Science.gov

Sample records for agricultural chemical transport

  1. Atmospheric Transport and Deposition of Agricultural Chemicals

    NASA Astrophysics Data System (ADS)

    Majewski, M. S.; Vogel, J. R.; Capel, P. D.

    2006-05-01

    Concentrations of more than 80 pesticides and select transformation products were measured in atmospheric deposition during two growing seasons in five agricultural areas across the United States. Rainfall samples were collected at study areas in California, Indiana, Maryland, and Nebraska. In the arid Yakima Valley of Washington, dry deposition for the same compounds was estimated using air concentration measurements and depositional models. In the predominantly corn, soybean, and alfalfa growing region of Nebraska, Indiana, and Maryland, the herbicides acetochlor, alachlor, atrazine, and metolachlor where the predominant pesticides detected, and the highest concentrations ranged from 0.64 microgram per liter (ug/L) for metolachlor in a small, predominantly dairy use dominated watershed in Maryland to 6.6 ug/L and 19 ug/L for atrazine in Indiana and Nebraska, respectively. California showed a different seasonal occurrence pattern and suite of detected pesticides because the rainy season occurs during the winter months and a wide variety of crops are grown throughout the year. With the exception of metolachlor (0.23 ug/L, max.), the corn and soybean herbicides were not used to any great extent in the California study area and were not detected. The insecticides diazinon (1.21 ug/L, max.) and chlorpyrifos (0.12 ug/L, max.) were detected in nearly every sample taken in California. The Washington study area was similar to California in terms of the variety of crops grown and the pesticides use, but it receives very little rainfall. Dry deposition was estimated at this site from air concentrations and particle settling velocities. The results of these studies show the importance of the atmosphere as an additional source of pesticide loading to agricultural watersheds.

  2. Chemical transport from paired agricultural and restored prairie watersheds

    USGS Publications Warehouse

    Schilling, K.E.

    2002-01-01

    A five-year record of streamflow and chemical sampling data was evaluated to assess the effects of large-scale prairie restoration on transport of NO3-N, Cl, and SO4 loads from paired 5000-ha watersheds located in Jasper County, Iowa. Water quality conditions monitored during land use conversion from row crop agriculture to native prairie in the Walnut Creek watershed were compared with a highly agricultural control watershed (Squaw Creek). Combining hydrograph separation with a load estimation program, baseflow and stormflow loads of NO3-N, Cl, and SO4 were estimated at upstream and downstream sites on Walnut Creek and a downstream site on Squaw Creek. Chemical export in both watersheds was found to occur primarily with baseflow, with baseflow transport greatest during the late summer and fall. Lower Walnut Creek watershed, which contained the restored prairie areas, exported less NO3-N and Cl compared with upper Walnut Creek and Squaw Creek watersheds. Average flow-weighted concentrations of NO3-N exceeded 10 mg/L in upper Walnut Creek and Squaw Creek, but were estimated to be 6.6 mg/L in lower Walnut Creek. Study results demonstrate the utility of partitioning loads into baseflow and stormflow components to identify sources of pollutant loading to streams.

  3. National, holistic, watershed-scale approach to understand the sources, transport, and fate of agricultural chemicals

    USGS Publications Warehouse

    Capel, P.D.; McCarthy, K.A.; Barbash, J.E.

    2008-01-01

    This paper is an introduction to the following series of papers that report on in-depth investigations that have been conducted at five agricultural study areas across the United States in order to gain insights into how environmental processes and agricultural practices interact to determine the transport and fate of agricultural chemicals in the environment. These are the first study areas in an ongoing national study. The study areas were selected, based on the combination of cropping patterns and hydrologic setting, as representative of nationally important agricultural settings to form a basis for extrapolation to unstudied areas. The holistic, watershed-scale study design that involves multiple environmental compartments and that employs both field observations and simulation modeling is presented. This paper introduces the overall study design and presents an overview of the hydrology of the five study areas. Copyright ?? 2008 by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America. All rights reserved.

  4. 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.

  5. 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

  6. 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

  7. 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.

  8. 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.

  9. 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.

  10. Water and Agricultural-Chemical Transport in a Midwestern, Tile-Drained Watershed: Implications for Conservation Practices

    USGS Publications Warehouse

    Baker, Nancy T.; Stone, Wesley W.; Frey, Jeffrey W.; Wilson, John T.

    2007-01-01

    The study of agricultural chemicals is one of five national priority topics being addressed by the National Water-Quality Assessment (NAWQA) Program in its second decade of studies, which began in 2001. Seven watersheds across the Nation were selected for the NAWQA agricultural-chemical topical study. The watersheds selected represent a range of agricultural settings - with varying crop types and agricultural practices related to tillage, irrigation, artificial drainage, and chemical use - as well as a range of landscapes with different geology, soils, topography, climate, and hydrology (Capel and others, 2004). Chemicals selected for study include nutrients (nitrogen and phosphorus) and about 50 commonly used pesticides. This study design leads to an improved understanding of many factors that can affect the movement of water and chemicals in different agricultural settings. 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 (Capel and others, 2004). This Fact Sheet highlights the results of the NAWQA agricultural chemical study in the Leary Weber Ditch Watershed in Hancock County, Indiana. This watershed was selected to represent a tile-drained, corn and soybean, humid area typical in the Midwest.

  11. 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.

  12. Evaluation of Unsaturated-Zone Solute-Transport Models for Studies of Agricultural Chemicals

    DTIC Science & Technology

    2005-01-01

    zone VS2DT – Variably Saturated Two Dimen- sional Transport vi Contents Abstract …………………………………………………………………………………… 1 Introduction...10 VS2DT ……………………………………………………………………………… 11 Simple models …………………………………………………………………………… 11 CALF ……………………………………………………………………………… 11 GLEAMS...water flux algorithm. The complex models, HYDRUS2D, LEACHP, RZWQM, and VS2DT , use Richards’ equation to simulate water flux and are well suited to

  13. Water-quality, water-level, and discharge data associated with the Mississippi embayment agricultural chemical-transport study, 2006-2008

    USGS Publications Warehouse

    Dalton, Melinda S.; Rose, Claire E.; Coupe, Richard H.

    2010-01-01

    In 2006, the Agricultural Chemicals: Sources, Transport and Fate study team (Agricultural Chemicals Team, ACT) of the U.S. Geological Survey National Water-Quality Assessment Program began a study in northwestern Mississippi to evaluate the influence of surface-water recharge on the occurrence of agriculturally related nutrients and pesticides in the Mississippi River Valley alluvial aquifer. The ACT study was composed in the Bogue Phalia Basin, an indicator watershed within the National Water-Quality Assessment Program Mississippi Embayment Study Unit and utilized several small, subbasins within the Bogue Phalia to evaluate surface and groundwater interaction and chemical transport in the Basin. Data collected as part of this ACT study include water-quality data from routine and incident-driven water samples evaluated for major ions, nutrients, organic carbon, physical properties, and commonly used pesticides in the area; discharge, gage height and water-level data for surface-water sites, the shallow alluvial aquifer, and hyporheic zone; additionally, agricultural data and detailed management activities were reported by land managers for farms within two subbasins of the Bogue Phalia Basin—Tommie Bayou at Pace, MS, and an unnamed tributary to Clear Creek near Napanee, MS.

  14. Agricultural chemical utilization and human health.

    PubMed Central

    Mushak, E W; Piver, W T

    1992-01-01

    The public is justifiably concerned about the human health effects of agricultural chemicals. The many gaps in information about the mechanisms of toxic action, human exposures, and the nature and extent of human health effects are large. Very few older pesticides, in particular, have been tested for human health effects. Workers who produce, harvest, store, transport, process, and prepare food and fibers are exposed to many chemicals that are potentially hazardous and that are used in agriculture. The occupational health of these workers has not been adequately studied, and protective efforts have sometimes been minimal. Valid and accurate risk assessment is best based on sound information about how chemicals, in this case agricultural chemicals, are involved in toxic events--their mechanisms of action. These health effects include tumor promotion, chronic and acute neurotoxicity, immunotoxicity, and reproductive and developmental toxicity. Another key part of risk assessment is exposure assessment. Fundamental studies of the toxicology of target organisms and nontarget organisms exposed to agricultural chemicals are needed to discover and develop better solutions to the problems of agricultural pest control, including better formulations, optimal application rates and public education in safety and alternative agricultural practices. The large number of pesticides that have never been adequately tested for effects on human health is particularly worrisome in light of emerging information about delayed nervous system effects. PMID:1396466

  15. 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.

  16. 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)

  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. Mechanical approach to chemical transport

    PubMed Central

    Kocherginsky, Nikolai; Gruebele, Martin

    2016-01-01

    Nonequilibrium thermodynamics describes the rates of transport phenomena with the aid of various thermodynamic forces, but often the phenomenological transport coefficients are not known, and the description is not easily connected with equilibrium relations. We present a simple and intuitive model to address these issues. Our model is based on Lagrangian dynamics for chemical systems with dissipation, so one may think of the model as physicochemical mechanics. Using one main equation, the model allows a systematic derivation of all transport and equilibrium equations, subject to the limitation that heat generated or absorbed in the system must be small for the model to be valid. A table with all major examples of transport and equilibrium processes described using physicochemical mechanics is given. In equilibrium, physicochemical mechanics reduces to standard thermodynamics and the Gibbs–Duhem relation, and we show that the First and Second Laws of thermodynamics are satisfied for our system plus bath model. Out of equilibrium, our model provides relationships between transport coefficients and describes system evolution in the presence of several simultaneous external fields. The model also leads to an extension of the Onsager–Casimir reciprocal relations for properties simultaneously transported by many components. PMID:27647899

  19. 78 FR 55278 - Chemical Transportation Advisory Committee

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-09-10

    ... 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 in... Committee: Chemical Transportation Advisory Committee. ADDRESSES: If you desire to submit comments on...

  20. 76 FR 34240 - Chemical Transportation Advisory Committee

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-06-13

    ... 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 the...: Chemical Transportation Advisory Committee. ADDRESSES: If you desire to submit comments on this...

  1. 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

  2. Rhamnolipid surface thermodynamic properties and transport in agricultural soil.

    PubMed

    Renfro, Tyler Dillard; Xie, Weijie; Yang, Guang; Chen, Gang

    2014-03-01

    Rhamnolipid is a biosurfactant produced by several Pseudomonas species, which can wet hydrophobic soils by lowering the cohesive and/or adhesive surface tension. Because of its biodegradability, rhamnolipid applications bring minimal adverse impact on the soil and groundwater as compared with that of chemical wetting agents. Subsequently, rhamnolipid applications have more advantages when used to improve irrigation in the agricultural soil, especially under draught conditions. In the presence of rhamnolipid, water surface tension dropped linearly with the increase of rhamnolipid concentration until the rhamnolipid critical micelle concentration (CMC) of 30 mg/L was reached. Below the CMC, rhamnolipid had linear adsorption isotherms on the soil with a partition coefficient of 0.126 L/kg. Rhamnolipid transport breakthrough curves had a broad and diffuse infiltration front, indicating retention of rhamnolipid on the soil increased with time. Rhamnolipid transport was found to be well represented by the advection-dispersion equation based on a local equilibrium assumption. When applied at concentrations above the CMC, the formed rhamnolipid micelles prevented rhamnolipid adsorption (both equilibrium adsorption and kinetic adsorption) in the soil. It was discovered in this research that rhamnolipid surface thermodynamic properties played the key role in controlling rhamnolipid transport. The attractive forces between rhamnolipid molecules contributed to micelle formation and facilitated rhamnolipid transport.

  3. 78 FR 67379 - Chemical Transportation Advisory Committee

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-11-12

    ... SECURITY Coast Guard Chemical Transportation Advisory Committee AGENCY: Coast Guard, DHS. ACTION: Committee Management; Notice of Federal Advisory Committee Meeting. SUMMARY: The Chemical Transportation Advisory... hazardous materials c. Update on Bulk Chemical Data Guide (Blue Book) d. Vessel to vessel transfer...

  4. Impacts of Climate Change on Indirect Human Exposure to Pathogens and Chemicals from Agriculture

    PubMed Central

    Boxall, Alistair B.A.; Hardy, Anthony; Beulke, Sabine; Boucard, Tatiana; Burgin, Laura; Falloon, Peter D.; Haygarth, Philip M.; Hutchinson, Thomas; Kovats, R. Sari; Leonardi, Giovanni; Levy, Leonard S.; Nichols, Gordon; Parsons, Simon A.; Potts, Laura; Stone, David; Topp, Edward; Turley, David B.; Walsh, Kerry; Wellington, Elizabeth M.H.; Williams, Richard J.

    2009-01-01

    Objective Climate change is likely to affect the nature of pathogens and chemicals in the environment and their fate and transport. Future risks of pathogens and chemicals could therefore be very different from those of today. In this review, we assess the implications of climate change for changes in human exposures to pathogens and chemicals in agricultural systems in the United Kingdom and discuss the subsequent effects on health impacts. Data sources In this review, we used expert input and considered literature on climate change; health effects resulting from exposure to pathogens and chemicals arising from agriculture; inputs of chemicals and pathogens to agricultural systems; and human exposure pathways for pathogens and chemicals in agricultural systems. Data synthesis We established the current evidence base for health effects of chemicals and pathogens in the agricultural environment; determined the potential implications of climate change on chemical and pathogen inputs in agricultural systems; and explored the effects of climate change on environmental transport and fate of different contaminant types. We combined these data to assess the implications of climate change in terms of indirect human exposure to pathogens and chemicals in agricultural systems. We then developed recommendations on future research and policy changes to manage any adverse increases in risks. Conclusions Overall, climate change is likely to increase human exposures to agricultural contaminants. The magnitude of the increases will be highly dependent on the contaminant type. Risks from many pathogens and particulate and particle-associated contaminants could increase significantly. These increases in exposure can, however, be managed for the most part through targeted research and policy changes. PMID:19440487

  5. 78 FR 16189 - Transportation of Agricultural Commodities

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-03-14

    ... controlled and operated by a beekeeper engaged in the seasonal transportation ] of bees. The exemption does... 391 for a beekeeper using a CMV for the seasonal transportation of bees, is also retained. Like...

  6. 77 FR 70453 - Chemical Transportation Advisory Committee

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-11-26

    ... From the Federal Register Online via the Government Publishing Office DEPARTMENT OF HOMELAND SECURITY Coast Guard Chemical Transportation Advisory Committee AGENCY: Coast Guard, DHS. ] ACTION: Committee Management; Notice of Federal Advisory Committee Meeting. SUMMARY: The Chemical...

  7. 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.

  8. 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...

  9. 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…

  10. AGRICULTURAL CHEMICALS SALES AND SERVICE. AGRICULTURAL SUPPLY - SALES AND SERVICE OCCUPATIONS, MODULE NUMBER 10.

    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 HIGH SCHOOL OR POST-SECONDARY STUDENTS FOR EMPLOYMENT IN AGRICULTURAL CHEMICAL SALES AND SERVICE. ONE OF A SERIES OF MODULES FOR AGRICULTURAL SUPPLY OCCUPATIONS, IT WAS DEVELOPED ON THE BASIS OF DATA FROM STATE STUDIES BY A NATIONAL TASK FORCE. APPLICABLE TO TWO LEVELS OF INSTRUCTION,…

  11. Toxicological procedures for assessing the carcinogenic potential of agricultural chemicals.

    PubMed

    Krewski, D; Clayson, D; Collins, B; Munro, I C

    1982-01-01

    Pesticides and other agricultural chemicals are now widely used throughout the world as a means of improving crop yields in order to meet the increasing demands being placed upon the global food supply. In Canada, the use of such chemicals is controlled through government regulations established jointly by the Department of Agriculture and the Department of National Health & Welfare. Such regulations require a detailed evaluation of the toxicological characteristics of the chemical prior to its being cleared for use. In this paper, procedures for assessing the carcinogenic potential of agricultural and other chemicals are discussed. Consideration is given to both the classical long-term in vivo carcinogen bioassay in rodent or other species and the more recently developed short-term in vitro tests based on genetic alterations in bacterial and other test systems.

  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. 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 ...

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

    USGS Publications Warehouse

    ,

    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. Using reverse osmosis to remove agricultural chemicals from groundwater

    SciTech Connect

    Baier, J.H.; Lykins, B.W.; Fronk, C.A.; Kramer, S.J.

    1987-01-01

    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 agricultural chemicals from groundwater. Tests of cellulose acetate; spiral-wound, thin-film composite; and hollow-fiber membranes showed that reverse osmosis should be considered for pesticide and organics removal. Pilot tests should be conducted on in-situ water to assure proper process design.

  16. 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.…

  17. 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 ...

  18. 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.

  19. 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)…

  20. DEVELOPMENT OF ADME DATA IN AGRICULTURAL CHEMICAL SAFETY ASSESSMENTS

    EPA Science Inventory

    DEVELOPMENT OF ADME DATA IN AGRICULTURAL CHEMICAL SAFETY ASSESSMENTS
    Pastoor, Timothy1, Barton, Hugh2
    1 Syngenta Crop Protection, Greensboro, NC, USA.
    2 EPA, Office of Research and Development-NHEERL, RTP, NC, USA.

    A multi-stakeholder series of discussions d...

  1. 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.

  2. Ecologically sustainable chemical recommendations for agricultural pest control?

    PubMed

    Thomson, Linda J; Hoffmann, Ary A

    2007-12-01

    Effective pest control remains an essential part of food production, and it is provided both by chemicals and by natural enemies within agricultural ecosystems. These methods of control are often in conflict because of the negative impact of chemicals on natural enemies. There are already well-established approaches such as those provided by the International Organization for Biological and Integrated Control-Pesticides and Beneficial Organisms for testing, collecting, and publishing information on responses of natural enemies to chemicals based on laboratory responses of specific organisms; however, these tests do not assess the cumulative impact of chemical inputs across an entire season or consider impacts on the complex communities of natural enemies that can provide effective pest control on a farm. Here, we explore the potential of different approaches for assessing the impact of chemicals on agricultural ecosystems and we propose a simple metric for sustainable chemical use on farms that minimizes overall impact on beneficial groups. We suggest ways in which the effectiveness of metrics can be extended to include persistence and habitat features. Such metrics can assist farmers in developing targets for sustainable chemical use as demonstrated in the viticultural industry.

  3. 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…

  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 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,…

  6. 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…

  7. 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.

  8. Modelling Cryptosporidium oocysts transport in small ungauged agricultural catchments.

    PubMed

    Tang, Jialiang; McDonald, Stephen; Peng, Xinhua; Samadder, Sukha R; Murphy, Thomas M; Holden, Nicholas M

    2011-06-01

    Cryptosporidium is an environmentally robust pathogen that has caused severe waterborne disease outbreaks worldwide. The main source of zoonotic Cryptosporidium parvum oocysts in human drinking water is likely to be from farm animals via catchment pathways with water as the main transport vector. The vast majority of small agricultural catchments are ungauged therefore it is difficult to use a process model to predict and understand the mechanisms and activities that regulate the risk of surface water contamination from agricultural areas. For this study, two ungauged agricultural catchments in Ireland were used to model Cryptosporidium oocyst transport using SWAT2005 on a daily basis with reference data from adjacent catchment gauging stations. The results indicated that SWAT2005 could simulate stream flow with good agreement between prediction and observation on a monthly basis (R(2) from 0.94 to 0.83 and E (efficiency) from 0.92 to 0.66), but Cryptosporidium oocyst concentration results were less reliable (R(2) from 0.20 to 0.37, P < 0.05; with poor E -0.37 to -2.57). A sensitivity analysis using independent parameter perturbation indicated that temperature was the most important parameter regulating oocyst transport in the study catchments and that the timing of manure application relative to the occurrence of water runoff event was critical. The results also showed that grazing management had little influence on predicted oocyst transport while fields fertilized with manure were the key critical source areas for microbial contaminations in the study catchments. It was concluded that the approach presented could be used to assist with understanding the epidemiology of waterborne cryptosporidiosis outbreaks and to improve catchment management for the safety of the general public health.

  9. Chemically driven fluid transport in long microchannels

    NASA Astrophysics Data System (ADS)

    Shen, Mingren; Ye, Fangfu; Liu, Rui; Chen, Ke; Yang, Mingcheng; Ripoll, Marisol

    2016-09-01

    Chemical gradients maintained along surfaces can drive fluid flows by diffusio-osmosis, which become significant at micro- and nano-scales. Here, by means of mesoscopic simulations, we show that a concentration drop across microchannels with periodically inhomogeneous boundary walls can laterally transport fluids over arbitrarily long distances along the microchannel. The driving field is the secondary local chemical gradient parallel to the channel induced by the periodic inhomogeneity of the channel wall. The flow velocity depends on the concentration drop across the channel and the structure and composition of the channel walls, but it is independent of the overall channel length. Our work thus presents new insight into the fluid transport in long microchannels commonly found in nature and is useful for designing novel micro- or nano-fluidic pumps.

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. 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…

  15. 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

  16. 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.

  17. Current United States Department of Agriculture-Agricultural Research Service research on understanding agrochemical fate and transport to prevent and mitigate adverse environmental impacts.

    PubMed

    Hapeman, Cathleen J; McConnell, Laura L; Rice, Clifford P; Sadeghi, Ali M; Schmidt, Walter F; McCarty, Gregory W; Starr, James L; Rice, Pamela J; Angier, Jonathan T; Harman-Fetcho, J A

    2003-01-01

    Environmentally and economically viable agriculture requires a variety of cultivation practices and pest management options as no one system will be appropriate for every situation. Agrochemicals are some of the many pest control tools used in an integrated approach to pest management. They are applied with the intent of maximizing efficacy while minimizing off-site movement; however, their judicious use demands a practical knowledge of their fate and effects in agricultural and natural ecosystems. Agrochemical distribution into environmental compartments is influenced by the physical and chemical properties of the agrochemical and environmental conditions, ie soil type and structure, and meteorological conditions. Agricultural Research Service (ARS) researchers working in the area of agrochemical fate have focused on accurately describing those processes that govern the transport, degradation and bioavailability of these chemicals under conditions reflecting actual agronomic practices. Results from ARS research concerning the environmental fate and effects of agrochemicals have led to the development of science-based management practices that will protect vulnerable areas of the ecosystem. The new challenge is to identify these vulnerable areas and the temporal and spatial variations prior to use of the chemical by predicting how it will behave in environmental matrices, and using that information, predict its transport and transformation within an air- or watershed. With the development of better predictive tools and GIS (Geographic Information System)-based modeling, the risks of agricultural management systems can be assessed at the watershed and basin levels, and management strategies can be identified that minimize negative environmental impacts.

  18. 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

  19. 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.

  20. 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.

  1. 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.

  2. 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.

  3. ACE-Asia Chemical Transport Modeling Overview

    NASA Astrophysics Data System (ADS)

    UNO, I.; Chin, M.; Collins, W.; Ginoux, P.; Rasch, P.; Carmichael, G. R.; Yienger, J. J.

    2001-12-01

    ACE-Asia (Asia Pacific Regional Aerosol Characterization Experiment) was designed to increase our understanding of how atmospheric aerosol particles affect the Earth?s climate system. The intensive observation period was carried out during March to May, 2001, and more than 100 researchers from several countries (United States, Japan, Korea, China, and many other Asian countries) participated using aircraft, a research vessel, surface stations and numerical models. Aerosol transport forecast activities played an important role during the ACE-Asia intensive observation period. Three independent modeling groups operated chemical transport models in forecast mode and participated in flight planning activities at the operations center. These models were: MATCH (Model of Atmospheric Transport and Chemistry; Rasch and Collins); GOCART (Georgia Tech/Goddard Global Ozone Chemistry Aerosol Radiation and Transport model; Chin and Ginour) and CFORS (Research Institute for Applied Mechanics, Kyushu University + University of Iowa - Chemical weather FORecast System; Uno, Carmichael and Yienger). The MATCH model used in ACE-Asia was a transport model applied for the Asia region, driven by NCEP forecast meteorology. A unique feature of this model was that it assimilated satellite derived optical depths into its forecast algorithm. The GOCART model provided global aerosol forecast using forecast meteorological fields provided by the Goddard Earth Observing System Data Assimilation System (GEOS DAS). The CFORS model provided regional forecasts using a limited area transport model coupled with Regional Meteorological Modeling System (RAMS), initialized by NCEP and JMA forecasts. All models produced 3-d aerosol forecast products consisting of aerosol mass distributions and optical depths for sulfate, black carbon, organic carbon, sea salt, and dust. In the field these model products were made available to all participating scientists via the Web, and were also presented during the

  4. Assessing the transfer of risk due to transportation of agricultural products.

    PubMed

    Li, Pei-Chiun; Shih, Hsiu-Ching; Ma, Hwong-Wen

    2015-02-01

    Health risk assessment (HRA) is the process used to estimate adverse health effects on humans. The importance and sensitivity of food chains to HRA have been observed, but the impact of the transportation of food has generally been ignored. This study developed an exposure assessment to demonstrate the significance of the transportation of agricultural products in HRA. The associated case study estimated the health risks derived from various sources of arsenic emissions in Taiwan. Two assessment scenarios, self-sufficiency and transportation of agricultural products, were compared to calculate risk transfer ratios that show the impact of agriculture transportation. The risk transfer ratios found by the study range from 0.22 to 42.10, indicating that the quantity of transportation of agricultural products is the critical factor. High air deposition and high agricultural production are the two main contributors to the effect of the transportation of agricultural products on HRA. Risk reduction measures could be applied to high-pollution areas as well as to areas with high agricultural productivity to reduce ingestion risks to residents. Certain areas that are sensitive to the transportation of agricultural products may incur more risks if emissions increase in agriculturally productive counties.

  5. 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.

  6. 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 ...

  7. 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

  8. Modelling E. coli transport in soil columns: simulation of wastewater reuse in agriculture.

    PubMed

    Smith, Edward; Badawy, Aimen

    2008-01-01

    Transport of E. coli bacteria was investigated in laboratory soil columns for three Egyptian agricultural soils, with aim toward determining a set of site specific criteria for safe and sustainable use of treated wastewater in irrigation in Egypt. In particular, the impacts of varying soil type and hydraulic loading rate (HLR) on E. coli effluent breakthrough curves were examined in the laboratory and simulated using the CXTFIT package to solve a one-dimensional mass transport equation that included advection, dispersion, adsorption, and straining/filtration. The attempt was made to measure the coefficients associated with each mass transfer process from independent experiments. The HLR used in irrigation was found to exert considerable influence on the impact of transport processes on E. coli breakthrough. At low HLRs, adsorption and straining/filtration are significant in addition to advection and dispersion. However, at high HLRs approaching flood irrigation, E. coli is essentially unaffected by reaction processes, with breakthrough a function of advection and dispersion only. Estimating Kd via independent batch experiments did not provide a suitable description of adsorption of E. coli in soil columns. To ensure safe and sustainable reuse of reclaimed wastewater in irrigation, guidelines should account for physical and chemical properties of the soil and other local conditions that may impact residual contaminant transport.

  9. 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%.

  10. 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…

  11. 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.

  12. 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

  13. 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.

  14. 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 ...

  15. EPA requires major agricultural chemical dealer to safely manage pesticides

    EPA Pesticide Factsheets

    SAN FRANCISCO - Today, the U.S. Environmental Protection Agency announced settlements with two associated companies for the improper storage and containment of agricultural pesticides. Fertizona, a large fertilizer and crop protection retailer, and

  16. Nitrate attenuation in agricultural catchments: Shifting balances between transport and reaction

    NASA Astrophysics Data System (ADS)

    Ocampo, Carlos J.; Oldham, Carolyn E.; Sivapalan, Murugesu

    2006-01-01

    Simultaneous observations, across multiple spatial and temporal scales, are needed to understand the complex interactions between hydrological and biogeochemical processes in catchments and the primary controls on NO3- availability and mobility. This paper addresses these issues by using data collected from a detailed field experiment, carried out on two topographically different hillslopes (one steep and the other flat) located within an agricultural catchment in Western Australia. Continuous hydrometric data and measurements of chemical tracers, geochemical parameters, and NO3- concentrations taken from the shallow perched aquifer across riparian, midslope, and upland locations were analyzed and interpreted through a simple process-based numerical model of transport and reaction. The NO3- concentration data indicated that the temporal and spatial patterns of NO3- concentrations within the hillslopes are linked to the state of hydrological connectivity of the three landscape units as the shallow perched aquifer developed during the winter. Significant NO3- attenuation occurs within the riparian zones after the transport of NO3- from midslope sources begins. Application of a mixing model, which partitions the riparian zones into three water source components, and the numerical model of NO3- transport and reaction indicates that different mechanisms, dilution in the steep hillslope and denitrification in the flat hillslope, are responsible for much of the observed NO3- attenuation in the riparian zones. In this way, this work highlights the importance of hillslope topography in determining the relative roles of transport and reaction in NO3- attenuation and export from riparian zones. The experimental results also supported the use of the Damköhler number, a simple dimensionless number that is a measure of the competition between transport and reaction processes, which allowed a favorable comparison of our findings with previous results published in the literature

  17. 78 FR 23773 - Chemical Transportation Advisory Committee

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-04-22

    ..., VA, to discuss marine transportation of hazardous materials. The meetings will be open to the public... matters relating to marine transportation of hazardous materials. The Committee advises, consults with... of Pollution from Ships (MARPOL) Annex II b. Requirements for Third-Party Surveyors of MARPOL...

  18. 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...

  19. Problems associated with the use of chemicals by agricultural workers.

    PubMed

    Baloch, U K

    1985-01-01

    The agricultural productivity in Pakistan is hampered by insects, diseases, and weeds, which are reported causing losses ranging up to 50%, estimated at a total value of over 900 million U.S. dollars. The use of pesticides in Pakistan started in 1954 with 254 metric tons of formulation, increasing to the level of 16,226 metric tons in 1976-77. Since the import and use of pesticides was in the public sector, the promulgation of the Agricultural Pesticides Ordinance was delayed to 1971 and the Rules to 1973. Under these Rules exist provisions necessary for the registration, marketing, and safe use of pesticides. Through the Agricultural Pesticides Technical Advisory Committee consisting of members drawn from the various Federal and Provincial agencies relevant to the subject, the Ministry of Food, Agriculture and Cooperatives, Government of Pakistan, is responsible for its implementation, but no regular agency for monitoring the implementation of the Rules exists. The extent of health hazards to agricultural workers as a result of exposure to pesticides, among other things, depends on the socioeconomic and educational background of their society, the local laws governing registration, and the scientific and regulatory institutional setup of the country. The above factors, of particular relevance to Pakistan, are discussed.

  20. 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.

  1. 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)…

  2. 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)

  3. 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.

  4. 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 ...

  5. 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.

  6. 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...

  7. 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.

  8. Comparison of contaminant transport in agricultural drainage water and urban stormwater runoff

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Transport of nitrogen and phosphorus from agricultural and urban landscapes to surface water bodies can cause adverse environmental impacts including hypoxia and harmful algal blooms. The main objective of this long-term study was to quantify and compare contaminant transport from a subsurface-drain...

  9. 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.

  10. 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.

  11. 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

  12. Insect chemical ecology research in the United States Department of Agriculture-Agricultural Research Service.

    PubMed

    Aldrich, Jeffrey R; Bartelt, Robert J; Dickens, Joseph C; Knight, Alan L; Light, Douglas M; Tumlinson, James H

    2003-01-01

    This multi-author paper reviews current work by USDA-ARS scientists in the field of chemical ecology. Work with pheromones, the discovery and development of the codling moth kairomone, studies on insect-plant interactions and chemically mediated tritrophic plant-insect interactions have led to practical methods for control of important insect pests.

  13. 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 ...

  14. 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

  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. 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...

  17. 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...

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

    PubMed

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

    2008-06-05

    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.

  19. 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.

  20. Agriculture

    EPA Pesticide Factsheets

    The EPA Agriculture Resource Directory offers comprehensive, easy-to-understand information about environmental stewardship on farms and ranches; commonsense, flexible approaches that are both environmentally protective and agriculturally sound.

  1. Amphibians and agricultural chemicals: review of the risks in a complex environment.

    PubMed

    Mann, Reinier M; Hyne, Ross V; Choung, Catherine B; Wilson, Scott P

    2009-11-01

    Agricultural landscapes, although often highly altered in nature, provide habitat for many species of amphibian. However, the persistence and health of amphibian populations are likely to be compromised by the escalating use of pesticides and other agricultural chemicals. This review examines some of the issues relating to exposure of amphibian populations to these chemicals and places emphasis on mechanisms of toxicity. Several mechanisms are highlighted, including those that may disrupt thyroid activity, retinoid pathways, and sexual differentiation. Special emphasis is also placed on the various interactions that may occur between different agro-chemicals and between chemicals and other environmental factors. We also examine the indirect effects on amphibian populations that occur when their surrounding pond communities are altered by chemicals.

  2. 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).

  3. Phosphorus Geochemistry and Transport along Groundwater Flow paths at Five Agricultural Watersheds, USA

    NASA Astrophysics Data System (ADS)

    Domagalski, J. L.; Johnson, H. M.

    2009-12-01

    Phosphorus chemistry and transport were studied at five agricultural watersheds representing a range of climatic conditions and cropping patterns at five locations within the United States (California, Washington, Nebraska, Indiana, Maryland). Orchards and row crops were the dominant land use at the California and Washington locations, while corn and soybeans were the main crops at the remaining three. Irrigation was required at the California and Washington sites, while rain supplied most or all of the water needs at the remainder. Phosphorus concentrations were assessed within the unsaturated zone, along groundwater flow paths of approximately one kilometer in length and at various depths, and across the sediment water interface of receiving streams in small agricultural basins. Baseflow loadings of phosphorus to some of the streams accounted for up to 20% of the annual load in some locations. Unsaturated zone concentrations tended to be higher than groundwater concentrations because of recently applied fertilizer or manure and the rapid downward movement of irrigation or rainwater. Long residence times in groundwater appeared to result in conditions close to chemical equilibrium. In most cases, sorption onto hydrous iron oxides and differences in major element chemistry explained the variation in observed phosphorus concentrations within and between study units. Concentrations of hydrous iron oxides in the aquifer material also affected the saturation levels of sorbed phosphorus relative to the amount dissolved. Solution pH had a major impact at the location in Maryland. Changes in pH from approximately 7 in the unsaturated zone to less than 5 in groundwater resulted in complete sequestration of phosphorus and under-saturation of the iron oxides along the flow path. Low iron oxide concentrations in the unsaturated zone and the aquifer resulted in uniformly higher concentrations at the Nebraska location. High loadings of phosphorus at an orchard in California

  4. 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.

  5. 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.

  6. 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...

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

    PubMed

    Van Hook, R I

    1978-12-01

    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

  8. 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

  9. 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.

  10. Measurement of gas transport properties for chemical vapor infiltration

    SciTech Connect

    Starr, T.L.; Hablutzel, N.

    1996-12-01

    In the chemical vapor infiltration (CVI) process for fabricating ceramic matrix composites (CMCs), transport of gas phase reactant into the fiber preform is a critical step. The transport can be driven by pressure or by concentration. This report describes methods for measuring this for CVI preforms and partially infiltrated composites. Results are presented for Nicalon fiber cloth layup preforms and composites, Nextel fiber braid preforms and composites, and a Nicalon fiber 3-D weave composite. The results are consistent with a percolating network model for gas transport in CVI preforms and composites. This model predicts inherent variability in local pore characteristics and transport properties, and therefore, in local densification during processing; this may lead to production of gastight composites.

  11. 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…

  12. Agricultural Chemical Safety. A Guide to Safe Handling of Pesticides. Teacher's Handbook, Student Manual, and Transparencies.

    ERIC Educational Resources Information Center

    Van de Vanter, Gordon L.

    Intended for teachers and students, this agricultural chemical safety package of instructional materials pertaining to the safe handling of pesticides was developed by Vocational Education Productions of California State Polytechnic College. Included are a teachers' handbook, a student manual, and 20 transparency masters. The teachers' handbook is…

  13. 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…

  14. 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

  15. 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

  16. 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.

  17. Combined physical and chemical nonequilibrium transport model for solution conduits.

    PubMed

    Field, Malcolm S; Leij, Feike J

    2014-02-01

    Solute transport in karst aquifers is primarily constrained to relatively complex and inaccessible solution conduits where transport is often rapid, turbulent, and at times constrictive. Breakthrough curves generated from tracer tests in solution conduits are typically positively-skewed with long tails evident. Physical nonequilibrium models to fit breakthrough curves for tracer tests in solution conduits are now routinely employed. Chemical nonequilibrium processes are likely important interactions, however. In addition to partitioning between different flow domains, there may also be equilibrium and nonequilibrium partitioning between the aqueous and solid phases. A combined physical and chemical nonequilibrium (PCNE) model was developed for an instantaneous release similar to that developed by Leij and Bradford (2009) for a pulse release. The PCNE model allows for partitioning open space in solution conduits into mobile and immobile flow regions with first-order mass transfer between the two regions to represent physical nonequilibrium in the conduit. Partitioning between the aqueous and solid phases proceeds either as an equilibrium process or as a first-order process and represents chemical nonequilibrium for both the mobile and immobile regions. Application of the model to three example breakthrough curves demonstrates the applicability of the combined physical and chemical nonequilibrium model to tracer tests conducted in karst aquifers, with exceptionally good model fits to the data. The three models, each from a different state in the United States, exhibit very different velocities, dispersions, and other transport properties with most of the transport occurring via the fraction of mobile water. Fitting the model suggests the potentially important interaction of physical and chemical nonequilibrium processes.

  18. 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

  19. 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.

  20. Toxic fables: the advertising and marketing of agricultural chemicals in the great plains, 1945-1985.

    PubMed

    Vail, David D

    2012-12-01

    This paper examines how pesticides and their technologies were sold to farmers and pilots throughout the midtwentieth century. It principally considers how marketing rhetoric and advertisement strategies used by chemical companies and aerial spraying firms influenced the practices and perspectives of farm producers in the Great Plains. In order to convince landowners and agricultural leaders to buy their pesticides, chemical companies generated advertisements that championed local crop health, mixture accuracy, livestock safety and a chemical-farming 'way of life' that kept fields healthy and productive. Combining notions of safety, accuracy and professionalism with pest eradication messages reinforced the standards that landowners, pilots and agriculturalists would hold regarding toxicity and risk when spraying their fields. As the politics of health changed in the aftermath of Rachel Carson's Silent Spring, these companies and aerial spraying outfits responded by keeping to a vision of agricultural health that required poisons for protection through technological accuracy.

  1. MOZART, a global chemical transport model for ozone and related chemical tracers: 1. Model description

    NASA Astrophysics Data System (ADS)

    Brasseur, G. P.; Hauglustaine, D. A.; Walters, S.; Rasch, P. J.; Müller, J.-F.; Granier, C.; Tie, X. X.

    1998-11-01

    We present a new global three-dimensional chemical-transport model (called MOZART) developed in the framework of the NCAR Community Climate Model (CCM) and aimed at studying the distribution and budget of tropospheric ozone and its precursors. The model, developed with a horizontal resolution of 2.8° in longitude and latitude, includes 25 levels in the vertical between the Earth's surface and an upper boundary located at approximately 35 km altitude. In its present configuration the model calculates the global distribution of 56 chemical constituents with a timestep of 20 min, and accounts for surface emission and deposition, large-scale advective transport, subscale convective and boundary layer exchanges, chemical and photochemical transformations, as well as wet scavenging. Transport is simulated "off line" from CCM with dynamical variables provided every 3 hours from preestablished history tapes. Advection is calculated using the semi-Lagrangian transport scheme [Rasch and Williamson, 1990] developed for the MATCH model of Rasch et al. [1997]. Convective and boundary layer transports are expressed according to Hack [1994] and Holtslag and Boville [1993], respectively. A detailed evaluation of the model results is provided in a companion paper [Hauglustaine et al., this issue]. An analysis of the spatial and temporal variability in the chemical fields predicted by the model suggests that regional events such as summertime ozone episodes in polluted areas can be simulated by MOZART.

  2. 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.

  3. Chemical usage in production agriculture: do crop insurance and off-farm work play a part?

    PubMed

    Chang, Hung-Hao; Mishra, Ashok K

    2012-08-30

    In recent years a growing body of literature in the agricultural policy arena has examined the association between crop insurance and off-farm employment. However, little is known about the extent to which these two activities may be related to environmental quality, in particular their impacts on fertilizer/chemical use of the farm. To fill this gap, this paper examines the effect of crop insurance and off-farm work on fertilizer/chemical expenses within the farm household framework. Quantile regression results from a national representative farm-level data show that off-farm work by the farm operator tends to decrease fertilizer/chemical expenses, and the effect is more pronounced at the higher percentiles of the distribution of fertilizer/chemical expense. In contrast, a positive effect of crop insurance on fertilizer/chemical expenses is evident, and the effect is robust across the entire distribution.

  4. 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.

  5. 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.

  6. Temporal trends of selected agricultural chemicals in Iowa's groundwater, 1982-1995: Are things getting better?

    USGS Publications Warehouse

    Kolpin, D.W.; Sneck-Fahrer, D.; Hallberg, G.R.; Libra, R.D.

    1997-01-01

    Since 1982, the Iowa Groundwater Monitoring (IGWM) Program has been used to sample untreated groundwater from Iowa municipal wells for selected agricultural chemicals. This long-term database was used to determine if concentrations of select agricultural chemicals in groundwater have changed with time. Nitrate, alachlor [2-chloro-2′-6′-diethyl-N-(methoxymethyl)-acetanilide], atrazine (2-chloro-4-ethylamino-6-isopropylamino-s-triazine), cyanazine [2-[[4-chloro-6-(ethylamino)-1,3,5-triazin-2-yl]amino]-2-methylpropionitrile)], and metolachlor [2-chloro-N-(2-ethyl-6-methylphenyl)-N-(2-methoxy-1-methylethyl) acetamide] were selected for this temporal analysis of the data. Conclusive temporal changes in frequency of detection and median chemical concentrations were found only for atrazine (decrease) and metolachlor (increase). The greatest temporal chemical changes occurred in the shallowest wells and in alluvial aquifers—both relating to groups of wells generally having the youngest groundwater age. The temporal patterns found for atrazine and metolachlor are consistent with their patterns of chemical use and/or application rates and are suggestive of a causal relation. Only continued data collection, however, will indicate if the trends in chemical concentrations described here represent long-term temporal patterns or only short-term changes in groundwater. No definitive answers could be made in regards to the question of overall improvements in groundwater quality with respect to agricultural chemical contamination and time, due to the inherent problems with the simplistic measurement of overall severity (summation of alachlor + atrazine + cyanazine + metolachlor concentrations) examined for this study. To adequately determine if there is an actual decreasing trend in the overall severity of contamination (improving groundwater quality), the collection of additional water-chemistry data and the investigation of other measures of severity are needed.

  7. Nonlocal reactive transport with physical and chemical heterogeneity: Localization errors

    SciTech Connect

    Cushman, J.H.; Hu, B.X.; Deng, F.W.

    1995-09-01

    The origin of nonlocality in {open_quotes}macroscale{close_quotes} models for subsurface chemical transport is illustrated. It is argued that media that are either nonperiodic (e.g., media with evolving heterogeneity) or periodic viewed on a scale wherein a unit cell is discernible must display some nonlocality in the mean. A metaphysical argument suggests that owing to the scarcity of information on natural scales of heterogeneity and on scales of observation associated with an instrument window, constitutive theories for the mean concentration should at the outset of any modeling effort always be considered nonlocal. The intuitive appeal to nonlocality is reinforced with an analytical derivation of the constitutive theory for a conservative tracer without appeal to any mathematical approximations. Comparisons are made between the fully nonlocal (FNL), nonlocal in time (NLT), and fully localized (FL) theories. For conservative transport, there is little difference between the first-order FL and FNL models for spatial moments up to and including the third. However, for conservative transport the first-order NLT model differs significantly from the FNL model in the third spatial moments. For reactive transport, all spatial moments differ between the FNL and FL models. The second transverse-horizontal and third longitudinal-horizontal moments for the NLT model differ from the FNL model. These results suggest that localized first-order transport models for conservative tracers are reasonable if only lower-order moments are desired. However, when the chemical reacts with its environment, the localization approximation can lead to significant error in all moments, and a FNL model will in general be required for accurate simulation. 18 refs., 9 figs., 1 tab.

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

    PubMed

    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.

  9. 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

  10. 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.

  11. 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.

  12. Mitigation of chemical attacks in enclosed public transportation facilities

    NASA Astrophysics Data System (ADS)

    Swansiger, William A.; Brockmann, John E.

    1998-12-01

    Public transportation facilities in the United States are vulnerable to attack by terrorists using chemical agents. This paper focuses on the problem of protecting the people in underground subway stations, which are among the most difficult facilities to protect. A nerve agent can produce symptoms in seconds to minutes, so immediate triggering of evacuation alarms and initiation of mitigation measures is necessary to minimize casualties in the station. The question of whether currently available chemical detectors are sufficiently capable and reliable to enable an automated response is addressed and augmentation possibilities are discussed. A number of concepts for mitigating chemical attacks are explored and their applicability to other transportation facilities is discussed. A possible near-term mitigation measure that is reviewed in some detail is the use of water sprays to scrub gasses and aerosols from the air. This technique may have applicability in the station at the point of agent release, as well as for detoxification of the air stream if selective venting is employed. Calculations show that with proper spray nozzle selection, the water pressure and flow rate available at some subway stations for fire suppression is sufficient for effective removal of Sarin from an air stream.

  13. Comparison of Contaminant Transport in Agricultural Drainage Water and Urban Stormwater Runoff.

    PubMed

    Ghane, Ehsan; Ranaivoson, Andry Z; Feyereisen, Gary W; Rosen, Carl J; Moncrief, John F

    2016-01-01

    Transport of nitrogen and phosphorus from agricultural and urban landscapes to surface water bodies can cause adverse environmental impacts. The main objective of this long-term study was to quantify and compare contaminant transport in agricultural drainage water and urban stormwater runoff. We measured flow rate and contaminant concentration in stormwater runoff from Willmar, Minnesota, USA, and in drainage water from subsurface-drained fields with surface inlets, namely, Unfertilized and Fertilized Fields. Commercial fertilizer and turkey litter manure were applied to the Fertilized Field based on agronomic requirements. Results showed that the City Stormwater transported significantly higher loads per unit area of ammonium, total suspended solids (TSS), and total phosphorus (TP) than the Fertilized Field, but nitrate load was significantly lower. Nitrate load transport in drainage water from the Unfertilized Field was 58% of that from the Fertilized Field. Linear regression analysis indicated that a 1% increase in flow depth resulted in a 1.05% increase of TSS load from the City Stormwater, a 1.07% increase in nitrate load from the Fertilized Field, and a 1.11% increase in TP load from the Fertilized Field. This indicates an increase in concentration with a rise in flow depth, revealing that concentration variation was a significant factor influencing the dynamics of load transport. Further regression analysis showed the importance of targeting high flows to reduce contaminant transport. In conclusion, for watersheds similar to this one, management practices should be directed to load reduction of ammonium and TSS from urban areas, and nitrate from cropland while TP should be a target for both.

  14. Comparison of Contaminant Transport in Agricultural Drainage Water and Urban Stormwater Runoff

    PubMed Central

    Ranaivoson, Andry Z.; Feyereisen, Gary W.; Rosen, Carl J.; Moncrief, John F.

    2016-01-01

    Transport of nitrogen and phosphorus from agricultural and urban landscapes to surface water bodies can cause adverse environmental impacts. The main objective of this long-term study was to quantify and compare contaminant transport in agricultural drainage water and urban stormwater runoff. We measured flow rate and contaminant concentration in stormwater runoff from Willmar, Minnesota, USA, and in drainage water from subsurface-drained fields with surface inlets, namely, Unfertilized and Fertilized Fields. Commercial fertilizer and turkey litter manure were applied to the Fertilized Field based on agronomic requirements. Results showed that the City Stormwater transported significantly higher loads per unit area of ammonium, total suspended solids (TSS), and total phosphorus (TP) than the Fertilized Field, but nitrate load was significantly lower. Nitrate load transport in drainage water from the Unfertilized Field was 58% of that from the Fertilized Field. Linear regression analysis indicated that a 1% increase in flow depth resulted in a 1.05% increase of TSS load from the City Stormwater, a 1.07% increase in nitrate load from the Fertilized Field, and a 1.11% increase in TP load from the Fertilized Field. This indicates an increase in concentration with a rise in flow depth, revealing that concentration variation was a significant factor influencing the dynamics of load transport. Further regression analysis showed the importance of targeting high flows to reduce contaminant transport. In conclusion, for watersheds similar to this one, management practices should be directed to load reduction of ammonium and TSS from urban areas, and nitrate from cropland while TP should be a target for both. PMID:27930684

  15. 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.

  16. 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

  17. 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.

  18. A novel model for estimating organic chemical bioconcentration in agricultural plants

    SciTech Connect

    Hung, H.; Mackay, D.; Di Guardo, A.

    1995-12-31

    There is increasing recognition that much human and wildlife exposure to organic contaminants can be traced through the food chain to bioconcentration in vegetation. For risk assessment, there is a need for an accurate model to predict organic chemical concentrations in plants. Existing models range from relatively simple correlations of concentrations using octanol-water or octanol-air partition coefficients, to complex models involving extensive physiological data. To satisfy the need for a relatively accurate model of intermediate complexity, a novel approach has been devised to predict organic chemical concentrations in agricultural plants as a function of soil and air concentrations, without the need for extensive plant physiological data. The plant is treated as three compartments, namely, leaves, roots and stems (including fruit and seeds). Data readily available from the literature, including chemical properties, volume, density and composition of each compartment; metabolic and growth rate of plant; and readily obtainable environmental conditions at the site are required as input. Results calculated from the model are compared with observed and experimentally-determined concentrations. It is suggested that the model, which includes a physiological database for agricultural plants, gives acceptably accurate predictions of chemical partitioning between plants, air and soil.

  19. Factors influencing Australian agricultural workers' self-efficacy using chemicals in the workplace.

    PubMed

    Blackman, Ian R

    2012-11-01

    A hypothetical model was formulated to explore which factors can simultaneously influence the self-reported ability of agricultural employees to embrace chemical safety practices. Eight variables were considered in the study, including the employees' gender, age, duration of current employment status, and whether they were employed full-time or part-time. The self-efficacy measures of 169 participants were then estimated by measuring their self-rated ability to understand and perform different chemical safety practices. Models identifying employee self-efficacy pathways leading to worker readiness to engage in chemical safety were then tested using Partial Least Squares Path Analysis. Study results suggest that employees' self-efficacy to successfully engage in safe chemical practices in their workplace can be directly predicted by four variables, with additional indirect effects offered by one other variable, which cumulatively account for 41% of the variance of employees' chemical safety self-efficacy scores. The most significant predictor variables that directly influenced employees' self-efficacy in adopting chemical safety practices in the workplace were worker age, gender, years of employment, and concurrent confidence (self-efficacy) arising from prior experience using chemicals in the workplace. The variables of employees' prior knowledge and understanding about the use of administrative controls and personal protective equipment to protect workers from chemical exposure had no direct influence on self-efficacy to handle chemical emergencies. Employees' unfamiliarity with risk control strategies and reliance on material safety data sheets for information suggest that ongoing and targeted training are necessary if chemical safety issues are to be addressed.

  20. 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.

  1. 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

  2. Spatial data in geographic information system format on agricultural chemical use, land use, cropping practices in the United States

    USGS Publications Warehouse

    Battaglin, W.A.; Goolsby, D.A.

    1995-01-01

    The spatial data in geographic information system format described in this report consist of estimates for all counties in the conterminous United States of the annual use of 96 herbicides in 1989; annual sales of nitrogen fertilizer, in tons, for 1985-91; and agricultural expenses, land use, chemical use, livestock holdings, and cropping practices in 1987. The source information, originally in tabular form, is summarized as digital polygon attribute data in the 18 geographic information system spatial data layers (coverages) provided. The information in these coverages can be used in estimating regional agricultural-chemical use or agricultural practices and in producing visual displays and mapping relative rates of agricultural-chemical use or agricultural practices across broad regions of the United States.

  3. 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.

  4. Controlling transport and chemical functionality of magnetic nanoparticles.

    PubMed

    Latham, Andrew H; Williams, Mary Elizabeth

    2008-03-01

    A wide range of metal, magnetic, semiconductor, and polymer nanoparticles with tunable sizes and properties can be synthesized by wet-chemical techniques. Magnetic nanoparticles are particularly attractive because their inherent superparamagnetic properties make them desirable for medical imaging, magnetic field assisted transport, and separations and analyses. With such applications on the horizon, synthetic routes for quickly and reliably rendering magnetic nanoparticle surfaces chemically functional have become an increasingly important focus. This Account describes common synthetic routes for making and functionalizing magnetic nanoparticles and discusses initial applications in magnetic field induced separations. The most widely studied magnetic nanoparticles are iron oxide (Fe2O3 and Fe3O4), cobalt ferrite (CoFe 2O4), iron platinum (FePt), and manganese ferrite (MnFe 2O4), although others have been investigated. Magnetic nanoparticles are typically prepared under either high-temperature organic phase or aqueous conditions, producing particles with surfaces that are stabilized by attached surfactants or associated ions. Although it requires more specialized glassware, high-temperature routes are generally preferred when a high degree of stability and low particle size dispersity is desired. Particles can be further modified with a secondary metal or polymer to create core-shell structures. The outer shells function as protective layers for the inner metal cores and alter the surface chemistry to enable postsynthetic modification of the surfactant chemistry. Efforts by our group as well as others have centered on pathways to yield nanoparticles with surfaces that are both easily functionalized and tunable in terms of the number and variety of attached species. Ligand place-exchange reactions have been shown quite successful for exchanging silanes, acids, thiols, and dopamine ligands onto the surfaces of some magnetic particles. Poly(ethylene oxide

  5. Chemical vapour transport of III-V semiconductor materials

    NASA Astrophysics Data System (ADS)

    Davis, Mervyn Howard

    Over the temperature range 770 to 1310 K, however, two bromides compete for prominence, dependent upon temperature. In both instances, it is shown that vapour transport becomes rate limited at low temperature. Further to the chemical vapour transport of indium phosphide, the dissociative sublimation of the compound has also been investigated. Raman spectroscopy has been used to identify high temperature molecular species involved in vapour transport of III-V semiconductor materials. Supplementary work has been performed on the thermochemistry of indium monobromide. The heat of formation of indium bromide crystals has been determined using a solution calormetric technique. Differential scanning calorimetry was used to measure the heat capacity and heat of fusion, of the salt. An entrainment study of the evaporation of liquid indium monobromide was undertaken to yield a value for its heat of vaporisation. Using a statistical thermodynamic approach, the heat capacity of the vapour was calculated. Collating the information, a value for the heat of formation of indium monobromide gas at 1000 K has been calculated for use in other thermodynamic calculations.

  6. 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

  7. Seasonal contrast in aerosol abundance over northern south Asia using a chemical transport model

    NASA Astrophysics Data System (ADS)

    Venkataraman, C.; Sadavarte, P.; Madhavan, B. L.; Kulkarni, S.; Carmichael, G. R.; Adhikary, B.; D'Allura, A.; Cherian, R.; Das, S.; Gupta, T.; Streets, D. G.; Wei, C.; Zhang, Q.

    2012-12-01

    Northern South-Asia, home to about half a billion people, experiences large aerosol abundances almost all year around. There are gaps in our understanding of seasonal variations in regional aerosol emissions, abundance and radiative effects. The present study uses chemical transport model simulations (at ~ 60km resolution), with regionally estimated emissions, to investigate the contrast in aerosol surface and columnar abundance during pre-monsoon transition, monsoon and inter-monsoon transition periods over than Gangetic plain (GP) and Tibetan plateau. The interplay between aerosol emissions and atmospheric transport is examined to explain the variability. Model predictions were evaluated with available in-situ measurements and AOD from AERONET and MODIS level-2 retrievals (at 10 km resolution) processed with quality weighting to the model resolution. During April, AOD was dominated by dust at most sites across the GP and Tibet. However, AOD from organic carbon (emitted from agricultural residue burning) is also significant at several sites (Pantnagar, Godavari, Kolkata, Dhaka, and at high altitude Pyramid and Lhasa sites), consistent with recently reported MISR climatology in this region. In contrast, during July and September, AOD was dominated by sulfate at all sites. In April, aerosols over the GP could be attributed to emissions from large industrial sources (thermal power plant, cement industries, iron & steel and other industries) and agricultural residue burning transported from the northwest, along with forest burning emissions transported from the east. Large fluxes of open burning emissions in the east GP, along with prevailing easterly wind flow into the GP led to an east-west gradient in anthropogenic aerosols. During July, there was little open burning, so aerosol concentrations were largely from industrial emissions transported out through the north. In the Tibet region, dust was predominant during both April and July. During September

  8. 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.

  9. 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

  10. 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

  11. 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.

  12. 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

  13. 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

    2014-10-29

    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.

  14. 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.

  15. 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.

  16. Interplay between chemical reactions and transport in structured spaces

    NASA Astrophysics Data System (ADS)

    Konkoli, Zoran

    2005-07-01

    The main motivation behind this study is to understand the interplay between the reactions and transport in a geometries that are not compact. Typical examples of compact geometries are a box or a sphere. A network made of containers C1,C2,…,CN and tubes is an example of the space that is structured and noncompact. In containers, particles react with the rate λ . Tubes connecting containers allow for the exchange of chemicals with the transport rate D . A situation is considered where a number of reactants is small and kinetics is noise dominated. A method is presented that can be used to calculate the average and higher moments of the reaction time. A number of different chemical reactions are studied and their performance compared in various ways. Two schemes are discussed in general, the reaction on a fixed geometry ensemble (ROGE) and the geometry on a fixed reaction ensemble, examples are given in the ROGE case. The most important findings are as follows. (i) There is a large number of reactions that run faster in a networklike geometry. Such reactions contain antagonistic catalytic influences in the intermediate stages of a reaction scheme that are best dealt with in a networklike structure. (ii) Antagonistic catalytic influences are hard to identify since they are strongly connected to the pattern of injected molecules (inject pattern) and depend on the choice of molecules that have to be synthesized at the end (task pattern). (iii) The reaction time depends strongly on the details of the inject and task patterns.

  17. Does exposure to agricultural chemicals increase the risk of prostate cancer among farmers?

    PubMed

    Parent, Marie-Elise; Désy, Marie; Siemiatycki, Jack

    2009-01-01

    Several studies suggest that farmers may be at increased risk of prostate cancer. The present analysis, based on a large population-based case-control study conducted among men in the Montreal area in the early 1980's, aim at identifying occupational chemicals which may be responsible for such increases. The original study enrolled 449 prostate cancer cases, nearly 4,000 patients with other cancers, as well as 533 population controls. Subjects were interviewed about their occupation histories, and a team of industrial hygienists assigned their past exposures using a checklist of some 300 chemicals. The present analysis was restricted to a study base of men who had worked as farmers earlier in their lives. There were a total of 49 men with prostate cancers, 127 with other cancers and 56 population controls. We created a pool of 183 controls combining the patients with cancers at sites other than the prostate and the population controls. We then estimated the odds ratio for prostate cancer associated with exposure to each of 10 agricultural chemicals, i.e., pesticides, arsenic compounds, acetic acid, gasoline engine emissions, diesel engine emissions, polycyclic aromatic hydrocarbons from petroleum, lubricating oils and greases, alkanes with >or=18 carbons, solvents, and mononuclear aromatic hydrocarbons. Based on a model adjusting for age, ethnicity, education, and respondent status, there was evidence of a two-fold excess risk of prostate cancer among farmers with substantial exposure to pesticides [odds ratio (OR)=2.3, 95% confidence interval (CI) 1.1-5.1], as compared to unexposed farmers. There was some suggestion, based on few subjects, of increased risks among farmers ever exposed to diesel engine emissions (OR=5.7, 95% CI 1.2-26.5). The results for pesticides are particularly noteworthy in the light of findings from previous studies. Suggestions of trends for elevated risks were noted with other agricultural chemicals, but these are largely novel and need

  18. Transport and Reactivity of Decontaminants to Provide Hazard Mitigation of Chemical Warfare Agents from Materials

    DTIC Science & Technology

    2016-06-01

    A combined approach was developed that integrated two types of testing—dilute liquid-phase reactor results to determine 18 chemical reactivity...TRANSPORT AND REACTIVITY OF DECONTAMINANTS TO PROVIDE HAZARD MITIGATION OF CHEMICAL ...2013 4. TITLE AND SUBTITLE Transport and Reactivity of Decontaminants to Provide Hazard Mitigation of Chemical Warfare Agents from Materials 5a

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

    PubMed

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

    2016-06-07

    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.

  20. Investigation of diamond deposition by chemical vapor transport with hydrogen

    NASA Astrophysics Data System (ADS)

    Piekarczyk, Wladyslaw; Messier, Russell F.; Roy, Rustum; Engdahl, Chris

    1990-12-01

    The carbon-hydrogen chemical vapor transport system was examined in accordance with a four-stage transport model. A result of this examination is that graphite co-deposition could be avoided when diamond is deposited from gas solutions under-saturated with respect to diamond. Actual deposition experiments showed that this unusual requirement can be fulfilled but only for the condition that the transport distance between the carbon source and the substrate surface is short. In such a case diamond can be deposited equally from super-saturated as well as from under-saturated gas solutions. On the basis of thermodynamic considerations a possible explanation of this unusual phenomenon is given. It is shown that there is a possibility of deposition of diamond from both super-saturated as well as under-saturated gas solutions but only on the condition that they are in a non-equilibrium state generally called the activated state. A model of the diamond deposition process consisting of two steps is proposed. In the first step diamond and graphite are deposited simultaneously. The most important carbon deposition reaction is C2H2(g) + 2 H(g) C(diamond graphite) + CH(g). The amount of co-deposited graphite is not a direct function of the saturation state of the gas phase. In the second step graphite is etched according to the most probable reaction C(graphite) + 4 H(g) CH4(g). Atomic hydrogen in a super-equilibrium concentration is necessary not only to etch graphite but also to precipitate and graphite. 1.

  1. 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

  2. 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.

  3. TRANSPORT

    EPA Science Inventory

    Presentation outline: transport principles, effective solubility; gasoline composition; and field examples (plume diving).
    Presentation conclusions: MTBE transport follows from - phyiscal and chemical properties and hydrology. Field examples show: MTBE plumes > benzene plu...

  4. Sorption, degradation and transport phenomena of alcohol ethoxysulfates in agricultural soils. Laboratory studies.

    PubMed

    Fernández-Ramos, C; Rodríguez-Gómez, R; Reis, M S; Zafra-Gómez, A; Verge, C; de Ferrer, J A; Pérez-Pascual, M; Vílchez, J L

    2017-03-01

    In the present work, laboratory studies were conducted in order to determine and model the sorption, degradation and transport processes of alcohol ethoxysulfates (AES), one of the most important groups of anionic surfactants. Adsorption/desorption isotherms were obtained for several structurally related AES ethoxymers (homologue AES-C12En with n = 0-10 ethoxymer units and homologue AES-C14En with n = 0-7 ethoxymer units) using a batch equilibrium method. Data were fitted to a linear and a Freundlich isotherm models. Additionally, experiments in continuous-flow soil columns were also carried out and the breakthrough curves observed for each compound were studied. Breakthrough curves were used to determine the fundamental parameters of the transport model (hydrodynamic dispersion coefficient, degradation rate constant and adsorption/desorption isotherm slope), that is the main phenomena that take place simultaneously when AES move through agricultural soil. When the results obtained for the AES ethoxymers are combined, they reveal a clear and consistent trend towards a sorption increase with the number of ethoxylated units and with the length of the alkyl chain that opens the possibility to estimate the values of the transport parameters for other structurally related ethoxymers.

  5. Occurrence of Agricultural Chemicals in Shallow Ground Water and the Unsaturated Zone, Northeast Nebraska Glacial Till, 2002-04

    USGS Publications Warehouse

    Stanton, Jennifer S.; Steele, Gregory V.; Vogel, Jason R.

    2007-01-01

    Agricultural chemicals applied at the land surface in northeast Nebraska can move downward, past the crop root zone, to ground water. Because agricultural chemicals applied at the land surface are more likely to be observed in the shallowest part of an aquifer, an assessment of shallow ground-water and unsaturated zone quality in the northeast Nebraska glacial till was completed between 2002 and 2004. Ground-water samples were collected at the first occurrence of ground water or just below the water table at 32 sites located in areas likely affected by agriculture. Four of the 32 sites were situated along a ground-water flow path with its downgradient end next to Maple Creek. Twenty-eight sites were installed immediately adjacent to agricultural fields throughout the glacial-till area. In addition to those 32 sites, two sites were installed in pastures to represent ground-water conditions in a non-cropland setting. Ground-water samples were analyzed for physical properties and concentrations of nitrogen and phosphorus compounds, selected pesticides and pesticide degradates, dissolved solids, major ions, trace elements, and dissolved organic carbon. Chlorofluorocarbons (CFCs) or sulfur hexafluoride (SF6) concentrations were analyzed at about 70 percent of the monitoring wells to estimate the residence time of ground water. Borehole-core samples were collected from 28 of the well boreholes. Sediment in the unsaturated zone was analyzed for nitrate, chloride, and ammonia concentrations. Analytical results indicated that the agricultural chemicals most often detected during this study were nitrates and herbicides. Nitrate as nitrogen (nitrate-N) concentrations (2003 median 9.53 milligrams per liter) indicated that human activity has affected the water quality of recently recharged ground water in approximately two-thirds of the wells near corn and soybean fields. The principal pesticide compounds that were detected reflect the most-used pesticides in the area and

  6. Influence of nonlinear chemical reactions on the transport coefficients in oscillatory Couette flow

    NASA Astrophysics Data System (ADS)

    Barik, Swarup; Dalal, D. C.

    2016-10-01

    A multiple-scale method of averaging is applied to the study of transport of a chemical species in oscillatory Couette flow where the species may undergoes a reversible phase exchange with the boundary wall and nonlinear chemical reactions both within the fluid and at the boundary wall. Analytical expressions are obtained for transport coefficients. The results shows how the transport coefficients are influenced by the reversible phase exchange reaction kinetics and the rate and degree of the nonlinear decay chemical reaction.

  7. Frontiers of sustainability: Environmentally sound agriculture, forestry, transportation, and power production

    SciTech Connect

    Dower, R.; Ditz, D.

    1998-11-01

    The book presents the first practical vision of the sustainable future of the United States and the steps needed to get there. Authors examine the environmental performance and trends in four key economic sectors; agriculture, electricity generation, transportation, and pulp and paper manufacturing. They map out and explore the implications of potentially dangerous trends and developments, and detail methods for reducing or managing emergency threats. Each chapter sets forth a technologically feasible vision of the future in which the unwanted trends one sees unfolding now are reversed. Frontiers of sustainability presents an adaptable formula for moving the United States toward a future that ensures generations to come a healthy stock of environmental and natural resource assets.

  8. 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.

  9. 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.

  10. 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

  11. 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.

  12. DNA Charge Transport: From Chemical Principles to the Cell

    PubMed Central

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

    2016-01-01

    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

  13. Ozone Measurements and a 3D Chemical Transport Model

    NASA Technical Reports Server (NTRS)

    Stolarski, Richard S.; Douglass, Anne R.; Frith, Stacey; Steenrod, Steven; Polansky, Brian

    2004-01-01

    We have used our three-dimensional chemical transport model (CTM) to calculate the expected reponse of stratospheric composition over the past 30 years to forcing by chlorine and bromine compounds, solar ultraviolet, and volcanic aerosols. The CTM uses off-line winds and temperatures fiom a 50-year run of the finite volume general circulation model (FVGCM). We compare the total column ozone and the ozone profile fiom the CTM output to a variety of data sources. These include a merged total ozone data set from TOMS and SBUV using the new version 8 algorithm. Total ozone fiom the CTM are compared to ground-station measurements of total ozone at specific locations. Ozone profiles are compared to satellite meausrements fiom SBUV, SAGE, and HALOE. Profiles are also compared to ozonesondes over several locations. The results of the comparisons are quantified by using a time-series statistical analysis to determine trends, solar cycle, and volcanic reponse in both the model and in the data. Initial results indicate that the model responds to forcings in a way that is similar to the observed atmospheric response. The model does seem to be more sensitive to the chlorine and bromine perturbation ihan is the data. Further details and comparisons wiii be discussed.

  14. 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.

  15. Does Exposure to Agricultural Chemicals Increase the Risk of Prostate Cancer among Farmers?

    PubMed Central

    Parent, Marie-Élise; Désy, Marie; Siemiatycki, Jack

    2009-01-01

    Several studies suggest that farmers may be at increased risk of prostate cancer. The present analysis, based on a large population-based case-control study conducted among men in the Montreal area in the early 1980’s, aim at identifying occupational chemicals which may be responsible for such increases. The original study enrolled 449 prostate cancer cases, nearly 4,000 patients with other cancers, as well as 533 population controls. Subjects were interviewed about their occupation histories, and a team of industrial hygienists assigned their past exposures using a checklist of some 300 chemicals. The present analysis was restricted to a study base of men who had worked as farmers earlier in their lives. There were a total of 49 men with prostate cancers, 127 with other cancers and 56 population controls. We created a pool of 183 controls combining the patients with cancers at sites other than the prostate and the population controls. We then estimated the odds ratio for prostate cancer associated with exposure to each of 10 agricultural chemicals, i.e., pesticides, arsenic compounds, acetic acid, gasoline engine emissions, diesel engine emissions, polycyclic aromatic hydrocarbons from petroleum, lubricating oils and greases, alkanes with ≥18 carbons, solvents, and mononuclear aromatic hydrocarbons. Based on a model adjusting for age, ethnicity, education, and respondent status, there was evidence of a two-fold excess risk of prostate cancer among farmers with substantial exposure to pesticides [odds ratio (OR)=2.3, 95% confidence interval (CI) 1.1–5.1], as compared to unexposed farmers. There was some suggestion, based on few subjects, of increased risks among farmers ever exposed to diesel engine emissions (OR=5.7, 95% CI 1.2–26.5). The results for pesticides are particularly noteworthy in the light of findings from previous studies. Suggestions of trends for elevated risks were noted with other agricultural chemicals, but these are largely novel and

  16. 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.

  17. 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.

  18. Fast analysis of high-energy compounds and agricultural chemicals in water with desorption electrospray ionization mass spectrometry.

    PubMed

    Mulligan, Christopher C; MacMillan, Denise K; Noll, Robert J; Cooks, R Graham

    2007-01-01

    Novel sampling and detection methods using desorption electrospray ionization (DESI) are examined in the detection of explosives (RDX, TNT, HMX, and TNB) and agricultural chemicals (atrazine, alachlor and acetochlor) from aqueous matrices and authentic contaminated groundwater samples. DESI allows analysis of solid and liquid compounds directly from surfaces of interest with little or no sample preparation. Significant savings in analysis time and sample preparation are realized. The methods investigated here include (i) immediate analysis of filter paper wetted with contaminated water samples without further sample preparation, (ii) rapid liquid-liquid extraction (LLE), and (iii) analyte extraction from contaminated groundwater samples on-site using solid-phase extraction (SPE) membranes, followed by direct DESI analysis of the membrane. The wetted filter paper experiment demonstrates the maximum sample throughput for DESI analysis of aqueous matrices but has inadequate sensitivity for some of these analytes. Both the LLE and the SPE methods have adequate sensitivity. The resulting SPE membranes and/or small volume solvent extracts produced in these experiments are readily transported to off-site facilities for direct analysis by DESI. This realizes a significant reduction in the costs of sample shipping compared with those for typical liter-sized samples of groundwater. Total analysis times for these preliminary DESI analyses are comparable with or shorter than those for GC/MS and limits of detection approach environmental action levels for these compounds while maintaining a modest relative standard deviation. Tandem mass spectrometric data is used to provide additional specificity as needed.

  19. 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...

  20. 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

  1. 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...

  2. Acoustic charge transport induced by the surface acoustic wave in chemical doped graphene

    NASA Astrophysics Data System (ADS)

    Zheng, Shijun; Zhang, Hao; Feng, Zhihong; Yu, Yuanyuan; Zhang, Rui; Sun, Chongling; Liu, Jing; Duan, Xuexin; Pang, Wei; Zhang, Daihua

    2016-10-01

    A graphene/LiNbO3 hybrid device is used to investigate the acoustic induced charge transport in chemical doped graphene. The chemical doping of graphene via its physisorption of gas molecules affects the surface acoustic wave (SAW) charge carrier transport in a manner different from electric field drift. That transport induces doping dependent macroscopic acoustoelectric current. The chemical doping can manipulate majority carriers and induces unique acoustoelectric features. The observation is explained by a classical relaxation model. Eventually the device based on acoustoelectric current is proved to outperform the common chemiresistor for chemicals. Our finding provides insight into acoustic charge carrier transport during chemical doping. The doping affects interaction of carriers with SAW phonon and facilitates the understanding of nanoscale acoustoelectric effect. The exploration inspires potential acoustoelectric application for chemical detection involving emerging 2D nanomaterials.

  3. 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.

  4. 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

  5. Distribution of organic carbon and chemicals in agricultural soils (BET method)

    NASA Astrophysics Data System (ADS)

    Schnitzler, F.; Séquaris, J.-M.; Berns, A. E.; Burauel, P.

    2009-04-01

    coefficients Kd and KOC indicate a stronger sorption of benzo[a]pyrene than benazolin derivates. Furthermore, a stronger binding of chemicals to the clay fraction than to the silt+sand fraction can be observed. The incorporation of maize straw increases the Kd values of benazolin and its metabolites in all fractions due to stronger metabolism of the herbicide[1]. The KOC of benzo[a]pyrene is more or less constant in the clay fraction after straw incorporation. However, an increase of the KOC value in the silt+sand fraction is observed, which can be related to the binding capacity of the OC straw derivates. In dissolved forms (DOC), they can be involved in co-transport processes of benzo[a]pyrene.

  6. 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

  7. 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.

  8. 78 FR 1765 - Requirements for Chemical Oxygen Generators Installed on Transport Category Airplanes

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-01-09

    ... Federal Aviation Administration 14 CFR Part 25 RIN 2120-AK14 Requirements for Chemical Oxygen Generators... requirements for chemical oxygen generators installed on transport category airplanes so the generators are... Committee COG--Chemical Oxygen Generator LOARC--Lavatory Oxygen Aviation Rulemaking Committee SaO 2...

  9. 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.

  10. 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)

  11. 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.

  12. 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.

  13. Preferential flow effects on transport and fate of chemicals and microorganisms in soils irrigated with wastewater

    NASA Astrophysics Data System (ADS)

    Puddu, Rita; Corrias, Roberto; Dessena, Maria Antonietta; Ferralis, Marcella; Marras, Gabriele; Pin, Paola; Spanu, Paola

    2010-05-01

    This work is part of a multidisciplinary research properly planned by the ENAS (Cagliari-Sardinia-Italy) to verify the consequences of urban wastewater reuse in irrigation practices on chemical, biological and hydrological behavior of agricultural soils of the Had as Soualem area (Morocco). The area consists of Fluventic Haploxerept soils, according to USDA Soil Taxonomy. Undisturbed large soil columns, 70 cm height and 20 cm diameter, were collected from plots, the locations of which were preliminarily individuated through a prior pedological study. The soils are characterized by an apparent structure, suggesting that preferential flow processes may occur in the study area, which may impact usable groundwater at depth. Wastewater reuse for irrigation simultaneously solves water shortage and wastewater disposal problems. Unfortunately, wastewaters generally contain high concentrations of suspended and dissolved solids, both organic and inorganic, and microbial contaminants (virus and bacteria) added to wastewater during domestic and industrial usage. Most of these contaminants are only partially removed during conventional sewage treatment so they remain in the irrigation water. Although adsorbing ions and microbes are relatively immobile within porous media, preferential flow and adsorption to mobile colloids can enhance their transport. There is limited knowledge regarding the role of preferential flow and colloidal transport on adsorbing contaminants. The main aim of this research is to determine the influence of preferential flow and colloids on wastewater contaminant transport. Leaching rates and arrival time of wastewater contaminants will be determined using field and laboratory measurements at the study sites in combination with preferential flow numerical modeling. To achieve these objectives the soil columns were analyzed for physical, chemical, and microbial characterization. At the laboratory, an experimental facility was set up and sensors for

  14. Reconnaissance of the occurrence of agricultural chemicals in ground water in Haywood, Lake, Obion and Shelby Counties, Tennessee

    USGS Publications Warehouse

    Hanchar, D.W.

    1991-01-01

    Data on the occurrence of agricultural chemicals in ground wafer in Tennessee are sparse. The surficial alluvial aquifer is an important source of domestic water supply in West Tennessee, and potentially is subject fo contamination from the application of agricultural chemicals in the area. Nineteen shallow wells completed in the alluvial aquifers in areas of high density agricultural use were sampled in the winter and again in the summer of 1988 to ascertain the occurrence of agricultural chemical in ground water. Although no triazine herbicides or organophosphorus insecticides were detected in any of the wells sampled, elevated nitrite plus nitrate (as nitrogen) concentrations were detected. Results from the winter sampling period indicate a range of nitrite plus nitrate (as nitrogen) concentrations of less than 0.1 to 7.8 milligrams per liter with a median concentration of 2.6 milligrams per liter. Results from the summer sampling period indicate a range of nitrite plus nitrate (as nitrogen) concentrations of less than 0.1 to 8.9 milligrams per liter, median, 2.5 milligrams per liter. The highest concentrations occurred in the shallowest wells, and, in one instance, in a shallow well near a heavily irrigated field.

  15. 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

  16. Hydrogeologic controls on nitrate transport in a small agricultural catchment, Iowa

    USGS Publications Warehouse

    Schilling, K.E.; Tomer, M.D.; Zhang, Y.-K.; Weisbrod, T.; Jacobson, P.; Cambardella, C.A.

    2007-01-01

    Effects of subsurface deposits 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 Iowa catchment. Subsurface deposits in the catchment consisted of upland areas of loess overlying weathered pre-Illinoian till, drained by two ephemeral drainageways that consisted of Holocene-age silty and organic rich alluvium. Water tables in upland areas fluctuated more than 4 m per year compared to less than 0.3 m in the drainageway. Water quality patterns showed a distinct spatial pattern, with groundwater in the drainageways having lower nitrate concentrations (10 mg L-1) as wells as lower pH, dissolved oxygen and redox, and higher ammonium and dissolved organic carbon levels. Several lines of evidence suggested that conditions are conducive for denitrification of groundwater flowing from uplands through the drainageways. Field-measured nitrate decay rates in the drainageways (???0.02 day-1) were consistent with other laboratory studies and regional patterns. Results from MODFLOW and MT3DMS simulations indicated that soils in the ephemeral drainageways could process all upland groundwater nitrate flowing through them. However, model-simulated tile drainage increased both water flux and nitrate loss from the upland catchment. Study results suggest that ephemeral drainageways can provide a natural nitrate treatment system in our upland glaciated catchments, offering management opportunities to reduce nitrate delivery to streams. Copyright 2007 by the American Geophysical Union.

  17. 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.

  18. 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 ...

  19. 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.

  20. 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.

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

    PubMed

    Govasmark, Espen; Stäb, Jessica; Holen, Børge; Hoornstra, Douwe; Nesbakk, Tommy; Salkinoja-Salonen, Mirja

    2011-12-01

    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(-1) DM) and copper (23-93 mg kg(-1) DM) concentrations, but also because of high cadmium (0.21-0.60 mg kg(-1) DM) concentrations in the liquid-ADR. In the screening of organic pollutants, only DEHP (9.7-62.1 mg kg(-1)) and ∑ PAH 16 (0.2-1.98 mg kg(-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(-1) DM) and thiabendazol (<0.14-0.73 mg kg(-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.

  2. 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.

  3. Chemical status of selenium in evaporation basins for disposal of agricultural drainage.

    PubMed

    Gao, S; Tanji, K K; Dahlgren, R A; Ryu, J; Herbel, M J; Higashi, R M

    2007-09-01

    Evaporation basins (or ponds) are the most commonly used facilities for disposal of selenium-laden saline agricultural drainage in the closed hydrologic basin portion of the San Joaquin Valley, California. However concerns remain for potential risk from selenium (Se) toxicity to water fowl in these evaporation basins. In this study, we examined the chemical status of Se in both waters and sediments in two currently operating evaporation pond facilities in the Tulare Lake Drainage District. Some of the saline ponds have been colonized by brine-shrimp (Artemia), which have been harvested since 2001. We evaluated Se concentration and speciation, including selenate [Se(VI)], selenite [Se(IV)], and organic Se [org-Se or Se(-II)] in waters and sediment extracts, and fractionation (soluble, adsorbed, organic matter (OM)-associated, and Se(0) and other resistant forms) in sediments and organic-rich surface detrital layers from the decay of algal blooms. Selenium in ponds without vascular plants exhibited similar behavior to wetlands with vascular plant present, indicating that similar Se transformation processes and mechanisms had resulted in Se immobilization and an increase of reduced Se species [Se(IV), org-Se, and Se(0)] from Se(VI)-dominated input waters. Selenium concentrations in most pond waters were significantly lower than the influent drainage water. This decrease of dissolved Se concentration was accompanied by the increase of reduced Se species. Selenium accumulated preferentially in sediments of the initial pond cell receiving drainage water. Brine-shrimp harvesting activities did not affect Se speciation but may have reduced Se accumulation in surface detrital and sediments.

  4. 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

  5. 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

    2014-08-29

    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.

  6. Interfacial Chemical Reactions and Transport Phenomena in Flow Systems.

    DTIC Science & Technology

    1982-01-01

    CONVESTIVE DIFFUSION ENERGY TRANSFER COMBUSTION THERMAL DIFFUSION FOULING INERTIAL IMPACTION THERMOPHORESIS LLJ HETEROGENEOUS CATALYSIS FLOW REACTORS...i) the influence of particle thermophoresis on mass transport across ,onisothermal boundary layers, and iiI) inertial effects on particle deposi- tion...Approach: We are currently developing theoretical methods to generalize the laws of convective mass and energy transfer to include thermophoresis

  7. Pesticide resistance from historical agricultural chemical exposure in Thamnocephalus platyurus (Crustacea: Anostraca).

    PubMed

    Brausch, John M; Smith, Philip N

    2009-02-01

    Extensive pesticide usage in modern agriculture represents a considerable anthropogenic stressor to freshwater ecosystems throughout the United States. Acute toxicity of three of the most commonly used agricultural pesticides (Methyl Parathion 4ec, Tempo SC Ultra, Karmex DF, and DDT) was determined in two different wild-caught strains of the fairy shrimp Thamnocephalus platyurus. Fairy shrimp collected from playas surrounded by native grasslands were between 200% and 400% more sensitive than fairy shrimp derived from playas in agricultural watersheds for Methyl Parathion 4ec, Tempo SC Ultra, and Karmex DF, likely due to the development of resistance. Additionally, reduced sensitivity to DDT was observed among fairy shrimp from agriculturally-impacted playas as compared to those from native grassland-dominated playas. These data suggest that fairy shrimp inhabiting playas in agricultural regions have developed some degree of resistance to a variety of agrochemicals in response to historical usage.

  8. 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

  9. 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 ...

  10. 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...

  11. 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...

  12. Distributed Model for Overland Hydrology, Sediment and Chemical Transport in Watersheds

    NASA Astrophysics Data System (ADS)

    Zhang, Z.; Johnson, B. E.; Dortch, M. S.

    2004-12-01

    Contaminants from non-point or distributed sources can adversely affect the quality of downstream waters and groundwater. Reliable models can help understanding the fate and transport of contaminants on the overland as well as the shallow subsurface and lead to better management strategies of the environmental response and security. In this study, a watershed is represented by discretizing contributing areas into a cascade of one dimensional (1D) overland flow using DEM data. A distributed watershed model is developed to simulate overland flow and processes of sediment and chemical detachment and their transport in runoff. The model, consisting of linked hydrology, sediment and chemical transport components, is physically based and process oriented. In the model, the overland flow component uses fully implicit nonlinear finite difference scheme combined with a linear scheme to numerically solve the 1D kinematic wave equations. The erosion and sediment transport component simulates the movement of eroded soil along with the movement of surface water, calculates the sediment transport capacity and the potential sediment supply, chooses whichever is less and routes it throughout the watershed. Erosion is the sum of splash detachment by raindrops and flow detachment by runoff. The process of chemical transport in the soluble phase is simulated by a 1D advection, diffusion and adsorption-desorption processes equation. Chemical transport by suspended sediment is described by the advection-diffusion equations with the sink-source term including erosion-deposition exchange processes. Both sediment and chemical transport components are developed as separate blocks of the watershed overland modeling system. A 1D model in overland studies can provide plenty of useful information without requiring many input parameters. The model will be incorporated into the Army Risk Assessment Modeling System (ARAMS) as a watershed module to satisfy the need for simulating hydrological

  13. [The discussion of the infiltrative model of chemical knowledge stepping into genetics teaching in agricultural institute or university].

    PubMed

    Zou, Ping; Luo, Pei-Gao

    2010-05-01

    Chemistry is an important group of basic courses, while genetics is one of the important major-basic courses in curriculum of many majors in agricultural institutes or universities. In order to establish the linkage between the major course and the basic course, the ability of application of the chemical knowledge previously learned in understanding genetic knowledge in genetics teaching is worthy of discussion for genetics teachers. In this paper, the authors advocate to apply some chemical knowledge previously learned to understand genetic knowledge in genetics teaching with infiltrative model, which could help students learn and understand genetic knowledge more deeply. Analysis of the intrinsic logistic relationship among the knowledge of different courses and construction of the integral knowledge network are useful for students to improve their analytic, comprehensive and logistic abilities. By this way, we could explore a new teaching model to develop the talents with new ideas and comprehensive competence in agricultural fields.

  14. 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. ...

  15. 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.

  16. Modeling acid transport in chemically amplified resist films

    NASA Astrophysics Data System (ADS)

    Patil, Abhijit A.; Doxastakis, Manolis; Stein, Gila E.

    2014-03-01

    The acid-catalyzed deprotection of glassy poly(4-hydroxystyrene-co-tert butyl acrylate) films was studied with infrared absorbance spectroscopy and stochastic simulations. Experimental data were interpreted with a simple description of subdiffusive acid transport coupled to second-order acid loss. This model predicts key attributes of observed deprotection rates, such as fast reaction at short times, slow reaction at long times, and a non-linear dependence on acid loading. The degree of anomalous character is reduced by increasing the post-exposure bake temperature or adding plasticizing agents to the polymer resin. These findings indicate that the acid mobility and overall deprotection kinetics are coupled to glassy matrix dynamics. Furthermore, the acid diffusion lengths were calculated from the anomalous transport model and compared with nanopattern line widths. The consistent scaling between experiments and simulations suggests that the anomalous diffusion model could be further developed into a predictive lithography tool.

  17. 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.

  18. Quantifying solute transport processes: are chemically "conservative" tracers electrically conservative?

    USGS Publications Warehouse

    Singha, Kamini; Li, Li; Day-Lewis, Frederick D.; Regberg, Aaron B.

    2012-01-01

    The concept of a nonreactive or conservative tracer, commonly invoked in investigations of solute transport, requires additional study in the context of electrical geophysical monitoring. Tracers that are commonly considered conservative may undergo reactive processes, such as ion exchange, thus changing the aqueous composition of the system. As a result, the measured electrical conductivity may reflect not only solute transport but also reactive processes. We have evaluated the impacts of ion exchange reactions, rate-limited mass transfer, and surface conduction on quantifying tracer mass, mean arrival time, and temporal variance in laboratory-scale column experiments. Numerical examples showed that (1) ion exchange can lead to resistivity-estimated tracer mass, velocity, and dispersivity that may be inaccurate; (2) mass transfer leads to an overestimate in the mobile tracer mass and an underestimate in velocity when using electrical methods; and (3) surface conductance does not notably affect estimated moments when high-concentration tracers are used, although this phenomenon may be important at low concentrations or in sediments with high and/or spatially variable cation-exchange capacity. In all cases, colocated groundwater concentration measurements are of high importance for interpreting geophysical data with respect to the controlling transport processes of interest.

  19. 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.

  20. Truck transport of hazardous chemicals: 1-butanol. Final report, September 1993-April 1995

    SciTech Connect

    1995-09-01

    The transport of hazardous materials by all modes is a major concern of the U.S. Department of Transportation. Estimates place the total amount of hazardous materials transported in the United States in excess of 1.5 billion tons per year. Highway, water, and rail account for nearly all hazardous materials shipments; air shipments are negligible. Fuels, such as gasoline and diesel, account for about half of all hazardous materials transported. Chemicals account for most of the remainder. This report presents estimates of truck shipments of 1-butanol, one of the 147 large-volume chemicals that account for at least 80 percent of U.S. truck shipments of hazardous chemicals. All of the reports in this series are based on the best available information at the time the research was conducted.

  1. Computation of transport coefficients of chemically reacting systems

    NASA Astrophysics Data System (ADS)

    Shmelkov, Yu. B.; Samuilov, E. V.

    2013-12-01

    A new method is proposed for computing the thermal conductivity of a gaseous mixture with regard for chemical reactions occurring therein, which enables the estimation of the thermal conductivity from each separate reaction to the chemical component of thermal conductivity. The method for determining the paired collision integrals, which is used in the work, is also briefly presented. The results computed by the proposed method are compared with experimental data and the data obtained by the existing computational methods in the temperature range from 500 to 2500 K under atmospheric pressure. The comparison was done both for pure gases and for the gaseous mixtures, including the combustion products of solid fuels. The obtained results may be applied for the development and design of systems related to heat exchange, gas dynamics, processing of solid and liquid fuels, for example, boiler aggregates, aviation engines, and in other applications.

  2. 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.

  3. Energy storage and transport by reversible chemical reactions

    NASA Astrophysics Data System (ADS)

    Beghi, G.

    Reversible thermochemical reactions are one of the possibilities to store and transport high temperature heat (800 K up to 1300 K). There are open cycles and closed cycles. Some reversible systems are described, as the SO2-SO3 system. A typical example of open cycle is the reaction for water decomposition. Results of a pilot plant to verify the decomposition of sulfuric acid are described; the technological feasibility of this method for hydrogen production is shown. The possibility to use other high temperature sources, as solar energy is discussed.

  4. Fate and Transport of Chemical Warfare Agents VX and HD ...

    EPA Pesticide Factsheets

    Report The intent of this investigation was to study the fate and transport of CWA applied to painted/sealed materials including the potential partitioning of CWA into permeable paints/sealants and subsequently into underlying porous materials. Based on the results obtained from this investigation, VX and sulfur mustard (HD) have the ability to permeate into paints and sealants, including in some cases the underlying porous materials. It is likely that other permeable materials besides paints and sealants may also show similar behavior.

  5. 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.

  6. 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.

  7. [Total contents of heavy metals and their chemical fractionation in agricultural soils at different locations of Beijing City].

    PubMed

    Chen, Zhi-Fan; Zhao, Ye; Guo, Ting-Zhong; Wang, Shui-Feng; Tian, Qing

    2013-06-01

    In this study, 23 groups of suited typical soil-wheat grain samples were collected from different locations of Beijing city (central city, suburban plain and exurban plain), the accumulation, chemical forms and bioavailability of heavy metals in arable soils under different human activity intensity were analyzed, and their source identifications and health risk were discussed. The results showed that (1) Urban soils exhibited Pb contamination with an average concentration (35.59 mg x kg(-1)) above the WHO limit, probably due to the emission of traffic activities and industrial processes. In addition, long-term sewage irrigation and other agricultural activities led to local metal contamination in the suburban agricultural soils. (2) Cu, Zn and Pb were predominantly associated with the residual (35%-75%) and organic (23%-53%) fractions, followed by Fe/Mn oxide (1%-19%), and very small proportion of carbonate (n. d.-5%) and exchangeable (n. d.-2%) fraction. Furthermore, compared with the suburban agricultural soils, Pb, Zn and Cu in the urban agricultural soils showed higher mobility, whereas the exurban agricultural soils presented the lowest mobility. For Cd, the order was contrary. Besides, Cd showed the highest bioavailability among the four metals in suburban and exurban arable soils due to its considerable proportion of exchangeable (13% -31%) and carbonate fractions (11%-27%). (3) Cd and Zn contents in wheat grains were largely dependent on the Fe/Mn ox. fractions in the studied soils (P < 0.05, r were 0.43-0.7). (4) Pb and Zn concentrations in wheat grains in some of the urban and suburban agricultural soils were above the standard limit, which might bring potential risk for the health of the local residents.

  8. Chemical characterisation of african dust transported to Canary Region

    NASA Astrophysics Data System (ADS)

    Gelado, M. D.; López, P.; Prieto, S.; Collado, C.; Hernández, J. J.

    2009-04-01

    African dust pulses have important effects on the climate conditions and the marine biogeochemistry in the Canary Region. Aerosol samples have been collected at three stations on Gran Canaria Island (Taliarte at sea level, Tafira 269 m a.s.l. and Pico de la Gorra 1930 m a.s.l.) during 2000-2008. Elemental characterisation of the collected mineral aerosol and back trajectories of the air masses are used to distinguish regional African sources of dust. Dust aerosol samples from North Sahara (Morocco, North Algeria and Tunisia), West and Central Sahara (20°-30°N, 18°W-50°E) and Sahel (0°-20°N, 18°W-50°E) have shown different Ca/Ti, Al/Ti and Fe/Al ratios. Ti appears as a better tracer element of specific source of dust than Fe, probably due to a less mineral alteration during the atmospheric transport.

  9. 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.

  10. Driving Pest Insect Populations: Agricultural Chemicals Lead to an Adaptive Syndrome in Nilaparvata Lugens Stål (Hemiptera: Delphacidae)

    PubMed Central

    You, Lin-Lin; Wu, You; Xu, Bing; Ding, Jun; Ge, Lin-Quan; Yang, Guo-Qin; Song, Qi-Sheng; Stanley, David; Wu, Jin-Cai

    2016-01-01

    The brown planthopper (BPH) is a devastating pest of rice throughout Asia. In this paper we document the BPH biogeographic range expansion in China over the 20-year period, 1992 to 2012. We posed the hypothesis that the range expansion is due to a syndrome of adaptations to the continuous presence of agricultural chemicals (insecticides and a fungicide) over the last 40 years. With respect to biogeography, BPH ranges have expanded by 13% from 1992 to 1997 and by another 3% from 1997 to 2012. In our view, such expansions may follow primarily from the enhancing effects of JGM, among other agricultural chemicals, and from global warming. JGM treatments led to increased thermotolerance, recorded as decreased mortality under heat stress at 40 ± 1 °C (down from 80% to 55%) and increased fecundity (by 49%) at 34 °C. At the molecular level, JGM treatments led to increased abundances of mRNA encoding Acetyl Co-A carboxylase (Acc) (up 25%) and Hsp70 (up 32%) in experimental BPH. RNAi silencing of Hsp70 and Acc eliminated the JGM effects on fecundity and silencing Hsp70 reduced JGM-induced thermotolerance. Integrated with global climate change scenarios, such syndromes in pest insect species have potential for regional- and global-scale agricultural disasters. PMID:27876748

  11. Driving Pest Insect Populations: Agricultural Chemicals Lead to an Adaptive Syndrome in Nilaparvata Lugens Stål (Hemiptera: Delphacidae).

    PubMed

    You, Lin-Lin; Wu, You; Xu, Bing; Ding, Jun; Ge, Lin-Quan; Yang, Guo-Qin; Song, Qi-Sheng; Stanley, David; Wu, Jin-Cai

    2016-11-23

    The brown planthopper (BPH) is a devastating pest of rice throughout Asia. In this paper we document the BPH biogeographic range expansion in China over the 20-year period, 1992 to 2012. We posed the hypothesis that the range expansion is due to a syndrome of adaptations to the continuous presence of agricultural chemicals (insecticides and a fungicide) over the last 40 years. With respect to biogeography, BPH ranges have expanded by 13% from 1992 to 1997 and by another 3% from 1997 to 2012. In our view, such expansions may follow primarily from the enhancing effects of JGM, among other agricultural chemicals, and from global warming. JGM treatments led to increased thermotolerance, recorded as decreased mortality under heat stress at 40 ± 1 °C (down from 80% to 55%) and increased fecundity (by 49%) at 34 °C. At the molecular level, JGM treatments led to increased abundances of mRNA encoding Acetyl Co-A carboxylase (Acc) (up 25%) and Hsp70 (up 32%) in experimental BPH. RNAi silencing of Hsp70 and Acc eliminated the JGM effects on fecundity and silencing Hsp70 reduced JGM-induced thermotolerance. Integrated with global climate change scenarios, such syndromes in pest insect species have potential for regional- and global-scale agricultural disasters.

  12. Gas transport model for chemical vapor infiltration. Topical report

    SciTech Connect

    Starr, T.L.

    1995-05-01

    A node-bond percolation model is presented for the gas permeability and pore surface area of the coarse porosity in woven fiber structures during densification by chemical vapor infiltration (CVI). Model parameters include the number of nodes per unit volume and their spatial distribution, and the node and bond radii and their variability. These parameters relate directly to structural features of the weave. Some uncertainty exists in the proper partition of the porosity between {open_quotes}node{close_quotes} and{open_quote}bond{close_quotes} and between intra-tow and inter-tow, although the total is constrained by the known fiber loading in the structure. Applied to cloth layup preforms the model gives good agreement with the limited number of available measurements.

  13. 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.

  14. 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

  15. 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.

  16. 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...

  17. 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...

  18. 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...

  19. Transport and transformation of nutrients and sediment in two agricultural watersheds in northeast Arkansas

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Agriculture is vital to Arkansas economy as it contributes $20 billion annually, double the average national contribution to the state GDP. Arkansas is ranked in the top 5 in rice, cotton seed and sorghum, and top 20 in soybean, corn for grain, and wheat production nationally. Despite the importance...

  20. 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.

  1. Driving pest populations: Agricultural chemicals lead to an adaptive syndrome in Nilaparvata lugens Stal (Hemiptera: Delphacidae)

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Some of the effects of contemporary climate change and agricultural practices include increased pest ranges and thermotolerances and phonological mismatches between pest insects and their natural enemies. The brown planthopper (BPH) Nilaparvata lugens Stål (Hemiptera: Delphacidae) is a serious pest ...

  2. Modeling fecal bacteria transport and retention in agricultural and urban soils under saturated and unsaturated flow conditions.

    PubMed

    Balkhair, Khaled S

    2017-03-01

    Pathogenic bacteria, that enter surface water bodies and groundwater systems through unmanaged wastewater land application, pose a great risk to human health. In this study, six soil column experiments were conducted to simulate the vulnerability of agricultural and urban field soils for fecal bacteria transport and retention under saturated and unsaturated flow conditions. HYDRUS-1D kinetic attachment and kinetic attachment-detachment models were used to simulate the breakthrough curves of the experimental data by fitting model parameters. Results indicated significant differences in the retention and drainage of bacteria between saturated and unsaturated flow condition in the two studied soils. Flow under unsaturated condition retained more bacteria than the saturated flow case. The high bacteria retention in the urban soil compared to agricultural soil is ascribed not only to the dynamic attachment and sorption mechanisms but also to the greater surface area of fine particles and low flow rate. All models simulated experimental data satisfactorily under saturated flow conditions; however, under variably saturated flow, the peak concentrations were overestimated by the attachment-detachment model and underestimated by the attachment model with blocking. The good match between observed data and simulated concentrations by the attachment model which was supported by the Akaike information criterion (AIC) for model selection indicates that the first-order attachment coefficient was sufficient to represent the quantitative and temporal distribution of bacteria in the soil column. On the other hand, the total mass balance of the drained and retained bacteria in all transport experiments was in the range of values commonly found in the literature. Regardless of flow conditions and soil texture, most of the bacteria were retained in the top 12 cm of the soil column. The approaches and the models used in this study have proven to be a good tool for simulating fecal

  3. 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

  4. Sensitivity of chemical tracers to meteorological parameters in the MOZART-3 chemical transport model

    NASA Astrophysics Data System (ADS)

    Kinnison, D. E.; Brasseur, G. P.; Walters, S.; Garcia, R. R.; Marsh, D. R.; Sassi, F.; Harvey, V. L.; Randall, C. E.; Emmons, L.; Lamarque, J. F.; Hess, P.; Orlando, J. J.; Tie, X. X.; Randel, W.; Pan, L. L.; Gettelman, A.; Granier, C.; Diehl, T.; Niemeier, U.; Simmons, A. J.

    2007-10-01

    The Model for Ozone and Related Chemical Tracers, version 3 (MOZART-3), which represents the chemical and physical processes from the troposphere through the lower mesosphere, was used to evaluate the representation of long-lived tracers and ozone using three different meteorological fields. The meteorological fields are based on (1) the Whole Atmosphere Community Climate Model, version 1b (WACCM1b), (2) the European Centre for Medium-Range Weather Forecasts (ECMWF) operational analysis, and (3) a new reanalysis for year 2000 from ECMWF called EXP471. Model-derived tracers (methane, water vapor, and total inorganic nitrogen) and ozone are compared to data climatologies from satellites. Model mean age of air was also derived and compared to in situ CO2 and SF6 data. A detailed analysis of the chemical fields simulated by MOZART-3 shows that even though the general features characterizing the three dynamical sets are rather similar, slight differences in winds and temperature can produce substantial differences in the calculated distributions of chemical tracers. The MOZART-3 simulations that use meteorological fields from WACCM1b and ECMWF EXP471 represented best the distribution of long-lived tracers and mean age of air in the stratosphere. There was a significant improvement using the ECMWF EXP471 reanalysis data product over the ECMWF operational data product. The effect of the quasi-biennial oscillation circulation on long-lived tracers and ozone is examined.

  5. Magnitude and costs of groundwater contamination from agricultural chemicals: a national perspective. Staff report

    SciTech Connect

    Nielsen, E.G.; Lee, L.K.

    1987-06-01

    Evidence is mounting that agricultural pesticide and fertilizer applications are causing groundwater contamination in some parts of the United States. A synthesis of national data has enabled researchers to identify regions potentially affected by contamination from pesticides and fertilizers and to estimate the number of people in these regions who rely on groundwater for their drinking water needs. The study found that pesticides and nitrates from fertilizers do not necessarily occur together in potentially contaminated regions.

  6. Molybdate transport in a chemically complex aquifer: Field measurements compared with solute-transport model predictions

    USGS Publications Warehouse

    Stollenwerk, K.G.

    1998-01-01

    A natural-gradient tracer test was conducted in an unconfined sand and gravel aquifer on Cape Cod, Massachusetts. Molybdate was included in the injectate to study the effects of variable groundwater chemistry on its aqueous distribution and to evaluate the reliability of laboratory experiments for identifying and quantifying reactions that control the transport of reactive solutes in groundwater. Transport of molybdate in this aquifer was controlled by adsorption. The amount adsorbed varied with aqueous chemistry that changed with depth as freshwater recharge mixed with a plume of sewage-contaminated groundwater. Molybdate adsorption was strongest near the water table where pH (5.7) and the concentration of the competing solutes phosphate (2.3 micromolar) and sulfate (86 micromolar) were low. Adsorption of molybdate decreased with depth as pH increased to 6.5, phosphate increased to 40 micromolar, and sulfate increased to 340 micromolar. A one-site diffuse-layer surface-complexation model and a two-site diffuse-layer surface-complexation model were used to simulate adsorption. Reactions and equilibrium constants for both models were determined in laboratory experiments and used in the reactive-transport model PHAST to simulate the two-dimensional transport of molybdate during the tracer test. No geochemical parameters were adjusted in the simulation to improve the fit between model and field data. Both models simulated the travel distance of the molybdate cloud to within 10% during the 2-year tracer test; however, the two-site diffuse-layer model more accurately simulated the molybdate concentration distribution within the cloud.

  7. 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

  8. 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.

  9. EPA Resolves Violations with Newport Beach, Calif. Company for Failure to Report Imported Agricultural Chemicals

    EPA Pesticide Factsheets

    LOS ANGELES -The U.S. Environmental Protection Agency settled its case against American Vanguard Corporation, located in Newport Beach, Calif., for failure to report toxic chemical substances imported by two of its subsidiary companies. American Vang

  10. 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

    2002-02-04

    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.

  11. 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.

  12. 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.

  13. 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.

  14. Overland flow transport of pathogens from agricultural land receiving faecal wastes.

    PubMed

    Tyrrel, S F; Quinton, J N

    2003-01-01

    Considerable investment has been made in recent years in improvements to the microbiological quality of urban wastewater discharges to surface waters, particularly in coastal towns, with the aim of reducing the exposure of bathers and surfers to gastrointestinal pathogens. As this source of pollution has come under greater control, attention has started to focus on diffuse catchment sources of faecal contamination which have been shown to be dominant during high river flows associated with storm events. This association with storm events suggests that rapidly responding hydrological pathways such as overland flow are likely to be important. The aim of this paper is to establish the current state of knowledge of pathogen transport processes in overland flow. In addition, the paper will attempt to convey the way that soil erosion science may aid our understanding of this environmental problem. The scale and nature of faecal waste applications to land in the UK is briefly reviewed, with data presented on both livestock slurry and manure, and human sewage sludge. Particular emphasis is placed on factors influencing the likelihood of pathogens making their way from infected livestock and humans to the soil surface, and therefore the chances of them being available for transport by overland flow. The literature relating to pathogen transport in overland flow is reviewed. Existing pathogen transport models treat pathogens as particles and link pathogen transport models to pathogen die-off kinetics. Such models do not attempt to describe the interactions that may occur between pathogens and soil and waste particles. Although conceptual models describing the possible states in which pathogen transport may occur have been proposed, an understanding of the factors controlling the partitioning of the microorganisms between the different states is only just beginning to emerge. The apparent poor performance of overland flow mitigation measures such as grass buffer strips in

  15. Homogenization of the transport behavior of nonlinearly adsorbing pollutants in physically and chemically heterogeneous aquifers

    NASA Astrophysics Data System (ADS)

    Attinger, Sabine; Dimitrova, Jiva; Kinzelbach, Wolfgang

    2009-05-01

    This paper addresses the question of how spatial variability in the hydraulic and chemical properties of groundwater systems affects the transport and sorption behavior of pollutants at the field scale. In this paper, we limit our investigations on pollutants that adsorb according to an equilibrium controlled nonlinear Freundlich sorption isotherm. The new contribution of this paper is take into account not only spatially variable Freundlich distribution coefficients KS but spatially variable Freundlich nonlinearity parameters p as well. Using a homogenization theory approach, we shortly review the impact of spatially variable hydraulic properties on the transport and extend the theory to spatially variable chemical properties. We show that spatially variable Freundlich exponents cause a very different field scale transport and sorption behavior than spatial variations in the distribution coefficients only since in the first case field scale Freundlich parameters and field scale dispersion coefficients become concentration dependent. In particular, field scale retardation is much larger than small-scale retardation.

  16. 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.

  17. 77 FR 59840 - Statutory Amendments Affecting Transportation of Agricultural Commodities and Farm Supplies

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-10-01

    ... retail store deliveries. Thus, it is clear Congress intended to limit this exemption to retail... transportation from a retail distribution point of the farm supply to a location (farm or other location where the farm supply product would be used) within a 100 air-mile radius of the retail distribution...

  18. Alteration of gene expression in human cells treated with the agricultural chemical diazinon: possible interaction in fetal development.

    PubMed

    Mankame, T; Hokanson, R; Fudge, R; Chowdhary, R; Busbee, D

    2006-05-01

    Agricultural chemicals frequently alter human health or development, typically because they have endocrine agonist or antagonist activities and alter hormone-regulation of gene expression. The insecticide, diazinon, was evaluated for gene expression disrupting activity using MCF-7 cells, an estrogen-dependent human cell line, to examine the capacity of the insecticide to disrupt gene expression essential for morphological development, immune system development or function, and/or central nervous system development and function. MCF-7 cells were treated with 30, 50 or 67 ppm diazinon, and gene expression was measured in treated cells compared to expression in untreated or estrogen-treated cells. DNA microarray analysis of diazinon-treated cells showed significant up- or down-regulation of a large number of genes compared to untreated cells. Of the 600 human genes on the Phase 1 chip utilized for these studies, two specific genes--calreticulin and TGF-beta3--were selected for corroboration using quantitative real time PCR (qrtPCR). qrtPCR, completed to assess gene expression levels for calreticulin and TGFbeta3, confirmed results showing significant up-regulation of these two genes obtained from the microarray data. These studies were designed to provide baseline data on the gene expression-altering capacity of a specific chemical, diazinon, and allow a partial assessment of the potentially deleterious effects associated with exposure of human cells to this chemical. Currently, it is not known whether results from cells in vitro can be extrapolated to human health consequences of chemical exposure.

  19. 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.

  20. 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.

  1. 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.

  2. 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.

  3. 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

  4. 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

  5. Carbon agent chemical vapor transport growth of Ga2O3 crystal

    NASA Astrophysics Data System (ADS)

    Jie, Su; Tong, Liu; Jingming, Liu; Jun, Yang; Guiying, Shen; Yongbiao, Bai; Zhiyuan, Dong; Youwen, Zhao

    2016-10-01

    Beta-type gallium oxide (β-Ga2O3) is a new attractive material for optoelectronic devices. Different methods had been tried to grow high quality β-Ga2O3 crystals. In this work, crystal growth of Ga2O3 has been carried out by chemical vapor transport (CVT) method in a closed quartz tube using C as transport agent and sapphire wafer as seed. The CVT mass flux has been analyzed by theoretical calculations based on equilibrium thermodynamics and 1D diffusional mass transport. The crystal growth experimental results are in agreement with the theoretical predictions. Influence factors of Ga2O3 crystal growth, such as temperature distribution, amount of C as transport agent used, have also been discussed. Structural (XRD) and optical (Raman spectroscopy, photoluminescence spectrum) properties of the CVT-Ga2O3 crystal are presented. Project supported by the National Natural Science Foundation of China (Nos. 61474104, 61504131).

  6. 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).

  7. 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.

  8. 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

  9. 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.

  10. Physical and Chemical Factors Influencing the Transport and Fate of Microorganisms in Soils with Preferential Flow

    NASA Astrophysics Data System (ADS)

    Wang, Y.; Bradford, S. A.; Simunek, J.

    2011-12-01

    Laboratory and numerical studies were conducted to investigate the influence of physical and chemical factors on the transport of E.coli O157:H7 and coliphage φX174 through preferential flow systems. Preferential flow systems were created in 13.2 cm diameter and 20 cm length columns by embedding sand lens of various grain size, length, and vertical position into finer textured matrix sand. Tracer solutions containing bromide and microbes were prepared at different ionic strength (IS) and sprayed onto the surface of the columns at desired steady rates using a rain simulator to achieve saturated or unsaturated conditions. Effluents were collected at the column bottom continuously and analyzed for concentrations of bromide, φX174, and E.coli. Complementary numerical simulations were conducted using the HYDRUS 2D code over a wider range of physical and chemical conditions, and to analyze bromide and microbe transport in the columns. Results indicated that preferential transport of the microbes was dependent on the hydraulic contrasts between the matrix and lens, the length of the lens, the size of microorganism, and the water saturation. The IS also influenced the preferential transport of microbes. In particular, increasing retention with IS decreased the overall microbe transport but increased the relative importance of preferential flow.

  11. 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.

  12. Physical and chemical properties of selected agricultural byproduct-based activated carbons and their ability to adsorb geosmin.

    PubMed

    Ng, Chilton; Losso, Jack N; Marshall, Wayne E; Rao, Ramu M

    2002-09-01

    The objectives of this study were to evaluate selected physical and chemical properties of agricultural byproduct-based activated carbons made from pecan shells and sugarcane bagasse, and compare those properties to a commercial coal-based activated carbon as well as to compare the adsorption efficiency of these carbons for geosmin. Comparison of the physical and chemical properties of pecan shell- and bagasse-based carbons to the commercial carbon, Calgon Filtrasorb 400, showed that pecan shell carbon, but not the bagasse carbon, compared favorably to Filtrasorb 400, especially in terms of surface area, bulk density, ash and attrition. A carbon dosage study done in a model system showed the amount of geosmin adsorbed to be greater for Filtrasorb 400 and the bagasse-based carbon at low carbon concentrations than for the pecan shell carbons, but geosmin adsorption was similar in all carbons at higher carbon dosages. Application of the Freundlich isotherm model to the adsorption data showed that carbons made by steam activation of pecan shells or sugarcane bagasse had geosmin adsorption characteristics most like those of the commercial carbon. In terms of physical, chemical and adsorptive properties, steam-activated pecan shell carbon most resembled the commercial carbon and has the potential to replace Filtrasorb 400 in applications involving removal of geosmin from aqueous environments.

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. 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.

  19. Surface chemical effects on colloid stability and transport through natural porous media

    USGS Publications Warehouse

    Puls, Robert W.; Paul, Cynthia J.; Clark, Donald A.

    1993-01-01

    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 retrieved from a sand and gravel aquifer on Cape Cod, MA. Previous studies have indicated enhanced stability and transport of iron oxide particles due to specific adsorption of some inorganic anions on the iron oxide surface. This phenomenon was further evaluated with an anionic surfactant, sodium dodecyl sulfate. Surfactants constitute a significant mass of the contaminant loading at the Cape Cod site and their presence may contribute to colloidal transport as a significant transport mechanism at the site. Other studies at the site have previously demonstrated the occurrence of this transport mechanism for iron phosphate particles. Photon correlation spectroscopy, micro-electrophoretic mobility, and scanning electron microscopy were used to evaluate particle stability, mobility and size. Adsorption of negatively charged organic and inorganic species onto the surface of the iron oxide particles was shown to significantly enhance particle stability and transport through alterations of the electrokinetic properties of the particle surface. Particle breakthrough generally occurred simultaneously with tritiated water, a conservative tracer. The extent of particle breakthrough was primarily dependent upon colloidal stability and surface charge.

  20. 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.

  1. Lagrangian transport model forecasts and a transport climatology for the Intercontinental Transport and Chemical Transformation 2002 (ITCT 2K2) measurement campaign

    NASA Astrophysics Data System (ADS)

    Forster, Caroline; Cooper, Owen; Stohl, Andreas; Eckhardt, Sabine; James, Paul; Dunlea, Edward; Nicks, Dennis K.; Holloway, John S.; Hübler, Gerd; Parrish, David D.; Ryerson, Tom B.; Trainer, Michael

    2004-04-01

    On the basis of Lagrangian tracer transport simulations this study presents an intercontinental transport climatology and tracer forecasts for the Intercontinental Transport and Chemical Transformation 2002 (ITCT 2K2) aircraft measurement campaign, which took place at Monterey, California, in April-May 2002 to measure Asian pollution arriving at the North American West Coast. For the climatology the average transport of an Asian CO tracer was calculated over a time period of 15 years using the particle dispersion model FLEXPART. To determine by how much the transport from Asia to North America during ITCT 2K2 deviated from the climatological mean, the 15-year average for April and May was compared with the average for April and May 2002 and that for the ITCT 2K2 period. It was found that 8% less Asian CO tracer arrived at the North American West Coast during the ITCT 2K2 period compared to the climatological mean. Below 8-km altitude, the maximum altitude of the research aircraft, 13% less arrived. Nevertheless, pronounced layers of Asian pollution were measured during 3 of the 13 ITCT 2K2 flights. FLEXPART was also successfully used as a forecasting tool for the flight planning during ITCT 2K2. It provided 3-day forecasts for three different anthropogenic CO tracers originating from Asia, North America, and Europe. In two case studies the forecast abilities of FLEXPART are analyzed and discussed by comparing the forecasts with measurement data and infrared satellite images. The model forecasts underestimated the measured CO enhancements by about a factor of 4, mainly because of an underestimation of the Asian emissions in the emission inventory and because of biomass-burning influence that was not modeled. Nevertheless, the intercontinental transport and dispersion of pollution plumes were qualitatively well predicted, and on the basis of the model results the aircraft could successfully be guided into the polluted air masses.

  2. 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.

  3. An agricultural biomass burning episode in eastern China: Transport, optical properties, and impacts on regional air quality

    NASA Astrophysics Data System (ADS)

    Wu, Yonghua; Han, Yong; Voulgarakis, Apostolos; Wang, Tijian; Li, Mengmeng; Wang, Yuan; Xie, Min; Zhuang, Bingling; Li, Shu

    2017-02-01

    Agricultural biomass burning (ABB) has been of particular concern due to its influence on air quality and atmospheric radiation, as it produces large amounts of gaseous and aerosol emissions. This paper presents an integrated observation of a significant ABB episode in Nanjing, China, during early June 2011, using combined ground-based and satellite sensors (Moderate Resolution Imaging Spectroradiometer, Atmospheric Infrared Sounder, Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO), and Ozone Monitoring Instrument products). The time-height distribution, optical properties, sources and transport of smoke, and its impacts on air quality are investigated. Lidar profiles indicate that the smoke aerosols are confined to the planetary boundary layer (PBL) and have a depolarization ratio of less than 0.08. The aerosol optical depths increase from 0.5 to 3.0 at 500 nm, while the extinction-related Angstrom exponent increases from 1.1 to 1.6 at the wavelength pair of 440-870 nm. The single-scattering albedo becomes lower at 670-1020 nm following the ABB intrusion and particularly shows a decreasing tendency between wavelengths of 440 to 1020 nm. The absorption Angstrom exponent (0.7) is smaller than 1.0, which may indicate the aged smoke particles mixed or coated with the urban aerosols. Surface particular matter PM10 and PM2.5 show a dramatic increase, reaching hourly mean of 800 µg/m3 and 485 µg/m3, respectively, which results in a heavy air pollution event. The stagnant and high-moisture weather provides favorable conditions for the aerosols to accumulate near the surface. Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) also illustrate that the large-scale aerosols are primarily present in the PBL and transported to the ocean, but some dense smoke plumes are misclassified as cloud or polluted dust. By comparing with the observations, we found that the Weather Research and Forecasting-Chemistry model captured the

  4. Probabilistic analysis of chemical agent release during transport of M55 rockets

    SciTech Connect

    Rhyne, W.R.; Robinette, R.J.; Ashwood, T.L.

    1985-09-01

    The results of a probabilistic analysis of the release of chemical agent from M55 rockets as a consequence of an accident during transport are presented. The M55 inventories stored at the Anniston Army Depot, the Lexington-Blue Grass Depot Activity, and the Umatilla Depot Activity were considered for transport by highway, rail, and/or air. For each mode of transportation, two types of packaging are considered: a simple vapor-barrier package and an armored and insulated package represented by a particular package called the Chemical Ammunition Package Transporter (CAMPACT). Five agent release categories were defined: accident damage to the shipping container of a ''leaker'' causing simple, unconfined agent release; simple agent release for a normal rocket; impact-induced rocket motor ignition; impact-induced burster detonation; and fire-induced release. These five categories were combined into two categories for comparisons with other studies: a simple release category and a maximum credible release category. 42 refs., 22 figs., 45 tabs.

  5. 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.

  6. 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.

  7. Airborne measurements of spectral direct aerosol radiative forcing in the Intercontinental chemical Transport Experiment/Intercontinental Transport and Chemical Transformation of anthropogenic pollution, 2004

    NASA Astrophysics Data System (ADS)

    Redemann, Jens; Pilewskie, Peter; Russell, Philip B.; Livingston, John M.; Howard, Steve; Schmid, Beat; Pommier, John; Gore, Warren; Eilers, James; Wendisch, Manfred

    2006-07-01

    As part of the INTEX-NA (Intercontinental chemical Transport Experiment-North America) and ITCT (Intercontinental Transport and Chemical Transformation of anthropogenic pollution) field studies, the NASA Ames 14-channel Airborne Tracking Sunphotometer (AATS-14) and a pair of Solar Spectral Flux Radiometers (SSFR) took measurements from aboard a Sky Research Jet stream 31 (J31) aircraft during 19 science flights over the Gulf of Maine during 12 July to 8 August 2004. The combination of coincident AATS-14 and SSFR measurements yields plots of net (downwelling minus upwelling) spectral irradiance as a function of aerosol optical depth (AOD) as measured along horizontal flight legs. By definition, the slope of these plots yields the instantaneous change in net irradiance per unit AOD change and is referred to as the instantaneous spectral aerosol radiative forcing efficiency, Ei (W m-2 nm-1). Numerical integration over a given spectral range yields the instantaneous broadband aerosol radiative forcing efficiency (W m-2). This technique for deriving Ei is called the aerosol gradient method. Within 10 case studies considered suitable for our analysis we found a high variability in the derived instantaneous aerosol forcing efficiencies for the visible wavelength range (350-700 nm), with a mean of -79.6 W m-2 and a standard deviation of 21.8 W m-2 (27%). An analytical conversion of the instantaneous forcing efficiencies to 24-hour-average values yielded -45.8 ± 13.1 W m-2 (mean ± std). We present spectrally resolved aerosol forcing efficiencies between 350 and 1670 nm, estimates of the midvisible aerosol single scattering albedo and a comparison of observed broadband forcing efficiencies to previously reported values.

  8. Space power systems: Producing transportation (and other chemical) fuels as an alternative to electricity generation

    NASA Astrophysics Data System (ADS)

    Wegeng, Robert S.; Mankins, John C.

    2009-11-01

    While most studies on space power systems target electricity generation as the energy product, industrialized nations also have a need for chemicals to support transportation and other purposes. This paper therefore describes an alternative target for the application of space power systems: the production of chemical fuels based on radiant energy beamed or reflected from orbiting platforms. If cost and efficiency targets can be achieved, Solar Thermochemical Plants—occupying a few square kilometers each—can potentially generate substantial quantities of transportation fuels, therefore enabling reductions in the consumption of petroleum and the emission of carbon dioxide. The specifics of the approach that are described in this paper include the concentration of radiant energy within ground-based systems so that high temperature heat is provided for thermochemical process networks. This scoping study includes the evaluation of various feedstock chemicals as input to the Solar Thermochemical Plant: natural gas, biomass and zero-energy chemicals (water and carbon dioxide); and the production of either hydrogen or long-chain hydrocarbons (i.e., Fischer-Tropsch fuels) as the Solar Fuel product of the plant.

  9. The synergistic effect of ultrasound and chemical penetration enhancers on chorioamnion mass transport.

    PubMed

    Azagury, Aharon; Khoury, Luai; Adato, Yair; Wolloch, Lior; Ariel, Ilana; Hallak, Mordechai; Kost, Joseph

    2015-02-28

    In our previous study we proposed the use of chemical penetration enhancers for noninvasive detection of fetus abnormalities that can also be utilized for direct fetal drug delivery. In an attempt to further increase the mass transport rate across the amniotic membrane, thus shortening the procedure and improving the applicability of the proposed procedure, the effect and mechanism of combining ultrasound exposure with chemical penetration enhancers' application were assessed. The combined effect was evaluated in vitro on post-delivery human amniotic membrane and ex vivo on rat's whole amniotic sac. Ultrasound effect has been assessed by dye experiments using a customized image analysis program. Additional insights of ultrasound effect's mechanism on biological membranes are presented. Previously we have determined that chemical penetration enhancers affect the fetal membranes via two mechanisms termed as 'extractors' and 'fluidizers'. In this study, we found that combining ultrasound with a 'fluidizer' CPE (e.g. bupivacaine) results in a synergistic enhancement (90-fold) of fetal membrane's mass transport, while combining ultrasound with 'extractors' (e.g. ethanol and NMP) results in an antagonistic effect. The combined procedure is faster and gain greater accuracy than the applications of sole chemical penetration enhancers.

  10. 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.

  11. 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

  12. 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.

  13. 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.

  14. 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 ...

  15. 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

  16. Budget of tropospheric ozone during TOPSE from two chemical transport models

    NASA Astrophysics Data System (ADS)

    Emmons, L. K.; Hess, P.; Klonecki, A.; Tie, X.; Horowitz, L.; Lamarque, J.-F.; Kinnison, D.; Brasseur, G.; Atlas, E.; Browell, E.; Cantrell, C.; Eisele, F.; Mauldin, R. L.; Merrill, J.; Ridley, B.; Shetter, R.

    2003-04-01

    The tropospheric ozone budget during the Tropospheric Ozone Production about the Spring Equinox (TOPSE) campaign has been studied using two chemical transport models (CTMs): HANK and the Model of Ozone and Related chemical Tracers, version 2 (MOZART-2). The two models have similar chemical schemes but use different meteorological fields, with HANK using MM5 (Pennsylvania State University, National Center for Atmospheric Research Mesoscale Modeling System) and MOZART-2 driven by European Centre for Medium-Range Weather Forecasts (ECMWF) fields. Both models simulate ozone in good agreement with the observations but underestimate NOx. The models indicate that in the troposphere, averaged over the northern middle and high latitudes, chemical production of ozone drives the increase of ozone seen in the spring. Both ozone gross chemical production and loss increase greatly over the spring months. The in situ production is much larger than the net stratospheric input, and the deposition and horizontal fluxes are relatively small in comparison to chemical destruction. The net production depends sensitively on the concentrations of H2O, HO2 and NO, which differ slightly in the two models. Both models underestimate the chemical production calculated in a steady state model using TOPSE measurements, but the chemical loss rates agree well. Measures of the stratospheric influence on tropospheric ozone in relation to in situ ozone production are discussed. Two different estimates of the stratospheric fraction of O3 in the Northern Hemisphere troposphere indicate it decreases from 30-50% in February to 15-30% in June. A sensitivity study of the effect of a perturbation in the vertical flux on tropospheric ozone indicates the contribution from the stratosphere is approximately 15%.

  17. Changes in bacterial community structure of agricultural land due to long-term organic and chemical amendments.

    PubMed

    Chaudhry, Vasvi; Rehman, Ateequr; Mishra, Aradhana; Chauhan, Puneet Singh; Nautiyal, Chandra Shekhar

    2012-08-01

    Community level physiological profiling and pyrosequencing-based analysis of the V1-V2 16S rRNA gene region were used to characterize and compare microbial community structure, diversity, and bacterial phylogeny from soils of chemically cultivated land (CCL), organically cultivated land (OCL), and fallow grass land (FGL) for 16 years and were under three different land use types. The entire dataset comprised of 16,608 good-quality sequences (CCL, 6,379; OCL, 4,835; FGL, 5,394); among them 12,606 sequences could be classified in 15 known phylum. The most abundant phylum were Proteobacteria (29.8%), Acidobacteria (22.6%), Actinobacteria (11.1%), and Bacteroidetes (4.7%), while 24.3% of the sequences were from bacterial domain but could not be further classified to any known phylum. Proteobacteria, Bacteroidetes, and Gemmatimonadetes were found to be significantly abundant in OCL soil. On the contrary, Actinobacteria and Acidobacteria were significantly abundant in CCL and FGL, respectively. Our findings supported the view that organic compost amendment (OCL) activates diverse group of microorganisms as compared with conventionally used synthetic chemical fertilizers. Functional diversity and evenness based on carbon source utilization pattern was significantly higher in OCL as compared to CCL and FGL, suggesting an improvement in soil quality. This abundance of microbes possibly leads to the enhanced level of soil organic carbon, soil organic nitrogen, and microbial biomass in OCL and FGL soils as collated with CCL. This work increases our current understanding on the effect of long-term organic and chemical amendment applications on abundance, diversity, and composition of bacterial community inhabiting the soil for the prospects of agricultural yield and quantity of soil.

  18. Influences of biomass burning during the Transport and Chemical Evolution Over the Pacific (TRACE-P) experiment identified by the regional chemical transport model

    NASA Astrophysics Data System (ADS)

    Tang, Youhua; Carmichael, Gregory R.; Woo, Jung-Hun; Thongboonchoo, Narisara; Kurata, Gakuji; Uno, Itsushi; Streets, David G.; Blake, Donald R.; Weber, Rodney J.; Talbot, Robert W.; Kondo, Yutaka; Singh, Hanwant B.; Wang, Tao

    2003-11-01

    Using a regional chemical transport model, STEM 2K1, and the emission inventory for the Transport and Chemical Evolution Over the Pacific (TRACE-P) period [Woo et al., , this issue], we successfully simulated important features of the biomass burning (BB) CO outflow. Simulated results agree well with the TRACE-P aircraft measurements and Thailand surface observations. On the basis of sensitivity studies with and without biomass emissions, we identified nine flight segments that are affected by biomass plumes during the TRACE-P period and compared the characteristics of the BB air masses with the other air masses. The BB air masses emitted from Southeast Asia contain relatively high HCN (ΔHCN/ΔCO ˜ 0.0015) and potassium (ΔK+/ΔCO ˜ 0.0038) but very low NOy (ΔNOy/ΔCO ˜ 0.005) mixing ratios, which may be associated with the special burning condition in this region. The biomass burning air masses have high ozone production efficiency. The observed ΔO3/ΔNOz values were ˜17 in biomass events and 1.7 in other events. The BB influence on the trace gas distributions can be divided into two categories: the influence through direct reactions and the influence caused by BB aerosols changing J values. These two influences are discussed for the BB-affected TRACE-P flights and for east Asia. The BB influences on chemical species are not only determined by the BB plume intensity but also by the ambient environment caused by other emissions. In Southeast Asia, where the biogenic emissions are very strong, the OH background concentration is low, and the BB gas-phase compounds mainly contribute to OH production. Arranged in the sensitivity to the J value change caused by BB aerosols, we have OH > HO2 > HCHO > O3 when evaluated on a regional average. Averaged over March, the biomass burning net influence is as high as 50% for OH, 40% for HO2, 60% for HCHO, and 10 ppbv for O3 for the layers below 1 km.

  19. 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

  20. 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.

  1. Internal Domains of Natural Porous Media Revealed: Critical Locations for Transport, Storage, and Chemical Reaction

    SciTech Connect

    Zachara, John M.; Brantley, Susan L.; Chorover, Jon D.; Ewing, Robert P.; Kerisit, Sebastien N.; Liu, Chongxuan; Perfect, E.; Rother, Gernot; Stack, Andrew G.

    2016-03-16

    Internal pore domains exist within rocks, lithic fragments, subsurface sediments and soil aggregates. These domains, which we term internal domains in porous media (IDPM), contain a significant fraction of their porosity as nanopores, dominate the reactive surface area of diverse porous media types, and are important locations for chemical reactivity and hydrocarbon storage. Traditionally difficult to interrogate, advances in instrumentation and imaging methods are providing new insights on the physical structures and chemical attributes of IDPM. In this review we: discuss analytical methods to characterize IDPM, evaluate what has been learned about their size distributions, connectivity, and extended structures; determine whether they exhibit unique chemical reactivity; and assess potential for their inclusion in reactive transport models. Three key findings are noteworthy. 1) A combination of methods now allows complete characterization of the porosity spectrum of natural materials and its connectivity; while imaging microscopies are providing three dimensional representations of the interconnected pore network. 2) Chemical reactivity in pores <10 nm is expected to be different from micro and macropores, yet research performed to date is inconclusive on the nature, direction, and magnitude of effect. 3) Existing continuum reactive transport models treat IDPM as a sub-grid feature with average, empirical, scale-dependent parameters; and are not formulated to include detailed information on pore networks. Overall we find that IDPM are key features controlling hydrocarbon release from shales in hydrofracking systems, organic matter stabilization and recalcitrance in soil, weathering and soil formation, and long term inorganic and organic contaminant behavior in the vadose zone and groundwater. We conclude with an assessment of impactful research opportunities to advance understanding of IDPM, and to incorporate their important effects in reactive transport models

  2. 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.

  3. 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.

  4. 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.

  5. A modeling approach for agricultural water management in citrus orchards: cost-effective irrigation scheduling and agrochemical transport simulation.

    PubMed

    Kourgialas, Nektarios N; Karatzas, George P

    2015-07-01

    The water flow and the mass transport of agrochemicals in the unsaturated and saturated zone were simulated in the extended alluvial basin of Keritis river in Crete, Greece (a predominantly flat and most productive citrus growing area) using the hydrological model MIKE SHE. This model was set up based on information on land use, geology, soil structure, meteorological data, as well as groundwater level data from pumping wells. Additionally, field measurements of the soil moisture at six different locations from three soil depths (0.1, 0.2, and 0.3 m) were used as targets to calibrate and validate the unsaturated flow model while for saturated condition, groundwater level data from three well locations were used. Following the modeling approach, the agrochemical mass transport simulation was performed as well, based on different application doses. After the successful calibration processes, the obtained 1D modeling results of soil moisture-pressure related to soil depth at different locations were used to design a proper and cost-effective irrigation programme (irrigation timing, frequency, application rates, etc.) for citrus orchards. The results of the present simulation showed a very good correlation with the field measurements. Based on these results, a proper irrigation plan can be designed at every site of the model domain reducing the water consumption up to 38% with respect to the common irrigation practices and ensuring the citrus water productivity. In addition, the effect of the proposed irrigation scheduling on citrus yield was investigated. Regarding the agrochemical concentration in the groundwater for all dose cases was below the maximum permissible limit. The only exception was for the highest dose in areas where the water table is high. Thus, this modeling approach could be used as a tool for appropriate water management in an agricultural area estimating at each time and location the availability of soil water, contributing to a cost

  6. Analytical models of the impact of two-phase sorption on subsurface transport of volatile chemicals

    SciTech Connect

    Shoemaker, C.A.; Culver, T.B.; Lion, L.W.; Peterson, M.G. )

    1990-04-01

    Unsaturated zone models incorporating the impact of vapor-phase sorption on transport of volatile organic compounds are presented with closed from solutions for one-and two-dimensional cases. In addition to vapor-phase sorption the models incorporate liquid-phase sorption, liquid advection, gaseous diffusion, and volatilization into soil air spaces and to the atmosphere. The motivation for incorporation of vapor-phase sorption arises from recent experimental results by the authors indicating that vapor-phase sorption may be orders of magnitude higher than liquid-phase sorption under certain soil conditions. The sensitivity analysis suggests that there is considerable interaction among the physical and chemical processes involved in transport of volatile organic compounds. Pollutant concentrations are most affected by the Henry's law constant and gaseous diffusion; the speed of movement of the material depends most upon the pore water velocity and vapor-phase sorption. The incorporation of vapor-phase sorption can significantly reduce model predictions of the transport speed and amount of volatile chemical reaching the groundwater under dry soil conditions. This result is of considerable practical significance since models currently used for remediation and regulation do not include vapor-phase sorption.

  7. Chemical Analysis of Aerosols for Characterization of Long-Range Transport at Mt. Lassen, CA

    NASA Astrophysics Data System (ADS)

    Harada, Y.; Waddell, J. A.; Cliff, S. S.; Perry, K. D.; Kelly, P. B.

    2004-12-01

    Effective regional air pollution regulation requires an understanding of long-range aerosol transport and natural aerosol chemistry. Sample collection was performed at the Interagency Monitoring of Protected Visual Environments (IMPROVE) sampling site on Mt. Lassen in the Sierra Nevada range at 1755 m elevation. The site is in Northern California at Longitude 121° 34' 40", Latitude 40° 32' 25". Size segregated and time resolved aerosol samples were collected with an 8 DRUM sampler from April 15th to May 24th 2002 as part of the NOAA Intercontinental Transport and Chemical Transformation Experiment (ITCT). The samples were analyzed with Synchrotron X-Ray Fluorescence (S-XRF) and Time of Flight mass spectroscopy (TOFMS). The total aerosol concentration exhibits a clear daily cycling of total mass, due to a nighttime down-slope air circulation from the free troposphere. The sulfate peaked in concentration during the night. Elemental data is suggestive of dust transport from continental Asia. The micron size ranges were dominated by nitrate, while the sub-micron size ranges had high levels of sulfate. Chemical analysis shows oceanic influence through strong correlations between methyl sulfonic acid (MSA), iodine, and oxalate. The appearance of the oceanic biogenic tracers in the sub-micron fraction is most likely a result of vertical mixing over the Pacific Ocean. MSA follows a diurnal pattern similar to sulfate, however the differences suggest both an oceanic and continental source for sulfate. The carbon particulate signal did not show any diurnal pattern during the measurement period.

  8. Internal Domains of Natural Porous Media Revealed: Critical Locations for Transport, Storage, and Chemical Reaction

    DOE PAGES

    Zachara, John; Brantley, Sue; Chorover, Jon; ...

    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

  9. 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.

  10. 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

  11. Internal Domains of Natural Porous Media Revealed: Critical Locations for Transport, Storage, and Chemical Reaction

    SciTech Connect

    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 methods 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.

  12. Formation of thermal flow fields and chemical transport in air and water by atmospheric plasma

    NASA Astrophysics Data System (ADS)

    Shimizu, Tetsuji; Iwafuchi, Yutaka; Morfill, Gregor E.; Sato, Takehiko

    2011-05-01

    Cold atmospheric plasma is a potential tool for medical purposes, e.g. disinfection/sterilization. In order for it to be effective and functional, it is crucial to understand the transport mechanism of chemically reactive species in air as well as in liquid. An atmospheric plasma discharge was produced between a platinum pin electrode and the surface of water. The thermal flow field of a cold atmospheric plasma as well as its chemical components was measured. A gas flow with a velocity of around 15 m s-1 to the water's surface was shown to be induced by the discharge. This air flow induced a circulating flow in the water from the discharge point at the water's surface because of friction. It was also demonstrated that the chemical components generated in air dissolved in water and the properties of the water changed. The reactive species were believed to be distributed mainly by convective transport in water, because the variation in the pH profile indicated by a methyl red solution resembled the induced flow pattern.

  13. Amino acid transporter mutants of Arabidopsis provides evidence that a non-mycorrhizal plant acquires organic nitrogen from agricultural soil.

    PubMed

    Ganeteg, Ulrika; Ahmad, Iftikhar; Jämtgård, Sandra; Aguetoni-Cambui, Camila; Inselsbacher, Erich; Svennerstam, Henrik; Schmidt, Susanne; Näsholm, Torgny

    2017-03-01

    Although organic nitrogen (N) compounds are ubiquitous in soil solutions, their potential role in plant N nutrition has been questioned. We performed a range of experiments on Arabidopsis thaliana genetically modified to enhance or reduce root uptake of amino acids. Plants lacking expression of the Lysine Histidine Transporter 1 (LHT1) displayed significantly lower contents of (13) C and (15) N label and of U-(13) C5 ,(15) N2 L-glutamine, as determined by liquid chromatography-mass spectrometry when growing in pots and supplied with dually labelled L-glutamine compared to wild type plants and LHT1-overexpressing plants. Slopes of regressions between accumulation of (13) C-labelled carbon and (15) N-labelled N were higher for LHT1-overexpressing plants than wild type plants, while plants lacking expression of LHT1 did not display a significant regression between the two isotopes. Uptake of labelled organic N from soil tallied with that of labelled ammonium for wild type plants and LHT1-overexpressing plants but was significantly lower for plants lacking expression of LHT1. When grown on agricultural soil plants lacking expression of LHT1 had the lowest, and plants overexpressing LHT1 the highest C/N ratios and natural δ(15) N abundance suggesting their dependence on different N pools. Our data show that LHT1 expression is crucial for plant uptake of organic N from soil.

  14. Ag-mediated charge transport during metal-assisted chemical etching of silicon nanowires.

    PubMed

    Geyer, Nadine; Fuhrmann, Bodo; Leipner, Hartmut S; Werner, Peter

    2013-05-22

    The charge transport mechanism during metal-assisted chemical etching of Si nanowires with contiguous metal films has been investigated. The experiments give a better insight how the charges and reaction products can penetrate to the etching front. The formation of a layer of porous Si between the metal film and the bulk Si is a prerequisite for the etching process. The electronic holes (positive charges) necessary for the etching of porous Si are generated at the surface of the metal in contact with the oxidative agent. Because of the insulating character of the thin walls of the porous Si, the transport of the electronic holes through this layer is not possible. Instead, it is found that the transport of electronic holes proceeds primarily by means of the Ag/Ag(+) redox pair circulating in the electrolyte and diffusing through the etched pores in the Si. The charge transport occurs without the ionic contribution at the positions where the metal is in direct contact with the Si. Here, an electropolishing process takes place, leading to an extensive removal of the Si and sinking in of the film into the Si substrate.

  15. 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

    2015-09-09

    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.

  16. 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.

  17. Solute transport with multiple equilibrium-controlled or kinetically controlled chemical reactions

    USGS Publications Warehouse

    Friedly, John C.; Rubin, Jacob

    1992-01-01

    A new approach is applied to the problem of modeling solute transport accompanied by many chemical reactions. The approach, based on concepts of the concentration space and its stoichiometric subspaces, uses elements of the subspaces as primary dependent variables. It is shown that the resulting model equations are compact in form, isolate the chemical reaction expressions from flow expressions, and can be used for either equilibrium or kinetically controlled reactions. The implications of the results on numerical algorithms for solving the equations are discussed. The application of the theory is illustrated throughout with examples involving a simple but broadly representative set of reactions previously considered in the literature. Numerical results are presented for four interconnected reactions: a homogeneous complexation reaction, two sorption reactions, and a dissolution/precipitation reaction. Three cases are considered: (1) four kinetically controlled reactions, (2) four equilibrium-controlled reactions, and (3) a system with two kinetically controlled reactions and two equilibrium-controlled reactions.

  18. A generalized quantum chemical approach for elastic and inelastic electron transports in molecular electronics devices

    NASA Astrophysics Data System (ADS)

    Jiang, Jun; Kula, Mathias; Luo, Yi

    2006-01-01

    A generalized quantum chemical approach for electron transport in molecular devices is developed. It allows one to treat devices where the metal electrodes and the molecule are either chemically or physically bonded on equal footing. An extension to include the vibration motions of the molecule has also been implemented which has produced the inelastic electron-tunneling spectroscopy of molecular electronics devices with unprecedented accuracy. Important information about the structure of the molecule and of metal-molecule contacts that are not accessible in the experiment are revealed. The calculated current-voltage (I-V) characteristics of different molecular devices, including benzene-1,4-dithiolate, octanemonothiolate [H(CH2)8S], and octanedithiolate [S(CH2)8S] bonded to gold electrodes, are in very good agreement with experimental measurements.

  19. 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...

  20. A modified Lagrangian-volumes method to simulate chemical transport in heterogeneous porous media

    NASA Astrophysics Data System (ADS)

    de Dreuzy, J.; Davy, P.

    2008-12-01

    Transport in subsurface environments is conditioned by physical and chemical processes in interaction, the most common being advection and dispersion for the physical processes and sorption for chemical reactions. Several numerical approaches have been developed to solve the complex set of equations governing this type of solute transport. These methods become time consuming in highly heterogeneous porous media having a broad-range velocity distribution. In this paper; we discuss a new efficient Lagrangian method. This method, modified from the Lagrangian-volumes approach, consists in dividing the aqueous phase in elementary volumes moved with the flow and interacting with the solid phase. Like in continuous time random walk algorithms, rather than keeping a constant time step, the time is adapted to the mesh velocity and computed so that an elementary volume crosses a mesh in a single numerical step. The modified Lagrangian-volume approach remains thus efficient whatever the velocity field. This approach is also highly flexible as it achieves a decoupling of the physical and chemical processes at the elementary volume scale, i.e. at the lowest considered scale, giving way to model virtually all possible chemical reactions. The modified Lagrangian volume approach can model both reactions between species in solution and sorption reactions. Reactions in solution are modeled by exchanges of solutes between Lagrangian volumes. For sorption reactions, the surface-to-volume ratio variability, a key parameter of sorption reactions, is accounted for by deforming the shape of the elementary volume. We implement and validate the algorithm on the specific case of the nonlinear Freundlich kinetic sorption in highly heterogeneous lognormal and multifractal permeability fields.

  1. 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.

  2. Integrating the Chemical Fluxes of Transported Sediments in Large Rivers: AN Attempt on the Ganga

    NASA Astrophysics Data System (ADS)

    France-Lanord, C.; Lupker, M.; Lavé, J.; Bouchez, J.; Galy, V.; Gaillardet, J.; Metivier, F.

    2010-12-01

    Large rivers are the main conveyors of continental material to the oceans through sediment and dissolved fluxes. The redistribution of elements is fundamental in Earth surface processes and central in various biogeochemical cycles. The nature of the exported continental material is a function of the processes operating in the river’s catchment. From external forcings such as climate, tectonics or anthropogenic activity, having a strong control on erosion and weathering, to transport dynamics and sediment storage in flood plain, chemical elements are segregated from source to sink. Evaluating the composition of the exported sediments is thus essential in our understanding of large scale processes. This raises the problem of integrating the sediments chemical composition both spatially in a river section and temporally during the hydrogram. Efforts have been made to precisely determine de total flux of transported material of major world rivers but the determination of associated chemical solid fluxes is still limited. Also it is now recognized that surface sediments composition does not reflect in most cases the average sediment composition (Galy et al. 2007; Bouchez et al. in press). Nevertheless, global chemical budgets still rely on simple averaging of the available data counting mainly on surface sediment samples. Hydrodynamic sorting of minerals exerts a first order control on the chemistry of sediments in the water column, segregating elements according to the flow dynamics and the water depth. This has to be accounted for in order to derive accurate chemical fluxes. This work is an attempt to integrate the chemical flux of the sediments transported by the Ganga. The river was sampled at various stages of the monsoon at the same location in Bangladesh between 2004 and 2010 using a point sampler to collect sediments throughout the water column. Sediments were analyzed for major elements and grain-size. The systematic use of Acoustic Doppler Current Profilers

  3. 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

  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, 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

  5. A reaction-based paradigm to model reactive chemical transport in groundwater with general kinetic and equilibrium reactions.

    PubMed

    Zhang, Fan; Yeh, Gour-Tsyh; Parker, Jack C; Brooks, Scott C; Pace, Molly N; Kim, Young-Jin; Jardine, Philip M; Watson, David B

    2007-06-16

    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 N(E) equilibrium reactions and a set of reactive transport equations of M-N(E) 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.

  6. MOZART, a global chemical transport model for ozone and related chemical tracers: 2. Model results and evaluation

    NASA Astrophysics Data System (ADS)

    Hauglustaine, D. A.; Brasseur, G. P.; Walters, S.; Rasch, P. J.; Müller, J.-F.; Emmons, L. K.; Carroll, M. A.

    1998-11-01

    In this second of two companion papers, we present results from a new global three-dimensional chemical transport model, called MOZART (model for ozone and related chemical tracers). MOZART is developed in the framework of the National Center for Atmospheric Research (NCAR) Community Climate Model (CCM) and includes a detailed representation of tropospheric chemistry. The model provides the distribution of 56 chemical species at a spatial resolution of 2.8° in both latitude and longitude, with 25 levels in the vertical (from the surface to level of 3 mbar) and a time step of 20 min. The meteorological information is supplied from a 2-year run of the NCAR Community Climate Model. The simulated distributions of ozone (O3) and its precursors are evaluated by comparison with observational data. The distribution of methane, nonmethane hydrocarbons (NMHCs), and CO are generally well simulated by the model. The model evaluation in the tropics stresses the need for a better representation of biomass burning emissions in order to evaluate the budget of carbon monoxide, nitrogen species, and ozone with more accuracy in these regions, MOZART reproduces the NO observations in most parts of the troposphere. Nitric acid, however, is overestimated over the Pacific by up to a factor of 10 and over continental regions by a factor of 2-3. Discrepancies are also found in the simulation of PAN in the upper troposphere and in biomass burning regions. These results highlight shortcomings in our understanding of the nitrogen budget in the troposphere. The seasonal cycle of ozone in the troposphere is generally well reproduced by the model in comparison with ozone soundings. MOZART tends, however, to underestimate O3 at higher latitudes, and specifically above 300 mbar. The global photochemical production and destruction of ozone in the troposphere are 3018 Tg/yr and 2511 Tg/yr, respectively (net ozone production of 507 Tg/yr). The stratospheric influx of O3 is estimated to be 391 Tg

  7. 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.

  8. Pretreated cheese whey wastewater management by agricultural reuse: chemical characterization and response of tomato plants Lycopersicon esculentum Mill. under salinity conditions.

    PubMed

    Prazeres, Ana R; Carvalho, Fátima; Rivas, Javier; Patanita, Manuel; Dôres, Jóse

    2013-10-01

    The agricultural reuse of pretreated industrial wastewater resulting from cheese manufacture is shown as a suitable option for its disposal and management. This alternative presents attractive advantages from the economic and pollution control viewpoints. Pretreated cheese whey wastewater (CWW) has high contents of biodegradable organic matter, salinity and nutrients, which are essential development factors for plants with moderate to elevated salinity tolerance. Five different pretreated CWW treatments (1.75 to 10.02 dS m(-1)) have been applied in the tomato plant growth. Fresh water was used as a control run (average salinity level=1.44 dS m(-1)). Chemical characterization and indicator ratios of the leaves, stems and roots were monitored. The sodium and potassium leaf concentrations increased linearly with the salinity level in both cultivars, Roma and Rio Grande. Similar results were found in the stem sodium content. However, the toxic sodium accumulations in the cv. Roma exceeded the values obtained in the cv. Rio Grande. In this last situation, K and Ca uptake, absorption, transport and accumulation capacities were presented as tolerance mechanisms for the osmotic potential regulation of the tissues and for the ion neutralization. Consequently, Na/Ca and Na/K ratios presented lower values in the cv. Rio Grande. Na/Ca ratio increased linearly with the salinity level in leaves and stems, regardless of the cultivar. Regarding the Na/K ratio, the values demonstrated competition phenomena between the ions for the cv. Rio Grande. Despite the high chloride content of the CWW, no significant differences were observed for this nutrient in the leaves and stems. Thus, no nitrogen deficiency was demonstrated by the interaction NO3(-)/Cl(-). Nitrogen also contributes to maintain the water potential difference between the tissues and the soil. Na, P, Cl and N radicular concentrations were maximized for high salinity levels (≥2.22 dS m(-1)) of the pretreated CWW.

  9. 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

  10. 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.

  11. 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

  12. Assessing the Source-to-Stream Transport of Benzotriazoles during Rainfall and Snowmelt in Urban and Agricultural Watersheds.

    PubMed

    Parajulee, Abha; Lei, Ying Duan; De Silva, Amila O; Cao, Xiaoshu; Mitchell, Carl P J; Wania, Frank

    2017-04-07

    While benzotriazoles (BTs) are ubiquitous in urban waters, their sources and transport remain poorly characterized. We aimed to elucidate the origin and hydrological pathways of BTs in Toronto, Canada, by quantifying three BTs, electrical conductivity, and δ(18)O in high-frequency streamwater samples taken during two rainfall and one snowmelt event in two watersheds with contrasting levels of urbanization. Average concentrations of total BTs (∑BT) were 1.3 to 110 times higher in the more urbanized Mimico Creek watershed relative to the primarily agricultural and suburban Little Rouge Creek. Strong correlations between upstream density of major roads and total BT concentrations or BT composition within all events implicate vehicle fluids as the key source of BTs in both watersheds. Sustained historical releases of BTs within the Mimico Creek watershed have likely led to elevated ∑BT in groundwater, with elevated concentrations observed during baseflow that are diluted by rainfall and surface runoff. In contrast, relatively constant concentrations, caused by mixing of equally contaminated baseflow and rainfall/surface runoff, are observed in the Little Rouge Creek throughout storm hydrographs, with an occasional first flush occurring at a subsite draining suburban land. During snowmelt, buildup of BTs in roadside snowpiles and preferential partitioning of BTs to the liquid phase of a melting snowpack leads to early peaks in ∑BT in both streams, except the sites in the Little Rouge Creek with low levels of vehicle traffic. Overall, a history of BT release and land use associated with urbanization have led to higher levels of BTs in urban areas and provide a glimpse into future BT dynamics in mixed use, (sub)urbanizing areas.

  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. Morphological, Chemical Surface, and Diffusive Transport Characterizations of a Nanoporous Alumina Membrane

    PubMed Central

    Vázquez, María I.; Romero, Virgina; Vega, Victor; García, Javier; Prida, Victor M.; Hernando, Blanca; Benavente, Juana

    2015-01-01

    Synthesis of a nanoporous alumina membrane (NPAM) by the two-step anodization method and its morphological and chemical surface characterization by analyzing Scanning Electron Microscopy (SEM) micrographs and X-Ray Photoelectron Spectroscopy (XPS) spectra is reported. Influence of electrical and diffusive effects on the NaCl transport across the membrane nanopores is determined from salt diffusion measurements performed with a wide range of NaCl concentrations, which allows the estimation of characteristic electrochemical membrane parameters such as the NaCl diffusion coefficient and the concentration of fixed charges in the membrane, by using an appropriated model and the membrane geometrical parameters (porosity and pore length). These results indicate a reduction of ~70% in the value of the NaCl diffusion coefficient through the membrane pores with respect to solution. The transport number of ions in the membrane pores (Na+ and Cl−, respectively) were determined from concentration potential measurements, and the effect of concentration-polarization at the membrane surfaces was also considered by comparing concentration potential values obtained with stirred solutions (550 rpm) and without stirring. From both kinds of results, a value higher than 0.05 M NaCl for the feed solution seems to be necessary to neglect the contribution of electrical interactions in the diffusive transport. PMID:28347115

  15. Projections of Demand for Waterborne Transportation, Ohio River Basin, 1980, 1990, 2000, 2020, 2040. Volume 8. Group VI. Chemicals & Chemical Fertilizers.

    DTIC Science & Technology

    1980-12-01

    provides three basic nutrients to the soil: nitrogen, potash , and phosphate. Movements of intermediate fertilizer materials are shipments of products...inexpensively stored and moved. b. Potassic Chemicals Fertilizers Potassic chemicals include muriate of potash , potassium muri- ate, potassium sulfate...sulfate of potash magnesia, and vegetable potash . These materials can move by any mode of transportation. 1. U.S. Army Corps of Engineers, Waterborne

  16. 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

  17. Time Resolved Chemical Analysis of Anthropogenic Aerosols in Norway, a Study of Long-Range Transport

    NASA Astrophysics Data System (ADS)

    Indresand, H.; Waddell, J. A.; Cliff, S. S.; Perry, K. D.; Yttri, K.; Dye, C.; Kelly, P. B.

    2004-12-01

    Anthropogenic fine particulate matter produced by the burning of carbonaceous fuels is a complex issue that transcends political and geographical boundaries. Anthropogenic fine aerosols are tranported to Norway from the British Isles and continental Europe. Two 3-DRUM impactor samplers were used to collect size-separated PM2.5 aerosol samples (2.5 - 1.15, 1.15-0.34, 0.34-0.1 µm Da) at two sites, Birkenes and Kjeller for a six-week period in June and July. The samples were analyzed with three-hour time resolution by Synchrotron X-ray Fluorescence and Time-of-Flight Mass Spectrometry. S-XRF determined three-hour mass averages for elements heavier than Na, while the TOFMS was used for chemical speciation as a function of time and size. Positive ion spectra showed K+, Na+ and organic molecular ions between 200 - 400 m/z. Negative ion spectra detected carbon clusters, Cl-, Br-, I-, NO2-, NO3-, CN-, CNO-, SO3-, HSO4-, methyl sulfonic acid (MSA), and various organic acid salts. The chemical signature of the sources are identified using high time resolution in combination with air mass back trajectories. Chemical modification of the aerosol during transport is examined as a function of particle size.

  18. 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.

  19. 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.

  20. 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

  1. 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.

  2. Sensitivity of transatlantic dust transport to chemical aging and related atmospheric processes

    NASA Astrophysics Data System (ADS)

    Abdelkader, Mohamed; Metzger, Swen; Steil, Benedikt; Klingmüller, Klaus; Tost, Holger; Pozzer, Andrea; Stenchikov, Georgiy; Barrie, Leonard; Lelieveld, Jos

    2017-03-01

    We present a sensitivity study on transatlantic dust transport, a process which has many implications for the atmosphere, the ocean and the climate. We investigate the impact of key processes that control the dust outflow, i.e., the emission flux, convection schemes and the chemical aging of mineral dust, by using the EMAC model following Abdelkader et al. (2015). To characterize the dust outflow over the Atlantic Ocean, we distinguish two geographic zones: (i) dust interactions within the Intertropical Convergence Zone (ITCZ), or the dust-ITCZ interaction zone (DIZ), and (ii) the adjacent dust transport over the Atlantic Ocean (DTA) zone. In the latter zone, the dust loading shows a steep and linear gradient westward over the Atlantic Ocean since particle sedimentation is the dominant removal process, whereas in the DIZ zone aerosol-cloud interactions, wet deposition and scavenging processes determine the extent of the dust outflow. Generally, the EMAC simulated dust compares well with CALIPSO observations; however, our reference model configuration tends to overestimate the dust extinction at a lower elevation and underestimates it at a higher elevation. The aerosol optical depth (AOD) over the Caribbean responds to the dust emission flux only when the emitted dust mass is significantly increased over the source region in Africa by a factor of 10. These findings point to the dominant role of dust removal (especially wet deposition) in transatlantic dust transport. Experiments with different convection schemes have indeed revealed that the transatlantic dust transport is more sensitive to the convection scheme than to the dust emission flux parameterization. To study the impact of dust chemical aging, we focus on a major dust outflow in July 2009. We use the calcium cation as a proxy for the overall chemical reactive dust fraction and consider the uptake of major inorganic acids (i.e., H2SO4, HNO3 and HCl) and their anions, i.e., sulfate (SO42-), bisulfate (HSO4

  3. 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...

  4. 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.

  5. 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

  6. Introductory lecture: atmospheric organic aerosols: insights from the combination of measurements and chemical transport models.

    PubMed

    Pandis, Spyros N; Donahue, Neil M; Murphy, Benjamin N; Riipinen, Ilona; Fountoukis, Christos; Karnezi, Eleni; Patoulias, David; Skyllakou, Ksakousti

    2013-01-01

    The formation, atmospheric evolution, properties, and removal of organic particulate matter remain some of the least understood aspects of atmospheric chemistry despite the importance of organic aerosol (OA) for both human health and climate change. Here, we summarize our recent efforts to deal with the chemical complexity of the tens of thousands of organic compounds in the atmosphere using the volatility-oxygen content framework (often called the 2D-Volatility Basis Set, 2D-VBS). Our current ability to measure the ambient OA concentration as a function of its volatility and oxygen to carbon (O:C) ratio is evaluated. The combination of a thermodenuder, isothermal dilution and Aerosol Mass Spectrometry (AMS) together with a mathematical aerosol dynamics model is a promising approach. The development of computational modules based on the 2D-VBS that can be used in chemical transport models (CTMs) is described. Approaches of different complexity are tested against ambient observations, showing the challenge of simulating the complex chemical evolution of atmospheric OA. The results of the simplest approach describing the net change due to functionalization and fragmentation are quite encouraging, reproducing both the observed OA levels and O : C in a variety of conditions. The same CTM coupled with source-apportionment algorithms can be used to gain insights into the travel distances and age of atmospheric OA. We estimate that the average age of OA near the ground in continental locations is 1-2 days and most of it was emitted (either as precursor vapors or particles) hundreds of kilometers away. Condensation of organic vapors on fresh particles is critical for the growth of these new particles to larger sizes and eventually to cloud condensation nuclei (CCN) sizes. The semivolatile organics currently simulated by CTMs are too volatile to condense on these tiny particles with high curvature. We show that chemical aging reactions converting these semivolatile

  7. 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.

  8. Control of Molecular Transport and Chemical Reaction Dynamics in Confined Volumes

    NASA Astrophysics Data System (ADS)

    Collier, Pat

    2010-03-01

    Understanding how confinement, crowding and reduced dimensionality modulate biochemical reactivity and reaction dynamics will aid in the discovery of functionality unique to nanoscale systems. Biochemical reaction kinetics in biomimetic reaction vessels with confined volumes present in microfabricated structures have been determined, including monitoring single-enzyme reaction kinetics in femtoliter-volume (10-15 L) chambers with millisecond mixing times, and the discovery and characterization of shear-induced redistribution of surfactant at the oil-water interface in femtoliter-volume droplets split off from larger aqueous plugs at a microfabricated T-junction, which resulted in increased interfacial adsorption of enzymes. The fabrication capabilities at the Center for Nanophase Materials Sciences at ORNL are extending these studies to nanoscale structures, interfaces and architectures, with the ability to control chemical reaction kinetics with precise spatiotemporal control of molecular/mass transport via integration with microfluidics.

  9. The transport of trace chemicals by planetary waves in the stratosphere. I Steady waves

    NASA Technical Reports Server (NTRS)

    Kurzeja, R. J.

    1981-01-01

    When dissipation is present a forced planetary wave will interact with the zonal flow in the stratosphere and cause acceleration of the zonal wind, mean-zonal diabatic heating and net transport of trace chemicals. Quasi-geostrophic scaling is used to derive expressions relating the above quantities to each other and to wave statistics for steady-state conditions and Newtonian cooling. Numerical calculations are presented for stationary wavenumber 1 which indicate that in the stratosphere the effect of the wave on the mean-zonal quantities is 1/5 to 1/20 that required by observations and models. In the mesosphere the calculated value is roughly 1/20 the required size. Reasons for this discrepancy are discussed.

  10. 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.

  11. 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.

  12. The 5th World Congress of chemical engineering: Technologies critical to a changing World. Volume II: Agriculture, food biotechnology biomedical electric power process safety

    SciTech Connect

    1996-12-31

    Volume 2 of the proceedings from the 5th World Congress of Chemical Engineering covers four major topic areas from which papers were selected for the database: Agriculture, Food; Biotechnology; Electric Power, and Process Safety. Pertinent subtopics include: Renewable Resource Engineering; Special Processes in the Food Industry; Advances in Metabolite Production; Advances in Fermentation and Cell Culture Engineering; Coal and Nuclear Central Station Power Plants; Large Natural Gas Fired Power Stations; Distributed Generation; Potential Impact of Biomass Energy; and Chemical Hazards in Plant Design. 29 papers were selected from Volume 1 for the database.

  13. Limits on the ability of global Eulerian models to resolve intercontinental transport of chemical plumes

    NASA Astrophysics Data System (ADS)

    Eastham, Sebastian D.; Jacob, Daniel J.

    2017-02-01

    Quasi-horizontal chemical plumes in the free troposphere can preserve their concentrated structure for over a week, enabling transport on intercontinental scales with important environmental impacts. Global Eulerian chemical transport models (CTMs) fail to preserve these plumes due to fast numerical dissipation. We examine the causes of this dissipation and how it can be cured. Goddard Earth Observing System (GEOS-5) meteorological data at 0.25° × 0.3125° horizontal resolution and ˜ 0.5 km vertical resolution in the free troposphere are used to drive a worldwide ensemble of GEOS-Chem CTM plumes at resolutions from 0.25° × 0.3125° to 4° × 5°, in both 2-D (horizontal) and 3-D. Two-dimensional simulations enable examination of the sensitivity of numerical dissipation to grid resolution. We show that plume decay is driven by flow divergence and shear, filamenting the plumes until GEOS-Chem's high-order advection scheme cannot resolve gradients and fast numerical diffusion ensues. This divergence can be measured by the Lyapunov exponent (λ) of the flow. Dissipation of plumes is much faster at extratropical latitudes than in the tropics and this can be explained by stronger divergence. The plume decay constant (α) is linearly related to λ, and increasing grid resolution provides only modest benefits toward plume preservation. Three-dimensional simulations show near-complete dissipation of plumes within a few days, independent of horizontal grid resolution and even in the tropics. This is because vertical grid resolution is inadequate in all cases to properly resolve plume gradients. We suggest that finer vertical grid resolution in the free troposphere is essential for models to resolve intercontinental plumes, while current horizontal resolution in these models (˜ 1°) is sufficient.

  14. Transport coefficients of heavy quarks around Tc at finite quark chemical potential

    NASA Astrophysics Data System (ADS)

    Berrehrah, H.; Gossiaux, P. B.; Aichelin, J.; Cassing, W.; Torres-Rincon, J. M.; Bratkovskaya, E.

    2014-11-01

    The interactions of heavy quarks with the partonic environment at finite temperature T and finite quark chemical potential μq are investigated in terms of transport coefficients within the dynamical quasiparticle model (DQPM) designed to reproduce the lattice-QCD (lQCD) results (including the partonic equation of state) in thermodynamic equilibrium. These results are confronted with those of nuclear many-body calculations close to the critical temperature Tc. The hadronic and partonic spatial diffusion coefficients join smoothly and show a pronounced minimum around Tc at μq=0 as well as at finite μq. Close to and above Tc its absolute value matches the lQCD calculations for μq=0 . The smooth transition of the heavy-quark transport coefficients from the hadronic to the partonic medium corresponds to a crossover in line with lattice calculations, and differs substantially from perturbative-QCD calculations which show a large discontinuity at Tc. This indicates that in the vicinity of Tc dynamically dressed massive partons should be the effective degrees of freedom in the quark-gluon plasma.

  15. Mixed brush of chemically and physically adsorbed polymers under shear: inverse transport of the physisorbed species.

    PubMed

    Pastorino, C; Müller, M

    2014-01-07

    We study mixed brushes under shear flow by molecular dynamics simulation with an explicit solvent. The primary brush is formed by chemically grafting polymers to a solid substrate, the secondary brush is comprised of shorter, physically end-adsorbed molecules that can laterally diffuse. By virtue of the immobility of the grafted end-points of the primary brush, its individual macromolecules perform a cyclic motion. If there is a well defined solvent-brush interface, this cyclic motion of the primary brush molecules will collectively result in the reversal of the flow inside of the primary brush. This backflow, linear in the shear rate, gives rise to the transport of the shorter, physically end-adsorbed molecules in the opposite direction of the solvent flow. We discuss which conditions are necessary to observe this counter-intuitive phenomenon. Comparing Poiseuille and Couette flow we demonstrate that the magnitude of the local shear rate at the brush-liquid interface dictates the cyclic motion and concomitant inversion of transport but that these universal effects are independent of the type of driving the flow.

  16. Chemical vapor transport and characterization of MnBi2Se4

    NASA Astrophysics Data System (ADS)

    Nowka, Christian; Gellesch, Markus; Enrique Hamann Borrero, Jorge; Partzsch, Sven; Wuttke, Christoph; Steckel, Frank; Hess, Christian; Wolter, Anja U. B.; Teresa Corredor Bohorquez, Laura; Büchner, Bernd; Hampel, Silke

    2017-02-01

    Layered metal chalcogenides such as MnBi2Se4 are interesting candidates for a wide field of applications such as for thermo- and photoelectrics. High-quality single crystals are necessary in order to investigate their properties which can be prepared by chemical vapor transport (CVT). The CVT of MnBi2Se4 has not been investigated until this point and is subject of the presented paper. We obtained needle-like MnBi2Se4 single crystals with a length up to 15 mm. The magnetic characterization has shown an antiferromagnetic transition around 14 K. Additionally, electrical transport described MnBi2Se4 as a narrow band-gap semiconductor (EGap=0.15 eV). Thermodynamic data for MnBi2Se4 at room temperature were determined to H ° = - 305 KJ ·mol-1 , S=321 J K-1·mol-1 and Cp = 167.568 + 25.979 ·10-3 · TJ ·K-1 ·mol-1 , respectively. Our results on CVT-grown single crystals confirm reported data from literature and complete the data set for MnBi2Se4.

  17. 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.

  18. 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.

  19. 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

  20. 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 ...

  1. 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.

  2. Chemical vapor transport and solid-state exchange synthesis of new copper selenite bromides

    NASA Astrophysics Data System (ADS)

    Charkin, Dmitri O.; Kayukov, Roman A.; Zagidullin, Karim A.; Siidra, Oleg I.

    2017-02-01

    A new dimorphic copper selenite bromide, Cu5(SeO3)4Br2 was obtained via chemical transport reactions. α-Cu5(SeO3)4Br2, monoclinic (1m) and β-Cu5(SeO3)4Br2, triclinic (1a) polymorphs were produced simultaneously upon reaction of amorphous, partially dehydrated copper selenite and copper bromide. 1m is similar to Cu5(SeO3)4Cl2, whereas 1a is distantly related to Ni5(SeO3)4Br2 and Co5(SeO3)4Br2. Attempts to reproduce synthesis of 1a via exchange reaction between Na2SeO3 and CuBr2 resulted in a new Na2[Cu7O2](SeO3)4Br4 (2). Current study demonstrates for the first time, that both chemical vapor and exchange reactions can be employed in preparation of new selenite halides.

  3. 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

  4. 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

  5. Chemical Processing and Transport in the Stratospheric Vortex and Subvortex from Satellite Measurements and Modeling

    NASA Astrophysics Data System (ADS)

    Santee, Michelle; Manney, Gloria; MacKenzie, Ian; Chipperfield, Martyn; Feng, Wuhu; Sander, Stanley; Froidevaux, Lucien; Livesey, Nathaniel; Bernath, Peter; Walker, Kaley; Boone, Chris

    A suite of atmospheric composition measurements from the Microwave Limb Sounder (MLS) on NASA's Aura satellite and the Atmospheric Chemistry Experiment Fourier Transform Spectrometer (ACE-FTS) on Canada's SCISAT-1 mission is used to study chemical processing in and dispersal of chemically-processed air from the lower stratospheric polar vortices. In particular, interannual and interhemispheric variability in chlorine activation and deactivation are investigated using measurements of ClO, HCl, and ClONO2. Theoretical understanding is assessed by comparing measurements to customized runs of the SLIMCAT 3D chemical transport model. Results are shown from a newly-updated version of the model that incorporates a sophisticated microphysical scheme as a fully-coupled module, allowing polar stratospheric cloud formation and sedimentation to be calculated interactively in full-chemistry simulations. The impact of recently-published ClOOCl absorption cross sections, which yield a stratospheric ClOOCl photolysis rate substantially lower than previous estimates, on the agreement between modelled and measured chlorine species is evaluated. In addition, measurements of HNO3 and O3 and SLIMCAT results are related to mixing diagnostics to track the springtime export of denitrified, ozone-depleted air from the "subvortex", the transition zone (potential temperatures of 350-450 K) between the region above of strong confinement inside the polar vortex and the region below of less restricted exchange with lower-latitude air. Particularly over Antarctica, such mixing of processed air out of the subvortex may significantly affect the composition of the midlatitude lowermost stratosphere and upper troposphere.

  6. Fine particulate matter source apportionment using a hybrid chemical transport and receptor model approach

    NASA Astrophysics Data System (ADS)

    Hu, Y.; Balachandran, S.; Pachon, J. E.; Baek, J.; Ivey, C.; Holmes, H.; Odman, M. T.; Mulholland, J. A.; Russell, A. G.

    2013-10-01

    A hybrid fine particulate matter (PM2.5) source apportionment approach based on a receptor-model (RM) species balance and species specific source impacts from a chemical transport model (CTM) equipped with a sensitivity analysis tool is developed to provide physically- and chemically-consistent relationships between source emissions and receptor impacts. This hybrid approach enhances RM results by providing initial estimates of source impacts from a much larger number of sources than are typically used in RMs, and provides source-receptor relationships for secondary species. Further, the method addresses issues of source collinearities, and accounts for emissions uncertainties. Hybrid method results also provide information on the resulting source impact uncertainties. We apply this hybrid approach to conduct PM2.5 source apportionment at Chemical Speciation Network (CSN) sites across the US. Ambient PM2.5 concentrations at these receptor sites were apportioned to 33 separate sources. Hybrid method results led to large changes of impacts from CTM estimates for sources such as dust, woodstove, and other biomass burning sources, but limited changes to others. The refinements reduced the differences between CTM-simulated and observed concentrations of individual PM2.5 species by over 98% when using a weighted least squared error minimization. The rankings of source impacts changed from the initial estimates, revealing that CTM-only results should be evaluated with observations. Assessment with RM results at six US locations showed that the hybrid results differ somewhat from commonly resolved sources. The hybrid method also resolved sources that typical RM methods do not capture without extra measurement information on unique tracers. The method can be readily applied to large domains and long (such as multi-annual) time periods to provide source impact estimates for management- and health-related studies.

  7. Fine particulate matter source apportionment using a hybrid chemical transport and receptor model approach

    NASA Astrophysics Data System (ADS)

    Hu, Y.; Balachandran, S.; Pachon, J. E.; Baek, J.; Ivey, C.; Holmes, H.; Odman, M. T.; Mulholland, J. A.; Russell, A. G.

    2014-06-01

    A hybrid fine particulate matter (PM2.5) source apportionment approach based on a receptor model (RM) species balance and species specific source impacts from a chemical transport model (CTM) equipped with a sensitivity analysis tool is developed to provide physically and chemically consistent relationships between source emissions and receptor impacts. This hybrid approach enhances RM results by providing initial estimates of source impacts from a much larger number of sources than are typically used in RMs, and provides source-receptor relationships for secondary species. Further, the method addresses issues of source collinearities and accounts for emissions uncertainties. We apply this hybrid approach to conduct PM2.5 source apportionment at Chemical Speciation Network (CSN) sites across the US. Ambient PM2.5 concentrations at these receptor sites were apportioned to 33 separate sources. Hybrid method results led to large changes of impacts from CTM estimates for sources such as dust, woodstoves, and other biomass-burning sources, but limited changes to others. The refinements reduced the differences between CTM-simulated and observed concentrations of individual PM2.5 species by over 98% when using a weighted least-squares error minimization. The rankings of source impacts changed from the initial estimates, further demonstrating that CTM-only results should be evaluated with observations. Assessment with RM results at six US locations showed that the hybrid results differ somewhat from commonly resolved sources. The hybrid method also resolved sources that typical RM methods do not capture without extra measurement information for unique tracers. The method can be readily applied to large domains and long (such as multi-annual) time periods to provide source impact estimates for management- and health-related studies.

  8. 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.

  9. 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

  10. 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.

  11. [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".

  12. 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.

  13. Soil structure, colloids, and chemical transport as affected by short-term reducing conditions: a laboratory study

    NASA Astrophysics Data System (ADS)

    de-Campos, A. B.; Mamedov, A. I.; Huang, C.; Wagner, L. E.

    2008-12-01

    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 effects of short-term reducing conditions on chemical and physical properties of the soils, colloids, and associated chemical/nutrients transport are still not well understood and was the objective of our study. A biogeochemical reactor was built to achieve reducing conditions. Three cultivated and three uncultivated soils with different organic carbon contents were incubated in the reactor for 1 hour and 3 days under anaerobic conditions. Effects of the redox state on soil structure (pore size distribution) and drainable porosity, colloids mobility, and chemical transport were determined using high energy moisture characteristic and analytical methods. After each treatment, the soil solution was collected for redox potential (Eh), pH, and electrical conductivity (EC) measurements, and chemical analysis of metals (Ca, Mg, K), nutrients (N, P), and dissolved organic carbon. Strongly reducing conditions were achieved after 3 days of incubation and were followed by a decrease in soil porosity and an increase in pH, EC, clay dispersion, swelling, colloids mobility, and associated chemical transport. The trend for each soil depended on their initial structural stability and chemical properties. The structure of cultivated soils and the leaching of nutrients and carbon from uncultivated soils were more sensitive to the redox state. A strong correlation was found between changes in Eh and drainable porosity. The role of short-term reducing conditions on changes in redox sensitive elements, organic matter decomposition, pH, and EC and their influence on soil structure and soil particles or colloids/chemical transport for both soil groups are discussed in the paper. This study

  14. Ecological and health risk-based characterization of agricultural soils contaminated with polycyclic aromatic hydrocarbons in the vicinity of a chemical plant in China.

    PubMed

    Liu, Geng; Niu, Junjie; Guo, Wenjiong; An, Xiangsheng; Zhao, Long

    2016-11-01

    Polycyclic aromatic hydrocarbons (PAHs) from chemical plants can cause serious pollution of surrounding agricultural soils. A comprehensive study of agricultural soils was conducted in the vicinity of a chemical plant in China to characterize the soil PAH concentration, as well as their composition and sources. Human health and a screening-level ecological risk assessment were conducted for PAH contamination in agricultural soils. The results showed that the total concentrations of 16 priority PAHs ranged from 250.49 to 9387.26 ng g(-1), with an average of 2780.42 ng g(-1). High molecular weight PAHs (four to six rings) were the dominant component, accounting for more than 60% of all PAHs. Principal component analysis (PCA) and positive matrix factorization model (PMF) suggested that diesel emissions, coal combustion, coke ovens, and fuel combustion and gasoline emissions were the main sources of PAHs in agricultural soils. The ecological risk assessment results based on the effects range-low (ERL), the effects range-median (ERM), and the ecological screening levels (ESL) indicated that the exposure to ∑PAH16 was >ERL, >ERM, and ≥ERL and ESL at 78.1% of the soil sampling stations, and could induce biological effects in mammals. The Bapeq concentrations posed a potential carcinogenic risk to humans. Further risk management and control of soil PAHs in these agricultural soils is required to ensure the safety of the biocoenosis and human health.

  15. 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.

  16. 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.

  17. Effect of chemical interactions in pentachlorophenol mixtures on skin and membrane transport.

    PubMed

    Baynes, Ronald E; Brooks, James D; Mumtaz, Moiz; Riviere, Jim E

    2002-10-01

    Pentachlorophenol (PCP) has been widely used as a pesticide, and topical exposure to a chemical mixture can alter its dermal absorption. The purpose of this study was to evaluate the influence of single and binary solvent systems (ethanol, EtOH, and water), a surfactant (6% sodium lauryl sulfate, SLS), and a rubifacient/vasodilator (1.28% methyl nicotinate, MNA) on PCP membrane transport, and to correlate these effects with physiochemical characteristics of the PCP mixtures. Partitioning, diffusion, and absorption parameters of (14)C-PCP at low (4 microg/cm(2)) and high (40 microg/cm(2)) doses were assessed in porcine skin and silastic membranes in vitro. In these 8-h, flow-through diffusion studies, PCP was dosed with the following vehicles: 100% EtOH, 100% water, 40% EtOH + 60% water, 40% EtOH + 60% water + SLS, 40% EtOH + 60% water + MNA, and 40% EtOH + 60% water + SLS + MNA. PCP absorption ranged from 1.55-15.62% for the high dose and 0.43-7.20% for the low dose. PCP absorption, flux, and apparent permeability were influenced by PCP solubility, and PCP apparent permeability was correlated with log PC (r2 = 0.66). Although PCP was very soluble in pure ethanol (100%), this vehicle evaporated very rapidly, and PCP absorption in ethanol was the lowest with this vehicle when compared to pure water (100%) or aqueous ethanol mixtures in general. MNA had no significant effect on membrane absorption or relative permeability R(P) in aqueous ethanol solutions, but the presence of the surfactant, SLS, significantly reduced PCP absorption and R(P) in both membrane systems. In conclusion, these studies demonstrated that modification in mixture composition with either a solvent and/or a surfactant can influence PCP diffusion in skin. Physicochemical interactions between these mixture components on the skin surface and stratum corneum contributed significantly to PCP transport, and these interactions were identified by simultaneously assessing chemical diffusion in biological

  18. 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

  19. 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…

  20. 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...

  1. 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...

  2. 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...

  3. Do goethite surfaces really control the transport and retention of multi-walled carbon nanotubes in chemically heterogeneous porous media?

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Transport and retention behavior of multiwalled carbon nanotubes (MWCNTs) was studied in mixtures of negatively charged quartz sand (QS) and positively charged goethite-coated sand (GQS) to assess the role of chemical heterogeneity. The linear equilibrium sorption model provided a good description o...

  4. Measurements of Sea Salt Aerosols in the Marine Boundary Layer and Free Troposphere: Vertical Transport and Chemical Transformation

    NASA Astrophysics Data System (ADS)

    Hudson, P. K.; Murphy, D. M.; Cziczo, D. J.; Thomson, D. S.

    2002-12-01

    During the Intercontinental Transport and Chemical Transformation (ITCT) mission (Monterey, CA, spring 2002) nearly 400,000 positive and negative mass spectra of single atmospheric aerosols were acquired using the PALMS (Particle Analysis by Laser Mass Spectrometry) instrument. The primary focus of the mission was to investigate the composition of air masses along the western coast of the United States. Of particular interest to the mission was to study the influence of anthropogenic emissions from Asia on aerosol composition. To accomplish these goals, the WP-3 aircraft, equipped with a suite of instruments including PALMS, covered a large spatial area flying from 0 - 8000 m altitude covering most of the western coastline from Canada to southern California including flights over the San Francisco and Los Angeles metropolitan areas. The in situ measurements of single particle aerosol mass spectra by PALMS allow for good spatial and vertical resolution of the aerosol composition. By observing the changes in aerosol composition as a function of altitude, the vertical transport of sea salt aerosols over marine and urban environments is examined. Using measurements of other chemical tracers along with the aerosol composition, the chemical processing of these aerosols during transport both vertically and inland can be discerned. These results add insight into the transport and chemical evolution of sea salt aerosol.

  5. 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...

  6. 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…

  7. Analysis of UARS data in the Southern Polar Vortex n September, 1992 Using a Chemical Transport Model

    NASA Technical Reports Server (NTRS)

    Chipperfield, M. P.; Santee, M. L.; Froidevaux, L.; Manney, G. L.; Read, W. G.; Waters, J. W.; Roche, A. E.; Russel, J. M.

    1996-01-01

    We have used a new, isentropic-coordinate three-dimensional chemical transport model to investigate the decay of C1O and evolution of other species in the Antarctic polar vortex during September, 1992. The model simulations cover the same southern hemisphere period studied in a companion data paper by Santee et al.

  8. 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...

  9. Transport of reacting solutes in porous media: Relation between mathematical nature of problem formulation and chemical nature of reactions

    USGS Publications Warehouse

    Rubin, Jacob

    1983-01-01

    Examples involving six broad reaction classes show that the nature of transport-affecting chemistry may have a profound effect on the mathematical character of solute transport problem formulation. Substantive mathematical diversity among such formulations is brought about principally by reaction properties that determine whether (1) the reaction can be regarded as being controlled by local chemical equilibria or whether it must be considered as being controlled by kinetics, (2) the reaction is homogeneous or heterogeneous, (3) the reaction is a surface reaction (adsorption, ion exchange) or one of the reactions of classical chemistry (e.g., precipitation, dissolution, oxidation, reduction, complex formation). These properties, as well as the choice of means to describe them, stipulate, for instance, (1) the type of chemical entities for which a formulation's basic, mass-balance equations should be written; (2) the nature of mathematical transformations needed to change the problem's basic equations into operational ones. These and other influences determine such mathematical features of problem formulations as the nature of the operational transport-equation system (e.g., whether it involves algebraic, partial-differential, or integro-partial-differential simultaneous equations), the type of nonlinearities of such a system, and the character of the boundaries (e.g., whether they are stationary or moving). Exploration of the reasons for the dependence of transport mathematics on transport chemistry suggests that many results of this dependence stem from the basic properties of the reactions' chemical-relation (i.e., equilibrium or rate) equations.

  10. 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

  11. 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

  12. 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

  13. 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 ...

  14. Dual-tracer transport experiments in a physically and chemically heterogeneous porous aquifer: effective transport parameters and spatial variability

    NASA Astrophysics Data System (ADS)

    Ptak, T.; Schmid, G.

    1996-08-01

    In order to investigate the effects of reactive transport processes within a heterogeneous porous aquifer, two small-scale forced gradient tracer tests were conducted at the 'Horkheimer Insel' field site. During the experiments, two fluorescent tracers were injected simultaneously in the same fully penetrating groundwater monitoring well, located approximately 10 m from the pumping well. Fluoresceine and Rhodamine WT were used to represent the classes of practically non-sorbing and sorbing solutes, respectively. Multilevel breakthrough curves with a temporal resolution of 1 min were measured for both tracers at different depths within the pumping well using fibre-optic fluorimeters. This paper presents the tracer test design, the fibre-optic fluorimetry instrumentation, the experimental results and the interpretation of the measured multilevel breakthrough curves in terms of temporal moments and effective transport parameters. Significant sorption of Rhodamine WT is apparent from the effective retardation factors. Furthermore, an enhanced tailing of Rhodamine WT breakthrough curves is observed, which is possibly caused by a variability of aquifer sorption properties. The determined effective parameters are spatially variable, suggesting that a complex numerical flow and transport modelling approach within a stochastic framework will be needed to adequately describe the transport behaviour observed in the two experiments. Therefore, the tracer test results will serve in future work for the validation of numerical stochastic transport simulations taking into account the spatial variability of hydraulic conductivity and sorption-related aquifer properties.

  15. Influence of sonophoresis and chemical penetration enhancers on percutaneous transport of penbutolol sulfate.

    PubMed

    Ita, Kevin B; Popova, Inna E

    2016-12-01

    The effect of ultrasound and chemical penetration enhancers on transcutaneous flux of penbutolol sulfate across split-thickness porcine skin was investigated. Penbutolol sulfate is a potent, noncardioselective beta-blocker, which is used for the management of hypertension. The drug is one of the most lipid soluble of the β-adrenoceptor antagonists used clinically. It has an n-octanol/pH 7.4 buffer partition coefficient of 179 compared to a value of 22 for propranolol. The amount of penbutolol sulfate transported across the skin is low. In this project, we studied the effect of sonophoresis and chemical penetration enhancers on transdermal delivery of penbutolol sulfate. Low-frequency sonophoresis at a frequency of 20 kHz increased transcutaneous flux of penbutolol sulfate by 3.5-fold (27.37 ± μg cm(-2) h(-1)) compared to passive delivery (7.82 ± 1.72 μg cm(-2) h(-1)). We also investigated the effect of 50% ethanol, 1% limonene and 2% isopropyl myristate (IPM) on transcutaneous permeation of penbutolol sulfate. IPM, ethanol and limonene at the concentration of 1%, 50% and 2%, respectively, increased the steady-state flux values of penbutolol sulfate 2.2- (17.07 ± 3.24 μg cm(-2) h(-1)), 2.6 - (19.40 ± 6.40 μg cm(-2) h(-1)) and 3.4-times (26.38 ± 5.01 μg cm(-2) h(-1)) compared to passive delivery (7.76 ± 2.9 μg cm(-2) h(-1)). The results demonstrate that although there were slight increases in flux values, ultrasound, ethanol, limonene and IPM did not significantly enhance the transdermal delivery of penbutolol sulfate. Future studies will examine ways of optimizing sonophoretic and chemical enhancer parameters to achieve flux enhancement.

  16. Evidences for redox reaction driven charge transfer and mass transport in metal-assisted chemical etching of silicon

    PubMed Central

    Kong, Lingyu; Dasgupta, Binayak; Ren, Yi; Mohseni, Parsian K.; Hong, Minghui; Li, Xiuling; Chim, Wai Kin; Chiam, Sing Yang

    2016-01-01

    In this work, we investigate the transport processes governing the metal-assisted chemical etching (MacEtch) of silicon (Si). We show that in the oxidation of Si during the MacEtch process, the transport of the hole charges can be accomplished by the diffusion of metal ions. The oxidation of Si is subsequently governed by a redox reaction between the ions and Si. This represents a fundamentally different proposition in MacEtch whereby such transport is understood to occur through hole carrier conduction followed by hole injection into (or electron extraction from) Si. Consistent with the ion transport model introduced, we showed the possibility in the dynamic redistribution of the metal atoms that resulted in the formation of pores/cracks for catalyst thin films that are ≲30 nm thick. As such, the transport of the reagents and by-products are accomplished via these pores/cracks for the thin catalyst films. For thicker films, we show a saturation in the etch rate demonstrating a transport process that is dominated by diffusion via metal/Si boundaries. The new understanding in transport processes described in this work reconcile competing models in reagents/by-products transport, and also solution ions and thin film etching, which can form the foundation of future studies in the MacEtch process. PMID:27824123

  17. Evidences for redox reaction driven charge transfer and mass transport in metal-assisted chemical etching of silicon

    NASA Astrophysics Data System (ADS)

    Kong, Lingyu; Dasgupta, Binayak; Ren, Yi; Mohseni, Parsian K.; Hong, Minghui; Li, Xiuling; Chim, Wai Kin; Chiam, Sing Yang

    2016-11-01

    In this work, we investigate the transport processes governing the metal-assisted chemical etching (MacEtch) of silicon (Si). We show that in the oxidation of Si during the MacEtch process, the transport of the hole charges can be accomplished by the diffusion of metal ions. The oxidation of Si is subsequently governed by a redox reaction between the ions and Si. This represents a fundamentally different proposition in MacEtch whereby such transport is understood to occur through hole carrier conduction followed by hole injection into (or electron extraction from) Si. Consistent with the ion transport model introduced, we showed the possibility in the dynamic redistribution of the metal atoms that resulted in the formation of pores/cracks for catalyst thin films that are ≲30 nm thick. As such, the transport of the reagents and by-products are accomplished via these pores/cracks for the thin catalyst films. For thicker films, we show a saturation in the etch rate demonstrating a transport process that is dominated by diffusion via metal/Si boundaries. The new understanding in transport processes described in this work reconcile competing models in reagents/by-products transport, and also solution ions and thin film etching, which can form the foundation of future studies in the MacEtch process.

  18. 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.

  19. The impact of horizontal transport on the chemical composition in the tropopause region: lightning NOx and streamers

    NASA Astrophysics Data System (ADS)

    Grewe, V.; Shindell, D. T.; Eyring, V.

    2004-01-01

    The chemical composition of the region of the extra-tropical tropopause is influenced by chemistry and transport processes of either troposphere and stratosphere. On the basis of simulations with the coupled chemistry-climate model ECHAM4.L39(DLR)/CHEM two specific chemistry-transport interactions are investigated aiming to determine their importance for the ozone budget in the tropopause region. First, the transport and chemistry of nitrogen oxides from tropical lightning are analyzed. Second, the impact of low ozone air masses transported from the tropics into higher latitudes by wave breaking events (so-called streamers) is investigated. The first mechanism leads to an increase of ozone in the order of 5-10%. This additional ozone is not only formed in the tropical upper troposphere and then transported into the lower-most stratosphere (LMS), but it is also produced in the LMS, where the production is small but the residence time is long. The second mechanism is only important in the area 100-30 hPa, where ozone is not solely chemically controlled. In the lowest stratosphere at around 30°N and 30°S ozone decreases by up to 80%. In the tropopause region ozone decreases by 30% in summer and 50% in winter. The analysis clearly shows that the interactions of transport and chemistry in the tropopause region are highly complex and a simulation of that area requests a reasonable representation of the troposphere and the stratosphere.

  20. Transport model of chemical secretion process for tracking exocytotic event dynamics using electroanalysis.

    PubMed

    Fan, Tai-Hsi; Fedorov, Andrei G

    2004-08-01

    A unified model is developed to analyze the key features of the chemical secretion process observed in experimental studies of various vesicles with application to electroanalytical measurements of vesicular exocytosis. The intimately coupled dynamics and kinetics are simultaneously resolved based on continuum fluid flow, mass transport, and linear elasticity theories combined with biomembrane mechanics. We report three case studies of exocytosis, including a large electroporated granule of the mast cell, a small and clear synaptic vesicle, and a medium size vesicle in the chromaffin cell. The simulation results for each case are compared with electroanalytical measurements from the literature. The results provide a theoretical ground for defining the rate-controlling step(s) of an exocytotic sequence, allowing interpretation of electroanalysis data. Thus, it provides a tool for theoretical verification of competing hypotheses of what controls/limits messenger release during exocytosis. Simulations show that the pore size, the pore opening velocity, and the swelling dynamics of the granule matrix play the key roles in controlling the messenger release kinetics.

  1. 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.

  2. 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.

  3. 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.

  4. Measurement of gas transport through fiber preforms and densified composites for chemical vapor infiltration

    SciTech Connect

    Starr, T.L.; Hablutzel, N.

    1998-05-01

    Gas transport via pressure-driven permeation or via concentration-driven diffusion is a key step in the chemical vapor infiltration (CVI) process. This paper describes methods for the measurement of these properties for CVI preforms and partially infiltrated composites. Results are presented for Nicalon-fiber cloth layup preforms and composites, Nextel-fiber braid preforms and composites, and a Nicalon-fiber three-dimensional (3-D) weave composite. The permeability of Nicalon cloth layup preforms is strongly dependent on the packing density over the range of 29--40 vol% but is only weakly dependent on the orientation of the alternating cloth layers. The permeability of Nextel braid preforms is dependent on the thread count and the weight for cloths with similar construction and packing density. The gas permeability of the finer wave (6.3 tows/cm (16 tows/in.)) is approximately one-half that of the coarser weave (3.5 tows/cm (9 tows/in.)). Results are reported for a small number of infiltrated composites with Nextel fiber reinforcement. Attempts to mount a Nicalon-fiber 3-D weave preform specimen have been unsuccessful. Results for a small number of composite specimens with 3-D weave reinforcement are reported.

  5. 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.

  6. Stratospheric Sulphur - 3D Chemical Transport Model Simulations and MIPAS/ENVISAT Satellite Measurements

    NASA Astrophysics Data System (ADS)

    Günther, Annika; Höpfner, Michael; Sinnhuber, Björn-Martin; Stiller, Gabriele; Clarmann, Thomas

    2016-04-01

    In this study processes that regulate the atmospheric distribution, and the budget of carbonyl sulphide (OCS), sulphur dioxide (SO2) and stratospheric sulphate aerosols are investigated in the upper troposphere / lower stratosphere. Sulphate aerosols impact the Earth's climate by backscattering parts of the incoming solar radiation. This negative radiative forcing can lead to reduced surface temperatures and is thought of as one reason for the recent global warming "hiatus". Our study is based on the comparison of modeled and observed data. An isentropic chemical transport model is used, spanning the region from 330 to 3000 K potential temperature (~ 8 - 66 km), driven by ERA-Interim Reanalysis data. The simulations are compared to observations from MIPAS (Michelson Interferometer for Passive Atmospheric Sounding), a limb sounder on the satellite ENVISAT that was operational from July 2002 to April 2012. The focus of our study lies on volcanically emitted SO2 and its dispersion, as main precursor for sulphate aerosol during volcanically perturbed times, with its simulated distribution and lifetime, in comparison to MIPAS SO2 measurements. Moreover data for OCS, as the main source for stratospheric sulphur during volcanically quiescent periods. Furthermore, first results of sulphuric aerosol-mass retrievals from MIPAS are presented. These will be combined with the gaseous sulphur species to obtain a global budget of stratospheric sulphur.

  7. 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

  8. Performance and cost of energy transport and storage systems for dish applications using reversible chemical reactions

    NASA Astrophysics Data System (ADS)

    Schredder, J. M.; Fujita, T.

    1984-10-01

    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.

  9. Synthesis inversion of atmospheric CO2 using the NIRE chemical transport model

    NASA Astrophysics Data System (ADS)

    Taguchi, Shoichi

    Seasonal variations of CO2 emissions from the land biota and oceans are retrieved by use of an inverse method. Concentrations of CO2, computed by an atmospheric chemical transport model (NIRE-CTM-93), are fitted to the observed CO2 concentrations in terms of annual mean concentrations between 1984 to 1985, one-year period components, half-year components, and a global trend averaged over the years 1979 to 1996. The emissions due to fossil fuel combustion, those from land biota consisting of thirteen land areas, and those from the ocean consisting of twelve oceanic areas, are considered. The problem is solved by a least squares method, using singular value decomposition. A prior estimate of the emissions due to fossil fuel combustion is used as a tight constraint. When the annual mean emission, the net flux from the land biota during the growing season, and the net flux from the ocean are loosely constrained to zero, the solution indicates that areas consist of two groups. That is, those areas with relatively reliable estimates and those without. No reliable estimates are obtained for Africa, tropical and South America, tropical Asia, the tropical and the South Atlantic Ocean, and the western tropical Pacific. A reasonable global budget is not obtained due to unreliable estimates. The amplitude of the seasonal variations over middle-latitude North America is found to be less than that of some tropical land areas.

  10. Synthesis of selenium doted pyrite single crystals prepared by chemical vapor transport

    NASA Astrophysics Data System (ADS)

    Diener, Alexander; Köppe, Ralf

    2012-06-01

    Selenium is of environmental concern due to a possible exposure of 79Se radionuclide from a high-level nuclear waste repository to the biosphere or enlarged concentrations in soils and lakes or wetlands, threatening to health of vertebrates. Pyrite on the contrary is the most common iron sulfide on earth's surface and noted for the incorporation of trace elements into its structure. In this study, we report the development of a high temperature synthesis of pure selenium doted pyrite, using solid AlBr3, Fe0, S0 and Se0 by means of a chemical vapor transport reaction in a 2-zone furnace with a gradient of 700 °C to 600 °C in a two reaction step. The amount of 1.1 wt% of homogeneously distributed selenium became incorporated into pyrite single-crystals with a size up to 0.5 cm in diameter. X-ray absorption fine-structure investigations were performed for the determination of the valence state and structural bonding of incorporated Se into pyrite. These reveal the predominant incorporation of Se0 into pyrite structure without further bonding. This result indicates that the formation of a FeSxSey condensed matter, accompanied with a substitution of sulfur by selenium, is not likely.

  11. MS-2 and poliovirus transport in porous media: Hydrophobic effects and chemical perturbations

    NASA Astrophysics Data System (ADS)

    Bales, Roger C.; Li, Shimin; Maguire, Kimberly M.; Yahya, Moyasar T.; Gerba, Charles P.

    1993-04-01

    In a series of pH 7 continuous-flow column experiments, removal of the bacteriophage MS-2 by attachment to silica beads had a strong, systematic dependence on the amount of hydrophobic surface present on the beads. With no hydrophobic surface, removal of phage at pH 5 was much greater than at pH 7. Release of attached phage at both pH values did occur, but was slow; breakthrough curves exhibited tailing. Poliovirus attached to silica beads at pH 5.5 much more than at pH 7.0, and attachment was also slowly reversible. Time scales for phage and poliovinis attachment were of the order of hours. The sticking efficiency factor (α), reflecting microscaie physicochemical influences on virus attachment, was in the range of 0.0007-0.02. Phage release was small but measurable under steady state conditions. Release was enhanced by lowering ionic strength and by introducing beef extract, a high-ionic-strength protein solution. Results show that viruses experience reversible attachment/detachment (sometimes termed sorption), that large chemical perturbations are needed to induce rapid virus detachment, and that viruses should be quite mobile in sandy porous media. Even small amounts of hydrophobic organic material in the porous media (≥0.001%) can retard virus transport.

  12. 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

  13. 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.

  14. Representations of transport, convection, and the hydrologic cycle in chemical transport models: Implications for the modeling of short-lived and soluble species

    NASA Astrophysics Data System (ADS)

    Rasch, P. J.; Mahowald, N. M.; Eaton, B. E.

    1997-12-01

    We compare chemical transport simulations performed in a model using archived meteorological data (an off-line transport model) to those performed in a model in which the meteorological data are predicted every time step (an on-line model). We identify the errors associated with using data sampled at timescales much longer than those operating in the atmosphere or in the on-line model, and strategies for ameleorating those errors. The evaluation is performed in the context of a global off-line chemical transport model called the Model of Atmospheric Transport and Chemistry (MATCH) for three test problems: (1) the passive advection of blobs initially concentrated in the lower and upper troposphere; (2) the surface emission of radon and its decay to lead; and (3) the removal of lead from the atmosphere by wet and dry deposition processes. These problems exercise the important processes of transport by resolved scale winds, rapid transport by smaller scale convection processes, and wet removal (which depends on the representation of the hydrologic cycle). We show that the errors in off-line model simulations (compared to the on-line simulations) can be made small when the sampling interval is order 6 hours or less. We also show that one can accurately reproduce the subgrid-scale processes within the off-line model, rather than needing to archive the results of those processes as input to the off-line model. This suggests that for the spatial and temporal scales treated in global models it is possible to treat many problems nearly as accurately in an off-line mode as one can with an on-line treatment.

  15. 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

  16. 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.

  17. The Global Food System as a Transport Pathway for Hazardous Chemicals: The Missing Link between Emissions and Exposure

    PubMed Central

    Ng, Carla A.; von Goetz, Natalie

    2016-01-01

    Background: Food is a major pathway for human exposure to hazardous chemicals. The modern food system is becoming increasingly complex and globalized, but models for food-borne exposure typically assume locally derived diets or use concentrations directly measured in foods without accounting for food origin. Such approaches may not reflect actual chemical intakes because concentrations depend on food origin, and representative analysis is seldom available. Processing, packaging, storage, and transportation also impart different chemicals to food and are not yet adequately addressed. Thus, the link between environmental emissions and realistic human exposure is effectively broken. Objectives: We discuss the need for a fully integrated treatment of the modern industrialized food system, and we propose strategies for using existing models and relevant supporting data sources to track chemicals during production, processing, packaging, storage, and transport. Discussion: Fate and bioaccumulation models describe how chemicals distribute in the environment and accumulate through local food webs. Human exposure models can use concentrations in food to determine body burdens based on individual or population characteristics. New models now include the impacts of processing and packaging but are far from comprehensive. We propose to close the gap between emissions and exposure by utilizing a wider variety of models and data sources, including global food trade data, processing, and packaging models. Conclusions: A comprehensive approach that takes into account the complexity of the modern global food system is essential to enable better prediction of human exposure to chemicals in food, sound risk assessments, and more focused risk abatement strategies. Citation: Ng CA, von Goetz N. 2017. The global food system as a transport pathway for hazardous chemicals: the missing link between emissions and exposure. Environ Health Perspect 125:1–7; http://dx.doi.org/10.1289/EHP

  18. 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.

  19. Ground-water flow, geochemistry, and effects of agricultural practices on nitrogen transport at study sites in the Piedmont and Coastal Plain physiographic provinces, Patuxent River basin, Maryland

    USGS Publications Warehouse

    McFarland, E. Randolph

    1997-01-01

    In an effort to improve water quality in Chesapeake Bay, agricultural practices are being promoted that are intended to reduce contaminant transport to the Bay. The effects of agricultural practices on nitrogen transport were assessed at two 10-acre study sites in the Patuxent River basin, Maryland, during 1986-92. Nitrogen load was larger in ground water than in surface runoff at both sites. At the study site in the Piedmont Province, nitrogen load in ground water decreased from 12 to 6 (lb/acre)/yr (pound per acre per year) as corn under no-till cultivation was replaced by no-till soybeans, continuous alfalfa, and contoured strip crops alternated among corn, alfalfa, and soybeans. At the study site in the Coastal Plain Province, no-till soybeans resulted in a nitrogen load in ground water of 12.55 (lb/acre)/yr, whereas conventional-till soybeans resulted in a nitrogen load in ground water of 11.51 (lb/acre)/yr.

  20. 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.

  1. Transport of chemical tracers from the boundary layer to stratosphere associated with the dynamics of the Asian summer monsoon

    NASA Astrophysics Data System (ADS)

    Pan, Laura L.; Honomichl, Shawn B.; Kinnison, Douglas E.; Abalos, Marta; Randel, William J.; Bergman, John W.; Bian, Jianchun

    2016-12-01

    Chemical transport associated with the dynamics of the Asian summer monsoon (ASM) system is investigated using model output from the National Center for Atmospheric Research (NCAR) Whole Atmosphere Community Climate Model run in specified dynamics mode. The 3-D day-to-day behavior of modeled carbon monoxide is analyzed together with dynamical fields and transport boundaries to identify preferred locations of uplifting from the boundary layer, the role of subseasonal-scale dynamics in the upper troposphere and lower stratosphere (UTLS), and the relationship of ASM transport and the stratospheric residual circulation. The model simulation of CO shows the intraseasonal east-west oscillation of the anticyclone may play an essential role in transporting convectively pumped boundary layer pollutants in the UTLS. A statistical analysis of 11 year CO also shows that the southern flank of the Tibetan plateau is a preferred location for boundary layer tracers to be lofted to the tropopause region. The vertical structure of a model tracer (E90) further shows that the rapid ASM vertical transport is only effective up to the tropopause level (around 400 K). The efficiency of continued vertical transport into the deep stratosphere is limited by the slow ascent associated with the zonal-mean residual circulation in the lower stratosphere during northern summer. Quasi-isentropic transport near the 400 K potential temperature level is likely the most effective process for ASM anticyclone air to enter the stratosphere.

  2. Acceptor-Compensated Charge Transport and Surface Chemical Reactions in Au-Implanted SnO2 Nanowires

    PubMed Central

    Katoch, Akash; Sun, Gun-Joo; Choi, Sun-Woo; Hishita, Shunichi; Kulish, Vadym V.; Wu, Ping; Kim, Sang Sub

    2014-01-01

    A new deep acceptor state is identified by density functional theory calculations, and physically activated by an Au ion implantation technique to overcome the high energy barriers. And an acceptor-compensated charge transport mechanism that controls the chemical sensing performance of Au-implanted SnO2 nanowires is established. Subsequently, an equation of electrical resistance is set up as a function of the thermal vibrations, structural defects (Au implantation), surface chemistry (1 ppm NO2), and solute concentration. We show that the electrical resistivity is affected predominantly not by the thermal vibrations, structural defects, or solid solution, but the surface chemistry, which is the source of the improved chemical sensing. The response and recovery time of chemical sensing is respectively interpreted from the transport behaviors of major and minor semiconductor carriers. This acceptor-compensated charge transport mechanism provides novel insights not only for sensor development but also for research in charge and chemical dynamics of nano-semiconductors. PMID:24713609

  3. Effects of chemical compositions and ensiling on the biogas productivity and degradation rates of agricultural and food processing by-products.

    PubMed

    Kafle, Gopi Krishna; Kim, Sang Hun

    2013-08-01

    The objective of this study was to investigate the effects of chemical compositions and ensiling on the biogas productivity and degradation rates of agricultural and food processing by-products (AFPBPs) using the biogas potential test. The AFPBPs were classified based on their chemical compositions (i.e., carbohydrate, protein and fat contents). The biogas and methane potentials of AFPBPs were calculated to range from 450 to 777 mL/g volatile solids (VS) and 260-543 mL/g VS, respectively. AFPBPs with high fat and protein contents produced significantly higher amounts of biogas than AFPBPs with high carbohydrate and low fat contents. The degradation rate was faster for AFPBPs with high carbohydrate contents compared to AFPBPs with high protein and fat contents. The lag phase and biogas production duration were lower when using ensiled AFPBPs than when using nonsilage AFPBPs. Among the four different silages tested, two silages significantly improved biogas production compared to the nonsilage AFPBPs.

  4. Chemical transport in a fissured rock: Verification of a numerical model

    SciTech Connect

    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{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

  5. 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

  6. 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

  7. 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.

  8. A review of approaches to estimate wildfire plume injection height within large scale atmospheric chemical transport models - Part 1

    NASA Astrophysics Data System (ADS)

    Paugam, R.; Wooster, M.; Freitas, S. R.; Martin, M. Val

    2015-03-01

    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. This 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 maybe quite different. This difference in atmospheric transport then may also affect the longevity, chemical conversion and fate of the plumes chemical consituents, 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. The use of satellite Earth observation (EO) data is commonly used for this, and detail the EO datasets capable of being used to remotely assess wildfire plume height distributions and the driving characteristics of the causal fires. We also discus 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 suggestion some future parameterization developments and ideas on EO data selection that maybe relevant to the instigation of enhanced methodologies aimed at injection height representation.

  9. 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.

  10. THE ACQUISITION AND APPLICATION OF ABSORPTION, DISTRIBUTION, METABOLISM, AND EXCRETION (ADME) DATA IN AGRICULTURAL CHEMICAL SAFETY ASSESSMENTS

    EPA Science Inventory

    A multi-sector international group of government, academic, and industry scientists has developed a proposal for an improved testing scheme for assessing the safety of crop protection chemicals. Incorporation of pharmacokinetic studies describing the absorption, distribution, me...

  11. High resolution simulations of aerosol microphysics in a global and regionally nested chemical transport model

    NASA Astrophysics Data System (ADS)

    Adams, P. J.; Marks, M.

    2015-12-01

    The aerosol indirect effect is the largest source of forcing uncertainty in current climate models. This effect arises from the influence of aerosols on the reflective properties and lifetimes of clouds, and its magnitude depends on how many particles can serve as cloud droplet formation sites. Assessing levels of this subset of particles (cloud condensation nuclei, or CCN) requires knowledge of aerosol levels and their global distribution, size distributions, and composition. A key tool necessary to advance our understanding of CCN is the use of global aerosol microphysical models, which simulate the processes that control aerosol size distributions: nucleation, condensation/evaporation, and coagulation. Previous studies have found important differences in CO (Chen, D. et al., 2009) and ozone (Jang, J., 1995) modeled at different spatial resolutions, and it is reasonable to believe that short-lived, spatially-variable aerosol species will be similarly - or more - susceptible to model resolution effects. The goal of this study is to determine how CCN levels and spatial distributions change as simulations are run at higher spatial resolution - specifically, to evaluate how sensitive the model is to grid size, and how this affects comparisons against observations. Higher resolution simulations are necessary supports for model/measurement synergy. Simulations were performed using the global chemical transport model GEOS-Chem (v9-02). The years 2008 and 2009 were simulated at 4ox5o and 2ox2.5o globally and at 0.5ox0.667o over Europe and North America. Results were evaluated against surface-based particle size distribution measurements from the European Supersites for Atmospheric Aerosol Research project. The fine-resolution model simulates more spatial and temporal variability in ultrafine levels, and better resolves topography. Results suggest that the coarse model predicts systematically lower ultrafine levels than does the fine-resolution model. Significant

  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. Numerical modeling of coupled thermal chemical reactive transport: simulation of a heat storage system

    NASA Astrophysics Data System (ADS)

    Shao, H.; Watanabe, N.; Singh, A. K.; Nagel, T.; Linder, M.; Woerner, A.; Kolditz, O.

    2012-12-01

    As a carbon-free energy supply technology, the operation time and final energy output of thermal solar power plants can be greatly extended if efficient thermal storage systems are applied. One of the proposed design of such system is to utilize reversible thermochemical reactions and its embedded reaction enthalpy, e.g. the Ca(OH)2/CaO hydration circle, in a fixed-bed gas-solid reactor (Schaube et al. 2011) The modeling of such a storage system involves multiple strongly-coupled physical and chemical processes. Seepage velocity is calculated by the nonlinear Forchheimer law. Gas phase density and viscosity are temperature, pressure and composition dependent. Also, heat transfer between gas and solid phases is largely influenced by the exothermal heat produced by the hydration of calcium oxide. Numerical solution of four governing PDEs include the mass balance, reactive transport, heat balance equations for gas and solid phases, which are implemented into the open source scientific software OpenGeoSys in a monolithic way. Based on it, a 2D numerical model, considering the boundary heat loss of the system, was set up to simulate the energy-storage and release circle. The high performance computing techniques were employed in two stages. First, the dynamic behavior of the heat storage system is simulated on a parallel platform. Second, a large number of processors are employed to perform sensitivity analysis, whereas the reaction rates and efficiency factor of heat transfer are parameterized so that the measured and simulated temperature profile fit with each other. The model showed that heat transfer coefficient between solid and gas phase, grain size of the filling material will influence the final performance greatly. By varying these factors, the calibrated model will be further applied to optimize the design of such energy storage system.

  14. A Novel Approach of Understanding and Incorporating Error of Chemical Transport Models into a Geostatistical Framework

    NASA Astrophysics Data System (ADS)

    Reyes, J.; Vizuete, W.; Serre, M. L.; Xu, Y.

    2015-12-01

    The EPA employs a vast monitoring network to measure ambient PM2.5 concentrations across the United States with one of its goals being to quantify exposure within the population. However, there are several areas of the country with sparse monitoring spatially and temporally. One means to fill in these monitoring gaps is to use PM2.5 modeled estimates from Chemical Transport Models (CTMs) specifically the Community Multi-scale Air Quality (CMAQ) model. CMAQ is able to provide complete spatial coverage but is subject to systematic and random error due to model uncertainty. Due to the deterministic nature of CMAQ, often these uncertainties are not quantified. Much effort is employed to quantify the efficacy of these models through different metrics of model performance. Currently evaluation is specific to only locations with observed data. Multiyear studies across the United States are challenging because the error and model performance of CMAQ are not uniform over such large space/time domains. Error changes regionally and temporally. Because of the complex mix of species that constitute PM2.5, CMAQ error is also a function of increasing PM2.5 concentration. To address this issue we introduce a model performance evaluation for PM2.5 CMAQ that is regionalized and non-linear. This model performance evaluation leads to error quantification for each CMAQ grid. Areas and time periods of error being better qualified. The regionalized error correction approach is non-linear and is therefore more flexible at characterizing model performance than approaches that rely on linearity assumptions and assume homoscedasticity of CMAQ predictions errors. Corrected CMAQ data are then incorporated into the modern geostatistical framework of Bayesian Maximum Entropy (BME). Through cross validation it is shown that incorporating error-corrected CMAQ data leads to more accurate estimates than just using observed data by themselves.

  15. The effect of chemically modified alginates on macrophage phenotype and biomolecule transport.

    PubMed

    Bygd, Hannah C; Bratlie, Kaitlin M

    2016-07-01

    Macrophage (MΦ) reprogramming has received significant attention in applications such as cancer therapeutics and tissue engineering where the host immune response to biomaterials is crucial in determining the success or failure of an implanted device. Polymeric systems can potentially be used to redirect infiltrating M1 MΦs toward a proangiogenic phenotype. This work exploits the concept of MΦ reprogramming in the engineering of materials for improving the longevity of tissue engineering scaffolds. We have investigated the effect of 13 different chemical modifications of alginate on MΦ phenotype. Markers of the M1 response-tumor necrosis factor-α (TNF-α) and inducible nitric oxide synthase-and the M2 response-arginase-were measured and used to determine the ability of the materials to alter MΦ phenotype. It was found that some modifications were able to reduce the pro-inflammatory response of M1 MΦs, others appeared to amplify the M2 phenotype, and the results for two materials suggested they were able to reprogram a MΦ population from M1 to M2. These findings were supplemented by studies done to examine the permselectivity of the materials. Diffusion of TNF-α was completely prevented through some of these materials, while up to 84% was found to diffuse through others. The diffusion of insulin through the materials was statistically consistent. These results suggest that the modification of these materials might alter mass transport in beneficial ways. The ability to control polarization of MΦ phenotypes with immunoprotective materials has the potential to augment the success of tissue engineering scaffolds. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 104A: 1707-1719, 2016.

  16. Initial results with the LLNL 2-D chemical-radiative-transport model of the troposphere and stratosphere

    SciTech Connect

    Wuebbles, D.J.; Connell, P.S.; Grant, K.E.; Tarp, R.; Taylor, K.E.

    1987-09-01

    Significant progress has been made at LLNL in the development of a zonally averaged (two-dimensional) chemical-radiative-transport model of the troposphere and stratosphere. Although further model development and refinement is being planned the LLNL 2-D model is currently ready to be applied to appropriately designed research studies of stratospheric chemical processes and interactions. Several such studies are now underway. This paper provides a description of the existing 2-D model and discusses some of the pertinent results for evaluating the capabilities of the model. Special attempts at improving the timing of the model are also discussed. 6 figs.

  17. 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.

  18. Estrogen transport in surface runoff from agricultural fields treated with two different application methods of dairy manure

    Technology Transfer Automated Retrieval System (TEKTRAN)

    While the land-application of animal manure provides many benefits, concerns exist regarding the subsequent transport of hormones and potential effects on aquatic ecosystems. This study compares two methods of dairy manure application, surface broadcasting and shallow disk injection, on the fate and...

  19. 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...

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

    SciTech Connect

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

    1994-01-01

    This paper presents results of measurements of dissolved methane found in ground water samples from Aichi Prefecture, Japan, taken from wells which were used for agricultural irrigation. It is a part of the overall program to account of methane sources and sinks in the environment. Detectable methane concentrations were found in more than half of the 131 samples taken. Based on the detected methane concentrations, and the estimated ground water usage, this source represents only 1.4% of the methane production from paddy fields in this geographic region.

  1. Species transport and chemical reaction in a MOCVD reactor and their influence on the GaN growth uniformity

    NASA Astrophysics Data System (ADS)

    Zhang, Zhi; Fang, Haisheng; Yao, Qingxia; Yan, Han; Gan, Zhiyin

    2016-11-01

    Fluid flow, heat transfer, and species transport with chemical reactions have been investigated for gallium nitride (GaN) growth in a commercial metal-organic chemical vapor deposition (MOCVD) reactor. Both the growth rate and the growth uniformity are investigated zone by zone, as the wafers are divided into three zones/groups according to their distances to the susceptor center. The results show that species transport in the reactor is affected by the inlet conditions, i.e., the premixed or non-premixed inlet, the inlet temperature, the total gas flow rate, and the V/III component ratio, and reveal that the premixed inlet condition is preferred for uniform growth. Especially, a large total flow rate or a low V/III ratio results in both increase of the growth rate and improvement of the growth uniformity.

  2. 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.

  3. 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

  4. Transport of cerium oxide nanoparticles in saturated silica media: influences of operational parameters and aqueous chemical conditions

    NASA Astrophysics Data System (ADS)

    Zhang, Zhaohan; Gao, Peng; Qiu, Ye; Liu, Guohong; Feng, Yujie; Wiesner, Mark

    2016-10-01

    This paper aimed to investigate the influences of operational parameters and aqueous chemical conditions on transport behaviors of cerium oxides nanoparticles (CeO2-NPs) in saturated silica media. Results indicated that increasing rates of attachment efficiency (α) were related with cationic types, and critical deposition concentration (CDC) for divalent cation (Ca2+ and Mg2+) were more than 31-fold of that for monovalent cation (Na+ and K+). Increase or reduction of electrolyte pH could both promote the mobility of CeO2-NPs in glass beads, while influence was more evident at alkaline conditions. α increased linearly with NPs concentrations, while decreased linearly with flow velocity in the column, and effects were related with electrolyte contents. Presence of surfactants could sharply decreased α, and SDS was more effective to facilitate CeO2-NPs transport than Triton X–100. With DOMs concentrations increasing, α firstly kept constant, then sharply declined, and finally reduced very slowly. The influence of DOMs on NPs deposition was in order of SA > HA > TA >  BSA. Overall, this study revealed that aqueous chemical conditions was crucial to NPs transport in porous media, and would provide significant information for our understanding on the fate and transport of nanoparticles in natural environment.

  5. Transport of cerium oxide nanoparticles in saturated silica media: influences of operational parameters and aqueous chemical conditions

    PubMed Central

    Zhang, Zhaohan; Gao, Peng; Qiu, Ye; Liu, Guohong; Feng, Yujie; Wiesner, Mark

    2016-01-01

    This paper aimed to investigate the influences of operational parameters and aqueous chemical conditions on transport behaviors of cerium oxides nanoparticles (CeO2-NPs) in saturated silica media. Results indicated that increasing rates of attachment efficiency (α) were related with cationic types, and critical deposition concentration (CDC) for divalent cation (Ca2+ and Mg2+) were more than 31-fold of that for monovalent cation (Na+ and K+). Increase or reduction of electrolyte pH could both promote the mobility of CeO2-NPs in glass beads, while influence was more evident at alkaline conditions. α increased linearly with NPs concentrations, while decreased linearly with flow velocity in the column, and effects were related with electrolyte contents. Presence of surfactants could sharply decreased α, and SDS was more effective to facilitate CeO2-NPs transport than Triton X–100. With DOMs concentrations increasing, α firstly kept constant, then sharply declined, and finally reduced very slowly. The influence of DOMs on NPs deposition was in order of SA > HA > TA >  BSA. Overall, this study revealed that aqueous chemical conditions was crucial to NPs transport in porous media, and would provide significant information for our understanding on the fate and transport of nanoparticles in natural environment. PMID:27694968

  6. Transport of cerium oxide nanoparticles in saturated silica media: influences of operational parameters and aqueous chemical conditions.

    PubMed

    Zhang, Zhaohan; Gao, Peng; Qiu, Ye; Liu, Guohong; Feng, Yujie; Wiesner, Mark

    2016-10-03

    This paper aimed to investigate the influences of operational parameters and aqueous chemical conditions on transport behaviors of cerium oxides nanoparticles (CeO2-NPs) in saturated silica media. Results indicated that increasing rates of attachment efficiency (α) were related with cationic types, and critical deposition concentration (CDC) for divalent cation (Ca(2+) and Mg(2+)) were more than 31-fold of that for monovalent cation (Na(+) and K(+)). Increase or reduction of electrolyte pH could both promote the mobility of CeO2-NPs in glass beads, while influence was more evident at alkaline conditions. α increased linearly with NPs concentrations, while decreased linearly with flow velocity in the column, and effects were related with electrolyte contents. Presence of surfactants could sharply decreased α, and SDS was more effective to facilitate CeO2-NPs transport than Triton X-100. With DOMs concentrations increasing, α firstly kept constant, then sharply declined, and finally reduced very slowly. The influence of DOMs on NPs deposition was in order of SA > HA > TA >  BSA. Overall, this study revealed that aqueous chemical conditions was crucial to NPs transport in porous media, and would provide significant information for our understanding on the fate and transport of nanoparticles in natural environment.

  7. Analysis of long-range transport of aerosols for Portugal using 3D chemical transport model and satellite measurements

    NASA Astrophysics Data System (ADS)

    Tchepel, O.; Ferreira, J.; Fernandes, A. P.; Basart, S.; Baldasano, J. M.; Borrego, C.

    2013-01-01

    The objective of this work is to assess the contribution of long-range transport of mineral dust from North Africa to the air pollution levels in Portugal based on a combination of a modelling approach and satellite observations. The Comprehensive Air Quality Model (CAMx) was applied together with the updated Dust REgional Atmospheric Model (BSC-DREAM8b) to characterise anthropogenic and natural sources of primary aerosols as well as secondary aerosols formation. The modelling results, after their validation and bias removing process, have been used in combination with aerosol measurements provided by Ozone Monitoring Instrument (OMI), using OMAERUV Level-2 v003 product, aiming to better understand the advantages and shortcomings of both, satellite and modelling aerosol data. The data analysis is presented for Portugal for July 2006 focusing on aerosol optical depth (AOD) at 500 nm and aerosol type. Based on the modelling results, the importance of the long-range transport of mineral dust was demonstrated for the simulation days, achieving a 60% contribution to AOD levels. The mineral dust is affecting atmospheric layers up to 6 km but peak concentrations are presented at layers below 2 km. The model predicts a complex mixture of different types of aerosol for the pixels classified by OMI as "mineral dust" and "sulphates". Although a good agreement between the model outputs and OMI observations has been found in terms of the spatial pattern and AOD correlation is about 0.48 for mineral dust, several problems were identified. The model is systematically underestimating the aerosol concentration at near ground level in comparison with the air quality monitoring stations, while OMI is in general overestimating AOD for the analysed period based on the comparison with AERONET data. Additionally, misclassification of mineral dust for some geographical locations and discontinuity in AOD values along the coastal line at water/land interface in the OMI data are discussed.

  8. 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.

  9. 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

  10. 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

  11. Computer program for calculation of complex chemical equilibrium compositions and applications. Supplement 1: Transport properties

    NASA Astrophysics Data System (ADS)

    Gordon, S.; McBride, B.; Zeleznik, F. J.

    1984-10-01

    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.

  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. 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.

  15. 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.

  16. 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.

  17. 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.

  18. 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

  19. Potential chemical and microbiological risks on human health from urban wastewater reuse in agriculture. Case study of wastewater effluents in Spain.

    PubMed

    Muñoz, Ivan; Tomàs, Núria; Mas, Jordi; García-Reyes, Juan Fracisco; Molina-Díaz, Antonio; Fernández-Alba, Amadeo R

    2010-05-01

    Potential health risks derived from wastewater reuse in agriculture have been evaluated with Risk Assessment modelling techniques, in a case study involving the effluents of two Spanish wastewater treatment plants. One of the plants applies primary and secondary treatment, and the other one applies an additional tertiary treatment. Health risks were assessed on the basis of ingesting contaminated food, due to exposure to: (i) 22 chemical pollutants, namely pharmaceuticals and personal care products (PPCPs), and priority pollutants included in the European Framework Directive, and (ii) microorganisms, namely enterovirus. Chemical Risk Assessment has been carried out following the European Commission's technical guidelines, while risks from exposure to viruses have been evaluated by means of Quantitative Microbial Risk Assessment, assuming a virus to coliform ratio of 1:10(5). The results of the chemical assessment show that there is a margin of safety above 100 for all substances, with the exception of gemfibrozil, for which the mean margin of safety (MOS) is above 100, but the lower bound of MOS with a 95 % confidence interval lies in the 3-4 range. A MOS under 100 was also found for 2,3,7,8-TCDD in one of the effluents. The assessment of risks from viruses shows a very low probability of infection. The overall results show that risks are lower for the plant applying tertiary treatment, especially concerning microbiological parameters.

  20. Transport and Chemical Production of Ozone in the East Asian Pacific Rim Region: -Modeling Study Based on Observation-

    NASA Astrophysics Data System (ADS)

    Akimoto, H.; Li, J.; Wang, Z.; Yamaji, K.; Pochanart, P.; Ohara, T.; Uno, I.; Gao, C.; Wang, X.; Tanimoto, H.; Kurokawa, J.

    2007-12-01

    Form satellite observational data, east-central China covering the North China Plain (NCP) and Yanzi Delta (YZD) has been identified as the most widely spread source area of air pollutants in the East Asian Pacific region. In order to quantify transport and chemical production of ozone in this region, both of observational and modeling studies in both of source and outflow region are necessary. In the present study, we investigated the budgets of ozone over East Asia by using regional chemical transport models (NAQPMS and CMAQ) based on observations at newly founded three mountain sites (Mt. Tai, Hua and Huang) in east-central China, and several sites from EANET and regional WMO/GAW. The observations show that a striking pattern of two sharp high ozone peaks in May-June and September-October at the three mountain sites. The budget analysis by the model confirms that maximum of net photochemical ozone production reaches 31.8, 15.1 and 11.4 ppb/day at Mt. Tai, Hua and Huang, respectively. The net chemical production dominates the formation of ozone maximum at Mt. Tai and Hua in June, and the importing transport also plays a comparable importance at Mt. Huang. In the outflow region at Oki, Japan, transport of ozone produced by East Asian emissions accounts up to 21 ppb in summer but less than 3 ppb in winter agreeing with the model analysis. The contribution of ozone due to East Asian emission is the largest (53.6%) in July-August, and somewhat smaller in May-June (34.0%) and September-October (30.7%) on the transect between Japan and the Asian continent.

  1. [Effects of agricultural activities and transgenic crops on agricultural biodiversity].

    PubMed

    Zhang, Xi-Tao; Luo, Hong-Bing; Li, Jun-Sheng; Huang, Hai; Liu, Yong-Bo

    2014-09-01

    Agricultural biodiversity is a key part of the ecosystem biodiversity, but it receives little concern. The monoculture, environmental pollution and habitat fragmentation caused by agricultural activities have threatened agricultural biodiversity over the past 50 years. To optimize agricultural management measures for crop production and environmental protection, we reviewed the effects of agricultural activities, including cultivation patterns, plastic mulching, chemical additions and the cultivation of transgenic crops, on agricultural biodiversity. The results showed that chemical pesticides and fertilizers had the most serious influence and the effects of transgenic crops varied with other factors like the specific transgene inserted in crops. The environmental risk of transgenic crops should be assessed widely through case-by-case methods, particularly its potential impacts on agricultural biodiversity. It is important to consider the protection of agricultural biodiversity before taking certain agricultural practices, which could improve agricultural production and simultaneously reduce the environmental impacts.

  2. 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

  3. 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

  4. 76 FR 12556 - Airworthiness Directives; Various Transport Category Airplanes Equipped With Chemical Oxygen...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-03-08

    ... 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 the lavatory. This AD was prompted by reports that the current design of these oxygen generators presents...

  5. Relations of Water Quality to Agricultural Chemical Use and Environmental Setting at Various Scales - Results from Selected Studies of the National Water-Quality Assessment Program

    USGS Publications Warehouse

    ,

    2008-01-01

    In 1991, the U.S. Geological Survey (USGS) began studies of 51 major river basins and aquifers across the United States as part of the National Water-Quality Assessment (NAWQA) Program to provide scientifically sound information for managing the Nation's water resources. The major goals of the NAWQA Program are to assess the status and long-term trends of the Nation's surface- and ground-water quality and to understand the natural and human factors that affect it (Gilliom and others, 1995). In 2001, the NAWQA Program began a second decade of intensive water-quality assessments. The 42 study units for this second decade were selected to represent a wide range of important hydrologic environments and potential contaminant sources. These NAWQA studies continue to address the goals of the first decade of the assessments to determine how water-quality conditions are changing over time. In addition to local- and regional-scale studies, NAWQA began to analyze and synthesize water-quality status and trends at the principal aquifer and major river-basin scales. This fact sheet summarizes results from four NAWQA studies that relate water quality to agricultural chemical use and environmental setting at these various scales: * Comparison of ground-water quality in northern and southern High Plains agricultural settings (principal aquifer scale); * Distribution patterns of pesticides and degradates in rain (local scale); * Occurrence of pesticides in shallow ground water underlying four agricultural areas (local and regional scales); and * Trends in nutrients and sediment over time in the Missouri River and its tributaries (major river-basin scale).

  6. 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.

  7. Effects of residential and agricultural land uses on the chemical quality of baseflow of small streams in the Croton Watershed, southeastern New York

    USGS Publications Warehouse

    Heisig, Paul M.

    2000-01-01

    Findings— Concentrations of selected chemical constituents in baseflow were strongly affected by the predominant land use in a given basin. Land uses included forested undeveloped, unsewered residential, sewered residential, and agricultural (horse and dairy farms). A positive linear relation was indicated for chloride concentration in baseflow and the basin's annual rate of road-salt application (or density of two-lane roads). Chloride concentration exhibits a relatively stable relation to road-salt application rate or 2-lane road density throughout the year. Positive linear relations were indicated for nitrate concentration in baseflow and the basins unsewered housing density. Nitrate is characterized by a different relation to unsewered housing density for each season, with the highest observed nitrate concentrations during the winter and the lowest concentrations during the summer. Baseflow nitrate concentrations in sewered basins, and in unsewered basins with riparian wetland buffers between residential development and the stream, were lower than concentrations predicted from unsewered-housing density.

  8. A nontoxic polypeptide oligomer with a fungicide potency under agricultural conditions which is equal or greater than that of their chemical counterparts.

    PubMed

    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.

  9. 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

  10. EnKF and 4D-Var data assimilation with chemical transport model BASCOE (version 05.06)

    NASA Astrophysics Data System (ADS)

    Skachko, Sergey; Ménard, Richard; Errera, Quentin; Christophe, Yves; Chabrillat, Simon

    2016-08-01

    We compare two optimized chemical data assimilation systems, one based on the ensemble Kalman filter (EnKF) and the other based on four-dimensional variational (4D-Var) data assimilation, using a comprehensive stratospheric chemistry transport model (CTM). This work is an extension of the Belgian Assimilation System for Chemical ObsErvations (BASCOE), initially designed to work with a 4D-Var data assimilation. A strict comparison of both methods in the case of chemical tracer transport was done in a previous study and indicated that both methods provide essentially similar results. In the present work, we assimilate observations of ozone, HCl, HNO3, H2O and N2O from EOS Aura-MLS data into the BASCOE CTM with a full description of stratospheric chemistry. Two new issues related to the use of the full chemistry model with EnKF are taken into account. One issue is a large number of error variance parameters that need to be optimized. We estimate an observation error variance parameter as a function of pressure level for each observed species using the Desroziers method. For comparison purposes, we apply the same estimate procedure in the 4D-Var data assimilation, where both scale factors of the background and observation error covariance matrices are estimated using the Desroziers method. However, in EnKF the background error covariance is modelled using the full chemistry model and a model error term which is tuned using an adjustable parameter. We found that it is adequate to have the same value of this parameter based on the chemical tracer formulation that is applied for all observed species. This is an indication that the main source of model error in chemical transport model is due to the transport. The second issue in EnKF with comprehensive atmospheric chemistry models is the noise in the cross-covariance between species that occurs when species are weakly chemically related at the same location. These errors need to be filtered out in addition to a

  11. A fugacity approach for modeling the transport of airborne organic chemicals in an air/plant/soil system

    SciTech Connect

    Oliver, L.D. ); McKone, T.E. )

    1991-05-01

    An important issue facing both public and private agencies is the identification and quantification of exposures by indirect pathways to toxic chemicals released to the atmosphere. With recent public concerns over pesticides such as malathion and alar in foods, greater attention is being given to the process of chemical uptake by plants. Whether chemicals taken up by plants can accumulate and ultimately enter the human food chain are important questions for determining health risks and safe levels of toxic air-pollutant emissions and pesticide application. A number of plant-toxicokinetic, or botanicokinetic,'' models have been developed to give estimates of how chemicals are partitioned and transported within plants. In this paper, we provide a brief review of these models, describing their main features and listing some of their advantages and disadvantages. We then describe and demonstrat