Science.gov

Sample records for agricultural chemical transport

  1. Studies by the U.S. Geological Survey on sources, transport, and fate of agricultural chemicals

    USGS Publications Warehouse

    Capel, Paul D.; Hamilton, Pixie A.; Erwin, Martha L.

    2004-01-01

    Information from these studies will help with decision-making related to chemical use, conservation, and other farming practices that are used to reduce runoff of agricultural chemicals and sediment from fields. This information also will benefit the U.S. Environmental Protection Agency, the Department of Agriculture, local and regional water managers, and agricultural chemical manufacturers who are involved in managing chemical use and pesticide registration.

  2. AGRICULTURAL CHEMICAL USAGE DATA

    EPA Science Inventory

    This report, which summarizes the use of agricultural chemicals is issued by the National Agricultural Statistics Service (NASS) as part of its series on Agricultural Chemical Usage. Other publications in the series present statistics for on-farm agricultural chemical usage for f...

  3. Occurrence and Transport of Agricultural Chemicals in Leary Weber Ditch Basin, Hancock County, Indiana, 2003-04

    USGS Publications Warehouse

    Baker, Nancy T.; Stone, Wesley W.; Wilson, John T.; Meyer, Michael T.

    2006-01-01

    Leary Weber Ditch Basin, Hancock County, Indiana, is one of seven first-order basins selected from across the United States as part of the Agricultural Chemicals: Source, Transport, and Fate study conducted by the National Water-Quality Assessment Program of the U.S. Geological Survey. The nationwide study was designed to increase the understanding of the links between the sources of water and agricultural chemicals (nutrients and pesticides) and the transport and fate of these chemicals through the environment. Agricultural chemicals were detected in Leary Weber Ditch and in every associated hydrologic compartment sampled during 2003 and 2004. Pesticides were detected more frequently in samples collected from overland flow and from the ditch itself and less frequently in ground-water samples. The lowest concentrations of pesticides and nutrients were detected in samples of rain, soil water, and ground water. The highest concentrations of pesticides and nutrients were detected in samples of tile-drain water, overland flow, and water from Leary Weber Ditch. Samples collected from the tile drain, overland flow and Leary Weber Ditch soon after chemical applications to the fields and coincident with rainfall and increased streamflow had higher concentrations of pesticides and nutrients than samples collected a longer time after the chemicals were applied. A mass-balance mixing analysis based on potassium concentrations indicated that tile drains are the primary contributor of water to Leary Weber Ditch, but overland flow is also an important contributor during periods of high-intensity rainfall. When maximum rainfall intensity was 0.5 inches per hour or lower, overland flow contributed about 10 percent and tile drains contributed about 90 percent of the flow to Leary Weber Ditch. When maximum rainfall intensity was 0.75 inches per hour or greater, overland flow contributed about 40 percent and tile drains contributed about 60 percent of the flow to the ditch. Ground

  4. What is needed to understand feedback mechanisms from agricultural and climate changes that can alter the hydrological system and the transport of sediments and agricultural chemicals?

    NASA Astrophysics Data System (ADS)

    Coupe, Richard; Payraudeau, Sylvain; Babcsányi, Izabella; Imfeld, Gwenaël

    2015-04-01

    Modern agriculture activities are constantly changing as producers try to produce a crop, keep their soils fertile, control pests, and prevent contamination of air and water resources. Because most of the world's arable land is already in production we must become more efficient if we are to feed and clothe the world's growing population as well as do this in a sustainable manner; leaving a legacy of fertile soil and clean water resources for our descendants. The objective of this paper is to demonstrate the importance of historical datasets and of developing new strategies to understand the effects of changing agricultural systems on the environment. Scientists who study agriculture and its effects on water must constantly adapt their strategies and evaluate how changing agricultural activities impact the environment. As well as understand from historical datasets on hydrology and agriculture how a changing climate or agricultural activity such as a change in tillage method might impact the processes that determine the movement of agricultural chemicals off of the target site. The 42.7 ha Hohrain (Rouffach, Alsace, France) vineyard experimental catchment offers several examples of how scientists have used historical data from this catchment to understand how the transport of agricultural chemicals may change due to a changing climate as well as how new strategies are developed for understanding the transport of agricultural chemicals. Runoff is a major process of pesticide transport from agricultural land to downstream aquatic ecosystems. The impact of rainfall characteristics on the transport of runoff-related pesticides is crucial to understanding how to prevent or minimize their movement now, but also in understanding how climate change might affect runoff. If we understand how rainfall characteristics affect the transport of pesticides, we can use climate change models to predict how those characteristics might change in the future and be better prepared for

  5. Effects of topography on the transport of agricultural chemicals to groundwater in a sand-plain setting

    USGS Publications Warehouse

    Delin, G.N.; Landon, M.K.

    2002-01-01

    Geochemical data were collected to investigate the effects of topography and focused recharge on the transport of agricultural chemicals to groundwater through sandy soils. The research was done at a topographically high (upland) site and a depressional (lowland) site within a corn field. Agricultural chemicals that move readily with water were most directly affected by focused recharge to the lowland site. Surface runoff of water to the lowland site was the primary cause for the generally greater flux of chloride, nitrate nitrogen, and sulfate compared with the upland site. Based on data from the unsaturated zone, for example, the average annual fluxes of these chemicals in 1992–1993 were 5.1, 3.4, and 1.7 times greater, respectively, at the lowland site. Study results indicate that consideration should be given to modifying site-specific management farming technology to account for varying recharge rates in different topographic settings. By reducing chemical application rates in topographic depressions, where focused recharge of chemicals occurs because of surface runoff, farmers could improve ground-water quality as well as reduce expenditures for agricultural chemicals.

  6. Effects of surface run-off on the transport of agricultural chemicals to ground water in a sandplain setting

    USGS Publications Warehouse

    Delin, G.N.; Landon, M.K.

    2002-01-01

    An experiment was conducted at a depressional (lowland) and an upland site in sandy soils to evaluate the effects of surface run-off on the transport of agricultural chemicals to ground water. Approximately 16.5 cm of water was applied to both sites during the experiment, representing a natural precipitation event with a recurrence interval of approximately 100 years. Run-off was quantified at the lowland site and was not detected at the upland site during the experiment. Run-off of water to the lowland site was the most important factor affecting differences in the concentrations and fluxes of the agricultural chemicals between the two sites. Run-off of water to the lowland site appears to have played a dual role by diluting chemical concentrations in the unsaturated zone as well as increasing the concentrations at the water table, compared to the upland site. Concentrations of chloride, nitrate and atrazine plus metabolites were noticeably greater at the water table than in the unsaturated zone at both sites. The estimated mass flux of chloride and nitrate to the water table during the test were 5-2 times greater, respectively, at the lowland site compared to the upland site, whereas the flux of sulfate and atrazine plus metabolites was slightly greater at the upland site. Results indicate that matrix flow of water and chemicals was the primary process causing the observed differences between the two sites. Results of the experiment illustrate the effects of heterogeneity and the complexity of evaluating chemical transport through the unsaturated zone. Copyright ?? 2002 Elsevier Science B.V.

  7. Effects of surface run-off on the transport of agricultural chemicals to ground water in a sandplain setting

    USGS Publications Warehouse

    Delin, Geoffrey N.; Landon, Matthew K.

    2002-01-01

    An experiment was conducted at a depressional (lowland) and an upland site in sandy soils to evaluate the effects of surface run-off on the transport of agricultural chemicals to ground water. Approximately 16.5 cm of water was applied to both sites during the experiment, representing a natural precipitation event with a recurrence interval of approximately 100 years. Run-off was quantified at the lowland site and was not detected at the upland site during the experiment. Run-off of water to the lowland site was the most important factor affecting differences in the concentrations and fluxes of the agricultural chemicals between the two sites. Run-off of water to the lowland site appears to have played a dual role by diluting chemical concentrations in the unsaturated zone as well as increasing the concentrations at the water table, compared to the upland site. Concentrations of chloride, nitrate and atrazine plus metabolites were noticeably greater at the water table than in the unsaturated zone at both sites. The estimated mass flux of chloride and nitrate to the water table during the test were 5–2 times greater, respectively, at the lowland site compared to the upland site, whereas the flux of sulfate and atrazine plus metabolites was slightly greater at the upland site. Results indicate that matrix flow of water and chemicals was the primary process causing the observed differences between the two sites. Results of the experiment illustrate the effects of heterogeneity and the complexity of evaluating chemical transport through the unsaturated zone.

  8. Evaluation of unsaturated-zone solute-transport models for studies of agricultural chemicals

    USGS Publications Warehouse

    Nolan, Bernard T.; Bayless, E. Randall; Green, Christopher T.; Garg, Sheena; Voss, Frank D.; Lampe, David C.; Barbash, Jack E.; Capel, Paul D.; Bekins, Barbara A.

    2005-01-01

    Of the models tested, RZWQM, HYDRUS2D, VS2DT, GLEAMS and PRZM had graphical user interfaces. Extensive documentation was available for RZWQM, HYDRUS2D, and VS2DT. RZWQM can explicitly simulate water and solute flux in macropores, and both HYDRUS2D and VS2DT can simulate water and solute flux in two dimensions. The version of RZWQM tested had a maximum simulation depth of 3 meters. The complex models simulate the formation, transport, and fate of degradates of up to three to five compounds including the parent, with the exception of VS2DT, which simulates the transport and fate of a single compound.

  9. Development of Nested, Heterogeneous Ground-Water Flow Models for Study of Transport and Fate of Agricultural Chemicals, Merced County, California

    NASA Astrophysics Data System (ADS)

    Phillips, S. P.; Green, C. T.; Zamora, C.

    2006-05-01

    Multi-scale models of ground-water flow were developed as part of a study of the transport and fate of agricultural chemicals by the National Water-Quality Assessment (NAWQA) Program of the US Geological Survey. Agricultural chemicals of interest included forms of nitrogen and selected pesticides A three- dimensional local-scale model (17 square km) surrounds a well-instrumented, 1-km transect near the Merced River within a principally agricultural land-use setting. This model is nested within a regional-scale model (2,700 square km) of northeastern San Joaquin Valley, California, which provides hydrologically reasonable boundary conditions for the local model. Boundary fluxes were passed from the regional to local model using a hydraulic-conductivity-weighted distribution. The heterogeneity of aquifer materials was incorporated explicitly into the regional and local models. Three-dimensional kriging was used to interpolate sediment texture data from about 3,500 drillers' logs in the regional model area. The resulting distribution of sediment texture was used to estimate hydraulic parameters for each cell in the 16-layer regional model. A subset of these data was used to generate multiple transition-probability-based realizations of hydrofacies distributions for the 110-layer local model. Explicit depiction of heterogeneity in hydraulic conductivity and porosity in the local model incorporates macro-scale hydrodynamic dispersion into the flow model, allowing more direct comparison of particle-tracking results to tracer-derived estimates of ground-water age. Water levels measured in multi-depth wells along the 1-km transect were used to calibrate the local model (median error 0.12 m). Two-dimensional heat-flow models calibrated using continuous multi-depth temperature data from below the bed of the Merced River suggest an annual range of ground-water inflow of about 0-2.4 cm/d for water year 2005. This estimate compares reasonably well to the 4 cm/d simulated in the

  10. Effects of recharge on the transport of agricultural chemicals at the Princeton, Minn. Management Systems Evaluation Area (MSEA), 1991-92

    USGS Publications Warehouse

    Delin, G.N.; Landon, M.K.

    1993-01-01

    Rates of water movement through the unsaturated zone greatly affect the amount and concentrations of agricultural chemicals that may reach the water table. For example, recharge can flush to the water table chemicals that have accumulated In the unsaturated zone during dry periods. A better understanding of how topography influences recharge and the movement of agricultural chemicals is needed. In 1991, the U.S. Geological Survey (USGS), with funding from the USGS Toxic Substances Hydrology Program, began studying the movement of water and agricultural chemicals to the water table at the Management Systems Evaluation Area (MSEA) near Princeton, Minnesota. Instruments were installed to measure the movement of moisture through the soil beneath a corn field. Samples of the recharge water were analyzed for concentrations of agricultural chemicals and tracers. Field recharge and tracer tests were simulated In the laboratory.

  11. Effects of focused recharge on the transport of agricultural chemicals at the Princeton, Minnesota Management Systems Evaluation Area, 1991-92

    USGS Publications Warehouse

    Delin, G.N.; Landon, M.K.

    1993-01-01

    The primary objective of this four-year research study is to evaluate the effects of transient recharge, topography, and subsurface heterogeneities on the flux of water and agricultural chemicals to ground water. To achieve this objective the approach was to (1) install instruments to sample and measure the movement of water through the unsaturated zone beneath topographically high and low areas of a corn field; (2) conduct recharge and tracer tests in the field to evaluate the movement of water and agricultural chemicals at both topographic settings; and (3) simulate the field recharge and tracer tests in the laboratory. The primary research hypothesis was that the vertical flux of water and agricultural chemicals is greater in topographically low areas than in topographically high areas.

  12. Transport of agricultural chemicals in surface flow, tileflow, and streamflow of Walnut Creek Watershed near Ames, Iowa, April 1991-September 1993

    USGS Publications Warehouse

    Soenksen, P.J.

    1996-01-01

    Chemical loss ratios indicated differences in the transport characteristics of the three subwatersheds. The downstream subwatershed, which has steeper terrain, a more-developed natural drainage system, and fewer tiles than the two upland subwatersheds, had the largest loss rates for all three chemicals 206 percent for nitrate as nitrogen (October 1992-September 1993) and 20 percent for atrazine and 2.9 percent for metolachlor (April-September 1993). For May-July 1993, when most of the herbicides were transported, the downstream subwatershed also had the largest cumulative unit discharge and the largest streamflow-to-precipitation ratios.

  13. Environment and chemicals in agriculture

    SciTech Connect

    Winteringham, F.W.P.

    1985-01-01

    The Commission of the European Communities and the Irish Government jointly organized a symposium in Dublin in October 1984, from which the papers in this book are presented. Environmental concerns related to intensive agriculture provided the impetus for the symposium. More than half of the papers deal with economic or extension aspects of environmental protection. It is stressed that uniform standards and regulations are not reasonable, since soils, climate, and farming systems vary. With respect to pesticide use, emphasis is placed on integrated pest management through improved pest forecasting, more specific targeting of pesticide applications, and farmer education. The development of pesticide resistance is a serious concern that will require research into new techniques for pest control. The primary environmental problem with fertilizers is the leaching of NO/sub 3/ into ground water, with many ears exceeding the acceptable level of 50 mg/L. The Netherlands, in particular, has the highest average rate of N fertilizer use in the world, 240 kg/ha, with about 400 kg/ha of N applied in areas with intensive dairy (Bos sp.) farming. Nevertheless, areas in the Netherlands where the NO/sub 3/ concentration in ground water exceeds 50 mg/L are associated with large amounts of manure produced in intensive pig and poultry farming, rather than with fertilizer applications. There is a need to balance nutrients added with those removed in intensive agricultural systems.

  14. LEACHING EVALUATION OF AGRICULTURAL CHEMICALS (LEACH) HANDBOOK

    EPA Science Inventory

    A methodology has been developed to assess potential pesticide leaching from the crop root zones in major (corn, soybean, wheat and cotton) crop growing areas of the United States. Use of the Leaching Evaluation of Agricultural Chemicals (LEACH) methodology provides an indication...

  15. Agricultural chemical export dynamics in a watershed

    NASA Astrophysics Data System (ADS)

    Tretkoff, Ernie

    2011-06-01

    chemicals filter through a catchment is important for managing water quality. Using a concept of the catchment as a physicochemical filter, Guan et al. examined nitrate, phosphate, and atrazine loads in the Little Vermillion River watershed, a tile-drained watershed in Illinois. They analyzed a 10-year data set using mathematical signal processing to investigate spatial and temporal patterns in chemical concentrations and discharge rate. They found that export of these chemicals had a linear relationship with streamflow at annual scales—the higher the streamflow, the more these chemicals were exported from the watershed. The researchers' approach helps identify the roles of different hydrological flow paths in controlling chemical export at different spatial and temporal scales and reveals that chemical inputs overwhelm normal biogeochemical processing in these agricultural systems, leading to high long-term average rates of export. (Water Resources Research, doi:10.1029/ 2010WR009997, 2011)

  16. Small agricultural impoundments affect pollutant transport

    NASA Astrophysics Data System (ADS)

    Balcerak, Ernie

    2013-03-01

    Reservoirs created by dams intercept runoff from upslope areas and thus are often sinks for fertilizers and other pollutants that would otherwise flow downstream. Most studies of solute transport through impoundments have focused on large, long-lived systems. However, small impoundments, such as those created for irrigation or livestock watering, are common in agricultural regions, and their total global surface area is comparable to that of large reservoirs. As these small systems mature, the impoundments fill with sediment, creating ecosystems with wetland-like characteristics. Because dams that create these small impoundments are more likely to be degraded, poorly maintained, or removed by their owners, it is important to understand how changes in such systems may affect pollutant transport.

  17. Agricultural Chemicals and Radiation. Ag Ed Environmental Education Series.

    ERIC Educational Resources Information Center

    Tulloch, Rodney W.

    The document is designed to be used as a resource in teaching vocational agriculture high school students about the environment. Agricultural chemicals are the major focus, with some attention to radiation. The importance of safety in agricultural chemical use is stressed, with descriptions of the pesticide label; protective clothing; respiratory…

  18. Chemical Transport--Coping with Disasters.

    ERIC Educational Resources Information Center

    Rawls, Rebecca L.

    1980-01-01

    Describes operations of CHEMTREC, a chemical emergency information system supported by the Chemical Manufacturer's Association. Presents data on transportation incidents involving hazardous materials and the most frequently involved chemicals in transportation incidents. (CS)

  19. Holistic Watershed-Scale Approach for Studying Agricultural Chemicals

    NASA Astrophysics Data System (ADS)

    Capel, P. D.; Domagalski, J. L.

    2006-05-01

    The USGS National Water-Quality Assessment (NAWQA) Program studied the water quality of 51 areas across the United States during its first decade (1991-2001). Analyses of results from that phase of the NAWQA Program indicated that detailed studies of the processes affecting water quality could aid in the interpretation of these data, help to determine the direction and scope of future monitoring studies, and add to the understanding of the sources, transport and fate of non-point source chemicals, such as from agriculture. Now in the second decade of investigations, the NAWQA Program has initiated new process-based detailed studies to increase our understanding at the scale of a small watershed (about 3-15 square kilometers), nested within the larger basins studied during the first decade. The holistic, mass-budget approach for small agricultural watersheds that was adopted includes processes, and measures water and chemicals in the atmosphere, surface water, tile drains, overland flow, and within various sub-surface environments including the vadose, saturated, and hyporheic zones. The primary chemicals of interest were nutrients (nitrogen and phosphorous), the triazine and acetanilide herbicides, and the organophosphorus insecticides. Extensive field observations were made, and numerical models were developed to simulate important environmental compartments and interfaces associated with the transport and fate of agricultural chemicals. It is well recognized that these field measurements and simulations cannot fully achieve a full mass budget at this scale, but the approach provides a useful means for comparisons of various processes in different environmental settings. The results gained using this approach will add to the general knowledge of environmental transport and fate processes, and have transfer value to unstudied areas and different scales of investigation. The five initial study areas started in 2002, included watersheds in California, Indiana

  20. Quantifying subsurface hydrology effects on chemical transport in drainage ditches using a 20-meter flume

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Agriculture drainage ditches serve as the veins of the Midwestern agricultural landscapes. The transport of chemical fertilizers and pesticides in these ditches affect the local and downstream ecosystems. Although much research has already been conducted on chemical transport in streams and drainage...

  1. Assessing Nutrient Transport Following Dredging of Agricultural Drainage Ditches

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Agricultural drainage ditches are vital for many agricultural landscapes in the U.S. Previous research has indicated that dredging agricultural drainage ditches may degrade water quality. In this study, we monitored nutrient transport in two drainage ditches for six years (2003-2008), during which t...

  2. 77 FR 70453 - Chemical Transportation Advisory Committee

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-11-26

    ... of the Federal Register (73 FR 3316). Docket: This notice, and documents or comments related to it... SECURITY Coast Guard Chemical Transportation Advisory Committee AGENCY: Coast Guard, DHS. ] ACTION: Committee Management; Notice of Federal Advisory Committee Meeting. SUMMARY: The Chemical...

  3. Chemical Equilibrium And Transport (CET)

    NASA Technical Reports Server (NTRS)

    Mcbride, B. J.

    1991-01-01

    Powerful, machine-independent program calculates theoretical thermodynamic properties of chemical systems. Aids in design of compressors, turbines, engines, heat exchangers, and chemical processing equipment.

  4. Chemical pollution from transportation vehicles.

    PubMed

    Starkman, E S

    1969-04-01

    Recent publicity on electrically powered vehicles notwithstanding, the gasoline engine will probably be the principal power plant for passenger cars for at least the next decade. Chemical pollutants discharged by the gasoline engine are now under partial control. Motor cars of 1968 and 1969 model discharge only about 30 percent as much carbon monoxide and unburned hydrocarbons as do older models. In theory, carbon monoxide, unburned hydrocarbons and oxides of nitrogen ultimately can be completely removed from gasoline engine exhaust. In order to accomplish this it would be necessary to modify cars to operate satisfactorily on a lean mixture and perhaps to use a catalyst in the exhaust system. Present designs of gas turbines for aircraft and for future projected application to ground vehicles yield pollutants (except for smoke) at levels below those of gasoline engines for a decade to come. It has also been shown possible to eliminate smoke as well as odor from the gas turbine. Thus with proper effort it is feasible to reduce pollution of the atmosphere due to transportation to an acceptable level, even if electrically or alternatively powered vehicles cannot be developed for a decade. PMID:4183827

  5. VOCATIONAL COMPETENCIES NEEDED FOR EMPLOYMENT IN THE AGRICULTURAL-CHEMICAL INDUSTRY IN MICHIGAN.

    ERIC Educational Resources Information Center

    CHRISTENSEN, MAYNARD; CLARK, RAYMOND M.

    THIS STUDY WAS CONDUCTED TO DETERMINE THE VOCATIONAL COMPETENCIES NEEDED FOR EMPLOYMENT BELOW THE MANUFACTURING LEVEL IN THE AGRICULTURAL-CHEMICAL INDUSTRY IN MICHIGAN. NINE FUNCTIONS PERFORMED IN THE INDUSTRY WERE LISTED--RESEARCH, TRANSPORTATION, PROCESSING, PUBLIC RELATIONS, SALES, SERVICE, OFFICE RECORDS AND MANAGEMENT, MAINTENANCE, AND…

  6. Transport of agricultural contaminants through karst soil

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Karst landscapes are common in many agricultural regions in the US. Well-developed karst landscapes are characterized by shallow soils, sinkholes, sinking streams, underground conduits, and springs. In these landscapes surface runoff is minimal and most recharge enters the subsurface relatively quic...

  7. Nitrogen fate and Transport in Diverse Agricultural Watersheds

    NASA Astrophysics Data System (ADS)

    Essaid, H.; McCarthy, K. A.; Baker, N. T.

    2010-12-01

    Nitrogen mass budgets have been estimated for ten agricultural watersheds located in a range of hydrologic settings in order to understand the factors controlling the fate of nitrogen applied at the surface. The watersheds, study areas of the Agricultural Chemical Sources, Transport and Fate study of the U.S. Geological Survey National Water Quality Assessment Program, are located in Indiana (IN), Iowa (IA), Maryland (MD), Nebraska (NE), Mississippi (MS) and Washington (WA). They range in size from 7 to 1254 km2, with four of the watersheds nested within larger watersheds. Surface water outflow (normalized to watershed area) ranged from 4 to 83 cm/yr. Crops planted include corn, soybean, small grains, rice, cotton, orchards and vegetables. “Surplus nitrogen” was determined for each watershed by subtracting estimates of crop uptake and volatilization from estimates of nitrogen input from atmospheric deposition, plant fixation, and fertilizer and manure applications for the period from 1987 to 2004. This surplus nitrogen is transported though the watershed via surface and subsurface flow paths, while simultaneously undergoing transformations (such as denitrification and in-stream processing) that result in less export of nitrogen from the watershed. Surface-water discharge and concentration data were used to estimate the export of nitrogen from the watersheds (groundwater outflow from the watersheds was minimal). Subtracting nitrogen export from surplus nitrogen provides an estimate of the net amount of nitrogen removal occurring during internal watershed transport. Watershed average nitrogen surplus ranged from 6 to 49 kg-N/ha. The more permeable and/or greater water flux watersheds (MD, NE, and WA) tended to have larger surplus nitrogen, possibly due to less crop uptake caused by greater leaching and runoff of nitrogen. Almost all of the surplus nitrogen in the low permeability (MS) and tile drained watersheds (IA, IN) was exported from the watershed with

  8. 76 FR 34240 - Chemical Transportation Advisory Committee

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-06-13

    ... public dockets in the January 17, 2008, issue of the Federal Register (73 FR 3316). Establishment of the... SECURITY Coast Guard Chemical Transportation Advisory Committee AGENCY: Coast Guard, DHS. ACTION: Committee... that the establishment of the Chemical Transportation Advisory Committee (CTAC) is necessary and in...

  9. 78 FR 67379 - Chemical Transportation Advisory Committee

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-11-12

    ..., issue of the Federal Register (73 FR 3316). Docket: This notice, and documents or comments related to it... SECURITY Coast Guard Chemical Transportation Advisory Committee AGENCY: Coast Guard, DHS. ACTION: Committee Management; Notice of Federal Advisory Committee Meeting. SUMMARY: The Chemical Transportation...

  10. 78 FR 55278 - Chemical Transportation Advisory Committee

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-09-10

    ... Federal Register (73 FR 3316). Re-Establishment of the Committee For the reasons set forth below, the... SECURITY Coast Guard Chemical Transportation Advisory Committee AGENCY: Coast Guard, DHS. ACTION: Committee... that the re- establishment of the Chemical Transportation Advisory Committee (CTAC) is necessary and...

  11. 78 FR 23773 - Chemical Transportation Advisory Committee

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-04-22

    ... January 17, 2008, issue of the Federal Register (73 FR 3316). Docket: This notice, and documents or... SECURITY Coast Guard Chemical Transportation Advisory Committee AGENCY: Coast Guard, DHS. ACTION: Committee Management; Notice of Federal Advisory Committee Meeting. SUMMARY: The Chemical Transportation...

  12. Agricultural Chemicals in Leary Weber Ditch Basin, Hancock County, Indiana, 2003-04

    USGS Publications Warehouse

    Baker, Nancy T.; Lathrop, Timothy R.

    2006-01-01

    Leary Weber Ditch Basin, Hancock County, Indiana, is part of an Agricultural Chemicals: Source, Transport, and Fate study conducted by the National Water-Quality Assessment Program of the U.S. Geological Survey. Water-quality samples were collected in Leary Weber Ditch and in the major hydrologic compartments of the Leary Weber Ditch Basin during 2003 and 2004. Hydrologic compartments that contribute water and agricultural chemicals to Leary Weber Ditch are rain water, overland-flow water, soil water, tile-drain water, and ground water. Samples were analyzed for selected pesticides, nutrients, and major ions.

  13. ORGANIC CHEMICAL TRANSPORT TO GROUNDWATER

    EPA Science Inventory

    The use of pesticides in the production of agricultural commodities is widespread. Since nearly one-half of the U.S. population relies on groundwater as their source for drinking water, contamination potential of groundwater, because of pesticide manufacture and use, must be unde...

  14. A Whole-System Approach to Understanding Agricultural Chemicals in the Environment

    USGS Publications Warehouse

    U.S. Geological Survey

    2009-01-01

    The effects of the use of agricultural chemicals and other practices associated with agriculture on the quality of streams and groundwater is well known; however, less is known about how those effects may vary across different geographic regions of the Nation. Scientists at the U.S. Geological Survey (USGS) are conducting studies on the transport and fate of agricultural chemicals in diverse agricultural settings across the country using comparable and consistent methodology and study designs (fig. 1; Capel and others, 2004; Capel and others, 2008). Assessments in five study areas have been completed, and the results highlight how environmental processes and agricultural practices interact to affect the movement and transformation of agricultural chemicals in the environment. The studies address major environmental compartments, including surface water, groundwater, the unsaturated zone, the streambed, and the atmosphere, as well as the pathways that interconnect these compartments. The study areas represent major agricultural settings, such as irrigated diverse cropping in the West and corn and soybean row cropping in the Midwest and, therefore, findings are relevant throughout much of the Nation.

  15. INFLUENCE OF MACROMOLECULES ON CHEMICAL TRANSPORT

    EPA Science Inventory

    Macromolecules in the pore fluid influence the mobility of hydrophobic compounds through soils. his study evaluated the significance of macromolecules in facilitating chemical transport under laboratory conditions. Partition coefficients between 14C-labeled hexachlorobenzene and ...

  16. THE USE OF CHEMICALS AS SOIL ADDITIVES. AGRICULTURAL CHEMICALS TECHNOLOGY, NUMBER 3.

    ERIC Educational Resources Information Center

    Ohio State Univ., Columbus. Center for Vocational and Technical Education.

    THE PURPOSE OF THIS GUIDE IS TO ASSIST TEACHERS IN PREPARING POST-SECONDARY STUDENTS FOR AGRICULTURAL CHEMICAL OCCUPATIONS. IT IS ONE OF A SERIES OF MODULES DEVELOPED BY A NATIONAL TASK FORCE ON THE BASIS OF STATE STUDY DATA. SECTIONS ARE (1) PHYSICAL AND CHEMICAL ALTERATION OF SOIL WITH CHEMICAL ADDITIVES, (2) TERMINOLOGY AND COMPUTATIONS, (3)…

  17. USING REVERSE OSMOSIS TO REMOVE AGRICULTURAL CHEMICALS FROM GROUNDWATER

    EPA Science Inventory

    Suffolk County, N.Y., has examined its groundwater for agricultural and organic contaminants since 1978. Recent discoveries of specific chemicals in private wells increased the concern over contamination and spurred a study to determine a cost-effective system for removing agricu...

  18. Commercial Agriculture and Modern Transport in Central America.

    ERIC Educational Resources Information Center

    Horst, Oscar H.

    1981-01-01

    Describes an exercise for use in college-level geography courses dealing with the tandem development of transport networks and commercial agriculture in Central America. Using six maps, the author shows the parallels between highway and railroad construction and commercial crops, (coffee, bananas, and cotton) in Central America between 1855-1975.…

  19. Transformation and Transport Processes of Nitrogen in Agricultural Systems

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The transformation and transport processes of nitrogen (N) in agricultural systems are discussed and information is provided on overall reservoir sizes for N. Nitrogen is ubiquitous in the environment and is required for the survival of all living things. It is also one of the most important essen...

  20. Transport and fate of microbial pathogens in agricultural settings

    Technology Transfer Automated Retrieval System (TEKTRAN)

    An understanding of the transport and survival of microbial pathogens (pathogens hereafter) in agricultural settings is needed to assess the risk of pathogen contamination to water and food resources, and to develop control strategies and treatment options. However, many knowledge gaps still remain ...

  1. Sorption and transport of atrazine in an agricultural soil

    NASA Astrophysics Data System (ADS)

    Hakan Akyol, Nihat

    2014-05-01

    Sorption and transport of atrazine in an agricultural soil Atrazine is one of the most commonly used herbicides in large quantity worldwide. The objective of this study was to perform some batch and column experiments to examine the transport of atrazine in an agricultural soil from Turkey. Batch experiments indicated that sorption isotherm was nonlinear with a freundlich isotherm over a range of concentration (0.2-10 mg/L) examined. Column experiments showed that transport of atrazine in the soil was moderately retarded compared to non-reactive tracer (R = 2.9-4.0). The degree of retardation decreased with increasing atrazine concentration and residance time had negligable impact on degree of sorption. Flow interruption tests in the column experiments indicated that the rate-limited desorption of atrazine mainly controlled the non-ideal transport of atrazine due to the presence of organic matter fraction (0.83 %) in the soil. Sorption and desorption behavior of atrazine in such soils could have important impacts for risk assessment of atrazine-contaminated soil and should be taken into account in the regulation, management, and remediation of atrazine-contaminated sites. Keywords: Atrazine, Agricultural soil, Batch, Column, Desorption, Rate-limited desorption, Sorption, Transport.

  2. Characterization of chemical agent transport in paints.

    PubMed

    Willis, Matthew P; Gordon, Wesley; Lalain, Teri; Mantooth, Brent

    2013-09-15

    A combination of vacuum-based vapor emission measurements with a mass transport model was employed to determine the interaction of chemical warfare agents with various materials, including transport parameters of agents in paints. Accurate determination of mass transport parameters enables the simulation of the chemical agent distribution in a material for decontaminant performance modeling. The evaluation was performed with the chemical warfare agents bis(2-chloroethyl) sulfide (distilled mustard, known as the chemical warfare blister agent HD) and O-ethyl S-[2-(diisopropylamino)ethyl] methylphosphonothioate (VX), an organophosphate nerve agent, deposited on to two different types of polyurethane paint coatings. The results demonstrated alignment between the experimentally measured vapor emission flux and the predicted vapor flux. Mass transport modeling demonstrated rapid transport of VX into the coatings; VX penetrated through the aliphatic polyurethane-based coating (100 μm) within approximately 107 min. By comparison, while HD was more soluble in the coatings, the penetration depth in the coatings was approximately 2× lower than VX. Applications of mass transport parameters include the ability to predict agent uptake, and subsequent long-term vapor emission or contact transfer where the agent could present exposure risks. Additionally, these parameters and model enable the ability to perform decontamination modeling to predict how decontaminants remove agent from these materials. PMID:23872337

  3. THE USE OF CHEMICALS AS FERTILIZERS. AGRICULTURAL CHEMICALS TECHNOLOGY, NUMBER 1.

    ERIC Educational Resources Information Center

    Ohio State Univ., Columbus. Center for Vocational and Technical Education.

    THE PURPOSE OF THIS GUIDE IS TO ASSIST TEACHERS IN PREPARING POST-SECONDARY STUDENTS FOR AGRICULTURAL CHEMICAL OCCUPATIONS. ONE OF A SERIES OF EIGHT MODULES, IT WAS DEVELOPED BY A NATIONAL TASK FORCE ON THE BASIS OF DATA FROM STATE STUDIES. SUBJECT MATTER AREAS ARE (1) CHEMICAL NUTRITION OF PLANTS, (2) PLANT GROWTH, (3) TERMINOLOGY,…

  4. THE USE OF CHEMICALS AS HERBICIDES. AGRICULTURAL CHEMICALS TECHNOLOGY, NUMBER 6.

    ERIC Educational Resources Information Center

    Ohio State Univ., Columbus. Center for Vocational and Technical Education.

    DEVELOPED BY A NATIONAL TASK FORCE ON THE BASIS OF STATE STUDIES, THIS MODULE IS ONE OF A SERIES DESIGNED TO ASSIST TEACHERS IN PREPARING POST-SECONDARY STUDENTS FOR ENTRY AND ADVANCEMENT IN AGRICULTURAL CHEMICAL OCCUPATIONS. THE SPECIFIC OBJECTIVES OF THIS MODULE ARE TO DEVELOP ABILITIES NECESSARY FOR OCCUPATIONS CONCERNED WITH CHEMICAL WEED…

  5. THE USE OF CHEMICALS TO CONTROL FIELD RODENTS AND OTHER PREDATORS. AGRICULTURAL CHEMICALS TECHNOLOGY, NUMBER 5.

    ERIC Educational Resources Information Center

    Ohio State Univ., Columbus. Center for Vocational and Technical Education.

    THE PURPOSE OF THIS GUIDE IS TO ASSIST TEACHERS IN PREPARING POST-SECONDARY STUDENTS FOR AGRICULTURAL CHEMICAL OCCUPATIONS. IT IS ONE OF A SERIES OF MODULES DEVELOPED BY A NATIONAL TASK FORCE ON THE BASIS OF DATA FROM STATE STUDIES. SECTIONS ARE (1) USE OF CHEMICALS FOR RODENT CONTROL AND ERADICATION, (2) TERMINOLOGY AND COMPUTATIONS, (3) RODENT…

  6. Drug Transport and Pharmacokinetics for Chemical Engineers

    ERIC Educational Resources Information Center

    Simon, Laurent; Kanneganti, Kumud; Kim, Kwang Seok

    2010-01-01

    Experiments in continuous-stirred vessels were proposed to introduce methods in pharmacokinetics and drug transport to chemical engineering students. The activities can be incorporated into the curriculum to illustrate fundamentals learned in the classroom. An appreciation for the role of pharmacokinetics in drug discovery will also be gained…

  7. Phosphorus transport in agricultural subsurface drainage: a review.

    PubMed

    King, Kevin W; Williams, Mark R; Macrae, Merrin L; Fausey, Norman R; Frankenberger, Jane; Smith, Douglas R; Kleinman, Peter J A; Brown, Larry C

    2015-03-01

    Phosphorus (P) loss from agricultural fields and watersheds has been an important water quality issue for decades because of the critical role P plays in eutrophication. Historically, most research has focused on P losses by surface runoff and erosion because subsurface P losses were often deemed to be negligible. Perceptions of subsurface P transport, however, have evolved, and considerable work has been conducted to better understand the magnitude and importance of subsurface P transport and to identify practices and treatments that decrease subsurface P loads to surface waters. The objectives of this paper were (i) to critically review research on P transport in subsurface drainage, (ii) to determine factors that control P losses, and (iii) to identify gaps in the current scientific understanding of the role of subsurface drainage in P transport. Factors that affect subsurface P transport are discussed within the framework of intensively drained agricultural settings. These factors include soil characteristics (e.g., preferential flow, P sorption capacity, and redox conditions), drainage design (e.g., tile spacing, tile depth, and the installation of surface inlets), prevailing conditions and management (e.g., soil-test P levels, tillage, cropping system, and the source, rate, placement, and timing of P application), and hydrologic and climatic variables (e.g., baseflow, event flow, and seasonal differences). Structural, treatment, and management approaches to mitigate subsurface P transport-such as practices that disconnect flow pathways between surface soils and tile drains, drainage water management, in-stream or end-of-tile treatments, and ditch design and management-are also discussed. The review concludes by identifying gaps in the current understanding of P transport in subsurface drains and suggesting areas where future research is needed. PMID:26023966

  8. Biosensor discovery of thyroxine transport disrupting chemicals

    SciTech Connect

    Marchesini, Gerardo R. Meimaridou, Anastasia; Haasnoot, Willem; Meulenberg, Eline; Albertus, Faywell; Mizuguchi, Mineyuki; Takeuchi, Makoto; Irth, Hubertus; Murk, Albertinka J.

    2008-10-01

    Ubiquitous chemicals may interfere with the thyroid system that is essential in the development and physiology of vertebrates. We applied a surface plasmon resonance (SPR) biosensor-based screening method for the fast screening of chemicals with thyroxine (T4) transport disrupting activity. Two inhibition assays using the main thyroid hormone transport proteins, T4 binding globulin (TBG) and transthyretin (TTR), in combination with a T4-coated biosensor chip were optimized and automated for screening chemical libraries. The transport protein-based biosensor assays were rapid, high throughput and bioeffect-related. A library of 62 chemicals including the natural hormones, polychlorinated biphenyls (PCBs), polybrominated diphenylethers (PBDEs) and metabolites, halogenated bisphenol A (BPA), halogenated phenols, pharmaceuticals, pesticides and other potential environmentally relevant chemicals was tested with the two assays. We discovered ten new active compounds with moderate to high affinity for TBG with the TBG assay. Strikingly, the most potent binding was observed with hydroxylated metabolites of the brominated diphenyl ethers (BDEs) BDE 47, BDE 49 and BDE 99, that are commonly found in human plasma. The TTR assay confirmed the activity of previously identified hydroxylated metabolites of PCBs and PBDEs, halogenated BPA and genistein. These results show that the hydroxylated metabolites of the ubiquitous PBDEs not only target the T4 transport at the TTR level, but also, and to a great extent, at the TBG level where most of the T4 in humans is circulating. The optimized SPR biosensor-based transport protein assay is a suitable method for high throughput screening of large libraries for potential thyroid hormone disrupting compounds.

  9. Pesticide regulations for agriculture: Chemically flawed regulatory practice.

    PubMed

    Gamble, Donald S; Bruccoleri, Aldo G

    2016-08-01

    Two categories of pesticide soil models now exist. Government regulatory agencies use pesticide fate and transport hydrology models, including versions of PRZM.gw. They have good descriptions of pesticide transport by water flow. Their descriptions of chemical mechanisms are unrealistic, having been postulated using the universally accepted but incorrect pesticide soil science. The objective of this work is to report experimental tests of a pesticide soil model in use by regulatory agencies and to suggest possible improvements. Tests with experimentally based data explain why PRZM.gw predictions can be wrong by orders of magnitude. Predictive spreadsheet models are the other category. They are experimentally based, with chemical stoichiometry applied to integral kinetic rate laws for sorption, desorption, intra-particle diffusion, and chemical reactions. They do not account for pesticide transport through soils. Each category of models therefore lacks what the other could provide. They need to be either harmonized or replaced. Some preliminary tests indicate that an experimental mismatch between the categories of models will have to be resolved. Reports of pesticides in the environment and the medical problems that overlap geographically indicate that government regulatory practice needs to account for chemical kinetics and mechanisms. Questions about possible cause and effect links could then be investigated. PMID:27166991

  10. Hygroscopic, Morphological, and Chemical Properties of Agricultural Aerosols

    NASA Astrophysics Data System (ADS)

    Hiranuma, N.; Brooks, S. D.; Cheek, L.; Thornton, D. C.; Auvermann, B. W.; Littleton, R.

    2007-12-01

    Agricultural fugitive dust is a significant source of localized air pollution in the semi-arid southern Great Plains. In the Texas Panhandle, daily episodes of ground-level fugitive dust emissions from the cattle feedlots are routinely observed in conjunction with increased cattle activity in the late afternoons and early evenings. We conducted a field study to characterize size-selected agricultural aerosols with respect to hygroscopic, morphological, and chemical properties and to attempt to identify any correlations between these properties. To explore the hygroscopic nature of agricultural particles, we have collected size-resolved aerosol samples using a cascade impactor system at a cattle feedlot in the Texas Panhandle and have used the Environmental Scanning Electron Microscope (ESEM) to determine the water uptake by individual particles in those samples as a function of relative humidity. To characterize the size distribution of agricultural aerosols as a function of time, A GRIMM aerosol spectrometer and Sequential Mobility Particle Sizer and Counter (SMPS) measurements were simultaneously performed in an overall size range of 11 nm to 20 µm diameters at a cattle feedlot. Complementary determination of the elemental composition of individual particles was performed using Energy Dispersive X-ray Spectroscopy (EDS). In addition to the EDS analysis, an ammonia scrubber was used to collect ammonia and ammonium in the gas and particulate phases, respectively. The concentration of these species was quantified offline via UV spectrophotometry at 640 nanometers. The results of this study will provide important particulate emission data from a feedyard, needed to improve our understanding of the role of agricultural particulates in local and regional air quality.

  11. THE USE OF CHEMICALS AS FUNGICIDES, BACTERICIDES AND NEMATOCIDES. AGRICULTURAL CHEMICALS TECHNOLOGY, NUMBER 4.

    ERIC Educational Resources Information Center

    Ohio State Univ., Columbus. Center for Vocational and Technical Education.

    THE PURPOSE OF THIS GUIDE IS TO ASSIST TEACHERS IN PREPARING POST-SECONDARY EDUCATION STUDENTS FOR AGRICULTURAL CHEMICAL OCCUPATIONS. ONE OF A SERIES FOR THESE OCCUPATIONS, THIS MODULE WAS DEVELOPED BY A NATIONAL TASK FORCE ON THE BASIS OF DATA FROM STATE STUDIES. SECTIONS ARE (1) PLANT DISEASE AND NEMATODE PREVENTION, CONTROL, OR ERADICATION WITH…

  12. THE USE OF CHEMICALS AS INSECTICIDES--PLANTS. AGRICULTURAL CHEMICALS TECHNOLOGY, NUMBER 2.

    ERIC Educational Resources Information Center

    Ohio State Univ., Columbus. Center for Vocational and Technical Education.

    THIS GUIDE IS ONE OF A SERIES DESIGNED TO PROVIDE GROUP INSTRUCTION AND INDIVIDUAL OCCUPATIONAL EXPERIENCE FOR POST-SECONDARY STUDENTS PREPARING FOR EMPLOYMENT AS AGRICULTURAL CHEMICAL TECHNICIANS. IT WAS DEVELOPED BY A NATIONAL TASK FORCE ON THE BASIS OF STATE STUDY DATA. THE OBJECTIVES ARE TO DEVELOP (1) INTEREST, APPRECIATION, AND UNDERSTANDING…

  13. Silicon refinement by chemical vapor transport

    NASA Technical Reports Server (NTRS)

    Olson, J.

    1984-01-01

    Silicon refinement by chemical vapor transport is discussed. The operating characteristics of the purification process, including factors affecting the rate, purification efficiency and photovoltaic quality of the refined silicon were studied. The casting of large alloy plates was accomplished. A larger research scale reactor is characterized, and it is shown that a refined silicon product yields solar cells with near state of the art conversion efficiencies.

  14. Chemically generated convective transport in microfluidic system

    NASA Astrophysics Data System (ADS)

    Shklyaev, Oleg; Das, Sambeeta; Altemose, Alicia; Shum, Henry; Balazs, Anna; Sen, Ayusman

    High precision manipulation of small volumes of fluid, containing suspended micron sized objects like cells, viruses, and large molecules, is one of the main goals in designing modern lab-on-a-chip devices which can find a variety of chemical and biological applications. To transport the cargo toward sensing elements, typical microfluidic devices often use pressure driven flows. Here, we propose to use enzymatic chemical reactions which decompose reagent into less dense products and generate flows that can transport particles. Density variations that lead to flow in the assigned direction are created between the place where reagent is fed into the solution and the location where it is decomposed by enzymes attached to the surface of the microchannel. When the reagent is depleted, the fluid motion stops and particles sediment to the bottom. We demonstrate how the choice of chemicals, leading to specific reaction rates, can affect the transport properties. In particular, we show that the intensity of the fluid flow, the final location of cargo, and the time for cargo delivery are controlled by the amount and type of reagent in the system.

  15. Transport of particle-associated elements in two agriculture-dominated boreal river systems.

    PubMed

    Marttila, Hannu; Saarinen, Tuomas; Celebi, Ahmet; Kløve, Bjørn

    2013-09-01

    Transport of particulate pollutants in fluvial systems can contribute greatly to total loads. Understanding transport mechanics under different hydrological conditions is key in successful load estimation. This study analysed trace elements and physico-chemical parameters in time-integrated suspended sediment samples, together with dissolved and total concentrations of pollutants, along two agriculture- and peatland-dominated boreal river systems. The samples were taken in a spatially and temporally comprehensive sampling programme during the ice-free seasons of 2010 and 2011. The hydrochemistry and transport of particle-bound elements in the rivers were strongly linked to intense land use and acid sulphate soils in the catchment area, with arable, pasture and peat areas in particular being main diffuse sources. There were significant seasonal and temporal variations in dissolved and particulate fluxes, but spatial variations were small. Continuous measurements of EC, turbidity and discharge proved to be an accurate indicator of dissolved and particulate fluxes. Overall, the results show that transport of particle-bound elements makes a major contribution to total transport fluxes in agriculture-dominated boreal rivers. PMID:23770550

  16. Cumulus parameterizations in chemical transport models

    NASA Astrophysics Data System (ADS)

    Mahowald, Natalie M.; Rasch, Philip J.; Prinn, Ronald G.

    1995-12-01

    Global three-dimensional chemical transport models (CTMs) are valuable tools for studying processes controlling the distribution of trace constituents in the atmosphere. A major uncertainty in these models is the subgrid-scale parametrization of transport by cumulus convection. This study seeks to define the range of behavior of moist convective schemes and point toward more reliable formulations for inclusion in chemical transport models. The emphasis is on deriving convective transport from meteorological data sets (such as those from the forecast centers) which do not routinely include convective mass fluxes. Seven moist convective parameterizations are compared in a column model to examine the sensitivity of the vertical profile of trace gases to the parameterization used in a global chemical transport model. The moist convective schemes examined are the Emanuel scheme [Emanuel, 1991], the Feichter-Crutzen scheme [Feichter and Crutzen, 1990], the inverse thermodynamic scheme (described in this paper), two versions of a scheme suggested by Hack [Hack, 1994], and two versions of a scheme suggested by Tiedtke (one following the formulation used in the ECMWF (European Centre for Medium-Range Weather Forecasting) and ECHAM3 (European Centre and Hamburg Max-Planck-Institut) models [Tiedtke, 1989], and one formulated as in the TM2 (Transport Model-2) model (M. Heimann, personal communication, 1992). These convective schemes vary in the closure used to derive the mass fluxes, as well as the cloud model formulation, giving a broad range of results. In addition, two boundary layer schemes are compared: a state-of-the-art nonlocal boundary layer scheme [Holtslag and Boville, 1993] and a simple adiabatic mixing scheme described in this paper. Three tests are used to compare the moist convective schemes against observations. Although the tests conducted here cannot conclusively show that one parameterization is better than the others, the tests are a good measure of the

  17. Soil chemical sensor and precision agricultural chemical delivery system and method

    DOEpatents

    Colburn, Jr., John W.

    1991-01-01

    A real time soil chemical sensor and precision agricultural chemical delivery system includes a plurality of ground-engaging tools in association with individual soil sensors which measure soil chemical levels. The system includes the addition of a solvent which rapidly saturates the soil/tool interface to form a conductive solution of chemicals leached from the soil. A multivalent electrode, positioned within a multivalent frame of the ground-engaging tool, applies a voltage or impresses a current between the electrode and the tool frame. A real-time soil chemical sensor and controller senses the electrochemical reaction resulting from the application of the voltage or current to the leachate, measures it by resistivity methods, and compares it against pre-set resistivity levels for substances leached by the solvent. Still greater precision is obtained by calibrating for the secondary current impressed through solvent-less soil. The appropriate concentration is then found and the servo-controlled delivery system applies the appropriate amount of fertilizer or agricultural chemicals substantially in the location from which the soil measurement was taken.

  18. Soil chemical sensor and precision agricultural chemical delivery system and method

    DOEpatents

    Colburn, J.W. Jr.

    1991-07-23

    A real time soil chemical sensor and precision agricultural chemical delivery system includes a plurality of ground-engaging tools in association with individual soil sensors which measure soil chemical levels. The system includes the addition of a solvent which rapidly saturates the soil/tool interface to form a conductive solution of chemicals leached from the soil. A multivalent electrode, positioned within a multivalent frame of the ground-engaging tool, applies a voltage or impresses a current between the electrode and the tool frame. A real-time soil chemical sensor and controller senses the electrochemical reaction resulting from the application of the voltage or current to the leachate, measures it by resistivity methods, and compares it against pre-set resistivity levels for substances leached by the solvent. Still greater precision is obtained by calibrating for the secondary current impressed through solvent-less soil. The appropriate concentration is then found and the servo-controlled delivery system applies the appropriate amount of fertilizer or agricultural chemicals substantially in the location from which the soil measurement was taken. 5 figures.

  19. Fate and transport of glyphosate and aminomethylphosphonic acid in surface waters of agricultural basins

    USGS Publications Warehouse

    Coupe, R.H.; Kalkhoff, S.J.; Capel, P.D.; Gregoire, C.

    2012-01-01

    Background: Glyphosate [N-(phosphonomethyl)glycine] is a herbicide used widely throughout the world in the production of many crops and is heavily used on soybeans, corn and cotton. Glyphosate is used in almost all agricultural areas of the United States, and the agricultural use of glyphosate has increased from less than 10 000 Mg in 1992 to more than 80 000 Mg in 2007. The greatest intensity of glyphosate use is in the midwestern United States, where applications are predominantly to genetically modified corn and soybeans. In spite of the increase in usage across the United States, the characterization of the transport of glyphosate and its degradate aminomethylphosphonic acid (AMPA) on a watershed scale is lacking. Results: Glyphosate and AMPA were frequently detected in the surface waters of four agricultural basins. The frequency and magnitude of detections varied across basins, and the load, as a percentage of use, ranged from 0.009 to 0.86% and could be related to three general characteristics: source strength, rainfall runoff and flow route. Conclusions: Glyphosate use in a watershed results in some occurrence in surface water; however, the watersheds most at risk for the offsite transport of glyphosate are those with high application rates, rainfall that results in overland runoff and a flow route that does not include transport through the soil. ?? 2011 Society of Chemical Industry.

  20. AN INNOVATIVE SYSTEM FOR BIOREMEDIATION OF AGRICULTURAL CHEMICALS FOR ENVIRONMENTAL SUSTAINABILITY

    EPA Science Inventory

    Agricultural chemicals (both inorganic and organic) in drainage discharge from watersheds have raised concerns about the quality of surface water resources. For example, hypoxia in the Gulf of Mexico has been related to the nutrients discharging from agricultural watersheds...

  1. Pdf - Transport equations for chemically reacting flows

    NASA Technical Reports Server (NTRS)

    Kollmann, W.

    1989-01-01

    The closure problem for the transport equations for pdf and the characteristic functions of turbulent, chemically reacting flows is addressed. The properties of the linear and closed equations for the characteristic functional for Eulerian and Lagrangian variables are established, and the closure problem for the finite-dimensional case is discussed for pdf and characteristic functions. It is shown that the closure for the scalar dissipation term in the pdf equation developed by Dopazo (1979) and Kollmann et al. (1982) results in a single integral, in contrast to the pdf, where double integration is required. Some recent results using pdf methods obtained for turbulent flows with combustion, including effects of chemical nonequilibrium, are discussed.

  2. Occurrence and Distribution of Agricultural Pesticides and Transport Modeling in Surface and Subsurface Environments

    NASA Astrophysics Data System (ADS)

    Chu, X.; Marino, M. A.

    2007-12-01

    The use of a variety of pesticides has increased dramatically during the past decades to improve agricultural efficiency and productivity. However, these agricultural chemicals are often washed to surface waters by runoff and leached through the vadose zone to ground water, thereby polluting waters and threatening human health as well as aquatic and terrestrial ecosystems. It is of particular importance to develop effective modeling tools to assess the induced nonpoint source pollution, to regulate the use of agricultural pesticides, and to circumvent further deterioration in water quality. Different physically-based pesticide transport models, ranging from simple analytical models to semidiscrete and more rigorous numerical models, are discussed. In particular, the effects of use of pesticides on their occurrence and distribution in surface and subsurface environments are examined in this study. A windows-based integrated pesticide transport model (IPTM) is used to simulate three-phase pesticide transport and transformation and quantify spatial and temporal distributions in a coupled canopy-soil system as well as pesticide loading potential to the adjacent surface water through surface runoff and erosion. Five different pesticides (diazinon, 2,4-D acid, DBCP, simazine, and lindane) are examined. It is found that occurrence and distribution of pesticides in the environment are closely related to their use and determined by a series of pesticide transport and transformation processes. The occurrence and use of pesticides follow extremely complex and dynamic patterns that are affected by numerous factors related to their use and properties, hydrology, and agricultural activities. It is also found that changes in pesticide use (application quantity, frequency, timing, and method) may result in distinct environmental fate of pesticides in terms of their occurrence extent as well as spatial and temporal distributions.

  3. Transport and attenuation of chloroacetanilides in an agricultural headwater catchment

    NASA Astrophysics Data System (ADS)

    Lefrancq, Marie; Imfeld, Gwenaël; Millet, Maurice; Payraudeau, Sylvain

    2015-04-01

    Chloroacetanilides (e.g., S-metolachlor and acetochlor) are pre-emergent herbicides used on corn and sugar beet and are applied to bare soil, which is prone to runoff and erosion. Some of these herbicides are chiral and the commercial products can be isomerically enriched in the enantiomer-S compared to the enantiomer-R as an example S-metolachlor 80/20% S to R . Determination of the transport of these herbicides in the dissolved and particulate phases of runoff water and degradation in agricultural catchments is currently lacking. The objectives of this study were i) to quantify over an corn growing season the export of chloroacetanilides and their main degradation products (ethane sulfonic (ESA) and oxanilic acid (OXA) degradates of metolachlor (MESA and MOXA) and acetochlor (AcESA and AcOXA)) in an 47 ha agricultural head-catchment in the dissolved and particulate phases, and ii) to evaluate S-metolachlor biodegradation from its application on the field to its export from the catchment using enantiomer analysis. Runoff, erosion, hydrochemistry and chloroacetanilide transport were evaluated at both the plot and catchment scales. Our results showed that an important amount of the pesticide load is missed when only the dissolved concentration of the parent compound is analysed. The total export coefficients for S-metolachlor and acetochlor and their degradation products were 11.4 and 11.8%, respectively, which includes both the dissolved and particulate loads. The partitioning of S-metolachlor and acetochlor between the dissolved and particulate phases varied widely over time and was linked to the suspended solid concentrations. Detection of S-metolachlor degradation products in runoff water was more frequent compared to that of acetochlor degradation products. Enrichment up to 37% of R-metolachlor was observed during the corn growing season, supporting enantioselective degradation of S-metolachlor. Our field study indicates the potential of enantiomer analyses for

  4. Loads and Transport Processes of Nutrients and Pesticides in Five Agricultural Watersheds

    NASA Astrophysics Data System (ADS)

    Domagalski, J. L.; Ator, S. W.; Lampe, D. C.; Baker, N. T.; Sandstrom, M. W.; Coupe, R. H.; Dileanis, P. D.

    2006-05-01

    A comparative study of five agricultural watersheds spanning a range of climatic and hydrologic conditions was completed as part of a larger study on the transport of nutrients and pesticides in multiple environmental compartments of small watersheds. Attention was given to the role of the unsaturated zone, ground water, the ground-water/surface-water interface, overland flow, and rain to account for the loads and to determine which compounds move through the environment in similar ways. In ephemeral streams, with little or no connection to shallow ground water such as in semi-arid settings, most of the chemical transport occurs following precipitation events. In contrast, some heavily irrigated agricultural watersheds, also in semi-arid environments but where the source of irrigation water is imported surface water, experience increases in ground-water levels and year-round stream flow as a result of ground water discharge to the stream through either the stream bed or through seeps (base flow). In those systems, total nitrogen is likely to be the most important agricultural compound with respect to the annual load, while pesticide transport may be minimal. Streams with a combination of base flow and substantial overland flow are more likely to transport significant quantities of phosphorus and pesticides relative to streams dominated by ground-water base flow. Streams fed by other subsurface processes, such as discharge from tile drains, are more like the ground-water base-flow-dominated systems with respect to nitrogen, phosphorus, and pesticides. In most cases, overland flow processes transport the greatest amount of unaltered pesticide compounds. However, some pesticide degradates, such as the daughter products of atrazine and metolachlor, are transported more effectively, or accumulate to a greater degree, in the unsaturated zone and ground water relative to the parent compounds, and a substantial amount of the annual load is contributed by ground water. Rain

  5. Atmospheric Fate and Transport of Agricultural Dust and Ammonia

    NASA Astrophysics Data System (ADS)

    Hiranuma, N.; Brooks, S. D.; Thornton, D. C.; Auvermann, B. W.; Fitz, D. R.

    2008-12-01

    Agricultural fugitive dust and odor are significant sources of localized air pollution in the semi-arid southern Great Plains. Daily episodes of ground-level fugitive dust emissions from the cattle feedlots associated with increased cattle activity in the early evenings are routinely observed, while consistently high ammonia is observed throughout the day. Here we present measurements of aerosol size distributions and concentrations of gas and particulate phase ammonia species collected at a feedlot in Texas during summers of 2006, 2007 and 2008. A GRIMM sequential mobility particle sizer and GRIMM 1.108 aerosol spectrometer were used to determine aerosol size distributions in the range of 10 nm to 20 µm aerodynamic diameter at the downwind and upwind edges of the facility. Using aqueous scrubbers, simultaneous measurements of both gas phase and total ammonia species present in the gas and particle phases were also collected. In addition to the continuous measurements at the edges of the facility, coincident aerosol and ammonia measurements were obtain at an additional site further downwind (~3.5 km). Taken together our measurements will be used to quantify aerosol and ammonia dispersion and transport. Relationships between the fate and transport of the aerosols and ammonia will be discussed.

  6. Subsurface transport of orthophosphate in five agricultural watersheds, USA

    USGS Publications Warehouse

    Domagalski, Joseph L.; Johnson, Henry M.

    2011-01-01

    Concentrations of dissolved orthophosphate (ortho P) in the unsaturated zone, groundwater, tile drains, and groundwater/stream water interfaces were assessed in five agricultural watersheds to determine the potential for subsurface transport. Concentrations of iron oxides were measured in the aquifer material and adsorption of ortho P on oxide surfaces was assessed by geochemical modeling. Attenuation of ortho P in these aquifers was attributed primarily to sorption onto iron oxides, and in one location onto clay minerals. Only one location showed a clear indication of phosphorus transport to a stream from groundwater discharge, although groundwater did contribute to the stream load elsewhere. Subsurface ortho P movement at a site in California resulted in a plume down gradient from orchards, which was attenuated by a 200 m thick riparian zone with natural vegetation. Iron oxides had an effect on phosphorus movement and concentrations at all locations, and groundwater chemistry, especially pH, exerted a major control on the amount of phosphorus adsorbed. Groundwater pH at a site in Maryland was below 5 and that resulted in complete sequestration of phosphorus and no movement toward the stream. Geochemical modeling indicated that as the surfaces approached saturation, groundwater concentrations of ortho P rise rapidly.

  7. Simulation of radionuclide transport in U. S. agriculture

    SciTech Connect

    Sharp, R.D.; Baes, C.F. III

    1982-01-01

    Because of the recent concern about the impact of energy technologies on man and related health effects, there has emerged a need for models to calculate or predict the effects of radionuclides on man. A general overview is presented of a model that calculates the ingrowth of radionuclides into man's food chain. The FORTRAN IV computer program TERRA, Transport of Environmentally Released Radionuclides in Agriculture, simulates the build-up of radionuclides in soil, four plant food compartments, in meat and milk from beef, and in the livestock food compartments that cause radionuclide build-up in milk and meat from beef. A large data set of spatially oriented parameters has been developed in conjunction with TERRA. This direct-access data set is called SITE, Specific Information on the Terrestrial Environment, and contains 35 parameters for each of 3525 half-degree longitude-latitude cells which define the lower 48 states. TERRA and SITE are used together as a package for determining radionuclide concentrations in man's food anywhere within the conterminous 48 states due to atmospheric releases.

  8. Using GIS and logistic regression to estimate agricultural chemical concentrations in rivers of the midwestern USA

    USGS Publications Warehouse

    Battaglin, W.A.

    1996-01-01

    Agricultural chemicals (herbicides, insecticides, other pesticides and fertilizers) in surface water may constitute a human health risk. Recent research on unregulated rivers in the midwestern USA documents that elevated concentrations of herbicides occur for 1-4 months following application in spring and early summer. In contrast, nitrate concentrations in unregulated rivers are elevated during the fall, winter and spring. Natural and anthropogenic variables of river drainage basins, such as soil permeability, the amount of agricultural chemicals applied or percentage of land planted in corn, affect agricultural chemical concentrations in rivers. Logistic regression (LGR) models are used to investigate relations between various drainage basin variables and the concentration of selected agricultural chemicals in rivers. The method is successful in contributing to the understanding of agricultural chemical concentration in rivers. Overall accuracies of the best LGR models, defined as the number of correct classifications divided by the number of attempted classifications, averaged about 66%.

  9. Quantification of chemical transport processes from soil to surface runoff

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Although there is a conceptual understanding on processes governing chemical transport from soil to surface runoff, there are little literature and research results actually quantifying these individual processes. We developed a laboratory flow cell and experimental procedures to quantify chemical ...

  10. Chemical substance transport in soils and its effect on groundwater quality.

    PubMed Central

    Khublarian, M G

    1989-01-01

    The problems of chemical substance applications in different spheres of industry and agriculture and their effects on groundwater quality and human health are described. Sources of groundwater contamination from industrial and municipal wastes, agricultural pollutants, etc., are listed. The experience in the application of chemical fertilizers and pesticides in the USSR is described. A brief estimation of groundwater salinity is given for various regions of the USSR where irrigation is practiced, as well as the experience in environmental protection. Special attention is given to methods of simulating water seepage and chemical substance transport in soils. Boundary problems for free-surface seepage and dissolved solids transport in porous media are stated, and methods of solution are described in the example of the hydrodynamic theory of seepage and dispersion. Some results of calculations with this method are presented. The influence of groundwater quality on the morbidity of the population is given and the main diseases and associated medical problems are listed. PMID:2559843

  11. Performance Objectives, Task Analysis, Learning Content, Content Limits, and Domain Referenced Tests for the Agricultural Chemicals Catalog. Final Report.

    ERIC Educational Resources Information Center

    Hamilton, William; And Others

    This document contains Indiana agricultural chemicals curriculum materials based on the Vocational-Technical Education Consortium of States (VTECS) Agricultural Chemicals Catalog. It is intended to improve preparation of high school and adult students for handling and using agricultural chemicals and for jobs as chemical salespersons or chemical…

  12. Symposium introduction: the first joint American Chemical Society Agricultural and Food Chemistry Division and the American Chemical Society International Chemical Sciences Chapter in Thailand

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The American Chemical Society (ACS) Agricultural and Food Chemistry Division (AGFD) and the ACS International Chemical Sciences Chapter in Thailand (ICSCT) worked together to stage the “1st Joint ACS AGFD - ACS ICSCT Symposium on Agricultural and Food Chemistry,” which was held in Bangkok, Thailand ...

  13. Nutrient Transport in Dredged Reaches of Agricultural Drainage Ditches

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Agricultural drainage ditches are a vital component of many of the more productive agricultural landscapes in the United States. These systems often require intensive management to ensure adequate removal of water from the system, but little is known about how ditch management affects nutrient losse...

  14. Thermodynamic and transport properties of gaseous tetrafluoromethane in chemical equilibrium

    NASA Technical Reports Server (NTRS)

    Hunt, J. L.; Boney, L. R.

    1973-01-01

    Equations and in computer code are presented for the thermodynamic and transport properties of gaseous, undissociated tetrafluoromethane (CF4) in chemical equilibrium. The computer code calculates the thermodynamic and transport properties of CF4 when given any two of five thermodynamic variables (entropy, temperature, volume, pressure, and enthalpy). Equilibrium thermodynamic and transport property data are tabulated and pressure-enthalpy diagrams are presented.

  15. Characterization of Transport Errors in Chemical Forecasts from a Global Tropospheric Chemical Transport Model

    NASA Technical Reports Server (NTRS)

    Bey, I.; Jacob, D. J.; Liu, H.; Yantosca, R. M.; Sachse, G. W.

    2004-01-01

    We propose a new methodology to characterize errors in the representation of transport processes in chemical transport models. We constrain the evaluation of a global three-dimensional chemical transport model (GEOS-CHEM) with an extended dataset of carbon monoxide (CO) concentrations obtained during the Transport and Chemical Evolution over the Pacific (TRACE-P) aircraft campaign. The TRACEP mission took place over the western Pacific, a region frequently impacted by continental outflow associated with different synoptic-scale weather systems (such as cold fronts) and deep convection, and thus provides a valuable dataset. for our analysis. Model simulations using both forecast and assimilated meteorology are examined. Background CO concentrations are computed as a function of latitude and altitude and subsequently subtracted from both the observed and the model datasets to focus on the ability of the model to simulate variability on a synoptic scale. Different sampling strategies (i.e., spatial displacement and smoothing) are applied along the flight tracks to search for systematic model biases. Statistical quantities such as correlation coefficient and centered root-mean-square difference are computed between the simulated and the observed fields and are further inter-compared using Taylor diagrams. We find no systematic bias in the model for the TRACE-P region when we consider the entire dataset (i.e., from the surface to 12 km ). This result indicates that the transport error in our model is globally unbiased, which has important implications for using the model to conduct inverse modeling studies. Using the First-Look assimilated meteorology only provides little improvement of the correlation, in comparison with the forecast meteorology. These general statements can be refined when the entire dataset is divided into different vertical domains, i.e., the lower troposphere (less than 2 km), the middle troposphere (2-6 km), and the upper troposphere (greater than

  16. Persistence and transport potential of chemicals in a multimedia environment

    SciTech Connect

    van de Meent, D.; McKone, T.E.; Parkerton, T.; Matthies, M.; Scheringer, M.; Wania, F.; Purdy, R.; Bennett, D.H.

    2000-02-01

    Persistence in the environment and potential for long-range transport are related since time in the environment is required for transport. A persistent chemical will travel longer distances than a reactive chemical that shares similar chemical properties. Scheringer (1997) has demonstrated the correlation between persistence and transport distance for different organic chemicals. However, this correlation is not sufficiently robust to predict one property from the other. Specific chemicals that are persistent mayor may not exhibit long-range transport potential. Persistence and long-range transport also present different societal concerns. Persistence concerns relate to the undesired possibility that chemicals produced and used now may somehow negatively affect future generations. Long-range transport concerns relate to the undesired presence of chemicals in areas where these compounds have not been used. Environmental policy decisions can be based on either or both considerations depending on the aim of the regulatory program. In this chapter, definitions and methods for quantifying persistence and transport potential of organic chemicals are proposed which will assist in the development of sound regulatory frameworks.

  17. Agricultural herbicide transport in a first-order intermittent stream, Nebraska, USA

    USGS Publications Warehouse

    Vogel, J.R.; Linard, J.I.

    2011-01-01

    The behavior of herbicides in surface waters is a function of many variables, including scale of the watershed, physical and chemical properties of the herbicide, physical and chemical properties of the soil, rainfall intensity, and time of year. In this study, the transport of 6 herbicides and 12 herbicide degradates was examined during the 2004 growing season in an intermediate-scale agricultural watershed (146 ha) that is drained by a first-order intermittent stream, and the mass load for each herbicide in the stream was estimated. The herbicide load during the first week of storm events after application ranged from 17% of annual load for trifluralin to 84% of annual load for acetochlor. The maximum weekly herbicide load in the stream was generally within the first 3 weeks after application for those compounds that were applied within the watershed during 2004, and later for herbicides not applied within the watershed during 2004 but still detected in the stream. The apparent dominant mode of herbicide transport in the stream-determined by analysis amongst herbicide and conservative ion concentrations at different points in the hydrograph and in base flow samples-was either overland runoff or shallow subsurface flow, depending on the elapsed time after application and type of herbicide. The load as a percentage of use (LAPU) for the parent compounds in this study was similar to literature values for those compounds applied by the farmer within the watershed, but smaller for those herbicides that had rainfall as their only source within the watershed.

  18. THE USE OF CHEMICALS IN THE FIELD OF FARM ANIMAL HEALTH (NUTRITION, ENTOMOLOGY, PATHOLOGY). AGRICULTURAL CHEMICALS TECHNOLOGY, NUMBER 7.

    ERIC Educational Resources Information Center

    Ohio State Univ., Columbus. Center for Vocational and Technical Education.

    DEVELOPED BY A NATIONAL TASK FORCE ON THE BASIS OF STATE STUDIES, THIS MODULE IS ONE OF A SERIES DESIGNED TO ASSIST TEACHERS IN PREPARING POST-SECONDARY STUDENTS FOR AGRICULTURAL CHEMICAL OCCUPATIONS. THE SPECIFIC OBJECTIVE OF THIS MODULE IS TO PREPARE TECHNICIANS IN THE FIELD OF THE USE OF CHEMICALS FOR ANIMAL HEALTH. SECTIONS INCLUDE -- (1)…

  19. Factors affecting leaching in agricultural areas and an assessment of agricultural chemicals in the ground water of Kansas

    USGS Publications Warehouse

    Perry, C.A.; Robbins, F.V.; Barnes, P.L.

    1988-01-01

    As assessment of hydrologic factors and agricultural practices that may affect the leaching of agricultural chemicals to groundwater was conducted to evaluate the extent and severity of chemical contamination of groundwater resources in Kansas. The climate of a particular area determines the length of the growing season and the availability of water, at the surface and in the ground, for the growth of plants. Climate, together with surficial geology, soil, and principal aquifers, determines the types of crops to be planted,types of tillage, conservation and irrigation practices, and affects the quantity and method of application of agricultural chemicals. Examination of groundwater nitrate-nitrogen data collected from 766 wells throughout Kansas during 1976-81 indicated that 13 of 14 geohydrologic regions had wells producing samples that exceeded the 10-mg/L drinking water standard determined by the U.S. Environmental Protection Agency. One or more herbicides were detected in water samples from 11 of 56 wells during 1985-86 located in areas susceptible to agricultural leaching. Atrazine was the most common herbicide that was detected; it was detected in water at 9 of 11 wells. Cyanazine was detected in water at three wells; metolachlor at two wells; and metribuzin, alachlor, simazine, and propazine were detected at one well each. (USGS)

  20. Effect of widespread agricultural chemical use on butterfly diversity across Turkish provinces.

    PubMed

    Pekin, Burak K

    2013-12-01

    Although agricultural intensification is thought to pose a significant threat to species, little is known about its role in driving biodiversity loss at regional scales. I assessed the effects of a major component of agricultural intensification, agricultural chemical use, and land-cover and climatic variables on butterfly diversity across 81 provinces in Turkey, where agriculture is practiced extensively but with varying degrees of intensity. I determined butterfly species presence in each province from data on known butterfly distributions and calculated agricultural chemical use as the proportion of agricultural households that use chemical fertilizers and pesticides. I used constrained correspondence analyses and regression-based multimodel inference to determine the effect of environmental variables on species composition and richness, respectively. The variation in butterfly species composition across the provinces was largely explained (78%) by the combination of agricultural chemical use, particularly pesticides, and climatic and land-cover variables. Although overall butterfly richness was primarily explained by climatic and land-cover variables, such as the area of natural vegetation cover, threatened butterfly richness and the relative number of threatened butterfly species decreased substantially as the proportion of agricultural households using pesticides increased. These findings suggest that widespread use of agricultural chemicals, or other components of agricultural intensification that may be collinear with pesticide use, pose an imminent threat to the biodiversity of Turkey. Accordingly, policies that mitigate agricultural intensification and promote low-input farming practices are crucial for protecting threatened species from extinction in rapidly industrializing nations such as Turkey. Efectos del Uso Extensivo de Agroquímicos sobre la Diversidad de Mariposas en Provincias Turcas. PMID:23869856

  1. CHEMICALS, RUNOFF, AND EROSION FROM AGRICULTURAL MANAGEMENT SYSTEMS - CREAMS

    EPA Science Inventory

    The CREAMS model can simulate pollutant movement on and from a field site, including such constituents as fertilizers (N and P), pesticides, and sediment. The effects of various agricultural practices can be assessed by simulation of the potential water, soil, nutrient, and pesti...

  2. AGRICULTURAL CHEMICAL SAFETY ASSESSMENT: A MULTISECTOR APPROACH TO THE MODERNIZATION OF HUMAN SAFETY REQUIREMENTS.

    EPA Science Inventory

    Better understanding of toxicological mechanisms, enhanced testing capabilities, and demands for more sophisticated data for safety and health risk assessment have generated international interest in improving the current testing paradigm for agricultural chemicals. To address th...

  3. Phosphorus transport by surface and subsurface flow pathways in an upland agricultural watershed

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Improved understanding of phosphorus transport by surface and subsurface flow pathways is critical to protecting water quality in agricultural watersheds. While considerable attention has been devoted to understanding phosphorus losses in overland flow, comparatively limited research has examined ph...

  4. Environmental fate and transport of chemical signatures from buried landmines -- Screening model formulation and initial simulations

    SciTech Connect

    Phelan, J.M.; Webb, S.W.

    1997-06-01

    The fate and transport of chemical signature molecules that emanate from buried landmines is strongly influenced by physical chemical properties and by environmental conditions of the specific chemical compounds. Published data have been evaluated as the input parameters that are used in the simulation of the fate and transport processes. A one-dimensional model developed for screening agricultural pesticides was modified and used to simulate the appearance of a surface flux above a buried landmine, estimate the subsurface total concentration, and show the phase specific concentrations at the ground surface. The physical chemical properties of TNT cause a majority of the mass released to the soil system to be bound to the solid phase soil particles. The majority of the transport occurs in the liquid phase with diffusion and evaporation driven advection of soil water as the primary mechanisms for the flux to the ground surface. The simulations provided herein should only be used for initial conceptual designs of chemical pre-concentration subsystems or complete detection systems. The physical processes modeled required necessary simplifying assumptions to allow for analytical solutions. Emerging numerical simulation tools will soon be available that should provide more realistic estimates that can be used to predict the success of landmine chemical detection surveys based on knowledge of the chemical and soil properties, and environmental conditions where the mines are buried. Additional measurements of the chemical properties in soils are also needed before a fully predictive approach can be confidently applied.

  5. Simulation of the environmental fate and transport of chemical signatures from buried landmines

    SciTech Connect

    Phelan, J.M.; Webb, S.W.

    1998-03-01

    The fate and transport of chemical signature molecules that emanate from buried landmines is strongly influenced by physical chemical properties and by environmental conditions of the specific chemical compounds. Published data have been evaluated as the input parameters that are used in the simulation of the fate and transport processes. A one-dimensional model developed for screening agricultural pesticides was modified and used to simulate the appearance of a surface flux above a buried landmine and estimate the subsurface total concentration. The physical chemical properties of TNT cause a majority of the mass released to the soil system to be bound to the solid phase soil particles. The majority of the transport occurs in the liquid phase with diffusion and evaporation driven advection of soil water as the primary mechanisms for the flux to the ground surface. The simulations provided herein should only be used for initial conceptual designs of chemical pre-concentration subsystems or complete detection systems. The physical processes modeled required necessary simplifying assumptions to allow for analytical solutions. Emerging numerical simulation tools will soon be available that should provide more realistic estimates that can be used to predict the success of landmine chemical detection surveys based on knowledge of the chemical and soil properties, and environmental conditions where the mines are buried. Additional measurements of the chemical properties in soils are also needed before a fully predictive approach can be confidently applied.

  6. ATMOSPHERIC TRANSPORT AND DEPOSITION OF AGRICULTURAL PESTICIDES TO SENSITIVE ECOSYSTEMS

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Off-site transport of pesticides from the point of application may occur by runoff to surface waters, leaching into sub-soil layers and groundwater, and via volatilization to the atmosphere. Atmospheric transport and subsequent deposition of pesticides may negatively affect sensitive wildlife speci...

  7. Simulating the reactive transport of nitrogen species in a regional irrigated agricultural groundwater system

    NASA Astrophysics Data System (ADS)

    Bailey, R. T.; Gates, T. K.

    2011-12-01

    The fate and transport of nitrogen (N) species in irrigated agricultural groundwater systems is governed by irrigation patterns, cultivation practices, aquifer-surface water exchanges, and chemical reactions such as oxidation-reduction, volatilization, and sorption, as well as the presence of dissolved oxygen (O2). We present results of applying the newly-developed numerical model RT3D-AG to a 50,400-ha regional study site within the Lower Arkansas River Valley in southeastern Colorado, where elevated concentrations of NO3 have been observed in both groundwater and surface water during the recent decade. Furthermore, NO3 has a strong influence on the fate and transport of other contaminants in the aquifer system such as selenium (Se) through inhibition of reduction of dissolved Se as well as oxidation of precipitate Se from outcropped and bedrock shale. RT3D-AG, developed by appending the multi-species reactive transport finite-difference model RT3D with modular packages that account for variably-saturated transport, the cycling of carbon (C) and N, and the fate and transport of O2 within the soil and aquifer system, simulates organic C and organic N decomposition and mineralization, oxidation-reduction reactions, and sorption. System sources/sinks consist of applied fertilizer and manure; crop uptake of ammonium (NH4) and NO3 during the growing season; mass of O2, NO3, and NH4 associated with irrigation water and canal seepage; mass of O2, NO3, and NH4 transferred to canals and the Arkansas River from the aquifer; and dead root mass and after-harvest stover mass incorporated into the soil organic matter at the end of the growing season. Chemical reactions are simulated using first-order Monod kinetics, wherein the rate of reaction is dependent on the concentration of the reactants as well as temperature and water content of the soil. Fertilizer and manure application timing and loading, mass of seasonal crop uptake, and end-of-season root mass and stover mass are

  8. Phosphorus transport in agricultural subsurface drainage: A review

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Phosphorus (P) loss from agricultural fields and watersheds has been an important water quality issue for decades because of the critical role P plays in eutrophication. Historically, most research focused on P losses by surface runoff and erosion because subsurface P losses were often deemed to be ...

  9. Data base of accident and agricultural statistics for transportation risk assessment

    SciTech Connect

    Saricks, C.L.; Williams, R.G.; Hopf, M.R.

    1989-11-01

    A state-level data base of accident and agricultural statistics has been developed to support risk assessment for transportation of spent nuclear fuels and high-level radioactive wastes. This data base will enhance the modeling capabilities for more route-specific analyses of potential risks associated with transportation of these wastes to a disposal site. The data base and methodology used to develop state-specific accident and agricultural data bases are described, and summaries of accident and agricultural statistics are provided. 27 refs., 9 tabs.

  10. Virus in Groundwater: Characterization of transport mechanisms and impacts on an agricultural area in Uruguay

    NASA Astrophysics Data System (ADS)

    Gamazo, P. A.; Colina, R.; Victoria, M.; Alvareda, E.; Burutaran, L.; Ramos, J.; Lopez, F.; Soler, J.

    2014-12-01

    In many areas of Uruguay groundwater is the only source of water for human consumption and for industrial-agricultural economic activities. Traditionally considered as a safe source, due to the "natural filter" that occurs in porous media, groundwater is commonly used without any treatment. The Uruguayan law requires bacteriological analysis for most water uses, but virological analyses are not mentioned in the legislation. In the Salto district, where groundwater is used for human consumption and for agricultural activities, bacterial contamination has been detected in several wells but no viruses analysis have been performed. The Republic University (UDELAR), with the support of the National Agency for Research and Innovation (ANII), is studying the incidence of virus in groundwater on an intensive agriculture area of the Salto district. In this area water is pumped from the "Salto Aquifer", a free sedimentary aquifer. Below this sedimentary deposit is the "Arapey" basaltic formation, which is also exploited for water productions on its fractured zones. A screening campaign has been performed searching for bacterial and viral contamination. Total and fecal coliforms have been found on several wells and Rotavirus and Adenovirus have been detected. A subgroup of the screening wells has been selected for an annual survey. On this subgroup, besides bacteria and viruses analysis, a standard physical and chemical characterization was performed. Results show a significant seasonal variation on microbiological contamination. In addition to field studies, rotavirus circulation experiments on columns are being performed. The objective of this experiments is to determinate the parameters that control virus transport in porous media. The results of the study are expected to provide an insight into the impacts of groundwater on Salto's viral gastroenterocolitis outbreaks.

  11. Proceedings of the frst joint american chemical society agricultural and food chemistry division – american chemical society international chemical sciences chapter in Thailand symposium on agricultural and food chemistry

    Technology Transfer Automated Retrieval System (TEKTRAN)

    This Proceedings is a compilation of papers from contributed oral and poster presentations presented at the first joint symposium organized by the American Chemical Society Agricultural and Food Chemistry Division and the American Chemical Society International Chemical Sciences Chapter in Thailand ...

  12. DETERMINANTS OF PERCEIVED AGRICULTURAL CHEMICAL RISK IN THREE WATERSHEDS IN THE MIDWESTERN UNITED STATES. (R825761)

    EPA Science Inventory

    Abstract

    Recent epidemiologic research on the relationship between agricultural chemical use and human health has focused on possible risks to both farmers and nonfarm publics through such avenues as airborne chemical drift and contamination of drinking water. While ag...

  13. Agricultural Chemical and Pesticide Hazards. Module SH-50. Safety and Health.

    ERIC Educational Resources Information Center

    Center for Occupational Research and Development, Inc., Waco, TX.

    This student module on agricultural chemical and pesticide hazards is one of 50 modules concerned with job safety and health. This module contains information concerning the safe handling, use, and storage of many chemicals that are frequently used in the control of pests. Following the introduction, 10 objectives (each keyed to a page in the…

  14. A TIERED APPROACH TO LIFE STAGES TESTING FOR AGRICULTURAL CHEMICAL SAFERY ASSESSMENT

    EPA Science Inventory

    A proposal has been developed by the Agricultural Chemical Safety Assessment (ACSA) Technical Committee of the ILSI Health and Environmental Sciences Institute (HESI) for an improved approach to assessing the safety of crop protection chemicals. The goal is to ensure that studie...

  15. A TIERED APPROACH TO LIFE STAGES TESTING FOR AGRICULTURAL CHEMICAL SAFETY ASSESSMENT

    EPA Science Inventory

    A proposal has been developed by the Agricultural Chemical Safety Assessment (ACSA) Technical Committee of the ILSI Health and Environmental Sciences Institute (HESI) for an improved approach to assessing the safety of crop protection chemicals. The goal is to ensure that studie...

  16. Chemical Kinetic Modeling of Advanced Transportation Fuels

    SciTech Connect

    PItz, W J; Westbrook, C K; Herbinet, O

    2009-01-20

    Development of detailed chemical kinetic models for advanced petroleum-based and nonpetroleum based fuels is a difficult challenge because of the hundreds to thousands of different components in these fuels and because some of these fuels contain components that have not been considered in the past. It is important to develop detailed chemical kinetic models for these fuels since the models can be put into engine simulation codes used for optimizing engine design for maximum efficiency and minimal pollutant emissions. For example, these chemistry-enabled engine codes can be used to optimize combustion chamber shape and fuel injection timing. They also allow insight into how the composition of advanced petroleum-based and non-petroleum based fuels affect engine performance characteristics. Additionally, chemical kinetic models can be used separately to interpret important in-cylinder experimental data and gain insight into advanced engine combustion processes such as HCCI and lean burn engines. The objectives are: (1) Develop detailed chemical kinetic reaction models for components of advanced petroleum-based and non-petroleum based fuels. These fuels models include components from vegetable-oil-derived biodiesel, oil-sand derived fuel, alcohol fuels and other advanced bio-based and alternative fuels. (2) Develop detailed chemical kinetic reaction models for mixtures of non-petroleum and petroleum-based components to represent real fuels and lead to efficient reduced combustion models needed for engine modeling codes. (3) Characterize the role of fuel composition on efficiency and pollutant emissions from practical automotive engines.

  17. Multiple species reactive chemical transport in groundwater: A verification exercise

    SciTech Connect

    Narasimhan, T.N.; Apps, J.A.; Zhu, Ming.

    1991-04-01

    Two multiple-species reactive chemical transport models (FASTCHEM and DYNAMIX) were tested against each other to check for consistency of solutions. For the particular problem studied, FASTCHEM and DYNAMIX led to differences in aqueous concentrations and mineral assemblages primarily because FASTCHEM ignores redox reactions in the transport phase of the calculations. Also, the spatial concentration profiles generated by FASTCHEM tend to be sharper than those generated by DYNAMIX because FASTCHEM is particularly designed to handle advection-dominated transport systems.

  18. "EFFECT OF NON-TARGET ORGANICS ON ORGANIC CHEMICAL TRANSPORT."

    EPA Science Inventory

    NRMRL/IO BOOK NRMRL-CIN-1363 Enfield*, C.G., Lien*, B.K., and Wood*, A.L. "Effect of Non-Target Organics on Organic Chemical Transport." Published in: Humic Substances and Chemical Contaminants, Chapter 23, C.E. Clapp, M.H.B. Hayes, et al (Ed.), Madison, WI: So...

  19. 18. VIEW OF THE CEILING, THE PIPING TRANSPORTED CHEMICALS FROM ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    18. VIEW OF THE CEILING, THE PIPING TRANSPORTED CHEMICALS FROM A CHEMICAL PREPARATION ROOM ON THE SECOND FLOOR TO THE FIRST FLOOR PROCESS AREAS. (6/12/73) - Rocky Flats Plant, Plutonium Recovery & Fabrication Facility, North-central section of plant, Golden, Jefferson County, CO

  20. Transport (Computer Programs for Chemical Engineering Education).

    ERIC Educational Resources Information Center

    Gordon, R., Ed.

    This work contains 21 computer programs intended for use in a chemical engineering education format. The programs represent appropriate homework exercises for undergraduate students. The intended academic level is listed for each example. Although the activities deal with specific problems, the computer programs represent the areas of kinetics,…

  1. Comparative study of transport processes of nitrogen, phosphorus, and herbicides to streams in five agricultural basins, USA

    USGS Publications Warehouse

    Domagalski, J.L.; Ator, S.; Coupe, R.; McCarthy, K.; Lampe, D.; Sandstrom, M.; Baker, N.

    2008-01-01

    Agricultural chemical transport to surface water and the linkage to other hydrological compartments, principally ground water, was investigated at five watersheds in semiarid to humid climatic settings. Chemical transport was affected by storm water runoff, soil drainage, irrigation, and how streams were linked to shallow ground water systems. Irrigation practices and timing of chemical use greatly affected nutrient and pesticide transport in the semiarid basins. Irrigation with imported water tended to increase ground water and chemical transport, whereas the use of locally pumped irrigation water may eliminate connections between streams and ground water, resulting in lower annual loads. Drainage pathways in humid environments are important because the loads may be transported in tile drains, or through varying combinations of ground water discharge, and overland flow. In most cases, overland flow contributed the greatest loads, but a significant portion of the annual load of nitrate and some pesticide degradates can be transported under base-flow conditions. The highest basin yields for nitrate were measured in a semiarid irrigated system that used imported water and in a stream dominated by tile drainage in a humid environment. Pesticide loads, as a percent of actual use (LAPU), showed the effects of climate and geohydrologic conditions. The LAPU values in the semiarid study basin in Washington were generally low because most of the load was transported in ground water discharge to the stream. When herbicides are applied during the rainy season in a semiarid setting, such as simazine in the California basin, LAPU values are similar to those in the Midwest basins. Copyright ?? 2008 by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America. All rights reserved.

  2. Pathogen transport in surface runoff from manured agricultural fields

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Research objective: Manure application to cultivated land is a sustainable approach for enhancing soil fertility and tilth. However, enteric pathogens are often common in manure and can be transported from the application site via runoff and potentially transmitted to livestock and humans. Our objec...

  3. CET89 - CHEMICAL EQUILIBRIUM WITH TRANSPORT PROPERTIES, 1989

    NASA Technical Reports Server (NTRS)

    Mcbride, B.

    1994-01-01

    Scientists and engineers need chemical equilibrium composition data to calculate the theoretical thermodynamic properties of a chemical system. This information is essential in the design and analysis of equipment such as compressors, turbines, nozzles, engines, shock tubes, heat exchangers, and chemical processing equipment. The substantial amount of numerical computation required to obtain equilibrium compositions and transport properties for complex chemical systems led scientists at NASA's Lewis Research Center to develop CET89, a program designed to calculate the thermodynamic and transport properties of these systems. CET89 is a general program which will calculate chemical equilibrium compositions and mixture properties for any chemical system with available thermodynamic data. Generally, mixtures may include condensed and gaseous products. CET89 performs the following operations: it 1) obtains chemical equilibrium compositions for assigned thermodynamic states, 2) calculates dilute-gas transport properties of complex chemical mixtures, 3) obtains Chapman-Jouguet detonation properties for gaseous species, 4) calculates incident and reflected shock properties in terms of assigned velocities, and 5) calculates theoretical rocket performance for both equilibrium and frozen compositions during expansion. The rocket performance function allows the option of assuming either a finite area or an infinite area combustor. CET89 accommodates problems involving up to 24 reactants, 20 elements, and 600 products (400 of which may be condensed). The program includes a library of thermodynamic and transport properties in the form of least squares coefficients for possible reaction products. It includes thermodynamic data for over 1300 gaseous and condensed species and transport data for 151 gases. The subroutines UTHERM and UTRAN convert thermodynamic and transport data to unformatted form for faster processing. The program conforms to the FORTRAN 77 standard, except for

  4. Retention and transport of nutrients in a mature agricultural impoundment

    NASA Astrophysics Data System (ADS)

    Powers, S. M.; Julian, J. P.; Doyle, M. W.; Stanley, E. H.

    2013-03-01

    Small impoundments intended for irrigation, livestock watering, and hydropower are numerous in agricultural regions of the world. Many of these artificial water bodies are well positioned to intercept fertilizer runoff and pollutants but could be vulnerable to long-term sedimentation, management intervention, or failure. We examined solute retention in a mature, sediment-filled, run-of-river impoundment created by a small, >100 year old dam in agricultural Wisconsin, United States. To do so, we measured instantaneous net fluxes of inorganic and organic solutes through the system, which contained wetlands. The impoundment was a persistent net sink for sulfate and, during the warm season only, a net sink for nitrate, ammonium, and soluble reactive phosphorus. There was also a negative relationship between nitrate and sulfate retention, suggestive of nitrate-stimulated sulfate production. Impoundment hydraulics were then altered by a management manipulation (dam removal) that caused mean water travel time to decrease by approximately 40%. Following manipulation, autoregressive modeling of solute time series indicated a decrease in mean net retention of nitrate, sulfate, ammonium, and soluble reactive phosphorus. There was also a decrease in the variability (coefficient of variation) of instantaneous net exports of dissolved organic nitrogen and dissolved organic phosphorus. These biogeochemical changes were consistent with predictions based on hydraulics (reduced water travel time), with the exception of ammonium release immediately following reservoir dewatering. Our results emphasize the biogeochemical importance of reservoir-wetland ecosystems, which are expanding with impoundment sedimentation but are threatened by infrastructure aging. We suggest that reservoir wetlands be considered in the management of dams and surface water pollution.

  5. Chemical method to enhance transungual transport and iontophoresis efficiency.

    PubMed

    Hao, Jinsong; Smith, Kelly A; Li, S Kevin

    2008-06-01

    Transungual transport is hindered by the inherent small effective pore size of the nail even when it is fully hydrated. The objectives of this study were to determine the effects of chemical enhancers thioglycolic acid (TGA), glycolic acid (GA), and urea (UR) on transungual transport and iontophoresis efficiency. In vitro passive and iontophoretic transport experiments of model permeants mannitol (MA), UR, and tetraethylammonium (TEA) ion across the fully hydrated, enhancer-treated and untreated human nail plates were performed in phosphate-buffered saline. The transport experiments consisted of several stages, alternating between passive and anodal iontophoretic transport at 0.1mA. Nail water uptake experiments were conducted to determine the water content of the enhancer-treated nails. The effects of the enhancers on transungual electroosmosis were also evaluated. Nails treated with GA and UR did not show any transport enhancement. Treatment with TGA at 0.5M enhanced passive and iontophoretic transungual transport of MA, UR, and TEA. Increasing the TGA concentration to 1.8M did not further increase TEA iontophoresis efficiency. The effect of TGA on the nail plates was irreversible. The present study shows the possibility of using a chemical enhancer to reduce transport hindrance in the nail plate and thus enhance passive and iontophoretic transungual transport. PMID:18321669

  6. A mathematical model for the transport and fate of organic chemicals in unsaturated/saturated soils.

    PubMed Central

    Lindstrom, F T; Piver, W T

    1985-01-01

    A mathematical model, simulating the transport and fate of nonionizable organic compounds in unsaturated/saturated porous media (soils) in a terrestrial microcosm has been developed. Using the principles of water mass, momentum, heat energy and chemical mass balance, the three fields: moisture, temperature, and liquid phase chemical concentration are solved for simultaneously by coupling the soil slab to an environmentally realistic air-soil interface (a dynamic free boundary) conditions and a prescribed height water table. The environmental conditions at the soil surface-air chamber interface are easily changed, via geometric scaling factors, to simulate either an open agricultural field or a landfill type of situation. Illustrative simulation runs examine the effects of different soil-chemical characteristics on hydrological and chemical concentration profiles. PMID:4029096

  7. Agricultural chemicals at the outlet of a shallow carbonate aquifer

    USGS Publications Warehouse

    Felton, G.K.

    1996-01-01

    A groundwater catchment, located in Woodford and Jessamine Counties in the Inner Bluegrass of Kentucky, was instrumented to develop long- term flow and water quality data. The land uses on this 1 620-ha catchment consist of approximately 59% in grasses consisting of beef farms, horse farms, and a golf course; 16% row crops; 6% orchard: 13% forest; and 6% residential. Water samples were analyzed twice a week for, Ca++, Mg++, Na+, Cl-, HCO3-, O4=, NO3-, total solids, suspended solids, fecal coliforms, fecal streptococci, and triazines. Flow rate and average ambient temperature were also recorded. No strong linear relationship was developed between chemical concentrations and other parameters. The transient nature of the system was emphasized by one event that drastically deviated from others. Pesticide data were summarized and the 'flushing' phenomena accredited to karst systems was discussed. The total solids content in the spring was consistent at approximately 2.06 mg/L. Fecal bacteria contamination was well above drinking water limits (fecal coliform and fetal streptococci averages were I 700 and 4 300 colony-forming-units/100 mL, respectively) and the temporal variation in bacterial contamination was not linked to any other variable.

  8. Nutrient Attenuation Under Natural Conditions in Agricultural Drainage Ditches

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Drainage ditches are common practice in agricultural landscapes with poorly drained soils. Even though high concentrations of nutrients and other agricultural chemicals have been reportedly associated with agricultural drainage ditches, processes affecting nutrient transport in these ditches are not...

  9. Chemical Composition of Wildland and Agricultural Biomass Burning Particles Measured Downwind During BBOP Study

    NASA Astrophysics Data System (ADS)

    Fortner, E.; Onasch, T. B.; Shilling, J.; Pekour, M. S.; Kleinman, L. I.; Sedlacek, A. J., III; Worsnop, D. R.

    2014-12-01

    The Biomass Burning Observation Project (BBOP), a Department of Energy (DOE) sponsored study, measured wildland fires in the Pacific Northwest and prescribed agricultural burns in the Central Southeastern US from the DOE Gulfstream-1 (G-1) aircraft platform over a four month period in 2013. The chemical composition of the emitted particulate emissions were characterized using an Aerodyne Soot Particle Aerosol Mass Spectrometer (SP-AMS) and will be presented in the context of the fire location and source. The SP-AMS was operated with both laser and resistively heated tungsten vaporizers, alternatively turning the laser vaporizer on and off. With the laser vaporizer off, the instrument operated as a standard HR-AMS. Under these sampling conditions, the non-refractory chemical composition of the biomass burning particles will be characterized as a function of the fuel type burned and the observed modified combustion efficiency and observed changes during downwind transport. Specific attention will focus on the level of oxidation (i.e., O:C, H:C, and OM:OC ratios), anhydrosugar, and aromatic content. With the laser vaporizer on, the SP-AMS was also sensitive to the refractory black carbon content, in addition to the non-refractory components, and will be presented within the context of technique-specific collection efficiencies. Under these sampling conditions, addition information on the mass of black carbon, the OM/BC ratio, and the RBC(coat-to-core) ratio will be examined, with a focus on correlating with the simultaneous optical measurements.

  10. Assessment of suspended matter transport in a large agricultural catchment using the MOHID water modelling system

    NASA Astrophysics Data System (ADS)

    David, Bailly; David, Brito; Chantha, Oeurng; Ramiro, Neves; Sabine, Sauvage; Sánchez-Pérez, José-Miguel

    2010-05-01

    Suspended sediment transport from agricultural catchments to stream networks is responsible for impaired water quality, reservoir sedimentation and the transport of sediment-bound pollutants (pesticides, particulate nutrients, metals and other adsorbed toxic substances). The dynamic of pollutants adsorbed on sediment and associated with particulate organic carbon, from land areas into stream network arises mainly from erosion and sedimentation processes. It is known that up to 90% of suspended sediment is transported during flood event and therefore quick flood events have a major impact on pollutant transport. This study - part of the EU AguaFlash (http://www.aguaflash-sudoe.eu/) project - examined and quantified suspended sediment dynamics from catchment to river (erosion, transport, deposition on hillside and in the river). Semi-distributed, physics-based watershed or reservoir models are generally used to simulate sediment dynamics. One of the limitations of this kind of modelling is that transport along agricultural field and the possibility of deposition of suspended sediments in hillslopes are not considered. Consequently, all sediments eroded are assumed to be accumulated in the river and the sediment and associated pollutant dynamics are over- or under-estimated. In our approach, the mechanistic physics-based water modelling system MOHID (http://www.mohid.com) was used to quantify soil erosion and sediment transport processes at the local and macroscopic scale. This paper present the erosion and transport mathematical model and modelling strategy used and compares our initial results with filed data obtained on an 1100 km² intensive agricultural catchment (Save catchment, South-west France) during 2007-2009 and with simulation data produced using SWAT (Soil and Water Assessment Tool, 2005 version). The contribution of the MOHID model compared with that of the semi-distributed SWAT model is discussed. Keywords: Erosion, suspended sediment, transport

  11. Studies of Trace Gas Chemical Cycles Using Observations, Inverse Methods and Global Chemical Transport Models

    NASA Technical Reports Server (NTRS)

    Prinn, Ronald G.

    2001-01-01

    For interpreting observational data, and in particular for use in inverse methods, accurate and realistic chemical transport models are essential. Toward this end we have, in recent years, helped develop and utilize a number of three-dimensional models including the Model for Atmospheric Transport and Chemistry (MATCH).

  12. Growth of zinc oxide by chemical vapor transport

    NASA Astrophysics Data System (ADS)

    Mikami, Makoto; Eto, Toshiaki; Wang, JiFeng; Masa, Yoshihiko; Isshiki, Minoru

    2005-04-01

    ZnO crystal growth by chemical vapor transport (CVT) is carried out using carbon as a transport agent. Under the optimum ΔT and growth temperature, a single crystal was grown. The carbon contamination is not detected by SIMS measurements and all the crystals are orange-red colored. It is claimed that the orange-red color is attributed to the shift of stoichiometry to zinc rich atmosphere.

  13. Agriculture

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Agriculture within the United States is varied and produces a large value ($200 billion in 2002) of production across a wide range of plant and animal production systems. Because of this diversity, changes in climate will likely impact agriculture throughout the United States. Climate affects crop, ...

  14. Pesticide fate and transport throughout unsaturated zones in five agricultural settings, USA

    USGS Publications Warehouse

    Hancock, T.C.; Sandstrom, M.W.; Vogel, J.R.; Webb, R.M.T.; Bayless, E.R.; Barbash, J.E.

    2008-01-01

    Pesticide transport through the unsaturated zone is a function of chemical and soil characteristics, application, and water recharge rate. The fate and transport of 82 pesticides and degradates were investigated at five different agricultural sites. Atrazine and metolachlor, as well as several of the degradates of atrazine, metolachlor, acetochlor, and alachlor, were frequently detected in soil water during the 2004 growing season, and degradates were generally more abundant than parent compounds. Metolachlor and atrazine were applied at a Nebraska site the same year as sampling, and focused recharge coupled with the short time since application resulted in their movement in the unsaturated zone 9 m below the surface. At other sites where the herbicides were applied 1 to 2 yr before sampling, only degradates were found in soil water. Transformations of herbicides were evident with depth and during the 4-mo sampling time and reflected the faster degradation of metolachlor oxanilic acid and persistence of metolachor ethanesulfonic acid. The fraction of metolachlor ethanesulfonic acid relative to metolachlor and metolachlor oxanilic acid increased from 0.3 to > 0.9 at a site in Maryland where the unsaturated zone was 5 m deep and from 0.3 to 0.5 at the shallowest depth. The flux of pesticide degradates from the deepest sites to the shallow ground water was greatest (3.0–4.9 μmol m−2 yr−1) where upland recharge or focused flow moved the most water through the unsaturated zone. Flux estimates based on estimated recharge rates and measured concentrations were in agreement with fluxes estimated using an unsaturated-zone computer model (LEACHM).

  15. Pesticide fate and transport throughout unsaturated zones in five agricultural settings, USA.

    PubMed

    Hancock, Tracy C; Sandstrom, Mark W; Vogel, Jason R; Webb, Richard M T; Bayless, E Randall; Barbash, Jack E

    2008-01-01

    Pesticide transport through the unsaturated zone is a function of chemical and soil characteristics, application, and water recharge rate. The fate and transport of 82 pesticides and degradates were investigated at five different agricultural sites. Atrazine and metolachlor, as well as several of the degradates of atrazine, metolachlor, acetochlor, and alachlor, were frequently detected in soil water during the 2004 growing season, and degradates were generally more abundant than parent compounds. Metolachlor and atrazine were applied at a Nebraska site the same year as sampling, and focused recharge coupled with the short time since application resulted in their movement in the unsaturated zone 9 m below the surface. At other sites where the herbicides were applied 1 to 2 yr before sampling, only degradates were found in soil water. Transformations of herbicides were evident with depth and during the 4-mo sampling time and reflected the faster degradation of metolachlor oxanilic acid and persistence of metolachor ethanesulfonic acid. The fraction of metolachlor ethanesulfonic acid relative to metolachlor and metolachlor oxanilic acid increased from 0.3 to >0.9 at a site in Maryland where the unsaturated zone was 5 m deep and from 0.3 to 0.5 at the shallowest depth. The flux of pesticide degradates from the deepest sites to the shallow ground water was greatest (3.0-4.9 micromol m(-2) yr(-1)) where upland recharge or focused flow moved the most water through the unsaturated zone. Flux estimates based on estimated recharge rates and measured concentrations were in agreement with fluxes estimated using an unsaturated-zone computer model (LEACHM). PMID:18453430

  16. Preventing Agricultural Chemical Exposure: A Safety Program Manual. Participatory Education with Farmworkers in Pesticide Safety.

    ERIC Educational Resources Information Center

    Wake Forest Univ., Winston-Salem, NC. Dept. of Family and Community Medicine.

    Preventing Agricultural Chemical Exposure among North Carolina Farmworkers (PACE) is a project designed to describe farmworker pesticide exposure and to develop an educational intervention to reduce farmworker pesticide exposure. The PACE project used a community participation framework to ensure that the community played a significant role in…

  17. Agricultural Chemical Use and White Male Cancer Mortality in Selected Rural Farm Counties.

    ERIC Educational Resources Information Center

    Stokes, C. Shannon; Brace, Kathy D.

    A study of 1,497 nonmetropolitan counties was conducted to test the possible contribution of agricultural chemical use to cancer mortality rates in rural counties. The dependent variables were 20-year age-adjusted mortality rates for 1950 to 1969 for five categories of cancer: genital, urinary, lymphatic, respiratory, and digestive. Because sex…

  18. OPEN BURNING OF AGRICULTURAL BIOMASS: PHYSICAL AND CHEMICAL PROPERTIES OF PARTICLE-PHASE EMISSIONS

    EPA Science Inventory

    This effort presents the physical and chemical characterization of PM2.5 emissions from simulated agricultural fires of surface residuals of two major grain crops, rice (Oryza sativa) and wheat (Triticum aestivum L). The O2 levels and CO/CO

  19. Chemical Pesticides and Human Health: The Urgent Need for a New Concept in Agriculture.

    PubMed

    Nicolopoulou-Stamati, Polyxeni; Maipas, Sotirios; Kotampasi, Chrysanthi; Stamatis, Panagiotis; Hens, Luc

    2016-01-01

    The industrialization of the agricultural sector has increased the chemical burden on natural ecosystems. Pesticides are agrochemicals used in agricultural lands, public health programs, and urban green areas in order to protect plants and humans from various diseases. However, due to their known ability to cause a large number of negative health and environmental effects, their side effects can be an important environmental health risk factor. The urgent need for a more sustainable and ecological approach has produced many innovative ideas, among them agriculture reforms and food production implementing sustainable practice evolving to food sovereignty. It is more obvious than ever that the society needs the implementation of a new agricultural concept regarding food production, which is safer for man and the environment, and to this end, steps such as the declaration of Nyéléni have been taken. PMID:27486573

  20. Chemical Pesticides and Human Health: The Urgent Need for a New Concept in Agriculture

    PubMed Central

    Nicolopoulou-Stamati, Polyxeni; Maipas, Sotirios; Kotampasi, Chrysanthi; Stamatis, Panagiotis; Hens, Luc

    2016-01-01

    The industrialization of the agricultural sector has increased the chemical burden on natural ecosystems. Pesticides are agrochemicals used in agricultural lands, public health programs, and urban green areas in order to protect plants and humans from various diseases. However, due to their known ability to cause a large number of negative health and environmental effects, their side effects can be an important environmental health risk factor. The urgent need for a more sustainable and ecological approach has produced many innovative ideas, among them agriculture reforms and food production implementing sustainable practice evolving to food sovereignty. It is more obvious than ever that the society needs the implementation of a new agricultural concept regarding food production, which is safer for man and the environment, and to this end, steps such as the declaration of Nyéléni have been taken. PMID:27486573

  1. CHEMICAL AND BIOLOGICAL CHARACTERIZATION OF PRODUCTS OF INCOMPLETE COMBUSTION FROM THE SIMULATED FIELD BURNING OF AGRICULTURAL PLASTIC

    EPA Science Inventory

    The article describes chemical and biological analyses performed to characterize products of incomplete combustion emitted during the simulated open field burning of agricultural plastic. The study highlights the benefits of a combined chemical/biological approach to characteizin...

  2. HYDROGEOLOGIC CONTROLS ON NITRATE TRANSPORT IN A SMALL AGRICULTURAL CATCHMENT, IOWA

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Effects of subsurface lithology on nitrate loss in stream riparian zones are recognized but little attention has been focused on similar processes occurring in upland agricultural settings. In this paper, we evaluated hydrogeologic controls on nitrate transport processes occurring in a small 7.6 ha ...

  3. TRANSPORT OF CHEMICAL CONTAMINANTS IN KARST TERRANES: OUTLINE AND SUMMARY

    EPA Science Inventory

    Chemical spills that reach an aquifer in karst terranes do not behave like those in granular or highly fractured aquifers. pills reaching diffuse-flow aquifers display relatively slow transport, are radially dispersive, and can be tracked through the use of monitoring wells. pill...

  4. EFFECT OF NON-TARGET ORGANICS ON ORGANIC CHEMICAL TRANSPORT

    EPA Science Inventory

    To improve our standard of living, man has synthesized organic compounds for use in products considered essential for life. These compounds are having and will continue to have a significant impact on the terrestrial environment. Understanding organic chemical transport through s...

  5. Agricultural chemicals in ground and surface water in a small watershed in Clayton County, Iowa, 1988-91

    USGS Publications Warehouse

    Kalkhoff, S.J.; Schaap, B.D.

    1995-01-01

    Nitrogen was present in all water samples from Deer Creek. Nitrate concentrations ranged from 0.70 to 17 mg/L. Alachlor was detected in 11 percent of the samples, atrazine in 69 percent, cyanazine in 19 percent, and metolachlor in 33 percent. Alachlor concentrations ranged from less than 0.10 to 0.53 ug/L, atrazine ranged from less than 0.10 to 55 ug/L, cyanazine ranged from less than 0.10 to 12 ug/L, and metolachlor ranged from less than 0.10 to 69 ug/L. Herbicide detections occurred most frequently in late spring and early summer during or just following chemical application. Overland flow is an important source of nitrogen and herbicides to Deer Creek. Substantial amounts of agricultural chemicals are transported from the watershed. As much as 4,700 pounds, or 6.7 pounds per acre, of nitrogen were estimated to be transported from the watershed in 1 year. Nitrogen loads transported from the Deer Creek watershed were less during dry years than during years with average or greater than average rainfall.

  6. Transport and transportation pathways of hazardous chemicals from solid waste disposal.

    PubMed Central

    Van Hook, R I

    1978-01-01

    To evaluate the impact of hazardous chemicals in solid wastes on man and other organisms, it is necessary to have information about amounts of chemical present, extent of exposure, and chemical toxicity. This paper addresses the question of organism exposure by considering the major physical and biological transport pathways and the physicochemical and biochemical transformations that may occur in sediments, soils, and water. Disposal of solid wastes in both terrestrial and oceanic environments is considered. Atmospheric transport is considered for emissions from incineration of solid wastes and for wind resuspension of particulates from surface waste deposits. Solid wastes deposited in terrestrial environments are subject to leaching by surface and ground waters. Leachates may then be transported to other surface waters and drinking water aquifers through hydrologic transport. Leachates also interact with natural organic matter, clays, and microorganisms in soils and sediments. These interactions may render chemical constituents in leachates more or less mobile, possibly change chemical and physical forms, and alter their biological activity. Oceanic waste disposal practices result in migration through diffusion and ocean currents. Surface area-to-volume ratios play a major role in the initial distributions of chemicals in the aquatic environment. Sediments serve as major sources and sinks of chemical contaminants. Food chain transport in both aquatic and terrestrial environments results in the movement of hazardous chemicals from lower to higher positions in the food web. Bioconcentration is observed in both terrestrial and aquatic food chains with certain elements and synthetic organics. Bioconcentration factors tend to be higher for synthetic organics, and higher in aquatic than in terrestrial systems. Biodilution is not atypical in terrestrial environments. Synergistic and antagonistic actions are common occurrences among chemical contaminants and can be

  7. PATHWAY: a simulation model of radionuclide-transport through agricultural food chains

    SciTech Connect

    Kirchner, T.B.; Whicker, F.W.; Otis, M.D.

    1982-01-01

    PATHWAY simulates the transport of radionuclides from fallout through an agricultural ecosystem. The agro-ecosystem is subdivided into several land management units, each of which is used either for grazing animals, for growing hay, or for growing food crops. The model simulates the transport of radionuclides by both discrete events and continuous, time-dependent processes. The discrete events include tillage of soil, harvest and storage of crops,and deposition of fallout. The continuous processes include the transport of radionuclides due to resuspension, weathering, rain splash, percolation, leaching, adsorption and desorption of radionuclides in the soil, root uptake, foliar absorption, growth and senescence of vegetation, and the ingestion assimilation, and excretion of radionuclides by animals. Preliminary validation studies indicate that the model dynamics and simulated values of radionuclide concentrations in several agricultural products agree well with measured values when the model is driven with site specific data on deposition from world-wide fallout.

  8. Agricultural chemicals in alluvial aquifers in Missouri after the 1993 flood

    USGS Publications Warehouse

    Heimann, D.C.; Richards, J.M.; Wilkison, D.H.

    1997-01-01

    Intense rains produced flooding during the spring and summer of 1993 over much of the midwestern USA including many agricultural areas of Missouri. Because of potential contamination from floodwater, an investigation was conducted to determine the changes in concentrations of agricultural chemicals in water samples from alluvial wells in Missouri after the flood. Water samples from 80 alluvial wells with historical data were collected in March, July, and November 1994, and analyzed for dissolved herbicides, herbicide metabolites, and nitrate (NO3). There were no statistically significant differences in the distribution of alachlor ((2,chloro-2'-6'-diethyl-N-[methoxymethyl]acetanilide), atrazine (2-chloro- 4-ethylamino-6-isopropylamino-1, 3, 5 triazine), and nitrate concentrations between pre- and postflood samples (?? = 0.05). The detection frequency of alachlor and atrazine in postflood samples was generally lower than the frequency in preflood samples. Analyses of agricultural chemicals in water samples from an intensely sampled well field indicate significant differences between the distribution of dissolved P concentrations in pre- and postflood samples (?? = 0.05). However, no significant differences were detected between the pre- and postflood distributions of NO3 or ammonia concentrations. Because of the numerous sources of temporal variability and the relatively short record of water-quality data for the study wells, a cause-and-effect relation between changes in agricultural chemical concentrations and a single factor of the 1993 flood is difficult to determine. Based on the results of this study, the 1993 flood did not cause widespread or long-term significant changes in concentrations of agricultural chemicals in water from alluvial aquifers in Missouri.

  9. Physico-chemical characteristics affect the spatial distribution of pesticide and transformation product loss to an agricultural brook.

    PubMed

    Gassmann, M; Olsson, O; Stamm, C; Weiler, M; Kümmerer, K

    2015-11-01

    Diffuse entry of pesticide residues from agriculture into rivers is spatially unevenly distributed. Therefore, the identification of critical source areas (CSAs) may support water quality management in agricultural catchments. In contrast to former studies, we followed the hypothesis that not only hydrological and topographical characteristics but also physico-chemical properties of pesticide residues have a major influence on their loss to rivers and on corresponding formation of CSAs. We designed a virtual experiment, i.e. a numerical experiment as close as possible to environmental conditions, in a headwater catchment where pronounced spatial differences in hydrological transport processes were identified in the past. 144 scenarios with different combinations of adsorption coefficients (KOC = 10-1000 ml/g) and transformation half-lives (DT50 = 3-60 days) for pesticide parent compounds (PCs) and their transformation products (TPs) were simulated using the catchment-scale spatially distributed reactive transport model ZIN-AgriTra. Export fractions of substances in the virtual experiment ranged from 0.001-15% for pesticides and 0.001-1.8% for TPs. The results of the scenario investigations suggest that more of the calculated export mass variability could be attributed to KOC than to DT50 for both PCs and TPs. CSAs for TPs were spatially more equally distributed in the catchment than for PC export which was likely an effect of changing physico-chemical properties during transformation. The ranking of highest export fields was different between PCs and TPs for most of the investigated scenarios but six fields appeared among the top ten export fields in 95% of the scenarios, which shows the influence of site characteristics such as tile drains or soil properties in the catchment. Thus, the highest export fields were determined by a combination of site characteristics and substance characteristics. Therefore, despite the challenge of widely differing physico-chemical

  10. Effects of Convective Transport on Chemical Signal Propagation in Epithelia

    PubMed Central

    Nebyla, Marek; Přibyl, Michal; Schreiber, Igor

    2012-01-01

    We study effects of convective transport on a chemical front wave representing a signal propagation at a simple (single layer) epithelium by means of mathematical modeling. Plug flow and laminar flow regimes were considered. We observed a nonmonotonous dependence of the propagation velocity on the ligand receptor binding constant under influence of the convective transport. If the signal propagates downstream, the region of high velocities becomes much broader and spreads over several orders of magnitude of the binding constant. When the convective transport is oriented against the propagating signal, either velocity of the traveling front wave is slowed down or the traveling front wave can stop or reverse the direction of propagation. More importantly, chemical signal in epithelial systems influenced by the convective transport can propagate almost independently of the ligand-receptor binding constant in a broad range of this parameter. Furthermore, we found that the effects of the convective transport becomes more significant in systems where either the characteristic dimension of the extracellular space is larger/comparable with the spatial extent of the ligand diffusion trafficking or the ligand-receptor binding/ligand diffusion rate ratio is high. PMID:22404921

  11. Forest Canopy Processes in a Regional Chemical Transport Model

    NASA Astrophysics Data System (ADS)

    Makar, Paul; Staebler, Ralf; Akingunola, Ayodeji; Zhang, Junhua; McLinden, Chris; Kharol, Shailesh; Moran, Michael; Robichaud, Alain; Zhang, Leiming; Stroud, Craig; Pabla, Balbir; Cheung, Philip

    2016-04-01

    Forest canopies have typically been absent or highly parameterized in regional chemical transport models. Some forest-related processes are often considered - for example, biogenic emissions from the forests are included as a flux lower boundary condition on vertical diffusion, as is deposition to vegetation. However, real forest canopies comprise a much more complicated set of processes, at scales below the "transport model-resolved scale" of vertical levels usually employed in regional transport models. Advective and diffusive transport within the forest canopy typically scale with the height of the canopy, and the former process tends to dominate over the latter. Emissions of biogenic hydrocarbons arise from the foliage, which may be located tens of metres above the surface, while emissions of biogenic nitric oxide from decaying plant matter are located at the surface - in contrast to the surface flux boundary condition usually employed in chemical transport models. Deposition, similarly, is usually parameterized as a flux boundary condition, but may be differentiated between fluxes to vegetation and fluxes to the surface when the canopy scale is considered. The chemical environment also changes within forest canopies: shading, temperature, and relativity humidity changes with height within the canopy may influence chemical reaction rates. These processes have been observed in a host of measurement studies, and have been simulated using site-specific one-dimensional forest canopy models. Their influence on regional scale chemistry has been unknown, until now. In this work, we describe the results of the first attempt to include complex canopy processes within a regional chemical transport model (GEM-MACH). The original model core was subdivided into "canopy" and "non-canopy" subdomains. In the former, three additional near-surface layers based on spatially and seasonally varying satellite-derived canopy height and leaf area index were added to the original model

  12. Chemical tracers illustrate pathways of solute discharge from artificially drained agricultural watersheds

    NASA Astrophysics Data System (ADS)

    Bowen, G. J.; Kennedy, C. D.; Bataille, C. P.; Liu, Z.; Ale, S.; VanDeVelde, J. H.; Roswell, C.; Bowling, L. C.

    2012-12-01

    Drainage tiles buried beneath many naturally poorly drained agricultural fields in the Midwestern U.S. are believed to "short circuit" pools of nitrate-laden soil water and shallow groundwater directly into streams that eventually discharge to the Mississippi River. Although much is known about the mechanisms controlling this regionally pervasive practice of artificial drainage at the field-plot scale, an integrative assessment of the effect of drainage density (i.e., the number of tile drains per unit area) on the transport of nutrients and solutes in streams at the catchment scale is lacking. To address this gap, we coupled hydrological pathway data from stable isotopes and conservative solute tracers with measurements of the flux of agricultural nitrate and road-salt chloride from two catchments lying within the Wabash River Basin, a major source of nitrate to the Mississippi River. The paired catchments differ primarily in drainage density (70% vs. 31%, by catchment area), with essentially all other agricultural management, land use, and soil drainage characteristics remaining equal. Our study revealed two significant hydrological responses to increased drainage density: (1) more near-surface storm event water (dilute in both nitrate and chloride) was transported early in the storm and (2) higher transport of chloride-laden pre-event soil water relative to shallow groundwater elevated in nitrate occurred later in the storm. These patterns are consistent with a proposed conceptual model in which increased drainage density results in (1) greater transport of soil water to streams and (2) a delayed rise in the water table. With respect to nutrient management implications, these results indicate that increased drainage density impacts subsurface pools of chloride and nitrate differently, a finding that we propose is linked to soil/ground water dynamics in artificially drained agricultural catchments.

  13. Radionuclides as indicators of sediment transport in agricultural watersheds that drain to Lake Erie.

    PubMed

    Matisoff, Gerald; Bonniwell, Everett C; Whiting, Peter J

    2002-01-01

    An issue in evaluating the success of agricultural management practices is the speed that eroded particles make their way through the downstream waters. In this study at Old Woman Creek (OWC) and Rock Creek (RC), two largely agricultural watersheds in Ohio, the flux of sediment and radionuclides (7Be, 210Pb, and 137Cs) in thunderstorm runoff was examined to better understand transport of eroded agricultural soils. The hydrograph in an agricultural area under no-till was similar in timing, but of lesser magnitude, than the hydrograph from a similar-sized area under conventional tillage. The activities of 210Pb and 7Be are linearly correlated and are higher in suspended sediments derived from no-till subbasins than those derived from conventionally tilled subbasins. A suspended sediment plume, identified by its unique radionuclide signature, was traced through 17 km of OWC stream channel in approximately 13.4 h (0.35 m/s). The downstream exponential decrease of 7Be activities in suspended sediments 3 to 12 h after passage of the sediment plume was used to estimate transport distances of suspended sediment from 2 to 17 km, respectively. Transport distances of suspended sediments were also calculated from wave kinematics and indicate that at OWC suspended sediment transport distances were longer in streams draining areas of no-till (19-26 km) than in the streams draining areas of conventional tillage (6-15 km). Suspended sediments travel 7 to 22 km at RC. The transport distances are long relative to the lengths of the stream channel and indicate that erosion control methods implemented in the watershed should be reflected quickly in downstream waters. PMID:11837446

  14. Movement of agricultural chemicals between surface water and ground water, lower Cedar River basin, Iowa

    USGS Publications Warehouse

    Squillace, Paul J.; Caldwell, J.P.; Schulmeyer, P.M.; Harvey, C.A.

    1996-01-01

    Bank storage is probably an important source of agricultural chemicals discharged from the alluvial aquifer but becomes depleted with time after surface runoff. Herbicides discharged from the alluvial aquifer during periods of extended base flow entered the alluvial aquifer with ground-water recharge at some distance from the river. The movement of nitrate between surface water and ground water is minor, when compared to the herbicides, even though nitrite was detected in the Cedar River during runoff.

  15. Towards personalized agriculture: what chemical genomics can bring to plant biotechnology

    PubMed Central

    Stokes, Michael E.; McCourt, Peter

    2014-01-01

    In contrast to the dominant drug paradigm in which compounds were developed to “fit all,” new models focused around personalized medicine are appearing in which treatments are developed and customized for individual patients. The agricultural biotechnology industry (Ag-biotech) should also think about these new personalized models. For example, most common herbicides are generic in action, which led to the development of genetically modified crops to add specificity. The ease and accessibility of modern genomic analysis, when wedded to accessible large chemical space, should facilitate the discovery of chemicals that are more selective in their utility. Is it possible to develop species-selective herbicides and growth regulators? More generally put, is plant research at a stage where chemicals can be developed that streamline plant development and growth to various environments? We believe the advent of chemical genomics now opens up these and other opportunities to “personalize” agriculture. Furthermore, chemical genomics does not necessarily require genetically tractable plant models, which in principle should allow quick translation to practical applications. For this to happen, however, will require collaboration between the Ag-biotech industry and academic labs for early stage research and development, a situation that has proven very fruitful for Big Pharma. PMID:25183965

  16. Manipulation of spin transport in graphene by surface chemical doping.

    PubMed

    Pi, K; Han, Wei; McCreary, K M; Swartz, A G; Li, Yan; Kawakami, R K

    2010-05-01

    The effects of surface chemical doping on spin transport in graphene are investigated by performing nonlocal measurements in ultrahigh vacuum while depositing gold adsorbates. We demonstrate manipulation of the gate-dependent nonlocal spin signal as a function of gold coverage. We discover that charged impurity scattering is not the dominant mechanism for spin relaxation in graphene, despite its importance for momentum scattering. Finally, unexpected enhancements of the spin lifetime illustrate the complex nature of spin relaxation in graphene. PMID:20482203

  17. Runoff, sediment transport, and water quality in a northern Illinois agricultural watershed before urban development, 1979-81

    USGS Publications Warehouse

    Allen, H.E., Jr.; Gray, J.R.

    1984-01-01

    A study designed to quantify and evaluate changes in runoff and sediment transport attributable to construction activities during urban development of a watershed required identification of pre-construction hydrologic conditions. Data collected before construction on a 2.81 sq m (7.28 sq km) agricultural watershed (upper Spring Creek) near Rockford, IL, show that during a 2-year period ending June 30, 1981, 2,890 tons (2,620 Mg) of suspended sediment were transported from the watershed. Of the 2 ,890 tons (2,620 Mg), 2,690 tons (2,440 Mg) or 93.1 % were transported during a storm in a 46.6-hour period of June 13-14, 1981. Runoff from a 0.031 sq m (0.080 sq km) subbasin (Spring Creek tributary) transported 33.9 tons (30.9 Mg) of suspended sediment during a 3.2-hour storm period on June 13, 1981. Regression models relating storm suspended-sediment yields and peak-water discharge per square mile for upper Spring Creek and Spring Creek tributary have average standard errors of 57 and 24 %, respectively. Trace amounts of currently banned pesticides, including Aldrin and DDT, were detected in streambed material samples. Documented sediment yields, chemical quality, and relations between runoff and sediment discharge provide baseline information for future evaluation of hydrologic conditions in the watershed. (USGS)

  18. Chemically generated convective transport of micron sized particles

    NASA Astrophysics Data System (ADS)

    Shklyaev, Oleg; Das, Sambeeta; Altemose, Alicia; Shum, Henry; Balazs, Anna; Sen, Ayusman

    2015-11-01

    A variety of chemical and biological applications require manipulation of micron sized objects like cells, viruses, and large molecules. Increasing the size of particles up to a micron reduces performance of techniques based on diffusive transport. Directional transport of cargo toward detecting elements reduces the delivery time and improves performance of sensing devices. We demonstrate how chemical reactions can be used to organize fluid flows carrying particles toward the assigned destinations. Convection is driven by density variations caused by a chemical reaction occurring at a catalyst or enzyme-covered target site. If the reaction causes a reduction in fluid density, as in the case of catalytic decomposition of hydrogen peroxide, then fluid and suspended cargo is drawn toward the target along the bottom surface. The intensity of the fluid flow and the time of cargo delivery are controlled by the amount of reagent in the system. After the reagent has been consumed, the fluid pump stops and particles are found aggregated on and around the enzyme-coated patch. The pumps are reusable, being reactivated upon injection of additional reagent. The developed technique can be implemented in lab-on-a-chip devices for transportation of micro-scale object immersed in solution.

  19. Transport Coefficients for the NASA Lewis Chemical Equilibrium Program

    NASA Technical Reports Server (NTRS)

    Svehla, Roger A.

    1995-01-01

    The new transport property data that will be used in the NASA Lewis Research Center's Chemical Equilibrium and Applications Program (CEA) is presented. It complements a previous publication that documented the thermodynamic and transport property data then in use. Sources of the data and a brief description of the method by which the data were obtained are given. Coefficients to calculate the viscosity, thermal conductivity, and binary interactions are given for either one, or usually, two temperature intervals, typically 300 to 1000 K and 1000 to 5000 K. The form of the transport equation is the same as used previously. The number of species was reduced from the previous database. Many species for which the data were estimated were eliminated from the database. Some ionneutral interactions were added.

  20. Transport and chemical loss rates in Saturn's inner plasma disk

    NASA Astrophysics Data System (ADS)

    Holmberg, M. K. G.; Wahlund, J.-E.; Vigren, E.; Cassidy, T. A.; Andrews, D. J.

    2016-03-01

    The Kronian moon Enceladus is constantly feeding its surrounding with new gas and dust, from cryovolcanoes located in its south polar region. Through photoionization and impact ionization of these neutrals, a plasma disk is created, which mainly contains hydrogen ions and water group ions. This paper investigates the importance of ion loss by outward radial transport and ion loss by dissociative recombination, which is the dominant chemical loss process in the inner plasma disk. We use plasma densities derived from several years of measurements by the Cassini Radio and Plasma Wave Science electric field power spectral density and Langmuir probe to calculate the total flux tube content NL2. Our calculation shows that NL2 agrees well with earlier estimates within dipole L shell 8. We also show that loss by transport dominates chemical loss between L shells 4 and 10. Using extrapolation of available measurements, we extend the study to include L shells 2.5 to 4. The results indicate that loss by transport dominates chemical loss also between L shells 2.5 and 4. The loss rate by transport is around five times larger at L shell 5, and the difference increases as L7.7 beyond L = 5, for the net ion population. Chemical loss may still be important for the structure of the plasma disk in the region closest to Enceladus (around ±0.5 RS) at 3.95 RS (1 RS = Saturn's equatorial radius = 60,268 km), since the transport and chemical loss rates only differ by a factor of ˜2 in this region. We also derive the total plasma content of the plasma disk between L shells 4 and 10 to be 1.9 × 1033 ions and the total ion source rate for the same region to be 5.8 × 1027 s-1. The estimated equatorial ion production rate P ranges from 2.6 × 10-5 cm-3 s-1 (at L = 10) to 1.1 × 10-4 cm-3 s-1 (at L = 4.8). The net mass loading rate is derived to be 123 kg/s for L shells 4 to 10.

  1. Transport of reactive chemicals in sediment-laden streams

    NASA Astrophysics Data System (ADS)

    Revelli, R.; Ridolfi, L.

    This paper deals with the transport of chemicals in a turbulent stream when both sorbing suspended load and decay reactions are present. These conditions, which can be found quite commonly in rivers, give rise to interesting behaviour. Important and not trivial processes are added and interact with the classical diffusive, advective, and dispersive mechanisms. Due to the sorption process, the chemical divides into an aqueous and a sorbed phase which follow different evolutions: the aqueous phase is regulated by turbulent diffusion, advection and shear, while the sorbed one undergoes the same fluid dynamic mechanisms but through the evolution of suspended sediment, which is also subjected to sedimentation. The evolutions of the two phases are not separate, as the sorption-desorption exchanges between the aqueous and sorbed phases connect their dynamics. In turn, the decay reactions, being able to modify the concentrations in the two phases, influence the sorption process and therefore the entire transport dynamics. A complex picture results where several nonlinear interactions occur. The main objective of the work is to obtain the one-dimensional partial differential equation that describes the temporal and spatial dynamics of the depth-averaged concentration of the chemical. Due to the existence of three well separated time scales in the whole transport process, the mathematical homogenization theory is adopted to average the two-dimensional model, and the most general case is dealt with in which sediment transport is unsteady while the reactions are nonlinear and different for the aqueous and sorbed phases. Finally, some examples of real cases are discussed where the influence of unsteady suspended sediment dynamics and the nonlinearity of reactions is analyzed, while the role of the several nonlinear differential terms in the model is highlighted.

  2. A Framework for Identifying Selective Chemical Applications for IPM in Dryland Agriculture.

    PubMed

    Umina, Paul A; Jenkins, Sommer; McColl, Stuart; Arthur, Aston; Hoffmann, Ary A

    2015-01-01

    Shifts to Integrated Pest Management (IPM) in agriculture are assisted by the identification of chemical applications that provide effective control of pests relative to broad-spectrum pesticides but have fewer negative effects on natural enemy (beneficial) groups that assist in pest control. Here, we outline a framework for identifying such applications and apply this framework to field trials involving the crop establishment phase of Australian dryland cropping systems. Several chemicals, which are not presently available to farmers in Australia, were identified as providing moderate levels of pest control and seedling protection, with the potential to be less harmful to beneficial groups including predatory mites, predatory beetles and ants. This framework highlights the challenges involved in chemically controlling pests while maintaining non-target populations when pest species are present at damaging levels. PMID:26694469

  3. A Framework for Identifying Selective Chemical Applications for IPM in Dryland Agriculture

    PubMed Central

    Umina, Paul A.; Jenkins, Sommer; McColl, Stuart; Arthur, Aston; Hoffmann, Ary A.

    2015-01-01

    Shifts to Integrated Pest Management (IPM) in agriculture are assisted by the identification of chemical applications that provide effective control of pests relative to broad-spectrum pesticides but have fewer negative effects on natural enemy (beneficial) groups that assist in pest control. Here, we outline a framework for identifying such applications and apply this framework to field trials involving the crop establishment phase of Australian dryland cropping systems. Several chemicals, which are not presently available to farmers in Australia, were identified as providing moderate levels of pest control and seedling protection, with the potential to be less harmful to beneficial groups including predatory mites, predatory beetles and ants. This framework highlights the challenges involved in chemically controlling pests while maintaining non-target populations when pest species are present at damaging levels. PMID:26694469

  4. Project LOCOST: Laser or Chemical Hybrid Orbital Space Transport

    NASA Technical Reports Server (NTRS)

    Dixon, Alan; Kost, Alicia; Lampshire, Gregory; Larsen, Rob; Monahan, Bob; Wright, Geoff

    1990-01-01

    A potential mission in the late 1990s is the servicing of spacecraft assets located in GEO. The Geosynchronous Operations Support Center (GeoShack) will be supported by a space transfer vehicle based at the Space Station (SS). The vehicle will transport cargo between the SS and the GeoShack. A proposed unmanned, laser or chemical hybrid orbital space transfer vehicle (LOCOST) can be used to efficiently transfer cargo between the two orbits. A preliminary design shows that an unmanned, laser/chemical hybrid vehicle results in the fuel savings needed while still providing fast trip times. The LOCOST vehicle receives a 12 MW laser beam from one Earth orbiting, solar pumped, iodide Laser Power Station (LPS). Two Energy Relay Units (ERU) provide laser beam support during periods of line-of-sight blockage by the Earth. The baseline mission specifies a 13 day round trip transfer time. The ship's configuration consist of an optical train, one hydrogen laser engine, two chemical engines, a 18 m by 29 m box truss, a mission-flexible payload module, and propellant tanks. Overall vehicle dry mass is 8,000 kg. Outbound cargo mass is 20,000 kg, and inbound cargo mass is 6,000 kg. The baseline mission needs 93,000 kg of propellants to complete the scenario. Fully fueled, outbound mission mass is 121,000 kg. A regeneratively cooled, single plasma, laser engine design producing a maximum of 768 N of thrust is utilized along with two traditional chemical engines. The payload module is designed to hold 40,000 kg of cargo, though the baseline mission specifies less. A proposed design of a laser/chemical hybrid vehicle provides a trip time and propellant efficient means to transport cargo from the SS to a GeoShack. Its unique, hybrid propulsion system provides safety through redundancy, allows baseline missions to be efficiently executed, while still allowing for the possibility of larger cargo transfers.

  5. Transport through a Heterogeneous Alluvial Aquifer beneath an Agricultural Riparian Buffer

    NASA Astrophysics Data System (ADS)

    Johnson, R.; Mather, A. L.; Smith, E. A.; Green, C. T.

    2012-12-01

    Riparian buffer zones between agricultural fields and streams are intended to attenuate the groundwater transport of non-point-source pollutants. However, if the spatial variability in the alluvial aquifer structure provides pathways for rapid transit across the buffer, the effectiveness for mitigating transport of pollutants to the stream may be limited. The main objective of this work was to examine the effects of alluvial aquifer heterogeneity on groundwater transport beneath an agricultural riparian buffer. This was assessed first by performing a natural-gradient tracer experiment and characterizing the site heterogeneity through hydraulic conductivity profiling. Second, the field hydraulic conductivity data were used with a meandering geostatistical model to represent aquifer heterogeneity and a numerical groundwater model was constructed to simulate the tracer experiment. The tracer experiment showed that a portion of the injected plume (~10% of the total mass) moved at high velocity, while a significant fraction of the mass moved slowly and remained near the injection location. Both the tracer test and the numerical modeling indicate that transport velocities of a meter per day are likely to be present in localized regions throughout the riparian buffer. This highlights the dependence of solute residence time in the riparian zone, and therefore the concentrations arriving in rivers, on the local geological structure.

  6. JOVIAN STRATOSPHERE AS A CHEMICAL TRANSPORT SYSTEM: BENCHMARK ANALYTICAL SOLUTIONS

    SciTech Connect

    Zhang Xi; Shia Runlie; Yung, Yuk L.

    2013-04-20

    We systematically investigated the solvable analytical benchmark cases in both one- and two-dimensional (1D and 2D) chemical-advective-diffusive systems. We use the stratosphere of Jupiter as an example but the results can be applied to other planetary atmospheres and exoplanetary atmospheres. In the 1D system, we show that CH{sub 4} and C{sub 2}H{sub 6} are mainly in diffusive equilibrium, and the C{sub 2}H{sub 2} profile can be approximated by modified Bessel functions. In the 2D system in the meridional plane, analytical solutions for two typical circulation patterns are derived. Simple tracer transport modeling demonstrates that the distribution of a short-lived species (such as C{sub 2}H{sub 2}) is dominated by the local chemical sources and sinks, while that of a long-lived species (such as C{sub 2}H{sub 6}) is significantly influenced by the circulation pattern. We find that an equator-to-pole circulation could qualitatively explain the Cassini observations, but a pure diffusive transport process could not. For slowly rotating planets like the close-in extrasolar planets, the interaction between the advection by the zonal wind and chemistry might cause a phase lag between the final tracer distribution and the original source distribution. The numerical simulation results from the 2D Caltech/JPL chemistry-transport model agree well with the analytical solutions for various cases.

  7. A multimedia fate and chemical transport modeling system for pesticides: I. Model development and implementation

    NASA Astrophysics Data System (ADS)

    Li, Rong; Scholtz, M. Trevor; Yang, Fuquan; Sloan, James J.

    2011-07-01

    We have combined the US EPA MM5/MCIP/SMOKE/CMAQ modeling system with a dynamic soil model, the pesticide emission model (PEM), to create a multimedia chemical transport model capable of describing the important physical and chemical processes involving pesticides in the soil, in the atmosphere, and on the surface of vegetation. These processes include: agricultural practices (e.g. soil tilling and pesticide application mode); advection and diffusion of pesticides, moisture, and heat in the soil; partitioning of pesticides between soil organic carbon and interstitial water and air; emissions from the soil to the atmosphere; gas-particle partitioning and transport in the atmosphere; and atmospheric chemistry and dry and wet deposition of pesticides to terrestrial and water surfaces. The modeling system was tested by simulating toxaphene in a domain that covers most of North America for the period from 1 January 2000 to 31 December 2000. The results show obvious transport of the pesticide from the heavily contaminated soils in the southern United States and Mexico to water bodies including the Atlantic Ocean, the Gulf of Mexico and the Great Lakes, leading to significant dry and wet deposition into these ecosystems. The spatial distributions of dry and wet depositions differ because of their different physical mechanisms; the former follows the distribution of air concentrations whereas the latter is more biased to the North East due to the effect of precipitation.

  8. Simulating variably-saturated reactive transport of selenium and nitrogen in agricultural groundwater systems

    NASA Astrophysics Data System (ADS)

    Bailey, Ryan T.; Gates, Timothy K.; Halvorson, Ardell D.

    2013-06-01

    Selenium (Se) contamination in environmental systems has become a major issue in many regions world-wide during the previous decades, with both elevated and deficient Se concentrations in groundwater, surface water, soils and associated cultivated crops reported. To provide a tool that can assess baseline conditions and explore remediation strategies, this paper presents a numerical model capable of simulating the reactive transport of Se species in large-scale variably-saturated groundwater systems influenced by agricultural practices. Developed by incorporating a Se reaction module into the multi-species, variably-saturated reactive transport model UZF-RT3D, model features include near-surface Se cycling due to agricultural practices, oxidation-reduction reactions, and the inclusion of a nitrogen (N) cycle and reaction module due to the dependence of Se transformation and speciation on the presence of nitrate (NO3). Although the primary motivation is applying the model to large-scale systems, this paper presents applications to agricultural soil profile systems to corroborate the near-surface module processes that are vital in estimating mass loadings to the saturated zone in large-scale fate and transport studies. The first application jointly tests the Se and N modules for corn test plots receiving varying loadings of fertilizer, whereas the second application tests the N module for fertilized and unfertilized test plots. Results indicate that the model is successful in reproducing observed measurements of Se and NO3 concentrations, particularly in lower soil layers and hence in regards to leaching. For the first application, the Ensemble Kalman Filter (EnKF) is used to condition model parameters, demonstrating the usefulness of the EnKF in real-world reactive transport systems.

  9. Ammonia emissions, transport, and deposition downwind of agricultural areas at local to regional scales

    NASA Astrophysics Data System (ADS)

    Zondlo, Mark; Pan, Da; Golston, Levi; Sun, Kang; Tao, Lei

    2016-04-01

    Ammonia (NH3) emissions from agricultural areas show extreme spatiotemporal variations, yet agricultural emissions dominate the global NH3 budget and ammoniated aerosols are a dominant component of unhealthy fine particulate matter. The emissions of NH3 and their deposition near and downwind of agricultural areas is complex. As part of a multi-year field intensive along the Colorado Front Range (including the NASA DISCOVER-AQ and NSF FRAPPE field experiments), we have examined temporal emissions of NH3 from feedlots, regional transport of ammonia and ammoniated aerosols from the plains to relatively pristine regions in Rocky Mountain National Park, and dry deposition and re-emission of grassland NH3 in the park. Eddy covariance measurements at feedlots and natural grasslands in the mountains were conducted with newly-developed open-path, eddy covariance laser-based sensors for NH3 (0.7 ng NH3/m2/s detection limit at 10 Hz). These measurements were coupled with other NH3/NHx measurements from mobile laboratories, aircraft, and satellite to examine the transport of NH3 from agricultural areas to cleaner regions downwind. At the farm level, eddy covariance NH3 fluxes showed a strong diurnal component correlated with temperature regardless of the season but with higher absolute emissions in summer than winter. While farm-to-farm variability (N=62 feedlots) was high, similar diurnal trends were observed at all sites regardless of individual farm type (dairy, beef, sheep, poultry, pig). Deposition at scales of several km showed relatively small deposition (10% loss) based upon NH3/CH4 tracer correlations, though the NH3 concentrations were so elevated (up to ppmv) that these losses should not be neglected when considering near-farm deposition. Ammonia was efficiently transported at least 150 km during upslope events to the Colorado Front Range (ele. 3000-4000 m) based upon aircraft, mobile laboratory, and model measurements. The gas phase lifetime of NH3 was estimated to

  10. Nonlocal reactive transport with physical, chemical, and biological heterogeneity

    NASA Astrophysics Data System (ADS)

    Hu, Bill X.; Cushman, John H.; Deng, Fei-Wen

    When a natural porous medium is viewed from an eulerian perspective, incomplete characterization of the hydraulic conductivity, chemical reactivity, and biological activity leads to nonlocal constitutive theories, irrespective of whether the medium has evolving heterogeneity with fluctuations over all scales. Within this framework a constitutive theory involving nonlocal dispersive and convective fluxes and nonlocal sources/sinks is developed for chemicals undergoing random linear nonequilibrium reactions and random equilibrium first-order decay in a random conductivity field. The resulting transport equations are solved exactly in Fourier-Laplace space and then numerically inverted to real space. Mean concentration contours and various spatial moments are presented graphically for several covariance structures. 1997 Published by Elsevier Science Ltd. All rights reserved

  11. Phosphorus and groundwater: Establishing links between agricultural use and transport to streams

    USGS Publications Warehouse

    Domagalski, Joseph L.; Johnson, Henry

    2012-01-01

    Leaching of applied fertilizer and surface runoff of phosphorus from the soil can contribute to excess growth of algae in downstream water bodies, a condition known as eutrophication. Excessive amounts of algae in eutrophic water bodies can cause large daily changes in the amount of dissolved oxygen in the water because oxygen concentrations tend to be high during daylight hours as a result of photosynthetic activity but then decrease at night. Low concentrations of dissolved oxygen can stress or kill sensitive species living in the water. This study examined concentrations and movement of phosphorus in the soils and groundwater in five agricultural settings across the United States characterized by differences in soil geochemistry, climate, irrigation usage, and cropping systems to assess potential phosphorus movement in the soil and groundwater under common agricultural conditions. The study design included assessment of a variety of agricultural practices, especially cropping patterns and irrigation, so that the factors that contribute to phosphorus movement to groundwater, or sequestration of the phosphorus to soil could be compared and examined. This type of information could potentially be used to formulate best management practices to limit the transport of phosphorus from the agricultural fields.

  12. Agricultural chemicals in groundwater of the midwestern United States: Relations to land use

    USGS Publications Warehouse

    Kolpin, D.W.

    1997-01-01

    To determine the relations between land use and concentrations of selected agricultural chemicals (nitrate, atrazine residue [atrazine (2-chloro-4-ethylamino-6-isopropylamino-s-triazine) + deethylatrazinc (2-amino-4-chloro-6-isopropylamino-s-triazine) + deisopropylatrazine (2-amino-4-chloro-6-ethylamino-s-triazine)], and alachlor residue [alachlor, [2-chloro-2′,6′-diethyl-N-(methoxymethyl) acetanilide] + alachlor ethanesulfonic acid (alachlor-ESA; 2-[(2,6-diethylphenyl)(methoxymethyl)amino]-2-oxoethanesulfonic acid)] in groundwater, detailed land use information based on accurate measurements from aerial photographs for the 1991 growing season was obtained within a 2-km radius surrounding 100 wells completed in near-surface unconsolidated aquifers in the midwestern USA. The most significant land use factors to the agricultural chemicals examined were: nitrate (amount of irrigated crop production, positive relation), atrazine residue (amount of irrigated crop production, positive relation), and alachlor residue (amount of highly erodible land, inverse relation). The investigation of smaller buffer sizes (size of circular area around sampled wells) proved insightful for this study. Additional land use factors having significant relations to all three agricultural chemicals were identified using these smaller buffer radii. The most significant correlations (correlation maxima) generally occurred at ≤500-m for nitrate and ≥1000-m for atrazine residue and alachlor residue. An attempt to improve the statistical relations to land use by taking hydrologic considerations into account (removing land outside the estimated most probable recharge area from the statistical analysis) was not as successful as anticipated. Only 45% of the nitrate, 32% of the atrazine residue, and 20% of the alachlor residue correlations were improved by a consideration of the estimated most probable recharge area.

  13. The Fate and Transport of Glyphosate and AMPA into Surface Waters of Agricultural Watersheds

    NASA Astrophysics Data System (ADS)

    Coupe, R.; Kalkhoff, S.; Capel, P.; Gregoire, C.

    2010-12-01

    Glyphosate [N-(phosphonomethyl)glycine] is a herbicide used widely throughout the world in the production of many crops, but is particularly heavily used on crops which are genetically modified to be glyphosate tolerant: predominately soybeans, corn, potatoes, and cotton. Glyphosate is used extensively in almost all agricultural areas of the United States, and annual application has increased from less than 10,000 Mg in 1992 to more than 80,000 Mg in 2007. The greatest areal use is in the Midwest where glyphosate is applied on genetically modified corn and soybeans. Although use is increasing, the characterization of glyphosate transport on the watershed scale is lacking. Glyphosate, and its degradate AMPA [aminomethylphosphoric acid], was frequently detected in the surface waters of four agricultural watersheds. The load as a percent of use of glyphosate ranged from 0.009 to 0.86 percent and can be related to three factors: source strength, hydrology, and flowpath. Glyphosate use within a watershed results in some occurrence in surface water at the part per billion level; however watersheds most at risk for the offsite transport of glyphosate are those with high application rates, rainfall that results in overland runoff, and a flowpath that does not include transport through the soil.

  14. Chemical Compounds Toxic to Invertebrates Isolated from Marine Cyanobacteria of Potential Relevance to the Agricultural Industry

    PubMed Central

    Essack, Magbubah; Alzubaidy, Hanin S.; Bajic, Vladimir B.; Archer, John A. C.

    2014-01-01

    In spite of advances in invertebrate pest management, the agricultural industry is suffering from impeded pest control exacerbated by global climate changes that have altered rain patterns to favour opportunistic breeding. Thus, novel naturally derived chemical compounds toxic to both terrestrial and aquatic invertebrates are of interest, as potential pesticides. In this regard, marine cyanobacterium-derived metabolites that are toxic to both terrestrial and aquatic invertebrates continue to be a promising, but neglected, source of potential pesticides. A PubMed query combined with hand-curation of the information from retrieved articles allowed for the identification of 36 cyanobacteria-derived chemical compounds experimentally confirmed as being toxic to invertebrates. These compounds are discussed in this review. PMID:25356733

  15. Chemical compounds toxic to invertebrates isolated from marine cyanobacteria of potential relevance to the agricultural industry.

    PubMed

    Essack, Magbubah; Alzubaidy, Hanin S; Bajic, Vladimir B; Archer, John A C

    2014-11-01

    In spite of advances in invertebrate pest management, the agricultural industry is suffering from impeded pest control exacerbated by global climate changes that have altered rain patterns to favour opportunistic breeding. Thus, novel naturally derived chemical compounds toxic to both terrestrial and aquatic invertebrates are of interest, as potential pesticides. In this regard, marine cyanobacterium-derived metabolites that are toxic to both terrestrial and aquatic invertebrates continue to be a promising, but neglected, source of potential pesticides. A PubMed query combined with hand-curation of the information from retrieved articles allowed for the identification of 36 cyanobacteria-derived chemical compounds experimentally confirmed as being toxic to invertebrates. These compounds are discussed in this review. PMID:25356733

  16. STREAM TRANSPORT AND AGRICULTURAL RUNOFF OF PESTICIDES FOR EXPOSURE ASSESSMENT: A METHODOLOGY. PART B. APPENDICES G THROUGH K

    EPA Science Inventory

    To predict the potential environmental or human health risk posed by agricultural pesticides, exposure assessments require the estimation of chemical concentrations in field runoff and in associated streams. In the report, a methodology is described for estimating the mean, maxim...

  17. Spills of Hydraulic Fracturing Chemicals on Agricultural Topsoil: Biodegradation, Sorption, and Co-contaminant Interactions.

    PubMed

    McLaughlin, Molly C; Borch, Thomas; Blotevogel, Jens

    2016-06-01

    Hydraulic fracturing frequently occurs on agricultural land. Yet the extent of sorption, transformation, and interactions among the numerous organic frac fluid and oil and gas wastewater constituents upon environmental release is hardly known. Thus, this study aims to advance our current understanding of processes that control the environmental fate and toxicity of commonly used hydraulic fracturing chemicals. Poly(ethylene glycol) surfactants were completely biodegraded in agricultural topsoil within 42-71 days, but their transformation was impeded in the presence of the biocide glutaraldehyde and was completely inhibited by salt at concentrations typical for oil and gas wastewater. At the same time, aqueous glutaraldehyde concentrations decreased due to sorption to soil and were completely biodegraded within 33-57 days. While no aqueous removal of polyacrylamide friction reducer was observed over a period of 6 months, it cross-linked with glutaraldehyde, further lowering the biocide's aqueous concentration. These findings highlight the necessity to consider co-contaminant effects when we evaluate the risk of frac fluid additives and oil and gas wastewater constituents in agricultural soils in order to fully understand their human health impacts, likelihood for crop uptake, and potential for groundwater contamination. PMID:27171137

  18. Open burning of agricultural biomass: Physical and chemical properties of particle-phase emissions

    NASA Astrophysics Data System (ADS)

    Hays, Michael D.; Fine, Philip M.; Geron, Christopher D.; Kleeman, Michael J.; Gullett, Brian K.

    We present the physical and chemical characterization of particulate matter (PM 2.5) emissions from simulated agricultural fires (AFs) of surface residuals of two major grain crops, rice ( Oryza sativa) and wheat ( Triticum aestivum L.). The O 2 levels and CO/CO 2 ratios of the open burn simulations are typical of the field fires of agricultural residues. In the AF plumes, we observe predominantly accumulation mode (100-1000 nm) aerosols. The mean PM 2.5 mass emission factors from replicate burns of the wheat and rice residuals are 4.7±0.04 and 13.0±0.3 g kg -1 of dry biomass, respectively. The combustion-derived PM emissions from wheat are enriched in K (31% weight/weight, w/w) and Cl (36% w/w), whereas the PM emissions from rice are largely carbonaceous (84% w/w). Molecular level gas chromatography/mass spectrometry analysis of PM 2.5 solvent extracts identifies organic matter that accounts for as much as 18% of the PM mass emissions. A scarcity of detailed PM-phase chemical emissions data from AFs required that comparisons among other biomass combustion groups (wildfire, woodstove, and fireplace) be made. Statistical tests for equal variance among these groups indicate that the degree to which molecular emissions vary is compound dependent. Analysis of variance testing shows significant differences in the mean values of certain n-alkane, polycyclic aromatic hydrocarbon (PAH), oxy-PAH, and sugar marker compounds common to the biomass combustion types. Individual pairwise comparisons of means at the combustion group level confirm this result but suggest that apportioning airborne PM to these sources may require a more comprehensive use of the chemical emissions fingerprints. Hierarchical clustering of source test observations using molecular markers indicates agricultural fuels as distinct from other types of biomass combustion or biomass species. Rough approximations of the total potential PM 2.5 emissions outputs from the combustion of the wheat and rice

  19. 3 Lectures: "Lagrangian Models", "Numerical Transport Schemes", and "Chemical and Transport Models"

    NASA Technical Reports Server (NTRS)

    Douglass, A.

    2005-01-01

    The topics for the three lectures for the Canadian Summer School are Lagrangian Models, numerical transport schemes, and chemical and transport models. In the first lecture I will explain the basic components of the Lagrangian model (a trajectory code and a photochemical code), the difficulties in using such a model (initialization) and show some applications in interpretation of aircraft and satellite data. If time permits I will show some results concerning inverse modeling which is being used to evaluate sources of tropospheric pollutants. In the second lecture I will discuss one of the core components of any grid point model, the numerical transport scheme. I will explain the basics of shock capturing schemes, and performance criteria. I will include an example of the importance of horizontal resolution to polar processes. We have learned from NASA's global modeling initiative that horizontal resolution matters for predictions of the future evolution of the ozone hole. The numerical scheme will be evaluated using performance metrics based on satellite observations of long-lived tracers. The final lecture will discuss the evolution of chemical transport models over the last decade. Some of the problems with assimilated winds will be demonstrated, using satellite data to evaluate the simulations.

  20. REDUCING THE ENVIRONMENTAL IMPACT OF AGRICULTURAL AND NON-AGRICULTURAL SYSTEMS: MITIGATING OFF-SITE TRANSPORT OF PESTICIDES WITH RUNOFF

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Water quality surveys have detected numerous pesticides in surface waters of urban and agricultural areas. The intense use of pesticides in highly managed turf systems and agriculture is of concern due to their potential adverse effects on the quality of surface waters, impacting drinking water reso...

  1. Source and transport factors influencing storm phosphorus losses in agricultural catchments

    NASA Astrophysics Data System (ADS)

    Shore, Mairead; Jordan, Phil; Mellander, Per-Erik; kelly-quinn, Mary; Wall, David; Murphy, Paul; Melland, Alice

    2014-05-01

    The relative risk of diffuse phosphorus (P) loss from agricultural land was assessed in a well-drained arable catchment and a poorly-drained grassland catchment and in two nested basins within each catchment. This research investigated the relative control of hydrology and soil P on P losses between basins. Quick flow (QF) P losses (defined here as both concentrations and loads), monitored in stream flow during four storm events, were compared with a dynamic metric of transport risk (QF magnitude) and a static metric of critical source area (CSA) risk (extent of highly-connected poorly-drained soils with excess plant-available soil P). The potential for static transport metrics of soil connectivity and soil drainage class, to predict relative QF magnitudes and P losses between basins was also investigated. In basins with similar CSA risk but with contrasting QF magnitudes, mean TRP (total molybdate-reactive P) losses were consistently higher in the basins which had the highest QF magnitudes. This suggests that basin hydrology, rather than hydrology of high-P soils only, determined relative TRP losses between hydrologically contrasting basins. Furthermore, static transport metrics of soil connectivity and soil drainage class reliably discerned relative QF magnitudes and TRP losses between these basins. However, for two of the storm events (both occurring during the hydrologically active season), PP (particulate P) concentrations were frequently higher in basins which had the lowest QF magnitudes and may be attributed to a higher proportion of bare soil in these basins at these times as a result of their predominantly arable nature. In basins with similar hydrology, relative TRP and PP losses did not reflect trends in CSA risk or QF magnitude. The dynamics of TRP and PP losses and QF magnitude between these basins varied across storms, thus could not be predicted using static metrics. Where differences in hydrological dynamics were large, storm TRP losses were well

  2. Processes controlling the episodic streamwater transport of atrazine and other agrichemicals in an agricultural watershed

    NASA Astrophysics Data System (ADS)

    Hyer, Kenneth E.; Hornberger, George M.; Herman, Janet S.

    2001-12-01

    Episodic streamwater transport of atrazine (a common agricultural herbicide) and nutrients has been observed throughout agricultural watersheds in the United States and poses a serious threat to the quality of its water resources. Catchment-scale atrazine and nutrient transport processes after agricultural application are still poorly understood, and predicting episodic streamwater composition remains an elusive goal. We instrumented a 1.2-km 2 agricultural catchment near Harrisonburg, Virginia, and examined streamwater, overland flow, soil water, groundwater, and rainfall during the summer of 1998. Storm chemographs demonstrated different patterns for constituents derived primarily from weathering (silica and calcium), compared to constituents derived primarily from early spring land applications (nitrate, atrazine, DOC, potassium, chloride, and sulfate). During storms, the concentrations of silica and calcium decreased, the atrazine response was variable, and the concentrations of nitrate, DOC, potassium, chloride, and sulfate increased; the elevated nitrate signal lagged several hours behind the other elevated constituents. Graphical and statistical analyses indicated a relatively stable spring-fed baseflow was modified by a mixture of overland flow and soil water. A rapid, short-duration overland-flow pulse dominated the streamflow early in the event and contributed most of the potassium, DOC, chloride, suspended sediment, and atrazine. A longer-duration soil-water pulse dominated the streamflow later in the event and contributed the nitrate as well as additional potassium, DOC, sulfate, and atrazine. The contributions to the episodic streamflow were quantified using a flushing model in which overland-flow and soil-water concentrations decreased exponentially with time during an episode. Flushing time constants for the overland-flow and soil-water reservoirs were calculated on a storm-by-storm basis using separate tracers for each time-variable reservoir

  3. Processes controlling the episodic streamwater transport of atrazine and other agrichemicals in an agricultural watershed

    USGS Publications Warehouse

    Hyer, Kenneth; Hornberger, George M.; Herman, Janet S.

    2001-01-01

    Episodic streamwater transport of atrazine (a common agricultural herbicide) and nutrients has been observed throughout agricultural watersheds in the United States and poses a serious threat to the quality of its water resources. Catchment-scale atrazine and nutrient transport processes after agricultural application are still poorly understood, and predicting episodic streamwater composition remains an elusive goal. We instrumented a 1.2-km2 agricultural catchment near Harrisonburg, Virginia, and examined streamwater, overland flow, soil water, groundwater, and rainfall during the summer of 1998. Storm chemographs demonstrated different patterns for constituents derived primarily from weathering (silica and calcium), compared to constituents derived primarily from early spring land applications (nitrate, atrazine, DOC, potassium, chloride, and sulfate). During storms, the concentrations of silica and calcium decreased, the atrazine response was variable, and the concentrations of nitrate, DOC, potassium, chloride, and sulfate increased; the elevated nitrate signal lagged several hours behind the other elevated constituents. Graphical and statistical analyses indicated a relatively stable spring-fed baseflow was modified by a mixture of overland flow and soil water. A rapid, short-duration overland-flow pulse dominated the streamflow early in the event and contributed most of the potassium, DOC, chloride, suspended sediment, and atrazine. A longer-duration soil–water pulse dominated the streamflow later in the event and contributed the nitrate as well as additional potassium, DOC, sulfate, and atrazine. The contributions to the episodic streamflow were quantified using a flushing model in which overland-flow and soil–water concentrations decreased exponentially with time during an episode. Flushing time constants for the overland-flow and soil–water reservoirs were calculated on a storm-by-storm basis using separate tracers for each time-variable reservoir

  4. Fate and transport of agriculturally applied fungicidal compounds, azoxystrobin and propiconazole.

    PubMed

    Edwards, Paul G; Murphy, Tracye M; Lydy, Michael J

    2016-03-01

    Fungicidal active ingredients azoxystrobin and propiconazole, individually and in combination, have been marketed worldwide in a range of fungicide treatment products for preventative and curative purposes, respectively. Their presence in streams located throughout the midwestern and southeastern United States warrant the need for research into the potential routes of transport of these fungicides in an agricultural field setting. Potential canopy penetration and drift effects of these fungicides during aerial and ground applications were studied in the current project. Canopy penetration was observed for both application types, however drift was associated only with the aerial application of these fungicides. Azoxystrobin and propiconazole persisted in the soil up to 301 d, with peak concentrations occurring approximately 30 d after application. The predominant mode of transport for these compounds was agricultural runoff water, with the majority of the fungicidal active ingredients leaving the target area during the first rain event following application. The timing of application in relation to the first rain event significantly affected the amount of loss that occurred, implying application practices should follow manufacturer recommended guidelines. PMID:26741551

  5. Parameterization of Aerosol Sinks in Chemical Transport Models

    NASA Technical Reports Server (NTRS)

    Colarco, Peter

    2012-01-01

    The modelers point of view is that the aerosol problem is one of sources, evolution, and sinks. Relative to evolution and sink processes, enormous attention is given to the problem of aerosols sources, whether inventory based (e.g., fossil fuel emissions) or dynamic (e.g., dust, sea salt, biomass burning). On the other hand, aerosol losses in models are a major factor in controlling the aerosol distribution and lifetime. Here we shine some light on how aerosol sinks are treated in modern chemical transport models. We discuss the mechanisms of dry and wet loss processes and the parameterizations for those processes in a single model (GEOS-5). We survey the literature of other modeling studies. We additionally compare the budgets of aerosol losses in several of the ICAP models.

  6. Mass transport measurements and modeling for chemical vapor infiltration

    SciTech Connect

    Starr, T.L.; Chiang, D.Y.; Fiadzo, O.G.; Hablutzel, N.

    1997-12-01

    This project involves experimental and modeling investigation of densification behavior and mass transport in fiber preforms and partially densified composites, and application of these results to chemical vapor infiltration (CVI) process modeling. This supports work on-going at ORNL in process development for fabrication of ceramic matrix composite (CMC) tubes. Tube-shaped composite preforms are fabricated at ORNL with Nextel{trademark} 312 fiber (3M Corporation, St. Paul, MN) by placing and compressing several layers of braided sleeve on a tubular mandrel. In terms of fiber architecture these preforms are significantly different than those made previously with Nicalon{trademark} fiber (Nippon Carbon Corp., Tokyo, Japan) square weave cloth. The authors have made microstructure and permeability measurements on several of these preforms and a few partially densified composites so as to better understand their densification behavior during CVI.

  7. TOXIWASP: A DYNAMIC MODEL FOR SIMULATING THE TRANSPORT AND FATE OF TOXIC CHEMICALS IN WATER BODIES

    EPA Science Inventory

    TOXIWASP is a dynamic model for simulating the transport and fate of toxic chemicals in water bodies. Two state variables are simulated: organic chemical and total sediment. The generalized chemical model can be used for problems requiring dynamic transport and loading capabiliti...

  8. New oilseed crops for fuels and chemicals: ecological and agricultural considerations

    SciTech Connect

    Draper, H.M. III

    1982-01-01

    A new approach to agriculture involving oilseed crops for fuels and chemicals is proposed. Such an approach to biomass energy would be designed to benefit the limited-resource farmer in the United States and the Third World, while at the same time not aggravating global ecological problems such as deforestation and desertification. Since food versus fuel conflicts arise when plants are grown for industrial uses on good lands, productivity questions are examined, with the conclusion that fundamental biological constraints will limit yields on marginal lands. Conventional vegetable oil crops are limited in their climatic requirements or are not well adapted to limited-resource farming; therefore, new oilseeds more adaptable to small farming are proposed. Such plants would be for specialty chemicals or to meet local energy needs. Chemicals produced would be low-volume, labor-intensive, and possibly high-priced. A list of 281 potential new oilseeds is provided, and each is classified according to potential, multiple product potential, and vegetative characteristics. Using climatic data which are available for most areas, a method of making rough productivity estimates for unconventional wild plant oilseeds is proposed, and example resource estimates are provided for the southeastern United States.

  9. Chemical transport through continental crust: (Annual) progress report, 1988

    SciTech Connect

    Not Available

    1989-03-20

    The main objective of these studies is to understand the extent and mechanisms of chemical migration over a range of temperatures and in diverse geologic media. During 1988--1989 we continued to attack these problems through studies in the granite-pegmatite systems of the Black Hills, South Dakota. Mineral chemistry, major element chemistry and trace element modeling of the Harney Peak Granite (Black Hills, South Dakota) suggest that 75% to 80% fractional crystallization was the dominant mechanism in producing evolved tourmaline-bearing granite (high B, Li, Rb, Cs, Be, Nb) from a biotite-muscovite granite. To evaluate the petrogenetic-evolutionary relations between the granite and the surrounding rare-element pegmatite field, over 500 K-feldspars (Kf) were analyzed from 60 unzoned to complexly zoned pegmatites. Pegmatites with Kf relatively high in Ba (>140 ppM) and relatively low in Rb (<1000 ppM) and Cs (<30 ppM) are distributed in regions of high pegmatite density (>200 pegmatites/sq. mile), whereas highly evolved pegmatites with Kf enriched in Rb (>4000 ppM) and Cs (>500 ppM) are distributed in regions of low pegmatite density (<100 pegmatites/sq. mile). The extent of pegmatite evolution as reflected in the Kf documents the relation between the degree of fractionation and internal zoning characteristics. Modeling of these data is a major task for the next grant year to provide new insights into chemical and thermal transport in the midcrust.

  10. A comparison of forest and agricultural shallow groundwater chemical status a century after land use change.

    PubMed

    Kellner, Elliott; Hubbart, Jason A; Ikem, Abua

    2015-10-01

    Considering the increasing pace of global land use change and the importance of groundwater quality to humans and aquatic ecosystems, studies are needed that relate land use types to patterns of groundwater chemical composition. Piezometer grids were installed in a remnant bottomland hardwood forest (BHF) and a historic agricultural field (Ag) to compare groundwater chemical composition between sites with contrasting land use histories. Groundwater was sampled monthly from June 2011 to June 2013, and analyzed for 50 physiochemical metrics. Statistical tests indicated significant differences (p<0.05) between the study sites for 32 out of 50 parameters. Compared to the Ag site, BHF groundwater was characterized by significantly (p<0.05) lower pH, higher electrical conductivity, and higher concentrations of total dissolved solids and inorganic carbon. BHF groundwater contained significantly (p<0.05) higher concentrations of all nitrogen species except nitrate, which was higher in Ag groundwater. BHF groundwater contained significantly (p<0.05) higher concentrations of nutrients such as sulfur, potassium, magnesium, calcium, and sodium, relative to the Ag site. Ag groundwater was characterized by significantly (p<0.05) higher concentrations of trace elements such as arsenic, cadmium, cobalt, copper, molybdenum, nickel, and titanium. Comparison of shallow groundwater chemical composition with that of nearby receiving water suggests that subsurface concentration patterns are the result of contrasting site hydrology and vegetation. Results detail impacts of surface vegetation alteration on subsurface chemistry and groundwater quality, thereby illustrating land use impacts on the lithosphere and hydrosphere. This study is among the first to comprehensively characterize and compare shallow groundwater chemical composition at sites with contrasting land use histories. PMID:26005752

  11. Agricultural chemical interchange between ground water and surface water, Cedar River basin, Iowa and Minnesota; a study description

    USGS Publications Warehouse

    Squillace, P.J.; Liszewski, M.J.; Thurman, E.M.

    1993-01-01

    A review of the data collected in the Cedar River basin, Iowa and Minnesota, indicates that atrazine is consistently detected in the main-stem river at concentrations greater than 0.10 microgram per liter even during periods of extended base flow. The primary source of atrazine in the river during these periods of base flow is not known. This study is designed to determine how atrazine and other agricultural chemicals move between ground water and surface water in an alluvial aquifer adjacent to a river. A site has been selected in an unfarmed area adjacent to the Cedar River near Bertram, Iowa, to determine how the concentrations of agricultural chemicals in the alluvial aquifer change as a result of bank storage of surface water. Research also is planned to determine the contribution of agricultural chemicals discharged by the alluvial aquifer into the river during base flow.

  12. INTEX-NA: Intercontinental Chemical Transport Experiment - North America

    NASA Technical Reports Server (NTRS)

    Singh, Hanwant B.; Jacob, D.; Pfister, L.; Hipskind, R. Stephen (Technical Monitor)

    2002-01-01

    INTEX-NA is an integrated atmospheric chemistry field experiment to be performed over North America using the NASA DC-8 and P-3B aircraft as its primary platforms. It seeks to understand the exchange of chemicals and aerosols between continents and the global troposphere. The constituents of interest are ozone and its precursors (hydrocarbons, NOX and HOX), aerosols, and the major greenhouse gases (CO2, CH4, N2O). INTEX-NA will provide the observational database needed to quantify inflow, outflow, and transformations of chemicals over North America. INTEX-NA is to be performed in two phases. Phase A will take place during the period of May-August 2004 and Phase B during March-June 2006. Phase A is in summer when photochemistry is most intense and climatic issues involving aerosols and carbon cycle are most pressing, and Phase B is in spring when Asian transport to North America is at its peak. INTEX-NA will coordinate its activities with concurrent measurement programs including satellites (e. g. Terra, Aura, Envisat), field activities undertaken by the North American Carbon Program (NACP), and other U.S. and international partners. However, it is being designed as a 'stand alone' mission such that its successful execution is not contingent on other programs. Synthesis of the ensemble of observation from surface, airborne, and space platforms, with the help of global/regional models is an important It is anticipated that approximately 175 flight hours for each of the aircraft (DC-8 and P-3B) will be required for each Phase. Principal operational sites are tentatively selected to be Bangor, ME; Wallops Island, VA; Seattle, WA; Rhinelander, WI; Lancaster, CA; and New Orleans, LA. These coastal and continental sites can support large missions and are suitable for INTEX-NA objectives. The experiment will be supported by forecasts from meteorological and chemical models, satellite observations, surface networks, and enhanced O3,-sonde releases. In addition to

  13. Review and analysis of parameters for assessing transport of environmentally released radionuclides through agriculture

    SciTech Connect

    Baes, C.F. III; Sharp, R.D.; Sjoreen, A.L.; Shor, R.W.

    1984-09-01

    Most of the default parameters incorporated into the TERRA computer code are documented including a literature review and systematic analysis of element-specific transfer parameters B/sub v/, B/sub r/, F/sub m/, F/sub f/, and K/sub d/. This review and analysis suggests default values which are consistent with the modeling approaches taken in TERRA and may be acceptable for most assessment applications of the computer code. However, particular applications of the code and additional analysis of elemental transport may require alternative default values. Use of the values reported herein in other computer codes simulating terrestrial transport is not advised without careful interpretation of the limitations and scope these analyses. An approach to determination of vegetation-specific interception fractions is also discussed. The limitations of this approach are many, and its use indicates the need for analysis of deposition, interception, and weathering processes. Judgement must be exercised in interpretation of plant surface concentrations generated. Finally, the location-specific agricultural, climatological, and population parameters in the default SITE data base documented. These parameters are intended as alternatives to average values currently used. Indeed, areas in the United States where intensive crop, milk, or beef production occurs will be reflected in the parameter values as will areas where little agricultural activity occurs. However, the original information sources contained some small error and the interpolation and conversion methods used will add more. Parameters used in TERRA not discussed herein are discussed in the companion report to this one - ORNL-5785. In the companion report the models employed in and the coding of TERRA are discussed. These reports together provide documentation of the TERRA code and its use in assessments. 96 references, 78 figures, 21 tables.

  14. Overland flow and sediment transport in an agricultural lowland catchments: a focus on tile drain export

    NASA Astrophysics Data System (ADS)

    Vandromme, Rosalie; Grangeon, Thomas; Cerdan, Olivier; Manière, Louis; Salvador Blanes, Sébastien; Foucher, Anthony; Chapalain, Marion; Evrard, Olivier; Le Gall, Marion

    2016-04-01

    Rural landscapes have been extensively modified by human activities in Western Europe since the beginning of the 20th century in order to intensify agricultural production. Cultivated areas often expanded at the expense of grassland and wetlands located in lowland areas (de Groot et al., 2002). Therefore, large modifications were made to the agricultural landscapes: stream redesign, land consolidation, removal of hedges, and installation of tile drainage networks to drain the hydromorphic soils. These changes modified sediment processes and resulted in large morphological alterations (e.g. channel bed incision, deposition of fine sediment, channel bank erosion). Accordingly, these alterations threaten water quality and prevent to meet the requirements of the European directives. Improving water quality requires a clear understanding of the hydrosedimentary dynamics in these lowland cultivated catchments. However, few studies were conducted in drained environments. To fill this research gap, a pilot study was started in cultivated catchment of the Loire River basin, France, where tile drain densities are very high (> 1.5 km/km²). Six hydro-sedimentary monitoring stations were installed in the Louroux catchment (24 km²). One of them was specifically dedicated to measuring water/sediment fluxes from tile drains. Water level and turbidity were continuously monitored and sediments were sampled during floods and low stage periods. Samples were measured for particle size distribution, and sediment tracing studies are currently being developed to quantify the contribution of potential sources (e.g. surface vs subsurface, lithologies) to river sediment. Hydro-sedimentary fluxes were quantified and modelled for some selected events. The catchment hydrosedimentary fluxes and their properties were shown to be impacted by tile drain sediment transport, especially regarding particle size distribution, with the dominant export of very fine particles (< 2 μm) from tile drains

  15. Phosphorus transport pathways to streams in tile-drained agricultural watersheds.

    PubMed

    Gentry, L E; David, M B; Royer, T V; Mitchell, C A; Starks, K M

    2007-01-01

    Agriculture is a major nonpoint source of phosphorus (P) in the Midwest, but how surface runoff and tile drainage interact to affect temporal concentrations and fluxes of both dissolved and particulate P remains unclear. Our objective was to determine the dominant form of P in streams (dissolved or particulate) and identify the mode of transport of this P from fields to streams in tile-drained agricultural watersheds. We measured dissolved reactive P (DRP) and total P (TP) concentrations and loads in stream and tile water in the upper reaches of three watersheds in east-central Illinois (Embarras River, Lake Fork of the Kaskaskia River, and Big Ditch of the Sangamon River). For all 16 water year by watershed combinations examined, annual flow-weighted mean TP concentrations were >0.1 mg L(-1), and seven water year by watershed combinations exceeded 0.2 mg L(-1). Concentrations of DRP and particulate P (PP) increased with stream discharge; however, particulate P was the dominant form during overland runoff events, which greatly affected annual TP loads. Concentrations of DRP and PP in tiles increased with discharge, indicating tiles were a source of P to streams. Across watersheds, the greatest DRP concentrations (as high as 1.25 mg L(-1)) were associated with a precipitation event that followed widespread application of P fertilizer on frozen soils. Although eliminating this practice would reduce the potential for overland runoff of P, soil erosion and tile drainage would continue to be important transport pathways of P to streams in east-central Illinois. PMID:17255628

  16. Atmospheric Transport During the Transport and Chemical Evolution over the Pacific TRACE-P Experiment

    NASA Technical Reports Server (NTRS)

    Fuelberg, Henry E.; Kiley, C. M.; Hannan, J. R.; Westberg, D. J.; Avery, M. A.; Newell, R. E.

    2003-01-01

    Atmospheric transport over the Pacific Basin is described during NASA's Transport and Chemical Evolution Over the Pacific Experiment (TRACE-P) that was conducted between February - April 2001. The mission included extensive chemical sampling from two aircraft based primarily in Hong Kong and Yokota Air Base, Japan. Meteorological conditions during TRACE-P changed rapidly due to the seasonal winter/spring transition and the decay of prolonged ENSO cold phase (La Nina) conditions. To document these changes, TRACE-P was divided into two halves, and mean flow patterns during each half are presented and discussed. Important circulation features are the semi-permanent Siberian anticyclone and transient middle latitude cyclones that form near eastern Asia and then move eastward over the northern Pacific. Five-day backward trajectories from the various flight tracks show that air sampled by the aircraft had been transported from a variety of locations. Some parcels remained over the tropical western North Pacific during the entire period, while other important origins were Southeast Asia, Africa, and central Asia. Patterns of satellite-derived precipitation and lightning are described. TRACE-P occurs during a neutral to weak La Nina period of relatively cold sea surface temperatures in the tropical Pacific. Compared to climatology, the TRACE-P period exhibits deep convection located west of its typical position; however, tropospheric flow patterns do not exhibit a strong La Nina signal. Circulation patterns during TRACE-P are found to be generally similar to those during NASA's PEM WEST-B mission that occurred in the same region during February - March 1994.

  17. DNA Charge Transport: from Chemical Principles to the Cell.

    PubMed

    Arnold, Anna R; Grodick, Michael A; Barton, Jacqueline K

    2016-01-21

    The DNA double helix has captured the imagination of many, bringing it to the forefront of biological research. DNA has unique features that extend our interest into areas of chemistry, physics, material science, and engineering. Our laboratory has focused on studies of DNA charge transport (CT), wherein charges can efficiently travel long molecular distances through the DNA helix while maintaining an exquisite sensitivity to base pair π-stacking. Because DNA CT chemistry reports on the integrity of the DNA duplex, this property may be exploited to develop electrochemical devices to detect DNA lesions and DNA-binding proteins. Furthermore, studies now indicate that DNA CT may also be used in the cell by, for example, DNA repair proteins, as a cellular diagnostic, in order to scan the genome to localize efficiently to damage sites. In this review, we describe this evolution of DNA CT chemistry from the discovery of fundamental chemical principles to applications in diagnostic strategies and possible roles in biology. PMID:26933744

  18. Charge transport in conjugated materials: insight from quantum chemical calculations

    NASA Astrophysics Data System (ADS)

    Beljonne, David; Cornil, J. P.; Calbert, J. P.; Bredas, Jean-Luc

    2001-06-01

    The electronic structure of neutral and singly charged conjugated molecular clusters is investigated by means of quantum-chemical calculations. We first assess the influence of interchain interactions on the nature of the singly charged species (polarons) in organic conjugated polymers. In a two- chain model aggregate, the polaron is found to be delocalized over the two conjugated chains for short interchain separation. Such a delocalization strongly affects the geometric and electronic relaxation phenomena induced by charge injection, which in turn lead to a dramatic spectral redistribution of the linear absorption cross section. We then consider pentacene clusters built from the experimental crystal structure and compute the HOMO and LUMO bandwidths, which are decisive parameters for charge transport in the limiting case of band-like motion (i.e., complete delocalization of the excess charge over a large number of interacting molecules). Very large bandwidths are obtained, in agreement with the remarkable electron and hole charge-carrier mobilities reported recently for ultrahigh purity pentacene single crystals.

  19. Fate and Transport of Agricultural Nutrients in Macro-porous Soils

    NASA Astrophysics Data System (ADS)

    Royem, A. A.; Walter, M. T.

    2010-12-01

    The major objective of this study is to address water quality problems associated with application of liquid manure to subsurface-drained agricultural lands. There are over 600 large and medium sized confined animal feeding operations (CAFOs) in New York, most of which utilize land application to manage this waste stream. Due to the regions shallow soil and humid weather, most fields have been equipped with tile drainage. The concern is that handling the manure is a liquefied state may enhance the likelihood of contamination of the tile drainage discharge and its potential impacts on downstream water quality. Laboratory studies were used to investigate how manure liquidity (percent solids) affects the transport of manure constituents through varying macropore sizes in the soil. Soil columns of 3 different macropore sizes (0, 1, 3 millimeter) were constructed, subjected to simulated rainfall over several weeks, and effluent was collected from both the soil matrix and macropores separately. Effluent samples were analyzed for soluble reactive phosphorus (SRP). As expected, the preliminary results show enhanced SRP transport through macropores with decreasing percent solids (i.e., more liquidy manure). The implications at field and watershed scales are still being investigated.

  20. Using Chemical Tracers to Estimate Pesticide Mass Discharge in an Agricultural Watershed

    NASA Astrophysics Data System (ADS)

    Simmons, A. N.; Allen-King, R. M.; Van Biersel, T. P.; Keller, C. K.; Smith, J. L.

    2001-12-01

    The goal of this research is to use environmental tracers to quantify the contributions of subsurface and surface runoff to predict the mass discharge of non-point source agricultural pollutants to rivers at multiple scales of study. Easily measured chemical tracers, such as electrical conductivity (EC), are used to distinguish ground and surface water contributions to the river system. The study area is the Missouri Flat Creek watershed, a 14,400 ha semi-arid dryland agricultural setting located near Pullman, WA. Ground and surface water samples are collected at approximately two-week intervals from an ephemeral stream and a tile drain located in actively farmed and topographically constrained fields ( ~20 ha), and from seven stream-gaging stations. Surface water discharge is monitored continuously. Samples are routinely analyzed for two pesticides (the insecticide lindane or gamma-hexachlorocyclohexane (HCH) and the herbicide triallate, S-(2,3,3-trichloroallyl) diisopropylthiocarbamate), a nutrient (nitrate), and the tracers EC and silica. Lindane is applied as a seed coating on most spring and fall crops in the region. Observed lindane concentrations in the different hydrologic reservoirs ranged over approximately two orders of magnitude, from typically less than the detection limit ( ~0.005 μ g/L) in most soil pore water and groundwater samples to a weighted mean of 0.25 μ g/L in field (ephemeral stream) surface runoff. A two-component, ground and surface water, hydrograph separation was performed using tile drain and ephemeral stream tracer concentrations from field plots to represent groundwater and surface runoff end-members. The hydrograph separation was used to predict lindane discharge. Reasonable agreement between model and observed lindane discharge timing and trend supports the hypothesis that in-stream pesticide is derived from annual surface runoff. During the high flow winter months, the model predictions are two to five times greater than

  1. Agricultural chemicals and the quality of prairie-pothole wetlands for adult and juvenile waterfowl -- what are the concerns?

    USGS Publications Warehouse

    Grue, C.E.; Tome, M.W.; Swanson, G.A.; Borthwick, S.M.; DeWeese, L.R.

    1988-01-01

    A review of the literature and results of ongoing studies indicates that the potential for agricultural chemicals, particularly aerially-applied insecticides, to enter prairie potholes and reduce the quality of these wetlands for waterfowl is great, and that a coordinated effort by farmers, wildlife managers, and regulatory agencies is needed to minimize these impacts

  2. Agricultural chemicals and the quality of prairie-pothole wetlands for adult and juvenile waterfowl - what are the concerns?

    USGS Publications Warehouse

    Grue, C.E.; Tome, M.W.; Swanson, G.A.; Borthwick, S.

    1988-01-01

    A review of the literature and results of ongoing studies indicates that the potential for agricultural chemicals, particularly aerially-applied insecticides, to enter prairie potholes and reduce the quality of these wetlands for waterfowl is great, and that a coordinated effort by farmers, wildlife managers, and regulatory agencies is needed to minimize these impacts.

  3. MODELING THREE-DIMENSIONAL SUBSURFACE FLOW, FATE AND TRANSPORT OF MICROBES AND CHEMICALS (3DFATMIC)

    EPA Science Inventory

    A three-dimensional model simulating the subsurface flow, microbial growth and degradation, microbial-chemical reaction, and transport of microbes and chemicals has been developed. he model is designed to solve the coupled flow and transport equations. asically, the saturated-uns...

  4. Combined physical and chemical nonequilibrium transport model: Analytical solution, moments, and application to colloids

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The transport of solutes and colloids in porous media is influenced by a variety of physical and chemical nonequilibrium processes. A combined physical–chemical nonequilibrium (PCNE) model was therefore used to describe general mass transport. The model partitions the pore space into “mobile” and “i...

  5. Studies of Trace Gas Chemical Cycles Using Inverse Methods and Global Chemical Transport Models

    NASA Technical Reports Server (NTRS)

    Prinn, Ronald G.

    2003-01-01

    We report progress in the first year, and summarize proposed work for the second year of the three-year dynamical-chemical modeling project devoted to: (a) development, testing, and refining of inverse methods for determining regional and global transient source and sink strengths for long lived gases important in ozone depletion and climate forcing, (b) utilization of inverse methods to determine these source/sink strengths using either MATCH (Model for Atmospheric Transport and Chemistry) which is based on analyzed observed wind fields or back-trajectories computed from these wind fields, (c) determination of global (and perhaps regional) average hydroxyl radical concentrations using inverse methods with multiple titrating gases, and (d) computation of the lifetimes and spatially resolved destruction rates of trace gases using 3D models. Important goals include determination of regional source strengths of methane, nitrous oxide, methyl bromide, and other climatically and chemically important biogenic/anthropogenic trace gases and also of halocarbons restricted by the Montreal protocol and its follow-on agreements and hydrohalocarbons now used as alternatives to the restricted halocarbons.

  6. Using molecular-scale tracers to investigate transport of agricultural pollutants in soil and water

    NASA Astrophysics Data System (ADS)

    Lloyd, C.; Michaelides, K.; Chadwick, D.; Dungait, J.; Evershed, R. P.

    2012-12-01

    We explore the use of molecular-scale tracers to investigate the transport of potential pollutants due to the application of slurry to soil. The molecular-scale approach allows us to separate the pollutants which are moved to water bodies through sediment-bound and dissolved transport pathways. Slurry is applied to agricultural land to as a soil-improver across a wide-range of topographic and climatic regimes, hence a set of experiments were designed to assess the effect of changing slope gradient and rainfall intensity on the transport of pollutants. The experiments were carried out using University of Bristol's TRACE (Test Rig for Advancing Connectivity Experiments) facility. The facility includes a dual axis soil slope (6 x 2.5 x 0.3 m3) and 6-nozzle rainfall simulator, which enables the manipulation of the slope to simulate different slope gradient and rainfall scenarios. Cattle slurry was applied to the top 1 metre strip of the experimental soil slope followed by four rainfall simulations, where the gradient (5° & 10°) and the rainfall intensity (60 & 120 mm hr-1) were co-varied. Leachate was sampled from different flow pathways (surface, subsurface and percolated) via multiple outlets on the slope throughout the experiments and soil cores were taken from the slope after each experiment. Novel tracers were used to trace the pollutants in both dissolved and sediment-bound forms. Fluorescence spectroscopy was used to trace dissolved slurry-derived material via water flow pathways, as the slurry was found to have a distinct signature compared with the soil. The fluorescence signatures of the leachates were compared with those of many organic compounds in order to characterise the origin of the signal. This allowed the assessment of the longevity of the signal in the environment to establish if it could be used as a robust long-term tracer of slurry material in water or if would be subject to transform processes through time. 5-βstanols, organic compounds

  7. Physical and chemical characterizations of biochars derived from different agricultural residues

    NASA Astrophysics Data System (ADS)

    Jindo, K.; Mizumoto, H.; Sawada, Y.; Sanchez-Monedero, M. A.; Sonoki, T.

    2014-08-01

    Biochar has received large attention as a strategy to tackle against carbon emission. Not only carbon fixation has been carried out but also other merits for agricultural application due to unique physical and chemical character such as absorption of contaminated compounds in soil, trapping ammonia and methane emission from compost, and enhancement of fertilizer quality. In our study, different local waste feed stocks (rice husk, rice straw, wood chips of apple tree (Malus Pumila) and oak tree (Quercus serrata)), in Aomori, Japan, were utilized for creating biochar with different temperature (400-800 °C). Concerning to the biochar production, the pyrolysis of lower temperature had more biochar yield than higher temperature pyrolysis process. On the contrary, surface areas and adsorption characters have been increased as increasing temperature. The proportions of carbon content in the biochars also increased together with increased temperatures. Infrared-Fourier spectra (FT-IR) and 13C-NMR were used to understand carbon chemical compositions in our biochars, and it was observed that the numbers of the shoulders representing aromatic groups, considered as stable carbon structure appeared as the temperature came closer to 600 °C, as well as in FT-IR. In rice materials, the peak assigned to SiO2, was observed in all biochars (400-800 °C) in FT-IR. We suppose that the pyrolysis at 600 °C creates the most recalcitrant character for carbon sequestration, meanwhile the pyrolysis at 400 °C produces the superior properties as a fertilizer by retaining volatile and easily labile compounds which promotes soil microbial activities.

  8. Biosensor recognition of thyroid-disrupting chemicals using transport proteins.

    PubMed

    Marchesini, Gerardo R; Meulenberg, Eline; Haasnoot, Willem; Mizuguchi, Mineyuki; Irth, Hubertus

    2006-02-15

    Novel surface plasmon resonance-based biosensor assays for the bioeffect-related screening of chemicals with thyroid-disrupting activity are described. Two thyroid transport proteins (TPs), thyroxine binding globulin (TBG) and recombinant transthyretin (rTTR), were applied in an inhibition assay format in a Biacore 3000 using CM5 biosensor chips coated with l-thyroxine (T4), the main hormone of the thyroid system. Assay conditions were optimized for the natural thyroid hormones, and known thyroid disruptors and structurally related compounds were selected as model compounds to be tested in both assays for their relative potency (RP) compared to T4. The chosen compounds were halogenated phenols, halogenated bisphenols, bisphenol A, 3,5-dichlorobiphenyl, and its hydroxylated metabolite 4-hydroxy-3,5-dichlorobiphenyl (4-OH PCB 14). The TBG-based assay was highly specific for T4, and the rTTR-based assay was sensitive toward several compounds, the highest sensitivity (RP = 4.4) being obtained with 4-OH PCB 14, followed by tetrabromobisphenol A (RP = 1.5) and tetrachlorobisphenol A (RP = 0.75). For the bioeffect-related screening of known and identification of possible new thyroid disruptors, the TPs-based biosensor assays were more sensitive (IC(50) of 13.7 +/- 1.3 and 8.6 +/- 0.7 nM for the rTTR and the TBG-based assay, respectively), easier to perform, and faster alternatives (10 min/sample) than the currently used methods such as radioligand binding assays and immunoprecipitation-HPLC. PMID:16478101

  9. [Interception Effect of Ecological Ditch on Nitrogen Transport in Agricultural Runoff in Subtropical China].

    PubMed

    Wang, Di; Li, Hong-fang; Liu, Feng; Wang, Yi; Zhong, Yuan-chun; He, Yang; Xiao, Run-fin; Wu, Jin-shui

    2016-05-15

    Interception effects of an ecological ditch, used to control agricultural non-point source pollution in subtropical China, on nitrogen transport in surface runoff were studied by monthly measuring the runoff volume and concentrations of ammonium nitrogen (NH₄⁺-N), nitrate nitrogen (NO₃⁻-N) and total nitrogen (TN) at the ditch inlet and outlet from 2013 to 2014. In addition, differences of NH₄⁺-N, NO₃⁻-N and TN removal were compared between 2013 and 2014. The results showed that the study ecological ditch worked effectively in N removal with average NH₄⁺-N, NO₃⁻-N and TN removal rates of 77.8%, 58.3%, and 48.7%; and their interception rates were 38.4, 59.6, and 171.1 kg · a⁻¹, respectively. The average proportion of NH₄⁺-N and NO₃⁻-N in TN was 47.5% at inlet, and 33.6% at outlet, which was significantly lower than that at inlet (P < 0.01). All hydrophytes in the ecological ditch were replaced by Myriophyllum aquaticum in 2014, which led to the increased average NO₃⁻-N and TN removal rates of 30.5% and 18.2%, respectively, Compared to in 2013. The vegetation of Myriophyllum aquaticum was beneficial to the improvement of N interception in ecological ditch. These findings clearly demonstrated that ecological ditch can substantially reduce N loss from surface runoff and be used as an important technique to prevent agricultural non-point N pollution. PMID:27506024

  10. Evaluation of Management Practices to Mitigate Pesticide Transport and Ecological Risk of Runoff from Agricultural and Turf Systems

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Highly managed biotic systems such as agricultural crops and golf courses often require multiple applications of pesticides that may be transported with runoff to surrounding surface waters. Pesticides have been detected in surface waters of rural and urban watersheds invoking concern of their sour...

  11. Streptococcus suis sorption on agricultural soils: role of soil physico-chemical properties.

    PubMed

    Zhao, Wenqiang; Liu, Xing; Huang, Qiaoyun; Cai, Peng

    2015-01-01

    Understanding pathogen sorption on natural soil particles is crucial to protect public health from soilborne and waterborne diseases. Sorption of pathogen Streptococcus suis on 10 agricultural soils was examined, and its correlations with soil physico-chemical properties were also elucidated. S. suis sorption isotherms conformed to the linear equation, with partition coefficients (Ks) ranging from 12.7 mL g(-1) to 100.1 mL g(-1). Bacteria were observed to sorb on the external surfaces of soil aggregates by scanning electron microscopy. Using Pearson correlation and linear regression analysis, solution pH was found to have significant negative correlations with Ks. Stepwise multiple regression and path analysis revealed that pH and cation exchange capacity (CEC) were the main factors influencing sorption behaviors. The obtained overall model (Ks=389.6-45.9×pH-1.3×CEC, R(2)=0.943, P<0.001) can accurately predict Ks values. However, the variability in Ks was less dependent on soil organic matter, specific surface area, soil texture and zeta potential, probably due to the internal-surface shielding phenomenon of soil aggregates. Additionally, the sorption trends cannot be interpreted by interaction energy barriers calculated using the Derjaguin-Landau-Verwey-Overbeek (DLVO) theory, suggesting the limits of DLVO theory in describing pathogen sorption on natural soils. Our results also indicated soil pH and CEC should be preferentially considered when modeling S. suis sorption process. PMID:24968305

  12. Long-term monitoring of nitrate transport to drainage from three agricultural clayey till fields

    NASA Astrophysics Data System (ADS)

    Ernstsen, V.; Olsen, P.; Rosenbom, A. E.

    2015-08-01

    The application of nitrogen (N) fertilisers to crops grown on tile-drained fields is required to sustain most modern crop production, but it poses a risk to the aquatic environment since tile drains facilitate rapid transport pathways with no significant reduction in nitrate. To maintain the water quality of the aquatic environment and the provision of food from highly efficient agriculture in line with the EU's Water Framework Directive and Nitrates Directive, field-scale knowledge is essential for introducing water management actions on-field or off-field and producing an optimal differentiated N-regulation in future. This study strives to provide such knowledge by evaluating on 11 years of nitrate-N concentration measurements in drainage from three subsurface-drained clayey till fields (1.3-2.3 ha) representing approximately 71 % of the surface sediments in Denmark dominated by clay. The fields differ in their inherent hydrogeological field settings (e.g. soil-type, geology, climate, drainage and groundwater table) and the agricultural management of the fields (e.g. crop type, type of N fertilisers and agricultural practices). The evaluation revealed three types of clayey till fields characterised by: (i) low net precipitation, high concentration of nitrate-N, and short-term low intensity drainage at air temperatures often below 5 °C; (ii) medium net precipitation, medium concentration of nitrate-N, and short-term medium-intensity drainage at air temperatures often above 5 °C; and (iii) high net precipitation, low concentration of nitrate-N and long-term high intensity drainage at air temperatures above 5 °C. For each type, on-field water management actions, such as the selection of crop types and introduction of catch crops, appeared relevant, whereas off-field actions only seemed relevant for the latter two field types given the temperature-dependent reduction potential of nitrate off-field. This initial well-documented field-scale knowledge from fields

  13. Dissolved Organic Matter Assisted Transport of Hormones Through An Agricultural Soil

    NASA Astrophysics Data System (ADS)

    Jann, S.; Totsche, K. U.; Koegel-Knabner, I.; Schiffer, B.; Meyer, H. H. D.

    In the last years the disrupting activity of steroidal sex hormones like estrogens has been discussed for various ecosystems and even for human fertility. Once released into the environment, steroids pose a severe risk to fauna and man. After excretion of the relevant compounds or their metabolites by the target animals, the transition of biologically active substances via dung or manure onto soils and into the groundwa- ter cannot be excluded. Yet there is only little knowledge on the stability, degradation and transport pathways of steroids in soils. Just as little is known about the fate of anabolic steroids which are licensed as growth promotants for farm animals in many meat-exporting countries outside the EU (e.g. USA, Australia). We therefore studied the transport of Trenbolone-17 and Melengestrolacetate (MGA) with col- umn experiments employing aggregated agricultural field soil materials (Luvisol E and Bt horizons). The columns (14.6 cm in height, 4.7 cm in diameter) were perco- lated from bottom to top using a peristaltic pump. The mean volumetric flow rate was kept constant throughout the experiments at 20 ml h-1. Chloride was used as nonreac- tive tracer. The flow regime is controlled by two flow regions reflecting the dual mode pore size distribution of the aggregated soil material. Our results show that although the very high KOC values U Trenbolone: 24311 within the E-horizon; 21622 within the Bt-horizon and MGA: 16708 within the E-horizon; 59459 within the Bt horizon - we observe a quick breakthrough of low concentrations of the hormones simultaneous with the non-reactive tracer chloride. This points to the fact that within aggregated field soil, the risk for deep seepage of low concentrations of hormones is high.

  14. Transport and Fate of Nitrate in Shallow Aquifers in Contrasting Agricultural Settings across the US.

    NASA Astrophysics Data System (ADS)

    Green, C. T.; Puckett, L. J.; Bohlke, J. F.; Phillips, S. P.; Denver, J. M.

    2006-05-01

    The fate of nitrate in four shallow aquifers was investigated with combined laboratory analyses, field measurements, and flow and transport modeling. In the summer of 2003, groundwater wells were installed along kilometer-scale transects in small, predominantly agricultural watersheds at four sites: the San Joaquin Valley, California; central Nebraska; the Yakima River basin, Washington; and the Delmarva Peninsula, Maryland. Groundwater data collected at these sites included potentiometric head, major element chemistry, nutrients, organic carbon, dissolved gases, nitrogen and oxygen isotopes in dissolved nitrate and nitrogen gas, and age dating tracers including chlorofluorocarbons, sulfur hexafluoride, and tritium. Sediment data included particle size distributions, organic matter content, and nitrogen and carbon isotopes of surface soils. For each site, 3-D flow and conservative transport of groundwater age tracers were simulated using boundary conditions interpolated from regional models. All sites had nitrate detections exceeding the Environmental Protection Agency's Maximum Contaminant Level (MCL) of 10 mg/L. At Maryland and California the median concentrations were above the MCL. At the study unit scale, sites with higher excess nitrogen gas concentrations tended to have older groundwater and lower dissolved oxygen. Concentrations of stable isotopes and excess dissolved nitrogen gas indicate little or no denitrifying activity at the Maryland and Washington sites, partial denitrification at the California site, and total denitrification across much of the Nebraska site. Estimates of age and excess nitrogen gas imply gradual denitrification rates of 1.4 ug NO3-N per day at the California site and a portion of the Nebraska site. Elsewhere at the Nebraska site, more rapid, complete denitrification occurs near the water table. The collected results from all four sites indicate that denitrification rates are highly variable and are only reliable for mitigating

  15. Sensitivity of chemical transport model simulations to the duration of chemical and transport operators: a case study with GEOS-Chem v10-01

    NASA Astrophysics Data System (ADS)

    Philip, S.; Martin, R. V.; Keller, C. A.

    2015-11-01

    Chemical transport models involve considerable computational expense. Fine temporal resolution offers accuracy at the expense of computation time. Assessment is needed of the sensitivity of simulation accuracy to the duration of chemical and transport operators. We conduct a series of simulations with the GEOS-Chem chemical transport model at different temporal and spatial resolutions to examine the sensitivity of simulated atmospheric composition to temporal resolution. Subsequently, we compare the tracers simulated with operator durations from 10 to 60 min as typically used by global chemical transport models, and identify the timesteps that optimize both computational expense and simulation accuracy. We found that longer transport timesteps increase concentrations of emitted species such as nitrogen oxides and carbon monoxide since a more homogeneous distribution reduces loss through chemical reactions and dry deposition. The increased concentrations of ozone precursors increase ozone production at longer transport timesteps. Longer chemical timesteps decrease sulfate and ammonium but increase nitrate due to feedbacks with in-cloud sulfur dioxide oxidation and aerosol thermodynamics. The simulation duration decreases by an order of magnitude from fine (5 min) to coarse (60 min) temporal resolution. We assess the change in simulation accuracy with resolution by comparing the root mean square difference in ground-level concentrations of nitrogen oxides, ozone, carbon monoxide and secondary inorganic aerosols with a finer temporal or spatial resolution taken as truth. Simulation error for these species increases by more than a factor of 5 from the shortest (5 min) to longest (60 min) temporal resolution. Chemical timesteps twice that of the transport timestep offer more simulation accuracy per unit computation. However, simulation error from coarser spatial resolution generally exceeds that from longer timesteps; e.g. degrading from 2° × 2.5° to 4° × 5

  16. Evaluation of a watershed model to simulate sediment transport in a small agricultural watershed in Indiana

    USGS Publications Warehouse

    Arihood, L.D.

    1989-01-01

    The streamflow and sediment components of the watershed model, ' Hydrologic Simulation Program-Fortran ', were evaluated using 2 years and 9 months of data from a 2.7-sq mi agricultural watershed in Indiana. Hydrographs of simulated sediment concentration generally have smaller peaks and longer recessions than do hydrographs of measured data. The attenuation of simulated peaks was partly caused by difficulties in designing a representative channel system. Simulated surface runoff during low-intensity rainfall was greater than measured surface runoff; this caused an overestimation of sediment concentration and discharge. Rainfalls of low intensity were mostly absorbed by the soil, but the model predicted that the amount of surface runoff from such storms would be large. The overly large volume of simulated surface runoff transported more sediment than actually occurred. The mean absolute error of mean sediment concentrations during storms is 45% of the measured average concentration. The error resulted from a combination of error in recording streamflow and rainfall, in simulating streamflows, and in simulating sedimentation processes. The largest percent errors are associated with simulated maximum streamflows and average sediment discharges. The root-mean-square errors are 93 and 102% of the measured maximum streamflow and average sediment discharges. (USGS)

  17. Preferential flow estimates to an agricultural tile drain with implications for glyphosate transport

    USGS Publications Warehouse

    Stone, W.W.; Wilson, J.T.

    2006-01-01

    Agricultural subsurface drains, commonly referred to as tile drains, are potentially significant pathways for the movement of fertilizers and pesticides to streams and ditches in much of the Midwest. Preferential flow in the unsaturated zone provides a route for water and solutes to bypass the soil matrix and reach tile drains faster than predicted by traditional displacement theory. This paper uses chloride concentrations to estimate preferential flow contributions to a tile drain during two storms in May 2004. Chloride, a conservative anion, was selected as the tracer because of differences in chloride concentrations between the two sources of water to the tile drain, preferential and matrix flow. A strong correlation between specific conductance and chloride concentration provided a mechanism to estimate chloride concentrations in the tile drain throughout the storm hydrographs. A simple mixing analysis was used to identify the preferential flow component of the storm hydrograph. During two storms, preferential flow contributed 11 and 51% of total storm tile drain flow; the peak contributions, 40 and 81%, coincided with the peak tile drain flow. Positive relations between glyphosate [N-(phosphonomethyl)glycine] concentrations and preferential flow for the two storms suggest that preferential flow is an important transport pathway to the tile drain. ?? ASA, CSSA, SSSA.

  18. Macro- and micro element enrichment in the runoff transported sediment on Hungarian agricultural watersheds

    NASA Astrophysics Data System (ADS)

    Farsang, Andrea; Barta, Károly

    2010-05-01

    The social and economic changes of the past twenty years have greatly affected the rural areas of Hungary, therefore the element transport, element balance of the agricultural areas has altered to a great extent. The changes of land use, changing some arable lands into monocultural vineyards, the privatisation of arable lands, the size changes of plots and their cultivation parallel to slope, all result in the increase of erosive and nutrient wash-off processes. The studied areas are situated in the catchment area of Lake Velence in North-West Hungary and in the Szekszárd Hills in South-West Hungary. The climate of these areas is moderately cool and dry. The annual average temperature is 9.5-9.8 oC; the volume of rainfall is 550-600 mm, with 50-55 % in form of severe summer rainstorms. The landuse of the studied plots is vineyard and arable land. The soil type in the catchment area of Lake-Velence is calcic Chernozem, and in the Szekszárd area is calcic Luvisol. The soil texture is a combination of loam and sandy loam. The average angle of slope is 4o, ranging from 1o to 6o. Measurements with sediment collectors were between 2004-2008 on two slopes in each area. The collectors were spaced at a distance of 25 m over a total length of 150-350 m. On the slopes (vineyard and arable land), we measured element redistribution due to rainfall with sediment collectors. The enrichment ratios (ER) (Duttmann, 1999; Boy & Ramos, 2002; Zhang et al., 2004) as a quotient of the concentration measured in the topsoil with that in the sediment were calculated. The sediment build-up in the collectors and the topsoil around the collectors was gathered after rainfall events. We calculated enrichment ratios as follows: ER(element)=Element concentration(sedim.)/ Element concentration(soil) The soil properties and elements taken into consideration included: pH (H2O), particle size distribution (%), organic matter content (OM, %), AL-P2O5 content and microelement (Zn, Cu, Ni, Pb, Cd

  19. Chemical and microbiological hazards associated with recycling of anaerobic digested residue intended for agricultural use

    SciTech Connect

    Govasmark, Espen; Staeb, Jessica; Holen, Borge; Hoornstra, Douwe; Nesbakk, Tommy; Salkinoja-Salonen, Mirja

    2011-12-15

    In the present study, three full-scale biogas plants (BGP) were investigated for the concentration of heavy metals, organic pollutants, pesticides and the pathogenic bacteria Bacillus cereus and Escherichia coli in the anaerobically digested residues (ADR). The BGPs mainly utilize source-separated organic wastes and industrial food waste as energy sources and separate the ADR into an ADR-liquid and an ADR-solid fraction by centrifugation at the BGP. According to the Norwegian standard for organic fertilizers, the ADR were classified as quality 1 mainly because of high zinc (132-422 mg kg{sup -1} DM) and copper (23-93 mg kg{sup -1} DM) concentrations, but also because of high cadmium (0.21-0.60 mg kg{sup -1} DM) concentrations in the liquid-ADR. In the screening of organic pollutants, only DEHP (9.7-62.1 mg kg{sup -1}) and {Sigma} PAH 16 (0.2-1.98 mg kg{sup -1} DM) were detected in high concentrations according to international regulations. Of the 250 pesticides analyzed, 11 were detected, but only imazalil (<0.30-5.77 mg kg{sup -1} DM) and thiabendazol (<0.14-0.73 mg kg{sup -1} DM) were frequently detected in the ADR-fiber. Concentrations of imazalil and thiabendazol were highest during the winter months, due to a high consumption of citrus fruits in Norway in this period. Ten percent of the ADR-liquid samples contained cereulide-producing B. cereus, whereas no verotoxigenic E. coli was detected. The authors conclude that the risk of chemical and bacterial contamination of the food chain or the environment from agricultural use of ADR seems low.

  20. Physical and Chemical Properties of Bench Sediments in Self-Formed Agricultural Drainage Channels

    NASA Astrophysics Data System (ADS)

    Brooker, M.; Witter, J.; Islam, K. R.; Mouser, P. J.

    2014-12-01

    Two-stage ditches are a novel approach to managing agricultural drainage and are designed with floodplain benches set within the banks of a standard, trapezoidal channel. The floodplain bench serves to attenuate pollutant loads in surface waters through (1) capture of sediments, (2) nutrient assimilation by vegetation, and (3) transformation of C and residual N and P by indigenous microorganisms. Two-stage channels have been constructed in the tri-state region of Ohio-Michigan-Indiana over the last decade with initial results indicating C and P sequestration and enhanced N removal via denitrification. However, the sustainability and the net ecosystem services provided by these designs are relatively unknown beyond this timeframe. To better characterize the properties of two-stage ditches aged more than a decade, we examined the physical and chemical properties of sediments in unplanned, self-formed floodplain benches across 5 distinct Midwest ecoregions. Established benches were selected from 3 locations within each ecoregion and sampled along depth and bench-positional gradients from geo-referenced sites. The sediment-bound C, N, and P concentrations were quantified along with soil texture and channel geomorphology. Nutrient concentrations did not differ across bench position (upstream, downstream, near bank, or near channel); however, significant differences were observed between ecoregions. Steeper slopes and higher benches were associated with higher sand content than surrounding soils and promoted greater storage of C and N. Gradual slopes, on the other hand, were associated with higher clay and silt content. Across these specific ecoregions, P storage declined with increasing depth. However, this was unexplained by the particle size distribution at these depths. Further research is therefore needed to investigate whether P is released from waterlogged sediments or there is biological redistribution of this nutrient across the column depth.

  1. Transport of suspended sediment and organic carbon during storm events in a large agricultural catchment, southwest France.

    NASA Astrophysics Data System (ADS)

    Chantha, Oeurng; Sabine, Sauvage; David, Baqué; Alexandra, Coynel; Eric, Maneux; Henri, Etcheber; José-Miguel, Sánchez-Pérez

    2010-05-01

    Intensive agriculture has led to environmental degradation through soil erosion and carbon loss transferred from agricultural land to the stream networks. Suspended sediment transport from the agricultural catchment to the watercourses is responsible for aquatic habitat degradation, reservoir sedimentation, and for transporting sediment associated pollutants (pesticides, nutrient, heavy metals and other toxic substances). Consequently, the temporal transport of suspended sediment (SS), dissolved and particulate organic carbon (DOC and POC) was investigated during 18 months from January 2008 to June 2009 within a large agricultural catchment in southwest France. This study is based on an extensive dataset with high temporal resolution using manual and automatic sampling, especially during 15 flood events. Two main objectives aim at: (i) studying temporal transport in suspended sediment (SS), DOC and POC with factors explaining their dynamics and (ii) analysing the relationships between discharge, SSC, DOC and POC during flood events. The study demonstrates there is a strong variability of SS, POC and DOC during flood events. The SS transport during different seasonal floods varied by event from 513 to 41 750 t; POC transport varied from 12 to 748 t and DOC transport varied from 9 to 218 t. The specific yield of the catchment represents 76 t km-2 y-1 of sediment, 1.8 t km-2 y-1 of POC and 0.7 t km-2 y-1 of DOC, respectively. The POC associated with sediment transport from the catchment accounted for ~2.5% of the total sediment load. Flood duration and flood magnitude are key factors in determining the sediment and organic carbon transport. Statistical analyses revealed strong correlations between total precipitation, flood discharge, total water yield with suspended sediment and organic transport. The relationships of SSC, POC and DOC versus discharge over temporal flood events resulted in different hysteresis patterns which were used to suggest those dissolved and

  2. Purified Si film formation from metallurgical-grade Si by hydrogen plasma induced chemical transport

    NASA Astrophysics Data System (ADS)

    Ohmi, Hiromasa; Goto, Akihiro; Kamada, Daiki; Hamaoka, Yoshinori; Kakiuchi, Hiroaki; Yasutake, Kiyoshi

    2009-11-01

    Purified Si film is prepared directly from metallurgical-grade Si (MG-Si) by using hydrogen plasma induced chemical transport at subatmospheric pressure. The purification mechanism is based on the different hydrogenation behaviors of the various impurity elements in MG-Si. The prepared Si films clearly had fewer typical metal impurities (Fe, Al, Ti, Cr, Mn, etc.) than those in the MG-Si. In particular, the Fe concentration was drastically reduced from 6900 mass ppm to less than 0.1 mass ppm by one time chemical transport. Furthermore, metal impurity concentrations were further reduced by repeating chemical transport deposition.

  3. Real-time Detection of Particulate Chemical Composition Near Agricultural Facilities Using Mass Spectrometry

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Agricultural facilities are the source of many types of particles and gases that can exhibit an influence on air quality. Emissions potentially impacting air quality from agricultural sources have become a concern for various state and federal regulatory agencies. Particle mass concentration influe...

  4. Water and solute transport in agricultural soils predicted by volumetric clay and silt contents.

    PubMed

    Karup, Dan; Moldrup, Per; Paradelo, Marcos; Katuwal, Sheela; Norgaard, Trine; Greve, Mogens H; de Jonge, Lis W

    2016-09-01

    Solute transport through the soil matrix is non-uniform and greatly affected by soil texture, soil structure, and macropore networks. Attempts have been made in previous studies to use infiltration experiments to identify the degree of preferential flow, but these attempts have often been based on small datasets or data collected from literature with differing initial and boundary conditions. This study examined the relationship between tracer breakthrough characteristics, soil hydraulic properties, and basic soil properties. From six agricultural fields in Denmark, 193 intact surface soil columns 20cm in height and 20cm in diameter were collected. The soils exhibited a wide range in texture, with clay and organic carbon (OC) contents ranging from 0.03 to 0.41 and 0.01 to 0.08kgkg(-1), respectively. All experiments were carried out under the same initial and boundary conditions using tritium as a conservative tracer. The breakthrough characteristics ranged from being near normally distributed to gradually skewed to the right along with an increase in the content of the mineral fines (particles ≤50μm). The results showed that the mineral fines content was strongly correlated to functional soil structure and the derived tracer breakthrough curves (BTCs), whereas the OC content appeared less important for the shape of the BTC. Organic carbon was believed to support the stability of the soil structure rather than the actual formation of macropores causing preferential flow. The arrival times of 5% and up to 50% of the tracer mass were found to be strongly correlated with volumetric fines content. Predicted tracer concentration breakthrough points as a function of time up to 50% of applied tracer mass could be well fitted to an analytical solution to the classical advection-dispersion equation. Both cumulative tracer mass and concentration as a function of time were well predicted from the simple inputs of bulk density, clay and silt contents, and applied tracer mass

  5. Water and solute transport in agricultural soils predicted by volumetric clay and silt contents

    NASA Astrophysics Data System (ADS)

    Karup, Dan; Moldrup, Per; Paradelo, Marcos; Katuwal, Sheela; Norgaard, Trine; Greve, Mogens H.; de Jonge, Lis W.

    2016-09-01

    Solute transport through the soil matrix is non-uniform and greatly affected by soil texture, soil structure, and macropore networks. Attempts have been made in previous studies to use infiltration experiments to identify the degree of preferential flow, but these attempts have often been based on small datasets or data collected from literature with differing initial and boundary conditions. This study examined the relationship between tracer breakthrough characteristics, soil hydraulic properties, and basic soil properties. From six agricultural fields in Denmark, 193 intact surface soil columns 20 cm in height and 20 cm in diameter were collected. The soils exhibited a wide range in texture, with clay and organic carbon (OC) contents ranging from 0.03 to 0.41 and 0.01 to 0.08 kg kg- 1, respectively. All experiments were carried out under the same initial and boundary conditions using tritium as a conservative tracer. The breakthrough characteristics ranged from being near normally distributed to gradually skewed to the right along with an increase in the content of the mineral fines (particles ≤ 50 μm). The results showed that the mineral fines content was strongly correlated to functional soil structure and the derived tracer breakthrough curves (BTCs), whereas the OC content appeared less important for the shape of the BTC. Organic carbon was believed to support the stability of the soil structure rather than the actual formation of macropores causing preferential flow. The arrival times of 5% and up to 50% of the tracer mass were found to be strongly correlated with volumetric fines content. Predicted tracer concentration breakthrough points as a function of time up to 50% of applied tracer mass could be well fitted to an analytical solution to the classical advection-dispersion equation. Both cumulative tracer mass and concentration as a function of time were well predicted from the simple inputs of bulk density, clay and silt contents, and applied tracer

  6. Potential impacts of agricultural chemicals on waterfowl and other wildlife inhabiting prairie wetlands: An evaluation of research needs and approaches

    USGS Publications Warehouse

    Grue, C.E.; DeWeese, L.R.; Mineau, P.; Swanson, G.A.; Foster, J.R.; Arnold, P.M.; Huckins, J.N.; Sheenan, P.J.; Marshall, W.K.; Ludden, A.P.

    1986-01-01

    The potential for agricultural chemicals to enter prairie-pothole wetlands and impact wildlife dependent on these wetlands for survival and reproduction appears to be great. However, the actual risk to wetland wildlife from the inputs of these chemicals cannot be adequately assessed at this time, because of insufficient data. Available data on the use of pesticides in the prairie-pothole region and the toxicity of these pesticides suggest that insecticides pose the greatest hazard to wetland wildlife, particularly birds. The majority of the most widely used insecticides within the region are very toxic to aquatic invertebrates and birds. Of particular concern are the impacts of agricultural chemicals on the quality of the remaining wetlands in the region and whether or not these impacts have contributed to observed declines in waterfowl populations. Although existing data suggest that adult and juvenile waterfowl may not be more sensitive to these chemicals than are other wetland wildlife, their food habits and feeding behaviors may make them more vulnerable to direct toxic effects or chemical-induced changes in the abundance of aquatic invertebrates. Laboratory and field studies in the United States and Canada are critically needed to assess these potential impacts.

  7. The Acquisition and Application of Absorption, Distribution, Metabolism, and Excretion (ADME) Data in Agricultural Chemical Safety Assessments

    SciTech Connect

    Barton, H. A.; Pastoor, Timothy P.; Baetcke, Karl; Chambers, Janice E.; Diliberto, Janet; Doerrer, Nancy G.; Driver, Jeffrey H.; Hastings, Charles E.; Iyengar, Seshadri; Krieger, Robert; Stahl, Bernhard; Timchalk, Chuck

    2006-01-01

    The ILSI Health and Environmental Sciences Institute (HESI) formed the Agricultural Chemical Safety Assessment (ACSA) Technical Committee in the year 2000 to design a toxicity testing scheme that would incorporate current understanding of pesticide toxicology and exposure and recognize the specificity of agricultural products. The purpose of and background for the ACSA project are described in detail in the companion paper by Carmichael et al. (2006). As the proposed tiered testing approach for agricultural chemical safety assessment evolved, the ACSA Technical Committee and its task forces (Carmichael et al., 2006; Cooper et al., 2006; Doe et al., 2006) worked toward the following objectives: (1) Provide information that can be applied to a range of relevant human exposure situations. (2) Characterize effects that have the potential to damage human health at exposure levels approximating those that might be encountered in the use of these compounds. (3) Avoid high doses that cause unnecessary public concern (e.g., safety assessments should focus on doses that are relevant to realistic human exposures while maintaining adequate power for the experimental studies to detect toxicity). (4) Use the minimum number of animals necessary to produce a thorough safety assessment of the chemicals of interest. (5) Inflict the minimum amount of distress on animals. (6) Minimize excessive and unnecessary use of resources by regulatory authorities and industry, which could be used to address other issues of concern. (7) Increase both the efficiency and relevance of the current safety assessment process.

  8. Modeling phosphorus transport in an agricultural watershed using the WEPP model.

    PubMed

    Perez-Bidegain, Mario; Helmers, Matthew J; Cruse, Rick

    2010-01-01

    The Water Erosion Prediction Project (WEPP) model has been tested for its ability to predict soil erosion, runoff, and sediment delivery over a wide range of conditions and scales for both hillslopes and watersheds. Since its release in 1995, there has been considerable interest in adding a chemical transport element to it. Total phosphorus (TP) loss at the watershed outlet was simulated as the product of TP in the soil, amount of sediment at the watershed outlet, and an enrichment ratio (ER) factor. WEPP can be coupled with a simple algorithm to simulate phosphorus transport bound to sediment at the watershed outlet. The objective of this work was to incorporate and test the ability of WEPP in estimatingTP loss with sediment at the small watershed scale. Two approaches were examined. One approach (P-EER) estimated ER according to an empirical relationship; the other approach used the ER calculated by WEPP (P-WER).The data used for model performance test were obtained from two side-by-side watersheds monitored between 1976 and 1980. The watershed sizes were 5.05 and 6.37 ha, and each was in a corn (Zea mays L.)-soybean [Glycine max (L.) Merr.] rotation. Measured and simulated results were compared for the period April to October in each year. There was no statistical difference between the mean measured and simulated TP loss. The Nash-Sutcliffe coefficient was 0.80 and 0.78 for the P-EER and P-WER methods, respectively. It was critical for both methods that WEPP adequately represent the biggest sediment yield events because sediment is the main driver for TP loss so that the model can adequately simulate TP losses bound to sediment. The P-WER method is recommended because it does not require use of empirical parameters to estimate TP loss at the watershed outlet. PMID:21284310

  9. SURFACE CHEMICAL EFFECTS ON COLLOID STABILITY AND TRANSPORT THROUGH NATURAL POROUS MEDIA

    EPA Science Inventory

    Surface chemical effects on colloidal stability and transport through porous media were investigated using laboratory column techniques. Approximately 100 nm diameter, spherical, iron oxide particles were synthesized as the mobile colloidal phase. The column packing material was ...

  10. Towards electron transport measurements in chemically modified graphene: effect of a solvent

    NASA Astrophysics Data System (ADS)

    Jacobsen, Arnhild; Koehler, Fabian M.; Stark, Wendelin J.; Ensslin, Klaus

    2010-12-01

    The chemical functionalization of graphene modifies the local electron density of carbon atoms and hence electron transport. Measuring these changes allows for a closer understanding of the chemical interaction and the influence of functionalization on the graphene lattice. However, not only chemistry, in this case diazonium chemistry, has an effect on electron transport. The latter is also influenced by defects and dopants resulting from different processing steps. Here, we show that the solvents used in the chemical reaction process change the transport properties. In more detail, the investigated combination of isopropanol and heating treatment reduces the doping concentration and significantly increases the mobility of graphene. Furthermore, isopropanol treatment alone increases the concentration of dopants and introduces an asymmetry between electron and hole transport, which might be difficult to distinguish from the effect of functionalization. The results shown in this work demand a closer look at the influence of solvents used for chemical modification in order to understand their influence.

  11. The fate of soil organic carbon upon erosion, transport and deposition in agricultural landscapes - A review of different concepts

    NASA Astrophysics Data System (ADS)

    Kirkels, F. M. S. A.; Cammeraat, L. H.; Kuhn, N. J.

    2014-12-01

    Erosion and deposition redistribute large quantities of sediment and soil organic carbon (SOC) in agricultural landscapes. In the perspective of global carbon cycling, the coupling between erosion processes and the fate of SOC is of particular interest. However, different concepts have been proposed to assess the impact of erosion-induced lateral and vertical carbon fluxes. On landscape scale, this resulted in contrasting conclusions if agricultural soils represent either a carbon sink or source. The large global area of arable soil and generally high erosion rates, make these insights important. In this review, we aim to give an overview of the different conceptual relations described governing C dynamics at sites of erosion, along the transport pathway and at depositional sites and the current state of knowledge on the fate of SOC upon erosion, transport and deposition in agricultural landscapes. The impact of erosion on SOC dynamics differs for sites of erosion, deposition and during transport, with further influences by agricultural practices (e.g. tillage and fertilisation). Controlling processes are the detachment of sediment and SOC, net primary production resulting in dynamic replacement and changes in mineralisation upon transport and deposition due to aggregate breakdown and deep burial, respectively. However, the exact magnitude and dominance of these processes are debated, resulting in a controversy whether arable land functions as a sink or source for atmospheric CO2. Global estimations range between a net sink strength of 0.06-1 versus a source of 0.27-1.14 Gt C yr- 1 for agricultural soils. An eco-geomorphologic approach, which encompasses physical- and biological-driven factors (e.g. spatio-temporal variation in biological, geomorphological and biological processes, environmental conditions, mineralisation, and net primary production) is of importance to balance the carbon budget and ascertain sink or source formation at landscape scale. High spatio

  12. Magnon spin transport driven by the magnon chemical potential in a magnetic insulator

    NASA Astrophysics Data System (ADS)

    Cornelissen, L. J.; Peters, K. J. H.; Bauer, G. E. W.; Duine, R. A.; van Wees, B. J.

    2016-07-01

    We develop a linear-response transport theory of diffusive spin and heat transport by magnons in magnetic insulators with metallic contacts. The magnons are described by a position-dependent temperature and chemical potential that are governed by diffusion equations with characteristic relaxation lengths. Proceeding from a linearized Boltzmann equation, we derive expressions for length scales and transport coefficients. For yttrium iron garnet (YIG) at room temperature we find that long-range transport is dominated by the magnon chemical potential. We compare the model's results with recent experiments on YIG with Pt contacts [L. J. Cornelissen et al., Nat. Phys. 11, 1022 (2015), 10.1038/nphys3465] and extract a magnon spin conductivity of σm=5 ×105 S/m. Our results for the spin Seebeck coefficient in YIG agree with published experiments. We conclude that the magnon chemical potential is an essential ingredient for energy and spin transport in magnetic insulators.

  13. Nitrogen transport within an agricultural landscape: insights on how hydrology, biogeochemistry, and the landscape intersect to control the fate and transport of nitrogen in the Mississippi Delta

    USGS Publications Warehouse

    Barlow, Jeannie R.; Kröger, Robert

    2014-01-01

    Nitrogen (N) is a ubiquitous contaminant throughout agricultural landscapes due to both the application of inorganic and organic fertilizers to agricultural fields and the general persistence of nitrate (NO3 ) in oxygenated aqueous environments (Denver et al. 2010; Domagalski et al. 2008; Green et al. 2008; Coupe 2001; Nolan and Stoner 2000). In order to understand why excess N occurs various hydrologic systems (environments), it is important to consider potential sources, the locations of these sources in the watershed, and the timing of the application of sources with respect to the movement of water. To learn how to manage N in a watershed, it is necessary to identify and quantify flow paths and biogeochemical conditions, which ultimately combine to determine transport and fate. If sources, transport mechanisms, and biogeochemical controls were uniformly distributed, it would be possible to manage N uniformly throughout a watershed. However, uniform conditions are rare to nonexistent in the natural world and in the landscape altered for agricultural production. In order to adjust management activities on the landscape to have the greatest effect, it is important to understand the fate and transport N within the intersection of hydrology and biogeochemistry, that is, to understand the extent and duration of the hydrologic and biogeochemical controls as N is routed through and among each hydrologic compartment.

  14. A Review of the Thermodynamic, Transport, and Chemical Reaction Rate Properties of High-temperature Air

    NASA Technical Reports Server (NTRS)

    Hansen, C Frederick; Heims, Steve P

    1958-01-01

    Thermodynamic and transport properties of high temperature air, and the reaction rates for the important chemical processes which occur in air, are reviewed. Semiempirical, analytic expressions are presented for thermodynamic and transport properties of air. Examples are given illustrating the use of these properties to evaluate (1) equilibrium conditions following shock waves, (2) stagnation region heat flux to a blunt high-speed body, and (3) some chemical relaxation lengths in stagnation region flow.

  15. An Inverse Analysis Approach to the Characterization of Chemical Transport in Paints

    PubMed Central

    Willis, Matthew P.; Stevenson, Shawn M.; Pearl, Thomas P.; Mantooth, Brent A.

    2014-01-01

    The ability to directly characterize chemical transport and interactions that occur within a material (i.e., subsurface dynamics) is a vital component in understanding contaminant mass transport and the ability to decontaminate materials. If a material is contaminated, over time, the transport of highly toxic chemicals (such as chemical warfare agent species) out of the material can result in vapor exposure or transfer to the skin, which can result in percutaneous exposure to personnel who interact with the material. Due to the high toxicity of chemical warfare agents, the release of trace chemical quantities is of significant concern. Mapping subsurface concentration distribution and transport characteristics of absorbed agents enables exposure hazards to be assessed in untested conditions. Furthermore, these tools can be used to characterize subsurface reaction dynamics to ultimately design improved decontaminants or decontamination procedures. To achieve this goal, an inverse analysis mass transport modeling approach was developed that utilizes time-resolved mass spectroscopy measurements of vapor emission from contaminated paint coatings as the input parameter for calculation of subsurface concentration profiles. Details are provided on sample preparation, including contaminant and material handling, the application of mass spectrometry for the measurement of emitted contaminant vapor, and the implementation of inverse analysis using a physics-based diffusion model to determine transport properties of live chemical warfare agents including distilled mustard (HD) and the nerve agent VX. PMID:25226346

  16. An inverse analysis approach to the characterization of chemical transport in paints.

    PubMed

    Willis, Matthew P; Stevenson, Shawn M; Pearl, Thomas P; Mantooth, Brent A

    2014-01-01

    The ability to directly characterize chemical transport and interactions that occur within a material (i.e., subsurface dynamics) is a vital component in understanding contaminant mass transport and the ability to decontaminate materials. If a material is contaminated, over time, the transport of highly toxic chemicals (such as chemical warfare agent species) out of the material can result in vapor exposure or transfer to the skin, which can result in percutaneous exposure to personnel who interact with the material. Due to the high toxicity of chemical warfare agents, the release of trace chemical quantities is of significant concern. Mapping subsurface concentration distribution and transport characteristics of absorbed agents enables exposure hazards to be assessed in untested conditions. Furthermore, these tools can be used to characterize subsurface reaction dynamics to ultimately design improved decontaminants or decontamination procedures. To achieve this goal, an inverse analysis mass transport modeling approach was developed that utilizes time-resolved mass spectroscopy measurements of vapor emission from contaminated paint coatings as the input parameter for calculation of subsurface concentration profiles. Details are provided on sample preparation, including contaminant and material handling, the application of mass spectrometry for the measurement of emitted contaminant vapor, and the implementation of inverse analysis using a physics-based diffusion model to determine transport properties of live chemical warfare agents including distilled mustard (HD) and the nerve agent VX. PMID:25226346

  17. Crystal growth of HfS 2 by chemical vapour transport with halogen (Cl, Br, I)

    NASA Astrophysics Data System (ADS)

    Fiechter, S.; Eckert, K.

    1988-05-01

    Single crystals of HfS 2 have been prepared by chemical vapour transport (CVT) with halogen. Depending on the transporting agent added, exergonic or endergonic transport was observed. Employing 0.5 mg/cm 3 chlorine or bromine in evacuated and sealed quartz ampoules, exergonic transport occurs. In a temperature gradient from 850 to 870 K transparent reddish-orange crystal platelets of pseudohexagonal shape (10×10×0.05 mm3) were obtained. Endergonic transport, found with iodine as transporting agent, first starts at higher temperatures (1270-1220 K). A thermochemical study of the vapour phase composition revealed that gaseous HfHal 4 and HfHal 3 ( Hal = Cl, Br) are responsible for the exergonic transport observed. Because of the higher stability of HfS 2 against iodine, CVT first starts at elevated temperatures. In the vapour phase Hfl and Hfl 2 dominate and effect a reversal of the transport direction.

  18. USER'S MANUAL FOR THE CHEMICAL TRANSPORT AND FATE MODEL (TOXIWASP), VSION 1

    EPA Science Inventory

    This manual describes the dynamic model TOXIWASP for simulating the transport and fate of toxic chemicals in water bodies. TOXIWASP combines the kinetic structure adapted from the Exposure Analysis Modeling System (EXAMS) with the transport framework provided by the Water Analysi...

  19. CONSISTENT USE OF THE KALMAN FILTER IN CHEMICAL TRANSPORT MODELS (CTMS) FOR DEDUCING EMISSIONS

    EPA Science Inventory

    Past research has shown that emissions can be deduced using observed concentrations of a chemical, a Chemical Transport Model (CTM), and the Kalman filter in an inverse modeling application. An expression was derived for the relationship between the "observable" (i.e., the con...

  20. MODELING MULTICOMPONENT ORGANIC CHEMICAL TRANSPORT IN THREE-FLUID-PHASE POROUS MEDIA

    EPA Science Inventory

    A two dimensional finite-element model was developed to predict coupled transient flow and multicomponent transport of organic chemicals which can partition between NAPL, water, gas and solid phases in porous media under the assumption of local chemical equilibrium. as-phase pres...

  1. MODELING MULTICOMPONENT ORGANIC CHEMICAL TRANSPORT IN THREE FLUID PHASE POROUS MEDIA

    EPA Science Inventory

    A two-dimensional finite-element model was developed to predict coupled transient flow and multicomponent transport of organic chemicals which can partition between nonaqueous phase liquid, water, gas and solid phases in porous media under the assumption of local chemical equilib...

  2. Wave Tank Studies On Formation And Transport Of OMA From The Chemically Dispersed Oil

    EPA Science Inventory

    The interaction of chemical dispersants and suspended sediments with crude oil influences the fate and transport of oil spills in coastal waters. A wave tank study was conducted to investigate the effects of chemical dispersants and mineral fines on dispersion of oil, formation ...

  3. CHEMICAL TRANSPORT FACILITATED BY COLLOIDAL-SIZED ORGANIC MOLECULES

    EPA Science Inventory

    The fluid passing through the pores of soils and geologic materials is not just water with dissolved inorganic chemicals, but a complex mixture of organic and inorganic molecules. Large organic molecules such as humic and fulvic materials may impact the movement of contaminants. ...

  4. From deposition to erosion: Spatial and temporal variability of sediment sources, storage, and transport in a small agricultural watershed

    NASA Astrophysics Data System (ADS)

    Florsheim, J. L.; Pellerin, B. A.; Oh, N. H.; Ohara, N.; Bachand, P. A. M.; Bachand, S. M.; Bergamaschi, B. A.; Hernes, P. J.; Kavvas, M. L.

    2011-09-01

    The spatial and temporal variability of sediment sources, storage, and transport were investigated in a small agricultural watershed draining the Coast Ranges and Sacramento Valley in central California. Results of field, laboratory, and historical data analysis in the Willow Slough fluvial system document changes that transformed a transport-limited depositional system to an effective erosion and transport system, despite a large sediment supply. These changes were caused by a combination of factors: (i) an increase in transport capacity, and (ii) hydrologic alteration. Alteration of the riparian zone and drainage network pattern during the past ~ 150 years included a twofold increase in straightened channel segments along with a baselevel change from excavation that increased slope, and increased sediment transport capacity by ~ 7%. Hydrologic alteration from irrigation water contributions also increased transport capacity, by extending the period with potential for sediment transport and erosion by ~ 6 months/year. Field measurements document Quaternary Alluvium as a modern source of fine sediment with grain size distributions characterized by 5 to 40% fine material. About 60% of an upland and 30% of a lowland study reach incised into this deposit exhibit bank erosion. During this study, the wet 2006 and relatively dry 2007 water years exhibited a range of total annual suspended sediment load spanning two orders of magnitude: ~ 108,500 kg/km 2/year during 2006 and 5,950 kg/km 2/year during 2007, only 5% of that during the previous year. Regional implications of this work are illustrated by the potential for a small tributary such as Willow Slough to contribute sediment - whereas large dams limit sediment supply from larger tributaries - to the Sacramento River and San Francisco Bay Delta and Estuary. This work is relevant to lowland agricultural river-floodplain systems globally in efforts to restore aquatic and riparian functions and where water quality

  5. From deposition to erosion: spatial and temporal variability of sediment sources, storage, and transport in a small agricultural watershed

    USGS Publications Warehouse

    Florsheim, J.L.; Pellerin, B.A.; Oh, N.H.; Ohara, N.; Bachand, P.A.M.; Bachand, Sandra M.; Bergamaschi, B.A.; Hernes, P.J.; Kavvas, M.L.

    2011-01-01

    The spatial and temporal variability of sediment sources, storage, and transport were investigated in a small agricultural watershed draining the Coast Ranges and Sacramento Valley in central California. Results of field, laboratory, and historical data analysis in the Willow Slough fluvial system document changes that transformed a transport-limited depositional system to an effective erosion and transport system, despite a large sediment supply. These changes were caused by a combination of factors: (i) an increase in transport capacity, and (ii) hydrologic alteration. Alteration of the riparian zone and drainage network pattern during the past ~ 150 years included a twofold increase in straightened channel segments along with a baselevel change from excavation that increased slope, and increased sediment transport capacity by ~ 7%. Hydrologic alteration from irrigation water contributions also increased transport capacity, by extending the period with potential for sediment transport and erosion by ~ 6 months/year. Field measurements document Quaternary Alluvium as a modern source of fine sediment with grain size distributions characterized by 5 to 40% fine material. About 60% of an upland and 30% of a lowland study reach incised into this deposit exhibit bank erosion. During this study, the wet 2006 and relatively dry 2007 water years exhibited a range of total annual suspended sediment load spanning two orders of magnitude: ~ 108,500 kg/km2/year during 2006 and 5,950 kg/km2/year during 2007, only 5% of that during the previous year. Regional implications of this work are illustrated by the potential for a small tributary such as Willow Slough to contribute sediment – whereas large dams limit sediment supply from larger tributaries – to the Sacramento River and San Francisco Bay Delta and Estuary. This work is relevant to lowland agricultural river–floodplain systems globally in efforts to restore aquatic and riparian functions and where water quality

  6. Oxidative stress and endocrine endpoints in white sucker (Catostomus commersoni) from a river impacted by agricultural chemicals.

    PubMed

    Dorval, Jocelyn; Leblond, Vincent; Deblois, Christian; Hontela, Alice

    2005-05-01

    The effects of agricultural chemicals on cortisol secretion, antioxidants, and lipid peroxidation were investigated in hepatic and adrenal tissue of white sucker (Catostomus commersoni) from a river (Yamaska) that drains an agricultural region in Québec (Canada). Plasma cholinesterase (ChE) activity, used as a biomarker of exposure to pesticides, was elevated in fish from the reference site compared to fish from the contaminated sites. Plasma concentrations of cortisol and thyroid hormones (T3 and T4) were higher in fish from the reference site compared to contaminated sites; reduced glutathione (GSH) levels, catalase (CAT), and glutathione peroxidase (GPx) activities were higher and lipid peroxidation (LPO) was lower. Levels of antioxidants (CAT, Gpx, and GSH) were higher (10-90%) and LPO levels were lower (50%) in the liver than in the adrenal tissue. The present in situ study provided evidence that antioxidants, lipid peroxidation, and plasma hormones were altered in fish sampled in areas impacted by agricultural chemicals. Endocrine-disrupting effects were associated with oxidative stress. The results suggest that antioxidants and lipid peroxidation could be used as markers of contaminant exposure in fish. PMID:16111011

  7. Chemical and biological characterization of products of incomplete combustion from the simulated field burning of agricultural plastic

    SciTech Connect

    Ryan, J.V.; Perry, E.; Linak, W.P.; DeMarini, D.M.; Williams, R.W.

    1989-01-01

    Chemical and biological analyses were performed to characterize products of incomplete combustion emitted during the simulated open-field burning of agricultural plastic. A small utility shed equipped with an air delivery system was used to simulate pile burning and forced-air-curtain incineration of a nonhalogenated agricultural plastic that reportedly consisted of polyethylene and carbon black. Emissions were analyzed for combustion gases; volatile, semi-volatile, and particulate organics; and toxic and mutagenic properties. Emission samples, as well as samples of the used (possibly pesticide-contaminated) plastic, were analyzed for the presence of several pesticides to which the plastic may have been exposed. When mutagenicity was evaluated by exposing Salmonella bacteria (Ames assay) to whole vapor and vapor/particulate emissions, no toxic or mutagenic effects were observed. However, organic extracts of the particulate samples were moderately mutagenic. The study highlights the benefits of a combined chemical/biological approach to the characterization of complex, multi-component combustion emissions. These results may not reflect those of other types of plastic that may be used for agricultural purposes, especially those containing halogens.

  8. Transport Properties of a Kinetic Model for Chemical Reactions without Barriers

    SciTech Connect

    Alves, Giselle M.; Kremer, Gilberto M.; Soares, Ana Jacinta

    2011-05-20

    A kinetic model of the Boltzmann equation for chemical reactions without energy barrier is considered here with the aim of evaluating the reaction rate and characterizing the transport coefficient of shear viscosity for the reactive system. The Chapman-Enskog solution of the Boltzmann equation is used to compute the chemical reaction effects, in a flow regime for which the reaction process is close to the final equilibrium state. Some numerical results are provided illustrating that the considered chemical reaction without energy barrier can induce an appreciable influence on the reaction rate and on the transport coefficient of shear viscosity.

  9. Assessment of rural ground-water contamination by agricultural chemicals in sensitive areas of Michigan

    SciTech Connect

    Ervin, J.L.; Kittleson, K.M.

    1988-04-01

    The vulnerability of drinking-water supplies to agricultural contamination in three Michigan counties is discussed. The results of nitrate and atrazine analysis of drinking water from 38 wells in those 3 counties is described. Widespread nitrate contamination was demonstrated in agricultural areas with vulnerable aquifers. In addition, atrazine, a widely used herbicide was found in 11 of the 38 wells samples, with concentrations and patterns not conforming to findings in other mid-western states. The need for a comprehensive inventory of the ground-water quality in rural areas of Michigan is emphasized in the report, which describes results from the first year of a 2-year study.

  10. Agricultural land application of pulp and paper mill sludges in the Donnacona area, Quebec: Chemical evaluation and crop response

    SciTech Connect

    Veillette, A.X.; Tanguay, M.G.

    1997-12-31

    Primary paper mill sludges from a thermomechanical pulp (TMP) mill were land applied at the rate of 20 metric ton per hectare (t/ha) for agricultural purposes in the Donnacona area, Quebec, in May 1994 and May 1995. Eleven agricultural sites featuring various crops were tested over two seasons to measure the impact of TMP primary paper mill sludges on soil, plant tissue and crop yield. Cereal and potato crops showed a significant increase in yield. TMP Primary sludges were also applied at the rate of 225 t/ha for land reclamation purposes of one site at the end of 1994. Soils were tested every second month. Chemical crop analyses were also performed. The first year crop response was satisfactory. Combined (primary and secondary) TMP sludges were added at the rate of 200 t/ha in the beginning of 1996. Soil, vadose zone water and crop analysis are being investigated. Impressive crop responses were obtained in the 1996 season.

  11. Adequacy of transport parameters obtained in soil column experiments for selected chemicals

    NASA Astrophysics Data System (ADS)

    Raymundo-Raymundo, E.; Nikolskii, Yu. N.; Guber, A. K.; Landeros-Sanchez, C.

    2012-07-01

    The transport parameters were determined for the 18O isotope (in the form of H2 18O), the Br- ion, and atrazine in intact columns of allophanic Andosol (Mexico State, Mexico). A one-dimensional model for the convective-dispersive transport of chemicals with account for the decomposition and equilibrium adsorption (HYDRUS-1D), which is widely applied for assessing the risk of the chemical and bacterial contamination of natural waters, was used. The model parameters were obtained by solving the inverse problem on the basis of laboratory experiments on the transport of the 18O isotope, the Br- ion, and atrazine in intact soil columns at a fixed filtration velocity. The hydrodynamic dispersion parameters determined for the 18O and Br- ions in one column were of the same order of magnitude, and those for atrazine were higher by 3-4 times. The obtained parameters were used to calculate the transport of these substances in another column with different values of the water content and filtration velocity. The transport process was adequately described only for the 18O isotope. In the case of the Br- ion, the model significantly underestimated the transport velocity; for atrazine, its peak concentration in the column was overestimated. The column study of the transport of the three chemical compounds showed that transport parameters could not be reliably predicted from the results of a single experiment, even when several compounds were used in this experiment.

  12. Chemical Status Of Selenium In Evaporation Basins For Disposal Of Agricultural Drainage.

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Evaporation basins (or ponds) are the most commonly used facilities to dispose selenium (Se)-laden agricultural drainage in the closed hydrologic basin portion of the San Joaquin Valley in California. However, there is a continuous concern on potential risk of Se in evaporation basin waters to water...

  13. Diffusion/Dispersion Transport of Chemically Reacting Species

    SciTech Connect

    Helgeson, Harold; Wenk, Hans-Rudolf

    2014-06-06

    The project characterized and quantified as a function of pressure, temperature and bulk composition the exergonic intra- and extracellular reactions catalyzed by thermo- and hyperthermophilic microbes at the oil-water interface in sedimentary basins. The reactions have been characterized and described quantitatively in terms of the chemical potentials of the components of the system in compositional hyperspace using thermodynamics, together with Gibbs free energy minimization and mass transfer computer experiments. A quantitative understanding of the biogeochemical processes responsible for the degradation of reservoired petroleum is fundamental to minimize the deleterious effects of microbial sulfidization and degradation processes.

  14. [Effects of composting with earthworm on the chemical and biological properties of agricultural organic wastes: a principal component analysis].

    PubMed

    Liu, Ting; Ren, Zong-Ling; Zhang, Chi; Chen, Xu-Fei; Zhou, Bo; Dai, Jun

    2012-03-01

    Taking mixed agricultural organic wastes cattle manure and rice straw (C:N = 28.7:1) as the substrate of earthworm Eisenia foetida, an experiment was conducted to study the effects of earthworm on the changes of the chemical and biological properties of wastes during vermi-composting. After 30 days of vermi-composting, the substrate' s pH and C/N decreased while the total P content increased significantly, and the total N, available N, dissolved organic carbon, available P content, microbial biomass-C, respiration rate, and microbial quotient increased by 8.5% , 2.6%, 1.8%, 6.3%, 21.2%, 4.4%, and 30.0% whereas the organic matter content and metabolic quotient decreased by 5.0% and 21.9%, respectively, as compared with natural composting. Vermi-composting made the substrate have higher invertase, acid phosphatase, and alkaline phosphatase activities but lower catalase and urease activities. Principal component analysis and discriminant analysis confirmed the significant differences in the substrate' s chemical and biological properties between vermi-composting and natural composting. This study indicated that vermi-composting was superior to natural composting, which could obviously improve the chemical and biological properties of composted organic materials, being a high efficient technology for the management of agricultural organic wastes. PMID:22720625

  15. Chemical changes in agricultural soils of Korea: data review and suggested countermeasures.

    PubMed

    Jo, I S; Koh, M H

    2004-01-01

    The monitoring of chemical properties, including heavy metals, in soils is necessary if better management and remediation practices are to be established for polluted soils. The National Institute of Agricultural Science and Technology initiated a monitoring study that investigated fertility and heavy metal contents of the benchmarked soils. The study covered paddy soils, upland soils, and horticultural soils in the plastic film houses, and orchard soils throughout the Korea from 1990 to 1998. Likewise, 4047 samples of paddy and 2534 samples of plastic house in 1999 and 2000 were analyzed through the Soil Environment Conservation Act. Soil chemical properties such as pH, organic matter, available phosphate and extractable calcium, magnesium and potassium contents, and heavy metal contents such as cadmium, copper, lead, zinc, arsenic, mercury, and cobalt contents were analyzed. The study showed that the average contents of organic matter, available phosphate, and extractable potassium rapidly increased in plastic house soils than in upland or paddy soils. Two kinds of fertilizer recommendation systems were established for the study: the standard levels by national soil average data for 77 crops and the recommendation by soil test for 70 crops. Standard nitrogen fertilizer application levels for cereal crops changed from 94 kg/ha in 1960s, 99 kg/ha in 1970s, 110 kg/ha in 1980s to 90 kg/ha in 1990s. The K2O-fertilizer also changed from 67 kg/ha in 1960s, 76 kg/ha in 1970s, 92 kg/ha in 1980s, and only 44 kg/ha in 1990s. In rice paddy fields, the average contents of Cd, Cu, Pb, and Zn in surface soils (0-15 cm depth) were 0.11 mg kg(-1) (ranged from 0 to 1.01), 4.70 mg kg(-1) (0-41.59), 4.84 mg kg(-1) (0-66.44), and 4.47 mg kg(-1) (0-96.70), respectively. In the uplands, the average contents of Cd, Cu, Pb, Zn, and As in surface soils (0-15 cm depth) were 0.135 mg kg(-1) (ranged from 0 to 0.660), 2.77 mg kg(-1) (0.07-78.24), 3.47 mg kg(-1) (0-43.00), 10.70 mg kg(-1) (0

  16. Some Sensitivity Studies of Chemical Transport Simulated in Models of the Soil-Plant-Litter System

    SciTech Connect

    Begovich, C.L.

    2002-10-28

    Fifteen parameters in a set of five coupled models describing carbon, water, and chemical dynamics in the soil-plant-litter system were varied in a sensitivity analysis of model response. Results are presented for chemical distribution in the components of soil, plants, and litter along with selected responses of biomass, internal chemical transport (xylem and phloem pathways), and chemical uptake. Response and sensitivity coefficients are presented for up to 102 model outputs in an appendix. Two soil properties (chemical distribution coefficient and chemical solubility) and three plant properties (leaf chemical permeability, cuticle thickness, and root chemical conductivity) had the greatest influence on chemical transport in the soil-plant-litter system under the conditions examined. Pollutant gas uptake (SO{sub 2}) increased with change in plant properties that increased plant growth. Heavy metal dynamics in litter responded to plant properties (phloem resistance, respiration characteristics) which induced changes in the chemical cycling to the litter system. Some of the SO{sub 2} and heavy metal responses were not expected but became apparent through the modeling analysis.

  17. Metal transport and chemical heterogeneity in early star forming systems

    NASA Astrophysics Data System (ADS)

    Ritter, Jeremy S.; Sluder, Alan; Safranek-Shrader, Chalence; Milosavljević, Miloš; Bromm, Volker

    2015-08-01

    To constrain the properties of the first stars with the chemical abundance patterns observed in metal-poor stars, one must identify any non-trivial effects that the hydrodynamics of metal dispersal can imprint on the abundances. We use realistic cosmological hydrodynamic simulations to quantify the distribution of metals resulting from one Population III supernova and from a small number of such supernovae exploding in close succession. Overall, supernova ejecta are highly inhomogeneously dispersed throughout the simulations. When the supernova bubbles collapse, quasi-virialized metal-enriched clouds, fed by fallback from the bubbles and by streaming of metal-free gas from the cosmic web, grow in the centres of the dark matter haloes. Partial turbulent homogenization on scales resolved in the simulation is observed only in the densest clouds where the vortical time-scales are short enough to ensure true homogenization on subgrid scales. However, the abundances in the clouds differ from the gross yields of the supernovae. Continuing the simulations until the cloud have gone into gravitational collapse, we predict that the abundances in second-generation stars will be deficient in the innermost mass shells of the supernova (if only one has exploded) or in the ejecta of the latest supernovae (when multiple have exploded). This indicates that hydrodynamics gives rise to biases complicating the identification of nucleosynthetic sources in the chemical abundance spaces of the surviving stars.

  18. Agricultural chemicals and prairie pothole wetlands: Meeting the needs of the resource and the farmer -- U.S. perspective

    USGS Publications Warehouse

    Grue, C.E.; Tome, M.W.; Messmer, T.A.; Henry, D.B.; Swanson, G.A.; DeWeese, L.R.

    1989-01-01

    Included are the reasons for concern over the effects of agrichemicals (pesticides and fertilizers) on prairie-pothole wetlands in the United States. Summarized are the results of studies conducted to date on this topic. Identified is additional research needed to assess the impacts of agrichemicals on these wetlands. Included is a discussion of management strategies and initiatives which we believe may minimize inputs of these chemicals and their impacts on wetlands and waterfowl within this portion of the prairie pothole region, while still meeting the needs of the agricultural community.

  19. The fate and transport of the Cry1Ab protein in an agricultural field and laboratory aquatic microcosms.

    PubMed

    Strain, Katherine E; Lydy, Michael J

    2015-08-01

    Genetically engineered crops expressing insecticidal crystalline proteins derived from Bacillus thuringiensis (Bt), were commercialized almost two decades ago as a means to manage agricultural pests. The Bt proteins are highly specific and only lethal upon ingestion, limiting the scope of toxicity to target insects. However, concern of exposure to non-target organisms and negative public perceptions regarding Bt crops has caused controversy surrounding their use. The objective of this research was to monitor the fate and transport of a Bt protein, Cry1Ab, in a large-scale agricultural field containing maize expressing the Cry1Ab protein and a non-Bt near isoline, and in aquatic microcosms. The highest environmental concentrations of the Cry1Ab protein were found in runoff water and sediment, up to 130ngL(-1) and 143ngg(-1) dry weight, respectively, with the Cry1Ab protein detected in both Bt and non-Bt maize fields. As surface runoff and residual crop debris can transport Bt proteins to waterways adjacent to agricultural fields, a series of laboratory experiments were conducted to determine the potential fate of the Cry1Ab protein under different conditions. The results showed that sediment type and temperature can influence the degradation of the Cry1Ab protein in an aquatic system and that the Cry1Ab protein can persist for up to two months. Although Cry1Ab protein concentrations measured in the field soil indicate little exposure to terrestrial organisms, the consistent input of Bt-contaminated runoff and crop debris into agricultural waterways is relevant to understanding potential consequences to aquatic species. PMID:25828252

  20. Nitrate fate and transport through current and former depressional wetlands in an agricultural landscape, Choptank Watershed, Maryland, United States

    USGS Publications Warehouse

    Denver, J.M.; Ator, S.W.; Lang, M.W.; Fisher, T.R.; Gustafson, A.B.; Fox, R.; Clune, J.W.; McCarty, G.W.

    2014-01-01

    Understanding local groundwater hydrology and geochemistry is critical for evaluating the effectiveness of wetlands at mitigating agricultural impacts on surface waters. The effectiveness of depressional wetlands at mitigating nitrate (NO3) transport from fertilized row crops, through groundwater, to local streams was examined in the watershed of the upper Choptank River, a tributary of Chesapeake Bay on the Atlantic Coastal Plain. Hydrologic, geochemical, and water quality data were collected from January of 2008 through December of 2009 from surface waters and networks of piezometers installed in and around current or former depressional wetlands of three major types along a gradient of anthropogenic alteration: (1) natural wetlands with native vegetation (i.e., forested); (2) prior-converted croplands, which are former wetlands located in cultivated fields; and (3) hydrologically restored wetlands, including one wetland restoration and one shallow water management area. These data were collected to estimate the orientation of groundwater flow paths and likely interactions of groundwater containing NO3 from agricultural sources with reducing conditions associated with wetlands of different types. Natural wetlands were found to have longer periods of soil saturation and reducing conditions conducive to denitrification compared to the other wetland types studied. Because natural wetlands are typically located in groundwater recharge areas along watershed divides, nitrogen (N) from nearby agriculture was not intercepted. However, these wetlands likely improve water quality in adjacent streams via dilution. Soil and geochemical conditions conducive to denitrification were also present in restored wetlands and prior-converted croplands, and substantial losses of agricultural NO3 were observed in groundwater flowing through these wetland sediments. However, delivery of NO3 from agricultural areas through groundwater to these wetlands resulting in opportunities for

  1. Fate and transport of glyphosate and aminomethylphosphonic acid in surface waters of agricultural basins

    USGS Publications Warehouse

    Gregoire, Caroline; Capel, Paul D.; Coupe, Richard H.; Kalkhoff, Stephen J.

    2011-01-01

    CONCLUSIONS: Glyphosate use in a watershed results in some occurrence in surface water; however, the watersheds most at risk for the offsite transport of glyphosate are those with high application rates, rainfall that results in overland runoff and a flow route that does not include transport through the soil.

  2. Impact of dredging on dissolved phosphorus transport in agricultural drainage ditches of the Atlantic Coastal Plain

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Drainage ditches can be a key conduit of phosphorus (P) between agricultural soils of the Atlantic coastal plain and local surface waters, including the Chesapeake Bay. This study sought to quantify the effect of a common ditch management practice, sediment dredging, on fate of P in drainage ditches...

  3. Metolachlor metabolite (MESA) reveals agricultural nitrate-N fate and transport in Choptank River watershed

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Nitrogen from agricultural activities contributes to the hypoxic zones and severe declines in water quality in the Gulf of Mexico and the Chesapeake Bay. The Federal Clean Water Act requires nitrogen load reductions to restore the integrity of these important waterways. Tools are needed to track t...

  4. Treatment of phosphorus transported from tile and ditch-drained agricultural fields using sorption materials

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Many flat, poorly drained soils, such as the Delmarva Peninsula, the upper Midwest, and certain areas of Europe such as Denmark and Netherlands, have been extensively drained through the construction of artificial drainage ditches and tiles to allow agriculture and other human activities. In additi...

  5. Nitrate transport and fluxes during storm-event discharge from a 12 ha tile-drained dryland agricultural field

    NASA Astrophysics Data System (ADS)

    Kelley, C. J.; Keller, C. K.; Brooks, E. S.; Smith, J. L.; Orr, C. H.; Evans, R. D.

    2012-12-01

    Tile drains shortcut natural soil hydrology and decrease the capacity of soils to buffer water and nutrient fluxes during storm events. Previous research at the Cook Agronomy Farm near Pullman, WA. found seasonal patterns for nutrient and water fluxes, larger during the winter and smaller during the summer. The objective of this study was to determine the effects storm events have on tile-drain water and nutrient fluxes from a dryland agricultural field. Our first hypothesis is that winter storm events activate shallow soil-water flow paths, resulting in rapid transport of precipitation and younger soil pore-water through the tile-drain system. These storm-event flow paths result in a decrease in tile-drain water electrical conductivity from a baseline of approximately 260 μS/cm to as low as 20 μS/ cm. Data suggest that storm events increase hydraulic conductivities in the upper profile as soil approaches saturation, increasing the contributions of relatively young soil water and possibly current storm-event precipitation to tile-drain discharge. Our second hypothesis is that the observed increase in discharge during storm events does not decrease nitrate concentrations in discharged water, because the storm-event flow paths also transport additional nitrate from the upper soil profile through the tile-drain system. If this hypothesis is correct, during storm events nitrate fluxes should increase, indicating rapid mobilization and potential flushing of soil nutrients through the vadose zone and tile-drain. If nitrate fluxes remain constant during storm events, then decreased tile-drain nitrate concentrations may be caused by the addition of low-nitrate or nitrate-free water. This would suggest that the nitrate leached from the system is present at the depth of the tile-drain and is not transported from near the soil surface to the tile-drain during storm-events, indicating flushing of soil nutrients from the rooting zone is not occurring at these temporal scales

  6. Waste ashes for use in agricultural production: I. Liming effect, contents of plant nutrients and chemical characteristics of some metals.

    PubMed

    Zhang, Fu-Shen; Yamasaki, S; Nanzyo, M

    2002-02-01

    The chemical characteristics of 89 municipal waste ashes, including food scrap ash (FSA), animal waste ash (AWA), horticulture waste ash (HWA), sewage sludge ash (SSA) and incinerator bottom ash (IBA), from various locations in Japan were examined with the aim of evaluating their suitability for use in agriculture. Although the waste ashes came from different sources and consisted of various materials, the gross elemental composition was similar. Acid neutralization capacity (liming effect) for the waste ashes was equivalent to 10-30% of CaO and followed the sequence SSA > IBA > AWA > FSA > HWA. Average P concentrations for the five types of waste ashes ranged from 10 to 29 g kg(-1) and average K concentrations ranged from 14 to 63 g kg(-1), respectively. Metal contents in the waste ashes were compared with levels in Japanese agricultural soils. K in the waste ashes was 1.3-6 times higher and Ca was 3-12 times higher; contents of the other metals in FSA, AWA and HWA were generally less than five times higher, but Ni, Cu, Zn, Cd, Sn, Pb in SSA or IBA were approximately 10-200 times higher than those in soils. Moreover, the ceiling amounts of waste ashes that may be applied to main Japanese agricultural soils were calculated by using soil contamination standards for Cu. Water solubility of P and metals in the waste ashes were also examined. PMID:11846166

  7. The utility of microspheres as surrogates for the transport of E. coli RS2g in partially saturated agricultural soil.

    PubMed

    Passmore, Joanna M; Rudolph, David L; Mesquita, Maria M F; Cey, Edwin E; Emelko, Monica B

    2010-02-01

    Polystyrene latex microspheres are widely used as surrogates for biocolloid transport in porous media; however, relatively few studies directly compare microsphere transport with that of the microorganism it is intended to represent, particularly at the field scale. Here, we compared the transport behaviour of a bacterium (Escherichia coli RS2g; 1.2 microm in diameter) and three different sized microspheres (1.1, 3.9, and 4.8 microm in diameter) within undisturbed agricultural field soil following infiltration under partially saturated conditions. The soil contained significant macroporosity. A tension infiltrometer was used to control the application of a transport solution containing Brilliant Blue FCF dye to two plots. A >2 log reduction in the concentration of all colloids was observed from the soil surface to 5 cm depth in both plots. The concentration of colloids in the soil was generally proportional to the intensity of soil dye staining; however, both the E. coli RS2g bacterium and the 1.1 microm microspheres appeared to be transported deeper than the other colloids and the visible dye along root holes at the bottom of the profile in both plots. The similarities in size and zeta potential of the 1.1 microm microspheres and the E. coli RS2g likely contributed to that outcome. Colloid concentrations in dyed soil by depth were similar between the two plots, despite differences in soil properties and infiltration patterns. The properties of the colloids and macropore density were the most important factors affecting colloid transport. These results suggest that microspheres with size and surface properties similar to the microbe of interest are useful surrogates to trace potential pathways of transport in the subsurface. PMID:19939432

  8. A regional monitoring network to investigate the occurrence of agricultural chemicals in near-surface aquifers of the midcontinental USA

    USGS Publications Warehouse

    Kolpin, D.W.; Goolsby, D.A.

    1995-01-01

    Previous state and national surveys conducted in the mid-continental USA have produced a wide range in results regarding the occurrence of agricultural chemicals in groundwater. At least some of these differences can be attributed to inconsistencies between the surveys, such as different analytical reporting limits. The US Geological Survey has designed a sampling network that is geographically and hydrogeologically representative of near-surface aquifers in the corn- and soybean-producing region of the midcontinental USA. More than 800 water quality samples have been collected from the network since 1991. Six of the seven most frequently detected compounds from this study were herbicide metabolites. A direct relation was determined between tritium content to herbicide and nitrate contamination. The unconsolidated aquifers sampled were found to be more susceptible to herbicide and nitrate contamination than the bedrock aquifers. Knowledge of the regional occurrence and distribution of agricultural chemicals acquired through the study of data collected at network sites will assist policy makers and planners with decisions regarding the protection of drinking-water supplies.

  9. Reactive Transport Modeling Approach and its Initial Saltcake Dilution Chemical Modeling

    SciTech Connect

    Onishi, Yasuo

    2002-11-29

    During waste retrieval, chemical reactions, waste property changes, and waste movements/mixing interact. Thus,to be accurate, a waste process assessment methodology must account for these physical and chemical waste characteristics and mechanisms. This study provides suggestions for column tests and simulation modeling efforts to investigate saltwell pumping of Hanford Tank S-112. In addition, GMIN chemical modeling was initiated for S-112 saltcake dilution with 50% and 100% water as the first step of evaluating the feasibility of the reactive transport code ARIEL as a waste retrieval assessment methodology. The chemical modeling predicted the S-112 saltcake chemistry reasonably well. Although it is too early to conclude the usefulness of this reactive transport modeling approach, it is worth further evaluating its applicability to the waste retrieval process.

  10. Harmonisation of food consumption data format for dietary exposure assessments of chemicals analysed in raw agricultural commodities.

    PubMed

    Boon, Polly E; Ruprich, Jiri; Petersen, Annette; Moussavian, Shahnaz; Debegnach, Francesca; van Klaveren, Jacob D

    2009-12-01

    In this paper, we present an approach to format national food consumption data at raw agricultural commodity (RAC) level. In this way, the data is both formatted in a harmonised way given the comparability of RACs between countries, and suitable to assess the dietary exposure to chemicals analysed in RACs at a European level. In this approach, consumption data needs to be converted to edible part of RAC (e-RAC) level using a RAC conversion database. To subsequently use this data in exposure assessments, both e-RACs and RACs analysed in chemical control programmes should be classified via a uniform system. Furthermore, chemical concentrations in RACs may need to be converted to e-RAC level using processing factors. To illustrate the use of this approach, we describe how the Dutch RAC conversion database was used to convert consumption data of four national consumption surveys to e-RAC level, and the use of the FAO/WHO Codex Classification system of Foods and Animal Feeds to harmonise the classification. We demonstrate that this approach works well for pesticides and glycoalkaloids, and is an essential step forward in the harmonisation of risk assessment procedures within Europe when addressing chemicals analysed in RACs by all national food control systems. PMID:19682531

  11. FATE AND TRANSPORT MODELING OF CONTAMINANTS OF CONCERN FROM A CAFO IN AN AGRICULTURAL WATERSHED

    EPA Science Inventory

    The groundwater flow and transport modeling effort will require hydrogeological site characterization and the development of a conceptual flow model for the site. Site characterization will involve an assessment of both the surface and subsurface and be accomplished through joint...

  12. Model of fecal coliform overland transport from agricultural lands fertilized with animal manure

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Risk assessment of surface water contamination after manure applications requires developing microbial transport models. Application of such models often leads to incorrect conclusions due to lack of calibration with experimental data and ignorance of spatial variability in bacterial concentrations....

  13. Modelling effects of chemical exposure on birds wintering in agricultural landscapes: The western burrowing owl (Athene cunicularia hypugaea) as a case study

    USGS Publications Warehouse

    Engelman, C.A.; Grant, W.E.; Mora, M.A.; Woodin, M.

    2012-01-01

    We describe an ecotoxicological model that simulates the sublethal and lethal effects of chronic, low-level, chemical exposure on birds wintering in agricultural landscapes. Previous models estimating the impact on wildlife of chemicals used in agro-ecosystems typically have not included the variety of pathways, including both dermal and oral, by which individuals are exposed. The present model contains four submodels simulating (1) foraging behavior of individual birds, (2) chemical applications to crops, (3) transfers of chemicals among soil, insects, and small mammals, and (4) transfers of chemicals to birds via ingestion and dermal exposure. We demonstrate use of the model by simulating the impacts of a variety of commonly used herbicides, insecticides, growth regulators, and defoliants on western burrowing owls (Athene cunicularia hypugaea) that winter in agricultural landscapes in southern Texas, United States. The model generated reasonable movement patterns for each chemical through soil, water, insects, and rodents, as well as into the owl via consumption and dermal absorption. Sensitivity analysis suggested model predictions were sensitive to uncertainty associated with estimates of chemical half-lives in birds, soil, and prey, sensitive to parameters associated with estimating dermal exposure, and relatively insensitive to uncertainty associated with details of chemical application procedures (timing of application, amount of drift). Nonetheless, the general trends in chemical accumulations and the relative impacts of the various chemicals were robust to these parameter changes. Simulation results suggested that insecticides posed a greater potential risk to owls of both sublethal and lethal effects than do herbicides, defoliants, and growth regulators under crop scenarios typical of southern Texas, and that use of multiple indicators, or endpoints provided a more accurate assessment of risk due to agricultural chemical exposure. The model should prove

  14. Modelling effects of chemical exposure on birds wintering in agricultural landscapes: The western burrowing owl (Athene cunicularia hypugaea) as a case study

    USGS Publications Warehouse

    Engelman, Catherine A.; Grant, William E.; Mora, Miguel A.; Woodin, Marc

    2012-01-01

    We describe an ecotoxicological model that simulates the sublethal and lethal effects of chronic, low-level, chemical exposure on birds wintering in agricultural landscapes. Previous models estimating the impact on wildlife of chemicals used in agro-ecosystems typically have not included the variety of pathways, including both dermal and oral, by which individuals are exposed. The present model contains four submodels simulating (1) foraging behavior of individual birds, (2) chemical applications to crops, (3) transfers of chemicals among soil, insects, and small mammals, and (4) transfers of chemicals to birds via ingestion and dermal exposure. We demonstrate use of the model by simulating the impacts of a variety of commonly used herbicides, insecticides, growth regulators, and defoliants on western burrowing owls (Athene cunicularia hypugaea) that winter in agricultural landscapes in southern Texas, United States. The model generated reasonable movement patterns for each chemical through soil, water, insects, and rodents, as well as into the owl via consumption and dermal absorption. Sensitivity analysis suggested model predictions were sensitive to uncertainty associated with estimates of chemical half-lives in birds, soil, and prey, sensitive to parameters associated with estimating dermal exposure, and relatively insensitive to uncertainty associated with details of chemical application procedures (timing of application, amount of drift). Nonetheless, the general trends in chemical accumulations and the relative impacts of the various chemicals were robust to these parameter changes. Simulation results suggested that insecticides posed a greater potential risk to owls of both sublethal and lethal effects than do herbicides, defoliants, and growth regulators under crop scenarios typical of southern Texas, and that use of multiple indicators, or endpoints provided a more accurate assessment of risk due to agricultural chemical exposure. The model should prove

  15. Investigating long-range transport of pollution to the Arctic troposphere using aircraft observations and a global chemical transport model

    NASA Astrophysics Data System (ADS)

    Monks, S.; Arnold, S.; Chipperfield, M.; Turquety, S.; Ancellet, G.; Law, K.; Schlager, H.

    2009-04-01

    Surface temperatures in the Arctic have increased more than in any other region over the past few decades. A better understanding of the processes governing this warming, including the role of short-lived greenhouse gases, is therefore urgently required. During summer 2008, the POLARCAT campaign aimed to collect an extensive gas-phase and aerosol dataset within the Arctic troposphere, which will aid the evaluation of our understanding of oxidant photochemistry and aerosol processing in the region. Previous comparisons of global chemical transport models have shown that they exhibit large variability in their Arctic chemical budgets, indicating that the processes controlling Arctic tropospheric composition are not well understood or represented within models. Here, we will use new trace-gas observations from the French ATR and German DLR Falcon aircraft during the POLARCAT experiment to evaluate the ability of a global chemical transport model (TOMCAT) to simulate the summertime transport of pollutants to the Arctic, and their impact on oxidant budgets. In particular, we aim to quantify the impact of anthropogenic and biomass burning sources on the Arctic tropospheric ozone budget. Initial results show that the model underestimates observed concentrations of CO which has led to a re-evaluation of the different sources of CO to the region. Model performance in the Arctic is highly sensitive to the treatment of boreal biomass burning emissions. Boreal biomass burning plumes were sampled frequently over the course of the campaign therefore accurate representation of emission injection heights and fire locations is essential. Model CO is improved with real-time satellite derived daily biomass burning emissions, however large uncertainties in these emissions result in large variability in the Arctic CO budget. We will also present results on the ability of the model to capture pollution transport pathways to the Arctic and contributions to the oxidant and NOy budgets

  16. Plea is made for meeting national objectives for safe maritime transport of hazardous chemicals through a productive partnership

    SciTech Connect

    Hayes, J.B.

    1980-01-01

    A plea is made for meeting national objectives for safe maritime transport of hazardous chemicals through a productive partnership between the chemical industry and the US Government and its agencies, particularly the US Coast Guard.

  17. A micro-mapping strategy to investigate mechanical and chemical mass transport in migmatite

    NASA Astrophysics Data System (ADS)

    Lanari, Pierre; Riel, Nicolas

    2016-04-01

    Migmatites are fantastic objects to study both mechanical and chemical mass transport occurring at mm to cm-scale. However, migmatitic outcrops are the result of complex space and time interactions between (i) melt producing reactions, (ii) melt gain/loss and (iii) retrograde reactions. This succession of events is recorded in the minerals and microstructures of migmatites, and accounts for their apparent complexity. In order to explore the controlling parameters of these chemico-mechanical mass transport, it is thus necessary to characterize in great details the compositional changes between the different migmatitic domains, such as between leucosome and residuum. In this contribution we show how suitable local effective bulk (LEB) compositions can be derived by means of standardized microprobe X-ray images, using the program XMapTools. For chemically heterogeneous samples, such as migmatites, these LEB allow to forward model the stable mineral assemblages for each domain. Those thermodynamic models are used to investigate the conditions of leucosome-residuum separation. The studied sample is a metapelite embedded within a metasedimentary xenolith in the Marcabeli pluton, El Oro Complex, Ecuador. The sample exhibits complex mineral patterns due to local melt redistribution (at mm to cm-scale). Such physical mass transport involves major changes that affect the local chemical composition observed today. At the same time gradients in chemical potential can be established between adjacent domains such as residuum and leucosome, thus triggering chemical interaction. Diffusive transport between domains aims to reduce such chemical potential gradients. Along a modelled P-T path the chemical and mineralogical evolution of micro-domains can be reconstructed for (at least the reactive parts of) the crystallization history.

  18. Long-term monitoring of nitrate-N transport to drainage from three agricultural clayey till fields

    NASA Astrophysics Data System (ADS)

    Ernstsen, V.; Olsen, P.; Rosenbom, A. E.

    2015-01-01

    The application of nitrogen (N) fertilisers to crops grown on tile-drained fields is necessary to sustain most modern crop production, but poses a risk to the aquatic environment since tile drains facilitate rapid transport pathways with no significant reduction in nitrate. To maintain the water quality of the aquatic environment and the provision of food from highly efficient agriculture in line with the EU's Water Framework Directive and Nitrates Directive, field-scale knowledge is imperative if there is to be differentiated N-regulation in future. This study describes nitrate-N leaching to drainage based on coherent monitoring of nitrate-N concentrations, the climate, the groundwater table and crop-specific parameters obtained over eleven years (2001-2011) at three subsurface-drained clayey till fields (1.3-2.3 ha). The monitoring results showed significant field differences in nitrate-N transport to drainage. Not only were these caused by periods of bare soil after short-season crops and N-fixing crops (pea), which have been shown to generate high nitrate-N concentrations in drainage, but by the hydrogeological field conditions that were shown to be the controlling factor of nitrate-N transport to drainage. The fields had the following characteristics: (A) the lowest mass transport (13 kg N ha-1) and fertiliser input had short-term and low-intensity drainage with the highest nitrate-N concentrations detected, representing 40% of net precipitation (226 mm) combined with low air temperatures, (B) the medium mass transport (14 kg N ha-1) had medium-term and medium-intensity drainage, representing 42% of net precipitation (471 mm) combined with periods of both low and higher air temperatures, (C) the highest mass transport (19 kg N ha-1) had long-term drainage, representing 68% of net precipitation (617 mm), but had the highest potential for in-situ soil denitrification and post-treatment (e.g. constructed wetlands) due to long periods with both high water

  19. Effects of “Aging” on Bioreactive Chemical Retention, Transformation, and Transport in Soil.

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The purpose of this paper is to illustrate how aging can affect the behavior of bioreactive chemicals in the soil. This paper will focus on the sorption process, which can directly or indirectly control transformation and transport processes. Most commonly, aging effects have been characterized by b...

  20. Computer program for calculation of thermodynamic and transport properties of complex chemical systems

    NASA Technical Reports Server (NTRS)

    Svehla, R. A.; Mcbride, B. J.

    1973-01-01

    Program performs calculations such as chemical equilibrium for assigned thermodynamic states, theoretical rocket performance for both equilibrium and frozen compositions during expansion, incident and reflected shock properties, and Chapman-Jouget detonation properties. Features include simplicity of input and storage of all thermodynamic and transport property data on master tape.

  1. Effects of “aging” on bioreactive chemical retention, transformation, and transport in soil

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The purpose of this paper is to illustrate how aging can affect the behavior of bioreactive chemicals in the soil. This paper will focus on the sorption process, which can directly or indirectly control transformation and transport processes. Most commonly, aging effects have been characterized by b...

  2. MATHEMATICAL MODEL FOR THE TRANSPORT AND FATE OF ORGANIC CHEMICALS IN UNSATURATED/SATURATED SOILS

    EPA Science Inventory

    A mathematical model, simulating the transport and fate of nonionizable organic compounds in unsaturated/saturated porous media (soils) in a terrestrial microcosm has been developed. Using the principles of water mass, momentum, heat energy and chemical mass balance, the three fi...

  3. Enhancing the design of in situ chemical barriers with multicomponent reactive transport modeling

    SciTech Connect

    Sevougian, S.D.; Steefel, C.I.; Yabusaki, S.B.

    1994-11-01

    This paper addresses the need for systematic control of field-scale performance in the emplacement and operation of in situ chemical treatment barriers; in particular, it addresses the issue of how the local coupling of reaction kinetics and material heterogeneities at the laboratory or bench scale can be accurately upscaled to the field. The authors have recently developed modeling analysis tools that can explicitly account for all relevant chemical reactions that accompany the transport of reagents and contaminants through a chemically and physically heterogeneous subsurface rock or soil matrix. These tools are incorporated into an enhanced design methodology for in situ chemical treatment technologies, and the new methodology is demonstrated in the ongoing design of a field experiment for the In Situ Redox Manipulation (ISRM) project at the U.S. Department of Energy (DOE) Hanford Site. The ISRM design approach, which systematically integrates bench-scale and site characterization information, provides an ideal test for the new reactive transport techniques. The need for the enhanced chemistry capability is demonstrated by an example that shows how intra-aqueous redox kinetics can affect the transport of reactive solutes. Simulations are carried out on massively parallel computer architectures to resolve the influence of multiscale heterogeneities on multicomponent, multidimensional reactive transport. The technology will soon be available to design larger-scale remediation schemes.

  4. Computational insights of water droplet transport on graphene sheet with chemical density

    NASA Astrophysics Data System (ADS)

    Zhang, Liuyang; Wang, Xianqiao

    2014-05-01

    Surface gradient has been emerging as an intriguing technique for nanoscale particle manipulation and transportation. Owing to its outstanding and stable chemical properties, graphene with covalently bonded chemical groups represents extraordinary potential for the investigation of nanoscale transport in the area of physics and biology. Here, we employ molecular dynamics simulations to investigate the fundamental mechanism of utilizing a chemical density on a graphene sheet to control water droplet motions on it. Simulation results have demonstrated that the binding energy difference among distinct segment of graphene in terms of interaction between the covalently bonded oxygen atoms on graphene and the water molecules provides a fundamental driving force to transport the water droplet across the graphene sheet. Also, the velocity of the water droplet has showed a strong dependence on the relative concentration of oxygen atoms between successive segments. Furthermore, a multi-direction channel provides insights to guide the transportation of objects towards a targeted position, separating the mixtures with a system of specific chemical functionalization. Our findings shed illuminating lights on the surface gradient method and therefore provide a feasible way to control nanoscale motion on the surface and mimic the channelless microfluidics.

  5. Computational insights of water droplet transport on graphene sheet with chemical density

    SciTech Connect

    Zhang, Liuyang; Wang, Xianqiao

    2014-05-21

    Surface gradient has been emerging as an intriguing technique for nanoscale particle manipulation and transportation. Owing to its outstanding and stable chemical properties, graphene with covalently bonded chemical groups represents extraordinary potential for the investigation of nanoscale transport in the area of physics and biology. Here, we employ molecular dynamics simulations to investigate the fundamental mechanism of utilizing a chemical density on a graphene sheet to control water droplet motions on it. Simulation results have demonstrated that the binding energy difference among distinct segment of graphene in terms of interaction between the covalently bonded oxygen atoms on graphene and the water molecules provides a fundamental driving force to transport the water droplet across the graphene sheet. Also, the velocity of the water droplet has showed a strong dependence on the relative concentration of oxygen atoms between successive segments. Furthermore, a multi-direction channel provides insights to guide the transportation of objects towards a targeted position, separating the mixtures with a system of specific chemical functionalization. Our findings shed illuminating lights on the surface gradient method and therefore provide a feasible way to control nanoscale motion on the surface and mimic the channelless microfluidics.

  6. ORGANIC COSOLVENT EFFECTS ON THE SORPTION AND TRANSPORT OF NEUTRAL ORGANIC CHEMICALS

    EPA Science Inventory

    Soil column miscible displacement techniques were used to investigate the effects of an organic cosolvent (methanol) on the sorption and transport of three neutral organic chemicals; naphthalene, phenanthrene, and the herbicide diuron, through a sandy surface soil. A two-domain, ...

  7. Modeling non-isothermal multiphase multi-species reactive chemical transport in geologic media

    SciTech Connect

    Tianfu Xu; Gerard, F.; Pruess, K.; Brimhall, G.

    1997-07-01

    The assessment of mineral deposits, the analysis of hydrothermal convection systems, the performance of radioactive, urban and industrial waste disposal, the study of groundwater pollution, and the understanding of natural groundwater quality patterns all require modeling tools that can consider both the transport of dissolved species as well as their interactions with solid (or other) phases in geologic media and engineered barriers. Here, a general multi-species reactive transport formulation has been developed, which is applicable to homogeneous and/or heterogeneous reactions that can proceed either subject to local equilibrium conditions or kinetic rates under non-isothermal multiphase flow conditions. Two numerical solution methods, the direct substitution approach (DSA) and sequential iteration approach (SIA) for solving the coupled complex subsurface thermo-physical-chemical processes, are described. An efficient sequential iteration approach, which solves transport of solutes and chemical reactions sequentially and iteratively, is proposed for the current reactive chemical transport computer code development. The coupled flow (water, vapor, air and heat) and solute transport equations are also solved sequentially. The existing multiphase flow code TOUGH2 and geochemical code EQ3/6 are used to implement this SIA. The flow chart of the coupled code TOUGH2-EQ3/6, required modifications of the existing codes and additional subroutines needed are presented.

  8. Physical and chemical characterization of biochars derived from different agricultural residues

    NASA Astrophysics Data System (ADS)

    Jindo, K.; Mizumoto, H.; Sawada, Y.; Sanchez-Monedero, M. A.; Sonoki, T.

    2014-12-01

    Biochar is widely recognized as an efficient tool for carbon sequestration and soil fertility. The understanding of its chemical and physical properties, which are strongly related to the type of the initial material used and pyrolysis conditions, is crucial to identify the most suitable application of biochar in soil. A selection of organic wastes with different characteristics (e.g., rice husk (RH), rice straw (RS), wood chips of apple tree (Malus pumila) (AB), and oak tree (Quercus serrata) (OB)) were pyrolyzed at different temperatures (400, 500, 600, 700, and 800 °C) in order to optimize the physicochemical properties of biochar as a soil amendment. Low-temperature pyrolysis produced high biochar yields; in contrast, high-temperature pyrolysis led to biochars with a high C content, large surface area, and high adsorption characteristics. Biochar obtained at 600 °C leads to a high recalcitrant character, whereas that obtained at 400 °C retains volatile and easily labile compounds. The biochar obtained from rice materials (RH and RS) showed a high yield and unique chemical properties because of the incorporation of silica elements into its chemical structure. The biochar obtained from wood materials (AB and OB) showed high carbon content and a high absorption character.

  9. From agricultural intensification to conservation: Sediment transport in the Raccoon River, Iowa, 1916-2009

    USGS Publications Warehouse

    Jones, C.S.; Schilling, K.E.

    2011-01-01

    Fluvial sediment is a ubiquitous pollutant that negatively aff ects surface water quality and municipal water supply treatment. As part of its routine water supply monitoring, the Des Moines Water Works (DMWW) has been measuring turbidity daily in the Raccoon River since 1916. For this study, we calibrated daily turbidity readings to modern total suspended solid (TSS) concentrations to develop an estimation of daily sediment concentrations in the river from 1916 to 2009. Our objectives were to evaluate longterm TSS patterns and trends, and relate these to changes in climate, land use, and agricultural practices that occurred during the 93-yr monitoring period. Results showed that while TSS concentrations and estimated sediment loads varied greatly from year to year, TSS concentrations were much greater in the early 20th century despite drier conditions and less discharge, and declined throughout the century. Against a backdrop of increasing discharge in the Raccoon River and widespread agricultural adaptations by farmers, sediment loads increased and peaked in the early 1970s, and then have slowly declined or remained steady throughout the 1980s to present. With annual sediment load concentrated during extreme events in the spring and early summer, continued sediment reductions in the Raccoon River watershed should be focused on conservation practices to reduce rainfall impacts and sediment mobilization. Overall, results from this study suggest that eff orts to reduce sediment load from the watershed appear to be working. ?? 2011 by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America.

  10. Coupling of hydrologic transport and chemical reactions in a stream affected by acid mine drainage

    USGS Publications Warehouse

    Kimball, B.A.; Broshears, R.E.; Bencala, K.E.; McKnight, Diane M.

    1994-01-01

    Experiments in St. Kevin Gulch, an acid mine drainage stream, examined the coupling of hydrologic transport to chemical reactions affecting metal concentrations. Injection of LiCl as a conservative tracer was used to determine discharge and residence time along a 1497-m reach. Transport of metals downstream from inflows of acidic, metal-rich water was evaluated based on synoptic samples of metal concentrations and the hydrologic characteristics of the stream. Transport of SO4 and Mn was generally conservative, but in the subreaches most affected by acidic inflows, transport was reactive. Both 0.1-??m filtered and particulate Fe were reactive over most of the stream reach. Filtered Al partitioned to the particulate phase in response to high instream concentrations. Simulations that accounted for the removal of SO4, Mn, Fe, and Al with first-order reactions reproduced the steady-state profiles. The calculated rate constants for net removal used in the simulations embody several processes that occur on a stream-reach scale. The comparison between rates of hydrologie transport and chemical reactions indicates that reactions are only important over short distances in the stream near the acidic inflows, where reactions occur on a comparable time scale with hydrologic transport and thus affect metal concentrations.

  11. A high-throughput screen for chemical inhibitors of exocytic transport in yeast

    PubMed Central

    Zhang, Lisha; Nebane, N. Miranda; Wennerberg, Krister; Li, Yujie; Neubauer, Valerie; Hobrath, Judith V.; McKellip, Sara; Rasmussen, Lynn; Shindo, Nice; Sosa, Melinda; Maddry, Joseph A.; Ananthan, Subramaniam; Piazza, Gary A.; White, E. Lucile; Harsay, Edina

    2010-01-01

    Most of the components of the membrane and protein traffic machinery were discovered by perturbing their functions, either with bioactive compounds or by mutations. However, the mechanisms responsible for exocytic transport vesicle formation at the Golgi and endosomes are still largely unknown. Both the exocytic traffic routes and the signaling pathways that regulate these routes are highly complex and robust, so that defects can be overcome by alternate pathways or mechanisms. A classical yeast genetic screen designed to account for the robustness of the exocytic pathway identified a novel conserved gene, AVL9, that functions in late exocytic transport. We now describe a chemical-genetic version of the mutant screen, in which we performed a high-throughput phenotypic screen of a large compound library and identified novel small molecule secretory inhibitors. In order to maximize the number and diversity of our hits, the screen was performed in a pdr5Δ snq2Δ mutant background, which lacks two transporters responsible for pleiotropic drug resistance. However, we found that deletion of both transporters reduced the fitness of our screen strain, whereas the pdr5Δ mutation had relatively small effect on growth and was also the more important transporter mutation for conferring sensitivity to our hits. In this and similar chemical-genetic yeast screens, using just a single pump mutation may be sufficient for increasing hit diversity while minimizing the physiological effects of transporter mutations. PMID:20461743

  12. Effect of variable annual precipitation and nutrient input on nitrogen and phosphorus transport from two Midwestern agricultural watersheds

    USGS Publications Warehouse

    Kalkhoff, Stephen J.; Hubbard, Laura E.; Tomer, Mark D.; James, D.E.

    2016-01-01

    Precipitation patterns and nutrient inputs affect transport of nitrate (NO3-N) and phosphorus (TP) from Midwest watersheds. Nutrient concentrations and yields from two subsurface-drained watersheds, the Little Cobb River (LCR) in southern Minnesota and the South Fork Iowa River (SFIR) in northern Iowa, were evaluated during 1996–2007 to document relative differences in timings and amounts of nutrients transported. Both watersheds are located in the prairie pothole region, but the SFIR exhibits a longer growing season and more livestock production. The SFIR yielded significantly more NO3-N than the LCR watershed (31.2 versus 21.3 kg NO3-N ha− 1 y− 1). The SFIR watershed also yielded more TP than the LCR watershed (1.13 versus 0.51 kg TP ha− 1 yr− 1), despite greater TP concentrations in the LCR. About 65% of NO3-N and 50% of TP loads were transported during April–June, and < 20% of the annual loads were transported later in the growing season from July–September. Monthly NO3-N and TP loads peaked in April from the LCR but peaked in June from the SFIR; this difference was attributed to greater snowmelt runoff in the LCR. The annual NO3-N yield increased with increasing annual runoff at a similar rate in both watersheds, but the LCR watershed yielded less annual NO3-N than the SFIR for a similar annual runoff. These two watersheds are within 150 km of one another and have similar dominant agricultural systems, but differences in climate and cropping inputs affected amounts and timing of nutrient transport.

  13. Effect of variable annual precipitation and nutrient input on nitrogen and phosphorus transport from two Midwestern agricultural watersheds.

    PubMed

    Kalkhoff, S J; Hubbard, L E; Tomer, M D; James, D E

    2016-07-15

    Precipitation patterns and nutrient inputs affect transport of nitrate (NO3-N) and phosphorus (TP) from Midwest watersheds. Nutrient concentrations and yields from two subsurface-drained watersheds, the Little Cobb River (LCR) in southern Minnesota and the South Fork Iowa River (SFIR) in northern Iowa, were evaluated during 1996-2007 to document relative differences in timings and amounts of nutrients transported. Both watersheds are located in the prairie pothole region, but the SFIR exhibits a longer growing season and more livestock production. The SFIR yielded significantly more NO3-N than the LCR watershed (31.2 versus 21.3kgNO3-Nha(-1)y(-1)). The SFIR watershed also yielded more TP than the LCR watershed (1.13 versus 0.51kgTPha(-1)yr(-1)), despite greater TP concentrations in the LCR. About 65% of NO3-N and 50% of TP loads were transported during April-June, and <20% of the annual loads were transported later in the growing season from July-September. Monthly NO3-N and TP loads peaked in April from the LCR but peaked in June from the SFIR; this difference was attributed to greater snowmelt runoff in the LCR. The annual NO3-N yield increased with increasing annual runoff at a similar rate in both watersheds, but the LCR watershed yielded less annual NO3-N than the SFIR for a similar annual runoff. These two watersheds are within 150 km of one another and have similar dominant agricultural systems, but differences in climate and cropping inputs affected amounts and timing of nutrient transport. PMID:27054493

  14. Assessment of hydrology, suspended sediment and particulate organic carbon transport in a large agricultural catchment using SWAT model

    NASA Astrophysics Data System (ADS)

    Chantha, Oeurng; Sabine, Sauvage; José-Miguel, Sánchez-Pérez

    2010-05-01

    Suspended sediment transport from agricultural catchments to stream networks is responsible for aquatic habitat degradation, reservoir sedimentation and the transport of sediment-bound pollutants (pesticides, particulate nutrients, heavy metals and other toxic substances). Quantifying and understanding the dynamics of suspended sediment transfer from agricultural land to watercourses is essential in controlling soil erosion and in implementing appropriate mitigation practices to reduce stream suspended sediment and associated pollutant loads, and hence improve surface water quality downstream. Gascogne area, southwest France, has been dominated by anthropogenic activities particularly intensive agriculture causing severe erosion in recent decades. This leads to a major threat to surface water quality due to soil erosion. Therefore, the catchment water quality has been continuously monitored since January 2007 and the historical data of hydrology and suspended sediment has existed since 1998. In this study, the Soil and Water Assessment Tool (SWAT 2005) was applied to assess hydrology, suspended sediment and particulate organic carbon in this catchment Agricultural management practices (crop rotation, planting date, fertilizer quantity and irrigations) were taken into the model for simulation period of 11 years (July, 1998 to March, 2009). The investigation was conducted using a 11-year streamflow and two years of suspended sediment record from January 2007 to March 2009. Modelling strategy with dominant landuse and soil type was chosen in this study. The SWAT generally performs satisfactorily and could simulate both daily and monthly runoff and sediment yield. The simulated daily and monthly runoff matched the observed values satisfactorily (ENash>0.5). For suspended sediment simulation, the simulated values were compared with the observed continuous suspended sediment derived from turbidity data. Based on the relationship between SSC and POC (R2 = 0.93), POC was

  15. Agricultural chemicals in Iowa's ground water, 1982-95: What are the trends?

    USGS Publications Warehouse

    Koplin, Dana W.; Hallberg, George; Sneck-Fahrer, D. A.; Libra, Robert

    1997-01-01

    The Iowa Department of Natural Resources. Geological Survey Bureau: the University of Iowa Hygienic Laboratory; and the U.S. Geological Survey (USGS) have been working together to address this question. As part of the Iowa Ground-Water Monitoring Program (IGWM). water samples have been collected from selected Iowa municipal wells since 1982. An examination of this data identified two trends: (1) concentrations of atrazine in Iowa's ground water generally were decreasing over time, and (2) concentrations of metolachlor generally were increasing. Continuing ground-water sampling can determine if these trends represent long-term changes in chemical concentrations.

  16. Solute transport dynamics in small, shallow groundwater-dominated agricultural catchments: insights from a high-frequency, multisolute 10 yr-long monitoring study

    NASA Astrophysics Data System (ADS)

    Aubert, A. H.; Gascuel-Odoux, C.; Gruau, G.; Akkal, N.; Faucheux, M.; Fauvel, Y.; Grimaldi, C.; Hamon, Y.; Jaffrézic, A.; Lecoz-Boutnik, M.; Molénat, J.; Petitjean, P.; Ruiz, L.; Merot, P.

    2013-04-01

    High-frequency, long-term and multisolute measurements are required to assess the impact of human pressures on water quality due to (i) the high temporal and spatial variability of climate and human activity and (ii) the fact that chemical solutes combine short- and long-term dynamics. Such data series are scarce. This study, based on an original and unpublished time series from the Kervidy-Naizin headwater catchment (Brittany, France), aims to determine solute transfer processes and dynamics that characterise this strongly human-impacted catchment. The Kervidy-Naizin catchment is a temperate, intensive agricultural catchment, hydrologically controlled by shallow groundwater. Over 10 yr, five solutes (nitrate, sulphate, chloride, and dissolved organic and inorganic carbon) were monitored daily at the catchment outlet and roughly every four months in the shallow groundwater. The concentrations of all five solutes showed seasonal variations but the patterns of the variations differed from one solute to another. Nitrate and chloride exhibit rather smooth variations. In contrast, sulphate as well as organic and inorganic carbon is dominated by flood flushes. The observed nitrate and chloride patterns are typical of an intensive agricultural catchment hydrologically controlled by shallow groundwater. Nitrate and chloride originating mainly from organic fertilisers accumulated over several years in the shallow groundwater. They are seasonally exported when upland groundwater connects with the stream during the wet season. Conversely, sulphate as well as organic and inorganic carbon patterns are not specific to agricultural catchments. These solutes do not come from fertilisers and do not accumulate in soil or shallow groundwater; instead, they are biogeochemically produced in the catchment. The results allowed development of a generic classification system based on the specific temporal patterns and source locations of each solute. It also considers the stocking period

  17. Methane in groundwater used for Japanese agriculture: Its relationship to other physico-chemical properties and possible tropospheric source strength

    NASA Astrophysics Data System (ADS)

    Watanabe, A.; Kimura, M.; Kasuya, M.; Kotake, M.; Katoh, T.

    1994-01-01

    The concentration of CH4 in 131 groundwater samples used for agriculture in Aichi Prefecture, central Japan, averaged 1.58 mgC l-1 for those water samples above detection (>0.006 mgC l-1), with the highest value of 18.4 mgC l-1. Methane was detected in more than half of the groundwater samples. The amount of CH4 released to the atmosphere because of agricultural groundwater use was estimated to be 2.00 × 107 gC yr-1 for a cultivated area of 8.61 × 104 ha, or about 1.4% of the CH4 production in paddy fields derived from soil organic matter in the same geographic area. Distribution of measurements of redox potential (Eh), chemical oxygen demand (COD), Fe, Mn, NH4-N, and NO3-N was clearly different between the CH4-detected and undetected samples; Eh values and NO3-N concentrations were lower while the other four factors were higher in the CH4-detected samples.

  18. 3D numerical simulation of the transport of chemical signature compounds from buried landmines

    NASA Astrophysics Data System (ADS)

    Irrazabal, Maik; Borrero, Ernesto; Briano, Julio G.; Castro, Miguel; Hernandez, Samuel P.

    2005-06-01

    The transport of the chemical signature compounds from buried landmines in a three-dimensional (3D) array has been numerically modeled using the finite-volume technique. Compounds such as trinitrotoluene, dinitrotoluene, and their degradation products, are semi volatile and somewhat soluble in water. Furthermore, they can strongly adsorb to the soil and undergo chemical and biological degradation. Consequently, the spatial and temporal concentration distributions of such chemicals depend on the mobility of the water and gaseous phases, their molecular and mechanical diffusion, adsorption characteristics, soil water content, compaction, and environmental factors. A 3D framework is required since two-dimensional (2D) symmetry may easily fade due to terrain topography: non-flat surfaces, soil heterogeneity, or underground fractures. The spatial and temporal distribution of the chemical-signature-compounds, in an inclined grid has been obtained. The fact that the chemicals may migrate horizontally, giving higher surface concentrations at positions not directly on top of the objects, emphasizes the need for understanding the transport mechanism when a chemical detector is used. Deformation in the concentration contours after rainfall is observed in the inclined surface and is attributed to both: the advective flux, and to the water flux at the surface caused by the slope. The analysis of the displacements in the position of the maximum concentrations at the surface, respect to the actual location of the mine, in an inclined system, is presented.

  19. Chemical and biological characterization of products of incomplete combustion from the simulated field burning of agricultural plastic

    SciTech Connect

    Linak, W.P.; Ryan, J.V.; Perry, E.; Williams, R.W.; DeMarini, D.M.

    1989-06-01

    Chemical and biological analyses were performed to characterize products of incomplete combustion emitted during the simulated open field burning of agricultural plastic. A small utility shed equipped with an air delivery system was used to simulate pile burning and forced-air-curtain incineration of a nonhalogenated agricultural plastic that reportedly consisted of polyethylene and carbon black. Emissions were analyzed for combustion gases; volatile, semi-volatile, and particulate organics; and toxic and mutagenic properties. Emission samples, as well as samples of the used (possibly pesticide-contaminated) plastic, were analyzed for the presence of several pesticides to which the plastic may have been exposed. Although a variety of alkanes, alkenes, and aromatic and polycyclic aromatic hydrocarbon (PAH) compounds were identified in the volatile, semi-volatile, and particulate fractions of these emissions, a substantial fraction of higher molecular weight organic material was not identified. No pesticides were identified in either combustion emission samples or dichloromethane washes of the used plastic. When mutagenicity was evaluated by exposing Salmonella bacteria (Ames assay) to whole vapor and vapor/particulate emissions, no toxic or mutagenic effects were observed. However, organic extracts of the particulate samples were moderately mutagenic. This mutagenicity compares approximately to that measured from residential wood heating on a revertant per unit heat release basis. Compared to pile burning, forced air slightly decreased the time necessary to burn a charge of plastic. There was not a substantial difference, however, in the variety or concentrations of organic compounds identified in samples from these two burn conditions. This study highlights the benefits of a combined chemical/biological approach to the characterization of complex, multi-component combustion emissions.

  20. Investigation of Soil Erosion and Phosphorus Transport within an Agricultural Watershed

    NASA Astrophysics Data System (ADS)

    Klik, A.; Jester, W.; Muhar, A.; Peinsitt, A.; Rampazzo, N.; Mentler, A.; Staudinger, B.; Eder, M.

    2003-04-01

    In a 40 ha agricultural used watershed in Austria, surface runoff, soil erosion and nutrient losses are measured spatially distributed with 12 small erosion plots. Crops during growing season 2002 are canola, corn, sunflower, winter wheat, winter barley, rye, sugar beets, and pasture. Canopy height and canopy cover are observed in 14-day intervals. Four times per year soil water content, shear stress and random roughness of the surface are measured in a 25 x 25 m grid (140 points). The same raster is sampled for soil texture analyses and content of different phosphorus fractions in the 0-10 cm soil depth. Spatially distributed data are used for geostatistical analysis. Along three transects hydrologic conditions of the hillslope position (top, middle, foot) are investigated by measuring soil water content and soil matrix potential. After erosive events erosion features (rills, deposition, ...) are mapped using GPS. All measured data will be used as input parameters for the Limburg Soil Erosion Model (LISEM).

  1. Electrical resistivity tomography as monitoring tool for unsaturated zone transport: an example of preferential transport of deicing chemicals.

    PubMed

    Wehrer, Markus; Lissner, Heidi; Bloem, Esther; French, Helen; Totsche, Kai Uwe

    2014-01-01

    Non-invasive spatially resolved monitoring techniques may hold the key to observe heterogeneous flow and transport behavior of contaminants in soils. In this study, time-lapse electrical resistivity tomography (ERT) was employed during an infiltration experiment with deicing chemical in a small field lysimeter. Deicing chemicals like potassium formate, which frequently impact soils on airport sites, were infiltrated during snow melt. Chemical composition of seepage water and the electrical response was recorded over the spring period 2010. Time-lapse electrical resistivity tomographs are able to show the infiltration of the melt water loaded with ionic constituents of deicing chemicals and their degradation product hydrogen carbonate. The tomographs indicate early breakthrough behavior in parts of the profile. Groundtruthing with pore fluid conductivity and water content variations shows disagreement between expected and observed bulk conductivity. This was attributed to the different sampling volume of traditional methods and ERT due to a considerable fraction of immobile water in the soil. The results show that ERT can be used as a soil monitoring tool on airport sites if assisted by common soil monitoring techniques. PMID:24194415

  2. Metolachlor metabolite (MESA) reveals agricultural nitrate-N fate and transport in Choptank River watershed

    USGS Publications Warehouse

    McCarty, Gregory W.; Hapeman, Cathleen J.; Rice, Clifford P.; Hively, W. Dean; McConnell, Laura L.; Sadeghi, Ali M.; Lang, Megan W.; Whitall, David R.; Bialek, Krystyna; Downey, Peter

    2014-01-01

    Over 50% of streams in the Chesapeake Bay watershed have been rated as poor or very poor based on the index of biological integrity. The Choptank River estuary, a Bay tributary on the eastern shore, is one such waterway, where corn and soybean production in upland areas of the watershed contribute significant loads of nutrients and sediment to streams. We adopted a novel approach utilizing the relationship between the concentration of nitrate-N and the stable, water-soluble herbicide degradation product MESA {2-[2-ethyl-N-(1-methoxypropan-2-yl)-6-methylanilino]-2-oxoethanesulfonic acid} to distinguish between dilution and denitrification effects on the stream concentration of nitrate-N in agricultural subwatersheds. The ratio of mean nitrate-N concentration/(mean MESA concentration * 1000) for 15 subwatersheds was examined as a function of percent cropland on hydric soil. This inverse relationship (R2 = 0.65, p 2 ≤ 0.99) for all eight sampling dates except one where R2 = 0.90. This very strong correlation indicates that nitrate-N was conserved in much of the Choptank River estuary, that dilution alone is responsible for the changes in nitrate-N and MESA concentrations, and more importantly nitrate-N loads are not reduced in the estuary prior to entering the Chesapeake Bay. Thus, a critical need exists to minimize nutrient export from agricultural production fields and to identify specific conservation practices to address the hydrologic conditions within each subwatershed. In well drained areas, removal of residual N within the cropland is most critical, and practices such as cover crops which sequester the residual N should be strongly encouraged. In poorly drained areas where denitrification can occur, wetland restoration and controlled drained structures that minimize ditch flow should be used to maximize denitrification.

  3. Chemodynamics: transport and behavior of chemicals in the environment--a problem in environmental health.

    PubMed Central

    Freed, V H; Chiou, C T; Haque, R

    1977-01-01

    In the manufacture and use of the several thousand chemicals employed by technological societies, portions of these chemicals escape or are intentionally introduced into the environment. The behavior, fate, and to some extent the effects produced by these chemicals are a result of a complex interaction of the properties of the chemical with the various processes governing transport, degradation, sequestration, and uptake by organisms. In addition, such processes as adsorption, evaporation, partitioning, and degradation are influenced by ambient conditions of temperature, air movement, moisture, presence of other chemicals, and the concentration and properties of the subject chemicals. These influence the level and extent of exposure to these chemicals that man might receive. Study of the physiochemical properties and extent of exposure to these chem;cals that man might receive. Study of the physiochemical properties of compounds in relation to these various processes has provided a basis for better understanding of the quantitative behavior. Such information is useful in development of predictive models on behavior and fate of the chemicals in relation to human exposure. Beyond this, it provides information that could be used to devise procedures of manufacture, use, and disposal that would minimize environmental contamination. Some of the physical principles involved in chemodynamics are presented in this review. PMID:598352

  4. Nesting biology of laughing gulls in relation to agricultural chemicals in south Texas, 1978-81

    USGS Publications Warehouse

    White, D.H.; Mitchell, C.A.; Prouty, R.M.

    1983-01-01

    Laughing Gulls (Larus atricilla) were studied along the south Texas coast during 1978-1981 to determine productivity and to evaluate the effects of environmental pollutants on reproduction. The average clutch-size was 2.6, ranging from 2.3-2.8. Sixty-six percent of the eggs hatched and 82% of the pairs hatched at least one egg. Productivity (fledglings/total nests) averaged 1.0 fledgling per nest. DDE and other organochlorine residues were low in eggs (usually <3 ppm wet weight) and were not suspected of causing reproductive problems. However, organophosphate pesticides sprayed on crops near the study areas reduced productivity by as much as 33% during 3 of 4 years, implying that certain of these chemicals may pose serious threats to the population.

  5. Efficient chemical equilibrium calculations for geochemical speciation and reactive transport modelling

    NASA Astrophysics Data System (ADS)

    Leal, Allan M. M.; Blunt, Martin J.; LaForce, Tara C.

    2014-04-01

    Chemical equilibrium calculations are essential for many environmental problems. It is also a fundamental tool for chemical kinetics and reactive transport modelling, since these applications may require hundreds to billions equilibrium calculations in a single simulation. Therefore, an equilibrium method for such critical applications must be very efficient, robust and accurate. In this work we demonstrate the potential effectiveness of a novel Gibbs energy minimisation algorithm for reactive transport simulations. The algorithm includes strategies to converge from poor initial guesses; capabilities to specify non-linear equilibrium constraints such as pH of an aqueous solution and activity or fugacity of a species; a rigorous phase stability test to determine the unstable phases; and a strategy to boost the convergence speed of the calculations to quadratic rates, requiring only few iterations to converge. We use this equilibrium method to solve geochemical problems relevant to carbon storage in saline aquifers, where aqueous, gaseous and minerals phases are present. The problems are formulated to mimic the ones found in kinetics and transport simulations, where a sequence of equilibrium calculations are performed, each one using the previous solution as the initial guess. The efficiency and convergence rates of the calculations are presented, which require an average of 1-2 iterations. These results indicate that critical applications such as chemical kinetics and reactive transport modelling can potentially benefit by using this multiphase equilibrium algorithm.

  6. New Potentiometric Wireless Chloride Sensors Provide High Resolution Information on Chemical Transport Processes in Streams

    NASA Astrophysics Data System (ADS)

    Smettem, Keith; Harris, Nick; Cranny, Andy; Klaus, Julian; Pfister, Laurent

    2016-04-01

    Quantifying the travel times, pathways and dispersion of solutes moving through stream environments is critical for understanding the biogeochemical cycling processes that control ecosystem functioning. Validation of stream solute transport and exchange process models requires data obtained from in-stream measurement of chemical concentration changes through time. This can be expensive and time consuming, leading to a need for cheap distributed sensor arrays that respond instantly and record chemical transport at points of interest on timescales of seconds. To meet this need we apply new, low-cost (in the order of a euro per sensor) potentiometric chloride sensors used in a distributed array to obtain data with high spatial and temporal resolution. The application here is to monitoring in-stream hydrodynamic transport and dispersive mixing of an injected chemical, in this case NaCl. We present data obtained from the distributed sensor array under baseflow conditions for three stream reaches in Luxembourg. Sensor results are comparable to data obtained from more expensive electrical conductivity meters and allow spatial resolution of hydrodynamic mixing processes and identification of chemical 'dead zones' in the study reaches.

  7. Atmospheric emissions and long-range transport of persistent organic chemicals

    NASA Astrophysics Data System (ADS)

    Scheringer, M.

    2010-12-01

    Persistent organic chemicals include several groups of halogenated compounds, such as polychlorinated biphenyls (PCBs), polybrominated diphenylethers (PBDEs), and polyfluorinated carboxylic acids (PFCAs). These chemicals remain for long times (years to decades) in the environment and cycle between different media (air, water, sediment, soil, vegetation, etc.). The environmental distribution of this type of chemicals can conveniently be analyzed by multimedia models. Multimedia models consist of a set of coupled mass balance equations for the environmental media considered; they can be set up at various scales from local to global. Two applications of multimedia models to airborne chemicals are discussed in detail: the day-night cycle of PCBs measured in air near the surface, and the atmospheric long-range transport of volatile precursors of PFCAs, formation of PFCAs by oxidation of these precursors, and subsequent deposition of PFCAs to the surface in remote regions such as the Arctic.

  8. Effects of chemical oxidants on perfluoroalkyl acid transport in one-dimensional porous media columns.

    PubMed

    McKenzie, Erica R; Siegrist, Robert L; McCray, John E; Higgins, Christopher P

    2015-02-01

    In situ chemical oxidation (ISCO) is a remediation approach that is often used to remediate soil and groundwater contaminated with fuels and chlorinated solvents. At many aqueous film-forming foam-impacted sites, perfluoroalkyl acids (PFAAs) can also be present at concentrations warranting concern. Laboratory experiments were completed using flow-through one-dimensional columns to improve our understanding of how ISCO (i.e., activated persulfate, permanganate, or catalyzed hydrogen peroxide) could affect the fate and transport of PFAAs in saturated porous media. While the resultant data suggest that standard ISCO is not a viable remediation strategy for PFAA decomposition, substantial changes in PFAA transport were observed upon and following the application of ISCO. In general, activated persulfate decreased PFAA transport, while permanganate and catalyzed hydrogen peroxide increased PFAA transport. PFAA sorption increased in the presence of increased aqueous polyvalent cation concentrations or decreased pH. The changes in contaminant mobility were greater than what would be predicted on the basis of aqueous chemistry considerations alone, suggesting that the application of ISCO results in changes to the porous media matrix (e.g., soil organic matter quality) that also influence transport. The application of ISCO is likely to result in changes in PFAA transport, where the direction (increased or decreased transport) and magnitude are dependent on PFAA characteristics, oxidant characteristics, and site-specific factors. PMID:25621878

  9. Electron donor concentrations in sediments and sediment properties at the agricultural chemicals team research site near New Providence, Iowa, 2006-07

    USGS Publications Warehouse

    Maharjan, Bijesh; Korom, Scott F.; Smith, Erik A.

    2013-01-01

    The concentrations of electron donors in aquifer sediments are important to the understanding of the fate and transport of redox-sensitive constituents in groundwater, such as nitrate. For a study by the U.S. Geological Survey National Water-Quality Assessment Program, 50 sediment samples were collected from below the water table from 11 boreholes at the U.S. Geological Survey Agricultural Chemicals Team research site near New Providence, Iowa, during 2006-07. All samples were analyzed for gravel, sand (coarse, medium, and fine), silt, clay, Munsell soil color, inorganic carbon content, and for the following electron donors: organic carbon, ferrous iron, and inorganic sulfide. A subset of 14 sediment samples also was analyzed for organic sulfur, but all of these samples had concentrations less than the method detection limit; therefore, the presence of this potential electron donor was not considered further. X-ray diffraction analyses provided important semi-quantitative information of well-crystallized dominant minerals within the sediments that might be contributing electron donors.

  10. Simulating Water and Nutrient Transport in an Urbanizing Agricultural Watershed with Lake-Level Regulation Using a Coupled Modeling Approach

    NASA Astrophysics Data System (ADS)

    Chen, X.; Motew, M.; Booth, E.; Carpenter, S. R.; Steven, L. I.; Kucharik, C. J.

    2015-12-01

    The Yahara River basin located in southern Wisconsin is a watershed with long-term eutrophication issues due largely to a thriving dairy industry upstream of the Madison chain of lakes. Steady phosphorus loading from manure production and other sources has contributed directly to blue-green algae blooms and poor water quality in the lakes and river system, and is often viewed as the most important environmental problem to solve in the region. In this study, the daily streamflow and monthly nitrogen (N), sediment and phosphorus (P) transport, as well as the lake levels in the Yahara River basin are simulated using a physically-based hydrologic routing model: the Terrestrial Hydrology Model with Biogeochemistry (THMB). The original model includes representation of water and nitrogen transport but as part of this work, P transport and lake regulation are added into the model. The modified THMB model is coupled with the AgroIBIS-VSF agroecosystem model to represent dynamic coupling between agricultural management in the watershed, and N, P, and sediment transport to lakes and streams. We will present model calibration and validation results that demonstrate the hydrologic routing capability of THMB for a spatial resolution of 220m, several orders of magnitude finer than attempted previously with THMB. The calibrated modeling system is being used to simulate the impacts of climate change and land management on biogeochemistry in the Yahara watershed under four different pathways of change to the year 2070 (Yahara 2070). These scenarios are Abandonment and Renewal, Accelerated Innovation, Connected Communities and Nested Watersheds, which are used to better understand how future decision-making influences the provisioning and trade-offs of ecosystem services.

  11. Transport and biogeochemical reaction of metals in a physically and chemically heterogeneous aquifer

    SciTech Connect

    Scheibe, Timothy D.; Fang, Yilin; Murray, Christopher J.; Roden, Eric E.; Chen, Jinsong; Chien, Yi-Ju; Brooks, Scott C.; Hubbard, Susan S.

    2006-06-01

    Biologically-mediated reductive dissolution and precipitation of metals and radionuclides plays a key role in their subsurface transport. Physical and chemical properties of natural aquifer systems, such as reactive iron oxide surface area and hydraulic conductivity, are often highly heterogeneous in complex ways that can exert significant control on transport, natural attenuation, and active remediation processes. Typically, however, few data on the detailed distribution of these properties are available for incorporation into predictive models. In this study, we integrate field-scale geophysical, hydrologic, and geochemical data from a well-characterized site with the results of laboratory batch reaction studies to formulate numerical models of reactive transport in a heterogeneous granular aquifer. The models incorporate several levels of coupling, including effects of ferrous iron sorption onto (and associated reduction of reactive surface area of) ferric iron surfaces, microbial growth and transport dynamics, and cross-correlation between hydraulic conductivity and initial ferric iron surface area. These models are then used to evaluate the impacts of physical and chemical heterogeneity on transport of trace levels of uranium under natural conditions, as well as the effectiveness of uranium reduction and immobilization upon introduction of a soluble electron donor (a potential biostimulation remedial strategy).

  12. Transport and biogeochemical reaction of metals in a physically and chemically heterogeneous aquifer

    SciTech Connect

    Scheibe, Timothy D.; Fang, Yilin; Murray, Christopher J; Roden, Eric E; Chen, Jinsong; Chien, Yi-Ju; Brooks, Scott C; Hubbard, Susan S

    2006-01-01

    Biologically mediated reductive dissolution and precipitation of metals and radionuclides play key roles in their subsurface transport. Physical and chemical properties of natural aquifer systems, such as reactive iron-oxide surface area and hydraulic conductivity, are often highly heterogeneous in complex ways that can exert significant control on transport, natural attenuation, and active remediation processes. Typically, however, few data on the detailed distribution of these properties are available for incorporation into predictive models. In this study, we integrate field-scale geophysical, hydrologic, and geochemical data from a well-characterized site with the results of laboratory batch-reaction studies to formulate two-dimensional numerical models of reactive transport in a heterogeneous granular aquifer. The models incorporate several levels of coupling, including effects of ferrous iron sorption onto (and associated reduction of reactive surface area of) ferric iron surfaces, microbial growth and transport dynamics, and cross-correlation between hydraulic conductivity and initial ferric iron surface area. These models are then used to evaluate the impacts of physical and chemical heterogeneity on transport of trace levels of uranium under natural conditions, as well as the effectiveness of uranium reduction and immobilization upon introduction of a soluble electron donor (a potential biostimulation remedial strategy).

  13. Effect of subsurface flow on nutrient transport between a eutrophic coastal lake and agricultural reclamation land

    NASA Astrophysics Data System (ADS)

    Onodera, S. I.; Saito, M.; Jin, G.; Hayakawa, A.; Maruyama, Y.

    2014-12-01

    We examined to confirm the effect of surface water-groundwater interaction on the nutrient transport in Hachiro-gata Lake of coastal Akita prefecture and nutrient transport with the water flow. The area of Hachiro-gata lake have decreased since 1960s due to the land reclamation. The reclamation land covered mainly at the east and south side to the Hachiro-gata Lake. The elevation of the reclamation land is about 3m lower than the lake water level. It suggests water flow in the underground between the lake and land would have the stable direction from the lake to the land. Because the eutrophication often occurs in Hachiro-gata Lake, the nutrient would be accumulated in sediment. We installed three piezometers at the bankside of the lake and reclamation land, respectively. The water levels were monitored from September to December in 2013 and May to August in 2014. In addition, water samples were collected in September and December in 2013, May in 2014. We confirmed water flow from the lake to the land with the hydraulic gradient from 0.05 to 0.1. In addition, DOC and phosphorus concentrations of groundwater were higher in the land than in the lake water. The lake water has recently eutrophic condition, and so many organic matter originated from phytoplankton are deposited. The porewater in the lake sediment near the bank had the high nutrient and DOC concentrations. Based on this research, we can make a hypothesis of nutrient transport from the lake to the land with groundwater flow.

  14. Metolachlor metabolite (MESA) reveals agricultural nitrate-N fate and transport in Choptank River watershed.

    PubMed

    McCarty, Gregory W; Hapeman, Cathleen J; Rice, Clifford P; Hively, W Dean; McConnell, Laura L; Sadeghi, Ali M; Lang, Megan W; Whitall, David R; Bialek, Krystyna; Downey, Peter

    2014-03-01

    Over 50% of streams in the Chesapeake Bay watershed have been rated as poor or very poor based on the index of biological integrity. The Choptank River estuary, a Bay tributary on the eastern shore, is one such waterway, where corn and soybean production in upland areas of the watershed contribute significant loads of nutrients and sediment to streams. We adopted a novel approach utilizing the relationship between the concentration of nitrate-N and the stable, water-soluble herbicide degradation product MESA {2-[2-ethyl-N-(1-methoxypropan-2-yl)-6-methylanilino]-2-oxoethanesulfonic acid} to distinguish between dilution and denitrification effects on the stream concentration of nitrate-N in agricultural subwatersheds. The ratio of mean nitrate-N concentration/(mean MESA concentration * 1000) for 15 subwatersheds was examined as a function of percent cropland on hydric soil. This inverse relationship (R(2)=0.65, p<0.001) takes into consideration not only dilution and denitrification of nitrate-N, but also the stream sampling bias of the croplands caused by extensive drainage ditch networks. MESA was also used to track nitrate-N concentrations within the estuary of the Choptank River. The relationship between nitrate-N and MESA concentrations in samples collected over three years was linear (0.95 ≤ R(2) ≤ 0.99) for all eight sampling dates except one where R(2)=0.90. This very strong correlation indicates that nitrate-N was conserved in much of the Choptank River estuary, that dilution alone is responsible for the changes in nitrate-N and MESA concentrations, and more importantly nitrate-N loads are not reduced in the estuary prior to entering the Chesapeake Bay. Thus, a critical need exists to minimize nutrient export from agricultural production fields and to identify specific conservation practices to address the hydrologic conditions within each subwatershed. In well drained areas, removal of residual N within the cropland is most critical, and practices such

  15. Observation of defects in mercury cadmium telluride crystals grown by chemical vapor transport

    NASA Technical Reports Server (NTRS)

    Irene, E. A.; Tierney, E.; Wiedemeier, H.; Chandra, D.

    1983-01-01

    A mixture of nitric and hydrochloric acids was found to yield etch pits on mercury cadmium telluride crystals grown by chemical vapor transport using iodine or mercuric iodide as the transport agent. Two types of pits were observed by optical microscopy: triangular pyramidal and round saucer shaped pits. Transmission electron microscopy confirmed that two types of defects were present: dislocations and second phase occlusions. The present study suggests that the defects are near the crystal surface and therefore will probably not significantly affect the electrical characteristics.

  16. FORTRAN 4 computer program for calculation of thermodynamic and transport properties of complex chemical systems

    NASA Technical Reports Server (NTRS)

    Svehla, R. A.; Mcbride, B. J.

    1973-01-01

    A FORTRAN IV computer program for the calculation of the thermodynamic and transport properties of complex mixtures is described. The program has the capability of performing calculations such as:(1) chemical equilibrium for assigned thermodynamic states, (2) theoretical rocket performance for both equilibrium and frozen compositions during expansion, (3) incident and reflected shock properties, and (4) Chapman-Jouguet detonation properties. Condensed species, as well as gaseous species, are considered in the thermodynamic calculation; but only the gaseous species are considered in the transport calculations.

  17. Metal adsorption by agricultural biosorbents: Adsorption isotherm, kinetic and biosorbents chemical structures.

    PubMed

    Sadeek, Sadeek A; Negm, Nabel A; Hefni, Hassan H H; Wahab, Mostafa M Abdel

    2015-11-01

    Biosorption of Cu(II), Co(II) and Fe(III) ions from aqueous solutions by rice husk, palm leaf and water hyacinth was investigated as a function of initial pH, initial heavy metal ions concentration and treatment time. The adsorption process was examined by two adsorption isotherms: Langmuir and Freundlich isotherms. The experimental data of biosorption process were analyzed using pseudo-first order, pseudo-second order kinetic models. The equilibrium biosorption isotherms showed that the three studied biosorbents possess high affinity and sorption capacity for Cu(II), Co(II) and Fe(III) ions. Rice husk showed more efficiency than palm leaf and water hyacinth. Adsorption of Cu(II) and Co(II) was more efficient in alkaline medium (pH 9) than neutral medium due to the high solubility of metal ion complexes. The metal removal efficiency of each biosorbent was correlated to its chemical structure. DTA studies showed formation of metal complex between the biosorbents and the metal ions. The obtained results showed that the tested biosorbents are efficient and alternate low-cost biosorbent for removal of heavy metal ions from aqueous media. PMID:26282929

  18. Chemicals from western hardwoods and agricultural residues. Appendix volume (manuscript copies). Semiannual report

    SciTech Connect

    Not Available

    1980-04-01

    This appendix volume contains papers on the following topics: the associative effects among organosolv lignin components; the effect of heating and quenching rates on volatiles produced from combustion-level-heat-flux pyrolysis of biomass; and the effect of particle size on volatiles produced from plasma pyrolysis of lignin. Organosolv lignins isolated under relatively mild conditions from angiosperms are composed of entities having low molecular weights. The extent to which an individual component may participate in association depends appreciably upon the relative proportions of the other species present. A simple conduction model is used to adequately predict the devolatilization rate of lignin pellets. The data reported has application to processes in which densified biomass is a fuel or feedstock and the heat transfer rate appears to limit the reaction rate. Models of biomass pyrolysis presented in the literature are reviewed for effect of particle size on product distribution. Compressed lignin pellets of varying sizes are pyrolyzed in a microwave plasma and char and volatile yields are reported as functions of particle size. Chemical analyses of noncondensible and condensible volatiles are presented and possible formation mechanisms are discussed.

  19. The effect of the 2011 flood on agricultural chemical and sediment movement in the lower Mississippi River Basin

    NASA Astrophysics Data System (ADS)

    Welch, H.; Coupe, R.; Aulenbach, B.

    2012-04-01

    Extreme hydrologic events, such as floods, can overwhelm a surface water system's ability to process chemicals and can move large amounts of material downstream to larger surface water bodies. The Mississippi River is the 3rd largest River in the world behind the Amazon in South America and the Congo in Africa. The Mississippi-Atchafalaya River basin grows much of the country's corn, soybean, rice, cotton, pigs, and chickens. This is large-scale modern day agriculture with large inputs of nutrients to increase yields and large applied amounts of crop protection chemicals, such as pesticides. The basin drains approximately 41% of the conterminous United States and is the largest contributor of nutrients to the Gulf of Mexico each spring. The amount of water and nutrients discharged from the Mississippi River has been related to the size of the low dissolved oxygen area that forms off of the coast of Louisiana and Texas each summer. From March through April 2011, the upper Mississippi River basin received more than five times more precipitation than normal, which combined with snow melt from the Missouri River basin, created a historic flood event that lasted from April through July. The U.S. Geological Survey, as part of the National Stream Quality Accounting Network (NASQAN), collected samples from six sites located in the lower Mississippi-Atchafalaya River basin, as well as, samples from the three flow-diversion structures or floodways: the Birds Point-New Madrid in Missouri and the Morganza and Bonnet Carré in Louisiana, from April through July. Samples were analyzed for nutrients, pesticides, suspended sediments, and particle size; results were used to determine the water quality of the river during the 2011 flood. Monthly loads for nitrate, phosphorus, pesticides (atrazine, glyphosate, fluometuron, and metolachlor), and sediment were calculated to quantify the movement of agricultural chemicals and sediment into the Gulf of Mexico. Nutrient loads were

  20. Modeling the transport of chemical warfare agents and simulants in polymeric substrates for reactive decontamination

    NASA Astrophysics Data System (ADS)

    Pearl, Thomas; Mantooth, Brent; Varady, Mark; Willis, Matthew

    2014-03-01

    Chemical warfare agent simulants are often used for environmental testing in place of highly toxic agents. This work sets the foundation for modeling decontamination of absorbing polymeric materials with the focus on determining relationships between agents and simulants. The correlations of agents to simulants must consider the three way interactions in the chemical-material-decontaminant system where transport and reaction occur in polymer materials. To this end, diffusion modeling of the subsurface transport of simulants and live chemical warfare agents was conducted for various polymer systems (e.g., paint coatings) with and without reaction pathways with applied decontamination. The models utilized 1D and 2D finite difference diffusion and reaction models to simulate absorption and reaction in the polymers, and subsequent flux of the chemicals out of the polymers. Experimental data including vapor flux measurements and dynamic contact angle measurements were used to determine model input parameters. Through modeling, an understanding of the relationship of simulant to live chemical warfare agent was established, focusing on vapor emission of agents and simulants from materials.

  1. Impacts of Land-Cover Change on Suspended Sediment Transport in Two Agricultural Watersheds

    USGS Publications Warehouse

    Schilling, K.E.; Isenhart, T.M.; Palmer, J.A.; Wolter, C.F.; Spooner, J.

    2011-01-01

    Suspended sediment is a major water quality problem, yet few monitoring studies have been of sufficient scale and duration to assess the effectiveness of land-use change or conservation practice implementation at a watershed scale. Daily discharge and suspended sediment export from two 5,000-ha watersheds in central Iowa were monitored over a 10-year period (water years 1996-2005). In Walnut Creek watershed, a large portion of land was converted from row crop to native prairie, whereas in Squaw Creek land use remained predominantly row crop agriculture. Suspended sediment loads were similar in both watersheds, exhibiting flashy behavior typical of incised channels. Modeling suggested that expected total soil erosion in Walnut Creek should have been reduced 46% relative to Squaw Creek due to changes in land use, yet measured suspended sediment loads showed no significant differences. Stream mapping indicated that Walnut Creek had three times more eroding streambank lengths than did Squaw Creek suggesting that streambank erosion dominated sediment sources in Walnut Creek and sheet and rill sources dominated sediment sources in Squaw Creek. Our results demonstrate that an accounting of all sources of sediment erosion and delivery is needed to characterize sediment reductions in watershed projects combined with long-term, intensive monitoring and modeling to account for possible lag times in the manifestation of the benefits of conservation practices on water quality. ?? 2011 American Water Resources Association.

  2. Chemical Composition of Martian Soil and Rocks: Complex Mixing and Sedimentary Transport

    NASA Technical Reports Server (NTRS)

    McLennan, Scott M.

    2000-01-01

    Chemical compositions of Martian soil and rocks indicate complex mixing relationships. Mixing of rock and soil clearly takes place and explains some of the chemical variation because sulfur, chlorine, magnesium, and perhaps iron are positively correlated due to their control from a secondary 'sedimentary' mineralogy (e.g., Mg- and possibly Fe-sulfate; Fe-oxides) that is present within the soils. Certain deviations from simple soil-rock mixing are consistent with mineralogical fractionation of detrital iron and titanium oxides during sedimentary transport.

  3. Development of hazard analysis by critical control points (HACCP) procedures to control organic chemical hazards in the agricultural production of raw food commodities.

    PubMed

    Ropkins, Karl; Ferguson, Andrew; Beck, Angus J

    2003-01-01

    Hazard Analysis by Critical Control Points (HACCP) is a systematic approach to the identification, assessment, and control of hazards in the food chain. Effective HACCP requires the consideration of all chemical microbiological, and physical hazards. However, current procedures focus primarily on microbiological and physical hazards, while chemical aspects of HACCP have received relatively little attention. In this article we discuss the application of HACCP to organic chemical contaminants and the problems that are likely to be encountered in agriculture. We also present generic templates for the development of organic chemical contaminant HACCP procedures for selected raw food commodities, that is, cereal crops,raw meats, and milk. PMID:12822674

  4. A Chemical Genetic Screen for Modulators of Exocytic Transport Identifies Inhibitors of a Transport Mechanism Linked to GTR2 Function▿

    PubMed Central

    Zhang, Lisha; Huang, Min; Harsay, Edina

    2010-01-01

    Membrane and protein traffic to the cell surface is mediated by partially redundant pathways that are difficult to perturb in ways that yield a strong phenotype. Such robustness is expected in a fine-tuned process, regulated by environmental cues, that is required for controlled cell surface growth and cell proliferation. Synthetic genetic interaction screens are especially valuable for investigating complex processes involving partially redundant pathways or mechanisms. In a previous study, we used a triple-synthetic-lethal yeast mutant screen to identify a novel component of the late exocytic transport machinery, Avl9. In a chemical-genetic version of the successful mutant screen, we have now identified small molecules that cause a rapid (within 15 min) accumulation of secretory cargo and abnormal Golgi compartment-like membranes at low concentration (<2 μM), indicating that the compounds likely target the exocytic transport machinery at the Golgi. We screened for genes that, when overexpressed, suppress the drug effects, and found that the Ras-like small GTPase, Gtr2, but not its homolog and binding partner, Gtr1, efficiently suppresses the toxic effects of the compounds. Furthermore, assays for suppression of the secretory defect caused by the compounds suggest that Gtr proteins can regulate a pathway that is perturbed by the compounds. Because avl9Δ and gtr mutants share some phenotypes, our results indicate that the small molecules identified by our chemical-genetic strategy are promising tools for understanding Avl9 function and the mechanisms that control late exocytic transport. PMID:19897736

  5. Organic polymer-metal nano-composites for opto-electronic sensing of chemicals in agriculture

    NASA Astrophysics Data System (ADS)

    Sarkisov, Sergey S.; Czarick, Michael; Fairchild, Brian D.; Liang, Yi; Kukhtareva, Tatiana; Curley, Michael J.

    2013-03-01

    Recent research findings led the team to conclude that a long lasting and inexpensive colorimetric sensor for monitoring ammonia emission from manure in confined animal feeding operations could eventually become feasible. The sensor uses robust method of opto-electronic spectroscopic measurement of the reversible change of the color of a sensitive nano-composite reagent film in response to ammonia. The film is made of a metal (gold, platinum, or palladium) nano-colloid in a polymer matrix with an ammonia-sensitive indicator dye additive. The response of the indicator dye (increase of the optical absorption in the region 550 to 650 nm) is enhanced by the nano-particles (~10 nm in size) in two ways: (a) concentration of the optical field near the nano-particle due to the plasmon resonance; and (b) catalytic acceleration of the chemical reaction of deprotonization of the indicator dye in the presence of ammonia and water vapor. This enhancement helps to make a miniature and rugged sensing element without compromising its sensitivity of less than 1 ppm for the range 0 to 100 ppm. The sensor underwent field tests in commercial broiler farms in Georgia, Alabama, and Arkansas and was compared against a commercial photoacoustic gas analyzer. The sensor output correlated well with the data from the photoacoustic analyzer (correlation coefficient not less than 0.9 and the linear regression slope after calibration close to 1.0) for several weeks of continuous operation. The sources of errors were analyzed and the conclusions on the necessary improvements and the potential use of the proposed device were made.

  6. Ion transport through chemically induced pores in protein-free phospholipid membranes.

    PubMed

    Gurtovenko, Andrey A; Anwar, Jamshed

    2007-11-29

    We address the possibility of being able to induce the trafficking of salt ions and other solutes across cell membranes without the use of specific protein-based transporters or pumps. On the basis of realistic atomic-scale molecular dynamics simulations, we demonstrate that transmembrane ionic leakage can be initiated by chemical means, in this instance through addition of dimethyl sulfoxide (DMSO), a solvent widely used in cell biology. Our results provide compelling evidence that the small amphiphilic solute DMSO is able to induce transient defects (water pores) in membranes and to promote a subsequent diffusive pore-mediated transport of salt ions. The findings are consistent with available experimental data and offer a molecular-level explanation for the experimentally observed activities of DMSO solvent as an efficient penetration enhancer and a cryoprotectant, as well as an analgesic. Our findings suggest that transient pore formation by chemical means could emerge as an important general principle for therapeutics. PMID:17983219

  7. Altered magnesium transport in slices of kidney cortex from chemically-induced diabetic rats

    SciTech Connect

    Hoskins, B.

    1981-10-01

    The uptake of magnesium-28 was measured in slices of kidney cortex from rats with alloxan-diabetes and from rats with streptozotocin-diabetes of increasing durations. In both forms of chemically-induced diabetes, magnesium-28 uptake by kidney cortex slices was significantly increased over uptake measured in kidney cortex slices from control rats. Immediate institution of daily insulin therapy to the diabetic rats prevented the diabetes-induced elevated uptake of magnesium without controlling blood glucose levels. Late institution of daily insulin therapy was ineffective in restoring the magnesium uptake to control values. These alterations in magnesium uptake occurred prior to any evidence of nephropathy (via the classic indices of proteinuria and increased BUN levels). The implications of these findings, together with our earlier demonstrations of altered calcium transport by kidney cortex slices from chemically-induced diabetic rats, are discussed in terms of disordered divalent cation transport being at least part of the basic pathogenesis underlying diabetic nephropathy.

  8. Temporal variability of atmospheric particulate matter and chemical composition during a growing season at an agricultural site in northeastern China.

    PubMed

    Chen, Weiwei; Tong, Daniel; Zhang, Shichun; Dan, Mo; Zhang, Xuelei; Zhao, Hongmei

    2015-12-01

    This study presents the observations of PM10 and PM2.5 concentrations at an agricultural site from April to October 2012 in Dehui city, China. Ambient air was sampled by filter-based samplers and online PM monitors. The filter samples were analyzed to determine the abundance of ionic/inorganic elements, organic carbon (OC) and elemental carbon (EC). The daily PM10 concentrations varied significantly over the monitoring period, with an average of 168±63 (in the range of 52-277)μg/m(3) during the land preparation/planting period (26 April-15 June), 85±65 (36-228)μg/m(3) during the growing season (16 June-25 September), and 207±88 (103-310)μg/m(3) during the harvest period (26 September-31 October). PM2.5 accounted for 44%, 56% and 66% of atmospheric PM10 during these periods, respectively. The PM10 diurnal variation showed a distinct peak from 16:00 to 21:00 (LST) during the growing and harvesting seasons, while a gradual increase throughout the daytime until 17:00 was observed during tilling season. Mineral dust elements (Al, Ca, Fe, and Mg) dominated the PM10 chemical composition during the tilling season; OC, NO3(-), SO4(2-) and NH4(+) during the growing season; and carbonaceous species (i.e., OC and EC) during the harvesting season. Our results indicate that the soil particles emitted by farm tillage and organic matter released from straw burning are the two most significant sources of PM10 emissions contributing to the recurring high pollution events in this region. Therefore, development of agricultural PM inventories from soil tillage and straw burning is prioritized to support air quality modeling. PMID:26702977

  9. Impact of fluid-rock chemical interactions on tracer transport in fractured rocks.

    PubMed

    Mukhopadhyay, Sumit; Liu, H-H; Spycher, N; Kennedy, B M

    2013-11-01

    In this paper, we investigate the impact of chemical interactions, in the form of mineral precipitation and dissolution reactions, on tracer transport in fractured rocks. When a tracer is introduced in fractured rocks, it moves through the fracture primarily by advection and it also enters the stagnant water of the surrounding rock matrix through diffusion. Inside the porous rock matrix, the tracer chemically interacts with the solid materials of the rock, where it can precipitate depending on the local equilibrium conditions. Alternatively, it can be dissolved from the solid phase of the rock matrix into the matrix pore water, diffuse into the flowing fluids of the fracture and is advected out of it. We show that such chemical interactions between the fluid and solid phases have significant impact on tracer transport in fractured rocks. We invoke the dual-porosity conceptualization to represent the fractured rocks and develop a semi-analytical solution to describe the transient transport of tracers in interacting fluid-rock systems. To test the accuracy and stability of the semi-analytical solution, we compare it with simulation results obtained with the TOUGHREACT simulator. We observe that, in a chemically interacting system, the tracer breakthrough curve exhibits a pseudo-steady state, where the tracer concentration remains more or less constant over a finite period of time. Such a pseudo-steady condition is not observed in a non-reactive fluid-rock system. We show that the duration of the pseudo-state depends on the physical and chemical parameters of the system, and can be exploited to extract information about the fractured rock system, such as the fracture spacing and fracture-matrix interface area. PMID:24077359

  10. Impact of fluid-rock chemical interactions on tracer transport in fractured rocks

    NASA Astrophysics Data System (ADS)

    Mukhopadhyay, Sumit; Liu, H.-H.; Spycher, N.; Kennedy, B. M.

    2013-11-01

    In this paper, we investigate the impact of chemical interactions, in the form of mineral precipitation and dissolution reactions, on tracer transport in fractured rocks. When a tracer is introduced in fractured rocks, it moves through the fracture primarily by advection and it also enters the stagnant water of the surrounding rock matrix through diffusion. Inside the porous rock matrix, the tracer chemically interacts with the solid materials of the rock, where it can precipitate depending on the local equilibrium conditions. Alternatively, it can be dissolved from the solid phase of the rock matrix into the matrix pore water, diffuse into the flowing fluids of the fracture and is advected out of it. We show that such chemical interactions between the fluid and solid phases have significant impact on tracer transport in fractured rocks. We invoke the dual-porosity conceptualization to represent the fractured rocks and develop a semi-analytical solution to describe the transient transport of tracers in interacting fluid-rock systems. To test the accuracy and stability of the semi-analytical solution, we compare it with simulation results obtained with the TOUGHREACT simulator. We observe that, in a chemically interacting system, the tracer breakthrough curve exhibits a pseudo-steady state, where the tracer concentration remains more or less constant over a finite period of time. Such a pseudo-steady condition is not observed in a non-reactive fluid-rock system. We show that the duration of the pseudo-state depends on the physical and chemical parameters of the system, and can be exploited to extract information about the fractured rock system, such as the fracture spacing and fracture-matrix interface area.

  11. Optical, physical and chemical properties of transported African mineral dust aerosols in the Mediterranean region

    NASA Astrophysics Data System (ADS)

    Denjean, Cyrielle; Di Biagio, Claudia; Chevaillier, Servanne; Gaimoz, Cécile; Grand, Noel; Loisil, Rodrigue; Triquet, Sylvain; Zapf, Pascal; Roberts, Greg; Bourrianne, Thierry; Torres, Benjamin; Blarel, Luc; Sellegri, Karine; Freney, Evelyn; Schwarzenbock, Alfons; Ravetta, François; Laurent, Benoit; Mallet, Marc; Formenti, Paola

    2014-05-01

    The transport of mineral dust aerosols is a global phenomenon with strong climate implications. Depending on the travel distance over source regions, the atmospheric conditions and the residence time in the atmosphere, various transformation processes (size-selective sedimentation, mixing, condensation of gaseous species, and weathering) can modify the physical and chemical properties of mineral dust, which, in turn, can change the dust's optical properties. The model predictions of the radiative effect by mineral dust still suffer of the lack of certainty of these properties, and their temporal evolution with transport time. Within the frame of the ChArMex project (Chemistry-Aerosol Mediterranean experiment, http://charmex.lsce.ipsl.fr/), two intensive airborne campaigns (TRAQA, TRansport and Air QuAlity, 18 June - 11 July 2012, and ADRIMED, Aerosol Direct Radiative Impact in the regional climate in the MEDiterranean region, 06 June - 08 July 2013) have been performed over the Central and Western Mediterranean, one of the two major transport pathways of African mineral dust. In this study we have set up a systematic strategy to determine the optical, physical and optical properties of mineral dust to be compared to an equivalent dataset for dust close to source regions in Africa. This study is based on airborne observations onboard the SAFIRE ATR-42 aircraft, equipped with state of the art in situ instrumentation to measure the particle scattering and backscattering coefficients (nephelometer at 450, 550, and 700 nm), the absorption coefficient (PSAP at 467, 530, and 660 nm), the extinction coefficient (CAPS at 530 nm), the aerosol optical depth (PLASMA at 340 to 1640 nm), the size distribution in the extended range 40 nm - 30 µm by the combination of different particle counters (SMPS, USHAS, FSSP, GRIMM) and the chemical composition obtained by filter sampling. The chemistry and transport model CHIMERE-Dust have been used to classify the air masses according to

  12. TRANSPORT SPECTROSCOPY OF CHEMICAL NANOSTRUCTURES: The Case of Metallic Single-Walled Carbon Nanotubes

    NASA Astrophysics Data System (ADS)

    Liang, Wenjie; Bockrath, Marc; Park, Hongkun

    2005-05-01

    Transport spectroscopy, a technique based on current-voltage measurements of individual nanostructures in a three-terminal transistor geometry, has emerged as a powerful new tool to investigate the electronic properties of chemically derived nanostructures. In this review, we discuss the utility of this approach using the recent studies of single-nanotube transistors as an example. Specifically, we discuss how transport measurements can be used to gain detailed insight into the electronic motion in metallic single-walled carbon nanotubes in several distinct regimes, depending on the coupling strength of the contacts to the nanotubes. Measurements of nanotube devices in these different conductance regimes have enabled a detailed analysis of the transport properties, including the experimental determination of all Hartree-Fock parameters that govern the electronic structure of metallic nanotubes and the demonstration of Fabry-Perot resonators based on the interference of electron waves.

  13. Effect of pH and soil structure on transport of sulfonamide antibiotics in agricultural soils.

    PubMed

    Park, Jong Yol; Huwe, Bernd

    2016-06-01

    We investigated the effect of solution pH and soil structure on transport of sulfonamide antibiotics (sulfamethoxazole, sulfadimethoxine and sulfamethazine) in combination with batch sorption tests and column experiments. Sorption isotherms properly conformed to Freundlich model, and sorption potential of the antibiotics is as follows; sulfadimethoxine > sulfamethoxazole > sulfamethazine. Decreasing pH values led to increased sorption potential of the antibiotics on soil material in pH range of 4.0-8.0. This likely resulted from abundance of neutral and positive-charged sulfonamides species at low pH, which electrostatically bind to sorption sites on soil surface. Due to destruction of macropore channels, lower hydraulic conductivities of mobile zone were estimated in the disturbed soil columns than in the undisturbed soil columns, and eventually led to lower mobility of the antibiotics in disturbed column. The results suggest that knowledge of soil structure and solution condition is required to predict fate and distribution of sulfonamide antibiotics in environmental matrix. PMID:26995452

  14. Determination of thermodynamic and transport parameters of naphthenic acids and organic process chemicals in oil sand tailings pond water.

    PubMed

    Wang, Xiaomeng; Robinson, Lisa; Wen, Qing; Kasperski, Kim L

    2013-07-01

    Oil sand tailings pond water contains naphthenic acids and process chemicals (e.g., alkyl sulphates, quaternary ammonium compounds, and alkylphenol ethoxylates). These chemicals are toxic and can seep through the foundation of the tailings pond to the subsurface, potentially affecting the quality of groundwater. As a result, it is important to measure the thermodynamic and transport parameters of these chemicals in order to study the transport behavior of contaminants through the foundation as well as underground. In this study, batch adsorption studies and column experiments were performed. It was found that the transport parameters of these chemicals are related to their molecular structures and other properties. The computer program (CXTFIT) was used to further evaluate the transport process in the column experiments. The results from this study show that the transport of naphthenic acids in a glass column is an equilibrium process while the transport of process chemicals seems to be a non-equilibrium process. At the end of this paper we present a real-world case study in which the transport of the contaminants through the foundation of an external tailings pond is calculated using the lab-measured data. The results show that long-term groundwater monitoring of contaminant transport at the oil sand mining site may be necessary to avoid chemicals from reaching any nearby receptors. PMID:23736740

  15. TERRA: a computer code for simulating the transport of environmentally released radionuclides through agriculture

    SciTech Connect

    Baes, C.F. III; Sharp, R.D.; Sjoreen, A.L.; Hermann, O.W.

    1984-11-01

    TERRA is a computer code which calculates concentrations of radionuclides and ingrowing daughters in surface and root-zone soil, produce and feed, beef, and milk from a given deposition rate at any location in the conterminous United States. The code is fully integrated with seven other computer codes which together comprise a Computerized Radiological Risk Investigation System, CRRIS. Output from either the long range (> 100 km) atmospheric dispersion code RETADD-II or the short range (<80 km) atmospheric dispersion code ANEMOS, in the form of radionuclide air concentrations and ground deposition rates by downwind location, serves as input to TERRA. User-defined deposition rates and air concentrations may also be provided as input to TERRA through use of the PRIMUS computer code. The environmental concentrations of radionuclides predicted by TERRA serve as input to the ANDROS computer code which calculates population and individual intakes, exposures, doses, and risks. TERRA incorporates models to calculate uptake from soil and atmospheric deposition on four groups of produce for human consumption and four groups of livestock feeds. During the environmental transport simulation, intermediate calculations of interception fraction for leafy vegetables, produce directly exposed to atmospherically depositing material, pasture, hay, and silage are made based on location-specific estimates of standing crop biomass. Pasture productivity is estimated by a model which considers the number and types of cattle and sheep, pasture area, and annual production of other forages (hay and silage) at a given location. Calculations are made of the fraction of grain imported from outside the assessment area. TERRA output includes the above calculations and estimated radionuclide concentrations in plant produce, milk, and a beef composite by location.

  16. Numerical Modeling of Global Atmospheric Chemical Transport with Wavelet-based Adaptive Mesh Refinement

    NASA Astrophysics Data System (ADS)

    Rastigejev, Y.; Semakin, A. N.

    2012-12-01

    In this work we present a multilevel Wavelet-based Adaptive Mesh Refinement (WAMR) method for numerical modeling of global atmospheric chemical transport problems. An accurate numerical simulation of such problems presents an enormous challenge. Atmospheric Chemical Transport Models (CTMs) combine chemical reactions with meteorologically predicted atmospheric advection and turbulent mixing. The resulting system of multi-scale advection-reaction-diffusion equations is extremely stiff, nonlinear and involves a large number of chemically interacting species. As a consequence, the need for enormous computational resources for solving these equations imposes severe limitations on the spatial resolution of the CTMs implemented on uniform or quasi-uniform grids. In turn, this relatively crude spatial resolution results in significant numerical diffusion introduced into the system. This numerical diffusion is shown to noticeably distort the pollutant mixing and transport dynamics for typically used grid resolutions. The developed WAMR method for numerical modeling of atmospheric chemical evolution equations presented in this work provides a significant reduction in the computational cost, without upsetting numerical accuracy, therefore it addresses the numerical difficulties described above. WAMR method introduces a fine grid in the regions where sharp transitions occur and cruder grid in the regions of smooth solution behavior. Therefore WAMR results in much more accurate solutions than conventional numerical methods implemented on uniform or quasi-uniform grids. The algorithm allows one to provide error estimates of the solution that are used in conjunction with appropriate threshold criteria to adapt the non-uniform grid. The method has been tested for a variety of problems including numerical simulation of traveling pollution plumes. It was shown that pollution plumes in the remote troposphere can propagate as well-defined layered structures for two weeks or more as

  17. Evaluation of the performance of four chemical transport models in predicting the aerosol chemical composition in Europe in 2005

    NASA Astrophysics Data System (ADS)

    Prank, Marje; Sofiev, Mikhail; Tsyro, Svetlana; Hendriks, Carlijn; Semeena, Valiyaveetil; Vazhappilly Francis, Xavier; Butler, Tim; Denier van der Gon, Hugo; Friedrich, Rainer; Hendricks, Johannes; Kong, Xin; Lawrence, Mark; Righi, Mattia; Samaras, Zissis; Sausen, Robert; Kukkonen, Jaakko; Sokhi, Ranjeet

    2016-05-01

    Four regional chemistry transport models were applied to simulate the concentration and composition of particulate matter (PM) in Europe for 2005 with horizontal resolution ~ 20 km. The modelled concentrations were compared with the measurements of PM chemical composition by the European Monitoring and Evaluation Programme (EMEP) monitoring network. All models systematically underestimated PM10 and PM2.5 by 10-60 %, depending on the model and the season of the year, when the calculated dry PM mass was compared with the measurements. The average water content at laboratory conditions was estimated between 5 and 20 % for PM2.5 and between 10 and 25 % for PM10. For majority of the PM chemical components, the relative underestimation was smaller than it was for total PM, exceptions being the carbonaceous particles and mineral dust. Some species, such as sea salt and NO3-, were overpredicted by the models. There were notable differences between the models' predictions of the seasonal variations of PM, mainly attributable to different treatments or omission of some source categories and aerosol processes. Benzo(a)pyrene concentrations were overestimated by all the models over the whole year. The study stresses the importance of improving the models' skill in simulating mineral dust and carbonaceous compounds, necessity for high-quality emissions from wildland fires, as well as the need for an explicit consideration of aerosol water content in model-measurement comparison.

  18. Modelling Water Flow, Heat Transport, Soil Freezing and Thawing, and Snow Processes in a Clayey, Subsurface Drained Agricultural Field

    NASA Astrophysics Data System (ADS)

    Warsta, L.; Turunen, M.; Koivusalo, H. J.; Paasonen-Kivekäs, M.; Karvonen, T.; Taskinen, A.

    2012-12-01

    Simulation of hydrological processes for the purposes of agricultural water management and protection in boreal environment requires description of winter time processes, including heat transport, soil freezing and thawing, and snow accumulation and melt. Finland is located north of the latitude of 60 degrees and has one third to one fourth of the total agricultural land area (2.3 milj. ha) on clay soils (> 30% of clay). Most of the clayey fields are subsurface drained to provide efficient drainage and to enable heavy machines to operate on the fields as soon as possible after the spring snowmelt. Generation of drainflow and surface runoff in cultivated fields leads to nutrient and sediment load, which forms the major share of the total load reaching surface waters at the national level. Water, suspended sediment, and soluble nutrients on clayey field surface are conveyed through the soil profile to the subsurface drains via macropore pathways as the clayey soil matrix is almost impermeable. The objective of the study was to develop the missing winter related processes into the FLUSH model, including soil heat transport, snow pack simulation and the effects of soil freezing and thawing on the soil hydraulic conductivity. FLUSH is an open source (MIT license), distributed, process-based model designed to simulate surface runoff and drainflow in clayey, subsurface drained agricultural fields. 2-D overland flow is described with the diffuse wave approximation of the Saint Venant equations and 3-D subsurface flow with a dual-permeability model. Both macropores and soil matrix are simulated with the Richards equation. Soil heat transport is described with a modified 3-D convection-diffusion equation. Runoff and groundwater data was available from different periods from January 1994 to April 1999 measured in a clayey, subsurface drained field section (3.6 ha) in southern Finland. Soil temperature data was collected in two locations (to a depth of 0.8 m) next to the

  19. Efficacy of management practices to mitigate the off-site movement and ecological risk of pesticides transported with runoff from agricultural and turf systems

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Highly managed biotic systems, such as agricultural crops and managed turf, often require multiple applications of pesticides that may be transported with runoff to areas beyond the intended target site. Pesticides have been detected in surface waters of rural and urban watersheds raising questions ...

  20. Short-term and long-term impacts of dredging on nutrient transport in agricultural ditches of the Lake Erie Basin, USA

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Agricultural drainage ditches are a common landscape feature in the Midwestern United States. Compared to natural streams in more pristine environments, little is known about nutrient fate and transport in these highly enriched systems, especially following human induced manipulations. Drainage di...

  1. Atrazine transport within a coastal zone in Southeastern Puerto Rico: a sensitivity analysis of an agricultural field model and riparian zone management model

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Water quality models are used to predict effects of conservation practices to mitigate the transport of herbicides to water bodies. We used two models - the Agricultural Policy/Environmental eXtender (APEX) and the Riparian Ecosystem Management Model (REMM) to predict the movement of atrazine from ...

  2. Origin of the relatively low transport mobility of graphene grown through chemical vapor deposition

    PubMed Central

    Song, H. S.; Li, S. L.; Miyazaki, H.; Sato, S.; Hayashi, K.; Yamada, A.; Yokoyama, N.; Tsukagoshi, K.

    2012-01-01

    The reasons for the relatively low transport mobility of graphene grown through chemical vapor deposition (CVD-G), which include point defect, surface contamination, and line defect, were analyzed in the current study. A series of control experiments demonstrated that the determinant factor for the low transport mobility of CVD-G did not arise from point defects or surface contaminations, but stemmed from line defects induced by grain boundaries. Electron microscopies characterized the presence of grain boundaries and indicated the polycrystalline nature of the CVD-G. Field-effect transistors based on CVD-G without the grain boundary obtained a transport mobility comparative to that of Kish graphene, which directly indicated the detrimental effect of grain boundaries. The effect of grain boundary on transport mobility was qualitatively explained using a potential barrier model. Furthermore, the conduction mechanism of CVD-G was also investigated using the temperature dependence measurements. This study can help understand the intrinsic transport features of CVD-G. PMID:22468224

  3. Mercury cycling in agricultural and managed wetlands of California: seasonal influences of vegetation on mercury methylation, storage, and transport

    USGS Publications Warehouse

    Windham-Myers, Lisamarie; Marvin-DiPasquale, Mark C.; Kakouros, Evangelos; Agee, Jennifer L.; Kieu, Le H.; Stricker, Craig A.; Fleck, Jacob A.; Ackerman, Joshua T.

    2013-01-01

    Plants are a dominant biologic and physical component of many wetland capable of influencing the internal pools and fluxes of methylmercury (MeHg). To investigate their role with respect to the latter, we examined the changing seasonal roles of vegetation biomass and Hg, C and N composition from May 2007-February 2008 in 3 types of agricultural wetlands (domesticated or white rice, wild rice, and fallow fields), and in adjacent managed natural wetlands dominated by cattail and bulrush (tule). We also determined the impact of vegetation on seasonal microbial Hg methylation rates, and Hg and MeHg export via seasonal storage in vegetation, and biotic consumption of rice seed. Despite a compressed growing season of ~ 3 months, annual net primary productivity (NPP) was greatest in white rice fields and carbon more labile (leaf median C:N ratio = 27). Decay of senescent litter (residue) was correlated with microbial MeHg production in winter among all wetlands. As agricultural biomass accumulated from July to August, THg concentrations declined in leaves but MeHg concentrations remained consistent, such that MeHg pools generally increased with growth. Vegetation provided a small, temporary, but significant storage term for MeHg in agricultural fields when compared with hydrologic export. White rice and wild rice seeds reached mean MeHg concentrations of 4.1 and 6.2 ng gdw- 1, respectively. In white rice and wild rice fields, seed MeHg concentrations were correlated with root MeHg concentrations (r = 0.90, p < 0.001), suggesting transport of MeHg to seeds from belowground tissues. Given the proportionally elevated concentrations of MeHg in rice seeds, white and wild rice crops may act as a conduit of MeHg into biota, especially waterfowl which forage heavily on rice seeds within the Central Valley of California, USA. Thus, while plant tissues and rhizosphere soils provide temporary storage for MeHg during the growing season, export of MeHg is enhanced post-harvest through

  4. Experimental investigation and modeling of uranium (VI) transport under variable chemical conditions

    USGS Publications Warehouse

    Kohler, M.; Curtis, G.P.; Kent, D.B.; Davis, J.A.

    1996-01-01

    The transport of adsorbing and complexing metal ions in porous media was investigated with a series of batch and column experiments and with reactive solute transport modeling. Pulses of solutions containing U(VI) were pumped through columns filled with quartz grains, and the breakthrough of U(VI) was studied as a function of variable solution composition (pH, total U(VI) concentration, total fluoride concentration, and pH-buffering capacity). Decreasing p H and the formation of nonadsorbing aqueous complexes with fluoride increased U(VI) mobility. A transport simulation with surface complexation model (SCM) parameters estimated from batch experiments was able to predict U(VI) retardation in the column experiments within 30%. SCM parameters were also estimated directly from transport data, using the results of three column experiments collected at different pH and U(VI) pulse concentrations. SCM formulations of varying complexity (multiple surface types and reaction stoichiometries) were tested to examine the trade-off between model simplicity and goodness of fit to breakthrough. A two-site model (weak- and strong-binding sites) with three surface complexation reactions fit these transport data well. With this reaction set the model was able to predict (1) the effects of fluoride complexation on U(VI) retardation at two different pH values and (2) the effects of temporal variability of pH on U(VI) transport caused by low p H buffering. The results illustrate the utility of the SCM approach in modeling the transport of adsorbing inorganic solutes under variable chemical conditions.

  5. Interactions of solutes and streambed sediment. 2. A dynamic analysis of coupled hydrologic and chemical processes that determine solute transport.

    USGS Publications Warehouse

    Bencala, K.E.

    1984-01-01

    Solute transport in streams is determined by the interaction of physical and chemical processes. Data from an injection experiment for chloride and several cations indicate significant influence of solute-streambed processes on transport in a mountain stream. These data are interpreted in terms of transient storage processes for all tracers and sorption processes for the cations. Process parameter values are estimated with simulations based on coupled quasi-two-dimensional transport and first-order mass transfer sorption. Comparative simulations demonstrate the relative roles of the physical and chemical processes in determining solute transport. -from Author

  6. Chemical characteristics of Northeast Asian fly ash particles: Implications for their long-range transportation

    NASA Astrophysics Data System (ADS)

    Inoue, Jun; Momose, Azusa; Okudaira, Takamoto; Murakami-Kitase, Akiko; Yamazaki, Hideo; Yoshikawa, Shusaku

    2014-10-01

    The chemical compositions of fly ash particles emitted in Northeast Asia were studied to better understand the long-range transportation of atmospheric pollutants. We examined the compositions of spheroidal carbonaceous particles (SCPs), a type of fly ash from several to ˜20 μm in diameter found in surface sediments in or near the main industrial cities of Japan, China, South Korea, and Taiwan. SCPs from different countries were found to vary; SCPs from Japan and South Korea were characterized by low Ti/Si and high S/Si ratios, whereas SCPs in China exhibited high Ti/Si and low S/Si ratios and particles from Taiwan showed high Ti/Si and S/Si ratios. We also examined the SCPs found in remote islands in the Sea of Japan, at least 100 km from any industrial city. On the basis of their chemical compositions, these SCPs were classified as Japan and Korea, China, and Taiwan types using discriminant analysis. The results indicated that 30-50% of the particles found in these islands were assigned to the China type, suggesting that most of these SCPs were probably transported from Chinese industrial regions to these islands. It implies that even large particulate pollutants of ˜10 μm, such as SCPs, could be transported long distances of ˜1000 km.

  7. Electromechanical and Chemical Sensing at the Nanoscale: DFT and Transport Modeling

    NASA Astrophysics Data System (ADS)

    Maiti, Amitesh

    Of the many nanoelectronic applications proposed for near to medium-term commercial deployment, sensors based on carbon nanotubes (CNT) and metal-oxide nanowires are receiving significant attention from researchers. Such devices typically operate on the basis of the changes of electrical response characteristics of the active component (CNT or nanowire) when subjected to an externally applied mechanical stress or the adsorption of a chemical or bio-molecule. Practical development of such technologies can greatly benefit from quantum chemical modeling based on density functional theory (DFT), and from electronic transport modeling based on non-equilibrium Green's function (NEGF). DFT can compute useful quantities like possible bond-rearrangements, binding energy, charge transfer, and changes to the electronic structure, while NEGF can predict changes in electronic transport behavior and contact resistance. Effects of surrounding medium and intrinsic structural defects can also be taken into account. In this work we review some recent DFT and transport investigations on (1) CNT-based nano-electromechanical sensors (NEMS) and (2) gas-sensing properties of CNTs and metal-oxide nanowires. We also briefly discuss our current understanding of CNT-metal contacts which, depending upon the metal, the deposition technique, and the masking method can have a significant effect on device performance.

  8. Visualizing chemical structure-subcellular localization relationships using fluorescent small molecules as probes of cellular transport

    PubMed Central

    2013-01-01

    Background To study the chemical determinants of small molecule transport inside cells, it is crucial to visualize relationships between the chemical structure of small molecules and their associated subcellular distribution patterns. For this purpose, we experimented with cells incubated with a synthetic combinatorial library of fluorescent, membrane-permeant small molecule chemical agents. With an automated high content screening instrument, the intracellular distribution patterns of these chemical agents were microscopically captured in image data sets, and analyzed off-line with machine vision and cheminformatics algorithms. Nevertheless, it remained challenging to interpret correlations linking the structure and properties of chemical agents to their subcellular localization patterns in large numbers of cells, captured across large number of images. Results To address this challenge, we constructed a Multidimensional Online Virtual Image Display (MOVID) visualization platform using off-the-shelf hardware and software components. For analysis, the image data set acquired from cells incubated with a combinatorial library of fluorescent molecular probes was sorted based on quantitative relationships between the chemical structures, physicochemical properties or predicted subcellular distribution patterns. MOVID enabled visual inspection of the sorted, multidimensional image arrays: Using a multipanel desktop liquid crystal display (LCD) and an avatar as a graphical user interface, the resolution of the images was automatically adjusted to the avatar’s distance, allowing the viewer to rapidly navigate through high resolution image arrays, zooming in and out of the images to inspect and annotate individual cells exhibiting interesting staining patterns. In this manner, MOVID facilitated visualization and interpretation of quantitative structure-localization relationship studies. MOVID also facilitated direct, intuitive exploration of the relationship between the

  9. Internal Domains of Natural Porous Media Revealed: Critical Locations for Transport, Storage, and Chemical Reaction

    DOE PAGESBeta

    Zachara, John; Brantley, Sue; Chorover, Jon; Ewing, Robert; Kerisit, Sebastien; Liu, Chongxuan; Perfect, Edmund; Rother, Gernot; Stack, Andrew G.

    2016-02-05

    Internal pore domains exist within rocks, lithic fragments, subsurface sediments, and soil aggregates. These domains, termed internal domains in porous media (IDPM), represent a subset of a material’s porosity, contain a significant fraction of their porosity as nanopores, dominate the reactive surface area of diverse media types, and are important locations for chemical reactivity and fluid storage. IDPM are key features controlling hydrocarbon release from shales in hydraulic fracture systems, organic matter decomposition in soil, weathering and soil formation, and contaminant behavior in the vadose zone and groundwater. It is traditionally difficult to interrogate, advances in instrumentation and imaging methodsmore » are providing new insights on the physical structures and chemical attributes of IDPM, and their contributions to system behaviors. We discuss analytical methods to characterize IDPM, evaluate information on their size distributions, connectivity, and extended structures; determine whether they exhibit unique chemical reactivity; and assess the potential for their inclusion in reactive transport models. Moreover, ongoing developments in measurement technologies and sensitivity, and computer-assisted interpretation will improve understanding of these critical features in the future. Finally, impactful research opportunities exist to advance understanding of IDPM, and to incorporate their effects in reactive transport models for improved environmental simulation and prediction.« less

  10. Numerical Simulation of the Transport and Speciation of Nonconservative Chemical Reactants in Rivers

    NASA Astrophysics Data System (ADS)

    Chapman, Bernard M.

    1982-02-01

    A computer model, previously used to simulate the transport of conservative chemical components in streams, has been used as a basis for a more complex model which includes the effects due to processes such as precipitation and sedimentation and adsorption onto stationary reactive surfaces which render the reactants nonconservative with respect to the flowing waters. The model uses, as before, the program MINEQL as a basis for the chemical equilibrium submodel. The physical transport submodel employs a convolution integral procedure, with an approximate form of the impulse function to solve a one-dimensional convective-diffusion equation. Although the model essentially assumes chemical equilibrium, a pseudokinetic treatment is necessary to deal with redissolution of precipitates and dissociation of surface species. Simple hypothetical examples are given to illustrate the operation of the model. The model is then applied to an experiment in which the base NaOH is injected into a creek draining an abandoned base metal mine. Concentrations of the metals Zn, Al, Cu, Fe, and Na in the flowing waters, expressed in terms of total metals and as suspended solids, are followed as a function of time and distance downstream. Significant sedimentation of the precipitates formed is evident, and the existence of substantial quantities of protons and/or metal ions, adsorbed on the streambed, is implied from the model calculations. The model was able to simulate successfully the major features observed. This simulation involved the simultaneous formation of five distinct precipitates and one surface species.

  11. Chemical Analysis of Drug Biocrystals: A Role for Counterion Transport Pathways in Intracellular Drug Disposition.

    PubMed

    Keswani, Rahul K; Baik, Jason; Yeomans, Larisa; Hitzman, Chuck; Johnson, Allison M; Pawate, Ashtamurthy S; Kenis, Paul J A; Rodriguez-Hornedo, Nair; Stringer, Kathleen A; Rosania, Gus R

    2015-07-01

    In mammals, highly lipophilic small molecule chemical agents can accumulate as inclusions within resident tissue macrophages. In this context, we characterized the biodistribution, chemical composition, and structure of crystal-like drug inclusions (CLDIs) formed by clofazimine (CFZ), a weakly basic lipophilic drug. With prolonged oral dosing, CFZ exhibited a significant partitioning with respect to serum and fat due to massive bioaccumulation and crystallization in the liver and spleen. The NMR, Raman, and powder X-ray diffraction (p-XRD) spectra of CLDIs isolated from the spleens of CFZ-treated mice matched the spectra of pure, CFZ hydrochloride crystals (CFZ-HCl). Elemental analysis revealed a 237-fold increase in chlorine content in CLDIs compared to untreated tissue samples and a 5-fold increase in chlorine content compared to CFZ-HCl, suggesting that the formation of CLDIs occurs through a chloride mediated crystallization mechanism. Single crystal analysis revealed that CFZ-HCl crystals had a densely packed orthorhombic lattice configuration. In vitro, CFZ-HCl formed at a pH of 4-5 only if chloride ions were present at sufficiently high concentrations (>50:1 Cl(-)/CFZ), indicating that intracellular chloride transport mechanisms play a key role in the formation of CLDIs. While microscopy and pharmacokinetic analyses clearly revealed crystallization and intracellular accumulation of the drug in vivo, the chemical and structural characterization of CLDIs implicates a concentrative, chloride transport mechanism, paralleling and thermodynamically stabilizing the massive bioaccumulation of a weakly basic drug. PMID:25926092

  12. Internal Domains of Natural Porous Media Revealed: Critical Locations for Transport, Storage, and Chemical Reaction.

    PubMed

    Zachara, John; Brantley, Sue; Chorover, Jon; Ewing, Robert; Kerisit, Sebastien; Liu, Chongxuan; Perfect, Edmund; Rother, Gernot; Stack, Andrew G

    2016-03-15

    Internal pore domains exist within rocks, lithic fragments, subsurface sediments, and soil aggregates. These domains, termed internal domains in porous media (IDPM), represent a subset of a material's porosity, contain a significant fraction of their porosity as nanopores, dominate the reactive surface area of diverse media types, and are important locations for chemical reactivity and fluid storage. IDPM are key features controlling hydrocarbon release from shales in hydraulic fracture systems, organic matter decomposition in soil, weathering and soil formation, and contaminant behavior in the vadose zone and groundwater. Traditionally difficult to interrogate, advances in instrumentation and imaging methods are providing new insights on the physical structures and chemical attributes of IDPM, and their contributions to system behaviors. Here we discuss analytical methods to characterize IDPM, evaluate information on their size distributions, connectivity, and extended structures; determine whether they exhibit unique chemical reactivity; and assess the potential for their inclusion in reactive transport models. Ongoing developments in measurement technologies and sensitivity, and computer-assisted interpretation will improve understanding of these critical features in the future. Impactful research opportunities exist to advance understanding of IDPM, and to incorporate their effects in reactive transport models for improved environmental simulation and prediction. PMID:26849204

  13. Chemical Analysis of Drug Biocrystals: A Role for Counterion Transport Pathways in Intracellular Drug Disposition

    PubMed Central

    Keswani, Rahul K.; Baik, Jason; Yeomans, Larisa; Hitzman, Chuck; Johnson, Allison; Pawate, Ashtamurthy; Kenis, Paul J. A.; Rodriguez-Hornedo, Nair; Stringer, Kathleen A.; Rosania, Gus R.

    2015-01-01

    In mammals, highly lipophilic small molecule chemical agents can accumulate as inclusions within resident tissue macrophages. In this context, we characterized the biodistribution, chemical composition and structure of crystal-like drug inclusions (CLDIs) formed by clofazimine (CFZ), a weakly basic lipophilic drug. With prolonged oral dosing, CFZ exhibited a significant partitioning with respect to serum and fat due to massive bioaccumulation and crystallization in the liver and spleen. The NMR, Raman and Powder X-ray diffraction (p-XRD) spectra of CLDIs isolated from the spleens of CFZ-treated mice matched the spectra of pure, CFZ hydrochloride crystals (CFZ-HCl). Elemental analysis revealed a 237-fold increase in chlorine content in CLDIs compared to untreated tissue samples, and a five-fold increase in chlorine content compared to CFZ-HCl, suggesting that the formation of CLDIs occurs through a chloride mediated crystallization mechanism. Single crystal analysis revealed that CFZ-HCl crystals had a densely-packed orthorhombic lattice configuration. In vitro, CFZ-HCl formed at a pH of 4–5 only if chloride ions were present at sufficiently high concentrations (>50:1 Cl−:CFZ), indicating that intracellular chloride transport mechanisms play a key role in the formation of CLDIs. While microscopy and pharmacokinetic analyses clearly revealed crystallization and intracellular accumulation of the drug in vivo, the chemical and structural characterization of CLDIs implicates a concentrative, chloride transport mechanism, paralleling and thermodynamically stabilizing, the massive bioaccumulation of a weakly basic drug. PMID:25926092

  14. 3DFATMIC: THREE DIMENSIONAL SUBSURFACE FLOW, FATE AND TRANSPORT OF MICROBES AND CHEMICALS MODEL - USER'S MANUAL VERSION 1.0

    EPA Science Inventory

    This document is the user's manual of 3DFATMIC, a 3-Dimensional Subsurface Flow, Fate and Transport of Microbes and Chemicals Model using a Lagrangian-Eulerian adapted zooming and peak capturing (LEZOOMPC) algorithm.

  15. Analysis of mass transport in an atmospheric pressure remote plasma-enhanced chemical vapor deposition process

    SciTech Connect

    Cardoso, R. P.; Belmonte, T.; Henrion, G.; Gries, T.; Tixhon, E.

    2010-01-15

    In remote microwave plasma enhanced chemical vapor deposition processes operated at atmospheric pressure, high deposition rates are associated with the localization of precursors on the treated surface. We show that mass transport can be advantageously ensured by convection for the heavier precursor, the lighter being driven by turbulent diffusion toward the surface. Transport by laminar diffusion is negligible. The use of high flow rates is mandatory to have a good mixing of species. The use of an injection nozzle with micrometer-sized hole enables us to define accurately the reaction area between the reactive species. The localization of the flow leads to high deposition rates by confining the reactive species over a small area, the deposition yield being therefore very high. Increasing the temperature modifies nonlinearly the deposition rates and the coating properties.

  16. REPRESENTING AEROSOL DYNAMICS AND PROPERTIES IN CHEMICAL TRANSPORT MODELS BY THE METHOD OF MOMENTS.

    SciTech Connect

    SCHWARTZ, S.E.; MCGRAW, R.; BENKOVITZ, C.M.; WRIGHT, D.L.

    2001-04-01

    Atmospheric aerosols, suspensions of solid or liquid particles, are an important multi-phase system. Aerosols scatter and absorb shortwave (solar) radiation, affecting climate (Charlson et al., 1992; Schwartz, 1996) and visibility; nucleate cloud droplet formation, modifying the reflectivity of clouds (Twomey et al., 1984; Schwartz and Slingo, 1996) as well as contributing to composition of cloudwater and to wet deposition (Seinfeld and Pandis, 1998); and affect human health through inhalation (NRC, 1998). Existing and prospective air quality regulations impose standards on concentrations of atmospheric aerosols to protect human health and welfare (EPA, 1998). Chemical transport and transformation models representing the loading and geographical distribution of aerosols and precursor gases are needed to permit development of effective and efficient strategies for meeting air quality standards, and for examining aerosol effects on climate retrospectively and prospectively for different emissions scenarios. Important aerosol properties and processes depend on their size distribution: light scattering, cloud nucleating properties, dry deposition, and penetration into airways of lungs. The evolution of the mass loading itself depends on particle size because of the size dependence of growth and removal processes. For these reasons it is increasingly recognized that chemical transport and transformation models must represent not just the mass loading of atmospheric particulate matter but also the aerosol microphysical properties and the evolution of these properties if aerosols are to be accurately represented in these models. If the size distribution of the aerosol is known, a given property can be evaluated as the integral of the appropriate kernel function over the size distribution. This has motivated the approach of determining aerosol size distribution, and of explicitly representing this distribution and its evolution in chemical transport models.

  17. Effects of Transport and Processing on Aerosol Chemical and Optical Properties Across the Gulf of Maine

    NASA Astrophysics Data System (ADS)

    Quinn, P.; Bates, T.; Baynard, T.; Onasch, T.; Coffman, D.; Covert, D.; Worsnop, D.; Goldan, P.; Kuster, B.; Degouw, J.; Stohl, A.

    2005-12-01

    NEAQS-ITCT 2004 took place in July and August to study natural and anthropogenic emissions from North America including the processing of gas and particle phase species during transport over the North Atlantic and the resulting impact on air quality and climate. During the experiment, measurements were made onboard the NOAA RV Ronald H. Brown with a ship track that extended from the coast along Cape Cod, MA, Boston, MA and Portland, ME, east into the Gulf of Maine and out to Chebogue Point, Nova Scotia. Although measurements on the ship were not made in a true Lagrangian sense, they reveal information about the effects of transport and processing on aerosol chemical and optical properties. Photochemical age based on measured toluene to benzene ratios can be used in this region to indicate 'younger' versus 'older' aerosol. This approach, coupled with FLEXPART estimates of source contributions and age, reveals that continental aerosol becomes more acidic as it ages with transport over the Gulf of Maine. The increasing acidity is due to the conversion of SO2 to SO4= with no further significant input of NH3 in the well-capped marine boundary layer to neutralize the aerosol. In addition, as the aerosol ages, the organic mass fraction decreases while the organics that are present become more oxidized. These same chemical features were observed in aerosol transported from the Ohio River Valley and beyond. In contrast, recently formed aerosol from urban centers along the Eastern Seaboard are neutralized, have a higher organic content, and the organics are less oxidized. The impact of the observed range of aerosol acidity, organic mass fraction, and degree of oxidation of the organic matter on the f(RH) of the aerosol will be described. Here, f(RH) refers to the dependence of light extinction on relative humidity.

  18. Controlling charge transport in blue organic light-emitting devices by chemical functionalization of host materials

    SciTech Connect

    Polikarpov, Evgueni; Koech, Phillip K.; Wang, Liang; Swensen, James S.; Cosimbescu, Lelia; Rainbolt, James E.; Von Ruden, Amber L.; Gaspar, Daniel J.; Padmaperuma, Asanga B.

    2011-01-18

    Generation of white light from OLEDs for general lighting applications requires a highly efficient blue component. However, a stable and power efficient blue OLED component with simple device architecture remains a significant challenge partly due to lack of appropriate host materials. Here we report the photophysical and device properties of ambipolar host phosphine oxide based materials. In this work, we studied the effect of the structural modification made to phosphine oxide-based hosts on the charge balance. We observed significant changes in charge transport within the host occurred upon small modifications to their chemical structure. As a result, an alteration of the chemical design of these materials allows for the control of charge balance of the OLED.

  19. Ionic Transport through Chemically Functionalized Hydrogen Peroxide-Sensitive Asymmetric Nanopores.

    PubMed

    Ali, Mubarak; Ahmed, Ishtiaq; Nasir, Saima; Ramirez, Patricio; Niemeyer, Christof M; Mafe, Salvador; Ensinger, Wolfgang

    2015-09-01

    We describe the fabrication of a chemical-sensitive nanofluidic device based on asymmetric nanopores whose transport characteristics can be modulated upon exposure to hydrogen peroxide (H2O2). We show experimentally and theoretically that the current-voltage curves provide a suitable method to monitor the H2O2-mediated change in pore surface characteristics from the electronic readouts. We demonstrate also that the single pore characteristics can be scaled to the case of a multipore membrane whose electric outputs can be readily controlled. Because H2O2 is an agent significant for medical diagnostics, the results should be useful for sensing nanofluidic devices. PMID:26310320

  20. Controlled VLS Growth of Indium, Gallium and Tin Oxide Nanowiresvia Chemical Vapor Transport

    SciTech Connect

    Johnson, M.C.; Aloni, S.; McCready, D.E.; Bourret-Courchesne, E.D.

    2006-03-13

    We utilized a vapor-liquid-solid growth technique to synthesize indium oxide, gallium oxide, and tin oxide nanowires using chemical vapor transport with gold nanoparticles as the catalyst. Using identical growth parameters we were able to synthesize single crystal nanowires typically 40-100 nm diameter and more than 10-100 microns long. The products were characterized by means of XRD, SEM and HRTEM. All the wires were grown under the same growth conditions with growth rates inversely proportional to the source metal vapor pressure. Initial experiments show that different transparent oxide nanowires can be grown simultaneously on a single substrate with potential application for multi-component gas sensors.

  1. Urban Pollution in the Nocturnal Boundary Layer: Chemical Processing and Vertical Transport

    NASA Astrophysics Data System (ADS)

    Stutz, J.; Flynn, C. J.; Rappenglück, B.; Lefer, B.; Brune, W. H.; Dibb, J. E.; Griffin, R. J.

    2007-12-01

    For many decades research on urban pollution and its chemistry has concentrated on processes occurring during the day. In recent years, however, it has become clear that transport and chemical processing at night can also play an important role for urban air quality. Various chemical pathways are known to remove gaseous pollutants, such as nitrogen oxides, ozone and hydrocarbons, as well as influence aerosol composition at night. The quantification of these processes is difficult due to the influence of vertical stability, which leads to a much slower vertical transport of trace gases emitted at the surface at night than during the day. As a consequence, chemistry at night is often very altitude dependent, making investigations in the NBL challenging. In recent years a number of field experiments have been performed where the nocturnal meteorology and the vertical distribution of the dominant trace gases at night have been observed. Here we will review the lessons learned in past studies and present results from a recent study in Houston, TX, which gives new insights into the meteorological and chemical processes at night. The TexAQS II Radical Measurement Project (TRAMP) was performed in August and September 2006, on the University of Houston campus. We will present data from a number of measurements, including a long-path Differential Optical Absorption Spectrometer, in situ instrumentation for gas phase compounds (O3, NO, NO2, CO, VOC), HOx radicals, aerosol size and composition, various meteorological and radiation parameters, and an aerosol LIDAR. The field observations will be compared to 1D model calculations which show the dominant chemical processes and allow the identification of gaps in our understanding of the polluted nocturnal urban boundary layer.

  2. Effects of carbon-based nanoparticles (CNPs) on the fate of endocrine disrupting chemicals (EDCs) in different agricultural soils.

    NASA Astrophysics Data System (ADS)

    Stumpe, Britta; Wolski, Sabrina; Marschner, Bernd

    2013-04-01

    Nanotechnology is a major innovative scientific and economic growth area. To date there is a lack about possible adverse effects that may be associated with manufactured nanomaterial in terrestrial environments. Since it is known that on the one hand carbon-based nanoparticles (CNPs) and endocrine disrupting chemicals (EDCs) strongly interact in wastewater and that on the other hand CNPs and EDCs are released together via wastewater irrigation to agricultural soils, knowledge of CNP effects on the EDC fate in the soil environment is needed for further risk assessments. The overall goal of this project is to gain a better understanding of interaction of CNPs with EDCs within the soil system. Three different soil samples were applied with different CNPs, EDCs and CNP-EDC complexes and incubated over a period of 6 weeks. The EDC mineralization as well as their uptake by soil microorganisms was monitored to describe impacts of the nanomaterial on the EDC fate. As quality control for the biological soil activity soil respiration, enzyme activities and the soil microbial biomass were monitored in all incubated soil samples. Clearly, EDCs bound in CNP complexes showed a decrease in mineralization. While the free EDCs showed a total mineralization of 34 to 45 %, the nano complexed EDCs were only mineralized to 12 to 15 %. Since no effects of the nanomaterial on the biological soil activity were observed, we conclude that the reduced EDC mineralization is directly linked to their interaction with the CNPs. Since additionally the EDC adsorption to CNPs reduced the EDC uptake by soil microorganism, we assume that CNPs generally form more or less recalcitrant aggregates which likely protect the associated EDCs from degradation.

  3. Chemical form of selenium affects its uptake, transport and glutathione peroxidase activity in the human intestinal Caco-2 cell model

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Determining the effect of selenium (Se) chemical form on uptake and transport in human intestinal cells is critical to assess Se bioavailability. In the present study, we measured the uptake and transport of various Se compounds in the human intestinal Caco-2 cell model. We found that two sources...

  4. High-frequency monitoring reveals nutrient sources and transport processes in an agriculture-dominated lowland water system

    NASA Astrophysics Data System (ADS)

    van der Grift, Bas; Broers, Hans Peter; Berendrecht, Wilbert; Rozemeijer, Joachim; Osté, Leonard; Griffioen, Jasper

    2016-05-01

    Many agriculture-dominated lowland water systems worldwide suffer from eutrophication caused by high nutrient loads. Insight in the hydrochemical functioning of embanked polder catchments is highly relevant for improving the water quality in such areas or for reducing export loads to downstream water bodies. This paper introduces new insights in nutrient sources and transport processes in a polder in the Netherlands situated below sea level using high-frequency monitoring technology at the outlet, where the water is pumped into a higher situated lake, combined with a low-frequency water quality monitoring programme at six locations within the drainage area. Seasonal trends and short-scale temporal dynamics in concentrations indicated that the NO3 concentration at the pumping station originated from N loss from agricultural lands. The NO3 loads appear as losses via tube drains after intensive rainfall events during the winter months due to preferential flow through the cracked clay soil. Transfer function-noise modelling of hourly NO3 concentrations reveals that a large part of the dynamics in NO3 concentrations during the winter months can be related to rainfall. The total phosphorus (TP) concentration and turbidity almost doubled during operation of the pumping station, which points to resuspension of particulate P from channel bed sediments induced by changes in water flow due to pumping. Rainfall events that caused peaks in NO3 concentrations did not results in TP concentration peaks. The rainfall induced and NO3 enriched quick interflow, may also be enriched in TP but retention of TP due to sedimentation of particulate P then results in the absence of rainfall induced TP concentration peaks. Increased TP concentrations associated with run-off events is only observed during a rainfall event at the end of a freeze-thaw cycle. All these observations suggest that the P retention potential of polder water systems is primarily due to the artificial pumping regime

  5. High-frequency monitoring reveals nutrient sources and transport processes in an agriculture-dominated lowland water system

    NASA Astrophysics Data System (ADS)

    van der Grift, B.; Broers, H. P.; Berendrecht, W. L.; Rozemeijer, J. C.; Osté, L. A.; Griffioen, J.

    2015-08-01

    Many agriculture-dominated lowland water systems worldwide suffer from eutrophication caused by high nutrient loads. Insight in the hydrochemical functioning of embanked polder catchments is highly relevant for improving the water quality in such areas. This paper introduces new insights in nutrient sources and transport processes in a low elevated polder in the Netherlands using high-frequency monitoring technology at the outlet, where the water is pumped into a higher situated lake, combined with a low-frequency water quality monitoring program at six locations within the drainage area. Seasonal trends and short scale temporal dynamics in concentrations indicated that the NO3 concentration at the pumping station originated from N-loss from agricultural lands. The NO3 loads appear as losses with drain water discharge after intensive rainfall events during the winter months due to preferential flow through the cracked clay soil. Transfer function-noise modelling of hourly NO3 concentrations reveals that a large part of the dynamics in NO3 concentrations during the winter months can be related to rainfall. The total phosphorus (TP) concentration almost doubled during operation of the pumping station which points to resuspension of particulate P from channel bed sediments induced by changes in water flow due to pumping. Rainfall events that caused peaks in NO3 concentrations did not results in TP concentration peaks. The by rainfall induced and NO3 enriched quick interflow, may also be enriched in TP but this is then buffered in the water system due to sedimentation of particulate P. Increased TP concentrations associated with run-off events is only observed during a rainfall event at the end of a freeze-thaw cycle. All these observations suggest that the P retention potential of polder water systems is highly due to the artificial pumping regime that buffers high flows. As the TP concentration is affected by operation of the pumping station, timing of sampling

  6. Effects of agriculture crop residue burning on aerosol properties and long-range transport over northern India: A study using satellite data and model simulations

    NASA Astrophysics Data System (ADS)

    Vijayakumar, K.; Safai, P. D.; Devara, P. C. S.; Rao, S. Vijaya Bhaskara; Jayasankar, C. K.

    2016-09-01

    Agriculture crop residue burning in the tropics is a major source of the global atmospheric aerosols and monitoring their long-range transport is an important element in climate change studies. In this paper, we study the effects of agriculture crop residue burning on aerosol properties and long-range transport over northern India during a smoke event that occurred between 09 and 17 November 2013, with the help of satellite measurements and model simulation data. Satellite data observations on aerosol properties suggested transport of particles from agriculture crop residue burning in Indo-Gangetic Plains (IGP) over large regions. Additionally, ECMWF winds at 850 hPa have been used to trace the source, path and spatial extent of smoke events. Most of the smoke aerosols, during the study period, travel from a west-to-east pathway from the source-to-sink region. Furthermore, aerosol vertical profiles from CALIPSO show a layer of thick smoke extending from surface to an altitude of about 3 km. Smoke aerosols emitted from biomass burning activity from Punjab have been found to be a major contributor to the deterioration of local air quality over the NE Indian region due to their long range transport.

  7. ABSORPTION DYNAMICS OF ORGANIC CHEMICAL TRANSPORT ACROSS TROUT GILLS AS RELATED TO OCTANOL-WATER PARTITION COEFFICIENT

    EPA Science Inventory

    An in vivo fish preparation was used that allowed a direct measure of the transport rates of 14 different organic chemicals across the gills of rainbow trout (Salmo gairdneri). The chemicals, all 14C labeled, were selected from five classes, encompassing a range of octanol-water ...

  8. A reaction-based paradigm to model reactive chemical transport in groundwater with general kinetic and equilibrium reactions

    SciTech Connect

    Zhang, Fan; Yeh, Gour-Tsyh; Parker, Jack C; Brooks, Scott C; Pace, Molly; Kim, Young Jin; Jardine, Philip M; Watson, David B

    2007-01-01

    This paper presents a reaction-based water quality transport model in subsurface flow systems. Transport of chemical species with a variety of chemical and physical processes is mathematically described by M partial differential equations (PDEs). Decomposition via Gauss-Jordan column reduction of the reaction network transforms M species reactive transport equations into two sets of equations: a set of thermodynamic equilibrium equations representing NE equilibrium reactions and a set of reactive transport equations of M-NE kinetic-variables involving no equilibrium reactions (a kinetic-variable is a linear combination of species). The elimination of equilibrium reactions from reactive transport equations allows robust and efficient numerical integration. The model solves the PDEs of kinetic-variables rather than individual chemical species, which reduces the number of reactive transport equations and simplifies the reaction terms in the equations. A variety of numerical methods are investigated for solving the coupled transport and reaction equations. Simulation comparisons with exact solutions were performed to verify numerical accuracy and assess the effectiveness of various numerical strategies to deal with different application circumstances. Two validation examples involving simulations of uranium transport in soil columns are presented to evaluate the ability of the model to simulate reactive transport with complex reaction networks involving both kinetic and equilibrium reactions.

  9. Purified Silicon Film Formation from Metallurgical-Grade Silicon by Hydrogen-Plasma-Induced Chemical Transport

    NASA Astrophysics Data System (ADS)

    Ohmi, Hiromasa; Yamada, Takahiro; Kakiuchi, Hiroaki; Yasutake, Kiyoshi

    2011-08-01

    A purified Si film is prepared directly from metallurgical-grade (MG) Si by chemical transport using sub-atmospheric pressure H2 plasma. The purification mechanism is based on the selective etching of Si using atomic H. It is demonstrated that the concentrations of most metal impurities (e.g., Fe, Cr, Ni, Ti, and Mn) in the prepared Si film are in the acceptable range for solar-grade Si material, or below the determination limit of the several impurity measuring methods employed in this study. From the infrared absorption measurements of the etching product produced by the reaction between H2 plasma and MG-Si, it is found that the main etching product is SiH4. Therefore, a remote-type chemical transport process is developed to produce SiH4 gas directly from MG-Si. Using other purifying principles (such as a pyrolysis filter in combination with this process), it is demonstrated that purified Si films about B, P and metal atoms can be produced from metallurgical-grade Si (<98% purity).

  10. Reactive chemical transport in ground-water hydrology: Challenges to mathematical modeling

    SciTech Connect

    Narasimhan, T.N.; Apps, J.A.

    1990-07-01

    For a long time, earth scientists have qualitatively recognized that mineral assemblages in soils and rocks conform to established principles of chemistry. In the early 1960's geochemists began systematizing this knowledge by developing quantitative thermodynamic models based on equilibrium considerations. These models have since been coupled with advective-dispersive-diffusive transport models, already developed by ground-water hydrologists. Spurred by a need for handling difficult environmental issues related to ground-water contamination, these models are being improved, refined and applied to realistic problems of interest. There is little doubt that these models will play an important role in solving important problems of engineering as well as science over the coming years. Even as these models are being used practically, there is scope for their improvement and many challenges lie ahead. In addition to improving the conceptual basis of the governing equations, much remains to be done to incorporate kinetic processes and biological mediation into extant chemical equilibrium models. Much also remains to be learned about the limits to which model predictability can be reasonably taken. The purpose of this paper is to broadly assess the current status of knowledge in modeling reactive chemical transport and to identify the challenges that lie ahead.

  11. Correlating Transport with Nanostructure and Chemical Identity in Radical Polymer Conducting Glasses

    NASA Astrophysics Data System (ADS)

    Boudouris, Bryan; Rostro, Lizbeth; Baradwaj, Aditya; Hay, Martha

    2015-03-01

    Radical polymers are an emerging class of macromolecules that are composed of non-conjugated backbones which bear stable radical groups at the pendant positions. Because of these stable radical sites, these glassy materials are able to conduct charge in the solid state through a series of oxidation-reduction (redox) reactions. Importantly, the redox-active behavior is controlled by both the local chemical environment of the radical polymer groups and by the nanoscale structure of the materials. Here, we demonstrate that proper control of the pendant group chemical functionality allows for the fabrication of transparent and conducting amorphous thin films which have solid-state hole mobility and electrical conductivity values on the same order as those seen in common conjugated, semicrystalline polymer systems [e.g., poly(3-hexylthiophene) (P3HT)]. Furthermore, we show that control of the nanostructure of the materials aids in facilitating transport in these radical polymer thin films. In turn, we implement simultaneous spectroscopic and electrical characterization measurements in order to elucidate the exact mechanism of charge transport in radical polymers. Finally, we demonstrate that, because there is ready control over the molecular properties of these materials, developing bendable and stretchable transparent conducting thin films is relatively straightforward with this unique class of organic electronic materials.

  12. Chemically assisted vapour transport for bulk ZnO crystal growth

    NASA Astrophysics Data System (ADS)

    Santailler, Jean-Louis; Audoin, Claire; Chichignoud, Guy; Obrecht, Rémy; Kaouache, Belkhiri; Marotel, Pascal; Pelenc, Denis; Brochen, Stéphane; Merlin, Jérémy; Bisotto, Isabelle; Granier, Carole; Feuillet, Guy; Levy, François

    2010-11-01

    A chemically assisted vapour phase transport (CVT) method is proposed for the growth of bulk ZnO crystals. Thermodynamic computations have confirmed the possibility of using CO as a sublimation activator for enhancing the sublimation rate of the feed material in a large range of pressures (10 -3 to 1 atm) and temperatures (800-1200 °C). Growth runs in a specific and patented design yielded single ZnO crystals up to 46 mm in diameter and 8 mm in thickness, with growth rates up to 400 μm/h. These values are compatible with an industrial production rate. N type ZnO crystals ( μ=182 cm 2/(V s) and n=7 10 15 cm -3) obtained by this CVT method (Chemical Vapour Transport) present a high level of purity (10-30 times better than hydrothermal ZnO crystals), which may be an advantage for obtaining p-type doped layers ([Li] and [Al] <10 +15 cm -3). Structural (HR-XRD), defect density (EPD), electrical (Hall measurements) and optical (photoluminescence) properties are presented.

  13. Agricultural production in the United States by county: a compilation of information from the 1974 census of agriculture for use in terrestrial food-chain transport and assessment models

    SciTech Connect

    Shor, R.W.; Baes, C.F. III; Sharp, R.D.

    1982-01-01

    Terrestrial food-chain models that simulate the transport of environmentally released radionuclides incorporate parameters describing agricultural production and practice. Often a single set of default parameters, such as that listed in USNRC Regulatory Guide 1.109, is used in lieu of site-specific information. However, the geographical diversity of agricultural practice in the United States suggests the limitations of a single set of default parameters for assessment models. This report documents default parameters with a county-wide resolution based on analysis of the 1974 US Census of Agriculture for use in terrestrial food chain models. Data reported by county, together with state-based information from the US Department of Agriculture, Economic and Statistics Service, provided the basis for estimates of model input parameters. This report also describes these data bases, their limitations, and lists default parameters by county. Vegetable production is described for four categories: leafy vegetables; vegetables and fruits exposed to airborne material; vegetables, fruits, and nuts protected from airborne materials; and grains. Livestock feeds were analyzed in categories of hay, silage, pasture, and grains. Pasture consumption was estimated from cattle and sheep inventories, their feed requirements, and reported quantities of harvested forage. The results were compared with assumed yields of the pasture areas reported. In addition, non-vegetable food production estimates including milk, beef, pork, lamb, poultry, eggs, goat milk, and honey are described. The agricultural parameters and land use information - in all 47 items - are tabulated in four appendices for each of the 3067 counties of the US reported to the Census of Agriculture, excluding those in Hawaii and Alaska.

  14. Modelling the optical properties of aerosols in a chemical transport model

    NASA Astrophysics Data System (ADS)

    Andersson, E.; Kahnert, M.

    2015-12-01

    According to the IPCC fifth assessment report (2013), clouds and aerosols still contribute to the largest uncertainty when estimating and interpreting changes to the Earth's energy budget. Therefore, understanding the interaction between radiation and aerosols is both crucial for remote sensing observations and modelling the climate forcing arising from aerosols. Carbon particles are the largest contributor to the aerosol absorption of solar radiation, thereby enhancing the warming of the planet. Modelling the radiative properties of carbon particles is a hard task and involves many uncertainties arising from the difficulties of accounting for the morphologies and heterogeneous chemical composition of the particles. This study aims to compare two ways of modelling the optical properties of aerosols simulated by a chemical transport model. The first method models particle optical properties as homogeneous spheres and are externally mixed. This is a simple model that is particularly easy to use in data assimilation methods, since the optics model is linear. The second method involves a core-shell internal mixture of soot, where sulphate, nitrate, ammonia, organic carbon, sea salt, and water are contained in the shell. However, by contrast to previously used core-shell models, only part of the carbon is concentrated in the core, while the remaining part is homogeneously mixed with the shell. The chemical transport model (CTM) simulations are done regionally over Europe with the Multiple-scale Atmospheric Transport and CHemistry (MATCH) model, developed by the Swedish Meteorological and Hydrological Institute (SMHI). The MATCH model was run with both an aerosol dynamics module, called SALSA, and with a regular "bulk" approach, i.e., a mass transport model without aerosol dynamics. Two events from 2007 are used in the analysis, one with high (22/12-2007) and one with low (22/6-2007) levels of elemental carbon (EC) over Europe. The results of the study help to assess the

  15. Determining rates of chemical weathering in soils - Solute transport versus profile evolution

    USGS Publications Warehouse

    Stonestrom, D.A.; White, A.F.; Akstin, K.C.

    1998-01-01

    SiO2 fluxes associated with contemporary solute transport in three deeply weathered granitoid profiles are compared to bulk SiO2 losses that have occurred during regolith development. Climates at the three profiles range from Mediterranean to humid to tropical. Due to shallow impeding alluvial layers at two of the profiles, and seasonally uniform rainfall at the third, temporal variations in hydraulic and chemical state variables are largely attenuated below depths of 1-2 m. This allows current SiO2 fluxes below the zone of seasonal variations to be estimated from pore-water concentrations and average hydraulic flux densities. Mean-annual SiO2 concentrations were 0.1-1.5 mM. Hydraulic conductivities for the investigated range of soil-moisture saturations ranged from 10-6 m s-1. Estimated hydraulic flux densities for quasi-steady portions of the profiles varied from 6 x 10-9 to 14 x 10-9 m s-1 based on Darcy's law and field measurements of moisture saturations and pressure heads. Corresponding fluid-residence times in the profiles ranged from 10 to 44 years. Total SiO2 losses, based on chemical and volumetric changes in the respective profiles, ranged from 19 to 110 kmoles SiO2 m-2 of land surface as a result of 0.2-0.4 Ma of chemical weathering. Extrapolation of contemporary solute fluxes to comparable time periods reproduced these SiO2 losses to about an order of magnitude. Despite the large range and non-linearity of measured hydraulic conductivities, solute transport rates in weathering regoliths can be estimated from characterization of hydrologic conditions at sufficiently large depths. The agreement suggests that current weathering rates are representative of long-term average weathering rates in the regoliths.SiO2 fluxes associated with contemporary solute transport in three deeply weathered granitoid profiles are compared to bulk SiO2 losses during regolith development. Due to shallow impeding alluvial layers at two of the profiles, and seasonally uniform

  16. Transport-induced shifts in condensate dew-point and composition in multicomponent systems with chemical reaction

    NASA Technical Reports Server (NTRS)

    Rosner, D. E.; Nagarajan, R.

    1985-01-01

    Partial heterogeneous condensation phenomena in multicomponent reacting systems are analyzed taking into consideration the chemical element transport phenomena. It is demonstrated that the dew-point surface temperature in chemically reactive systems is not a purely thermodynamic quantity, but is influenced by the multicomponent diffusion and Soret-mass diffusion phenomena. Several distinct dew-points are shown to exist in such systems and, as a result of transport constraints, the 'sharp' locus between two chemically distinct condensates is systematically moved to a difference mainstream composition.

  17. A nested grid formulation for chemical transport over Asia: Applications to CO

    NASA Astrophysics Data System (ADS)

    Wang, Yuxuan X.; McElroy, Michael B.; Jacob, Daniel J.; Yantosca, Robert M.

    2004-11-01

    A global three-dimensional chemical transport model (GEOS-CHEM) was modified to permit treatment of a limited spatial regime with resolution higher than that adopted for the global background. Identified as a one-way nested grid formulation, the model was applied to a simulation of CO over Asia during spring 2001. Differences between results obtained using the nested grid (resolution 1° × 1°), the coarse global model (resolution 4° × 5°), and the intermediate global model (resolution 2° × 2.5°) are discussed. The higher-resolution model allows for more efficient, advection-related, ventilation of the lower atmosphere, reflecting the significance of localized regions of intense upward motion not resolved in a coarser-resolution simulation. Budget analysis suggests that upward transfer to higher altitudes through large-scale advection provides the major sink for CO below 4 km. Horizontal advection, mainly through the north boundary, contributes a net source of CO to the window domain despite the polluted nature of the study region. The nested-grid model is shown to provide good agreement with measurements made during the Transport and Chemical Evolution over the Pacific (TRACE-P) campaign in spring 2001, notably better than the low-resolution model in simulating frontal lifting process and differences across the boundary separating the regions of cyclonic and anticyclonic flow. The high-resolution window approach also allows us to differentiate transport mechanisms for individual subregions of China on a much finer scale than was possible previously. Suggestions are made as to how to allow for subgrid vertical advective motions in the low-resolution model through a carefully designed and broadly tested eddy diffusion treatment.

  18. Impact of long-term wastewater irrigation on sorption and transport of atrazine in Mexican agricultural soils.

    PubMed

    Müller, K; Duwig, C; Prado, B; Siebe, C; Hidalgo, C; Etchevers, J

    2012-01-01

    In the Mezquital Valley, Mexico, crops have been irrigated with untreated municipal wastewater for more than a century. Atrazine has been applied to maize and alfalfa grown in the area for weed control for 15 years. Our objectives were to analyse (i) how wastewater irrigation affects the filtering of atrazine, and (ii) if the length of irrigation has a significant impact. We compared atrazine sorption to Phaeozems that have been irrigated with raw wastewater for 35 (P35) and 85 (P85) years with sorption to a non-irrigated (P0) Phaeozem soil under rainfed agriculture. The use of bromide as an inert water tracer in column experiments and the subsequent analysis of the tracers' breakthrough curves allowed the calibration of the hydrodynamic parameters of a two-site non equilibrium convection-dispersion model. The quality of the irrigation water significantly altered the soils' hydrodynamic properties (hydraulic conductivity, dispersivity and the size of pores that are hydraulically active). The impacts on soil chemical properties (total organic carbon content and pH) were not significant, while the sodium adsorption ratio was significantly increased. Sorption and desorption isotherms, determined in batch and column experiments, showed enhanced atrazine sorption and reduced and slower desorption in wastewater-irrigated soils. These effects increased with the length of irrigation. The intensified sorption-desorption hysteresis in wastewater-irrigated soils indicated that the soil organic matter developed in these soils had fewer high-energy, easily accessible sorption sites available, leading to lower and slower atrazine desorption rates. This study leads to the conclusion that wastewater irrigation decreases atrazine mobility in the Mezquital valley Phaeozems by decreasing the hydraulic conductivity and increasing the soil's sorption capacity. PMID:22022786

  19. Constraining chemical geothermometry with reactive transport models: An example study of the Dixie Valley geothermal area

    NASA Astrophysics Data System (ADS)

    Wanner, C.; Peiffer, L.; Spycher, N.; Sonnenthal, E. L.; Iovenitti, J. L.; Kennedy, B. M.

    2012-12-01

    In this study, 1D and 2D reactive transport simulations of the Dixie Valley geothermal area (Nevada, USA) were performed using Toughreact [1] to evaluate the fluid flow pathways and rates of equilibration of hydrothermal fluids. Modeling studies were combined with new multicomponent geothermometry, which is being used to estimate the temperature of geothermal reservoirs based on chemical analysis of geothermal springs. The concept is based on the assumption of chemical equilibrium between the thermal fluid and minerals of the reservoir rock [2]. If re-equilibration occurs between the reservoir at depth and the surface, then the 'deep' chemical signature of the fluid is lost and the obtained reservoir temperature is underestimated. The simulations were run for a vertical cross-section that has been structurally and geologically characterized. Model calibration was performed using available site information such as chemical analysis of geothermal springs, isotherms inferred from geothermal wells and results of a previous flow simulation study [3]. Model runs included the simulation of typical near-surface processes such as dilution, mixing and salt leaching occurring at the Dixie Valley geothermal area. Each reactive transport model produced 'synthetic' waters that were processed using the multicomponent chemical geothermometer code GeoT [4]. This code computes the saturation indices of reservoir minerals as a function of the temperature. Reservoir temperature is inferred when mineral saturation indices all cluster around zero. GeoT results were also compared with classical solute geothermometers (silica, Na-K-(Ca), K-Mg) [5]. Simulation results reveal that a minimum vertical fluid velocity on the order of a meter per day is needed to preserve the geochemical signature of a geothermal reservoir and to predict its temperature. The simulations also show that deep geochemical signatures are well preserved if fracture surfaces are partially coated by secondary minerals

  20. Acoustic wave detection of chemical species electrokinetically transported within a capillary tube.

    PubMed

    Li, Paul C H; Prasad, Ronald

    2003-06-01

    For the first time, we report the acoustic wave detection of chemical species being transported in a capillary tube to a region where acoustic coupling occurs. The measured parameter was a change in phase, which was originally only attributed to a change in solution density as the analyte passed by the detection region. Accordingly, we report the detection of change in phase as various chemical species (e.g. Cy5 dye, Cy5-derivatized glycine and underivatized glycine) were introduced into and migrated along a capillary tube through electrokinetic processes. To improve detection sensitivity, we modified various experimental parameters, such as run buffer concentration, capillary wall thickness and transducer frequency. Although acoustic wave detection was feasible, the peak width and detection limit were inadequate as compared to conventional detection methods for HPLC or CE. Nevertheless, the effects of various physical and chemical relaxation processes on acoustic wave absorption were discussed, and this has shed some light on explaining some observations, which cannot be explained by density differences alone. Accordingly, the acoustic wave method is suggested to investigate these processes, as studied in ultrasonic relaxation spectroscopy, in a flow system. PMID:12866892

  1. Bacteriophage adsorption during transport through porous media: Chemical perturbations and reversibility

    USGS Publications Warehouse

    Bales, R.C.; Hinkle, S.R.; Kroeger, T.W.; Stocking, K.; Gerba, C.P.

    1991-01-01

    In a series of seven column experiments, attachment of the bacteriophage PRD-1 and MS-2 to silica beads at pH's 5.0-5.5 was at least partially reversible; however, release of attached phage was slow and breakthrough curves exhibited significant tailing. Rate coefficients for attachment and detachment were on the order of 10-4 and 10-6-10-4 s-1, respectively. Corresponding time scales were hours for attachment and days for detachment. The sticking efficiency (??) for phage attachment was near 0.01. The rate of phage release was enhanced by raising pH and introducing surface-active chemical species, illustrating the importance of chemical perturbations in promoting biocolloid transport. In a series of batch experiments, MS-2 adsorbed strongly to a hydrophobic surface, octadecyltrichlorosilane-bonded silica, at both pH's 5 and 7. Adsorption to the unbonded silica at pH 5 was linear, but was 2.5 (with Ca2+) to 0.25% (without Ca2+) of that to the bonded surface. Neither MS-2 nor PRD-1 adsorbed to unbonded silica at pH 7. Hydrophobic effects appear to be important for adsorption of even relatively hydrophilic biocolloids. ?? 1991 American Chemical Society.

  2. Chemically- and mechanically-mediated influences on the transport and mechanical characteristics of rock fractures

    SciTech Connect

    Min, K.-B.; Rutqvist, J.; Elsworth, D.

    2009-02-01

    A model is presented to represent changes in the mechanical and transport characteristics of fractured rock that result from coupled mechanical and chemical effects. The specific influence is the elevation of dissolution rates on contacting asperities, which results in a stress- and temperature-dependent permanent closure. A model representing this pressure-dissolution-like behavior is adapted to define the threshold and resulting response in terms of fundamental thermodynamic properties of a contacting fracture. These relations are incorporated in a stress-stiffening model of fracture closure to define the stress- and temperature-dependency of aperture loss and behavior during stress and temperature cycling. These models compare well with laboratory and field experiments, representing both decoupled isobaric and isothermal responses. The model was applied to explore the impact of these responses on heated structures in rock. The result showed a reduction in ultimate induced stresses over the case where chemical effects were not incorporated, with permanent reduction in final stresses after cooling to ambient conditions. Similarly, permeabilities may be lower than they were in the case where chemical effects were not considered, with a net reduction apparent even after cooling to ambient temperature. These heretofore-neglected effects may have a correspondingly significant impact on the performance of heated structures in rock, such as repositories for the containment of radioactive wastes.

  3. Investigation of chemical properties and transport phenomena associated with pollutants in the atmospheric boundary layer

    NASA Astrophysics Data System (ADS)

    Holmes, Heather A.

    Under the Clean Air Act, the U.S. Environmental Protection Agency is required to determine which air pollutants are harmful to human health, then regulate, monitor and establish criteria levels for these pollutants. To accomplish this and for scientific advancement, integration of knowledge from several disciplines is required including: engineering, atmospheric science, chemistry and public health. Recently, a shift has been made to establish interdisciplinary research groups to better understand the atmospheric processes that govern the transport of pollutants and chemical reactions of species in the atmospheric boundary layer (ABL). The primary reason for interdisciplinary collaboration is the need for atmospheric processes to be treated as a coupled system, and to design experiments that measure meteorological, chemical and physical variables simultaneously so forecasting models can be improved (i.e., meteorological and chemical process models). This dissertation focuses on integrating research disciplines to provide a more complete framework to study pollutants in the ABL. For example, chemical characterization of particulate matter (PM) and the physical processes governing PM distribution and mixing are combined to provide more comprehensive data for source apportionment. Data from three field experiments were utilized to study turbulence, meteorological and chemical parameters in the ABL. Two air quality field studies were conducted on the U.S./Mexico border. The first was located in Yuma, AZ to investigate the spatial and temporal variability of PM in an urban environment and relate chemical properties of ambient aerosols to physical findings. The second border air quality study was conducted in Nogales, Sonora, Mexico to investigate the relationship between indoor and outdoor air quality in order to better correlate cooking fuel types and home activities to elevated indoor PM concentrations. The final study was executed in southern Idaho and focused on

  4. Use of vegetated agricultural drainage ditches to decrease pesticide transport from tomato and alfalfa fields in California, USA

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Irrigation and storm water runoff from agricultural fields has the potential to cause impairment to downstream aquatic receiving systems. Over the last several years, scientists have discovered the benefit of using edge-of-field practices, such as vegetated agricultural drainage ditches, in the mit...

  5. Chemical Tracers as an Indicator of Transport in the UT/LS

    NASA Astrophysics Data System (ADS)

    Moore, F. L.; Hurst, D. F.; Elkins, J. W.; Nance, J. D.; Dutton, G. S.; Hall, B. D.

    2009-12-01

    Previous airborne studies have proven the scientific value of chemical tracers in examining transport of the Upper Troposphere and Lower Stratosphere (UT/LS). ESRL scientists operated two airborne gas chromatographs on the NCAR G-V during the NSF sponsored Stratosphere-Troposphere Analyses of Regional Transport START-08 campaign over the midlatitudes of central North America. The Unmanned aircraft systems Chromatograph for Atmospheric Trace Species (UCATS) is comprised of a two-channel electron capture detection-gas chromatograph (ECD-GC), an ozone absorption photometer, and a water vapor tunable diode laser spectrometer. It measures N2O and SF6 every 70 seconds on one EC-GC channel, and H2, CO, and CH4 every 140 seconds on the second channel. PAN and Trace Hydrohalocarbon ExpeRiment (PANTHER) is a six-channel gas chromatograph with four ECD-GC channels and two mass selective detector-gas chromatograph (MSD-GC) channels that double the sampling rate to 180 seconds by using two traps and columns. The ECD-GC channels measure N2O, SF6, CFC-11, CFC-12, halon-1211, and PAN once every 70 seconds, H2, CH4, and CO once every 140 seconds. The two MSD-GC channels measure methyl halides (CH3I, CH3Cl, CH3I), HCFCs (22, 141b, 142b), HFC-134a, sulfur gases (COS and CS2) once every 180 seconds. These data represent a diversity of atmospheric lifetimes and are useful in examining transport in UT/LS. One example is the tracer-tracer correlation plot of N2O versus SF6, which shows three distinction regions of transport, LS, tropospause transition, and UT. Tropospheric gradients for both gases are apparent in the UT region. Other correlations will be shown in this presentation. A comparison of common species measured between UCATS and PANTHER shows a better than one percent agreement between the two instruments.

  6. Spatial/temporal photocurrent and electronic transport in monolayer molybdenum disulfide grown by chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Yang, Zhengfeng; Grassi, Roberto; Freitag, Marcus; Lee, Yi-Hsien; Low, Tony; Zhu, Wenjuan

    2016-02-01

    We systematically investigate the spatial/temporal photocurrent in photodetectors and electronic transport in transistors/Hall-bar devices based on monolayer MoS2 grown by chemical vapor deposition (CVD). We found that the maximum photocurrent occurs when the laser spot is close to the metal/MoS2 contact and is tunable by the applied drain voltage, which can be explained by the modulation of the local electric field at the Schottky barrier, consistent with predictions from our quantum transport simulation. We observed that the maximum photocurrent at drain contact is much larger than the one at the source contact, and the DC currents show rectifying behavior. These phenomena can be explained by the different Schottky barrier heights at the two contacts. By measuring Hall-bar structure at various temperatures from 100 K to 400 K, we extracted the barrier heights at the source and drain contacts, separately. We found that the barrier height at drain contact is about 50 mV larger than the one at the source contact, consistent with the photocurrent and DC current observations. We measured the photocurrent at various powers, and a photoresponsivity of 3.07 mA/W was extracted at low powers. When the power increases above 20 μW, the photocurrent starts to saturate. Temporal response of the photocurrent is also dependent on the laser power. At high laser powers, photocurrent overshoot was observed. The photocurrent saturation at high powers and the overshoot in temporal photocurrent are likely due to the same mechanism: an accumulation of electrons in the channel, flattening out the band structure, since the laser spot is located near the drain contact in these measurements. These studies of photocurrents and electronic transport in CVD MoS2 highlight the importance of the contacts in the electronic/optoelectronic devices and reveal the physical mechanism of the photocurrent/electronic transport in these devices.

  7. Chemical characteristics and source apportionment of PM2.5 during the harvest season in eastern China's agricultural regions

    NASA Astrophysics Data System (ADS)

    Li, Jianfeng; Song, Yu; Mao, Yi; Mao, Zhichun; Wu, Yusheng; Li, Mengmeng; Huang, Xin; He, Qichao; Hu, Min

    2014-08-01

    To determine the contribution of the open burning of wheat straw residues to local PM2.5 during the harvest season of June 2013, PM2.5 was sampled in an agricultural region in eastern China. The sampling site was approximately 1 km from the nearest wheat field. Chemical compositions were analyzed, and source apportionment was undertaken using the positive matrix factorization model. The average PM2.5 concentration was 110.7 μg/m3, containing 36.4 μg/m3 organics, 7.3 μg/m3 EC, 6.0 μg/m3 potassium (K) and 4.9 μg/m3 chloride ion (Cl-). The sampling period was divided into three phases: the pre-local-burning phase (Phase 1), the local-burning phase (Phase 2) and the post-local-burning phase (Phase 3). In Phase 2, the concentrations of PM2.5 and the organics, EC, K and Cl- in PM2.5 were 163.6 μg/m3, 59.0 μg/m3, 12.2 μg/m3, 11.0 μg/m3 and 10.8 μg/m3, respectively, which were all remarkably higher than in both Phase 1 and Phase 3. Eight sources of PM2.5 were determined, including two types of wheat residue burning sources, which showed a significant difference in Cl- content. The atmospheric relative humidity (RH) and the aging process of PM2.5 might be the causes: only fresh particulate emissions from wheat residue burning could feature high-concentration Cl- under high RH conditions. In Phase 2, wheat residue burning contributed 51.3% of PM2.5, 75.8% of OC, 74.5% of EC, 90.1% of K and 104.1% of Cl-. These percentages were lower in Phases 1 and 3 than in Phase 2. Wheat residue burning caused such severe air pollution that it's necessary to prohibit the open burning of crop residues in order to protect public health and the environment.

  8. Nonpoint-source agricultural chemicals in ground water in Nebraska; preliminary results for six areas of the High Plains Aquifer

    USGS Publications Warehouse

    Chen, Hsiu-Hsiung; Druliner, A.D.

    1987-01-01

    The reconnaissance phase of a study to determine the occurrence of agricultural chemicals from nonpoint sources in groundwater in six areas, which represented the major provinces of the High Plains aquifer in Nebraska is described. In 1984, water from 82 wells in the 6 study areas was analyzed for nitrate, and water from 57 of the 82 wells was analyzed for triazine herbicides. Data for 9 of the 21 independent variables suspected of affecting concentrations of nitrate and triazine herbicides in groundwater were compiled from the 82 well sites. The variables and their ranges are: hydraulic gradient (XI), 0.006-0.0053; hydraulic conductivity (X2), 5-149 ft/day; specific discharge (X3), 0.0128-0.2998 ft/day; depth to water (X4), 3-239 ft; well depth (X5), 40-550 ft; annual precipitation (X6), 12.0-39.3 inches; soil permeability (X7), 0.76-9.0 inches; irrigation well density (X8), 0-8 irrigation wells/ sq mi; and annual nitrogen fertilizer use (X9), 0-260 lbs of nitrogen/acre. Nitrate concentrations ranged from < 0.1 to 45 mg/L as nitrogen. Triazine herbicide concentrations were detected in samples from five of the six study areas in concentrations ranging from < 0.1 to 2.3 mg/L. Statistical tests indicated that there were significant differences in nitrate concentrations among the six study areas, while no significant differences in triazine herbicide concentrations were found. Concentrations of nitrate and triazine herbicide were significantly larger in more intensively irrigated areas. Preliminary correlations with the independent variables and nitrate concentrations indicated significant relations at the 95% confidence level with variables X2, X5, and X8. Correlations with triazine herbicide concentrations indicated significant relations with variables X2 , X3, X5, X6, and X8, and with nitrate concentrations (X10). By using a simple multiple regression technique, variables X5, X8, and X9 explained about 51% of the variation in nitrate concentrations. Variables X3

  9. Sorption and Transport of Pharmaceutical chemicals in Organic- and Mineral-rich Soils

    NASA Astrophysics Data System (ADS)

    Vulava, V. M.; Schwindaman, J.; Murphey, V.; Kuzma, S.; Cory, W.

    2011-12-01

    OC, again indicating that these PhACs preferentially partition into the soil OM. Such a correlation was absent for cetirizine. Breakthrough curves of PhACs measured in homogeneous packed soil columns indicated that PhAC transport was affected by chemical nonequilibrium processes depending on the soil and PhAC chemistry. The shape of the breakthrough curves indicated that there were two distinct sorption sites - OM and clay minerals - which influence nonequilibrium transport of these compounds. The retardation factor estimated using the distribution coefficient, Kd, measured from the sorption experiments was very similar to the measured value. While the sorption and transport data do not provide mechanistic information regarding the nature of PhAC interaction with chemical reactive components within geological materials, they do provide important information regarding potential fate of such compounds in the environment. The results also show the role that soil OM and mineral surfaces play in sequestering or transporting these chemicals. These insights have implications to the quality of the water resources in our communities.

  10. [Cumulative risk assessment for consumers of agricultural crops polluted with one chemical class pesticide residues (case of triazole fungicides)].

    PubMed

    Koval'chuk, N M; Omel'chuk, S T

    2011-01-01

    Different indices of cumulative risk assessment of combination of residues of pesticides which may simultaneously be present in raw agricultural crops, based on toxic evaluation of such combination have been presented. Risk for population health due to consumption of raw agricultural crops with triazole residues is acceptable on hazard index, point of departure index and cumulative risk index, exceeds allowable level on criterion "total margin of exposure". PMID:22768736

  11. Long-range transport of Saharan dust and chemical transformations over the Eastern Mediterranean

    NASA Astrophysics Data System (ADS)

    Athanasopoulou, E.; Protonotariou, A.; Papangelis, G.; Tombrou, M.; Mihalopoulos, N.; Gerasopoulos, E.

    2016-09-01

    Three recent Saharan dust outbreaks during different seasons (4-6 days in winter of 2009, late autumn of 2010 and summer of 2011) are selected in order to study the chemical footprint and aging processes of dust intrusions over the Eastern Mediterranean (EM). The applied model system (PMCAMx, WRF and GEOS-CHEM) and methodology are found competent to reproduce dust production, long-range transport and chemical transformations over the EM, with the synergistic use of synoptic patterns analysis, optical depth retrievals, back-trajectories, surface and satellite aerosol measurements. The dust loads were high during the cold period events and much lighter during summertime, when transport was mainly in the free troposphere. In all cases, dust originated from the northwest and/or west Saharan desert and reached the EM from the west/southwest. Sensitivity runs underlie the effect of dust transport on the chemical constituents of aerosols over the EM and show a large impact on calcium (70-90% of maximum daily values 2-5 μg m-3), with its gradient at surface level being around -10% per 100 km along the dust pathway. For the cold period cases, this value can also be considered analogous to the dust dissipation ratio, because the plume is vertically extended down to the surface layers. Interestingly, the surface particulate nitrate concentrations over the EM are reversely affected by the approaching dust loads, exhibiting the highest values (up to 6 μg m-3) and the largest dust fraction (ca. 70%) during summertime. This is attributed to the enhanced nitric acid formation under high atmospheric temperature and insolation, its uptake onto the carbonate dust particles, and their effective accumulation, due to low deposition rates over the sea and scarce precipitation. Sulfate formation onto dust particles is found insignificant (rapid reaction with ammonia and/or sea-salt), while the influence of dust and sea-salt on sodium, when spatio-temporal averages are calculated, is

  12. Nonlocal transport of chemically reactive, degradable species in heterogeneous porous media. Final report

    SciTech Connect

    Cushman, J.H.

    1998-07-30

    One of the most significant challenges facing environmental engineers and scientists is predicting the movement and degradation of chemicals in hierarchical porous media. The distribution of subsurface properties is poorly known because of the inaccessibility of the subsurface environment and the random nature of the geologic deposition process. In addition, the subsurface often possesses distinct physical, chemical and biological hierarchies, which complicates the ability to successfully characterize and thus predict property distributions and processes with information from a limited number of sample locations over a limited number of scales. Knowledge of the spatial structure of microbial populations and activities and the dynamic environmental factors that control this spatial structure are important in characterizing sites for remediation and disposal, and for the ability to effectively deliver nutrients to promote degradation and stabilization. To do so effectively requires a correct theoretical formulation of the problem, implementation of this formulation for predictive purposes, and even more importantly knowledge of what should be measured and how and when to measure it. The contents of this report is as follows: (Section 2) statement of goals, (Section 3) development of nonlocal models for chemical transport with uncertainty in biological, physical and chemical data, (Section 4) a discussion of molecular-scale phenomena of relevance to adsorption and flow in nanoporous materials such as clays, (Section 5) meso and macroscale models of flow in, and deformation of, clays, (Section 6) collaborative efforts with DOE labs, (Section 7) P.I. awards, (Section 8) publications resulting from the research efforts supported through this grant, and finally students supported under this grant.

  13. Insight into the numerical challenges of implementing 2-dimensional SOA models in atmospheric chemical transport models

    NASA Astrophysics Data System (ADS)

    Napier, W. J.; Ensberg, J. J.; Seinfeld, J. H.

    2014-10-01

    The new generation of secondary organic aerosol (SOA) models that represent gas- and particle-phase chemistry and thermodynamic partitioning using discrete two-dimensional grids (e.g. SOM, 2D-VBS) cannot be efficiently implemented into three-dimensional atmospheric chemical transport models (CTMs) due to the large number of bins (tracers) required. In this study, we introduce a novel mathematical framework, termed the Oxidation State/Volatility Moment Method, that is designed to address these computational burdens so as to allow the new generation of SOA models to be implemented into CTMs. This is accomplished by mapping the two-dimensional grids onto probability distributions that conserve carbon and oxygen mass. Assessment of the Moment Method strengths (speed, carbon and oxygen conservation) and weaknesses (numerical drift) provide valuable insight that can guide future development of SOA modules for atmospheric CTMs.

  14. Effects of growth pressure on morphology of ZnO nanostructures by chemical vapor transport

    NASA Astrophysics Data System (ADS)

    Babu, Eadi Sunil; Kim, Sungjin; Song, Jung-Hoon; Hong, Soon-Ku

    2016-08-01

    The effect of growth pressure on the morphology of the ZnO nanostructures in chemical vapor transport by using Zn powder and oxygen as source materials has been investigated. Highly uniform aligned ZnO nanorods or multifaceted tripod structures were grown depending on the growth pressure. The mechanism governing the morphology change was explained by the relative concentration of Zn vapor and supersaturation based on experimental observations. It was concluded that heterogeneous nucleation on the substrate is enhanced at low growth pressure, while homogeneous nucleation from vapor phase is enhanced at high growth pressure. The difference resulted in different morphology of ZnO nanostructures. ZnO nanorods grown at optimized condition were used for the fabrication of gas sensor for the detection of H2 gas.

  15. Chemical and Aerosol Signatures of Biomass Burning via Long Range Transport observed at Storm Peak Laboratory

    NASA Astrophysics Data System (ADS)

    Hallar, A. G.; Obrist, D.; McCubbin, I. B.; Fain, X.; Rahn, T.

    2008-12-01

    The Desert Research Institute operates a high elevation facility, Storm Peak Laboratory (SPL), located on the Steamboat Springs Ski Resort in Colorado at an elevation 3.2 km. During the spring of 2008, two field projects were conducted at SPL; Storm Peak Cloud and Aerosol Characterization (SPACC) and a State of Colorado Mercury Monitoring project. Measurements of gaseous elemental mercury (GEM), along with CO, ozone and aerosol concentrations and aerosol size distributions will be presented from April 28 to July 1st 2008. This work focuses on specific case studies pertaining to long range transport events. Specifically, high levels of GEM and CO will be presented from May 15, 2008. This data will be coupled with HYSPLIT backtrajectories, chemical modeling via MOZART, and satellite imagery (MODIS) to present evidence that Siberian wildfires impacted the air quality at Storm Peak Laboratory.

  16. Transport properties of monolayer MoS2 grown by chemical vapor deposition.

    PubMed

    Schmidt, Hennrik; Wang, Shunfeng; Chu, Leiqiang; Toh, Minglin; Kumar, Rajeev; Zhao, Weijie; Neto, A H Castro; Martin, Jens; Adam, Shaffique; Özyilmaz, Barbaros; Eda, Goki

    2014-01-01

    Recent success in the growth of monolayer MoS2 via chemical vapor deposition (CVD) has opened up prospects for the implementation of these materials into thin film electronic and optoelectronic devices. Here, we investigate the electronic transport properties of individual crystallites of high quality CVD-grown monolayer MoS2. The devices show low temperature mobilities up to 500 cm(2) V(-1) s(-1) and a clear signature of metallic conduction at high doping densities. These characteristics are comparable to the electronic properties of the best mechanically exfoliated monolayers in literature, verifying the high electronic quality of the CVD-grown materials. We analyze the different scattering mechanisms and show that the short-range scattering plays a dominant role in the highly conducting regime at low temperatures. Additionally, the influence of optical phonons as a limiting factor is discussed. PMID:24640984

  17. A three-dimensional chemical transport model of the stratosphere: Midlatitude results

    NASA Astrophysics Data System (ADS)

    KamińSki, Jacek W.; McConnell, John C.; Boville, Byron A.

    1996-12-01

    A prototype robust three-dimensional global chemical transport model (CTM) has been developed in order to facilitate a realistic simulation of stratospheric chemistry and dynamics. The current application is for a 100-day run from August 10 to November 17 using the average (ensemble) of 10 dynamical runs (realizations) of the CCMl. The CTM results are compared with observations and two-dimensional model results. A comparison of the midlatitude model results with satellite observations, stratospheric and mesospheric sounder (SAMS) and Halogen Occultation Experiment (HALOE), showed that the model can simulate relatively well, at least on the timescale of the simulation, the distribution and formation of long-lived species (N2O, CH4, and H20). The distribution of short-lived species was compared with some satellite measurements, limb infrared monitor of the stratosphere (LIMS) and Stratospheric Aerosol and Gas Experiment (SAGE II), and two-dimensional model results, and was found to be consistent.

  18. Deduction of emissions of source gases using an objective inversion algorithm and a chemical transport model

    NASA Technical Reports Server (NTRS)

    Brown, Margaret

    1993-01-01

    An inversion algorithm, constructed to deduce the emissions of a source gas required to produce a specified surface concentration, is applied to the observed surface concentrations of CFC 11, methylchloroform, and methane, using a two-dimensional chemical transport model. The information utilized for this deduction process is limited to the measured atmospheric concentration of the source gas, including the associated standard deviations of these measurements. In this way the amount of objective information available in these measurements is assessed. The algorithm is shown to be capable of producing a latitudinal emissions distribution as well as the error bounds on the deduced emission distribution. The 'ill posed' nature of this inverse problem is discussed as well as the implications this has on the spatial and temporal resolution at which emissions can be resolved. Finally, a methane emission distribution is deduced which has the expected seasonal variations and consistent with results from other, more subjective, deduction studies.

  19. Comprehensive 1D Modelling of Reactive Chemical Transport in Unsaturated Soil

    NASA Astrophysics Data System (ADS)

    Wissmeier, L.; Barry, D. A.

    2007-12-01

    Computer models for simulating environmental processes of water flow, solute transport and geochemical reactions have greatly advanced during recent years. However, there is still demand for the development of programs that a capable of simulating the numerous interactions between physical transport processes and biogeochemical reactions in natural soils. We present a new tool for simulating transient vadose zone flow and solute transport according to the moisture- based form of Richards' equation within the widely used geochemical software PHREEQC. The direct implementation into the geochemical framework provides access to comprehensive geochemical models, giving capabilities beyond existing software for coupled unsaturated flow and reaction. Possible reactions include complex aqueous speciation, cation exchange, equilibrium phase dissolution and precipitation, formation of solid solutions, redox reactions, gas phase exchange, surface adsorption considering electrostatics and kinetic reactions with user-defined rate equations, among others. As a result of the close coupling procedure, the influence of geochemical reactions on water content, e.g., through dissolution or precipitation of water-containing phases, can be investigated. For the solution of the partial differential equations of flow and transport, an explicit finite-difference formulation with a second-order space discretization and first-order time discretization was employed. The use of integrated diffusivities transforms Richards' equation into a simple advection-diffusion equation. Changes in water content and solute concentration were conceptualized as local kinetic reactions of individual elements where changes in moisture content result from fluxes of oxygen and hydrogen across cell boundaries. Reactions and chemical element transport are coupled via sequential two-step operator splitting. The scheme was implemented into PHREEQC without any source code modification such that it can be applied by

  20. Electron transport characteristics of silicon nanowires by metal-assisted chemical etching

    SciTech Connect

    Qi, Yangyang; Wang, Zhen; Zhang, Mingliang; Wang, Xiaodong Ji, An; Yang, Fuhua

    2014-03-15

    The electron transport characteristics of silicon nanowires (SiNWs) fabricated by metal-assisted chemical etching with different doping concentrations were studied. By increasing the doping concentration of the starting Si wafer, the resulting SiNWs were prone to have a rough surface, which had important effects on the contact and the electron transport. A metal-semiconductor-metal model and a thermionic field emission theory were used to analyse the current-voltage (I-V) characteristics. Asymmetric, rectifying and symmetric I-V curves were obtained. The diversity of the I-V curves originated from the different barrier heights at the two sides of the SiNWs. For heavily doped SiNWs, the critical voltage was one order of magnitude larger than that of the lightly doped, and the resistance obtained by differentiating the I-V curves at large bias was also higher. These were attributed to the lower electron tunnelling possibility and higher contact barrier, due to the rough surface and the reduced doping concentration during the etching process.

  1. Ozone formation during an episode over Europe: A 3-D chemical/transport model simulation

    NASA Technical Reports Server (NTRS)

    Berntsen, Terje; Isaksen, Ivar S. A.

    1994-01-01

    A 3-D regional photochemical tracer/transport model for Europe and the Eastern Atlantic has been developed based on the NASA/GISS CTM. The model resolution is 4x5 degrees latitude and longitude with 9 layers in the vertical (7 in the troposphere). Advective winds, convection statistics and other meteorological data from the NASA/GISS GCM are used. An extensive gas-phase chemical scheme based on the scheme used in our global 2D model has been incorporated in the 3D model. In this work ozone formation in the troposphere is studied with the 3D model during a 5 day period starting June 30. Extensive local ozone production is found and the relationship between the source regions and the downwind areas are discussed. Variations in local ozone formation as a function of total emission rate, as well as the composition of the emissions (HC/NO(x)) ratio and isoprene emissions) are elucidated. An important vertical transport process in the troposphere is by convective clouds. The 3D model includes an explicit parameterization of this process. It is shown that this process has significant influence on the calculated surface ozone concentrations.

  2. Groundwater flow path dynamics and nitrogen transport potential in the riparian zone of an agricultural headwater catchment

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Stream riparian zones are often thought of as areas that provide natural remediation for groundwater contaminants, especially agricultural nitrogen (N). While denitrification and vegetative uptake tend to be efficient N removal processes in slow moving shallow groundwater, these mechanisms decrease ...

  3. Inverse modeling of atmospheric mercury emissions using a global chemical transport model and surface observations

    NASA Astrophysics Data System (ADS)

    Song, S.; Selin, N. E.

    2012-12-01

    We use inverse modeling in combination with worldwide observational data to constrain atmospheric mercury fluxes and associated uncertainties from anthropogenic and natural sources. Though atmospheric transport is a critical pathway of global mercury transport, large uncertainties exist in estimating the magnitudes and temporal variabilities of mercury emissions to the atmosphere from both natural and anthropogenic processes. Previous estimations have primarily used a so-called "bottom-up" approach, which extrapolates the few direct measurements to larger regions or uses simplified process models to estimate fluxes. Here, we apply a "top-down" or inverse modeling approach. Worldwide surface observations of total gaseous mercury (TGM) and simulations from a global chemical transport model (GEOS-Chem version 9-01-02 with a 2 by 2.5 degree horizontal resolution) are combined to estimate mercury fluxes. Time-invariant anthropogenic emission and seasonally varying fluxes (e.g., ocean evasion, biomass burning, and soil volatilization) are optimally estimated by Kalman filter between 2005 and 2009 at a monthly time resolution. The reference source spatial distributions are shown in Figure 1. We collected data from 16 measurement sites with high precision and frequency, covering most active stations during our period of study. The observations and reference model outputs at 4 representative sites are compared in Figure 2. We test the inverse model by comparing model-measurement fits between the reference model and optimized emissions.igure 1. Mercury reference source spatial distributions. Annually averaged patterns are shown in log scale. igure 2. Comparison of TGM monthly mean observations between observations (black, shown with standard deviations) and reference model results (red) at 4 representative sites.

  4. Behavioral, biological, and chemical perspectives on atypical agents targeting the dopamine transporterɸ

    PubMed Central

    Reith, Maarten E.A.; Blough, Bruce E.; Hong, Weimin C.; Jones, Kymry T.; Schmitt, Kyle C.; Baumann, Michael H.; Partilla, John S.; Rothman, Richard B.; Katz, Jonathan L.

    2014-01-01

    Background Treatment of Stimulant-Use Disorders remains a formidable challenge, and the dopamine transporter (DAT) remains a potential target for antagonist or agonist-like substitution therapies. Methods This review focuses on DAT ligands, such as benztropine, GBR 12909, modafinil, and DAT substrates derived from phenethylamine or cathinone that have atypical DAT-inhibitor effects, either in vitro or in vivo. The compounds are described from a molecular mechanistic, behavioral, and medicinal-chemical perspective. Results Possible mechanisms for atypicality at the molecular level can be deduced from the conformational cycle for substrate translocation. For each conformation, a crystal structure of a bacterial homolog is available, with a possible role of cholesterol, which is also present in the crystal of drosophila DAT. Although there is a direct relationship between behavioral potencies of most DAT inhibitors and their DAT affinities, a number of compounds bind to the DAT and inhibit dopamine uptake but do not share cocaine-like effects. Such atypical behavior, depending on the compound, may be related to slow DAT association, combined sigma-receptor actions, or bias for cytosol-facing DAT. Some structures are sterically small enough to serve as DAT substrates but large enough to also inhibit transport. Such compounds may display partial DA releasing effects, and may be combined with release or uptake inhibition at other monoamine transporters. Conclusions Mechanisms of atypical DAT inhibitors may serve as targets for the development of treatments for stimulant abuse. These mechanisms are novel and their further exploration may produce compounds with unique therapeutic potential as treatments for stimulant abuse. PMID:25548026

  5. A multimedia fate and chemical transport modeling system for pesticides: II. Model evaluation

    NASA Astrophysics Data System (ADS)

    Li, Rong; Scholtz, M. Trevor; Yang, Fuquan; Sloan, James J.

    2011-07-01

    Pesticides have adverse health effects and can be transported over long distances to contaminate sensitive ecosystems. To address problems caused by environmental pesticides we developed a multimedia multi-pollutant modeling system, and here we present an evaluation of the model by comparing modeled results against measurements. The modeled toxaphene air concentrations for two sites, in Louisiana (LA) and Michigan (MI), are in good agreement with measurements (average concentrations agree to within a factor of 2). Because the residue inventory showed no soil residues at these two sites, resulting in no emissions, the concentrations must be caused by transport; the good agreement between the modeled and measured concentrations suggests that the model simulates atmospheric transport accurately. Compared to the LA and MI sites, the measured air concentrations at two other sites having toxaphene soil residues leading to emissions, in Indiana and Arkansas, showed more pronounced seasonal variability (higher in warmer months); this pattern was also captured by the model. The model-predicted toxaphene concentration fraction on particles (0.5-5%) agrees well with measurement-based estimates (3% or 6%). There is also good agreement between modeled and measured dry (1:1) and wet (within a factor of less than 2) depositions in Lake Ontario. Additionally this study identified erroneous soil residue data around a site in Texas in a published US toxaphene residue inventory, which led to very low modeled air concentrations at this site. Except for the erroneous soil residue data around this site, the good agreement between the modeled and observed results implies that both the US and Mexican toxaphene soil residue inventories are reasonably good. This agreement also suggests that the modeling system is capable of simulating the important physical and chemical processes in the multimedia compartments.

  6. Chemical Interference with Iron Transport Systems to Suppress Bacterial Growth of Streptococcus pneumoniae

    PubMed Central

    Zhang, Liang; Li, Nan; Han, Junlong; Zhang, Jing; Sun, Xuesong; He, Qing-Yu

    2014-01-01

    Iron is an essential nutrient for the growth of most bacteria. To obtain iron, bacteria have developed specific iron-transport systems located on the membrane surface to uptake iron and iron complexes such as ferrichrome. Interference with the iron-acquisition systems should be therefore an efficient strategy to suppress bacterial growth and infection. Based on the chemical similarity of iron and ruthenium, we used a Ru(II) complex R-825 to compete with ferrichrome for the ferrichrome-transport pathway in Streptococcus pneumoniae. R-825 inhibited the bacterial growth of S. pneumoniae and stimulated the expression of PiuA, the iron-binding protein in the ferrichrome-uptake system on the cell surface. R-825 treatment decreased the cellular content of iron, accompanying with the increase of Ru(II) level in the bacterium. When the piuA gene (SPD_0915) was deleted in the bacterium, the mutant strain became resistant to R-825 treatment, with decreased content of Ru(II). Addition of ferrichrome can rescue the bacterial growth that was suppressed by R-825. Fluorescence spectral quenching showed that R-825 can bind with PiuA in a similar pattern to the ferrichrome-PiuA interaction in vitro. These observations demonstrated that Ru(II) complex R-825 can compete with ferrichrome for the ferrichrome-transport system to enter S. pneumoniae, reduce the cellular iron supply, and thus suppress the bacterial growth. This finding suggests a novel antimicrobial approach by interfering with iron-uptake pathways, which is different from the mechanisms used by current antibiotics. PMID:25170896

  7. Chemical reactivity and long-range transport potential of polycyclic aromatic hydrocarbons--a review.

    PubMed

    Keyte, Ian J; Harrison, Roy M; Lammel, Gerhard

    2013-12-21

    Polycyclic aromatic hydrocarbons (PAHs) are of considerable concern due to their well-recognised toxicity and especially due to the carcinogenic hazard which they present. PAHs are semi-volatile and therefore partition between vapour and condensed phases in the atmosphere and both the vapour and particulate forms undergo chemical reactions. This article briefly reviews the current understanding of vapour-particle partitioning of PAHs and the PAH deposition processes, and in greater detail, their chemical reactions. PAHs are reactive towards a number of atmospheric oxidants, most notably the hydroxyl radical, ozone, the nitrate radical (NO3) and nitrogen dioxide. Rate coefficient data are reviewed for reactions of lower molecular weight PAH vapour with these species as well as for heterogeneous reactions of higher molecular weight compounds. Whereas the data for reactions of the 2-3-ring PAH vapour are quite extensive and generally consistent, such data are mostly lacking for the 4-ring PAHs and the heterogeneous rate data (5 and more rings), which are dependent on the substrate type and reaction conditions, are less comprehensive. The atmospheric reactions of PAH lead to the formation of oxy and nitro derivatives, reviewed here, too. Finally, the capacity of PAHs for long range transport and the results of numerical model studies are described. Research needs are identified. PMID:24077263

  8. Control of Chemical, Thermal, and Gas Transport Properties in Dense Phosphazene Polymer Membranes.

    SciTech Connect

    Christopher J. Orme; Frederick F. Stewart; Mark L. Stone; Mason K. Harrup; Thomas A. Luther; Eric S. Peterson

    2005-10-01

    Polyphosphazenes are hybrid polymers having organic pendant groups attached to an inorganic backbone. Phosphazene polymers can be tailored to specific applications through the attachment of a variety of different pendant groups to the phosphazene backbone. Applications for which these polymers have proven useful include solid polymer electrolytes for batteries and fuel cells, as well as, membranes for gas and liquid separations. In past work, phosphazene polymers have been synthesized using mixtures of pendant groups with differing chemical affinities. Specific ratios of hydrophobic and hydrophilic pendant groups were placed on the phosphazene backbone with a goal of demonstrating control of solubility, and therefore chemical selectivity. In this work, a series of phosphazene homo-polymers were synthesized having varying amounts of hydrophobic and hydrophilic character on each individual pendant group. Polymers were synthesized having a hydrophilic portion next to the polymer backbone and the hydrophobic portion on the terminal end of the pendant group. The effects of these combined hydrophobic/hydrophilic pendant groups on polymer morphology and gas transport properties are presented. The following data will be addressed: thermal characterization, pure gas permeability on seven gases (Ar, H2, O2, N2, CO2, and CH4 ), and ideal selectivity for the gas pairs: O2/N2, H2/CO2, CO2/H2, CO2/CH4 and CO2/N2.

  9. Responses of physical, chemical, and biological indicators of water quality to a gradient of agricultural land use in the Yakima River Basin, Washington

    USGS Publications Warehouse

    Cuffney, T.F.; Meador, M.R.; Porter, S.D.; Gurtz, M.E.

    2000-01-01

    The condition of 25 stream sites in the Yakima River Basin, Washington, were assessed by the U.S. Geological Survey's National Water-Quality Assessment Program. Multimetric condition indices were developed and used to rank sites on the basis of physical, chemical, and biological characteristics. These indices showed that sites in the Cascades and Eastern Cascades ecoregions were largely unimpaired. In contrast, all but two sites in the Columbia Basin ecoregion were impaired, some severely. Agriculture (nutrients and pesticides) was the primary factor associated with impairment and all impaired sites were characterized by multiple indicators of impairment. All indices of biological condition (fish, invertebrates, and algae) declined as agricultural intensity increased. The response exhibited by invertebrates and algae suggested a threshold response with conditions declining precipitously at relatively low levels of agricultural intensity and little response at moderate to high levels of agricultural intensity. This pattern of response suggests that the success of mitigation will vary depending upon where on the response curve the mitigation is undertaken. Because the form of the community condition response is critical to effective water-quality management, the National Water-Quality Assessment Program is conducting studies to examine the response of biota to gradients of land-use intensity and the relevance of these responses to water-quality management. These land-use gradient pilot studies will be conducted in several urban areas starting in 1999.

  10. Influence of different chemical treatments on transport of Alcaligenes paradoxus in porous media.

    PubMed Central

    Gross, M J; Logan, B E

    1995-01-01

    Seven chemicals, three buffers, and a salt solution known to affect bacterial attachment were tested to quantify their abilities to enhance the penetration of Alcaligenes paradoxus in porous media. Chemical treatments included Tween 20 (a nonionic surfactant that affects hydrophobic interactions), sodium dodecyl sulfate (an anionic surfactant), EDTA (a cell membrane permeabilizer that removes outer membrane lipopolysaccharides), sodium PPi (a surface charge modifier), sodium periodate (an oxidizer that cleaves surface polysaccharides), lysozyme (an enzyme that cleaves cell wall components), and proteinase K (a nonspecific protease that cleaves peptide bonds). Buffers included MOPS [3-(N-morpholino)propanesulfonic acid], Tris, phosphate, and an unbuffered solution containing only NaCl. Transport characteristics in the porous media were compared by using a sticking coefficient, alpha, defined as the rate at which particles stick to a grain of medium divided by the rate at which they strike the grain. Tween 20 reduced alpha by 2.5 orders of magnitude, to alpha = 0.0016, and was the most effective chemical treatment for decreasing bacterial attachment to glass beads in buffered solutions. Similar reductions in alpha were achieved in unbuffered solutions by reducing the solution ionic strength to 0.01 mM. EDTA, protease, and other treatments designed to alter cell structures did not reduce alpha by more than an order of magnitude. The number of bacteria retained by the porous media was decreased by treatments that made A. paradoxus more hydrophobic and less electrostatically charged, although alpha was poorly correlated with electrophoretic mobility and hydrophobicity index measurements at lower alpha values.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:7646012

  11. Observation operator for the assimilation of aerosol type resolving satellite measurements into a chemical transport model

    NASA Astrophysics Data System (ADS)

    Schroedter-Homscheidt, M.; Elbern, H.; Holzer-Popp, T.

    2010-11-01

    Modelling of aerosol particles with chemical transport models is still based mainly on static emission databases while episodic emissions cannot be treated sufficiently. To overcome this situation, a coupling of chemical mass concentration modelling with satellite-based measurements relying on physical and optical principles has been developed. This study deals with the observation operator for a component-wise assimilation of satellite measurements. It treats aerosol particles classified into water soluble, water insoluble, soot, sea salt and mineral dust containing aerosol particles in the atmospheric boundary layer as separately assimilated aerosol components. It builds on a mapping of aerosol classes used both in observation and model space taking their optical and chemical properties into account. Refractive indices for primary organic carbon particles, anthropogenic particles, and secondary organic species have been defined based on a literature review. Together with a treatment of different size distributions in observations and model state, this allows transforming the background from mass concentrations into aerosol optical depths. A two-dimensional, variational assimilation is applied for component-wise aerosol optical depths. Error covariance matrices are defined based on a validation against AERONET sun photometer measurements. Analysis fields are assessed threefold: (1) through validation against AERONET especially in Saharan dust outbreak situations, (2) through comparison with the British Black Smoke and Sulphur Dioxide Network for soot-containing particles, and (3) through comparison with measurements of the water soluble components SO4, NH4, and NO3 conducted by the EMEP (European Monitoring and Evaluation Programme) network. Separately, for the water soluble, the soot and the mineral dust aerosol components a bias reduction and subsequent a root mean square error reduction is observed in the analysis for a test period from July to November 2003

  12. Observation operator for the assimilation of aerosol type resolving satellite measurements into a chemical transport model

    NASA Astrophysics Data System (ADS)

    Schroedter-Homscheidt, M.; Elbern, H.; Holzer-Popp, T.

    2010-06-01

    Modelling of aerosol particles with chemical transport models is still based mainly on static emission databases while episodic emissions can not be treated sufficiently. To overcome this situation, a coupling of chemical mass concentration modelling with satellite-based measurements relying on physical and optical principles has been developed. This study deals with the observation operator for a component-wise assimilation of satellite measurements. It treats aerosol particles classified into water soluble, water insoluble, soot, sea salt and mineral dust containing aerosol particles in the atmospheric boundary layer as separately assimilated aerosol components. It builds on a mapping of aerosol classes used both in observation and model space taking their optical and chemical properties into account. Refractive indices for primary organic carbon particles, anthropogenic particles, and secondary organic species have been defined based on a literature review. Together with a treatment of different size distributions in observations and model state, this allows transforming the background from mass concentrations into aerosol optical depths. A two-dimensional, variational assimilation is applied for component-wise aerosol optical depths. Error covariance matrices are defined based on a validation against AERONET sun photometer measurements. Analysis fields are assessed threefold: (1) through validation against AERONET especially in Saharan dust outbreak situations, (2) through comparison with the British Black Smoke and Sulphur Dioxide Network for soot-containing particles, and (3) through comparison with measurements of the water soluble components SO4, NH4, and NO3 conducted by the EMEP (European Monitoring and Evaluation Programme) network. Separately, for the water soluble, the soot and the mineral dust aerosol components a bias reduction and subsequent a root mean square error reduction is observed in the analysis for a test period from July to November 2003

  13. Improving Lightning NO(x) Parameterizations for Global Chemical Transport Models

    NASA Technical Reports Server (NTRS)

    Pickering, Kenneth E.; Ott, Lesley E.; DeCaria, Alex J.; Stenchikov, Georgiy L.; Allen, Dale J.; Tao, Wei-Kuo

    2006-01-01

    Parameterization of lightning NO(x) in global chemical transport models requires a method to specify the temporal and geographic distribution of flash rates, an estimate of NO production per flash, and a method to specify the effective vertical distribution of NO production. Flash rate parameterizations using the upward convective cloud mass flux have been developed and tested for several GCM and assimilated meteorological data sets. This parameterization and others involving the cloud-top height and convective precipitation provide a generally acceptable climatological distribution of flashes after normalization with satellite data. However, considerable improvement in terms of geographic and temporal variability may be achieved in the future using cloud microphysics data available from next-generation GCMs. Cloud-resolving case-study simulations of convective transport and lightning NO production have yielded results which are directly applicable to the NO production per flash and the vertical NO distribution portions of the global model lightning parameterizations. In this work we have used cloud-resolving models (the Goddard Cumulus Ensemble Model (GCE) and MM5) to drive an off-line cloud-scale chemical transport model (CSCTM). The CSCTM, in conjunction with aircraft measurements of NO(x) in thunderstorms and ground-based lightning observations, has been used to constrain the amount of NO produced per flash. Observed lightning flash rates have been incorporated into the CSCTM, and several scenarios of NO production per intracloud (IC) and per cloud-to-ground (CG) flash have been tested in each of several case study storms. The resulting NO(x) mixing ratios are compared with aircraft measurements taken within the storm (typically the anvil region) to determine the most likely NO production scenario. The range of values of NO production per flash (or per meter of lightning channel length) that have been deduced from the model will be shown and compared with

  14. Monitoring the fate and transport of deicing chemicals in lysimeter experiments

    NASA Astrophysics Data System (ADS)

    Lißner, H.; Wehrer, M.; Totsche, K. U.

    2012-04-01

    Large amounts of the deicing chemicals (DIC) propylene glycol (PG) and formate are spread for removal of snow and ice on the aircrafts and airfields every winter. A considerable amount of these chemicals are carried into surrounding areas, where they mix with snow and infiltrate in the soil during snowmelt. Even though DIC are easily degradable, the high mobility and the high biological oxygen demand of PG in particular can influence the hydrogeochemistry of the unsaturated and saturated zone. The aims of the study were to evaluate and quantify transport of deicing chemicals during snowmelt under field conditions, and to study effects of DIC degradation on the hydrogeochemistry of the unsaturated zone. Eight undisturbed soil cores (0.3 m x 1 m, 0.071 m3) were retrieved at the Gardermoen Airport, Norway, and installed as non-weighable small scale lysimeters at a nearby field site. Before snowmelt in March 2010, a mix of snow containing 350 g/m2 PG, 71 g/m2 formate, and 17 g/m2 of bromide were added to the lysimeters. To determine the fate and transport of PG we monitored PG and its metabolites, bromide, manganese, and iron in the seepage water. High cumulative infiltration and marginal degradation of PG during the snowmelt period allowed up to 50 % of the PG to leave the upper, microbially most active, region of the soil. Only marginal concentrations of formate were analysed in all lysimeters, indicating fast degradation and favoured metabolism by soil bacteria compared to PG. Low contents of metabolites and the concurrent breakthrough of PG and Br in the seepage water even imply that PG was not significantly degraded before June. Redox values down to 200 mV in April, the detection of propionate and manganese, as well as a rise in pH, suggest partially anearobic localities in the soil, not only during high soil water saturation in April and May but also during summer when PG degradation was very efficient. In the longterm, the intense depletion of electron acceptors

  15. Status of the solar and infrared radiation submodels in the LLNL 1-D and 2-D chemical-transport models

    SciTech Connect

    Grant, K.E.; Taylor, K.E.; Ellis, J.S.; Wuebbles, D.J.

    1987-07-01

    The authors have implemented a series of state of the art radiation transport submodels in previously developed one dimensional and two dimensional chemical transport models of the troposphere and stratosphere. These submodels provide the capability of calculating accurate solar and infrared heating rates. They are a firm basis for further radiation submodel development as well as for studying interactions between radiation and model dynamics under varying conditions of clear sky, clouds, and aerosols. 37 refs., 3 figs.

  16. Factors affecting the fate and transport of glyphosate and AMPA into surface waters of agricultural watersheds in the United States and Europe

    NASA Astrophysics Data System (ADS)

    Coupe, R.; Kalkhoff, S.; Capel, P.; Gregoire, C.

    2012-04-01

    Glyphosate [N-(phosphonomethyl)glycine] is a herbicide used extensively in almost all agricultural and urban areas of the United States and Europe. Although, glyphosate is used widely throughout the world in the production of many crops, it is predominately used in the United States on soybeans, corn, potatoes, and cotton that have been genetically modified to be tolerant to glyphosate. From 1992 to 2007, the agricultural use of glyphosate has increased from less than 10,000 Mg to more than 80,000 Mg, respectively. The greatest areal use is in the midwestern United States where glyphosate is applied on transgenic corn and soybeans. Because of the difficulty and expense in analyzing for glyphosate and AMPA (aminomethylphosphonic acid, a primary glyphosate degradate) in water, there have been only small scale studies on the fate and transport of glyphosate. The characterization of the transport of glyphosate and AMPA on a watershed scale is lacking. Glyphosate and AMPA were frequently detected in the surface waters of 4 agricultural watersheds in studies conducted by the U.S. Geological Survey in the United States and at the Laboratory of Hydrology and Geochemistry of Strasbourg. Two of these basins were located in the midwestern United States where the major crops are corn and soybean, the third is located the lower Mississippi River Basin where the major crops are soybean, corn, rice, and cotton, and the fourth was located near Strasbourg, France where the use of glyphosate was on a vineyard. The load as a percent of use ranged from 0.009 to 0.86 percent and could be related to 3 factors: source strength, hydrology, and flowpath. Glyphosate use in a watershed results in some occurrence in surface water at the part per billion level; however, those watersheds most at risk for the offsite transport of glyphosate are those with high application rates, rainfall that results in overland runoff, and a flowpath that does not include transport through the soil.

  17. Environmental genotoxicity assessment along the transport routes of chemical munitions leading to the dumping areas in the Baltic Sea.

    PubMed

    Baršienė, Janina; Butrimavičienė, Laura; Grygiel, Włodzimierz; Stunžėnas, Virmantas; Valskienė, Roberta; Greiciūnaitė, Janina; Stankevičiūtė, Milda

    2016-02-15

    The frequencies of micronuclei (MN), nuclear buds (NB) and nuclear buds on filament (NBf) were examined in 660 specimens of herring (Clupea harengus) collected in 2009-2014 at 65 study stations located mainly along the chemical munition transport routes in the Baltic Sea. The frequency of nuclear abnormalities was strongly increased in herring caught at four stations located close to chemical munition dumping sites, or CWAs - substances (chemical warfare agents) in sediments. Significant increase of MN, NB and NBf was observed in fish caught November 2010-2013 compared to 2009. The most significantly increased genotoxicity responses were recorded in fish caught at stations along CW (chemical weapons) transport routes, close to the Bornholm CW dumping area, in zones with CWAs in sediments and with oil-gas platforms. PMID:26763319

  18. Biotechnology and Agriculture.

    ERIC Educational Resources Information Center

    Kenney, Martin

    Even at this early date in the application of biotechnology to agriculture, it is clear that agriculture may provide the largest market for new or less expensive biotechnologically manufactured products. The chemical and pharmaceutical industries that hold important positions in agricultural inputs are consolidating their positions by purchasing…

  19. Sensitivity of chemistry-transport model simulations to the duration of chemical and transport operators: a case study with GEOS-Chem v10-01

    NASA Astrophysics Data System (ADS)

    Philip, Sajeev; Martin, Randall V.; Keller, Christoph A.

    2016-05-01

    Chemistry-transport models involve considerable computational expense. Fine temporal resolution offers accuracy at the expense of computation time. Assessment is needed of the sensitivity of simulation accuracy to the duration of chemical and transport operators. We conduct a series of simulations with the GEOS-Chem chemistry-transport model at different temporal and spatial resolutions to examine the sensitivity of simulated atmospheric composition to operator duration. Subsequently, we compare the species simulated with operator durations from 10 to 60 min as typically used by global chemistry-transport models, and identify the operator durations that optimize both computational expense and simulation accuracy. We find that longer continuous transport operator duration increases concentrations of emitted species such as nitrogen oxides and carbon monoxide since a more homogeneous distribution reduces loss through chemical reactions and dry deposition. The increased concentrations of ozone precursors increase ozone production with longer transport operator duration. Longer chemical operator duration decreases sulfate and ammonium but increases nitrate due to feedbacks with in-cloud sulfur dioxide oxidation and aerosol thermodynamics. The simulation duration decreases by up to a factor of 5 from fine (5 min) to coarse (60 min) operator duration. We assess the change in simulation accuracy with resolution by comparing the root mean square difference in ground-level concentrations of nitrogen oxides, secondary inorganic aerosols, ozone and carbon monoxide with a finer temporal or spatial resolution taken as "truth". Relative simulation error for these species increases by more than a factor of 5 from the shortest (5 min) to longest (60 min) operator duration. Chemical operator duration twice that of the transport operator duration offers more simulation accuracy per unit computation. However, the relative simulation error from coarser spatial resolution generally

  20. Impact Assessment and Participant Profiles of Extension's Education Programs for Agricultural Chemical/Seed Retailers and Crop Advisors.

    ERIC Educational Resources Information Center

    Schmitt, Michael A.; Durgan, Beverly R.; Iverson, Sarah M.

    2000-01-01

    Responses from 698 agriculture professionals indicate that extension programs have positive agronomic and environmental impact and attendance was influenced more by topics and speakers than cost. Greater impact can be achieved through partnerships with companies, associations, and agencies to target professionals who will be able to use or…

  1. Non-Hodgkin Lymphoma and Occupational Exposure to Agricultural Pesticide Chemical Groups and Active Ingredients: A Systematic Review and Meta-Analysis

    PubMed Central

    Schinasi, Leah; Leon, Maria E.

    2014-01-01

    This paper describes results from a systematic review and a series of meta-analyses of nearly three decades worth of epidemiologic research on the relationship between non-Hodgkin lymphoma (NHL) and occupational exposure to agricultural pesticide active ingredients and chemical groups. Estimates of associations of NHL with 21 pesticide chemical groups and 80 active ingredients were extracted from 44 papers, all of which reported results from analyses of studies conducted in high-income countries. Random effects meta-analyses showed that phenoxy herbicides, carbamate insecticides, organophosphorus insecticides and the active ingredient lindane, an organochlorine insecticide, were positively associated with NHL. In a handful of papers, associations between pesticides and NHL subtypes were reported; B cell lymphoma was positively associated with phenoxy herbicides and the organophosphorus herbicide glyphosate. Diffuse large B-cell lymphoma was positively associated with phenoxy herbicide exposure. Despite compelling evidence that NHL is associated with certain chemicals, this review indicates the need for investigations of a larger variety of pesticides in more geographic areas, especially in low- and middle-income countries, which, despite producing a large portion of the world’s agriculture, were missing in the literature that were reviewed. PMID:24762670

  2. Effect of Agricultural Amendments on Cajanus cajan (Pigeon Pea) and Its Rhizospheric Microbial Communities--A Comparison between Chemical Fertilizers and Bioinoculants.

    PubMed

    Gupta, Rashi; Bisaria, V S; Sharma, Shilpi

    2015-01-01

    Inoculation of leguminous seeds with bioinoculants has been practiced in agriculture for decades to ameliorate grain yield by enhanced growth parameters and soil fertility. However, effective enhancement of plant growth parameters results not only from the direct effects these bioinoculants impose on them but also from their non-target effects. The ability of bioinoculants to reduce the application of chemicals for obtaining optimum yield of legume appears to be of great ecological and economic importance. In the present study, we compared the influence of seed inoculation of Cajanus cajan with a microbial consortium, comprising Bacillus megaterium, Pseudomonas fluorescens and Trichoderma harzianum, with that of application of chemical fertilizers on plant's growth parameters and its rhizospheric microbial communities. Real-time PCR assay was carried out to target the structure (16S rRNA) and function (nitrogen cycle) of rhizospheric microbiota, using both DNA and RNA as markers. The results showed that the microbial consortium was the most efficient in increasing grain yield (2.5-fold), even better than the recommended dose of chemical fertilizers (by 1.2-fold) and showed enhancement in nifH and amoA transcripts by 2.7- and 2.0-fold, respectively. No adverse effects of bioinoculants' application were observed over the rhizospheric microbial community, rendering the consortium to be safe for release in agricultural fields. PMID:26231030

  3. Effect of Agricultural Amendments on Cajanus cajan (Pigeon Pea) and Its Rhizospheric Microbial Communities – A Comparison between Chemical Fertilizers and Bioinoculants

    PubMed Central

    Gupta, Rashi; Bisaria, V. S.; Sharma, Shilpi

    2015-01-01

    Inoculation of leguminous seeds with bioinoculants has been practiced in agriculture for decades to ameliorate grain yield by enhanced growth parameters and soil fertility. However, effective enhancement of plant growth parameters results not only from the direct effects these bioinoculants impose on them but also from their non-target effects. The ability of bioinoculants to reduce the application of chemicals for obtaining optimum yield of legume appears to be of great ecological and economic importance. In the present study, we compared the influence of seed inoculation of Cajanus cajan with a microbial consortium, comprising Bacillus megaterium, Pseudomonas fluorescens and Trichoderma harzianum, with that of application of chemical fertilizers on plant’s growth parameters and its rhizospheric microbial communities. Real-time PCR assay was carried out to target the structure (16S rRNA) and function (nitrogen cycle) of rhizospheric microbiota, using both DNA and RNA as markers. The results showed that the microbial consortium was the most efficient in increasing grain yield (2.5-fold), even better than the recommended dose of chemical fertilizers (by 1.2-fold) and showed enhancement in nifH and amoA transcripts by 2.7- and 2.0-fold, respectively. No adverse effects of bioinoculants' application were observed over the rhizospheric microbial community, rendering the consortium to be safe for release in agricultural fields. PMID:26231030

  4. Effects of deviations from stoichiometry, oxygen excess and substitution of Cr for Fe on the chemical transport of hematite with TeCl 4 as a transporting agent

    NASA Astrophysics Data System (ADS)

    Peshev, P.; Toshev, A.; Krabbes, G.; Gerlach, U.; Opperman, H.

    1984-02-01

    Single crystals of pure hematite (α-Fe 2O 3) and hematite in which the iron is partially replaced by chromium (Fe 2- yCr yO 3) can be obtained by chemical transport using TeCl 4 as a transporting agent. A thermodynamic analysis has shown the transport to be substantially affected by some additional conditions such as slight deviations from stoichiometry and small amounts of excess oxygen and dopants. The transport of pure, practically stoichiometric hematite occurs at temperatures above 900°C in the direction from the hot to the cold zone. At pressures below 1 MPa and temperatures ranging from 750 to 900°C (which correspond to about 12 mg/ml TeCl 4), the transport proceeds in the opposite direction. However, in a similar temperature range, the transport reaction proceeds in the direction hot → cold again, on introducing small excess oxygen amounts into the ampoule and in cases when the hematite shows some oxygen deficiency. From a mixture of Fe 2O 3/Fe 3O 4, the hematite is transferred to the cold zone. Chromium-containing hematite is also transported to the cold zone. The composition of the mixed Fe 2- yCr yO 3 crystals obtained is different from that of the initial substance. All results of the thermodynamic analysis were confirmed by experiments.

  5. Influences of land-ocean-atmosphere dynamics and emissions sectors on atmospheric chemical transport during VOCALS REx

    NASA Astrophysics Data System (ADS)

    Spak, S.; Mena, M.; Carmichael, G. R.

    2009-12-01

    Measurements and modeling from the VOCALS REx campaign have identified a range of transport regimes based on synoptic meteorology, and suggested roles for the marine boundary layer inversion, downslope katabatic winds from the Andean cordillera, and Hadley cell subsidence as primary causes for observed aerosol and trace gas concentration gradients over the Southeast Pacific. This study employs atmospheric chemical transport modeling and airmass trajectory analyses to more directly address the influence of orographic winds, boundary layer dynamics, coastal circulations, and large-scale circulation by the subtropical high on the diurnal and episodic variability of pollution transport in the region. Using hourly simulations with the Weather Research and Forecasting model and the STEM chemical transport model at 12 km x 12 km resolution, we introduce tracer emissions within and above the boundary layer at representative locations--including the western slopes of the Andes, on-shore and off-shore coastal areas, metropolitan Santiago, the Chilean altiplano, and the free troposphere over the open ocean--and follow their transport and fate throughout the REx experiment of October-November 2008. Comparison between trajectories and tracer concentrations illustrate long range airmass history and allow for an understanding of the representativeness of instantaneous trajectories on transport phenomena. We further assess the contributions of emissions from power generation, copper smelters, natural sources, and anthropogenic area sources to aerosol concentrations over the Southeast Pacific, identifying their role in each transport regime.

  6. Chemical contaminants in the Wadden Sea: Sources, transport, fate and effects

    NASA Astrophysics Data System (ADS)

    Laane, R. W. P. M.; Vethaak, A. D.; Gandrass, J.; Vorkamp, K.; Köhler, A.; Larsen, M. M.; Strand, J.

    2013-09-01

    The Wadden Sea receives contaminants from various sources and via various transport routes. The contaminants described in this overview are various metals (Cd, Cu, Hg, Pb and Zn) and various organic contaminants (polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs) and lindane (hexachlorocyclohexane, γ-HCH)). In addition, information is presented about other and emerging contaminants such as antifouling biocides (e.g. TBT and Irgarol), brominated flame retardants (BFRs), poly- and perfluorinated compounds (PFCs) and pharmaceutical and personal care products (PPCPs). Special attention is given to biogeochemical processes that contribute to the mobilization of contaminants in the surface sediments of the Wadden Sea. Finally, the effects on organisms of contaminants are reviewed and discussed. The main source of contaminants in the Wadden Sea are the rivers Rhine (via de Dutch coastal zone), Elbe and Weser. The Wadden Sea is not a sink for contaminants and adsorbed contaminants are transported from east to west. The surface sediments of the Wadden Sea are an important source for contaminants to the water above. The input and concentration of most contaminants have significantly decreased in water, sediments, organisms (e.g., mussel, flounder and bird eggs) in various parts of the Wadden Sea in the last three decades. Remarkably, the Cd concentration in mussels is increasing the last decades. In recent decades, the effects of contaminants on organisms (e.g., flounder, seal) have fallen markedly. Most of the affected populations have recovered, except for TBT induced effects in snails. Little is known about the concentration and effects of most emerging contaminants and the complex environmental mixtures of contaminants. It is recommended to install an international coordinated monitoring programme for contaminants and their effects in the whole Wadden Sea and to identify the chemical contaminants that really cause the effect.

  7. Mixing and transport during pharmaceutical twin-screw wet granulation: experimental analysis via chemical imaging.

    PubMed

    Kumar, Ashish; Vercruysse, Jurgen; Toiviainen, Maunu; Panouillot, Pierre-Emmanuel; Juuti, Mikko; Vanhoorne, Valérie; Vervaet, Chris; Remon, Jean Paul; Gernaey, Krist V; De Beer, Thomas; Nopens, Ingmar

    2014-07-01

    Twin-screw granulation is a promising continuous alternative for traditional batch high shear wet granulation (HSWG). The extent of HSWG in a twin screw granulator (TSG) is greatly governed by the residence time of the granulation materials in the TSG and degree of mixing. In order to determine the residence time distribution (RTD) and mixing in TSG, mostly visual observation and particle tracking methods are used, which are either inaccurate and difficult for short RTD, or provide an RTD only for a finite number of preferential tracer paths. In this study, near infrared chemical imaging, which is more accurate and provides a complete RTD, was used. The impact of changes in material throughput (10-17 kg/h), screw speed (500-900 rpm), number of kneading discs (2-12) and stagger angle (30-90°) on the RTD and axial mixing of the material was characterised. The experimental RTD curves were used to calculate the mean residence time, mean centred variance and the Péclet number to determine the axial mixing and predominance of convective over dispersive transport. The results showed that screw speed is the most influential parameter in terms of RTD and axial mixing in the TSG and established a significant interaction between screw design parameters (number and stagger angle of kneading discs) and the process parameters (material throughput and number of kneading discs). The results of the study will allow the development and validation of a transport model capable of predicting the RTD and macro-mixing in the TSG. These can later be coupled with a population balance model in order to predict granulation yields in a TSG more accurately. PMID:24768925

  8. The satellite and chemical transport model tandem: constraining TM5 with AURA observations

    NASA Astrophysics Data System (ADS)

    Verstraeten, Willem W.; Neu, Jessica L.; Williams, Jason E.; Bowman, Kevin W.; Worden, John R.; (K. F.) Boersma, Folkert

    2015-04-01

    Satellite-based studies focusing on tropospheric ozone (O3) and nitrogen dioxide (NO2) have the potential to close the gap left by previous studies on air quality. After all, satellites can provide large-scale robust observational evidence that both O3 precursor concentrations and tropospheric O3 levels are rapidly changing over source receptor areas. Chemical transport models (CTM) significantly contribute to our understanding on transport patterns, production and destruction of tropospheric air constituents, but the infrequently update of emission inventories and the slow implementation of updates on chemical reactions and reaction rates slow down the widespread use. Satellite observations of tropospheric NO2 have the potential to improve and update anthropogenic NOx emissions in a near-continuous way and may provide information on the life time of NOx, impacting the production and destruction of many air constituents including O3. Here we show the increased ability of the CTM TM5 to reproduce the 2005-2010 observed strong and rapid rise in free tropospheric ozone of 0.8% per year over China from TES (Tropospheric Emission Spectrometer, onboard AURA), once OMI (Ozone Monitoring Instrument, onboard AURA) NO2 measurements were implemented in TM5 to update NOx emissions. What is more, MLS observations (Microwave Limb Sounder, onboard AURA) on stratospheric ozone demonstrate its potential to constrain the stratosphere-troposphere exchange (STE) in TM5 which is mainly driven by ECMWF meteorological fields. The use of MLS observations of stratospheric O3 improved the TM5 modelled trends in tropospheric O3 significantly. Thanks to the TM5 input updates from satellite observations, the impact of Asian O3 and its precursors on the western United States could be quantified showing a large import from China to the West. Here we also show that deriving NOx life times from OMI NO2 observations to evaluate new rate constants of the reaction NO2 + OH => HNO3 in TM5 is a

  9. Evaluation of a Three-Dimensional Chemical Transport Model (PMCAMx) in the Mexico City Metropolitan Area

    NASA Astrophysics Data System (ADS)

    Tsimpidi, A. P.; Karydis, V. A.; Zavala, M.; Lei, W.; Molina, L. T.; Pandis, S. N.

    2007-05-01

    Atmospheric aerosols have adverse effects on human health, contribute to the visibility reduction and influence the energy balance of the planet. A three-dimensional chemical transport model (PMCAMx) (Gaydos et al., 2007) is used to simulate the particular matter (PM) mass composition distribution in the Mexico City Metropolitan Area (MCMA). PMCAMx uses the framework of CAMx (ENVIRON, 2002) modelling the processes of horizontal and vertical advection, horizontal and vertical dispersion, wet and dry deposition, and gas-phase chemistry. In addition to the above, PMCAMx includes three detailed aerosol modules: inorganic aerosol growth (Gaydos et al., 2003; Koo et al., 2003a), aqueous-phase chemistry (Fahey and Pandis, 2001), and secondary organic aerosol formation and growth (Koo et al., 2004). The aerosol thermodynamic model ISORROPIA has been improved as it now simulates explicitly the chemistry of Ca, Mg, and K salts and is linked to PMCAMx. The hybrid approach (Koo et al., 2003b) for modelling aerosol dynamics is applied in order to accurately simulate the inorganic components in coarse mode. This approach assumes that the smallest particles are in equilibrium while the condensation/evaporation equation is solved for the larger ones. The new CMU organic aerosol model, which is based on the splitting of the organic aerosol volatility range in discrete bins, is also used. The model predictions are evaluated against the PM and vapour concentration measurements from the MCMA-2003 Campaign (Molina et al., 2007). References Gaydos, T., Pinder, R., Koo, B., Fahey, Κ., Yarwood, G., and Pandis, S. N., (2007). Development and application of a three-dimensional Chemical Transport Model, PMCAMx. Atmospheric Environment, in press. ENVIRON (2002). User's guide to the comprehensive air quality model with extensions (CAMx). Version 3.10. Report prepared by ENVIRON International corporation, Novato, CA Gaydos, T., Koo, B., and Pandis, S. N., (2003). Development and application of

  10. Self-propelling surfactant droplets in chemically-confined microfluidics--cargo transport, drop-splitting and trajectory control.

    PubMed

    Sinz, David K N; Darhuber, Anton A

    2012-02-21

    We demonstrate the applicability of self-propulsion as a passive driving mechanism for droplets in chemically-confined microfluidics. The droplets can be used to transport considerably sized solid cargo particles. We implemented thermal actuation as a steering mechanism for the droplets at fluidic junctions. PMID:22246050

  11. A Survey of the Role of Thermodynamics and Transport Properties in Chemical Engineering University Education in Europe and the USA

    ERIC Educational Resources Information Center

    Ahlstrom, Peter; Aim, Karel; Dohrn, Ralf; Elliott, J. Richard; Jackson, George; Jaubert, Jean-Noel; Macedo, Eugenia A.; Pokki, Juha-Pekka; Reczey, Kati; Victorov, Alexey; Zilnik, Ljudmila Fele; Economou, Ioannis G.

    2010-01-01

    A survey on the teaching of thermodynamics and transport phenomena in chemical engineering curricula in European and US Universities was performed and results are presented here. Overall, 136 universities and colleges responded to the survey, out of which 81 from Europe and 55 from the USA. In most of the institutions responding at least two…

  12. Xenobiotic Metabolizing Enzyme and Transporter Gene Expression in Primary Cultures of Human Hepatocytes Modulated by ToxCast Chemicals

    EPA Science Inventory

    ToxCast chemicals were assessed for induction or suppression of xenobiotic metabolizing enzyme and transporter gene expression using primary human hepatocytes. The mRNA levels of 14 target and 2 control genes were measured: ABCB1, ABCB11, ABCG2, SLCO1B1, CYP1A1, CYP1A2, CYP2B6, C...

  13. Transport and Fate of Bacteria in Porous Media: Coupled Effects of Chemical Conditions and Pore Space Geometry

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Experimental and theoretical studies were undertaken to explore the coupling effects of chemical conditions and pore space geometry on bacteria transport in porous media. The retention of Escherichia coli D21g was investigated in a series of batch and column experiments with solutions of different i...

  14. Modulation of Xenobiotic Metabolizing Enzyme and Transporter Gene Expression in Primary Cultures of Human Hepatocytes by ToxCast Chemicals

    EPA Science Inventory

    ToxCast chemicals were assessed for induction or suppression of xenobiotic metabolizing enzyme and transporter gene expression using primary human hepatocytes. The mRNA levels of 14 target and 2 control genes were measured: ABCB1, ABCB11, ABCG2, SLCO1B1, CYP1A1, CYP1A2, CYP2B6, C...

  15. REPORT ON THE HOMELAND SECURITY WORKSHOP ON TRANSPORT AND DISPOSAL OF WASTES FROM FACILITIES CONTAMINATED WITH CHEMICAL AND BIOLOGICAL AGENTS

    EPA Science Inventory

    This report summarizes discussions from the "Homeland Security Workshop on Transport and Disposal of Wastes From Facilities Contaminated With Chemical or Biological Agents." The workshop was held on May 28-30, 2003, in Cincinnati, Ohio, and its objectives were to:

    .Documen...

  16. EFFECTS OF SELECTED NEUROACTIVE CHEMICALS ON CALCIUM TRANSPORTING SYSTEMS IN RAT CEREBELLUM AND ON SURVIVAL OF CEREBELLAR GRANULE CELLS

    EPA Science Inventory

    This investigation examined the effects of several neuroactive chemicals on Ca2+ -transporting systems and cytotoxicity in vitro. 5Ca2+ -uptake as a measure of Ca2+s -sequestration, was determined n mitochondria and microsomes, isolated from cerebella of adult male Long-Evans hoo...

  17. Temporal Changes in Aqu/C60 Physical-Chemical, Deposition, and Transport Characteristics in Aqueous Systems

    EPA Science Inventory

    Little is known about how temporal changes in the physical–chemical properties of C60 aggregates formed in aqueous systems (termed aqu/C60) can impact transport pathways contributing to ecological exposures. In this study three aqu/C60 suspensions of short-term (100 days), interm...

  18. Soil structure, colloids, and chemical transport as affected by short-term reducing conditions: a laboratory study

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Upland soils in the Midwestern US often undergo reducing conditions when soils are temporally flooded during the spring and remain water saturated for days or weeks. Short-term reducing conditions change the chemistry of the soil and may affect soil structure and solution chemical transport. The eff...

  19. MOBILIZATION AND TRANSPORT OF SOIL PARTICLES DURING INFILTRATION EXPERIMENTS IN AN AGRICULTURAL FIELD, SHENANDOAH VALLEY, VIRGINIA. (R824772)

    EPA Science Inventory

    Evidence that fine particles mobilized and transported in
    soils and aquifers can have a profound influence on
    contaminant migration has spawned much interest recently
    in understanding colloid transport in natural materials.
    Repeated infiltration experiments on an i...

  20. Transport, ultrastructural localization, and distribution of chemical forms of lead in radish (Raphanus sativus L.).

    PubMed

    Wang, Yan; Shen, Hong; Xu, Liang; Zhu, Xianwen; Li, Chao; Zhang, Wei; Xie, Yang; Gong, Yiqin; Liu, Liwang

    2015-01-01

    Lead (Pb), a ubiquitous but highly toxic heavy metal (HM), is harmful to human health through various pathways including by ingestion of contaminated vegetables. Radish is a worldwide root vegetable crop with significant health and nutritional benefits. However, little is known about Pb translocation and distribution within radish plants after its uptake by the roots. In this study, Pb stress was induced using Pb(NO3)2 in hydroponic culture, aiming to characterize the transport, ultrastructural localization, and distribution of chemical forms of Pb in different tissues of radish. The results showed that the majority of Pb (85.76-98.72%) was retained in underground organs including lateral roots, root heads and taproot skins, while a small proportion of Pb was absorbed by root flesh (0.44-1.56%) or transported to the shoot (1.28-14.24%). A large proportion of Pb (74.11-99.30%) was integrated with undissolved Pb oxalate, protein and pectates forming Pb-phosphate complexes. Moreover, a low-Pb-accumulating line of radish showed a higher proportion of Pb in water-soluble form compared with a high-Pb-accumulating line. Subcellular distribution analysis showed that a large proportion of Pb was bound to cell wall fraction in lateral roots (71.08-80.40%) and taproot skin (46.22-77.94%), while the leaves and roots had 28.36-39.37% and 27.35-46.51% of Pb stored in the soluble fraction, respectively. Furthermore, transmission electron microscopy (TEM) revealed Pb precipitates in intercellular space, cell wall, plasma lemma and vacuoles. Fractionation results also showed the accumulation of Pb on the cell wall, intercellular space and vacuole, and low uptake of undissolved Pb oxalate, protein, pectates and Pb-phosphate complexes, which might be due to low transport efficiency and Pb tolerance of radish. These findings would provide insight into molecular mechanism of Pb uptake and translocation in radish and facilitate development of low-Pb-content cultivars in root vegetable

  1. Inputs and Fluvial Transport of Pharmaceutical Chemicals in An Urban Watershed

    NASA Astrophysics Data System (ADS)

    Foster, G. D.; Shala, L.

    2006-05-01

    Pharmaceuticals and personal care products (PPCPs) are classes of emerging chemical contaminants thought to enter the aquatic environment primarily through wastewater treatment plant (WTP) discharges. As the use of drugs is expected to rise with the aging demographics of the human population and with more river water being diverted to meet potable water demands, the presence of PPCPs in surface water is becoming an issue of public concern. The intent of our study was to quantify potential WTP inputs of PPCPs to rivers in the Wasington, DC (USA) region, and to investigate the fluvial transport of PPCPs in the Anacostia River (AR), the mainstem of a highly contaminated urban watershed in Washington, DC. The approach was to sample WTP water at various stages of treatment, and to measure seasonal concentrations of PPCPs in fluvial transport in the AR. Surface water from the AR was collected through the use of automated samplers during normal flow and storm flow regimes near the head of tide of the AR, just upstream from the confluence of the Northeast (NE) and Northwest (NW) Branches, the two prominent drainages in the watershed. The water samples were filtered to separate river particles from water, and the filtered water was extracted using solid phase extraction (SPE) cartridges. The filters were extracted by sonication in methanol. The SPE and filter extracts were analyzed for a group of widely distributed PPCPs as trimethylsilyl derivatives by using gas chromatography/mass spectrometry. The most frequently detected PPCPs at WTPs included ibuprofen, caffeine, naproxen and triclosan, which ranged from 45 μg/L (caffeine) to 5 μg/L (triclosan) in WTP influent and from 0.08 μg/L (triclosan) to 0.02 μg/L (ibuprofen) in effluent water. Similar PPCPs were detected in both the NE and NW Branches of the AR, but higher concentrations on average were observed in the NE Branch, which receives WTP effluent upstream from the sampling point. The incidence of PPCPs correlated

  2. Transport, ultrastructural localization, and distribution of chemical forms of lead in radish (Raphanus sativus L.)

    PubMed Central

    Wang, Yan; Shen, Hong; Xu, Liang; Zhu, Xianwen; Li, Chao; Zhang, Wei; Xie, Yang; Gong, Yiqin; Liu, Liwang

    2015-01-01

    Lead (Pb), a ubiquitous but highly toxic heavy metal (HM), is harmful to human health through various pathways including by ingestion of contaminated vegetables. Radish is a worldwide root vegetable crop with significant health and nutritional benefits. However, little is known about Pb translocation and distribution within radish plants after its uptake by the roots. In this study, Pb stress was induced using Pb(NO3)2 in hydroponic culture, aiming to characterize the transport, ultrastructural localization, and distribution of chemical forms of Pb in different tissues of radish. The results showed that the majority of Pb (85.76–98.72%) was retained in underground organs including lateral roots, root heads and taproot skins, while a small proportion of Pb was absorbed by root flesh (0.44–1.56%) or transported to the shoot (1.28–14.24%). A large proportion of Pb (74.11–99.30%) was integrated with undissolved Pb oxalate, protein and pectates forming Pb–phosphate complexes. Moreover, a low-Pb-accumulating line of radish showed a higher proportion of Pb in water-soluble form compared with a high-Pb-accumulating line. Subcellular distribution analysis showed that a large proportion of Pb was bound to cell wall fraction in lateral roots (71.08–80.40%) and taproot skin (46.22–77.94%), while the leaves and roots had 28.36–39.37% and 27.35–46.51% of Pb stored in the soluble fraction, respectively. Furthermore, transmission electron microscopy (TEM) revealed Pb precipitates in intercellular space, cell wall, plasma lemma and vacuoles. Fractionation results also showed the accumulation of Pb on the cell wall, intercellular space and vacuole, and low uptake of undissolved Pb oxalate, protein, pectates and Pb–phosphate complexes, which might be due to low transport efficiency and Pb tolerance of radish. These findings would provide insight into molecular mechanism of Pb uptake and translocation in radish and facilitate development of low-Pb-content cultivars

  3. Use of vegetated agricultural drainage ditches to decrease pesticide transport from tomato and alfalfa fields in California: runoff toxicity

    Technology Transfer Automated Retrieval System (TEKTRAN)

    This study was performed to investigate the potential of vegetated drainage ditches for mitigating the impact of agricultural irrigation runoff on downstream aquatic ecosystems. Water column toxicity to larval fathead minnow (Pimephales promelas), and the amphipod, Hyalella azteca, was measured for ...

  4. Modeling lightning-NOx chemistry at sub-grid scale in a global chemical transport model

    NASA Astrophysics Data System (ADS)

    Gressent, A.; Sauvage, B.; Cariolle, D.; Evans, M.; Leriche, M.; Mari, C.; Thouret, V.

    2015-12-01

    For the first time, a plume-in-grid approach is implemented in a chemical transport model (CTM) to parameterize the effects of the non-linear reactions occurring within high concentrated NOx plumes from lightning NOx emissions (LNOx) in the upper troposphere. It is characterized by a set of parameters including the plume lifetime, the effective reaction rate constant related to NOx-O3 chemical interactions and the fractions of NOx conversion into HNO3 within the plume. Parameter estimates were made using the DSMACC chemical box model, simple plume dispersion simulations and the mesoscale 3-D Meso-NH model. In order to assess the impact of the LNOx plume approach on the NOx and O3 distributions at large scale, simulations for the year 2006 were performed using the GEOS-Chem global model with a horizontal resolution of 2° × 2.5°. The implementation of the LNOx parameterization implies NOx and O3 decrease at large scale over the region characterized by a strong lightning activity (up to 25 and 8 %, respectively, over Central Africa in July) and a relative increase downwind of LNOx emissions (up to 18 and 2 % for NOx and O3, respectively, in July) are derived. The calculated variability of NOx and O3 mixing ratios around the mean value according to the known uncertainties on the parameter estimates is maximum over continental tropical regions with ΔNOx [-33.1; +29.7] ppt and ΔO3 [-1.56; +2.16] ppb, in January, and ΔNOx [-14.3; +21] ppt and ΔO3 [-1.18; +1.93] ppb, in July, mainly depending on the determination of the diffusion properties of the atmosphere and the initial NO mixing ratio injected by lightning. This approach allows (i) to reproduce a more realistic lightning NOx chemistry leading to better NOx and O3 distributions at the large scale and (ii) focus on other improvements to reduce remaining uncertainties from processes related to NOx chemistry in CTM.

  5. Agricultural Aircraft for Site-Specific Agriculture

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Agricultural aircraft provide a convenient platform to aid in precision agriculture, in which pesticide, fertilizer or other field inputs are applied only where they are needed. This saves on chemical and farm resources, and reduces environmental loading. Remote sensing is used to spot areas of the ...

  6. Colloids in groundwater: Their mobilization, subsurface transport, and sorption affinity for toxic chemicals

    SciTech Connect

    Not Available

    1991-01-01

    During the initial project period, we have pursued several activities with the overall goal of characterizing the roles of colloid in groundwater. First, we have collected soil cores from a site where we have previously found large quantities of kaolinite colloids in the groundwater. We have intensely investigated these cores to test our hypothesis that the colloids have been mobilized as a result of iron oxide dissolution. Next, we have constructed a soil core system in our laboratory with which we are attempting to mimic the factors that we think are governing colloid transport in the subsurface. Finally, we have pursued the issue of how well organic chemicals bind to the kinds of colloids that we are seeing at field sites. Together, with our knowledge of colloid mobility, we anticipate that this sorption data will enable us to predict the influence of groundwater colloids on contaminant fates in the subsurface. Our progress in each of these activities is described in this report. 7 refs., 12 figs.

  7. Interpretation of Trace Gas Data Using Inverse Methods and Global Chemical Transport Models

    NASA Technical Reports Server (NTRS)

    Prinn, Ronald G.

    1997-01-01

    This is a theoretical research project aimed at: (1) development, testing, and refining of inverse methods for determining regional and global transient source and sink strengths for long lived gases important in ozone depletion and climate forcing, (2) utilization of inverse methods to determine these source/sink strengths which use the NCAR/Boulder CCM2-T42 3-D model and a global 3-D Model for Atmospheric Transport and Chemistry (MATCH) which is based on analyzed observed wind fields (developed in collaboration by MIT and NCAR/Boulder), (3) determination of global (and perhaps regional) average hydroxyl radical concentrations using inverse methods with multiple titrating gases, and, (4) computation of the lifetimes and spatially resolved destruction rates of trace gases using 3-D models. Important goals include determination of regional source strengths of methane, nitrous oxide, and other climatically and chemically important biogenic trace gases and also of halocarbons restricted by the Montreal Protocol and its follow-on agreements and hydrohalocarbons used as alternatives to the restricted halocarbons.

  8. Structure Enhancement Relationship of Chemical Penetration Enhancers in Drug Transport across the Stratum Corneum

    PubMed Central

    Chantasart, Doungdaw; Li, S. Kevin

    2012-01-01

    The stratum corneum is a major barrier of drug penetration across the skin in transdermal delivery. For effective transdermal drug delivery, skin penetration enhancers are used to overcome this barrier. In the past decades, a number of research studies were conducted to understand the mechanisms of skin penetration enhancers and to develop a structure enhancement relationship. Such understanding allows effective prediction of the effects of skin penetration enhancers, assists topical and transdermal formulation development, and avoids extensive enhancer screening in the transdermal delivery industry. In the past two decades, several hypotheses on chemical enhancer-induced penetration enhancement for transport across the skin lipoidal pathway have been examined based on a systematic approach. Particularly, a hypothesis that skin penetration enhancement is directly related to the concentration of the enhancers in the stratum corneum lipid domain was examined. A direct relationship between skin penetration enhancer potency (based on enhancer aqueous concentration in the diffusion cell chamber) and enhancer n-octanol-water partition coefficient was also established. The nature of the microenvironment of the enhancer site of action in the stratum corneum lipid domain was found to be mimicked by n-octanol. The present paper reviews the work related to these hypotheses and the relationships between skin penetration enhancement and enhancer concentration in the drug delivery media and stratum corneum lipids. PMID:24300181

  9. Performance and cost of energy transport and storage systems for dish applications using reversible chemical reactions

    NASA Technical Reports Server (NTRS)

    Schredder, J. M.; Fujita, T.

    1984-01-01

    The use of reversible chemical reactions for energy transport and storage for parabolic dish networks is considered. Performance and cost characteristics are estimated for systems using three reactions (sulfur-trioxide decomposition, steam reforming of methane, and carbon-dioxide reforming of methane). Systems are considered with and without storage, and in several energy-delivery configurations that give different profiles of energy delivered versus temperature. Cost estimates are derived assuming the use of metal components and of advanced ceramics. (The latter reduces the costs by three- to five-fold). The process that led to the selection of the three reactions is described, and the effects of varying temperatures, pressures, and heat exchanger sizes are addressed. A state-of-the-art survey was performed as part of this study. As a result of this survey, it appears that formidable technical risks exist for any attempt to implement the systems analyzed in this study, especially in the area of reactor design and performance. The behavior of all components and complete systems under thermal energy transients is very poorly understood. This study indicates that thermochemical storage systems that store reactants as liquids have efficiencies below 60%, which is in agreement with the findings of earlier investigators.

  10. Bioassessment of contaminant transport and distribution in aquatic ecosystems by chemical analysis of burrowing mayflies (Hexagenia)

    USGS Publications Warehouse

    Steingraeber, M.T.; Wiener, J.G.

    1995-01-01

    Burrowing mayfly nymphs (Ephemeroptera) inhabit and ingest fine-grained sediments and detritus that may be enriched with metals and persistent organic compounds. The burrowing nymphs can externally adsorb and internally assimilate these contaminants, providing a link for the food chain transfer of potentially toxic substances from sediments to organisms in higher trophic levels. The emergent adults are short-lived and do not feed, thus their gut contents do not contribute greatly to their total contaminant burden. These characteristics make Hexagenia spp. And certain other burrowing mayflies useful for assessing ecosystem contamination. General protocols are presented for the collection, processing and analysis of emergent mayflies to assess the spatial distribution and bioaccumulation of sediment-associated contaminants in aquatic ecosystems. Two essential components of this bioassessment approach are a network of on-site volunteers with the materials and instructions needed to correctly collect and store samples and quality assurance procedures to estimate the accuracy of chemical analyses. The utility of this approach is demonstrated with an example of its application to the Upper Mississippi River (USA). Determination of cadmium, mercury and polychlorinated biphenyl congeners in emergent Hexagenia bilineata from a 1250 km reach of this river revealed (1) several source areas of contaminants and (2) distinct patterns in the bioaccumulation (and apparent sediment-associated transport) of each residue on both small and large spatial scales.

  11. Pathogen and chemical transport in the karst limestone of the Biscayne aquifer: 2. Chemical retention from diffusion and slow advection

    USGS Publications Warehouse

    Shapiro, A.M.; Renken, R.A.; Harvey, R.W.; Zygnerski, M.R.; Metge, D.W.

    2008-01-01

    A tracer experiment, using a nonreactive tracer, was conducted as part of an investigation of the potential for chemical and pathogen migration to public supply wells that draw groundwater from the highly transmissive karst limestone of the Biscayne aquifer in southeastern Florida. The tracer was injected into the formation over approximately 1 h, and its recovery was monitored at a pumping well approximately 100 m from the injection well. The first detection of the tracer occurred after approximately 5 h, and the peak concentration occurred at about 8 h after the injection. The tracer was still detected in the production well more than 6 days after injection, and only 42% of the tracer mass was recovered. It is hypothesized that a combination of chemical diffusion and slow advection resulted in significant retention of the tracer in the formation, despite the high transmissivity of the karst limestone. The tail of the breakthrough curve exhibited a straight-line behavior with a slope of -2 on a log-log plot of concentration versus time. The -2 slope is hypothesized to be a function of slow advection, where the velocities of flow paths are hypothesized to range over several orders of magnitude. The flow paths having the slowest velocities result in a response similar to chemical diffusion. Chemical diffusion, due to chemical gradients, is still ongoing during the declining limb of the breakthrough curve, but this process is dwarfed by the magnitude of the mass flux by slow advection.

  12. Development of a Global Tropospheric Aerosol Chemical Transport Model MASINGAR and its Application to the Dust Storm Forecasting

    NASA Astrophysics Data System (ADS)

    Tanaka, T. Y.

    2002-12-01

    We are developing a new three-dimensional aerosol chemical transport model coupled with the MRI/JMA98 GCM, named Model of Aerosol Species IN the Global AtmospheRe (MASINGAR), for the study of atmospheric aerosols and related trace species. MASINGAR treats four major aerosol species that include nss-sulfate, carbonaceous, mineral dust, and sea-salt aerosols. The model accounts for large-scale advective transport, subgrid-scale eddy diffusive and convective transport, surface emission and deposition, wet deposition, as well as chemical reactions. The advective transport is calculated using the semi-Lagrangian transport scheme. Parameterization of convective transport is based on the convective mass flux by Arakawa-Schubert scheme. The space and time resolution of the model are variable, with a standard resolution of T42 (2.8ox2.8o) and 30 levels (up to 0.8hPa). In addition, the model has a built-in four-dimensional data assimilation with assimilated meteorological field, which enables the model to perform a realistic simulation on a specific period and short-period forecast of aerosols. The model was applied to the numerical forecasting of dust storm in spring, 2002, when the first intensive observational period of Aeolian Dust Experiment on the Climatic impact (ADEC) project was conducted. The model simulation of mineral dust aerosol suggests that the synoptic scale aerosol events can be simulated by MASINGAR.

  13. Enhancement of Bacterial Transport in Aerobic and Anaerobic Environments: Assessing the Effect of Metal Oxide Chemical Heterogeneities

    SciTech Connect

    T.C. Onstott

    2005-09-30

    The goal of our research was to understand the fundamental processes that control microbial transport in physically and chemically heterogeneous aquifers and from this enhanced understanding determine the requirements for successful, field-scale delivery of microorganisms to metal contaminated subsurface sites. Our specific research goals were to determine; (1) the circumstances under which the preferential adsorption of bacteria to Fe, Mn, and Al oxyhydroxides influences field-scale bacterial transport, (2) the extent to which the adhesion properties of bacterial cells affect field-scale bacterial transport, (3) whether microbial Fe(III) reduction can enhance field-scale transport of Fe reducing bacteria (IRB) and other microorganisms and (4) the effect of field-scale physical and chemical heterogeneity on all three processes. Some of the spin-offs from this basic research that can improve biostimulation and bioaugmentation remediation efforts at contaminated DOE sites have included; (1) new bacterial tracking tools for viable bacteria; (2) an integrated protocol which combines subsurface characterization, laboratory-scale experimentation, and scale-up techniques to accurately predict field-scale bacterial transport; and (3) innovative and inexpensive field equipment and methods that can be employed to enhance Fe(III) reduction and microbial transport and to target microbial deposition under both aerobic and anaerobic conditions.

  14. Three-dimensional Wavelet-based Adaptive Mesh Refinement for Global Atmospheric Chemical Transport Modeling

    NASA Astrophysics Data System (ADS)

    Rastigejev, Y.; Semakin, A. N.

    2013-12-01

    Accurate numerical simulations of global scale three-dimensional atmospheric chemical transport models (CTMs) are essential for studies of many important atmospheric chemistry problems such as adverse effect of air pollutants on human health, ecosystems and the Earth's climate. These simulations usually require large CPU time due to numerical difficulties associated with a wide range of spatial and temporal scales, nonlinearity and large number of reacting species. In our previous work we have shown that in order to achieve adequate convergence rate and accuracy, the mesh spacing in numerical simulation of global synoptic-scale pollution plume transport must be decreased to a few kilometers. This resolution is difficult to achieve for global CTMs on uniform or quasi-uniform grids. To address the described above difficulty we developed a three-dimensional Wavelet-based Adaptive Mesh Refinement (WAMR) algorithm. The method employs a highly non-uniform adaptive grid with fine resolution over the areas of interest without requiring small grid-spacing throughout the entire domain. The method uses multi-grid iterative solver that naturally takes advantage of a multilevel structure of the adaptive grid. In order to represent the multilevel adaptive grid efficiently, a dynamic data structure based on indirect memory addressing has been developed. The data structure allows rapid access to individual points, fast inter-grid operations and re-gridding. The WAMR method has been implemented on parallel computer architectures. The parallel algorithm is based on run-time partitioning and load-balancing scheme for the adaptive grid. The partitioning scheme maintains locality to reduce communications between computing nodes. The parallel scheme was found to be cost-effective. Specifically we obtained an order of magnitude increase in computational speed for numerical simulations performed on a twelve-core single processor workstation. We have applied the WAMR method for numerical

  15. Hydrogeologic and agricultural-chemical data for the South Skunk River alluvial aquifer at a site in Story County, Iowa, 1992-93

    USGS Publications Warehouse

    Buchmiller, R.C.

    1995-01-01

    A reconnaissance study was conducted during 1992-93 to collect background hydrogeologic and agricultural-chemical data for the South Skunk River alluvial aquifer near Ames, Iowa. Observation wells were drilled to characterize the surficial geologic materials of a field-scale study site and to provide locations for collecting waterlevel and agricultural-chemical data. Walnut Creek, a tributary to the South Skunk River, forms a lateral boundary on the northern edge of the field site. Water-level measurements showed a hydraulic-head gradient towards the South Skunk River under both wet and dry conditions at the study site. Walnut Creek appears to be losing water to the aquifer during most hydrologic conditions. More than 20 milligrams per liter of nitrate as nitrogen were present consistently in water from the southeastern part of the study site. Nitrate-as-nitrogen concentrations in water samples from other locations routinely did not exceed 10 milligrams per liter. The herbicide atrazine was detected most often, 36 of 38 times, in water samples collected from observation wells adjacent to Walnut Creek. Atrazine was not used on the study site during 1992-93 but was found frequently in water samples from Walnut Creek. Therefore, Walnut Creek appears to be a source of herbicide contamination to the alluvial aquifer.

  16. The Effects of Long-Range Transport of Agricultural Smoke on AOD in Houston, TX: Insights from NASA SEAC4RS and DISCOVER-AQ

    NASA Astrophysics Data System (ADS)

    Beyersdorf, A. J.; Ziemba, L. D.; Anderson, B. E.; Chen, G.; Corr, C.; Crumeyrolle, S.; Moore, R.; Thornhill, K. L., II; Winstead, E.

    2014-12-01

    In September 2013, the NASA P-3B performed systematic in-situ profiles throughout the Houston, TX area as part of the DISCOVER-AQ project. During this campaign, smoke originating from agricultural fires in the Mississippi River Valley contributed up to 80% of the aerosol optical depths (AODs) and thus complicated estimation of ground-level PM2.5 from AOD. Comparison with measurements of fresh agricultural fires during both DISCOVER-AQ and SEAC4RS showed that these lofted layers were considerably aged with higher single scattering albedos and water-uptake potential (f(RH)). This more hygroscopic aged smoke (with f(RH)'s of 1.5) created higher AODs than would be obtained if fresh smoke (f(RH) on the order of 1.1) had been present. In addition, profiling done as part of SEAC4RS throughout the Southeast will be compared to ground-based PM2.5 allowing for determination of background aerosol vertical distributions in the region and the extent of the smoke transport. Historic long-term measurements of AOD (from AERONET) and PM2.5 (from ground-based monitoring sites) will also be addressed to determine the frequency of these long-range transport events.

  17. Pathogen and chemical transport in the karst limestone of the Biscayne aquifer: 1. Revised conceptualization of groundwater flow

    USGS Publications Warehouse

    Renken, R.A.; Cunningham, K.J.; Shapiro, A.M.; Harvey, R.W.; Zygnerski, M.R.; Metge, D.W.; Wacker, M.A.

    2008-01-01

    The Biscayne aquifer is a highly transmissive karst limestone that serves as the sole source of drinking water to over two million residents in south Florida. The aquifer is characterized by eogenetic karst, where the most transmissive void space can be an interconnected, touching-vug, biogenically influenced porosity of biogenic origin. Public supply wells in the aquifer are in close proximity to lakes established by surface mining. The mining of the limestone has occurred to the same depths as the production wells, which has raised concerns about pathogen and chemical transport from these surface water bodies. Hydraulic and forced gradient tracer tests were conducted to augment geologic and geophysical studies and to develop a hydrogeologic conceptual model of groundwater flow and chemical transport in the Biscayne aquifer. Geologic and geophysical data indicate multiple, areally extensive subhorizontal preferential flow zones of vuggy limestone separated by rock with a matrix pore system. The hydraulic response from an aquifer test suggests that the Biscayne aquifer behaves as a dual-porosity medium; however, the results of the tracer test showed rapid transport similar to other types of karst. The tracer test and concurrent temperature logging revealed that only one of the touching-vug flow zones dominates transport near the production wells. On the basis of the rising limb of the breakthrough curve, the dispersivity is estimated to be less than 3% of the tracer travel distance, which suggests that the fastest flow paths in the formation are likely to yield limited dilution of chemical constituents.

  18. Numerical Modeling of Coupled Variably-Saturated Fluid Flow and Reactive Transport with Fast and Slow Chemical Reactions

    SciTech Connect

    LI, MING-HSU; SIEGEL, MALCOLM D.; YEH, GOUR-TSYH

    1999-09-20

    The couplings among chemical reaction rates, advective and diffusive transport in fractured media or soils, and changes in hydraulic properties due to precipitation and dissolution within fractures and in rock matrix are important for both nuclear waste disposal and remediation of contaminated sites. This paper describes the development and application of LEHGC2.0, a mechanistically-based numerical model for simulation of coupled fluid flow and reactive chemical transport including both fast and slow reactions invariably saturated media. Theoretical bases and numerical implementations are summarized, and two example problems are demonstrated. The first example deals with the effect of precipitation-dissolution on fluid flow and matrix diffusion in a two-dimensional fractured media. Because of the precipitation and decreased diffusion of solute from the fracture into the matrix, retardation in the fractured medium is not as large as the case wherein interactions between chemical reactions and transport are not considered. The second example focuses on a complicated but realistic advective-dispersive-reactive transport problem. This example exemplifies the need for innovative numerical algorithms to solve problems involving stiff geochemical reactions.

  19. Control of transport and magnetism in ferromagnetic semiconducting superlattices through growth conditions and chemical surface effects

    NASA Astrophysics Data System (ADS)

    Kreutz, Theodore Carlton

    2003-10-01

    Within the emerging area of spintronics, magnetic semiconductors have been the subject of many recent studies. Advances in magnetizing traditional semiconductors like GaAs, through the introduction of Mn, have been the focus of many experiments. Recently, studies have focused on ferromagnetic semiconducting superlattices, where half-monolayer MnAs planes are separated by GaAs spacers. These structures have only recently been grown, and it is of particular interest to discover the properties of this material, and if it can be used in future spintronic devices. We have studied changes in the magnetic and transport properties of ferromagnetic semiconducting superlattices as a function of temperature, superlattice period and substrate growth temperature. We have measured the resistance, Hall resistance and magnetoresistance over a wide range of temperatures. We see that as the period of the superlattice increases, the per-layer resistance and the Curie temperature reach saturation values at approximately the same value. We also find that electrical transport is predominantly through hopping conduction. The anomalous Hall effect dominates the Hall resistance. With the period fixed, we vary the substrate temperature during growth and observe that higher substrate temperatures lead to less resistive samples. Also, for samples with high substrate temperatures, we find that the anomalous Hall coefficient can flip in sign. We also observe changes in the magnetic anisotropy as we vary the period of the superlattice and the substrate temperature. We observe this change with planar Hall effect as well as SQUID magnetometry measurements. Samples with short periods show cubic magnetic anisotropy whereas samples with larger period show uniaxial anisotropy. We then determine the anisotropy constants for this material. We also see that the switching is dominated by domain pinning processes. Finally, we are able to change the Curie temperature of ½ ML MnAs planes in GaAs through the

  20. Secondary organic aerosol in the global aerosol - chemical transport model Oslo CTM2

    NASA Astrophysics Data System (ADS)

    Hoyle, C. R.; Berntsen, T.; Myhre, G.; Isaksen, I. S. A.

    2007-11-01

    The global chemical transport model Oslo CTM2 has been extended to include the formation, transport and deposition of secondary organic aerosol (SOA). Precursor hydrocarbons which are oxidised to form condensible species include both biogenic species such as terpenes and isoprene, as well as species emitted predominantly by anthropogenic activities (toluene, m-xylene, methylbenzene and other aromatics). A model simulation for 2004 gives an annual global SOA production of approximately 55 Tg. Of this total, 2.5 Tg is found to consist of the oxidation products of anthropogenically emitted hydrocarbons, and about 15 Tg is formed by the oxidation products of isoprene. The global production of SOA is increased to about 69 Tg yr-1 by allowing semi-volatile species to partition to ammonium sulphate aerosol. This brings modelled organic aerosol values closer to those observed, however observations in Europe remain significantly underestimated. Allowing SOA to partition into ammonium sulphate aerosol increases the contribution of anthropogenic SOA from about 4.5% to 9.4% of the total production. Total modelled organic aerosol (OA) values are found to represent a lower fraction of the measured values in winter (when primary organic aerosol (POA) is the dominant OA component) than in summer, which may be an indication that estimates of POA emissions are too low. Additionally, for measurement stations where the summer OA values are higher than in winter, the model generally underestimates the increase in summertime OA. In order to correctly model the observed increase in OA in summer, additional SOA sources or formation mechanisms may be necessary. The importance of NO3 as an oxidant of SOA precursors is found to vary regionally, causing up to 50%-60% of the total amount of SOA near the surface in polluted regions and less than 25% in more remote areas, if the yield of condensible oxidation products for β-pinene is used for NO3 oxidation of all terpenes. Reducing the yield

  1. Agriculture Education. Agriculture Structures.

    ERIC Educational Resources Information Center

    Stuttgart Public Schools, AR.

    This curriculum guide is designed for group instruction of secondary agricultural education students enrolled in one or two semester-long courses in agriculture structures. The guide presents units of study in the following areas: (1) shop safety, (2) identification and general use of hand tools, (3) power tools, (4) carpentry, (5) blueprint…

  2. Role of chemical reactions of arylamine hole transport materials in operational degradation of organic light-emitting diodes

    SciTech Connect

    Kondakov, Denis Y.

    2008-10-15

    We report that the representative arylamine hole transport materials undergo chemical transformations in operating organic light-emitting diode (OLED) devices. Although the underlying chemical mechanisms are too complex to be completely elucidated, structures of several identified degradation products point at dissociations of relatively weak carbon-nitrogen and carbon-carbon bonds in arylamine molecules as the initiating step. Considering the photochemical reactivities, the bond dissociation reactions of arylamines occur by the homolysis of the lowest singlet excited states formed by recombining charge carriers in the operating OLED device. The subsequent chemical reactions are likely to yield long-lived, stabilized free radicals capable of acting as deep traps--nonradiative recombination centers and fluorescence quenchers. Their presence in the hole transport layer results in irreversible hole trapping and manifests as a positive fixed charge. The extent and localization of chemical transformations in several exemplary devices suggest that the free radical reactions of hole transporting materials, arylamines, can be sufficient to account for the observed luminance efficiency loss and voltage rise in operating OLEDs. The relative bond strengths and excited state energies of OLED materials appear to have a determining effect on the operational stability of OLED devices.

  3. CHEMICAL TRANSPORT IN A FISSURED BOCK: VERIFICATION OF A NUMERICAL MODEL

    SciTech Connect

    Rasmuson, A.; Narasimhan, T.N.; Neretnieks, I.

    1982-04-01

    Numerical models for simulating chemical transport in fissured rocks constitute powerful tools for evaluating the acceptability of geological nuclear waste repositories. Due to the very long-term, high toxicity of some nuclear waste products, the models are required to predict, in certain cases, the spatial and temporal distribution of chemical concentration less than 0.001% of the concentration released from the repository. Whether numerical models can provide such accuracies is a major question addressed in the present work. To this end, we have verified a numerical model, TRUMP, which solves the advective diffusion equation in general three dimensions with or without decay and source terms. The method is based on an integrated finite-difference approach. The model was verified against known analytic solution of the one-dimensional advection-diffusion problem as well as the problem of advection-diffusion in a system of parallel fractures separated by spherical particles. The studies show that as long as the magnitude of advectance is equal to or less than that of conductance for the closed surface bounding any volume element in the region (that is, numerical Peclet number <2), the numerical method can indeed match the analytic solution within errors of ±10{sup -3} % or less. The realistic input parameters used in the sample calculations suggest that such a range of Peclet numbers is indeed likely to characterize deep groundwater systems in granitic and ancient argillaceous systems. Thus TRUMP in its present form does provide a viable tool for use in nuclear waste evaluation studies. A sensitivity analysis based on the analytic solution suggests that the errors in prediction introduced due to uncertainties in input parameters is likely to be larger than the computational inaccuracies introduced by the numerical model. Currently, a disadvantage in the TRUMP model is that the iterative method of solving the set of simultaneous equations is rather slow when time

  4. Chemical Transport in a Fissured Rock: Verification of a Numerical Model

    NASA Astrophysics Data System (ADS)

    Rasmuson, A.; Narasimhan, T. N.; Neretnieks, I.

    1982-10-01

    Numerical models for simulating chemical transport in fissured rocks constitute powerful tools for evaluating the acceptability of geological nuclear waste repositories. Due to the very long-term, high toxicity of some nuclear waste products, the models are required to predict, in certain cases, the spatial and temporal distribution of chemical concentration less than 0.001% of the concentration released from the repository. Whether numerical models can provide such accuracies is a major question addressed in the present work. To this end we have verified a numerical model, TRUMP, which solves the advective diffusion equation in general three dimensions, with or without decay and source terms. The method is based on an integrated finite difference approach. The model was verified against known analytic solution of the one-dimensional advection-diffusion problem, as well as the problem of advection-diffusion in a system of parallel fractures separated by spherical particles. The studies show that as long as the magnitude of advectance is equal to or less than that of conductance for the closed surface bounding any volume element in the region (that is, numerical Peclet number <2), the numerical method can indeed match the analytic solution within errors of ±10-3% or less. The realistic input parameters used in the sample calculations suggest that such a range of Peclet numbers is indeed likely to characterize deep groundwater systems in granitic and ancient argillaceous systems. Thus TRUMP in its present form does provide a viable tool for use in nuclear waste evaluation studies. A sensitivity analysis based on the analytic solution suggests that the errors in prediction introduced due to uncertainties in input parameters are likely to be larger than the computational inaccuracies introduced by the numerical model. Currently, a disadvantage in the TRUMP model is that the iterative method of solving the set of simultaneous equations is rather slow when time

  5. Chemical Control of Lead Sulfide Quantum Dot Shape, Self-Assembly, and Charge Transport

    NASA Astrophysics Data System (ADS)

    McPhail, Martin R.

    Lead(II) sulfide quantum dots (PbS QDs) are a promising excitonic material for numerous application that require that control of fluxes of charge and energy at nanoscale interfaces, such as solar energy conversion, photo- and electrocatalysis, light emitting diodes, chemical sensing, single-electron logic elements, field effect transistors, and photovoltaics. PbS QDs are particularly suitable for photonics applications because they exhibit size-tunable band-edge absorption and fluorescence across the entire near-infrared spectrum, undergo efficient multi-exciton generation, exhibit a long radiative lifetime, and possess an eight-fold degenerate ground-state. The effective integration of PbS QDs into these applications requires a thorough understanding of how to control their synthesis, self-assembly, and charge transport phenomena. In this document, I describe a series of experiments to elucidate three levels of chemical control on the emergent properties of PbS QDs: (1) the role of surface chemistry in controlling PbS QD shape during solvothermal synthesis, (2) the role of QD shape and ligand functionalization in self-assembly at a liquid-air interface, and (3) the role of QD packing structure on steady-state conductivity and transient current dynamics. At the synthetic level (1), I show that the final shape and surface chemistry of PbS QDs is highly sensitive to the formation of organosulfur byproducts by commonly used sulfur reagents. The insight into PbS QD growth gained from this work is then developed to controllably tune PbS QD shape from cubic to octahedral to hexapodal while maintaining QD size. At the following level of QD self-assembly (2), I show how QD size and shape dictate packing geometry in extended 2D arrays and how this packing can be controllably interrupted in mixed monolayers. I also study the role of ligand structure on the reorganization of QD arrays at a liquid-air interface and find that the specific packing defects in QD arrays vary

  6. A review of approaches to estimate wildfire plume injection height within large-scale atmospheric chemical transport models

    NASA Astrophysics Data System (ADS)

    Paugam, R.; Wooster, M.; Freitas, S.; Martin, M. Val

    2016-01-01

    Landscape fires produce smoke containing a very wide variety of chemical species, both gases and aerosols. For larger, more intense fires that produce the greatest amounts of emissions per unit time, the smoke tends initially to be transported vertically or semi-vertically close by the source region, driven by the intense heat and convective energy released by the burning vegetation. The column of hot smoke rapidly entrains cooler ambient air, forming a rising plume within which the fire emissions are transported. The characteristics of this plume, and in particular the height to which it rises before releasing the majority of the smoke burden into the wider atmosphere, are important in terms of how the fire emissions are ultimately transported, since for example winds at different altitudes may be quite different. This difference in atmospheric transport then may also affect the longevity, chemical conversion, and fate of the plumes chemical constituents, with for example very high plume injection heights being associated with extreme long-range atmospheric transport. Here we review how such landscape-scale fire smoke plume injection heights are represented in larger-scale atmospheric transport models aiming to represent the impacts of wildfire emissions on component of the Earth system. In particular we detail (i) satellite Earth observation data sets capable of being used to remotely assess wildfire plume height distributions and (ii) the driving characteristics of the causal fires. We also discuss both the physical mechanisms and dynamics taking place in fire plumes and investigate the efficiency and limitations of currently available injection height parameterizations. Finally, we conclude by suggesting some future parameterization developments and ideas on Earth observation data selection that may be relevant to the instigation of enhanced methodologies aimed at injection height representation.

  7. Light-Activated Amino Acid Transport Systems in Halobacterium halobium Envelope Vesicles: Role of Chemical and Electrical Gradients

    NASA Technical Reports Server (NTRS)

    MacDonald, Russell E.; Greene, Richard V.; Lanyi, Janos K.

    1977-01-01

    The accumulation of 20 commonly occurring L-amino acids by cell envelope vesicles of Halobacterium halobium, in response to light-induced membrane potential and an artificially created sodium gradient, has been studied. Nineteen of these amino acids are actively accumulated under either or both of these conditions. Glutamate is unique in that its uptake is driven only by a chemical gradient for sodium. Amino acid concentrations at half-maximal uptake rates (Km) and maximal transport rates (V(sub max) have been determined for the uptake of all 19 amino acids. The transport systems have been partially characterized with respect to groups of amino acids transported by common carriers, cation effects, and relative response to the electrical and chemical components of the sodium gradient, the driving forces for uptake. The data presented clearly show that the carrier systems, which are responsible for uptake of individual amino acids, are as variable in their properties as those found in other organisms, i. e., some are highly specific for individual amino acids, some transport several amino acids competitively, some are activated by a chemical gradient of sodium only, and some function also in the complete absence of such a gradient. For all amino acids, Na(+) and K(+) are both required for maximal rate of uptake. The carriers for L-leucine and L-histidine are symmetrical in that these amino acids are transported in both directions across the vesicle membrane. It is suggested that coupling of substrate transport to metabolic energy via transient ionic gradients may be a general phenomenon in procaryotes.

  8. Development of a variational flux inversion system (INVICAT v1.0) using the TOMCAT chemical transport model

    NASA Astrophysics Data System (ADS)

    Wilson, C.; Chipperfield, M. P.; Gloor, M.; Chevallier, F.

    2014-10-01

    We present a new variational inverse transport model, named INVICAT (v1.0), which is based on the global chemical transport model TOMCAT, and a new corresponding adjoint transport model, ATOMCAT. The adjoint model is constructed through manually derived discrete adjoint algorithms, and includes subroutines governing advection, convection and boundary layer mixing, all of which are linear in the TOMCAT model. We present extensive testing of the adjoint and inverse models, and also thoroughly assess the accuracy of the TOMCAT forward model's representation of atmospheric transport through comparison with observations of the atmospheric trace gas SF6. The forward model is shown to perform well in comparison with these observations, capturing the latitudinal gradient and seasonal cycle of SF6 to within acceptable tolerances. The adjoint model is shown, through numerical identity tests and novel transport reciprocity tests, to be extremely accurate in comparison with the forward model, with no error shown at the level of accuracy possible with our machines. The potential for the variational system as a tool for inverse modelling is investigated through an idealised test using simulated observations, and the system demonstrates an ability to retrieve known fluxes from a perturbed state accurately. Using basic off-line chemistry schemes, the inverse model is ready and available to perform inversions of trace gases with relatively simple chemical interactions, including CH4, CO2 and CO.

  9. Development of a variational flux inversion system (INVICAT v1.0) within the TOMCAT chemical transport model

    NASA Astrophysics Data System (ADS)

    Wilson, C.; Chipperfield, M. P.; Gloor, M.; Chevallier, F.

    2013-12-01

    We present a new variational inverse transport model, named INVICAT (v1.0), which is based upon the global chemical transport model TOMCAT, and a new corresponding adjoint transport model, ATOMCAT. The adjoint model is constructed through manually derived discrete adjoint algorithms, and includes subroutines governing advection, convection and boundary layer mixing. We present extensive testing of the adjoint and inverse models, and also thoroughly assess the accuracy of the TOMCAT forward model's representation of atmospheric transport through comparison with observations of the atmospheric trace gas SF6. The forward model is shown to perform well in comparison with these observations, capturing the latitudinal gradient and seasonal cycle of SF6 to within acceptable tolerances. The adjoint model is shown, through numerical identity tests and novel transport reciprocity tests, to be extremely accurate in comparison with the forward model, with no error shown at the level of accuracy possible with our machines. The potential for the variational system as a tool for inverse modelling is investigated through an idealised test using simulated observations, and the system demonstrates an ability to retrieve known fluxes from a perturbed state accurately. Using basic off-line chemistry schemes, the inverse model is ready and available to perform inversions of trace gases with relatively simple chemical interactions, including CH4, CO2 and CO.

  10. Regional scale ozone data assimilation using an ensemble Kalman filter and the CHIMERE chemical transport model

    NASA Astrophysics Data System (ADS)

    Gaubert, B.; Coman, A.; Foret, G.; Meleux, F.; Ung, A.; Rouil, L.; Ionescu, A.; Candau, Y.; Beekmann, M.

    2014-02-01

    An ensemble Kalman filter (EnKF) has been coupled to the CHIMERE chemical transport model in order to assimilate ozone ground-based measurements on a regional scale. The number of ensembles is reduced to 20, which allows for future operational use of the system for air quality analysis and forecast. Observation sites of the European ozone monitoring network have been classified using criteria on ozone temporal variability, based on previous work by Flemming et al. (2005). This leads to the choice of specific subsets of suburban, rural and remote sites for data assimilation and for evaluation of the reference run and the assimilation system. For a 10-day experiment during an ozone pollution event over Western Europe, data assimilation allows for a significant improvement in ozone fields: the RMSE is reduced by about a third with respect to the reference run, and the hourly correlation coefficient is increased from 0.75 to 0.87. Several sensitivity tests focus on an a posteriori diagnostic estimation of errors associated with the background estimate and with the spatial representativeness of observations. A strong diurnal cycle of both these errors with an amplitude up to a factor of 2 is made evident. Therefore, the hourly ozone background error and the observation error variances are corrected online in separate assimilation experiments. These adjusted background and observational error variances provide a better uncertainty estimate, as verified by using statistics based on the reduced centered random variable. Over the studied 10-day period the overall EnKF performance over evaluation stations is found relatively unaffected by different formulations of observation and simulation errors, probably due to the large density of observation sites. From these sensitivity tests, an optimal configuration was chosen for an assimilation experiment extended over a three-month summer period. It shows a similarly good performance as the 10-day experiment.

  11. Optimization of air monitoring networks using chemical transport model and search algorithm

    NASA Astrophysics Data System (ADS)

    Araki, Shin; Iwahashi, Koki; Shimadera, Hikari; Yamamoto, Kouhei; Kondo, Akira

    2015-12-01

    Air monitoring network design is a critical issue because monitoring stations should be allocated properly so that they adequately represent the concentrations in the domain of interest. Although the optimization methods using observations from existing monitoring networks are often applied to a network with a considerable number of stations, they are difficult to be applied to a sparse network or a network under development: there are too few observations to define an optimization criterion and the high number of potential monitor location combinations cannot be tested exhaustively. This paper develops a hybrid of genetic algorithm and simulated annealing to combine their power to search a big space and to find local optima. The hybrid algorithm as well as the two single algorithms are applied to optimize an air monitoring network of PM2.5, NO2 and O3 respectively, by minimization of the mean kriging variance derived from simulated values of a chemical transport model instead of observations. The hybrid algorithm performs best among the algorithms: kriging variance is on average about 4% better than for GA and variability between trials is less than 30% compared to SA. The optimized networks for the three pollutants are similar and maps interpolated from the simulated values at these locations are close to the original simulations (RMSE below 9% relative to the range of the field). This also holds for hourly and daily values although the networks are optimized for annual values. It is demonstrated that the method using the hybrid algorithm and the model simulated values for the calculation of the mean kriging variance is of benefit to the optimization of air monitoring networks.

  12. Insights into Chemical Transport and Oxidative Processing in the Arctic Springtime

    NASA Astrophysics Data System (ADS)

    Apel, E. C.; Hornbrook, R. S.; Flocke, F. M.; Hall, S. R.; Hills, A. J.; Montzka, D.; Orlando, J. J.; Turnipseed, A. A.; Ullmann, K.; Weinheimer, A. J.; Mauldin, L.; Riemer, D. D.; Shepson, P. B.; Sive, B. C.; Staebler, R. M.; Blake, N. J.

    2015-12-01

    Gas-phase volatile organic compounds (VOCs) were measured at several levels between the snow surface and 6 m in the Arctic boundary layer in Barrow, Alaska for the OASIS-2009 field campaign during March and April 2009, as part of the International Polar Year (IPY). Nonmethane hydrocarbons (NMHCs) from C4-C8 and oxygenated VOCs, including alcohols, aldehydes and ketones were quantified multiple times per hour, day and night during the campaign using in-situ fast gas chromatography-mass spectrometry (fast-GC/MS). Samples were also collected in canisters two to three times daily and subsequently analyzed for C2-C8 NMHCs. The NMHCs and aldehydes all showed decreasing mixing ratios with time during the experiment whereas acetone and MEK showed increases. These results are interpreted in the context of a box model and a 3D chemical transport model. After adjusting for seasonal trends in the VOCs, acetone, MEK and 2-pentanone were all negatively correlated with O3, while NMHCs, methanol, ethanol, acetaldehyde, propanal and butanal were all positively correlated with O3. Several ozone depletion events (ODEs) during the study provided an opportunity to investigate the large perturbations due to halogen chemistry on the production and loss of VOCs in the air masses at the sampling site. Notably, aldehyde mixing ratios dropped below the detection limit of the instrument (< 3 pptv) during the ODEs. The NCAR Master Mechanism (MM) (0-D box model), which was updated to include halogen chemistry, was able to reproduce the bromine explosion and showed consistency with key observations including the aldehyde data. Further, no clear positive or negative air-snow flux could be identified for any of the VOCs observed by fast-GC/MS during the study.

  13. Inferring global and regional methane sources and sinks using isotopic observations and atmospheric chemical transport models

    NASA Astrophysics Data System (ADS)

    Rigby, M. L.; Wenger, A.; O'Doherty, S.; Lunt, M. F.; Ganesan, A.; Manning, A.; Prinn, R. G.

    2015-12-01

    Measurements of the major isotopologues of atmospheric methane have the potential to improve our understanding of the methane budget at the global and regional scale. Using global and regional chemical transport models, we can predict the atmospheric variations in 13C-CH4 and D-CH4, for given assumptions about source isotope ratios and fractionation due to methane sinks. This information can then be used to test the impact that various measurement techniques, technologies and sampling strategies have on our knowledge of the methane budget. We show that, at the global scale, an extensive and accurate network of isotopic measurements can lead to a reduction in the uncertainties in the major global sources. Furthermore, measurements of the D/H ratio in methane may provide some level of uncertainty reduction in the magnitude of the OH sink. Uncertainties can be reduced with improved precision and accuracy of the atmospheric observations. However, to make the most of an atmospheric methane isotope network, we show that the characterisation of source isotope ratios must also be improved. Finally, we put the theory into practice by deriving sector-specific methane sources at the national scale using 13C-CH4 samples collected as part of the Greenhouse gAs Uk and Global Emissions (GAUGE) project. GAUGE measurements are made from a tall tower site to the east of the UK, a background station on the west coast of Ireland and during intensive aircraft sampling campaigns. We will discuss the challenges and benefits associated with adding isotopic information to a national greenhouse gas sampling network and outline a strategy for improvements in the future.

  14. Nesting biology of laughing gulls Larus atricilla in relation to agricultural chemicals in south Texas USA 1978-1981

    USGS Publications Warehouse

    White, D.H.; Mitchell, C.A.; Prouty, R.M.

    1983-01-01

    Various aspects of the breeding biology of Laughing Gulls (Larus atricilla) have been studied extensively in Florida (Dinsmore and Schreiber 1974, Schreiber et al. 1979, Schreiber and Schreiber 1980), New Jersey (Bongiorno 1970, Burger and Beer 1976, Burger 1976, Montevecchi 1978), and Massachusetts (Noble and Wurm 1943), but little is known of their yearly fledging success in Texas or elsewhere. The Laughing Gull is a common colonial nester along most of the Texas coast, second only to the Cattle Egret (Bubulcus ibis) in breeding abundance; however, the Laughing Gull may be threatened in Texas because of suspected declines at certain traditional nesting locales (Blacklock et al. 1979). Since Laughing Gulls often nest in proximity to agricultural and industrial areas, we were concerned that environmental pollutants might be adversely affecting productivity. In 1978-1981 we conducted studies along the south Texas coast to learn more about the nesting ecology of Laughing Gulls and to evaluate the effects of environmental contaminants on reproduction.

  15. Chemical properties of urban waste ash produced by open burning on the Jos Plateau: implications for agriculture.

    PubMed

    Pasquini, M W; Alexander, M J

    2004-02-01

    Urban centres produce most of the world's waste and between a third and a half goes uncollected. The answer to the problem of waste disposal lies partly in agriculture, as waste can be extremely nutrient-rich. In the last decade there has been a tremendous increase in the developing world in total city area under informal food production and there are many examples of waste recycling onto the urban or peri-urban plots. Farmers on the Jos Plateau, Nigeria, have developed a successful soil fertility management strategy based on the combination of inorganic fertilisers, manure and urban waste ash. This study sought to provide some preliminary data on urban waste ash produced by open burning and used in farming in a developing country. Ash samples were collected from different locations around Jos and tested for C, N, pH, P, Na, K, Ca, Mg, Fe, Mn, Zn, Cu, Ni, Cd and Pb. It was found that ash is an effective liming material (because of the high pH, and high Ca, Mg and K contents), and has the potential to contribute significant quantities of micro-nutrients such as Mn, Zn and Cu. Ash, however, is far from being a homogenous material and its variability means that its fertilising potential will vary between batches and that, even if mean and median levels are low, there is the risk of the formation of localised areas of soil with excessive heavy metal contents (this is particularly the case with Pb). Further research is required to determine the plant-availability of these elements in the ash and to assess the wider environmental and health implications of uncontrolled, open burning of waste as a means of producing ash for agricultural purposes. PMID:14967513

  16. Effect of variable annual precipitation and nutrient input on nitrogen and phosphorus transport from two Midwestern agricultural watersheds

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Precipitation patterns and nutrient inputs impact transport of nitrate (NO3-N) and phosphorus (TP) from Midwest watersheds. Nutrient concentrations and yields from two subsurface-drained watersheds, the Little Cobb River (LCR) in southern Minnesota and the South Fork Iowa River (SFIR) in northern Io...

  17. A Model to Couple Flow, Thermal and Reactive Chemical Transport, and Geo-mechanics in Variably Saturated Media

    NASA Astrophysics Data System (ADS)

    Yeh, G. T.; Tsai, C. H.

    2015-12-01

    This paper presents the development of a THMC (thermal-hydrology-mechanics-chemistry) process model in variably saturated media. The governing equations for variably saturated flow and reactive chemical transport are obtained based on the mass conservation principle of species transport supplemented with Darcy's law, constraint of species concentration, equation of states, and constitutive law of K-S-P (Conductivity-Degree of Saturation-Capillary Pressure). The thermal transport equation is obtained based on the conservation of energy. The geo-mechanic displacement is obtained based on the assumption of equilibrium. Conventionally, these equations have been implicitly coupled via the calculations of secondary variables based on primary variables. The mechanisms of coupling have not been obvious. In this paper, governing equations are explicitly coupled for all primary variables. The coupling is accomplished via the storage coefficients, transporting velocities, and conduction-dispersion-diffusion coefficient tensor; one set each for every primary variable. With this new system of equations, the coupling mechanisms become clear. Physical interpretations of every term in the coupled equations will be discussed. Examples will be employed to demonstrate the intuition and superiority of these explicit coupling approaches. Keywords: Variably Saturated Flow, Thermal Transport, Geo-mechanics, Reactive Transport.

  18. Evaluating Gas-Phase Transport And Detection Of Noble Gas Signals From Underground Nuclear Explosions Using Chemical Tracers

    NASA Astrophysics Data System (ADS)

    Carrigan, C. R.; Hunter, S. L.; Sun, Y.; Wagoner, J. L.; Ruddle, D.; Anderson, G.; Felske, D.; Myers, K.; Zucca, J. J.; Emer, D. F.; Townsend, M.; Drellack, S.; Chipman, V.; Snelson, C. M.

    2013-12-01

    The 1993 Non-Proliferation Experiment (NPE) involved detonating 1 kiloton of chemical explosive in a subsurface cavity which also contained bottles of tracer gases (ref 1). That experiment provided an improved understanding of transport processes relevant to the detection of noble gas signals at the surface emanating from a clandestine underground nuclear explosion (UNE). As an alternative to performing large chemical detonations to simulate gas transport from UNEs, we have developed a test bed for subsurface gas transport, sampling and detection studies using a former UNE cavity. The test bed site allows for the opportunity to evaluate pathways to the surface created by the UNE as well as possible transport mechanisms including barometric pumping and cavity pressurization (ref 2). With the test bed we have monitored long-term chemical tracers as well as newly injected tracers. In order to perform high temporal resolution tracer gas monitoring, we have also developed a Subsurface Gas Smart Sampler (SGSS) which has application during an actual On Site Inspection (OSI) and is available for deployment in OSI field exercises planned for 2014. Deployment of five SGSS at the remote test bed has provided unparalleled detail concerning relationships involving tracer gas transport to the surface, barometric fluctuations and temporal variations in the natural radon concentration. We anticipate that the results of our tracer experiments will continue to support the development of improved noble gas detection technology for both OSI and International Monitoring System applications. 1. C.R. Carrigan et al., 1996, Nature, 382, p. 528. 2. Y. Sun and C.R. Carrigan, 2012, Pure Appl. Geophys., DOI 10.1007/s00024-012-0514-4.

  19. Residence time, chemical and isotopic analysis of nitrate in the groundwater and surface water of a small agricultural watershed in the Coastal Plain, Bucks Branch, Sussex County, Delaware

    USGS Publications Warehouse

    Clune, John W.; Denver, Judith M.

    2012-01-01

    Nitrate is a common contaminant in groundwater and surface water throughout the Nation, and water-resource managers need more detailed small-scale watershed research to guide conservation efforts aimed at improving water quality. Concentrations of nitrate in Bucks Branch are among the highest in the state of Delaware and a scientific investigation was performed to provide water-quality information to assist with the management of agriculture and water resources. A combination of major-ion chemistry, nitrogen isotopic composition and age-dating techniques was used to estimate the residence time and provide a chemical and isotopic analysis of nitrate in the groundwater in the surficial aquifer of the Bucks Branch watershed in Sussex County, Delaware. The land use was more than 90 percent agricultural and most nitrogen inputs were from manure and fertilizer. The apparent median age of sampled groundwater is 18 years and the estimated residence time of groundwater contributing to the streamflow for the entire Bucks Branch watershed at the outlet is approximately 19 years. Concentrations of nitrate exceeded the U.S. Environmental Protection Agency drinking-water standard of 10 milligrams per liter (as nitrogen) in 60 percent of groundwater samples and 42 percent of surface-water samples. The overall geochemistry in the Bucks Branch watershed indicates that agriculture is the predominant source of nitrate contamination and the observed patterns in major-ion chemistry are similar to those observed in other studies on the Mid-Atlantic Coastal Plain. The pattern of enrichment in nitrogen and oxygen isotopes (δ15N and δ18O) of nitrate in groundwater and surface water indicates there is some loss of nitrate through denitrification, but this process is not sufficient to remove all of the nitrate from groundwater discharging to streams, and concentrations of nitrate in streams remain elevated.

  20. Herbicide Transport and Transformations in the Unsaturated Zone of Three Small Agricultural Basins with Corn and Soybean Row Crops

    NASA Astrophysics Data System (ADS)

    Hancock, T. C.; Vogel, J. R.; Sandstrom, M. W.; Capel, P. D.; Bayless, R. E.; Webb, R. M.

    2006-05-01

    In the United States, herbicides are among the most significant nonpoint-source pollutants and were applied to 95% of all fields in corn production and 97% of all fields in soybean production in 2003 and 2004. The United States Geological Survey (USGS) has conducted a study on select herbicides in the unsaturated zone under corn and soybean fields in three predominantly agricultural basins: Morgan Creek (Maryland), Leary Weber Ditch within Sugar Creek (Indiana), and Maple Creek (Nebraska). In 2004, the Morgan Creek and Leary Weber Ditch fields were in soybeans and the Maple Creek fields were in corn. The Maple Creek fields were irrigated, whereas those in Morgan Creek and Leary Weber Ditch were not. Similarities and differences in agricultural management practices, climatic conditions, and natural features, such as soil types and geology, were evaluated as part of the study. In general, the amounts of herbicides entering the unsaturated zone from rain in these basins were minor (1%) compared to amounts commonly applied to the land surface during agricultural practices. Few herbicides were detected on solid core samples from the unsaturated zones of these basins. An exception was found at a Morgan Creek site in an upland recharge area with sandier soils. Here, atrazine concentrations were highest in the near surface solids and decreased with depth. In the unsaturated-zone porewater of the Morgan Creek Basin, parent triazine and acetanilide herbicides were detected and only at the site in the upland recharge area at relatively low concentrations at depths greater than 4 meters, probably because these compounds had not been applied for several years. At the Morgan Creek and Leary Weber Ditch sites, acetanilide metabolites were frequently detected in the unsaturated-zone porewater. In general, the fraction of metolachlor ethane sulfonic acid (ESA) relative to the total mass of parent and metabolites increased with depth overall and at several individual sampling

  1. A Nontoxic Polypeptide Oligomer with a Fungicide Potency under Agricultural Conditions Which Is Equal or Greater than That of Their Chemical Counterparts

    PubMed Central

    Monteiro, Sara; Carreira, Alexandra; Freitas, Regina; Pinheiro, Ana Margarida; Ferreira, Ricardo Boavida

    2015-01-01

    There are literally hundreds of polypeptides described in the literature which exhibit fungicide activity. Tens of them have had attempted protection by patent applications but none, as far as we are aware, have found application under real agricultural conditions. The reasons behind may be multiple where the sensitivity to the Sun UV radiation can come in first place. Here we describe a multifunctional glyco-oligomer with 210 kDa which is mainly composed by a 20 kDa polypeptide termed Blad that has been previously shown to be a stable intermediary product of β-conglutin catabolism. This oligomer accumulates exclusively in the cotyledons of Lupinus species, between days 4 and 12 after the onset of germination. Blad-oligomer reveals a plethora of biochemical properties, like lectin and catalytic activities, which are not unusual per si, but are remarkable when found to coexist in the same protein molecule. With this vast range of chemical characteristics, antifungal activity arises almost as a natural consequence. The biological significance and potential technological applications of Blad-oligomer as a plant fungicide to agriculture, its uniqueness stems from being of polypeptidic in nature, and with efficacies which are either equal or greater than the top fungicides currently in the market are addressed. PMID:25849076

  2. Estimation of Atmospheric Methane Surface Fluxes Using a Global 3-D Chemical Transport Model

    NASA Astrophysics Data System (ADS)

    Chen, Y.; Prinn, R.

    2003-12-01

    Accurate determination of atmospheric methane surface fluxes is an important and challenging problem in global biogeochemical cycles. We use inverse modeling to estimate annual, seasonal, and interannual CH4 fluxes between 1996 and 2001. The fluxes include 7 time-varying seasonal (3 wetland, rice, and 3 biomass burning) and 3 steady aseasonal (animals/waste, coal, and gas) global processes. To simulate atmospheric methane, we use the 3-D chemical transport model MATCH driven by NCEP reanalyzed observed winds at a resolution of T42 ( ˜2.8° x 2.8° ) in the horizontal and 28 levels (1000 - 3 mb) in the vertical. By combining existing datasets of individual processes, we construct a reference emissions field that represents our prior guess of the total CH4 surface flux. For the methane sink, we use a prescribed, annually-repeating OH field scaled to fit methyl chloroform observations. MATCH is used to produce both the reference run from the reference emissions, and the time-dependent sensitivities that relate individual emission processes to observations. The observational data include CH4 time-series from ˜15 high-frequency (in-situ) and ˜50 low-frequency (flask) observing sites. Most of the high-frequency data, at a time resolution of 40-60 minutes, have not previously been used in global scale inversions. In the inversion, the high-frequency data generally have greater weight than the weekly flask data because they better define the observational monthly means. The Kalman Filter is used as the optimal inversion technique to solve for emissions between 1996-2001. At each step in the inversion, new monthly observations are utilized and new emissions estimates are produced. The optimized emissions represent deviations from the reference emissions that lead to a better fit to the observations. The seasonal processes are optimized for each month, and contain the methane seasonality and interannual variability. The aseasonal processes, which are less variable, are

  3. Fate and transport of tylosin-resistant bacteria and macrolide resistance genes in artificially drained agricultural fields receiving swine manure.

    PubMed

    Luby, Elizabeth M; Moorman, Thomas B; Soupir, Michelle L

    2016-04-15

    Application of manure from swine treated with antibiotics introduces antibiotics and antibiotic resistance genes to soil with the potential for further movement in drainage water, which may contribute to the increase in antibiotic resistance in non-agricultural settings. We compared losses of antibiotic-resistant Enterococcus and macrolide-resistance (erm and msrA) genes in water draining from plots with or without swine manure application under chisel plow and no till conditions. Concentrations of ermB, ermC and ermF were all >10(9)copies g(-1) in manure from tylosin-treated swine, and application of this manure resulted in short-term increases in the abundance of these genes in soil. Abundances of ermB, ermC and ermF in manured soil returned to levels identified in non-manured control plots by the spring following manure application. Tillage practices yielded no significant differences (p>0.10) in enterococci or erm gene concentrations in drainage water and were therefore combined for further analysis. While enterococci and tylosin-resistant enterococci concentrations in drainage water showed no effects of manure application, ermB and ermF concentrations in drainage water from manured plots were significantly higher (p<0.01) than concentrations coming from non-manured plots. ErmB and ermF were detected in 78% and 44%, respectively, of water samples draining from plots receiving manure. Although ermC had the highest concentrations of the three genes in drainage water, there was no effect of manure application on ermC abundance. MsrA was not detected in manure, soil or water. This study is the first to report significant increases in abundance of resistance genes in waters draining from agricultural land due to manure application. PMID:26874610

  4. Radiative Effect of Clouds on Tropospheric Chemistry in a Global Three-Dimensional Chemical Transport Model

    NASA Technical Reports Server (NTRS)

    Liu, Hongyu; Crawford, James H.; Pierce, Robert B.; Norris, Peter; Platnick, Steven E.; Chen, Gao; Logan, Jennifer A.; Yantosca, Robert M.; Evans, Mat J.; Kittaka, Chieko; Feng, Yan; Tie, Xuexi

    2006-01-01

    Clouds exert an important influence on tropospheric photochemistry through modification of solar radiation that determines photolysis frequencies (J-values). We assess the radiative effect of clouds on photolysis frequencies and key oxidants in the troposphere with a global three-dimensional (3-D) chemical transport model (GEOS-CHEM) driven by assimilated meteorological observations from the Goddard Earth Observing System data assimilation system (GEOS DAS) at the NASA Global Modeling and Assimilation Office (GMAO). We focus on the year of 2001 with the GEOS-3 meteorological observations. Photolysis frequencies are calculated using the Fast-J radiative transfer algorithm. The GEOS-3 global cloud optical depth and cloud fraction are evaluated and generally consistent with the satellite retrieval products from the Moderate Resolution Imaging Spectroradiometer (MODIS) and the International Satellite Cloud Climatology Project (ISCCP). Results using the linear assumption, which assumes linear scaling of cloud optical depth with cloud fraction in a grid box, show global mean OH concentrations generally increase by less than 6% because of the radiative effect of clouds. The OH distribution shows much larger changes (with maximum decrease of approx.20% near the surface), reflecting the opposite effects of enhanced (weakened) photochemistry above (below) clouds. The global mean photolysis frequencies for J[O1D] and J[NO2] in the troposphere change by less than 5% because of clouds; global mean O3 concentrations in the troposphere increase by less than 5%. This study shows tropical upper tropospheric O3 to be less sensitive to the radiative effect of clouds than previously reported (approx.5% versus approx.20-30%). These results emphasize that the dominant effect of clouds is to influence the vertical redistribution of the intensity of photochemical activity while global average effects remain modest, again contrasting with previous studies. Differing vertical distributions

  5. Evaluation of the RAQMS Regional Model During the Intercontinental Chemical Transport Experiment-North America

    NASA Astrophysics Data System (ADS)

    Liu, H.; Pierce, R.; Crawford, J. H.; Considine, D. B.; Al-Saadi, J. A.; Kittaka, C.; Hitchman, M.; Tripoli, G. J.

    2009-12-01

    The Intercontinental Chemical Transport Experiment-North America (INTEX-A) field campaign took place over North America (NA) and the Atlantic during July-August 2004. Among the goals of INTEX-A were to characterize the composition of the troposphere over NA and the outflow of pollution from NA, and to validate satellite observations of tropospheric composition. We test and improve the regional component of the Real-time Air Quality Modeling System (RAQMSN) using the comprehensive dataset, including surface, ozonesonde, aircraft, and satellite measurements of ozone and its precursors obtained during INTEX-A. We show that RAQMSN is able to reproduce the major characteristics of tropospheric ozone-CO-NOx-hydrocarbon chemistry over NA during INTEX-A. RAQMSN CO and tropospheric NO2 columns are highly correlated with those of MOPITT and SCIAMACHY, respectively. The model high NO2 bias in the Ohio River Valley reflects the fact that the emission inventory used did not take into account the reduced power plant NOx emissions from this region in 2004 as a result of pollution control programs. The model simulates well the strong day-to-day variability of O3 in the tropopause region as seen in the IONS (INTEX Ozonesonde Network Study) ozonesonde data, but shows more stratospherically influenced air in the upper troposphere (UT). The model is also able to simulate the westerly outflow of O3 to the Atlantic as revealed by the tropospheric ozone residual (TOR, July-August 2005-2008 climatology) data from OMI/MLS. We compare RAQMSN simulations with NASA DC-8 in-situ CO, NO2, O3, and total PAN observations during INTEX-A. The simulated CO is within 10 ppbv of the observations except below 900 hPa where the model is about 40 ppbv too high, consistent with a recent report that the national anthropogenic emission inventory from the US EPA is too high by 60% in summer. While overestimated in the boundary layer, NO2 and PAN are underestimated in the UT. Model lightning NOx emissions are

  6. Characterizing chemical transport of ozone and fine particles in the Great Lakes region

    NASA Astrophysics Data System (ADS)

    Spak, Scott N.

    This dissertation presents a science framework relevant to evaluating impacts of land use policy scenarios, energy technologies, and climate on urban and regional air quality. Emerging from collaboration with urban planners, this work provides a means for employing atmospheric chemical transport modeling to understand environmental ramifications of long-term, spatially disaggregated changes in population and automobile emissions at the census tract level, and to assess the sensitivity of these changes to densification strategies. Toward these goals, the framework is used to evaluate model skill in resolving contemporary characteristics of ozone (O3) and speciated fine particles (PM2.5) in the Great Lakes region of North America, and to quantitatively explore meteorological processes that bring about observed features of these pollutants in the region. The Great Lakes were chosen due to a population concentrated in sprawling metropolitan areas, consistently high and widespread pollutant burdens, and seasonal effects of the lakes on the atmosphere. In annual simulation at 36 km resolution, the Community Multiscale Air Quality model is evaluated using speciated PM2.5 measurements taken at regulatory monitoring networks orientated to sample urban, rural, and remote areas. Performance relative to ad-hoc regional modeling goals and prior studies is average to excellent for most species throughout the year. Both pollution episodes and seasonality are captured. The Great Lakes affect pollution seasonality: strong winds advect aerosols around the deep marine boundary layer to lower surface PM2.5 in fall and winter, while O3 over the lakes is enhanced throughout the year, driven by temperature in the cool seasons and lake breeze circulation in spring and summer. Simulations confirm observational evidence that rural and small-city sources are responsible for most regional PM2.5. Sensitivities to urban and rural reductions are of comparable magnitude on a percentage basis

  7. Constrained positive matrix factorization: Elemental ratios, spatial distinction, and chemical transport model source contributions

    NASA Astrophysics Data System (ADS)

    Sturtz, Timothy M.

    Source apportionment models attempt to untangle the relationship between pollution sources and the impacts at downwind receptors. Two frameworks of source apportionment models exist: source-oriented and receptor-oriented. Source based apportionment models use presumed emissions and atmospheric processes to estimate the downwind source contributions. Conversely, receptor based models leverage speciated concentration data from downwind receptors and apply statistical methods to predict source contributions. Integration of both source-oriented and receptor-oriented models could lead to a better understanding of the implications sources have on the environment and society. The research presented here investigated three different types of constraints applied to the Positive Matrix Factorization (PMF) receptor model within the framework of the Multilinear Engine (ME-2): element ratio constraints, spatial separation constraints, and chemical transport model (CTM) source attribution constraints. PM10-2.5 mass and trace element concentrations were measured in Winston-Salem, Chicago, and St. Paul at up to 60 sites per city during two different seasons in 2010. PMF was used to explore the underlying sources of variability. Information on previously reported PM10-2.5 tire and brake wear profiles were used to constrain these features in PMF by prior specification of selected species ratios. We also modified PMF to allow for combining the measurements from all three cities into a single model while preserving city-specific soil features. Relatively minor differences were observed between model predictions with and without the prior ratio constraints, increasing confidence in our ability to identify separate brake wear and tire wear features. Using separate data, source contributions to total fine particle carbon predicted by a CTM were incorporated into the PMF receptor model to form a receptor-oriented hybrid model. The level of influence of the CTM versus traditional PMF was

  8. Xenobiotic-metabolizing enzyme and transporter gene expression in primary cultures of human hepatocytes modulated by ToxCast chemicals.

    PubMed

    Rotroff, Daniel M; Beam, Andrew L; Dix, David J; Farmer, Adam; Freeman, Kimberly M; Houck, Keith A; Judson, Richard S; LeCluyse, Edward L; Martin, Matthew T; Reif, David M; Ferguson, Stephen S

    2010-02-01

    Primary human hepatocyte cultures are useful in vitro model systems of human liver because when cultured under appropriate conditions the hepatocytes retain liver-like functionality such as metabolism, transport, and cell signaling. This model system was used to characterize the concentration- and time-response of the 320 ToxCast chemicals for changes in expression of genes regulated by nuclear receptors. Fourteen gene targets were monitored in quantitative nuclease protection assays: six representative cytochromes P-450, four hepatic transporters, three Phase II conjugating enzymes, and one endogenous metabolism gene involved in cholesterol synthesis. These gene targets are sentinels of five major signaling pathways: AhR, CAR, PXR, FXR, and PPARalpha. Besides gene expression, the relative potency and efficacy for these chemicals to modulate cellular health and enzymatic activity were assessed. Results demonstrated that the culture system was an effective model of chemical-induced responses by prototypical inducers such as phenobarbital and rifampicin. Gene expression results identified various ToxCast chemicals that were potent or efficacious inducers of one or more of the 14 genes, and by inference the 5 nuclear receptor signaling pathways. Significant relative risk associations with rodent in vivo chronic toxicity effects are reported for the five major receptor pathways. These gene expression data are being incorporated into the larger ToxCast predictive modeling effort. PMID:20574906

  9. End-to-End Trajectory for Conjunction Class Mars Missions Using Hybrid Solar-Electric/Chemical Transportation System

    NASA Technical Reports Server (NTRS)

    Chai, Patrick R.; Merrill, Raymond G.; Qu, Min

    2016-01-01

    NASA's Human Spaceflight Architecture Team is developing a reusable hybrid transportation architecture in which both chemical and solar-electric propulsion systems are used to deliver crew and cargo to exploration destinations. By combining chemical and solar-electric propulsion into a single spacecraft and applying each where it is most effective, the hybrid architecture enables a series of Mars trajectories that are more fuel efficient than an all chemical propulsion architecture without significant increases to trip time. The architecture calls for the aggregation of exploration assets in cislunar space prior to departure for Mars and utilizes high energy lunar-distant high Earth orbits for the final staging prior to departure. This paper presents the detailed analysis of various cislunar operations for the EMC Hybrid architecture as well as the result of the higher fidelity end-to-end trajectory analysis to understand the implications of the design choices on the Mars exploration campaign.

  10. Advective-diffusive/dispersive transport of chemically reacting species in hydrothermal systems. Final report, FY83-85

    SciTech Connect

    Lichtner, P.C.; Helgeson, H.C.

    1986-06-20

    A general formulation of multi-phase fluid flow coupled to chemical reactions was developed based on a continuum description of porous media. A preliminary version of the computer code MCCTM was constructed which implemented the general equations for a single phase fluid. The computer code MCCTM incorporates mass transport by advection-diffusion/dispersion in a one-dimensional porous medium coupled to reversible and irreversible, homogeneous and heterogeneous chemical reactions. These reactions include aqueous complexing, oxidation/reduction reactions, ion exchange, and hydrolysis reactions of stoichiometric minerals. The code MCCTM uses a fully implicit finite difference algorithm. The code was tested against analytical calculations. Applications of the code included investigation of the propagation of sharp chemical reaction fronts, metasomatic alteration of microcline at elevated temperatures and pressures, and ion-exchange in a porous column. Finally numerical calculations describing fluid flow in crystalline rock in the presence of a temperature gradient were compared with experimental results for quartzite.

  11. Impact of acid effluent from Kawah Ijen crater lake on irrigated agricultural soils: Soil chemical processes and plant uptake

    NASA Astrophysics Data System (ADS)

    van Rotterdam-Los, A. M. D.; Heikens, A.; Vriend, S. P.; van Bergen, M. J.; van Gaans, P. F. M.

    2008-12-01

    Volcanogenic contamination of irrigation water, caused by effluent from the hyperacid Ijen crater lake, has severely affected the properties of agricultural soils in East Java, Indonesia. From a comparison of acidified topsoil with subsoil and with top- and subsoil in a reference area, we identified processes responsible for changes in soil and soil solution chemistry induced by acid irrigation water, with emphasis on the nutrients Ca, Mg, Fe, and Mn, and on Al, which may become phytotoxic under acid conditions in soils. Compositional data for bulk soil composition and selective extractions with 1 M KCl and 0.2 M acid ammonium oxalate are used in a mass balance approach to specify element fluxes, including uptake by rice plants. The results show that input via irrigation water has produced an increase in the total aluminum content in the affected topsoil, which is of the same order of magnitude as the increase in labile Al. High bioavailability of Al, as reflected by concentrations in KCl extracts, is consistent with elevated concentrations observed in rice plants. In contrast, and despite the high input via irrigation water, Ca and Mg concentrations have decreased in all measured soil fractions through dissolution of amorphous phases and minerals, and through competition of Al for adsorption sites on the exchange complex and plant roots. Strong leaching is also evident for Fe and especially Mn. In terms of the overall mass balance of the topsoil, plant uptake of Al, Ca, Fe, Mg and Mn is negligible. If the use of acid irrigation would be stopped and the soil pH were to increase to values above 4.5, the observed phytotoxicity of Al will be halted. However, crops may then become fully dependent on the input from irrigation water or fertilizer for essential elements, due to the previous removal from the topsoil through leaching.

  12. Computer program for calculation of complex chemical equilibrium compositions and applications. Supplement 1: Transport properties

    NASA Technical Reports Server (NTRS)

    Gordon, S.; Mcbride, B.; Zeleznik, F. J.

    1984-01-01

    An addition to the computer program of NASA SP-273 is given that permits transport property calculations for the gaseous phase. Approximate mixture formulas are used to obtain viscosity and frozen thermal conductivity. Reaction thermal conductivity is obtained by the same method as in NASA TN D-7056. Transport properties for 154 gaseous species were selected for use with the program.

  13. SIMULATING INTEGRATED MULTIMEDIA CHEMICAL FATE AND TRANSPORT FOR NATIONAL RISK ASSESSMENTS

    EPA Science Inventory

    The site-based multimedia, multipathway and multireceptor risk assessment (3MRA) approach is comprised of source, fate and transport, exposure and risk modules. The main interconnected multimedia fate and transport modules are: watershed, air, surface water, vadose zone and sat...

  14. Quantifying Fluxes of Chemical and Biological Species in Great Lakes Watersheds: A Reactive Transport Modeling Framework

    NASA Astrophysics Data System (ADS)

    Niu, J.; Phanikumar, M. S.

    2012-12-01

    Understanding and quantifying the interactions between hydro-climatic processes and the fate and transport of aquatic pollutants and the resultant threats to human and ecosystem health is a high priority research area in many parts of the world. In the Great Lakes region, harmful algal blooms, increased beach closures due to microbiological pollution and drinking water related issues continue to be causes for concern in recent years highlighting the need for accurate transport models. In this presentation we describe the development of a watershed-scale multi-component reactive transport modeling framework to describe fluxes of nutrients and bacteria exported to the Great Lakes. We describe an operator-splitting strategy combined with a particle transport modeling approach with reactions to describe transport in different hydrologic units with interactions between domains. The algorithms are tested using analytical solutions (where available), data from plot-scale experiments and monitoring data from watersheds in the Great Lakes region.

  15. Watershed Analysis of Nitrate Transport as a Result of Agricultural Inputs for Varying Land Use/Land Cover and Soil Type

    NASA Astrophysics Data System (ADS)

    Scott, M. E.; Sykes, J. F.

    2006-12-01

    The Grand River Watershed is one of the largest watersheds in southwestern Ontario with an area of approximately 7000 square kilometers. Ninety percent of the watershed is classified as rural, and 80 percent of the watershed population relies on groundwater as their source of drinking water. Management of the watershed requires the determination of the effect of agricultural practices on long-term groundwater quality and to identify locations within the watershed that are at a higher risk of contamination. The study focuses on the transport of nitrate through the root zone as a result of agricultural inputs with attenuation due to biodegradation. The driving force for transport is spatially and temporally varying groundwater recharge that is a function of land use/land cover, soil and meteorological inputs that yields 47,229 unique soil columns within the watershed. Fertilizer sources are determined from Statistics Canada's Agricultural Census and include livestock manure and a popular commercial fertilizer, urea. Accounting for different application rates yields 60,066 unique land parcels of which 22,809 are classified as croplands where manure and inorganic fertilizes are directly applied. The transport for the croplands is simulated over a 14-year period to investigate the impact of seasonal applications of nitrate fertilizers on the concentration leaching from the root zone to the water table. Based on land use/land cover maps, ArcView GIS is used to define the location of fertilizer applications within the watershed and to spatially visualize data and analyze results. The large quantity of input data is stored and managed using MS-Access and a relational database management system. Nitrogen transformations and ammonium and nitrate uptake by plants and transport through the soil column are simulated on a daily basis using Visual Basic for Applications (VBA) within MS-Access modules. Nitrogen transformations within the soil column were simplified using

  16. Abcb4 acts as multixenobiotic transporter and active barrier against chemical uptake in zebrafish (Danio rerio) embryos

    PubMed Central

    2013-01-01

    Background In mammals, ABCB1 constitutes a cellular “first line of defense” against a wide array of chemicals and drugs conferring cellular multidrug or multixenobiotic resistance (MDR/MXR). We tested the hypothesis that an ABCB1 ortholog serves as protection for the sensitive developmental processes in zebrafish embryos against adverse compounds dissolved in the water. Results Indication for ABCB1-type efflux counteracting the accumulation of chemicals in zebrafish embryos comes from experiments with fluorescent and toxic transporter substrates and inhibitors. With inhibitors present, levels of fluorescent dyes in embryo tissue and sensitivity of embryos to toxic substrates were generally elevated. We verified two predicted sequences from zebrafish, previously annotated as abcb1, by cloning; our synteny analyses, however, identified them as abcb4 and abcb5, respectively. The abcb1 gene is absent in the zebrafish genome and we explored whether instead Abcb4 and/or Abcb5 show toxicant defense properties. Quantitative real-time polymerase chain reaction (qPCR) analyses showed the presence of transcripts of both genes throughout the first 48 hours of zebrafish development. Similar to transporter inhibitors, morpholino knock-down of Abcb4 increased accumulation of fluorescent substrates in embryo tissue and sensitivity of embryos toward toxic compounds. In contrast, morpholino knock-down of Abcb5 did not exert this effect. ATPase assays with recombinant protein obtained with the baculovirus expression system confirmed that dye and toxic compounds act as substrates of zebrafish Abcb4 and inhibitors block its function. The compounds tested comprised model substrates of human ABCB1, namely the fluorescent dyes rhodamine B and calcein-am and the toxic compounds vinblastine, vincristine and doxorubicin; cyclosporin A, PSC833, MK571 and verapamil were applied as inhibitors. Additionally, tests were performed with ecotoxicologically relevant compounds: phenanthrene (a

  17. Thermal-chemical-mechanical feedback during fluid-rock interactions: Implications for chemical transport and scales of equilibria in the crust

    SciTech Connect

    Dutrow, Barbara

    2008-08-13

    Our research evaluates the hypothesis that feedback amongst thermal-chemical-mechanical processes operative in fluid-rock systems alters the fluid flow dynamics of the system which, in turn, affects chemical transport and temporal and spatial scales of equilibria, thus impacting the resultant mineral textural development of rocks. Our methods include computational experimentation and detailed analyses of fluid-infiltrated rocks from well-characterized terranes. This work focuses on metamorphic rocks and hydrothermal systems where minerals and their textures are utilized to evaluate pressure (P), temperature (T), and time (t) paths in the evolution of mountain belts and ore deposits, and to interpret tectonic events and the timing of these events. Our work on coupled processes also extends to other areas where subsurface flow and transport in porous media have consequences such as oil and gas movement, geothermal system development, transport of contaminants, nuclear waste disposal, and other systems rich in fluid-rock reactions. Fluid-rock systems are widespread in the geologic record. Correctly deciphering the products resulting from such systems is important to interpreting a number of geologic phenomena. These systems are characterized by complex interactions involving time-dependent, non-linear processes in heterogeneous materials. While many of these interactions have been studied in isolation, they are more appropriately analyzed in the context of a system with feedback. When one process impacts another process, time and space scales as well as the overall outcome of the interaction can be dramatically altered. Our goals to test this hypothesis are: to develop and incorporate algorithms into our 3D heat and mass transport code to allow the effects of feedback to be investigated numerically, to analyze fluid infiltrated rocks from a variety of terranes at differing P-T conditions, to identify subtle features of the infiltration of fluids and/or feedback, and

  18. The occurrence and transport of agricultural pesticides in the Tuttle Creek lake-stream system, Kansas and Nebraska

    USGS Publications Warehouse

    Bevans, Hugh E.; Fromm, Carla Hyde; Watkins, Sharon A.

    1995-01-01

    Median monthly atrazine concentrations detected in surface-water samples from the Big Blue River basin (1977-86) exceeded the U.S. Environmental Protection Agency health-advisory level (3.0 micrograms per liter) during May through September. Herbicide loads transported from the basin in 1986, expressed in tons and in percentage of amount applied, were alachlor (1.2 tons, 0.23 percent), atrazine (19 tons, 2.2 percent), and metolachlor (2.2 tons, 2.7 percent).

  19. Groundwater recharge and agricultural contamination

    USGS Publications Warehouse

    Böhlke, J.K.

    2002-01-01

    Agriculture has had direct and indirect effects on the rates and compositions of groundwater recharge and aquifer biogeochemistry. Direct effects include dissolution and transport of excess quantities of fertilizers and associated materials and hydrologic alterations related to irrigation and drainage. Some indirect effects include changes in water-rock reactions in soils and aquifers caused by increased concentrations of dissolved oxidants, protons, and major ions. Agrilcultural activities have directly or indirectly affected the concentrations of a large number of inorganic chemicals in groundwater, for example NO3-, N2, Cl, SO42-, H+, P, C, K, Mg, Ca, Sr, Ba, Ra, and As, as well a wide variety of pesticides and other organic compounds. For reactive contaminants like NO3-, a combination of chemical, isotopic, and environmental-tracer analytical approaches might be required to resolve changing inputs from subsequent alterations as causes of concentration gradients in groundwater. Groundwater records derived from multi-component hydrostratigraphic data can be used to quantify recharge rates and residence times of water and dissolved contaminants, document past variations in recharging contaminant loads, and identify natural contaminant-remediation processes. These data indicate that many of the world's surficial aquifers contain transient records of changing agricultural contamination from the last half of the 20th century. The transient agricultural groundwater signal has important implications for long-term trends and spatial heterogeneity in discharge.

  20. 76 FR 12556 - Airworthiness Directives; Various Transport Category Airplanes Equipped With Chemical Oxygen...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-03-08

    ... 12866, (2) Is not a ``significant rule'' under DOT Regulatory Policies and Procedures (44 FR 11034... Category Airplanes Equipped With Chemical Oxygen Generators Installed in a Lavatory AGENCY: Federal... affected airplanes identified above. This AD requires modifying the chemical oxygen generators in...

  1. Field lysimeters for the study of fate and transport of explosive chemicals in soils under variable environmental conditions

    NASA Astrophysics Data System (ADS)

    Molina, Gloria M.; Padilla, Ingrid; Pando, Miguel; Pérez, Diego D.

    2006-05-01

    Landmines and other buried explosive devices pose in an immense threat in many places of the world, requiring large efforts on detection and neutralization of these objects. Many of the available detection techniques require the presence of chemicals near the soil-atmospheric surface. The presence of explosive related chemicals (ERCs) near this surface and their relation to the location of landmines, however, depends on the source characteristics and on fate and transport processes that affect their movement in soils. Fate and transport processes of ERC is soils may be interrelated with each other and are influenced by chemical characteristics and interrelated soil and environmental factors. Accurate detection of ERCs near the soil surface must, therefore, take into the variability of ERC concentration distributions near the soil surface as affected by fate and transport processes controlled interrelated environmental factors. To effectively predict the concentration distributions of ERCs in soils and near soil surfaces, it is necessary to have good understanding of parameters values that control these processes. To address this need, field lysimeters have been designed and developed at the University of Puerto Rico, Mayaguez .This paper presents the design of two field lysimeter used to study the fate and transport behavior of ERC in the field subjected to varying uncontrolled subtropical environmental conditions in two different soils. Both lysimeters incorporate pressure and concentration sampling ports, thermocouples, and a drainage system. Hydrus-2D was used to simulate soil moisture and drainage in the lysimeter for average environmental conditions in the study for the two soils used. The field lysimeters allow collection and monitoring of spatial and temporal ERC concentrations under variable, uncontrolled environmental conditions.

  2. Transport and Chemical Evolution over the Pacific (TRACE-P)Aircraft Mission: Design, Execution, and First Results

    NASA Technical Reports Server (NTRS)

    Jacob, Daniel J.; Crawford, James H.; Kleb, Mary M.; Connors, Vickie S.; Bendura, Richard J.; Raper, James L.; Sachse, Glen W.; Gille, John C.; Emmons, Louisa; Heald, Colette L.

    2003-01-01

    The NASA Transport and Chemical Evolution over the Pacific (TRACE-P) aircraft mission was conducted in February-April 2001 over the NW Pacific (1) to characterize the Asian chemical outflow and relate it quantitatively to its sources and (2) to determine its chemical evolution. It used two aircraft, a DC-8 and a P-3B, operating out of Hong Kong and Yokota Air Force Base (near Tokyo), with secondary sites in Hawaii, Wake Island, Guam, Okinawa, and Midway. The aircraft carried instrumentation for measurements of long-lived greenhouse gases, ozone and its precursors, aerosols and their precursors, related species, and chemical tracers. Five chemical transport models (CTMs) were used for chemical forecasting. Customized bottom-up emission inventories for East Asia were generated prior to the mission to support chemical forecasting and to serve as a priori for evaluation with the aircraft data. Validation flights were conducted for the Measurements Of Pollution In The Troposphere (MOPITT) satellite instrument and revealed little bias (6 plus or minus 2%) in the MOPITT measurements of CO columns. A major event of transpacific Asian pollution was characterized through combined analysis of TRACE-P and MOPITT data. The TRACE-P observations showed that cold fronts sweeping across East Asia and the associated warm conveyor belts (WCBs) are the dominant pathway for Asian outflow to the Pacific in spring. The WCBs lift both anthropogenic and biomass burning (SE Asia) effluents to the free troposphere, resulting in complex chemical signatures. The TRACE-P data are in general consistent with a priori emission inventories, lending confidence in our ability to quantify Asian emissions from socioeconomic data and emission factors. However, the residential combustion source in rural China was found to be much larger than the a priori, and there were also unexplained chemical enhancements (HCN, CH3Cl, OCS, alkylnitrates) in Chinese urban plumes. The Asian source of CCl4 was found to

  3. Phosphorus Transport at the Field Scale by Monitoring Groundwater and Interflow Discharge in Hydrologically Sensitive Areas in Agricultural Fields

    NASA Astrophysics Data System (ADS)

    Flores-Lopez, F.; Geohring, L.; Steenhuis, T.

    2004-05-01

    Quantification of nonpoint source of phosphorus losses through agricultural land is important because hydrologically active areas can significantly affect water quality. In this study we examined phosphorus concentration and phosphorus losses from hydrologically sensitive areas and upland areas located in valley soils in the Cannosville basin in Catskill Mountains. Phosphorus concentrations as low as 0.01 - 0.02 mg/L in water increase the algael bloom in lakes and reservoirs and the Cannosville basin is currently restricted to 0.02mg/L. We measured grab surface water samples taken along the creeks to study the phosphorus concentration in the sub-superficial runoff that drains water from the surrounding hills. Also we installed two different transects of piezometers, one line upstream and one line downstream, to study the role of the groundwater component and its effect in the hydrologically sensitive areas. We generally found low phosphorus concentration in the grab surface water samples and the groundwater samples taken in the piezometers. Sampling during the highest creek flow has resulted in the highest concentrations, generally near 0.05 mg/L of dissolved reactive phosphorus. These concentrations were slightly higher than the concentrations in most of the wells, which were around 0.03 mg/L. Sampling is ongoing to determine the effects snow melt contributions. Results will be presented to show the seasonal effects of phosphorus in the hydrologically sensitive areas.

  4. TACK—a program coupling chemical kinetics with a two-dimensional transport model in geochemical systems

    NASA Astrophysics Data System (ADS)

    Källvenius, Göran; Ekberg, Christian

    2003-05-01

    The Transport And Chemical Kinetics (TACK) program has been designed to make predictions of the chemistry in the vicinity of a planned repository for nuclear waste, i.e. SFL 3-5, where SFL is the Swedish abbreviation for "Swedish repository for long-lived waste". This implies modelling transport and chemistry in fractured rock. The system concerned in the modelling of SFL is leaching water from decommissioning waste in concrete. The concrete will raise the pH in the water to between 12 and 13.5. So far, only a few calculations have been made on such systems. Coupled transport and chemical reaction programs should be used, since the system is important for safety assessments of the repository. At least two of programs can be used for this kind of problem, for example OS3D/GIMRT and PHAST. As it is also important to consider the uncertainty of the model, the TACK program fills an important purpose here. A slightly different approach to the problem may give significantly different results. Because validation is generally not possible, using several programs is the only key to identifying conceptual uncertainties. To illustrate this point, comparative calculations have been made between TACK and the PHAST program. The calculations gave qualitatively similar result but quantitatively somewhat differing results. The TACK program couples the well known PHREEQC geochemical program with a two-dimensional transport model. The PHREEQC calculations include speciation of solutions and mineral reactions involving kinetics. The reasons for choosing this program are that it is quite a general one and is relatively stable at the high pH values present in the systems used. The transport phenomena taken into account in the model are advection, diffusion and dispersion in two dimensions.

  5. Modeling the coupling between flow and transport developed by chemical reactions and density differences using TOUGHREACT.

    SciTech Connect

    Kim, Jeongkon; Scwartz, Franklin W.; Shi, Jianyou; Xu, Tianfu

    2003-04-01

    A complex pattern of coupling between fluid flow and mass transport develops when heterogeneous reactions occur. For instance, dissolution and precipitation reactions can change the physical properties of a medium, such as permeability and pore geometry. These changes influence fluid flow, which in turn impact the composition of dissolved constituents and solid-phase, and the rate and direction of advective transport. Two-dimensional modeling studies using TOUGHREACT were conducted to investigate the coupling between flow and transport developed as a consequence of difference in density, dissolution/precipitation, and medium heterogeneity. The model includes equilibrium reactions for aqueous species, kinetic reactions between the solid phases and aqueous constituents, and full coupling of porosity and permeability changes resulting from precipitation and dissolution reactions in porous media. Generally, the evolutions in the concentrations of the aqueous phase are intimately related to the reaction-front dynamics. Plugging of the medium contributed to significant transients in patterns of flow and mass transport.

  6. Analysis of Cooperative Behavior in Multiple Kinesins Motor Protein Transport by Varying Structural and Chemical Properties

    PubMed Central

    Uppulury, Karthik; Efremov, Artem K.; Driver, Jonathan W.; Jamison, D. Kenneth

    2012-01-01

    Intracellular transport is a fundamental biological process during which cellular materials are driven by enzymatic molecules called motor proteins. Recent optical trapping experiments and theoretical analysis have uncovered many features of cargo transport by multiple kinesin motor protein molecules under applied loads. These studies suggest that kinesins cooperate negatively under typical transport conditions, although some productive cooperation could be achieved under higher applied loads. However, the microscopic origins of this complex behavior are still not well understood. Using a discrete-state stochastic approach we analyze factors that affect the cooperativity among kinesin motors during cargo transport. Kinesin cooperation is shown to be largely unaffected by the structural and mechanical parameters of a multiple motor complex connected to a cargo, but much more sensitive to biochemical parameters affecting motor-filament affinities. While such behavior suggests the net negative cooperative responses of kinesins will persist across a relatively wide range of cargo types, it is also shown that the rates with which cargo velocities relax in time upon force perturbations are influenced by structural factors that affect the free energies of and load distributions within a multiple kinesin complex. The implications of these later results on transport phenomena where loads change temporally, as in the case of bidirectional transport, are discussed. PMID:24489614

  7. Determination of the composition of the organic matter chemically stabilized by agricultural soil clay minerals: Spectroscopy and Density Fractionation

    NASA Astrophysics Data System (ADS)

    Oufqir, Sofia; Bloom, Paul; Toner, Brandy; Hatcher, Patrick

    2014-05-01

    The interactions between soil organic matter and clay minerals are considered important processes because of their ability to sequester C in soil for long periods of time, and hence control C in the global C cycle when present. However, differing results have been reported regarding the composition of the soil organic matter - aromatic fractions versus aliphatic fractions - associated with clay minerals. To clarify this critical issue and better understand the C sequestration process in soils, we aimed to determine the nature of the chemically bound natural organic matter on clay surfaces, and to probe the speciation and spatial distribution of C in the soil clay nanoparticles using direct spectroscopic measurements namely solid-state CP-MAS and DP-MAS 13C NMR spectroscopy, x-ray diffraction spectroscopy (XRD), and scanning transmission x-ray microscopy (STXM). We tested the hypotheses that peptides and polysaccharides are stabilized by the smectite-illite clay while the lipids and black carbon are a separate phase; and that they are evenly distributed on clay surfaces. A soil clay fraction (5.5% organic C) was isolated from the surface of a prairie soil (Mollisol) in southwestern Minnesota, characterized by a pH 6.0, 32.5% clay content, and 3.7% organic carbon, using a sonication-sedimentation-siphoning process in distilled water. Then was subjected to density separation combined with low energy ultrasonic dispersion to separate the free organic and black C (light fraction) from the chemically bound C (heavy fraction). The XRD results indicated a dominance of interstratified smectite-illite clays in soil. The 13C-NMR spectra of the soil clay fraction suggested that polysaccharides and polypeptides are the prevailing components of the organic matter associated with the mineral clay, with only a minor component of aromatic C. The light fraction has strong alkyl C-H bands characteristic of fatty acids plus strong C-O bands characteristic of polysaccharides, including

  8. Chemical Potential of Triethylene Glycol Adsorbed on Surfaces Relevant to Gas Transport and Processing - Studies Using Molecular Dynamics Simulations

    NASA Astrophysics Data System (ADS)

    Kvamme, B.; Olsen, R.; Sjöblom, S.; Leirvik, K. N.; Kuznetsova, T.

    2014-12-01

    Natural gas will inevitably contain trace amounts of water and other impurities during different stages of processing and transport. Glycols, such as triethylene glycol (TEG), will in many cases follow the water. The glycol contents of the gas can originate from preceding glycol-drying units or it can be a residue from the direct injection of glycols used to prevent hydrate formation. Thus, it is important to know how glycol contents will affect the different paths leading to hydrate formation. Glycols may in some cases dominate the condensed water phase. If this occurs, it will lead to the well-documented shift in the hydrate stability curve, due to the altered activity of the water. A great deal of information on the molecular path of a glycol through the system can be obtained from calculating the chemical potential. Due to difficulties in measuring interfacial chemical potentials, these often need to be estimated using theoretical tools. We used molecular dynamics (MD) to study how TEG behaves in the vicinity of mineral surfaces such as calcite and hematite. Many methods exist for estimating chemical potentials based on MD trajectories. These include techniques such as free energy perturbation theory (FEP) and thermodynamic integration (TI). Such methods require sufficient sampling of configurations where free energy is to be estimated. Thus, it can be difficult to estimate chemical potentials on surfaces. There are several methods to circumvent this problem, such as blue moon sampling and umbrella sampling. These have been considered and the most important have been used to estimate chemical potentials of TEG adsorbed on the mineral surfaces. The resulting chemical potentials were compared to the chemical potential of TEG in bulk water, which was estimated using temperature thermodynamic integration.

  9. Hydrogeology, Chemical Characteristics, and Transport Processes in the Zone of Contribution of a Public-Supply Well in York, Nebraska

    USGS Publications Warehouse

    Landon, Matthew K.; Clark, Brian R.; McMahon, Peter B.; McGuire, Virginia L.; Turco, Michael J.

    2008-01-01

    In 2001, the U.S. Geological Survey, as part of the National Water Quality Assessment (NAWQA) Program, initiated a topical study of Transport of Anthropogenic and Natural Contaminants (TANC) to PSW (public-supply wells). Local-scale and regional-scale TANC study areas were delineated within selected NAWQA study units for intensive study of processes effecting transport of contaminants to PSWs. This report describes results from a local-scale TANC study area at York, Nebraska, within the High Plains aquifer, including the hydrogeology and geochemistry of a 108-square-kilometer study area that contains the zone of contribution to a PSW selected for study (study PSW), and describes factors controlling the transport of selected anthropogenic and natural contaminants to PSWs. Within the local-scale TANC study area, the High Plains aquifer is approximately 75 m (meter) thick, and includes an unconfined aquifer, an upper confining unit, an upper confined aquifer, and a lower confining unit with lower confined sand lenses (units below the upper confining unit are referred to as confined aquifers) in unconsolidated alluvial and glacial deposits overlain by loess and underlain by Cretaceous shale. From northwest to southeast, land use in the local-scale TANC study area changes from predominantly irrigated agricultural land to residential and commercial land in the small community of York (population approximately 8,100). For the purposes of comparing water chemistry, wells were classified by degree of aquifer confinement (unconfined and confined), depth in the unconfined aquifer (shallow and deep), land use (urban and agricultural), and extent of mixing in wells in the confined aquifer with water from the unconfined aquifer (mixed and unmixed). Oxygen (delta 18O) and hydrogen (delta D) stable isotopic values indicated a clear isotopic contrast between shallow wells in the unconfined aquifer (hereinafter, unconfined shallow wells) and most monitoring wells in the confined

  10. Recent Advances in Detailed Chemical Kinetic Models for Large Hydrocarbon and Biodiesel Transportation Fuels

    SciTech Connect

    Westbrook, C K; Pitz, W J; Curran, H J; Herbinet, O; Mehl, M

    2009-03-30

    n-Hexadecane and 2,2,4,4,6,8,8-heptamethylnonane represent the primary reference fuels for diesel that are used to determine cetane number, a measure of the ignition property of diesel fuel. With the development of chemical kinetics models for these two primary reference fuels for diesel, a new capability is now available to model diesel fuel ignition. Also, we have developed chemical kinetic models for a whole series of large n-alkanes and a large iso-alkane to represent these chemical classes in fuel surrogates for conventional and future fuels. Methyl decanoate and methyl stearate are large methyl esters that are closely related to biodiesel fuels, and kinetic models for these molecules have also been developed. These chemical kinetic models are used to predict the effect of the fuel molecule size and structure on ignition characteristics under conditions found in internal combustion engines.

  11. Transportation.

    ERIC Educational Resources Information Center

    Crank, Ron

    This instructional unit is one of 10 developed by students on various energy-related areas that deals specifically with transportation and energy use. Its objective is for the student to be able to discuss the implication of energy usage as it applies to the area of transportation. Some topics covered are efficiencies of various transportation…

  12. Efficient Activation of Pathogenic ΔPhe501 Mutation in Monocarboxylate Transporter 8 by Chemical and Pharmacological Chaperones.

    PubMed

    Braun, Doreen; Schweizer, Ulrich

    <