Brief Summary of Minutes of Annual Meeting

The 2006 meeting of W-1082 'Evaluating the Physical and Biological Availability of Pesticides and Pharmaceuticals in Agricultural Contexts' was held on January 4 and 5, 2007 at the University of Hawaii, Honolulu, HI. Chittaranjan Ray hosted the meeting. Lee Sommers (Administrative Advisor) provided an overview of the budget outlook for the coming year, new funding areas such as Biofuels and food for fitness. He also provided an overview of the Creating Research, Extension and Teaching Excellence for the 21st century (CREATE-21) initiative and referred members to the web site for further details. He noted that the Western directors are emphasizing accountability for multi-state research projects, requiring reports showing the impact of each committee. Dr. Sommers congratulated the group on a successful proposal. Members discussed progress on the outputs and milestones specified in the proposal and approaches to increase the impact of the committee. The meeting included presentations of research reports by all participants. Elections were not conducted, as officers will now serve two-year terms. Mark Radosevich will serve as chair for the next W-1082 meeting, and Clinton Williams will serve as secretary. Clinton Williams will host the next meeting in St. George, UT. Date of next meeting was discussed but not finalized.

Objective 1. To identify and quantify fundamental chemical, physical, and biological processes relevant to agricultural pesticides and pharmaceuticals in the environment Sorption hysteresis. Sander et al. [2006] conducted conditioning-annealing experiments on a peat soil and a soil humic acid to confirm a glassy polymer model for sorption hysteresis. A glassy polymer, poly(vinylchloride), and a rubbery polymer, polyethylene, were included for comparison. Using chlorobenzene as a conditioning agent and polychlorinated benzenes as test compounds in a second sorption step, conditioning effects observed as shift in the isotherm toward higher sorbed concentrations were found in all solids except polyethylene. The conditioning effect for the two SOM solids, probed by the enhancement in the sorption distribution coefficient of 1,2,4-trichlorobenzene, relaxed upon sample annealing at temperatures between 45C and 91C in a manner similar to the relaxation of free volume and enthalpy of glassy polymers. Relaxation of the conditioning effect in the SOM solids depended on annealing temperature and, at a given temperature, followed a double additive exponential rate law with a non-zero constant term descriptive of the final state that depends inversely on temperature. By extrapolation, it could be predicted that the conditioning effect may never completely relax at environmentally relevant temperatures. The results provide compelling evidence for the glassy, non-equilibrium nature of natural organic matter solids and for irreversible structural expansion as a cause of irreversible sorption phenomena. We have also identified a heretofore-unrecognized source of artificial hysteresis that may occur simultaneously with true hysteresis [Sander and Pignatello, 2006]. The study involved sorption of benzene, toluene, and nitrobenzene, both singly and in pairs, to wood charcoal, a black carbon model substance. A previous study [Sander and Pignatello Environ. Sci. Technol., 39: 1606-1615 (2005)] showed these similarly sized compounds compete for the same set of sorption sites on the char. Single-solute sorption of these compounds was weakly hysteretic at high concentrations. Comparable degrees of hysteresis for these compounds was taken as evidence that hysteresis is true and caused by sorbate-induced deformation of char pores. Hysteresis of a target solute in the presence of a competitor was generally weak at low co-solute concentration but became stronger as co-solute concentration increased. We attribute this growing hysteresis with co-solute concentration to a competitor dilution effect. The competitor dilution effect arises when the target solute re-equilibrates from a sorption state in which competition is relatively high, to a desorption state in which competition is relatively low because the competitor has been diluted along with the target solute. Simulations based on Ideal Adsorbed Solution Theory, a thermodynamic competitive model, support the contribution of the competitor dilution artifact to hysteresis. The co-solute also causes an increase in the linearity of the isotherm, also due to competition thermodynamics. The competitor dilution effect can play a role in pollutant behavior in real systems containing multiple contaminants when competing solutes are diluted or degraded; the target solute may appear to be less accessible with time due to this effect. Influence of humic substances on the surface activity of biomass char. Environmental black carbon (BC), which includes charcoal and soot particles emitted to the environment, is believed to play an important role in sorption of anthropogenic organic compounds in soils and sediments due to its high porosity and surface area. It is possible, however, that naturally-occurring organic matter attenuates the surface activity of BC. We previously found [Kwon and Pignatello, 2005] that aging of prepared wood char particles in a soil-water suspension lead over a few week period to a strong decline in char total surface area (TSA, by N2 adsorption at 77 K using the B.E.T. equation), and a more modest decline in the solid-water distribution ratio of benzene. The findings indicate that N2 is an unsuitable probe for microporosity in BC and natural organic matter in geosorbents. They also show that adsorption of organic compounds to BC may be attenuated by exposure to humic substances in soil over time. Identify mechanisms of ciprofloxacin interaction with metal cations. Interactions of fluoroquinolones with metal cations may play an important regulatory role in the reactions of these antibiotics with both minerals and organic matter. For example, HA carboxylate groups may bind to Cipro via a bivalent metal cation bridge analogous to that between Cipro carboxylates.. The high affinity of fluorquinolones for oxide minerals and layer silicates is attributed to the binding of the antibiotic to structural metal centers at the surfaces of the minerals or to exchangeable cations in clay mineral interlayers facilitated by deprotonated carboxylate moieties of the fluoroquinolones (Nowara et al. 1997, Zhang et al. 2005, Gu et al. 2005). By contrast, adsorption by clays is decreased by about two orders of magnitude when a decarboxylated fluoroquinolone derivative is used as an adsorptive (Nowara et al. 1997). Molecular simulation may prove useful for gaining insights into these interactions and accordingly our MD simulation results will be applied to help understand the binding mechanisms of fluoroquinolone derivatives with organic matter and clays in both soil and aquatic environments. Quantifying the Availability of Clay Surfaces in Soils for Adsorption of Nitrocyanobenzene and Diuron. Coverage of clay surfaces by soil organic matter (SOM) may limit the efficacy of the soil mineral fractions for adsorption of organic contaminants and pesticides. Two methods were scrutinized for quantitatively assessing the availability of clay surfaces in a smectitic Webster A-horizon soil for sorption of p-nitrocyanobenzene (p-NCB) and diuron. One method described previously involves the summation of independent contributions of SOM and swelling clays to sorption of organic solutes. For this method, several assumptions must be made and/or procedural difficulties overcome in the determination of certain terms in the equation proposed for calculating the fractional availability of mineral surfaces (fa). To alleviate the methodological limitations, we developed an alternative approach for determining fa. Good agreement between fa values was obtained from both methods for p-NCB but not diuron. For p-NCB sorption, fa values varied between 0.55 and 0.71. For diuron sorption, our alternative equation estimated fa values varied between 0.41 and 0.61; the other approach yielded negative values. The results demonstrate that SOM does reduce the availability of clay surfaces hence suppressing sorption by the Webster A-horizon soil. Our newly developed method provides more reasonable estimates of the availability of soil-clay surfaces for sorption than an earlier published approach. Ionic Strength-Induced Formation of Smectite Quasicrystals Enhances Nitroaromatic Compound Sorption. Sorption of organic contaminants by soils is a determinant controlling their transport and fate in the environment. The influence of ionic strength on nitroaromatic compound sorption by K+- and Ca2+-saturated smectite was examined. Sorption of 1,3-dinitrobenzene by K-smectite increased as KCl ionic strength increased from 0.01 to 0.30 M. In contrast, sorption by Ca-smectite at CaCl2 ionic strengths of 0.015 and 0.15 M remained essentially the same. The salting-out effect on the decrease of 1,3-dinitrobenzene aqueous solubility within this ionic strength range was <1.5 % relative to the solubility in pure water. This decrease of solubility is insufficient to account for the observed increase of sorption by K-smectite with increasing KCl ionic strength. X-ray diffraction patterns and light absorbance of K-clay suspensions indicated the aggregation of clay particles and the formation of quasicrystal structures as KCl ionic strength increased. Sorption enhancement is attributed to the formation of better-ordered K-clay quasicrystals with reduced interlayer distances, rather than the salting-out effect. Dehydration of 1,3-dinitrobenzene is apparently a significant driving force for sorption, and we show for the first time that sorption of small, planar, neutral organic molecules, viz. 1,3-dinitrobenzene, causes previously expanded clay interlayers to dehydrate and collapse in aqueous suspension. Development of a reliable analytical procedure for monitoring low hormone concentrations in environmental matrices. The commercial use of growth promotants in animal production, and especially in so called concentrated animal feeding operations (CAFOs), creates high enough concentrations of endocrine disrupting chemicals to cause environmental impact, and even naturally occurring hormone levels from some livestock may be cause for concern. Research reports on hormone behavior in the environment indicate their high dissipation through sorption on soil matrices, and degradation by soil microorganisms. However, taking into account the long contact times, and long distances covered by hormones in soil before they reach surface or groundwater, it is surprising that hormone dissipation is incomplete. Frequently, in published sorption studies, hormone concentrations span the range of relatively high concentrations reported for animal manures. However, hormone concentrations comparable with the relatively low levels determined in surface water and groundwater samples, are an area of opportunity for exploration in terms of sorption studies. Having this in mind, we have revisited the problem of hormone sorption with the intention to cover the full span of relevant hormone concentrations, including low, ng L-1, hormone concentrations typically occurring in surface water, groundwater, or manure-unamended soil solution. This became possible owing to the development of more precise analytical methods, such as introducing the highly sensitive mass spectrometric techniques into the analytical procedure, allowing the determination of hormone concentrations at ng L-1 levels. Sorption and degradation of veterinary pharmaceuticals. We continue to investigate the sorption and degradation of veterinary pharmaceuticals. Sorption and aerobic degradation studies with cobalt-radiated (sterile) and untreated soil systems were conducted for a synthetic androgen used in the beef industry (trenbolone isomers) and its primary metabolite (trendione); and two ionophore antibiotics monensin and lasalocid common to CAFOs and their primary metabolites. The 17a and 17b isomers of trenbolone appear to follow similar degradation pathways. Degradation is primarily, but not completely, microbial, and concentration-dependent rates were observed. At applied concentrations of 1 mg/kg, half lives ranged from 5-14 h whereas at applied concentrations of 10 mg/kg, half lives increased to 2-3 days. Some concentration dependence seemed apparent for trendione as well with half lives ranging from 3 to 4 days. Degradation of trendione generated from trenbolone was well predicted using rates estimated from independent trendione degradation studies. Degradation of trenbolone to trendione to unknown metabolites was well described assuming pseudo-first order rate processes, no reversible degradation, and no impact from sorption. We recently monitored hormones in manures excreted by cattle implanted with Ravoler-S (140 mg TBA and 28 mg estradiol). Manure from the pits was sampled after mixing immediately prior to flushing to lagoons, which were sampled every 2 weeks starting with the 4th week after implanting. Trenbolone exhibited the highest hormone concentration in both the manure ( > 2 mg/L) and the lagoon (> 0.12 mg/L). Hormone concentrations in cell 2 were the greatest at 4 weeks after implants, but below 0.03 ug/L except for trendione (~ 0.14 mg/L). Tetracycline transformation by manganese oxide. Tetracycline antibiotics comprise a class of broad spectrum antimicrobial agents finding application in human therapy, animal husbandry, aquaculture and fruit crop production. To better understand the processes affecting these antibiotics in soils and sediments, the kinetics of oxytetracycline transformation by a hydrous manganese oxide (MnO2) were investigated as a function of reactant concentration, pH and temperature. Oxytetracycline was rapidly degraded by MnO2. Initial reaction rates exhibited pronounced pH dependence, increasing as pH decreased. Reaction of oxytetracycline with MnO2 was accompanied by generation of MnII ions, suggesting oxidative transformation of the antibiotic. At pH 5.6, apparent reaction orders for oxytetracycline and MnO2 were 0.7 and 0.8. Reaction order with respect to H+ was 0.6 between pH 4 and 9. Initial reaction rates increased by a factor of ~2.4 for 10°C temperature increases; the apparent activation energy (60 kJ"mol-1) was consistent with a surface-controlled reaction. Reactivity of tetracycline antibiotics toward MnO2 increased in the following order: rolitetracycline H oxytetracycline d tetracycline H meclocycline < chlortetracycline. The initial rate of chlortetracycline degradation by MnO2 was substantially larger than that of the other tetracycline antibiotics investigated. MnO2 reactivity toward oxytetracycline decreased with time; a retarded rate equation was used to describe oxytetracycline reaction with MnO2 under declining rate conditions. This study indicates that natural manganese oxides in soils and sediments are likely to promote appreciable degradation of tetracycline antibiotics, and that reaction rates are strongly dependent on reaction time scale and solution conditions. Tetracycline association with dissolved humic substances. The effect of solution chemistry and sorbate-to-sorbent ratio on the interaction of the antibiotic tetracycline with Elliott soil humic acid (ESHA) was investigated using equilibrium dialysis and FITEQL modeling. Tetracycline speciation strongly influenced its sorption to ESHA over the entire pH range studied. Sorption was strongly pH-dependent with a maximum around pH 4.3, and competition with H+ and electrolyte cation (Na+) was evident. The pH-dependent trend is consistent with complexation between the cationic/zwitterionic species of tetracycline and deprotonated sites in ESHA (mainly carboxylic functional groups) as the primary underlying sorption mechanism. Modification of ESHA by Ca2+ addition increased tetracycline sorption suggesting that ternary complex formation (ESHA-metal-tetracycline) may be important at higher multivalent metal concentrations. The macroscopic data (pH-envelope and sorption isotherms) were successfully modeled using a discrete log K function with the FITEQL 4.0 chemical equilibrium program indicating that ESHA-tetracycline interaction could be reasonably represented as complex formation of a monoacid with discrete sites in humic acid. Sorption-desorption hysteresis was observed; both sorption and desorption isotherms were well described by the Freundlich equation. Livestock Antibiotic Effects on Nitrogen Cycling by Soil Microorganisms. This study showed for the first time that all FDA-approved antibiotics used in the poultry industry inhibited at least one N cycling reaction. The extent of inhibition depended on antibiotic concentration and presence of soil minerals. Inhibition of N cycling reactions through land application of antibiotic-laden livestock manure could have favorable or detrimental effects on soil fertility and water quality, depending on the dominant N form in the manure and soils. Antibiotic effects on denitrification were moderated by the soil mineral montmorillonite, presumably by reducing antibiotic exposure to sensitive bacteria. Diversity, Composition and Geographical Distribution of Microbial Communities in California Salt Marsh Sediments Contaminated with Pesticides, Metals and Antibiotics. The strong relationships observed between pollutant concentrations and some of the microbial indicators indicated the potential of application of microbial community analyses in assessments of the ecosystem health of salt marshes. The results of our study illustrate the importance of considering non-anthropogenic variables in the design and interpretation of ecosystem biomarkers, indicators and other monitoring tools. Whole Genome Analysis of Methyl Tert-Butyl Ether (MTBE)-Degrading Beta-Proteobacterium Methylibium petroleiphilum PM1. In this study, we analyzed the whole genome sequence of Methylibium petroleiphilum PM1. Genome analysis of PM1 reveals a ~4-Mb circular chromosome and ~600-kb megaplasmid containing 3831 and 646 genes, respectively. Aromatic hydrocarbon and alkane degradation, metal resistance, and methylotrophy are encoded on the chromosome. The megaplasmid contains an unusual t-RNA island, numerous insertion sequences and large repeated elements including a 40 kb region also present on the chromosome and a 29 kb tandem repeat encoding phosphonate transport and cobalamin biosynthesis. The megaplasmid also codes for alkane degradation and plays an essential role in MTBE degradation. Discrepancies between the IS element distribution pattern, the distribution of best BLASTP hits among major phylogenetic groups, and G+C content of the chromosome (69.2%) and plasmid (66%) together with comparative genome hybridization experiments suggest the plasmid was recently acquired and may carry the genetic information responsible for PM1s ability to degrade MTBE. Comparative genomic hybridization analysis with PM1-like MTBE-degrading environmental isolates (~99% identical 16S rDNA sequences) showed that this plasmid was highly conserved (ca. 99% identical), whereas, the chromosomes were too diverse to conduct resequencing analysis. PM1s genome sequence now provides a foundation to investigate MTBE biodegradation and explore genetic regulation of multiple biodegradation pathways in M. petroleiphilum and other MTBE-degrading betaproteobacteria. Influence of soil aging on sorption and bioavailability of simazine. Characterization of pesticide bioavailability, particularly in aged soils, is of continued interest because this information is necessary for environmental risk assessment. However, pesticide bioavailability in aged soils has been characterized by a variety of methods with limited success, due in part to methodological limitations. The objective of this study was to use solvent extraction methods to correlate simazine residue bioavailability in aged soils to simazine mineralization using a simazine-mineralizing bacterium. Soils from Brazil, Hawaii, and the midwestern United States were treated with UL-ring-labeled [14C]simazine and incubated for up to 8 weeks. At the end of each incubation period, soils were either incubated further, extracted with 0.01 M CaCl2, or extracted with aqueous methanol (80:20 v/v methanol/water). In a parallel experiment, after each incubation period, soils were inoculated with the bacterium Pseudomonas sp. strain ADP, which is capable of rapidly mineralizing simazine, and 14CO2 was determined. The inoculated soil samples were then extracted with 0.01 N CaCl2 and with aqueous methanol. This allowed for the evaluation of the bioavailability of aged simazine residues, without the contribution of simazine desorption from soil. Results of these studies indicated that simazine sorption to soil increased with aging and that amounts of simazine in aged soils extracted by 0.01 M CaCl2 and aqueous methanol were highly correlated to amounts of simazine mineralized by Pseudomonas sp. strain ADP. Consequently, 0.01 M CaCl2/methanol-extractable simazine in aged soils can be used to estimate bioavailable residues. This technique may be useful in determining the bioavailability of other s-triazine compounds in soils. Influence of Cry1Ac toxin on mineralization and bioavailability of glyphosate in soil. The impact of transgenic plants containing Bacillus thuringiensis (Bt) toxin on soil processes has received recent attention. In these studies, we examined the influence of the lepidopterean Bt Cry1Ac toxin on mineralization and bioavailability of the herbicide glyphosate in two different soils. The addition of 0.25-1.0 g g-1 soil of purified Cry1Ac toxin did not significantly affect glyphosate mineralization and sorption in either a sandy loam or a sandy soil. In contrast, extractable glyphosate decreased over the 28 day incubation period in both soils. Our findings suggest that the reduction in the bioavailabily of glyphosate was not influenced by the presence of Cry1Ac toxin but rather the results of aging or sorption processes. Results from this investigation suggest that the presence of moderate concentrations of Bt-derived Cry1Ac toxin would have no appreciable impact on processes controlling the fate of glyphosate in soils. Objective 2: Integrate chemical and biological process information for use in models applicable across different spatial and temporal scales. Assessment of the vulnerability of farmstead and rural domestic wells to agrichemical contamination. Rural domestic wells, particularly the farmstead wells are not regulated for meeting water quality criteria. As a result, the quality of water pumped from these wells is not tested. It is up to the farmers or well owners to test the water. Recent surveys of ground water pumped from these wells shows the presence of nitrate, pesticides, and their metabolites. As a result, owners/users of these wells are at risk by consuming the contaminated waters. Testing individual wells in a regional setting by regulating agencies is not feasible due to cost and logistics. Traditional modeling approaches are also not suitable to predict the contamination potential of water drawn from a well due to the lack of parameters that are needed in these models to predict contaminant transport. Further, many of the parameters vary in space and time and interact with each other. In our earlier research, we used artificial neural networks (ANNs) as alternative modeling approach to predict the contamination potential of domestic and farmstead wells using data from several states. In this year, we used data from statewide monitoring well network for pesticide and nitrate assessment in Illinois. Sampling results from 159 wells were used for analysis. Well depth, depth to mid-section of the screen, depth to aquifer material, hydraulic conductivity, and drainage class of the overburden material were used as input variables. Transport of selected endocrine disrupting chemicals from wastewater through a Hawaiian Oxisol. Additional experiments (beyond that reported in 2005) were conducted to examine the leachability of two estrogen hormones (17-beta estradiol and estrone) and two surfactant degradation products (octylphenol and nonylphenol) for an Oxisol found on the island of Oahu. Batch sorption experiments were conducted for these four chemicals using soils from two depths: 0-2 ft (referred to as topsoil) and 13-15 ft (referred to as saprolite). Leaching media were (a) deionized water spiked with small amounts of CaCl2 to represent the salts leached out of the columns and (b) recycled water from a local wastewater treatment plant. All four compounds adsorbed strongly to the soil collected from both depths. However, octylphenol and nonylphenol degraded during the sorption experiment. The Freundlich model was suitable to describe the sorption isotherm. Sorption nonlinearity was relatively higher for the saprolite compared to the topsoil. Both physical and chemical nonequilibrium processes were found to affect the mobility of these chemicals in the soil. Transport of these compounds was enhanced with recycled water due to the presence of dissolved organic carbon. Ambient pH had little effect on sorption. Breakthrough experiments in small columns failed to produce any measurable concentrations. Finally, a thin (1 cm) layer of soil was packed in sand to produce breakthroughs. It was difficult to fit the obtain breakthrough to numerical models. Simulating Herbicide Volatilization From Bare Soil Affected By Atmospheric Conditions And Limited Solubility In Water. A numerical model that simulates pesticide fate was developed to predict the behavior of triallate after application to a field soil. The model has options that allow water and/or heat transport, and can limit simulated aqueous phase concentrations to triallate solubility in water. Several methods for describing the volatilization boundary condition were tested to assess the accuracy in predicting the volatilization rate, including an approach that requires no atmospheric information and an approach that couples soil and atmospheric processes. Four scenarios were constructed and simulated, to compare with measured volatilization rates. The peak measured volatilization rate (168 g ha1 hr1) was most accurately predicted with the scenario that included the most complex model (100 g ha1 hr1). The simplest model over predicted the peak rate (251 g ha1 hr1) and the others under predicted the peak rate (16  67 g ha1 hr1). The simulations that limited aqueous solubility provided relatively similar values for the total emissions (21%  36% of applied triallate), indicating that simplified models may compare well with measurements (31% of applied). A prospective simulation over a period of 100 days showed that applying triallate to the soil surface would ultimately lead to atmospheric emissions of 80% of the applied material with 6% remaining in soil. Incorporating triallate to depth of 10 cm would reduce emissions to less than 5% and lead to 41% remaining in soil. Objective 3. Provide stakeholders with tools for developing strategies to ensure sustainable agriculture and to protect natural resource systems. Chemical Leaching and Evaluation of Risk System (CLERS). An ARC/GIS-based simulation tool is used to calculate leaching characteristics of pesticides based upon soil physical/chemical properties, depth to water, recharge rate, and pesticide properties. The model is used to calculate leaching of existing and new chemicals coming to Hawaii on island-wide scale. Variability in soil organic carbon at various soil classification groups and the variabilities in half-life and organic carbon partition coefficients are taken into consideration while developing this GIS-based model. Digital soil information, variation of recharge, and the depth to ground water are now included in the database. The model is now used by the Hawaii Department of Agriculture and pesticide registrants to evaluate relative attenuation of pesticides. If a new chemical appears to be significantly mobile compared to two reference chemicals (one that is frequently observed in drinking waters and the other has never been found so far), restrictive measures will be taken by the state for the registration of these compounds. The updated pesticide leaching assessment model CLERS is now used by the State of Hawaii for pesticide registration. Currently, the State is examining the model for leachability assessment of fipronil, imidacloprid, s-metolachlor, sulfometurin methyl, and trifloxystrobin. Leaching of Selected Chemicals in Various Hawaii Soils . Four existing and two new chemicals (four herbicides, one fungicides, and one insecticide) were tested at five sites (three on Oahu, one each on Maui and Kauai) to evaluate their leaching under diverse soil conditions. The leaching study took place over a period of 16 weeks. Laboratory batch sorption and aerobic degradation half-life studies were also completed. In addition, a column experiment was carried out to obtain transport parameters in an undisturbed core. We have conducted displacement experiments with these five chemicals along with atrazine and bromide in one undisturbed column with two flow interruptions. All samples have been analyzed. A draft report was prepared. We are working on three papers. Measuring Herbicide Volatilization from Bare Soil. A field experiment was conducted to measure surface dissipation and volatilization of the herbicide triallate after application to bare soil using micrometeorological, chamber, and soil-loss methods. The volatilization rate was measured continuously for 6.5 days and the range in the daily peak values for the integrated horizontal flux method were from 32.4 (day 5) and 235.2 g ha-1 d-1 (day 1), for the theoretical profile shape method were from 31.5 and 213.0 g ha-1 d-1, and for the flux chamber were from 15.7 to 47.8 g ha-1 d-1. Soil samples were taken within 30 min after application and the measured mass of triallate was 8.75 kg ha-1. The measured triallate mass in the soil at the end of the experiment was approximately 6 kg ha-1. The triallate dissipation rate, obtained by soil sampling, was approximately 334 g ha-1 d-1 (98 g d-1) and the average rate of volatilization was 361 g ha-1 d-1. Soil sampling at the end of the experiment showed that approximately 31% (0.803kg/2.56kg) of the triallate mass was lost from the soil. Significant volatilization of triallate is possible when applied directly to the soil surface without incorporation.

Accinelli, C., W. C. Koskinen, and M. J. Sadowsky. 2006. Influence of Cry1Ac toxin on mineralization and bioavailability of glyphosate in soil. J. Agric. Food Chem. 54:164-169. Accinelli, C., W. C. Koskinen, and M. J. Sadowsky. 2006. Influence of Cry1Ac toxin on mineralization and bioavailability of glyphosate in soil. J. Agric. Food Chem. 54:164-169. Bondarenko, S., Zheng, W., Yates, S.R., and Gan, J. 2006. Dehalogenation of halogenated fumigants by polysulfide salts. Journal of Agricultural & Food Chemistry. 54:5503-5508. Bradford, S.A., Simunek, J., Bettahar, M., van Genuchten, M.Th., S.R. Yates. 2006. Significance of straining in colloid deposition: Evidence and implications. Water Resources Research. 42 (12): Art. No. W12S15 Charles, S.M., H. Li, B.J. Teppen, and S.A. Boyd, 2006, Quantifying the Availability of Clay Surfaces in Soils for Adsorption of Organic Contaminants and Pesticides. Environmental Science and Technology, 40:7751-7756. Charles, S.M., B.J. Teppen, H. Li, D.A. Laird, and S.A. Boyd. 2006. Exchangeable Cation Hydration Properties Strongly Influence Soil Sorption of Nitroaromatic Compounds, Soil Science Society of America Journal, 70:1470-1479. Chen, J. J. Lichwa, M. Snehota, S. Mohanty, and C. Ray. 2006. Determination of hormones and non-ionic surfactants in aqueous samples using LS-ESI-MS-MS and GC-MS, Chromatographia, 64(7/8): 413-418 Cruz-Guzmán, M., R. Celis, M. C. Hermosín, W. C. Koskinen, E. A. Nater and J. Cornejo. 2006. Heavy metal adsorption by montmorillonites modified with natural organic cations. Soil Sci. Soc. Am. J. 70:215-221. Cordova-Kreylos, A., Cao, Y., Green, P., Hwang, H., Kuivila, K.M., LaMontagne, M.G., Van de Werfhorst, L.C., Holden, P.A., and K.M. Scow. 2006. Diversity, Composition, and Geographical Distribution of Microbial Communities in California Salt Marsh Sediments. Appl. Environ. Microb. 72(5):3357-3366. Koskinen, W. C., M. J. Calderon, P. J. Rice, and J. Cornejo. 2006. Sorption-desorption of flucarbazone and propoxycarbazone and their benzenesulfonamide and triazolinone metabolites in two soils. Pest Manage. Sci. 62:598-602. Koskinen, W. C, T. E. Ochsner, B. M. Stephens, and R. S. Kookana. 2006. Sorption of isoxaflutole diketonitrile degradate (DKN) and dicamba in unsaturated soil. J. Environ Sci. Health B. 41:1071-1083. Koskinen, W. C., P. J. Rice, and J. Seebinger. 2006. Experimental variability in characterization of cyfluthrin sorption to soil. J. Environ. Sci. Health, Part B. 41:323-331. Li, H., Brian J. Teppen, David A. Laird, Cliff T. Johnston, and Stephen A. Boyd, 2006, Effects of Increasing Potassium Chloride and Calcium Chloride Ionic Strength on Pesticide Sorption by Potassium- and Calcium-Smectite, Soil Science Society of America Journal, 70:1889-1895. Nakatsu, C.H., Hristova, K., Hanada, S., Meng, X.Y., Hanson, J.R., Scow, K.M., and Y. Kamagata. 2006. Methylibium petroleiphilum gen. nov., sp. Nov., a novel methyl tert-butyl ether-degrading methylotroph of the Betaproteobacteria. Int. J. Syst. Evol. Micr. 56:983-989. Ochsner, T. E., B. M. Stephens, W. C. Koskinen, and R. S. Kookana. 2006. Sorption of a hydrophilic pesticide: effects of soil water content. Soil Sci. Soc. Am. J. 70:1991-1997. Papiernik, S. K., W. C. Koskinen, L. Cox, P. J. Rice, S. A. Clay, N. R. Werdin-Pfisterer, and K. A. Norberg. 2006. Sorption-desorption of imidacloprid and its metabolites in soil and vadose zone materials. J. Agric. Food Chem. 54:8163-8170. Papiernik, S. K., W. C. Koskinen, L. Cox, P. J. Rice, S. A. Clay, N. R. Werdin-Pfisterer, and K. A. Norberg. 2006. Sorption-Desorption of Imidacloprid and Its Metabolites in Soil and Vadose Zone Materials. J. Agric. Food Chem. 54:8163-8170 Pignatello, J.J., Y. Lu, E.J. LeBoeuf, W. Huang, J. Song and B. Xing. 2006. Nonlinear and competitive sorption of apolar compounds in black carbon-free natural organic materials J. Environ. Qual.35: 1049-1059. Pignatello, J. J., S. Kwon, and Y. Lu. 2006. Effect of Natural Organic Substances on the Surface and Adsorptive Properties of Environmental Black Carbon (char): Attenuation of Surface Activity by Humic and Fulvic Acids Environ. Sci. Technol., 40: 7757-7763. Regitano, J. B., W. C. Koskinen, and M. J. Sadowsky. 2006. Influence of soil aging on sorption and bioavailability of simazine. J. Ag. Food Chem. 54:1373-1379. Regitano, J. B., W. C. Koskinen, and M. J. Sadowsky. 2006. Influence of soil aging on sorption-desorption and bioavailability of simazine. J. Agric. Food Chem. 54:1373-1379 Roberts, M.G., H.Li, B.J. Teppen, and S.A. Boyd. 2006. Sorption of Nitroaromatics by Ammonium- and Organic Ammonium-Exchanged Smectite: Shifts from Adsorption/Complexation to a Partition-Dominated Process. Clays and Clay Minerals, 54:426-434. Sander, M., Y. Lu, and J.J. Pignatello, 2006. Conditioning-Annealing Studies of Natural Organic Matter Solids Linking Irreversible Sorption to Irreversible Structural Expansion Environ. Sci. Technol., 40: 170-178. [Correction, 40: 6518 (2006)] Sander, M. and J.J. Pignatello. 2006. On the Reversibility of Sorption to Black Carbon: Distinguishing True Hysteresis from Artificial Hysteresis Caused by Dilution of a Competing Adsorbate Environ. Sci. Technol., ASAP article. Sadowsky, M. J., W. C. Koskinen, J. Seebinger, B. L. Barber, and E. Kandeler. 2006. Automated robotic assay of phosphomonoesterase activity in soils. SSSAJ 70:378-381. Sadowsky, M. J., W. C. Koskinen, J. Seebinger, B. L. Barber, and E. Kandeler. 2006. Automated robotic assay of alkaline phosphomonoesterase activity in soils. Soil Sci. Soc. Am. J. 70:378-381. Sahoo, G.B., C. Ray, E. Mehnert, and D. A. Keefer. 2006. Use of Neural Networks to Assess Shallow Ground Water Contamination within the Illinois State Monitoring Well Network for Pesticides, The Science of the Total Environment, 367: 234-251. Shapir, N., G. Cheng, M. J. Sadowsky, and L. P. Wackett. 2006. Purification and characterization of TrzF: Biuret hydrolysis by allophanate hydrolase supports growth. Appl. Environ. Microbiol. 72:2491-2495. Shapir, N., C. Pedersen, O. Gil, L. Strong, J. Seffernick, M. J. Sadowsky, and L. P. Wackett. 2006. TrzN from Arthrobacter aurescens TC1 is a zinc amidohydrolase. J. Bacteriol. 188:58595864. Vaneet Aggarwal, Hui Li, and Brian J. Teppen, 2006, Triazine Adsorption by Saponite and Beidellite Clay Minerals, Environmental Toxicology and Chemistry, 25:392-399. Vaneet Aggarwal, Hui Li, Stephen A. Boyd, and Brian J. Teppen, 2006, Enhanced sorption of trichloroethene by smectite clay exchanged with Cs+, Environmental Science and Technology, 40: 894-899. Wang, D., S. W. Fraedrich, J. Juzwik, K. Spokas, Y. Zhang, and W. C. Koskinen. 2006. Fumigant distribution in forest nursery soils under water seal and plastic film after application of dazomet, metam-sodium and chloropicrin. Pest Manag. Sci. 62: 263-273. Wang, Q., Bradford, S.A., Zheng, W., and Yates, S.R. 2006. Degradation kinetics of manure-derived sulfadimethoxine in soil. Journal of Agricultural & Food Chemistry. 54:157-163. Wang, Q., Bradford, S.A., Zheng, W., and Yates, S.R. 2006. Sulfadimethoxine degradation as affected by initial concentration, moisture, and temperature. Journal Environmental Quality. 35:21622169. Yates, S.R. 2006. Measuring herbicide volatilization from bare soils. Environmental Science and Technology. 40:3223 -3228. Yates, S.R. 2006.Simulating herbicide volatilization from bare soil affected by limited solubility in water. Environmental Science and Technology. 40:6963-6968. Zheng, W., Yates, S.R., Papiernik, S.K. and Wang, Q.Q. 2006. Reducing 1,3-dichloropropene emissions from soil columns amended with thiourea. Environmental Science and Technology. 40:2402-2407. Zheng, W., Yates, S.R., Papiernik, S.K., Guo, M., and Gan, J. 2006. Dechlorination of chloropicrin and 1,3-dichloropropene by hydrogen sulfide species: Redox and nucleophilic substitution reactions. Journal of Agricultural & Food Chemistry. 54:2280-2287. Zheng, W., Yates, S.R., and Papiernik, S.K. 2006. Conversion of metam sodium and emission of fumigant from soil columns, Atmospheric Environment. 40:70467056. Zheng, W., S. R. Yates, S. K. Papiernik, M. Guo, and J. Gan. 2006. Dechlorination of chloropicrin and 1,3-dichloropropene by hydrogen sulfide species: Redox and nucleophilic substitution reactions. J. Agric. Food Chem. 54:2280-2287. Zheng, W., S. R. Yates, S. K. Papiernik, and Q. Wang. 2006. Reducing 1,3-dichloropropene emissions from soil columns amended with thiourea. Environ. Sci. Technol. 40:2402-2407. Zheng, W., S. R. Yates, S. K. Papiernik, and J. Nunez. 2006. Conversion of metam sodium and emission of fumigant from soil columns. Atmos. Environ. 40:7046-7056.