Diagnosing phosphorus limitations in natural terrestrial ecosystems in carbon cycle models.

PubMed

Sun, Yan; Peng, Shushi; Goll, Daniel S; Ciais, Philippe; Guenet, Bertrand; Guimberteau, Matthieu; Hinsinger, Philippe; Janssens, Ivan A; Peñuelas, Josep; Piao, Shilong; Poulter, Benjamin; Violette, Aurélie; Yang, Xiaojuan; Yin, Yi; Zeng, Hui

2017-07-01

Most of the Earth System Models (ESMs) project increases in net primary productivity (NPP) and terrestrial carbon (C) storage during the 21st century. Despite empirical evidence that limited availability of phosphorus (P) may limit the response of NPP to increasing atmospheric CO 2 , none of the ESMs used in the previous Intergovernmental Panel on Climate Change assessment accounted for P limitation. We diagnosed from ESM simulations the amount of P need to support increases in carbon uptake by natural ecosystems using two approaches: the demand derived from (1) changes in C stocks and (2) changes in NPP. The C stock-based additional P demand was estimated to range between -31 and 193 Tg P and between -89 and 262 Tg P for Representative Concentration Pathway (RCP) 2.6 and RCP8.5, respectively, with negative values indicating a P surplus. The NPP-based demand, which takes ecosystem P recycling into account, results in a significantly higher P demand of 648-1606 Tg P for RCP2.6 and 924-2110 Tg P for RCP8.5. We found that the P demand is sensitive to the turnover of P in decomposing plant material, explaining the large differences between the NPP-based demand and C stock-based demand. The discrepancy between diagnosed P demand and actual P availability (potential P deficit) depends mainly on the assumptions about availability of the different soil P forms. Overall, future P limitation strongly depends on both soil P availability and P recycling on ecosystem scale.

FOREST-BGC, A general model of forest ecosystem processes for regional applications. II. Dynamic carbon allocation and nitrogen budgets.

PubMed

Running, Steven W.; Gower, Stith T.

1991-01-01

A new version of the ecosystem process model FOREST-BGC is presented that uses stand water and nitrogen limitations to alter the leaf/root/stem carbon allocation fraction dynamically at each annual iteration. Water deficit is defined by integrating a daily soil water deficit fraction annually. Current nitrogen limitation is defined relative to a hypothetical optimum foliar N pool, computed as maximum leaf area index multiplied by maximum leaf nitrogen concentration. Decreasing availability of water or nitrogen, or both, reduces the leaf/root carbon partitioning ratio. Leaf and root N concentrations, and maximum leaf photosynthetic capacity are also redefined annually as functions of nitrogen availability. Test simulations for hypothetical coniferous forests were performed for Madison, WI and Missoula, MT, and showed simulated leaf area index ranging from 4.5 for a control stand at Missoula, to 11 for a fertilized stand at Madison, with Year 50 stem carbon biomasses of 31 and 128 Mg ha(-1), respectively. Total nitrogen incorporated into new tissue ranged from 34 kg ha(-1) year(-1) for the unfertilized Missoula stand, to 109 kg ha(-1) year(-1) for the fertilized Madison stand. The model successfully showed dynamic annual carbon partitioning controlled by water and nitrogen limitations.

EXTRACELLULAR ENZYME ACTIIVTY AS A SURROGATE FOR NUTRIENTS AND NUTRIENT HISTORY IN GREAT LAKES WETLANDS

EPA Science Inventory

Great Lakes ecosystems are generally thought to be P-limited, but N-limitation may be more common than previously suspected. N-limitation should be most obvious in freshwater coastal wetlands, where the anaerobic oxidation of organic carbon may be limited by nitrate availability...

Carbon Supply and Photoacclimation Cross Talk in the Green Alga Chlamydomonas reinhardtii1[OPEN

PubMed Central

Fristedt, Rikard; Dinc, Emine

2016-01-01

Photosynthetic organisms are exposed to drastic changes in light conditions, which can affect their photosynthetic efficiency and induce photodamage. To face these changes, they have developed a series of acclimation mechanisms. In this work, we have studied the acclimation strategies of Chlamydomonas reinhardtii, a model green alga that can grow using various carbon sources and is thus an excellent system in which to study photosynthesis. Like other photosynthetic algae, it has evolved inducible mechanisms to adapt to conditions where carbon supply is limiting. We have analyzed how the carbon availability influences the composition and organization of the photosynthetic apparatus and the capacity of the cells to acclimate to different light conditions. Using electron microscopy, biochemical, and fluorescence measurements, we show that differences in CO2 availability not only have a strong effect on the induction of the carbon-concentrating mechanisms but also change the acclimation strategy of the cells to light. For example, while cells in limiting CO2 maintain a large antenna even in high light and switch on energy-dissipative mechanisms, cells in high CO2 reduce the amount of pigments per cell and the antenna size. Our results show the high plasticity of the photosynthetic apparatus of C. reinhardtii. This alga is able to use various photoacclimation strategies, and the choice of which to activate strongly depends on the carbon availability. PMID:27637747

Diagnosing phosphorus limitations in natural terrestrial ecosystems in carbon cycle models

DOE PAGES

Sun, Yan; Peng, Shushi; Goll, Daniel S.; ...

2017-04-28

Most of the Earth System Models (ESMs) project increases in net primary productivity (NPP) and terrestrial carbon (C) storage during the 21st century. Despite empirical evidence that limited availability of phosphorus (P) may limit the response of NPP to increasing atmospheric CO 2, none of the ESMs used in the previous Intergovernmental Panel on Climate Change assessment accounted for P limitation. We diagnosed from ESM simulations the amount of P need to support increases in carbon uptake by natural ecosystems using two approaches: the demand derived from changes in C stocks and changes in NPP. The C stock-based additional Pmore » demand was estimated to range between -31 and 193 Tg P and between -89 and 262 Tg P for Representative Concentration Pathway (RCP) 2.6 and RCP8.5, respectively, with negative values indicating a P surplus. The NPP-based demand, which takes ecosystem P recycling into account, results in a significantly higher P demand of 648–1606 Tg P for RCP2.6 and 924–2110 Tg P for RCP8.5. We found that the P demand is sensitive to the turnover of P in decomposing plant material, explaining the large differences between the NPP-based demand and C stock-based demand. The discrepancy between diagnosed P demand and actual P availability (potential P deficit) depends mainly on the assumptions about availability of the different soil P forms. Altogether, future P limitation strongly depends on both soil P availability and P recycling on ecosystem scale.« less

Trade-offs for food production, nature conservation and climate limit the terrestrial carbon dioxide removal potential.

PubMed

Boysen, Lena R; Lucht, Wolfgang; Gerten, Dieter

2017-10-01

Large-scale biomass plantations (BPs) are a common factor in climate mitigation scenarios as they promise double benefits: extracting carbon from the atmosphere and providing a renewable energy source. However, their terrestrial carbon dioxide removal (tCDR) potentials depend on important factors such as land availability, efficiency of capturing biomass-derived carbon and the timing of operation. Land availability is restricted by the demands of future food production depending on yield increases and population growth, by requirements for nature conservation and, with respect to climate mitigation, avoiding unfavourable albedo changes. We integrate these factors in one spatially explicit biogeochemical simulation framework to explore the tCDR opportunity space on land available after these constraints are taken into account, starting either in 2020 or 2050, and lasting until 2100. We find that assumed future needs for nature protection and food production strongly limit tCDR potentials. BPs on abandoned crop and pasture areas (~1,300 Mha in scenarios of either 8.0 billion people and yield gap reductions of 25% until 2020 or 9.5 billion people and yield gap reductions of 50% until 2050) could, theoretically, sequester ~100 GtC in land carbon stocks and biomass harvest by 2100. However, this potential would be ~80% lower if only cropland was available or ~50% lower if albedo decreases were considered as a factor restricting land availability. Converting instead natural forest, shrubland or grassland into BPs could result in much larger tCDR potentials ̶ but at high environmental costs (e.g. biodiversity loss). The most promising avenue for effective tCDR seems to be improvement of efficient carbon utilization pathways, changes in dietary trends or the restoration of marginal lands for the implementation of tCDR. © 2017 John Wiley & Sons Ltd.

Labile dissolved organic carbon supply limits hyporheic denitrification

Treesearch

Jay P. Zarnetske; Roy Haggerty; Steven M. Wondzell; Michelle A. Baker

2012-01-01

We used an in situ steady state 15N-labeled nitrate and acetate well-to-wells injection experiment to determine how the availability of labile dissolved organic carbon as acetate influences microbial denitrification in the hyporheic zone of an upland (third-order) agricultural stream.

Redox flow batteries with serpentine flow fields: Distributions of electrolyte flow reactant penetration into the porous carbon electrodes and effects on performance

NASA Astrophysics Data System (ADS)

Ke, Xinyou; Prahl, Joseph M.; Alexander, J. Iwan D.; Savinell, Robert F.

2018-04-01

Redox flow batteries with flow field designs have been demonstrated to boost their capacities to deliver high current density and power density in medium and large-scale energy storage applications. Nevertheless, the fundamental mechanisms involved with improved current density in flow batteries with serpentine flow field designs have been not fully understood. Here we report a three-dimensional model of a serpentine flow field over a porous carbon electrode to examine the distributions of pressure driven electrolyte flow penetrations into the porous carbon electrodes. We also estimate the maximum current densities associated with stoichiometric availability of electrolyte reactant flow penetrations through the porous carbon electrodes. The results predict reasonably well observed experimental data without using any adjustable parameters. This fundamental work on electrolyte flow distributions of limiting reactant availability will contribute to a better understanding of limits on electrochemical performance in flow batteries with serpentine flow field designs and should be helpful to optimizing flow batteries.

NASA's Carbon Cycle OSSE Initiative - Informing future space-based observing strategies through advanced modeling and data assimilation

NASA Astrophysics Data System (ADS)

Ott, L.; Sellers, P. J.; Schimel, D.; Moore, B., III; O'Dell, C.; Crowell, S.; Kawa, S. R.; Pawson, S.; Chatterjee, A.; Baker, D. F.; Schuh, A. E.

2017-12-01

Satellite observations of carbon dioxide (CO2) and methane (CH4) are critically needed to improve understanding of the contemporary carbon budget and carbon-climate feedbacks. Though current carbon observing satellites have provided valuable data in regions not covered by surface in situ measurements, limited sampling of key regions and small but spatially coherent biases have limited the ability to estimate fluxes at the time and space scales needed for improved process-level understanding and informed decision-making. Next generation satellites will improve coverage in data sparse regions, either through use of active remote sensing, a geostationary vantage point, or increased swath width, but all techniques have limitations. The relative strengths and weaknesses of these approaches and their synergism have not previously been examined. To address these needs, a significant subset of the US carbon modeling community has come together with support from NASA to conduct a series of coordinated observing system simulation experiments (OSSEs), with close collaboration in framing the experiments and in analyzing the results. Here, we report on the initial phase of this initiative, which focused on creating realistic, physically consistent synthetic CO2 and CH4 observational datasets for use in inversion and signal detection experiments. These datasets have been created using NASA's Goddard Earth Observing System Model (GEOS) to represent the current state of atmospheric carbon as well as best available estimates of expected flux changes. Scenarios represented include changes in urban emissions, release of permafrost soil carbon, changes in carbon uptake in tropical and mid-latitude forests, changes in the Southern Ocean sink, and changes in both anthropogenic and natural methane emissions. This GEOS carbon `nature run' was sampled by instrument simulators representing the most prominent observing strategies with a focus on consistently representing the impacts of random errors and limitations in viewing due to clouds and aerosols. Statistical analyses of these synthetic datasets provide a simple, objective method for evaluating mission design choices. These datasets will also be made publicly available for use by the international carbon modeling community and in mission planning activities.

Phosphorus limitation and heat stress decrease calcification in Emiliania huxleyi

NASA Astrophysics Data System (ADS)

Gerecht, Andrea C.; Šupraha, Luka; Langer, Gerald; Henderiks, Jorijntje

2018-02-01

Calcifying haptophytes (coccolithophores) sequester carbon in the form of organic and inorganic cellular components (coccoliths). We examined the effect of phosphorus (P) limitation and heat stress on particulate organic and inorganic carbon (calcite) production in the coccolithophore Emiliania huxleyi. Both environmental stressors are related to rising CO2 levels and affect carbon production in marine microalgae, which in turn impacts biogeochemical cycling. Using semi-continuous cultures, we show that P limitation and heat stress decrease the calcification rate in E. huxleyi. However, using batch cultures, we show that different culturing approaches (batch versus semi-continuous) induce different physiologies. This affects the ratio of particulate inorganic (PIC) to organic carbon (POC) and complicates general predictions on the effect of P limitation on the PIC  /  POC ratio. We found heat stress to increase P requirements in E. huxleyi, possibly leading to lower standing stocks in a warmer ocean, especially if this is linked to lower nutrient input. In summary, the predicted rise in global temperature and resulting decrease in nutrient availability may decrease CO2 sequestration by E. huxleyi through lower overall carbon production. Additionally, the export of carbon may be diminished by a decrease in calcification and a weaker coccolith ballasting effect.

Towards a more complete SOCCR: Establishing a Coastal Carbon Data Network

NASA Astrophysics Data System (ADS)

Pidgeon, E.; Howard, J.; Tang, J.; Kroeger, K. D.; Windham-Myers, L.

2015-12-01

The 2007 State of the Carbon Cycle Report (SOCCR) was highly influential in ensuring components of the carbon cycle were accounted for in national policy and related management. However, while SOCCR detailed the significance of North American coastal wetlands, it was not until recently that leading governments began to fully recognized these ecosystems for their carbon sequestration and storage capacity and hence the significant role coastal ecosystems can play in GHG emission reductions strategies, offset mechanisms, coastal management strategies and climate mitigation policy. The new attention on coastal carbon systems has exposed limitations in terms of data availability and data quality, as well as insufficient knowledge of coastal carbon distributions, characteristics and coastal carbon cycle processes. In addition to restricting scientific progress, lack of comprehensive, comparable, and quality-controlled coastal carbon data is hindering progress towards carbon based conservation and coastal management. To directly address those limitations, we are developing a Global Science and Data Network for Coastal "Blue" Carbon, with support from the Carbon Cycle Interagency Working Group. Goals include: • Improving basic and applied science on carbon and GHG cycling in vegetated coastal ecosystems; • Supporting a coastal carbon and associated GHG data archive for use by the science community, coastal and climate practitioners and other data users; • Building the capacity of coastal carbon stakeholders globally to collect and interpret high quality coastal carbon science and data; • Providing a forum and mechanism to promote exchange and collaboration between scientists and coastal carbon data users globally; and • Outreach activities to ensure the best available data are globally accessible and that science is responsive to the needs of coastal managers and policy-makers.

Plant allocation of carbon to defense as a function of herbivory, light and nutrient availability

USGS Publications Warehouse

DeAngelis, Donald L.; Ju, Shu; Liu, Rongsong; Bryant, John P.; Gourley, Stephen A.

2012-01-01

We use modeling to determine the optimal relative plant carbon allocations between foliage, fine roots, anti-herbivore defense, and reproduction to maximize reproductive output. The model treats these plant components and the herbivore compartment as variables. Herbivory is assumed to be purely folivory. Key external factors include nutrient availability, degree of shading, and intensity of herbivory. Three alternative functional responses are used for herbivory, two of which are variations on donor-dependent herbivore (models 1a and 1b) and one of which is a Lotka–Volterra type of interaction (model 2). All three were modified to include the negative effect of chemical defenses on the herbivore. Analysis showed that, for all three models, two stable equilibria could occur, which differs from most common functional responses when no plant defense component is included. Optimal strategies of carbon allocation were defined as the maximum biomass of reproductive propagules produced per unit time, and found to vary with changes in external factors. Increased intensity of herbivory always led to an increase in the fractional allocation of carbon to defense. Decreases in available limiting nutrient generally led to increasing importance of defense. Decreases in available light had little effect on defense but led to increased allocation to foliage. Decreases in limiting nutrient and available light led to decreases in allocation to reproduction in models 1a and 1b but not model 2. Increases in allocation to plant defense were usually accompanied by shifts in carbon allocation away from fine roots, possibly because higher plant defense reduced the loss of nutrients to herbivory.

The role of heterotrophic bacteria in iron-limited ocean ecosystems

NASA Astrophysics Data System (ADS)

Tortell, Philippe D.; Maldonado, Maria T.; Price, Nell M.

1996-09-01

IRON availability limits phytoplankton growth in large areas of the world's oceans1-3 and may influence the strength of the biological carbon pump4,5. Very little is known of the iron requirements of oceanic heterotrophic bacteria, which constitute up to 50% of the total particulate organic carbon in open ocean waters6,7 and are important in carbon cycling as remineralizers of dissolved organic matter and hence producers of CO2 (ref. 8). Here we report that oceanic bacteria contain more iron per biomass than phytoplankton. In the subarctic Pacific, they constitute a large fraction of biogenic iron and account for 20-45% of biological iron uptake. Bacterial iron quotas in the field are similar to those of iron-deficient laboratory cultures, which exhibit reduced elec-tron transport, slow growth, and low carbon growth efficiency. Heterotrophic bacteria therefore play a major role in the biogeo-chemical cycling of iron. In situ iron limitation of heterotrophic metabolism may have profound effects on carbon flux in the ocean.

Nitrogen attenuation of terrestrial carbon cycle response to global environmental factors

USGS Publications Warehouse

Jain, A.A.; Yang, Xiaojuan; Kheshgi, H.; McGuire, A. David; Post, W.; Kicklighter, David W.

2009-01-01

Nitrogen cycle dynamics have the capacity to attenuate the magnitude of global terrestrial carbon sinks and sources driven by CO2 fertilization and changes in climate. In this study, two versions of the terrestrial carbon and nitrogen cycle components of the Integrated Science Assessment Model (ISAM) are used to evaluate how variation in nitrogen availability influences terrestrial carbon sinks and sources in response to changes over the 20th century in global environmental factors including atmospheric CO2 concentration, nitrogen inputs, temperature, precipitation and land use. The two versions of ISAM vary in their treatment of nitrogen availability: ISAM-NC has a terrestrial carbon cycle model coupled to a fully dynamic nitrogen cycle while ISAM-C has an identical carbon cycle model but nitrogen availability is always in sufficient supply. Overall, the two versions of the model estimate approximately the same amount of global mean carbon uptake over the 20th century. However, comparisons of results of ISAM-NC relative to ISAM-C reveal that nitrogen dynamics: (1) reduced the 1990s carbon sink associated with increasing atmospheric CO2 by 0.53 PgC yr−1 (1 Pg = 1015g), (2) reduced the 1990s carbon source associated with changes in temperature and precipitation of 0.34 PgC yr−1 in the 1990s, (3) an enhanced sink associated with nitrogen inputs by 0.26 PgC yr−1, and (4) enhanced the 1990s carbon source associated with changes in land use by 0.08 PgC yr−1 in the 1990s. These effects of nitrogen limitation influenced the spatial distribution of the estimated exchange of CO2 with greater sink activity in high latitudes associated with climate effects and a smaller sink of CO2 in the southeastern United States caused by N limitation associated with both CO2 fertilization and forest regrowth. These results indicate that the dynamics of nitrogen availability are important to consider in assessing the spatial distribution and temporal dynamics of terrestrial carbon sources and sinks.

Mangrove production and carbon sinks: A revision of global budget estimates

USGS Publications Warehouse

Bouillon, S.; Borges, A.V.; Castaneda-Moya, E.; Diele, K.; Dittmar, T.; Duke, N.C.; Kristensen, E.; Lee, S.-Y.; Marchand, C.; Middelburg, J.J.; Rivera-Monroy, V. H.; Smith, T. J.; Twilley, R.R.

2008-01-01

Mangrove forests are highly productive but globally threatened coastal ecosystems, whose role in the carbon budget of the coastal zone has long been debated. Here we provide a comprehensive synthesis of the available data on carbon fluxes in mangrove ecosystems. A reassessment of global mangrove primary production from the literature results in a conservative estimate of ???-218 ?? 72 Tg C a-1. When using the best available estimates of various carbon sinks (organic carbon export, sediment burial, and mineralization), it appears that >50% of the carbon fixed by mangrove vegetation is unaccounted for. This unaccounted carbon sink is conservatively estimated at ??? 112 ?? 85 Tg C a-1, equivalent in magnitude to ??? 30-40% of the global riverine organic carbon input to the coastal zone. Our analysis suggests that mineralization is severely underestimated, and that the majority of carbon export from mangroves to adjacent waters occurs as dissolved inorganic carbon (DIC). CO2 efflux from sediments and creek waters and tidal export of DIC appear to be the major sinks. These processes are quantitatively comparable in magnitude to the unaccounted carbon sink in current budgets, but are not yet adequately constrained with the limited published data available so far. Copyright 2008 by the American Geophysical Union.

Pyrolysis temperature-dependent release of dissolved organic carbon from plant, manure, and biorefinery wastes

USDA-ARS?s Scientific Manuscript database

Limited information is available to understand the chemical structure of biochar’s labile dissolved organic carbon (DOC) fraction that will change amended soil’s DOC composition. This study utilized the high sensitivity of fluorescence excitation-emission (EEM) spectrophotometry to understand the s...

Impact of seawater carbonate chemistry on the calcification of marine bivalves

NASA Astrophysics Data System (ADS)

Thomsen, J.; Haynert, K.; Wegner, K. M.; Melzner, F.

2015-01-01

Bivalve calcification, particular of the early larval stages is highly sensitive to the change of ocean carbonate chemistry resulting from atmospheric CO2 uptake. Earlier studies suggested that declining seawater [CO32-] and thereby lowered carbonate saturation affect shell production. However, disturbances of physiological processes such as acid-base regulation by adverse seawater pCO2 and pH can affect calcification in a secondary fashion. In order to determine the exact carbonate system component by which growth and calcification are affected it is necessary to utilize more complex carbonate chemistry manipulations. As single factors, pCO2 had no and [HCO3-] and pH only limited effects on shell growth, while lowered [CO32-] strongly impacted calcification. Dissolved inorganic carbon (CT) limiting conditions led to strong reductions in calcification, despite high [CO32-], indicating that [HCO3-] rather than [CO32-] is the inorganic carbon source utilized for calcification by mytilid mussels. However, as the ratio [HCO3-] / [H+] is linearly correlated with [CO32-] it is not possible to differentiate between these under natural seawater conditions. Therefore, the availability of [HCO3-] combined with favorable environmental pH determines calcification rate and an equivalent of about 80 μmol kg-1 [CO32-] is required to saturate inorganic carbon supply for calcification in bivalves. Below this threshold biomineralization rates rapidly decline. A comparison of literature data available for larvae and juvenile mussels and oysters originating from habitats differing substantially with respect to prevailing carbonate chemistry conditions revealed similar response curves. This suggests that the mechanisms which determine sensitivity of calcification in this group are highly conserved. The higher sensitivity of larval calcification seems to primarily result from the much higher relative calcification rates in early life stages. In order to reveal and understand the mechanisms that limit or facilitate adaptation to future ocean acidification, it is necessary to better understand the physiological processes and their underlying genetics that govern inorganic carbon assimilation for calcification.

Input related microbial carbon dynamic of soil organic matter in particle size fractions

NASA Astrophysics Data System (ADS)

Gude, A.; Kandeler, E.; Gleixner, G.

2012-04-01

This paper investigated the flow of carbon into different groups of soil microorganisms isolated from different particle size fractions. Two agricultural sites of contrasting organic matter input were compared. Both soils had been submitted to vegetation change from C3 (Rye/Wheat) to C4 (Maize) plants, 25 and 45 years ago. Soil carbon was separated into one fast-degrading particulate organic matter fraction (POM) and one slow-degrading organo-mineral fraction (OMF). The structure of the soil microbial community were investigated using phospholipid fatty acids (PLFA), and turnover of single PLFAs was calculated from the changes in their 13C content. Soil enzyme activities involved in the degradation of carbohydrates was determined using fluorogenic MUF (methyl-umbelliferryl phosphate) substrates. We found that fresh organic matter input drives soil organic matter dynamic. Higher annual input of fresh organic matter resulted in a higher amount of fungal biomass in the POM-fraction and shorter mean residence times. Fungal activity therefore seems essential for the decomposition and incorporation of organic matter input into the soil. As a consequence, limited litter input changed especially the fungal community favouring arbuscular mycorrhizal fungi. Altogether, supply and availability of fresh plant carbon changed the distribution of microbial biomass, the microbial community structure and enzyme activities and resulted in different priming of soil organic matter. Most interestingly we found that only at low input the OMF fraction had significantly higher calculated MRT for Gram-positive and Gram-negative bacteria suggesting high recycling of soil carbon or the use of other carbon sources. But on average all microbial groups had nearly similar carbon uptake rates in all fractions and both soils, which contrasted the turnover times of bulk carbon. Hereby the microbial carbon turnover was always faster than the soil organic carbon turnover and higher carbon input reduced the carbon storage efficiency from 51 % in the low input to 20 %. These findings suggest that microbial community preferentially assimilated fresh carbon sources but also used recycled existing soil carbon. However, the priming rate was drastically reduced under carbon limitation. In consequence at high carbon availability more carbon was respired to activate the existing soil carbon (priming) whereas at low carbon availability new soil carbon was formed at higher efficiencies.

Carbon storage in seagrass soils: long-term nutrient history exceeds the effects of near-term nutrient enrichment

NASA Astrophysics Data System (ADS)

Armitage, A. R.; Fourqurean, J. W.

2016-01-01

The carbon sequestration potential in coastal soils is linked to aboveground and belowground plant productivity and biomass, which in turn, is directly and indirectly influenced by nutrient input. We evaluated the influence of long-term and near-term nutrient input on aboveground and belowground carbon accumulation in seagrass beds, using a nutrient enrichment (nitrogen and phosphorus) experiment embedded within a naturally occurring, long-term gradient of phosphorus availability within Florida Bay (USA). We measured organic carbon stocks in soils and above- and belowground seagrass biomass after 17 months of experimental nutrient addition. At the nutrient-limited sites, phosphorus addition increased the carbon stock in aboveground seagrass biomass by more than 300 %; belowground seagrass carbon stock increased by 50-100 %. Soil carbon content slightly decreased ( ˜ 10 %) in response to phosphorus addition. There was a strong but non-linear relationship between soil carbon and Thalassia testudinum leaf nitrogen : phosphorus (N : P) or belowground seagrass carbon stock. When seagrass leaf N : P exceeded an approximate threshold of 75 : 1, or when belowground seagrass carbon stock was less than 100 g m-2, there was less than 3 % organic carbon in the sediment. Despite the marked difference in soil carbon between phosphorus-limited and phosphorus-replete areas of Florida Bay, all areas of the bay had relatively high soil carbon stocks near or above the global median of 1.8 % organic carbon. The relatively high carbon content in the soils indicates that seagrass beds have extremely high carbon storage potential, even in nutrient-limited areas with low biomass or productivity.

Carbon storage in seagrass soils: long-term nutrient history exceeds the effects of near-term nutrient enrichment

NASA Astrophysics Data System (ADS)

Armitage, A. R.; Fourqurean, J. W.

2015-10-01

The carbon sequestration potential in coastal soils is linked to aboveground and belowground plant productivity and biomass, which in turn, is directly and indirectly influenced by nutrient input. We evaluated the influence of long-term and near-term nutrient input on aboveground and belowground carbon accumulation in seagrass beds, using a nutrient enrichment (nitrogen and phosphorus) experiment embedded within a naturally occurring, long-term gradient of phosphorus availability within Florida Bay (USA). We measured organic carbon stocks in soils and above- and belowground seagrass biomass after 17 months of experimental nutrient addition. At the nutrient-limited sites, phosphorus addition increased the carbon stock in aboveground seagrass biomass by more than 300 %; belowground seagrass carbon stock increased by 50-100 %. Soil carbon content slightly decreased (~ 10 %) in response to phosphorus addition. There was a strong but non-linear relationship between soil carbon and Thalassia testudinum leaf nitrogen: phosphorus (N : P) or belowground seagrass carbon stock. When seagrass leaf N : P exceeded a threshold of 75 : 1, or when belowground seagrass carbon stock was less than 100 g m-2, there was less than 3 % organic carbon in the sediment. Despite the marked difference in soil carbon between phosphorus-limited and phosphorus-replete areas of Florida Bay, all areas of the bay had relatively high soil carbon stocks near or above the global median of 1.8 % organic carbon. The relatively high carbon content in the soils indicates that seagrass beds have extremely high carbon storage potential, even in nutrient-limited areas with low biomass or productivity.

Overcoming the energetic limitations of syngas fermentation.

PubMed

Molitor, Bastian; Marcellin, Esteban; Angenent, Largus T

2017-12-01

The fermentation of synthesis gas (including carbon monoxide, carbon dioxide, and hydrogen) with anaerobic acetogens is an established biotechnological process that has recently been transferred to a commercial scale. The natural product spectrum of acetogens is natively restricted to acetate, ethanol, and 2,3-butanediol but is rapidly expanding to heterologous products. Syngas fermentation can achieve high carbon-efficiencies; however, the underlying metabolism is operating at a thermodynamic limit. This necessitates special enzymatic properties for energy conservation by acetogens. Therefore, the availability of cellular energy is considered to restrain the efficient production of energy-intense products with complex production pathways. The optimization of the feed-gas composition and other process parameters, genetic engineering, and integration with other biotechnologies is required to overcome this limitation. Copyright © 2017 Elsevier Ltd. All rights reserved.

Overview of the physiological ecology of carbon metabolism in seagrasses.

PubMed

Touchette; Burkholder

2000-07-30

The small but diverse group of angiosperms known as seagrasses form submersed meadow communities that are among the most productive on earth. Seagrasses are frequently light-limited and, despite access to carbon-rich seawaters, they may also sustain periodic internal carbon limitation. They have been regarded as C3 plants, but many species appear to be C3-C4 intermediates and/or have various carbon-concentrating mechanisms to aid the Rubisco enzyme in carbon acquisition. Photorespiration can occur as a C loss process that may protect photosynthetic electron transport during periods of low CO(2) availability and high light intensity. Seagrasses can also become photoinhibited in high light (generally>1000 µE m(-2) s(-1)) as a protective mechanism that allows excessive light energy to be dissipated as heat. Many photosynthesis-irradiance curves have been developed to assess light levels needed for seagrass growth. However, most available data (e.g. compensation irradiance I(c)) do not account for belowground tissue respiration and, thus, are of limited use in assessing the whole-plant carbon balance across light gradients. Caution is recommended in use of I(k) (saturating irradiance for photosynthesis), since seagrass photosynthesis commonly increases under higher light intensities than I(k); and in estimating seagrass productivity from H(sat) (duration of daily light period when light equals or exceeds I(k)) which varies considerably among species and sites, and which fails to account for light-limited photosynthesis at light levels less than I(k). The dominant storage carbohydrate in seagrasses is sucrose (primarily stored in rhizomes), which generally forms more than 90% of the total soluble carbohydrate pool. Seagrasses with high I(c) levels (suggesting lower efficiency in C acquisition) have relatively low levels of leaf carbohydrates. Sucrose-P synthase (SPS, involved in sucrose synthesis) activity increases with leaf age, consistent with leaf maturation from carbon sink to source. Unlike terrestrial plants, SPS apparently is not light-activated, and is positively influenced by increasing temperature and salinity. This response may indicate an osmotic adjustment in marine angiosperms, analogous to increased SPS activity as a cryoprotectant response in terrestrial non-halophytic plants. Sucrose synthase (SS, involved in sucrose metabolism and degradation in sink tissues) of both above- and belowground tissues decreases with tissue age. In belowground tissues, SS activity increases under low oxygen availability and with increasing temperatures, likely indicating increased metabolic carbohydrate demand. Respiration in seagrasses is primarily influenced by temperature and, in belowground tissues, by oxygen availability. Aboveground tissues (involved in C assimilation and other energy-costly processes) generally have higher respiration rates than belowground (mostly storage) tissues. Respiration rates increase with increasing temperature (in excess of 40 degrees C) and increasing water-column nitrate enrichment (Z. marina), which may help to supply the energy and carbon needed to assimilate and reduce nitrate. Seagrasses translocate oxygen from photosynthesizing leaves to belowground tissues for aerobic respiration. During darkness or extended periods of low light, belowground tissues can sustain extended anerobiosis. Documented alternate fermentation pathways have yielded high alanine, a metabolic 'strategy' that would depress production of the more toxic product ethanol, while conserving carbon skeletons and assimilated nitrogen. In comparison to the wealth of information available for terrestrial plants, little is known about the physiological ecology of seagrasses in carbon acquisition and metabolism. Many aspects of their carbon metabolism - controls by interactive environmental factors; and the role of carbon metabolism in salt tolerance, growth under resource-limited conditions, and survival through periods of dormancy - remain to be resolved as directions in future research. Such research will strengthen the understanding needed to improve management and protection of these environmentally important marine angiosperms.

Permafrost carbon—climate feedback is sensitive to deep soil carbon decomposability but not deep soil nitrogen dynamics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Koven, Charles D.; Lawrence, David M.; Riley, William J.

Permafrost soils contain enormous amounts of organic carbon whose stability is contingent on remaining frozen. With future warming, these soils may release carbon to the atmosphere and act as a positive feedback to climate change. Significant uncertainty remains on the postthaw carbon dynamics of permafrost-affected ecosystems, in particular since most of the carbon resides at depth where decomposition dynamics may differ from surface soils, and since nitrogen mineralized by decomposition may enhance plant growth. Here we show, using a carbon–nitrogen model that includes permafrost processes forced in an unmitigated warming scenario, that the future carbon balance of the permafrost regionmore » is highly sensitive to the decomposability of deeper carbon, with the net balance ranging from 21 Pg C to 164 Pg C losses by 2300. Increased soil nitrogen mineralization reduces nutrient limitations, but the impact of deep nitrogen on the carbon budget is small due to enhanced nitrogen availability from warming surface soils and seasonal asynchrony between deeper nitrogen availability and plant nitrogen demands. The future carbon balance of this region is projected to hinge more on the rate and extent of permafrost thaw and soil decomposition than on enhanced nitrogen availability for vegetation growth resulting from permafrost thaw.« less

Permafrost carbon—climate feedback is sensitive to deep soil carbon decomposability but not deep soil nitrogen dynamics

DOE PAGES

Koven, Charles D.; Lawrence, David M.; Riley, William J.

2015-03-09

Permafrost soils contain enormous amounts of organic carbon whose stability is contingent on remaining frozen. With future warming, these soils may release carbon to the atmosphere and act as a positive feedback to climate change. Significant uncertainty remains on the postthaw carbon dynamics of permafrost-affected ecosystems, in particular since most of the carbon resides at depth where decomposition dynamics may differ from surface soils, and since nitrogen mineralized by decomposition may enhance plant growth. Here we show, using a carbon–nitrogen model that includes permafrost processes forced in an unmitigated warming scenario, that the future carbon balance of the permafrost regionmore » is highly sensitive to the decomposability of deeper carbon, with the net balance ranging from 21 Pg C to 164 Pg C losses by 2300. Increased soil nitrogen mineralization reduces nutrient limitations, but the impact of deep nitrogen on the carbon budget is small due to enhanced nitrogen availability from warming surface soils and seasonal asynchrony between deeper nitrogen availability and plant nitrogen demands. The future carbon balance of this region is projected to hinge more on the rate and extent of permafrost thaw and soil decomposition than on enhanced nitrogen availability for vegetation growth resulting from permafrost thaw.« less

Permafrost carbon−climate feedback is sensitive to deep soil carbon decomposability but not deep soil nitrogen dynamics

PubMed Central

Koven, Charles D.; Lawrence, David M.; Riley, William J.

2015-01-01

Permafrost soils contain enormous amounts of organic carbon whose stability is contingent on remaining frozen. With future warming, these soils may release carbon to the atmosphere and act as a positive feedback to climate change. Significant uncertainty remains on the postthaw carbon dynamics of permafrost-affected ecosystems, in particular since most of the carbon resides at depth where decomposition dynamics may differ from surface soils, and since nitrogen mineralized by decomposition may enhance plant growth. Here we show, using a carbon−nitrogen model that includes permafrost processes forced in an unmitigated warming scenario, that the future carbon balance of the permafrost region is highly sensitive to the decomposability of deeper carbon, with the net balance ranging from 21 Pg C to 164 Pg C losses by 2300. Increased soil nitrogen mineralization reduces nutrient limitations, but the impact of deep nitrogen on the carbon budget is small due to enhanced nitrogen availability from warming surface soils and seasonal asynchrony between deeper nitrogen availability and plant nitrogen demands. Although nitrogen dynamics are highly uncertain, the future carbon balance of this region is projected to hinge more on the rate and extent of permafrost thaw and soil decomposition than on enhanced nitrogen availability for vegetation growth resulting from permafrost thaw. PMID:25775603

Interacting Effects of Light and Iron Availability on the Coupling of Photosynthetic Electron Transport and CO2-Assimilation in Marine Phytoplankton

PubMed Central

Schuback, Nina; Schallenberg, Christina; Duckham, Carolyn; Maldonado, Maria T.; Tortell, Philippe D.

2015-01-01

Iron availability directly affects photosynthesis and limits phytoplankton growth over vast oceanic regions. For this reason, the availability of iron is a crucial variable to consider in the development of active chlorophyll a fluorescence based estimates of phytoplankton primary productivity. These bio-optical approaches require a conversion factor to derive ecologically-relevant rates of CO2-assimilation from estimates of electron transport in photosystem II. The required conversion factor varies significantly across phytoplankton taxa and environmental conditions, but little information is available on its response to iron limitation. In this study, we examine the role of iron limitation, and the interacting effects of iron and light availability, on the coupling of photosynthetic electron transport and CO2-assimilation in marine phytoplankton. Our results show that excess irradiance causes increased decoupling of carbon fixation and electron transport, particularly under iron limiting conditions. We observed that reaction center II specific rates of electron transport (ETRRCII, mol e- mol RCII-1 s-1) increased under iron limitation, and we propose a simple conceptual model for this observation. We also observed a strong correlation between the derived conversion factor and the expression of non-photochemical quenching. Utilizing a dataset from in situ phytoplankton assemblages across a coastal – oceanic transect in the Northeast subarctic Pacific, this relationship was used to predict ETRRCII: CO2-assimilation conversion factors and carbon-based primary productivity from FRRF data, without the need for any additional measurements. PMID:26171963

Interacting Effects of Light and Iron Availability on the Coupling of Photosynthetic Electron Transport and CO2-Assimilation in Marine Phytoplankton.

PubMed

Schuback, Nina; Schallenberg, Christina; Duckham, Carolyn; Maldonado, Maria T; Tortell, Philippe D

2015-01-01

Iron availability directly affects photosynthesis and limits phytoplankton growth over vast oceanic regions. For this reason, the availability of iron is a crucial variable to consider in the development of active chlorophyll a fluorescence based estimates of phytoplankton primary productivity. These bio-optical approaches require a conversion factor to derive ecologically-relevant rates of CO2-assimilation from estimates of electron transport in photosystem II. The required conversion factor varies significantly across phytoplankton taxa and environmental conditions, but little information is available on its response to iron limitation. In this study, we examine the role of iron limitation, and the interacting effects of iron and light availability, on the coupling of photosynthetic electron transport and CO2-assimilation in marine phytoplankton. Our results show that excess irradiance causes increased decoupling of carbon fixation and electron transport, particularly under iron limiting conditions. We observed that reaction center II specific rates of electron transport (ETR(RCII), mol e- mol RCII(-1) s(-1)) increased under iron limitation, and we propose a simple conceptual model for this observation. We also observed a strong correlation between the derived conversion factor and the expression of non-photochemical quenching. Utilizing a dataset from in situ phytoplankton assemblages across a coastal--oceanic transect in the Northeast subarctic Pacific, this relationship was used to predict ETR(RCII): CO2-assimilation conversion factors and carbon-based primary productivity from FRRF data, without the need for any additional measurements.

Carbon Budgets as a Guide to Deep Decarbonisation

NASA Astrophysics Data System (ADS)

Rogelj, J.

2017-12-01

Halting global mean temperature rise requires a limit on the cumulative amount of net CO2 disposed of in the atmosphere. Remaining within the limits of such carbon budgets over the 21st century will require a profound transformation of how our societies use and produce energy, crops, and materials. To understand the options available to stay within stringent carbon budget constraints, global transformation pathways are being devised with integrated models of the energy-economy-land system. This presentation will look at how the latest insights of such pathways affect carbon budgets. Estimates of carbon budgets compatible with a given temperature limit depend on the anticipated temperature contribution at peak warming of non-CO2 forcers. Integrated transformation pathways allow to understand the projected extend of these contributions, as well as estimate the maximum conceivable rate of emissions reductions over the coming decades. The latter directly informs the lower end of future cumulative CO2 emissions and can thus provide an estimate for minimum peak warming over the 21st century - a measure which can be compared to the ambitious long-term temperature goal of the UNFCCC Paris Agreement.

Shifting terrestrial feedbacks from CO2 fertilization to global warming

NASA Astrophysics Data System (ADS)

Peñuelas, Josep; Ciais, Philippe; Janssens, Ivan; Canadell, Josep; Obersteiner, Michael; Piao, Shilong; Vautard, Robert; Sardans Jordi Sardans, Jordi

2016-04-01

Humans are increasingly fertilizing the planet. Our activities are increasing atmospheric concentrations of carbon dioxide, nitrogen inputs to ecosystems and global temperatures. Individually and combined, they lead to biospheric availability of carbon and nitrogen, enhanced metabolic activity, and longer growing seasons. Plants can consequently grow more and take up more carbon that can be stored in ecosystem carbon pools, thus enhancing carbon sinks for atmospheric CO2. Data on the increased strength of carbon sinks are, however, inconclusive: Some data (eddy covariance, short-term experiments on elevated CO2 and nutrient fertilization) suggest that biospheric carbon uptake is already effectively increasing but some other data suggest it is not, or are not general and conclusive (tree-ring, forest inventory). The combined land-ocean CO2 sink flux per unit of excess atmospheric CO2 above preindustrial levels declined over 1959-2012 by a factor of about 1/3, implying that CO2 sinks increased more slowly than excess CO2. We will discuss the available data, and the discussion will drive us to revisit our projections for enhanced carbon sinks. We will reconsider the performance of the modulators of increased carbon uptake in a CO2 fertilized and warmed world: nutrients, climate, land use and pollution. Nutrient availability in particular plays a crucial role. A simple mass-balance approach indicates that limited phosphorus availability and the corresponding N:P imbalances can jointly reduce the projected future carbon storage by natural ecosystems during this century. We then present a new paradigm: we are shifting from a fertilization to a warming era. Compared to the historical period, future impacts of warming will be larger than the benefits of CO2 fertilization given nutrient limitations, management and disturbance (which reduces C stocks and thus sequestration potential) and because CO2 will decrease by 2050 in RCP2.6, meaning loss of CO2 fertilization, and CO2 stabilizes by 2060 in RCP4.5. So in light of the Paris agreement, it is more important to investigate climate change impacts on carbon stocks than to expect a continuation of increasing sink due to CO2 fertilization, which will have only a small role or disappear in RCP2.6 during this century.

Carbon dynamics in trees: feast or famine?

Treesearch

Anna Sala; David R. Woodruff; Fredrick C. Meinzer

2012-01-01

Research on the degree to which carbon (C) availability limits growth in trees, as well as recent trends in climate change and concurrent increases in drought related tree mortality, have led to a renewed focus on the physiological mechanisms associated with tree growth responses to current and future climate. This has led to some dispute over the role of stored...

Imaging Carbon Nanotubes in High Performance Polymer Composites via Magnetic Force Microscope

NASA Technical Reports Server (NTRS)

Lillehei, Peter T.; Park, Cheol; Rouse, Jason H.; Siochi, Emilie J.; Bushnell, Dennis M. (Technical Monitor)

2002-01-01

Application of carbon nanotubes as reinforcement in structural composites is dependent on the efficient dispersion of the nanotubes in a high performance polymer matrix. The characterization of such dispersion is limited by the lack of available tools to visualize the quality of the matrix/carbon nanotube interaction. The work reported herein demonstrates the use of magnetic force microscopy (MFM) as a promising technique for characterizing the dispersion of nanotubes in a high performance polymer matrix.

Development of an Advanced Respirometer for Experimental Studies of Benthic Rate Processes

NASA Astrophysics Data System (ADS)

Barry, J. P.; Buck, K. R.; Okuda, C.; Risi, M.; Parker, M.; Levesque, C.

2005-05-01

Rates of carbon remineralization and nutrient cycling by seafloor biotic assemblages are influenced by the availability of organic material, temperature, and oxygen availability, among other factors. The relative importance of various factors in controlling carbon cycling by the sediment community is poorly constrained, in part by technological limits on experiments that evaluate independently the effects of these factors. We have developed an advanced respiration chamber system capable of repeated rate measurements during a single deployment, with added capabilities for manipulating conditions within replicate chambers to test hypotheses concerning biogeochemical cycling by the benthos. The ROV-deployed respiration system has 12 syringes for tracer injection or sample withdrawal from 3 respiration chambers, pH, oxygen, and temperature sensors, stirring paddles, and a recirculation pump. The pump system is used to flush each chamber at preprogrammed intervals or oxygen tensions. Areas of investigation that are enabled by the system include the effects various factors on benthic oxygen consumptions (e.g. hypercapnia (elevated CO2), acidosis, ambient oxygen availability, temperature, organic carbon availability), rates of nutrient regeneration by the benthos in response to organic enrichments (labile and refractory organic carbon), time lags in carbon uptake and trophic pathways in responses to organic enrichment.

Photosynthetic response to globally increasing CO2 of co-occurring temperate seagrass species.

PubMed

Borum, Jens; Pedersen, Ole; Kotula, Lukasz; Fraser, Matthew W; Statton, John; Colmer, Timothy D; Kendrick, Gary A

2016-06-01

Photosynthesis of most seagrass species seems to be limited by present concentrations of dissolved inorganic carbon (DIC). Therefore, the ongoing increase in atmospheric CO2 could enhance seagrass photosynthesis and internal O2 supply, and potentially change species competition through differential responses to increasing CO2 availability among species. We used short-term photosynthetic responses of nine seagrass species from the south-west of Australia to test species-specific responses to enhanced CO2 and changes in HCO3 (-) . Net photosynthesis of all species except Zostera polychlamys were limited at pre-industrial compared to saturating CO2 levels at light saturation, suggesting that enhanced CO2 availability will enhance seagrass performance. Seven out of the nine species were efficient HCO3 (-) users through acidification of diffusive boundary layers, production of extracellular carbonic anhydrase, or uptake and internal conversion of HCO3 (-) . Species responded differently to near saturating CO2 implying that increasing atmospheric CO2 may change competition among seagrass species if co-occurring in mixed beds. Increasing CO2 availability also enhanced internal aeration in the one species assessed. We expect that future increases in atmospheric CO2 will have the strongest impact on seagrass recruits and sparsely vegetated beds, because densely vegetated seagrass beds are most often limited by light and not by inorganic carbon. © 2015 John Wiley & Sons Ltd.

Incorporating phosphorus cycling into global modeling efforts: a worthwhile, tractable endeavor

DOE Office of Scientific and Technical Information (OSTI.GOV)

Reed, Sasha C.; Yang, Xiaojuan; Thornton, Peter E.

2015-06-25

Myriad field, laboratory, and modeling studies show that nutrient availability plays a fundamental role in regulating CO 2 exchange between the Earth's biosphere and atmosphere, and in determining how carbon pools and fluxes respond to climatic change. Accordingly, global models that incorporate coupled climate-carbon cycle feedbacks made a significant advance with the introduction of a prognostic nitrogen cycle. Here we propose that incorporating phosphorus cycling represents an important next step in coupled climate-carbon cycling model development, particularly for lowland tropical forests where phosphorus availability is often presumed to limit primary production. We highlight challenges to including phosphorus in modeling effortsmore » and provide suggestions for how to move forward.« less

Incorporating phosphorus cycling into global modeling efforts: a worthwhile, tractable endeavor

USGS Publications Warehouse

Reed, Sasha C.; Yang, Xiaojuan; Thornton, Peter E.

2015-01-01

Myriad field, laboratory, and modeling studies show that nutrient availability plays a fundamental role in regulating CO2 exchange between the Earth's biosphere and atmosphere, and in determining how carbon pools and fluxes respond to climatic change. Accordingly, global models that incorporate coupled climate–carbon cycle feedbacks made a significant advance with the introduction of a prognostic nitrogen cycle. Here we propose that incorporating phosphorus cycling represents an important next step in coupled climate–carbon cycling model development, particularly for lowland tropical forests where phosphorus availability is often presumed to limit primary production. We highlight challenges to including phosphorus in modeling efforts and provide suggestions for how to move forward.

40 CFR 458.32 - Effluent limitations guidelines representing the degree of effluent reduction attainable by the...

Code of Federal Regulations, 2010 CFR

2010-07-01

... technology currently available. 458.32 Section 458.32 Protection of Environment ENVIRONMENTAL PROTECTION... Carbon Black Channel Process Subcategory § 458.32 Effluent limitations guidelines representing the degree of effluent reduction attainable by the application of the best practicable control technology...

40 CFR 458.22 - Effluent limitations guidelines representing the degree of effluent reduction attainable by the...

Code of Federal Regulations, 2010 CFR

2010-07-01

... technology currently available. 458.22 Section 458.22 Protection of Environment ENVIRONMENTAL PROTECTION... Carbon Black Thermal Process Subcategory § 458.22 Effluent limitations guidelines representing the degree of effluent reduction attainable by the application of the best practicable control technology...

IMPACT ON WATER DISTRIBUTION SYSTEM BIOFILM DENSITIES FROM REVERSE OSMOSIS MEMBRANE TREATMENT OF SUPPLY WATER

EPA Science Inventory

The quality of potable water is such that the concentration of nutrients available for growth of microorganisms within distribution systems is limited. In such systems carbon is often the growth limiting nutrient. Research conducted in the Netherlands has indicated that low level...

Microbial community-level physiological profiling based on O2 consumption as an indicator of nitrogen status of agricultural soils

USDA-ARS?s Scientific Manuscript database

Nitrogen-limited soil microbial activity has important implications for soil carbon storage and nutrient availability, but previous methods for assessing resource limitation have been restricted, due to enrichment criteria (i.e., long incubation periods, high substrate amendments) and/or logistical ...

Speleothem records of acid sulphate deposition and organic carbon mobilisation

NASA Astrophysics Data System (ADS)

Wynn, Peter; Fairchild, Ian; Bourdin, Clement; Baldini, James; Muller, Wolfgang; Hartland, Adam; Bartlett, Rebecca

2017-04-01

Dramatic increases in measured surface water DOC in recent decades have been variously attributed to either temperature rise, or destabilisation of long-term soil carbon pools following sulphur peak emissions status. However, whilst both drivers of DOC dynamics are plausible, they remain difficult to test due to the restricted nature of the available records of riverine DOC flux (1978 to present), and the limited availability of SO2 emissions inventory data at the regional scale. Speleothems offer long term records of both sulphur and carbon. New techniques to extract sulphur concentrations and isotopes from speleothem calcite have enabled archives of pollution history and environmental acidification to be reconstructed. Due to the large dynamic range in sulphur isotopic values from end member sources (marine aerosol +21 ‰ to continental biogenic emissions -30 ‰) and limited environmental fractionation under oxidising conditions, sulphur isotopes form an ideal tracer of industrial pollution and environmental acidification in the palaeo-record. We couple this acidification history to the carbon record, using organic matter fluorescence and trace metals. Trace metal ratios and abundance can be used to infer the type and size of organic ligand and are therefore sensitive to changes in temperature as a driver of organic carbon processing and biodegradation. This allows fluorescent properties and ratios of trace metals in speleothem carbonate to be used to represent both the flux of organic carbon into the cave as well as the degradation pathway. Here we present some of the first results of this work, exploring sulphur acidification as a mechanistic control on carbon solubility and export throughout the twentieth century.

Sorption and leaching potential of isoproturon and atrazine in low organic carbon soil of Pakistan under a wheat-maize rotation

USDA-ARS?s Scientific Manuscript database

Limited data are available on the sorption and leaching of pesticides in agricultural soils of Pakistan with low soil organic carbon (OC). Sorption potential of two widely used pesticides, isoproturon and atrazine, was determined using the batch equilibration method on soils from 0-35 cm, 35-70 and ...

Carbon dioxide diffusion across stomata and mesophyll and photo-biochemical processes as affected by growth CO2 and phosphorus nutrition in cotton

USDA-ARS?s Scientific Manuscript database

Nutrients such as phosphorus availability may exert a major control over plant response to rising atmospheric carbon dioxide concentration (CO2), which is projected to double by the end of 21st century. Elevated CO2 may overcome the diffusional limitation to photosynthesis posed by stomata and mesop...

Increased Ratio of Electron Transport to Net Assimilation Rate Supports Elevated Isoprenoid Emission Rate in Eucalypts under Drought1[W][OPEN

PubMed Central

Dani, Kaidala Ganesha Srikanta; Jamie, Ian McLeod; Prentice, Iain Colin; Atwell, Brian James

2014-01-01

Plants undergoing heat and low-CO2 stresses emit large amounts of volatile isoprenoids compared with those in stress-free conditions. One hypothesis posits that the balance between reducing power availability and its use in carbon assimilation determines constitutive isoprenoid emission rates in plants and potentially even their maximum emission capacity under brief periods of stress. To test this, we used abiotic stresses to manipulate the availability of reducing power. Specifically, we examined the effects of mild to severe drought on photosynthetic electron transport rate (ETR) and net carbon assimilation rate (NAR) and the relationship between estimated energy pools and constitutive volatile isoprenoid emission rates in two species of eucalypts: Eucalyptus occidentalis (drought tolerant) and Eucalyptus camaldulensis (drought sensitive). Isoprenoid emission rates were insensitive to mild drought, and the rates increased when the decline in NAR reached a certain species-specific threshold. ETR was sustained under drought and the ETR-NAR ratio increased, driving constitutive isoprenoid emission until severe drought caused carbon limitation of the methylerythritol phosphate pathway. The estimated residual reducing power unused for carbon assimilation, based on the energetic status model, significantly correlated with constitutive isoprenoid emission rates across gradients of drought (r2 > 0.8) and photorespiratory stress (r2 > 0.9). Carbon availability could critically limit emission rates under severe drought and photorespiratory stresses. Under most instances of moderate abiotic stress levels, increased isoprenoid emission rates compete with photorespiration for the residual reducing power not invested in carbon assimilation. A similar mechanism also explains the individual positive effects of low-CO2, heat, and drought stresses on isoprenoid emission. PMID:25139160

Dielectric relaxation of ethylene carbonate and propylene carbonate from molecular dynamics simulations

DOE PAGES

Chaudhari, Mangesh I.; You, Xinli; Pratt, Lawrence R.; ...

2015-11-24

Ethylene carbonate (EC) and propylene carbonate (PC) are widely used solvents in lithium (Li)-ion batteries and supercapacitors. Ion dissolution and diffusion in those media are correlated with solvent dielectric responses. Here, we use all-atom molecular dynamics simulations of the pure solvents to calculate dielectric constants and relaxation times, and molecular mobilities. The computed results are compared with limited available experiments to assist more exhaustive studies of these important characteristics. As a result, the observed agreement is encouraging and provides guidance for further validation of force-field simulation models for EC and PC solvents.

Effects of Growth Rate and Limiting Substrate on Glucose Metabolism in Escherichia coli1

PubMed Central

Wright, D. N.; Lockhart, W. R.

1965-01-01

Wright, D. N. (Iowa State University, Ames), and W. R. Lockhart. Effects of growth rate and limiting substrate on glucose metabolism in Escherichia coli. J. Bacteriol. 89:1082–1085. 1965.—Escherichia coli was grown in continuous culture at various rates in a defined medium with either glucose of (NH4)2SO4 as the rate-limiting substrate. Cellular content of polysaccharide (“glycogen”) is greater in cells grown under nitrogen limitation with glucose available in excess, and is greater in rapidly grown than in slowly grown cells. The ability of cells to carry on endogenous respiration, as measured by tetrazolium reduction, can be correlated with their glycogen content. In carbon-limited cultures, the proportion of substrate glucose diverted to glycogen production is least for cells grown slowly, which may reflect greater energy requirements for cell maintenance in such cultures. The activity of glucose-6-phosphate dehydrogenase (indicating function of a C-1 preferential pathway for glucose degradation) is greater in rapidly grown cells, confirming earlier observations in batch cultures. Activity of this enzyme is also greater in nitrogen-limited than in carbon-limited cells, suggesting that there may be catabolic repression of the Embden-Meyerhoff pathway when glucose is available in excess. PMID:14276099

Carbon allocation, source-sink relations and plant growth: do we need to revise our carbon centric concepts?

NASA Astrophysics Data System (ADS)

Körner, Christian

2014-05-01

Since the discovery that plants 'eat air' 215 years ago, carbon supply was considered the largely unquestioned top driver of plant growth. The ease at which CO2 uptake (C source activity) can be measured, and the elegant algorithms that describe the responses of photosynthesis to light, temperature and CO2 concentration, explain why carbon driven growth and productivity became the starting point of all process based vegetation models. Most of these models, nowadays adopt other environmental drivers, such as nutrient availability, as modulating co-controls, but the carbon priority is retained. Yet, if we believe in the basic rules of stoichometry of all life, there is an inevitable need of 25-30 elements other then carbon, oxygen and hydrogen to build a healthy plant body. Plants compete for most of these elements, and their availability (except for N) is finite per unit land area. Hence, by pure plausibility, it is a highly unlikely situation that carbon plays the rate limiting role of growth under natural conditions, except in deep shade or on exceptionally fertile soils. Furthermore, water shortage and low temperature, both act directly upon tissue formation (meristems) long before photosynthetic limitations come into play. Hence, plants will incorporate C only to the extent other environmental drivers permit. In the case of nutrients and mature ecosystems, this sink control of plant growth may be masked in the short term by a tight, almost closed nutrient cycle or by widening the C to other element ratio. Because source and sink activity must match in the long term, it is not possible to identify the hierarchy of growth controls without manipulating the environment. Dry matter allocation to C rich structures and reserves may provide some stoichimetric leeway or periodic escapes from the more fundamental, long-term environmental controls of growth and productivity. I will explain why carbon centric explanations of growth are limited or arrive at plausible answers for the wrong reason. Suggested reading: Fatichi, Leuzinger, Körner (2013) Moving beyond photosynthesis: from carbon source to sink-driven vegetation modeling. New Phytologist. Körner C (2013) Growth controls photosynthesis - mostly. Nova Acta Leopoldina 391:273-283.

Inorganic carbon availability in benthic diatom communities: photosynthesis and migration.

PubMed

Marques da Silva, Jorge; Cruz, Sónia; Cartaxana, Paulo

2017-09-05

Diatom-dominated microphytobenthos (MPB) is the main primary producer of many intertidal and shallow subtidal environments, being therefore of critical importance to estuarine and coastal food webs. Owing to tidal cycles, intertidal MPB diatoms are subjected to environmental conditions far more variable than the ones experienced by pelagic diatoms (e.g. light, temperature, salinity, desiccation and nutrient availability). Nevertheless, benthic diatoms evolved adaptation mechanisms to these harsh conditions, including the capacity to move within steep physical and chemical gradients, allowing them to perform photosynthesis efficiently. In this contribution, we will review present knowledge on the effects of dissolved inorganic carbon (DIC) availability on photosynthesis and productivity of diatom-dominated MPB. We present evidence of carbon limitation of photosynthesis in benthic diatom mats and highly productive MPB natural communities. Furthermore, we hypothesize that active vertical migration of epipelic motile diatoms could overcome local depletion of DIC in the photic layer, providing the cells alternately with light and inorganic carbon supply. The few available longer-term experiments on the effects of inorganic carbon enrichment on the productivity of diatom-dominated MPB have yielded inconsistent results. Therefore, further studies are needed to properly assess the response of MPB communities to increased CO 2 and ocean acidification related to climate change.This article is part of the themed issue 'The peculiar carbon metabolism in diatoms'. © 2017 The Author(s).

Seasonal patterns in soil N availability in the arctic tundra in response to accelerated snowmelt and warming

NASA Astrophysics Data System (ADS)

Darrouzet-Nardi, A.; Wallenstein, M. D.; Steltzer, H.; Sullivan, P.; Melle, C.; Segal, A.; Weintraub, M. N.

2010-12-01

Arctic soils contain large stocks of carbon (C) and may act as a significant CO2 source in response to climate warming. However, nitrogen (N) availability limits both plant growth and decomposition in many Arctic sites, and may thus be a key constraint on climate-carbon feedbacks. While current models of tundra ecosystems and their responses to climate change assume that N limits plant growth and C limits decomposition, there is strong evidence to the contrary showing that N can also limit decomposition. For example, the production of both new microbial biomass and enzymes that degrade organic matter appear to be limited by N during the summer. N availability is strongly seasonal: we have previously observed relatively high availability early in the growing season followed by a pronounced crash in tussock tundra soils. To investigate the drivers of N availability throughout the season, we used a field manipulation of tussock tundra growing season length (~4 days acceleration of snowmelt) and air temperature (open top chambers) and a laboratory soil N addition in both early and late season. Nutrient availability throughout the field season was measured at high temporal resolution (25 measurements from soil thaw through early plant senescence). Results from a laboratory experiment in which N was added to early season and late season soils suggests that soil respiration is in fact N limited at both times of the season, though this limitation is temperature dependent with effects most pronounced at 10°C. High-resolution measurements of nutrients in the soil solution and extractable N throughout the season showed that although a nutrient crash in N can be observed mid-season, N availability can still fluctuate later in the season. Finally, effects of the extended growing season and increased air temperature have so far had few effects on soil nutrient N dynamics throughout the summer growing season, suggesting either an insensitivity of N availability to these manipulations or an interannual time lag in the onset of change.

Power sources for search and rescue 406 MHz beacons

NASA Technical Reports Server (NTRS)

Attia, Alan I.; Perrone, David E.

1987-01-01

The results of a study directed at the selection of a commercially available, safe, low cost, light weight and long storage life battery for search and rescue (Sarsat) 406 MHz emergency beacons are presented. In the course of this work, five electrochemical systems (lithium-manganese dioxide, lithium-carbon monofluoride, lithium-silver vanadium oxide, alkaline cells, and cadmium-mercuric oxide) were selected for limited experimental studies to determine their suitability for this application. Two safe, commercially available batteries (lithium-manganese dioxide and lithium-carbon monofluoride) which meet the near term requirements and several alternatives for the long term were identified.

An empirical model of the phytoplankton chlorophyll : carbon ratio-the conversion factor between productivity and growth rate

USGS Publications Warehouse

Cloern, James E.; Grenz, Christian; Vidergar-Lucas, Lisa

1995-01-01

We present an empirical model that describes the ratio of phytoplankton chlorophyll a to carbon, Chl: C, as a function of temperature, daily irradiance, and nutrient-limited growth rate. Our model is based on 219 published measurements of algal cultures exposed to light-limited or nutrient-limited growth conditions. We illustrate an approach for using this estimator of Chl: C to calculate phytoplankton population growth rate from measured primary productivity. This adaptive Chl: C model gives rise to interactive light-nutrient effects in which growth efficiency increases with nutrient availability under low-light conditions. One implication of this interaction is the enhancement of phytoplankton growth efficiency, in addition to enhancement of biomass yield, as a response to eutrophication.

Low-cost carbon-silicon nanocomposite anodes for lithium ion batteries.

PubMed

Badi, Nacer; Erra, Abhinay Reddy; Hernandez, Francisco C Robles; Okonkwo, Anderson O; Hobosyan, Mkhitar; Martirosyan, Karen S

2014-01-01

The specific energy of the existing lithium ion battery cells is limited because intercalation electrodes made of activated carbon (AC) materials have limited lithium ion storage capacities. Carbon nanotubes, graphene, and carbon nanofibers are the most sought alternatives to replace AC materials but their synthesis cost makes them highly prohibitive. Silicon has recently emerged as a strong candidate to replace existing graphite anodes due to its inherently large specific capacity and low working potential. However, pure silicon electrodes have shown poor mechanical integrity due to the dramatic expansion of the material during battery operation. This results in high irreversible capacity and short cycle life. We report on the synthesis and use of carbon and hybrid carbon-silicon nanostructures made by a simplified thermo-mechanical milling process to produce low-cost high-energy lithium ion battery anodes. Our work is based on an abundant, cost-effective, and easy-to-launch source of carbon soot having amorphous nature in combination with scrap silicon with crystalline nature. The carbon soot is transformed in situ into graphene and graphitic carbon during mechanical milling leading to superior elastic properties. Micro-Raman mapping shows a well-dispersed microstructure for both carbon and silicon. The fabricated composites are used for battery anodes, and the results are compared with commercial anodes from MTI Corporation. The anodes are integrated in batteries and tested; the results are compared to those seen in commercial batteries. For quick laboratory assessment, all electrochemical cells were fabricated under available environment conditions and they were tested at room temperature. Initial electrochemical analysis results on specific capacity, efficiency, and cyclability in comparison to currently available AC counterpart are promising to advance cost-effective commercial lithium ion battery technology. The electrochemical performance observed for carbon soot material is very interesting given the fact that its production cost is away cheaper than activated carbon. The cost of activated carbon is about $15/kg whereas the cost to manufacture carbon soot as a by-product from large-scale milling of abundant graphite is about $1/kg. Additionally, here, we propose a method that is environmentally friendly with strong potential for industrialization.

Low-cost carbon-silicon nanocomposite anodes for lithium ion batteries

PubMed Central

2014-01-01

The specific energy of the existing lithium ion battery cells is limited because intercalation electrodes made of activated carbon (AC) materials have limited lithium ion storage capacities. Carbon nanotubes, graphene, and carbon nanofibers are the most sought alternatives to replace AC materials but their synthesis cost makes them highly prohibitive. Silicon has recently emerged as a strong candidate to replace existing graphite anodes due to its inherently large specific capacity and low working potential. However, pure silicon electrodes have shown poor mechanical integrity due to the dramatic expansion of the material during battery operation. This results in high irreversible capacity and short cycle life. We report on the synthesis and use of carbon and hybrid carbon-silicon nanostructures made by a simplified thermo-mechanical milling process to produce low-cost high-energy lithium ion battery anodes. Our work is based on an abundant, cost-effective, and easy-to-launch source of carbon soot having amorphous nature in combination with scrap silicon with crystalline nature. The carbon soot is transformed in situ into graphene and graphitic carbon during mechanical milling leading to superior elastic properties. Micro-Raman mapping shows a well-dispersed microstructure for both carbon and silicon. The fabricated composites are used for battery anodes, and the results are compared with commercial anodes from MTI Corporation. The anodes are integrated in batteries and tested; the results are compared to those seen in commercial batteries. For quick laboratory assessment, all electrochemical cells were fabricated under available environment conditions and they were tested at room temperature. Initial electrochemical analysis results on specific capacity, efficiency, and cyclability in comparison to currently available AC counterpart are promising to advance cost-effective commercial lithium ion battery technology. The electrochemical performance observed for carbon soot material is very interesting given the fact that its production cost is away cheaper than activated carbon. The cost of activated carbon is about $15/kg whereas the cost to manufacture carbon soot as a by-product from large-scale milling of abundant graphite is about $1/kg. Additionally, here, we propose a method that is environmentally friendly with strong potential for industrialization. PMID:25114651

CO2-induced photosynthetic and stoichiometric responses to phosphorus limitation

NASA Astrophysics Data System (ADS)

de Boer, Hugo; di Lallo, Giacomo; van Dijk, Jerry

2017-04-01

Carbon fertilisation from rising atmospheric CO2 concentrations increases the productivity of plants globally. Meanwhile, the global cycles of Nitrogen (N) and Phosphorus (P) are also altered due to anthropogenic emissions. In general, the additional supply of N is expected to exceed that of P, leading to an increase in P limitation in natural ecosystems. Although the direct carbon fertilisation effect and the interaction with available N is relatively well understood, it remains uncertain how carbon fertilisation is confounded by the availability of P. It is hypothesised that (i) the photosynthetic P-use efficiency increases at elevated CO2 owing to a direct increase in photosynthesis and (ii) the photosynthetic maximum carboxylation rate (Vcmax) and electron transport rate (Jmax) are down-regulated in response to a combination of elevated CO2 and P-limitation via a coordinated reduction of leaf N and P content per unit leaf area. In this study we examined the hypothesised effects of P limitation and CO2 fertilisation on the photosynthetic and stoichiometric responses of three plant species: Holcus lanatus (C3 grass), Panicum miliaceum (C4 grass) and Solanum dulcamara (C3 herb). Individuals of these species were grown at sub-ambient (150 ppm), modern (450 ppm) and elevated CO2 concentrations (800 ppm) and exposed to an N:P treatment consisting of either severe nitrogen limitation at an N:P ratio of 1:1, or severe P limitation at an N:P ratio of 45:1, with a similar supply rate of N. Our results show significant effects of growth CO2 and P supply on Vcmax and Jmax, as well as the whole-plant biomass at the point of harvest. Interaction effects between growth CO2 and P supply were observed for the light-saturated photosynthesis rate, stomatal conductance, leaf P content, and the N:P ratio of the leaf. No significant change in the leaf N content was observed across treatments. These results suggest that limited availability of P constrains the biochemical potential for plants to up-regulate Vcmax and Jmax. This effect is most prominently expressed at low CO2 growth conditions, which induce strong up-regulation of Vcmax and Jmax when P is not limiting. Conversely, the down-regulation of Vcmax and Jmax at elevated CO2 is more pronounced when P is limiting. Hence, the combined effects of rising CO2 and additional P limitation may result in additional down-regulation of Vcmax and Jmax and a subsequent waning of the CO2 fertilisation effect. These results highlight the need to consider P limitation in global vegetation models when studying carbon fertilisation effects.

Historic Emissions from Deforestation and Forest Degradation in Mato Grosso, Brazil: 1. Source Data Uncertainties

NASA Technical Reports Server (NTRS)

Morton, Douglas C.; Sales, Marcio H.; Souza, Carlos M., Jr.; Griscom, Bronson

2011-01-01

Historic carbon emissions are an important foundation for proposed efforts to Reduce Emissions from Deforestation and forest Degradation and enhance forest carbon stocks through conservation and sustainable forest management (REDD+). The level of uncertainty in historic carbon emissions estimates is also critical for REDD+, since high uncertainties could limit climate benefits from mitigation actions. Here, we analyzed source data uncertainties based on the range of available deforestation, forest degradation, and forest carbon stock estimates for the Brazilian state of Mato Grosso during 1990-2008. Results: Deforestation estimates showed good agreement for multi-year trends of increasing and decreasing deforestation during the study period. However, annual deforestation rates differed by >20% in more than half of the years between 1997-2008, even for products based on similar input data. Tier 2 estimates of average forest carbon stocks varied between 99-192 Mg C/ha, with greatest differences in northwest Mato Grosso. Carbon stocks in deforested areas increased over the study period, yet this increasing trend in deforested biomass was smaller than the difference among carbon stock datasets for these areas. Conclusions: Patterns of spatial and temporal disagreement among available data products provide a roadmap for future efforts to reduce source data uncertainties for estimates of historic forest carbon emissions. Specifically, regions with large discrepancies in available estimates of both deforestation and forest carbon stocks are priority areas for evaluating and improving existing estimates. Full carbon accounting for REDD+ will also require filling data gaps, including forest degradation and secondary forest, with annual data on all forest transitions.

Microbial respiration and DOC composition in leachates from Holocene and Pleistocene soils from the Kolyma River basin in Eastern Siberia

NASA Astrophysics Data System (ADS)

Lewis, K.; Schade, J. D.; Sobczak, W. V.; Holmes, R. M.; Zimov, N.; Bulygina, E. B.; Chandra, S.; Bunn, A. G.; Russell-Roy, L.; Seybold, E. C.

2010-12-01

Permafrost is generally considered a long-term sink for carbon that remains locked away from the global carbon cycle. Anthropogenic climate change is likely to lead to thawing of permafrost and deepening of the soil active layer. Consequently, this carbon sink may become unlocked and available for bacterial decomposition, returning stored carbon to the active carbon cycle, with potentially severe consequences for atmospheric CO2 concentrations. The Kolyma watershed, in the Eastern Siberian Arctic, is underlain by continuous permafrost, often referred to as Yedoma, which provides a unique environment to study potential consequences of permafrost thaw for carbon dynamics in aquatic and terrestrial ecosystems. In order to predict the potential consequences of a major carbon input from thawing permafrost, we assessed the relative bioavailabilty of soil carbon by measuring rates of microbial consumption and changes in DOM composition in soil leachates. At two spatially distinct sample sites, soil was collected throughout the profile from the active layer and from permafrost, including soils from both Holocene and Pleistocene-era permafrost. To evaluate the rates of carbon processing and potential linkages to N and P cycles, we conducted a series of bottle experiments in which we measured biological oxygen demand as a proxy for carbon processing and assessed changes in the composition of dissolved organic carbon using spectral analyses. Experiments were conducted on leachate collected from each soil type. Each experiment included treatments in which leachates were enriched with nitrogen and phosphorus to determine whether carbon processing in soils was nutrient limited. We found substantial variation in oxygen consumption, with Yedoma soils generally exhibiting higher rates than Holocene soils, suggesting higher concentrations of labile carbon. We found no evidence of nutrient limitation of carbon processing in any soil leachates. Spectral slope analysis suggests that carbon processing increased the proportion of heavy aromatic carbon compounds in all but one soil type, suggesting that small molecular weight compounds are consumed first. The exception was the most active Yedoma soil, which showed the opposite effect, indicating an increase in the proportion of small molecules due to the presence of a different, and perhaps more digestible, form of carbon. These results suggest strong spatial variation in the amount and form of available carbon, as well as qualitative differences in the dynamics of carbon processing.

A mechanistic, globally-applicable model of plant nitrogen uptake, retranslocation and fixation

NASA Astrophysics Data System (ADS)

Fisher, J. B.; Tan, S.; Malhi, Y.; Fisher, R. A.; Sitch, S.; Huntingford, C.

2008-12-01

Nitrogen is one of the nutrients that can most limit plant growth, and nitrogen availability may be a controlling factor on biosphere responses to climate change. We developed a plant nitrogen assimilation model based on a) advective transport through the transpiration stream, b) retranslocation whereby carbon is expended to resorb nitrogen from leaves, c) active uptake whereby carbon is expended to acquire soil nitrogen, and d) biological nitrogen fixation whereby carbon is expended for symbiotic nitrogen fixers. The model relies on 9 inputs: 1) net primary productivity (NPP), 2) plant C:N ratio, 3) available soil nitrogen, 4) root biomass, 5) transpiration rate, 6) saturated soil depth,7) leaf nitrogen before senescence, 8) soil temperature, and 9) ability to fix nitrogen. A carbon cost of retranslocation is estimated based on leaf nitrogen and compared to an active uptake carbon cost based on root biomass and available soil nitrogen; for nitrogen fixers both costs are compared to a carbon cost of fixation dependent on soil temperature. The NPP is then allocated to optimize growth while maintaining the C:N ratio. The model outputs are total plant nitrogen uptake, remaining NPP available for growth, carbon respired to the soil and updated available soil nitrogen content. We test and validate the model (called FUN: Fixation and Uptake of Nitrogen) against data from the UK, Germany and Peru, and run the model under simplified scenarios of primary succession and climate change. FUN is suitable for incorporation into a land surface scheme of a General Circulation Model and will be coupled with a soil model and dynamic global vegetation model as part of a land surface model (JULES).

Biomass of active microorganisms is not limited only by available carbon in the rhizosphere

NASA Astrophysics Data System (ADS)

Gilmullina, Aliia

2017-04-01

Microbial activity is generally limited by carbon (C) availability. The easily available substrate release by roots creates so called "hotspots" in the rhizosphere that drives microbial activity removing C limitation. We simulated a gradient of root exudates by glucose addition at different concentrations to stimulate the activation of microbial biomass (MB). Glucose was added at the rates lower than MB (5, 10, 25 and 50%) and at the rates similar or higher than MB (100, 150, 200, 250, 300 and 400%). During incubation CO2 efflux was measured by conductometry, the size of active MB and specific growth rate were estimated by substrate-induced growth response method. We tested a hypothesis that glucose addition exceeding 100% MB is able to activate major fraction of soil microbial community. Addition of glucose at concentrations higher than 5% decreased specific growth rate, demonstrating the shift of microbial community from r-strategy to K-strategy. The percentage of active MB grew up by the increase of glucose concentration. The treatment with glucose at 100% presented a dramatic shift in the activation of MB up to 14%. Contrary to our hypothesis, further increase in glucose rate caused moderate stimulation of active MB up to 22% of total MB. Furthermore, glucose addition above 200% did not increase the fraction of active biomass indicating glucose oversaturation and possible limitation by other nutrients. The results suggest that despite the fact that C is the most important limitation factor, limitless C supply is not able to activate MB up to 100%. Thus, if the rhizosphere is limited by nutrients, the fraction of active biomass remains at low level despite an excess of available C.

Uncertainties in the temperature sensitivity of decomposition in tropical and subtropical ecosystems: Implications for models

NASA Astrophysics Data System (ADS)

Holland, Elisabeth A.; Neff, Jason C.; Townsend, Alan R.; McKeown, Becky

2000-12-01

Tropical ecosystems play a central role in the global carbon cycle. Large changes in tropical temperature over geologic time and the significant responses of tropical ecosystems to shorter-term variations such as El Niño/La Niña argue for a robust understanding of the temperature sensitivity of tropical decomposition. To examine the responsiveness of heterotrophic respiration to temperature, we measured rates of heterotrophic respiration from a wide range of tropical soils in a series of laboratory incubations. Under conditions of optimal soil water and nonlimiting substrate availability, heterotrophic respiration rose exponentially with rising temperature. The meanQ10measured across all temperature ranges in these short-term incubations was 2.37, but there was significant variation inQ10s across sites. The source of this variation could not be explained by soil carbon or nitrogen content, soil texture, site climate, or lignin to nitrogen ratio. At the beginning of the incubation, heterotrophic respiration increased exponentially with temperature for all sites, despite the fact that the fluxes differed by an order of magnitude. When substrate availability became limiting later in the incubation, the temperature response changed, and heterotrophic response declined above 35°C. The documented changes in temperature sensitivity with substrate availability argue for using temperature relationships developed under optimal conditions of substrate availability for models which include temperature regulation of heterotrophic respiration. To evaluate the significance of this natural variation in temperature control over decomposition, we used the Century ecosystem model gridded for the areas between the tropics of Cancer and Capricorn. These simulations used the mean and upper and lower confidence limits of the normalized exponential temperature response of our experimental studies. We found that systems with the lowest temperature sensitivity accumulated a total of 70 Pg more carbon in soil organic carbon and respired 5.5 Pg yr-1 less carbon compared to the systems with the highest sensitivity.

Changes in carbon allocation to aboveground versus belowground forest components is driven by a trade-off involving mycorrhizal fungi, not fine roots

NASA Astrophysics Data System (ADS)

Ouimette, A.; Ollinger, S. V.; Hobbie, E. A.; Lepine, L. C.; Stephens, R.; Rowe, R.; Vadeboncoeur, M. A.; Tumber-Davila, S. J.

2017-12-01

Species composition and resource availability exert a strong influence on the dynamics of carbon allocation among different forest ecosystem components. Recent work in temperate forests has highlighted a tradeoff between carbon allocation to aboveground woody tissues (access to light), and belowground to fine roots (access to soil nutrients). Although root-associated mycorrhizal fungi are crucial for N acquisition and can receive 20% or more of annual net primary production, most studies fail to explicitly include carbon allocation to mycorrhizal fungi. In part, this is due to the inherent difficulties in accurately quantifying fungal production. We took several approaches to quantify production of mycorrhizal fungi, including a carbon budget approach and isotopic techniques. Here we present data on patterns of carbon allocation to aboveground (wood and foliar production), and belowground components (production of fine roots and mycorrhizal fungi), across temperate forest stands spanning a range of nitrogen availability and species composition. We found that as the proportion of conifer species decreased, and stand nitrogen availability increased, both the absolute amount and the fraction of net primary production increased for foliage, aboveground wood, and fine roots ("a rising tide lifts all boats"). While allocation to plant pools increased, allocation to mycorrhizal fungi significantly decreased with decreasing conifer dominance and increasing soil nitrogen availability. We did not find a strong trade-off between carbon allocation to fine roots and aboveground wood or foliage. Instead, a negative relationship is seen between allocation to mycorrhizal fungi and other plant pools. Effort to estimate carbon allocation to mycorrhizal fungi is important for gaining a more complete understanding of how ecosystems respond to changes in growth-limiting resources.

Response of Microbial Soil Carbon Mineralization Rates to Oxygen Limitations

NASA Astrophysics Data System (ADS)

Keiluweit, M.; Denney, A.; Nico, P. S.; Fendorf, S. E.

2014-12-01

The rate of soil organic matter (SOM) mineralization is known to be controlled by climatic factors as well as molecular structure, mineral-organic associations, and physical protection. What remains elusive is to what extent oxygen (O2) limitations impact overall rates of microbial SOM mineralization (oxidation) in soils. Even within upland soils that are aerobic in bulk, factors limiting O2 diffusion such as texture and soil moisture can result in an abundance of anaerobic microsites in the interior of soil aggregates. Variation in ensuing anaerobic respiration pathways can further impact SOM mineralization rates. Using a combination of (first) aggregate model systems and (second) manipulations of intact field samples, we show how limitations on diffusion and carbon bioavailability interact to impose anaerobic conditions and associated respiration constraints on SOM mineralization rates. In model aggregates, we examined how particle size (soil texture) and amount of dissolved organic carbon (bioavailable carbon) affect O2 availability and distribution. Monitoring electron acceptor profiles (O2, NO3-, Mn and Fe) and SOM transformations (dissolved, particulate, mineral-associated pools) across the resulting redox gradients, we then determined the distribution of operative microbial metabolisms and their cumulative impact on SOM mineralization rates. Our results show that anaerobic conditions decrease SOM mineralization rates overall, but those are partially offset by the concurrent increases in SOM bioavailability due to transformations of protective mineral phases. In intact soil aggregates collected from soils varying in texture and SOM content, we mapped the spatial distribution of anaerobic microsites. Optode imaging, microsensor profiling and 3D tomography revealed that soil texture regulates overall O2 availability in aggregate interiors, while particulate SOM in biopores appears to control the fine-scale distribution of anaerobic microsites. Collectively, our results suggest that texture and particulate organic matter content are useful predictors for the impact of O2 limitations on SOM mineralization rates.

Integrated carbon and chlorine isotope modeling: applications to chlorinated aliphatic hydrocarbons dechlorination.

PubMed

Jin, Biao; Haderlein, Stefan B; Rolle, Massimo

2013-02-05

We propose a self-consistent method to predict the evolution of carbon and chlorine isotope ratios during degradation of chlorinated hydrocarbons. The method treats explicitly the cleavage of isotopically different C-Cl bonds and thus considers, simultaneously, combined carbon-chlorine isotopologues. To illustrate the proposed modeling approach we focus on the reductive dehalogenation of chlorinated ethenes. We compare our method with the currently available approach, in which carbon and chlorine isotopologues are treated separately. The new approach provides an accurate description of dual-isotope effects regardless of the extent of the isotope fractionation and physical characteristics of the experimental system. We successfully applied the new approach to published experimental results on dehalogenation of chlorinated ethenes both in well-mixed systems and in situations where mass-transfer limitations control the overall rate of biodegradation. The advantages of our self-consistent dual isotope modeling approach proved to be most evident when isotope fractionation factors of carbon and chlorine differed significantly and for systems with mass-transfer limitations, where both physical and (bio)chemical transformation processes affect the observed isotopic values.

Steady-State Growth under Inorganic Carbon Limitation Conditions Increases Energy Consumption for Maintenance and Enhances Nitrous Oxide Production in Nitrosomonas europaea.

PubMed

Mellbye, Brett L; Giguere, Andrew; Chaplen, Frank; Bottomley, Peter J; Sayavedra-Soto, Luis A

2016-06-01

Nitrosomonas europaea is a chemolithoautotrophic bacterium that oxidizes ammonia (NH3) to obtain energy for growth on carbon dioxide (CO2) and can also produce nitrous oxide (N2O), a greenhouse gas. We interrogated the growth, physiological, and transcriptome responses of N. europaea to conditions of replete (>5.2 mM) and limited inorganic carbon (IC) provided by either 1.0 mM or 0.2 mM sodium carbonate (Na2CO3) supplemented with atmospheric CO2 IC-limited cultures oxidized 25 to 58% of available NH3 to nitrite, depending on the dilution rate and Na2CO3 concentration. IC limitation resulted in a 2.3-fold increase in cellular maintenance energy requirements compared to those for NH3-limited cultures. Rates of N2O production increased 2.5- and 6.3-fold under the two IC-limited conditions, increasing the percentage of oxidized NH3-N that was transformed to N2O-N from 0.5% (replete) up to 4.4% (0.2 mM Na2CO3). Transcriptome analysis showed differential expression (P ≤ 0.05) of 488 genes (20% of inventory) between replete and IC-limited conditions, but few differences were detected between the two IC-limiting treatments. IC-limited conditions resulted in a decreased expression of ammonium/ammonia transporter and ammonia monooxygenase subunits and increased the expression of genes involved in C1 metabolism, including the genes for RuBisCO (cbb gene cluster), carbonic anhydrase, folate-linked metabolism of C1 moieties, and putative C salvage due to oxygenase activity of RuBisCO. Increased expression of nitrite reductase (gene cluster NE0924 to NE0927) correlated with increased production of N2O. Together, these data suggest that N. europaea adapts physiologically during IC-limited steady-state growth, which leads to the uncoupling of NH3 oxidation from growth and increased N2O production. Nitrification, the aerobic oxidation of ammonia to nitrate via nitrite, is an important process in the global nitrogen cycle. This process is generally dependent on ammonia-oxidizing microorganisms and nitrite-oxidizing bacteria. Most nitrifiers are chemolithoautotrophs that fix inorganic carbon (CO2) for growth. Here, we investigate how inorganic carbon limitation modifies the physiology and transcriptome of Nitrosomonas europaea, a model ammonia-oxidizing bacterium, and report on increased production of N2O, a potent greenhouse gas. This study, along with previous work, suggests that inorganic carbon limitation may be an important factor in controlling N2O emissions from nitrification in soils and wastewater treatment. Copyright © 2016, American Society for Microbiology. All Rights Reserved.

Steady-State Growth under Inorganic Carbon Limitation Conditions Increases Energy Consumption for Maintenance and Enhances Nitrous Oxide Production in Nitrosomonas europaea

PubMed Central

Giguere, Andrew; Chaplen, Frank; Bottomley, Peter J.

2016-01-01

ABSTRACT Nitrosomonas europaea is a chemolithoautotrophic bacterium that oxidizes ammonia (NH3) to obtain energy for growth on carbon dioxide (CO2) and can also produce nitrous oxide (N2O), a greenhouse gas. We interrogated the growth, physiological, and transcriptome responses of N. europaea to conditions of replete (>5.2 mM) and limited inorganic carbon (IC) provided by either 1.0 mM or 0.2 mM sodium carbonate (Na2CO3) supplemented with atmospheric CO2. IC-limited cultures oxidized 25 to 58% of available NH3 to nitrite, depending on the dilution rate and Na2CO3 concentration. IC limitation resulted in a 2.3-fold increase in cellular maintenance energy requirements compared to those for NH3-limited cultures. Rates of N2O production increased 2.5- and 6.3-fold under the two IC-limited conditions, increasing the percentage of oxidized NH3-N that was transformed to N2O-N from 0.5% (replete) up to 4.4% (0.2 mM Na2CO3). Transcriptome analysis showed differential expression (P ≤ 0.05) of 488 genes (20% of inventory) between replete and IC-limited conditions, but few differences were detected between the two IC-limiting treatments. IC-limited conditions resulted in a decreased expression of ammonium/ammonia transporter and ammonia monooxygenase subunits and increased the expression of genes involved in C1 metabolism, including the genes for RuBisCO (cbb gene cluster), carbonic anhydrase, folate-linked metabolism of C1 moieties, and putative C salvage due to oxygenase activity of RuBisCO. Increased expression of nitrite reductase (gene cluster NE0924 to NE0927) correlated with increased production of N2O. Together, these data suggest that N. europaea adapts physiologically during IC-limited steady-state growth, which leads to the uncoupling of NH3 oxidation from growth and increased N2O production. IMPORTANCE Nitrification, the aerobic oxidation of ammonia to nitrate via nitrite, is an important process in the global nitrogen cycle. This process is generally dependent on ammonia-oxidizing microorganisms and nitrite-oxidizing bacteria. Most nitrifiers are chemolithoautotrophs that fix inorganic carbon (CO2) for growth. Here, we investigate how inorganic carbon limitation modifies the physiology and transcriptome of Nitrosomonas europaea, a model ammonia-oxidizing bacterium, and report on increased production of N2O, a potent greenhouse gas. This study, along with previous work, suggests that inorganic carbon limitation may be an important factor in controlling N2O emissions from nitrification in soils and wastewater treatment. PMID:27016565

Vertically aligned carbon nanotubes black coatings from roll-to-roll deposition process

NASA Astrophysics Data System (ADS)

Goislard de Monsabert, Thomas; Papciak, L.; Sangar, A.; Descarpentries, J.; Vignal, T.; de Longiviere, Xavier; Porterat, D.; Mestre, Q.; Hauf, H.

2017-09-01

Vertically aligned carbon nanotubes (VACNTs) have recently attracted growing interest as a very efficient light absorbing material over a broad spectral range making them a superior coating in space optics applications such as radiometry, optical calibration, and stray light elimination. However, VACNT coatings available to-date most often result from batch-to-batch deposition processes thus potentially limiting the manufacturing repeatability, substrate size and cost efficiency of this material.

Multiple-element semiquantitative analysis of one-milligram geochemical samples by D.C. arc emission spectrography

USGS Publications Warehouse

Rait, N.

1981-01-01

A modified method is described for a 1-mg sample multi-element semiquantitative spectrographic analysis. This method uses a direct-current arc source, carbon instead of graphite electrodes, and an 80% argon-20% oxygen atmosphere instead of air. Although this is a destructive method, an analysis can be made for 68 elements in all mineral and geochemical samples. Carbon electrodes have been an aid in improving the detection limits of many elements. The carbon has a greater resistance to heat conductance and develops a better tip, facilitating sample volatilization and counter balancing the cooling effect of a flow of the argon-oxygen mixture around the anode. Where such an argon-oxygen atmosphere is used instead of air, the cyanogen band lines are greatly diminished in intensity, and thus more spectral lines of analysis elements are available for use; the spectral background is also lower. The main advantage of using the carbon electrode and the 80% argon-20% oxygen atmosphere is the improved detection limits of 36 out of 68 elements. The detection limits remain the same for 23 elements, and are not as good for only nine elements. ?? 1981.

Carbon Accumulation and Nitrogen Pool Recovery during Transitions from Savanna to Forest in Central Brazil

NASA Astrophysics Data System (ADS)

Pellegrini, A.; Hoffmann, W. A.; Franco, A. C.

2014-12-01

The expansion of tropical forest into savanna may potentially be a large carbon sink, but little is known about the patterns of carbon sequestration during transitional forest formation. Moreover, it is unclear how nutrient limitation, due to extended exposure to firedriven nutrient losses, may constrain carbon accumulation. Here, we sampled plots that spanned a woody biomass gradient from savanna to transitional forest in response to differential fire protection in central Brazil. These plots were used to investigate how the process of transitional forest formation affects the size and distribution of carbon (C) and nitrogen (N) pools. This was paired with a detailed analysis of the nitrogen cycle to explore possible connections between carbon accumulation and nitrogen limitation. An analysis of carbon pools in the vegetation, upper soil, and litter shows that the transition from savanna to transitional forest can result in a fourfold increase in total carbon (from 43 to 179 Mg C/ha) with a doubling of carbon stocks in the litter and soil layers. Total nitrogen in the litter and soil layers increased with forest development in both the bulk (+68%) and plant-available (+150%) pools, with the most pronounced changes occurring in the upper layers. However, the analyses of nitrate concentrations, nitrate : ammonium ratios, plant stoichiometry of carbon and nitrogen, and soil and foliar nitrogen isotope ratios suggest that a conservative nitrogen cycle persists throughout forest development, indicating that nitrogen remains in low supply relative to demand. Furthermore, the lack of variation in underlying soil type (>20 cm depth) suggests that the biogeochemical trends across the gradient are driven by vegetation. Our results provide evidence for high carbon sequestration potential with forest encroachment on savanna, but nitrogen limitation may play a large and persistent role in governing carbon sequestration in savannas or other equally fire-disturbed tropical landscapes. In turn, the link between forest development and nitrogen pool recovery creates a framework for evaluating potential positive feedbacks on savanna-forest boundaries.

Organic Matter Quality and its Influence on Carbon Turnover and Stabilization in Northern Peatlands

NASA Astrophysics Data System (ADS)

Turetsky, M. R.; Wieder, R. K.

2002-12-01

Peatlands cover 3-5 % of the world's ice-free land area, but store about 33 % of global terrestrial soil carbon. Peat accumulation in northern regions generally is controlled by slow decomposition, which may be limited by cold temperatures and water-logging. Poor organic matter quality also may limit decay, and microbial activity in peatlands likely is regulated by the availability of labile carbon and/or nutrients. Conversely, carbon in recalcitrant soil structures may be chemically protected from microbial decay, particularly in peatlands where carbon can be buried in anaerobic soils. Soil organic matter quality is controlled by plant litter chemical composition and the susceptibility of organic compounds to decomposition through time. There are a number of techniques available for characterizing organic quality, ranging from chemical proximate or elemental analysis to more qualitative methods such as nuclear magenetic resonance, pyrolysis/mass spectroscopy, and Fourier transform infrared spectroscopy. We generally have relied on proximate analysis for quantitative determination of several organic fractions (i.e., water-soluble carbohydrates, soluble nonpolars, water-soluble phenolics, holocellulose, and acid insoluble material). Our approaches to studying organic matter quality in relation to C turnover in peatlands include 1) 14C labelling of peatland vegetation along a latitudinal gradient in North America, allowing us to follow the fate of 14C tracer in belowground organic fractions under varying climates, 2) litter bag studies focusing on the role of individual moss species in litter quality and organic matter decomposition, and 3) laboratory incubations of peat to explore relationships between organic matter quality and decay. These studies suggest that proximate organic fractions vary in lability, but that turnover of organic matter is influenced both by plant species and climate. Across boreal peatlands, measures of soil recalcitrance such as acid insoluble material (AIM) and AIM/N were significant predictors of decomposition. However, when limited to individual peatland features or bryophyte species, soluble proximate fractions were better predictors of organic matter decay. This suggests that decomposition within single litter or peat types is controlled by the size of relatively small, labile carbon pools. As peatlands store the majority of soil carbon in the boreal forest, the influences of peat quality on carbon storage and turnover should be considered in understanding the fate of carbon in northern ecosystems.

Historic emissions from deforestation and forest degradation in Mato Grosso, Brazil: 1) source data uncertainties

PubMed Central

2011-01-01

Background Historic carbon emissions are an important foundation for proposed efforts to Reduce Emissions from Deforestation and forest Degradation and enhance forest carbon stocks through conservation and sustainable forest management (REDD+). The level of uncertainty in historic carbon emissions estimates is also critical for REDD+, since high uncertainties could limit climate benefits from credited mitigation actions. Here, we analyzed source data uncertainties based on the range of available deforestation, forest degradation, and forest carbon stock estimates for the Brazilian state of Mato Grosso during 1990-2008. Results Deforestation estimates showed good agreement for multi-year periods of increasing and decreasing deforestation during the study period. However, annual deforestation rates differed by > 20% in more than half of the years between 1997-2008, even for products based on similar input data. Tier 2 estimates of average forest carbon stocks varied between 99-192 Mg C ha-1, with greatest differences in northwest Mato Grosso. Carbon stocks in deforested areas increased over the study period, yet this increasing trend in deforested biomass was smaller than the difference among carbon stock datasets for these areas. Conclusions Estimates of source data uncertainties are essential for REDD+. Patterns of spatial and temporal disagreement among available data products provide a roadmap for future efforts to reduce source data uncertainties for estimates of historic forest carbon emissions. Specifically, regions with large discrepancies in available estimates of both deforestation and forest carbon stocks are priority areas for evaluating and improving existing estimates. Full carbon accounting for REDD+ will also require filling data gaps, including forest degradation and secondary forest, with annual data on all forest transitions. PMID:22208947

Algae Biofuels Co-Location Assessment Tool for Canada

DOE Office of Scientific and Technical Information (OSTI.GOV)

2011-11-29

The Algae Biofuels Co-Location Assessment Tool for Canada uses chemical stoichiometry to estimate Nitrogen, Phosphorous, and Carbon atom availability from waste water and carbon dioxide emissions streams, and requirements for those same elements to produce a unit of algae. This information is then combined to find limiting nutrient information and estimate potential productivity associated with waste water and carbon dioxide sources. Output is visualized in terms of distributions or spatial locations. Distances are calculated between points of interest in the model using the great circle distance equation, and the smallest distances found by an exhaustive search and sort algorithm.

Ecological Limits to Terrestrial Carbon Dioxide Removal Strategies

NASA Astrophysics Data System (ADS)

Smith, L. J.; Torn, M. S.; Jones, A. D.

2011-12-01

Carbon dioxide removal from the atmosphere through terrestrial carbon sequestration and bioenergy (biological CDR) is a proposed climate change mitigation strategy. Biological CDR increases the carbon storage capacity of soils and biomass through changes in land cover and use, including reforestation, afforestation, conversion of land to agriculture for biofuels, conversion of degraded land to grassland, and alternative management practices such as conservation tillage. While biological CDR may play a valuable role in future climate change mitigation, many of its proponents fail to account for the full range of biological, biophysical, hydrologic, and economic complexities associated with proposed land use changes. In this analysis, we identify and discuss a set of ecological limits and impacts associated with terrestrial CDR. The capacity of biofuels, soils, and other living biomass to sequester carbon may be constrained by nutrient and water availability, soil dynamics, and local climate effects, all of which can change spatially and temporally in unpredictable ways. Even if CDR is effective at sequestering CO2, its associated land use and land cover changes may negatively impact ecological resources by compromising water quality and availability, degrading soils, reducing biodiversity, displacing agriculture, and altering local climate through albedo and evapotranspiration changes. Measures taken to overcome ecological limitations, such as fertilizer addition and irrigation, may exacerbate these impacts even further. The ecological considerations and quantitative analyses that we present highlight uncertainties introduced by ecological complexity, disagreements between models, perverse economic incentives, and changing environmental factors. We do not reject CDR as a potentially valuable strategy for climate change mitigation; ecosystem protection, restoration, and improved management practices could enhance soil fertility and protect biodiversity while reducing increases in atmospheric CO2. Rather, we emphasize the importance of evaluating the full set of biological, physical, economic, and political realities that accompany land-use changes and manipulations to the carbon cycle. While the immediate goal of biological CDR is to reduce atmospheric CO2 concentrations, its ultimate goal in mitigating climate change is to reduce the threats to ecosystems and society. Sequestering carbon at the cost of ecosystem health would not be a sensible approach.

Effects of soil freezing and thawing on vegetation carbon density in Siberia: A modeling analysis with the Lund-Potsdam-Jena Dynamic Global Vegetation Model (LPJ-DGVM)

NASA Astrophysics Data System (ADS)

Beer, C.; Lucht, W.; Gerten, D.; Thonicke, K.; Schmullius, C.

2007-03-01

The current latitudinal gradient in biomass suggests a climate-driven limitation of biomass in high latitudes. Understanding of the underlying processes, and quantification of their relative importance, is required to assess the potential carbon uptake of the biosphere in response to anticipated warming and related changes in tree growth and forest extent in these regions. We analyze the hydrological effects of thawing and freezing of soil on vegetation carbon density (VCD) in permafrost-dominated regions of Siberia using a process-based biogeochemistry-biogeography model, the Lund-Potsdam-Jena Dynamic Global Vegetation Model (LPJ-DGVM). The analysis is based on spatially explicit simulations of coupled daily thaw depth, site hydrology, vegetation distribution, and carbon fluxes influencing VCD subject to climate, soil texture, and atmospheric CO2 concentration. LPJ represents the observed high spring peak of runoff of large Arctic rivers, and simulates a realistic fire return interval of 100 to 200 years in Siberia. The simulated VCD changeover from taiga to tundra is comparable to inventory-based information. Without the consideration of freeze-thaw processes VCD would be overestimated by a factor of 2 in southern taiga to a factor of 5 in northern forest tundra, mainly because available soil water would be overestimated with major effects on fire occurrence and net primary productivity. This suggests that forest growth in high latitudes is not only limited by temperature, radiation, and nutrient availability but also by the availability of liquid soil water.

Incorporating phosphorus cycling into global modeling efforts: a worthwhile, tractable endeavor.

PubMed

Reed, Sasha C; Yang, Xiaojuan; Thornton, Peter E

2015-10-01

324 I. 324 II. 325 III. 326 IV. 327 328 References 328 SUMMARY: Myriad field, laboratory, and modeling studies show that nutrient availability plays a fundamental role in regulating CO2 exchange between the Earth's biosphere and atmosphere, and in determining how carbon pools and fluxes respond to climatic change. Accordingly, global models that incorporate coupled climate-carbon cycle feedbacks made a significant advance with the introduction of a prognostic nitrogen cycle. Here we propose that incorporating phosphorus cycling represents an important next step in coupled climate-carbon cycling model development, particularly for lowland tropical forests where phosphorus availability is often presumed to limit primary production. We highlight challenges to including phosphorus in modeling efforts and provide suggestions for how to move forward. No claim to original US government works New Phytologist © 2015 New Phytologist Trust.

Optimization of nitrogen and phosphorus limitation for better biodegradable plastic production and organic removal using single fed-batch mixed cultures and renewable resources.

PubMed

Din, M F M; Ujang, Z; van Loosdrecht, M C M; Ahmad, A; Sairan, M F

2006-01-01

The process for the production of biodegradable plastic material (polyhydroxyalkanoates, PHAs) from microbial cells by mixed-bacterial cultivation using readily available waste (renewable resources) is the main consideration nowadays. These observations have shown impressive results typically under high carbon fraction, COD/N and COD/P (usually described as nutrient-limiting conditions) and warmest temperature (moderate condition). Therefore, the aim of this work is predominantly to select mixed cultures under high storage responded by cultivation on a substrate - non limited in a single batch reactor with shortest period for feeding and to characterize their storage response by using specific and kinetics determination. In that case, the selected-fixed temperature is 30 degrees C to establish tropical conditions. During the accumulated steady-state period, the cell growth was inhibited by high PHA content within the cells because of the carbon reserve consumption. From the experiments, there is no doubt about the PHA accumulation even at high carbon fraction ratio. Apparently, the best accumulation occurred at carbon fraction, 160 +/- 7.97 g COD/g N (PHAmean, = 44.54% of dried cells). Unfortunately, the highest PHA productivity was achieved at the high carbon fraction, 560 +/- 1.62 g COD/g N (0.152 +/- 0.17 g/l. min). Overall results showed that with high carbon fraction induced to the cultivation, the PO4 and NO3 can remove up to 20% in single cultivation.

Expert assessment concludes negative emissions scenarios may not deliver

NASA Astrophysics Data System (ADS)

Vaughan, Naomi E.; Gough, Clair

2016-09-01

Many integrated assessment models (IAMs) rely on the availability and extensive use of biomass energy with carbon capture and storage (BECCS) to deliver emissions scenarios consistent with limiting climate change to below 2 °C average temperature rise. BECCS has the potential to remove carbon dioxide (CO2) from the atmosphere, delivering ‘negative emissions’. The deployment of BECCS at the scale assumed in IAM scenarios is highly uncertain: biomass energy is commonly used but not at such a scale, and CCS technologies have been demonstrated but not commercially established. Here we present the results of an expert elicitation process that explores the explicit and implicit assumptions underpinning the feasibility of BECCS in IAM scenarios. Our results show that the assumptions are considered realistic regarding technical aspects of CCS but unrealistic regarding the extent of bioenergy deployment, and development of adequate societal support and governance structures for BECCS. The results highlight concerns about the assumed magnitude of carbon dioxide removal achieved across a full BECCS supply chain, with the greatest uncertainty in bioenergy production. Unrealistically optimistic assumptions regarding the future availability of BECCS in IAM scenarios could lead to the overshoot of critical warming limits and have significant impacts on near-term mitigation options.

Diurnal variation in the coupling of photosynthetic electron transport and carbon fixation in iron-limited phytoplankton in the NE subarctic Pacific

NASA Astrophysics Data System (ADS)

Schuback, N.; Flecken, M.; Maldonado, M. T.; Tortell, P. D.

2015-10-01

Active chlorophyll a fluorescence approaches, including fast repetition rate fluorometry (FRRF), have the potential to provide estimates of phytoplankton primary productivity at unprecedented spatial and temporal resolution. FRRF-derived productivity rates are based on estimates of charge separation at PSII (ETRRCII), which must be converted into ecologically relevant units of carbon fixation. Understanding sources of variability in the coupling of ETRRCII and carbon fixation provides physiological insight into phytoplankton photosynthesis, and is critical for the application of FRRF as a primary productivity measurement tool. In the present study, we simultaneously measured phytoplankton carbon fixation and ETRRCII in the iron-limited NE subarctic Pacific, over the course of a diurnal cycle. We show that rates of ETRRCII are closely tied to the diurnal cycle in light availability, whereas rates of carbon fixation appear to be influenced by endogenous changes in metabolic energy allocation under iron-limited conditions. Unsynchronized diurnal oscillations of the two rates led to 3.5 fold changes in the conversion factor coupling ETRRCII and carbon fixation (Φe:C / nPSII). Consequently, diurnal variability in phytoplankton carbon fixation cannot be adequately captured with FRRF approaches if a constant conversion factor is applied. Utilizing several auxiliary photophysiological measurements, we observed that a high conversion factor is associated with conditions of excess light, and correlates with the expression of non-photochemical quenching (NPQ) in the pigment antenna, as derived from FRRF measurements. The observed correlation between NPQ and the conversion factor Φe:C / nPSII has the potential to improve estimates of phytoplankton carbon fixation rates from FRRF measurements alone.

Diurnal variation in the coupling of photosynthetic electron transport and carbon fixation in iron-limited phytoplankton in the NE subarctic Pacific

NASA Astrophysics Data System (ADS)

Schuback, Nina; Flecken, Mirkko; Maldonado, Maria T.; Tortell, Philippe D.

2016-02-01

Active chlorophyll a fluorescence approaches, including fast repetition rate fluorometry (FRRF), have the potential to provide estimates of phytoplankton primary productivity at an unprecedented spatial and temporal resolution. FRRF-derived productivity rates are based on estimates of charge separation in reaction center II (ETRRCII), which must be converted into ecologically relevant units of carbon fixation. Understanding sources of variability in the coupling of ETRRCII and carbon fixation provides physiological insight into phytoplankton photosynthesis and is critical for the application of FRRF as a primary productivity measurement tool. In the present study, we simultaneously measured phytoplankton carbon fixation and ETRRCII in the iron-limited NE subarctic Pacific over the course of a diurnal cycle. We show that rates of ETRRCII are closely tied to the diurnal cycle in light availability, whereas rates of carbon fixation appear to be influenced by endogenous changes in metabolic energy allocation under iron-limited conditions. Unsynchronized diurnal oscillations of the two rates led to 3.5-fold changes in the conversion factor between ETRRCII and carbon fixation (Kc / nPSII). Consequently, diurnal variability in phytoplankton carbon fixation cannot be adequately captured with FRRF approaches if a constant conversion factor is applied. Utilizing several auxiliary photophysiological measurements, we observed that a high conversion factor is associated with conditions of excess light and correlates with the increased expression of non-photochemical quenching (NPQ) in the pigment antenna, as derived from FRRF measurements. The observed correlation between NPQ and Kc / nPSII requires further validation but has the potential to improve estimates of phytoplankton carbon fixation rates from FRRF measurements alone.

21 CFR 177.2400 - Perfluorocarbon cured elastomers.

Code of Federal Regulations, 2014 CFR

2014-04-01

... as are provided: Substances Limitations Carbon black (channel process of furnace combustion process... Park, MD 20740, or available for inspection at the National Archives and Records Administration (NARA....archives.gov/federal_register/code_of_federal_regulations/ibr_locations.html. (2) Thermogravimetry...

Carbon Pools in a Temperate Heathland Resist Changes in a Future Climate

NASA Astrophysics Data System (ADS)

Ambus, P.; Reinsch, S.; Nielsen, P. L.; Michelsen, A.; Schmidt, I. K.; Mikkelsen, T. N.

2014-12-01

The fate of recently plant assimilated carbon was followed into ecosystem carbon pools and fluxes in a temperate heathland after a 13CO2 pulse in the early growing season in a 6-year long multi-factorial climate change experiment. Eight days after the pulse, recently assimilated carbon was significantly higher in storage organs (rhizomes) of the grass Deschampsia flexuosa under elevated atmospheric CO2 concentration. Experimental drought induced a pronounced utilization of recently assimilated carbon belowground (roots, microbes, dissolved organic carbon) potentially counterbalancing limited nutrient availability. The fate of recently assimilated carbon was not affected by moderate warming. The full factorial combination of elevated CO2, warming and drought simulating future climatic conditions as expected for Denmark in 2075 did not change short-term carbon turnover significantly compared to ambient conditions. Overall, climate factors interacted in an unexpected way resulting in strong resilience of the heathland in terms of short-term carbon turnover in a future climate.

Habitat, not resource availability, limits consumer production in lake ecosystems

USGS Publications Warehouse

Craig, Nicola; Jones, Stuart E.; Weidel, Brian C.; Solomon, Christopher T.

2015-01-01

Food web productivity in lakes can be limited by dissolved organic carbon (DOC), which reduces fish production by limiting the abundance of their zoobenthic prey. We demonstrate that in a set of 10 small, north temperate lakes spanning a wide DOC gradient, these negative effects of high DOC concentrations on zoobenthos production are driven primarily by availability of warm, well-oxygenated habitat, rather than by light limitation of benthic primary production as previously proposed. There was no significant effect of benthic primary production on zoobenthos production after controlling for oxygen, even though stable isotope analysis indicated that zoobenthos do use this resource. Mean whole-lake zoobenthos production was lower in high-DOC lakes with reduced availability of oxygenated habitat, as was fish biomass. These insights improve understanding of lake food webs and inform management in the face of spatial variability and ongoing temporal change in lake DOC concentrations.

Performance Characterization of Polyimide-Carbon Fiber Composites for Future Hypersonic Vehicles

DTIC Science & Technology

2010-08-01

already being processed for leading edge primary structures and engine components for present and future stealth aircraft. In addition to describing our...The form of entry is the last name, first name, middle initial, and additional qualifiers separated by commas, e.g. Smith, Richard, Jr. 7...availability or distribution limitations of the report. If additional limitations/restrictions or special markings are indicated, follow agency

Energetic Limitations on Microbial Respiration of Organic Compounds using Aqueous Fe(III) Complexes

NASA Astrophysics Data System (ADS)

Naughton, H.; Fendorf, S. E.

2015-12-01

Soil organic matter constitutes up to 75% of the terrestrial carbon stock. Microorganisms mediate the breakdown of organic compounds and the return of carbon to the atmosphere, predominantly through respiration. Microbial respiration requires an electron acceptor and an electron donor such as small fatty acids, organic acids, alcohols, sugars, and other molecules that differ in oxidation state of carbon. Carbon redox state affects how much energy is required to oxidize a molecule through respiration. Therefore, different organic compounds should offer a spectrum of energies to respiring microorganisms. However, microbial respiration has traditionally focused on the availability and reduction potential of electron acceptors, ignoring the organic electron donor. We found through incubation experiments that the organic compound serving as electron donor determined how rapidly Shewanella putrefaciens CN32 respires organic substrate and the extent of reduction of the electron acceptor. We simulated a range of energetically favorable to unfavorable electron acceptors using organic chelators bound to Fe(III) with equilibrium stability constants ranging from log(K) of 11.5 to 25.0 for the 1:1 complex, where more stable complexes are less favorable for microbial respiration. Organic substrates varied in nominal oxidation state of carbon from +2 to -2. The most energetically favorable substrate, lactate, promoted up to 30x more rapid increase in percent Fe(II) compared to less favorable substrates such as formate. This increased respiration on lactate was more substantial with less stable Fe(III)-chelate complexes. Intriguingly, this pattern contradicts respiration rate predicted by nominal oxidation state of carbon. Our results suggest that organic substrates will be consumed so long as the energetic toll corresponding to the electron donor half reaction is counterbalanced by the energy available from the electron accepting half reaction. We propose using the chemical structure of organic matter, elucidated with techniques such as FT-ICR MS, to improve microbial decomposition and carbon cycling models by incorporating energetic limitations due to carbon oxidation.

A limited role for carbonic anhydrase in C 4 photosynthesis as revealed by a ca1ca2 double mutant in maize.

DOE PAGES

Studer, Anthony J.; Gandin, Anthony; Kolbe, Allison R.; ...

2014-04-04

Carbonic anhydrase (CA) catalyzes the first biochemical step of the carbon concentrating mechanism of C 4 plants, and in C 4 monocots, it has been suggested that CA activity is near limiting for photosynthesis. Here, we test this hypothesis through the characterization of transposon induced mutant alleles of Ca1 and Ca2 in Zea mays. In addition, these two isoforms account for more than 85% of the CA transcript pool. A significant change in isotopic discrimination is observed in mutant plants, which have as little as 3% of wild-type CA activity, but surprisingly, photosynthesis is not reduced under current or elevatedmore » pCO 2. However, growth and rates of photosynthesis under sub-ambient pCO 2 are significantly impaired in the mutants. These findings suggest, that while CA is not limiting for C 4 photosynthesis in Z. mays at current pCO 2, it likely maintains high rates of photosynthesis when CO 2 availability is reduced. Current atmospheric CO 2 levels now exceed 400 ppm (~40.53 Pa) and contrast the low CO 2 partial pressure (pCO 2) conditions under which C 4 plants expanded their range ~10 million years ago when the global atmospheric CO 2 was below 300 ppm (~30.40 Pa). Thus, as CO 2 levels continue to rise, selective pressures for high levels of CA may be limited to arid climates where stomatal closure reduces CO 2 availability to the leaf.« less

Does energy availability predict gastropod reproductive strategies?

PubMed Central

McClain, Craig R.; Filler, Ryan; Auld, Josh R.

2014-01-01

The diversity of reproductive strategies in nature is shaped by a plethora of factors including energy availability. For example, both low temperatures and limited food availability could increase larval exposure to predation by slowing development, selecting against pelagic and/or feeding larvae. The frequency of hermaphroditism could increase under low food availability as population density (and hence mate availability) decreases. We examine the relationship between reproductive/life-history traits and energy availability for 189 marine gastropod families. Only larval type was related to energy availability with the odds of having planktotrophic larvae versus direct development decreasing by 1% with every one-unit increase in the square root of carbon flux. Simultaneous hermaphroditism also potentially increases with carbon flux, but this effect disappears when accounting for evolutionary relationships among taxa. Our findings are in contrast to some theory and empirical work demonstrating that hermaphroditism should increase and planktotrophic development should decrease with decreasing productivity. Instead, they suggest that some reproductive strategies are too energetically expensive at low food availabilities, or arise only when energy is available, and others serve to capitalize on opportunities for aggregation or increased energy availability. PMID:25009058

Transient simulations of historical climate change including interactive carbon emissions from land-use change.

NASA Astrophysics Data System (ADS)

Matveev, A.; Matthews, H. D.

2009-04-01

Carbon fluxes from land conversion are among the most uncertain variables in our understanding of the contemporary carbon cycle, which limits our ability to estimate both the total human contribution to current climate forcing and the net effect of terrestrial biosphere changes on atmospheric CO2 increases. The current generation of coupled climate-carbon models have made significant progress in simulating the coupled climate and carbon cycle response to anthropogenic CO2 emissions, but do not typically include land-use change as a dynamic component of the simulation. In this work we have incorporated a book-keeping land-use carbon accounting model into the University of Victoria Earth System Climate Model (UVic ESCM), and intermediate-complexity coupled climate-carbon model. The terrestrial component of the UVic ESCM allows an aerial competition of five plant functional types (PFTs) in response to climatic conditions and area availability, and tracks the associated changes in affected carbon pools. In order to model CO2 emissions from land conversion in the terrestrial component of the model, we calculate the allocation of carbon to short and long-lived wood products following specified land-cover change, and use varying decay timescales to estimate CO2 emissions. We use recently available spatial datasets of both crop and pasture distributions to drive a series of transient simulations and estimate the net contribution of human land-use change to historical carbon emissions and climate change.

Manganese, Iron, and sulfur cycling in Louisiana continental shelf sediments

EPA Science Inventory

Sulfate reduction is considered the primary pathway for organic carbon remineralization on the northern Gulf of Mexico Louisiana continental shelf (LCS) where bottom waters are seasonally hypoxic, yet limited information is available on the importance of iron and manganese cyclin...

Impact of seawater carbonate chemistry on the calcification of marine bivalves

NASA Astrophysics Data System (ADS)

Thomsen, J.; Haynert, K.; Wegner, K. M.; Melzner, F.

2015-07-01

Bivalve calcification, particularly of the early larval stages, is highly sensitive to the change in ocean carbonate chemistry resulting from atmospheric CO2 uptake. Earlier studies suggested that declining seawater [CO32-] and thereby lowered carbonate saturation affect shell production. However, disturbances of physiological processes such as acid-base regulation by adverse seawater pCO2 and pH can affect calcification in a secondary fashion. In order to determine the exact carbonate system component by which growth and calcification are affected it is necessary to utilize more complex carbonate chemistry manipulations. As single factors, pCO2 had no effects and [HCO3-] and pH had only limited effects on shell growth, while lowered [CO32-] strongly impacted calcification. Dissolved inorganic carbon (CT) limiting conditions led to strong reductions in calcification, despite high [CO32-], indicating that [HCO3-] rather than [CO32-] is the inorganic carbon source utilized for calcification by mytilid mussels. However, as the ratio [HCO3-] / [H+] is linearly correlated with [CO32-] it is not possible to differentiate between these under natural seawater conditions. An equivalent of about 80 μmol kg-1 [CO32-] is required to saturate inorganic carbon supply for calcification in bivalves. Below this threshold biomineralization rates rapidly decline. A comparison of literature data available for larvae and juvenile mussels and oysters originating from habitats differing substantially with respect to prevailing carbonate chemistry conditions revealed similar response curves. This suggests that the mechanisms which determine sensitivity of calcification in this group are highly conserved. The higher sensitivity of larval calcification seems to primarily result from the much higher relative calcification rates in early life stages. In order to reveal and understand the mechanisms that limit or facilitate adaptation to future ocean acidification, it is necessary to better understand the physiological processes and their underlying genetics that govern inorganic carbon assimilation for calcification.

Limitation of egg production in Calanus finmarchicus in the field: A stoichiometric analysis

NASA Astrophysics Data System (ADS)

Mayor, Daniel J.; Anderson, Thomas R.; Pond, David W.; Irigoien, Xabier

2009-11-01

The egg production of marine copepods correlates with a range of variables, including the availability of organic carbon (C), nitrogen (N) and the polyunsaturated fatty acids (PUFAs) 20:5( n-3) (EPA) and 22:6( n-3) (DHA). However, an understanding of which substrates limit egg production in the natural environment has yet to be reached. The quantities of C, N, EPA and DHA ingested, derived from parental biomass, and invested in eggs by female Calanus finmarchicus during a 5-day incubation experiment were examined using stoichiometric theory to determine which substrate was limiting. The majority of each substrate was derived from parental biomass, and therefore the existing stoichiometric theory is developed to include this route of supply. The females were essentially devoid of lipid reserves, as evidenced by the lack of the storage fatty acids 20:1( n-9) and 22:1( n-11), and carbon limitation was predicted under most of the scenarios examined. Nitrogen limitation was only apparent when carbon and nitrogen utilisation efficiencies were assumed to be high (0.5) and low (0.4) respectively. PUFAs were assumed to be utilised with high efficiency (0.9), and were never predicted to limit production. This work highlights the need for a more detailed understanding of the maintenance requirements that marine copepods have for C, N, EPA, and DHA and hence the efficiencies with these substrates can be utilised for growth.

Photoredox activation of carbon dioxide for amino acid synthesis in continuous flow

NASA Astrophysics Data System (ADS)

Seo, Hyowon; Katcher, Matthew H.; Jamison, Timothy F.

2017-05-01

Although carbon dioxide (CO2) is highly abundant, its low reactivity has limited its use in chemical synthesis. In particular, methods for carbon-carbon bond formation generally rely on two-electron mechanisms for CO2 activation and require highly activated reaction partners. Alternatively, radical pathways accessed via photoredox catalysis could provide new reactivity under milder conditions. Here we demonstrate the direct coupling of CO2 and amines via the single-electron reduction of CO2 for the photoredox-catalysed continuous flow synthesis of α-amino acids. By leveraging the advantages of utilizing gases and photochemistry in flow, a commercially available organic photoredox catalyst effects the selective α-carboxylation of amines that bear various functional groups and heterocycles. The preliminary mechanistic studies support CO2 activation and carbon-carbon bond formation via single-electron pathways, and we expect that this strategy will inspire new perspectives on using this feedstock chemical in organic synthesis.

VizieR Online Data Catalog: Carbon-enhanced metal-poor (CEMP) star abundances (Yoon+, 2016)

NASA Astrophysics Data System (ADS)

Yoon, J.; Beers, T. C.; Placco, V. M.; Rasmussen, K. C.; Carollo, D.; He, S.; Hansen, T. T.; Roederer, I. U.; Zeanah, J.

2017-03-01

We have endeavored to compile a list that is as complete as possible of carbon-enhanced metal-poor (CEMP); CEMP-s (and CEMP-r/s) and CEMP-no stars having [Fe/H]<-1.0 and [C/Fe]>=+0.7 with available high-resolution spectroscopic abundance information. We have only considered stars with claimed detections or lower limits for carbon, along with several critical elemental-abundance ratios, such as [Ba/Fe] and [Eu/Fe]. The great majority of our sample comes from the literature compilation of Placco+ (2014, J/ApJ/797/21). See section 2 for further details. (2 data files).

Constraint-Based Modeling Highlights Cell Energy, Redox Status and α-Ketoglutarate Availability as Metabolic Drivers for Anthocyanin Accumulation in Grape Cells Under Nitrogen Limitation

PubMed Central

Soubeyrand, Eric; Colombié, Sophie; Beauvoit, Bertrand; Dai, Zhanwu; Cluzet, Stéphanie; Hilbert, Ghislaine; Renaud, Christel; Maneta-Peyret, Lilly; Dieuaide-Noubhani, Martine; Mérillon, Jean-Michel; Gibon, Yves; Delrot, Serge; Gomès, Eric

2018-01-01

Anthocyanin biosynthesis is regulated by environmental factors (such as light, temperature, and water availability) and nutrient status (such as carbon, nitrogen, and phosphate nutrition). Previous reports show that low nitrogen availability strongly enhances anthocyanin accumulation in non carbon-limited plant organs or cell suspensions. It has been hypothesized that high carbon-to-nitrogen ratio would lead to an energy excess in plant cells, and that an increase in flavonoid pathway metabolic fluxes would act as an “energy escape valve,” helping plant cells to cope with energy and carbon excess. However, this hypothesis has never been tested directly. To this end, we used the grapevine Vitis vinifera L. cultivar Gamay Teinturier (syn. Gamay Freaux or Freaux Tintorier, VIVC #4382) cell suspension line as a model system to study the regulation of anthocyanin accumulation in response to nitrogen supply. The cells were sub-cultured in the presence of either control (25 mM) or low (5 mM) nitrate concentration. Targeted metabolomics and enzyme activity determinations were used to parametrize a constraint-based model describing both the central carbon and nitrogen metabolisms and the flavonoid (phenylpropanoid) pathway connected by the energy (ATP) and reducing power equivalents (NADPH and NADH) cofactors. The flux analysis (2 flux maps generated, for control and low nitrogen in culture medium) clearly showed that in low nitrogen-fed cells all the metabolic fluxes of central metabolism were decreased, whereas fluxes that consume energy and reducing power, were either increased (upper part of glycolysis, shikimate, and flavonoid pathway) or maintained (pentose phosphate pathway). Also, fluxes of flavanone 3β-hydroxylase, flavonol synthase, and anthocyanidin synthase were strongly increased, advocating for a regulation of the flavonoid pathway by alpha-ketoglutarate levels. These results strongly support the hypothesis of anthocyanin biosynthesis acting as an energy escape valve in plant cells, and they open new possibilities to manipulate flavonoid production in plant cells. They do not, however, support a role of anthocyanins as an effective mechanism for coping with carbon excess in high carbon to nitrogen ratio situations in grape cells. Instead, constraint-based modeling output and biomass analysis indicate that carbon excess is dealt with by vacuolar storage of soluble sugars. PMID:29868039

Constraint-Based Modeling Highlights Cell Energy, Redox Status and α-Ketoglutarate Availability as Metabolic Drivers for Anthocyanin Accumulation in Grape Cells Under Nitrogen Limitation.

PubMed

Soubeyrand, Eric; Colombié, Sophie; Beauvoit, Bertrand; Dai, Zhanwu; Cluzet, Stéphanie; Hilbert, Ghislaine; Renaud, Christel; Maneta-Peyret, Lilly; Dieuaide-Noubhani, Martine; Mérillon, Jean-Michel; Gibon, Yves; Delrot, Serge; Gomès, Eric

2018-01-01

Anthocyanin biosynthesis is regulated by environmental factors (such as light, temperature, and water availability) and nutrient status (such as carbon, nitrogen, and phosphate nutrition). Previous reports show that low nitrogen availability strongly enhances anthocyanin accumulation in non carbon-limited plant organs or cell suspensions. It has been hypothesized that high carbon-to-nitrogen ratio would lead to an energy excess in plant cells, and that an increase in flavonoid pathway metabolic fluxes would act as an "energy escape valve," helping plant cells to cope with energy and carbon excess. However, this hypothesis has never been tested directly. To this end, we used the grapevine Vitis vinifera L. cultivar Gamay Teinturier (syn. Gamay Freaux or Freaux Tintorier, VIVC #4382) cell suspension line as a model system to study the regulation of anthocyanin accumulation in response to nitrogen supply. The cells were sub-cultured in the presence of either control (25 mM) or low (5 mM) nitrate concentration. Targeted metabolomics and enzyme activity determinations were used to parametrize a constraint-based model describing both the central carbon and nitrogen metabolisms and the flavonoid (phenylpropanoid) pathway connected by the energy (ATP) and reducing power equivalents (NADPH and NADH) cofactors. The flux analysis (2 flux maps generated, for control and low nitrogen in culture medium) clearly showed that in low nitrogen-fed cells all the metabolic fluxes of central metabolism were decreased, whereas fluxes that consume energy and reducing power, were either increased (upper part of glycolysis, shikimate, and flavonoid pathway) or maintained (pentose phosphate pathway). Also, fluxes of flavanone 3β-hydroxylase, flavonol synthase, and anthocyanidin synthase were strongly increased, advocating for a regulation of the flavonoid pathway by alpha-ketoglutarate levels. These results strongly support the hypothesis of anthocyanin biosynthesis acting as an energy escape valve in plant cells, and they open new possibilities to manipulate flavonoid production in plant cells. They do not, however, support a role of anthocyanins as an effective mechanism for coping with carbon excess in high carbon to nitrogen ratio situations in grape cells. Instead, constraint-based modeling output and biomass analysis indicate that carbon excess is dealt with by vacuolar storage of soluble sugars.

Influence of iron availability on nutrient consumption ratio of diatoms in oceanic waters

NASA Astrophysics Data System (ADS)

Takeda, Shigenobu

1998-06-01

The major nutrients (nitrate, phosphate and silicate) needed for phytoplankton growth are abundant in the surface waters of the subarctic Pacific, equatorial Pacific and Southern oceans, but this growth is limited by the availability of iron. Under iron-deficient conditions, phytoplankton exhibit reduced uptake of nitrate and lower cellular levels of carbon, nitrogen and phosphorus. Here I describe seawater and culture experiments which show that iron limitation can also affect the ratio of consumed silicate to nitrate and phosphate. In iron-limited waters from all three of the aforementioned environments, addition of iron to phytoplankton assemblages in incubation bottles halved the silicate:nitrate and silicate:phosphate consumption ratios, in spite of the preferential growth of diatoms (silica-shelled phytoplankton). The nutrient consumption ratios of the phytoplankton assemblage from the Southern Ocean were similar to those of an iron-deficient laboratory culture of Antarctic diatoms, which exhibit increased cellular silicon or decreased cellular nitrogen and phosphorus in response to iron limitation. Iron limitation therefore increases the export of biogenic silicon, relative to nitrogen and phosphorus, from the surface to deeper waters. These findings suggest how the sedimentary records of carbon and silicon deposition in the glacial Southern Ocean can be consistent with the idea that changes in productivity, and thus in drawdown of atmospheric CO2, during the last glaciation were stimulated by changes in iron inputs from atmospheric dust.

Managing Carbon on Federal Public Lands: Opportunities and Challenges in Southwestern Colorado.

PubMed

Dilling, Lisa; Kelsey, Katharine C; Fernandez, Daniel P; Huang, Yin D; Milford, Jana B; Neff, Jason C

2016-08-01

Federal lands in the United States have been identified as important areas where forests could be managed to enhance carbon storage and help mitigate climate change. However, there has been little work examining the context for decision making for carbon in a multiple-use public land environment, and how science can support decision making. This case study of the San Juan National Forest and the Bureau of Land Management Tres Rios Field Office in southwestern Colorado examines whether land managers in these offices have adequate tools, information, and management flexibility to practice effective carbon stewardship. To understand how carbon was distributed on the management landscape we added a newly developed carbon map for the SJNF-TRFO area based on Landsat TM texture information (Kelsey and Neff in Remote Sens 6:6407-6422. doi: 10.3390/rs6076407 , 2014). We estimate that only about 22 % of the aboveground carbon in the SJNF-TRFO is in areas designated for active management, whereas about 38 % is in areas with limited management opportunities, and 29 % is in areas where natural processes should dominate. To project the effects of forest management actions on carbon storage, staff of the SJNF are expected to use the Forest Vegetation Simulator (FVS) and extensions. While identifying FVS as the best tool generally available for this purpose, the users and developers we interviewed highlighted the limitations of applying an empirically based model over long time horizons. Future research to improve information on carbon storage should focus on locations and types of vegetation where carbon management is feasible and aligns with other management priorities.

Managing Carbon on Federal Public Lands: Opportunities and Challenges in Southwestern Colorado

NASA Astrophysics Data System (ADS)

Dilling, Lisa; Kelsey, Katharine C.; Fernandez, Daniel P.; Huang, Yin D.; Milford, Jana B.; Neff, Jason C.

2016-08-01

Federal lands in the United States have been identified as important areas where forests could be managed to enhance carbon storage and help mitigate climate change. However, there has been little work examining the context for decision making for carbon in a multiple-use public land environment, and how science can support decision making. This case study of the San Juan National Forest and the Bureau of Land Management Tres Rios Field Office in southwestern Colorado examines whether land managers in these offices have adequate tools, information, and management flexibility to practice effective carbon stewardship. To understand how carbon was distributed on the management landscape we added a newly developed carbon map for the SJNF-TRFO area based on Landsat TM texture information (Kelsey and Neff in Remote Sens 6:6407-6422. doi: 10.3390/rs6076407, 2014). We estimate that only about 22 % of the aboveground carbon in the SJNF-TRFO is in areas designated for active management, whereas about 38 % is in areas with limited management opportunities, and 29 % is in areas where natural processes should dominate. To project the effects of forest management actions on carbon storage, staff of the SJNF are expected to use the Forest Vegetation Simulator (FVS) and extensions. While identifying FVS as the best tool generally available for this purpose, the users and developers we interviewed highlighted the limitations of applying an empirically based model over long time horizons. Future research to improve information on carbon storage should focus on locations and types of vegetation where carbon management is feasible and aligns with other management priorities.

Aligned carbon nanotube, graphene and graphite oxide thin films via substrate-directed rapid interfacial deposition

NASA Astrophysics Data System (ADS)

D'Arcy, Julio M.; Tran, Henry D.; Stieg, Adam Z.; Gimzewski, James K.; Kaner, Richard B.

2012-05-01

A procedure for depositing thin films of carbon nanostructures is described that overcomes the limitations typically associated with solution based methods. Transparent and conductively continuous carbon coatings can be grown on virtually any type of substrate within seconds. Interfacial surface tension gradients result in directional fluid flow and film spreading at the water/oil interface. Transparent films of carbon nanostructures are produced including aligned ropes of single-walled carbon nanotubes and assemblies of single sheets of chemically converted graphene and graphite oxide. Process scale-up, layer-by-layer deposition, and a simple method for coating non-activated hydrophobic surfaces are demonstrated.A procedure for depositing thin films of carbon nanostructures is described that overcomes the limitations typically associated with solution based methods. Transparent and conductively continuous carbon coatings can be grown on virtually any type of substrate within seconds. Interfacial surface tension gradients result in directional fluid flow and film spreading at the water/oil interface. Transparent films of carbon nanostructures are produced including aligned ropes of single-walled carbon nanotubes and assemblies of single sheets of chemically converted graphene and graphite oxide. Process scale-up, layer-by-layer deposition, and a simple method for coating non-activated hydrophobic surfaces are demonstrated. Electronic supplementary information (ESI) available: Droplet coalescence, catenoid formation, mechanism of film growth, scanning electron micrographs showing carbon nanotube alignment, flexible transparent films of SWCNTs, AFM images of a chemically converted graphene film, and SEM images of SWCNT free-standing thin films. See DOI: 10.1039/c2nr00010e

40 CFR 52.672 - Approval of plans.

Code of Federal Regulations, 2014 CFR

2014-07-01

....672 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR PROGRAMS (CONTINUED... County Air Quality Maintenance Area Second 10-year Carbon Monoxide Limited Maintenance Plan submitted by... meeting the requirements of Clean Air Act section 169A and 40 CFR 51.308(e) regarding Best Available...

Using N-Limiting Growth Conditions to Remove Atrazine from Groundwater: Laboratory Studies.

USDA-ARS?s Scientific Manuscript database

Typically, respiratory redox reactions are the driving mechanism behind in situ bioremediations that use a carbon substrate. This is because electron (e-) donor availability generally restricts subsurface microbial activity. Thus, microbial growth and respiration can be greatly stimulated by the a...

Availability of phosphate for phytoplankton and bacteria and of labile organic carbon for bacteria at different pCO2 levels in a mesocosm study

NASA Astrophysics Data System (ADS)

Tanaka, T.; Thingstad, T. F.; Løvdal, T.; Grossart, H.-P.; Larsen, A.; Schulz, K. G.; Riebesell, U.

2007-11-01

Availability of phosphate for phytoplankton and bacteria and of labile organic carbon for bacteria at different pCO2 levels were studied in a mesocosm experiment (PeECE III). Using nutrient-depleted SW Norwegian fjord waters, three different levels of pCO2 (350 μatm: 1×CO2; 750 μatm: 2×CO2; 1050 μatm: 3×CO2) were set up, and nitrate and phosphate were added at the start of the experiment in order to induce a phytoplankton bloom. Despite similar responses of total particulate P concentration and phosphate turnover time at the three different pCO2 levels, the size distribution of particulate P and 33PO4 uptake suggested that phosphate transferred to the >10 μm fraction was greater in the 3×CO2 mesocosm during the first 6-10 days when phosphate concentration was high. During the period of phosphate depletion (after Day 12), specific phosphate affinity and specific alkaline phosphatase activity (APA) suggested a P-deficiency (i.e. suboptimal phosphate supply) but not a P-limitation for the phytoplankton and bacterial community at the three different pCO2 levels. Although specific phosphate affinity and specific APA tended to be higher in 3×CO2 than in 2×CO2 and 1×CO2 mesocosms during the phosphate depletion period, no statistical differences were found. Responses of specific glucose affinity for bacteria were similar at the three different pCO2 levels. Measured specific glucose affinities were consistently much lower than the theoretical maximum predicted from the diffusion-limited model, suggesting that bacterial growth was not limited by the availability of labile dissolved organic carbon. These results suggest that availability of phosphate and glucose was similar at the three different pCO2 levels.

Soil Microbial Properties and Plant Growth Responses to Carbon and Water Addition in a Temperate Steppe: The Importance of Nutrient Availability

PubMed Central

Guo, Chengyuan; Wang, Renzhong; Xiao, Chunwang

2012-01-01

Background Global climatic change is generally expected to stimulate net primary production, and consequently increase soil carbon (C) input. The enhanced C input together with potentially increased precipitation may affect soil microbial processes and plant growth. Methodology/Principal Findings To examine the effects of C and water additions on soil microbial properties and plant growth, we conducted an experiment lasting two years in a temperate steppe of northeastern China. We found that soil C and water additions significantly affected microbial properties and stimulated plant growth. Carbon addition significantly increased soil microbial biomass and activity but had a limited effect on microbial community structure. Water addition significantly increased soil microbial activity in the first year but the response to water decreased in the second year. The water-induced changes of microbial activity could be ascribed to decreased soil nitrogen (N) availability and to the shift in soil microbial community structure. However, no water effect on soil microbial activity was visible under C addition during the two years, likely because C addition alleviated nutrient limitation of soil microbes. In addition, C and water additions interacted to affect plant functional group composition. Water addition significantly increased the ratio of grass to forb biomass in C addition plots but showed only minor effects under ambient C levels. Our results suggest that soil microbial activity and plant growth are limited by nutrient (C and N) and water availability, and highlight the importance of nutrient availability in modulating the responses of soil microbes and plants to potentially increased precipitation in the temperate steppe. Conclusions/Significance Increased soil C input and precipitation would show significant effects on soil microbial properties and plant growth in the temperate steppe. These findings will improve our understanding of the responses of soil microbes and plants to the indirect and direct climate change effects. PMID:22496905

Nitrogen-Related Constraints of Carbon Uptake by Large-Scale Forest Expansion: Simulation Study for Climate Change and Management Scenarios

NASA Astrophysics Data System (ADS)

Kracher, Daniela

2017-11-01

Increase of forest areas has the potential to increase the terrestrial carbon (C) sink. However, the efficiency for C sequestration depends on the availability of nutrients such as nitrogen (N), which is affected by climatic conditions and management practices. In this study, I analyze how N limitation affects C sequestration of afforestation and how it is influenced by individual climate variables, increased harvest, and fertilizer application. To this end, JSBACH, the land component of the Earth system model of the Max Planck Institute for Meteorology is applied in idealized simulation experiments. In those simulations, large-scale afforestation increases the terrestrial C sink in the 21st century by around 100 Pg C compared to a business as usual land-use scenario. N limitation reduces C sequestration roughly by the same amount. The relevance of compensating effects of uptake and release of carbon dioxide by plant productivity and soil decomposition, respectively, gets obvious from the simulations. N limitation of both fluxes compensates particularly in the tropics. Increased mineralization under global warming triggers forest expansion, which otherwise is restricted by N availability. Due to compensating higher plant productivity and soil respiration, the global net effect of warming for C sequestration is however rather small. Fertilizer application and increased harvest enhance C sequestration as well as boreal expansion. The additional C sequestration achieved by fertilizer application is offset to a large part by additional emissions of nitrous oxide.

Interactions between cold and water limitation along a climate gradient produce sharp thresholds in ecosystem type, carbon balance, and water cycling

NASA Astrophysics Data System (ADS)

Kelly, A. E.; Goulden, M.; Fellows, A. W.

2013-12-01

California's Mediterranean climate supports a broad diversity of ecosystem types, including Sequoia forests in the mid-montane Sierra Nevada. Understanding how winter cold and summer drought interact to produce the lush forest in the Sierra is critical to predicting the impacts of projected climate change on California's ecosystems, water supply, and carbon cycling. We investigated how smooth gradients of temperature and water availability produced sharp thresholds in biomass, productivity, growing season, water use, and ultimately ecosystem type and function. We used the climate gradient of the western slope of the Sierra Nevada as a study system. Four eddy covariance towers were situated in the major ecosystem types of the Sierra Nevada at approximately 800-m elevation intervals. Eddy flux data were combined with remote sensing and direct measurements of biomass, productivity, soil available water, and evapotranspiration to understand how weather and available water control ecosystem production and function. We found that production at the high elevation lodgepole site at 2700 m was strongly limited by winter cold. Production at the low elevation oak woodland site at 400 m was strongly limited by summer drought. The yellow pine site at 1200 m was only 4 °C cooler than the oak woodland site, yet had an order of magnitude more biomass and productivity with year-round growth. The mixed conifer site at 2000 m is 3.5 °C warmer than the lodgepole forest, yet also has higher biomass, ten times higher productivity, and year-round growth. We conclude that there is a broad climatological 'sweet spot' within the Sierra Nevada, in which the Mediterranean climate can support large-statured forest with high growth rates. The range of the mid-elevation forest was sharply bounded by water limitation at the lower edge and cold limitation at the upper edge despite small differences in precipitation and temperature across these boundaries. Our results suggest that small changes in precipitation or winter warming could markedly alter ecosystem structure and function as well as carbon and water cycling in the Sierra Nevada.

Understanding of polyhydroxybutyrate production under carbon and phosphorus-limited growth conditions in non-axenic continuous culture.

PubMed

Cavaillé, Laëtitia; Albuquerque, Maria; Grousseau, Estelle; Lepeuple, Anne-Sophie; Uribelarrea, Jean-Louis; Hernandez-Raquet, Guillermina; Paul, Etienne

2016-02-01

In a waste into resource strategy, a selection of polyhydroxybutyrate (PHB)-accumulating organisms from activated sludge was achieved in an open continuous culture under acetic acid and phosphorus limitation. Once the microbial population was selected at a dilution rate (D), an increase in phosphorus limitation degree was applied in order to study the intracellular phosphorus plasticity of selected bacteria and the resulting capacity to produce PHB. Whatever D, all selected populations were able to produce PHB. At a D, the phosphorus availability determined the phosphorus-cell content which in turn fixed the amount of cell. All the remaining carbon was thus directed toward PHB. By decreasing D, microorganisms adapted more easily to higher phosphorus limitation leading to higher PHB content. A one-stage continuous reactor operated at D=0.023h(-)(1) gave reliable high PHB productivity with PHB content up to 80%. A two-stage reactor could ensure better productivity while allowing tuning product quality. Copyright © 2015 Elsevier Ltd. All rights reserved.

Forest canopy hydraulics

Treesearch

David R. Woodruff; Frederick C. Meinzer; Katherine A. McCulloh

2016-01-01

Water and carbon cycles are strongly coordinated and water availability is a primary limiting factor in many terrestrial ecosystems. Photosynthesis requires sufficient water supply to leaves and constraints on delivery at any point in the hydraulic continuum can lead to stomatal closure and reduced photosynthesis. Thus, maximizing water transport enhances assimilation...

Using Nitrogen Limiting Growth Conditions to Remove Atrazine from Groundwater: Laboratory Studies

USDA-ARS?s Scientific Manuscript database

In the past microbial redox reactions have been the driving mechanism behind in situ bioremediations that use a carbon substrate. This is because subsurface microbial activity is generally restricted by electron (e-) donor availability and microbial activity, growth and respiration, can be stimulat...

Has water limited our imagination for aridland biogeochemistry?

PubMed

Austin, Amy T

2011-05-01

The classic ecological paradigm for deserts, that all processes are controlled by water availability, has limited our imagination for exploring other controls on the cycling of carbon and nutrients in aridland ecosystems. This review of recent studies identifies alternative mechanisms that challenge the idea that all soil processes in aridlands are proximately water-limited, and highlights the significance of photodegradation of aboveground litter and the overriding importance of spatial heterogeneity as a modulator of biotic responses to water availability. Aridlands currently occupy >30% of the terrestrial land surface and are expanding. It is therefore critical to incorporate these previously unappreciated mechanisms in our understanding of aridland biogeochemistry to mitigate the effects of desertification and global change. Copyright © 2011 Elsevier Ltd. All rights reserved.

Quantifying uncertainty in national forest carbon stocks: challenges and opportunities for the United States National Greenhouse Gas Inventory

NASA Astrophysics Data System (ADS)

Clough, B.; Russell, M.; Domke, G. M.; Woodall, C. W.

2016-12-01

Uncertainty estimates are needed to establish confidence in national forest carbon stocks and to verify changes reported to the United Nations Framework Convention on Climate Change. Good practice guidance from the Intergovernmental Panel on Climate Change stipulates that uncertainty assessments should neither exaggerate nor underestimate the actual error within carbon stocks, yet methodological guidance for forests has been hampered by limited understanding of how complex dynamics give rise to errors across spatial scales (i.e., individuals to continents). This talk highlights efforts to develop a multi-scale, data-driven framework for assessing uncertainty within the United States (US) forest carbon inventory, and focuses on challenges and opportunities for improving the precision of national forest carbon stock estimates. Central to our approach is the calibration of allometric models with a newly established legacy biomass database for North American tree species, and the use of hierarchical models to link these data with the Forest Inventory and Analysis (FIA) database as well as remote sensing datasets. Our work suggests substantial risk for misestimating key sources of uncertainty including: (1) attributing more confidence in allometric models than what is warranted by the best available data; (2) failing to capture heterogeneity in biomass stocks due to environmental variation at regional scales; and (3) ignoring spatial autocorrelation and other random effects that are characteristic of national forest inventory data. Our results suggest these sources of error may be much higher than is generally assumed, though these results must be understood with the limited scope and availability of appropriate calibration data in mind. In addition to reporting on important sources of uncertainty, this talk will discuss opportunities to improve the precision of national forest carbon stocks that are motivated by our use of data-driven forecasting including: (1) improving the taxonomic and geographic scope of available biomass data; (2) direct attribution of landscape-level heterogeneity in biomass stocks to specific ecological processes; and (3) integration of expert opinion and meta-analysis to lessen the influence of often highly variable datasets on biomass stock forecasts.

Highly Enhanced Raman Scattering on Carbonized Polymer Films.

PubMed

Yoon, Jong-Chul; Hwang, Jongha; Thiyagarajan, Pradheep; Ruoff, Rodney S; Jang, Ji-Hyun

2017-06-28

We have discovered a carbonized polymer film to be a reliable and durable carbon-based substrate for carbon enhanced Raman scattering (CERS). Commercially available SU8 was spin coated and carbonized (c-SU8) to yield a film optimized to have a favorable Fermi level position for efficient charge transfer, which results in a significant Raman scattering enhancement under mild measurement conditions. A highly sensitive CERS (detection limit of 10 -8 M) that was uniform over a large area was achieved on a patterned c-SU8 film and the Raman signal intensity has remained constant for 2 years. This approach works not only for the CMOS-compatible c-SU8 film but for any carbonized film with the correct composition and Fermi level, as demonstrated with carbonized-PVA (poly(vinyl alcohol)) and carbonized-PVP (polyvinylpyrollidone) films. Our study certainly expands the rather narrow range of Raman-active material platforms to include robust carbon-based films readily obtained from polymer precursors. As it uses broadly applicable and cheap polymers, it could offer great advantages in the development of practical devices for chemical/bio analysis and sensors.

Contrasting Strategies of Photosynthetic Energy Utilization Drive Lifestyle Strategies in Ecologically Important Picoeukaryotes

PubMed Central

Halsey, Kimberly H.; Milligan, Allen J.; Behrenfeld, Michael J.

2014-01-01

The efficiency with which absorbed light is converted to net growth is a key property for estimating global carbon production. We previously showed that, despite considerable evolutionary distance, Dunaliella tertiolecta (Chlorophyceae) and Thalassiosira weissflogii (Bacillariophyceae) share a common strategy of photosynthetic energy utilization and nearly identical light energy conversion efficiencies. These findings suggested that a single model might be appropriate for describing relationships between measures of phytoplankton production. This conclusion was further evaluated for Ostreococcus tauri RCC1558 and Micromonas pusilla RCC299 (Chlorophyta, Prasinophyceae), two picoeukaryotes with contrasting geographic distributions and swimming abilities. Nutrient-dependent photosynthetic efficiencies in O. tauri were similar to the previously studied larger algae. Specifically, absorption-normalized gross oxygen and carbon production and net carbon production were independent of nutrient limited growth rate. In contrast, all measures of photosynthetic efficiency were strongly dependent on nutrient availability in M. pusilla. This marked difference was accompanied by a diminished relationship between Chla:C and nutrient limited growth rate and a remarkably greater efficiency of gross-to-net energy conversion than the other organisms studied. These results suggest that the cost-benefit of decoupling pigment concentration from nutrient availability enables motile organisms to rapidly exploit more frequent encounters with micro-scale nutrient patches in open ocean environments. PMID:24957026

The implications of microbial and substrate limitation for the fates of carbon in different organic soil horizon types of boreal forest ecosystems: a mechanistically based model analysis

USGS Publications Warehouse

He, Y.; Zhuang, Q.; Harden, Jennifer W.; McGuire, A. David; Fan, Z.; Liu, Y.; Wickland, Kimberly P.

2014-01-01

The large amount of soil carbon in boreal forest ecosystems has the potential to influence the climate system if released in large quantities in response to warming. Thus, there is a need to better understand and represent the environmental sensitivity of soil carbon decomposition. Most soil carbon decomposition models rely on empirical relationships omitting key biogeochemical mechanisms and their response to climate change is highly uncertain. In this study, we developed a multi-layer microbial explicit soil decomposition model framework for boreal forest ecosystems. A thorough sensitivity analysis was conducted to identify dominating biogeochemical processes and to highlight structural limitations. Our results indicate that substrate availability (limited by soil water diffusion and substrate quality) is likely to be a major constraint on soil decomposition in the fibrous horizon (40–60% of soil organic carbon (SOC) pool size variation), while energy limited microbial activity in the amorphous horizon exerts a predominant control on soil decomposition (>70% of SOC pool size variation). Elevated temperature alleviated the energy constraint of microbial activity most notably in amorphous soils, whereas moisture only exhibited a marginal effect on dissolved substrate supply and microbial activity. Our study highlights the different decomposition properties and underlying mechanisms of soil dynamics between fibrous and amorphous soil horizons. Soil decomposition models should consider explicitly representing different boreal soil horizons and soil–microbial interactions to better characterize biogeochemical processes in boreal forest ecosystems. A more comprehensive representation of critical biogeochemical mechanisms of soil moisture effects may be required to improve the performance of the soil model we analyzed in this study.

The effect of nitrate and phosphate availability on Emiliania huxleyi (NZEH) physiology under different CO2 scenarios.

PubMed

Rouco, Mónica; Branson, Oscar; Lebrato, Mario; Iglesias-Rodríguez, M Débora

2013-01-01

Growth and calcification of the marine coccolithophorid Emiliania huxleyi is affected by ocean acidification and macronutrients limitation and its response varies between strains. Here we investigated the physiological performance of a highly calcified E. huxleyi strain, NZEH, in a multiparametric experiment. Cells were exposed to different CO2 levels (ranging from 250 to 1314 μatm) under three nutrient conditions [nutrient replete (R), nitrate limited (-N), and phosphate limited (-P)]. We focused on calcite and organic carbon quotas and on nitrate and phosphate utilization by analyzing the activity of nitrate reductase (NRase) and alkaline phosphatase (APase), respectively. Particulate inorganic (PIC) and organic (POC) carbon quotas increased with increasing CO2 under R conditions but a different pattern was observed under nutrient limitation. The PIC:POC ratio decreased with increasing CO2 in nutrient limited cultures. Coccolith length increased with CO2 under all nutrient conditions but the coccosphere volume varied depending on the nutrient treatment. Maximum APase activity was found at 561 μatm of CO2 (pH 7.92) in -P cultures and in R conditions, NRase activity increased linearly with CO2. These results suggest that E. huxleyi's competitive ability for nutrient uptake might be altered in future high-CO2 oceans. The combined dataset will be useful in model parameterizations of the carbon cycle and ocean acidification.

Structural CNT Composites. Part I; Developing a Carbon Nanotube Filament Winder

NASA Technical Reports Server (NTRS)

Sauti, Godfrey; Kim, Jae-Woo; Wincheski, Russell A.; Antczak, Andrew; Campero, Jamie C.; Luong, Hoa H.; Shanahan, Michelle H.; Stelter, Christopher J.; Siochi, Emilie J.

2015-01-01

Carbon nanotube (CNT) based materials promise advances in the production of high strength and multifunctional components for aerospace and other applications. Specifically, in tension dominated applications, the latest CNT based filaments are yielding composite properties comparable to or exceeding composites from more established fibers such as Kevlar and carbon fiber. However, for the properties of these materials to be fully realized at the component level, suitable manufacturing processes have to be developed. These materials handle differently from conventional fibers, with different wetting characteristics and behavior under load. The limited availability of bulk forms also requires that the equipment be scaled down accordingly to tailor the process development approach to material availability. Here, the development of hardware and software for filament winding of carbon nanotube based tapes and yarns is described. This hardware features precision guidance of the CNT material and control of the winding tension over a wide range in an open architecture that allows for effective process control and troubleshooting during winding. Use of the filament winder to develop CNT based Composite Overwrapped Pressure Vessels (COPVs) shall also be discussed.

Microbial community and nitrogen cycling shift with snowmelt in high-elevation barren soils of Mount Rainier National Park

NASA Astrophysics Data System (ADS)

Simpson, A.; Zabowski, D.

2015-12-01

Climate change and nutrient deposition have the potential to accelerate soil formation in high-elevation sediments recently exposed by glacier or snow melt. This process has implications not only for ecosystem formation on Earth but for the formation of Earth-like ecosystems on other planets and icy moons. Research into microbial communities shifting from subnival to mesotrophic conditions has mainly focused on changes on respiration and biomass, and is generally limited to one or two well-studied geographical locations. In particular, more information is needed on microbial shifts in snow-covered volcanic sediments, which may prove the closest analog to the most 'habitable' non-terrestrial environments for Earth microorganisms. We sampled in volcanic soil and sediment along gradients of elevation and snowmelt - dry soil, moist soil next to snowpack, and soil underneath snowpack - at the Muir Snowfields at Mount Rainier National Park, in order to investigate changes in carbon and nitrogen compounds, microbial diversity and gene expression. Initial results show a decrease in available ammonium and increase in microbial biomass carbon in exposed sediment with increasing soil moisture, and a sharp decrease in microbial C:N ratios after snowmelt and drying. Available/labile organic carbon and organic nitrogen decrease strongly with elevation, while microbial biomass carbon and nitrogen and mineral nitrogen compounds show no change with elevation. Though gene expression data is needed for confirmation, we hypothesize that these snowfields receive strong wind-borne deposits of carbon and nitrogen but that chemoautotrophic communities under semi-permanent snowpack do not shift to more mesotrophic communities until after exposed sediment has already begun to desiccate, limiting soil formation.

76 FR 8157 - National Ambient Air Quality Standards for Carbon Monoxide

Federal Register 2010, 2011, 2012, 2013, 2014

2011-02-11

... alternative mechanisms of CO- induced effects independent of limited oxygen availability (2000 AQCD, section 5... Concentrations B. Health Effects Information 1. Carboxyhemoglobin as Biomarker and Mechanism of Toxicity 2. Nature of Effects 3. At-Risk Populations 4. Potential Impacts on Public Health C. Human Exposure and Dose...

Simple models to predict grassland ecosystem C exchange and actual evapotranspiration using NDVI and environmental variables

USDA-ARS?s Scientific Manuscript database

Semiarid grasslands contribute significantly to net terrestrial carbon flux as plant productivity and heterotrophic respiration in these moisture-limited systems are correlated with metrics related to water availability (e.g., precipitation, Actual EvapoTranspiration or AET). These variables are als...

Are gas exchange responses to resource limitation and defoliation linked to source:sink relationships?

PubMed

Pinkard, E A; Eyles, A; O'Grady, A P

2011-10-01

Productivity of trees can be affected by limitations in resources such as water and nutrients, and herbivory. However, there is little understanding of their interactive effects on carbon uptake and growth. We hypothesized that: (1) in the absence of defoliation, photosynthetic rate and leaf respiration would be governed by limiting resource(s) and their impact on sink limitation; (2) photosynthetic responses to defoliation would be a consequence of changing source:sink relationships and increased availability of limiting resources; and (3) photosynthesis and leaf respiration would be adjusted in response to limiting resources and defoliation so that growth could be maintained. We tested these hypotheses by examining how leaf photosynthetic processes, respiration, carbohydrate concentrations and growth rates of Eucalyptus globulus were influenced by high or low water and nitrogen (N) availability, and/or defoliation. Photosynthesis of saplings grown with low water was primarily sink limited, whereas photosynthetic responses of saplings grown with low N were suggestive of source limitation. Defoliation resulted in source limitation. Net photosynthetic responses to defoliation were linked to the degree of resource availability, with the largest responses measured in treatments where saplings were ultimately source rather than sink limited. There was good evidence of acclimation to stress, enabling higher rates of C uptake than might otherwise have occurred. © 2011 Blackwell Publishing Ltd.

The application of carbon isotope discrimination of charred wheat grains to reconstruct Late Holocene climate change and identify water management strategy in northwest China

NASA Astrophysics Data System (ADS)

Wang, W.; An, C.; Duan, F.; Zhao, Y.; Cao, Z.

2017-12-01

The AMS 14C dating and corresponding carbon stable isotope datum of charred wheat grains from archaeological sites in northwest China especially Hexi Corridor and Xinjiang have been collected widely to study its potential roles in reconstructing past climate change and identifying water management strategies through comparison with integrated regional humidity index, carbon isotope data of wheat grown under modern irrigation environment from study area and Mediterranean charred wheat carbon isotope data. The results suggest (1) carbon isotope discrimination values of charred wheat both in Hexi corridor and Xinjiang could respond well to regional moisture change, and there are also good positive correlation relationship between them (2) in contrast to consistent relationship between decreased carbon isotope discrimination values of charred wheat and dry climate condition, increased carbon isotope discrimination values does not represent wetter regional climate completely and may also reveal effects of human irrigation activities. The higher carbon isotope discrimination value of charred wheat which occurred in the Hexi Corridor from 4000 to 3850 a BP, 2100 a BP and 550 a BP and in Tianshan area of Xinjiang from 3730 a BP could be likely to be related with human activities (3) the carbon isotope discrimination value of charred wheat may have a certain limit which is generally not beyond 19‰. And this upper limit could influence its availability in reflecting abrupt change of precipitation/humidity especially rapid wetter trend. We conclude that carbon isotope analysis of charred wheat grains could be a good tool for reconstructing past climate change and identifying ancient irrigation practices.

The changing Arctic carbon cycle: using the past to understand terrestrial-aquatic linkages

NASA Astrophysics Data System (ADS)

Anderson, N. J.; van Hardenbroek, M.; Jones, V.; McGowan, S.; Langdon, P. G.; Whiteford, E.; Turner, S.; Edwards, M. E.

2016-12-01

Predicted shifts in terrestrial vegetation cover associated with Arctic warming are altering the delivery and processing of carbon to aquatic ecosystems. This process could determine whether lakes are net carbon sources or sinks and, because lake density is high in many Arctic areas, may alter regional carbon budgets. Lake sediment records integrate information from within the lake and its catchment and can be used quantify past vegetation shifts associated with known climatic episodes of warmer (Holocene Thermal Maximum) and cooler (Neoglacial) conditions. We analysed sediment cores located in different Arctic vegetation biomes (tundra, shrub, forested) in Greenland, Norway and Alaska and used biochemical (algal pigments, stable isotopes) remains to evaluate whether past vegetation shifts were associated with changes in ecosystem carbon processing and biodiversity. When lake catchments were sparsely vegetated and soil vegetation was limited ultra-violet radiation (UVR) screening pigments indicate clear lake waters, scarce dissolved organic carbon/ matter (DOC/M). Moderate vegetation development (birch scrub in Norway; herb tundra in Greenland) appears to enhance delivery of DOM to lakes, and to stimulate algal production which is apparently linked to heterotrophic carbon processing pathways (e.g. algal mixotrophy, nutrient release via the microbial loop). Mature forest cover (in Alaska and Norway) supressed lake autotrophic production, most likely because coloured DOM delivered from catchment vegetation limited light availability. During wetter periods when mires developed lake carbon processing also changed, indicating that hydrological delivery of terrestrial DOM is also important. Therefore, future changes in Arctic vegetation and precipitation patterns are highly likely to alter the way that arctic ecosystems process carbon. Our approach provides an understanding of how ecosystem diversity and carbon processing respond to past climate change and the difficulty of identifying the drivers of state changes in the arctic.

Pseudowollastonite Carbonation Could Enable New Frontiers in Carbon Storage

NASA Astrophysics Data System (ADS)

Plattenberger, D.; Tao, Z.; Ling, F. T.; Peters, C. A.; Clarens, A. F.

2017-12-01

One of the primary challenges of CO2 mineral trapping is that precipitation reactions are reversible. A wide range of solid magnesium, iron, or calcium carbonates (such as magnesite, MgCO3) can be synthesized by reacting mineral silicates (such as olivine, Mg2SiO4) with CO2 to produce mineral carbonates. However, if CO2 remains present at high concentrations, as would be the case in many subsurface environments, the carbonate minerals could re-dissolve, making the precipitated carbonates impermanent forms of storage. In this work, we study pseudowollastonite (CaSiO3), a crystalline form of calcium silicate that is common in slags, cement, and calcium-rich volcanic formations, for its potential to produce other secondary mineral phases that may be resistant to dissolution under low pH conditions. These secondary mineral precipitation phases have morphologies and X-ray diffraction patterns that resemble both calcium silicate hydrate gels as well as crystalline calcium silicate carbonate hydrates. The combination of these phases forms a complex system that may resist acid attack while providing strength and limiting flow in the subsurface environment. High pressure and temperature column experiments carried out in our lab show that pseudowollastonite carbonation effectively lowers permeability in columns of sintered glass beads. Many of the pore throats are clogged by precipitates, as seen using micro X-ray tomography of intact columns and electron microscopy of thin sections. The spatial distribution of the products suggests that calcite forms toward the inlet of the columns where the pCO2 is highest. This forms a barrier that reduces, but does not eliminate, the availability of CO2 deeper in the porous media where the secondary phases precipitate. The existence of the calcite zone drives the reduction in permeability and the depth of this zone is self-limiting, which could have important implications for limiting leakage and unwanted migration of CO2 in some instances.

Multiscale assessment of water limitations on forest carbon cycling in the western United States

NASA Astrophysics Data System (ADS)

Berner, L. T.; Law, B. E.

2016-12-01

Water is a key environmental constraint on carbon uptake, storage, and release by forests in the western United States. Climate in this region is becoming warmer and drier, thus highlighting the need to better understand how forest carbon cycling responds to variation in water availability. Here, we describe how forest carbon cycling varied spatially along local to regional gradients in climatic water availability. We examined local variation in net primary productivity (NPP) and aboveground biomass (AGB) using 12 intensive field plots in Oregon's Cascade Mountains. Regional analysis of forest NPP and AGB was based on federal forest inventories (>8,000 plots) in Washington, Oregon, and California, multiple biomass maps and MODIS NPP (2003-2012). We also quantified annual forest AGB mortality due to bark beetles and fires across the region from 2003-2012 by combining several disturbance and biomass data sets. Over each spatial extent, forest NPP and AGB increased curvilinearly with average growing-year climate moisture index, computed as the cumulative difference between precipitation and potential evapotranspiration from October-September and averaged over preceding decades. Thus, climatic water availability strongly constrains forest carbon uptake and storage, particularly in the driest areas, but also in the wettest. Forest AGB mortality rates from bark beetles and fires peaked in moderately dry forests and then declining rapidly in the wettest areas. Annual forest AGB mortality from bark beetles was about twice as high as from fires. Bark beetle impacts were most pronounced in the Rock Mountains, while fire impacts were most pronounced in western portion of the region. Our multiscale analysis based on field inventory and remote sensing data sets demonstrates that climatic water availability is a key environmental constraint on forest carbon cycling in the western US. Consequently, continued warming and drying can be expected to have substantial impacts on forest carbon cycling in this region over the coming century.

Evaluation of coral reef carbonate production models at a global scale

NASA Astrophysics Data System (ADS)

Jones, N. S.; Ridgwell, A.; Hendy, E. J.

2014-09-01

Calcification by coral reef communities is estimated to account for half of all carbonate produced in shallow water environments and more than 25% of the total carbonate buried in marine sediments globally. Production of calcium carbonate by coral reefs is therefore an important component of the global carbon cycle. It is also threatened by future global warming and other global change pressures. Numerical models of reefal carbonate production are essential for understanding how carbonate deposition responds to environmental conditions including future atmospheric CO2 concentrations, but these models must first be evaluated in terms of their skill in recreating present day calcification rates. Here we evaluate four published model descriptions of reef carbonate production in terms of their predictive power, at both local and global scales, by comparing carbonate budget outputs with independent estimates. We also compile available global data on reef calcification to produce an observation-based dataset for the model evaluation. The four calcification models are based on functions sensitive to combinations of light availability, aragonite saturation (Ωa) and temperature and were implemented within a specifically-developed global framework, the Global Reef Accretion Model (GRAM). None of the four models correlated with independent rate estimates of whole reef calcification. The temperature-only based approach was the only model output to significantly correlate with coral-calcification rate observations. The absence of any predictive power for whole reef systems, even when consistent at the scale of individual corals, points to the overriding importance of coral cover estimates in the calculations. Our work highlights the need for an ecosystem modeling approach, accounting for population dynamics in terms of mortality and recruitment and hence coral cover, in estimating global reef carbonate budgets. In addition, validation of reef carbonate budgets is severely hampered by limited and inconsistent methodology in reef-scale observations.

Development of gas chromatographic methods for the analyses of organic carbonate-based electrolytes

NASA Astrophysics Data System (ADS)

Terborg, Lydia; Weber, Sascha; Passerini, Stefano; Winter, Martin; Karst, Uwe; Nowak, Sascha

2014-01-01

In this work, novel methods based on gas chromatography (GC) for the investigation of common organic carbonate-based electrolyte systems are presented, which are used in lithium ion batteries. The methods were developed for flame ionization detection (FID), mass spectrometric detection (MS). Further, headspace (HS) sampling for the investigation of solid samples like electrodes is reported. Limits of detection are reported for FID. Finally, the developed methods were applied to the electrolyte system of commercially available lithium ion batteries as well as on in-house assembled cells.

Magnesium hydroxide extracted from a magnesium-rich mineral for CO2 sequestration in a gas-solid system.

PubMed

Lin, Pao-Chung; Huang, Cheng-Wei; Hsiao, Ching-Ta; Teng, Hsisheng

2008-04-15

Magnesium hydroxide extracted from magnesium-bearing minerals is considered a promising agent for binding CO2 as a carbonate mineral in a gas-solid reaction. An efficient extraction route consisting of hydrothermal treatment on serpentine in HCl followed by NaOH titration for Mg(OH)2 precipitation was demonstrated. The extracted Mg(OH)2 powder had a mean crystal domain size as small as 12 nm and an apparent surface area of 54 m2/g. Under one atmosphere of 10 vol% CO2/N2, carbonation of the serpentine-derived Mg(OH)2 to 26% of the stoichiometric limit was achieved at 325 degrees C in 2 h; while carbonation of a commercially available Mg(OH)2, with a mean crystal domain size of 33 nm and an apparent surface area of 3.5 m2/g, reached only 9% of the stoichiometric limit. The amount of CO2 fixation was found to be inversely proportional to the crystal domain size of the Mg(OH)2 specimens. The experimental data strongly suggested that only a monolayer of carbonates was formed on the crystal domain boundary in the gas-solid reaction, with little penetration of the carbonates into the crystal domain.

Infrared On-Orbit Inspection of Shuttle Orbiter Reinforced Carbon-Carbon Using Solar Heating

NASA Technical Reports Server (NTRS)

Howell, P. A.; Winfree, W. P.; Cramer, K. Elliott

2005-01-01

Thermographic nondestructive inspection techniques have been shown to provide quantitative, large area damage detection capabilities for the ground inspection of the reinforced carbon-carbon (RCC) used for the wing leading edge of the Shuttle orbiter. The method is non-contacting and able to inspect large areas in a relatively short inspection time. Thermal nondestructive evaluation (NDE) inspections have been shown to be applicable for several applications to the Shuttle in preparation for return to flight, including for inspection of RCC panels during impact testing, and for between-flight orbiter inspections. The focus of this work is to expand the capabilities of the thermal NDE methodology to enable inspection by an astronaut during orbital conditions. The significant limitations of available resources, such as weight and power, and the impact of these limitations on the inspection technique are discussed, as well as the resultant impact on data analysis and processing algorithms. Of particular interest is the impact to the inspection technique resulting from the use of solar energy as a heat source, the effect on the measurements due to working in the vacuum of space, and the effect of changes in boundary conditions, such as radiation losses seen by the material, on the response of the RCC. The resultant effects on detectability limits are discussed. Keywords: Nondestructive Evaluation, Shuttle, on-orbit inspection, thermography, infrared

Model of carbon fixation in microbial mats from 3,500 Myr ago to the present

NASA Technical Reports Server (NTRS)

Rothschild, Lynn J.; Mancinelli, Rocco L.

1990-01-01

Using modern microbial mats as analogs for ancient stromatolites, it is shown that the rate of carbon fixation is higher at the greater levels of atmospheric CO2 that were probably present in the past. It is suggested that carbon fixation in microbial mats was not carbon-limited during the early Precambrian, but became carbon-limited as the supply of inorganic carbon decreased. Carbon limitation led to a lower rate of carbon fixation, especially towards the end of the Precambrian.

Atomistic modeling of carbon Cottrell atmospheres in bcc iron

NASA Astrophysics Data System (ADS)

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

2013-01-01

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

The carbon charging of pines at the climatic treeline: a global comparison.

PubMed

Hoch, Günter; Körner, Christian

2003-03-01

The carbon charging of pines across the treeline ecotone of three different climatic zones (Mexico 19 degrees N Pinus hartwegii, Swiss Alps 46 degrees N P. cembra and northern Sweden 68 degrees N P. sylvestris) was analyzed, to test whether a low-temperature-driven carbon shortage can explain high-elevation tree limits, and whether the length of the growing season affects the trees' carbon balance. We quantified the concentrations of non-structural carbohydrates (NSC) and lipids (acylglycerols) in all tree organs at three dates during the growing seasons across elevational transects from the upper end of the closed, tall forest (timberline) to the uppermost location where groups of trees > or =3 m in height occur (treeline). Mean ground temperatures during the growing season at the treelines were similar (6.1+/-0.7 degrees C) irrespective of latitude. Across the individual transects, the concentrations of NSC and lipids increased with elevation in all organs. By the end of the growing season, all three species had very similar total mobile carbon (TMC) concentrations at the treeline (ca. 6% TMC in the aboveground dry biomass), suggesting no influence of the length of the growing season on tree carbon charging. At a temperate lowland reference site P. sylvestris reached only ca. 4% TMC in the aboveground dry biomass, with the 2% difference largely explained by higher lipid concentrations of treeline pines. We conclude that carbon availability is unlikely to be the cause of the altitudinal tree limit. It seems rather that low temperatures directly affect sink activity at the treeline, with surplus carbon stored in osmotically inactive compounds.

Growing Rocks: Implications of Lithification for Microbial Communities and Nutrient Cycling

NASA Astrophysics Data System (ADS)

Corman, J. R.; Poret-Peterson, A. T.; Elser, J. J.

2014-12-01

Lithifying microbial communities ("microbialites") have left their signature on Earth's rock record for over 3.4 billion years and are regarded as important players in paleo-biogeochemical cycles. In this project, we study extant microbialites to understand the interactions between lithification and resource availability. All microbes need nutrients and energy for growth; indeed, nutrients are often a factor limiting microbial growth. We hypothesize that calcium carbonate deposition can sequester bioavailable phosphorus (P) and expect the growth of microbialites to be P-limited. To test our hypothesis, we first compared nutrient limitation in lithifying and non-lithifying microbial communities in Río Mesquites, Cuatro Ciénegas. Then, we experimentally manipulated calcification rates in the Río Mesquites microbialites. Our results suggest that lithifying microbialites are indeed P-limited, while non-lithifying, benthic microbial communities tend towards co-limitation by nitrogen (N) and P. Indeed, in microbialites, photosynthesis and aerobic respiration responded positively to P additions (P<0.05). Organic carbon (OC) additions caused shifts in bacterial community composition based on analysis of 16S rRNA genes. Unexpectedly, calcification rates increased with OC additions (P<0.05), but not with P additions, suggesting that sulfate reduction may be an important pathway for calcification. Experimental reductions in calcification rates caused changes to microbial biomass OC and P concentrations (P<0.01 and P<0.001, respectively), although shifts depended on whether calcification was decreased abiotically or biotically. These results show that resource availability does influence microbialite formation and that lithification may promote phosphorus limitation; however, further investigation is required to understand the mechanism by which the later occurs.

Observing terrestrial ecosystems and the carbon cycle from space

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schimel, David; Pavlick, Ryan; Fisher, Joshua B.

2015-02-06

Modeled terrestrial ecosystem and carbon cycle feedbacks contribute substantial uncertainty to projections of future climate. The limitations of current observing networks contribute to this uncertainty. Here we present a current climatology of global model predictions and observations for photosynthesis, biomass, plant diversity and plant functional diversity. Carbon cycle tipping points occur in terrestrial regions where fluxes or stocks are largest, and where biological variability is highest, the tropics and Arctic/Boreal zones. Global observations are predominately in the mid-latitudes and are sparse in high and low latitude ecosystems. Observing and forecasting ecosystem change requires sustained observations of sufficient density in timemore » and space in critical regions. Using data and theory available now, we can develop a strategy to detect and forecast terrestrial carbon cycle-climate interactions, by combining in situ and remote techniques.« less

Benefit-cost analysis of commercially available activated carbon filters for indoor ozone removal in single-family homes.

PubMed

Aldred, J R; Darling, E; Morrison, G; Siegel, J; Corsi, R L

2016-06-01

This study involved the development of a model for evaluating the potential costs and benefits of ozone control by activated carbon filtration in single-family homes. The modeling effort included the prediction of indoor ozone with and without activated carbon filtration in the HVAC system. As one application, the model was used to predict benefit-to-cost ratios for single-family homes in 12 American cities in five different climate zones. Health benefits were evaluated using disability-adjusted life-years and included city-specific age demographics for each simulation. Costs of commercially available activated carbon filters included capital cost differences when compared to conventional HVAC filters of similar particle removal efficiency, energy penalties due to additional pressure drop, and regional utility rates. The average indoor ozone removal effectiveness ranged from 4 to 20% across the 12 target cities and was largely limited by HVAC system operation time. For the parameters selected in this study, the mean predicted benefit-to-cost ratios for 1-inch filters were >1.0 in 10 of the 12 cities. The benefits of residential activated carbon filters were greatest in cities with high seasonal ozone and HVAC usage, suggesting the importance of targeting such conditions for activated carbon filter applications. © 2015 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Global economic consequences of deploying bioenergy with carbon capture and storage (BECCS)

NASA Astrophysics Data System (ADS)

Muratori, Matteo; Calvin, Katherine; Wise, Marshall; Kyle, Page; Edmonds, Jae

2016-09-01

Bioenergy with carbon capture and storage (BECCS) is considered a potential source of net negative carbon emissions and, if deployed at sufficient scale, could help reduce carbon dioxide emissions and concentrations. However, the viability and economic consequences of large-scale BECCS deployment are not fully understood. We use the Global Change Assessment Model (GCAM) integrated assessment model to explore the potential global and regional economic impacts of BECCS. As a negative-emissions technology, BECCS would entail a net subsidy in a policy environment in which carbon emissions are taxed. We show that by mid-century, in a world committed to limiting climate change to 2 °C, carbon tax revenues have peaked and are rapidly approaching the point where climate mitigation is a net burden on general tax revenues. Assuming that the required policy instruments are available to support BECCS deployment, we consider its effects on global trade patterns of fossil fuels, biomass, and agricultural products. We find that in a world committed to limiting climate change to 2 °C, the absence of CCS harms fossil-fuel exporting regions, while the presence of CCS, and BECCS in particular, allows greater continued use and export of fossil fuels. We also explore the relationship between carbon prices, food-crop prices and use of BECCS. We show that the carbon price and biomass and food crop prices are directly related. We also show that BECCS reduces the upward pressure on food crop prices by lowering carbon prices and lowering the total biomass demand in climate change mitigation scenarios. All of this notwithstanding, many challenges, both technical and institutional, remain to be addressed before BECCS can be deployed at scale.

Upscaling nitrogen-mycorrhizal effects to quantify CO2 fertilization.

NASA Astrophysics Data System (ADS)

Terrer, C.; Franklin, O.; Kaiser, C.; Vicca, S.; Stocker, B.; Prentice, I. C.; Soudzilovskaia, N.

2016-12-01

Terrestrial ecosystems sequester annually about a quarter of anthropogenic carbon dioxide (CO2) emissions. However, it has been proposed that nitrogen (N) availability will limit plants' capacity to absorb increasing quantities of CO2 in the atmosphere. Experiments in which plants are fumigated with elevated CO2 show contrasting results, leaving open the debate of whether the magnitude of the CO2 fertilization effect will be limited by N. By synthesizing data from CO2 experiments through meta-analysis, we found that the magnitude of the CO2 fertilization effect can be explained based on the interaction between N availability and type of mycorrhizal association. Indeed, N availability is the most important driver of the CO2 fertilization effect, however, plants that associate with ectomycorrhizal fungi can overcome N limitations and grow about 30% more under 650ppm than under 400ppm of atmospheric CO2. On the other hand, plants that associate with arbuscular mycorrhizal fungi show no CO2 fertilization effect under low N availability. Using this framework, we quantified biomass responses to CO2 as a function of the soil parameters that determine N availability for the two mycorrhizal types. Then, by overlaying the distribution of mycorrhizal plants with global projections of the soil parameters that determine N availability, we estimated the amount of extra CO2 that terrestrial plants can sequester in biomass for an increase in CO2, as well as the distribution of the CO2 fertilization effect. This synthesis reconciles contrasting views of the role of N in terrestrial carbon uptake and emphasizes the plant control on N availability through interaction with ectomycorrhizal fungi. Large-scale ecosystem models should account for the influence of nitrogen and mycorrhizae reported here, which will improve representation of the CO2 fertilization effect, critical for projecting ecosystem responses and feedbacks to climate change.

Effect of Global Regulators RpoS and Cyclic-AMP/CRP on the Catabolome and Transcriptome of Escherichia coli K12 during Carbon- and Energy-Limited Growth

PubMed Central

Egli, Thomas

2015-01-01

For heterotrophic microbes, limited availability of carbon and energy sources is one of the major nutritional factors restricting the rate of growth in most ecosystems. Physiological adaptation to this hunger state requires metabolic versatility which usually involves expression of a wide range of different catabolic pathways and of high-affinity carbon transporters; together, this allows for simultaneous utilization of mixtures of carbonaceous compounds at low concentrations. In Escherichia coli the stationary phase sigma factor RpoS and the signal molecule cAMP are the major players in the regulation of transcription under such conditions; however, their interaction is still not fully understood. Therefore, during growth of E. coli in carbon-limited chemostat culture at different dilution rates, the transcriptomes, expression of periplasmic proteins and catabolomes of strains lacking one of these global regulators, either rpoS or adenylate cyclase (cya), were compared to those of the wild-type strain. The inability to synthesize cAMP exerted a strong negative influence on the expression of alternative carbon source uptake and degradation systems. In contrast, absence of RpoS increased the transcription of genes belonging to high-affinity uptake systems and central metabolism, presumably due to reduced competition of σD with σS. Phenotypical analysis confirmed this observation: The ability to respire alternative carbon substrates and to express periplasmic high-affinity binding proteins was eliminated in cya and crp mutants, while these properties were not affected in the rpoS mutant. As expected, transcription of numerous stress defence genes was negatively affected by the rpoS knock-out mutation. Interestingly, several genes of the RpoS stress response regulon were also down-regulated in the cAMP-negative strain indicating a coordinated global regulation. The results demonstrate that cAMP is crucial for catabolic flexibility during slow, carbon-limited growth, whereas RpoS is primarily involved in the regulation of stress response systems necessary for the survival of this bacterium under hunger conditions. PMID:26204448

An Optimal Centralized Carbon Dioxide Repository for Florida, USA

PubMed Central

Poiencot, Brandon; Brown, Christopher

2011-01-01

For over a decade, the United States Department of Energy, and engineers, geologists, and scientists from all over the world have investigated the potential for reducing atmospheric carbon emissions through carbon sequestration. Numerous reports exist analyzing the potential for sequestering carbon dioxide at various sites around the globe, but none have identified the potential for a statewide system in Florida, USA. In 2005, 83% of Florida’s electrical energy was produced by natural gas, coal, or oil (e.g., fossil fuels), from power plants spread across the state. In addition, only limited research has been completed on evaluating optimal pipeline transportation networks to centralized carbon dioxide repositories. This paper describes the feasibility and preliminary locations for an optimal centralized Florida-wide carbon sequestration repository. Linear programming optimization modeling is used to plan and route an idealized pipeline network to existing Florida power plants. Further analysis of the subsurface geology in these general locations will provide insight into the suitability of the subsurface conditions and the available capacity for carbon sequestration at selected possible repository sites. The identification of the most favorable site(s) is also presented. PMID:21695024

An optimal centralized carbon dioxide repository for Florida, USA.

PubMed

Poiencot, Brandon; Brown, Christopher

2011-04-01

For over a decade, the United States Department of Energy, and engineers, geologists, and scientists from all over the world have investigated the potential for reducing atmospheric carbon emissions through carbon sequestration. Numerous reports exist analyzing the potential for sequestering carbon dioxide at various sites around the globe, but none have identified the potential for a statewide system in Florida, USA. In 2005, 83% of Florida's electrical energy was produced by natural gas, coal, or oil (e.g., fossil fuels), from power plants spread across the state. In addition, only limited research has been completed on evaluating optimal pipeline transportation networks to centralized carbon dioxide repositories. This paper describes the feasibility and preliminary locations for an optimal centralized Florida-wide carbon sequestration repository. Linear programming optimization modeling is used to plan and route an idealized pipeline network to existing Florida power plants. Further analysis of the subsurface geology in these general locations will provide insight into the suitability of the subsurface conditions and the available capacity for carbon sequestration at selected possible repository sites. The identification of the most favorable site(s) is also presented.

Effects of Nutrient Enrichment on Microbial Communities and Carbon Cycling in Wetland Soils

NASA Astrophysics Data System (ADS)

Hartman, W.; Neubauer, S. C.; Richardson, C. J.

2013-12-01

Soil microbial communities are responsible for catalyzing biogeochemical transformations underlying critical wetland functions, including cycling of carbon (C) and nutrients, and emissions of greenhouse gasses (GHG). Alteration of nutrient availability in wetland soils may commonly occur as the result of anthropogenic impacts including runoff from human land uses in uplands, alteration of hydrology, and atmospheric deposition. However, the impacts of altered nutrient availability on microbial communities and carbon cycling in wetland soils are poorly understood. To assess these impacts, soil microbial communities and carbon cycling were determined in replicate experimental nutrient addition plots (control, +N, +P, +NP) across several wetland types, including pocosin peat bogs (NC), freshwater tidal marshes (GA), and tidal salt marshes (SC). Microbial communities were determined by pyrosequencing (Roche 454) extracted soil DNA, targeting both bacteria (16S rDNA) and fungi (LSU) at a depth of ca. 1000 sequences per plot. Wetland carbon cycling was evaluated using static chambers to determine soil GHG fluxes, and plant inclusion chambers were used to determine ecosystem C cycling. Soil bacterial communities responded to nutrient addition treatments in freshwater and tidal marshes, while fungal communities did not respond to treatments in any of our sites. We also compared microbial communities to continuous biogeochemical variables in soil, and found that bacterial community composition was correlated only with the content and availability of soil phosphorus, while fungi responded to phosphorus stoichiometry and soil pH. Surprisingly, we did not find a significant effect of our nutrient addition treatments on most metrics of carbon cycling. However, we did find that several metrics of soil carbon cycling appeared much more related to soil phosphorus than to nitrogen or soil carbon pools. Finally, while overall microbial community composition was weakly correlated with soil carbon cycling, our work did identify a small number of individual taxonomic groups that were more strongly correlated with soil CO2 flux. These results suggest that a small number of microbial groups may potentially serve as keystone taxa (and functional indicators), which simple community fingerprinting approaches may overlook. Our results also demonstrate strong effects of soil phosphorus availability on both microbial communities and soil carbon cycling, even in wetland types traditionally considered to be nitrogen limited.

Readily Available Fluorescent Probe for Carbon Monoxide Imaging in Living Cells.

PubMed

Feng, Weiyong; Liu, Dandan; Feng, Shumin; Feng, Guoqiang

2016-11-01

Carbon monoxide (CO) is an important gasotransmitter in living systems and its fluorescent detection is of particular interest. However, fluorescent detection of CO in living cells is still challenging due to lack of effective probes. In this paper, a readily available fluorescein-based fluorescent probe was developed for rapid detection of CO. This probe can be used to detect CO in almost wholly aqueous solution under mild conditions and shows high selectivity and sensitivity for CO with colorimetric and remarkable fluorescent turn-on signal changes. The detection limit of this probe for CO is as low as 37 nM with a linear range of 0-30 μM. More importantly, this probe (1 μM dose) can be conveniently used for fluorescent imaging CO in living cells.

Coupled nutrient cycling determines tropical forest trajectory under elevated CO2.

NASA Astrophysics Data System (ADS)

Bouskill, N.; Zhu, Q.; Riley, W. J.

2017-12-01

Tropical forests have a disproportionate capacity to affect Earth's climate relative to their areal extent. Despite covering just 12 % of land surface, tropical forests account for 35 % of global net primary productivity and are among the most significant of terrestrial carbon stores. As atmospheric CO2 concentrations increase over the next century, the capacity of tropical forests to assimilate and sequester anthropogenic CO2 depends on limitation by multiple factors, including the availability of soil nutrients. Phosphorus availability has been considered to be the primary factor limiting metabolic processes within tropical forests. However, recent evidence points towards strong spatial and temporal co-limitation of tropical forests by both nitrogen and phosphorus. Here, we use the Accelerated Climate Modeling for Energy (ACME) Land Model (ALMv1-ECA-CNP) to examine how nutrient cycles interact and affect the trajectory of the tropical forest carbon sink under, (i) external nutrient input, (ii) climate (iii) elevated CO2, and (iv) a combination of 1-3. ALMv1 includes recent theoretical advances in representing belowground competition between roots, microbes and minerals for N and P uptake, explicit interactions between the nitrogen and phosphorus cycles (e.g., phosphatase production and nitrogen fixation), the dynamic internal allocation of plant N and P resources, and the integration of global datasets of plant physiological traits. We report nutrient fertilization (N, P, N+P) predictions for four sites in the tropics (El Verde, Puerto Rico, Barro Colorado Island, Panama, Manaus, Brazil and the Osa Peninsula, Coast Rica) to short-term nutrient fertilization (N, P, N+P), and benchmarking of the model against a meta-analysis of forest fertilization experiments. Subsequent simulations focus on the interaction of the carbon, nitrogen, and phosphorus cycles across the tropics with a focus on the implications of coupled nutrient cycling and the fate of the tropical forest carbon sink. Our results highlight the importance of transient CNP allocation, leaf-level stoichiometric controls on photosynthesis, and trade-offs between above and belowground plant investments.

Time-resolved analysis of nonlinear optical limiting for laser synthesized carbon nanoparticles

NASA Astrophysics Data System (ADS)

Chen, G. X.; Hong, M. H.

2010-11-01

Nonlinear optical limiting materials have attracted much research interest in recent years. Carbon nanoparticles suspended in liquids show a strong nonlinear optical limiting function. It is important to investigate the nonlinear optical limiting process of carbon nanoparticles for further improving their nonlinear optical limiting performance. In this study, carbon nanoparticles were prepared by laser ablation of a carbon target in tetrahydrofuran (THF). Optical limiting properties of the samples were studied with 532-nm laser light, which is in the most sensitive wavelength band for human eyes. The shape of the laser pulse plays an important role for initializing the nonlinear optical limiting effect. Time-resolved analysis of laser pulses discovered 3 fluence stages of optical limiting. Theoretical simulation indicates that the optical limiting is initialized by a near-field optical enhancement effect.

Terrestrial nitrogen–carbon cycle interactions at the global scale

PubMed Central

Zaehle, S.

2013-01-01

Interactions between the terrestrial nitrogen (N) and carbon (C) cycles shape the response of ecosystems to global change. However, the global distribution of nitrogen availability and its importance in global biogeochemistry and biogeochemical interactions with the climate system remain uncertain. Based on projections of a terrestrial biosphere model scaling ecological understanding of nitrogen–carbon cycle interactions to global scales, anthropogenic nitrogen additions since 1860 are estimated to have enriched the terrestrial biosphere by 1.3 Pg N, supporting the sequestration of 11.2 Pg C. Over the same time period, CO2 fertilization has increased terrestrial carbon storage by 134.0 Pg C, increasing the terrestrial nitrogen stock by 1.2 Pg N. In 2001–2010, terrestrial ecosystems sequestered an estimated total of 27 Tg N yr−1 (1.9 Pg C yr−1), of which 10 Tg N yr−1 (0.2 Pg C yr−1) are due to anthropogenic nitrogen deposition. Nitrogen availability already limits terrestrial carbon sequestration in the boreal and temperate zone, and will constrain future carbon sequestration in response to CO2 fertilization (regionally by up to 70% compared with an estimate without considering nitrogen–carbon interactions). This reduced terrestrial carbon uptake will probably dominate the role of the terrestrial nitrogen cycle in the climate system, as it accelerates the accumulation of anthropogenic CO2 in the atmosphere. However, increases of N2O emissions owing to anthropogenic nitrogen and climate change (at a rate of approx. 0.5 Tg N yr−1 per 1°C degree climate warming) will add an important long-term climate forcing. PMID:23713123

Terrestrial nitrogen-carbon cycle interactions at the global scale.

PubMed

Zaehle, S

2013-07-05

Interactions between the terrestrial nitrogen (N) and carbon (C) cycles shape the response of ecosystems to global change. However, the global distribution of nitrogen availability and its importance in global biogeochemistry and biogeochemical interactions with the climate system remain uncertain. Based on projections of a terrestrial biosphere model scaling ecological understanding of nitrogen-carbon cycle interactions to global scales, anthropogenic nitrogen additions since 1860 are estimated to have enriched the terrestrial biosphere by 1.3 Pg N, supporting the sequestration of 11.2 Pg C. Over the same time period, CO2 fertilization has increased terrestrial carbon storage by 134.0 Pg C, increasing the terrestrial nitrogen stock by 1.2 Pg N. In 2001-2010, terrestrial ecosystems sequestered an estimated total of 27 Tg N yr(-1) (1.9 Pg C yr(-1)), of which 10 Tg N yr(-1) (0.2 Pg C yr(-1)) are due to anthropogenic nitrogen deposition. Nitrogen availability already limits terrestrial carbon sequestration in the boreal and temperate zone, and will constrain future carbon sequestration in response to CO2 fertilization (regionally by up to 70% compared with an estimate without considering nitrogen-carbon interactions). This reduced terrestrial carbon uptake will probably dominate the role of the terrestrial nitrogen cycle in the climate system, as it accelerates the accumulation of anthropogenic CO2 in the atmosphere. However, increases of N2O emissions owing to anthropogenic nitrogen and climate change (at a rate of approx. 0.5 Tg N yr(-1) per 1°C degree climate warming) will add an important long-term climate forcing.

On the potential for CO2 mineral storage in continental flood basalts – PHREEQC batch- and 1D diffusion–reaction simulations

PubMed Central

2012-01-01

Continental flood basalts (CFB) are considered as potential CO2 storage sites because of their high reactivity and abundant divalent metal ions that can potentially trap carbon for geological timescales. Moreover, laterally extensive CFB are found in many place in the world within reasonable distances from major CO2 point emission sources. Based on the mineral and glass composition of the Columbia River Basalt (CRB) we estimated the potential of CFB to store CO2 in secondary carbonates. We simulated the system using kinetic dependent dissolution of primary basalt-minerals (pyroxene, feldspar and glass) and the local equilibrium assumption for secondary phases (weathering products). The simulations were divided into closed-system batch simulations at a constant CO2 pressure of 100 bar with sensitivity studies of temperature and reactive surface area, an evaluation of the reactivity of H2O in scCO2, and finally 1D reactive diffusion simulations giving reactivity at CO2 pressures varying from 0 to 100 bar. Although the uncertainty in reactive surface area and corresponding reaction rates are large, we have estimated the potential for CO2 mineral storage and identified factors that control the maximum extent of carbonation. The simulations showed that formation of carbonates from basalt at 40 C may be limited to the formation of siderite and possibly FeMg carbonates. Calcium was largely consumed by zeolite and oxide instead of forming carbonates. At higher temperatures (60 – 100 C), magnesite is suggested to form together with siderite and ankerite. The maximum potential of CO2 stored as solid carbonates, if CO2 is supplied to the reactions unlimited, is shown to depend on the availability of pore space as the hydration and carbonation reactions increase the solid volume and clog the pore space. For systems such as in the scCO2 phase with limited amount of water, the total carbonation potential is limited by the amount of water present for hydration of basalt. PMID:22697910

Differential Nutrient Limitation of Soil Microbial Biomass and Metabolic Quotients (qCO2): Is There a Biological Stoichiometry of Soil Microbes?

PubMed Central

Hartman, Wyatt H.; Richardson, Curtis J.

2013-01-01

Background Variation in microbial metabolism poses one of the greatest current uncertainties in models of global carbon cycling, and is particularly poorly understood in soils. Biological Stoichiometry theory describes biochemical mechanisms linking metabolic rates with variation in the elemental composition of cells and organisms, and has been widely observed in animals, plants, and plankton. However, this theory has not been widely tested in microbes, which are considered to have fixed ratios of major elements in soils. Methodology/Principal Findings To determine whether Biological Stoichiometry underlies patterns of soil microbial metabolism, we compiled published data on microbial biomass carbon (C), nitrogen (N), and phosphorus (P) pools in soils spanning the global range of climate, vegetation, and land use types. We compared element ratios in microbial biomass pools to the metabolic quotient qCO2 (respiration per unit biomass), where soil C mineralization was simultaneously measured in controlled incubations. Although microbial C, N, and P stoichiometry appeared to follow somewhat constrained allometric relationships at the global scale, we found significant variation in the C∶N∶P ratios of soil microbes across land use and habitat types, and size-dependent scaling of microbial C∶N and C∶P (but not N∶P) ratios. Microbial stoichiometry and metabolic quotients were also weakly correlated as suggested by Biological Stoichiometry theory. Importantly, we found that while soil microbial biomass appeared constrained by soil N availability, microbial metabolic rates (qCO2) were most strongly associated with inorganic P availability. Conclusions/Significance Our findings appear consistent with the model of cellular metabolism described by Biological Stoichiometry theory, where biomass is limited by N needed to build proteins, but rates of protein synthesis are limited by the high P demands of ribosomes. Incorporation of these physiological processes may improve models of carbon cycling and understanding of the effects of nutrient availability on soil C turnover across terrestrial and wetland habitats. PMID:23526933

Nutrient demand and fungal access to resources control the carbon allocation to the symbiotic partners in tripartite interactions of Medicago truncatula.

PubMed

Kafle, Arjun; Garcia, Kevin; Wang, Xiurong; Pfeffer, Philip E; Strahan, Gary D; Bücking, Heike

2018-06-02

Legumes form tripartite interactions with arbuscular mycorrhizal (AM) fungi and rhizobia, and both root symbionts exchange nutrients against carbon from their host. The carbon costs of these interactions are substantial, but our current understanding of how the host controls its carbon allocation to individual root symbionts is limited. We examined nutrient uptake and carbon allocation in tripartite interactions of Medicago truncatula under different nutrient supply conditions, and when the fungal partner had access to nitrogen, and followed the gene expression of several plant transporters of the SUT and SWEET family. Tripartite interactions led to synergistic growth responses and stimulated the phosphate and nitrogen uptake of the plant. Plant nutrient demand but also fungal access to nutrients played an important role for the carbon transport to different root symbionts, and the plant allocated more carbon to rhizobia under nitrogen demand, but more carbon to the fungal partner when nitrogen was available. These changes in carbon allocation were consistent with changes in the SUT and SWEET expression. Our study provides important insights into how the host plant controls its carbon allocation under different nutrient supply conditions and changes its carbon allocation to different root symbionts to maximize its symbiotic benefits. This article is protected by copyright. All rights reserved.

Carbon-based Fresnel optics for hard x-ray astronomy.

PubMed

Braig, Christoph; Zizak, Ivo

2018-03-10

We investigate the potential of large-scale diffractive-refractive normal-incidence transmission lenses for the development of space-based hard x-ray telescopes with an angular resolution in the range of (10 -6 -10 -3 )  arcsec over a field of view that is restricted by the available detector size. Coherently stepped achromatic lenses with diameters up to 5 m for compact apertures and 13 m in the case of segmentation provide an access to spectrally resolved imaging within keV-wide bands around the design energy between 10 and 30 keV. Within an integration time of 10 6   s, a photon-limited 5σ sensitivity down to (10 -9 -10 -7 )  s -1  cm -2  keV -1 can be achieved depending on the specific design. An appropriate fabrication strategy, feasible nowadays with micro-optical technologies, is considered and relies on the availability of high-purity carbon or polymer membranes. X-ray fluorescence measurements of various commercially available carbon-based materials prove for most of them the existence of a virtually negligible contamination by critical trace elements such as transition metals on the ppm level.

Carbon footprint and cost-effectiveness of cataract surgery.

PubMed

Venkatesh, Rengaraj; van Landingham, Suzanne W; Khodifad, Ashish M; Haripriya, Aravind; Thiel, Cassandra L; Ramulu, Pradeep; Robin, Alan L

2016-01-01

This article raises awareness about the cost-effectiveness and carbon footprint of various cataract surgery techniques, comparing their relative carbon emissions and expenses: manual small-incision cataract surgery (MSICS), phacoemulsification, and femtosecond laser-assisted cataract surgery. As the most commonly performed surgical procedure worldwide, cataract surgery contributes significantly to global climate change. The carbon footprint of a single phacoemulsification cataract surgery is estimated to be comparable to that of a typical person's life for 1 week. Phacoemulsification has been estimated to be between 1.4 and 4.7 times more expensive than MSICS; however, given the lower degree of postoperative astigmatism and other potential complications, phacoemulsification may still be preferable to MSICS in relatively resource-rich settings requiring high levels of visual function. Limited data are currently available regarding the environmental and financial impact of femtosecond laser-assisted cataract surgery; however, in its current form, it appears to be the least cost-effective option. Cataract surgery has a high value to patients. The relative environmental impact and cost of different types of cataract surgery should be considered as this treatment becomes even more broadly available globally and as new technologies are developed and implemented.

A first-order analysis of the potential role of CO2 fertilization to affect the global carbon budget: A comparison of four terrestrial biosphere models

USGS Publications Warehouse

Kicklighter, D.W.; Bruno, M.; Donges, S.; Esser, G.; Heimann, Martin; Helfrich, J.; Ift, F.; Joos, F.; Kaduk, J.; Kohlmaier, G.H.; McGuire, A.D.; Melillo, J.M.; Meyer, R.; Moore, B.; Nadler, A.; Prentice, I.C.; Sauf, W.; Schloss, A.L.; Sitch, S.; Wittenberg, U.; Wurth, G.

1999-01-01

We compared the simulated responses of net primary production, heterotrophic respiration, net ecosystem production and carbon storage in natural terrestrial ecosystems to historical (1765 to 1990) and projected (1990 to 2300) changes of atmospheric CO2 concentration of four terrestrial biosphere models: the Bern model, the Frankfurt Biosphere Model (FBM), the High-Resolution Biosphere Model (HRBM) and the Terrestrial Ecosystem Model (TEM). The results of the model intercomparison suggest that CO2 fertilization of natural terrestrial vegetation has the potential to account for a large fraction of the so-called 'missing carbon sink' of 2.0 Pg C in 1990. Estimates of this potential are reduced when the models incorporate the concept that CO2 fertilization can be limited by nutrient availability. Although the model estimates differ on the potential size (126 to 461 Pg C) of the future terrestrial sink caused by CO2 fertilization, the results of the four models suggest that natural terrestrial ecosystems will have a limited capacity to act as a sink of atmospheric CO2 in the future as a result of physiological constraints and nutrient constraints on NPP. All the spatially explicit models estimate a carbon sink in both tropical and northern temperate regions, but the strength of these sinks varies over time. Differences in the simulated response of terrestrial ecosystems to CO2 fertilization among the models in this intercomparison study reflect the fact that the models have highlighted different aspects of the effect of CO2 fertilization on carbon dynamics of natural terrestrial ecosystems including feedback mechanisms. As interactions with nitrogen fertilization, climate change and forest regrowth may play an important role in simulating the response of terrestrial ecosystems to CO2 fertilization, these factors should be included in future analyses. Improvements in spatially explicit data sets, whole-ecosystems experiments and the availability of net carbon exchange measurements across the globe will also help to improve future evaluations of the role of CO2 fertilization on terrestrial carbon storage.

Insights from a network of long-term measurements of biosphere-atmospheric exchanges of water vapor and carbon dioxide in a water-limited semiarid region

NASA Astrophysics Data System (ADS)

Scott, Russell; Biederman, Joel

2017-04-01

Around one-third of Earth's land surface is classified as semiarid, and carbon dioxide exchange in these regions has been shown to be an important regulator of both the trend and interannual variability of the terrestrial carbon sink. Fifteen years ago, when we began making measurements of biosphere-atmospheric exchanges of energy, water vapor, and carbon dioxide using eddy covariance in southern Arizona USA, there was paucity of semiarid observations in flux networks like AmeriFlux and EuroFlux. We started by establishing riparian sites across a woody plant encroachment gradient to quantify the productivity and consumptive plant water use along a iconic and ecologically important desert river. Soon thereafter, we added semiarid grassland, shrubland, and savanna sites that do not have access to groundwater in order to better understand how water limitation and changes in vegetation structure affect ecosystem productivity. Here, we highlight the value of multiyear, multisite flux data for addressing regional to global scale problems associated with groundwater pumping, land cover change, drought, and climate change. For the riparian sites, we find that ecosystem water availability is altered by vegetation structure such that ecosystems with more deeply rooted trees have higher productivity but at a cost of greater groundwater use. For the non-riparian sites, precipitation strongly controls ecosystem water availability and the resultant productivity, but differences in ecosystem structure impact water use efficiency due to the partitioning of evapotranspiration into its component sources. Also, the productivity at sites with more grass, and less woody, plants responds more quickly to precipitation fluctuations including long-term drought conditions. In semiarid regions, variability in water and carbon fluxes is much larger than in more mesic climes. Across our riparian and non-riparian sites, access to more stable groundwater reserves reduces variability in water and carbon fluxes and can decouple ecosystem productivity from precipitation. Finally, we show that the 8% increase in carbon dioxide concentrations over the period of our measurements may be altering ecosystem water use efficiency, a result that is expected and has been reported for northeastern US forests.

An Energy Balance Model to Predict Chemical Partitioning in a Photosynthetic Microbial Mat

NASA Technical Reports Server (NTRS)

Hoehler, Tori M.; Albert, Daniel B.; DesMarais, David J.

2006-01-01

Studies of biosignature formation in photosynthetic microbial mat communities offer potentially useful insights with regards to both solar and extrasolar astrobiology. Biosignature formation in such systems results from the chemical transformation of photosynthetically fixed carbon by accessory microorganisms. This fixed carbon represents a source not only of reducing power, but also energy, to these organisms, so that chemical and energy budgets should be coupled. We tested this hypothesis by applying an energy balance model to predict the fate of photosynthetic productivity under dark, anoxic conditions. Fermentation of photosynthetically fixed carbon is taken to be the only source of energy available to cyanobacteria in the absence of light and oxygen, and nitrogen fixation is the principal energy demand. The alternate fate for fixed carbon is to build cyanobacterial biomass with Redfield C:N ratio. The model predicts that, under completely nitrogen-limited conditions, growth is optimized when 78% of fixed carbon stores are directed into fermentative energy generation, with the remainder allocated to growth. These predictions were compared to measurements made on microbial mats that are known to be both nitrogen-limited and populated by actively nitrogen-fixing cyanobacteria. In these mats, under dark, anoxic conditions, 82% of fixed carbon stores were diverted into fermentation. The close agreement between these independent approaches suggests that energy balance models may provide a quantitative means of predicting chemical partitioning within such systems - an important step towards understanding how biological productivity is ultimately partitioned into biosignature compounds.

All-carbon suspended nanowire sensors as a rapid highly-sensitive label-free chemiresistive biosensing platform.

PubMed

Thiha, Aung; Ibrahim, Fatimah; Muniandy, Shalini; Dinshaw, Ignatius Julian; Teh, Swe Jyan; Thong, Kwai Lin; Leo, Bey Fen; Madou, Marc

2018-06-01

Nanowire sensors offer great potential as highly sensitive electrochemical and electronic biosensors because of their small size, high aspect ratios, and electronic properties. Nevertheless, the available methods to fabricate carbon nanowires in a controlled manner remain limited to expensive techniques. This paper presents a simple fabrication technique for sub-100 nm suspended carbon nanowire sensors by integrating electrospinning and photolithography techniques. Carbon Microelectromechanical Systems (C-MEMS) fabrication techniques allow fabrication of high aspect ratio carbon structures by patterning photoresist polymers into desired shapes and subsequent carbonization of resultant structures by pyrolysis. In our sensor platform, suspended nanowires were deposited by electrospinning while photolithography was used to fabricate support structures. We have achieved suspended carbon nanowires with sub-100 nm diameters in this study. The sensor platform was then integrated with a microfluidic chip to form a lab-on-chip device for label-free chemiresistive biosensing. We have investigated this nanoelectronics label-free biosensor's performance towards bacterial sensing by functionalization with Salmonella-specific aptamer probes. The device was tested with varying concentrations of Salmonella Typhimurium to evaluate sensitivity and various other bacteria to investigate specificity. The results showed that the sensor is highly specific and sensitive in detection of Salmonella with a detection limit of 10 CFU mL -1 . Moreover, this proposed chemiresistive assay has a reduced turnaround time of 5 min and sample volume requirement of 5 µL which are much less than reported in the literature. Copyright © 2018 Elsevier B.V. All rights reserved.

Starved Escherichia coli preserve reducing power under nitric oxide stress

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gowers, Glen-Oliver F.; Robinson, Jonathan L.; Brynildsen, Mark P., E-mail: mbrynild@princeton.edu

Nitric oxide (NO) detoxification enzymes, such as NO dioxygenase (NOD) and NO reductase (NOR), are important to the virulence of numerous bacteria. Pathogens use these defense systems to ward off immune-generated NO, and they do so in environments that contain additional stressors, such as reactive oxygen species, nutrient deprivation, and acid stress. NOD and NOR both use reducing equivalents to metabolically deactivate NO, which suggests that nutrient deprivation could negatively impact their functionality. To explore the relationship between NO detoxification and nutrient deprivation, we examined the ability of Escherichia coli to detoxify NO under different levels of carbon source availabilitymore » in aerobic cultures. We observed failure of NO detoxification under both carbon source limitation and starvation, and those failures could have arisen from inabilities to synthesize Hmp (NOD of E. coli) and/or supply it with sufficient NADH (preferred electron donor). We found that when limited quantities of carbon source were provided, NO detoxification failed due to insufficient NADH, whereas starvation prevented Hmp synthesis, which enabled cells to maintain their NADH levels. This maintenance of NADH levels under starvation was confirmed to be dependent on the absence of Hmp. Intriguingly, these data show that under NO stress, carbon-starved E. coli are better positioned with regard to reducing power to cope with other stresses than cells that had consumed an exhaustible amount of carbon. -- Highlights: •Carbon source availability is critical to aerobic E. coli NO detoxification. •Carbon source starvation, under NO stress, preserves intracellular NADH levels. •Preservation of NADH depends on starvation-dependent inhibition of Hmp induction.« less

Soil respiration characteristics in different land uses and response of soil organic carbon to biochar addition in high-latitude agricultural area.

PubMed

Ouyang, Wei; Geng, Xiaojun; Huang, Wejia; Hao, Fanghua; Zhao, Jinbo

2016-02-01

The farmland tillage practices changed the soil chemical properties, which also impacted the soil respiration (R s ) process and the soil carbon conservation. Originally, the farmland in northeast China had high soil carbon content, which was decreased in the recent decades due to the tillage practices. To better understand the R s dynamics in different land use types and its relationship with soil carbon loss, soil samples at two layers (0-15 and 15-30 cm) were analyzed for organic carbon (OC), total nitrogen (TN), total phosphorus (TP), total carbon (TC), available nitrogen (AN), available phosphorus (AP), soil particle size distribution, as well as the R s rate. The R s rate of the paddy land was 0.22 (at 0-15 cm) and 3.01 (at 15-30 cm) times of the upland. The average concentrations of OC and clay content in cultivated areas were much lower than in non-cultivated areas. The partial least squares analysis suggested that the TC and TN were significantly related to the R s process in cultivated soils. The upland soil was further used to test soil CO2 emission response at different biochar addition levels during 70-days incubation. The measurement in the limited incubation period demonstrated that the addition of biochar improved the soil C content because it had high concentration of pyrogenic C, which was resistant to mineralization. The analysis showed that biochar addition can promote soil OC by mitigating carbon dioxide (CO2) emission. The biochar addition achieved the best performance for the soil carbon conservation in high-latitude agricultural area due to the originally high carbon content.

Estimates of carbon allocation to ectomycorrhizal fungi in a temperate forest

NASA Astrophysics Data System (ADS)

Ouimette, A.; Ollinger, S. V.; Vadeboncoeur, M. A.; Hobbie, E. A.

2012-12-01

The capacity of temperate and boreal forests to grow and sequester carbon (C) is limited by the amount of available nitrogen (N) in soils. While the importance of N to carbon storage is well known, we lack a thorough understanding of the mechanisms of N acquisition and the belowground carbon investment required for trees to compete for N. Resolving these uncertainties is critical for predicting future carbon budgets, given expected changes in climate, N deposition, atmospheric CO2, and tree species distribution. Some of the greatest uncertainties surrounding belowground C-N interactions involve the symbiotic fungi that serve as an interface between trees and various forms of N they acquire. Nearly all temperate and boreal forest trees have associations with one of two types of fungi: ectomycorrhizal (ECM) or arbuscular mycorrhizal (AM) fungi. Both types of fungi provide trees with soil nitrogen and other nutrients necessary for growth and in return receive carbon (sugars) from trees. Understanding the differences between these fungal groups is important because they differ dramatically in their carbon requirements and in their ability to access different forms of N. ECM fungi have higher carbon demand, more extensive hyphae (fungal roots), and much stronger capabilities to break down soil organic matter than AM fungi. Despite their importance in the terrestrial C cycle, mycorrhizal fungi are distinctly absent from forest ecosystem C and N models, primarily due to a lack of quantitative data on carbon allocation to mycorrhizal fungi in forests. Quantifying carbon allocation to mycorrhizal fungi is inherently difficult given their small (microscopic) size and lack of specific quantitative biomarkers. Here we present simple measurements that make use of natural abundance N stable isotope data (δ15N) of plant and soil pools, as well as forest C and N budget data, to provide estimates of C allocation to ECM fungi across temperate forest stands with a range of soil N availabilities and species composition. Results show that the fraction of NPP allocated to ECM fungi is related to soil N availability and tree functional type (coniferous vs. broadleaf). These estimates of C allocation will help parameterize ecosystem models to specifically include ECM fungi.

When microbes and consumers determine the limiting nutrient of autotrophs: a theoretical analysis

PubMed Central

Cherif, Mehdi; Loreau, Michel

2008-01-01

Ecological stoichiometry postulates that differential nutrient recycling of elements such as nitrogen and phosphorus by consumers can shift the element that limits plant growth. However, this hypothesis has so far considered the effect of consumers, mostly herbivores, out of their food-web context. Microbial decomposers are important components of food webs, and might prove as important as consumers in changing the availability of elements for plants. In this theoretical study, we investigate how decomposers determine the nutrient that limits plants, both by feeding on nutrients and organic carbon released by plants and consumers, and by being fed upon by omnivorous consumers. We show that decomposers can greatly alter the relative availability of nutrients for plants. The type of limiting nutrient promoted by decomposers depends on their own elemental composition and, when applicable, on their ingestion by consumers. Our results highlight the limitations of previous stoichiometric theories of plant nutrient limitation control, which often ignored trophic levels other than plants and herbivores. They also suggest that detrital chains play an important role in determining plant nutrient limitation in many ecosystems. PMID:18854301

Quantifying Fast and Slow Responses of Terrestrial Carbon Exchange across a Water Availability Gradient in North American Flux Sites

NASA Astrophysics Data System (ADS)

Biederman, J. A.; Scott, R. L.; Goulden, M.

2014-12-01

Climate change is predicted to increase the frequency and severity of water limitation, altering terrestrial ecosystems and their carbon exchange with the atmosphere. Here we compare site-level temporal sensitivity of annual carbon fluxes to interannual variations in water availability against cross-site spatial patterns over a network of 19 eddy covariance flux sites. This network represents one order of magnitude in mean annual productivity and includes western North American desert shrublands and grasslands, savannahs, woodlands, and forests with continuous records of 4 to 12 years. Our analysis reveals site-specific patterns not identifiable in prior syntheses that pooled sites. We interpret temporal variability as an indicator of ecosystem response to annual water availability due to fast-changing factors such as leaf stomatal response and microbial activity, while cross-site spatial patterns are used to infer ecosystem adjustment to climatic water availability through slow-changing factors such as plant community and organic carbon pools. Using variance decomposition, we directly quantify how terrestrial carbon balance depends on slow- and fast-changing components of gross ecosystem production (GEP) and total ecosystem respiration (TER). Slow factors explain the majority of variance in annual net ecosystem production (NEP) across the dataset, and their relative importance is greater at wetter, forest sites than desert ecosystems. Site-specific offsets from spatial patterns of GEP and TER explain one third of NEP variance, likely due to slow-changing factors not directly linked to water, such as disturbance. TER and GEP are correlated across sites as previously shown, but our site-level analysis reveals surprisingly consistent linear relationships between these fluxes in deserts and savannahs, indicating fast coupling of TER and GEP in more arid ecosystems. Based on the uncertainty associated with slow and fast factors, we suggest a framework for improved prediction of terrestrial carbon balance. We will also present results of ongoing work to quantify fast and slow contributions to the relationship between evapotranspiration and precipitation across a precipitation gradient.

Nutrient control of eukaryote cell growth: a systems biology study in yeast.

PubMed

Gutteridge, Alex; Pir, Pinar; Castrillo, Juan I; Charles, Philip D; Lilley, Kathryn S; Oliver, Stephen G

2010-05-24

To elucidate the biological processes affected by changes in growth rate and nutrient availability, we have performed a comprehensive analysis of the transcriptome, proteome and metabolome responses of chemostat cultures of the yeast, Saccharomyces cerevisiae, growing at a range of growth rates and in four different nutrient-limiting conditions. We find significant changes in expression for many genes in each of the four nutrient-limited conditions tested. We also observe several processes that respond differently to changes in growth rate and are specific to each nutrient-limiting condition. These include carbohydrate storage, mitochondrial function, ribosome synthesis, and phosphate transport. Integrating transcriptome data with proteome measurements allows us to identify previously unrecognized examples of post-transcriptional regulation in response to both nutrient and growth-rate signals. Our results emphasize the unique properties of carbon metabolism and the carbon substrate, the limitation of which induces significant changes in gene regulation at the transcriptional and post-transcriptional level, as well as altering how many genes respond to growth rate. By comparison, the responses to growth limitation by other nutrients involve a smaller set of genes that participate in specific pathways. See associated commentary http://www.biomedcentral.com/1741-7007/8/62.

What would optimal vegetation do when confronted with steadily increasing atmospheric CO2

NASA Astrophysics Data System (ADS)

Roderick, M. L.; Donohue, R. J.; Yang, Y.; McVicar, T.; Farquhar, G. D.

2015-12-01

The ongoing increase in atmospheric CO2 presents an interesting opportunity for primary producers. An increase in the substrate availability would, with all else equal, stimulate fixation of carbon from the atmosphere. But all else is not necessarily equal and this is only the beginning of a cascade of changes that can ultimately be traced back to the stomatal regulation of water-carbon exchanges. We first discuss theoretical expectations and then deduce how vegetation might respond to changing CO2 in water- and energy-limited environments. We then use satellite observations to test the theoretical expectations.

Thermodynamically controlled preservation of organic carbon in floodplains

NASA Astrophysics Data System (ADS)

Boye, Kristin; Noël, Vincent; Tfaily, Malak M.; Bone, Sharon E.; Williams, Kenneth H.; Bargar, John R.; Fendorf, Scott

2017-06-01

Organic matter decomposition in soils and terrestrial sediments has a prominent role in the global carbon cycle. Carbon stocks in anoxic environments, such as wetlands and the subsurface of floodplains, are large and presumed to decompose slowly. The degree of microbial respiration in anoxic environments is typically thought to depend on the energetics of available terminal electron acceptors such as nitrate or sulfate; microbes couple the reduction of these compounds to the oxidation of organic carbon. However, it is also possible that the energetics of the organic carbon itself can determine whether it is decomposed. Here we examined water-soluble organic carbon by Fourier-transform ion-cyclotron-resonance mass spectrometry to compare the chemical composition and average nominal oxidation state of carbon--a metric reflecting whether microbial oxidation of organic matter is thermodynamically favourable--in anoxic (sulfidic) and oxic (non-sulfidic) floodplain sediments. We observed distinct minima in the average nominal oxidation state of water-soluble carbon in sediments exhibiting anoxic, sulfate-reducing conditions, suggesting preservation of carbon compounds with nominal oxidation states below the threshold that makes microbial sulfate reduction thermodynamically favourable. We conclude that thermodynamic limitations constitute an important complement to other mechanisms of carbon preservation, such as enzymatic restrictions and mineral association, within anaerobic environments.

Carbon-Based Regenerable Sorbents for the Combined Carbon Dioxide and Ammonia Removal for the Primary Life Support System (PLSS)

NASA Technical Reports Server (NTRS)

Wojtowicz, Marek A.; Cosgrove, Joseph E.; Serio, Michael A.; Manthina, Venkata; Singh, Prabhakar; Chullen, Cinda

2014-01-01

Results are presented on the development of reversible sorbents for the combined carbon dioxide and trace-contaminant (TC) removal for use in Extravehicular Activities (EVAs). Since ammonia is the most important TC to be captured, data on TC sorption presented in this paper are limited to ammonia, with results relevant to other TCs to be reported at a later time. The currently available life support systems use separate units for carbon dioxide, trace contaminants, and moisture control, and the long-term objective is to replace the above three modules with a single one. Furthermore, the current TC-control technology involves the use of a packed bed of acid-impregnated granular charcoal, which is non-regenerable, and the carbon-based sorbent under development in this project can be regenerated by exposure to vacuum at room temperature. The objective of this study was to demonstrate the feasibility of using carbon sorbents for the reversible, concurrent sorption of carbon dioxide and ammonia. Several carbon sorbents were fabricated and tested, and multiple adsorption/vacuum-regeneration cycles were demonstrated at room temperature, and also a carbon surface conditioning technique that enhances the combined carbon dioxide and ammonia sorption without impairing sorbent regeneration.

Nitrogen limitation, 15N tracer retention, and growth response in intact and Bromus tectorum-invaded Artemisia tridentata ssp. wyomingensis communities

USGS Publications Warehouse

Witwicki, Dana L.; Doescher, Paul S.; Pyke, David A.; DeCrappeo, Nicole M.; Perakis, Steven S.

2012-01-01

Annual grass invasion into shrub-dominated ecosystems is associated with changes in nutrient cycling that may alter nitrogen (N) limitation and retention. Carbon (C) applications that reduce plant-available N have been suggested to give native perennial vegetation a competitive advantage over exotic annual grasses, but plant community and N retention responses to C addition remain poorly understood in these ecosystems. The main objectives of this study were to (1) evaluate the degree of N limitation of plant biomass in intact versus B. tectorum-invaded sagebrush communities, (2) determine if plant N limitation patterns are reflected in the strength of tracer 15N retention over two growing seasons, and (3) assess if the strength of plant N limitation predicts the efficacy of carbon additions intended to reduce soil N availability and plant growth. Labile C additions reduced biomass of exotic annual species; however, growth of native A. tridentata shrubs also declined. Exotic annual and native perennial plant communities had divergent responses to added N, with B. tectorum displaying greater ability to use added N to rapidly increase aboveground biomass, and native perennials increasing their tissue N concentration but showing little growth response. Few differences in N pools between the annual and native communities were detected. In contrast to expectations, however, more 15N was retained over two growing seasons in the invaded annual grass than in the native shrub community. Our data suggest that N cycling in converted exotic annual grasslands of the northern Intermountain West, USA, may retain N more strongly than previously thought.

Nutrient availability constrains the hydraulic architecture and water relations of savannah trees.

Treesearch

S.J. Bucci; F.G. Scholz; G. Goldstein; F.C. Meinzer; A.C. Franco; P.I. Campanello; R. Villalobos-Vega; M. Bustamante; F. Miralles-Wilhelm

2006-01-01

Several plant functional traits were studied in five dominant woody savanna species in a Brazilian savanna to determine whether removal of nutrient limitations has an effect on carbon allocation, water relations, and hydraulic architecture. Four treatments consisting of a control, and nitrogen (N), phosphorus (P), and N plus P additions were maintained for 5 years....

Climate-mediated nitrogen and carbon dynamics in a tropical watershed

NASA Astrophysics Data System (ADS)

Ballantyne, A. P.; Baker, P. A.; Fritz, S. C.; Poulter, B.

2011-06-01

Climate variability affects the capacity of the biosphere to assimilate and store important elements, such as nitrogen and carbon. Here we present biogeochemical evidence from the sediments of tropical Lake Titicaca indicating that large hydrologic changes in response to global glacial cycles during the Quaternary were accompanied by major shifts in ecosystem state. During prolonged glacial intervals, lake level was high and the lake was in a stable nitrogen-limited state. In contrast, during warm dry interglacials lake level fell and rates of nitrogen concentrations increased by a factor of 4-12, resulting in a fivefold to 24-fold increase in organic carbon concentrations in the sediments due to increased primary productivity. Observed periods of increased primary productivity were also associated with an apparent increase in denitrification. However, the net accumulation of nitrogen during interglacial intervals indicates that increased nitrogen supply exceeded nitrogen losses due to denitrification, thereby causing increases in primary productivity. Although primary productivity in tropical ecosystems, especially freshwater ecosystems, tends to be nitrogen limited, our results indicate that climate variability may lead to changes in nitrogen availability and thus changes in primary productivity. Therefore some tropical ecosystems may shift between a stable state of nitrogen limitation and a stable state of nitrogen saturation in response to varying climatic conditions.

A highly resilient mesoporous SiOx lithium storage material engineered by oil-water templating.

PubMed

Park, Eunjun; Park, Min-Sik; Lee, Jaewoo; Kim, Ki Jae; Jeong, Goojin; Kim, Jung Ho; Kim, Young-Jun; Kim, Hansu

2015-02-01

Mesoporous silicon-based materials gained considerable attention as high-capacity lithium-storage materials. However, the practical use is still limited by the complexity and limited number of available synthetic routes. Here, we report carbon-coated porous SiOx as high capacity lithium storage material prepared by using a sol-gel reaction of hydrogen silsesquioxane and oil-water templating. A hydrophobic oil is employed as a pore former inside the SiOx matrix and a precursor for carbon coating on the SiOx . The anode exhibits a high capacity of 730 mAh g(-1) and outstanding cycling performance over 100 cycles without significant dimensional changes. Carbon-coated porous SiOx also showed highly stable thermal reliability comparable to that of graphite. These promising properties come from the mesopores in the SiOx matrix, which ensures reliable operation of lithium storage in SiOx . The scalable sol-gel process presented here can open up a new avenue for the versatile preparation of porous SiOx lithium storage materials. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Nitrate ammonification in mangrove soils: a hidden source of nitrite?

PubMed Central

Balk, Melike; Laverman, Anniet M.; Keuskamp, Joost A.; Laanbroek, Hendrikus J.

2015-01-01

Nitrate reduction is considered to be a minor microbial pathway in the oxidation of mangrove-derived organic matter due to a limited supply of nitrate in mangrove soils. At a limited availability of this electron acceptor compared to the supply of degradable carbon, nitrate ammonification is thought to be the preferential pathway of nitrate reduction. Mangrove forest mutually differ in their productivity, which may lead to different available carbon to nitrate ratios in their soil. Hence, nitrate ammonification is expected to be of more importance in high- compared to low-productive forests. The hypothesis was tested in flow-through reactors that contain undisturbed mangrove soils from high-productive Avicennia germinans and Rhizophora mangle forests in Florida and low-productive Avicennia marina forests in Saudi Arabia. Nitrate was undetectable in the soils from both regions. It was assumed that a legacy of nitrate ammonification would be reflected by a higher ammonium production from these soils upon the addition of nitrate. Unexpectedly, the soils from the low-productive forests in Saudi Arabia produced considerably more ammonium than the soils from the high-productive forests in Florida. Hence, other environmental factors than productivity must govern the selection of nitrate ammonification or denitrification. A rather intriguing observation was the 1:1 production of nitrite and ammonium during the consumption of nitrate, more or less independent from sampling region, location, sampling depth, mangrove species and from the absence or presence of additional degradable carbon. This 1:1 ratio points to a coupled production of ammonium and nitrite by one group of nitrate-reducing microorganisms. Such a production of nitrite will be hidden by the presence of active nitrite-reducing microorganisms under the nitrate-limited conditions of most mangrove forest soils. PMID:25784903

Nitrate ammonification in mangrove soils: a hidden source of nitrite?

PubMed

Balk, Melike; Laverman, Anniet M; Keuskamp, Joost A; Laanbroek, Hendrikus J

2015-01-01

Nitrate reduction is considered to be a minor microbial pathway in the oxidation of mangrove-derived organic matter due to a limited supply of nitrate in mangrove soils. At a limited availability of this electron acceptor compared to the supply of degradable carbon, nitrate ammonification is thought to be the preferential pathway of nitrate reduction. Mangrove forest mutually differ in their productivity, which may lead to different available carbon to nitrate ratios in their soil. Hence, nitrate ammonification is expected to be of more importance in high- compared to low-productive forests. The hypothesis was tested in flow-through reactors that contain undisturbed mangrove soils from high-productive Avicennia germinans and Rhizophora mangle forests in Florida and low-productive Avicennia marina forests in Saudi Arabia. Nitrate was undetectable in the soils from both regions. It was assumed that a legacy of nitrate ammonification would be reflected by a higher ammonium production from these soils upon the addition of nitrate. Unexpectedly, the soils from the low-productive forests in Saudi Arabia produced considerably more ammonium than the soils from the high-productive forests in Florida. Hence, other environmental factors than productivity must govern the selection of nitrate ammonification or denitrification. A rather intriguing observation was the 1:1 production of nitrite and ammonium during the consumption of nitrate, more or less independent from sampling region, location, sampling depth, mangrove species and from the absence or presence of additional degradable carbon. This 1:1 ratio points to a coupled production of ammonium and nitrite by one group of nitrate-reducing microorganisms. Such a production of nitrite will be hidden by the presence of active nitrite-reducing microorganisms under the nitrate-limited conditions of most mangrove forest soils.

Soil fertility limits carbon sequestration by forest ecosystems in a CO2-enriched atmosphere

Treesearch

Ram Oren; David S. Ellsworth; Kurt H. Johnsen; Nathan Phillips; Brent E. Ewers; Chris Maier; Karina V.R. Schafer; Heather McCarthy; George Hendrey; Steven G. McNulty; Gabriel G. Katul

2001-01-01

Northern mid-latitude forests are a large terrestrial carbon sink. Ignoring nutrient limitations, large increases in carbon sequestration from carbon dioxide (CO2) fertilization are expected in these forests. Yet, forests are usually relegated to sites of moderate to poor fertility, where tree growth is often limited by nutrient supply, in...

Plant Nitrogen Uptake in Terrestrial Biogeochemical Models

NASA Astrophysics Data System (ADS)

Marti, Alejandro; Cox, Peter; Sitch, Stephen; Jones, Chris; Liddicoat, spencer

2013-04-01

Most terrestrial biogeochemical models featured in the last Intergovernmental Panel on Climate Change (IPPC) Assessment Report highlight the importance of the terrestrial Carbon sequestration and feedbacks between the terrestrial Carbon cycle and the climate system. However, these models have been criticized for overestimating predicted Carbon sequestration and its potential climate feedback when calculating the rate of future climate change because they do not account for the Carbon sequestration constraints caused by nutrient limitation, particularly Nitrogen (N). This is particularly relevant considering the existence of a substantial deficit of Nitrogen for plants in most areas of the world. To date, most climate models assume that plants have access to as much Nitrogen as needed, but ignore the nutrient requirements for new vegetation growth. Determining the natural demand and acquisition for Nitrogen and its associated resource optimization is key when accounting for the Carbon sequestration constrains caused by nutrient limitation. The few climate models that include C-N dynamics have illustrated that the stimulation of plant growth over the coming century may be two to three times smaller than previously predicted. This reduction in growth is partially offset by an increase in the availability of nutrients resulting from an accelerated rate of decomposition of dead plants and other organic matter that occurring with a rise in temperature. However, this offset does not counterbalance the reduced level of plant growth calculated by natural nutrient limitations. Additionally, Nitrogen limitation is also expected to become more pronounced in some ecosystems as atmospheric CO2 concentration increases; resulting in less new growth and higher atmospheric CO2 concentrations than originally expected. This study compares alternative models of plant N uptake as found in different terrestrial biogeochemical models against field measurements, and introduces a new N-uptake model to the Joint UK Land Environment Simulator (JULES).. Acknowledgements This work has been funded by the European Commission FP7-PEOPLE-ITN-2008 Marie Curie Action: "Greencycles II: FP7-PEOPLE-ITN-2008 Marie Curie Action: "Networks for Initial Training"

Calcification in a marginal sea - influence of seawater [Ca2+] and carbonate chemistry on bivalve shell formation

NASA Astrophysics Data System (ADS)

Thomsen, Jörn; Ramesh, Kirti; Sanders, Trystan; Bleich, Markus; Melzner, Frank

2018-03-01

In estuarine coastal systems such as the Baltic Sea, mussels suffer from low salinity which limits their distribution. Anthropogenic climate change is expected to cause further desalination which will lead to local extinctions of mussels in the low saline areas. It is commonly accepted that mussel distribution is limited by osmotic stress. However, along the salinity gradient, environmental conditions for biomineralization are successively becoming more adverse as a result of reduced [Ca2+] and dissolved inorganic carbon (CT) availability. In larvae, calcification is an essential process starting during early development with formation of the prodissoconch I (PD I) shell, which is completed under optimal conditions within 2 days. Experimental manipulations of seawater [Ca2+] start to impair PD I formation in Mytilus larvae at concentrations below 3 mM, which corresponds to conditions present in the Baltic at salinities below 8 g kg-1. In addition, lowering dissolved inorganic carbon to critical concentrations (< 1 mM) similarly affected PD I size, which was well correlated with calculated ΩAragonite and [Ca2+][HCO3-] / [H+] in all treatments. Comparing results for larvae from the western Baltic with a population from the central Baltic revealed a significantly higher tolerance of PD I formation to lowered [Ca2+] and [Ca2+][HCO3-] / [H+] in the low saline adapted population. This may result from genetic adaptation to the more adverse environmental conditions prevailing in the low saline areas of the Baltic. The combined effects of lowered [Ca2+] and adverse carbonate chemistry represent major limiting factors for bivalve calcification and can thereby contribute to distribution limits of mussels in the Baltic Sea.

CO2 and vitamin B12 interactions determine bioactive trace metal requirements of a subarctic Pacific diatom.

PubMed

King, Andrew L; Sañudo-Wilhelmy, Sergio A; Leblanc, Karine; Hutchins, David A; Fu, Feixue

2011-08-01

Phytoplankton growth can be limited by numerous inorganic nutrients and organic growth factors. Using the subarctic diatom Attheya sp. in culture studies, we examined how the availability of vitamin B(12) and carbon dioxide partial pressure (pCO(2)) influences growth rate, primary productivity, cellular iron (Fe), cobalt (Co), zinc (Zn) and cadmium (Cd) quotas, and the net use efficiencies (NUEs) of these bioactive trace metals (mol C fixed per mol cellular trace metal per day). Under B(12)-replete conditions, cells grown at high pCO(2) had lower Fe, Zn and Cd quotas, and used those trace metals more efficiently in comparison with cells grown at low pCO(2). At high pCO(2), B(12)-limited cells had ~50% lower specific growth and carbon fixation rates, and used Fe ~15-fold less efficiently, and Zn and Cd ~3-fold less efficiently, in comparison with B(12)-replete cells. The observed higher Fe, Zn and Cd NUE under high pCO(2)/B(12)-replete conditions are consistent with predicted downregulation of carbon-concentrating mechanisms. Co quotas of B(12)-replete cells were ∼5- to 14-fold higher in comparison with B(12)-limited cells, suggesting that >80% of cellular Co of B(12)-limited cells was likely from B(12). Our results demonstrate that CO(2) and vitamin B(12) interactively influence growth, carbon fixation, trace metal requirements and trace metal NUE of this diatom. This suggests the need to consider complex feedback interactions between multiple environmental factors for this biogeochemically critical group of phytoplankton in the last glacial maximum as well as the current and future changing ocean.

Disrupted carbon cycling in restored and unrestored urban streams: Critical timescales and controls

USGS Publications Warehouse

Larsen, L. G.; Harvey, Judson

2017-01-01

Carbon fixation and respiration in flowing waterways play significant roles in global and regional carbon budgets, yet how land use and watershed management interact with temporal disturbances (storms) to influence metabolism remains poorly understood. Here, we combine long-term with synoptic sampling of metabolism and its variable controls in neighboring watersheds of the Chesapeake Bay to resolve limiting factors and critical timescales associated with recovery from disturbance. We found that, relative to predictions of the river continuum concept, focal streams have “disrupted” carbon cycles, with carbon balances closer to zero, and, in some cases, tighter coupling between gross primary production (GPP) and ecosystem respiration (ER), attributable to carbon limitation. Carbon became limiting to ER where flashy storm hydrographs and simplified channel geomorphology inhibited accumulation of fine sediment. Shannon entropy analysis of timescales revealed that fine sediment served as a time-release capsule for nutrients and carbon over 4–6 months, fueling biogeochemical transformations. Loss of fines through hydraulic disturbance had up to 30-d impacts on GPP and 50-d impacts on ER in the stream with carbon limitation. In contrast, where GPP and ER were not tightly coupled, recovery occurred within 1 d. Results suggest that a complex interplay between nutrient and carbon limitation and mechanical and chemical disturbance governs patterns and consequences of disrupted carbon cycling in urban streams. Carbon limitation and tight GPP/ER coupling enhance the vulnerability of stream ecosystem functions, but best management practices that target stormflow reduction and channel geomorphic diversity can break that coupling and minimize carbon cycle disruptions.

Carbon availability triggers the decomposition of plant litter and assimilation of nitrogen by an ectomycorrhizal fungus

PubMed Central

Rineau, F; Shah, F; Smits, M M; Persson, P; Johansson, T; Carleer, R; Troein, C; Tunlid, A

2013-01-01

The majority of nitrogen in forest soils is found in organic matter–protein complexes. Ectomycorrhizal fungi (EMF) are thought to have a key role in decomposing and mobilizing nitrogen from such complexes. However, little is known about the mechanisms governing these processes, how they are regulated by the carbon in the host plant and the availability of more easily available forms of nitrogen sources. Here we used spectroscopic analyses and transcriptome profiling to examine how the presence or absence of glucose and/or ammonium regulates decomposition of litter material and nitrogen mobilization by the ectomycorrhizal fungus Paxillus involutus. We found that the assimilation of nitrogen and the decomposition of the litter material are triggered by the addition of glucose. Glucose addition also resulted in upregulation of the expression of genes encoding enzymes involved in oxidative degradation of polysaccharides and polyphenols, peptidases, nitrogen transporters and enzymes in pathways of the nitrogen and carbon metabolism. In contrast, the addition of ammonium to organic matter had relatively minor effects on the expression of transcripts and the decomposition of litter material, occurring only when glucose was present. On the basis of spectroscopic analyses, three major types of chemical modifications of the litter material were observed, each correlated with the expression of specific sets of genes encoding extracellular enzymes. Our data suggest that the expression of the decomposition and nitrogen assimilation processes of EMF can be tightly regulated by the host carbon supply and that the availability of inorganic nitrogen as such has limited effects on saprotrophic activities. PMID:23788332

40 CFR Table 3 to Subpart Jjjjjj... - Operating Limits for Boilers With Emission Limits

Code of Federal Regulations, 2012 CFR

2012-07-01

... performance test demonstrating compliance with the PM emission limitation. 4. Dry sorbent or carbon injection control Maintain the sorbent or carbon injection rate at or above the lowest 2-hour average sorbent flow... emissions limitation. When your boiler operates at lower loads, multiply your sorbent or carbon injection...

Evaluation of coral reef carbonate production models at a global scale

NASA Astrophysics Data System (ADS)

Jones, N. S.; Ridgwell, A.; Hendy, E. J.

2015-03-01

Calcification by coral reef communities is estimated to account for half of all carbonate produced in shallow water environments and more than 25% of the total carbonate buried in marine sediments globally. Production of calcium carbonate by coral reefs is therefore an important component of the global carbon cycle; it is also threatened by future global warming and other global change pressures. Numerical models of reefal carbonate production are needed for understanding how carbonate deposition responds to environmental conditions including atmospheric CO2 concentrations in the past and into the future. However, before any projections can be made, the basic test is to establish model skill in recreating present-day calcification rates. Here we evaluate four published model descriptions of reef carbonate production in terms of their predictive power, at both local and global scales. We also compile available global data on reef calcification to produce an independent observation-based data set for the model evaluation of carbonate budget outputs. The four calcification models are based on functions sensitive to combinations of light availability, aragonite saturation (Ωa) and temperature and were implemented within a specifically developed global framework, the Global Reef Accretion Model (GRAM). No model was able to reproduce independent rate estimates of whole-reef calcification, and the output from the temperature-only based approach was the only model to significantly correlate with coral-calcification rate observations. The absence of any predictive power for whole reef systems, even when consistent at the scale of individual corals, points to the overriding importance of coral cover estimates in the calculations. Our work highlights the need for an ecosystem modelling approach, accounting for population dynamics in terms of mortality and recruitment and hence calcifier abundance, in estimating global reef carbonate budgets. In addition, validation of reef carbonate budgets is severely hampered by limited and inconsistent methodology in reef-scale observations.

Integrated core-log petrofacies analysis in the construction of a reservoir geomodel: A case study of a mature Mississippian carbonate reservoir using limited data

USGS Publications Warehouse

Bhattacharya, S.; Doveton, J.H.; Carr, T.R.; Guy, W.R.; Gerlach, P.M.

2005-01-01

Small independent operators produce most of the Mississippian carbonate fields in the United States mid-continent, where a lack of integrated characterization studies precludes maximization of hydrocarbon recovery. This study uses integrative techniques to leverage extant data in an Osagian and Meramecian (Mississippian) cherty carbonate reservoir in Kansas. Available data include petrophysical logs of varying vintages, limited number of cores, and production histories from each well. A consistent set of assumptions were used to extract well-level porosity and initial saturations, from logs of different types and vintages, to build a geomodel. Lacking regularly recorded well shut-in pressures, an iterative technique, based on material balance formulations, was used to estimate average reservoir-pressure decline that matched available drillstem test data and validated log-analysis assumptions. Core plugs representing the principal reservoir petrofacies provide critical inputs for characterization and simulation studies. However, assigning plugs among multiple reservoir petrofacies is difficult in complex (carbonate) reservoirs. In a bottom-up approach, raw capillary pressure (Pc) data were plotted on the Super-Pickett plot, and log- and core-derived saturation-height distributions were reconciled to group plugs by facies, to identify core plugs representative of the principal reservoir facies, and to discriminate facies in the logged interval. Pc data from representative core plugs were used for effective pay evaluation to estimate water cut from completions, in infill and producing wells, and guide-selective perforations for economic exploitation of mature fields. The results from this study were used to drill 22 infill wells. Techniques demonstrated here can be applied in other fields and reservoirs. Copyright ?? 2005. The American Association of Petroleum Geologists. All rights reserved.

Design of activated carbon/activated carbon asymmetric capacitors

NASA Astrophysics Data System (ADS)

Piñeiro-Prado, Isabel; Salinas-Torres, David; Ruiz Rosas, Ramiro; Morallon, Emilia; Cazorla-Amoros, Diego

2016-03-01

Supercapacitors are energy storage devices that offer a high power density and a low energy density in comparison with batteries. Their limited energy density can be overcome by using asymmetric configuration in mass electrodes, where each electrode works within their maximum available potential window, rendering the maximum voltage output of the system. Such asymmetric capacitors must be optimized through careful electrochemical characterization of the electrodes for accurate determination of the capacitance and the potential stability limits. The results of the characterization are then used for optimizing mass ratio of the electrodes from the balance of stored charge. The reliability of the design largely depends on the approach taken for the electrochemical characterization. Therefore, the performance could be lower than expected and even the system could break down, if a well thought out procedure is not followed. In this work, a procedure for the development of asymmetric supercapacitors based on activated carbons is detailed. Three activated carbon materials with different textural properties and surface chemistry have been systematically characterized in neutral aqueous electrolyte. The asymmetric configuration of the masses of both electrodes in the supercapacitor has allowed to cover a higher potential window, resulting in an increase of the energy density of the three devices studied when compared with the symmetric systems, and an improved cycle life.

Alkali injection system with controlled CO.sub.2 /O.sub.2 ratios for combustion of coal

DOEpatents

Berry, Gregory F.

1988-01-01

A high temperature combustion process for an organic fuel containing sulfur n which the nitrogen of air is replaced by carbon dioxide for combination with oxygen with the ratio of CO.sub.2 /O.sub.2 being controlled to generate combustion temperatures above 2000 K. for a gas-gas reaction with SO.sub.2 and an alkali metal compound to produce a sulfate and in which a portion of the carbon-dioxide rich gas is recycled for mixing with oxygen and/or for injection as a cooling gas upstream from heating exchangers to limit fouling of the exchangers, with the remaining carbon-dioxide rich gas being available as a source of CO.sub.2 for oil recovery and other purposes.

Methane Post-Processing for Oxygen Loop Closure

NASA Technical Reports Server (NTRS)

Greenwood, Zachary W.; Abney, Morgan B.; Miller, Lee

2016-01-01

State-of-the-art United States Atmospheric Revitalization carbon dioxide (CO2) reduction is based on the Sabatier reaction process, which recovers approximately 50% of the oxygen (O2) from crew metabolic CO2. Oxygen recovery from carbon dioxide is constrained by the limited availability of reactant hydrogen. Post-processing of methane to recover hydrogen with the Umpqua Research Company Plasma Pyrolysis Assembly (PPA) has the potential to further close the Atmospheric Revitalization oxygen loop. The PPA decomposes methane into hydrogen and hydrocarbons, predominantly acetylene, and a small amount of solid carbon. The hydrogen must then be purified before it can be recycled for additional oxygen recovery. Long duration testing and evaluation of a four crew-member sized PPA and a discussion of hydrogen recycling system architectures are presented.

Single-wall nanohorn structure and distribution of incorporated materials

NASA Astrophysics Data System (ADS)

Maigne, Alan; Gloter, Alexandre; Ajima, Kumiko; Colliex, Christian; Iijima, Sumio

2005-03-01

Single-wall carbon nanohorns (SWNHs) are unique spherical-aggregates of single-wall carbon quasi-nanotubes. So far, the observable area has been limited to the aggregate surfaces. We studied core-region structure with TEM using thickness measurement method, EELS, and EDS, and found that carbon density was uniform over the whole aggregate. This result allows to modelize the core-region and to clarify previous models of SWNHs. We used same tools to investigate the incorporation of materials such as fullerenes or platinium compounds. We found that particles can even be incorporated in the core-region and that their distribution in the aggregate depends on their concentration. The information available with these models should be useful in the study of SWNH applications to, for example, drug delivery system.

Two decades of warming increases diversity of a potentially lignolytic bacterial community

PubMed Central

Pold, Grace; Melillo, Jerry M.; DeAngelis, Kristen M.

2015-01-01

As Earth's climate warms, the massive stores of carbon found in soil are predicted to become depleted, and leave behind a smaller carbon pool that is less accessible to microbes. At a long-term forest soil-warming experiment in central Massachusetts, soil respiration and bacterial diversity have increased, while fungal biomass and microbially-accessible soil carbon have decreased. Here, we evaluate how warming has affected the microbial community's capability to degrade chemically-complex soil carbon using lignin-amended BioSep beads. We profiled the bacterial and fungal communities using PCR-based methods and completed extracellular enzyme assays as a proxy for potential community function. We found that lignin-amended beads selected for a distinct community containing bacterial taxa closely related to known lignin degraders, as well as members of many genera not previously noted as capable of degrading lignin. Warming tended to drive bacterial community structure more strongly in the lignin beads, while the effect on the fungal community was limited to unamended beads. Of those bacterial operational taxonomic units (OTUs) enriched by the warming treatment, many were enriched uniquely on lignin-amended beads. These taxa may be contributing to enhanced soil respiration under warming despite reduced readily available C availability. In aggregate, these results suggest that there is genetic potential for chemically complex soil carbon degradation that may lead to extended elevated soil respiration with long-term warming. PMID:26042112

Predominant role of water in regulating the tree-growth response to diurnal asymmetric warmin

NASA Astrophysics Data System (ADS)

Chen, Z.; Xia, J.; Cui, E.

2017-12-01

Growth of the Northern Hemisphere trees is affected by diurnal asymmetric warming, which is generally considered to touch off carbon assimilation and increment of carbon storage. Asymmetric effects of diurnal warming on vegetation greenness were validated in previous researches, however, the effect of diurnal warming on wood tissue which stores most carbon of a whole plant is still unknown. Here, we combined ring-width index (RWI), remote sensing-based normalized difference vegetation index (NDVI) and climate datasets to detect the effects of daytime and night-time warming on vegetation growth, respectively. Our results indicate that daytime warming enhances NDVI but has neutral effect on tree woody growth over the Northern Hemisphere. Response of wood growth to daytime warming is linearly regulated by soil water availability. The underlying mechanism of different response of canopy and wood growth to daytime warming may attribute to the biomass change, that is, allocation to foliage tissues increased at the expense of wood tissue under warming and water-limited conditions. Night-time warming show neutral effects on NDVI and RWI over the Northern Hemisphere, and the neutral Tmin-NDVI correlations result from the non-linear mediation of soil water availability. Our results highlight the current greening trend under daytime warming does not mean higher carbon sink capacity, the warming-drying climate may impair the large carbon sink of global forests.

Mycorrhiza-mediated competition between plants and decomposers drives soil carbon storage.

PubMed

Averill, Colin; Turner, Benjamin L; Finzi, Adrien C

2014-01-23

Soil contains more carbon than the atmosphere and vegetation combined. Understanding the mechanisms controlling the accumulation and stability of soil carbon is critical to predicting the Earth's future climate. Recent studies suggest that decomposition of soil organic matter is often limited by nitrogen availability to microbes and that plants, via their fungal symbionts, compete directly with free-living decomposers for nitrogen. Ectomycorrhizal and ericoid mycorrhizal (EEM) fungi produce nitrogen-degrading enzymes, allowing them greater access to organic nitrogen sources than arbuscular mycorrhizal (AM) fungi. This leads to the theoretical prediction that soil carbon storage is greater in ecosystems dominated by EEM fungi than in those dominated by AM fungi. Using global data sets, we show that soil in ecosystems dominated by EEM-associated plants contains 70% more carbon per unit nitrogen than soil in ecosystems dominated by AM-associated plants. The effect of mycorrhizal type on soil carbon is independent of, and of far larger consequence than, the effects of net primary production, temperature, precipitation and soil clay content. Hence the effect of mycorrhizal type on soil carbon content holds at the global scale. This finding links the functional traits of mycorrhizal fungi to carbon storage at ecosystem-to-global scales, suggesting that plant-decomposer competition for nutrients exerts a fundamental control over the terrestrial carbon cycle.

An optimization model for carbon capture & storage/utilization vs. carbon trading: A case study of fossil-fired power plants in Turkey.

PubMed

Ağralı, Semra; Üçtuğ, Fehmi Görkem; Türkmen, Burçin Atılgan

2018-06-01

We consider fossil-fired power plants that operate in an environment where a cap and trade system is in operation. These plants need to choose between carbon capture and storage (CCS), carbon capture and utilization (CCU), or carbon trading in order to obey emissions limits enforced by the government. We develop a mixed-integer programming model that decides on the capacities of carbon capture units, if it is optimal to install them, the transportation network that needs to be built for transporting the carbon captured, and the locations of storage sites, if they are decided to be built. Main restrictions on the system are the minimum and maximum capacities of the different parts of the pipeline network, the amount of carbon that can be sold to companies for utilization, and the capacities on the storage sites. Under these restrictions, the model aims to minimize the net present value of the sum of the costs associated with installation and operation of the carbon capture unit and the transportation of carbon, the storage cost in case of CCS, the cost (or revenue) that results from the emissions trading system, and finally the negative revenue of selling the carbon to other entities for utilization. We implement the model on General Algebraic Modeling System (GAMS) by using data associated with two coal-fired power plants located in different regions of Turkey. We choose enhanced oil recovery (EOR) as the process in which carbon would be utilized. The results show that CCU is preferable to CCS as long as there is sufficient demand in the EOR market. The distance between the location of emission and location of utilization/storage, and the capacity limits on the pipes are an important factor in deciding between carbon capture and carbon trading. At carbon prices over $15/ton, carbon capture becomes preferable to carbon trading. These results show that as far as Turkey is concerned, CCU should be prioritized as a means of reducing nation-wide carbon emissions in an environmentally and economically rewarding manner. The model developed in this study is generic, and it can be applied to any industry at any location, as long as the required inputs are available. Copyright © 2018 Elsevier Ltd. All rights reserved.

Nutrient Limitation of Microbial Mediated Decomposition and Arctic Soil Chronology

NASA Astrophysics Data System (ADS)

Melle, C. J.; Darrouzet-Nardi, A.; Wallenstein, M. D.

2012-12-01

Soils of northern permafrost regions currently contain twice as much carbon as the entire Earth's atmosphere. Traditionally, environmental constraints have limited microbial activity resulting in restricted decomposition of soil organic matter in these systems and accumulation of massive amounts of soil organic carbon (SOC), however climate change is reducing the constraints of decomposition in arctic permafrost regions. Carbon cycling in nutrient poor, arctic ecosystems is tightly coupled to other biogeochemical cycles. Several studies have suggested strong nitrogen limitations of primary productivity and potentially warm-season microbial activity in these nutrient deficient soils. Nitrogen is required for microbial extracellular enzyme production which drives the decomposition of soil organic matter (SOM). Nitrogen limited arctic soils may also experience limitation via labile carbon availability despite the SOM rich environment due to low extracellular enzyme production. Few studies have directly addressed nutrient induced microbial limitation in SOC rich arctic tundra soils, and even less is known about the potential for nutrient co-limitation. Additionally, through the process of becoming deglaciated, sites within close proximity to one another may have experienced drastic differences in their effective soil ages due to the varied length of their active histories. Many soil properties and nutrient deficiencies are directly related to soil age, however this chronology has not previously been a focus of research on nutrient limitation of arctic soil microbial activity. Understanding of nutrient limitations, as well as potential co-limitation, on arctic soil microbial activity has important implications for carbon cycling and the ultimate fate of the current arctic SOC reservoir. Analyses of nutrient limitation on soils of a single site are not adequate for fully understanding the controls on soil microbial activity across a vast land mass with large variation in effective soil age. My research is focused on addressing the questions of the extent of microbial N limitation in arctic tundra soils, the potential for co-limitation of labile C despite a high SOC environment, and the dependence, if any, nutrient limitation may have on the effective age of the soil. I have addressed these questions by conducting a laboratory soil incubation of factorial design with treatments of amended glucose, amended ammonium nitrate, and a control consisting of an addition of an equivalent volume of deionized water. Moist acid tundra soils possessing similar soil properties from two arctic sites of close proximity yet with varying deglaciation chronologies were utilized in my study. Soil properties of C-mineralization via respiration, microbial biomass, and nitrogen content in the forms of ammonium, nitrate, and total free amino acids and microbial extra-cellular enzyme production were assayed to determine the microbial response to the experimental treatments. Through the results of this work, I hope to better our understanding of biogeochemical cycling within arctic tundra ecosystems and the response to climate change by contributing to existing knowledge of nutrient limitation on microbial mediated decomposition of SOC in the arctic and how this may differ in soils of varying effective age.

Nitrate removal, communities of denitrifiers and adverse effects in different carbon substrates for use in denitrification beds

PubMed Central

Warneke, Sören; Schipper, Louis A.; Matiasek, Michael G.; Scow, Kate M.; Cameron, Stewart; Bruesewitz, Denise A.; McDonald, Ian R.

2012-01-01

Denitrification beds are containers filled with wood by-products that serve as a carbon and energy source to denitrifiers, which reduce nitrate ( NO3−) from point source discharges into non-reactive dinitrogen (N2) gas. This study investigates a range of alternative carbon sources and determines rates, mechanisms and factors controlling NO3− removal, denitrifying bacterial community, and the adverse effects of these substrates. Experimental barrels (0.2 m3) filled with either maize cobs, wheat straw, green waste, sawdust, pine woodchips or eucalyptus woodchips were incubated at 16.8 °C or 27.1 °C (outlet temperature), and received NO3− enriched water (14.38 mg N L−1 and 17.15 mg N L−1). After 2.5 years of incubation measurements were made of NO3−−N removal rates, in vitro denitrification rates (DR), factors limiting denitrification (carbon and nitrate availability, dissolved oxygen, temperature, pH, and concentrations of NO3−, nitrite and ammonia), copy number of nitrite reductase (nirS and nirK ) and nitrous oxide reductase (nosZ ) genes, and greenhouse gas production (dissolved nitrous oxide (N2O) and methane), and carbon (TOC) loss. Microbial denitrification was the main mechanism for NO3−−N removal. Nitrate–N removal rates ranged from 1.3 (pine woodchips) to 6.2 g N m−3 d−1 (maize cobs), and were predominantly limited by C availability and temperature (Q10 = 1.2) when NO3−−N outlet concentrations remained above 1 mg L−1. The NO3−−N removal rate did not depend directly on substrate type, but on the quantity of microbially available carbon, which differed between carbon sources. The abundance of denitrifying genes (nirS, nirK and nosZ ) was similar in replicate barrels under cold incubation, but varied substantially under warm incubation, and between substrates. Warm incubation enhanced growth of nirS containing bacteria and bacteria that lacked the nosZ gene, potentially explaining the greater N2O emission in warmer environments. Maize cob substrate had the highest NO3−−N removal rate, but adverse effects include TOC release, dissolved N2O release and substantial carbon consumption by non-denitrifiers. Wood-chips removed less than half of NO3− removed by maize cobs, but provided ideal conditions for denitrifying bacteria, and adverse effects were not observed. Therefore we recommend the combination of maize cobs and woodchips to enhance NO3− removal while minimizing adverse effects in denitrification beds. PMID:21880343

Proxies for soil organic carbon derived from remote sensing

NASA Astrophysics Data System (ADS)

Rasel, S. M. M.; Groen, T. A.; Hussin, Y. A.; Diti, I. J.

2017-07-01

The possibility of carbon storage in soils is of interest because compared to vegetation it contains more carbon. Estimation of soil carbon through remote sensing based techniques can be a cost effective approach, but is limited by available methods. This study aims to develop a model based on remotely sensed variables (elevation, forest type and above ground biomass) to estimate soil carbon stocks. Field observations on soil organic carbon, species composition, and above ground biomass were recorded in the subtropical forest of Chitwan, Nepal. These variables were also estimated using LiDAR data and a WorldView 2 image. Above ground biomass was estimated from the LiDAR image using a novel approach where the image was segmented to identify individual trees, and for these trees estimates of DBH and Height were made. Based on AIC (Akaike Information Criterion) a regression model with above ground biomass derived from LiDAR data, and forest type derived from WorldView 2 imagery was selected to estimate soil organic carbon (SOC) stocks. The selected model had a coefficient of determination (R2) of 0.69. This shows the scope of estimating SOC with remote sensing derived variables in sub-tropical forests.

Changes in Root Decomposition Rates Across Soil Depths

NASA Astrophysics Data System (ADS)

Hicks Pries, C.; Porras, R. C.; Castanha, C.; Torn, M. S.

2016-12-01

Over half of global soil organic carbon (SOC) is stored in subsurface soils (>30 cm). Turnover times of soil organic carbon (SOC) increases with depth as evidenced by radiocarbon ages of 1,000 to more than 10,000 years in many deep soil horizons but the reasons for this increase are unclear. Many factors that potentially control SOC decomposition change with depth such as increased protection of SOC in aggregates or organo-mineral complexes and increased spatial heterogeneity of SOC "hotspots" like roots, which limit the accessibility of SOC to microbes. Lower concentrations of organic matter at depth may inhibit microbial activity due to energy limitation, and the microbial community itself changes with depth. To investigate how SOC decomposition differs with depth, we inserted a 13C-labeled fine root substrate into three depths (15, 50, and 90 cm) in a coniferous forest Alfisol and measured the root carbon remaining in particulate (>2 mm), bulk (< 2mm), free light, and mineral soil fractions over 2.5 years. We also characterized how the microbial community and SOC changed with depth. Initial rates of decomposition were unaffected by soil depth—50% of root carbon was lost from all depths within the first year. However, after 2.5 years, decomposition rates were affected by soil depth with only 15% of the root carbon remaining at 15 cm while 35% remained at 90 cm. Microbial communities, based on phospholipid fatty acid analysis, changed with depth—fungal biomarkers decreased whereas actinomycetes biomarkers increased. However, the preferences of different microbial groups for the 13C-labeled root carbon were consistent with depth. In contrast, the amount of mineral-associated SOC did not change with depth. Thus, decreased decomposition rates in this deep soil are not due to mineral associations limiting SOC availability, but may instead be due to changes in microbial communities, particularly in the microbes needed to carry out the later stages of root decomposition.

Coupling and uncoupling of triglyceride and beta-carotene production by Dunaliella salina under nitrogen limitation and starvation.

PubMed

Bonnefond, Hubert; Moelants, Nina; Talec, Amélie; Mayzaud, Patrick; Bernard, Olivier; Sciandra, Antoine

2017-01-01

Nitrogen starvation and limitation are known to induce important physiological changes especially in lipid metabolism of microalgae (triglycerides, membrane lipids, beta-carotene, etc.). Although little information is available for Dunaliella salina , it is a promising microalga for biofuel production and biotechnological applications due to its ability to accumulate lipid together with beta-carotene. Batch and chemostat experiments with various degrees of nitrogen limitation, ranging from starvation to nitrogen-replete conditions, were carried out to study carbon storage dynamics (total carbon, lipids, and beta-carotene) in steady state cultures of D. salina . A new protocol was developed in order to manage the very high beta-carotene concentrations and to more accurately separate and quantify beta-carotene and triglycerides by chromatography. Biomass evolution was appropriately described by the Droop model on the basis of the nitrogen quota dynamics. Triglycerides and beta-carotene were both strongly anti-correlated with nitrogen quota highlighting their carbon sink function in nitrogen depletion conditions. Moreover, these two valuable molecules were correlated each other for nitrogen replete conditions or moderated nitrogen limitations (N:C ratio higher than 0.04). Under nitrogen starvation, i.e., for very low N:C ratio, the dynamic revealed, for the first time, uncoupled part (higher triglyceride accumulation than beta-carotene), possibly because of shortage in key proteins involved in the stabilization of lipid droplets. This study motivates the accurate control of the microalgal nitrogen quota in order to optimize lipid productivity.

Contextualizing Wetlands Within a River Network to Assess Nitrate Removal and Inform Watershed Management

NASA Astrophysics Data System (ADS)

Czuba, Jonathan A.; Hansen, Amy T.; Foufoula-Georgiou, Efi; Finlay, Jacques C.

2018-02-01

Aquatic nitrate removal depends on interactions throughout an interconnected network of lakes, wetlands, and river channels. Herein, we present a network-based model that quantifies nitrate-nitrogen and organic carbon concentrations through a wetland-river network and estimates nitrate export from the watershed. This model dynamically accounts for multiple competing limitations on nitrate removal, explicitly incorporates wetlands in the network, and captures hierarchical network effects and spatial interactions. We apply the model to the Le Sueur Basin, a data-rich 2,880 km2 agricultural landscape in southern Minnesota and validate the model using synoptic field measurements during June for years 2013-2015. Using the model, we show that the overall limits to nitrate removal rate via denitrification shift between nitrate concentration, organic carbon availability, and residence time depending on discharge, characteristics of the waterbody, and location in the network. Our model results show that the spatial context of wetland restorations is an important but often overlooked factor because nonlinearities in the system, e.g., deriving from switching of resource limitation on denitrification rate, can lead to unexpected changes in downstream biogeochemistry. Our results demonstrate that reduction of watershed-scale nitrate concentrations and downstream loads in the Le Sueur Basin can be most effectively achieved by increasing water residence time (by slowing the flow) rather than by increasing organic carbon concentrations (which may limit denitrification). This framework can be used toward assessing where and how to restore wetlands for reducing nitrate concentrations and loads from agricultural watersheds.

Energy limitation of cyanophage development: implications for marine carbon cycling.

PubMed

Puxty, Richard J; Evans, David J; Millard, Andrew D; Scanlan, David J

2018-05-01

Marine cyanobacteria are responsible for ~25% of the fixed carbon that enters the ocean biosphere. It is thought that abundant co-occurring viruses play an important role in regulating population dynamics of cyanobacteria and thus the cycling of carbon in the oceans. Despite this, little is known about how viral infections 'play-out' in the environment, particularly whether infections are resource or energy limited. Photoautotrophic organisms represent an ideal model to test this since available energy is modulated by the incoming light intensity through photophosphorylation. Therefore, we exploited phototrophy of the environmentally relevant marine cyanobacterium Synechococcus and monitored growth of a cyanobacterial virus (cyanophage). We found that light intensity has a marked effect on cyanophage infection dynamics, but that this is not manifest by a change in DNA synthesis. Instead, cyanophage development appears energy limited for the synthesis of proteins required during late infection. We posit that acquisition of auxiliary metabolic genes (AMGs) involved in light-dependent photosynthetic reactions acts to overcome this limitation. We show that cyanophages actively modulate expression of these AMGs in response to light intensity and provide evidence that such regulation may be facilitated by a novel mechanism involving light-dependent splicing of a group I intron in a photosynthetic AMG. Altogether, our data offers a mechanistic link between diurnal changes in irradiance and observed community level responses in metabolism, i.e., through an irradiance-dependent, viral-induced release of dissolved organic matter (DOM).

Pathways to Carbon-Negative Liquid Biofuels

NASA Astrophysics Data System (ADS)

Woolf, D.; Lehmann, J.

2017-12-01

Many climate change mitigation scenarios assume that atmospheric carbon dioxide removal will be delivered at scale using bioenergy power generation with carbon capture and storage (BECCS). However, other pathways to negative emission technologies (NETs) in the energy sector are possible, but have received relatively little attention. Given that the costs, benefits and life-cycle emissions of technologies vary widely, more comprehensive analyses of the policy options for NETs are critical. This study provides a comparative assessment of the potential pathways to carbon-negative liquid biofuels. It is often assumed that that decarbonisation of the transport sector will include use of liquid biofuels, particularly for applications that are difficult to electrify such as aviation and maritime transport. However, given that biomass and land on which to grow it sustainably are limiting factors in the scaling up of both biofuels and NETs, these two strategies compete for shared factors of production. One way to circumvent this competition is carbon-negative biofuels. Because capture of exhaust CO2 in the transport sector is impractical, this will likely require carbon capture during biofuel production. Potential pathways include, for example, capture of CO2 from fermentation, or sequestration of biochar from biomass pyrolysis in soils, in combination with thermochemical or bio-catalytic conversion of syngas to alcohols or alkanes. Here we show that optimal pathway selection depends on specific resource constraints. As land availability becomes increasingly limiting if bioenergy is scaled up—particularly in consideration that abandoned degraded land is widely considered to be an important resource that does not compete with food fiber or habitat—then systems which enhance land productivity by increasing soil fertility using soil carbon sequestration become increasingly preferable compared to bioenergy systems that deplete or degrade the land resource on which they depend.

Effect of nitrate, organic carbon, and temperature on potential denitrification rates in nitrate-rich riverbed sediments

USGS Publications Warehouse

Pfenning, K.S.; McMahon, P.B.

1997-01-01

A study conducted in 1994 as part of the US Geological Survey's National Water-Quality Assessment Program, South Platte River Basin investigation, examined the effect of certain environmental factors on potential denitrification rates in nitrate-rich riverbed sediments. The acetylene block technique was used to measure nitrous oxide (N2O) production rates in laboratory incubations of riverbed sediments to evaluate the effect of varying nitrate concentrations, organic carbon concentrations and type, and water temperature on potential denitrification rates. Sediment incubations amended with nitrate, at concentrations ranging from 357 to 2142 ??mol l-1 (as measured in the field), produced no significant increase (P > 0.05) in N2O production rates, indicating that the denitrification potential in these sediments was not nitrate limited. In contrast, incubations amended with acetate as a source of organic carbon, at concentrations ranging from 0 to 624 ??mol l-1, produced significant increases (P < 0.05) in N2O production rates with increased organic carbon concentration, indicating that the denitrification potential in these sediments was organic carbon limited. Furthermore, N2O production rates also were affected by the type of organic carbon available as an electron donor. Acetate and surface-water-derived fulvic acid supported higher N2O production rates than groundwater-derived fulvic acid or sedimentary organic carbon. Lowering incubation temperatures from 22 to 4??C resulted in about a 77% decrease in the N2O production rates. These results help to explain findings from previous studies indicating that only 15-30% of nitrate in groundwater was denitrified before discharging to the South Platte River and that nitrate concentrations in the river generally were higher in winter than in summer.

Fabrication and modeling of electrochemical double-layer capacitors using carbon nano-onion electrode structures

NASA Astrophysics Data System (ADS)

Parigi, Fabio

Electrochemical capacitors or ultracapacitors (UCs) that are commercially available today overcome battery limitations in terms of charging time (from tens of minutes to seconds) and limited lifetime (from a few thousand cycles up to more than one million) but still lack specific energy and energy density (2-5% of a lithium ion battery). The latest innovations in carbon nanomaterials, such as carbon nanotubes as an active electrode material for UCs, can provide up to five times as much energy and deliver up to seven times more power than today's activated carbon electrodes. Further improvements in UC power density have been achieved by using state-of-the-art carbon nano-onions (CNOs) for ultracapacitor electrodes. CNO UCs could exhibit up to five times the power density of single-wall CNT UCs and could substantially contribute to reducing the size of an energy storage system as well as the volume and weight, thus improving device performance. This dissertation describes the fabrication of CNO electrodes as part of an UC device, the measurement and analysis of the new electrode's performance as an energy storage component, and development of a new circuit model that accurately describes the CNO UC electrical behavior. The novel model is based on the impedance spectra of CNO UCs and cyclic voltammetry measurements. Further, the model was validated using experimental data and simulation. My original contributions are the fabrication process for reliable and repeatable electrode fabrication and the modeling of a carbon nano-onion ultracapacitor. The carbon nano-onion ultracapacitor model, composed of a resistor, an inductor, a capacitor (RLC), and a constant phase element (CPE), was developed along with a parameter extraction procedure for the benefit of other users. The new model developed, proved to be more accurate than previously reported UC models.

Mining Genomes of Marine Cyanobacteria for Elements of Zinc Homeostasis

PubMed Central

Barnett, James P.; Millard, Andrew; Ksibe, Amira Z.; Scanlan, David J.; Schmid, Ralf; Blindauer, Claudia Andrea

2012-01-01

Zinc is a recognized essential element for the majority of organisms, and is indispensable for the correct function of hundreds of enzymes and thousands of regulatory proteins. In aquatic photoautotrophs including cyanobacteria, zinc is thought to be required for carbonic anhydrase and alkaline phosphatase, although there is evidence that at least some carbonic anhydrases can be cambialistic, i.e., are able to acquire in vivo and function with different metal cofactors such as Co2+ and Cd2+. Given the global importance of marine phytoplankton, zinc availability in the oceans is likely to have an impact on both carbon and phosphorus cycles. Zinc concentrations in seawater vary over several orders of magnitude, and in the open oceans adopt a nutrient-like profile. Most studies on zinc handling by cyanobacteria have focused on freshwater strains and zinc toxicity; much less information is available on marine strains and zinc limitation. Several systems for zinc homeostasis have been characterized in the freshwater species Synechococcus sp. PCC 7942 and Synechocystis sp. PCC 6803, but little is known about zinc requirements or zinc handling by marine species. Comparative metallo-genomics has begun to explore not only the putative zinc proteome, but also specific protein families predicted to have an involvement in zinc homeostasis, including sensors for excess and limitation (SmtB and its homologs as well as Zur), uptake systems (ZnuABC), putative intracellular zinc chaperones (COG0523) and metallothioneins (BmtA), and efflux pumps (ZiaA and its homologs). PMID:22514551

Using landsat time-series and lidar to inform aboveground carbon baseline estimation in Minnesota

Treesearch

Ram K. Deo; Grant M. Domke; Matthew B. Russell; Christopher W. Woodall; Michael J. Falkowski

2015-01-01

Landsat data has long been used to support forest monitoring and management decisions despite the limited success of passive optical remote sensing for accurate estimation of structural attributes such as aboveground biomass. The archive of publicly available Landsat images dating back to the 1970s can be used to predict historic forest biomass dynamics. In addition,...

The hydraulic limitation hypothesis revisited.

PubMed

Ryan, Michael G; Phillips, Nathan; Bond, Barbara J

2006-03-01

We proposed the hydraulic limitation hypothesis (HLH) as a mechanism to explain universal patterns in tree height, and tree and stand biomass growth: height growth slows down as trees grow taller, maximum height is lower for trees of the same species on resource-poor sites and annual wood production declines after canopy closure for even-aged forests. Our review of 51 studies that measured one or more of the components necessary for testing the hypothesis showed that taller trees differ physiologically from shorter, younger trees. Stomatal conductance to water vapour (g(s)), photosynthesis (A) and leaf-specific hydraulic conductance (K L) are often, but not always, lower in taller trees. Additionally, leaf mass per area is often greater in taller trees, and leaf area:sapwood area ratio changes with tree height. We conclude that hydraulic limitation of gas exchange with increasing tree size is common, but not universal. Where hydraulic limitations to A do occur, no evidence supports the original expectation that hydraulic limitation of carbon assimilation is sufficient to explain observed declines in wood production. Any limit to height or height growth does not appear to be related to the so-called age-related decline in wood production of forests after canopy closure. Future work on this problem should explicitly link leaf or canopy gas exchange with tree and stand growth, and consider a more fundamental assumption: whether tree biomass growth is limited by carbon availability.

Model-experiment interaction to improve representation of phosphorus limitation in land models

NASA Astrophysics Data System (ADS)

Norby, R. J.; Yang, X.; Cabugao, K. G. M.; Childs, J.; Gu, L.; Haworth, I.; Mayes, M. A.; Porter, W. S.; Walker, A. P.; Weston, D. J.; Wright, S. J.

2015-12-01

Carbon-nutrient interactions play important roles in regulating terrestrial carbon cycle responses to atmospheric and climatic change. None of the CMIP5 models has included routines to represent the phosphorus (P) cycle, although P is commonly considered to be the most limiting nutrient in highly productive, lowland tropical forests. Model simulations with the Community Land Model (CLM-CNP) show that inclusion of P coupling leads to a smaller CO2 fertilization effect and warming-induced CO2 release from tropical ecosystems, but there are important uncertainties in the P model, and improvements are limited by a dearth of data. Sensitivity analysis identifies the relative importance of P cycle parameters in determining P availability and P limitation, and thereby helps to define the critical measurements to make in field campaigns and manipulative experiments. To improve estimates of P supply, parameters that describe maximum amount of labile P in soil and sorption-desorption processes are necessary for modeling the amount of P available for plant uptake. Biochemical mineralization is poorly constrained in the model and will be improved through field observations that link root traits to mycorrhizal activity, phosphatase activity, and root depth distribution. Model representation of P demand by vegetation, which currently is set by fixed stoichiometry and allometric constants, requires a different set of data. Accurate carbon cycle modeling requires accurate parameterization of the photosynthetic machinery: Vc,max and Jmax. Relationships between the photosynthesis parameters and foliar nutrient (N and P) content are being developed, and by including analysis of covariation with other plant traits (e.g., specific leaf area, wood density), we can provide a basis for more dynamic, trait-enabled modeling. With this strong guidance from model sensitivity and uncertainty analysis, field studies are underway in Puerto Rico and Panama to collect model-relevant data on P supply and demand functions. New FACE and soil warming experiments in P-limited ecosystems in subtropical Australia, and tropical Brazil, Puerto Rico, and Panama will provide important benchmarks for the performance of P-enabled models under future conditions.

Soil Organic Matter recovery on eroding alluvial surfaces on Iceland

NASA Astrophysics Data System (ADS)

Kuhn, N. J.; Würsch, M.; Hunziker, M.; Şórsson, J.

2012-04-01

Soil Erosion has been assessed to have no significant effect on greenhouse gas releases due to the balance between decomposition, burial, and uptake from the atmosphere through photosynthesis by vegetation and subsequent litter decomposition. The validity of the "zero-emission" balance of soil erosion is limited to sites where vegetation growth is not limited by soil degradation. In this study, the recovery of soil organic matter on sites subject to severe erosion and subsequent soil reclamation by the introduction of Lupinus nootkatensis is studied. Preliminary results indicate that the recovery is extremely slow (scale of decades). In particular, an incipient soil development, including the availability of freely available nitrogen, appear to limit the establishment of a closed vegetation cover. These results therefore indicate that in situations where land degradation leads to a complete destruction of the fertile soil layer, the assumption of dynamic replacement of eroded soil Carbon stocks cannot be applied.

Isotope fractionation during the anaerobic consumption of acetate by methanogenic and sulfate-reducing microorganisms

NASA Astrophysics Data System (ADS)

Gövert, D.; Conrad, R.

2009-04-01

During the anaerobic degradation of organic matter in anoxic sediments and soils acetate is the most important substrate for the final step in production of CO2 and/or CH4. Sulfate-reducing bacteria (SRB) and methane-producing archaea both compete for the available acetate. Knowledge about the fractionation of 13C/12C of acetate carbon by these microbial groups is still limited. Therefore, we determined carbon isotope fractionation in different cultures of acetate-utilizing SRB (Desulfobacter postgatei, D. hydrogenophilus, Desulfobacca acetoxidans) and methanogens (Methanosarcina barkeri, M. acetivorans). Including literature values (e.g., Methanosaeta concilii), isotopic enrichment factors (epsilon) ranged between -35 and +2 permil, possibly involving equilibrium isotope effects besides kinetic isotope effects. The values of epsilon were dependent on the acetate-catabolic pathway of the particular microorganism, the methyl or carboxyl position of acetate, and the relative availability or limitation of the substrate acetate. Patterns of isotope fractionation in anoxic lake sediments and rice field soil seem to reflect the characteristics of the microorganisms actively involved in acetate catabolism. Hence, it might be possible using environmental isotopic information to determine the type of microbial metabolism converting acetate to CO2 and/or CH4.

Optimal Plant Carbon Allocation Implies a Biological Control on Nitrogen Availability

NASA Astrophysics Data System (ADS)

Prentice, I. C.; Stocker, B. D.

2015-12-01

The degree to which nitrogen availability limits the terrestrial C sink under rising CO2 is a key uncertainty in carbon cycle and climate change projections. Results from ecosystem manipulation studies and meta-analyses suggest that plant C allocation to roots adjusts dynamically under varying degrees of nitrogen availability and other soil fertility parameters. In addition, the ratio of biomass production to GPP appears to decline under nutrient scarcity. This reflects increasing plant C exudation into the soil (Cex) with decreasing nutrient availability. Cex is consumed by an array of soil organisms and may imply an improvement of nutrient availability to the plant. Thus, N availability is under biological control, but incurs a C cost. In spite of clear observational support, this concept is left unaccounted for in Earth system models. We develop a model for the coupled cycles of C and N in terrestrial ecosystems to explore optimal plant C allocation under rising CO2 and its implications for the ecosystem C balance. The model follows a balanced growth approach, accounting for the trade-offs between leaf versus root growth and Cex in balancing C fixation and N uptake. We assume that Cex is proportional to root mass, and that the ratio of N uptake (Nup) to Cex is proportional to inorganic N concentration in the soil solution. We further assume that Cex is consumed by N2-fixing processes if the ratio of Nup:Cex falls below the inverse of the C cost of N2-fixation. Our analysis thereby accounts for the feedbacks between ecosystem C and N cycling and stoichiometry. We address the question of how the plant C economy will adjust under rising atmospheric CO2 and what this implies for the ecosystem C balance and the degree of N limitation.

Active Control of pH in the Bioculture System Through Carbon Dioxide Control

NASA Technical Reports Server (NTRS)

Monhollon, Luke; Pletcher, David; Hauss, Jessica

2016-01-01

For successful cell research, the growth culture environment must be tightly controlled. Deviance from the optimal conditions will mask the desired variable being analyzed or lead to inconstancies in the results. In standard laboratories, technology and procedures are readily available for the reliable control of variables such as temperature, pH, nutrient loading, and dissolved gases. Due to the nature of spaceflight, and the inherent constraints to engineering designs, these same elements become a challenge to maintain at stable values by both automated and manual approaches. Launch mass, volume, and power usage create significant constraints to cell culture systems; nonetheless, innovative solutions for active environmental controls are available. The acidity of the growth media cannot be measured through standard probes due to the degradation of electrodes and reliance on indicators for chromatography. Alternatively, carbon dioxide sensors are capable of monitoring the pH by leveraging the relationship between the partial pressure of carbon dioxide and carbonic acid in solution across a membrane. In microgravity cell growth systems, the gas delivery system can be used to actively maintain the media at the proper acidity by maintaining a suitable gas mixture around permeable tubing. Through this method, launch mass and volume are significantly reduced through the efficient use of the limited gas supply in orbit.

Personal Vehicles Evaluated against Climate Change Mitigation Targets.

PubMed

Miotti, Marco; Supran, Geoffrey J; Kim, Ella J; Trancik, Jessika E

2016-10-18

Meeting global climate change mitigation goals will likely require that transportation-related greenhouse gas emissions begin to decline within the next two decades and then continue to fall. A variety of vehicle technologies and fuels are commercially available to consumers today that can reduce the emissions of the transportation sector. Yet what are the best options, and do any suffice to meet climate policy targets? Here, we examine the costs and carbon intensities of 125 light-duty vehicle models on the U.S. market today and evaluate these models against U.S. emission-reduction targets for 2030, 2040, and 2050 that are compatible with the goal of limiting mean global temperature rise to 2 °C above preindustrial levels. Our results show that consumers are not required to pay more for a low-carbon-emitting vehicle. Across the diverse set of vehicle models and powertrain technologies examined, a clean vehicle is usually a low-cost vehicle. Although the average carbon intensity of vehicles sold in 2014 exceeds the climate target for 2030 by more than 50%, we find that most hybrid and battery electric vehicles available today meet this target. By 2050, only electric vehicles supplied with almost completely carbon-free electric power are expected to meet climate-policy targets.

Protistan Predation Affects Trichloroethene Biodegradation in a Bedrock Aquifer▿

PubMed Central

Cunningham, Joseph J.; Kinner, Nancy E.; Lewis, Maureen

2009-01-01

Despite extensive research on the bottom-up force of resource availability (e.g., electron donors and acceptors), slow biodegradation rates and stalling at cis-dichloroethene (cDCE) and vinyl chloride continue to be observed in aquifers contaminated with trichloroethene (TCE). The objective of this research was to gauge the impact of the top-down force of protistan predation on TCE biodegradation in laboratory microcosms. When indigenous bacteria from an electron donor-limited TCE-contaminated bedrock aquifer were present, the indigenous protists inhibited reductive dechlorination altogether. The presence of protists during organic carbon-amended conditions caused the bacteria to elongate (length:width, ≥10:1), but reductive dechlorination was still inhibited. When a commercially available dechlorinating bacterial culture and an organic carbon amendment were added in he presence of protists, the elongated bacteria predominated and reductive dechlorination stalled at cDCE. When protists were removed under organic carbon-amended conditions, reductive dechlorination stalled at cDCE, whereas in the presence organic carbon and bacterial amendments, the total chlorinated ethene concentration decreased, indicating TCE was converted to ethene and/or CO2. The data suggested that indigenous protists grazed dechlorinators to extremely low levels, inhibiting dechlorination altogether. Hence, in situ bioremediation/bioaugmentation may not be successful in mineralizing TCE unless the top-down force of protistan predation is inhibited. PMID:19820148

Control of leaf expansion: a developmental switch from metabolics to hydraulics.

PubMed

Pantin, Florent; Simonneau, Thierry; Rolland, Gaëlle; Dauzat, Myriam; Muller, Bertrand

2011-06-01

Leaf expansion is the central process by which plants colonize space, allowing energy capture and carbon acquisition. Water and carbon emerge as main limiting factors of leaf expansion, but the literature remains controversial about their respective contributions. Here, we tested the hypothesis that the importance of hydraulics and metabolics is organized according to both dark/light fluctuations and leaf ontogeny. For this purpose, we established the developmental pattern of individual leaf expansion during days and nights in the model plant Arabidopsis (Arabidopsis thaliana). Under control conditions, decreases in leaf expansion were observed at night immediately after emergence, when starch reserves were lowest. These nocturnal decreases were strongly exaggerated in a set of starch mutants, consistent with an early carbon limitation. However, low-light treatment of wild-type plants had no influence on these early decreases, implying that expansion can be uncoupled from changes in carbon availability. From 4 d after leaf emergence onward, decreases of leaf expansion were observed in the daytime. Using mutants impaired in stomatal control of transpiration as well as plants grown under soil water deficit or high air humidity, we gathered evidence that these diurnal decreases were the signature of a hydraulic limitation that gradually set up as the leaf developed. Changes in leaf turgor were consistent with this pattern. It is concluded that during the course of leaf ontogeny, the predominant control of leaf expansion switches from metabolics to hydraulics. We suggest that the leaf is better armed to buffer variations in the former than in the latter.

Control of Leaf Expansion: A Developmental Switch from Metabolics to Hydraulics1[W][OA

PubMed Central

Pantin, Florent; Simonneau, Thierry; Rolland, Gaëlle; Dauzat, Myriam; Muller, Bertrand

2011-01-01

Leaf expansion is the central process by which plants colonize space, allowing energy capture and carbon acquisition. Water and carbon emerge as main limiting factors of leaf expansion, but the literature remains controversial about their respective contributions. Here, we tested the hypothesis that the importance of hydraulics and metabolics is organized according to both dark/light fluctuations and leaf ontogeny. For this purpose, we established the developmental pattern of individual leaf expansion during days and nights in the model plant Arabidopsis (Arabidopsis thaliana). Under control conditions, decreases in leaf expansion were observed at night immediately after emergence, when starch reserves were lowest. These nocturnal decreases were strongly exaggerated in a set of starch mutants, consistent with an early carbon limitation. However, low-light treatment of wild-type plants had no influence on these early decreases, implying that expansion can be uncoupled from changes in carbon availability. From 4 d after leaf emergence onward, decreases of leaf expansion were observed in the daytime. Using mutants impaired in stomatal control of transpiration as well as plants grown under soil water deficit or high air humidity, we gathered evidence that these diurnal decreases were the signature of a hydraulic limitation that gradually set up as the leaf developed. Changes in leaf turgor were consistent with this pattern. It is concluded that during the course of leaf ontogeny, the predominant control of leaf expansion switches from metabolics to hydraulics. We suggest that the leaf is better armed to buffer variations in the former than in the latter. PMID:21474437

Linking FRRF Derived Photophysiology with Carbon-based Primary Productivity: Insights from Concepts of Cellular Energy Allocation

NASA Astrophysics Data System (ADS)

Schuback, N.; Schallenberg, C.; Duckham, C.; Flecken, M.; Maldonado, M. T.; Tortell, P. D.

2016-02-01

Active chlorophyll a fluorescence approaches, including fast repetition rate fluorometry (FRRF), have the potential to provide estimates of phytoplankton primary productivity at unprecedented spatial and temporal resolution. FRRF-derived productivity rates are based on estimates of charge separation in photosystem II (ETRRCII), which must be converted into ecologically relevant units of carbon fixation. Understanding sources of variability in the coupling of ETRRCII and carbon fixation provides important physiological insight into phytoplankton photosynthesis, and is critical for the application of FRRF as a primary productivity measurement tool. We present data from a series of experiments during which we simultaneously measured phytoplankton carbon fixation and ETRRCII in the iron-limited NE subarctic Pacific. Our results show significant variability of the derived conversion factor (Ve:C/nPSII), with highest values observed under conditions of excess excitation pressure at the level of photosystem II, caused by high light and/or low iron. Our results will be discussed in the context of metabolic plasticity, which evolved in phytoplankton to simultaneously maximize growth and provide photoprotection under fluctuating light and limiting nutrient availabilities. Because the derived conversion factor is associated with conditions of excess light, it correlates with the expression of non-photochemical quenching (NPQ) in the pigment antenna, also derived from FRRF measurements. Our results demonstrate a significant correlation between NPQ and the conversion factor Ve:C/nPSII, and the potential of this relationship to improve FRRF-based estimates of phytoplankton carbon fixation rates is discussed.

Modelling system dynamics and phytoplankton diversity at Ranchi lake using the carbon and nutrient mass balance equations.

PubMed

Mukherjee, B; Nivedita, M; Mukherjee, D

2014-05-01

Modelling system dynamics in a hyper-eutrophic lake is quite complex especially with a constant influx of detergents and sewage material which continually changes the state variables and interferes with the assessment of the chemical rhythm occurring in polluted conditions as compared to unpolluted systems. In this paper, a carbon and nutrient mass balance model for predicting system dynamics in a complex environment was studied. Studies were conducted at Ranchi lake to understand the altered environmental dynamics in hyper-eutrophic conditions, and its impact on the plankton community. The lake was monitored regularly for five years (2007 - 2011) and the data collected on the carbon flux, nitrates, phosphates and silicates was used to design a mass balance model for evaluating and predicting the system. The model was then used to correlate the chemical rhythm with that of the phytoplankton dynamics and diversity. Nitrates and phosphates were not limiting (mean nitrate and phosphate concentrations were 1.74 and 0.83 mgl⁻¹ respectively). Free carbon dioxide was found to control the system and, interacting with other parameters determined the diversity and dynamics of the plankton community. N/P ratio determined which group of phytoplankton dominated the community, above 5 it favoured the growth of chlorophyceae while below 5 cyanobacteria dominates. TOC/TIC ratio determined the abundance. The overall system was controlled by the availability of free carbon dioxide which served as a limiting factor.

Thermodynamically controlled preservation of organic carbon in floodplains

DOE PAGES

Boye, Kristin; Noel, Vincent; Tfaily, Malak M.; ...

2017-05-01

Organic matter decomposition in soils and terrestrial sediments has a prominent role in the global carbon cycle. Carbon stocks in anoxic environments, such as wetlands and the subsurface of floodplains, are large and presumed to decompose slowly. The degree of microbial respiration in anoxic environments is typically thought to depend on the energetics of available terminal electron acceptors such as nitrate or sulfate; microbes couple the reduction of these compounds to the oxidation of organic carbon. But, it is also possible that the energetics of the organic carbon itself can determine whether it is decomposed. We examined water-soluble organic carbonmore » by Fourier-transform ion-cyclotron-resonance mass spectrometry to compare the chemical composition and average nominal oxidation state of carbon—a metric reflecting whether microbial oxidation of organic matter is thermodynamically favourable—in anoxic (sulfidic) and oxic (non-sulfidic) floodplain sediments. We also observed distinct minima in the average nominal oxidation state of water-soluble carbon in sediments exhibiting anoxic, sulfate-reducing conditions, suggesting preservation of carbon compounds with nominal oxidation states below the threshold that makes microbial sulfate reduction thermodynamically favourable. Finally, we show that thermodynamic limitations constitute an important complement to other mechanisms of carbon preservation, such as enzymatic restrictions and mineral association, within anaerobic environments.« less

The leaching of inorganic species from activated carbons produced from waste tyre rubber.

PubMed

San Miguel, G; Fowler, G D; Sollars, C J

2002-04-01

Waste tyre rubber can be used as a precursor for the production of high quality activated carbons. However, there is concern that inorganic impurities present in the rubber feed may restrict their use in liquid phase applications with high purity requirements. This paper presents an investigation of the presence and the leaching of inorganic species from activated carbons derived from waste tyre rubber. For the purpose of this work, a number of carbons were produced, characterised for their BET surface area and analysed for their inorganic composition. Subsequently, a number of tests were performed to evaluate the leaching of different inorganic species into solution at various pH values and carbon doses. Results showed that rubber-derived carbons contained elevated concentrations of sulphur and zinc, as well as traces of other metals such as lead, cadmium, chromium and molybdenum. Inorganic levels were significantly affected by production conditions, particularly degree of carbon activation and the nature of the gasification agent. However, leaching tests showed that the availability of these species in neutral pH conditions was very limited. Results demonstrated that, when using carbons doses comparable to those employed in water treatment works, only sulphur levels exceeded, in some occasions, health based quality standards proposed for drinking water.

Increased tree carbon storage in response to nitrogen deposition in the US

NASA Astrophysics Data System (ADS)

Quinn Thomas, R.; Canham, Charles D.; Weathers, Kathleen C.; Goodale, Christine L.

2010-01-01

Human activities have greatly accelerated emissions of both carbon dioxide and biologically reactive nitrogen to the atmosphere. As nitrogen availability often limits forest productivity, it has long been expected that anthropogenic nitrogen deposition could stimulate carbon sequestration in forests. However, spatially extensive evidence for deposition-induced stimulation of forest growth has been lacking, and quantitative estimates from models and plot-level studies are controversial. Here, we use forest inventory data to examine the impact of nitrogen deposition on tree growth, survival and carbon storage across the northeastern and north-central USA during the 1980s and 1990s. We show a range of growth and mortality responses to nitrogen deposition among the region's 24 most common tree species. Nitrogen deposition (which ranged from 3 to 11kgha-1yr-1) enhanced the growth of 11 species and decreased the growth of 3 species. Nitrogen deposition enhanced growth of all tree species with arbuscular mycorrhizal fungi associations. In the absence of disturbances that reduced carbon stocks by more than 50%, above-ground biomass increment increased by 61kg of carbon per kg of nitrogen deposited, amounting to a 40% enhancement over pre-industrial conditions. Extrapolating to the globe, we estimate that nitrogen deposition could increase tree carbon storage by 0.31Pg carbon yr-1.

Thermodynamically controlled preservation of organic carbon in floodplains

DOE Office of Scientific and Technical Information (OSTI.GOV)

Boye, Kristin; Noel, Vincent; Tfaily, Malak M.

Organic matter decomposition in soils and terrestrial sediments has a prominent role in the global carbon cycle. Carbon stocks in anoxic environments, such as wetlands and the subsurface of floodplains, are large and presumed to decompose slowly. The degree of microbial respiration in anoxic environments is typically thought to depend on the energetics of available terminal electron acceptors such as nitrate or sulfate; microbes couple the reduction of these compounds to the oxidation of organic carbon. But, it is also possible that the energetics of the organic carbon itself can determine whether it is decomposed. We examined water-soluble organic carbonmore » by Fourier-transform ion-cyclotron-resonance mass spectrometry to compare the chemical composition and average nominal oxidation state of carbon—a metric reflecting whether microbial oxidation of organic matter is thermodynamically favourable—in anoxic (sulfidic) and oxic (non-sulfidic) floodplain sediments. We also observed distinct minima in the average nominal oxidation state of water-soluble carbon in sediments exhibiting anoxic, sulfate-reducing conditions, suggesting preservation of carbon compounds with nominal oxidation states below the threshold that makes microbial sulfate reduction thermodynamically favourable. Finally, we show that thermodynamic limitations constitute an important complement to other mechanisms of carbon preservation, such as enzymatic restrictions and mineral association, within anaerobic environments.« less

Atmospheric Entry Studies for Venus Missions: 45 Sphere-Cone Rigid Aeroshells and Ballistic Entries

NASA Technical Reports Server (NTRS)

Prabhu, Dinesh K.; Spilker, Thomas R.; Allen, Gary A., Jr.; Hwang, Helen H.; Cappuccio, Gelsomina; Moses, Robert W.

2013-01-01

The present study considers direct ballistic entries into the atmosphere of Venus using a 45deg sphere-cone rigid aeroshell, a legacy shape that has been used successfully in the past in the Pioneer Venus Multiprobe Mission. For a number of entry mass and heatshield diameter combinations (i.e., various ballistic coefficients) and entry velocities, the trajectory space in terms of entry flight path angles between skip out and -30deg is explored with a 3DoF trajectory code, TRAJ. From these trajectories, the viable entry flight path angle space is determined through the use of mechanical and thermal performance limits on the thermal protection material and science payload; the thermal protection material of choice is entry-grade carbon phenolic, for which a material thermal response model is available. For mechanical performance, a 200 g limit is placed on the peak deceleration load experienced by the science instruments, and 10 bar is assumed as the pressure limit for entry-grade carbon-phenolic material. For thermal performance, inflection points in the total heat load distribution are used as cut off criteria. Analysis of the results shows the existence of a range of critical ballistic coefficients beyond which the steepest possible entries are determined by the pressure limit of the material rather than the deceleration load limit.

Tropical wetlands: A missing link in the global carbon cycle?

PubMed Central

Sjögersten, Sofie; Black, Colin R; Evers, Stephanie; Hoyos-Santillan, Jorge; Wright, Emma L; Turner, Benjamin L

2014-01-01

Tropical wetlands are not included in Earth system models, despite being an important source of methane (CH4) and contributing a large fraction of carbon dioxide (CO2) emissions from land use, land use change, and forestry in the tropics. This review identifies a remarkable lack of data on the carbon balance and gas fluxes from undisturbed tropical wetlands, which limits the ability of global change models to make accurate predictions about future climate. We show that the available data on in situ carbon gas fluxes in undisturbed forested tropical wetlands indicate marked spatial and temporal variability in CO2 and CH4 emissions, with exceptionally large fluxes in Southeast Asia and the Neotropics. By upscaling short-term measurements, we calculate that approximately 90 ± 77 Tg CH4 year−1 and 4540 ± 1480 Tg CO2 year−1 are released from tropical wetlands globally. CH4 fluxes are greater from mineral than organic soils, whereas CO2 fluxes do not differ between soil types. The high CO2 and CH4 emissions are mirrored by high rates of net primary productivity and litter decay. Net ecosystem productivity was estimated to be greater in peat-forming wetlands than on mineral soils, but the available data are insufficient to construct reliable carbon balances or estimate gas fluxes at regional scales. We conclude that there is an urgent need for systematic data on carbon dynamics in tropical wetlands to provide a robust understanding of how they differ from well-studied northern wetlands and allow incorporation of tropical wetlands into global climate change models. PMID:26074666

Achieving deep cuts in the carbon intensity of U.S. automobile transportation by 2050: complementary roles for electricity and biofuels.

PubMed

Scown, Corinne D; Taptich, Michael; Horvath, Arpad; McKone, Thomas E; Nazaroff, William W

2013-08-20

Passenger cars in the United States (U.S.) rely primarily on petroleum-derived fuels and contribute the majority of U.S. transportation-related greenhouse gas (GHG) emissions. Electricity and biofuels are two promising alternatives for reducing both the carbon intensity of automotive transportation and U.S. reliance on imported oil. However, as standalone solutions, the biofuels option is limited by land availability and the electricity option is limited by market adoption rates and technical challenges. This paper explores potential GHG emissions reductions attainable in the United States through 2050 with a county-level scenario analysis that combines ambitious plug-in hybrid electric vehicle (PHEV) adoption rates with scale-up of cellulosic ethanol production. With PHEVs achieving a 58% share of the passenger car fleet by 2050, phasing out most corn ethanol and limiting cellulosic ethanol feedstocks to sustainably produced crop residues and dedicated crops, we project that the United States could supply the liquid fuels needed for the automobile fleet with an average blend of 80% ethanol (by volume) and 20% gasoline. If electricity for PHEV charging could be supplied by a combination of renewables and natural-gas combined-cycle power plants, the carbon intensity of automotive transport would be 79 g CO2e per vehicle-kilometer traveled, a 71% reduction relative to 2013.

A time resolved metabolomics study: the influence of different carbon sources during growth and starvation of Bacillus subtilis.

PubMed

Meyer, Hanna; Weidmann, Hendrikje; Mäder, Ulrike; Hecker, Michael; Völker, Uwe; Lalk, Michael

2014-07-01

In its natural environment, the soil, the Gram-positive model bacterium Bacillus subtilis frequently encounters nutrient limitation and other stress factors. Efficient adaptation mechanisms are necessary to cope with this wide range of environmental challenges. The ability to utilize diverse carbon sources represents a key adaptation process that allows B. subtilis to thrive in its natural habitat. To gain a comprehensive insight into the metabolism of B. subtilis, global metabolite analyses were performed during growth with glucose alone or glucose with either malate, fumarate or citrate as carbon/energy sources. Furthermore, to achieve a comprehensive coverage of a wide range of chemically different metabolites, complementary GC-MS, LC-MS and (1)H-NMR analyses were applied. This study reveals that the availability of different carbon sources results in different extracellular metabolite profiles whereas a regulated intracellular metabolite equilibrium was observed. In addition, the typical energy-starvation induced activation of the general stress sigma factor σ(B) was only observed upon entry into the stationary phase with glucose or glucose and malate as carbon sources.

Model-based analysis of environmental controls over ecosystem primary production in an alpine tundra dry meadow

DOE PAGES

Fan, Zhaosheng; Neff, Jason C.; Wieder, William R.

2016-02-10

We investigated several key limiting factors that control alpine tundra productivity by developing an ecosystem biogeochemistry model. The model simulates the coupled cycling of carbon (C), nitrogen (N), and phosphorus (P) and their interactions with gross primary production (GPP). It was parameterized with field observations from an alpine dry meadow ecosystem using a global optimization strategy to estimate the unknown parameters. The model, along with the estimated parameters, was first validated against independent data and then used to examine the environmental controls over plant productivity. Our results show that air temperature is the strongest limiting factor to GPP in themore » early growing season, N availability becomes important during the middle portion of the growing season, and soil moisture is the strongest limiting factors by late in the growing season. Overall, the controls over GPP during the growing season, from strongest to weakest, are soil moisture content, air temperature, N availability, and P availability. This simulation provides testable predictions of the shifting nature of physical and nutrient limitations on plant growth. The model also indicates that changing environmental conditions in the alpine will likely lead to changes in productivity. For example, warming eliminates the control of P availability on GPP and makes N availability surpass air temperature to become the second strongest limiting factor. In contrast, an increase in atmospheric nutrient deposition eliminates the control of N availability and enhances the importance of P availability. Furthermore, these analyses provide a quantitative and conceptual framework that can be used to test predictions and refine ecological analyses at this long-term ecological research site.« less

Model-based analysis of environmental controls over ecosystem primary production in an alpine tundra dry meadow

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fan, Zhaosheng; Neff, Jason C.; Wieder, William R.

We investigated several key limiting factors that control alpine tundra productivity by developing an ecosystem biogeochemistry model. The model simulates the coupled cycling of carbon (C), nitrogen (N), and phosphorus (P) and their interactions with gross primary production (GPP). It was parameterized with field observations from an alpine dry meadow ecosystem using a global optimization strategy to estimate the unknown parameters. The model, along with the estimated parameters, was first validated against independent data and then used to examine the environmental controls over plant productivity. Our results show that air temperature is the strongest limiting factor to GPP in themore » early growing season, N availability becomes important during the middle portion of the growing season, and soil moisture is the strongest limiting factors by late in the growing season. Overall, the controls over GPP during the growing season, from strongest to weakest, are soil moisture content, air temperature, N availability, and P availability. This simulation provides testable predictions of the shifting nature of physical and nutrient limitations on plant growth. The model also indicates that changing environmental conditions in the alpine will likely lead to changes in productivity. For example, warming eliminates the control of P availability on GPP and makes N availability surpass air temperature to become the second strongest limiting factor. In contrast, an increase in atmospheric nutrient deposition eliminates the control of N availability and enhances the importance of P availability. Furthermore, these analyses provide a quantitative and conceptual framework that can be used to test predictions and refine ecological analyses at this long-term ecological research site.« less

40 CFR 60.34b - Emission guidelines for municipal waste combustor operating practices.

Code of Federal Regulations, 2010 CFR

2010-07-01

... approval, a State plan shall include emission limits for carbon monoxide at least as protective as the emission limits for carbon monoxide listed in table 3 of this subpart. table 3 provides emission limits for the carbon monoxide concentration level for each type of designated facility. (b) For approval, a...

Simultaneous tracking of drug molecules and carriers using aptamer-functionalized fluorescent superstable gold nanorod-carbon nanocapsules during thermo-chemotherapy

NASA Astrophysics Data System (ADS)

Wang, Xue-Wei; Gao, Wei; Fan, Huanhuan; Ding, Ding; Lai, Xiao-Fang; Zou, Yu-Xiu; Chen, Long; Chen, Zhuo; Tan, Weihong

2016-04-01

Controlling and monitoring the drug delivery process is critical to its intended therapeutic function. Many nanocarrier systems for drug delivery have been successfully developed. However, biocompatibility, stability, and simultaneously tracing drugs and nanocarriers present significant limitations. Herein, we have fabricated a multifunctional nanocomposite by coating the gold nanorod (AuNR) with a biocompatible, superstable and fluorescent carbon layer, obtaining the AuNR@carbon core-shell nanocapsule. In this system, the carbon shell, originally obtained in aqueous glucose solutions and, therefore, biocompatible in physiological environments, could be simply loaded with cell-specific aptamers and therapeutic molecules through π-π interactions, a useful tool for cancer-targeted cellular imaging and therapy. Moreover, such a stable and intrinsic fluorescence effect of the AuNR@carbon enabled simultaneous tracking of released therapeutic molecules and nanocarriers under thermo-chemotherapy. The AuNR@carbons had high surface areas and stable shells, as well as unique optical and photothermal properties, making them promising nanostructures for biomedical applications.Controlling and monitoring the drug delivery process is critical to its intended therapeutic function. Many nanocarrier systems for drug delivery have been successfully developed. However, biocompatibility, stability, and simultaneously tracing drugs and nanocarriers present significant limitations. Herein, we have fabricated a multifunctional nanocomposite by coating the gold nanorod (AuNR) with a biocompatible, superstable and fluorescent carbon layer, obtaining the AuNR@carbon core-shell nanocapsule. In this system, the carbon shell, originally obtained in aqueous glucose solutions and, therefore, biocompatible in physiological environments, could be simply loaded with cell-specific aptamers and therapeutic molecules through π-π interactions, a useful tool for cancer-targeted cellular imaging and therapy. Moreover, such a stable and intrinsic fluorescence effect of the AuNR@carbon enabled simultaneous tracking of released therapeutic molecules and nanocarriers under thermo-chemotherapy. The AuNR@carbons had high surface areas and stable shells, as well as unique optical and photothermal properties, making them promising nanostructures for biomedical applications. Electronic supplementary information (ESI) available: Experimental details and characterization data for all new compounds. See DOI: 10.1039/c6nr00369a

Switching of metabolic programs in response to light availability is an essential function of the cyanobacterial circadian output pathway

PubMed Central

Puszynska, Anna M; O'Shea, Erin K

2017-01-01

The transcription factor RpaA is the master regulator of circadian transcription in cyanobacteria, driving genome-wide oscillations in mRNA abundance. Deletion of rpaA has no effect on viability in constant light conditions, but renders cells inviable in cycling conditions when light and dark periods alternate. We investigated the mechanisms underlying this viability defect, and demonstrate that the rpaA- strain cannot maintain appropriate energy status at night, does not accumulate carbon reserves during the day, and is defective in transcription of genes crucial for utilization of carbohydrate stores at night. Reconstruction of carbon utilization pathways combined with provision of an external carbon source restores energy charge and viability of the rpaA- strain in light/dark cycling conditions. Our observations highlight how a circadian output pathway controls and temporally coordinates essential pathways in carbon metabolism to maximize fitness of cells facing periodic energy limitations. DOI: http://dx.doi.org/10.7554/eLife.23210.001 PMID:28430105

Gas Transfer Controls Carbon Limitation During Biomass Production by Marine Microalgae.

PubMed

Tamburic, Bojan; Evenhuis, Christian R; Suggett, David J; Larkum, Anthony W D; Raven, John A; Ralph, Peter J

2015-08-24

This study presents the first in-depth analysis of CO2 limitation on the biomass productivity of the biofuel candidate marine microalga Nannochloropsis oculata. Net photosynthesis decreased by 60% from 125 to 50 μmol O2 L(-1)h(-1) over a 12 h light cycle as a direct result of carbon limitation. Continuous dissolved O2 and pH measurements were used to develop a detailed diurnal mechanism for the interaction between photosynthesis, gas exchange and carbonate chemistry in the photo-bioreactor. Gas exchange determined the degree of carbon limitation experienced by the algae. Carbon limitation was confirmed by delivering more CO2 , which increased net photosynthesis back to its steady-state maximum. This study highlights the importance of maintaining replete carbon concentrations in photo-bioreactors and other culturing facilities, either by constant pH operation or preferably by designing a feedback loop based on the dissolved O2 concentration. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Physical and Economic Integration of Carbon Capture Methods with Sequestration Sinks

NASA Astrophysics Data System (ADS)

Murrell, G. R.; Thyne, G. D.

2007-12-01

Currently there are several different carbon capture technologies either available or in active development for coal- fired power plants. Each approach has different advantages, limitations and costs that must be integrated with the method of sequestration and the physiochemical properties of carbon dioxide to evaluate which approach is most cost effective. For large volume point sources such as coal-fired power stations, the only viable sequestration sinks are either oceanic or geological in nature. However, the carbon processes and systems under consideration produce carbon dioxide at a variety of pressure and temperature conditions that must be made compatible with the sinks. Integration of all these factors provides a basis for meaningful economic comparisons between the alternatives. The high degree of compatibility between carbon dioxide produced by integrated gasification combined cycle technology and geological sequestration conditions makes it apparent that this coupling currently holds the advantage. Using a basis that includes complete source-to-sink sequestration costs, the relative cost benefit of pre-combustion IGCC compared to other post-combustion methods is on the order of 30%. Additional economic benefits arising from enhanced oil recovery revenues and potential sequestration credits further improve this coupling.

Elemental stoichiometry indicates predominant influence of potassium and phosphorus limitation on arbuscular mycorrhizal symbiosis in acidic soil at high altitude.

PubMed

Khan, Mohammad Haneef; Meghvansi, Mukesh K; Gupta, Rajeev; Veer, Vijay

2015-09-15

The functioning of high-altitude agro-ecosystems is constrained by the harsh environmental conditions, such as low temperatures, acidic soil, and low nutrient supply. It is therefore imperative to investigate the site-specific ecological stoichiometry with respect to AM symbiosis in order to maximize the arbuscular mycorrhizal (AM) benefits for the plants in such ecosystems. Here, we assess the elemental stoichiometry of four Capsicum genotypes grown on acidic soil at high altitude in Arunachal Pradesh, India. Further, we try to identify the predominant resource limitations influencing the symbioses of different Capsicum genotypes with the AM fungi. Foliar and soil elemental stoichiometric relations of Capsicum genotypes were evaluated with arbuscular mycorrhizal (AM) colonization and occurrence under field conditions. AM fungal diversity in rhizosphere, was estimated through PCR-DGGE profiling. Results demonstrated that the symbiotic interaction of various Capsicum genotypes with the AM fungi in acidic soil was not prominent in the study site as evident from the low range of root colonization (21-43.67%). In addition, despite the rich availability of carbon in plant leaves as well as in soil, the carbon-for-phosphorus trade between AMF and plants appeared to be limited. Our results provide strong evidences of predominant influence of the potassium-limitation, in addition to phosphorus-limitation, on AM symbiosis with Capsicum in acidic soil at high altitude. We also conclude that the potassium should be considered in addition to carbon, nitrogen, and phosphorus in further studies investigating the stoichiometric relationships with the AMF symbioses in high altitude agro-ecosystems. Copyright © 2015 Elsevier GmbH. All rights reserved.

Reproductive failure in Arabidopsis thaliana under transient carbohydrate limitation: flowers and very young siliques are jettisoned and the meristem is maintained to allow successful resumption of reproductive growth.

PubMed

Lauxmann, Martin A; Annunziata, Maria G; Brunoud, Géraldine; Wahl, Vanessa; Koczut, Andrzej; Burgos, Asdrubal; Olas, Justyna J; Maximova, Eugenia; Abel, Christin; Schlereth, Armin; Soja, Aleksandra M; Bläsing, Oliver E; Lunn, John E; Vernoux, Teva; Stitt, Mark

2016-04-01

The impact of transient carbon depletion on reproductive growth in Arabidopsis was investigated by transferring long-photoperiod-grown plants to continuous darkness and returning them to a light-dark cycle. After 2 days of darkness, carbon reserves were depleted in reproductive sinks, and RNA in situ hybridization of marker transcripts showed that carbon starvation responses had been initiated in the meristem, anthers and ovules. Dark treatments of 2 or more days resulted in a bare-segment phenotype on the floral stem, with 23-27 aborted siliques. These resulted from impaired growth of immature siliques and abortion of mature and immature flowers. Depolarization of PIN1 protein and increased DII-VENUS expression pointed to rapid collapse of auxin gradients in the meristem and inhibition of primordia initiation. After transfer back to a light-dark cycle, flowers appeared and formed viable siliques and seeds. A similar phenotype was seen after transfer to sub-compensation point irradiance or CO2 . It also appeared in a milder form after a moderate decrease in irradiance and developed spontaneously in short photoperiods. We conclude that Arabidopsis inhibits primordia initiation and aborts flowers and very young siliques in C-limited conditions. This curtails demand, safeguarding meristem function and allowing renewal of reproductive growth when carbon becomes available again. © 2015 John Wiley & Sons Ltd.

Increased forest ecosystem carbon and nitrogen storage from nitrogen rich bedrock.

PubMed

Morford, Scott L; Houlton, Benjamin Z; Dahlgren, Randy A

2011-08-31

Nitrogen (N) limits the productivity of many ecosystems worldwide, thereby restricting the ability of terrestrial ecosystems to offset the effects of rising atmospheric CO(2) emissions naturally. Understanding input pathways of bioavailable N is therefore paramount for predicting carbon (C) storage on land, particularly in temperate and boreal forests. Paradigms of nutrient cycling and limitation posit that new N enters terrestrial ecosystems solely from the atmosphere. Here we show that bedrock comprises a hitherto overlooked source of ecologically available N to forests. We report that the N content of soils and forest foliage on N-rich metasedimentary rocks (350-950 mg N kg(-1)) is elevated by more than 50% compared with similar temperate forest sites underlain by N-poor igneous parent material (30-70 mg N kg(-1)). Natural abundance N isotopes attribute this difference to rock-derived N: (15)N/(14)N values for rock, soils and plants are indistinguishable in sites underlain by N-rich lithology, in marked contrast to sites on N-poor substrates. Furthermore, forests associated with N-rich parent material contain on average 42% more carbon in above-ground tree biomass and 60% more carbon in the upper 30 cm of the soil than similar sites underlain by N-poor rocks. Our results raise the possibility that bedrock N input may represent an important and overlooked component of ecosystem N and C cycling elsewhere.

Examining the coupling of carbon and nitrogen cycles in Southern Appalachian streams: Understanding the role of dissolved organic nitrogen

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lutz, Brian D; Bernhardt, Emily; Roberts, Brian

Although regional and global models of nitrogen (N) cycling typically focus on nitrate, dissolved organic nitrogen (DON) is the dominant form of nitrogen export from many watersheds and thus the dominant form of dissolved N in many streams. Our understanding of the processes controlling DON export from temperate forests is poor. In pristine systems, where biological N limitation is common, N contained in recalcitrant organic matter (OM) can dominate watershed N losses. This recalcitrant OM often has moderately constrained carbon:nitrogen (C:N) molar ratios ({approx}25-55) and therefore, greater DON losses should be observed in sites where there is greater total dissolvedmore » organic carbon (DOC) loss. In regions where anthropogenic N pollution is high, it has been suggested that increased inorganic N availability can reduce biological demand for organic N and therefore increase watershed DON losses. This would result in a positive correlation between inorganic and organic N concentrations across sites with varying N availability. In four repeated synoptic surveys of stream water chemistry from forested watersheds along an N loading gradient in the southern Appalachians, we found surprisingly little correlation between DON and DOC concentrations. Further, we found that DON concentrations were always significantly correlated with watershed N loading and stream water [NO{sub 3}{sup -}] but that the direction of this relationship was negative in three of the four surveys. The C:N molar ratio of dissolved organic matter (DOM) in streams draining watersheds with high N deposition was very high relative to other freshwaters. This finding, together with results from bioavailability assays in which we directly manipulated C and N availabilities, suggests that heterotrophic demand for labile C can increase as a result of dissolved inorganic N (DIN) loading, and that heterotrophs can preferentially remove N-rich molecules from DOM. These results are inconsistent with the two prevailing hypotheses that dominate interpretations of watershed DON loss. Therefore, we propose a new hypothesis, the indirect carbon control hypothesis, which recognizes that heterotrophic demand for N-rich DOM can keep stream water DON concentrations low when N is not limiting and heterotrophic demand for labile C is high.« less

Filled carbon nanotubes in biomedical imaging and drug delivery.

PubMed

Martincic, Markus; Tobias, Gerard

2015-04-01

Carbon nanotubes have been advocated as promising candidates in the biomedical field in the areas of diagnosis and therapy. In terms of drug delivery, the use of carbon nanotubes can overcome some limitations of 'free' drugs by improving the formulation of poorly water-soluble drugs, allowing targeted delivery and even enabling the co-delivery of two or more drugs for combination therapy. Two different approaches are currently being explored for the delivery of diagnostic and therapeutic agents by carbon nanotubes, namely attachment of the payload to the external sidewalls or encapsulation into the inner cavities. Although less explored, the latter confers additional stability to the chosen diagnostic or therapeutic agents, and leaves the backbone structure of the nanotubes available for its functionalization with dispersing and targeting moieties. Several drug delivery systems and diagnostic agents have been developed in the last years employing the inner tubular cavities of carbon nanotubes. The research discussed in this review focuses on the use of carbon nanotubes that contain in their interior drug molecules and diagnosis-related compounds. The approaches employed for the development of such nanoscale vehicles along with targeting and releasing strategies are discussed. The encapsulation of both biomedical contrast agents and drugs inside carbon nanotubes is further expanding the possibilities to allow an early diagnosis and treatment of diseases.

Enhanced production of green tide algal biomass through additional carbon supply.

PubMed

de Paula Silva, Pedro H; Paul, Nicholas A; de Nys, Rocky; Mata, Leonardo

2013-01-01

Intensive algal cultivation usually requires a high flux of dissolved inorganic carbon (Ci) to support productivity, particularly for high density algal cultures. Carbon dioxide (CO2) enrichment can be used to overcome Ci limitation and enhance productivity of algae in intensive culture, however, it is unclear whether algal species with the ability to utilise bicarbonate (HCO3 (-)) as a carbon source for photosynthesis will benefit from CO2 enrichment. This study quantified the HCO3 (-) affinity of three green tide algal species, Cladophora coelothrix, Cladophora patentiramea and Chaetomorpha linum, targeted for biomass and bioenergy production. Subsequently, we quantified productivity and carbon, nitrogen and ash content in response to CO2 enrichment. All three species had similar high pH compensation points (9.7-9.9), and grew at similar rates up to pH 9, demonstrating HCO3 (-) utilization. Algal cultures enriched with CO2 as a carbon source had 30% more total Ci available, supplying twenty five times more CO2 than the control. This higher Ci significantly enhanced the productivity of Cladophora coelothrix (26%), Chaetomorpha linum (24%) and to a lesser extent for Cladophora patentiramea (11%), compared to controls. We demonstrated that supplying carbon as CO2 can enhance the productivity of targeted green tide algal species under intensive culture, despite their clear ability to utilise HCO3 (-).

Carbon limitation patterns in buried and open urban streams

EPA Science Inventory

Urban streams alternate between darkened buried segments dominated by heterotrophic processes and lighted open segments dominated by autotrophic processes. We hypothesized that labile carbon leaking from autotrophic cells would reduce heterotrophic carbon limitation in open chan...

Parameterization of Nitrogen Limitation for a Dynamic Ecohydrological Model: a Case Study from the Luquillo Critical Zone Observatory

NASA Astrophysics Data System (ADS)

Bastola, S.; Bras, R. L.

2017-12-01

Feedbacks between vegetation and the soil nutrient cycle are important in ecosystems where nitrogen limits plant growth, and consequently influences the carbon balance in the plant-soil system. However, many biosphere models do not include such feedbacks, because interactions between carbon and the nitrogen cycle can be complex, and remain poorly understood. In this study we coupled a nitrogen cycle model with an eco-hydrological model by using the concept of carbon cost economics. This concept accounts for different "costs" to the plant of acquiring nitrogen via different pathways. This study builds on tRIBS-VEGGIE, a spatially explicit hydrological model coupled with a model of photosynthesis, stomatal resistance, and energy balance, by combining it with a model of nitrogen recycling. Driven by climate and spatially explicit data of soils, vegetation and topography, the model (referred to as tRIBS-VEGGIE-CN) simulates the dynamics of carbon and nitrogen in the soil-plant system; the dynamics of vegetation; and different components of the hydrological cycle. The tRIBS-VEGGIE-CN is applied in a humid tropical watershed at the Luquillo Critical Zone Observatory (LCZO). The region is characterized by high availability and cycling of nitrogen, high soil respiration rates, and large carbon stocks.We drive the model under contemporary CO2 and hydro-climatic forcing and compare results to a simulation under doubling CO2 and a range of future climate scenarios. The results with parameterization of nitrogen limitation based on carbon cost economics show that the carbon cost of the acquisition of nitrogen is 14% of the net primary productivity (NPP) and the N uptake cost for different pathways vary over a large range depending on leaf nitrogen content, turnover rates of carbon in soil and nitrogen cycling processes. Moreover, the N fertilization simulation experiment shows that the application of N fertilizer does not significantly change the simulated NPP. Furthermore, an experiment with doubling of the CO2 concentration level shows a significant increase of the NPP and turnover of plant tissues. The simulation with future climate scenarios shows consistent decrease in NPP but the uncertainties in projected NPP arising from selection of climate model and scenario is large.

Growth and evaluation of AgGaS2 and AgGaSe2 for infrared nonlinear applications

NASA Technical Reports Server (NTRS)

Byer, R. L.; Feigelson, R. S.

1986-01-01

Significant advances were made in the growth technology of silver thiogallate (AgGaS2) and silver selenogallate (AgGaSe2). High efficiency harmonic generation of carbon dioxide laser radiation and tunable infrared parametric oscillation were demonstrated using these materials. Nonliner frequency conversion in the infrared was limited by the optical properties and the size of the available nonlinear materials. The development of these materials has reduced some of the limitations and generated wide interest. The continued development and application of AgGaS2 and AgGaSe2 now appears assured.

Climate-mediated spatiotemporal variability in the terrestrial productivity across Europe

NASA Astrophysics Data System (ADS)

Wu, X.; Mahecha, M. D.; Reichstein, M.; Ciais, P.; Wattenbach, M.; Babst, F.; Frank, D.; Zang, C.

2013-11-01

Quantifying the interannual variability (IAV) of the terrestrial productivity and its sensitivity to climate is crucial for improving carbon budget predictions. However, the influence of climate and other mechanisms underlying the spatiotemporal patterns of IAV of productivity are not well understood. In this study we investigated the spatiotemporal patterns of IAV of historical observations of crop yields, tree ring width, remote sensing retrievals of FAPAR and NDVI, and other variables relevant to the terrestrial productivity in Europe in tandem with a set of climate variables. Our results reveal distinct spatial patterns in the IAV of most variables linked to terrestrial productivity. In particular, we find higher IAV in water-limited regions of Europe (Mediterranean and temperate continental Europe) compared to other regions. Our results further indicate that variations in the water balance during active growing season exert a more pronounced and direct effect than variations of temperature on explaining the spatial patterns in IAV of productivity related variables in temperate Europe. We also observe a~temporally increasing trend in the IAV of terrestrial productivity and an increasing sensitivity of productivity to water availability in dry regions of Europe, which is likely attributable to the recently increased IAV of water availability in these regions. These findings suggest nonlinear responses of carbon fluxes to climate variability in Europe and that the IAV of terrestrial productivity has become more sensitive and more vulnerable to changes in water availability in the dry regions in Europe. The changing climate sensitivity of terrestrial productivity accompanied by the changing IAV of climate could impact carbon stocks and the net carbon balance of European ecosystems.

Npr1 Ser/Thr Protein Kinase Links Nitrogen Source Quality and Carbon Availability with the Yeast Nitrate Transporter (Ynt1) Levels*

PubMed Central

Martín, Yusé; González, Yelvis V.; Cabrera, Elisa; Rodríguez, Celia; Siverio, José M.

2011-01-01

Ynt1, the single high affinity nitrate and nitrite transporter of the yeast Hansenula polymorpha, is regulated by the quality of nitrogen sources. Preferred nitrogen sources cause Ynt1 dephosphorylation, ubiquitinylation, endocytosis, and vacuolar degradation. In contrast, under nitrogen limitation Ynt1 is phosphorylated and sorted to the plasma membrane. We show here the involvement of the Ser/Thr kinase HpNpr1 in Ynt1 phosphorylation and regulation of Ynt1 levels in response to nitrogen source quality and the availability of carbon. In Δnpr1, Ynt1 phosphorylation does not take place, although Ynt1 ubiquitin conjugates increase. As a result, in this strain Ynt1 is sorted to the vacuole, from both plasma membrane and the later biosynthetic pathway in nitrogen-free conditions and nitrate. In contrast, overexpression of NPR1 blocks down-regulation of Ynt1, increasing Ynt1 phosphorylation at Ser-244 and -246 and reducing ubiquitinylation. Furthermore, Npr1 is phosphorylated in response to the preferred nitrogen sources, and indeed it is dephosphorylated in nitrogen-free medium. Under conditions where Npr1 is phosphorylated, Ynt1 is not and vice versa. We show for the first time that carbon starvation leads to Npr1 phosphorylation, whereas Ynt1 is dephosphorylated and degraded in the vacuole. Rapamycin prevents this, indicating a possible role of the target of rapamycin signaling pathway in this process. We concluded that Npr1 plays a key role in adapting Ynt1 levels to the nitrogen quality and availability of a source of carbon. PMID:21652715

Successional dynamics drive tropical forest nutrient limitation

NASA Astrophysics Data System (ADS)

Chou, C.; Hedin, L. O. O.

2017-12-01

It is increasingly recognized that nutrients such as N and P may significantly constrain the land carbon sink. However, we currently lack a complete understanding of these nutrient cycles in forest ecosystems and how to incorporate them into Earth System Models. We have developed a framework of dynamic forest nutrient limitation, focusing on the role of secondary forest succession and canopy gap disturbances as bottlenecks of high plant nutrient demand and limitation. We used succession biomass data to parameterize a simple ecosystem model and examined the dynamics of nutrient limitation throughout tropical secondary forest succession. Due to the patterns of biomass recovery in secondary tropical forests, we found high nutrient demand from rapid biomass accumulation in the earliest years of succession. Depending on previous land use scenarios, soil nutrient availability may also be low in this time period. Coupled together, this is evidence that there may be high biomass nutrient limitation early in succession, which is partially met by abundant symbiotic nitrogen fixation from certain tree species. We predict a switch from nitrogen limitation in early succession to one of three conditions: (i) phosphorus only, (ii) phosphorus plus nitrogen, or (iii) phosphorus, nitrogen, plus light co-limitation. We will discuss the mechanisms that govern the exact trajectory of limitation as forests build biomass. In addition, we used our model to explore scenarios of tropical secondary forest impermanence and the impacts of these dynamics on ecosystem nutrient limitation. We found that secondary forest impermanence exacerbates nutrient limitation and the need for nitrogen fixation early in succession. Together, these results indicate that biomass recovery dynamics early in succession as well as their connection to nutrient demand and limitation are fundamental for understanding and modeling nutrient limitation of the tropical forest carbon sink.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kim, J.S.; Sokol, R.C.; Liu, X.

Microbial dechlorination of polychlorinated biphenyls (PCBs) often stops although a significant number of removable chlorines remain. To determine the reason for the cessation, we investigated the limitation of organic carbon, PCB bioavailability, and inhibition by metabolic products. Enrichment with carbon sources did not induce additional chlorination, indicating the plateau was not due to depletion of organic carbon. The bioavailability was not limiting, since a subcritical micelle concentration of the surfactant, which enhanced desorption without inhibiting dechlorinating microorganisms, failed to lower the plateau. Neither was it due to accumulation of metabolites, since no additional dechlorination was detected when plateau sediments weremore » incubated with fresh medium. Similarly, dechlorination was not inhibited in freshly spiked sediment slurries. Dechlorination ended up at the same level with nearly identical congener profiles, regardless of treatment. These results indicate that cessation of dechlorination was due to the accumulation of daughter congeners, which cannot be used as electron acceptors by microbes. To determine whether the decreasing availability affected the microorganisms, we determined the population dynamics of dechlorinators using the most probable number technique. The growth dynamics of the dechlorinators mirrored the time course of dechlorination. It started when the population increased by two orders of magnitude. Once dechlorination stopped the dechlorinating population also began to decrease. When dechlorinators were inoculated into PCB-free sediments, the population decreased over time. The decrease of the population as dechlorination ceased confirms that the diminishing availability of congeners was the reason for the incomplete dechlorination. Recent findings have shown that a second phase of dechlorination of certain congeners can occur after a long lag. 45 refs., 8 figs.« less

NEMA, a functional-structural model of nitrogen economy within wheat culms after flowering. II. Evaluation and sensitivity analysis.

PubMed

Bertheloot, Jessica; Wu, Qiongli; Cournède, Paul-Henry; Andrieu, Bruno

2011-10-01

Simulating nitrogen economy in crop plants requires formalizing the interactions between soil nitrogen availability, root nitrogen acquisition, distribution between vegetative organs and remobilization towards grains. This study evaluates and analyses the functional-structural and mechanistic model of nitrogen economy, NEMA (Nitrogen Economy Model within plant Architecture), developed for winter wheat (Triticum aestivum) after flowering. NEMA was calibrated for field plants under three nitrogen fertilization treatments at flowering. Model behaviour was investigated and sensitivity to parameter values was analysed. Nitrogen content of all photosynthetic organs and in particular nitrogen vertical distribution along the stem and remobilization patterns in response to fertilization were simulated accurately by the model, from Rubisco turnover modulated by light intercepted by the organ and a mobile nitrogen pool. This pool proved to be a reliable indicator of plant nitrogen status, allowing efficient regulation of nitrogen acquisition by roots, remobilization from vegetative organs and accumulation in grains in response to nitrogen treatments. In our simulations, root capacity to import carbon, rather than carbon availability, limited nitrogen acquisition and ultimately nitrogen accumulation in grains, while Rubisco turnover intensity mostly affected dry matter accumulation in grains. NEMA enabled interpretation of several key patterns usually observed in field conditions and the identification of plausible processes limiting for grain yield, protein content and root nitrogen acquisition that could be targets for plant breeding; however, further understanding requires more mechanistic formalization of carbon metabolism. Its strong physiological basis and its realistic behaviour support its use to gain insights into nitrogen economy after flowering.

Carbon-cycle effects of differences in soil moisture and soil extracellular enzyme activity at sites representing different land-use histories in high-elevation Ecuadorian páramo landscapes

NASA Astrophysics Data System (ADS)

McKnight, J.; Harden, C. P.; Schaeffer, S. M.

2016-12-01

Ecuadorian páramo grasslands are important regional soil carbon sinks. In the páramo of the Mazar Wildlife Reserve, differences in soil carbon content among different types of land use may reflect changes in soil carbon-acquisition related microbial enzyme activity after land cover and soil moisture are altered; however, this hypothesis has not been tested explicitly for Ecuadorian páramos. This study used a fluorescence enzyme assay to assess the activities of four different extracellular enzymes representing carbon acquisition: α-glucosidase, β-glucosidase, β-D-cellulobiohydrolase, and β-xylosidase in Andean páramo soils. Acquisition activities were also measured for nitrogen (N-acetyl-β-glucosidase and leucine aminopeptidase) and phosphorus (phosphatase) to assess stoichiometric differences between land-uses, which can affect soil microbial activity related to carbon acquisition. Soils were analyzed from four land uses: native forest, grass páramo, recently burned grass páramo, and non-native pine plantation. Carbon acquisition activity was highest at the pine site (678 nmol h-1 g-1) and lowest at the recently burned páramo site (252 nmol h-1 g-1), indicating the lowest and highest available soil carbon, respectively. Carbon-acquisition EE activity was significantly higher at the grass páramo site (595 nmol h-1 g-1) than at the recently burned páramo and native forest sites. At the grass páramo site, a history of burning as a management strategy and high carbon-acquisition EE activity could indicate the presence of pyrogenic soil organic matter, which is more resistant to microbial decomposition. Soils at the native forest and both grassland sites were phosphorus limited, and soil at the pine site had higher nitrogen-acquisition activity, indicative of a shift to nitrogen-limited soil stoichiometric conditions. To our knowledge these are the first data reported for soil extracellular enzyme activities for Ecuadorian páramos.

Carbon monoxide measurement in the global atmospheric sampling program

NASA Technical Reports Server (NTRS)

Dudzinski, T. J.

1979-01-01

The carbon monoxide measurement system used in the NASA Global Atmospheric Sampling Program (GASP) is described. The system used a modified version of a commercially available infrared absorption analyzer. The modifications increased the sensitivity of the analyzer to 1 ppmv full scale, with a limit of detectability of 0.02 ppmv. Packaging was modified for automatic, unattended operation in an aircraft environment. The GASP system is described along with analyzer operation, calibration procedures, and measurement errors. Uncertainty of the CO measurement over a 2-year period ranged from + or - 3 to + or - 13 percent of reading, plus an error due to random fluctuation of the output signal + or - 3 to + or - 15 ppbv.

Asymmetric synthesis of isoindolones by chiral cyclopentadienyl-rhodium(III)-catalyzed C-H functionalizations.

PubMed

Ye, Baihua; Cramer, Nicolai

2014-07-21

Directed Cp*Rh(III)-catalyzed carbon-hydrogen (C-H) bond functionalizations have evolved as a powerful strategy for the construction of heterocycles. Despite their high value, the development of related asymmetric reactions is largely lagging behind due to a limited availability of robust and tunable chiral cyclopentadienyl ligands. Rhodium complexes comprising a chiral Cp ligand with an atropchiral biaryl backbone enables an asymmetric synthesis of isoindolones from arylhydroxamates and weakly alkyl donor/acceptor diazo derivatives as one-carbon component under mild conditions. The complex guides the substrates with a high double facial selectivity yielding the chiral isoindolones in good yields and excellent enantioselectivities. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Asymmetric Methods for the Synthesis of Flavanones, Chromanones, and Azaflavanones

PubMed Central

Nibbs, Antoinette E.

2012-01-01

Flavanones, chromanones, and related structures are privileged natural products that display a wide variety of biological activities. Although flavanoids are abundant in nature, there are a limited number of available general and efficient synthetic methods for accessing molecules of this class in a stereoselective manner. Their structurally simple architectures belie the difficulties involved in installation and maintenance of the stereogenic configuration at the C2 position, which can be sensitive and can undergo epimerization under mildly acidic, basic, and thermal reaction conditions. This review presents the methods currently used to access these related structures. The synthetic methods include manipulation of the flavone/flavanone core, carbon-carbon bond formation, and carbon–heteroatom bond formation. PMID:22876166

A correlated ab initio study of linear carbon-chain radicals CnH (n = 2-7)

NASA Technical Reports Server (NTRS)

Woon, D. E.; Loew, G. H. (Principal Investigator)

1995-01-01

Linear carbon-chain radicals CnH for n = 2-7 have been studied with correlation consistent valence and core-valence basis sets and the coupled cluster method RCCSD(T). Equilibrium structures, rotational constants, and dipole moments are reported and compared with available experimental data. The ground state of the even-n series changes from 2 sigma+ to 2 pi as the chain is extended. For C4H, the 2 sigma+ state was found to lie only 72 cm-1 below the 2 pi state in the estimated complete basis set limit for valence correlation. The C2H- and C3H- anions have also been characterized.

A Versatile Route to Unstable Diazo Compounds via Oxadiazolines and their Use in Aryl-Alkyl Cross-Coupling Reactions.

PubMed

Greb, Andreas; Poh, Jian-Siang; Greed, Stephanie; Battilocchio, Claudio; Pasau, Patrick; Blakemore, David C; Ley, Steven V

2017-12-22

Coupling of readily available boronic acids and diazo compounds has emerged recently as a powerful metal-free carbon-carbon bond forming method. However, the difficulty in forming the unstable diazo compound partner in a mild fashion has hitherto limited their general use and the scope of the transformation. Here, we report the application of oxadiazolines as precursors for the generation of an unstable family of diazo compounds using flow UV photolysis and their first use in divergent protodeboronative and oxidative C(sp 2 )-C(sp 3 ) cross-coupling processes, with excellent functional-group tolerance. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Carbon mineralization in surface and subsurface soils in a subtropical mixed forest in central China

NASA Astrophysics Data System (ADS)

Liu, F.; Tian, Q.

2014-12-01

About a half of soil carbon is stored in subsurface soil horizons, their dynamics have the potential to significantly affect carbon balancing in terrestrial ecosystems. However, the main factors regulating subsurface soil carbon mineralization are poorly understood. As affected by mountain humid monsoon, the subtropical mountains in central China has an annual precipitation of about 2000 mm, which causes strong leaching of ions and nutrition. The objectives of this study were to monitor subsurface soil carbon mineralization and to determine if it is affected by nutrient limitation. We collected soil samples (up to 1 m deep) at three locations in a small watershed with three soil layers (0-10 cm, 10-30 cm, below 30 cm). For the three layers, soil organic carbon (SOC) ranged from 35.8 to 94.4 mg g-1, total nitrogen ranged from 3.51 to 8.03 mg g-1, microbial biomass carbon (MBC) ranged from 170.6 to 718.4 μg g-1 soil. We measured carbon mineralization with the addition of N (100 μg N/g soil), P (50 μg P/g soil), and liable carbon (glucose labeled by 5 atom% 13C, at five levels: control, 10% MBC, 50% MBC, 100% MBC, 200% MBC). The addition of N and P had negligible effects on CO2 production in surface soil layers; in the deepest soil layer, the addition of N and P decreased CO2 production from 4.32 to 3.20 μg C g-1 soil carbon h-1. Glucose addition stimulated both surface and subsurface microbial mineralization of SOC, causing priming effects. With the increase of glucose addition rate from 10% to 200% MBC, the primed mineralization rate increased from 0.19 to 3.20 μg C g-1 soil carbon h-1 (fifth day of glucose addition). The magnitude of priming effect increased from 28% to 120% as soil layers go deep compare to the basal CO2 production (fifth day of 200% MBC glucose addition, basal CO2 production rate for the surface and the deepest soil was 11.17 and 2.88 μg C g-1 soil carbon h-1). These results suggested that the mineralization of subsurface carbon is more sensitive to nutrient addition, and carbon mineralization in this layer is likely limited by carbon availability. Thus, any changes in environment conditions (global warming, nitrogen deposition, precipitation pattern change etc.) that affect the distribution of fresh carbon in soil profiles could then stimulate the release of deep soil carbon.

Plant Nitrogen Uptake in Terrestrial Biogeochemical Models

NASA Astrophysics Data System (ADS)

Marti Donati, A.; Cox, P.; Smith, M. J.; Purves, D.; Sitch, S.; Jones, C. D.

2013-12-01

Most terrestrial biogeochemical models featured in the last Intergovernmental Panel on Climate Change (IPPC) Assessment Report highlight the importance of the terrestrial Carbon sequestration and feedbacks between the terrestrial Carbon cycle and the climate system. However, these models have been criticized for overestimating predicted Carbon sequestration and its potential climate feedback when calculating the rate of future climate change because they do not account for the Carbon sequestration constraints caused by nutrient limitation, particularly Nitrogen (N). This is particularly relevant considering the existence of a substantial deficit of Nitrogen for plants in most areas of the world. To date, most climate models assume that plants have access to as much Nitrogen as needed, but ignore the nutrient requirements for new vegetation growth. Determining the natural demand and acquisition for Nitrogen and its associated resource optimization is key when accounting for the Carbon sequestration constrains caused by nutrient limitation. The few climate models that include C-N dynamics have illustrated that the stimulation of plant growth over the coming century may be significantly smaller than previously predicted. However, models exhibit wide differences in their predictive accuracy and lead to widely diverging and inconsistent projections accounting for an uncertain Carbon sequestration decrease due to Nitrogen limitation ranging from 7 to 64%. This reduction in growth is partially offset by an increase in the availability of nutrients resulting from an accelerated rate of decomposition of dead plants and other organic matter that occurring with a rise in temperature. However, this offset does not counterbalance the reduced level of plant growth calculated by natural nutrient limitations. Additionally, Nitrogen limitation is also expected to become more pronounced in some ecosystems as atmospheric CO2 concentration increases; resulting in less new growth and higher atmospheric CO2 concentrations than originally expected. This study compares the differences in the predictions of alternative models of plant N uptake found in different terrestrial biogeochemical models with the predictions from a new N-uptake model developed under the Joint UK Land Environment Simulator (JULES) framework. We implement a methodology for the construction, parameterization and evaluation of N uptake models to fully decompose all the N uptake component processes in terms of their parameter uncertainty and the accuracy of their predictions with respect to different empirical data sets. Acknowledgements This work has been funded by the European Commission FP7-PEOPLE-ITN-2008 Marie Curie Action: "Greencycles II: FP7-PEOPLE-ITN-2008 Marie Curie Action: "Networks for Initial Training"

Investigating Reaction-Driven Cracking

NASA Astrophysics Data System (ADS)

Kelemen, P. B.; Hirth, G.; Savage, H. M.

2013-12-01

Many metamorphic reactions lead to large volume changes, and potentially to reaction-driven cracking [1,2]. Large-scale hydration of mantle peridotite to produce serpentine or talc is invoked to explain the rheology of plate boundaries, the nature of earthquakes, and the seismic properties of slow-spread ocean crust and the 'mantle wedge' above subduction zones. Carbonation of peridotite may be an important sink in the global carbon cycle. Zones of 100% magnesite + quartz replacing peridotite, up to 200 m thick, formed where oceanic mantle was thrust over carbonate-bearing metasediments in Oman. Talc + carbonate is an important component of the matrix in subduction mélanges at Santa Catalina Island , California, and the Sanbagawa metamorphic belt, Japan. Engineered systems to emulate natural mineral carbonation could provide relatively inexpensive CO2 capture and storage [3]. More generally, engineered reaction-driven cracking could supplement or replace hydraulic fracture in geothermal systems, solution mining, and extraction of tight oil and gas. The controls on reaction-driven cracking are poorly understood. Hydration and carbonation reactions can be self-limiting, since they potentially reduce permeability and armor reactive surfaces [4]. Also, in some cases, hydration or carbonation may take place at constant volume. Small changes in volume due to precipitation of solid products increases stress, destabilizing solid reactants, until precipitation and dissolution rates become equal at a steady state stress [5]. In a third case, volume change due to precipitation of solid products causes brittle failure. This has been invoked on qualitative grounds to explain, e.g., complete serpentinization of mantle peridotite [6]. Below ~ 300°C, the available potential energy for hydration and carbonation of olivine could produce stresses of 100's of MPa [2], sufficient to fracture rocks to 10 km depth or more, causing brittle failure below the steady state stress required for constant volume replacement. Natural examples have fracture energy densities due to strain energy density of 100's of MPa [2]. Despite theory and observation, until now lab experiments on peridotite hydration and carbonation have not produced reaction-driven cracking. Slow kinetics and limited reactive surface area in low porosity samples may be the cause. Also, maximum stress may be limited by 'disjoining pressure', above which nano-films along grain boundaries collapse, and crystal growth essentially ceases [7]. To address these issues, we've begun experiments on analog materials with fast reaction rates, e.g., CaO + H2O = Ca(OH)2, to efficiently investigate the role of confining pressure and other factors on reaction-driven fracture events. Intriguingly, commercially available 'demolition mortar', largely CaO, produces stresses of 70 MPa or more around 1 inch bore holes at room T and P [8], even though there is a free surface at the top of the borehole, and hydration in a 'closed' system creates ~ 40% air-filled pore space. [1] Jamtveit et al EPSL 08 [2] Kelemen & Hirth EPSL 12 [3] Kelemen et al AREPS 11 [4] Aharonov et al JGR 98 [5] Fletcher & Merino GCA 01 [6] Macdonald & Fyfe T'phys 85 [7] Espinosa-Marzal & Scherer GSL Special Papers 10 [8] Laefer et al Mag Concrete Res 10

Climatic implications of Nitrogen constraints on terrestrial C sequestration estimates in CMIP5 model projection

NASA Astrophysics Data System (ADS)

Zaehle, S.; Jones, C.; Robertson, E.; Lamarque, J.; Houlton, B. Z.

2012-12-01

Nitrogen is an essential nutrient for living organisms and a key mediator of carbon cycle processes. An increasing number of global terrestrial ecosystem models has been recently developed. These models show that nitrogen dynamics strongly affect terrestrial carbon budget projections for the 21st century as they tend to significantly reduce the carbon sequestration capacity of the terrestrial biosphere in response to CO2 fertilization and to modify the climate sensitivity of the global carbon cycle. However, only one of these models (included into two Earth system models) has been used in the CMIP5 study. Therefore the effect of C:N interactions on the CMIP5 projections can only be estimated indirectly. Here, we analyze results of 13 Earth system models from four RCP scenarios (RCP 2.6, 4.5, 6.0, 8.5) with respect to the implied nitrogen requirement to afford the simulated terrestrial carbon sequestration. We compare this N demand to scenarios of changes in terrestrial N availability due to natural variability in the N cycle, as well as changes in biological nitrogen fixation, nitrogen deposition, and ecosystem stoichiometry. Unlike previous studies of a similar type, we base our analyses on a grid-cell basis and explicitly track changes in the carbon and nitrogen cycles over time, and analyze multiple scenarios with different rates of climatic and atmospheric CO2 abundance changes. Consistent with current understanding, the emerging geographic pattern shows N limitation that is stronger in temperate/boreal ecosystems than tropical ecosystems and in pristine areas than highly polluted areas. While the extent and distribution of implied N limitation varies widely between the models, all show some nitrogen limitation of the simulated C sequestration. The magnitude of the N limitation is clearly scenario-dependent, mostly due to the different rates of increased atmospheric CO2 abundance and therefore the extend of CO2 fertilization. Under the most extreme scenario (RCP8.5), an implied nitrogen deficit of 1.9-18.8 Pg N would reduce terrestrial C sequestration by 92-400 Pg C. Assuming the average airborne fraction of 0.6 in the RCP 8.5 scenarios (Jones et al. in review) would cause an increase in atmospheric CO2 abundance of 26-113 ppm by the year 2100, implying an added radiative forcing of 0.15-0.61 Wm-2.

Nitrogen Deposition: A Component of Global Change Analyses

DOE Office of Scientific and Technical Information (OSTI.GOV)

Norby, Richard J.

1997-12-31

The global cycles of carbon and nitrogen are being perturbed by human activities that increase the transfer from large pools of nonreactive forms of the elements to reactive forms that are essential to the functioning of the terrestrial biosphere. The cycles are closely linked at all scales, and global change analyses must consider carbon and nitrogen cycles together. The increasing amount of nitrogen originating from fossil fuel combustion and deposited to terrestrial ecosystems as nitrogen oxides could increase the capacity of ecosystems to sequester carbon thereby removing some of the excess carbon dioxide from the atmosphere and slowing the developmentmore » of greenhouse warming. Several global and ecosystem models have calculated the amount of carbon sequestration that can be attributed to nitrogen deposition based on assumptions about the allocation of nitrogen among ecosystem components with different carbon-nitrogen ratios. They support the premise that nitrogen deposition is responsible for a an increasing terrestrial carbon sink since industrialization began, but there are large uncertainties related to the continued capacity of ecosystems to retain exogenous nitrogen. Whether terrestrial ecosystems continue to sequester additional carbon will depend in part on their response to increasing atmospheric carbon dioxide concentrations, which is widely thought to be constrained by limited nitrogen availability. Ecosystem models generally support the conclusion that the responses of ecosystems to increasing concentrations of carbon dioxide will be larger, and the range of possible responses will be wider, in ecosystems with increased nitrogen inputs originating as atmospheric deposition.« less

Centennial-scale reductions in nitrogen availability in temperate forests of the United States

USGS Publications Warehouse

McLauchlan, Kendra K.; Gerhart, Laci M.; Battles, John J.; Craine, Joseph M.; Elmore, Andrew J.; Higuera, Phil E.; Mack, Michelle M; McNeil, Brendan E.; Nelson, David M.; Pederson, Neil; Perakis, Steven

2017-01-01

Forests cover 30% of the terrestrial Earth surface and are a major component of the global carbon (C) cycle. Humans have doubled the amount of global reactive nitrogen (N), increasing deposition of N onto forests worldwide. However, other global changes—especially climate change and elevated atmospheric carbon dioxide concentrations—are increasing demand for N, the element limiting primary productivity in temperate forests, which could be reducing N availability. To determine the long-term, integrated effects of global changes on forest N cycling, we measured stable N isotopes in wood, a proxy for N supply relative to demand, on large spatial and temporal scales across the continental U.S.A. Here, we show that forest N availability has generally declined across much of the U.S. since at least 1850 C.E. with cool, wet forests demonstrating the greatest declines. Across sites, recent trajectories of N availability were independent of recent atmospheric N deposition rates, implying a minor role for modern N deposition on the trajectory of N status of North American forests. Our results demonstrate that current trends of global changes are likely to be consistent with forest oligotrophication into the foreseeable future, further constraining forest C fixation and potentially storage.

Effect of exposure to sunlight and phosphorus-limitation on bacterial degradation of coloured dissolved organic matter (CDOM) in freshwater.

PubMed

Kragh, Theis; Søndergaard, Morten; Tranvik, Lars

2008-05-01

This study reports on the interacting effect of photochemical conditioning of dissolved organic matter and inorganic phosphorus on the metabolic activity of bacteria in freshwater. Batch cultures with lake-water bacteria and dissolved organic carbon (DOC) extracted from a humic boreal river were arranged in an experimental matrix of three levels of exposure to simulated sunlight and three levels of phosphorus concentration. We measured an increase in bacterial biomass, a decrease in DOC and bacterial respiration as CO(2) production and O(2) consumption over 450 h. These measurements were used to calculate bacterial growth efficiency (BGE). Bacterial degradation of DOC increased with increasing exposure to simulated sunlight and availability of phosphorus and no detectable growth occurred on DOC that was not pre-exposed to simulated sunlight. The outcome of photochemical degradation of DOC changed with increasing availability of phosphorus, resulting in an increase in BGE from about 5% to 30%. Thus, the availability of phosphorus has major implications for the quantitative transfer of carbon in microbial food webs.

Export production in the New-Zealand region since the Last Glacial Maximum

NASA Astrophysics Data System (ADS)

Durand, Axel; Chase, Zanna; Noble, Taryn L.; Bostock, Helen; Jaccard, Samuel L.; Kitchener, Priya; Townsend, Ashley T.; Jansen, Nils; Kinsley, Les; Jacobsen, Geraldine; Johnson, Sean; Neil, Helen

2017-07-01

Increased export production (EP) in the Subantarctic Zone (SAZ) of the Southern Ocean due to iron fertilisation has been proposed as a key mechanism for explaining carbon drawdown during the last glacial maximum (LGM). This work reconstructs marine EP since the LGM at four sites around New Zealand. For the first time in this region, 230-Thorium-normalised fluxes of biogenic opal, carbonate, excess barium, and organic carbon are presented. In Subtropical Waters and the SAZ, these flux variations show that EP has not changed markedly since the LGM. The only exception is a site currently north of the subtropical front. Here we suggest the subtropical front shifted over the core site between 18 and 12 ka, driving increased EP. To understand why EP remained mostly low and constant elsewhere, lithogenic fluxes at the four sites were measured to investigate changes in dust deposition. At all sites, lithogenic fluxes were greater during the LGM compared to the Holocene. The positive temporal correlation between the Antarctic dust record and lithogenic flux at a site in the Tasman Sea shows that regionally, increased dust deposition contributed to the high glacial lithogenic fluxes. Additionally, it is inferred that lithogenic material from erosion and glacier melting deposited on the Campbell Plateau during the deglaciation (18-12 ka). From these observations, it is proposed that even though increased glacial dust deposition may have relieved iron limitation within the SAZ around New Zealand, the availability of silicic acid limited diatom growth and thus any resultant increase in carbon export during the LGM. Therefore, silicic acid concentrations have remained low since the LGM. This result suggests that both silicic acid and iron co-limit EP in the SAZ around New Zealand, consistent with modern process studies.

75 FR 18153 - Certain Large Diameter Carbon and Alloy Seamless Standard, Line, and Pressure Pipe From Japan...

Federal Register 2010, 2011, 2012, 2013, 2014

2010-04-09

... Carbon and Alloy Seamless Standard, Line, and Pressure Pipe From Japan: Extension of Time Limit for... review of the antidumping duty order on certain large diameter carbon and alloy seamless standard, line... Carbon and Alloy Seamless Standard, Line and Pressure Pipe from Japan: Extension of Time Limit for...

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

B. E. Law; E. Falgeb; L. Guc

2002-12-02

The objective of this research was to compare seasonal and annual estimates of CO2 and water vapor exchange across sites in forests, grasslands, crops, and tundra that are part of an international network called FLUXNET, and to investigating the responses of vegetation to environmental variables. FLUXNETs goals are to understand the mechanisms controlling the exchanges of CO2, water vapor and energy across a spectrum of time and space scales, and to provide information for modeling of carbon and water cycling across regions and the globe. At a subset of sites, net carbon uptake (net ecosystem exchange, the net of photosynthesismore » and respiration) was greater under diffuse than under direct radiation conditions, perhaps because of a more efficient distribution of non-saturating light conditions for photosynthesis, lower vapor pressure deficit limitation to photosynthesis, and lower respiration associated with reduced temperature. The slope of the relation between monthly gross ecosystem production and evapotranspiration was similar between biomes, except for tundra vegetation, showing a strong linkage between carbon gain and water loss integrated over the year (slopes=3.4 g CO2/kg H2O for grasslands, 3.2 for deciduous broadleaf forests, 3.1 for crops, 2.4 for evergreen conifers, and 1.5 for tundra vegetation). The ratio of annual ecosystem respiration to gross photosynthesis averaged 0.83, with lower values for grasslands, presumably because of less investment in respiring plant tissue compared with forests. Ecosystem respiration was weakly correlated with mean annual temperature across biomes, in spite of within site sensitivity over shorter temporal scales. Mean annual temperature and site water balance explained much of the variation in gross photosynthesis. Water availability limits leaf area index over the long-term, and inter-annual climate variability can limit carbon uptake below the potential of the leaf area present.« less

REPORT TO CONGRESS ON BLACK CARBON

EPA Science Inventory

The Report to Congress on Black Carbon describes domestic and international sources of black carbon emissions, and summarizes available scientific information on the climate effects of black carbon. Further, the Report evaluates available black carbon mitigation options and thei...

Lactic acid production from xylose by Geobacillus stearothermophilus strain 15

NASA Astrophysics Data System (ADS)

Kunasundari, B.; Naresh, S.; Chu, J. E.

2017-09-01

Lactic acid is an important compound with a wide range of industrial applications. The present study tested the efficiency of xylose, as a sole carbon source to be converted to lactic acid by Geobacillus stearothermophilus strain 15. To the best of our knowledge, limited information is available on the directed fermentation of xylose to lactic acid by this bacterium. The effects of different parameters such as temperature, pH, incubation time, agitation speed, concentrations of nitrogen and carbon sources on the lactic acid production were investigated statistically. It was found that the bacterium exhibited poor assimilation of xylose to lactic acid. Temperature, agitation rate and incubation time were determined to improve the lactic acid production slightly. The highest lactic acid yield obtained was 8.9% at 45°C, 300 RPM, 96 h, pH of 6.0 with carbon and nitrogen source concentrations were fixed at 5% w/v.

Hollow carbon nanobubbles: monocrystalline MOF nanobubbles and their pyrolysis† †Electronic supplementary information (ESI) available. See DOI: 10.1039/c6sc04903f Click here for additional data file.

PubMed Central

Zhang, Wei; Jiang, Xiangfen; Zhao, Yanyi; Carné-Sánchez, Arnau; Malgras, Victor; Kim, Jeonghun; Kim, Jung Ho; Wang, Shaobin; Jiang, Ji-Sen

2017-01-01

While bulk-sized metal–organic frameworks (MOFs) face limits to their utilization in various research fields such as energy storage applications, nanoarchitectonics is believed to be a possible solution. It is highly challenging to realize MOF nanobubbles with monocrystalline frameworks. By a spatially controlled etching approach, here, we can achieve the synthesis of zeolitic imidazolate framework (ZIF-8) nanobubbles with a uniform size of less than 100 nm. Interestingly, the ZIF-8 nanobubbles possess a monocrystalline nanoshell with a thickness of around 10 nm. Under optimal pyrolytic conditions, the ZIF-8 nanobubbles can be converted into hollow carbon nanobubbles while keeping their original shapes. The structure of the nanobubble enhances the fast Na+/K+ ion intercalation performance. Such remarkable improvement cannot be realized by conventional MOFs or their derived carbons. PMID:28580098

Scenarios for optimizing potato productivity in a lunar CELSS

NASA Technical Reports Server (NTRS)

Wheeler, R. M.; Morrow, R. C.; Tibbitts, T. W.; Bula, R. J.

1992-01-01

The use of controlled ecological life support system (CELSS) in the development and growth of large-scale bases on the Moon will reduce the expense of supplying life support materials from Earth. Such systems would use plants to produce food and oxygen, remove carbon dioxide, and recycle water and minerals. In a lunar CELSS, several factors are likely to be limiting to plant productivity, including the availability of growing area, electrical power, and lamp/ballast weight for lighting systems. Several management scenarios are outlined in this discussion for the production of potatoes based on their response to irradiance, photoperiod, and carbon dioxide concentration. Management scenarios that use 12-hr photoperiods, high carbon dioxide concentrations, and movable lamp banks to alternately irradiate halves of the growing area appear to be the most efficient in terms of growing area, electrical power, and lamp weights. However, the optimal scenario will be dependent upon the relative 'costs' of each factor.

Automobiles and global warming: Alternative fuels and other options for carbon dioxide emissions reduction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sagar, A.D.

Automobiles are a source of considerable pollution at the global level, including a significant fraction of the total greenhouse gas emissions. Alternative fuels have received some attention as potential options to curtail the carbon dioxide emissions from motor vehicles. This article discusses the feasibility and desirability (from a technical as well as a broader environmental perspective) of the large-scale production and use of alternative fuels as a strategy to mitigate automotive carbon dioxide emissions. Other options such as improving vehicle efficiency and switching to more efficient modes of passenger transportation are also discussed. These latter options offer an effective andmore » immediate way to tackle the greenhouse and other pollutant emission from automobiles, especially as the limitations of currently available alternative fuels and the technological and other constraints for potential future alternatives are revealed.« less

Review of Manganese Processing for Production of TRIP/TWIP Steels, Part 2: Reduction Studies

NASA Astrophysics Data System (ADS)

Elliott, R.; Coley, K.; Mostaghel, S.; Barati, M.

2018-02-01

Production of ultrahigh-manganese steels is expected to result in significant increase in demand for low-carbon (LC) ferromanganese (FeMn) and silicomanganese (SiMn). Current manganese processing techniques are energy intensive and typically yield a high-carbon product. The present work therefore reviews available literature regarding carbothermic reduction of Mn oxides and ores, with the objective of identifying opportunities for future process development to mitigate the cost of LC FeMn and SiMn. In general, there is consensus that carbothermic reduction of Mn oxides and ores is limited by gasification of carbon. Conditions which enhance or bypass this step (e.g., by application of CH4) show higher rates of reduction at lower temperatures. This phenomenon has potential application in solid-state reduction of Mn ore. Other avenues for process development include optimization of the prereduction step in conventional FeMn production and metallothermic reduction as a secondary reduction step.

A numerical study of tropospheric ozone in the springtime in East Asia

NASA Astrophysics Data System (ADS)

Zhang, Meigen; Xu, Yongfu; Itsushi, Uno; Hajime, Akimoto

2004-04-01

The Models-3 Community Multi-scale Air Quality modeling system (CMAQ) coupled with the Regional Atmospheric Modeling System (RAMS) is applied to East Asia to study the transport and photochemical transformation of tropospheric ozone in March 1998. The calculated mixing ratios of ozone and carbon monoxide are compared with ground level observations at three remote sites in Japan and it is found that the model reproduces the observed features very well. Examination of several high episodes of ozone and carbon monoxide indicates that these elevated levels are found in association with continental outflow, demonstrating the critical role of the rapid transport of carbon monoxide and other ozone precursors from the continental boundary layer. In comparison with available ozonesonde data, it is found that the model-calculated ozone concentrations are generally in good agreement with the measurements, and the stratospheric contribution to surface ozone mixing ratios is quite limited.

Iron-sulfur-carbon relationships in organic-carbon-rich sequences I: Cretaceous Western Interior seaway

USGS Publications Warehouse

Dean, W.E.; Arthur, M.A.

1989-01-01

Cretaceous marine strata deposited in shallow to intermediate depths in the Western Interior seaway of North America show considerable variation in organic-carbon enrichment and degree of pyrite formation. The extreme range of paleoceanographic and depositional conditions that occurred in this seaway provide a unique opportunity to examine the effects of iron-, carbon-, and sulfur-limitation on pyrite formation in one region over about 30 my. Ternary diagrams of the system Fe-S-OC, together with some measure of the reactivity of organic matter (pyrolysis hydrogen index), provide a rapid means of recognizing iron-, carbon-, and sulfur-limitation on pyrite formation in a series of samples from a single lithologic unit. Iron limitation is indicated by a concentration of data along a line of constant S/Fe ratio on a Fe-S-OC ternary diagram. Carbon limitation is indicated by a concentration of data along a line of constant S/OC ratio. Sulfur-limitation is suggested by the lack of a systematic Fe-S-OC relationship and residual organic matter that is high in abundance and reactivity. -from Authors

Maize source leaf adaptation to nitrogen deficiency affects not only nitrogen and carbon metabolism but also control of phosphate homeostasis.

PubMed

Schlüter, Urte; Mascher, Martin; Colmsee, Christian; Scholz, Uwe; Bräutigam, Andrea; Fahnenstich, Holger; Sonnewald, Uwe

2012-11-01

Crop plant development is strongly dependent on the availability of nitrogen (N) in the soil and the efficiency of N utilization for biomass production and yield. However, knowledge about molecular responses to N deprivation derives mainly from the study of model species. In this article, the metabolic adaptation of source leaves to low N was analyzed in maize (Zea mays) seedlings by parallel measurements of transcriptome and metabolome profiling. Inbred lines A188 and B73 were cultivated under sufficient (15 mM) or limiting (0.15 mM) nitrate supply for up to 30 d. Limited availability of N caused strong shifts in the metabolite profile of leaves. The transcriptome was less affected by the N stress but showed strong genotype- and age-dependent patterns. N starvation initiated the selective down-regulation of processes involved in nitrate reduction and amino acid assimilation; ammonium assimilation-related transcripts, on the other hand, were not influenced. Carbon assimilation-related transcripts were characterized by high transcriptional coordination and general down-regulation under low-N conditions. N deprivation caused a slight accumulation of starch but also directed increased amounts of carbohydrates into the cell wall and secondary metabolites. The decrease in N availability also resulted in accumulation of phosphate and strong down-regulation of genes usually involved in phosphate starvation response, underlining the great importance of phosphate homeostasis control under stress conditions.

Prospective CO 2 saline resource estimation methodology: Refinement of existing US-DOE-NETL methods based on data availability

DOE PAGES

Goodman, Angela; Sanguinito, Sean; Levine, Jonathan S.

2016-09-28

Carbon storage resource estimation in subsurface saline formations plays an important role in establishing the scale of carbon capture and storage activities for governmental policy and commercial project decision-making. Prospective CO 2 resource estimation of large regions or subregions, such as a basin, occurs at the initial screening stages of a project using only limited publicly available geophysical data, i.e. prior to project-specific site selection data generation. As the scale of investigation is narrowed and selected areas and formations are identified, prospective CO 2 resource estimation can be refined and uncertainty narrowed when site-specific geophysical data are available. Here, wemore » refine the United States Department of Energy – National Energy Technology Laboratory (US-DOE-NETL) methodology as the scale of investigation is narrowed from very large regional assessments down to selected areas and formations that may be developed for commercial storage. In addition, we present a new notation that explicitly identifies differences between data availability and data sources used for geologic parameters and efficiency factors as the scale of investigation is narrowed. This CO 2 resource estimation method is available for screening formations in a tool called CO 2-SCREEN.« less

Prospective CO 2 saline resource estimation methodology: Refinement of existing US-DOE-NETL methods based on data availability

DOE Office of Scientific and Technical Information (OSTI.GOV)

Goodman, Angela; Sanguinito, Sean; Levine, Jonathan S.

Carbon storage resource estimation in subsurface saline formations plays an important role in establishing the scale of carbon capture and storage activities for governmental policy and commercial project decision-making. Prospective CO 2 resource estimation of large regions or subregions, such as a basin, occurs at the initial screening stages of a project using only limited publicly available geophysical data, i.e. prior to project-specific site selection data generation. As the scale of investigation is narrowed and selected areas and formations are identified, prospective CO 2 resource estimation can be refined and uncertainty narrowed when site-specific geophysical data are available. Here, wemore » refine the United States Department of Energy – National Energy Technology Laboratory (US-DOE-NETL) methodology as the scale of investigation is narrowed from very large regional assessments down to selected areas and formations that may be developed for commercial storage. In addition, we present a new notation that explicitly identifies differences between data availability and data sources used for geologic parameters and efficiency factors as the scale of investigation is narrowed. This CO 2 resource estimation method is available for screening formations in a tool called CO 2-SCREEN.« less

Physiological and Transcriptional Responses of Saccharomyces cerevisiae to Zinc Limitation in Chemostat Cultures †

PubMed Central

De Nicola, Raffaele; Hazelwood, Lucie A.; De Hulster, Erik A. F.; Walsh, Michael C.; Knijnenburg, Theo A.; Reinders, Marcel J. T.; Walker, Graeme M.; Pronk, Jack T.; Daran, Jean-Marc; Daran-Lapujade, Pascale

2007-01-01

Transcriptional responses of the yeast Saccharomyces cerevisiae to Zn availability were investigated at a fixed specific growth rate under limiting and abundant Zn concentrations in chemostat culture. To investigate the context dependency of this transcriptional response and eliminate growth rate-dependent variations in transcription, yeast was grown under several chemostat regimens, resulting in various carbon (glucose), nitrogen (ammonium), zinc, and oxygen supplies. A robust set of genes that responded consistently to Zn limitation was identified, and the set enabled the definition of the Zn-specific Zap1p regulon, comprised of 26 genes and characterized by a broader zinc-responsive element consensus (MHHAACCBYNMRGGT) than so far described. Most surprising was the Zn-dependent regulation of genes involved in storage carbohydrate metabolism. Their concerted down-regulation was physiologically relevant as revealed by a substantial decrease in glycogen and trehalose cellular content under Zn limitation. An unexpectedly large number of genes were synergistically or antagonistically regulated by oxygen and Zn availability. This combinatorial regulation suggested a more prominent involvement of Zn in mitochondrial biogenesis and function than hitherto identified. PMID:17933919

Interfacial Thermal Conductance Limit and Thermal Rectification Across Vertical Carbon Nanotube/Graphene Nanoribbon-Silicon Interfaces

DTIC Science & Technology

2013-01-01

Interfacial thermal conductance limit and thermal rectification across vertical carbon nanotube/graphene nanoribbon-silicon interfaces Ajit K...054308 (2013) Investigation on interfacial thermal resistance and phonon scattering at twist boundary of silicon J. Appl. Phys. 113, 053513 (2013...2013 to 00-00-2013 4. TITLE AND SUBTITLE Interfacial thermal conductance limit and thermal rectification across vertical carbon nanotube/graphene

Identifying the underlying causes of biological instability in a full-scale drinking water supply system.

PubMed

Nescerecka, Alina; Juhna, Talis; Hammes, Frederik

2018-05-15

Changes in bacterial concentration and composition in drinking water during distribution are often attributed to biological (in)stability. Here we assessed temporal biological stability in a full-scale distribution network (DN) supplied with different types of source water: treated and chlorinated surface water and chlorinated groundwater produced at three water treatment plants (WTP). Monitoring was performed weekly during 12 months in two locations in the DN. Flow cytometric total and intact cell concentration (ICC) measurements showed considerable seasonal fluctuations, which were different for two locations. ICC varied between 0.1-3.75 × 10 5  cells mL -1 and 0.69-4.37 × 10 5  cells mL -1 at two locations respectively, with ICC increases attributed to temperature-dependent bacterial growth during distribution. Chlorinated water from the different WTP was further analysed with a modified growth potential method, identifying primary and secondary growth limiting compounds. It was observed that bacterial growth in the surface water sample after chlorination was primarily inhibited by phosphorus limitation and secondly by organic carbon limitation, while carbon was limiting in the chlorinated groundwater samples. However, the ratio of available nutrients changed during distribution, and together with disinfection residual decay, this resulted in higher bacterial growth potential detected in the DN than at the WTP. In this study, bacterial growth was found to be higher (i) at higher water temperatures, (ii) in samples with lower chlorine residuals and (iii) in samples with less nutrient (carbon, phosphorus, nitrogen, iron) limitation, while this was significantly different between the samples of different origin. Thus drinking water microbiological quality and biological stability could change during different seasons, and the extent of these changes depends on water temperature, the water source and treatment. Furthermore, differences in primary growth limiting nutrients in different water sources could contribute to biological instability in the network, where mixing occurs. Copyright © 2018 Elsevier Ltd. All rights reserved.

Using a spatially-distributed hydrologic biogeochemistry model with a nitrogen transport module to study the spatial variation of carbon processes in a Critical Zone Observatory

DOE PAGES

Shi, Yuning; Eissenstat, David M.; He, Yuting; ...

2018-05-12

Terrestrial carbon processes are affected by soil moisture, soil temperature, nitrogen availability and solar radiation, among other factors. Most of the current ecosystem biogeochemistry models represent one point in space, and have limited characterization of hydrologic processes. Therefore these models can neither resolve the topographically driven spatial variability of water, energy, and nutrient, nor their effects on carbon processes. A spatially-distributed land surface hydrologic biogeochemistry model, Flux-PIHM-BGC, is developed by coupling the Biome-BGC model with a physically-based land surface hydrologic model, Flux-PIHM. In the coupled system, each Flux-PIHM model grid couples a 1-D Biome-BGC model. In addition, a topographic solarmore » radiation module and an advection-driven nitrogen transport module are added to represent the impact of topography on nutrient transport and solar energy distribution. Because Flux-PIHM is able to simulate lateral groundwater flow and represent the land surface heterogeneities caused by topography, Flux-PIHM-BGC is capable of simulating the complex interaction among water, energy, nutrient, and carbon in time and space. The Flux-PIHM-BGC model is tested at the Susquehanna/Shale Hills Critical Zone Observatory. Model results show that distributions of carbon and nitrogen stocks and fluxes are strongly affected by topography and landscape position, and tree growth is nitrogen limited. The predicted aboveground and soil carbon distributions generally agree with the macro patterns observed. Although the model underestimates the spatial variation, the predicted watershed average values are close to the observations. Lastly, the coupled Flux-PIHM-BGC model provides an important tool to study spatial variations in terrestrial carbon and nitrogen processes and their interactions with environmental factors, and to predict the spatial structure of the responses of ecosystems to climate change.« less

Assessing Land Management Change Effects on Forest Carbon and Emissions Under Changing Climate

NASA Astrophysics Data System (ADS)

Law, B. E.

2014-12-01

There has been limited focus on fine-scale land management change effects on forest carbon under future environmental conditions (climate, nitrogen deposition, increased atmospheric CO2). Forest management decisions are often made at the landscape to regional levels before analyses have been conducted to determine the potential outcomes and effectiveness of such actions. Scientists need to evaluate plausible land management actions in a timely manner to help shape policy and strategic land management. Issues of interest include species-level adaptation to climate, resilience and vulnerability to mortality within forested landscapes and regions. Efforts are underway to improve land system model simulation of future mortality related to climate, and to develop and evaluate plausible land management options that could help mitigate or avoid future die-offs. Vulnerability to drought-related mortality varies among species and with tree size or age. Predictors of species ability to survive in specific environments are still not resolved. A challenge is limited observations for fine-scale (e.g. 4 km2) modeling, particularly physiological parameters. Uncertainties are primarily associated with future land management and policy decisions. They include the interface with economic factors and with other ecosystem services (biodiversity, water availability, wildlife habitat). The outcomes of future management scenarios should be compared with business-as-usual management under the same environmental conditions to determine the effects of management changes on forest carbon and net emissions to the atmosphere. For example, in the western U.S., land system modeling and life cycle assessment of several management options to reduce impacts of fire reduced long-term forest carbon gain and increased carbon emissions compared with business-as-usual management under future environmental conditions. The enhanced net carbon uptake with climate and reduced fire emissions after thinning did not compensate for the increased wood removals over 90 years, leading to reduced net biome production. Analysis of land management change scenarios at fine scales is needed, and should consider other ecological values in addition to carbon.

Using a spatially-distributed hydrologic biogeochemistry model with a nitrogen transport module to study the spatial variation of carbon processes in a Critical Zone Observatory

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shi, Yuning; Eissenstat, David M.; He, Yuting

Terrestrial carbon processes are affected by soil moisture, soil temperature, nitrogen availability and solar radiation, among other factors. Most of the current ecosystem biogeochemistry models represent one point in space, and have limited characterization of hydrologic processes. Therefore these models can neither resolve the topographically driven spatial variability of water, energy, and nutrient, nor their effects on carbon processes. A spatially-distributed land surface hydrologic biogeochemistry model, Flux-PIHM-BGC, is developed by coupling the Biome-BGC model with a physically-based land surface hydrologic model, Flux-PIHM. In the coupled system, each Flux-PIHM model grid couples a 1-D Biome-BGC model. In addition, a topographic solarmore » radiation module and an advection-driven nitrogen transport module are added to represent the impact of topography on nutrient transport and solar energy distribution. Because Flux-PIHM is able to simulate lateral groundwater flow and represent the land surface heterogeneities caused by topography, Flux-PIHM-BGC is capable of simulating the complex interaction among water, energy, nutrient, and carbon in time and space. The Flux-PIHM-BGC model is tested at the Susquehanna/Shale Hills Critical Zone Observatory. Model results show that distributions of carbon and nitrogen stocks and fluxes are strongly affected by topography and landscape position, and tree growth is nitrogen limited. The predicted aboveground and soil carbon distributions generally agree with the macro patterns observed. Although the model underestimates the spatial variation, the predicted watershed average values are close to the observations. Lastly, the coupled Flux-PIHM-BGC model provides an important tool to study spatial variations in terrestrial carbon and nitrogen processes and their interactions with environmental factors, and to predict the spatial structure of the responses of ecosystems to climate change.« less

Decomposition of plant materials in marine sediment exposed to different electron acceptors (O 2, NO 3-, and SO 42-), with emphasis on substrate origin, degradation kinetics, and the role of bioturbation

NASA Astrophysics Data System (ADS)

Kristensen, Erik; Holmer, Marianne

2001-02-01

Carbon mineralization of fresh and aged diatoms ( Skeletonema costatum) and barley hay ( Hordeum vulgare) was followed for 23 to 35 d in sandy and silty sediment. By the use of a thin-layer flow-through technique, it was possible to expose the sediment selectively for oxygen, nitrate or sulfate as electron acceptors in the terminal oxidation of organic carbon. Decomposition took place in two basic stages. Mineralization of the rapidly leachable fraction of the fresh materials occurred rapidly and with the same constant rate regardless of the electron acceptor available, indicating that the dissolved organic carbon released initially was labile and readily available for all heterotrophic respirers. In the case of diatoms, decay of the remaining, more refractory, particulate fraction of fresh and aged diatoms were strikingly similar, although both were degraded 5 to 10 times faster under oxic than anoxic conditions. Most of the particulate remains of diatoms after leaching apparently belong to one fraction, which maintains the same degradability even after prolonged aging. With respect to hay, the late divergence in rates of aerobic and anaerobic decay (a factor of 4 to 5 for aged hay only after 20 d) indicated that the larger hay particles (<500 μm) became exhausted in labile organic matter much slower through time than fine-particulate diatoms (˜20 μm). Anaerobic carbon mineralization rates of diatoms and hay particulates with sulfate and nitrate as electron acceptors were similar or up to two times faster with sulfate. The generally low levels of dissolved organic carbon in all incubations after the initial leaching phase suggest that the limiting step of decomposition under both aerobic and anaerobic decay is the initial hydrolytic attack on the complex particulate remains. Based on a volumetric model, we show that the exposure of anoxic subsurface sediment containing partly degraded organic material to oxygen via irrigated worm burrows or by reworking may significantly enhance total sediment carbon oxidation. The enhancement in the irrigation case increases linearly with density (up to 80%) and is higher than the density-independent enhancement (10%) in the reworking case when abundance is above a lower limit of ˜400 individuals/m 2.

Climate seasonality limits leaf carbon assimilation and wood productivity in tropical forests

DOE PAGES

Wagner, Fabien H.; Hérault, Bruno; Bonal, Damien; ...

2016-04-28

Here, the seasonal climate drivers of the carbon cycle in tropical forests remain poorly known, although these forests account for more carbon assimilation and storage than any other terrestrial ecosystem. Based on a unique combination of seasonal pan-tropical data sets from 89 experimental sites (68 include aboveground wood productivity measurements and 35 litter productivity measurements), their associated canopy photosynthetic capacity (enhanced vegetation index, EVI) and climate, we ask how carbon assimilation and aboveground allocation are related to climate seasonality in tropical forests and how they interact in the seasonal carbon cycle. We found that canopy photosynthetic capacity seasonality responds positivelymore » to precipitation when rainfall is < 2000 mm yr -1 (water-limited forests) and to radiation otherwise (light-limited forests). On the other hand, independent of climate limitations, wood productivity and litterfall are driven by seasonal variation in precipitation and evapotranspiration, respectively. Consequently, light-limited forests present an asynchronism between canopy photosynthetic capacity and wood productivity. First-order control by precipitation likely indicates a decrease in tropical forest productivity in a drier climate in water-limited forest, and in current light-limited forest with future rainfall < 2000 mm yr -1.« less

Climate seasonality limits leaf carbon assimilation and wood productivity in tropical forests

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wagner, Fabien H.; Hérault, Bruno; Bonal, Damien

Here, the seasonal climate drivers of the carbon cycle in tropical forests remain poorly known, although these forests account for more carbon assimilation and storage than any other terrestrial ecosystem. Based on a unique combination of seasonal pan-tropical data sets from 89 experimental sites (68 include aboveground wood productivity measurements and 35 litter productivity measurements), their associated canopy photosynthetic capacity (enhanced vegetation index, EVI) and climate, we ask how carbon assimilation and aboveground allocation are related to climate seasonality in tropical forests and how they interact in the seasonal carbon cycle. We found that canopy photosynthetic capacity seasonality responds positivelymore » to precipitation when rainfall is < 2000 mm yr -1 (water-limited forests) and to radiation otherwise (light-limited forests). On the other hand, independent of climate limitations, wood productivity and litterfall are driven by seasonal variation in precipitation and evapotranspiration, respectively. Consequently, light-limited forests present an asynchronism between canopy photosynthetic capacity and wood productivity. First-order control by precipitation likely indicates a decrease in tropical forest productivity in a drier climate in water-limited forest, and in current light-limited forest with future rainfall < 2000 mm yr -1.« less

The effects of phosphorus limitation on carbon metabolism in diatoms.

PubMed

Brembu, Tore; Mühlroth, Alice; Alipanah, Leila; Bones, Atle M

2017-09-05

Phosphorus is an essential element for life, serving as an integral component of nucleic acids, lipids and a diverse range of other metabolites. Concentrations of bioavailable phosphorus are low in many aquatic environments. Microalgae, including diatoms, apply physiological and molecular strategies such as phosphorus scavenging or recycling as well as adjusting cell growth in order to adapt to limiting phosphorus concentrations. Such strategies also involve adjustments of the carbon metabolism. Here, we review the effect of phosphorus limitation on carbon metabolism in diatoms. Two transcriptome studies are analysed in detail, supplemented by other transcriptome, proteome and metabolite data, to gain an overview of different pathways and their responses. Phosphorus, nitrogen and silicon limitation responses are compared, and similarities and differences discussed. We use the current knowledge to propose a suggestive model for the carbon flow in phosphorus-replete and phosphorus-limited diatom cells.This article is part of the themed issue 'The peculiar carbon metabolism in diatoms'. © 2017 The Authors.

The effects of phosphorus limitation on carbon metabolism in diatoms

PubMed Central

Alipanah, Leila

2017-01-01

Phosphorus is an essential element for life, serving as an integral component of nucleic acids, lipids and a diverse range of other metabolites. Concentrations of bioavailable phosphorus are low in many aquatic environments. Microalgae, including diatoms, apply physiological and molecular strategies such as phosphorus scavenging or recycling as well as adjusting cell growth in order to adapt to limiting phosphorus concentrations. Such strategies also involve adjustments of the carbon metabolism. Here, we review the effect of phosphorus limitation on carbon metabolism in diatoms. Two transcriptome studies are analysed in detail, supplemented by other transcriptome, proteome and metabolite data, to gain an overview of different pathways and their responses. Phosphorus, nitrogen and silicon limitation responses are compared, and similarities and differences discussed. We use the current knowledge to propose a suggestive model for the carbon flow in phosphorus-replete and phosphorus-limited diatom cells. This article is part of the themed issue ‘The peculiar carbon metabolism in diatoms’. PMID:28717016

Coupling of soil respiration and nutrient mineralization: What is the role of land use?

NASA Astrophysics Data System (ADS)

Gan, Huei Ying; Schoening, Ingo; Schrumpf, Marion

2017-04-01

Microbial decomposition of soil organic matter (SOM) is coupling carbon (C) and nutrient mineralization. In order to meet their stoichiometric requirements for growth, it can be assumed that microbes have to mineralize (or remove) relative more organic carbon (OC) to acquire limiting nutrients at sites with large carbon-to-nutrient (C:N, C:P, C:S) ratios of SOM. Land use and management intensities are important controls for belowground C and nutrient availabilities, but their effect on the combined carbon and nutrient mineralization and carbon use efficiency (CUE) have rarely been addressed. The main objective of this study was to test the effect of land use (forest versus grassland), forest management (unmanaged beech forest and age-class managed coniferous and deciduous forests) and grassland management (fertilized and unfertilized meadow, mown pasture and pasture) on the stoichiometry of mineralized C, N, P and S. We incubated a total of 120 topsoil samples (0-10 cm) from three German study regions with different soil types for two weeks in microlysimeters and measured CO2 evolution and leachable organic carbon (DOC) and nutrients (NH4+, NO3-, SO42- and PO43-). The relationships between metabolic quotient (microbial respiration per unit microbial biomass; qCO2) and soil nutrient concentrations were compared between different land use and management. Preliminary results showed that qCO2 was significantly higher (p<0.001) in forests than grasslands. This supports our hypothesis that under higher nutrient limitations in forest, more energy may be allocated for maintenance than growth. In forest, qCO2 was strongly correlated to C:N ratio (r =0.84, p<0.001), while C:N was less strongly correlated with qCO2 in the grasslands (r =0.35, p>0.05). As C:N ratio was significantly higher (p<0.05) in forests (14.9±0.3) than grasslands (10.0±0.3), this finding agreed with previous studies that more C per unit microbial C is respired under lower N availability. Similary in forests, qCO2 was found to be strongly correlated to inorganic P (Olsen) content (r =0.82, p<0.001), whereas weaker correlation was observed in the grasslands (r =0.47, p>0.05). The stronger correlation in forests might indicate higher P limitation as compared to grasslands. Soil pH showed strong negative effect on qCO2 in the forests (r =-0.68, p<0.005) while positively correlated to qCO2 in the grasslands (r =0.42, p<0.05). This indicates that lower soil pH in forests results in higher qCO2 and lower CUE, but higher soil pH in the grasslands could also constrain microbial activities and result in lower CUE. Our first results suggest that qCO2 is affected by land use, and that this effect could be due to differences in nutrient availability. More analysis will follow to elucidate the interactions between qCO2 and other nutrients, and how is this affected by forest and grassland management.

Indoor air quality in Portuguese archives: a snapshot on exposure levels.

PubMed

Pinheiro, A C; Viegas, C; Viegas, S; Veríssimo, C; Brandão, J; Macedo, M F

2012-01-01

Indoor air quality recently entered legislation in Portugal. Several parameters must be evaluated and kept within limits in order to obtain a certification for air quality and energy consumption. Certification parameters were analyzed in two Portuguese archives in order to assess indoor air quality both for people attending or working on these premises and for maintenance of a written heritage that must be retained for future generations. Carbon monoxide (CO) and carbon dioxide (CO₂), formaldehyde, and fungal counts were kept within stipulated limits. Relative humidity (RH), volatile organic compounds (VOC), particulate matter (PM₁₀), and ozone (O₃) showed values above legislated levels and justified the implementation of corrective measures. In terms of conservation, studies on the limit values are still needed, but according to the available international guidelines, some of the analyzed parameters such as PM₁₀, O₃, and RH were also above desirable values. Corrective measures were proposed to these institutions. Although this study was only of a short duration, it proved valuable in assessing potential eventual problems and constitutes the first Portuguese indoor air quality assessment taking into consideration both aspects of an archive such as human health and heritage safekeeping.

Carbon balance of a grazed savanna grassland ecosystem in South Africa

NASA Astrophysics Data System (ADS)

Räsänen, Matti; Aurela, Mika; Vakkari, Ville; Beukes, Johan P.; Tuovinen, Juha-Pekka; Van Zyl, Pieter G.; Josipovic, Miroslav; Venter, Andrew D.; Jaars, Kerneels; Siebert, Stefan J.; Laurila, Tuomas; Rinne, Janne; Laakso, Lauri

2017-03-01

Tropical savannas and grasslands are estimated to contribute significantly to the total primary production of all terrestrial vegetation. Large parts of African savannas and grasslands are used for agriculture and cattle grazing, but the carbon flux data available from these areas are limited. This study explores carbon dioxide fluxes measured with the eddy covariance method for 3 years at a grazed savanna grassland in Welgegund, South Africa. The tree cover around the measurement site, grazed by cattle and sheep, was around 15 %. The night-time respiration was not significantly dependent on either soil moisture or soil temperature on a weekly temporal scale, whereas on an annual timescale higher respiration rates were observed when soil temperatures were higher. The carbon dioxide balances of the years 2010-2011, 2011-2012 and 2012-2013 were -85 ± 16, 67 ± 20 and 139 ± 13 gC m-2 yr-1, respectively. The yearly variation was largely determined by the changes in the early wet season fluxes (September to November) and in the mid-growing season fluxes (December to January). Early rainfall enhanced the respiratory capacity of the ecosystem throughout the year, whereas during the mid-growing season high rainfall resulted in high carbon uptake.

Highlighting the relative effects of surface characteristics and porosity on CO2 capture by adsorbents templated from melamine-based polyaminals

NASA Astrophysics Data System (ADS)

Rehman, Adeela; Park, Soo-Jin

2018-02-01

Heteroatom doping along with well-tuned porosity are considered as significant characteristics of a porous carbon material for various potential applications. However, it is a challenging task to tune a single parameter while retaining the other variables unaffected, and this is considered a limiting factor in rational and systematic research. In the present work, in situ nitrogen-enriched microporous carbon materials were prepared by direct carbonization of conjugated porous polyaminals at two different temperatures. To evaluate the role of nitrogen doping in gas adsorption, a comparison was made with commercially available high-surface-area (2093 m2/g) microporous petroleum-pitch-based activated carbon (AC) deprived of nitrogen functionalities. It was found that the CO2 adsorption capacity of MPA-2-700, carbonized melamine based polyaminal at 700 °C, (186.1 mg/g at 273 K/1 bar with a surface area of 403 m2/g) was significantly higher than that of AC (111.0 mg/g at 273 K/1 bar). Our results present valuable insight into designing porous adsorbents with optimized surface polarity and textural characteristics as promising candidates for CO2 capture.

Effect of carbon limitation on photosynthetic electron transport in Nannochloropsis oculata.

PubMed

Zavřel, Tomáš; Szabó, Milán; Tamburic, Bojan; Evenhuis, Christian; Kuzhiumparambil, Unnikrishnan; Literáková, Petra; Larkum, Anthony W D; Raven, John A; Červený, Jan; Ralph, Peter J

2018-04-01

This study describes the impacts of inorganic carbon limitation on the photosynthetic efficiency and operation of photosynthetic electron transport pathways in the biofuel-candidate microalga Nannochloropsis oculata. Using a combination of highly-controlled cultivation setup (photobioreactor), variable chlorophyll a fluorescence and transient spectroscopy methods (electrochromic shift (ECS) and P 700 redox kinetics), we showed that net photosynthesis and effective quantum yield of Photosystem II (PSII) decreased in N. oculata under carbon limitation. This was accompanied by a transient increase in total proton motive force and energy-dependent non-photochemical quenching as well as slightly elevated respiration. On the other hand, under carbon limitation the rapid increase in proton motive force (PMF, estimated from the total ECS signal) was also accompanied by reduced conductivity of ATP synthase to protons (estimated from the rate of ECS decay in dark after actinic illumination). This indicates that the slow operation of ATP synthase results in the transient build-up of PMF, which leads to the activation of fast energy dissipation mechanisms such as energy-dependent non-photochemical quenching. N. oculata also increased content of lipids under carbon limitation, which compensated for reduced NAPDH consumption during decreased CO 2 fixation. The integrated knowledge of the underlying energetic regulation of photosynthetic processes attained with a combination of biophysical methods may be used to identify photo-physiological signatures of the onset of carbon limitation in microalgal cultivation systems, as well as to potentially identify microalgal strains that can better acclimate to carbon limitation. Copyright © 2018 Elsevier B.V. All rights reserved.

Tropical forest soil microbial communities couple iron and carbon biogeochemistry

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dubinsky, E.A.; Silver, W.L.; Firestone, M.K.

2009-10-15

We report that iron-reducing bacteria are primary mediators of anaerobic carbon oxidation in upland tropical soils spanning a rainfall gradient (3500 - 5000 mm yr-1) in northeast Puerto Rico. The abundant rainfall and high net primary productivity of these tropical forests provide optimal soil habitat for iron-reducing and iron-oxidizing bacteria. Spatially and temporally dynamic redox conditions make iron-transforming microbial communities central to the belowground carbon cycle in these wet tropical forests. The exceedingly high abundance of iron-reducing bacteria (up to 1.2 x 10{sup 9} cells per gram soil) indicated that they possess extensive metabolic capacity to catalyze the reduction ofmore » iron minerals. In soils from the higher rainfall sites, measured rates of ferric iron reduction could account for up to 44 % of organic carbon oxidation. Iron reducers appeared to compete with methanogens when labile carbon availability was limited. We found large numbers of bacteria that oxidize reduced iron at sites with high rates of iron reduction and large numbers of iron-reducers. the coexistence of large populations of ironreducing and iron-oxidizing bacteria is evidence for rapid iron cycling between its reduced and oxidized states, and suggests that mutualistic interactions among these bacteria ultimately fuel organic carbon oxidation and inhibit CH4 production in these upland tropical forests.« less

Emission control devices, fuel additive, and fuel composition changes.

PubMed Central

Piver, W T

1977-01-01

Emission control devices are installed to meet the exhaust standards of the Clean Air Act for carbon monoxide and hydrocarbons, and it is necessary to know, from a public health point of view, how exhaust emissions may be affected by changes in fuel additives and fuel composition. Since these topics are concerned with developing technologies, the available literature on exhaust emission characteristics and the limited information on health effects, is reviewed. PMID:71235

Resource-limited heterotrophic prokaryote production and its potential environmental impact associated with Mn nodule exploitation in the northeast equatorial pacific.

PubMed

Hyun, Jung-Ho

2006-08-01

Shipboard enrichment incubation experiments were performed to elucidate the limiting resources for heterotrophic prokaryotic production and to discuss the potential impact of bottom water and sediment discharges in relation to manganese (Mn) nodule exploitation on the heterotrophic prokaryotes in the oligotrophic northeast equatorial Pacific. Compared to an unamended control, the production of heterotrophic prokaryotes increased 25-fold in water samples supplemented with amino acids (i.e., organic carbon plus nitrogen), whereas the production increased five and two times, respectively, in samples supplemented with either glucose or ammonium alone. These results indicate that heterotrophic prokaryote production in the northeast equatorial Pacific was co-limited by the availability of dissolved organic carbon and inorganic nitrogen. In samples from the nutrient-depleted surface mixed layer (10-m depth), the addition of a slurry of bottom water and sediment doubled heterotrophic prokaryote production compared to an unamended control, whereas sonicating the slurry prior to addition quadrupled the production rate. However, little difference was observed between an unamended control and slurry-amended samples in the subsurface chlorophyll a (Chl a) maximum (SCM) layer. Thus, the impact of slurry discharge is more significant at the nutrient-depleted surface mixed layer than at the high-nutrient SCM layer. The greatly enhanced prokaryote production resulting from the addition of sonicated slurry further suggests that dissociated organic carbon may directly stimulate heterotrophic prokaryote production in the surface mixed layer. Overall, the results suggest that the surface discharge of bottom water and sediments during manganese nodule exploitation could have a significant environmental impact on the production of heterotrophic prokaryotes that are currently resource limited.

The Use of Carbon-Fiber-Reinforced (CFR) PEEK Material in Orthopedic Implants: A Systematic Review

PubMed Central

Li, Chuan Silvia; Vannabouathong, Christopher; Sprague, Sheila; Bhandari, Mohit

2015-01-01

Carbon-fiber-reinforced polyetheretherketone (CFR-PEEK) has been successfully used in orthopedic implants. The aim of this systematic review is to investigate the properties, technical data, and safety of CFR-PEEK biomaterial and to evaluate its potential for new innovation in the design of articulating medical devices. A comprehensive search in PubMed and EMBASE was conducted to identify articles relevant to the outcomes of CFR-PEEK orthopedic implants. The search was also expanded by reviewing the reference sections of selected papers and references and benchmark reports provided by content experts. A total of 23 articles were included in this review. There is limited literature available assessing the performance of CFR-PEEK, specifically as an implant material for arthroplasty systems. Nevertheless, available studies strongly support CFR-PEEK as a promising and suitable material for orthopedic implants because of its biocompatibility, material characteristics, and mechanical durability. Future studies should continue to investigate CFR-PEEK’s potential benefits. PMID:25780341

Sewage input reduces the consumption of Rhizophora mangle propagules by crabs in a subtropical mangrove system.

PubMed

Boehm, Frederike Ricarda; Sandrini-Neto, Leonardo; Moens, Tom; da Cunha Lana, Paulo

2016-12-01

Mangrove forests are highly productive and play a major role in global carbon cycling. Their carbon accumulation can be influenced through the consumption of nutrient-poor leaves and propagules by herbivore crabs. Anthropogenic nutrient input from sewage contamination is widespread in these often naturally nutrient-limited ecosystems. We hypothesised that sewage-mediated nutrient input to mangrove stands of Paranaguá Bay (southern Brazil), would alter the nutrient sources available for crabs, e.g. through microphytobenthos increase, and that this would reflect in their feeding behaviour. We predicted that propagules of Rhizophora mangle in contaminated stands would experience lower grazing pressure from their two main local consumers (Ucides cordatus and Goniopsis cruentata). We compared herbivory rates on R. mangle propagules in sewage contaminated and uncontaminated mangrove stands. We found that herbivory rates were significantly lower in contaminated than uncontaminated forests, but this pattern could not be clearly attributed to increased nutrient availability. Copyright © 2016 Elsevier Ltd. All rights reserved.

3 D Network-Structured Crumpled Graphene/Carbon Nanotube/Polyaniline Composites for Supercapacitors.

PubMed

Jo, Eun H; Jang, Hee D; Chang, Hankwon; Kim, Sun K; Choi, Ji-Hyuk; Lee, Chong M

2017-05-22

Crumpled graphene (CGR) is considered a promising supercapacitor material to achieve high power and energy density because it could overcome the disadvantages of 2 D GR sheets such as aggregation during the electrode fabrication process, reduction of the available surface area, and limitation of the electron and ion transport. Even though CGR shows good results, carbon materials are limited in terms of their capacitance performance. Here, we report highly enhanced supercapacitor materials by fabricating a 3 D composite containing CGR, carbon nanotubes (CNTs), and polyaniline (PANI). The CNTs increased the basal spacing and bridged the defects for electron transfer between the GR sheets in CGR. PANI can enhance the rate of conduction of electrons and offer high pseudocapacitance originating from its redox reactions. The synergistic effect of the CNTs and PANI may also result in a higher electrochemical capacitance and better stability than each individual component as electrode materials for supercapacitors in a two-electrode system. More importantly, the performance of the supercapacitors can be further enhanced by employing 2 D GR as the binder for the composite electrodes, resulting in specific capacitance of 456 F g -1 , rate capability of 89 %, and cyclic stability of 97 % after 1000 cycles. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Carbonate-sensitive phytotransferrin controls high-affinity iron uptake in diatoms

NASA Astrophysics Data System (ADS)

McQuaid, Jeffrey B.; Kustka, Adam B.; Oborník, Miroslav; Horák, Aleš; McCrow, John P.; Karas, Bogumil J.; Zheng, Hong; Kindeberg, Theodor; Andersson, Andreas J.; Barbeau, Katherine A.; Allen, Andrew E.

2018-03-01

In vast areas of the ocean, the scarcity of iron controls the growth and productivity of phytoplankton. Although most dissolved iron in the marine environment is complexed with organic molecules, picomolar amounts of labile inorganic iron species (labile iron) are maintained within the euphotic zone and serve as an important source of iron for eukaryotic phytoplankton and particularly for diatoms. Genome-enabled studies of labile iron utilization by diatoms have previously revealed novel iron-responsive transcripts, including the ferric iron-concentrating protein ISIP2A, but the mechanism behind the acquisition of picomolar labile iron remains unknown. Here we show that ISIP2A is a phytotransferrin that independently and convergently evolved carbonate ion-coordinated ferric iron binding. Deletion of ISIP2A disrupts high-affinity iron uptake in the diatom Phaeodactylum tricornutum, and uptake is restored by complementation with human transferrin. ISIP2A is internalized by endocytosis, and manipulation of the seawater carbonic acid system reveals a second-order dependence on the concentrations of labile iron and carbonate ions. In P. tricornutum, the synergistic interaction of labile iron and carbonate ions occurs at environmentally relevant concentrations, revealing that carbonate availability co-limits iron uptake. Phytotransferrin sequences have a broad taxonomic distribution and are abundant in marine environmental genomic datasets, suggesting that acidification-driven declines in the concentration of seawater carbonate ions will have a negative effect on this globally important eukaryotic iron acquisition mechanism.

Enhanced Production of Green Tide Algal Biomass through Additional Carbon Supply

PubMed Central

de Paula Silva, Pedro H.; Paul, Nicholas A.; de Nys, Rocky; Mata, Leonardo

2013-01-01

Intensive algal cultivation usually requires a high flux of dissolved inorganic carbon (Ci) to support productivity, particularly for high density algal cultures. Carbon dioxide (CO2) enrichment can be used to overcome Ci limitation and enhance productivity of algae in intensive culture, however, it is unclear whether algal species with the ability to utilise bicarbonate (HCO3 −) as a carbon source for photosynthesis will benefit from CO2 enrichment. This study quantified the HCO3 − affinity of three green tide algal species, Cladophora coelothrix, Cladophora patentiramea and Chaetomorpha linum, targeted for biomass and bioenergy production. Subsequently, we quantified productivity and carbon, nitrogen and ash content in response to CO2 enrichment. All three species had similar high pH compensation points (9.7–9.9), and grew at similar rates up to pH 9, demonstrating HCO3 − utilization. Algal cultures enriched with CO2 as a carbon source had 30% more total Ci available, supplying twenty five times more CO2 than the control. This higher Ci significantly enhanced the productivity of Cladophora coelothrix (26%), Chaetomorpha linum (24%) and to a lesser extent for Cladophora patentiramea (11%), compared to controls. We demonstrated that supplying carbon as CO2 can enhance the productivity of targeted green tide algal species under intensive culture, despite their clear ability to utilise HCO3 −. PMID:24324672

40 CFR Table 6 to Subpart Jjjjjj... - Establishing Operating Limits

Code of Federal Regulations, 2014 CFR

2014-07-01

... Dry sorbent or activated carbon injection rate operating parameters Establish a site-specific minimum sorbent or activated carbon injection rate operating limit according to § 63.11211(b) Data from the sorbent or activated carbon injection rate monitors and the mercury performance stack tests (a) You must...

40 CFR Table 6 to Subpart Jjjjjj... - Establishing Operating Limits

Code of Federal Regulations, 2013 CFR

2013-07-01

... Dry sorbent or activated carbon injection rate operating parameters Establish a site-specific minimum sorbent or activated carbon injection rate operating limit according to § 63.11211(b) Data from the sorbent or activated carbon injection rate monitors and the mercury performance stack tests (a) You must...

A Correlated Ab Initio Study of Linear Carbon-Chain Radicals C(sub n)H (n=2-7)

NASA Technical Reports Server (NTRS)

Woon, David E.

1995-01-01

Linear carbon-chain radicals C(sub n) H for n = 2-7 have been studied with correlation consistent valence and core-valence basis sets and the coupled cluster method RCCSD(T). Equilibrium structures, rotational constants, and dipole moments are reported and compared with available experimental data. The ground state of the even-n series changes from 2Sigma(+) to 2Pi as the chain is extended. For C4H, the 2Sigma(+) state was found to lie only 72 cm(exp -1) below the 2Pi state in the estimated complete basis set limit for valence correlation. The C2H(-) and C3H(-) anions have also been characterized.

Graphitization in Carbon MEMS and Carbon NEMS

NASA Astrophysics Data System (ADS)

Sharma, Swati

Carbon MEMS (CMEMS) and Carbon NEMS (CNEMS) are an emerging class of miniaturized devices. Due to the numerous advantages such as scalable manufacturing processes, inexpensive and readily available precursor polymer materials, tunable surface properties and biocompatibility, carbon has become a preferred material for a wide variety of future sensing applications. Single suspended carbon nanowires (CNWs) integrated on CMEMS structures fabricated by electrospinning of SU8 photoresist on photolithographially patterned SU8 followed by pyrolysis are utilized for understanding the graphitization process in micro and nano carbon materials. These monolithic CNW-CMEMS structures enable the fabrication of very high aspect ratio CNWs of predefined length. The CNWs thus fabricated display core---shell structures having a graphitic shell with a glassy carbon core. The electrical conductivity of these CNWs is increased by about 100% compared to glassy carbon as a result of enhanced graphitization. We explore various tunable fabrication and pyrolysis parameters to improve graphitization in the resulting CNWs. We also suggest gas-sensing application of the thus fabricated single suspended CNW-CMEMS devices by using the CNW as a nano-hotplate for local chemical vapor deposition. In this thesis we also report on results from an optimization study of SU8 photoresist derived carbon electrodes. These electrodes were applied to the simultaneous detection of traces of Cd(II) and Pb(II) through anodic stripping voltammetry and detection limits as low as 0.7 and 0.8 microgL-1 were achieved. To further improve upon the electrochemical behavior of the carbon electrodes we elucidate a modified pyrolysis technique featuring an ultra-fast temperature ramp for obtaining bubbled porous carbon from lithographically patterned SU8. We conclude this dissertation by suggesting the possible future works on enhancing graphitization as well as on electrochemical applications

Biochar from sugarcane filtercake reduces soil CO2 emissions relative to raw residue and improves water retention and nutrient availability in a highly-weathered tropical soil.

PubMed

Eykelbosh, Angela Joy; Johnson, Mark S; Santos de Queiroz, Edmar; Dalmagro, Higo José; Guimarães Couto, Eduardo

2014-01-01

In Brazil, the degradation of nutrient-poor Ferralsols limits productivity and drives agricultural expansion into pristine areas. However, returning agricultural residues to the soil in a stabilized form may offer opportunities for maintaining or improving soil quality, even under conditions that typically promote carbon loss. We examined the use of biochar made from filtercake (a byproduct of sugarcane processing) on the physicochemical properties of a cultivated tropical soil. Filtercake was pyrolyzed at 575°C for 3 h yielding a biochar with increased surface area and porosity compared to the raw filtercake. Filtercake biochar was primarily composed of aromatic carbon, with some residual cellulose and hemicellulose. In a three-week laboratory incubation, CO2 effluxes from a highly weathered Ferralsol soil amended with 5% biochar (dry weight, d.w.) were roughly four-fold higher than the soil-only control, but 23-fold lower than CO2 effluxes from soil amended with 5% (d.w.) raw filtercake. We also applied vinasse, a carbon-rich liquid waste from bioethanol production typically utilized as a fertilizer on sugarcane soils, to filtercake- and biochar-amended soils. Total CO2 efflux from the biochar-amended soil in response to vinasse application was only 5% of the efflux when vinasse was applied to soil amended with raw filtercake. Furthermore, mixtures of 5 or 10% biochar (d.w.) in this highly weathered tropical soil significantly increased water retention within the plant-available range and also improved nutrient availability. Accordingly, application of sugarcane filtercake as biochar, with or without vinasse application, may better satisfy soil management objectives than filtercake applied to soils in its raw form, and may help to build soil carbon stocks in sugarcane-cultivating regions.

Biochar from Sugarcane Filtercake Reduces Soil CO2 Emissions Relative to Raw Residue and Improves Water Retention and Nutrient Availability in a Highly-Weathered Tropical Soil

PubMed Central

Eykelbosh, Angela Joy; Johnson, Mark S.; Santos de Queiroz, Edmar; Dalmagro, Higo José; Guimarães Couto, Eduardo

2014-01-01

In Brazil, the degradation of nutrient-poor Ferralsols limits productivity and drives agricultural expansion into pristine areas. However, returning agricultural residues to the soil in a stabilized form may offer opportunities for maintaining or improving soil quality, even under conditions that typically promote carbon loss. We examined the use of biochar made from filtercake (a byproduct of sugarcane processing) on the physicochemical properties of a cultivated tropical soil. Filtercake was pyrolyzed at 575°C for 3 h yielding a biochar with increased surface area and porosity compared to the raw filtercake. Filtercake biochar was primarily composed of aromatic carbon, with some residual cellulose and hemicellulose. In a three-week laboratory incubation, CO2 effluxes from a highly weathered Ferralsol soil amended with 5% biochar (dry weight, d.w.) were roughly four-fold higher than the soil-only control, but 23-fold lower than CO2 effluxes from soil amended with 5% (d.w.) raw filtercake. We also applied vinasse, a carbon-rich liquid waste from bioethanol production typically utilized as a fertilizer on sugarcane soils, to filtercake- and biochar-amended soils. Total CO2 efflux from the biochar-amended soil in response to vinasse application was only 5% of the efflux when vinasse was applied to soil amended with raw filtercake. Furthermore, mixtures of 5 or 10% biochar (d.w.) in this highly weathered tropical soil significantly increased water retention within the plant-available range and also improved nutrient availability. Accordingly, application of sugarcane filtercake as biochar, with or without vinasse application, may better satisfy soil management objectives than filtercake applied to soils in its raw form, and may help to build soil carbon stocks in sugarcane-cultivating regions. PMID:24897522

Climate-mediated spatiotemporal variability in terrestrial productivity across Europe

NASA Astrophysics Data System (ADS)

Wu, X.; Babst, F.; Ciais, P.; Frank, D.; Reichstein, M.; Wattenbach, M.; Zang, C.; Mahecha, M. D.

2014-06-01

Quantifying the interannual variability (IAV) of the terrestrial ecosystem productivity and its sensitivity to climate is crucial for improving carbon budget predictions. In this context it is necessary to disentangle the influence of climate from impacts of other mechanisms underlying the spatiotemporal patterns of IAV of the ecosystem productivity. In this study we investigated the spatiotemporal patterns of IAV of historical observations of European crop yields in tandem with a set of climate variables. We further evaluated if relevant remote-sensing retrievals of NDVI (normalized difference vegetation index) and FAPAR (fraction of absorbed photosynthetically active radiation) depict a similar behaviour. Our results reveal distinct spatial patterns in the IAV of the analysed proxies linked to terrestrial productivity. In particular, we find higher IAV in water-limited regions of Europe (Mediterranean and temperate continental Europe) compared to other regions in both crop yield and remote-sensing observations. Our results further indicate that variations in the water balance during the active growing season exert a more pronounced and direct effect than variations of temperature on explaining the spatial patterns in IAV of productivity-related variables in temperate Europe. Overall, we observe a temporally increasing trend in the IAV of terrestrial productivity and an increasing sensitivity of productivity to water availability in dry regions of Europe during the 1975-2009 period. In the same regions, a simultaneous increase in the IAV of water availability was detected. These findings suggest intricate responses of carbon fluxes to climate variability in Europe and that the IAV of terrestrial productivity has become potentially more sensitive to changes in water availability in the dry regions in Europe. The changing sensitivity of terrestrial productivity accompanied by the changing IAV of climate is expected to impact carbon stocks and the net carbon balance of European ecosystems.

The Optimal Lateral Root Branching Density for Maize Depends on Nitrogen and Phosphorus Availability1[C][W][OPEN

PubMed Central

Postma, Johannes Auke; Dathe, Annette; Lynch, Jonathan Paul

2014-01-01

Observed phenotypic variation in the lateral root branching density (LRBD) in maize (Zea mays) is large (1–41 cm−1 major axis [i.e. brace, crown, seminal, and primary roots]), suggesting that LRBD has varying utility and tradeoffs in specific environments. Using the functional-structural plant model SimRoot, we simulated the three-dimensional development of maize root architectures with varying LRBD and quantified nitrate and phosphorus uptake, root competition, and whole-plant carbon balances in soils varying in the availability of these nutrients. Sparsely spaced (less than 7 branches cm−1), long laterals were optimal for nitrate acquisition, while densely spaced (more than 9 branches cm−1), short laterals were optimal for phosphorus acquisition. The nitrate results are mostly explained by the strong competition between lateral roots for nitrate, which causes increasing LRBD to decrease the uptake per unit root length, while the carbon budgets of the plant do not permit greater total root length (i.e. individual roots in the high-LRBD plants stay shorter). Competition and carbon limitations for growth play less of a role for phosphorus uptake, and consequently increasing LRBD results in greater root length and uptake. We conclude that the optimal LRBD depends on the relative availability of nitrate (a mobile soil resource) and phosphorus (an immobile soil resource) and is greater in environments with greater carbon fixation. The median LRBD reported in several field screens was 6 branches cm−1, suggesting that most genotypes have an LRBD that balances the acquisition of both nutrients. LRBD merits additional investigation as a potential breeding target for greater nutrient acquisition. PMID:24850860

Microscopic Structure and Solubility Predictions of Multifunctional Solids in Supercritical Carbon Dioxide: A Molecular Simulation Study.

PubMed

Noroozi, Javad; Paluch, Andrew S

2017-02-23

Molecular dynamics simulations were employed to both estimate the solubility of nonelectrolyte solids, such as acetanilide, acetaminophen, phenacetin, methylparaben, and lidocaine, in supercritical carbon dioxide and understand the underlying molecular-level driving forces. The solubility calculations involve the estimation of the solute's limiting activity coefficient, which may be computed using conventional staged free-energy calculations. For the case of lidocaine, wherein the infinite dilution approximation is not appropriate, we demonstrate how the activity coefficient at finite concentrations may be estimated without additional effort using the dilute solution approximation and how this may be used to further understand the solvation process. Combining with experimental pure-solid properties, namely, the normal melting point and enthalpy of fusion, solubilities were estimated. The results are in good quantitative agreement with available experimental data, suggesting that molecular simulations may be a powerful tool for understanding supercritical processes and the design of carbon dioxide-philic molecular systems. Structural analyses were performed to shed light on the microscopic details of the solvation of different functional groups by carbon dioxide and the observed solubility trends.

Participatory Carbon Monitoring System in Community Forests of Nepal

NASA Astrophysics Data System (ADS)

Karki, S.

2016-12-01

With the adoption of climate change agreement, Reducing emissions from deforestation and forest degradation (REDD) has advanced as a performance based policy instruments to curtailing the deforestation and forest degradation. Developing countries are working to get REDD ready. However, the readiness assessment process entails criteria such as REDD+ Safeguards are met, monitoring and reporting of emission reductions are verified (MRV). For counties to have MRV in place, technical know-how on measuring forest carbon and capacity of the human resources are limited. International Centre for Integrated Mountain Development (ICIMOD) together with its national partners implemented REDD+ pilot project from 2009-2013 in 105 community forests (CF) of three watersheds namely Charnawati, Kayarkhola and Ludikhola in Nepal. This paper discuss prototype of the participatory carbon monitoring and measurement approach tested in these105 CFs that is systematic, transparent, and cost effective. Additionally it will demonstrate the enhanced carbon stock data from 2010-2013 assembled at ICIMOD Regional Database Initiative are made freely available. Such application can be scaled up or considered in decision making for performance based payment schemes.

Methanotrophic marine molluscan (Bivalvia, Mytilidae) symbiosis: mussels fueled by gas

DOE Office of Scientific and Technical Information (OSTI.GOV)

Childress, J.J.; Fisher, C.R.; Brooks, J.M.

An undescribed mussel (family Mytilidae), which lives in the vicinity of hydrocarbon seeps in the Gulf of Mexico, consumes methane (the principal component of natural gas) at a high rate. The methane consumption is limited to the gills of these animals and is apparently due to the abundant intracellular bacteria found there. This demonstrates a methane-based symbiosis between an animal and intracellular bacteria. Methane consumption is dependent on the availability of oxygen and is inhibited by acetylene. The consumption of methane by these mussels is associated with a dramatic increase in oxygen consumption and carbon dioxide production. As the methanemore » consumption of the bivalve can exceed its carbide dioxide production, the symbiosis may be able to entirely satisfy its carbon needs from methane uptake. The very light (delta/sup 13/C = -51 to -57 per mil) stable carbon isotope ratios found in this animal support methane (delta/sup 13/C = -45 per mil at this site) as the primary carbon source for both the mussels and their symbionts. 19 references, 2 figures, 1 table.« less

Water availability limits tree productivity, carbon stocks, and carbon residence time in mature forests across the western US

NASA Astrophysics Data System (ADS)

Berner, Logan T.; Law, Beverly E.; Hudiburg, Tara W.

2017-01-01

Water availability constrains the structure and function of terrestrial ecosystems and is projected to change in many parts of the world over the coming century. We quantified the response of tree net primary productivity (NPP), live biomass (BIO), and mean carbon residence time (CRT = BIO / NPP) to spatial variation in water availability in the western US. We used forest inventory measurements from 1953 mature stands (> 100 years) in Washington, Oregon, and California (WAORCA) along with satellite and climate data sets covering the western US. We summarized forest structure and function in both domains along a 400 cm yr-1 hydrologic gradient, quantified with a climate moisture index (CMI) based on the difference between precipitation and reference evapotranspiration summed over the water year (October-September) and then averaged annually from 1985 to 2014 (CMIwy). Median NPP, BIO, and CRT computed at 10 cm yr-1 intervals along the CMIwy gradient increased monotonically with increasing CMIwy across both WAORCA (rs = 0.93-0.96, p < 0.001) and the western US (rs = 0.93-0.99, p < 0.001). Field measurements from WAORCA showed that median NPP increased from 2.2 to 5.6 Mg C ha-1 yr-1 between the driest and wettest 5 % of sites, while BIO increased from 26 to 281 Mg C ha-1 and CRT increased from 11 to 49 years. The satellite data sets revealed similar changes over the western US, though these data sets tended to plateau in the wettest areas, suggesting that additional efforts are needed to better quantify NPP and BIO from satellites in high-productivity, high-biomass forests. Our results illustrate that long-term average water availability is a key environmental constraint on tree productivity, carbon storage, and carbon residence time in mature forests across the western US, underscoring the need to assess potential ecosystem response to projected warming and drying over the coming century.

Competition for light and water in a coupled soil-plant system

DOE PAGES

Manoli, Gabriele; Huang, Cheng -Wei; Bonetti, Sara; ...

2017-08-14

Here, it is generally accepted that resource availability shapes the structure and function of many ecosystems. Within the soil-plant-atmosphere (SPA) system, resource availability fluctuates in space and time whereas access to resources by individuals is further impacted by plant-to-plant competition. Likewise, transport and transformation of resources within an individual plant is governed by numerous interacting biotic and abiotic processes. The work here explores the co-limitations on water losses and carbon uptake within the SPA arising from fluctuating resource availability and competition. In particular, the goal is to unfold the interplay between plant access and competition for water and light, asmore » well as the impact of transport/redistribution processes on leaf-level carbon assimilation and water fluxes within forest stands. A framework is proposed that couples a three-dimensional representation of soil-root exchanges with a one-dimensional description of stem water flow and storage, canopy photosynthesis, and transpiration. The model links soil moisture redistribution, root water uptake, xylem water flow and storage, leaf potential and stomatal conductance as driven by supply and demand for water and carbon. The model is then used to investigate plant drought resilience of overstory-understory trees simultaneously competing for water and light. Simulation results reveal that understory-overstory interactions increase ecosystem resilience to drought (i.e. stand-level carbon assimilation rates and water fluxes can be sustained at lower root-zone soil water potentials). This resilience enhancement originates from reduced transpiration (due to shading) and hydraulic redistribution in soil supporting photosynthesis over prolonged periods of drought. In particular, the presence of different rooting systems generates localized hydraulic redistribution fluxes that sustain understory transpiration through overstory-understory interactions. Such complex SPA dynamics cannot be properly summarized by equivalent ecosystem-scale Resistor-Capacitor (RC) rep- resentation. However our results show that, with proper averaging across water flow paths, RC models can provide reasonable estimates of stand-level water and carbon fluxes during inter-storm periods.« less

Competition for light and water in a coupled soil-plant system

NASA Astrophysics Data System (ADS)

Manoli, Gabriele; Huang, Cheng-Wei; Bonetti, Sara; Domec, Jean-Christophe; Marani, Marco; Katul, Gabriel

2017-10-01

It is generally accepted that resource availability shapes the structure and function of many ecosystems. Within the soil-plant-atmosphere (SPA) system, resource availability fluctuates in space and time whereas access to resources by individuals is further impacted by plant-to-plant competition. Likewise, transport and transformation of resources within an individual plant is governed by numerous interacting biotic and abiotic processes. The work here explores the co-limitations on water losses and carbon uptake within the SPA arising from fluctuating resource availability and competition. In particular, the goal is to unfold the interplay between plant access and competition for water and light, as well as the impact of transport/redistribution processes on leaf-level carbon assimilation and water fluxes within forest stands. A framework is proposed that couples a three-dimensional representation of soil-root exchanges with a one-dimensional description of stem water flow and storage, canopy photosynthesis, and transpiration. The model links soil moisture redistribution, root water uptake, xylem water flow and storage, leaf potential and stomatal conductance as driven by supply and demand for water and carbon. The model is then used to investigate plant drought resilience of overstory-understory trees simultaneously competing for water and light. Simulation results reveal that understory-overstory interactions increase ecosystem resilience to drought (i.e. stand-level carbon assimilation rates and water fluxes can be sustained at lower root-zone soil water potentials). This resilience enhancement originates from reduced transpiration (due to shading) and hydraulic redistribution in soil supporting photosynthesis over prolonged periods of drought. In particular, the presence of different rooting systems generates localized hydraulic redistribution fluxes that sustain understory transpiration through overstory-understory interactions. Such complex SPA dynamics cannot be properly summarized by equivalent ecosystem-scale Resistor-Capacitor (RC) representation. However our results show that, with proper averaging across water flow paths, RC models can provide reasonable estimates of stand-level water and carbon fluxes during inter-storm periods.

Hydrology-oriented forest management trade-offs. A modeling framework coupling field data, simulation results and Bayesian Networks.

PubMed

Garcia-Prats, Alberto; González-Sanchis, María; Del Campo, Antonio D; Lull, Cristina

2018-10-15

Hydrology-oriented forest management sets water as key factor of the forest management for adaptation due to water is the most limiting factor in the Mediterranean forest ecosystems. The aim of this study was to apply Bayesian Network modeling to assess potential indirect effects and trade-offs when hydrology-oriented forest management is applied to a real Mediterranean forest ecosystem. Water, carbon and nitrogen cycles, and forest fire risk were included in the modeling framework. Field data from experimental plots were employed to calibrate and validate the mechanistic Biome-BGCMuSo model that simulates the storage and flux of water, carbon, and nitrogen between the ecosystem and the atmosphere. Many other 50-year long scenarios with different conditions to the ones measured in the field experiment were simulated and the outcomes employed to build the Bayesian Network in a linked chain of models. Hydrology-oriented forest management was very positive insofar as more water was made available to the stand because of an interception reduction. This resource was made available to the stand, which increased the evapotranspiration and its components, the soil water content and a slightly increase of deep percolation. Conversely, Stemflow was drastically reduced. No effect was observed on Runof due to the thinning treatment. The soil organic carbon content was also increased which in turn caused a greater respiration. The long-term effect of the thinning treatment on the LAI was very positive. This was undoubtedly due to the increased vigor generated by the greater availability of water and nutrients for the stand and the reduction of competence between trees. This greater activity resulted in an increase in GPP and vegetation carbon, and therefore, we would expect a higher carbon sequestration. It is worth emphasizing that this extra amount of water and nutrients was taken up by the stand and did not entail any loss of nutrients. Copyright © 2018 Elsevier B.V. All rights reserved.

Competition for light and water in a coupled soil-plant system

DOE Office of Scientific and Technical Information (OSTI.GOV)

Manoli, Gabriele; Huang, Cheng -Wei; Bonetti, Sara

Here, it is generally accepted that resource availability shapes the structure and function of many ecosystems. Within the soil-plant-atmosphere (SPA) system, resource availability fluctuates in space and time whereas access to resources by individuals is further impacted by plant-to-plant competition. Likewise, transport and transformation of resources within an individual plant is governed by numerous interacting biotic and abiotic processes. The work here explores the co-limitations on water losses and carbon uptake within the SPA arising from fluctuating resource availability and competition. In particular, the goal is to unfold the interplay between plant access and competition for water and light, asmore » well as the impact of transport/redistribution processes on leaf-level carbon assimilation and water fluxes within forest stands. A framework is proposed that couples a three-dimensional representation of soil-root exchanges with a one-dimensional description of stem water flow and storage, canopy photosynthesis, and transpiration. The model links soil moisture redistribution, root water uptake, xylem water flow and storage, leaf potential and stomatal conductance as driven by supply and demand for water and carbon. The model is then used to investigate plant drought resilience of overstory-understory trees simultaneously competing for water and light. Simulation results reveal that understory-overstory interactions increase ecosystem resilience to drought (i.e. stand-level carbon assimilation rates and water fluxes can be sustained at lower root-zone soil water potentials). This resilience enhancement originates from reduced transpiration (due to shading) and hydraulic redistribution in soil supporting photosynthesis over prolonged periods of drought. In particular, the presence of different rooting systems generates localized hydraulic redistribution fluxes that sustain understory transpiration through overstory-understory interactions. Such complex SPA dynamics cannot be properly summarized by equivalent ecosystem-scale Resistor-Capacitor (RC) rep- resentation. However our results show that, with proper averaging across water flow paths, RC models can provide reasonable estimates of stand-level water and carbon fluxes during inter-storm periods.« less

Dynamics of transparent exopolymer particles (TEP) during the VAHINE mesocosm experiment in the New Caledonian lagoon

NASA Astrophysics Data System (ADS)

Berman-Frank, Ilana; Spungin, Dina; Rahav, Eyal; Van Wambeke, France; Turk-Kubo, Kendra; Moutin, Thierry

2016-07-01

In the marine environment, transparent exopolymeric particles (TEP) produced from abiotic and biotic sources link the particulate and dissolved carbon pools and are essential vectors enhancing vertical carbon flux. We characterized spatial and temporal dynamics of TEP during the VAHINE experiment that investigated the fate of diazotroph-derived nitrogen and carbon in three replicate dissolved inorganic phosphorus (DIP)-fertilized 50 m3 enclosures in the oligotrophic New Caledonian lagoon. During the 23 days of the experiment, we did not observe any depth-dependent changes in TEP concentrations in the three sampled depths (1, 6, 12 m). TEP carbon (TEP-C) content averaged 28.9 ± 9.3 and 27.0 ± 7.2 % of total organic carbon (TOC) in the mesocosms and surrounding lagoon respectively and was strongly and positively coupled with TOC during P2 (i.e., days 15-23). TEP concentrations in the mesocosms declined for the first 9 days after DIP fertilization (P1 = days 5-14) and then gradually increased during the second phase. Temporal changes in TEP concentrations paralleled the growth and mortality rates of the diatom-diazotroph association of Rhizosolenia and Richelia that predominated the diazotroph community during P1. By P2, increasing total primary and heterotrophic bacterial production consumed the supplemented P and reduced availability of DIP. For this period, TEP concentrations were negatively correlated with DIP availability and turnover time of DIP (TDIP), while positively associated with enhanced alkaline phosphatase activity (APA) that occurs when the microbial populations are P stressed. During P2, increasing bacterial production (BP) was positively correlated with higher TEP concentrations, which were also coupled with the increased growth rates and aggregation of the unicellular cyanobacterial Group C (UCYN-C) diazotrophs that bloomed during this period. We conclude that the composite processes responsible for the formation and breakdown of TEP yielded a relatively stable TEP pool available as both a carbon source and facilitating aggregation and flux throughout the experiment. TEP were probably mostly influenced by abiotic physical processes during P1, while biological activity (BP, diazotrophic growth and aggregation, export production) mainly impacted TEP concentrations during P2 when DIP availability was limited.

See the forest for the trees: Whole-plant allocation patterns and regulatory mechanisms in Norway spruce

NASA Astrophysics Data System (ADS)

Huang, Jianbei; Behrendt, Thomas; Hammerbacher, Almuth; Weinhold, Alexander; Hellén, Heidi; Reichelt, Michael; Wisthaler, Armin; Dam, Nicole; Trumbore, Susan; Hartmann, Henrik

2017-04-01

For more than 40 years plant carbon (C) allocation have been of central interest to plant scientists. Most studies on C allocation focus on either biomass partitioning (e.g., root:shoot ratios), particular fluxes (e.g., non-structural carbohydrate, NSC; biogenic emissions of volatile organic compounds, VOCs) or short-term proportional allocation patterns (e.g., pulse-chase studies using isotopic tracers). However, a thorough understanding of C allocation priorities, especially at the whole-plant level, requires assessing all of these aspects together. We investigated C allocation trade-off in Norway spruce (Picea abies) saplings by assessing whole-plant fluxes (assimilation, respiration and VOCs) and biomass partitioning (structural biomass; NSC; secondary metabolites, SMs). The study was carried out over 8 weeks and allowed us, by modifying atmospheric CO2 concentrations ([CO2]), manipulating plant carbon (C) availability. Treatments included control (400 ppm), carbon compensation (down to 120 ppm) and starvation (down to 50 ppm) C availability levels. Reductions in [CO2] aimed to reveal plant allocation strategies assuming that pools receiving more C than others under C limitation have a high allocation priority. Respiration was less sensitive to declining [CO2] compared to assimilation, NSC and SMs. Strong declines in NSC at low [CO2] suggest that respiration was maintained by using stored NSC. Furthermore, reduced NSC and SMs concentrations also indicate preferential C allocation to growth over NSC and SMs at low C availability. SMs decreased to a lesser extent than NSC in old needles, and remained relatively constant in branches until death from starvation. These results suggest that pools of stored NSC may serve as a buffer for respiration or growth under C limitation but also that SMs remain largely inaccessible for metabolism once they are stored in tissues. VOCs emissions, however, showed contrasting responses to [CO2]; oxygenated VOCs (methanol and acetone) decreased whereas monoterpene and sesquiterpene emissions slightly increased with decreasing [CO2]. Our experimental design provides an excellent platform for studying control mechanisms of C allocation. The range of C availabilities applied in our study will allow partitioning compensatory mechanisms (e.g., up-regulation of C storage due to sugar signalling at high C availability) from evolutionary programming (e.g., storage formation to increase long-term survival at expense of other functions with decreasing C availability). Such partitioning is corroborated via phytohormone and transcriptome analysis, and results will hopefully be available at the time of presentation.

Ability of LANDSAT-8 Oli Derived Texture Metrics in Estimating Aboveground Carbon Stocks of Coppice Oak Forests

NASA Astrophysics Data System (ADS)

Safari, A.; Sohrabi, H.

2016-06-01

The role of forests as a reservoir for carbon has prompted the need for timely and reliable estimation of aboveground carbon stocks. Since measurement of aboveground carbon stocks of forests is a destructive, costly and time-consuming activity, aerial and satellite remote sensing techniques have gained many attentions in this field. Despite the fact that using aerial data for predicting aboveground carbon stocks has been proved as a highly accurate method, there are challenges related to high acquisition costs, small area coverage, and limited availability of these data. These challenges are more critical for non-commercial forests located in low-income countries. Landsat program provides repetitive acquisition of high-resolution multispectral data, which are freely available. The aim of this study was to assess the potential of multispectral Landsat 8 Operational Land Imager (OLI) derived texture metrics in quantifying aboveground carbon stocks of coppice Oak forests in Zagros Mountains, Iran. We used four different window sizes (3×3, 5×5, 7×7, and 9×9), and four different offsets ([0,1], [1,1], [1,0], and [1,-1]) to derive nine texture metrics (angular second moment, contrast, correlation, dissimilar, entropy, homogeneity, inverse difference, mean, and variance) from four bands (blue, green, red, and infrared). Totally, 124 sample plots in two different forests were measured and carbon was calculated using species-specific allometric models. Stepwise regression analysis was applied to estimate biomass from derived metrics. Results showed that, in general, larger size of window for deriving texture metrics resulted models with better fitting parameters. In addition, the correlation of the spectral bands for deriving texture metrics in regression models was ranked as b4>b3>b2>b5. The best offset was [1,-1]. Amongst the different metrics, mean and entropy were entered in most of the regression models. Overall, different models based on derived texture metrics were able to explain about half of the variation in aboveground carbon stocks. These results demonstrated that Landsat 8 derived texture metrics can be applied for mapping aboveground carbon stocks of coppice Oak Forests in large areas.

Measurement of Near-Surface Carbon Dioxide Concentrations with an Open-Path Tunable Diode Laser Sensor and a Non-Dispersive Infrared Sensor at the Bonanza Creek Long Term Ecological Research Site near Fairbanks, Alaska

NASA Astrophysics Data System (ADS)

Bailey, D. M.; Caine, K. M.; Miller, J. H. H.

2016-12-01

Continuous collection of carbon dioxide (CO2) concentrations is imperative in understanding seasonal and inter-annual variability of carbon feedbacks above thawing permafrost. Permafrost makes up one-quarter of the Earth's terrestrial surface and has the potential to release twice the amount of carbon than is currently in the atmosphere if global temperatures continue to increase. A collaborative effort with the University of Alaska - Fairbanks, NASA Goddard Space Flight Center, and our group at George Washington University is underway to monitor these feedbacks near Fairbanks, Alaska. In June 2016, we deployed an open-path tunable diode laser sensor along with a non-dispersive infrared (NDIR) sensor at the Bonanza Creek Long Term Ecological Research Site as an exploratory study for their use in collecting near-surface CO2 concentrations above thawing permafrost. The open-path instrument (OPI) collected spatially-integrated measurements approximately 1.5 meters above the surface of a young thermokarst bog over a 15-day period whereas the NDIR sensor collected localized measurements 1 meter above the surface for 16 days. Near-continuous measurements were achieved with the NDIR sensor which was limited only by the availability of solar-produced power. The OPI measurements were further limited by maintaining laser alignment under changing environmental conditions. However, the campaign achieved a nearly 80% duty cycle for the entire test period. Here we compare both the localized and spatially-integrated carbon dioxide measurements and their observed diurnal concentration cycles, whose magnitude showed a strong dependence on daily weather at the test site.

Carbon Dioxide Laser Fiber Optics In Endoscopy

NASA Astrophysics Data System (ADS)

Fuller, Terry A.

1982-12-01

Carbon dioxide laser surgery has been limited to a great extent to surgical application on the integument and accessible cavities such as the cervix, vagina, oral cavities, etc. This limitation has been due to the rigid delivery systems available to all carbon dioxide lasers. Articulating arms (series of hollow tubes connected by articulating mirrors) have provided an effective means of delivery of laser energy to the patient as long as the lesion was within the direct line of sight. Even direct line-of-sight applications were restricted to physical dimension of the articulating arm or associated hand probes, manipulators and hollow tubes. The many attempts at providing straight endoscopic systems to the laser only stressed the need for a fiber optic capable of carrying the carbon dioxide laser wavelength. Rectangular and circular hollow metal waveguides, hollow dielectric waveguides have proven ineffective to the stringent requirements of a flexible surgical delivery system. One large diameter (1 cm) fiber optic delivery system, incorporates a toxic thalliumAbased fiber optic material. The device is an effective alternative to an articulating arm for external or conventional laser surgery, but is too large and stiff to use as a flexible endoscopic tool. The author describes the first highly flexible inexpensive series of fiber optic systems suitable for either conventional or endoscopic carbon dioxide laser surgery. One system (IRFLEX 3) has been manufactured by Medlase, Inc. for surgical uses capable of delivering 2000w, 100 mJ pulsed energy and 15w continuous wave. The system diameter is 0.035 inches in diameter. Surgically suitable fibers as small as 120 um have been manufactured. Other fibers (IRFLEX 142,447) have a variety of transmission characteristics, bend radii, etc.

Fe-rich carbonate chimney in Okinawa Trough Implication for Fe-driven Microbial Anaerobic Oxidation of Methane (AMO)

NASA Astrophysics Data System (ADS)

Peng, X.; Guo, Z.

2016-12-01

Marine sediments associated with cold seeps at continental margins discharge substantial amounts of methane. Microbial anaerobic oxidation of methane (AMO) is a key biogeochemical process in these environments, which can trigger the formation of carbonate chimneys within sediments. The exact biogeochemical mechanism of how AMO control the formation of carbonate chimneys and influence their mineralogy and chemistry remains poorly constrained. Here, we use nano-scale secondary ion mass spectrometry to characterize the petrology and geochemistry of methane-derived Fe-rich carbonate chimneys formed between 5-7 Ma in the Northern Okinawa Trough. We find abundant framboid pyrites formed in the authigenic carbonates in the chimneys, indicating a non-Fe limitation sedimentary system. The δ13C values of carbonate (-18.9‰ to -45.9‰, PDB) show their probable origin from a mixing source of biogenic and thermogenic methane. The δ34S values range from -3.9 ± 0.5‰ to 23.2 ± 0.5‰ (VCDT), indicative of a strong exhaustion of sulfates in a local sulfate pool. We proposed that Fe-rich carbonate chimneys formed at the bottom of the sulfate-methane transition zone, beneath which Fe-driven AOM may happen and provide available ferrous for the extensive precipitation of pyrite in carbonate chimneys. The accumulation of reductive Fe in sediments via this process may widely occur in other analogous settings, with important application for Fe and S biogeochemical cycling within deep sediments at continental margins.

REPORT TO CONGRESS ON BLACK CARBON | Science ...

EPA Pesticide Factsheets

The Report to Congress on Black Carbon describes domestic and international sources of black carbon emissions, and summarizes available scientific information on the climate effects of black carbon. Further, the Report evaluates available black carbon mitigation options and their potential for protecting climate, public health, and the environment. The EPA Advisory Council on Clean Air Compliance Analysis has peer-reviewed the report. In the October 2009 Interior Appropriations bill, Congress requested that EPA, in consultation with other Federal agencies, study the emissions and impacts of black carbon in the US and internationally. To fulfill this charge, EPA has conducted an intensive effort to compile, assess, and summarize available scientific information on the current and future impacts of black carbon, and to evaluate the effectiveness of available mitigation approaches and technologies for protecting climate, public health, and the environment.

75 FR 54805 - Approval and Promulgation of Air Quality Implementation Plans; Minnesota; Carbon Monoxide (CO...

Federal Register 2010, 2011, 2012, 2013, 2014

2010-09-09

... Promulgation of Air Quality Implementation Plans; Minnesota; Carbon Monoxide (CO) Limited Maintenance Plan for... June 16, 2010, to revise the Minnesota State Implementation Plan (SIP) for carbon monoxide (CO) under the Clean Air Act (CAA). The State has submitted a limited maintenance plan for CO showing continued...

40 CFR 60.2115 - What if I do not use a wet scrubber, fabric filter, activated carbon injection, selective...

Code of Federal Regulations, 2013 CFR

2013-07-01

..., fabric filter, activated carbon injection, selective noncatalytic reduction, or an electrostatic... Limitations and Operating Limits § 60.2115 What if I do not use a wet scrubber, fabric filter, activated... carbon injection, selective noncatalytic reduction, fabric filter, or an electrostatic precipitator or...

40 CFR 60.5175 - How do I establish operating limits if I do not use a wet scrubber, fabric filter, electrostatic...

Code of Federal Regulations, 2012 CFR

2012-07-01

... I do not use a wet scrubber, fabric filter, electrostatic precipitator, activated carbon injection..., fabric filter, electrostatic precipitator, activated carbon injection, or afterburner, or if I limit... device other than a wet scrubber, fabric filter, electrostatic precipitator, activated carbon injection...

40 CFR 60.5175 - How do I establish operating limits if I do not use a wet scrubber, fabric filter, electrostatic...

Code of Federal Regulations, 2014 CFR

2014-07-01

... I do not use a wet scrubber, fabric filter, electrostatic precipitator, activated carbon injection..., fabric filter, electrostatic precipitator, activated carbon injection, or afterburner, or if I limit... device other than a wet scrubber, fabric filter, electrostatic precipitator, activated carbon injection...

40 CFR 60.5175 - How do I establish operating limits if I do not use a wet scrubber, fabric filter, electrostatic...

Code of Federal Regulations, 2013 CFR

2013-07-01

... I do not use a wet scrubber, fabric filter, electrostatic precipitator, activated carbon injection..., fabric filter, electrostatic precipitator, activated carbon injection, or afterburner, or if I limit... device other than a wet scrubber, fabric filter, electrostatic precipitator, activated carbon injection...

40 CFR 60.5175 - How do I establish operating limits if I do not use a wet scrubber, fabric filter, electrostatic...

Code of Federal Regulations, 2011 CFR

2011-07-01

... I do not use a wet scrubber, fabric filter, electrostatic precipitator, activated carbon injection..., fabric filter, electrostatic precipitator, activated carbon injection, or afterburner, or if I limit... device other than a wet scrubber, fabric filter, electrostatic precipitator, activated carbon injection...

76 FR 62039 - Certain Hot-Rolled Carbon Steel Flat Products From India: Final Results of 2009-2010 Antidumping...

Federal Register 2010, 2011, 2012, 2013, 2014

2011-10-06

... DEPARTMENT OF COMMERCE International Trade Administration [A-533-820] Certain Hot-Rolled Carbon... administrative review of the antidumping duty order on certain hot-rolled carbon steel flat products from India (``hot-rolled steel'') manufactured by Ispat Industries Limited (``Ispat''), JSW Steel Limited (``JSW...

76 FR 2344 - Certain Hot-Rolled Carbon Steel Flat Products From India: Notice of Preliminary Results of...

Federal Register 2010, 2011, 2012, 2013, 2014

2011-01-13

... DEPARTMENT OF COMMERCE International Trade Administration [A-533-820] Certain Hot-Rolled Carbon... administrative review of the antidumping duty order on certain hot-rolled carbon steel flat products from India (``Indian Hot-Rolled'') manufactured by Essar Steel Limited (``Essar''), Ispat Industries Limited (``Ispat...

Possible nutrient limiting factor in long term operation of closed aquatic ecosystem

NASA Astrophysics Data System (ADS)

Hao, Zongjie; Li, Yanhui; Cai, Wenkai; Wu, Peipei; Liu, Yongding; Wang, Gaohong

2012-03-01

To investigate nutrient limitation effect on the community metabolism of closed aquatic ecosystem and possible nutrient limiting factors in the experimental food chains, depletion of inorganic chemicals including carbon, nitrogen and phosphorous was tested. A closed aquatic ecosystem lab module consisting of Chlorella pyrenoidosa and Chlamydomonas reinhardtii, Daphnia magna and associated unidentified microbes was established. Closed ecological systems receive no carbon dioxide; therefore, we presumed carbon as a first limiting factor. The results showed that the algae population in the nutrient saturated group was statistically higher than that in the nutrient limited groups, and that the chlorophyll a content of algae in the phosphorus limited group was the highest among the limited groups. However, the nitrogen limited group supported the most Daphnia, followed by the carbon limited group, the nutrient saturated group and the phosphorus limited group. Redundancy analysis showed that the total phosphorus contents were correlated significantly with the population of algae, and that the amount of soluble carbohydrate as feedback of nutrient depletion was correlated with the number of Daphnia. Thus, these findings suggest that phosphorus is the limiting factor in the operation of closed aquatic ecosystem. The results presented herein have important indications for the future construction of long term closed ecological system.

Potential for Carbon Sequestration in European Soils: Preliminary Estimates for Five Scenarios Using Results from Long-Term Experiments

DOE Data Explorer

Smith, P. [University of Aberdeen, Aberdeen, UK; Powlson, D. [University of Aberdeen, Aberdeen, UK; Glendining, M. [University of Aberdeen, Aberdeen, UK; Smith, J. [University of Aberdeen, Aberdeen, UK

2003-01-01

One of the main options for carbon mitigation identified by the IPCC is the sequestration of carbon in soils. In this paper we use statistical relationships derived from European long-term experiments to explore the potential for carbon sequestration in soils in the European Union. We examine five scenarios, namely (a) the amendment of arable soils with animal manure, (b) the amendment of arable soils with sewage sludge, (c) the incorporation of cereal straw into the soils in which it was grown, (d) the afforestation of surplus arable land through natural woodland regeneration, and (e) extensification of agriculture through ley-arable farming. Our calculations suggest only limited potential to increase soil carbon stocks over the next century by addition of animal manure, sewage sludge or straw (<15 Tg C y^–1), but greater potential through extensification of agriculture (~40 Tg C y^–1) or through the afforestation of surplus arable land (~50 Tg C y^–1). We estimate that extensification could increase the total soil carbon stock of the European Union by 17%. Afforestation of 30% of present arable land would increase soil carbon stocks by about 8% over a century and would substitute up to 30 Tg C y^–1 of fossil fuel carbon if the wood were used as biofuel. However, even the afforestation scenario, with the greatest potential for carbon mitigation, can sequester only 0.8% of annual global anthropogenic CO2-carbon. Our figures suggest that, although efforts in temperate agriculture can contribute to global carbon mitigation, the potential is small compared to that available through reducing anthropogenic CO2 emissions by halting tropical and sub-tropical deforestation or by reducing fossil fuel burning.

Soil Organic Carbon and Below Ground Biomass: Development of New GLOBE Special Measurements

NASA Technical Reports Server (NTRS)

Levine, Elissa; Haskett, Jonathan

1999-01-01

A scientific consensus is building that changes in the atmospheric concentrations of radiatively active gases are changing the climate (IPCC, 1990). One of these gases CO2 has been increasing in concentration due to additions from anthropogenic sources that are primarily industrial and land use related. The soil contains a very large pool of carbon, estimated at 1550 Gt (Lal 1995) which is larger than the atmospheric and biosphere pools of carbon combined (Greenland, 1995). The flux between the soil and the atmosphere is very large, 60 Pg C/yr (Lal 1997), and is especially important because the soil can act as either a source or a sink for carbon. On any given landscape, as much as 50% of the biomass that provides the major source of carbon can be below ground. In addition, the movement of carbon in and out of the soil is mediated by the living organisms. At present, there is no widespread sampling of soil biomass in any consistent or coordinated manner. Current large scale estimates of soil carbon are limited by the number and widely dispersed nature of the data points available. A measurement of the amount of carbon in the soil would supplement existing carbon data bases as well as provide a benchmark that can be used to determine whether the soil is storing carbon or releasing it to the atmosphere. Information on the below ground biomass would be a valuable addition to our understanding of net primary productivity and standing biomass. The addition of these as special measurements within GLOBE would be unique in terms of areal extent and continuity, and make a real contribution to scientific understanding of carbon dynamics.

Water- and Plant-Mediated Responses of Ecosystem Carbon Fluxes to Warming and Nitrogen Addition on the Songnen Grassland in Northeast China

PubMed Central

Jiang, Li; Guo, Rui; Zhu, Tingcheng; Niu, Xuedun; Guo, Jixun; Sun, Wei

2012-01-01

Background Understanding how grasslands are affected by a long-term increase in temperature is crucial to predict the future impact of global climate change on terrestrial ecosystems. Additionally, it is not clear how the effects of global warming on grassland productivity are going to be altered by increased N deposition and N addition. Methodology/Principal Findings In-situ canopy CO2 exchange rates were measured in a meadow steppe subjected to 4-year warming and nitrogen addition treatments. Warming treatment reduced net ecosystem CO2 exchange (NEE) and increased ecosystem respiration (ER); but had no significant impacts on gross ecosystem productivity (GEP). N addition increased NEE, ER and GEP. However, there were no significant interactions between N addition and warming. The variation of NEE during the four experimental years was correlated with soil water content, particularly during early spring, suggesting that water availability is a primary driver of carbon fluxes in the studied semi-arid grassland. Conclusion/Significance Ecosystem carbon fluxes in grassland ecosystems are sensitive to warming and N addition. In the studied water-limited grassland, both warming and N addition influence ecosystem carbon fluxes by affecting water availability, which is the primary driver in many arid and semiarid ecosystems. It remains unknown to what extent the long-term N addition would affect the turn-over of soil organic matter and the C sink size of this grassland. PMID:23028848

Fog interception by Sequoia sempervirens (D. Don) crowns decouples physiology from soil water deficit.

PubMed

Simonin, Kevin A; Santiago, Louis S; Dawson, Todd E

2009-07-01

Although crown wetting events can increase plant water status, leaf wetting is thought to negatively affect plant carbon balance by depressing photosynthesis and growth. We investigated the influence of crown fog interception on the water and carbon relations of juvenile and mature Sequoia sempervirens trees. Field observations of mature trees indicated that fog interception increased leaf water potential above that of leaves sheltered from fog. Furthermore, observed increases in leaf water potential exceeded the maximum water potential predicted if soil water was the only available water source. Because field observations were limited to two mature trees, we conducted a greenhouse experiment to investigate how fog interception influences plant water status and photosynthesis. Pre-dawn and midday branchlet water potential, leaf gas exchange and chlorophyll fluorescence were measured on S. sempervirens saplings exposed to increasing soil water deficit, with and without overnight canopy fog interception. Sapling fog interception increased leaf water potential and photosynthesis above the control and soil water deficit treatments despite similar dark-acclimated leaf chlorophyll fluorescence. The field observations and greenhouse experiment show that fog interception represents an overlooked flux into the soil-plant-atmosphere continuum that temporarily, but significantly, decouples leaf-level water and carbon relations from soil water availability.

Variations in Amazon forest productivity correlated with foliar nutrients and modelled rates of photosynthetic carbon supply

PubMed Central

Mercado, Lina M.; Patiño, Sandra; Domingues, Tomas F.; Fyllas, Nikolaos M.; Weedon, Graham P.; Sitch, Stephen; Quesada, Carlos Alberto; Phillips, Oliver L.; Aragão, Luiz E. O. C.; Malhi, Yadvinder; Dolman, A. J.; Restrepo-Coupe, Natalia; Saleska, Scott R.; Baker, Timothy R.; Almeida, Samuel; Higuchi, Niro; Lloyd, Jon

2011-01-01

The rate of above-ground woody biomass production, WP, in some western Amazon forests exceeds those in the east by a factor of 2 or more. Underlying causes may include climate, soil nutrient limitations and species composition. In this modelling paper, we explore the implications of allowing key nutrients such as N and P to constrain the photosynthesis of Amazon forests, and also we examine the relationship between modelled rates of photosynthesis and the observed gradients in WP. We use a model with current understanding of the underpinning biochemical processes as affected by nutrient availability to assess: (i) the degree to which observed spatial variations in foliar [N] and [P] across Amazonia affect stand-level photosynthesis; and (ii) how these variations in forest photosynthetic carbon acquisition relate to the observed geographical patterns of stem growth across the Amazon Basin. We find nutrient availability to exert a strong effect on photosynthetic carbon gain across the Basin and to be a likely important contributor to the observed gradient in WP. Phosphorus emerges as more important than nitrogen in accounting for the observed variations in productivity. Implications of these findings are discussed in the context of future tropical forests under a changing climate. PMID:22006971

CHEMICAL FIXATION OF CO2 IN COAL COMBUSTION PRODUCTS AND RECYCLING THROUGH BIOSYSTEMS

DOE Office of Scientific and Technical Information (OSTI.GOV)

C. Henry Copeland; Paul Pier; Samantha Whitehead

2003-12-15

This Annual Technical Progress Report presents the principle results in enhanced growth of algae using coal combustion products as a catalyst to increase bicarbonate levels in solution. A co-current reactor is present that increases the gas phase to bicarbonate transfer rate by a factor of five to nine. The bicarbonate concentration at a given pH is approximately double that obtained using a control column of similar construction. Algae growth experiments were performed under laboratory conditions to obtain baseline production rates and to perfect experimental methods. The final product of this initial phase in algae production is presented. Algal growth canmore » be limited by several factors, including the level of bicarbonate available for photosynthesis, the pH of the growth solution, nutrient levels, and the size of the cell population, which determines the available space for additional growth. In order to supply additional CO2 to increase photosynthesis and algal biomass production, fly ash reactor has been demonstrated to increase the available CO2 in solution above the limits that are achievable with dissolved gas alone. The amount of dissolved CO2 can be used to control pH for optimum growth. Periodic harvesting of algae can be used to maintain algae in the exponential, rapid growth phase. An 800 liter scale up demonstrated that larger scale production is possible. The larger experiment demonstrated that indirect addition of CO2 is feasible and produces significantly less stress on the algal system. With better harvesting methods, nutrient management, and carbon dioxide management, an annual biomass harvest of about 9,000 metric tons per square kilometer (36 MT per acre) appears to be feasible. To sequester carbon, the algal biomass needs to be placed in a permanent location. If drying is undesirable, the biomass will eventually begin to aerobically decompose. It was demonstrated that algal biomass is a suitable feed to an anaerobic digester to produce methane. The remaining carbonaceous material is essentially bio-inactive and is permanently sequestered. The feasibility of using algae to convert carbon dioxide to a biomass has been demonstrated. This biomass provides a sustainable means to produce methane, ethanol, and/or bio diesel. The first application of concept demonstrated by the project could be to use algal biomass production to capture carbon dioxide associated with ethanol production.« less

Reducing greenhouse gas emissions in agriculture without compromising food security?

NASA Astrophysics Data System (ADS)

Frank, Stefan; Havlík, Petr; Soussana, Jean-François; Levesque, Antoine; Valin, Hugo; Wollenberg, Eva; Kleinwechter, Ulrich; Fricko, Oliver; Gusti, Mykola; Herrero, Mario; Smith, Pete; Hasegawa, Tomoko; Kraxner, Florian; Obersteiner, Michael

2017-10-01

To keep global warming possibly below 1.5 °C and mitigate adverse effects of climate change, agriculture, like all other sectors, will have to contribute to efforts in achieving net negative emissions by the end of the century. Cost-efficient distribution of mitigation across regions and economic sectors is typically calculated using a global uniform carbon price in climate stabilization scenarios. However, in reality such a carbon price would substantially affect food availability. Here, we assess the implications of climate change mitigation in the land use sector for agricultural production and food security using an integrated partial equilibrium modelling framework and explore ways of relaxing the competition between mitigation in agriculture and food availability. Using a scenario that limits global warming cost-efficiently across sectors to 1.5 °C, results indicate global food calorie losses ranging from 110-285 kcal per capita per day in 2050 depending on the applied demand elasticities. This could translate into a rise in undernourishment of 80-300 million people in 2050. Less ambitious greenhouse gas (GHG) mitigation in the land use sector reduces the associated food security impact significantly, however the 1.5 °C target would not be achieved without additional reductions outside the land use sector. Efficiency of GHG mitigation will also depend on the level of participation globally. Our results show that if non-Annex-I countries decide not to contribute to mitigation action while other parties pursue their mitigation efforts to reach the global climate target, food security impacts in these non-Annex-I countries will be higher than if they participate in a global agreement, as inefficient mitigation increases agricultural production costs and therefore food prices. Land-rich countries with a high proportion of emissions from land use change, such as Brazil, could reduce emissions with only a marginal effect on food availability. In contrast, agricultural mitigation in high population (density) countries, such as China and India, would lead to substantial food calorie loss without a major contribution to global GHG mitigation. Increasing soil carbon sequestration on agricultural land would allow reducing the implied calorie loss by 65% when sticking to the initially estimated land use mitigation requirements, thereby limiting the impact on undernourishment to 20-75 million people, and storing significant amounts of carbon in soils.

The contribution of leaching to the rapid release of nutrients and carbon in the early decay of wetland vegetation

USGS Publications Warehouse

Davis, S. E.; Childers, D.L.; Noe, G.B.

2006-01-01

Our goal was to quantify the coupled process of litter turnover and leaching as a source of nutrients and fixed carbon in oligotrophic, nutrient-limited wetlands. We conducted poisoned and non-poisoned incubations of leaf material from four different perennial wetland plants (Eleocharis spp., Cladium jamaicense, Rhizophora mangle and Spartina alterniflora) collected from different oligotrophic freshwater and estuarine wetland settings. Total phosphorus (TP) release from the P-limited Everglades plant species (Eleocharis spp., C. jamaicense and R. mangle) was much lower than TP release by the salt marsh plant S. alterniflora from N-limited North Inlet (SC). For most species and sampling times, total organic carbon (TOC) and TP leaching losses were much greater in poisoned than non-poisoned treatments, likely as a result of epiphytic microbial activity. Therefore, a substantial portion of the C and P leached from these wetland plant species was bio-available to microbial communities. Even the microbes associated with S. alterniflora from N-limited North Inlet showed indications of P-limitation early in the leaching process, as P was removed from the water column. Leaves of R. mangle released much more TOC per gram of litter than the other species, likely contributing to the greater waterborne [DOC] observed by others in the mangrove ecotone of Everglades National Park. Between the two freshwater Everglades plants, C. jamaicense leached nearly twice as much P than Eleocharis spp. In scaling this to the landscape level, our observed leaching losses combined with higher litter production of C. jamaicense compared to Eleocharis spp. resulted in a substantially greater P leaching from plant litter to the water column and epiphytic microbes. In conclusion, leaching of fresh plant litter can be an important autochthonous source of nutrients in freshwater and estuarine wetland ecosystems. ?? Springer 2006.

Long-term nitrogen deposition linked to reduced water use efficiency in forests with low phosphorus availability.

PubMed

Huang, Zhiqun; Liu, Bao; Davis, Murray; Sardans, Jordi; Peñuelas, Josep; Billings, Sharon

2016-04-01

The impact of long-term nitrogen (N) deposition is under-studied in phosphorus (P)-limited subtropical forests. We exploited historically collected herbarium specimens to investigate potential physiological responses of trees in three subtropical forests representing an urban-to-rural gradient, across which N deposition has probably varied over the past six decades. We measured foliar [N] and [P] and stable carbon (δ(13) C), oxygen (δ(18) O) and nitrogen (δ(15) N) isotopic compositions in tissue from herbarium specimens of plant species collected from 1947 to 2014. Foliar [N] and N : P increased, and δ(15) N and [P] decreased in the two forests close to urban centers. Consistent with recent studies demonstrating that N deposition in the region is (15) N-depleted, these data suggest that the increased foliar [N] and N : P, and decreased [P], may be attributable to atmospheric deposition and associated enhancement of P limitation. Estimates of intrinsic water use efficiency calculated from foliar δ(13) C decreased by c. 30% from the 1950s to 2014, contrasting with multiple studies investigating similar parameters in N-limited forests. This effect may reflect decreased photosynthesis, as suggested by a conceptual model of foliar δ(13) C and δ(18) O. Long-term N deposition may exacerbate P limitation and mitigate projected increases in carbon stocks driven by elevated CO2 in forests on P-limited soils. © 2015 The Authors. New Phytologist © 2015 New Phytologist Trust.

Can plants grow in quasi-vacuum?

NASA Technical Reports Server (NTRS)

Andre, M.; Richaud, C.

1986-01-01

It was found that the growth of plants is possible under absolute pressure 14 times lower than the atmospheric pressure. In first approximation, plants ignore the absence of nitrogen and only react to the partial pressure of O2. Hence the growth of plantlets was delayed under low pressures of O2 in both cases with and without nitrogen. The CO2 availability being limited by the carbon content of the seed, the final results after 20 days were very similar.

An experimental study of basaltic glass-H2O-CO2 interaction at 22 and 50 °C: Implications for subsurface storage of CO2

NASA Astrophysics Data System (ADS)

Galeczka, Iwona; Wolff-Boenisch, Domenik; Oelkers, Eric H.; Gislason, Sigurdur R.

2014-02-01

A novel high pressure column flow reactor was used to investigate the evolution of solute chemistry along a 2.3 m flow path during pure water- and CO2-charged water-basaltic glass interaction experiments at 22 and 50 °C and 10-5.7 to 22 bars partial pressure of CO2. Experimental results and geochemical modelling showed the pH of injected pure water evolved rapidly from 6.7 to 9-9.5 and most of the iron released to the fluid phase was subsequently consumed by secondary minerals, similar to natural meteoric water-basalt systems. In contrast to natural systems, however, the aqueous aluminium concentration remained relatively high along the entire flow path. The aqueous fluid was undersaturated with respect to basaltic glass and carbonate minerals, but supersaturated with respect to zeolites, clays, and Fe hydroxides. As CO2-charged water replaced the alkaline fluid within the column, the fluid briefly became supersaturated with respect to siderite. Basaltic glass dissolution in the column reactor, however, was insufficient to overcome the pH buffer capacity of CO2-charged water. The pH of this CO2-charged water rose from an initial 3.4 to only 4.5 in the column reactor. This acidic reactive fluid was undersaturated with respect to carbonate minerals but supersaturated with respect to clays and Fe hydroxides at 22 °C, and with respect to clays and Al hydroxides at 50 °C. Basaltic glass dissolution in the CO2-charged water was closer to stoichiometry than in pure water. The mobility and aqueous concentration of several metals increased significantly with the addition of CO2 to the inlet fluid, and some metals, including Mn, Cr, Al, and As exceeded the allowable drinking water limits. Iron became mobile and the aqueous Fe2+/Fe3+ ratio increased along the flow path. Although carbonate minerals did not precipitate in the column reactor in response to CO2-charged water-basaltic glass interaction, once this fluid exited the reactor, carbonates precipitated as the fluid degassed at the outlet. Substantial differences were found between the results of geochemical modelling calculations and the observed chemical evolution of the fluids during the experiments. These differences underscore the need to improve the models before they can be used to predict with confidence the fate and consequences of carbon dioxide injected into the subsurface. The pH increase from 3.4 to 4.5 of the CO2-rich inlet fluid does not immobilize toxic elements at ambient temperature but immobilizes Al and Cr at 50 °C. This indicates that further neutralization of CO2-charged water is required for decreased toxic element mobility. The CO2-charged water injection enhances the mobility of redox sensitive Fe2+ significantly making it available for the storage of injected carbon as iron carbonate minerals. The precipitation of aluminosilicates likely occurred at a pH of 4.2-4.5 in CO2-charged waters. These secondary phases can (1) fill the available pore space and therefore clog the host rock in the vicinity of the injection well, and (2) incorporate some divalent cations limiting their availability for carbon storage. The inability of simple reactive transport models to describe accurately the fluid evolution in this well constrained one dimensional flow system suggests that significant improvements need to be made to such models before we can predict with confidence the fate and consequences of injecting carbon dioxide into the subsurface. Column reactors such as that used in this study could be used to facilitate ex situ carbon mineral storage. Carbonate precipitation at the outlet of the reactor suggests that the harvesting of divalent metals from rocks using CO2-charged waters could potentially be upscaled to an industrial carbonation process.

Bacterial invasion potential in water is determined by nutrient availability and the indigenous community.

PubMed

Van Nevel, Sam; De Roy, Karen; Boon, Nico

2013-09-01

In drinking water (DW) and the distribution systems, bacterial growth and biofilm formation have to be controlled both for limiting taste or odour development and preventing clogging or biocorrosion problems. After a contamination with undesired bacteria, factors like nutrient availability and temperature will influence the survival of these invaders. Understanding the conditions enabling invaders to proliferate is essential for a holistic approach towards microbial risk assessment in DW. Pseudomonas putida was used as a model invader because this easy-growing bacterium can use a wide range of substrates. Invasion experiments in oligo- to eutrophic waters showed the requirement of both a carbon and phosphate source for survival of P. putida in DW. Addition of C, N and P enabled P. putida to grow in DW from 5.80 × 10(4) to 1.84 × 10(8) cells mL(-1) and survive for at least 12 days. However, in surface water with similar nutrient concentrations, P. putida did not survive, indicating the concomitant importance of the present indigenous microbial community of the specific water sample. Either extensive carbon or phosphate limitation can be used in water treatment design in order to obtain a DW which is not susceptible for unwanted bacterial growth. © 2013 Federation of European Microbiological Societies. Published by John Wiley & Sons Ltd. All rights reserved.

Enzymology under global change: organic nitrogen turnover in alpine and sub-Arctic soils.

PubMed

Weedon, James T; Aerts, Rien; Kowalchuk, George A; van Bodegom, Peter M

2011-01-01

Understanding global change impacts on the globally important carbon storage in alpine, Arctic and sub-Arctic soils requires knowledge of the mechanisms underlying the balance between plant primary productivity and decomposition. Given that nitrogen availability limits both processes, understanding the response of the soil nitrogen cycle to shifts in temperature and other global change factors is crucial for predicting the fate of cold biome carbon stores. Measurements of soil enzyme activities at different positions of the nitrogen cycling network are an important tool for this purpose. We review a selection of studies that provide data on potential enzyme activities across natural, seasonal and experimental gradients in cold biomes. Responses of enzyme activities to increased nitrogen availability and temperature are diverse and seasonal dynamics are often larger than differences due to experimental treatments, suggesting that enzyme expression is regulated by a combination of interacting factors reflecting both nutrient supply and demand. The extrapolation from potential enzyme activities to prediction of elemental nitrogen fluxes under field conditions remains challenging. Progress in molecular '-omics' approaches may eventually facilitate deeper understanding of the links between soil microbial community structure and biogeochemical fluxes. In the meantime, accounting for effects of the soil spatial structure and in situ variations in pH and temperature, better mapping of the network of enzymatic processes and the identification of rate-limiting steps under different conditions should advance our ability to predict nitrogen fluxes.

Breakdown of the coral-algae symbiosis: towards formalising a linkage between warm-water bleaching thresholds and the growth rate of the intracellular zooxanthellae

NASA Astrophysics Data System (ADS)

Wooldridge, S. A.

2012-07-01

Impairment of the photosynthetic machinery of the algal endosymbiont ("zooxanthellae") is the proximal trigger for the thermal breakdown of the coral-algae symbiosis ("coral bleaching"). Yet, the primary site of thermal damage is not well resolved. In this perspective essay, I consider further a recent hypothesis which proposes an energetic disruption to the carbon-concentrating mechanisms (CCMs) of the coral host, and the resultant onset of CO2-limitation within the photosynthetic "dark reactions", as a unifying cellular mechanism. The hypothesis identifies the enhanced retention of photosynthetic carbon for zooxanthellae (re)growth following an initial irradiance-driven expulsion event as the cause of the energetic disruption. If true, then it implies that the onset of the bleaching syndrome and setting of upper thermal bleaching limits are emergent attributes of the coral symbiosis that are ultimately underpinned by the characteristic growth profile of the intracellular zooxanthellae; which is known to depend not just on temperature, but also external (seawater) nutrient availability and zooxanthellae genotype. Here, I review this proposed bleaching linkage at a variety of observational scales, and find it to be parsimonious with the available evidence. This provides a new standpoint to consider the future prospects of the coral symbiosis in an era of rapid environmental change, including the now crucial importance of reef water quality in co-determining thermal bleaching resistance.

75 FR 28557 - Circular Welded Carbon Steel Pipes and Tubes From Thailand: Extension of Time Limit for Final...

Federal Register 2010, 2011, 2012, 2013, 2014

2010-05-21

... Steel Pipes and Tubes From Thailand: Extension of Time Limit for Final Results of Antidumping Duty... carbon steel pipes and tubes from Thailand. See Circular Welded Carbon Steel Pipes and Tubes from Thailand: Preliminary Results and Rescission, in Part, of Antidumping Duty Administrative Review, 75 FR...

77 FR 27428 - Certain Magnesia Carbon Bricks From the People's Republic of China: Extension of Time Limit for...

Federal Register 2010, 2011, 2012, 2013, 2014

2012-05-10

... Bricks From the People's Republic of China: Extension of Time Limit for the Preliminary Results of... opportunity to request an administrative review on the antidumping order on certain magnesia carbon bricks... initiated an antidumping duty administrative review on certain magnesia carbon bricks from the PRC, covering...

76 FR 34044 - Carbon and Certain Alloy Steel Wire Rod From Mexico: Extension of Time Limits for the Preliminary...

Federal Register 2010, 2011, 2012, 2013, 2014

2011-06-10

... DEPARTMENT OF COMMERCE International Trade Administration [A-201-830] Carbon and Certain Alloy Steel Wire Rod From Mexico: Extension of Time Limits for the Preliminary Results of Fifth Antidumping... carbon and certain alloy steel wire rod from Mexico, covering the period October 1, 2009, through...

40 CFR Table 3 to Subpart Jjjjjj... - Operating Limits for Boilers With Emission Limits

Code of Federal Regulations, 2013 CFR

2013-07-01

... as defined in § 63.11237. 4. Dry sorbent or activated carbon injection control Maintain the 30-day rolling average sorbent or activated carbon injection rate at or above the minimum sorbent injection rate or minimum activated carbon injection rate as defined in § 63.11237. When your boiler operates at...

77 FR 2511 - Certain Welded Carbon Steel Pipe and Tube From Turkey: Extension of Time Limit for Preliminary...

Federal Register 2010, 2011, 2012, 2013, 2014

2012-01-18

... DEPARTMENT OF COMMERCE International Trade Administration [A-489-501] Certain Welded Carbon Steel Pipe and Tube From Turkey: Extension of Time Limit for Preliminary Results of Antidumping Duty... certain welded carbon steel pipe and tube from Turkey covering the period May 1, 2010, through April 30...

76 FR 3083 - Certain Welded Carbon Steel Pipe and Tube From Turkey: Extension of Time Limit for Preliminary...

Federal Register 2010, 2011, 2012, 2013, 2014

2011-01-19

... DEPARTMENT OF COMMERCE International Trade Administration [A-489-501] Certain Welded Carbon Steel Pipe and Tube From Turkey: Extension of Time Limit for Preliminary Results of Antidumping Duty... welded carbon steel pipe and tube from Turkey covering the period May 1, 2009, through April 30, 2010...

75 FR 3896 - Certain Welded Carbon Steel Pipe and Tube from Turkey: Extension of Time Limit for Preliminary...

Federal Register 2010, 2011, 2012, 2013, 2014

2010-01-25

... DEPARTMENT OF COMMERCE International Trade Administration [A-489-501] Certain Welded Carbon Steel Pipe and Tube from Turkey: Extension of Time Limit for Preliminary Results of Antidumping Duty... antidumping duty order on certain welded carbon steel pipe and tube from Turkey covering the period May 1...

Soil Carbon Inputs and Ecosystem Respiration: a Field Priming Experiment in Arctic Coastal Tundra

NASA Astrophysics Data System (ADS)

Vaughn, L. S.; Zhu, B.; Bimueller, C.; Curtis, J. B.; Chafe, O.; Bill, M.; Abramoff, R. Z.; Torn, M. S.

2016-12-01

In Arctic ecosystems, climate change is expected to influence soil carbon stocks through changes in both plant carbon inputs and organic matter decomposition. This study addresses the potential for a priming effect, an interaction between these changes in which root-derived carbon inputs alter SOM decomposition rates via microbial biomass increases, co-metabolism of substrates, induced nitrogen limitation, or other possible mechanisms. The priming effect has been observed in numerous laboratory and greenhouse experiments, and is increasingly included in ecosystem models. Few studies, however, have evaluated the priming effect with in situ field manipulations. In a two-year field experiment in Barrow, Alaska, we tested for a priming effect under natural environmental variability. In September 2014 and August 2015, we added 6.1g of 13C-labeled glucose to 25cm diameter mesocosms, 15cm below the soil surface in the mineral soil layer. Over the following month, we quantified effects on the rate and temperature sensitivity of native (non-glucose) ecosystem respiration and GPP. Following the 2014 treatment, soil samples were collected at 1 and 3 weeks for microbial biomass carbon and 13C/12C analysis, and ion exchange membranes were buried for one week to assess nitrate and ammonium availability. In contrast with many laboratory incubation studies using soils from a broad range of ecosystems, we observed no significant priming effect. In spite of a clear signal of 13C-glucose decomposition in respired CO2 and microbial biomass, we detected no treatment effect on background ecosystem respiration or total microbial biomass carbon. Our findings suggest that glucose taken up by microbes was not used for production of additional SOM-decomposing enzymes, possibly due to stoichiometric limitations on enzyme production. To best inform models representing complex and dynamic ecosystems, this study calls for further research relating theory, laboratory findings, and field experimentation.

The significance of microbial processes in hydrogeology and geochemistry

NASA Astrophysics Data System (ADS)

Chapelle, Francis H.

Microbial processes affect the chemical composition of groundwater and the hydraulic properties of aquifers in both contaminated and pristine groundwater systems. The patterns of water-chemistry changes that occur depend upon the relative abundance of electron donors and electron acceptors. In many pristine aquifers, where microbial metabolism is limited by the availability of electron donors (usually organic matter), dissolved inorganic carbon (DIC) accumulates slowly along aquifer flow paths and available electron acceptors are consumed sequentially in the order dissolved oxygen >nitrate>Fe(III)>sulfate>CO2 (methanogenesis). In aquifers contaminated by anthropogenic contaminants, an excess of available organic carbon often exists, and microbial metabolism is limited by the availability of electron acceptors. In addition to changes in groundwater chemistry, the solid matrix of the aquifer is affected by microbial processes. The production of carbon dioxide and organic acids can lead to increased mineral solubility, which can lead to the development of secondary porosity and permeability. Conversely, microbial production of carbonate, ferrous iron, and sulfide can result in the precipitation of secondary calcite or pyrite cements that reduce primary porosity and permeability in groundwater systems. Les processus microbiologiques peuvent affecter la composition chimique de l'eau souterraine et les propriétés hydrauliques des nappes aussi bien dans les systèmes aquifères pollués que dans les systèmes indemnes de pollution. Les changements de chimisme des eaux qui se produisent dépendent de l'abondance relative des donneurs et des accepteurs d'électrons. Dans les aquifères non contaminés, où le métabolisme microbien est limité par la disponibilité des donneurs d'électrons (en général la matière organique), le carbone minéral dissous (CMD) s'accumule lentement le long des axes d'écoulement souterrain et les accepteurs d'électrons disponibles sont consommés de façon séquentielle, dans l'ordre oxygène dissous>nitrate>fer (III)>sulfate>CO2 (méthanogenèse). Dans les aquifères pollués par des contaminants d'origine humaine, il existe un excès de carbone organique disponible et le métabolisme microbien est limité par la disponibilité des accepteurs d'électrons. En plus des modifications du chimisme des eaux souterraines, la matrice encaissante de l'aquifère est affectée par des processus microbiens. La production de dioxyde de carbone et d'acides organiques peut conduire à accroître la solubilité de minéraux, ce qui peut produire un développement de la porosité secondaire et de la perméabilité. Inversement, la production microbienne de carbonate, de fer ferreux et de sulfure peut provoquer la précipitation de ciments de calcite secondaire ou de pyrite qui réduisent la porosité primaire et la perméabilité dans les nappes. Los procesos microbianos afectan la composición química y las propiedades hidráulicas de los acuíferos, independientemente de su grado de contaminación. Los cambios en la química de las aguas dependen de la abundancia relativa entre donantes y receptores de electrones. En muchos acuíferos no contaminados, donde el metabolismo de los microbios está limitado por la disponibilidad de donantes de electrones (normalmente materia orgánica), el carbono inorgánico disuelto (CID) se acumula lentamente a lo largo de las líneas de flujo y los receptores de electrones se consumen sucesivamente en el siguiente orden: oxígeno disuelto>nitrato>Fe (III)>sulfato>CO2 (metanogénesis). En los acuíferos que presentan contaminación antrópica, existe un exceso de carbono orgánico disponible y entonces el metabolismo de los microbios se encuentra limitado por la disponibilidad de receptores de electrones. Además de los cambios en la química de las aguas, los procesos microbianos afectan también a la matriz sólida del acuífero la producción de CO2 y de ácidos orgánicos puede dar lugar a una mayor solubilidad del mineral, lo que supone un aumento en porosidad secundaria y permeabilidad. Por el contrario, los procesos microbianos pueden dar lugar a la producción de carbonato, ión ferroso y sulfuro, precipitando calcita o pirita y reduciendo la porosidad primaria y la permeabilidad.

Nitrogen Availability Dampens the Positive Impacts of CO2 Fertilization on Terrestrial Ecosystem Carbon and Water Cycles

NASA Astrophysics Data System (ADS)

He, Liming; Chen, Jing M.; Croft, Holly; Gonsamo, Alemu; Luo, Xiangzhong; Liu, Jane; Zheng, Ting; Liu, Ronggao; Liu, Yang

2017-11-01

The magnitude and variability of the terrestrial CO2 sink remain uncertain, partly due to limited global information on ecosystem nitrogen (N) and its cycle. Without N constraint in ecosystem models, the simulated benefits from CO2 fertilization and CO2-induced increases in water use efficiency (WUE) may be overestimated. In this study, satellite observations of a relative measure of chlorophyll content are used as a proxy for leaf photosynthetic N content globally for 2003-2011. Global gross primary productivity (GPP) and evapotranspiration are estimated under elevated CO2 and N-constrained model scenarios. Results suggest that the rate of global GPP increase is overestimated by 85% during 2000-2015 without N limitation. This limitation is found to occur in many tropical and boreal forests, where a negative leaf N trend indicates a reduction in photosynthetic capacity, thereby suppressing the positive vegetation response to enhanced CO2 fertilization. Based on our carbon-water coupled simulations, enhanced CO2 concentration decreased stomatal conductance and hence increased WUE by 10% globally over the 1982 to 2015 time frame. Due to increased anthropogenic N application, GPP in croplands continues to grow and offset the weak negative trend in forests due to N limitation. Our results also show that the improved WUE is unlikely to ease regional droughts in croplands because of increases in evapotranspiration, which are associated with the enhanced GPP. Although the N limitation on GPP increase is large, its associated confidence interval is still wide, suggesting an urgent need for better understanding and quantification of N limitation from satellite observations.

Analogous nutrient limitations in unicellular diazotrophs and Prochlorococcus in the South Pacific Ocean.

PubMed

Moisander, Pia H; Zhang, Ruifeng; Boyle, Edward A; Hewson, Ian; Montoya, Joseph P; Zehr, Jonathan P

2012-04-01

Growth limitation of phytoplankton and unicellular nitrogen (N(2)) fixers (diazotrophs) were investigated in the oligotrophic Western South Pacific Ocean. Based on change in abundances of nifH or 23S rRNA gene copies during nutrient-enrichment experiments, the factors limiting net growth of the unicellular diazotrophs UCYN-A (Group A), Crocosphaera watsonii, γ-Proteobacterium 24774A11, and the non-diazotrophic picocyanobacterium Prochlorococcus, varied within the region. At the westernmost stations, numbers were enhanced by organic carbon added as simple sugars, a combination of iron and an organic chelator, or iron added with phosphate. At stations nearest the equator, the nutrient-limiting growth was not apparent. Maximum net growth rates for UCYN-A, C. watsonii and γ-24774A11 were 0.19, 0.61 and 0.52 d(-1), respectively, which are the first known empirical growth rates reported for the uncultivated UCYN-A and the γ-24774A11. The addition of N enhanced total phytoplankton biomass up to 5-fold, and the non-N(2)-fixing Synechococcus was among the groups that responded favorably to N addition. Nitrogen was the major nutrient-limiting phytoplankton biomass in the Western South Pacific Ocean, while availability of organic carbon or iron and organic chelator appear to limit abundances of unicellular diazotrophs. Lack of phytoplankton response to nutrient additions in the Pacific warm pool waters suggests diazotroph growth in this area is controlled by different factors than in the higher latitudes, which may partially explain previously observed variability in community composition in the region.

Association of dissolved mercury with dissolved organic carbon in U.S. rivers and streams: The role of watershed soil organic carbon

NASA Astrophysics Data System (ADS)

Stoken, Olivia M.; Riscassi, Ami L.; Scanlon, Todd M.

2016-04-01

Streams and rivers are important pathways for the export of atmospherically deposited mercury (Hg) from watersheds. Dissolved Hg (HgD) is strongly associated with dissolved organic carbon (DOC) in stream water, but the ratio of HgD to DOC is highly variable between watersheds. In this study, the HgD:DOC ratios from 19 watersheds were evaluated with respect to Hg wet deposition and watershed soil organic carbon (SOC) content. On a subset of sites where data were available, DOC quality measured by specific ultra violet absorbance at 254 nm, was considered as an additional factor that may influence HgD:DOC . No significant relationship was found between Hg wet deposition and HgD:DOC, but SOC content (g m-2) was able to explain 81% of the variance in the HgD:DOC ratio (ng mg-1) following the form: HgD:DOC=17.8*SOC-0.41. The inclusion of DOC quality as a secondary predictor variable explained only an additional 1% of the variance. A mathematical framework to interpret the observed power-law relationship between HgD:DOC and SOC suggests Hg supply limitation for adsorption to soils with relatively large carbon pools. With SOC as a primary factor controlling the association of HgD with DOC, SOC data sets may be utilized to predict stream HgD:DOC ratios on a more geographically widespread basis. In watersheds where DOC data are available, estimates of HgD may be readily obtained. Future Hg emissions policies must consider soil-mediated processes that affect the transport of Hg and DOC from terrestrial watersheds to streams for accurate predictions of water quality impacts.

The Northern Circumpolar Soil Carbon Database: spatially distributed datasets of soil coverage and soil carbon storage in the northern permafrost regions

NASA Astrophysics Data System (ADS)

Hugelius, G.; Tarnocai, C.; Broll, G.; Canadell, J. G.; Kuhry, P.; Swanson, D. K.

2012-08-01

High latitude terrestrial ecosystems are key components in the global carbon (C) cycle. Estimates of global soil organic carbon (SOC), however, do not include updated estimates of SOC storage in permafrost-affected soils or representation of the unique pedogenic processes that affect these soils. The Northern Circumpolar Soil Carbon Database (NCSCD) was developed to quantify the SOC stocks in the circumpolar permafrost region (18.7 × 106 km2). The NCSCD is a polygon-based digital database compiled from harmonized regional soil classification maps in which data on soil order coverage has been linked to pedon data (n = 1647) from the northern permafrost regions to calculate SOC content and mass. In addition, new gridded datasets at different spatial resolutions have been generated to facilitate research applications using the NCSCD (standard raster formats for use in Geographic Information Systems and Network Common Data Form files common for applications in numerical models). This paper describes the compilation of the NCSCD spatial framework, the soil sampling and soil analyses procedures used to derive SOC content in pedons from North America and Eurasia and the formatting of the digital files that are available online. The potential applications and limitations of the NCSCD in spatial analyses are also discussed. The database has the doi:10.5879/ecds/00000001. An open access data-portal with all the described GIS-datasets is available online at: http://dev1.geo.su.se/bbcc/dev/ncscd/.

The Northern Circumpolar Soil Carbon Database: spatially distributed datasets of soil coverage and soil carbon storage in the northern permafrost regions

NASA Astrophysics Data System (ADS)

Hugelius, G.; Tarnocai, C.; Broll, G.; Canadell, J. G.; Kuhry, P.; Swanson, D. K.

2013-01-01

High-latitude terrestrial ecosystems are key components in the global carbon (C) cycle. Estimates of global soil organic carbon (SOC), however, do not include updated estimates of SOC storage in permafrost-affected soils or representation of the unique pedogenic processes that affect these soils. The Northern Circumpolar Soil Carbon Database (NCSCD) was developed to quantify the SOC stocks in the circumpolar permafrost region (18.7 × 106 km2). The NCSCD is a polygon-based digital database compiled from harmonized regional soil classification maps in which data on soil order coverage have been linked to pedon data (n = 1778) from the northern permafrost regions to calculate SOC content and mass. In addition, new gridded datasets at different spatial resolutions have been generated to facilitate research applications using the NCSCD (standard raster formats for use in geographic information systems and Network Common Data Form files common for applications in numerical models). This paper describes the compilation of the NCSCD spatial framework, the soil sampling and soil analytical procedures used to derive SOC content in pedons from North America and Eurasia and the formatting of the digital files that are available online. The potential applications and limitations of the NCSCD in spatial analyses are also discussed. The database has the doi:10.5879/ecds/00000001. An open access data portal with all the described GIS-datasets is available online at: http://www.bbcc.su.se/data/ncscd/.

Use of carbon paste electrodes for the voltammetric detection of silver leached from the oxidative dissolution of silver nanoparticles

NASA Astrophysics Data System (ADS)

Mullaugh, Katherine M.; Pearce, Olivia M.

2017-04-01

The widespread use of silver nanoparticles (Ag NPs) in consumer goods has raised concerns about the release of silver in environmental waters. Of particular concern is the oxidative dissolution of Ag NPs to release Ag+ ions, which are highly toxic to many aquatic organisms. Here, we have investigated the application of differential pulse stripping voltammetry (DPSV) with carbon paste electrodes (CPEs) in monitoring the oxidation of Ag NPs. Using a commercially available, unmodified carbon paste and 60-s deposition times, a detection limit of 3 nM Ag+ could be achieved. We demonstrate its selectivity for free Ag+ ions over Ag nanoparticles, allowing for analysis of the oxidation of Ag NPs without the need for separation of ions and nanoparticles prior to analysis. We applied this approach to investigate the effect of pH in the oxidative dissolution of Ag NPs, demonstrating the usefulness of CPEs in studies of this type.

Negative impacts of high temperatures on growth of black spruce forests intensify with the anticipated climate warming.

PubMed

Girardin, Martin P; Hogg, Edward H; Bernier, Pierre Y; Kurz, Werner A; Guo, Xiao Jing; Cyr, Guillaume

2016-02-01

An increasing number of studies conclude that water limitations and heat stress may hinder the capacity of black spruce (Picea mariana (Mill.) B.S.P.) trees, a dominant species of Canada's boreal forests, to grow and assimilate atmospheric carbon. However, there is currently no scientific consensus on the future of these forests over the next century in the context of widespread climate warming. The large spatial extent of black spruce forests across the Canadian boreal forest and associated variability in climate, demography, and site conditions pose challenges for projecting future climate change responses. Here we provide an evaluation of the impacts of climate warming and drying, as well as increasing [CO2 ], on the aboveground productivity of black spruce forests across Canada south of 60°N for the period 1971 to 2100. We use a new extensive network of tree-ring data obtained from Canada's National Forest Inventory, spatially explicit simulations of net primary productivity (NPP) and its drivers, and multivariate statistical modeling. We found that soil water availability is a significant driver of black spruce interannual variability in productivity across broad areas of the western to eastern Canadian boreal forest. Interannual variability in productivity was also found to be driven by autotrophic respiration in the warmest regions. In most regions, the impacts of soil water availability and respiration on interannual variability in productivity occurred during the phase of carbohydrate accumulation the year preceding tree-ring formation. Results from projections suggest an increase in the importance of soil water availability and respiration as limiting factors on NPP over the next century due to warming, but this response may vary to the extent that other factors such as carbon dioxide fertilization, and respiration acclimation to high temperature, contribute to dampening these limitations. © 2015 Her Majesty the Queen in Right of Canada. Reproduced with the permission of the Minister of Natural Resources Canada.

Estimating phosphorus availability for microbial growth in an emerging landscape

USGS Publications Warehouse

Schmidt, S.K.; Cleveland, C.C.; Nemergut, D.R.; Reed, S.C.; King, A.J.; Sowell, P.

2011-01-01

Estimating phosphorus (P) availability is difficult—particularly in infertile soils such as those exposed after glacial recession—because standard P extraction methods may not mimic biological acquisition pathways. We developed an approach, based on microbial CO2 production kinetics and conserved carbon:phosphorus (C:P) ratios, to estimate the amount of P available for microbial growth in soils and compared this method to traditional, operationally-defined indicators of P availability. Along a primary succession gradient in the High Andes of Perú, P additions stimulated the growth-related (logistic) kinetics of glutamate mineralization in soils that had been deglaciated from 0 to 5 years suggesting that microbial growth was limited by soil P availability. We then used a logistic model to estimate the amount of C incorporated into biomass in P-limited soils, allowing us to estimate total microbial P uptake based on a conservative C:P ratio of 28:1 (mass:mass). Using this approach, we estimated that there was < 1 μg/g of microbial-available P in recently de-glaciated soils in both years of this study. These estimates fell well below estimates of available soil P obtained using traditional extraction procedures. Our results give both theoretical and practical insights into the kinetics of C and P utilization in young soils, as well as show changes in microbial P availability during early stages of soil development.

Resource Legacies of Organic and Conventional Management Differentiate Soil Microbial Carbon Use

PubMed Central

Arcand, Melissa M.; Levy-Booth, David J.; Helgason, Bobbi L.

2017-01-01

Long-term contrasts in agricultural management can shift soil resource availability with potential consequences to microbial carbon (C) use efficiency (CUE) and the fate of C in soils. Isothermal calorimetry was combined with 13C-labeled glucose stable isotope probing (SIP) of 16S rRNA genes to test the hypothesis that organically managed soils would support microbial communities with greater thermodynamic efficiency compared to conventional soils due to a legacy of lower resource availability and a resultant shift toward communities supportive of more oligotrophic taxa. Resource availability was greater in conventionally managed soils, with 3.5 times higher available phosphorus, 5% more nitrate, and 36% more dissolved organic C. The two management systems harbored distinct glucose-utilizing populations of Proteobacteria and Actinobacteria, with a higher Proteobacteria:Actinobacteria ratio (2.4 vs. 0.7) in conventional soils. Organically managed soils also harbored notable activity of Firmicutes. Thermodynamic efficiency indices were similar between soils, indicating that glucose was metabolized at similar energetic cost. However, differentially abundant glucose utilizers in organically managed soils were positively correlated with soil organic matter (SOM) priming and negatively correlated to soil nutrient and carbon availability, respiration, and heat production. These correlation patterns were strongly reversed in the conventionally managed soils indicating clear differentiation of microbial functioning related to soil resource availability. Fresh C addition caused proportionally more priming of SOM decomposition (57 vs. 51%) in organically managed soils likely due to mineralization of organic nutrients to satisfy microbial demands during glucose utilization in these more resource deprived soils. The additional heat released from SOM oxidation may explain the similar community level thermodynamic efficiencies between management systems. Restoring fertility to soils with a legacy of nutrient limitation requires a balanced supply of both nutrients and energy to protect stable SOM from microbial degradation. These results highlight the need to consider managing C for the energy it provides to ıcritical biological processes that underpin soil health. PMID:29230199

A two-fold increase of carbon cycle sensitivity to tropical temperature variations.

PubMed

Wang, Xuhui; Piao, Shilong; Ciais, Philippe; Friedlingstein, Pierre; Myneni, Ranga B; Cox, Peter; Heimann, Martin; Miller, John; Peng, Shushi; Wang, Tao; Yang, Hui; Chen, Anping

2014-02-13

Earth system models project that the tropical land carbon sink will decrease in size in response to an increase in warming and drought during this century, probably causing a positive climate feedback. But available data are too limited at present to test the predicted changes in the tropical carbon balance in response to climate change. Long-term atmospheric carbon dioxide data provide a global record that integrates the interannual variability of the global carbon balance. Multiple lines of evidence demonstrate that most of this variability originates in the terrestrial biosphere. In particular, the year-to-year variations in the atmospheric carbon dioxide growth rate (CGR) are thought to be the result of fluctuations in the carbon fluxes of tropical land areas. Recently, the response of CGR to tropical climate interannual variability was used to put a constraint on the sensitivity of tropical land carbon to climate change. Here we use the long-term CGR record from Mauna Loa and the South Pole to show that the sensitivity of CGR to tropical temperature interannual variability has increased by a factor of 1.9 ± 0.3 in the past five decades. We find that this sensitivity was greater when tropical land regions experienced drier conditions. This suggests that the sensitivity of CGR to interannual temperature variations is regulated by moisture conditions, even though the direct correlation between CGR and tropical precipitation is weak. We also find that present terrestrial carbon cycle models do not capture the observed enhancement in CGR sensitivity in the past five decades. More realistic model predictions of future carbon cycle and climate feedbacks require a better understanding of the processes driving the response of tropical ecosystems to drought and warming.

Estimating global "blue carbon" emissions from conversion and degradation of vegetated coastal ecosystems.

PubMed

Pendleton, Linwood; Donato, Daniel C; Murray, Brian C; Crooks, Stephen; Jenkins, W Aaron; Sifleet, Samantha; Craft, Christopher; Fourqurean, James W; Kauffman, J Boone; Marbà, Núria; Megonigal, Patrick; Pidgeon, Emily; Herr, Dorothee; Gordon, David; Baldera, Alexis

2012-01-01

Recent attention has focused on the high rates of annual carbon sequestration in vegetated coastal ecosystems--marshes, mangroves, and seagrasses--that may be lost with habitat destruction ('conversion'). Relatively unappreciated, however, is that conversion of these coastal ecosystems also impacts very large pools of previously-sequestered carbon. Residing mostly in sediments, this 'blue carbon' can be released to the atmosphere when these ecosystems are converted or degraded. Here we provide the first global estimates of this impact and evaluate its economic implications. Combining the best available data on global area, land-use conversion rates, and near-surface carbon stocks in each of the three ecosystems, using an uncertainty-propagation approach, we estimate that 0.15-1.02 Pg (billion tons) of carbon dioxide are being released annually, several times higher than previous estimates that account only for lost sequestration. These emissions are equivalent to 3-19% of those from deforestation globally, and result in economic damages of $US 6-42 billion annually. The largest sources of uncertainty in these estimates stems from limited certitude in global area and rates of land-use conversion, but research is also needed on the fates of ecosystem carbon upon conversion. Currently, carbon emissions from the conversion of vegetated coastal ecosystems are not included in emissions accounting or carbon market protocols, but this analysis suggests they may be disproportionally important to both. Although the relevant science supporting these initial estimates will need to be refined in coming years, it is clear that policies encouraging the sustainable management of coastal ecosystems could significantly reduce carbon emissions from the land-use sector, in addition to sustaining the well-recognized ecosystem services of coastal habitats.

Exploring the Interactions between Land Use, Climate Change and Carbon Cycle using Satellite Measurements

NASA Astrophysics Data System (ADS)

Ray, R. L.; Fares, A.; He, Y.; Awal, R.; Risch, E.

2017-12-01

Most climate change impacts are linked to terrestrial vegetation productivity, carbon stocks and land use change. Changes in land use and climate drive the dynamics of terrestrial carbon cycle. These carbon cycle dynamics operate at different spatial and temporal scales. Quantification of the spatial and temporal variability of carbon flux has been challenging because land-atmosphere-carbon exchange is influenced by many factors, including but not limited to, land use change and climate change and variability. The study of terrestrial carbon cycle, mainly gross primary product (GPP), net ecosystem exchange (NEE), soil organic carbon (SOC) and ecosystem respiration (Re) and their interactions with land use and climate change, are critical to understanding the terrestrial ecosystem. The main objective of this study was to examine the interactions among land use, climate change and terrestrial carbon cycling in the state of Texas using satellite measurements. We studied GPP, NEE, Re and SOC distributions for five selected major land covers and all ten climate zones in Texas using Soil Moisture Active Passive (SMAP) carbon products. SMAP Carbon products (Res=9 km) were compared with observed CO2 flux data measured at EC flux site on Prairie View A&M University Research Farm. Results showed the same land cover in different climate zones has significantly different carbon sequestration potentials. For example, cropland of the humid climate zone has higher (-228 g C/m2) carbon sequestration potentials than the semiarid climate zone (-36 g C/m2). Also, shrub land in the humid zone and in the semiarid zone showed high (-120 g C/m2) and low (-36 g C/m2) potentials of carbon sequestration, respectively, in the state. Overall, the analyses indicate CO2 storage and exchange respond differently to various land covers, and environments due to differences in water availability, root distribution and soil properties.

Where does the carbon go? A model–data intercomparison of vegetation carbon allocation and turnover processes at two temperate forest free-air CO2 enrichment sites

PubMed Central

De Kauwe, Martin G; Medlyn, Belinda E; Zaehle, Sönke; Walker, Anthony P; Dietze, Michael C; Wang, Ying-Ping; Luo, Yiqi; Jain, Atul K; El-Masri, Bassil; Hickler, Thomas; Wårlind, David; Weng, Ensheng; Parton, William J; Thornton, Peter E; Wang, Shusen; Prentice, I Colin; Asao, Shinichi; Smith, Benjamin; McCarthy, Heather R; Iversen, Colleen M; Hanson, Paul J; Warren, Jeffrey M; Oren, Ram; Norby, Richard J

2014-01-01

Elevated atmospheric CO2 concentration (eCO2) has the potential to increase vegetation carbon storage if increased net primary production causes increased long-lived biomass. Model predictions of eCO2 effects on vegetation carbon storage depend on how allocation and turnover processes are represented. We used data from two temperate forest free-air CO2 enrichment (FACE) experiments to evaluate representations of allocation and turnover in 11 ecosystem models. Observed eCO2 effects on allocation were dynamic. Allocation schemes based on functional relationships among biomass fractions that vary with resource availability were best able to capture the general features of the observations. Allocation schemes based on constant fractions or resource limitations performed less well, with some models having unintended outcomes. Few models represent turnover processes mechanistically and there was wide variation in predictions of tissue lifespan. Consequently, models did not perform well at predicting eCO2 effects on vegetation carbon storage. Our recommendations to reduce uncertainty include: use of allocation schemes constrained by biomass fractions; careful testing of allocation schemes; and synthesis of allocation and turnover data in terms of model parameters. Data from intensively studied ecosystem manipulation experiments are invaluable for constraining models and we recommend that such experiments should attempt to fully quantify carbon, water and nutrient budgets. PMID:24844873

Sustainable wastewater treatment of temporary events: the Dranouter Music Festival case study.

PubMed

Van Hulle, S W H; Audenaert, W; Decostere, B; Hogie, J; Dejans, P

2008-01-01

Music festivals and other temporary events, such as bicycle races, lay a heavy burden on the surrounding environment. Treatment of the wastewater originating from such events is necessary if no municipal treatment plant is available. This study demonstrated that activated carbon is a performant technique for the treatment of wastewaters originating from these temporary events. Freundlich isotherms and maximum operational linear velocity (6 m/h) were determined on a lab-scale set-up. A pilot-scale set up was used to treat part (5%) of the total volume of the Dranouter Music Festival shower wastewater. On average 90% removal of COD and suspended solids concentration was obtained. Application of the activated carbon filter resulted in the fact that the local discharge limits were met without operational problems. IWA Publishing 2008.

Supercapacitors specialities - Materials review

DOE Office of Scientific and Technical Information (OSTI.GOV)

Obreja, Vasile V. N.

The electrode material is a key component for supercapacitor cell performance. As it is known, performance comparison of commercial available batteries and supercapacitors reveals significantly lower energy storage capability for supercapacitor devices. The energy density of commercial supercapacitor cells is limited to 10 Wh/kg whereas that of common lead acid batteries reaches 35-40 Wh/kg. For lithium ion batteries a value higher than 100 Wh/kg is easily available. Nevertheless, supercapacitors also known as ultracapacitors or electrochemical capacitors have other advantages in comparison with batteries. As a consequence, many efforts have been made in the last years to increase the storage energymore » density of electrochemical capacitors. A lot of results from published work (research and review papers, patents and reports) are available at this time. The purpose of this review is a presentation of the progress to date for the use of new materials and approaches for supercapacitor electrodes, with focus on the energy storage capability for practical applications. Many reported results refer to nanostructured carbon based materials and the related composites, used for the manufacture of experimental electrodes. A specific capacitance and a specific energy are seldom revealed as the main result of the performed investigation. Thus for nanoprous (activated) carbon based electrodes a specific capacitance up to 200-220 F/g is mentioned for organic electrolyte, whereas for aqueous electrolyte, the value is limited to 400-500 F/g. Significant contribution to specific capacitance is possible from fast faradaic reactions at the electrode-electrolyte interface in addition to the electric double layer effect. The corresponding energy density is limited to 30-50 Wh/kg for organic electrolyte and to 12-17 Wh/kg for aqueous electrolyte. However such performance indicators are given only for the carbon material used in electrodes. For a supercapacitor cell, where two electrodes and also other materials for cell assembling and packaging are used, the above mentioned values have to be divided by a factor higher than four. As a consequence, the specific energy of a prototype cell, hardly could exceed 10 Wh/kg because of difficulties with the existing manufacturing technology. Graphene based materials and carbon nanotubes and different composites have been used in many experiments reported in the last years. Nevertheless in spite of the outstanding properties of these materials, significant increase of the specific capacitance or of the specific energy in comparison with activated or nanoporous carbon is not achieved. Use of redox materials as metal oxides or conducting polymers in combination with different nanostructured carbon materials (nanocomposite electrodes) has been found to contribute to further increase of the specific capacitance or of the specific energy. Nevertheless, few results are reported for practical cells with such materials. Many results are reported only for a three electrode system and significant difference is possible when the electrode is used in a practical supercapacitor cell. Further improvement in the electrode manufacture and more experiments with supercapacitor cells with the known electrochemical storage materials are required. Device prototypes and commercial products with an energy density towards 15-20 Wh/kg could be realized. These may be a milestone for further supercapacitor device research and development, to narrow the storage energy gap between batteries and supercapacitors.« less

Supercapacitors specialities - Materials review

NASA Astrophysics Data System (ADS)

Obreja, Vasile V. N.

2014-06-01

The electrode material is a key component for supercapacitor cell performance. As it is known, performance comparison of commercial available batteries and supercapacitors reveals significantly lower energy storage capability for supercapacitor devices. The energy density of commercial supercapacitor cells is limited to 10 Wh/kg whereas that of common lead acid batteries reaches 35-40 Wh/kg. For lithium ion batteries a value higher than 100 Wh/kg is easily available. Nevertheless, supercapacitors also known as ultracapacitors or electrochemical capacitors have other advantages in comparison with batteries. As a consequence, many efforts have been made in the last years to increase the storage energy density of electrochemical capacitors. A lot of results from published work (research and review papers, patents and reports) are available at this time. The purpose of this review is a presentation of the progress to date for the use of new materials and approaches for supercapacitor electrodes, with focus on the energy storage capability for practical applications. Many reported results refer to nanostructured carbon based materials and the related composites, used for the manufacture of experimental electrodes. A specific capacitance and a specific energy are seldom revealed as the main result of the performed investigation. Thus for nanoprous (activated) carbon based electrodes a specific capacitance up to 200-220 F/g is mentioned for organic electrolyte, whereas for aqueous electrolyte, the value is limited to 400-500 F/g. Significant contribution to specific capacitance is possible from fast faradaic reactions at the electrode-electrolyte interface in addition to the electric double layer effect. The corresponding energy density is limited to 30-50 Wh/kg for organic electrolyte and to 12-17 Wh/kg for aqueous electrolyte. However such performance indicators are given only for the carbon material used in electrodes. For a supercapacitor cell, where two electrodes and also other materials for cell assembling and packaging are used, the above mentioned values have to be divided by a factor higher than four. As a consequence, the specific energy of a prototype cell, hardly could exceed 10 Wh/kg because of difficulties with the existing manufacturing technology. Graphene based materials and carbon nanotubes and different composites have been used in many experiments reported in the last years. Nevertheless in spite of the outstanding properties of these materials, significant increase of the specific capacitance or of the specific energy in comparison with activated or nanoporous carbon is not achieved. Use of redox materials as metal oxides or conducting polymers in combination with different nanostructured carbon materials (nanocomposite electrodes) has been found to contribute to further increase of the specific capacitance or of the specific energy. Nevertheless, few results are reported for practical cells with such materials. Many results are reported only for a three electrode system and significant difference is possible when the electrode is used in a practical supercapacitor cell. Further improvement in the electrode manufacture and more experiments with supercapacitor cells with the known electrochemical storage materials are required. Device prototypes and commercial products with an energy density towards 15-20 Wh/kg could be realized. These may be a milestone for further supercapacitor device research and development, to narrow the storage energy gap between batteries and supercapacitors.

Economic mitigation challenges: how further delay closes the door for achieving climate targets

NASA Astrophysics Data System (ADS)

Luderer, Gunnar; Pietzcker, Robert C.; Bertram, Christoph; Kriegler, Elmar; Meinshausen, Malte; Edenhofer, Ottmar

2013-09-01

While the international community aims to limit global warming to below 2 ° C to prevent dangerous climate change, little progress has been made towards a global climate agreement to implement the emissions reductions required to reach this target. We use an integrated energy-economy-climate modeling system to examine how a further delay of cooperative action and technology availability affect climate mitigation challenges. With comprehensive emissions reductions starting after 2015 and full technology availability we estimate that maximum 21st century warming may still be limited below 2 ° C with a likely probability and at moderate economic impacts. Achievable temperature targets rise by up to ˜0.4 ° C if the implementation of comprehensive climate policies is delayed by another 15 years, chiefly because of transitional economic impacts. If carbon capture and storage (CCS) is unavailable, the lower limit of achievable targets rises by up to ˜0.3 ° C. Our results show that progress in international climate negotiations within this decade is imperative to keep the 2 ° C target within reach.

Biosynthesis of higher alcohol flavour compounds by the yeast Saccharomyces cerevisiae: impact of oxygen availability and responses to glucose pulse in minimal growth medium with leucine as sole nitrogen source.

PubMed

Espinosa Vidal, Esteban; de Morais, Marcos Antonio; François, Jean Marie; de Billerbeck, Gustavo M

2015-01-01

Higher alcohol formation by yeast is of great interest in the field of fermented beverages. Among them, medium-chain alcohols impact greatly the final flavour profile of alcoholic beverages, even at low concentrations. It is widely accepted that amino acid metabolism in yeasts directly influences higher alcohol formation, especially the catabolism of aromatic and branched-chain amino acids. However, it is not clear how the availability of oxygen and glucose metabolism influence the final higher alcohol levels in fermented beverages. Here, using an industrial Brazilian cachaça strain of Saccharomyces cerevisiae, we investigated the effect of oxygen limitation and glucose pulse on the accumulation of higher alcohol compounds in batch cultures, with glucose (20 g/l) and leucine (9.8 g/l) as the carbon and nitrogen sources, respectively. Fermentative metabolites and CO2 /O2 balance were analysed in order to correlate the results with physiological data. Our results show that the accumulation of isoamyl alcohol by yeast is independent of oxygen availability in the medium, depending mainly on leucine, α-keto-acids and/or NADH pools. High-availability leucine experiments showed a novel and unexpected accumulation of isobutanol, active amyl alcohol and 2-phenylethanol, which could be attributed to de novo biosynthesis of valine, isoleucine and phenylalanine and subsequent outflow of these pathways. In carbon-exhausted conditions, our results also describe, for the first time, the metabolization of isoamyl alcohol, isobutanol, active amyl alcohol but not of 2-phenylethanol, by yeast strains in stationary phase, suggesting a role for these higher alcohols as carbon source for cell maintenance and/or redox homeostasis during this physiological phase. Copyright © 2014 John Wiley & Sons, Ltd.

Woven TPS Enabling Missions Beyond Heritage Carbon Phenolic

NASA Technical Reports Server (NTRS)

Stackpoole, Mairead; Venkatapathy, Ethiraj; Feldman, Jay

2013-01-01

Woven Thermal Protection Systems (WTPS) is a new TPS concept that is funded by NASAs Office of the Chief Technologist (OCT) Game Changing Division. The WTPS project demonstrates the potential for manufacturing many TPS architectures capable of performances demanded by the many potential solar system exploration missions. Currently, missions that encounter heat fluxes in the range of 1500 4000 W/sq cm and pressures greater than 1.5 atm have very limited TPS options - only one proven material, fully dense Carbon Phenolic, is currently available for these missions. However, fully dense carbon phenolic is only mass efficient at heat fluxes greater than 4000 W/sq cm, and current mission designs suffer this mass inefficiency for lack of an alternative mid-density TPS. WTPS not only bridges this TPS gap but also offers a replacement for carbon phenolic, which itself requires a significant and costly redevelopment effort to re-establish its capability for use in the high heat flux missions recently prioritized in the NRC Decadal survey, including probe missions to Venus, Saturn and Neptune. This presentation will introduce some woven TPS architectures considered in this project and summarize some recent arc jet testing to evaluate the performance of fully dense and mid density WTPS. Performance comparisons to heritage carbon phenolic will be drawn where applicable.

Gas Fermentation-A Flexible Platform for Commercial Scale Production of Low-Carbon-Fuels and Chemicals from Waste and Renewable Feedstocks.

PubMed

Liew, FungMin; Martin, Michael E; Tappel, Ryan C; Heijstra, Björn D; Mihalcea, Christophe; Köpke, Michael

2016-01-01

There is an immediate need to drastically reduce the emissions associated with global fossil fuel consumption in order to limit climate change. However, carbon-based materials, chemicals, and transportation fuels are predominantly made from fossil sources and currently there is no alternative source available to adequately displace them. Gas-fermenting microorganisms that fix carbon dioxide (CO2) and carbon monoxide (CO) can break this dependence as they are capable of converting gaseous carbon to fuels and chemicals. As such, the technology can utilize a wide range of feedstocks including gasified organic matter of any sort (e.g., municipal solid waste, industrial waste, biomass, and agricultural waste residues) or industrial off-gases (e.g., from steel mills or processing plants). Gas fermentation has matured to the point that large-scale production of ethanol from gas has been demonstrated by two companies. This review gives an overview of the gas fermentation process, focusing specifically on anaerobic acetogens. Applications of synthetic biology and coupling gas fermentation to additional processes are discussed in detail. Both of these strategies, demonstrated at bench-scale, have abundant potential to rapidly expand the commercial product spectrum of gas fermentation and further improve efficiencies and yields.

Massive radius-dependent flow slippage in carbon nanotubes.

PubMed

Secchi, Eleonora; Marbach, Sophie; Niguès, Antoine; Stein, Derek; Siria, Alessandro; Bocquet, Lydéric

2016-09-08

Measurements and simulations have found that water moves through carbon nanotubes at exceptionally high rates owing to nearly frictionless interfaces. These observations have stimulated interest in nanotube-based membranes for applications including desalination, nano-filtration and energy harvesting, yet the exact mechanisms of water transport inside the nanotubes and at the water-carbon interface continue to be debated because existing theories do not provide a satisfactory explanation for the limited number of experimental results available so far. This lack of experimental results arises because, even though controlled and systematic studies have explored transport through individual nanotubes, none has met the considerable technical challenge of unambiguously measuring the permeability of a single nanotube. Here we show that the pressure-driven flow rate through individual nanotubes can be determined with unprecedented sensitivity and without dyes from the hydrodynamics of water jets as they emerge from single nanotubes into a surrounding fluid. Our measurements reveal unexpectedly large and radius-dependent surface slippage in carbon nanotubes, and no slippage in boron nitride nanotubes that are crystallographically similar to carbon nanotubes, but electronically different. This pronounced contrast between the two systems must originate from subtle differences in the atomic-scale details of their solid-liquid interfaces, illustrating that nanofluidics is the frontier at which the continuum picture of fluid mechanics meets the atomic nature of matter.

Massive radius-dependent flow slippage in carbon nanotubes

NASA Astrophysics Data System (ADS)

Secchi, Eleonora; Marbach, Sophie; Niguès, Antoine; Stein, Derek; Siria, Alessandro; Bocquet, Lydéric

2016-09-01

Measurements and simulations have found that water moves through carbon nanotubes at exceptionally high rates owing to nearly frictionless interfaces. These observations have stimulated interest in nanotube-based membranes for applications including desalination, nano-filtration and energy harvesting, yet the exact mechanisms of water transport inside the nanotubes and at the water-carbon interface continue to be debated because existing theories do not provide a satisfactory explanation for the limited number of experimental results available so far. This lack of experimental results arises because, even though controlled and systematic studies have explored transport through individual nanotubes, none has met the considerable technical challenge of unambiguously measuring the permeability of a single nanotube. Here we show that the pressure-driven flow rate through individual nanotubes can be determined with unprecedented sensitivity and without dyes from the hydrodynamics of water jets as they emerge from single nanotubes into a surrounding fluid. Our measurements reveal unexpectedly large and radius-dependent surface slippage in carbon nanotubes, and no slippage in boron nitride nanotubes that are crystallographically similar to carbon nanotubes, but electronically different. This pronounced contrast between the two systems must originate from subtle differences in the atomic-scale details of their solid-liquid interfaces, illustrating that nanofluidics is the frontier at which the continuum picture of fluid mechanics meets the atomic nature of matter.

Gas Fermentation—A Flexible Platform for Commercial Scale Production of Low-Carbon-Fuels and Chemicals from Waste and Renewable Feedstocks

PubMed Central

Liew, FungMin; Martin, Michael E.; Tappel, Ryan C.; Heijstra, Björn D.; Mihalcea, Christophe; Köpke, Michael

2016-01-01

There is an immediate need to drastically reduce the emissions associated with global fossil fuel consumption in order to limit climate change. However, carbon-based materials, chemicals, and transportation fuels are predominantly made from fossil sources and currently there is no alternative source available to adequately displace them. Gas-fermenting microorganisms that fix carbon dioxide (CO2) and carbon monoxide (CO) can break this dependence as they are capable of converting gaseous carbon to fuels and chemicals. As such, the technology can utilize a wide range of feedstocks including gasified organic matter of any sort (e.g., municipal solid waste, industrial waste, biomass, and agricultural waste residues) or industrial off-gases (e.g., from steel mills or processing plants). Gas fermentation has matured to the point that large-scale production of ethanol from gas has been demonstrated by two companies. This review gives an overview of the gas fermentation process, focusing specifically on anaerobic acetogens. Applications of synthetic biology and coupling gas fermentation to additional processes are discussed in detail. Both of these strategies, demonstrated at bench-scale, have abundant potential to rapidly expand the commercial product spectrum of gas fermentation and further improve efficiencies and yields. PMID:27242719

Biomass enables the transition to a carbon-negative power system across western North America

NASA Astrophysics Data System (ADS)

Sanchez, Daniel L.; Nelson, James H.; Johnston, Josiah; Mileva, Ana; Kammen, Daniel M.

2015-03-01

Sustainable biomass can play a transformative role in the transition to a decarbonized economy, with potential applications in electricity, heat, chemicals and transportation fuels. Deploying bioenergy with carbon capture and sequestration (BECCS) results in a net reduction in atmospheric carbon. BECCS may be one of the few cost-effective carbon-negative opportunities available should anthropogenic climate change be worse than anticipated or emissions reductions in other sectors prove particularly difficult. Previous work, primarily using integrated assessment models, has identified the critical role of BECCS in long-term (pre- or post-2100 time frames) climate change mitigation, but has not investigated the role of BECCS in power systems in detail, or in aggressive time frames, even though commercial-scale facilities are starting to be deployed in the transportation sector. Here, we explore the economic and deployment implications for BECCS in the electricity system of western North America under aggressive (pre-2050) time frames and carbon emissions limitations, with rich technology representation and physical constraints. We show that BECCS, combined with aggressive renewable deployment and fossil-fuel emission reductions, can enable a carbon-negative power system in western North America by 2050 with up to 145% emissions reduction from 1990 levels. In most scenarios, the offsets produced by BECCS are found to be more valuable to the power system than the electricity it provides. Advanced biomass power generation employs similar system design to advanced coal technology, enabling a transition strategy to low-carbon energy.

Serpentinization-Influenced Groundwater Harbors Extremely Low Diversity Microbial Communities Adapted to High pH

PubMed Central

Twing, Katrina I.; Brazelton, William J.; Kubo, Michael D. Y.; Hyer, Alex J.; Cardace, Dawn; Hoehler, Tori M.; McCollom, Tom M.; Schrenk, Matthew O.

2017-01-01

Serpentinization is a widespread geochemical process associated with aqueous alteration of ultramafic rocks that produces abundant reductants (H2 and CH4) for life to exploit, but also potentially challenging conditions, including high pH, limited availability of terminal electron acceptors, and low concentrations of inorganic carbon. As a consequence, past studies of serpentinites have reported low cellular abundances and limited microbial diversity. Establishment of the Coast Range Ophiolite Microbial Observatory (California, U.S.A.) allowed a comparison of microbial communities and physicochemical parameters directly within serpentinization-influenced subsurface aquifers. Samples collected from seven wells were subjected to a range of analyses, including solute and gas chemistry, microbial diversity by 16S rRNA gene sequencing, and metabolic potential by shotgun metagenomics, in an attempt to elucidate what factors drive microbial activities in serpentinite habitats. This study describes the first comprehensive interdisciplinary analysis of microbial communities in hyperalkaline groundwater directly accessed by boreholes into serpentinite rocks. Several environmental factors, including pH, methane, and carbon monoxide, were strongly associated with the predominant subsurface microbial communities. A single operational taxonomic unit (OTU) of Betaproteobacteria and a few OTUs of Clostridia were the almost exclusive inhabitants of fluids exhibiting the most serpentinized character. Metagenomes from these extreme samples contained abundant sequences encoding proteins associated with hydrogen metabolism, carbon monoxide oxidation, carbon fixation, and acetogenesis. Metabolic pathways encoded by Clostridia and Betaproteobacteria, in particular, are likely to play important roles in the ecosystems of serpentinizing groundwater. These data provide a basis for further biogeochemical studies of key processes in serpentinite subsurface environments. PMID:28298908

Metaproteomics of a gutless marine worm and its symbiotic microbial community reveal unusual pathways for carbon and energy use

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kleiner, Manuel; Wentrop, C.; Lott, C.

Low nutrient and energy availability has led to the evolution of numerous strategies for overcoming these limitations, of which symbiotic associations represent a key mechanism. Particularly striking are the associations between chemosynthetic bacteria and marine animals that thrive in nutrient-poor environments such as the deep-sea because the symbionts allow their hosts to grow on inorganic energy and carbon sources such as sulfide and CO2. Remarkably little is known about the physiological strategies that enable chemosynthetic symbioses to colonize oligotrophic environments. In this study, we used metaproteomics and metabolomics to investigate the intricate network of metabolic interactions in the chemosynthetic associationmore » between Olavius algarvensis, a gutless marine worm, and its bacterial symbionts. We propose novel pathways for coping with energy and nutrient limitation, some of which may be widespread in both free-living and symbiotic bacteria. These include (i) a pathway for symbiont assimilation of the host waste products acetate, propionate, succinate and malate, (ii) the potential use of carbon monoxide as an energy source, a substrate previously not known to play a role in marine invertebrate symbioses, (iii) the potential use of hydrogen as an energy source, (iv) the strong expression of high affinity uptake transporters, and (v) novel energy efficient steps in CO2 fixation and sulfate reduction. The high expression of proteins involved in pathways for energy and carbon uptake and conservation in the O. algarvensis symbiosis indicates that the oligotrophic nature of its environment exerted a strong selective pressure in shaping these associations.« less

Serpentinization-Influenced Groundwater Harbors Extremely Low Diversity Microbial Communities Adapted to High pH.

PubMed

Twing, Katrina I; Brazelton, William J; Kubo, Michael D Y; Hyer, Alex J; Cardace, Dawn; Hoehler, Tori M; McCollom, Tom M; Schrenk, Matthew O

2017-01-01

Serpentinization is a widespread geochemical process associated with aqueous alteration of ultramafic rocks that produces abundant reductants (H 2 and CH 4 ) for life to exploit, but also potentially challenging conditions, including high pH, limited availability of terminal electron acceptors, and low concentrations of inorganic carbon. As a consequence, past studies of serpentinites have reported low cellular abundances and limited microbial diversity. Establishment of the Coast Range Ophiolite Microbial Observatory (California, U.S.A.) allowed a comparison of microbial communities and physicochemical parameters directly within serpentinization-influenced subsurface aquifers. Samples collected from seven wells were subjected to a range of analyses, including solute and gas chemistry, microbial diversity by 16S rRNA gene sequencing, and metabolic potential by shotgun metagenomics, in an attempt to elucidate what factors drive microbial activities in serpentinite habitats. This study describes the first comprehensive interdisciplinary analysis of microbial communities in hyperalkaline groundwater directly accessed by boreholes into serpentinite rocks. Several environmental factors, including pH, methane, and carbon monoxide, were strongly associated with the predominant subsurface microbial communities. A single operational taxonomic unit (OTU) of Betaproteobacteria and a few OTUs of Clostridia were the almost exclusive inhabitants of fluids exhibiting the most serpentinized character. Metagenomes from these extreme samples contained abundant sequences encoding proteins associated with hydrogen metabolism, carbon monoxide oxidation, carbon fixation, and acetogenesis. Metabolic pathways encoded by Clostridia and Betaproteobacteria, in particular, are likely to play important roles in the ecosystems of serpentinizing groundwater. These data provide a basis for further biogeochemical studies of key processes in serpentinite subsurface environments.

Organic carbon, and not copper, controls denitrification in oxygen minimum zones of the ocean

NASA Astrophysics Data System (ADS)

Ward, Bess B.; Tuit, Caroline B.; Jayakumar, Amal; Rich, Jeremy J.; Moffett, James; Naqvi, S. Wajih A.

2008-12-01

Incubation experiments under trace metal clean conditions and ambient oxygen concentrations were used to investigate the response of microbial assemblages in oxygen minimum zones (OMZs) to additions of organic carbon and copper, two factors that might be expected to limit denitrification in the ocean. In the OMZs of the Eastern Tropical North and South Pacific, denitrification appeared to be limited by organic carbon; exponential cell growth and rapid nitrate and nitrite depletion occurred upon the addition of small amounts of carbon, but copper had no effect. In the OMZ of the Arabian Sea, neither carbon nor copper appeared to be limiting. We hypothesize that denitrification is variable in time and space in the OMZs in ways that may be predictable based on links to the episodic supply of organic substrates from overlying productive surface waters.

Carbon source-sink limitations differ between two species with contrasting growth strategies.

PubMed

Burnett, Angela C; Rogers, Alistair; Rees, Mark; Osborne, Colin P

2016-11-01

Understanding how carbon source and sink strengths limit plant growth is a critical knowledge gap that hinders efforts to maximize crop yield. We investigated how differences in growth rate arise from source-sink limitations, using a model system comparing a fast-growing domesticated annual barley (Hordeum vulgare cv. NFC Tipple) with a slow-growing wild perennial relative (Hordeum bulbosum). Source strength was manipulated by growing plants at sub-ambient and elevated CO 2 concentrations ([CO 2 ]). Limitations on vegetative growth imposed by source and sink were diagnosed by measuring relative growth rate, developmental plasticity, photosynthesis and major carbon and nitrogen metabolite pools. Growth was sink limited in the annual but source limited in the perennial. RGR and carbon acquisition were higher in the annual, but photosynthesis responded weakly to elevated [CO 2 ] indicating that source strength was near maximal at current [CO 2 ]. In contrast, photosynthetic rate and sink development responded strongly to elevated [CO 2 ] in the perennial, indicating significant source limitation. Sink limitation was avoided in the perennial by high sink plasticity: a marked increase in tillering and root:shoot ratio at elevated [CO 2 ], and lower non-structural carbohydrate accumulation. Alleviating sink limitation during vegetative development could be important for maximizing growth of elite cereals under future elevated [CO 2 ]. © 2016 John Wiley & Sons Ltd.

Effect of inorganic N enrichment on basal pelagic production in boreal unproductive lakes along a gradient of DOC concentration - results after 1 year of fertilization

NASA Astrophysics Data System (ADS)

Deininger, Anne; Bergström, Ann-Kristin

2013-04-01

Input of inorganic nitrogen (N) in boreal unproductive lakes is steadily increasing due to anthropogenic deposition and usage of artificial fertilizers. N enrichment is predicted to have a major impact on the ecosystem productivity and food web structure in unproductive clear-water and humic lakes. For a long time, pelagic primary production (PP) has been mainly regarded as being phosphorus (P) limited. However, recent studies have shown that this is not true for unproductive lakes in northern Sweden, where phytoplankton is mainly N limited. Addition of inorganic N should therefore increase phytoplankton growth in these lake ecosystems. Bacterial production (BP) in the pelagic habitat, on the other hand, is usually limited by P. Nevertheless, elevated N could have a stimulating effect on BP through enhanced leakage of dissolved organic carbon (DOC) from phytoplankton following enhanced N availability and higher PP. Further, unproductive lakes vary naturally in their DOC content which affects overall nutrient- (N and P), energy- and carbon availability (light, C) for the basal producers (phytoplankton, bacteria). It is still not clear how higher inorganic N availability affects primary- and bacterial production in the pelagic in lakes with varying DOC content. We subsequently assessed this question by conducting whole-lake fertilization experiments with inorganic N additions in 6 lakes with varying DOC concentrations (2 low DOC; 2 medium DOC; 2 high DOC). For each DOC level one lake functioned as a reference and one was fertilized with N. Year 2011 was a reference year (all lakes) and 2012 was the first year of fertilization (i.e. in 3 lakes). Measurements included basal productivity such as primary production and bacteria production, lake water chemistry and physical parameters (i.e. light, temperature). The results of this study will help to develop a conceptual understanding of how increased inorganic N availability (through land use such as forestry and/or enhanced N deposition) affects basal productivity in boreal lakes which can have consequences for overall whole lake-ecosystem productivity and functioning.

Astronomical observations of solid phase carbon

NASA Technical Reports Server (NTRS)

Jura, M.

1990-01-01

In the outer envelopes of red giants, when the gas cools sufficiently, molecules and solids form. Thermodynamically, the most stable molecule is CO, and it is usually assumed that all the available carbon and oxygen are consumed in the formation of this molecule (Salpeter 1977). If the carbon abundance is greater than the oxygen abundance, then the carbon left over after the formation of CO is available for solid grains. Because carbon is by far the most abundant species available for making solids in these environments, researchers anticipate that the grains are composed of nearly pure carbon in some form. The observations which can be used to infer the nature of this solid phase carbon are discussed. The observations of the dust around carbon-rich red giants are discussed. These results are then placed into their broader astrophysical context.

Hard-Soft Composite Carbon as a Long-Cycling and High-Rate Anode for Potassium-Ion Batteries

DOE PAGES

Jian, Zelang; Hwang, Sooyeon; Li, Zhifei; ...

2017-05-05

There exist tremendous needs for sustainable storage solutions for intermittent renewable energy sources, such as solar and wind energy. Thus, systems based on Earth-abundant elements deserve much attention. Potassium-ion batteries represent a promising candidate because of the abundance of potassium resources. As for the choices of anodes, graphite exhibits encouraging potassium-ion storage properties; however, it suffers limited rate capability and poor cycling stability. Here in this paper, nongraphitic carbons as K-ion anodes with sodium carboxymethyl cellulose as the binder are systematically investigated. Compared to hard carbon and soft carbon, a hard–soft composite carbon with 20 wt% soft carbon distributed inmore » the matrix phase of hard carbon microspheres exhibits highly amenable performance: high capacity, high rate capability, and very stable long-term cycling. In contrast, pure hard carbon suffers limited rate capability, while the capacity of pure soft carbon fades more rapidly.« less

Hard-Soft Composite Carbon as a Long-Cycling and High-Rate Anode for Potassium-Ion Batteries

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jian, Zelang; Hwang, Sooyeon; Li, Zhifei

There exist tremendous needs for sustainable storage solutions for intermittent renewable energy sources, such as solar and wind energy. Thus, systems based on Earth-abundant elements deserve much attention. Potassium-ion batteries represent a promising candidate because of the abundance of potassium resources. As for the choices of anodes, graphite exhibits encouraging potassium-ion storage properties; however, it suffers limited rate capability and poor cycling stability. Here in this paper, nongraphitic carbons as K-ion anodes with sodium carboxymethyl cellulose as the binder are systematically investigated. Compared to hard carbon and soft carbon, a hard–soft composite carbon with 20 wt% soft carbon distributed inmore » the matrix phase of hard carbon microspheres exhibits highly amenable performance: high capacity, high rate capability, and very stable long-term cycling. In contrast, pure hard carbon suffers limited rate capability, while the capacity of pure soft carbon fades more rapidly.« less

Effects of Soil Temperature and Moisture on Soil Respiration on the Tibetan Plateau

PubMed Central

Chang, Xiaofeng; Wang, Shiping; Xu, Burenbayin; Luo, Caiyun; Zhang, Zhenhua; Wang, Qi; Rui, Yichao; Cui, Xiaoying

2016-01-01

Understanding of effects of soil temperature and soil moisture on soil respiration (Rs) under future warming is critical to reduce uncertainty in predictions of feedbacks to atmospheric CO2 concentrations from grassland soil carbon. Intact cores with roots taken from a full factorial, 5-year alpine meadow warming and grazing experiment in the field were incubated at three different temperatures (i.e. 5, 15 and 25°C) with two soil moistures (i.e. 30 and 60% water holding capacity (WHC)) in our study. Another experiment of glucose-induced respiration (GIR) with 4 h of incubation was conducted to determine substrate limitation. Our results showed that high temperature increased Rs and low soil moisture limited the response of Rs to temperature only at high incubation temperature (i.e. 25°C). Temperature sensitivity (Q10) did not significantly decrease over the incubation period, suggesting that substrate depletion did not limit Rs. Meanwhile, the carbon availability index (CAI) was higher at 5°C compared with 15 and 25°C incubation, but GIR increased with increasing temperature. Therefore, our findings suggest that warming-induced decrease in Rs in the field over time may result from a decrease in soil moisture rather than from soil substrate depletion, because warming increased root biomass in the alpine meadow. PMID:27798671

Nitrogen and carbon source-sink relationships in trees at the Himalayan treelines compared with lower elevations.

PubMed

Li, Mai-He; Xiao, Wen-Fa; Shi, Peili; Wang, San-Gen; Zhong, Yong-De; Liu, Xing-Liang; Wang, Xiao-Dan; Cai, Xiao-Hu; Shi, Zuo-Min

2008-10-01

No single hypothesis or theory has been widely accepted for explaining the functional mechanism of global alpine/arctic treeline formation. The present study tested whether the alpine treeline is determined by (1) the needle nitrogen content associated with photosynthesis (carbon gain); (2) a sufficient source-sink ratio of carbon; or (3) a sufficient C-N ratio. Nitrogen does not limit the growth and development of trees studied at the Himalayan treelines. Levels of non-structural carbohydrates (NSC) in trees were species-specific and site-dependent; therefore, the treeline cases studied did not show consistent evidence of source/carbon limitation or sink/growth limitation in treeline trees. However, results of the combined three treelines showed that the treeline trees may suffer from a winter carbon shortage. The source capacity and the sink capacity of a tree influence its tissue NSC concentrations and the carbon balance; therefore, we suggest that the persistence and development of treeline trees in a harsh alpine environment may require a minimum level of the total NSC concentration, a sufficiently high sugar:starch ratio, and a balanced carbon source-sink relationship.

CO2 diffusion into pore spaces limits weathering rate of an experimental basalt landscape

USGS Publications Warehouse

van Haren, Joost; Dontsova, Katerina; Barron-Gafford, Greg A.; Troch, Peter A.; Chorover, Jon; DeLong, Stephen B.; Breshears, David D.; Huxman, Travis E.; Pelletier, Jon D.; Saleska, Scott; Zeng, Xubin; Ruiz, Joaquin

2017-01-01

Basalt weathering is a key control over the global carbon cycle, though in situ measurements of carbon cycling are lacking. In an experimental, vegetation-free hillslope containing 330 m3 of ground basalt scoria, we measured real-time inorganic carbon dynamics within the porous media and seepage flow. The hillslope carbon flux (0.6–5.1 mg C m–2 h–1) matched weathering rates of natural basalt landscapes (0.4–8.8 mg C m–2 h–1) despite lacking the expected field-based impediments to weathering. After rainfall, a decrease in CO2 concentration ([CO2]) in pore spaces into solution suggested rapid carbon sequestration but slow reactant supply. Persistent low soil [CO2] implied that diffusion limited CO2 supply, while when sufficiently dry, reaction product concentrations limited further weathering. Strong influence of diffusion could cause spatial heterogeneity of weathering even in natural settings, implying that modeling studies need to include variable soil [CO2] to improve carbon cycling estimates associated with potential carbon sequestration methods.

Barriers to the development of forest carbon offsetting: Insights from British Columbia, Canada.

PubMed

Peterson St-Laurent, Guillaume; Hagerman, Shannon; Hoberg, George

2017-12-01

In recent years, the provision of economic incentives through carbon financing and carbon offsetting has been central to efforts at forest carbon mitigation. However, notwithstanding their potentially important roles in climate policy, forest carbon offsets face numerous barriers which have limited widespread implementation worldwide. This paper uses the case study of the Canadian province of British Columbia to explore the barriers associated with achieving widespread implementation of forest carbon offsets in the next several decades. Drawing on interviews with experts from government, non-governmental organizations, the private sector and First Nations, six main barriers are identified and discussed: (1) deficiencies of carbon markets, (2) limited economic benefits, (3) uncertain climate effectiveness, (4) negative public opinion, (5) limited and uncertain property rights, and (6) governance issues. While respondents from different sectors agreed on various points, divergence was also observed, notably on the trade-off between generating environmentally sound offsets and promoting cost-effective ways to achieve mitigation. We discuss these differences in the context of the goals and objectives of different actors, and offer insights for understanding the uptake (or not) of carbon offset policies. Copyright © 2017 Elsevier Ltd. All rights reserved.

Land use strategies to mitigate climate change in carbon dense temperate forests.

PubMed

Law, Beverly E; Hudiburg, Tara W; Berner, Logan T; Kent, Jeffrey J; Buotte, Polly C; Harmon, Mark E

2018-04-03

Strategies to mitigate carbon dioxide emissions through forestry activities have been proposed, but ecosystem process-based integration of climate change, enhanced CO 2 , disturbance from fire, and management actions at regional scales are extremely limited. Here, we examine the relative merits of afforestation, reforestation, management changes, and harvest residue bioenergy use in the Pacific Northwest. This region represents some of the highest carbon density forests in the world, which can store carbon in trees for 800 y or more. Oregon's net ecosystem carbon balance (NECB) was equivalent to 72% of total emissions in 2011-2015. By 2100, simulations show increased net carbon uptake with little change in wildfires. Reforestation, afforestation, lengthened harvest cycles on private lands, and restricting harvest on public lands increase NECB 56% by 2100, with the latter two actions contributing the most. Resultant cobenefits included water availability and biodiversity, primarily from increased forest area, age, and species diversity. Converting 127,000 ha of irrigated grass crops to native forests could decrease irrigation demand by 233 billion m 3 ⋅y -1 Utilizing harvest residues for bioenergy production instead of leaving them in forests to decompose increased emissions in the short-term (50 y), reducing mitigation effectiveness. Increasing forest carbon on public lands reduced emissions compared with storage in wood products because the residence time is more than twice that of wood products. Hence, temperate forests with high carbon densities and lower vulnerability to mortality have substantial potential for reducing forest sector emissions. Our analysis framework provides a template for assessments in other temperate regions. Copyright © 2018 the Author(s). Published by PNAS.

Infrastructure Shapes Differences in the Carbon Intensities of Chinese Cities.

PubMed

Zheng, Bo; Zhang, Qiang; Davis, Steven J; Ciais, Philippe; Hong, Chaopeng; Li, Meng; Liu, Fei; Tong, Dan; Li, Haiyan; He, Kebin

2018-05-15

The carbon intensity of economic activity, or CO 2 emissions per unit GDP, is a key indicator of the climate impacts of a given activity, business, or region. Although it is well-known that the carbon intensity of countries varies widely according to their level of economic development and dominant industries, few studies have assessed disparities in carbon intensity at the level of cities due to limited availability of data. Here, we present a detailed new inventory of emissions for 337 Chinese cities (every city in mainland China including 333 prefecture-level divisions and 4 province-level cities, Beijing, Tianjin, Shanghai, and Chongqing) in 2013, which we use to evaluate differences of carbon intensity between cities and the causes of those differences. We find that cities' average carbon intensity is 0.84 kg of CO 2 per dollar of gross domestic product (kgCO 2 per $GDP), but individual cities span a large range: from 0.09 to 7.86 kgCO 2 per $GDP (coefficient of variation of 25%). Further analysis of economic and technological drivers of variations in cities' carbon intensity reveals that the differences are largely due to disparities in cities' economic structure that can in turn be traced to past investment-led growth. These patterns suggest that "carbon lock-in" via socio-economic and infrastructural inertia may slow China's efforts to reduce emissions from activities in urban areas. Policy instruments targeted to accelerate the transition of urban economies from investment-led to consumption-led growth may thus be crucial to China meeting both its economic and climate targets.

Land use strategies to mitigate climate change in carbon dense temperate forests

PubMed Central

Hudiburg, Tara W.; Berner, Logan T.; Kent, Jeffrey J.; Buotte, Polly C.; Harmon, Mark E.

2018-01-01

Strategies to mitigate carbon dioxide emissions through forestry activities have been proposed, but ecosystem process-based integration of climate change, enhanced CO2, disturbance from fire, and management actions at regional scales are extremely limited. Here, we examine the relative merits of afforestation, reforestation, management changes, and harvest residue bioenergy use in the Pacific Northwest. This region represents some of the highest carbon density forests in the world, which can store carbon in trees for 800 y or more. Oregon’s net ecosystem carbon balance (NECB) was equivalent to 72% of total emissions in 2011–2015. By 2100, simulations show increased net carbon uptake with little change in wildfires. Reforestation, afforestation, lengthened harvest cycles on private lands, and restricting harvest on public lands increase NECB 56% by 2100, with the latter two actions contributing the most. Resultant cobenefits included water availability and biodiversity, primarily from increased forest area, age, and species diversity. Converting 127,000 ha of irrigated grass crops to native forests could decrease irrigation demand by 233 billion m3⋅y−1. Utilizing harvest residues for bioenergy production instead of leaving them in forests to decompose increased emissions in the short-term (50 y), reducing mitigation effectiveness. Increasing forest carbon on public lands reduced emissions compared with storage in wood products because the residence time is more than twice that of wood products. Hence, temperate forests with high carbon densities and lower vulnerability to mortality have substantial potential for reducing forest sector emissions. Our analysis framework provides a template for assessments in other temperate regions. PMID:29555758

The production of cyanobacterial carbon under nitrogen-limited cultivation and its potential for nitrate removal.

PubMed

Huang, Yingying; Li, Panpan; Chen, Guiqin; Peng, Lin; Chen, Xuechu

2018-01-01

Harmful cyanobacterial blooms (CyanoHABs) represent a serious threat to aquatic ecosystems. A beneficial use for these harmful microorganisms would be a promising resolution of this urgent issue. This study applied a simple method, nitrogen limitation, to cultivate cyanobacteria aimed at producing cyanobacterial carbon for denitrification. Under nitrogen-limited conditions, the common cyanobacterium, Microcystis, efficiently used nitrate, and had a higher intracellular C/N ratio. More importantly, organic carbons easily leached from its dry powder; these leachates were biodegradable and contained a larger amount of dissolved organic carbon (DOC) and carbohydrates, but a smaller amount of dissolved total nitrogen (DTN) and proteins. When applied to an anoxic system with a sediment-water interface, a significant increase of the specific NO X - -N removal rate was observed that was 14.2 times greater than that of the control. This study first suggests that nitrogen-limited cultivation is an efficient way to induce organic and carbohydrate accumulation in cyanobacteria, as well as a high C/N ratio, and that these cyanobacteria can act as a promising carbon source for denitrification. The results indicate that application as a carbon source is not only a new way to utilize cyanobacteria, but it also contributes to nitrogen removal in aquatic ecosystems, further limiting the proliferation of CyanoHABs. Copyright © 2017. Published by Elsevier Ltd.

Large Scale Reduction of Graphite Oxide Project

NASA Technical Reports Server (NTRS)

Calle, Carlos; Mackey, Paul; Falker, John; Zeitlin, Nancy

2015-01-01

This project seeks to develop an optical method to reduce graphite oxide into graphene efficiently and in larger formats than currently available. Current reduction methods are expensive, time-consuming or restricted to small, limited formats. Graphene has potential uses in ultracapacitors, energy storage, solar cells, flexible and light-weight circuits, touch screens, and chemical sensors. In addition, graphite oxide is a sustainable material that can be produced from any form of carbon, making this method environmentally friendly and adaptable for in-situ reduction.

Non-PGM cathode catalysts for fuel cell application derived from heat treated heteroatomic amines precursors

DOEpatents

Serov, Alexey; Halevi, Barr; Artyushkova, Kateryna; Atanassov, Plamen B; Martinez, Ulises A

2017-04-25

A method of preparing M-N--C catalysts utilizing a sacrificial support approach and inexpensive and readily available polymer precursors as the source of nitrogen and carbon is disclosed. Exemplary polymer precursors include non-porphyrin precursors with no initial catalytic activity. Examples of suitable non-catalytic non-porphyrin precursors include, but are not necessarily limited to low molecular weight precursors that form complexes with iron such as 4-aminoantipirine, phenylenediamine, hydroxysuccinimide, ethanolamine, and the like.

A nitrogen-rich septage-effluent plume in a glacial aquifer, Cape Cod, Massachusetts, February 1990 through December 1992

USGS Publications Warehouse

Desimone, Leslie A.; Barlow, Paul M.; Howes, Brian L.

1996-01-01

Physical, chemical, and microbial processes controlled transport of a nitrogen-rich ground-water plume through a glacial aquifer. Lithologic heterogeneity and vertical head gradients influenced plume movement and geometry. Nitrate was the predominant nitrogen form and oxygen was depleted in the ground-water plume. However, denitrification transformed only 2 percent of plume nitrogen because of limited organic-carbon availability. Aerobic respiration, nitrification and cation exchange (unsaturated zone) and ammonium sorption (saturated zone) had larger effects.

Fabrication and characterization of branched carbon nanostructures.

PubMed

Malik, Sharali; Nemoto, Yoshihiro; Guo, Hongxuan; Ariga, Katsuhiko; Hill, Jonathan P

2016-01-01

Carbon nanotubes (CNTs) have atomically smooth surfaces and tend not to form covalent bonds with composite matrix materials. Thus, it is the magnitude of the CNT/fiber interfacial strength that limits the amount of nanomechanical interlocking when using conventional CNTs to improve the structural behavior of composite materials through reinforcement. This arises from two well-known, long standing problems in this research field: (a) inhomogeneous dispersion of the filler, which can lead to aggregation and (b) insufficient reinforcement arising from bonding interactions between the filler and the matrix. These dispersion and reinforcement issues could be addressed by using branched multiwalled carbon nanotubes (b-MWCNTs) as it is known that branched fibers can greatly enhance interfacial bonding and dispersability. Therefore, the use of b-MWCNTs would lead to improved mechanical performance and, in the case of conductive composites, improved electrical performance if the CNT filler was better dispersed and connected. This will provide major benefits to the existing commercial application of CNT-reinforced composites in electrostatic discharge materials (ESD): There would be also potential usage for energy conversion, e.g., in supercapacitors, solar cells and Li-ion batteries. However, the limited availability of b-MWCNTs has, to date, restricted their use in such technological applications. Herein, we report an inexpensive and simple method to fabricate large amounts of branched-MWCNTs, which opens the door to a multitude of possible applications.

Effects of harvesting on spatial and temporal diversity of carbon stocks in a boreal forest landscape.

PubMed

Ter-Mikaelian, Michael T; Colombo, Stephen J; Chen, Jiaxin

2013-10-01

Carbon stocks in managed forests of Ontario, Canada, and in harvested wood products originated from these forests were estimated for 2010-2100. Simulations included four future forest harvesting scenarios based on historical harvesting levels (low, average, high, and maximum available) and a no-harvest scenario. In four harvesting scenarios, forest carbon stocks in Ontario's managed forest were estimated to range from 6202 to 6227 Mt C (millions of tons of carbon) in 2010, and from 6121 to 6428 Mt C by 2100. Inclusion of carbon stored in harvested wood products in use and in landfills changed the projected range in 2100 to 6710-6742 Mt C. For the no-harvest scenario, forest carbon stocks were projected to change from 6246 Mt C in 2010 to 6680 Mt C in 2100. Spatial variation in projected forest carbon stocks was strongly related to changes in forest age (r = 0.603), but had weak correlation with harvesting rates. For all managed forests in Ontario combined, projected carbon stocks in combined forest and harvested wood products converged to within 2% difference by 2100. The results suggest that harvesting in the boreal forest, if applied within limits of sustainable forest management, will eventually have a relatively small effect on long-term combined forest and wood products carbon stocks. However, there was a large time lag to approach carbon equality, with more than 90 years with a net reduction in stored carbon in harvested forests plus wood products compared to nonharvested boreal forest which also has low rates of natural disturbance. The eventual near equivalency of carbon stocks in nonharvested forest and forest that is harvested and protected from natural disturbance reflects both the accumulation of carbon in harvested wood products and the relatively young age at which boreal forest stands undergo natural succession in the absence of disturbance.

Resolving model parameter values from carbon and nitrogen stock measurements in a wide range of tropical mature forests using nonlinear inversion and regression trees

USGS Publications Warehouse

Liu, S.; Anderson, P.; Zhou, G.; Kauffman, B.; Hughes, F.; Schimel, D.; Watson, Vicente; Tosi, Joseph

2008-01-01

Objectively assessing the performance of a model and deriving model parameter values from observations are critical and challenging in landscape to regional modeling. In this paper, we applied a nonlinear inversion technique to calibrate the ecosystem model CENTURY against carbon (C) and nitrogen (N) stock measurements collected from 39 mature tropical forest sites in seven life zones in Costa Rica. Net primary productivity from the Moderate-Resolution Imaging Spectroradiometer (MODIS), C and N stocks in aboveground live biomass, litter, coarse woody debris (CWD), and in soils were used to calibrate the model. To investigate the resolution of available observations on the number of adjustable parameters, inversion was performed using nine setups of adjustable parameters. Statistics including observation sensitivity, parameter correlation coefficient, parameter sensitivity, and parameter confidence limits were used to evaluate the information content of observations, resolution of model parameters, and overall model performance. Results indicated that soil organic carbon content, soil nitrogen content, and total aboveground biomass carbon had the highest information contents, while measurements of carbon in litter and nitrogen in CWD contributed little to the parameter estimation processes. The available information could resolve the values of 2-4 parameters. Adjusting just one parameter resulted in under-fitting and unacceptable model performance, while adjusting five parameters simultaneously led to over-fitting. Results further indicated that the MODIS NPP values were compressed as compared with the spatial variability of net primary production (NPP) values inferred from inverse modeling. Using inverse modeling to infer NPP and other sensitive model parameters from C and N stock observations provides an opportunity to utilize data collected by national to regional forest inventory systems to reduce the uncertainties in the carbon cycle and generate valuable databases to validate and improve MODIS NPP algorithms.

Subarctic physicochemical weathering of serpentinized peridotite

NASA Astrophysics Data System (ADS)

Ulven, O. I.; Beinlich, A.; Hövelmann, J.; Austrheim, H.; Jamtveit, B.

2017-06-01

Frost weathering is effective in arctic and subarctic climate zones where chemical reactions are limited by the reduced availability of liquid water and the prevailing low temperature. However, small scale mineral dissolution reactions are nevertheless important for the generation of porosity by allowing infiltration of surface water with subsequent fracturing due to growth of ice and carbonate minerals. Here we combine textural and mineralogical observations in natural samples of partly serpentinized ultramafic rocks with a discrete element model describing the fracture mechanics of a solid when subject to pressure from the growth of ice and carbonate minerals in surface-near fractures. The mechanical model is coupled with a reaction-diffusion model that describes an initial stage of brucite dissolution as observed during weathering of serpentinized harzburgites and dunites from the Feragen Ultramafic Body (FUB), SE-Norway. Olivine and serpentine are effectively inert at relevant conditions and time scales, whereas brucite dissolution produces well-defined cm to dm thick weathering rinds with elevated porosity that allows influx of water. Brucite dissolution also increases the water saturation state with respect to hydrous Mg carbonate minerals, which are commonly found as infill in fractures in the fresh rock. This suggests that fracture propagation is at least partly driven by carbonate precipitation. Dissolution of secondary carbonate minerals during favorable climatic conditions provides open space available for ice crystallization that drives fracturing during winter. Our model reproduces the observed cm-scale meandering fractures that propagate into the fresh part of the rock, as well as dm-scale fractures that initiate the breakup of larger domains. Rock disintegration increases the reactive surface area and hence the rate of chemical weathering, enhances transport of dissolved and particulate matter in the weathering fluid, and facilitates CO2 uptake by carbonate precipitation. Our observations have implications for element cycling and CO2 sequestration in natural gravel and mine tailings.

Limits to reproductive success of Sarracenia purpurea (Sarraceniaceae).

PubMed

Ne'eman, Gidi; Ne'eman, Rina; Ellison, Aaron M

2006-11-01

Plant biologists have an enduring interest in assessing components of plant fitness and determining limits to seed set. Consequently, the relative contributions of resource and pollinator availability have been documented for a large number of plant species. We experimentally examined the roles of resource and pollen availability on seed set by the northern pitcher plant Sarracenia purpurea. We were able to distinguish the relative contributions of carbon (photosynthate) and mineral nutrients (nitrogen) to reproductive success. We also determined potential pollinators of this species. The bees Bombus affinis and Augochlorella aurata and the fly Fletcherimyia fletcheri were the only floral visitors to S. purpurea that collected pollen. Supplemental pollination increased seed set by <10%, a much lower percentage than would be expected, given data from noncarnivorous, animal-pollinated taxa. Seed set was reduced by 14% in plants that could not capture prey and by another 23% in plants whose pitcher-shaped leaves were also prevented from photosynthesizing. We conclude that resources are more important than pollen availability in determining seed set by this pitcher plant and that reproductive output may be another "cost" of the carnivorous habit.

Limitations and information needs for engineered nanomaterial-specific exposure estimation and scenarios: recommendations for improved reporting practices

NASA Astrophysics Data System (ADS)

Clark, Katherine; van Tongeren, Martie; Christensen, Frans M.; Brouwer, Derk; Nowack, Bernd; Gottschalk, Fadri; Micheletti, Christian; Schmid, Kaspar; Gerritsen, Rianda; Aitken, Rob; Vaquero, Celina; Gkanis, Vasileios; Housiadas, Christos; de Ipiña, Jesús María López; Riediker, Michael

2012-09-01

The aim of this paper is to describe the process and challenges in building exposure scenarios for engineered nanomaterials (ENM), using an exposure scenario format similar to that used for the European Chemicals regulation (REACH). Over 60 exposure scenarios were developed based on information from publicly available sources (literature, books, and reports), publicly available exposure estimation models, occupational sampling campaign data from partnering institutions, and industrial partners regarding their own facilities. The primary focus was on carbon-based nanomaterials, nano-silver (nano-Ag) and nano-titanium dioxide (nano-TiO2), and included occupational and consumer uses of these materials with consideration of the associated environmental release. The process of building exposure scenarios illustrated the availability and limitations of existing information and exposure assessment tools for characterizing exposure to ENM, particularly as it relates to risk assessment. This article describes the gaps in the information reviewed, recommends future areas of ENM exposure research, and proposes types of information that should, at a minimum, be included when reporting the results of such research, so that the information is useful in a wider context.

A uniform bacterial growth potential assay for different water types.

PubMed

Farhat, Nadia; Hammes, Frederik; Prest, Emmanuelle; Vrouwenvelder, Johannes

2018-06-06

The bacterial growth potential is important to understand and manage bacterial regrowth-related water quality concerns. Bacterial growth potential depends on growth promoting/limiting compounds, therefore, nutrient availability is the key factor governing bacterial growth potential. Selecting proper tools for bacterial growth measurement is essential for routine implementation of the growth potential measurement. This study proposes a growth potential assay that is universal and can be used for different water types and soil extract without restrictions of pure culture or cultivability of the bacterial strain. The proposed assay measures the sample bacterial growth potential by using the indigenous community as inocula. Flow cytometry (FCM) and adenosine tri-phosphate (ATP) were used to evaluate the growth potential of six different microbial communities indigenous to the sample being analyzed, with increasing carbon concentrations. Bottled mineral water, non-chlorinated tap water, seawater, river water, wastewater effluent and a soil organic carbon extract were analyzed. Results showed that indigenous bacterial communities followed normal batch growth kinetics when grown on naturally present organic carbon. Indigenous bacterial growth could detect spiked organic carbon concentrations as low as 10 μg/L. The indigenous community in all samples responded proportionally to the increase in acetate-carbon and proportional growth could be measured with both FCM and ATP. Bacterial growth was proportional to the carbon concentration but not the same proportion factor for the different water samples tested. The effect of inoculating the same water with different indigenous microbial communities on the growth potential was also examined. The FCM results showed that the highest increase in total bacterial cell concentration was obtained with bacteria indigenous to the water sample. The growth potential assay using indigenous bacterial community revealed consistent results of bacterial growth in all the different samples tested and therefore providing a fast, more stable, and accurate approach for monitoring the biological stability of waters compared to the previously developed assays. The growth potential assay can be used to aid in detecting growth limitations by compounds other than organic carbon. Copyright © 2018 Elsevier Ltd. All rights reserved.

Development of land-use regression models for fine particles and black carbon in peri-urban South India.

PubMed

Sanchez, Margaux; Ambros, Albert; Milà, Carles; Salmon, Maëlle; Balakrishnan, Kalpana; Sambandam, Sankar; Sreekanth, V; Marshall, Julian D; Tonne, Cathryn

2018-09-01

Land-use regression (LUR) has been used to model local spatial variability of particulate matter in cities of high-income countries. Performance of LUR models is unknown in less urbanized areas of low-/middle-income countries (LMICs) experiencing complex sources of ambient air pollution and which typically have limited land use data. To address these concerns, we developed LUR models using satellite imagery (e.g., vegetation, urbanicity) and manually-collected data from a comprehensive built-environment survey (e.g., roads, industries, non-residential places) for a peri-urban area outside Hyderabad, India. As part of the CHAI (Cardiovascular Health effects of Air pollution in Telangana, India) project, concentrations of fine particulate matter (PM 2.5 ) and black carbon were measured over two seasons at 23 sites. Annual mean (sd) was 34.1 (3.2) μg/m 3 for PM 2.5 and 2.7 (0.5) μg/m 3 for black carbon. The LUR model for annual black carbon explained 78% of total variance and included both local-scale (energy supply places) and regional-scale (roads) predictors. Explained variance was 58% for annual PM 2.5 and the included predictors were only regional (urbanicity, vegetation). During leave-one-out cross-validation and cross-holdout validation, only the black carbon model showed consistent performance. The LUR model for black carbon explained a substantial proportion of the spatial variability that could not be captured by simpler interpolation technique (ordinary kriging). This is the first study to develop a LUR model for ambient concentrations of PM 2.5 and black carbon in a non-urban area of LMICs, supporting the applicability of the LUR approach in such settings. Our results provide insights on the added value of manually-collected built-environment data to improve the performance of LUR models in settings with limited data availability. For both pollutants, LUR models predicted substantial within-village variability, an important feature for future epidemiological studies. Copyright © 2018 The Authors. Published by Elsevier B.V. All rights reserved.

78 FR 28205 - Notice of Availability of the Draft Environmental Impact Statement for the Lake Charles Carbon...

Federal Register 2010, 2011, 2012, 2013, 2014

2013-05-14

... Lake Charles Carbon Capture and Sequestration Project (DOE/EIS-0464D) AGENCY: U.S. Department of Energy...) announces the availability of the Lake Charles Carbon Capture and Sequestration Project Draft [[Page 28206... potential environmental impacts associated with the Lake Charles Carbon Capture and Sequestration Project...

Introgression of physiological traits for a comprehensive improvement of drought adaptation in crop plants

NASA Astrophysics Data System (ADS)

Sreeman, Sheshshayee M.; Vijayaraghavareddy, Preethi; Sreevathsa, Rohini; Rajendrareddy, Sowmya; Arakesh, Smitharani; Bharti, Pooja; Dharmappa, Prathibha; Soolanayakanahally, Raju

2018-04-01

Burgeoning population growth, industrial demand and the predicted global climate change resulting in erratic monsoon rains are expected to severely limit fresh water availability for agriculture both in irrigated and rainfed ecosystems. In order to remain food and nutrient secure, agriculture research needs to focus on devising strategies to save water in irrigated conditions and to develop superior cultivars with improved water productivity to sustain yield under rainfed conditions. Recent opinions accruing in the scientific literature strongly favour the adoption of a “trait based” approach for increasing water productivity especially the traits associated with maintenance of positive tissue turgor and maintenance of increased carbon assimilation as the most relevant traits to improve crop growth rates under water limiting conditions and to enhance water productivity. The advent of several water saving agronomic practices notwithstanding, a genetic enhancement strategy of introgressing distinct physiological, morphological and cellular mechanisms on to a single elite genetic background is essential for achieving a comprehensive improvement in drought adaptation in crop plants. The significant progress made in genomics, though would provide the necessary impetus, a clear understanding of the “traits” to be introgressed is the most essential need of the hour. Water uptake by a better root architecture, water conservation by preventing unproductive transpiration is crucial for maintaining positive tissue water relations. Improved carbon assimilation associated with carboxylation capacity and mesophyll conductance is equally important in sustaining crop growth rates under water limited conditions. Besides these major traits, we summarized the available information in literature on classifying various drought adaptive traits. We provide evidences that water-use efficiency when introgressed with moderately higher transpiration, would significantly enhance growth rates and water productivity in rice through an improved photosynthetic capacity.

Short Term Soil Respiration Response to Fire in a Semi-arid Ecosystem

NASA Astrophysics Data System (ADS)

Rozin, A. G.

2015-12-01

In the Intermountain West (USA), fire is an important driver of carbon cycling in the environment. Increasing frequency and severity of fires, either through management actions or wildfires, is expected with changing climates in the Western United States. When burning is used as a management tool, it may be beneficial and control the growth of nuisance vegetation, promote the regeneration of grasses and forage species, and reduce hazardous fuel loads to minimize the risk of future wildfires. However, high intensity wildfires often have a negative effect, resulting in a loss of carbon storage and a shift of vegetation communities. This delays recovery of the ecosystem for years or decades and alters the historic fire regime. A 2000 acre prescribed burn in the Reynolds Creek Critical Zone Observatory provided the opportunity to quantify pre and post-burn soil carbon stores and soil carbon losses by heterotrophic respiration. Pre and post-burn soil samples were collected for physical and biogeochemical characterization to quantify substrate availability and possible limitations for heterotrophic respiration. CO2 fluxes were continuously monitored in situ before and immediately after the fire to understand the short-term response of soil respiration to varying burn severities.

Multi-walled carbon nanotubes: A cytotoxicity study in relation to functionalization, dose and dispersion.

PubMed

Zhou, Lulu; Forman, Henry Jay; Ge, Yi; Lunec, Joseph

2017-08-01

Chemical functionalization broadens carbon nanotube (CNT) applications, conferring new functions, but at the same time potentially altering toxicity. Although considerable experimental data related to CNT toxicity, at the molecular and cellular levels, have been reported, there is very limited information available for the corresponding mechanism involved (e.g. cell apoptosis and genotoxicity). The threshold dose for safe medical application in relation to both pristine and functionalized carbon nanotubes remains ambiguous. In this study, we evaluated the in vitro cytotoxicity of pristine and functionalized (OH, COOH) multi-walled carbon nanotubes (MWCNTs) for cell viability, oxidant detection, apoptosis and DNA mutations, to determine the non-toxic dose and influence of functional group in a human lung-cancer cell line exposed to 1-1000μg/ml MWCNTs for 24, 48 and 72h. The findings suggest that pristine MWCNTs induced more cell death than functionalized MWCNTs while functionalized MWCNTs are more genotoxic compared to their pristine form. The level of both dose and dispersion in the matrix used should be taken into consideration before applying further clinical applications of MWCNTs. Copyright © 2017 Elsevier Ltd. All rights reserved.

The impact of climate change on ecosystem carbon dynamics at the Scandinavian mountain birch forest-tundra heath ecotone.

PubMed

Sjögersten, Sofie; Wookey, Philip A

2009-02-01

Changes in temperature and moisture resulting from climate change are likely to strongly modify the ecosystem carbon sequestration capacity in high-latitude areas, both through vegetation shifts and via direct warming effects on photosynthesis and decomposition. This paper offers a synthesis of research addressing the potential impacts of climate warming on soil processes and carbon fluxes at the forest-tundra ecotone in Scandinavia. Our results demonstrated higher rates of organic matter decomposition in mountain birch forest than in tundra heath soils, with markedly shallower organic matter horizons in the forest. Field and laboratory experiments suggest that increased temperatures are likely to increase CO2 efflux from both tundra and forest soil providing moisture availability does not become limiting for the decomposition process. Furthermore, colonization of tundra heath by mountain birch forest would increase rates of decomposition, and thus CO2 emissions, from the tundra heath soils, which currently store substantial amounts of potentially labile carbon. Mesic soils underlying both forest and tundra heath are currently weak sinks of atmospheric methane, but the strength of this sink could be increased with climate warming and/or drying.

A Supercompressible, Elastic, and Bendable Carbon Aerogel with Ultrasensitive Detection Limits for Compression Strain, Pressure, and Bending Angle.

PubMed

Zhuo, Hao; Hu, Yijie; Tong, Xing; Chen, Zehong; Zhong, Linxin; Lai, Haihong; Liu, Linxiang; Jing, Shuangshuang; Liu, Qingzhong; Liu, Chuanfu; Peng, Xinwen; Sun, Runcang

2018-05-01

Ultralight and compressible carbon materials have promising applications in strain and pressure detection. However, it is still difficult to prepare carbon materials with supercompressibility, elasticity, stable strain-electrical signal response, and ultrasensitive detection limits, due to the challenge in structural regulation. Herein, a new strategy to prepare a reduced graphene oxide (rGO)-based lamellar carbon aerogels with unexpected and integrated performances by designing wave-shape rGO layers and enhancing the interaction among the rGO layers is demonstrated. Addition of cellulose nanocrystalline and low-molecular-weight carbon precursors enhances the interaction among rGO layers and thus produces an ultralight, flexible, and superstable structure. The as-prepared carbon aerogel displays a supercompressibility (undergoing an extreme strain of 99%) and elasticity (100% height retention after 10 000 cycles at a strain of 30%), as well as stable strain-current response (at least 10 000 cycles). Particularly, the carbon aerogel is ultrasensitive for detecting tiny change in strain (0.012%) and pressure (0.25 Pa), which are the lowest detection limits for compressible carbon materials reported in the literature. Moreover, the carbon aerogel exhibits excellent bendable performance and can detect an ultralow bending angle of 0.052°. Additionally, the carbon aerogel also demonstrates its promising application as wearable devices. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Standard Operating Procedure - Manufacture of Carbon Fibre Reinforced Plastic Waveguides and Slotted Waveguide Antennas, Version 1.0

DTIC Science & Technology

2011-06-01

aerospace grade carbon fibre reinforced plastic (CFRP) prepreg . RELEASE LIMITATION Approved for public release UNCLASSIFIED Report...arrays manufactured from aerospace grade carbon fibre reinforced plastic (CFRP) prepreg . 15. SUBJECT TERMS 16. SECURITY CLASSIFICATION OF: 17. LIMITATION...CFRP) prepreg tape and fabric. This report details Version 1.0 of a Standard Operating Procedure for this manufacture. UNCLASSIFIED

76 FR 56395 - Certain Welded Carbon Steel Pipe and Tube From Turkey: Notice of Extension of Time Limit for...

Federal Register 2010, 2011, 2012, 2013, 2014

2011-09-13

... Pipe and Tube From Turkey: Notice of Extension of Time Limit for Final Results of Antidumping Duty... antidumping order on certain welded carbon steel pipe and tube from Turkey for the period May 1, 2009, through April 30, 2010. See Certain Welded Carbon Steel Pipe and Tube From Turkey; Notice of Preliminary Results...

Modelling impacts of temperature, and acidifying and eutrophying deposition on DOC trends

NASA Astrophysics Data System (ADS)

Sawicka, Kasia; Rowe, Ed; Evans, Chris; Monteith, Don; Vanguelova, Elena; Wade, Andrew; Clark, Joanna

2017-04-01

Surface water dissolved organic carbon (DOC) concentrations in large parts of the northern hemisphere have risen over the past three decades, raising concern about enhanced contributions of carbon to the atmosphere and seas and oceans. The effect of declining acid deposition has been identified as a key control on DOC trends in soil and surface waters, since pH and ionic strength affect sorption and desorption of DOC. However, since DOC is derived mainly from recently-fixed carbon, and organic matter decomposition rates are considered sensitive to temperature, uncertainty persists regarding the extent to the relative importance of different drivers that affect these upward trends. We ran the dynamic model MADOC (Model of Acidity and Soil Organic Carbon) for a range of UK soils (podzols, gleysols and peatland), for which the time-series were available, to consider the likely relative importance of decreased deposition of sulphate and chloride, accumulation of reactive N, and higher temperatures, on DOC production in different soils. Modelled patterns of DOC change generally agreed favourably with measurements collated over 10-20 years, but differed markedly between sites. While the acidifying effect of sulphur deposition appeared to be the predominant control on the observed soil water DOC trends in all the soils considered other than a blanket peat, the model suggested that over the long term, the effects of nitrogen deposition on N-limited soils may have been sufficient to elevate the DOC recovery trajectory significantly. The second most influential cause of rising DOC in the model simulations was N deposition in ecosystems that are N-limited and respond with stimulated plant growth. Although non-marine chloride deposition made some contribution to acidification and recovery, it was not amongst the main drivers of DOC change. Warming had almost no effect on modelled historic DOC trends, but may prove to be a significant driver of DOC in future via its influence on nutrient availability and productivity. This suggests that current and future DOC concentrations could also exceed preindustrial levels due to the increased productivity of N enriched ecosystems, having important implications for drinking water catchment management and the setting and pursuit of appropriate restoration targets.

Low-Light Anoxygenic Photosynthesis and Fe-S-Biogeochemistry in a Microbial Mat

PubMed Central

Haas, Sebastian; de Beer, Dirk; Klatt, Judith M.; Fink, Artur; Rench, Rebecca McCauley; Hamilton, Trinity L.; Meyer, Volker; Kakuk, Brian; Macalady, Jennifer L.

2018-01-01

We report extremely low-light-adapted anoxygenic photosynthesis in a thick microbial mat in Magical Blue Hole, Abaco Island, The Bahamas. Sulfur cycling was reduced by iron oxides and organic carbon limitation. The mat grows below the halocline/oxycline at 30 m depth on the walls of the flooded sinkhole. In situ irradiance at the mat surface on a sunny December day was between 0.021 and 0.084 μmol photons m-2 s-1, and UV light (<400 nm) was the most abundant part of the spectrum followed by green wavelengths (475–530 nm). We measured a light-dependent carbon uptake rate of 14.5 nmol C cm-2 d-1. A 16S rRNA clone library of the green surface mat layer was dominated (74%) by a cluster (>97% sequence identity) of clones affiliated with Prosthecochloris, a genus within the green sulfur bacteria (GSB), which are obligate anoxygenic phototrophs. Typical photopigments of brown-colored GSB, bacteriochlorophyll e and (β-)isorenieratene, were abundant in mat samples and their absorption properties are well-adapted to harvest light in the available green and possibly even UV-A spectra. Sulfide from the water column (3–6 μmol L-1) was the main source of sulfide to the mat as sulfate reduction rates in the mats were very low (undetectable-99.2 nmol cm-3 d-1). The anoxic water column was oligotrophic and low in dissolved organic carbon (175–228 μmol L-1). High concentrations of pyrite (FeS2; 1–47 μmol cm-3) together with low microbial process rates (sulfate reduction, CO2 fixation) indicate that the mats function as net sulfide sinks mainly by abiotic processes. We suggest that abundant Fe(III) (4.3–22.2 μmol cm-3) is the major source of oxidizing power in the mat, and that abiotic Fe-S-reactions play the main role in pyrite formation. Limitation of sulfate reduction by low organic carbon availability along with the presence of abundant sulfide-scavenging iron oxides considerably slowed down sulfur cycling in these mats. PMID:29755448

Low-Light Anoxygenic Photosynthesis and Fe-S-Biogeochemistry in a Microbial Mat.

PubMed

Haas, Sebastian; de Beer, Dirk; Klatt, Judith M; Fink, Artur; Rench, Rebecca McCauley; Hamilton, Trinity L; Meyer, Volker; Kakuk, Brian; Macalady, Jennifer L

2018-01-01

We report extremely low-light-adapted anoxygenic photosynthesis in a thick microbial mat in Magical Blue Hole, Abaco Island, The Bahamas. Sulfur cycling was reduced by iron oxides and organic carbon limitation. The mat grows below the halocline/oxycline at 30 m depth on the walls of the flooded sinkhole. In situ irradiance at the mat surface on a sunny December day was between 0.021 and 0.084 μmol photons m -2 s -1 , and UV light (<400 nm) was the most abundant part of the spectrum followed by green wavelengths (475-530 nm). We measured a light-dependent carbon uptake rate of 14.5 nmol C cm -2 d -1 . A 16S rRNA clone library of the green surface mat layer was dominated (74%) by a cluster (>97% sequence identity) of clones affiliated with Prosthecochloris , a genus within the green sulfur bacteria (GSB), which are obligate anoxygenic phototrophs. Typical photopigments of brown-colored GSB, bacteriochlorophyll e and (β-)isorenieratene, were abundant in mat samples and their absorption properties are well-adapted to harvest light in the available green and possibly even UV-A spectra. Sulfide from the water column (3-6 μmol L -1 ) was the main source of sulfide to the mat as sulfate reduction rates in the mats were very low (undetectable-99.2 nmol cm -3 d -1 ). The anoxic water column was oligotrophic and low in dissolved organic carbon (175-228 μmol L -1 ). High concentrations of pyrite (FeS 2 ; 1-47 μmol cm -3 ) together with low microbial process rates (sulfate reduction, CO 2 fixation) indicate that the mats function as net sulfide sinks mainly by abiotic processes. We suggest that abundant Fe(III) (4.3-22.2 μmol cm -3 ) is the major source of oxidizing power in the mat, and that abiotic Fe-S-reactions play the main role in pyrite formation. Limitation of sulfate reduction by low organic carbon availability along with the presence of abundant sulfide-scavenging iron oxides considerably slowed down sulfur cycling in these mats.

Recapturing nutrients from dairy waste using biochar

NASA Astrophysics Data System (ADS)

Sarkhot, D.; Ghezzehei, T. A.; Berhe, A. A.

2009-12-01

Biochar or biomass derived black carbon is known to be highly resistant to decomposition with half-life periods ranging from hundreds of years to millennia. It is also reported to enhance soil productivity due to high nutrient retention and favorable effects on soil pH, water retention capacity as well as microbial population. Brazilian Terra Preta soils have shown the potential of biochar for long-term carbon sequestration capacity and productivity of soil and many researchers have now focused on utilizing this phenomenon to create fertile, carbon-rich soils, called Terra Preta Nova. Although the highly adsorptive nature of biochar is well characterized, the potential for using biochar in environmental cleanup efforts is relatively unexplored. Dairy waste is a source of significant water pollution because it introduces excess nutrients such as phosphates and nitrates into the soil and water system. Since many soils have limited capacity to retain nitrate and phosphate, especially for long periods of time, the utility of dairy waste manure to enhance soil fertility and nutrient availability to plants is limited. Here, we present results from a project that we started to determine the potential of biochar to recover the excess nutrients from dairy flushed manure. In this initial study, a commercially available biochar amendment was ground and used in a batch sorption experiment with the dairy flushed manure from a local dairy in Merced, California. Four manure dilutions viz. 10, 25, 50 and 100%, and three shaking times, viz. 1, 12 and 24 hours were used for this study. We then calculated the amount of ammonia, nitrate and phosphate adsorbed by the biochar using differences in nutrient concentrations before and after the sorption experiment. Biochar showed significant capacity of adsorbing these nutrients, suggesting a potential for controlling the dairy pollution. The resulting enriched biochar can potentially act as a slow release fertilizer and enhance soil productivity as well as increasing the long-term carbon sequestration potential of soils. We are currently initiating further research to determine the desorption potenial of the biochar sorbed nutrients in soil.

Synthesis and applications of carbon nanomaterials for energy generation and storage.

PubMed

Notarianni, Marco; Liu, Jinzhang; Vernon, Kristy; Motta, Nunzio

2016-01-01

The world is facing an energy crisis due to exponential population growth and limited availability of fossil fuels. Over the last 20 years, carbon, one of the most abundant materials found on earth, and its allotrope forms such as fullerenes, carbon nanotubes and graphene have been proposed as sources of energy generation and storage because of their extraordinary properties and ease of production. Various approaches for the synthesis and incorporation of carbon nanomaterials in organic photovoltaics and supercapacitors have been reviewed and discussed in this work, highlighting their benefits as compared to other materials commonly used in these devices. The use of fullerenes, carbon nanotubes and graphene in organic photovoltaics and supercapacitors is described in detail, explaining how their remarkable properties can enhance the efficiency of solar cells and energy storage in supercapacitors. Fullerenes, carbon nanotubes and graphene have all been included in solar cells with interesting results, although a number of problems are still to be overcome in order to achieve high efficiency and stability. However, the flexibility and the low cost of these materials provide the opportunity for many applications such as wearable and disposable electronics or mobile charging. The application of carbon nanotubes and graphene to supercapacitors is also discussed and reviewed in this work. Carbon nanotubes, in combination with graphene, can create a more porous film with extraordinary capacitive performance, paving the way to many practical applications from mobile phones to electric cars. In conclusion, we show that carbon nanomaterials, developed by inexpensive synthesis and process methods such as printing and roll-to-roll techniques, are ideal for the development of flexible devices for energy generation and storage - the key to the portable electronics of the future.

A Global Assessment of Rain-Dissolved Organic Carbon

NASA Astrophysics Data System (ADS)

Safieddine, S.; Heald, C. L.

2017-12-01

Precipitation is the largest physical removal pathway of atmospheric organic carbon from the atmosphere. The removed carbon is transferred to the land and ocean in the form of dissolved organic carbon (DOC). Limited measurements have hindered efforts to characterize global DOC. In this poster presentation, we show the first simulated global DOC distribution based on a GEOS-Chem model simulation of the atmospheric reactive carbon budget. Over the ocean, simulated DOC concentrations are between 0.1 to 1 mgCL-1 with a total of 85 TgCyr-1 deposited. DOC concentrations are higher inland, ranging between 1 and 10 mgCL-1, producing a total of 188 TgCyr-1 terrestrial organic wet deposition. We compare the 2010 simulated DOC to a 30-year synthesis of available DOC measurements over different environments. Despite imperfect matching of observational and simulated time intervals, the model is able to reproduce much of the spatial variability of DOC (r= 0.63), with a low bias of 35%. We compare the global average carbon oxidation state (OSc) of both atmospheric and dissolved organic carbon, as a simple metric for describing the chemical composition of organics. In the global atmosphere reactive organic carbon (ROC) is dominated by hydrocarbons and ketones, and OSc, ranges from -1.8 to -0.6. In the dissolved form, formaldehyde, formic acid, primary and secondary semi-volatiles organic aerosol dominate the DOC concentrations. The increase in solubility upon oxidation leads to a global increase in OSc in rainwater with -0.6<=OSc <=0. This simulation provides new insight into the current model representation of the flow of atmospheric and rain-dissolved organic carbon, and new opportunities to use observations and simulations to understand the DOC reaching land and ocean.

Synthesis and applications of carbon nanomaterials for energy generation and storage

PubMed Central

Notarianni, Marco; Liu, Jinzhang; Vernon, Kristy

2016-01-01

Summary The world is facing an energy crisis due to exponential population growth and limited availability of fossil fuels. Over the last 20 years, carbon, one of the most abundant materials found on earth, and its allotrope forms such as fullerenes, carbon nanotubes and graphene have been proposed as sources of energy generation and storage because of their extraordinary properties and ease of production. Various approaches for the synthesis and incorporation of carbon nanomaterials in organic photovoltaics and supercapacitors have been reviewed and discussed in this work, highlighting their benefits as compared to other materials commonly used in these devices. The use of fullerenes, carbon nanotubes and graphene in organic photovoltaics and supercapacitors is described in detail, explaining how their remarkable properties can enhance the efficiency of solar cells and energy storage in supercapacitors. Fullerenes, carbon nanotubes and graphene have all been included in solar cells with interesting results, although a number of problems are still to be overcome in order to achieve high efficiency and stability. However, the flexibility and the low cost of these materials provide the opportunity for many applications such as wearable and disposable electronics or mobile charging. The application of carbon nanotubes and graphene to supercapacitors is also discussed and reviewed in this work. Carbon nanotubes, in combination with graphene, can create a more porous film with extraordinary capacitive performance, paving the way to many practical applications from mobile phones to electric cars. In conclusion, we show that carbon nanomaterials, developed by inexpensive synthesis and process methods such as printing and roll-to-roll techniques, are ideal for the development of flexible devices for energy generation and storage – the key to the portable electronics of the future. PMID:26925363

The potential of land management to decrease global warming from climate change

NASA Astrophysics Data System (ADS)

Mayer, A.; Hausfather, Z.; Jones, A. D.; Silver, W. L.

2016-12-01

Recent evidence suggests that negative emissions (i.e. sequestration) is critical to slow climate change (IPCC, 2013; Gasser et al, 2015). Agricultural (crop and grazing) lands have the potential to act as a significant carbon sink. These ecosystems cover a significant proportion of the global land surface, and are largely degraded with regard to soil carbon due to previous management practices (Bai et al, 2008). However, few studies have examined the required scale of land management interventions that would be required to make a significant contribution to a portfolio of efforts aimed at limiting anthropogenic influences on global mean temperature. To address this, we modelled the quantitative effect of a range of soil carbon sequestration rates on global temperature to 2100. Results showed that by assuming a baseline emissions scenario outlined in RCP 2.6, the sequestration of an additional 0.7 Pg C per year through improved agricultural land management practices would produce a reduction of 0.1 degrees C from predicted global temperatures by the year 2100. We also compiled previous estimates of global carbon sequestration potential of agricultural soils to compare with our theoretical prediction to determine whether carbon sequestration through existing land management practices has potential to significantly reduce global temperatures. Assuming long-term soil carbon uptake, the combined potential of agricultural land management-based mitigation approaches exceeded 0.25 degrees C warming reduction by the year 2100. However, results were highly sensitive to potential carbon saturation, defined as the maximum threshold for carbon storage in soil. Our results suggest that current land management technologies and available land area exist and could make a measureable impact on warming reduction. Results also highlighted potential carbon saturation as a key gap in knowledge.

Carbon-Starvation Induces Cross-Resistance to Thermal, Acid, and Oxidative Stress in Serratia marcescens

PubMed Central

Pittman, Joseph R.; Kline, La’Kesha C.; Kenyon, William J.

2015-01-01

The broad host-range pathogen Serratia marcescens survives in diverse host and non-host environments, often enduring conditions in which the concentration of essential nutrients is growth-limiting. In such environments, carbon and energy source starvation (carbon-starvation) is one of the most common forms of stress encountered by S. marcescens. Related members of the family Enterobacteriaceae are known to undergo substantial changes in gene expression and physiology in response to the specific stress of carbon-starvation, enabling non-spore-forming cells to survive periods of prolonged starvation and exposure to other forms of stress (i.e., starvation-induced cross-resistance). To determine if carbon-starvation also results in elevated levels of cross-resistance in S. marcescens, both log-phase and carbon-starved cultures, depleted of glucose before the onset of high cell-density stationary-phase, were grown in minimal media at either 30 °C or 37 °C and were then challenged for resistance to high temperature (50 °C), low pH (pH 2.8), and oxidative stress (15 mM H2O2). In general, carbon-starved cells exhibited a higher level of resistance to thermal stress, acid stress, and oxidative stress compared to log-phase cells. The extent of carbon-starvation-induced cross-resistance was dependent on incubation temperature and on the particular strain of S. marcescens. In addition, strain- and temperature-dependent variations in long-term starvation survival were also observed. The enhanced stress-resistance of starved S. marcescens cells could be an important factor in their survival and persistence in many non-host environments and within certain host microenvironments where the availability of carbon sources is suboptimal for growth. PMID:27682115

A three-dimensional microelectrode array composed of vertically aligned ultra-dense carbon nanotube networks

NASA Astrophysics Data System (ADS)

Nick, C.; Yadav, S.; Joshi, R.; Schneider, J. J.; Thielemann, C.

2015-07-01

Electrodes based on carbon nanotubes are a promising approach to manufacture highly sensitive sensors with a low limit of signal detection and a high signal-to-noise ratio. This is achieved by dramatically increasing the electrochemical active surface area without increasing the overall geometrical dimensions. Typically, carbon nanotube electrodes are nearly planar and composed of randomly distributed carbon nanotube networks having a limited surface gain for a specific geometrical surface area. To overcome this limitation, we have introduced vertically aligned carbon nanotube (VACNT) networks as electrodes, which are arranged in a microelectrode pattern of 60 single electrodes. Each microelectrode features a very high aspect ratio of more than 300 and thus a dramatically increased surface area. These microelectrodes composed of VACNT networks display dramatically decreased impedance over the entire frequency range compared to planar microelectrodes caused by the enormous capacity increase. This is experimentally verified by electrochemical impedance spectroscopy and cyclic voltammetry.

Possibilities and limitations of advanced transmission electron microscopy for carbon-based nanomaterials

PubMed Central

Bittencourt, Carla; Van Tendeloo, Gustaaf

2015-01-01

Summary A major revolution for electron microscopy in the past decade is the introduction of aberration correction, which enables one to increase both the spatial resolution and the energy resolution to the optical limit. Aberration correction has contributed significantly to the imaging at low operating voltages. This is crucial for carbon-based nanomaterials which are sensitive to electron irradiation. The research of carbon nanomaterials and nanohybrids, in particular the fundamental understanding of defects and interfaces, can now be carried out in unprecedented detail by aberration-corrected transmission electron microscopy (AC-TEM). This review discusses new possibilities and limits of AC-TEM at low voltage, including the structural imaging at atomic resolution, in three dimensions and spectroscopic investigation of chemistry and bonding. In situ TEM of carbon-based nanomaterials is discussed and illustrated through recent reports with particular emphasis on the underlying physics of interactions between electrons and carbon atoms. PMID:26425406

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pezeshki, Alan M.; Sacci, Robert L.; Delnick, Frank M.

Here, an improved method for quantitative measurement of the charge transfer, finite diffusion, and ohmic overpotentials in redox flow batteries using electrochemical impedance spectroscopy is presented. The use of a pulse dampener in the hydraulic circuit enables the collection of impedance spectra at low frequencies with a peristaltic pump, allowing the measurement of finite diffusion resistances at operationally relevant flow rates. This method is used to resolve the rate-limiting processes for the V 2+/V 3+ redox couple on carbon felt and carbon paper electrodes in the vanadium redox flow battery. Carbon felt was limited by both charge transfer and ohmicmore » resistance, while carbon paper was limited by charge transfer, finite diffusion, and ohmic resistances. The influences of vanadium concentration and flow field design also are quantified.« less

Remediation of Contaminated Soils By Supercritical Carbon Dioxide Extraction

NASA Astrophysics Data System (ADS)

Ferri, A.; Zanetti, M. C.; Banchero, M.; Fiore, S.; Manna, L.

The contaminants that can be found in soils are many, inorganic, like heavy metals, as well as organic. Among the organic contaminants, oil and coal refineries are responsi- ble for several cases of soil contamination with PAHs (Polycyclic Aromatic Hydrocar- bons). Polynuclear aromatic hydrocarbons (PAHs) have toxic, carcinogenic and mu- tagenic effects. Limits have been set on the concentration of most contaminants, and growing concern is focusing on soil contamination issues. USA regulations set the maximum acceptable level of contamination by PAHs equal to 40 ppm at residential sites and 270 ppm at industrial sites. Stricter values are usually adopted in European Countries. Supercritical carbon dioxide extraction is a possible alternative technology to remove volatile organic compounds from contaminated soils. Supercritical fluid extraction (SFE) offers many advantages over conventional solvent extraction. Super- critical fluids combine gaseous properties as a high diffusion coefficient, and liquid properties as a high solvent power. The solvent power is strongly pressure-dependent near supercritical conditions: selective extractions are possible without changing the solvent. Solute can be separate from the solvent depressurising the system; therefore, it is possible to recycle the solvent and recover the contaminant. Carbon dioxide is frequently used as supercritical fluid, because it has moderate critical conditions, it is inert and available in pure form. In this work, supercritical fluid extraction technology has been used to remove a polynuclear aromatic hydrocarbon from contaminated soils. The contaminant choice for the experiment has been naphthalene since several data are available in literature. G. A. Montero et al. [1] studied soil remediation with supercrit- ical carbon dioxide extraction technology; these Authors have found that there was a mass-transfer limitation. In the extraction vessel, the mass transfer coefficient in- creases with the superficial velocity of the supercritical carbon dioxide; therefore, the mass transfer resistance can be reduced increasing such velocity. In this work, higher values of superficial velocity were investigated. The experimental apparatus includes a pump, an extraction vessel, an adjustable restrictor and a trap to collect the extracted substance. Liquid carbon dioxide coming from a cylinder with a dip-tube is cooled by a cryostatic bath and then it is compressed by a pneumatic drive pump (the max- imum available pressure is 69 MPa). Subsequently, the pressurised current flows into 1 a heating coil and then into the extraction vessel, which is contained in a stove; the outlet flow is depressurised in an adjustable restrictor and the extracted substance is collected in a trap by dissolution into a solvent. The extracted naphthalene quantity was obtained by weighting the solvent and measuring the naphthalene concentration with a gas chromatograph. The soil sample is a sandy soil geologically representative of the North of Italy that was sampled and physically and chemically characterized: particle-size distribution analysis, diffractometric analysis, Cation Exchange Capac- ity, Total Organic Carbon, iron content and manganese content in order to evaluate the potential sorption degree. The soil was artificially polluted by means of a naphta- lene and methylene chloride solution. The experimental work consists in a number of naphthalene extractions from the spiked soil, that were carried out at different operat- ing conditions, temperature, pressure and flow rate by means of supercritical carbon dioxide evaluating the corresponding recovery efficiencies. The results obtained were analysed and compared in order to determine which parameters influence the system. [1] G. A. Montero, T.D. Giorgio, and K. B. Schnelle, Jr..Removal of Hazardous ,1994, Contaminants form Soils by Supercritical Fluid Extraction. Innovations in Supercriti- cal Fluids. ACS Symposium Series, 608, 280-197. 2

Environmental aspects of health care in the Grampian NHS region and the place of telehealth

PubMed Central

Wootton, Richard; Tait, Alex; Croft, Amanda

2010-01-01

Detailed information about the composition of the carbon footprint of the NHS in the Grampian health region, and in Scotland generally, is not available at present. Based on the limited information available, our best guess is that travel emissions in Grampian are substantial, perhaps 49,000 tonnes CO2 per year. This is equivalent to 233 million km of car travel per year. A well-established telemedicine network in the Grampian region, which saves over 2000 patient journeys a year from community hospitals, avoids about 260,000 km travel per year, or about 59 tonnes CO2 per year. Therefore using telehealth as it has been used historically (primarily to facilitate hospital-to-hospital interactions) seems unlikely to have a major environmental impact – although of course there may be other good reasons for persevering with conventional telehealth. On the other hand, telehealth might be useful in reducing staff travel and to a lesser extent, visitor travel. It looks particularly promising for reducing outpatient travel, where substantial carbon savings might be made by reconfiguring the way that certain services are provided. PMID:20511579

Plant traits and trait-based vegetation modeling in the Arctic

NASA Astrophysics Data System (ADS)

Xu, C.; Sevanto, S.; Iversen, C. M.; Salmon, V. G.; Rogers, A.; Wullschleger, S.; Wilson, C. J.

2017-12-01

Arctic tundra environments are characterized by extremely cold temperatures, strong winds, short growing season and thin, nutrient-poor soil layer impacted by permafrost. To survive in this environment vascular plants have developed traits that simultaneously promote high productivity under favorable environments, and survival in harsh conditions. To improve representation of Arctic tundra vegetation in Earth System Models we surveyed plant trait data bases for key trait parameters that influence modeled ecosystem carbon balance, and compared the traits within plant families occurring in the boreal, temperate and arctic zones. The parameters include photosynthetic carbon uptake efficiency (Vcmax and Jmax), root:shoot ratio, and root and leaf nitrogen content, and we focused on woody shrubs. Our results suggest that root nitrogen content in non-nitrogen fixing tundra shrubs is lower than in representatives of the same families in the boreal or temperate zone. High tissue nitrogen concentrations have been related to high vulnerability to drought. The low root nitrogen concentrations in tundra shrubs may thus be an indication of acclimation to shallow soils, and frequent freezing that has a similar impact on the plant conductive tissue as drought. With current nitrogen availability, nitrogen limitation reduces the benefits of increased temperatures and longer growing seasons to the tundra ecosystem carbon balance. Thawing of permafrost will increase nitrogen availability, and promote plant growth and carbon uptake, but it could also make the shrubs more vulnerable to freeze-thaw cycles, with the overall result of reduced shrub coverage. The final outcome of warming temperatures and thawing of permafrost on tundra shrubs will thus depend on the relative speed of warming and plant acclimation.

Climate-driven trends in contemporary ocean productivity.

PubMed

Behrenfeld, Michael J; O'Malley, Robert T; Siegel, David A; McClain, Charles R; Sarmiento, Jorge L; Feldman, Gene C; Milligan, Allen J; Falkowski, Paul G; Letelier, Ricardo M; Boss, Emmanuel S

2006-12-07

Contributing roughly half of the biosphere's net primary production (NPP), photosynthesis by oceanic phytoplankton is a vital link in the cycling of carbon between living and inorganic stocks. Each day, more than a hundred million tons of carbon in the form of CO2 are fixed into organic material by these ubiquitous, microscopic plants of the upper ocean, and each day a similar amount of organic carbon is transferred into marine ecosystems by sinking and grazing. The distribution of phytoplankton biomass and NPP is defined by the availability of light and nutrients (nitrogen, phosphate, iron). These growth-limiting factors are in turn regulated by physical processes of ocean circulation, mixed-layer dynamics, upwelling, atmospheric dust deposition, and the solar cycle. Satellite measurements of ocean colour provide a means of quantifying ocean productivity on a global scale and linking its variability to environmental factors. Here we describe global ocean NPP changes detected from space over the past decade. The period is dominated by an initial increase in NPP of 1,930 teragrams of carbon a year (Tg C yr(-1)), followed by a prolonged decrease averaging 190 Tg C yr(-1). These trends are driven by changes occurring in the expansive stratified low-latitude oceans and are tightly coupled to coincident climate variability. This link between the physical environment and ocean biology functions through changes in upper-ocean temperature and stratification, which influence the availability of nutrients for phytoplankton growth. The observed reductions in ocean productivity during the recent post-1999 warming period provide insight on how future climate change can alter marine food webs.

Distinct Microbial Limitations in Litter and Underlying Soil Revealed by Carbon and Nutrient Fertilization in a Tropical Rainforest

PubMed Central

Fanin, Nicolas; Barantal, Sandra; Fromin, Nathalie; Schimann, Heidy; Schevin, Patrick; Hättenschwiler, Stephan

2012-01-01

Human-caused alterations of the carbon and nutrient cycles are expected to impact tropical ecosystems in the near future. Here we evaluated how a combined change in carbon (C), nitrogen (N) and phosphorus (P) availability affects soil and litter microbial respiration and litter decomposition in an undisturbed Amazonian rainforest in French Guiana. In a fully factorial C (as cellulose), N (as urea), and P (as phosphate) fertilization experiment we analyzed a total of 540 litterbag-soil pairs after a 158-day exposure in the field. Rates of substrate-induced respiration (SIR) measured in litter and litter mass loss were similarly affected by fertilization showing the strongest stimulation when N and P were added simultaneously. The stimulating NP effect on litter SIR increased considerably with increasing initial dissolved organic carbon (DOC) concentrations in litter, suggesting that the combined availability of N, P, and a labile C source has a particularly strong effect on microbial activity. Cellulose fertilization, however, did not further stimulate the NP effect. In contrast to litter SIR and litter mass loss, soil SIR was reduced with N fertilization and showed only a positive effect in response to P fertilization that was further enhanced with additional C fertilization. Our data suggest that increased nutrient enrichment in the studied Amazonian rainforest can considerably change microbial activity and litter decomposition, and that these effects differ between the litter layer and the underlying soil. Any resulting change in relative C and nutrient fluxes between the litter layer and the soil can have important consequences for biogeochemical cycles in tropical forest ecosystems. PMID:23272052

SoilGrids1km — Global Soil Information Based on Automated Mapping

PubMed Central

Hengl, Tomislav; de Jesus, Jorge Mendes; MacMillan, Robert A.; Batjes, Niels H.; Heuvelink, Gerard B. M.; Ribeiro, Eloi; Samuel-Rosa, Alessandro; Kempen, Bas; Leenaars, Johan G. B.; Walsh, Markus G.; Gonzalez, Maria Ruiperez

2014-01-01

Background Soils are widely recognized as a non-renewable natural resource and as biophysical carbon sinks. As such, there is a growing requirement for global soil information. Although several global soil information systems already exist, these tend to suffer from inconsistencies and limited spatial detail. Methodology/Principal Findings We present SoilGrids1km — a global 3D soil information system at 1 km resolution — containing spatial predictions for a selection of soil properties (at six standard depths): soil organic carbon (g kg−1), soil pH, sand, silt and clay fractions (%), bulk density (kg m−3), cation-exchange capacity (cmol+/kg), coarse fragments (%), soil organic carbon stock (t ha−1), depth to bedrock (cm), World Reference Base soil groups, and USDA Soil Taxonomy suborders. Our predictions are based on global spatial prediction models which we fitted, per soil variable, using a compilation of major international soil profile databases (ca. 110,000 soil profiles), and a selection of ca. 75 global environmental covariates representing soil forming factors. Results of regression modeling indicate that the most useful covariates for modeling soils at the global scale are climatic and biomass indices (based on MODIS images), lithology, and taxonomic mapping units derived from conventional soil survey (Harmonized World Soil Database). Prediction accuracies assessed using 5–fold cross-validation were between 23–51%. Conclusions/Significance SoilGrids1km provide an initial set of examples of soil spatial data for input into global models at a resolution and consistency not previously available. Some of the main limitations of the current version of SoilGrids1km are: (1) weak relationships between soil properties/classes and explanatory variables due to scale mismatches, (2) difficulty to obtain covariates that capture soil forming factors, (3) low sampling density and spatial clustering of soil profile locations. However, as the SoilGrids system is highly automated and flexible, increasingly accurate predictions can be generated as new input data become available. SoilGrids1km are available for download via http://soilgrids.org under a Creative Commons Non Commercial license. PMID:25171179

Soil and vegetation parameter uncertainty on future terrestrial carbon sinks

NASA Astrophysics Data System (ADS)

Kothavala, Z.; Felzer, B. S.

2013-12-01

We examine the role of the terrestrial carbon cycle in a changing climate at the centennial scale using an intermediate complexity Earth system climate model that includes the effects of dynamic vegetation and the global carbon cycle. We present a series of ensemble simulations to evaluate the sensitivity of simulated terrestrial carbon sinks to three key model parameters: (a) The temperature dependence of soil carbon decomposition, (b) the upper temperature limits on the rate of photosynthesis, and (c) the nitrogen limitation of the maximum rate of carboxylation of Rubisco. We integrated the model in fully coupled mode for a 1200-year spin-up period, followed by a 300-year transient simulation starting at year 1800. Ensemble simulations were conducted varying each parameter individually and in combination with other variables. The results of the transient simulations show that terrestrial carbon uptake is very sensitive to the choice of model parameters. Changes in net primary productivity were most sensitive to the upper temperature limit on the rate of photosynthesis, which also had a dominant effect on overall land carbon trends; this is consistent with previous research that has shown the importance of climatic suppression of photosynthesis as a driver of carbon-climate feedbacks. Soil carbon generally decreased with increasing temperature, though the magnitude of this trend depends on both the net primary productivity changes and the temperature dependence of soil carbon decomposition. Vegetation carbon increased in some simulations, but this was not consistent across all configurations of model parameters. Comparing to global carbon budget observations, we identify the subset of model parameters which are consistent with observed carbon sinks; this serves to narrow considerably the future model projections of terrestrial carbon sink changes in comparison with the full model ensemble.

Nonlinear Interactions between Climate and Atmospheric Carbon Dioxide Drivers of Terrestrial and Marine Carbon Cycle Changes

NASA Astrophysics Data System (ADS)

Hoffman, F. M.; Randerson, J. T.; Moore, J. K.; Goulden, M.; Fu, W.; Koven, C.; Swann, A. L. S.; Mahowald, N. M.; Lindsay, K. T.; Munoz, E.

2017-12-01

Quantifying interactions between global biogeochemical cycles and the Earth system is important for predicting future atmospheric composition and informing energy policy. We applied a feedback analysis framework to three sets of Historical (1850-2005), Representative Concentration Pathway 8.5 (2006-2100), and its extension (2101-2300) simulations from the Community Earth System Model version 1.0 (CESM1(BGC)) to quantify drivers of terrestrial and ocean responses of carbon uptake. In the biogeochemically coupled simulation (BGC), the effects of CO2 fertilization and nitrogen deposition influenced marine and terrestrial carbon cycling. In the radiatively coupled simulation (RAD), the effects of rising temperature and circulation changes due to radiative forcing from CO2, other greenhouse gases, and aerosols were the sole drivers of carbon cycle changes. In the third, fully coupled simulation (FC), both the biogeochemical and radiative coupling effects acted simultaneously. We found that climate-carbon sensitivities derived from RAD simulations produced a net ocean carbon storage climate sensitivity that was weaker and a net land carbon storage climate sensitivity that was stronger than those diagnosed from the FC and BGC simulations. For the ocean, this nonlinearity was associated with warming-induced weakening of ocean circulation and mixing that limited exchange of dissolved inorganic carbon between surface and deeper water masses. For the land, this nonlinearity was associated with strong gains in gross primary production in the FC simulation, driven by enhancements in the hydrological cycle and increased nutrient availability. We developed and applied a nonlinearity metric to rank model responses and driver variables. The climate-carbon cycle feedback gain at 2300 was 42% higher when estimated from climate-carbon sensitivities derived from the difference between FC and BGC than when derived from RAD. We re-analyzed other CMIP5 model results to quantify the effects of such nonlinearities on their projected climate-carbon cycle feedback gains.

Are Salps A Silver Bullet Against Global Warming And Ocean Acidification?

NASA Astrophysics Data System (ADS)

Kithil, P. W.

2006-12-01

Oceanic uptake of 25 billion tons CO2 annually introduced into the atmosphere from carbon fuels must be mitigated to prevent further widespread changes in ocean biochemistry and potentially severe anthropogenic climate change. Larry Madin of Woods Hole Oceanographic Institute and his colleagues have measured the carbon sequestration in the excretia produced by dense swarms of Salps of up to 4,000 tons per day over a 100,000 km2 ocean region, equivalent to over 14 thousand tons of CO2 per day. This poses several questions: 1. Given the ocean surface of 372 million km2, does the Madin report imply a potential removal of 20 billion tons of CO2 per year 80% of emissions? 2. What might be the natural limitations on widespread propagation of Salps, and how would these effect the carbon sequestration actually achieved? 3. What mechanism could encourage the propagation of Salps throughout the oceans? Since Salps feast on phytoplankton which require sunlight and sufficient nutrients, we must first reduce the available ocean by perhaps 60% as a seasonal limit on phytoplankton growth and allow 60% further limit for poor nutrient availability and assuming some ocean regions are an unfavorable environment for Salps. Combined, the net ocean area over which Salps could sequester carbon is thus 36%, or 134 million km2. Assuming Madin's values for carbon sequestration are achievable over this ocean region, about 7.2 billion tons of CO2 could be sequestered annually, equal to 29% of mankind's current fossil-fuel CO2 output. This converts to a carbon equivalent of 1.96 billion tons per year. The mechanism we propose to encourage widespread propagation of Salps is forced upwelling using Atmocean's arrays of wave-driven deep ocean pumps to bring up large volumes of cold, nutrient-rich deep ocean to enhance the ocean's primary production, absorbing CO2 and producing oxygen. The pump simply comprises a buoy, flexible tube, cylinder with valve, cable to connect the buoy and cylinder, and solar panel to power communications & provide remote control. Adjacent pumps are connected at the bottom to maintain relative position. If required, periodic seafloor anchoring can maintain absolute position within an ocean basin. Deployment is low cost as the pumps self-deploy when dropped into the ocean from barges. Pumps would not be deployed in ocean shipping channels, regions used by recreational boaters, nor where excessive tides or currents exist. In a global application, 1,340 arrays each 100,000 km2 are needed to cover the 134 million km2 calculated above. Assuming one pump per square km costing 2,000, an investment of 268 billion is needed. Using a five year payback, this investment is recouped if the carbon credit price is 26.80 per ton applied to sequestering 1.96 billion tons per year of carbon. This is not dramatically different from today's carbon credit price of about 15 per ton. Assuming a governmental mandate of carbon sequestration, today's price could easily increase many-fold, making ocean sequestration using forced upwelling economically attractive. Additional benefits of widespread forced upwelling include: 1 Buffering of ocean pH by removing CO2 during photosynthesis; 2 Possible cooling the upper mixed layer upstream from coral reefs to reduce bleaching from ocean hotspots; 3 Possible mitigation of rapid climate change by enhancing the mixing of arctic/Greenland meltwater; 4 Enhancement of wild fish populations; and, 5 Reduced hurricane intensity, achieved by cooling the upper mixed layer upon approach of a tropical storm in high risk regions such as the Gulf of Mexico.

Global comparison reveals biogenic weathering as driven by nutrient limitation at ecosystem scale

NASA Astrophysics Data System (ADS)

Boy, Jens; Godoy, Roberto; Dechene, Annika; Shibistova, Olga; Amir, Hamid; Iskandar, Issi; Fogliano, Bruno; Boy, Diana; McCulloch, Robert; Andrino, Alberto; Gschwendtner, Silvia; Marin, Cesar; Sauheitl, Leopold; Dultz, Stefan; Mikutta, Robert; Guggenberger, Georg

2017-04-01

A substantial contribution of biogenic weathering in ecosystem nutrition, especially by symbiotic microorganisms, has often been proposed, but large-scale in vivo studies are still missing. Here we compare a set of ecosystems spanning from the Antarctic to tropical forests for their potential biogenic weathering and its drivers. To address biogenic weathering rates, we installed mineral mesocosms only accessible for bacteria and fungi for up to 4 years, which contained freshly broken and defined nutrient-baring minerals in soil A horizons of ecosystems along a gradient of soil development differing in climate and plant species communities. Alterations of the buried minerals were analyzed by grid-intersection, confocal lascer scanning microscopy, energy-dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy on the surface and on thin sections. On selected sites, carbon fluxes were tracked by 13C labeling, and microbial community was identified by DNA sequencing. In young ecosystems (protosoils) biogenic weathering is almost absent and starts after first carbon accumulation by aeolian (later litter) inputs and is mainly performed by bacteria. With ongoing soil development and appearance of symbiotic (mycorrhized) plants, nutrient availability in soil increasingly drove biogenic weathering, and fungi became the far more important players than bacteria. We found a close relation between fungal biogenic weathering and available potassium across all 16 forested sites in the study, regardless of the dominant mycorrhiza type (AM or EM), climate, and plant-species composition. We conclude that nutrient limitations at ecosystem scale are generally counteracted by adapted fungal biogenic weathering. The close relation between fungal weathering and plant-available nutrients over a large range of severely contrasting ecosystems points towards a direct energetic support of these weathering processes by the photoautotrophic community, making biogenic weathering a directional on-demand process common in all types of ecosystems.

Transcriptome Analysis of Polyhydroxybutyrate Cycle Mutants Reveals Discrete Loci Connecting Nitrogen Utilization and Carbon Storage in Sinorhizobium meliloti

PubMed Central

Nordeste, Ricardo

2017-01-01

ABSTRACT Polyhydroxybutyrate (PHB) and glycogen polymers are produced by bacteria as carbon storage compounds under unbalanced growth conditions. To gain insights into the transcriptional mechanisms controlling carbon storage in Sinorhizobium meliloti, we investigated the global transcriptomic response to the genetic disruption of key genes in PHB synthesis and degradation and in glycogen synthesis. Under both nitrogen-limited and balanced growth conditions, transcriptomic analysis was performed with genetic mutants deficient in PHB synthesis (phbA, phbB, phbAB, and phbC), PHB degradation (bdhA, phaZ, and acsA2), and glycogen synthesis (glgA1). Three distinct genomic regions of the pSymA megaplasmid exhibited altered expression in the wild type and the PHB cycle mutants that was not seen in the glycogen synthesis mutant. An Fnr family transcriptional motif was identified in the upstream regions of a cluster of genes showing similar transcriptional patterns across the mutants. This motif was found at the highest density in the genomic regions with the strongest transcriptional effect, and the presence of this motif upstream of genes in these regions was significantly correlated with decreased transcript abundance. Analysis of the genes in the pSymA regions revealed that they contain a genomic overrepresentation of Fnr family transcription factor-encoding genes. We hypothesize that these loci, containing mostly nitrogen utilization, denitrification, and nitrogen fixation genes, are regulated in response to the intracellular carbon/nitrogen balance. These results indicate a transcriptional regulatory association between intracellular carbon levels (mediated through the functionality of the PHB cycle) and the expression of nitrogen metabolism genes. IMPORTANCE The ability of bacteria to store carbon and energy as intracellular polymers uncouples cell growth and replication from nutrient uptake and provides flexibility in the use of resources as they are available to the cell. The impact of carbon storage on cellular metabolism would be reflected in global transcription patterns. By investigating the transcriptomic effects of genetically disrupting genes involved in the PHB carbon storage cycle, we revealed a relationship between intracellular carbon storage and nitrogen metabolism. This work demonstrates the utility of combining transcriptome sequencing with metabolic pathway mutations for identifying underlying gene regulatory mechanisms. Author Video: An author video summary of this article is available. PMID:28905000

Assessing the resources and mitigation potential of European forests

NASA Astrophysics Data System (ADS)

Hasenauer, Hubert; Neumann, Mathias; Moreno, Adam; Running, Steve

2017-04-01

Today 40 % of the European land area is covered with forests managed for the provision of ecosystem services including timber production. Forests store large amounts of carbon and are the main resource for the growing demand of a bio-based economy. They are also a major source for biodiversity. Thus a consistent pan-European gridded data set on the state of forest resources is essential for researchers, policy makers and conservationists to study and understand the European forests for the global carbon cycle independent of political boundaries. The purpose of this study is to use existing European data to develop a consistent pan-European data set for Net Primary Production (NPP), live tree carbon per hectare, volume per hectare, mean tree height and mean tree age by integrating remotely sensed satellite data and harmonized NFI data from 13 different European countries. We provide new NPP estimates using the MOD17 algorithm by collating a newly down-scaled daily climate dataset across Europe. By consolidating these two independent productivity data sources (top down satellite versus bottom up terrestrial forest NFI data) for assessing forest resources in Europe, we are able to detect and quantify forest management impacts. We produce a pan-European map for each of the five key variables on a 0.133° grid representing the time period 2000-2010. The results show distinct differences in the carbon storage of European forests due to biophysical limits and regional historic drivers in forest management, which directly affect the carbon mitigation option of European forests. We use this data to assess the state of forest resources across Europe showing that mountainous regions have the highest carbon and volume per hectare values, central Europe has the tallest mean tree heights and Austria and Northern Scandinavia have the oldest mean tree ages. Cross-validation of the data indicates that the error varies by forest characteristic but shows negligible biases for all. We also use this data to examine climate limitations on potential forest structure, relevant for assessing potential timber assortments or suitability as wildlife habitat. The results suggest: (i) Boreal forests are limited by minimum temperature, the Mediterranean forests by maximum temperature and temperate forests by both temperature and precipitation. As a result of changing climate during the last 50 years, the potential average diameter at breast height, which can be achieved in Europe, has decreased by 5.0 %. A similar result is evident for the potential basal area per hectare with a decrease of 6.5 %. (ii) European forests exhibit an annual average carbon uptake of 577 gC/m2/year, which can be considered as the carbon sequestration potential and/or available resource for the increasing demand of a growing bio-economy.

Seeking Ways to Break Energy Storage Limits

DTIC Science & Technology

2016-05-02

system sizes that we simulated. 15. SUBJECT TERMS density functional theory, guest-host structures, carbon nanotubes , free atom limit, geometry...unlimited. iii Contents List of Figures iv 1. Introduction 1 2. Xenon-Buckminsterfullerene (Xe-C60) 3 3. Xe-C980 4 4. Xe-Carbon Nanotube (CNT) 4 5...calculations. 4. Xe-Carbon Nanotube (CNT) Because of our inability to attain guest-host complexes that would achieve energies in excess of the

40 CFR Table 3 to Subpart Kkkk of... - Emission Limits for Affected Sources Using the Control Efficiency/Outlet Concentration Compliance...

Code of Federal Regulations, 2011 CFR

2011-07-01

... affected source a. reduce emissions of total HAP, measured as THC (as carbon), a by 97 percent; orb. limit emissions of total HAP, measured as THC (as carbon), a to 20 ppmvd at the control device outlet and use a PTE. 2. in an existing affected source a. reduce emissions of total HAP, measured as THC (as carbon...

40 CFR Table 3 to Subpart Kkkk of... - Emission Limits for Affected Sources Using the Control Efficiency/Outlet Concentration Compliance...

Code of Federal Regulations, 2010 CFR

2010-07-01

... affected source a. reduce emissions of total HAP, measured as THC (as carbon), a by 97 percent; orb. limit emissions of total HAP, measured as THC (as carbon), a to 20 ppmvd at the control device outlet and use a PTE. 2. in an existing affected source a. reduce emissions of total HAP, measured as THC (as carbon...

Mineral Ecology: Surface Specific Colonization and Geochemical Drivers of Biofilm Accumulation, Composition, and Phylogeny

PubMed Central

Jones, Aaron A.; Bennett, Philip C.

2017-01-01

This study tests the hypothesis that surface composition influences microbial community structure and growth of biofilms. We used laboratory biofilm reactors (inoculated with a diverse subsurface community) to explore the phylogenetic and taxonomic variability in microbial communities as a function of surface type (carbonate, silicate, aluminosilicate), media pH, and carbon and phosphate availability. Using high-throughput pyrosequencing, we found that surface type significantly controlled ~70–90% of the variance in phylogenetic diversity regardless of environmental pressures. Consistent patterns also emerged in the taxonomy of specific guilds (sulfur-oxidizers/reducers, Gram-positives, acidophiles) due to variations in media chemistry. Media phosphate availability was a key property associated with variation in phylogeny and taxonomy of whole reactors and was negatively correlated with biofilm accumulation and α-diversity (species richness and evenness). However, mineral-bound phosphate limitations were correlated with less biofilm. Carbon added to the media was correlated with a significant increase in biofilm accumulation and overall α-diversity. Additionally, planktonic communities were phylogenetically distant from those in biofilms. All treatments harbored structurally (taxonomically and phylogenetically) distinct microbial communities. Selective advantages within each treatment encouraged growth and revealed the presence of hundreds of additional operational taxonomix units (OTU), representing distinct consortiums of microorganisms. Ultimately, these results provide evidence that mineral/rock composition significantly influences microbial community structure, diversity, membership, phylogenetic variability, and biofilm growth in subsurface communities. PMID:28400754

40 CFR 458.43 - Effluent limitations guidelines representing the degree of effluent reduction attainable by the...

Code of Federal Regulations, 2012 CFR

2012-07-01

... Carbon Black Lamp Process Subcategory § 458.43 Effluent limitations guidelines representing the degree of..., controlled by this paragraph, which may be discharged from the carbon black lamp process by a point source...

40 CFR 458.43 - Effluent limitations guidelines representing the degree of effluent reduction attainable by the...

Code of Federal Regulations, 2013 CFR

2013-07-01

... Carbon Black Lamp Process Subcategory § 458.43 Effluent limitations guidelines representing the degree of..., controlled by this paragraph, which may be discharged from the carbon black lamp process by a point source...

40 CFR 458.43 - Effluent limitations guidelines representing the degree of effluent reduction attainable by the...

Code of Federal Regulations, 2014 CFR

2014-07-01

... Carbon Black Lamp Process Subcategory § 458.43 Effluent limitations guidelines representing the degree of..., controlled by this paragraph, which may be discharged from the carbon black lamp process by a point source...

The role of C:N:P stoichiometry in affecting denitrification in sediments from agricultural surface and tile-water wetlands.

PubMed

Grebliunas, Brian D; Perry, William L

2016-01-01

Nutrient stoichiometry within a wetland is affected by the surrounding land use, and may play a significant role in the removal of nitrate (NO3-N). Tile-drained, agricultural watersheds experience high seasonal inputs of NO3-N, but low phosphorus (PO4-P) and dissolved organic carbon (DOC) loads relative to surface water dominated systems. This difference may present stoichiometric conditions that limit denitrification within receiving waterways. We investigated how C:N:P ratios affected denitrification rates of sediments from tile-drained mitigation wetlands incubated for: 0, 5, 10, and 20 days. We then tested whether denitrification rates of sediments from surface-water and tile-drained wetlands responded differently to C:N ratios of 2:1 versus 4:1. Ratios of C:N:P (P < 0.05) and incubation length (P < 0.05) had a significant effect on denitrification in tile-drained wetland sediments. Carbon limitation of denitrification became evident at elevated NO3-N concentrations (20 mg L(-1)). Denitrification measured from tile water and surface water wetland sediments increased significantly (P < 0.05) at the 2:1 and 4:1 C:N treatments. The results from both experiments suggest wetland sediments provide a limiting pool of labile DOC to maintain prolonged NO3-N removal. Also, DOC limitation became more evident at elevated NO3-N concentrations (20 mg L(-1)). Irrespective of NO3-N concentrations, P did not limit denitrification rates. In addition to wetting period, residence time, and maintenance of anaerobic conditions, the availability of labile DOC is playing an important limiting role in sediment denitrification within mitigation wetlands.

Thick-shelled, grazer-protected diatoms decouple ocean carbon and silicon cycles in the iron-limited Antarctic Circumpolar Current

PubMed Central

Assmy, Philipp; Smetacek, Victor; Montresor, Marina; Klaas, Christine; Henjes, Joachim; Strass, Volker H.; Arrieta, Jesús M.; Bathmann, Ulrich; Berg, Gry M.; Breitbarth, Eike; Cisewski, Boris; Friedrichs, Lars; Fuchs, Nike; Herndl, Gerhard J.; Jansen, Sandra; Krägefsky, Sören; Latasa, Mikel; Peeken, Ilka; Röttgers, Rüdiger; Scharek, Renate; Schüller, Susanne E.; Steigenberger, Sebastian; Webb, Adrian; Wolf-Gladrow, Dieter

2013-01-01

Diatoms of the iron-replete continental margins and North Atlantic are key exporters of organic carbon. In contrast, diatoms of the iron-limited Antarctic Circumpolar Current sequester silicon, but comparatively little carbon, in the underlying deep ocean and sediments. Because the Southern Ocean is the major hub of oceanic nutrient distribution, selective silicon sequestration there limits diatom blooms elsewhere and consequently the biotic carbon sequestration potential of the entire ocean. We investigated this paradox in an in situ iron fertilization experiment by comparing accumulation and sinking of diatom populations inside and outside the iron-fertilized patch over 5 wk. A bloom comprising various thin- and thick-shelled diatom species developed inside the patch despite the presence of large grazer populations. After the third week, most of the thinner-shelled diatom species underwent mass mortality, formed large, mucous aggregates, and sank out en masse (carbon sinkers). In contrast, thicker-shelled species, in particular Fragilariopsis kerguelensis, persisted in the surface layers, sank mainly empty shells continuously, and reduced silicate concentrations to similar levels both inside and outside the patch (silica sinkers). These patterns imply that thick-shelled, hence grazer-protected, diatom species evolved in response to heavy copepod grazing pressure in the presence of an abundant silicate supply. The ecology of these silica-sinking species decouples silicon and carbon cycles in the iron-limited Southern Ocean, whereas carbon-sinking species, when stimulated by iron fertilization, export more carbon per silicon. Our results suggest that large-scale iron fertilization of the silicate-rich Southern Ocean will not change silicon sequestration but will add carbon to the sinking silica flux. PMID:24248337

29 CFR 1917.24 - Carbon monoxide.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 29 Labor 7 2010-07-01 2010-07-01 false Carbon monoxide. 1917.24 Section 1917.24 Labor Regulations...) MARINE TERMINALS Marine Terminal Operations § 1917.24 Carbon monoxide. (a) Exposure limits. The carbon... employees shall be removed from the enclosed space if the carbon monoxide concentration exceeds a ceiling of...

Engineering the productivity of recombinant Escherichia coli for limonene formation from glycerol in minimal media.

PubMed

Willrodt, Christian; David, Christian; Cornelissen, Sjef; Bühler, Bruno; Julsing, Mattijs K; Schmid, Andreas

2014-08-01

The efficiency and productivity of cellular biocatalysts play a key role in the industrial synthesis of fine and bulk chemicals. This study focuses on optimizing the synthesis of (S)-limonene from glycerol and glucose as carbon sources using recombinant Escherichia coli. The cyclic monoterpene limonene is extensively used in the fragrance, food, and cosmetic industries. Recently, limonene also gained interest as alternative jet fuel of biological origin. Key parameters that limit the (S)-limonene yield, related to genetics, physiology, and reaction engineering, were identified. The growth-dependent production of (S)-limonene was shown for the first time in minimal media. E. coli BL21 (DE3) was chosen as the preferred host strain, as it showed low acetate formation, fast growth, and high productivity. A two-liquid phase fed-batch fermentation with glucose as the sole carbon and energy source resulted in the formation of 700 mg L(org) (-1) (S)-limonene. Specific activities of 75 mU g(cdw) (-1) were reached, but decreased relatively quickly. The use of glycerol as a carbon source resulted in a prolonged growth and production phase (specific activities of ≥50 mU g(cdw) (-1) ) leading to a final (S)-limonene concentration of 2,700 mg L(org) (-1) . Although geranyl diphosphate (GPP) synthase had a low solubility, its availability appeared not to limit (S)-limonene formation in vivo under the conditions investigated. GPP rerouting towards endogenous farnesyl diphosphate (FPP) formation also did not limit (S)-limonene production. The two-liquid phase fed-batch setup led to the highest monoterpene concentration obtained with a recombinant microbial biocatalyst to date. Copyright © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Anoxygenic photosynthesis controls oxygenic photosynthesis in a cyanobacterium from a sulfidic spring.

PubMed

Klatt, Judith M; Al-Najjar, Mohammad A A; Yilmaz, Pelin; Lavik, Gaute; de Beer, Dirk; Polerecky, Lubos

2015-03-01

Before the Earth's complete oxygenation (0.58 to 0.55 billion years [Ga] ago), the photic zone of the Proterozoic oceans was probably redox stratified, with a slightly aerobic, nutrient-limited upper layer above a light-limited layer that tended toward euxinia. In such oceans, cyanobacteria capable of both oxygenic and sulfide-driven anoxygenic photosynthesis played a fundamental role in the global carbon, oxygen, and sulfur cycle. We have isolated a cyanobacterium, Pseudanabaena strain FS39, in which this versatility is still conserved, and we show that the transition between the two photosynthetic modes follows a surprisingly simple kinetic regulation controlled by this organism's affinity for H2S. Specifically, oxygenic photosynthesis is performed in addition to anoxygenic photosynthesis only when H2S becomes limiting and its concentration decreases below a threshold that increases predictably with the available ambient light. The carbon-based growth rates during oxygenic and anoxygenic photosynthesis were similar. However, Pseudanabaena FS39 additionally assimilated NO3 (-) during anoxygenic photosynthesis. Thus, the transition between anoxygenic and oxygenic photosynthesis was accompanied by a shift of the C/N ratio of the total bulk biomass. These mechanisms offer new insights into the way in which, despite nutrient limitation in the oxic photic zone in the mid-Proterozoic oceans, versatile cyanobacteria might have promoted oxygenic photosynthesis and total primary productivity, a key step that enabled the complete oxygenation of our planet and the subsequent diversification of life. Copyright © 2015, American Society for Microbiology. All Rights Reserved.

Anoxygenic Photosynthesis Controls Oxygenic Photosynthesis in a Cyanobacterium from a Sulfidic Spring

PubMed Central

Al-Najjar, Mohammad A. A.; Yilmaz, Pelin; Lavik, Gaute; de Beer, Dirk; Polerecky, Lubos

2015-01-01

Before the Earth's complete oxygenation (0.58 to 0.55 billion years [Ga] ago), the photic zone of the Proterozoic oceans was probably redox stratified, with a slightly aerobic, nutrient-limited upper layer above a light-limited layer that tended toward euxinia. In such oceans, cyanobacteria capable of both oxygenic and sulfide-driven anoxygenic photosynthesis played a fundamental role in the global carbon, oxygen, and sulfur cycle. We have isolated a cyanobacterium, Pseudanabaena strain FS39, in which this versatility is still conserved, and we show that the transition between the two photosynthetic modes follows a surprisingly simple kinetic regulation controlled by this organism's affinity for H2S. Specifically, oxygenic photosynthesis is performed in addition to anoxygenic photosynthesis only when H2S becomes limiting and its concentration decreases below a threshold that increases predictably with the available ambient light. The carbon-based growth rates during oxygenic and anoxygenic photosynthesis were similar. However, Pseudanabaena FS39 additionally assimilated NO3− during anoxygenic photosynthesis. Thus, the transition between anoxygenic and oxygenic photosynthesis was accompanied by a shift of the C/N ratio of the total bulk biomass. These mechanisms offer new insights into the way in which, despite nutrient limitation in the oxic photic zone in the mid-Proterozoic oceans, versatile cyanobacteria might have promoted oxygenic photosynthesis and total primary productivity, a key step that enabled the complete oxygenation of our planet and the subsequent diversification of life. PMID:25576611

Insights from a network of long-term measurements of biosphere-atmospheric exchanges of water vapor and carbon dioxide in southern Arizona

NASA Astrophysics Data System (ADS)

Scott, R. L.; Barron-Gafford, G.; Biederman, J. A.

2016-12-01

Around one-third of Earth's land surface is classified as semiarid, and carbon dioxide exchange in these regions has been shown to be an important regulator of both the trend and interannual variability of the terrestrial carbon sink. Fifteen years ago, when we began making measurements of biosphere-atmospheric exchanges of energy, water vapor, and carbon dioxide using eddy covariance in southern Arizona USA, there was paucity of semiarid observations in flux networks like Ameriflux. We started by establishing riparian sites across a woody plant encroachment gradient to quantify the productivity and consumptive plant water use along a iconic and ecologically important desert river. Soon thereafter, we added semiarid grassland, shrubland, and savanna sites that do not have access to groundwater in order to better understand how water limitation and changes in vegetation structure affect ecosystem productivity. Here, we highlight the value of multiyear, multisite flux data for addressing regional to global scale problems associated with groundwater pumping, land cover change, drought, and climate change. For the riparian sites, we find that ecosystem water availability is altered by vegetation structure such that ecosystems with more deeply rooted trees have higher productivity but at a cost of greater groundwater use. For the non-riparian sites, precipitation strongly controls ecosystem water availability and the resultant productivity, but differences in ecosystem structure impact water use efficiency due to the partitioning of evapotranspiration into its component sources. Also, the productivity at sites with more grass, and less woody, plants responds more quickly to precipitation fluctuations including long-term drought conditions. In semiarid regions, variability in water and carbon fluxes is much larger than in more mesic climes. Across our riparian and non-riparian sites, access to more stable groundwater reserves reduces variability in water and carbon fluxes and can decouple ecosystem productivity from precipitation. Finally, we show that the 8% increase in carbon dioxide concentrations over the period of our measurements has not resulted in any apparent changes in ecosystem water use efficiency that is expected and has been reported for northeastern US forests.

Scientific Challenges in Sustainable Energy Technology

NASA Astrophysics Data System (ADS)

Lewis, Nathan

2006-03-01

This presentation will describe and evaluate the challenges, both technical, political, and economic, involved with widespread adoption of renewable energy technologies. First, we estimate the available fossil fuel resources and reserves based on data from the World Energy Assessment and World Energy Council. In conjunction with the current and projected global primary power production rates, we then estimate the remaining years of supply of oil, gas, and coal for use in primary power production. We then compare the price per unit of energy of these sources to those of renewable energy technologies (wind, solar thermal, solar electric, biomass, hydroelectric, and geothermal) to evaluate the degree to which supply/demand forces stimulate a transition to renewable energy technologies in the next 20-50 years. Secondly, we evaluate the greenhouse gas buildup limitations on carbon-based power consumption as an unpriced externality to fossil-fuel consumption, considering global population growth, increased global gross domestic product, and increased energy efficiency per unit of globally averaged GDP, as produced by the Intergovernmental Panel on Climate Change (IPCC). A greenhouse gas constraint on total carbon emissions, in conjunction with global population growth, is projected to drive the demand for carbon-free power well beyond that produced by conventional supply/demand pricing tradeoffs, at potentially daunting levels relative to current renewable energy demand levels. Thirdly, we evaluate the level and timescale of R&D investment that is needed to produce the required quantity of carbon-free power by the 2050 timeframe, to support the expected global energy demand for carbon-free power. Fourth, we evaluate the energy potential of various renewable energy resources to ascertain which resources are adequately available globally to support the projected global carbon-free energy demand requirements. Fifth, we evaluate the challenges to the chemical sciences to enable the cost-effective production of carbon-free power on the needed scale by the 2050 timeframe. Finally, we discuss the effects of a change in primary power technology on the energy supply infrastructure and discuss the impact of such a change on the modes of energy consumption by the energy consumer and additional demands on the chemical sciences to support such a transition in energy supply.

The effect of limited availability of N or water on C allocation to fine roots and annual fine root turnover in Alnus incana and Salix viminalis.

PubMed

Rytter, Rose-Marie

2013-09-01

The effect of limited nitrogen (N) or water availability on fine root growth and turnover was examined in two deciduous species, Alnus incana L. and Salix viminalis L., grown under three different regimes: (i) supply of N and water in amounts which would not hamper growth, (ii) limited N supply and (iii) limited water supply. Plants were grown outdoors during three seasons in covered and buried lysimeters placed in a stand structure and filled with quartz sand. Computer-controlled irrigation and fertilization were supplied through drip tubes. Production and turnover of fine roots were estimated by combining minirhizotron observations and core sampling, or by sequential core sampling. Annual turnover rates of fine roots <1 mm (5-6 year(-1)) and 1-2 mm (0.9-2.8 year(-1)) were not affected by changes in N or water availability. Fine root production (<1 mm) differed between Alnus and Salix, and between treatments in Salix; i.e., absolute length and biomass production increased in the order: water limited < unlimited < N limited. Few treatment effects were detected for fine roots 1-2 mm. Proportionally more C was allocated to fine roots (≤2 mm) in N or water-limited Salix; 2.7 and 2.3 times the allocation to fine roots in the unlimited regime, respectively. Estimated input to soil organic carbon increased by ca. 20% at N limitation in Salix. However, future studies on fine root decomposition under various environmental conditions are required. Fine root growth responses to N or water limitation were less pronounced in Alnus, thus indicating species differences caused by N-fixing capacity and slower initial growth in Alnus, or higher fine root plasticity in Salix. A similar seasonal growth pattern across species and treatments suggested the influence of outer stimuli, such as temperature and light.

The effect of metal (hydr)oxide nano-enabling on intraparticle mass transport of organic contaminants in hybrid granular activated carbon.

PubMed

Garcia, Jose; Markovski, Jasmina; McKay Gifford, J; Apul, Onur; Hristovski, Kiril D

2017-05-15

The overarching goal of this study was to ascertain the changes in intraparticle mass transport rates for organic contaminants resulting from nano-enabled hybridization of commercially available granular activated carbon (GAC). Three different nano-enabled hybrid media were fabricated by in-situ synthesizing titanium dioxide nanoparticles inside the pores of GAC sorbent, characterized, and evaluated for removal of two model organic contaminants under realistic conditions to obtain the intraparticle mass transport (pore and surface diffusion) coefficients. The results validated the two hypotheses that: (H1) the pore diffusion rates of organic contaminants linearly decrease with decrease in cumulative pore volume caused by increase in metal (hydr)oxide nanoparticle content inside the pores of the hybrid GAC sorbent; and (H2) introduction of metal (hydr)oxide nanoparticles initially increases surface diffusivity, but additional loading causes its decrease as the increase in metal (hydr)oxide nanoparticles content continues to reduce the porosity of the GAC sorbent. Nano-enabled hybridization of commercially available GAC with metal (hydr)oxides has the potential to significantly increase the intraparticle mass transport limitations for organic contaminants. Introduction of metal (hydr)oxide nanoparticles inside the pores of a pristine sorbent causes the pore diffusion rates of organic contaminants to decrease as the cumulative pore volume is reduced. In contrast, the introduction of limited amounts of metal (hydr)oxide nanoparticles appears to facilitate the surface diffusion rates of these contaminants. Copyright © 2017 Elsevier B.V. All rights reserved.

The limits of crop productivity

NASA Technical Reports Server (NTRS)

Bugbee, Bruce; Monje, Oscar

1992-01-01

The component processes that govern yield limits in food crops are reviewed and how each process can be individually measured is described. The processes considered include absorption of photosynthetic radiation by green tissue, carbon-fixation efficiency in photosynthesis, carbon use efficiency in respiration, biomass allocation to edible products, and efficiency of photosynthesis and respiration. The factors limiting yields in optimal environments are considered.

Spatially explicit modeling of particulate nutrient flux in Large global rivers

NASA Astrophysics Data System (ADS)

Cohen, S.; Kettner, A.; Mayorga, E.; Harrison, J. A.

2017-12-01

Water, sediment, nutrient and carbon fluxes along river networks have undergone considerable alterations in response to anthropogenic and climatic changes, with significant consequences to infrastructure, agriculture, water security, ecology and geomorphology worldwide. However, in a global setting, these changes in fluvial fluxes and their spatial and temporal characteristics are poorly constrained, due to the limited availability of continuous and long-term observations. We present results from a new global-scale particulate modeling framework (WBMsedNEWS) that combines the Global NEWS watershed nutrient export model with the spatially distributed WBMsed water and sediment model. We compare the model predictions against multiple observational datasets. The results indicate that the model is able to accurately predict particulate nutrient (Nitrogen, Phosphorus and Organic Carbon) fluxes on an annual time scale. Analysis of intra-basin nutrient dynamics and fluxes to global oceans is presented.

The future of evapotranspiration: Global requirements for ecosystem functioning, carbon and climate feedbacks, agricultural management, and water resources

NASA Astrophysics Data System (ADS)

Fisher, Joshua B.; Melton, Forrest; Middleton, Elizabeth; Hain, Christopher; Anderson, Martha; Allen, Richard; McCabe, Matthew F.; Hook, Simon; Baldocchi, Dennis; Townsend, Philip A.; Kilic, Ayse; Tu, Kevin; Miralles, Diego D.; Perret, Johan; Lagouarde, Jean-Pierre; Waliser, Duane; Purdy, Adam J.; French, Andrew; Schimel, David; Famiglietti, James S.; Stephens, Graeme; Wood, Eric F.

2017-04-01

The fate of the terrestrial biosphere is highly uncertain given recent and projected changes in climate. This is especially acute for impacts associated with changes in drought frequency and intensity on the distribution and timing of water availability. The development of effective adaptation strategies for these emerging threats to food and water security are compromised by limitations in our understanding of how natural and managed ecosystems are responding to changing hydrological and climatological regimes. This information gap is exacerbated by insufficient monitoring capabilities from local to global scales. Here, we describe how evapotranspiration (ET) represents the key variable in linking ecosystem functioning, carbon and climate feedbacks, agricultural management, and water resources, and highlight both the outstanding science and applications questions and the actions, especially from a space-based perspective, necessary to advance them.

The Future of Evapotranspiration: Global Requirements for Ecosystem Functioning, Carbon and Climate Feedbacks, Agricultural Management, and Water Resources

NASA Technical Reports Server (NTRS)

Fisher, Joshua B.; Melton, Forrest; Middleton, Elizabeth; Hain, Christopher; Anderson, Martha; Allen, Richard; McCabe, Matthew F.; Hook, Simon; Baldocchi, Dennis; Townsend, Philip A.;

The hybrid nanostructure of MnCo2O4.5 nanoneedle/carbon aerogel for symmetric supercapacitors with high energy density

NASA Astrophysics Data System (ADS)

Hao, Pin; Zhao, Zhenhuan; Li, Liyi; Tuan, Chia-Chi; Li, Haidong; Sang, Yuanhua; Jiang, Huaidong; Wong, C. P.; Liu, Hong

2015-08-01

Current applications of carbon-based supercapacitors are limited by their low energy density. One promising strategy to enhance the energy density is to couple metal oxides with carbon materials. In this study, a porous MnCo2O4.5 nanoneedle/carbon aerogel hybrid nanostructure was synthesized by assembling MnCo2O4.5 nanoneedle arrays on the surface of channel walls of hierarchical porous carbon aerogels derived from chitosan for the supercapacitor application. The synthetic process of the hybrid nanostructure involves two steps, i.e. the growth of Mn-Co precursors on carbon aerogel by a hydrothermal process and the conversion of the precursor into MnCo2O4.5 nanoneedles by calcination. The carbon aerogel exhibits a high electrical conductivity, high specific surface area and porous structure, ensuring high electrochemical performance of the hybrid nanostructure when coupled with the porous MnCo2O4.5 nanoneedles. The symmetric supercapacitor using the MnCo2O4.5 nanoneedle/carbon aerogel hybrid nanostructure as the active electrode material exhibits a high energy density of about 84.3 Wh kg-1 at a power density of 600 W kg-1. The voltage window is as high as 1.5 V in neutral aqueous electrolytes. Due to the unique nanostructure of the electrodes, the capacitance retention reaches 86% over 5000 cycles.Current applications of carbon-based supercapacitors are limited by their low energy density. One promising strategy to enhance the energy density is to couple metal oxides with carbon materials. In this study, a porous MnCo2O4.5 nanoneedle/carbon aerogel hybrid nanostructure was synthesized by assembling MnCo2O4.5 nanoneedle arrays on the surface of channel walls of hierarchical porous carbon aerogels derived from chitosan for the supercapacitor application. The synthetic process of the hybrid nanostructure involves two steps, i.e. the growth of Mn-Co precursors on carbon aerogel by a hydrothermal process and the conversion of the precursor into MnCo2O4.5 nanoneedles by calcination. The carbon aerogel exhibits a high electrical conductivity, high specific surface area and porous structure, ensuring high electrochemical performance of the hybrid nanostructure when coupled with the porous MnCo2O4.5 nanoneedles. The symmetric supercapacitor using the MnCo2O4.5 nanoneedle/carbon aerogel hybrid nanostructure as the active electrode material exhibits a high energy density of about 84.3 Wh kg-1 at a power density of 600 W kg-1. The voltage window is as high as 1.5 V in neutral aqueous electrolytes. Due to the unique nanostructure of the electrodes, the capacitance retention reaches 86% over 5000 cycles. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr04421a

Size and Carbon Content of Sub-seafloor Microbial Cells

NASA Astrophysics Data System (ADS)

Braun, S.; Morono, Y.; Littmann, S.; Jørgensen, B. B.; Lomstein, B. A.

2015-12-01

Into the seafloor, a radical decline in nutrient and energy availability poses strong metabolic demands to any residing life. However, a sedimentary microbial ecosystem seems to maintain itself close to what we understand to be the energetic limit of life. Since a complex sediment matrix is interfering with the analysis of whole cells and sub-cellular compounds such as cell wall and membrane molecules, little is known about the physiological properties of cells in the deep biosphere. Here we focus on the size and carbon content of cells from a 90-m sediment drill core retrieved in October 2013 at Landsort Deep, Baltic Sea, in 437 meters water depth. To determine their shape and volume, cells were separated from the sediment matrix by multi-layer density centrifugation and visualized via fluorescence microscopy (FM), scanning electron microscopy (SEM), and stimulated emission depletion microscopy (STED). Total cell-carbon was calculated from amino acid-carbon, which was analyzed by high-performance liquid chromatography after cells had additionally been purified by fluorescence activated cell sorting (FACS). Cell-carbon turnover times were estimated using an amino acid racemization model that is based on the built-in molecular clock of aspartic acid, which due to racemization alternates between the D- and L-isomeric configurations over timescales of thousands of years at low in-situ temperatures (≈4˚C). We find that the majority of microbial cells in the sediment have coccoid or rod-shaped morphology, and that absolute values for cell volume are strongly dependent on the method used, spanning three orders of magnitude from approximately 0.001 to 1 µm3 for both coccoid and rod-shaped cells. From the surface to the deepest sample measured (≈60 mbsf), cell volume decreases by an order of magnitude, and carbon content is in the lower range (<20 fg C cell-1) of what has been reported in the literature as conversion factors. Cell-carbon is turned over approximately every 50-600 years, and total carbon oxidation rates decrease from ≈3400 to <60 nmol cm-3 yr-1 with depth, as inferred from amino acid racemization modeling. Given the large extent of marine sediments on Earth, our data will shed light on the energetic limits of life on our planet and will be important for estimating global biomass budgets.

Carbon storage potential of Columbia River flood basalt

NASA Astrophysics Data System (ADS)

Wells, R. K.; Xiong, W.; Giammar, D.; Skemer, P. A.

2017-12-01

Basalt reservoirs are an important option for sequestering carbon through dissolution of host rock and precipitation of stable carbonate minerals. This study seeks to understand the nature of dissolution and surface roughening processes and their influence on the timing and spatial distribution of carbonation, in static experiments at 150 °C and 100 bar CO2. Intact samples and cores with milled pathways from Ca-rich and Fe-rich Columbia River flood basalt formations were reacted for up to 40 weeks. Experimental specimens were analyzed using SEM-EDS, microprobe, and μCT scanning, Raman spectroscopy, and 2D profilometer to characterize changes in composition and surface roughness. ICP-MS was used to examine bulk fluid chemistry. Initial dissolution of olivine grains results in higher Mg2+ and Fe2+ concentrations within the bulk solution in the first week of reaction. However, once available olivine grains are gone, Ca-rich pyroxene becomes the primary contributor of Ca2+, Mg2+, and Fe2+ within the bulk solution. The complete dissolution of olivine grains resulted in pits up to 200 μm deep. Dissolution of other minerals resulted in the formation of microscale textures, primarily along grain boundaries and fractures. The surface roughness increased by factors of up to 42, while surface area increased 20%. Based on these results, pyroxene is the sustaining contributor of divalent metal cations during dissolution of basalt, and the limited connectivity of olivine and pyroxene grains limits the exposure of new reactive surface areas. Within 6 weeks, aragonite precipitated in Ca-rich basalt samples, while Fe-rich samples precipitated of siderite. The highest concentration of carbonates occurs 1/3 into milled pathways, which simulate dead-end fractures, in low porosity basalts, and near the fracture tip in high porosity basalts. Even at elevated temperatures, the fractures are not blocked nor filled within 40 weeks of reaction. When vesicles are present, carbonates can precipitate within these pores even when the pores do not appear to connect to the main fracture pathway. Based on our experimental results, we estimate the carbon storage potential of the Ca-rich formations within the Columbia River flood basalt to be 47 kg CO2/m3, which could be reached in 38 years at a constant carbonation rate of 1.24 ± 0.54 kg CO2/m3yr.

Distribution and Diversity of Rhodopsin-Producing Microbes in the Chesapeake Bay.

PubMed

Maresca, Julia A; Miller, Kelsey J; Keffer, Jessica L; Sabanayagam, Chandran R; Campbell, Barbara J

2018-07-01

Although sunlight is an abundant source of energy in surface environments, less than 0.5% of the available photons are captured by (bacterio)chlorophyll-dependent photosynthesis in plants and bacteria. Metagenomic data indicate that 30 to 60% of the bacterial genomes in some environments encode rhodopsins, retinal-based photosystems found in heterotrophs, suggesting that sunlight may provide energy for more life than previously suspected. However, quantitative data on the number of cells that produce rhodopsins in environmental systems are limited. Here, we use total internal reflection fluorescence microscopy to show that the number of free-living microbes that produce rhodopsins increases along the salinity gradient in the Chesapeake Bay. We correlate this functional data with environmental data to show that rhodopsin abundance is positively correlated with salinity and with indicators of active heterotrophy during the day. Metagenomic and metatranscriptomic data suggest that the microbial rhodopsins in the low-salinity samples are primarily found in Actinobacteria and Bacteroidetes , while those in the high-salinity samples are associated with SAR-11 type Alphaproteobacteria IMPORTANCE Microbial rhodopsins are common light-activated ion pumps in heterotrophs, and previous work has proposed that heterotrophic microbes use them to conserve energy when organic carbon is limiting. If this hypothesis is correct, rhodopsin-producing cells should be most abundant where nutrients are most limited. Our results indicate that in the Chesapeake Bay, rhodopsin gene abundance is correlated with salinity, and functional rhodopsin production is correlated with nitrate, bacterial production, and chlorophyll a We propose that in this environment, where carbon and nitrogen are likely not limiting, heterotrophs do not need to use rhodopsins to supplement ATP synthesis. Rather, the light-generated proton motive force in nutrient-rich environments could be used to power energy-dependent membrane-associated processes, such as active transport of organic carbon and cofactors, enabling these organisms to more efficiently utilize exudates from primary producers. Copyright © 2018 American Society for Microbiology.

The C-household of young broad-leaved and conifer tree species exposed to long-term carbon limitation by shading

NASA Astrophysics Data System (ADS)

Weber, Raphael; Hoch, Günter

2017-04-01

Non-structural carbohydrates (NSC, i.e. free sugars and starch) are regarded as freely available carbon (C) reserves in plants. They are often quantified to estimate a plant's C-balance, assuming that NSC are controlled by the net-balance between photo-assimilation and C-usage (respiration, growth and other sinks). Within a recent field experiment, we investigated the extent, to which C-reserves (NSC) can be formed in young trees against prevailing C-sink demands (growth) under C-limitation. A total of almost 1000 individuals of two-year-old tree saplings from 6 deciduous, broadleaved species and 4 evergreen conifer species were planted on a field side. Half of the trees per species were treated with long-term C-limitation by exposing them to continuous deep shade conditions (5% of natural PPFD) under a permanent shading tent. C gas-exchange, growth and NSC tissue concentrations were analyzed in shaded and unshaded saplings for two consecutive years. Three months after the beginning of the experiment, leaf photosynthesis acclimatized to the low light conditions, with leaves of shaded trees showing significantly higher SLA and lower light saturation and maximum photosynthesis. During the second season of the experiment, most species exhibited very strong reductions in NSC, but much less pronounced reductions in growth. In contrast, other species, with few exceptions, kept NSC concentrations similar to unshaded controls, while growth virtually stopped under deep shade. In conclusion, we found species-specific strategies in the trees' C-household after two years of C-limitation, that fall into two major carbon allocation strategies: 1) "C-spenders", which deplete C reserves in order to keep up significant growth, and 2) "C-savers", which reduce C sink activities to a minimum in order to store substantial amounts of C reserves. Overall, early-successional species tended to follow the first strategy, while late-successional species tended to save higher C reserve pools in trade-off with growth.

Evaluation of Characterization Techniques for Carbon-Carbon Composites

DTIC Science & Technology

1992-05-01

Enhancement of Resin (50X) 51 28 Confocal Image of Reticulated , Vitreous Carbon Foam 53 29 Schemmtic Principle of Backscattered Electron Microscopy for...future. 7.2 Confocal Microscopy Both carbon - carbon composites and reticulated vitreous carbon foams were submitted to Sarastro, Inc. to evaluate...indicate 1-micron resolutions are possible; however, the depth penetration is limited even further at these parameters. Six reticulated vitreous carbon

Coccolithophores put a CAP on calcification and carbon

NASA Astrophysics Data System (ADS)

Rickaby, R. E. M.; Lee, R. B. Y.; Mavridou, D. A. I.; Papadakos, G.; McClelland, H. L. O.; Anderson, C. J.

2014-12-01

Unlike the majority of biomineralization, mediated via proteins, the coccolithophores employ acidic polysaccharides (CAPs) as the template for the multitude of intricate calcium carbonate liths which are precipitated inside their cells and expelled to form an external spherical armour. Massive accumulations of these calcium carbonate coccoliths (we estimate a flux of ~ 6x1025 liths/year) form sediments on the deep seafloor, a dominant sink of carbon from the atmosphere over geological timescales, and a buffer for seawater chemistry. This acidic, coccolith-associated polysaccharide (CAP) plays a dual role, likely determined by the calcifying vesicle chemistry, promoting and limiting precipitation. We have developed and demonstrated novel techniques for the extraction and characterisation of these biomineral-mediating molecules, encapsulated and preserved within liths from sediments as old as the Mesozoic. Modern cultures of extant coccolithophores show that the composition of CAP is distinctive for different species, and even strains of e.g. Emiliania huxleyi, suggestive that interactions with galacturonic acid residues are key to dictating the architecture of the liths. Furthermore, it appears that the galacturonic acid content reflects an adaptive response of the CAP to the chemistry within the coccolith vesicle where calcification is induced; in particular the size of the internal carbon pool and inferred saturation state. Extraction of CAPs from the Coccolithale fraction of sediments suggests that the galacturonic acid content of these relatively large and inefficient carbon concentrators evolves in response to declining CO2 availability and thus may provide a novel means for reconstructing paleo pCO2.

Diver Down: Remote Sensing of Carbon Climate Feedbacks

NASA Astrophysics Data System (ADS)

Schimel, D.; Chatterjee, A.; Baker, D. F.; Basu, S.; Denning, A. S.; Schuh, A. E.; Crowell, S.; Jacobson, A. R.; Bowman, K. W.; Liu, J.; O'Dell, C.

2016-12-01

What controls the rate of increase of CO2 and CH4 in the atmosphere? It may seem self-evident but actually remains mysterious. The increases of CO2 and CH4 result from a combination of forcing from anthropogenic emissions and Earth System feedbacks that dampen or amplify the effects of those emissions on atmospheric concentrations. The fraction of anthropogenic CO2 remaining in the atmosphere has remained remarkably constant over the last 59 years but has shown recent dynamics and if it changes in the future, will affect the climate impact of any given fossil fuel regime. While greenhouse gases affect the global atmosphere, their sources and sinks are remarkably heterogeneous in time and space, and traditional in situ observing systems do not provide the coverage and resolution to quantify carbon-climate feedbacks or reduce the uncertainty of model predictions. Here we describe an methodology for estimating critical carbon-climate feedback effects of current spaceborne XCO2 measurements, developed by the OCO-2 Flux Group, and applied to OCO-2 and GOSAT data. The methodology allows integration of the space-based carbon budgets with other global data sets, and exposes the impact of residual bias error on the estimated fluxes, allowing the uncertainty of the estimated feedbacks to be quantified. The approach is limited by the short timeseries currently available, but suggests dramatic changes to the carbon cycle over the recent past. We present the methodology, early results and implications for a future, sustained carbon observing system.

Theoretical Investigations of Well-Defined Graphene Nanostructures: Catalysis, Spectroscopy, and Development of Novel Fragment-Based Models

NASA Astrophysics Data System (ADS)

Noffke, Benjamin W.

Carbon materials have the potential to replace some precious metals in renewable energy applications. These materials are particularly attractive because of the elemental abundance and relatively low nuclear mass of carbon, implying economically feasible and lightweight materials. Targeted design of carbon materials is hindered by the lack of fundamental understanding that is required to tailor their properties for the desired application. However, most available synthetic methods to create carbon materials involve harsh conditions that limit the control of the resulting structure. Without a well-defined structure, the system is too complex and fundamental studies cannot be definitive. This work seeks to gain fundamental understanding through the development and application of efficient computational models for these systems, in conjunction with experiments performed on soluble, well-defined graphene nanostructures prepared by our group using a bottom-up synthetic approach. Theory is used to determine mechanistic details for well-defined carbon systems in applications of catalysis and electrochemical transformations. The resulting computational models do well to explain previous observations of carbon materials and provide suggestions for future directions. However, as the system size of the nanostructures gets larger, the computational cost can become prohibitive. To reduce the computational scaling of quantum chemical calculations, a new fragmentation scheme has been developed that addresses the challenges of fragmenting conjugated molecules. By selecting fragments that retain important structural characteristics in graphene, a more efficient method is achieved. The new method paves the way for an automated, systematic fragmentation scheme of graphene molecules.

RBE and related modeling in carbon-ion therapy

NASA Astrophysics Data System (ADS)

Karger, Christian P.; Peschke, Peter

2018-01-01

Carbon ion therapy is a promising evolving modality in radiotherapy to treat tumors that are radioresistant against photon treatments. As carbon ions are more effective in normal and tumor tissue, the relative biological effectiveness (RBE) has to be calculated by bio-mathematical models and has to be considered in the dose prescription. This review (i) introduces the concept of the RBE and its most important determinants, (ii) describes the physical and biological causes of the increased RBE for carbon ions, (iii) summarizes available RBE measurements in vitro and in vivo, and (iv) describes the concepts of the clinically applied RBE models (mixed beam model, local effect model, and microdosimetric-kinetic model), and (v) the way they are introduced into clinical application as well as (vi) their status of experimental and clinical validation, and finally (vii) summarizes the current status of the use of the RBE concept in carbon ion therapy and points out clinically relevant conclusions as well as open questions. The RBE concept has proven to be a valuable concept for dose prescription in carbon ion radiotherapy, however, different centers use different RBE models and therefore care has to be taken when transferring results from one center to another. Experimental studies significantly improve the understanding of the dependencies and limitations of RBE models in clinical application. For the future, further studies investigating quantitatively the differential effects between normal tissues and tumors are needed accompanied by clinical studies on effectiveness and toxicity.

Impacts of Human Induced Nitrogen Deposition on Ecosystem Carbon Sequestration and Water Balance in China

NASA Astrophysics Data System (ADS)

Sheng, M.; Yang, D.; Tang, J.; Lei, H.

2017-12-01

Enhanced plant biomass accumulation in response to elevated atmospheric CO2 concentration could dampen the future rate of increase in CO2 levels and associated climate warming. However, many experiments around the world reported that nitrogen availability could limit the sustainability of the ecosystems' response to elevated CO2. In the recent 20 years, atmospheric nitrogen deposition, primarily from fossil fuel combustion, has increased sharply about 25% in China and meanwhile, China has the highest carbon emission in the world, implying a large opportunity to increase vegetation greenness and ecosystem carbon sequestration. Moreover, the water balance of the ecosystem will also change. However, in the future, the trajectory of increasing nitrogen deposition from fossil fuel use is to be controlled by the government policy that shapes the energy and industrial structure. Therefore, the historical and future trajectories of nitrogen deposition are likely very different, and it is imperative to understand how changes in nitrogen deposition will impact the ecosystem carbon sequestration and water balance in China. We here use the Community Land Model (CLM 4.5) to analyze how the change of nitrogen deposition has influenced and will influence the ecosystem carbon and water cycle in China at a high spatial resolution (0.1 degree). We address the following questions: 1) what is the contribution of the nitrogen deposition on historical vegetation greenness? 2) How does the change of nitrogen deposition affect the carbon sequestration? 3) What is its influence to water balance? And 4) how different will be the influence of the nitrogen deposition on ecosystem carbon and water cycling in the future?

Spatial variation in the ecological relationships among the components of Beijing's carbon metabolic system.

PubMed

Xia, Linlin; Fath, Brian D; Scharler, Ursula M; Zhang, Yan

2016-02-15

In this paper, we construct a spatially explicit model of carbon metabolism for the flows of carbon among the components of an urban area. We used the model to identify spatial heterogeneity in the ecological relationships within a carbon metabolic network. We combined land-use and cover type maps for Beijing from 1990 to 2010 with empirical coefficients and socioeconomic data to quantify the flows. We used utility analysis to determine the ecological relationships between the components of the system and analyzed their changes during urban development. We used ArcGIS to analyze their spatial variation. We found that the positive utilities in Beijing decreased over time and that negative relationships mostly outweighed positive relationships after 2000. The main ecological relationships were distributed throughout the entire urban area before 2000; subsequently, exploitation, control, and mutualism relationships became concentrated in the southeast, leaving competition relationships to dominate the northwest. Mutualism relationships were most common for natural components, but were not stable because they were easily disturbed by urban expansion. Transportation and industrial land and urban land were the most important contributors to exploitation and control relationships and may be important indicators of spatial adjustment. Increasing competition relationships unbalanced the carbon metabolism, and limitations on the area of land available for development and on the water resources led to increasingly serious competition. The results provide an objective basis for planning adjustments to Beijing's land-use patterns to improve its carbon metabolism and reduce carbon emission. Copyright © 2015 Elsevier B.V. All rights reserved.

Predicting Phenologic Response to Water Stress and Implications for Carbon Uptake across the Southeast U.S.

NASA Astrophysics Data System (ADS)

Lowman, L.; Barros, A. P.

2016-12-01

Representation of plant photosynthesis in modeling studies requires phenologic indicators to scale carbon assimilation by plants. These indicators are typically the fraction of photosynthetically active radiation (FPAR) and leaf area index (LAI) which represent plant responses to light and water availability, as well as temperature constraints. In this study, a prognostic phenology model based on the growing season index is adapted to determine the phenologic indicators of LAI and FPAR at the sub-daily scale based on meteorological and soil conditions. Specifically, we directly model vegetation green-up and die-off responses to temperature, vapor pressure deficit, soil water potential, and incoming solar radiation. The indices are based on the properties of individual plant functional types, driven by observational data and prior modeling applications. First, we describe and test the sensitivity of the carbon uptake response to predicted phenology for different vegetation types. Second, the prognostic phenology model is incorporated into a land-surface hydrology model, the Duke Coupled Hydrology Model with Prognostic Vegetation (DCHM-PV), to demonstrate the impact of dynamic phenology on modeled carbon assimilation rates and hydrologic feedbacks. Preliminary results show reduced carbon uptake rates when incorporating a prognostic phenology model that match well against the eddy-covariance flux tower observations. Additionally, grassland vegetation shows the most variability in LAI and FPAR tied to meteorological and soil conditions. These results highlight the need to incorporate vegetation-specific responses to water limitation in order to accurately estimate the terrestrial carbon storage component of the global carbon budget.

Stable carbon, nitrogen and sulfur isotopes in non-carbonate fractions of cold-seep carbonates

NASA Astrophysics Data System (ADS)

Feng, Dong; Peng, Yongbo; Peckmann, Jörn; Roberts, Harry; Chen, Duofu

2017-04-01

Sulfate-driven anaerobic oxidation of methane (AOM) supports chemosynthesis-based communities and limits the release of methane from marine sediments. This process promotes the formation of carbonates close to the seafloor along continental margins. The geochemical characteristics of the carbonate minerals of these rocks are increasingly understood, questions remain about the geochemical characteristics of the non-carbonate fractions. Here, we report stable carbon, nitrogen and sulfur isotope patterns in non-carbonate fractions of seep carbonates. The authigenic carbonates were collected from three modern seep provinces (Black Sea, Gulf of Mexico, and South China Sea) and three ancient seep deposits (Marmorito, northern Italy, Miocene; SR4 deposit of the Lincoln Creek Formation and Whiskey Creek, western Washington, USA, Eocene to Oligocene). The δ13C values of non-carbonate fractions range from ˜-25‰ to -80‰ VPDB. These values indicate that fossil methane mixed with varying amounts of pelagic organic matter is the dominant source of carbon in these fractions. The relatively small offset between the δ34S signatures of the non-carbonate fractions and the respective sulfide minerals suggests that locally produced hydrogen sulfide is the main source of sulfur in seep environments. The δ15N values of the non-carbonate fractions are generally lower than the corresponding values of deep-sea sediments, suggesting that organic nitrogen is mostly of a local origin. This study reveals the potential of using δ13C, δ15N, δ34S values to discern seep and non-seep deposits. In cases where δ13Ccarbonate values are only moderately low due to mixing processes and lipid biomarkers have been erased in the course of burial, it is difficult to trace back AOM owing to the lack of other records. This problem is even more pronounced when authigenic carbonate is not available in ancient seep environments. Acknowledgments: The authors thank BOEM and NOAA for their years' support of the deep-sea dives. Funding was provided by the NSF of China (Grants: 41422602 and 41373085) and the "Hundred Talents Program" of CAS.

CAM Photosynthesis in Submerged Aquatic Plants

USGS Publications Warehouse

Keeley, J.E.

1998-01-01

Crassulacean acid metabolism (CAM) is a CO2-concentrating mechanism selected in response to aridity in terrestrial habitats, and, in aquatic environments, to ambient limitations of carbon. Evidence is reviewed for its presence in five genera of aquatic vascular plants, including Isoe??tes, Sagittaria, Vallisneria, Crassula, and Littorella. Initially, aquatic CAM was considered by some to be an oxymoron, but some aquatic species have been studied in sufficient detail to say definitively that they possess CAM photosynthesis. CO2-concentrating mechanisms in photosynthetic organs require a barrier to leakage; e.g., terrestrial C4 plants have suberized bundle sheath cells and terrestrial CAM plants high stomatal resistance. In aquatic CAM plants the primary barrier to CO2 leakage is the extremely high diffusional resistance of water. This, coupled with the sink provided by extensive intercellular gas space, generates daytime CO2(Pi) comparable to terrestrial CAM plants. CAM contributes to the carbon budget by both net carbon gain and carbon recycling, and the magnitude of each is environmentally influenced. Aquatic CAM plants inhabit sites where photosynthesis is potentially limited by carbon. Many occupy moderately fertile shallow temporary pools that experience extreme diel fluctuations in carbon availability. CAM plants are able to take advantage of elevated nighttime CO2 levels in these habitats. This gives them a competitive advantage over non-CAM species that are carbon starved during the day and an advantage over species that expend energy in membrane transport of bicarbonate. Some aquatic CAM plants are distributed in highly infertile lakes, where extreme carbon limitation and light are important selective factors. Compilation of reports on diel changes in titratable acidity and malate show 69 out of 180 species have significant overnight accumulation, although evidence is presented discounting CAM in some. It is concluded that similar proportions of the aquatic and terrestrial floras have evolved CAM photosynthesis. Aquatic Isoe??tes (Lycophyta) represent the oldest lineage of CAM plants and cladistic analysis supports an origin for CAM in seasonal wetlands, from which it has radiated into oligotrophic lakes and into terrestrial habitats. Temperate Zone terrestrial species share many characteristics with amphibious ancestors, which in their temporary terrestrial stage, produce functional stomata and switch from CAM to C3. Many lacustrine Isoe??tes have retained the phenotypic plasticity of amphibious species and can adapt to an aerial environment by development of stomata and switching to C3. However, in some neotropical alpine species, adaptations to the lacustrine environment are genetically fixed and these constitutive species fail to produce stomata or loose CAM when artificially maintained in an aerial environment. It is hypothesized that neotropical lacustrine species may be more ancient in origin and have given rise to terrestrial species, which have retained most of the characteristics of their aquatic ancestry, including astomatous leaves, CAM and sediment-based carbon nutrition.

Prevention of clogging in a biological trickle-bed reactor removing toluene from contaminated air.

PubMed

Weber, F J; Hartmans, S

1996-04-05

Removal of organic compounds like toluene from waste gases with a trickle-bed reactor can result in clogging of the reactor due to the formation of an excessive amount of biomass. We therefore limited the amount of nutrients available for growth, to prevent clogging of the reactor. As a consequence of this nutrient limitation a lower removal rate was observed. However, when a fungal culture was used to inoculate the reactor, the toluene removal rate under nutrient limiting conditions was higher. Over a period of 375 days, an average removal rate of 27 g C/(m(3) h) was obtained with the reactor inoculated with the fungal culture. From the carbon balance over the reactor and the nitrogen availability it was concluded that, under these nutrient-limited conditions, large amounts of carbohydrates are probably formed. We also studied the application of a NaOH wash to remove excess biomass, as a method to prevent clogging. Under these conditions an average toluene removal rate of 35 g C/(m(3) h) was obtained. After about 50 days there was no net increase in the biomass content of the reactor. The amount of biomass which was formed in the reactor equaled the amount removed by the NaOH wash.

Molecular Dynamics Modeling of Carbon Nanotube Composite Fracture Using ReaxFF

NASA Technical Reports Server (NTRS)

Jensen, Benjamin D.; Wise, Kristopher E.; Odegard, Gregory M.

2016-01-01

Carbon nanotube (CNT) fiber reinforced composites with specific tensile strengths and moduli approaching those of aerospace grade carbon fiber composites have recently been reported. This achievement was enabled by the emerging availability of high N/tex yarns in kilometer-scale quantities. While the production of this yarn is an impressive advance, its strength is still much lower than that of the individual CNTs comprising the yarn. Closing this gap requires understanding load transfer between CNTs at the nanometer dimensional scale. This work uses reactive molecular dynamics simulations to gain an understanding at the nanometer scale of the key factors that determine CNT nanocomposite mechanical performance, and to place more realistic upper bounds on the target properties. While molecular dynamics simulations using conventional force fields can predict elastic properties, the ReaxFF reactive forcefield can also model fracture behavior because of its ability to accurately describe bond breaking and formation during a simulation. The upper and lower bounds of CNT composite properties are investigated by comparing systems composed of CNTs continuously connected across the periodic boundary with systems composed of finite length CNTs. These lengths, effectively infinite for the continuous tubes and an aspect ratio of 13 for the finite length case, result from practical limitations on the number of atoms that can be included in a simulation. Experimentally measured aspect ratios are typically on the order of 100,000, so the calculated results should represent upper and lower limits on experimental mechanical properties. Finally, the effect of various degrees of covalent crosslinking between the CNTs and amorphous carbon matrix is considered to identify the amount of CNT-matrix covalent bonding that maximizes overall composite properties.

Quantification of the proliferation of arbuscular mycorrhizal fungi in soil

NASA Astrophysics Data System (ADS)

Zhang, Ning; Lilje, Osu; McGee, Peter

2013-04-01

Good soil structure is important for sustaining agricultural production and preserving functions of the soil ecosystem. Soil aggregation is a critically important component of soil structure. Stable aggregates enable water infiltration, gas exchange for biological activities of plant roots and microorganisms, living space and surfaces for soil microbes, and contribute to stabilization of organic matter and storage of organic carbon (OC) in soil. Soil aggregation involves fine roots, organic matter and hyphae of arbuscular mycorrhizal (AM) fungi. Hyphal proliferation is essential for soil aggregation and sequestration of OC in soil. We do not yet have a mechanism to directly quantify the density of hyphae in soil. Organic materials and available phosphorus are two of the major factors that influence fungi in soil. Organic materials are a source of energy for saprotrophic microbes. Fungal hyphae increase in the presence of organic matter. Phosphorus is an important element usually found in ecosystems. The low availability of phosphorus limits the biological activity of microbes. AM fungi benefit plants by delivering phosphorus to the root system. However, the density and the length of hyphae of AM fungi do not appear to be influenced by available phosphorus. A number of indirect methods have been used to visualize distribution of fungi in soil. Reliable analyses of soil are limited because of soil characteristics. Soils are fragile, and fragility limits opportunity for non-destructive analysis. The soil ecosystem is complex. Soil particles are dense and the density obscures the visualization of fungal hyphae. Fungal hyphae are relatively fine and information at the small scale (<250µm) is key to understanding how fungi respond to environmental stimuli. This experiment tested whether organic carbon (starch), phosphorus (K2HPO4) and their mixture influences proliferation of hyphae of AM fungi. Hyphae were quantified in an artificial soil matrix using micro-computer aided tomography. Micro-computer aided tomography provides three dimensional images of hyphal ramification through electron lucent materials and enables the visualization and quantification of hyphae. Starch and the mixture of starch plus K2HPO4, stimulated hyphal proliferation, while K2HPO4 alone did not change the density of hyphae. The images also indicate that fungal hyphae attached to the surfaces of the particles rather than grow through the spaces between them. The capacity to quantify hyphae in three-dimensional space allows a wide range of questions to now be addressed. Apart from studying mechanisms of carbon turnover, more complex processes may now be considered. Soil is commonly thought of as a black box. That black box is now a shade of grey.

Soil Phosphorus Stoichiometry Drives Carbon Turnover Along a Soil C Gradient Spanning Mineral and Organic Soils Under Rice Cultivation

NASA Astrophysics Data System (ADS)

Hartman, W.; Ye, R.; Horwath, W. R.; Tringe, S. G.

2014-12-01

Soil carbon (C) cycling is linked to the availability of nutrients like nitrogen (N) and phosphorus (P). However, the role of soil P in influencing soil C turnover and accumulation is poorly understood, with most models focusing on C:N ratios based on the assumption that terrestrial ecosystems are N limited. To determine the effects of N and P availability on soil C turnover, we compared soil respiration over the course of a growing season in four adjacent rice fields with 5%, 10%, 20% and 25% soil C. In each of these fields, plots were established to test the effect of N additions on plant growth, using control and N addition treatments (80 kg N/ha urea). Although soil P was not manipulated in parallel, prior work has shown soil P concentrations decline markedly with increasing soil C content. Soil CO2 flux was monitored using static chambers at biweekly intervals during the growing season, along with porewater dissolved organic C and ammonium. Soils were collected at the end of the growing season, and tested for total C, N, and P, extractable N and P, pH, base cations and trace metals. Soil DNA was also extracted for 16S rRNA sequencing to profile microbial communities. Soil N additions significantly increased CO2 flux and soil C turnover (seasonal CO2 flux per unit soil C) in 5% and 10% C fields, but not in 20% or 25% C fields. Soil C content was closely related to soil N:P stoichiometry, with N:P ratios of ca. 12, 16, 24, and 56 respectively in the 5, 10, 20 and 25% C fields. Seasonal CO2 fluxes (per m2) were highest in 10% C soils. However, soil C turnover was inversely related to soil C concentrations, with the greatest C turnover at the lowest values of soil C. Soil C turnover showed stronger relationships with soil chemical parameters than seasonal CO2 fluxes alone, and the best predictors of soil C turnover were soil total and extractable N:P ratios, along with extractable P alone. Our results show that soil P availability and stoichiometry influence the turnover of soil C, even where primary producers are clearly limited by N. Prior work has suggested these contrasting patterns in nutrient limitation may arise due to stoichiometric differences among plants and soil microbes. We hypothesize that differences in soil carbon turnover may in part reflect shifts in metabolism of microbial communities associated with stoichiometric variation in soils.

Input of easily available organic C and N stimulates microbial decomposition of soil organic matter in arctic permafrost soil

PubMed Central

Wild, Birgit; Schnecker, Jörg; Alves, Ricardo J. Eloy; Barsukov, Pavel; Bárta, Jiří; Čapek, Petr; Gentsch, Norman; Gittel, Antje; Guggenberger, Georg; Lashchinskiy, Nikolay; Mikutta, Robert; Rusalimova, Olga; Šantrůčková, Hana; Shibistova, Olga; Urich, Tim; Watzka, Margarete; Zrazhevskaya, Galina; Richter, Andreas

2014-01-01

Rising temperatures in the Arctic can affect soil organic matter (SOM) decomposition directly and indirectly, by increasing plant primary production and thus the allocation of plant-derived organic compounds into the soil. Such compounds, for example root exudates or decaying fine roots, are easily available for microorganisms, and can alter the decomposition of older SOM (“priming effect”). We here report on a SOM priming experiment in the active layer of a permafrost soil from the central Siberian Arctic, comparing responses of organic topsoil, mineral subsoil, and cryoturbated subsoil material (i.e., poorly decomposed topsoil material subducted into the subsoil by freeze–thaw processes) to additions of 13C-labeled glucose, cellulose, a mixture of amino acids, and protein (added at levels corresponding to approximately 1% of soil organic carbon). SOM decomposition in the topsoil was barely affected by higher availability of organic compounds, whereas SOM decomposition in both subsoil horizons responded strongly. In the mineral subsoil, SOM decomposition increased by a factor of two to three after any substrate addition (glucose, cellulose, amino acids, protein), suggesting that the microbial decomposer community was limited in energy to break down more complex components of SOM. In the cryoturbated horizon, SOM decomposition increased by a factor of two after addition of amino acids or protein, but was not significantly affected by glucose or cellulose, indicating nitrogen rather than energy limitation. Since the stimulation of SOM decomposition in cryoturbated material was not connected to microbial growth or to a change in microbial community composition, the additional nitrogen was likely invested in the production of extracellular enzymes required for SOM decomposition. Our findings provide a first mechanistic understanding of priming in permafrost soils and suggest that an increase in the availability of organic carbon or nitrogen, e.g., by increased plant productivity, can change the decomposition of SOM stored in deeper layers of permafrost soils, with possible repercussions on the global climate. PMID:25089062

Switching between nitrogen and glucose limitation: Unraveling transcriptional dynamics in Escherichia coli.

PubMed

Löffler, Michael; Simen, Joana Danica; Müller, Jan; Jäger, Günter; Laghrami, Salaheddine; Schäferhoff, Karin; Freund, Andreas; Takors, Ralf

2017-09-20

Transcriptional control under nitrogen and carbon-limitation conditions have been well analyzed for Escherichia coli. However, the transcriptional dynamics that underlie the shift in regulatory programs from nitrogen to carbon limitation is not well studied. In the present study, cells were cultivated at steady state under nitrogen (ammonia)-limited conditions then shifted to carbon (glucose) limitation to monitor changes in transcriptional dynamics. Nitrogen limitation was found to be dominated by sigma 54 (RpoN) and sigma 38 (RpoS), whereas the "housekeeping" sigma factor 70 (RpoD) and sigma 38 regulate cellular status under glucose limitation. During the transition, nitrogen-mediated control was rapidly redeemed and mRNAs that encode active uptake systems, such as ptsG and manXYZ, were quickly amplified. Next, genes encoding facilitators such as lamB were overexpressed, followed by high affinity uptake systems such as mglABC and non-specific porins such as ompF. These regulatory programs are complex and require well-equilibrated and superior control. At the metabolome level, 2-oxoglutarate is the likely component that links carbon- and nitrogen-mediated regulation by interacting with major regulatory elements. In the case of dual glucose and ammonia limitation, sigma 24 (RpoE) appears to play a key role in orchestrating these complex regulatory networks. Copyright © 2017 Elsevier B.V. All rights reserved.

Estimating Global “Blue Carbon” Emissions from Conversion and Degradation of Vegetated Coastal Ecosystems

PubMed Central

Murray, Brian C.; Crooks, Stephen; Jenkins, W. Aaron; Sifleet, Samantha; Craft, Christopher; Fourqurean, James W.; Kauffman, J. Boone; Marbà, Núria; Megonigal, Patrick; Pidgeon, Emily; Herr, Dorothee; Gordon, David; Baldera, Alexis

2012-01-01

Recent attention has focused on the high rates of annual carbon sequestration in vegetated coastal ecosystems—marshes, mangroves, and seagrasses—that may be lost with habitat destruction (‘conversion’). Relatively unappreciated, however, is that conversion of these coastal ecosystems also impacts very large pools of previously-sequestered carbon. Residing mostly in sediments, this ‘blue carbon’ can be released to the atmosphere when these ecosystems are converted or degraded. Here we provide the first global estimates of this impact and evaluate its economic implications. Combining the best available data on global area, land-use conversion rates, and near-surface carbon stocks in each of the three ecosystems, using an uncertainty-propagation approach, we estimate that 0.15–1.02 Pg (billion tons) of carbon dioxide are being released annually, several times higher than previous estimates that account only for lost sequestration. These emissions are equivalent to 3–19% of those from deforestation globally, and result in economic damages of $US 6–42 billion annually. The largest sources of uncertainty in these estimates stems from limited certitude in global area and rates of land-use conversion, but research is also needed on the fates of ecosystem carbon upon conversion. Currently, carbon emissions from the conversion of vegetated coastal ecosystems are not included in emissions accounting or carbon market protocols, but this analysis suggests they may be disproportionally important to both. Although the relevant science supporting these initial estimates will need to be refined in coming years, it is clear that policies encouraging the sustainable management of coastal ecosystems could significantly reduce carbon emissions from the land-use sector, in addition to sustaining the well-recognized ecosystem services of coastal habitats. PMID:22962585

Water vs. carbon: An evaluation of SMAP soil moisture and OCO-2 solar-induced fluorescence to characterize global plant stress

NASA Astrophysics Data System (ADS)

Purdy, A. J.; Fisher, J.; Goulden, M.; Randerson, J. T.; Famiglietti, J. S.

2017-12-01

Plants link the carbon and water cycles through photosynthesis and evapotranspiration (ET). When plants take in CO2 for photosynthesis, water evaporates to the atmosphere. This exchange of carbon and water is sensitive to a number of environmental variables including: soil water availability, temperature, atmospheric water vapor, and radiation. When the atmospheric demand for water is high, plants avoid hydraulic failure by regulating the amount of water exiting leaves at the expense of inhibiting carbon uptake. Over time, stress caused by this response limits plant growth and can even result in death by carbon starvation. With increasing atmospheric demand for water, impending expansion of arid regions, and more frequent droughts, understanding how vegetation responds to regulate photosynthesis and ET is important to quantify potential feedbacks between the carbon and water cycles. Despite its importance, to what extent plants respond to stressful conditions is an open science question. An important step forward is to characterize the dominant controls in these stress events and identify geographic areas that are vulnerable to climate change. The 2015-2016 El Nino and subsequent 2016-2017 La Nina transition provides an opportunity to quantify the extent and magnitude of vegetation regulation of these carbon and water variables in response to changes in environmental conditions. We present results from a space-based analysis using global observations of solar induced fluorescence (SIF) from the Orbiting Carbon Observatory-2 (OCO-2), soil moisture from Soil Moisture Active Passive (SMAP), and two widely used ET models (PT-JPL and MOD-16) to characterize the dominant controls on gross primary production and ET.

Selection of pecan shell-based activated carbons for removal of organic and inorganic impurities from water.

PubMed

Niandou, Mohamed A S; Novak, Jeffrey M; Bansode, Rishipal R; Yu, Jianmei; Rehrah, Djaafar; Ahmedna, Mohamed

2013-01-01

Activated carbons are a byproduct from pyrolysis and have value as a purifying agent. The effectiveness of activated carbons is dependent on feedstock selection and pyrolysis conditions that modify their surface properties. Therefore, pecan shell-based activated carbons (PSACs) were prepared by soaking shells in 50% (v/v) HPO or 25 to 50% of KOH-NaHCO followed by pyrolysis at 400 to 700°C under a N atmosphere. Physically activated PSACs were produced by pyrolysis at 700°C under N followed by activation with steam or CO at 700 to 900°C. Physicochemical, surface, and adsorption properties of the PSACs were compared with two commercially available activated carbons. The average mass yield of PSACs with respect to the initial mass of the biomass was about 20 and 34% for physically activated and chemically activated carbons, respectively. Acid-activated carbons exhibited higher surface area, higher bulk density, and lower ash content compared with steam- or CO-activated carbons and the two commercial products. Base activation led to the development of biochar with moderate to high surface area with surface charges suitable for adsorption of anionic species. Regardless of the activation method, PSACs had high total surface area ranging from 400 to 1000 m g, better pore size distribution, and more surface charges than commercial samples. Our results also showed that PSACs were effective in removing inorganic contaminants such as Cu and NO as well as organic contaminants such as atrazine and metolachlor. This study showed that pyrolysis conditions and activation had a large influence on the PSAC's surface characteristics, which can limit its effectiveness as a custom sorbent for targeted water contaminants. Copyright © by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America, Inc.

Direct gas-solid carbonation of serpentinite residues in the absence and presence of water vapor: a feasibility study for carbon dioxide sequestration.

PubMed

Veetil, Sanoopkumar Puthiya; Pasquier, Louis-César; Blais, Jean-François; Cecchi, Emmanuelle; Kentish, Sandra; Mercier, Guy

2015-09-01

Mineral carbonation of serpentinite mining residue offers an environmentally secure and permanent storage of carbon dioxide. The strategy of using readily available mining residue for the direct treatment of flue gas could improve the energy demand and economics of CO2 sequestration by avoiding the mineral extraction and separate CO2 capture steps. The present is a laboratory scale study to assess the possibility of CO2 fixation in serpentinite mining residues via direct gas-solid reaction. The degree of carbonation is measured both in the absence and presence of water vapor in a batch reactor. The gas used is a simulated gas mixture reproducing an average cement flue gas CO2 composition of 18 vol.% CO2. The reaction parameters considered are temperature, total gas pressure, time, and concentration of water vapor. In the absence of water vapor, the gas-solid carbonation of serpentinite mining residues is negligible, but the residues removed CO2 from the feed gas possibly due to reversible adsorption. The presence of small amount of water vapor enhances the gas-solid carbonation, but the measured rates are too low for practical application. The maximum CO2 fixation obtained is 0.07 g CO2 when reacting 1 g of residue at 200 °C and 25 barg (pCO2 ≈ 4.7) in a gas mixture containing 18 vol.% CO2 and 10 vol.% water vapor in 1 h. The fixation is likely surface limited and restricted due to poor gas-solid interaction. It was identified that both the relative humidity and carbon dioxide-water vapor ratio have a role in CO2 fixation regardless of the percentage of water vapor.

Metal-organic frameworks as selectivity regulators for hydrogenation reactions

NASA Astrophysics Data System (ADS)

Zhao, Meiting; Yuan, Kuo; Wang, Yun; Li, Guodong; Guo, Jun; Gu, Lin; Hu, Wenping; Zhao, Huijun; Tang, Zhiyong

2016-11-01

Owing to the limited availability of natural sources, the widespread demand of the flavouring, perfume and pharmaceutical industries for unsaturated alcohols is met by producing them from α,β-unsaturated aldehydes, through the selective hydrogenation of the carbon-oxygen group (in preference to the carbon-carbon group). However, developing effective catalysts for this transformation is challenging, because hydrogenation of the carbon-carbon group is thermodynamically favoured. This difficulty is particularly relevant for one major category of heterogeneous catalyst: metal nanoparticles supported on metal oxides. These systems are generally incapable of significantly enhancing the selectivity towards thermodynamically unfavoured reactions, because only the edges of nanoparticles that are in direct contact with the metal-oxide support possess selective catalytic properties; most of the exposed nanoparticle surfaces do not. This has inspired the use of metal-organic frameworks (MOFs) to encapsulate metal nanoparticles within their layers or inside their channels, to influence the activity of the entire nanoparticle surface while maintaining efficient reactant and product transport owing to the porous nature of the material. Here we show that MOFs can also serve as effective selectivity regulators for the hydrogenation of α,β-unsaturated aldehydes. Sandwiching platinum nanoparticles between an inner core and an outer shell composed of an MOF with metal nodes of Fe3+, Cr3+ or both (known as MIL-101; refs 19, 20, 21) results in stable catalysts that convert a range of α,β-unsaturated aldehydes with high efficiency and with significantly enhanced selectivity towards unsaturated alcohols. Calculations reveal that preferential interaction of MOF metal sites with the carbon-oxygen rather than the carbon-carbon group renders hydrogenation of the former by the embedded platinum nanoparticles a thermodynamically favoured reaction. We anticipate that our basic design strategy will allow the development of other selective heterogeneous catalysts for important yet challenging transformations.

Metal-organic frameworks as selectivity regulators for hydrogenation reactions.

PubMed

Zhao, Meiting; Yuan, Kuo; Wang, Yun; Li, Guodong; Guo, Jun; Gu, Lin; Hu, Wenping; Zhao, Huijun; Tang, Zhiyong

2016-11-03

Owing to the limited availability of natural sources, the widespread demand of the flavouring, perfume and pharmaceutical industries for unsaturated alcohols is met by producing them from α,β-unsaturated aldehydes, through the selective hydrogenation of the carbon-oxygen group (in preference to the carbon-carbon group). However, developing effective catalysts for this transformation is challenging, because hydrogenation of the carbon-carbon group is thermodynamically favoured. This difficulty is particularly relevant for one major category of heterogeneous catalyst: metal nanoparticles supported on metal oxides. These systems are generally incapable of significantly enhancing the selectivity towards thermodynamically unfavoured reactions, because only the edges of nanoparticles that are in direct contact with the metal-oxide support possess selective catalytic properties; most of the exposed nanoparticle surfaces do not. This has inspired the use of metal-organic frameworks (MOFs) to encapsulate metal nanoparticles within their layers or inside their channels, to influence the activity of the entire nanoparticle surface while maintaining efficient reactant and product transport owing to the porous nature of the material. Here we show that MOFs can also serve as effective selectivity regulators for the hydrogenation of α,β-unsaturated aldehydes. Sandwiching platinum nanoparticles between an inner core and an outer shell composed of an MOF with metal nodes of Fe 3+ , Cr 3+ or both (known as MIL-101; refs 19, 20, 21) results in stable catalysts that convert a range of α,β-unsaturated aldehydes with high efficiency and with significantly enhanced selectivity towards unsaturated alcohols. Calculations reveal that preferential interaction of MOF metal sites with the carbon-oxygen rather than the carbon-carbon group renders hydrogenation of the former by the embedded platinum nanoparticles a thermodynamically favoured reaction. We anticipate that our basic design strategy will allow the development of other selective heterogeneous catalysts for important yet challenging transformations.

Elastic limit and microplastic response of hardened steels

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zaccone, M.A.; Krauss, G.

Tempered martensite-retained austenite microstructures were produced by direct quenching a series of 41XX medium carbon steels, direct quenching and reheating a series of five 0.8C-Cr-Ni-Mo steels and intercritically austenitizing at various temperatures, and quenching a SAE 52100 steel. All specimens were tempered either at 150 C or at 200 C. Specimens were subjected to compression and tension testing in the microstrain regime to determine the elastic limits and microplastic response of the microstructures. The retained austenite and matrix carbon content of the intercritically austenized specimens were measured by X-ray diffraction and Mossbauer spectroscopy. The elastic limit of the microstructures decreasesmore » with increasing amounts of retained austenite. Refining of the austenite distribution increases the elastic limit. Low elastic limits are mainly due to low flow stresses in the austenite and not internal stresses. The elastic limit correlates with the largest austenite free-mean path by a Hall-Petch type equation. The elastic limit increases with decreasing intercritical austenitizing temperature in the SAE 52100 due to a lower carbon content in the matrix reducing the retained austenite levels and retained carbides that refine grain size and, therefore, the austenite distribution in quenched specimens. In the microplastic region, the strain is accommodated by successively smaller austenite regions until the flow strength matches that of the martensite. Reheating and quenching refines the microstructure and renders the austenite unstable in the microplastic regime, causing transformation of the austenite to martensite by a strain-induced mechanism. The transformation of austenite to martensite occurs by a stress-assisted mechanism in medium carbon steels. The low elastic limits in medium carbon steels were due to the inability of the strain from the stress-assisted transformation to balance the plastic strain accumulated in the austenite.« less

Applications for carbon fibre recovered from composites

NASA Astrophysics Data System (ADS)

Pickering; Liu, Z.; Turner, TA; Wong, KH

2016-07-01

Commercial operations to recover carbon fibre from waste composites are now developing and as more recovered fibre becomes available new applications for recovered fibre are required. Opportunities to use recovered carbon fibre as a structural reinforcement are considered involving the use of wet lay processes to produce nonwoven mats. Mats with random in-plane fibre orientation can readily be produced using existing commercial processes. However, the fibre volume fraction, and hence the mechanical properties that can be achieved, result in composites with limited mechanical properties. Fibre volume fractions of 40% can be achieved with high moulding pressures of over 100 bar, however, moulding at these pressures results in substantial fibre breakage which reduces the mean fibre length and the properties of the composite manufactured. Nonwoven mats made from aligned, short carbon fibres can achieve higher fibre volume fractions with lower fibre breakage even at high moulding pressure. A process for aligning short fibres is described and a composite of over 60% fibre volume fraction has been manufactured at a pressures up to 100 bar with low fibre breakage. Further developments of the alignment process have been undertaken and a composite of 46% fibre volume fraction has been produced moulded at a pressure of 7 bar in an autoclave, exhibiting good mechanical properties that compete with higher grade materials. This demonstrates the potential for high value applications for recovered carbon fibre by fibre alignment.

Carbon allocation in forest ecosystems

Treesearch

Creighton M. Litton; James W. Raich; Michael G. Ryan

2007-01-01

Carbon allocation plays a critical role in forest ecosystem carbon cycling. We reviewed existing literature and compiled annual carbon budgets for forest ecosystems to test a series of hypotheses addressing the patterns, plasticity, and limits of three components of allocation: biomass, the amount of material present; flux, the flow of carbon to a component per unit...

Understanding the Impact of Land Management on Carbon Losses from Peatlands

NASA Astrophysics Data System (ADS)

Savage, A.; Holden, J.; Wainwright, J.

2010-05-01

British peatlands have historically been managed in many different ways to provide an income for rural communities. Such practices involve heather burning on grouse shooting estates, sheep grazing, drainage to increase the area of land available for agriculture and afforestation. Carbon budget calculations for unmanaged peatlands have demonstrated that peatlands are carbon sinks. At present, little is known about how management affects carbon stocks, and whether one strategy might be favoured over another in the future, from a carbon stock preservation perspective. As the need to safeguard carbon stocks rises up the political agenda, questions are being asked about how peatlands should be managed to limit carbon losses. Carbon cycling in peat is governed by four drivers (Laiho, 2006), environmental conditions (e.g. temperature, water table level), substrate quality (e.g. how recalcitrant the peat is), nutrients (e.g. nitrogen required to synthesis the carbon stocks) and microbial community (e.g. are the microbes present able to utilise the available substrate). Changes in one or more of these drivers will influence the carbon budget of a peatland. How land management influences these drivers is unclear at present. Carbon budget calculations carried out by Worrall et al. (2003 and 2009) indicate that carbon dioxide and dissolved organic carbon (DOC) account for the greatest losses of carbon from peatland systems. If climate change predictions are realised, peatlands are expected to become sources of carbon as rising temperatures and falling water tables will result in increased rates of carbon mineralisation and subsequent losses of carbon. By investigating the influence of land management on these key carbon loss pathways, more accurate predictions of the effects of climate change on UK peatlands can be made. A field study was carried out in the British uplands to determine how carbon losses vary between differently managed peatlands, and to identify some of the underlying causes for such variations. The study focused on three of the driving factors identified by Laiho (2006): substrate quality, environmental conditions and nutrients. In addition, the physical properties of the peat - bulk density and air filled porosity which will control rates of gas and water movement within the peat profile, were studied. This paper will present the results of the work which was carried out at the Moor House, National Nature Reserve. The work involved collection of peat cores from burnt, grazed, drained, afforested and unmanaged areas of peat. The chemical and physical properties of the peat that are relevant to carbon cycling (e.g. nutrients, metals, substrate quality, air filled porosity) were analysed and compared between sites, and correlated with carbon losses which were measured on a fortnightly basis; and meteorological and hydrological data which were collected throughout the study period. Based on these results, suggestions for peatland management strategies that preserve carbon stocks will be presented. Laiho, R. (2006) "Decomposition in peatlands: Reconciling seemingly contrasting results on the impacts of lowered water levels." Soil Biology & Biochemistry 38(8): 2011-2024. Worrall, F. et al. (2003) "Carbon budget for a British upland peat catchment." Science of the Total Environment 312(1-3): 133-146. Worrall, F. et al. (2009) "The Multi-Annual Carbon Budget of a Peat-Covered Catchment" Science of the Total Environment 407: 4084-4094

Weldability of an iron meteorite by Friction Stir Spot Welding: A contribution to in-space manufacturing

NASA Astrophysics Data System (ADS)

Evans, William Todd; Neely, Kelsay E.; Strauss, Alvin M.; Cook, George E.

2017-11-01

Friction Stir Welding has been proposed as an efficient and appropriate method for in space welding. It has the potential to serve as a viable option for assembling large scale space structures. These large structures will require the use of natural in space materials such as those available from iron meteorites. Impurities present in most iron meteorites limit its ability to be welded by other space welding techniques such as electron beam laser welding. This study investigates the ability to weld pieces of in situ Campo del Cielo meteorites by Friction Stir Spot Welding. Due to the rarity of the material, low carbon steel was used as a model material to determine welding parameters. Welded samples of low carbon steel, invar, and Campo del Cielo meteorite were compared and found to behave in similar ways. This study shows that meteorites can be Friction Stir Spot Welded and that they exhibit properties analogous to that of FSSW low carbon steel welds. Thus, iron meteorites can be regarded as another viable option for in-space or Martian construction.

Diet and mobility in Early Medieval Bavaria: a study of carbon and nitrogen stable isotopes.

PubMed

Hakenbeck, Susanne; McManus, Ellen; Geisler, Hans; Grupe, Gisela; O'Connell, Tamsin

2010-10-01

This study investigates patterns of mobility in Early Medieval Bavaria through a combined study of diet and associated burial practice. Carbon and nitrogen isotope ratios were analyzed in human bone samples from the Late Roman cemetery of Klettham and from the Early Medieval cemeteries of Altenerding and Straubing-Bajuwarenstrasse. For dietary comparison, samples of faunal bone from one Late Roman and three Early Medieval settlement sites were also analyzed. The results indicate that the average diet was in keeping with a landlocked environment and fairly limited availability of freshwater or marine resources. The diet appears not to have changed significantly from the Late Roman to the Early Medieval period. However, in the population of Altenerding, there were significant differences in the diet of men and women, supporting a hypothesis of greater mobility among women. Furthermore, the isotopic evidence from dietary outliers is supported by "foreign" grave goods and practices, such as artificial skull modification. These results reveal the potential of carbon and nitrogen isotope analysis for questions regarding migration and mobility. © 2010 Wiley-Liss, Inc.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xiong, W; Zhou, Yunshen; Hou, Wenjia

Direct formation of graphene with controlled number of graphitic layers on dielectric surfaces is highly desired for practical applications. Despite significant progress achieved in understanding the formation of graphene on metallic surfaces through chemical vapor deposition (CVD) of hydrocarbons, very limited research is available elucidating the graphene formation process via rapid thermal processing (RTP) of solid-state amorphous carbon, through which graphene is formed directly on dielectric surfaces accompanied by autonomous nickel evaporation. It is suggested that a metastable hexagonal nickel carbide (Ni 3C) intermediate phase plays a critical role in transforming amorphous carbon to 2D crystalline graphene and contributing tomore » the autonomous Ni evaporation. Temperature resolved carbon and nickel evolution in the RTP process is investigated using Auger electron spectroscopic (AES) depth profiling and glancing-angle X-ray diffraction (GAXRD). Formation, migration and decomposition of the hexagonal Ni 3C are confirmed to be responsible for the formation of graphene and the evaporation of Ni at 1100 °C. The Ni 3C-assisted graphene formation mechanism expands the understanding of Ni-catalyzed graphene formation, and provides insightful guidance for controlled growth of graphene through the solid-state transformation process.« less

An evaluation of the impact of forest biomass harvest for biofuels on carbon storage in the US west coast states under different management scenarios

NASA Astrophysics Data System (ADS)

Hudiburg, T. M.; Law, B. E.

2009-12-01

Mitigation strategies to reduce fossil fuel emissions of carbon dioxide have lead to investigation of alternative sources of fuels. National and state forest policies have been implemented to both reduce risk of wildfire and promote use of forest biomass as a secondary biofuels energy source. However, the cost and biomass availability have been estimated without quantifying the impact on current and future terrestrial carbon balances. This study uses a combination of Federal Inventory Analysis data (FIA) and supplementary plot data for Washington, Oregon and California to quantify the current forest carbon stocks, net ecosystem production (NEP), and net biome production (NBP = NEP - removals) for the period from 2001-2006. Varying management treatments were applied to determine the net cost, carbon debt, and biofuels energy potential. The treatments were designed to meet multiple objectives emphasizing carbon storage, economic gain, or energy production. The hazardous fuels reduction treatment minimizes carbon loss by only harvesting biomass in forested areas classified by moderate to high risk fire condition classes (FRCC class). This scenario assumes no additional harvest in ecoregions characterized by long fire return intervals (>100 years) such as the Coast Range and the West Cascades and limits removals to an 18 in diameter at breast height (DBH). The energy production treatment maximizes biomass removal by harvesting areas regardless of FRCC class and allows removals up to a 24 inch DBH. Statewide estimates of carbon for 2001-2006 prior to harvest scenarios for California, Oregon, and Washington respectively are as follows: 1) Total land-based carbon stocks (excluding soils) averages 1680, 1663, and 1278 Tg C; 2) NEP is positive in most ecoregions averaging 213, 180, and 191 g C m-2 yr-1; 3) Actual harvest removals averaged 2.7, 6.5, and 5.1 Tg C yr-1 for the same period. In Oregon, the amount of biomass available for biofuels varies from 128 g C m-2 in the hazardous fuels reduction treatment versus 185 g C m-2 in the energy production treatment. Removal of this biomass over the next 20 years is estimated to result in an additional 4 Tg C yr-1 (a 60% increase) in harvest removals for the hazardous fuels reduction treatment and an additional 14 Tg C yr-1 (216% increase) for the energy production treatment. Even in a minimal removals scenario and assuming no other disturbance losses (i.e. insects and fire), Oregon forest NBP will be significantly reduced with the potential to become a carbon source.