers can result in choices about development types that result in increased carbon storage, but that the effects are highly sensitive to the price of carbon and the basis for calculating payments. The experiments highlight the need for integrated modeling, but also point to specific needs for

  16. Assessing the dynamic material criticality of infrastructure transitions: A case of low carbon electricity

    International Nuclear Information System (INIS)

    Highlights: • We present a method to analyse material criticality of infrastructure transitions. • Criticality is defined as the potential for, and exposure to, supply disruption. • Our method is dynamic reducing the probability of lock-in to at-risk technologies. • We show that supply disruption potential is reducing but exposure is increasing. - Abstract: Decarbonisation of existing infrastructure systems requires a dynamic roll-out of technology at an unprecedented scale. The potential disruption in supply of critical materials could endanger such a transition to low-carbon infrastructure and, by extension, compromise energy security more broadly because low carbon technologies are reliant on these materials in a way that fossil-fuelled energy infrastructure is not. Criticality is currently defined as the combination of the potential for supply disruption and the exposure of a system of interest to that disruption. We build on this definition and develop a dynamic approach to quantifying criticality, which monitors the change in criticality during the transition towards a low-carbon infrastructure goal. This allows us to assess the relative risk of different technology pathways to reach a particular goal and reduce the probability of being ‘locked in’ to currently attractive but potentially future-critical technologies. To demonstrate, we apply our method to criticality of the proposed UK electricity system transition, with a focus on neodymium. We anticipate that the supply disruption potential of neodymium will decrease by almost 30% by 2050; however, our results show the criticality of low carbon electricity production increases ninefold over this period, as a result of increasing exposure to neodymium-reliant technologies

  17. Molecular dynamics study of Ar flow and He flow inside carbon nanotube junction as a molecular nozzle and diffuser

    OpenAIRE

    Itsuo Hanasaki, Akihiro Nakatani and Hiroshi Kitagawa

    2004-01-01

    A carbon nanotube junction consists of two connected nanotubes with different diameters. It has been extensively investigated as a molecular electronic device since carbon nanotubes can be metallic and semiconductive, depending on their structure. However, a carbon nanotube junction can also be viewed as a nanoscale nozzle andv diffuser. Here, we focus on the nanotube junction from the perspective of an intersection between machine, material and device. We have conducted a molecular dynamics ...

  18. Reproductive dynamics and potential annual fecundity of South Pacific albacore tuna (Thunnus alalunga).

    Science.gov (United States)

    Farley, Jessica H; Williams, Ashley J; Hoyle, Simon D; Davies, Campbell R; Nicol, Simon J

    2013-01-01

    The reproductive biology of albacore tuna, Thunnus alalunga, in the South Pacific Ocean was investigated with samples collected during broad-scale sampling between 2006 and 2011. Histology was done in a single laboratory according to standard protocols and the data analysed using generalized linear mixed-effects models. The sex ratio of albacore was female biased for fish smaller than approximately 60 cm FL and between 85 and 95 cm, and progressively more male biased above 95 cm FL. Spawning activity was synchronised across the region between 10°S and 25°S during the austral spring and summer where sea surface temperatures were ≥24 °C. The average gonad index varied among regions, with fish in easterly longitudes having heavier gonads for their size than fish in westerly longitudes. Albacore, while capable of spawning daily, on average spawn every 1.3 days during the peak spawning months of October to December. Spawning occurs around midnight and the early hours of the morning. Regional variation in spawning frequency and batch fecundity were not significant. The proportion of active females and the spawning fraction increased with length and age, and mature small and young fish were less active at either end of the spawning season than larger, older fish. Batch fecundity estimates ranged from 0.26 to 2.83 million oocytes with a mean relative batch fecundity of 64.4 oocytes per gram of body weight. Predicted batch fecundity and potential annual fecundity increased with both length and age. This extensive set of reproductive parameter estimates provides many of the first quantitative estimates for this population and will substantially improve the quality of biological inputs to the stock assessment for South Pacific albacore. PMID:23565258

  19. Human population and atmospheric carbon dioxide growth dynamics: Diagnostics for the future

    Science.gov (United States)

    Hüsler, A. D.; Sornette, D.

    2014-10-01

    We analyze the growth rates of human population and of atmospheric carbon dioxide by comparing the relative merits of two benchmark models, the exponential law and the finite-time-singular (FTS) power law. The later results from positive feedbacks, either direct or mediated by other dynamical variables, as shown in our presentation of a simple endogenous macroeconomic dynamical growth model describing the growth dynamics of coupled processes involving human population (labor in economic terms), capital and technology (proxies by CO2 emissions). Human population in the context of our energy intensive economies constitutes arguably the most important underlying driving variable of the content of carbon dioxide in the atmosphere. Using some of the best databases available, we perform empirical analyses confirming that the human population on Earth has been growing super-exponentially until the mid-1960s, followed by a decelerated sub-exponential growth, with a tendency to plateau at just an exponential growth in the last decade with an average growth rate of 1.0% per year. In contrast, we find that the content of carbon dioxide in the atmosphere has continued to accelerate super-exponentially until 1990, with a transition to a progressive deceleration since then, with an average growth rate of approximately 2% per year in the last decade. To go back to CO2 atmosphere contents equal to or smaller than the level of 1990 as has been the broadly advertised goals of international treaties since 1990 requires herculean changes: from a dynamical point of view, the approximately exponential growth must not only turn to negative acceleration but also negative velocity to reverse the trend.

  20. Long-term impacts of manure amendments on carbon and greenhouse gas dynamics of rangelands.

    Science.gov (United States)

    Owen, Justine J; Parton, William J; Silver, Whendee L

    2015-12-01

    Livestock manure is applied to rangelands as an organic fertilizer to stimulate forage production, but the long-term impacts of this practice on soil carbon (C) and greenhouse gas (GHG) dynamics are poorly known. We collected soil samples from manured and nonmanured fields on commercial dairies and found that manure amendments increased soil C stocks by 19.0 ± 7.3 Mg C ha(-1) and N stocks by 1.94 ± 0.63 Mg N ha(-1) compared to nonmanured fields (0-20 cm depth). Long-term historical (1700-present) and future (present-2100) impacts of management on soil C and N dynamics, net primary productivity (NPP), and GHG emissions were modeled with DayCent. Modeled total soil C and N stocks increased with the onset of dairying. Nitrous oxide (N2 O) emissions also increased by ~2 kg N2 O-N ha(-1)  yr(-1) . These emissions were proportional to total N additions and offset 75-100% of soil C sequestration. All fields were small net methane (CH4 ) sinks, averaging -4.7 ± 1.2 kg CH4 -C ha(-1)  yr(-1) . Overall, manured fields were net GHG sinks between 1954 and 2011 (-0.74 ± 0.73 Mg CO2 e ha(-1)  yr(-1) , CO2 e are carbon dioxide equivalents), whereas nonmanured fields varied around zero. Future soil C pools stabilized 40-60 years faster in manured fields than nonmanured fields, at which point manured fields were significantly larger sources than nonmanured fields (1.45 ± 0.52 Mg CO2 e ha(-1)  yr(-1) and 0.51 ± 0.60 Mg CO2 e ha(-1)  yr(-1) , respectively). Modeling also revealed a large background loss of soil C from the passive soil pool associated with the shift from perennial to annual grasses, equivalent to 29.4 ± 1.47 Tg CO2 e in California between 1820 and 2011. Manure applications increased NPP and soil C storage, but plant community changes and GHG emissions decreased, and eventually eliminated, the net climate benefit of this practice. PMID:26183573

  1. Annual water, sediment, nutrient, and organic carbon fluxes in river basins: A global meta-analysis as a function of scale

    Science.gov (United States)

    Mutema, M.; Chaplot, V.; Jewitt, G.; Chivenge, P.; Blöschl, G.

    2015-11-01

    Process controls on water, sediment, nutrient, and organic carbon exports from the landscape through runoff are not fully understood. This paper provides analyses from 446 sites worldwide to evaluate the impact of environmental factors (MAP and MAT: mean annual precipitation and temperature; CLAY and BD: soil clay content and bulk density; S: slope gradient; LU: land use) on annual exports (RC: runoff coefficients; SL: sediment loads; TOCL: organic carbon losses; TNL: nitrogen losses; TPL: phosphorus losses) from different spatial scales. RC was found to increase, on average, from 18% at local scale (in headwaters), 25% at microcatchment and subcatchment scale (midreaches) to 41% at catchment scale (lower reaches of river basins) in response to multiple factors. SL increased from microplots (468 g m-2 yr-1) to plots (901 g m-2 yr-1), accompanied by decreasing TOCL and TNL. Climate was a major control masking the effects of other factors. For example, RC, SL, TOCL, TNL, and TPL tended to increase with MAP at all spatial scales. These variables, however, decreased with MAT. The impact of CLAY, BD, LU, and S on erosion variables was largely confined to the hillslope scale, where RC, SL, and TOCL decreased with CLAY, while TNL and TPL increased. The results contribute to better understanding of water, nutrient, and carbon cycles in terrestrial ecosystems and should inform river basin modeling and ecosystem management. The important role of spatial climate variability points to a need for comparative research in specific environments at nested spatiotemporal scales.

  2. Annual Dynamics of Green House Gases in a Swedish Boreal Forested Catchment

    Science.gov (United States)

    Oquist, M. G.; Klemedtsson, L.; Bishop, K.; Grip, H.; Laudon, H.; Nilsson, M.

    2003-04-01

    We investigated the spatial and temporal variation of CO_2, CH_4 and N_2O in a boreal forested catchment with respect to their atmospheric exchange and their below-ground concentration dynamics. The measurements were carried out at three sites distributed along a gently sloping 22 m transect draining into a small creek. Vegetation was dominated by a 95 year old Norway spruce stand and soil types ranged from organic (a riparian zone histosol) to mineral (podzol on sandy till). Soil gas concentrations (at 5, 10, 20, 40 and 60 cm depth) were measured weekly for 18 months, while gas fluxes were measured weekly during the snow-free season and at 4 campaigns during the winter season. During the growing season average CO_2 efflux from the three sites ranged from 0.7--1.8 g m-2 d-1, while CH_4 displayed a net uptake rate of 0.1--0.3 mg m-2 d-1. Detectable amounts of N_2O emissions appeared sporadically, but never exceeded 0.04 mg m-2 d-1. The variation in CO_2 flux had the same temporal pattern as the variation in soil temperature (5--25 cm depth; r^2 = 0.6--0.85), while ca 40% of the differences in CH_4 consumption could be accounted for by the variations in soil moisture in the top 20 cm. During winter, fluxes of CO_2 and CH_4 were of the same order of magnitude as during summer, but the N_2O emissions were considerably higher, averaging around 0.4 mg m-2 d-1. Furthermore, soil gas concentrations of N_2O during winter showed a strong positive temperature correlation with a ca10-fold increase in concentration per ^oC (r^2 = 0.93). Our results stress the importance of the winter season for the greenhouse gas dynamics of the boreal landscape, and also that both N_2O and CH_4 exchange have the potential to influence how these ecosystems interact with the Earth's radiative balance. Moreover, the strength of atmospheric CH_4 consumption rates in these systems appears to be indifferent to season, which has implications for regional estimates of CH_4 budgets. The temperature

  3. Molecular dynamics study of the stability of a carbon nanotube atop a catalytic nanoparticle

    CERN Document Server

    Verkhovtsev, Alexey V; Solov'yov, Andrey V

    2014-01-01

    The stability of a single-walled carbon nanotube placed on top of a catalytic nickel nanoparticle is investigated by means of molecular dynamics simulations. As a case study, we consider the $(12,0)$ nanotube consisting of 720 carbon atoms and the icosahedral Ni$_{309}$ cluster. An explicit set of constant-temperature simulations is performed in order to cover a broad temperature range from 400 to 1200 K, at which a successful growth of carbon nanotubes has been achieved experimentally by means of chemical vapor deposition. The stability of the system depending on parameters of the involved interatomic interactions is analyzed. It is demonstrated that different scenarios of the nanotube dynamics atop the nanoparticle are possible depending on the parameters of the Ni-C potential. When the interaction is weak the nanotube is stable and resembles its highly symmetric structure, while an increase of the interaction energy leads to the abrupt collapse of the nanotube in the initial stage of simulation. In order t...

  4. Dynamic hybrid life cycle assessment of energy and carbon of multicrystalline silicon photovoltaic systems.

    Science.gov (United States)

    Zhai, Pei; Williams, Eric D

    2010-10-15

    This paper advances the life cycle assessment (LCA) of photovoltaic systems by expanding the boundary of the included processes using hybrid LCA and accounting for the technology-driven dynamics of embodied energy and carbon emissions. Hybrid LCA is an extended method that combines bottom-up process-sum and top-down economic input-output (EIO) methods. In 2007, the embodied energy was 4354 MJ/m(2) and the energy payback time (EPBT) was 2.2 years for a multicrystalline silicon PV system under 1700 kWh/m(2)/yr of solar radiation. These results are higher than those of process-sum LCA by approximately 60%, indicating that processes excluded in process-sum LCA, such as transportation, are significant. Even though PV is a low-carbon technology, the difference between hybrid and process-sum results for 10% penetration of PV in the U.S. electrical grid is 0.13% of total current grid emissions. Extending LCA from the process-sum to hybrid analysis makes a significant difference. Dynamics are characterized through a retrospective analysis and future outlook for PV manufacturing from 2001 to 2011. During this decade, the embodied carbon fell substantially, from 60 g CO(2)/kWh in 2001 to 21 g/kWh in 2011, indicating that technological progress is realizing reductions in embodied environmental impacts as well as lower module price. PMID:20860380

  5. Iron reduction and carbon dynamics during redox fluctuations in soil slurries from Luquillo CZO (Puerto Rico)

    Science.gov (United States)

    Barcellos, D.; Silver, W. L.; Pett-Ridge, J.; Thompson, A.

    2015-12-01

    Iron minerals play an important role in the dynamics of nutrients and soil carbon in tropical ecosystems. Because soils often experience fluctuations between oxic and anoxic conditions (redox fluctuations) the pool of reactive Fe(III) phases is under continuous flux. The oxidation of soluble Fe(II) during oxic conditions can generate Fe(III) phase of variable crystallinity with potentially different susceptibility to Fe(III) reduction during subsequent anoxic periods. We hypothesize that the coupled rates of iron reduction and carbon mineralization will respond to differences in the frequency of redox shifts and the length of the oxic and anoxic periods (Tao(oxic) and Tao(anoxic). To test this, we subjected soil from the upper 15 cm of the Bisley watershed in the Luquillo critical zone observatory (LCZO), Puerto Rico, to five redox fluctuations scenarios. The treatments included either a fixed anoxic period of 6 d with oxic periods of 8, 24, and 72 h (3 treatments); or a fixed anoxic period of 2 d with oxic periods of 8 or 24 h (2 treatments). Results from a preliminary experiment indicated iron reduction rates increased when the oxic period was decreased below 10 h. We are completing analysis of the full dataset from the experiment above and will present Fe(II) concentrations and gas phase concentrations (CO2 emissions). Results from this experiment will further constrain the type of redox dynamics that influence soil Fe reduction and carbon mineralization.

  6. Use of mathematical models for assessing the pool and dynamics of carbon in forest soils

    Science.gov (United States)

    Komarov, A. S.

    2008-12-01

    The contribution of forest soils to the total carbon budget and to the emission of greenhouse gases is an important problem involved in many international programs, including the Kyoto Protocol. Direct measurements of the carbon pool in forest soils and its changes are slow and expensive; therefore, mathematical models are proposed in different countries for describing the dynamics of soil organic matter (SOM). The models differ in complexity and consider different processes of SOM mineralization and humification. The input parameters include model coefficients (these are usually the rates of decomposition and humification of different SOM compartments) and the initial values for different SOM pools. The coefficients can be estimated in special laboratory and field experiments, but the characteristics of the initial values for different SOM pools are usually absent. In this case, some assumptions about the character of SOM accumulation, which depends on forest vegetation, are used. The most realistic is the use of databases on the pools of carbon and other elements related to the types of forest or habitat conditions, including the primarily water regime and soil fertility. Under some suppositions, the agreement conditions between the main parameters of the SOM and forest vegetation can be formulated to assess the initial SOM pools in the forest litter and mineral horizons of the soil. An example of assessing the prediction of forest soil dynamics in Leningrad oblast was considered.

  7. Molecular dynamics studies of aromatic hydrocarbon liquids: Annual progress report, September 1, 1986-August 31, 1987

    International Nuclear Information System (INIS)

    Algorithms for molecular dynamics simulations on supercomputers have been developed and simulations performed for fluids of nonspherical molecules modeled using the following potentials: two-center and three-center Lennard-Jones potentials in order to study phase-equilibria in these fluids, oblate and prolate Gaussian overlap potential (original and modified potentials), and dipolar and quadrupolar spheres. Simulation results have been used to test predictive methods: a nonspherical reference potential based thermodynamic perturbation theory and a sphericalized potential method. Both these methods work well for fluids modeled using the modified Gaussian overlap potential and the sphericalized potential method is, surprisingly, shown to work well for polar fluids also. Work is underway to model liquid benzene. 17 refs

  8. Comparing the intra-annual wood formation of three European species (Fagus sylvatica, Quercus petraea and Pinus sylvestris) as related to leaf phenology and non-structural carbohydrate dynamics.

    Science.gov (United States)

    Michelot, Alice; Simard, Sonia; Rathgeber, Cyrille; Dufrêne, Eric; Damesin, Claire

    2012-08-01

    Monitoring cambial phenology and intra-annual growth dynamics is a useful approach for characterizing the tree growth response to climate change. However, there have been few reports concerning intra-annual wood formation in lowland temperate forests with high time resolution, especially for the comparison between deciduous and coniferous species. The main objective of this study was to determine how the timing, duration and rate of radial growth change between species as related to leaf phenology and the dynamics of non-structural carbohydrates (NSC) under the same climatic conditions. We studied two deciduous species, Fagus sylvatica L. and Quercus petraea (Matt.) Liebl., and an evergreen conifer, Pinus sylvestris L. During the 2009 growing season, we weekly monitored (i) the stem radial increment using dendrometers, (ii) the xylem growth using microcoring and (iii) the leaf phenology from direct observations of the tree crowns. The NSC content was also measured in the eight last rings of the stem cores in April, June and August 2009. The leaf phenology, NSC storage and intra-annual growth were clearly different between species, highlighting their contrasting carbon allocation. Beech growth began just after budburst, with a maximal growth rate when the leaves were mature and variations in the NSC content were low. Thus, beech radial growth seemed highly dependent on leaf photosynthesis. For oak, earlywood quickly developed before budburst, which probably led to the starch decrease quantified in the stem from April to June. For pine, growth began before the needles unfolding and the lack of NSC decrease during the growing season suggested that the substrates for radial growth were new assimilates of the needles from the previous year. Only for oak, the pattern determined from the intra-annual growth measured using microcoring differed from the pattern determined from dendrometer data. For all species, the ring width was significantly influenced by growth duration

  9. Project Summary (2012-2015) – Carbon Dynamics of the Greater Everglades Watershed and Implications of Climate Change

    Energy Technology Data Exchange (ETDEWEB)

    Hinkle, Ross [University of Central Florida; Benscoter, Brian [Florida Atlantic University; Comas, Xavier [Florida Atlantic University; Sumner, David [USGS; DeAngelis, Donald [USGS

    2015-04-07

    Carbon Dynamics of the Greater Everglades Watershed and Implications of Climate Change The objectives of this project are to: 1) quantify above- and below-ground carbon stocks of terrestrial ecosystems along a seasonal hydrologic gradient in the headwaters region of the Greater Everglades watershed; 2) develop budgets of ecosystem gaseous carbon exchange (carbon dioxide and methane) across the seasonal hydrologic gradient; 3) assess the impact of climate drivers on ecosystem carbon exchange in the Greater Everglades headwater region; and 4) integrate research findings with climate-driven terrestrial ecosystem carbon models to examine the potential influence of projected future climate change on regional carbon cycling. Note: this project receives a one-year extension past the original performance period - David Sumner (USGS) is not included in this extension.

  10. The effect of carbon plastic truss structures of solar arrays on dynamical characteristics of their drive mechanism

    Science.gov (United States)

    Shatikhin, V. Ye.; Semenov, L. P.; Artemenko, Yu. H.; Ihnatovych, S. R.

    We consider the effect of carbon plastic truss structures on dynamical characteristics of drive mechanism of space vehicle solar arrays. An analysis is made for frequencies of own oscillations of the truss structures of solar arrays and for dynamical characteristics of their drive mechanism for the case of structures from the carbon and plastic as well as from the aluminium alloy AMh-6. We substantiate the advantages of the manufacturing of truss structures of frameworks from the carbon and plastic by the winding method in respect of deriving a higher rigidity of a structure.

  11. Modeling Soil Carbon Dynamics in Northern Forests: Effects of Spatial and Temporal Aggregation of Climatic Input Data.

    Science.gov (United States)

    Dalsgaard, Lise; Astrup, Rasmus; Antón-Fernández, Clara; Borgen, Signe Kynding; Breidenbach, Johannes; Lange, Holger; Lehtonen, Aleksi; Liski, Jari

    2016-01-01

    Boreal forests contain 30% of the global forest carbon with the majority residing in soils. While challenging to quantify, soil carbon changes comprise a significant, and potentially increasing, part of the terrestrial carbon cycle. Thus, their estimation is important when designing forest-based climate change mitigation strategies and soil carbon change estimates are required for the reporting of greenhouse gas emissions. Organic matter decomposition varies with climate in complex nonlinear ways, rendering data aggregation nontrivial. Here, we explored the effects of temporal and spatial aggregation of climatic and litter input data on regional estimates of soil organic carbon stocks and changes for upland forests. We used the soil carbon and decomposition model Yasso07 with input from the Norwegian National Forest Inventory (11275 plots, 1960-2012). Estimates were produced at three spatial and three temporal scales. Results showed that a national level average soil carbon stock estimate varied by 10% depending on the applied spatial and temporal scale of aggregation. Higher stocks were found when applying plot-level input compared to country-level input and when long-term climate was used as compared to annual or 5-year mean values. A national level estimate for soil carbon change was similar across spatial scales, but was considerably (60-70%) lower when applying annual or 5-year mean climate compared to long-term mean climate reflecting the recent climatic changes in Norway. This was particularly evident for the forest-dominated districts in the southeastern and central parts of Norway and in the far north. We concluded that the sensitivity of model estimates to spatial aggregation will depend on the region of interest. Further, that using long-term climate averages during periods with strong climatic trends results in large differences in soil carbon estimates. The largest differences in this study were observed in central and northern regions with strongly

  12. Changes in ecosystem structure related to the type and extent of woody cover alter carbon dynamics and surface energy exchange in central Texas ecosystems.

    Science.gov (United States)

    Litvak, M. E.; Heilman, J.; McInnes, K.; Owens, K.; Kjelgaard, J.; Thijs, A.

    2006-12-01

    sensitive to changes in ecosystem structure. Woody encroachment is widely presumed to reduce sensitivity of carbon and energy exchange to rainfall and drought because deep root systems of woody plants provide access to water stored at depths unavailable to grasses. Data from our three sites challenge this presumption. Our data suggest that in karst terrain characterized by shallow soils underlain by limestone bedrock, effective root systems of dominant woody plants are shallow. The differential responses of the herbaceous component and the woody species to temperature extremes, summer droughts and large summer precipitation events provide a mechanistic understanding of carbon cycling in these ecosystems, and how woody species, in particular, alter both seasonal and annual carbon dynamics in Texas savanna rangelands.

  13. An Industrial-Based Consortium to Develop Premium Carbon Products from Coal, Annual Progress Report, October 1, 2005 through September 30, 2006

    Energy Technology Data Exchange (ETDEWEB)

    Miller, Bruce G

    2006-09-29

    Since 1998, The Pennsylvania State University has been successfully managing the Consortium for Premium Carbon Products from Coal (CPCPC), which is a vehicle for industry-driven research on the promotion, development, and transfer of innovative technology on premium carbon produces from coal to the U.S. industry. The CPCPC is an initiative being led by Penn State, its co-charter member West Virginia University (WVU), and the U.S. Department of Energy's (DOE) National Energy Technology Laboratory (NETL), who also provides the base funding for the program, with Penn State responsible for consortium management. CPCPC began in 1998 under DOE Cooperative Agreement No. DE-FC26-98FT40350. This agreement ended November 2004 but the CPCPC activity has continued under the present cooperative agreement, No. DE-FC26-03NT41874, which started October 1, 2003. The objective of the second agreement is to continue the successful operation of the CPCPC. The CPCPC has enjoyed tremendous success with its organizational structure, that includes Penn State and WVU as charter members, numerous industrial affiliate members, and strategic university affiliate members together with NETL, forming a vibrant and creative team for innovative research in the area of transforming coal to carbon products. The key aspect of CPCPC is its industry-led council that selects proposals submitted by CPCPC members to ensure CPCPC target areas have strong industrial support. Base funding for the selected projects is provided by NETL with matching funds from industry. At the annual funding meeting held in October 2003, ten projects were selected for funding. Subcontracts were let from Penn State to the subcontractors on March 1, 2004. Nine of the ten 2004 projects were completed during the previous annual reporting period and their final reports were submitted with the previous annual report (i.e., 10/01/04-09/30/05). The final report for the remaining project, which was submitted during this reporting

  14. Assessing the Impact of Landscape Evolution on Carbon Dynamics: A Coupled Physically-Based Modelling Approach

    Science.gov (United States)

    Dialynas, Y. G.; Bastola, S.; Billings, S. A.; Bras, R. L.

    2014-12-01

    Soil erosion and deposition play an important role in the global carbon (C) cycle, constituting an important driver of atmospheric CO2. Clarification of the net effect of landscape evolution on the C cycle may be achieved using coupled fully-distributed modelling of hydro-geomorphic and biogeochemical processes. We developed a distributed model of soil organic C (SOC) dynamics within an existing coupled physically-based hydro-geomorphic model (tRIBS - Erosion) to simulate the effects of soil erosion and deposition on C dynamics at basin scale. The SOC mass balance is analytically formulated at each cell using temporally variant, continuous vertical profiles of SOC content and SOC production and oxidation rate constants derived from SOC turnover characteristics. Landscape evolution feedbacks on C dynamics include the redistribution of eroded SOC, and the alteration of the SOC production and oxidation throughout the corresponding vertical profiles due to geomorphic perturbations. At each time step, model outputs include lateral and vertical C fluxes, and SOC content, at each soil column. We applied the model to the Calhoun Experimental Forest in South Carolina, which constitutes a forest recovering from agricultural land degradation prior to the mid-20th century. To test performance we carried out a point comparison against a spreadsheet-based model, SOrCERO (Soil Organic Carbon, Erosion, Replacement, and Oxidation) of SOC dynamics, which estimates effects of SOC erosion and altered SOC production and oxidation on CO2 release at an eroding profile. At a point, time integrated results from the two models were comparable. The proposed model has the additional advantage of being able to quantify C sinks and sources across the landscape in a spatially explicit manner, by systematically accounting for topographic controls on C dynamics. Sensitivity analysis suggested that the alteration of SOC production and oxidation due to landscape evolution and management practices

  15. Carbon nanorings with inserted acenes: breaking symmetry in excited state dynamics.

    Science.gov (United States)

    Franklin-Mergarejo, R; Alvarez, D Ondarse; Tretiak, S; Fernandez-Alberti, S

    2016-01-01

    Conjugated cycloparaphenylene rings have unique electronic properties being the smallest segments of carbon nanotubes. Their conjugated backbones support delocalized electronic excitations, which dynamics is strongly influenced by cyclic geometry. Here we present a comparative theoretical study of the electronic and vibrational energy relaxation and redistribution in photoexcited cycloparaphenylene carbon nanorings with inserted naphthalene, anthracene, and tetracene units using non-adiabatic excited-state molecular dynamics simulations. Calculated excited state structures reflect modifications of optical selection rules and appearance of low-energy electronic states localized on the acenes due to gradual departure from a perfect circular symmetry. After photoexcitation, an ultrafast electronic energy relaxation to the lowest excited state is observed on the time scale of hundreds of femtoseconds in all molecules studied. Concomitantly, the efficiency of the exciton trapping in the acene raises when moving from naphthalene to anthracene and to tetracene, being negligible in naphthalene, and ~60% and 70% in anthracene and tetracene within the first 500 fs after photoexcitation. Observed photoinduced dynamics is further analyzed in details using induced molecular distortions, delocatization properties of participating electronic states and non-adiabatic coupling strengths. Our results provide a number of insights into design of cyclic molecular systems for electronic and light-harvesting applications. PMID:27507429

  16. Carbon nanorings with inserted acenes: breaking symmetry in excited state dynamics

    Science.gov (United States)

    Franklin-Mergarejo, R.; Alvarez, D. Ondarse; Tretiak, S.; Fernandez-Alberti, S.

    2016-08-01

    Conjugated cycloparaphenylene rings have unique electronic properties being the smallest segments of carbon nanotubes. Their conjugated backbones support delocalized electronic excitations, which dynamics is strongly influenced by cyclic geometry. Here we present a comparative theoretical study of the electronic and vibrational energy relaxation and redistribution in photoexcited cycloparaphenylene carbon nanorings with inserted naphthalene, anthracene, and tetracene units using non-adiabatic excited-state molecular dynamics simulations. Calculated excited state structures reflect modifications of optical selection rules and appearance of low-energy electronic states localized on the acenes due to gradual departure from a perfect circular symmetry. After photoexcitation, an ultrafast electronic energy relaxation to the lowest excited state is observed on the time scale of hundreds of femtoseconds in all molecules studied. Concomitantly, the efficiency of the exciton trapping in the acene raises when moving from naphthalene to anthracene and to tetracene, being negligible in naphthalene, and ~60% and 70% in anthracene and tetracene within the first 500 fs after photoexcitation. Observed photoinduced dynamics is further analyzed in details using induced molecular distortions, delocatization properties of participating electronic states and non-adiabatic coupling strengths. Our results provide a number of insights into design of cyclic molecular systems for electronic and light-harvesting applications.

  17. Monitoring and Modeling Carbon Dynamics at a Network of Intensive Sites in the USA and Mexico

    Science.gov (United States)

    Birdsey, R.; Wayson, C.; Johnson, K. D.; Pan, Y.; Angeles, G.; De Jong, B. H.; Andrade, J. L.; Dai, Z.

    2013-05-01

    The Forest Services of the USA and Mexico, supported by NASA and USAID, have begun to establish a network of intensive forest carbon monitoring sites. These sites are used for research and teaching, developing forest management practices, and forging links to the needs of communities. Several of the sites have installed eddy flux towers to basic meteorology data and daily estimates of forest carbon uptake and release, the processes that determine forest growth. Field sampling locations at each site provide estimates of forest biomass and carbon stocks, and monitor forest dynamic processes such as growth and mortality rates. Remote sensing facilitates scaling up to the surrounding landscapes. The sites support information requirements for implementing programs such as Reducing Emissions from Deforestation and Forest Degradation (REDD+), enabling communities to receive payments for ecosystem services such as reduced carbon emissions or improved forest management. In addition to providing benchmark data for REDD+ projects, the sites are valuable for validating state and national estimates from satellite remote sensing and the national forest inventory. Data from the sites provide parameters for forest models that support strategic management analysis, and support student training and graduate projects. The intensive monitoring sites may be a model for other countries in Latin America. Coordination among sites in the USA, Mexico and other Latin American countries can ensure harmonization of approaches and data, and share experiences and knowledge among countries with emerging opportunities for implementing REDD+ and other conservation programs.

  18. Effect of Management Practices on Seasonal Dynamics of Organic Carbon in Soils Under Bamboo Plantations

    Institute of Scientific and Technical Information of China (English)

    ZHOU Guo-Mo; XU Jian-Ming; JIANG Pei-Kun

    2006-01-01

    Soil samples for conventional management (CM) and intensive management (IM) practices were taken over a year at2-month intervals to determine the effect of management practices on soil organic carbon (SOC) and to quantify seasonal dynamics in SOC for bamboo (Phyllostachys pubescens Mazel ex H. de Lehaie) stands. The results with IM compared to CM showed large decreases in total organic carbon (TOC), microbial biomass carbon (MBC), water-soluble organic carbon (WSOC), and the MBC/TOC ratio in the soils. With all IM plots in the 0-20 cm depth across sampling periods,average decreases compared with CM were: TOC, 12.1%; MBC, 26.1%; WSOC, 29.3%; the MBC/TOC ratio, 16.1%;and the WSOC/TOC ratio, 20.0%. Due to seasonal changes of climate, seasonal variations were observed in MBC and WSOC. Soil MBC in the 0-20 cm depth in September compared to May were 122.9% greater for CM and 57.6% greater for IM. However, due primarily to soil temperature, soil MBC was higher during the July to November period, whereas because of soil moisture, WSOC was lower in July and January. This study revealed that intensive management in bamboo plantations depleted the soil C pool; therefore, soil quality with IM should be improved through application of organic manures.

  19. Ultrafast carrier dynamics of carbon nanodots in different pH environments.

    Science.gov (United States)

    Sui, Laizhi; Jin, Wuwei; Li, Suyu; Liu, Dunli; Jiang, Yuanfei; Chen, Anmin; Liu, Hang; Shi, Ying; Ding, Dajun; Jin, Mingxing

    2016-02-01

    Ultrafast carrier relaxation dynamics in fluorescent carbon nanodots is investigated by femtosecond transient absorption spectra at different pH environments so as to understand the mechanism of fluorescence for the first time. Utilizing multi-wavelength global analysis to fit the measured signal via a sequential model, four different relaxation channels are found, which are attributed to electron-electron scattering and surface state trapping, optical phonon scattering, acoustic phonon scattering and electron-hole recombination respectively. The results reveal that the surface states are mainly composed of different oxygen-containing functional groups (epoxy, carbonyl and carboxyl) and carbon atoms on the edge of the carbon backbone and can effectively trap a large number of photo-excited electrons. The deprotonation of carboxyl groups at high pH will change the distribution of π electron cloud density between the carbon backbone and surface states and consequently, compared with the excited electrons in the acidic and neutral environments, those in the alkaline environment can be more easily trapped by the surface within 1 ps, thereby giving rise to stronger fluorescence emission. PMID:26763126

  20. Growth dynamics of carbon-metal particles and nanotubes synthesized by CO2 laser vaporization

    Science.gov (United States)

    Kokai, F.; Takahashi, K.; Yudasaka, M.; Iijima, S.

    To study the growth of carbon-Co/Ni particles and single-wall carbon nanotubes (SWNTs) by 20 ms CO2 laser-pulse irradiation of a graphite-Co/Ni (1.2 at.%) target in an Ar gas atmosphere (600 Torr), we used emission imaging spectroscopy and shadowgraphy with a temporal resolution of 1.67 ms. Wavelength-selected emission images showed that C2 emission was strong in the region close to the target (within 2 cm), while for the same region the blackbody radiation from the large clusters or particles increased with increasing distance from the target. Shadowgraph images showed that the viscous flow of carbon and metal species formed a mushroom or a turbulent cloud spreading slowly into the Ar atmosphere, indicating that particles and SWNTs continued to grow as the ejected material cooled. In addition, emission imaging spectroscopy at 1200 °C showed that C2 and hot clusters and particles with higher emission intensities were distributed over much wider areas. We discuss the growth dynamics of the particles and SWNTs through the interaction of the ambient Ar with the carbon and metal species released from the target by the laser pulse.

  1. Motion and energy dissipation of single-walled carbon nanotube on graphite by molecular dynamics simulation

    International Nuclear Information System (INIS)

    The motion and energy dissipation of carbon nanotubes (CNTs) have important influence on their application. This paper investigated the sliding of single-walled carbon nanotubes (SWCNTs) on a graphite substrate using molecular dynamics simulation. An interesting phenomenon was observed in the commensurate interface. The carbon nanotube slid in not only the initial velocity direction but also perpendicular to the initial velocity with only a slight rolling in the later stage of motion. The direction and distance of motion were related to the initial interfacial configuration when the CNT started to slide and presented a certain degree of randomness. This phenomenon could be attributed to the SWCNT not having a platform on the bottom, which caused a low interfacial potential barrier. Therefore, no obvious ‘stick-slip’ occurred. In the incommensurate state, the SWCNT slid on the graphite substrate in the initial direction for the process, and the velocity slowly decreased. The temperature slightly influenced the carbon nanotube’s motion mainly because of random thermal fluctuations. (papers)

  2. Nonlinear dynamics of bi-layered graphene sheet, double-walled carbon nanotube and nanotube bundle

    Science.gov (United States)

    Gajbhiye, Sachin O.; Singh, S. P.

    2016-05-01

    Due to strong van der Waals (vdW) interactions, the graphene sheets and nanotubes stick to each other and form clusters of these corresponding nanostructures, viz. bi-layered graphene sheet (BLGS), double-walled carbon nanotube (DWCNT) and nanotube bundle (NB) or ropes. This research work is concerned with the study of nonlinear dynamics of BLGS, DWCNT and NB due to nonlinear interlayer vdW forces using multiscale atomistic finite element method. The energy between two adjacent carbon atoms is represented by the multibody interatomic Tersoff-Brenner potential, whereas the nonlinear interlayer vdW forces are represented by Lennard-Jones 6-12 potential function. The equivalent nonlinear material model of carbon-carbon bond is used to model it based on its force-deflection relation. Newmark's algorithm is used to solve the nonlinear matrix equation governing the motion of the BLGS, DWCNT and NB. An impulse and harmonic excitations are used to excite these nanostructures under cantilevered, bridged and clamped boundary conditions. The frequency responses of these nanostructures are computed, and the dominant resonant frequencies are identified. Along with the forced vibration of these structures, the eigenvalue extraction problem of armchair and zigzag NB is also considered. The natural frequencies and corresponding mode shapes are extracted for the different length and boundary conditions of the nanotube bundle.

  3. Revised estimates of the annual net flux of carbon to the atmosphere from changes in land use and land management 1850-2000

    International Nuclear Information System (INIS)

    Recent analyses of land-use change in the US and China, together with the latest estimates of tropical deforestation and afforestation from the FAO, were used to calculate a portion of the annual flux of carbon between terrestrial ecosystems and the atmosphere. The calculated flux includes only that portion of the flux resulting from direct human activity. In most regions, activities included the conversion of natural ecosystems to cultivated lands and pastures, including shifting cultivation, harvest of wood (for timber and fuel) and the establishment of tree plantations. In the US, woody encroachment and woodland thickening as a result of fire suppression were also included. The calculated flux of carbon does not include increases or decreases in carbon storage as a result of environmental changes (e.g.; increasing concentrations of CO2, N deposition, climatic change or pollution). Globally, the long-term (1850-2000) flux of carbon from changes in land use and management released 156 PgC to the atmosphere, about 60% of it from the tropics. Average annual fluxes during the 1980s and 1990s were 2.0 and 2.2 PgC/yr, respectively, dominated by releases of carbon from the tropics. Outside the tropics, the average net flux of carbon attributable to land-use change and management decreased from a source of 0.06 PgC/yr during the 1980s to a sink of 0.02 PgC/yr during the 1990s. According to the analyses summarized here, changes in land use were responsible for sinks in North America and Europe and for small sources in other non-tropical regions. The revisions were as large as 0.3 PgC/yr in individual regions but were largely offsetting, so that the global estimate for the 1980s was changed little from an earlier estimate. Uncertainties and recent improvements in the data used to calculate the flux of carbon from land-use change are reviewed, and the results are compared to other estimates of flux to evaluate the extent to which processes other than land-use change and

  4. Molecular Dynamics Simulation of Carbon Dioxide in Single-Walled Carbon Nanotubes in the Presence of Water: Structure and Diffusion Studies

    OpenAIRE

    Svoboda, M; Brennan, J.K.; Lísal, M. (Martin)

    2016-01-01

    We present a molecular dynamics study on the structure and diffusion of carbon dioxide in single-walled carbon nanotubes (SWCNTs) in the presence of water. We consider (10,10) and (15,15) SWCNTs of nanotube diameter 13.6 and 20.3 angstrom, respectively, with amounts of pre-adsorbed water equal to 0, 0.025, 0.1, and 0.2 g/cm(3). The density of the carbon dioxide in the SWCNTs corresponds to the maximum amount adsorbed at 300 K and 37.6 bar, as previously determined by grand canonical Monte Car...

  5. Optical approaches to examining the dynamics of dissolved organic carbon in optically complex inland waters

    International Nuclear Information System (INIS)

    Optical approaches were developed to examine the relationship between the optically active and the optically inactive fractions of dissolved organic carbon in inland waters. A multiple linear regression model was developed on the basis of an extensive dataset from Taihu Lake, and validated employing data from another large shallow eutrophic lake (Chaohu Lake) in southern China. The model was used to estimate the concentration of dissolved organic matter (n = 191) using the absorption characteristics of its chromophoric fraction with a high correlation coefficient (R2 = 0.62) and a low root mean squared error (RMSE = 9.67%). This intra-ecosystem validity allows us to improve our understanding of carbon dynamics using optical remote sensing approaches for these optically complex lakes, where multiple sources and sinks of dissolved organic matter were present. (letter)

  6. Compressive characteristics of single walled carbon nanotube with water interactions investigated by using molecular dynamics simulation

    International Nuclear Information System (INIS)

    The elastic properties of single walled carbon nanotube (SWCNT) with surrounding water interactions are studied using molecular dynamics simulation technique. The compressive loading characteristic of carbon nanotubes (CNTs) in a fluidic medium such as water is critical for its role in determining the lifetime and stability of CNT based nano-fluidic devices. In this paper, we conducted a comprehensive analysis on the effect of geometry, chirality and density of encapsulated water on the elastic properties of SWCNT. Our studies show that defect density and distribution can strongly impact the compressive resistance of SWCNTs in water. Further studies were conducted on capped SWCNTs with varying densities of encapsulated water, which is necessary to understand the strength of CNT as a potential drug carrier. The results obtained from this paper will help determining the potential applications of CNTs in the field of nano-electromechanical systems (NEMS) such as nano-biological and nano-fluidic devices.

  7. Compressive characteristics of single walled carbon nanotube with water interactions investigated by using molecular dynamics simulation

    Energy Technology Data Exchange (ETDEWEB)

    Wong, C.H., E-mail: chwong@ntu.edu.sg; Vijayaraghavan, V.

    2014-01-24

    The elastic properties of single walled carbon nanotube (SWCNT) with surrounding water interactions are studied using molecular dynamics simulation technique. The compressive loading characteristic of carbon nanotubes (CNTs) in a fluidic medium such as water is critical for its role in determining the lifetime and stability of CNT based nano-fluidic devices. In this paper, we conducted a comprehensive analysis on the effect of geometry, chirality and density of encapsulated water on the elastic properties of SWCNT. Our studies show that defect density and distribution can strongly impact the compressive resistance of SWCNTs in water. Further studies were conducted on capped SWCNTs with varying densities of encapsulated water, which is necessary to understand the strength of CNT as a potential drug carrier. The results obtained from this paper will help determining the potential applications of CNTs in the field of nano-electromechanical systems (NEMS) such as nano-biological and nano-fluidic devices.

  8. Future active layer dynamics and carbon dioxide production from thawing permafrost layers in Northeast Greenland

    DEFF Research Database (Denmark)

    Hollesen, Jørgen; Elberling, Bo; Jansson, P.E.

    2011-01-01

    Thawing permafrost and the resulting mineralization of previously frozen organic carbon (C) is considered an important future feedback from terrestrial ecosystems to the atmosphere. Here, we use a dynamic process oriented permafrost model, the CoupModel, to link surface and subsurface temperatures...... from a moist permafrost soil in High-Arctic Greenland with observed heat production and carbon dioxide (CO2) release rates from decomposition of previously frozen organic matter. Observations show that the maximum thickness of the active layer at the end of the summer has increased 1 cm yr-1 since 1996...... soil respiration rates in a respiration model to predict the corresponding depth-integrated CO2 production from permafrost layers between 0.7 and 2 m below the surface. Results show an increase from present values of <40 g C m-2 yr-1 to between 120 and 213 g C m-2 yr-1 depending on the magnitude of...

  9. Plasma species dynamics in a laser produced carbon plasma expanding in low pressure neutral gas background

    Science.gov (United States)

    Ruiz, H. M.; Guzmán, F.; Favre, M.; Bhuyan, H.; Chuaqui, H.; Wyndham, E.

    2012-06-01

    We present time and space resolved spectroscopic observations of a laser produced carbon plasma, in an argon background. An Nd:YAG laser pulse, 370 mJ, 3.5 ns, at 1.06 μm, with a fluence of 6.8 J/cm2, is used to produce a plasma from a solid graphite target, at a base pressure of 0.5 mTorr, and with 80 mTorr Argon background. The spectral emission in the visible is recorded with 15 ns time resolution. 20 ns time resolution plasma imagining, filtered at characteristic carbon species emission wavelengths, is used to study the dynamics of the expanding plasma. Two different fronts with ionic or molecular compositions are seen to detach from de laser target plasma.

  10. Molecular Dynamics Simulations of the Thermal Conductivity of Single-Wall Carbon Nanotubes

    Science.gov (United States)

    Osman, M.; Srivastava, Deepak; Govindan,T. R. (Technical Monitor)

    2000-01-01

    Carbon nanotubes (CNT) have very attractive electronic, mechanical. and thermal properties. Recently, measurements of thermal conductivity in single wall CNT mats showed estimated thermal conductivity magnitudes ranging from 17.5 to 58 W/cm-K at room temperature. which are better than bulk graphite. The cylinderical symmetry of CNT leads to large thermal conductivity along the tube axis, additionally, unlike graphite. CNTs can be made into ropes that can be used as heat conducting pipes for nanoscale applications. The thermal conductivity of several single wall carbon nanotubes has been calculated over temperature range from l00 K to 600 K using non-equilibrium molecular dynamics using Tersoff-Brenner potential for C-C interactions. Thermal conductivity of single wall CNTs shows a peaking behavior as a function of temperature. Dependence of the peak position on the chirality and radius of the tube will be discussed and explained in this presentation.

  11. Cyclic occurrence of fire and its role in carbon dynamics along an edaphic moisture gradient in longleaf pine ecosystems.

    Directory of Open Access Journals (Sweden)

    Andrew Whelan

    Full Text Available Fire regulates the structure and function of savanna ecosystems, yet we lack understanding of how cyclic fire affects savanna carbon dynamics. Furthermore, it is largely unknown how predicted changes in climate may impact the interaction between fire and carbon cycling in these ecosystems. This study utilizes a novel combination of prescribed fire, eddy covariance (EC and statistical techniques to investigate carbon dynamics in frequently burned longleaf pine savannas along a gradient of soil moisture availability (mesic, intermediate and xeric. This research approach allowed us to investigate the complex interactions between carbon exchange and cyclic fire along the ecological amplitude of longleaf pine. Over three years of EC measurement of net ecosystem exchange (NEE show that the mesic site was a net carbon sink (NEE = -2.48 tonnes C ha(-1, while intermediate and xeric sites were net carbon sources (NEE = 1.57 and 1.46 tonnes C ha(-1, respectively, but when carbon losses due to fuel consumption were taken into account, all three sites were carbon sources (10.78, 7.95 and 9.69 tonnes C ha(-1 at the mesic, intermediate and xeric sites, respectively. Nonetheless, rates of NEE returned to pre-fire levels 1-2 months following fire. Consumption of leaf area by prescribed fire was associated with reduction in NEE post-fire, and the system quickly recovered its carbon uptake capacity 30-60 days post fire. While losses due to fire affected carbon balances on short time scales (instantaneous to a few months, drought conditions over the final two years of the study were a more important driver of net carbon loss on yearly to multi-year time scales. However, longer-term observations over greater environmental variability and additional fire cycles would help to more precisely examine interactions between fire and climate and make future predictions about carbon dynamics in these systems.

  12. Intra-annual water store and stable isotope dynamics for Himalayan basins of Nepal

    Science.gov (United States)

    Hannah, D. M.; Fairchild, I. J.; Boomer, I.; Pokhrel, A.; Kansakar, S. R.

    2009-04-01

    Isotope-based hydrograph separations are applied commonly to reveal the sources, mixing-ratios and timing of river flow and so evaluate runoff generation mechanisms. In this context, rivers draining the Himalayas have received limited attention despite their high sensitivity to climate change and their importance for regional and global water budgets and biogeochemical cycles. Seasonal variation in river water isotope compositions is not well documented for this high mountain region. Hence, this research aims to determine the nature and dynamics of water store contributions to river flow for Himalayan basins of Nepal over a hydrological year by undertaking a study of ^18O and ^D variation in river water and rainfall for two sub-basins of the Trishuli river with contrasting hydrology: (a) glacierized Langtang Khola and (b) rain-fed Phalankhu Khola. Weekly water samples were taken from April 2004-March 2005 at 4 river sites (in each sub-basin and above and below their confluences) and from two aggregate rainfall collectors. Sampling locations were paired with river and precipitation gauges. Isotopic data yield tight and internally consistent arrays that facilitate interpretation in relation to rainfall amount and isotopic composition, and river discharge data, and thus quantification of changing water store contributions (i.e. rainfall including summer monsoon, snow- and ice-melt, and groundwater), over the hydrological year, and between basins. This research provides a key baseline study during the current period of Himalayan glacier recession.

  13. Remote sensing techniques to monitor nitrogen-driven carbon dynamics in field corn

    Science.gov (United States)

    Corp, Lawrence A.; Middleton, Elizabeth M.; Campbell, Petya K. E.; Huemmrich, K. Fred; Cheng, Yen-Ben; Daughtry, Craig S. T.

    2009-08-01

    Patterns of change in vegetation growth and condition are one of the primary indicators of the present and future ecological status of the globe. Nitrogen (N) is involved in photochemical processes and is one of the primary resources regulating plant growth. As a result, biological carbon (C) sequestration is driven by N availability. Large scale monitoring of photosynthetic processes are currently possible only with remote sensing systems that rely heavily on passive reflectance (R) information. Unlike R, fluorescence (F) emitted from chlorophyll is directly related to photochemical reactions and has been extensively used for the elucidation of the photosynthetic pathways. Recent advances in passive fluorescence instrumentation have made the remote acquisition of solar-induced fluorescence possible. The goal of this effort is to evaluate existing reflectance and emerging fluorescence methodologies for determining vegetation parameters related to photosynthetic function and carbon sequestration dynamics in plants. Field corn N treatment levels of 280, 140, 70, and 0 kg N / ha were sampled from an intensive test site for a multi-disciplinary project, Optimizing Production Inputs for Economic and Environmental Enhancement (OPE). Aircraft, near-ground, and leaf-level measurements were used to compare and contrast treatment effects within this experiment site assessed with both reflectance and fluorescence approaches. A number of spectral indices including the R derivative index D730/D705, the normalized difference of R750 vs. R705, and simple ratio R800/R750 differentiated three of the four N fertilization rates and yielded high correlations to three important carbon parameters: C:N, light use efficiency, and grain yield. These results advocate the application of hyperspectral sensors for remotely monitoring carbon cycle dynamics in terrestrial ecosystems.

  14. Application of fast pyrolysis biochar to a loamy soil - Effects on carbon and nitrogen dynamics and potential for carbon sequestration

    Energy Technology Data Exchange (ETDEWEB)

    Bruun, E.W.

    2011-05-15

    Thermal decomposition of biomass in an oxygen-free environment (pyrolysis) produces bio-oil, syngas, and char. All three products can be used to generate energy, but an emerging new use of the recalcitrant carbon-rich char (biochar) is to apply it to the soil in order to enhance soil fertility and at the same time mitigate climate change by sequestering carbon in the soil. In general, the inherent physicochemical characteristics of biochars make these materials attractive agronomic soil conditioners. However, different pyrolysis technologies exist, i.e. slow pyrolysis, fast pyrolysis, and full gasification systems, and each of these influence the biochar quality differently. As of yet, there is only limited knowledge on the effect of applying fast pyrolysis biochar (FP-biochar) to soil. This PhD project provides new insights into the short-term impacts of adding FP-biochar to soil on the greenhouse gas (GHG) emissions and on soil carbon and nitrogen dynamics. The FP-biochars investigated in the thesis were generated at different reactor temperatures by fast pyrolysis of wheat straw employing a Pyrolysis Centrifuge Reactor (PCR). The carbohydrate content ranged from more than 35 % in FP-biochars made at a low reactor temperature (475 deg. C) down to 3 % in FP-biochars made at high temperatures (575 deg. C). The relative amount of carbohydrates in the FP-biochar was found to be correlated to the short-term degradation rates of the FP-biochars when applied to soil. Fast and slow pyrolysis of wheat straw resulted in two different biochar types with each their distinct physical structures and porosities, carbohydrate contents, particle sizes, pH values, BET surface areas, and elemental compositions. These different physicochemical properties obviously have different impacts on soil processes, which underscores that results obtained from soil studies using slow pyrolysis biochars (SP-biochar) are not necessarily applicable for FP-biochars. For example, the incorporation

  15. Seasonal spectral dynamics and carbon fluxes at core EOS sites using EO-1 Hyperion images

    Science.gov (United States)

    Lagomasino, D.; Campbell, P.; Price, R. M.

    2010-12-01

    Fluxes of water and carbon into the atmosphere are critical components in order to monitor and predict climate change. Spatial heterogeneity and seasonal changes in vegetation contribute to ambiguities in regional and global CO2 and water cycle dynamics. Satellite remote sensing is essential for monitoring the spatial and temporal dynamics of various vegetation types for the purposes of determining carbon and water fluxes. Satellite data from the EO-1 Hyperion sensor was acquired for five Earth Observing Satellite (EOS) sites, Mongu (Zambia, Africa), Konza Prairie (Kansas, USA), Duke Forest (North Carolina, USA), Barrow (Alaska, USA) and Sevilleta (New Mexico, USA). Each EOS site represented a distinct vegetative ecosystem type; hardwood forest, grassland, evergreen forest, lichens, and shrubland/grassland respectively. Satellite data was atmospherically corrected using the Atmosphere CORrection Now (ACORN) model and subsequently, the spectral reflectance data was extracted in the vicinity of existing flux towers. The EO-1 Hyperion sensor proved advantageous because of its high and continuous spectral resolution (10 nm intervals from 355 to 2578 nm wavelengths). The high spectral resolution allowed us calculate biophysical indices based on specific wavelengths in the electromagnetic spectrum that are associated with alterations in foliar chemistry and plant membrane structure (i.e., vegetation stress) brought upon by many environmental factors. Previous studies have focused on relationships within a specific site or vegetation community. This study however, incorporated many sites with different vegetation types and various geographic locations throughout the world. Monitoring the fluctuations in vegetation stress with contemporaneous environmental conditions and carbon flux measurements from each site will provide better insight into water and carbon flux dynamics in many different biomes. Noticeable spectral signatures were identified based on site specific

  16. Molecular dynamics simulation for flow characteristics in nanochannels and single walled carbon nanotubes

    International Nuclear Information System (INIS)

    Flows in graphite-, diamond- and silicon-walled nanochannels are discussed by performing molecular dynamics simulations. Flows in carbon nanotubes (CNTs) and graphene- walled nanochannels are also investigated. It is found that the flow rate in the graphite-walled channel tends to be the largest because of its slippery wall structure by the short bond length and the high molecular density of the CNTs. The flow rate in the single walled CNT at a very narrow diameter tends to increase although such a tendency is not seen in the graphene-walled channel.

  17. Molecular Dynamical Simulation of Water/Ice Phase Transitions within Carbon Nanotubes under Various Pressures

    International Nuclear Information System (INIS)

    A molecular dynamics simulation is performed for water confined within carbon nanotubes with diameters 11.00 Å and 12.38 Å. Under pressures from 0.1 MPa to 500 MPa the simulations are carried out by cooling from 300 K to 240 K. Water molecules tend to transform from disordered to ordered with different configurations (square, pentagonal, hexagonal and hexagonal plus a chain). It is concluded that denser structures may appear under high pressures. (condensed matter: structure, mechanical and thermal properties)

  18. The Environmental Effect on the Dynamical Behaviors of Single-Walled Carbon Nanotube in Water

    OpenAIRE

    Yan Yan; Weizhong Li; Wenquan Wang

    2014-01-01

    The paper investigates the dynamical behaviors of single-walled carbon nanotube (SWCNT) in water, focusing on the effect of external environment (i.e., water) on SWCNT. The SWCNT-water system comprises three constituent parts, that is, the SWCNT, the absorbed layer of water molecules, and the water flow around the water layer. The SWCNT and the absorbed layer of water are modeled as two-layer thin shells coupled via the interlayer vdW interaction, and the water surrounding the absorbed water ...

  19. Dynamic measurement of mercury adsorption and oxidation on activated carbon in simulated cement kiln flue gas

    DEFF Research Database (Denmark)

    Zheng, Yuanjing; Jensen, Anker Degn; Windelin, Christian;

    2012-01-01

    of the sulfite converter is short and typically within 2min. Dynamic mercury adsorption and oxidation tests on commercial activated carbons Darco Hg and HOK standard were performed at 150°C using simulated cement kiln gas and a fixed bed reactor system. It is shown that the converter and analyzer...... applied. A sodium sulfite-based converter material was prepared by dry impregnation of sodium sulfite and calcium sulfate powders on zeolite pellets using water glass as binder. The sulfite converter works well at 500°C with less than 10ppmv HCl in the simulated cement kiln flue gas. The 95% response time...

  20. Dynamic response of carbon nanotube field-effect transistors analyzed by S-parameters measurement

    International Nuclear Information System (INIS)

    Carbon nanotube field-effect transistors (CN-FET) with a metallic back gate have been fabricated. By assembling a number of CNs in parallel, driving currents in the mA range have been obtained. The dynamic response of the CN-FETs has been investigated through S-parameters measurements. A current gain (|H 21|2) cut-off frequency (f t) of 8 GHz, and a maximum stable gain (MSG) value of 10 dB at 1 GHz have been obtained. The extraction of an equivalent circuit is proposed

  1. Dynamic response of carbon nanotube field-effect transistors analyzed by S-parameters measurement

    Energy Technology Data Exchange (ETDEWEB)

    Bethoux, J.-M. [Institut d' Electronique, de Microelectronique et de Nanotechnologie, C.N.R.S. U.M.R. 8520, BP 60069, F-59652, Villeneuve d' Ascq Cedex (France); Happy, H. [Institut d' Electronique, de Microelectronique et de Nanotechnologie, C.N.R.S. U.M.R. 8520, BP 60069, F-59652, Villeneuve d' Ascq Cedex (France)]. E-mail: henri.happy@iemn.univ-lille1.fr; Dambrine, G. [Institut d' Electronique, de Microelectronique et de Nanotechnologie, C.N.R.S. U.M.R. 8520, BP 60069, F-59652, Villeneuve d' Ascq Cedex (France); Derycke, V. [Laboratoire d' Electronique Moleculaire, SPEC, Commissariat a l' Energie Atomique, Saclay F-91191, Gif sur Yvette Cedex (France); Goffman, M. [Laboratoire d' Electronique Moleculaire, SPEC, Commissariat a l' Energie Atomique, Saclay F-91191, Gif sur Yvette Cedex (France); Bourgoin, J.-P. [Laboratoire d' Electronique Moleculaire, SPEC, Commissariat a l' Energie Atomique, Saclay F-91191, Gif sur Yvette Cedex (France)

    2006-12-15

    Carbon nanotube field-effect transistors (CN-FET) with a metallic back gate have been fabricated. By assembling a number of CNs in parallel, driving currents in the mA range have been obtained. The dynamic response of the CN-FETs has been investigated through S-parameters measurements. A current gain (|H {sub 21}|{sup 2}) cut-off frequency (f {sub t}) of 8 GHz, and a maximum stable gain (MSG) value of 10 dB at 1 GHz have been obtained. The extraction of an equivalent circuit is proposed.

  2. Carbon and Nitrogen Cycling in Urban Landscapes: Global, Regional Dynamics and Case Studies.

    Science.gov (United States)

    Svirejeva-Hopkins, A.; Nardoto, G. B.; Schellnhuber, H.

    2008-12-01

    The urban population has been growing rapidly in the last decades and is predicted to continue its exponential trend, especially in the developing countries, which would create additional pressure on the environment by overpopulated unsustainable cities and will continue to substantially change the main Biogeochemical cycles. Such disturbances in the main driving cycle of the Biosphere (global carbon cycle) and the nitrogen cycle, induced by sprawling urban human activities, lead to global, regional and local environmental problems, i.e. global warming, photochemical smog, stratospheric ozone depletion, soil acidification, nitrate pollution of surface and ground water, coastal ecosystem disturbances. Since urban areas are expected to continue their rapid expansion in the 21st century, accompanied by growing energy production, increased food demand, expanding transportation and industrialization it becomes more and more important to be able to describe and forecast the dynamics of biogeochemical functioning of these landscapes (which have altered characteristics compared to the natural ecosystems). Moreover, from the environmental policy perspective, a high density of people makes cities focal points of vulnerability to global environmental change. The model based on the forecasting the dynamics of urban area growth, allows us to forecast the dynamics of Carbon and Nitrogen on the urban territories at different scales. However, nitrogen cycle is very complex and is closely interlinked with the other major biogeochemical cycles, such as oxygen and water. The system of water supply and liquid waste carried by water out of the system 'city' is investigated. In order to better understand the mechanisms of cycling, we consider the case studies, when we investigated the detailed fluxes of Carbon and Nitrogen in Sao Paolo (Brazil) and Paris (France). When we know the yearly amounts of carbon and nitrogen, produced by a city, we should be capable of coming up with what

  3. Study of reduction of dynamic modulus of elasticity irradiated carbon materials during thermal annealing

    International Nuclear Information System (INIS)

    The reduction during thermal annealing up to 2500 deg C of dynamic modulus of elastisity for carbon materials with different properties and irradiated with different neutron fluence at 70-1050 deg C, is examined. The modules ''reset'', i. e. it's decrease lower the value inherent in the material before irradiation, is shown to occur as a results of radiation graphite ''swelling'' and it's subsequent thermal annealing. A supposition is expressed that the observed effect is stipulated by the formation and propagation of unrestorable microfracting

  4. Coupling sediment flow-paths with organic carbon dynamics across a Mediterranean catchment

    Directory of Open Access Journals (Sweden)

    C. Boix-Fayos

    2014-05-01

    Full Text Available Terrestrial sedimentation buries large amounts of organic carbon (OC annually, contributing to the terrestrial carbon sink. The temporal significance of this sink will strongly depend on the attributes of the depositional environment, but also on the characteristics of the OC reaching these sites and its stability upon deposition. The goal of this study was to characterise the OC during transport and stored in the depositional settings of a medium sized catchment (111 km2 in SE Spain, to better understand how soil erosion and sediment transport processes determine catchment scale OC redistribution. Total Organic Carbon (TOC, Mineral-Associated Organic Carbon (MOC, Particulate Organic Carbon (POC, Total Nitrogen (N and particle size distributions were determined for soils (i, suspended sediments (ii and sediments stored in a variety of sinks such as sediment wedges behind check-dams (iii, channel bars (iv, a small delta in the conjunction of the channel and a reservoir downstream (v and the reservoir at the outlet of the catchment (vi. The data show that the OC content of sediments was approximately half of that in soils (9.42 ± 9.01 g kg−1 vs. 20.45 ± 7.71 g kg−1, respectively with important variation between sediment deposits. Selectivity of mineral and organic material during transport and deposition increased in a downstream direction. The OC mineralisation, burial or formation occurred in sediments depending on their transport process and on the post-sedimentary conditions. Upstream sediments showed low OC contents because they were partially mobilised by non-selective erosion processes affecting deeper soil layers. We hypothesise that the relatively short transport distances, the effective preservation of OC in micro-aggregates and the burial of sediments in the alluvial wedges give rise to low OC mineralisation, with C : N ratios similar to those in soils. Deposits in middle stream areas (fluvial bars were enriched in sand, selected

  5. Implications of agricultural encroachment on the carbon and greenhouse gas dynamics in tropical African wetlands.

    Science.gov (United States)

    Saunders, Matthew; Kansiime, Frank; Jones, Michael

    2015-04-01

    Cyperus papyrus L. (papyrus) wetlands dominate the permanently inundated wetlands of tropical East Africa and support the livelihoods of millions of people in rural sub-Saharan Africa through the provision of multiple ecosystem services such as the supply of drinking water, fish protein, building materials and biofuels. These wetlands are also extremely important in local and regional scale biogeochemical cycles due to their extensive spatial distribution, high rates of photosynthetic carbon dioxide (CO2) assimilation, long-term carbon (C) sequestration in the form of peat and the control of water loss through evapotranspiration. However, these wetlands are facing significant anthropogenic pressures due to the increasing demand for agricultural land where the papyrus plants are removed and replaced with subsistence crops such as cocoyam (Colocasia esculenta). Eddy covariance measurements were made on an undisturbed papyrus wetland and a cocoyam dominated wetland on the Ugandan shoreline of Lake Victoria to better understand the impacts of agricultural encroachment on the C sequestration potential of these wetlands. Peak rates of net photosynthetic CO2 assimilation at the papyrus wetland were over 40 μmol CO2 m-2 s-1, even under increasing vapour pressure deficit (≥2 kPa), while maximum rates of assimilation at the cocoyam site were 28 μmol CO2 m-2 s-1. Annual rates of papyrus net primary productivity (NPP) were amongst the highest recorded for wetland systems globally (3.09 kg C m-2 yr-1) and the continual regeneration of the papyrus plants, due to an absence of pronounced seasonal climatic variability, can lead to significant C accumulation in the above and belowground biomass (≥88 t C ha-1). Where these wetlands remain inundated and anaerobic conditions prevail, significant detrital and peat deposits can form further increasing the combined C sink capacity of these ecosystems to over 700 t C ha-1. The C sink strength of these wetlands is however offset by

  6. Forest Biomass, Carbon Stocks, and Macrofungal Dynamics: A Case Study in Costa Rica

    Directory of Open Access Journals (Sweden)

    Carlos Rojas

    2014-01-01

    Full Text Available There are few published studies providing information about macrofungal biology in a context of forest dynamics in tropical areas. For this study, a characterization of above-ground standing tree biomass and carbon stocks was performed for four different forest subtypes within two life zones in Costa Rica. Fungal productivity and reproductive success were estimated and analyzed in the context of the forest systems studied and results showed fungal dynamics to be a complex and challenging topic. In the present study, fungal productivity was higher in forest patches with more tree density but independent from life zones, whereas fungal biomass was higher in premontane areas with ectomycorrhizal dominant trees. Even though some observed patterns could be explained in terms of climatic differences and biotic relationships, the high fungal productivity observed in dry forests was an interesting finding and represents a topic for further studies.

  7. Dynamic Behavior of Nanocomposites Reinforced with Multi-Walled Carbon Nanotubes (MWCNTs

    Directory of Open Access Journals (Sweden)

    Chun-Yu Lai

    2013-06-01

    Full Text Available The influence of multi-walled carbon nanotubes (MWCNT on the structural dynamic behavior of MWCNT/epoxy nanocomposites was investigated. Two different types of MWCNTs, pristine MWCNT and functionalized MWCNT, were used in this study. Carboxylic acid-functionalized MWCNTs (MWCNT-COOH were obtained by oxidation pristine MWCNTs via sonication in sulfuric-nitric acid and characterized by Fourier transform infrared spectroscopy (FTIR. Dynamic behaviors of the MWCNT reinforced nanocomposite including the natural frequency and damping ratio were determined using free vibration test. Experimental results showed that the damping ratio of the nanocomposite decreases with the increase of the MWCNT addition, while the natural frequency is increasing with the increase of the MWCNT addition. Functionalized MWCNTs improved the interfacial bonding between the nanotubes and epoxy resin resulting in the reduction of the interfacial energy dissipation ability and enhancement of the stiffness.

  8. Symmetry-adapted non-equilibrium molecular dynamics of chiral carbon nanotubes under tensile loading

    Science.gov (United States)

    Aghaei, Amin; Dayal, Kaushik

    2011-06-01

    We report on non-equilibrium molecular dynamics calculations of chiral single-wall carbon nanotubes using the framework of Objective Structures. This enables us to adapt molecular dynamics to the symmetry of chiral nanotubes and efficiently simulate these systems with small unit cells. We outline the method and the adaptation of a conventional thermostat and barostat to this setting. We then apply the method in order to examine the behavior of nanotubes with various chiralities subject to a constant extensional strain rate. We examine the effects of temperature, strain rate, and pre-compression/pre-tension. We find a range of failure mechanisms, including the formation of Stone-Wales defects, the opening of voids, and the motion of atoms out of the cross-section.

  9. Molecular dynamics simulation of an argon cluster filled inside carbon nanotubes

    International Nuclear Information System (INIS)

    The effects of the diameters of single-walled carbon nanotubes (SWCNTs) (7.83 Å to 27.40 Å) and temperature (20 K–45 K) on the equilibrium structure of an argon cluster are systematically studied by molecular dynamics simulation with consideration of the SWCNTs to be fixed. Since the diameters of SWCNTs with different chiralities increase when temperature is fixed at 20 K, the equilibrium structures of the argon cluster transform from monoatomic chains to helical and then to multishell coaxial cylinders. Chirality has almost no noticeable influence on these cylindrosymmetric structures. The effects of temperature and a non-equilibrium sudden heating process on the structures of argon clusters in SWCNTs are also studied by molecular dynamics simulation. (condensed matter: structural, mechanical, and thermal properties)

  10. Size dependency and potential field influence on deriving mechanical properties of carbon nanotubes using molecular dynamics

    Directory of Open Access Journals (Sweden)

    K.G.S. Dilrukshi

    2015-07-01

    Full Text Available A thorough understanding on the mechanical properties of carbon nanotube (CNT is essential in extending the advanced applications of CNT based systems. However, conducting experiments to estimate mechanical properties at this scale is extremely challenging. Therefore, development of mechanistic models to estimate the mechanical properties of CNTs along with the integration of existing continuum mechanics concepts is critically important. This paper presents a comprehensive molecular dynamics simulation study on the size dependency and potential function influence of mechanical properties of CNT. Commonly used reactive bond order (REBO and adaptive intermolecular reactive bond order (AIREBO potential functions were considered in this regard. Young’s modulus and shear modulus of CNTs are derived by integrating classical continuum mechanics concepts with molecular dynamics simulations. The results indicate that the potential function has a significant influence on the estimated mechanical properties of CNTs, and the influence of potential field is much higher when studying the torsional behaviour of CNTs than the tensile behaviour.

  11. Dynamical analysis of high-pressure supercritical carbon dioxide jet in well drilling

    Institute of Scientific and Technical Information of China (English)

    DU Yu-kun; WANG Rui-he; NI Hong-jian; HUANG Zhi-yuan; LI Mu-kun

    2013-01-01

    This paper presents the design of an experimental setup and mathematical and physical models to determine the dynamical characteristics o