Brief Summary of Minutes of Annual Meeting

The 2007 meeting of W-1082 Evaluating the Physical and Biological Availability of Pesticides and Pharmaceuticals in Agricultural Contexts was held on January 14 and 15, 2008 in St. George, UT hosted by Clinton Williams. Lee Sommers (Administrative Advisor) provided an overview of the budget outlook for the coming year and the Farm Bill. 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. 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. Jack Watson was elected Secretary and Clinton Williams will become Chair of the committee. It was determined by consensus of the attending members that next years meeting would be hosted by Jay Gan at UC Riverside on Jan. 8-9, 2009.

Objective 1. To identify and quantify fundamental chemical, physical, and biological processes relevant to agricultural pesticides and pharmaceuticals in the environment Modeling tillage-induced redistribution of soil mass and its constituents within different landscapes. - Soil movement by tillage (tillage erosion) is recognized as a major force in redistributing soil in cultivated landscapes. The redistribution of soil constituents is affected by soil movement by tillage and mixing of subsoil into the tilled layer. Tillage erosion affects soil productivity and environmental quality by redistributing soil mass and soil constituents in the landscape. In this study, a model (TillTM) was developed to simulate the tillage erosion process. The TillTM model is a diffusion model, which is conceptually simple. This model was used to describe the redistribution of soil mass and soil organic carbon (an example soil constituent) on landscapes with different topographic features. We determined that the rate of soil movement by tillage is mainly dependent on topography, whereas the redistribution of soil constituents was primarily affected by landscape topography, tillage direction, and time. The TillTM model was tested against field measurements. It was shown that the TillTM model can precisely estimate the pattern of soil constituent redistribution by tillage, but may require detailed field measurements to accurately represent the changing contents of soil constituents in the landscape. These results will enable land managers, extension personnel, consultants, and agricultural researchers to predict the effects of tillage erosion on the movement of soil mass and soil constituents in landscapes and to better describe landscapes affected by tillage erosion. These results will be useful in designing and evaluating cropping practices to reduce soil erosion. Herbicide sorption coefficients in relation to soil properties and terrain attributes on a cultivated prairie.- Pesticide fate models are used to assess the risk of water contamination by pesticides on a national basis. Sorption coefficients (measures of the extent to which pesticides are bound to the soil) are important variables in pesticide fate models. Accounting for the variation in pesticide sorption coefficients across landscapes could reduce uncertainties in regional-scale assessments of pesticide behavior. In these experiments, we measured the sorption coefficients of two common herbicides, 2,4-D and glyphosate, in 286 soil samples collected throughout a hilly field. Soil properties are highly variable in this field because erosion has removed topsoil from some areas of the field. Herbicide sorption coefficients are dependent on soil properties and thus were also highly variable. We found that including information about slope curvature and other factors describing the terrain could improve predictions of herbicide sorption in this field. The changes in soil properties and terrain factors had a larger impact on the sorption of a herbicide that is weakly bound by the soil (2,4-D) than for a herbicide that is strongly bound (glyphosate). These results suggest that this approach may help increase the accuracy of pesticide fate models. These results will help guide additional research to determine how including information about field terrain can improve pesticide fate models. Effects of soil fumigants on methanogenic activity. - Methane is a potent greenhouse gas. Soils from various agricultural experiment stations, forest nurseries, and a landfill were evaluated for effects of three soil fumigants on methane oxidation capacities. All three fumigants evaluated significantly reduced methane oxidation rates in historically non-fumigated soils. Chloropicrin universally decreased oxidation capacity regardless of fumigation history. These results support the conclusion that methane oxidation effects are fumigant specific and that prior fumigation history plays a vital role in determining the impact on the methane oxidizer community. This research documents some of the impacts of human activity on the amount of greenhouse gases in the atmosphere. The oxidation of methane by soil bacteria is the only known biological sink for atmospheric methane. Without this sink, atmospheric methane levels could potentially increase, resulting in a larger greenhouse effect. This research documents the impacts of soil fumigants on these bacteria and thereby creates the foundation for examining better soil fumigation practices to minimize this impact. Sorption reversibility: distinguishing true hysteresis from artificial hysteresis caused by dilution of a competitor - Sorption in soils and sediments is generally modeled as a reversible process. However, sorption hysteresis is a commonly observed phenomenon. If due to real causes and not experimental artifacts, hysteresis has important implications for the mobility and bioavailability of anthropogenic chemicals. We examined the reversibility of sorption by wood char from water of benzene, toluene, and nitrobenzene, both singly and in pairs. Artificial causes of hysteresis such as slow diffusion and mass loss were ruled out in controls. Single-solute sorption was weakly hysteretic at high concentrations and approximately the same for the three adsorbates; this finding is taken as evidence that hysteresis is true and supports irreversible pore deformation by the incoming adsorbate as the cause, as demonstrated in previous studies for natural organic matter. Simulations using a thermodynamic competition model, Ideal Adsorbed Solution Theory, support the hypothesis. Laccase-mediated Michael addition of sulfapyridine to a model humic constituent - Chemical incorporation of sulfonamide antimicrobials into natural organic matter may represent an important process influencing the fate of these synthetic, bacteriostatic agents in soil and sediment environments. We show that fungal laccase-mediated reaction of sulfapyridine with the ortho-dihydroxyphenol protocatechuic acid yields a Michael adduct. To enable elucidation of the covalent linkage(s) formed between sulfapyridine and protocatechuic acid by NMR, we synthesized 15N-enriched sulfapyridine. 1H-15N heteronuclear multiple bond correlation experiments and tandem mass spectrometry demonstrated that the sulfapyridine anilinic nitrogen engaged in a Michael addition reaction to oxidized protocatechuic acid forming of an anilinoquinone. Michael adducts are substantially more stable than the previously reported imine linkages between sulfonamides and 2,6-dimethoxyphenols. Formation of Michael adducts between sulfonamide antimicrobials and quinone-like structures in soil organic matter is expected to result in their immobilization and reduced biological activity. 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 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. Mineralization of the Bacillus thuringiensis Cry1Ac endotoxin in soil - Cconflicting information on persistence of this class of insecticidal toxins exists. In the present study, 14C from glucose was incorporated into the B. thuringiensis Cry1Ac endotoxins and radiolabeled toxin was used to study its mineralization in soil samples incubated under controlled conditions. Fifty-nine percent of the radio-labeled Cry1Ac was recovered as 14CO2 at the end of the 20-day incubation period. Addition of 4.5% of corn residues stimulated mineralization of [14C]Cry1Ac toxin. Since low mineralization (approximately 6%) of the radio-labeled toxin was observed in autoclaved soil, our findings indicate a major role of microbial processes in the dissipation of the Cry1Ac endotoxin. This study demonstrates that there would be no risk of bioaccumulation of Cry1Ac in soil eventually released by Bt-protected crops. This study demonstrates that there would be no risk of bioaccumulation of the Cry1Ac toxin in soil eventually released by Bt-protected crops and that producers can safely use these crops. Effects of the Fluoroquinolone Antibiotic Ciprofloxacin on Estuarine Sediment Microbial Communities. - Fluoroquinolones, a widely used class of antibiotics, are frequently detected in sediments and surface waters. Given their antimicrobial properties, the presence of these compounds may alter the composition of microbial communities and promote antibiotic resistance in the environment. The purpose of this study was to measure sorption, and effects of ciprofloxacin on microbial community composition, in sediment samples from three California salt marshes. Sediments were exposed to a ciprofloxacin concentration gradient (0 to 200 µgml-1 ciprofloxacin) and microbial community composition characterized using phospholipid fatty acid (PLFA) analysis. Sorption coefficients, expressed as log Kd, were calculated from fits using the Freundlich isotherm model. Ciprofloxacin strongly sorbed to all sediments and had log Kd values, ranging from 2.9 to 4.3. Clay content was positively (r2=0.98) and pH negatively (r2=0.99) correlated to Kd values. Biomass, richness, sulfate reducer and gram-negative bacterial markers increased with ciprofloxacin concentrations, while the 17cy/precursor and saturated/unsaturated biomarker ratios, indicators of starvation stress, decreased. The magnitude of the effect of ciprofloxacin on microbial communities was inversely correlated to the degree of sorption to the sediments. Despite the fact that ciprofloxacin is a wide-spectrum antibiotic, its impact on sediment microbial communities was selective and appeared to favor sulfate reducing bacteria and gram-negative bacteria. Impacts of Triclosan and Triclocarban on Soil Microbial Communities. - Triclosan (TCS), [2,4,4-trichloro-2-hydroxydiphenylether], and Triclocarban (TCC), [N-(4-chlorophenyl)-N-(3,4-dichlorophenyl)-urea], are broad range antibacterial agents widely used in common household products (i.e. shampoo, soap, detergent, toothpaste, cosmetics, sanitizers, etc). Preliminary experiments were performed to explore the potential effects on TCS and TCC on soil microbial communities, using phospholipid fatty acid (PLFA) analysis as a screening method. Biomass decreased in both TCS (from 65.2 to 43.9 nmol/g dry soil) and TCC (from 65.2 to 44.7 nmol/g dry soil) treatments in comparison to the controls. The decrease of biomass was higher at 100-ug/g TCS and TCC treatments. On exposure to 10-ug/g TCC, the community was no different from an unexposed community, whereas exposure to 10-ug/g TCS, a relatively low concentration, substantially altered the community composition. At 100-ug/g, both compounds affected the community and the responses were quite variable. In conclusion, the more strongly sorbedTCC had less of an impact than the more water soluble TCS, perhaps due to differences in availability or toxicity. Fungal biomarkers remained unchanged, but abundance of monounsaturated fatty acids decreased in antimicrobial treated soils. Carbamazepine Distribution in a Treatment Wetland Receiving Effluent from a Sewage Treatment Facility - Artificially constructed wetlands offer a low cost treatment alternative to remove a number of pollutants found in effluent water from industry, mining, agriculture, and urban areas. Wetlands can be used to mechanically remove suspended solids through sedimentation. Dissolved nutrients, biochemical oxygen demand (BOD), heavy metals, and potentially harmful anthropogenic compounds can all be removed in constructed wetlands through geochemical and biological processes. The anti-epileptic drug carbamazepine has been shown to be recalcitrant in sewer treatment facilities and in the environment. Carbamazepine concentrations were measured on two different dates within a 1.2 ha treatment wetland that receives treated municipal effluent. On July 7, 2005 carbamazepine concentration ranged from 5.6 ng L-1 to 45.1 ng L-1. The concentration at the inlet was 22.8 ng L-1 and 23.4 ng L-1 at the outlet. The highest concentration was found internally within the wetland and the outlet concentration was higher than the inlet. Carbamazepine concentrations from the August 9, 2005 sampling were significantly lower than the July sampling event and ranged from 1.0 ng L-1 to 5.4 ng L-1. The concentration at the inlet was 10.6 ng L-1 and 3.2 ng L-1 at the outlet. Results indicate that there is evidence for carbamazepine removal within the wetland due to photodegradation and sorption followed by sedimentation. Concentrations within the wetland are also highly variable and depend on loading from the treatment plant as well as potential dilution due to precipitation. Hydroxyatrazine N-ethylaminohydrolase (AtzB): An amidohydrolase superfamily enzyme catalyzing deamination and dechlorination - Hydroxyatrazine N-ethylaminohydrolase (AtzB) is the sole enzyme known to catalyze the hydrolytic conversion of hydroxyatrazine to N-isopropylammelide. AtzB, therefore, serves as the point of intersection of multiple s-triazine biodegradative pathways and is completely essential for microbial growth on s-triazine hebicides. Here, atzB was cloned from Pseudomonas sp. ADP, purified to homogeneity, and characterized. AtzB was found to be dimeric, with subunit and holoenzyme molecular weights of 52 kDa and 105 kDa, respectively. The kcat and Km of AtzB with hydroxyatrazine as a substrate were 3 sec-1 and 20 µM, respectively. Purified AtzB had a 1:1 zinc to subunit stoichiometry. Sequence analysis revealed that AtzB contained the conserved mononuclear amidohydrolase superfamily active site residues: His74, His76, His245, Glu248, His280, and Asp331. An intensive in vitro investigation into the substrate specificity of AtzB revealed that 20 of the 51 substrate analogs tested were substrates for AtzB; this allowed for the identification of specific substrate structural features required for catalysis. Substrates required a monohydroxylated s-triazine ring with a minimum of one primary or secondary amine substituent, and either a chloride or amine leaving group. AtzB catalyzed both deamination and dechlorination reactions with rates within a range of one order of magnitude. This differs from AtzA and TrzN, which do not catalyze deamination reactions, and AtzC, which is not known to catalyze dechlorination reactions. Environmental fate of two sulfonamide antimicrobials agents in soil - Veterinary antimicrobial agents have been detected in a number of environmental samples, including agricultural soils. In this study, we investigated the persistence and sorption of the sulfonamides sulfamethazine (SMZ) and sulfachloropyridine (SCP) in soil and their potential effects on soil microorganisms. The sulfonamides dissipated more rapidly from the silt loam soil as compared to the sandy soil. Average half-lives of SMZ and SPC among the two soils were 18.6 and 21.3 days, respectively. The presence of liquid swine slurry (5% v/w) decreased sulfonamide persistence in the silt loam soil. The lower persistence of the antimicrobials in liquid swine slurry-amended soil was likely due to higher microbial activity, as compared to unamended soil, and/or to the greater bioavailability of the sulfonamides to degrading microorganisms, as estimated by sorption isotherms. Concentrations of SMZ and SPC up to 100 g g-1 had no effect on antimicrobial degradation rates and soil microorganisms. These studies suggest that higher sulfonamide concentrations would be necessary to affect the main processes controlling their environmental fates in soil, but at the concentrations normally found in the environment, there would be little or no effects. Formation and fate of nitrosamines from pesticides and pharmaceuticals in environmental matrices and (under conditions of) the human digestive tract. - We determined the formation of nitrosamine derivatives of nitrosatable pesticides and pharmaceuticals (a) in the presence of nitrite in vitro, emphasizing conditions simulating the human digestive tract and (b) during chloramination for disinfection of drinking water. (a) Nitrosation from Reaction with Nitrite at Acidic pH. Aqueous phase experiments provided strong evidence for the formation nitrosamine derivatives of atrazine (ATZ), ethambutol (ETB), furosemide (FSM), procainamide (PCA) and ranitidine (RTD) from reaction with nitrite under acidic conditions. Evidence of small amounts of nitrosamine derivatives of cefadroxil (CFD) and metoprolol (MTP) was also found but not confirmed. Considerable loss of parent compound was observed for ETB, FSM, PCA and RTD. The rate of transformation for ATZ was relatively slow. HPLC and LS/MS analyses demonstrated that ETB, FSM, RTD, and ATZ, in the presence of nitrite at pH 3, were nitrosated to produce mono-N-nitrosoethambutol (MNEB) and di-N-nitrosoethambutol (DNEB), N-nitrosofurosemide (NFSM), N-nitrosoranitinde (NRTD), and mono-N-nitrosoatrazine (MNAT) as the primary transformation product. For PCA, LC/MS analyses indicated that a small quantity of the expected N-nitrosoprocainamide (NPCA) was produced while hydroxy-procainamide (HCPA) was produced as the major transformation product. (b) Nitrosation from Reaction with Chloramines. The potential for amine pharmaceuticals and atrazine to form nitroso compounds (NOCs) and their derivatives from reaction with monochloramines (MC) at neutral pH was also evaluated. A Cl:N ratio of 0.7:1 was optimum for the formation of MC, but no dichloramine (DC) was formed. At a Cl:N ratio of 1.1:1, the MC concentration decreased as DC increased. These results indicate that the production of chloramines is highly dependent upon pH, and the ratio of chlorine to ammonia-nitrogen. Reaction with chloramines resulted in considerable loss of cefadroxil (CFD), chlorpheneramine (CPA), furosemide (FSM), metoprolol (MPL), ranitidine (RTD), and atrazine (ATZ). The pharmaceuticals showed relatively high transformation rates on a molar basis under standardized conditions. By comparison, the rate of ATZ transformation was relatively slow. The loss of parent compound during 4-h incubations was consistently greater than after 1 h. Atrazine-Degrading Microbial Populations in Soils and Wetlands: Linking Degradation to Diversity - Using Bio-Sep® beads containing varying concentrations of atrazine, we were able to monitor shifts in microbial community structure due to in situ enrichment using atrazine as a substrate in agricultural soils that varied in their atrazine exposure history. Fluorescent in situ hybridization (FISH) with 16S rDNA-based phylogenic probes and 16S rDNA denaturing gradient gel electrophoresis (DGGE) were used to assess the community composition of bacteria that colonized the beads. Atrazine dissipation in soil in which the beads were deployed was rapid indicating that atrazine-degrading bacteria responsive to atrazine additions were present in the soils selected for bead deployment. DGGE analysis revealed that the soil and bead communities were distinctly different. Atrazine concentration within the beads appeared to influence the community composition to a greater extent than the prior atrazine treatment history to the soils in which the beads were buried. Eubacterial biomass increased by approximately 5-40 fold in atrazine containing beads relative to atrazine-free beads suggesting an enrichment in atrazine-degrading bacteria within the baited beads. The phylogenetic distribution within the bead communities varied depending upon i) atrazine concentration and ii) the prior history of atrazine application to the soil in which the beads were buried. In beads buried in soil with a recent history of atrazine application, the abundance of Actinobacteria increased approximately 80 fold in beads containing 20 mg atrazine kg-1 of beads. In the beads from non-history soil, Actinobacteria were enriched by only 10 fold while the greatest enrichment was observed for the gamma-Proteobacteria and Planctomycetes which increased by 60 and 25 fold respectively. While a number of atrazine-degrading bacteria classified within the gamma-Proteobacteria have been isolated, no such bacteria have been described within the Planctomycetes. Very few cultivated representatives from this phylum have been reported but their apparent role in protein decomposition and anaerobic ammonia oxidation (Anammox reaction) has been documented. In enrichment cultures derived from soil incubated Bio-Sep beads, bacteria from this phylum were detected and we hypothesize that the growth of these bacteria in atrazine-degrading enrichment cultures is supported by oxidation of alkylamines released during the degradation of atrazine by other members of the consortia. Attempts to isolate these bacteria to date have been unsuccessful. At the higher atrazine concentration (200 mg atrazine kg-1 of beads) the gamma Proteobacteria were enriched by 120 and 230 fold in the beads buried in history and non-history soil, respectively. The alpha-Proteobacteria were enriched to a much lesser extent; 10 and 20 fold in the history and non-history beads, respectively. Interestingly, the relative enrichment of Actinobacteria and Planctomycetes that were observed at the lower atrazine concentration did not occur in beads containing the higher atrazine concentration of 200 mg atrazine kg-1 of beads. The results demonstrate that BioSep beads are a suitable matrix for recruiting a highly diverse subset of the bacterial community involved in atrazine degradation and have the potential for isolation of other novel soil bacteria with unique metabolic phenotypes such production of antibiotics, other pharmaceuticals, and commercially valuable enzymes. Objective 2: Integrate chemical and biological process information for use in models applicable across different spatial and temporal scales. Transport of selected endocrine disrupting chemicals from wastewater through a Hawaiian Oxisol - Additional experiments (beyond that reported in 2006) were conducted to examine the leachability of two estrogen hormones (17-beta estradiol and estrone) for three soils found on the island of Oahu. One of the three soils is an Oxisol and samples were collected from two depths: 0.6 m and 2.5 m. The second soil is a Mollisol and it was collected from similar depths. The third soil is volcanic cinder, which was collected from 0.3 m below ground. Batch sorption experiments were conducted for these two chemicals using (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 animal waste lagoon. The two compounds adsorbed strongly to the Oxisol and Mollisol collected from both depths. However, they weakly adsorbed to volcanic cinder. In column tests, both physical and chemical nonequilibrium processes were found to affect the mobility of these chemicals. Transport of these compounds was enhanced with lagoon effluent due to the presence of dissolved organic carbon. Pathogen Transport in Hawaii Soils - We are studying the transport of two bacteria viruses (MS-2 and jX-174) in the same three soils described above. In general, the Oxisols and Mollisols are effective in attenuating the transport of these two bacteriaphages. However, in the Mollisol we found breakthroughs in less than 25 pore volumes when lagoon effluent was injected along with the phages. For cinder, breakthrough was quick. All transport experiments were conducted in saturated conditions with low-ionic strength buffers. Also, two specific organic buffers (TRIS  pH 8 and MES  pH 5.5) were tested to examine their effect on transport. In selected cases, TRIS produced breakthroughs of jX-174. Formation and fate of nitrosamines from pesticides and pharmaceuticals in environmental matrices and (under conditions of) the human digestive tract - In a related project (funded through the USDA-CSREES National Integrated Water Quality Program), we are developing index models to assess vulnerability to contamination from pesticide leaching and runoff based solely on landscape characteristics (landscape perspective) and on both landscape and pesticide properties (landscape and chemical perspective). Details were provided in the initial proposal. The emphasis of the past year has been on refining the landscape vulnerability model. We have introduced mathematical functions for all process variables into the model. The model is currently being applied to map landscape vulnerability to pesticide leaching, solution runoff, and particle adsorbed runoff in the four-county Blue River watershed at the Nebraska-Kansas border. Objective 3. Provide stakeholders with tools for developing strategies to ensure sustainable agriculture and to protect natural resource systems. Leaching of Selected Chemicals in Various Hawaii Soils - The State of Hawaii uses an ARC/GIS-based screening tool to assess leachability of a pesticide based upon soil physical/chemical properties, depth to water, recharge rate, and pesticide properties. Modeling aquifer recovery in response to the ban certain agricultural chemicals in Hawaii - DBCP and ethylene dibromide (EDB) were extensively used in 1960s and 1970s in Hawaiian pineapple. Unfortunately, this use has lead to widespread ground water contamination. DBCP was banned for use in Hawaii in 1978 and EDB was banned 5 years later. As of 2007, many of the contaminated wells show concentrations at their peak. We developed a set of linked models to estimate the concentrations as they moved through the vadose zone to the basal ground water. In the absence of measured data, various inverse methods were employed to estimate reasonable transport parameters for water and chemicals. We showed that the residual contamination can exist for several more decades although these chemicals were banned for use three decades ago.

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