WorldWideScience

Sample records for atmospheric carbon exchange

  1. Rapid exchange between atmospheric CO2 and carbonate anion intercalated within magnesium rich layered double hydroxide.

    Science.gov (United States)

    Sahoo, Pathik; Ishihara, Shinsuke; Yamada, Kazuhiko; Deguchi, Kenzo; Ohki, Shinobu; Tansho, Masataka; Shimizu, Tadashi; Eisaku, Nii; Sasai, Ryo; Labuta, Jan; Ishikawa, Daisuke; Hill, Jonathan P; Ariga, Katsuhiko; Bastakoti, Bishnu Prasad; Yamauchi, Yusuke; Iyi, Nobuo

    2014-10-22

    The carbon cycle, by which carbon atoms circulate between atmosphere, oceans, lithosphere, and the biosphere of Earth, is a current hot research topic. The carbon cycle occurring in the lithosphere (e.g., sedimentary carbonates) is based on weathering and metamorphic events so that its processes are considered to occur on the geological time scale (i.e., over millions of years). In contrast, we have recently reported that carbonate anions intercalated within a hydrotalcite (Mg0.75Al0.25(OH)2(CO3)0.125·yH2O), a class of a layered double hydroxide (LDH), are dynamically exchanging on time scale of hours with atmospheric CO2 under ambient conditions. (Ishihara et al., J. Am. Chem. Soc. 2013, 135, 18040-18043). The use of (13)C-labeling enabled monitoring by infrared spectroscopy of the dynamic exchange between the initially intercalated (13)C-labeled carbonate anions and carbonate anions derived from atmospheric CO2. In this article, we report the significant influence of Mg/Al ratio of LDH on the carbonate anion exchange dynamics. Of three LDHs of various Mg/Al ratios of 2, 3, or 4, magnesium-rich LDH (i.e., Mg/Al ratio = 4) underwent extremely rapid exchange of carbonate anions, and most of the initially intercalated carbonate anions were replaced with carbonate anions derived from atmospheric CO2 within 30 min. Detailed investigations by using infrared spectroscopy, scanning electron microscopy, powder X-ray diffraction, elemental analysis, adsorption, thermogravimetric analysis, and solid-state NMR revealed that magnesium rich LDH has chemical and structural features that promote the exchange of carbonate anions. Our results indicate that the unique interactions between LDH and CO2 can be optimized simply by varying the chemical composition of LDH, implying that LDH is a promising material for CO2 storage and/or separation.

  2. Ecosystem-atmosphere exchange of carbon in a heathland under future climatic conditions

    Energy Technology Data Exchange (ETDEWEB)

    Bang Selsted, M.

    2010-07-15

    Global change is a reality. Atmospheric CO{sub 2} levels are rising as well as mean global temperature and precipitation patterns are changing. These three environmental factors have separately and in combination effect on ecosystem processes. Terrestrial ecosystems hold large amounts of carbon, why understanding plant and soil responses to such changes are necessary, as ecosystems potentially can ameliorate or accelerate global change. To predict the feedback of ecosystems to the atmospheric CO{sub 2} concentrations experiments imitating global change effects are therefore an important tool. This work on ecosystem-atmosphere exchange of carbon in a heathland under future climatic conditions, shows that extended summer drought in combination with elevated temperature will ensure permanent dryer soil conditions, which decreases carbon turnover, while elevated atmospheric CO{sub 2} concentrations will increase carbon turnover. In the full future climate scenario, carbon turnover is over all expected to increase and the heathland to become a source of atmospheric CO{sub 2}. The methodology of static chamber CO{sub 2} flux measurements and applying the technology in a FACE (free air CO{sub 2} enrichment) facility is a challenge. Fluxes of CO{sub 2} from soil to atmosphere depend on a physical equilibrium between those two medias, why it is important to keep the CO{sub 2} gradient between soil and atmosphere unchanged during measurement. Uptake to plants via photosynthesis depends on a physiological process, which depends strongly on the atmospheric CO{sub 2} concentration. Photosynthesis and respiration run in parallel during measurements of net ecosystem exchange, and these measurements should therefore be performed with care to both the atmospheric CO{sub 2} concentration and the CO{sub 2} soil-atmosphere gradient. (author)

  3. Carbon exchange between the atmosphere and subtropical forested cypress and pine wetlands

    Science.gov (United States)

    Shoemaker, W. Barclay; Anderson, Frank E.; Barr, Jordan G.; Graham, Scott L.; Botkin, Daniel B.

    2015-01-01

    Carbon dioxide exchange between the atmosphere and forested subtropical wetlands is largely unknown. Here we report a first step in characterizing this atmospheric–ecosystem carbon (C) exchange, for cypress strands and pine forests in the Greater Everglades of Florida as measured with eddy covariance methods at three locations (Cypress Swamp, Dwarf Cypress and Pine Upland) for 2 years. Links between water and C cycles are also examined at these three sites, as are methane emission measured only at the Dwarf Cypress site. Each forested wetland showed net C uptake from the atmosphere both monthly and annually, as indicated by the net ecosystem exchange (NEE) of carbon dioxide (CO2). For this study, NEE is the difference between photosynthesis and respiration, with negative values representing uptake from the atmosphere that is retained in the ecosystem or transported laterally via overland flow (unmeasured for this study). Atmospheric C uptake (NEE) was greatest at the Cypress Swampp (−900 to −1000 g C m2 yr−1), moderate at the Pine Upland (−650 to −700 g C m2 yr−1) and least at the Dwarf Cypress (−400 to −450 g C m2 yr−1). Changes in NEE were clearly a function of seasonality in solar insolation, air temperature and flooding, which suppressed heterotrophic soil respiration. We also note that changes in the satellite-derived enhanced vegetation index (EVI) served as a useful surrogate for changes in NEE at these forested wetland sites.

  4. Prediction of carbon exchanges between China terrestrial ecosystem and atmosphere in 21st century

    Institute of Scientific and Technical Information of China (English)

    JI JinJun; HUANG Mei; LI KeRang

    2008-01-01

    The projected changes in carbon exchange between China terrestrial ecosystem and the atmosphere and vegetation and soil carbon storage during the 21st century were investigated using an atmos-phere-vegetation interaction model (AVIM2). The results show that in the coming 100 a, for SRES B2 scenario and constant atmospheric CO2 concentration, the net primary productivity (NPP) of terrestrial ecosystem in China will be decreased slowly, and vegetation and soil carbon storage as well as net ecosystem productivity (NEP) will also be decreased. The carbon sink for China terrestrial ecosystem in the beginning of the 20th century will become totally a carbon source by the year of 2020, while for B2 scenario and changing atmospheric CO2 concentration, NPP for China will increase continuously from 2.94 GtC.a-1 by the end of the 20th century to 3.99 GtC.a-1 by the end of the 21st century, and vegetation and soil carbon storage will increase to 110.3 GtC. NEP in China will keep rising during the first and middle periods of the 21st century, and reach the peak around 2050s, then will decrease gradually and approach to zero by the end of the 21st century.

  5. Prediction of carbon exchanges between China terrestrial ecosystem and atmosphere in 21st century

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    The projected changes in carbon exchange between China terrestrial ecosystem and the atmosphere and vegetation and soil carbon storage during the 21st century were investigated using an atmos-phere-vegetation interaction model (AVIM2). The results show that in the coming 100 a, for SRES B2 scenario and constant atmospheric CO2 concentration, the net primary productivity (NPP) of terrestrial ecosystem in China will be decreased slowly, and vegetation and soil carbon storage as well as net ecosystem productivity (NEP) will also be decreased. The carbon sink for China terrestrial ecosystem in the beginning of the 20th century will become totally a carbon source by the year of 2020, while for B2 scenario and changing atmospheric CO2 concentration, NPP for China will increase continuously from 2.94 GtC·a?1 by the end of the 20th century to 3.99 GtC·a?1 by the end of the 21st century, and vegetation and soil carbon storage will increase to 110.3 GtC. NEP in China will keep rising during the first and middle periods of the 21st century, and reach the peak around 2050s, then will decrease gradually and approach to zero by the end of the 21st century.

  6. Carbon exchange between the atmosphere and subtropical forested cypress and pine wetlands

    Directory of Open Access Journals (Sweden)

    W. B. Shoemaker

    2014-11-01

    Full Text Available Carbon dioxide exchange between the atmosphere and forested subtropical wetlands is largely unknown. Here we report a first step in characterizing this atmospheric–ecosystem carbon (C exchange, for cypress strands and pine forests in the Greater Everglades of Florida as measured with eddy covariance methods at three locations (Cypress Swamp, Dwarf Cypress and Pine Upland for one year. Links between water and C cycles are examined at these three sites, and methane emission measured only at the Dwarf Cypress site. Each forested wetland showed net C uptake (retained in the soil and biomass or transported laterally via overland flow from the atmosphere monthly and annually. Net ecosystem exchange (NEE of carbon dioxide (CO2 (difference between photosynthesis and respiration, with negative values representing net ecosystem uptake was greatest at the Cypress Swamp (−1000 g C m-2 year-1, moderate at the Pine Upland (−900 g C m-2 year-1, and least at the Dwarf Cypress (−500 g C m-2 year-1. Methane emission was a negligible part of the C (12 g C m-2 year-1 budget when compared to NEE. However, methane (CH4 production was considerable in terms of global warming potential, as about 20 g CH4 emitted per m2 year was equivalent to about 500 g CO2 emitted per m2 year}. Changes in NEE were clearly a function of seasonality in solar insolation, air temperature and water availability from rainfall. We also note that changes in the satellite-derived enhanced-vegetation index (EVI served as a useful surrogate for changes in net and gross atmospheric–ecosystem C exchange at these forested wetland sites.

  7. North America's net terrestrial carbon exchange with the atmosphere 1990–2009

    Directory of Open Access Journals (Sweden)

    A. W. King

    2014-07-01

    Full Text Available Scientific understanding of the global carbon cycle is required for developing national and international policy to mitigate fossil-fuel CO2 emissions by managing terrestrial carbon uptake. Toward that understanding and as a contribution to the REgional Carbon Cycle Assessment and Processes (RECCAP project, this paper provides a synthesis of net land–atmosphere CO2 exchange for North America over the period (1990–2009. This synthesis is based on results from three different methods: atmospheric inversion, inventory-based methods and terrestrial biosphere modeling. All methods indicate that the North America land surface was a sink for atmospheric CO2, with a net transfer from atmosphere to land. Estimates ranged from −890 to −280 Tg C yr−1, where the atmospheric inversion estimate forms the lower bound of that range (a larger land-sink and the inventory-based estimate the upper (a smaller land sink. Integrating across estimates, "best" estimates (i.e., measures of central tendency are −472 ± 281 Tg C yr−1 based on the mean and standard deviation of the distribution and −360 Tg C yr−1 (with an interquartile range of −496 to −337 based on the median. Considering both the fossil-fuel emissions source and the land sink, our analysis shows that North America was, however, a net contributor to the growth of CO2 in the atmosphere in the late 20th and early 21st century. The continent's CO2 source to sink ratio for this time period was likely in the range of 4 : 1 to 3 : 1.

  8. A Carbon Flux Super Site. New Insights and Innovative Atmosphere-Terrestrial Carbon Exchange Measurements and Modeling

    Energy Technology Data Exchange (ETDEWEB)

    Leclerc, Monique Y. [The University of Georgia Research Foundation, Athens, GA (United States)

    2014-11-17

    This final report presents the main activities and results of the project “A Carbon Flux Super Site: New Insights and Innovative Atmosphere-Terrestrial Carbon Exchange Measurements and Modeling” from 10/1/2006 to 9/30/2014. It describes the new AmeriFlux tower site (Aiken) at Savanna River Site (SC) and instrumentation, long term eddy-covariance, sodar, microbarograph, soil and other measurements at the site, and intensive field campaigns of tracer experiment at the Carbon Flux Super Site, SC, in 2009 and at ARM-CF site, Lamont, OK, and experiments in Plains, GA. The main results on tracer experiment and modeling, on low-level jet characteristics and their impact on fluxes, on gravity waves and their influence on eddy fluxes, and other results are briefly described in the report.

  9. Controls on mangrove forest-atmosphere carbon dioxide exchanges in western Everglades National Park

    Science.gov (United States)

    Barr, Jordan G.; Engel, Vic; Fuentes, Jose D.; Zieman, Joseph C.; O'Halloran, Thomas L.; Smith, Thomas J.; Anderson, Gordon H.

    2010-01-01

    We report on net ecosystem production (NEP) and key environmental controls on net ecosystem exchange (NEE) of carbon dioxide (CO2) between a mangrove forest and the atmosphere in the coastal Florida Everglades. An eddy covariance system deployed above the canopy was used to determine NEE during January 2004 through August 2005. Maximum daytime NEE ranged from -20 to -25 μmol (CO2) m-2 s-1 between March and May. Respiration (Rd) was highly variable (2.81 ± 2.41 μmol (CO2) m-2 s-1), reaching peak values during the summer wet season. During the winter dry season, forest CO2 assimilation increased with the proportion of diffuse solar irradiance in response to greater radiative transfer in the forest canopy. Surface water salinity and tidal activity were also important controls on NEE. Daily light use efficiency was reduced at high (>34 parts per thousand (ppt)) compared to low (d by ~0.9 μmol (CO2) m-2 s-1 and nighttime Rd by ~0.5 μmol (CO2) m-2 s-1. The forest was a sink for atmospheric CO2, with an annual NEP of 1170 ± 127 g C m-2 during 2004. This unusually high NEP was attributed to year-round productivity and low ecosystem respiration which reached a maximum of only 3 g C m-2 d-1. Tidal export of dissolved inorganic carbon derived from belowground respiration likely lowered the estimates of mangrove forest respiration. These results suggest that carbon balance in mangrove coastal systems will change in response to variable salinity and inundation patterns, possibly resulting from secular sea level rise and climate change.

  10. Ocean-atmosphere exchange of organic carbon and CO2 surrounding the Antarctic Peninsula

    Science.gov (United States)

    Ruiz-Halpern, S.; Calleja, M. Ll.; Dachs, J.; Del Vento, S.; Pastor, M.; Palmer, M.; Agustí, S.; Duarte, C. M.

    2014-05-01

    Exchangeable organic carbon (OC) dynamics and CO2 fluxes in the Antarctic Peninsula during austral summer were highly variable, but the region appeared to be a net sink for OC and nearly in balance for CO2. Surface exchangeable dissolved organic carbon (EDOC) measurements had a 43 ± 3 (standard error, hereafter SE) μmol C L-1 overall mean and represented around 66% of surface non-purgeable dissolved organic carbon (DOC) in Antarctic waters, while the mean concentration of the gaseous fraction of organic carbon (GOC H-1) was 46 ± 3 SE μmol C L-1. There was a tendency towards low fugacity of dissolved CO2 (fCO2-w) in waters with high chlorophyll a (Chl a) content and high fCO2-w in areas with high krill densities. However, such relationships were not found for EDOC. The depth profiles of EDOC were also quite variable and occasionally followed Chl a profiles. The diel cycles of EDOC showed two distinct peaks, in the middle of the day and the middle of the short austral dark period, concurrent with solar radiation maxima and krill night migration patterns. However, no evident diel pattern for GOC H-1 or CO2 was observed. The pool of exchangeable OC is an important and active compartment of the carbon budget surrounding the Antarctic Peninsula and adds to previous studies highlighting its importance in the redistribution of carbon in marine environments.

  11. Ecosystem-atmosphere exchange of carbon in a heathland under future climatic conditions

    DEFF Research Database (Denmark)

    Selsted, Merete Bang

    understanding plant and soil responses to such changes are necessary, as ecosystems potentially can ameliorate or accelerate global change. To predict the feedback of ecosystems to the atmospheric CO2 concentrations experiments imitating global change effects are therefore an important tool. This work......Global change is a reality. Atmospheric CO2 levels are rising as well as mean global temperature and precipitation patterns are changing. These three environmental factors have separately and in combination effect on ecosystem processes. Terrestrial ecosystems hold large amounts of carbon, why....... Fluxes of CO2 from soil to atmosphere depend on a physical equilibrium between those two medias, why it is important to keep the CO2 gradient between soil and atmosphere unchanged during measurement. Uptake to plants via photosynthesis depends on a physiological process, which depends strongly...

  12. Ecosystem-Atmosphere Exchange of Carbon, Water and Energy over a Mixed Deciduous Forest in the Midwest

    Energy Technology Data Exchange (ETDEWEB)

    Danilo Dragoni; Hans Peter Schmid; C.S.B. Grimmond; J.C. Randolph; J.R. White

    2012-12-17

    During the project period we continued to conduct long-term (multi-year) measurements, analysis, and modeling of energy and mass exchange in and over a deciduous forest in the Midwestern United States, to enhance the understanding of soil-vegetation-atmosphere exchange of carbon. At the time when this report was prepared, results from nine years of measurements (1998 - 2006) of above canopy CO2 and energy fluxes at the AmeriFlux site in the Morgan-Monroe State Forest, Indiana, USA (see Table 1), were available on the Fluxnet database, and the hourly CO2 fluxes for 2007 are presented here (see Figure 1). The annual sequestration of atmospheric carbon by the forest is determined to be between 240 and 420 g C m-2 a-1 for the first ten years. These estimates are based on eddy covariance measurements above the forest, with a gap-filling scheme based on soil temperature and photosynthetically active radiation. Data gaps result from missing data or measurements that were rejected in qua)lity control (e.g., during calm nights). Complementary measurements of ecological variables (i.e. inventory method), provided an alternative method to quantify net carbon uptake by the forest, partition carbon allocation in each ecosystem components, and reduce uncertainty on annual net ecosystem productivity (NEP). Biometric datasets are available on the Fluxnext database since 1998 (with the exclusion of 2006). Analysis for year 2007 is under completion.

  13. Simulating carbon exchange using a regional atmospheric model coupled to an advanced land-surface model

    Directory of Open Access Journals (Sweden)

    H. W. Ter Maat

    2010-08-01

    Full Text Available This paper is a case study to investigate what the main controlling factors are that determine atmospheric carbon dioxide content for a region in the centre of The Netherlands. We use the Regional Atmospheric Modelling System (RAMS, coupled with a land surface scheme simulating carbon, heat and momentum fluxes (SWAPS-C, and including also submodels for urban and marine fluxes, which in principle should include the dominant mechanisms and should be able to capture the relevant dynamics of the system. To validate the model, observations are used that were taken during an intensive observational campaign in central Netherlands in summer 2002. These include flux-tower observations and aircraft observations of vertical profiles and spatial fluxes of various variables.

    The simulations performed with the coupled regional model (RAMS-SWAPS-C are in good qualitative agreement with the observations. The station validation of the model demonstrates that the incoming shortwave radiation and surface fluxes of water and CO2 are well simulated. The comparison against aircraft data shows that the regional meteorology (i.e. wind, temperature is captured well by the model. Comparing spatially explicitly simulated fluxes with aircraft observed fluxes we conclude that in general latent heat fluxes are underestimated by the model compared to the observations but that the latter exhibit large variability within all flights. Sensitivity experiments demonstrate the relevance of the urban emissions of carbon dioxide for the carbon balance in this particular region. The same tests also show the relation between uncertainties in surface fluxes and those in atmospheric concentrations.

  14. Tree-Ring Carbon Isotopic Constraints on Carbon-Water Exchanges between Atmosphere and Biosphere in Drought Regions in Northwestern China

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    The comparison between the carbon isotope and the index of ring width of a pine disc from the Tuomuer Peak region in Xinjiang shows that the effects of climate changes on the tree-ring growth and carbon isotopic fractionation varies with time. The reason is probably relative to the characters of climate changes and adaptability of the tree-ring growth to climate changes. The relationships between the atmospheric CO2 level and the revised d 13Cair by the tree-ring carbon isotope indicate that the carbon cycle is not in a steady state, but under a stage-change condition in this area. It also can be concluded that the ratio of CO2 from the terrestrial eco-system has increased, and the flux of CO2 exchange between the atmosphere and the biosphere was gradually increasing over the past century. In addition, the results also confirm the validity and superiority of the carbon isotope to the research of the water-use efficiency.

  15. Carbon exchange between ecosystems and atmosphere in the Czech Republic is affected by climate factors

    Energy Technology Data Exchange (ETDEWEB)

    Marek, Michal V., E-mail: marek.mv@czechglobe.cz [Global Change Research Centres, Academy of Science of the Czech Republic, Belidla 4a CZ-60300 Brno (Czech Republic); Institute of Forest Ecology Forestry Faculty, Mendel University Brno, Zemedelska 3, CZ-614 00 (Czech Republic); Janous, Dalibor; Taufarova, Klara; Havrankova, Katerina; Pavelka, Marian; Kaplan, Veroslav [Global Change Research Centres, Academy of Science of the Czech Republic, Belidla 4a CZ-60300 Brno (Czech Republic); Markova, Irena [Institute of Forest Ecology Forestry Faculty, Mendel University Brno, Zemedelska 3, CZ-614 00 (Czech Republic)

    2011-05-15

    By comparing five ecosystem types in the Czech Republic over several years, we recorded the highest carbon sequestration potential in an evergreen Norway spruce forest (100%) and an agroecosystem (65%), followed by European beech forest (25%) and a wetland ecosystem (20%). Because of a massive ecosystem respiration, the final carbon gain of the grassland was negative. Climate was shown to be an important factor of carbon uptake by ecosystems: by varying the growing season length (a 22-d longer season in 2005 than in 2007 increased carbon sink by 13%) or by the effect of short- term synoptic situations (e.g. summer hot and dry days reduced net carbon storage by 58% relative to hot and wet days). Carbon uptake is strongly affected by the ontogeny and a production strategy which is demonstrated by the comparison of seasonal course of carbon uptake between coniferous (Norway spruce) and deciduous (European beech) stands. - Highlights: > Highest carbon sequestration potential in evergreen Norway spruce forest (100%) and an agroecosystem (65%), followed by European beech forest (25%) and a wetland ecosystem (20%). > The final carbon gain of the grassland was negative (massive ecosystem respiration). > Climate is important factor of net primary productivity. > Carbon uptake is strongly affected by the ontogeny and a production strategy of ecosystem. - Identification of the apparent differences in the carbon storage by different ecosystem types.

  16. The importance of freshwater systems to the net atmospheric exchange of carbon dioxide and methane with a rapidly changing high Arctic watershed

    Science.gov (United States)

    Emmerton, Craig A.; St. Louis, Vincent L.; Lehnherr, Igor; Graydon, Jennifer A.; Kirk, Jane L.; Rondeau, Kimberly J.

    2016-10-01

    A warming climate is rapidly changing the distribution and exchanges of carbon within high Arctic ecosystems. Few data exist, however, which quantify exchange of both carbon dioxide (CO2) and methane (CH4) between the atmosphere and freshwater systems, or estimate freshwater contributions to total catchment exchange of these gases, in the high Arctic. During the summers of 2005 and 2007-2012, we quantified CO2 and CH4 concentrations in, and atmospheric exchange with, common freshwater systems in the high Arctic watershed of Lake Hazen, Nunavut, Canada. We identified four types of biogeochemically distinct freshwater systems in the watershed; however mean CO2 concentrations (21-28 µmol L-1) and atmospheric exchange (-0.013 to +0.046 g C-CO2 m-2 day-1) were similar between these systems. Seasonal flooding of ponds bordering Lake Hazen generated considerable CH4 emissions to the atmosphere (+0.008 g C-CH4 m-2 day-1), while all other freshwater systems were minimal emitters of this gas (climates than in the past, which may have implications for moisture availability, landscape cover, and the exchange of CO2 and CH4 of underproductive but expansive polar semidesert ecosystems.

  17. The exchange of carbon dioxide between wet arctic tundra and the atmosphere at the Lena River Delta, Northern Siberia

    Directory of Open Access Journals (Sweden)

    L. Kutzbach

    2007-06-01

    Full Text Available The exchange fluxes of carbon dioxide between wet arctic polygonal tundra and the atmosphere were investigated by the micrometeorological eddy covariance method. The investigation site was situated in the centre of the Lena River Delta in Northern Siberia (72°22' N, 126°30' E. The study region is characterized by a polar and distinctly continental climate, very cold and ice-rich permafrost and its position at the interface between the Eurasian continent and the Arctic Ocean. The soils at the site are characterized by high organic matter content, low nutrient availability and pronounced water logging. The vegetation is dominated by sedges and mosses. The micrometeorological campaigns were performed during the periods July–October 2003 and May–July 2004 which included the period of snow and soil thaw as well as the beginning of soil refreeze. The main CO2 exchange processes, the gross photosynthesis and the ecosystem respiration, were found to be of a generally low intensity. The gross photosynthesis accumulated to –432 g m−2 over the photosynthetically active period (June–September. The contribution of mosses to the gross photosynthesis was estimated to be about 40%. The diurnal trend of the gross photosynthesis was mainly controlled by the incoming photosynthetically active radiation. During midday the photosynthetic apparatus of the canopy was frequently near saturation and represented the limiting factor on gross photosynthesis. The synoptic weather conditions strongly affected the exchange fluxes of CO2 by changes in cloudiness, precipitation and pronounced changes of air temperature. The ecosystem respiration accumulated to +327 g m−2 over the photosynthetically active period, which corresponds to 76% of the CO2 uptake by photosynthesis. However, the ecosystem respiration continued at substantial rates during autumn when photosynthesis had ceased and the soils

  18. Atmospheric carbon exchange associated with vegetation and soils in urban and suburban land uses

    Energy Technology Data Exchange (ETDEWEB)

    Rowntree, R.A. [Northeastern Forest Experiment Station, Berkeley, CA (United States)

    1993-12-31

    In studies of the global C cycle prior to the 1980s, urban ecosystems were largely ignored, in part because them were inadequate measures of phytomass and soil carbon for the various land uses associated with cities. In the last decade, progress has been made in gathering urban vegetation data and recently, estimates of urban land use carbon storage and fluxes have been attempted. Demographic trends in many countries suggest that urban areas are growing. Thus it is important to discover the appropriate concepts and methods for understanding greenhouse gas fluxes from urban-related vegetation and soils.

  19. Modeling coupled interactions of carbon, water, and ozone exchange between terrestrial ecosystems and the atmosphere. I: model description.

    Science.gov (United States)

    Nikolov, Ned; Zeller, Karl F

    2003-01-01

    A new biophysical model (FORFLUX) is presented to study the simultaneous exchange of ozone, carbon dioxide, and water vapor between terrestrial ecosystems and the atmosphere. The model mechanistically couples all major processes controlling ecosystem flows trace gases and water implementing recent concepts in plant eco-physiology, micrometeorology, and soil hydrology. FORFLUX consists of four interconnected modules-a leaf photosynthesis model, a canopy flux model, a soil heat-, water- and CO2- transport model, and a snow pack model. Photosynthesis, water-vapor flux and ozone uptake at the leaf level are computed by the LEAFC3 sub-model. The canopy module scales leaf responses to a stand level by numerical integration of the LEAFC3model over canopy leaf area index (LAI). The integration takes into account (1) radiative transfer inside the canopy, (2) variation of foliage photosynthetic capacity with canopy depth, (3) wind speed attenuation throughout the canopy, and (4) rainfall interception by foliage elements. The soil module uses principles of the diffusion theory to predict temperature and moisture dynamics within the soil column, evaporation, and CO2 efflux from soil. The effect of soil heterogeneity on field-scale fluxes is simulated employing the Bresler-Dagan stochastic concept. The accumulation and melt of snow on the ground is predicted using an explicit energy balance approach. Ozone deposition is modeled as a sum of three fluxes- ozone uptake via plant stomata, deposition to non-transpiring plant surfaces, and ozone flux into the ground. All biophysical interactions are computed hourly while model projections are made at either hourly or daily time step. FORFLUX represents a comprehensive approach to studying ozone deposition and its link to carbon and water cycles in terrestrial ecosystems.

  20. Climate control of terrestrial carbon exchange across biomes and continents

    NARCIS (Netherlands)

    Yi, C.; Jacobs, C.M.J.; Moors, E.J.; Elbers, J.A.

    2010-01-01

    Understanding the relationships between climate and carbon exchange by terrestrial ecosystems is critical to predict future levels of atmospheric carbon dioxide because of the potential accelerating effects of positive climate–carbon cycle feedbacks. However, directly observed relationships between

  1. Climate control of terrestrial carbon exchange across biomes and continents

    DEFF Research Database (Denmark)

    Yi, Chuixiang; Ricciuto, Daniel; Li, Runze

    2010-01-01

    Understanding the relationships between climate and carbon exchange by terrestrial ecosystems is critical to predict future levels of atmospheric carbon dioxide because of the potential accelerating effects of positive climate–carbon cycle feedbacks. However, directly observed relationships betwe...

  2. Elevated atmospheric carbon dioxide effects on soybean and sorghum gas exchange in conventional and no-tillage systems.

    Science.gov (United States)

    Prior, S A; Runion, G B; Rogers, H H; Arriaga, F J

    2010-01-01

    Increasing atmospheric CO(2) concentration has led to concerns about potential effects on production agriculture. In the fall of 1997, a study was initiated to compare the response of two crop management systems (conventional tillage and no-tillage) to elevated CO(2). The study used a split-plot design replicated three times with two management systems as main plots and two atmospheric CO(2) levels (ambient and twice ambient) as split plots using open-top chambers on a Decatur silt loam soil (clayey, kaolinitic, thermic Rhodic Paleudults). The conventional system was a grain sorghum [Sorghum bicolor (L.) Moench.] and soybean [Glycine max (L.) Merr.] rotation with winter fallow and spring tillage practices. In the no-tillage system, sorghum and soybean were rotated, and three cover crops were used [crimson clover (Trifolium incarnatum L.), sunn hemp (Crotalaria juncea L.), and wheat (Triticum aestivum L.)]. Over multiple growing seasons, the effect of management and CO(2) concentration on leaf-level gas exchange during row crop (soybean in 1999, 2001, and 2003; sorghum in 2000, 2002, and 2004) reproductive growth were evaluated. Treatment effects were fairly consistent across years. In general, higher photosynthetic rates were observed under CO(2) enrichment (more so with soybean) regardless of residue management practice. Elevated CO(2) led to decreases in stomatal conductance and transpiration, which resulted in increased water use efficiency. The effects of management system on gas exchange measurements were infrequently significant, as were interactions of CO(2) and management. These results suggest that better soil moisture conservation and high rates of photosynthesis can occur in both tillage systems in CO(2)-enriched environments during reproductive growth.

  3. Snowpack-atmosphere gas exchanges of carbon dioxide, ozone, and nitrogen oxides at a hardwood forest site in northern Michigan

    Directory of Open Access Journals (Sweden)

    Brian Seok

    2015-03-01

    Full Text Available Abstract Snowpack-atmosphere gas exchanges of CO2, O3, and NOx (NO + NO2 were investigated at the University of Michigan Biological Station (UMBS, a mid-latitude, low elevation hardwood forest site, during the 2007–2008 winter season. An automated trace gas sampling system was used to determine trace gas concentrations in the snowpack at multiple depths continuously throughout the snow-covered period from two adjacent plots. One natural plot and one with the soil covered by a Tedlar sheet were setup for investigating whether the primary source of measured trace gases was biogenic (i.e., from the soil or non-biogenic (i.e., from the snowpack. The results were compared with the “White on Green” study conducted at the Niwot Ridge (NWT Long Term Ecological Research site in Colorado. The average winter CO2 flux ± s.e. from the soil at UMBS was 0.54 ± 0.037 µmol m-2 s-1 using the gradient diffusion method and 0.71 ± 0.012 µmol m-2 s-1 using the eddy covariance method, and in a similar range as found for NWT. Observed snowpack-O3 exchange was also similar to NWT. However, nitrogen oxides (NOx fluxes from snow at UMBS were 10 times smaller than those at NWT, and fluxes were bi-directional with the direction of the flux dependent on NOx concentrations in ambient air. The compensation point for the change in the direction of NOx flux was estimated to be 0.92 nmol mol-1. NOx in snow also showed diurnal dependency on incident radiation. These NOx dynamics in the snow at UMBS were notably different compared to NWT, and primarily determined by snow-atmosphere interactions rather than by soil NOx emissions.

  4. Carbon neutron star atmospheres

    CERN Document Server

    Suleimanov, V F; Pavlov, G G; Werner, K

    2013-01-01

    The accuracy of measuring the basic parameters of neutron stars is limited in particular by uncertainties in chemical composition of their atmospheres. For example, atmospheres of thermally - emitting neutron stars in supernova remnants might have exotic chemical compositions, and for one of them, the neutron star in CasA, a pure carbon atmosphere has recently been suggested by Ho & Heinke (2009). To test such a composition for other similar sources, a publicly available detailed grid of carbon model atmosphere spectra is needed. We have computed such a grid using the standard LTE approximation and assuming that the magnetic field does not exceed 10^8 G. The opacities and pressure ionization effects are calculated using the Opacity Project approach. We describe the properties of our models and investigate the impact of the adopted assumptions and approximations on the emergent spectra.

  5. The Seasonal Cycle of Satellite Chlorophyll Fluorescence Observations and its Relationship to Vegetation Phenology and Ecosystem Atmosphere Carbon Exchange

    Science.gov (United States)

    Joiner, J.; Yoshida, Y.; Vasilkov, A. P.; Schaefer, K.; Jung, M.; Guanter, L.; Zhang, Y; Garrity, S.; Middleton, E. M.; Huemmrich, K. F.; Gu, L.; Marchesini, L. Belelli

    2014-01-01

    Mapping of terrestrial chlorophyll uorescence from space has shown potentialfor providing global measurements related to gross primary productivity(GPP). In particular, space-based fluorescence may provide information onthe length of the carbon uptake period that can be of use for global carboncycle modeling. Here, we examine the seasonal cycle of photosynthesis asestimated from satellite fluorescence retrievals at wavelengths surroundingthe 740nm emission feature. These retrievals are from the Global OzoneMonitoring Experiment 2 (GOME-2) flying on the MetOp A satellite. Wecompare the fluorescence seasonal cycle with that of GPP as estimated froma diverse set of North American tower gas exchange measurements. Because the GOME-2 has a large ground footprint (40 x 80km2) as compared with that of the flux towers and requires averaging to reduce random errors, we additionally compare with seasonal cycles of upscaled GPP in the satellite averaging area surrounding the tower locations estimated from the Max Planck Institute for Biogeochemistry (MPI-BGC) machine learning algorithm. We also examine the seasonality of absorbed photosynthetically-active radiation(APAR) derived with reflectances from the MODerate-resolution Imaging Spectroradiometer (MODIS). Finally, we examine seasonal cycles of GPP as produced from an ensemble of vegetation models. Several of the data-driven models rely on satellite reflectance-based vegetation parameters to derive estimates of APAR that are used to compute GPP. For forested sites(particularly deciduous broadleaf and mixed forests), the GOME-2 fluorescence captures the spring onset and autumn shutoff of photosynthesis as delineated by the tower-based GPP estimates. In contrast, the reflectance-based indicators and many of the models tend to overestimate the length of the photosynthetically-active period for these and other biomes as has been noted previously in the literature. Satellite fluorescence measurements therefore show potential for

  6. Ecosystem carbon balance in a drier future: land-atmosphere exchanges of CO2, water and energy across semiarid southwestern North America

    Science.gov (United States)

    Biederman, J. A.; Scott, R. L.; Goulden, M.; Litvak, M. E.; Kolb, T.; Yépez, E. A.; Oechel, W. C.; Meyers, T. P.; Papuga, S. A.; Ponce-Campos, G.; Krofcheck, D. J.; Maurer, G. E.; Dore, S.; Garatuza, J.; Bell, T. W.; Krishnan, P.

    2015-12-01

    The southwest US and northwest Mexico are predicted to become warmer and drier, increasing disturbance, shifting ecosystem composition, and altering global CO2 cycling. However, direct measurements of ecosystem land-atmosphere carbon and water exchange in this region have lagged behind those in wetter regions. In this presentation we present a synthesis of CO2, water, and energy exchanges made at 25 Southwest eddy covariance sites (3-10 years each, n = 174 years). This regional gradient includes desert shrublands, grasslands, savannas, and forests and spans ranges of 200 - 800 mm in mean annual precipitation and 2 - 24 ⁰C mean annual temperature, a climate space that has been underrepresented in flux databases and publications. We compare measured fluxes against state-of-the-art remote sensing and modeling products representing current best regional estimates. We find that 65% of annual net ecosystem production of CO2 (NEP) is explained by water availability. Meanwhile, most of the unexplained NEP variability is related to site-specific differences persisting over the observation years, suggesting slow-changing controls such as demography (plant type, age, structure) and legacies of disturbance. Disturbances that kill plants without removing biomass, such as drought, tend to decrease productivity and increase respiration, shifting sites from carbon sinks to sources. However, following disturbances that removed biomass, such as fire, both productivity and respiration decline, with minimal impacts on NEP. Remote sensing and modeling match mean CO2 uptake measurements across spatial gradients in climate and plant functional type. However, measured uptake reveals 200-400% greater interannual variability than model estimates. High variability and sensitivity to water help us understand why semiarid ecosystems dominate the interannual variability of the terrestrial carbon sink in global accounting studies.

  7. The exchange of energy, water and carbon dioxide between wet arctic tundra and the atmosphere at the Lena River Delta, Northern Siberia

    Energy Technology Data Exchange (ETDEWEB)

    Kutzbach, L.

    2006-07-01

    The ecosystem-scale exchange fluxes of energy, water and carbon dioxide between wet arctic tundra and the atmosphere were investigated by the micrometeorological eddy covariance method. The investigation site was the centre of the Lena River Delta in Northern Siberia characterised by a polar and distinctly continental climate, very cold and ice-rich permafrost and its position at the interface between the Eurasian continent and the Arctic Ocean. The measurements were performed on the surface of a Holocene river terrace characterised by wet polygonal tundra. The soils at the site are characterised by high organic matter content, low nutrient availability and pronounced water logging. The vegetation is dominated by sedges and mosses. The fluctuations of the H{sub 2}O and CO{sub 2} concentrations were measured with a closed-path infrared gas analyser. The fast-response eddy covariance measurements were supplemented by a set of slow-response meteorological and soil-meteorological measurements. The combined datasets of the two campaigns 2003 and 2004 were used to characterise the seasonal course of the energy, water and CO{sub 2} fluxes and the underlying processes for the synthetic measurement period May 28..October 21 2004/2003 including the period of snow and soil thawing as well as the beginning of refreezing. The synthetic measurement period 2004/2003 was characterised by a long snow ablation period and a late start of the growing season. On the other hand, the growing season ended also late due to high temperatures and snow-free conditions in September. The cumulative summer energy partitioning was characterised by low net radiation, large ground heat flux, low latent heat flux and very low sensible heat flux compared to other tundra sites. These findings point out the major importance of the very cold permafrost for the summer energy budget of the tundra in Northern Siberia. (orig./SR)

  8. A modelling approach for simulation of water and carbon dioxide exchange between multi-species tropical rain forest and the atmosphere

    DEFF Research Database (Denmark)

    Olchev, A.; Ibrom, Andreas; Ross, T.;

    2008-01-01

    of the physical and biological processes on the leaf, tree (plant) and stand levels that allows to apply this model for prediction of atmospheric fluxes for the different vegetation types from grasslands and agricultural crops to vertically structured mono-specific and mixed forest stands represented by one.......g. height, crown shape, stem diameter, root depth) and biological properties (e.g. leaf stomatal conductance, photosynthesis and respiration rates, etc.). Mixfor-SVAT assumes that trees of the different species are evenly distributed over some homogeneous ground surface area......, precipitation rate and global radiation) at some height above a plant canopy within the atmospheric surface layer. For simulation of exchange processes within a multi-specific forest stand Mixfor-SVAT uses both averaged and species specific biophysical parameters of the trees describing their structure (e...

  9. Quantifying Net Carbon Exchanges Between the Atmosphere and Terrestrial Biosphere in the Arctic: What Have We Learned through Decade Regional Modeling Studies?

    Science.gov (United States)

    Zhuang, Q.

    2014-12-01

    Observed Arctic warming has been projected to continue in this century. Permafrost degradation is thus expected to continue, exposing large amounts of carbon for decomposition. Dynamics of Arctic landscape and hydrology are complicated due to changing climate and thawing permafrost, affecting the carbon biogeochemical cycling in the region. Further, human activities together with changing climate transform the regional land use and land cover, including wildfires, logging, and agricultural land conversion. This presentation will review the effects of factors, controls, and processes as well as landscape types (e.g., forests vs. lakes) on carbon biogeochemistry based on regional modeling studies and observations. Specific effects on carbon dynamics to be discussed will include: 1) thawing permafrost; 2) fire disturbances; 2) atmospheric carbon dioxide; 3) inorganic and organic nitrogen uptake by plants; 4) priming; 5) aerobic and anaerobic organic matter decomposition; and 6) various complexities of microbial physiology of soils. Partitioning the contribution of these processes to regional carbon dynamics shall help us improve the terrestrial biogeochemistry models, an important component of Earth System Models that are used to project our future climate.

  10. Chemistry Of Atmospheric Brown Carbon

    Energy Technology Data Exchange (ETDEWEB)

    Laskin, Alexander; Laskin, Julia; Nizkorodov, Sergey

    2015-05-27

    Organic carbon (OC) accounts for a large fraction of atmospheric aerosol and has profound effects on air quality, atmospheric chemistry and climate forcing. Molecular composition of the OC and its evolution during common processes of atmospheric aging have been a subject of extensive research over the last decade (see reviews of Ervens et al.,1 Hallquist et al.,2 Herckes et al.,3 Carlton et al.,4 Kroll and Seinfeld,5 Rudich et al.,6 and Kanakidou et al.7). Even though many fundamental advances have been reported in these studies, our understanding of the climate-related properties of atmospheric OC is still incomplete and the specific ways in which OC impacts atmospheric environment and climate forcing are just beginning to be understood. This review covers one topic of particular interest in this area –environmental chemistry of light-absorbing aerosol OC and its impact on radiative forcing.

  11. Investigation of the influence of atmospheric stability and turbulence on land-atmosphere exchange

    Science.gov (United States)

    Osibanjo, O.; Holmes, H.

    2015-12-01

    Surface energy fluxes are exchanged between the surface of the earth and the atmosphere and impact weather, climate, and air quality. The radiation from the sun triggers the surface-atmosphere interaction during the day as heat is transmitted to the surface and the surface heats the air directly above generating wind (i.e., thermal turbulence) that transports heat, moisture, and momentum in the atmospheric boundary layer (ABL). This process is impacted by greenhouse gasses (i.e., water vapor, carbon dioxide and other trace gases) that absorb heat emitted by the earth's surface. The concentrations of atmospheric greenhouse gasses are increasing leading to changes in ABL dynamics as a result of the changing surface energy balance. The ABL processes are important to characterize because they are difficult to parameterize in global and regional scale atmospheric models. Empirical data can be collected using eddy covariance micrometeorological methods to measure turbulent fluxes (e.g., sensible heat, moisture, and CO2) and quantify the exchange between the surface and the atmosphere. The objective of this work is to calculate surface fluxes using observational data collected during one week in September 2014 from a monitoring site in Echo, Oregon. The site is located in the Columbia Basin with rolling terrain, irrigated farmland, and over 100 wind turbines. The 10m tower was placed in a small valley depression to isolate nighttime cold air pools. This work will present observations of momentum, sensible heat, moisture, and carbon dioxide fluxes from data collected at a sampling frequency of 10Hz at four heights. Atmospheric stability is determined using Monin-Obukov length and flux Richardson number, and the impact of stability on surface-atmosphere exchange is investigated. This work will provide a better understanding of surface fluxes and mixing, particularly during stable ABL periods, and the results can be used to compare with numerical models.

  12. Atmospheric turbulence triggers pronounced diel pattern in karst carbonate geochemistry

    Directory of Open Access Journals (Sweden)

    M. Roland

    2013-01-01

    Full Text Available CO2 exchange between terrestrial ecosystems and the atmosphere is key to understanding the feedbacks between climate change and the land surface. In regions with carbonaceous parent material, CO2 exchange patterns occur that cannot be explained by biological processes, such as disproportionate outgassing during daytime or nighttime CO2 uptake during periods when all vegetation is senescent. Neither of these phenomena can be attributed to carbonate weathering reactions, since their CO2 exchange rates are too small. Soil ventilation induced by high atmospheric turbulence is found to explain atypical CO2 exchange between carbonaceous systems and the atmosphere. However, by strongly altering subsurface CO2 concentrations, ventilation can be expected to influence carbonate weathering rates. By imposing ventilation-driven CO2 outgassing in a carbonate weathering model, we show here that carbonate geochemistry is accelerated and does play a surprisingly large role in the observed CO2 exchange patterns. We found that by rapidly depleting soil CO2 during daytime, ventilation disturbs soil carbonate equilibria and therefore strongly magnifies daytime carbonate precipitation and associated CO2 production. At night, ventilation ceases and the depleted CO2 concentrations increase steadily. Dissolution of carbonate is now enhanced, which consumes CO2 and largely compensates for the enhanced daytime carbonate precipitation. This is why only a relatively small effect on global carbonate weathering rates is to be expected. On the short term, however, ventilation has a drastic effect on synoptic carbonate weathering rates, resulting in a pronounced diel pattern that exacerbates the non-biological behavior of soil-atmosphere CO2 exchanges in dry regions with carbonate soils.

  13. Carbon Dioxide Exchange Between the Atmosphere and an Alpine Shrubland Meadow During the Growing Season on the Qinghai-Tibetan Plateau

    Institute of Scientific and Technical Information of China (English)

    Liang ZHAO; Ying-Nian LI; Song GU; Xing-Quan ZHAO; Shi-Xiao XU; Gui-Rui YU

    2005-01-01

    In the present study, we used the eddy covariance method to measure CO2 exchange between the atmosphere and an alpine shrubland meadow ecosystem (37°36′ N, 101o18′ E; 3 250 m a.s.l.) on the Qinghai-Tibetan Plateau, China, during the growing season in 2003, from 20 April to 30 September. This meadow is dominated by formations ofPotentillafruticosa L. The soil is Mol-Cryic Cambisols. During the study period, the meadow was not grazed. The maximum rates of CO2 uptake and release derived from the latitudes. Daily CO2 uptake during the measurement period indicated that the alpine shrubland meadow ecosystem may behave as a sink of atmospheric CO2 during the growing season. The daytime CO2 uptake was correlated exponentially or linearly with the daily photosynthetic photon flux density each month. The daytime average water use efficiency of the ecosystem was 6.47 mg CO2/g H2O. The efficiency of the ecosystem increased with a decrease in vapor pressure deficit.

  14. Spatial and temporal patterns of biotic exchanges of CO{sub 2} between the atmosphere and tropical landscapes and their role in the global carbon balance. Progress report

    Energy Technology Data Exchange (ETDEWEB)

    Richards, J.F.; Flint, E.P.

    1993-10-01

    Since mid-September we have been engaged in final revision of the data base for South and Southeast Asia. In October we revised our second chapter for the forthcoming volume Effects of Land Use Change on Atmospheric Carbon Dioxide Concentrations, edited by Virginia Dale. ``Trends in Carbon Content of Vegetation in South and Southeast Asia Associated with Changes in Land Use``, in response to a second round of reviews. Both this chapter and `` Century of Land Use Change in South and Southeast Asia`` (submitted in revised form in July) are have been accepted and are now in the hands of the technical editor. our time series of land use data and carbon content estimates for live vegetation in 93 zones comprising thirteen Asian nations at four dates was finalized in the course of manuscript revision. We sent machine-readable copies of the spreadsheets containing tabular data for Southeast Asia to CDIAC in October, and the following month delivered the South Asian data. At the same time, we sent these files to the research groups of Sandra Brown and Charlie Hall, who have entered this information in their geographic information systems, and also to Skee Houghton.

  15. Reconciling estimates of the contemporary North American carbon balance among terrestrial biosphere models, atmospheric inversions and a new approach for estimating net ecosystem exchange from inventory-based data

    Energy Technology Data Exchange (ETDEWEB)

    Hayes, Daniel J [ORNL; Turner, David P [Oregon State University, Corvallis; Stinson, Graham [Pacific Forestry Centre, Canadian Forest Service; Mcguire, David [University of Alaska; Wei, Yaxing [ORNL; West, Tristram O. [Joint Global Change Research Institute, PNNL; Heath, Linda S. [USDA Forest Service; De Jong, Bernardus [ECOSUR; McConkey, Brian G. [Agriculture and Agri-Food Canada; Birdsey, Richard A. [U.S. Department of Agriculture Forest Service; Kurz, Werner [Canadian Forest Service; Jacobson, Andrew [NOAA ESRL and CIRES; Huntzinger, Deborah [University of Michigan; Pan, Yude [U.S. Department of Agriculture Forest Service; Post, Wilfred M [ORNL; Cook, Robert B [ORNL

    2012-01-01

    We develop an approach for estimating net ecosystem exchange (NEE) using inventory-based information over North America (NA) for a recent 7-year period (ca. 2000 2006). The approach notably retains information on the spatial distribution of NEE, or the vertical exchange between land and atmosphere of all non-fossil fuel sources and sinks of CO2, while accounting for lateral transfers of forest and crop products as well as their eventual emissions. The total NEE estimate of a 327 252 TgC yr1 sink for NA was driven primarily by CO2 uptake in the Forest Lands sector (248 TgC yr1), largely in the Northwest and Southeast regions of the US, and in the Crop Lands sector (297 TgC yr1), predominantly in the Midwest US states. These sinks are counteracted by the carbon source estimated for the Other Lands sector (+218 TgC yr1), where much of the forest and crop products are assumed to be returned to the atmosphere (through livestock and human consumption). The ecosystems of Mexico are estimated tobe a small net source (+18 TgC yr1) due to land use change between 1993 and 2002. We compare these inventorybased estimates with results from a suite of terrestrial biosphere and atmospheric inversion models, where the mean continental-scale NEE estimate for each ensemble is 511 TgC yr1 and 931 TgC yr1, respectively. In the modeling approaches, all sectors, including Other Lands, were generally estimated to be a carbon sink, driven in part by assumed CO2 fertilization and/or lack of consideration of carbon sources from disturbances and product emissions. Additional fluxes not measured by the inventories, although highly uncertain, could add an additional 239 TgC yr1 to the inventory-based NA sink estimate, thus suggesting some convergence with the modeling approaches.

  16. Reconciling estimates of the contemporary North American carbon balance among terrestrial biosphere models, atmospheric inversions, and a new approach for estimating net ecosystem exchange from inventory-based data

    Science.gov (United States)

    Hayes, Daniel J.; Turner, David P.; Stinson, Graham; McGuire, A. David; Wei, Yaxing; West, Tristram O.; Heath, Linda S.; de Jong, Bernardus; McConkey, Brian G.; Birdsey, Richard A.; Kurz, Werner A.; Jacobson, Andrew R.; Huntzinger, Deborah N.; Pan, Yude; Post, W. Mac; Cook, Robert B.

    2012-01-01

    We develop an approach for estimating net ecosystem exchange (NEE) using inventory-based information over North America (NA) for a recent 7-year period (ca. 2000–2006). The approach notably retains information on the spatial distribution of NEE, or the vertical exchange between land and atmosphere of all non-fossil fuel sources and sinks of CO2, while accounting for lateral transfers of forest and crop products as well as their eventual emissions. The total NEE estimate of a -327 ± 252 TgC yr-1 sink for NA was driven primarily by CO2 uptake in the Forest Lands sector (-248 TgC yr-1), largely in the Northwest and Southeast regions of the US, and in the Crop Lands sector (-297 TgC yr-1), predominantly in the Midwest US states. These sinks are counteracted by the carbon source estimated for the Other Lands sector (+218 TgC yr-1), where much of the forest and crop products are assumed to be returned to the atmosphere (through livestock and human consumption). The ecosystems of Mexico are estimated to be a small net source (+18 TgC yr-1) due to land use change between 1993 and 2002. We compare these inventory-based estimates with results from a suite of terrestrial biosphere and atmospheric inversion models, where the mean continental-scale NEE estimate for each ensemble is -511 TgC yr-1 and -931 TgC yr-1, respectively. In the modeling approaches, all sectors, including Other Lands, were generally estimated to be a carbon sink, driven in part by assumed CO2 fertilization and/or lack of consideration of carbon sources from disturbances and product emissions. Additional fluxes not measured by the inventories, although highly uncertain, could add an additional -239 TgC yr-1 to the inventory-based NA sink estimate, thus suggesting some convergence with the modeling approaches.

  17. Atmospheric exchange of carbon dioxide and methane of a small water body and a floating mat in the Luther Marsh peatland, Ontario, Canada

    Science.gov (United States)

    Burger, Magdalena; Berger, Sina; Blodau, Christian

    2015-04-01

    Recent investigations have suggested that small water bodies cover larger areas in northern peatlands than previously assumed. Their role in the carbon cycle and gas exchange rates are poorly constrained so far. To address this issue we measured CO2 and CH4 fluxes on a small water body (ca. 700 m2) and the surrounding floating mat in the Luther Marsh peatland in Ontario, Canada from July to September 2014. To this end we used closed chambers combined with a portable Los Gatos high-resolution trace gas analyzer at different water depths and distances from the shore on the pond and with different dominating plant types on the floating mat surrounding the pond. In addition, CO2 concentrations were recorded in high temporal resolution using an infrared sensor system during selected periods. Air and water temperature, humidity and temperature of the floating mat, wind speed and direction, photosynthetically active radiation, air pressure and relative humidity were also recorded as auxiliary data at the study site. The results show that pond and floating mat were sources of methane throughout the whole measuring period. Methane emissions via the ebullition pathway occurred predominantly near the shore and on the floating mat. During the daytime measurements the floating mat acted as a net sink and the pond as a net source of CO2. The dynamics of CO2 exchange was also strongly time dependent, as CO2 emissions from the pond strongly increased after mid-August. This suggests that photosynthesis was more affected by seasonal decline than respiration process in the pond and that the allochthonous component of the CO2 flux increased in relative importance towards fall.

  18. Exotic Spartina alterniflora invasion alters ecosystem-atmosphere exchange of CH4 and N2O and carbon sequestration in a coastal salt marsh in China.

    Science.gov (United States)

    Yuan, Junji; Ding, Weixin; Liu, Deyan; Kang, Hojeong; Freeman, Chris; Xiang, Jian; Lin, Yongxin

    2015-04-01

    Coastal salt marshes are sensitive to global climate change and may play an important role in mitigating global warming. To evaluate the impacts of Spartina alterniflora invasion on global warming potential (GWP) in Chinese coastal areas, we measured CH4 and N2O fluxes and soil organic carbon sequestration rates along a transect of coastal wetlands in Jiangsu province, China, including open water; bare tidal flat; and invasive S. alterniflora, native Suaeda salsa, and Phragmites australis marshes. Annual CH4 emissions were estimated as 2.81, 4.16, 4.88, 10.79, and 16.98 kg CH4 ha(-1) for open water, bare tidal flat, and P. australis, S. salsa, and S. alterniflora marshes, respectively, indicating that S. alterniflora invasion increased CH4 emissions by 57-505%. In contrast, negative N2O fluxes were found to be significantly and negatively correlated (P carbon sequestration rate of S. alterniflora marsh amounted to 3.16 Mg C ha(-1) yr(-1) in the top 100 cm soil profile, a value that was 2.63- to 8.78-fold higher than in native plant marshes. The estimated GWP was 1.78, -0.60, -4.09, and -1.14 Mg CO2 eq ha(-1) yr(-1) in open water, bare tidal flat, P. australis marsh and S. salsa marsh, respectively, but dropped to -11.30 Mg CO2 eq ha(-1) yr(-1) in S. alterniflora marsh. Our results indicate that although S. alterniflora invasion stimulates CH4 emissions, it can efficiently mitigate increases in atmospheric CO2 and N2O along the coast of China.

  19. The long-term carbon cycle, fossil fuels and atmospheric composition.

    Science.gov (United States)

    Berner, Robert A

    2003-11-20

    The long-term carbon cycle operates over millions of years and involves the exchange of carbon between rocks and the Earth's surface. There are many complex feedback pathways between carbon burial, nutrient cycling, atmospheric carbon dioxide and oxygen, and climate. New calculations of carbon fluxes during the Phanerozoic eon (the past 550 million years) illustrate how the long-term carbon cycle has affected the burial of organic matter and fossil-fuel formation, as well as the evolution of atmospheric composition.

  20. Oxygen isotopic composition of carbon dioxide in the middle atmosphere

    OpenAIRE

    Liang, Mao-Chang; Blake, Geoffrey A.; Lewis, Brenton R.; Yung, Yuk L.

    2007-01-01

    The isotopic composition of long-lived trace molecules provides a window into atmospheric transport and chemistry. Carbon dioxide is a particularly powerful tracer, because its abundance remains >100 parts per million by volume (ppmv) in the mesosphere. Here, we successfully reproduce the isotopic composition of CO2 in the middle atmosphere, which has not been previously reported. The mass-independent fractionation of oxygen in CO2 can be satisfactorily explained by the exchange reaction with...

  1. Regional Ecosystem-Atmosphere CO2 Exchange Via Atmospheric Budgets

    Energy Technology Data Exchange (ETDEWEB)

    Davis, K J; Richardson, S J; Miles, N L

    2007-03-07

    Inversions of atmospheric CO2 mixing ratio measurements to determine CO2 sources and sinks are typically limited to coarse spatial and temporal resolution. This limits our ability to evaluate efforts to upscale chamber- and stand-level CO2 flux measurements to regional scales, where coherent climate and ecosystem mechanisms govern the carbon cycle. As a step towards the goal of implementing atmospheric budget or inversion methodology on a regional scale, a network of five relatively inexpensive CO2 mixing ratio measurement systems was deployed on towers in northern Wisconsin. Four systems were distributed on a circle of roughly 150-km radius, surrounding one centrally located system at the WLEF tower near Park Falls, WI. All measurements were taken at a height of 76 m AGL. The systems used single-cell infrared CO2 analyzers (Licor, model LI-820) rather than the siginificantly more costly two-cell models, and were calibrated every two hours using four samples known to within ± 0.2 ppm CO2. Tests prior to deployment in which the systems sampled the same air indicate the precision of the systems to be better than ± 0.3 ppm and the accuracy, based on the difference between the daily mean of one system and a co-located NOAA-ESRL system, is consistently better than ± 0.3 ppm. We demonstrate the utility of the network in two ways. We interpret regional CO2 differences using a Lagrangian parcel approach. The difference in the CO2 mixing ratios across the network is at least 2-3 ppm, which is large compared to the accuracy and precision of the systems. Fluxes estimated assuming Lagrangian parcel transport are of the same sign and magnitude as eddy-covariance flux measurements at the centrally-located WLEF tower. These results indicate that the network will be useful in a full inversion model. Second, we present a case study involving a frontal passage through the region. The progression of a front across the network is evident; changes as large as four ppm in one minute

  2. Climate control of terrestrial carbon exchange across biomes and continents

    Energy Technology Data Exchange (ETDEWEB)

    Yi Chuixiang; Wolbeck, John; Xu Xiyan [School of Earth and Environmental Sciences, Queens College, City University of New York, NY 11367 (United States); Ricciuto, Daniel [Environmental Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831 (United States); Li Runze [Department of Statistics, Pennsylvania State University, University Park, PA 16802 (United States); Nilsson, Mats [Department of Forest Ecology, Swedish University of Agricultural Sciences, SE-901 83 Umeaa (Sweden); Aires, Luis [CESAM and Department of Environmental Engineering, School of Technology and Management, Polytechnic Institute of Leiria (Portugal); Albertson, John D [Department of Civil and Environmental Engineering, Duke University, Durham, NC 22708-0287 (United States); Ammann, Christof [Federal Research Station Agroscope Reckenholz-Taenikon, Reckenholzstrasse 191, 8046 Zuerich (Switzerland); Arain, M Altaf [School of Geography and Earth Sciences, McMaster University, Hamilton, ON, L8S 4K1 (Canada); De Araujo, Alessandro C [Instituto Nacional de Pesquisas da Amazonia, Programa LBA, Campus-II, Manaus-Amazonas 69060 (Brazil); Aubinet, Marc [University of Liege, Gembloux Agro-Bio Tech, Unit of Biosystem Physics, 2 Passage des Deportes, 5030 Gembloux (Belgium); Aurela, Mika [Finnish Meteorological Institute, Climate Change Research, FI-00101 Helsinki (Finland); Barcza, Zoltan [Department of Meteorology, Eoetvoes Lorand University, H-1117 Budapest, Pazmany setany 1/A (Hungary); Barr, Alan [Climate Research Division, Environment Canada, Saskatoon, SK, S7N 3H5 (Canada); Berbigier, Paul [INRA, UR1263 EPHYSE, Villenave d' Ornon F-33883 (France); Beringer, Jason [School of Geography and Environmental Science, Monash University, Clayton, Victoria 3800 (Australia); Bernhofer, Christian [Institute of Hydrology and Meteorology, Dresden University of Technology, Pienner Strasse 23, D-01737, Tharandt (Germany)

    2010-07-15

    Understanding the relationships between climate and carbon exchange by terrestrial ecosystems is critical to predict future levels of atmospheric carbon dioxide because of the potential accelerating effects of positive climate-carbon cycle feedbacks. However, directly observed relationships between climate and terrestrial CO{sub 2} exchange with the atmosphere across biomes and continents are lacking. Here we present data describing the relationships between net ecosystem exchange of carbon (NEE) and climate factors as measured using the eddy covariance method at 125 unique sites in various ecosystems over six continents with a total of 559 site-years. We find that NEE observed at eddy covariance sites is (1) a strong function of mean annual temperature at mid- and high-latitudes, (2) a strong function of dryness at mid- and low-latitudes, and (3) a function of both temperature and dryness around the mid-latitudinal belt (45 deg. N). The sensitivity of NEE to mean annual temperature breaks down at {approx} 16 deg. C (a threshold value of mean annual temperature), above which no further increase of CO{sub 2} uptake with temperature was observed and dryness influence overrules temperature influence.

  3. Climate control of terrestrial carbon exchange across biomes and continents

    Energy Technology Data Exchange (ETDEWEB)

    Ricciuto, Daniel M [ORNL; Gu, Lianhong [ORNL

    2010-07-01

    Understanding the relationships between climate and carbon exchange by terrestrial ecosystems is critical to predict future levels of atmospheric carbon dioxide because of the potential accelerating effects of positive climate carbon cycle feedbacks. However, directly observed relationships between climate and terrestrial CO2 exchange with the atmosphere across biomes and continents are lacking. Here we present data describing the relationships between net ecosystem exchange of carbon (NEE) and climate factors as measured using the eddy covariance method at 125 unique sites in various ecosystems over six continents with a total of 559 site-years. We find that NEE observed at eddy covariance sites is (1) a strong function of mean annual temperature at mid- and high-latitudes, (2) a strong function of dryness at mid- and low-latitudes, and (3) a function of both temperature and dryness around the mid-latitudinal belt (45 N). The sensitivity of NEE to mean annual temperature breaks down at ~ 16 C (a threshold value of mean annual temperature), above which no further increase of CO2 uptake with temperature was observed and dryness influence overrules temperature influence.

  4. Carbon nanotube heat-exchange systems

    Science.gov (United States)

    Hendricks, Terry Joseph; Heben, Michael J.

    2008-11-11

    A carbon nanotube heat-exchange system (10) and method for producing the same. One embodiment of the carbon nanotube heat-exchange system (10) comprises a microchannel structure (24) having an inlet end (30) and an outlet end (32), the inlet end (30) providing a cooling fluid into the microchannel structure (24) and the outlet end (32) discharging the cooling fluid from the microchannel structure (24). At least one flow path (28) is defined in the microchannel structure (24), fluidically connecting the inlet end (30) to the outlet end (32) of the microchannel structure (24). A carbon nanotube structure (26) is provided in thermal contact with the microchannel structure (24), the carbon nanotube structure (26) receiving heat from the cooling fluid in the microchannel structure (24) and dissipating the heat into an external medium (19).

  5. Time dependences of atmospheric Carbon dioxide fluxes

    CERN Document Server

    DeSalvo, Riccardo

    2014-01-01

    Understanding the lifetime of CO2 in the atmosphere is critical for predictions regarding future climate changes. A simple mass conservation analysis presented here generates tight estimations for the atmosphere's retention time constant. The analysis uses a leaky integrator model that combines the observed deficit (only less than 40% of CO2 produced from combustion of fossil fuels is actually retained in the atmosphere, while more than 60% is continuously shed) with the exponential growth of fossil fuel burning. It reveals a maximum characteristic time of less than 23 year for the transfer of atmospheric CO2 to a segregation sink. This time constant is further constrained by the rapid disappearance of 14C after the ban of atmospheric atomic bomb tests, which provides a lower limit of 18 years for this transfer. The study also generates evaluations of other CO2 fluxes, exchange time constants and volumes exchanged. Analysis of large harmonic oscillations of atmospheric CO2 concentration, often neglected in th...

  6. Using a Regional Cluster of AmeriFlux Sites in Central California to Advance Our Knowledge on Decadal-Scale Ecosystem-Atmosphere Carbon Dioxide Exchange

    Energy Technology Data Exchange (ETDEWEB)

    Baldocchi, Dennis [Univ. of California, Berkeley, CA (United States)

    2015-03-24

    Continuous eddy convariance measurements of carbon dioxide, water vapor and heat were measured continuously between an oak savanna and an annual grassland in California over a 4 year period. These systems serve as representative sites for biomes in Mediterranean climates and experience much seasonal and inter-annual variability in temperature and precipitation. These sites hence serve as natural laboratories for how whole ecosystem will respond to warmer and drier conditions. The savanna proved to be a moderate sink of carbon, taking up about 150 gC m-2y-1 compared to the annual grassland, which tended to be carbon neutral and often a source during drier years. But this carbon sink by the savanna came at a cost. This ecosystem used about 100 mm more water per year than the grassland. And because the savanna was darker and rougher its air temperature was about 0.5 C warmer. In addition to our flux measurements, we collected vast amounts of ancillary data to interpret the site and fluxes, making this site a key site for model validation and parameterization. Datasets consist of terrestrial and airborne lidar for determining canopy structure, ground penetrating radar data on root distribution, phenology cameras monitoring leaf area index and its seasonality, predawn water potential, soil moisture, stem diameter and physiological capacity of photosynthesis.

  7. Atmosphere-interior exchange on hot rocky exoplanets

    CERN Document Server

    Kite, Edwin S; Schaefer, Laura; Gaidos, Eric

    2016-01-01

    We provide estimates of atmospheric pressure and surface composition on short-period rocky exoplanets with dayside magma pools and silicate vapor atmospheres. Atmospheric pressure tends toward vapor-pressure equilibrium with surface magma, and magma-surface composition is set by the competing effects of fractional vaporization and surface-interior exchange. We use basic models to show how surface-interior exchange is controlled by the planet's temperature, mass, and initial composition. We assume that mantle rock undergoes bulk melting to form the magma pool, and that winds flow radially away from the substellar point. With these assumptions, we find that: (1) atmosphere-interior exchange is fast when the planet's bulk-silicate FeO concentration is low, and slow when FeO concentration is high; (2) magma pools are compositionally well-mixed for substellar temperatures $\\lesssim$ 2400 K, but compositionally variegated and rapidly variable for substellar temperatures $\\gtrsim$ 2400 K; (3) currents within the mag...

  8. Drought sensitivity of Amazonian carbon balance revealed by atmospheric measurements.

    Science.gov (United States)

    Gatti, L V; Gloor, M; Miller, J B; Doughty, C E; Malhi, Y; Domingues, L G; Basso, L S; Martinewski, A; Correia, C S C; Borges, V F; Freitas, S; Braz, R; Anderson, L O; Rocha, H; Grace, J; Phillips, O L; Lloyd, J

    2014-02-06

    Feedbacks between land carbon pools and climate provide one of the largest sources of uncertainty in our predictions of global climate. Estimates of the sensitivity of the terrestrial carbon budget to climate anomalies in the tropics and the identification of the mechanisms responsible for feedback effects remain uncertain. The Amazon basin stores a vast amount of carbon, and has experienced increasingly higher temperatures and more frequent floods and droughts over the past two decades. Here we report seasonal and annual carbon balances across the Amazon basin, based on carbon dioxide and carbon monoxide measurements for the anomalously dry and wet years 2010 and 2011, respectively. We find that the Amazon basin lost 0.48 ± 0.18 petagrams of carbon per year (Pg C yr(-1)) during the dry year but was carbon neutral (0.06 ± 0.1 Pg C yr(-1)) during the wet year. Taking into account carbon losses from fire by using carbon monoxide measurements, we derived the basin net biome exchange (that is, the carbon flux between the non-burned forest and the atmosphere) revealing that during the dry year, vegetation was carbon neutral. During the wet year, vegetation was a net carbon sink of 0.25 ± 0.14 Pg C yr(-1), which is roughly consistent with the mean long-term intact-forest biomass sink of 0.39 ± 0.10 Pg C yr(-1) previously estimated from forest censuses. Observations from Amazonian forest plots suggest the suppression of photosynthesis during drought as the primary cause for the 2010 sink neutralization. Overall, our results suggest that moisture has an important role in determining the Amazonian carbon balance. If the recent trend of increasing precipitation extremes persists, the Amazon may become an increasing carbon source as a result of both emissions from fires and the suppression of net biome exchange by drought.

  9. Gas-exchange, water use efficiency and yield responses of elite potato (Solanum tuberosum L.) cultivars to changes in atmospheric carbon dioxide concentration, temperature and relative humidity

    DEFF Research Database (Denmark)

    Kaminski, Kacper Piotr; Sørensen, Kirsten Kørup; Nielsen, Kåre Lehmann

    2014-01-01

    In spite of the agricultural importance of potato (Solanum tuberosum L.), most plant physiology studies have not accounted for the effect of the interaction between elevated carbon dioxide concentration ([CO2]) and other consequences of climate change on WUE. In 2010, a first controlled environment...... photosynthetic water use efficiency (pWUE) by stimulation in net photosynthesis rate (62 and 43% increase of An) with coincident decline in both stomatal conductance (21 and 43% decrease of gs) and leaf transpiration rate (19 and 40% decrease of E) resulting in pWUE increments of 89 and 147%. Furthermore...... stomatal conductance (25%) with a simultaneous drop in transpiration rate although not significant. The ratio Ci/Ca was in contrast to the first experiment significantly higher in plants grown at elevated [CO2]. Despite this photosynthetic acclimation, concurrent stimulation of aboveground and belowground...

  10. Direct Measurements of the Surface-Atmosphere Exchange of Ammonia

    Science.gov (United States)

    Tevlin, A.; Murphy, J. G.; Wentworth, G.; Gregoire, P.

    2012-12-01

    As the dominant atmospheric base, ammonia plays an important role in the formation and growth of inorganic aerosols. Surface-atmosphere exchange of ammonia has been observed to occur as a bidirectional flux governed by the relative magnitudes of atmospheric gas phase concentration and a temperature-dependent surface compensation point. In order to better characterise the links between gas-particle and surface-atmosphere exchanges, more direct measurements of these exchanges are necessary. Eddy Covariance (EC) can provide the most direct surface-atmosphere flux measurements, but its requirement for high frequency data combined with the reactive nature of ammonia have limited its application for this species. In order to address this lack, an investigation into the instrumental sensitivity and time response requirements for EC ammonia flux measurements was carried out using a Quantum Cascade-Tunable Infrared Laser Differential Absorption Spectrometer (QC-TILDAS) capable of measuring ammonia concentration at 10 Hz. Time response was additionally improved through the use of a heated sample line and custom glass inlet, and the system was deployed over a short grass field in rural Ontario. The ammonia measurements were used along with three dimensional sonic anemometer wind speed data to calculate EC ammonia fluxes. When combined with simultaneous measurements of the inorganic composition of gas and particle phases made by Ambient Ion Monitor - Ion Chromatography (AIM-IC), these flux measurements can provide insight into the links between gas-particle and surface-atmosphere exchange.

  11. Reconciling estimates of the contemporary North American carbon balance among terrestrial biosphere models, atmospheric inversions and a new approach for estimating net ecosystem exchange from inventory-based data

    Energy Technology Data Exchange (ETDEWEB)

    Hayes, D. J.; Turner, D. P.; Stinson, Graham; McGuire, A. David; Wei, Yaxing; West, Tristram O.; Heath, L.; deJong, B.; McConkey, Brian; Birdsey, Richard A.; Kurz, Werner; Jacobson, Andy; Huntzinger, Deborah N.; Pan, Y.; Post, W. M.; Cook, R. B.

    2012-04-02

    While fossil fuel emissions are calculated with relatively high precision, understanding the fate of those emissions with respect to sequestration in terrestrial ecosystems requires data and methods that can reduce uncertainties in the diagnosis of land-based CO2 sinks. The wide range in the land surface flux estimates is related to a number of factors, but most generally because of the different methodologies used to develop estimates of carbon stocks and flux, and the uncertainties inherent in each approach. The alternative approaches to estimating continental scale carbon fluxes that we explored here can be broadly classified as applying a top-down or bottom-up perspective. Top-down approaches calculate land-atmosphere carbon fluxes based on atmospheric budgets and inverse modeling. Bottom-up approaches rely primarily on measurements of carbon stock changes (the inventory approach) or on spatially distributed simulations of carbon stocks and/or fluxes using process-based modeling (the forward modelapproach).

  12. Atmospheric carbon dioxide and the global carbon cycle

    Energy Technology Data Exchange (ETDEWEB)

    Trabalka, J R [ed.

    1985-12-01

    This state-of-the-art volume presents discussions on the global cycle of carbon, the dynamic balance among global atmospheric CO2 sources and sinks. Separate abstracts have been prepared for the individual papers. (ACR)

  13. Regional atmospheric CO2 inversion reveals seasonal and geographic differences in Amazon net biome exchange.

    Science.gov (United States)

    Alden, Caroline B; Miller, John B; Gatti, Luciana V; Gloor, Manuel M; Guan, Kaiyu; Michalak, Anna M; van der Laan-Luijkx, Ingrid T; Touma, Danielle; Andrews, Arlyn; Basso, Luana S; Correia, Caio S C; Domingues, Lucas G; Joiner, Joanna; Krol, Maarten C; Lyapustin, Alexei I; Peters, Wouter; Shiga, Yoichi P; Thoning, Kirk; van der Velde, Ivar R; van Leeuwen, Thijs T; Yadav, Vineet; Diffenbaugh, Noah S

    2016-10-01

    Understanding tropical rainforest carbon exchange and its response to heat and drought is critical for quantifying the effects of climate change on tropical ecosystems, including global climate-carbon feedbacks. Of particular importance for the global carbon budget is net biome exchange of CO2 with the atmosphere (NBE), which represents nonfire carbon fluxes into and out of biomass and soils. Subannual and sub-Basin Amazon NBE estimates have relied heavily on process-based biosphere models, despite lack of model agreement with plot-scale observations. We present a new analysis of airborne measurements that reveals monthly, regional-scale (~1-8 × 10(6)  km(2) ) NBE variations. We develop a regional atmospheric CO2 inversion that provides the first analysis of geographic and temporal variability in Amazon biosphere-atmosphere carbon exchange and that is minimally influenced by biosphere model-based first guesses of seasonal and annual mean fluxes. We find little evidence for a clear seasonal cycle in Amazon NBE but do find NBE sensitivity to aberrations from long-term mean climate. In particular, we observe increased NBE (more carbon emitted to the atmosphere) associated with heat and drought in 2010, and correlations between wet season NBE and precipitation (negative correlation) and temperature (positive correlation). In the eastern Amazon, pulses of increased NBE persisted through 2011, suggesting legacy effects of 2010 heat and drought. We also identify regional differences in postdrought NBE that appear related to long-term water availability. We examine satellite proxies and find evidence for higher gross primary productivity (GPP) during a pulse of increased carbon uptake in 2011, and lower GPP during a period of increased NBE in the 2010 dry season drought, but links between GPP and NBE changes are not conclusive. These results provide novel evidence of NBE sensitivity to short-term temperature and moisture extremes in the Amazon, where monthly and sub

  14. Atmosphere-earth angular momentum exchange and ENSO cycle

    Institute of Scientific and Technical Information of China (English)

    钱维宏; 丑纪范

    1996-01-01

    The time series of the earth’s rotation rate, eastern equatorial Pacific sea surface temperature (Tss), sea level pressure (Psl) and atmospheric angular momentum (Maa) during 1976 -1989 are used to study the relation between atmosphere-earth angular momentum exchange and ENSO cycle. The result shows that (i) there are synergetic relationships among the variations of solid earth’s rotation, eastern equatorial Pacific T,, Psl, different latitude zonal Maa and global Maa; (ii) local atmosphere-ocean interaction over low-latitude area can form ENSO-like cycle through Hadley circulation; (iii) the solid earth and global atmosphere-ocean interaction can form some aperiodic behavior and asynchronous oscillations by mountain torque and earth spin anomalous friction torque acting on each component of solid earth-ocean-atmosphere system; and (iv) actual ENSO cycle is a phenomenon reflecting in Pacific basin through interaction among solid earth, global ocean and the atmosphere.

  15. Exchange of carbonyl sulfide (COS) between wheat soil and atmosphere

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The exchange of COS between wheat soil and atmosphere was investigated by using a dynamic enclosure. The investigated soil type acted as a significant sink for the trace gas COS. Atmospheric COS mixing ratios and temperature were found to be the physicochemical parameters controlling the uptake. The uptake reached maximum about 0.6×10-12 mol·g-1·h-1 at 15-20℃ under natural ambient atmospheric conditions. The measured uptake values agree well with that calculated by Guenther algorithm.

  16. Exchange processes between a coniferous forest and the atmosphere

    NARCIS (Netherlands)

    Bosveld, F.C.

    1999-01-01

    This thesis deals with the research question: which processes are relevant in controlling the exchange fluxes between the forest and the atmosphere and how can this control be quantified? Answering this question is relevant for research in the fields of air pollution, weather and climate and remote

  17. Methanol exchange between grassland and the atmosphere

    Directory of Open Access Journals (Sweden)

    A. Brunner

    2007-01-01

    Full Text Available Concentrations and fluxes of methanol were measured above two differently managed grassland fields (intensive and extensive in central Switzerland during summer 2004. The measurements were performed with a proton-transfer-reaction mass-spectrometer and fluxes were determined by the eddy covariance method. The observed methanol emission showed a distinct diurnal cycle and was strongly correlated with global radiation and water vapour flux. Mean and maximum daily emissions were found to depend on grassland species composition and, for the intensive field, also on the growing state. The extensive field with a more complex species composition had higher emissions than the graminoid-dominated intensive field, both on an area and on a biomass basis. A simple parameterisation depending on the water vapour flux and the leaf area index allowed a satisfying simulation of the temporal variation of methanol emissions over the growing phase. Accumulated carbon losses due to methanol emissions accounted for 0.024 and 0.048% of net primary productivity for the intensive and extensive field, respectively. The integral methanol emissions over the growing periods were more than one order of magnitude higher than the emissions related to cut and drying events.

  18. Atmospheric deposition of organic carbon via precipitation

    Science.gov (United States)

    Iavorivska, Lidiia; Boyer, Elizabeth W.; DeWalle, David R.

    2016-12-01

    Atmospheric deposition is the major pathway for removal of organic carbon (OC) from the atmosphere, affecting both atmospheric and landscape processes. Transfers of OC from the atmosphere to land occur as wet deposition (via precipitation) and as dry deposition (via surface settling of particles and gases). Despite current understanding of the significance of organic carbon inputs with precipitation to carbon budgets, transfers of organic matter between the atmosphere and land are not explicitly included in most carbon cycle models due to limited data, highlighting the need for further information. Studies regarding the abundance of OC in precipitation are relatively sparse, in part due to the fact that concentrations of organics in precipitation and their associated rates of atmospheric deposition are not routinely measured as a part of major deposition monitoring networks. Here, we provide a new data synthesis from 83 contemporary studies published in the peer reviewed literature where organic matter in precipitation was measured around the world. We compiled data regarding the concentrations of organic carbon in precipitation and associated rates of atmospheric deposition of organic carbon. We calculated summary statistics in a common set of units, providing insights into the magnitude and regional variability of OC in precipitation. A land to ocean gradient is evident in OC concentrations, with marine sites generally showing lower values than continental sites. Our synthesis highlights gaps in the data and challenges for data intercomparison. There is a need to concentrate sampling efforts in areas where anthropogenic OC emissions are on the rise (Asia, South America), as well as in remote sites suggesting background conditions, especially in Southern Hemisphere. It is also important to acquire more data for marine rainwater at various distances from the coast in order to assess a magnitude of carbon transfer between the land and the ocean. Our integration of

  19. 'Carbon-Money Exchange' to contain global warming and deforestation

    Energy Technology Data Exchange (ETDEWEB)

    Nagase, Kozo E-mail: nagase@de.mbn.or.jp

    2005-07-01

    This paper builds a basic theory of 'Carbon-Money Exchange' in which carbon as currency in nature's household (ecosystems) and money as currency in humankind's household (economy) are exchanged just like in a foreign exchange. The simple chemical equation below makes it possible (CO{sub 2}{yields}C+O{sub 2}=C+O{sub 2}{yields}CO{sub 2}). The left-hand side represents the work of plants to remove atmospheric CO{sub 2}. The right-hand side represents the work of humans as fossil fuel consumers to produce it. The exchange of the two currencies is possible by copying the fossil fuel market. The paper concludes that this new exchange can automatically contain global warming and deforestation, replacing onerous emissions trading. Moreover, it could revolutionize the conventional economy, creating counter-capitalism, or 'carbonism'.

  20. Atmosphere-interior Exchange on Hot, Rocky Exoplanets

    Science.gov (United States)

    Kite, Edwin S.; Fegley, Bruce, Jr.; Schaefer, Laura; Gaidos, Eric

    2016-09-01

    We provide estimates of atmospheric pressure and surface composition on short-period, rocky exoplanets with dayside magma pools and silicate-vapor atmospheres. Atmospheric pressure tends toward vapor-pressure equilibrium with surface magma, and magma-surface composition is set by the competing effects of fractional vaporization and surface-interior exchange. We use basic models to show how surface-interior exchange is controlled by the planet’s temperature, mass, and initial composition. We assume that mantle rock undergoes bulk melting to form the magma pool, and that winds flow radially away from the substellar point. With these assumptions, we find that: (1) atmosphere-interior exchange is fast when the planet’s bulk-silicate FeO concentration is low, and slow when the planet’s bulk-silicate FeO concentration is high; (2) magma pools are compositionally well mixed for substellar temperatures ≲2400 K, but compositionally variegated and rapidly variable for substellar temperatures ≳2400 K; (3) currents within the magma pool tend to cool the top of the solid mantle (“tectonic refrigeration”) (4) contrary to earlier work, many magma planets have time-variable surface compositions.

  1. Lake-Atmosphere Greenhouse Gas Exchange in Relation to Atmospheric Forcing and Water Clarity

    Science.gov (United States)

    Heiskanen, J. J.; Ojala, A.; Mammarella, I.; Vesala, T.

    2015-12-01

    Even though lakes cover only 2 % of the world's land surface, it has been estimated that lakes release about 10 % of the carbon fixed annually by the terrestrial ecosystems back to the atmosphere. A critical parameter in the gas exchange estimates is the gas transfer velocity (k), which is governed by turbulence. The aim of our study was to assess the current global CO2 evasion estimates from lakes to the atmosphere by comparing parameterizations for kand the significance of wind and heat flux to the gas transfer in small lakes. To improve future predictions of gas evasion from lakes, we focused on the changes in water clarity and how they affect water column physics and processes in the air-water interface. We studied a small boreal lake and used the eddy covariance (EC) method for the high precision data needed, and therefore also aimed to improve the EC methodology on lakes. The air-water gas transfer was related to both wind and heat loss during times of seasonal stratification, but only to wind during autumn overturn. When wind-induced thermocline tilting and resulting spatial variability in surface water CO2 concentrations was accounted for, average k derived from the measurements dropped from 6.0 cm h-1 to 5.2 cm h-1. This was still over twice the estimate (2.2 cm h-1) calculated with a widely used model for kin lakes suggesting that the global estimates of gas evasion from lakes might be underestimations. Water clarity was a significant parameter defining the thermal stratification of the lake: a change from clear to dark water would lead to shorter stratification period and lower water column temperatures in small lakes and therefore have significant impact on the lake-atmosphere exchange processes. Figure 1. The isotherms of Lake Kuivajärvi throughout the open-water period 2013. The top left are the measured temperatures and the others are modeled with LAKE model using fixed light extinction coefficient, Kd. The horizontal dashed black line represents

  2. Challenges in quantifying biosphere-atmosphere exchange of nitrogen species

    DEFF Research Database (Denmark)

    Sutton, M.A.; Nemitz, E.; Erisman, J.W.

    2007-01-01

    Recent research in nitrogen exchange with the atmosphere has separated research communities according to N form. The integrated perspective needed to quantify the net effect of N on greenhouse-gas balance is being addressed by the NitroEurope Integrated Project (NEU). Recent advances have depended...... progress has been made in modelling N fluxes, especially for N2O, NO and bi-directional NH3 exchange. Landscape analysis represents an emerging challenge to address the spatial interactions between farms, fields, ecosystems, catchments and air dispersion/deposition. European up-scaling of N fluxes...

  3. Marine atmospheric corrosion of carbon steels

    Energy Technology Data Exchange (ETDEWEB)

    Morcillo, M.; Alcantara, J.; Diaz, I.; Chico, B.; Simancas, J.; Fuente, D. de la

    2015-07-01

    Basic research on marine atmospheric corrosion of carbon steels is a relatively young scientific field and there continue to be great gaps in this area of knowledge. The presence of akaganeite in the corrosion products that form on steel when it is exposed to marine atmospheres leads to a notable increase in the corrosion rate. This work addresses the following issues: (a) environmental conditions necessary for akaganeite formation; (b) characterisation of akaganeite in the corrosion products formed; (c) corrosion mechanisms of carbon steel in marine atmospheres; (d) exfoliation of rust layers formed in highly aggressive marine atmospheres; (e) long-term corrosion rate prediction; and (f) behaviour of weathering steels. Field research has been carried out at Cabo Vilano wind farm (Camarinas, Galicia) in a wide range of atmospheric salinities and laboratory work involving the use of conventional atmospheric corrosion techniques and near-surface and bulk sensitive analytical techniques: scanning electron microscopy (SEM)/energy dispersive spectrometry (EDS), X-ray diffraction (XRD), Mossbauer spectroscopy and SEM/μRaman spectroscopy. (Author)

  4. Long-range transport of continentally-derived particulate carbon in the marine atmosphere: evidence from stable carbon isotope studies

    OpenAIRE

    Cachier, Héléne; BUAT-MÉNARD, PATRICK; Fontugne, Michel; Chesselet, Roger

    2011-01-01

    Since 1979, we have investigated marine and non-marine sources of particulate carbon in the marine atmosphere from measurements of carbon concentration and isotopic composition 13C/12C). Aerosol samples were collected, mostly during the Sea/Air Exchange (SEAREX) Program experiments, in the northern and southern hemispheres (Sargasso Sea, Enewetak Atoll, Peru upwelling, American Samoa, New Zealand, Amsterdam Island). The concentration and the isotopic composition of particulate carbon of marin...

  5. 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...

  6. Photochemical processing of aqueous atmospheric brown carbon

    Directory of Open Access Journals (Sweden)

    R. Zhao

    2015-01-01

    Full Text Available Atmospheric Brown Carbon (BrC is a collective term for light absorbing organic compounds in the atmosphere. While the identification of BrC and its formation mechanisms is currently a central effort in the community, little is known about the atmospheric removal processes of aerosol BrC. As a result, we report a series of laboratory studies of photochemical processing of BrC in the aqueous phase, by direct photolysis and OH oxidation. Solutions of ammonium sulfate mixed with glyoxal (GLYAS or methylglyoxal (MGAS are used as surrogates for a class of secondary BrC mediated by imine intermediates. Three nitrophenol species, namely 4-nitrophenol, 5-nitroguaiacol and 4-nitrocatechol, were investigated as a class of water soluble BrC originating from biomass burning. Photochemical processing induced significant changes in the absorptive properties of BrC. The imine-mediated BrC solutions exhibited rapid photo-bleaching with both direct photolysis and OH oxidation, with atmospheric half-lives of minutes to a few hours. The nitrophenol species exhibited photo-enhancement in the visible range during direct photolysis and the onset of OH oxidation, but rapid photo-bleaching was induced by further OH exposure on an atmospheric timescale of an hour or less. To illustrate atmospheric relevance of this work, we also performed direct photolysis experiments on water soluble organic carbon extracted from biofuel combustion samples and observed rapid changes in optical properties of these samples as well. Overall, these experiments indicate that atmospheric models need to incorporate representations of atmospheric processing of BrC species to accurately model their radiative impacts.

  7. Photochemical processing of aqueous atmospheric brown carbon

    Directory of Open Access Journals (Sweden)

    R. Zhao

    2015-06-01

    Full Text Available Atmospheric brown carbon (BrC is a collective term for light absorbing organic compounds in the atmosphere. While the identification of BrC and its formation mechanisms is currently a central effort in the community, little is known about the atmospheric removal processes of aerosol BrC. As a result, we report on a series of laboratory studies of photochemical processing of BrC in the aqueous phase, by direct photolysis and OH oxidation. Solutions of ammonium sulfate mixed with glyoxal (GLYAS or methylglyoxal (MGAS are used as surrogates for a class of secondary BrC mediated by imine intermediates. Three nitrophenol species, namely 4-nitrophenol, 5-nitroguaiacol and 4-nitrocatechol, were investigated as a class of water-soluble BrC originating from biomass burning. Photochemical processing induced significant changes in the absorptive properties of BrC. The imine-mediated BrC solutions exhibited rapid photo-bleaching with both direct photolysis and OH oxidation, with atmospheric half-lives of minutes to a few hours. The nitrophenol species exhibited photo-enhancement in the visible range during direct photolysis and the onset of OH oxidation, but rapid photo-bleaching was induced by further OH exposure on an atmospheric timescale of an hour or less. To illustrate the atmospheric relevance of this work, we also performed direct photolysis experiments on water-soluble organic carbon extracted from biofuel combustion samples and observed rapid changes in the optical properties of these samples as well. Overall, these experiments indicate that atmospheric models need to incorporate representations of atmospheric processing of BrC species to accurately model their radiative impacts.

  8. Photochemical processing of aqueous atmospheric brown carbon

    Science.gov (United States)

    Zhao, R.; Lee, A. K. Y.; Huang, L.; Li, X.; Yang, F.; Abbatt, J. P. D.

    2015-06-01

    Atmospheric brown carbon (BrC) is a collective term for light absorbing organic compounds in the atmosphere. While the identification of BrC and its formation mechanisms is currently a central effort in the community, little is known about the atmospheric removal processes of aerosol BrC. As a result, we report on a series of laboratory studies of photochemical processing of BrC in the aqueous phase, by direct photolysis and OH oxidation. Solutions of ammonium sulfate mixed with glyoxal (GLYAS) or methylglyoxal (MGAS) are used as surrogates for a class of secondary BrC mediated by imine intermediates. Three nitrophenol species, namely 4-nitrophenol, 5-nitroguaiacol and 4-nitrocatechol, were investigated as a class of water-soluble BrC originating from biomass burning. Photochemical processing induced significant changes in the absorptive properties of BrC. The imine-mediated BrC solutions exhibited rapid photo-bleaching with both direct photolysis and OH oxidation, with atmospheric half-lives of minutes to a few hours. The nitrophenol species exhibited photo-enhancement in the visible range during direct photolysis and the onset of OH oxidation, but rapid photo-bleaching was induced by further OH exposure on an atmospheric timescale of an hour or less. To illustrate the atmospheric relevance of this work, we also performed direct photolysis experiments on water-soluble organic carbon extracted from biofuel combustion samples and observed rapid changes in the optical properties of these samples as well. Overall, these experiments indicate that atmospheric models need to incorporate representations of atmospheric processing of BrC species to accurately model their radiative impacts.

  9. Linking the lithogenic, atmospheric, and biogenic cycles of silicate, carbonate, and organic carbon in the ocean

    Science.gov (United States)

    Smith, S. V.; Gattuso, J.-P.

    2009-07-01

    Geochemical theory describes long term cycling of atmospheric CO2 between the atmosphere and rocks at the Earth surface in terms of rock weathering and precipitation of sedimentary minerals. Chemical weathering of silicate rocks takes up atmospheric CO2, releases cations and HCO3- to water, and precipitates SiO2, while CaCO3 precipitation consumes Ca2+ and HCO3- and releases one mole of CO2 to the atmosphere for each mole of CaCO3 precipitated. At steady state, according to this theory, the CO2 uptake and release should equal one another. In contradiction to this theory, carbonate precipitation in the present surface ocean releases only about 0.6 mol of CO2 per mole of carbonate precipitated. This is a result of the buffer effect described by Ψ, the molar ratio of net CO2 gas evasion to net CaCO3 precipitation from seawater in pCO2 equilibrium with the atmosphere. This asymmetry in CO2 flux between weathering and precipitation would quickly exhaust atmospheric CO2, posing a conundrum in the classical weathering and precipitation cycle. While often treated as a constant, Ψ actually varies as a function of salinity, pCO2, and temperature. Introduction of organic C reactions into the weathering-precipitation couplet largely reconciles the relationship. ψ in the North Pacific Ocean central gyre rises from 0.6 to 0.9, as a consequence of organic matter oxidation in the water column. ψ records the combined effect of CaCO3 and organic reactions and storage of dissolved inorganic carbon in the ocean, as well as CO2 gas exchange between the ocean and atmosphere. Further, in the absence of CaCO3 reactions, Ψ would rise to 1.0. Similarly, increasing atmospheric pCO2 over time, which leads to ocean acidification, alters the relationship between organic and inorganic C reactions and carbon storage in the ocean. Thus, the carbon reactions and ψ can cause large variations in oceanic carbon storage with little exchange with the atmosphere.

  10. Linking the lithogenic, atmospheric, and biogenic cycles of silicate, carbonate, and organic carbon in the ocean

    Directory of Open Access Journals (Sweden)

    S. V. Smith

    2009-07-01

    Full Text Available Geochemical theory describes long term cycling of atmospheric CO2 between the atmosphere and rocks at the Earth surface in terms of rock weathering and precipitation of sedimentary minerals. Chemical weathering of silicate rocks takes up atmospheric CO2, releases cations and HCO3 to water, and precipitates SiO2, while CaCO3 precipitation consumes Ca2+ and HCO3 and releases one mole of CO2 to the atmosphere for each mole of CaCO3 precipitated. At steady state, according to this theory, the CO2 uptake and release should equal one another. In contradiction to this theory, carbonate precipitation in the present surface ocean releases only about 0.6 mol of CO2 per mole of carbonate precipitated. This is a result of the buffer effect described by Ψ, the molar ratio of net CO2 gas evasion to net CaCO3 precipitation from seawater in pCO2 equilibrium with the atmosphere. This asymmetry in CO2 flux between weathering and precipitation would quickly exhaust atmospheric CO2, posing a conundrum in the classical weathering and precipitation cycle.

    While often treated as a constant, Ψ actually varies as a function of salinity, pCO2, and temperature. Introduction of organic C reactions into the weathering-precipitation couplet largely reconciles the relationship. ψ in the North Pacific Ocean central gyre rises from 0.6 to 0.9, as a consequence of organic matter oxidation in the water column. ψ records the combined effect of CaCO3 and organic reactions and storage of dissolved inorganic carbon in the ocean, as well as CO2 gas exchange between the ocean and atmosphere. Further, in the absence of CaCO3 reactions, Ψ would rise to 1.0. Similarly, increasing atmospheric pCO2

  11. Regolith-atmosphere exchange of water in Mars' recent past

    Science.gov (United States)

    Steele, Liam J.; Balme, Matthew R.; Lewis, Stephen R.

    2017-03-01

    We investigate the exchange of water vapour between the regolith and atmosphere of Mars, and how it varies with different orbital parameters, atmospheric dust contents and surface water ice reservoirs. This is achieved through the coupling of a global circulation model (GCM) and a regolith diffusion model. GCM simulations are performed for hundreds of Mars years, with additional one-dimensional simulations performed for 50 kyr. At obliquities ɛ =15∘ and 30°, the thermal inertia and albedo of the regolith have more control on the subsurface water distribution than changes to the eccentricity or solar longitude of perihelion. At ɛ =45∘ , atmospheric water vapour abundances become much larger, allowing stable subsurface ice to form in the tropics and mid-latitudes. The circulation of the atmosphere is important in producing the subsurface water distribution, with increased water content in various locations due to vapour transport by topographically-steered flows and stationary waves. As these circulation patterns are due to topographic features, it is likely the same regions will also experience locally large amounts of subsurface water at different epochs. The dustiness of the atmosphere plays an important role in the distribution of subsurface water, with a dusty atmosphere resulting in a wetter water cycle and increased stability of subsurface ice deposits.

  12. A high-altitude balloon platform for determining exchange of carbon dioxide over agricultural landscapes

    Science.gov (United States)

    Bouche, Angie; Beck-Winchatz, Bernhard; Potosnak, Mark J.

    2016-11-01

    The exchange of carbon dioxide between the terrestrial biosphere and the atmosphere is a key process in the global carbon cycle. Given emissions from fossil fuel combustion and the appropriation of net primary productivity by human activities, understanding the carbon dioxide exchange of cropland agroecosystems is critical for evaluating future trajectories of climate change. In addition, human manipulation of agroecosystems has been proposed as a technique of removing carbon dioxide from the atmosphere via practices such as no-tillage and cover crops. We propose a novel method of measuring the exchange of carbon dioxide over croplands using a high-altitude balloon (HAB) platform. The HAB methodology measures two sequential vertical profiles of carbon dioxide mixing ratio, and the surface exchange is calculated using a fixed-mass column approach. This methodology is relatively inexpensive, does not rely on any assumptions besides spatial homogeneity (no horizontal advection) and provides data over a spatial scale between stationary flux towers and satellite-based inversion calculations. The HAB methodology was employed during the 2014 and 2015 growing seasons in central Illinois, and the results are compared to satellite-based NDVI values and a flux tower located relatively near the launch site in Bondville, Illinois. These initial favorable results demonstrate the utility of the methodology for providing carbon dioxide exchange data over a large (10-100 km) spatial area. One drawback is its relatively limited temporal coverage. While recruiting citizen scientists to perform the launches could provide a more extensive dataset, the HAB methodology is not appropriate for providing estimates of net annual carbon dioxide exchange. Instead, a HAB dataset could provide an important check for upscaling flux tower results and verifying satellite-derived exchange estimates.

  13. Assessment of model estimates of land–atmosphere CO2 exchange across Northern Eurasia

    Directory of Open Access Journals (Sweden)

    M. A. Rawlins

    2015-02-01

    Full Text Available A warming climate is altering land–atmosphere exchanges of carbon, with a potential for increased vegetation productivity as well as the mobilization of permafrost soil carbon stores. Here we investigate land–atmosphere carbon dioxide (CO2 dynamics through analysis of net ecosystem productivity (NEP and its component fluxes of gross primary productivity (GPP and ecosystem respiration (ER and soil carbon residence time, simulated by a set of land surface models (LSMs over a region spanning the drainage basin of northern Eurasia. The retrospective simulations were conducted over the 1960–2009 record and at 0.5° resolution, which is a scale common among many global carbon and climate model simulations. Model performance benchmarks were drawn from comparisons against both observed CO2 fluxes derived from site-based eddy covariance measurements as well as regional-scale GPP estimates based on satellite remote sensing data. The site-based comparisons show the timing of peak GPP to be well simulated. Modest overestimates in model GPP and ER are also found, which are relatively higher for two boreal forest validation sites than the two tundra sites. Across the suite of model simulations, NEP increases by as little as 0.01 to as much as 0.79 g C m−2 yr−2, equivalent to 3 to 340% of the respective model means, over the analysis period. For the multimodel average the increase is 135% of the mean from the first to last ten years of record (1960–1969 vs 2000–2009, with a weakening CO2 sink over the latter decades. Vegetation net primary productivity increased by 8 to 30% from the first to last ten years, contributing to soil carbon storage gains, while model mean residence time for soil organic carbon decreased by 10% (−5 to −16%. This suggests that inputs to the soil carbon pool exceeded losses, resulting in a net gain amid a decrease in residence time. Our analysis points to improvements in model elements controlling vegetation

  14. Atmospheric Lifetime of Fossil Fuel Carbon Dioxide

    Science.gov (United States)

    Archer, David; Eby, Michael; Brovkin, Victor; Ridgwell, Andy; Cao, Long; Mikolajewicz, Uwe; Caldeira, Ken; Matsumoto, Katsumi; Munhoven, Guy; Montenegro, Alvaro; Tokos, Kathy

    2009-05-01

    CO2 released from combustion of fossil fuels equilibrates among the various carbon reservoirs of the atmosphere, the ocean, and the terrestrial biosphere on timescales of a few centuries. However, a sizeable fraction of the CO2 remains in the atmosphere, awaiting a return to the solid earth by much slower weathering processes and deposition of CaCO3. Common measures of the atmospheric lifetime of CO2, including the e-folding time scale, disregard the long tail. Its neglect in the calculation of global warming potentials leads many to underestimate the longevity of anthropogenic global warming. Here, we review the past literature on the atmospheric lifetime of fossil fuel CO2 and its impact on climate, and we present initial results from a model intercomparison project on this topic. The models agree that 20-35% of the CO2 remains in the atmosphere after equilibration with the ocean (2-20 centuries). Neutralization by CaCO3 draws the airborne fraction down further on timescales of 3 to 7 kyr.

  15. Hard Carbon Films Deposited under Various Atmospheres

    Science.gov (United States)

    Wei, M.-K.; Chen, S.-C.; Wu, T. C.; Lee, Sanboh

    1998-03-01

    Using a carbon target ablated with an XeCl-excimer laser under various gas atmospheres at different pressures, hard carbon was deposited on silicon, iron and tungsten carbide substrates. The hardness, friction coefficient, and wear rate of the film against steel are better than pure substrate material, respectively, so that it has potential to be used as a protective coating for micromechanical elements. The influences of gas pressure, gas atmosphere, and power density of laser irradiation on the thermal stability of film were analyzed by means of Raman-spectroscope, time-of-flight method, and optical emission spectrum. It was found that the film deposited under higher pressure has less diamond-like character. The film deposited under rest gas or argon atmosphere was very unstable and looked like a little graphite-like character. The film deposited at high vacuum (10-5 mbar rest gas) was the most stable and looked like the most diamond-like character. The film deposited at higher power density was more diamond-like than that at lower power density.

  16. Legacies of an ice storm on the long-term carbon exchange of a temperate forest

    Science.gov (United States)

    Dunn, A. L.; Morgan, K.

    2010-12-01

    Atmosphere-biosphere exchange of carbon is governed by processes operating on a variety of timescales, from diurnal to seasonal to decadal and beyond. Disturbance events, such as fire, insect outbreaks, and ice storms, are infrequent but exert an impact on atmosphere-biosphere exchanges that may persist for many years. Quantification of the role of these biophysical pulses on carbon exchange is therefore critical to accurately model the global carbon cycle. In this study, we investigate the long-term effect of an ice storm on forest-atmosphere carbon exchange. In December 2008, an ice storm affected Harvard Forest, a temperate forest located in north-central Massachusetts. As a result of this ice storm, tree mortality rates were elevated above the background mortality rate of 0.6 Mg C ha-1 yr-1 measured by Barford et al. (2001). Mortality rates in the year of the ice storm in the study area ranged from 1.1 Mg C ha-1 yr-1 in a 19-year-old forest stand to 8.7 Mg C ha-1 yr-1 in an 84-year-old red pine plantation. The woody debris generated by this disturbance event represented a significant increase in the pool of respirable aboveground carbon. The woody debris respiration model of Liu et al (2006) is used to estimate the legacy of this disturbance event on fluxes of carbon to the atmosphere in future years. Results from this study have implications for modeling carbon cycle response to infrequent, large-scale disturbance events.

  17. High atmosphere-ocean exchange of semivolatile aromatic hydrocarbons

    Science.gov (United States)

    González-Gaya, Belén; Fernández-Pinos, María-Carmen; Morales, Laura; Méjanelle, Laurence; Abad, Esteban; Piña, Benjamin; Duarte, Carlos M.; Jiménez, Begoña; Dachs, Jordi

    2016-06-01

    Polycyclic aromatic hydrocarbons, and other semivolatile aromatic-like compounds, are an important and ubiquitous fraction of organic matter in the environment. The occurrence of semivolatile aromatic hydrocarbons is due to anthropogenic sources such as incomplete combustion of fossil fuels or oil spills, and other biogenic sources. However, their global transport, fate and relevance for the carbon cycle have been poorly assessed, especially in terms of fluxes. Here we report a global assessment of the occurrence and atmosphere-ocean fluxes of 64 polycyclic aromatic hydrocarbons analysed in paired atmospheric and seawater samples from the tropical and subtropical Atlantic, Pacific and Indian oceans. The global atmospheric input of polycyclic aromatic hydrocarbons to the global ocean is estimated at 0.09 Tg per month, four times greater than the input from the Deepwater Horizon spill. Moreover, the environmental concentrations of total semivolatile aromatic-like compounds were 102-103 times higher than those of the targeted polycyclic aromatic hydrocarbons, with a relevant contribution of an aromatic unresolved complex mixture. These concentrations drive a large global deposition of carbon, estimated at 400 Tg C yr-1, around 15% of the oceanic CO2 uptake.

  18. The Role of Chemistry in Atmosphere-Forest Exchange (Invited)

    Science.gov (United States)

    Thornton, J. A.; Wolfe, G. M.; Bouvier-Brown, N. C.; Goldstein, A. H.; Park, J.; McKay, M.; Matross, D. M.; Mao, J.; Brune, W. H.; Lafranchi, B. W.; Browne, E. C.; Min, K.; Wooldridge, P. J.; Cohen, R. C.; Crounse, J.; Faloona, I. C.; Gilman, J. B.; Kuster, W. C.; de Gouw, J. A.; Huisman, A. J.; Keutsch, F. N.

    2010-12-01

    Forest-atmosphere exchange of hydrocarbons, ozone, oxidized nitrogen and other reactive species impacts both atmospheric composition and ecosystem productivity, with broad implications for air quality and climate. Recent interpretations of measured ozone and acyl peroxy nitrate fluxes have inferred that intra-canopy chemistry plays an important role in governing both the sign and magnitude of the atmosphere-forest flux of these compounds. I review these observational insights and present results from a recently constructed 1-D vertically-resolved chemical transport model (CAFE) developed for analysis and interpretation of observations made during the Biosphere Effects on Aerosols and Photochemistry Experiment (BEARPEX). The model incorporates a fully resolved forest canopy; emissions from which are parameterized, in many cases, to match leaf-level and top-of-canopy fluxes measured at the ponderosa pine plantation. Model chemistry is based on the Master Chemical Mechanism (MCM), with several additions to simulate the oxidation of monoterpenes and sesquiterpenes not in the current MCM. The base model underestimates measured noontime OH concentrations by a factor of six. As a result we invoke enhanced OH-recycling from first generation isoprene and 2-methyl-3-buten-2-ol peroxy radicals to reconcile model and observed HOx components. Noting a few other aspects of model performance, I will focus on the model predictions of chemistry-induced fluxes. The model qualitatively reproduces the inferred sensitivity to intra-canopy chemistry for both ozone and acyl peroxy nitrates. In both cases, however, the model underestimates the observed exchange velocity suggesting non-stomatal losses (depositional or chemical) remain underestimated in the canopy. As an example of the potential importance of intra-canopy chemistry, the meteorological and structural characteristics of the forest are varied within the model. An intriguing result is that acyl peroxy nitrate (e.g., PAN) fluxes

  19. Carbon Monoxide Affecting Planetary Atmospheric Chemistry

    Science.gov (United States)

    He, Chao; Horst, Sarah

    2016-10-01

    Atmospheric hazes are present in a range of solar system and extrasolar planetary atmospheres, and organic hazes, such as that in Titan's atmosphere, could be a source of prebiotic molecules.1 However, the chemistry occurring in planetary atmospheres and the resulting chemical structures are still not clear. Numerous experimental simulations2 have been carried out in the laboratory to understand the chemistry in N2/CH4 atmospheres, but very few simulations4 have included CO in their initial gas mixtures, which is an important component in many N2/CH4 atmospheres including Titan, Triton, and Pluto.3 Here we have conducted a series of atmosphere simulation experiments using AC glow discharge (cold plasma) as energy source to irradiate reactions in gas mixtures of CO, CH4, and N2 with a range of CO mixing ratios (from 0, 0.05%, 0.2%, 0.5%, 1%, 2.5%, to 5%) at low temperature (~100 K). Gas phase products are monitored during the reaction by quadrupole mass spectrometer (MS), and solid phase products are analyzed by solution-state nuclear magnetic resonance spectroscopy (NMR). MS results show that with the increase of CO in the initial gases, the production of nitrogenous organic molecules increases while the production of hydrogen molecules decreases in the gas phase. NMR measurements of the solid phase products show that with the increase of CO, hydrogen atoms bonded to nitrogen or oxygen in unsaturated structures increase while those bonded to saturated carbon decrease, which means more unsaturated species and less saturated species formed with the addition of CO. MS and NMR results demonstrate that the inclusion of CO affects the compositions of both gas and solid phase products, indicating that CO has an important impact on the chemistry occurring in our experiments and probably in planetary atmospheres.1. Hörst, S. M., et al. 2012, AsBio, 12, 8092. Cable, M. L., et al. 2012, Chem. Rev., 112, 18823. Lutz, B. L., et al. 1983, Sci, 220, 1374; Greaves, J. S., et al

  20. Charge Exchange Reaction in Dopant-Assisted Atmospheric Pressure Chemical Ionization and Atmospheric Pressure Photoionization.

    Science.gov (United States)

    Vaikkinen, Anu; Kauppila, Tiina J; Kostiainen, Risto

    2016-08-01

    The efficiencies of charge exchange reaction in dopant-assisted atmospheric pressure chemical ionization (DA-APCI) and dopant-assisted atmospheric pressure photoionization (DA-APPI) mass spectrometry (MS) were compared by flow injection analysis. Fourteen individual compounds and a commercial mixture of 16 polycyclic aromatic hydrocarbons were chosen as model analytes to cover a wide range of polarities, gas-phase ionization energies, and proton affinities. Chlorobenzene was used as the dopant, and methanol/water (80/20) as the solvent. In both techniques, analytes formed the same ions (radical cations, protonated molecules, and/or fragments). However, in DA-APCI, the relative efficiency of charge exchange versus proton transfer was lower than in DA-APPI. This is suggested to be because in DA-APCI both dopant and solvent clusters can be ionized, and the formed reagent ions can react with the analytes via competing charge exchange and proton transfer reactions. In DA-APPI, on the other hand, the main reagents are dopant-derived radical cations, which favor ionization of analytes via charge exchange. The efficiency of charge exchange in both DA-APPI and DA-APCI was shown to depend heavily on the solvent flow rate, with best efficiency seen at lowest flow rates studied (0.05 and 0.1 mL/min). Both DA-APCI and DA-APPI showed the radical cation of chlorobenzene at 0.05-0.1 mL/min flow rate, but at increasing flow rate, the abundance of chlorobenzene M(+.) decreased and reagent ion populations deriving from different gas-phase chemistry were recorded. The formation of these reagent ions explains the decreasing ionization efficiency and the differences in charge exchange between the techniques. Graphical Abstract ᅟ.

  1. Assessment of model estimates of land-atmosphere CO2 exchange across Northern Eurasia

    Science.gov (United States)

    Rawlins, M. A.; McGuire, A. D.; Kimball, J. S.; Dass, P.; Lawrence, D.; Burke, E.; Chen, X.; Delire, C.; Koven, C.; MacDougall, A.; Peng, S.; Rinke, A.; Saito, K.; Zhang, W.; Alkama, R.; Bohn, T. J.; Ciais, P.; Decharme, B.; Gouttevin, I.; Hajima, T.; Ji, D.; Krinner, G.; Lettenmaier, D. P.; Miller, P.; Moore, J. C.; Smith, B.; Sueyoshi, T.

    2015-07-01

    A warming climate is altering land-atmosphere exchanges of carbon, with a potential for increased vegetation productivity as well as the mobilization of permafrost soil carbon stores. Here we investigate land-atmosphere carbon dioxide (CO2) cycling through analysis of net ecosystem productivity (NEP) and its component fluxes of gross primary productivity (GPP) and ecosystem respiration (ER) and soil carbon residence time, simulated by a set of land surface models (LSMs) over a region spanning the drainage basin of Northern Eurasia. The retrospective simulations cover the period 1960-2009 at 0.5° resolution, which is a scale common among many global carbon and climate model simulations. Model performance benchmarks were drawn from comparisons against both observed CO2 fluxes derived from site-based eddy covariance measurements as well as regional-scale GPP estimates based on satellite remote-sensing data. The site-based comparisons depict a tendency for overestimates in GPP and ER for several of the models, particularly at the two sites to the south. For several models the spatial pattern in GPP explains less than half the variance in the MODIS MOD17 GPP product. Across the models NEP increases by as little as 0.01 to as much as 0.79 g C m-2 yr-2, equivalent to 3 to 340 % of the respective model means, over the analysis period. For the multimodel average the increase is 135 % of the mean from the first to last 10 years of record (1960-1969 vs. 2000-2009), with a weakening CO2 sink over the latter decades. Vegetation net primary productivity increased by 8 to 30 % from the first to last 10 years, contributing to soil carbon storage gains. The range in regional mean NEP among the group is twice the multimodel mean, indicative of the uncertainty in CO2 sink strength. The models simulate that inputs to the soil carbon pool exceeded losses, resulting in a net soil carbon gain amid a decrease in residence time. Our analysis points to improvements in model elements

  2. Assessment of model estimates of land-atmosphere CO2 exchange across northern Eurasia

    Science.gov (United States)

    Rawlins, M.A.; McGuire, A.D.; Kimball, J.S.; Dass, P.; Lawrence, D.; Burke, E.; Chen, X.; Delire, C.; Koven, C.; MacDougall, A.; Peng, S.; Rinke, A.; Saito, K.; Zhang, W.; Alkama, R.; Bohn, T. J.; Ciais, P.; Decharme, B.; Gouttevin, I.; Hajima, T.; Ji, D.; Krinner, G.; Lettenmaier, D.P.; Miller, P.; Moore, J.C.; Smith, B.; Sueyoshi, T.

    2015-01-01

    A warming climate is altering land-atmosphere exchanges of carbon, with a potential for increased vegetation productivity as well as the mobilization of permafrost soil carbon stores. Here we investigate land-atmosphere carbon dioxide (CO2) cycling through analysis of net ecosystem productivity (NEP) and its component fluxes of gross primary productivity (GPP) and ecosystem respiration (ER) and soil carbon residence time, simulated by a set of land surface models (LSMs) over a region spanning the drainage basin of Northern Eurasia. The retrospective simulations cover the period 1960–2009 at 0.5° resolution, which is a scale common among many global carbon and climate model simulations. Model performance benchmarks were drawn from comparisons against both observed CO2 fluxes derived from site-based eddy covariance measurements as well as regional-scale GPP estimates based on satellite remote-sensing data. The site-based comparisons depict a tendency for overestimates in GPP and ER for several of the models, particularly at the two sites to the south. For several models the spatial pattern in GPP explains less than half the variance in the MODIS MOD17 GPP product. Across the models NEP increases by as little as 0.01 to as much as 0.79 g C m−2 yr−2, equivalent to 3 to 340 % of the respective model means, over the analysis period. For the multimodel average the increase is 135 % of the mean from the first to last 10 years of record (1960–1969 vs. 2000–2009), with a weakening CO2 sink over the latter decades. Vegetation net primary productivity increased by 8 to 30 % from the first to last 10 years, contributing to soil carbon storage gains. The range in regional mean NEP among the group is twice the multimodel mean, indicative of the uncertainty in CO2 sink strength. The models simulate that inputs to the soil carbon pool exceeded losses, resulting in a net soil carbon gain amid a decrease in residence time. Our analysis points to improvements in model

  3. Challenges in quantifying biosphere-atmosphere exchange of nitrogen species

    Energy Technology Data Exchange (ETDEWEB)

    Sutton, M.A. [Centre for Ecology and Hydrology (CEH), Edinburgh Research Station, Bush Estate, Penicuik, EH26 0QB (United Kingdom)], E-mail: ms@ceh.ac.uk; Nemitz, E. [Centre for Ecology and Hydrology (CEH), Edinburgh Research Station, Bush Estate, Penicuik, EH26 0QB (United Kingdom); Erisman, J.W. [ECN, Clean Fossil Fuels, PO Box 1, 1755 ZG Petten (Netherlands); Beier, C. [Riso National Laboratory, PO Box 49, DK-4000 Roskilde (Denmark); Bahl, K. Butterbach [Institute of Meteorology and Climate Research, Atmos. Environ. Research (IMK-IFU), Research Centre Karlsruhe GmbH, Kreuzeckbahnstr. 19, 82467 Garmisch-Partenkirchen (Germany); Cellier, P. [INRA Unite Mixte de Recherche, 78850 Thiverval-Grignon (France); Vries, W. de [Alterra, Green World Research, PO Box 47, 6700 AA Wageningen (Netherlands); Cotrufo, F. [Dip. Scienze Ambientali, Seconda Universita degli Studi di Napoli, via Vivaldi 43, 81100 Caserta (Italy); Skiba, U.; Di Marco, C.; Jones, S. [Centre for Ecology and Hydrology (CEH), Edinburgh Research Station, Bush Estate, Penicuik, EH26 0QB (United Kingdom); Laville, P.; Soussana, J.F.; Loubet, B. [INRA Unite Mixte de Recherche, 78850 Thiverval-Grignon (France); Twigg, M.; Famulari, D. [Centre for Ecology and Hydrology (CEH), Edinburgh Research Station, Bush Estate, Penicuik, EH26 0QB (United Kingdom); Whitehead, J.; Gallagher, M.W. [School of Earth, Atmospheric and Environmental Sciences, University of Manchester, Williamson Building, Oxford Road, Manchester, M13 9PL (United Kingdom); Neftel, A.; Flechard, C.R. [Agroscope FAL Reckenholz, Federal Research Station for Agroecology and Agriculture, PO Box, CH 8046 Zurich (Switzerland)] (and others)

    2007-11-15

    Recent research in nitrogen exchange with the atmosphere has separated research communities according to N form. The integrated perspective needed to quantify the net effect of N on greenhouse-gas balance is being addressed by the NitroEurope Integrated Project (NEU). Recent advances have depended on improved methodologies, while ongoing challenges include gas-aerosol interactions, organic nitrogen and N{sub 2} fluxes. The NEU strategy applies a 3-tier Flux Network together with a Manipulation Network of global-change experiments, linked by common protocols to facilitate model application. Substantial progress has been made in modelling N fluxes, especially for N{sub 2}O, NO and bi-directional NH{sub 3} exchange. Landscape analysis represents an emerging challenge to address the spatial interactions between farms, fields, ecosystems, catchments and air dispersion/deposition. European up-scaling of N fluxes is highly uncertain and a key priority is for better data on agricultural practices. Finally, attention is needed to develop N flux verification procedures to assess compliance with international protocols. - Current N research is separated by form; the challenge is to link N components, scales and issues.

  4. A tenuous carbon dioxide atmosphere on Jupiter's moon Callisto

    Science.gov (United States)

    Carlson, R. W.

    1999-01-01

    An off-limb scan of Callisto was conducted by the Galileo near-infrared mapping spectrometer to search for a carbon dioxide atmosphere. Airglow in the carbon dioxide nu3 band was observed up to 100 kilometers above the surface and indicates the presence of a tenuous carbon dioxide atmosphere with surface pressure of 7.5 x 10(-12) bar and a temperature of about 150 kelvin, close to the surface temperature. A lifetime on the order of 4 years is suggested, based on photoionization and magnetospheric sweeping. Either the atmosphere is transient and was formed recently or some process is currently supplying carbon dioxide to the atmosphere.

  5. Regional-Scale Carbon Flux Partitioning Using Atmospheric Carbonyl Sulfide

    Science.gov (United States)

    Abu-Naser, M.; Campbell, J. E.; Berry, J. A.

    2011-12-01

    Simultaneous analysis of atmospheric concentrations of carbonyl sulfide (COS) and carbon dioxide (CO2) has been proposed as an approach to partitioning gross primary production and respiration fluxes at regional and global scales. The basis for this approach was that the observation and regional gradients in atmospheric CO2 are dominated by net ecosystem fluxes while regional gradients in atmospheric COS are dominated by GPP-related plant uptake. Here we investigate the spatial and temporal gradients in airborne COS and CO2 measurements in comparison to flux estimates from ecosystem models and eddy covariance methods over North America. The spatial gradients in the ecosystem relative uptake (ERU), the normalized ratio of COS and CO2 vertical gradients, were consistent with the theoretical relationship to flux estimates from ecosystem models and eddy covariance methods. The seasonality of the gross primary productivity flux estimates was consistent with airborne observations in the midwestern region but had mixed results in the southeastern region. Inter-annual changes in the ERU and regional drought index data suggested a potential relationship between drought stress and low ratios of gross primary production to net ecosystem exchange.

  6. Physiological parameters controlling plant-atmosphere ammonia exchange

    Science.gov (United States)

    Schjoerring, Jan K.; Husted, Søren; Mattsson, Marie

    Recent advances in characterizing the influence of different physiological and environmental parameters on NH 3 exchange between plants and the atmosphere are presented. A central parameter in controlling the rate and direction of NH 3 fluxes is the NH 3 compensation point. It may vary from below 1 to over 20 nmol NH 3 mol -1 air. High compensation points seem to be a result of high tissue N status, rapid absorption of NH +4 from the root medium and/or low activity of glutamine synthetase, a key enzyme in NH +4 assimilation. These conditions cause the NH +4 concentration in leaf apoplast and leaf cells to increase. The NH 3 compensation point also depends on plant developmental stage with peaks in NH 3 emission related to leaf senescence and N remobilization. The leaf temperature has a profound influence on the NH 3 compensation point: an increase in temperature from 15 to 30°C may cause a plant to switch from being a strong sink for atmospheric NH 3 to being a significant NH 3 source. Stomatal conductance for NH 3 relative to that of water vapour increases with tissue N status and with leaf senescence. At a given leaf temperature, the NH 3 compensation point can be successfully predicted on basis of the pH and NH +4 concentration in the apoplast of the mesophyll cells.

  7. Regional atmospheric CO2 inversion reveals seasonal and geographic differences in Amazon net biome exchange

    NARCIS (Netherlands)

    Alden, C.B.; Miller, J.B.; Gatti, L.V.; Gloor, M.M.; Laan-Luijkx, van der I.T.; Krol, M.C.; Guan, K.; Michalak, A.M.; Touma, T.; Andrew, A.; Basso, L.S.; Correia, C.S.C.; Domingues, L.G.; Joiner, J.; Lyapustin, A.; Peters, W.; Shiga, Y.P.; Thoning, K.; Velde, van der I.R.; Leeuwen van, T.T.; Yadav, V.; Diffenbaugh, N.S.

    2016-01-01

    Understanding tropical rainforest carbon exchange and its response to heat and drought is critical for quantifying the effects of climate change on tropical ecosystems, including global climate–carbon feedbacks. Of particular importance
    for the global carbon budget is net biome exchange of CO2 w

  8. Regional atmospheric CO2 inversion reveals seasonal and geographic differences in Amazon net biome exchange

    NARCIS (Netherlands)

    Alden, Caroline B.; Miller, John B.; Gatti, Luciana V.; Gloor, Manuel M.; Guan, Kaiyu; Michalak, Anna M.; van der Laan-Luijkx, Ingrid T.; Touma, Danielle; Andrews, Arlyn; Basso, Luana S.; Correia, Caio S. C.; Domingues, Lucas G.; Joiner, Joanna; Krol, Maarten C.; Lyapustin, Alexei I.; Peters, Wouter; Shiga, Yoichi P.; Thoning, Kirk; van der Velde, Ivar R.; van Leeuwen, Thijs T.; Yadav, Vineet; Diffenbaugh, Noah S.

    2016-01-01

    Understanding tropical rainforest carbon exchange and its response to heat and drought is critical for quantifying the effects of climate change on tropical ecosystems, including global climate-carbon feedbacks. Of particular importance for the global carbon budget is net biome exchange of CO2 with

  9. A multiscale and multidisciplinary investigation of ecosystem-atmosphere CO2 exchange over the rocky mountains of colorado

    Science.gov (United States)

    Sun, Jielun; Oncley, S.P.; Burns, Sean P.; Stephens, B.B.; Lenschow, D.H.; Campos, T.; Monson, Russell K.; Schimel, D.S.; Sacks, W.J.; De Wekker, S. F. J.; Lai, C.-T.; Lamb, B.; Ojima, D.; Ellsworth, P.Z.; Sternberg, L.S.L.; Zhong, S.; Clements, C.; Moore, D.J.P.; Anderson, D.E.; Watt, A.S.; Hu, Jiawen; Tschudi, M.; Aulenbach, S.; Allwine, E.; Coons, T.

    2010-01-01

    A field study combined with modeling investigation demonstrated that the organization of CO2 transport by mountain terrain strongly affects the regional CO2 budget. Atmospheric dynamics can lead to complicated flows generated by inhomogeneous landscapes, topography or synoptic weather systems. The field campaign conducted of a ground deployment, the Carbon in the Mountain Experiment (CME04), and an aircraft deployment of the national Center for Atmospheric Research (NCAR) C-130, the Airborne Carbon in the Mountains Experiment (ACME04) over the period of spring to fall of 2004 to cover the seasonal variation of ecosystem-atmosphere carbon exchange. The role of the mountain circulation in CO2 transport can be played over seemingly flat terrain by mesoscale flows generated by various physical processes. The three dimensional observation strategy considered can also be applied over flat terrain.

  10. On the quantification of atmospheric carbonate carbon by thermal/optical analysis protocols

    OpenAIRE

    A. Karanasiou; Diapouli, E; Viana, M; Alastuey, A.; Querol, X.; C. Reche; Eleftheriadis, K.

    2010-01-01

    Carbonaceous species, usually classified into two categories, organic carbon (OC) and elemental carbon (EC), constitute an important component of the atmospheric aerosol. Carbonate carbon (CC), or inorganic carbon, another constituent of carbonaceous material, is often not considered in many atmospheric chemistry studies. The reason for this may be its low contribution to fine particle mass in most areas studied, along with the difficulties in its analytical determination in atmospheric aeros...

  11. Carbon cycle: A hump in ocean-air exchange

    Science.gov (United States)

    Reddy, Christopher M.

    2016-06-01

    Semivolatile organic compounds from fossil fuels or incomplete combustion are ubiquitous. A suite of circumglobal measurements of their oceanic and atmospheric concentrations reveals large carbon fluxes through the deposition of these compounds.

  12. Marine atmospheric corrosion of carbon steels

    Directory of Open Access Journals (Sweden)

    Morcillo, Manuel

    2015-06-01

    Full Text Available Basic research on marine atmospheric corrosion of carbon steels is a relatively young scientific field and there continue to be great gaps in this area of knowledge. The presence of akaganeite in the corrosion products that form on steel when it is exposed to marine atmospheres leads to a notable increase in the corrosion rate. This work addresses the following issues: (a environmental conditions necessary for akaganeite formation; (b characterisation of akaganeite in the corrosion products formed; (c corrosion mechanisms of carbon steel in marine atmospheres; (d exfoliation of rust layers formed in highly aggressive marine atmospheres; (e long-term corrosion rate prediction; and (f behaviour of weathering steels. Field research has been carried out at Cabo Vilano wind farm (Camariñas, Galicia in a wide range of atmospheric salinities and laboratory work involving the use of conventional atmospheric corrosion techniques and near-surface and bulk sensitive analytical techniques: scanning electron microscopy (SEM/energy dispersive spectrometry (EDS, X-ray diffraction (XRD, Mössbauer spectroscopy and SEM/μRaman spectroscopy.La investigación fundamental en corrosión atmosférica marina de aceros al carbono es un campo científico relativamente joven que presenta grandes lagunas de conocimiento. La formación de akaganeíta en los productos de corrosión que se forman sobre el acero cuando se expone a atmósferas marinas conduce a un incremento notable de la velocidad de corrosión. En el trabajo se abordan las siguientes cuestiones: (a condiciones ambientales necesarias para la formación de akaganeíta, (b caracterización de la akaganeíta en los productos de corrosión formados, (c mecanismos de corrosión del acero al carbono en atmósferas marinas, (d exfoliación de las capas de herrumbre formadas en atmósferas marinas muy agresivas, (e predicción de la velocidad de corrosión a largo plazo, y (f comportamiento de aceros patinables. La

  13. Upper-ocean-to-atmosphere radiocarbon offsets imply fast deglacial carbon dioxide release.

    Science.gov (United States)

    Rose, Kathryn A; Sikes, Elisabeth L; Guilderson, Thomas P; Shane, Phil; Hill, Tessa M; Zahn, Rainer; Spero, Howard J

    2010-08-26

    Radiocarbon in the atmosphere is regulated largely by ocean circulation, which controls the sequestration of carbon dioxide (CO(2)) in the deep sea through atmosphere-ocean carbon exchange. During the last glaciation, lower atmospheric CO(2) levels were accompanied by increased atmospheric radiocarbon concentrations that have been attributed to greater storage of CO(2) in a poorly ventilated abyssal ocean. The end of the ice age was marked by a rapid increase in atmospheric CO(2) concentrations that coincided with reduced (14)C/(12)C ratios (Delta(14)C) in the atmosphere, suggesting the release of very 'old' ((14)C-depleted) CO(2) from the deep ocean to the atmosphere. Here we present radiocarbon records of surface and intermediate-depth waters from two sediment cores in the southwest Pacific and Southern oceans. We find a steady 170 per mil decrease in Delta(14)C that precedes and roughly equals in magnitude the decrease in the atmospheric radiocarbon signal during the early stages of the glacial-interglacial climatic transition. The atmospheric decrease in the radiocarbon signal coincides with regionally intensified upwelling and marine biological productivity, suggesting that CO(2) released by means of deep water upwelling in the Southern Ocean lost most of its original depleted-(14)C imprint as a result of exchange and isotopic equilibration with the atmosphere. Our data imply that the deglacial (14)C depletion previously identified in the eastern tropical North Pacific must have involved contributions from sources other than the previously suggested carbon release by way of a deep Southern Ocean pathway, and may reflect the expanded influence of the (14)C-depleted North Pacific carbon reservoir across this interval. Accordingly, shallow water masses advecting north across the South Pacific in the early deglaciation had little or no residual (14)C-depleted signals owing to degassing of CO(2) and biological uptake in the Southern Ocean.

  14. Variability in carbon exchange of European croplands

    NARCIS (Netherlands)

    Moors, E.J.; Jacobs, C.M.J.; Jans, W.W.P.; Supit, I.; Werners, S.E.; Kutsch, W.L.; Elbers, J.A.; Kruijt, B.

    2010-01-01

    The estimated net ecosystem exchange (NEE) of CO2 based on measurements at 17 flux sites in Europe for 45 cropping periods showed an average loss of -38 gC m-2 per cropping period. The cropping period is defined as the period after sowing or planting until harvest. The variability taken as the stand

  15. Oxygen Atom Recombination in Carbon Dioxide Atmospheres

    Science.gov (United States)

    Jamieson, Corey; Garcia, R. M.; Pejakovic, D. A.; Kalogerakis, K. S.

    2009-09-01

    Understanding processes involving atomic oxygen is crucial for the study and modeling of composition, energy transfer, airglow, and transport dynamics in planetary atmospheres. Significant gaps and uncertainties exist in our understanding of the above processes, and often the relevant input from laboratory measurements is missing or outdated. We are conducting experiments to measure the rate coefficients for O + O + CO2 and O + O2 + CO2 recombination and investigate the O2 excited states produced following O-atom recombination. These laboratory measurements are key input for a quantitative understanding and reliable modeling of the atmospheres of the CO2 planets and their airglow. An ArF excimer laser with 193-nm pulsed output radiation is employed to partially photodissociate carbon dioxide. In an ambient-pressure (760 Torr) background of CO2, the O atoms produced recombine in a time scale of a few milliseconds. Detection of laser-induced fluorescence at 845 nm following two-photon excitation near 226 nm monitors the decay of the oxygen atom population. From the temporal evolution of the signal we can extract the rate coefficients for recombination of O + O and O + O2 in the presence of CO2. We also use fluorescence and resonance-enhanced multi-photon ionization techniques to detect the products of the O-atom recombination and subsequent relaxation in CO2. This work is supported by the US National Science Foundation's (NSF) Planetary Astronomy Program. Rosanne Garcia's participation was funded by the NSF Research Experiences for Undergraduates (REU) Program.

  16. The effect of atmospheric aerosol particles and clouds on net ecosystem exchange in the Amazon

    Science.gov (United States)

    Cirino, G. G.; Souza, R. A. F.; Adams, D. K.; Artaxo, P.

    2014-07-01

    Carbon cycling in the Amazon is closely linked to atmospheric processes and climate in the region as a consequence of the strong coupling between the atmosphere and biosphere. This work examines the effects of changes in net radiation due to atmospheric aerosol particles and clouds on the net ecosystem exchange (NEE) of CO2 in the Amazon region. Some of the major environmental factors affecting the photosynthetic activity of plants, such as air temperature and relative humidity, were also examined. An algorithm for clear-sky irradiance was developed and used to determine the relative irradiance, f, which quantifies the percentage of solar radiation absorbed and scattered due to atmospheric aerosol particles and clouds. Aerosol optical depth (AOD) was calculated from irradiances measured with the MODIS (Moderate Resolution Imaging Spectroradiometer) sensor, onboard the Terra and Aqua satellites, and was validated with ground-based AOD measurements from AERONET (Aerosol Robotic Network) sun photometers. Carbon fluxes were measured using eddy covariance technique at the Large-Scale Biosphere-Atmosphere Experiment in Amazonia (LBA) flux towers. Two sites were studied: the Jaru Biological Reserve (RBJ), located in Rondonia, and the Cuieiras Biological Reserve at the K34 LBA tower (located in a preserved region in the central Amazon). Analysis was performed continuously from 1999 to 2009 at K34 and from 1999 to 2002 at RBJ, and includes wet, dry and transition seasons. In the Jaru Biological Reserve, a 29% increase in carbon uptake (NEE) was observed when the AOD ranged from 0.10 to 1.5 at 550 nm. In the Cuieiras Biological Reserve, the aerosol effect on NEE was smaller, accounting for an approximate 20% increase in NEE. High aerosol loading (AOD above 3 at 550 nm) or high cloud cover leads to reductions in solar flux and strong decreases in photosynthesis up to the point where NEE approaches zero. The observed increase in NEE is attributed to an enhancement (~50%) in

  17. The effect of atmospheric aerosol particles and clouds on Net Ecosystem Exchange in Amazonia

    Science.gov (United States)

    Cirino, G. G.; Souza, R. F.; Adams, D. K.; Artaxo, P.

    2013-11-01

    Carbon cycling in Amazonia is closely linked to atmospheric processes and climate in the region as a consequence of the strong coupling between the atmosphere and biosphere. This work examines the effects of changes in net radiation due to atmospheric aerosol particles and clouds on the Net Ecosystem Exchange (NEE) of CO2 in the Amazon region. Some of the major environmental factors affecting the photosynthetic activity of plants, such as air temperature and relative humidity were also examined. An algorithm for clear-sky irradiance was developed and used to determine the relative irradiance f, which quantifies the percentage of solar radiation absorbed and scattered due to atmospheric aerosol particles and clouds. Aerosol optical depth (AOD) was calculated from irradiances measured with the MODIS (Moderate Resolution Imaging Spectroradiometer) sensor, onboard the TERRA and AQUA satellites, and was validated with ground-based AOD measurements from AERONET sun photometers. Carbon fluxes were measured using eddy-correlation techniques at LBA (The Large Scale Biosphere-Atmosphere Experiment in Amazonia) flux towers. Two sites were studied: the Biological Reserve of Jaru (located in Rondonia) and the Cuieiras Biological Reserve (located in a preserved region in central Amazonia). In the Jaru Biological Reserve, a 29% increase in carbon uptake (NEE) was observed when the AOD ranged from 0.10 to 1.5. In the Cuieiras Biological Reserve, this effect was smaller, accounting for an approximately 20% increase in NEE. High aerosol loading (AOD above 3 at 550 nm) or cloud cover leads to reductions in solar flux and strong decreases in photosynthesis up to the point where NEE approaches 0. The observed increase in NEE is attributed to an enhancement (~50%) in the diffuse fraction of photosynthetic active radiation (PAR). Significant changes in air temperature and relative humidity resulting from changes in solar radiation fluxes under high aerosol loading were also observed at

  18. North America's net terrestrial CO2 exchange with the atmosphere 1990-2009

    Science.gov (United States)

    King, A. W.; Andres, R. J.; Davis, K. J.; Hafer, M.; Hayes, D. J.; Huntzinger, D. N.; de Jong, B.; Kurz, W. A.; McGuire, A. D.; Vargas, R.; Wei, Y.; West, T. O.; Woodall, C. W.

    2015-01-01

    Scientific understanding of the global carbon cycle is required for developing national and international policy to mitigate fossil fuel CO2 emissions by managing terrestrial carbon uptake. Toward that understanding and as a contribution to the REgional Carbon Cycle Assessment and Processes (RECCAP) project, this paper provides a synthesis of net land-atmosphere CO2 exchange for North America (Canada, United States, and Mexico) over the period 1990-2009. Only CO2 is considered, not methane or other greenhouse gases. This synthesis is based on results from three different methods: atmospheric inversion, inventory-based methods and terrestrial biosphere modeling. All methods indicate that the North American land surface was a sink for atmospheric CO2, with a net transfer from atmosphere to land. Estimates ranged from -890 to -280 Tg C yr-1, where the mean of atmospheric inversion estimates forms the lower bound of that range (a larger land sink) and the inventory-based estimate using the production approach the upper (a smaller land sink). This relatively large range is due in part to differences in how the approaches represent trade, fire and other disturbances and which ecosystems they include. Integrating across estimates, "best" estimates (i.e., measures of central tendency) are -472 ± 281 Tg C yr-1 based on the mean and standard deviation of the distribution and -360 Tg C yr-1 (with an interquartile range of -496 to -337) based on the median. Considering both the fossil fuel emissions source and the land sink, our analysis shows that North America was, however, a net contributor to the growth of CO2 in the atmosphere in the late 20th and early 21st century. With North America's mean annual fossil fuel CO2 emissions for the period 1990-2009 equal to 1720 Tg C yr-1 and assuming the estimate of -472 Tg C yr-1 as an approximation of the true terrestrial CO2 sink, the continent's source : sink ratio for this time period was 1720:472, or nearly 4:1.

  19. North America's net terrestrial CO2 exchange with the atmosphere 1990–2009

    Science.gov (United States)

    King, A.W.; Andres, R.J.; Davis, K.J.; Hafer, M.; Hayes, D.J.; Huntzinger, Deborah N.; de Jong, Bernardus; Kurz, W.A.; McGuire, Anthony; Vargas, Rodrigo I.; Wei, Y.; West, Tristram O.; Woodall, Christopher W.

    2015-01-01

    Scientific understanding of the global carbon cycle is required for developing national and international policy to mitigate fossil fuel CO2 emissions by managing terrestrial carbon uptake. Toward that understanding and as a contribution to the REgional Carbon Cycle Assessment and Processes (RECCAP) project, this paper provides a synthesis of net land–atmosphere CO2 exchange for North America (Canada, United States, and Mexico) over the period 1990–2009. Only CO2 is considered, not methane or other greenhouse gases. This synthesis is based on results from three different methods: atmospheric inversion, inventory-based methods and terrestrial biosphere modeling. All methods indicate that the North American land surface was a sink for atmospheric CO2, with a net transfer from atmosphere to land. Estimates ranged from −890 to −280 Tg C yr−1, where the mean of atmospheric inversion estimates forms the lower bound of that range (a larger land sink) and the inventory-based estimate using the production approach the upper (a smaller land sink). This relatively large range is due in part to differences in how the approaches represent trade, fire and other disturbances and which ecosystems they include. Integrating across estimates, "best" estimates (i.e., measures of central tendency) are −472 ± 281 Tg C yr−1 based on the mean and standard deviation of the distribution and −360 Tg C yr−1 (with an interquartile range of −496 to −337) based on the median. Considering both the fossil fuel emissions source and the land sink, our analysis shows that North America was, however, a net contributor to the growth of CO2 in the atmosphere in the late 20th and early 21st century. With North America's mean annual fossil fuel CO2 emissions for the period 1990–2009 equal to 1720 Tg C yr−1 and assuming the estimate of −472 Tg C yr−1 as an approximation of the true terrestrial CO2 sink, the continent's source : sink ratio for this time period was

  20. Microchannel Heat Exchangers with Carbon Dioxide

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, Y.; Ohadi, M.M.; Radermacher, R.

    2001-09-15

    The objective of the present study was to determine the performance of CO{sub 2} microchannel evaporators and gas coolers in operational conditions representing those of residential heat pumps. A set of breadboard prototype microchannel evaporators and gas coolers was developed and tested. The refrigerant in the heat exchangers followed a counter cross-flow path with respect to the airflow direction. The test conditions corresponded to the typical operating conditions of residential heat pumps. In addition, a second set of commercial microchannel evaporators and gas coolers was tested for a less comprehensive range of operating conditions. The test results were reduced and a comprehensive data analysis, including comparison with the previous studies in this field, was performed. Capacity and pressure drop of the evaporator and gas cooler for the range of parameters studied were analyzed and are documented in this report. A gas cooler performance prediction model based on non-dimensional parameters was also developed and results are discussed as well. In addition, in the present study, experiments were conducted to evaluate capacities and pressure drops for sub-critical CO{sub 2} flow boiling and transcritical CO{sub 2} gas cooling in microchannel heat exchangers. An extensive review of the literature failed to indicate any previous systematic study in this area, suggesting a lack of fundamental understanding of the phenomena and a lack of comprehensive data that would quantify the performance potential of CO{sub 2} microchannel heat exchangers for the application at hand. All experimental tests were successfully conducted with an energy balance within {+-}3%. The only exceptions to this were experiments at very low saturation temperatures (-23 C), where energy balances were as high as 10%. In the case of evaporators, it was found that a lower saturation temperature (especially when moisture condensation occurs) improves the overall heat transfer coefficient

  1. Spatio-temporal patterns of forest carbon dioxide exchange based on global eddy covariance measurements

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    Spatio-temporal patterns and driving mechanisms of forest carbon dioxide (CO2) exchange are the key issues on terrestrial ecosystem carbon cycles, which are the basis for developing and validating ecosystem carbon cycle models, assessing and predicting the role of forests in global carbon balance. Eddy covariance (EC) technique, an important method for measuring energy and material exchanges between terrestrial ecosystems and the atmosphere, has made a great contribution to understanding CO2 exchanges in the biosphere during the past decade. Here, we synthesized published EC flux measurements at various forest sites in the global network of eddy flux tower sites (FLUXNET) and regional flux networks. Our objective was to explore spatio-temporal patterns and driving factors on forest carbon fluxes, i.e. net ecosystem productivity (NEP), gross primary productivity (GPP) and total ecosystem respiration (TER). Globally, forest NEP exhibited a significant latitudinal pattern jointly controlled by GPP and TER. The NEP decreased in an order of warm temperate forest > cold temperate and tropical rain forests > boreal and subalpine forests. Mean annual temperature (MAT) made a greater contribution to forest carbon fluxes than sum of annual precipitation (SAP). As MAT increased, the GPP increased linearly, whereas the TER increased exponentially, resulting in the NEP decreasing beyond an MAT threshold of 20°C. The GPP, TER and NEP varied substantially when the SAP was less than 1500 mm, but tended to increase with increasing SAP. Temporal dynamics in forest carbon fluxes and determinants depended upon time scales. NEP showed a significant interannual variability mainly driven by climate fluctuations and different responses of the GPP and TER to environmental forcing. In a longer term, forest carbon fluxes had a significant age effect. The ecosystem was a net carbon source right after clearcutting, gradually switched to a net carbon sink when the relative stand age (i

  2. Preliminary Assessment of Mercury Atmosphere-Surface Exchange Parameterizations for Incorporation into Chemical Transport Models

    Science.gov (United States)

    Khan, T.; Agnan, Y.; Obrist, D.; Selin, N. E.; Urban, N. R.; Wu, S.; Perlinger, J. A.

    2015-12-01

    Inadequate representation of process-based mechanisms of exchange behavior of elemental mercury (Hg0) and decoupled treatment of deposition and emission are two major limitations of parameterizations of atmosphere-surface exchange flux commonly incorporated into chemical transport models (CTMs). Of nineteen CTMs for Hg0 exchange we reviewed (ten global, nine regional), eight global and seven regional models have decoupled treatment of Hg0 deposition and emission, two global models include no parameterization to account for emission, and the remaining two regional models include coupled deposition and emission parameterizations (i.e., net atmosphere-surface exchange). The performance of atmosphere-surface exchange parameterizations in CTMs depends on parameterization uncertainty (in terms of both accuracy and precision) and feasibility of implementation. We provide a comparison of the performance of three available parameterizations of net atmosphere-surface exchange. To evaluate parameterization accuracy, we compare predicted exchange fluxes to field measurements conducted over a variety of surfaces compiled in a recently developed global database of terrestrial Hg0 surface-atmosphere exchange flux measurements. To assess precision, we estimate the sensitivity of predicted fluxes to the imprecision in parameter input values, and compare this sensitivity to that derived from analysis of the global Hg0 flux database. Feasibility of implementation is evaluated according to the availability of input parameters, computational requirements, and the adequacy of uncertainty representation. Based on this assessment, we provide suggestions for improved treatment of Hg0 net exchange processes in CTMs.

  3. Equal exchange: Determining a fair price for carbon

    Energy Technology Data Exchange (ETDEWEB)

    Hodes, G.; Kamel, S.

    2007-12-14

    This first volume in the new series CD4CDM Perspective Series focuses on determining an equal exchange between carbon buyers and sellers in CDM transactions. Contributors to this volume represent a wide spectrum of the various market actors that are interacting in order to realize both successful and equitable carbon transactions. The following issues are discussed: Global carbon price dynamics; CDM project risk profiles and/or premiums; Importance of time factors and delivery guarantees; Impact of regulatory drivers and post-Kyoto outlook; Region-specific outlooks; Strategies, contracting models and approaches. (BA)

  4. Carbon isotopes characterize rapid changes in atmospheric carbon dioxide during the last deglaciation

    Science.gov (United States)

    Bauska, Thomas K.; Baggenstos, Daniel; Brook, Edward J.; Mix, Alan C.; Marcott, Shaun A.; Petrenko, Vasilii V.; Schaefer, Hinrich; Lee, James E.

    2016-01-01

    An understanding of the mechanisms that control CO2 change during glacial–interglacial cycles remains elusive. Here we help to constrain changing sources with a high-precision, high-resolution deglacial record of the stable isotopic composition of carbon in CO2 (δ13C-CO2) in air extracted from ice samples from Taylor Glacier, Antarctica. During the initial rise in atmospheric CO2 from 17.6 to 15.5 ka, these data demarcate a decrease in δ13C-CO2, likely due to a weakened oceanic biological pump. From 15.5 to 11.5 ka, the continued atmospheric CO2 rise of 40 ppm is associated with small changes in δ13C-CO2, consistent with a nearly equal contribution from a further weakening of the biological pump and rising ocean temperature. These two trends, related to marine sources, are punctuated at 16.3 and 12.9 ka with abrupt, century-scale perturbations in δ13C-CO2 that suggest rapid oxidation of organic land carbon or enhanced air–sea gas exchange in the Southern Ocean. Additional century-scale increases in atmospheric CO2 coincident with increases in atmospheric CH4 and Northern Hemisphere temperature at the onset of the Bølling (14.6–14.3 ka) and Holocene (11.6–11.4 ka) intervals are associated with small changes in δ13C-CO2, suggesting a combination of sources that included rising surface ocean temperature. PMID:26976561

  5. Two perspectives on the coupled carbon, water, and energy exchange in the planetary boundary layer

    Directory of Open Access Journals (Sweden)

    M. Combe

    2014-04-01

    Full Text Available Understanding the interactions between the land surface and the atmosphere is key to model boundary-layer meteorology and cloud formation, as well as carbon cycling and crop yield. In this study we explore these interactions in the exchange of water, heat, and CO2 in a cropland–atmosphere system at the diurnal and local scale. We thereto couple an atmospheric mixed-layer model (MXL to two land-surface schemes, developed from two different perspectives: while one land-surface scheme (A-gs simulates vegetation from an atmospheric point of view, the other (GECROS simulates vegetation from a carbon-storage point of view. We calculate surface fluxes of heat, moisture and carbon, as well as the resulting atmospheric state and boundary-layer dynamics, over a maize field in the Netherlands, for a day on which we have a rich set of observations available. Particular emphasis is placed on understanding the role of upper atmosphere conditions like subsidence, in comparison to the role of surface forcings like soil moisture. We show that the atmospheric-oriented model (MXL-A-gs outperforms the carbon storage-oriented model (MXL-GECROS on this diurnal scale. This performance strongly depends on the sensitivity of the modelled stomatal conductance to water stress, which is implemented differently in each model. This sensitivity also influences the magnitude of the surface fluxes of CO2, water and heat (surface control, and subsequently impacts the boundary-layer growth and entrainment fluxes (upper atmosphere control, which alter the atmospheric state. These findings suggest that observed CO2 mole fractions in the boundary layer can reflect strong influences of both the surface and upper atmospheric conditions, and the interpretation of CO2 mole fraction variations depends on the assumed land-surface coupling. We illustrate this with a sensitivity analysis where increased subsidence, typical for periods of drought, can induce a change of 12 ppm in

  6. Carbon monoxide exchange and partitioning of a managed mountain meadow

    Science.gov (United States)

    Hammerle, Albin; Kitz, Florian; Spielmann, Felix; Gerdel, Katharina; Wohlfahrt, Georg

    2016-04-01

    With an average mole fraction of 100 ppb carbon monoxide (CO) plays a critical role in atmospheric chemistry and thus has an indirect global warming potential. While sources/sinks of CO on land at least partially cancel out each other, the magnitude of CO sources and sinks is highly uncertain. Even if direct CO fluxes from/to land ecosystems are very much likely clearly lower in magnitude compared to anthropogenic emissions, biomass burning, emissions from chemical precursors and the OH sink, it may be premature to neglect any direct contributions of land ecosystems to the CO budget. In addition, changes in global climate and resulting changes in global productivity may require re-evaluating older data and assumptions. One major reason for the large uncertainty is a general scarcity of empirical data. An additional factor contributing to the uncertainty is the lack of ecosystem-scale CO exchange measurements, i.e. CO flux data that encompass all sources and sinks within an ecosystem. Here we present data on continuous eddy covariance measurements of CO-fluxes above a managed mountain grassland in combination with soil chamber flux measurements, within- and above-canopy concentration profiles and an inverse Lagrangian analysis to disentangle sinks and sources of CO. Results show the grassland ecosystem to be a net source for CO during daytime, with increasing flux rates at higher solar radiation. At night, if at all, the meadow is a slight sink for CO. The same holds true regarding the soil flux measurements. Additionally, a two-month rainout experiment revealed hardly any differences in CO soil fluxes between rainout- and control-plots unless extremely dry conditions were reached.

  7. Exchange equilibria between bicarbonate, carbonate, chloride and bromide on dowex 1 x 8.

    Science.gov (United States)

    Lundström, U; Olin, A

    1984-07-01

    The exchange reaction 2R(+)HCO(3)(2-) + CO(3)(2-) right harpoon over left harpoon R(2)(+) CO(3)(2-) + 2HCO(3)(2-) has been studied on Dowex 1 x 8 in the presence of bicarbonate solution in equilibrium with atmospheric carbon dioxide (open system). The experiments showed, as theory predicts, that the composition of the resin phase is independent of the concentration of the bicarbonate solution. The mole fraction of carbonate at equilibrium is about 0.4 and the equilibrium constant is 0.15M at 20 degrees . With this value of the constant, the composition of the ion-exchanger for various bicarbonate concentrations has been calculated for a closed system. At [HCO(3)(-)] Chromatographie enrichment of bromide from fresh water.

  8. Process Model for Studying Regional 13C Stable Isotope Exchange between Vegetation and Atmosphere

    Science.gov (United States)

    Chen, J. M.; Chen, B.; Huang, L.; Tans, P.; Worthy, D.; Ishizawa, M.; Chan, D.

    2007-12-01

    The variation of the stable isotope 13CO2 in the air in exchange with land ecosystems results from fractionation processes in both plants and soil during photosynthesis and respiration. Its diurnal and seasonal variations therefore contain information on the carbon cycle. We developed a model (BEPS-iso) to simulate its exchange between vegetation and the atmosphere. To be useful for regional carbon cycle studies, the model has the following characteristics: (i) it considers the turbulent mixing in the vertical profile from the soil surface to the top of the planetary boundary layer (PBL); (ii) it scales individual leaf photosynthetic discrimination to the whole canopy through the separation of sunlit and shaded leaf groups; (iii) through simulating leaf-level photosynthetic processes, it has the capacity to mechanistically examine isotope discrimination resulting from meteorological forcings, such as radiation, precipitation and humidity; and (iv) through complete modeling of radiation, energy and water fluxes, it also simulates soil moisture and temperature needed for estimating ecosystem respiration and the 13C signal from the soil. After validation using flask data acquired at 20 m level on a tower near Fraserdale, Ontario, Canada, during intensive campaigns (1998-2000), the model has been used for several purposes: (i) to investigate the diurnal and seasonal variations in the disequilibrium in 13C fractionation between ecosystem respiration and photosynthesis, which is an important step in using 13C measurements to separate these carbon cycle components; (ii) to quantify the 13C rectification in the PBL, which differs significantly from CO2 rectification because of the diurnal and seasonal disequilibriums; and (iii) to model the 13C spatial and temporal variations over the global land surface for the purpose of CO2 inversion using 13C as an additional constraint.

  9. Atomistic modeling of carbon Cottrell atmospheres in bcc iron

    Science.gov (United States)

    Veiga, R. G. A.; Perez, M.; Becquart, C. S.; Domain, C.

    2013-01-01

    Atomistic simulations with an EAM interatomic potential were used to evaluate carbon-dislocation binding energies in bcc iron. These binding energies were then used to calculate the occupation probability of interstitial sites in the vicinity of an edge and a screw dislocation. The saturation concentration due to carbon-carbon interactions was also estimated by atomistic simulations in the dislocation core and taken as an upper limit for carbon concentration in a Cottrell atmosphere. We obtained a maximum concentration of 10 ± 1 at.% C at T = 0 K within a radius of 1 nm from the dislocation lines. The spatial carbon distributions around the line defects revealed that the Cottrell atmosphere associated with an edge dislocation is denser than that around a screw dislocation, in contrast with the predictions of the classical model of Cochardt and colleagues. Moreover, the present Cottrell atmosphere model is in reasonable quantitative accord with the three-dimensional atom probe data available in the literature.

  10. Dissolved inorganic carbon and stable carbon isotopic evolution of neutral mine drainage interacting with atmospheric CO{sub 2(g)}

    Energy Technology Data Exchange (ETDEWEB)

    Abongwa, Pride Tamasang, E-mail: abongwa@okstate.edu; Atekwana, Eliot Anong; Puckette, James

    2016-03-01

    We investigated the spatial variations in the concentrations of dissolved inorganic carbon (DIC), the stable carbon isotopic composition (δ{sup 13}C) of DIC and the δ{sup 13}C of carbonate precipitated from neutral mine drainage interacting with the atmospheric CO{sub 2(g)}. We assessed the chemical, DIC and δ{sup 13}C{sub DIC} evolution of the mine drainage and the δ{sup 13}C evolution of carbonate precipitates for a distance of 562 m from the end of an 8 km tunnel that drains a mine. Our results show that as the mine drainage interacts with atmospheric CO{sub 2(g)} the outgassing of CO{sub 2} due to the high initial partial pressure of CO{sub 2} (pCO{sub 2}) causes the DIC to evolve under kinetic conditions followed by equilibration and then under equilibrium conditions. The carbonate evolution was characterized by spatial increases in pH, decreasing concentrations of Ca{sup 2+} and DIC and by the precipitation of carbonate. The δ{sup 13}C{sub DIC} showed a larger enrichment from the tunnel exit to 38 m, moderate continuous enrichment to 318 m and almost no enrichment to 562 m. On the other hand, the δ{sup 13}C of the carbonate precipitates also showed large enrichment from the tunnel exit to 38 m, moderate enrichment to 318 m after which the δ{sup 13}C remained nearly constant. The enrichment in the δ{sup 13}C of the DIC and the carbonate precipitates from 0 to 38 m from kinetic fractionation caused by CO{sub 2(g)} outgassing was followed by a mix of kinetic fractionation and equilibrium fractionation controlled by carbon exchange between DIC and atmospheric CO{sub 2(g)} to 318 m and then by equilibrium fractionation from 318 to 562 m. From the carbonate evolution in this neutral mine drainage, we estimated that 20% of the carbon was lost via CO{sub 2} outgassing, 12% was sequestered in sediments in the drainage ponds from calcite precipitation and the remainder 68% was exported to the local stream. - Highlights: • We assess the δ{sup 13}C in a

  11. Heat exchange performance of stainless steel and carbon foams modified with carbon nano fibers

    NARCIS (Netherlands)

    Tuzovskaya, I.; Pacheco Benito, S.; Chinthaginjala, J.K.; Reed, C.P.; Lefferts, L.; Meer, van der T.H.

    2012-01-01

    Carbon nanofibers (CNF), with fishbone and parallel wall structures, were grown by catalytic chemical vapor deposition on the surface of carbon foam and stainless steel foam, in order to improve their heat exchange performance. Enhancement in heat transfer efficiency between 30% and 75% was achieved

  12. Carbon Dioxide in Exoplanetary Atmospheres: Rarely Dominant Compared to Carbon Monoxide and Water

    CERN Document Server

    Heng, Kevin

    2015-01-01

    We present a comprehensive study of the abundance of carbon dioxide in exoplanetary atmospheres. We construct analytical models of systems in chemical equilibrium that include carbon monoxide, carbon dioxide, water, methane and acetylene and relate the equilibrium constants of the chemical reactions to temperature and pressure via the tabulated Gibbs free energies. We prove that such chemical systems may be described by a quintic equation for the mixing ratio of methane. By examining the abundances of these molecules across a broad range of temperatures (spanning equilibrium temperatures from 600 to 2500 K), pressures (via temperature-pressure profiles that explore albedo and opacity variations) and carbon-to-oxygen ratios (from 0.1 to 100), we conclude that carbon dioxide is subdominant compared to carbon monoxide and water. Atmospheric mixing does not alter this conclusion if carbon dioxide is subdominant everywhere in the atmosphere. Carbon dioxide and carbon monoxide may attain comparable abundances if th...

  13. In-pore exchange and diffusion of carbonate solvent mixtures in nanoporous carbon

    Science.gov (United States)

    Alam, Todd M.; Osborn Popp, Thomas M.

    2016-08-01

    High resolution magic angle spinning (HRMAS) 1H NMR spectroscopy has been used to resolve different surface and in-pore solvent environments of ethylene carbonate (EC) and dimethyl carbonate (DMC) mixtures absorbed within nanoporous carbon (NPC). Two dimensional (2D) 1H HRMAS NMR exchange measurements revealed that the inhomogeneous broadened in-pore resonances have pore-to-pore exchange rates on the millisecond timescale. Pulsed-field gradient (PFG) NMR diffusometry revealed the in-pore self-diffusion constants for both EC and DMC were reduced by up to a factor of five with respect to the diffusion in the non-absorbed solvent mixtures.

  14. Atmospheric pressure plasma surface modification of carbon fibres

    DEFF Research Database (Denmark)

    Kusano, Yukihiro; Løgstrup Andersen, Tom; Michelsen, Poul

    2008-01-01

    Carbon fibres are continuously treated with dielectric barrier discharge plasma at atmospheric pressure in various gas conditions for adhesion improvement in mind. An x-ray photoelectron spectroscopic analysis indicated that oxygen is effectively introduced onto the carbon fibre surfaces by He, He...

  15. Entrainment process of carbon dioxide in the atmospheric boundary layer

    NARCIS (Netherlands)

    Vilà-Guerau de Arellano, J.; Gioli, B.; Miglietta, F.; Jonker, H.J.J.; Klein Baltink, H.; Hutjes, R.W.A.; Holtslag, A.A.M.

    2004-01-01

    Aircraft and surface measurements of turbulent thermodynamic variables and carbon dioxide (CO2) were taken above a grassland in a convective atmospheric boundary layer. The observations were analyzed to assess the importance of the entrainment process for the distribution and evolution of carbon dio

  16. ION EXCHANGE PERFORMANCE OF TITANOSILICATES, GERMANATES AND CARBON NANOTUBES

    Energy Technology Data Exchange (ETDEWEB)

    Alsobrook, A. N.; Hobbs, D. T.

    2013-04-24

    This report presents a summary of testing the affinity of titanosilicates (TSP), germanium-substituted titanosilicates (Ge-TSP) and multiwall carbon nanotubes (MWCNT) for lanthanide ions in dilute nitric acid solution. The K-TSP ion exchanger exhibited the highest affinity for lanthanides in dilute nitric acid solutions. The Ge-TSP ion exchanger shows promise as a material with high affinity, but additional tests are needed to confirm the preliminary results. The MWCNT exhibited much lower affinities than the K-TSP in dilute nitric acid solutions. However, the MWCNT are much more chemically stable to concentrated nitric acid solutions and, therefore, may candidates for ion exchange in more concentrated nitric acid solutions. This technical report serves as the deliverable documenting completion of the FY13 research milestone, M4FT-13SR0303061 – measure actinide and lanthanide distribution values in nitric acid solutions with sodium and potassium titanosilicate materials.

  17. Carbonate and Bicarbonate Ion Transport in Alkaline Anion Exchange Membranes

    Science.gov (United States)

    2013-06-25

    Bicarbonate Ion Transport in Alk Block 13: Supplementary Note © 2013 . Published in Journal of the Electrochemical Society , Vol. Ed. 0 160, (9) (2013...for public release; distribution is unlimited. ... 60325.7-CH-II F994 Journal of The Electrochemical Society , 160 (9) F994-F999 (2013) 0013-4651/2013...160(9)/F994/6/$31.00 © The Electrochemical Society Carbonate and Bicarbonate Ion Transport in Alkaline Anion Exchange Membranes Andrew M. Kiss,a

  18. Measurement of absorption and charge exchange of $\\pi^+$ on carbon

    CERN Document Server

    Ieki, K; Berkman, S; Bhadra, S; Cao, C; de Perio, P; Hayato, Y; Ikeda, M; Kanazawa, Y; Kim, J; Kitching, P; Mahn, K; Nakaya, T; Nicholson, M; Olchanski, K; Rettie, S; Tanaka, H A; Wilking, M J; Tobayama, S; Yamauchi, T; Yen, S; Yokoyama, M

    2015-01-01

    The combined cross section for absorption and charge exchange interactions of positively charged pions with carbon nuclei for the momentum range 200 MeV/c to 300 MeV/c have been measured with the DUET experiment at TRIUMF. The uncertainty is reduced by nearly half compared to previous experiments. This result will be a valuable input to existing models to constrain pion interactions with nuclei.

  19. Diagnosing Model Errors in Canopy-Atmosphere Exchange Using Empirical Orthogonal Functions

    Science.gov (United States)

    Drewry, D.; Albertson, J.

    2004-12-01

    Multi-layer canopy process models (MLCPMs) have been established as tools for estimating local-scale canopy-atmosphere scalar (carbon dioxide, heat and water vapor) exchange as well as testing hypotheses regarding the mechanistic functioning of complex vegetated land surfaces and the interactions between vegetation and the local microenvironment. These model frameworks are composed of a coupled set of component submodels relating radiation attenuation and absorption, photosynthesis, turbulent mixing, stomatal conductance, surface energy balance and soil and subsurface processes. Submodel formulations have been validated for a variety of ecosystems under varying environmental conditions. However, each submodel component requires parameter values that are known to vary seasonally as canopy structure changes, and over shorter periods characterized by shifts in the environmental regime. The temporal dependence of submodel parameters limits application of MLCPMs to short-term integrations for which a specific parameterization can be trusted. We present a novel application of empirical orthogonal function (EOF) analysis to the identification of the primary source of MLCPM error. Carbon dioxide (CO2) concentration profiles, a commonly collected and underutilized data source, are the observed quantity in this analysis. The technique relies on an ensemble of model runs transformed to EOF space to determine the characteristic patterns of model error associated with specific submodel parameters. These patterns provide a basis onto which error residual (modeled - measured) CO2 concentration profiles can be projected to identify the primary source of model error. Synthetic tests and application to field data collected at Duke Forest (North Carolina, USA) are presented.

  20. Proton-exchanged LiNbO(3) waveguides: relevance of atmospheric environment during annealing.

    Science.gov (United States)

    Loni, A; De La Rue, R M

    1992-08-20

    The relevance of the type of atmosphere used during the annealing of proton-exchanged LiNbO(3) planar waveguides is discussed. The experimental evidence, based on a comparison of the refractive-index profiles of waveguides annealed under wet O(2), dry O(2), or ambient atmospheres, with various gas flow rates, suggests that the atmosphere type does not influence the properties of the resulting waveguide.

  1. Exchange of carbonyl sulfide (COS) between the atmosphere and various soils in China

    OpenAIRE

    Liu, J; C. Geng; Mu, Y; Zhang, Y; Wu, H

    2009-01-01

    Using a dynamic enclosure, the exchange fluxes of carbonyl sulfide (COS) between the atmosphere and 18 soils from 10 provinces in China were investigated. The emission or uptake of COS from the soils was highly dependent on the soil type, soil temperature, soil moisture, and atmospheric COS mixing ratio. In general, with the only exception being paddy soils, the soils in this investigation acted as sinks for atmospheric COS under wide ranges of soil temperature and soil moisture. Two i...

  2. Exchange of carbonyl sulfide (COS) between the atmosphere and various soils in China

    OpenAIRE

    Liu, J; C. Geng; Mu, Y; Zhang, Y.; Xu, Z.; Wu, H

    2010-01-01

    Using a dynamic enclosure, the exchange rates of carbonyl sulfide (COS) between the atmosphere and 18 soils from 12 provinces in China were investigated. The emission or uptake of COS from the soils was highly dependent on the soil type, soil temperature, soil moisture, and atmospheric COS mixing ratio. In general, with the only exception being paddy soils, the soils in this investigation acted as sinks for atmospheric COS under wide ranges of soil temperature and soil moisture. Two intensive...

  3. The travel-related carbon dioxide emissions of atmospheric researchers

    Directory of Open Access Journals (Sweden)

    A. Stohl

    2008-04-01

    Full Text Available Most atmospheric scientists agree that greenhouse gas emissions have already caused significant changes to the global climate system and that these changes will accelerate in the near future. At the same time, atmospheric scientists who – like other scientists – rely on international collaboration and information exchange travel a lot and, thereby, cause substantial emissions of carbon dioxide (CO2. In this paper, the CO2 emissions of the employees working at an atmospheric research institute (the Norwegian Institute for Air Research, NILU caused by all types of business travel (conference visits, workshops, field campaigns, instrument maintainance, etc. were calculated for the years 2005–2007. It is estimated that more than 90% of the emissions were caused by air travel, 3% by ground travel and 5% by hotel usage. The travel-related annual emissions were between 1.9 and 2.4 t CO2 per employee or between 3.9 and 5.5 t CO2 per scientist. For comparison, the total annual per capita CO2 emissions are 4.5 t worldwide, 1.2 t for India, 3.8 t for China, 5.9 t for Sweden and 19.1 t for Norway. The travel-related CO2 emissions of a NILU scientist, occurring in 24 days of a year on average, exceed the global average annual per capita emission. Norway's per-capita CO2 emissions are among the highest in the world, mostly because of the emissions from the oil industry. If the emissions per NILU scientist derived in this paper are taken as representative for the average Norwegian researcher, travel by Norwegian scientists would nevertheless account for a substantial 0.2% of Norway's total CO2 emissions. Since most of the travel-related emissions are due to air travel, water vapor emissions, ozone production and contrail formation further increase the relative importance of NILU's travel in terms of radiative forcing.

  4. Atmospheric oxidation of carbon disulfide (CS2)

    Science.gov (United States)

    Zeng, Zhe; Altarawneh, Mohammednoor; Dlugogorski, Bogdan Z.

    2017-02-01

    This contribution investigates primary steps governing the OH-initiated atmospheric oxidation of CS2. Our approach comprises high-level density functional theory calculation of energies and optimisation of molecular structures as well as RRKM-ME analysis for estimating pressure-dependent reaction rate constants. We find the overall reaction OH + CS2 → OCS + SH too slow to account for the formation of the reported experimental products. The initial reaction of OH with CS2 proceeds to produce an S-adduct, SCS(OH). Species-formation history for the system OH + CS2 indicates that, the S-adduct represents the most plausible product with a barrier-less addition process and a stability amounting to 48.5 kJ/mol, in reference to the separated reactants. This adduct then undergoes a bimolecular reaction with atmospheric O2 yielding OCS and HOSO, rather than dissociating back into its separated reactants. We also find that further atmospheric oxidation of the C-adduct (if formed) yields two of the major experimental products namely OCS and SO2. The kinetic analysis provided in this study explains the atmospheric fate of reduced sulfur species, an important S-bearing group in the global cycle of sulfur.

  5. Mycorrhizal mediation of soil organic carbon decomposition under elevated atmospheric carbon dioxide

    Science.gov (United States)

    Significant effort in global change research has recently been directed towards assessing the potential of soil as a carbon sink under future atmospheric carbon dioxide scenarios. Attention has focused on the impact of elevated carbon dioxide on plant interactions with mycorrhizae, a symbiotic soil...

  6. The effects on the atmosphere of a major nuclear exchange

    Energy Technology Data Exchange (ETDEWEB)

    1985-01-01

    Most of the earth's population would survive the immediate horrors of a nuclear holocaust, but what long-term climatological changes would affect their ability to secure food and shelter. This sobering report considers the effects of fine dust from ground-level detonations, of smoke from widespread fires, and of chemicals released into the atmosphere. The authors use mathematical models of atmospheric processes and data from natural situations - e.g., volcanic eruptions and arctic haze - to draw their conclusions.

  7. Technical Note: A simple method for air–sea gas exchange measurements in mesocosms and its application in carbon budgeting

    Directory of Open Access Journals (Sweden)

    J. Czerny

    2013-03-01

    Full Text Available Mesocosms as large experimental units provide the opportunity to perform elemental mass balance calculations, e.g. to derive net biological turnover rates. However, the system is in most cases not closed at the water surface and gases exchange with the atmosphere. Previous attempts to budget carbon pools in mesocosms relied on educated guesses concerning the exchange of CO2 with the atmosphere. Here, we present a simple method for precise determination of air–sea gas exchange in mesocosms using N2O as a deliberate tracer. Beside the application for carbon budgeting, transfer velocities can be used to calculate exchange rates of any gas of known concentration, e.g. to calculate aquatic production rates of climate relevant trace gases. Using an arctic KOSMOS (Kiel Off Shore Mesocosms for future Ocean Simulation experiment as an exemplary dataset, it is shown that the presented method improves accuracy of carbon budget estimates substantially. Methodology of manipulation, measurement, data processing and conversion to CO2 fluxes are explained. A theoretical discussion of prerequisites for precise gas exchange measurements provides a guideline for the applicability of the method under various experimental conditions.

  8. A simple method for air/sea gas exchange measurement in mesocosms and its application in carbon budgeting

    Directory of Open Access Journals (Sweden)

    J. Czerny

    2012-09-01

    Full Text Available Mesocosms as large experimental vessels principally provide the opportunity of performing elemental budget calculations e.g. to derive net biological turnover rates. However, the system is in most cases not closed at the water surface and gases can exchange with the atmosphere. Previous attempts to budget carbon pools in mesocosms relied on educated guesses concerning the exchange of CO2 with the atmosphere. Nevertheless, net primary production rates derived from these budget calculations were, despite large uncertainties in air/sea gas exchange, often more reasonable than cumulative extrapolations of bioassays. While bioassays have limitations representing the full spectrum of trophic levels and abiotic conditions inside the mesocosms, calculating dissolved inorganic carbon uptake inside the mesocosms has the potential to deliver net community production rates representative of the enclosed system. Here, we present a simple method for precise determination of air/sea gas exchange velocities in mesocosms using N2O as a deliberate tracer. Beside the application for carbon budgeting, exchange velocities can be used to calculate exchange rates of any gas of known concentration, e.g. to calculate aquatic production rates of climate relevant trace gases. Using an arctic (Kiel Off Shore Mesocosms for future Ocean Simulation mesocosm experiment as an exemplary dataset, it is shown that application of the presented method largely improves accuracy of carbon budget estimates. Methodology of manipulation, measurement, data processing and conversion to CO2 fluxes are explained. A theoretical discussion of prerequisites for precise gas exchange measurements provides a guideline for the applicability of the method under various experimental conditions.

  9. Photodissociation of carbon dioxide in the Mars upper atmosphere

    Science.gov (United States)

    Barth, C. A.

    1974-01-01

    Calculation of the intensity of two of the emissions produced during the dissociative excitation of carbon dioxide in the upper atmosphere of Mars by solar ultraviolet radiation. The calculation tangential column emission rates of the atomic oxygen 2972-A line and the carbon monoxide Cameron bands produced by the photodissociative mechanism are found to be factors of 3 and 10, respectively, smaller than the emission rates observed by Mariner ultraviolet spectrometers.

  10. Atmospheric deposition of organic and black carbon to the global oceans

    Science.gov (United States)

    Jurado, Elena; Dachs, Jordi; Duarte, Carlos M.; Simó, Rafel

    Atmospheric deposition of total organic carbon (OC) and black carbon (BC) is lacking or not fully accounted in most current models of the global carbon cycling, specially those fluxes related to gas phase OC. Here, we develop and apply a methodology to estimate wet and dry deposition of total OC to the oceans, based on monthly satellite measurements of aerosol size distributions, wind speed, etc., and estimates of deposition for aerosols and organic compounds. The parameterization of dry deposition velocities account for the dependence of turbulent transport with aerosol diameter, wind speed and the formation of marine aerosol, etc. Gravitational settling is estimated as a function of wet particle diameter, thus including hygroscopic growth due to ambient humidity. Global dry deposition of aerosol OC is estimated to be 11 Tg C y -1 and wet deposition of particle and gaseous OC are estimated as 47 and 187 Tg C y -1, respectively. Due to their pulsing variability, wet deposition fluxes can be important locally and as a temporal source of OC to surface waters. Dry and wet deposition of black carbon to the global ocean are estimated to be 2 and 10 Tg C yr -1, respectively, with higher fluxes in the northern hemisphere and for inter-tropical regions. Finally, considerations on the potential magnitude of the hitherto neglected gross air-sea diffusive exchange fluxes of OC are discussed. Even though the magnitude and direction of these cannot be constrained here, evidence of its important role is given. This study, thus, shows that there is an important spatial and temporal variability in atmosphere-ocean exchanges of OC and BC at different scales, and calls for the need for further research on the important role that these exchanges play in the global carbon cycle.

  11. The influence of water vapor on atmospheric exchange measurements with an ICOS* based Laser absorption analyzer

    Science.gov (United States)

    Bunk, Rüdiger; Quan, Zhi; Wandel, Matthias; Yi, Zhigang; Bozem, Heiko; Kesselmeier, Jürgen

    2014-05-01

    Carbonyl sulfide and carbon monoxide are both atmospheric trace gases of high interest. Recent advances in the field of spectroscopy have enabled instruments that measure the concentration of the above and other trace gases very fast and with good precision. Increasing the effective path length by reflecting the light between two mirrors in a cavity, these instruments reach impressive sensitivities. Often it is possible to measure the concentration of more than one trace gas at the same time. The OCS/CO2 Analyzer by LGR (Los Gatos Research, Inc.) measures the concentration of water vapor [H2O], carbonyl sulfide [COS], carbon dioxide [CO2] and carbon monoxide [CO] simultaneously. For that the cavity is saturated with light, than the attenuation of light is measured as in standard absorption spectroscopy. The instrument proved to be very fast with good precision and to be able to detect even very low concentrations, especially for COS (as low as 30ppt in the case of COS). However, we observed a rather strong cross sensitivity to water vapor. Altering the water vapor content of the sampled air with two different methods led to a change in the perceived concentration of COS, CO and CO2. This proved especially problematic for enclosure (cuvette) measurements, where the concentrations of one of the above species in an empty cuvette are compared to the concentration of another cuvette containing a plant whose exchange of trace gases with the atmosphere is of interest. There, the plants transpiration leads to a large difference in water vapor content between the cuvettes and that in turn produces artifacts in the concentration differences between the cuvettes for the other above mentioned trace gases. For CO, simultaneous measurement with a UV-Emission Analyzer (AL 5002, Aerolaser) and the COS/CO Analyzer showed good agreement of perceived concentrations as long as the sample gas was dry and an increasing difference in perceived concentration when the sample gas was

  12. Continuous In-situ Measurements of Carbonyl Sulfide to Constrain Ecosystem Carbon and Water Exchange

    Science.gov (United States)

    Rastogi, B.; Kim, Y.; Berkelhammer, M. B.; Noone, D. C.; Lai, C. T.; Hollinger, D. Y.; Bible, K.; Leen, J. B.; Gupta, M.; Still, C. J.

    2014-12-01

    Understanding the processes that control the terrestrial exchange of carbon and water are critical for examining the role of forested ecosystems in changing climates. A small but increasing number of studies have identified Carbonyl Sulfide (OCS) as a potential tracer for photosynthesis. OCS is hydrolyzed by an irreversible reaction in leaf mesophyll cells that is catalyzed by the enzyme, carbonic anhydrase. Leaf-level field and greenhouse studies indicate that OCS uptake is controlled by stomatal activity and that the ratio of OCS and CO2 uptake is reasonably constant. Existing studies on ecosystem OCS exchange have been based on laboratory measurements or short field campaigns and therefore little information on OCS exchange in a natural ecosystem over longer timescales is available. The objective of this study is to further assess the stability of OCS as a tracer for canopy photosynthesis in an active forested ecosystem and also to assess its utility for constraining transpiration, since both fluxes are mediated by canopy stomatal conductance. An off-axis integrated cavity output spectroscopy analyzer (Los Gatos Research Inc.) was deployed at the Wind River Experimental Forest in Washington (45.8205°N, 121.9519°W). Canopy air was sampled from three heights to measure vertical gradients of OCS within the canopy, and OCS exchange between the forest and the atmosphere. Here we take advantage of simultaneous measurements of the stable isotopologues of H2O and CO2 at corresponding heights as well as NEE (Net Ecosystem Exchange) from eddy covariance measurements to compare GPP (Gross Primary Production) and transpiration estimates from a variety of independent techniques. Our findings seek to allow assessment of the environmental and ecophysicological controls on evapotranspiration rates, which are projected to change in coming decades, and are otherwise poorly constrained.

  13. Atmospheric pressure plasma treatment of glassy carbon for adhesion improvement

    DEFF Research Database (Denmark)

    Kusano, Yukihiro; Mortensen, Henrik Junge; Stenum, Bjarne

    2007-01-01

    Glassy carbon plates were treated with an atmospheric pressure dielectric barrier discharge (DBD). He gas, gas mixtures of He and reactive gases such as O2, CO2 and NH3, Ar gas and Ar/NH3 gas mixture were used as treatment gases. The oxygen and nitrogen contents on the surface as well as defect...

  14. Phase relation between global temperature and atmospheric carbon dioxide

    CERN Document Server

    Stallinga, Peter

    2013-01-01

    The primary ingredient of Anthropogenic Global Warming hypothesis is the assumption that atmospheric carbon dioxide variations are the cause for temperature variations. In this paper we discuss this assumption and analyze it on basis of bi-centenary measurements and using a relaxation model which causes phase shifts and delays.

  15. Modelling short-term variability in carbon and water exchange in a temperate Scots pine forest

    Directory of Open Access Journals (Sweden)

    M. H. Vermeulen

    2015-02-01

    Full Text Available Vegetation – atmosphere carbon and water exchange at one particular site can strongly vary from year to year, and understanding this interannual variability in carbon and water exchange (IAVcw is a critical factor in projecting future ecosystem changes. However, the mechanisms driving this IAVcw are not well understood. We used data on carbon and water fluxes from a multi-year Eddy Covariance study (1997–2009 in a Dutch Scots pine forest and forced a process-based ecosystem model (LPJ-GUESS with local data to, firstly, test whether the model can explain IAVcw and seasonal carbon and water exchange from direct environmental factors only. Initial model runs showed low correlations with estimated annual gross primary productivity (GPP and annual actual evapotranspiration (AET, while monthly and daily fluxes showed high correlations. The model underestimated GPP and AET during winter and drought events. Secondly, we adapted the temperature inhibition function of photosynthesis to account for the observation that at this particular site, trees continue to assimilate at very low atmospheric temperatures (up to daily averages of −10 °C, resulting in a net carbon sink in winter. While we were able to improve daily and monthly simulations during winter by lowering the modelled minimum temperature threshold for photosynthesis, this did not increase explained IAVcw at the site. Thirdly, we implemented three alternative hypotheses concerning water uptake by plants in order to test which one best corresponds with the data. In particular, we analyse the effects during the 2003 heatwave. These simulations revealed a strong sensitivity of the modelled fluxes during dry and warm conditions, but no single formulation was consistently superior in reproducing the data for all time scales and the overall model-data match for IAVcw could not be improved. Most probably access to deep soil water leads to higher AET and GPP simulated during the heat wave of 2003

  16. Multiyear high-resolution carbon exchange over European croplands from the integration of observed crop yields into CarbonTracker Europe

    Science.gov (United States)

    Combe, Marie; Vilà-Guerau de Arellano, Jordi; de Wit, Allard; Peters, Wouter

    2016-04-01

    Carbon exchange over croplands plays an important role in the European carbon cycle over daily-to-seasonal time scales. Not only do crops occupy one fourth of the European land area, but their photosynthesis and respiration are large and affect CO2 mole fractions at nearly every atmospheric CO2 monitoring site. A better description of this crop carbon exchange in our CarbonTracker Europe data assimilation system - which currently treats crops as unmanaged grasslands - could strongly improve its ability to constrain terrestrial carbon fluxes. Available long-term observations of crop yield, harvest, and cultivated area allow such improvements, when combined with the new crop-modeling framework we present. This framework can model the carbon fluxes of 10 major European crops at high spatial and temporal resolution, on a 12x12 km grid and 3-hourly time-step. The development of this framework is threefold: firstly, we optimize crop growth using the process-based WOrld FOod STudies (WOFOST) agricultural crop growth model. Simulated yields are downscaled to match regional crop yield observations from the Statistical Office of the European Union (EUROSTAT) by estimating a yearly regional parameter for each crop species: the yield gap factor. This step allows us to better represent crop phenology, to reproduce the observed multiannual European crop yields, and to construct realistic time series of the crop carbon fluxes (gross primary production, GPP, and autotrophic respiration, Raut) on a fine spatial and temporal resolution. Secondly, we combine these GPP and Raut fluxes with a simple soil respiration model to obtain the total ecosystem respiration (TER) and net ecosystem exchange (NEE). And thirdly, we represent the horizontal transport of carbon that follows crop harvest and its back-respiration into the atmosphere during harvest consumption. We distribute this carbon using observations of the density of human and ruminant populations from EUROSTAT. We assess the model

  17. Evidence for super-exponentially accelerating atmospheric carbon dioxide growth

    CERN Document Server

    Hüsler, Andreas D

    2011-01-01

    We analyze the growth rates of atmospheric carbon dioxide and human population, 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. Our empirical calibrations confirm that human population has decelerated from its previous super-exponential growth until 1960 to ``just' an exponential growth, but with no sign of more deceleration. As for atmospheric CO2 content, we find that it is at least exponentially increasing and most likely characterized by an accelerating growth rate as off 2009, consistent with an unsustainable FTS power law regime announcing a drastic change of regime. The coexistence of a quasi-exponential growth of human population with a super-exponential growth of carbon dioxide content in the atmosphere is a diagnostic of insignificant impr...

  18. Development of Carbon Sequestration Options by Studying Carbon Dioxide-Methane Exchange in Hydrates

    Science.gov (United States)

    Horvat, Kristine Nicole

    Gas hydrates form naturally at high pressures (>4 MPa) and low temperatures (climate change point of view, a 100 ppm increase in atmospheric carbon dioxide (CO2) levels over the past century is of urgent concern. A potential solution to both of these issues is to simultaneously exchange CH4 with CO 2 in natural hydrate reserves by forming more stable CO2 hydrates. This approach would minimize disturbances to the host sediment matrix of the seafloor while sequestering CO2. Understanding hydrate growth over time is imperative to prepare for large scale CH4 extraction coupled with CO2 sequestration. In this study, we performed macroscale experiments in a 200 mL high-pressure Jerguson cell that mimicked the pressure-temperature conditions of the seafloor. A total of 13 runs were performed under varying conditions. These included the formation of CH4 hydrates, followed by a CO2 gas injection and CO2 hydrate formation followed by a CH4 gas injection. Results demonstrated that once gas hydrates formed, they show "memory effect" in subsequent charges, irrespective of the two gases injected. This was borne out by the induction time data for hydrate formation that reduced from 96 hours for CH4 and 24 hours for CO2 to instant hydrate formation in both cases upon injection of a secondary gas. During the study of CH4-CO2 exchange where CH4 hydrates were first formed and CO2 gas was injected into the system, gas chromatographic (GC) analysis of the cell indicated a pure CH4 gas phase, i.e., all injected CO2 gas entered the hydrate phase and remained trapped in hydrate cages for several hours, though over time some CO2 did enter the gas phase. Alternatively, during the CH 4-CO2 exchange study where CO2 hydrates were first formed, the injected CH4 initially entered the hydrate phase, but quickly gaseous CO2 exchanged with CH4 in hydrates to form more stable CO2 hydrates. These results are consistent with the better thermodynamic stability of CO2 hydrates, and this appears to be a

  19. Growing season carbon dioxide exchange in flooded non-mulching and non-flooded mulching cotton.

    Directory of Open Access Journals (Sweden)

    Zhi-guo Li

    Full Text Available There is much interest in the role that agricultural practices might play in sequestering carbon to help offset rising atmospheric CO₂ concentrations. However, limited information exists regarding the potential for increased carbon sequestration of different management strategies. The objective of this study was to quantify and contrast carbon dioxide exchange in traditional non-mulching with flooding irrigation (TF and plastic film mulching with drip irrigation (PM cotton (Gossypium hirsutum L. fields in northwest China. Net primary productivity (NPP, soil heterotrophic respiration (R(h and net ecosystem productivity (NEP were measured during the growing seasons in 2009 and 2010. As compared with TF, PM significantly increased the aboveground and belowground biomass and the NPP (340 g C m⁻² season⁻¹ of cotton, and decreased the R(h (89 g C m⁻² season⁻¹ (p<0.05. In a growing season, PM had a higher carbon sequestration in terms of NEP of ∼ 429 g C m⁻² season⁻¹ than the TF. These results demonstrate that conversion of this type of land use to mulching practices is an effective way to increase carbon sequestration in the short term in cotton systems of arid areas.

  20. Gas exchanges in soybean as affected by landfill biogas atmosphere

    Energy Technology Data Exchange (ETDEWEB)

    Marchiol, L.; Zerbi, G. (Univ. di Udine (Italy). Dipt. di Produzione Vegetale e Tecnologie Agrarie); Mori, A.; Leita, L. (Ist. Sperimentale per la Nutrizione delle Piante-Sezione di Gorizia (Italy))

    A problem in the ecological restoration of closed landfills is the production of potentially toxic gases by decomposition of refuse that affects the root system and physiology of plants growing on these sites. The aim of the present study was to assess the effects induced by landfill biogas contamination on gas-exchanges of soybean [Glycine max (L.) Merr.]. Simulated landfill and control gases were supplied to soybean plants under laboratory conditions for 10 d. The composition of the simulated landfill gas used was: 16% O[sub 2], 8% CO[sub 2], 3% CH[sub 4], and 73% N[sub 2]; a control gas was also tested. Photosynthesis and stomatal conductance were significantly affected by the gas treatment after 3 d; in the course of the experiment, biogas treatment progressively reduced A[sub max] in light-saturation curves. The fresh and dry weight, leaf area and leaf chlorophyll content were not affected by the treatment. A metabolic adaptation to the biogas in the roots of treated plants was related to the disappearance of a fraction of the protein pool.

  1. Assessing net ecosystem carbon exchange of U S terrestrial ecosystems by integrating eddy covariance flux measurements and satellite observations

    Energy Technology Data Exchange (ETDEWEB)

    Zhuang, Qianlai [Purdue University; Law, Beverly E. [Oregon State University; Baldocchi, Dennis [University of California, Berkeley; Ma, Siyan [University of California, Berkeley; Chen, Jiquan [University of Toledo, Toledo, OH; Richardson, Andrew [Harvard University; Melillo, Jerry [Marine Biological Laboratory; Davis, Ken J. [Pennsylvania State University; Hollinger, D. [USDA Forest Service; Wharton, Sonia [University of California, Davis; Falk, Matthias [University of California, Davis; Paw, U. Kyaw Tha [University of California, Davis; Oren, Ram [Duke University; Katulk, Gabriel G. [Duke University; Noormets, Asko [North Carolina State University; Fischer, Marc [Lawrence Berkeley National Laboratory (LBNL); Verma, Shashi [University of Nebraska; Suyker, A. E. [University of Nebraska, Lincoln; Cook, David R. [Argonne National Laboratory (ANL); Sun, G. [USDA Forest Service; McNulty, Steven G. [USDA Forest Service; Wofsy, Steve [Harvard University; Bolstad, Paul V [University of Minnesota; Burns, Sean [University of Colorado, Boulder; Monson, Russell K. [University of Colorado, Boulder; Curtis, Peter [Ohio State University, The, Columbus; Drake, Bert G. [Smithsonian Environmental Research Center, Edgewater, MD; Foster, David R. [Harvard University; Gu, Lianhong [ORNL; Hadley, Julian L. [Harvard University; Litvak, Marcy [University of New Mexico, Albuquerque; Martin, Timothy A. [University of Florida, Gainesville; Matamala, Roser [Argonne National Laboratory (ANL); Meyers, Tilden [NOAA, Oak Ridge, TN; Oechel, Walter C. [San Diego State University; Schmid, H. P. [Indiana University; Scott, Russell L. [USDA ARS; Torn, Margaret S. [Lawrence Berkeley National Laboratory (LBNL)

    2011-01-01

    More accurate projections of future carbon dioxide concentrations in the atmosphere and associated climate change depend on improved scientific understanding of the terrestrial carbon cycle. Despite the consensus that U.S. terrestrial ecosystems provide a carbon sink, the size, distribution, and interannual variability of this sink remain uncertain. Here we report a terrestrial carbon sink in the conterminous U.S. at 0.63 pg C yr 1 with the majority of the sink in regions dominated by evergreen and deciduous forests and savannas. This estimate is based on our continuous estimates of net ecosystem carbon exchange (NEE) with high spatial (1 km) and temporal (8-day) resolutions derived from NEE measurements from eddy covariance flux towers and wall-to-wall satellite observations from Moderate Resolution Imaging Spectroradiometer (MODIS). We find that the U.S. terrestrial ecosystems could offset a maximum of 40% of the fossil-fuel carbon emissions. Our results show that the U.S. terrestrial carbon sink varied between 0.51 and 0.70 pg C yr 1 over the period 2001 2006. The dominant sources of interannual variation of the carbon sink included extreme climate events and disturbances. Droughts in 2002 and 2006 reduced the U.S. carbon sink by 20% relative to a normal year. Disturbances including wildfires and hurricanes reduced carbon uptake or resulted in carbon release at regional scales. Our results provide an alternative, independent, and novel constraint to the U.S. terrestrial carbon sink.

  2. Atmospheric ammonia exchange on a heathland in Denmark

    Science.gov (United States)

    Hansen, Birgitte; Nørnberg, Per; Rasmussen, Keld Rømer

    Passive flux samplers were used to determine the ammonia exchange on an inland heath in Denmark over the last 2 years. The samplers measured the horizontal ammonia flux directly. Data were sampled continuously for periods of 1-4 weeks. The micro-meteorological gradient method was used with passive flux samplers and cup anemometers at different heights above the vegetation in order to calculate the vertical fluxes of ammonia. First a fixed sampler system was used with tubes mounted in four orthogonal horizontal directions. This system has been successfully applied to measure the emission from fertilized crops. Adapting this type of sampler to measure the deposition to heathlands did not prove to be straightforward. The precision of the calculated ammonia concentrations was too poor to give an acceptable accuracy for the concentration gradient. The problems were (a) driving rain which entered the tubes, (b) too few measuring points in each concentration profile, and (c) too long sampling periods to allow for the low-concentration levels above the heath area and the detection limits. Therefore, a passive flux sampler mounted on a wind vane and fitted with a rain shelter was developed. Results from the first 5 weekly periods are very promising, yielding accurate concentration gradients. The advantages of the passive flux samplers on the wind vane are (a) the minimum measuring period can be approximately halved compared to the fixed samplers, (b) some of the directional correction terms used with the fixed passive flux samplers are dispensed with, and (c) the field and laboratory work is minimized.

  3. Oxygen Isotopic Composition of Carbon Dioxide in the Middle Atmosphere

    Science.gov (United States)

    Liang, M.; Blake, G. A.; Lewis, B. R.; Yung, Y. L.

    2005-12-01

    The isotopic composition of long-lived trace gases provides a window into atmospheric transport and chemistry. Carbon dioxide is a particularly powerful tracer, because its abundance remains >100 ppmv in the mesosphere. Current models consider O3 as the main source of O(1D) in the mesosphere, but we note that the photolysis of 16O17O and 16O18O by solar Lyman-α radiation yields O(1D) 10-100 times more enriched in 17O and 18O than that from ozone photodissociation. We therefore incorporate both photochemical sources into stratospheric and mesospheric chemical transport models that quantitatively predict the unusual enhancement of 17O in CO2 from the middle atmosphere. New laboratory and atmospheric measurements are proposed to test our model and validate the use of CO2 isotopic fractionation as a tracer of atmospheric chemical and dynamical processes. Once fully understood the `anomalous' oxygen signature in CO2 can be used in turn to study biogeochemical cycles, in particular to constrain the gross carbon fluxes between the atmosphere and terrestrial biosphere.

  4. Plasma reactor for deposition of carbon nanowalls at atmospheric pressure

    Science.gov (United States)

    Dimitrov, Zh; Mitev, D.; Kiss'ovski, Zh

    2016-10-01

    In this study a novel plasma reactor for deposition of carbon nanowalls at atmospheric pressure is constructed and characterized. A low power microwave discharge is used as a plasma source and working gas of Ar/H2/CH4 gas mixture. The substrate is heated by plasma flame and its temperature is in the range 600-700 C. The chemical composition of the plasma and the gas mixture effect on the concentration of the various particles in the plasma is investigated by optical emission spectroscopy. The emission spectrum of the plasma jet in Ar/H2/CH4 mixture shows the presence of carbon (Swan band) and an intensive line of CH (388 nm), which are necessary species for deposition of carbon nanostructures. Additional voltage in the range from -20 V to -100 V is applied in order to ensure the vertical growth of graphene walls. Results of deposited carbon nanostructures on metal substrate are shown.

  5. Oxygen and carbon discovered in exoplanet atmosphere `blow-off'

    Science.gov (United States)

    2004-02-01

    Oxygen and carbon discovered in exoplanet atmosphere ‘blow-off’ hi-res Size hi-res: 1096 kb Credits: ESA/Alfred Vidal-Madjar (Institut d’Astrophysique de Paris, CNRS, France) Oxygen and carbon discovered in exoplanet atmosphere ‘blow-off’ This artist’s impression shows an extended ellipsoidal envelope - the shape of a rugby-ball - of oxygen and carbon discovered around the well-known extrasolar planet HD 209458b. An international team of astronomers led by Alfred Vidal-Madjar (Institut d’Astrophysique de Paris, CNRS, France) observed the first signs of oxygen and carbon in the atmosphere of a planet beyond our Solar System for the first time using the NASA/ESA Hubble Space Telescope. The atoms of carbon and oxygen are swept up from the lower atmosphere with the flow of escaping atmospheric atomic hydrogen - like dust in a supersonic whirlwind - in a process called atmospheric ‘blow off’. Oxygen and carbon have been detected in the atmosphere of a planet beyond our Solar System for the first time. Scientists using the NASA/ESA Hubble Space Telescope have observed the famous extrasolar planet HD 209458b passing in front of its parent star, and found oxygen and carbon surrounding the planet in an extended ellipsoidal envelope - the shape of a rugby-ball. These atoms are swept up from the lower atmosphere with the flow of the escaping atmospheric atomic hydrogen, like dust in a supersonic whirlwind. The team led by Alfred Vidal-Madjar (Institut d’Astrophysique de Paris, CNRS, France) reports this discovery in a forthcoming issue of Astrophysical Journal Letters. The planet, called HD 209458b, may sound familiar. It is already an extrasolar planet with an astounding list of firsts: the first extrasolar planet discovered transiting its sun, the first with an atmosphere, the first observed to have an evaporating hydrogen atmosphere (in 2003 by the same team of scientists) and now the first to have an atmosphere containing oxygen and carbon. Furthermore

  6. Evidence for atmospheric carbon dioxide variability over the Gulf Stream

    Science.gov (United States)

    Bufton, J. L.

    1984-01-01

    Two airborne surveys of atmospheric carbon dioxide concentration have been conducted over the Gulf Stream off the east coast of Virginia and North Carolina on September 7-8, 1983. In situ CO2 data were acquired at an aircraft altitude of 300 m on trajectories that transcected the Gulf Stream near 36 deg N 73 deg W. Data show evidence of a CO2 concentration increase by 4 ppm to 15 ppm above the nominal atmospheric background value of 345 ppm. These enhanced values were associated with the physical location of the Gulf Stream prior to the passage of a weak cold front.

  7. Modal character of atmospheric black carbon size distributions

    Science.gov (United States)

    Berner, A.; Sidla, S.; Galambos, Z.; Kruisz, C.; Hitzenberger, R.; ten Brink, H. M.; Kos, G. P. A.

    1996-08-01

    Samples of atmospheric aerosols, collected with cascade impactors in the urban area of Vienna (Austria) and at a coastal site on the North Sea, were investigated for black carbon (BC) as the main component of absorbing material and for mass. The size distributions are structured. The BC distributions of these samples show a predominant mode, the accumulation aerosol, in the upper submicron size range, a less distinct finer mode attributable to fresh emissions from combustion sources, and a distinct coarse mode of unclear origin. It is important to note that some parameters of the accumulation aerosol are related statistically, indicating the evolution of the atmospheric accumulation aerosol.

  8. Carbon dioxide exchange of a perennial bioenergy crop cultivation on a mineral soil

    Science.gov (United States)

    Lind, Saara E.; Shurpali, Narasinha J.; Peltola, Olli; Mammarella, Ivan; Hyvönen, Niina; Maljanen, Marja; Räty, Mari; Virkajärvi, Perttu; Martikainen, Pertti J.

    2016-03-01

    One of the strategies to reduce carbon dioxide (CO2) emissions from the energy sector is to increase the use of renewable energy sources such as bioenergy crops. Bioenergy is not necessarily carbon neutral because of greenhouse gas (GHG) emissions during biomass production, field management and transportation. The present study focuses on the cultivation of reed canary grass (RCG, Phalaris arundinacea L.), a perennial bioenergy crop, on a mineral soil. To quantify the CO2 exchange of this RCG cultivation system, and to understand the key factors controlling its CO2 exchange, the net ecosystem CO2 exchange (NEE) was measured from July 2009 until the end of 2011 using the eddy covariance (EC) method. The RCG cultivation thrived well producing yields of 6200 and 6700 kg DW ha-1 in 2010 and 2011, respectively. Gross photosynthesis (GPP) was controlled mainly by radiation from June to September. Vapour pressure deficit (VPD), air temperature or soil moisture did not limit photosynthesis during the growing season. Total ecosystem respiration (TER) increased with soil temperature, green area index and GPP. Annual NEE was -262 and -256 g C m-2 in 2010 and 2011, respectively. Throughout the study period from July 2009 until the end of 2011, cumulative NEE was -575 g C m-2. Carbon balance and its regulatory factors were compared to the published results of a comparison site on drained organic soil cultivated with RCG in the same climate. On this mineral soil site, the RCG had higher capacity to take up CO2 from the atmosphere than on the comparison site.

  9. Static opaque chamber-based technique for determination of net exchange of CO2 between terrestrial ecosystem and atmosphere

    Institute of Scientific and Technical Information of China (English)

    ZOU Jianwen; HUANG Yao; ZHENG Xunhua; WANG Yuesi; CHEN Yuquan

    2004-01-01

    Terrestrial carbon cycling is one of the hotspots in global change issues. In this paper, we presented the rationale for determination of net exchange of CO2 between terrestrial and the atmosphere (NEE) and the methods for measuring several relevant components. Three key processes for determination of NEE were addressed, including the separation of shoot autotrophic respiration from total CO2 emissions of the ecosystem, the partition of root respiration from soil CO2 efflux, and the quantification of rhizodeposition C from NPP. With an understanding of the processes involved in the CO2 exchange between terrestrial and the atmosphere, we estimated NEE of rice ecosystem in Nanjing based on field measurements of CO2 emissions and several relevant biotic components as well as abiotic factors. The field measurements of CO2 emissions were made over the rice-growing seasons in 2001 and 2002 with the static opaque chamber method. Calculations indicated that the seasonal pattern of NEE is comparable for two seasons. Either net carbon emission or fractional carbon fixation occurred during 3 weeks after rice transplanting and thereafter net carbon fixation appeared with an increasing trend as rice growing. Higher net carbon fixation occurred in the rice developmental period from elongating to heading. A decline trend in the fixation was documented after rice heading. The mean daily NEE was -6.06 gC·m-2 in 2001 season and -7.95 gC·m-2 in 2002 season, respectively. These values were comparable to the results obtained by Campbell et al. Who made field measurements with the Bowen ratio-energy balance technique in irrigated rice, Texas USA. Moreover, the mean daily NEE in this study was also comparable to the values obtained from a Japanese rice paddy with the eddy covariance method under the similar water regime, either drainage course or waterlogged. It is concluded that NEE determined by the static opaque chamber method is comparable and in agreement with those measured by

  10. Exchange of nitrogen dioxide (NO2) between plants and the atmosphere under laboratory and field conditions

    Science.gov (United States)

    Breuninger, C.; Meixner, F. X.; Thielmann, A.; Kuhn, U.; Dindorf, T.; Kesselmeier, J.

    2012-04-01

    Nitric oxide (NO), nitrogen dioxide (NO2), often denoted as nitrogen oxides (NOx), and ozone (O3) are considered as most important compounds in atmospheric chemistry. In remote areas NOx concentration is related to biological activities of soils and vegetation. The emitted NOx will not entirely be subject of long range transport through the atmosphere. Aside oxidation of NO2 by the OH radical (forming HNO3), a considerable part of it is removed from the atmosphere through the uptake of NO2 by plants. The exchange depends on stomatal activity and on NO2 concentrations in ambient air. It is known that NO2 uptake by plants represents a large NO2 sink, but the magnitude and the NO2 compensation point concentration are still under discussion. Our dynamic chamber system allows exchange measurements of NO2 under field conditions (uncontrolled) as well as studies under controlled laboratory conditions including fumigation experiments. For NO2 detection we used a highly NO2 specific blue light converter (photolytic converter) with subsequent chemiluminescence analysis of the generated NO. Furthermore, as the exchange of NO2 is a complex interaction of transport, chemistry and plant physiology, in our field experiments we determined fluxes of NO, NO2, O3, CO2 and H2O. For a better knowledge of compensation point values for the bi-directional NO2 exchange we investigated a primary representative of conifers, Picea abies, under field and laboratory conditions, and re-analyzed older field data of the deciduous tree Quercus robur.

  11. Regional Carbon Fluxes and Atmospheric Carbon Dynamics in the Southern Great Plains during the 2007 Mid Continent Intensive of NACP

    Science.gov (United States)

    Torn, M. S.; Fischer, M. L.; Riley, W. J.; Jackson, T. J.; Avissar, R.; Biraud, S. C.; Billesbach, D. P.; Sweeney, C.; Tans, P. P.; Berry, J. A.

    2006-12-01

    In June 2007, an intensive regional campaign will take place in the Southern Great Plains (SGP) to estimate land-atmosphere exchanges of CO2, water, and energy at 1 to 100 km scales. The primary goals of this North American Carbon Program (NACP) campaign are to evaluate top-down and bottom-up estimates of regional fluxes and to understand the influence of moisture gradients, surface heterogeneity, and atmospheric transport patterns on these fluxes (and their estimation). The work will be integrated with the Cloud and Land Surface Interaction Campaign (CLASIC), centered on the US DOE Atmospheric Radiation Measurement Program SGP region. CLASIC will focus on interactions among the land surface, convective boundary layer, and cumulus clouds, and will utilize an array of atmospheric measurements. Carbon and meteorological data streams and logistical resources will be available to other NACP researchers. Carbon flux and concentration data will be collected from tower and airborne platforms. Eddy flux towers will be deployed in the four major land cover types, distributed over the region's SE to NW precipitation gradient. In addition, CO2, water, and energy fluxes will be observed with the Duke Helicopter Observation Platform (HOP) at various heights in the boundary layer, including in the surface layer (the few meters near the surface). Two aircraft will carry precise CO2 measurement systems and NOAA12-flask packages for carbon cycle gases and isotopes. Continuous CO2 and CO concentrations, NOAA flasks, and isotope diel flasks (14C, 13C, and 18O) will also be collected from a centrally located 60 m tower. Flights are planned to constrain simple boundary layer budget models and to conduct Lagrangian air mass following experiments. A distributed model of land surface fluxes will be run off line and coupled to MM5 with tracer capability. In addition to characterizing the influence of the land surface on the atmosphere, the aircraft data (in combination with observations of

  12. Plant use for reduction of atmospheric carbon dioxide

    Energy Technology Data Exchange (ETDEWEB)

    Shinada, Y. (and others) (CRIEPI, Abiko-shi (Japan). Abiko Research Lab.)

    1992-01-01

    The paper reports the possible reduction of atmospheric carbon dioxide by forestation, marine plants proliferation, and microalgal mass culture. Costs and current technical situations were examined by means of hearing from specialists engaged in reforestation programs and by surveying the literature. The results can be summarized as follows: 1. Forestation (a) forestable land area - Possible total land area for forestation is estimated to be about 210 million hectares in all the world. If all of the area were forested, it would be possible to reserve 21 billion tons of carbon. (b) key factors for forestation - Land acquisition and consent by residents are the most important factors to succeed in forestation in developing countries. (c) costs for forestation - Foresting costs are 150-300 thousand yen per hectare and storing atmospheric carbon by forestation costs 2 thousand yen per one ton of carbon. 2. Current situations of marine plants proliferation - It is technically posible to proliferate kelp, gulfweed, and so on; however, costs for making one hectare of growth base will be more than 100-300 million yen. 3. Use of microorganisms - An alternative food production system by using microalgal mass cultivation will have some advantges to reduce conversion of forests to cropland and emission of other greenhouse-effect gases (e.g. methane, nitrous oxide) from agriculture. It is estimated that microalgal mass culture would be lower in costs than marine plants proliferation.

  13. An Important Supplement to NAA in Study on Atmosphere Pollution:Determination of Black Carbon

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    <正>Light absorption in the atmosphere is dominated by elemental carbon (EC), sometimes called black carbon (BC). Black carbon is an important indication of man-made pollution in airborne particulate matter

  14. The behavior of 14C and 13C in estuarine water: Effects of In situ CO2 production and atmospheric exchange

    Science.gov (United States)

    Spiker, Elliott C.

    1980-01-01

    The effects of nonconservative sources (inputs) and sinks (outputs) of carbon are indicated by the behavior of Δ14C and δ13C of the total dissolved inorganic carbon (ΣCO2) in San Francisco Bay and Chesapeake Bay. Isotopic distributions and model calculations indicate that in North San Francisco Bay the net CO2 flux to the atmosphere and carbon utilization in the water column are balanced by benthic production. Municipal waste appears to be a dominant source in South San Francisco Bav. In Chesapeake Bay, atmospheric exchange has increased the Δ14C and δ13C in the surface water. Decomposition of organic matter in the water column is indicated to be the dominant source of excess ΣCO2 in the deep water.

  15. Discovery of carbon monoxide in the upper atmosphere of Pluto

    CERN Document Server

    Greaves, J S; Friberg, P

    2011-01-01

    Pluto's icy surface has changed colour and its atmosphere has swelled since its last closest approach to the Sun in 1989. The thin atmosphere is produced by evaporating ices, and so can also change rapidly, and in particular carbon monoxide should be present as an active thermostat. Here we report the discovery of gaseous CO via the 1.3mm wavelength J=2-1 rotational transition, and find that the line-centre signal is more than twice as bright as a tentative result obtained by Bockelee-Morvan et al. in 2000. Greater surface-ice evaporation over the last decade could explain this, or increased pressure could have caused the atmosphere to expand. The gas must be cold, with a narrow line-width consistent with temperatures around 50 K, as predicted for the very high atmosphere, and the line brightness implies that CO molecules extend up to approximately 3 Pluto radii above the surface. The upper atmosphere must have changed markedly over only a decade since the prior search, and more alterations could occur by the...

  16. Atmospheric Plasma Deposition of Diamond-like Carbon Coatings

    Energy Technology Data Exchange (ETDEWEB)

    Ladwig, Angela

    2008-01-23

    material that may be treated. The deposition of DLC at atmospheric pressure has been demonstrated by several researchers. Izake, et al [53] and Novikov and Dymont [54] have demonstrated an electrochemical process that is carried out with organic compounds such as methanol and acetylene dissolved in ammonia. This process requires that the substrates be immersed in the liquid [53-54]. The atmospheric pressure deposition of DLC was also demonstrated by Kulik, et al. utilizing a plasma torch. However, this process requires operating temperatures in excess of 800 oC [55]. In this report, we investigate the deposition of diamond-like carbon films using a low temperature, atmospheric pressure plasma-enhanced chemical vapor deposition (PECVD) process. The films were characterized by solid-state carbon-13 nuclear magnetic resonance (13C NMR) and found to have a ratio of sp2 to sp3 carbon of 43 to 57%. The films were also tested for adhesion, coefficient of friction, and dielectric strength.

  17. Effects of Carbonate on Exchangeability and Bioavailability of Exogenous Neodymium in Soil

    Institute of Scientific and Technical Information of China (English)

    徐仲均; 李德成; 杨剑虹; 彭安

    2001-01-01

    The effects of carbonate on the exchangeability and the bioavailability of exogenous neodymium in soil were studied by 147Nd isotopic tracer method. Exchangeable Nd was extracted by 1 mol*L-1 NaAc (pH8.2) in the experiment. The results indicate that whether carbonate exists in soil or not, beyond 99% of exogenous Nd is adsorbed by soil. Low-concentration carbonate (0.8~1.6 g*kg-1) can reduce exchangeable Nd concentration in soil, while high-concentration carbonate (4.0 g*kg-1) impacts little on the exchangeable Nd concentration. In addition, carbonate of 0.8~1.6 g*kg-1 in soil can inhibit wheat seedlings to absorb Nd. However, when the carbonate concentration rises to 4.0 g*kg-1, the inhibition will become indistinct.

  18. Comparison of methods for the quantification of carbonate carbon in atmospheric PM10 aerosol samples

    Science.gov (United States)

    Jankowski, Nicole; Schmidl, Christoph; Marr, Iain L.; Bauer, Heidi; Puxbaum, Hans

    Carbonate carbon (CC) represents an important fraction of atmospheric PM10 along with organic carbon (OC) and elemental carbon (EC), if specific sources (e.g. street abrasion, construction sites, desert dust) contribute to its composition. However, analytical methods for an easy and unambiguous determination of CC in atmospheric aerosols collected on filter matrices are scarce. We propose here a method for the determination of CC based on a heating pretreatment of the sample to remove OC and EC, followed by a total carbon determination to measure CC. This procedure is used for the correction of EC also determined by a heating pretreatment (Cachier, H., Bremond, M.P., Buat-Ménard, P., 1989. Determination of atmospheric soot carbon with a simple thermal method. Tellus 41B, 379-390) but without previous HCl fumigation, as proposed. Comparison of the carbon remaining after the proposed thermal treatment at 460 °C for 60 min in an oxygen stream showed good correlation for the carbonate carbon derived by calculation from the ionic balance for ambient air and street dust samples. Using the "three step" combustion technique it is now possible to determine OC, EC and CC by the use of a TC analyser in the concentration range of 2-200 μg carbon per sample aliquot, with good precision (3-5% RSD for TC and 5-10% for CC) and accuracy. In ambient air samples from a sampling site in Vienna with elevated PM10 levels ("Liesing") CC values as high as 25% of TC and 27% CO 32-; for street dust samples 32% of TC and 25% CO 32- of total PM10 mass were observed.

  19. Carbon-specific analysis of humic-like substances in atmospheric aerosol and precipitation samples.

    Science.gov (United States)

    Limbeck, Andreas; Handler, Markus; Neuberger, Bernhard; Klatzer, Barbara; Puxbaum, Hans

    2005-11-15

    A new approach for the carbon-specific determination of humic-like substances (HULIS) in atmospheric aerosols is presented. The method is based on a two-step isolation procedure of HULIS and the determination of HULIS carbon with a dissolved organic carbon analyzer. In the first step, a C18 solid-phase extraction is performed to separate HULIS from inorganic and hydrophilic organic sample constituents in aqueous sample solutions. The second isolation step is conducted on a strong anion exchanger to separate HULIS from remaining carbonaceous compounds. This ion chromatographic separation step including the subsequent on-line detection of HULIS carbon was performed fully automated to avoid the risk of sample contamination and to enhance the reproducibility of the method. With a 5-mL sample volume, a limit of detection of 1.0 mg C/L was obtained; this corresponds to an absolute amount of 5 microg of HULIS carbon. The reproducibility of the method given as the relative standard deviation was 4.3% (n = 10). The method was applied for the determination of water-soluble HULIS in airborne particulate matter. PM10 concentrations at an urban site in Vienna, Austria, ranged from around 0.1 to 1.8 microg of C/m(3) (n = 49); the fraction of water-soluble HULIS in OC was 12.1 +/- 7.2% (n = 49).

  20. Process-Scale Modeling of Atmosphere-Snowpack Exchange of Nitrogen Oxides

    Science.gov (United States)

    Murray, K. A.; Doskey, P. V.; Ganzeveld, L.

    2013-12-01

    Snowpack over glacial ice is a reservoir for reactive nitrogen gases. Previous studies indicate nitrogen oxides (NOx) are generated in snowpack interstitial air through photolysis of nitrate (NO3-). Gradients in NOx mixing ratios between snowpack interstitial air and the overlying atmosphere regulate exchange of NOx with snowpack, which affects the Arctic ozone budget and climate. To better understand the dynamics of cryosphere-atmosphere exchange of NOx in the Arctic, we collected 2 years of meteorological and chemical data in and above the snowpack at Summit, Greenland. The comprehensive dataset indicates NOx emissions are episodic, with NOx enhancements in snowpack in early spring during high wind speed events (10-20 mph), which elevate NOx levels to ~500 pptv at depths of 2.5 m. Analysis of the observations will be based upon application of a 1-D process-scale model of atmosphere-snowpack exchange of NOx. The model will include representations of the snowpack chemistry in gas and aqueous phases, mass transfer of chemical species between phases, and physical transport by diffusion and wind pumping. The model will calculate the chemical and physical tendencies in three dimensions: depth, time, and intensity. Analysis of the tendencies will allow us to perform model sensitivity tests of pertinent snowpack physical and chemical processes. The end-goal of the project is to simplify the major tendencies into a parameterized model add-on for use in global models to determine the importance of properly representing snowpack in global model simulations.

  1. A dynamic leaf gas-exchange strategy is conserved in woody plants under changing ambient CO2: evidence from carbon isotope discrimination in paleo and CO2 enrichment studies

    Science.gov (United States)

    Rising atmospheric [CO2], ca, is expected to affect stomatal regulation of leaf gas-exchange of woody plants, thus influencing energy fluxes as well as carbon (C), water and nutrient cycling of forests. Researchers have reported that stomata regulate leaf gas-exchange around &ldq...

  2. Ecosystem-atmosphere exchange of CO2 in a temperate herbaceous peatland in the Sanjiang Plain of northeast China

    Science.gov (United States)

    Zhu, Xiaoyan; Song, Changchun; Swarzenski, Christopher M.; Guo, Yuedong; Zhang, Xinhow; Wang, Jiaoyue

    2015-01-01

    Northern peatlands contain a considerable share of the terrestrial carbon pool, which will be affected by future climatic variability. Using the static chamber technique, we investigated ecosystem respiration and soil respiration over two growing seasons (2012 and 2013) in a Carex lasiocarpa-dominated peatland in the Sanjiang Plain in China. We synchronously monitored the environmental factors controlling CO2 fluxes. Ecosystem respiration during these two growing seasons ranged from 33.3 to 506.7 mg CO2–C m−2 h−1. Through step-wise regression, variations in soil temperature at 10 cm depth alone explained 73.7% of the observed variance in log10(ER). The mean Q10 values ranged from 2.1 to 2.9 depending on the choice of depth where soil temperature was measured. The Q10 value at the 10 cm depth (2.9) appears to be a good representation for herbaceous peatland in the Sanjiang Plain when applying field-estimation based Q10values to current terrestrial ecosystem models due to the most optimized regression coefficient (63.2%). Soil respiration amounted to 57% of ecosystem respiration and played a major role in peatland carbon balance in our study. Emphasis on ecosystem respiration from temperate peatlands in the Sanjiang Plain will improve our basic understanding of carbon exchange between peatland ecosystem and the atmosphere.

  3. Mechanisms controlling soil carbon sequestration under atmospheric nitrogen deposition

    Energy Technology Data Exchange (ETDEWEB)

    R.L. Sinsabaugh; D.R. Zak; D.L. Moorhead

    2008-02-19

    Increased atmospheric nitrogen (N) deposition can alter the processing and storage of organic carbon in soils. In 2000, we began studying the effects of simulated atmospheric N deposition on soil carbon dynamics in three types of northern temperate forest that occur across a wide geographic range in the Upper Great Lakes region. These ecosystems range from 100% oak in the overstory (black oak-white oak ecosystem; BOWO) to 0% overstory oak (sugar maple-basswood; SMBW) and include the sugar maple-red oak ecosystem (SMRO) that has intermediate oak abundance. The leaf litter biochemistry of these ecosystems range from highly lignified litter (BOWO) to litter of low lignin content (SMBW). We selected three replicate stands of each ecosystem type and established three plots in each stand. Each plot was randomly assigned one of three levels of N deposition (0, 30 & 80 kg N ha-1 y-1) imposed by adding NaNO3 in six equal increments applied over the growing season. Through experiments ranging from the molecular to the ecosystem scales, we produced a conceptual framework that describes the biogeochemistry of soil carbon storage in N-saturated ecosystems as the product of interactions between the composition of plant litter, the composition of the soil microbial community and the expression of extracellular enzyme activities. A key finding is that atmospheric N deposition can increase or decrease the soil C storage by modifying the expression of extracellular enzymes by soil microbial communities. The critical interactions within this conceptual framework have been incorporated into a new class of simulations called guild decomposition models.

  4. Foliage/atmosphere exchange of mercury in a subtropical coniferous forest in south China

    Science.gov (United States)

    Luo, Yao; Duan, Lei; Driscoll, Charles T.; Xu, Guangyi; Shao, Mengshu; Taylor, Mariah; Wang, Shuxiao; Hao, Jiming

    2016-07-01

    Foliage/atmosphere exchange is an important pathway of deposition and loss in the biogeochemical mercury (Hg) cycle of terrestrial ecosystems. The foliage/atmosphere fluxes of Hg0 were observed over four seasons in a Masson pine (Pinus massoniana) forest in south China. Hg0 exchange showed a bidirectional process but without clear compensation point. Hg0 emissions peaked midday in all four seasons, probably associated with Hg photoreduction on needle surface. Peaks in Hg0 adsorption/deposition often occurred in the morning, especially in spring and autumn. Although current-year needles accumulated Hg at a rate of 19.4 µg m-2 yr-1, they were a net Hg0 source of 1.7 µg m-2 yr-1 to the atmosphere as their release of Hg exceeded inputs. In addition, previous-year needles emitted Hg0 at an average rate of 9.2 µg m-2 yr-1. Based on the mass balance of Hg in the forest canopy, the dry deposition of Hg was estimated 52.5 µg m-2 yr-1, much higher than the wet deposition (to 14.4 µg m-2 yr-1). Although Hg in the atmosphere is considered the main source of Hg in folia, soil water may contribute to Hg0 emission by plant transpiration. These processes should be further studied in the future.

  5. Global observations and modeling of atmosphere-surface exchange of elemental mercury: a critical review

    Science.gov (United States)

    Zhu, Wei; Lin, Che-Jen; Wang, Xun; Sommar, Jonas; Fu, Xuewu; Feng, Xinbin

    2016-04-01

    Reliable quantification of air-surface fluxes of elemental Hg vapor (Hg0) is crucial for understanding mercury (Hg) global biogeochemical cycles. There have been extensive measurements and modeling efforts devoted to estimating the exchange fluxes between the atmosphere and various surfaces (e.g., soil, canopies, water, snow, etc.) in the past three decades. However, large uncertainties remain due to the complexity of Hg0 bidirectional exchange, limitations of flux quantification techniques and challenges in model parameterization. In this study, we provide a critical review on the state of science in the atmosphere-surface exchange of Hg0. Specifically, the advancement of flux quantification techniques, mechanisms in driving the air-surface Hg exchange and modeling efforts are presented. Due to the semi-volatile nature of Hg0 and redox transformation of Hg in environmental media, Hg deposition and evasion are influenced by multiple environmental variables including seasonality, vegetative coverage and its life cycle, temperature, light, moisture, atmospheric turbulence and the presence of reactants (e.g., O3, radicals, etc.). However, the effects of these processes on flux have not been fundamentally and quantitatively determined, which limits the accuracy of flux modeling. We compile an up-to-date global observational flux database and discuss the implication of flux data on the global Hg budget. Mean Hg0 fluxes obtained by micrometeorological measurements do not appear to be significantly greater than the fluxes measured by dynamic flux chamber methods over unpolluted surfaces (p = 0.16, one-tailed, Mann-Whitney U test). The spatiotemporal coverage of existing Hg0 flux measurements is highly heterogeneous with large data gaps existing in multiple continents (Africa, South Asia, Middle East, South America and Australia). The magnitude of the evasion flux is strongly enhanced by human activities, particularly at contaminated sites. Hg0 flux observations in East

  6. Exchange of carbon-bound hydrogen atoms ortho to the hydroxyl group in tyrosine.

    Science.gov (United States)

    Martin, R B; Morlino, V J

    1965-10-22

    The carbon-bound hydrogen atoms of tyrosine that exchange with solvent protons in strongly acid solutions at about 100 degrees C are not the methylene hydrogen atoms but a pair on the aromatic ring. Of the two pairs of protons on the aromatic ring, observed in the proton magnetic resonance spectra, the pair at higher field undergoes exchange in 2.4N DCI at 100 degrees C. Other hydrogen atoms, attached either to aliphatic or aromatic carbon atoms, exhibit no noticeable exchange under the same conditions. From a chemicalshift analysis the exchanging protons are assigned as those ortho to the hydroxyl group on the aromatic ring.

  7. Carbon mass-balance modeling and carbon isotope exchange processes in the Curonian Lagoon

    Science.gov (United States)

    Barisevičiūtė, Rūta; Žilius, Mindaugas; Ertürk, Ali; Petkuvienė, Jolita

    2016-04-01

    The Curonian lagoon one of the largest coastal lagoons in Europe is located in the southeastern part of the Baltic Sea and lies along the Baltic coast of Lithuania and the Kaliningrad region of Russia. It is influenced by a discharge of the Nemunas and other smaller rivers and saline water of the Baltic Sea. The narrow (width 0.4 km, deep 8-14 m) Klaipėda Strait is the only way for fresh water run-off and brackish water intrusions. This research is focused on carbon isotope fractionations related with air - water exchange, primary production and organic carbon sedimentation, mineralization and uptake from both marine and terrestrial sources.

  8. Hierarchy carbon paper for the gas diffusion layer of proton exchange membrane fuel cells

    Science.gov (United States)

    Du, Chunyu; Wang, Baorong; Cheng, Xinqun

    This communication described the fabrication of a hierarchy carbon paper, and its application to the gas diffusion layer (GDL) of proton exchange membrane (PEM) fuel cells. The carbon paper was fabricated by growing carbon nanotubes (CNTs) on carbon fibers via covalently assembling metal nanocatalysts. Surface morphology observation revealed a highly uniform distribution of hydrophobic materials within the carbon paper. The contact angle to water of this carbon paper was not only very large but also particularly even. Polarization measurements verified that the hierarchy carbon paper facilitated the self-humidifying of PEM fuel cells, which could be mainly attributed to its higher hydrophobic property as diagnosed by electrochemical impedance spectroscopy (EIS).

  9. The Stable and Radio- Carbon Isotopic Content of Labile and Refractory Carbon in Atmospheric Particulate Matter

    Science.gov (United States)

    McNichol, A. P.; Rosenheim, B. E.; Gerlach, D. S.; Hayes, J. M.

    2006-12-01

    Studies of the isotopic content of atmospheric particulate matter are hampered by difficulties in chemically defining the pools of carbon and analytically isolating the different pools. We are conducting studies on reference materials and atmospheric aerosol samples to develop a method to measure stable and radio- carbon isotopes on the labile and refractory carbon. We are using a flow-through combustion system that allows us to combust, collect and measure the isotopic content of the gases produced at all stages of heating/oxidizing. We compare our results to those measured using a chemothermal oxidation method (CTO) (Gustafsson et al., 2001). In this method, refractory carbon is defined as the material remaining after pre- combusting a sample at 375°C in the presence of oxygen for 24 hours. The reference materials are diesel soot, apple leaves and a hybrid of the two (DiesApple), all from NIST. These provide carbon with two well-defined fractions -- the soot provides refractory carbon that is radiocarbon dead and the apple leaves provide organic carbon that is radiocarbon modern. Radiocarbon results from DiesApple indicate that the "refractory" carbon defined by the CTO method is actually a mixture of old and modern carbon that contains over 25% modern carbon. This suggests that charred material formed from the apples leaves during the pre-combustion step is contributing to the fraction we identify as refractory carbon. We are studying this by analyzing the individual materials and the mixture using our flow-through system. First results with this system indicate that the refractory fraction trapped from the DiesApple contains much less modern carbon than the CTO method, less than 7%. We will present detailed concentration and isotopic results of the generation of carbon dioxide during programmed combustion of each of the reference materials. We studied the radiocarbon content of both the total carbon (TC) and refractory carbon in the fine particulate matter (PM

  10. Atmospheric corrosion of carbon steel resulting from short term exposures

    Energy Technology Data Exchange (ETDEWEB)

    Balasubramanian, R.; Cook, D.C.; Perez, T.; Reyes, J. [Department of Physics, Old Dominion University, Norfolk, VA 23529 (United States)

    1998-12-31

    The study of corrosion products from short term atmospheric exposures of carbon steel, is very important to understand the processes that lead to corrosion of steels, and ultimately improve the performance of such steel in highly corrosive environments. Many regions along the Gulf of Mexico have extremely corrosive environments due to high mean annual temperature, humidity, time-of-wetness and every high atmospheric pollutants. The process the formation of corrosion products resulting from short term exposure of carbon steel, both as a function of environmental conditions and exposure time, has been investigated. Two sets of coupons were exposed at marine and marine locations, in Campeche, Mexico. Each set was exposed between 1 and 12 months to study the corrosion as a function of time. During the exposure periods, the relative humidity, rainfall, mean temperature, wind speed and wind direction were monitored along with the chloride and sulfur dioxide concentrations in the air. The corroded coupons were analyzed by Moessbauer, Raman, Infrared spectroscopies and X-ray diffraction in order to completely identify the oxides and map their location in the corrosion coating. Scattering and transmission Moessbauer analysis showed some layering of the oxides with lepidocrocite and akaganeite closer to the surface. The fraction of akaganeite phase increased at sites with higher chloride concentrations. A detailed analysis on the development of the oxide phases as a function of exposure time and environmental conditions will be presented. (Author)

  11. A human needs approach to reducing atmospheric carbon

    Energy Technology Data Exchange (ETDEWEB)

    Moriarty, Patrick [Department of Industrial Design, Monash University, P.O. Box 197, Caulfield East 3145, Vic. (Australia); Honnery, Damon [Department of Mechanical and Aerospace Engineering, Monash University, P.O. Box 31, 3800 Vic. (Australia)

    2010-02-15

    Recent research has shown that once CO{sub 2} has been emitted to the atmosphere, it will take centuries for natural removal. Clearly, the longer we delay deep reductions in CO{sub 2}, the greater the risk that total greenhouse gas emissions will exceed prudent limits for avoiding dangerous anthropogenic change. We evaluate the three possible technical approaches for climate change mitigation: emission reduction methods, post-emission draw down of CO{sub 2} from the atmosphere, and geoengineering. We find that the first two approaches are unlikely to deliver the timely reductions in CO{sub 2} needed, while geoengineering methods either deliver too little or are too risky. Given the deep uncertainties in both future climate prediction and energy availability, it seems safest to actively plan for a much lower energy future. We propose a general 'shrink and share' approach to reductions in both fossil-fuel use and carbon emissions, with basic human needs satisfaction replacing economic growth as the focus for economic activity. Only with deep cuts in energy and carbon can we avoid burdening future generations with the high energy costs of air capture. (author)

  12. Carbonyl sulfide and dimethyl sulfide exchange between lawn and the atmosphere

    Science.gov (United States)

    Geng, Chunmei; Mu, Yujing

    2004-06-01

    The exchange of carbonyl sulfide (COS) between lawn and the atmosphere was investigated by using a static enclosure under natural field conditions. The results indicated that the lawn acted as a sink for atmospheric COS and a source of dimethyl sulfide (DMS). The exchange fluxes of COS and DMS ranged between -3.24 pmol m-2 s-1 and -94.52 pmol m-2 s-1, and between 0 and 3.14 pmol m-2 s-1, respectively. The lawn was capable of continuously absorbing COS in nighttime as well as in daytime. The COS fluxes depended strongly on the ambient COS mixing ratios. The dependency of DMS emission fluxes on temperature was observed in November 2002. Soil also acted as a sink for COS during our study. However, the COS exchange fluxes of the lawn were much higher than that of the soil. The average COS and DMS fluxes were much higher in spring than in autumn and in summer. The daytime vertical profiles of COS also indicated that the lawn acted as a net sink for COS.

  13. Evolution of Initial Atmospheric Corrosion of Carbon Steel in an Industrial Atmosphere

    Science.gov (United States)

    Pan, Chen; Han, Wei; Wang, Zhenyao; Wang, Chuan; Yu, Guocai

    2016-12-01

    The evolution of initial corrosion of carbon steel exposed to an industrial atmosphere in Shenyang, China, has been investigated by gravimetric, XRD, SEM/EDS and electrochemical techniques. The kinetics of the corrosion process including the acceleration and deceleration processes followed the empirical equation D = At n . The rust formed on the steel surface was bi-layered, comprised of an inner and outer layer. The outer layer was formed within the first 245 days and had lower iron content compared to the inner layer. However, the outer layer disappeared after 307 days of exposure, which is considered to be associated with the depletion of Fe3O4. The evolution of the rust layer formed on the carbon steel has also been discussed.

  14. Advances in understanding, models and parameterizations of biosphere-atmosphere ammonia exchange

    Directory of Open Access Journals (Sweden)

    C. R. Flechard

    2013-07-01

    Full Text Available Atmospheric ammonia (NH3 dominates global emissions of total reactive nitrogen (Nr, while emissions from agricultural production systems contribute about two-thirds of global NH3 emissions; the remaining third emanates from oceans, natural vegetation, humans, wild animals and biomass burning. On land, NH3 emitted from the various sources eventually returns to the biosphere by dry deposition to sink areas, predominantly semi-natural vegetation, and by wet and dry deposition as ammonium (NH4+ to all surfaces. However, the land/atmosphere exchange of gaseous NH3 is in fact bi-directional over unfertilized as well as fertilized ecosystems, with periods and areas of emission and deposition alternating in time (diurnal, seasonal and space (patchwork landscapes. The exchange is controlled by a range of environmental factors, including meteorology, surface layer turbulence, thermodynamics, air and surface heterogeneous-phase chemistry, canopy geometry, plant development stage, leaf age, organic matter decomposition, soil microbial turnover, and, in agricultural systems, by fertilizer application rate, fertilizer type, soil type, crop type, and agricultural management practices. We review the range of processes controlling NH3 emission and uptake in the different parts of the soil-canopy-atmosphere continuum, with NH3 emission potentials defined at the substrate and leaf levels by different [NH4+] / [H+] ratios (Γ. Surface/atmosphere exchange models for NH3 are necessary to compute the temporal and spatial patterns of emissions and deposition at the soil, plant, field, landscape, regional and global scales, in order to assess the multiple environmental impacts of airborne and deposited NH3 and NH4+. Models of soil/vegetation/atmosphere NH3 exchange are reviewed from the substrate and leaf scales to the global scale. They range from simple steady-state, "big leaf" canopy resistance models, to dynamic, multi-layer, multi-process, multi

  15. Atmospheric monitoring for fugitive emissions from geological carbon storage

    Science.gov (United States)

    Loh, Z. M.; Etheridge, D.; Luhar, A.; Leuning, R.; Jenkins, C.

    2013-12-01

    We present a multi-year record of continuous atmospheric CO2 and CH4 concentration measurements, flask sampling (for CO2, CH4, N2O, δ13CO2 and SF6) and CO2 flux measurements at the CO2CRC Otway Project (http://www.co2crc.com.au/otway/), a demonstration site for geological storage of CO2 in south-western Victoria, Australia. The measurements are used to develop atmospheric methods for operational monitoring of large scale CO2 geological storage. Characterization of emission rates ideally requires concentration measurements upwind and downwind of the source, along with knowledge of the atmospheric turbulence field. Because only a single measurement location was available for much of the measurement period, we develop techniques to filter the record and to construct a ';pseudo-upwind' measurement from our dataset. Carbon dioxide and methane concentrations were filtered based on wind direction, downward shortwave radiation, atmospheric stability and hour-to-hour changes in CO2 flux. These criteria remove periods of naturally high concentration due to the combined effects of biogenic respiration, stable atmospheric conditions and pre-existing sources (both natural and anthropogenic), leaving a reduced data set, from which a fugitive leak from the storage reservoir, the ';(potential) source sector)', could more easily be detected. Histograms of the filtered data give a measure of the background variability in both CO2 and CH4. Comparison of the ';pseudo-upwind' dataset histogram with the ';(potential) source sector' histogram shows no statistical difference, placing limits on leakage to the atmosphere over the preceding two years. For five months in 2011, we ran a true pair of up and downwind CO2 and CH4 concentration measurements. During this period, known rates of gas were periodically released at the surface (near the original injection point). These emissions are clearly detected as elevated concentrations of CO2 and CH4 in the filtered data and in the measured

  16. Seaweeds and halophytes to remove carbon from the atmosphere

    Energy Technology Data Exchange (ETDEWEB)

    Glenn, E.P.; Kent, K.J.; Thompson, T.L.; Frye, R.J. (Arizona Univ., Tucson, AZ (USA). Environmental Research Lab.)

    1991-02-01

    The utility industry and other interested parties have investigated strategies to mitigate the buildup of atmospheric CO{sub 2}. One option that has been considered is the planting of trees on a massive scale to absorb carbon through photosynthesis. A dilemma of using tree plantations, however, is that they might occupy land that will be needed for food production or other needs for an expected doubling of human population in the tropical regions. We evaluated seaweeds and salt-tolerant terrestrial plants (halophytes) to be grown on the coastal shelves and salt deserts of the world as possible alternatives to tree plantations. An estimated 1.3 {times} 10{sup 6} km{sup 2} of continental shelf and 1.3 {times} 10{sup 6} km{sup 2} of salt desert may be usable for seaweed and halophyte plantations. The production rates of managed seaweed and halophyte plantings are similar to managed tree plantations. Seaweeds and halophytes could conceivably absorb 10--20% of annual fossil fuel carbon emissions through biomass production, similar to estimates made for tree plantations. Present costs of halophyte biomass production are similar to costs of tree biomass production, whereas seaweed biomass is much more expensive to produce using existing technologies. Storage of seaweed carbon might be accomplished by allowing it to enter the sediment detritus chain whereas halophyte carbon might be sequestered in the soil, or used as biomass fuel. As has been concluded for reforestation, these saline biomass crops could at best help delay rather than solve the carbon dioxide build-up problem. 1 fig., 13 tabs.

  17. South Atlantic interbasin exchanges of mass, heat, salt and anthropogenic carbon

    Science.gov (United States)

    Evans, G. R.; McDonagh, E. L.; King, B. A.; Bryden, H. L.; Bakker, D. C. E.; Brown, P. J.; Schuster, U.; Speer, K. G.; van Heuven, S. M. A. C.

    2017-02-01

    The exchange of mass, heat, salt and anthropogenic carbon (Cant) between the South Atlantic, south of 24°S, and adjacent ocean basins is estimated from hydrographic data obtained during 2008-2009 using an inverse method. Transports of anthropogenic carbon are calculated across the western (Drake Passage), eastern (30°E) and northern (24°S) boundaries. The freshwater overturning transport of 0.09 Sv is southward, consistent with an overturning circulation that exports freshwater from the North Atlantic, and consistent with a bistable Meridional Overturning Circulation (MOC), under conditions of excess freshwater perturbation. At 30°E, net eastward Antarctic Circumpolar Current (ACC) transport, south of the Subtropical Front, is compensated by a 15.9 ± 2.3 Sv westward flow along the Antarctic boundary. The region as a whole is a substantial sink for atmospheric anthropogenic carbon of 0.51 ± 0.37 Pg C yr-1, of which 0.18 ± 0.12 Pg C yr-1 accumulates and is stored within the water column. At 24°S, a 20.2 Sv meridional overturning is associated with a 0.11 Pg C yr-1 Cant overturning. The remainder is transported into the Atlantic Ocean north of 24°S (0.28 ± 0.16 Pg C yr-1) and Indian sector of Southern Ocean (1.12 ± 0.43 Pg C yr-1), having been enhanced by inflow through Drake Passage (1.07 ± 0.44 Pg C yr-1). This underlines the importance of the South Atlantic as a crucial element of the anthropogenic carbon sink in the global oceans.

  18. Towards a Carbon Nanotube Ionization Source for Planetary Atmosphere Exploration

    Science.gov (United States)

    Oza, A. V.; Leblanc, F.; Berthelier, J. J.; Becker, J.; Coulomb, R.; Gilbert, P.; Hong, N. T.; Lee, S.; Vettier, L.

    2015-12-01

    The characterization of planetary exospheres today, relies on the development of a highly efficient ionization source, due to the scant neutral molecules (n atmospheres provide insight on to physical processes known to occur such as: space weathering, magneto-atmosphere interactions, as well as atmospheric escape mechanisms, all of which are being heavily investigated via current 3D Monte Carlo simulations (Turc et al. 2014, Leblanc et al. 2016 in prep) at LATMOS. Validation of these studies will rely on in-situ observations in the coming decades. Neutral detection strongly depends on electron-impact ionization which via conventional cathode-sources, such as thermal filaments (heated up to 2000 K), may only produce the target ionization essential for energy-measurements with large power consumption. Carbon nanotubes (CNTs) however are ideal low-power, cold cathodes, when subject to moderate electric fields (E ~ 1 MV / m). We present our current device, a small CNT chip, of emission area 15 mm2, emitting electrons that pass through an anode grid and subsequent electrostatic analyzer. The device currently extracts hundreds of µAmperes with applied external voltages ~ -150 Volts, approaching minimum power consumption plasma sputtering the icy regolith with heavy ions and electrons (keV < E < MeV), producing predominately molecular oxygen (Johnson et al. 2002).

  19. Characteristics of brown carbon in the urban Po Valley atmosphere

    Science.gov (United States)

    Costabile, Francesca; Gilardoni, Stefania; Barnaba, Francesca; Di Ianni, Antonio; Di Liberto, Luca; Dionisi, Davide; Manigrasso, Maurizio; Paglione, Marco; Poluzzi, Vanes; Rinaldi, Matteo; Facchini, Maria Cristina; Gobbi, Gian Paolo

    2017-01-01

    We investigate optical-microphysical-chemical properties of brown carbon (BrC) in the urban ambient atmosphere of the Po Valley. In situ ground measurements of aerosol spectral optical properties, PM1 chemical composition (HR-ToF-AMS), and particle size distributions were carried out in Bologna. BrC was identified through its wavelength dependence of light absorption at visible wavelengths, as indicated by the absorption Ångström exponent (AAE). We found that BrC occurs in particles with a narrow monomodal size distribution peaking in the droplet mode, enriched in ammonium nitrate and poor in black carbon (BC), with a strong dependance on OA-to-BC ratios, and SSA530 of 0.98 ± 0.01. We demonstrate that specific complex refractive index values (k530 = 0.017 ± 0.001) are necessary in addition to a proper particle size range to match the large AAEs measured for this BrC (AAE467 - 660 = 3.2 ± 0.9 with values up to 5.3). In terms of consistency of these findings with literature, this study i. provides experimental evidence of the size distribution of BrC associated with the formation of secondary aerosol;ii. shows that in the lower troposphere AAE increases with increasing OA-to-BC ratios rather than with increasing OA - contributing to sky radiometer retrieval techniques (e.g., AERONET);iii. extends the dependence of AAE on BC-to-OA ratios previously observed in chamber experiments to ambient aerosol dominated by wood-burning emissions. These findings are expected to bear important implications for atmospheric modeling studies and remote sensing observations as regards the parametrization and identification of BrC in the atmosphere.

  20. [Size distributions of organic carbon (OC) and elemental carbon (EC) in Shanghai atmospheric particles].

    Science.gov (United States)

    Wang, Guang-Hua; Wei, Nan-Nan; Liu, Wei; Lin, Jun; Fan, Xue-Bo; Yao, Jian; Geng, Yan-Hong; Li, Yu-Lan; Li, Yan

    2010-09-01

    Size distributions of organic carbon (OC), elemental carbon (EC) and secondary organic carbon (SOC) in atmospheric particles with size range from 7.20 microm, collected in Jiading District, Shanghai were determined. For estimating size distribution of SOC in these atmospheric particles, a method of determining (OC/EC)(pri) in atmospheric particles with different sizes was discussed and developed, with which SOC was estimated. According to the correlation between OC and EC, main sources of the particles were also estimated roughly. The size distributions of OC and SOC showed a bi-modal with peaks in the particles with size of 3.0 microm, respectively. EC showed both of a bi-modal and tri-modal. Compared with OC, EC was preferably enriched in particles with size of particles (particles. OC and EC were preferably enriched in fine particles (particles with different sizes accounted for 15.7%-79.1% of OC in the particles with corresponding size. Concentrations of SOC in fine aerosols ( 3.00 microm) accounted for 41.4% and 43.5% of corresponding OC. Size distributions of OC, EC and SOC showed time-dependence. The correlation between OC and EC showed that the main contribution to atmospheric particles in Jiading District derived from light petrol vehicles exhaust.

  1. Influence of anodic surface treatment of activated carbon on adsorption and ion exchange properties

    Energy Technology Data Exchange (ETDEWEB)

    Park, S.J.; Kim, K.D.

    1999-10-01

    The effect of anodic surface treatment of activated carbon on adsorption and ion exchange characteristics was investigated in the condition of 35 wt% NaOH electrolyte for 60 s. The acid and base values were determined by a titration technique, and surface and pore structures were studied in terms of BET volumetric measurement with N{sub 2} adsorption. The ion exchange capacity of the anodized activated carbons was characterized by a dry weight capacity technique. It was observed that an increase in current intensity leads to an increase in the surface functional groups of activated carbons, resulting in increasing pH, acid-base values, and anion-cation exchange capacities, without significant change of surface and pore structures (i.e., specific surface area, total pore volume, micropore volume, and average pore diameter). Also, anodically treated activated carbons are more effectively evaluated on the base value or cation exchange capacity than on the oppose properties in this electrolytic system.

  2. ROLE OF LEAF SURFACE WATER IN THE BI-DIRECTIONAL AMMONIA EXCHANGE BETWEEN THE ATMOSPHERE AND TERRESTRIAL BIOSPHERE

    Science.gov (United States)

    A field experiment was conducted to study the ammonia exchange between plants and the atmosphere in a soybean field in Duplin County, North Carolina during the summer of 2002. Measurements indicate that the net canopy-scale ammonia exchange is bi-directional and has a significant...

  3. The Arctic Ocean marine carbon cycle: evaluation of air-sea CO2 exchanges, ocean acidification impacts and potential feedbacks

    Directory of Open Access Journals (Sweden)

    N. R. Bates

    2009-11-01

    Full Text Available At present, although seasonal sea-ice cover mitigates atmosphere-ocean gas exchange, the Arctic Ocean takes up carbon dioxide (CO2 on the order of −66 to −199 Tg C year−1 (1012 g C, contributing 5–14% to the global balance of CO2 sinks and sources. Because of this, the Arctic Ocean has an important influence on the global carbon cycle, with the marine carbon cycle and atmosphere-ocean CO2 exchanges sensitive to Arctic Ocean and global climate change feedbacks. In the near-term, further sea-ice loss and increases in phytoplankton growth rates are expected to increase the uptake of CO2 by Arctic Ocean surface waters, although mitigated somewhat by surface warming in the Arctic. Thus, the capacity of the Arctic Ocean to uptake CO2 is expected to alter in response to environmental changes driven largely by climate. These changes are likely to continue to modify the physics, biogeochemistry, and ecology of the Arctic Ocean in ways that are not yet fully understood. In surface waters, sea-ice melt, river runoff, cooling and uptake of CO2 through air-sea gas exchange combine to decrease the calcium carbonate (CaCO3 mineral saturation states (Ω of seawater while seasonal phytoplankton primary production (PP mitigates this effect. Biological amplification of ocean acidification effects in subsurface waters, due to the remineralization of organic matter, is likely to reduce the ability of many species to produce CaCO3 shells or tests with profound implications for Arctic marine ecosystems

  4. The Arctic Ocean marine carbon cycle: evaluation of air-sea CO2 exchanges, ocean acidification impacts and potential feedbacks

    Directory of Open Access Journals (Sweden)

    J. T. Mathis

    2009-07-01

    Full Text Available At present, although seasonal sea-ice cover mitigates atmosphere-ocean gas exchange, the Arctic Ocean takes up carbon dioxide (CO2 on the order of −65 to −175 Tg C year−1, contributing 5–14% to the global balance of CO2 sinks and sources. Because of this, the Arctic Ocean is an important influence on the global carbon cycle, with the marine carbon cycle and atmosphere-ocean CO2 exchanges sensitive to Arctic Ocean and global climate change feedbacks. In the near-term, further sea-ice loss and increases in phytoplankton growth rates are expected to increase the uptake of CO2 by Arctic surface waters, although mitigated somewhat by surface warming in the Arctic. Thus, the capacity of the Arctic Ocean to uptake CO2 is expected to alter in response to environmental changes driven largely by climate. These changes are likely to continue to modify the physics, biogeochemistry, and ecology of the Arctic Ocean in ways that are not yet fully understood. In surface waters, sea-ice melt, river runoff, cooling and uptake of CO2 through air-sea gas exchange combine to decrease the calcium carbonate (CaCO3 mineral saturation states (Ω of seawater that is counteracted by seasonal phytoplankton primary production (PP. Biological processes drive divergent trajectories for Ω in surface and subsurface waters of Arctic shelves with subsurface water experiencing undersaturation with respect to aragonite and calcite. Thus, in response to increased sea-ice loss, warming and enhanced phytoplankton PP, the benthic ecosystem of the Arctic shelves are expected to be negatively impacted by the biological amplification of ocean acidification. This in turn reduces the ability of many species to produce CaCO3 shells or tests with profound implications for Arctic marine ecosystems.

  5. Atmospheric Carbon Dioxide and the Global Carbon Cycle: The Key Uncertainties

    Science.gov (United States)

    Peng, T. H.; Post, W. M.; DeAngelis, D. L.; Dale, V. H.; Farrell, M. P.

    1987-12-01

    The biogeochemical cycling of carbon between its sources and sinks determines the rate of increase in atmospheric CO{sub 2} concentrations. The observed increase in atmospheric CO{sub 2} content is less than the estimated release from fossil fuel consumption and deforestation. This discrepancy can be explained by interactions between the atmosphere and other global carbon reservoirs such as the oceans, and the terrestrial biosphere including soils. Undoubtedly, the oceans have been the most important sinks for CO{sub 2} produced by man. But, the physical, chemical, and biological processes of oceans are complex and, therefore, credible estimates of CO{sub 2} uptake can probably only come from mathematical models. Unfortunately, one- and two-dimensional ocean models do not allow for enough CO{sub 2} uptake to accurately account for known releases. Thus, they produce higher concentrations of atmospheric CO{sub 2} than was historically the case. More complex three-dimensional models, while currently being developed, may make better use of existing tracer data than do one- and two-dimensional models and will also incorporate climate feedback effects to provide a more realistic view of ocean dynamics and CO{sub 2} fluxes. The instability of current models to estimate accurately oceanic uptake of CO{sub 2} creates one of the key uncertainties in predictions of atmospheric CO{sub 2} increases and climate responses over the next 100 to 200 years.

  6. Gas exchange and the coagulation system of the blood during the effect on the body of high concentrations of oxygen and carbon dioxide

    Science.gov (United States)

    Palosh, L.; Agadzhanyan, N. A.; Davydov, G. A.; Rybakov, B. K.; Sergiyenko, A. S.

    1974-01-01

    Maximum permissible concentrations of oxygen and carbon dioxide in a controlled atmosphere were determined by evaluating their effects on human gas exchange, blood coagulation, and tolerances to acute hypoxia, acceleration, and physical loads. It was found that functional disturbances depend on the concentration of respiratory gases and the length of stay in an altered atmosphere. By changing the atmospheric composition and by bringing the gaseous environment into accordance with the work and rest regimen and energy expenditures, the general reactivity of the body changes favorably.

  7. Brown carbon: a significant atmospheric absorber of solar radiation?

    Directory of Open Access Journals (Sweden)

    Y. Feng

    2013-09-01

    Full Text Available Several recent observational studies have shown organic carbon aerosols to be a significant source of absorption of solar radiation. The absorbing part of organic aerosols is referred to as "brown" carbon (BrC. Using a global chemical transport model and a radiative transfer model, we estimate for the first time the enhanced absorption of solar radiation due to BrC in a global model. The simulated wavelength dependence of aerosol absorption, as measured by the absorption Ångström exponent (AAE, increases from 0.9 for non-absorbing organic carbon to 1.2 (1.0 for strongly (moderately absorbing BrC. The calculated AAE for the strongly absorbing BrC agrees with AERONET spectral observations at 440–870 nm over most regions but overpredicts for the biomass burning-dominated South America and southern Africa, in which the inclusion of moderately absorbing BrC has better agreement. The resulting aerosol absorption optical depth increases by 18% (3% at 550 nm and 56% (38% at 380 nm for strongly (moderately absorbing BrC. The global simulations suggest that the strongly absorbing BrC contributes up to +0.25 W m−2 or 19% of the absorption by anthropogenic aerosols, while 72% is attributed to black carbon, and 9% is due to sulfate and non-absorbing organic aerosols coated on black carbon. Like black carbon, the absorption of BrC (moderately to strongly inserts a warming effect at the top of the atmosphere (TOA (0.04 to 0.11 W m−2, while the effect at the surface is a reduction (−0.06 to −0.14 W m−2. Inclusion of the strongly absorption of BrC in our model causes the direct radiative forcing (global mean of organic carbon aerosols at the TOA to change from cooling (−0.08 W m−2 to warming (+0.025 W m−2. Over source regions and above clouds, the absorption of BrC is higher and thus can play an important role in photochemistry and the hydrologic cycle.

  8. Brown carbon: a significant atmospheric absorber of solar radiation?

    Directory of Open Access Journals (Sweden)

    Y. Feng

    2013-01-01

    Full Text Available Several recent observational studies have shown organic carbon aerosols to be a significant source of absorption of solar radiation. The absorbing part of organic aerosols is referred to as brown carbon. Comparisons with observations indicate that model-simulated aerosol absorption is under-estimated in global models, one of the reasons being the neglect of brown carbon. Using a global chemical transport model coupled with a radiative transfer model, we estimate for the first time the enhanced absorption of solar radiation due to "brown" carbon (BrC in a global model. When BrC is included, the simulated wavelength dependence of aerosol absorption, as measured by the Angstrom exponent increases from 0.9 to 1.2 and thus agrees better with AERONET spectral observations at 440–870 nm. The resulting absorbing aerosol optical depth increases by 3–18% at 550 nm and up to 56% at 350 nm. The global simulations suggest that BrC contributes up to +0.25 W m−2 or 19% of the absorption by anthropogenic aerosols, of which 72% is attributed to black carbon, and 9% is due to sulfate and non-absorbing organic aerosols coated on black carbon. Like black carbon, the overall forcing of BrC at the top of the atmosphere (TOA is a warming effect (+0.11 W m−2, while the effect at the surface is a reduction or dimming (−0.14 W m−2. Because of the inclusion of BrC in our model, the direct radiative effect of organic carbonaceous aerosols changes from cooling (−0.08 W m−2 to warming (+0.025 W m−2 at the TOA, on a global mean basis. Over source regions and above clouds, the absorption of BrC is more significant and thus can play an important role in photochemistry and the hydrologic cycle.

  9. Observations of the uptake of carbonyl sulfide (COS by trees under elevated atmospheric carbon dioxide concentrations

    Directory of Open Access Journals (Sweden)

    L. Sandoval-Soto

    2012-02-01

    Full Text Available Global change affects ecosystems to adapt to elevated atmospheric concentrations of carbon dioxide (CO2. We understand that carbonyl sulfide (COS, a trace gas which is involved in building up the stratospheric sulfate aerosol layer, is taken up by vegetation with the same triad of the enzmyes which are metabolizing the CO2, i.e. Ribulose-1,5-bisphosphate Carboxylase-Oxygenase (Rubisco, Phosphoenolpyruvate Carboxylase (PEP-Co and carbonic anhydrase (CA. Therefore, we discuss a physiological/biochemical adaptation of these enzymes to affect the sink strength of vegetation for COS. We investigated the adaption of two European tree species, Fagus sylvatica and Quercus ilex, grown inside chambers under elevated CO2 and determined the exchange characteristics and the content of CA after a 1–2 yr period of adaption from 350 ppm to 800 ppm CO2. We could demonstrate that the COS compensation point, the CA activity and the deposition velocities may change and cause a decrease of the COS uptake by plant ecosystems. As a consequence, the atmospheric COS level may rise leading to higher input of this trace gas into the stratosphere and causing a higher energy reflection by the stratospheric sulfur aerosol into space, thus counteracting the direct radiative forcing by the tropospheric COS.

  10. The travel-related carbon dioxide emissions of atmospheric researchers

    Science.gov (United States)

    Stohl, A.

    2008-11-01

    Most atmospheric scientists agree that greenhouse gas emissions have already caused significant changes to the global climate system and that these changes will accelerate in the near future. At the same time, atmospheric scientists who like other scientists rely on international collaboration and information exchange travel a lot and, thereby, cause substantial emissions of CO2. In this paper, the CO2 emissions of the employees working at an atmospheric research institute (the Norwegian Institute for Air Research, NILU) caused by all types of business travel (conference visits, workshops, field campaigns, instrument maintainance, etc.) were calculated for the years 2005 2007. It is estimated that more than 90% of the emissions were caused by air travel, 3% by ground travel and 5% by hotel usage. The travel-related annual emissions were between 1.9 and 2.4 t CO2 per employee or between 3.9 and 5.5 t CO2 per scientist. For comparison, the total annual per capita CO2 emissions are 4.5 t worldwide, 1.2 t for India, 3.8 t for China, 5.9 t for Sweden and 19.1 t for Norway. The travel-related CO2 emissions of a NILU scientist, occurring in 24 days of a year on average, exceed the global average annual per capita emission. Norway's per-capita CO2 emissions are among the highest in the world, mostly because of the emissions from the oil industry. If the emissions per NILU scientist derived in this paper are taken as representative for the average Norwegian researcher, travel by Norwegian scientists would nevertheless account for a substantial 0.2% of Norway's total CO2 emissions. Since most of the travel-related emissions are due to air travel, water vapor emissions, ozone production and contrail formation further increase the relative importance of NILU's travel in terms of radiative forcing.

  11. Atmospheric aerosol brown carbon in the high Himalayas

    Science.gov (United States)

    Kirillova, Elena; Decesari, Stefano; Marinoni, Angela; Bonasoni, Paolo; Vuillermoz, Elisa; Facchini, M. Cristina; Fuzzi, Sandro

    2016-04-01

    Anthropogenic light-absorbing atmospheric aerosol can reach very high concentrations in the planetary boundary layer in South-East Asia ("brown clouds"), affecting atmospheric transparency and generating spatial gradients of temperature over land with a possible impact on atmospheric dynamics and monsoon circulation. Besides black carbon (BC), an important light-absorbing component of anthropogenic aerosols is the organic carbon component known as 'brown carbon' (BrC). In this research, we provided first measurements of atmospheric aerosol BrC in the high Himalayas during different seasons. Aerosol sampling was conducted at the GAW-WMO Global station "Nepal Climate Observatory-Pyramid" (NCO-P) located in the high Khumbu valley at 5079 m a.s.l. in the foothills of Mt. Everest. PM10 aerosol samples were collected from July 2013 to November 2014. The sampling strategy was set up in order to discriminate the daytime valley breeze bringing polluted air masses up to the observatory and free tropospheric air during nighttime. Water-soluble BrC (WS-BrC) and methanol-soluble BrC (MeS-BrC) were extracted and analyzed using a UV/VIS spectrophotometer equipped with a 50 cm liquid waveguide capillary cell. In the polluted air masses, the highest levels of the BrC light absorption coefficient at 365 nm (babs365) were observed during the pre-monsoon season (1.83±1.46 Mm-1 for WS-BrC and 2.86±2.49 Mm-1 for MeS-BrC) and the lowest during the monsoon season (0.21±0.22 Mm-1 for WS-BrC and 0.32±0.29 Mm-1 for MeS-BrC). The pre-monsoon season is the most frequently influenced by a strong atmospheric brown cloud (ABC) transport to NCO-P due to increased convection and mixing layer height over South Asia combined with the highest up-valley wind speed and the increase of the emissions from open fires due to the agricultural practice along the Himalayas foothills and the Indo-Gangetic Plain. In contrast, the monsoon season is characterized by a weakened valley wind regime and an

  12. Controlling factors of biosphere-atmosphere ammonia exchange at a semi-natural peatland site

    Science.gov (United States)

    Brummer, C.; Richter, U.; Smith, J. J.; Delorme, J. P.; Kutsch, W. L.

    2014-12-01

    Recent advancements in laser spectrometry offer new opportunities to investigate net biosphere-atmosphere exchange of ammonia. During a three month field campaign from February to May 2014, we tested the performance of a quantum cascade laser within an eddy-covariance setup. The laser was operated at a semi-natural peatland site that is surrounded by highly fertilized agricultural land and intensive livestock production (~1 km distance). Ammonia concentrations were highly variable between 2 and almost 100 ppb with an average value of 15 ppb. Different concentration patterns could be identified. The variability was closely linked to the timing of management practices and the prevailing local climate, particularly wind direction, temperature and surface wetness with the latter indicating higher non-stomatal uptake under wet conditions leading to decreased concentrations. Average ammonia fluxes were around -15 ng N m-2 s-1 at the beginning of the campaign in February and shifted towards a neutral average exchange regime of -1 to 0 ng N m-2 s-1 in April and May. Intriguingly, during the time of decreasing ammonia uptake, concentrations were considerably rising, which clearly indicated N saturation in the predominant vegetation such as bog heather, purple moor-grass, and cotton grass. The cumulative net uptake for the period of investigation was ~300 g N ha-1. This stresses the importance of a thorough method inter-comparison, e.g. with denuder systems in combination with dry deposition modeling. As previous results from the latter methods showed an annual uptake of ~9 kg N ha-1 for the same site, the implementation of adequate ammonia compensation point parameterizations become crucial in surface-atmosphere exchange schemes for bog vegetation. Through their high temporal resolution, robustness and continuous measurement mode, quantum cascade lasers will help assessing the effects of atmospheric N loads to vulnerable N-limited ecosystems such as peatlands.

  13. Carbon Abundances In The Light Of 3D Model Stellar Atmospheres

    DEFF Research Database (Denmark)

    Collet, Remo

    ) hydrodynamic modelling of stellar atmospheres and stellar spectra. In this contribution, I describe quantitatively the impact of realistic, time-dependent, 3D hydrodynamic model atmospheres on the spectroscopic determination of carbon abundances from CH molecular lines for stars with a wide range of stellar...... carbon abundance corrections on the oxygen abundance in carbon-enhanced metal-poor (CEMP) stars and show that such corrections are extremely sensitive to the atmospheric C/O ratio....

  14. Advances in understanding, models and parameterisations of biosphere-atmosphere ammonia exchange

    Directory of Open Access Journals (Sweden)

    C. R. Flechard

    2013-03-01

    Full Text Available Atmospheric ammonia (NH3 dominates global emissions of total reactive nitrogen (Nr, while emissions from agricultural production systems contribute about two thirds of global NH3 emissions; the remaining third emanates from oceans, natural vegetation, humans, wild animals and biomass burning. On land, NH3 emitted from the various sources eventually returns to the biosphere by dry deposition to sink areas, predominantly semi-natural vegetation, and by wet and dry deposition as ammonium (NH4+ to all surfaces. However, the land/atmosphere exchange of gaseous NH3 is in fact bi-directional over unfertilized as well as fertilized ecosystems, with periods and areas of emission and deposition alternating in time (diurnal, seasonal and space (patchwork landscapes. The exchange is controlled by a range of environmental factors, including meteorology, surface layer turbulence, thermodynamics, air and surface heterogeneous-phase chemistry, canopy geometry, plant development stage, leaf age, organic matter decomposition, soil microbial turnover, and, in agricultural systems, by fertilizer application rate, fertilizer type, soil type, crop type, and agricultural management practices. We review the range of processes controlling NH3 emission and uptake in the different parts of the soil-canopy-atmosphere continuum, with NH3 emission potentials defined at the substrate and leaf levels by different [NH4+] / [H+] ratios (Γ. Surface/atmosphere exchange models for NH3 are necessary to compute the temporal and spatial patterns of emissions and deposition at the soil, plant, field, landscape, regional and global scales, in order to assess the multiple environmental impacts of air-borne and deposited NH3 and NH4+. Models of soil/vegetation/atmosphereem NH3 exchange are reviewed from the substrate and leaf scales to the global scale. They range from simple steady-state, "big leaf" canopy resistance models, to dynamic, multi-layer, multi

  15. Mineral carbonation of gaseous carbon dioxide using a clay-hosted cation exchange reaction.

    Science.gov (United States)

    Kang, Il-Mo; Roh, Ki-Min

    2013-01-01

    The mineral carbonation method is still a challenge in practical application owing to: (1) slow reaction kinetics, (2) high reaction temperature, and (3) continuous mineral consumption. These constraints stem from the mode of supplying alkaline earth metals through mineral acidification and dissolution. Here, we attempt to mineralize gaseous carbon dioxide into calcium carbonate, using a cation exchange reaction of vermiculite (a species of expandable clay minerals). The mineralization is operated by draining NaCI solution through vermiculite powders and continuously dropping into the pool of NaOH solution with CO2 gas injected. The mineralization temperature is regulated here at 293 and 333 K for 15 min. As a result of characterization, using an X-ray powder diffractometer and a scanning electron microscopy, two types of pure CaCO3 polymorphs (vaterite and calcite) are identified as main reaction products. Their abundance and morphology are heavily dependent on the mineralization temperature. Noticeably, spindle-shaped vaterite, which is quite different from a typical vaterite morphology (polycrystalline spherulite), forms predominantly at 333 K (approximately 98 wt%).

  16. The role of ozone atmosphere-snow gas exchange on polar, boundaru-layer tropospheric ozone - a review sensitivity analysis

    NARCIS (Netherlands)

    Helmig, D.; Ganzeveld, L.N.; Butler, T.; Oltmans, S.

    2007-01-01

    Recent research on snowpack processes and atmosphere-snow gas exchange has demonstrated that chemical and physical interactions between the snowpack and the overlaying atmosphere have a substantial impact on the composition of the lower troposphere. These observations also imply that ozone depositio

  17. An Overview of the Regional Experiments for Land-Atmosphere Exchanges 2012 (Reflex 2012 Campaign

    Directory of Open Access Journals (Sweden)

    Timmermans Wim J.

    2015-12-01

    Full Text Available The REFLEX 2012 campaign was initiated as part of a training course on the organization of an airborne campaign to support advancement of the understanding of land-atmosphere interaction processes. This article describes the campaign, its objectives and observations, remote as well as in situ. The observations took place at the experimental Las Tiesas farm in an agricultural area in the south of Spain. During the period of ten days, measurements were made to capture the main processes controlling the local and regional land-atmosphere exchanges. Apart from multi-temporal, multi-directional and multi-spatial space-borne and airborne observations, measurements of the local meteorology, energy fluxes, soil temperature profiles, soil moisture profiles, surface temperature, canopy structure as well as leaf-level measurements were carried out. Additional thermo-dynamical monitoring took place at selected sites.

  18. Contribution of different grass species to plant-atmosphere ammonia exchange in intensively managed grassland

    Science.gov (United States)

    Mattsson, M.; Herrmann, B.; Jones, S.; Neftel, A.; Sutton, M. A.; Schjoerring, J. K.

    2009-01-01

    Species diversity in grasslands usually declines with increasing input of nitrogen from fertilizers or atmospheric deposition. Conversely, species diversity may also impact the build-up of soil and plant nitrogen pools. One important pool is NH3/NH4+ which also can be exchanged between plant leaves and the atmosphere. Limited information is available on how plant-atmosphere ammonia exchange is related to species diversity in grasslands. We have here investigated grass species abundance and different foliar nitrogen pools in 4-year-old intensively managed grassland. Apoplastic pH and NH4+ concentrations of the 8 most abundant species (Lolium perenne, Phleum pratense, Festuca pratensis, Lolium multiflorum, Poa pratensis, Dactylis glomerata, Holcus lanatus, Bromus mollis) were used to calculate stomatal NH3 compensation points. Apoplastic NH4+ concentrations differed considerably among the species, ranging from 13 to 117 μM, with highest values in Festuca pratensis. Also apoplastic pH values varied, from pH 6.0 in Phleum pratense to 6.9 in Dactylis glomerata. The observed differences in apoplastic NH4+ and pH resulted in a large span of predicted values for the stomatal NH3 compensation point which ranged between 0.20 and 6.57 nmol mol-1. Three species (Lolium perenne, Festuca pratensis and Dactylis glomerata) had sufficiently high NH3 compensation point and abundance to contribute to the bi-directional NH3 fluxes recorded over the whole field. The other 5 grass species had NH3 compensation points considerably below the atmospheric NH3 concentration and were thus not likely to contribute to NH3 emission but only to NH3 uptake from the atmosphere. Evaluated across species, leaf bulk-tissue NH4+ concentrations correlated well (r2=0.902) with stomatal NH3 compensation points calculated on the basis of the apoplastic bioassay. This suggests that leaf tissue NH4+ concentrations combined with data for the frequency distribution of the corresponding species can be used for

  19. A comprehensive estimate for loss of atmospheric carbon tetrachloride (CCl4) to the ocean

    Science.gov (United States)

    Butler, James H.; Yvon-Lewis, Shari A.; Lobert, Jurgen M.; King, Daniel B.; Montzka, Stephen A.; Bullister, John L.; Koropalov, Valentin; Elkins, James W.; Hall, Bradley D.; Hu, Lei; Liu, Yina

    2016-09-01

    Extensive undersaturations of carbon tetrachloride (CCl4) in Pacific, Atlantic, and Southern Ocean surface waters indicate that atmospheric CCl4 is consumed in large amounts by the ocean. Observations made on 16 research cruises between 1987 and 2010, ranging in latitude from 60° N to 77° S, show that negative saturations extend over most of the surface ocean. Corrected for physical effects associated with radiative heat flux, mixing, and air injection, these anomalies were commonly on the order of -5 to -10 %, with no clear relationship to temperature, productivity, or other gross surface water characteristics other than being more negative in association with upwelling. The atmospheric flux required to sustain these undersaturations is 12.4 (9.4-15.4) Gg yr-1, a loss rate implying a partial atmospheric lifetime with respect to the oceanic loss of 183 (147-241) yr and that ˜ 18 (14-22) % of atmospheric CCl4 is lost to the ocean. Although CCl4 hydrolyzes in seawater, published hydrolysis rates for this gas are too slow to support such large undersaturations, given our current understanding of air-sea gas exchange rates. The even larger undersaturations in intermediate depth waters associated with reduced oxygen levels, observed in this study and by other investigators, strongly suggest that CCl4 is ubiquitously consumed at mid-depth, presumably by microbiota. Although this subsurface sink creates a gradient that drives a downward flux of CCl4, the gradient alone is not sufficient to explain the observed surface undersaturations. Since known chemical losses are likewise insufficient to sustain the observed undersaturations, this suggests a possible biological sink for CCl4 in surface or near-surface waters of the ocean. The total atmospheric lifetime for CCl4, based on these results and the most recent studies of soil uptake and loss in the stratosphere is now 32 (26-43) yr.

  20. Short-range atmospheric dispersion of carbon dioxide

    Energy Technology Data Exchange (ETDEWEB)

    Cortis, A.; Oldenburg, C.M.

    2009-11-01

    We present a numerical study aimed at quantifying the effects of concentration-dependent density on the spread of a seeping plume of CO{sub 2} into the atmosphere such as could arise from a leaking geologic carbon sequestration site. Results of numerical models can be used to supplement field monitoring estimates of CO{sub 2} seepage flux by modelling transport and dispersion between the source emission and concentration-measurement points. We focus on modelling CO{sub 2} seepage dispersion over relatively short distances where density effects are likely to be important. We model dense gas dispersion using the steady-state Reynolds-averaged Navier-Stokes equations with density dependence in the gravity term. Results for a two-dimensional system show that a density dependence emerges at higher fluxes than prior estimates. A universal scaling relation is derived that allows estimation of the flux from concentrations measured downwind and vice versa.

  1. Atmospheric Ozone And Its Biosphere - Atmosphere Exchange In A Mangrove Forest Ecosystem A Case Study From Sundarbans NE Coast Of India

    Directory of Open Access Journals (Sweden)

    Manab Kumar Dutta

    2015-01-01

    Full Text Available ABSTRACT Temporal variation of atmospheric O3 and its biosphere atmosphere exchange were monitored in the Sundarbans mangrove forest from January 2011 to December 2011 on bimonthly basis. O3 mixing ratios at 10 m and 20 m heights over the forest atmosphere ranged between 14.66 1.88 to 37.90 0.91 and 19.32 6.27 to 39.80 10.13 ppbv respectively having maximal premonsoon and minimal monsoon periods. Average daytime O3 mixing ratio was 1.69 times higher than nighttime indicates significant photo chemical production of O3 in forest atmosphere. Annual averaged O3 mixing ratio in 10 m height was 13.2 lower than 20 m height induces exchange of O3 across mangrove biosphere atmosphere interface depending upon micrometeorological conditions of the forest ecosystem. Annual average biosphere atmosphere O3 exchange flux in this mangrove forest environment was 0.441 g m-2 s-1. Extrapolating the value for entire forest surface area the mangrove ecosystem acts as a sink of 58.4GgO3 annually indicating significant contribution of Sundarbans mangroves towards regional atmospheric O3 budget as well as climate change.

  2. North American CO2 exchange: intercomparison of modeled estimates with results from a fine-scale atmospheric inversion

    Directory of Open Access Journals (Sweden)

    M. Fischer

    2011-07-01

    Full Text Available Robust estimates of regional-scale terrestrial CO2 exchange are needed to support carbon management policies and to improve the predictive ability of models representing carbon-climate feedbacks. Large discrepancies remain, however, both among and between CO2 flux estimates from atmospheric inverse models and terrestrial biosphere models. Improved atmospheric inverse models that provide robust estimates at sufficiently fine spatial scales could prove especially useful for monitoring efforts, while also serving as a validation tool for process-based assumptions in terrestrial biosphere models. A growing network of continental sites collecting continuous CO2 measurements provides the information needed to drive such models. This study presents results from a regional geostatistical inversion over North America for 2004, taking advantage of continuous data from the nine sites operational in that year, as well as available flask and aircraft observations. The approach does not require explicit prior flux estimates, resolves fluxes at finer spatiotemporal scales than previous North American inversion studies, and uses a Lagrangian transport model coupled with high-resolution winds (i.e. WRF-STILT to resolve near-field influences around measurement locations. The estimated fluxes are used in an inter-comparison with other inversion studies and a suite of terrestrial biosphere model estimates collected through the North American Carbon Program Regional and Continental Interim Synthesis. Differences among inversions are found to be smallest in areas of the continent best-constrained by the atmospheric data, pointing to the value of an expanded measurement network. Aggregation errors in previous coarser-scale inversion studies are likely to explain a portion of the remaining spread. The spatial patterns from a geostatistical inversion that includes auxiliary environmental variables from the North American Regional Reanalysis were similar to those from

  3. Synthesis of porous carbon fibers with strong anion exchange functional groups.

    Science.gov (United States)

    Zheng, Weihua; Hu, Jingtian; Han, Zheshen; Wang, Zixing; Zheng, Zhen; Langer, James; Economy, James

    2015-06-18

    Hybrid porous carbon fibers with strong anion-exchangeable functional groups (HACAX) were synthesized by alkylation of pyrolyzed polyacrylonitrile. HACAX exhibits generic stable positively charged functional groups. This expands the applications of porous carbon media for interacting with anions without adjusting pH, such as Cr(vi) adsorption at natural pH.

  4. Ocean-Atmosphere coupling and CO2 exchanges in the Southwestern Atlantic Ocean

    Science.gov (United States)

    Souza, R.; Pezzi, L. P.; Carmargo, R.; Acevedo, O. C.

    2013-05-01

    The establishment of the INTERCONF Program (Air-Sea Interactions at the Brazil-Malvinas Confluence Zone) in 2004 and subsequent developing of projects such as the SIMTECO (Integrated System for Monitoring the Weather, the Climate and the Ocean in the South of Brazil) and ACEx (Atlantic Ocean Carbon Experiment) from 2010 in Brazil brought to light the importance of understanding the impact of the Southwestern Atlantic Ocean's mesoscale variability on the modulation of the atmospheric boundary layer (ABL) at the synoptic scale. Recent results of all these projects showed that the ABL modulation, as well as the ocean-atmosphere turbulent (heat, momentum and CO2) fluxes are dependent on the behavior of the ocean's surface thermal gradients, especially those found in the Brazil-Malvinas Confluence Zone and at the southern coast off Brazil during the winter. As expected, when atmospheric large scale systems are not present over the study area, stronger heat fluxes are found over regions of higher sea surface temperature (SST) including over warm core eddies shed towards the subantarctic (cold) environment. In the coastal region off southern Brazil, the wintertime propagation of the Brazilian Costal Current (La Plata Plume) acts rising the chlorophyll concentration over the continental shelf as well as diminishing considerably the SST - hence producing prominent across-shore SST gradients towards the offshore region dominated by the Brazil Current waters. Owing to that, heat fluxes are directed towards the ocean in coastal waters that are also responsible for the carbon sinking off Brazil in wintertime. All this description is dependent on the synoptic atmospheric cycle and strongly perturbed when transient systems (cold fronts, subtropical cyclones) are present in the area. However, remote sensing data used here suggest that the average condition of the atmosphere directly responding to the ocean's mesoscale variability appears to imprint a signal that extends from the

  5. The Chemistry of Atmosphere-Forest Exchange (CAFE Model – Part 1: Model description and characterization

    Directory of Open Access Journals (Sweden)

    G. M. Wolfe

    2010-09-01

    Full Text Available We present the Chemistry of Atmosphere-Forest Exchange (CAFE model, a vertically-resolved 1-D chemical transport model designed to probe the details of near-surface reactive gas exchange. CAFE integrates all key processes, including turbulent diffusion, emission, deposition and chemistry, throughout the forest canopy and mixed layer. It is the first model of its kind to incorporate the Master Chemical Mechanism (MCM and a suite of reactions for the oxidation of monoterpenes and sesquiterpenes, providing a more comprehensive description of the oxidative chemistry occurring within and above the forest. We use CAFE to simulate a young Ponderosa pine forest in the Sierra Nevada, CA. Utilizing meteorological constraints from the BEARPEX-2007 field campaign, we assess the sensitivity of modeled fluxes to parameterizations of diffusion, laminar sublayer resistance and radiation extinction. To characterize the general chemical environment of this forest, we also present modeled mixing ratio profiles of biogenic hydrocarbons, hydrogen oxides and reactive nitrogen. The vertical profiles of these species demonstrate a range of structures and gradients that reflect the interplay of physical and chemical processes within the forest canopy, which can influence net exchange.

  6. The Chemistry of Atmosphere-Forest Exchange (CAFE Model – Part 1: Model description and characterization

    Directory of Open Access Journals (Sweden)

    G. M. Wolfe

    2011-01-01

    Full Text Available We present the Chemistry of Atmosphere-Forest Exchange (CAFE model, a vertically-resolved 1-D chemical transport model designed to probe the details of near-surface reactive gas exchange. CAFE integrates all key processes, including turbulent diffusion, emission, deposition and chemistry, throughout the forest canopy and mixed layer. CAFE utilizes the Master Chemical Mechanism (MCM and is the first model of its kind to incorporate a suite of reactions for the oxidation of monoterpenes and sesquiterpenes, providing a more comprehensive description of the oxidative chemistry occurring within and above the forest. We use CAFE to simulate a young Ponderosa pine forest in the Sierra Nevada, CA. Utilizing meteorological constraints from the BEARPEX-2007 field campaign, we assess the sensitivity of modeled fluxes to parameterizations of diffusion, laminar sublayer resistance and radiation extinction. To characterize the general chemical environment of this forest, we also present modeled mixing ratio profiles of biogenic hydrocarbons, hydrogen oxides and reactive nitrogen. The vertical profiles of these species demonstrate a range of structures and gradients that reflect the interplay of physical and chemical processes within the forest canopy, which can influence net exchange.

  7. Fourier Transform Spectrometer measurements of Atmospheric Carbon Dioxide and Methane

    Science.gov (United States)

    Kivi, Rigel; Heikkinen, Pauli; Chen, Huilin; Hatakka, Juha; Laurila, Tuomas

    2016-04-01

    Ground based remote sensing measurements of column CO2 and CH4 using Fourier Transform Spectrometers (FTS) within the Total Carbon Column Observing Network (TCCON) are known for high precision and accuracy. These measurements are performed at various locations globally and they have been widely used in carbon cycle studies and validation of space born measurements. The relevant satellite missions include the Orbiting Carbon Observatory-2 (OCO-2) by the National Aeronautics and Space Administration (NASA); the SCanning Imaging Absorption SpectroMeter for Atmospheric CHartographY (SCIAMACHY) by the European Space Agency (ESA); the Greenhouse gases Observing SATellite (GOSAT) by the Japan Aerospace Exploration Agency (JAXA) and the upcoming Sentinel-5 Precursor mission, which is an ESA mission and scheduled for launch in 2016. Results of the column CO2 and CH4 measurements at Sodankylä in northern Finland (at 67.4° N, 26.6° E) are reported in this study. The measurements have been performed on regular basis since the beginning of the program in early 2009. We also present evaluation of the data quality of the ground based measurements and comparisons with the available satellite based retrievals. In case of comparisons between the GOSAT and ground based retrievals of CO2 and CH4 no significant biases were found. Sodankylä is one of the northernmost stations in the TCCON network. However, the data coverage has been relatively good thanks to the progress towards automation of the FTS measurement system. At Sodankylä the retrievals have been also compared with the balloon borne AirCore measurements at the site. AirCore sampling system is directly related to the World Meteorological Organization in situ trace gas measurement scales. The balloon platform allows sampling in both stratosphere and troposphere, which is a benefit, compared to the aircraft in situ measurements.

  8. Observations of the uptake of carbonyl sulfide (COS by trees under elevated atmospheric carbon dioxide concentrations

    Directory of Open Access Journals (Sweden)

    L. Sandoval-Soto

    2012-08-01

    Full Text Available Global change forces ecosystems to adapt to elevated atmospheric concentrations of carbon dioxide (CO2. We understand that carbonyl sulfide (COS, a trace gas which is involved in building up the stratospheric sulfate aerosol layer, is taken up by vegetation with the same triad of the enzymes which are metabolizing CO2, i.e. ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco, phosphoenolpyruvate carboxylase (PEP-Co and carbonic anhydrase (CA. Therefore, we discuss a physiological/biochemical acclimation of these enzymes affecting the sink strength of vegetation for COS. We investigated the acclimation of two European tree species, Fagus sylvatica and Quercus ilex, grown inside chambers under elevated CO2, and determined the exchange characteristics and the content of CA after a 1–2 yr period of acclimation from 350 ppm to 800 ppm CO2. We demonstrate that a compensation point, by definition, does not exist. Instead, we propose to discuss a point of uptake affinity (PUA. The results indicate that such a PUA, the CA activity and the deposition velocities may change and may cause a decrease of the COS uptake by plant ecosystems, at least as long as the enzyme acclimation to CO2 is not surpassed by an increase of atmospheric COS. As a consequence, the atmospheric COS level may rise causing an increase of the radiative forcing in the troposphere. However, this increase is counterbalanced by the stronger input of this trace gas into the stratosphere causing a stronger energy reflection by the stratospheric sulfur aerosol into space (Brühl et al., 2012. These data are very preliminary but may trigger a discussion on COS uptake acclimation to foster measurements with modern analytical instruments.

  9. Uncertainities in carbon dioxide radiative forcing in atmospheric general circulation models

    Energy Technology Data Exchange (ETDEWEB)

    Cess, R.D.; Zhang, M.H. (State Univ. of New York, Stony Brook, NY (United States)); Potter, G.L.; Gates, W.L.; Taylor, K.E. (Lawrence Livermore National Laboratory, CA (United States)); Colman, R.A.; Fraser, J.R.; McAvaney, B.J. (Bureau of Meterorology Research Centre, Victoria (Australia)); Dazlich, D.A.; Randall, D.A. (Colorado State Univ., Fort Collins, CO (United States)); Del Genio, A.D.; Lacis, A.A. (Goddard Institute for Space Studies, New York, NY (United States)); Esch, M.; Roeckner, E. (Max Planck Institute for Meteorology, Hamburg (Germany)); Galin, V. (Russian Academy of Sciences, Moscow (Russian Federation)); Hack, J.J.; Kiehl, J.T. (National Center for Atmospheric Research, Boulder, CO (United States)); Ingram, W.J. (Hadley Centre for Climate Prediction and Research, Berkshire (United Kingdom)); Le Treut, H.; Lli, Z.X. (Laboratoire de Meteorologie Dynamique, Paris (France)); Liang, X.Z.; Wang, W.C. (State Univ. of New York, Albany, NY (United States)); Mahfouf,

    1993-11-19

    Global warming, caused by an increase in the concentrations of greenhouse gases, is the direct result of greenhouse gas-induced radiative forcing. When a doubling of atmospheric carbon dioxide is considered, this forcing differed substantially among 15 atmospheric general circulation models. Although there are several potential causes, the largest contributor was the carbon dioxide radiation parameterizations of the models.

  10. Understanding global cycling of atmosphere-surface exchangeable pollutants and its implications

    Science.gov (United States)

    Selin, N. E.; Giang, A.; Song, S.; Pike-thackray, C.; Friedman, C. L.

    2014-12-01

    We combine modeling approaches with data analysis to provide quantitative constraints on the global biogeochemical cycling of pollutants such as mercury (Hg) and persistent organic pollutants (POPs). These pollutants, released by human activities, continue to cycle between land, ocean, and atmosphere surfaces, extending their effective lifetimes in the environment. Measurement data are limited for all of these substances, providing few constraints on the magnitude of surface-atmosphere fluxes and thus the timescales of their cycling. This limits our ability to trace emissions to impacts for these substances, particularly in the context of both ongoing policies and climate change. We present a suite of modeling and analysis tools, including uncertainty analysis, that can provide quantitative constraints on cycling for these data-limited problems, and we illustrate their applicability through examples of Hg and selected POPs. Specifically, we summarize recent insights from inverse modeling of mercury, polynomial chaos-based methods for PAHs. Finally, we assess how uncertainty in timescales affects the entire emissions-to-impacts pathway for atmosphere-surface exchangeable pollutants. We discuss the implications of this analysis for policies under the Stockholm and Minamata Conventions.

  11. Exchange of carbonyl sulfide (COS between the atmosphere and various soils in China

    Directory of Open Access Journals (Sweden)

    J. Liu

    2009-11-01

    Full Text Available Using a dynamic enclosure, the exchange fluxes of carbonyl sulfide (COS between the atmosphere and 18 soils from 10 provinces in China were investigated. The emission or uptake of COS from the soils was highly dependent on the soil type, soil temperature, soil moisture, and atmospheric COS mixing ratio. In general, with the only exception being paddy soils, the soils in this investigation acted as sinks for atmospheric COS under wide ranges of soil temperature and soil moisture. Two intensively investigated wheat soils and one forest soil, had optimal soil temperatures for COS uptake of around 15°C, and the optimal soil water content varied from 13 to 58%. The two paddy soils, exponentially COS emission fluxes increased with increasing soil temperature, and decreased COS emission fluxes with increased soil water content. However, negligible emission was found when the paddy soils were under waterlogging status. The observed compensation points for various soils were different and increased significantly with soil temperature. The laboratory simulation agreed with the preliminary field measurements for the paddy soil in Jiaxing, Zhejiang province.

  12. Exchange of carbonyl sulfide (COS) between the atmosphere and various soils in China

    Science.gov (United States)

    Liu, J.; Geng, C.; Mu, Y.; Zhang, Y.; Xu, Z.; Wu, H.

    2010-02-01

    Using a dynamic enclosure, the exchange rates of carbonyl sulfide (COS) between the atmosphere and 18 soils from 12 provinces in China were investigated. The emission or uptake of COS from the soils was highly dependent on the soil type, soil temperature, soil moisture, and atmospheric COS mixing ratio. In general, with the only exception being paddy soils, the soils in this investigation acted as sinks for atmospheric COS under wide ranges of soil temperature and soil moisture. Two intensively investigated wheat soils and one forest soil had optimal soil temperatures for COS uptake of around 15 °C, and the optimal soil water content varied from 13% to 58%. COS emission rates from the two paddy soils increased exponentially with increment of the soil temperature, and decreased with increasing the soil water content. However, negligible emission was found when the paddy soils were under waterlogging status. The observed compensation points for various soils were different and increased significantly with soil temperature. The laboratory simulation agreed with the preliminary field measurements for the paddy soil in Jiaxing, Zhejiang province.

  13. Exchange of carbonyl sulfide (COS between the atmosphere and various soils in China

    Directory of Open Access Journals (Sweden)

    J. Liu

    2010-02-01

    Full Text Available Using a dynamic enclosure, the exchange rates of carbonyl sulfide (COS between the atmosphere and 18 soils from 12 provinces in China were investigated. The emission or uptake of COS from the soils was highly dependent on the soil type, soil temperature, soil moisture, and atmospheric COS mixing ratio. In general, with the only exception being paddy soils, the soils in this investigation acted as sinks for atmospheric COS under wide ranges of soil temperature and soil moisture. Two intensively investigated wheat soils and one forest soil had optimal soil temperatures for COS uptake of around 15 °C, and the optimal soil water content varied from 13% to 58%. COS emission rates from the two paddy soils increased exponentially with increment of the soil temperature, and decreased with increasing the soil water content. However, negligible emission was found when the paddy soils were under waterlogging status. The observed compensation points for various soils were different and increased significantly with soil temperature. The laboratory simulation agreed with the preliminary field measurements for the paddy soil in Jiaxing, Zhejiang province.

  14. Carbonyl sulfide exchange on an ecosystem scale: soil represents a dominant sink for atmospheric COS

    Science.gov (United States)

    Kuhn, U.; Ammann, C.; Wolf, A.; Meixner, F. X.; Andreae, M. O.; Kesselmeier, J.

    The soil/plant/atmosphere exchange of carbonyl sulfide (COS) was investigated in an open oak woodland ecosystem at a rural site in northern California. Measurements of atmospheric concentrations of COS were made in June and in December 1994. We found a significant diel cycle with a drop of COS levels by approximately 150 ppt during the night in both seasons. The mean COS daytime background mixing ratios showed a distinct seasonal difference with 465±77 ppt in summer and 375±56 ppt in winter. The nighttime bulk COS flux into the ecosystem was estimated using a micrometeorological model. To address the observed depletion of COS during stable nocturnal boundary layer conditions, the potential of various ecosystem compartments to act as a sink for COS was investigated. Studies using dynamic enclosures flushed with ambient air excluded vegetation as an important sink during nighttime due to high stomatal resistance. Results from soil chamber measurements indicate that the soil can act as a dominant sink for atmospheric COS.

  15. The impacts of recent permafrost thaw on land-atmosphere greenhouse gas exchange

    Science.gov (United States)

    Hayes, Daniel J.; Kicklighter, David W.; McGuire, Anthony; Chen, Min; Zhuang, Qianlai; Yuan, Fengming; Melillo, Jerry M.; Wullschleger, Stan D.

    2014-01-01

    Permafrost thaw and the subsequent mobilization of carbon (C) stored in previously frozen soil organic matter (SOM) have the potential to be a strong positive feedback to climate. As the northern permafrost region experiences as much as a doubling of the rate of warming as the rest of the Earth, the vast amount of C in permafrost soils is vulnerable to thaw, decomposition and release as atmospheric greenhouse gases. Diagnostic and predictive estimates of high-latitude terrestrial C fluxes vary widely among different models depending on how dynamics in permafrost, and the seasonally thawed 'active layer' above it, are represented. Here, we employ a process-based model simulation experiment to assess the net effect of active layer dynamics on this 'permafrost carbon feedback' in recent decades, from 1970 to 2006, over the circumpolar domain of continuous and discontinuous permafrost. Over this time period, the model estimates a mean increase of 6.8 cm in active layer thickness across the domain, which exposes a total of 11.6 Pg C of thawed SOM to decomposition. According to our simulation experiment, mobilization of this previously frozen C results in an estimated cumulative net source of 3.7 Pg C to the atmosphere since 1970 directly tied to active layer dynamics. Enhanced decomposition from the newly exposed SOM accounts for the release of both CO2 (4.0 Pg C) and CH4 (0.03 Pg C), but is partially compensated by CO2 uptake (0.3 Pg C) associated with enhanced net primary production of vegetation. This estimated net C transfer to the atmosphere from permafrost thaw represents a significant factor in the overall ecosystem carbon budget of the Pan-Arctic, and a non-trivial additional contribution on top of the combined fossil fuel emissions from the eight Arctic nations over this time period.

  16. Catchment-Wide Atmospheric Greenhouse Gas Exchange as Influenced by Land Use Diversity

    DEFF Research Database (Denmark)

    Herbst, Mathias; Friborg, Thomas; Ringgaard, Rasmus

    2011-01-01

    The turbulent fl uxes of carbon dioxide between the land surface and the atmosphere were measured with the eddy covariance technique above three contrasO ng land use types in the Skjern River catchment in western Denmark, namely an agricultural area, a forest plantation, and a wet grassland....... The measurements also included the turbulent fl uxes of methane above the wet grassland and of nitrous oxide above the agricultural area and ran continuously throughout the year 2009. The highest CO2 uptake rates (around 30 µmol m-2 s-1) were observed at the agricultural site; however, the site was a CO2 sink only...

  17. The Relationship between Variations in Regional Inverse-estimated Net Carbon Exchange and Climate

    Science.gov (United States)

    Gurney, K. R.; Zhang, X.

    2012-12-01

    Quantitative understanding of the mechanisms by which the terrestrial biosphere removes roughly 1/3 of the annual global industrial CO2 emissions remains a central question in the study of interactions between the atmosphere and terrestrial biosphere. Process understanding of these mechanisms is also crucial to reliable projections of climate change and policy consideration at national as well as the international levels. We present a systematic analysis of the relationship between net tropical terrestrial carbon fluxes and climate variations in both space and time. We utilize net carbon exchange (NCE) from the TransCom Atmospheric CO2 Inversion Intercomparison, level 2 resutls (TransCom3) and gridded global temperature and precipitation. Our hypothesis is that that the evolution of the carbon fluxes is strongly related to large-scale El Niño-Southern Oscillation (ENSO) transmuted to the tropical land regions through temperature and precipitation variations and that these relationships can be quantified separately for each of the major tropical land regions. This information provides insight into the feedback between climate change and the carbon cycle in key global land regions. Though analysis of complete monthly time series show relationships between NCE anomalies and temperature and precipitation, these relationships are best analyzed by isolating specific seasons within the calendar year. Our results indicate a significant positive NCE-temperature relationship for the tropical America (rmax=0.68; pAsia, by contrast shows significant correlation to both temperature and precipitation though with February/March NCE anomalies leading the May/June temperature and precipitation anomalies by four months. Further exploration is performed with a global correlation analysis. This shows that the NCE-temperature relationship starts in the eastern equatorial Pacific and in the Indian Ocean with the onset of correlation at a 12 and 6 month lag, respectively., This

  18. Characterisation of porous carbon electrode materials used in proton exchange membrane fuel cells via gas adsorption

    Science.gov (United States)

    Watt-Smith, M. J.; Rigby, S. P.; Ralph, T. R.; Walsh, F. C.

    Porous carbon materials are typically used in both the substrate (typically carbon paper) and the electrocatalyst supports (often platinised carbon) within proton exchange membrane fuel cells. Gravimetric nitrogen adsorption has been studied at a carbon paper substrate, two different Pt-loaded carbon paper electrodes and three particulate carbon blacks. N 2 BET surface areas and surface fractal dimensions were determined using the fractal BET and Frenkel-Halsey-Hill models for all but one of the materials studied. The fractal dimensions of the carbon blacks obtained from gas adsorption were compared with those obtained independently by small angle X-ray scattering and showed good agreement. Density functional theory was used to characterise one of the carbon blacks, as the standard BET model was not applicable.

  19. Glacial – interglacial atmospheric CO2 change: a possible "standing volume" effect on deep-ocean carbon sequestration

    Directory of Open Access Journals (Sweden)

    L. C. Skinner

    2009-05-01

    Full Text Available So far, the exploration of possible mechanisms for glacial atmospheric CO2 draw-down and marine carbon sequestration has focussed almost exclusively on dynamic or kinetic processes (i.e. variable mixing-, equilibration- or export rates. Here an attempt is made to underline instead the possible importance of changes in the standing volumes of intra-oceanic carbon reservoirs (i.e. different water-masses in setting the total marine carbon inventory. By way of illustration, a simple mechanism is proposed for enhancing the carbon storage capacity of the deep sea, which operates via an increase in the volume of relatively carbon-enriched AABW-like deep-water filling the ocean basins. Given the hypsometry of the ocean floor and an active biological pump, the water-mass that fills more than the bottom 3 km of the ocean will essentially determine the carbon content of the marine reservoir. A set of simple box-model experiments confirm the expectation that a deep sea dominated by AABW-like deep-water holds more CO2, prior to any additional changes in ocean overturning rate, biological export or ocean-atmosphere exchange. The magnitude of this "standing volume effect" might be as large as the contributions that have been attributed to carbonate compensation, the thermodynamic solubility pump or the biological pump for example. If incorporated into the list of factors that have contributed to marine carbon sequestration during past glaciations, this standing volume mechanism may help to reduce the amount of glacial – interglacial CO2 change that remains to be explained by other mechanisms that are difficult to assess in the geological archive, such as reduced mass transport or mixing rates in particular. This in turn could help narrow the search for forcing conditions capable of pushing the global carbon cycle between glacial and interglacial modes.

  20. Eddy covariance measurements of annual carbon dioxide exchange in two natural ecosystems of the northwestern Italian Alps

    Science.gov (United States)

    Galvagno, Marta; Migliavacca, Mirco; Cremonese, Edoardo; Busetto, Lorenzo; Cogliati, Sergio; Colombo, Roberto; Manca, Giovanni; Meroni, Michele; Morra di Cella, Umberto; Rossini, Micol

    2010-05-01

    In consequence of the relationship between climate change and atmospheric greenhouse gases concentrations, a prime issue of recent researches is the quantification of the carbon balance of terrestrial biomes. In the last decades an increasing number of monitoring sites has recently been implemented worldwide, with the aim to better understand and quantify how inter-annual climate fluctuations affect net carbon exchange and the length of growing season over different vegetation types, land uses and climates. Eddy covariance (EC) technique is a widespread method that provide a direct measure of net carbon dioxide exchange across the biosphere-atmosphere interface by measuring the covariance between fluctuations in vertical wind velocity and CO2 mixing ratio. Two long-term monitoring sites have been equipped in the northwest Italian Alps (Aosta Valley) with the aim of quantify the annual carbon dioxide sequestration by grassland and forest ecosystems in relation to climate change. Grasslands and European larch forests (Larix decidua, Mill.) are the most representative vegetation types of this alpine region. The grassland site, located at an elevation of 2160 m asl, has been equipped in summer 2008 in an abandoned pasture with Nardus stricta as dominant species. European larch stand is located at 2050 m asl, at a distance of ~8 km from the grassland, and measurements has started in winter 2009. Both sites have been equipped with the same eddy flux system mounted at 2.5 m and 20 m above the ground in the grassland and in the larch forest, respectively. Both sites were equipped with a basic EC system: a3D sonic anemometer and an open-path infrared gas analyser (LI-7500, LICOR Inc.). Along EC the main meteorological variables are measured (e.g. air temperature, humidity, precipitation, photosynthetically active radiation, PAR, , soil water content, snow height etc..). In order to link annual sites productivity to the growing seasons length, phenological observations are

  1. APPLICATION OF AN INORGANIC ION EXCHANGER α—Zr(HPO4)2·H2O IN ELECTROREDUCTION OF CARBON MONOXIDE

    Institute of Scientific and Technical Information of China (English)

    HAOJinku; ZHAOWeijun; 等

    1993-01-01

    Gas phase reduction of carbon monoxide to formaldehyde and ethylene was found in electrochemical cell with an inorganic ion exchanger α-Zr(HPO4)2·H2O used as solid proton-conducting electrolyte at room temperature and atmospheric pressure.The type and amount of the electroreduction of CO depend on the different metal electrodes and current densities,which gives a lank between heterogeneous catalysis and electrochemistry.

  2. Measurements of hydrogen peroxide and formaldehyde exchange between the atmosphere and surface snow at Summit, Greenland

    Energy Technology Data Exchange (ETDEWEB)

    Jacobi, H.W.; Frey, M.M.; Hutterli, M.A.; Bales, R.C. [University of Arizona, Tucson, AZ (United States). Dept. of Hydrology and Water Resources; Schrems, O. [Alfred Wegener Inst. for Polar and Marine Research, Bremerhaven (Germany); Cullen, N.J.; Steffen, K. [University of Colorado, Boulder, CO (United States). CIRES; Koehler, C. [Manchester High School, Earth and Space Science, CT (United States)

    2002-06-01

    Tower-based measurements of hydrogen peroxide (H{sub 2}O{sub 2}) and formaldehyde (HCHO) exchange were performed above the snowpack of the Greenland ice sheet. H{sub 2}O{sub 2} and HCHO fluxes were measured continuously between 16 June and 7 July 2000, at the Summit Environmental Observatory. The fluxes were determined using coil scrubber-aqueous phase fluorometry systems together with micrometeorological techniques. Both compounds exhibit strong diel cycles in the observed concentrations as well as in the fluxes with emission from the snow during the day and the evening and deposition during the night. The averaged diel variations of the observed fluxes were in the range of +1.3x10{sup 13} molecules m{sup -2} s{sup -1} (deposition) and -1.6x10{sup 13} molecules m{sup -2} s{sup -1} (emission) for H{sub 2}O{sub 2} and +1.1x10{sup 12} and -4.2x10{sup 12} molecules m{sup -2} s{sup -1} for HCHO, while the net exchange per day for both compounds were much smaller. During the study period of 22 days on average (0.8{sub -4.3}{sup +4.6}x10{sup 17} molecules m{sup -2} of H{sub 2}O{sub 2} were deposited and (7.0{sub -12.2}{sup +12.6})x10{sup 16} molecules m{sup -2} of HCHO were emitted from the snow per day. A comparison with the inventory in the gas phase demonstrates that the exchange influences the diel variations in the boundary layer above snow covered areas. Flux measurements during and after the precipitation of new snow shows that <16% of the H{sub 2}O{sub 2} and more than 25% of the HCHO originally present in the new snow were available for fast release to the atmospheric boundary layer within hours after precipitation. This release can effectively disturb the normally observed diel variations of the exchange between the surface snow and the atmosphere, thus perturbing also the diel variations of corresponding gas-phase concentrations. (Author)

  3. Impact of increasing inflow of warm Atlantic water on the sea-air exchange of carbon dioxide and methane in the Laptev Sea

    Science.gov (United States)

    Wâhlström, Iréne; Dieterich, Christian; Pemberton, Per; Meier, H. E. Markus

    2016-07-01

    The Laptev Sea is generally a sink for atmospheric carbon dioxide and a source of methane to the atmosphere. We investigate how sensitive the net sea-air exchange of carbon dioxide and methane in the Laptev Sea are to observed changes in the inflow of Atlantic water into the Arctic Ocean and in atmospheric conditions occurring after 1990. Using a time-dependent coupled physical-biogeochemical column model, both the physical and biogeochemical effects are investigated in a series of sensitivity experiments. The forcing functions are kept constant at 40 year climatological values except successively selected drivers that vary in time. Their effects are examined by comparing two periods, 1971-1989 and 1991-2009. We find that the flux of carbon dioxide is more sensitive to the increased Atlantic water inflow than the methane exchange. The increased volume transport of water in the Atlantic layer increases the ocean net uptake of carbon dioxide more than the warming of the incoming bottom water as the vertical advection is enhanced in the first case. The methane cycling is mainly affected by the increase in temperature, irrespective of whether the warming originates from the atmosphere or the incoming bottom water, causing increased outgassing to the atmosphere. In summary, our results suggest that the observed changes in the atmosphere and ocean potentially had a substantial impact on carbon dioxide uptake on the Siberian Shelf. However, the results suggest that the impact on the outgassing of methane might have been relatively modest compared to the interannual variability of sea-air fluxes of methane.

  4. Tracing the fate of carbon and the atmospheric evolution of Mars

    CERN Document Server

    Hu, Renyu; Ehlmann, Bethany L; Yung, Yuk L

    2015-01-01

    The climate of Mars likely evolved from a warmer, wetter early state to the cold, arid current state. However, no solutions for this evolution have previously been found to satisfy the observed geological features and isotopic measurements of the atmosphere. Here we show that a family of solutions exist, invoking no missing reservoirs or loss processes. Escape of carbon via CO photodissociation and sputtering enriches heavy carbon (13C) in the Martian atmosphere, partially compensated by moderate carbonate precipitation. The current atmospheric 13C/12C and rock and soil carbonate measurements indicate an early atmosphere with a surface pressure <1 bar. Only scenarios with large amounts of carbonate formation in open lakes permit higher values up to 1.8 bar. The evolutionary scenarios are fully testable with data from the MAVEN mission and further studies of the isotopic composition of carbonate in the Martian rock record through time.

  5. Atmospheric black carbon and sulfate concentrations in Northeast Greenland

    Directory of Open Access Journals (Sweden)

    A. Massling

    2015-04-01

    Full Text Available Measurements of Black Carbon (BC in aerosols at the high Arctic field site Villum Research Station (VRS at Station Nord in North Greenland showed a seasonal variation in BC concentrations with a maximum in winter and spring at ground level. The data was obtained using a Multi Angle Absorption Photometer (MAAP. A similar seasonal pattern was found for sulfate concentrations with a maximum level during winter and spring analyzed by ion chromatography. A correlation between BC and sulfate concentrations was observed over the years 2011 to 2013. This finding gives the hint that most likely transport of primary emitted BC particles to the Arctic was accompanied by aging of the aerosols through condensational processes. This process may have led to the formation of secondary inorganic matter and further transport of BC particles as cloud processing and further washout of particles is less likely based on the typically observed transport patterns of air masses arriving at VRS. Additionally, concentrations of EC (elemental carbon based on a thermo-optical method were determined and compared to BC measurements. Model estimates of the climate forcing due to BC in the Arctic are based on contributions of long-range transported BC during spring and summer. The measured concentrations were here compared with model results obtained by the Danish Hemispheric Model, DEHM. Good agreement between measured and modeled concentrations of both BC and sulfate was observed. The dominant source is found to be combustion of fossil fuel with biomass burning as a minor though significant source. During winter and spring the Arctic atmosphere is known to be impacted by long-range transport of BC and associated with the Arctic haze phenomenon.

  6. Influence of the soil-atmosphere exchange on the hydric profile induced in soil-structure system

    Directory of Open Access Journals (Sweden)

    A. Al Qadad

    2012-06-01

    Full Text Available Soil-atmosphere exchange leads to a moisture change in the soil. This can cause major damage to engineering structures due to the soil expansion and shrinkage. The soil-atmosphere exchange is related to several parameters, in particular the soil characteristics and climate conditions. The presence of an engineering structure causes a variation of the hydraulic profile in the soil, which can lead to heterogeneous soil movement and consequently to structural damage. This paper presents a coupled numerical model based on the consideration of both water flow in unsaturated soils and soil-atmosphere exchange. After the validation of the model, the paper presents its use for the analysis of the influence of the presence of structures on moisture change induced under climatic conditions recorded in a semi-arid region. Analysis shows that the presence of the structure leads to important change in the moisture distribution, in particular in the vicinity of the structure.

  7. Thermodynamics of a dry atmosphere at different surface exchange rates and rotation speeds

    CERN Document Server

    Pascale, Salvatore; Lucarini, Valerio; Wang, Yixiong

    2012-01-01

    We study the combined effect of the rotation speed {\\Omega} and of the surface exchange rate - quantified by a surface turbulent relaxation timescale {\\tau} - on the dissipative properties of an Earth-like dry atmosphere. The rotation speed {\\Omega} is varied between one tenth and eight times that of the Earth {\\Omega} \\approx 7.29\\cdot10-5 rad-1 and {\\tau} from 45 minutes to 500 days. We study the circulation regimes induced by such parametric variations through two key dimensionless parameters, the thermal Rossby number Ro and the frictional dimensionless number Ff. An extensive analysis is performed by using nonequilibrium thermodynamics diagnostic tools such as material entropy production, efficiency, meridional heat transport and kinetic energy dissipation. The thermal dissipation associated with the sensible heat flux is found to depend mainly on the surface properties and to be almost independent from the rotation rate, whereas the dissipation of kinetic energy depends in a nontrivial way on both. Slow...

  8. Lateral transport of soil carbon and land-atmosphere CO2 flux induced by water erosion in China.

    Science.gov (United States)

    Yue, Yao; Ni, Jinren; Ciais, Philippe; Piao, Shilong; Wang, Tao; Huang, Mengtian; Borthwick, Alistair G L; Li, Tianhong; Wang, Yichu; Chappell, Adrian; Van Oost, Kristof

    2016-06-14

    Soil erosion by water impacts soil organic carbon stocks and alters CO2 fluxes exchanged with the atmosphere. The role of erosion as a net sink or source of atmospheric CO2 remains highly debated, and little information is available at scales larger than small catchments or regions. This study attempts to quantify the lateral transport of soil carbon and consequent land-atmosphere CO2 fluxes at the scale of China, where severe erosion has occurred for several decades. Based on the distribution of soil erosion rates derived from detailed national surveys and soil carbon inventories, here we show that water erosion in China displaced 180 ± 80 Mt C⋅y(-1) of soil organic carbon during the last two decades, and this resulted a net land sink for atmospheric CO2 of 45 ± 25 Mt C⋅y(-1), equivalent to 8-37% of the terrestrial carbon sink previously assessed in China. Interestingly, the "hotspots," largely distributed in mountainous regions in the most intensive sink areas (>40 g C⋅m(-2)⋅y(-1)), occupy only 1.5% of the total area suffering water erosion, but contribute 19.3% to the national erosion-induced CO2 sink. The erosion-induced CO2 sink underwent a remarkable reduction of about 16% from the middle 1990s to the early 2010s, due to diminishing erosion after the implementation of large-scale soil conservation programs. These findings demonstrate the necessity of including erosion-induced CO2 in the terrestrial budget, hence reducing the level of uncertainty.

  9. Lateral transport of soil carbon and land-atmosphere CO2 flux induced by water erosion in China

    Science.gov (United States)

    Yue, Yao; Ni, Jinren; Ciais, Philippe; Piao, Shilong; Wang, Tao; Huang, Mengtian; Borthwick, Alistair G. L.; Li, Tianhong; Wang, Yichu; Chappell, Adrian; Van Oost, Kristof

    2016-06-01

    Soil erosion by water impacts soil organic carbon stocks and alters CO2 fluxes exchanged with the atmosphere. The role of erosion as a net sink or source of atmospheric CO2 remains highly debated, and little information is available at scales larger than small catchments or regions. This study attempts to quantify the lateral transport of soil carbon and consequent land-atmosphere CO2 fluxes at the scale of China, where severe erosion has occurred for several decades. Based on the distribution of soil erosion rates derived from detailed national surveys and soil carbon inventories, here we show that water erosion in China displaced 180 ± 80 Mt Cṡy-1 of soil organic carbon during the last two decades, and this resulted a net land sink for atmospheric CO2 of 45 ± 25 Mt Cṡy-1, equivalent to 8-37% of the terrestrial carbon sink previously assessed in China. Interestingly, the “hotspots,” largely distributed in mountainous regions in the most intensive sink areas (>40 g Cṡm-2ṡy-1), occupy only 1.5% of the total area suffering water erosion, but contribute 19.3% to the national erosion-induced CO2 sink. The erosion-induced CO2 sink underwent a remarkable reduction of about 16% from the middle 1990s to the early 2010s, due to diminishing erosion after the implementation of large-scale soil conservation programs. These findings demonstrate the necessity of including erosion-induced CO2 in the terrestrial budget, hence reducing the level of uncertainty.

  10. Global warming and marine carbon cycle feedbacks on future atmospheric CO2

    Science.gov (United States)

    Joos; Plattner; Stocker; Marchal; Schmittner

    1999-04-16

    A low-order physical-biogeochemical climate model was used to project atmospheric carbon dioxide and global warming for scenarios developed by the Intergovernmental Panel on Climate Change. The North Atlantic thermohaline circulation weakens in all global warming simulations and collapses at high levels of carbon dioxide. Projected changes in the marine carbon cycle have a modest impact on atmospheric carbon dioxide. Compared with the control, atmospheric carbon dioxide increased by 4 percent at year 2100 and 20 percent at year 2500. The reduction in ocean carbon uptake can be mainly explained by sea surface warming. The projected changes of the marine biological cycle compensate the reduction in downward mixing of anthropogenic carbon, except when the North Atlantic thermohaline circulation collapses.

  11. Atmospheric dust accumulation on native and non-native species: effects on gas exchange parameters.

    Science.gov (United States)

    González, Juan A; Prado, Fernando E; Piacentini, Ruben D

    2014-05-01

    Plants are continuously exposed to atmospheric particulate matter (dust), and their leaves are the main receptors of deposited dust. The objective of this study was to assess the effects of dust deposition on leaf gas exchange parameters of 17 native and non-native tree and shrub species growing in Gran San Miguel de Tucumán in northwestern Argentina. Maximum assimilation rate (), stomatal conductance (), transpiration rate (), internal CO concentration (), and instantaneous water-use efficiency (WUE) were measured in cleaned leaves (CL) and dusted leaves (DL) of different species on November 2010, July 2011, and September 2011. In almost all studied species, gas exchange parameters were significantly affected by dust deposition. Values for , , and of DL were significantly reduced in 11, 12, and 14 species compared with CL. Morphological leaf traits seem to be related to reduction. Indeed, L. and (Mart. ex DC.) Standl. species with pubescent leaves and thick ribs showed the highest reduction percentages. Contrarily, and WUE were increased in DL but were less responsive to dust deposition than other parameters. Increases of and WUE were significant in 5 and 11 species, respectively. Correlation analyses between /, /, and / pairs showed significant positive linear correlations in CL and DL of many studied species, including small and tall plants. These results suggest that leaf stomatal factors and shade-induced effect by accumulated dust are primarily responsible for the observed reductions in photosynthesis rate of DL.

  12. Review and parameterisation of bi-directional ammonia exchange between vegetation and the atmosphere

    Science.gov (United States)

    Massad, R.-S.; Nemitz, E.; Sutton, M. A.

    2010-11-01

    Current deposition schemes used in atmospheric chemical transport models do not generally account for bi-directional exchange of ammonia (NH3). Bi-directional exchange schemes, which have so far been applied at the plot scale, can be included in transport models, but need to be parameterised with appropriate values of the ground layer compensation point (χg), stomatal compensation point (χs) and cuticular resistance (Rw). We review existing measurements of χg, χs as well as Rw and compile a comprehensive dataset from which we then propose generalised parameterisations. χs is related to Γs, the non-dimensional ratio of [NH4+]apo and [H+]apo in the apoplast, through the temperature dependence of the combined Henry and dissociation equilibrium. The meta-analysis suggests that the nitrogen (N) input is the main driver of the apoplastic and bulk leaf concentrations of ammonium (NH4 apomodel for example). In principle, the parameterisations should be applicable to other climates, though there is a need for more underpinning data, with the uncertainties being especially large for tropical and subtropical conditions.

  13. Carbon exchange in Western Siberian watershed mires and implication for the greenhouse effect. A spatial temporal modeling approach

    Energy Technology Data Exchange (ETDEWEB)

    Borren, W.

    2007-01-19

    The vast watershed mires of Western Siberia formed a significant sink of carbon during the Holocene. Because of their large area these mires might play an important role in the carbon exchange between terrestrial ecosystems and the atmosphere. However, estimation of the Holocene and future carbon balance of whole Western Siberian mires is hampered by the lack of spatially resolved models. The main objective was to assess the carbon exchange fluxes of the mires using a 3-D dynamic approach. These exchange fluxes comprise the sequestration of carbon dioxide (CO2) by peat growth, the emission of methane (CH4) by anaerobic peat decay and the emission of CO2 by aerobic peat decay. From the detailed analysis of peat cores from different sites in the southern taiga of Western Siberia, it emerged that Holocene peat growth and carbon accumulation had different trends, caused by variations in vegetation succession. These differences were strongly influenced by the position in the landscape. Therefore, the effect of climatic change on mire development varied spatially. The indirect effects of climate change through local hydrology appeared to be more important than direct influences of changes in precipitation and temperature. Mire development is closely connected to hydrological dynamics. In the thesis a 3-D dynamic modeling approach is described that makes use of groundwater modeling. In successive timesteps peat growth and decay as well as mire type distribution were calculated, depending on hydrological conditions. The model was forced with a paleo-precipitation record to include variable climatic input. The model results show the Holocene development of a watershed mire from a few small spots to a contiguous mire landscape. As hydrology is the major limiting factor, the mire development is most sensitive to precipitation and evapotranspiration. Under unchanged conditions the mire will grow further, eventually reaching its maximum peat thickness around 11400 yr A.D. Under

  14. An observational constraint on stomatal function in forests: evaluating coupled carbon and water vapor exchange with carbon isotopes in the Community Land Model (CLM4.5)

    Science.gov (United States)

    Raczka, Brett; Duarte, Henrique F.; Koven, Charles D.; Ricciuto, Daniel; Thornton, Peter E.; Lin, John C.; Bowling, David R.

    2016-09-01

    Land surface models are useful tools to quantify contemporary and future climate impact on terrestrial carbon cycle processes, provided they can be appropriately constrained and tested with observations. Stable carbon isotopes of CO2 offer the potential to improve model representation of the coupled carbon and water cycles because they are strongly influenced by stomatal function. Recently, a representation of stable carbon isotope discrimination was incorporated into the Community Land Model component of the Community Earth System Model. Here, we tested the model's capability to simulate whole-forest isotope discrimination in a subalpine conifer forest at Niwot Ridge, Colorado, USA. We distinguished between isotopic behavior in response to a decrease of δ13C within atmospheric CO2 (Suess effect) vs. photosynthetic discrimination (Δcanopy), by creating a site-customized atmospheric CO2 and δ13C of CO2 time series. We implemented a seasonally varying Vcmax model calibration that best matched site observations of net CO2 carbon exchange, latent heat exchange, and biomass. The model accurately simulated observed δ13C of needle and stem tissue, but underestimated the δ13C of bulk soil carbon by 1-2 ‰. The model overestimated the multiyear (2006-2012) average Δcanopy relative to prior data-based estimates by 2-4 ‰. The amplitude of the average seasonal cycle of Δcanopy (i.e., higher in spring/fall as compared to summer) was correctly modeled but only when using a revised, fully coupled An - gs (net assimilation rate, stomatal conductance) version of the model in contrast to the partially coupled An - gs version used in the default model. The model attributed most of the seasonal variation in discrimination to An, whereas interannual variation in simulated Δcanopy during the summer months was driven by stomatal response to vapor pressure deficit (VPD). The model simulated a 10 % increase in both photosynthetic discrimination and water-use efficiency (WUE

  15. Estimating Terrestrial Wood Biomass from Observed Concentrations of Atmospheric Carbon Dioxide

    NARCIS (Netherlands)

    Schaefer, K. M.; Peters, W.; Carvalhais, N.; van der Werf, G.; Miller, J.

    2008-01-01

    We estimate terrestrial disequilibrium state and wood biomass from observed concentrations of atmospheric CO2 using the CarbonTracker system coupled to the SiBCASA biophysical model. Starting with a priori estimates of carbon flux from the land, ocean, and fossil fuels, CarbonTracker estimates net c

  16. Measuring the biosphere-atmosphere exchange of total reactive nitrogen by eddy covariance

    Science.gov (United States)

    Ammann, C.; Wolff, V.; Marx, O.; Brümmer, C.; Neftel, A.

    2012-11-01

    The (net) exchange of reactive nitrogen (Nr) with the atmosphere is an important driver for ecosystem productivity and greenhouse gas exchange. The exchange of airborne Nr includes various trace compounds that usually require different specific measurement techniques, and up to now fast response instruments suitable for eddy covariance measurements are only available for few of these compounds. Here we present eddy covariance flux measurements with a recently introduced converter (TRANC) for the sum of all Nr compounds (∑Nr). Measurements were performed over a managed grassland field with phases of net emission and net deposition of ∑Nr and alternating dominance of oxidized (NOX) and reduced species (NH3). Spectral analysis of the eddy covariance data exhibited the existence of covariance function peaks at a reasonable time lag related to the sampling tube residence time under stationary conditions. Using ogive analysis, the high-frequency damping was quantified to 19%-26% for a low measurement height of 1.2 m and to about 10% for 4.8 m measurement height. ∑Nr concentrations and fluxes were compared to parallel NO and NO2 measurements by dynamic chambers and NH3 measurements by the aerodynamic gradient technique. The average concentration results indicate that the main compounds NO2 and NH3 were converted by the TRANC system with an efficiency of near 100%. With an optimised sample inlet also the fluxes of these compounds were recovered reasonably well including net deposition and net emission phases. The study shows that the TRANC system is suitable for fast response measurements of oxidized and reduced nitrogen compounds and can be used for continuous eddy covariance flux measurements of total reactive nitrogen.

  17. Cryogenic Heat-Exchanger Design for Freeze-out Removal of Carbon Dioxide from Landfill Gas

    Science.gov (United States)

    Chang, Ho-Myung; Chung, Myung Jin; Park, Seong Bum

    A cryogenic heat exchanger to remove carbon dioxide from landfill gas (LFG) is proposed and designed for applications to LNG production in distributed-scale. Since the major components of LFG are methane and carbon dioxide, CO2 removal is a significant pre-process in the liquefaction systems. A new and simple approach is proposed to directly remove carbon dioxide as frost on the surface wall along the cooling passage in a liquefying heat exchanger and to install two identical heat exchangers in parallel for alternative switching. As a first step of feasibility study, combined heat and mass transfer analysis is performed on the freeze-out process of CO2 in a counterflow heat exchanger, where CH4-CO2 mixture is cooled below its frost temperature in thermal contact with cold refrigerant. Engineering correlations for the analogy of heat and mass transfer are incorporated into numerical heat exchanger analysis with detailed fluid properties. The developed analytical model is used to estimate the distribution of CO2 accumulation and the required heat exchanger size with latent thermal load for the cryogenic CO2 removal in various operating conditions.

  18. Development of ion-exchange collectors for monitoring atmospheric deposition of inorganic pollutants in Alaska parklands

    Science.gov (United States)

    Brumbaugh, William G.; Arms, Jesse W.; Linder, Greg L.; Melton, Vanessa D.

    2016-09-19

    -stage arrangement. With the modified IEC design, ammonium, nitrate, and sulfate ions were determined with a precision of between 5 and 10 percent relative standard deviation for the low loads that happen in remote areas of Alaska. Results from 2012 field studies demonstrated that the targeted ions were stable and fully retained on the IEC during field deployment and could be fully recovered by extraction in the laboratory. Importantly, measurements of annual loads determined by combining snowpack and IEC sampling at sites near National Atmospheric Deposition Program monitoring stations was comparable to results obtained by the National Atmospheric Deposition Program.Field studies completed in 2014 included snowpack and IEC samples to measure depositional loads; the results were compared to concentrations of similar substances in co-located moss samples. Analyses of constituents in snow and IECs included ammonium, nitrate, and sulfate ions; and a suite of trace metals. Constituent measurements in Hylocomium splendens moss included total nitrogen, phosphorous, and sulfur, and trace metals. To recover ammonium ions and metal ions from the upper cation-exchange column, a two-step extraction procedure was developed from laboratory spiking experiments. The 2014 studies determined that concentrations of certain metals, nitrogen, and sulfur in tissues of Hylocomium splendens moss reflected differences in presumptive deposition from local atmospheric sources. Moss tissues collected from two sites farthest from urban locales had the lowest levels of total nitrogen and sulfur, whereas tissues collected from three of the urban sites had the greatest concentrations of many of the trace metals. Moss tissue concentrations of three trace metals (cobalt, chromium, and nickel) were strongly (positively) Spearman’s rank correlated (pExploratory models indicated linear uptake of the three metals by Hylocomium splendens moss and nonlinear uptake of sulfur from sulfate.Our results provided useful

  19. The model study of water mass and energy exchange between the inland water body and atmosphere

    Institute of Scientific and Technical Information of China (English)

    SUN ShuFen; YAN JinFeng; XIA Nan; LI Qian

    2008-01-01

    Based on a one-dimensional eddy diffusion model, a model to study the water mass and energy exchange between the water body (such as lake and wetland) and the atmosphere is developed, which takes the phase change process due to the seasonal melting and freezing of water and the convection mixing process of en-ergy caused by temperature stratification into consideration. The model uses en-thalpy instead of temperature as predictive variable, which will help to deal with the phase change process and to design an efficient numerical scheme for obtaining the solution more easily. The performance of the model and the rationality of taking convection mixing into the consideration are validated by using observed data of Kinneret Lake in Israel and Lower Two Medicine Lake in Montana State in America. The comparison of model results with observed data indicates that the model pre-sented here is capable of describing the physical process of water mass and en-ergy between the water body (lake and wetland) and atmosphere. Comparison of the result from wetland with shallow and deep lakes under the same forcing condi-tions shows that the evaporation from wetland is much greater than that from lakes,which accords with the real observation fact and physical mechanism.

  20. The model study of water mass and energy exchange between the inland water body and atmosphere

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    Based on a one-dimensional eddy diffusion model,a model to study the water mass and energy exchange between the water body(such as lake and wetland) and the atmosphere is developed,which takes the phase change process due to the seasonal melting and freezing of water and the convection mixing process of energy caused by temperature stratification into consideration. The model uses enthalpy instead of temperature as predictive variable,which will help to deal with the phase change process and to design an efficient numerical scheme for obtaining the solution more easily. The performance of the model and the rationality of taking convection mixing into the consideration are validated by using observed data of Kinneret Lake in Israel and Lower Two Medicine Lake in Montana State in America. The comparison of model results with observed data indicates that the model presented here is capable of describing the physical process of water mass and energy between the water body(lake and wetland) and atmosphere. Comparison of the result from wetland with shallow and deep lakes under the same forcing conditions shows that the evaporation from wetland is much greater than that from lakes,which accords with the real observation fact and physical mechanism.

  1. Sensitivity of temperate desert steppe carbon exchange to seasonal droughts and precipitation variations in Inner Mongolia, China.

    Directory of Open Access Journals (Sweden)

    Fulin Yang

    Full Text Available Arid grassland ecosystems have significant interannual variation in carbon exchange; however, it is unclear how environmental factors influence carbon exchange in different hydrological years. In this study, the eddy covariance technique was used to investigate the seasonal and interannual variability of CO₂ flux over a temperate desert steppe in Inner Mongolia, China from 2008 to 2010. The amounts and times of precipitation varied significantly throughout the study period. The precipitation in 2009 (186.4 mm was close to the long-term average (183.9±47.6 mm, while the precipitation in 2008 (136.3 mm and 2010 (141.3 mm was approximately a quarter below the long-term average. The temperate desert steppe showed carbon neutrality for atmospheric CO₂ throughout the study period, with a net ecosystem carbon dioxide exchange (NEE of -7.2, -22.9, and 26.0 g C m⁻² yr⁻¹ in 2008, 2009, and 2010, not significantly different from zero. The ecosystem gained more carbon in 2009 compared to other two relatively dry years, while there was significant difference in carbon uptake between 2008 and 2010, although both years recorded similar annual precipitation. The results suggest that summer precipitation is a key factor determining annual NEE. The apparent quantum yield and saturation value of NEE (NEE(sat and the temperature sensitivity coefficient of ecosystem respiration (R(eco exhibited significant variations. The values of NEE(sat were -2.6, -2.9, and -1.4 µmol CO₂ m⁻² s⁻¹ in 2008, 2009, and 2010, respectively. Drought suppressed both the gross primary production (GPP and R(eco, and the drought sensitivity of GPP was greater than that of R(eco. The soil water content sensitivity of GPP was high during the dry year of 2008 with limited soil moisture availability. Our results suggest the carbon balance of this temperate desert steppe was not only sensitive to total annual precipitation, but also to its seasonal distribution.

  2. Climatic consequences of very high carbon dioxide levels in the earth's early atmosphere

    Science.gov (United States)

    Kasting, James F.; Ackerman, Thomas P.

    1986-01-01

    The possible consequences of very high carbon dioxide concentrations in the earth's early atmosphere have been investigated with a radiative-convective climate model. The early atmosphere would apparently have been stable against the onset of a runaway greenhouse (that is, the complete evaporation of the oceans) for carbon dioxide pressures up to at least 100 bars. A 10- to 20-bar carbon dioxide atmosphere, such as may have existed during the first several hundred million years of the earth's history, would have had a surface temperature of approximately 85 to 110 C. The early stratosphere should have been dry, thereby precluding the possibility of an oxygenic prebiotic atmosphere caused by photodissociation of water vapor followed by escape of hydrogen to space. Earth's present atmosphere also appears to be stable against a carbon dioxide-induced runaway greenhouse.

  3. Sensitivity of land-atmosphere exchanges to overshooting PBL thermals in an idealized coupled model

    Directory of Open Access Journals (Sweden)

    Ian T. Baker

    2009-11-01

    Full Text Available The response of atmospheric carbon dioxide to a given amount of surface flux is inversely proportional to the depth of the planetary boundary layer (PBL. Overshooting thermals that entrain free tropospheric air down into the boundary layer modify the characteristics and depth of the mixed layer through the insertion of energy and mass. In addition, entrainment "dilutes" the effects of surface fluxes on scalar quantities (temperature, water vapor, carbon dioxide, etc. in the PBL. Therefore, incorrect simulation of PBL depth can lead to linear errors in estimates of carbon dioxide fluxes in inverse models. Dilution by entrainment directly alters the surface-air gradients in scalar properties, which serve as the "driving force" for surface fluxes. In addition, changes in near-surface temperature and water vapor affect surface fluxes through physiological processes in plant canopies (e.g. stomatal conductance. Although overshooting thermals are important in the physical world, their effects are unresolved in most regional models. We explore the sensitivity of surface fluxes and PBL scalars to the intensity of PBL top entrainment by manipulating its strength in an idealized version of the coupled SiB-RAMS model. An entrainment parameterization based on the virtual potential temperature flux at the surface is implemented into SiB-RAMS to produce a warmer and drier mixed layer, to alter the surface fluxes, and to increase the depth of the PBL. These variations produce modified CO2 concentrations and vary with the strength of the parameterized entrainment.

  4. Evaluation of variations in CO2 gas exchange in the atmosphere of the BTLSS with plants grown in a conveyor mode on the soil-like substrate

    Science.gov (United States)

    Velichko, Vladimir; Tikhomirov, Alexander A.; Tikhomirova, Natalia; Ushakova, Sofya

    2016-07-01

    The soil-like substrate (SLS) included in the bioregenerative life support system (BLSS) exerts a substantial effect on its gas exchange. This effect is determined by the non-uniform rate of organic matter degradation in the SLS, on the one hand, and by the variable intensity of photosynthesis of the plants grown on it, on the other. The purpose of this study was to compare CO2 variations in the atmosphere of the higher plants - SLS system at different intervals in uneven-aged higher plant conveyers. The study showed that CO2 concentration could reach and exceed the levels of atmospheric carbon dioxide acceptable for humans (over 1%) even when the conveyer interval was rather short. CO2 variations in the atmosphere of the higher plants - SLS system were determined not only by the frequency of adding plant waste to the SLS and the mass of the waste but also by the amount of the harvested actively photosynthesizing plant biomass. At the same time, no significant differences were found in the mineral and production components between the plants in different experiments. Results of the study can be used to optimize the conveyor interval and the associated effectiveness of mineralization of the plant waste added to the SLS and to stabilize the CO2 gas exchange. This study was carried out in the IBP SB RAS and supported by the grant of the Russian Science Foundation (Project No. 14-14-00599).

  5. Stable isotope composition of atmospheric carbon monoxide. A modelling study

    Energy Technology Data Exchange (ETDEWEB)

    Gromov, Sergey S.

    2014-11-01

    This study aims at an improved understanding of the stable carbon and oxygen isotope composition of the carbon monoxide (CO) in the global atmosphere by means of numerical simulations. At first, a new kinetic chemistry tagging technique for the most complete parameterisation of isotope effects has been introduced into the Modular Earth Submodel System (MESSy) framework. Incorporated into the ECHAM/MESSy Atmospheric Chemistry (EMAC) general circulation model, an explicit treatment of the isotope effects on the global scale is now possible. The expanded model system has been applied to simulate the chemical system containing up to five isotopologues of all carbon- and oxygen-bearing species, which ultimately determine the δ{sup 13}C, δ{sup 18}O and Δ{sup 17}O isotopic signatures of atmospheric CO. As model input, a new stable isotope-inclusive emission inventory for the relevant trace gases has been compiled. The uncertainties of the emission estimates and of the resulting simulated mixing and isotope ratios have been analysed. The simulated CO mixing and stable isotope ratios have been compared to in-situ measurements from ground-based observatories and from the civil-aircraft-mounted CARIBIC-1 measurement platform. The systematically underestimated {sup 13}CO/{sup 12}CO ratios of earlier, simplified modelling studies can now be partly explained. The EMAC simulations do not support the inferences of those studies, which suggest for CO a reduced input of the highly depleted in {sup 13}C methane oxidation source. In particular, a high average yield of 0.94 CO per reacted methane (CH{sub 4}) molecule is simulated in the troposphere, to a large extent due to the competition between the deposition and convective transport processes affecting the CH{sub 4} to CO reaction chain intermediates. None of the other factors, assumed or disregarded in previous studies, however hypothesised to have the potential in enriching tropospheric CO in {sup 13}C, were found significant

  6. Simultaneous reproduction of global carbon exchange and storage of terrestrial forest ecosystems

    Science.gov (United States)

    Kondo, M.; Ichii, K.

    2012-12-01

    Understanding the mechanism of the terrestrial carbon cycle is essential for assessing the impact of climate change. Quantification of both carbon exchange and storage is the key to the understanding, but it often associates with difficulties due to complex entanglement of environmental and physiological factors. Terrestrial ecosystem models have been the major tools to assess the terrestrial carbon budget for decades. Because of its strong association with climate change, carbon exchange has been more rigorously investigated by the terrestrial biosphere modeling community. Seeming success of model based assessment of carbon budge often accompanies with the ill effect, substantial misrepresentation of storage. In practice, a number of model based analyses have paid attention solely on terrestrial carbon fluxes and often neglected carbon storage such as forest biomass. Thus, resulting model parameters are inevitably oriented to carbon fluxes. This approach is insufficient to fully reduce uncertainties about future terrestrial carbon cycles and climate change because it does not take into account the role of biomass, which is equivalently important as carbon fluxes in the system of carbon cycle. To overcome this issue, a robust methodology for improving the global assessment of both carbon budget and storage is needed. One potentially effective approach to identify a suitable balance of carbon allocation proportions for each individual ecosystem. Carbon allocations can influence the plant growth by controlling the amount of investment acquired from photosynthesis, as well as carbon fluxes by controlling the carbon content of leaves and litter, both are active media for photosynthesis and decomposition. Considering those aspects, there may exist the suitable balance of allocation proportions enabling the simultaneous reproduction of carbon budget and storage. The present study explored the existence of such suitable balances of allocation proportions, and examines the

  7. Carbon allocation and carbon isotope fluxes in the plant-soil-atmosphere continuum: a review

    Science.gov (United States)

    Brüggemann, N.; Gessler, A.; Kayler, Z.; Keel, S. G.; Badeck, F.; Barthel, M.; Boeckx, P.; Buchmann, N.; Brugnoli, E.; Esperschütz, J.; Gavrichkova, O.; Ghashghaie, J.; Gomez-Casanovas, N.; Keitel, C.; Knohl, A.; Kuptz, D.; Palacio, S.; Salmon, Y.; Uchida, Y.; Bahn, M.

    2011-11-01

    The terrestrial carbon (C) cycle has received increasing interest over the past few decades, however, there is still a lack of understanding of the fate of newly assimilated C allocated within plants and to the soil, stored within ecosystems and lost to the atmosphere. Stable carbon isotope studies can give novel insights into these issues. In this review we provide an overview of an emerging picture of plant-soil-atmosphere C fluxes, as based on C isotope studies, and identify processes determining related C isotope signatures. The first part of the review focuses on isotopic fractionation processes within plants during and after photosynthesis. The second major part elaborates on plant-internal and plant-rhizosphere C allocation patterns at different time scales (diel, seasonal, interannual), including the speed of C transfer and time lags in the coupling of assimilation and respiration, as well as the magnitude and controls of plant-soil C allocation and respiratory fluxes. Plant responses to changing environmental conditions, the functional relationship between the physiological and phenological status of plants and C transfer, and interactions between C, water and nutrient dynamics are discussed. The role of the C counterflow from the rhizosphere to the aboveground parts of the plants, e.g. via CO2 dissolved in the xylem water or as xylem-transported sugars, is highlighted. The third part is centered around belowground C turnover, focusing especially on above- and belowground litter inputs, soil organic matter formation and turnover, production and loss of dissolved organic C, soil respiration and CO2 fixation by soil microbes. Furthermore, plant controls on microbial communities and activity via exudates and litter production as well as microbial community effects on C mineralization are reviewed. A further part of the paper is dedicated to physical interactions between soil CO2 and the soil matrix, such as CO2 diffusion and dissolution processes within the

  8. A comparison of atmospheric composition using the Carbon Bond and Regional Atmospheric Chemistry Mechanisms

    Directory of Open Access Journals (Sweden)

    G. Sarwar

    2013-03-01

    Full Text Available We incorporate the recently developed Regional Atmospheric Chemistry Mechanism (version 2, RACM2 into the Community Multiscale Air Quality modeling system for comparison with the existing 2005 Carbon Bond mechanism with updated toluene chemistry (CB05TU. Compared to CB05TU, RACM2 enhances the domain-wide monthly mean hydroxyl radical concentrations by 46% and nitric acid by 26%. However, it reduces hydrogen peroxide by 2%, peroxyacetic acid by 94%, methyl hydrogen peroxide by 19%, peroxyacetyl nitrate by 40%, and organic nitrate by 41%. RACM2 predictions generally agree better with the observed data than the CB05TU predictions. RACM2 enhances ozone for all ambient levels leading to higher bias at low (70 ppbv concentrations. The RACM2 ozone predictions are also supported by increased ozone production efficiency that agrees better with observations. Compared to CB05TU, RACM2 enhances the domain-wide monthly mean sulfate by 10%, nitrate by 6%, ammonium by 10%, anthropogenic secondary organic aerosols by 42%, biogenic secondary organic aerosols by 5%, and in-cloud secondary organic aerosols by 7%. Increased inorganic and organic aerosols with RACM2 agree better with observed data. While RACM2 enhances ozone and secondary aerosols by relatively large margins, control strategies developed for ozone or fine particles using the two mechanisms do not differ appreciably.

  9. A comparison of atmospheric composition using the Carbon Bond and Regional Atmospheric Chemistry Mechanisms

    Directory of Open Access Journals (Sweden)

    G. Sarwar

    2013-10-01

    Full Text Available We incorporate the recently developed Regional Atmospheric Chemistry Mechanism (version 2, RACM2 into the Community Multiscale Air Quality modeling system for comparison with the existing 2005 Carbon Bond mechanism with updated toluene chemistry (CB05TU. Compared to CB05TU, RACM2 enhances the domain-wide monthly mean hydroxyl radical concentrations by 46% and nitric acid by 26%. However, it reduces hydrogen peroxide by 2%, peroxyacetic acid by 94%, methyl hydrogen peroxide by 19%, peroxyacetyl nitrate by 40%, and organic nitrate by 41%. RACM2 enhances ozone compared to CB05TU at all ambient levels. Although it exhibited greater overestimates at lower observed concentrations, it displayed an improved performance at higher observed concentrations. The RACM2 ozone predictions are also supported by increased ozone production efficiency that agrees better with observations. Compared to CB05TU, RACM2 enhances the domain-wide monthly mean sulfate by 10%, nitrate by 6%, ammonium by 10%, anthropogenic secondary organic aerosols by 42%, biogenic secondary organic aerosols by 5%, and in-cloud secondary organic aerosols by 7%. Increased inorganic and organic aerosols with RACM2 agree better with observed data. Any air pollution control strategies developed using the two mechanisms do not differ appreciably.

  10. Predicting Carbonate Ion Transport in Alkaline Anion Exchange Materials

    Science.gov (United States)

    2012-01-01

    Electrochemical Society , 2013. 2. Wilson K. S. Chiu, "Part 1. Role of the 3-D Electrode Microstructure on Charge Transfer, Mass Transfer, and Electrochemical Reactions in Solid Oxide Fuel Cells; Part 2. Ion and Water Transport in Alkaline Anion Exchange Membranes," technical seminar for the Army Research Laboratory (host: Dr. Deryn Chu), Adelphi, MD, August 13, 2012. (c) Presentations Number of Presentations: 2.00 Non Peer-Reviewed Conference Proceeding publications (other than abstracts): Received Paper TOTAL: Number of Non Peer-Reviewed

  11. Highly precise atmospheric oxygen measurements as a tool to detect leaks of carbon dioxide from Carbon Capture and Storage sites

    NARCIS (Netherlands)

    van Leeuwen, Charlotte

    2015-01-01

    In Carbon Capture and Storage (CCS), carbon dioxide (CO2) from fossil fuel combustion is stored underground into a geological formation. Although the storage of CO2 is considered as safe, leakage to the atmosphere is an important concern and monitoring is necessary. Detecting and quantifying leaks o

  12. Carbon nanotube inner phase chemistry: the Cl- exchange SN2 reaction.

    Science.gov (United States)

    Halls, Mathew D; Raghavachari, Krishnan

    2005-10-01

    Density functional calculations have been carried out to investigate the nature of the inner phase of a (6,6) carbon nanotube, using the Cl(-) exchange S(N)2 reaction as an indicator. Inside the carbon nanotube the classical barrier height increases by 6.6 kcal/mol due to the nanotube polarizability. This suggests that the inner phase environment can be considered a form of solid solvation, offering the possibility of obtaining altered guest properties and reactivity through dielectric stabilization.

  13. [Plant responses to elevated atmospheric carbon dioxide and transmission to other trophic levels]. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Lincoln, D.E.

    1995-10-01

    This program investigated how host plant responses to elevated atmospheric carbon dioxide may be transmitted to other trophic levels, especially leaf eating insects, and alter consumption of leaves and impare their function. Study results included the following findings: increased carbon dioxide to plants alters feeding by insect herbivores; leaves produced under higher carbon conditions contain proportionally less nitrogen; insect herbivores may have decreased reproduction under elevated carbon dioxide.

  14. Seasonal effects of irrigation on land-atmosphere latent heat, sensible heat, and carbon fluxes in semiarid basin

    Science.gov (United States)

    Zeng, Yujin; Xie, Zhenghui; Liu, Shuang

    2017-02-01

    Irrigation, which constitutes ˜ 70 % of the total amount of freshwater consumed by the human population, is significantly impacting land-atmosphere fluxes. In this study, using the improved Community Land Model version 4.5 (CLM4.5) with an active crop model, two high-resolution (˜ 1 km) simulations investigating the effects of irrigation on latent heat (LH), sensible heat (SH), and carbon fluxes (or net ecosystem exchange, NEE) from land to atmosphere in the Heihe River basin in northwestern China were conducted using a high-quality irrigation dataset compiled from 1981 to 2013. The model output and measurements from remote sensing demonstrated the capacity of the developed models to reproduce ecological and hydrological processes. The results revealed that the effects of irrigation on LH and SH are strongest during summer, with a LH increase of ˜ 100 W m-2 and a SH decrease of ˜ 60 W m-2 over intensely irrigated areas. However, the reactions are much weaker during spring and autumn when there is much less irrigation. When the irrigation rate is below 5 mm day-1, the LH generally increases, whereas the SH decreases with growing irrigation rates. However, when the irrigation threshold is in excess of 5 mm day-1, there is no accrued effect of irrigation on the LH and SH. Irrigation produces opposite effects to the NEE during spring and summer. During the spring, irrigation yields more discharged carbon from the land to the atmosphere, increasing the NEE value by 0.4-0.8 gC m-2 day-1, while the summer irrigation favors crop fixing of carbon from atmospheric CO2, decreasing the NEE value by ˜ 0.8 gC m-2 day-1. The repercussions of irrigation on land-atmosphere fluxes are not solely linked to the irrigation amount, and other parameters (especially the temperature) also control the effects of irrigation on LH, SH, and NEE.

  15. Black-carbon absorption enhancement in the atmosphere determined by particle mixing state

    Science.gov (United States)

    Liu, Dantong; Whitehead, James; Alfarra, M. Rami; Reyes-Villegas, Ernesto; Spracklen, Dominick V.; Reddington, Carly L.; Kong, Shaofei; Williams, Paul I.; Ting, Yu-Chieh; Haslett, Sophie; Taylor, Jonathan W.; Flynn, Michael J.; Morgan, William T.; McFiggans, Gordon; Coe, Hugh; Allan, James D.

    2017-02-01

    Atmospheric black carbon makes an important but poorly quantified contribution to the warming of the global atmosphere. Laboratory and modelling studies have shown that the addition of non-black-carbon materials to black-carbon particles may enhance the particles’ light absorption by 50 to 60% by refracting and reflecting light. Real-world experimental evidence for this `lensing’ effect is scant and conflicting, showing that absorption enhancements can be less than 5% or as large as 140%. Here we present simultaneous quantifications of the composition and optical properties of individual atmospheric black-carbon particles. We show that particles with a mass ratio of non-black carbon to black carbon of less than 1.5, which is typical of fresh traffic sources, are best represented as having no absorption enhancement. In contrast, black-carbon particles with a ratio greater than 3, which is typical of biomass-burning emissions, are best described assuming optical lensing leading to an absorption enhancement. We introduce a generalized hybrid model approach for estimating scattering and absorption enhancements based on laboratory and atmospheric observations. We conclude that the occurrence of the absorption enhancement of black-carbon particles is determined by the particles’ mass ratio of non-black carbon to black carbon.

  16. Optimization of the sintering atmosphere for high-density hydroxyapatite-carbon nanotube composites.

    Science.gov (United States)

    White, Ashley A; Kinloch, Ian A; Windle, Alan H; Best, Serena M

    2010-10-06

    Hydroxyapatite-carbon nanotube (HA-CNT) composites have the potential for improved mechanical properties over HA for use in bone graft applications. Finding an appropriate sintering atmosphere for this composite presents a dilemma, as HA requires water in the sintering atmosphere to remain phase pure and well hydroxylated, yet CNTs oxidize at the high temperatures required for sintering. The purpose of this study was to optimize the atmosphere for sintering these composites. While the reaction between carbon and water to form carbon monoxide and hydrogen at high temperatures (known as the 'water-gas reaction') would seem to present a problem for sintering these composites, Le Chatelier's principle suggests this reaction can be suppressed by increasing the concentration of carbon monoxide and hydrogen relative to the concentration of carbon and water, so as to retain the CNTs and keep the HA's structure intact. Eight sintering atmospheres were investigated, including standard atmospheres (such as air and wet Ar), as well as atmospheres based on the water-gas reaction. It was found that sintering in an atmosphere of carbon monoxide and hydrogen, with a small amount of water added, resulted in an optimal combination of phase purity, hydroxylation, CNT retention and density.

  17. Solid Carbon Produced in an Inductively Coupled Plasma Torch with a Titan Like Atmosphere

    Directory of Open Access Journals (Sweden)

    D. Vacher

    2013-01-01

    Full Text Available Solid carbon is deposited on the surfaces of an inductively coupled plasma torch operating with a Titan like atmosphere plasma gas. The frame of the initial research is the study of the radiative properties of plasma encountered around a spacecraft during its hypersonic entry in upper layers of planetary atmosphere. Deposition of carbon is observed not only on the quartz tube outside the inductor but also on the ceramic protection of the torch injector. Carbon exhibits two types of morphology more or less dense and it is analyzed by various analytic devices as MEB, SEM, TEM, EDS and Raman spectroscopy. The gathered carbon powder shows the presence of nanostructured particles.

  18. Diurnal and seasonal variation of carbon dioxide exchange from a former true raised bog.

    NARCIS (Netherlands)

    Nieveen, J.P.; Jacobs, C.M.J.; Jacobs, A.F.G.

    1998-01-01

    Carbon dioxide exchange was measured, using the eddy covariance technique, during a one and a half year period in 1994 and 1995. The measurements took place over a former true raised bog, characterized by a shallow peat layer and a vegetation dominated by Molinia caerulea. The growing season extende

  19. CO2 exchange and carbon balance in two grassland sites on eutrophic drained peat soils

    NARCIS (Netherlands)

    Veenendaal, E.M.; Kolle, O.; Leffelaar, P.A.; Schrier-Uijl, A.P.; Huissteden, van J.; Walsem, van J.D.; Moller, F.; Berendse, F.

    2007-01-01

    In this study we investigated the role of intensive and extensive dairy farm practices on CO2 exchange and the carbon balance of peatlands by means of eddy covariance (EC) measurements. Year long EC measurements were made in two adjacent farm sites on peat soil in the western part of the Netherlands

  20. Estimation of net ecosystem carbon exchange for the conterminous United States by combining MODIS and AmeriFlux data

    Energy Technology Data Exchange (ETDEWEB)

    Xiao, Jingfeng; Zhuang, Qianlai; Baldocchi, Dennis D.; Bolstad, Paul V.; Burns, Sean P.; Chen, Jiquan; Cook, David R.; Curtis, Peter S.; Drake, Bert G.; Foster, David R.; Gu, Lianhong; Hadley, Julian L.; Hollinger, David Y.; Katul, Gabriel G.; Law, Beverly E.; Litvak, Marcy; Ma, Siyan; Martin, Timothy A.; Matamala, Roser; McNulty, Steve; Meyers, Tilden P.; Monson, Russell K.; Munger, J. William; Noormets, Asko; Oechel, Walter C.; Oren, Ram; Richardson, Andrew D.; Schmid, Hans Peter; Scott, Russell L.; Starr, Gregory; Sun, Ge; Suyker, Andrew E.; Torn, Margaret S.; Paw, Kyaw; Verma, Shashi B.; Wharton, Sonia; Wofsy, Steven C.

    2008-10-01

    Eddy covariance flux towers provide continuous measurements of net ecosystem carbon exchange (NEE) for a wide range of climate and biome types. However, these measurements only represent the carbon fluxes at the scale of the tower footprint. To quantify the net exchange of carbon dioxide between the terrestrial biosphere and the atmosphere for regions or continents, flux tower measurements need to be extrapolated to these large areas. Here we used remotely sensed data from the Moderate Resolution Imaging Spectrometer (MODIS) instrument on board the National Aeronautics and Space Administration's (NASA) Terra satellite to scale up AmeriFlux NEE measurements to the continental scale. We first combined MODIS and AmeriFlux data for representative U.S. ecosystems to develop a predictive NEE model using a modified regression tree approach. The predictive model was trained and validated using eddy flux NEE data over the periods 2000-2004 and 2005-2006, respectively. We found that the model predicted NEE well (r = 0.73, p < 0.001). We then applied the model to the continental scale and estimated NEE for each 1 km x 1 km cell across the conterminous U.S. for each 8-day interval in 2005 using spatially explicit MODIS data. The model generally captured the expected spatial and seasonal patterns of NEE as determined from measurements and the literature. Our study demonstrated that our empirical approach is effective for scaling up eddy flux NEE measurements to the continental scale and producing wall-to-wall NEE estimates across multiple biomes. Our estimates may provide an independent dataset from simulations with biogeochemical models and inverse modeling approaches for examining the spatiotemporal patterns of NEE and constraining terrestrial carbon budgets over large areas.

  1. Estimation of Net Ecosystem Carbon Exchange for the Conterminous UnitedStates by Combining MODIS and AmeriFlux Data

    Energy Technology Data Exchange (ETDEWEB)

    Xiao, Jingfeng; Zhuang, Qianlai; Baldocchi, Dennis D.; Law, Beverly E.; Richardson, Andrew D.; Chen, Jiquan; Oren, Ram; Starr, Gregory; Noormets, Asko; Ma, Siyan; Verma, Shashi B.; Wharton, Sonia; Wofsy, Steven C.; Bolstad, Paul V.; Burns, Sean P.; Cook, David R.; Curtis, Peter S.; Drake, Bert G.; Falk, Matthias; Fischer, Marc L.; Foster, David R.; Gu, Lianhong; Hadley, Julian L.; Hollinger, David Y.; Katul, Gabriel G.; Litvak, Marcy; Martin, Timothy A.; Matamala, Roser; McNulty, Steve; Meyers, Tilden P.; Monson, Russell K.; Munger, J. William; Oechel, Walter C.; U, Kyaw Tha Paw; Schmid, Hans Peter; Scott, Russell L.; Sun, Ge; Suyker, Andrew E.; Torn, Margaret S.

    2009-03-06

    Eddy covariance flux towers provide continuous measurements of net ecosystem carbon exchange (NEE) for a wide range of climate and biome types. However, these measurements only represent the carbon fluxes at the scale of the tower footprint. To quantify the net exchange of carbon dioxide between the terrestrial biosphere and the atmosphere for regions or continents, flux tower measurements need to be extrapolated to these large areas. Here we used remotely-sensed data from the Moderate Resolution Imaging Spectrometer (MODIS) instrument on board NASA's Terra satellite to scale up AmeriFlux NEE measurements to the continental scale. We first combined MODIS and AmeriFlux data for representative U.S. ecosystems to develop a predictive NEE model using a regression tree approach. The predictive model was trained and validated using NEE data over the periods 2000-2004 and 2005-2006, respectively. We found that the model predicted NEE reasonably well at the site level. We then applied the model to the continental scale and estimated NEE for each 1 km x 1 km cell across the conterminous U.S. for each 8-day period in 2005 using spatially-explicit MODIS data. The model generally captured the expected spatial and seasonal patterns of NEE. Our study demonstrated that our empirical approach is effective for scaling up eddy flux NEE measurements to the continental scale and producing wall-to-wall NEE estimates across multiple biomes. Our estimates may provide an independent dataset from simulations with biogeochemical models and inverse modeling approaches for examining the spatiotemporal patterns of NEE and constraining terrestrial carbon budgets for large areas.

  2. EXCHANGE

    Energy Technology Data Exchange (ETDEWEB)

    Boltz, J.C. (ed.)

    1992-09-01

    EXCHANGE is published monthly by the Idaho National Engineering Laboratory (INEL), a multidisciplinary facility operated for the US Department of Energy (DOE). The purpose of EXCHANGE is to inform computer users about about recent changes and innovations in both the mainframe and personal computer environments and how these changes can affect work being performed at DOE facilities.

  3. Field investigations of nitrogen dioxide (NO2 exchange between plants and the atmosphere

    Directory of Open Access Journals (Sweden)

    J. Kesselmeier

    2013-01-01

    Full Text Available The nitrogen dioxide (NO2 exchange between the atmosphere and needles of Picea abies L. (Norway Spruce was studied under uncontrolled field conditions using a dynamic chamber system. This system allows measurements of the flux density of the reactive NO-NO2-O3 triad and additionally of the non-reactive trace gases CO2 and H2O. For the NO2 detection a highly NO2 specific blue light converter was used, which was coupled to chemiluminescence detection of the photolysis product NO. This NO2 converter excludes known interferences with other nitrogen compounds, which occur by using more unspecific NO2 converters. Photo-chemical reactions of NO, NO2, and O3 inside the dynamic chamber were considered for the determination of NO2 flux densities, NO2 deposition velocities, as well as NO2 compensation point concentrations. The calculations are based on a bi-variate weighted linear regression analysis (y- and x-errors considered. The NO2 deposition velocities for spruce, based on projected needle area, ranged between 0.07 and 0.42 mm s−1. The calculated NO2 compensation point concentrations ranged from 2.4 ± 9.63 to 29.0 ± 16.30 nmol m−3 (0.05–0.65 ppb but the compensation point concentrations were all not significant in terms of compensation point concentration is unequal to zero. These data challenge the existence of a NO2 compensation point concentration for spruce. Our study resulted in lower values of NO2 gas exchange flux densities, NO2 deposition velocities and NO2 compensation point concentrations in comparison to most previous studies. It is essential to use a more specific NO2 analyzer than used in previous studies and to consider photo-chemical reactions between NO, NO2, and O3 inside the chamber.

  4. Factorial Based Response Surface Modeling with Confidence Intervals for Optimizing Thermal Optical Transmission Analysis of Atmospheric Black Carbon

    Science.gov (United States)

    We demonstrate how thermal-optical transmission analysis (TOT) for refractory light-absorbing carbon in atmospheric particulate matter was optimized with empirical response surface modeling. TOT employs pyrolysis to distinguish the mass of black carbon (BC) from organic carbon (...

  5. Recent advances in developing COS as a tracer of Biosphere-atmosphere exchange of CO2

    Science.gov (United States)

    Asaf, D.; Stimler, K.; Yakir, D.

    2012-04-01

    Potential use of COS as tracer of CO2 flux into vegetation, based on its co-diffusion with CO2 into leaves without outflux, stimulated research on COS-CO2 interactions. Atmospheric measurements by NOAA in recent years, across a global latitudinal transect, indicated a ratio of the seasonal drawdowns in COS and CO2 (normalized to their respective ambient concentrations) of about 6. We carried out leaf-scale gas exchange measurements of COS and CO2 in 22 plant species of deciduous, evergreen trees, grasses, and shrubs, under a range of light intensities and ambient COS concentrations (using mid IR laser spectroscopy). A narrow range in the normalized ratio of the net uptake rates of COS and CO2 (termed leaf relative uptake; LRU) was observed with a mean value of 1.61±0.26. These results reflect the dominance of stomatal conductance over both COS and CO2 uptake, imposing a relatively constant ratio between the two fluxes, except under low light conditions when CO2, but not COS, metabolism is light limited. A relatively constant ratio under common ambient conditions will facilitate the application of COS as a tracer of gross photosynthesis from leaf to global scales. We also report first eddy flux measurements of COS/CO2 at the ecosystem scales. Preliminarily results indicate a ratio of the COS flux, Fcos, to net ecosystem CO2 exchange, NEE, of 3-5 (termed ecosystem relative uptake; ERU). Combining measurements of COS and CO2 and the new information on their ratios at different scales should permit the direct estimation of gross CO2 uptake, GPP, by land ecosystems according to: GPP=NEE*ERU/LRU. In addition, we show that COS effect on stomatal conductance may require a special attention. Increasing COS concentrations between 250 and 2800 pmol mol-1 (enveloping atmospheric levels) stimulate stomatal conductance. It seems likely that the stomata are responding to H2S produced in the leaves from COS.

  6. Atmospheric CO2 capture by algae: Negative carbon dioxide emission path.

    Science.gov (United States)

    Moreira, Diana; Pires, José C M

    2016-09-01

    Carbon dioxide is one of the most important greenhouse gas, which concentration increase in the atmosphere is associated to climate change and global warming. Besides CO2 capture in large emission point sources, the capture of this pollutant from atmosphere may be required due to significant contribution of diffuse sources. The technologies that remove CO2 from atmosphere (creating a negative balance of CO2) are called negative emission technologies. Bioenergy with Carbon Capture and Storage may play an important role for CO2 mitigation. It represents the combination of bioenergy production and carbon capture and storage, keeping carbon dioxide in geological reservoirs. Algae have a high potential as the source of biomass, as they present high photosynthetic efficiencies and high biomass yields. Their biomass has a wide range of applications, which can improve the economic viability of the process. Thus, this paper aims to assess the atmospheric CO2 capture by algal cultures.

  7. Land Surface-atmosphere Exchange In The Natural Landscapes(on The Cabauw Station)

    Science.gov (United States)

    Panin, G.; Kohsiek, W.; Nasonov, A.; Bernhofer, Ch.

    In line with earlier observations the Cabauw data (17568 half hour fluxes) show imbal- ances of the energy budget 50-200 W/m2 during daytime conditions. Measurements of all components of the balance equation of heat, averaged over half hour periods, show that, within the framework of the used measuring techniques, the heat balance is not closed. The sum of fluxes of heat LE+H which is going into the atmosphere is less than Rn-G. The main cause of this systematic imbalance is not the experimental methodol- ogy but a conceptual deficiency. It is related to the fact that the energy-mass exchange between the complex (horizontally inhomogeneous) land surface and the atmosphere is determined by applying theories that are based on the hypothesis of stationary and horizontal homogeneity (SHH). Using the experimental results of the Cabauw station, it was detected that the underestimation of the turbulent fluxes is related to the ter- rain inhomogeneity. To systematize the correction for this effect a parameterization is suggested which empirically makes use of the involved inhomogenity scale in the environment of a site. This parameterization incorporates seasonal and wind direction effects. For parameterization of the energy imbalance the coefficient Kf is proposed. This coefficient can be interpreted as a measure of inhomogeneity and supposedly compromises the low frequency range of the covariance spectrum and possibly other coherent fluxes escaping covariance flux measurements, and serves as an expression of inhomogeneity and nonstationarity (INH). The average value Kf of the Cabauw station is in line with the data of FIFE, KUREX TARTEX and SADE. The paper aims to serve as a contribution to the ongoing discussion on how to account for different types and scales of land surface inhomogeneities inside cells of models such as global climate models, as well as mesoscale models.

  8. Diurnal and annual exchanges of mass and energy between an aspen-hazelnut forest and the atmosphere: Testing the mathematical model Ecosys with data from the BOREAS experiment

    Science.gov (United States)

    Grant, R. F.; Black, T. A.; den Hartog, G.; Berry, J. A.; Neumann, H. H.; Blanken, P. D.; Yang, P. C.; Russell, C.; Nalder, I. A.

    1999-11-01

    There is much uncertainty about the net carbon (C) exchange of boreal forest ecosystems, although this exchange may be an important part of global C dynamics. To resolve this uncertainty, net C exchange has been measured at several sites in the boreal forest of Canada as part of the Boreal Ecosystem-Atmosphere Study (BOREAS). One of these sites is the Southern Old Aspen site at which diurnal CO2 and energy (radiation, latent, and sensible heat) fluxes were measured during 1994 using eddy correlation techniques at different positions within a mixed 70 year old aspen-hazelnut forest. These measurements were used to test a complex ecosystem model "ecosys" in which mass and energy exchanges between terrestrial ecosystems and the atmosphere are simulated hourly under diverse conditions of soil, management, and climate. These simulations explained between 70% and 80% of diurnal variation in ecosystem CO2 and energy fluxes measured during three 1 week intervals in late April, early June, and mid-July. Total annual CO2 fluxes indicated that during 1994, aspen was a net sink of 540 (modeled) versus 670 (measured) g C m-2 yr-1, while hazelnut plus soil were a net source of 472 (modeled) versus 540 (measured) g C m-2 yr-1. The aspen-hazelnut forest at the BOREAS site was therefore estimated to be a net sink of about 68 (modeled) versus 130 (measured) g C m-2 yr-1 during 1994. Long-term simulations indicated that this sink may be larger during cooler years and smaller during warmer years because C fixation in the model was less sensitive to temperature than respiration. These simulations also indicated that the magnitude of this sink declines with forest age because respiration increases with respect to fixation as standing phytomass grows. Confidence in the predictive capabilities of ecosystem models at decadal or centennial timescales is improved by well-constrained tests of these models at hourly timescales.

  9. Environmental controls over carbon dioxide and water vapor exchange of terrestrial vegetation

    DEFF Research Database (Denmark)

    Law, B.E.; Falge, E.; Gu, L.;

    2002-01-01

    . FLUXNETs goals are to understand the mechanisms controlling the exchanges of CO2, water vapor and energy across a spectrum of time and space scales, and to provide information for modeling of carbon and water cycling across regions and the globe. At a subset of sites, net carbon uptake (net ecosystem......The objective of this research was to compare seasonal and annual estimates of CO2 and water vapor exchange across sites in forests, grasslands, crops, and tundra that are part of an international network called FLUXNET, and to investigating the responses of vegetation to environmental variables...... associated with reduced temperature. The slope of the relation between monthly gross ecosystem production and evapotranspiration was similar between biomes. except for tundra vegetation, showing a strong linkage between carbon gain and water loss integrated over the year (slopes = 3.4 g CO2/kg H2O...

  10. Old and Not-So-Old: Examining Changes in Forest Ecosystem Carbon Exchange With Stand Age in the Upper Midwest U.S.

    Science.gov (United States)

    Desai, A. R.; Cook, B.; Davis, K. J.; Bolstad, P.; Carey, E.; Martin, J.; Kreller, L.; Wang, W.

    2003-12-01

    Forest stand age is an important determinant of ecosystem carbon uptake. Though there are biometric measurements and ecological models for forests of all ages, there are few stand-scale eddy-flux measurements of net carbon exchange in older forests, though the number is increasing. In order to scale carbon fluxes from sites to regions, where stands of multiple ages may exist, it is necessary to measure to the effect of stand age on carbon exchange. Measuring the effect of stand age on carbon exchange is also necessary when trying to predict future or past carbon exchange (scaling across time). Many researchers have noted that site disturbance history is the fundamental factor in determining carbon uptake by forests over time scales of decades to centuries. The 8,500 ha Sylvania Wilderness in the upper peninsula of Michigan is one of several large tracts of old-growth forest in the Midwest. Trees range from 0-350 years old. Primary species are sugar maple, eastern hemlock and yellow birch. Catastrophic disturbance is rare. A research plot near the wilderness was established in late 2001 to measure the net ecosystem exchange (NEE) of carbon and water using eddy-flux, component flux and biometric methods. This site is part of the Chequamegon Ecosystem Atmosphere Study (ChEAS, http://cheas.psu.edu), a loose affiliation of researchers conducting carbon and water research in northern Wisconsin and upper Michigan. Another similar research plot within ChEAS and not far from Sylvania is the Willow Creek mature uplands site. This forest is about 70 years old and the primary species are sugar maple, basswood and green ash. The site had presettlement old-growth vegetation similar to what is currently seen in the Sylvania Wilderness. Thus, the carbon exchange seen at Sylvania may be representative of carbon uptake at Willow Creek had it not been logged in the early 20th century, and may also represent the future (or past) carbon uptake for similar forests in northern Wisconsin

  11. Dynamic responses of atmospheric carbon dioxide concentration to global temperature changes between 1850 and 2010

    Science.gov (United States)

    Wang, Weile; Nemani, Ramakrishna

    2016-02-01

    Changes in Earth's temperature have significant impacts on the global carbon cycle that vary at different time scales, yet to quantify such impacts with a simple scheme is traditionally deemed difficult. Here, we show that, by incorporating a temperature sensitivity parameter (1.64 ppm yr-1 °C-1) into a simple linear carbon-cycle model, we can accurately characterize the dynamic responses of atmospheric carbon dioxide (CO2) concentration to anthropogenic carbon emissions and global temperature changes between 1850 and 2010 ( r 2 > 0.96 and the root-mean-square error reservoir (~12 year) approximates the long-term temperature sensitivity of global atmospheric CO2 concentration (~15 ppm °C-1), generally consistent with previous estimates based on reconstructed CO2 and climate records over the Little Ice Age. Our results suggest that recent increases in global surface temperatures, which accelerate the release of carbon from the surface reservoirs into the atmosphere, have partially offset surface carbon uptakes enhanced by the elevated atmospheric CO2 concentration and slowed the net rate of atmospheric CO2 sequestration by global land and oceans by ~30% since the 1960s. The linear modeling framework outlined in this paper thus provides a useful tool to diagnose the observed atmospheric CO2 dynamics and monitor their future changes.

  12. Carbon film coating on gas diffusion layer for proton exchange membrane fuel cells

    Science.gov (United States)

    Lin, Jui-Hsiang; Chen, Wei-Hung; Su, Shih-Hsuan; Liao, Yuan-Kai; Ko, Tse-Hao

    This study discusses a novel process to increase the performance of proton exchange membrane fuel cells (PEMFC). In order to improve the electrical conductivity and reduce the surface indentation of the carbon fibers, we modified the carbon fibers with pitch-based carbon materials (mesophase pitch and coal tar pitch). Compared with the gas diffusion backing (GDB), GDB-A240 and GDB-MP have 32% and 33% higher current densities at 0.5 V, respectively. Self-made carbon paper with the addition of a micro-porous layer (MPL) (GDL-A240 and GDL-MP) show improved performance compared with GDB-A240 and GDB-MP. The current densities of GDL-A240 and GDL-MP at 0.5 V increased by 37% and 31% compared with GDL, respectively. This study combines these two effects (carbon film and MPL coating) to promote high current density in a PEMFC.

  13. Development of a Model for Water and Heat Exchange Between the Atmosphere and a Water Body

    Institute of Scientific and Technical Information of China (English)

    SUN Shufen; YAN Jinfeng; XIA Nan; SUN Changhai

    2007-01-01

    A model for studying the heat and mass exchange between the atmosphere and a water body is developed,in which the phase change process of water freezing in winter and melting in summer and the function of the convective mixing process are taken into consideration. The model uses enthalpy rather than temperature as the predictive variable. It helps to set up governing equations more concisely, to deal with the phase change process more easily, and make the numerical scheme simpler. The model is verified by observed data from Lake Kinneret for a non-frozen lake in summer time, and Lake Lower Two Medicine for a frozen lake in winter time. Reasonably good agreements between the model simulations and observed data indicate that the model can serve as a component for a water body in a land surface model. In order to more efficiently apply the scheme in a climate system model, a sensitivity study of various division schemes with less layers in the vertical direction in the water body is conducted. The results of the study show that the division with around 10 vertical layers could produce a prediction accuracy that is comparable to the fine division with around 40 layers.

  14. Monitoring and modelling of biosphere/atmosphere exchange of gases and aerosols in Europe

    Energy Technology Data Exchange (ETDEWEB)

    Erisman, Jan Willem [Energy Research Centre of the Netherlands (ECN), P.O. Box 1, 1755 ZG Petten (Netherlands)]. E-mail: erisman@ecn.nl; Vermeulen, Alex [Energy Research Centre of the Netherlands (ECN), P.O. Box 1, 1755 ZG Petten (Netherlands); Hensen, Arjan [Energy Research Centre of the Netherlands (ECN), P.O. Box 1, 1755 ZG Petten (Netherlands); Flechard, Chris [Energy Research Centre of the Netherlands (ECN), P.O. Box 1, 1755 ZG Petten (Netherlands); Daemmgen, Ulrich [Federal Agricultural Research Centre, Institute of Agroecology, D-38116 Braunschweig, (Germany); Fowler, David [CEH, Bush Estate, Penicuik, Midlothian EH26 0QB (United Kingdom); Sutton, Mark [CEH, Bush Estate, Penicuik, Midlothian EH26 0QB (United Kingdom); Gruenhage, Ludger [Institute for Plant Ecology, Justus-Liebig-University, D-35392 Giessen (Germany); Tuovinen, Juha-Pekka [Finnish Meteorological Institute, FIN-00810 Helsinki (Finland)

    2005-02-01

    Monitoring and modelling of deposition of air pollutants is essential to develop and evaluate policies to abate the effects related to air pollution and to determine the losses of pollutants from the atmosphere. Techniques for monitoring wet deposition fluxes are widely applied. A recent intercomparison experiment, however, showed that the uncertainty in wet deposition is relatively high, up to 40%, apart from the fact that most samplers are biased because of a dry deposition contribution. Wet deposition amounts to about 80% of the total deposition in Europe with a range of 10-90% and uncertainty should therefore be decreased. During recent years the monitoring of dry deposition has become possible. Three sites have been operational for 5 years. The data are useful for model development, but also for model evaluation and monitoring of progress in policy. Data show a decline in SO{sub 2} dry deposition, whereas nitrogen deposition remained constant. Furthermore, surface affinities for pollutants changed leading to changes in deposition. Deposition models have been further developed and tested with dry deposition measurements and total deposition measurements on forests as derived from throughfall data. The comparison is reasonable given the measurement uncertainties. Progress in ozone surface exchange modelling and monitoring shows that stomatal uptake can be quantified with reasonable accuracy, but external surface uptake yields highest uncertainty. - Monitoring and modelling of the deposition of sulphur and nitrogen components and the exposure of ozone has gained much progress through the research within BIATEX.

  15. Development of ion-exchange collectors for monitoring atmospheric deposition of inorganic pollutants in Alaska parklands

    Science.gov (United States)

    Brumbaugh, William G.; Arms, Jesse W.; Linder, Greg L.; Melton, Vanessa D.

    2016-09-19

    -stage arrangement. With the modified IEC design, ammonium, nitrate, and sulfate ions were determined with a precision of between 5 and 10 percent relative standard deviation for the low loads that happen in remote areas of Alaska. Results from 2012 field studies demonstrated that the targeted ions were stable and fully retained on the IEC during field deployment and could be fully recovered by extraction in the laboratory. Importantly, measurements of annual loads determined by combining snowpack and IEC sampling at sites near National Atmospheric Deposition Program monitoring stations was comparable to results obtained by the National Atmospheric Deposition Program.Field studies completed in 2014 included snowpack and IEC samples to measure depositional loads; the results were compared to concentrations of similar substances in co-located moss samples. Analyses of constituents in snow and IECs included ammonium, nitrate, and sulfate ions; and a suite of trace metals. Constituent measurements in Hylocomium splendens moss included total nitrogen, phosphorous, and sulfur, and trace metals. To recover ammonium ions and metal ions from the upper cation-exchange column, a two-step extraction procedure was developed from laboratory spiking experiments. The 2014 studies determined that concentrations of certain metals, nitrogen, and sulfur in tissues of Hylocomium splendens moss reflected differences in presumptive deposition from local atmospheric sources. Moss tissues collected from two sites farthest from urban locales had the lowest levels of total nitrogen and sulfur, whereas tissues collected from three of the urban sites had the greatest concentrations of many of the trace metals. Moss tissue concentrations of three trace metals (cobalt, chromium, and nickel) were strongly (positively) Spearman’s rank correlated (p<0.05) with annual depositional loads of those metals. In addition, moss sulfur concentrations were positively rank correlated with annual depositional loads of sulfate

  16. Spatially explicit simulation of peatland hydrology and carbon dioxide exchange

    Energy Technology Data Exchange (ETDEWEB)

    Sonnentag, O.

    2008-08-01

    A recent version of the Boreal Ecosystem Productivity Simulator (BEPS) was extended and modified to include northern peatlands. This thesis evaluated the BEPS-TerrainLab using observations made at the Mer Bleue bog located near Ottawa, Ontario, and the Sandhill fen located near Prince Albert, Saskatchewan. The code was revised to represent the multi-layer canopy and processes related to energy, water vapour and carbon dioxide fluxes through remotely-sensed leaf area index (LAI) maps. A quick and reliable method was also developed to determine shrub LAI with the LAI-2000 plant canopy analyzer. A large number of LAI data was collected at the Mer Bleue bog for the development of a new remote sensing-based methodology using multiple end member spectral unmixing to allow for separate tree and shrub LAI mapping in ombrotrophic peatlands. The methodology was also adapted for use in minerotrophic peatlands and their surrounding landscapes. These LAI maps within the BEPS-TerrainLab represented the tree and shrub layers of the Mer Bleue bog and the tree and shrub/sedge layers of the Sandhill fen. The study examined the influence of mesoscale topography (Mer Bleue bog) and macro- and mesoscale topography (Sandhill fen) on wetness, evapotranspiration, and gross primary productivity during the snow-free period of 2004. The results suggested that a peatland type-specific differentiation of macro- and mesoscale topographic effects on hydrology should be included in future peatland ecosystem modelling efforts in order to allow for a more realistic simulation of the soil water balance in peatlands and to reduce uncertainties in carbon dioxide and methane annual fluxes from wetlands.

  17. Constraining regional scale carbon budgets at the US West Coast using a high-resolution atmospheric inverse modeling approach

    Science.gov (United States)

    Goeckede, M.; Michalak, A. M.; Vickers, D.; Turner, D.; Law, B.

    2009-04-01

    The study presented is embedded within the NACP (North American Carbon Program) West Coast project ORCA2, which aims at determining the regional carbon balance of the US states Oregon, California and Washington. Our work specifically focuses on the effect of disturbance history and climate variability, aiming at improving our understanding of e.g. drought stress and stand age on carbon sources and sinks in complex terrain with fine-scale variability in land cover types. The ORCA2 atmospheric inverse modeling approach has been set up to capture flux variability on the regional scale at high temporal and spatial resolution. Atmospheric transport is simulated coupling the mesoscale model WRF (Weather Research and Forecast) with the STILT (Stochastic Time Inverted Lagrangian Transport) footprint model. This setup allows identifying sources and sinks that influence atmospheric observations with highly resolved mass transport fields and realistic turbulent mixing. Terrestrial biosphere carbon fluxes are simulated at spatial resolutions of up to 1km and subdaily timesteps, considering effects of ecoregion, land cover type and disturbance regime on the carbon budgets. Our approach assimilates high-precision atmospheric CO2 concentration measurements and eddy-covariance data from several sites throughout the model domain, as well as high-resolution remote sensing products (e.g. LandSat, MODIS) and interpolated surface meteorology (DayMet, SOGS, PRISM). We present top-down modeling results that have been optimized using Bayesian inversion, reflecting the information on regional scale carbon processes provided by the network of high-precision CO2 observations. We address the level of detail (e.g. spatial and temporal resolution) that can be resolved by top-down modeling on the regional scale, given the uncertainties introduced by various sources for model-data mismatch. Our results demonstrate the importance of accurate modeling of carbon-water coupling, with the

  18. Compact Instrument for Measurement of Atmospheric Carbon Monoxide Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Southwest Sciences proposed the development of a rugged, compact, and automated instrument for the high sensitivity measurement of tropospheric carbon monoxide...

  19. Compact Instrument for Measurement of Atmospheric Carbon Monoxide Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Southwest Sciences proposes to continue the development of a rugged, compact, and automated instrument for the high sensitivity measurement of tropospheric carbon...

  20. Review and parameterisation of bi-directional ammonia exchange between vegetation and the atmosphere

    Directory of Open Access Journals (Sweden)

    R.-S. Massad

    2010-11-01

    Full Text Available Current deposition schemes used in atmospheric chemical transport models do not generally account for bi-directional exchange of ammonia (NH3. Bi-directional exchange schemes, which have so far been applied at the plot scale, can be included in transport models, but need to be parameterised with appropriate values of the ground layer compensation point (χg, stomatal compensation point (χs and cuticular resistance (Rw. We review existing measurements of χg, χs as well as Rw and compile a comprehensive dataset from which we then propose generalised parameterisations. χs is related to Γs, the non-dimensional ratio of [NH4+]apo and [H+]apo in the apoplast, through the temperature dependence of the combined Henry and dissociation equilibrium. The meta-analysis suggests that the nitrogen (N input is the main driver of the apoplastic and bulk leaf concentrations of ammonium (NH4 apo, NH4 bulk. For managed ecosystems, the main source of N is fertilisation which is reflected in a peak value of χs a few days following application, but also alters seasonal values of NH4 apo and NH4 bulk. We propose a parameterisation for χs which includes peak values as a function of amount and type of fertiliser application which gradually decreases to a background value. The background χs is based on total N input to the ecosystem as a yearly fertiliser application and N deposition (Ndep. For non-managed ecosystems, χs is parameterised based solely on the link with Ndep.

    For Rw we propose a general parameterisation as a function of atmospheric relative humidity (RH, incorporating a minimum value (

  1. Review and parameterisation of bi-directional ammonia exchange between vegetation and the atmosphere

    Directory of Open Access Journals (Sweden)

    R.-S. Massad

    2010-04-01

    Full Text Available Current deposition schemes used in atmospheric chemical transport models do not generally account for bi-directional exchange of ammonia (NH3. Bi-directional exchange schemes, which have so far been applied at the plot scale, can be included in transport models, but need to be parameterised with appropriate values of the stomatal compensation point (χs and cuticular resistance (Rw. We here review existing measurements of χs as well as Rw and compile a comprehensive dataset from which we then propose generalised parameterisations. χs is related to Γs, the non-dimensional ratio of [NH4+]apo and [H+]apo in the apoplast, through the temperature dependence of the combined Henry and solubility equilibrium. The meta-analysis suggests that the nitrogen (N input is the main driver of the apoplastic and bulk leaf concentrations of ammonium (NH+4 apo, NH+4 bulk. For managed ecosystems, the main source of N is fertilisation which is reflected in a peak value of χs a few days following application, but also alters seasonal values of NH+4 apo and NH+4 bulk. We propose a parameterisation for χs which includes peak values as a function of amount and type of fertiliser application which gradually decreases to a background value. The background χs is set based on total N input to the ecosystem as a yearly fertiliser application and N deposition (Ndep. For non-managed ecosystems, χs is parameterised based solely on the link with Ndep.

    For Rw we propose a general parameterisation as a function of atmospheric Relative Humidity (RH, incorporating a minimum value (R w(min, which depends on the ratio of atmospheric acid

  2. Impact of Willow Invasion on Vegetation Water and Carbon Exchange in the Florida Everglades

    Science.gov (United States)

    Budny, M. L.; Benscoter, B.

    2014-12-01

    Southern coastal willow (Salix caroliniana) is native to the Florida Everglades, commonly found on drier landforms like levees and tree islands. Shortened periods of inundation due to water management have led to the encroachment and expansion of these shrubs in sawgrass (Cladium jamaicense) marsh communities. The broadleaf willow is morphologically and physiologically different from the graminoid sedge sawgrass, with possible consequence for microhabitat conditions and ecosystem function. Willow is often assumed to have greater rates of transpiration, thereby affecting wetland water management, and may have concurrent differences in photosynthesis and carbon exchange. However, the ecophysiological impact of the willow invasion has not been quantified. We assessed differences in plant water and carbon exchange between willow and sawgrass at Blue Cypress Conservation Area, an impounded sawgrass peatland within the St. John's River Water Management District (SJRWMD). Plant transpiration and net CO2 exchange (photosynthesis and autotrophic respiration) were measured on fully expanded, non-damaged leaves of sawgrass and willow using a portable infrared gas analyzer (LI-6400XT, LI-COR, Lincoln, NE, U.S.A.). The results obtained from this study will provide a better understanding of ecophysiological changes that occur within marsh communities with shrub expansion, which will have cascading impacts on soil accretion and turnover, microclimate, and water quality Understanding the implications of willow expansion will improve landscape models of wetland water and carbon exchange as well as inform water management decisions.

  3. Carbon allocation and carbon isotope fluxes in the plant-soil-atmosphere continuum: a review

    Directory of Open Access Journals (Sweden)

    N. Brüggemann

    2011-04-01

    Full Text Available The terrestrial carbon (C cycle has received increasing interest over the past few decades, however, there is still a lack of understanding of the fate of newly assimilated C allocated within plants and to the soil, stored within ecosystems and lost to the atmosphere. Stable carbon isotope studies can give novel insights into these issues. In this review we provide an overview of an emerging picture of plant-soil-atmosphere C fluxes, as based on C isotope studies, and identify processes determining related C isotope signatures. The first part of the review focuses on isotopic fractionation processes within plants during and after photosynthesis. The second major part elaborates on plant-internal and plant-rhizosphere C allocation patterns at different time scales (diel, seasonal, interannual, including the speed of C transfer and time lags in the coupling of assimilation and respiration, as well as the magnitude and controls of plant-soil C allocation and respiratory fluxes. Plant responses to changing environmental conditions, the functional relationship between the physiological and phenological status of plants and C transfer, and interactions between C, water and nutrient dynamics are discussed. The role of the C counterflow from the rhizosphere to the aboveground parts of the plants, e.g. via CO2 dissolved in the xylem water or as xylem-transported sugars, is highlighted. The third part is centered around belowground C turnover, focusing especially on above- and belowground litter inputs, soil organic matter formation and turnover, production and loss of dissolved organic C, soil respiration and CO2 fixation by soil microbes. Furthermore, plant controls on microbial communities and activity via exudates and litter production as well as microbial community effects on C mineralization are reviewed. The last part of the paper is dedicated to physical interactions between soil CO2 and the soil matrix, such as CO

  4. What Controls the Net Forest-Atmosphere Exchange of Carbonyl Sulfide? Results from 2 Years of Eddy Flux Measurements and SiB Model Simulations

    Science.gov (United States)

    Wehr, R. A.; Commane, R.; Baker, I. T.; Munger, J. W.; Saleska, S. R.; Wofsy, S. C.

    2015-12-01

    Carbonyl sulfide (OCS) is currently a focus of ground-, aircraft-, and satellite-based measurements as well as of model development, owing mainly to its potential use as a large-scale proxy for gross primary production (GPP). OCS is taken up by leaves and either taken up or emitted by soils, depending on the circumstances. Because OCS is destroyed by the enzyme carbonic anhydrase within the leaf rather than by any light-dependent reaction, the leaf uptake is expected to be related to the conductance of the diffusive pathway into the leaf (stomata + mesophyll + leaf boundary air layer) rather than to GPP directly, though GPP and the diffusive conductance are often strongly correlated. Here we use 2 years of eddy covariance measurements of the net ecosystem-atmosphere exchange of OCS, along with measurements of the vertical profile of OCS within the forest, to investigate the controls on ecosystem-scale OCS uptake and emission. We compare the OCS measurements, and simultaneous CO2 isotope flux and profile measurements, to predictions from the Simple Biosphere (SiB) model, which has been used to simulate OCS and 13CO2 fluxes for both vegetation and soils but has not yet been systematically tested against these relatively novel tracers. We thereby address the key question: How can measurements of the net ecosystem-atmosphere OCS exchange contribute to empirical quantification of stomatal conductance and GPP and to improving process-based ecosystem models?

  5. Electrochemical stability of carbon nanofibers in proton exchange membrane fuel cells

    Energy Technology Data Exchange (ETDEWEB)

    Alvarez, Garbine [Energy Department, CIDETEC-IK4, Po Miramon, 196, 20009 San Sebastian (Spain); Alcaide, Francisco, E-mail: falcaide@cidetec.es [Energy Department, CIDETEC-IK4, Po Miramon, 196, 20009 San Sebastian (Spain); Miguel, Oscar [Energy Department, CIDETEC-IK4, Po Miramon, 196, 20009 San Sebastian (Spain); Cabot, Pere L. [Laboratori d' Electroquimica de Materials i del Medi Ambient, Dept. Quimica Fisica, Universitat de Barcelona, Marti i Franques, 1-11, 08028 Barcelona (Spain); Martinez-Huerta, M.V.; Fierro, J.L.G. [Instituto de Catalisis y Petroleoquimica (CSIC), Marie Curie 2, Cantoblanco, 28049 Madrid (Spain)

    2011-10-30

    This fundamental study deals with the electrochemical stability of several non-conventional carbon based catalyst supports, intended for low temperature proton exchange membrane fuel cell (PEMFC) cathodes. Electrochemical surface oxidation of raw and functionalized carbon nanofibers, and carbon black for comparison, was studied following a potential step treatment at 25.0 deg. C in acid electrolyte, which mimics the operating conditions of low temperature PEMFCs. Surface oxidation was characterized using cyclic voltammetry, X-ray photoelectron spectroscopy (XPS), and contact angle measurements. Cyclic voltammograms clearly showed the presence of the hydroquinone/quinone couple. Furthermore, identification of carbonyl, ether, hydroxyl and carboxyl surface functional groups were made by deconvolution of the XPS spectra. The relative increase in surface oxides on carbon nanofibers during the electrochemical oxidation treatment is significantly smaller than that on carbon black. This suggests that carbon nanofibers are more resistant to the electrochemical corrosion than carbon black under the experimental conditions used in this work. This behaviour could be attributed to the differences found in the microstructure of both kinds of carbons. According to these results, carbon nanofibers possess a high potential as catalyst support to increase the durability of catalysts used in low temperature PEMFC applications.

  6. Carbon allocation and carbon isotope fluxes in the plant-soil-atmosphere continuum: a review

    Directory of Open Access Journals (Sweden)

    N. Brüggemann

    2011-11-01

    Full Text Available The terrestrial carbon (C cycle has received increasing interest over the past few decades, however, there is still a lack of understanding of the fate of newly assimilated C allocated within plants and to the soil, stored within ecosystems and lost to the atmosphere. Stable carbon isotope studies can give novel insights into these issues. In this review we provide an overview of an emerging picture of plant-soil-atmosphere C fluxes, as based on C isotope studies, and identify processes determining related C isotope signatures. The first part of the review focuses on isotopic fractionation processes within plants during and after photosynthesis. The second major part elaborates on plant-internal and plant-rhizosphere C allocation patterns at different time scales (diel, seasonal, interannual, including the speed of C transfer and time lags in the coupling of assimilation and respiration, as well as the magnitude and controls of plant-soil C allocation and respiratory fluxes. Plant responses to changing environmental conditions, the functional relationship between the physiological and phenological status of plants and C transfer, and interactions between C, water and nutrient dynamics are discussed. The role of the C counterflow from the rhizosphere to the aboveground parts of the plants, e.g. via CO2 dissolved in the xylem water or as xylem-transported sugars, is highlighted. The third part is centered around belowground C turnover, focusing especially on above- and belowground litter inputs, soil organic matter formation and turnover, production and loss of dissolved organic C, soil respiration and CO2 fixation by soil microbes. Furthermore, plant controls on microbial communities and activity via exudates and litter production as well as microbial community effects on C mineralization are reviewed. A further part of the paper is dedicated to physical interactions between soil CO2 and the soil matrix, such as

  7. FINAL REPORT: A Study of the Abundance and 13C/12C Ratio of Atmospheric Carbon Dioxide to Advance the Scientific Understanding of Terrestrial Processes Regulating the GCC

    Energy Technology Data Exchange (ETDEWEB)

    Keeling, R. F.; Piper, S. C.

    2008-12-23

    The main objective of this project was to continue research to develop carbon cycle relationships related to the land biosphere based on remote measurements of atmospheric CO2 concentration and its isotopic composition. The project continued time-series observations of atmospheric carbon dioxide and isotopic composition begun by Charles D. Keeling at remote sites, including Mauna Loa, the South Pole, and eight other sites. The program also included the development of methods for measuring radiocarbon content in the collected CO2 samples and carrying out radiocarbon measurements in collaboration with Tom Guilderson of Lawrence Berkeley National Laboratory (LLNL). The radiocarbon measurements can provide complementary information on carbon exchange rates with the land and oceans and emissions from fossil-fuel burning. Using models of varying complexity, the concentration and isotopic measurements were used to establish estimates of the spatial and temporal variations in the net CO2 exchange with the atmosphere, the storage of carbon in the land and oceans, and variable isotopic discrimination of land plants.

  8. Atmospheric oxygen regulation at low Proterozoic levels by incomplete oxidative weathering of sedimentary organic carbon

    Science.gov (United States)

    Daines, Stuart J.; Mills, Benjamin J. W.; Lenton, Timothy M.

    2017-02-01

    It is unclear why atmospheric oxygen remained trapped at low levels for more than 1.5 billion years following the Paleoproterozoic Great Oxidation Event. Here, we use models for erosion, weathering and biogeochemical cycling to show that this can be explained by the tectonic recycling of previously accumulated sedimentary organic carbon, combined with the oxygen sensitivity of oxidative weathering. Our results indicate a strong negative feedback regime when atmospheric oxygen concentration is of order pO2~0.1 PAL (present atmospheric level), but that stability is lost at pO2biological productivity and resultant organic carbon burial drove the Great Oxidation Event.

  9. Modelling the atmosphere of the carbon-rich Mira RU Vir

    CERN Document Server

    Rau, G; Hron, J; Aringer, B; Groenewegen, M A T; Nowotny, W

    2015-01-01

    Context. We study the atmosphere of the carbon-rich Mira RU Vir using the mid-infrared high spatial resolution interferometric observations from VLTI/MIDI. Aims. The aim of this work is to analyse the atmosphere of the carbon-rich Mira RU Vir, with state of the art models, in this way deepening the knowledge of the dynamic processes at work in carbon-rich Miras. Methods. We compare spectro-photometric and interferometric measurements of this carbon-rich Mira AGB star, with the predictions of different kinds of modelling approaches (hydrostatic model atmospheres plus MOD-More Of Dusty, self-consistent dynamic model atmospheres). A geometric model fitting tool is used for a first interpretation of the interferometric data. Results. The results show that a joint use of different kind of observations (photometry, spectroscopy, interferometry) is essential to shed light on the structure of the atmosphere of a carbon-rich Mira. The dynamic model atmospheres fit well the ISO spectrum in the wavelength range {\\lambda...

  10. H2O and CO2 exchange between a sphagnum mire ecosystem and the atmosphere

    Science.gov (United States)

    Olchev, Alexander; Volkova, Elena; Karataeva, Tatiana; Novenko, Elena

    2013-04-01

    The modern climatic conditions are strongly influenced by both internal variability of climatic system, and various external natural and anthropogenic factors (IPCC 2007). Significant increase of concentration of greenhouse gases in the atmosphere and especially the growth of atmospheric CO2 due to human activity are considered as the main factors that are responsible for modern global warming and climate changes. A significant part of anthropogenic CO2 is absorbed from the atmosphere by land biota and especially by vegetation cover. However, it is still not completely clear what is the role of different land ecosystems and especially forests and mires in global cycles of H2O and CO2 and what is a sensitivity of these ecosystems to climate changes. Within the framework of this study the spatial and temporal variability of H2O and CO2 fluxes between a mire ecosystem and the atmosphere was described using results of the field measurements and modeling approach. For the study a mire ecosystem located in Tula region in European part of Russia was selected. The selected mire has karst origin, depth of peat float is 2.5-3.0 m (depth of depression is more than 10 meter), area is about 1 ha. The mire vegetation is characterized by sedge and sphagnum mosses cover. The mire is surrounded by broad-leaved forest of about 20 meter high. To describe the temporal and spatial patterns of H2O and CO2 fluxes within selected mire the chamber method was applied. The measurement were carried out along transect from mire edge to center from June to September of 2012. For measurements the transparent ventilated chambers combined with portable infrared CO2/H2O analyzer LI-840 (Li-Cor, USA) was used. To estimate the gross primary production and respiration of different type of vegetation within the mire the measurements were conducted both under actual light conditions and artificial shading. Results of the experimental studies showed that the maximal CO2 fluxes was observed in central

  11. Effects of seasonal drought on net carbon dioxide exchange from a woody-plant-encroached semiarid grassland

    Science.gov (United States)

    Scott, Russell L.; Jenerette, G. Darrel; Potts, Daniel L.; Huxman, Travis E.

    2009-12-01

    Annual precipitation in the central and southern warm-desert region of North America is distributed climatologically between summer and winter periods with two prominent dry periods between them. We used energy and carbon dioxide (CO2) fluxes from eddy covariance along with standard meteorological and soil moisture measurements at a semiarid savanna in southern Arizona, United States, to better understand the consequences of warm or cool season drought on ecosystem CO2 exchange in these bimodally forced water-limited regions. Over the last 100 years, this historic grassland has converted to a savanna by the encroachment of the native mesquite tree (Prosopis velutina Woot.). During each of the 4 years of observation (2004-2007), annual precipitation (P) was below average, but monsoon (July-September) P was both above and below average while cool-season (December-March) P was always less than average by varying degrees. The ecosystem was a net source of CO2 to the atmosphere, ranging from 14 to 95 g C m-2 yr-1 with the strength of the source increasing with decreasing precipitation. When the rainfall was closest to the long-term average in its distribution and amount, the ecosystem was essentially carbon neutral. Summer drought resulted in increased carbon losses due mainly to a shortening of the growing season and the length of time later in the season when photosynthetic gain exceeds respiration loss. Severe cool season drought led to decreased spring carbon uptake and seemingly enhanced summer respiration, resulting in conditions that led to the greatest annual net carbon loss.

  12. Toward Reducing Uncertainties in Biospheric Carbon Uptake in the American West: An Atmospheric Perspective

    Science.gov (United States)

    Lin, J. C.; Stephens, B. B.; Mallia, D.; Wu, D.; Jacobson, A. R.

    2015-12-01

    Despite the need for an understanding of terrestrial biospheric carbon fluxes to account for carbon cycle feedbacks and predict future CO2 concentrations, knowledge of such fluxes at the regional scale remains poor. This is particularly true in mountainous areas, where lack of observations combined with difficulties in their interpretation lead to significant uncertainties. Yet mountainous regions are also where significant forest cover and biomass are found—areas that have the potential to serve as carbon sinks. In particular, understanding carbon fluxes in the American West is of critical importance for the U.S. carbon budget, as the large area and biomass indicate potential for carbon sequestration. However, disturbances such as drought, insect outbreak, and wildfires in this region can introduce significant perturbations to the carbon cycle and thereby affect the amount of carbon sequestered by vegetation in the Rockies. To date, there have been few atmospheric CO2 observations in the American Rockies due to a combination of difficulties associated with logistics and interpretation of the measurements in the midst of complex terrain. Among the few sites are those associated with NCAR's Regional Atmospheric Continuous CO2 Network in the Rocky Mountains (Rocky RACCOON). As CO2 observations in mountainous areas increase in the future, it is imperative that they can be properly interpreted to yield information about biospheric carbon fluxes. In this paper, we will present CO2 observations from RACCOON, along with atmospheric simulations that attempt to extract information about biospheric carbon fluxes in the Western U.S. from these observations. We show that atmospheric models can significantly misinterpret the CO2 observations, leading to large errors in the retrieved biospheric fluxes, due to erroneous atmospheric flows. Recommendations for ways to minimize such errors and properly link the CO2 concentrations to biospheric fluxes are discussed.

  13. Structure and Metal Exchange in the Cadmium Carbonic anhydrase of Marine Diatoms

    Energy Technology Data Exchange (ETDEWEB)

    Xu,Y.; Feng, l.; Jeffrey, P.; Shi, Y.; Morel, F.

    2008-01-01

    Carbonic anhydrase, a zinc enzyme found in organisms from all kingdoms, catalyses the reversible hydration of carbon dioxide and is used for inorganic carbon acquisition by phytoplankton. In the oceans, where zinc is nearly depleted, diatoms use cadmium as a catalytic metal atom in cadmium carbonic anhydrase (CDCA). Here we report the crystal structures of CDCA in four distinct forms: cadmium-bound, zinc-bound, metal-free and acetate-bound. Despite lack of sequence homology, CDCA is a structural mimic of a functional {beta}-carbonic anhydrase dimer, with striking similarity in the spatial organization of the active site residues. CDCA readily exchanges cadmium and zinc at its active site--an apparently unique adaptation to oceanic life that is explained by a stable opening of the metal coordinating site in the absence of metal. Given the central role of diatoms in exporting carbon to the deep sea, their use of cadmium in an enzyme critical for carbon acquisition establishes a remarkable link between the global cycles of cadmium and carbon.

  14. Numerical sensitivity study of the nocturnal low-level jet over a forest canopy and implications for nocturnal surface exchange of carbon dioxide and other trace gases

    DEFF Research Database (Denmark)

    Sogachev, Andrey; Leclerc, M.Y.; Duarte, H.F.

    2010-01-01

    in the nocturnal boundary layer, several studies demonstrated the role of nocturnal jets in transporting moisture, ozone, and other trace gases between the biosphere and the lower atmosphere (Mathieu et al., 2005; Karipot et al., 2006; 2007; 2008; 2009). This study suggests that SCADIS, because of its simplicity...... and low computational demand, has potential as a research tool regarding surface–atmosphere gaseous exchange in the nocturnal boundary layer, especially if carbon dioxide, water vapor, ozone and other gases are released or deposited inside the forest canopy.......The development of a wind speed maximum in the nocturnal boundary layer, commonly referred to as a low-level jet (LLJ) (Blackadar, 1957), is a common feature of the vertical structure of the atmospheric boundary layer (ABL) and impacts the meteorology and the local climate of a region. A variety...

  15. Use of the electrosurgical unit in a carbon dioxide atmosphere.

    Science.gov (United States)

    Culp, William C; Kimbrough, Bradly A; Luna, Sarah; Maguddayao, Aris J; Eidson, Jack L; Paolino, David V

    2016-01-01

    The electrosurgical unit (ESU) utilizes an electrical discharge to cut and coagulate tissue and is often held above the surgical site, causing a spark to form. The voltage at which the spark is created, termed the breakdown voltage, is governed by the surrounding gaseous environment. Surgeons are now utilizing the ESU laparoscopically with carbon dioxide insufflation, potentially altering ESU operating characteristics. This study examines the clinical implications of altering gas composition by measuring the spark gap distance as a marker of breakdown voltage and use of the ESU on a biologic model, both in room air and carbon dioxide. Paschen's Law predicted a 35% decrease in gap distance in carbon dioxide, while testing revealed an average drop of 37-47% as compared to air. However, surgical model testing revealed no perceivable clinical difference. Electrosurgery can be performed in carbon dioxide environments, although surgeons should be aware of potentially altered ESU performance.

  16. A comparison between energy transfer and atmospheric turbulent exchanges over alpine meadow and banana plantation

    Science.gov (United States)

    Ding, Zhangwei; Ma, Yaoming; Wen, Zhiping; Ma, Weiqiang

    2016-04-01

    Banana plantation and alpine meadow ecosystems in southern China and the Tibetan Plateau are unique in the underlying surfaces they exhibit. In this study, we used eddy covariance and a micrometeorological tower to examine the characteristics of land surface energy exchanges over a banana plantation in southern China and an alpine meadow in the Tibetan Plateau from May 2010 to August 2012. The results showed that the diurnal and seasonal variations in upward shortwave radiation flux and surface soil heat flux were larger over the alpine meadow than over the banana plantation surface. Dominant energy partitioning varied with season. Latent heat flux was the main consumer of net radiation flux in the growing season, whereas sensible heat flux was the main consumer during other periods. The Monin-Obukhov similarity theory was employed for comparative purposes, using sonic anemometer observations of flow over the surfaces of banana plantations in the humid southern China monsoon region and the semi-arid areas of the TP, and was found to be applicable. Over banana plantation and alpine meadow areas, the average surface albedo and surface aerodynamic roughness lengths under neutral atmospheric conditions were ~0.128 and 0.47m, and ~0.223 and 0.01m, respectively. During the measuring period, the mean annual bulk transfer coefficients for momentum and sensible heat were 1.47×10-2 and 7.13×10-3, and 2.91×10-3 and 1.96×10-3, for banana plantation and alpine meadow areas, respectively. This is the first time in Asia that long-term open field measurements have been taken with the specific aim of making comparisons between banana plantation and alpine meadow surfaces.

  17. Kinetic study of coals gasification into carbon dioxide atmosphere

    OpenAIRE

    Korotkikh A.G.; Slyusarskiy K.V.

    2015-01-01

    The solid fuel gasification process was investigated to define chemical reactions rate and activation energy for a gas-generator designing and regime optimizing. An experimental procedure includes coal char samples of Kuznetskiy and Kansko-Achinskiy deposits consequent argon pyrolysis into argon and oxidating into carbon dioxide with different temperatures. The thermogravimetric analysis data of coal char gasification into carbon dioxide was obtained in the temperature range 900–1200 ºC. The ...

  18. The Chemistry of Atmosphere-Forest Exchange (CAFE Model – Part 2: Application to BEARPEX-2007 observations

    Directory of Open Access Journals (Sweden)

    G. M. Wolfe

    2011-02-01

    Full Text Available In a companion paper, we introduced the Chemistry of Atmosphere-Forest Exchange (CAFE model, a vertically-resolved 1-D chemical transport model designed to probe the details of near-surface reactive gas exchange. Here, we apply CAFE to noontime observations from the 2007 Biosphere Effects on Aerosols and Photochemistry Experiment (BEARPEX-2007. In this work we evaluate the CAFE modeling approach, demonstrate the significance of in-canopy chemistry for forest-atmosphere exchange and identify key shortcomings in the current understanding of intra-canopy processes.

    CAFE generally reproduces BEARPEX-2007 observations but requires an enhanced radical recycling mechanism to overcome a factor of 6 underestimate of hydroxyl (OH concentrations observed during a warm (~29 °C period. Modeled fluxes of acyl peroxy nitrates (APN are quite sensitive to gradients in chemical production and loss, demonstrating that chemistry may perturb forest-atmosphere exchange even when the chemical timescale is long relative to the canopy mixing timescale. The model underestimates peroxy acetyl nitrate (PAN fluxes by 50% and the exchange velocity by nearly a factor of three under warmer conditions, suggesting that near-surface APN sinks are underestimated relative to the sources. Nitric acid typically dominates gross dry N deposition at this site, though other reactive nitrogen (NOy species can comprise up to 28% of the N deposition budget under cooler conditions. Upward NO2 fluxes cause the net above-canopy NOy flux to be ~30% lower than the gross depositional flux. CAFE under-predicts ozone fluxes and exchange velocities by ~20%. Large uncertainty in the parameterization of cuticular and ground deposition precludes conclusive attribution of non-stomatal fluxes to chemistry or surface uptake. Model-measurement comparisons of vertical concentration gradients for several emitted species suggests that the lower canopy airspace may be

  19. Improved Electrodes for High Temperature Proton Exchange Membrane Fuel Cells using Carbon Nanospheres.

    Science.gov (United States)

    Zamora, Héctor; Plaza, Jorge; Cañizares, Pablo; Lobato, Justo; Rodrigo, Manuel A

    2016-05-23

    This work evaluates the use of carbon nanospheres (CNS) in microporous layers (MPL) of high temperature proton exchange membrane fuel cell (HT-PEMFC) electrodes and compares the characteristics and performance with those obtained using conventional MPL based on carbon black. XRD, hydrophobicity, Brunauer-Emmett-Teller theory, and gas permeability of MPL prepared with CNS were the parameters evaluated. In addition, a short life test in a fuel cell was carried out to evaluate performance under accelerated stress conditions. The results demonstrate that CNS is a promising alternative to traditional carbonaceous materials because of its high electrochemical stability and good electrical conductivity, suitable to be used in this technology.

  20. Surface-atmosphere exchange of ammonia over peatland using QCL-based eddy-covariance measurements and inferential modeling

    DEFF Research Database (Denmark)

    Zöll, Undine; Brümmer, Christian; Schrader, Frederik;

    2016-01-01

    Recent advances in laser spectrometry offer new opportunities to investigate ecosystem-atmosphere exchange of environmentally relevant trace gases. In this study, we demonstrate the applicability of a quantum cascade laser (QCL) absorption spectrometer to continuously measure ammonia concentratio...... as important additional instruments within long-term monitoring research infrastructures such as ICOS or NEON at sites with strong nearby ammonia sources leading to relatively high mean background concentrations and fluxes....

  1. Soil atmosphere exchange of Carbonyl Sulfide (COS) regulated by diffusivity depending on water-filled pore space

    OpenAIRE

    H. Van Diest; Kesselmeier, J.

    2007-01-01

    The exchange of carbonyl sulfide (COS) between soil and the atmosphere was investigated for three arable soils from Germany, China and Finland and one forest soil from Siberia for parameterization in the relation to ambient carbonyl sulfide (COS) concentration, soil water content (WC) and air temperature. All investigated soils acted as significant sinks for COS. A clear and distinct uptake optimum was found for the German, Chinese, Finnish and Siberian soils at 11.5%, 9%, 11.5%, and 9% soil ...

  2. Electrosorptive desalination by carbon nanotubes and nanofibres electrodes and ion-exchange membranes.

    Science.gov (United States)

    Li, Haibo; Gao, Yang; Pan, Likun; Zhang, Yanping; Chen, Yiwei; Sun, Zhuo

    2008-12-01

    A novel membrane capacitive deionization (MCDI) device, integrating both the advantages of carbon nanotubes and carbon nanofibers (CNTs-CNFs) composite film and ion-exchange membrane, was proposed with high removal efficiency, low energy consumption and low cost. The CNTs-CNFs film was synthesized by low pressure and low temperature thermal chemical vapor deposition. Several experiments were conducted to compare desalination performance of MCDI with capacitive deionization (CDI), showing that salt removal of the MCDI system was 49.2% higher than that of the CDI system. The electrosorption isotherms of MCDI and CDI show both of them follow Langmuir adsorption, indicating no change in adsorption behavior when ion-exchange membranes are introduced into CDI system. The better desalination performance of MCDI than that of CDI is due to the minimized ion desorption during electrosorption.

  3. Carbon exchange between a shelf sea and the ocean: The Hebrides Shelf, west of Scotland

    Science.gov (United States)

    Painter, Stuart C.; Hartman, Susan E.; Kivimäe, Caroline; Salt, Lesley A.; Clargo, Nicola M.; Bozec, Yann; Daniels, Chris J.; Jones, Sam C.; Hemsley, Victoria S.; Munns, Lucie R.; Allen, Stephanie R.

    2016-07-01

    Global mass balance calculations indicate the majority of particulate organic carbon (POC) exported from shelf seas is transferred via downslope exchange processes. Here we demonstrate the downslope flux of POC from the Hebrides Shelf is approximately 3- to 5-fold larger per unit length/area than the global mean. To reach this conclusion, we quantified the offshore transport of particulate and dissolved carbon fractions via the "Ekman Drain," a strong downwelling feature of the NW European Shelf circulation, and subsequently compared these fluxes to simultaneous regional air-sea CO2 fluxes and onshore wind-driven Ekman fluxes to constrain the carbon dynamics of this shelf. Along the shelf break, we estimate a mean offshelf total carbon (dissolved + particulate) flux of 4.2 tonnes C m-1 d-1 compared to an onshelf flux of 4.5 tonnes C m-1 d-1. Organic carbon represented 3.3% of the onshelf carbon flux but 6.4% of the offshelf flux indicating net organic carbon export. Dissolved organic carbon represented 95% and POC 5% of the exported organic carbon pool. When scaled along the shelf break the total offshelf POC flux (0.007 Tg C d-1) was found to be 3 times larger than the regional air-sea CO2 ingassing flux (0.0021 Tg C d-1), an order of magnitude larger than the particulate inorganic carbon flux (0.0003 Tg C d-1) but far smaller than the DIC (2.03 Tg C d-1) or DOC (0.13 Tg C d-1) fluxes. Significant spatial heterogeneity in the Ekman drain transport confirms that offshelf carbon fluxes via this mechanism are also spatially heterogeneous.

  4. Modelling the impact of soil Carbonic Anhydrase on the net ecosystem exchange of OCS at Harvard forest using the MuSICA model

    Science.gov (United States)

    Launois, Thomas; Ogée, Jérôme; Commane, Roisin; Wehr, Rchard; Meredith, Laura; Munger, Bill; Nelson, David; Saleska, Scott; Wofsy, Steve; Zahniser, Mark; Wingate, Lisa

    2016-04-01

    The exchange of CO2 between the terrestrial biosphere and the atmosphere is driven by photosynthetic uptake and respiratory loss, two fluxes currently estimated with considerable uncertainty at large scales. Model predictions indicate that these biosphere fluxes will be modified in the future as CO2 concentrations and temperatures increase; however, it still unclear to what extent. To address this challenge there is a need for better constraints on land surface model parameterisations. Additional atmospheric tracers of large-scale CO2 fluxes have been identified as potential candidates for this task. In particular carbonyl sulphide (OCS) has been proposed as a complementary tracer of gross photosynthesis over land, since OCS uptake by plants is dominated by carbonic anhydrase (CA) activity, an enzyme abundant in leaves that catalyses CO2 hydration during photosynthesis. However, although the mass budget at the ecosystem is dominated by the flux of OCS into leaves, some OCS is also exchanged between the atmosphere and the soil and this component of the budget requires constraining. In this study, we adapted the process-based isotope-enabled model MuSICA (Multi-layer Simulator of the Interactions between a vegetation Canopy and the Atmosphere) to include the transport, reaction, diffusion and production of OCS within a forested ecosystem. This model was combined with 3 years (2011-2013) of in situ measurements of OCS atmospheric concentration profiles and fluxes at the Harvard Forest (Massachussets, USA) to test hypotheses on the mechanisms responsible for CA-driven uptake by leaves and soils as well as possible OCS emissions during litter decomposition. Model simulations over the three years captured well the impact of diurnally and seasonally varying environmental conditions on the net ecosystem OCS flux. A sensitivity analysis on soil CA activity and soil OCS emission rates was also performed to quantify their impact on the vertical profiles of OCS inside the

  5. Climate and site management as driving factors for the atmospheric greenhouse gas exchange of a restored wetland

    DEFF Research Database (Denmark)

    Herbst, Mathias; Friborg, Thomas; Schelde, Kirsten;

    2013-01-01

    The atmospheric greenhouse gas (GHG) budget of a restored wetland in western Denmark was established for the years 2009–2011 from eddy covariance measurements of carbon dioxide (CO2) and methane (CH4) fluxes. The water table in the wetland, which was restored in 2002, was unregulated, and the veg......The atmospheric greenhouse gas (GHG) budget of a restored wetland in western Denmark was established for the years 2009–2011 from eddy covariance measurements of carbon dioxide (CO2) and methane (CH4) fluxes. The water table in the wetland, which was restored in 2002, was unregulated...... the atmosphere. However, in terms of the full annual GHG budget (assuming that 1 g CH4 is equivalent to 25 g CO2 with respect to the greenhouse effect over a time horizon of 100 years) the wetland was a sink in 2009, a source in 2010 and neutral in 2011. Complementary observations of meteorological factors...

  6. Nitroguanidine Wastewater Pollution Control Technology: Phase III. Ion Exchange and Carbon Adsorption Treatment

    Science.gov (United States)

    1984-03-01

    SD are synthetic cross-linked resins provided as moist spherical beads nominally of 50 percent water content. The clinoptilolite was supplied presized...Na+ i3 provided by a resin (either naturally occurring or synthetic ). Usually, the resin is prepared in a fixed-bed column, and hard water ion is...these :.ons as well as NQ. I/’ I . , I * MATERIALS AND METHODS RESINS AND CARBONS Three ion-exchange materials were studied: clinoptilolite , an

  7. Evaluating the Carbon Cycle of a Coupled Atmosphere-Biosphere Model

    Energy Technology Data Exchange (ETDEWEB)

    Delire, C; Foley, J A; Thompson, S

    2002-08-21

    We investigate how well a coupled biosphere-atmosphere model, CCM3-IBIS, can simulate the functioning of the terrestrial biosphere and the carbon cycling through it. The simulated climate is compared to observations, while the vegetation cover and the carbon cycle are compared to an offline version of the biosphere model IBIS forced with observed climatic variables. The simulated climate presents some local biases that strongly affect the vegetation (e.g., a misrepresentation of the African monsoon). Compared to the offline model, the coupled model simulates well the globally averaged carbon fluxes and vegetation pools. The zonal mean carbon fluxes and the zonal mean seasonal cycle are also well represented except between 0{sup o} and 20{sup o}N due to the misrepresentation of the African monsoon. These results suggest that, despite regional biases in climate and ecosystem simulations, this coupled atmosphere-biosphere model can be used to explore geographic and temporal variations in the global carbon cycle.

  8. Correlation between charge transfer and exchange coupling in carbon-based magnetic materials

    Energy Technology Data Exchange (ETDEWEB)

    Nguyen, Anh Tuan, E-mail: tuanna@hus.edu.vn [Faculty of Physics, VNU University of Science, 334 Nguyen Trai, Thanh Xuan, Ha Noi (Viet Nam); Science and Technology Department, Vietnam National University, Hanoi, 144 Xuan Thuy, Cau Giay, Hanoi (Viet Nam); Japan Advanced Institute of Science and Technology, 1-1, Asahidai, Nomi, Ishikawa, 923-1292 Japan (Japan); Nguyen, Van Thanh; Nguyen, Huy Sinh [Faculty of Physics, VNU University of Science, 334 Nguyen Trai, Thanh Xuan, Ha Noi (Viet Nam); Pham, Thi Tuan Anh [Faculty of Physics, VNU University of Science, 334 Nguyen Trai, Thanh Xuan, Ha Noi (Viet Nam); Faculty of Science, College of Hai Duong, Nguyen Thi Due, Hai Duong (Viet Nam); Do, Viet Thang [Faculty of Physics, VNU University of Science, 334 Nguyen Trai, Thanh Xuan, Ha Noi (Viet Nam); Faculty of Science, Haiphong University, 171 Phan Dang Luu, Kien An, Hai Phong (Viet Nam); Dam, Hieu Chi [Japan Advanced Institute of Science and Technology, 1-1, Asahidai, Nomi, Ishikawa, 923-1292 Japan (Japan)

    2015-10-15

    Several forms of carbon-based magnetic materials, i.e. single radicals, radical dimers, and alternating stacks of radicals and diamagnetic molecules, have been investigated using density-functional theory with dispersion correction and full geometry optimization. Our calculated results demonstrate that the C{sub 31}H{sub 15} (R{sub 4}) radical has a spin of ½. However, in its [R{sub 4}]{sub 2} dimer structure, the net spin becomes zero due to antiferromagnetic spin-exchange between radicals. To avoid antiferromagnetic spin-exchange of identical face-to-face radicals, eight alternating stacks, R{sub 4}/D{sub 2m}/R{sub 4} (with m = 3-10), were designed. Our calculated results show that charge transfer (Δn) between R{sub 4} radicals and the diamagnetic molecule D{sub 2m} occurs with a mechanism of spin exchange (J) in stacks. The more electrons that transfer from R{sub 4} to D{sub 2m}, the stronger the ferromagnetic spin-exchange in stacks. In addition, our calculated results show that Δn can be tailored by adjusting the electron affinity (E{sub a}) of D{sub 2m}. The correlation between Δn, E{sub a}, m, and J is discussed. These results give some hints for the design of new ferromagnetic carbon-based materials.

  9. Carbon exchange fluxes over peatlands in Western Siberia: Possible feedback between land-use change and climate change

    Energy Technology Data Exchange (ETDEWEB)

    Fleischer, Elisa, E-mail: elisa.fleischer@uni-muenster.de [Institute of Landscape Ecology, Climatology Research Group, University of Münster, Münster (Germany); Khashimov, Ilhom, E-mail: nixonlp@mail.ru [Institute of Earth Science, Physical Geography and Geoecology Department, Tyumen State University, Tyumen (Russian Federation); Hölzel, Norbert, E-mail: nhoelzel@uni-muenster.de [Institute of Landscape Ecology, Biodiversity and Ecosystem Research Group, University of Münster, Münster (Germany); Klemm, Otto, E-mail: otto.klemm@uni-muenster.de [Institute of Landscape Ecology, Climatology Research Group, University of Münster, Münster (Germany)

    2016-03-01

    The growing demand for agricultural products has been leading to an expansion and intensification of agriculture around the world. More and more unused land is currently reclaimed in the regions of the former Soviet Union. Driven by climate change, the Western Siberian grain belt might, in a long-term, even expand into the drained peatland areas to the North. It is crucial to study the consequences of this land-use change with respect to the carbon cycling as this is still a major knowledge gap. We present for the first time data on the atmosphere-ecosystem exchange of carbon dioxide and methane of an arable field and a neighboring unused grassland on peat soil in Western Siberia. Eddy covariance measurements were performed over one vegetation period. No directed methane fluxes were found due to an effective drainage of the study sites. The carbon dioxide fluxes appeared to be of high relevance for the global carbon and greenhouse gas cycles. They showed very site-specific patterns resulting from the development of vegetation: the persistent plants of the grassland were able to start photosynthesizing soon after snow melt, while the absence of vegetation on the managed field lead to a phase of emissions until the oat plants started to grow in June. The uptake peak of the oat field is much later than that of the grassland, but larger due to a rapid plant growth. Budgeting the whole measurement period, the grassland served as a carbon sink, whereas the oat field was identified to be a carbon source. The conversion from non-used grasslands on peat soil to cultivated fields in Western Siberia is therefore considered to have a positive feedback on climate change. - Highlights: • Grasslands on drained peat soil can act as carbon sinks. • Arable fields on drained peat act as carbon sources due to long phases of bare soil. • CH{sub 4} emissions from drained peatlands seem to play a smaller role than CO{sub 2} fluxes. • Conversion from grassland to arable field has

  10. Recent pause in the growth rate of atmospheric CO2 due to enhanced terrestrial carbon uptake

    Science.gov (United States)

    Keenan, Trevor F.; Prentice, I. Colin; Canadell, Josep G.; Williams, Christopher A.; Wang, Han; Raupach, Michael; Collatz, G. James

    2016-11-01

    Terrestrial ecosystems play a significant role in the global carbon cycle and offset a large fraction of anthropogenic CO2 emissions. The terrestrial carbon sink is increasing, yet the mechanisms responsible for its enhancement, and implications for the growth rate of atmospheric CO2, remain unclear. Here using global carbon budget estimates, ground, atmospheric and satellite observations, and multiple global vegetation models, we report a recent pause in the growth rate of atmospheric CO2, and a decline in the fraction of anthropogenic emissions that remain in the atmosphere, despite increasing anthropogenic emissions. We attribute the observed decline to increases in the terrestrial sink during the past decade, associated with the effects of rising atmospheric CO2 on vegetation and the slowdown in the rate of warming on global respiration. The pause in the atmospheric CO2 growth rate provides further evidence of the roles of CO2 fertilization and warming-induced respiration, and highlights the need to protect both existing carbon stocks and regions, where the sink is growing rapidly.

  11. [Comparison of Monitoring Methods of Organic Carbon and Element Carbon in Atmospheric Fine Particles].

    Science.gov (United States)

    Pang, Bo; Ji, Dong-sheng; Liu, Zi-rui; Zhu, Bin; Wang, Yue-si

    2016-04-15

    Accurate measurement of organic carbon (OC) and elemental carbon (EC) in atmospheric fine particulate is an important scientific basis for studying the formation and source apportionment of carbonaceous aerosol. The selection of different analysis programs will lead to difference in the OC and EC concentrations, and further result in the misjudgment of the results. The OC and EC concentrations observed using three temperature protocols including RT-Quartz ( R) , NIOSH 5040 (N) and Fast-TC (F) were compared and analyzed in combination with the degree of air pollution in Beijing. The results showed that there was no significant difference in the TC (TC = OC + EC), OC and EC concentrations observed using R, N and F protocols and certain deviation was found among the TC (TC = OC + EC) , OC and EC concentrations. For TC, the results observed using R protocol were 5% lower than those using N protocol; hut 1% higher than those using F protocol. For OC, the results obtained using R were 9% lower than those using N protocol and 1% higher than those using F protocol. For EC, the results obtained using R were 20% higher than those using N protocol and 11% lower than those using F protocol. The variation coefficients for TC, OC and EC obtained based on R protocol were less than the other two temperature protocols under different air quality degrees. The slopes of regression curves of TC, OC and EC between on-line analysis using R protocol and off-line analysis were 1.21,1. 14 and 1.35, respectively. The correlation coefficients of TC, OC and EC were 0.99, 0.99 and 0.98, respectively. In contrast with the Black carbon ( BC) concentrations monitored by multi-angle absorption spectrophotometer (MAAP), the EC concentrations measured by on-line OC/EC analyzer using R protocol were obviously lower. When the BC concentrations were less than or equal to 8 gg*m3, the EC/BC ratio was 0.39. While the EC/BC ratio was 0.88, when the BC concentrations were greater than 8 ggm3. The variation

  12. Effects of ploughing on land-atmosphere exchange of greenhouse gases in a managed temperate grassland in central Scotland

    Science.gov (United States)

    Helfter, Carole; Drewer, Julia; Anderson, Margaret; Scholtes, Bob; Rees, Bob; Skiba, Ute

    2015-04-01

    Grasslands are important ecosystems covering > 20% and > 30% of EU and Scotland's land area respectively. Management practices such as grazing, fertilisation and ploughing can have significant short- and long-term effects on greenhouse gas exchange. Here we report on two separate ploughing events two years apart in adjacent grasslands under common management. The Easter Bush grassland, located 10 km south of Edinburgh (55° 52'N, 3° 2'W), comprises two fields separated by a fence and is used for grazing by sheep and cattle. The vegetation is predominantly Lolium perenne (> 90%) growing on poorly drained clay loam. The fields receive several applications of mineral fertiliser a year in spring and summer. Net ecosystem exchange (NEE) of carbon dioxide (CO2) has been monitored continuously by eddy-covariance (EC) since 2002 which has demonstrated that the site is a consistent yet variable sink of atmospheric CO2. The EC system comprises a LI-COR 7000 closed-path analyser and a Gill Instruments Windmaster Pro ultrasonic anemometer mounted atop a 2.5 m mast located along the fence line separating the fields. In addition, fluxes of nitrous oxide (N2O), methane (CH4)and CO2were measured with static chambers installed along transects in each field. Gas samples collected from the chambers were analysed by gas chromatography and fluxes calculated for each 60-minute sampling period. The ploughing events in 2012 and 2014 exhibited multiple similarities in terms of NEE. The light response (i.e. relationship between CO2 flux, and photosynthetically active radiation, PAR) of the NF and SF during the month preceding each ploughing event was of comparable magnitude in both years. Following ploughing, CO2 uptake ceased in the ploughed field for approximately one month and full recovery of the photosynthetic potential was observed after ca. 2 months. During the month following the 2014 ploughing event, the ploughed NF released on average 333 ± 17 mg CO2-C m-2 h-1. In contrast, the

  13. Net carbon exchange across the Arctic tundra-boreal forest transition in Alaska 1981-2000

    Science.gov (United States)

    Thompson, Catharine Copass; McGuire, A.D.; Clein, J.S.; Chapin, F. S.; Beringer, J.

    2006-01-01

    Shifts in the carbon balance of high-latitude ecosystems could result from differential responses of vegetation and soil processes to changing moisture and temperature regimes and to a lengthening of the growing season. Although shrub expansion and northward movement of treeline should increase carbon inputs, the effects of these vegetation changes on net carbon exchange have not been evaluated. We selected low shrub, tall shrub, and forest tundra sites near treeline in northwestern Alaska, representing the major structural transitions expected in response to warming. In these sites, we measured aboveground net primary production (ANPP) and vegetation and soil carbon and nitrogen pools, and used these data to parameterize the Terrestrial Ecosystem Model. We simulated the response of carbon balance components to air temperature and precipitation trends during 1981-2000. In areas experiencing warmer and dryer conditions, Net Primary Production (NPP) decreased and heterotrophic respiration (R H ) increased, leading to a decrease in Net Ecosystem Production (NEP). In warmer and wetter conditions NPP increased, but the response was exceeded by an increase in R H ; therefore, NEP also decreased. Lastly, in colder and wetter regions, the increase in NPP exceeded a small decline in R H , leading to an increase in NEP. The net effect for the region was a slight gain in ecosystem carbon storage over the 20 year period. This research highlights the potential importance of spatial variability in ecosystem responses to climate change in assessing the response of carbon storage in northern Alaska over the last two decades. ?? Springer 2005.

  14. The Role of Explicitly Modeling Bryophytes in Simulating Carbon Exchange and Permafrost Dynamics of an Arctic Coastal Tundra at Barrow, Alaska

    Science.gov (United States)

    Yuan, F.; Thornton, P. E.; McGuire, A. D.; Oechel, W. C.; Yang, B.; Tweedie, C. E.; Rogers, A.; Norby, R. J.

    2013-12-01

    Bryophyte cover is greater than 50% in many Arctic tundra ecosystems. In regions of the Arctic where shrubs are expanding it is expected that bryophyte cover will be substantially reduced. Such a loss in cover could influence the hydrological, biogeochemical, and permafrost dynamics of Arctic tundra ecosystems. The explicit representation of bryophyte physiological and biophysical processes in large-scale ecological and land surface models is rare, and we hypothesize that the representation of bryophytes has consequences for estimates of the exchange of water, energy, and carbon by these models. This study explicitly represents the effects of bryophyte function and structure on the exchange of carbon (e.g., summer photosynthesis effects) and energy (e.g., summer insulation effects) with the atmosphere in the Community Land Model (CLM-CN). The modified model was evaluated for its ability to simulate C exchange, soil temperature, and soil moisture since the 1970s at Barrow, Alaska through comparison with data from AmeriFlux sites, USDA Soil Climate Networks observation sites at Barrow, and other sources. We also compare the outputs of the CLM-CN simulations with those of the recently developed Dynamical Organic Soil coupled Terrestrial Ecosystem Model (DOS-TEM). Overall, our evaluation indicates that bryophytes are important contributors to land-atmospheric C exchanges in Arctic tundra and that they play an important role to permafrost thermal and hydrological processes which are critical to permafrost stability. Our next step in this study is to examine the climate system effects of explicitly representing bryophyte dynamics in the land surface model. Key Words: Bryophytes, Arctic coastal tundra, Vegetation composition, Net Ecosystem Exchange, Permafrost, Land Surface Model, Terrestrial Ecosystem Model

  15. Kinetic study of coals gasification into carbon dioxide atmosphere

    Directory of Open Access Journals (Sweden)

    Korotkikh A.G.

    2015-01-01

    Full Text Available The solid fuel gasification process was investigated to define chemical reactions rate and activation energy for a gas-generator designing and regime optimizing. An experimental procedure includes coal char samples of Kuznetskiy and Kansko-Achinskiy deposits consequent argon pyrolysis into argon and oxidating into carbon dioxide with different temperatures. The thermogravimetric analysis data of coal char gasification into carbon dioxide was obtained in the temperature range 900–1200 ºC. The mass loss and gasification time dependencies from temperature were defined to calculate chemical reaction frequency factor and activation energy. Two coal char gasification physico-mathematical models were proposed and recommendations for them were formed.

  16. Elevated atmospheric carbon dioxide concentration: effects of increased carbon input in a Lolium perenne soil on microorganisms and decomposition

    NARCIS (Netherlands)

    Ginkel, van J.H.; Gorissen, A.; Polci, D.

    2000-01-01

    Effects of ambient and elevated atmospheric CO2 concentrations (350 and 700 μl l-1) on net carbon input into soil, the production of root-derived material and the subsequent microbial transformation were investigated. Perennial ryegrass plants (L. perenne L.) were labelled in a continuously labelled

  17. The increasing importance of atmospheric demand for ecosystem water and carbon fluxes

    Science.gov (United States)

    Novick, Kimberly A.; Ficklin, Darren L.; Stoy, Paul C.; Williams, Christopher A.; Bohrer, Gil; Oishi, A. Christopher; Papuga, Shirley A.; Blanken, Peter D.; Noormets, Asko; Sulman, Benjamin N.; Scott, Russell L.; Wang, Lixin; Phillips, Richard P.

    2016-11-01

    Soil moisture supply and atmospheric demand for water independently limit--and profoundly affect--vegetation productivity and water use during periods of hydrologic stress. Disentangling the impact of these two drivers on ecosystem carbon and water cycling is difficult because they are often correlated, and experimental tools for manipulating atmospheric demand in the field are lacking. Consequently, the role of atmospheric demand is often not adequately factored into experiments or represented in models. Here we show that atmospheric demand limits surface conductance and evapotranspiration to a greater extent than soil moisture in many biomes, including mesic forests that are of particular importance to the terrestrial carbon sink. Further, using projections from ten general circulation models, we show that climate change will increase the importance of atmospheric constraints to carbon and water fluxes in all ecosystems. Consequently, atmospheric demand will become increasingly important for vegetation function, accounting for >70% of growing season limitation to surface conductance in mesic temperate forests. Our results suggest that failure to consider the limiting role of atmospheric demand in experimental designs, simulation models and land management strategies will lead to incorrect projections of ecosystem responses to future climate conditions.

  18. 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

  19. Towards multi-tracer data-assimilation: biomass burning and carbon isotope exchange in SiBCASA

    Directory of Open Access Journals (Sweden)

    I. R. van der Velde

    2014-01-01

    Full Text Available We present an enhanced version of the SiBCASA photosynthetic/biogeochemical model for a future integration with a multi-tracer data-assimilation system. We extended the model with (a biomass burning emissions from the SiBCASA carbon pools using remotely sensed burned area from Global Fire Emissions Database (GFED version 3.1, (b a new set of 13C pools that cycle consistently through the biosphere, and (c, a modified isotopic discrimination scheme to estimate variations in 13C exchange as a~response to stomatal conductance. Previous studies suggest that the observed variations of atmospheric 13C/12C are driven by processes specifically in the terrestrial biosphere rather than in the oceans. Therefore, we quantify in this study the terrestrial exchange of CO2 and 13CO2 as a function of environmental changes in humidity and biomass burning. Based on an assessment of observed respiration signatures we conclude that SiBCASA does well in simulating global to regional plant discrimination. The global mean discrimination value is 15.2‰, and ranges between 4 and 20‰ depending on the regional plant phenology. The biomass burning emissions (annually and seasonally compare favorably to other published values. However, the observed short-term changes in discrimination and the respiration 13C signature are more difficult to capture. We see a too weak drought response in SiBCASA and too slow return of anomalies in respiration. We demonstrate possible ways to improve this, and discuss the implications for our current capacity to interpret atmospheric 13C observations.

  20. Atmospheric nitrogen deposition promotes carbon loss from peat bogs

    NARCIS (Netherlands)

    Bragazza, L.; Freeman, C.; Jones, T.; Rydin, H.; Limpens, J.; Fenner, N.; Ellis, T.; Gerdol, R.; Hajek, M.; Hajek, T.; Iacumin, P.; Kutnar, L.; Tahvanainen, T.; Toberman, H.

    2006-01-01

    Peat bogs have historically represented exceptional carbon (C) sinks because of their extremely low decomposition rates and consequent accumulation of plant remnants as peat. Among the factors favoring that peat accumulation, a major role is played by the chemical quality of plant litter itself, whi

  1. Atmospheric Carbon Injection Linked to End-Triassic Mass Extinction

    NARCIS (Netherlands)

    Ruhl, M.; Bonis, N.R.; Reichart, G.J.; Sinninghe Damsté, J.S.; Kürschner, W.M.

    2011-01-01

    The end-Triassic mass extinction (similar to 201.4 million years ago), marked by terrestrial ecosystem turnover and up to similar to 50% loss in marine biodiversity, has been attributed to intensified volcanic activity during the break-up of Pangaea. Here, we present compound-specific carbon-isotope

  2. Optimization of an Atmospheric Carbon Source for Extremophile Cyanobacteria

    Science.gov (United States)

    Beaubien, Courtney

    This thesis examines the use of the moisture swing resin materials employed at the Center for Negative Carbon Emissions (CNCE) in order to provide carbon dioxide from ambient air to photobioreactors containing extremophile cyanobacteria cultured at the Arizona Center for Algae Technology and Innovation (AzCATI). For this purpose, a carbon dioxide feeding device was designed, built, and tested. The results indicate how much resin should be used with a given volume of algae medium: approximately 500 grams of resin can feed 1% CO2 at about three liters per minute to a ten liter medium of the Galdieria sulphuraria 5587.1 strain for one hour (equivalent to about 0.1 grams of carbon dioxide per hour per seven grams of algae). Using the resin device, the algae grew within their normal growth range: 0.096 grams of ash-free dry weight per liter over a six hour period. Future applications in which the resin-to-algae process can be utilized are discussed.

  3. Fiscal Year 1998 Annual Report, Carbon Dioxide Information Analysis Center, World Data Center -- A for Atmospheric Trace Gases

    Energy Technology Data Exchange (ETDEWEB)

    Cushman, R.M.; Boden, T.A.; Hook, L.A.; Jones, S.B.; Kaiser, D.P.; Nelson, T.R.

    1999-03-01

    Once again, the most recent fiscal year was a productive one for the Carbon Dioxide Information Analysis Center (CDIAC) at Oak Ridge National Laboratory (ORNL), as well as a year for change. The FY 1998 in Review section in this report summarizes quite a few new and updated data and information products, and the ''What's Coming in FY 1999'' section describes our plans for this new fiscal year. During FY 1998, CDIAC began a data-management system for AmeriFlux, a long-term study of carbon fluxes between the terrestrial biosphere of the Western Hemisphere and the atmosphere. The specific objectives of AmeriFlux are to establish an infrastructure for guiding, collecting, synthesizing, and disseminating long-term measurements of CO{sub 2}, water, and energy exchange from a variety of ecosystems; collect critical new information to help define the current global CO{sub 2} budget; enable improved predictions of future concentrations of atmospheric CO{sub 2}; and enhance understanding of carbon fluxes. Net Ecosystem Production (NEP), and carbon sequestration in the terrestrial biosphere. The data-management system, available from CDIAC'S AmeriFlux home page (http://cdiac.esd.ornl.gov/programs/ameriflux/ ) is intended to provide consistent, quality-assured, and documented data across all AmeriFlux sites in the US, Canada, Costa Rica, and Brazil. It is being developed by Antoinette Brenkert and Tom Boden, with assistance from Susan Holladay (who joined CDIAC specifically to support the AmeriFlux data-management effort).

  4. Escape of Mars atmospheric carbon through time by photochemical means

    Science.gov (United States)

    Luhmann, J. G.; Kim, J.; Nagy, A. F.

    Luhmann et al. recently suggested that sputtering of the Martian atmosphere by re-entering O(+) pickup ions could have provided a significant route of escape for CO2 and its products throughout Mars' history. They estimated that the equivalent of C in an approximately 140-mbar CO2 atmosphere should have been lost this way if the Sun and solar wind evolved according to available models. Another source of escaping C (and O) that is potentially important is the dissociative recombination of ionospheric CO(+) near the exobase. We have evaluated the loss rates due to this process for 'ancient' solar EUV radiation fluxes of 1, 3, and 6 times the present flux in order to calculate the possible cumulative loss over the last 3.5 Gyr.

  5. Carbon-foam finned tubes in air-water heat exchangers

    Energy Technology Data Exchange (ETDEWEB)

    Yu Qijun [Department of Mechanical and Materials Engineering, University of Western Ontario, London, ON, N6A 5B8 (Canada)]. E-mail: qyu4@eng.uwo.ca; Straatman, Anthony G. [Department of Mechanical and Materials Engineering, University of Western Ontario, London, ON, N6A 5B8 (Canada)]. E-mail: astraatman@eng.uwo.ca; Thompson, Brian E. [Department of Mechanical Engineering, University of Ottawa, Ottawa, ON, K1N 6N5 (Canada)]. E-mail: thompson@eng.uottawa.ca

    2006-02-01

    An engineering model is formulated to account for the effects of porosity and pore diameter on the hydrodynamic and thermal performance of a carbon-foam finned tube heat exchanger. The hydrodynamic and thermal resistances are obtained from well-established correlations that are extended herein to account for the influence of the porous carbon foam. The influence of the foam is characterized on the basis of a unit-cube geometric model that describes the internal structure, the exposed surface, the permeability and the effective conductivity as a function of porosity and pore diameter. The engineering model is validated by comparison with experiments that characterize heat transfer in an air-water radiator made from porous carbon foam. The model is also used in to conduct a parametric study to show the influence of the porosity and pore diameter of the foam. The parametric study suggests that in comparison to conventional aluminum finned-tube radiators, improvements of approximately 15% in thermal performance are possible without changing the frontal area, or the air flow rate and pressure drop. The engineering model developed herein can be used by engineers to assess quantitatively the suitability of porous carbon foam as a fin material in the design of air-water heat exchangers.

  6. Carbon-foam finned tubes in air-water heat exchangers

    Energy Technology Data Exchange (ETDEWEB)

    Yu, Qijun; Straatman, Anthony G. [Department of Mechanical and Materials Engineering, The University of Western Ontario, London, ON (Canada); Thompson, Brian E. [Department of Mechanical Engineering, The University of Ottawa, Ottawa, ON (Canada)

    2006-02-01

    An engineering model is formulated to account for the effects of porosity and pore diameter on the hydrodynamic and thermal performance of a carbon-foam finned tube heat exchanger. The hydrodynamic and thermal resistances are obtained from well-established correlations that are extended herein to account for the influence of the porous carbon foam. The influence of the foam is characterized on the basis of a unit-cube geometric model that describes the internal structure, the exposed surface, the permeability and the effective conductivity as a function of porosity and pore diameter. The engineering model is validated by comparison with experiments that characterize heat transfer in an air-water radiator made from porous carbon foam. The model is also used in to conduct a parametric study to show the influence of the porosity and pore diameter of the foam. The parametric study suggests that in comparison to conventional aluminum finned-tube radiators, improvements of approximately 15% in thermal performance are possible without changing the frontal area, or the air flow rate and pressure drop. The engineering model developed herein can be used by engineers to assess quantitatively the suitability of porous carbon foam as a fin material in the design of air-water heat exchangers. (author)

  7. Sensitivity of Prosopis velutina to Summer Rainfall and Consequences for Seasonal Patterns of Ecosystem Carbon Exchange

    Science.gov (United States)

    Potts, D. L.; Cable, J. M.; Scott, R. L.; Williams, D. G.; Goodrich, D. C.; Huxman, T. E.

    2005-12-01

    Future changes in dryland vegetation composition will interact with climate variability to influence carbon and water cycling in unforeseen ways. Observed increases in the density of woody plants in North America's savanna ecosystems may be an important terrestrial carbon sink and could alter patterns of regional hydrologic cycling. During the 2005 growing season we compared seasonal patterns of Prosopis velutina plant water status and leaf gas exchange in upland and riparian savannas. Previous work suggested the plant size class constrained alluvial groundwater access and that mature individuals were less sensitive to the onset of summer rains at the riparian site. We predicted that at the upland site, where groundwater was unavailable, mature and juvenile plants would respond similarly to the onset of summer rains. Furthermore, we predicted that this increased sensitivity by the dominant vegetation to seasonal rainfall would be reflected in NEE data collected by eddy-covariance at both sites. Results indicate that mesquite performance and the duration and magnitude of ecosystem carbon exchanges are tightly linked to precipitation at the upland site. Comparing upland and riparian sites demonstrates how seasonal pattern of precipitation, plant-available alluvial groundwater and vegetation structure interact to govern ecosystem carbon balance in savanna ecosystems.

  8. Performance testing of cross flow heat exchanger operating in the atmosphere of flue gas particulate with vapor condensation

    Directory of Open Access Journals (Sweden)

    Nuntaphan, A.

    2006-05-01

    Full Text Available Performance testing of a cross flow heat exchanger operating under the atmosphere of flue gas particulate from combustion was carried out in this work. This heat exchanger exchanges heat between flue gas from the fuel oil combustion and cold water. The heat exchanger is composed of a spiral finned tube bank having 3 rows and 8 tubes per row with a staggered arrangement. The fin spacings considered are 2.85 and 6.10 mm. The theories of thermodynamics and heat transfer are used for analyzing the performance of this system.In this experiment, the flue gas temperature of 200ºC from combustion having 0.35 kg/s mass flow rate flows along outside surface of the heat exchanger and transfers heat to the 25ºC cooling water having 0.15 kg/s mass flow rate flowing in the tube side. Each experiment uses 750 hr for testing. During the testing, part of flue gas condenses on the heat transfer surface.From the experiment, it was found that the heat transfer rate of both heat exchangers tended to decrease with time while the airside pressure drop increased. These results come from the fouling on the heat transfer surface. Moreover, it is found that the heat exchanger having 2.85 mm fin spacing has an approximately 4 times higher fouling resistance than that of the 6.10 mm fin spacing.In this work a model for calculating the fouling resistance is also developed as a the function of time. The model is developed from that of Kern and Seaton and the mean deviation of the model is 0.789.

  9. Robust optical carbon dioxide isotope analyzer Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Isotopic analysis of carbon dioxide is an important tool for characterization of the exchange and transformation of carbon between the biosphere and the atmosphere....

  10. The effect of environmental variables on atmospheric corrosion of carbon steel in Shenyang

    Institute of Scientific and Technical Information of China (English)

    WANG Chuan; WANG ZhenYao; KE Wei

    2009-01-01

    A study was carried out in order to investigate the effect of contaminants and meteorological variables on the rust layer of carbon steel exposed in Shenyang urban atmosphere. Seven kinds of contaminants and twelve kinds of meteorological parameters were also registered in order to correlate the data with respect to corrosion rate and the stepwise multiple regression analysis was carried out in order to obtain the best regression model. The sum of rainfall time as well as sunshine time and the concentration of H_2S could stimulate initial atmospheric corrosion of carbon steel. The initial atmospheric corrosion kinetics of carbon steel was observed to follow the cubic equation. The corrosion products were analyzed by XRD and the transformation of phases in different periods was discussed.

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

    Energy Technology Data Exchange (ETDEWEB)

    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.

  12. Detection of carbon monoxide and water absorption lines in an exoplanet atmosphere.

    Science.gov (United States)

    Konopacky, Quinn M; Barman, Travis S; Macintosh, Bruce A; Marois, Christian

    2013-03-22

    Determining the atmospheric structure and chemical composition of an exoplanet remains a formidable goal. Fortunately, advancements in the study of exoplanets and their atmospheres have come in the form of direct imaging--spatially resolving the planet from its parent star--which enables high-resolution spectroscopy of self-luminous planets in jovian-like orbits. Here, we present a spectrum with numerous, well-resolved molecular lines from both water and carbon monoxide from a massive planet orbiting less than 40 astronomical units from the star HR 8799. These data reveal the planet's chemical composition, atmospheric structure, and surface gravity, confirming that it is indeed a young planet. The spectral lines suggest an atmospheric carbon-to-oxygen ratio that is greater than that of the host star, providing hints about the planet's formation.

  13. Seasonal variation of carbon exchange of typical forest ecosystems along the eastern forest transect in China

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    <正>The long-term and continuous carbon fluxes of Changbaishan temperate mixed forest (CBS), Qianyanzhou subtropical evergreen coniferous forest (QYZ), Dinghushan subtropical evergreen mixed forest (DHS) and Xishuangbana tropical rainforest (XSBN) have been measured with eddy covariance techniques. In 2003, different responses of carbon exchange to the environment appeared across the four ecosystems. At CBS, the carbon exchange was mainly determined by radiation and temperature. 0℃and 10℃were two important temperature thresholds; the former determined the length of the growing season and the latter affected the magnitude of carbon exchange. The maximum net ecosystem exchange (NEE) of CBS occurred in early summer because maximum ecosystem photosynthesis (GPP) occurred earlier than maximum ecosystem respiration (Rθ). During summer, QYZ experienced severe drought and NEE decreased significantly mainly as a result of the depression of GPP. At DHS and XSBN, NEE was higher in the drought season than the wet season, especially the conversion between carbon sink and source occurring during the transition season at XSBN. During the wet season, increased fog and humid weather resulted from the plentiful rainfall, the ecosystem GPP was dispressed. The Q10 and annual respiration of XSBN were the highest among the four ecosystems, while the average daily respiration of CBS during the growing season was the highest. Annual NEE of CBS, QYZ, DHS and XSBN were 181.5, 360.9, 536.2 and -320.0 g·C·m-2·a-1, respectively. From CBS to DHS, the temperature and precipitation increased with the decrease in latitude. The ratio of WEE/Rθincreased with latitude, while Rθ/Gpp, ecosystem light use efficiency (LUE), precipitation use efficiency and average daily GPP decreased gradually. However, XSBN usually escaped such latitude trend probably because of the influence of the south-west monsoon climate which does not affect the other ecosystems. Long-term measurement and more research

  14. Constraints from atmospheric CO2 and satellite-based vegetation activity observations on current land carbon cycle trends

    Directory of Open Access Journals (Sweden)

    S. Zaehle

    2012-11-01

    Full Text Available Terrestrial ecosystem models used for Earth system modelling show a significant divergence in future patterns of ecosystem processes, in particular carbon exchanges, despite a seemingly common behaviour for the contemporary period. An in-depth evaluation of these models is hence of high importance to achieve a better understanding of the reasons for this disagreement. Here, we develop an extension for existing benchmarking systems by making use of the complementary information contained in the observational records of atmospheric CO2 and remotely-sensed vegetation activity to provide a firm set of diagnostics of ecosystem responses to climate variability in the last 30 yr at different temporal and spatial scales. The selection of observational characteristics (traits specifically considers the robustness of information given the uncertainties in both data and evaluation analysis. In addition, we provide a baseline benchmark, a minimum test that the model under consideration has to pass, to provide a more objective, quantitative evaluation framework. The benchmarking strategy can be used for any land surface model, either driven by observed meteorology or coupled to a climate model. We apply this framework to evaluate the offline version of the MPI-Earth system model's land surface scheme JSBACH. We demonstrate that the complementary use of atmospheric CO2 and satellite based vegetation activity data allows to pinpoint specific model failures that would not be possible by the sole use of atmospheric CO2 observations.

  15. Effect of Forest Fire on Regional Carbon Dioxide Exchange Over Boreal Forest in Interior Alaska

    Science.gov (United States)

    Iwata, H.; Otsuki, M.; Harazono, Y.; Ueyama, M.; Iwata, T.

    2010-12-01

    Forest fire is a major disturbance in boreal forest ecosystems and significantly influences carbon exchange processes by combustion of vegetation and surface organic soils. In Interior Alaska, area of 7.6x106 ha was burned during 2000-2009 by forest fires. Fire occurrence frequency in the next decade may increase with current warming trend. Hence, it is important to include carbon dioxide (CO2) exchange at fire scars to accurately estimate regional CO2 exchange. To quantify CO2 exchange, CO2 flux and meteorological data were obtained at an undisturbed black spruce forest and a fire scar (five years after fire) in Interior Alaska, and responses of photosynthesis and respiration to meteorological variables were examined in each site. Photosynthesis at the fire scar was reduced to approximately 50 % of photosynthesis at the undisturbed black spruce forest due to loss of vegetation. Respiration at the fire scar was also reduced to 50 % of the undisturbed black spruce forest. This is attributable to decrease of biomass and surface organic matter. Annual net exchanges of CO2 at both sites were uptake of 519 and 256 gCO2/m2/year for the undisturbed black spruce forest and the fire scar, respectively. We used light-use efficiency model to estimate spatial distributions of photosynthesis and respiration using remote sensing imagery, NCEP/NCAR reanalysis meteorology and NASA solar radiation. The model was parameterized using observations at the undisturbed black spruce forest and the fire scar. Estimated regional average of CO2 uptake was reduced by 10 % compared to an estimated value with which fire scars were not included. Further improvement is expected by incorporating severity of forest fires that determine reduction of photosynthesis and respiration after fires.

  16. Evaluating the Contributions of Atmospheric Deposition of Carbon and Other Nutrients to Nitrification in Alpine Environments

    Science.gov (United States)

    Oldani, K. M.; Mladenov, N.; Williams, M. W.

    2013-12-01

    The Colorado Front Range of the Rocky Mountains contains undeveloped, barren soils, yet in this environment there is strong evidence for a microbial role in increased nitrogen (N) export. Barren soils in alpine environments are severely carbon-limited, which is the main energy source for microbial activity and sustenance of life. It has been shown that atmospheric deposition can contain high amounts of organic carbon (C). Atmospheric pollutants, dust events, and biological aerosols, such as bacteria, may be important contributors to the atmospheric organic C load. In this stage of the research we evaluated seasonal trends in the chemical composition and optical spectroscopic (fluorescence and UV-vis absorbance) signatures of snow, wet deposition, and dry deposition in an alpine environment at Niwot Ridge in the Rocky Mountains of Colorado to obtain a better understanding of the sources and chemical character of atmospheric deposition. Our results reveal a positive trend between dissolved organic carbon concentrations and calcium, nitrate and sulfate concentrations in wet and dry deposition, which may be derived from such sources as dust and urban air pollution. We also observed the presence of seasonally-variable fluorescent components that may be attributed to fluorescent pigments in bacteria. These results are relevant because atmospheric inputs of carbon and other nutrients may influence nitrification in barren, alpine soils and, ultimately, the export of nitrate to alpine watersheds.

  17. Carbon oxidation state as a metric for describing the chemistry of atmospheric organic aerosol.

    Science.gov (United States)

    Kroll, Jesse H; Donahue, Neil M; Jimenez, Jose L; Kessler, Sean H; Canagaratna, Manjula R; Wilson, Kevin R; Altieri, Katye E; Mazzoleni, Lynn R; Wozniak, Andrew S; Bluhm, Hendrik; Mysak, Erin R; Smith, Jared D; Kolb, Charles E; Worsnop, Douglas R

    2011-02-01

    A detailed understanding of the sources, transformations and fates of organic species in the environment is crucial because of the central roles that they play in human health, biogeochemical cycles and the Earth's climate. However, such an understanding is hindered by the immense chemical complexity of environmental mixtures of organics; for example, atmospheric organic aerosol consists of at least thousands of individual compounds, all of which likely evolve chemically over their atmospheric lifetimes. Here, we demonstrate the utility of describing organic aerosol (and other complex organic mixtures) in terms of average carbon oxidation state, a quantity that always increases with oxidation, and is readily measured using state-of-the-art analytical techniques. Field and laboratory measurements of the average carbon oxidation state, using several such techniques, constrain the chemical properties of the organics and demonstrate that the formation and evolution of organic aerosol involves simultaneous changes to both carbon oxidation state and carbon number.

  18. Climate and site management as driving factors for the atmospheric greenhouse gas exchange of a restored wetland

    DEFF Research Database (Denmark)

    Herbst, Mathias; Friborg, Thomas; Schelde, Kirsten;

    2012-01-01

    The full atmospheric greenhouse gas (GHG) budget of a restored wetland in Western Denmark could be established for the years 2009–2011 from eddy covariance measurements of carbon dioxide (CO2) and methane (CH4) fluxes. The water table in the wetland, being restored in 2002, was unregulated...... the atmosphere. However, in terms of the annual GHG budget (assuming that 1 g CH4 is equivalent to 25 g CO2 with respect to the greenhouse effect) the wetland was a sink in 2009, a source in 2010 and neutral in 2011. Complementary observations of meteorological factors and management activities were used...

  19. Interfacial behavior between atmospheric-plasma-fluorinated carbon fibers and poly(vinylidene fluoride).

    Science.gov (United States)

    Ho, Kingsley K C; Lamoriniere, Steven; Kalinka, Gerhard; Schulz, Eckhard; Bismarck, Alexander

    2007-09-15

    Atmospheric-plasma fluorination was used to introduce fluorine functionalities onto the surface of carbon fibers without affecting their bulk properties. The interfacial adhesion between atmospheric-plasma-fluorinated carbon fibers and poly(vinylidene fluoride) (PVDF) was studied by means of direct wetting measurements and single fiber pullout tests. Measured contact angles of PVDF melt droplets on modified carbon fibers show that short exposure times of carbon fibers to atmospheric-plasma fluorination (corresponding to a degree of surface fluorination of F/C = 0.01 (1.1%)) leads to improved wettability of the fibers by PVDF melts. The apparent interfacial shear strength as a measure of practical adhesion, determined by the single-fiber pullout test, increases by 65% under optimal treatment conditions. The improved practical adhesion is not due to the formation of transcrystalline regions around the fibers or a change of the bulk matrix crystallinity or to an increased surface roughness; it seems to be due to the compatibilization of the interface caused of the atmospheric-plasma fluorination of the carbon fibers.

  20. Interannual variability of carbon cycle implied by a 2-D atmospheric transport model

    Institute of Scientific and Technical Information of China (English)

    LI Can; XU Li; SHAO Min; ZHANG Ren-jian

    2004-01-01

    A 2-dimensional atmospheric transport model is deployed in a simplified CO2 inverse study. Calculated carbon flux distribution for the interval from 1981 to 1997 confirms the existence of a terrestrial carbon sink in mid-high latitude area of North Hemisphere. Strong interannual variability exists in carbon flux patterns, implying a possible link with ENSO and other natural episodes such as Pinatubo volcano eruption in 1991. Mechanism of this possible link was investigated with statistic method. Correlation analysis indicated that in North Hemisphere, climatic factors such as temperature and precipitation, to some extend, could influence the carbon cycle process of land and ocean, thus cause considerable change in carbon flux distribution. In addition, correlation study also demonstrated the possible important role of Asian terrestrial ecosystems in carbon cycle.

  1. 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.

  2. Measurement of pion double charge exchange on carbon-13, carbon-14, magnesium-26, and iron-56

    Energy Technology Data Exchange (ETDEWEB)

    Seidl, P.A.

    1985-02-01

    Cross sections for the /sup 13,14/C,/sup 26/Mg,/sup 56/Fe(..pi../sup +/,..pi../sup -/)/sup 13,14/O,/sup 26/Si,/sup 56/Ni reactions were measured with the Energetic Pion Channel and Spectrometer at the Clinton P. Anderson Meson Physics Facility for 120 less than or equal to T/sub ..pi../ less than or equal to 292 MeV and 0 less than or equal to theta less than or equal to 50. The double isobaric analog states (DIAS) are of primary interest. In addition, cross sections for transitions to /sup 14/O(0/sup +/, 5.92 MeV), /sup 14/O(2/sup +/, 7.77 MeV), /sup 56/Ni(gs), /sup 13/O(gs), and /sup 13/O(4.21 MeV) are presented. The /sup 13/O(4.21 MeV) state is postulated to have J/sup ..pi../ = 1/2/sup -/. The data are compared to previously measured double-charge-exchange cross sections on other nuclei, and the systematics of double charge exchange on T greater than or equal to 1 target nuclei leading to the DIAS are studied. Near the ..delta../sub 33/ resonance, cross sections for the DIAS transitions are in disagreement with calculations in which the reaction is treated as sequential charge exchange through the free pion-nucleon amplitude, while for T/sub ..pi../ > 200 MeV the anomalous features of the 164 MeV data are not apparent. This is evidence for significant higher order contributions to the double-charge-exchange amplitude near the reasonable energy. Two theoretical approaches that include two nucleon processes are applied to the DIAS data. 64 references.

  3. Impacts of a decadal drainage disturbance on surface-atmosphere fluxes of carbon dioxide in a permafrost ecosystem

    Science.gov (United States)

    Kittler, Fanny; Burjack, Ina; Corradi, Chiara A. R.; Heimann, Martin; Kolle, Olaf; Merbold, Lutz; Zimov, Nikita; Zimov, Sergey; Göckede, Mathias

    2016-09-01

    Hydrologic conditions are a major controlling factor for carbon exchange processes in high-latitude ecosystems. The presence or absence of water-logged conditions can lead to significant shifts in ecosystem structure and carbon cycle processes. In this study, we compared growing season CO2 fluxes of a wet tussock tundra ecosystem from an area affected by decadal drainage to an undisturbed area on the Kolyma floodplain in northeastern Siberia. For this comparison we found the sink strength for CO2 in recent years (2013-2015) to be systematically reduced within the drained area, with a minor increase in photosynthetic uptake due to a higher abundance of shrubs outweighed by a more pronounced increase in respiration due to warmer near-surface soil layers. Still, in comparison to the strong reduction of fluxes immediately following the drainage disturbance in 2005, recent CO2 exchange with the atmosphere over this disturbed part of the tundra indicate a higher carbon turnover, and a seasonal amplitude that is comparable again to that within the control section. This indicates that the local permafrost ecosystem is capable of adapting to significantly different hydrologic conditions without losing its capacity to act as a net sink for CO2 over the growing season. The comparison of undisturbed CO2 flux rates from 2013-2015 to the period of 2002-2004 indicates that CO2 exchange with the atmosphere was intensified, with increased component fluxes (ecosystem respiration and gross primary production) over the past decade. Net changes in CO2 fluxes are dominated by a major increase in photosynthetic uptake, resulting in a stronger CO2 sink in 2013-2015. Application of a MODIS-based classification scheme to separate the growing season into four sub-seasons improved the interpretation of interannual variability by illustrating the systematic shifts in CO2 uptake patterns that have occurred in this ecosystem over the past 10 years and highlighting the important role of the late

  4. Nitrogen and Carbon Dynamics Across Trophic Levels Along an Atmospheric Nitrogen Deposition Gradient

    Science.gov (United States)

    Wissinger, B. D.; Bell, M. D.; Newingham, B. A.

    2011-12-01

    Atmospheric nitrogen deposition has altered soil biogeochemical processes and plant communities across the United States. Prior investigations have demonstrated these alterations; however, little is known about the effects of elevated nitrogen on higher trophic levels. Building upon previous research that revealed an atmospheric nitrogen deposition gradient from the San Bernardino Mountains through Joshua Tree National Park in California, we investigated atmospheric nitrogen and its effects on soils, plants, and harvester ants. We measured nitrogen and carbon concentrations, along with carbon and nitrogen stable isotopes, across trophic levels at eighteen urban and unpopulated sites along the deposition gradient. Carbon and nitrogen attributes were determined in atmospheric nitric acid, soil, Larrea tridentata and Ambrosia dumosa leaves, seeds from selected plant species, and ants. We predicted carbon and nitrogen ratios and isotopes to change in areas with higher nitrogen deposition and vary along the deposition gradient. Nitrogen (p=0.02) and carbon (p=0.05) concentrations, as well as C:N ratios (p=<0.001), significantly differed in Messor pergandei individuals among sites; however, no correlation was found between these carbon and nitrogen attributes and the nitrogen deposition gradient (%N r2=0.02, %C r2=0.007, C:N r2=0.02). The δ15N and δ13C values of the ants, leaf tissues, and seeds measured across the gradient follow similar patterns with r2 values all below 0.20. Our results suggest the current and previous rates of nitrogen deposition in this area are not enough to modify nitrogen and carbon concentrations and isotope values. Compensatory nitrogen cycling processes in the soil may reduce the effects of increased nitrogen on plants and thus higher trophic levels. Nitrogen and carbon dynamics across trophic levels might change after longer ecosystem exposure to elevated nitrogen; however, other abiotic and biotic factors are likely driving current

  5. The effect of atmospheric carbon dioxide concentrations on the performance of the mangrove Avicennia germinans over a range of salinities.

    Science.gov (United States)

    Reef, Ruth; Winter, Klaus; Morales, Jorge; Adame, Maria Fernanda; Reef, Dana L; Lovelock, Catherine E

    2015-07-01

    By increasing water use efficiency and carbon assimilation, increasing atmospheric CO2 concentrations could potentially improve plant productivity and growth at high salinities. To assess the effect of elevated CO2 on the salinity response of a woody halophyte, we grew seedlings of the mangrove Avicennia germinans under a combination of five salinity treatments [from 5 to 65 parts per thousand (ppt)] and three CO2 concentrations (280, 400 and 800 ppm). We measured survivorship, growth rate, photosynthetic gas exchange, root architecture and foliar nutrient and ion concentrations. The salinity optima for growth shifted higher with increasing concentrations of CO2 , from 0 ppt at 280 ppm to 35 ppt at 800 ppm. At optimal salinity conditions, carbon assimilation rates were significantly higher under elevated CO2 concentrations. However, at salinities above the salinity optima, salinity had an expected negative effect on mangrove growth and carbon assimilation, which was not alleviated by elevated CO2 , despite a significant improvement in photosynthetic water use efficiency. This is likely due to non-stomatal limitations to growth at high salinities, as indicated by our measurements of foliar ion concentrations that show a displacement of K(+) by Na(+) at elevated salinities that is not affected by CO2 . The observed shift in the optimal salinity for growth with increasing CO2 concentrations changes the fundamental niche of this species and could have significant effects on future mangrove distribution patterns and interspecific interactions.

  6. Cation exchange resin nanocomposites based on multi-walled carbon nanotubes

    Science.gov (United States)

    Fathy, Mahmoud; Abdel Moghny, Th.; Awad Allah, Ahmed Elsayed; Alblehy, AbdElhamid

    2014-01-01

    Carbon nanotubes (CNTs) are of great interest due to their potential applications in different fields such as water treatment and desalination. The increasing exploitation of multi-walled carbon nanotubes (MWCNTs) into many industrial processes has raised considerable concerns for environmental applications. The interactions of soluble salt with MWNCTs influence in the total salt content in saline water. In this work, we synthesized two cation exchange resins nano composites from polystyrene divinylbenzene copolymer (PSDVB) and pristine MWNCTs. The prepared compounds were characterized using infra red spectroscopy, thermal stability, X-ray diffraction, and electro scan microscope. Also, the ion capacities of prepared cation exchange resins were determined by titration. Based on the experimental results, it was found that the thermal stability of prepared nanocomposites in the presence of MWNCTs increased up to 617 °C. The X-ray of PSDVB and its sulfonated form exhibits amorphous pattern texture structure, whereas the nano composite exhibits amorphous structure with indication peak at 20° and 26° for the PSDVB and MWCNTs, respectively. The ion-exchange capacity increased from 225.6 meq/100 g to 466 mg/100 g for sulfonated PSDVB and sulfonated PSDVB MWNCTs-pristine, respectively.

  7. Climate effects on atmospheric carbon dioxide over the last century

    Science.gov (United States)

    Rafelski, Lauren Elmegreen; Piper, Stephen C.; Keeling, Ralph F.

    2009-11-01

    The buildup of atmospheric CO2 since 1958 is surprisingly well explained by the simple premise that 57% of the industrial emissions (fossil fuel burning and cement manufacture) has remained airborne. This premise accounts well for the rise both before and after 1980 despite a decrease in the growth rate of fossil fuel CO2 emissions, which occurred at that time, and by itself should have caused the airborne fraction to decrease. In contrast, the buildup prior to 1958 was not simply proportional to cumulative fossil fuel emissions, and notably included a period during the 1940s when CO2 growth stalled despite continued fossil fuel emissions. Here we show that the constancy of the airborne fraction since 1958 can be in part explained by decadal variations in global land air temperature, which caused a warming-induced release of CO2 from the land biosphere to the atmosphere. We also show that the 1940s plateau may be related to these decadal temperature variations. Furthermore, we show that there is a close connection between the phenomenology producing CO2 variability on multidecadal and El Niño timescales.

  8. The carbon isotope composition of atmospheric CO 2 in Paris

    Science.gov (United States)

    Widory, David; Javoy, Marc

    2003-10-01

    One characteristic of air pollution in the urban environment is high CO 2 concentrations resulting from human activities. Determining the relative contributions of the different CO 2 sources can be addressed simply and elegantly by combining isotope and concentration measurements. Using this approach on atmospheric CO 2 samples collected in Paris, its suburbs and the open country provides fairly accurate conclusions. Our results show that air pollution within the first few metres above ground results basically from binary mixtures among which road traffic is the main contributor and, in particular, vehicles using unleaded gasoline (˜90% of the total). Heating sources, which account for 50% of the CO 2 input below the atmospheric inversion level, and vehicles using diesel contribute very little. Human respiration has a recognisable signature at street level under certain circumstances. The combined isotope and concentration analysis provides a sensitive tracer of local variations, even detecting the occasional prevalence of human respiration and the onset of actions in which natural gas is burnt. It also detects surprising inlets of 'clean air' (CO 2-wise) in the very centre of the city.

  9. Theoretical constraints on oxygen and carbon dixoide concentrations in the Precambrian atmosphere

    Science.gov (United States)

    Kasting, James F.

    1987-01-01

    Theoretical arguments which bear on the time histories of atmospheric oxygen and carbon dioxide during the Precambrian are reviewed and extended. It is shown that reasonably tight constraints can be placed on atmospheric pCO2 during the early and late Proterozoic, based on the observation that parts of the earth were glaciated at those times. It is demonstrated that an upper bound on early Proterozoic pO2 can be derived from a simple box model of the atmosphere-ocean system.

  10. Experimental Study of Water Exchange Between Regolith and Atmosphere Under Martian Conditions: Thermodynamics and Spectroscopy

    Science.gov (United States)

    Pommerol, A.; Schmitt, B.; Brissaud, O.

    2008-03-01

    We have designed a facility to measure near-infrared reflectance spectra of martian regolith analogs under martian surface temperature and humidity. We present adsorption isotherm and exchange kinetics between water and JSC Mars-1 regolith simulant.

  11. Carbon assimilation in Eucalyptus urophylla grown under high atmospheric CO2 concentrations: A proteomics perspective.

    Science.gov (United States)

    Santos, Bruna Marques Dos; Balbuena, Tiago Santana

    2017-01-06

    Photosynthetic organisms may be drastically affected by the future climate projections of a considerable increase in CO2 concentrations. Growth under a high concentration of CO2 could stimulate carbon assimilation-especially in C3-type plants. We used a proteomics approach to test the hypothesis of an increase in the abundance of the enzymes involved in carbon assimilation in Eucalyptus urophylla plants grown under conditions of high atmospheric CO2. Our strategy allowed the profiling of all Calvin-Benson cycle enzymes and associated protein species. Among the 816 isolated proteins, those involved in carbon fixation were found to be the most abundant ones. An increase in the abundance of six key enzymes out of the eleven core enzymes involved in carbon fixation was detected in plants grown at a high CO2 concentration. Proteome changes were corroborated by the detection of a decrease in the stomatal aperture and in the vascular bundle area in Eucalyptus urophylla plantlets grown in an environment of high atmospheric CO2. Our proteomics approach indicates a positive metabolic response regarding carbon fixation in a CO2-enriched atmosphere. The slight but significant increase in the abundance of the Calvin enzymes suggests that stomatal closure did not prevent an increase in the carbon assimilation rates.

  12. Atmospheric oxygen regulation at low Proterozoic levels by incomplete oxidative weathering of sedimentary organic carbon

    Science.gov (United States)

    Daines, Stuart J.; Mills, Benjamin J. W.; Lenton, Timothy M.

    2017-01-01

    It is unclear why atmospheric oxygen remained trapped at low levels for more than 1.5 billion years following the Paleoproterozoic Great Oxidation Event. Here, we use models for erosion, weathering and biogeochemical cycling to show that this can be explained by the tectonic recycling of previously accumulated sedimentary organic carbon, combined with the oxygen sensitivity of oxidative weathering. Our results indicate a strong negative feedback regime when atmospheric oxygen concentration is of order pO2∼0.1 PAL (present atmospheric level), but that stability is lost at pO2<0.01 PAL. Within these limits, the carbonate carbon isotope (δ13C) record becomes insensitive to changes in organic carbon burial rate, due to counterbalancing changes in the weathering of isotopically light organic carbon. This can explain the lack of secular trend in the Precambrian δ13C record, and reopens the possibility that increased biological productivity and resultant organic carbon burial drove the Great Oxidation Event. PMID:28148950

  13. Atmospheric phenanthrene pollution modulates carbon allocation in red clover (Trifolium pratense L.)

    Energy Technology Data Exchange (ETDEWEB)

    Desalme, Dorine, E-mail: dorine.desalme@univ-fcomte.fr [Universite de Franche-Comte, CNRS, UMR 6249, Chrono-environnement, BP 71427, F-25211 Montbeliard Cedex (France); Binet, Philippe [Universite de Franche-Comte, CNRS, UMR 6249, Chrono-environnement, BP 71427, F-25211 Montbeliard Cedex (France); Epron, Daniel [Nancy Universite, UMR 1137, Ecologie et Ecophysiologie Forestieres, Faculte des Sciences, BP 70239, F- 54506 Vandoeuvre-les-Nancy Cedex (France); INRA, UMR 1137, Ecologie et Ecophysiologie Forestieres, Centre INRA de Nancy, F- 54280 Champenoux (France); Bernard, Nadine; Gilbert, Daniel; Toussaint, Marie-Laure [Universite de Franche-Comte, CNRS, UMR 6249, Chrono-environnement, BP 71427, F-25211 Montbeliard Cedex (France); Plain, Caroline [Nancy Universite, UMR 1137, Ecologie et Ecophysiologie Forestieres, Faculte des Sciences, BP 70239, F- 54506 Vandoeuvre-les-Nancy Cedex (France); INRA, UMR 1137, Ecologie et Ecophysiologie Forestieres, Centre INRA de Nancy, F- 54280 Champenoux (France); Chiapusio, Genevieve, E-mail: genevieve.chiapusio@univ-fcomte.fr [Universite de Franche-Comte, CNRS, UMR 6249, Chrono-environnement, BP 71427, F-25211 Montbeliard Cedex (France)

    2011-10-15

    The influence of atmospheric phenanthrene (PHE) exposure (160 {mu}g m{sup -3}) during one month on carbon allocation in clover was investigated by integrative (plant growth analysis) and instantaneous {sup 13}CO{sub 2} pulse-labelling approaches. PHE exposure diminished plant growth parameters (relative growth rate and net assimilation rate) and disturbed photosynthesis (carbon assimilation rate and chlorophyll content), leading to a 25% decrease in clover biomass. The root-shoot ratio was significantly enhanced (from 0.32 to 0.44). Photosynthates were identically allocated to leaves while less allocated to stems and roots. PHE exposure had a significant overall effect on the {sup 13}C partitioning among clover organs as more carbon was retained in leaves at the expense of roots and stems. The findings indicate that PHE decreases root exudation or transfer to symbionts and in leaves, retains carbon in a non-structural form diverting photosynthates away from growth and respiration (emergence of an additional C loss process). - Highlights: > Atmospheric PHE decreased growth, biomass partitioning and C allocation in clover. > C allocation was modified in favor of leaves but at the expense of roots and stems. > In roots, a decreased carbon exudation or allocation to symbionts was proposed. > In leaves, carbon was retained in a non-structural form as secondary metabolites. > BVOC emission was suggested as another loss process than respiration and exudation. - Exposure of clover to atmospheric PHE affected not only its growth, but also biomass partitioning and C allocation among its organs.

  14. Supercritical fluid chromatography coupled with in-source atmospheric pressure ionization hydrogen/deuterium exchange mass spectrometry for compound speciation.

    Science.gov (United States)

    Cho, Yunju; Choi, Man-Ho; Kim, Byungjoo; Kim, Sunghwan

    2016-04-29

    An experimental setup for the speciation of compounds by hydrogen/deuterium exchange (HDX) with atmospheric pressure ionization while performing chromatographic separation is presented. The proposed experimental setup combines the high performance supercritical fluid chromatography (SFC) system that can be readily used as an inlet for mass spectrometry (MS) and atmospheric pressure photo ionization (APPI) or atmospheric pressure chemical ionization (APCI) HDX. This combination overcomes the limitation of an approach using conventional liquid chromatography (LC) by minimizing the amount of deuterium solvents used for separation. In the SFC separation, supercritical CO2 was used as a major component of the mobile phase, and methanol was used as a minor co-solvent. By using deuterated methanol (CH3OD), AP HDX was achieved during SFC separation. To prove the concept, thirty one nitrogen- and/or oxygen-containing standard compounds were analyzed by SFC-AP HDX MS. The compounds were successfully speciated from the obtained SFC-MS spectra. The exchange ions were observed with as low as 1% of CH3OD in the mobile phase, and separation could be performed within approximately 20min using approximately 0.24 mL of CH3OD. The results showed that SFC separation and APPI/APCI HDX could be successfully performed using the suggested method.

  15. Impact of land use change on the land atmosphere carbon flux of South and South East Asia: A Synthesis of Dynamic Vegetation Model Results

    Science.gov (United States)

    Cervarich, M.; Shu, S.; Jain, A. K.; Poulter, B.; Stocker, B.; Arneth, A.; Viovy, N.; Kato, E.; Wiltshire, A.; Koven, C.; Sitch, S.; Zeng, N.; Friedlingstein, P.

    2015-12-01

    Understanding our present day carbon cycle and possible solutions to recent increases in atmospheric carbon dioxide is dependent upon quantifying the terrestrial carbon budget. Currently, global land cover and land use change is estimated to emit 0.9 PgC yr-1 compared to emissions due to fossil fuel combustion and cement production of 8.4 PgC yr-1. South and Southeast Asia (India, Nepal, Bhutan, Bangladesh, Burma, Thailand, Laos, Vietnam, Cambodia, Malaysia, Philippines, Indonesia, Pakistan, Myanmar, and Singapore) is a region of rapid land cover and land use change due to the continuous development of agriculture, deforestation, reforestation, afforestation, and the increased demand of land for people to live. In this study, we synthesize outputs of nine models participated in Global Carbon Budget Project to identify the carbon budget of South and southeast Asia, diagnose the contribution of land cover and land use change to carbon emissions and assess areas of uncertainty in the suite of models. Uncertainty is determined using the standard deviation and the coefficient of variation of net ecosystem exchange and its component parts. Results show the region's terrestrial biosphere was a source of carbon emissions from the 1980 to the early 1990s. During the same time period, land cover and land use change increasingly contributed to carbon emission. In the most recent two decades, the region became a carbon sink since emission due to land cover land use changes. Spatially, the greatest total emissions occurred in the tropical forest of Southeast Asia. Additionally, this is the subregion with the greatest uncertainty and greatest biomass. Model uncertainty is shown to be proportional to total biomass. The atmospheric impacts of ENSO are shown to suppress the net biosphere productivity in South and Southeast Asia leading to years of increased carbon emissions.

  16. The Martian paleoclimate and enhanced atmospheric carbon dioxide

    Science.gov (United States)

    Cess, R. D.; Owen, T.; Ramanathan, V.

    1980-01-01

    Current evidence indicates that the Martian surface is abundant with water presently in the form of ice, while the atmosphere was at one time more massive with a past surface pressure of as much as 1 atm of CO2. In an attempt to understand the Martian paleoclimate, a past CO2-H2O greenhouse was modeled and global temperatures which are consistent with an earlier presence of liquid surface water are found in agreement with the extensive evidence for past fluvial erosion. An important aspect of the CO2-H2O greenhouse model is the detailed inclusion of CO2 hot bands. For a surface pressure of 1 atm of CO2, the present greenhouse model predicts a global mean surface temperature of 294 K, but if the hot bands are excluded, a surface temperature of only 250 K is achieved.

  17. On carbon monoxide cooling in the solar atmosphere

    Science.gov (United States)

    Mauas, Pablo J.; Avrett, Eugene H.; Loeser, Rudolf

    1990-01-01

    The CO cooling rate for models of the solar atmosphere using the detailed line-by-line CO opacity in the fundamental band, and carrying out a full radiative transfer calculation for each line is computed. The importance of the different assumptions that have been made to obtain the CO cooling rate and find that when detailed optical depth effects are taken into account, the calculated CO cooling rate at line optical depths near unity can be smaller than optically thin estimates by more than an order of magnitude is studied. It is found that CO cooling does not account for the missing source of radiative cooling in the temperature minimum region of the quiet sun.

  18. On carbon monoxide cooling in the solar atmosphere

    Energy Technology Data Exchange (ETDEWEB)

    Mauas, P.J.; Avrett, E.H.; Loeser, R. (Harvard-Smithsonian Center for Astrophysics, Cambridge, MA (USA))

    1990-07-01

    The CO cooling rate for models of the solar atmosphere using the detailed line-by-line CO opacity in the fundamental band, and carrying out a full radiative transfer calculation for each line is computed. The importance of the different assumptions that have been made to obtain the CO cooling rate and find that when detailed optical depth effects are taken into account, the calculated CO cooling rate at line optical depths near unity can be smaller than optically thin estimates by more than an order of magnitude is studied. It is found that CO cooling does not account for the missing source of radiative cooling in the temperature minimum region of the quiet sun. 30 refs.

  19. Charge exchange and energy loss of slow highly charged ions in 1 nm thick carbon nanomembranes.

    Science.gov (United States)

    Wilhelm, Richard A; Gruber, Elisabeth; Ritter, Robert; Heller, René; Facsko, Stefan; Aumayr, Friedrich

    2014-04-18

    Experimental charge exchange and energy loss data for the transmission of slow highly charged Xe ions through ultrathin polymeric carbon membranes are presented. Surprisingly, two distinct exit charge state distributions accompanied by charge exchange dependent energy losses are observed. The energy loss for ions exhibiting large charge loss shows a quadratic dependency on the incident charge state indicating that equilibrium stopping force values do not apply in this case. Additional angle resolved transmission measurements point on a significant contribution of elastic energy loss. The observations show that regimes of different impact parameters can be separated and thus a particle's energy deposition in an ultrathin solid target may not be described in terms of an averaged energy loss per unit length.

  20. Carbon composite bipolar plate for high-temperature proton exchange membrane fuel cells (HT-PEMFCs)

    Science.gov (United States)

    Lee, Dongyoung; Lee, Dai Gil

    2016-09-01

    A carbon/epoxy composite bipolar plate is an ideal substitute for the brittle graphite bipolar plate for lightweight proton exchange membrane fuel cells (PEMFCs) because of its high specific strength and stiffness. However, conventional carbon/epoxy composite bipolar plates are not applicable for high-temperature PEMFCs (HT-PEMFCs) because these systems are operated at higher temperatures than the glass transition temperatures of conventional epoxies. Therefore, in this study, a cyanate ester-modified epoxy is adopted for the development of a carbon composite bipolar plate for HT-PEMFCs. The composite bipolar plate with exposed surface carbon fibers is produced without any surface treatments or coatings to increase the productivity and is integrated with a silicone gasket to reduce the assembly cost. The developed carbon composite bipolar plate exhibits not only superior electrical properties but also high thermo-mechanical properties. In addition, a unit cell test is performed, and the results are compared with those of the conventional graphite bipolar plate.

  1. A comparison of sulfur-free and ambient air enclosure techniques for measuring the exchange of reduced sulfur gases between soils and the atmosphere

    Science.gov (United States)

    Castro, Mark S.; Galloway, James N.

    1991-08-01

    The exchange of reduced sulfur gases between the atmosphere and forest soils in the Shaver Hollow watershed (Shenandoah National Park, Virginia) were measured with sulfur-free and ambient air enclosures at least twice a month from March through November 1989. Soils within sulfur-free enslosures were sources of carbonyl sulfide (COS) and carbon disulfide (CS2). Atmospheric fluxes of COS and CS2 ranged from 0.77 to 13.03 ng COS-S/sq m-min and from 2.04 to 15.74 ng CS2-S/sq m-min. In contrast, soils within ambient air enclosures were sinks for COS and CS2. Uptake rates of COS and CS2 ranged from 2.78 to 16.20 ng COS-S/sq m-min and from 3.42 to 26.62 ng CS2-S/sq m-min. The discrepancy in the direction of these fluxes was caused by the flux-measurement techniques.

  2. Soil-atmosphere greenhouse-gas exchange in a bioretention system

    Science.gov (United States)

    Daly, E.; Chan, H.; Beringer, J.; Livesley, S. J.

    2011-12-01

    Bioretention systems are a popular green-technology for the management of urban stormwater runoff in many countries. They typically consist of a trench filled with a highly permeable soil medium that supports vegetation; runoff is diverted to bioretention systems and, by percolating through the filter medium, is subjected to a number of treatment processes. Nitrogen (N) is one of the key pollutants targeted by bioretention systems, which are able to reduce N concentrations considerably from inflow to outflow. To increase N removal, a saturated zone at the bottom of the filter medium is often artificially generated, to both enhance the denitrification process and increase the water available to the vegetation between inflow events. Although studies on the N-removal performance of bioretention systems are widely available in the literature, less is known about the exchange of greenhouse gases (GHG), especially nitrous oxide (N2O), between the bioretention systems and the atmosphere. Here, we present an experimental pilot study to measure N2O and CO2 soil emissions in a bioretention system installed on the Clayton Campus of Monash University in Melbourne, Australia. The bioretention system is divided into three cells, each 15 m2; the system as a whole receives water run-off from 4500 m2 of impervious car park. We monitored two cells with mostly sandy-loam vegetated with native sedges (mainly Carex Appressa and Lomandra Longifolia), one with and one without a saturated zone. Three manual flux chambers were installed in both cells. Gas flux samples were taken twice a week at about 11 am between the 2nd of March and the 18th of May 2011 (late summer and fall). Since October 2010, air-phase soil CO2 concentration profiles were measured continuously using solid-state infrared CO2 transmitters (GMT-221 model, Vaisala, Finland), along with soil moisture and soil temperature. Preliminary analysis of the chamber data (March only) showed that N2O fluxes were in general below 50

  3. Exchange of carbonyl sulfide (COS), a potential tracer of gross primary productivity, between grassland ecosystem components and the atmosphere

    Science.gov (United States)

    Whelan, M.; Rhew, R. C.

    2013-12-01

    Recently, measurements of carbonyl sulfide (COS) exchange have been used as an independent constraint for estimates of gross primary productivity over terrestrial ecosystems and continents. CO2 is both taken up and released by plants, whereas COS is usually only consumed and at a predictable ratio to CO2. Most of the underlying theoretical assumptions of this method have been verified, however the problem of parsing leaf exchange from other terrestrial sources and sinks of COS is still under investigation. In ecosystems that experience distinct periods of growing and senescence, it is possible to assess COS fluxes in situ when no green plants are present and compare to measurements during the growing season. Taking advantage of this seasonal pattern, we have investigated COS exchange from March 2012 to March 2013 in a Mediterranean grassland outside of Santa Cruz, CA, U.S.A (37.0°N, 122°W). Through lab-based incubation experiments, we found that net COS uptake of grassland soil can be reduced by increased soil moisture. We evaluated this claim in the field with monthly field deployments of static flux chambers over the in-tact soil and plant system. In the dry summer, artificial rain amendments caused COS net uptake to decrease, sometimes leading to overall net production to the atmosphere, in agreement with lab experiments. During the wet growing season, water additions caused over 2x increase in COS uptake from the atmosphere. Contrary to what has been previously claimed, soil exchange of COS is not negligible in grassland ecosystems.

  4. Effective Route to Graphitic carbon Nitride from Ball-Milled Amorphous carbon in NH3 Atmosphere Under Annealing

    Institute of Scientific and Technical Information of China (English)

    费振义; 刘玉先

    2003-01-01

    Graphitic carbon nitride (g-C3N4) powders were successfully synthesized from ball-milled amorphous carbon under NHs atmosphere at high temperature, for the first time to the best of our knowledge. The combined characteristic data obtained by x-ray diffraction, high-resolution transmission-electron microscopy, electron energy loss spectroscopy, Raman spectroscopy, energy dispersive spectroscopic analysis, and Fourier transformation infrared spectroscopy provide substantial evidence for the graphite-like sp2-bonded structure with C3N4 stoichiometry.

  5. Micrometeorological Measurement of Fetch- and Atmospheric Stability-Dependent Air- Water Exchange of Legacy Semivolatile Organic Contaminants in Lake Superior

    Science.gov (United States)

    Perlinger, J. A.; Tobias, D. E.; Rowe, M. D.

    2008-12-01

    Coastal waters including the Laurentian Great Lakes are particularly susceptible to local, regional, and long- range transport and deposition of semivolatile organic contaminants (SOCs) as gases and/or associated with particles. Recently-marketed SOCs can be expected to undergo net deposition in surface waters, whereas legacy SOCs such as polychlorinated biphenyls (PCBs) are likely to be at equilibrium with respect to air-water exchange, or, if atmospheric concentrations decrease through, e.g., policy implementation, to undergo net gas emission. SOC air-water exchange flux is usually estimated using the two-film model. This model describes molecular diffusion through the air and water films adjacent to the air-water interface. Air-water exchange flux is estimated as the product of SOC fugacity, typically based on on-shore gaseous concentration measurements, and a transfer coefficient, the latter which is estimated from SOC properties and environmental conditions. The transfer coefficient formulation commonly applied neglects resistance to exchange in the internal boundary layer under atmospherically stable conditions, and the use of on-shore gaseous concentration neglects fetch-dependent equilibration, both of which will tend to cause overestimation of flux magnitude. Thus, for legacy chemicals or in any highly contaminated surface water, the rate at which the water is cleansed through gas emission tends to be over-predicted using this approach. Micrometeorological measurement of air-water exchange rates of legacy SOCs was carried out on ships during four transect experiments during off-shore flow in Lake Superior using novel multicapillary collection devices and thermal extraction technology to measure parts-per-quadrillion SOC levels. Employing sensible heat in the modified Bowen ratio, fluxes at three over-water stations along the transects were measured, along with up-wind, onshore gaseous concentration and aqueous concentration. The atmosphere was unstable for

  6. Carbon use in root respiration as affected by elevated atmospheric O-2

    NARCIS (Netherlands)

    Lambers, H; Stulen, [No Value; vanderWerf, A

    1996-01-01

    The use of fossil fuel is predicted to cause an increase of the atmospheric CO2 concentration, which will affect the global pattern of temperature and precipitation. It is therefore essential to incorporate effects of temperature and water supply on the carbon requirement for root respiration of pla

  7. Cleaning of carbon materials from flat surfaces and castellation gaps by an atmospheric pressure plasma jet

    Energy Technology Data Exchange (ETDEWEB)

    Stancu, C. [National Institute for Laser, Plasma and Radiation Physics, Atomistilor Str. 409, PO Box Mg36, Magurele-Bucharest, 077125 (Romania); Alegre, D. [Laboratorio Nacional de Fusión, As. Euratom/Ciemat, Avda. Complutense 22, 28040, Madrid (Spain); Ionita, E.R.; Mitu, B. [National Institute for Laser, Plasma and Radiation Physics, Atomistilor Str. 409, PO Box Mg36, Magurele-Bucharest, 077125 (Romania); Grisolia, C. [CEA, IRFM, F-13108, Saint-Paul-lez-Durance (France); Tabares, F.L. [Laboratorio Nacional de Fusión, As. Euratom/Ciemat, Avda. Complutense 22, 28040, Madrid (Spain); Dinescu, G., E-mail: dinescug@infim.ro [National Institute for Laser, Plasma and Radiation Physics, Atomistilor Str. 409, PO Box Mg36, Magurele-Bucharest, 077125 (Romania)

    2016-02-15

    Highlights: • Atmospheric plasma jets operated with nitrogen, oxygen and their mixtures are used for cleaning surfaces of carbon residues • Efficient plasma jet cleaning of carbon deposits from flat surfaces and inside gaps of castellated surfaces is demonstrated • Plasma jet cleaning is more effective at the gaps entrance and on their bottom - Abstract: A study of the removal of carbon layers from flat and castellated surfaces by a plasma jet source operated in open atmosphere is presented. Amorphous hydrogenated carbon films deposited on silicon substrates, on aluminium made castellated surfaces, and graphitic carbon plates were used. The erosion effects of plasmas generated either in pure argon, nitrogen or in their mixtures with hydrogen, ammonia, oxygen are compared. Highest erosion was obtained with nitrogen and nitrogen/oxygen plasmas. Plasmas in argon and containing hydrogen, and ammonia have shown a low erosion rate. A large removal rate by pure nitrogen plasma jet of 3.2 mg/min was found by scanning graphitic carbon flat surfaces for optimum process parameters. Adding small quantities of oxygen led to a removal rate enhancement by a factor of 3. Finally, the integral removal rate of amorphous hydrogenated carbon deposited in gaps 23 mm deep and 0.5 mm wide was of the order of 0.35 mg/min. The layer elimination was more efficient at the top and at the bottom of the gaps, precisely where the thickest codeposits develop in a nuclear fusion device.

  8. Reduced impact logging minimally alters tropical rainforest carbon and energy exchange.

    Science.gov (United States)

    Miller, Scott D; Goulden, Michael L; Hutyra, Lucy R; Keller, Michael; Saleska, Scott R; Wofsy, Steven C; Figueira, Adelaine Michela Silva; da Rocha, Humberto R; de Camargo, Plinio B

    2011-11-29

    We used eddy covariance and ecological measurements to investigate the effects of reduced impact logging (RIL) on an old-growth Amazonian forest. Logging caused small decreases in gross primary production, leaf production, and latent heat flux, which were roughly proportional to canopy loss, and increases in heterotrophic respiration, tree mortality, and wood production. The net effect of RIL was transient, and treatment effects were barely discernable after only 1 y. RIL appears to provide a strategy for managing tropical forest that minimizes the potential risks to climate associated with large changes in carbon and water exchange.

  9. FTIR study of carbon monoxide adsorption on ion-exchanged X, Y and mordenite type zeolites

    Directory of Open Access Journals (Sweden)

    R. HERCIGONJA

    2003-05-01

    Full Text Available In this work Fourier transform infrared (FTIR study has been applied to study the adsorption of carbon monoxide on transition metal (Mn+, Co2+, Ni2+ ion-exchanged zeolites type Y, X and mordenites. The adsorption of CO at room temperature produces overlapping IR absorption bands in the 2120–2200 cm-1 region. The frequency of the band around 2200 cm-1 is found to be dependent not only on the charge-balancing transition metal cation, but also on the framework composition. The frequencies of the band near 1600 cm-1 was found to be dependent on the Si/Al ratio of the investigated zeolites.

  10. Reduced impact logging minimally alters tropical rainforest carbon and energy exchange

    Science.gov (United States)

    Miller, Scott D.; Goulden, Michael L.; Hutyra, Lucy R.; Keller, Michael; Saleska, Scott R.; Wofsy, Steven C.; Figueira, Adelaine Michela Silva; da Rocha, Humberto R.; de Camargo, Plinio B.

    2011-01-01

    We used eddy covariance and ecological measurements to investigate the effects of reduced impact logging (RIL) on an old-growth Amazonian forest. Logging caused small decreases in gross primary production, leaf production, and latent heat flux, which were roughly proportional to canopy loss, and increases in heterotrophic respiration, tree mortality, and wood production. The net effect of RIL was transient, and treatment effects were barely discernable after only 1 y. RIL appears to provide a strategy for managing tropical forest that minimizes the potential risks to climate associated with large changes in carbon and water exchange. PMID:22087005

  11. Sensitivity of the air-sea CO2 exchange in the Baltic Sea and Danish inner waters to atmospheric short-term variability

    NARCIS (Netherlands)

    Lanso, A. S.; Bendtsen, J.; Christensen, J. H.; Sorensen, L. L.; Chen, Huilin; Meijer, H. A. J.; Geels, C.

    2015-01-01

    Minimising the uncertainties in estimates of air-sea CO2 exchange is an important step toward increasing the confidence in assessments of the CO2 cycle. Using an atmospheric transport model makes it possible to investigate the direct impact of atmospheric parameters on the air-sea CO2 flux along wit

  12. Scaling up of Carbon Exchange Dynamics from AmeriFlux Sites to a Super-Region in the Eastern United States

    Energy Technology Data Exchange (ETDEWEB)

    Hans Peter Schmid; Craig Wayson

    2009-05-05

    The primary objective of this project was to evaluate carbon exchange dynamics across a region of North America between the Great Plains and the East Coast. This region contains about 40 active carbon cycle research (AmeriFlux) sites in a variety of climatic and landuse settings, from upland forest to urban development. The core research involved a scaling strategy that uses measured fluxes of CO{sub 2}, energy, water, and other biophysical and biometric parameters to train and calibrate surface-vegetation-atmosphere models, in conjunction with satellite (MODIS) derived drivers. To achieve matching of measured and modeled fluxes, the ecosystem parameters of the models will be adjusted to the dynamically variable flux-tower footprints following Schmid (1997). High-resolution vegetation index variations around the flux sites have been derived from Landsat data for this purpose. The calibrated models are being used in conjunction with MODIS data, atmospheric re-analysis data, and digital land-cover databases to derive ecosystem exchange fluxes over the study domain.

  13. The role of carbon in fungal nutrient uptake and transport: implications for resource exchange in the arbuscular mycorrhizal symbiosis.

    Science.gov (United States)

    Fellbaum, Carl R; Mensah, Jerry A; Pfeffer, Philip E; Kiers, E Toby; Bücking, Heike

    2012-11-01

    The arbuscular mycorrhizal (AM) symbiosis, which forms between plant hosts and ubiquitous soil fungi of the phylum Glomeromycota, plays a key role for the nutrient uptake of the majority of land plants, including many economically important crop species. AM fungi take up nutrients from the soil and exchange them for photosynthetically fixed carbon from the host. While our understanding of the exact mechanisms controlling carbon and nutrient exchange is still limited, we recently demonstrated that (i) carbon acts as an important trigger for fungal N uptake and transport, (ii) the fungus changes its strategy in response to an exogenous supply of carbon, and that (iii) both plants and fungi reciprocally reward resources to those partners providing more benefit. Here, we summarize recent research findings and discuss the implications of these results for fungal and plant control of resource exchange in the AM symbiosis.

  14. Novel applications of carbon isotopes in atmospheric CO2: what can atmospheric measurements teach us about processes in the biosphere?

    Directory of Open Access Journals (Sweden)

    J. W. C. White

    2011-05-01

    Full Text Available Conventionally, measurements of carbon isotopes in atmospheric CO2 (δ13CO2 have been used to partition fluxes between terrestrial and ocean carbon pools. However, novel analytical approaches combined with an increase in the spatial extent and frequency of δ13CO2 measurements allow us to conduct a global analysis of δ13CO2 variability to infer the isotopic composition of source CO2 to the atmosphere (δs. This global analysis yields coherent seasonal patterns of isotopic enrichment. Our results indicate that seasonal values of δs are more highly correlated with vapor pressure deficit (r=0.404 than relative humidity (r=0.149. We then evaluate two widely used stomatal conductance models and determine that Leuning Model, which is primarily driven by vapor pressure deficit is more effective globally at predicting δs (RMSE = 1.7 ‰ than the Ball-Berry model, which is driven by relative humidity (RMSE = 2.8 ‰. Thus stomatal conductance on a global scale may be more sensitive to changes in vapor pressure deficit than relative humidity. This approach highlights a new application of using δ13CO2 measurements to test global models.

  15. Determination of technical readiness for an atmospheric carbon imaging spectrometer

    Science.gov (United States)

    Mobilia, Joseph; Kumer, John B.; Palmer, Alice; Sawyer, Kevin; Mao, Yalan; Katz, Noah; Mix, Jack; Nast, Ted; Clark, Charles S.; Vanbezooijen, Roel; Magoncelli, Antonio; Baraze, Ronald A.; Chenette, David L.

    2013-09-01

    The geoCARB sensor uses a 4-channel push broom slit-scan infrared imaging grating spectrometer to measure the absorption spectra of sunlight reflected from the ground in narrow wavelength regions. The instrument is designed for flight at geostationary orbit to provide mapping of greenhouse gases over continental scales, several times per day, with a spatial resolution of a few kilometers. The sensor provides multiple daily maps of column-averaged mixing ratios of CO2, CH4, and CO over the regions of interest, which enables flux determination at unprecedented time, space, and accuracy scales. The geoCARB sensor development is based on our experience in successful implementation of advanced space deployed optical instruments for remote sensing. A few recent examples include the Atmospheric Imaging Assembly (AIA) and Helioseismic and Magnetic Imager (HMI) on the geostationary Solar Dynamics Observatory (SDO), the Space Based Infrared System (SBIRS GEO-1) and the Interface Region Imaging Spectrograph (IRIS), along with sensors under development, the Near Infared camera (NIRCam) for James Webb (JWST), and the Global Lightning Mapper (GLM) and Solar UltraViolet Imager (SUVI) for the GOES-R series. The Tropospheric Infrared Mapping Spectrometer (TIMS), developed in part through the NASA Instrument Incubator Program (IIP), provides an important part of the strong technological foundation for geoCARB. The paper discusses subsystem heritage and technology readiness levels for these subsystems. The system level flight technology readiness and methods used to determine this level are presented along with plans to enhance the level.

  16. Atmospheric black carbon and sulfate concentrations in Northeast Greenland

    Science.gov (United States)

    Massling, A.; Nielsen, I. E.; Kristensen, D.; Christensen, J. H.; Sørensen, L. L.; Jensen, B.; Nguyen, Q. T.; Nøjgaard, J. K.; Glasius, M.; Skov, H.

    2015-08-01

    Measurements of equivalent black carbon (EBC) in aerosols at the high Arctic field site Villum Research Station (VRS) at Station Nord in North Greenland showed a seasonal variation in EBC concentrations with a maximum in winter and spring at ground level. Average measured concentrations were about 0.067 ± 0.071 for the winter and 0.011 ± 0.009 for the summer period. These data were obtained using a multi-angle absorption photometer (MAAP). A similar seasonal pattern was found for sulfate concentrations with a maximum level during winter and spring analyzed by ion chromatography. Here, measured average concentrations were about 0.485 ± 0.397 for the winter and 0.112 ± 0.072 for the summer period. A correlation between EBC and sulfate concentrations was observed over the years 2011 to 2013 stating a correlation coefficient of R2 = 0.72. This finding gives the hint that most likely transport of primary emitted BC particles to the Arctic was accompanied by aging of the aerosols through condensational processes. BC and sulfate are known to have only partly similar sources with respect to their transport pathways when reaching the high Arctic. Aging processes may have led to the formation of secondary inorganic matter and further transport of BC particles as cloud processing and further washout of particles is less likely based on the typically observed transport patterns of air masses arriving at VRS. Additionally, concentrations of EC (elemental carbon) based on a thermo-optical method were determined and compared to EBC measurements. EBC measurements were generally higher, but a correlation between EC and EBC resulted in a correlation coefficient of R2 = 0.64. Model estimates of the climate forcing due to BC in the Arctic are based on contributions of long-range transported BC during spring and summer. The measured concentrations were here compared with model results obtained by the Danish Eulerian Hemispheric Model, DEHM. Good agreement between measured and

  17. Observation of Large Enhancement of Charge Exchange Cross Sections with Neutron-Rich Carbon Isotopes

    CERN Document Server

    Tanihata, I; Kanungo, R; Ameil, F; Atkinson, J; Ayyad, Y; Cortina-Gil, D; Dillmann, I; Estradé, A; Evdokimov, A; Farinon, F; Geissel, H; Guastalla, G; Janik, R; Knoebel, R; Kurcewicz, J; Litvinov, Yu A; Marta, M; Mostazo, M; Mukha, I; Nociforo, C; Ong, H J; Pietri, S; Prochazka, A; Scheidenberger, C; Sitar, B; Strmen, P; Takechi, M; Tanaka, J; Toki, H; Vargas, J; Winfield, J S; Weick, H

    2015-01-01

    Production cross sections of nitrogen isotopes from high-energy carbon isotopes on hydrogen and carbon targets have been measured for the first time for a wide range of isotopes. The fragment separator FRS at GSI was used to deliver C isotope beams. The cross sections of the production of N isotopes were determined by charge measurements of forward going fragments. The cross sections show a rapid increase with the number of neutrons in the projectile. Since the production of nitrogen is mostly due to charge exchange reactions below the proton separation energies, the present data suggests a concentration of Gamow-Teller and Fermi transition strength at low excitation energies for neutron-rich isotopes. It was also observed that the cross sections were enhanced much more strongly for neutron rich isotopes in the C-target data.

  18. Atmospheric carbon dioxide concentrations before 2.2 billion years ago

    Science.gov (United States)

    Rye, R.; Kuo, P. H.; Holland, H. D.

    1995-01-01

    The composition of the Earth's early atmosphere is a subject of continuing debate. In particular, it has been suggested that elevated concentrations of atmospheric carbon dioxide would have been necessary to maintain normal surface temperatures in the face of lower solar luminosity in early Earth history. Fossil weathering profiles, known as palaeosols, have provided semi-quantitative constraints on atmospheric oxygen partial pressure (pO2) before 2.2 Gyr ago. Here we use the same well studied palaeosols to constrain atmospheric pCO2 between 2.75 and 2.2 Gyr ago. The observation that iron lost from the tops of these profiles was reprecipitated lower down as iron silicate minerals, rather than as iron carbonate, indicates that atmospheric pCO2 must have been less than 10(-1.4) atm--about 100 times today's level of 360 p.p.m., and at least five times lower than that required in one-dimensional climate models to compensate for lower solar luminosity at 2.75 Gyr. Our results suggest that either the Earth's early climate was much more sensitive to increases in pCO2 than has been thought, or that one or more greenhouse gases other than CO2 contributed significantly to the atmosphere's radiative balance during the late Archaean and early Proterozoic eons.

  19. Carbon oxidation state as a metric for describing the chemistry of atmospheric organic aerosol

    Energy Technology Data Exchange (ETDEWEB)

    Massachusetts Institute of Technology; Kroll, Jesse H.; Donahue, Neil M.; Jimenez, Jose L.; Kessler, Sean H.; Canagaratna, Manjula R.; Wilson, Kevin R.; Altieri, Katye E.; Mazzoleni, Lynn R.; Wozniak, Andrew S.; Bluhm, Hendrik; Mysak, Erin R.; Smith, Jared D.; Kolb, Charles E.; Worsnop, Douglas R.

    2010-11-05

    A detailed understanding of the sources, transformations, and fates of organic species in the environment is crucial because of the central roles that organics play in human health, biogeochemical cycles, and Earth's climate. However, such an understanding is hindered by the immense chemical complexity of environmental mixtures of organics; for example, atmospheric organic aerosol consists of at least thousands of individual compounds, all of which likely evolve chemically over their atmospheric lifetimes. Here we demonstrate the utility of describing organic aerosol (and other complex organic mixtures) in terms of average carbon oxidation state (OSC), a quantity that always increases with oxidation, and is readily measured using state-of-the-art analytical techniques. Field and laboratory measurements of OSC , using several such techniques, constrain the chemical properties of the organics and demonstrate that the formation and evolution of organic aerosol involves simultaneous changes to both carbon oxidation state and carbon number (nC).

  20. Observations of Recent Arctic Sea Ice Volume Loss and Its Impact on Ocean-Atmosphere Energy Exchange and Ice Production

    Science.gov (United States)

    Kurtz, N. T.; Markus, T.; Farrell, S. L.; Worthen, D. L.; Boisvert, L. N.

    2011-01-01

    Using recently developed techniques we estimate snow and sea ice thickness distributions for the Arctic basin through the combination of freeboard data from the Ice, Cloud, and land Elevation Satellite (ICESat) and a snow depth model. These data are used with meteorological data and a thermodynamic sea ice model to calculate ocean-atmosphere heat exchange and ice volume production during the 2003-2008 fall and winter seasons. The calculated heat fluxes and ice growth rates are in agreement with previous observations over multiyear ice. In this study, we calculate heat fluxes and ice growth rates for the full distribution of ice thicknesses covering the Arctic basin and determine the impact of ice thickness change on the calculated values. Thinning of the sea ice is observed which greatly increases the 2005-2007 fall period ocean-atmosphere heat fluxes compared to those observed in 2003. Although there was also a decline in sea ice thickness for the winter periods, the winter time heat flux was found to be less impacted by the observed changes in ice thickness. A large increase in the net Arctic ocean-atmosphere heat output is also observed in the fall periods due to changes in the areal coverage of sea ice. The anomalously low sea ice coverage in 2007 led to a net ocean-atmosphere heat output approximately 3 times greater than was observed in previous years and suggests that sea ice losses are now playing a role in increasing surface air temperatures in the Arctic.

  1. Comparative analysis of carbon, water, and energy exchanges in co-located mid-latitude forests at various stages of development

    Science.gov (United States)

    Williams, C. A.; Munger, J. W.; Hadley, J.; Fitzjarrald, D. R.

    2010-12-01

    Biosphere-atmosphere exchanges of mass and energy vary with forest type, stand age, and following disturbance, but the degree, character, and persistence of these variations remain poorly understood. This work explores such gradients by synthesizing across a local network of flux tower sites within Harvard Forest (central Massachusetts). We examine how CO2, H2O, and energy exchanges compare among mature and intermediate aged deciduous forests, a mature hemlock forest, and a newly instrumented site in the early stages of secondary succession following a recent clearcut. We find markedly lower growing season evapotranspiration in the hemlock stand compared to adjacent deciduous forests, lower still in the revegetating clearcut. Daytime net ecosystem carbon exchange follows a similar pattern, with highest uptake in the deciduous forests, intermediate in the hemlock site, and lowest in the clearcut. This is true despite sizeable midday uptake in the clearcut during the second growing season post-harvest. Large nighttime CO2 emissions from the clearcut indicate high respiration rates of the early succession vegetation as well as vigorous decomposition of the abundant woody debris and litter left onsite after harvest. Surface albedo and corresponding net radiation are both surprisingly consistent across these adjacent cover types. Implications for water resources and carbon balance of New England landscapes will be discussed, particularly within the contexts of human and natural disturbances, such as harvesting and Hemlock Wooly Adelgid infestations.

  2. Climate Sensitivity, Sea Level, and Atmospheric Carbon Dioxide

    Science.gov (United States)

    Hansen, James; Sato, Makiko; Russell, Gary; Kharecha, Pushker

    2013-01-01

    Cenozoic temperature, sea level and CO2 covariations provide insights into climate sensitivity to external forcings and sea-level sensitivity to climate change. Climate sensitivity depends on the initial climate state, but potentially can be accurately inferred from precise palaeoclimate data. Pleistocene climate oscillations yield a fast-feedback climate sensitivity of 3+/-1deg C for a 4 W/sq m CO2 forcing if Holocene warming relative to the Last Glacial Maximum (LGM) is used as calibration, but the error (uncertainty) is substantial and partly subjective because of poorly defined LGM global temperature and possible human influences in the Holocene. Glacial-to-interglacial climate change leading to the prior (Eemian) interglacial is less ambiguous and implies a sensitivity in the upper part of the above range, i.e. 3-4deg C for a 4 W/sq m CO2 forcing. Slow feedbacks, especially change of ice sheet size and atmospheric CO2, amplify the total Earth system sensitivity by an amount that depends on the time scale considered. Ice sheet response time is poorly defined, but we show that the slow response and hysteresis in prevailing ice sheet models are exaggerated. We use a global model, simplified to essential processes, to investigate state dependence of climate sensitivity, finding an increased sensitivity towards warmer climates, as low cloud cover is diminished and increased water vapour elevates the tropopause. Burning all fossil fuels, we conclude, would make most of the planet uninhabitable by humans, thus calling into question strategies that emphasize adaptation to climate change.

  3. Toward restoring the net carbon sink function of degraded peatlands: Short-term response in CO2 exchange to ecosystem-scale restoration

    Science.gov (United States)

    Waddington, J. M.; Strack, M.; Greenwood, M. J.

    2010-03-01

    Northern peatlands represent a globally important stock of soil carbon and have acted as a net sink of atmospheric CO2 throughout the Holocene. Disturbance for horticultural peat extraction disrupts ecosystem function and converts these ecosystems to large, persistent sources of carbon dioxide (CO2). This study investigates the effect of ecosystem-scale restoration on growing season CO2 exchange in a peatland by comparing a restored site to a neighboring nonrestored section for 1 year prerestoration (1999) and 3 years postrestoration (2000-2002). Prior to restoration, less than 23% of the site was vegetated, and it was a source of 245 g C m-2 to the atmosphere during the growing season (May to early October). Following restoration, the water table remained deep, and soil moisture was significantly higher than the nonrestored section. By the third year postrestoration, vegetation covered 50% of the restored peatland. Moss covered 90% of this vegetated area. Vegetation productivity at the restored site was also enhanced with gross ecosystem photosynthesis under full light conditions significantly higher at the restored site at both moss and herbaceous plots by 2002. While this increase in vegetation productivity provided fresh substrate and resulted in higher CO2 production potential for restored site peat, ecosystem respiration was similar to or lower than that at the nonrestored site for both bare peat and vegetated areas because of the generally wetter site conditions resulting from restoration. By upscaling chamber CO2 exchange measurements to the ecosystem level, on the basis of the relative proportion of each surface cover type, we determined the site was a net sink of ˜20 ± 5 g C m-2 during the growing season only 2 years postrestoration. Combining our results with previous work on CH4 emissions and dissolved organic carbon export, we suggest that this degraded peatland ecosystem will likely return to a net carbon sink in 6 to 10 years postrestoration.

  4. Eddy covariance flux measurements of net ecosystem carbon dioxide exchange from a lowland peatland flux tower network in England and Wales

    Science.gov (United States)

    Morrison, Ross; Balzter, Heiko; Burden, Annette; Callaghan, Nathan; Cumming, Alenander; Dixon, Simon; Evans, Jonathan; Kaduk, Joerg; Page, Susan; Pan, Gong; Rayment, Mark; Ridley, Luke; Rylett, Daniel; Worrall, Fred; Evans, Christopher

    2016-04-01

    Peatlands store disproportionately large amounts of soil carbon relative to other terrestrial ecosystems. Over recent decades, the large amount of carbon stored as peat has proved vulnerable to a range of land use pressures as well as the increasing impacts of climate change. In temperate Europe and elsewhere, large tracts of lowland peatland have been drained and converted to agricultural land use. Such changes have resulted in widespread losses of lowland peatland habitat, land subsidence across extensive areas and the transfer of historically accumulated soil carbon to the atmosphere as carbon dioxide (CO2). More recently, there has been growth in activities aiming to reduce these impacts through improved land management and peatland restoration. Despite a long history of productive land use and management, the magnitude and controls on greenhouse gas emissions from lowland peatland environments remain poorly quantified. Here, results of surface-atmosphere measurements of net ecosystem CO2 exchange (NEE) from a network of seven eddy covariance (EC) flux towers located at a range of lowland peatland ecosystems across the United Kingdom (UK) are presented. This spatially-dense peatland flux tower network forms part of a wider observation programme aiming to quantify carbon, water and greenhouse gas balances for lowland peatlands across the UK. EC measurements totalling over seventeen site years were obtained at sites exhibiting large differences in vegetation cover, hydrological functioning and land management. The sites in the network show remarkable spatial and temporal variability in NEE. Across sites, annual NEE ranged from a net sink of -194 ±38 g CO2-C m-2 yr-1 to a net source of 784±70 g CO2-C m-2 yr-1. The results suggest that semi-natural sites remain net sinks for atmospheric CO2. Sites that are drained for intensive agricultural production range from a small net sink to the largest observed source for atmospheric CO2 within the flux tower network

  5. Short and Long Term Impacts of Forest Bioenergy Production on Atmospheric Carbon Dioxide Emissions

    Science.gov (United States)

    Hudiburg, T.; Law, B. E.; Luyssaert, S.; Thornton, P. E.

    2011-12-01

    Temperate forest annual net uptake of CO2 from the atmosphere is equivalent to ~16% of the annual fossil fuel emissions in the United States. Mitigation strategies to reduce emissions of carbon dioxide have lead to investigation of alternative sources of energy including forest biomass. The prospect of forest derived bioenergy has led to implementation of new forest management strategies based on the assumption that they will reduce total CO2 emissions to the atmosphere by simultaneously reducing the risk of wildfire and substituting for fossil fuels. The benefit of managing forests for bioenergy substitution of fossil fuels versus potential carbon sequestration by reducing harvest needs to be evaluated. This study uses a combination of Federal Forest Inventory data (FIA), remote sensing, and a coupled carbon-nitrogen ecosystem process model (CLM4-CN) to predict net atmospheric CO2 emissions from forest thinning for bioenergy production in Oregon under varying future management and climate scenarios. We use life-cycle assessment (LCA) incorporating both the forest and forest product sinks and sources of carbon dioxide. Future modeled results are compared with a reduced harvest scenario to determine the potential for increased carbon sequestration in forest biomass. We find that Oregon forests are a current strong sink of 7.5 ± 1.7 Tg C yr-1 or 61 g C m-2 yr-1. (NBP; NEP minus removals from fire and harvest). In the short term, we find that carbon dynamics following harvests for fire prevention and large-scale bioenergy production lead to 2-15% higher emissions over the next 20 years compared to current management, assuming 100% effectiveness of fire prevention. Given the current sink strength, analysis of the forest sector in Oregon demonstrates that increasing harvest levels by all practices above current business-as-usual levels increases CO2 emissions to the atmosphere as long as the region's sink persists. In the long-term, we find that projected changes in

  6. Global emission inventory and atmospheric transport of black carbon. Evaluation of the associated exposure

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Rong

    2015-06-01

    This thesis presents research focusing on the improvement of high-resolution global black carbon (BC) emission inventory and application in assessing the population exposure to ambient BC. A particular focus of the thesis is on the construction of a high-resolution (both spatial and sectorial) fuel consumption database, which is used to develop the emission inventory of black carbon. Above all, the author updates the global emission inventory of black carbon, a resource subsequently used to study the atmospheric transport of black carbon over Asia with the help of a high-resolution nested model. The thesis demonstrates that spatial bias in fuel consumption and BC emissions can be reduced by means of the sub-national disaggregation approach. Using the inventory and nested model, ambient BC concentrations can be better validated against observations. Lastly, it provides a complete uncertainty analysis of global black carbon emissions, and this uncertainty is taken into account in the atmospheric modeling, helping to better understand the role of black carbon in regional and global air pollution.

  7. A neutron star with a carbon atmosphere in the Cassiopeia A supernova remnant.

    Science.gov (United States)

    Ho, Wynn C G; Heinke, Craig O

    2009-11-05

    The surface of hot neutron stars is covered by a thin atmosphere. If there is accretion after neutron-star formation, the atmosphere could be composed of light elements (H or He); if no accretion takes place or if thermonuclear reactions occur after accretion, heavy elements (for example, Fe) are expected. Despite detailed searches, observations have been unable to confirm the atmospheric composition of isolated neutron stars. Here we report an analysis of archival observations of the compact X-ray source in the centre of the Cassiopeia A supernova remnant. We show that a carbon atmosphere neutron star (with low magnetic field) produces a good fit to the spectrum. Our emission model, in contrast with others, implies an emission size consistent with theoretical predictions for the radius of neutron stars. This result suggests that there is nuclear burning in the surface layers and also identifies the compact source as a very young ( approximately 330-year-old) neutron star.

  8. Cassini finds an oxygen-carbon dioxide atmosphere at Saturn's icy moon Rhea.

    Science.gov (United States)

    Teolis, B D; Jones, G H; Miles, P F; Tokar, R L; Magee, B A; Waite, J H; Roussos, E; Young, D T; Crary, F J; Coates, A J; Johnson, R E; Tseng, W-L; Baragiola, R A

    2010-12-24

    The flyby measurements of the Cassini spacecraft at Saturn's moon Rhea reveal a tenuous oxygen (O(2))-carbon dioxide (CO(2)) atmosphere. The atmosphere appears to be sustained by chemical decomposition of the surface water ice under irradiation from Saturn's magnetospheric plasma. This in situ detection of an oxidizing atmosphere is consistent with remote observations of other icy bodies, such as Jupiter's moons Europa and Ganymede, and suggestive of a reservoir of radiolytic O(2) locked within Rhea's ice. The presence of CO(2) suggests radiolysis reactions between surface oxidants and organics or sputtering and/or outgassing of CO(2) endogenic to Rhea's ice. Observations of outflowing positive and negative ions give evidence for pickup ionization as a major atmospheric loss mechanism.

  9. Role of Carbonic Anhydrase as an Activator in Carbonate Rock Dissolution and Its Implication for Atmospheric CO2 Sink

    Institute of Scientific and Technical Information of China (English)

    刘再华

    2001-01-01

    The conversion of CO2 into H+ and is a relatively slow reaction. Hence, its kinetics may be rate determining in carbonate rock dissolution. Carbonic anhydrase (CA), which is widespread in nature, was used to catalyze the CO2 conversion process in dissolution experiments of limestone and dolomite. It was found that the rate of dissolution increases by a factor of about 10 after the addition of CA at a high CO2 partial pressure (Pco2) for limestone and about 3 at low Pco2 for dolomite. This shows that reappraisal is necessary for the importance of chemical weathering (including carbonate rock dissolution and silicate weathering) in the atmospheric CO2 sink and the mysterious missing sink in carbon cycling. It is doubtless that previous studies of weathering underestimated weathering rates due to the ignorance of CA as an activator in weathering, thus the contribution of weathering to the atmospheric CO2 sink is also underestimated. This finding also shows the need to examine the situ distribution and activity of CA in different waters and to investigate the role of CA in weathering.``

  10. Soil atmosphere exchange of carbonyl sulfide (COS) regulated by diffusivity depending on water-filled pore space

    Science.gov (United States)

    van Diest, H.; Kesselmeier, J.

    2008-04-01

    The exchange of carbonyl sulfide (COS) between soil and the atmosphere was investigated for three arable soils from Germany, China and Finland and one forest soil from Siberia for parameterization in the relation to ambient carbonyl sulfide (COS) concentration, soil water content (WC) and air temperature. All investigated soils acted as sinks for COS. A clear and distinct uptake optimum was found for the German, Chinese, Finnish and Siberian soils at 11.5%, 9%, 11.5%, and 9% soil WC, respectively, indicating that the soil WC acts as an important biological and physical parameter for characterizing the exchange of COS between soils and the atmosphere. Different optima of deposition velocities (Vd) as observed for the Chinese, Finnish and Siberian boreal soil types in relation to their soil WC, aligned at 19% in relation to the water-filled pore space (WFPS), indicating the dominating role of gas diffusion. This interpretation was supported by the linear correlation between Vd and bulk density. We suggest that the uptake of COS depends on the diffusivity dominated by WFPS, a parameter depending on soil WC, soil structure and porosity of the soil.

  11. Soil atmosphere exchange of carbonyl sulfide (COS regulated by diffusivity depending on water-filled pore space

    Directory of Open Access Journals (Sweden)

    H. Van Diest

    2008-04-01

    Full Text Available The exchange of carbonyl sulfide (COS between soil and the atmosphere was investigated for three arable soils from Germany, China and Finland and one forest soil from Siberia for parameterization in the relation to ambient carbonyl sulfide (COS concentration, soil water content (WC and air temperature. All investigated soils acted as sinks for COS. A clear and distinct uptake optimum was found for the German, Chinese, Finnish and Siberian soils at 11.5%, 9%, 11.5%, and 9% soil WC, respectively, indicating that the soil WC acts as an important biological and physical parameter for characterizing the exchange of COS between soils and the atmosphere. Different optima of deposition velocities (Vd as observed for the Chinese, Finnish and Siberian boreal soil types in relation to their soil WC, aligned at 19% in relation to the water-filled pore space (WFPS, indicating the dominating role of gas diffusion. This interpretation was supported by the linear correlation between Vd and bulk density. We suggest that the uptake of COS depends on the diffusivity dominated by WFPS, a parameter depending on soil WC, soil structure and porosity of the soil.

  12. Soil atmosphere exchange of Carbonyl Sulfide (COS regulated by diffusivity depending on water-filled pore space

    Directory of Open Access Journals (Sweden)

    H. Van Diest

    2007-10-01

    Full Text Available The exchange of carbonyl sulfide (COS between soil and the atmosphere was investigated for three arable soils from Germany, China and Finland and one forest soil from Siberia for parameterization in the relation to ambient carbonyl sulfide (COS concentration, soil water content (WC and air temperature. All investigated soils acted as significant sinks for COS. A clear and distinct uptake optimum was found for the German, Chinese, Finnish and Siberian soils at 11.5%, 9%, 11.5%, and 9% soil WC, respectively, indicating that the soil WC acts as an important biological and physical parameter for characterizing the exchange of COS between soils and the atmosphere. Different optima of deposition velocities (Vd as observed for the Chinese, Finnish and Siberian boreal soil types in relation to their soil WC, aligned at 19% in relation to the water-filled pore space (WFPS, indicating the dominating role of gas diffusion. This interpretation was supported by the linear correlation between Vd and bulk density. We suggest that the uptake of COS depends on the diffusivity dominated by WFPS, a parameter depending on soil WC, soil structure and porosity of the soil.

  13. Nested atmospheric inversion for the terrestrial carbon sources and sinks in China

    Directory of Open Access Journals (Sweden)

    F. Jiang

    2013-08-01

    Full Text Available In this study, we establish a nested atmospheric inversion system with a focus on China using the Bayesian method. The global surface is separated into 43 regions based on the 22 TransCom large regions, with 13 small regions in China. Monthly CO2 concentrations from 130 GlobalView sites and 3 additional China sites are used in this system. The core component of this system is an atmospheric transport matrix, which is created using the TM5 model with a horizontal resolution of 3° × 2°. The net carbon fluxes over the 43 global land and ocean regions are inverted for the period from 2002 to 2008. The inverted global terrestrial carbon sinks mainly occur in boreal Asia, South and Southeast Asia, eastern America and southern South America. Most China areas appear to be carbon sinks, with strongest carbon sinks located in Northeast China. From 2002 to 2008, the global terrestrial carbon sink has an increasing trend, with the lowest carbon sink in 2002. The inter-annual variation (IAV of the land sinks shows remarkable correlation with the El Niño Southern Oscillation (ENSO. The terrestrial carbon sinks in China also show an increasing trend. However, the IAV in China is not the same as that of the globe. There is relatively stronger land sink in 2002, lowest sink in 2006, and strongest sink in 2007 in China. This IAV could be reasonably explained with the IAVs of temperature and precipitation in China. The mean global and China terrestrial carbon sinks over the period 2002–2008 are −3.20 ± 0.63 and −0.28 ± 0.18 PgC yr−1, respectively. Considering the carbon emissions in the form of reactive biogenic volatile organic compounds (BVOCs and from the import of wood and food, we further estimate that China's land sink is about −0.31 PgC yr−1.

  14. Surface-atmosphere exchange of ammonia over peatland using QCL-based eddy-covariance measurements and inferential modeling

    Science.gov (United States)

    Zöll, Undine; Brümmer, Christian; Schrader, Frederik; Ammann, Christof; Ibrom, Andreas; Flechard, Christophe R.; Nelson, David D.; Zahniser, Mark; Kutsch, Werner L.

    2016-09-01

    Recent advances in laser spectrometry offer new opportunities to investigate ecosystem-atmosphere exchange of environmentally relevant trace gases. In this study, we demonstrate the applicability of a quantum cascade laser (QCL) absorption spectrometer to continuously measure ammonia concentrations at high time resolution and thus to quantify the net exchange between a seminatural peatland ecosystem and the atmosphere based on the eddy-covariance approach. Changing diurnal patterns of both ammonia concentration and fluxes were found during different periods of the campaign. We observed a clear tipping point in early spring with decreasing ammonia deposition velocities and increasingly bidirectional fluxes that occurred after the switch from dormant vegetation to CO2 uptake but was triggered by a significant weather change. While several biophysical parameters such as temperature, radiation, and surface wetness were identified to partially regulate ammonia exchange at the site, the seasonal concentration pattern was clearly dominated by agricultural practices in the surrounding area. Comparing the results of a compensation point model with our measurement-based flux estimates showed considerable differences in some periods of the campaign due to overestimation of non-stomatal resistances caused by low acid ratios. The total cumulative campaign exchange of ammonia after 9 weeks, however, differed only in a 6 % deviation with 911 and 857 g NH3-N ha-1 deposition being found by measurements and modeling, respectively. Extrapolating our findings to an entire year, ammonia deposition was lower than reported by Hurkuck et al. (2014) for the same site in previous years using denuder systems. This was likely due to a better representation of the emission component in the net signal of eddy-covariance fluxes as well as better adapted site-specific parameters in the model. Our study not only stresses the importance of high-quality measurements for studying and assessing land

  15. Forest-atmosphere exchange of ozone: sensitivity to very reactive biogenic VOC emissions and implications for in-canopy photochemistry

    Directory of Open Access Journals (Sweden)

    G. M. Wolfe

    2011-05-01

    Full Text Available Understanding the fate of ozone within and above forested environments is vital to assessing the anthropogenic impact on ecosystems and air quality at the urban-rural interface. Observed forest-atmosphere exchange of ozone is often much faster than explicable by stomatal uptake alone, suggesting the presence of additional ozone sinks within the canopy. Using the Chemistry of Atmosphere-Forest Exchange (CAFE model in conjunction with summer noontime observations from the 2007 Biosphere Effects on Aerosols and Photochemistry Experiment (BEARPEX-2007, we explore the viability and implications of the hypothesis that ozonolysis of very reactive but yet unidentified biogenic volatile organic compounds (BVOC can influence the forest-atmosphere exchange of ozone. Non-stomatal processes typically generate 67% of the observed ozone flux, but reactions of ozone with measured BVOC, including monoterpenes and sesquiterpenes, can account for only 2% of this flux during the selected timeframe. By incorporating additional emissions and chemistry of a proxy for very reactive VOC (VRVOC that undergo rapid ozonolysis, we demonstrate that an in-canopy chemical ozone sink of ~2×108 molecules cm−3 s−1 can close the ozone flux budget. Even in such a case, the 65 min chemical lifetime of ozone is much longer than the canopy residence time of ~2 min, highlighting that chemistry can influence reactive trace gas exchange even when it is "slow" relative to vertical mixing. This level of VRVOC ozonolysis could enhance OH and RO2 production by as much as 1 pptv s−1 and substantially alter their respective vertical profiles depending on the actual product yields. Reaction products would also contribute significantly to the oxidized VOC budget and, by extension, secondary organic aerosol mass. Given the potentially significant ramifications of a chemical ozone flux for both in-canopy chemistry and estimates of ozone

  16. The Chemistry of Atmosphere-Forest Exchange (CAFE Model – Part 2: Application to BEARPEX-2007 observations

    Directory of Open Access Journals (Sweden)

    G. M. Wolfe

    2010-09-01

    Full Text Available In a companion paper, we have introduced the Chemistry of Atmosphere-Forest Exchange (CAFE model, a vertically-resolved 1-D chemical transport model designed to probe the details of near-surface reactive gas exchange. Here, we use CAFE to interpret noontime observations from the 2007 phase of the Biosphere Effects on Aerosols and Photochemistry Experiment (BEARPEX-2007, conducted at a young Ponderosa pine plantation in the western Sierra Nevada. The model reproduces many features of the BEARPEX-2007 data and offers new insights into the forest-atmosphere exchange of reactive molecules at this location. Nitrogen oxide (NOx = NO + NO2 fluxes are driven by soil emissions of NO, while the partitioning between NO and NO2 fluxes is sensitive to in-canopy photochemical gradients. Enhanced thermolysis at the ground increases downward acyl peroxy nitrate (APN fluxes by as much as 50%, in general agreement with previous findings. APN fluxes are also influenced by in-canopy chemical production, especially when their formation is tied closely to oxidation of BVOC emissions. Gross dry N deposition is typically dominated by nitric acid, though other reactive nitrogen (NOy species can comprise up to 28% of the N deposition budget under cooler conditions. Upward NO2 fluxes cause the net above-canopy NOy flux to be ~30% lower than the gross depositional flux. Model-measurement comparison of hydrogen peroxide mixing ratios suggests this molecule deposits at the aerodynamic limit. CAFE under-predicts ozone fluxes by ~20%, which may indicate additional in-canopy chemical losses that are missing from the current model.

  17. Comprehensive Characterization of Atmospheric Organic Carbon using Multiple High-Resolution Mass Spectrometric Instruments

    Science.gov (United States)

    Kroll, J. H.; Hunter, J. F.; Isaacman-VanWertz, G. A.

    2015-12-01

    Accurate modeling of major atmospheric chemical processes (oxidant cycling, aerosol formation, etc.) requires understanding the identity, chemistry, and lifecycle (emission, reaction, and deposition) of atmospheric organic species. Such an understanding is generally limited by the wide diversity in chemical structure, properties, and reactivity of atmospheric organics, posing major challenges in detection and quantification. However the last several years have seen the development of several new techniques for the measurement of a wide range of carbon-containing compounds, including low-volatility, oxidized species that have traditionally been difficult to measure. Many of these new techniques are based on high-resolution mass spectrometry, enabling the unambiguous identification of individual ions, and hence the elemental ratios and carbon oxidation state of the organic species; most also provide information on volatility and/or carbon number distributions of the molecular species. While a single instrument can generally measure only species of a particular class (occupying a localized region of "chemical space"), here we show that the combined measurements from multiple instruments can provide a comprehensive picture of the chemical composition of the entire organic mixture. From these combined measurements, the organic species can be described not only in terms of organic carbon mass but also in terms of distributions of key ensemble properties (such as oxidation state and volatility), and thus can be used to populate and constrain the various reduced-dimensionality chemical spaces that have been put forth as frameworks for describing atmospheric organic chemistry. We apply this general measurement approach both to field data, providing information on ambient organic species, and to laboratory (chamber) studies, providing insight into the chemical transformations that organic species undergo upon atmospheric oxidation.

  18. Quantifying Carbon-Climate Processes at the Regional Scale Using Atmospheric Carbonyl Sulfide

    Energy Technology Data Exchange (ETDEWEB)

    Campbell, Elliott [Univ. of California, Merced, CA (United States); Berry, Joe [Carnegie Inst. of Washington, Washington, DC (United States); Torn, Margaret [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); David, Billesbach [Univ. of Nebraska, Lincoln, NE (United States); Seibt, Ulrike [Univ. of California, Los Angeles, CA (United States)

    2013-10-08

    Atmospheric carbonyl sulfide (COS) analysis has the potentially transformative capability for partitioning the regional carbon flux into respiration and photosynthesis components. This emerging approach is based on the observation that continental atmospheric CO2 gradients are dominated by net ecosystem fluxes while continental atmospheric COS gradients are dominated by photosynthesis-related plant uptake. Regional flux partitioning represents a critical knowledge gap due to a lack of robust methods for regional-scale flux partitioning and large uncertainties in forecasting carbon-climate feedbacks. Our completed project characterized the relationship between COS and CO2 surface fluxes using a novel measurement and modeling system in a winter wheat field at the U.S. Department of Energy?s Atmospheric and Radiation Measurement program Central Facility (DOE-ARM CF). The scope of this project included canopy flux measurements, soil flux measurements, regional atmospheric modeling, and analysis of COS and CO2 airborne observations at SGP. Three critical discoveries emerged from this investigation: (1) the new measurement system provided the first field evidence of a robust relationship between COS leaf fluxes and GPP; (2) a previously unknown seasonal soil source of COS was observed and characterized; (3) the regional atmospheric analysis of airborne measurements provided the first COS-based constraints on GPP parameterizations used in earth systems models. Dissemination of these results includes three publications [Billesbach et al., In Press; Campbell et al., In Preparation; Seibt et al., In Review], three presentations at the AGU Fall Meeting (2012), and four invited presentations to department seminars. We have leveraged this foundational project to continue our work on understanding carbon cycle processes at large scales through one funded project (DOE Lab Fee, 2012-2015) and one proposal that is under review (DOE/NASA/USDA/NOAA, 2014-2016).

  19. A Southern Hemisphere atmospheric history of carbon monoxide from South Pole firn air

    Science.gov (United States)

    Verhulst, K. R.; Aydin, M.; Novelli, P. C.; Holmes, C. D.; Prather, M. J.; Saltzman, E. S.

    2013-12-01

    Carbon monoxide (CO) is a reactive trace gas and is important to tropospheric photochemistry as a major sink of hydroxyl radicals (OH). Major sources of CO are fossil fuel combustion, linked mostly to automotive emissions, biomass burning, and oxidation of atmospheric methane. Understanding changes in carbon monoxide over the past century will improve our understanding of man's influence on the reactivity of the atmosphere. Little observational information is available about CO levels and emissions prior to the 1990s, particularly for the Southern Hemisphere. The NOAA global flask network provides the most complete instrumental record of CO, extending back to 1988. Annually averaged surface flask measurements suggest atmospheric CO levels at South Pole were relatively stable from 2004-2009 at about 51 nmol mol-1 [Novelli and Masarie, 2013]. In this study, a 20th century atmospheric history of CO is reconstructed from South Pole firn air measurements, using a 1-D firn air diffusion model. Firn air samples were collected in glass flasks from two adjacent holes drilled from the surface to 118 m at South Pole, Antarctica during the 2008/2009 field season and CO analysis was carried out by NOAA/CCG. Carbon monoxide levels increase from about 45 nmol mol-1 in the deepest firn sample at 116 m to 52 nmol mol-1 at 107 m, and remain constant at about 51-52 nmol mol-1 at shallower depths. Atmospheric histories based on the firn air reconstructions suggest that CO levels over Antarctica increased by roughly 40% (from about 36 to 50 nmol mol-1) between 1930-1990, at a rate of about 0.18 nmol mol-1 yr-1. Firn air and surface air results suggest the rate of CO increase at South Pole slowed considerably after 1990. The firn air-based atmospheric history is used to infer changes in Southern Hemisphere CO emissions over the 20th century.

  20. Unusual ultra-hydrophilic, porous carbon cuboids for atmospheric-water capture.

    Science.gov (United States)

    Hao, Guang-Ping; Mondin, Giovanni; Zheng, Zhikun; Biemelt, Tim; Klosz, Stefan; Schubel, René; Eychmüller, Alexander; Kaskel, Stefan

    2015-02-02

    There is significant interest in high-performance materials that can directly and efficiently capture water vapor, particularly from air. Herein, we report a class of novel porous carbon cuboids with unusual ultra-hydrophilic properties, over which the synergistic effects between surface heterogeneity and micropore architecture is maximized, leading to the best atmospheric water-capture performance among porous carbons to date, with a water capacity of up to 9.82 mmol g(-1) at P/P0 =0.2 and 25 °C (20% relative humidity or 6000 ppm). Benefiting from properties, such as defined morphology, narrow pore size distribution, and high heterogeneity, this series of functional carbons may serve as model materials for fundamental research on carbon chemistry and the advance of new types of materials for water-vapor capture as well as other applications requiring combined highly hydrophilic surface chemistry, developed hierarchical porosity, and excellent stability.

  1. Heat Exchangers for Condensation and Evaporation Applications Operating in a Low Pressure Atmosphere

    Directory of Open Access Journals (Sweden)

    Petr Kracík

    2012-01-01

    Full Text Available This paper presents a state-of-the-art study of a heat transfer process in liquid spraying heat exchangers placed in a vacuum chamber. The experimental case studied here describes the behavior of a falling film evaporation and condensation mode on horizontal tube bundles. The study aims to obtain the heat transfer coefficient and its correlations by means of a mathematical model.

  2. Impact of nitrogen fertilization on soil–Atmosphere greenhouse gas exchanges in eucalypt plantations with different soil characteristics in southern China

    Science.gov (United States)

    Zhang, Kai; Zheng, Hua; Chen, Falin; Li, Ruida; Yang, Miao; Ouyang, Zhiyun; Lan, Jun; Xiang, Xuewu

    2017-01-01

    Nitrogen (N) fertilization is necessary to sustain productivity in eucalypt plantations, but it can increase the risk of greenhouse gas emissions. However, the response of soil greenhouse gas emissions to N fertilization might be influenced by soil characteristics, which is of great significance for accurately assessing greenhouse gas budgets and scientific fertilization in plantations. We conducted a two-year N fertilization experiment (control [CK], low N [LN], middle N [MN] and high N [HN] fertilization) in two eucalypt plantations with different soil characteristics (higher and lower soil organic carbon sites [HSOC and LSOC]) in Guangxi, China, and assessed soil–atmosphere greenhouse gas exchanges. The annual mean fluxes of soil CO2, CH4, and N2O were separately 153–266 mg m-2 h-1, -55 –-40 μg m-2 h-1, and 11–95 μg m-2 h-1, with CO2 and N2O emissions showing significant seasonal variations. N fertilization significantly increased soil CO2 and N2O emissions and decreased CH4 uptake at both sites. There were significant interactions of N fertilization and SOC level on soil CO2 and N2O emissions. At the LSOC site, the annual mean flux of soil CO2 emission was only significantly higher than the CK treatment in the HN treatment, but, at the HSOC site, the annual mean flux of soil CO2 emission was significantly higher for both the LN (or MN) and HN treatments in comparison to the CK treatment. Under the CK and LN treatments, the annual mean flux of N2O emission was not significantly different between HSOC and LSOC sites, but under the HN treatment, it was significantly higher in the HSOC site than in the LSOC site. Correlation analysis showed that changes in soil CO2 and N2O emissions were significantly related to soil dissolved organic carbon, ammonia, nitrate and pH. Our results suggested significant interactions of N fertilization and soil characteristics existed in soil–atmosphere greenhouse gas exchanges, which should be considered in assessing

  3. Cometary X-rays : solar wind charge exchange in cometary atmospheres

    NARCIS (Netherlands)

    Bodewits, Dennis

    2007-01-01

    The interaction of the solar wind with the planets and the interstellar medium is of key importance for the evolution of our solar system. The interaction with Earth's atmosphere is best known for the northern light. In case of Mars, the interaction with the solar wind might have lead to the erosion

  4. Thermal Analysis of the Decomposition of Ammonium Uranyl Carbonate (AUC) in Different Atmospheres

    DEFF Research Database (Denmark)

    Hälldahl, L.; Sørensen, Ole Toft

    1979-01-01

    The intermediate products formed during thermal decomposition of ammonium uranyl carbonate (AUC) in different atmospheres, (air, helium and hydrogen) have been determined by thermal analysis, (TG, and DTA) and X-ray analysis. The endproducts observed are U3O8 and UO2 in air/He and hydrogen, respe......, respectively. The following intermediate products were observed in all atmospheres: http://www.sciencedirect.com.globalproxy.cvt.dk/cache/MiamiImageURL/B6THV-44K80TV-FB-1/0?wchp=dGLzVlz-zSkWW X-ray diffraction analysis showed that these phases were amorphous....

  5. Carbon allocation changes: an adaptive response to variations in atmospheric CO2

    Science.gov (United States)

    Harrison, Sandy; Li, Guangqi; Prentice, Iain Colin

    2016-04-01

    Given the ubiquity of nutrient constraints on primary production, an optimal carbon allocation strategy is expected to increase total below-ground allocation (fine root production and turnover, allocation to mycorrhizae and carbon exudation to the rhizophere) as atmospheric CO2 concentration increases. Conversely, below-ground allocation should be reduced when atmospheric CO2 concentrations were low, as occurred during glacial times. Using a coupled generic primary production and tree-growth model, we quantify the changes in carbon allocation that are required to explain the apparent homoeostasis of tree radial growth during recent decades and between glacial and interglacial conditions. These results suggest a resolution of the apparent paradox of continuing terrestrial CO2 uptake (a consequence of CO2 fertilization) and the widespread lack of observed enhancement of stem growth in trees. Adaptive shifts in carbon allocation are thus a key feature that should to be accounted for in models to predict tree growth and future timber harvests, as well as in large-scale ecosystem and carbon cycle models.

  6. Formation of oxygen complexes in controlled atmosphere at surface of doped glassy carbon

    Indian Academy of Sciences (India)

    Aleksandra A Perić-Grujić; Tatjana M Vasiljević; Olivera M Nešković; Miomir V Veljković; Zoran V Laušević; Mila D Laušević

    2006-10-01

    The effects of boron and phosphorus incorporation in phenolic resin precursor to the oxidation resistance of glassy carbon have been studied. In order to reveal the nature and composition of the oxygen complexes formed at the surface of doped glassy carbon, under controlled atmosphere, the surface of the samples was cleaned under vacuum up to 1273 K. Specific functional groups, subsequently formed under dry CO2 or O2 atmosphere on the surface of boron-doped and phosphorus-doped glassy carbon samples, were examined using the temperature-programmed desorption method combined with mass spectrometric analysis. Characterization of surface properties of undoped and doped samples has shown that in the presence of either boron or phosphorus heteroatoms, a lower amount of oxygen complexes formed after CO2 exposure, while, typically, higher amount of oxygen complexes formed after O2 exposure. It has been concluded that the surface of undoped glassy carbon has a greater affinity towards CO2, while in the presence of either boron or phosphorus heteroatoms, the glassy carbon surface affinity becomes greater towards O2, under experimental conditions.

  7. Evaluation and Certification of Ambersorb 4652 for use in Activated Carbon Ion Exchange Filters for the International Space Station

    Science.gov (United States)

    Adam, Niklas; Cox, Trey; Larner, Katherine; Carter, Donald; Kouba, Coy

    2017-01-01

    In order to reduce the infiltration of dimethylsilanediol (DMSD) and other organosilicon containing species through the Multifiltration Beds (MF Beds), an alternate activated carbon was found to replace the obsolete Barnabey Cheney 580-26 activated carbon. The carbon that removed the most organosilicon compounds in testing1 was a synthetic activated carbon named Schunk 4652 which later became Ambersorb 4652. Since activated carbon has a large capacity for iodine (I2), and is used in the Activated Carbon Ion Exchange (ACTEX) filters on the International Space Station (ISS), testing was performed on the Ambersorb 4652 carbon to determine the effectiveness of the material for use in ACTEX filters to remove iodine. This work summarizes the testing and the certification of Ambersorb 4652 for use in the ACTEX filters for the ISS.

  8. Atmospheric black carbon deposition and characterization of biomass burning tracers in a northern temperate forest

    Science.gov (United States)

    Santos, F.; Fraser, M. P.; Bird, J. A.

    2014-10-01

    Aerosol black carbon (BC) is considered the second largest contributor to global warming after CO2, and is known to increase the atmosphere's temperature, decrease the albedo in snow/ice, and influence the properties and distribution of clouds. BC is thought to have a long mean residence time in soils, and its apparent stability may represent a significant stable sink for atmospheric CO2. Despite recent efforts to quantify BC in the environment, the quantification of BC deposition rates from the atmosphere to terrestrial ecosystems remains scarse. To better understand the contribution of atmospheric BC inputs to soils via dry deposition and its dominant emission sources, atmospheric fine particle (PM2.5) were collected at the University of Michigan Biological Station from July to September in 2010 and 2011. PM2.5 samples were analyzed for organic C, BC, and molecular markers including particulate sugars, carboxylic acids, n-alkanes, polycyclic aromatic hydrocarbons, and cholestane. Average atmospheric BC concentrations in northern Michigan were 0.048 ± 0.06 μg m-3 in summer 2010, and 0.049 ± 0.064 μg m-3 in summer 2011. Based on atmospheric concentrations, particulate deposition calculations, and documented soil BC, we conclude that atmospheric deposition is unlikely to comprise a significant input pathway for BC in northern forest ecosystem. The major organic tracers identified in fine particulates (e.g. levoglucosan and docosanoic acid) suggest that ambient PM2.5 concentrations were mainly influenced by biomass burning and epicuticular plant waxes. These results provide baseline data needed for future assessments of atmospheric BC in rural temperate forests.

  9. Titration of the Earth: Ocean-Atmosphere Evolution Recorded in Marine Carbonates

    Science.gov (United States)

    Kah, L. C.

    2012-12-01

    The enzymatic production of carbonate biominerals marks a clear association between biological processes and carbonate mineral formation. Prior to the evolution of skeletonizing metazoans, however, biotic activity played a less critical role in the morphological development of carbonate minerals. Instead, carbonate mineral morphology was more strongly affected by abiotic parameters that affect carbonate nucleation and growth. The texture of non-enzymatically controlled carbonate precipitation in the Precambrian may therefore provide us with an additional window through which to observe fundamental changes in the chemical evolution of the global ocean. The Precambrian ocean experienced a progressive evolution from CO2-rich and O2-poor, to CO2-poor and O2-rich. Changes in CO2-availability fundamentally affect marine carbonate saturation state, which is reflected primarily in the rate of crystal growth. By contrast, redox evolution appears to have played a fundamental role in regulating carbonate precipitation via the differential inhibition of mineral nucleation. Carbonate mineral textures that indicate differential nucleation and growth can be traced both spatially and temporally in the Precambrian sedimentary record. Textures that are dominated by high rates of growth relative to nucleation are common in Archean, and become progressively restricted in their distribution by the latter Proterozoic. Spatial restriction, particularly of fabrics associated with redox-controlled nucleation, suggesting the development of chemically discrete oceanic environments. Such observations are consistent with recent models of suggesting that ocean oxygenation occurred in a top-down fashion, with well-oxygenated surface waters underlain by either anoxic deep-waters or oxygen-depleted substrate pore-waters. Deciphering relationships among these environments permits attribution of carbonate fabrics to specific geochemical conditions within the water column and provides critical

  10. Direct synthesis of multilayer graphene on an insulator by Ni-induced layer exchange growth of amorphous carbon

    Science.gov (United States)

    Murata, H.; Toko, K.; Saitoh, N.; Yoshizawa, N.; Suemasu, T.

    2017-01-01

    Multilayer graphene (MLG) growth on arbitrary substrates is desired for incorporating carbon wiring and heat spreaders into electronic devices. We investigated the metal-induced layer exchange growth of a sputtered amorphous C layer using Ni as a catalyst. A MLG layer uniformly formed on a SiO2 substrate at 600 °C by layer exchange between the C and Ni layers. Raman spectroscopy and electron microscopy showed that the resulting MLG layer was highly oriented and contained relatively few defects. The present investigation will pave the way for advanced electronic devices integrated with carbon materials.

  11. Net ecosystem carbon exchange in three contrasting Mediterranean ecosystems – the effect of drought

    Directory of Open Access Journals (Sweden)

    T. S. David

    2007-09-01

    Full Text Available Droughts reduce gross primary production (GPP and ecosystem respiration (Reco, contributing to most of the inter-annual variability in terrestrial carbon sequestration. In seasonally dry climates (Mediterranean, droughts result from reductions in annual rainfall and changes in rain seasonality. We compared carbon fluxes measured by the eddy covariance technique in three contrasting ecosystems in southern Portugal: an evergreen oak woodland (savannah-like with ca.~21% tree crown cover, a grassland dominated by herbaceous annuals and a coppiced short-rotation eucalyptus plantation. During the experimental period (2003–2006 the eucalyptus plantation was always the strongest sink for carbon: net ecosystem exchange rate (NEE between −861 and −399 g C m−2 year−1. The oak woodland and the grassland were much weaker sinks for carbon: NEE varied in the oak woodland between −140 and −28 g C m−2 year−1 and in the grassland between −190 and +49 g C m−2 year−1. The eucalyptus stand had higher GPP and a lower proportion of GPP spent in respiration than the other systems. The higher GPP resulted from high leaf area duration (LAD, as a surrogate for the photosynthetic photon flux density absorbed by the canopy. The eucalyptus had also higher rain use efficiency (GPP per unit of rain volume and light use efficiency (the daily GPP per unit incident photosynthetic photon flux density than the other two ecosystems. The effects of a severe drought could be evaluated during the hydrological-year (i.e., from October to September of 2004–2005. Between October 2004 and June 2005 the precipitation was only 40% of the long-term average. In 2004–2005 all ecosystems had GPP lower than in wetter years and carbon sequestration was strongly restricted (less negative NEE. The grassland was a net source of carbon dioxide (+49 g C m−2 year−1. In the oak woodland a large proportion of GPP resulted from carbon assimilated by its annual vegetation

  12. Carbon isotope evidence implying high O2/CO2 ratios in the Permo-Carboniferous atmosphere

    Science.gov (United States)

    Beerling, D. J.; Lake, J. A.; Berner, R. A.; Hickey, L. J.; Taylor, D. W.; Royer, D. L.

    2002-11-01

    Theoretical models predict a marked increase in atmospheric O2 to ∼35% during the Permo-Carboniferous (∼300 Ma) occurring against a low (∼0.03%) CO2 level. An upper O2 value of 35%, however, remains disputed because ignition data indicate that excessive global forest fires would have ensued. This uncertainty limits interpretation of the role played by atmospheric oxygen in Late Paleozoic biotic evolution. Here, we describe new results from laboratory experiments with vascular land plants that establish that a rise in O2 to 35% increases isotopic fractionation (Δ13C) during growth relative to control plants grown at 21% O2. Despite some effect of the background atmospheric CO2 level on the magnitude of the increase, we hypothesize that a substantial Permo-Carboniferous rise in O2 could have imprinted a detectable geochemical signature in the plant fossil record. Over 50 carbon isotope measurements on intact carbon from four fossil plant clades with differing physiological ecologies and ranging in age from Devonian to Cretaceous reveal a substantial Δ13C anomaly (5‰) occurring between 300 and 250 Ma. The timing and direction of the Δ13C excursion is consistent with the effects of a high O2 atmosphere on plants, as predicted from photosynthetic theory and observed in our experiments. Preliminary calibration of the fossil Δ13C record against experimental data yields a predicted O2/CO2 mixing ratio of the ancient atmosphere consistent with that calculated from long-term models of the global carbon and oxygen cycles. We conclude that further work on the effects of O2 in the combustion of plant materials and the spread of wildfire is necessary before existing data can be used to reliably set the upper limit for paleo-O2 levels.

  13. Productivity and carbon dioxide exchange of leguminous crops: estimates from flux tower measurements

    Science.gov (United States)

    Gilmanov, Tagir G.; Baker, John M.; Bernacchi, Carl J.; Billesbach, David P.; Burba, George G.; Castro, Saulo; Chen, Jiquan; Eugster, Werner; Fischer, Marc L.; Gamon, John A.; Gebremedhin, Maheteme T.; Glenn, Aaron J.; Griffis, Timothy J.; Hatfield, Jerry L.; Heuer, Mark W.; Howard, Daniel M.; Leclerc, Monique Y.; Loescher, Henry W.; Marloie, Oliver; Meyers, Tilden P.; Olioso, Albert; Phillips, Rebecca L.; Prueger, John H.; Skinner, R. Howard; Suyker, Andrew E.; Tenuta, Mario; Wylie, Bruce K.

    2014-01-01

    Net CO2 exchange data of legume crops at 17 flux tower sites in North America and three sites in Europe representing 29 site-years of measurements were partitioned into gross photosynthesis and ecosystem respiration by using the nonrectangular hyperbolic light-response function method. The analyses produced net CO2 exchange data and new ecosystem-scale ecophysiological parameter estimates for legume crops determined at diurnal and weekly time steps. Dynamics and annual totals of gross photosynthesis, ecosystem respiration, and net ecosystem production were calculated by gap filling with multivariate nonlinear regression. Comparison with the data from grain crops obtained with the same method demonstrated that CO2 exchange rates and ecophysiological parameters of legumes were lower than those of maize (Zea mays L.) but higher than for wheat (Triticum aestivum L.) crops. Year-round annual legume crops demonstrated a broad range of net ecosystem production, from sinks of 760 g CO2 m–2 yr–1 to sources of –2100 g CO2 m–2 yr–1, with an average of –330 g CO2 m–2 yr–1, indicating overall moderate CO2–source activity related to a shorter period of photosynthetic uptake and metabolic costs of N2 fixation. Perennial legumes (alfalfa, Medicago sativa L.) were strong sinks for atmospheric CO2, with an average net ecosystem production of 980 (range 550–1200) g CO2 m–2 yr–1.

  14. A new chemical scheme to study carbon-rich exoplanet atmospheres

    CERN Document Server

    Venot, Olivia; Agúndez, Marcelino; Decin, Leen; Bounaceur, Roda

    2015-01-01

    Atmospheres with a high C/O ratio are expected to contain an important quantity of hydrocarbons, including heavy molecules (with more than 2 carbon atoms). To study correctly these C-rich atmospheres, a chemical scheme adapted to this composition is necessary. We have implemented a chemical scheme that can describe the kinetics of species with up to 6 carbon atoms. This chemical scheme has been developed with specialists of combustion and validated through experiments on a wide range of T and P. This chemical network is available on the online database KIDA. We have created a grid of 12 models to explore different thermal profiles and C/O ratios. For each of them, we have compared the chemical composition determined with a C0-C2 chemical scheme (species with up to 2 carbon atoms) and with the C0-C6 scheme. We found no difference in the results obtained with the two schemes when photolyses are not included in the model, whatever the temperature of the atmosphere. In contrast, when there is photochemistry, diff...

  15. Chemical and toxicological evolution of carbon nanotubes during atmospherically relevant aging processes.

    Science.gov (United States)

    Liu, Yongchun; Liggio, John; Li, Shao-Meng; Breznan, Dalibor; Vincent, Renaud; Thomson, Errol M; Kumarathasan, Premkumari; Das, Dharani; Abbatt, Jonathan; Antiñolo, María; Russell, Lynn

    2015-03-03

    The toxicity of carbon nanotubes (CNTs) has received significant attention due to their usage in a wide range of commercial applications. While numerous studies exist on their impacts in water and soil ecosystems, there is a lack of information on the exposure to CNTs from the atmosphere. The transformation of CNTs in the atmosphere, resulting in their functionalization, may significantly alter their toxicity. In the current study, the chemical modification of single wall carbon nanotubes (SWCNTs) via ozone and OH radical oxidation is investigated through studies that simulate a range of expected tropospheric particulate matter (PM) lifetimes, in order to link their chemical evolution to toxicological changes. The results indicate that the oxidation favors carboxylic acid functionalization, but significantly less than other studies performed under nonatmospheric conditions. Despite evidence of functionalization, neither O3 nor OH radical oxidation resulted in a change in redox activity (potentially giving rise to oxidative stress) or in cytotoxic end points. Conversely, both the redox activity and cytotoxicity of SWCNTs significantly decreased when exposed to ambient urban air, likely due to the adsorption of organic carbon vapors. These results suggest that the effect of gas-particle partitioning of organics in the atmosphere on the toxicity of SWCNTs should be investigated further.

  16. Plants, Weathering, and the Evolution of Atmospheric Carbon Dioxide and Oxygen

    Energy Technology Data Exchange (ETDEWEB)

    Berner, Robert A

    2008-02-05

    Over the past six years we have published 24 papers that can be divided into three sections: (1) Study of plants and weathering, (2) modeling the evolution of atmospheric CO2 over Phanerozoic time (past 550 million years). (3) Modeling of atmospheric O2 over Phanerozoic time. References to papers published acknowledging this grant can be found at the end of this report and almost all are supplied in pdf form. (1) In the temperate forests of the Cascade Mountains, USA, calcium and magnesium meet vastly different fates beneath angiosperms vs gymnosperms. Calcium is leached beneath both groves of trees, but leached 20-40% more beneath the angiosperms. Magnesium is retained in the forest system beneath the angiosperms and leached from beneath the gymnosperms. (2) We have shown that climate and CO2, based on both carbon cycle modeling and hundreds of independent proxies for paleo-CO2, correlate very well over the past 550 million year. In a recent paper we use this correlation to deduce the sensitivity of global mean temperature to a doubling of atmospheric CO2, and results are in excellent agreement with the results of climatologists based on the historical record and on theoretical climate models (GCM’s).(3) We have shown that concentrations of atmospheric oxygen, calculated by a combined carbon-sulfur cycle model, over the past 550 million years have varied with and influenced biological evolution.

  17. Chitosan/silica coated carbon nanotubes composite proton exchange membranes for fuel cell applications.

    Science.gov (United States)

    Liu, Hai; Gong, Chunli; Wang, Jie; Liu, Xiaoyan; Liu, Huanli; Cheng, Fan; Wang, Guangjin; Zheng, Genwen; Qin, Caiqin; Wen, Sheng

    2016-01-20

    Silica-coated carbon nanotubes (SCNTs), which were obtained by a simple sol-gel method, were utilized in preparation of chitosan/SCNTs (CS/SCNTs) composite membranes. The thermal and oxidative stability, morphology, mechanical properties, water uptake and proton conductivity of CS/SCNTs composite membranes were investigated. The insulated and hydrophilic silica layer coated on CNTs eliminates the risk of electronic short-circuiting and enhances the interaction between SCNTs and chitosan to ensure the homogenous dispersion of SCNTs, although the water uptake of CS/SCNTs membranes is reduced owing to the decrease of the effective number of the amino functional groups of chitosan. The CS/SCNTs composite membranes are superior to the pure CS membrane in thermal and oxidative stability, mechanical properties and proton conductivity. The results of this study suggest that CS/SCNTs composite membranes exhibit promising potential for practical application in proton exchange membranes.

  18. Effect of an Internal Heat Exchanger on Performance of the Transcritical Carbon Dioxide Refrigeration Cycle with an Expander

    OpenAIRE

    Zhenying Zhang; Lili Tian; Yanhua Chen; Lirui Tong

    2014-01-01

    The effect of the internal heat exchanger (IHE) on the performance of the transcritical carbon dioxide refrigeration cycle with an expander is analyzed theoretically on the basis of the first and second laws of thermodynamics. The possible parameters affecting system efficiency such as heat rejection pressure, gas cooler outlet temperature, evaporating temperature, expander isentropic efficiency and IHE effectiveness are investigated. It is found that the IHE addition in the carbon dioxide re...

  19. Dynamics of Carbon Dioxide Exchange and Transport: The First Year of OCO-2 Observations

    Science.gov (United States)

    Wennberg, P. O.; Wunch, D.; O'Dell, C.; Frankenberg, C.; Fisher, B.; Mandrake, L.; Osterman, G. B.; Eldering, A.; Crisp, D.; Gunson, M. R.

    2015-12-01

    We describe observed gradients in space and time in the total column measurements of carbon dioxide (XCO2) during the first year of the OCO-2 mission.Writing this abstract in July, we make several predictions that will be tested in the coming months (in order to bat at least 0.500 while mixing metaphors we include some slam dunks): 1) Global XCO2 in Oct/Nov 2015 is larger than XCO2 in Oct/Nov 2014; 2) Averaged over the year, XCO2 in the Northern Hemisphere is greater than XCO2 in the Southern Hemisphere; 3) The increase in global atmospheric carbon dioxide during 2014/15 will be the largest on record due to a combination of increased fossil emissions and the intensifying El Nino [e.g. Wang et al., PNAS, 110, 13061, 2013]; 4) Summertime drawdown in Northern Hemisphere carbon dioxide will be muted compared with past years due to enhanced transport from the subtropics and enhanced respiration in the Boreal forest associated with anomalously warm surface temperatures at high latitudes in summer 2015 [e.g. Wunch et al., ACP, 13, 9447, 2012].

  20. A Comparison of Process-Scale Modeling and Measurements of Atmosphere-Snowpack Exchange of Nitrogen Oxides at Summit, Greenland

    Science.gov (United States)

    Murray, K. A.; Helmig, D.; Kramer, L. J.; Doskey, P. V.; Van Dam, B. A.; Seok, B.; Ganzeveld, L.

    2015-12-01

    Snowpack over glacial ice is a reservoir for reactive nitrogen gases. Previous studies indicate nitrogen oxides (NOx) are generated in snowpack interstitial air through photolysis of nitrate (NO3-). Gradients in NOx mixing ratios between snowpack interstitial air and the overlying atmosphere regulate NOx surface exchange, which affects the Arctic ozone budget and climate. To better understand the dynamics of cryosphere-atmosphere exchange of NOx in the Arctic, we use a 1-D process-scale model to evaluate measurements of NOxin and above the snowpack during March-May 2009 at Summit, Greenland. The model is based upon the processes previously presented in the snowpack chemistry and physics model, MISTRA-SNOW, which represents snow grains as spheres with surfaces uniformly coated by an aqueous phase. Modeled profiles of NO, NO2, and O3 up to ~ 2 meters deep into the snowpack for March-May 2009 have been compared to measured profiles and will be presented. During the March-May time period at Summit, low irradiances are observed during March, diurnal irradiance profiles are observed during April, and the sun never sets in May. The model results suggest a key chemical pathway for the formation of NO2 during "nighttime" that was previously unexplained. In addition, modeled 24-hour NOx fluxes are compared to measured NOx fluxes from a MET tower at Summit. Modeled fluxes of NOx in April 2009 are the same order of magnitude as the measurements; however, modeled fluxes of NOx deviate up to one order of magnitude from measurements in May 2009. A detailed analysis of the modeled/measured flux comparison will be presented.

  1. Study on elution ability of salicylic acid on ion exchange resins in supercritical carbon dioxide

    Institute of Scientific and Technical Information of China (English)

    Ping YUAN; Jianguo CAI; Junjie GONG; Xiu DENG

    2009-01-01

    The elution ability of salicylic acid on ion exchange resins in supercritical carbon dioxide has been studied. Some factors influencing elution recovery,including entrainer, temperature, pressure and the flow rate of supercritical fluid CO2 are discussed in this work.The addition of a small amount of entrainer, such as ethanol, triethanolamine and their mixture to supercritical CO2 can cause dramatic effects on the elution ability. The results show that the salicylic acid can be only slightly eluted from the resin with supercritical CO2 alone with temperatures ranging from 307.15 to 323.15K and pressures ranging from 10 to 30MPa. Meanwhile, with the same T, P conditions, 40.58% and 73.08% salicylic acid can be eluted from the ion exchange resin with ethanol and ethanol + triethanolamine as the entrainer, respec-tively. An improved PR equation of state with VDWl mixing rules is used to calculate the elution recovery of salicylic acid in supercritical CO2 and the results agree well with the experimental data.

  2. Dynamics of carbon-hydrogen and carbon-methyl exchanges in the collision of 3P atomic carbon with propene

    Science.gov (United States)

    Lee, Shih-Huang; Chen, Wei-Kan; Chin, Chih-Hao; Huang, Wen-Jian

    2013-11-01

    We investigated the dynamics of the reaction of 3P atomic carbon with propene (C3H6) at reactant collision energy 3.8 kcal mol-1 in a crossed molecular-beam apparatus using synchrotron vacuum-ultraviolet ionization. Products C4H5, C4H4, C3H3, and CH3 were observed and attributed to exit channels C4H5 + H, C4H4 + 2H, and C3H3 + CH3; their translational-energy distributions and angular distributions were derived from the measurements of product time-of-flight spectra. Following the addition of a 3P carbon atom to the C=C bond of propene, cyclic complex c-H2C(C)CHCH3 undergoes two separate stereoisomerization mechanisms to form intermediates E- and Z-H2CCCHCH3. Both the isomers of H2CCCHCH3 in turns decompose to C4H5 + H and C3H3 + CH3. A portion of C4H5 that has enough internal energy further decomposes to C4H4 + H. The three exit channels C4H5 + H, C4H4 + 2H, and C3H3 + CH3 have average translational energy releases 13.5, 3.2, and 15.2 kcal mol-1, respectively, corresponding to fractions 0.26, 0.41, and 0.26 of available energy deposited to the translational degrees of freedom. The H-loss and 2H-loss channels have nearly isotropic angular distributions with a slight preference at the forward direction particularly for the 2H-loss channel. In contrast, the CH3-loss channel has a forward and backward peaked angular distribution with an enhancement at the forward direction. Comparisons with reactions of 3P carbon atoms with ethene, vinyl fluoride, and vinyl chloride are stated.

  3. Hot Oxygen and Carbon Escape from the Early Atmosphere of Mars

    Science.gov (United States)

    Amerstorfer, U.; Gröller, H.; Lichtenegger, H.; Lammer, H.; Tian, F.

    2015-12-01

    Nowadays, the atmosphere of Mars is commonly assumed to be much different than in the early times of its evolution. Especially, the escape of water and carbon dioxide is thought to have formed its shape during millions of years. Also the Sun emitted a higher EUV flux in former times, influencing the particle environment around Mars.We study the escape of oxygen and carbon from the early Martian atmosphere for different EUV fluxes with a Monte-Carlo model. We consider different possible sources of hot oxygen and carbon atoms in the thermosphere, e.g. dissociative recombination of O2+ , CO+ and CO2+ , photodissociation of O2 and CO, and other reactions like charge transfer. From the calculated production rate profiles we can get insights into the importance of the different source reactions. The resulting energy distribution functions at the exobase level are used to study the exospheric densities and the escape of hot oxygen and carbon. We discuss the escape rates of those atoms and the importance of different source processes compared to the present situation at Mars.This work receives funding from the Austrian Science Fund (FWF): P 24247.

  4. Carbon Flux to the Atmosphere from Land-Use Changes: 1850 to 1990

    Energy Technology Data Exchange (ETDEWEB)

    Houghton, R.A.

    2001-02-22

    The database documented in this numeric data package, a revision to a database originally published by the Carbon Dioxide Information Analysis Center (CDIAC) in 1995, consists of annual estimates, from 1850 through 1990, of the net flux of carbon between terrestrial ecosystems and the atmosphere resulting from deliberate changes in land cover and land use, especially forest clearing for agriculture and the harvest of wood for wood products or energy. The data are provided on a year-by-year basis for nine regions (North America, South and Central America, Europe, North Africa and the Middle East, Tropical Africa, the Former Soviet Union, China, South and Southeast Asia, and the Pacific Developed Region) and the globe. Some data begin earlier than 1850 (e.g., for six regions, areas of different ecosystems are provided for the year 1700) or extend beyond 1990 (e.g., fuelwood harvest in South and Southeast Asia, by forest type, is provided through 1995). The global net flux during the period 1850 to 1990 was 124 Pg of carbon (1 petagram = 10{sup 15} grams). During this period, the greatest regional flux was from South and Southeast Asia (39 Pg of carbon), while the smallest regional flux was from North Africa and the Middle East (3 Pg of carbon). For the year 1990, the global total net flux was estimated to be 2.1 Pg of carbon.

  5. Surface Energy in Nanocrystalline Carbon Thin Films: Effect of Size Dependence and Atmospheric Exposure.

    Science.gov (United States)

    Kumar, Manish; Javid, Amjed; Han, Jeon Geon

    2017-03-14

    Surface energy (SE) is the most sensitive and fundamental parameter for governing the interfacial interactions in nanoscale carbon materials. However, on account of the complexities involved of hybridization states and surface bonds, achieved SE values are often less in comparison with their theoretical counterparts and strongly influenced by stability aspects. Here, an advanced facing-target pulsed dc unbalanced magnetron-sputtering process is presented for the synthesis of undoped and H/N-doped nanocrystalline carbon thin films. The time-dependent surface properties of the undoped and H/N-doped nanocrystalline carbon thin films are systematically studied. The advanced plasma process induced the dominant deposition of high-energy neutral carbon species, consequently controlling the intercolumnar spacing of nanodomain morphology and surface anisotropy of electron density. As a result, significantly higher SE values (maximum = 79.24 mJ/m(2)) are achieved, with a possible window of 79.24-66.5 mJ/m(2) by controlling the experimental conditions. The intrinsic (size effects and functionality) and extrinsic factors (atmospheric exposure) are resolved and explained on the basis of size-dependent cohesive energy model and long-range van der Waals interactions between hydrocarbon molecules and the carbon surface. The findings anticipate the enhanced functionality of nanocrystalline carbon thin films in terms of selectivity, sensitivity, and stability.

  6. Purification of Single Wall Carbon Nanotubes as a Function of UV Wavelength, Atmosphere, and Temperature

    Energy Technology Data Exchange (ETDEWEB)

    Kurst, K. E.; Dillon, A. C.; Yang, S.; Lehman, J. H.

    2008-01-01

    We investigate the purification of as-prepared single wall carbon nanotubes (SWCNTs) by exposure to pulsed 193 and 248 nm laser light, as well as lamp wavelengths of 254 and 185 nm. Raman spectroscopy before and after laser exposure indicates the removal of non-nanotube material without modification of the distribution of tube diameter for material exposed to a 248 nm laser, while 193 nm laser light does not selectively oxidize carbon impurities. The mechanism of purification is further considered in the context of atmosphere (oxygen, ozone, nitrogen or partial vacuum) and temperature (measured average and calculated maximum). A mathematical model for pulsed laser heating is used to estimate the maximum temperature achieved during laser excitation. We attribute the purification of nanotube samples to photophysical interactions of the pulsed 248 nm photons in resonance with sp{sup 2} carbon.

  7. Qualification of Sub-Atmospheric Pressure Sensors for the Cryomagnet Bayonet Heat Exchangers of the Large Hadron Collider

    Science.gov (United States)

    Bager, T.; Casas-Cubillos, J.; Jeanmonod, N.

    2006-04-01

    The superconducting magnets of the Large Hadron Collider (LHC) will be cooled at 1.9 K by distributed cooling loops working with saturated two-phase superfluid helium flowing in 107 m long bayonet heat exchangers located in each magnet cold-mass cell. The temperature of the magnets could be difficult to control because of the large dynamic heat load variations. Therefore, it is foreseen to measure the heat exchangers pressure to feed the regulation loops with the corresponding saturation temperature. The required uncertainty of the sub-atmospheric saturation pressure measurement shall be of the same order of the one associated to the magnet thermometers, in pressure it translates as ±5 Pa at 1.6 kPa. The transducers shall be radiation hard as they will endure, in the worst case, doses up to 10 kGy and 1015 neutronsṡcm-2 over 10 years. The sensors under evaluation were installed underground in the dump section of the SPS accelerator with a radiation environment close to the one expected for the LHC. The monitoring equipment was installed in a remote radiation protected area. This paper presents the results of the radiation qualification campaign with emphasis on the reliability and accuracy of the pressure sensors under the test conditions.

  8. Qualification of Sub-atmospheric Pressure Sensors for the Cryomagnet Bayonet Heat Exchangers of the Large Hadron Collider

    CERN Document Server

    Jeanmonod, N; Casas-Cubillos, J

    2006-01-01

    The superconducting magnets of the Large Hadron Collider (LHC) will be cooled at 1.9 K by distributed cooling loops working with saturated two-phase superfluid helium flowing in 107 m long bayonet heat exchangers [1] located in each magnet cold-mass cell. The temperature of the magnets could be difficult to control because of the large dynamic heat load variations. Therefore, it is foreseen to measure the heat exchangers pressure to feed the regulation loops with the corresponding saturation temperature. The required uncertainty of the sub-atmospheric saturation pressure measurement shall be of the same order of the one associated to the magnet thermometers, in pressure it translates as ±5 Pa at 1.6 kPa. The transducers shall be radiation hard as they will endure, in the worst case, doses up to 10 kGy and 10**15 neutrons·cm**-2 over 10 years. The sensors under evaluation were installed underground in the dump section of the SPS accelerator with a radiation environment close to the one expected for the L...

  9. CO2 exchange and Carbon balance in two grassland sites on eutrophic drained peat soils

    Directory of Open Access Journals (Sweden)

    F. Möller

    2007-05-01

    Full Text Available In this study we investigated the role of intensive and extensive dairy farm practices on CO2 exchange and the carbon balance of peatlands by means of eddy covariance (EC measurements. Year long EC measurements were made in two adjacent farm sites on peat soil in the western part of the Netherlands. One site (Stein is a new meadow bird reserve and is managed predominantly by mowing in June and August. The second site (Oukoop is an intensive dairy farm. Minimum ecosystem flux of the grass sward (range −2 to −34 μmol CO2 m−2 s−1 showed a close and similar linear relationship with Leaf Area Index (LAI; range 1 to 5 except in maturing hay meadows, where minimum ecosystem flux did not decrease further. Apparent quantum yield varied between −0.02 and −0.08 (mean −0.045 μmol CO2 μmol−1 photons at both sites and was significantly correlated with LAI during the growth season. Ecosystem Respiration at 10°C (R10 calculated from the year round data set was 3.47 μmol CO2 m−2 s−1 at Stein and 3.64 μmol CO2 m−2 s−1 at Oukoop. Both sites were a source of carbon in winter and a sink during summer, with net ecosystem exchange varying between 50 to 100 mmol CO2m−2 d−1 in winter to below −400 mmol CO2 m−2 d−1 in summer. Periodically both sites became a source after mowing. Net annual ecosystem exchange (NEE for Stein was −8.4 g C m−2 a−1 and for Oukoop 122.4 g C m−2 a−1, the difference between the sites was mainly due a difference in GEP (101 g C m−2 a−1. However when biomass removal, manure applications and estimates of methane emissions are taken into account, both eutrophic peat meadows are a strong source for C ((462 g C m−2 a−1 and 465 g C m−2 a−1 at Stein and Oukoop, respectively.

  10. A methodology for estimating seasonal cycles of atmospheric CO2 resulting from terrestrial net ecosystem exchange (NEE fluxes using the Transcom T3L2 pulse-response functions

    Directory of Open Access Journals (Sweden)

    K. R. Gurney

    2012-09-01

    Full Text Available We present a method for translating modeled terrestrial net ecosystem exchange (NEE fluxes of carbon into the corresponding seasonal cycles in atmospheric CO2. The method is based on the pulse-response functions from the Transcom 3 Level 2 (T3L2 atmospheric tracer transport model (ATM intercomparison. The new pulse-response method is considerably faster than a full forward ATM simulation, allowing CO2 seasonal cycles to be computed in seconds, rather than the days or weeks required for a forward simulation. Further, the results provide an estimate of the range of transport uncertainty across 13 different ATMs associated with the translation of surface NEE fluxes into an atmospheric signal. We evaluate the method against the results of archived forward ATM simulations from T3L2. The latter are also used to estimate the uncertainties associated with oceanic and fossil fuel influences. We present a regional breakdown at selected monitoring sites of the contribution to the atmospheric CO2 cycle from the 11 different T3L2 land regions. A test case of the pulse-response code, forced by NEE fluxes from the Community Land Model, suggests that for many terrestrial models, discrepancies between model results and observed atmospheric CO2 cycles will be large enough to clearly transcend ATM uncertainties.

  11. Scanning imaging absorption spectrometer for atmospheric chartography carbon monoxide total columns: statistical evaluation and comparison with chemistry transport model results

    NARCIS (Netherlands)

    de Laat, A.T.J.; Gloudemans, A.M.S.; Aben, I.; Krol, M.C.; Meirink, J.F.; van der Werf, G.R.; Schrijver, H.

    2007-01-01

    This paper presents a detailed statistical analysis of one year (September 2003 to August 2004) of global Scanning Imaging Absorption Spectrometer for Atmospheric Chartography (SCIAMACHY) carbon monoxide (CO) total column retrievals from the Iterative Maximum Likelihood Method (IMLM) algorithm, vers

  12. Scanning Imaging Absorption Spectrometer for Atmospheric Chartography carbon monoxide total columns: Statistical evaluation and comparison with chemistry transport model results

    NARCIS (Netherlands)

    Laat, de A.T.J.; Gloudemans, A.M.S.; Aben, I.; Krol, M.C.; Meirink, J.F.; Werf, van der G.R.; Schrijver, H.

    2007-01-01

    This paper presents a detailed statistical analysis of one year (September 2003 to August 2004) of global Scanning Imaging Absorption Spectrometer for Atmospheric Chartography (SCIAMACHY) carbon monoxide (CO) total column retrievals from the Iterative Maximum Likelihood Method (IMLM) algorithm, vers

  13. Atmospheric deposition of inorganic nitrogen in Spanish forests of Quercus ilex measured with ion-exchange resins and conventional collectors.

    Science.gov (United States)

    García-Gomez, Héctor; Izquieta-Rojano, Sheila; Aguillaume, Laura; González-Fernández, Ignacio; Valiño, Fernando; Elustondo, David; Santamaría, Jesús M; Àvila, Anna; Fenn, Mark E; Alonso, Rocío

    2016-09-01

    Atmospheric nitrogen deposition is one of the main threats for biodiversity and ecosystem functioning. Measurement techniques like ion-exchange resin collectors (IECs), which are less expensive and time-consuming than conventional methods, are gaining relevance in the study of atmospheric deposition and are recommended to expand monitoring networks. In the present work, bulk and throughfall deposition of inorganic nitrogen were monitored in three different holm oak forests in Spain during two years. The results obtained with IECs were contrasted with a conventional technique using bottle collectors and with a literature review of similar studies. The performance of IECs in comparison with the conventional method was good for measuring bulk deposition of nitrate and acceptable for ammonium and total dissolved inorganic nitrogen. Mean annual bulk deposition of inorganic nitrogen ranged 3.09-5.43 kg N ha(-1) according to IEC methodology, and 2.42-6.83 kg N ha(-1) y(-1) using the conventional method. Intra-annual variability of the net throughfall deposition of nitrogen measured with the conventional method revealed the existence of input pulses of nitrogen into the forest soil after dry periods, presumably originated from the washing of dry deposition accumulated in the canopy. Important methodological recommendations on the IEC method and discussed, compiled and summarized.

  14. Chromium Isotopes in Carbonate Rocks: New Insights into Proterozoic Atmospheric Oxygenation

    Science.gov (United States)

    Kah, L. C.; Gilleaudeau, G. J.; Frei, R.; Kaufman, A. J.; Azmy, K.; Bartley, J. K.; Chernyavskiy, P.; Knoll, A. H.

    2015-12-01

    There has been a long-standing debate in geobiology about the role that Earth's oxygenation played in the evolution of complex life. Temporal linkages exist between the Great Oxidation Event (GOE) and the evolution of eukaryotes, as well as Neoproterozoic rise in oxygen and the diversification of metazoans. Further advances have been hampered, however, by the lack of direct proxies that mark specific levels of atmospheric pO2 in the geologic past. Chromium (Cr) isotopes show promise in this regard because the oxidation of Cr during terrestrial weathering—which results in isotopic fractionation—is dependent on a specific threshold of atmospheric pO2 (0.1-1% of the present atmospheric level [PAL]). This threshold value broadly coincides with recent estimates of the oxygen requirements of early animals. Here we report new Cr-isotope data from four late Mesoproterozoic carbonate-dominated successions. Samples were collected from the Turukhansk Uplift (Siberia), the El Mreiti Group (Mauritania), the Vazante Group (Brazil), and the Angmaat Formation (Canada). We emphasize the application of Cr-isotopes to carbonate rocks because the broad temporal range of this lithology in the geologic record provides an opportunity to significantly expand our understanding of Proterozoic oxygenation on shorter time scales. Our data indicate that pO2 levels required to support early animals were attained long before Neoproterozoic metazoan diversification, although the large degree of isotopic heterogeneity in our dataset may indicate that pO2 > 0.1-1% PAL was only a transient phenomenon in the Mesoproterozoic. This study demonstrates the utility of Cr-isotopes as an atmospheric redox proxy in carbonate rocks and helps inform future avenues of research on Proterozoic pO2 thresholds.

  15. Carbon Observations from Geostationary Earth Orbit as Part of an Integrated Observing System for Atmospheric Composition

    Science.gov (United States)

    Edwards, D. P.

    2015-12-01

    This presentation describes proposed satellite carbon measurements from the CHRONOS mission. The primary goal of this experiment is to measure the atmospheric pollutants carbon monoxide (CO) and methane (CH4) from geostationary orbit, with hourly observations of North America at high spatial resolution. CHRONOS observations would provide measurements not currently available or planned as part of a surface, suborbital and satellite integrated observing system for atmospheric composition over North America. Carbon monoxide is produced by combustion processes such as urban activity and wildfires, and serves as a proxy for other combustion pollutants that are not easily measured. Methane has diverse anthropogenic sources ranging from fossil fuel production, animal husbandry, agriculture and waste management. The impact of gas exploration in the Western States of the USA and oil extraction from the Canadian tar sands will be particular foci of the mission, as will the poorly-quantified natural CH4 emissions from wetlands and thawing permafrost. In addition to characterizing pollutant sources, improved understanding of the domestic CH4 budget is a priority for policy decisions related to short-lived climate forcers. A primary motivation for targeting CO is its value as a tracer of atmospheric pollution, and CHRONOS measurements will provide insight into local and long-range transport across the North American continent, as well as the processes governing the entrainment and venting of pollution in and out of the planetary boundary layer. As a result of significantly improved characterization of diurnal changes in atmospheric composition, CHRONOS observations will find direct societal applications for air quality regulation and forecasting. We present a quantification of this expected improvement in the prediction of near-surface concentrations when CHRONOS measurements are used in Observation System Simulation Experiments (OSSEs). If CHRONOS and the planned NASA Earth

  16. 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.

  17. Erythrocyte-like hollow carbon capsules and their application in proton exchange membrane fuel cells.

    Science.gov (United States)

    Kim, Jung Ho; Yu, Jong-Sung

    2010-12-14

    Hierarchical nanostructured erythrocyte-like hollow carbon (EHC) with a hollow hemispherical macroporous core of ca. 230 nm in diameter and 30-40 nm thick mesoporous shell was synthesized and explored as a cathode catalyst support in a proton exchange membrane fuel cell (PEMFC). The morphology control of EHC was successfully achieved using solid core/mesoporous shell (SCMS) silica template and different styrene/furfuryl alcohol mixture compositions by a nanocasting method. The EHC-supported Pt (20 wt%) cathodes prepared have demonstrated markedly enhanced catalytic activity towards oxygen reduction reactions (ORRs) and greatly improved PEMFC polarization performance compared to carbon black Vulcan XC-72 (VC)-supported ones, probably due to the superb structural characteristics of the EHC such as uniform size, well-developed porosity, large specific surface area and pore volume. In particular, Pt/EHC cathodes exhibited ca. 30-60% higher ORR activity than a commercial Johnson Matthey Pt catalyst at a low catalyst loading of 0.2 mg Pt cm(-2).

  18. Carbon Supported Ag Nanoparticles as High Performance Cathode Catalyst for Anion Exchange Membrane Fuel Cell

    Directory of Open Access Journals (Sweden)

    Le eXin

    2013-09-01

    Full Text Available A solution phase-based nanocapsule method was successfully developed to synthesize non-precious metal catalyst - carbon supported Ag nanoparticles (Ag/C. XRD patterns and TEM image show Ag nanoparticles with a small average size (5.4 nm and narrow size distribution (2-9 nm are uniformly dispersed on the carbon black Vulcan XC-72 support. The intrinsic activity and pathway of oxygen reduction reaction (ORR on the Ag/C and commercial Pt/C were investigated using rotating ring disc electrode (RRDE tests at room temperature. The results confirmed that the 4-electron pathway of ORR proceeds on small Ag nanoparticles, and showed comparable ORR activities on the self-prepared Ag/C and a commercial Pt/C. A single H2-O2 anion exchange membrane fuel cell with the Ag/C cathode catalyst exhibited an open circuit potential of 0.98 V and a peak power density of 190 mW/cm2 at 80 oC.

  19. Enhanced catalytic properties from platinum nanodots covered carbon nanotubes for proton-exchange membrane fuel cells

    Energy Technology Data Exchange (ETDEWEB)

    Tang, Zhe; Chua, Daniel H.C. [Department of Materials Science and Engineering, National University of Singapore, 7 Engineering Drive 1, Singapore 117574 (Singapore); Poh, Chee Kok; Tian, Zhiqun; Lin, Jianyi [Institute of Chemical and Engineering Sciences, 1 Pesek Road, Jurong Island, Singapore 627833 (Singapore); Lee, Kian Keat [NUS Nanoscience and Nanotechnology Initiative (NUSNNI), 2 Science Drive 3, Singapore 117542 (Singapore)

    2010-01-01

    An efficient fabrication method for carbon nanotube (CNT)-based electrode with a nanosized Pt catalyst is developed for high efficiency proton-exchange membrane fuel cells (PEMFC). The integrated Pt/CNT layer is prepared by in situ growth of a CNT layer on carbon paper and subsequent direct sputter-deposition of the Pt catalyst. Both scanning electron microscopy (SEM) and transmission electron microscopy (TEM) demonstrate that this Pt/CNT layer consists of a highly porous CNT layer covered by well-dispersed Pt nanodots with a narrow size distribution. Compared with conventional gas-diffusion layer assisted electrodes, the CNT-based electrode with a Pt/CNT layer acting as a combined gas-diffusion layer and catalyst layer shows pronounced improvement in polarization tests. A high maximum power density of 595 mW cm{sup -2} is observed for a low Pt loading of 0.04 mg cm{sup -2} at the cathode. (author)

  20. Changing surface-atmosphere energy exchange and refreezing capacity of the lower accumulation area, West Greenland

    DEFF Research Database (Denmark)

    Charalampidis, C.; Van As, D.; Box, J. E.;

    2015-01-01

    .78), as meltwater was present at the ice sheet surface. Consequently, during the 2012 melt season, the ice sheet surface absorbed 28 % (213 MJ m-2) more solar radiation than the average of all other years. A surface energy balance model is used to evaluate the seasonal and interannual variability of all surface...... energy fluxes. The model reproduces the observed melt rates as well as the SMB for each season. A sensitivity analysis reveals that 71 % of the additional solar radiation in 2012 was used for melt, corresponding to 36 % (0.64 m) of the 2012 surface lowering. The remaining 64 % (1.14 m) of surface...... lowering resulted from high atmospheric temperatures, up to a +2.6 °C daily average, indicating that 2012 would have been a negative SMB year at this site even without the melt-albedo feedback. Longer time series of SMB, regional temperature, and remotely sensed albedo (MODIS) show that 2012 was the first...

  1. Quantifying the roles of ocean circulation and biogeochemistry in governing ocean carbon-13 and atmospheric carbon dioxide at the last glacial maximum

    OpenAIRE

    Tagliabue, A.; L. Bopp; Roche, D. M.; N. Bouttes; J.-C. Dutay; Alkama, R.; Kageyama, M.; Michel, E.; Paillard, D.

    2009-01-01

    We use a state-of-the-art ocean general circulation and biogeochemistry model to examine the impact of changes in ocean circulation and biogeochemistry in governing the change in ocean carbon-13 and atmospheric CO2 at the last glacial maximum (LGM). We examine 5 different realisations of the ocean's overturning circulation produced by a fully coupled atmosphere-ocean model under LGM forcing and suggested changes in the atmospheric deposition of iron and phytoplankton ph...

  2. Atmospheric Ionic Deposition in Tropical Sites of Central Sulawesi Determined by Ion Exchange Resin Collectors and Bulk Water Collector.

    Science.gov (United States)

    Köhler, S; Jungkunst, H F; Gutzler, C; Herrera, R; Gerold, G

    2012-09-01

    In the light of global change, the necessity to monitor atmospheric depositions that have relevant effects on ecosystems is ever increasing particularly for tropical sites. For this study, atmospheric ionic depositions were measured on tropical Central Sulawesi at remote sites with both a conventional bulk water collector system (BWS collector) and with a passive ion exchange resin collector system (IER collector). The principle of IER collector to fix all ionic depositions, i.e. anions and cations, has certain advantages referring to (1) post-deposition transformation processes, (2) low ionic concentrations and (3) low rainfall and associated particulate inputs, e.g. dust or sand. The ionic concentrations to be measured for BWS collectors may easily fall below detection limits under low deposition conditions which are common for tropical sites of low land use intensity. Additionally, BWS collections are not as independent from the amount of rain fallen as are IER collections. For this study, the significant differences between both collectors found for nearly all measured elements were partly correlated to the rainfall pattern, i.e. for calcium, magnesium, potassium and sodium. However, the significant differences were, in most cases, not highly relevant. More relevant differences between the systems were found for aluminium and nitrate (434-484 %). Almost five times higher values for nitrate clarified the advantage of the IER system particularly for low deposition rate which is one particularity of atmospheric ionic deposition in tropical sites of extensive land use. The monthly resolution of the IER data offers new insights into the temporal distribution of annual ionic depositions. Here, it did not follow the tropical rain pattern of a drier season within generally wet conditions.

  3. Atmospheric pCO2 control on speleothem stable carbon isotope compositions

    Science.gov (United States)

    Breecker, Daniel O.

    2017-01-01

    The stable carbon isotope compositions of C3 plants are controlled by the carbon isotope composition of atmospheric CO2 (δ13Ca) and by the stomatal response to water stress. These relationships permit the reconstruction of ancient environments and assessment of the water use efficiency of forests. It is currently debated whether the δ13C values of C3 plants are also controlled by atmospheric pCO2. Here I show that globally-averaged speleothem δ13C values closely track atmospheric pCO2 over the past 90 kyr. After accounting for other possible effects, this coupling is best explained by a C3 plant δ13C sensitivity of - 1.6 ± 0.3 ‰ / 100 ppmV CO2 during the Quaternary. This is consistent with 20th century European forest tree ring δ13C records, providing confidence in the result and suggesting that the modest pCO2-driven increase in water use efficiency determined for those ecosystems and simulated by land surface models accurately approximates the global average response. The δ13C signal from C3 plants is transferred to speleothems relatively rapidly. Thus, the effect of atmospheric pCO2 should be subtracted from new and existing speleothem δ13C records so that residual δ13C shifts can be interpreted in light of the other factors known to control spleleothem δ13C values. Furthermore, global average speleothem δ13C shifts may be used to develop a continuous radiometric chronology for Pleistocene atmospheric pCO2 fluctuations and, by correlation, ice core climate records.

  4. Centennial evolution of the atmospheric methane budget: what do the carbon isotopes tell us?

    Directory of Open Access Journals (Sweden)

    K. R. Lassey

    2006-06-01

    Full Text Available Little is known about how the methane source inventory and sinks have evolved over recent centuries. New and detailed records of methane mixing ratio and isotopic composition (12CH4, 13CH4 and 14CH4 from analyses of air trapped in polar ice and firn can enhance this knowledge. We use existing bottom-up constructions of the source history, including ''EDGAR''-based constructions, to assemble a model of the evolving global budget for methane and for its carbon isotope composition through the 20th century. By matching such budgets to atmospheric data, we examine the constraints imposed by isotope information on those budget evolutions. Balancing both 12CH4 and 13CH4 budgets requires participation by a highly-fractionating atmospheric sink such as active chlorine (removing at least 10 Tg yr-1, which has been proposed independently. Examining a companion budget evolution for 14CH4 exposes uncertainties in inferring the fossil-methane source from atmospheric 14CH4 data. Specifically, methane evolution during the nuclear era is sensitive to the cycling dynamics of ''bomb 14C'' (originating from atmospheric weapons tests through the biosphere. In addition, since ca 1970, direct production and release of 14CH4 from nuclear-power facilities is influential but poorly quantified. Atmospheric 14CH4 determinations in the nuclear era have the potential to better characterize biospheric carbon cycling and to better quantify the ill-determined nuclear-power source.

  5. Soil-atmosphere carbonyl sulfide (COS) exchange in a tropical rainforest at La Selva, Costa Rica

    Science.gov (United States)

    Sun, W.; Maseyk, K. S.; Juarez, S.; Lett, C.; Seibt, U. H.

    2014-12-01

    Carbonyl sulfide (COS) has recently been proposed as a promising tracer for partitioning ecosystem carbon assimilation due to the close analogy between leaf uptake processes of COS and CO2. This emerging framework requires accurate characterization of the source and sink components of COS, including soil fluxes. Here we present the first direct, continuous observations of soil COS fluxes for 4 months at a tropical rainforest, La Selva Biological Station, Costa Rica. Three soil plots with contrasting water content were selected for chamber measurements. Our observations confirmed that soils are principally COS sinks, with daily mean COS fluxes averaged across all chambers ranging from -3 to 0 pmol m-2 s-1. When compared with net ecosystem COS uptake which peaks around -30 pmol m-2 s-1, their contributions should be considered in ecosystem COS balance. We did not find a temperature optimum, but soil COS uptake slightly increased with soil temperature, indicating biotic control on soil COS fluxes. Diurnal cycles of COS fluxes were observed during drying out periods after rain. The diel periodicity of COS fluxes was probably obscured by frequent raining at the site. Diffusional control of soil COS fluxes is shown from increasing soil COS uptake at lower soil water-filled pore space. These confirm that soil COS fluxes are mediated both by soil physical and biological factors. Using a depth-resolved diffusion-reaction model with data-driven enzyme activity parameterization, we simulated the COS fluxes from measured soil environmental variables, consistent with observations. This modeling scheme is useful for separating soil COS fluxes from net ecosystem COS fluxes, which lends support to the emergent COS-based approach of carbon flux partitioning.

  6. Using Atmospheric δ13C of CO2 observations to link the water and carbon cycles with climate

    Science.gov (United States)

    Alden, C. B.; Miller, J. B.; White, J. W.; Yadav, V.; Michalak, A. M.; Andrews, A. E.; Huang, L.

    2013-12-01

    The ratio of stable carbon isotopes, 13C:12C in atmospheric CO2 (expressed as δ13C) offers unique insights into atmosphere-land CO2 fluxes and the modulating effects of stomatal conductance on this exchange. Photosynthesis discriminates against 13CO2 during uptake. The magnitude of this fractionation is strongly dependent upon ambient CO2 concentrations and water availability, as well as on the mix of C3 and C4 vegetation types. C3 and C4 plants have very different discrimination because of carboxylation pathways, and C3 stomatal conductance varies with water availability because stomata close to reduce transpiration when plants are water stressed. Further, plant stomata respond to ambient CO2 concentrations in order to optimize leaf internal [CO2] while reducing transpirative water loss. Atmospheric δ13C therefore carries information about local and upwind drought conditions and the consequent likelihood of ground-to-atmosphere water transfer via transpiration, and the balance of latent and sensible heat fluxes, as well as about local and upwind distributions of C3 and C4 vegetation and variability therein. δ13C offers a unique lens through which to identify key thresholds and relationships between climate anomalies/change and the modulating climate impacts of plant biosphere response. By unraveling this relationship at local to continental scales, we stand to gain crucial understanding of the drivers of land CO2 uptake variability as well as knowledge of how to predict future climate impacts on the carbon cycle and vice versa. We use a two-step Bayesian inversion model to optimize 1x1 degree and 3-hourly (interpreted at regional and weekly to monthly scales) fields of δ13C of assimilated biomass over North America for the year 2010, using influence functions generated with FLEXPART, driven by National Centers for Environmental Prediction Global Forecast System meteorology. Prior fluxes and fossil fuel, ocean and fire fluxes are from CarbonTracker 2011, and

  7. Enhanced oxidative weathering in glaciated mountain catchments: A stabilising feedback on atmospheric carbon dioxide?

    Science.gov (United States)

    Horan, K.; Hilton, R. G.; Burton, K. W.; Selby, D. S.; Ottley, C. J.

    2015-12-01

    Mountain belts act as sources of carbon dioxide (CO2) to the atmosphere if physical erosion and exhumation expose rock-derived organic carbon ('petrogenic' organic carbon, OCpetro) to chemical weathering. Estimates suggest 15x1021g of carbon is stored in rocks globally as OCpetro, ~25,000 times the amount of carbon in the pre-industrial atmosphere. Alongside volcanic and metamorphic degassing, OCpetro weathering is thought to be the main source of CO2 to the atmosphere over geological timescales. Erosion in mountain river catchments has been shown to enhance oxidative weathering and CO2 release. However, we still lack studies which quantify this process. In addition, it is not clear how glaciation may impact OCpetro oxidation. In analogy with silicate weathering, large amounts of fine sediment in glacial catchments may enhance oxidative weathering. Here we quantify oxidative weathering in nine catchments draining OCpetro bearing rocks in the western Southern Alps, New Zealand. Using rhenium (Re) as a tracer of oxidative weathering, we develop techniques to precisely measure Re concentration at sub-ppt levels in river waters. Using [Re]water/[Re]rock as a weathering tracer, we estimate that the weathering efficiency in glacial catchments is >4 times that of non-glacial catchments. Combining this with the OCpetro content of rocks and dissolved Re flux, we estimate the CO2 release by OCpetro oxidation. The analysis suggests that non-glacial catchments in the western Southern Alps release similar amounts of CO2 as catchments in Taiwan where erosion rates are comparable. In this mountain belt, the CO2 release does not negate CO2 drawdown by silicate weathering and by riverine transfer of organic matter. Based on our results, we propose that mountain glaciation may greatly enhance OCpetro oxidation rates. Depending on the global fluxes involved, this provides a feedback to damp low atmospheric CO2 levels and global cooling. During glacial periods (low CO2, low global

  8. The carbon isotopic compositions of Non-methane Hydrocarbons in atmosphere

    Institute of Scientific and Technical Information of China (English)

    PENG Lin; ZHANG HuiMin; REN ZhaoFang; MU Ling; SHI RuiLiang; CHANG LiPing; LI Fan

    2009-01-01

    Carbon isotopic compositions of atmospheric Non-methane Hydrocarbons (NMHCs) in the urban areas of Taiyuan and Lanzhou in summer were reported and the sources of NMHCs are discussed.Carbon isotopic ratios (δ13C) of vehicle exhaust,coal-combustion exhaust,fuel volatiles and cooking exhaust were also measured with thermal desorption-gas chromatography-isotope ratio-mass spectrometry (TD-GC-IR-MS).δ13C values of NMHCs in the urban areas of Lanzhou and Taiyuan range from -32.3‰ to -22.3‰ and from -32.8‰ to -18.1‰.δ13C values of vehicle exhaust,coal-combustion exhaust,fuel volatiles and cooking exhaust are -32.5‰--21.7‰,-24.5‰--22.3‰,-32.5%--27.4‰ and -31.6‰--24.5‰,respectively.The data indicate that vehicle exhaust and cooking exhaust make a significant contribution to the atmospheric NMHCs.Therefore,to reduce emissions of vehicle exhaust and cook-ing exhaust is critical for controlling atmospheric NMHCs pollution in summer.

  9. Atmospheric lithium abundances of the carbon giants AQ And, HK Lyr, UX Dra, and WZ Cas

    Science.gov (United States)

    Yakovina, L. A.; Pavlenko, Ya. V.

    2012-01-01

    The LTE lithium abundances, log N (Li), have been determined for the atmospheres of the four carbon giants AQ And, HK Lyr, UX Dra, and WZ Cas, applying the synthetic-spectrum technique to the LiI λ670.8 nm resonance doublet. We used estimates of the effective temperatures T eff, metallicities, elemental abundances, and carbon-isotope ratios for these stars from the literature [12C/13C]. The resulting lithium abundances depend significantly on the adopted T eff, so that we can find each star's range of possible log N(Li) values for a given range of effective temperatures (Δ T eff = 200-300 K). The uncertainty in the derived log N(Li) values is 1.3 for AQ And and UX Dra, 0.5 for HK Lyr, and 0.8 for WZ Cas. Our most probable log N(Li) values (or ranges) are -1.25 for AQ And, -1.2 for HK Lyr, -1.0 ≤ log N(Li) ≤ +0.3 for UX Dra, and 4.3 ≤ log N(Li) ≤ 4.8 for WZ Cas. The derived C/O ratios for the stellar atmospheres also depend on T eff. Possible uncertainties in other atmospheric parameters do not change log N(Li) by more than 0.2.

  10. Compositional variability of the Venusian atmosphere above the clouds: sulphur dioxide and carbon monoxide

    Science.gov (United States)

    Marcq, Emmanuel; Belyaev, Denis; Lellouch, Emmanuel; Encrenaz, Therese; Montmessin, Franck; Bertaux, Jean-Loup

    The layers of the Venusian atmosphere located at cloud top level is a complex transitional region where intense solar radiation interacts with a fairly dense gaseous medium and particulate matter - ultimately, the cloud particles themselves are a by-product of this interaction. In a stark contrast with the lowermost troposphere, spatial and temporal variations in temperature and composition are easily noticeable. In this talk we will focus on two gaseous species, carbon monoxide (CO) and sulphur dioxide (SO _{2}), whose sources and sinks are reversed: whereas carbon monoxide is produced by photo-dissociation of the main atmospheric constituent CO _{2} and oxidised below the clouds, SO _{2} is destroyed by UV solar radiation above the clouds and replenished from the lower atmosphere. Yet, these two species exhibit very different variation patterns. SO _{2} temporal variations range from very rapid (within a few hours) and large (by a relative factor exceeding 10) variations to secular phases of increases and decreases spanning decades. Its average latitudinal distribution ranges from a decrease with increasing latitude during SO _{2}-rich phases and a possible reversal during SO _{2}-poor phases. In contrast, CO does not exhibit significant secular, nor short-term variability, but clear horizontal trends have been measured, both with respect to latitude and local solar time.

  11. Using NASA Techniques to Atmospherically Correct AWiFS Data for Carbon Sequestration Studies

    Science.gov (United States)

    Holekamp, Kara L.

    2007-01-01

    Carbon dioxide is a greenhouse gas emitted in a number of ways, including the burning of fossil fuels and the conversion of forest to agriculture. Research has begun to quantify the ability of vegetative land cover and oceans to absorb and store carbon dioxide. The USDA (U.S. Department of Agriculture) Forest Service is currently evaluating a DSS (decision support system) developed by researchers at the NASA Ames Research Center called CASA-CQUEST (Carnegie-Ames-Stanford Approach-Carbon Query and Evaluation Support Tools). CASA-CQUEST is capable of estimating levels of carbon sequestration based on different land cover types and of predicting the effects of land use change on atmospheric carbon amounts to assist land use management decisions. The CASA-CQUEST DSS currently uses land cover data acquired from MODIS (the Moderate Resolution Imaging Spectroradiometer), and the CASA-CQUEST project team is involved in several projects that use moderate-resolution land cover data derived from Landsat surface reflectance. Landsat offers higher spatial resolution than MODIS, allowing for increased ability to detect land use changes and forest disturbance. However, because of the rate at which changes occur and the fact that disturbances can be hidden by regrowth, updated land cover classifications may be required before the launch of the Landsat Data Continuity Mission, and consistent classifications will be needed after that time. This candidate solution investigates the potential of using NASA atmospheric correction techniques to produce science-quality surface reflectance data from the Indian Remote Sensing Advanced Wide-Field Sensor on the RESOURCESAT-1 mission to produce land cover classification maps for the CASA-CQUEST DSS.

  12. Phenol-Formaldehyde Resin-Based Carbons for CO2 Separation at Sub-Atmospheric Pressures

    Directory of Open Access Journals (Sweden)

    Noelia Álvarez-Gutiérrez

    2016-03-01

    Full Text Available The challenge of developing effective separation and purificatio