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Soil aggregate stabilization and carbon sequestration: Feedbacks through organomineral associations

Description: Primary production (specifically, the rate and quality of C transfer below ground) and soil microbial activity (specifically, the rates of C transformation and decay) are recognized as the overall biological processes governing soil organic C (SOC) dynamics. These two processes and, hence, SOC cycling and storage are controlled by complex underlying biotic and abiotic interactions and feedbacks, most of which can be tied in one way or another to the influences of the five state factors related to soil formation, and many of which are sensitive to management practices. Overall, C input rates and quality are largely dependent on climate (especially temperature and precipitation), vegetation type and landscape, soil type, and management practices. Decomposition processes and turnover rates, however, are greatly influenced by climate, the type and quality of organic matter (e.g., N content and the ratios of C:N and lignin:N), chemical or physicochemical associations of organic matter (OM) with soil mineral components, and the location of OM within the soil.
Date: December 31, 1996
Creator: Jastrow, J.D. & Miller, R.M.
Partner: UNT Libraries Government Documents Department

Mechanisms of dissolved organic carbon cycling in an ocean margin. Final technical report

Description: Dissolved organic carbon (DOC) is the largest reservoir of organic carbon in the ocean, and the objectives of this project were to investigate the mechanisms and pathways of DOC formation and consumption in seawater. Carbohydrates are the most abundant form of DOC, and this project included measurements of dissolved carbohydrates as well as DOC to help delineate the cycling of DOC. Many of the methods and approaches for investigating DOC production were developed as part of this project.
Date: November 24, 1997
Creator: Benner, R.
Partner: UNT Libraries Government Documents Department

DEVELOPMENT OF A CARBON MANAGEMENT GEOGRAPHIC INFORMATION SYSTEM (GIS) FOR THE UNITED STATES

Description: The Lab for Energy and Environment (LFEE) at MIT is developing a Geographic Information System (GIS) for carbon management. The GIS will store, integrate, and manipulate information relating to the components of carbon management systems. Additionally, the GIS can be used to interpret and analyze the effect of developing these systems. In the first year of this three year project, we focused on two tasks: (1) specifying the system design--defining in detail the GIS data requirements, the types of analyses that can be conducted, and the forms of output we will produce, as well as designing the computer architecture of the GIS and (2) creating the ''core'' datasets--identifying data sources and converting them into a form accessible by the GIS.
Date: March 1, 2004
Creator: Herzog, Howard J.
Partner: UNT Libraries Government Documents Department

Models for evaluation of energy technology and policy options to maximize low carbon source penetration in the United States energy supply.

Description: An initial version of a Systems Dynamics (SD) modeling framework was developed for the analysis of a broad range of energy technology and policy questions. The specific question selected to demonstrate this process was 'what would be the carbon and import implications of expanding nuclear electric capacity to provide power for plug in hybrid vehicles?' Fifteen SNL SD energy models were reviewed and the US Energy and Greenhouse gas model (USEGM) and the Global Nuclear Futures model (GEFM) were identified as the basis for an initial modeling framework. A basic U.S. Transportation model was created to model U.S. fleet changes. The results of the rapid adoption scenario result in almost 40% of light duty vehicles being PHEV by 2040 which requires about 37 GWy/y of additional electricity demand, equivalent to about 25 new 1.4 GWe nuclear plants. The adoption rate of PHEVs would likely be the controlling factor in achieving the associated reduction in carbon emissions and imports.
Date: December 1, 2009
Creator: Pickard, Paul S.; Kataoka, Dawn; Reno, Marissa Devan; Malczynski, Leonard A.; Peplinski, William J.; Roach, Jesse D. et al.
Partner: UNT Libraries Government Documents Department

Assessment of Contribution of Contemporary Carbon Sources to Size-Fractionated Particulate Matter and Time-Resolved Bulk Particulate Matter Using the Measurement of Radiocarbon

Description: This study was motivated by a desire to improve understanding of the sources contributing to the carbon that is an important component of airborne particulate matter (PM). The ultimate goal of this project was to lay a ground work for future tools that might be easily implemented with archived or routinely collected samples. A key feature of this study was application of radiocarbon measurement that can be interpreted to indicate the relative contributions from fossil and non-fossil carbon sources of atmospheric PM. Size-resolved PM and time-resolved PM{sub 10} collected from a site in Sacramento, CA in November 2007 (Phase I) and March 2008 (Phase II) were analyzed for radiocarbon and source markers such as levoglucosan, cholesterol, and elemental carbon. Radiocarbon data indicates that the contributions of non-fossil carbon sources were much greater than that from fossil carbon sources in all samples. Radiocarbon and source marker measurements confirm that a greater contribution of non-fossil carbon sources in Phase I samples was highly likely due to residential wood combustion. The present study proves that measurement of radiocarbon and source markers can be readily applied to archived or routinely collected samples for better characterization of PM sources. More accurate source apportionment will support ARB in developing more efficient control strategies.
Date: April 16, 2009
Creator: Hwang, H M; Young, T M & Buchholz, B A
Partner: UNT Libraries Government Documents Department

Southeast Regional Carbon Sequestration Partnership (SECARB)

Description: Work during the first six months of the project mainly concentrated on contracts execution and collection of data to characterize the region and input of that data into the geographical information system (GIS) system. Data was collected for source characterization, transportation options and terrestrial options. In addition, discussions were held to determine the extent of the geologic information that would be needed for the project. In addition, activities associated with the regulatory, permitting and safety issues were completed. Outreach activities are in the formative stages.
Date: March 31, 2004
Creator: Baskin, Kathryn A.
Partner: UNT Libraries Government Documents Department

Relative Contributions of Fossil and Contemporary Carbon sources to PM 2.5 Aerosols at Nine IMPROVE Network Sites

Description: Particulate matter aerosols contribute to haze diminishing vistas and scenery at National Parks and Wilderness Areas within the United States. To increase understanding of the sources of carbonaceous aerosols at these settings, the total carbon loading and {sup 14}C/C ratio of PM 2.5 aerosols at nine IMPROVE (Interagency Monitoring for Protection Of Visual Environments) network sites were measured. Aerosols were collected weekly in the summer and winter at one rural site, two urban sites, five sites located in National Parks and one site located in a Wildlife Preserve. The carbon measurements together with the absence of {sup 14}C in fossil carbon materials and the known {sup 14}C/C levels in contemporary carbon materials were used to derive contemporary and fossil carbon contents of the particulate matter. Contemporary and fossil carbon aerosol loadings varied across the sites and suggest different percentages of carbon source inputs. The urban sites had the highest fossil carbon loadings that comprised around 50% of the total carbon aerosol loading. The Wildlife Preserve and National Park sites together with the rural site had much lower fossil carbon loading components. At these sites, variations in the total carbon aerosol loading were dominated by non-fossil carbon sources. This suggests that reduction of anthroprogenic sources of fossil carbon aerosols may result in little decrease in carbonaceous aerosol loading at many National Parks and rural areas.
Date: June 26, 2006
Creator: Bench, G; Fallon, S; Schichtel, B; Malm, W & McDade, C
Partner: UNT Libraries Government Documents Department

Worldwide organic soil carbon and nitrogen data

Description: The objective of the research presented in this package was to identify data that could be used to estimate the size of the soil organic carbon pool under relatively undisturbed soil conditions. A subset of the data can be used to estimate amounts of soil carbon storage at equilibrium with natural soil-forming factors. The magnitude of soil properties so defined is a resulting nonequilibrium values for carbon storage. Variation in these values is due to differences in local and geographic soil-forming factors. Therefore, information is included on location, soil nitrogen content, climate, and vegetation along with carbon density and variation.
Date: September 1, 1986
Creator: Zinke, P.J.; Stangenberger, A.G.; Post, W.M.; Emanual, W.R. & Olson, J.S.
Partner: UNT Libraries Government Documents Department

PLAINS CO2 REDUCTION PARTNERSHIP

Description: The PCOR Partnership is off to a very exciting and ambitious start. Task 1 activities have included the planning and execution of an internal kickoff meeting, participation in the DOE's national kickoff meeting, and the planning and execution of the first meeting of the PCOR Partnership at the Energy & Environmental Research Center (EERC). Task 2 activities have focused on developing effective and critical partnerships. A plan has been developed to utilize Dakota Gasification Company's (DGC) experience and data with respect to their participation in the enhanced oil recovery project at Weyburn, Saskatchewan. A solid line of communication has been developed with the Interstate Oil & Gas Compact Commission (IOGCC) for the mutual benefit of the PCOR Partnership and IOGCC's compensatory efforts. Task 3 activities have been focused on developing a foundation of background materials in order to avoid a duplication of efforts and provide the best outreach and educational materials possible. Progress in Task 4, Characterization and Evaluation, has included the development of a database format, the preliminary collection of data regarding CO{sub 2} sources and sinks, and data on the performance and costs for CO{sub 2} separation, capture, and treatment to prepare the fluid for pipeline transportation. Task 5 activities have resulted in a conceptual model for screening and qualitatively assessing sequestration options. Task 5 activities have also been useful in structuring data collection and other activities in Tasks 2, 3, and 5.
Date: January 1, 2004
Creator: Erickson, Thomas A.
Partner: UNT Libraries Government Documents Department

Strategies for enhancing the effectiveness of metagenomic-based enzyme discovery in lignocellulytic microbial communities

Description: Producing cellulosic biofuels from plant material has recently emerged as a key U.S. Department of Energy goal. For this technology to be commercially viable on a large scale, it is critical to make production cost efficient by streamlining both the deconstruction of lignocellulosic biomass and fuel production. Many natural ecosystems efficiently degrade lignocellulosic biomass and harbor enzymes that, when identified, could be used to increase the efficiency of commercial biomass deconstruction. However, ecosystems most likely to yield relevant enzymes, such as tropical rain forest soil in Puerto Rico, are often too complex for enzyme discovery using current metagenomic sequencing technologies. One potential strategy to overcome this problem is to selectively cultivate the microbial communities from these complex ecosystems on biomass under defined conditions, generating less complex biomass-degrading microbial populations. To test this premise, we cultivated microbes from Puerto Rican soil or green waste compost under precisely defined conditions in the presence dried ground switchgrass (Panicum virgatum L.) or lignin, respectively, as the sole carbon source. Phylogenetic profiling of the two feedstock-adapted communities using SSU rRNA gene amplicon pyrosequencing or phylogenetic microarray analysis revealed that the adapted communities were significantly simplified compared to the natural communities from which they were derived. Several members of the lignin-adapted and switchgrass-adapted consortia are related to organisms previously characterized as biomass degraders, while others were from less well-characterized phyla. The decrease in complexity of these communities make them good candidates for metagenomic sequencing and will likely enable the reconstruction of a greater number of full length genes, leading to the discovery of novel lignocellulose-degrading enzymes adapted to feedstocks and conditions of interest.
Date: March 1, 2010
Creator: DeAngelis, K.M.; Gladden, J.G.; Allgaier, M.; D'haeseleer, P.; Fortney, J.L.; Reddy, A. et al.
Partner: UNT Libraries Government Documents Department

Climate implications of carbonaceous aerosols: An aerosol microphysical study using the GISS/MATRIX climate model

Description: Recently, attention has been drawn towards black carbon aerosols as a likely short-term climate warming mitigation candidate. However the global and regional impacts of the direct, cloud-indirect and semi-direct forcing effects are highly uncertain, due to the complex nature of aerosol evolution and its climate interactions. Black carbon is directly released as particle into the atmosphere, but then interacts with other gases and particles through condensation and coagulation processes leading to further aerosol growth, aging and internal mixing. A detailed aerosol microphysical scheme, MATRIX, embedded within the global GISS modelE includes the above processes that determine the lifecycle and climate impact of aerosols. This study presents a quantitative assessment of the impact of microphysical processes involving black carbon, such as emission size distributions and optical properties on aerosol cloud activation and radiative forcing. Our best estimate for net direct and indirect aerosol radiative forcing change is -0.56 W/m{sup 2} between 1750 and 2000. However, the direct and indirect aerosol effects are very sensitive to the black and organic carbon size distribution and consequential mixing state. The net radiative forcing change can vary between -0.32 to -0.75 W/m{sup 2} depending on these carbonaceous particle properties. Assuming that sulfates, nitrates and secondary organics form a coating shell around a black carbon core, rather than forming a uniformly mixed particles, changes the overall net radiative forcing from a negative to a positive number. Black carbon mitigation scenarios showed generally a benefit when mainly black carbon sources such as diesel emissions are reduced, reducing organic and black carbon sources such as bio-fuels, does not lead to reduced warming.
Date: April 9, 2010
Creator: Bauer, Susanne E.; Menon, Surabi; Koch, Dorothy; Bond, Tami & Tsigaridis, Kostas
Partner: UNT Libraries Government Documents Department

Implications of Wall Recycling and Carbon Source Locations on Core Plasma Fueling and Impurity Content in DIII-D

Description: Measurement and modeling of the 2-D poloidal D{alpha} intensity distribution in DIII-D low and medium density L-mode and ELMy H-mode plasmas indicate that hydrogen neutrals predominantly fuel the core from the divertor X-point region. The 2-D distribution of neutral deuterium and low-charge-state carbon were measured in the divertor and the high-field side midplane scrape-off layer (SOL) using tangentially viewing cameras. The emission in the high-field SOL at the equatorial plane was found to be three to four orders of magnitude lower than at the strike points in the divertor, suggesting a strong divertor particle source. Modeling using the UEDGE/DEGAS codes predicted the poloidal fueling distribution to be dependent on the direction of the ion Bx{Delta}B drift. In plasmas with the Bx{Delta}B drift into the divertor stronger fueling from the inner divertor than from the outer is predicted, due to a lower-temperature and higher-density plasma in the inner leg. UEDGE simulations with carbon produced by both physical and chemical sputtering at the divertor plates and walls only are in agreement with a large set of diagnostic data. The simulations indicate flow reversal in the inner divertor that augments the leakage of carbon ions from the divertor into the core.
Date: October 14, 2004
Creator: Groth, M; Porter, G D; Boedo, J A; Brooks, N H; Fenstermacher, M E; Groebner, R J et al.
Partner: UNT Libraries Government Documents Department

Top Value-Added Chemicals from Biomass - Volume II—Results of Screening for Potential Candidates from Biorefinery Lignin

Description: This report evaluates lignin’s role as a renewable raw material resource. Opportunities that arise from utilizing lignin fit into one of three categories: 1)power, fuel and syngas (generally near-term opportunities) 2) macromolecules (generally medium-term opportunities) 3) aromatics and miscellaneous monomers (long-term opportunities). Biorefineries will receive and process massive amounts of lignin. For this reason, how lignin can be best used to support the economic health of the biorefinery must be defined. An approach that only considers process heat would be shortsighted. Higher value products present economic opportunities and the potential to significantly increase the amount of liquid transportation fuel available from biomass. In this analysis a list of potential uses of lignin was compiled and sorted into “product types” which are broad classifications (listed above as power—fuel—syngas; macromolecules; and aromatics). In the first “product type” (power—fuel—gasification) lignin is used purely as a carbon source and aggressive means are employed to break down its polymeric structure. In the second “product type” (macromolecules) the opposite extreme is considered and advantage of the macromolecular structure imparted by nature is retained in high-molecular weight applications. The third “product type” (aromatics) lies somewhere between the two extremes and employs technologies that would break up lignin’s macromolecular structure but maintain the aromatic nature of the building block molecules. The individual opportunities were evaluated based on their technical difficulty, market, market risk, building block utility, and whether a pure material or a mixture would be produced. Unlike the “Sugars Top 10” report it was difficult to identify the ten best opportunities, however, the potential opportunities fell nicely into near-, medium- and long-term opportunities. Furthermore, the near-, medium- and long-term opportunities roughly align with the three “product types.” From this analysis a list of technical barriers was developed which can be used to identify research needs. Lignin presents ...
Date: October 1, 2007
Creator: Holladay, John E.; White, James F.; Bozell, Joseph J. & Johnson, David
Partner: UNT Libraries Government Documents Department

Simulation of the carbon cycle in the oceans. Annual report, Third year, September 15, 1992--September 14, 1993

Description: In this report, the authors conclude that the average oceanic uptake of anthropogenic CO{sub 2}, as determined from four different ocean models and normalized to the observed mean penetration depth of bomb{sup {minus}1} {sup 4}C (analogue to anthropogenic CO{sub 2}), is 2.0 {plus_minus} 0.5 GtC/yr (decade 1980--1989). This oceanic uptake plus the year-to-year growth of the atmospheric CO{sub 2} content together are less by 1.8 {plus_minus} 1.2 GtC/yr than the estimated anthropogenic CO{sub 2} emissions from fossil fuels and land use.
Date: October 1, 1993
Creator: Siegenthaler, U.
Partner: UNT Libraries Government Documents Department

Seasonal study of carbon dioxide in the southern extreme of the pacific sector, Antarctic Ocean. Progress report

Description: This report describes the progress made during the six-month period between December 1, 1993, when this grant was awarded, and May 1, 1994. The major aim of this investigation is to measure the distribution of the total CO{sub 2} concentration and pCO{sub 2} in seawater in the Pacific sector of the extreme Southern Ocean as far south as 78{degrees}S. The areas investigated include the continental shelf areas in the Ross, Amundsen and Bellingshausen Seas ad the off-shore deep water areas as far north as 67{degrees}S. The measurements were made aboard the R/VIB Nathaniel B. Palmer between February 14, 1994 and April 5, 1994, and the preliminary results are briefly described in this report. This expedition constitutes the first of a pair expeditions. The first is designed investigate oceanic CO{sub 2} sink/source conditions during the austral summer The second expedition, which is designed for the following winter, has been scheduled for September, 1994.
Date: May 5, 1994
Creator: Takahashi, Taro; Goddard, J. G.; Rubin, S. I. & Breger, D.
Partner: UNT Libraries Government Documents Department

Burial, remineralization and utilization of organic matter at the seafloor under a strong western boundary current. Annual progress report, 1 May 1993--30 April 1994

Description: The overall objectives of this project are to quantify the rates of organic carbon export from the southern mid-Atlantic Bight and to quantify the rates at which carbon is exchanged between the inorganic and organic pools within the bottom sediments. The strategy for achieving these goals is to quantify the rates of benthic exchange and burial of bioactive elements including oxidants (such as oxygen, nitrate, sulfate), micronutrient, and carbon system parameters on the continental shelf, slope and rise regions within and adjacent to the south portion of the mid-Atlantic Bight. This information, in conjunction with burial rates provided by others in this program, will be used to determine the locations and rates of export and oxidative loss of organic matter from the shelf. During this past funding period, three expeditions were completed to the study region, successfully conducting 6 in situ benthic flux chamber experiments. The results provide an initial assessment of the magnitude and location of organic matter export from the southern Middle Atlantic Bight shelf and of the importance of this region as a supplier of organic carbon to the North Atlantic Ocean Basin.
Date: December 30, 1993
Creator: Jahnke, R.A.
Partner: UNT Libraries Government Documents Department

SiC-BASED HYDROGEN SELECTIVE MEMBRANES FOR WATER-GAS-SHIFT REACTION

Description: This technical report summarizes our activities conducted in Yr II. In Yr I we successfully demonstrated the feasibility of preparing the hydrogen selective SiC membrane with a chemical vapor deposition (CVD) technique. In addition, a SiC macroporous membrane was fabricated as a substrate candidate for the proposed SiC membrane. In Yr II we have focused on the development of a microporous SiC membrane as an intermediate layer between the substrate and the final membrane layer prepared from CVD. Powders and supported thin silicon carbide films (membranes) were prepared by a sol-gel technique using silica sol precursors as the source of silicon, and phenolic resin as the source of carbon. The powders and films were prepared by the carbothermal reduction reaction between the silica and the carbon source. The XRD analysis indicates that the powders and films consist of SiC, while the surface area measurement indicates that they contain micropores. SEM and AFM studies of the same films also validate this observation. The powders and membranes were also stable under different corrosive and harsh environments. The effects of these different treatments on the internal surface area, pore size distribution, and transport properties, were studied for both the powders and the membranes using the aforementioned techniques and XPS. Finally the SiC membrane materials are shown to have satisfactory hydrothermal stability for the proposed application. In Yr III, we will focus on the demonstration of the potential benefit using the SiC membrane developed from Yr I and II for the water-gas-shift (WGS) reaction.
Date: October 16, 2001
Creator: Liu, Paul K.T.
Partner: UNT Libraries Government Documents Department

Nutrient limitation and microbially mediated chemistry: studies using tuff inoculum obtained from the Exploratory Studies Facility, Yucca Mountain

Description: Flow-through bioreactors are used to investigate the relationship between the supply (and limitation) of major nutrients required by microorganisms (C, N, P, S) and effluent chemistry to obtain data that can be useful to develop models of microbially mediated aqueous chemistry. The bioreactors were inoculated with crushed tuff from Yucca Mountain. Six of the 14 bioreactor experiments currently in operation have shown growth, which occurred in as few as 5 days and as much as a few months after initiation of the experiment. All of the bioreactors exhibiting growth contained glucose as a carbon source, but other nutritional components varied. Chemical signatures of each bioreactor were compared to each other and selected results were compared to computer simulations of the equivalent abiotic chemical reactions. At 21 C, the richest medium formulation produced a microbial community that lowered the effluent pH from 6.4 to as low as 3.9. The same medium formulation at 50 C produced no significant change in pH but caused a significant increase in Cl after a period of 200 days. Variations in concentrations of other elements, some of which appear to be periodic (Ca, Mg, etc.) also occur. Bioreactors fed with low C, N, P, S media showed growth, but had stabilized at lower cell densities. The room temperature bioreactor in this group exhibited a phospholipid fatty acid (PLFA) signature of sulfur- or iron-reducing bacteria, which produced a significant chemical signature in the effluent from that bioreactor. Growth had not been observed yet in the alkaline bioreactors, even in those containing glucose. The value of combining detailed chemical and community (e.g., ester-linked PLFA) analyses, long-duration experiments, and abiotic chemical models to distinguish chemical patterns is evident. Although all of the bioreactors contain the same initial microorganisms and mineral constituents, PLFA analysis demonstrates that both input chemistry and ...
Date: October 30, 1998
Creator: Chen, C. I.; Chuu, Y. J.; Meike, A.; Ringelberg, D. & Sawvel, A.
Partner: UNT Libraries Government Documents Department

Particle Flows in Pumped DIII-D Discharges

Description: The dynamics of particle flows in the DIII-D tokamak for two divertor configurations is considered. Fuel and intrinsic carbon impurity flows are analyzed using experimental data and 2D fluid plasma simulations. The flows in puff and pump experiments done in an open and a closed divertor geometry are described. It is shown that the flow of fuel particles is sensitive to divertor geometry. The pumping efficiency of the DIII-D cryopumps is a factor of 2 higher in a closed geometry than an open. The core refueling rate of an open divertor is a factor of 2 higher than that of a closed divertor. In contrast, the flow of impurity carbon particles is insensitive to divertor geometry. Both the core carbon content and the fraction of the carbon source which penetrates to the core is unchanged between an open and closed divertor. In addition, the core impurity content is found to be insensitive to the amplitude of gas puffing in the simulations.
Date: May 17, 2000
Creator: Porter, G.D.; Rognlien, T.D.; Rensink, M.E.; Wolf, N. & West, W.P.
Partner: UNT Libraries Government Documents Department

Seasonal variation in carbon dioxide exchange over a Mediterranean annual grassland in California

Description: Understanding how environmental variables affect the processes that regulate the carbon flux over grassland is critical for large-scale modeling research, since grasslands comprise almost one-third of the earth's natural vegetation. To address this issue, fluxes of CO{sub 2} (F{sub c}, flux toward the surface is negative) were measured over a Mediterranean, annual grassland in California, USA for 2 years with the eddy covariance method. To interpret the biotic and abiotic factors that modulate F{sub c} over the course of a year we decomposed net ecosystem CO{sub 2} exchange into its constituent components, ecosystem respiration (R{sub eco}) and gross primary production (GPP). Daytime R{sub eco} was extrapolated from the relationship between temperature and nighttime F{sub c} under high turbulent conditions. Then, GPP was estimated by subtracting daytime values of F{sub c} from daytime estimates of R{sub eco}. Results show that most of carbon exchange, both photosynthesis and respiration, was limited to the wet season (typically from October to mid-May). Seasonal variations in GPP followed closely to changes in leaf area index, which in turn was governed by soil moisture, available sunlight and the timing of the last frost. In general, R{sub eco} was an exponential function of soil temperature, but with season-dependent values of Q{sub 10}. The temperature-dependent respiration model failed immediately after rain events, when large pulses of R{sub eco} were observed. Respiration pulses were especially notable during the dry season when the grass was dead and were the consequence of quickly stimulated microbial activity. Integrated values of GPP, R{sub eco}, and net ecosystem exchange (NEE) were 867, 735, and -132g C m{sup -2}, respectively, for the 2000-2001 season, and 729, 758, and 29g C m{sup -2} for the 2001-2002 season. Thus, the grassland was a moderate carbon sink during the first season and a weak carbon source during the ...
Date: May 1, 2004
Creator: Xu, L & Baldocchi, D
Partner: UNT Libraries Government Documents Department

Integrated Field, Laboratory, and Modeling Studies to Determine the Effects of Linked Microbial and Physical Spatial Heterogeneity on Engineered Vadose Zone Bioremediation

Description: The objective of the project at large was to experiment with new methods for bioremediation of carbon tetrachloride plumes in the soils at the Hanford Site in Richland, WA. Traditionally, biostimulation occurs via pumping of liquid nutrient solution into the vadose zone, however an alternate methodology utilizes the introduction of gaseous nutrients, specifically nitrogen, phosphorus and carbon sources. The movement of liquid through the vadose zone tends to disperse contaminant plumes, and/or cause biofouling (excessive microbial growth) in the vicinity of injection wells. Alternatively, gas-phase nutrient introduction yields greater dispersion of molecules and little to no displacement of target plumes. Once vapor-phase molecules solubilize into soil water, they become bioavailable and should thus encourage colonization and degradation. The feasibility of this method of nutrient delivery was studied in an experimental laboratory system, the goal of which was to observe, in situ, microbial colonization in response to gaseous nutrient injection. It was hoped that these observations would aid in predictive modeling of microbial behavior in field scale bioremediation.
Date: June 1, 2003
Creator: Brockman, Fred J. & Selker, John S.
Partner: UNT Libraries Government Documents Department

Leakage and Seepage in the Near-Surface Environment: An Integrated Approach to Monitoring and Detection

Description: Monitoring and detection of leakage and seepage of carbon dioxide (CO{sub 2}) in the near-surface environment is needed to ensure the safety and effectiveness of geologic carbon sequestration. Large leakage fluxes, e.g., through leaking wells, will be easier to detect and monitor than slow and diffuse leakage and seepage. The challenge of detecting slow leakage and seepage is discerning a leakage or seepage signal from within the natural background variations in CO{sub 2} concentration and flux that are controlled by a variety of coupled processes in soil. Although there are no direct examples of leaking geologic carbon sequestration sites on which to base a proposed verification approach, we have been guided by our prior simulation studies of CO{sub 2} leakage and seepage, which showed that large CO{sub 2} concentrations can develop in the shallow subsurface even for relatively small CO{sub 2} leakage fluxes. A variety of monitoring technologies exists for measuring CO{sub 2} concentration and flux, but there is a gap between instrument performance and the detection of a leakage or seepage signal from within large natural background variability. We propose an integrated approach to monitoring and verification. The first part of our proposed approach is to characterize and understand the natural ecosystem before CO{sub 2} injection occurs so that future anomalies can be recognized. Measurements of natural CO{sub 2} fluxes using accumulation chamber (AC) and eddy correlation (EC) approaches, soil CO{sub 2} concentration profiles with depth, and carbon isotope compositions of CO{sub 2} are needed to characterize the natural state of the system prior to CO{sub 2} injection. From this information, modeling needs to be carried out to enhance understanding of carbon sources and sinks so that anomalies can be recognized and subject to closer scrutiny as potential leakage or seepage signals. Long-term monitoring using AC, EC, and soil-gas ...
Date: December 18, 2003
Creator: Oldenburg, Curtis M. & Lewicki, Jennifer L.
Partner: UNT Libraries Government Documents Department

Superlubricity and wearless sliding in diamondlike carbon films.

Description: Diamondlike carbon (DLC) films have attracted great interest in recent years mainly because of their unusual optical, electrical, mechanical, and tribological properties. Such properties are currently being exploited for a wide range of engineering applications including magnetic hard disks, gears, sliding and roller bearings, scratch resistant glasses, biomedical implants, etc. Systematic studies on carbon-based materials in our laboratory have led to the development of a new class of amorphous DLC films that provide extremely low friction and wear coefficients of 0.001 to 0.005 and 10{sup -11} to 10{sup -10} mm{sup 3} /N.m, respectively, when tested in inert-gas or high-vacuum environments. These films were produced in highly hydrogenated gas discharge plasmas by a plasma enhanced chemical vapor deposition process at room temperature. The carbon source gases used in the deposition of these films included methane, acetylene, and ethylene. Tribological studies in our laboratory have established a very close correlation between the composition of the plasmas and the friction and wear coefficients of the resultant DLC films. Specifically, the friction and wear coefficients of DLC films grown in plasmas with higher hydrogen-to-carbon ratios were much lower than films derived from source gases with lower hydrogen-to-carbon ratios. Fundamental tribological and surface analytical studies have led us to conclude that hydrogen (within the film, as well as on the sliding surfaces) is extremely important for the superlubricity and wearless sliding behavior of these films. Based on these studies, a mechanistic model is proposed to explain the superlow friction and wear properties of the new DLC films.
Date: December 13, 2001
Creator: Erdemir, A.
Partner: UNT Libraries Government Documents Department