WorldWideScience

Sample records for net co2 uptake

  1. Rain events decrease boreal peatland net CO2 uptake through reduced light availability.

    Science.gov (United States)

    Nijp, Jelmer J; Limpens, Juul; Metselaar, Klaas; Peichl, Matthias; Nilsson, Mats B; van der Zee, Sjoerd E A T M; Berendse, Frank

    2015-06-01

    Boreal peatlands store large amounts of carbon, reflecting their important role in the global carbon cycle. The short-term exchange and the long-term storage of atmospheric carbon dioxide (CO2 ) in these ecosystems are closely associated with the permanently wet surface conditions and are susceptible to drought. Especially, the single most important peat forming plant genus, Sphagnum, depends heavily on surface wetness for its primary production. Changes in rainfall patterns are expected to affect surface wetness, but how this transient rewetting affects net ecosystem exchange of CO2 (NEE) remains unknown. This study explores how the timing and characteristics of rain events during photosynthetic active periods, that is daytime, affect peatland NEE and whether rain event associated changes in environmental conditions modify this response (e.g. water table, radiation, vapour pressure deficit, temperature). We analysed an 11-year time series of half-hourly eddy covariance and meteorological measurements from Degerö Stormyr, a boreal peatland in northern Sweden. Our results show that daytime rain events systematically decreased the sink strength of peatlands for atmospheric CO2 . The decrease was best explained by rain associated reduction in light, rather than by rain characteristics or drought length. An average daytime growing season rain event reduced net ecosystem CO2 uptake by 0.23-0.54 gC m(-2) . On an annual basis, this reduction of net CO2 uptake corresponds to 24% of the annual net CO2 uptake (NEE) of the study site, equivalent to a 4.4% reduction of gross primary production (GPP) during the growing season. We conclude that reduced light availability associated with rain events is more important in explaining the NEE response to rain events than rain characteristics and changes in water availability. This suggests that peatland CO2 uptake is highly sensitive to changes in cloud cover formation and to altered rainfall regimes, a process hitherto largely

  2. Elevated CO2 maintains grassland net carbon uptake under a future heat and drought extreme.

    Science.gov (United States)

    Roy, Jacques; Picon-Cochard, Catherine; Augusti, Angela; Benot, Marie-Lise; Thiery, Lionel; Darsonville, Olivier; Landais, Damien; Piel, Clément; Defossez, Marc; Devidal, Sébastien; Escape, Christophe; Ravel, Olivier; Fromin, Nathalie; Volaire, Florence; Milcu, Alexandru; Bahn, Michael; Soussana, Jean-François

    2016-05-31

    Extreme climatic events (ECEs) such as droughts and heat waves are predicted to increase in intensity and frequency and impact the terrestrial carbon balance. However, we lack direct experimental evidence of how the net carbon uptake of ecosystems is affected by ECEs under future elevated atmospheric CO2 concentrations (eCO2). Taking advantage of an advanced controlled environment facility for ecosystem research (Ecotron), we simulated eCO2 and extreme cooccurring heat and drought events as projected for the 2050s and analyzed their effects on the ecosystem-level carbon and water fluxes in a C3 grassland. Our results indicate that eCO2 not only slows down the decline of ecosystem carbon uptake during the ECE but also enhances its recovery after the ECE, as mediated by increases of root growth and plant nitrogen uptake induced by the ECE. These findings indicate that, in the predicted near future climate, eCO2 could mitigate the effects of extreme droughts and heat waves on ecosystem net carbon uptake.

  3. Drought Rapidly Diminishes the Large Net CO2 Uptake in 2011 Over Semi-Arid Australia

    Science.gov (United States)

    Ma, Xuanlong; Huete, Alfredo; Cleverly, James; Eamus, Derek; Chevallier, Frederic; Joiner, Joanna; Poulter, Benjamin; Zhang, Yongguang; Guanter, Luis; Meyer, Wayne; hide

    2016-01-01

    Each year, terrestrial ecosystems absorb more than a quarter of the anthropogenic carbon emissions, termed as land carbon sink. An exceptionally large land carbon sink anomaly was recorded in 2011, of which more than half was attributed to Australia. However, the persistence and spatially attribution of this carbon sink remain largely unknown. Here we conducted an observation-based study to characterize the Australian land carbon sink through the novel coupling of satellite retrievals of atmospheric CO2 and photosynthesis and in-situ flux tower measures. We show the 2010-11 carbon sink was primarily ascribed to savannas and grasslands. When all biomes were normalized by rainfall, shrublands however, were most efficient in absorbing carbon. We found the 2010-11 net CO2 uptake was highly transient with rapid dissipation through drought. The size of the 2010-11 carbon sink over Australia (0.97 Pg) was reduced to 0.48 Pg in 2011-12, and was nearly eliminated in 2012-13 (0.08 Pg). We further report evidence of an earlier 2000-01 large net CO2 uptake, demonstrating a repetitive nature of this land carbon sink. Given a significant increasing trend in extreme wet year precipitation over Australia, we suggest that carbon sink episodes will exert greater future impacts on global carbon cycle.

  4. Drought rapidly diminishes the large net CO2 uptake in 2011 over semi-arid Australia

    Science.gov (United States)

    Ma, Xuanlong; Huete, Alfredo; Cleverly, James; Eamus, Derek; Chevallier, Frédéric; Joiner, Joanna; Poulter, Benjamin; Zhang, Yongguang; Guanter, Luis; Meyer, Wayne; Xie, Zunyi; Ponce-Campos, Guillermo

    2016-01-01

    Each year, terrestrial ecosystems absorb more than a quarter of the anthropogenic carbon emissions, termed as land carbon sink. An exceptionally large land carbon sink anomaly was recorded in 2011, of which more than half was attributed to Australia. However, the persistence and spatially attribution of this carbon sink remain largely unknown. Here we conducted an observation-based study to characterize the Australian land carbon sink through the novel coupling of satellite retrievals of atmospheric CO2 and photosynthesis and in-situ flux tower measures. We show the 2010–11 carbon sink was primarily ascribed to savannas and grasslands. When all biomes were normalized by rainfall, shrublands however, were most efficient in absorbing carbon. We found the 2010–11 net CO2 uptake was highly transient with rapid dissipation through drought. The size of the 2010–11 carbon sink over Australia (0.97 Pg) was reduced to 0.48 Pg in 2011–12, and was nearly eliminated in 2012–13 (0.08 Pg). We further report evidence of an earlier 2000–01 large net CO2 uptake, demonstrating a repetitive nature of this land carbon sink. Given a significant increasing trend in extreme wet year precipitation over Australia, we suggest that carbon sink episodes will exert greater future impacts on global carbon cycle. PMID:27886216

  5. Greater deciduous shrub abundance extends tundra peak season and increases modeled net CO2 uptake.

    Science.gov (United States)

    Sweet, Shannan K; Griffin, Kevin L; Steltzer, Heidi; Gough, Laura; Boelman, Natalie T

    2015-06-01

    Satellite studies of the terrestrial Arctic report increased summer greening and longer overall growing and peak seasons since the 1980s, which increases productivity and the period of carbon uptake. These trends are attributed to increasing air temperatures and reduced snow cover duration in spring and fall. Concurrently, deciduous shrubs are becoming increasingly abundant in tundra landscapes, which may also impact canopy phenology and productivity. Our aim was to determine the influence of greater deciduous shrub abundance on tundra canopy phenology and subsequent impacts on net ecosystem carbon exchange (NEE) during the growing and peak seasons in the arctic foothills region of Alaska. We compared deciduous shrub-dominated and evergreen/graminoid-dominated community-level canopy phenology throughout the growing season using the normalized difference vegetation index (NDVI). We used a tundra plant-community-specific leaf area index (LAI) model to estimate LAI throughout the green season and a tundra-specific NEE model to estimate the impact of greater deciduous shrub abundance and associated shifts in both leaf area and canopy phenology on tundra carbon flux. We found that deciduous shrub canopies reached the onset of peak greenness 13 days earlier and the onset of senescence 3 days earlier compared to evergreen/graminoid canopies, resulting in a 10-day extension of the peak season. The combined effect of the longer peak season and greater leaf area of deciduous shrub canopies almost tripled the modeled net carbon uptake of deciduous shrub communities compared to evergreen/graminoid communities, while the longer peak season alone resulted in 84% greater carbon uptake in deciduous shrub communities. These results suggest that greater deciduous shrub abundance increases carbon uptake not only due to greater leaf area, but also due to an extension of the period of peak greenness, which extends the period of maximum carbon uptake. © 2015 John Wiley & Sons Ltd.

  6. Increasing summer net CO2 uptake in high northern ecosystems inferred from atmospheric inversions and comparisons to remote-sensing NDVI

    Science.gov (United States)

    Welp, Lisa R.; Patra, Prabir K.; Rödenbeck, Christian; Nemani, Rama; Bi, Jian; Piper, Stephen C.; Keeling, Ralph F.

    2016-07-01

    Warmer temperatures and elevated atmospheric CO2 concentrations over the last several decades have been credited with increasing vegetation activity and photosynthetic uptake of CO2 from the atmosphere in the high northern latitude ecosystems: the boreal forest and arctic tundra. At the same time, soils in the region have been warming, permafrost is melting, fire frequency and severity are increasing, and some regions of the boreal forest are showing signs of stress due to drought or insect disturbance. The recent trends in net carbon balance of these ecosystems, across heterogeneous disturbance patterns, and the future implications of these changes are unclear. Here, we examine CO2 fluxes from northern boreal and tundra regions from 1985 to 2012, estimated from two atmospheric inversions (RIGC and Jena). Both used measured atmospheric CO2 concentrations and wind fields from interannually variable climate reanalysis. In the arctic zone, the latitude region above 60° N excluding Europe (10° W-63° E), neither inversion finds a significant long-term trend in annual CO2 balance. The boreal zone, the latitude region from approximately 50-60° N, again excluding Europe, showed a trend of 8-11 Tg C yr-2 over the common period of validity from 1986 to 2006, resulting in an annual CO2 sink in 2006 that was 170-230 Tg C yr-1 larger than in 1986. This trend appears to continue through 2012 in the Jena inversion as well. In both latitudinal zones, the seasonal amplitude of monthly CO2 fluxes increased due to increased uptake in summer, and in the arctic zone also due to increased fall CO2 release. These findings suggest that the boreal zone has been maintaining and likely increasing CO2 sink strength over this period, despite browning trends in some regions and changes in fire frequency and land use. Meanwhile, the arctic zone shows that increased summer CO2 uptake, consistent with strong greening trends, is offset by increased fall CO2 release, resulting in a net neutral

  7. Increasing summer net CO2 uptake in high northern ecosystems inferred from atmospheric inversions and comparisons to remote-sensing NDVI

    Directory of Open Access Journals (Sweden)

    L. R. Welp

    2016-07-01

    Full Text Available Warmer temperatures and elevated atmospheric CO2 concentrations over the last several decades have been credited with increasing vegetation activity and photosynthetic uptake of CO2 from the atmosphere in the high northern latitude ecosystems: the boreal forest and arctic tundra. At the same time, soils in the region have been warming, permafrost is melting, fire frequency and severity are increasing, and some regions of the boreal forest are showing signs of stress due to drought or insect disturbance. The recent trends in net carbon balance of these ecosystems, across heterogeneous disturbance patterns, and the future implications of these changes are unclear. Here, we examine CO2 fluxes from northern boreal and tundra regions from 1985 to 2012, estimated from two atmospheric inversions (RIGC and Jena. Both used measured atmospheric CO2 concentrations and wind fields from interannually variable climate reanalysis. In the arctic zone, the latitude region above 60° N excluding Europe (10° W–63° E, neither inversion finds a significant long-term trend in annual CO2 balance. The boreal zone, the latitude region from approximately 50–60° N, again excluding Europe, showed a trend of 8–11 Tg C yr−2 over the common period of validity from 1986 to 2006, resulting in an annual CO2 sink in 2006 that was 170–230 Tg C yr−1 larger than in 1986. This trend appears to continue through 2012 in the Jena inversion as well. In both latitudinal zones, the seasonal amplitude of monthly CO2 fluxes increased due to increased uptake in summer, and in the arctic zone also due to increased fall CO2 release. These findings suggest that the boreal zone has been maintaining and likely increasing CO2 sink strength over this period, despite browning trends in some regions and changes in fire frequency and land use. Meanwhile, the arctic zone shows that increased summer CO2 uptake, consistent with strong greening trends, is offset by

  8. Does Elevated CO2 Alter Silica Uptake in Trees?

    Directory of Open Access Journals (Sweden)

    Robinson W. Fulweiler

    2015-01-01

    Full Text Available Human activities have greatly altered global carbon (C and N (N cycling. In fact, atmospheric concentrations of carbon dioxide (CO2 have increased 40% over the last century and the amount of N cycling in the biosphere has more than doubled. In an effort to understand how plants will respond to continued global carbon dioxide fertilization, long-term free-air CO2 enrichment (FACE experiments have been conducted at sites around the globe. Here we examine how atmospheric CO2 enrichment and N fertilization affects the uptake of silicon (Si in the Duke Forest, North Carolina, a stand dominated by Pinus taeda (loblolly pine, and five hardwood species. Specifically, we measured foliar biogenic silica (BSi concentrations in five deciduous and one coniferous species across three treatments: CO2 enrichment, N enrichment, and N and CO2 enrichment. We found no consistent trends in foliar Si concentration under elevated CO2, N fertilization, or combined elevated CO2 and N fertilization. However, two-thirds of the tree species studied here have Si foliar concentrations greater than well-known Si accumulators, such as grasses. Based on net primary production values and aboveground Si concentrations in these trees, we calculated forest Si uptake rates under control and elevated CO2 concentrations. Due largely to increased primary production, elevated CO2 enhanced the magnitude of Si uptake between 20% and 26%, likely intensifying the terrestrial silica pump. This uptake of Si by forests has important implications for Si export from terrestrial systems, with the potential to impact C sequestration and higher trophic levels in downstream ecosystems.

  9. Understanding and predicting trends in north Atlantic CO2 uptake

    Science.gov (United States)

    Halloran, Paul; Lebehot, Alice; Watson, Andy; McNeall, Doug; Ford, David; Schuster, Ute

    2017-04-01

    To determine the maximum carbon dioxide (CO2) emissions society must commit to, to remain below a given atmospheric CO2 threshold, the scientific community must robustly quantify what proportion of human emitted CO2 will be taken up by the land and marine carbon reservoirs. The North Atlantic Ocean is the most intense marine sink of anthropogenic CO2 on the planet, accounting for about a fifth of the global oceanic anthropogenic CO2 uptake, despite covering just 15% of the global ocean area. Carefully assessing uncertainties, we quantify the real-world trend in North Atlantic CO2 uptake over the past two decades. Comparing this to results from state-of-the-art climate models, we find that models are systematically underestimating the observed CO2 uptake trend. By performing a set of targeted climate model simulations, we diagnose and account for this bias, and produce the first set of observation-informed future ocean CO2 uptake predictions.

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

    Science.gov (United States)

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

    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...

  11. Continuous measurements of net CO2 exchange by vegetation and soils in a suburban landscape

    Science.gov (United States)

    Peters, Emily B.; McFadden, Joseph P.

    2012-09-01

    In a suburban neighborhood of Minneapolis-Saint Paul, Minnesota, USA, we simultaneously measured net CO2 exchange of trees using sap flow and leaf gas exchange measurements, net CO2exchange of a turfgrass lawn using eddy covariance from a portable tower, and total surface-atmosphere CO2 fluxes (FC) using an eddy covariance system on a tall tower. Two years of continuous measurements showed that net CO2exchange varied among vegetation types, with the largest growing-season (Apr-Nov) net CO2 uptake on a per cover area basis from evergreen needleleaf trees (-603 g C m-2), followed by deciduous broadleaf trees (-216 g C m-2), irrigated turfgrass (-211 g C m-2), and non-irrigated turfgrass (-115 g C m-2). Vegetation types showed seasonal patterns of CO2exchange similar to those observed in natural ecosystems. Scaled-up net CO2 exchange from vegetation and soils (FC(VegSoil)) agreed closely with landscape FC measurements from the tall tower at times when fossil fuel emissions were at a minimum. Although FC(VegSoil) did not offset fossil fuel emissions on an annual basis, the temporal pattern of FC(VegSoil) did significantly alter the seasonality of FC. Total growing season FC(VegSoil)in recreational land-use areas averaged -165 g C m-2 and was dominated by turfgrass CO2 exchange (representing 77% of the total), whereas FC(VegSoil) in residential areas averaged -124 g C m-2 and was dominated by trees (representing 78% of the total). Our results suggest urban vegetation types can capture much of the variability required to predict seasonal patterns and differences in FC(VegSoil) that could result from changes in land use or vegetation composition in temperate cities.

  12. Growing season net ecosystem CO2 exchange of two desert ecosystems with alkaline soils in Kazakhstan

    Science.gov (United States)

    Li, Longhui; Chen, Xi; van der Tol, Christiaan; Luo, Geping; Su, Zhongbo

    2014-01-01

    Central Asia is covered by vast desert ecosystems, and the majority of these ecosystems have alkaline soils. Their contribution to global net ecosystem CO2 exchange (NEE) is of significance simply because of their immense spatial extent. Some of the latest research reported considerable abiotic CO2 absorption by alkaline soil, but the rate of CO2 absorption has been questioned by peer communities. To investigate the issue of carbon cycle in Central Asian desert ecosystems with alkaline soils, we have measured the NEE using eddy covariance (EC) method at two alkaline sites during growing season in Kazakhstan. The diurnal course of mean monthly NEE followed a clear sinusoidal pattern during growing season at both sites. Both sites showed significant net carbon uptake during daytime on sunny days with high photosynthetically active radiation (PAR) but net carbon loss at nighttime and on cloudy and rainy days. NEE has strong dependency on PAR and the response of NEE to precipitation resulted in an initial and significant carbon release to the atmosphere, similar to other ecosystems. These findings indicate that biotic processes dominated the carbon processes, and the contribution of abiotic carbon process to net ecosystem CO2 exchange may be trivial in alkaline soil desert ecosystems over Central Asia. PMID:24455157

  13. Responses of soil CO2 efflux to changes in plant CO2 uptake and transpiration

    Science.gov (United States)

    Balogh, János; de Luca, Giulia; Mészáros, Ádám; Trieber, Júlia; Gecse, Bernadett; Fóti, Szilvia; Pintér, Krisztina; Nagy, Zoltán

    2017-04-01

    Biotic drivers of soil respiration represent a significant supply-side (plant) control of the process. Those biotic drivers that integrate over longer time periods are useful in describing the phenological changes and physiological state of the vegetation, but they are not suitable to explain the diel variability of soil respiration. Two plant physiological processes, acting in opposite directions, could be relevant at diel timescale: (1) photosynthesis, and (2) transpiration. Firstly, it was recently found that photosynthesis has a time-lagged (a few hours) positive effect on the respiration of roots and root-associated microbes. This can be explainedby an increase in easily accessible non-structural hydrocarbon sources for the roots and root-associated organisms within this period. Secondly, it was found that the effect of transpiration could reduce root respiration due to CO2 transport through the transpiration stream, and this effect is expected to be immediate. Removing the effect of the abiotic drivers from the soil efflux signal could help to clarify the role of other driving variables. In the present study, we conducted manipulation measurements in lab environment to be able to detect the effects of the plant physiological variables (CO2 uptake, transpiration) on soil CO2 efflux. Plant individuals were planted into field soil samples in small pots. Transpiration manipulation was done by regulating vapour pressure of the air around the plant canopy and by inhibitors. Photosynthesis manipulation consisted of programmed absence of light. Isotopic signatures of soil respiration were used for estimating the contribution of the autotrophic and heterotrophic soil respiration components. 13CO2 concentration of the CO2 efflux of the different soil components was measured continuously in open system by cavity ring-down spectroscopy (Picarro G1101-i gas analyser). Keeling-plot approach was also used to calculate the isotopic signals of the sources. According to the

  14. Nitrogen uptake, distribution, turnover, and efficiency of use in a CO2-enriched sweetgum forest

    Energy Technology Data Exchange (ETDEWEB)

    Norby, Richard J [ORNL; Iversen, Colleen M [ORNL

    2006-01-01

    The Progressive Nitrogen Limitation (PNL) hypothesis suggests that ecosystems in a CO2-enriched atmosphere will sequester C and N in long-lived biomass and soil organic pools, thereby limiting available N and constraining the continued response of net primary productivity to elevated [CO2]. Here, we present a six-year record of N dynamics of a sweetgum (Liquidambar styraciflua) stand exposed to elevated [CO2] in the free-air CO2 enrichment (FACE) experiment at Oak Ridge, Tennessee, USA. We also evaluate the concept of PNL for this ecosystem from the perspective of N uptake, content, distribution, and turnover, and N-use efficiency. Leaf N content was 11% lower on a leaf mass basis (NM) and 7% lower on a leaf area basis (N{sub A}) in CO2-enriched trees. However, there was no effect of [CO2] on total canopy N content. Resorption of N during senescence was not altered by [CO2], so NM of litter, but not total N content, was reduced. The NM of fine roots was not affected, but the total amount of N required for fine-root production increased significantly, reflecting the large stimulation of fine-root production in this stand. Hence, total N requirement of the trees was higher in elevated [CO2], and the increased requirement was met through an increase in N uptake rather than increased retranslocation of stored reserves. Increased N uptake was correlated with increased net primary productivity (NPP). N-use efficiency, however, did not change with CO2 enrichment because increased N productivity was offset by lower mean residence time of N in the trees. None of the measured responses of plant N dynamics in this ecosystem indicated the occurrence of PNL, and the stimulation of NPP by elevated [CO2] was sustained for the first six years of the experiment. Although there are some indications of developing changes in the N economy, the N supply in the soil at this site may be sufficient to meet an increasing demand for available N, especially as the roots of CO2-enriched trees

  15. Young Daughter Cladodes Affect CO2 Uptake by Mother Cladodes of Opuntia ficus-indica

    Science.gov (United States)

    PIMIENTA-BARRIOS, EULOGIO; ZAÑUDO-HERNANDEZ, JULIA; ROSAS-ESPINOZA, VERONICA C.; VALENZUELA-TAPIA, AMARANTA; NOBEL, PARK S.

    2004-01-01

    • Background and Aims Drought damages cultivated C3, C4 and CAM plants in the semi-arid lands of central Mexico. Drought damage to Opuntia is common when mother cladodes, planted during the dry spring season, develop young daughter cladodes that behave like C3 plants, with daytime stomatal opening and water loss. In contrast, wild Opuntia are less affected because daughter cladodes do not develop on them under extreme drought conditions. The main objective of this work is to evaluate the effects of the number of daughter cladodes on gas exchange parameters of mother cladodes of Opuntia ficus-indica exposed to varying soil water contents. • Methods Rates of net CO2 uptake, stomatal conductance, intercellular CO2 concentration, chlorophyll content and relative water content were measured in mature mother cladodes with a variable number of daughter cladodes growing in spring under dry and wet conditions. • Key Results Daily carbon gain by mother cladodes was reduced as the number of daughter cladodes increased to eight, especially during drought. This was accompanied by decreased mother cladode relative water content, suggesting movement of water from mother to daughter cladodes. CO2 assimilation was most affected in phase IV of CAM (late afternoon net CO2 uptake) by the combined effects of daughter cladodes and drought. Rainfall raised the soil water content, decreasing the effects of daughter cladodes on net CO2 uptake by mother cladodes. • Conclusions Daughter cladodes significantly hasten the effects of drought on mother cladodes by competition for the water supply and thus decrease daily carbon gain by mother cladodes, mainly by inhibiting phase IV of CAM. PMID:15567805

  16. How do land management practices affect net ecosystem CO2 exchange of an invasive plant infestation?

    Science.gov (United States)

    Sonnentag, O.; Detto, M.; Runkle, B.; Kelly, M.; Baldocchi, D. D.

    2009-12-01

    Ecosystem gas and energy exchanges of invasive plant infestations under different land management practices have been subject of few studies and thus little is known. Our goal is to characterize seasonal changes in net ecosystem CO2 exchange (NEE) through the processes of photosynthesis (GEP) and ecosystem respiration (Reco) of a grassland used as pasture yet infested by perennial pepperweed (Lepidium latifolium) in California’s Sacramento-San Joaquin River Delta. We analyze eddy-covariance supported by environmental and canopy-scale hyperspectral reflectance measurements acquired in 2007-2009. Our study covers three summer drought periods with slightly different land management practices. Over the study period the site was subject to year-round grazing, and in 2008 the site was additionally mowed. Specific questions we address are a) how does pepperweed flowering affect GEP, b) does a mowing event affect NEE mainly through GEP or Reco, and c) can the combined effects of phenology and mowing on pepperweed NEE potentially be tracked using routinely applied remote sensing techniques? Preliminary results indicate that pepperweed flowering drastically decreases photosynthetic CO2 uptake due to shading by the dense arrangement of white flowers at the canopy top, causing the infestation to be almost CO2 neutral. In contrast, mowing causes the infestation to act as moderate net CO2 sink, mainly due to increased CO2 uptake during regrowth. We demonstrate that spectral regions other than commonly-used red and near-infrared might be more promising for pepperweed monitoring because of its spectral uniqueness during the flowering phase. Our results have important implications for land-use land-cover (LULC) change studies when biological invasions and their management alter ecosystem structure and functioning but not necessarily the respective LULC class.

  17. Spring Hydrology Determines Summer Net Carbon Uptake in Northern Ecosystems

    Science.gov (United States)

    Yi, Yonghong; Kimball, John; Reichle, Rolf H.

    2014-01-01

    Increased photosynthetic activity and enhanced seasonal CO2 exchange of northern ecosystems have been observed from a variety of sources including satellite vegetation indices (such as the Normalized Difference Vegetation Index; NDVI) and atmospheric CO2 measurements. Most of these changes have been attributed to strong warming trends in the northern high latitudes (greater than or equal to 50N). Here we analyze the interannual variation of summer net carbon uptake derived from atmospheric CO2 measurements and satellite NDVI in relation to surface meteorology from regional observational records. We find that increases in spring precipitation and snow pack promote summer net carbon uptake of northern ecosystems independent of air temperature effects. However, satellite NDVI measurements still show an overall benefit of summer photosynthetic activity from regional warming and limited impact of spring precipitation. This discrepancy is attributed to a similar response of photosynthesis and respiration to warming and thus reduced sensitivity of net ecosystem carbon uptake to temperature. Further analysis of boreal tower eddy covariance CO2 flux measurements indicates that summer net carbon uptake is positively correlated with early growing-season surface soil moisture, which is also strongly affected by spring precipitation and snow pack based on analysis of satellite soil moisture retrievals. This is attributed to strong regulation of spring hydrology on soil respiration in relatively wet boreal and arctic ecosystems. These results document the important role of spring hydrology in determining summer net carbon uptake and contrast with prevailing assumptions of dominant cold temperature limitations to high-latitude ecosystems. Our results indicate potentially stronger coupling of boreal/arctic water and carbon cycles with continued regional warming trends.

  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, Deborah N.; de Jong, Bernardus; Kurz, W.A.; McGuire, A. David; 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

  19. Air-sea CO2 fluxes along the coast of Chile: From CO2 outgassing in central northern upwelling waters to CO2 uptake in southern Patagonian fjords

    Science.gov (United States)

    Torres, Rodrigo; Pantoja, Silvio; Harada, Naomi; GonzáLez, Humberto E.; Daneri, Giovanni; Frangopulos, MáXimo; Rutllant, José A.; Duarte, Carlos M.; Rúiz-Halpern, Sergio; Mayol, Eva; Fukasawa, Masao

    2011-09-01

    Carbon system parameters measured during several expeditions along the coast of Chile (23°S-56°S) have been used to show the main spatial and temporal trends of air-sea CO2 fluxes in the coastal waters of the eastern South Pacific. Chilean coastal waters are characterized by strong pCO2 gradients between the atmosphere and the surface water, with high spatial and temporal variability. On average, the direction of the carbon flux changes from CO2 outgassing at the coastal upwelling region to CO2 sequestering at the nonupwelling fjord region in Chilean Patagonia. Estimations of surface water pCO2 along the Patagonian fjord region showed that, while minimum pCO2 levels (strong CO2 undersaturation) occurs during the spring and summer period, maximum levels (including CO2 supersaturation) occur during the austral winter. CO2 uptake in the Patagonia fjord region during spring-summer is within the order of -5 mol C m-2 yr-1, indicating a significant regional sink of atmospheric CO2 during that season. We suggest that the CO2 sink at Patagonia most probably exceeds the CO2 source exerted by the coastal upwelling system off central northern Chile.

  20. Mapping Daily Net CO2 Flux From Grasslands Using Remote Sensing

    Science.gov (United States)

    Holifield, C.; Emmerich, W.; Moran, M. S.; Bryant, R.; Verdugo, C.

    2003-12-01

    The daily net carbon dioxide (CO2) flux from extensive grassland ecosystems is an important component of the global carbon cycle. In previous studies, instantaneous net CO2 flux was estimated using a Water Deficit Index (WDI) determined from the relation between surface reflectance and temperature. The mean absolute difference between measured and WDI-derived CO2 flux was 0.23 over a range of CO2 flux values from -0.10 to 1.10 (mg m-2 s-1). The objective of this study was to determine daily net CO2 flux from instantaneous estimates for a semiarid grassland site in Southeast Arizona. This objective was reached through two main steps. First, a linear relationship (R2 = 0.95) was found between instantaneous net CO2 flux and net daytime (6 a.m. to 6 p.m.) flux and used to generate maps of daytime CO2 flux. Second, a field study was conducted to relate night time flux measurements to daytime measurements. These relations made it possible to map daily (24-hour) net CO2 flux from a single satellite image and basic meteorological information. A limitation of this approach is the dependence upon empirical relations for deriving daytime and night time estimates from instantaneous measurements. On the other hand, the empirical relations derived at this location were strong and consistent for the six-year study period.

  1. Acclimation of nitrogen uptake capacity of rice to elevated atmospheric CO2 concentration

    Science.gov (United States)

    Shimono, Hiroyuki; Bunce, James A.

    2009-01-01

    Background and Aims Nitrogen (N) is a major factor affecting yield gain of crops under elevated atmospheric carbon dioxide concentrations [CO2]. It is well established that elevated [CO2] increases root mass, but there are inconsistent reports on the effects on N uptake capacity per root mass. In the present study, it was hypothesized that the responses of N uptake capacity would change with the duration of exposure to elevated [CO2]. Methods The hypothesis was tested by measuring N uptake capacity in rice plants exposed to long-term and short-term [CO2] treatments at different growth stages in plants grown under non-limiting N conditions in hydroponic culture. Seasonal changes in photosynthesis rate and transpiration rate were also measured. Key Results In the long-term [CO2] study, leaf photosynthetic responses to intercellular CO2 concentration (Ci) were not affected by elevated [CO2] before the heading stage, but the initial slope in this response was decreased by elevated [CO2] at the grain-filling stage. Nitrate and ammonium uptake capacities per root dry weight were not affected by elevated [CO2] at panicle initiation, but thereafter they were reduced by elevated [CO2] by 31–41 % at the full heading and mid-ripening growth stages. In the short-term study (24 h exposures), elevated [CO2] enhanced nitrate and ammonium uptake capacities at the early vegetative growth stage, but elevated [CO2] decreased the uptake capacities at the mid-reproductive stage. Conclusions This study showed that N uptake capacity was downregulated under long-term exposure to elevated [CO2] and its response to elevated [CO2] varied greatly with growth stage. PMID:18952623

  2. CARVE: Net Ecosystem CO2 Exchange and Regional Carbon Budgets for Alaska, 2012-2014

    Data.gov (United States)

    National Aeronautics and Space Administration — This data set provides estimates of 3-hourly net ecosystem CO2 exchange (NEE) at 0.5-degree resolution over the state of Alaska for 2012-2014. The NEE estimates are...

  3. CO2NET: Red Europea del Dióxido de Carbono

    OpenAIRE

    Arenillas, A.

    2006-01-01

    CO2NET es una red temática Europea constituida por distintas Instituciones, entros de Investigación y Desarrollo y empresas involucradas en tecnologías para la itigación del CO2. Entre sus actividades se encuentra facilitar la colaboración entre sus miembros en el marco de proyectos europeos sobre captura y almacenamiento de CO2.

  4. CO2 uptake of Opuntia ficus-indica (L. Mill. whole trees and single cladodes, in relation to plant water status and cladode age

    Directory of Open Access Journals (Sweden)

    Giorgia Liguori

    2013-02-01

    Full Text Available Most of net photosynthesis determinations in Opuntia ficus-indica come from measurements on individual cladodes. However, they have limitations when used to scale up to whole canopy gas exchange, because a large variability of carbon assimilation may occur within the canopy, due to, among others, differences in cladode age and intercepted radiation or individual cladode response to abiotic stresses. The aim of this work was to evaluate the application of open gas exchange chambers, simultaneously applied around the whole canopy, to measure net CO2 uptake, continuously over a 24 h period, in single Opuntia ficus-indica (L. Mill. potted trees and in relation with their water status. Net CO2 uptake was also measured for single cladodes differentiated by age. O. ficus-indica trees continued their photosynthetic activity 60 days after the irrigation was stopped, when soil water content was lower than 5%. At this stage, current-year and 1-year-old cladodes had become flaccid but still the daily net CO2 uptake of non-irrigated trees kept the same rate than at the beginning of the experiment, while watered trees had doubled their net CO2 uptake. The highest instantaneous rates and total daily net CO2 uptake for both well-watered and non-irrigated trees occurred 60 days after the onset of the dry period, when maximal instantaneous rates were 11.1 in well-watered trees and 8.4 mol m–2 s–1 in non-irrigated trees. During the drought period, the chlorenchyma fresh weight decreased by 45% and 30%, in 1- and 2-yearold drought cladodes respectively, and marginally increased in currentyear ones (+20%. Net CO2 uptake for 1-year-old and 2-year-old cladodes changed only at highest photosynthetic photon flux density and temperatures, and average seasonal net CO2 uptake of 2-year-old cladodes was 15% lower than for 1-year-old ones. Whole-tree gas exchange measurements applied for the first time to O. ficus-indica indicated that whole cactus pear trees maintain

  5. The role of biological rates in the simulated warming effect on oceanic CO2 uptake

    Science.gov (United States)

    Cao, Long; Zhang, Han

    2017-05-01

    Marine biology plays an important role in the ocean carbon cycle. However, the effect of warming-induced changes in biological rates on oceanic CO2 uptake has been largely overlooked. We use an Earth system model of intermediate complexity to investigate the effect of temperature-induced changes in biological rates on oceanic uptake of atmospheric CO2 and compare it with the effects from warming-induced changes in CO2 solubility and ocean mixing and circulation. Under the representative CO2 concentration pathway RCP 8.5 and its extension, by year 2500, relative to the simulation without warming effect on the ocean carbon cycle, CO2-induced warming reduces cumulative oceanic CO2 uptake by 469 Pg C, of which about 20% is associated with the warming-induced change in marine biological rates. In our simulations, the bulk effect of biological-mediated changes on CO2 uptake is smaller than that mediated by changes in CO2 solubility and ocean mixing and circulation. However, warming-induced changes in individual biological rates, including phytoplankton growth, phytoplankton mortality, and detritus remineralization, are found to affect oceanic CO2 uptake by an amount greater than or comparable to that caused by changes in CO2 solubility and ocean physics. Our simulations, which include only a few temperature-dependent biological processes, demonstrate the important role of biological rates in the oceanic CO2 uptake. In reality, many more complicated biological processes are sensitive to temperature change, and their responses to warming could substantially affect oceanic uptake of atmospheric CO2.

  6. Environment or development? Lifetime net CO2 exchange and control of the expression of Crassulacean acid metabolism in Mesembryanthemum crystallinum.

    Science.gov (United States)

    Winter, Klaus; Holtum, Joseph A M

    2007-01-01

    The relative influence of plant age and environmental stress signals in triggering a shift from C(3) photosynthesis to Crassulacean acid metabolism (CAM) in the annual halophytic C(3)-CAM species Mesembryanthemum crystallinum was explored by continuously monitoring net CO(2) exchange of whole shoots from the seedling stage until seed set. Plants exposed to high salinity (400 mm NaCl) in hydroponic culture solution or grown in saline-droughted soil acquired between 11% and 24% of their carbon via net dark CO(2) uptake involving CAM. In contrast, plants grown under nonsaline, well-watered conditions were capable of completing their life cycle by operating in the C(3) mode without ever exhibiting net CO(2) uptake at night. These observations are not consistent with the widely expressed view that the induction of CAM by high salinity in M. crystallinum represents an acceleration of preprogrammed developmental processes. Rather, our study demonstrates that the induction of the CAM pathway for carbon acquisition in M. crystallinum is under environmental control.

  7. Light-dependent bicarbonate uptake and CO2 efflux in the marine microalga Nannochloropsis gaditana.

    Science.gov (United States)

    Huertas, I E; Espie, G S; Colman, B; Lubian, L M

    2000-06-01

    Inorganic carbon (Ci) uptake and efflux has been investigated in the marine microalga Nannochloropsis gaditana Lubian by monitoring CO2 fluxes in cell suspensions using mass spectrometry. Addition of H13CO3- to cell suspensions in the dark caused a transient increase in the CO2 concentration in the medium far in excess of the equilibrium CO2 concentration. The magnitude of this release was dependent on the length of time the cells had been kept in the dark. Once equilibrium between the Ci species had been achieved, a CO2 efflux was observed after saturating light intensity was applied to the cells. External carbonic anhydrase (CA) was not detected nor does this species demonstrate a capacity to take up CO2 by active transport. Photosynthetic O2 evolution and the release CO2 in the dark depend on HCO3- uptake since both were inhibited by the anion exchange inhibitor, 4,4'-diisothiocyanatostilbene-2,2'-disulfonic acid (DIDS). The bicarbonate uptake mechanism requires light but can also continue for short periods in the dark. Ethoxyzolamide, a CA inhibitor, markedly inhibited CO2 efflux in the dark, indicating that CO2 efflux was dependent upon the intracellular dehydration of HCO3-. These results indicate that Nannochloropsis possesses a bicarbonate uptake system which causes the accumulation of high intracellular Ci levels and an internal CA which maintains the equilibrium between CO2 and HCO3- and thus causes a subsequent release of CO2 to the external medium.

  8. Decomposition of Net CO2 Emission in the Wuhan Metropolitan Area of Central China

    Directory of Open Access Journals (Sweden)

    Xin Yang

    2016-08-01

    Full Text Available Policy-makers have been sharing growing concerns that climate change has significant impacts on human society and economic activates. Knowledge of the influencing factors of CO2 emission is the crucial step to reduce it. In this paper, both CO2 emission and CO2 sink on a city-level of the nine cities in Wuhan Metropolitan Area are calculated using the Intergovernmental Panel on Climate Change approach. Moreover, the logarithmic mean Divisia index (LMDI model was employed to decompose the net CO2 emission from 2001 to 2009. Results showed that (1 the largest amount of CO2 emission comes from energy while the largest amount CO2 sink comes from cropland; (2 economic level (S was the largest positive driving factor for net CO2 emission growth in the Wuhan Metropolitan Area, population (P also played a positive driving role, but with very weak contribution; and as negative inhibiting factors, energy structure (E and energy efficiency (C significantly reduced the net CO2 emission.

  9. Soil CO2 Uptake in Deserts and Its Implications to the Groundwater Environment

    Directory of Open Access Journals (Sweden)

    Wenfeng Wang

    2016-09-01

    Full Text Available Recent studies of soil carbon cycle in arid and semi-arid ecosystems demonstrated that there exists an abiotic CO2 absorption by saline-alkali soils (Aa at desert ecosystems and suggested potential contributions of CO2 dissolution beneath deserts to the terrestrial ecosystems carbon balance. However, the overall importance of such soil CO2 uptake is still undetermined and its implications to the groundwater environment remain unaddressed. In this manuscript, a simple method is proposed for the direct computation of Aa from the total soil CO2 flux (Fa as well as for the evaluation of Aa importance to Fa. An artificial soil-groundwater system was employed to investigate the implications to groundwater environment and it was found that soil CO2 uptake in deserts can contribute a possible influence on the evolution of the groundwater environment, providing that the absorbed CO2 largely remained in the soil-groundwater system.

  10. Assessing the potential long-term increase of oceanic fossil fuel CO2 uptake due to CO2-calcification feedback

    Science.gov (United States)

    Ridgwell, A.; Zondervan, I.; Hargreaves, J. C.; Bijma, J.; Lenton, T. M.

    2007-07-01

    Plankton manipulation experiments exhibit a wide range of sensitivities of biogenic calcification to simulated anthropogenic acidification of the ocean, with the "lab rat" of planktic calcifiers, Emiliania huxleyi apparently not representative of calcification generally. We assess the implications of this observational uncertainty by creating an ensemble of realizations of an Earth system model that encapsulates a comparable range of uncertainty in calcification response to ocean acidification. We predict that a substantial reduction in marine carbonate production is possible in the future, with enhanced ocean CO2 sequestration across the model ensemble driving a 4-13% reduction in the year 3000 atmospheric fossil fuel CO2 burden. Concurrent changes in ocean circulation and surface temperatures in the model contribute about one third to the increase in CO2 uptake. We find that uncertainty in the predicted strength of CO2-calcification feedback seems to be dominated by the assumption as to which species of calcifier contribute most to carbonate production in the open ocean.

  11. Assessing the potential long-term increase of oceanic fossil fuel CO2 uptake due to CO2-calcification feedback

    Directory of Open Access Journals (Sweden)

    T. M. Lenton

    2007-07-01

    Full Text Available Plankton manipulation experiments exhibit a wide range of sensitivities of biogenic calcification to simulated anthropogenic acidification of the ocean, with the "lab rat" of planktic calcifiers, Emiliania huxleyi apparently not representative of calcification generally. We assess the implications of this observational uncertainty by creating an ensemble of realizations of an Earth system model that encapsulates a comparable range of uncertainty in calcification response to ocean acidification. We predict that a substantial reduction in marine carbonate production is possible in the future, with enhanced ocean CO2 sequestration across the model ensemble driving a 4–13% reduction in the year 3000 atmospheric fossil fuel CO2 burden. Concurrent changes in ocean circulation and surface temperatures in the model contribute about one third to the increase in CO2 uptake. We find that uncertainty in the predicted strength of CO2-calcification feedback seems to be dominated by the assumption as to which species of calcifier contribute most to carbonate production in the open ocean.

  12. 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; Touma, Danielle; Andrews, Arlyn; Basso, Luana G.; hide

    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 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 (Approx.1-8 x 10(exp -6) km2) 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

  13. High net CO2 and CH4 release at a eutrophic shallow lake on a formerly drained fen

    Science.gov (United States)

    Franz, Daniela; Koebsch, Franziska; Larmanou, Eric; Augustin, Jürgen; Sachs, Torsten

    2016-05-01

    Drained peatlands often act as carbon dioxide (CO2) hotspots. Raising the groundwater table is expected to reduce their CO2 contribution to the atmosphere and revitalise their function as carbon (C) sink in the long term. Without strict water management rewetting often results in partial flooding and the formation of spatially heterogeneous, nutrient-rich shallow lakes. Uncertainties remain as to when the intended effect of rewetting is achieved, as this specific ecosystem type has hardly been investigated in terms of greenhouse gas (GHG) exchange. In most cases of rewetting, methane (CH4) emissions increase under anoxic conditions due to a higher water table and in terms of global warming potential (GWP) outperform the shift towards CO2 uptake, at least in the short term.Based on eddy covariance measurements we studied the ecosystem-atmosphere exchange of CH4 and CO2 at a shallow lake situated on a former fen grassland in northeastern Germany. The lake evolved shortly after flooding, 9 years previous to our investigation period. The ecosystem consists of two main surface types: open water (inhabited by submerged and floating vegetation) and emergent vegetation (particularly including the eulittoral zone of the lake, dominated by Typha latifolia). To determine the individual contribution of the two main surface types to the net CO2 and CH4 exchange of the whole lake ecosystem, we combined footprint analysis with CH4 modelling and net ecosystem exchange partitioning.The CH4 and CO2 dynamics were strikingly different between open water and emergent vegetation. Net CH4 emissions from the open water area were around 4-fold higher than from emergent vegetation stands, accounting for 53 and 13 g CH4 m-2 a-1 respectively. In addition, both surface types were net CO2 sources with 158 and 750 g CO2 m-2 a-1 respectively. Unusual meteorological conditions in terms of a warm and dry summer and a mild winter might have facilitated high respiration rates. In sum, even after 9

  14. Net primary production and seasonal CO2 and CH4 fluxes in a Trapa natans L. meadow

    Directory of Open Access Journals (Sweden)

    Marco BARTOLI

    2010-08-01

    Full Text Available The main hypothesis of this work is that Trapa natans L. and similar floating leaved macrophytes are only temporary sinks of atmospheric carbon dioxide and that they favour water hypoxia and large methane efflux from sediment to the atmosphere, due to their shading effect and scarce ability to transfer oxygen to submerged tissues. For this purpose, from April to August 2005, T. natans production, dissolved O2, CO2 and CH4 concentrations in the water column and CO2 and CH4 fluxes across the wateratmosphere interface were measured in an oxbow lake (Lanca di Po, Northern Italy where a monospecific floating mat of water chestnut develops. Net primary production by T. natans was determined via biomass harvesting while gas fluxes were determined via short-term incubations of light and dark floating chambers. From July onwards, when the water surface of the oxbow lake was entirely colonized by the plant, the dense canopy resulted in a physical barrier for light and water reareation. As a consequence of sediment and plant respiration, persistent hypoxia and often anoxia, and CO2 and CH4 supersaturation occurred in the water column. Net primary production of T. natans, calculated at peak biomass, was 13.05 ± 0.32 mol CO2 m-2. The T. natans mat was a net sink for atmospheric CO2 from mid June to mid August, with an uptake peak measured at the beginning of July (229 mmol m-2 d-1; estimated net ecosystem metabolism was ≤10.09 ± 1.90 mol CO2 m-2. Contextually, during the vegetative period of T. natans, the oxbow lake was a net source of methane (9.52 ± 2.10 mol m-2, and the resulting CH4 to CO2 flux ratio across the water-atmosphere interface was ≥0.94. The large methane release was probably due to the persistent hypoxia and anoxia induced by the T. natans meadow, which uncoupled methane production from methane oxidation.

  15. Biophysical controls on net ecosystem CO2 exchange over a semiarid shrubland in northwest China

    Science.gov (United States)

    Jia, X.; Zha, T. S.; Wu, B.; Zhang, Y. Q.; Gong, J. N.; Qin, S. G.; Chen, G. P.; Qian, D.; Kellomäki, S.; Peltola, H.

    2014-09-01

    The carbon (C) cycling in semiarid and arid areas remains largely unexplored, despite the wide distribution of drylands globally. Rehabilitation practices have been carried out in many desertified areas, but information on the C sequestration capacity of recovering vegetation is still largely lacking. Using the eddy-covariance technique, we measured the net ecosystem CO2 exchange (NEE) over a recovering shrub ecosystem in northwest China throughout 2012 in order to (1) quantify NEE and its components and to (2) examine the dependence of C fluxes on biophysical factors at multiple timescales. The annual budget showed a gross ecosystem productivity (GEP) of 456 g C m-2 yr-1 (with a 90% prediction interval of 449-463 g C m-2 yr-1) and an ecosystem respiration (Re) of 379 g C m-2 yr-1 (with a 90% prediction interval of 370-389 g C m-2 yr-1), resulting in a net C sink of 77 g C m-2 yr-1 (with a 90% prediction interval of 68-87 g C m-2 yr-1). The maximum daily NEE, GEP and Re were -4.7, 6.8 and 3.3 g C m-2 day-1, respectively. Both the maximum C assimilation rate (i.e., at the optimum light intensity) and the quantum yield varied over the growing season, being higher in summer and lower in spring and autumn. At the half-hourly scale, water deficit exerted a major control over daytime NEE, and interacted with other stresses (e.g., heat and photoinhibition) in constraining C fixation by the vegetation. Low soil moisture also reduced the temperature sensitivity of Re (Q10). At the synoptic scale, rain events triggered immediate pulses of C release from the ecosystem, followed by peaks of CO2 uptake 1-2 days later. Over the entire growing season, leaf area index accounted for 45 and 65% of the seasonal variation in NEE and GEP, respectively. There was a linear dependence of daily Re on GEP, with a slope of 0.34. These results highlight the role of abiotic stresses and their alleviation in regulating C cycling in the face of an increasing frequency and intensity of extreme

  16. CO2 uptake potential due to concrete carbonation: A case study

    Directory of Open Access Journals (Sweden)

    Edna Possan

    2017-06-01

    Full Text Available The cement manufacturing process accounts for about 5% CO2 (carbon dioxide released into the atmosphere. However, during its life cycle, concrete may capture CO2 through carbonation, in order to, partially, offset the impact of its production. Thus, this paper aims at studying the CO2 uptake potential of the Itaipu Dam due to concrete carbonation of such material. So, 155 cores were extracted from the concrete dam in different points to measure carbonation depth. In order to evaluate its influence on carbonation, the measurement of internal moisture distribution in concrete was also carried out. The results have shown that carbonation takes part of the whole dam area, indicating CO2 uptake potential. Up to the present moment, 13,384 tons of CO2 have been absorbed by concrete carbonation of the Itaipu Dam.

  17. Calculating CO2 uptake for existing concrete structures during and after service life.

    Science.gov (United States)

    Andersson, Ronny; Fridh, Katja; Stripple, Håkan; Häglund, Martin

    2013-10-15

    This paper presents a model that can calculate the uptake of CO2 in all existing concrete structures, including its uptake after service life. This is important for the calculation of the total CO2 uptake in the society and its time dependence. The model uses the well-documented cement use and knowledge of how the investments are distributed throughout the building sector to estimate the stock of concrete applications in a country. The depth of carbonation of these applications is estimated using two models, one theoretical and one based on field measurements. The maximum theoretical uptake potential is defined as the amount of CO2 that is emitted during calcination at the production of Portland cement, but the model can also, with some adjustments, be used for the other cement types. The model has been applied on data from Sweden and the results show a CO2 uptake in 2011 in all existing structures of about 300,000 tonnes, which corresponds to about 17% of the total emissions (calcination and fuel) from the production of new cement for use in Sweden in the same year. The study also shows that in the years 2030 and 2050, an increase in the uptake in crushed concrete, from 12,000 tonnes today to 200,000 and 500,000 tonnes of CO2, respectively, could be possible if the waste handling is redesigned.

  18. Biotic, abiotic, and management controls on the net ecosystem CO2 exchange of European mountain grassland ecosystems

    DEFF Research Database (Denmark)

    Wohlfahrt, Georg; Friborg, Thomas; Johansson et.al., Paul Torbjörn

    2008-01-01

    The net ecosystem carbon dioxide (CO2) exchange (NEE) of nine European mountain grassland ecosystems was measured during 2002-2004 using the eddy covariance method. Overall, the availability of photosynthetically active radiation (PPFD) was the single most important abiotic influence factor for NEE....... Its role changed markedly during the course of the season, PPFD being a better predictor for NEE during periods favorable for CO2 uptake, which was spring and autumn for the sites characterized by summer droughts (southern sites) and (peak) summer for the Alpine and northern study sites. This general...... pattern was interrupted by grassland management practices, that is, mowing and grazing, when the variability in NEE explained by PPFD decreased in concert with the amount of aboveground biomass (BMag). Temperature was the abiotic influence factor that explained most of the variability in ecosystem...

  19. 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

  20. Rising atmospheric CO2 leads to large impact of biology on Southern Ocean CO2 uptake via changes of the Revelle factor.

    Science.gov (United States)

    Hauck, J; Völker, C

    2015-03-16

    The Southern Ocean is a key region for global carbon uptake and is characterized by a strong seasonality with the annual CO2 uptake being mediated by biological carbon drawdown in summer. Here we show that the contribution of biology to CO2 uptake will become even more important until 2100. This is the case even if biological production remains unaltered and can be explained by the decreasing buffer capacity of the ocean as its carbon content increases. The same amount of biological carbon drawdown leads to a more than twice as large reduction in CO2(aq) concentration and hence to a larger CO2 gradient between ocean and atmosphere that drives the gas exchange. While the winter uptake south of 44°S changes little, the summer uptake increases largely and is responsible for the annual mean response. The combination of decreasing buffer capacity and strong seasonality of biological carbon drawdown introduces a strong and increasing seasonality in the anthropogenic carbon uptake. Decrease of buffer capacity leads to stronger summer CO2 uptake in the futureBiology will contribute more to future CO2 uptake in Southern OceanSeasonality affects anthropogenic carbon uptake strongly.

  1. [Net CO2 exchange and carbon isotope flux in Acacia mangium plantation].

    Science.gov (United States)

    Zou, Lu-Liu; Sun, Gu-Chou; Zhao, Ping; Cai, Xi-An; Zeng, Xiao-Ping; Wang, Quan

    2009-11-01

    By using stable carbon isotope technique, the leaf-level 13C discrimination was integrated to canopy-scale photosynthetic discrimination (Deltacanopy) through weighted the net CO2 assimilation (Anet) of sunlit and shaded leaves and the stand leaf area index (L) in an A. mangium plantation, and the carbon isotope fluxes from photosynthesis and respiration as well as their net exchange flux were obtained. There was an obvious diurnal variation in Deltacanopy, being lower at dawn and at noon time (18.47 per thousand and 19.87 per thousand, respectively) and the highest (21.21 per thousand) at dusk. From the end of November to next May, the Deltacanopy had an increasing trend, with an annual average of (20.37 +/- 0.29) per thousand. The carbon isotope ratios of CO2 from autotrophic respiration (excluding daytime foliar respiration) and heterotrophic respiration were respectively (- 28.70 +/- 0.75) per thousand and (- 26.75 +/- 1.3) per thousand in average. The delta13 C of nighttime ecosystem-respired CO2 in May was the lowest (-30.14 per thousand), while that in November was the highest (-28.01 per thousand). The carbon isotope flux of CO2 between A. mangium forest and atmosphere showed a midday peak of 178.5 and 217 micromol x m(-2) x s(-1) x per thousand in May and July, with the daily average of 638.4 and 873.2 micromol x m(-2) x s(-1) x per thousand, respectively. The carbon isotope flux of CO2 absorbed by canopy leaves was 1.6-2.5 times higher than that of CO2 emitted from respiration, suggesting that a large sum of CO2 was absorbed by A. mangium, which decreased the atmospheric CO2 concentration and improved the environment.

  2. Exceptional gravimetric and volumetric CO2 uptake in a palladated NbO-type MOF utilizing cooperative acidic and basic, metal-CO2 interactions.

    Science.gov (United States)

    Spanopoulos, I; Bratsos, I; Tampaxis, C; Vourloumis, D; Klontzas, E; Froudakis, G E; Charalambopoulou, G; Steriotis, T A; Trikalitis, P N

    2016-08-18

    A novel NbO-type MOF is reported based on a palladated organic linker, showing a remarkable gravimetric and volumetric CO2 uptake, reaching 201.8 cm(3) g(-1) (9.0 mmol g(-1), 39.7 wt%) and 187.8 cm(3) cm(-3) at 273 K and 1 bar, respectively. Accurate theoretical calculations revealed that the exceptional CO2 uptake is due to the combination of Lewis base Pd(ii)-CO2 (24.3 kJ mol(-1)) and Lewis acid Cu(ii)-CO2 (30.3 kJ mol(-1)) interactions, as well as synergistic pore size effects.

  3. Effects of elevated CO2 on soil organic matter turnover and plant nitrogen uptake: First results from a dual labeling mesocosm experiment

    Science.gov (United States)

    Eder, Lucia Muriel; Weber, Enrico; Schrumpf, Marion; Zaehle, Sönke

    2017-04-01

    The response of plant growth to elevated concentrations of CO2 (eCO2) is often constrained by plant nitrogen (N) uptake. To overcome potential N limitation, plants may invest photosynthetically fixed carbon (C) into N acquiring strategies, including fine root biomass, root exudation, or C allocation to mycorrhizal fungi. In turn, these strategies may affect the decomposition of soil organic matter, leading to uncertainties in net effects of eCO2 on C storage. To gain more insight into these plant-soil C-N-interactions, we combined C and N stable isotope labeling in a mesocosm experiment. Saplings of Fagus sylvatica L. were exposed to a 13CO2 enriched atmosphere at near ambient (380 ppm) or elevated (550 ppm) CO2 concentrations for four months of the vegetation period in 2016. Aboveground and belowground net CO2 fluxes were measured separately and the 13C label enabled partitioning of total soil CO2 efflux into old, soil derived and new, plant-derived C. We used ingrowth cores to assess effects of eCO2on belowground C allocation and plant N uptake in more detail and in particular we evaluated the relative importance of ectomycorrhizal associations. In the soil of each sapling, ingrowth cores with different mesh sizes allowed fine roots or only mycorrhizal hyphae to penetrate. In one type of ingrowth core each, we incorporated fine root litter that was enriched in 15N. Additionally, total N uptake was estimated by using 15N enriched saplings and unlabeled control plants. We found that eCO2 increased aboveground net CO2 exchange rates by 19% and total soil respiration by 11%. The eCO2 effect for GPP and also for NPP was positive (+23% and +11%, respectively). By combining gaseous C fluxes with data on new and old C stocks in bulk soil and plants through destructive harvesting in late autumn 2016, we will be able to infer net effects of eCO2 on the fate of C in these mesocosms. Biomass allocation patterns can reveal physiological responses to high C availability under

  4. The declining uptake rate of atmospheric CO2 by land and ocean sinks

    Directory of Open Access Journals (Sweden)

    M. R. Raupach

    2014-07-01

    Full Text Available Through 1959–2012, an airborne fraction (AF of 0.44 of total anthropogenic CO2 emissions remained in the atmosphere, with the rest being taken up by land and ocean CO2 sinks. Understanding of this uptake is critical because it greatly alleviates the emissions reductions required for climate mitigation, and also reduces the risks and damages that adaptation has to embrace. An observable quantity that reflects sink properties more directly than the AF is the CO2 sink rate (kS, the combined land–ocean CO2 sink flux per unit excess atmospheric CO2 above preindustrial levels. Here we show from observations that kS declined over 1959–2012 by a factor of about 1 / 3, implying that CO2 sinks increased more slowly than excess CO2. Using a carbon–climate model, we attribute the decline in kS to four mechanisms: slower-than-exponential CO2 emissions growth (~ 35% of the trend, volcanic eruptions (~ 25%, sink responses to climate change (~ 20%, and nonlinear responses to increasing CO2, mainly oceanic (~ 20%. The first of these mechanisms is associated purely with the trajectory of extrinsic forcing, and the last two with intrinsic, feedback responses of sink processes to changes in climate and atmospheric CO2. Our results suggest that the effects of these intrinsic, nonlinear responses are already detectable in the global carbon cycle. Although continuing future decreases in kS will occur under all plausible CO2 emission scenarios, the rate of decline varies between scenarios in non-intuitive ways because extrinsic and intrinsic mechanisms respond in opposite ways to changes in emissions: extrinsic mechanisms cause kS to decline more strongly with increasing mitigation, while intrinsic mechanisms cause kS to decline more strongly under high-emission, low-mitigation scenarios as the carbon–climate system is perturbed further from a near-linear regime.

  5. Large Diurnal Warming Events in the Upper Ocean and Their Implications for CO2 Uptake

    Science.gov (United States)

    Soloviev, A.

    2001-12-01

    Strong dependence of the CO2 solubility on temperature suggests that the large diurnal warming events may cause significant deviations from the bulk flux formulation. Since under low wind speed conditions the air-sea gas exchange is smaller but nonzero, the effect of large diurnal warming events on the estimate of CO2 uptake cannot be ignored. Large diurnal warming events develop under low wind speed conditions and are usually localized within the upper few meters of the ocean. With rear exception, the large diurnal events are undetected during shipboard surveys and are mostly unaccounted at estimating the CO2 uptake by the ocean. A stochastic model of the diurnal cycle and a cool skin model, which are forced by the global heat, mass, and momentum fluxes, elucidate the geographical distribution of the large diurnal warming events as well as their seasonal, and, at some extent, inter-annual variability. Since the diurnal cycle under low wind speed conditions is a strongly non-linear process, a composite diurnal cycle rather than a simple parameterization forced by averaged heat and momentum fluxes is used. The correction for sea surface temperature relating to the large diurnal warming events is used to exrapolate pCO2 to the sea surface. The JGOFS data sets from BATS, HOT, and the Arabian Sea Process Study are used to refine these techniques in different regions. This work leads to an improved estimate of the global CO2 uptake by oceans.

  6. Daily variation in net primary production and net calcification in coral reef communities exposed to elevated pCO2

    Science.gov (United States)

    Comeau, Steeve; Edmunds, Peter J.; Lantz, Coulson A.; Carpenter, Robert C.

    2017-07-01

    The threat represented by ocean acidification (OA) for coral reefs has received considerable attention because of the sensitivity of calcifiers to changing seawater carbonate chemistry. However, most studies have focused on the organismic response of calcification to OA, and only a few have addressed community-level effects, or investigated parameters other than calcification, such as photosynthesis. Light (photosynthetically active radiation, PAR) is a driver of biological processes on coral reefs, and the possibility that these processes might be perturbed by OA has important implications for community function. Here we investigate how CO2 enrichment affects the relationships between PAR and community net O2 production (Pnet), and between PAR and community net calcification (Gnet), using experiments on three coral communities constructed to match (i) the back reef of Mo'orea, French Polynesia, (ii) the fore reef of Mo'orea, and (iii) the back reef of O'ahu, Hawaii. The results were used to test the hypothesis that OA affects the relationship between Pnet and Gnet. For the three communities tested, pCO2 did not affect the Pnet-PAR relationship, but it affected the intercept of the hyperbolic tangent curve fitting the Gnet-PAR relationship for both reef communities in Mo'orea (but not in O'ahu). For the three communities, the slopes of the linear relationships between Pnet and Gnet were not affected by OA, although the intercepts were depressed by the inhibitory effect of high pCO2 on Gnet. Our result indicates that OA can modify the balance between net calcification and net photosynthesis of reef communities by depressing community calcification, but without affecting community photosynthesis.

  7. Daily variation in net primary production and net calcification in coral reef communities exposed to elevated pCO2

    Directory of Open Access Journals (Sweden)

    S. Comeau

    2017-07-01

    Full Text Available The threat represented by ocean acidification (OA for coral reefs has received considerable attention because of the sensitivity of calcifiers to changing seawater carbonate chemistry. However, most studies have focused on the organismic response of calcification to OA, and only a few have addressed community-level effects, or investigated parameters other than calcification, such as photosynthesis. Light (photosynthetically active radiation, PAR is a driver of biological processes on coral reefs, and the possibility that these processes might be perturbed by OA has important implications for community function. Here we investigate how CO2 enrichment affects the relationships between PAR and community net O2 production (Pnet, and between PAR and community net calcification (Gnet, using experiments on three coral communities constructed to match (i the back reef of Mo'orea, French Polynesia, (ii the fore reef of Mo'orea, and (iii the back reef of O'ahu, Hawaii. The results were used to test the hypothesis that OA affects the relationship between Pnet and Gnet. For the three communities tested, pCO2 did not affect the Pnet–PAR relationship, but it affected the intercept of the hyperbolic tangent curve fitting the Gnet–PAR relationship for both reef communities in Mo'orea (but not in O'ahu. For the three communities, the slopes of the linear relationships between Pnet and Gnet were not affected by OA, although the intercepts were depressed by the inhibitory effect of high pCO2 on Gnet. Our result indicates that OA can modify the balance between net calcification and net photosynthesis of reef communities by depressing community calcification, but without affecting community photosynthesis.

  8. Tetrahedral tetrazolate frameworks for high CO2 and H2 uptake.

    Science.gov (United States)

    Wang, Fei; Hou, Duan-Chuan; Yang, Hui; Kang, Yao; Zhang, Jian

    2014-02-28

    Three tetrahedral tetrazolate frameworks with two different 4-connected topologies including lonsdaleite (lon, for 1) and diamond (dia, for 2 and 3) have been synthesized, and the lon-type framework with high CO2 and H2 uptake capacity can irreversibly transform to the dia-type framework via solvent-exchange.

  9. High prevalence of diffusive uptake of CO2 by macroalgae in a temperate subtidal ecosystem.

    Science.gov (United States)

    Cornwall, Christopher E; Revill, Andrew T; Hurd, Catriona L

    2015-05-01

    Productivity of most macroalgae is not currently considered limited by dissolved inorganic carbon (DIC), as the majority of species have CO2-concentrating mechanisms (CCM) allowing the active uptake of DIC. The alternative, diffusive uptake of CO2 (non-CCM), is considered rare (0-9% of all macroalgal cover in a given ecosystem), and identifying species without CCMs is important in understanding factors controlling inorganic carbon use by eukaryotic algae. CCM activity has higher energetic requirements than diffusive CO2 uptake, therefore when light is low, CCM activity is reduced in favour of diffusive CO2 uptake. We hypothesized that the proportional cover of macroalgae without CCMs (red and green macroalgae) would be low (green macroalgae (two species). The proportion of non-CCM species increased with depth at three of four sites. 35% of species tested had significantly depleted δ(13)C values at deeper depths. Non-CCM macroalgae are more abundant in some temperate reefs than previously thought. If ocean acidification benefits non-CCM species, the ramifications for subtidal macroalgal assemblages could be larger than previously considered.

  10. Age-dependent impacts of peatland restoration on the net ecosystem CO2 exchange of blanket bogs in Northern Scotland

    Science.gov (United States)

    Hambley, Graham; Hill, Timothy; Saunders, Matthew; Arn Teh, Yit

    2015-04-01

    The Flow Country of Northern Scotland is the largest area of contiguous blanket bog in the UK covering an area in excess of 400 km2. This region is the single largest peat and soil C repository in the UK, and plays a key role in mediating regional atmospheric exchanges of greenhouse gases (GHGs) such as carbon dioxide (CO2), methane (CH4) and water vapour (H2O). However, these peatlands were subject to significant afforestation in the 1980s, where large areas of blanket bog were drained and planted with Sitka spruce (Picea sitchensis) and Lodgepole Pine (Pinus contorta), resulting in modifications to micro-topographic features, vegetation composition and soil properties such as bulk density and water holding capacity, all of which are known to influence the production and emission of key GHGs. Since the late 1990s restoration work has been undertaken to remove forest plantations and to restore the peatland areas by raising the water table, predominantly by drain and furrow blocking, in order to encourage the recolonisation of Sphagnum species. Here we report findings from an eddy covariance study of CO2 and H2O exchange from an unmanaged peatland and a chronosequence of restored peatland sites, which were felled in 1998 and 2004. Located within the Forsinard Flows National Nature Reserve in Northern Scotland, these sites are being studied to better understand the key drivers of carbon dynamics in these ecosystems and also assess the age-dependent impacts of peatland restoration on the net CO2 sink strength. Preliminary data show rates of CO2 uptake increased with time since restoration, with peak assimilation rates of -9.9 and -14.4 micro mol CO2 m-2 s-1 measured at the 10 and 16 year old restoration sites, respectively. Carbon losses through ecosystem respiration followed a similar pattern. The data collected to date indicates that while peatland restoration is actively increasing CO2 uptake at each of the sites, more long-term observational data is required to

  11. Increases in nitrogen uptake rather than nitrogen-use efficiency support higher rates of temperate forest productivity under elevated CO2.

    Science.gov (United States)

    Finzi, Adrien C; Norby, Richard J; Calfapietra, Carlo; Gallet-Budynek, Anne; Gielen, Birgit; Holmes, William E; Hoosbeek, Marcel R; Iversen, Colleen M; Jackson, Robert B; Kubiske, Mark E; Ledford, Joanne; Liberloo, Marion; Oren, Ram; Polle, Andrea; Pritchard, Seth; Zak, Donald R; Schlesinger, William H; Ceulemans, Reinhart

    2007-08-28

    Forest ecosystems are important sinks for rising concentrations of atmospheric CO(2). In previous research, we showed that net primary production (NPP) increased by 23 +/- 2% when four experimental forests were grown under atmospheric concentrations of CO(2) predicted for the latter half of this century. Because nitrogen (N) availability commonly limits forest productivity, some combination of increased N uptake from the soil and more efficient use of the N already assimilated by trees is necessary to sustain the high rates of forest NPP under free-air CO(2) enrichment (FACE). In this study, experimental evidence demonstrates that the uptake of N increased under elevated CO(2) at the Rhinelander, Duke, and Oak Ridge National Laboratory FACE sites, yet fertilization studies at the Duke and Oak Ridge National Laboratory FACE sites showed that tree growth and forest NPP were strongly limited by N availability. By contrast, nitrogen-use efficiency increased under elevated CO(2) at the POP-EUROFACE site, where fertilization studies showed that N was not limiting to tree growth. Some combination of increasing fine root production, increased rates of soil organic matter decomposition, and increased allocation of carbon (C) to mycorrhizal fungi is likely to account for greater N uptake under elevated CO(2). Regardless of the specific mechanism, this analysis shows that the larger quantities of C entering the below-ground system under elevated CO(2) result in greater N uptake, even in N-limited ecosystems. Biogeochemical models must be reformulated to allow C transfers below ground that result in additional N uptake under elevated CO(2).

  12. Acclimation to Very Low CO2: Contribution of Limiting CO2 Inducible Proteins, LCIB and LCIA, to Inorganic Carbon Uptake in Chlamydomonas reinhardtii1[OPEN

    Science.gov (United States)

    Spalding, Martin H.

    2014-01-01

    The limiting-CO2 inducible CO2-concentrating mechanism (CCM) of microalgae represents an effective strategy to capture CO2 when its availability is limited. At least two limiting-CO2 acclimation states, termed low CO2 and very low CO2, have been demonstrated in the model microalga Chlamydomonas reinhardtii, and many questions still remain unanswered regarding both the regulation of these acclimation states and the molecular mechanism underlying operation of the CCM in these two states. This study examines the role of two proteins, Limiting CO2 Inducible A (LCIA; also named NAR1.2) and LCIB, in the CCM of C. reinhardtii. The identification of an LCIA-LCIB double mutant based on its inability to survive in very low CO2 suggests that both LCIA and LCIB are critical for survival in very low CO2. The contrasting effects of individual mutations in LCIB and LCIA compared with the effects of LCIB-LCIA double mutations on growth and inorganic carbon-dependent photosynthetic O2 evolution reveal distinct roles of LCIA and LCIB in the CCM. Although both LCIA and LCIB are essential for very low CO2 acclimation, LCIB appears to function in a CO2 uptake system, whereas LCIA appears to be associated with a HCO3− transport system. The contrasting and complementary roles of LCIA and LCIB in acclimation to low CO2 and very low CO2 suggest a possible mechanism of differential regulation of the CCM based on the inhibition of HCO3− transporters by moderate to high levels of CO2. PMID:25336519

  13. Long-Term Drainage Reduces CO2 Uptake and CH4 Emissions in a Siberian Permafrost Ecosystem

    Science.gov (United States)

    Kittler, Fanny; Heimann, Martin; Kolle, Olaf; Zimov, Nikita; Zimov, Sergei; Göckede, Mathias

    2017-12-01

    Permafrost landscapes in northern high latitudes with their massive organic carbon stocks are an important, poorly known, component of the global carbon cycle. However, in light of future Arctic warming, the sustainability of these carbon pools is uncertain. To a large part, this is due to a limited understanding of the carbon cycle processes because of sparse observations in Arctic permafrost ecosystems. Here we present an eddy covariance data set covering more than 3 years of continuous CO2 and CH4 flux observations within a moist tussock tundra ecosystem near Chersky in north-eastern Siberia. Through parallel observations of a disturbed (drained) area and a control area nearby, we aim to evaluate the long-term effects of a persistently lowered water table on the net vertical carbon exchange budgets and the dominating biogeochemical mechanisms. Persistently drier soils trigger systematic shifts in the tundra ecosystem carbon cycle patterns. Both, uptake rates of CO2 and emissions of CH4 decreased. Year-round measurements emphasize the importance of the non-growing season—in particular the "zero-curtain" period in the fall—to the annual budget. Approximately 60% of the CO2 uptake in the growing season is lost during the cold seasons, while CH4 emissions during the non-growing season account for 30% of the annual budget. Year-to-year variability in temperature conditions during the late growing season was identified as the primary control of the interannual variability observed in the CO2 and CH4 fluxes.

  14. Summer extreme climatic event in the future: impact on the net CO2 and water fluxes of an upland grassland and buffering impact of elevated atmospheric CO2

    Science.gov (United States)

    Roy, Jacques; Ravel, Olivier; Landais, Damien; Piel, Clément; Defossez, Marc; Escape, Christophe; Devidal, Sébastien; Didier, Philippe; Bahn, Michael; Volaire, Florence; Augusti, Angela; Soussana, Jean-François; Picon-Cochard, Catherine

    2013-04-01

    Extreme climatic events are expected to be more frequent and intense in a few decades, but they will also occur in a climatic context different from the current one. In the Montpellier Ecotron, we studied the response of intact grassland monoliths (1m², 60 cm deep) sampled in an upland grassland of the French Massif Central. The first year the grasslands were acclimated to the average climatic conditions of the years around 2050 (+ 4 °C and - 56 mm for summer precipitations). The second year, the same climate was maintained but in half of the experimental units we imposed a summer drought and heat wave (50 % reduction of precipitations for a month and then 100 % precipitation reduction combined with a 3,4 °C increase in temperature for two weeks). A CO2 treatment (520 vs 380 µmol/mol) was crossed with the climatic treatment. Net CO2 fluxes were measured continuously during the second year of the experiment. The extreme climatic event induced a total senescence of the canopy whatever the CO2 treatment. The interactive effect of elevated CO2 with the drought treatment was significant at the onset of the drought and particularly large in the fall after the recovery period, with a net photosynthesis twice as high in the (extreme climate+ CO2) treatment compared to the control. Integrated over the year, elevated CO2 totally buffered the impact of the extreme climatic event on net CO2 exchanges. These results are discussed together with the evapotranspiration and soil humidity data.

  15. Analysing global ecosystem CO2 uptake capacity with plant trait data

    Science.gov (United States)

    van de Weg, Martine; Sadat Musavi, Talie; van Bodegom, Peter; Kattge, Jens; Mahecha, Miguel; Reichstein, Markus; Bahn, Michael

    2014-05-01

    Given the modulating role of vegetation in the global carbon cycle, there is a demand for simple and general scaling relationships of vegetation characteristics and ecosystem CO2-uptake and emissions. On a leaf level, is it well established that plant trait foliar nitrogen (N) relates strongly with leaf level CO2. Furthermore, ecosystem productivity or CO2 uptake capacity have been related directly with whole-canopy N concentrations for a variety of ecosystems such as grasslands, and boreal, temporal and tropical forests. However, studies on the global validity of these leaf and ecosystem level relationships have been lacking up to date. The arrival of the large plant trait database TRY database offers the opportunity to link plant trait and ecosystem functioning on a global scale. In this study, we used CO2 flux data from the FLUXNET database, with plant trait (Narea) data from TRY and Narea measurements from a selection of FLUXNET sites as well. For 83 global FLUXNET sites, which had information available on species composition, we derived the light saturated gross primary productivity (GPP1000). We used MODIS LAI and fPAR, together with the species' relative height and abundance data, to up-scale the TRY derived Narea values to a canopy value per site (Ncanopy). For this calculation we assumed that top canopy leaves contribute more to CO2 uptake, and used a Lambert-Beer canopy light extinction principle to weigh the relative contribution per species to the final Ncanopy value. For our analyses, we divided the sites in five different vegetation classes: broad leaved forests, needle leaved forests, grasslands, crops and (sub)arctic non-forest vegetation. Site-measured Nareadata corroborated well with TRY derived Narea data, giving confidence in using a database such as TRY for global analyses like ours. Ncanopy alone explained 18 % of the observed variation in maximum (90th percentile) GPP1000 with a linear model. When adding the different vegetation types as a

  16. Increased CO2 uptake due to sea ice growth and decay in the Nordic Seas

    DEFF Research Database (Denmark)

    Rysgaard, S.; Bendtsen, J.; Pedersen, L. T.

    2009-01-01

    uptake in the Nordic Seas is currently unknown. We present evidence from 50 localities in the Arctic Ocean that dissolved inorganic carbon is rejected together with brine from growing sea ice and that sea ice melting during summer is rich in carbonates. Model calculations show that melting of sea ice......The uptake rates of atmospheric CO2 in the Nordic Seas are among the highest in the world's oceans. This has been ascribed mainly to a strong biological drawdown, but chemical processes within the sea ice itself have also been suggested to play a role. The importance of sea ice for the carbon...

  17. The effects of clouds and aerosols on net ecosystem CO2 exchange over semi-arid Loess Plateau of Northwest China

    Directory of Open Access Journals (Sweden)

    T. Wang

    2010-09-01

    Full Text Available The impacts of clouds and atmospheric aerosols on the terrestrial carbon cycle at semi-arid Loess Plateau in Northwest China are investigated, by using the observation data obtained at the SACOL (Semi-Arid Climate and Environment Observatory of Lanzhou University site. Daytime (solar elevation angles of larger than 50° net ecosystem exchange (NEE of CO2 obtained during the midgrowing season (July–August are analyzed with respect to variations in the diffuse radiation, cloud cover and aerosol optical depth (AOD. Results show a significant impact by clouds on the CO2 uptake by the grassland (with smaller LAI values located in a semi-arid region, quite different from areas covered by forests and crops. The light saturation levels in the canopy are low, with a value of about 434.8 W m−2. Thus, under overcast conditions of optically thick clouds, the CO2 uptake increases with increasing clearness index (the ratio of global solar radiation received at the Earth surface to the extraterrestrial irradiance at a plane parallel to the Earth surface, and a maximum CO2 uptake and light use efficiency of vegetation occur with the clearness index of about 0.37 and lower air temperature. Under other sky conditions, CO2 uptake decreases with cloudiness but light use efficiency is enhanced, due to increased diffuse fraction of PAR. Additionally, under cloudy conditions, changes in the NEE of CO2 also result from the interactions of many environmental factors, especially the air temperature. In contrast to its response to changes in solar radiation, the carbon uptake shows a slightly negative response to increased AOD. The reason for the difference in the response of the semi-arid grassland from that of the forest and crop lands may be due to the difference in the canopy's architectural structure.

  18. Analysing net CO2 exchanges over an arable crop across multiple scales

    Science.gov (United States)

    Blei, Emanuel; Toet, Sylvia; Revill, Andrew; Solis Parejo, Jose; Keane, Ben; Vallack, Harry; Stockdale, James; Ineson, Phil; Levy, Pete; Skiba, Ute; Drewer, Julia; Famulari, Daniela; Williams, Mathew

    2015-04-01

    There is a critical need to better understand and up-scale greenhouse gas fluxes from agricultural activities to support adaptation and mitigation activities at national scales. A major unknown is the intrinsic scale of variability in fluxes from chamber to field scales. This variation is linked to heterogeneity in management, soils and microclimate. We made greenhouse gas fluxes measurements on a commercially operated rapeseed-oil field in the east of England for a month from the start of the growing season until the second fertiliser application (18th March to 16th April 2014). Our methods included using (1) sporadic box chamber measurements of light response curves of CO2 exchanges; (2) a novel automated cable-operated chamber system (SkyLine) developed by the University of York to measure CO2 fluxes continuously from 18 chambers in the field; (3) an Eddy covariance system measuring CO2 fluxes from a larger area on another part of the same field. For each data set a simple model resolving gross primary production and ecosystem respiration, and using LAI, photosynthetically active radiation (PAR) and air temperature as drivers, was tuned to estimate net ecosystem exchange (NEE) for rapeseed oil. We assess the model performance and parameter estimates across the three methods and discuss the implications for scaling fluxes and correcting biases in upscaling.

  19. Conversion of a moderately rewetted fen to a shallow lake - implications for net CO2 exchange

    Science.gov (United States)

    Koebsch, Franziska; Glatzel, Stephan; Hofmann, Joachim; Forbrich, Inke; Jurasinski, Gerald

    2013-04-01

    Extensive rewetting projects to re-establish the natural carbon (C) sequestration function of degraded peatlands are currently taking place in Europe and North-America. Year-round flooding provides a robust measure to prevent periods of drought that are associated with ongoing peat mineralization and to initiate the accumulation of new organic matter. Here, we present measurements of net carbon dioxide (CO2) exchange during the gradual conversion of a moderately rewetted fen to a shallow lake. When we started our measurements in 2009, mean growing season water level (MWGL) was 0 cm. In 2010 the site was flooded throughout the year with MWGL of 36 cm. Extraordinary strong rainfalls in July 2011 resulted in a further increase of MWGL to 56 cm. Measurements of net ecosystem exchange (NEE) were conducted during growing seasons (May-October) using the Eddy Covariance method. Information about vegetation vitality was deduced from the enhanced vegetation index (EVI) based on MODIS data. Ecosystem respiration (Reco) and gross ecosystem production (GEP) were high during vegetation period 2009 (1273.4 and -1572.1 g CO2-C m-2), but decreased by 61 and 46% respectively when the fen was flooded throughout 2010. Under water-logged conditions, heterotrophic respiration declines and gas exchange is limited. Moreover, flooding is a severe stress factor for plants and decreases autotrophic respiration and photosynthesis. However, in comparison to 2010, rates of Reco and GEP doubled during the beginning of growing season 2011, indicating plastic response strategies of wetland plants to flooding. Presumably, plants were not able to cope with the further increase of water levels to up to 120 cm in June/July 2011, resulting in another drop of GEP and Reco. The effects of plant vitality on GEP were confirmed by the remote sensed vegetation index. Throughout all three growing seasons, the fen was a distinct net CO2 sink (2009: -333.3±12.3, 2010: -294.1±8.4, -352.4±5.1 g CO2-C m-2

  20. Impact on CO2 Uptake of MWCNT after Acid Treatment Study

    Directory of Open Access Journals (Sweden)

    Michal Zgrzebnicki

    2017-01-01

    Full Text Available Greenhouse effect is responsible for keeping average temperature of Earth’s atmosphere at level of about 288 K. Its intensification leads to warming of our planet and may contribute to adverse changes in the environment. The most important pollution intensifying greenhouse effect is anthropogenic carbon dioxide. This particular gas absorbs secondary infrared radiation, which in the end leads to an increase of average temperature of Earth’s atmosphere. Main source of CO2 is burning of fossil fuels, like oil, natural gas, and coal. Therefore, to reduce its emission, a special CO2 capture and storage technology is required. Carbonaceous materials are promising materials for CO2 sorbents. Thus multiwalled carbon nanotubes, due to the lack of impurities like ash in activated carbons, were chosen as a model material for investigation of acid treatment impact on CO2 uptake. Remarkable 43% enhancement of CO2 sorption capacity was achieved at 273 K and relative pressure of 0.95. Samples were also thoroughly characterized in terms of texture (specific surface area measurement, transmission electron microscope and chemical composition (X-ray photoelectron spectroscopy.

  1. Net energy payback and CO2 emissions from three midwestern wind farms: An update

    Science.gov (United States)

    White, S.W.

    2006-01-01

    This paper updates a life-cycle net energy analysis and carbon dioxide emissions analysis of three Midwestern utility-scale wind systems. Both the Energy Payback Ratio (EPR) and CO2 analysis results provide useful data for policy discussions regarding an efficient and low-carbon energy mix. The EPR is the amount of electrical energy produced for the lifetime of the power plant divided by the total amount of energy required to procure and transport the materials, build, operate, and decommission the power plants. The CO2 analysis for each power plant was calculated from the life-cycle energy input data. A previous study also analyzed coal and nuclear fission power plants. At the time of that study, two of the three wind systems had less than a full year of generation data to project the life-cycle energy production. This study updates the analysis of three wind systems with an additional four to eight years of operating data. The EPR for the utility-scale wind systems ranges from a low of 11 for a two-turbine system in Wisconsin to 28 for a 143-turbine system in southwestern Minnesota. The EPR is 11 for coal, 25 for fission with gas centrifuge enriched uranium and 7 for gaseous diffusion enriched uranium. The normalized CO2 emissions, in tonnes of CO2 per GW eh, ranges from 14 to 33 for the wind systems, 974 for coal, and 10 and 34 for nuclear fission using gas centrifuge and gaseous diffusion enriched uranium, respectively. ?? Springer Science+Business Media, LLC 2007.

  2. Atmospheric CO2 observations and models suggest strong carbon uptake by forests in New Zealand

    Science.gov (United States)

    Steinkamp, Kay; Mikaloff Fletcher, Sara E.; Brailsford, Gordon; Smale, Dan; Moore, Stuart; Keller, Elizabeth D.; Baisden, W. Troy; Mukai, Hitoshi; Stephens, Britton B.

    2017-01-01

    A regional atmospheric inversion method has been developed to determine the spatial and temporal distribution of CO2 sinks and sources across New Zealand for 2011-2013. This approach infers net air-sea and air-land CO2 fluxes from measurement records, using back-trajectory simulations from the Numerical Atmospheric dispersion Modelling Environment (NAME) Lagrangian dispersion model, driven by meteorology from the New Zealand Limited Area Model (NZLAM) weather prediction model. The inversion uses in situ measurements from two fixed sites, Baring Head on the southern tip of New Zealand's North Island (41.408° S, 174.871° E) and Lauder from the central South Island (45.038° S, 169.684° E), and ship board data from monthly cruises between Japan, New Zealand, and Australia. A range of scenarios is used to assess the sensitivity of the inversion method to underlying assumptions and to ensure robustness of the results. The results indicate a strong seasonal cycle in terrestrial land fluxes from the South Island of New Zealand, especially in western regions covered by indigenous forest, suggesting higher photosynthetic and respiratory activity than is evident in the current a priori land process model. On the annual scale, the terrestrial biosphere in New Zealand is estimated to be a net CO2 sink, removing 98 (±37) Tg CO2 yr-1 from the atmosphere on average during 2011-2013. This sink is much larger than the reported 27 Tg CO2 yr-1 from the national inventory for the same time period. The difference can be partially reconciled when factors related to forest and agricultural management and exports, fossil fuel emission estimates, hydrologic fluxes, and soil carbon change are considered, but some differences are likely to remain. Baseline uncertainty, model transport uncertainty, and limited sensitivity to the northern half of the North Island are the main contributors to flux uncertainty.

  3. Air-sea CO2 fluxes along the coast of Chile: From CO2 outgassing in central northern upwelling waters to CO2 uptake in southern Patagonian fjords

    OpenAIRE

    Torres, Rodrigo; Duarte, Carlos M.; Ruiz-Halpern, Sergio; Fukasawa, Masao

    2011-01-01

    Carbon system parameters measured during several expeditions along the coast of Chile (23°S-56°S) have been used to show the main spatial and temporal trends of air-sea CO2 fluxes in the coastal waters of the eastern South Pacific. Chilean coastal waters are characterized by strong pCO2 gradients between the atmosphere and the surface water, with high spatial and temporal variability. On average, the direction of the carbon flux changes from CO2 outgassing at the coastal upwelling region to C...

  4. Environment or Development? Lifetime Net CO2 Exchange and Control of the Expression of Crassulacean Acid Metabolism in Mesembryanthemum crystallinum1

    Science.gov (United States)

    Winter, Klaus; Holtum, Joseph A.M.

    2007-01-01

    The relative influence of plant age and environmental stress signals in triggering a shift from C3 photosynthesis to Crassulacean acid metabolism (CAM) in the annual halophytic C3-CAM species Mesembryanthemum crystallinum was explored by continuously monitoring net CO2 exchange of whole shoots from the seedling stage until seed set. Plants exposed to high salinity (400 mm NaCl) in hydroponic culture solution or grown in saline-droughted soil acquired between 11% and 24% of their carbon via net dark CO2 uptake involving CAM. In contrast, plants grown under nonsaline, well-watered conditions were capable of completing their life cycle by operating in the C3 mode without ever exhibiting net CO2 uptake at night. These observations are not consistent with the widely expressed view that the induction of CAM by high salinity in M. crystallinum represents an acceleration of preprogrammed developmental processes. Rather, our study demonstrates that the induction of the CAM pathway for carbon acquisition in M. crystallinum is under environmental control. PMID:17056756

  5. Inferring CO2 Fluxes from OCO-2 for Assimilation into Land Surface Models to Calculate Net Ecosystem Exchange

    Science.gov (United States)

    Prouty, R.; Radov, A.; Halem, M.; Nearing, G. S.

    2016-12-01

    Investigations of mid to high latitude atmospheric CO2 show a growing seasonal amplitude. Land surface models poorly predict net ecosystem exchange (NEE) and are unable to substantiate these sporadic observations. An investigation of how the biosphere has reacted to changes in atmospheric CO2 is essential to our understanding of potential climate-vegetation feedbacks. A global, seasonal investigation of CO2-flux is then necessary in order to assimilate into land surface models for improving the prediction of annual NEE. The Atmospheric Radiation Measurement program (ARM) of DOE collects CO2-flux measurements (in addition to CO2 concentration and various other meteorological quantities) at several towers located around the globe at half hour temporal frequencies. CO2-fluxes are calculated via the eddy covariance technique, which utilizes CO2-densities and wind velocities to calculate CO2-fluxes. The global coverage of CO2 concentrations as provided by the Orbiting Carbon Observatory (OCO-2) provide satellite-derived CO2 concentrations all over the globe. A framework relating the satellite-inferred CO2 concentrations collocated with the ground-based ARM as well as Ameriflux stations would enable calculations of CO2-fluxes far from the station sites around the entire globe. Regression techniques utilizing deep-learning neural networks may provide such a framework. Additionally, meteorological reanalysis allows for the replacement of the ARM multivariable meteorological variables needed to infer the CO2-fluxes. We present the results of inferring CO2-fluxes from OCO-2 CO2 concentrations for a two year period, Sept. 2014- Sept. 2016 at the ARM station located near Oklahoma City. A feed-forward neural network (FFNN) is used to infer relationships between the following data sets: F([ARM CO2-density], [ARM Meteorological Data]) = [ARM CO2-Flux] F([OCO-2 CO2-density],[ARM Meteorological Data]) = [ARM CO2-Flux] F([ARM CO2-density],[Meteorological Reanalysis]) = [ARM CO2-Flux

  6. Sea-ice melt CO2-carbonate chemistry in the western Arctic Ocean: meltwater contributions to air-sea CO2 gas exchange, mixed layer properties and rates of net community production under sea ice

    Science.gov (United States)

    Bates, N. R.; Garley, R.; Frey, K. E.; Shake, K. L.; Mathis, J. T.

    2014-01-01

    The carbon dioxide (CO2)-carbonate chemistry of sea-ice melt and co-located, contemporaneous seawater has rarely been studied in sea ice covered oceans. Here, we describe the CO2-carbonate chemistry of sea-ice melt (both above sea ice as "melt ponds" and below sea ice as "interface waters") and mixed layer properties in the western Arctic Ocean in the early summer of 2010 and 2011. At nineteen stations, the salinity (~ 0.5 to 1500 μatm) with the majority of melt ponds acting as potentially strong sources of CO2 to the atmosphere. The pH of melt pond waters was also highly variable ranging from mildly acidic (6.1 to 7) to slightly more alkaline than underlying seawater (8 to 10.7). All of observed melt ponds had very low (pH/Ωaragonite than the co-located mixed layer beneath. Sea-ice melt thus contributed to the suppression of mixed layer pCO2 enhancing the surface ocean's capacity to uptake CO2 from the atmosphere. Meltwater contributions to changes in mixed-layer DIC were also used to estimate net community production rates (mean of 46.9 ±29.8 g C m-2 for the early-season period) under sea-ice cover. Although sea-ice melt is a transient seasonal feature, above-ice melt pond coverage can be substantial (10 to > 50%) and under-ice interface melt water is ubiquitous during this spring/summer sea-ice retreat. Our observations contribute to growing evidence that sea-ice CO2-carbonate chemistry is highly variable and its contribution to the complex factors that influence the balance of CO2 sinks and sources (and thereby ocean acidification) is difficult to predict in an era of rapid warming and sea ice loss in the Arctic Ocean.

  7. Laminated adsorbents with very rapid CO2 uptake by freeze-casting of zeolites.

    Science.gov (United States)

    Ojuva, Arto; Akhtar, Farid; Tomsia, Antoni P; Bergström, Lennart

    2013-04-10

    Structured zeolite 13X monoliths with a laminated structure and hierarchical macro-/microporosity were prepared by freeze-casting aqueous suspensions of zeolite 13X powder, bentonite, and polyethylene glycol. Colloidally stable suspensions with a low viscosity at both room temperature and near freezing could be prepared at alkaline conditions where both the zeolite 13X powder and bentonite carry a negative surface charge. Slow directional freezing of the suspensions led to the formation of well-defined and thin lamellar pores and pore walls while fast freezing resulted in more cylindrical pores. The wall thickness, which varied between 8 and 35 μm, increased with increasing solids loading of the suspension. Thermal treatment at 1053 K of the freeze-cast bodies containing between 9 and 17 wt % bentonite resulted in mechanically stable zeolite 13X monoliths. The monoliths displayed a carbon dioxide uptake capacity of 4-5 mmol/g and an uptake kinetics characterized by a very fast initial uptake where more than 50% of the maximum uptake was reached within 15 s. Freeze-cast laminated zeolite monoliths could be used to improve the volumetric efficiency and reduce the cycle time, of importance in, for example, biogas upgrading and CO2 separation from flue gas.

  8. Environmental dependencies of plant CO2 uptake in theory, data, and simulations

    Science.gov (United States)

    Wang, Han; Prentice, Colin; Keenan, Trevor; Peng, Shushi; Piao, Shilong; Cornwell, William; Davis, Tyler; Wright, Ian; Peng, Changhui

    2016-04-01

    The rate of carbon uptake by land plants depends on the light use efficiency (LUE) of photosynthesis. LUE is the ratio of primary production to light absorbed by foliage. This in turn depends on the ratio of leaf-internal to ambient carbon dioxide partial pressures (χ). However, current state-of-the-art land ecosystem models represent the environmental dependencies of these two key quantities in an empirical and incomplete way. Their modeled values have not been systematically tested against observations, a situation contributing to the many uncertainties afflicting current model estimates and future projections of terrestrial carbon uptake. We present a theory for the dependencies of χ and LUE on growing-season air temperature, vapour pressure deficit (VPD), CO2 concentration and elevation based on two hypotheses rooted in eco-physiological optimality. Theoretically derived environmental dependencies of χ and LUE are shown to be precisely and quantitatively consistent with global data sets of (a) stable carbon isotope measurements, and (b) gross primary production derived from CO2 flux measurements. The modeled environmental dependencies of χ and LUE according to seven state-of-the-art land ecosystem models participating in the TRENDY2 model intercomparison project are then derived from model outputs and compared with the theoretical relationships as a benchmark. The results show large discrepancies among model-predicted relationships of χ and LUE to temperature and VPD both in spatial and temporal dimensions. The influence of elevation on χ and LUE is also inconsistent among models, as is their predicted sensitivity to CO2 enrichment. This work suggests that a top-priority task for land ecosystem models should be to reformulate the environmental drivers of χ and LUE relationships to be consistent with observations. It also indicates that eco-physiological optimality hypotheses provide a promising route to an improved predictive understanding of terrestrial

  9. Physical-Biogeochemical Interactions that Alter the Uptake of Atmospheric CO2 in the Barents Sea

    Science.gov (United States)

    Signorini, S. R.; Hakkinen, S. M.; McClain, C. R.

    2009-04-01

    The Barents Sea is characterized by significant calcification rates during summer promoted by intense coccolithophore blooms that peak during August. Coccolithophores, among which Emiliania huxleyi (E. huxleyi) is the most abundant and widespread species, are considered to be the most productive calcifying organisms on Earth. They inhabit the surface layer (MLD 20m) in highly stratified waters where light intensity is high. E. huxleyi often forms massive blooms in temperate and sub-polar oceans. Coupling of the coccolithophore organic carbon and carbonate pumps interact to consume (photosynthesis) and produce (calcification) CO2. The so-called Rain Ratio, defined as the ratio of particulate inorganic carbon (PIC) to particulate organic carbon (POC) in exported biogenic matter, determines the relative strength of the two biological carbon pumps and influences the flux of CO2 across the surface ocean - atmosphere interface. Here we use a combination of satellite ocean color algorithms, coupled ice-ocean model products, an SST-dependent pCO2 algorithm, and gas exchange parameterization to describe the seasonal and decadal variability of the air-sea CO2 flux in the Barents Sea. Model-derived SST and SSS (1955-2008) are used in conjunction with the pCO2 algorithm and carbonate chemistry to derive decadal trends of sea-air CO2 flux, pH and calcite saturation state. Phytoplankton and calcite production have strong spatial variability. Nutrient supply, biomass and calcite concentrations are modulated by light and MLD seasonal cycle. The size, intensity, and location of coccolithophore blooms vary from year to year, but the peak bloom is always in June in the Central Basin of the sub-polar North Atlantic (45oW - 10oW, 50oN - 65oN) and August in the Barents Sea. Calcification rates range from 5% to 27% of net primary production. The Barents Sea PIC production is about twice that of the Central Basin. Predicted freshening and warming of polar seas may increase stratification

  10. Modelling effects of seasonal variation in water table depth on net ecosystem CO2 exchange of a tropical peatland

    Science.gov (United States)

    Mezbahuddin, M.; Grant, R. F.; Hirano, T.

    2014-02-01

    Seasonal variation in water table depth (WTD) determines the balance between aggradation and degradation of tropical peatlands. Longer dry seasons together with human interventions (e.g. drainage) can cause WTD drawdowns making tropical peatland C storage highly vulnerable. Better predictive capacity for effects of WTD on net CO2 exchange is thus essential to guide conservation of tropical peat deposits. Mathematical modelling of basic eco-hydrological processes under site-specific conditions can provide such predictive capacity. We hereby deploy a process-based mathematical model ecosys to study effects of seasonal variation in WTD on net ecosystem productivity (NEP) of a drainage affected tropical peat swamp forest at Palangkaraya, Indonesia. Simulated NEP suggested that the peatland was a C source (NEP ~ -2 g C m-2 d-1, where a negative sign represents a C source and a positive sign a C sink) during rainy seasons with shallow WTD, C neutral or a small sink (NEP ~ +1 g C m-2 d-1) during early dry seasons with intermediate WTD and a substantial C source (NEP ~ -4 g C m-2 d-1) during late dry seasons with deep WTD from 2002 to 2005. These values were corroborated by regressions (P 0.8, intercepts approaching 0 and slopes approaching 1. We also simulated a gradual increase in annual NEP from 2002 (-609 g C m-2) to 2005 (-373 g C m-2) with decreasing WTD which was attributed to declines in duration and intensity of dry seasons following the El Niño event of 2002. This increase in modelled NEP was corroborated by EC-gap filled annual NEP estimates. Our modelling hypotheses suggested that (1) poor aeration in wet soils during shallow WTD caused slow nutrient (predominantly phosphorus) mineralization and consequent slow plant nutrient uptake that suppressed gross primary productivity (GPP) and hence NEP (2) better soil aeration during intermediate WTD enhanced nutrient mineralization and hence plant nutrient uptake, GPP and NEP and (3) deep WTD suppressed NEP through a

  11. Experimental warming of a mountain tundra increases soil CO2 effluxes and enhances CH4 and N2O uptake at Changbai Mountain, China.

    Science.gov (United States)

    Zhou, Yumei; Hagedorn, Frank; Zhou, Chunliang; Jiang, Xiaojie; Wang, Xiuxiu; Li, Mai-He

    2016-02-16

    Climatic warming is expected to particularly alter greenhouse gas (GHG) emissions from soils in cold ecosystems such as tundra. We used 1 m(2) open-top chambers (OTCs) during three growing seasons to examine how warming (+0.8-1.2 °C) affects the fluxes of carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) from alpine tundra soils. Results showed that OTC warming increased soil CO2 efflux by 141% in the first growing season and by 45% in the second and third growing season. The mean CH4 flux of the three growing seasons was -27.6 and -16.7 μg CH4-C m(-2)h(-1) in the warmed and control treatment, respectively. Fluxes of N2O switched between net uptake and emission. Warming didn't significantly affect N2O emission during the first and the second growing season, but stimulated N2O uptake in the third growing season. The global warming potential of GHG was clearly dominated by soil CO2 effluxes (>99%) and was increased by the OTC warming. In conclusion, soil temperature is the main controlling factor for soil respiration in this tundra. Climate warming will lead to higher soil CO2 emissions but also to an enhanced CH4 uptake with an overall increase of the global warming potential for tundra.

  12. Association between sap flow-derived and eddy covariance-derived measurements of forest canopy CO2 uptake.

    Science.gov (United States)

    Klein, Tamir; Rotenberg, Eyal; Tatarinov, Fyodor; Yakir, Dan

    2016-01-01

    The carbon sink intensity of the biosphere depends on the balance between gross primary productivity (GPP) of forest canopies and ecosystem respiration. GPP, however, cannot be directly measured and estimates are not well constrained. A new approach relying on canopy transpiration flux measured as sap flow, and water-use efficiency inferred from carbon isotope analysis (GPPSF ) has been proposed, but not tested against eddy covariance-based estimates (GPPEC ). Here we take advantage of parallel measurements using the two approaches at a semi-arid pine forest site to compare the GPPSF and GPPEC estimates on diurnal to annual timescales. GPPSF captured the seasonal dynamics of GPPEC (GPPSF  = 0.99 × GPPEC , r(2)  = 0.78, RMSE = 0.82, n = 457 d) with good agreement at the annual timescale (653 vs 670 g C m(-2)  yr(-1) ). Both methods showed that GPP ranged between 1 and 8 g C m(-2)  d(-1) , and the GPPSF /GPPEC ratio was between 0.5 and 2.0 during 82% of the days. Carbon uptake dynamics at the individual tree scale conformed with leaf scale rates of net assimilation. GPPSF can produce robust estimations of tree- and canopy-scale rates of CO2 uptake, providing constraints and greatly extending current GPPEC estimations. © 2015 The Authors. New Phytologist © 2015 New Phytologist Trust.

  13. Methylcellulose-Directed Synthesis of Nanocrystalline Zeolite NaA with High CO2 Uptake

    Directory of Open Access Journals (Sweden)

    Dilshod Shakarova

    2014-07-01

    Full Text Available Zeolite NaA nanocrystals with a narrow particle size distribution were prepared by template-free hydrothermal synthesis in thermo-reversible methylcellulose gels. The effects of the amount of methylcellulose, crystallization time and hydrothermal treatment temperature on the crystallinity and particle size distribution of the zeolite NaA nanocrystals were investigated. We found that the thermogelation of methylcellulose in the alkaline Na2O-SiO2-Al2O3-H2O system played an important role in controlling the particle size. The synthesized zeolite nanocrystals are highly crystalline, as demonstrated by X-ray diffraction (XRD, and scanning electron microscopy (SEM shows that the nanocrystals can also display a well-defined facetted morphology. Gas adsorption studies on the synthesized nanocrystalline zeolite NaA showed that nanocrystals with a size of 100 nm displayed a high CO2 uptake capacity (4.9 mmol/g at 293 K at 100 kPa and a relatively rapid uptake rate compared to commercially available, micron-sized particles. Low-cost nanosized zeolite adsorbents with a high and rapid uptake are important for large scale gas separation processes, e.g., carbon capture from flue gas.

  14. Net ecosystem CO2 exchange and evapotranspiration of a sphagnum mire: field measurements and model simulations

    Science.gov (United States)

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

    2014-05-01

    The spatial and temporal variability of net ecosystem exchange of CO2 (NEE) and evapotranspiration (ET) of a karst-hole sphagnum peat mire situated at the boundary between broad-leaved and forest-steppe zones in the central part of European Russia (54.06N, 37.59E, 260 m a.s.l.) was described using results of field measurements and simulations with Mixfor-3D model. The area of the mire is about 1.2 ha and it is surrounded by a broadleaved forest stand. It is a typical peat mire according to water and mineral supply as well as to vegetation composition. The vegetation of the peripheral parts of the mire is typical eutrophic whereas the vegetation in its central part is represented by meso-oligothrophic plant communities. To describe the spatial variability of NEE and ET within the mire a portable measuring system consisting of a transparent ventilated chamber combined with an infrared CO2 and H2O analyzer LI-840A (Li-Cor, USA) was used. The measurements were provided along a transect from the southern peripheral part of the mire to its center under sunny clear-sky weather conditions in the period from May to September of 2012 and from May 2013 to October 2013. The chamber method was used for measurements of NEE and ET fluxes because of small size of the mire, a very uniform surrounding forest stand and the mosaic mire vegetation. All these factors promote very heterogeneous exchange conditions within the mire and make it difficult to apply, for example, an eddy covariance method that is widely used for flux measurements in the field. The results of the field measurements showed a significant spatial and temporal variability of NEE and ET that was mainly influenced by incoming solar radiation, air temperature and ground water level. During the entire growing season the central part of the mire was a sink of CO2 for the atmosphere (up to 6.8±4.2 µmol m-2 s-1 in June) whereas its peripheral part, due to strong shading by the surrounding forest, was mainly a source of

  15. Net Heterotrophy in the Amazon Continental Shelf Changes Rapidly to a Sink of CO2 in the Outer Amazon Plume

    Directory of Open Access Journals (Sweden)

    Nathalie Lefèvre

    2017-09-01

    Full Text Available The Amazon continental shelf and adjacent oceanic area were sampled for inorganic and organic carbon parameters in order to improve data coverage and understanding of carbon cycling dynamics within this important region. Seasonal coverage of the Amazon plume on the French Guiana continental shelf further north, was provided by CO2 monitoring using a merchant ship sailing from France to French Guiana (2006–2016. Salinity ranged from 1 to 36 (transects in April 2013, and May 2014. At salinity below 10, strong outgassing was observed with fugacity of CO2 (fCO2 over 2,000 μatm. This region displayed net heterotrophy, fueled by organic matter with terrestrial origin, as shown by δ13C and δ15N values of suspended particles. A δ13C cross shelf average of −31% was measured during May 2014, contrasting with oceanic values in excess of −20%. The reactivity of this terrestrial material resulted in the local production of dissolved inorganic and organic carbon as well as fluorescent humic compounds. Further offshore, the dilution of freshwater by ocean waters created a sink for CO2, enhanced by biological activity. The strongest CO2 drawdowns, associated with high chlorophyll a concentrations, were observed on the French Guiana continental shelf in the outer Amazon plume, with fCO2 values below 150 μatm. Here, a CO2 sink was present almost throughout the year, with a seasonal maximum of −9.2 mmol CO2 m−2d−1 observed in June 2015. However, both the CO2 and salinity distributions could vary significantly within a few days, confirming the presence of many eddies in this region. The Amazon continental shelf hence behaved as a transition zone between an inshore source of CO2 to the atmosphere and an offshore sink. Some marine phytoplankton production was detected but occurred mainly close to the French Guiana shelf. A mean net CO2 outgassing of 44 ± 43.6 mmol m−2d−1 was estimated for the area. Quantifying the CO2 flux for the entire Amazon

  16. Elevated Nitrogen Deposition Enhances the Net CO2 Sink Strength in Alberta Bogs along a Post-fire Chronosequence

    Science.gov (United States)

    Wieder, R. K.; Vile, M. A.; Albright, C. M.; Scott, K. D.

    2014-12-01

    About 30% of the landscape of northern Alberta, Canada is occupied by peatlands, which persist at the low end range of both mean annual precipitation (pattern emerged that N additions enhanced the net CO2 sink strength of the bogs, with no effect on ecosystem respiration. Net primary production of Sphagnum fuscum, the dominant peat-forming moss, was not affected by N addition, suggesting that the overall response of NEE to N addition is the result of enhanced growth of ericaceous shrubs. These findings suggest that while elevated N deposition in the AOSR may enhance the strength of the overall CO2 sink of bogs in the short term, in the longer term, increased shrub growth has the potential to shade Sphagnum mosses, compromising the future bog CO2sink strength across the region.

  17. The effects of water management on the CO2 uptake of Sphagnum moss in a reclaimed peatland

    Directory of Open Access Journals (Sweden)

    C.M. Brown

    2017-07-01

    Full Text Available To harvest Sphagnum on a cyclic basis and rapidly accumulate biomass, active water management is necessary. The goal of this study is to determine the hydrological conditions that will maximise CO2 uptake in Sphagnum farming basins following the moss-layer transfer technique. Plot CO2 uptake doubled from the first growing season to the second, but growth was not uniform across the site. Results indicate that the seasonal oscillations in water table (WT position were more important than actual WT position for estimating Sphagnum ground cover and CO2 uptake when the seasonal WT is shallow (< -25 cm. Plots with higher productivity had a WT range (seasonal maximum – minimum less than 15 cm, a WT position which did not fluctuate more than ± 7.5 cm, and a low WT standard deviation. Each basin was a CO2 source during the second growing season, and seasonal modelled NEE ranged from 107.1 to 266.8 g CO2 m-2. Decomposition from the straw mulch accounted for over half of seasonal respiration, and the site is expected to become a CO2 sink as the straw mulch decomposes and moss cover increases. This study highlights the importance of maintaining stable moisture conditions to increase Sphagnum growth and CO2 sink functions.

  18. Elevated CO2 and warming effects on CH4 uptake in a semiarid grassland below optimum soil moisture

    Science.gov (United States)

    Dijkstra, Feike A.; Morgan, Jack A.; von Fischer, Joseph C.; Follett, Ronald F.

    2011-03-01

    Semiarid rangelands are a significant global sink for methane (CH4), but this sink strength may be altered by climate change. Methane uptake is sensitive to soil moisture showing a hump-shaped relationship with a distinct optimum soil moisture level. Both CO2 and temperature affect soil moisture, but the direction of CH4 uptake response may depend on if the system is below or above the soil moisture optimum. Most climate change studies on CH4 uptake have been conducted in mesic environments with soil moisture levels typically above optimum, but little is known about responses in drier systems with suboptimal soil water. We studied effects of atmospheric CO2 (ambient versus 600 ppm), and temperature (ambient versus 1.5/3.0°C warmer day/night) on CH4 uptake during two growing seasons in a full factorial semiarid grassland field experiment in Wyoming, United States. We observed typical hump-shaped relationships between CH4 uptake and water filled pore space. Averaged over a range of soil moisture conditions, CH4 uptake was not affected by elevated CO2, but significantly decreased with warming in both seasons (25% in the first and 13% in the second season). Warming showed the strongest reduction and elevated CO2 showed the strongest increase in CH4 uptake when soils were below optimum moisture, indicating that these effects are particularly strong when soils are dry. Thus, directional effects of elevated CO2 and warming on CH4 uptake in semiarid grasslands can be opposite to their effects in mesic ecosystems because semiarid grasslands are often below optimum soil moisture for methane uptake.

  19. Atmospheric CO2 uptake throughout bio-enhanced brucite-water reaction at Montecastelli serpentinites (Italy)

    Science.gov (United States)

    Bedini, Federica; Boschi, Chiara; Ménez, Benedicte; Perchiazzi, Natale; Zanchetta, Giovanni

    2014-05-01

    In the last several years, interactions between microorganisms and minerals have intrigued and catched the interest of the scientific community. Montecastelli serpentinites (Tuscany, Italy) are characterized by CO2-mineral carbonation, an important process which leads to spontaneous formation of carbonate phases uptaking atmospheric CO2. In the studied areas carbonate precipitates, mainly hydrated Mg-carbonates, are present in form of crusts, coating and spherules on exposed rock surfaces, and filling rock fractures. Petrographic and mineralogical observations revealed that Tuscan brucite-rich serpentinites hosts preserve their original chemical compositions with typical mesh-textured serpentine (± brucite) after olivine, magnetite-rich mesh rims and relicts of primary spinel. Representative hydrated carbonate samples have been collected in three different areas and analyzed to investigate the role of biological activity and its influence in the serpentine-hydrated Mg-carbonates reaction. The different types of whitish precipitates have been selected under binocular microscope for XRD analyses performed at the Dipartimento di Scienze della Terra (University of Pisa, Italy): their mineralogical composition consists of mainly hydromagnesite and variable amount of other metastable carbonate phases (i.e. nesquehonite, manasseite, pyroaurite, brugnatellite and aragonite). Moreover, the crystallinity analysis of whitish crust and spherules have been carried out by detailed and quantitative XRD analyses to testify a possible biologically controlled growth, inasmuch as the crystal structure of biominerals could be affected by many lattice defects (i.e. dislocations, twinning, etc.) and this observation cause low crystallinity of the mineral. The presence of microbial cells and relicts of organic matter has already been detected by confocal laser scanning microscopy (CLSM) combined with Raman spectromicroscopy in a previous study (Bedini et al., 2013). The presence of

  20. Temporally-resolved Study of Atmosphere-lake Net CO2 Exchange at Lochaber Lake, Nova Scotia, Canada

    Science.gov (United States)

    Spafford, L. A.; Risk, D. A.

    2016-12-01

    Lakes are carbon gateways with immense processing capacity, acting as either sinks or sources for CO2. As climate change exacerbates weather extremes, carbon stored within permafrost and soils is liberated to water systems, altering aquatic carbon budgets and light availability for photosynthesis. The functional response of lakes to climate change is uncertain, and continuous data of lake respiration and its drivers are lacking. This study used high-frequency measurements of CO2 exchange during a growing season by a novel technique to quantify the net flux of carbon at a small deep oligotrophic lake in eastern Nova Scotia, Canada, and to examine the influence of environmental forcings. We installed 3 floating Forced Diffusion dynamic membrane chambers on the lake, coupled to a valving multiplexer and a single Vaisala GMP 343 CO2 analyzer. This low-power system sampled lake-atmosphere CO2 exchange at several points from shore every hour for over 100 days in the growing season. At the same frequency we also collected automated measurements of wind velocity, photosynthetically active radiation (PAR), dissolved CO2, air and water temperature. Manual measurement campaigns measured chlorophyll `a', DOC, surface methane (CH4), and CO2 flux by manual static floating chamber to confirm the automated measurements. The lake was a net source for carbon, on average emitting 0.038 µmol CO2/m2/s or 4.967 g CO2/s over the entire lake, but we did observe significant temporal variation across diel cycles, and along with changing weather. Approximately 48 hours after every rain event, we observed an increase in littoral CO2 release by the lake. Wind speed, air temperature, and distance from shore were also drivers of variation, as the littoral zone tended to release less CO2 during the course of our study. This work shows the variable influence of environmental drivers of lake carbon flux, as well as the utility of low-power automated chambers for observing aquatic net CO2 exchange.

  1. Land use affects the net ecosystem CO2 exchange and its components in mountain grasslands

    Science.gov (United States)

    Schmitt, M.; Bahn, M.; Wohlfahrt, G.; Tappeiner, U.; Cernusca, A.

    2010-08-01

    Changes in land use and management have been strongly affecting mountain grassland, however, their effects on the net ecosystem exchange of CO2 (NEE) and its components have not yet been well documented. We analysed chamber-based estimates of NEE, gross primary productivity (GPP), ecosystem respiration (R) and light use efficiency (LUE) of six mountain grasslands differing in land use and management, and thus site fertility, for the growing seasons of 2002 to 2008. The main findings of the study are that: (1) land use and management affected seasonal NEE, GPP and R, which all decreased from managed to unmanaged grasslands; (2) these changes were explained by differences in leaf area index (LAI), biomass and leaf-area-independent changes that were likely related to photosynthetic physiology; (3) diurnal variations of NEE were primarily controlled by photosynthetically active photon flux density and soil and air temperature; seasonal variations were associated with changes in LAI; (4) parameters of light response curves were generally closely related to each other, and the ratio of R at a reference temperature/ maximum GPP was nearly constant across the sites; (5) similarly to our study, maximum GPP and R for other grasslands on the globe decreased with decreasing land use intensity, while their ratio remained remarkably constant. We conclude that decreasing intensity of management and, in particular, abandonment of mountain grassland lead to a decrease in NEE and its component processes. While GPP and R are generally closely coupled during most of the growing season, GPP is more immediately and strongly affected by land management (mowing, grazing) and season. This suggests that management and growing season length, as well as their possible future changes, may play an important role for the annual C balance of mountain grassland.

  2. Land use affects the net ecosystem CO2 exchange and its components in mountain grasslands

    Directory of Open Access Journals (Sweden)

    A. Cernusca

    2010-08-01

    Full Text Available Changes in land use and management have been strongly affecting mountain grassland, however, their effects on the net ecosystem exchange of CO2 (NEE and its components have not yet been well documented. We analysed chamber-based estimates of NEE, gross primary productivity (GPP, ecosystem respiration (R and light use efficiency (LUE of six mountain grasslands differing in land use and management, and thus site fertility, for the growing seasons of 2002 to 2008. The main findings of the study are that: (1 land use and management affected seasonal NEE, GPP and R, which all decreased from managed to unmanaged grasslands; (2 these changes were explained by differences in leaf area index (LAI, biomass and leaf-area-independent changes that were likely related to photosynthetic physiology; (3 diurnal variations of NEE were primarily controlled by photosynthetically active photon flux density and soil and air temperature; seasonal variations were associated with changes in LAI; (4 parameters of light response curves were generally closely related to each other, and the ratio of R at a reference temperature/ maximum GPP was nearly constant across the sites; (5 similarly to our study, maximum GPP and R for other grasslands on the globe decreased with decreasing land use intensity, while their ratio remained remarkably constant. We conclude that decreasing intensity of management and, in particular, abandonment of mountain grassland lead to a decrease in NEE and its component processes. While GPP and R are generally closely coupled during most of the growing season, GPP is more immediately and strongly affected by land management (mowing, grazing and season. This suggests that management and growing season length, as well as their possible future changes, may play an important role for the annual C balance of mountain grassland.

  3. Can increased nitrogen uptake at elevated CO2 be explained by an hypothesis of optimal root function?

    Science.gov (United States)

    McMurtrie, R. E.; Norby, R. J.; Näsholm, T.; Iversen, C.; Dewar, R. C.; Medlyn, B. E.

    2011-12-01

    Forest free-air CO2 enrichment (FACE) experiments have shown that annual nitrogen (N) uptake increases when trees are grown at elevated CO2 (eCO2) and that increased N uptake is critical for a sustained growth response to eCO2. Processes contributing to increased N uptake at eCO2 may include: accelerated decomposition of soil organic matter due to enhanced root carbon (C) exudation (so-called rhizosphere priming); increased C allocation to fine roots and increased root production at depth, both of which enhance N acquisition; differences in soil N availability with depth; changes in the abundance of N in chemical forms with differing mobility in soil; and reduced N concentrations, reduced maintenance respiration rates, and increased longevities of deeper roots. These processes have been synthesised in a model of annual N uptake in relation to the spatial distribution of roots. We hypothesise that fine roots are distributed spatially in order to maximise annual N uptake. The optimisation hypothesis leads to equations for the optimal vertical distribution of root biomass in relation to the distribution of available soil N and for maximum annual N uptake. We show how maximum N uptake and rooting depth are related to total root mass, and compare the optimal solution with an empirical function that has been fitted to root-distribution data from all terrestrial biomes. Finally, the model is used to explore the consequences of rhizosphere priming at eCO2 as observed at the Duke forest FACE experiment (Drake et al. 2011, Ecology Letters 14: 349-357) and of increasing N limitation over time as observed at the Oak Ridge FACE experiment (Norby et al. 2010, Proc. Nat. Acad. Sci. USA 107: 19368-19373).

  4. Net ecosystem exchange of CO2 and carbon balance for eight temperate organic soils under agricultural management

    DEFF Research Database (Denmark)

    Elsgaard, Lars; Görres, C.-M.; Hoffmann, Carl Christian

    2012-01-01

    This study presents the first annual estimates of net ecosystem exchange (NEE) of CO2 and net ecosystem carbon balances (NECB) of contrasting Danish agricultural peatlands. Studies were done at eight sites representing permanent grasslands (PG) and rotational (RT) arable soils cropped to barley......) sites, NEE (mean ± standard error, SE) was 5.1 ± 0.9 and 8.6 ± 2.0 Mg C ha−1 yr−1, respectively, but with the overall lowest value observed for potato cropping (3.5 Mg C ha−1 yr−1). This was partly attributed to a short-duration vegetation period and drying of the soil especially in potato ridges. NECB...... and temperate climate zones. It was stressed that evaluation of emission factors should explicitly differentiate between data representing net C balance from a soil perspective and CO2-C balance from an atmospheric perspective. Modelling of inter-annual variability in NEE for three selected sites during a 21...

  5. Net mineralization of N at deeper soil depths as a potential mechanism for sustained forest production under elevated [CO2

    Energy Technology Data Exchange (ETDEWEB)

    Iversen, Colleen M [ORNL; Hooker, Toby [Utah State University (USU); Classen, Aimee T [University of Tennessee, Knoxville (UTK); Norby, Richard J [ORNL

    2011-01-01

    Elevated atmospheric [CO2] is projected to increase forest production, which could increase ecosystem carbon (C) storage. However, sustained forest production will depend on the nutrient balance of the forested ecosystem. Our aim was to examine the causes and consequences of increased fine-root production and mortality throughout the soil profile under elevated CO2 with respect to potential gross nitrogen (N) cycling rates. Our study was conducted in a CO2-enriched sweetgum (Liquidambar styraciflua L.) plantation in Oak Ridge, TN, USA. We used isotope pool dilution methodology to measure potential gross N cycling rates in laboratory incubations of soil from four depth increments to 60 cm. Our objectives were two-fold: (1) determine whether N is available for root acquisition in deeper soil, and (2) determine whether increased inputs of labile C from greater fine-root mortality at depth under elevated [CO2] had altered N cycling rates. While gross N fluxes declined with soil depth, we found that N is potentially available for roots to access, especially below 15 cm depth where microbial consumption of mineral N was reduced. Overall, up to 60% of potential gross N mineralization, and 100% of potential net N mineralization, occurred below 15-cm depth at this site. This finding was supported by in situ measurements from ion-exchange resins, where total inorganic N availability at 55 cm depth was equal to or greater than N availability at 15 cm depth. While it is likely that trees grown under elevated [CO2] are accessing a larger pool of inorganic N by mining deeper soil, we found no effect of elevated [CO2] on potential gross or net N cycling rates. Thus, increased root exploration of the soil volume under elevated [CO2] may be more important than changes in potential gross N cycling rates in sustaining forest responses to rising atmospheric CO2.

  6. Increase in observed net carbon dioxide uptake by land and oceans during the past 50 years.

    Science.gov (United States)

    Ballantyne, A P; Alden, C B; Miller, J B; Tans, P P; White, J W C

    2012-08-02

    One of the greatest sources of uncertainty for future climate predictions is the response of the global carbon cycle to climate change. Although approximately one-half of total CO(2) emissions is at present taken up by combined land and ocean carbon reservoirs, models predict a decline in future carbon uptake by these reservoirs, resulting in a positive carbon-climate feedback. Several recent studies suggest that rates of carbon uptake by the land and ocean have remained constant or declined in recent decades. Other work, however, has called into question the reported decline. Here we use global-scale atmospheric CO(2) measurements, CO(2) emission inventories and their full range of uncertainties to calculate changes in global CO(2) sources and sinks during the past 50 years. Our mass balance analysis shows that net global carbon uptake has increased significantly by about 0.05 billion tonnes of carbon per year and that global carbon uptake doubled, from 2.4 ± 0.8 to 5.0 ± 0.9 billion tonnes per year, between 1960 and 2010. Therefore, it is very unlikely that both land and ocean carbon sinks have decreased on a global scale. Since 1959, approximately 350 billion tonnes of carbon have been emitted by humans to the atmosphere, of which about 55 per cent has moved into the land and oceans. Thus, identifying the mechanisms and locations responsible for increasing global carbon uptake remains a critical challenge in constraining the modern global carbon budget and predicting future carbon-climate interactions.

  7. Elevated uptake of CO2 over Europe inferred from GOSAT XCO2 retrievals: a real phenomenon or an artefact of the analysis?

    Science.gov (United States)

    Feng, L.; Palmer, P. I.; Parker, R. J.; Deutscher, N. M.; Feist, D. G.; Kivi, R.; Morino, I.; Sussmann, R.

    2015-01-01

    Estimates of the natural CO2 flux over Europe inferred from in situ measurements of atmospheric CO2 mole fraction have been used previously to check top-down flux estimates inferred from space-borne dry-air CO2 column (XCO2) retrievals. Recent work has shown that CO2 fluxes inferred from XCO2 data from the Japanese Greenhouse gases Observing SATellite (GOSAT) have a larger seasonal amplitude and a more negative annual net CO2 balance than those inferred from the in situ data. The causes of this enhanced European CO2 uptake have since become the focus of recent studies. We show this elevated uptake over Europe could largely be explained by mis-fitting data due to regional biases. We establish a reference in situ inversion that uses an Ensemble Kalman Filter (EnKF) to assimilate surface flask data and the XCO2 data from the surface-based Total Carbon Column Observing Network (TCCON). The same EnKF system is also used to assimilate two, independent versions of GOSAT XCO2 data. We find that the GOSAT-inferred European terrestrial biosphere uptake peaks during the summer, similar to the reference inversion, but the net annual flux is 1.18 ± 0.1 GtC a-1 compared to a value of 0.56 ± 0.1 GtC a-1 for our control inversion that uses only in situ data. To reconcile these two estimates, we have performed a series of numerical experiments that assimilate observations with biases or assimilate synthetic observations for which part or all of the GOSAT XCO2 data are replaced with model data. We find that 50-80% of the elevated European uptake in 2010 inferred from GOSAT data is due to retrievals outside the immediate European region, while most of the remainder can be explained by a sub-ppm retrieval bias over Europe. We have used data assimilation techniques to estimate monthly GOSAT XCO2 biases from the joint assimilation of in situ observations and GOSAT XCO2 retrievals. We find a monthly varying bias of up to 0.5 ppm can explain an overestimate of the annual sink of up to 0

  8. Pore space partition and charge separation in cage-within-cage indium-organic frameworks with high CO2 uptake.

    Science.gov (United States)

    Zheng, Shou-Tian; Bu, Julia T; Li, Yufei; Wu, Tao; Zuo, Fan; Feng, Pingyun; Bu, Xianhui

    2010-12-08

    The integration of negatively charged single-metal building blocks {In(CO2)4} and positively charged trimeric clusters {In3O} leads to three unique cage-within-cage-based porous materials, which exhibit not only high hydrothermal, thermal, and photochemical stability but also attractive structural features contributing to a very high CO2 uptake capacity of up to 119.8 L/L at 273 K and 1 atm.

  9. Net ecosystem CO2 exchange of an invasive plant infestation: new insights on the effects of phenology and management practices on structure and functioning

    Science.gov (United States)

    Sonnentag, Oliver; Detto, Matteo; Runkle, Benjamin; Hatala, Jaclyn; Vargas, Rodrigo; Kelly, Maggi; Baldocchi, Dennis

    2010-05-01

    effects of measurement year and flowering/ mowing on the variable parameters of the non-linear responses of FA to light and FAR to air temperature. We address two specific questions with our research. First, how do year-round grazing and spring mowing affect the timing (i.e., onset) of pepperweed's key phenological phases? Second, we focus on pepperweed flowering, the spectrally most notable phenological phase. Thus we ask does the onset of flowering trigger changes in structural canopy development (i.e., z0m) and functioning (i.e., FA; FAR)? Over the summers (1 May - 30 September) of 2007 and 2009 the site was either almost neutral with respect to CO2 (-26 g C m-2 period-1 in 2007) or a moderate net CO2 source (89 g C m-2 period-1 in 2009). In contrast, the pepperweed infestation acted as a net CO2 sink (-162 g C m-2 period-1) over the summer of 2008 when the site was mowed once in May during flowering to reduce the reproductive success of pepperweed. Preliminary results show that year-round grazing inhibited the accumulation of dead stalks causing earlier pepperweed green-up. The onset of flowering had no substantial impact on z0m. In contrast, the onset of flowering significantly reduced maximum photosynthetic capacity compared to non-flowering pepperweed, resulting in reduced photosynthetic CO2 uptake. Similarly, FAR was slightly reduced in response to flowering, most likely due to the due to the close coupling of growth respiration to FA. In contrast, mowing early during flowering prevented the decrease in photosynthetic CO2 uptake and the associated decrease in FAR due to immediate pepperweed regrowth. Our study highlights the impact of invasive plants' unique ecophysiological features and applied management practices on net ecosystem CO2 exchange of infested ecosystems.

  10. Arbuscular mycorrhiza improve growth, nitrogen uptake, and nitrogen use efficiency in wheat grown under elevated CO2.

    Science.gov (United States)

    Zhu, Xiancan; Song, Fengbin; Liu, Shengqun; Liu, Fulai

    2016-02-01

    Effects of the arbuscular mycorrhizal (AM) fungus Rhizophagus irregularis on plant growth, carbon (C) and nitrogen (N) accumulation, and partitioning was investigated in Triticum aestivum L. plants grown under elevated CO2 in a pot experiment. Wheat plants inoculated or not inoculated with the AM fungus were grown in two glasshouse cells with different CO2 concentrations (400 and 700 ppm) for 10 weeks. A (15)N isotope labeling technique was used to trace plant N uptake. Results showed that elevated CO2 increased AM fungal colonization. Under CO2 elevation, AM plants had higher C concentration and higher plant biomass than the non-AM plants. CO2 elevation did not affect C and N partitioning in plant organs, while AM symbiosis increased C and N allocation into the roots. In addition, plant C and N accumulation, (15)N recovery rate, and N use efficiency (NUE) were significantly higher in AM plants than in non-AM controls under CO2 enrichment. It is concluded that AM symbiosis favors C and N partitioning in roots, increases C accumulation and N uptake, and leads to greater NUE in wheat plants grown at elevated CO2.

  11. In Vitro Comparison of the Effects of Diode Laser and CO2 Laser on Topical Fluoride Uptake in Primary Teeth

    Directory of Open Access Journals (Sweden)

    Zahra Bahrololoomi

    2016-04-01

    Full Text Available Objectives: Fluoride therapy is important for control and prevention of dental caries. Laser irradiation can increase fluoride uptake especially when combined with topical fluoride application. The objective of this study was to compare the effects of CO2 and diode lasers on enamel fluoride uptake in primary teeth.Materials and Methods: Forty human primary molars were randomly assigned to four groups (n=10. The roots were removed and the crowns were sectioned mesiodistally into buccal and lingual halves as the experimental and control groups. All samples were treated with 5% sodium fluoride (NaF varnish. The experimental samples in the four groups were irradiated with 5 or 7W diode or 1 or 2W CO2 laser for 15 seconds and were compared with the controls in terms of fluoride uptake, which was determined using an ion selective electrode after acid dissolution of the specimens. Data were analyzed by SPSS version 16 using ANOVA treating the control measurements as covariates.Results: The estimated amount of fluoride uptake was 59.5± 16.31 ppm, 66.5± 14.9 ppm, 78.6± 12.43 ppm and 90.4± 11.51 ppm for 5W and 7 W diode and 1W and 2 W CO2 lasers, respectively, which were significantly greater than the values in the conventional topical fluoridation group (P<0.005. There were no significant differences between 7W diode laser and 1W CO2 laser, 5W and 7W diode laser, or 1W and 2W CO2 laser in this regard.Conclusion: The results showed that enamel surface irradiation by CO2 and diode lasers increases the fluoride uptake.

  12. Coupled eco-hydrology and biogeochemistry algorithms enable the simulation of water table depth effects on boreal peatland net CO2 exchange

    Science.gov (United States)

    Mezbahuddin, Mohammad; Grant, Robert F.; Flanagan, Lawrence B.

    2017-12-01

    Water table depth (WTD) effects on net ecosystem CO2 exchange of boreal peatlands are largely mediated by hydrological effects on peat biogeochemistry and the ecophysiology of peatland vegetation. The lack of representation of these effects in carbon models currently limits our predictive capacity for changes in boreal peatland carbon deposits under potential future drier and warmer climates. We examined whether a process-level coupling of a prognostic WTD with (1) oxygen transport, which controls energy yields from microbial and root oxidation-reduction reactions, and (2) vascular and nonvascular plant water relations could explain mechanisms that control variations in net CO2 exchange of a boreal fen under contrasting WTD conditions, i.e., shallow vs. deep WTD. Such coupling of eco-hydrology and biogeochemistry algorithms in a process-based ecosystem model, ecosys, was tested against net ecosystem CO2 exchange measurements in a western Canadian boreal fen peatland over a period of drier-weather-driven gradual WTD drawdown. A May-October WTD drawdown of ˜ 0.25 m from 2004 to 2009 hastened oxygen transport to microbial and root surfaces, enabling greater microbial and root energy yields and peat and litter decomposition, which raised modeled ecosystem respiration (Re) by 0.26 µmol CO2 m-2 s-1 per 0.1 m of WTD drawdown. It also augmented nutrient mineralization, and hence root nutrient availability and uptake, which resulted in improved leaf nutrient (nitrogen) status that facilitated carboxylation and raised modeled vascular gross primary productivity (GPP) and plant growth. The increase in modeled vascular GPP exceeded declines in modeled nonvascular (moss) GPP due to greater shading from increased vascular plant growth and moss drying from near-surface peat desiccation, thereby causing a net increase in modeled growing season GPP by 0.39 µmol CO2 m-2 s-1 per 0.1 m of WTD drawdown. Similar increases in GPP and Re caused no significant WTD effects on modeled

  13. Coupled eco-hydrology and biogeochemistry algorithms enable the simulation of water table depth effects on boreal peatland net CO2 exchange

    Directory of Open Access Journals (Sweden)

    M. Mezbahuddin

    2017-12-01

    Full Text Available Water table depth (WTD effects on net ecosystem CO2 exchange of boreal peatlands are largely mediated by hydrological effects on peat biogeochemistry and the ecophysiology of peatland vegetation. The lack of representation of these effects in carbon models currently limits our predictive capacity for changes in boreal peatland carbon deposits under potential future drier and warmer climates. We examined whether a process-level coupling of a prognostic WTD with (1 oxygen transport, which controls energy yields from microbial and root oxidation–reduction reactions, and (2 vascular and nonvascular plant water relations could explain mechanisms that control variations in net CO2 exchange of a boreal fen under contrasting WTD conditions, i.e., shallow vs. deep WTD. Such coupling of eco-hydrology and biogeochemistry algorithms in a process-based ecosystem model, ecosys, was tested against net ecosystem CO2 exchange measurements in a western Canadian boreal fen peatland over a period of drier-weather-driven gradual WTD drawdown. A May–October WTD drawdown of  ∼  0.25 m from 2004 to 2009 hastened oxygen transport to microbial and root surfaces, enabling greater microbial and root energy yields and peat and litter decomposition, which raised modeled ecosystem respiration (Re by 0.26 µmol CO2 m−2 s−1 per 0.1 m of WTD drawdown. It also augmented nutrient mineralization, and hence root nutrient availability and uptake, which resulted in improved leaf nutrient (nitrogen status that facilitated carboxylation and raised modeled vascular gross primary productivity (GPP and plant growth. The increase in modeled vascular GPP exceeded declines in modeled nonvascular (moss GPP due to greater shading from increased vascular plant growth and moss drying from near-surface peat desiccation, thereby causing a net increase in modeled growing season GPP by 0.39 µmol CO2 m−2 s−1 per 0.1 m of WTD drawdown. Similar increases in

  14. Estimates of European uptake of CO2 inferred from GOSAT XCO2 retrievals: sensitivity to measurement bias inside and outside Europe

    Science.gov (United States)

    Feng, L.; Palmer, P. I.; Parker, R. J.; Deutscher, N. M.; Feist, D. G.; Kivi, R.; Morino, I.; Sussmann, R.

    2016-02-01

    Estimates of the natural CO2 flux over Europe inferred from in situ measurements of atmospheric CO2 mole fraction have been used previously to check top-down flux estimates inferred from space-borne dry-air CO2 column (XCO2) retrievals. Several recent studies have shown that CO2 fluxes inferred from XCO2 data from the Japanese Greenhouse gases Observing SATellite (GOSAT) and the Scanning Imaging Absorption Spectrometer for Atmospheric CHartographY (SCIAMACHY) have larger seasonal amplitudes and a more negative annual net CO2 balance than those inferred from the in situ data. The cause of this elevated European uptake of CO2 is still unclear, but some recent studies have suggested that this is a genuine scientific phenomenon. Here, we put forward an alternative hypothesis and show that realistic levels of bias in GOSAT data can result in an erroneous estimate of elevated uptake over Europe. We use a global flux inversion system to examine the relationship between measurement biases and estimates of CO2 uptake from Europe. We establish a reference in situ inversion that uses an Ensemble Kalman Filter (EnKF) to assimilate conventional surface mole fraction observations and XCO2 retrievals from the surface-based Total Carbon Column Observing Network (TCCON). We use the same EnKF system to assimilate two independent versions of GOSAT XCO2 data. We find that the GOSAT-inferred European terrestrial biosphere uptake peaks during the summer, similar to the reference inversion, but the net annual flux is 1.40 ± 0.19 GtC a-1 compared to a value of 0.58 ± 0.14 GtC a-1 for our control inversion that uses only in situ data. To reconcile these two estimates, we perform a series of numerical experiments that assimilate observations with added biases or assimilate synthetic observations for which part or all of the GOSAT XCO2 data are replaced with model data. We find that for our global flux inversions, a large portion (60-90 %) of the elevated European uptake inferred from

  15. Estimates of European uptake of CO2 inferred from GOSAT XCO2 retrievals: sensitivity to measurement bias inside and outside Europe

    Directory of Open Access Journals (Sweden)

    L. Feng

    2016-02-01

    Full Text Available Estimates of the natural CO2 flux over Europe inferred from in situ measurements of atmospheric CO2 mole fraction have been used previously to check top-down flux estimates inferred from space-borne dry-air CO2 column (XCO2 retrievals. Several recent studies have shown that CO2 fluxes inferred from XCO2 data from the Japanese Greenhouse gases Observing SATellite (GOSAT and the Scanning Imaging Absorption Spectrometer for Atmospheric CHartographY (SCIAMACHY have larger seasonal amplitudes and a more negative annual net CO2 balance than those inferred from the in situ data. The cause of this elevated European uptake of CO2 is still unclear, but some recent studies have suggested that this is a genuine scientific phenomenon. Here, we put forward an alternative hypothesis and show that realistic levels of bias in GOSAT data can result in an erroneous estimate of elevated uptake over Europe. We use a global flux inversion system to examine the relationship between measurement biases and estimates of CO2 uptake from Europe. We establish a reference in situ inversion that uses an Ensemble Kalman Filter (EnKF to assimilate conventional surface mole fraction observations and XCO2 retrievals from the surface-based Total Carbon Column Observing Network (TCCON. We use the same EnKF system to assimilate two independent versions of GOSAT XCO2 data. We find that the GOSAT-inferred European terrestrial biosphere uptake peaks during the summer, similar to the reference inversion, but the net annual flux is 1.40 ± 0.19 GtC a−1 compared to a value of 0.58 ± 0.14 GtC a−1 for our control inversion that uses only in situ data. To reconcile these two estimates, we perform a series of numerical experiments that assimilate observations with added biases or assimilate synthetic observations for which part or all of the GOSAT XCO2 data are replaced with model data. We find that for our global flux inversions, a large portion (60–90 % of the

  16. Enhanced CO2 uptake at a shallow Arctic Ocean seep field overwhelms the positive warming potential of emitted methane

    Science.gov (United States)

    Pohlman, John W.; Greinert, Jens; Ruppel, Carolyn; Silyakova, Anna; Vielstädte, Lisa; Casso, Michael; Mienert, Jürgen; Bünz, Stefan

    2017-05-01

    Continued warming of the Arctic Ocean in coming decades is projected to trigger the release of teragrams (1 Tg = 106 tons) of methane from thawing subsea permafrost on shallow continental shelves and dissociation of methane hydrate on upper continental slopes. On the shallow shelves (biological uptake of carbon dioxide (CO2) has the potential to offset the positive warming potential of emitted methane, a process that has not received detailed consideration for these settings. Continuous sea-air gas flux data collected over a shallow ebullitive methane seep field on the Svalbard margin reveal atmospheric CO2 uptake rates (-33,300 ± 7,900 μmol m-2ṡd-1) twice that of surrounding waters and ˜1,900 times greater than the diffusive sea-air methane efflux (17.3 ± 4.8 μmol m-2ṡd-1). The negative radiative forcing expected from this CO2 uptake is up to 231 times greater than the positive radiative forcing from the methane emissions. Surface water characteristics (e.g., high dissolved oxygen, high pH, and enrichment of 13C in CO2) indicate that upwelling of cold, nutrient-rich water from near the seafloor accompanies methane emissions and stimulates CO2 consumption by photosynthesizing phytoplankton. These findings challenge the widely held perception that areas characterized by shallow-water methane seeps and/or strongly elevated sea-air methane flux always increase the global atmospheric greenhouse gas burden.

  17. Atmospheric CO(2) and mycorrhiza effects on biomass allocation and nutrient uptake of nodulated pea (Pisum sativum L.) plants.

    Science.gov (United States)

    Gavito, M E; Curtis, P S; Mikkelsen, T N; Jakobsen, I

    2000-11-01

    The effect of ambient and elevated atmospheric CO(2) on biomass partitioning and nutrient uptake of mycorrhizal and non-mycorrhizal pea plants grown in pots in a controlled environment was studied. The hypothesis tested was that mycorrhizae would increase C assimilation by increasing photosynthetic rates and reduce below-ground biomass allocation by improving nutrient uptake. This effect was expected to be more pronounced at elevated CO(2) where plant C supply and nutrient demand would be increased. The results showed that mycorrhizae did not interact with atmospheric CO(2) concentration in the variables measured. Mycorrhizae did not affect photosynthetic rates, had no effect on root weight or root length density and almost no effect on nutrient uptake, but still significantly increased shoot weight and reduced root/shoot ratio at harvest. Elevated CO(2) increased photosynthetic rates with no evidence for down-regulation, increased shoot weight and nutrient uptake, had no effect on root weight, and actually reduced root/shoot ratio at harvest. Non-mycorrhizal plants growing at both CO(2) concentrations had lower shoot weight than mycorrhizal plants with similar nutritional status and photosynthetic rates. It is suggested that the positive effect of mycorrhizal inoculation was caused by an enhanced C supply and C use in mycorrhizal plants than in non-mycorrhizal plants. The results indicate that plant growth was not limited by mineral nutrients, but partially source and sink limited for carbon. Mycorrhizal inoculation and elevated CO(2) might have removed such limitations and their effects on above-ground biomass were independent, positive and additive.

  18. Partitioning net ecosystem carbon exchange into net assimilation and respiration using 13CO2 measurements: A cost-effective sampling strategy

    Science.gov (United States)

    OgéE, J.; Peylin, P.; Ciais, P.; Bariac, T.; Brunet, Y.; Berbigier, P.; Roche, C.; Richard, P.; Bardoux, G.; Bonnefond, J.-M.

    2003-06-01

    The current emphasis on global climate studies has led the scientific community to set up a number of sites for measuring the long-term biosphere-atmosphere net CO2 exchange (net ecosystem exchange, NEE). Partitioning this flux into its elementary components, net assimilation (FA), and respiration (FR), remains necessary in order to get a better understanding of biosphere functioning and design better surface exchange models. Noting that FR and FA have different isotopic signatures, we evaluate the potential of isotopic 13CO2 measurements in the air (combined with CO2 flux and concentration measurements) to partition NEE into FR and FA on a routine basis. The study is conducted at a temperate coniferous forest where intensive isotopic measurements in air, soil, and biomass were performed in summer 1997. The multilayer soil-vegetation-atmosphere transfer model MuSICA is adapted to compute 13CO2 flux and concentration profiles. Using MuSICA as a "perfect" simulator and taking advantage of the very dense spatiotemporal resolution of the isotopic data set (341 flasks over a 24-hour period) enable us to test each hypothesis and estimate the performance of the method. The partitioning works better in midafternoon when isotopic disequilibrium is strong. With only 15 flasks, i.e., two 13CO2 nighttime profiles (to estimate the isotopic signature of FR) and five daytime measurements (to perform the partitioning) we get mean daily estimates of FR and FA that agree with the model within 15-20%. However, knowledge of the mesophyll conductance seems crucial and may be a limitation to the method.

  19. Net sea–air CO2 flux uncertainties in the Bay of Biscay based on the choice of wind speed products and gas transfer parameterizations

    Directory of Open Access Journals (Sweden)

    P. Otero

    2013-05-01

    Full Text Available The estimation of sea–air CO2 fluxes is largely dependent on wind speed through the gas transfer velocity parameterization. In this paper, we quantify uncertainties in the estimation of the CO2 uptake in the Bay of Biscay resulting from the use of different sources of wind speed such as three different global reanalysis meteorological models (NCEP/NCAR 1, NCEP/DOE 2 and ERA-Interim, one high-resolution regional forecast model (HIRLAM-AEMet, winds derived under the Cross-Calibrated Multi-Platform (CCMP project, and QuikSCAT winds in combination with some of the most widely used gas transfer velocity parameterizations. Results show that net CO2 flux estimations during an entire seasonal cycle (September 2002–September 2003 may vary by a factor of ~ 3 depending on the selected wind speed product and the gas exchange parameterization, with the highest impact due to the last one. The comparison of satellite- and model-derived winds with observations at buoys advises against the systematic overestimation of NCEP-2 and the underestimation of NCEP-1. In the coastal region, the presence of land and the time resolution are the main constraints of QuikSCAT, which turns CCMP and ERA-Interim in the preferred options.

  20. Net photosynthesis in Sphagnum mosses has increased in response to the last century's 100 ppm increase in atmospheric CO2

    Science.gov (United States)

    Serk, Henrik; Nilsson, Mats; Schleucher, Jurgen

    2017-04-01

    Peatlands store >25% of the global soil C pool, corresponding to 1/3 of the contemporary CO2-C in the atmosphere. The majority of the accumulated peat is made up by remains of Sphagnum peat mosses. Thus, understanding how various Sphagnum functional groups respond, and have responded, to increasing atmospheric CO2 and temperature constitutes a major challenge for our understanding of the role of peatlands under a changing climate. We have recently demonstrated (Ehlers et al., 2015, PNAS) that the abundance ratio of two deuterium isotopomers (molecules carrying D at specific intramolecular positions, here D6R/S) of photosynthetic glucose reflects the ratio of oxygenation to carboxylation metabolic fluxes at Rubisco. The photosynthetic glucose is prepared from various plant carbohydrates including cellulose. This finding has been established in CO2 manipulation experiments and observed in carbohydrate derived glucose isolated from herbarium samples of all investigated C-3 species. The isotopomer ratio is connected to specific enzymatic processes thus allowing for mechanistic implicit interpretations. Here we demonstrate a clear increase in net photosynthesis of Sphagnum fuscum in response to the increase of 100 ppm CO2 during the last century as deduced from analysis on S. fuscum remains from peat cores. The D6R/S ratio declines from bottom to top in peat cores, indicating CO2-driven reduction of photorespiration in contemporary moss biomass. In contrast to the hummock-forming S. fuscum, hollow-growing species, e.g. S. majus did not show this response or gave significantly weaker response, suggesting important ecological consequences of rising CO2 on peatland ecosystem services. We hypothesize that photosynthesis in hollow-growing species under water saturation is fully or partly disconnected from the atmospheric CO2 partial pressure and thus showing weaker or no response to increased atmospheric CO2. To further test the field observations we grow both hummock and

  1. Co-ordination of NDH and Cup proteins in CO2 uptake in cyanobacterium Synechocystis sp. PCC 6803.

    Science.gov (United States)

    Han, Xunling; Sun, Nan; Xu, Min; Mi, Hualing

    2017-06-01

    High and low affinity CO2-uptake systems containing CupA (NDH-1MS) and CupB (NDH-1MS'), respectively, have been identified in Synechocystis sp. PCC 6803, but it is yet unknown how the complexes function in CO2 uptake. In this work, we found that deletion of cupB significantly lowered the growth of cells, and deletion of both cupA and cupB seriously suppressed the growth below pH 7.0 even under 3% CO2. The rate of photosynthetic oxygen evolution was decreased slightly by deletion of cupA but significantly by deletion of cupB and more severely by deletion of both cupA and cupB, especially in response to changed pH conditions under 3% CO2. Furthermore, we found that assembly of CupB into NDH-1MS' was dependent on NdhD4 and NdhF4. NDH-1MS' was not affected in the NDH-1MS-degradation mutant and NDH-1MS was not affected in the NDH-1MS'-degradation mutants, indicating the existence of independent CO2-uptake systems under high CO2 conditions. The light-induced proton gradient across thylakoid membranes was significantly inhibited in ndhD-deletion mutants, suggesting that NdhDs functions in proton pumping. The carbonic anhydrase activity was suppressed partly in the cupA- or cupB-deletion mutant but severely in the mutant with both cupA and cupB deletion, indicating that CupA and CupB function in conversion of CO2 to HCO3-. In turn, deletion of cup genes lowered the transthylakoid membrane proton gradient and deletion of ndhDs decreased the CO2 hydration. Our results suggest that NDH-1M provides an alkaline region to activate Cup proteins involved in CO2 uptake. © The Author 2017. Published by Oxford University Press on behalf of the Society for Experimental Biology.

  2. Soil trace gas emissions (CH4 and N2O) offset the CO2 uptake in poplar short rotation coppice

    Science.gov (United States)

    Zenone, Terenzio; Zona, Donatella; Gelfand, Iya; Gielen, Bert; camino serrano, Marta; Ceulemans, Reinhart

    2015-04-01

    The need for renewable energy sources will lead to a considerable expansion in the planting of dedicated fast-growing biomass crops across Europe. Among them poplar (Populus spp) is the most widely planted as short rotation coppice (SRC) and an increase in the surface area of large-scale SRC poplar plantations might thus be expected. In this study we report the greenhouse gas fluxes (GHG) of carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) measured using the eddy covariance technique in a SRC plantation for bioenergy production during the period 2010-2013. The plantation was established in April 2010 on 18.4 ha of former agricultural land with a density of 8000 plants ha-1; the above-ground biomass was harvested on February 2012 and 2014.The whole GHG balance of the four years of the study was 1.90 (± 1.37) Mg CO2eq ha-1; this indicated that soil trace gas emissions offset the CO2 uptake by the plantation. CH4 and N2O almost equally contributed to offset the CO2 uptake of -5.28 (±0.67) Mg CO2eq ha-1 with an overall emission of 3.56 (± 0.35) Mg CO2eq ha-1 of N2O and of 3.53 (± 0.85) Mg CO2eq ha-1 of CH4. N2O emissions mostly occurred during a single peak a few months after the site was converted into SRC and represented 44% of the entire N2O loss during the entire study. Accurately capturing these emission events proved to be critical for correct estimates of the GHG balance. The self-organizing map (SOM) technique graphically showed the relationship between the CO2 fluxes and the principal environmental variables but failed to explain the variability of the soil trace gas emissions. The nitrogen content in the soil and the water table depth were the two drivers that best explained the variability in N2O and CH4 respectively. This study underlines the importance of the "non-CO2 GHG" on the overall balance as well as the impact of the harvest on the CO2 uptake rate. Further long-term investigations of soil trace gas emissions should also monitor the N

  3. CO2 uptake by a stand of Douglas fir: flux measurements compared with model calculations

    NARCIS (Netherlands)

    Vermetten, A.W.M.; Ganzeveld, L.; Jeuken, A.; Hofschreuder, P.; Mohren, G.M.J.

    1994-01-01

    Fluxes of CO2 were calculated by the gradient method from concentration differences, measured in the surface roughness layer above a Douglas fir stand in the Netherlands during a full year (1989). The annual course of the CO2 flux density clearly showed the influence of temperature and incoming

  4. Statistical partitioning of a three-year time series of direct urban net CO2 flux measurements into biogenic and anthropogenic components

    Science.gov (United States)

    Menzer, Olaf; McFadden, Joseph P.

    2017-12-01

    Eddy covariance flux measurements are increasingly used to quantify the net carbon dioxide exchange (FC) in urban areas. FC represents the sum of anthropogenic emissions, biogenic carbon release from plant and soil respiration, and carbon uptake by plant photosynthesis. When FC is measured in natural ecosystems, partitioning into respiration and photosynthesis is a well-established procedure. In contrast, few studies have partitioned FC at urban flux tower sites due to the difficulty of accounting for the temporal and spatial variability of the multiple sources and sinks. Here, we partitioned a three-year time series of flux measurements from a suburban neighborhood of Minneapolis-Saint Paul, Minnesota, USA. We segregated FC into one subset that captured fluxes from a residential neighborhood and into another subset that covered a golf course. For both land use types we modeled anthropogenic flux components based on winter data and extrapolated them to the growing season, to estimate gross primary production (GPP) and ecosystem respiration (Reco) at half-hourly, daily, monthly and annual scales. During the growing season, GPP had the largest magnitude (up to - 9.83 g C m-2 d-1) of any component CO2 flux, biogenic or anthropogenic, and both GPP and Reco were more dynamic seasonally than anthropogenic fluxes. Owing to the balancing of Reco against GPP, and the limitations of the growing season in a cold temperate climate zone, the net biogenic flux was only 1.5%-4.5% of the anthropogenic flux in the dominant residential land use type, and between 25%-31% of the anthropogenic flux in highly managed greenspace. Still, the vegetation sink at our site was stronger than net anthropogenic emissions on 16-20 days over the residential area and on 66-91 days over the recreational area. The reported carbon flux sums and dynamics are a critical step toward developing models of urban CO2 fluxes within and across cities that differ in vegetation cover.

  5. Enhanced CO2 uptake at a shallow Arctic Ocean seep field overwhelms the positive warming potential of emitted methane

    Science.gov (United States)

    Greinert, Jens; Silyakova, Anna; Vielstädte, Lisa; Casso, Michael; Mienert, Jürgen; Bünz, Stefan

    2017-01-01

    Continued warming of the Arctic Ocean in coming decades is projected to trigger the release of teragrams (1 Tg = 106 tons) of methane from thawing subsea permafrost on shallow continental shelves and dissociation of methane hydrate on upper continental slopes. On the shallow shelves (methane released from the seafloor may reach the atmosphere and potentially amplify global warming. On the other hand, biological uptake of carbon dioxide (CO2) has the potential to offset the positive warming potential of emitted methane, a process that has not received detailed consideration for these settings. Continuous sea−air gas flux data collected over a shallow ebullitive methane seep field on the Svalbard margin reveal atmospheric CO2 uptake rates (−33,300 ± 7,900 μmol m−2⋅d−1) twice that of surrounding waters and ∼1,900 times greater than the diffusive sea−air methane efflux (17.3 ± 4.8 μmol m−2⋅d−1). The negative radiative forcing expected from this CO2 uptake is up to 231 times greater than the positive radiative forcing from the methane emissions. Surface water characteristics (e.g., high dissolved oxygen, high pH, and enrichment of 13C in CO2) indicate that upwelling of cold, nutrient-rich water from near the seafloor accompanies methane emissions and stimulates CO2 consumption by photosynthesizing phytoplankton. These findings challenge the widely held perception that areas characterized by shallow-water methane seeps and/or strongly elevated sea−air methane flux always increase the global atmospheric greenhouse gas burden. PMID:28484018

  6. Diurnal and Seasonal Variations in the Net Ecosystem CO2 Exchange of a Pasture in the Three-River Source Region of the Qinghai-Tibetan Plateau.

    Directory of Open Access Journals (Sweden)

    Bin Wang

    Full Text Available Carbon dioxide (CO2 exchange between the atmosphere and grassland ecosystems is very important for the global carbon balance. To assess the CO2 flux and its relationship to environmental factors, the eddy covariance method was used to evaluate the diurnal cycle and seasonal pattern of the net ecosystem CO2 exchange (NEE of a cultivated pasture in the Three-River Source Region (TRSR on the Qinghai-Tibetan Plateau from January 1 to December 31, 2008. The diurnal variations in the NEE and ecosystem respiration (Re during the growing season exhibited single-peak patterns, the maximum and minimum CO2 uptake observed during the noon hours and night; and the maximum and minimum Re took place in the afternoon and early morning, respectively. The minimum hourly NEE rate and the maximum hourly Re rate were -7.89 and 5.03 μmol CO2 m-2 s-1, respectively. The NEE and Re showed clear seasonal variations, with lower values in winter and higher values in the peak growth period. The highest daily values for C uptake and Re were observed on August 12 (-2.91 g C m-2 d-1 and July 28 (5.04 g C m-2 day-1, respectively. The annual total NEE and Re were -140.01 and 403.57 g C m-2 year-1, respectively. The apparent quantum yield (α was -0.0275 μmol μmol-1 for the entire growing period, and the α values for the pasture's light response curve varied with the leaf area index (LAI, air temperature (Ta, soil water content (SWC and vapor pressure deficit (VPD. Piecewise regression results indicated that the optimum Ta and VPD for the daytime NEE were 14.1°C and 0.65 kPa, respectively. The daytime NEE decreased with increasing SWC, and the temperature sensitivity of respiration (Q10 was 3.0 during the growing season, which was controlled by the SWC conditions. Path analysis suggested that the soil temperature at a depth of 5 cm (Tsoil was the most important environmental factor affecting daily variations in NEE during the growing season, and the photosynthetic photon

  7. CO2 uptake and ecophysiological parameters of the grain crops of midcontinent North America: estimates from flux tower measurements

    Science.gov (United States)

    Gilmanov, Tagir; Wylie, Bruce; Tieszen, Larry; Meyers, Tilden P.; Baron, Vern S.; Bernacchi, Carl J.; Billesbach, David P.; Burba, George G.; Fischer, Marc L.; Glenn, Aaron J.; Hanan, Niall P.; Hatfield, Jerry L.; Heuer, Mark W.; Hollinger, Steven E.; Howard, Daniel M.; Matamala, Roser; Prueger, John H.; Tenuta, Mario; Young, David G.

    2013-01-01

    We analyzed net CO2 exchange data from 13 flux tower sites with 27 site-years of measurements over maize and wheat fields across midcontinent North America. A numerically robust “light-soil temperature-VPD”-based method was used to partition the data into photosynthetic assimilation and ecosystem respiration components. Year-round ecosystem-scale ecophysiological parameters of apparent quantum yield, photosynthetic capacity, convexity of the light response, respiration rate parameters, ecological light-use efficiency, and the curvature of the VPD-response of photosynthesis for maize and wheat crops were numerically identified and interpolated/extrapolated. This allowed us to gap-fill CO2 exchange components and calculate annual totals and budgets. VPD-limitation of photosynthesis was systematically observed in grain crops of the region (occurring from 20 to 120 days during the growing season, depending on site and year), determined by the VPD regime and the numerical value of the curvature parameter of the photosynthesis-VPD-response, σVPD. In 78% of the 27 site-years of observations, annual gross photosynthesis in these crops significantly exceeded ecosystem respiration, resulting in a net ecosystem production of up to 2100 g CO2 m−2 year−1. The measurement-based photosynthesis, respiration, and net ecosystem production data, as well as the estimates of the ecophysiological parameters, provide an empirical basis for parameterization and validation of mechanistic models of grain crop production in this economically and ecologically important region of North America.

  8. Enhanced terrestrial carbon uptake linked to a recent pause in the growth rate of atmospheric CO2

    Science.gov (United States)

    Keenan, T. F.; Prentice, I. C. C.; Canadell, J.; Williams, C. A.; Wang, H.; Collatz, G. J.

    2016-12-01

    The terrestrial carbon sink is increasing, yet the mechanisms responsible for its long-term 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 process-based global vegetation models, we examine the causes and consequences of the enhancement of the terrestrial carbon sink. We show that over the past century the enhanced sink is largely due to the effect of elevated CO2 on photosynthesis dominating over warming induced increases in respiration. The slowdown in global warming since the start of the 21st century is shown to have increased the sink, leading to a pause in the growth rate of atmospheric CO2, and providing further evidence of the relative roles of CO2 fertilization and warming induced respiration. The effect of enhanced terrestrial carbon uptake on the atmospheric CO2 growth rate highlights the need to protect both existing carbon stocks and those areas where the sink is growing most rapidly.

  9. Spatial variability of CO2 uptake in polygonal tundra: assessing low-frequency disturbances in eddy covariance flux estimates

    Directory of Open Access Journals (Sweden)

    N. Pirk

    2017-06-01

    Full Text Available The large spatial variability in Arctic tundra complicates the representative assessment of CO2 budgets. Accurate measurements of these heterogeneous landscapes are, however, essential to understanding their vulnerability to climate change. We surveyed a polygonal tundra lowland on Svalbard with an unmanned aerial vehicle (UAV that mapped ice-wedge morphology to complement eddy covariance (EC flux measurements of CO2. The analysis of spectral distributions showed that conventional EC methods do not accurately capture the turbulent CO2 exchange with a spatially heterogeneous surface that typically features small flux magnitudes. Nonlocal (low-frequency flux contributions were especially pronounced during snowmelt and introduced a large bias of −46 gC m−2 to the annual CO2 budget in conventional methods (the minus sign indicates a higher uptake by the ecosystem. Our improved flux calculations with the ogive optimization method indicated that the site was a strong sink for CO2 in 2015 (−82 gC m−2. Due to differences in light-use efficiency, wetter areas with low-centered polygons sequestered 47 % more CO2 than drier areas with flat-centered polygons. While Svalbard has experienced a strong increase in mean annual air temperature of more than 2 K in the last few decades, historical aerial photographs from the site indicated stable ice-wedge morphology over the last 7 decades. Apparently, warming has thus far not been sufficient to initiate strong ice-wedge degradation, possibly due to the absence of extreme heat episodes in the maritime climate on Svalbard. However, in Arctic regions where ice-wedge degradation has already initiated the associated drying of landscapes, our results suggest a weakening of the CO2 sink in polygonal tundra.

  10. Spatial variability of CO2 uptake in polygonal tundra: assessing low-frequency disturbances in eddy covariance flux estimates

    Science.gov (United States)

    Pirk, Norbert; Sievers, Jakob; Mertes, Jordan; Parmentier, Frans-Jan W.; Mastepanov, Mikhail; Christensen, Torben R.

    2017-06-01

    The large spatial variability in Arctic tundra complicates the representative assessment of CO2 budgets. Accurate measurements of these heterogeneous landscapes are, however, essential to understanding their vulnerability to climate change. We surveyed a polygonal tundra lowland on Svalbard with an unmanned aerial vehicle (UAV) that mapped ice-wedge morphology to complement eddy covariance (EC) flux measurements of CO2. The analysis of spectral distributions showed that conventional EC methods do not accurately capture the turbulent CO2 exchange with a spatially heterogeneous surface that typically features small flux magnitudes. Nonlocal (low-frequency) flux contributions were especially pronounced during snowmelt and introduced a large bias of -46 gC m-2 to the annual CO2 budget in conventional methods (the minus sign indicates a higher uptake by the ecosystem). Our improved flux calculations with the ogive optimization method indicated that the site was a strong sink for CO2 in 2015 (-82 gC m-2). Due to differences in light-use efficiency, wetter areas with low-centered polygons sequestered 47 % more CO2 than drier areas with flat-centered polygons. While Svalbard has experienced a strong increase in mean annual air temperature of more than 2 K in the last few decades, historical aerial photographs from the site indicated stable ice-wedge morphology over the last 7 decades. Apparently, warming has thus far not been sufficient to initiate strong ice-wedge degradation, possibly due to the absence of extreme heat episodes in the maritime climate on Svalbard. However, in Arctic regions where ice-wedge degradation has already initiated the associated drying of landscapes, our results suggest a weakening of the CO2 sink in polygonal tundra.

  11. Enhanced terrestrial carbon uptake: global drivers and implications for the growth rate of atmospheric CO2.

    Science.gov (United States)

    Keenan, Trevor F.; Prentice, Colin; Canadell, Josep; Williams, Christopher; Han, Wang; Riley, William; Zhu, Qing; Koven, Charlie; Chambers, Jeff

    2017-04-01

    In this presentation we will focus on using decadal changes in the global carbon cycle to better understand how ecosystems respond to changes in CO2 concentration, temperature, and water and nutrient availability. Using global carbon budget estimates, ground, atmospheric and satellite observations, and multiple process-based global vegetation models, we examine the causes and consequences of the long-term changes in the terrestrial carbon sink. We show that over the past century the sink has been greatly enhanced, largely due to the effect of elevated CO2 on photosynthesis dominating over warming induced increases in respiration. We also examine the relative roles of greening, water and nutrients, along with individual events such as El Nino. We show that a slowdown in the rate of warming over land since the start of the 21st century likely led to a large increase in the sink, and that this increase was sufficient to lead to a pause in the growth rate of atmospheric CO2. We also show that the recent El Nino resulted in the highest growth rate of atmospheric CO2 ever recorded. Our results provide evidence of the relative roles of CO2 fertilization and warming induced respiration in the global carbon cycle, along with an examination of the impact of climate extremes.

  12. Forest productivity under elevated CO2 and O3: positive feedbacks to soil N cycling sustain decade-long net primary productivity enhancement by CO2

    Science.gov (United States)

    Donald R. Zak; Kurt S. Pregitzer; Mark E. Kubiske; Andrew J. Burton

    2011-01-01

    The accumulation of anthropogenic CO2 in the Earth's atmosphere, and hence the rate of climate warming, is sensitive to stimulation of plant growth by higher concentrations of atmospheric CO2. Here, we synthesise data from a field experiment in which three developing northern forest communities have been exposed to...

  13. Effects of winter temperature and summer drought on net ecosystem exchange of CO2 in a temperate peatland

    Science.gov (United States)

    Helfter, Carole; Campbell, Claire; Dinsmore, Kerry; Drewer, Julia; Coyle, Mhairi; Anderson, Margaret; Skiba, Ute; Nemitz, Eiko; Billett, Michael; Sutton, Mark

    2014-05-01

    Northern peatlands are one of the most important global sinks of atmospheric carbon dioxide (CO2); their ability to sequester C is a natural feedback mechanism controlled by climatic variables such as precipitation, temperature, length of growing season and period of snow cover. In the UK it has been predicted that peatlands could become a net source of carbon in response to climate change with climate models predicting a rise in global temperature of ca. 3oC between 1961-1990 and 2100. Land-atmosphere exchange of CO2in peatlands exhibits marked seasonal and inter-annual variations, which have significant short- and long-term effects on carbon sink strength. Net ecosystem exchange (NEE) of CO2 has been measured continuously by eddy-covariance (EC) at Auchencorth Moss (55° 47'32 N, 3° 14'35 W, 267 m a.s.l.), a temperate peatland in central Scotland, since 2002. Auchencorth Moss is a low-lying, ombrotrophic peatland situated ca. 20 km south-west of Edinburgh. Peat depth ranges from 5 m and the site has a mean annual precipitation of 1155 mm. The vegetation present within the flux measurement footprint comprises mixed grass species, heather and substantial areas of moss species (Sphagnum spp. and Polytrichum spp.). The EC system consists of a LiCOR 7000 closed-path infrared gas analyser for the simultaneous measurement of CO2 and water vapour and of a Gill Windmaster Pro ultrasonic anemometer. Over the 10 year period, the site was a consistent yet variable sink of CO2 ranging from -34.1 to -135.9 g CO2-C m-2 yr-1 (mean of -69.1 ± 33.6 g CO2-C m-2 yr-1). Inter-annual variability in NEE was positively correlated to the length of the growing seasons and mean winter air temperature explained 93% of the variability in summertime sink strength, indicating a phenological memory-effect. Plant development and productivity were stunted by colder winters causing a net reduction in the annual carbon sink strength of this peatland where autotrophic processes are thought to be

  14. Glycine uptake in heath plants and soil microbes responds to elevated temperature, CO2 and drought

    DEFF Research Database (Denmark)

    Andresen, Luise C.; Michelsen, Anders; Jonasson, Sven

    2009-01-01

    Temperate terrestrial ecosystems are currently exposed to climatic and air quality changes with increased atmospheric CO2, increased temperature and prolonged droughts. The responses of natural ecosystems to these changes are focus for research, due to the potential feedbacks to the climate. We...

  15. Effects of elevated CO2, warming and drought episodes on plant carbon uptake in a temperate heath ecosystem are controlled by soil water status

    DEFF Research Database (Denmark)

    Albert, Kristian Rost; Ro-Poulsen, H.; Mikkelsen, Teis Nørgaard

    2011-01-01

    The impact of elevated CO2, periodic drought and warming on photosynthesis and leaf characteristics of the evergreen dwarf shrub Calluna vulgaris in a temperate heath ecosystem was investigated. Photosynthesis was reduced by drought in midsummer and increased by elevated CO2 throughout the growing...... season, whereas warming only stimulated photosynthesis early in the year. At the beginning and end of the growing season, a T × CO2 interaction synergistically stimulated plant carbon uptake in the combination of warming and elevated CO2. At peak drought, the D × CO2 interaction antagonistically down......-regulated photosynthesis, suggesting a limited ability of elevated CO2 to counteract the negative effect of drought. The response of photosynthesis in the full factorial combination (TDCO2) could be explained by the main effect of experimental treatments (T, D, CO2) and the two-factor interactions (D × CO2, T × CO2...

  16. Accelerating carbon uptake in the Northern Hemisphere: evidence from the interhemispheric difference of atmospheric CO2 concentrations

    Directory of Open Access Journals (Sweden)

    Yuxuan Wang

    2013-11-01

    Full Text Available Previous studies have indicated that the regression slope between the interhemispheric difference (IHD of CO2 mixing ratios and fossil fuel (FF CO2 emissions was rather constant at about 0.5 ppm/Pg C yr−1 during 1957–2003. In this study, we found that the average regression slopes between the IHD of CO2 mixing ratios and IHD of FF emissions for 16 sites in the Northern Hemisphere (NH decreased from 0.69±0.12 ppm/Pg C yr−1 during 1982–1991 to 0.37±0.06 ppm/Pg C yr−1 during 1996–2008 (IHD of CO2 defined as the differences between each site and the South Pole, SPO. The largest difference was found in summer and autumn. The change in the spatial distribution of FF emissions driven by fast increasing Asian emissions may explain the slope change at three sites located north of 60°N but not at the other sites. A 30-yr SF6 simulation with time-varying meteorology and constant emissions suggests no significant difference in the decadal average and seasonal variation of interhemispheric exchange time (τ ex between the two periods. Based on the hemispheric net carbon fluxes derived from a two-box model, we attributed 75% of the regression slope decrease at NH sites south of 60°N to the acceleration of net carbon sink increase in the NH and 25% to the weakening of net carbon sink increase in the SH during 1996–2008. The growth rate of net carbon sink in the NH has increased by a factor of about three from 0.028±0.023 [mean±2σ] Pg C yr−2 during 1982–1991 to 0.093±0.033 Pg C yr−2 during 1996–2008, exceeding the percentage increase in the growth rate of IHD of FF emissions between the two periods (45%. The growth rate of net carbon sink in the SH has reduced 62% from 0.058±0.018 Pg C yr−2 during 1982–1991 to 0.022±0.012 Pg C yr−2 during 1996–2008.

  17. Significant long-term increase of fossil fuel CO2 uptake from reduced marine calcification

    Science.gov (United States)

    Ridgwell, A.; Zondervan, I.; Hargreaves, J. C.; Bijma, J.; Lenton, T. M.

    2006-11-01

    Analysis of available plankton manipulation experiments demonstrates a previously unrecognized wide range of sensitivities of biogenic calcification to simulated anthropogenic acidification of the ocean, with the "lab rat" of planktic calcifiers, Emiliania huxleyi not representative of calcification generally. We assess the implications of the experimental uncertainty in plankton calcification response by creating an ensemble of realizations of an Earth system model that encapsulates a comparable range of uncertainty in calcification response. We predict a substantial future reduction in marine carbonate production, with ocean CO2 sequestration across the model ensemble enhanced by between 62 and 199 PgC by the year 3000, equivalent to a reduction in the atmospheric fossil fuel CO2 burden at that time of up to 13%. Concurrent changes in ocean circulation and surface temperatures contribute about one third to the overall importance of reduced plankton calcification.

  18. CO2 uptake of a mature Acacia mangium plantation estimated from sap flow measurements and stable carbon isotope discrimination

    Science.gov (United States)

    Wang, H.; Zhao, P.; Zou, L. L.; McCarthy, H. R.; Zeng, X. P.; Ni, G. Y.; Rao, X. Q.

    2014-03-01

    A simple, nondestructive method for the estimation of canopy CO2 uptake is important for understanding the CO2 exchange between forest and atmosphere. Canopy CO2 uptake (FCO2) of a subtropical mature A. mangium plantation was estimated by combining sap flow measurements and stable carbon isotope discrimination (Δ) in Southern China from 2004 to 2007. The mechanistic relationship linking FCO2, Δ in leaf sap, and sap flow-based canopy stomatal conductance (Gs) was applied in our study. No significant seasonal variations were observed in Δ or in the ratio of the intercellular and ambient CO2 concentrations (Ci/Ca), although diurnal Ci/Ca varied between sunlit and shaded leaves. A sensitivity analysis showed that estimates of FCO2 were more sensitive to dynamics in Gs than in Ca and Δ. By using seasonally and canopy averaged Ci/Ca values, we obtained an acceptable estimate of FCO2 compared to other estimates. FCO2 exhibited similar diurnal variation to that of Gs. Large seasonal variation in FCO2 was attributed to the responsiveness of Gs to vapor pressure deficit, photosynthetically active radiation, and soil moisture deficit. Our estimate of FCO2 for a mature A. mangium plantation (2.13 ± 0.40 gC m-2 d-1) approached the lower range of values for subtropical mixed forests, probably due to lower mean canopy stomatal conductance, higher Ci/Ca, and greater tree height than other measured forests. Our estimate was also lower than values determined by satellite-based modeling or carbon allocation studies, suggesting the necessity of stand level flux data for verification. Qualitatively, the sap flux/stable isotope results compared well with gas exchange results. Differences in results between the two approaches likely reflected variability due to leaf position and age, which should be reduced for the combined sap flux and isotope technique, as it uses canopy average values of Gs and Ci/Ca.

  19. Enhanced uptake and photoactivation of topical methyl aminolevulinate after fractional CO2 laser pretreatment

    DEFF Research Database (Denmark)

    Haedersdal, M; Katsnelson, J; Sakamoto, F H

    2011-01-01

    Photodynamic therapy (PDT) of thick skin lesions is limited by topical drug uptake. Ablative fractional resurfacing (AFR) creates vertical channels that may facilitate topical PDT drug penetration and improve PDT-response in deep skin layers. The purpose of this study was to evaluate whether pre...

  20. Enhanced uptake and photoactivation of topical methyl aminolevulinate after fractional CO2 laser pretreatment

    DEFF Research Database (Denmark)

    Haedersdal, M; Katsnelson, J; Sakamoto, F H

    2011-01-01

    Photodynamic therapy (PDT) of thick skin lesions is limited by topical drug uptake. Ablative fractional resurfacing (AFR) creates vertical channels that may facilitate topical PDT drug penetration and improve PDT-response in deep skin layers. The purpose of this study was to evaluate whether pre......-treating the skin with AFR before topically applied methyl aminolevulinate (MAL) could enable a deep PDT-response....

  1. Sea-ice melt CO2-carbonate chemistry in the western Arctic Ocean: meltwater contributions to air-sea CO2 gas exchange, mixed-layer properties and rates of net community production under sea ice

    Science.gov (United States)

    Bates, N. R.; Garley, R.; Frey, K. E.; Shake, K. L.; Mathis, J. T.

    2014-12-01

    The carbon dioxide (CO2)-carbonate chemistry of sea-ice melt and co-located, contemporaneous seawater has rarely been studied in sea-ice-covered oceans. Here, we describe the CO2-carbonate chemistry of sea-ice melt (both above sea-ice as "melt ponds" and below sea-ice as "interface waters") and mixed-layer properties in the western Arctic Ocean in the early summer of 2010 and 2011. At 19 stations, the salinity (∼0.5 to 1500 μatm) with the majority of melt ponds acting as potentially strong sources of CO2 to the atmosphere. The pH of melt pond waters was also highly variable ranging from mildly acidic (6.1 to 7) to slightly more alkaline than underlying seawater (>8.2 to 10.8). All of the observed melt ponds had very low (pH/Ωaragonite than the co-located mixed layer beneath. Sea-ice melt thus contributed to the suppression of mixed-layer pCO2, thereby enhancing the surface ocean's capacity to uptake CO2 from the atmosphere. Our observations contribute to growing evidence that sea-ice CO2-carbonate chemistry is highly variable and its contribution to the complex factors that influence the balance of CO2 sinks and sources (and thereby ocean acidification) is difficult to predict in an era of rapid warming and sea-ice loss in the Arctic Ocean.

  2. Increases in nitrogen uptake rather than nitrogen-use efficiency support higher rates of temperate forest productivity under elevated CO2

    NARCIS (Netherlands)

    Finzi, A.C.; Norby, R.J.; Calfapietra, C.; Gallet-Budynek, A.; Gielen, B.; Holmes, W.E.; Hoosbeek, M.R.; Iversen, C.M.; Jackson, R.B.; Kubiske, M.E.; Ledford, J.; Liberloo, M.; Oren, R.; Polle, A.; Pritchard, S.; Zak, D.R.; Schlesinger, W.H.; Ceulemans, R.

    2007-01-01

    Forest ecosystems are important sinks for rising concentrations of atmospheric CO2. In previous research, we showed that net primary production (NPP) increased by 23 ± 2% when four experimental forests were grown under atmospheric concentrations of CO2 predicted for the latter half of this century.

  3. A biophysical approach using water deficit factor for daily estimations of evapotranspiration and CO2 uptake in Mediterranean environments

    Science.gov (United States)

    Helman, David; Lensky, Itamar M.; Osem, Yagil; Rohatyn, Shani; Rotenberg, Eyal; Yakir, Dan

    2017-09-01

    Estimations of ecosystem-level evapotranspiration (ET) and CO2 uptake in water-limited environments are scarce and scaling up ground-level measurements is not straightforward. A biophysical approach using remote sensing (RS) and meteorological data (RS-Met) is adjusted to extreme high-energy water-limited Mediterranean ecosystems that suffer from continuous stress conditions to provide daily estimations of ET and CO2 uptake (measured as gross primary production, GPP) at a spatial resolution of 250 m. The RS-Met was adjusted using a seasonal water deficit factor (fWD) based on daily rainfall, temperature and radiation data. We validated our adjusted RS-Met with eddy covariance flux measurements using a newly developed mobile lab system and the single active FLUXNET station operating in this region (Yatir pine forest station) at a total of seven forest and non-forest sites across a climatic transect in Israel (280-770 mm yr-1). RS-Met was also compared to the satellite-borne MODIS-based ET and GPP products (MOD16 and MOD17, respectively) at these sites.Results show that the inclusion of the fWD significantly improved the model, with R = 0.64-0.91 for the ET-adjusted model (compared to 0.05-0.80 for the unadjusted model) and R = 0.72-0.92 for the adjusted GPP model (compared to R = 0.56-0.90 of the non-adjusted model). The RS-Met (with the fWD) successfully tracked observed changes in ET and GPP between dry and wet seasons across the sites. ET and GPP estimates from the adjusted RS-Met also agreed well with eddy covariance estimates on an annual timescale at the FLUXNET station of Yatir (266 ± 61 vs. 257 ± 58 mm yr-1 and 765 ± 112 vs. 748 ± 124 gC m-2 yr-1 for ET and GPP, respectively). Comparison with MODIS products showed consistently lower estimates from the MODIS-based models, particularly at the forest sites. Using the adjusted RS-Met, we show that afforestation significantly increased the water use efficiency (the ratio of carbon uptake to ET) in this region

  4. Glacial meltwater and primary production are drivers of strong CO2 uptake in fjord and coastal waters adjacent to the Greenland Ice Sheet

    Directory of Open Access Journals (Sweden)

    L. Meire

    2015-04-01

    Full Text Available The Greenland Ice Sheet releases large amounts of freshwater, which strongly influences the physical and chemical properties of the adjacent fjord systems and continental shelves. Glacial meltwater input is predicted to strongly increase in the future, but the impact of meltwater on the carbonate dynamics of these productive coastal systems remains largely unquantified. Here we present seasonal observations of the carbonate system over the year 2013 in the surface waters of a west Greenland fjord (Godthåbsfjord influenced by tidewater outlet glaciers. Our data reveal that the surface layer of the entire fjord and adjacent continental shelf are undersaturated in CO2 throughout the year. The average annual CO2 uptake within the fjord is estimated to be 65 g C m−2 yr−1, indicating that the fjord system is a strong sink for CO2. The largest CO2 uptake occurs in the inner fjord near to the Greenland Ice Sheet and high glacial meltwater input during the summer months correlates strongly with low pCO2 values. This strong CO2 uptake can be explained by the thermodynamic effect on the surface water pCO2 resulting from the mixing of fresh glacial meltwater and ambient saline fjord water, which results in a CO2 uptake of 1.8 mg C kg−1 of glacial ice melted. We estimated that 28% of the CO2 uptake can be attributed to the input of glacial meltwater, while the remaining part is due to high primary production. Our findings imply that glacial melt\\-water is an important driver for undersaturation in CO2 in fjord and coastal waters adjacent to large ice sheets.

  5. Diurnal and Seasonal Variations in the Net Ecosystem CO2 Exchange of a Pasture in the Three-River Source Region of the Qinghai?Tibetan Plateau

    OpenAIRE

    Wang, Bin; Jin, Haiyan; Li, Qi; Chen, Dongdong; Zhao,Liang; Tang, Yanhong; Kato, Tomomichi; Gu, Song

    2017-01-01

    Carbon dioxide (CO2) exchange between the atmosphere and grassland ecosystems is very important for the global carbon balance. To assess the CO2 flux and its relationship to environmental factors, the eddy covariance method was used to evaluate the diurnal cycle and seasonal pattern of the net ecosystem CO2 exchange (NEE) of a cultivated pasture in the Three-River Source Region (TRSR) on the Qinghai?Tibetan Plateau from January 1 to December 31, 2008. The diurnal variations in the NEE and eco...

  6. Facile Carbonization of Microporous Organic Polymers into Hierarchically Porous Carbons Targeted for Effective CO2 Uptake at Low Pressures.

    Science.gov (United States)

    Gu, Shuai; He, Jianqiao; Zhu, Yunlong; Wang, Zhiqiang; Chen, Dongyang; Yu, Guipeng; Pan, Chunyue; Guan, Jianguo; Tao, Kai

    2016-07-20

    The advent of microporous organic polymers (MOPs) has delivered great potential in gas storage and separation (CCS). However, the presence of only micropores in these polymers often imposes diffusion limitations, which has resulted in the low utilization of MOPs in CCS. Herein, facile chemical activation of the single microporous organic polymers (MOPs) resulted in a series of hierarchically porous carbons with hierarchically meso-microporous structures and high CO2 uptake capacities at low pressures. The MOPs precursors (termed as MOP-7-10) with a simple narrow micropore structure obtained in this work possess moderate apparent BET surface areas ranging from 479 to 819 m(2) g(-1). By comparing different activating agents for the carbonization of these MOPs matrials, we found the optimized carbon matrials MOPs-C activated by KOH show unique hierarchically porous structures with a significant expansion of dominant pore size from micropores to mesopores, whereas their microporosity is also significantly improved, which was evidenced by a significant increase in the micropore volume (from 0.27 to 0.68 cm(3) g(-1)). This maybe related to the collapse and the structural rearrangement of the polymer farmeworks resulted from the activation of the activating agent KOH at high temperature. The as-made hierarchically porous carbons MOPs-C show an obvious increase in the BET surface area (from 819 to 1824 m(2) g(-1)). And the unique hierarchically porous structures of MOPs-C significantly contributed to the enhancement of the CO2 capture capacities, which are up to 214 mg g(-1) (at 273 K and 1 bar) and 52 mg g(-1) (at 273 K and 0.15 bar), superior to those of the most known MOPs and porous carbons. The high physicochemical stabilities and appropriate isosteric adsorption heats as well as high CO2/N2 ideal selectivities endow these hierarchically porous carbon materials great potential in gas sorption and separation.

  7. Carbon cycling of Lake Kivu (East Africa: net autotrophy in the epilimnion and emission of CO2 to the atmosphere sustained by geogenic inputs.

    Directory of Open Access Journals (Sweden)

    Alberto V Borges

    Full Text Available We report organic and inorganic carbon distributions and fluxes in a large (>2000 km2 oligotrophic, tropical lake (Lake Kivu, East Africa, acquired during four field surveys, that captured the seasonal variations (March 2007-mid rainy season, September 2007-late dry season, June 2008-early dry season, and April 2009-late rainy season. The partial pressure of CO2 (pCO2 in surface waters of the main basin of Lake Kivu showed modest spatial (coefficient of variation between 3% and 6%, and seasonal variations with an amplitude of 163 ppm (between 579±23 ppm on average in March 2007 and 742±28 ppm on average in September 2007. The most prominent spatial feature of the pCO2 distribution was the very high pCO2 values in Kabuno Bay (a small sub-basin with little connection to the main lake ranging between 11,213 ppm and 14,213 ppm (between 18 and 26 times higher than in the main basin. Surface waters of the main basin of Lake Kivu were a net source of CO2 to the atmosphere at an average rate of 10.8 mmol m(-2 d(-1, which is lower than the global average reported for freshwater, saline, and volcanic lakes. In Kabuno Bay, the CO2 emission to the atmosphere was on average 500.7 mmol m(-2 d(-1 (∼46 times higher than in the main basin. Based on whole-lake mass balance of dissolved inorganic carbon (DIC bulk concentrations and of its stable carbon isotope composition, we show that the epilimnion of Lake Kivu was net autotrophic. This is due to the modest river inputs of organic carbon owing to the small ratio of catchment area to lake surface area (2.15. The carbon budget implies that the CO2 emission to the atmosphere must be sustained by DIC inputs of geogenic origin from deep geothermal springs.

  8. Above- and Below-ground Biomass, Net Ecosystem Carbon Exchange, and Soil Respiration in a Poplar Populus deltoides Bartr.) stand : Changes after 3 years of Growth under Elevated CO2

    Science.gov (United States)

    Barron-Gafford, G. A.; Grieve, K.; Bil, K.; Kudeyarov, V.; Handley, L.; Murthy, R.

    2003-12-01

    Stands of cottonwood (Populus deltoides Bartr.) trees were grown as a coppiced system under ambient (40 Pa), twice ambient (80 Pa), and three times ambient (120 Pa) partial pressure CO2 for the past three years in the Intensively-managed Forest Mesocosm (IFM) of the Biosphere 2 Center. Over three years Net Ecosystem CO2 exchange (NECE) was measured continuously and in the third year, nine whole trees were harvested from each CO2 treatment over the growing season. Both above- and below-ground parameters were measured. Three years of growth under elevated CO2 showed the expected stimulation in foliar biomass (8.7, 11.9, and 13.1 kg for the 40, 80, and 120 Pa treatments, respectively). Rates of NECE also followed an expected increase with elevated atmospheric CO2 concentrations, with maximum CO2 uptake rates reaching 10.5, 15.6, and 19.6 μ moles m-2 s-1 in the 40, 80, and 120 Pa treatments, respectively. However, above ground woody biomass and root biomass were not much stimulated beyond 80 Pa CO2. Wood/foliage and above/below ground biomass ratios reflect this decline. Under conditions of non-limiting nutrients and water, we found consistent increases in the above/below ground biomass ratio and wood to foliage biomass ratios in the 80 compared to the 40 Pa pCO2. Woody biomass production and the above/below ground biomass ratio were lower under the 120 Pa than any other treatment. Although biomass production did not change appreciably between 80 and 120 Pa CO2 treatments, both substrate induced and in-situ soil respiration values are also significantly higher in the 120Pa treatment, though no differences were present prior to CO2 treatments (Murthy et al. 2003). The unique closed-system operation of the IFM allowed for measures of soil CO2 efflux to be measured at both the soil collar and stand scales using a box model that takes into account all inputs and outputs from the stand. In-situ soil respiration rates increased significantly with increased atmospheric CO2

  9. Further observations of a decreasing atmospheric CO2 uptake capacity in the Canada Basin (arctic Ocean) due to sea ice loss

    DEFF Research Database (Denmark)

    Else, B.G.T.; Galley, R.J.; Lansard, B.

    2013-01-01

    . Galley, B. Lansard, D. G. Barber, K. Brown, L. A. Miller, A. Mucci, T. N. Papakyriakou, J.-É. Tremblay, and S. Rysgaard (2013), Further observations of a decreasing atmospheric CO2 uptake capacity in the Canada Basin (Arctic Ocean) due to sea ice loss, Geophys. Res. Lett., 40, 1132–1137, doi:10.1002/grl...

  10. Oceanic and terrestrial biospheric CO2 uptake estimated from atmospheric potential oxygen observed at Ny-Ålesund, Svalbard, and Syowa, Antarctica

    Directory of Open Access Journals (Sweden)

    Shigeyuki Ishidoya

    2012-10-01

    Full Text Available Simultaneous measurements of the atmospheric O2/N2 ratio and CO2 concentration were made at Ny-Ålesund, Svalbard, and Syowa, Antarctica for the period 2001–2009. Based on these measurements, the observed atmospheric potential oxygen (APO values were calculated. The APO variations produced by changes in the oceanic heat content were estimated using an atmospheric transport model and heat-driven air–sea O2 (N2 fluxes, and then subtracted from observed interannual variations of APO. The oceanic CO2 uptake derived from the resulting ‘corrected’ secular trend of APO showed interannual variability of less than ±0.6 GtC yr−1, significantly smaller than that derived from the ‘uncorrected’ trend of APO (±0.9 GtC yr−1. The average CO2 uptake during the period 2001–2009 was estimated to be 2.9±0.7 and 0.8±0.9 GtC yr−1 for the ocean and terrestrial biosphere, respectively. By excluding the influence of El Niño around 2002–2003, the terrestrial biospheric CO2 uptake for the period 2004–2009 increased to 1.5±0.9 GtC yr−1, while the oceanic uptake decreased slightly to 2.8±0.8 GtC yr−1.

  11. Stimulated Respiration and Net Photosynthesis in Cassiopeia sp. during Glucose Enrichment Suggests in hospite CO2 Limitation of Algal Endosymbionts

    Directory of Open Access Journals (Sweden)

    Nils Rädecker

    2017-08-01

    Full Text Available The endosymbiosis between cnidarians and dinoflagellates of the genus Symbiodinium is key to the high productivity of tropical coral reefs. In this endosymbiosis, Symbiodinium translocate most of their photosynthates to their animal host in exchange for inorganic nutrients. Among these, carbon dioxide (CO2 derived from host respiration helps to meet the carbon requirements to sustain photosynthesis of the dinoflagellates. Nonetheless, recent studies suggest that productivity in symbiotic cnidarians such as corals is CO2-limited. Here we show that glucose enrichment stimulates respiration and gross photosynthesis rates by 80 and 140%, respectively, in the symbiotic upside-down jellyfish Cassiopeia sp. from the Central Red Sea. Our findings show that glucose was rapidly consumed and respired within the Cassiopeia sp. holobiont. The resulting increase of CO2 availability in hospite in turn likely stimulated photosynthesis in Symbiodinium. Hence, the increase of photosynthesis under these conditions suggests that CO2 limitation of Symbiodinium is a common feature of stable cnidarian holobionts and that the stimulation of holobiont metabolism may attenuate this CO2 limitation.

  12. Emergent climate and CO2sensitivities of net primary productivity in ecosystem models do not agree with empirical data in temperate forests of eastern North America.

    Science.gov (United States)

    Rollinson, Christine R; Liu, Yao; Raiho, Ann; Moore, David J P; McLachlan, Jason; Bishop, Daniel A; Dye, Alex; Matthes, Jaclyn H; Hessl, Amy; Hickler, Thomas; Pederson, Neil; Poulter, Benjamin; Quaife, Tristan; Schaefer, Kevin; Steinkamp, Jörg; Dietze, Michael C

    2017-07-01

    Ecosystem models show divergent responses of the terrestrial carbon cycle to global change over the next century. Individual model evaluation and multimodel comparisons with data have largely focused on individual processes at subannual to decadal scales. Thus far, data-based evaluations of emergent ecosystem responses to climate and CO 2 at multidecadal and centennial timescales have been rare. We compared the sensitivity of net primary productivity (NPP) to temperature, precipitation, and CO 2 in ten ecosystem models with the sensitivities found in tree-ring reconstructions of NPP and raw ring-width series at six temperate forest sites. These model-data comparisons were evaluated at three temporal extents to determine whether the rapid, directional changes in temperature and CO 2 in the recent past skew our observed responses to multiple drivers of change. All models tested here were more sensitive to low growing season precipitation than tree-ring NPP and ring widths in the past 30 years, although some model precipitation responses were more consistent with tree rings when evaluated over a full century. Similarly, all models had negative or no response to warm-growing season temperatures, while tree-ring data showed consistently positive effects of temperature. Although precipitation responses were least consistent among models, differences among models to CO 2 drive divergence and ensemble uncertainty in relative change in NPP over the past century. Changes in forest composition within models had no effect on climate or CO 2 sensitivity. Fire in model simulations reduced model sensitivity to climate and CO 2 , but only over the course of multiple centuries. Formal evaluation of emergent model behavior at multidecadal and multicentennial timescales is essential to reconciling model projections with observed ecosystem responses to past climate change. Future evaluation should focus on improved representation of disturbance and biomass change as well as the

  13. Effects of rhizopheric nitric oxide (NO) on N uptake in Fagus sylvatica seedlings depend on soil CO2 concentration, soil N availability and N source.

    Science.gov (United States)

    Dong, Fang; Simon, Judy; Rienks, Michael; Lindermayr, Christian; Rennenberg, Heinz

    2015-08-01

    Rhizospheric nitric oxide (NO) and carbon dioxide (CO2) are signalling compounds known to affect physiological processes in plants. Their joint influence on tree nitrogen (N) nutrition, however, is still unknown. Therefore, this study investigated, for the first time, the combined effect of rhizospheric NO and CO2 levels on N uptake and N pools in European beech (Fagus sylvatica L.) seedlings depending on N availability. For this purpose, roots of seedlings were exposed to one of the nine combinations (i.e., low, ambient, high NO plus CO2 concentration) at either low or high N availability. Our results indicate a significant effect of rhizospheric NO and/or CO2 concentration on organic and inorganic N uptake. However, this effect depends strongly on NO and CO2 concentration, N availability and N source. Similarly, allocation of N to different N pools in the fine roots of beech seedlings also shifted with varying rhizospheric gas concentrations and N availability. © The Author 2015. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

  14. Australian net (1950s-1990) soil organic carbon erosion: implications for CO2 emission and land-atmosphere modelling

    Science.gov (United States)

    The debate remains unresolved about soil erosion substantially offsetting fossil fuel emissions and acting as an important source or sink of CO2. There is little historical land use and management context to this debate, which is central to Australia's recent past of European settlement, agricultura...

  15. Residence time control on hot moments of net nitrate production and uptake in the hyporheic zone

    Science.gov (United States)

    Briggs, Martin A.; Lautz, Laura K.; Hare, Danielle K.

    2014-01-01

    The retention capacity for biologically available nitrogen within streams can be influenced by dynamic hyporheic zone exchange, a process that may act as either a net source or net sink of dissolved nitrogen. Over 5 weeks, nine vertical profiles of streambed chemistry (NO3- and NH4+) were collected above two beaver dams along with continuous high-resolution vertical hyporheic flux data. The results indicate a non-linear relation of net NO3- production followed by net uptake in the hyporheic zone as a function of residence time. This Lagrangian-based relation is consistent through time and across varied morphology (bars, pools, glides) above the dams, even though biogeochemical and environmental factors varied. The empirical continuum between net NO3- production and uptake and residence time is useful for identifying two crucial residence time thresholds: the transition to anaerobic respiration, which corresponds to the time of peak net nitrate production, and the net sink threshold, which is defined by a net uptake in NO3- relative to streamwater. Short-term hyporheic residence time variability at specific locations creates hot

  16. A theoretical framework for the net land-to-atmosphere CO2 flux and its implications in the definition of "emissions from land-use change"

    Directory of Open Access Journals (Sweden)

    T. Gasser

    2013-06-01

    Full Text Available We develop a theoretical framework and analysis of the net land-to-atmosphere CO2 flux in order to discuss possible definitions of "emissions from land-use change". The terrestrial biosphere is affected by two perturbations: the perturbation of the global carbon-climate-nitrogen system (CCN with elevated atmospheric CO2, climate change and nitrogen deposition; and the land-use change perturbation (LUC. Here, we progressively establish mathematical definitions of four generic components of the net land-to-atmosphere CO2 flux. The two first components are the fluxes that would be observed if only one perturbation occurred. The two other components are due to the coupling of the CCN and LUC perturbations, which shows the non-linear response of the terrestrial carbon cycle. Thanks to these four components, we introduce three possible definitions of "emissions from land-use change" that are indeed used in the scientific literature, often without clear distinctions, and we draw conclusions as for their absolute and relative behaviors. Thanks to the OSCAR v2 model, we provide quantitative estimates of the differences between the three definitions, and we find that comparing results from studies that do not use the same definition can lead to a bias of up to 20% between estimates of those emissions. After discussion of the limitations of the framework, we conclude on the three major points of this study that should help the community to reconcile modeling and observation of emissions from land-use change. The appendix mainly provides more detailed mathematical expressions of the four components of the net land-to-atmosphere CO2 flux.

  17. A theoretical framework for the net land-to-atmosphere CO2 flux and its implications in the definition of "emissions from land-use change"

    Science.gov (United States)

    Gasser, T.; Ciais, P.

    2013-06-01

    We develop a theoretical framework and analysis of the net land-to-atmosphere CO2 flux in order to discuss possible definitions of "emissions from land-use change". The terrestrial biosphere is affected by two perturbations: the perturbation of the global carbon-climate-nitrogen system (CCN) with elevated atmospheric CO2, climate change and nitrogen deposition; and the land-use change perturbation (LUC). Here, we progressively establish mathematical definitions of four generic components of the net land-to-atmosphere CO2 flux. The two first components are the fluxes that would be observed if only one perturbation occurred. The two other components are due to the coupling of the CCN and LUC perturbations, which shows the non-linear response of the terrestrial carbon cycle. Thanks to these four components, we introduce three possible definitions of "emissions from land-use change" that are indeed used in the scientific literature, often without clear distinctions, and we draw conclusions as for their absolute and relative behaviors. Thanks to the OSCAR v2 model, we provide quantitative estimates of the differences between the three definitions, and we find that comparing results from studies that do not use the same definition can lead to a bias of up to 20% between estimates of those emissions. After discussion of the limitations of the framework, we conclude on the three major points of this study that should help the community to reconcile modeling and observation of emissions from land-use change. The appendix mainly provides more detailed mathematical expressions of the four components of the net land-to-atmosphere CO2 flux.

  18. What drives the seasonal pattern of δ13C in the net land-atmosphere CO2 exchange across the United States?

    Science.gov (United States)

    Raczka, B. M.; Dlugokencky, E. J.; Ehleringer, J. R.; Lai, C. T.; Pataki, D. E.; Saleska, S. R.; Torn, M. S.; Vaughn, B. H.; Wehr, R. A.; Bowling, D. R.

    2016-12-01

    The seasonal pattern of δ13C of atmospheric CO2 depends upon both local and non-local land-atmosphere exchange and atmospheric transport. It has been suggested that the seasonal pattern is driven primarily from local variation in the δ13C of the net CO2 flux (exchange between vegetation and the atmosphere) as a result of variation of stomatal conductance of the vegetation. Here we study local variation of δ13C of the land-atmosphere exchange at 7 sites across the United States representing forests (Harvard, Howland, Niwot Ridge, Wind River), grasslands (Southern Great Plains, Rannell Prairie) and an urban center (Salt Lake City). Using a simple 2-part mixing model with background corrections we find that the δ13C of the net exchange of CO2 was most enriched at the grassland sites (-18.9 o/oo), and most depleted at the urban site (-29.6 o/oo) due to the contribution of C4 photosynthesis and fossil fuel emissions, respectively. The amplitude of the seasonal cycle was most pronounced at the C3/C4 grassland and the urban sites. In contrast, the forested sites have a reduced seasonal cycle, and remain almost constant during the growing season (0.49 o/oo change). Furthermore, by accounting for relatively fast δ13C variations in non-local sources at Niwot Ridge we find that the seasonal pattern in δ13C of net exchange is eliminated altogether. These results support the idea that a coherent, global seasonal pattern in δ13C of net exchange is influenced by seasonal transitions in C3/C4 grass, and the intensity and seasonal timing of fossil fuel emissions. This will have important implications for studies that use δ13C to constrain large-scale carbon fluxes.

  19. Light environment alters ozone uptake per net photosynthetic rate in black cherry trees.

    Science.gov (United States)

    Fredericksen, T S; Kolb, T E; Skelly, J M; Steiner, K C; Joyce, B J; Savage, J E

    1996-05-01

    Foliar ozone uptake rates of different-sized black cherry (Prunus serotina Ehrh.) trees were compared within a deciduous forest and adjacent openings in north-central Pennsylvania during one growing season. Study trees included open-grown seedlings and saplings, forest understory seedlings and saplings, and sunlit and shaded portions of mature canopy tree crowns. Instantaneous ozone uptake rates were highest in high-light environments primarily because of higher stomatal conductances. Low ozone uptake rates of seedlings and saplings in the forest understory could be attributed partially to lower average ambient ozone concentrations compared to the canopy and open environments. Among the tree size and light combinations tested, ozone uptake rates were highest in open-grown seedlings and lowest in forest-grown seedlings. Despite lower ozone uptake rates of foliage in shaded environments, ozone uptake per net photosynthesis of foliage in shaded environments was significantly higher than that of foliage in sunlit environments because of weaker coupling between net photosynthesis and stomatal conductance in shaded environments. The potential for greater ozone injury in shaded environments as a result of greater ozone uptake per net photosynthesis is consistent with previous reports of greater ozone injury in shaded foliage than in sunlit foliage.

  20. IntermIttent PreventIve treatment and Bed nets uPtake among ...

    African Journals Online (AJOL)

    IntErMIttEnt PrEvEntIvE trEAtMEnt And BEd nEts uPtAkE AMong PrEgnAnt woMEn. In kEnyA s. M. karoki, Bsc, MsC, Ministry of ... The use of intermittent preventive treatment in pregnancy (IPTp) and long-lasting insecticide treated nets ..... was conducted through the structured operational research and training Initiative (sort.

  1. Arbuscular mycorrhiza improve growth, nitrogen uptake, and nitrogen use efficiency in wheat grown under elevated CO2

    DEFF Research Database (Denmark)

    Zhu, Xiancan; Song, Fengbin; Liu, Shengqun

    2016-01-01

    Effects of the arbuscular mycorrhizal (AM) fungus Rhizophagus irregularis on plant growth, carbon (C) and nitrogen (N) accumulation, and partitioning was investigated in Triticum aestivum L. plants grown under elevated CO2 in a pot experiment. Wheat plants inoculated or not inoculated with the AM...

  2. Iron-light colimitation in a global ocean biogeochemical model and the sensitivity of oceanic CO2 uptake to dust deposition

    Science.gov (United States)

    Nickelsen, L.; Oschlies, A.

    2012-12-01

    The iron hypothesis of glacial-interglacial cycles states that glacial increases in the deposition of dust enhanced the concentrations of the micronutrient iron in the ocean where it triggered phytoplankton growth and thus CO2 uptake. Indeed, iron fertilization experiments find that phytoplankton needs iron in particular for nitrate uptake, light harvesting, synthesis of chlorophyll and in the electron transport chain of photosynthesis. Previous global biogeochemical models used to extrapolate results from local culture and field experiments have suggested that the sensitivity of ocean biogeochemistry to changes in dust deposition is too low to account for the observed glacial-interglacial changes of atmospheric CO2 concentrations. Here we show that this sensitivity is increased significantly when iron-light colimitation, i.e. the impact of iron on light harvesting capabilities and chlorophyll synthesis, is explicitly considered in a global biogeochemical ocean model. Iron-light colimitation increases the shift of export production to higher latitudes at high dust deposition and amplifies iron limitation at low dust deposition. Our results suggest that iron fertilization by increased dust deposition may explain a substantially larger portion of the observed past CO2 variability than thought previously. Our results emphasize the role of iron as a key limiting nutrient for phytoplankton in the ocean, with a high potential for changes in oceanic iron supply affecting the global carbon cycle and climate.

  3. Complex climatic and CO2 controls on net primary productivity of temperate dryland ecosystems over central Asia during 1980-2014

    Science.gov (United States)

    Zhang, Chi; Ren, Wei

    2017-09-01

    Central Asia covers a large land area of 5 × 106 km2 and has unique temperate dryland ecosystems, with over 80% of the world's temperate deserts, which has been experiencing dramatic warming and drought in the recent decades. How the temperate dryland responds to complex climate change, however, is still far from clear. This study quantitatively investigates terrestrial net primary productivity (NPP) in responses to temperature, precipitation, and atmospheric CO2 during 1980-2014, by using the Arid Ecosystem Model, which can realistically predict ecosystems' responses to changes in climate and atmospheric CO2 according to model evaluation against 28 field experiments/observations. The simulation results show that unlike other middle-/high-latitude regions, NPP in central Asia declined by 10% (0.12 × 1015 g C) since the 1980s in response to a warmer and drier climate. The dryland's response to warming was weak, while its cropland was sensitive to the CO2 fertilization effect (CFE). However, the CFE was inhibited by the long-term drought from 1998 to 2008 and the positive effect of warming on photosynthesis was largely offset by the enhanced water deficit. The complex interactive effects among climate drivers, unique responses from diverse ecosystem types, and intensive and heterogeneous climatic changes led to highly complex NPP changing patterns in central Asia, of which 69% was dominated by precipitation variation and 20% and 9% was dominated by CO2 and temperature, respectively. The Turgay Plateau in northern Kazakhstan and southern Xinjiang in China are hot spots of NPP degradation in response to climate change during the past three decades and in the future.

  4. Isolating and Quantifying the Effects of Climate and CO2 Changes (1980–2014 on the Net Primary Productivity in Arid and Semiarid China

    Directory of Open Access Journals (Sweden)

    Xia Fang

    2017-02-01

    Full Text Available Although the net primary productivity (NPP of arid/semiarid ecosystem is generally thought to be controlled by precipitation, other factors like CO2 fertilization effect and temperature change may also have important impacts, especially in the cold temperate areas of the northern China, where significant warming was reported in the recent decades. However, the impacts of climate and atmospheric CO2 changes to the NPP dynamics in the arid and semiarid areas of China (ASA-China is still unclear, hindering the development of climate adaptation strategy. Based on numeric experiments and factorial analysis, this study isolated and quantified the effects of climate and CO2 changes between 1980–2014 on ASA-China’s NPP, using the Arid Ecosystem Model (AEM that performed well in predicting ecosystems’ responses to climate/CO2 change according to our evaluation based on 21 field experiments. Our results showed that the annual variation in NPP was dominated by changes in precipitation, which reduced the regional NPP by 10.9 g·C/(m2·year. The precipitation-induced loss, however, has been compensated by the CO2 fertilization effect that increased the regional NPP by 14.9 g·C/(m2·year. The CO2 fertilization effect particularly benefited the extensive croplands in the Northern China Plain, but was weakened in the dry grassland of the central Tibetan Plateau due to suppressed plant activity as induced by a drier climate. Our study showed that the climate change in ASA-China and the ecosystem’s responses were highly heterogeneous in space and time. There were complex interactive effects among the climate factors, and different plant functional types (e.g., phreatophyte vs. non-phreatophyte could have distinct responses to similar climate change. Therefore, effective climate-adaptive strategies should be based on careful analysis of local climate pattern and understanding of the characteristic responses of the dominant species. Particularly, China

  5. Effect of voluntary hyperventilation with supplemental CO2 on pulmonary O2 uptake and leg blood flow kinetics during moderate-intensity exercise.

    Science.gov (United States)

    Chin, Lisa M K; Heigenhauser, George J F; Paterson, Donald H; Kowalchuk, John M

    2013-12-01

    Pulmonary O2 uptake (V(O₂p)) and leg blood flow (LBF) kinetics were examined at the onset of moderate-intensity exercise, during hyperventilation with and without associated hypocapnic alkalosis. Seven male subjects (25 ± 6 years old; mean ± SD) performed alternate-leg knee-extension exercise from baseline to moderate-intensity exercise (80% of estimated lactate threshold) and completed four to six repetitions for each of the following three conditions: (i) control [CON; end-tidal partial pressure of CO2 (P(ET, CO₂)) ~40 mmHg], i.e. normal breathing with normal inspired CO2 (0.03%); (ii) hypocapnia (HYPO; P(ET, CO₂) ~20 mmHg), i.e. sustained hyperventilation with normal inspired CO2 (0.03%); and (iii) normocapnia (NORMO; P(ET, CO₂) ~40 mmHg), i.e. sustained hyperventilation with elevated inspired CO2 (~5%). The V(O₂p) was measured breath by breath using mass spectrometry and a volume turbine. Femoral artery mean blood velocity was measured by Doppler ultrasound, and LBF was calculated from femoral artery diameter and mean blood velocity. Phase 2 V(O₂p) kinetics (τV(O₂p)) was different (P hyperventilation manoeuvre itself (i.e. independent of induced hypocapnic alkalosis) may contribute to the slower V(O₂p) kinetics observed during HYPO.

  6. Tunable rare-earth fcu-MOFs: A platform for systematic enhancement of CO2 adsorption energetics and uptake

    KAUST Repository

    Xue, Dongxu

    2013-05-22

    A series of fcu-MOFs based on rare-earth (RE) metals and linear fluorinated/nonfluorinated, homo/heterofunctional ligands were targeted and synthesized. This particular fcu-MOF platform was selected because of its unique structural characteristics combined with the ability/potential to dictate and regulate its chemical properties (e.g., tuning of the electron-rich RE metal ions and high localized charge density, a property arising from the proximal positioning of polarizing tetrazolate moieties and fluoro-groups that decorate the exposed inner surfaces of the confined conical cavities). These features permitted a systematic gas sorption study to evaluate/elucidate the effects of distinctive parameters on CO2-MOF sorption energetics. Our study supports the importance of the synergistic effect of exposed open metal sites and proximal highly localized charge density toward materials with enhanced CO2 sorption energetics. © 2013 American Chemical Society.

  7. Targeted Enhancement of H2 and CO2 Uptake for Autotrophic Production of Biodiesel in the Lithoautotrophic Bacterium Ralsonia Eutropha

    Energy Technology Data Exchange (ETDEWEB)

    Eckert, C. A.; Sullivan, R.; Johnson, C.; Yu, J.; Maness, P. C.

    2013-01-01

    CO2 and H2 are promising feedstocks for production of valuable biocompounds. Ralstonia eutropha utilizes these feedstocks to generate energy (ATP) and reductant (NAD(P)H) via oxidation of H2 by a membrane-bound (MBH) and a soluble hydrogenase (SH) for CO2 fixation by the Calvin-Benson-Bassham (CBB) cycle. Increased expression of the enzyme that fixes CO2 (RubisCO) resulted in 6-fold activity improvement in vitro, while increased expression of the MBH operon or the SH operon plus MBH operon maturation factors necessary for activity resulted in a 10-fold enhancement. Current research involves genetic manipulation of two endogenous cbb operons for increased expression, analysis of expression and activity of CBB/MBH/SH, cofactor ratios, and downstream products during autotrophic growth in control versus enhanced strains, and development of strategies for long-term, optimal overexpression. These studies will improve our understanding of autotrophic metabolism and provide a chassis strain for autotrophic production of biodiesel and other valuable carbon biocompounds.

  8. Impact of sulfuric and nitric acids on carbonate dissolution, and the associated deficit of CO2 uptake in the upper-middle reaches of the Wujiang River, China

    Science.gov (United States)

    Huang, Qi-bo; Qin, Xiao-qun; Liu, Peng-yu; Zhang, Lian-kai; Su, Chun-tian

    2017-08-01

    Carbonate weathering and the CO2 consumption in karstic area are extensive affected by anthropogenic activities, especially sulfuric and nitric acids usage in the upper-middle reaches of Wujiang River, China. The carbonic acid would be substituted by protons from sulfuric and nitric acids which can be reduce CO2 absorption. Therefore, The goal of this study was to highlight the impacts of sulfuric and nitric acids on carbonate dissolution and the associated deficit of CO2 uptaking during carbonate weathering. The hydrochemistries and carbon isotopic signatures of dissolved inorganic carbon from groundwater were measured during the rainy season (July; 41 samples) and post-rainy season (October; 26 samples). Our results show that Ca2 + and Mg2 + were the dominant cations (55.87-98.52%), and HCO3- was the dominant anion (63.63-92.87%). The combined concentrations of Ca2 + and Mg2 + commonly exceeded the equivalent concentration of HCO3-, with calculated [Ca2 + + Mg2 +]/[HCO3-] equivalent ratios of 1.09-2.12. The mean measured groundwater δ13CDIC value (- 11.38‰) was higher than that expected for carbonate dissolution mediated solely by carbonic acid (- 11.5‰), and the strong positive correlation of these values with [SO42 - + NO3-]/HCO3- showed that additional SO42 - and NO3- were required to compensate for this cation excess. Nitric and sulfuric acids are, therefore, suggested to have acted as the additional proton-promoted weathering agents of carbonate in the region, alongside carbonic acid. The mean contribution of atmospheric/pedospheric CO2 to the total aquatic HCO3- decreased by 15.67% (rainy season) and 14.17% (post-rainy season) due to the contributions made by these acids. The annual mean deficit of soil CO2 uptake by carbonate weathering across the study area was 14.92%, which suggests that previous workers may have overestimated the absorption of CO2 by carbonate weathering in other karstic areas worldwide.

  9. High air-sea CO2 uptake rates in nearshore and shelf areas of Southern Greenland: Temporal and spatial variability

    DEFF Research Database (Denmark)

    Rysgaard, S.; Mortensen, J.; Juul-Pedersen, T.

    2012-01-01

    The present study is based on hourly samplings of wind speed, monthly sampling sessions of temperature, salinity, dissolved inorganic carbon, alkalinity, nutrients, primary productivity and vertical export in the outer sill region (station GF3) of a sub-arctic SW Greenland fjord (Godthabsfjord...... productivity of 76-106 g C m(-2) yr(-1). Furthermore, the estimated vertical export of phytoplankton carbon to depths below 60 m of 38-89 g C m(-2) suggests that a large fraction of the mineralization (release of CO2) occurs in deeper waters in the outer sill region of the fjord. However...

  10. Current net ecosystem exchange of CO2 in a young mixed forest: any heritage from the previous ecosystem?

    Science.gov (United States)

    Violette, Aurélie; Heinesch, Bernard; Erpicum, Michel; Carnol, Monique; Aubinet, Marc; François, Louis

    2013-04-01

    For 15 years, networks of flux towers have been developed to determine accurate carbon balance with the eddy-covariance method and determine if forests are sink or source of carbon. However, for prediction of the evolution of carbon cycle and climate, major uncertainties remain on the ecosystem respiration (Reco, which includes the respiration of above ground part of trees, roots respiration and mineralization of the soil organic matter), the gross primary productivity (GPP) and their difference, the net ecosystem exchange (NEE) of forests. These uncertainties are consequences of spatial and inter-annual variability, driven by previous and current climatic conditions, as well as by the particular history of the site (management, diseases, etc.). In this study we focus on the carbon cycle in two mixed forests in the Belgian Ardennes. The first site, Vielsalm, is a mature stand mostly composed of beeches (Fagus sylvatica) and douglas fir (Pseudotsuga menziesii) from 80 to 100 years old. The second site, La Robinette, was covered before 1995 with spruces. After an important windfall and a clear cutting, the site was replanted, between 1995 and 2000, with spruces (Piceas abies) and deciduous species (mostly Betula pendula, Aulnus glutinosa and Salix aurita). The challenge here is to highlight how initial conditions can influence the current behavior of the carbon cycle in a growing stand compared to a mature one, where initial conditions are supposed to be forgotten. A modeling approach suits particularly well for sensitivity tests and estimation of the temporal lag between an event and the ecosystem response. We use the forest ecosystem model ASPECTS (Rasse et al., Ecological Modelling 141, 35-52, 2001). This model predicts long-term forest growth by calculating, over time, hourly NEE. It was developed and already validated on the Vielsalm forest. Modelling results are confronted to eddy-covariance data on both sites from 2006 to 2011. The main difference between both

  11. Carbon cycling in the epilimnion of Lake Kivu (East Africa): surface net autotrophy and emission of CO2 to the atmosphere sustained by geogenic inputs

    Science.gov (United States)

    Borges, Alberto V.; Bouillon, Steven; Morana, Cédric D. T.; Servais, Pierre; Descy, Jean-Pierre; Darchambeau, François

    2013-04-01

    Lake Kivu [2.50°S 1.59°S 29.37°E 28.83°E] is one of the East African great lakes (2370 km2 surface area, 550 km3 volume). It is a deep (maximum depth of 485 m) meromictic lake, with an oxic mixolimnion down to 70 m maximum, and a deep monolimnion rich in dissolved gases and nutrients. Lake Kivu is permanently stratified (meromictic) and deep layers receive heat, salts, and CO2 from deep geothermal springs. Seasonality of the physical and chemical vertical structure and biological activity in surface waters of Lake Kivu is driven by the oscillation between the dry season (June-September) and the rainy season (October-May), the former characterized by a deepening of the mixolimnion. This seasonal mixing favours the input of dissolved nutrients and the development of diatoms, while, during the rest of the year, the phytoplankton assemblage is dominated by cyanobacteria, chrysophytes and cryptophytes. Huge amounts of CO2 and methane (CH4) (300 km3 and 60 km3, respectively, at 0°C and 1 atm] are dissolved in the deep layers of Lake Kivu. The CO2 is mainly geogenic. Large scale industrial extraction of CH4 from the deep layers of Lake Kivu is planned which could affect the ecology and biogeochemical cycling of C of the lake and change for instance the emission of greenhouse gases such as CH4 and CO2. Here, we report a data set covering the seasonality of CO2 dynamics and fluxes, in conjunction with mass balances of C, and process rate measurements (primary production and bacterial production). In order to capture the seasonal variations of the studied quantities, four cruises were carried out in Lake Kivu on 15/03-29/03/2007 (mid rainy season), 28/08-10/09/2007 (late dry season), 21/06-03/07/2008 (early dry season) and 21/04-05/05/2009 (late rainy season). We show that the lake is a modest source of CO2 to the atmosphere but which is sustained by geogenic inputs from depth rather than net heterotrophy as reported in lakes in general. Indeed we provide several lines

  12. Regulation of nitrogen uptake and assimilation: Effects of nitrogen source, root-zone pH, and aerial CO2 concentration on growth and productivity of soybeans

    Science.gov (United States)

    Raper, C. D.; Tolley-Henry, L.

    1989-01-01

    An important feature of controlled-environment crop production systems such as those to be used for life support of crews during space exploration is the efficient utilization of nitrogen supplies. Making decisions about the best sources of these supplies requires research into the relationship between nitrogen source and the physiological processes which regulate vegetative and reproductive plant growth. Work done in four areas within this research objective is reported: (1) experiments on the effects of root-zone pH on preferential utilization of NO3(-) versus NH4(+) nitrogen; (2) investigation of processes at the whole-plant level that regulate nitrogen uptake; (3) studies of the effects of atmospheric CO2 and NO3(-) supply on the growth of soybeans; and (4) examination of the role of NO3(-) uptake in enhancement of root respiration.

  13. A new method to estimate photosynthetic parameters through net assimilation rate-intercellular space CO2 concentration (A-Ci ) curve and chlorophyll fluorescence measurements.

    Science.gov (United States)

    Moualeu-Ngangue, Dany P; Chen, Tsu-Wei; Stützel, Hartmut

    2017-02-01

    Gas exchange (GE) and chlorophyll fluorescence (CF) measurements are widely used to noninvasively study photosynthetic parameters, for example the rates of maximum Rubisco carboxylation (Vcmax ), electron transport rate (J), daytime respiration (Rd ) and mesophyll conductance (gm ). Existing methods for fitting GE data (net assimilation rate-intercellular space CO2 concentration (A-Ci ) curve) are based on two assumptions: gm is unvaried with CO2 concentration in the intercellular space (Ci ); and light absorption (α) and the proportion of quanta absorbed by photosystem II (β) are constant in the data set. These may result in significant bias in estimating photosynthetic parameters. To avoid the above-mentioned hypotheses, we present a new method for fitting A-Ci curves and CF data simultaneously. This method was applied to a data set obtained from cucumber (Cucumis sativus) leaves of various leaf ages and grown under eight different light conditions. The new method had significantly lower root mean square error and a lower rate of failures compared with previously published methods (6.72% versus 24.1%, respectively) and the effect of light conditions on Vcmax and J was better observed. Furthermore, the new method allows the estimation of a new parameter, the fraction of incoming irradiance harvested by photosystem II, and the dependence of gm on Ci . © 2016 The Authors. New Phytologist © 2016 New Phytologist Trust.

  14. Can hydrographic data provide evidence that the rate of oceanic uptake of anthropogenic CO2 is increasing?

    Directory of Open Access Journals (Sweden)

    William Carlisle Thacker

    Full Text Available Predictions of the rate of accumulation of anthropogenic carbon dioxide in the Pacific Ocean near 32°S and 150°W based on the P16 surveys of 1991 and 2005 and on the P06 surveys of 1992 and 2003 underestimate the amount found in the P06 survey of 2009-2010, suggesting an increasing uptake rate. Assuming the accumulation rate to be constant over the two decades, analyses using all five surveys lead to upward revision of the rates based only on the first four. On the other hand, accumulation rates estimated for 2003-2010 are significantly greater than those for 1991-2003, again suggesting an increasing uptake rate. In addressing this question it is important to acknowledge the limitations of the repeat hydrography and consequent uncertainties of estimated accumulation rates.

  15. IntermIttent PreventIve treatment and Bed nets uPtake among ...

    African Journals Online (AJOL)

    East African Medical Journal Vol: 93 No. 10 (Supplement) October 2016. IntErMIttEnt PrEvEntIvE trEAtMEnt And BEd nEts uPtAkE AMong PrEgnAnt woMEn. In kEnyA s. M. karoki, Bsc, MsC, Ministry of Health, national Malaria Control Programme, nairobi, kenya, L. kariuki, Bsc, vector Borne disease unit, nairobi, kenya, P. o.

  16. Response of net ecosystem CO2 exchange and evapotranspiration of boreal forest ecosystems to projected future climate changes: results of a modeling study

    Science.gov (United States)

    Olchev, Alexander; Kurbatova, Julia

    2014-05-01

    It is presented the modeling results describing the possible response of net ecosystem exchange of CO2 (NEE), gross (GPP) and net (NPP) primary production, as well as evapotranspiration (ET) of spruce forest ecosystems situated at central part of European part of Russia at the southern boundary of boreal forest community to projected future changes of climatic conditions and forest species composition. A process-based MixFor-SVAT model (Olchev et al 2002, 2008, 2009) has been used to describe the CO2 and H2O fluxes under present and projected future climate conditions. The main advantage of MixFor-SVAT is its ability not only to describe seasonal and daily dynamics of total CO2 and H2O fluxes at an ecosystem level, but also to adequately estimate the contributions of soil, forest understorey, and various tree species in overstorey into total ecosystem fluxes taking into account their individual responses to changes in environmental conditions as well as the differences in structure and biophysical properties. Results of modeling experiments showed that projected changes of climate conditions (moderate scenario A1B IPCC) and forest species composition at the end of 21 century can lead to small increase of annual evapotranspiration as well as to growth of NEE, GPP and NPP of the forests in case if the projected increase in temperature and elevated CO2 in the atmosphere in future will be strictly balanced with growth of available nutrients and water in plant and soil. It is obvious that any deficit of e.g. nitrogen in leaves (due to reduced transpiration, nitrogen availability in soil, etc.) may lead to decreases in the photosynthesis and respiration rates of trees and, as a consequence, to decreases in the GPP and NEE of entire forest ecosystem. Conducted modeling experiments have demonstrated that a 20% reduction of available nitrogen in tree leaves in a monospesific spruce forest stand may result in a 14% decrease in NEE, a 8% decrease in NPP, and a 4% decrease in

  17. A new approach to measure gross CO2 fluxes in leaves. Gross CO2 assimilation, photorespiration, and mitochondrial respiration in the light in tomato under drought stress.

    Science.gov (United States)

    Haupt-Herting, S; Klug, K; Fock, H P

    2001-05-01

    We developed a new method using 13CO2 and mass spectrometry to elucidate the role of photorespiration as an alternative electron dissipating pathway under drought stress. This was achieved by experimentally distinguishing between the CO2 fluxes into and out of the leaf. The method allows us to determine the rates of gross CO2 assimilation and gross CO2 evolution in addition to net CO2 uptake by attached leaves during steady-state photosynthesis. Furthermore, a comparison between measurements under photorespiratory and non-photorespiratory conditions may give information about the contribution of photorespiration and mitochondrial respiration to the rate of gross CO2 evolution at photosynthetic steady state. In tomato (Lycopersicon esculentum Mill. cv Moneymaker) leaves, drought stress decreases the rates of net and gross CO2 uptake as well as CO2 release from photorespiration and mitochondrial respiration in the light. However, the ratio of photorespiratory CO2 evolution to gross CO2 assimilation rises with water deficit. Also the contribution of re-assimilation of (photo) respiratory CO2 to gross CO2 assimilation increases under drought.

  18. Impact of clear and cloudy sky conditions on the vertical distribution of photosynthetic CO2 uptake within a spruce canopy

    Czech Academy of Sciences Publication Activity Database

    Urban, Otmar; Klem, Karel; Ač, Alexander; Havránková, Kateřina; Holišová, Petra; Navrátil, M.; Zitová, Martina; Kozlová, Klára; Pokorný, Radek; Šprtová, Miroslava; Tomášková, Ivana; Špunda, Vladimír; Grace, J.

    2012-01-01

    Roč. 26, č. 1 (2012), s. 46-55 ISSN 0269-8463 R&D Projects: GA MŠk 2B06068; GA MŽP(CZ) SP/2D1/93/07; GA AV ČR IAA600870701; GA MŠk(CZ) ED1.1.00/02.0073; GA MŠk(CZ) LM2010007 Institutional research plan: CEZ:AV0Z60870520 Keywords : afternoon depression of photosynthesis * daily course * diffuse/direct radiation * eddy covariance * light response curve * light use efficiency * light response curve * light use efficiency * net ecosystem production * photorespiration * stomatal conductance Subject RIV: EH - Ecology , Behaviour Impact factor: 4.861, year: 2012

  19. Does vapor pressure deficit drive the seasonality of δ13C of the net land-atmosphere CO2 exchange across the United States?

    Science.gov (United States)

    Raczka, B.; Biraud, S. C.; Ehleringer, J. R.; Lai, C.-T.; Miller, J. B.; Pataki, D. E.; Saleska, S. R.; Torn, M. S.; Vaughn, B. H.; Wehr, R.; Bowling, D. R.

    2017-08-01

    The seasonal pattern of the carbon isotope content (δ13C) of atmospheric CO2 depends on local and nonlocal land-atmosphere exchange and atmospheric transport. Previous studies suggested that the δ13C of the net land-atmosphere CO2 flux (δsource) varies seasonally as stomatal conductance of plants responds to vapor pressure deficit of air (VPD). We studied the variation of δsource at seven sites across the United States representing forests, grasslands, and an urban center. Using a two-part mixing model, we calculated the seasonal δsource for each site after removing background influence and, when possible, removing δ13C variation of nonlocal sources. Compared to previous analyses, we found a reduced seasonal (March-September) variation in δsource at the forest sites (0.5‰ variation). We did not find a consistent seasonal relationship between VPD and δsource across forest (or other) sites, providing evidence that stomatal response to VPD was not the cause of the global, coherent seasonal pattern in δsource. In contrast to the forest sites, grassland and urban sites had a larger seasonal variation in δsource (5‰) dominated by seasonal transitions in C3/C4 grass productivity and in fossil fuel emissions, respectively. Our findings were sensitive to the location used to account for atmospheric background variation within the mixing model method that determined δsource. Special consideration should be given to background location depending on whether the intent is to understand site level dynamics or regional scale impacts of land-atmosphere exchange. The seasonal amplitude in δ13C of land-atmosphere CO2 exchange (δsource) varied across land cover types and was not driven by seasonal changes in vapor pressure deficit. The largest seasonal amplitudes of δsource were at grassland and urban sites, driven by changes in C3/C4 grass productivity and fossil fuel emissions, respectively. Mixing model approaches may incorrectly calculate δsource when

  20. Can elevated CO(2) improve salt tolerance in olive trees?

    Science.gov (United States)

    Melgar, Juan Carlos; Syvertsen, James P; García-Sánchez, Francisco

    2008-04-18

    We compared growth, leaf gas exchange characteristics, water relations, chlorophyll fluorescence, and Na(+) and Cl(-) concentration of two cultivars ('Koroneiki' and 'Picual') of olive (Olea europaea L.) trees in response to high salinity (NaCl 100mM) and elevated CO(2) (eCO(2)) concentration (700microLL(-1)). The cultivar 'Koroneiki' is considered to be more salt sensitive than the relatively salt-tolerant 'Picual'. After 3 months of treatment, the 9-month-old cuttings of 'Koroneiki' had significantly greater shoot growth, and net CO(2) assimilation (A(CO(2))) at eCO(2) than at ambient CO(2), but this difference disappeared under salt stress. Growth and A(CO(2)) of 'Picual' did not respond to eCO(2) regardless of salinity treatment. Stomatal conductance (g(s)) and leaf transpiration were decreased at eCO(2) such that leaf water use efficiency (WUE) increased in both cultivars regardless of saline treatment. Salt stress increased leaf Na(+) and Cl(-) concentration, reduced growth and leaf osmotic potential, but increased leaf turgor compared with non-salinized control plants of both cultivars. Salinity decreased A(CO(2)), g(s), and WUE, but internal CO(2) concentrations in the mesophyll were not affected. eCO(2) increased the sensitivity of PSII and chlorophyll concentration to salinity. eCO(2) did not affect leaf or root Na(+) or Cl(-) concentrations in salt-tolerant 'Picual', but eCO(2) decreased leaf and root Na(+) concentration and root Cl(-) concentration in the more salt-sensitive 'Koroneiki'. Na(+) and Cl(-) accumulation was associated with the lower water use in 'Koroneiki' but not in 'Picual'. Although eCO(2) increased WUE in salinized leaves and decreased salt ion uptake in the relatively salt-tolerant 'Koroneiki', growth of these young olive trees was not affected by eCO(2).

  1. A Study of the Short-term Variability of Seawater pCO2 near Östergarnsholm

    OpenAIRE

    Persson Söderman, Jennie

    2014-01-01

    In this study, an analysis of upwelling and biological activities impact on the seawater pCO2 variability was done to improve the knowledge about the pCO2 variability in seawater in the Baltic Sea. During upwelling activity, CO2 rich waters are upwelled to the surface. This influences air-sea CO2 flux and thus the net uptake/emission of CO2 by the sea. pCO2 and SST measurements from a SAMI sensor, located at the Östergarnsholm site in the Baltic Sea, and SST satellite data, was used to ident...

  2. Process coupling and control over the response of net ecosystem CO2 exchange to climate variability and insect disturbance in subalpine forests of the Western US

    Science.gov (United States)

    Monson, R. K.; Moore, D. J.; Trahan, N. A.; Scott-Denton, L.; Burns, S. P.; Hu, J.; Bowling, D. R.

    2011-12-01

    Following ten years of studies in subalpine forest ecosystems of the Western US, we have concluded that the tight coupling between gross primary productivity (GPP) and the autotrophic component of soil respiration (Ra) drives responses of net ecosystem CO2 exchange (NEE) to climate variability and insect disturbance. This insight has been gained through long-term eddy flux observations, manipulative plot experiments, analyses of dynamics in the stable isotope compositions of CO2 and H2O, and chamber gas-exchange measurements. Using past observations from these studies, we deployed model-data assimilation techniques and forecast weather/climate modeling to estimate how the coupling between GPP and Ra is likely to affect future (Year 2100) dynamics in NEE. The amount of winter snow and its melting dynamics in the spring represents the dominant control over interannual variation in GPP. Using the SIPNET ecosystem process model, combined with knowledge about the stable isotope content of different water sources, we estimated that approximately 75% of growing season GPP is coupled to the use of snowmelt water, whereas approximately 25% is coupled to summer rain. The tight coupling between GPP and winter snow pack drives a similar tight coupling between soil respiration (Rs) and winter snow pack. Manipulation of snow pack on forest plots has shown that Rs increases with increased snow pack, and this effect disappears when trees are girdled, which stops the transfer of GPP to roots and the soil rhizosphere. Higher-than-normal winter snowpacks cause the carbon isotope ratios of soil-respired CO2 to be depleted in 13C, reflecting a signal of lower photosynthetic water-use efficiency in the GPP that is transferred to the soil rhizosphere. Large-scale forest disturbance due to catastrophic tree mortality from mountain pine beetle attack causes an initial (2-3 year) reduction in Rs, which is attributable to the loss of GPP and its effect on Ra. This near-term reduction in Rs

  3. On the difference in the net ecosystem exchange of CO2 between deciduous and evergreen forests in the southeastern United States.

    Science.gov (United States)

    Novick, Kimberly A; Oishi, A Christopher; Ward, Eric J; Siqueira, Mario B S; Juang, Jehn-Yih; Stoy, Paul C

    2015-02-01

    The southeastern United States is experiencing a rapid regional increase in the ratio of pine to deciduous forest ecosystems at the same time it is experiencing changes in climate. This study is focused on exploring how these shifts will affect the carbon sink capacity of southeastern US forests, which we show here are among the strongest carbon sinks in the continental United States. Using eight-year-long eddy covariance records collected above a hardwood deciduous forest (HW) and a pine plantation (PP) co-located in North Carolina, USA, we show that the net ecosystem exchange of CO2 (NEE) was more variable in PP, contributing to variability in the difference in NEE between the two sites (ΔNEE) at a range of timescales, including the interannual timescale. Because the variability in evapotranspiration (ET) was nearly identical across the two sites over a range of timescales, the factors that determined the variability in ΔNEE were dominated by those that tend to decouple NEE from ET. One such factor was water use efficiency, which changed dramatically in response to drought and also tended to increase monotonically in nondrought years (P temperate climates. Additional variability in the fluxes at long-time scales may be attributable to slowly evolving factors, including canopy structure and increases in dormant season air temperature. Taken together, study results suggest that the carbon sink in the southeastern United States may become more variable in the future, owing to a predicted increase in drought frequency and an increase in the fractional cover of southern pines. © 2014 John Wiley & Sons Ltd.

  4. Sea ice contribution to the air-sea CO(2) exchange in the Arctic and Southern Oceans

    DEFF Research Database (Denmark)

    Rysgaard...[], Søren; Bendtsen, Jørgen; Delille, B.

    2011-01-01

    Although salt rejection from sea ice is a key process in deep-water formation in ice-covered seas, the concurrent rejection of CO(2) and the subsequent effect on air-sea CO(2) exchange have received little attention. We review the mechanisms by which sea ice directly and indirectly controls the air......-sea CO(2) exchange and use recent measurements of inorganic carbon compounds in bulk sea ice to estimate that oceanic CO(2) uptake during the seasonal cycle of sea-ice growth and decay in ice-covered oceanic regions equals almost half of the net atmospheric CO(2) uptake in ice-free polar seas. This sea......-ice driven CO(2) uptake has not been considered so far in estimates of global oceanic CO(2) uptake. Net CO(2) uptake in sea-ice-covered oceans can be driven by; (1) rejection during sea-ice formation and sinking of CO(2)-rich brine into intermediate and abyssal oceanic water masses, (2) blocking of air...

  5. Ground vegetation reduces forest floor net CH4 uptake in a boreal upland forest

    Science.gov (United States)

    Pihlatie, Mari; Kieloaho, Antti-Jussi; Halmeenmäki, Elisa; Ryhti, Kira; Heinonsalo, Jussi

    2017-04-01

    Boreal upland forests are considered as an important sink for the greenhouse gas methane (CH4) due to CH4 oxidizing microbes in the soil. Recent studies have reported significant CH4 emissions from trees in both upland and wetland forests, however, contribution of ground vegetation to the net CH4 exchange has not been assessed. As the processes and process drivers of the CH4 emissions from vegetation are still poorly understood, partitioning the CH4 exchange in forest ecosystems to soil, ground vegetation and trees is a way to improve our understanding of the CH4 cycling processes in forest ecosystems. We measured the forest floor CH4 exchange at a Scots pine dominated boreal upland forest in Southern Finland (SMEAR II station) during the growing season 2015. The forest floor consisted of mostly shrubs of bilberry (Vaccinium myrtillus), lingonberry (Vaccinium vitis-idaea), heather (Calluna vulgaris), and forest floor mosses (Pleurozium schreberi, Hylocomium splendens, and Dicranum polysetum). We measured the CH4 fluxes using transparent chambers under three vegetation treatments: normal vegetation (normal), shrubs only (shrubs), and non-vegetated (cut), and under three soil trenching treatments: control, 50 μm mesh (roots of trees and shrubs excluded), and 1 μm mesh (roots of trees and shrubs, and microbes excluded). Forest floor acted as a sink of CH4 in all the vegetation and trenching treatments. Presence of ground layer vegetation significantly reduced the forest floor CH4 uptake, whereas soil trenching did not affect the CH4 exchange. Over the period of May - October 2015, the mean forest floor CH4 fluxes were -53.7 (± 3.1 SE), -96.7 (± 3.7), and -91.4 (± 4.3) μg CH4 m2 h-1 from normal, shrubs and cut treatments, respectively. The presence of ground vegetation hence nearly halved the forest floor CH4 uptake compared to the shrubs only and cut treatments. As the largest difference between normal and shrubs treatments were the absence of mosses, our

  6. Global CO2 fluxes estimated from GOSAT retrievals of total column CO2

    Directory of Open Access Journals (Sweden)

    S. Basu

    2013-09-01

    Full Text Available We present one of the first estimates of the global distribution of CO2 surface fluxes using total column CO2 measurements retrieved by the SRON-KIT RemoTeC algorithm from the Greenhouse gases Observing SATellite (GOSAT. We derive optimized fluxes from June 2009 to December 2010. We estimate fluxes from surface CO2 measurements to use as baselines for comparing GOSAT data-derived fluxes. Assimilating only GOSAT data, we can reproduce the observed CO2 time series at surface and TCCON sites in the tropics and the northern extra-tropics. In contrast, in the southern extra-tropics GOSAT XCO2 leads to enhanced seasonal cycle amplitudes compared to independent measurements, and we identify it as the result of a land–sea bias in our GOSAT XCO2 retrievals. A bias correction in the form of a global offset between GOSAT land and sea pixels in a joint inversion of satellite and surface measurements of CO2 yields plausible global flux estimates which are more tightly constrained than in an inversion using surface CO2 data alone. We show that assimilating the bias-corrected GOSAT data on top of surface CO2 data (a reduces the estimated global land sink of CO2, and (b shifts the terrestrial net uptake of carbon from the tropics to the extra-tropics. It is concluded that while GOSAT total column CO2 provide useful constraints for source–sink inversions, small spatiotemporal biases – beyond what can be detected using current validation techniques – have serious consequences for optimized fluxes, even aggregated over continental scales.

  7. Elevated CO2 alters distribution of nodal leaf area and enhances nitrogen uptake contributing to yield increase of soybean cultivars grown in Mollisols.

    Science.gov (United States)

    Jin, Jian; Li, Yansheng; Liu, Xiaobing; Wang, Guanghua; Tang, Caixian; Yu, Zhenhua; Wang, Xiaojuan; Herbert, Stephen J

    2017-01-01

    Understanding how elevated CO2 affects dynamics of nodal leaf growth and N assimilation is crucial for the construction of high-yielding canopy via breeding and N management to cope with the future climate change. Two soybean cultivars were grown in two Mollisols differing in soil organic carbon (SOC), and exposed to ambient CO2 (380 ppm) or elevated CO2 (580 ppm) throughout the growth stages. Elevated CO2 induced 4-5 more nodes, and nearly doubled the number of branches. Leaf area duration at the upper nodes from R5 to R6 was 4.3-fold greater and that on branches 2.4-fold higher under elevated CO2 than ambient CO2, irrespective of cultivar and soil type. As a result, elevated CO2 markedly increased the number of pods and seeds at these corresponding positions. The yield response to elevated CO2 varied between the cultivars but not soils. The cultivar-specific response was likely attributed to N content per unit leaf area, the capacity of C sink in seeds and N assimilation. Elevated CO2 did not change protein concentration in seeds of either cultivar. These results indicate that elevated CO2 increases leaf area towards the upper nodes and branches which in turn contributes yield increase.

  8. Simulation of anthropogenic CO2 uptake in the CCSM3.1 ocean circulation-biogeochemical model: comparison with data-based estimates

    Directory of Open Access Journals (Sweden)

    S. Khatiwala

    2012-04-01

    Full Text Available The global ocean has taken up a large fraction of the CO2 released by human activities since the industrial revolution. Quantifying the oceanic anthropogenic carbon (Cant inventory and its variability is important for predicting the future global carbon cycle. The detailed comparison of data-based and model-based estimates is essential for the validation and continued improvement of our prediction capabilities. So far, three global estimates of oceanic Cant inventory that are "data-based" and independent of global ocean circulation models have been produced: one based on the Δ C* method, and two that are based on constraining surface-to-interior transport of tracers, the TTD method and a maximum entropy inversion method (GF. The GF method, in particular, is capable of reconstructing the history of Cant inventory through the industrial era. In the present study we use forward model simulations of the Community Climate System Model (CCSM3.1 to estimate the Cant inventory and compare the results with the data-based estimates. We also use the simulations to test several assumptions of the GF method, including the assumption of constant climate and circulation, which is common to all the data-based estimates. Though the integrated estimates of global Cant inventories are consistent with each other, the regional estimates show discrepancies up to 50 %. The CCSM3 model underestimates the total Cant inventory, in part due to weak mixing and ventilation in the North Atlantic and Southern Ocean. Analyses of different simulation results suggest that key assumptions about ocean circulation and air-sea disequilibrium in the GF method are generally valid on the global scale, but may introduce errors in Cant estimates on regional scales. The GF method should also be used with caution when predicting future oceanic anthropogenic carbon uptake.

  9. Simulation of anthropogenic CO2 uptake in the CCSM3.1 ocean circulation-biogeochemical model: comparison with data-based estimates

    Science.gov (United States)

    Wang, S.; Moore, J. K.; Primeau, F. W.; Khatiwala, S.

    2012-04-01

    The global ocean has taken up a large fraction of the CO2 released by human activities since the industrial revolution. Quantifying the oceanic anthropogenic carbon (Cant) inventory and its variability is important for predicting the future global carbon cycle. The detailed comparison of data-based and model-based estimates is essential for the validation and continued improvement of our prediction capabilities. So far, three global estimates of oceanic Cant inventory that are "data-based" and independent of global ocean circulation models have been produced: one based on the Δ C* method, and two that are based on constraining surface-to-interior transport of tracers, the TTD method and a maximum entropy inversion method (GF). The GF method, in particular, is capable of reconstructing the history of Cant inventory through the industrial era. In the present study we use forward model simulations of the Community Climate System Model (CCSM3.1) to estimate the Cant inventory and compare the results with the data-based estimates. We also use the simulations to test several assumptions of the GF method, including the assumption of constant climate and circulation, which is common to all the data-based estimates. Though the integrated estimates of global Cant inventories are consistent with each other, the regional estimates show discrepancies up to 50 %. The CCSM3 model underestimates the total Cant inventory, in part due to weak mixing and ventilation in the North Atlantic and Southern Ocean. Analyses of different simulation results suggest that key assumptions about ocean circulation and air-sea disequilibrium in the GF method are generally valid on the global scale, but may introduce errors in Cant estimates on regional scales. The GF method should also be used with caution when predicting future oceanic anthropogenic carbon uptake.

  10. Tundra ecosystems observed to be CO2 sources due to differential amplification of the carbon cycle.

    Science.gov (United States)

    Belshe, E F; Schuur, E A G; Bolker, B M

    2013-10-01

    Are tundra ecosystems currently a carbon source or sink? What is the future trajectory of tundra carbon fluxes in response to climate change? These questions are of global importance because of the vast quantities of organic carbon stored in permafrost soils. In this meta-analysis, we compile 40 years of CO2 flux observations from 54 studies spanning 32 sites across northern high latitudes. Using time-series analysis, we investigated if seasonal or annual CO2 fluxes have changed over time, and whether spatial differences in mean annual temperature could help explain temporal changes in CO2 flux. Growing season net CO2 uptake has definitely increased since the 1990s; the data also suggest (albeit less definitively) an increase in winter CO2 emissions, especially in the last decade. In spite of the uncertainty in the winter trend, we estimate that tundra sites were annual CO2 sources from the mid-1980s until the 2000s, and data from the last 7 years show that tundra continue to emit CO2 annually. CO2 emissions exceed CO2 uptake across the range of temperatures that occur in the tundra biome. Taken together, these data suggest that despite increases in growing season uptake, tundra ecosystems are currently CO2 sources on an annual basis. © 2013 John Wiley & Sons Ltd/CNRS.

  11. Bio Energy with CCS (BECCS). Large potential for BioSNG at low CO2 avoidance cost

    Energy Technology Data Exchange (ETDEWEB)

    Carbo, M.C.; Smit, R.; Van der Drift, A.; Jansen, D. [ECN Biomass, Coal and Environment, Petten (Netherlands)

    2010-12-15

    The introduction slide of this presentation states that Bio Energy with CCS (BECCS) is conversion of biomass to electricity/heat/fuels/ products combined with CO2 capture and storage. The conclusions are formulated as follows: Incremental cost for CO2 capture and storage is low; CO2 separation equipment implemented regardless of application CCS; Retrofit application of CCS is straightforward; CO2 avoidance costs for BioSNG are competitive with CCS in fossil fired power plants; Accounting for net CO2-uptake from atmosphere lowers avoidance costs and accelerates deployment; Scale-up of indirect gasification technology is needed.

  12. The non-steady-state oceanic CO2 signal: its importance, magnitude and a novel way to detect it

    Science.gov (United States)

    McNeil, B. I.; Matear, R. J.

    2012-09-01

    The ocean's role has been pivotal in modulating rising atmospheric CO2 levels since the industrial revolution, sequestering over a quarter of all fossil-fuel derived CO2 emissions. Net oceanic uptake of CO2 has roughly doubled between the 1960's (~1 Pg C yr-1) and 2000's (~2 Pg C yr-1), with expectations it will continue to absorb even more CO2 with rising future atmospheric CO2 levels. However, recent CO2 observational analyses along with numerous model predictions suggest the rate of oceanic CO2 uptake is already slowing, largely as a result of a natural decadal-scale outgassing signal. This recent and unexpected CO2 outgassing signal represents a paradigm-shift in our understanding of the oceans role in modulating atmospheric CO2. Current tracer-based estimates for the ocean storage of anthropogenic CO2 assume the ocean circulation and biology is in steady state, thereby missing the new and potentially important "non-steady-state" CO2 outgassing signal. By combining data-based techniques that assume the ocean is in steady-state, with techniques that constrain the net oceanic CO2 uptake signal, we show how to extract the non-steady-state CO2 signal from observations. Over the entire industrial era, the non-steady-state CO2 outgassing signal (~13 ± 10 Pg C) is estimated to represent about 9% of the total net CO2 inventory change (~142 Pg C). However between 1989 and 2007, the non-steady-state CO2 outgassing signal (~6.3 Pg C) has likely increased to be ~18% of net oceanic CO2 storage over that period (~36 Pg C), a level which cannot be ignored. The present uncertainty of our data-based techniques for oceanic CO2 uptake limit our capacity to quantify the non-steady-state CO2 signal, however with more data and better certainty estimates across a~range of diverse methods, this important and growing CO2 signal could be better constrained in the future.

  13. The non-steady state oceanic CO2 signal: its importance, magnitude and a novel way to detect it

    Science.gov (United States)

    McNeil, B. I.; Matear, R. J.

    2013-04-01

    The role of the ocean has been pivotal in modulating rising atmospheric CO2 levels since the industrial revolution, sequestering nearly half of all fossil-fuel derived CO2 emissions. Net oceanic uptake of CO2 has roughly doubled between the 1960s (~1 Pg C yr-1) and 2000s (~2 Pg C yr-1), with expectations that it will continue to absorb even more CO2 with rising future atmospheric CO2 levels. However, recent CO2 observational analyses along with numerous model predictions suggest the rate of oceanic CO2 uptake is already slowing, largely as a result of a natural decadal-scale outgassing signal. This recent CO2 outgassing signal represents a significant shift in our understanding of the oceans role in modulating atmospheric CO2. Current tracer-based estimates for the ocean storage of anthropogenic CO2 assume the ocean circulation and biology is in steady state, thereby missing the new and potentially important "non-steady state" CO2 outgassing signal. By combining data-based techniques that assume the ocean is in a steady state, with techniques that constrain the net oceanic CO2 uptake signal, we show how to extract the non-steady state CO2 signal from observations. Over the entire industrial era, the non-steady state CO2 outgassing signal (~13 ± 10 Pg C) is estimated to represent about 9% of the total net CO2 inventory change (~142 Pg C). However, between 1989 and 2007, the non-steady state CO2 outgassing signal (~6.3 Pg C) has likely increased to be ~18% of net oceanic CO2 storage over that period (~36 Pg C). The present uncertainty of our data-based techniques for oceanic CO2 uptake limit our capacity to quantify the non-steady state CO2 signal, however with more data and better certainty estimates across a range of diverse methods, this important and growing CO2 signal could be better constrained in the future.

  14. The non-steady state oceanic CO2 signal: its importance, magnitude and a novel way to detect it

    Directory of Open Access Journals (Sweden)

    B. I. McNeil

    2013-04-01

    Full Text Available The role of the ocean has been pivotal in modulating rising atmospheric CO2 levels since the industrial revolution, sequestering nearly half of all fossil-fuel derived CO2 emissions. Net oceanic uptake of CO2 has roughly doubled between the 1960s (~1 Pg C yr−1 and 2000s (~2 Pg C yr−1, with expectations that it will continue to absorb even more CO2 with rising future atmospheric CO2 levels. However, recent CO2 observational analyses along with numerous model predictions suggest the rate of oceanic CO2 uptake is already slowing, largely as a result of a natural decadal-scale outgassing signal. This recent CO2 outgassing signal represents a significant shift in our understanding of the oceans role in modulating atmospheric CO2. Current tracer-based estimates for the ocean storage of anthropogenic CO2 assume the ocean circulation and biology is in steady state, thereby missing the new and potentially important "non-steady state" CO2 outgassing signal. By combining data-based techniques that assume the ocean is in a steady state, with techniques that constrain the net oceanic CO2 uptake signal, we show how to extract the non-steady state CO2 signal from observations. Over the entire industrial era, the non-steady state CO2 outgassing signal (~13 ± 10 Pg C is estimated to represent about 9% of the total net CO2 inventory change (~142 Pg C. However, between 1989 and 2007, the non-steady state CO2 outgassing signal (~6.3 Pg C has likely increased to be ~18% of net oceanic CO2 storage over that period (~36 Pg C. The present uncertainty of our data-based techniques for oceanic CO2 uptake limit our capacity to quantify the non-steady state CO2 signal, however with more data and better certainty estimates across a range of diverse methods, this important and growing CO2 signal could be better constrained in the future.

  15. Traditional Nets Interfere with the Uptake of Long-Lasting Insecticidal Nets in the Peruvian Amazon: The Relevance of Net Preference for Achieving High Coverage and Use

    OpenAIRE

    Koen Peeters Grietens; Joan Muela Ribera; Veronica Soto; Alex Tenorio; Sarah Hoibak; Angel Rosas Aguirre; Elizabeth Toomer; Hugo Rodriguez; Alejandro Llanos Cuentas; Umberto D'Alessandro; Dionicia Gamboa; Annette Erhart

    2013-01-01

    BACKGROUND: While coverage of long-lasting insecticide-treated nets (LLIN) has steadily increased, a growing number of studies report gaps between net ownership and use. We conducted a mixed-methods social science study assessing the importance of net preference and use after Olyset(R) LLINs were distributed through a mass campaign in rural communities surrounding Iquitos, the capital city of the Amazonian region of Peru. METHODS: The study was conducted in the catchment area of the Paujil a...

  16. Carbonyl sulfide exchange in a temperate loblolly pine forest grown under ambient and elevated CO2

    Directory of Open Access Journals (Sweden)

    B. C. Sive

    2010-01-01

    Full Text Available Vegetation, soil and ecosystem level carbonyl sulfide (COS exchange was observed at Duke Forest, a temperate loblolly pine forest, grown under ambient (Ring 1, R1 and elevated (Ring 2, R2 CO2. During calm meteorological conditions, ambient COS mixing ratios at the top of the forest canopy followed a distinct diurnal pattern in both CO2 growth regimes, with maximum COS mixing ratios during the day (R1=380±4 pptv and R2=373±3 pptv, daytime mean ± standard error and minimums at night (R1=340±6 pptv and R2=346±5 pptv, nighttime mean ± standard error reflecting a significant nighttime sink. Nocturnal vegetative uptake (−11 to −21 pmol m−2s−1, negative values indicate uptake from the atmosphere dominated nighttime net ecosystem COS flux estimates (−10 to −30 pmol m−2s−1 in both CO2 regimes. In comparison, soil uptake (−0.8 to −1.7 pmol m−2 s−1 was a minor component of net ecosystem COS flux. In both CO2 regimes, loblolly pine trees exhibited substantial COS consumption overnight (50% of daytime rates that was independent of CO2 assimilation. This suggests current estimates of the global vegetative COS sink, which assume that COS and CO2 are consumed simultaneously, may need to be reevaluated. Ambient COS mixing ratios, species specific diurnal patterns of stomatal conductance, temperature and canopy position were the major factors influencing the vegetative COS flux at the branch level. While variability in branch level vegetative COS consumption measurements in ambient and enhanced CO2 environments could not be attributed to CO2 enrichment effects, estimates of net ecosystem COS flux based on ambient canopy mixing ratio measurements suggest less nighttime uptake of COS in R2, the CO2 enriched environment.

  17. The role of North Atlantic Ocean circulation and biological sequestration on atmospheric CO2 uptake during the last deglaciation (CL Division Outstanding ECS Award Lecture)

    Science.gov (United States)

    Muschitiello, Francesco; D'Andrea, William J.; Dokken, Trond M.; Schmittner, Andreas

    2017-04-01

    Understanding the impact of ocean circulation on the global atmospheric CO2 budget is of paramount importance for anticipating the consequences of projected future changes in Atlantic Meridional Overturning Circulation (AMOC). In particular, the efficiency of the oceanic biological pump can impact atmospheric CO2 through changes in vertical carbon export mediated by variations in the nutrient inventory of the North Atlantic basin. However, the causal relationship between North Atlantic Ocean circulation, biological carbon sequestration, and atmospheric CO2 is poorly understood. Here we present new high-resolution planktic-benthic 14C data and biomarker records from an exceptionally well-dated marine core from the Nordic Seas spanning the last deglaciation ( 15,000-10,000 years BP). The records document for the first time large and rapid atmospheric CO2 drawdowns and increase in plankton stocks during major North Atlantic cooling events. Using transient climate simulations from a fully coupled climate-biosphere model, we show that minor perturbations of the North Atlantic biological pump resulting from surface freshening and AMOC weakening can have a major impact on the global atmospheric CO2 budget. Furthermore, our data help clarifying the timing and magnitude of the deglacial CO2 signal recorded in Antarctic ice cores. We conclude that the global CO2 budget is more sensitive to perturbations in North Atlantic circulation than previously thought, which has significance in the future debate of the AMOC response to anthropogenic warming.

  18. Comparison of net CO2 fluxes measured with open- and closed-path infrared gas analyzers in an urban complex environment

    DEFF Research Database (Denmark)

    Järvi, L.; Mammarella, I.; Eugster, W.

    2009-01-01

    and their suitability to accurately measure CO2 exchange in such non-ideal landscape. In addition, this study examined the effect of open-path sensor heating on measured fluxes in urban terrain, and these results were compared with similar measurements made above a temperate beech forest in Denmark. The correlation...... improved the performance of the open-path analyzer by reducing discrepancies in NSE at the urban site to 2% and decreasing the difference in NSE from 67% to 7% at the forest site. Overall, the site-specific approach gave the best results at both sites and, if possible, it should be preferred in the sensor...

  19. A uniform, quality controlled Surface Ocean CO2 Atlas (SOCAT

    Directory of Open Access Journals (Sweden)

    B. Pfeil

    2013-04-01

    Full Text Available A well-documented, publicly available, global data set of surface ocean carbon dioxide (CO2 parameters has been called for by international groups for nearly two decades. The Surface Ocean CO2 Atlas (SOCAT project was initiated by the international marine carbon science community in 2007 with the aim of providing a comprehensive, publicly available, regularly updated, global data set of marine surface CO2, which had been subject to quality control (QC. Many additional CO2 data, not yet made public via the Carbon Dioxide Information Analysis Center (CDIAC, were retrieved from data originators, public websites and other data centres. All data were put in a uniform format following a strict protocol. Quality control was carried out according to clearly defined criteria. Regional specialists performed the quality control, using state-of-the-art web-based tools, specially developed for accomplishing this global team effort. SOCAT version 1.5 was made public in September 2011 and holds 6.3 million quality controlled surface CO2 data points from the global oceans and coastal seas, spanning four decades (1968–2007. Three types of data products are available: individual cruise files, a merged complete data set and gridded products. With the rapid expansion of marine CO2 data collection and the importance of quantifying net global oceanic CO2 uptake and its changes, sustained data synthesis and data access are priorities.

  20. Enhanced Selectivity and Uptake Capacity of CO2 and Toluene Adsorption in Co0.5 M0.33 MoS4 (M= Sb or Y) Chalcogels by Impregnated Metal Salts

    KAUST Repository

    Adhiam, Fatima Abdullah Ahmed

    2017-11-17

    The synthesis of metal chalcogenide aerogels Co0.5M0.33MoS4 (M= Sb or Y) by the sol-gel method is reported. In this system, the building blocks [MoS4]2− chelated with Co2+ and (Sb3+) or (Y3+) salts in nonaqueous solvents forming amorphous networks with a gel property. The chalcogels obtained after supercritical drying have BET surface areas of 176 m2 g−1 (Co0.5Sb0.33MoS4) and 145 m2 g−1 (Co0.5Y0.33MoS4). Electron microscopy and physisorption studies reveal that the new materials are porous with wide pore size distribution and average pore width of 16 nm. These chalcogels show higher adsorption capacity of toluene vapor (Co0.5Sb0.33MoS4: 387 mg g−1) and (Co0.5Y0.33MoS4: 304 mg g−1) over cyclohexane vapor and high selectivity of CO2 over CH4 or H2, Co0.5Sb0.33MoS4 (CO2/H2: 80 and CO2/CH4: 21), Co0.5Y0.33MoS4 (CO2/H2: 27 and CO2/CH4: 15). We also demonstrated that the impregnation of various metal species like Li+, Mg2+, and Ni2+ significantly enhanced the uptake capacity and selectivity of toluene and CO2 adsorptions in the chacogels.

  1. Traditional nets interfere with the uptake of long-lasting insecticidal nets in the Peruvian Amazon: the relevance of net preference for achieving high coverage and use.

    Directory of Open Access Journals (Sweden)

    Koen Peeters Grietens

    Full Text Available BACKGROUND: While coverage of long-lasting insecticide-treated nets (LLIN has steadily increased, a growing number of studies report gaps between net ownership and use. We conducted a mixed-methods social science study assessing the importance of net preference and use after Olyset® LLINs were distributed through a mass campaign in rural communities surrounding Iquitos, the capital city of the Amazonian region of Peru. METHODS: The study was conducted in the catchment area of the Paujil and Cahuide Health Centres (San Juan district between July 2007 and November 2008. During a first qualitative phase, participant observation and in-depth interviews collected information on key determinants for net preference and use. In a second quantitative phase, a survey among recently confirmed malaria patients evaluated the acceptability and use of both LLINs and traditional nets, and a case control study assessed the association between net preference/use and housing structure (open vs. closed houses. RESULTS: A total of 10 communities were selected for the anthropological fieldwork and 228 households participated in the quantitative studies. In the study area, bed nets are considered part of the housing structure and are therefore required to fulfil specific architectural and social functions, such as providing privacy and shelter, which the newly distributed Olyset® LLINs ultimately did not. The LLINs' failure to meet these criteria could mainly be attributed to their large mesh size, transparency and perceived ineffectiveness to protect against mosquitoes and other insects, resulting in 63.3% of households not using any of the distributed LLINs. Notably, LLIN usage was significantly lower in houses with no interior or exterior walls (35.2% than in those with walls (73.8% (OR = 5.2, 95CI [2.2; 12.3], p<0.001. CONCLUSION: Net preference can interfere with optimal LLIN use. In order to improve the number of effective days of LLIN protection per dollar

  2. Traditional nets interfere with the uptake of long-lasting insecticidal nets in the Peruvian Amazon: the relevance of net preference for achieving high coverage and use.

    Science.gov (United States)

    Grietens, Koen Peeters; Muela Ribera, Joan; Soto, Veronica; Tenorio, Alex; Hoibak, Sarah; Aguirre, Angel Rosas; Toomer, Elizabeth; Rodriguez, Hugo; Llanos Cuentas, Alejandro; D'Alessandro, Umberto; Gamboa, Dionicia; Erhart, Annette

    2013-01-01

    While coverage of long-lasting insecticide-treated nets (LLIN) has steadily increased, a growing number of studies report gaps between net ownership and use. We conducted a mixed-methods social science study assessing the importance of net preference and use after Olyset® LLINs were distributed through a mass campaign in rural communities surrounding Iquitos, the capital city of the Amazonian region of Peru. The study was conducted in the catchment area of the Paujil and Cahuide Health Centres (San Juan district) between July 2007 and November 2008. During a first qualitative phase, participant observation and in-depth interviews collected information on key determinants for net preference and use. In a second quantitative phase, a survey among recently confirmed malaria patients evaluated the acceptability and use of both LLINs and traditional nets, and a case control study assessed the association between net preference/use and housing structure (open vs. closed houses). A total of 10 communities were selected for the anthropological fieldwork and 228 households participated in the quantitative studies. In the study area, bed nets are considered part of the housing structure and are therefore required to fulfil specific architectural and social functions, such as providing privacy and shelter, which the newly distributed Olyset® LLINs ultimately did not. The LLINs' failure to meet these criteria could mainly be attributed to their large mesh size, transparency and perceived ineffectiveness to protect against mosquitoes and other insects, resulting in 63.3% of households not using any of the distributed LLINs. Notably, LLIN usage was significantly lower in houses with no interior or exterior walls (35.2%) than in those with walls (73.8%) (OR = 5.2, 95CI [2.2; 12.3], ppreference can interfere with optimal LLIN use. In order to improve the number of effective days of LLIN protection per dollar spent, appropriate quantitative and qualitative methods for collecting

  3. CO2-neutral fuels

    Directory of Open Access Journals (Sweden)

    Goede A. P. H.

    2015-01-01

    Full Text Available The need for storage of renewable energy (RE generated by photovoltaic, concentrated solar and wind arises from the fact that supply and demand are ill-matched both geographically and temporarily. This already causes problems of overcapacity and grid congestion in countries where the fraction of RE exceeds the 20% level. A system approach is needed, which focusses not only on the energy source, but includes conversion, storage, transport, distribution, use and, last but not least, the recycling of waste. Furthermore, there is a need for more flexibility in the energy system, rather than relying on electrification, integration with other energy systems, for example the gas network, would yield a system less vulnerable to failure and better adapted to requirements. For example, long-term large-scale storage of electrical energy is limited by capacity, yet needed to cover weekly to seasonal demand. This limitation can be overcome by coupling the electricity net to the gas system, considering the fact that the Dutch gas network alone has a storage capacity of 552 TWh, sufficient to cover the entire EU energy demand for over a month. This lecture explores energy storage in chemicals bonds. The focus is on chemicals other than hydrogen, taking advantage of the higher volumetric energy density of hydrocarbons, in this case methane, which has an approximate 3.5 times higher volumetric energy density. More importantly, it allows the ready use of existing gas infrastructure for energy storage, transport and distribution. Intermittent wind electricity generated is converted into synthetic methane, the Power to Gas (P2G scheme, by splitting feedstock CO2 and H2O into synthesis gas, a mixture of CO and H2. Syngas plays a central role in the synthesis of a range of hydrocarbon products, including methane, diesel and dimethyl ether. The splitting is accomplished by innovative means; plasmolysis and high-temperature solid oxygen electrolysis. A CO2-neutral fuel

  4. CO2-neutral fuels

    Science.gov (United States)

    Goede, A. P. H.

    2015-08-01

    The need for storage of renewable energy (RE) generated by photovoltaic, concentrated solar and wind arises from the fact that supply and demand are ill-matched both geographically and temporarily. This already causes problems of overcapacity and grid congestion in countries where the fraction of RE exceeds the 20% level. A system approach is needed, which focusses not only on the energy source, but includes conversion, storage, transport, distribution, use and, last but not least, the recycling of waste. Furthermore, there is a need for more flexibility in the energy system, rather than relying on electrification, integration with other energy systems, for example the gas network, would yield a system less vulnerable to failure and better adapted to requirements. For example, long-term large-scale storage of electrical energy is limited by capacity, yet needed to cover weekly to seasonal demand. This limitation can be overcome by coupling the electricity net to the gas system, considering the fact that the Dutch gas network alone has a storage capacity of 552 TWh, sufficient to cover the entire EU energy demand for over a month. This lecture explores energy storage in chemicals bonds. The focus is on chemicals other than hydrogen, taking advantage of the higher volumetric energy density of hydrocarbons, in this case methane, which has an approximate 3.5 times higher volumetric energy density. More importantly, it allows the ready use of existing gas infrastructure for energy storage, transport and distribution. Intermittent wind electricity generated is converted into synthetic methane, the Power to Gas (P2G) scheme, by splitting feedstock CO2 and H2O into synthesis gas, a mixture of CO and H2. Syngas plays a central role in the synthesis of a range of hydrocarbon products, including methane, diesel and dimethyl ether. The splitting is accomplished by innovative means; plasmolysis and high-temperature solid oxygen electrolysis. A CO2-neutral fuel cycle is

  5. Temporal variations in air-sea CO2 exchange near large kelp beds near San Diego, California

    Science.gov (United States)

    Ikawa, Hiroki; Oechel, Walter C.

    2015-01-01

    This study presents nearly continuous air-sea CO2 flux for 7 years using the eddy covariance method for nearshore water near San Diego, California, as well as identifying environmental processes that appear to control temporal variations in air-sea CO2 flux at different time scales using time series decomposition. Monthly variations in CO2 uptake are shown to be positively influenced by photosynthetically active photon flux density (PPFD) and negatively related to wind speeds. In contrast to the monthly scale, wind speeds often influenced CO2 uptake positively on an hourly scale. Interannual variations in CO2 flux were not correlated with any independent variables, but did reflect surface area of the adjacent kelp bed in the following year. Different environmental influences on CO2 flux at different temporal scales suggest the importance of long-term flux monitoring for accurately identifying important environmental processes for the coastal carbon cycle. Overall, the study area was a strong CO2 sink into the sea (CO2 flux of ca. -260 g C m-2 yr-1). If all coastal areas inhabited by macrophytes had a similar CO2 uptake rate, the net CO2 uptake from these areas alone would roughly equal the net CO2 sink estimated for the entire global coastal ocean to date. A similar-strength CO2 flux, ranging between -0.09 and -0.01 g C m-2 h-1, was also observed over another kelp bed from a pilot study of boat-based eddy covariance measurements.

  6. Chemical microenvironments and single-cell carbon and nitrogen uptake in field-collected colonies of Trichodesmium under different pCO2.

    Science.gov (United States)

    Eichner, Meri J; Klawonn, Isabell; Wilson, Samuel T; Littmann, Sten; Whitehouse, Martin J; Church, Matthew J; Kuypers, Marcel Mm; Karl, David M; Ploug, Helle

    2017-06-01

    Gradients of oxygen (O2) and pH, as well as small-scale fluxes of carbon (C), nitrogen (N) and O2 were investigated under different partial pressures of carbon dioxide (pCO2) in field-collected colonies of the marine dinitrogen (N2)-fixing cyanobacterium Trichodesmium. Microsensor measurements indicated that cells within colonies experienced large fluctuations in O2, pH and CO2 concentrations over a day-night cycle. O2 concentrations varied with light intensity and time of day, yet colonies exposed to light were supersaturated with O2 (up to ~200%) throughout the light period and anoxia was not detected. Alternating between light and dark conditions caused a variation in pH levels by on average 0.5 units (equivalent to 15 nmol l(-1) proton concentration). Single-cell analyses of C and N assimilation using secondary ion mass spectrometry (SIMS; large geometry SIMS and nanoscale SIMS) revealed high variability in metabolic activity of single cells and trichomes of Trichodesmium, and indicated transfer of C and N to colony-associated non-photosynthetic bacteria. Neither O2 fluxes nor C fixation by Trichodesmium were significantly influenced by short-term incubations under different pCO2 levels, whereas N2 fixation increased with increasing pCO2. The large range of metabolic rates observed at the single-cell level may reflect a response by colony-forming microbial populations to highly variable microenvironments.

  7. Assessment of accuracy of the Vacu-Med 17053 calibrator for ventilation, oxygen uptake (V(O(2))), and carbon dioxide production (V(CO(2))).

    Science.gov (United States)

    Bunn, Jennifer A; Pittsley, Jesse L; Baker, Scott V; Yates, Jw

    2011-04-01

    Few have examined the accuracy of mechanical calibrators used to calibrate metabolic monitors. To evaluate the Vacu-Med 17053 motorized syringe calibrator for accuracy against the accepted standard method: the Douglas bag. We tested oxygen consumption values (V(O(2))) of 522-3,210 mL/min. We mixed room air and calibration gases in the pumping syringes of the Vacu-Med 17053 and evacuated those gases into a Douglas bag, measured the Douglas bag volumes and concentrations, and converted to pulmonary ventilation, V(O(2)), and carbon dioxide production (V(CO(2))). The Vacu-Med 17053 calibrator overestimated V(O(2)) by a mean 28.6 mL/min (1.3% error), underestimated V(CO(2)) by 6.9 mL/min (-1.7% error), and underestimated pulmonary ventilation by 0.98 L/min (-1.4% error). The V(O(2)) and V(CO(2)) differences between the calibrator and the Douglas bag were larger at higher V(O(2)) levels. The V(O(2)) and V(CO(2)) differences might be attributable to fluctuations of the calibrator settings. The Vacu-Med 17053 calibrator was accurate with the application of a mathematical correction.

  8. Expression of a Low CO2–Inducible Protein, LCI1, Increases Inorganic Carbon Uptake in the Green Alga Chlamydomonas reinhardtii[W][OA

    Science.gov (United States)

    Ohnishi, Norikazu; Mukherjee, Bratati; Tsujikawa, Tomoki; Yanase, Mari; Nakano, Hirobumi; Moroney, James V.; Fukuzawa, Hideya

    2010-01-01

    Aquatic photosynthetic organisms can modulate their photosynthesis to acclimate to CO2-limiting stress by inducing a carbon-concentrating mechanism (CCM) that includes carbonic anhydrases and inorganic carbon (Ci) transporters. However, to date, Ci-specific transporters have not been well characterized in eukaryotic algae. Previously, a Chlamydomonas reinhardtii mutant (lcr1) was identified that was missing a Myb transcription factor. This mutant had reduced light-dependent CO2 gas exchange (LCE) activity when grown under CO2-limiting conditions and did not induce the CAH1 gene encoding a periplasmic carbonic anhydrase, as well as two as yet uncharacterized genes, LCI1 and LCI6. In this study, LCI1 was placed under the control of the nitrate reductase promoter, allowing for the induction of LCI1 expression by nitrate in the absence of other CCM components. When the expression of LCI1 was induced in the lcr1 mutant under CO2-enriched conditions, the cells showed an increase in LCE activity, internal Ci accumulation, and photosynthetic affinity for Ci. From experiments using indirect immunofluorescence, LCI1–green fluorescent protein fusions, and cell fractionation procedures, it appears that LCI1 is mainly localized to the plasma membrane. These results provide strong evidence that LCI1 may contribute to the CCM as a component of the Ci transport machinery in the plasma membrane. PMID:20870960

  9. Annual CO2 budget and seasonal CO2 exchange signals at a High Arctic permafrost site on Spitsbergen, Svalbard archipelago

    Science.gov (United States)

    Lüers, J.; Westermann, S.; Piel, K.; Boike, J.

    2014-01-01

    The annual variability of CO2 exchange in most ecosystems is primarily driven by the activities of plants and soil microorganisms. However, little is known about the carbon balance and its controlling factors outside the growing season in arctic regions dominated by soil freeze/thaw-processes, long-lasting snow cover, and several months of darkness. This study presents a complete annual cycle of the CO2 net ecosystem exchange (NEE) dynamics for a High Arctic tundra area on the west coast of Svalbard based on eddy-covariance flux measurements. The annual cumulative CO2 budget is close to zero grams carbon per square meter per year, but shows a very strong seasonal variability. Four major CO2 exchange seasons have been identified. (1) During summer (ground snow-free), the CO2 exchange occurs mainly as a result of biological activity, with a predominance of strong CO2 assimilation by the ecosystem. (2) The autumn (ground snow-free or partly snow-covered) is dominated by CO2 respiration as a result of biological activity. (3) In winter and spring (ground snow-covered), low but persistent CO2 release occur, overlain by considerable CO2 exchange events in both directions associated with changes of air masses and air and atmospheric CO2 pressure. (4) The snow melt season (pattern of snow-free and snow-covered areas), where both, meteorological and biological forcing, resulting in a visible carbon uptake by the high arctic ecosystem. Data related to this article are archived under: http://doi.pangaea.de/10.1594/PANGAEA.809507.

  10. Proximity to safety-net clinics and HPV vaccine uptake among low-income, ethnic minority girls.

    Science.gov (United States)

    Tsui, Jennifer; Singhal, Rita; Rodriguez, Hector P; Gee, Gilbert C; Glenn, Beth A; Bastani, Roshan

    2013-04-12

    Human Papillomavirus (HPV) vaccine uptake remains low. Although publicly funded programs provide free or low cost vaccines to low-income children, barriers aside from cost may prevent disadvantaged girls from getting vaccinated. Prior studies have shown distance to health care as a potential barrier to utilizing pediatric preventive services. This study examines whether HPV vaccines are geographically accessible for low-income girls in Los Angeles County and whether proximity to safety-net clinics is associated with vaccine initiation. Interviews were conducted in multiple languages with largely immigrant, low-income mothers of girls ages 9 to 18 via a county health hotline to assess uptake and correlates of uptake. Addresses of respondents and safety-net clinics that provide the HPV vaccine for free or low cost were geo-coded and linked to create measures of geographic proximity. Logistic regression models were estimated for each proximity measure on HPV vaccine initiation while controlling for other factors. On average, 83% of the 468 girls had at least one clinic within 3-miles of their residence. The average travel time on public transportation to the nearest clinic among all girls was 21min. Average proximity to clinics differed significantly by race/ethnicity. Latinas had both the shortest travel distances (2.2 miles) and public transportation times (16min) compared to other racial/ethnic groups. The overall HPV vaccine initiation rate was 25%. Increased proximity to the nearest clinic was not significantly associated with initiation. By contrast, daughter's age and insurance status were significantly associated with increased uptake. This study is among the first to examine geographic access to HPV vaccines for underserved girls. Although the majority of girls live in close proximity to safety-net vaccination services, rates of initiation were low. Expanding clinic outreach in this urban area is likely more important than increasing geographic access to the

  11. Annual cycle of air-sea CO2 exchange in an Arctic Polynya Region

    Science.gov (United States)

    Else, B. G. T.; Papakyriakou, T. N.; Asplin, M. G.; Barber, D. G.; Galley, R. J.; Miller, L. A.; Mucci, A.

    2013-04-01

    the Canadian International Polar Year projects in the Cape Bathurst polynya region, we measured a near-complete annual cycle of sea surface CO2 (pCO2sw), atmospheric CO2 (pCO2atm), sea surface temperature (SST), salinity (S), and wind speed (U). In this paper, we combine these data with ancillary measurements of sea ice concentration (Ci) to estimate the mean annual (September 2007-September 2008) air-sea CO2 exchange for the region. For the non-freezing seasons the exchange was calculated using a standard bulk aerodynamic approach, whereas during the freezing seasons we extrapolated eddy covariance measurements of CO2 exchange. Our results show that in 2007-08 the region served as a net sink of atmospheric CO2 at a mean rate of -10.1 ± 6.5 mmol m- 2 d- 1. The strongest calculated uptake rate occurred in the fall when wind velocities were highest, pCO2sw was significantly lower than pCO2atm, and ice was beginning to form. Atmospheric CO2 uptake was calculated to occur (at lower rates) throughout the rest of the year, except for a brief period of outgassing during late July. Using archival U, Ci, and pCO2sw data for the region, we found that winds in 2007-08 were 25-35 % stronger than the decadal mean and were predominately easterly, which appears to have induced a relatively late freeze-up (by ˜ 3 weeks relative to mean conditions) and an early polynya opening (by ˜ 4 weeks). In turn, these conditions may have given rise to a higher CO2 uptake than normal. Estimated winter CO2 exchange through leads and small polynya openings made up more than 50% of the total CO2 uptake, consistent with recent observations of enhanced CO2 exchange associated with open water components of the winter icescape. Our calculations for the Cape Bathurst polynya region are consistent with past studies that estimated the total winter CO2 uptake in Arctic coastal polynyas to be on the order of 1012 g C yr- 1.

  12. Control of the mid-summer net community production and nitrogen fixation in the central Baltic Sea: An approach based on pCO2 measurements on a cargo ship

    Science.gov (United States)

    Schneider, B.; Gustafsson, E.; Sadkowiak, B.

    2014-08-01

    Automated measurements of the surface CO2 partial pressure, pCO2, were performed since 2003 on a cargo ship along a transect between Helsinki in the Gulf of Finland and Lübeck/Gdynia in the southwest of the Baltic Sea. The temporal and spatial resolution of the measurements amounted to 2-4 days and about 2 nautical miles, respectively. Based on temperature and salinity records and on the mean alkalinity, the total CO2 concentrations, CT, were calculated from the mean pCO2 in the northeastern Gotland Sea. The CT data were used to establish a CO2 mass balance for the period from mid-June to the beginning of August in 2005, 2008, 2009 and 2011. Taking into account the air-sea CO2 gas exchange, the mass balance yielded the net organic matter (Corg) production which is fuelled by nitrogen fixation at this time of the year. Several production events were detected with rates up to 8 μmol-C L- 1 d- 1. The production rates were not related to temperature, but showed a distinct correlation with the rate of the temperature increase. This led to the conclusion that the exposure of nitrogen fixing cyanobacteria to irradiance is the dominating control for the Corg production. Therefore, we suggest using the ratio of irradiance to the mixed layer depth as a variable for the parameterization of nitrogen fixation in biogeochemical models. The Corg production and thus the nitrogen fixation rates remained almost constant as long as continuous rising temperatures indicated favorable irradiation conditions. A limitation of the rates by phosphate or any other factor could not be detected. Based on the C/N ratio of particulate organic matter during a cyanobacteria bloom, the Corg production was used to estimate the mid-summer nitrogen fixation. The values varied from 102 mmol m- 2 to 214 mmol m- 2 (mean: 138 mmol m- 2) for the different years and did not show any correlation with the phosphate excess after the spring nitrate depletion.

  13. The importance of biomass net uptake for a trace metal budget in a forest stand in north-eastern France

    Energy Technology Data Exchange (ETDEWEB)

    Gandois, L. [Universite de Toulouse, UPS, INP, EcoLab - Laboratoire d' ecologie fonctionnelle, ENSAT, Avenue de l' Agrobiopole, F-31326 Castanet-Tolosan (France); CNRS, EcoLab, F-31326 Castanet-Tolosan (France); Nicolas, M. [ONF, Direction technique RENECOFOR, Bd de Constance 77300 Fontainebleau (France); VanderHeijden, G. [INRA, centre de Nancy, Equipe BEF, 54280 Champenoux (France); Probst, A., E-mail: anne.probst@ensat.fr [Universite de Toulouse, UPS, INP, EcoLab -Laboratoire d' ecologie fonctionnelle, ENSAT, Avenue de l' Agrobiopole, F-31326 Castanet-Tolosan (France); CNRS, EcoLab, F-31326 Castanet-Tolosan (France)

    2010-11-01

    The trace metal (TM: Cd, Cu, Ni, Pb and Zn) budget (stocks and annual fluxes) was evaluated in a forest stand (silver fir, Abies alba Miller) in north-eastern France. Trace metal concentrations were measured in different tree compartments in order to assess TM partitioning and dynamics in the trees. Inputs included bulk deposition, estimated dry deposition and weathering. Outputs were leaching and biomass exportation. Atmospheric deposition was the main input flux. The estimated dry deposition accounted for about 40% of the total trace metal deposition. The relative importance of leaching (estimated by a lumped parameter water balance model, BILJOU) and net biomass uptake (harvesting) for ecosystem exportation depended on the element. Trace metal distribution between tree compartments (stem wood and bark, branches and needles) indicated that Pb was mainly stored in the stem, whereas Zn and Ni, and to a lesser extent Cd and Cu, were translocated to aerial parts of the trees and cycled in the ecosystem. For Zn and Ni, leaching was the main output flux (> 95% of the total output) and the plot budget (input-output) was negative, whereas for Pb the biomass net exportation represented 60% of the outputs and the budget was balanced. Cadmium and Cu had intermediate behaviours, with 18% and 30% of the total output relative to biomass exportation, respectively, and the budgets were negative. The net uptake by biomass was particularly important for Pb budgets, less so for Cd and Cu and not very important for Zn and Ni in such forest stands.

  14. OPTIMALITY PRINCIPLE INTEGRATES PLANT RESPONSES TO ELEVATED CO2 AND SOIL NITROGEN AVAILABILITY

    Science.gov (United States)

    Franklin, O.

    2009-12-01

    INTRODUCTION Soil N availability is of particular importance for the response of forests to elevated CO2 (eCO2) because it often limits tree growth responses to eCO2 and changes C allocation among foliage, wood and root systems. Clearly, understanding the interactive effects of eCO2 and soil N availability is essential for accurate projections of forest responses to rising atmospheric CO2. HYPOTHESIS Plants acclimate to soil N availability and atmospheric CO2 by maximizing net growth through three nested optimizations operating on different time scales: short term - vertical canopy N distribution, medium term - Leaf area index (LAI) for a given total canopy N (Nc) and longer term - Nc and root allocation. N uptake is a function of root exploration for N (fine root production) and soil N availability. RESULTS The model explained a range of observed forest CO2 responses of productivity and LAI in FACE experiments (Franklin et al. 2009) (Franklin 2007). N use efficiency increased with soil N availability, which is in line with recent findings regarding resource use efficiency, but contrasts with some earlier conceptual models. The model gives rise to a relationship between root production and total plant N demand, which implies that root production and N uptake is always increased by eCO2 (fig. 1). The increased N uptake associated with increased demand for fine-root production may lead to declining soil N availability (progressive N limitation), which was observed in the ORNL FACE experiment. The principle of maximization of net growth to control allocation could serve as a basis for simplification and generalization of foliage/stem/root allocation in larger scale forest models. REFERENCES Franklin O. (2007) Optimal nitrogen allocation controls tree responses to elevated CO 2. New Phytologist, 174, 811-822 Franklin O., McMurtrie R.E., Iversen C.M., Crous K.Y., Finzi A.C., Tissue D.T., Ellsworth D.S., Oren R. & Norby R.J. (2009) Forest fine-root production and

  15. Atmospheric CO2 enrichment facilitates cation release from soil.

    Science.gov (United States)

    Cheng, L; Zhu, J; Chen, G; Zheng, X; Oh, N-H; Rufty, T W; Richter, D deB; Hu, S

    2010-03-01

    Atmospheric CO(2) enrichment generally stimulates plant photosynthesis and nutrient uptake, modifying the local and global cycling of bioactive elements. Although nutrient cations affect the long-term productivity and carbon balance of terrestrial ecosystems, little is known about the effect of CO(2) enrichment on cation availability in soil. In this study, we present evidence for a novel mechanism of CO(2)-enhancement of cation release from soil in rice agricultural systems. Elevated CO(2) increased organic C allocation belowground and net H(+) excretion from roots, and stimulated root and microbial respiration, reducing soil redox potential and increasing Fe(2+) and Mn(2+) in soil solutions. Increased H(+), Fe(2+), and Mn(2+) promoted Ca(2+) and Mg(2+) release from soil cation exchange sites. These results indicate that over the short term, elevated CO(2) may stimulate cation release from soil and enhance plant growth. Over the long-term, however, CO(2)-induced cation release may facilitate cation losses and soil acidification, negatively feeding back to the productivity of terrestrial ecosystems.

  16. Atmospheric 14CO2 Constraints on and Modeling of Net Carbon Fluxes 06-ERD-031 An LLNL Exploratory Research in the Directorate's Final Report

    Energy Technology Data Exchange (ETDEWEB)

    Guilderson, T P; Cameron-Smith, P; Bergmann, D; Graven, H D; Keeling, R; Boering, K; Caldeira, K

    2009-03-18

    A critical scientific question is: 'what are the present day sources and sinks of carbon dioxide (CO{sub 2}) in the natural environment, and how will these sinks evolve under rising CO{sub 2} concentrations and expected climate change and ecosystem response'? Sources and sinks of carbon dioxide impart their signature on the distribution, concentration, and isotopic composition of CO{sub 2}. Spatial and temporal trends (variability) provide information on the net surface (atmosphere to ocean, atmosphere to terrestrial biosphere) fluxes. The need to establish more reliable estimates of sources and sinks of CO{sub 2} has lead to an expansion of CO{sub 2} measurement programs over the past decade and the development of new methodologies for tracing carbon flows. These methodologies include high-precision pCO{sub 2}, {delta}{sup 13}CO{sub 2}, and [O{sub 2}/N{sub 2}] measurements on atmospheric constituents that, when combined, have allowed estimates of the net terrestrial and oceanic fluxes at decadal timescales. Major gaps in our understanding remain however, and resulting flux estimates have large errors and are comparatively unconstrained. One potentially powerful approach to tracking carbon flows is based on observations of the {sup 14}C/{sup 12}C ratio of atmospheric CO{sub 2}. This ratio can be used to explicitly distinguish fossil-fuel CO{sub 2} from other sources of CO{sub 2} and also provide constraints on the mass and turnover times of carbon in land ecosystems and on exchange rates of CO{sub 2} between air and sea. Here we demonstrated measurement of {sup 14}C/{sup 12}C ratios at 1-2{per_thousand} on archived and currently collected air samples. In parallel we utilized the LLNL-IMPACT global atmospheric chemistry transport model and the TransCom inversion algorithm to utilize these data in inversion estimates of carbon fluxes. This project has laid the foundation for a more expanded effort in the future, involving collaborations with other air

  17. A Synthesized Model-Observation Approach to Constraining Gross Urban CO2 Fluxes Using 14CO2 and carbonyl sulfide

    Science.gov (United States)

    LaFranchi, B. W.; Campbell, J. E.; Cameron-Smith, P. J.; Bambha, R.; Michelsen, H. A.

    2013-12-01

    Urbanized regions are responsible for a disproportionately large percentage (30-40%) of global anthropogenic greenhouse gas (GHG) emissions, despite covering only 2% of the Earth's surface area [Satterthwaite, 2008]. As a result, policies enacted at the local level in these urban areas can, in aggregate, have a large global impact, both positive and negative. In order to address the scientific questions that are required to drive these policy decisions, methods are needed that resolve gross CO2 flux components from the net flux. Recent work suggests that the critical knowledge gaps in CO2 surface fluxes could be addressed through the combined analysis of atmospheric carbonyl sulfide (COS) and radiocarbon in atmospheric CO2 (14CO2) [e.g. Campbell et al., 2008; Graven et al., 2009]. The 14CO2 approach relies on mass balance assumptions about atmospheric CO2 and the large differences in 14CO2 abundance between fossil and natural sources of CO2 [Levin et al., 2003]. COS, meanwhile, is a potentially transformative tracer of photosynthesis because its variability in the atmosphere has been found to be influenced primarily by vegetative uptake, scaling linearly will gross primary production (GPP) [Kettle et al., 20027]. Taken together, these two observations provide constraints on two of the three main components of the CO2 budget at the urban scale: photosynthesis and fossil fuel emissions. The third component, respiration, can then be determined by difference if the net flux is known. Here we present a general overview of our synthesized model-observation approach for improving surface flux estimates of CO2 for the upwind fetch of a ~30m tower located in Livermore, CA, USA, a suburb (pop. ~80,000) at the eastern edge of the San Francisco Bay Area. Additionally, we will present initial results from a one week observational intensive, which includes continuous CO2, CH4, CO, SO2, NOx, and O3 observations in addition to measurements of 14CO2 and COS from air samples

  18. Spatial variability of surface pCO2 and air-sea CO2 flux in the Amundsen Sea Polynya, Antarctica

    Directory of Open Access Journals (Sweden)

    L. Mu

    2014-12-01

    Full Text Available Abstract Partial pressure of CO2 (pCO2 and dissolved oxygen (DO in the surface waters of the Amundsen Sea Polynya (ASP were measured during austral summer 2010–2011 on the Amundsen Sea Polynya International Research Expedition (ASPIRE. Surface pCO2 in the central polynya was as low as 130 µatm, mainly due to strong net primary production. Comparing saturation states of pCO2 and DO distinguished dominant factors (biological activity, temperature, upwelling, and ice melt controlling pCO2 across regions. Air-sea CO2 flux, estimated using average shipboard winds, showed high spatial variability (-52 to 25 mmol C m-2 d-1 related to these factors. The central region exhibited a high flux of -36 ± 8.4 mmol C m-2 d-1, which is ∼ 50% larger than that reported for the peak of the bloom in the well-studied Ross Sea, comparable to high rates reported for the Chukchi Sea, and significantly higher than reported for most continental shelves around the world. This central region (∼ 20,000 km2 accounted for 85% of the CO2 uptake for the entire open water area. Margins with lower algal biomass accounted for ∼ 15% of regional carbon uptake, likely resulting from pCO2 reductions by sea ice melt. During ASPIRE we also observed pCO2 up to 490 µatm in a small region near the Dotson Ice Shelf with an efflux of 11 ± 5.4 mmol C m-2 d-1 that offset about 3% of the uptake in the much larger central region. Overall, the 2010–2011 ASP was a large net sink for atmospheric CO2 with a spatially averaged flux density of -18 ± 14 mmol C m-2 d-1. This high flux suggests a disproportionate influence on the uptake of CO2 by the Southern Ocean. Since the region has experienced a significant increase in open water duration (1979–2013, we speculate about whether this CO2 sink will increase with future climate-driven change.

  19. Iron availability, nitrate uptake, and exportable new production in the subarctic Pacific. [phytoplankton population growth support and atmospheric CO2 removal

    Science.gov (United States)

    Banse, Karl

    1991-01-01

    This paper presents a critique of experimental data and papers by Martin et al. (1989, 1990), who suggested that the phytoplankton growth is iron-limited and that, small additions of iron to large subarctic ocean areas might be a way of removing significant amounts of atmospheric CO2 by increasing phytoplancton growth. Data are presented to show that, in the summer of 1987, the phytoplankton assemblage as a whole was not iron limited, as measured by the bulk removal of nitrate or by the increase of chlorophyll. It is suggested that grazing normally prevents the phytoplankton from reaching concentrations that reduce the iron (and nitrate) to levels that depress division rates drastically.

  20. CO2 blood test

    Science.gov (United States)

    Bicarbonate test; HCO3-; Carbon dioxide test; TCO2; Total CO2; CO2 test - serum; Acidosis - CO2; Alkalosis - CO2 ... The CO2 test is most often done as part of an electrolyte or basic metabolic panel. Changes in your ...

  1. RuP2 pool size indicated by CO2 assimilation following the abrupt loss of light.

    Science.gov (United States)

    Cary, J W; Kleinkopf, G E

    1986-01-01

    Measurement of the changes in CO2 uptake by single leaves following the abrupt onset of darkness were made on sugarbeets (Beta vulgaris L.) and (Phaseolus vulgaris L.) The shape of the CO2 dark response curve was analyzed with respect to the reaction kinetics of CO2, RuP2 and RuP2 carboxylase. It was concluded that the net uptake of CO2 in the dark from a 1% O2 atmosphere can be approximately related to the pool size of the RuP2 substrate in the chloroplasts of C3 plants. This information was combined with CO2 levels and decay rates of the response curves to infer changes in carboxylase activity. Preliminary data are presented showing the relative concentration changes in RuP2 as light intensity decreases and as water stress increases. The method may prove useful in studies of plant response to environmental stresses.

  2. 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.

  3. Elevated CO2 and ozone reduce nitrogen acquisition by Pinus halepensis from its mycorrhizal symbiont.

    Science.gov (United States)

    Kytöviita, Minna-Maarit; Le Thiec, Didier; Dizengremel, Pierre

    2001-03-01

    The effects of 700 µmol mol-1 CO2 and 200 nmol mol-1 ozone on photosynthesis in Pinus halepensis seedlings and on N translocation from its mycorrhizal symbiont, Paxillus involutus, were studied under nutrient-poor conditions. After 79 days of exposure, ozone reduced and elevated CO2 increased net assimilation rate. However, the effect was dependent on daily accumulated exposure. No statistically significant differences in total plant mass accumulation were observed, although ozone-treated plants tended to be smaller. Changes in atmospheric gas concentrations induced changes in allocation of resources: under elevated ozone, shoots showed high priority over roots and had significantly elevated N concentrations. As a result of different shoot N concentration and net carbon assimilation rates, photosynthetic N use efficiency was significantly increased under elevated CO2 and decreased under ozone. The differences in photosynthesis were mirrored in the growth of the fungus in symbiosis with the pine seedlings. However, exposure to CO2 and ozone both reduced the symbiosis-mediated N uptake. The results suggest an increased carbon cost of symbiosis-mediated N uptake under elevated CO2, while under ozone, plant N acquisition is preferentially shifted towards increased root uptake.

  4. Underwater photosynthesis and respiration in leaves of submerged wetland plants: gas films improve CO2 and O2 exchange

    DEFF Research Database (Denmark)

    Colmer, Timothy David; Pedersen, Ole

    2007-01-01

    Many wetland plants have gas films on submerged leaf surfaces. We tested the hypotheses that leaf gas films enhance CO(2) uptake for net photosynthesis (P(N)) during light periods, and enhance O(2) uptake for respiration during dark periods. Leaves of four wetland species that form gas films, and......(N) was enhanced up to sixfold. Gas films on submerged leaves enable continued gas exchange via stomata and thus bypassing of cuticle resistance, enhancing exchange of O(2) and CO(2) with the surrounding water, and therefore underwater P(N) and respiration.......Many wetland plants have gas films on submerged leaf surfaces. We tested the hypotheses that leaf gas films enhance CO(2) uptake for net photosynthesis (P(N)) during light periods, and enhance O(2) uptake for respiration during dark periods. Leaves of four wetland species that form gas films......, and two species that do not, were used. Gas films were also experimentally removed by brushing with 0.05% (v/v) Triton X. Net O(2) production in light, or O(2) consumption in darkness, was measured at various CO(2) and O(2) concentrations. When gas films were removed, O(2) uptake in darkness was already...

  5. High net calcium uptake explains the hypersensitivity of the freshwater pulmonate snail, Lymnaea stagnalis, to chronic lead exposure.

    Science.gov (United States)

    Grosell, Martin; Brix, Kevin V

    2009-03-09

    Previous studies have shown that freshwater pulmonate snails of the genus Lymnaea are exceedingly sensitive to chronic Pb exposure. An EC20 of influx was significantly inhibited (39%) and corresponding net Ca(2+) flux was significantly reduced from 224 to -23nmolg(-1)h(-1). An 85% increase in Cl(-) influx was also observed, while Na(+) ion transport appeared unaffected. Finally, a marked alkalosis of extracellular fluid was observed with pH increasing from 8.35 in the control to 8.65 in the 18.9microgl(-1) Pb-exposed group. Results based on direct measurement of Ca(2+) influx in 1g snails gave an influx nearly an order of magnitude higher (750nmolg(-1)h(-1)) than in comparably sized fish in similar water chemistry. Under control conditions, specific growth rate in newly hatched snails was estimated at 16.7% per day over the first 38-day post-hatch and whole body Ca(2+) concentrations were relatively constant at approximately 1100nmolg(-1) over this period. Based on these data, it is estimated that newly hatched snails have net Ca(2+) uptake rates on the order of 7600nmolg(-1)h(-1). A model was developed integrating these data and measured inhibition of Ca(2+) influx rates of 13.4% and 38.7% in snails exposed to 2.7 and 18.9microgl(-1)Pb, respectively. The model estimates 45% and 83% reductions in newly hatched snail growth after 30-day exposure in these two Pb-exposed groups. These results compare well with previous direct measurements of 47% and 90% reductions in growth at similar Pb concentrations, indicating the high net Ca(2+) uptake is the controlling factor in observed Pb hypersensitivity.

  6. From chemolithoautotrophs to electrolithoautotrophs: CO2 fixation by Fe(II)-oxidizing bacteria coupled with direct uptake of electrons from solid electron sources.

    Science.gov (United States)

    Ishii, Takumi; Kawaichi, Satoshi; Nakagawa, Hirotaka; Hashimoto, Kazuhito; Nakamura, Ryuhei

    2015-01-01

    At deep-sea vent systems, hydrothermal emissions rich in reductive chemicals replace solar energy as fuels to support microbial carbon assimilation. Until recently, all the microbial components at vent systems have been assumed to be fostered by the primary production of chemolithoautotrophs; however, both the laboratory and on-site studies demonstrated electrical current generation at vent systems and have suggested that a portion of microbial carbon assimilation is stimulated by the direct uptake of electrons from electrically conductive minerals. Here we show that chemolithoautotrophic Fe(II)-oxidizing bacterium, Acidithiobacillus ferrooxidans, switches the electron source for carbon assimilation from diffusible Fe(2+) ions to an electrode under the condition that electrical current is the only source of energy and electrons. Site-specific marking of a cytochrome aa3 complex (aa3 complex) and a cytochrome bc1 complex (bc1 complex) in viable cells demonstrated that the electrons taken directly from an electrode are used for O2 reduction via a down-hill pathway, which generates proton motive force that is used for pushing the electrons to NAD(+) through a bc1 complex. Activation of carbon dioxide fixation by a direct electron uptake was also confirmed by the clear potential dependency of cell growth. These results reveal a previously unknown bioenergetic versatility of Fe(II)-oxidizing bacteria to use solid electron sources and will help with understanding carbon assimilation of microbial components living in electronically conductive chimney habitats.

  7. From Chemolithoautotrophs to Electrolithoautotrophs: CO2 Fixation by Fe(II-Oxidizing Bacteria Coupled with Direct Uptake of Electrons from Solid Electron Sources

    Directory of Open Access Journals (Sweden)

    Takumi eIshii

    2015-09-01

    Full Text Available At deep-sea vent systems, hydrothermal emissions rich in reductive chemicals replace solar energy as fuels to support microbial carbon assimilation. Until recently, all the microbial components at vent systems have been assumed to be fostered by the primary production of chemolithoautotrophs; however, both the laboratory and on-site studies demonstrated electrical current generation at vent systems and have suggested that a portion of microbial carbon assimilation is stimulated by the direct uptake of electrons from electrically conductive minerals. Here we show that chemolithoautotrophic Fe(II-oxidizing bacterium, Acidithiobacillus ferrooxidans, switches the electron source for carbon assimilation from diffusible Fe2+ ions to an electrode under the condition that electrical current is the only source of energy and electrons. Site-specific marking of a cytochrome aa3 complex (aa3 complex and a cytochrome bc1 complex (bc1 complex in viable cells demonstrated that the electrons taken directly from an electrode are used for O2 reduction via a down-hill pathway, which generates proton motive force that is used for pushing the electrons to NAD+ through a bc1 complex. Activation of carbon dioxide fixation by a direct electron uptake was also confirmed by the clear potential dependency of cell growth. These results reveal a previously unknown bioenergetic versatility of Fe(II-oxidizing bacteria to use solid electron sources and will help with understanding carbon assimilation of microbial components living in electronically conductive chimney habitats.

  8. The role of vegetation in the CO2 flux from a tropical urban neighbourhood

    Science.gov (United States)

    Velasco, E.; Roth, M.; Tan, S. H.; Quak, M.; Nabarro, S. D. A.; Norford, L.

    2013-10-01

    Urban surfaces are usually net sources of CO2. Vegetation can potentially have an important role in reducing the CO2 emitted by anthropogenic activities in cities, particularly when vegetation is extensive and/or evergreen. A direct and accurate estimation of carbon uptake by urban vegetation is difficult due to the particular characteristics of the urban ecosystem and high variability in tree distribution and species. Here, we investigate the role of urban vegetation in the CO2 flux from a residential neighbourhood in Singapore using two different approaches. CO2 fluxes measured directly by eddy covariance are compared with emissions estimated from emissions factors and activity data. The latter includes contributions from vehicular traffic, household combustion, soil respiration and human breathing. The difference between estimated emissions and measured fluxes should approximate the flux associated with the aboveground vegetation. In addition, a tree survey was conducted to estimate the annual CO2 sequestration using allometric equations and an alternative model of the metabolic theory of ecology for tropical forests. Palm trees, banana plants and turfgrass were also included in the survey with their annual CO2 uptake obtained from published growth rates. Both approaches agree within 2% and suggest that vegetation sequesters 8% of the total emitted CO2 in the residential neighbourhood studied. An uptake of 1.4 ton km-2 day-1 (510 ton km-2 yr-1) was estimated as the difference between assimilation by photosynthesis minus the aboveground biomass respiration during daytime (4.0 ton km-2 day-1) and release by plant respiration at night (2.6 ton km-2 day-1). However, when soil respiration is added to the daily aboveground flux, the biogenic component becomes a net source amounting to 4% of the total CO2 flux and represents the total contribution of urban vegetation to the carbon flux to the atmosphere.

  9. The role of vegetation in the CO2 flux from a tropical urban neighbourhood

    Directory of Open Access Journals (Sweden)

    E. Velasco

    2013-10-01

    Full Text Available Urban surfaces are usually net sources of CO2. Vegetation can potentially have an important role in reducing the CO2 emitted by anthropogenic activities in cities, particularly when vegetation is extensive and/or evergreen. A direct and accurate estimation of carbon uptake by urban vegetation is difficult due to the particular characteristics of the urban ecosystem and high variability in tree distribution and species. Here, we investigate the role of urban vegetation in the CO2 flux from a residential neighbourhood in Singapore using two different approaches. CO2 fluxes measured directly by eddy covariance are compared with emissions estimated from emissions factors and activity data. The latter includes contributions from vehicular traffic, household combustion, soil respiration and human breathing. The difference between estimated emissions and measured fluxes should approximate the flux associated with the aboveground vegetation. In addition, a tree survey was conducted to estimate the annual CO2 sequestration using allometric equations and an alternative model of the metabolic theory of ecology for tropical forests. Palm trees, banana plants and turfgrass were also included in the survey with their annual CO2 uptake obtained from published growth rates. Both approaches agree within 2% and suggest that vegetation sequesters 8% of the total emitted CO2 in the residential neighbourhood studied. An uptake of 1.4 ton km−2 day−1 (510 ton km−2 yr−1 was estimated as the difference between assimilation by photosynthesis minus the aboveground biomass respiration during daytime (4.0 ton km−2 day−1 and release by plant respiration at night (2.6 ton km−2 day−1. However, when soil respiration is added to the daily aboveground flux, the biogenic component becomes a net source amounting to 4% of the total CO2 flux and represents the total contribution of urban vegetation to the carbon flux to the atmosphere.

  10. Application of Ann for Prediction of Co2+, Cd2+ and Zn2+ Ions Uptake by R. Squarrosus Biomass in Single and Binary Mixtures

    Directory of Open Access Journals (Sweden)

    Nemeček Peter

    2014-06-01

    Full Text Available Discharge of heavy metals into aquatic ecosystems has become a matter of concern over the last few decades. The search for new technologies involving the removal of toxic metals from wastewaters has directed the attention to biosorption, based on metal binding capacities of various biological materials. Degree of sorbent affinity for the sorbate determines its distribution between the solid and liquid phases and this behavior can be described by adsorption isotherm models (Freundlich and Langmuir isotherm models representing the classical approach. In this study, an artificial neural network (ANN was proposed to predict the sorption efficiency in single and binary component solutions of Cd2+, Zn2+ and Co2+ ions by biosorbent prepared from biomass of moss Rhytidiadelphus squarrosus. Calculated non-linear ANN models presented in this paper are advantageous for its capability of successful prediction, which can be problematic in the case of classical isotherm approach. Quality of prediction was proved by strong agreement between calculated and measured data, expressed by the coefficient of determination in both, single and binary metal systems (R2= 0.996 and R2= 0.987, respectively. Another important benefit of these models is necessity of significantly smaller amount of data (about 50% for the model calculation. Also, it is possible to calculate Qeq for all studied metals by one combined ANN model, which totally overcomes a classical isotherm approach

  11. CO2-Neutral Fuels

    NARCIS (Netherlands)

    Goede, A.; van de Sanden, M. C. M.

    2016-01-01

    Mimicking the biogeochemical cycle of System Earth, synthetic hydrocarbon fuels are produced from recycled CO2 and H2O powered by renewable energy. Recapturing CO2 after use closes the carbon cycle, rendering the fuel cycle CO2 neutral. Non-equilibrium molecular CO2 vibrations are key to high energy

  12. Effects of elevated CO2 and nitrogen deposition on ecosystem carbon fluxes on the Sanjiang plain wetland in Northeast China.

    Directory of Open Access Journals (Sweden)

    Jianbo Wang

    Full Text Available BACKGROUND: Increasing atmospheric CO2 and nitrogen (N deposition across the globe may affect ecosystem CO2 exchanges and ecosystem carbon cycles. Additionally, it remains unknown how increased N deposition and N addition will alter the effects of elevated CO2 on wetland ecosystem carbon fluxes. METHODOLOGY/PRINCIPAL FINDINGS: Beginning in 2010, a paired, nested manipulative experimental design was used in a temperate wetland of northeastern China. The primary factor was elevated CO2, accomplished using Open Top Chambers, and N supplied as NH4NO3 was the secondary factor. Gross primary productivity (GPP was higher than ecosystem respiration (ER, leading to net carbon uptake (measured by net ecosystem CO2 exchange, or NEE in all four treatments over the growing season. However, their magnitude had interannual variations, which coincided with air temperature in the early growing season, with the soil temperature and with the vegetation cover. Elevated CO2 significantly enhanced GPP and ER but overall reduced NEE because the stimulation caused by the elevated CO2 had a greater impact on ER than on GPP. The addition of N stimulated ecosystem C fluxes in both years and ameliorated the negative impact of elevated CO2 on NEE. CONCLUSION/SIGNIFICANCE: In this ecosystem, future elevated CO2 may favor carbon sequestration when coupled with increasing nitrogen deposition.

  13. Accelerating Net Terrestrial Carbon Uptake During the Warming Hiatus Due to Reduced Respiration

    Science.gov (United States)

    Ballantyne, Ashley; Smith, William; Anderegg, William; Kauppi, Pekka; Sarmiento, Jorge; Tans, Pieter; Shevliakova, Elena; Pan, Yude; Poulter, Benjamin; Anav, Alessandro; hide

    2017-01-01

    The recent warming hiatus presents an excellent opportunity to investigate climate sensitivity of carbon cycle processes. Here we combine satellite and atmospheric observations to show that the rate of net biome productivity (NBP) has significantly accelerated from - 0.007 +/- 0.065 PgC yr(exp -2) over the warming period (1982 to 1998) to 0.119 +/- 0.071 PgC yr(exp -2) over the warming hiatus (19982012). This acceleration in NBP is not due to increased primary productivity, but rather reduced respiration that is correlated (r = 0.58; P = 0.0007) and sensitive ( y = 4.05 to 9.40 PgC yr(exp -1) per C) to land temperatures. Global land models do not fully capture this apparent reduced respiration over the warming hiatus; however, an empirical model including soil temperature and moisture observations better captures the reduced respiration.

  14. Recent global CO2 flux inferred from atmospheric CO2 observations and its regional analyses

    Directory of Open Access Journals (Sweden)

    J. M. Chen

    2011-11-01

    Full Text Available The net surface exchange of CO2 for the years 2002–2007 is inferred from 12 181 atmospheric CO2 concentration data with a time-dependent Bayesian synthesis inversion scheme. Monthly CO2 fluxes are optimized for 30 regions of the North America and 20 regions for the rest of the globe. Although there have been many previous multiyear inversion studies, the reliability of atmospheric inversion techniques has not yet been systematically evaluated for quantifying regional interannual variability in the carbon cycle. In this study, the global interannual variability of the CO2 flux is found to be dominated by terrestrial ecosystems, particularly by tropical land, and the variations of regional terrestrial carbon fluxes are closely related to climate variations. These interannual variations are mostly caused by abnormal meteorological conditions in a few months in the year or part of a growing season and cannot be well represented using annual means, suggesting that we should pay attention to finer temporal climate variations in ecosystem modeling. We find that, excluding fossil fuel and biomass burning emissions, terrestrial ecosystems and oceans absorb an average of 3.63 ± 0.49 and 1.94 ± 0.41 Pg C yr−1, respectively. The terrestrial uptake is mainly in northern land while the tropical and southern lands contribute 0.62 ± 0.47, and 0.67 ± 0.34 Pg C yr−1 to the sink, respectively. In North America, terrestrial ecosystems absorb 0.89 ± 0.18 Pg C yr−1 on average with a strong flux density found in the south-east of the continent.

  15. On the causes of trends in the seasonal amplitude of atmospheric CO2.

    Science.gov (United States)

    Piao, Shilong; Liu, Zhuo; Wang, Yilong; Ciais, Philippe; Yao, Yitong; Peng, Shushi; Chevallier, Frédéric; Friedlingstein, Pierre; Janssens, Ivan A; Peñuelas, Josep; Sitch, Stephen; Wang, Tao

    2018-02-01

    No consensus has yet been reached on the major factors driving the observed increase in the seasonal amplitude of atmospheric CO 2 in the northern latitudes. In this study, we used atmospheric CO 2 records from 26 northern hemisphere stations with a temporal coverage longer than 15 years, and an atmospheric transport model prescribed with net biome productivity (NBP) from an ensemble of nine terrestrial ecosystem models, to attribute change in the seasonal amplitude of atmospheric CO 2 . We found significant (p 50°N), consistent with previous observations that the amplitude increased faster at Barrow (Arctic) than at Mauna Loa (subtropics). The multi-model ensemble mean (MMEM) shows that the response of ecosystem carbon cycling to rising CO 2 concentration (eCO 2 ) and climate change are dominant drivers of the increase in AMP P -T and AMP T -P in the high latitudes. At the Barrow station, the observed increase of AMP P -T and AMP T -P over the last 33 years is explained by eCO 2 (39% and 42%) almost equally than by climate change (32% and 35%). The increased carbon losses during the months with a net carbon release in response to eCO 2 are associated with higher ecosystem respiration due to the increase in carbon storage caused by eCO 2 during carbon uptake period. Air-sea CO 2 fluxes (10% for AMP P -T and 11% for AMP T -P ) and the impacts of land-use change (marginally significant 3% for AMP P -T and 4% for AMP T -P ) also contributed to the CO 2 measured at Barrow, highlighting the role of these factors in regulating seasonal changes in the global carbon cycle. © 2017 John Wiley & Sons Ltd.

  16. Southern Ocean CO2 sink: the contribution of the sea ice

    DEFF Research Database (Denmark)

    Delille, B.; Vancoppenolle, Martin; Geilfus, Nicolas-Xavier

    2014-01-01

    undersaturation while the underlying oceanic waters remains slightly oversaturated. The decrease from winter to summer of pCO2 in the brines is driven by dilution with melting ice, dissolution of carbonate crystals, and net primary production. As the ice warms, its permeability increases, allowing CO2 transfer......We report first direct measurements of the partial pressure of CO2 (pCO2) within Antarctic pack sea ice brines and related CO2 fluxes across the air-ice interface. From late winter to summer, brines encased in the ice change from a CO2 large oversaturation, relative to the atmosphere, to a marked...... at the air-sea ice interface. The sea ice changes from a transient source to a sink for atmospheric CO2. We upscale these observations to the whole Antarctic sea ice cover using the NEMO-LIM3 large-scale sea ice-ocean and provide first esti- mates of spring and summer CO2 uptake from the atmosphere...

  17. Seasonal, diel, and tidal CO2 variation in the Bay of Fundy

    Science.gov (United States)

    Horwitz, Rachel; Burt, William J.; Hay, Alex; Thomas, Helmuth

    2017-04-01

    Anthropogenic CO2 emissions acidify the oceans and have potentially adverse effects for ecosystems, living marine resources, and the fisheries and mariculture industries that depend on them. Assessing the vulnerability of these resources to ocean acidification requires a detailed understanding of both the system's natural variability and its response to the ocean's uptake of anthropogenic CO2. A cabled-to-shore observatory was installed in Grand Passage, a tidal channel in the Bay of Fundy, Nova Scotia. Measurements from a CO2 sensor, CTD, and ADCP provide year-long time series of pCO2, temperature, salinity, and currents. The dominant seasonal cycle of pCO2 indicates a spring bloom in April and May, and net respiration from November through March. This seasonal cycle is modulated by a large diel cycle in summertime, and by equal contributions from diel and tidal variation in winter. The oceanic CO2 partial pressure (pCO2) is higher than the atmospheric pCO2 for most of the year, indicating an annual average balance between respiration and outgassing at this site. Further analysis aims to link observations in this tidal channel to the larger Bay of Fundy - Gulf of Maine carbon system.

  18. Net root growth and nutrient acquisition in response to predicted climate change in two contrasting heathland species

    DEFF Research Database (Denmark)

    Arndal, M.F.; Merrild, M.P.; Michelsen, A.

    2013-01-01

    colonization, and fine root N and P uptake by root assay of Deschampsia flexuosa and Calluna vulgaris.Net root growth increased under elevated CO2, warming and drought, with additive effects among the factors. Arbuscular mycorrhizal colonization increased in response to elevated CO2, while ericoid mycorrhizal...

  19. Internal respiration of Amazon tree stems greatly exceeds external CO2 efflux

    Directory of Open Access Journals (Sweden)

    J. Q. Chambers

    2012-12-01

    Full Text Available Respiration in tree stems is an important component of forest carbon balance. The rate of CO2 efflux from the stem has often been assumed to be a measure of stem respiration. However, recent work in temperate forests has demonstrated that stem CO2 efflux can either overestimate or underestimate respiration rate because of emission or removal of CO2 by transport in xylem water. Here, we studied gas exchange from stems of tropical forest trees using a new approach to better understand respiration in an ecosystem that plays a key role in the global carbon cycle. Our main questions were (1 is internal CO2 transport important in tropical trees, and, if so, (2 does this transport result in net release of CO2 respired in the roots at the stem, or does it cause the opposite effect of net removal of stem-respired CO2? To answer these questions, we measured the ratio of stem CO2 efflux to O2 influx. This ratio, defined here as apparent respiratory quotient (ARQ, is expected to equal 1.0 if carbohydrates are the substrate for respiration, and the net transport of CO2 in the xylem water is negligible. Using a stem chamber approach to quantifying ARQ, we found values of 0.66 ± 0.18. These low ARQ values indicate that a large portion of respired CO2 (~ 35% is not emitted locally, and is probably transported upward in the stem. ARQ values of 0.21 ± 0.10 were found for the steady-state gas concentration within the stem, sampled by in-stem equilibration probes. These lower values may result from the proximity to the xylem water stream. In contrast, we found ARQ values of 1.00 ± 0.13 for soil respiration. Our results indicate the existence of a considerable internal flux of CO2 in the stems of tropical trees. If the transported CO2 is used in the canopy as a substrate for photosynthesis, it could account for up to 10% of the C fixed by the tree, and perhaps serve as a mechanism that buffers the response of the tree to changing CO2 levels. Our results also

  20. Distribution of sea-air CO2 fluxes in the Patagonian Sea: Seasonal, biological and thermal effects

    Science.gov (United States)

    Kahl, Lucía C.; Bianchi, Alejandro A.; Osiroff, Ana Paula; Pino, Diana Ruiz; Piola, Alberto R.

    2017-07-01

    Sea-air CO2 fluxes (FCO2) in the Patagonian Sea (PS) were studied using observations collected in 2000-2006. Based on the PS frontal structures and the thermal and biological contributions to FCO2 we present a regional subdivision between distinct regimes that provide new insights on the processes that control these fluxes. The coastal regime (CR) is a net source of atmospheric CO2 (4.9 × 10-3 mol m-2 d-1) while the open shelf regime (SHR) is a net CO2 sink (-6.0 × 10-3 mol m-2 d-1). The interface between these two regions closely follows the location of along-shore fronts. In addition, based on the nature of the processes that drive the FCO2, the PS is subdivided between northern (NR) and southern (SR) regions. Both, NR and SR are CO2 sinks, but the CO2 uptake is significantly higher in NR (-6.4 × 10-3 mol m-2 d-1) than in SR (-0.5 × 10-3 mol m-2 d-1). The data reveal a strong seasonality in FCO2. The mean CO2 capture throughout the PS in austral spring is -5.8 × 10-3 mol m-2 d-1, reaching values lower than -50 × 10-3 mol m-2 d-1 in NR, while in winter FCO2 is close to equilibrium in SR. The analysis of the biological and thermal effects (BE and TE, respectively) on seasonal pCO2 variability indicates that regions of CO2 emission are dominated by the TE while regions of CO2 uptake are dominated by the BE. Our results indicate that the biological pump is the dominant process determining the sea-air CO2 flux in the PS.

  1. Whole-plant growth and N utilization in transgenic rice plants with increased or decreased Rubisco content under different CO2 partial pressures.

    Science.gov (United States)

    Sudo, Emi; Suzuki, Yuji; Makino, Amane

    2014-11-01

    Ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) strongly limits photosynthesis at lower CO2 concentration [CO2] whereas [corrected] Rubisco limitation is cancelled by elevated [CO2]. Therefore, increase or reduction in Rubisco content by transformation with a sense or an antisense RBCS construct are expected to alter the biomass production under different CO2 levels. RBCS-sense (125% Rubisco of wild-type) and -antisense (35% Rubisco of wild-type) rice (Oryza sativa L.) plants were grown for 63 days at three different CO2 levels: low [CO2] (28 Pa), normal [CO2] (40 Pa) and elevated [CO2] (120 Pa). The biomass of RBCS-sense plants was 32% and 15% greater at low [CO2] and normal [CO2] than that of the wild-type plants, respectively, but did not differ at elevated [CO2]. Conversely, the biomass of RBCS-antisense plants was the smallest at low [CO2]. Thus, overproduction of Rubisco was effective for biomass production at low [CO2]. Greater biomass production at low [CO2] in RBCS-sense plants was caused by an increase in the net assimilation rate, and associated with an increase in the amount of N uptake. Furthermore, Rubisco overproduction in RBCS-sense plants was also promoted at low [CO2]. Although it seems that low [CO2]-growth additionally stimulates the effect of RBCS overexpression, such a phenomenon observed at low [CO2] was mediated through an increase in total leaf N content. Thus, the dependence of the growth improvement in RBCS-sense rice on growth [CO2] was closely related to the degree of Rubisco overproduction which was accompanied not only by leaf N content but also by whole plant N content. © The Author 2014. Published by Oxford University Press on behalf of Japanese Society of Plant Physiologists. All rights reserved. For permissions, please email: journals.permissions@oup.com.

  2. State of the Carbon Cycle - Consequences of Rising Atmospheric CO2

    Science.gov (United States)

    Moore, David J.; Cooley, Sarah R.; Alin, Simone R.; Brown, Molly; Butman, David E.; French, Nancy H. F.; Johnson, Zackary I.; Keppel-Aleks; Lohrenz, Steven E.; Ocko, Ilissa; hide

    2016-01-01

    The rise of atmospheric CO2, largely attributable to human activity through fossil fuel emissions and land-use change, has been dampened by carbon uptake by the ocean and terrestrial biosphere. We outline the consequences of this carbon uptake as direct and indirect effects on terrestrial and oceanic systems and processes for different regions of North America and the globe. We assess the capacity of these systems to continue to act as carbon sinks. Rising CO2 has decreased seawater pH; this process of ocean acidification has impacted some marine species and altered fundamental ecosystem processes with further effects likely. In terrestrial ecosystems, increased atmospheric CO2 causes enhanced photosynthesis, net primary production, and increased water-use efficiency. Rising CO2 may change vegetation composition and carbon storage, and widespread increases in water use efficiency likely influence terrestrial hydrology and biogeochemical cycling. Consequences for human populations include changes to ecosystem services including cultural activities surrounding land use, agricultural or harvesting practices. Commercial fish stocks have been impacted and crop production yields have been changed as a result of rising CO2. Ocean and terrestrial effects are contingent on, and feedback to, global climate change. Warming and modified precipitation regimes impact a variety of ecosystem processes, and the combination of climate change and rising CO2 contributes considerable uncertainty to forecasting carbon sink capacity in the ocean and on land. Disturbance regime (fire and insects) are modified with increased temperatures. Fire frequency and intensity increase, and insect lifecycles are disrupted as temperatures move out of historical norms. Changes in disturbance patterns modulate the effects of rising CO2 depending on ecosystem type, disturbance frequency, and magnitude of events. We discuss management strategies designed to limit the rise of atmospheric CO2 and reduce

  3. State of the Carbon Cycle - Consequences of Rising Atmospheric CO2

    Science.gov (United States)

    Moore, D. J.; Cooley, S. R.; Alin, S. R.; Brown, M. E.; Butman, D. E.; French, N. H. F.; Johnson, Z. I.; Keppel-Aleks, G.; Lohrenz, S. E.; Ocko, I.; Shadwick, E. H.; Sutton, A. J.; Potter, C. S.; Yu, R. M. S.

    2016-12-01

    The rise of atmospheric CO2, largely attributable to human activity through fossil fuel emissions and land-use change, has been dampened by carbon uptake by the ocean and terrestrial biosphere. We outline the consequences of this carbon uptake as direct and indirect effects on terrestrial and oceanic systems and processes for different regions of North America and the globe. We assess the capacity of these systems to continue to act as carbon sinks. Rising CO2 has decreased seawater pH; this process of ocean acidification has impacted some marine species and altered fundamental ecosystem processes with further effects likely. In terrestrial ecosystems, increased atmospheric CO2 causes enhanced photosynthesis, net primary production, and increased water-use efficiency. Rising CO2 may change vegetation composition and carbon storage, and widespread increases in water use efficiency likely influence terrestrial hydrology and biogeochemical cycling. Consequences for human populations include changes to ecosystem services including cultural activities surrounding land use, agricultural or harvesting practices. Commercial fish stocks have been impacted and crop production yields have been changed as a result of rising CO2. Ocean and terrestrial effects are contingent on, and feedback to, global climate change. Warming and modified precipitation regimes impact a variety of ecosystem processes, and the combination of climate change and rising CO2 contributes considerable uncertainty to forecasting carbon sink capacity in the ocean and on land. Disturbance regime (fire and insects) are modified with increased temperatures. Fire frequency and intensity increase, and insect lifecycles are disrupted as temperatures move out of historical norms. Changes in disturbance patterns modulate the effects of rising CO2 depending on ecosystem type, disturbance frequency, and magnitude of events. We discuss management strategies designed to limit the rise of atmospheric CO2 and reduce

  4. CO2NNIE

    DEFF Research Database (Denmark)

    Krogh, Benjamin Bjerre; Andersen, Ove; Lewis-Kelham, Edwin

    2015-01-01

    We propose a system for calculating the personalized annual fuel consumption and CO2 emissions from transportation. The system, named CO2NNIE, estimates the fuel consumption on the fastest route between the frequent destinations of the user. The travel time and fuel consumption estimated are based......% of the actual fuel consumption (4.6% deviation on average). We conclude, that the system provides new detailed information on CO2 emissions and fuel consumption for any make and model....

  5. Isotopic tracers for net primary productivity for a terrestrial esocystem ...

    African Journals Online (AJOL)

    The coupling effect of vapour release and CO2 uptake during photosynthesis plays an important role in the carbon and hydrologic cycles. The water use efficiency (WUE) for transpiration was used in calculating the net primary productivity (NPP) for terrestrial ecosystem. Three parameters were used in calculating the water ...

  6. Key knowledge and data gaps in modelling the influence of CO2 concentration on the terrestrial carbon sink.

    Science.gov (United States)

    Pugh, T A M; Müller, C; Arneth, A; Haverd, V; Smith, B

    2016-09-20

    Primary productivity of terrestrial vegetation is expected to increase under the influence of increasing atmospheric carbon dioxide concentrations ([CO2]). Depending on the fate of such additionally fixed carbon, this could lead to an increase in terrestrial carbon storage, and thus a net terrestrial sink of atmospheric carbon. Such a mechanism is generally believed to be the primary global driver behind the observed large net uptake of anthropogenic CO2 emissions by the biosphere. Mechanisms driving CO2 uptake in the Terrestrial Biosphere Models (TBMs) used to attribute and project terrestrial carbon sinks, including that from increased [CO2], remain in large parts unchanged since those models were conceived two decades ago. However, there exists a large body of new data and understanding providing an opportunity to update these models, and directing towards important topics for further research. In this review we highlight recent developments in understanding of the effects of elevated [CO2] on photosynthesis, and in particular on the fate of additionally fixed carbon within the plant with its implications for carbon turnover rates, on the regulation of photosynthesis in response to environmental limitations on in-plant carbon sinks, and on emergent ecosystem responses. We recommend possible avenues for model improvement and identify requirements for better data on core processes relevant to the understanding and modelling of the effect of increasing [CO2] on the global terrestrial carbon sink. Copyright © 2016 The Authors. Published by Elsevier GmbH.. All rights reserved.

  7. Partitioning of photosynthetic electron flow between CO2 and O 2 reduction in a C 3 leaf (Phaseolus vulgaris L.) at different CO 2 concentrations and during drought stress.

    Science.gov (United States)

    Cornic, G; Briantais, J M

    1991-01-01

    Photosystem II chlorophyll fluorescence and leaf net gas exchanges (CO2 and H2O) were measured simultaneously on bean leaves (Phaseolus vulgaris L.) submitted either to different ambient CO2 concentrations or to a drought stress. When leaves are under photorespiratory conditions, a simple fluorescence parameter ΔF/ Fm (B. Genty et al. 1989, Biochem. Biophys. Acta 990, 87-92; ΔF = difference between maximum, Fm, and steady-state fluorescence emissions) allows the calculation of the total rate of photosynthetic electron-transport and the rate of electron transport to O2. These rates are in agreement with the measurements of leaf O2 absorption using (18)O2 and the kinetic properties of ribulose-1,5bisphosphate carboxylase/oxygenase. The fluorescence parameter, ΔF/Fm, showed that the allocation of photosynthetic electrons to O2 was increased during the desiccation of a leaf. Decreasing leaf net CO2 uptake, either by decreasing the ambient CO2 concentration or by dehydrating a leaf, had the same effect on the partitioning of photosynthetic electrons between CO2 and O2 reduction. It is concluded that the decline of net CO2 uptake of a leaf under drought stress is only due, at least for a mild reversible stress (causing at most a leaf water deficit of 35%), to stomatal closure which leads to a decrease in leaf internal CO2 concentration. Since, during the dehydration of a leaf, the calculated internal CO2 concentration remained constant or even increased we conclude that this calculation is misleading under such conditions.

  8. CO2 laser resurfacing.

    Science.gov (United States)

    Fitzpatrick, R E

    2001-07-01

    The CO2 Laser offers a variety of unique features in resurfacing facial photodamage and acne scarring. These include hemostasis, efficient removal of the epidermis in a single pass, thermally induced tissue tightening, and safe, predictable tissue interaction. Knowledge of these mechanisms will result in the capability of using the CO2 laser effectively and safely whether the goal is superficial or deep treatment.

  9. CO2 uit buitenlucht

    NARCIS (Netherlands)

    Weel, van P.A.; Vanthoor, B.H.E.

    2016-01-01

    The supply of additional CO2 in a greenhouse will be restricted in the future. The concentration in outside air has risen above 400 ppm. This may open the possibility to blow this air through the canopy to increase growth. In this project, the vertical CO2 concentration was measured in a vertical

  10. Transient nature of CO2 fertilization in arctic tundra

    Science.gov (United States)

    Walter C. Oechel; Sid Cowles; Nancy Grulke; Steven J. Hastings; Bill Lawrence; Tom Prudhomme; George Riechers; Boyd Strain; David Tissue; George. Vourlitis

    1994-01-01

    There has been much debate about the effect of increased atmospheric CO2 concentrations on plant net primary production1,3 and on net ecosystem CO2 flux3–10. Apparently conflicting experimental findings could be the result of differences in genetic potential11–15...

  11. Outsourcing CO2 Emissions

    Science.gov (United States)

    Davis, S. J.; Caldeira, K. G.

    2009-12-01

    CO2 emissions from the burning of fossil fuels are the primary cause of global warming. Much attention has been focused on the CO2 directly emitted by each country, but relatively little attention has been paid to the amount of emissions associated with consumption of goods and services in each country. This consumption-based emissions inventory differs from the production-based inventory because of imports and exports of goods and services that, either directly or indirectly, involved CO2 emissions. Using the latest available data and reasonable assumptions regarding trans-shipment of embodied carbon through third-party countries, we developed a global consumption-based CO2 emissions inventory and have calculated associated consumption-based energy and carbon intensities. We find that, in 2004, 24% of CO2 emissions are effectively outsourced to other countries, with much of the developed world outsourcing CO2 emissions to emerging markets, principally China. Some wealthy countries, including Switzerland and Sweden, outsource over half of their consumption-based emissions, with many northern Europeans outsourcing more than three tons of emissions per person per year. The United States is both a big importer and exporter of emissions embodied in trade, outsourcing >2.6 tons of CO2 per person and at the same time as >2.0 tons of CO2 per person are outsourced to the United States. These large flows indicate that CO2 emissions embodied in trade must be taken into consideration when considering responsibility for increasing atmospheric greenhouse gas concentrations.

  12. Photosynthetic stimulation under long-term CO2 enrichment and fertilization is sustained across a closed Populus canopy profile (EUROFACE).

    Science.gov (United States)

    Liberloo, Marion; Tulva, Ingmar; Raïm, Olaf; Kull, Olevi; Ceulemans, Reinhart

    2007-01-01

    The long-term response of leaf photosynthesis to rising CO2 concentrations [CO2] depends on biochemical and morphological feedbacks. Additionally, responses to elevated [CO2] might depend on the nutrient availability and the light environment, affecting the net carbon uptake of a forest stand. After 6 yr of exposure to free-air CO2 enrichment (EUROFACE) during two rotation cycles (with fertilization during the second cycle), profiles of light, leaf characteristics and photosynthetic parameters were measured in the closed canopy of a poplar (Populus) short-rotation coppice. Net photosynthetic rate (A(growth)) was 49% higher in poplars grown in elevated [CO2], independently of the canopy position. Jmax significantly increased (15%), whereas leaf carboxylation capacity (Vcmax), leaf nitrogen (N(a)) and chlorophyll (Chl(a)) were unaffected in elevated [CO2]. Leaf mass per unit area (LMA) increased in the upper canopy. Fertilization created more leaves in the top of the crown. These results suggest that the photosynthetic stimulation by elevated [CO2] in a closed-canopy poplar coppice might be sustained in the long term. The absence of any down-regulation, given a sufficient sink capacity and nutrient availability, provides more carbon for growth and storage in this bioenergy plantation.

  13. Spring photosynthetic recovery of boreal Norway spruce under conditions of elevated [CO(2)] and air temperature.

    Science.gov (United States)

    Wallin, Göran; Hall, Marianne; Slaney, Michelle; Räntfors, Mats; Medhurst, Jane; Linder, Sune

    2013-11-01

    Accumulated carbon uptake, apparent quantum yield (AQY) and light-saturated net CO2 assimilation (Asat) were used to assess the responses of photosynthesis to environmental conditions during spring for three consecutive years. Whole-tree chambers were used to expose 40-year-old field-grown Norway spruce trees in northern Sweden to an elevated atmospheric CO2 concentration, [CO2], of 700 μmol CO2 mol(-1) (CE) and an air temperature (T) between 2.8 and 5.6 °C above ambient T (TE), during summer and winter. Net shoot CO2 exchange (Anet) was measured continuously on 1-year-old shoots and was used to calculate the accumulated carbon uptake and daily Asat and AQY. The accumulated carbon uptake, from 1 March to 30 June, was stimulated by 33, 44 and 61% when trees were exposed to CE, TE, and CE and TE combined, respectively. Air temperature strongly influenced the timing and extent of photosynthetic recovery expressed as AQY and Asat during the spring. Under elevated T (TE), the recovery of AQY and Asat commenced ∼10 days earlier and the activity of these parameters was significantly higher throughout the recovery period. In the absence of frost events, the photosynthetic recovery period was less than a week. However, frost events during spring slowed recovery so that full recovery could take up to 60 days to complete. Elevated [CO2] stimulated AQY and Asat on average by ∼10 and ∼50%, respectively, throughout the recovery period, but had minimal or no effect on the onset and length of the photosynthetic recovery period during the spring. However, AQY, Asat and Anet all recovered at significantly higher T (average +2.2 °C) in TE than in TA, possibly caused by acclimation or by shorter days and lower light levels during the early part of the recovery in TE compared with TA. The results suggest that predicted future climate changes will cause prominent stimulation of photosynthetic CO2 uptake in boreal Norway spruce forest during spring, mainly caused by elevated T

  14. Forest fine-root production and nitrogen use under elevated CO2: Contrasting responses explained by a common principle

    Energy Technology Data Exchange (ETDEWEB)

    Franklin, Oscar [International Institute for Applied Systems Analysis; McMurtrie, Ross E [ORNL; Iversen, Colleen M [ORNL; Crous, Kristine [University of Michigan; Finzi, Adrien C [Boston University; Tissue, David Thomas [ORNL; Ellsworth, David [ORNL; Oren, Ram [ORNL; Norby, Richard J [ORNL

    2009-01-01

    Despite the importance of nitrogen (N) limitation of forest carbon (C) sequestration at rising atmospheric CO2 concentration, the mechanisms responsible are not well understood. To elucidate the interactive effects of elevated CO2 (eCO2) and soil N availability on forest productivity and C allocation, we hypothesized that 1) trees maximize fitness by allocating N and C to maximize their net growth, and 2) that N uptake is controlled by root exploration for N. We tested this model using data collected in FACE sites dominated by evergreen (Pinus taeda; Duke Forest) and deciduous (Liquidambar styraciflua; Oak Ridge National Laboratory ORNL) trees. The model explained 80-95% of variation in productivity and N-uptake data among eCO2, N fertilization and control treatments over six years. The model explains why fine-root production increased, and why N uptake increased despite reduced soil N availability under eCO2 at ORNL and Duke. In agreement with observations at other sites, soil N availability reduced below a critical level diminishes all eCO2 responses. At Duke, a negative feedback between reduced soil N availability and N uptake counteracted progressive reduction in soil N availability at eCO2. At ORNL, decreasing soil N availability was perpetuated as it generated no reduction in N uptake, due to strongly increased production of fast turnover fine-roots. This implies that species with fast root turnover could be more prone to progressive N limitation of carbon sequestration in woody biomass than species with slow root turnover, such as evergreens.

  15. Temporal and spatial variation in CO2 exchange in a salt marsh dominated estuary (PIE LTER)

    Science.gov (United States)

    Forbrich, I.; Giblin, A. E.; Morris, J. T.; Hopkinson, C.

    2016-12-01

    Salt marshes are important carbon sinks, but large uncertainties about current rates of carbon exchange with the atmosphere and the ocean remain. These need to be constrained for a better assessment of changes in long-term drivers such as sea level and climate. At the Plum Island Ecosystems LTER, we are expecting a transition from the current Spartina patens dominated high marsh to a more frequently flooded Spartina alterniflora dominated low marsh with increasing sea level. We have set up two eddy covariance sites, one in a high marsh (starting in 2013) and one in a low marsh (starting in 2015) to study net ecosystem CO2 exchange and evapotranspiration (ET). We use a broad-band NDVI to monitor phenology at both sites, which is tightly coupled to the CO2 fluxes. While the temporal dynamics do not vary much between the years, the magnitude in NDVI and CO2 fluxes does: For the high marsh site, we observe lower NDVI (and smaller overall net CO2 uptake) in years with low rainfall during the growing season, e.g. in 2014 and likely in 2016. In 2014, a low rainfall period occurred at the beginning of the growing season, during which ET was slightly higher than in other years, which likely increased soil salinity. In 2016, the period of low rainfall has extended much longer into the growing season (on-going) which seems to have an overall stronger effect (i.e. decrease) on low marsh net CO2 uptake than on the high marsh. We will discuss our findings in the context of salt marsh hydrology and carbon cycling in high and low marsh.

  16. Short-term variability of surface carbon dioxide and sea-air CO2 fluxes in the shelf waters of the Galician coastal upwelling system

    Directory of Open Access Journals (Sweden)

    Alba Marina Cobo-Viveros

    2013-01-01

    Full Text Available Using data collected during the DYBAGA and ECO cruises, remote sensing chlorophyll-a estimations and the averaged upwelling index of the previous fortnight (Iw’, we studied the variability of the sea surface CO2 fugacity (fCO2 over the Galician continental shelf during three seasonal cycles. Sea surface salinity (SSS distribution controlled fCO2 mainly in spring, while sea surface temperature (SST did so during periods of intense cooling in November and warming in June. The uptake of carbon by photosynthetic activity, which was more intense during spring and autumn, masked the surface increase in the dissolved inorganic carbon concentration during upwelling events, especially during spring. A significant low correlation between fCO2 and Iw’ was found during spring and summer when upwelling events were observed, whereas no relationship was observed during the downwelling period. High fCO2 exceeding atmospheric values was only found during the summer stratification breakdown. Although sea-air CO2 fluxes showed a marked inter-annual variability, surface waters off the Galician coast were net sinks for atmospheric CO2 in every seasonal cycle, showing a lower CO2 uptake (~65% compared to previously published values. Marked inter-annual changes in the sea-air CO2 fluxes seem to be influenced by fresh water inputs on the continental shelf under different meteorological scenarios.

  17. CO2 Emission Factors for Coals

    Directory of Open Access Journals (Sweden)

    P. Orlović-Leko

    2015-03-01

    (calcite and siderite directly contribute CO2 when they decompose during coal combustion. Variations in the maceral content can also influence CO2 emissions; high inertinite contents increase CO2 emissions. Sulphur in coal reduces EF(CO2. Fuel analysis is very important when estimating greenhouse gas emissions and emission factors. In this preliminary study, based on the results of the fuel analysis, CO2 emission factors for coals and peat from Livno, B&H have been calculated. EF(CO2 is defined as the amount of carbon dioxide emission per unit net calorific values of the fuel. Net calorific value (the lower heating value corresponds to the heat produced by combustion where total water in the combustion products exists as water vapour. The EF(CO2 obtained for sub-bituminous coal, lignite and peat were: 98.7, 109.5, and 147.9 t TJ−1, respectively, which correspond to the following net calorific values: 20.6, 11.5 and 3.6 MJ kg−1. The heating value is generally known to increase with the increase in carbon content (this parameter is connected with the degree of coalification, coal age. The other indispensable parameters are hydrogen, which has a positive effect on the net calorific value, and oxygen and water which impact the net calorific value negatively. The differences in net calorific values can be explained in part by the difference of total moisture content among the different fuel types. The CO2 emission factors calculated in this study were compared with those of IPCC. A significant difference was observed for peat (39.5 %, followed by lignite (8.2 % and sub-bituminous coal (4.3 %.

  18. Forest response to elevated CO2 is conserved across a broad range of productivity

    Science.gov (United States)

    Norby, Richard J.; DeLucia, Evan H.; Gielen, Birgit; Calfapietra, Carlo; Giardina, Christian P.; King, John S.; Ledford, Joanne; McCarthy, Heather R.; Moore, David J. P.; Ceulemans, Reinhart; De Angelis, Paolo; Finzi, Adrien C.; Karnosky, David F.; Kubiske, Mark E.; Lukac, Martin; Pregitzer, Kurt S.; Scarascia-Mugnozza, Giuseppe E.; Schlesinger, William H.; Oren, Ram

    2005-01-01

    Climate change predictions derived from coupled carbon-climate models are highly dependent on assumptions about feedbacks between the biosphere and atmosphere. One critical feedback occurs if C uptake by the biosphere increases in response to the fossil-fuel driven increase in atmospheric [CO2] (“CO2 fertilization”), thereby slowing the rate of increase in atmospheric [CO2]. Carbon exchanges between the terrestrial biosphere and atmosphere are often first represented in models as net primary productivity (NPP). However, the contribution of CO2 fertilization to the future global C cycle has been uncertain, especially in forest ecosystems that dominate global NPP, and models that include a feedback between terrestrial biosphere metabolism and atmospheric [CO2] are poorly constrained by experimental evidence. We analyzed the response of NPP to elevated CO2 (≈550 ppm) in four free-air CO2 enrichment experiments in forest stands. We show that the response of forest NPP to elevated [CO2] is highly conserved across a broad range of productivity, with a stimulation at the median of 23 ± 2%. At low leaf area indices, a large portion of the response was attributable to increased light absorption, but as leaf area indices increased, the response to elevated [CO2] was wholly caused by increased light-use efficiency. The surprising consistency of response across diverse sites provides a benchmark to evaluate predictions of ecosystem and global models and allows us now to focus on unresolved questions about carbon partitioning and retention, and spatial variation in NPP response caused by availability of other growth limiting resources. PMID:16330779

  19. CO2 and CH4 fluxes across a Nuphar lutea (L. Sm. stand

    Directory of Open Access Journals (Sweden)

    Scott C. Neubauer

    2012-01-01

    Full Text Available Floating-leaved rhizophytes can significantly alter net carbon dioxide (CO2 and methane (CH4 exchanges with the atmosphere in freshwater shallow environments. In particular, CH4 efflux can be enhanced by the aerenchyma-mediated mass flow, while CO2 release from supersaturated waters can be reversed by the plant uptake. Additionally, the floating leaves bed can hamper light penetration and oxygen (O2 diffusion from the atmosphere, thus altering the dissolved gas dynamics in the water column. In this study, net fluxes of CO2 and CH4 were measured seasonally across vegetated [Nuphar lutea (L. Sm.] and free water surfaces in the Busatello wetland (Northern Italy. Concomitantly, dissolved gas concentrations were monitored in the water column and N. lutea leaf production was estimated by means of biomass harvesting. During the vegetative period (May-August, the yellow waterlily stand resulted a net sink for atmospheric carbon (from 97.5 to 110.6 g C-CO2 m-2, while the free water surface was a net carbon source (166.3 g C-CO2 m-2. Both vegetated and plant-free areas acted as CH4 sources, with an overall carbon release comprised between 71.6 and 113.3 g C-CH4 m-2. On the whole, water column chemistry was not affected by the presence of the floating leaves; moreover, no significant differences in CH4 efflux were evidenced between the vegetated and plant-free areas. In general, this study indicates that the colonization of shallow aquatic ecosystems by N. lutea might not have the same drastic effect reported for free-floating macrophytes.

  20. Nitrogen Limitation is Reducing the Enhancement of NPP by Elevated CO2 in a Deciduous Forest

    Science.gov (United States)

    Norby, R. J.; Warren, J. M.; Iversen, C. M.; Medlyn, B. E.; McMurtrie, R. E.; Hoffman, F. M.

    2008-12-01

    Accurate model representation of the long-term response of forested ecosystems to elevated atmospheric CO2 concentrations (eCO2) is important for predictions of future concentrations of CO2. For biogeochemical models that predict the response of net primary productivity (NPP) to eCO2, free-air CO2 enrichment (FACE) experiments provide the only source of data for comparison. A synthesis of forest FACE experiments reported a 23% increase in NPP in eCO2, and this result has been used as a model benchmark. Here, we provide new evidence from a FACE experiment in a deciduous forest in Tennessee that N limitation has significantly reduced the stimulation of NPP by eCO2, consistent with predictions from ecosystem and global models that incorporate N feedbacks. The Liquidambar styraciflua stand has been exposed to current ambient atmospheric CO2 or air enriched with CO2 to 550 ppm since 1998. Results from the first 6 years of the experiment indicated that NPP was significantly enhanced by eCO2 and that this was a consistent and sustained response. Now, with 10 years of data, our analysis must be revised. The response of NPP to eCO2 has declined from 24% in 2001-2003 to 9% in 2007. The diminishing response to eCO2 since 2004 coincides with declining NPP in ambient CO2 plots. Productivity of this forest stand is limited by N availability, and the steady decline in forest NPP is closely related to changes in the N economy, as evidenced by declining foliar N concentrations. There is a strong linear relationship between foliar [N] and NPP, and the steeper slope in eCO2 indicates that the NPP response to eCO2 should diminish as foliar N declines. Increased fine-root production and root proliferation deeper in the soil have sustained N uptake, but not to an extent sufficient to benefit aboveground production. The mechanistic basis of the N effect on NPP resides in the photosynthetic machinery. The linear relationships between Jmax and Vcmax with foliar [N] did not change from 1998

  1. Nitrogen Limitation is Reducing the Enhancement of NPP by Elevated CO2 in a Deciduous Forest

    Energy Technology Data Exchange (ETDEWEB)

    Norby, Richard J [ORNL; Warren, Jeffrey [ORNL; Iversen, Colleen M [ORNL; Medlyn, Belinda [Macquarie University; McMurtrie, Ross [University of New South Wales; Hoffman, Forrest M [ORNL

    2008-01-01

    Accurate model representation of the long-term response of forested ecosystems to elevated atmospheric CO2 concentrations (eCO2) is important for predictions of future concentrations of CO2. For biogeochemical models that predict the response of net primary productivity (NPP) to eCO2, free-air CO2 enrichment (FACE) experiments provide the only source of data for comparison. A synthesis of forest FACE experiments reported a 23% increase in NPP in eCO2, and this result has been used as a model benchmark. Here, we provide new evidence from a FACE experiment in a deciduous forest in Tennessee that N limitation has significantly reduced the stimulation of NPP by eCO2, consistent with predictions from ecosystem and global models that incorporate N feedbacks. The Liquidambar styraciflua stand has been exposed to current ambient atmospheric CO2 or air enriched with CO2 to 550 ppm since 1998. Results from the first 6 years of the experiment indicated that NPP was significantly enhanced by eCO2 and that this was a consistent and sustained response. Now, with 10 years of data, our analysis must be revised. The response of NPP to eCO2 has declined from 24% in 2001-2003 to 9% in 2007. The diminishing response to eCO2 since 2004 coincides with declining NPP in ambient CO2 plots. Productivity of this forest stand is limited by N availability, and the steady decline in forest NPP is closely related to changes in the N economy, as evidenced by declining foliar N concentrations. There is a strong linear relationship between foliar [N] and NPP, and the steeper slope in eCO2 indicates that the NPP response to eCO2 should diminish as foliar N declines. Increased fine-root production and root proliferation deeper in the soil have sustained N uptake, but not to an extent sufficient to benefit aboveground production. The mechanistic basis of the N effect on NPP resides in the photosynthetic machinery. The linear relationships between Jmax and Vcmax with foliar [N] did not change from 1998

  2. Alterations in microbial community composition with increasing fCO2: a mesocosm study in the eastern Baltic Sea

    Science.gov (United States)

    Crawfurd, Katharine J.; Alvarez-Fernandez, Santiago; Mojica, Kristina D. A.; Riebesell, Ulf; Brussaard, Corina P. D.

    2017-08-01

    Ocean acidification resulting from the uptake of anthropogenic carbon dioxide (CO2) by the ocean is considered a major threat to marine ecosystems. Here we examined the effects of ocean acidification on microbial community dynamics in the eastern Baltic Sea during the summer of 2012 when inorganic nitrogen and phosphorus were strongly depleted. Large-volume in situ mesocosms were employed to mimic present, future and far future CO2 scenarios. All six groups of phytoplankton enumerated by flow cytometry ( cell diameter) showed distinct trends in net growth and abundance with CO2 enrichment. The picoeukaryotic phytoplankton groups Pico-I and Pico-II displayed enhanced abundances, whilst Pico-III, Synechococcus and the nanoeukaryotic phytoplankton groups were negatively affected by elevated fugacity of CO2 (fCO2). Specifically, the numerically dominant eukaryote, Pico-I, demonstrated increases in gross growth rate with increasing fCO2 sufficient to double its abundance. The dynamics of the prokaryote community closely followed trends in total algal biomass despite differential effects of fCO2 on algal groups. Similarly, viral abundances corresponded to prokaryotic host population dynamics. Viral lysis and grazing were both important in controlling microbial abundances. Overall our results point to a shift, with increasing fCO2, towards a more regenerative system with production dominated by small picoeukaryotic phytoplankton.

  3. Alterations in microbial community composition with increasing fCO2: a mesocosm study in the eastern Baltic Sea

    Directory of Open Access Journals (Sweden)

    K. J. Crawfurd

    2017-08-01

    Full Text Available Ocean acidification resulting from the uptake of anthropogenic carbon dioxide (CO2 by the ocean is considered a major threat to marine ecosystems. Here we examined the effects of ocean acidification on microbial community dynamics in the eastern Baltic Sea during the summer of 2012 when inorganic nitrogen and phosphorus were strongly depleted. Large-volume in situ mesocosms were employed to mimic present, future and far future CO2 scenarios. All six groups of phytoplankton enumerated by flow cytometry ( <  20 µm cell diameter showed distinct trends in net growth and abundance with CO2 enrichment. The picoeukaryotic phytoplankton groups Pico-I and Pico-II displayed enhanced abundances, whilst Pico-III, Synechococcus and the nanoeukaryotic phytoplankton groups were negatively affected by elevated fugacity of CO2 (fCO2. Specifically, the numerically dominant eukaryote, Pico-I, demonstrated increases in gross growth rate with increasing fCO2 sufficient to double its abundance. The dynamics of the prokaryote community closely followed trends in total algal biomass despite differential effects of fCO2 on algal groups. Similarly, viral abundances corresponded to prokaryotic host population dynamics. Viral lysis and grazing were both important in controlling microbial abundances. Overall our results point to a shift, with increasing fCO2, towards a more regenerative system with production dominated by small picoeukaryotic phytoplankton.

  4. Capnography: monitoring CO2.

    Science.gov (United States)

    Casey, Georgina

    2015-10-01

    MONITORING RESPIRATORY and metabolic function by using capnography to measure end tidal carbon dioxide is standard practice in anaesthesia. It is also becoming more common in intensive care units and during procedural sedation. End tidal carbon dioxide (EtCO2) monitoring may also be used to assess effectiveness of cardiopulmonary resuscitation. Capnography is now emerging in general medical and surgical wards to monitor respiratory depression in patients using opioid analgesics. Using EtCO2 to monitor respiratory function offers many benefits over pulse oximetry. It is important to understand the differences between these two monitoring methods, and why capnography is increasingly favoured in many situations. An understanding of the physiological processes involved in CO2 excretion allows nurses to use capnography in a safe and meaningful way, while monitoring at-risk patients in acute care.

  5. CO2-strategier

    DEFF Research Database (Denmark)

    Jørgensen, Michael Søgaard

    2008-01-01

    I 2007 henvendte Lyngby-Taarbæk kommunens Agenda 21 koordinator sig til Videnskabsbutikken og spurgte om der var interesse for at samarbejde om CO2-strategier. Da Videnskabsbutikken DTU er en åben dør til DTU for borgerne og deres organisationer, foreslog Videnskabsbutikken DTU at Danmarks...... Naturfredningsforening’s lokalkomité for Lyngby blev en del af samarbejdet for at få borgerne i kommunen involveret i arbejdet med at udvikle strategier for reduktion af CO2. Siden sommeren 2007 har Videnskabsbutikken DTU, Lyngby-Taarbæk kommune og Danmarks Naturfredningsforening i Lyngby-Taarbæk samarbejdet om analyse...... og innovation i forhold til CO2-strategier....

  6. CO2 cycle

    Science.gov (United States)

    Titus, Timothy N.; Byrne, Shane; Colaprete, Anthony; Forget, Francois; Michaels, Timothy I.; Prettyman, Thomas H.

    2017-01-01

    This chapter discusses the use of models, observations, and laboratory experiments to understand the cycling of CO2 between the atmosphere and seasonal Martian polar caps. This cycle is primarily controlled by the polar heat budget, and thus the emphasis here is on its components, including solar and infrared radiation, the effect of clouds (water- and CO2-ice), atmospheric transport, and subsurface heat conduction. There is a discussion about cap properties including growth and regression rates, albedos and emissivities, grain sizes and dust and/or water-ice contamination, and curious features like cold gas jets and araneiform (spider-shaped) terrain. The nature of the residual south polar cap is discussed as well as its long-term stability and ability to buffer atmospheric pressures. There is also a discussion of the consequences of the CO2 cycle as revealed by the non-condensable gas enrichment observed by Odyssey and modeled by various groups.

  7. Carbon sequestration by afforestation and revegetation as a means of limiting net-CO2 emissions in Iceland. COST E21 Workshop. Contribution of forests and forestry to mitigate greenhouse effects. Joensuu (Finland. 28-30 Sep 2000

    Directory of Open Access Journals (Sweden)

    Sigurdsson B.D.

    2000-01-01

    Full Text Available Iceland has lost about 95/ of its woodlands and 50/ of its vegetative cover during the 1,100 years of human settlement. Efforts to reclaim lost woodlands and herbaceous ecosystems have been continuing since the early 20th century. It is emphasised that for Icelandic conditions, effective carbon sequestration can be achieved by restoring (reclaiming herbaceous ecosystems on carbon-poor soils. Since 1990, about 4,000 ha per year have been afforested or revegetated. In 1995, the estimated C-sequestration of those areas was 65,100 t CO2, or 2.9/ of the national emissions for that year. In 1999, the estimated sequestration was up in 127,600 t CO2, or 4.7/ of the predicted CO2 emissions for the year 2000.

  8. The ins and outs of CO2.

    Science.gov (United States)

    Raven, John A; Beardall, John

    2016-01-01

    It is difficult to distinguish influx and efflux of inorganic C in photosynthesizing tissues; this article examines what is known and where there are gaps in knowledge. Irreversible decarboxylases produce CO2, and CO2 is the substrate/product of enzymes that act as carboxylases and decarboxylases. Some irreversible carboxylases use CO2; others use HCO3(-). The relative role of permeation through the lipid bilayer versus movement through CO2-selective membrane proteins in the downhill, non-energized, movement of CO2 is not clear. Passive permeation explains most CO2 entry, including terrestrial and aquatic organisms with C3 physiology and biochemistry, terrestrial C4 plants and all crassulacean acid metabolism (CAM) plants, as well as being part of some mechanisms of HCO3(-) use in CO2 concentrating mechanism (CCM) function, although further work is needed to test the mechanism in some cases. However, there is some evidence of active CO2 influx at the plasmalemma of algae. HCO3(-) active influx at the plasmalemma underlies all cyanobacterial and some algal CCMs. HCO3(-) can also enter some algal chloroplasts, probably as part of a CCM. The high intracellular CO2 and HCO3(-) pools consequent upon CCMs result in leakage involving CO2, and occasionally HCO3(-). Leakage from cyanobacterial and microalgal CCMs involves up to half, but sometimes more, of the gross inorganic C entering in the CCM; leakage from terrestrial C4 plants is lower in most environments. Little is known of leakage from other organisms with CCMs, though given the leakage better-examined organisms, leakage occurs and increases the energetic cost of net carbon assimilation. © The Author 2015. Published by Oxford University Press on behalf of the Society for Experimental Biology.

  9. The ins and outs of CO2

    Science.gov (United States)

    Raven, John A.; Beardall, John

    2016-01-01

    It is difficult to distinguish influx and efflux of inorganic C in photosynthesizing tissues; this article examines what is known and where there are gaps in knowledge. Irreversible decarboxylases produce CO2, and CO2 is the substrate/product of enzymes that act as carboxylases and decarboxylases. Some irreversible carboxylases use CO2; others use HCO3 –. The relative role of permeation through the lipid bilayer versus movement through CO2-selective membrane proteins in the downhill, non-energized, movement of CO2 is not clear. Passive permeation explains most CO2 entry, including terrestrial and aquatic organisms with C3 physiology and biochemistry, terrestrial C4 plants and all crassulacean acid metabolism (CAM) plants, as well as being part of some mechanisms of HCO3 – use in CO2 concentrating mechanism (CCM) function, although further work is needed to test the mechanism in some cases. However, there is some evidence of active CO2 influx at the plasmalemma of algae. HCO3 – active influx at the plasmalemma underlies all cyanobacterial and some algal CCMs. HCO3 – can also enter some algal chloroplasts, probably as part of a CCM. The high intracellular CO2 and HCO3 – pools consequent upon CCMs result in leakage involving CO2, and occasionally HCO3 –. Leakage from cyanobacterial and microalgal CCMs involves up to half, but sometimes more, of the gross inorganic C entering in the CCM; leakage from terrestrial C4 plants is lower in most environments. Little is known of leakage from other organisms with CCMs, though given the leakage better-examined organisms, leakage occurs and increases the energetic cost of net carbon assimilation. PMID:26466660

  10. On the nature of the oxygen uptake in the light by Chondrus crispus. Effects of inhibitors, temperature and light intensity.

    Science.gov (United States)

    Brechignac, F; Furbank, R T

    1987-01-01

    The nature of the different processes of O2 uptake involved in the light in the red macroalga Chondrus crispus Stackhouse (Rhodophyta, Gigartinales) was investigated. At limiting CO2, INH (2.5 mM) did not alter the O2 uptake rate. Glycolate was not excreted and did not accumulate within the cells. KCN reduced the rate of O2 uptake in the light by 76% at limiting CO2 and by 43% at saturating CO2, but caused > 95% inhibition of O2 evolution. DCMU (5 μM) totally blocked the photosynthetic electron transport chain, but allowed a residual O2 uptake of 3.0±0.6 μmol O2 .h(-1).g(-1) FW, irrespective of the CO2 concentration. In saturating CO2, a high light intensity pretreatment significantly stimulated the rate of O2 uptake compared to net O2 evolution, suggesting the persistence, in the light, of mitochondrial respiration. Irrespective of the CO2 concentration, the optimum temperature for O2 evolution was 17°C whereas dark O2 uptake increased linearly with temperature. In contrast, O2 uptake in the light showed an optimum at 17°C in limiting CO2, and 21-25° C in saturating CO2; its Q10 was 2.4 at limiting CO2, a value close to that of RuBP oxygenase, and 3.1 at saturating CO2, a value close to that of dark respiration. It is concluded that: 1) mitochondrial respiration and Mehler reaction are both involved at all CO2 concentrations, 2) RuBP oxygenase activity cannot account for more than 45%, and Mehler reaction for less than 20%, of the total O2 uptake observed in the light at limiting CO2.

  11. Year-round CH4 and CO2 flux dynamics in two contrasting freshwater ecosystems of the subarctic

    Directory of Open Access Journals (Sweden)

    M. Jammet

    2017-11-01

    Full Text Available Lakes and wetlands, common ecosystems of the high northern latitudes, exchange large amounts of the climate-forcing gases methane (CH4 and carbon dioxide (CO2 with the atmosphere. The magnitudes of these fluxes and the processes driving them are still uncertain, particularly for subarctic and Arctic lakes where direct measurements of CH4 and CO2 emissions are often of low temporal resolution and are rarely sustained throughout the entire year. Using the eddy covariance method, we measured surface–atmosphere exchange of CH4 and CO2 during 2.5 years in a thawed fen and a shallow lake of a subarctic peatland complex. Gas exchange at the fen exhibited the expected seasonality of a subarctic wetland with maximum CH4 emissions and CO2 uptake in summer, as well as low but continuous emissions of CH4 and CO2 throughout the snow-covered winter. The seasonality of lake fluxes differed, with maximum CO2 and CH4 flux rates recorded at spring thaw. During the ice-free seasons, we could identify surface CH4 emissions as mostly ebullition events with a seasonal trend in the magnitude of the release, while a net CO2 flux indicated photosynthetic activity. We found correlations between surface CH4 emissions and surface sediment temperature, as well as between diel CO2 uptake and diel solar input. During spring, the breakdown of thermal stratification following ice thaw triggered the degassing of both CH4 and CO2. This spring burst was observed in 2 consecutive years for both gases, with a large inter-annual variability in the magnitude of the CH4 degassing. On the annual scale, spring emissions converted the lake from a small CO2 sink to a CO2 source: 80 % of total annual carbon emissions from the lake were emitted as CO2. The annual total carbon exchange per unit area was highest at the fen, which was an annual sink of carbon with respect to the atmosphere. Continuous respiration during the winter partly counteracted the fen summer sink by accounting for

  12. Year-round CH4 and CO2 flux dynamics in two contrasting freshwater ecosystems of the subarctic

    Science.gov (United States)

    Jammet, Mathilde; Dengel, Sigrid; Kettner, Ernesto; Parmentier, Frans-Jan W.; Wik, Martin; Crill, Patrick; Friborg, Thomas

    2017-11-01

    Lakes and wetlands, common ecosystems of the high northern latitudes, exchange large amounts of the climate-forcing gases methane (CH4) and carbon dioxide (CO2) with the atmosphere. The magnitudes of these fluxes and the processes driving them are still uncertain, particularly for subarctic and Arctic lakes where direct measurements of CH4 and CO2 emissions are often of low temporal resolution and are rarely sustained throughout the entire year. Using the eddy covariance method, we measured surface-atmosphere exchange of CH4 and CO2 during 2.5 years in a thawed fen and a shallow lake of a subarctic peatland complex. Gas exchange at the fen exhibited the expected seasonality of a subarctic wetland with maximum CH4 emissions and CO2 uptake in summer, as well as low but continuous emissions of CH4 and CO2 throughout the snow-covered winter. The seasonality of lake fluxes differed, with maximum CO2 and CH4 flux rates recorded at spring thaw. During the ice-free seasons, we could identify surface CH4 emissions as mostly ebullition events with a seasonal trend in the magnitude of the release, while a net CO2 flux indicated photosynthetic activity. We found correlations between surface CH4 emissions and surface sediment temperature, as well as between diel CO2 uptake and diel solar input. During spring, the breakdown of thermal stratification following ice thaw triggered the degassing of both CH4 and CO2. This spring burst was observed in 2 consecutive years for both gases, with a large inter-annual variability in the magnitude of the CH4 degassing. On the annual scale, spring emissions converted the lake from a small CO2 sink to a CO2 source: 80 % of total annual carbon emissions from the lake were emitted as CO2. The annual total carbon exchange per unit area was highest at the fen, which was an annual sink of carbon with respect to the atmosphere. Continuous respiration during the winter partly counteracted the fen summer sink by accounting for, as both CH4 and CO2, 33

  13. CO2NSL (Datalogger)

    DEFF Research Database (Denmark)

    Andersen, Sune Sick

    ,1500 street lamps around Copenhagen will be changed for light sources with low power consumption. Technical and Environmental turn down the energy as a part of Copenhagen goal of reducing the citys CO2 emissions by 20 percent by the end of year 2015. But how much power will the new lamps comsume? And can...

  14. Use of sediment CO2 by submersed rooted plants.

    Science.gov (United States)

    Winkel, Anders; Borum, Jens

    2009-05-01

    Submersed plants have different strategies to overcome inorganic carbon limitation. It is generally assumed that only small rosette species (isoetids) are able to utilize the high sediment CO(2) availability. The present study examined to what extent five species of submersed freshwater plants with different morphology and growth characteristics (Lobelia dortmanna, Lilaeopsis macloviana, Ludwigia repens, Vallisneria americana and Hydrocotyle verticillata) are able to support photosynthesis supplied by uptake of CO(2) from the sediment. Gross photosynthesis was measured in two-compartment split chambers with low inorganic carbon availability in leaf compartments and variable CO(2) availability (0 to >8 mmol L(-1)) in root compartments. Photosynthetic rates based on root-supplied CO(2) were compared with maximum rates obtained at saturating leaf CO(2) availability, and (14)C experiments were conducted for two species to localize bottlenecks for utilization of sediment CO(2). All species except Hydrocotyle were able to use sediment CO(2), however, with variable efficiency, and with the isoetid, Lobelia, as clearly the most effective and the elodeid, Ludwigia, as the least efficient. At a water column CO(2) concentration in equilibrium with air, Lobelia, Lilaeopsis and Vallisneria covered >75% of their CO(2) requirements by sediment uptake, and sediment CO(2) contributed substantially to photosynthesis at water CO(2) concentrations up to 1000 micromol L(-1). For all species except Ludwigia, the shoot to root ratio on an areal basis was the single factor best explaining variability in the importance of sediment CO(2). For Ludwigia, diffusion barriers limited uptake or transport from roots to stems and transport from stems to leaves. Submersed plants other than isoetids can utilize sediment CO(2), and small and medium sized elodeids with high root to shoot area in particular may benefit substantially from uptake of sediment CO(2) in low alkaline lakes.

  15. Effects of free atmospheric CO2 enrichment (FACE), N fertilization and poplar genotype on the physical protection of carbon in the mineral soil of a poplar plantation after five years

    NARCIS (Netherlands)

    Hoosbeek, M.R.; Vos, J.M.; Bakker, E.J.; Scarascia-Mugnozza, G.

    2006-01-01

    Free air CO2 enrichment (FACE) experiments in aggrading forests and plantations have demonstrated significant increases in net primary production (NPP) and C storage in forest vegetation. The extra C uptake may also be stored in forest floor litter and in forest soil. After five years of FACE

  16. Projecting the CO2 and Climatic Change Effects on the Net Primary Productivity of the Urban Ecosystems in Phoenix, AZ in the 21st Century under Multiple RCP (Representative Concentration Pathway) Scenarios

    National Research Council Canada - National Science Library

    Chunbo Chen; Chi Zhang

    2017-01-01

    .... As a key indicator of ecological health, net primary productivity (NPP) provides valuable information about the performance of urban ecosystem in response to the changes in urban climate and atmosphere in the 21st century...

  17. Effects of elevated CO2 and increased nitrogen deposition on photosynthesis and growth of understory plants in spruce model ecosystems.

    Science.gov (United States)

    Hättenschwiler, Stephan; Körner, Christian

    1996-04-01

    We studied the effects of atmospheric CO2 enrichment (280, 420 and 560 μl CO2 l-1) and increased N deposition (0,30 and 90 kg ha-1 year-1) on the spruce-forest understory species Oxalis acetosella, Homogyne alpina and Rubus hirtus. Clones of these species formed the ground cover in nine 0.7 m2 model ecosystems with 5-year-old Picea abies trees (leaf area index of approx 2.2). Communities grew on natural forest soil in a simulated montane climate. Independently of N deposition, the rate of light-saturated net photosynthesis of leaves grown and measured at 420 μl CO2 l-1 was higher in Oxalis and in Homogyne, but was not significantly different in Rubus compared to leaves grown and measured at the pre-industrial CO2 concentration of 280 μl l-1. Remarkably, further CO2 enrichment to 560 μl l-1 caused no additional increase of CO2 uptake. With increasing CO2 supply concentrations of non-structural carbohydrates in leaves increased and N concentrations decreased in all species, whereas N deposition had no significant effect on these traits. Above-ground biomass and leaf area production were not significantly affected by elevated CO2 in the more vigorously growing species O. acetosella and R. hirtus, but the "slow growing" H. alpina produced almost twice as much biomass and 50% more leaf area per plant under 420 μl CO2 l-1 compared to 280 μl l-1 (again no further stimulation at 560 μl l-1). In contrast, increased N addition stimulated growth in Oxalis and Rubus but had no effect on Homogyne. In Oxalis (only) biomass per plant was positively correlated with microhabitat quantum flux density at low CO2, but not at high CO2 indicating carbon saturation. On the other hand, the less shade-tolerant Homogyne profited from CO2 enrichment at all understory light levels facilitating its spread into more shady micro-habitats under elevated CO2. These species-specific responses to CO2 and N deposition will affect community structure. The non-linear responses to elevated CO2 of

  18. Multispectral confocal microscopy images and artificial neural nets to monitor the photosensitizer uptake and degradation in Candida albicans cells

    Science.gov (United States)

    Romano, Renan A.; Pratavieira, Sebastião.; da Silva, Ana P.; Kurachi, Cristina; Guimarães, Francisco E. G.

    2017-07-01

    This study clearly demonstrates that multispectral confocal microscopy images analyzed by artificial neural networks provides a powerful tool to real-time monitoring photosensitizer uptake, as well as photochemical transformations occurred.

  19. Land Use Effects on Net Greenhouse Gas Fluxes in the US Great Plains: Historical Trends and Model Projections

    Science.gov (United States)

    Del Grosso, S. J.; Parton, W. J.; Ojima, D. S.; Mosier, A. R.; Mosier, A. R.; Paustian, K.; Peterson, G. A.

    2001-12-01

    We present maps showing regional patterns of land use change and soil C levels in the US Great Plains during the 20th century and time series of net greenhouse gas fluxes associated with different land uses. Net greenhouse gas fluxes were calculated by accounting for soil CO2 fluxes, the CO2 equivalents of N2O emissions and CH4 uptake, and the CO2 costs of N fertilizer production. Both historical and modern agriculture in this region have been net sources of greenhouse gases. The primary reason for this, prior to 1950, is that agriculture mined soil C and resulted in net CO2 emissions. When chemical N fertilizer became widely used in the 1950's agricultural soils began to sequester CO2-C but these soils were still net greenhouse gas sources if the effects of increased N2O emissions and decreased CH4 uptake are included. The sensitivity of net greenhouse gas fluxes to conventional and alternative land uses was explored using the DAYCENT ecosystem model. Model projections suggest that conversion to no-till, reduction of the fallow period, and use of nitrification inhibitors can significantly decrease net greenhouse gas emissions in dryland and irrigated systems, while maintaining or increasing crop yields.

  20. The unique rht-MOF platform, ideal for pinpointing the functionalization and CO 2 adsorption relationship

    KAUST Repository

    Luebke, Ryan

    2012-01-01

    The uniqueness of the rht-MOF platform, based on the singular (3,24)-connected net, allows for the facile design and synthesis of functionalized materials for desired applications. Here we designed a nitrogen-rich trefoil hexacarboxylate (trigonal tri-isophthalate) ligand, which serves to act as the trigonal molecular building block while concurrently coding the formation of the targeted truncated cuboctahedral supermolecular building block (in situ), and enhancing the CO 2 uptake in the resultant rht-MOF. © 2012 The Royal Society of Chemistry.

  1. Nitrogen Fertilization Modifies the Phenology of Ground CO2 Efflux in a Boreal Scots Pine Forest

    Science.gov (United States)

    Marshall, J. D.; Näsholm, T.; Linder, S.; Tarvainen, L.; Peichl, M.; Lundmark, T.

    2015-12-01

    Problems with the extraction of ecosystem respiration rates from eddy covariance data have led to renewed interest in chamber-based estimates of CO2 efflux from near the ground surface. However, chamber measurements frequently have their own issues. Here we describe the results of a study using large (≈2 m radius), transparent chambers over intact ground vegetation to describe the net efflux of CO2 and its environmental controls during the growing season at Rosinedal, a research site in northern Sweden. Measurements were made at thirty-minute intervals over the course of three growing seasons in a heavily fertilized and an unfertilized Scots pine stand. Ammonium nitrate was added at rates of 100 kg N ha-1 for the first five years, after which the rate was halved but the additions continued. The CO2 efflux results were simultaneously fitted to a nonlinear model describing the exponential increase in dark efflux with temperature, the Michaelis-Menten saturation of light-driven CO2 uptake in photosynthesis, the reduction in efflux due to soil drying, and a residual term that we ascribe to weekly shifts in the photosynthate partitioning of canopy trees to belowground processes. We found the expected exponential increase in dark efflux with temperature, however the net efflux in daytime was often negative, reflecting the high GPP of the ground vegetation, especially in dense canopies of bilberry (Vaccinium myrtillus L.). There was a clear reduction in dark efflux under dry conditions. The empirical phenology parameters increased sharply in early July, around the time that leaf expansion and rapid cambial growth were completed. This increase was more pronounced on the control plot than on the fertilized plot, consistent with expectations based on the notion that N fertilization should favor aboveground partitioning. The empirical "partitioning coefficient" shifted net efflux by nearly as much as the seasonal temperature range. Dark efflux of CO2 was nearly halved as a

  2. Global carbon - nitrogen - phosphorus cycle interactions: A key to solving the atmospheric CO2 balance problem?

    Science.gov (United States)

    Peterson, B. J.; Mellillo, J. M.

    1984-01-01

    If all biotic sinks of atmospheric CO2 reported were added a value of about 0.4 Gt C/yr would be found. For each category, a very high (non-conservative) estimate was used. This still does not provide a sufficient basis for achieving a balance between the sources and sinks of atmospheric CO2. The bulk of the discrepancy lies in a combination of errors in the major terms, the greatest being in a combination of errors in the major terms, the greatest being in the net biotic release and ocean uptake segments, but smaller errors or biases may exist in calculations of the rate of atmospheric CO2 increase and total fossil fuel use as well. The reason why biotic sinks are not capable of balancing the CO2 increase via nutrient-matching in the short-term is apparent from a comparison of the stoichiometry of the sources and sinks. The burning of fossil fuels and forest biomass releases much more CO2-carbon than is sequestered as organic carbon.

  3. Elevated CO2 enhances leaf senescence during extreme heat and drought in a temperate forest

    Energy Technology Data Exchange (ETDEWEB)

    Warren, Jeffrey [ORNL; Norby, Richard J [ORNL; Wullschleger, Stan D [ORNL

    2011-01-01

    In 2007, an extreme drought and acute heat wave damaged ecosystems across the southeastern US, including a 19-year-old Liquidambar styraciflua L. (sweetgum) tree plantation exposed to long-term elevated CO2 treatments. Stem sap velocities in trees exposed to ambient (A) or elevated (E) CO2 were analyzed to assess potential interactions between CO2 and these weather extremes. Leaf temperature (Tleaf) and net carbon uptake (GPP) were modeled based on patterns of sap velocity to estimate indirect impacts of CO2-reduced transpiration on premature leaf senescence. Elevated CO2 reduced sap flow by 28% during early summer, and by up to 45% late in the drought during record-setting high air temperatures. Canopy transpiration and conductance declined more rapidly in ECO2 plots, resulting in ECO2 Tleaf up to 45 C, which was 1-2 C greater than ACO2 Tleaf. Pre-drought GPP was ~7% greater in ECO2 plots, then declined to 30% less than ACO2 GPP as the drought progressed. Leaf abscission peaked during this period, and was 30% greater for ECO2 trees. While ECO2 can reduce leaf-level water use under droughty conditions, acute drought or heat conditions may induce excessive stomatal closure that could offset benefits of ECO2 to temperate forest species during extreme weather events.

  4. Physiographic position modulates the influence of temperature and precipitation as controls over leaf and ecosystem level CO2 flux in shrubland ecosystems

    Science.gov (United States)

    Barron-Gafford, G. A.; Scott, R. L.; Jenerette, G. D.; Hamerlynck, E. P.; Huxman, T. E.

    2010-12-01

    Conversion of semiarid grasslands to shrublands may alter the sensitivity of CO2 exchange of both the dominant plants and the entire ecosystem to variation in air temperature and precipitation. We used a combination of leaf-level gas exchange experimentation and ecosystem-level eddy covariance monitoring techniques to quantify the temperature sensitivity of a riparian and upland shrubland across seasonal periods of differing precipitation input in southeastern Arizona, USA. Maximum rates of net CO2 uptake were estimated from a Lorentzian peak function fitted to net uptake plotted against air temperature, with optimum temperature being that at which maximum uptake occurred. The convexity of the temperature response function was quantified by the range of temperatures over which a leaf or an ecosystem assimilated 50% and 75% of maximum net CO2 uptake. We quantified the temperature response of both the dominant vegetative components within both semiarid shrublands of differing physiographic position and the ecosystems themselves to examine how temperature sensitivity varies with access to stable groundwater. By repeatedly measuring CO2 uptake across a wide range of temperatures and estimating soil respiration, we quantified the temperature sensitivity of these systems, computed changes in those responses due to periods of precipitation input, and estimated the role of component fluxes in driving ecosystem-scale responses. We found that having a connectivity to stable groundwater sources decoupled leaf-and ecosystem-scale temperature sensitivity relative to comparable sites lacking such access. Access to groundwater not only resulted in the temperature sensitivity of the riparian shrubland being nearly half that of the upland throughout all seasonal periods, but also actual rates of net ecosystem productivity (NEP) being 1.5X greater when precipitation was relatively abundant and five times greater when it was not. Maxima rates of NEP were nine times more responsive to

  5. Scrub-Oak Biomass Stimulation by CO2 Enrichment: Sustained 11 Years But Mediated by Precipitation and Contrasting Species Responses

    Science.gov (United States)

    Seiler, T.; Li, J.; Dijkstra, P.; Anderson, H.; Johnson, D.; Hinkle, R.; Drake, B.

    2007-12-01

    Terrestrial ecosystems may mitigate rising atmospheric carbon dioxide concentration (CO2) through increased carbon uptake and sequestration in plant biomass. Elevated CO2 commonly produces initial stimulation of photosynthesis and growth, but due primarily to complex interactions with climate related factors (i.e. water, light and nutrients), uncertainty regarding long-term biomass response persists. After 11 years of CO2 enrichment (ambient and ambient + 350 ppm) using open-top chambers, aboveground biomass stimulation was sustained in a Florida scrub-oak ecosystem, yielding a 67% increase at final harvest in June 2007. The scrub oaks Quercus geminata and Quercus myrtifolia represented 85% of total ecosystem aboveground biomass but displayed contrasting responses to elevated CO2. Q. myrtifolia showed consistent increase in shoot biomass over the course of the study (128% stimulation by elevated CO2) while shoot biomass of Q. geminata was not significantly increased (+6% difference between treatments). Both species displayed long-term mean stimulation of net leaf photosynthesis to elevated CO2 under saturated light conditions: stimulation of photosynthesis in Q. myrtifolia was nearly twice that in Q. geminata (63% and 35%, respectively). Over the course of the study, Q. geminata consistently displayed photosynthetic acclimation via reductions in maximum carboxylation rate (Vcmax) and maximum rate of electron transport (Jmax) while Q. myrtifolia photosynthesis did not acclimate to elevated CO2. Inter-annual variation in Q. myrtifolia annual biomass increment was correlated with rainfall and elevated CO2 stimulation of absolute biomass accumulation was greatest in wet years. This effect was muted at the ecosystem level because CO2 stimulation of biomass in Q. geminata, which utilizes the water table to a greater extent than Q. myrtifolia, showed no relationship with rainfall. These advantages afforded to Q. myrtifolia by elevated CO2 produced a significant change in

  6. Non-photosynthetic enhancement of growth by high CO2 level in the nitrophilic seaweed Ulva rigida C. Agardh (Chlorophyta).

    Science.gov (United States)

    Gordillo, F J; Niell, F X; Figueroa, F L

    2001-05-01

    The effects of increased CO2 levels (10,000 microl l(-1)) in cultures of the green nitrophilic macroalga Ulva rigida C. Agardh were tested under conditions of N saturation and N limitation, using nitrate as the only N source. Enrichment with CO2 enhanced growth, while net photosynthesis, gross photosynthesis, dark respiration rates and soluble protein content decreased. The internal C pool remained constant at high CO2, while the assimilated C that was released to the external medium was less than half the values obtained under ambient CO2 levels. This higher retention of C provided the source for extra biomass production under N saturation. In N-sufficient thalli, nitrate-uptake rate and the activity of nitrate reductase (EC 1.6.6.1) increased under high CO2 levels. This did not affect the N content or the internal C:N balance, implying that the extra N-assimilation capacity led to the production of new biomass in proportion to C. Growth enhancement by increased level of CO2 was entirely dependent on the enhancement effect of CO2 on N-assimilation rates. The increase in nitrate reductase activity at high CO2 was not related to soluble carbohydrates or internal C. This indicates that the regulation of N assimilation by CO2 in U. rigida might involve a different pathway from that proposed for higher plants. The role of organic C release as an effective regulatory mechanism maintaining the internal C:N balance in response to different CO2 levels is discussed.

  7. Biological soil crusts as key drivers for CO2 fluxes in semiarid ecosystems

    Science.gov (United States)

    Chamizo, Sonia; Miralles, Isabel; Rodríguez-Caballero, Emilio; Ortega, Raúl; Ladrón de Guevara, Mónica; Luna, Lourdes; Cantón, Yolanda

    2014-05-01

    , these CO2 emissions were compensated, during several days following the rain, by CO2 fixation through photosynthesis, thus resulting in a positive net flux or net uptake of CO2. However, differences were observed between BSC types. Moss-dominated BSCs, regardless being more developed than cyanobacteria and lichen BSCs, showed lower net photosynthesis rates because of their higher respiration rates. These findings support the idea that BSCs act as important C sinks during the periods when they are active, although the rate of CO2 assimilation may greatly depend on the type of BSC. The results of this study demonstrate the need to consider the effect of different types of BSC in C balance models on local to global scales to improve our knowledge on C quantification and to make more accurate predictions of the effects of climate change in arid and semiarid regions where this type of soil cover is a key ecosystem component.

  8. Downregulation of net phosphorus-uptake capacity is inversely related to leaf phosphorus-resorption proficiency in four species from a phosphorus-impoverished environment.

    Science.gov (United States)

    de Campos, Mariana C R; Pearse, Stuart J; Oliveira, Rafael S; Lambers, Hans

    2013-03-01

    Previous research has suggested a trade-off between the capacity of plants to downregulate their phosphorus (P) uptake capacity and their efficiency of P resorption from senescent leaves in species from P-impoverished environments. To investigate this further, four Australian native species (Banksia attenuata, B. menziesii, Acacia truncata and A. xanthina) were grown in a greenhouse in nutrient solutions at a range of P concentrations [P]. Acacia plants received between 0 and 500 µm P; Banksia plants received between 0 and 10 µm P, to avoid major P-toxicity symptoms in these highly P-sensitive species. For both Acacia species, the net P-uptake rates measured at 10 µm P decreased steadily with increasing P supply during growth. In contrast, in B. attenuata, the net rate of P uptake from a solution with 10 µm P increased linearly with increasing P supply during growth. The P-uptake rate of B. menziesii showed no significant response to P supply in the growing medium. Leaf [P] of the four species supported this finding, with A. truncata and A. xanthina showing an increase up to a saturation value of 19 and 21 mg P g(-1) leaf dry mass, respectively (at 500 µm P), whereas B. attenuata and B. menziesii both exhibited a linear increase in leaf [P], reaching 10 and 13 mg P g(-1) leaf dry mass, respectively, without approaching a saturation point. The Banksia plants grown at 10 µm P showed mild symptoms of P toxicity, i.e. yellow spots on some leaves and drying and curling of the tips of the leaves. Leaf P-resorption efficiency was 69 % (B. attenuata), 73 % (B. menziesii), 34 % (A. truncata) and 36 % (A. xanthina). The P-resorption proficiency values were 0·08 mg P g(-1) leaf dry mass (B. attenuata and B. menziesii), 0·32 mg P g(-1) leaf dry mass (A. truncata) and 0·36 mg P g(-1) leaf dry mass (A. xanthina). Combining the present results with additional information on P-remobilization efficiency and the capacity to downregulate P-uptake capacity for two other

  9. No snow for Christmas: the impact of the 2015 extreme winter on CO2 fluxes in European mountain grasslands

    Science.gov (United States)

    Cremonese, Edoardo; Galvagno, Marta; Hammerle, Albin; Filippa, Gianluca; Wohlfahrt, Georg

    2016-04-01

    The increasing frequency in extreme climate events is very likely to impact the Alps since this region is characterized by very sensitive ecosystems. Typical alpine ecosystems such as mountain grasslands, show a strong seasonality in carbon uptake and release mostly driven by the onset and the end of the snow season. Extreme climate events, such as long warm and/or dry periods, could change typical snow cover temporal pattern, thereby altering the duration of the period of CO2 uptake and release. In recent years many studies have analyzed the impact of delayed or anticipated snowmelt on alpine plant phenology, growth and carbon cycling. However, little is known on the effects of a delayed onset of the snow season. During 2015 the whole planet witnessed several record-breaking warm spells which exceptionally warmed the Alps where the temperature anomaly reached +4°C during both the autumn and winter periods. In particular, the onset of the 2015 winter in the Alps was marked by one of the most prolonged lack of snow in years. In this study, we investigate and discuss the impact of the altered temperature and precipitation pattern during the autumn/winter 2015 on the net ecosystem CO2 exchange of mountain grasslands at high and low altitudes measured by means of the eddy covariance method. In particular we test the following hypotheses: (i) The presence of a snowpack impedes plant photosynthesis, while without a snowpack, plant net CO2 uptake may be possible even during wintertime provided temperatures are warm enough. (ii) Below a snowpack, soil temperatures are around zero degrees Celsius, allowing for microbial activity resulting in intermediate soil respiration; without a snow cover soil temperatures may be either lower or higher than zero degrees Celsius, decreasing or increasing soil respiration. The magnitude and direction of the net ecosystem CO2 exchange of mountain grassland ecosystems is governed by the complex interplay of the factors addressed in

  10. Air-Sea CO2 fluxes on the Scotian Shelf: seasonal to multi-annual variability

    Directory of Open Access Journals (Sweden)

    J. E. Salisbury

    2010-11-01

    Full Text Available We develop an algorithm to compute pCO2 in the Scotian Shelf region (NW Atlantic from satellite-based estimates of chlorophyll-a concentration, sea-surface temperature, and observed wind speed. This algorithm is based on a high-resolution time-series of pCO2 observations from an autonomous mooring. At the mooring location (44.3° N and 63.3° W, the surface waters act as a source of CO2 to the atmosphere over the annual scale, with an outgassing of −1.1 mol C m−2 yr−1 in 2007/2008. A hindcast of air-sea CO2 fluxes from 1999 to 2008 reveals significant variability both spatially and from year to year. Over the decade, the shelf-wide annual air-sea fluxes range from an outgassing of −1.70 mol C m−2 yr−1 in 2002, to −0.02 mol C m−2 yr−1 in 2006. There is a gradient in the air-sea CO2 flux between the northeastern Cabot Strait region which acts as a net sink of CO2 with an annual uptake of 0.50 to 1.00 mol C m−2 yr−1, and the southwestern Gulf of Maine region which acts as a source ranging from −0.80 to −2.50 mol C m−2 yr−1. There is a decline, or a negative trend, in the air-sea pCO2 gradient of 23 μatm over the decade, which can be explained by a cooling of 1.3 °C over the same period. Regional conditions govern spatial, seasonal, and interannual variability on the Scotian Shelf, while multi-annual trends appear to be influenced by larger scale processes.

  11. Calibration and application of B/Ca, Cd/Ca, and δ11B in Neogloboquadrina pachyderma (sinistral) to constrain CO2 uptake in the subpolar North Atlantic during the last deglaciation

    Science.gov (United States)

    Yu, Jimin; Thornalley, David J. R.; Rae, James W. B.; McCave, Nick I.

    2013-06-01

    The North Atlantic and Norwegian Sea are prominent sinks of atmospheric CO2 today, but their roles in the past remain poorly constrained. In this study, we attempt to use B/Ca and δ11B ratios in the planktonic foraminifera Neogloboquadrina pachyderma (sinistral variety) to reconstruct subsurface water pH and pCO2 changes in the polar North Atlantic during the last deglaciation. Comparison of core-top results with nearby hydrographic data shows that B/Ca in N. pachyderma (s) is mainly controlled by seawater B(OH)4-/HCO3- with a roughly constant partition coefficient KD=B>/CaCaCO3BOH 4->/HCO3>¯seawater of 1.48 ± 0.15 × 10-3 (2σ), and δ11B in this species is offset below δ11B of the borate in seawater by 3.38 ± 0.71‰ (2σ). These values represent our best estimates with the sparse available hydrographic data close to our core-tops. More culturing and sediment trap work is needed to improve our understanding of boron incorporation into N. pachyderma (s). Application of a constant KD of 1.48 × 10-3 to high resolution N. pachyderma (s) B/Ca records from two adjacent cores off Iceland shows that subsurface pCO2 at the habitat depth of N. pachyderma (s) ( 50 m) generally followed the atmospheric CO2 trend but with negative offsets of 10-50 ppmv during 19-10 ka. These B/Ca-based reconstructions are supported by independent estimates from low-resolution δ11B measurements in the same cores. We also calibrate and apply Cd/Ca in N. pachyderma (s) to reconstruct nutrient levels for the same down cores. Like today's North Atlantic, past subsurface pCO2 variability off Iceland was significantly correlated with nutrient changes that might be linked to surface nutrient utilization and mixing within the upper water column. Because surface pCO2 (at 0 m water depth) is always lower than at deeper depths and if the application of a constant KD is valid, our results suggest that the polar North Atlantic has remained a CO2 sink during the calcification seasons of N. pachyderma

  12. Variability of annual CO2 exchange from Dutch grasslands

    Directory of Open Access Journals (Sweden)

    A. Schrier-Uijl

    2007-10-01

    .3% and 486 gC m−2 a−1 (34.8%, respectively. However, the inter-site standard deviation of NEE was similar to the interannual one, amounting to 207 gC m−2 a−1. Large differences occur due to soil type. The grasslands on organic (peat soils show a mean net release of CO2 of 220±90 g C m−2 a−1 while the grasslands on mineral (clay and sand soils show a mean net uptake of CO2 of 90±90 g C m−2 a−1. If a weighing with the fraction of grassland on organic (20% and mineral soils (80% is applied, an average NEE of 28 ±90 g C m−2 a−1 is found. The results from the analysis illustrate the need for regionally specific and spatially explicit CO2 emission estimates from grassland.

  13. Regional assimilation of CO2 and δ13C surface data to assess terrestrial biosphere models under drought stress

    Science.gov (United States)

    van der Velde, I. R.; Miller, J. B.; Alden, C. B.; Andrews, A. E.; Schaefer, K. M.; Peters, W.; Tans, P. P.; Vaughn, B. H.; White, J. W. C.

    2016-12-01

    Observed atmospheric carbon dioxide (CO2) and the ratios of its stable isotopologue 13CO2/12CO2 (δ13C) contain unique signals of large-scale drought stress that affect the biosphere. When plants experience physiological stress due to heat and drought at leaf level they respond by closing their stomata. This is a safety mechanism that prevents excessive water loss at the expense of carbon uptake, and it changes the overall water-use efficiency. During photosynthesis, 12CO2 is preferentially assimilated over 13CO2, leaving the atmosphere enriched in 13CO2. Water stress slightly changes the ratio of 13CO2 and 12CO2 molecules being removed from the atmosphere, i.e., a reduction of canopy isotope discrimination (Δ), and its changes are evident in atmospheric δ13C.To improve our understanding of the coupled vegetation-atmosphere system we are developing an ensemble Kalman filter assimilation of high precision measurements of CO2 and δ13C from air samples collected over North America. It uses footprints provided by WRF-STILT that allows for efficient atmospheric transport simulations on a much higher horizontal resolution than with a global Eulerian transport model. To force consistency with atmospheric CO2 and δ13C observations we will optimize regional net terrestrial CO2 exchange (NEE) and Δ from a terrestrial biosphere model. We will carefully evaluate the sensitivity of the optimized parameters to uncertainties in the terrestrial biosphere fluxes, observations, time/space aggregation methods, and boundary conditions. Our main questions are: (i) what signal-to-noise in the data, as interpreted by the model, is large enough to robustly estimate Δ and NEE? and (ii) how do the optimized NEE and Δ that are based on the atmospheric constraint compare with the predicted NEE and Δ that are based on biophysical parameterizations? Our ability to accurately predict the responses of the terrestrial biosphere to changing humidity and soil moisture regimes is currently

  14. Land Use Effects on Atmospheric C-13 Imply a Sizable Terrestrial CO2 Sink in Tropical Latitudes

    Science.gov (United States)

    Townsend, Alan R.; Asner, Gregory P.; Tans, Pieter P.; White, James W. C.

    2000-01-01

    Records of atmospheric CO2 and 13-CO2, can be used to distinguish terrestrial vs. oceanic exchanges of CO2 with the atmosphere. However, this approach has proven difficult in the tropics, partly due to extensive land conversion from C-3 to C-4 vegetation. We estimated the effects of such conversion on biosphere-atmosphere C-13 exchange for 1991 through 1999, and then explored how this 'land-use disequilibrium' altered the partitioning of net atmospheric CO2 exchanges between ocean and land using NOAA-CMDL data and a 2D, zonally averaged atmospheric transport model. Our results show sizable CO2 uptake in C-3-dominated tropical regions in seven of the nine years; 1997 and 1998, which included a strong ENSO event, are near neutral. Since these fluxes include any deforestation source, our findings imply either that such sources are smaller than previously estimated, and/or the existence of a large terrestrial CO2 sink in equatorial latitudes.

  15. How much CO2 does vegetation capture in tropical cities? Case study of a residential neighborhood in Singapore

    Science.gov (United States)

    Velasco, E.; Roth, M.; Tan, S.; Quak, M.; Seth, N.; Norford, L.

    2012-12-01

    Urban vegetation might have an important role in reducing the CO2 emitted by anthropogenic activities in cities, particularly in cities with extensive and/or evergreen vegetation. In a few urban sites negative daytime CO2 fluxes during the growing season have been observed. These sites correspond to suburban neighborhoods with abundant vegetation and low population density. Usually urban surfaces are net sources of CO2 modulated in some cases by vegetation during daytime. A direct and accurate estimation of carbon uptake by urban vegetation is a difficult task due to the particular characteristics of the urban ecosystem and high variability in tree distribution and species. Here, we investigate the role of urban vegetation in the CO2 flux from a residential neighborhood in Singapore using two different approaches. CO2 fluxes measured directly by eddy covariance were compared with emissions estimated by emissions factors and activity data. The latter includes contributions from vehicular traffic, household combustion, soil respiration and human breathing. The difference between estimated emissions and measured fluxes should primarily correspond to the biogenic flux. Independently, a tree survey was conducted to estimate the annual CO2 sequestration using allometric equations and an alternative model of the theory of metabolic ecology for tropical forests. This model predicts the biomass growth rate of woody trees as a function of their size. Palm trees were also included in the survey, but their annual CO2 uptake was obtained from growth curves/rates published in the literature. Both approaches suggest that vegetation captures between 5% and 8% of the CO2 emitted in this neighborhood. Annual uptakes of 510 and 324 ton km-2 were obtained from the difference between measured fluxes and estimated emissions, and the approach based on allometric equations, respectively. The difference between both approaches can be due to uncertainties in the emissions estimates and

  16. Effects of permafrost melting on CO2 and CH4 exchange of a poorly drained black spruce lowland

    Science.gov (United States)

    Wickland, K.P.; Striegl, R.G.; Neff, J.C.; Sachs, T.

    2006-01-01

    Permafrost melting is occurring in areas of the boreal forest region where large amounts of carbon (C) are stored in organic soils. We measured soil respiration, net CO2 flux, and net CH4 flux during May-September 2003 and March 2004 in a black spruce lowland in interior Alaska to better understand how permafrost thaw in poorly drained landscapes affects land-atmosphere CO2 and CH4 exchange. Sites included peat soils underlain by permafrost at ???0.4 m depth (permafrost plateau, PP), four thermokarst wetlands (TW) having no permafrost in the upper 2.2 m, and peat soils bordering the thermokarst wetlands having permafi7ost at ???0.5 in depth (thermokarst edges, TE). Soil respiration rates were not significantly different among the sites, and 5-cm soil temperature explained 50-91% of the seasonal variability in soil respiration within the sites. Groundcover vegetation photosynthesis (calculated as net CO2 minus soil respiration) was significantly different among the sites (TW > TE > PP), which can be partly attributed to the difference in photosynthetically active radiation reaching the ground at each site type. Methane emission rates were 15 to 28 times greater fi7om TW than from TE and PP. We modeled annual soil respiration and groundcover vegetation photosynthesis using soil temperature and radiation data, and CH4 flux by linear interpolation. We estimated all sites as net C gas sources to the atmosphere (not including tree CO2 uptake at PP and TE), although the ranges in estimates when accounting for errors were large enough that TE and TW may have been net C sinks. Copyright 2006 by the American Geophysical Union.

  17. Simulated effect of calcification feedback on atmospheric CO2 and ocean acidification

    Science.gov (United States)

    Zhang, Han; Cao, Long

    2016-01-01

    Ocean uptake of anthropogenic CO2 reduces pH and saturation state of calcium carbonate materials of seawater, which could reduce the calcification rate of some marine organisms, triggering a negative feedback on the growth of atmospheric CO2. We quantify the effect of this CO2-calcification feedback by conducting a series of Earth system model simulations that incorporate different parameterization schemes describing the dependence of calcification rate on saturation state of CaCO3. In a scenario with SRES A2 CO2 emission until 2100 and zero emission afterwards, by year 3500, in the simulation without CO2-calcification feedback, model projects an accumulated ocean CO2 uptake of 1462 PgC, atmospheric CO2 of 612 ppm, and surface pH of 7.9. Inclusion of CO2-calcification feedback increases ocean CO2 uptake by 9 to 285 PgC, reduces atmospheric CO2 by 4 to 70 ppm, and mitigates the reduction in surface pH by 0.003 to 0.06, depending on the form of parameterization scheme used. It is also found that the effect of CO2-calcification feedback on ocean carbon uptake is comparable and could be much larger than the effect from CO2-induced warming. Our results highlight the potentially important role CO2-calcification feedback plays in ocean carbon cycle and projections of future atmospheric CO2 concentrations. PMID:26838480

  18. Forecasting global atmospheric CO2

    Science.gov (United States)

    Agustí-Panareda, A.; Massart, S.; Chevallier, F.; Boussetta, S.; Balsamo, G.; Beljaars, A.; Ciais, P.; Deutscher, N. M.; Engelen, R.; Jones, L.; Kivi, R.; Paris, J.-D.; Peuch, V.-H.; Sherlock, V.; Vermeulen, A. T.; Wennberg, P. O.; Wunch, D.

    2014-11-01

    A new global atmospheric carbon dioxide (CO2) real-time forecast is now available as part of the pre-operational Monitoring of Atmospheric Composition and Climate - Interim Implementation (MACC-II) service using the infrastructure of the European Centre for Medium-Range Weather Forecasts (ECMWF) Integrated Forecasting System (IFS). One of the strengths of the CO2 forecasting system is that the land surface, including vegetation CO2 fluxes, is modelled online within the IFS. Other CO2 fluxes are prescribed from inventories and from off-line statistical and physical models. The CO2 forecast also benefits from the transport modelling from a state-of-the-art numerical weather prediction (NWP) system initialized daily with a wealth of meteorological observations. This paper describes the capability of the forecast in modelling the variability of CO2 on different temporal and spatial scales compared to observations. The modulation of the amplitude of the CO2 diurnal cycle by near-surface winds and boundary layer height is generally well represented in the forecast. The CO2 forecast also has high skill in simulating day-to-day synoptic variability. In the atmospheric boundary layer, this skill is significantly enhanced by modelling the day-to-day variability of the CO2 fluxes from vegetation compared to using equivalent monthly mean fluxes with a diurnal cycle. However, biases in the modelled CO2 fluxes also lead to accumulating errors in the CO2 forecast. These biases vary with season with an underestimation of the amplitude of the seasonal cycle both for the CO2 fluxes compared to total optimized fluxes and the atmospheric CO2 compared to observations. The largest biases in the atmospheric CO2 forecast are found in spring, corresponding to the onset of the growing season in the Northern Hemisphere. In the future, the forecast will be re-initialized regularly with atmospheric CO2 analyses based on the assimilation of CO2 products retrieved from satellite measurements and

  19. Climate-dependent CO2 emissions from lakes

    Science.gov (United States)

    Kosten, Sarian; Roland, FáBio; da Motta Marques, David M. L.; van Nes, Egbert H.; Mazzeo, NéStor; Sternberg, Leonel Da S. L.; Scheffer, Marten; Cole, Jon J.

    2010-06-01

    Inland waters, just as the world's oceans, play an important role in the global carbon cycle. While lakes and reservoirs typically emit CO2, they also bury carbon in their sediment. The net CO2 emission is largely the result of the decomposition or preservation of terrestrially supplied carbon. What regulates the balance between CO2 emission and carbon burial is not known, but climate change and temperature have been hypothesized to influence both processes. We analyzed patterns in carbon dioxide partial pressure (pCO2) in 83 shallow lakes over a large climatic gradient in South America and found a strong, positive correlation with temperature. The higher pCO2 in warmer lakes may be caused by a higher, temperature-dependent mineralization of organic carbon. This pattern suggests that cool lakes may start to emit more CO2 when they warm up because of climate change.

  20. Effect of Injecting Hydrogen Peroxide into Heavy Clay Loam Soil on Plant Water Status, NET CO2 Assimilation, Biomass, and Vascular Anatomy of Avocado Trees Efecto de la Inyección de Peróxido de Hidrógeno en Suelo Franco Arcilloso Pesado, sobre el Estado Hídrico, Asimilación Neta de CO2, Biomasa y Anatomía Vascular de Paltos

    Directory of Open Access Journals (Sweden)

    Pilar M Gil M

    2009-03-01

    Full Text Available In Chile, avocado (Persea americana Mill. orchards are often located in poorly drained, low-oxygen soils, situation which limits fruit production and quality. The objective of this study was to evaluate the effect of injecting soil with hydrogen peroxide (H2O2 as a source of molecular oxygen, on plant water status, net CO2 assimilation, biomass and anatomy of avocado trees set in clay loam soil with water content maintained at field capacity. Three-year-old ‘Hass’ avocado trees were planted outdoors in containers filled with heavy loam clay soil with moisture content sustained at field capacity. Plants were divided into two treatments, (a H2O2 injected into the soil through subsurface drip irrigation and (b soil with no H2O2 added (control. Stem and root vascular anatomical characteristics were determined for plants in each treatment in addition to physical soil characteristics, net CO2 assimilation (A, transpiration (T, stomatal conductance (gs, stem water potential (SWP, shoot and root biomass, water use efficiency (plant biomass per water applied [WUEb]. Injecting H2O2 into the soil significantly increased the biomass of the aerial portions of the plant and WUEb, but had no significant effect on measured A, T, gs, or SWP. Xylem vessel diameter and xylem/phloem ratio tended to be greater for trees in soil injected with H2O2 than for controls. The increased biomass of the aerial portions of plants in treated soil indicates that injecting H2O2 into heavy loam clay soils may be a useful management tool in poorly aerated soil.En Chile, los huertos de palto (Persea americana Mill. se ubican comúnmente en suelos pobremente drenados con bajo contenido de oxígeno, lo que limita producción y calidad de fruta. El objetivo de este estudio fue evaluar el efecto de la inyección de peróxido de hidrógeno (H2O2 al suelo como fuente de O2, sobre el estado hídrico, asimilación de CO2, biomasa y anatomía de paltos en suelo franco arcilloso con

  1. CO2 as a refrigerant

    CERN Document Server

    2014-01-01

    A first edition, the IIR guide “CO2 as a Refrigerant” highlights the application of carbon dioxide in supermarkets, industrial freezers, refrigerated transport, and cold stores as well as ice rinks, chillers, air conditioning systems, data centers and heat pumps. This guide is for design and development engineers needing instruction and inspiration as well as non-technical experts seeking background information on a specific topic. Written by Dr A.B. Pearson, a well-known expert in the field who has considerable experience in the use of CO2 as a refrigerant. Main topics: Thermophysical properties of CO2 – Exposure to CO2, safety precautions – CO2 Plant Design – CO2 applications – Future prospects – Standards and regulations – Bibliography.

  2. Transient nature of CO2 fertilization in Arctic tundra

    Science.gov (United States)

    Oechel, Walter C.; Cowles, Sid; Grulke, Nancy; Hastings, Steven J.; Lawrence, Bill; Prudhomme, Tom; Riechers, George; Strain, Boyd; Tissue, David; Vourlitis, George

    1994-10-01

    THERE has been much debate about the effect of increased atmospheric CO2 concentrations on plant net primary production1,3 and on net ecosystem CO2 flux3-10. Apparently conflicting experimental findings could be the result of differences in genetic potential11-15 and resource availability16-20, different experimental conditions21-24 and the fact that many studies have focused on individual components of the system2,21,25-27 rather than the whole ecosystem. Here we present results of an in situ experiment on the response of an intact native ecosystem to elevated CO2. An undisturbed patch of tussock tundra at Toolik Lake, Alaska, was enclosed in greenhouses in which the CO2 level, moisture and temperature could be controlled28, and was subjected to ambient (340 p.p.m.) and elevated (680 p.p.m.) levels of CO2 and temperature (+4 °C). Air humidity, precipitation and soil water table were maintained at ambient control levels. For a doubled CO2 level alone, complete homeostasis of the CO2 flux was re-established within three years, whereas the regions exposed to a combination of higher temperatures and doubled CO2 showed persistent fertilization effect on net ecosystem carbon sequestration over this time. This difference may be due to enhanced sink activity from the direct effects of higher temperatures on growth16,29-33 and to indirect effects from enhanced nutrient supply caused by increased mineralization10,11,19,27,34. These results indicate that the responses of native ecosystems to elevated CO2 may not always be positive, and are unlikely to be straightforward. Clearly, CO2 fertilization effects must always be considered in the context of genetic limitation, resource availability and other such factors.

  3. A Data Base of Nutrient Use, Water Use, CO2 Exchange, and Ethylene Production by Soybeans in a Controlled Environment

    Science.gov (United States)

    Wheeler, R. M.; Mackowiak, C. L.; Peterson, B. V.; Sager, J. C.; Knott, W. M.; Berry, W. L.; Sharifi, M. R.

    1998-01-01

    A data set is given describing daily nutrient and water uptake, carbon dioxide (CO2) exchange, ethylene production, and carbon and nutrient partitioning from a 20 sq m stand of soybeans (Glycine max (L.) Merr. cv. McCall] for use in bioregenerative life support systems. Stand CO2 exchange rates were determined from nocturnal increases in CO2 (respiration) and morning drawdowns (net photosynthesis) to a set point of 1000 micromol/ mol each day (i.e., a closed system approach). Atmospheric samples were analyzed throughout growth for ethylene using gas chromatography with photoionization detection (GC/PH)). Water use was monitored by condensate production from the humidity control system, as well as water uptake from the nutrient solution reservoirs each day. Nutrient uptake data were determined from daily additions of stock solution and acid to maintain an EC of 0.12 S/m and pH of 5.8. Dry mass yields of seeds, pods (without seeds), leaves, stems, and roots are provided, as well as elemental and proximate nutritional compositions of the tissues. A methods section is included to qualify any assumptions that might be required for the use of the data in plant growth models, along with a daily event calendar documenting set point adjustments and the occasional equipment or sensor failure.

  4. Stopped-Flow Spectrophotometric Study of the Kinetics and Mechanism of CO2 Uptake by cis-[Cr(C2O4(BaraNH2(OH22]+ Cation and the Acid-Catalyzed Decomposition of cis-[Cr(C2O4(BaraNH2OCO2]− Anion in Aqueous Solution

    Directory of Open Access Journals (Sweden)

    Lech Chmurzyński

    2011-09-01

    Full Text Available The kinetics of CO2 uptake by the cis-[Cr(C2O4(BaraNH2(OH22]+ complex cation and the acid hydrolysis of the cis-[Cr(C2O4(BaraNH2OCO2]− complex anion (where BaraNH2 denotes methyl 3-amino-2,3-dideoxy-b-D-arabino-hexopyranoside were studied using the stopped-flow technique. The reactions under study were investigated in aqueous solution in the 288–308 K temperature range. In the case of the reaction between CO2 and cis-[Cr(C2O4(BaraNH2(OH22]+ cation variable pH values (6.82–8.91 and the constant ionic strength of solution (H+, Na+, ClO4− = 1.0 were used. Carbon dioxide was generated by the reaction between sodium pyruvate and hydrogen peroxide. The acid hydrolysis of cis-[Cr(C2O4(BaraNH2OCO2]− was investigated for varying concentrations of H+ ions (0.01–2.7 M. The obtained results enabled the determination of the number of steps of the studied reactions. Based on the kinetic equations, rate constants were determined for each step. Finally, mechanisms for both reactions were proposed and discussed. Based on the obtained results it was concluded that the carboxylation (CO2 uptake reactions of cis-[Cr(C2O4(BaraNH2(OH22]+ and the decarboxylation (acid hydrolysis of the cis-[Cr(C2O4(BaraNH2OCO2]− are the opposite of each other.

  5. Highly efficient CO2 sorbents: development of synthetic, calcium-rich dolomites.

    Science.gov (United States)

    Filitz, Rainer; Kierzkowska, Agnieszka M; Broda, Marcin; Müller, Christoph R

    2012-01-03

    The reaction of CaO with CO(2) is a promising approach for separating CO(2) from hot flue gases. The main issue associated with the use of naturally occurring CaCO(3), that is, limestone, is the rapid decay of its CO(2) capture capacity over repeated cycles of carbonation and calcination. Interestingly, dolomite, a naturally occurring equimolar mixture of CaCO(3) and MgCO(3), possesses a CO(2) uptake that remains almost constant with cycle number. However, owing to the large quantity of MgCO(3) in dolomite, the total CO(2) uptake is comparatively small. Here, we report the development of a synthetic Ca-rich dolomite using a coprecipitation technique, which shows both a very high and a stable CO(2) uptake over repeated cycles of calcination and carbonation. To obtain such an excellent CO(2) uptake characteristic it was found to be crucial to mix the Ca(2+) and Mg(2+) on a molecular level, that is, within the crystalline lattice. For sorbents which were composed of mixtures of microscopic crystals of CaCO(3) and MgCO(3), a decay behavior similar to natural limestone was observed. After 15 cycles, the CO(2) uptake of the best sorbent was 0.51 g CO(2)/g sorbent exceeding the CO(2) uptake of limestone by almost 100%.

  6. Enzymes in CO2 Capture

    DEFF Research Database (Denmark)

    Fosbøl, Philip Loldrup; Gladis, Arne; Thomsen, Kaj

    The enzyme Carbonic Anhydrase (CA) can accelerate the absorption rate of CO2 into aqueous solutions by several-fold. It exist in almost all living organisms and catalyses different important processes like CO2 transport, respiration and the acid-base balances. A new technology in the field...... of carbon capture is the application of enzymes for acceleration of typically slow ternary amines or inorganic carbonates. There is a hidden potential to revive currently infeasible amines which have an interesting low energy consumption for regeneration but too slow kinetics for viable CO2 capture. The aim...... of this work is to discuss the measurements of kinetic properties for CA promoted CO2 capture solvent systems. The development of a rate-based model for enzymes will be discussed showing the principles of implementation and the results on using a well-known ternary amine for CO2 capture. Conclusions...

  7. CO2 Sequestration short course

    Energy Technology Data Exchange (ETDEWEB)

    DePaolo, Donald J. [Lawrence Berkeley National Laboratory; Cole, David R [The Ohio State University; Navrotsky, Alexandra [University of California-Davis; Bourg, Ian C [Lawrence Berkeley National Laboratory

    2014-12-08

    Given the public’s interest and concern over the impact of atmospheric greenhouse gases (GHGs) on global warming and related climate change patterns, the course is a timely discussion of the underlying geochemical and mineralogical processes associated with gas-water-mineral-interactions encountered during geological sequestration of CO2. The geochemical and mineralogical processes encountered in the subsurface during storage of CO2 will play an important role in facilitating the isolation of anthropogenic CO2 in the subsurface for thousands of years, thus moderating rapid increases in concentrations of atmospheric CO2 and mitigating global warming. Successful implementation of a variety of geological sequestration scenarios will be dependent on our ability to accurately predict, monitor and verify the behavior of CO2 in the subsurface. The course was proposed to and accepted by the Mineralogical Society of America (MSA) and The Geochemical Society (GS).

  8. Positive feedback between increasing atmospheric CO2 and ecosystem productivity

    Science.gov (United States)

    Gelfand, I.; Hamilton, S. K.; Robertson, G. P.

    2009-12-01

    Increasing atmospheric CO2 will likely affect both the hydrologic cycle and ecosystem productivity. Current assumptions that increasing CO2 will lead to increased ecosystem productivity and plant water use efficiency (WUE) are driving optimistic predictions of higher crop yields as well as greater availability of freshwater resources due to a decrease in evapotranspiration. The plant physiological response that drives these effects is believed to be an increase in carbon uptake either by (a) stronger CO2 gradient between the stomata and the atmosphere, or by (b) reduced CO2 limitation of enzymatic carboxylation within the leaf. The (a) scenario will lead to increased water use efficiency (WUE) in plants. However, evidence for increased WUE is mostly based on modeling studies, and experiments producing a short duration or step-wise increase in CO2 concentration (e.g. free-air CO2 enrichment). We hypothesize that the increase in atmospheric CO2 concentration is having a positive effect on ecosystem productivity and WUE. To investigate this hypothesis, we analyzed meteorological, ANPP, and soil CO2 flux datasets together with carbon isotopic ratio (13C/12C) of archived plant samples from the long term ecological research (LTER) program at Kellogg Biological Station. The datasets were collected between 1989 and 2007 (corresponding to an increase in atmospheric CO2 concentration of ~33 ppmv at Mauna Loa). Wheat (Triticum aestivum) samples taken from 1989 and 2007 show a significant decrease in the C isotope discrimination factor (Δ) over time. Stomatal conductance is directly related to Δ, and thus Δ is inversely related to plant intrinsic WUE (iWUE). Historical changes in the 13C/12C ratio (δ13C) in samples of a perennial forb, Canada goldenrod (Solidago canadensis), taken from adjacent successional fields, indicate changes in Δ upon uptake of CO2 as well. These temporal trends in Δ suggest a positive feedback between the increasing CO2 concentration in the

  9. CARNOL PROCESS FOR CO2 MITIGATION FROM POWER PLANTS AND THE TRANSFORMATION SECTOR

    Science.gov (United States)

    The report describes an alternative mitigation process that would convert waste carbon dioxide (CO2) to carbon an methanol using natural gas as process feedstock. The process yields 1 mole of methanol from each mole of CO2 recovered, resulting in a net zero CO2 emission when the ...

  10. Survey report of FY 1997 on the trends of novel CO2 fixation technology using bacteria and microalgae; 1997 nendo chosa hokokusho (saikin sorui wo riyoshita atarashii nisanka tanso kotei gijutsu no doko chosa)

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1998-03-01

    For this survey, the latest technology trends relating to microbial functions are summarized to recover and effectively utilize CO2, typical greenhouse effect gas, using microbial functions. Systematic survey and analysis are conducted concerning the microorganisms useful for fixing CO2, CO2 uptake mechanism during the microbial reactions, utilization methods of solar light and useful energy sources except solar light, highly efficient production of useful materials, and usage of produced useful materials. Research has concentrated on use of biological activities for this purpose through design of bioreactors using microorganisms (bacteria and microalgae) for efficient CO2 fixation. For the process to have net CO2 fixation as assessed by its life cycle and to make the process economically feasible, it is essential not only to fix CO2 merely in the form of biomass but in addition to convert it to useful materials by the catalytic activities of the organisms. Three categories were set for the survey, i.e., microorganisms with CO2 fixation ability, available energy for CO2 fixation, and target CO2 fixation products. 169 refs., 49 figs., 14 tabs.

  11. CO2 emissions from German drinking water reservoirs.

    Science.gov (United States)

    Saidi, Helmi; Koschorreck, Matthias

    2017-03-01

    Globally, reservoirs are a significant source of atmospheric CO2. However, precise quantification of greenhouse gas emissions from drinking water reservoirs on the regional or national scale is still challenging. We calculated CO2 fluxes for 39 German drinking water reservoirs during a period of 22years (1991-2013) using routine monitoring data in order to quantify total emission of CO2 from drinking water reservoirs in Germany and to identify major drivers. All reservoirs were a net CO2 source with a median flux of 167gCm-2y-1, which makes gaseous emissions a relevant process for the carbon budget of each reservoir. Fluxes varied seasonally with median fluxes of 13, 48, and 201gCm-2y-1 in spring, summer, and autumn respectively. Differences between reservoirs appeared to be primarily caused by the concentration of CO2 in the surface water rather than by the physical gas transfer coefficient. Consideration of short term fluctuations of the gas transfer coefficient due to varying wind speed had only a minor effect on the annual budgets. High CO2 emissions only occurred in reservoirs with pHemissions correlated exponentially with pH but not with dissolved organic carbon (DOC). There was significant correlation between land use in the catchment and CO2 emissions. In total, German drinking water reservoirs emit 44000t of CO2 annually, which makes them a negligible CO2 source (emissions) in Germany. Copyright © 2017 Elsevier B.V. All rights reserved.

  12. Implications of overestimated anthropogenic CO2 emissions on East Asian and global land CO2 flux inversion

    Science.gov (United States)

    Saeki, Tazu; Patra, Prabir K.

    2017-12-01

    Measurement and modelling of regional or country-level carbon dioxide (CO2) fluxes are becoming critical for verification of the greenhouse gases emission control. One of the commonly adopted approaches is inverse modelling, where CO2 fluxes (emission: positive flux, sink: negative flux) from the terrestrial ecosystems are estimated by combining atmospheric CO2 measurements with atmospheric transport models. The inverse models assume anthropogenic emissions are known, and thus the uncertainties in the emissions introduce systematic bias in estimation of the terrestrial (residual) fluxes by inverse modelling. Here we show that the CO2 sink increase, estimated by the inverse model, over East Asia (China, Japan, Korea and Mongolia), by about 0.26 PgC year-1 (1 Pg = 1012 g) during 2001-2010, is likely to be an artifact of the anthropogenic CO2 emissions increasing too quickly in China by 1.41 PgC year-1. Independent results from methane (CH4) inversion suggested about 41% lower rate of East Asian CH4 emission increase during 2002-2012. We apply a scaling factor of 0.59, based on CH4 inversion, to the rate of anthropogenic CO2 emission increase since the anthropogenic emissions of both CO2 and CH4 increase linearly in the emission inventory. We find no systematic increase in land CO2 uptake over East Asia during 1993-2010 or 2000-2009 when scaled anthropogenic CO2 emissions are used, and that there is a need of higher emission increase rate for 2010-2012 compared to those calculated by the inventory methods. High bias in anthropogenic CO2 emissions leads to stronger land sinks in global land-ocean flux partitioning in our inverse model. The corrected anthropogenic CO2 emissions also produce measurable reductions in the rate of global land CO2 sink increase post-2002, leading to a better agreement with the terrestrial biospheric model simulations that include CO2-fertilization and climate effects.

  13. Elevated CO2 decreases the Photorespiratory NH3 production but does not decrease the NH3 compensation point in rice leaves.

    Science.gov (United States)

    Miyazawa, Shin-Ichi; Hayashi, Kentaro; Nakamura, Hirofumi; Hasegawa, Toshihiro; Miyao, Mitsue

    2014-09-01

    The exchange of gaseous NH3 between the atmosphere and plants plays a pivotal role in controlling the global NH3 cycle. Photorespiration generates NH3 through oxygenation instead of carboxylation by the CO2-fixing enzyme, ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBisCO). The future increase in the atmospheric CO2 concentration, [CO2], is expected to reduce plant NH3 production by suppressing RuBisCO oxygenation (Vo). We measured the net leaf NH3 uptake rate (FNH3) across NH3 concentrations in the air (na) ranging from 0.2 to 1.6 nmol mol(-1) at three [CO2] values (190, 360 and 750 µmol mol(-1)) using rice plants. We analyzed leaf NH3 gas exchange using a custom-made whole-leaf chamber system, and determined the NH3 compensation point (γ), a measure of potential NH3 emission, as the x-intercept of the linear relationship of FNH3 as a function of na. Our γ values were lower than those reported for other plant species. γ did not decrease under elevated [CO2], although leaf NH4 (+) content decreased with decreasing Vo at higher [CO2]. This was also the case for γ estimated from the pH and NH4 (+) concentration of the leaf apoplast solution (γ'). γ' of rice plants, grown at elevated [CO2] for months in a free-air CO2 enrichment facility, was also not decreased by elevated [CO2]. These results suggest that suppression of RuBisCO oxygenation by elevated [CO2] does not decrease potential leaf NH3 emission in rice plants. © The Author 2014. Published by Oxford University Press on behalf of Japanese Society of Plant Physiologists. All rights reserved. For permissions, please email: journals.permissions@oup.com.

  14. Microbial dissolution of calcite at T = 28 °C and ambient pCO 2

    Science.gov (United States)

    Jacobson, Andrew D.; Wu, Lingling

    2009-04-01

    This study used batch reactors to quantify the mechanisms and rates of calcite dissolution in the presence and absence of a single heterotrophic bacterial species ( Burkholderia fungorum). Experiments were conducted at T = 28°C and ambient pCO 2 over time periods spanning either 21 or 35 days. Bacteria were supplied with minimal growth media containing either glucose or lactate as a C source, NH 4+ as an N source, and H 2PO 4- as a P source. Combining stoichiometric equations for microbial growth with an equilibrium mass-balance model of the H 2O-CO 2-CaCO 3 system demonstrates that B. fungorum affected calcite dissolution by modifying pH and alkalinity during utilization of ionic N and C species. Uptake of NH 4+ decreased pH and alkalinity, whereas utilization of lactate, a negatively charged organic anion, increased pH and alkalinity. Calcite in biotic glucose-bearing reactors dissolved by simultaneous reaction with H 2CO 3 generated by dissolution of atmospheric CO 2 (H 2CO 3 + CaCO 3 → Ca 2+ + 2HCO 3-) and H + released during NH 4+ uptake (H + + CaCO 3 → Ca 2+ + HCO 3-). Reaction with H 2CO 3 and H + supplied ˜45% and 55% of the total Ca 2+ and ˜60% and 40% of the total HCO 3-, respectively. The net rate of microbial calcite dissolution in the presence of glucose and NH 4+ was ˜2-fold higher than that observed for abiotic control experiments where calcite dissolved only by reaction with H 2CO 3. In lactate bearing reactors, most H + generated by NH 4+ uptake reacted with HCO 3- produced by lactate oxidation to yield CO 2 and H 2O. Hence, calcite in biotic lactate-bearing reactors dissolved by reaction with H 2CO 3 at a net rate equivalent to that calculated for abiotic control experiments. This study suggests that conventional carbonate equilibria models can satisfactorily predict the bulk fluid chemistry resulting from microbe-calcite interactions, provided that the ionic forms and extent of utilization of N and C sources can be constrained. Because

  15. Simulating Remediation of CO2 Leakage from Geological Storage Sites

    Science.gov (United States)

    Zhang, Y.; Oldenburg, C. M.; Benson, S. M.

    2003-12-01

    One strategy to reduce net greenhouse gas emissions is to inject carbon dioxide (CO2) deep into subsurface formations where presumably it would be stored indefinitely. Although geologic storage formations will be carefully selected, CO2 injected into a target formation may unexpectedly migrate upwards and ultimately seep out at the ground surface, creating a potential hazard to human beings and ecosystems. In this case, CO2 that has leaked from the geologic storage site is considered a contaminant, and remediation strategies such as passive venting and active pumping are needed. The purpose of this study is to investigate remediation strategies for CO2 leakage from geologic storage sites. We use the integral finite-difference code TOUGH2 to simulate the remediation of CO2 in subsurface systems. We consider the components of water, CO2 and air, and model flow and transport in aqueous and gas phases subject to a variety of initial and boundary conditions including passive venting and active pumping. We have investigated the time it takes for a gas plume of CO2 to be removed from the vadose zone both by natural attenuation processes and by active extraction wells. The time for removal is parameterized in terms of a CO2 plume half-life, defined as the time required for one-half of the CO2 mass to be removed. Initial simulations show that barometric pressure fluctuations enhance the removal of CO2 from the vadose zone, but that CO2 trapped near the water table is difficult to remove by either passive or active remediation approaches. This work was supported by a Cooperative Research and Development Agreement (CRADA) between BP Corporation North America, as part of the CO2 Capture Project (CCP), and the U.S. Department of Energy (DOE) through the National Energy Technologies Laboratory (NETL), and by the U.S. Department of Energy under contract DE-AC03-76SF00098.

  16. Development of sustainable CO2 conversion processes for the methanol production

    DEFF Research Database (Denmark)

    Roh, Kosan; Nguyen, Tuan B.H.; Suriyapraphadilok, Uthaiporn

    2015-01-01

    Utilization of CO2 feedstock through CO2 conversion for producing valuable chemicals as an alternative to sequestration of the captured CO2 is attracting increasing attention in recent studies. Indeed, the methanol production process via thermochemical CO2 conversion reactions is considered a prime...... considered. The two methanol plants are developed using Aspen Plus®, the commercial process simulator. The net CO2 flows and methanol production costs are evaluated using ECON® and compared with those of the conventional methanol plant, which uses two-stage reforming. It is verified that the combined...... reforming process has to be integrated with the existing conventional methanol plant to obtain a reduced CO2 emission as well as lowered production costs. On the other hand, the CO2 hydrogenation based methanol plant could achieve a reduction of net CO2 emission at a reasonable production cost only...

  17. Deep CO2 soil inhalation / exhalation induced by synoptic pressure changes and atmospheric tides in a carbonated semiarid steppe

    Directory of Open Access Journals (Sweden)

    E. P. Sánchez-Cañete

    2013-10-01

    Full Text Available Knowledge of all the mechanisms and processes involved in soil CO2 emissions is essential to close the global carbon cycle. Apart from molecular diffusion, the main physical component of such CO2 exchange is soil ventilation. Advective CO2 transport, through soil or snow, has been correlated with the wind speed, friction velocity or pressure (p. Here we examine variations in subterranean CO2 molar fractions (χc over two years within a vertical profile (1.5 m in a semiarid ecosystem, as influenced by short-timescale p changes. Analyses to determine the factors involved in the variations in subterranean χc were differentiated between the growing period and the dry period. In both periods it was found that variations in deep χc (0.5–1.5 m were due predominantly to static p variations and not to wind or biological influences. Within a few hours, the deep χc can vary by fourfold, showing a pattern with two cycles per day, due to p oscillations caused by atmospheric tides. By contrast, shallow χc (0.15 m generally has one cycle per day as influenced by biological factors like soil water content and temperature in both periods, while the wind was an important factor in shallow χc variations only during the dry period. Evidence of emissions was registered in the atmospheric boundary layer by eddy covariance during synoptic pressure changes when subterranean CO2 was released; days with rising barometric pressure – when air accumulated belowground, including soil-respired CO2 – showed greater ecosystem uptake than days with falling pressure. Future assessments of the net ecosystem carbon balance should not rely exclusively on Fick's law to calculate soil CO2 effluxes from profile data.

  18. Connecting CO2. Feasibility study CO2 network Southwest Netherlands; Connecting CO2. Haalbaarheidsstudie CO2-netwerk Zuidwest-Nederland

    Energy Technology Data Exchange (ETDEWEB)

    Rutten, M.

    2009-06-10

    An overview is given of supply and demand of CO2 in the region Southwest Netherlands and the regions Antwerp and Gent in Belgium. Also attention is paid to possible connections between these regions [Dutch] Een inventarisatie wordt gegeven van vraag en aanbod van CO2 in de regio Zuidwest- Nederland en de regios Antwerpen en Gent in Belgie. Ook worden mogelijke koppelingen tussen de regios besproken.

  19. Reducing CO2 from shipping – do non-CO2 effects matter?

    Directory of Open Access Journals (Sweden)

    M. S. Eide

    2013-04-01

    yr. The major ship types show significant differences in the short-term radiative forcing. For instance, the direct SO4 forcing from tankers is 30% higher than for container and bulk. The net long-term effects on RF are similar due to similar CO2 forcing. We assess an emission scenario where the reduction inventory is sustained on the fleet as it steadily diminishes over time due to scrapping and disappears in 2040. We find a net temperature increase lasting until approximately 2080. We conclude that changes in non-CO2 emission does matter significantly if reductions of CO2 emissions are made on the year 2010 cargo shipping fleet. In sum, we find that emission changes motivated by CO2 reductions in shipping will be beneficial from a long-term climate perspective, and that there are positive environmental and health effects identified as concentrations of key short-lived pollutants are reduced.

  20. Altered Carbon Isotope Discrimination of C3 Plants Under Very High pCO2 Levels

    Science.gov (United States)

    Panetta, R. J.; Schubert, B.; Jahren, H.

    2009-12-01

    . We speculate that this decreased variability may reflect fundamentally altered patterns of net carbon uptake, which then affect net isotopic fractionation. A.H. Jahren, N.C. Arens and S.A. Harbeson, 2008. Prediction of atmospheric δ13CO2 using fossil plant tissues. Reviews of Geophysics, 46/2006RG0002. H. Poorter and E. Garnier, 1996. Plant growth analysis: an evaluation of experimental design and computational methods. Journal of Experimental Botany, 47/1343-1351.

  1. Method for tracing simulated CO2 leak in terrestrial environment with a 13CO2 tracer

    Science.gov (United States)

    Moni, Christophe; Rasse, Daniel

    2013-04-01

    recorded at the surface following a (60 x 60 cm) grid sampling pattern. Finally, at the end of the growing season the oats crop was harvested following a (50x50 cm) grid sampling pattern and each collected cereal bundle was tested for its isotopic signature. Results showed that the isotopic monitoring of the simulated CO2 leaks enabled to characterize finely the 3 dimensional extent of the leak within the soil-atmosphere continuum, including the assimilation of leaking CO2 by the vegetation. Acknowlegment RISCS is funded by the EC 7th Framework Programme and by industry partners ENEL I&I, Statoil, Vattenfall AB, E.ON and RWE. R&D partners are BGS, CERTH, IMARES, OGS, PML, SINTEF, University of Nottingham, Sapienza Università di Roma, Quintessa, CO2GeoNet, Bioforsk, BGR and ZERO. Four R&D institutes outside Europe participate in RISCS: CO2CRC from Australia, University of Regina from Canada and Montana State and Stanford Universities from the USA. For more information please go to the website (www.riscs-co2.eu) or contact the project coordinator David Jones (e-mail: dgj@bgs.ac.uk tel. + 44 (0)115 936 3576).

  2. A Quantitative Investigation of CO2 Sequestration by Mineral Carbonation

    CERN Document Server

    Mohammad, Muneer

    2015-01-01

    Anthropogenic activities have led to a substantial increase in carbon dioxide (CO2), a greenhouse gas (GHG), contributing to heightened concerns of global warming. In the last decade alone CO2 emissions increased by 2.0 ppm/yr. globally. In the year 2009, United States and China contributed up to 43.4% of global CO2 emissions. CO2 capture and sequestration have been recognized as promising solutions to mitigate CO2 emissions from fossil fuel based power plants. Typical techniques for carbon capture include post-combustion capture, pre-combustion capture and oxy-combustion capture, which are under active research globally. Mineral carbonation has been investigated as a suitable technique for long term storage of CO2. Sequestration is a highly energy intensive process and the additional energy is typically supplied by the power plant itself. This leads to a reduction in net amount of CO2 captured because of extra CO2 emitted. This paper presents a quantitative analysis of the energy consumption during sequestra...

  3. Efficient electrochemical CO2 conversion powered by renewable energy.

    Science.gov (United States)

    Kauffman, Douglas R; Thakkar, Jay; Siva, Rajan; Matranga, Christopher; Ohodnicki, Paul R; Zeng, Chenjie; Jin, Rongchao

    2015-07-22

    The catalytic conversion of CO2 into industrially relevant chemicals is one strategy for mitigating greenhouse gas emissions. Along these lines, electrochemical CO2 conversion technologies are attractive because they can operate with high reaction rates at ambient conditions. However, electrochemical systems require electricity, and CO2 conversion processes must integrate with carbon-free, renewable-energy sources to be viable on larger scales. We utilize Au25 nanoclusters as renewably powered CO2 conversion electrocatalysts with CO2 → CO reaction rates between 400 and 800 L of CO2 per gram of catalytic metal per hour and product selectivities between 80 and 95%. These performance metrics correspond to conversion rates approaching 0.8-1.6 kg of CO2 per gram of catalytic metal per hour. We also present data showing CO2 conversion rates and product selectivity strongly depend on catalyst loading. Optimized systems demonstrate stable operation and reaction turnover numbers (TONs) approaching 6 × 10(6) molCO2 molcatalyst(-1) during a multiday (36 h total hours) CO2 electrolysis experiment containing multiple start/stop cycles. TONs between 1 × 10(6) and 4 × 10(6) molCO2 molcatalyst(-1) were obtained when our system was powered by consumer-grade renewable-energy sources. Daytime photovoltaic-powered CO2 conversion was demonstrated for 12 h and we mimicked low-light or nighttime operation for 24 h with a solar-rechargeable battery. This proof-of-principle study provides some of the initial performance data necessary for assessing the scalability and technical viability of electrochemical CO2 conversion technologies. Specifically, we show the following: (1) all electrochemical CO2 conversion systems will produce a net increase in CO2 emissions if they do not integrate with renewable-energy sources, (2) catalyst loading vs activity trends can be used to tune process rates and product distributions, and (3) state-of-the-art renewable-energy technologies are sufficient

  4. El Niño Southern Oscillation (ENSO enhances CO2 exchange rates in freshwater Marsh ecosystems in the Florida everglades.

    Directory of Open Access Journals (Sweden)

    Sparkle L Malone

    Full Text Available This research examines the relationships between El Niño Southern Oscillation (ENSO, water level, precipitation patterns and carbon dioxide (CO2 exchange rates in the freshwater wetland ecosystems of the Florida Everglades. Data was obtained over a 5-year study period (2009-2013 from two freshwater marsh sites located in Everglades National Park that differ in hydrology. At the short-hydroperiod site (Taylor Slough; TS and the long-hydroperiod site (Shark River Slough; SRS fluctuations in precipitation patterns occurred with changes in ENSO phase, suggesting that extreme ENSO phases alter Everglades hydrology which is known to have a substantial influence on ecosystem carbon dynamics. Variations in both ENSO phase and annual net CO2 exchange rates co-occurred with changes in wet and dry season length and intensity. Combined with site-specific seasonality in CO2 exchanges rates, El Niño and La Niña phases magnified season intensity and CO2 exchange rates at both sites. At TS, net CO2 uptake rates were higher in the dry season, whereas SRS had greater rates of carbon sequestration during the wet season. As La Niña phases were concurrent with drought years and extended dry seasons, TS became a greater sink for CO2 on an annual basis (-11 to -110 g CO2 m-2 yr-1 compared to El Niño and neutral years (-5 to -43.5 g CO2 m-2 yr-1. SRS was a small source for CO2 annually (1.81 to 80 g CO2 m-2 yr-1 except in one exceptionally wet year that was associated with an El Niño phase (-16 g CO2 m-2 yr-1. Considering that future climate predictions suggest a higher frequency and intensity in El Niño and La Niña phases, these results indicate that changes in extreme ENSO phases will significantly alter CO2 dynamics in the Florida Everglades.

  5. El Niño Southern Oscillation (ENSO) enhances CO2 exchange rates in freshwater Marsh ecosystems in the Florida everglades.

    Science.gov (United States)

    Malone, Sparkle L; Staudhammer, Christina L; Oberbauer, Steven F; Olivas, Paulo; Ryan, Michael G; Schedlbauer, Jessica L; Loescher, Henry W; Starr, Gregory

    2014-01-01

    This research examines the relationships between El Niño Southern Oscillation (ENSO), water level, precipitation patterns and carbon dioxide (CO2) exchange rates in the freshwater wetland ecosystems of the Florida Everglades. Data was obtained over a 5-year study period (2009-2013) from two freshwater marsh sites located in Everglades National Park that differ in hydrology. At the short-hydroperiod site (Taylor Slough; TS) and the long-hydroperiod site (Shark River Slough; SRS) fluctuations in precipitation patterns occurred with changes in ENSO phase, suggesting that extreme ENSO phases alter Everglades hydrology which is known to have a substantial influence on ecosystem carbon dynamics. Variations in both ENSO phase and annual net CO2 exchange rates co-occurred with changes in wet and dry season length and intensity. Combined with site-specific seasonality in CO2 exchanges rates, El Niño and La Niña phases magnified season intensity and CO2 exchange rates at both sites. At TS, net CO2 uptake rates were higher in the dry season, whereas SRS had greater rates of carbon sequestration during the wet season. As La Niña phases were concurrent with drought years and extended dry seasons, TS became a greater sink for CO2 on an annual basis (-11 to -110 g CO2 m-2 yr-1) compared to El Niño and neutral years (-5 to -43.5 g CO2 m-2 yr-1). SRS was a small source for CO2 annually (1.81 to 80 g CO2 m-2 yr-1) except in one exceptionally wet year that was associated with an El Niño phase (-16 g CO2 m-2 yr-1). Considering that future climate predictions suggest a higher frequency and intensity in El Niño and La Niña phases, these results indicate that changes in extreme ENSO phases will significantly alter CO2 dynamics in the Florida Everglades.

  6. Photosynthetic responses to elevated CO(2) and O(3) in Quercus ilex leaves at a natural CO(2) spring.

    Science.gov (United States)

    Paoletti, E; Seufert, G; Della Rocca, G; Thomsen, H

    2007-06-01

    Photosynthetic stimulation and stomatal conductance (Gs) depression in Quercus ilex leaves at a CO(2) spring suggested no down-regulation. The insensitivity of Gs to a CO(2) increase (from ambient 1500 to 2000 micromol mol(-1)) suggested stomatal acclimation. Both responses are likely adaptations to the special environment of CO(2) springs. At the CO(2)-enriched site, not at the control site, photosynthesis decreased 9% in leaves exposed to 2x ambient O(3) concentrations in branch enclosures, compared to controls in charcoal-filtered air. The stomatal density reduction at high CO(2) was one-third lower than the concomitant Gs reduction, so that the O(3) uptake per single stoma was lower than at ambient CO(2). No significant variation in monoterpene emission was measured. Higher trichome and mesophyll density were recorded at the CO(2)-enriched site, accounting for lower O(3) sensitivity. A long-term exposure to H(2)S, reflected by higher foliar S-content, and CO(2) might depress the antioxidant capacity of leaves close to the vent and increase their O(3) sensitivity.

  7. Modelling the diurnal and seasonal dynamics of soil CO2 exchange in a semiarid ecosystem with high plant–interspace heterogeneity

    Directory of Open Access Journals (Sweden)

    J. Gong

    2018-01-01

    Full Text Available We used process-based modelling to investigate the roles of carbon-flux (C-flux components and plant–interspace heterogeneities in regulating soil CO2 exchanges (FS in a dryland ecosystem with sparse vegetation. To simulate the diurnal and seasonal dynamics of FS, the modelling considered simultaneously the CO2 production, transport and surface exchanges (e.g. biocrust photosynthesis, respiration and photodegradation. The model was parameterized and validated with multivariate data measured during the years 2013–2014 in a semiarid shrubland ecosystem in Yanchi, northwestern China. The model simulation showed that soil rewetting could enhance CO2 dissolution and delay the emission of CO2 produced from rooting zone. In addition, an ineligible fraction of respired CO2 might be removed from soil volumes under respiration chambers by lateral water flows and root uptakes. During rewetting, the lichen-crusted soil could shift temporally from net CO2 source to sink due to the activated photosynthesis of biocrust but the restricted CO2 emissions from subsoil. The presence of plant cover could decrease the root-zone CO2 production and biocrust C sequestration but increase the temperature sensitivities of these fluxes. On the other hand, the sensitivities of root-zone emissions to water content were lower under canopy, which may be due to the advection of water flows from the interspace to canopy. To conclude, the complexity and plant–interspace heterogeneities of soil C processes should be carefully considered to extrapolate findings from chamber to ecosystem scales and to predict the ecosystem responses to climate change and extreme climatic events. Our model can serve as a useful tool to simulate the soil CO2 efflux dynamics in dryland ecosystems.

  8. Modelling the diurnal and seasonal dynamics of soil CO2 exchange in a semiarid ecosystem with high plant-interspace heterogeneity

    Science.gov (United States)

    Gong, Jinnan; Wang, Ben; Jia, Xin; Feng, Wei; Zha, Tianshan; Kellomäki, Seppo; Peltola, Heli

    2018-01-01

    We used process-based modelling to investigate the roles of carbon-flux (C-flux) components and plant-interspace heterogeneities in regulating soil CO2 exchanges (FS) in a dryland ecosystem with sparse vegetation. To simulate the diurnal and seasonal dynamics of FS, the modelling considered simultaneously the CO2 production, transport and surface exchanges (e.g. biocrust photosynthesis, respiration and photodegradation). The model was parameterized and validated with multivariate data measured during the years 2013-2014 in a semiarid shrubland ecosystem in Yanchi, northwestern China. The model simulation showed that soil rewetting could enhance CO2 dissolution and delay the emission of CO2 produced from rooting zone. In addition, an ineligible fraction of respired CO2 might be removed from soil volumes under respiration chambers by lateral water flows and root uptakes. During rewetting, the lichen-crusted soil could shift temporally from net CO2 source to sink due to the activated photosynthesis of biocrust but the restricted CO2 emissions from subsoil. The presence of plant cover could decrease the root-zone CO2 production and biocrust C sequestration but increase the temperature sensitivities of these fluxes. On the other hand, the sensitivities of root-zone emissions to water content were lower under canopy, which may be due to the advection of water flows from the interspace to canopy. To conclude, the complexity and plant-interspace heterogeneities of soil C processes should be carefully considered to extrapolate findings from chamber to ecosystem scales and to predict the ecosystem responses to climate change and extreme climatic events. Our model can serve as a useful tool to simulate the soil CO2 efflux dynamics in dryland ecosystems.

  9. Potential gains from CO2 trading in the EU

    DEFF Research Database (Denmark)

    Svendsen, Gert Tinggaard; Vesterdal, Morten

    2003-01-01

    the EU could reduce the total abatement costs by 32 % compared to a system with no trading. In comparison, a Community-wide system containing only the electricity and steam sector would reduce the total abatement costs by 13 % only. Though a tradable CO2 permit market for the power and steam sector can......A new Green Paper from the European Commission on emissions trading foresees the setting-up of a CO2 trading system within the EU for the energy sector. Because any such international environmental agreement is self-enforcing, the participants must have an economic net gain from joining...... the proposed system. Our contribution is therefore to follow the Green Paper proposal and investigate whether member countries and the largest industrial boilers in the electricity sector actually will get significant net gains from CO2 trade in the European Union rather than undertaking domestic actions...

  10. ROOT-GROWTH AND FUNCTIONING UNDER ATMOSPHERIC CO2 ENRICHMENT

    NARCIS (Netherlands)

    STULEN, [No Value; DENHERTOG, J

    This paper examines the extent to which atmospheric CO2 enrichment may influence growth of plant roots and function in terms of uptake of water and nutrients, and carbon allocation towards symbionts. It is concluded that changes in dry matter allocation greatly depend on the experimental conditions

  11. Use of sediment CO2 by submersed rooted plants

    DEFF Research Database (Denmark)

    Winkel, Anders; Borum, Jens

    2009-01-01

    freshwater plants with different morphology and growth characteristics (Lobelia dortmanna, Lilaeopsis macloviana, Ludwigia repens, Vallisneria americana and Hydrocotyle verticillata) are able to support photosynthesis supplied by uptake of CO2 from the sediment. Methods: Gross photosynthesis was measured......Background and Aims: Submersed plants have different strategies to overcome inorganic carbon limitation. It is generally assumed that only small rosette species (isoetids) are able to utilize the high sediment CO2 availability. The present study examined to what extent five species of submersed......, the shoot to root ratio on an areal basis was the single factor best explaining variability in the importance of sediment CO2. For Ludwigia, diffusion barriers limited uptake or transport from roots to stems and transport from stems to leaves. Conclusions: Submersed plants other than isoetids can utilize...

  12. Coccolithophore surface distributions in the North Atlantic and their modulation of the air-sea flux of CO2 from 10 years of satellite Earth observation data

    Directory of Open Access Journals (Sweden)

    J. D. Shutler

    2013-04-01

    Full Text Available Coccolithophores are the primary oceanic phytoplankton responsible for the production of calcium carbonate (CaCO3. These climatically important plankton play a key role in the oceanic carbon cycle as a major contributor of carbon to the open ocean carbonate pump (~50% and their calcification can affect the atmosphere-to-ocean (air-sea uptake of carbon dioxide (CO2 through increasing the seawater partial pressure of CO2 (pCO2. Here we document variations in the areal extent of surface blooms of the globally important coccolithophore, Emiliania huxleyi, in the North Atlantic over a 10-year period (1998–2007, using Earth observation data from the Sea-viewing Wide Field-of-view Sensor (SeaWiFS. We calculate the annual mean sea surface areal coverage of E. huxleyi in the North Atlantic to be 474 000 ± 104 000 km2, which results in a net CaCO3 carbon (CaCO3-C production of 0.14–1.71 Tg CaCO3-C per year. However, this surface coverage (and, thus, net production can fluctuate inter-annually by −54/+8% about the mean value and is strongly correlated with the El Niño/Southern Oscillation (ENSO climate oscillation index (r=0.75, pE. huxleyi blooms in the North Atlantic can increase the pCO2 and, thus, decrease the localised air-sea flux of atmospheric CO2. In regions where the blooms are prevalent, the average reduction in the monthly air-sea CO2 flux can reach 55%. The maximum reduction of the monthly air-sea CO2 flux in the time series is 155%. This work suggests that the high variability, frequency and distribution of these calcifying plankton and their impact on pCO2 should be considered if we are to fully understand the variability of the North Atlantic air-to-sea flux of CO2. We estimate that these blooms can reduce the annual N. Atlantic net sink atmospheric CO2 by between 3–28%.

  13. Seasonal and diurnal dynamics of CO2 balance in two hemi-boreal forests in Estonia

    Science.gov (United States)

    Mander, Ülo

    2013-04-01

    Two eddy towers, one in the mixed Norway spruce - Silver birch forest in Liispõllu (58°16'N 27°16'E tower height 20 m) and another one in Scots pine forest in Soontaga (58°01'N 26°04'E; 36 m) both located in southern Estonia - were equipped with CO2/H2O analyzer for mixing ratio of CO2 (Licor 7200 Li-Cor Inc, Lincoln, NE, USA) and 3-D ultrasonic anemometer for wind measurements (Gill Windmaster Pro; Solent, Lymington, UK) and used for measurement of carbon dioxide balance and net ecosystem exchange (NEE). In Liispõllu, the studies were conducted in Auguat and September 2011 above the forest canopies and at 1.5 m above the soil surface.. In Soontaga, measurements lasted from April to October 2012. The data acquisition system consists of the LI-7550 Analyzer Interface Unit, 3G wireless router and analog-to-digital converter that were used to record turbulence and scalar signals. Signals from the sensor and anemometer were recorded 20 times sec-1. The eddy fluxes were averaged over 30 minute time intervals. The flux calculations and corrections of were done using EddyPro program. In addition, soil respiration was measured with automatic chambers in Liispõllu and with closed chambers in Soontaga twice a month from April to October 2011 and 2012. In both study areas around the towers, soil physical and chemical parameters in 3 depths, biomass of trees and understory species, C sequestration in biomass and litter decay has been measured. In Soontaga pine forest the average monthly CO2 flux varied from -59.2 to -388.8 mg m-2 h-1 showing a regular seasonal temperature-related variation. CO2 flux from lowered in spring and summer as plants consume the gas through photosynthesis and days are longer, and rise during the autumn and winter as plants go dormant, die and decay and when also the daytime is shorter. The average monthly flux over the analyzed period was -246.5 mg m-2 h-1. In consequence, the CO2 sequestration from the atmosphere was highest in June. In Liisp

  14. Tundra is a consistent source of CO2 at a site with progressive permafrost thaw during 6 years of chamber and eddy covariance measurements

    Science.gov (United States)

    Celis, Gerardo; Mauritz, Marguerite; Bracho, Rosvel; Salmon, Verity G.; Webb, Elizabeth E.; Hutchings, Jack; Natali, Susan M.; Schädel, Christina; Crummer, Kathryn G.; Schuur, Edward A. G.

    2017-06-01

    Current and future warming of high-latitude ecosystems will play an important role in climate change through feedbacks to the global carbon cycle. This study compares 6 years of CO2 flux measurements in moist acidic tundra using autochambers and eddy covariance (Tower) approaches. We found that the tundra was an annual source of CO2 to the atmosphere as indicated by net ecosystem exchange using both methods with a combined mean of 105 ± 17 g CO2 C m-2 y-1 across methods and years (Tower 87 ± 17 and Autochamber 123 ± 14). The difference between methods was largest early in the observation period, with Autochambers indicated a greater CO2 source to the atmosphere. This discrepancy diminished through time, and in the final year the Autochambers measured a greater sink strength than tower. Active layer thickness was a significant driver of net ecosystem carbon exchange, gross ecosystem primary productivity, and Reco and could account for differences between Autochamber and Tower. The stronger source initially attributed lower summer season gross primary production (GPP) during the first 3 years, coupled with lower ecosystem respiration (Reco) during the first year. The combined suppression of GPP and Reco in the first year of Autochamber measurements could be the result of the experimental setup. Root damage associated with Autochamber soil collar installation may have lowered the plant community's capacity to fix C, but recovered within 3 years. While this ecosystem was a consistent CO2 sink during the summer, CO2 emissions during the nonsummer months offset summer CO2 uptake each year.

  15. The Kok effect in Vicia faba cannot be explained solely by changes in chloroplastic CO2 concentration.

    Science.gov (United States)

    Buckley, Thomas N; Vice, Heather; Adams, Mark A

    2017-08-31

    The Kok effect - an abrupt decline in quantum yield (QY) of net CO2 assimilation at low photosynthetic photon flux density (PPFD) - is widely used to estimate respiration in the light (R), which assumes the effect is caused by light suppression of R. A recent report suggested much of the Kok effect can be explained by declining chloroplastic CO2 concentration (cc ) at low PPFD. Several predictions arise from the hypothesis that the Kok effect is caused by declining cc , and we tested these predictions in Vicia faba. We measured CO2 exchange at low PPFD, in 2% and 21% oxygen, in developing and mature leaves, which differed greatly in R in darkness. Our results contradicted each of the predictions based on the cc effect: QY exceeded the theoretical maximum value for photosynthetic CO2 uptake; QY was larger in 21% than 2% oxygen; and the change in QY at the Kok effect breakpoint was unaffected by oxygen. Our results strongly suggest the Kok effect arises largely from a progressive decline in R with PPFD that includes both oxygen-sensitive and -insensitive components. We suggest an improved Kok method that accounts for high cc at low PPFD. © 2017 The Authors. New Phytologist © 2017 New Phytologist Trust.

  16. The CO2nnect activities

    Science.gov (United States)

    Eugenia, Marcu

    2014-05-01

    Climate change is one of the biggest challenges we face today. A first step is the understanding the problem, more exactly what is the challenge and the differences people can make. Pupils need a wide competencies to meet the challenges of sustainable development - including climate change. The CO2nnect activities are designed to support learning which can provide pupils the abilities, skills, attitudes and awareness as well as knowledge and understanding of the issues. The project "Together for a clean and healthy world" is part of "The Global Educational Campaign CO2nnect- CO2 on the way to school" and it was held in our school in the period between February and October 2009. It contained a variety of curricular and extra-curricular activities, adapted to students aged from 11 to 15. These activities aimed to develop in students the necessary skills to understanding man's active role in improving the quality of the environment, putting an end to its degrading process and to reducing the effects of climate changes caused by the human intervention in nature, including transport- a source of CO2 pollution. The activity which I propose can be easily adapted to a wide range of age groups and linked to the curricula of many subjects: - Investigate CO2 emissions from travel to school -Share the findings using an international database -Compare and discuss CO2 emissions -Submit questions to a climate- and transport expert -Partner with other schools -Meet with people in your community to discuss emissions from transport Intended learning outcomes for pupils who participate in the CO2nnect campaign are: Understanding of the interconnected mobility- and climate change issue climate change, its causes and consequences greenhouse-gas emissions from transport and mobility the interlinking of social, environmental, cultural and economic aspects of the local transport system how individual choices and participation can contribute to creating a more sustainable development

  17. Technical insight on the requirements for CO2-saturated growth of microalgae in photobioreactors.

    Science.gov (United States)

    Yuvraj; Padmanabhan, Padmini

    2017-06-01

    Microalgal cultures are usually sparged with CO 2 -enriched air to preclude CO 2 limitation during photoautotrophic growth. However, the CO 2 vol% specifically required at operating conditions to meet the carbon requirement of algal cells in photobioreactor is never determined and 1-10% v/v CO 2 -enriched air is arbitrarily used. A scheme is proposed and experimentally validated for Chlorella vulgaris that allows computing CO 2 -saturated growth feasible at given CO 2 vol% and volumetric O 2 mass-transfer coefficient (k L a) O . CO 2 sufficiency in an experiment can be theoretically established to adjust conditions for CO 2 -saturated growth. The methodology completely eliminates the requirement of CO 2 electrode for online estimation of dissolved CO 2 to determine critical CO 2 concentration (C crit ), specific CO 2 uptake rate (SCUR), and volumetric CO 2 mass-transfer coefficient (k L a) C required for the governing CO 2 mass-transfer equation. C crit was estimated from specific O 2 production rate (SOPR) measurements at different dissolved CO 2 concentrations. SCUR was calculated from SOPR and photosynthetic quotient (PQ) determined from the balanced stoichiometric equation of growth. Effect of light attenuation and nutrient depletion on biomass estimate is also discussed. Furthermore, a simple design of photosynthetic activity measurement system was used, which minimizes light attenuation by hanging a low depth (ca. 10 mm) culture over the light source.

  18. Reducing cement's CO2 footprint

    Science.gov (United States)

    van Oss, Hendrik G.

    2011-01-01

    The manufacturing process for Portland cement causes high levels of greenhouse gas emissions. However, environmental impacts can be reduced by using more energy-efficient kilns and replacing fossil energy with alternative fuels. Although carbon capture and new cements with less CO2 emission are still in the experimental phase, all these innovations can help develop a cleaner cement industry.

  19. Improving soil CO2 efflux estimates from in-situ soil CO2 sensors with gas transport measurements

    Science.gov (United States)

    Sanchez-Canete, E. P.; Barron-Gafford, G.; Van Haren, J. L. M.; Scott, R. L.

    2015-12-01

    Correctly estimating soil carbon dioxide (CO2) fluxes emitted to the atmosphere is essential because they are a large component of the ecosystem carbon balance. Continuous estimates of soil CO2 flux, especially when paired with eddy covariance measurements of whole-ecosystem CO­2 exchange, help to disaggregate net ecosystem CO2 exchange. Most researchers estimate soil CO2 fluxes by applying the gradient method; however, this is only appropriate in the absence of advective or convective processes. Given the rarity of such static states, we must move toward measurement techniques that will allow us to quantify the dynamic soil efflux system with gas transport by convective, advective and molecular diffusion processes. Convective processes are mainly relevant in caves, where values of relative humidity, temperature and CO2 molar fraction determine the buoyancy of the external-internal air masses. These convective processes also are important in large fractures when temperature differences between surface and depth can generate convection, transporting CO2 from deep layers to the atmosphere. Advective processes occur both in caves and in soils, and the CO2 exchanges are mainly due to three factors: wind, changes in atmospheric pressure, and changes in the water table. Molecular diffusion processes are being widely applied in the determination of soil-atmosphere gas exchanges by applying the gradient method. However, the use of the gradient method can yield inappropriate flux estimates due to the uncertainties mainly associated with the inappropriate determination of the soil diffusion coefficient. Therefore, in-situ methods to determine diffusion coefficient are necessary to obtain accurate CO2 fluxes. If this is resolved, the gradient method has great potential to become the most used technique to monitor atmosphere-soil CO2 exchanges within the next few years. Here we review the state of the science and describe a series of field measurements for significantly

  20. Long-term Nutrient Fertilization Increases CO2 Loss in Arctic Tundra

    Science.gov (United States)

    Graham, L. M.; Natali, S.; Rastetter, E. B.; Shaver, G. R.; Risk, D. A.; Loranty, M. M.; Jastrow, J. D.

    2015-12-01

    As anthropogenic climate change warms the Arctic, organic carbon (C) trapped in permafrost is at an increased risk of being released to the atmosphere as carbon dioxide (CO2). At the same time, higher rates of decomposition may increase nutrient availability and enhance plant growth, leading to an uptake of C that may offset respiratory losses. Arctic tundra ecosystems are highly nitrogen (N) limited, and the indirect effects of warming on nutrient availability will be the most likely outcome of increased temperature on plant productivity. This study aims to understand the effects of nutrient addition on arctic CO2 and H2O exchange in a tundra ecosystem at Toolik Lake Field Station, Alaska. The nutrient addition experiment, which began in 2006, is comprised of 7 fertilization treatments: 0.5, 1, 2, 5, and 10 g m-2 of N as NO3- and NH4+ (1:1) with 0.25, 0.5, 1, 2.5, and 5 g m-2 of phosphorus as PO43-; 5 g m-2 of N as NO3-; 5 g m-2 of N as NH4+, and one control plot. Plot-level CO2 and H2O exchange was measured at 5 light levels 7 times over a four-week period in June and July 2015. We measured ecosystem CO2 and H2O exchange using a rectangular plexiglass chamber (0.49 m2) that was connected to an infrared gas analyzer (LI-840). Other ecosystem variables measured include thaw depth, soil moisture and temperature, and normalized difference vegetation index. After 10 years of nutrient addition, fertilization significantly altered ecosystem C cycling. Soil respiration was greatest in the highest fertilization treatment (2.97 μmol m-2 s-1), increasing linearly with nutrient level at a rate of 0.133 μmol m-2 s-1 per g m-2 of N added (R2=0.914). Net CO2 uptake was greatest under highest fertilization (-2.06 μmol m-2 s-1), decreasing linearly with nutrient addition at a rate of -0.068 μmol m-2 s-1 per g m-2 of N added (R2=0.687). These results suggest that as nutrients become more available under a warmer climate, plant productivity increases may not offset respiratory

  1. The impact of elevated CO2 concentrations on soil microbial community, soil organic matter storage and nutrient cycling at a natural CO2 vent in NW Bohemia

    Science.gov (United States)

    Nowak, Martin; Beulig, Felix; von Fischer, Joe; Muhr, Jan; Kuesel, Kirsten; Trumbore, Susan

    2014-05-01

    Natural CO2 vents or 'mofettes' are diffusive or advective exhalations of geogenic CO2 from soils. These structures occur at several places worldwide and in most cases they are linked to volcanic activity. Characteristic for mofette soils are high CO2 concentrations of up to more than 90% as well as a lack of oxygen, low pH values and reducing conditions. Mofette soils usually are considered to be sites of carbon accumulation, which is not only due to the absence of oxygen, but might also result from lower plant litter quality due to CO2 fertilization of CO2 influenced plants and reduced availability of N and P for the decomposer community. Furthermore, fermentation processes and the formation of reduced elements by anoxic decomposition might fuel chemo-lithoautotrophic or mixotrophic microbial CO2 uptake, a process which might have important ecological functions by closing internal element cycles, formation of trace gasses as well as by re-cycling and storing of carbon. Several studies of microbial community structure revealed a shift towards CO2 utilizing prokaryotes in moffete soils compared to a reference site. Here, we use combined stable and radiocarbon isotope data from mofette soils in NW Bohemia to quantify the contribution of geogenic CO2 to soil organic carbon formation within mofette soils, either resulting from plant litter or from microbial CO2 uptake. This is possible because the geogenic CO2 has a distinct isotopic signature (δ13C = -2 o Δ14C = -1000 ) that is very different from the isotopic signature of atmospheric CO2. First results show that mofette soils have a high Corg content (20 to 40 %) compared to a reference site (2 to 20 %) and soil organic matter is enriched in 13C as well as depleted in 14C. This indicates that geogenic CO2 is re-fixed and stored as SOM. In order to quantify microbial contribution to CO2 fixation and SOM storage, microbial CO2 uptake rates were determined by incubating mofette soils with 13CO2 labelled gas. The

  2. Fang CO2 med Aminosyrer

    DEFF Research Database (Denmark)

    Lerche, Benedicte Mai

    2010-01-01

    Med såkaldte “carbon capture-teknikker” er det muligt at rense røgen fra kulfyrede kraftværker, således at den er næsten helt fri for drivhusgassen CO2. Kunsten er at gøre processen tilstrækkeligt billig. Et lovende fangstredskab i denne proces er aminosyrer.......Med såkaldte “carbon capture-teknikker” er det muligt at rense røgen fra kulfyrede kraftværker, således at den er næsten helt fri for drivhusgassen CO2. Kunsten er at gøre processen tilstrækkeligt billig. Et lovende fangstredskab i denne proces er aminosyrer....

  3. The CO2 footprint of new nitrogen creation

    Science.gov (United States)

    Houlton, B. Z.

    2012-12-01

    For billions of years, in the absence of substantial human influence, the essential nutrient nitrogen (N) entered terrestrial ecosystems at naturally low rates. Today, human actions (i.e., Haber-Bosch fertilizer production, fossil fuel combustion) have dramatically reshaped the N cycle from its background state, more than doubling terrestrial N circulation, resulting in large increases in anthropogenic N deposition inputs to ecosystems globally. While producing many unwanted side-effects, increased N in both rain water and dry particulate matter has been purported in accelerated rates of forest CO2 uptake, thus slowing the pace of climate change. However, this perspective does not consider the amount of CO2 released to the atmosphere during new N creation. Here I analyze the gross CO2 footprint of N input pathways, including the CO2 released during N fixation vs. that which is consumed by forest vegetation per unit of N input. This analysis indicates the following C/N conversion efficiencies during fixation: lightening = 0; Haber-Bosch = 0.49; symbiotic fixation = 10; asymbiotic fixation = 50; fossil fuel fixation = 220. Thus, lightening envisions the highest forest CO2 uptake return (100 %) followed by Haber-Bosch N (99), symbiotic N fixation (88) and asymbiotic N fixation (neutral), and lastly, fossil fuel fixation (-279). In addition, widespread and well-documented negative interactions between excess N and biological N fixation further undermine any potential positive effects of fossil-fuel N deposition on terrestrial C storage. Thus, recapturing Haber-Bosch N by natural vegetation combined with policies that target reductions in fossil fuel N sources are proposed as the most effective means for maximizing the positive benefits of anthropocene N on terrestrial CO2 uptake and storage.

  4. Incidence of increased 68Ga-DOTANOC uptake in the pancreatic head in a large series of extrapancreatic NET patients studied with sequential PET/CT.

    Science.gov (United States)

    Castellucci, Paolo; Pou Ucha, Javier; Fuccio, Chiara; Rubello, Domenico; Ambrosini, Valentina; Montini, Gian Carlo; Pettinato, Vincenzina; Malizia, Claudio; Lodi, Filippo; Fanti, Stefano

    2011-06-01

    The aim of our retrospective study was to assess the incidence of increased uptake of (68)Ga-DOTANOC in the head of the pancreas among a large population of patients with extrapancreatic neuroendocrine tumors studied with serial (68)Ga-DOTANOC PET/CT. Patients who had undergone at least two (68)Ga-DOTANOC PET/CT studies over time were included. Uptake in the head of the pancreas was measured and compared with uptake in normal liver parenchyma (target-to-liver ratio). Patients were followed up for 6-24 mo. We reviewed 245 studies performed on 100 patients and classified the pancreatic uptake as either diffuse or focal. Twenty-three patients (66 scans) showed diffuse uptake; 8 patients (16 scans) showed focal uptake. None of these 31 patients had negative findings on their subsequent scans, and vice versa. During follow-up, localization of neuroendocrine tumors in the pancreas was not suspected in any patient. Focal and diffuse uptake of (68)Ga-DOTANOC in the head of the pancreas occurred, respectively, in 23% and 8% of the patients. The main finding of our study was that increased pancreatic uptake was stable over time.

  5. Outsourcing CO2 within China.

    Science.gov (United States)

    Feng, Kuishuang; Davis, Steven J; Sun, Laixiang; Li, Xin; Guan, Dabo; Liu, Weidong; Liu, Zhu; Hubacek, Klaus

    2013-07-09

    Recent studies have shown that the high standard of living enjoyed by people in the richest countries often comes at the expense of CO2 emissions produced with technologies of low efficiency in less affluent, developing countries. Less apparent is that this relationship between developed and developing can exist within a single country's borders, with rich regions consuming and exporting high-value goods and services that depend upon production of low-cost and emission-intensive goods and services from poorer regions in the same country. As the world's largest emitter of CO2, China is a prominent and important example, struggling to balance rapid economic growth and environmental sustainability across provinces that are in very different stages of development. In this study, we track CO2 emissions embodied in products traded among Chinese provinces and internationally. We find that 57% of China's emissions are related to goods that are consumed outside of the province where they are produced. For instance, up to 80% of the emissions related to goods consumed in the highly developed coastal provinces are imported from less developed provinces in central and western China where many low-value-added but high-carbon-intensive goods are produced. Without policy attention to this sort of interprovincial carbon leakage, the less developed provinces will struggle to meet their emissions intensity targets, whereas the more developed provinces might achieve their own targets by further outsourcing. Consumption-based accounting of emissions can thus inform effective and equitable climate policy within China.

  6. Do anthropogenic aerosols enhance CO2 uptake by plants?

    Science.gov (United States)

    Strada, S.; Unger, N.

    2013-12-01

    Plant productivity (photosynthesis) is tightly connected to the supply of solar radiation and water and to surface temperature. Solar radiation reaching the Earth's surface and the water cycle are strongly modified by anthropogenic aerosols. Aerosols reduce the amount of global radiation and surface temperature, and they modify the partitioning between direct and diffuse radiation. Moreover, they modify cloud radiative properties and lifetime. These aerosols effects may influence Gross Primary Productivity (GPP): (1) by intensifying the diffuse-radiation fertilization effect (i.e. plant productivity is more efficient under diffuse light whose amount may increase due to aerosol loading); (2) by modifying water supply through suppression/enhancement of rainfall; (3) by reducing surface temperature. Among aerosol impacts on GPP, it is unclear if there exists a prevailing one, or if the prevailing impact varies across ecosystems. Feedbacks to GPP from the effects of biogenic secondary organic aerosol (BSOA) formed from vegetation reactive carbon emissions have not been investigated. Moreover, human-made pollution and biomass burning induce high ozone concentrations that simultaneously reduce plant productivity. We apply satellite observations and global model simulations to investigate the spatial pattern in the relationship between aerosols and plant productivity across different ecosystems, and whether plants control their diffuse radiation environment through the reactive carbon emissions. We quantify the correlation between MODIS GPP and: (1) fine-fraction Aerosol Optical Depth from MODIS (fAOD); (2) ozone levels in the middle troposphere from TES. The analysis of satellite data reveals strong positive correlation between GPP and fAOD in temperate and boreal ecosystems, and strong negative correlation in tropical ecosystems. The tropical ecosystem also presents strong negative correlation between GPP and O3. Simulations using Yale-E2 global carbon-chemistry-climate model seem to confirm this behavior. We perform fully coupled simulations with Yale-E2 for the present-day climatic state that differ in the amount of anthropogenic pollution emissions: (a) a control run forced with present day anthropogenic emissions and (b) a perturbed run that represents the pre-human preindustrial natural aerosol loading. In a further set of sensitivity simulations, we isolate the relative magnitudes of (1), (2), and (3) above in impacting GPP.

  7. Strain development in smectite clays upon exposure to CO2

    Science.gov (United States)

    de Jong, S. M.; Spiers, C. J.; Busch, A.

    2012-04-01

    Smectites (or swelling clays) are common constituents of claystones, mudstones and shales and are often present in the caprocks and faults sealing potential CO2 storage reservoirs. Their crystal structure is comprised of alternating silicate layers separated by an interlayer region, containing cations and water molecules. As the water molecules are easily exchanged between this region and the intergranular pore space, the structure can expand or shrink depending on factors such as temperature, water activity and clay composition. Whereas the water uptake and swelling properties of smectite clays have been studied extensively, fewer studies have been directed at possible interactions with CO2. However, several scenarios including shrinkage (dehydration) and swelling (surface adsorption or uptake of CO2 into the interlayer region) of the crystals are conceivable, which could have significant implications for caprock and fault integrity. To investigate possible effects of CO2 on the swelling properties of smectite clays, we performed unconfined volumetric strain measurements on compacted pellets of montmorillonite (SWy-1), which is a common type of smectite, and on smectite-bearing shale. This was done using an optical cell. We probed the macroscopic response of the pressed samples to assess the overall strain response to exposure to CO2 at typical P-T conditions expected in carbon dioxide storage sites, i.e. at a temperature of 45°C and CO2 pressures up to 15MPa. Samples were heat-treated prior to exposure to CO2 to obtain a defined hydration state (d001-spacing). This was determined independently using X-ray diffraction methods. Our results show that montmorillonite SWy-1 swells almost instantaneously (in a few seconds) to an equilibrium state, when placed in contact with (supercritical) CO2 for the conditions PCO2 ≤ 8 MPa, T = 45°C. Maximum swelling is observed for an initial d001 spacing of 11Å, reaching 2.4 ± 0.45% at a CO2 pressure of 15MPa. Only minor

  8. Detecting regional patterns of changing CO2 flux in Alaska.

    Science.gov (United States)

    Parazoo, Nicholas C; Commane, Roisin; Wofsy, Steven C; Koven, Charles D; Sweeney, Colm; Lawrence, David M; Lindaas, Jakob; Chang, Rachel Y-W; Miller, Charles E

    2016-07-12

    With rapid changes in climate and the seasonal amplitude of carbon dioxide (CO2) in the Arctic, it is critical that we detect and quantify the underlying processes controlling the changing amplitude of CO2 to better predict carbon cycle feedbacks in the Arctic climate system. We use satellite and airborne observations of atmospheric CO2 with climatically forced CO2 flux simulations to assess the detectability of Alaskan carbon cycle signals as future warming evolves. We find that current satellite remote sensing technologies can detect changing uptake accurately during the growing season but lack sufficient cold season coverage and near-surface sensitivity to constrain annual carbon balance changes at regional scale. Airborne strategies that target regular vertical profile measurements within continental interiors are more sensitive to regional flux deeper into the cold season but currently lack sufficient spatial coverage throughout the entire cold season. Thus, the current CO2 observing network is unlikely to detect potentially large CO2 sources associated with deep permafrost thaw and cold season respiration expected over the next 50 y. Although continuity of current observations is vital, strategies and technologies focused on cold season measurements (active remote sensing, aircraft, and tall towers) and systematic sampling of vertical profiles across continental interiors over the full annual cycle are required to detect the onset of carbon release from thawing permafrost.

  9. Microporous carbonaceous adsorbents for CO2 separation via selective adsorption

    KAUST Repository

    Zhao, Yunfeng

    2015-01-01

    Selective adsorption of CO2 has important implications for many energy and environment-related processes, which require the separation of CO2 from other gases (e.g. N2 and CH4) with high uptakes and selectivity. The development of high-performance adsorbents is one of the most promising solutions to the success of these processes. The present review is focused on the state-of-the-art of carbon-based (carbonaceous) adsorbents, covering microporous inorganic carbons and microporous organic polymers, with emphasis on the correlation between their textural and compositional properties and their CO2 adsorption/separation performance. Special attention is given to the most recently developed materials that were not covered in previous reviews. We summarize various effective strategies (N-doping, surface functionalization, extra-framework ions, molecular design, and pore size engineering) for enhancing the CO2 adsorption capacity and selectivity of carbonaceous adsorbents. Our discussion focuses on CO2/N2 separation and CO2/CH4 separation, while including an introduction to the methods and criteria used for evaluating the performance of the adsorbents. Critical issues and challenges regarding the development of high-performance adsorbents as well as some overlooked facts and misconceptions are also discussed, with the aim of providing important insights into the design of novel carbonaceous porous materials for various selective adsorption based applications. This journal is © The Royal Society of Chemistry.

  10. LBA-ECO CD-01 Simulated Atmospheric Circulation, CO2 Variation, Tapajos: August 2001

    Data.gov (United States)

    National Aeronautics and Space Administration — ABSTRACT: This data set consists of a single NetCDF file containing simulated three dimensional winds and CO2 concentrations centered on the Tapajos National Forest...

  11. LBA-ECO CD-01 Simulated Atmospheric Circulation, CO2 Variation, Tapajos: August 2001

    Data.gov (United States)

    National Aeronautics and Space Administration — This data set consists of a single NetCDF file containing simulated three dimensional winds and CO2 concentrations centered on the Tapajos National Forest in Brazil...

  12. Negative CO2 emissions via subsurface mineral carbonation in fractured peridotite

    Science.gov (United States)

    Kelemen, P. B.; Matter, J.

    2014-12-01

    Uptake of CO2 from surface water via mineral carbonation in peridotite can be engineered to achieve negative CO2 emissions. Reaction with peridotite, e.g., CO2 + olivine (A), serpentine (B) and brucite (C), forms inert, non-toxic, solid carbonates such as magnesite. Experimental studies show that A can be 80% complete in a few hours with 30 micron powders and elevated P(CO2) [1,2,3]. B is slower, but in natural systems the rate of B+C is significant [4]. Methods for capture of dilute CO2 via mineral carbonation [4,5,6,7] are not well known, though CO2 storage via mineral carbonation has been discussed for decades [8,9]. Where crushed peridotite is available, as in mine tailings, increased air or water flow could enhance CO2 uptake at a reasonable cost [4,5]. Here we focus on enhancing subsurface CO2 uptake from surface water flowing in fractured peridotite, in systems driven by thermal convection such as geothermal power plants. Return of depleted water to the surface would draw down CO2 from the air [6,7]. CO2 uptake from water, rate limited by flow in input and output wells, could exceed 1000 tons CO2/yr [7]. If well costs minus power sales were 0.1M to 1M and each system lasts 10 years this costs oil industry. Uptake of 1 Gt CO2/yr at 1000 t/well/yr requires 1M wells, comparable to the number of producing oil and gas wells in the USA. Subsurface CO2 uptake could first be applied in coastal, sub-seafloor peridotite with onshore drilling. Sub-seafloor peridotite is extensive off Oman, New Caledonia and Papua New Guinea, with smaller amounts off Spain, Morocco, USA, etc. This would be a regional contribution, used in parallel with other methods elsewhere. To achieve larger scale is conceivable. There is a giant mass of seafloor peridotite along slow-spreading mid-ocean ridges. Could robotic drills enhance CO2 uptake at a reasonable cost, while fabric chimneys transport CO2-depleted water to the sea surface? Does anyone know James Cameron's phone number? [1] O

  13. Physical Activation of Oil Palm Empty Fruit Bunch via CO2 Activation Gas for CO2 Adsorption

    Science.gov (United States)

    Joseph, C. G.; Quek, K. S.; Daud, W. M. A. W.; Moh, P. Y.

    2017-06-01

    In this study, different parameters for the preparation of activated carbon were investigated for their yield and CO2 capture capabilities. The activated carbon was prepared from Oil Palm Empty Fruit Bunch (OPEFB) via a 2-step physical activation process. The OPEFB was pyrolyzed under inert conditions at 500 °C and activated via CO2. A 2-factorial design was employed and the effects of activation temperature, activation dwell time and gas flow rate on yield and CO2 capture capabilities were compared and studied. The yield obtained ranged from between 20 - 26, whereby the temperature was determined to be the most significant factor in influencing CO2 uptake. The CO2 capture capacity was determined using Temperature Programmed Desorption (TPD) technique. The CO2 uptake of EFB activated carbon achieved was between 1.85 - 2.09 mmol/g. TPD analysis has shown that the surface of AC were of basic nature. AC was found to be able to withhold the CO2 up to 663°C before maximum desorption occurs. The surface area and pore size of OPEFB obtained from BET analysis is 2.17 m2 g-1 and 0.01 cm3 g-1. After activation, both surface area and pore size increased with a maximum observed surface area and pore size of 548.07 m2 g-1 and 0.26 cm3 g-1. Surface morphology, functional groups, pore size and surface area were analyzed using SEM, FT-IR, TPD and BET.

  14. Substantial global carbon uptake by cement carbonation

    Science.gov (United States)

    Xi, Fengming; Davis, Steven J.; Ciais, Philippe; Crawford-Brown, Douglas; Guan, Dabo; Pade, Claus; Shi, Tiemao; Syddall, Mark; Lv, Jie; Ji, Lanzhu; Bing, Longfei; Wang, Jiaoyue; Wei, Wei; Yang, Keun-Hyeok; Lagerblad, Björn; Galan, Isabel; Andrade, Carmen; Zhang, Ying; Liu, Zhu

    2016-12-01

    Calcination of carbonate rocks during the manufacture of cement produced 5% of global CO2 emissions from all industrial process and fossil-fuel combustion in 2013. Considerable attention has been paid to quantifying these industrial process emissions from cement production, but the natural reversal of the process--carbonation--has received little attention in carbon cycle studies. Here, we use new and existing data on cement materials during cement service life, demolition, and secondary use of concrete waste to estimate regional and global CO2 uptake between 1930 and 2013 using an analytical model describing carbonation chemistry. We find that carbonation of cement materials over their life cycle represents a large and growing net sink of CO2, increasing from 0.10 GtC yr-1 in 1998 to 0.25 GtC yr-1 in 2013. In total, we estimate that a cumulative amount of 4.5 GtC has been sequestered in carbonating cement materials from 1930 to 2013, offsetting 43% of the CO2 emissions from production of cement over the same period, not including emissions associated with fossil use during cement production. We conclude that carbonation of cement products represents a substantial carbon sink that is not currently considered in emissions inventories.

  15. RODZAJE METOD SEKWESTRACJI CO2

    Directory of Open Access Journals (Sweden)

    Zofia LUBAŃSKA

    Full Text Available Z pojęciem ochrony środowiska wiąże się bardzo szeroko w ostatnim czasie omawiane zagadnienie dotyczące ograniczenia emisji CO2. Konsekwencją globalnych zmian klimatu wywołanego przez ludzi jest wzrost stężenia atmosferycznego gazów cieplarnianych, które powodują nasilający się efekt cieplarniany. Wzrasta na świecie liczba ludności, a co za tym idzie wzrasta konsumpcja na jednego mieszkańca, szczególnie w krajach szeroko rozwiniętych gospodarczo. Protokół z Kioto ściśle określa działania jakie należy podjąć w celu zmniejszenia stężenia dwutlenku węgla w atmosferze. Pomimo maksymalnej optymalizacji procesu spalania paliw kopalnianych wykorzystywanych do produkcji energii, zastosowania odnawialnych źródeł energii zmiana klimatu jest nieunikniona i konsekwentnie będzie postępować przez kolejne dekady. Prognozuje się, że duże znaczenie odegra nowoczesna technologia, która ma za zadanie wychwycenie CO2 a następnie składowanie go w odpowiednio wybranych formacjach geologicznych (CCS- Carbon Capture and Storage. Eksperci są zgodni, że ta technologia w niedalekiej przyszłości stanie się rozwiązaniem pozwalającym ograniczyć ogromną ilość emisji CO2 pochodzącą z procesów wytwarzania energii z paliw kopalnych. Z analiz Raportu IPCC wynika, iż technologia CSS może się przyczynić do ok. 20% redukcji emisji dwutlenku węgla przewidzianej do 2050 roku [3]. Zastosowanie jej napotyka na wiele barier, nie tylko technologicznych i ekonomicznych, ale także społecznych. Inną metodą dającą ujemne źródło emisji CO2 jest możliwość wykorzystania obszarów leśnych o odpowiedniej strukturze drzewostanu. Środkiem do tego celu, oprócz ograniczenia zużycia emisjogennych paliw kopalnych (przy zachowaniu zasad zrównoważonego rozwoju może być intensyfikacja zalesień. Zwiększanie lesistości i prawidłowa gospodarka leśna należy do najbardziej efektywnych sposobów kompensowania

  16. Simulated effect of calcification feedback on atmospheric CO2 and ocean acidification

    OpenAIRE

    Han Zhang; Long Cao

    2016-01-01

    Ocean uptake of anthropogenic CO2 reduces pH and saturation state of calcium carbonate materials of seawater, which could reduce the calcification rate of some marine organisms, triggering a negative feedback on the growth of atmospheric CO2. We quantify the effect of this CO2-calcification feedback by conducting a series of Earth system model simulations that incorporate different parameterization schemes describing the dependence of calcification rate on saturation state of CaCO3. In a scen...

  17. Plant nutrient mobilization in temperate heathland responds to elevated CO2, temperature and drought

    DEFF Research Database (Denmark)

    Andresen, Louise C.; Michelsen, Anders; Jonasson, Sven

    2010-01-01

    when combined with CO2 and drought. Below Deschampsia, the net nitrification rate decreased in response to drought and, while phosphorus availability and microbial P immobilization decreased, but nitrification increased in response to elevated CO2. Furthermore, leaf litter decomposition of both species...

  18. Daily Changes in CO2 and Water Vapor Exchange, Chlorophyll Fluorescence, and Leaf Water Relations in the Halophyte Mesembryanthemum crystallinum during the Induction of Crassulacean Acid Metabolism in Response to High NaCl Salinity 1

    Science.gov (United States)

    Winter, Klaus; Gademann, Rolf

    1991-01-01

    Simultaneous measurements of net CO2 exchange, water vapor exchange, and leaf water relations were performed in Mesembryanthemum crystallinum during the development of crassulacean acid metabolism (CAM) in response to high NaCl salinity in the rooting medium. Determinations of chlorophyll a fluorescence were used to estimate relative changes in electron transport rate. Alterations in leaf mass per unit area, which—on a short-term basis—largely reflect changes in water content, were recorded continuously with a beta-gauge. Turgor pressure of mesophyll cells was determined with a pressure probe. As reported previously (K Winter, DJ von Willert [1972] Z Pflanzenphysiol 67: 166-170), recently expanded leaves of plants grown under nonsaline conditions showed gas-exchange characteristics of a C3 plant. Although these plants were not exposed to any particular stress treatment, water content and turgor pressure regularly decreased toward the end of the 12 hour light periods and recovered during the following 12 hours of darkness. When the NaCl concentration of the rooting medium was raised to 400 millimolar, in increments of 100 millimolar given at the onset of the photoperiods for 4 consecutive days, leaf water content and turgor pressure decreased by as much as 30 and 60%, respectively, during the course of the photoperiods. These transient decreases probably triggered the induction of the biochemical machinery which is required for CAM to operate. After several days at 400 millimolar NaCl, when leaves showed features typical of CAM, overall turgor pressure and leaf mass per unit area had increased above the levels before onset of the salt treatment, and diurnal alterations in leaf water content were reduced. Net carbon gain during photoperiods and average intercellular CO2 partial pressures at which net CO2 uptake occurred, progressively decreased upon salinization. Reversible diurnal depressions in leaf conductance and net CO2 uptake, with minima recorded in the

  19. Modeling Atmospheric CO2 Processes to Constrain the Missing Sink

    Science.gov (United States)

    Kawa, S. R.; Denning, A. S.; Erickson, D. J.; Collatz, J. C.; Pawson, S.

    2005-01-01

    We report on a NASA supported modeling effort to reduce uncertainty in carbon cycle processes that create the so-called missing sink of atmospheric CO2. Our overall objective is to improve characterization of CO2 source/sink processes globally with improved formulations for atmospheric transport, terrestrial uptake and release, biomass and fossil fuel burning, and observational data analysis. The motivation for this study follows from the perspective that progress in determining CO2 sources and sinks beyond the current state of the art will rely on utilization of more extensive and intensive CO2 and related observations including those from satellite remote sensing. The major components of this effort are: 1) Continued development of the chemistry and transport model using analyzed meteorological fields from the Goddard Global Modeling and Assimilation Office, with comparison to real time data in both forward and inverse modes; 2) An advanced biosphere model, constrained by remote sensing data, coupled to the global transport model to produce distributions of CO2 fluxes and concentrations that are consistent with actual meteorological variability; 3) Improved remote sensing estimates for biomass burning emission fluxes to better characterize interannual variability in the atmospheric CO2 budget and to better constrain the land use change source; 4) Evaluating the impact of temporally resolved fossil fuel emission distributions on atmospheric CO2 gradients and variability. 5) Testing the impact of existing and planned remote sensing data sources (e.g., AIRS, MODIS, OCO) on inference of CO2 sources and sinks, and use the model to help establish measurement requirements for future remote sensing instruments. The results will help to prepare for the use of OCO and other satellite data in a multi-disciplinary carbon data assimilation system for analysis and prediction of carbon cycle changes and carbodclimate interactions.

  20. Soil CO2 CH4 and N2O fluxes from an afforested lowland raised peatbog in Scotland: implications for drainage and restoration

    Directory of Open Access Journals (Sweden)

    J. I. L. Morison

    2013-02-01

    Full Text Available The effect of tree (lodgepole pine planting with and without intensive drainage on soil greenhouse gas (GHG fluxes was assessed after 45 yr at a raised peatbog in West Flanders Moss, central Scotland. Fluxes of CO2 CH4 and N2O from the soil were monitored over a 2-yr period every 2 to 4 weeks using the static opaque chamber method in a randomised experimental block trial with the following treatments: drained and planted (DP, undrained and planted (uDP, undrained and unplanted (uDuP and for reference also from an adjoining near-pristine area of bog at East Flanders Moss (n-pris. There was a strong seasonal pattern in both CO2 and CH4 effluxes which were significantly higher in late spring and summer months because of warmer temperatures. Effluxes of N2O were low and no significant differences were observed between the treatments. Annual CH4 emissions increased with the proximity of the water table to the soil surface across treatments in the order: DP 4 m−2 yr−1, respectively. For CO2, effluxes increased in the order uDP 2 m−2 yr−1, respectively. CO2 effluxes dominated the total net GHG emission, calculated using the global warming potential (GWP of the three GHGs for each treatment (76–98%, and only in the n-pris site was CH4 a substantial contribution (23%. Based on soil effluxes only, the near pristine (n-pris peatbog had 43% higher total net GHG emission compared with the DP treatment because of high CH4 effluxes and the DP treatment had 33% higher total net emission compared with the uDP because drainage increased CO2 effluxes. Restoration is likely to increase CH4 emissions, but reduce CO2 effluxes. Our study suggests that if estimates of CO2 uptake by vegetation from similar peatbog sites were included, the total net GHG emission of restored peatbog would still be higher than that of the peatbog with trees.

  1. CO2 and CH4 fluxes from oil palm plantations in Sumatra, Indonesia: effects of palm age and environmental conditions

    Science.gov (United States)

    Meijide, A.; Hassler, E.; Corre, M. D.; June, T.; Sabajo, C.; Veldkamp, E.; Knohl, A.

    2015-12-01

    Global increasing demand of palm oil is leading to the expansion of oil palm plantations, particularly in SE Asia, which in Sumatran lowlands has resulted in a 21% forest area loss. Large photosynthesis rates are expected for oil palms, due to their high growth and yield production. However, there is very limited information on their effect on carbon dioxide (CO2) fluxes and their sink or source strength at ecosystem scale. For methane (CH4) fluxes, research has mainly focused in oil palm plantations located on peatlands, but no information is available at ecosystem level from plantations on mineral soils. With the aim of studying CO2 fluxes during the non-productive and productive phases of oil palm cultivation, an eddy covariance (EC) tower was installed in a 2 year old oil palm plantation, where it was measuring for 8 months, and was subsequently moved to a 12 year old plantation, both in the province of Jambi, Sumatra. The EC system consisted of a Licor 7500A and an ultrasonic Metek anemometer, operating at 10 Hz, installed on a 7m and 22m tower respectively. In the 12 year old plantation, the tower was also equipped with a Los Gatos FGGA-24EP, to assess CH4 fluxes. Chamber measurements were also carried out to obtain information on respiration and CH4 fluxes from the soil. Radiation was the major driver controlling net carbon uptake, while soil moisture did not play a significant role. Average net ecosystem exchange in the hours of the day with higher radiation for the whole measurement period was 10 μmol m-2 s-1 for the 2 year old plantation and -22 μmol m-2 s-1 in the 12 year old. The analysis of the cumulative fluxes show that the non-productive plantation was a carbon source of around 636 g CO2 m-2 during the 8 months of measurements, while in the productive period, it acted as a strong carbon sink (-794 g CO2 m-2 yr-1). Methane uptake was observed in the soil in both plantations and also for the whole ecosystem in the 12 year old one, but its

  2. Reconciliation of top-down and bottom-up CO2 fluxes in Siberian larch forest

    Science.gov (United States)

    Takata, Kumiko; Patra, Prabir K.; Kotani, Ayumi; Mori, Junko; Belikov, Dmitry; Ichii, Kazuhito; Saeki, Tazu; Ohta, Takeshi; Saito, Kazuyuki; Ueyama, Masahito; Ito, Akihiko; Maksyutov, Shamil; Miyazaki, Shin; Burke, Eleanor J.; Ganshin, Alexander; Iijima, Yoshihiro; Ise, Takeshi; Machiya, Hirokazu; Maximov, Trofim C.; Niwa, Yosuke; O’ishi, Ryo’ta; Park, Hotaek; Sasai, Takahiro; Sato, Hisashi; Tei, Shunsuke; Zhuravlev, Ruslan; Machida, Toshinobu; Sugimoto, Atsuko; Aoki, Shuji

    2017-12-01

    Carbon dioxide (CO2) fluxes by different methods vary largely at global, regional and local scales. The net CO2 fluxes by three bottom-up methods (tower observation (TWR), biogeochemical models (GTM), and a data-driven model (SVR)), and an ensemble of atmospheric inversions (top-down method, INV) are compared in Yakutsk, Siberia for 2004–2013. The region is characterized by highly homogeneous larch forest on a flat terrain. The ecosystem around Yakutsk shows a net sink of CO2 by all the methods (means during 2004–2007 were 10.9 g C m‑2 month‑1 by TWR, 4.28 g C m‑2 month‑1 by GTM, 5.62 g C m‑2 month‑1 and 0.863 g C m‑2 month‑1 by SVR at two different scales, and 4.89 g C m‑2 month‑1 by INV). Absorption in summer (June–August) was smaller by three bottom-up methods (ranged from 88.1 to 191.8 g C m‑2 month‑1) than the top-down method (223.6 g C m‑2 month‑1). Thus the peak-to-trough amplitude of the seasonal cycle is greater for the inverse models than bottom-up methods. The monthly-mean seasonal cycles agree among the four methods within the range of inter-model variations. The interannual variability estimated by an ensemble of inverse models and a site-scale data-driven model (the max-min range was 35.8 g C m‑2 month‑1and 34.2 g C m‑2 month‑1) is more similar to that of the tower observation (42.4 g C m‑2 month‑1) than those by the biogeochemical models and the large-scale data-driven model (9.5 g C m‑2 month‑1 and 1.45 g C m‑2 month‑1). The inverse models and tower observations captured a reduction in CO2 uptake after 2008 due to unusual waterlogging.

  3. Preliminary evidences of CCM operation and its down regulation in relation to increasing CO2 levels in natural phytoplankton assemblages from the coastal waters of Bay of Bengal

    Science.gov (United States)

    Biswas, Haimanti; Rahman Shaik, Aziz Ur; Bandyopadhyay, Debasmita

    2014-05-01

    Bay of Bengal (BoB), a low productive part of the North Indian Ocean, often possesses low CO2 levels in its surface water and diatoms dominate the phytoplankton communities. Virtually no studies are available from this area reporting how this diatom dominated phytoplankton community would respond any increase in dissolved CO2 levels either naturally or anthopogenically. In most of the marine phytoplankton, the inefficiency of the sole carbon fixing enzyme Rubisco necessitates the need of concentrating dissolved inorganic carbon (DIC) (mostly as HCO3) inside the cell in excess of the ambient water concentrations in order to maintain high rate of photosynthesis under low CO2 levels through an energy consuming carbon concentration mechanisms (CCMs). The ubiquitous enzyme carbonic anhydrase (CA) plays a vital role in CCMs by converting HCO3- to CO2 and usually utilizes the trace metal zinc (Zn) as a cofactor. However, it is evident in many marine phytoplankton species that with increasing external CO2 levels, CCMs can be down-regulated leading to energetic savings which can be reallocated to growth; although exceptions occur. Hence, in order to predict their responses to the projected changes, it is imperative to understand their carbon metabolism patterns. We have conducted a series of incubation experiments in microcosms with natural phytoplankton communities from the coastal waters of BoB under different CO2 levels. Our results revealed that the rate of net photosynthetic oxygen evolution and biomass build-up increased in response to increasing CO2 levels. The depletion in δ13CPOM values were more in the high CO2 treatments relative to the low CO2 treated cells (control), indicating that dissolved CO2 uptake was higher when CO2 levels were increased. When additional Zn was added to the low CO2 treated cells, net photosynthetic oxygen evolution rate was increased significantly than that of the untreated control. It is likely that upon the supply of Zn under low CO2

  4. Anomalous CO2 Emissions in Different Ecosystems Around the World

    Science.gov (United States)

    Sanchez-Canete, E. P.; Moya Jiménez, M. R.; Kowalski, A. S.; Serrano-Ortiz, P.; López-Ballesteros, A.; Oyonarte, C.; Domingo, F.

    2016-12-01

    As an important tool for understanding and monitoring ecosystem dynamics at ecosystem level, the eddy covariance (EC) technique allows the assessment of the diurnal and seasonal variation of the net ecosystem exchange (NEE). Despite the high temporal resolution data available, there are still many processes (in addition to photosynthesis and respiration) that, although they are being monitored, have been neglected. Only a few authors have studied anomalous CO2 emissions (non biological), and have related them to soil ventilation, photodegradation or geochemical processes. The aim of this study is: 1) to identify anomalous short term CO2 emissions in different ecosystems distributed around the world, 2) to determine the meteorological variables that are influencing these emissions, and 3) to explore the potential processes that can be involved. We have studied EC data together with other meteorological ancillary variables obtained from the FLUXNET database (version 2015) and have found more than 50 sites with anomalous CO2 emissions in different ecosystem types such as grasslands, croplands or savannas. Data were filtered according to the FLUXNET quality control flags (only data with quality control flag equal to 0 was used) and correlation analysis were performed with NEE and ancillary data. Preliminary results showed strong and highly significant correlations between meteorological variables and anomalous CO2 emissions. Correlation results showed clear differing behaviors between ecosystems types, which could be related to the different processes involved in the anomalous CO2 emissions. We suggest that anomalous CO2 emissions are happening globally and therefore, their contribution to the global net ecosystem carbon balance requires further investigation in order to better understand its drivers.

  5. Mineral nutrition and elevated [CO(2)] interact to modify δ(13)C, an index of gas exchange, in Norway spruce.

    Science.gov (United States)

    Marshall, John D; Linder, Sune

    2013-11-01

    The effects of the past century's increase in atmospheric CO2 concentration ([CO2]) have been recorded in the stable carbon isotope composition (δ(13)C) of the annual growth rings of trees. The isotope record frequently shows increases in photosynthetic CO2 uptake relative to stomatal conductance, which estimates the CO2 concentration gradient across the stomata (ca - ci). This variable, which is one control over the net photosynthetic rate, has been suggested as a homeostatic gas-exchange set point that is easy to estimate from δ(13)C and [CO2]. However, in high-latitude conifer forests, the literature is mixed; some studies show increases in (ca - ci) and others show homeostasis. Here we present leaf and tree-ring δ(13)C data from a controlled experiment that tested factorial combinations of elevated [CO2] (365 and 700 ∝mol mol(-1)) and fertilization on mature Norway spruce (Picea abies (L.) Karst.) trees in northern Sweden. We found first that the leaf carbon pool was contaminated by the current photosynthate in the older leaf cohorts. This is the reverse of the common observation that older photosynthate reserves can be used to produce new tissue; here the older tissue contains recent photosynthate. We found that the tree-ring data lack such contamination and in any case they better integrate over the canopy and the growing season than do leaves. In the second and third years of treatment, elevated [CO2] alone increased (ca - ci) by 38%; when combined with fertilization, it increased (ca - ci) by 60%. The results of this study support the idea that annual rings provide a clearer isotopic signal than do foliage age-classes. The tree-ring data show that inferred (ca - ci) depends not only on [CO2], but also on mineral-nutrient status. The differences in (ca - ci) are sufficiently large to account for the treatment-induced increase in wood-volume production in these stands.

  6. Exchange of CO2 in Arctic tundra: impacts of meteorological variations and biological disturbance

    Directory of Open Access Journals (Sweden)

    E. López-Blanco

    2017-10-01

    Full Text Available An improvement in our process-based understanding of carbon (C exchange in the Arctic and its climate sensitivity is critically needed for understanding the response of tundra ecosystems to a changing climate. In this context, we analysed the net ecosystem exchange (NEE of CO2 in West Greenland tundra (64° N across eight snow-free periods in 8 consecutive years, and characterized the key processes of net ecosystem exchange and its two main modulating components: gross primary production (GPP and ecosystem respiration (Reco. Overall, the ecosystem acted as a consistent sink of CO2, accumulating −30 g C m−2 on average (range of −17 to −41 g C m−2 during the years 2008–2015, except 2011 (source of 41 g C m−2, which was associated with a major pest outbreak. The results do not reveal a marked meteorological effect on the net CO2 uptake despite the high interannual variability in the timing of snowmelt and the start and duration of the growing season. The ranges in annual GPP (−182 to −316 g C m−2 and Reco (144 to 279 g C m−2 were  > 5 fold larger than the range in NEE. Gross fluxes were also more variable (coefficients of variation are 3.6 and 4.1 % respectively than for NEE (0.7 %. GPP and Reco were sensitive to insolation and temperature, and there was a tendency towards larger GPP and Reco during warmer and wetter years. The relative lack of sensitivity of NEE to meteorology was a result of the correlated response of GPP and Reco. During the snow-free season of the anomalous year of 2011, a biological disturbance related to a larvae outbreak reduced GPP more strongly than Reco. With continued warming temperatures and longer growing seasons, tundra systems will increase rates of C cycling. However, shifts in sink strength will likely be triggered by factors such as biological disturbances, events that will challenge our forecasting of C states.

  7. Exchange of CO2 in Arctic tundra: impacts of meteorological variations and biological disturbance

    Science.gov (United States)

    López-Blanco, Efrén; Lund, Magnus; Williams, Mathew; Tamstorf, Mikkel P.; Westergaard-Nielsen, Andreas; Exbrayat, Jean-François; Hansen, Birger U.; Christensen, Torben R.

    2017-10-01

    An improvement in our process-based understanding of carbon (C) exchange in the Arctic and its climate sensitivity is critically needed for understanding the response of tundra ecosystems to a changing climate. In this context, we analysed the net ecosystem exchange (NEE) of CO2 in West Greenland tundra (64° N) across eight snow-free periods in 8 consecutive years, and characterized the key processes of net ecosystem exchange and its two main modulating components: gross primary production (GPP) and ecosystem respiration (Reco). Overall, the ecosystem acted as a consistent sink of CO2, accumulating -30 g C m-2 on average (range of -17 to -41 g C m-2) during the years 2008-2015, except 2011 (source of 41 g C m-2), which was associated with a major pest outbreak. The results do not reveal a marked meteorological effect on the net CO2 uptake despite the high interannual variability in the timing of snowmelt and the start and duration of the growing season. The ranges in annual GPP (-182 to -316 g C m-2) and Reco (144 to 279 g C m-2) were > 5 fold larger than the range in NEE. Gross fluxes were also more variable (coefficients of variation are 3.6 and 4.1 % respectively) than for NEE (0.7 %). GPP and Reco were sensitive to insolation and temperature, and there was a tendency towards larger GPP and Reco during warmer and wetter years. The relative lack of sensitivity of NEE to meteorology was a result of the correlated response of GPP and Reco. During the snow-free season of the anomalous year of 2011, a biological disturbance related to a larvae outbreak reduced GPP more strongly than Reco. With continued warming temperatures and longer growing seasons, tundra systems will increase rates of C cycling. However, shifts in sink strength will likely be triggered by factors such as biological disturbances, events that will challenge our forecasting of C states.

  8. Assumption Centred Modelling of Ecosystem Responses to CO2 at Six US Atmospheric CO2 Enrichment Experiments.

    Science.gov (United States)

    Walker, A. P.; De Kauwe, M. G.; Medlyn, B. E.; Zaehle, S.; Luus, K. A.; Ryan, E.; Xia, J.; Norby, R. J.

    2015-12-01

    Plant photosynthetic rates increase and stomatal apertures decrease in response to elevated atmospheric CO[2] (eCO2), increasing both plant carbon (C) availability and water use efficiency. These physiological responses to eCO2 are well characterised and understood, however the ecological effects of these responses as they cascade through a suite of plant and ecosystem processes are complex and subject to multiple interactions and feedbacks. Therefore the response of the terrestrial carbon sink to increasing atmospheric CO[2] remains the largest uncertainty in global C cycle modelling to date, and is a huge contributor to uncertainty in climate change projections. Phase 2 of the FACE Model-Data Synthesis (FACE-MDS) project synthesises ecosystem observations from five long-term Free-Air CO[2] Enrichment (FACE) experiments and one open top chamber (OTC) experiment to evaluate the assumptions of a suite of terrestrial ecosystem models. The experiments are: The evergreen needleleaf Duke Forest FACE (NC), the deciduous broadleaf Oak Ridge FACE (TN), the prairie heating and FACE (WY), and the Nevada desert FACE, and the evergreen scrub oak OTC (FL). An assumption centered approach is being used to analyse: the interaction between eCO2 and water limitation on plant productivity; the interaction between eCO2 and temperature on plant productivity; whether increased rates of soil decomposition observed in many eCO2 experiments can account for model deficiencies in N uptake shown during Phase 1 of the FACE-MDS; and tracing carbon through the ecosystem to identify the exact cause of changes in ecosystem C storage.

  9. A young afforestation area in Iceland was a moderate sink to CO2 only a decade after scarification and establishment

    Directory of Open Access Journals (Sweden)

    B. D. Sigurdsson

    2009-12-01

    Full Text Available This study reports on three years (2004–2006 of measurements of net ecosystem exchange (NEE over a young Siberian larch plantation in Iceland established on previously grazed heathland pasture that had been scarified prior to planting. The study evaluated the variation of NEE and its component fluxes, gross primary production (GPP and ecosystem respiration (Re, with the aim to clarify how climatic factors controlled the site's carbon balance. The young plantation acted as a relatively strong sink for CO2 during all of the three years, with an annual net sequestration of −102, −154, and −67 g C m−2 for 2004, 2005, and 2006, respectively. This variation was more related to variation in carbon efflux (Re than carbon uptake (GPP. The abiotic factors that showed the strongest correlation to Re were air temperature during the growing season and soil water potential. The GPP mostly followed the seasonal pattern in irradiance, except in 2005, when the plantation experienced severe spring frost damage that set the GPP back to zero. It was not expected that the rather slow-growing Siberian larch plantation would be such a strong sink for atmospheric CO2 only twelve years after site preparation and afforestation.

  10. Evaluating Productivity Predictions Under Elevated CO2 Conditions: Multi-Model Benchmarking Across FACE Experiments

    Science.gov (United States)

    Cowdery, E.; Dietze, M.

    2016-12-01

    As atmospheric levels of carbon dioxide levels continue to increase, it is critical that terrestrial ecosystem models can accurately predict ecological responses to the changing environment. Current predictions of net primary productivity (NPP) in response to elevated atmospheric CO2 concentration are highly variable and contain a considerable amount of uncertainty.The Predictive Ecosystem Analyzer (PEcAn) is an informatics toolbox that wraps around an ecosystem model and can be used to help identify which factors drive uncertainty. We tested a suite of models (LPJ-GUESS, MAESPA, GDAY, CLM5, DALEC, ED2), which represent a range from low to high structural complexity, across a range of Free-Air CO2 Enrichment (FACE) experiments: the Kennedy Space Center Open Top Chamber Experiment, the Rhinelander FACE experiment, the Duke Forest FACE experiment and the Oak Ridge Experiment on CO2 Enrichment. These tests were implemented in a novel benchmarking workflow that is automated, repeatable, and generalized to incorporate different sites and ecological models. Observational data from the FACE experiments represent a first test of this flexible, extensible approach aimed at providing repeatable tests of model process representation.To identify and evaluate the assumptions causing inter-model differences we used PEcAn to perform model sensitivity and uncertainty analysis, not only to assess the components of NPP, but also to examine system processes such nutrient uptake and and water use. Combining the observed patterns of uncertainty between multiple models with results of the recent FACE-model data synthesis project (FACE-MDS) can help identify which processes need further study and additional data constraints. These findings can be used to inform future experimental design and in turn can provide informative starting point for data assimilation.

  11. Sea-air exchange patterns along the central and outer East Siberian Arctic Shelf as inferred from continuous CO2, stable isotope, and bulk chemistry measurements

    Science.gov (United States)

    Humborg, Christoph; Geibel, Marc C.; Anderson, Leif G.; Björk, Göran; Mörth, Carl-Magnus; Sundbom, Marcus; Thornton, Brett F.; Deutsch, Barbara; Gustafsson, Erik; Gustafsson, Bo; Ek, Jörgen; Semiletov, Igor

    2017-07-01

    This large-scale quasi-synoptic study gives a comprehensive picture of sea-air CO2 fluxes during the melt season in the central and outer Laptev Sea (LS) and East Siberian Sea (ESS). During a 7 week cruise we compiled a continuous record of both surface water and air CO2 concentrations, in total 76,892 measurements. Overall, the central and outer parts of the ESAS constituted a sink for CO2, and we estimate a median uptake of 9.4 g C m-2 yr-1 or 6.6 Tg C yr-1. Our results suggest that while the ESS and shelf break waters adjacent to the LS and ESS are net autotrophic systems, the LS is a net heterotrophic system. CO2 sea-air fluxes for the LS were 4.7 g C m-2 yr-1, and for the ESS we estimate an uptake of 7.2 g C m-2 yr-1. Isotopic composition of dissolved inorganic carbon (δ13CDIC and δ13CCO2) in the water column indicates that the LS is depleted in δ13CDIC compared to the Arctic Ocean (ArcO) and ESS with an offset of 0.5‰ which can be explained by mixing of δ13CDIC-depleted riverine waters and 4.0 Tg yr-1 respiration of OCter; only a minor part (0.72 Tg yr-1) of this respired OCter is exchanged with the atmosphere. Property-mixing diagrams of total organic carbon and isotope ratio (δ13CSPE-DOC) versus dissolved organic carbon (DOC) concentration diagram indicate conservative and nonconservative mixing in the LS and ESS, respectively. We suggest land-derived particulate organic carbon from coastal erosion as an additional significant source for the depleted δ13CDIC.

  12. Constraining gross primary production and ecosystem respiration estimates for North America using atmospheric observations of carbonyl sulfide (OCS) and CO2

    Science.gov (United States)

    He, W.; Ju, W.; Chen, H.; Peters, W.; van der Velde, I.; Baker, I. T.; Andrews, A. E.; Zhang, Y.; Launois, T.; Campbell, J. E.; Suntharalingam, P.; Montzka, S. A.

    2016-12-01

    Carbonyl sulfide (OCS) is a promising novel atmospheric tracer for studying carbon cycle processes. OCS shares a similar pathway as CO2 during photosynthesis but not released through a respiration-like process, thus could be used to partition Gross Primary Production (GPP) from Net Ecosystem-atmosphere CO2 Exchange (NEE). This study uses joint atmospheric observations of OCS and CO2 to constrain GPP and ecosystem respiration (Re). Flask data from tower and aircraft sites over North America are collected. We employ our recently developed CarbonTracker (CT)-Lagrange carbon assimilation system, which is based on the CT framework and the Weather Research and Forecasting - Stochastic Time-Inverted Lagrangian Transport (WRF-STILT) model, and the Simple Biosphere model with simulated OCS (SiB3-OCS) that provides prior GPP, Re and plant uptake fluxes of OCS. Derived plant OCS fluxes from both process model and GPP-scaled model are tested in our inversion. To investigate the ability of OCS to constrain GPP and understand the uncertainty propagated from OCS modeling errors to constrained fluxes in a dual-tracer system including OCS and CO2, two inversion schemes are implemented and compared: (1) a two-step scheme, which firstly optimizes GPP using OCS observations, and then simultaneously optimizes GPP and Re using CO2 observations with OCS-constrained GPP in the first step as prior; (2) a joint scheme, which simultaneously optimizes GPP and Re using OCS and CO2 observations. We will evaluate the result using an estimated GPP from space-borne solar-induced fluorescence observations and a data-driven GPP upscaled from FLUXNET data with a statistical model (Jung et al., 2011). Preliminary result for the year 2010 shows the joint inversion makes simulated mole fractions more consistent with observations for both OCS and CO2. However, the uncertainty of OCS simulation is larger than that of CO2. The two-step and joint schemes perform similarly in improving the consistence with

  13. Passive CO2 concentration in higher plants.

    Science.gov (United States)

    Sage, Rowan F; Khoshravesh, Roxana

    2016-06-01

    Photorespiratory limitations on C3 photosynthesis are substantial in warm, low CO2 conditions. To compensate, certain plants evolved mechanisms to actively concentrate CO2 around Rubisco using ATP-supported CO2 pumps such as C4 photosynthesis. Plants can also passively accumulate CO2 without additional ATP expenditure by localizing the release of photorespired and respired CO2 around Rubisco that is diffusively isolated from peripheral air spaces. Passive accumulation of photorespired CO2 occurs when glycine decarboxylase is localized to vascular sheath cells in what is termed C2 photosynthesis, and through forming sheaths of chloroplasts around the periphery of mesophyll cells. The peripheral sheaths require photorespired CO2 to re-enter chloroplasts where it can be refixed. Passive accumulation of respiratory CO2 is common in organs such as stems, fruits and flowers, due to abundant heterotrophic tissues and high diffusive resistance along the organ periphery. Chloroplasts within these organs are able to exploit this high CO2 to reduce photorespiration. CO2 concentration can also be enhanced passively by channeling respired CO2 from roots and rhizomes into photosynthetic cells of stems and leaves via lacunae, aerenchyma and the xylem stream. Through passive CO2 concentration, C3 species likely improved their carbon economy and maintained fitness during episodes of low atmospheric CO2. Copyright © 2016 Elsevier Ltd. All rights reserved.

  14. The CO2 emission registries; De CO2 registers

    Energy Technology Data Exchange (ETDEWEB)

    De Witt Wijnen, H.R. [De Brauw Blackstone Westbroek, Den Haag (Netherlands)

    2004-02-01

    The European Commission has made a first draft available of the Regulation for a standardized and secured system of CO2 -emissions registries. Transactions under the European emissions trading scheme will be settled in accordance with the rules of this Regulation. This article gives a summary of the Regulation and describes the way emissions transactions are going to take place. Any person can open an account in an emissions register. The relation between the Kyoto Protocol and the Regulation is discussed, such as the role of the Commitment Period Reserve. Emission Reductions will not qualify as registered goods under Dutch law, as information on individual accounts will not be made public. [Dutch] Begin november van het vorig jaar heeft de Europese Commissie een concept voor commentaar laten circuleren van een verordening inzake een gestandaardiseerd en beveiligd stelsel van registers (de 'Register Verordening'). Aangezien er op dit moment hard gewerkt wordt aan een wijziging van de Wet milieubeheer in verband met de invoering van een hoofdstuk inzake de handel in emissierechten, lijkt het nuttig om de Register Verordening thans al te bespreken. De Wet milieubeheer zal de Register Verordening hebben te volgen. Bovendien zal kennismaking met de Register Verordening het begrip voor de beoogde werking van de toekomstige Europese emissiehandel vergroten. In dit artikel is mede gebruik gemaakt van wetenswaardigheden opgedaan tijdens een bijeenkomst met de opstellers van de Register Verordening in november 2003.

  15. CO2 Fertilization: What Models Can Talk to Observations

    Science.gov (United States)

    Wang, W.; Nemani, R. R.; Schaefer, K. M.; Schwalm, C. R.; Huntzinger, D. N.; Zhang, G.; Xiong, J.

    2013-12-01

    Of the nearly 10 PgC carbon human beings currently emit into the atmosphere every year, only ~50% stays in the air while the rest is absorbed by the world's oceans and lands. This so-called airborne ratio has stayed surprisingly stable in the past five decades, strongly suggesting that natural carbon sinks strengthening with the increasing atmospheric CO2 concentration. For terrestrial carbon sinks, it implies the fertilization of CO2 on vegetation primary production. However, measurements on-the-ground seem to deliver inconsistent messages regarding the magnitude and the spatio-temporal extent of the fertilization effect, whose identification is likely obscured by concurrent changes in climate and human activities as well as other biological processes (e.g., respiration). In contrast, carefully designed ecosystem-model experiments provide a controlled environment to disentangle the different effects exerted by all the interacting processes. In this study, we use ensemble model results from the Multi-scale Synthesis and Terrestrial Model Intercomparison Project (MsTMIP) to evaluate the effect of CO2 fertilization on global terrestrial gross primary production (GPP). By comparing the model simulations sequentially with controlled climate, atmospheric CO2 concentration, nitrogen deposition, and other factors, we find that a spatially rather homogenous fertilization of CO2 on in the model simulated GPP. However, the net effects of the CO2 fertilization are complicated, in particular, by different ecosystem responses to changes in temperature and precipitation at different geo-locations. As such, the model results coming out from MsTMIP may help in guiding a more reliable evaluation of the CO2 fertilization effect in the observations.

  16. Epoxy based oxygen enriched porous carbons for CO2 capture

    Science.gov (United States)

    Tiwari, Deepak; Bhunia, Haripada; Bajpai, Pramod K.

    2017-08-01

    Oxygen enriched carbon adsorbents were successfully synthesized for the first time from template zeolite and epoxy resin as precursor using a nanocasting technique. Carbonization and CO2 activation were performed at various temperatures (500-800 °C) to prepare different carbon structure adsorbents. Several characterization techniques were used to characterize the textural structure, oxygen content and surface functional groups of the adsorbents. The carbon adsorbents show high oxygen content (47.51%), highest surface area (SBET = 686.37 m2 g-1) and pore volume (0.60 cm3 g-1), respectively. The materials were evaluated thermogravimetrically at different adsorption temperatures (30-100 °C) and CO2 concentrations (6-100%). Adsorbent prepared at 700 °C exhibited highest CO2 uptake of 0.91 mmol g-1 due to high surface basicity. Further, regeneration studies of adsorbent exhibited easy regenerability and stability over four multiple adsorptions-desorption cycles. Kinetic models for CO2 adsorption at various CO2 concentrations and temperatures were studied and it was found that the fractional order provided best fitting for the adsorption behavior with an error of less than 3%. The experimental data for CO2 adsorption were analyzed using different isothermal models and found that the Freundlich isothermal model presented perfect fit among all isotherm models depicting heterogeneous adsorbent surface. The isosteric heat of adsorption was estimated to be 11.75 kJ mol-1, indicating physiosorption process. Overall, the above results suggested that the synthesized adsorbent using nanocasting technique provides a feasible way for CO2 capture from point source due to their environmentally benign nature, low cost and stable adsorption capacity.

  17. The ins and outs of CO2

    National Research Council Canada - National Science Library

    Raven, John A; Beardall, John

    2016-01-01

    ...; this article examines what is known and where there are gaps in knowledge. Irreversible decarboxylases produce CO2, and CO2 is the substrate/product of enzymes that act as carboxylases and decarboxylases...

  18. ISLSCP II Globalview: Atmospheric CO2 Concentrations

    Data.gov (United States)

    National Aeronautics and Space Administration — The GlobalView Carbon Dioxide (CO2) data product contains synchronized and smoothed time series of atmospheric CO2 concentrations at selected sites that were created...

  19. CO2 Capture for Cement Technology

    DEFF Research Database (Denmark)

    Pathi, Sharat Kumar

    Production of cement is an energy intensive process and is the source of considerable CO2emissions. Itis estimated that the cement industry contributes around 8% of total global CO2emissions. CO2is oneof the major greenhouse gases. In the atmosphere, the CO2concentration has increased from 310...... ppmvin 1960 to 390 ppmv in 2012, probably due to human activity. A lot of research is being carried out forreducing CO2emissions from large stationary sources. Ofwhich, the carbonate looping process is anew process and has the potential to reduce CO2emissions with lower energy penalties. Most of thework...... performed recently has focused on CO2capture from fossil fuel-based power plants. Inherently,this process is especially suitablefor cement plants, as CaO used for CO2capture is also a majoringredient for clinker production. Thus, a detailed investigation was carried outto study the applicationof...

  20. CO2 Virtual Science Data Environment API

    Data.gov (United States)

    National Aeronautics and Space Administration — The CO2 Virtual Data Environment is a comprehensive effort at bringing together the models, data, and tools necessary to perform research on atmospheric CO2.This...

  1. ISLSCP II Globalview: Atmospheric CO2 Concentrations

    Data.gov (United States)

    National Aeronautics and Space Administration — ABSTRACT: The GlobalView Carbon Dioxide (CO2) data product contains synchronized and smoothed time series of atmospheric CO2 concentrations at selected sites that...

  2. Environmental Impact and Nutritional Improvement of Elevated CO2 Treatment: A Case Study of Spinach Production

    Directory of Open Access Journals (Sweden)

    Yuna Seo

    2017-10-01

    Full Text Available The agriculture sector is known to be the one of the major contributors to global greenhouse gas (GHG emissions. At the same time, global climate changes have affected the agriculture sector. In order to strengthen the sustainable development of agriculture, it is important to promote environmentally friendly farming and simultaneously increase the economic value. To improve the productivity of agriculture, technical advancements have occurred. Among those, we have focused on CO2 treatment in cultivation. We aimed to clarify the effectiveness of the elevated CO2 treatment of spinach based on GHG emission and the economic value using the eco-efficiency score. We assumed that nutrition could represent the value of the vegetable. We measured weights, vitamin C, and CO2 emissions of elevated CO2 treatment and conventional production. We used life cycle assessment (LCA to estimate CO2 emissions. CO2 emissions of a 100-g bouquet of spinach were estimated from agricultural inputs, farming, transport, and distribution center processes at a model spinach farm in Japan. CO2 emission of elevated CO2 treatment was 29.0 g-CO2, and was 49.0 g-CO2 for conventional production. The net weight of a bouquet of elevated CO2-treated spinach was 1.69-fold greater than that of conventional production. Vitamin C per 100 g spinach produced via elevated CO2 treatment was 15.1 mg, and that of conventional production was 13.5 mg on average. Finally, based on the above results, we assessed the eco-efficiency scores of the elevated CO2 treatment and conventional production of spinach, enabling integration of the nutritional value and the environmental impact. The score showed that elevated CO2 treatment (0.76 was 2.9-fold more efficient than conventional production (0.26. This study suggested that elevated CO2 treatment could enhance growth and nutritional value of spinach, and further contribute to CO2 reduction.

  3. Effects of elevated atmospheric CO2 on respiratory rates in mature leaves of two rice cultivars grown at a free-air CO2 enrichment site and analyses of the underlying mechanisms.

    Science.gov (United States)

    Noguchi, Ko; Tsunoda, Tomonori; Miyagi, Atsuko; Kawai-Yamada, Maki; Sugiura, Daisuke; Miyazawa, Shin-Ichi; Tokida, Takeshi; Usui, Yasuhiro; Nakamura, Hirofumi; Sakai, Hidemitsu; Hasegawa, Toshihiro

    2018-02-01

    Respiratory CO2 efflux and O2 uptake rates in leaves change in response to the growth CO2 concentration ([CO2]). The degrees of change vary depending on the responses of cellular processes such as nitrogen (N) assimilation and organic acids accumulation to growth [CO2]. However, the underlying mechanisms remain unclear. Here, we examined the respiratory characteristics of mature leaves of two rice varieties with different yield capacities at different growth stages under ambient and elevated [CO2] conditions at a free-air CO2 enrichment site. We also examined effect of increased water temperature to leaf respiration. We measured the rates of CO2 efflux and O2 uptake, and determined N contents, primary metabolite contents, and maximal activities of respiratory enzymes. The leaf CO2 efflux rates decreased in plants grown at elevated [CO2] in both varieties, and were higher in high-yielding Takanari than in Koshihikari. The leaf O2 uptake rates showed little changes with respect to growth [CO2] and variety. The increased water temperature did not significantly affect the CO2 efflux and O2 uptake rates. The N and amino acids contents were significantly higher in Takanari than in Koshihikari. The enhanced N assimilation in Takanari may have consumed more respiratory NADH, leading to higher CO2 efflux rates. In Koshihikari, the ratio of TCA cycle intermediates changed and maximal activities of enzymes in the TCA cycle decreased at elevated [CO2]. Therefore, the decreased rates of CO2 efflux in Koshihikari may be due to the decreased activities of TCA cycle enzymes at elevated [CO2]. © The Author 2018. Published by Oxford University Press on behalf of Japanese Society of Plant Physiologists. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.

  4. The positive net radiative greenhouse gas forcing of increasing methane emissions from a thawing boreal forest-wetland landscape.

    Science.gov (United States)

    Helbig, Manuel; Chasmer, Laura E; Kljun, NatasCha; Quinton, William L; Treat, Claire C; Sonnentag, Oliver

    2017-06-01

    At the southern margin of permafrost in North America, climate change causes widespread permafrost thaw. In boreal lowlands, thawing forested permafrost peat plateaus ('forest') lead to expansion of permafrost-free wetlands ('wetland'). Expanding wetland area with saturated and warmer organic soils is expected to increase landscape methane (CH4 ) emissions. Here, we quantify the thaw-induced increase in CH4 emissions for a boreal forest-wetland landscape in the southern Taiga Plains, Canada, and evaluate its impact on net radiative forcing relative to potential long-term net carbon dioxide (CO2 ) exchange. Using nested wetland and landscape eddy covariance net CH4 flux measurements in combination with flux footprint modeling, we find that landscape CH4 emissions increase with increasing wetland-to-forest ratio. Landscape CH4 emissions are most sensitive to this ratio during peak emission periods, when wetland soils are up to 10 °C warmer than forest soils. The cumulative growing season (May-October) wetland CH4 emission of ~13 g CH4  m-2 is the dominating contribution to the landscape CH4 emission of ~7 g CH4  m-2 . In contrast, forest contributions to landscape CH4 emissions appear to be negligible. The rapid wetland expansion of 0.26 ± 0.05% yr-1 in this region causes an estimated growing season increase of 0.034 ± 0.007 g CH4  m-2  yr-1 in landscape CH4 emissions. A long-term net CO2 uptake of >200 g CO2  m-2  yr-1 is required to offset the positive radiative forcing of increasing CH4 emissions until the end of the 21st century as indicated by an atmospheric CH4 and CO2 concentration model. However, long-term apparent carbon accumulation rates in similar boreal forest-wetland landscapes and eddy covariance landscape net CO2 flux measurements suggest a long-term net CO2 uptake between 49 and 157 g CO2  m-2  yr-1 . Thus, thaw-induced CH4 emission increases likely exert a positive net radiative greenhouse gas forcing through the 21st century.

  5. An inorganic CO2 diffusion and dissolution process explains negative CO2 fluxes in saline/alkaline soils

    Science.gov (United States)

    Ma, Jie; Wang, Zhong-Yuan; Stevenson, Bryan A.; Zheng, Xin-Jun; Li, Yan

    2013-01-01

    An ‘anomalous' negative flux, in which carbon dioxide (CO2) enters rather than is released from the ground, was studied in a saline/alkaline soil. Soil sterilization disclosed an inorganic process of CO2 dissolution into (during the night) and out of (during the day) the soil solution, driven by variation in soil temperature. Experimental and modeling analysis revealed that pH and soil moisture were the most important determinants of the magnitude of this inorganic CO2 flux. In the extreme cases of air-dried saline/alkaline soils, this inorganic process was predominant. While the diurnal flux measured was zero sum, leaching of the dissolved inorganic carbon in the soil solution could potentially effect net carbon ecosystem exchange. This finding implies that an inorganic module should be incorporated when dealing with the CO2 flux of saline/alkaline land. Neglecting this inorganic flux may induce erroneous or misleading conclusions in interpreting CO2 fluxes of these ecosystems. PMID:23778238

  6. Carbon Dioxide (CO2) in Blood

    Science.gov (United States)

    ... https://medlineplus.gov/labtests/carbondioxideco2inblood.html Carbon Dioxide (CO2) in Blood To use the sharing features on ... please enable JavaScript. What is a Carbon Dioxide (CO2) Blood Test? Carbon dioxide (CO2) is an odorless, ...

  7. Prognose CO2-emissie glastuinbouw 2020

    NARCIS (Netherlands)

    Velden, van der Nico; Smit, Pepijn

    2016-01-01

    The greenhouse horticulture sector and government agreed in a covenant on a CO2 emission budget
    for 2020. It appeared that the 2014 CO2 emissions were considerably lower than this CO2 emission
    budget. The covenant signatories also agreed that an interim evaluation would be carried out

  8. Bench-Scale Testing and Process Performance Projections of CO2 Capture by CO2–Binding Organic Liquids (CO2BOLs) With and Without Polarity-Swing-Assisted Regeneration

    Energy Technology Data Exchange (ETDEWEB)

    Zheng, Feng; Heldebrant, David J.; Mathias, Paul M.; Koech, Phillip K.; Bhakta, Mukund; Freeman, Charles J.; Bearden, Mark D.; Zwoster, Andy

    2016-01-12

    This manuscript provides a detailed analysis of a continuous flow, bench scale study of the CO2BOL solvent platform with and without its Polarity Swing Assisted Regeneration (PSAR). This study encompassed four months of continuous flow testing of a candidate CO2BOL with a thermal regeneration and PSAR regeneration using decane antisolvent. In both regeneration schemes, steady state capture of >90 %CO2 was achieved using simulated flue gas at acceptable L/G ratios. Aspen Plus™ modeling was performed to assess process performance compared to previous equilibrium performance projections. This paper also includes net power projections, and comparisons to DOE’s Case 10 amine baseline.

  9. Technical note: Evaluation of three machine learning models for surface ocean CO2 mapping

    Science.gov (United States)

    Zeng, Jiye; Matsunaga, Tsuneo; Saigusa, Nobuko; Shirai, Tomoko; Nakaoka, Shin-ichiro; Tan, Zheng-Hong

    2017-04-01

    Reconstructing surface ocean CO2 from scarce measurements plays an important role in estimating oceanic CO2 uptake. There are varying degrees of differences among the 14 models included in the Surface Ocean CO2 Mapping (SOCOM) inter-comparison initiative, in which five models used neural networks. This investigation evaluates two neural networks used in SOCOM, self-organizing maps and feedforward neural networks, and introduces a machine learning model called a support vector machine for ocean CO2 mapping. The technique note provides a practical guide to selecting the models.

  10. The polar ocean and glacial cycles in atmospheric CO(2) concentration.

    Science.gov (United States)

    Sigman, Daniel M; Hain, Mathis P; Haug, Gerald H

    2010-07-01

    Global climate and the atmospheric partial pressure of carbon dioxide () are correlated over recent glacial cycles, with lower during ice ages, but the causes of the changes are unknown. The modern Southern Ocean releases deeply sequestered CO(2) to the atmosphere. Growing evidence suggests that the Southern Ocean CO(2) 'leak' was stemmed during ice ages, increasing ocean CO(2) storage. Such a change would also have made the global ocean more alkaline, driving additional ocean CO(2) uptake. This explanation for lower ice-age , if correct, has much to teach us about the controls on current ocean processes.

  11. Net loss of CaCO3 from coral reef communities due to human induced seawater acidification

    Science.gov (United States)

    Andersson, A.J.; Kuffner, I.B.; MacKenzie, F.T.; Jokiel, P.L.; Rodgers, K.S.; Tan, A.

    2009-01-01

    Acidification of seawater owing to oceanic uptake of atmospheric CO2 originating from human activities such as burning of fossil fuels and land-use changes has raised serious concerns regarding its adverse effects on corals and calcifying communities. Here we demonstrate a net loss of calcium carbonate (CaCO3) material as a result of decreased calcification and increased carbonate dissolution from replicated subtropical coral reef communities (n=3) incubated in continuous-flow mesocosms subject to future seawater conditions. The calcifying community was dominated by the coral Montipora capitata. Daily average community calcification or Net Ecosystem Calcification (NEC=CaCO3 production – dissolution) was positive at 3.3 mmol CaCO3 m−2 h−1 under ambient seawater pCO2 conditions as opposed to negative at −0.04 mmol CaCO3 m−2h−1 under seawater conditions of double the ambient pCO2. These experimental results provide support for the conclusion that some net calcifying communities could become subject to net dissolution in response to anthropogenic ocean acidification within this century. Nevertheless, individual corals remained healthy, actively calcified (albeit slower than at present rates), and deposited significant amounts of CaCO3 under the prevailing experimental seawater conditions of elevated pCO2.

  12. A chloroplast pump model for the CO2 concentrating mechanism in the diatom Phaeodactylum tricornutum.

    Science.gov (United States)

    Hopkinson, Brian M

    2014-09-01

    Prior analysis of inorganic carbon (Ci) fluxes in the diatom Phaeodactylum tricornutum has indicated that transport of Ci into the chloroplast from the cytoplasm is the major Ci flux in the cell and the primary driving force for the CO2 concentrating mechanism (CCM). This flux drives the accumulation of Ci in the chloroplast stroma and generates a CO2 deficit in the cytoplasm, inducing CO2 influx into the cell. Here, the "chloroplast pump" model of the CCM in P. tricornutum is formalized and its consistency with data on CO2 and HCO3 (-) uptake rates, carbonic anhydrase (CA) activity, intracellular Ci concentration, intracellular pH, and RubisCO characteristics is assessed. The chloroplast pump model can account for the major features of the data. Analysis of photosynthetic and Ci uptake rates as a function of external Ci concentration shows that the model has the most difficulty obtaining sufficiently low cytoplasmic CO2 concentrations to support observed CO2 uptake rates at low external Ci concentrations and achieving high rates of photosynthesis. There are multiple ways in which model parameters can be varied, within a plausible range, to match measured rates of photosynthesis and CO2 uptake. To increase CO2 uptake rates, CA activity can be increased, kinetic characteristics of the putative chloroplast pump can be enhanced to increase HCO3 (-) export, or the cytoplasmic pH can be raised. To increase the photosynthetic rate, the permeability of the pyrenoid to CO2 can be reduced or RubisCO content can be increased.

  13. Forest succession at elevated CO2

    Energy Technology Data Exchange (ETDEWEB)

    Clark, James S.; Schlesinger, William H.

    2002-02-01

    We tested hypotheses concerning the response of forest succession to elevated CO2 in the FACTS-1 site at the Duke Forest. We quantified growth and survival of naturally recruited seedlings, tree saplings, vines, and shrubs under ambient and elevated CO2. We planted seeds and seedlings to augment sample sites. We augmented CO2 treatments with estimates of shade tolerance and nutrient limitation while controlling for soil and light effects to place CO2 treatments within the context of natural variability at the site. Results are now being analyzed and used to parameterize forest models of CO2 response.

  14. CO2-induced seawater acidification affects physiological performance of the marine diatom Phaeodactylum tricornutum

    Directory of Open Access Journals (Sweden)

    U. Riebesell

    2010-09-01

    Full Text Available CO2/pH perturbation experiments were carried out under two different pCO2 levels (39.3 and 101.3 Pa to evaluate effects of CO2-induced ocean acidification on the marine diatom Phaeodactylum tricornutum. After acclimation (>20 generations to ambient and elevated CO2 conditions (with corresponding pH values of 8.15 and 7.80, respectively, growth and photosynthetic carbon fixation rates of high CO2 grown cells were enhanced by 5% and 12%, respectively, and dark respiration stimulated by 34% compared to cells grown at ambient CO2. The half saturation constant (Km for carbon fixation (dissolved inorganic carbon, DIC increased by 20% under the low pH and high CO2 condition, reflecting a decreased affinity for HCO3– or/and CO2 and down-regulated carbon concentrating mechanism (CCM. In the high CO2 grown cells, the electron transport rate from photosystem II (PSII was photoinhibited to a greater extent at high levels of photosynthetically active radiation, while non-photochemical quenching was reduced compared to low CO2 grown cells. This was probably due to the down-regulation of CCM, which serves as a sink for excessive energy. The balance between these positive and negative effects on diatom productivity will be a key factor in determining the net effect of rising atmospheric CO2 on ocean primary production.

  15. CO2 clearance by membrane lungs.

    Science.gov (United States)

    Sun, Liqun; Kaesler, Andreas; Fernando, Piyumindri; Thompson, Alex J; Toomasian, John M; Bartlett, Robert H

    2017-10-01

    Commercial membrane lungs are designed to transfer a specific amount of oxygen per unit of venous blood flow. Membrane lungs are much more efficient at removing CO2 than adding oxygen, but the range of CO2 transfer is rarely reported. Commercial membrane lungs were studied with the goal of evaluating CO2 removal capacity. CO2 removal was measured in 4 commercial membrane lungs under standardized conditions. CO2 clearance can be greater than 4 times that of oxygen at a given blood flow when the gas to blood flow ratio is elevated to 4:1 or 8:1. The CO2 clearance was less dependent on surface area and configuration than oxygen transfer. Any ECMO system can be used for selective CO2 removal.

  16. Comparison of Sea-Air CO2 Flux Estimates Using Satellite-Based Versus Mooring Wind Speed Data

    Science.gov (United States)

    Sutton, A. J.; Sabine, C. L.; Feely, R. A.; Wanninkhof, R. H.

    2016-12-01

    The global ocean is a major sink of anthropogenic CO2, absorbing approximately 27% of CO2 emissions since the beginning of the industrial revolution. Any variation or change in the ocean CO2 sink has implications for future climate. Observations of sea-air CO2 flux have relied primarily on ship-based underway measurements of partial pressure of CO2 (pCO2) combined with satellite, model, or multi-platform wind products. Direct measurements of ΔpCO2 (seawater - air pCO2) and wind speed from moored platforms now allow for high-resolution CO2 flux time series. Here we present a comparison of CO2 flux calculated from moored ΔpCO2 measured on four moorings in different biomes of the Pacific Ocean in combination with: 1) Cross-Calibrated Multi-Platform (CCMP) winds or 2) wind speed measurements made on ocean reference moorings excluded from the CCMP dataset. Preliminary results show using CCMP winds overestimates CO2 flux on average by 5% at the Kuroshio Extension Observatory, Ocean Station Papa, WHOI Hawaii Ocean Timeseries Station, and Stratus. In general, CO2 flux seasonality follows patterns of seawater pCO2 and SST with periods of CO2 outgassing during summer and CO2 uptake during winter at these locations. Any offsets or seasonal biases in CCMP winds could impact global ocean sink estimates using this data product. Here we present patterns and trends between the two CO2 flux estimates and discuss the potential implications for tracking variability and change in global ocean CO2 uptake.

  17. Extraction of stevia glycosides with CO2 + water, CO2 + ethanol, and CO2 + water + ethanol

    Directory of Open Access Journals (Sweden)

    A. Pasquel

    2000-09-01

    Full Text Available Stevia leaves are an important source of natural sugar substitute. There are some restrictions on the use of stevia extract because of its distinctive aftertaste. Some authors attribute this to soluble material other than the stevia glycosides, even though it is well known that stevia glycosides have to some extent a bitter taste. Therefore, the purpose of this work was to develop a process to obtain stevia extract of a better quality. The proposed process includes two steps: i Pretreatment of the leaves by SCFE; ii Extraction of the stevia glycosides by SCFE using CO2 as solvent and water and/or ethanol as cosolvent. The mean total yield for SCFE pretreatment was 3.0%. The yields for SCFE with cosolvent of stevia glycosides were below 0.50%, except at 120 bar, 16°C, and 9.5% (molar of water. Under this condition, total yield was 3.4%. The quality of the glycosidic fraction with respect to its capacity as sweetener was better for the SCFE extract as compared to extract obtained by the conventional process. The overall extraction curves were well described by the Lack extended model.

  18. Enhancement of CO2Affinity in a Polymer of Intrinsic Microporosity by Amine Modification.

    Science.gov (United States)

    Mason, Christopher R; Maynard-Atem, Louise; Heard, Kane W J; Satilmis, Bekir; Budd, Peter M; Friess, Karel; Lanc̆, Marek; Bernardo, Paola; Clarizia, Gabriele; Jansen, Johannes C

    2014-02-11

    Nitrile groups in the polymer of intrinsic microporosity PIM-1 were reduced to primary amines using borane complexes. In adsorption experiments, the novel amine-PIM-1 showed higher CO 2 uptake and higher CO 2 /N 2 sorption selectivity than the parent polymer, with very evident dual-mode sorption behavior. In gas permeation with six light gases, the individual contributions of solubility and diffusion to the overall permeability was determined via time-lag analysis. The high CO 2 affinity drastically restricts diffusion at low pressures and lowers CO 2 permeability compared to the parent PIM-1. Furthermore, the size-sieving properties of the polymer are increased, which can be attributed to a higher stiffness of the system arising from hydrogen bonding of the amine groups. Thus, for the H 2 /CO 2 gas pair, whereas PIM-1 favors CO 2 , amine-PIM-1 shows permselectivity toward H 2 , breaking the Robeson 2008 upper bound.

  19. Evaluation of 11 terrestrial carbon-nitrogen cycle models against observations from two temperate Free-Air CO2 Enrichment studies.

    Science.gov (United States)

    Zaehle, Sönke; Medlyn, Belinda E; De Kauwe, Martin G; Walker, Anthony P; Dietze, Michael C; Hickler, Thomas; Luo, Yiqi; Wang, Ying-Ping; El-Masri, Bassil; Thornton, Peter; Jain, Atul; Wang, Shusen; Warlind, David; Weng, Ensheng; Parton, William; Iversen, Colleen M; Gallet-Budynek, Anne; McCarthy, Heather; Finzi, Adrien; Hanson, Paul J; Prentice, I Colin; Oren, Ram; Norby, Richard J

    2014-05-01

    We analysed the responses of 11 ecosystem models to elevated atmospheric [CO2 ] (eCO2 ) at two temperate forest ecosystems (Duke and Oak Ridge National Laboratory (ORNL) Free-Air CO2 Enrichment (FACE) experiments) to test alternative representations of carbon (C)-nitrogen (N) cycle processes. We decomposed the model responses into component processes affecting the response to eCO2 and confronted these with observations from the FACE experiments. Most of the models reproduced the observed initial enhancement of net primary production (NPP) at both sites, but none was able to simulate both the sustained 10-yr enhancement at Duke and the declining response at ORNL: models generally showed signs of progressive N limitation as a result of lower than observed plant N uptake. Nonetheless, many models showed qualitative agreement with observed component processes. The results suggest that improved representation of above-ground-below-ground interactions and better constraints on plant stoichiometry are important for a predictive understanding of eCO2 effects. Improved accuracy of soil organic matter inventories is pivotal to reduce uncertainty in the observed C-N budgets. The two FACE experiments are insufficient to fully constrain terrestrial responses to eCO2 , given the complexity of factors leading to the observed diverging trends, and the consequential inability of the models to explain these trends. Nevertheless, the ecosystem models were able to capture important features of the experiments, lending some support to their projections. © 2014 The Authors. New Phytologist © 2014 New Phytologist Trust.

  20. CO2 flux from Javanese mud volcanism

    Science.gov (United States)

    Queißer, M.; Burton, M. R.; Arzilli, F.; Chiarugi, A.; Marliyani, G. I.; Anggara, F.; Harijoko, A.

    2017-06-01

    Studying the quantity and origin of CO2 emitted by back-arc mud volcanoes is critical to correctly model fluid-dynamical, thermodynamical, and geochemical processes that drive their activity and to constrain their role in the global geochemical carbon cycle. We measured CO2 fluxes of the Bledug Kuwu mud volcano on the Kendeng Fold and thrust belt in the back arc of Central Java, Indonesia, using scanning remote sensing absorption spectroscopy. The data show that the expelled gas is rich in CO2 with a volume fraction of at least 16 vol %. A lower limit CO2 flux of 1.4 kg s-1 (117 t d-1) was determined, in line with the CO2 flux from the Javanese mud volcano LUSI. Extrapolating these results to mud volcanism from the whole of Java suggests an order of magnitude total CO2 flux of 3 kt d-1, comparable with the expected back-arc efflux of magmatic CO2. After discussing geochemical, geological, and geophysical evidence we conclude that the source of CO2 observed at Bledug Kuwu is likely a mixture of thermogenic, biogenic, and magmatic CO2, with faulting controlling potential pathways for magmatic fluids. This study further demonstrates the merit of man-portable active remote sensing instruments for probing natural gas releases, enabling bottom-up quantification of CO2 fluxes.

  1. CO2 flux from Javanese mud volcanism.

    Science.gov (United States)

    Queißer, M; Burton, M R; Arzilli, F; Chiarugi, A; Marliyani, G I; Anggara, F; Harijoko, A

    2017-06-01

    Studying the quantity and origin of CO2 emitted by back-arc mud volcanoes is critical to correctly model fluid-dynamical, thermodynamical, and geochemical processes that drive their activity and to constrain their role in the global geochemical carbon cycle. We measured CO2 fluxes of the Bledug Kuwu mud volcano on the Kendeng Fold and thrust belt in the back arc of Central Java, Indonesia, using scanning remote sensing absorption spectroscopy. The data show that the expelled gas is rich in CO2 with a volume fraction of at least 16 vol %. A lower limit CO2 flux of 1.4 kg s-1 (117 t d-1) was determined, in line with the CO2 flux from the Javanese mud volcano LUSI. Extrapolating these results to mud volcanism from the whole of Java suggests an order of magnitude total CO2 flux of 3 kt d-1, comparable with the expected back-arc efflux of magmatic CO2. After discussing geochemical, geological, and geophysical evidence we conclude that the source of CO2 observed at Bledug Kuwu is likely a mixture of thermogenic, biogenic, and magmatic CO2, with faulting controlling potential pathways for magmatic fluids. This study further demonstrates the merit of man-portable active remote sensing instruments for probing natural gas releases, enabling bottom-up quantification of CO2 fluxes.

  2. Porous Organic Polymers for CO2 Capture

    KAUST Repository

    Teng, Baiyang

    2013-05-01

    Carbon dioxide (CO2) has long been regarded as the major greenhouse gas, which leads to numerous negative effects on global environment. The capture and separation of CO2 by selective adsorption using porous materials proves to be an effective way to reduce the emission of CO2 to atmosphere. Porous organic polymers (POPs) are promising candidates for this application due to their readily tunable textual properties and surface functionalities. The objective of this thesis work is to develop new POPs with high CO2 adsorption capacities and CO2/N2 selectivities for post-combustion effluent (e.g. flue gas) treatment. We will also exploit the correlation between the CO2 capture performance of POPs and their textual properties/functionalities. Chapters Two focuses on the study of a group of porous phenolic-aldehyde polymers (PPAPs) synthesized by a catalyst-free method, the CO2 capture capacities of these PPAPs exceed 2.0 mmol/g at 298 K and 1 bar, while keeping CO2/N2 selectivity of more than 30 at the same time. Chapter Three reports the gas adsorption results of different hyper-cross-linked polymers (HCPs), which indicate that heterocyclo aromatic monomers can greatly enhance polymers’ CO2/N2 selectivities, and the N-H bond is proved to the active CO2 adsorption center in the N-contained (e.g. pyrrole) HCPs, which possess the highest selectivities of more than 40 at 273 K when compared with other HCPs. Chapter Four emphasizes on the chemical modification of a new designed polymer of intrinsic microporosity (PIM) with high CO2/N2 selectivity (50 at 273 K), whose experimental repeatability and chemical stability prove excellent. In Chapter Five, we demonstrate an improvement of both CO2 capture capacity and CO2/N2 selectivity by doping alkali metal ions into azo-polymers, which leads a promising method to the design of new porous organic polymers.

  3. Utility of deep sea CO2 release experiments in understanding the biology of a high-CO2 ocean: Effects of hypercapnia on deep sea meiofauna

    Science.gov (United States)

    Barry, James P.; Buck, Kurt R.; Lovera, Chris; Kuhnz, Linda; Whaling, Patrick J.

    2005-09-01

    Oceanic CO2 levels are expected to rise during the next 2 centuries to levels not seen for 10-150 million years by the uptake of atmospheric CO2 in surface waters or potentially through the disposal of waste CO2 in the deep sea. Changes in ocean chemistry caused by CO2 influx may have broad impacts on ocean ecosystems. Physiological processes animals use to cope with CO2-related stress are known, but the range of sensitivities and effects of changes in ocean chemistry on most ocean life remain unclear. We evaluate the effectiveness of various designs for in situ CO2 release experiments in producing stable perturbations in seawater chemistry over experimental seafloor plots, as is desirable for evaluating the CO2 sensitivities of deep sea animals. We also discuss results from a subset of these experiments on the impacts of hypercapnia on deep sea meiofauna, in the context of experimental designs. Five experiments off central California show that pH perturbations were greatest for experiments using "point source" CO2 pools surrounded by experimental plots. CO2 enclosure experiments with experimental plots positioned within a circular arrangement of CO2 pools had more moderate pH variation. The concentration of dissolution plumes from CO2 pools were related to the speed and turbulence of near-bottom currents, which influence CO2 dissolution and advection. Survival of meiofauna (nematodes, amoebae, euglenoid flagellates) was low after episodic severe hypercapnia but lower and variable where pH changes ranged from 0 to 0.2 pH units below normal.

  4. Molten Salt Promoting Effect in Double Salt CO2 Absorbents

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Keling; Li, Xiaohong S.; Chen, Haobo; Singh, Prabhakar; King, David L.

    2016-01-01

    The purpose of this paper is to elaborate on the concept of molten salts as catalysts for CO2 absorption by MgO, and extend these observations to the MgO-containing double salt oxides. We will show that the phenomena involved with CO2 absorption by MgO and MgO-based double salts are similar and general, but with some important differences. This paper focuses on the following key concepts: i) identification of conditions that favor or disfavor participation of isolated MgO during double salt absorption, and investigation of methods to increase the absorption capacity of double salt systems by including MgO participation; ii) examination of the relationship between CO2 uptake and melting point of the promoter salt, leading to the recognition of the role of pre-melting (surface melting) in these systems; and iii) extension of the reaction pathway model developed for the MgO-NaNO3 system to the double salt systems. This information advances our understanding of MgO-based CO2 absorption systems for application with pre-combustion gas streams.

  5. Rapid adaptation of harmful cyanobacteria to rising CO2.

    Science.gov (United States)

    Sandrini, Giovanni; Ji, Xing; Verspagen, Jolanda M H; Tann, Robert P; Slot, Pieter C; Luimstra, Veerle M; Schuurmans, J Merijn; Matthijs, Hans C P; Huisman, Jef

    2016-08-16

    Rising atmospheric CO2 concentrations are likely to affect many ecosystems worldwide. However, to what extent elevated CO2 will induce evolutionary changes in photosynthetic organisms is still a major open question. Here, we show rapid microevolutionary adaptation of a harmful cyanobacterium to changes in inorganic carbon (Ci) availability. We studied the cyanobacterium Microcystis, a notorious genus that can develop toxic cyanobacterial blooms in many eutrophic lakes and reservoirs worldwide. Microcystis displays genetic variation in the Ci uptake systems BicA and SbtA, where BicA has a low affinity for bicarbonate but high flux rate, and SbtA has a high affinity but low flux rate. Our laboratory competition experiments show that bicA + sbtA genotypes were favored by natural selection at low CO2 levels, but were partially replaced by the bicA genotype at elevated CO2 Similarly, in a eutrophic lake, bicA + sbtA strains were dominant when Ci concentrations were depleted during a dense cyanobacterial bloom, but were replaced by strains with only the high-flux bicA gene when Ci concentrations increased later in the season. Hence, our results provide both laboratory and field evidence that increasing carbon concentrations induce rapid adaptive changes in the genotype composition of harmful cyanobacterial blooms.

  6. CaO-Based CO2 Sorbents Effectively Stabilized by Metal Oxides.

    Science.gov (United States)

    Naeem, Muhammad Awais; Armutlulu, Andac; Imtiaz, Qasim; Müller, Christoph R

    2017-08-18

    Calcium looping (i.e., CO2 capture by CaO) is a promising second-generation CO2 capture technology. CaO, derived from naturally occurring limestone, offers an inexpensive solution, but due to the harsh operating conditions of the process, limestone-derived sorbents undergo a rapid capacity decay induced by the sintering of CaCO3 . Here, we report a Pechini method to synthesize cyclically stable, CaO-based CO2 sorbents with a high CO2 uptake capacity. The sorbents synthesized feature compositional homogeneity in combination with a nanostructured and highly porous morphology. The presence of a single (Al2 O3 or Y2 O3 ) or bimetal oxide (Al2 O3 -Y2 O3 ) provides cyclic stability, except for MgO which undergoes a significant increase in its particle size with the cycle number. We also demonstrate a direct relationship between the CO2 uptake and the morphology of the synthesized sorbents. After 30 cycles of calcination and carbonation, the best performing sorbent, containing an equimolar mixture of Al2 O3 and Y2 O3 , exhibits a CO2 uptake capacity of 8.7 mmol CO2  g(-1) sorbent, which is approximately 360 % higher than that of the reference limestone. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  7. Regional CO2 flux estimates for 2009-2010 based on GOSAT and ground-based CO2 observations

    Science.gov (United States)

    Maksyutov, S.; Takagi, H.; Valsala, V. K.; Saito, M.; Oda, T.; Saeki, T.; Belikov, D. A.; Saito, R.; Ito, A.; Yoshida, Y.; Morino, I.; Uchino, O.; Andres, R. J.; Yokota, T.

    2013-09-01

    We present the application of a global carbon cycle modeling system to the estimation of monthly regional CO2 fluxes from the column-averaged mole fractions of CO2 (XCO2) retrieved from spectral observations made by the Greenhouse gases Observing SATellite (GOSAT). The regional flux estimates are to be publicly disseminated as the GOSAT Level 4 data product. The forward modeling components of the system include an atmospheric tracer transport model, an anthropogenic emissions inventory, a terrestrial biosphere exchange model, and an oceanic flux model. The atmospheric tracer transport was simulated using isentropic coordinates in the stratosphere and was tuned to reproduce the age of air. We used a fossil fuel emission inventory based on large point source data and observations of nighttime lights. The terrestrial biospheric model was optimized by fitting model parameters to observed atmospheric CO2 seasonal cycle, net primary production data, and a biomass distribution map. The oceanic surface pCO2 distribution was estimated with a 4-D variational data assimilation system based on reanalyzed ocean currents. Monthly CO2 fluxes of 64 sub-continental regions, between June 2009 and May 2010, were estimated from GOSAT FTS SWIR Level 2 XCO2 retrievals (ver. 02.00) gridded to 5° × 5° cells and averaged on a monthly basis and monthly-mean GLOBALVIEW-CO2 data. Our result indicated that adding the GOSAT XCO2 retrievals to the GLOBALVIEW data in the flux estimation brings changes to fluxes of tropics and other remote regions where the surface-based data are sparse. The uncertainties of these remote fluxes were reduced by as much as 60% through such addition. Optimized fluxes estimated for many of these regions, were brought closer to the prior fluxes by the addition of the GOSAT retrievals. In most of the regions and seasons considered here, the estimated fluxes fell within the range of natural flux variabilities estimated with the component models.

  8. Regional CO2 flux estimates for 2009–2010 based on GOSAT and ground-based CO2 observations

    Directory of Open Access Journals (Sweden)

    S. Maksyutov

    2013-09-01

    Full Text Available We present the application of a global carbon cycle modeling system to the estimation of monthly regional CO2 fluxes from the column-averaged mole fractions of CO2 (XCO2 retrieved from spectral observations made by the Greenhouse gases Observing SATellite (GOSAT. The regional flux estimates are to be publicly disseminated as the GOSAT Level 4 data product. The forward modeling components of the system include an atmospheric tracer transport model, an anthropogenic emissions inventory, a terrestrial biosphere exchange model, and an oceanic flux model. The atmospheric tracer transport was simulated using isentropic coordinates in the stratosphere and was tuned to reproduce the age of air. We used a fossil fuel emission inventory based on large point source data and observations of nighttime lights. The terrestrial biospheric model was optimized by fitting model parameters to observed atmospheric CO2 seasonal cycle, net primary production data, and a biomass distribution map. The oceanic surface pCO2 distribution was estimated with a 4-D variational data assimilation system based on reanalyzed ocean currents. Monthly CO2 fluxes of 64 sub-continental regions, between June 2009 and May 2010, were estimated from GOSAT FTS SWIR Level 2 XCO2 retrievals (ver. 02.00 gridded to 5° × 5° cells and averaged on a monthly basis and monthly-mean GLOBALVIEW-CO2 data. Our result indicated that adding the GOSAT XCO2 retrievals to the GLOBALVIEW data in the flux estimation brings changes to fluxes of tropics and other remote regions where the surface-based data are sparse. The uncertainties of these remote fluxes were reduced by as much as 60% through such addition. Optimized fluxes estimated for many of these regions, were brought closer to the prior fluxes by the addition of the GOSAT retrievals. In most of the regions and seasons considered here, the estimated fluxes fell within the range of natural flux variabilities estimated with the component models.

  9. Metal-Organic Framework-Stabilized CO2/Water Interfacial Route for Photocatalytic CO2Conversion.

    Science.gov (United States)

    Luo, Tian; Zhang, Jianling; Li, Wei; He, Zhenhong; Sun, Xiaofu; Shi, Jinbiao; Shao, Dan; Zhang, Bingxing; Tan, Xiuniang; Han, Buxing

    2017-11-29

    Here, we propose a CO 2 /water interfacial route for photocatalytic CO 2 conversion by utilizing a metal-organic framework (MOF) as both an emulsifier and a catalyst. The CO 2 reduction occurring at the CO 2 /water interface produces formate with remarkably enhanced efficiency as compared with that in conventional solvent. The route is efficient, facile, adjustable, and environmentally benign, which is applicable for the CO 2 transformation photocatalyzed by different kinds of MOFs.

  10. Long-term surface pCO2 trends from observations and models

    Directory of Open Access Journals (Sweden)

    Jerry F. Tjiputra

    2014-05-01

    Full Text Available We estimate regional long-term surface ocean pCO2 growth rates using all available underway and bottled biogeochemistry data collected over the past four decades. These observed regional trends are compared with those simulated by five state-of-the-art Earth system models over the historical period. Oceanic pCO2 growth rates faster than the atmospheric growth rates indicate decreasing atmospheric CO2 uptake, while ocean pCO2 growth rates slower than the atmospheric growth rates indicate increasing atmospheric CO2 uptake. Aside from the western subpolar North Pacific and the subtropical North Atlantic, our analysis indicates that the current observation-based basin-scale trends may be underestimated, indicating that more observations are needed to determine the trends in these regions. Encouragingly, good agreement between the simulated and observed pCO2 trends is found when the simulated fields are subsampled with the observational coverage. In agreement with observations, we see that the simulated pCO2 trends are primarily associated with the increase in surface dissolved inorganic carbon (DIC associated with atmospheric carbon uptake, and in part by warming of the sea surface. Under the RCP8.5 future scenario, DIC continues to be the dominant driver of pCO2 trends, with little change in the relative contribution of SST. However, the changes in the hydrological cycle play an increasingly important role. For the contemporary (1970–2011 period, the simulated regional pCO2 trends are lower than the atmospheric growth rate over 90% of the ocean. However, by year 2100 more than 40% of the surface ocean area has a higher oceanic pCO2 trend than the atmosphere, implying a reduction in the atmospheric CO2 uptake rate. The fastest pCO2 growth rates are projected for the subpolar North Atlantic, while the high-latitude Southern Ocean and eastern equatorial Pacific have the weakest growth rates, remaining below the atmospheric pCO2 growth rate. Our work

  11. Urine as a CO2 absorbent.

    Science.gov (United States)

    Aguilar, Manuel Jiménez

    2012-04-30

    The aim of this work was to investigate the effect of urine on the absorption of greenhouse gases such as CO(2). Human urine diluted with olive-oil-mill wastewaters (OMW) could be used to capture CO(2) from flue gas of coal-fired power plant and convert CO(2) emissions into valuable fertilizers (mainly, NH(4)HCO(3)) that can enhance CO(2) sequestration into soil and subsoil layers. Thus, the CO(2) emissions could be reduced between 0.1 and 1%. The proposed strategy requires further research to increase CO(2) absorption and assess the risks associated with wastewater reuse and xenobiotics in the agroecological environment. Copyright © 2012 Elsevier B.V. All rights reserved.

  12. CO2 Capture by Cement Raw Meal

    DEFF Research Database (Denmark)

    Pathi, Sharat Kumar; Lin, Weigang; Illerup, Jytte Boll

    2013-01-01

    The cement industry is one of the major sources of CO2 emissions and is likely to contribute to further increases in the near future. The carbonate looping process has the potential to capture CO2 emissions from the cement industry, in which raw meal for cement production could be used...... as the sorbent. Cyclic experiments were carried out in a TGA apparatus using industrial cement raw meal and synthetic raw meal as sorbents, with limestone as the reference. The results show that the CO2 capture capacities of the cement raw meal and the synthetic raw meal are comparable to those of pure limestone....... The CO2 capture capacity of limestone in the raw meal is lower than for pure limestone. The difference in the CO2 capture capacity decreases with an increase in cycle number. The calcination conditions and composition are major factors that influence the CO2 capture capacity of limestone. At 850 °C in N2...

  13. Advanced technology development reducing CO2 emissions

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Dong Sup

    2010-09-15

    Responding to Korean government policies on green growth and global energy/ environmental challenges, SK energy has been developing new technologies to reduce CO2 emissions by 1) CO2 capture and utilization, 2) efficiency improvement, and 3) Li-ion batteries. The paper introduces three advanced technologies developed by SK energy; GreenPol, ACO, and Li-ion battery. Contributing to company vision, a more energy and less CO2, the three technologies are characterized as follows. GreenPol utilizes CO2 as a feedstock for making polymer. Advanced Catalytic Olefin (ACO) reduces CO2 emission by 20% and increase olefin production by 17%. Li-ion Batteries for automotive industries improves CO2 emission.

  14. CO2 Hydration Shell Structure and Transformation.

    Science.gov (United States)

    Zukowski, Samual R; Mitev, Pavlin D; Hermansson, Kersti; Ben-Amotz, Dor

    2017-07-06

    The hydration-shell of CO2 is characterized using Raman multivariate curve resolution (Raman-MCR) spectroscopy combined with ab initio molecular dynamics (AIMD) vibrational density of states simulations, to validate our assignment of the experimentally observed high-frequency OH band to a weak hydrogen bond between water and CO2. Our results reveal that while the hydration-shell of CO2 is highly tetrahedral, it is also occasionally disrupted by the presence of entropically stabilized defects associated with the CO2-water hydrogen bond. Moreover, we find that the hydration-shell of CO2 undergoes a temperature-dependent structural transformation to a highly disordered (less tetrahedral) structure, reminiscent of the transformation that takes place at higher temperatures around much larger oily molecules. The biological significance of the CO2 hydration shell structural transformation is suggested by the fact that it takes place near physiological temperatures.

  15. Bosch - An alternate CO2 reduction technology

    Science.gov (United States)

    Heppner, D. B.; Hallick, T. M.; Clark, D. C.; Quattrone, P. D.

    1979-01-01

    The Bosch process is the most promising CO2 reduction concept for future prolonged space missions. The paper presents the design of a three-person-capacity preprototype B-CRS (Bosch-based CO2 Reduction Subsystem). It is sized to reduce 3.0 kg/d CO2 generated by the crew and to supply the product water to an O2 generation subsystem to obtain O2. The design supports future development of the B-CRS as an alternative CO2 reduction subsystem to the Sabatier-based process presently under test at NASA. The discussion covers the Bosch CO2 reduction concept, process and hardware description, performance parameters, design specifications, subsystem schematic and operation, mechanical subsystem summary, control/monitor instrumentation, and subsystem packaging. A B-CRS with a proven technological base is an attractive CO2 reduction subsystem that eliminates overboard venting.

  16. Continued global warming after CO2 emissions stoppage

    Science.gov (United States)

    Frölicher, Thomas; Winton, Michael; Sarmiento, Jorge

    2014-05-01

    Recent studies have suggested that global mean surface temperature would remain approximately constant on multi-century timescales after CO2 emissions are stopped. Here we use Earth system model simulations of such a stoppage to demonstrate that in some models, surface temperature may actually increase on multi-century timescales after an initial century-long decrease. For example, global mean surface temperature may increase by 0.6°C after a carbon emissions stoppage at 2-degree. This increase occurs in spite of a decline in radiative forcing that exceeds the decline in ocean heat uptake—a circumstance that would otherwise be expected to lead to a decline in global temperature. The reason is that the warming effect of decreasing ocean heat uptake together with feedback effects arising in response to the geographic structure of ocean heat uptake overcompensates the cooling effect of decreasing atmospheric CO2 on multi-century timescales. Our study also reveals that equilibrium climate sensitivity estimates based on a widely used method of regressing the Earth's energy imbalance against surface temperature change are biased. Uncertainty in the magnitude of the feedback effects associated with the magnitude and geographic distribution of ocean heat uptake therefore contributes substantially to the uncertainty in allowable carbon emissions for a given multi-century warming target.

  17. CO2 Activation over Catalytic Surfaces.

    Science.gov (United States)

    Álvarez, Andrea; Borges, Marta; Corral-Pérez, Juan José; Olcina, Joan Giner; Hu, Lingjun; Cornu, Damien; Huang, Rui; Stoian, Dragos; Urakawa, Atsushi

    2017-11-17

    This article describes the main strategies to activate and convert carbon dioxide (CO2 ) into valuable chemicals over catalytic surfaces. Coherent elements such as common intermediates are identified in the different strategies and concisely discussed based on the reactivity of CO2 with the aim to understand the decisive factors for selective and efficient CO2 conversion. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  18. CO2 Allowance and Electricity Price Interaction

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2007-07-01

    With the introduction of CO2 emission constraints on power generators in the European Union, climate policy is starting to have notable effects on energy markets. This paper sheds light on the links between CO2 prices, electricity prices, and electricity costs to industry. It is based on a series of interviews with industrial and electricity stakeholders, as well as a rich literature seeking to estimate the exact effect of CO2 prices on electricity prices.

  19. Tuning the Surface Polarity of Microporous Organic Polymers for CO2 Capture.

    Science.gov (United States)

    Chen, Jian; Li, He; Zhong, Mingmei; Yang, Qihua

    2017-09-05

    CO2 capture is very important to reduce the CO2 concentration in atmosphere. Herein, we report the preparation of microporous polymers with tunable surface polarity for CO2 capture. Porous polymers functionalized with -NH2 , -SO3 H, and -SO3 Li have been successfully prepared by using a post-synthesis modification of microporous polymers (P-PhPh3 prepared with 1,3,5-triphenylbenzene as the monomer and AlCl3 as the catalyst) by chemical transformations, such as nitration-reduction, sulfonation, and cationic exchange. The CO2 adsorption selectivity (CO2 /N2 and CO2 /H2 ) and isosteric heats of the microporous polymers increase markedly after modification, P-PhPh3 -NH2 and P-PhPh3 -SO3 Li afford higher CO2 uptake capacity than P-PhPh3 at pressures of less than 0.15 bar due to the enhanced interaction between CO2 and the -NH2 and -SO3 Li functional groups. Moreover, functionalized porous polymers could be stably used for CO2 capture. Surface modification is an efficient approach to tune the CO2 capture properties of porous polymers. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  20. Can seasonal and interannual variation in landscape CO2 fluxes be detected by atmospheric observations of CO2 concentrations made at a tall tower?

    Science.gov (United States)

    Smallman, T. L.; Williams, M.; Moncrieff, J. B.

    2013-08-01

    The Weather Research and Forecasting (WRF) meteorological model has been coupled to the Soil Plant Atmosphere (SPA) terrestrial ecosystem model, hereafter known as WRF-SPA. SPA generates realistic land-atmosphere exchanges through fully coupled hydrological, carbon and energy cycles. Here we have used WRF-SPA to investigate regional scale observations of atmospheric CO2 concentrations made over a multi-annual period from a tall tower in Scotland. WRF-SPA realistically models both seasonal and daily cycles, predicting CO2 at the tall tower (R2 = 0.67, RMSE = 3.5 ppm, bias = 0.58 ppm), indicating realistic transport, and appropriate source sink distribution and magnitude of CO2 exchange. We have highlighted a consistent post harvest increase in model-observation residuals in atmospheric CO2 concentrations. This increase in model-observation residuals post harvest is likely related to a lack of an appropriate representation of uncultivated components (~ 36% of agricultural holding in Scotland) of agricultural land (e.g., hedgerows and forest patches) which continue to photosynthesise after the crop has been harvested. Through the use of ecosystem specific CO2 tracers we have shown that tall tower observations here do not detect a representative fraction of Scotland's ecosystem CO2 uptake. Cropland CO2 uptake is the dominant ecosystem signal detected at the tall tower, consistent with the dominance of cropland in the area surrounding the tower. However cropland is over-represented in the atmospheric CO2 concentrations simulated to be at the tall tower, relative to the simulated surface cropland CO2 uptake. Observations made at the tall tower were able to detect seasonal variation in ecosystem CO2 uptake, however a majority of variation was only detected for croplands. We have found evidence that interannual variation in weather has a greater impact than interannual variation of the simulated land surface CO2 exchange on tall tower observations for the simulated years

  1. Changes in gene expression, cell physiology and toxicity of the harmful cyanobacterium Microcystis aeruginosa at elevated CO2

    Directory of Open Access Journals (Sweden)

    Giovanni eSandrini

    2015-05-01

    Full Text Available Rising CO2 concentrations may have large effects on aquatic microorganisms. In this study, we investigated how elevated pCO2 affects the harmful freshwater cyanobacterium Microcystis aeruginosa. This species is capable of producing dense blooms and hepatotoxins called microcystins. Strain PCC 7806 was cultured in chemostats that were shifted from low to high pCO2 conditions. This resulted in a transition from a C-limited to a light-limited steady state, with a ~2.7 fold increase of the cyanobacterial biomass and ~2.5 fold more microcystin per cell. Cells increased their chlorophyll a and phycocyanin content, and raised their PSI/PSII ratio at high pCO2. Surprisingly, cells had a lower dry weight and contained less carbohydrates, which might be an adaptation to improve the buoyancy of Microcystis when light becomes more limiting at high p