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Cereal rye (Secale cereale) cover crops supply many agroecosystem services in cropping systems including the provision of allelochemicals for weed suppression. Understanding the distinction between root and shoot relative contributions of these allelochemicals (such as phenolic acids) should provide better insight for residue management following termination of a cereal rye cover crop. A field experiment examining root and shoot contributions of phenolic acids to soil was conducted in 2015 at Beltsville, Maryland. Tissue and soil (0–10 cm) phenolic acid concentrations were analyzed over time using liquid chromatography–mass spectrometry. Cereal rye roots were found to be the primary contributor of phenolic acids to soil. Further, soil phenolic acid concentrations were unaffected by tillage or soil depth. Overall, the phenolic acid concentrations of coumaric > vanillic > 4-hydroxybenzoic acid increased in soils during the first 3–7 days after cereal rye termination and then decreased to initial concentrations after 56 days. Our research forms a basis for future allelopathy research. Specifically, there is a need to understand the contribution of roots to phenolic acid release in soils. Building this body of knowledge will improve our ability to employ allelopathy as part of a multi-tactic weed management system.

An important component of assessing the hazards of anticoagulant rodenticides to non-target wildlife is observations in exposed free-ranging individuals. The objective of this study was to determine whether environmentally realistic, sublethal first-generation anticoagulant rodenticide (FGAR) exposures via prey can result in direct or indirect adverse effects to free-flying raptors. We offered black-tailed prairie dogs (Cynomys ludovicianus) that had fed on Rozol® Prairie Dog Bait (Rozol, 0.005% active ingredient chlorophacinone, CPN) to six wild-caught red-tailed hawks (RTHA, Buteo jamaicensis), and also offered black-tailed prairie dogs that were not exposed to Rozol to another two wild-caught RTHAs for 7 days. On day 6, blood was collected to determine CPN's effects on blood clotting time. On day 7, seven of the eight RTHAs were fitted with VHF radio telemetry transmitters and the RTHAs were released the following day and were monitored for 33 days. Prothrombin time (PT) and Russell's viper venom time confirmed that the CPN-exposed RTHAs were exposed to and were adversely affected by CPN. Four of the six CPN-exposed RTHAs exhibited ptiloerection, an indication of thermoregulatory dysfunction due to CPN toxicity, but no signs of intoxication were observed in the reference hawk or the remaining two CPN-exposed RTHAs. Of note is that PT values were associated with ptiloerection duration and frequency; therefore, sublethal CPN exposure can directly or indirectly evoke adverse effects in wild birds. Although our sample sizes were small, this study is a first to relate coagulation times to adverse clinical signs in free-ranging birds.

The nitrification process was simulated using benchtop bioreactors to gain insight into the fate of the antimicrobials triclosan (TCS) and triclocarban (TCC), as well their transformation products, during wastewater treatment. Currently, little information exists on the impact of nitrification treatment on concentrations of TCC, TCC degradation products, and TCS degradation products. Reactors were run using samples collected from a large municipal wastewater treatment plant at two pH ranges (6.5–7.5 and 8.5–9.5) for 171 h to simulate an extended hydraulic retention time (HRT). TCS was degraded under both pH conditions, with a 28.5% overall reduction in solids samples when the pH range was 6.5–7.5 and an overall reduction of 83.2% in solids samples when the pH ranged 8.5–9.5. Methyltriclosan (MeTCS) was formed in solids samples during both treatment conditions. MeTCS formed the most rapidly during the first 25 h of treatment at pH 8.5–9.5. Levels of 2,4-dichlorophenol, a TCS photolysis product, and TCC did not change over the 171 h treatment period, indicating that nitrification is not an effective treatment for reduction of these compounds. Three TCC dechlorination products and triclosan-O-sulfate were not observed at or above the limit of quantitation in any bioreactor samples.

Characterization of the soil metabolome contributes to our understanding of how soil microbial community functions, central to sustainable agriculture, are impacted by agricultural management practices. The aim of this study was to refine the Bligh-Dyer 2-phase extraction method, commonly used in soil phospholipid fatty acid analysis (PLFA), to enhance soil metabolite detection and use this refined method to look at the impact of specific crop production factors on the soil metabolome. We modified the Bligh-Dyer 2-phase extraction method through the addition of the volatile salt, 0.25 M ammonium bicarbonate, to increase the number of metabolites extracted from soil. A greenhouse pot study with three soil types and two crop species was conducted, and soil metabolites extracted using this refined Bligh-Dyer 2-phase extraction, to determine the impact of soil type and crop species treatments on the soil metabolome. Numerous amino acids, carbohydrates, TCA cycle intermediates, and fatty acids as well as the potentially inhibitory compounds ferulic acid, caffeic acid, oxalic acid, and quinic acid differed significantly with treatment. At the onset of the greenhouse pot experiment the three soil types differed significantly in metabolite composition and at the end of the 6 week experiment both soil and crop had significant impacts on the soil metabolome. Substituting the volatile salt 0.25 M ammonium bicarbonate for phosphate buffer in the Bligh-Dyer 2-phase extraction did not significantly impact PLFA analysis of the three soils. The extract was also found to be useable in lipidomic analysis. We conclude that the addition of this volatile salt to the Bligh-Dyer 2-phase extraction provided an effective method for analysis of both the soil metabolome and soil PLFA.

Ethanol extract of cell mass of Serratia marcescens strain N4-5, when applied as a treatment to cucumber seed, has been shown to provide control of the oomycete soil-borne plant pathogen Pythium ultimum equivalent to that provided by a seed-treatment chemical pesticide in some soils. Two dominant compounds in this extract, prodigiosin and the serratamolide serrawetin W1, were identified based on mass and collision induced dissociation mass fragmentation spectra. An additional four compounds with M+H+ masses (487, 541, 543, and 571) consistent with serratamolides reported in the literature were also detected. Several other compounds with M+H+ masses of 488, 536, 684, 834, 906, and 908 m/z were detected in this ethanol extract inconsistently over multiple liquid chromatography coupled with tandem mass spectrometry (LC/MS–MS) runs. A purified preparation of prodigiosin provided control of damping-off of cucumber caused by P. ultimum when applied as a seed treatment while ethanol extract of cell mass of strain Tn246, a transposon-mutant-derivative of strain N4-5, did not. Strain Tn246 contained a mini-Tn5 Km insertion in a prodigiosin biosynthetic gene and was deficient in production of prodigiosin. All other compounds detected in N4-5 extract were detected in the Tn246 extract. This is the first report demonstrating that prodigiosin can control a plant disease. Other compounds in ethanol extract of strain N4-5 may contribute to disease control.

We previously discovered a method to estimate the groundwater mean residence time using the changes in the enantiomeric ratio of metolachlor ethanesulfonic acid (MESA), (2-[(2-ethyl-6-methylphenyl)(2-methoxy-1-methylethyl)amino]-2-oxoethanesulfonic acid), a metabolite of the herbicide metolachlor. However, many grab samples would be needed for each watershed over an extended period, and this is not practical. Thus, we examined the use of a polar organic chemical integrative sampler (POCIS) deployed for 28 days combined with a modified liquid chromatography-mass spectrometry LC-MS/MS method to provide a time-weighted average of the MESA enantiomeric ratio. POCISs equipped with hydrophilic-lipophilic-balanced (HLB) discs were deployed at five sites across the United States where metolachlor was used before and after 1999 and compared the effectiveness of the POCIS to capture MESA versus grab samples. In addition, an in situ POCIS sampling rate (Rs) for MESA was calculated (0.15 L/day), the precision of MESA extraction from stored POCIS discs was determined, and the effectiveness of HLB to extract MESA was examined. Finally, using molecular modeling, the influence of the asymmetric carbon of metolachlor degradation on the MESA enantiomeric ratio was predicted to be negligible. Results of this work will be used in projects to discern the groundwater mean residence times, to evaluate the delivery of nitrate-N from groundwater to surface waters under various soil, agronomic, and land use conditions, and to examine the effectiveness of conservation practices.

Varroa destructor mites (Acari: Varroidae) are harmful ectoparasites of Apis mellifera honey bees. Female foundresses of wax-capped pupal host cells and their daughters feed on host fluids from open wounds on the host's integument. Details of V. destructor mite nutrition are forthcoming, and little is known about the potential physical effects on hosts from mite feeding. Chemical analysis of waste excretions can infer details of animals’ nutrition. Here, chemical analysis by high-performance liquid chromatography/mass spectrometry (HPLC-MS/MS) of mite excretions showed that the purine content of V. destructor waste consists of guanine with traces of hypoxanthine. Traces of uric acid and caffeine were also detected. Concentrations of guanine attenuated over time and excretions collected from senescing mites did not contain detectable guanine. Non-reproducing individual female mites maintained in vitro, housed in gelatin capsules and provided a honey bee pupa, deposited an average of nearly 18 excretions daily, mostly on the host's integument rather than on the capsule wall. The weight and volume of excretions suggest mites can consume nearly a microlitre of host fluids each day. Compounded over 10 days, this together with open wounds, could lead to substantial water loss and stress to developing pupae.

The fate of four phthalate plasticizers during wastewater treatment processes at six different wastewater treatment plants (WWTPs) was investigated. Concentrations of benzyl butyl phthalate (BBP), di(2-ethylhexyl) phthalate (DEHP), diisononyl phthalate (DiNP), and diisodecyl phthalate (DiDP) were determined prior to either aerobic or anaerobic (conventional and advanced) treatment, after treatment, and in final, dewatered solids. Despite their elevated use worldwide, the fate of DiNP and DiDP during wastewater treatment have not been well characterized. DEHP was readily degraded during aerobic treatments while anaerobic digestion resulted in either no significant change in concentrations or an increase in concentration, in the case of more advanced anaerobic processes (thermal hydrolysis pretreatment and a two-phase acid/gas process). Impacts of the various treatment systems on DiNP, DiDP, and BBP concentrations were more varied - anaerobic digestion led to significant decreases, increases, or no significant change for these compounds, depending on the treatment facility, while aerobic treatment was generally effective at degrading the compounds. Additionally, thermal hydrolysis pretreatment of sludge prior to anaerobic digestion resulted in increases in DiNP, DiDP, and BBP concentrations. The predicted environmental concentrations for all four compounds in soils after a single biosolids application were calculated and the risk quotients for DEHP in soils were determined. The estimated toxicity risk for DEHP in soils treated with a single application of sludge from any of the six studied WWTPs is lower than the level of concern for acute and chronic risk, as defined by the US EPA.

Since the 1950's, the broad-spectrum, organochlorine insecticide endosulfan (6,7,8, 9,10,10-hexachloro-1,5,5a,6,9,9a-hexahydro-6,9-methano-2,4,3-benzodioxathiepine-3-oxide) has been used on numerous crops. Due to its persistence, bioaccumulation, long-range transport, and adverse effects to human health and ecosystems, it was officially identified as a persistent organic pollutant (POP) in 2011. The last uses in the United States were phased out in 2016. Endosulfan consists of two diastereomers, α-endosulfan and β-endosulfan, and while the α-isomer exists as two asymmetrical, twist-chair enantiomers which interchange, the β-isomer is a symmetrical-chair conformation. In addition, the β-isomer was found to isomerize to the α-isomer. Gradient Temperature Raman Spectroscopy (GTRS) enables identification the molecular sites at which bending vibrational modes becomes twisting or wagging vibrational modes. Previous studies using GTRS and chemical calculations afforded evidence for specific bond movements and the irreversibility of the isomerization mechanism. However, not all of the vibrational modes observed in the spectra could be explained. Thus, new analyses of the GTRS data were conducted to examine the effects of torsional forces on the bond movement, which allowed for the identification of all the peaks. These newly-identified torsional forces provide further confirmation of the isomerization mechanism and its irreversibility. Finally, this isomerization explains why β-endosulfan is rarely detected in the atmosphere.

To better address how much groundwater contributes to the loadings of pollutants from agriculture we developed a specific dating tool for groundwater residence times. This tool is based on metolachlor ethane sulfonic acid, which is a major soil metabolite of metolachlor. The chiral forms of metolachlor ethane sulfonic acid (MESA) and the chiral forms of metolachlor were examined over a 6-year period in samples of groundwater and water from a groundwater-fed stream in a riparian buffer zone. This buffer zone bordered cropland receiving annual treatments with metolachlor. Racemic (rac) metolachlor was applied for two years in the neighboring field, and subsequently S -metolachlor was used which is enriched by 88% with the S -enantiomer. Chiral analyses of the samples showed an exponential increase in abundance of the S -enantiomeric forms for MESA as a function of time for both the first order riparian buffer stream ( R 2 = 0.80) and for groundwater within the riparian buffer ( R 2 = 0.96). However, the S -enrichment values for metolachlor were consistently high indicating different delivery mechanisms for MESA and metolachlor. A mean residence time of 3.8 years was determined for depletion of the initially-applied rac-metolachlor. This approach could be useful in dating groundwater and determining the effectiveness of conservation measures. One sentence summary A mean residence time of 3.8 years was calculated for groundwater feeding a first-order stream by plotting the timed-decay for the R -enantiomer of metolachlor ethane sulfonic acid.

Riparian buffers are known to mitigate hydrologic losses of nutrients and other contaminants as they exit agricultural fields. The vegetation of riparian buffers can also trap atmospheric contaminants, and these pollutants can subsequently be delivered via rain to the riparian buffer floor. These processes, however, are poorly understood especially for pesticide residues. Therefore, we conducted a four-year study examining stemflow and throughfall to a riparian buffer which was adjacent a cultured Zea mays field treated with atrazine and metolachlor. Stemflow is rain contacting the tree canopy traveling down smaller to larger branches and down the tree trunk, whereas throughfall is rain that may or may not contact leaves and branches and reaches the earth. Stemflow concentrations of the herbicides were larger than throughfall concentrations and accounted for 5-15% of the atrazine and 6-66% of the metolachlor depositional fluxes under the canopy. Larger depositional fluxes were measured when leaves were more fully emerged and temperatures and humidity were elevated. Rain collected outside the riparian buffer on the field side and on the back side revealed the trees trapped the herbicide residues. Herbicide loading to the riparian buffer stream was found to be linked to tree canopy deposition and subsequent washoff during rain events. These results indicate that in agricultural areas canopy washoff can be an important source of pesticides to surface waters.

Nitrogen pollution in watersheds containing significant cropland area is generally problematic. Conservation practices intended to reduce nitrate-N (NO3--N) export from watersheds are being implemented by many regions without necessary tools to assess effectiveness of abatement. A commonly used herbicide metolachlor degrades in the vadose zone of croplands to form two metabolites (metolachlor ethane sulfonic acid (MESA) and metolachlor oxanilic acid (MOXA)) which are both highly soluble in soils. Study of metabolite fates in a first order watershed provided evidence that transport of these metabolites to stream water is highly correlated to transport of agricultural NO3--N that also forms in the cropland vadose zone. Linear models describing the relationships of stream flux of MESA and MOXA to NO3--N flux generated goodness of fit values of 0.93 and 0.81, respectively. These findings support a conclusion that both MESA and MOXA act as excellent transport analogs of NO3--N and become strongly correlated to agricultural NO3--N leaching from the cropland vadose zone. Moreover, their use as conservative tracers in agricultural watersheds can provide valuable information concerning movement and fate of agricultural nitrogen at watershed scales of observation.

A common response of plant leaves and roots to stress, biotic or abiotic, is the oxidative burst. In leaves, this results in reactive oxygen species being produced within the apoplast, the space surrounding the responding cells. A second response that occurs in the tobacco apoplast during this period is the production and accumulation of phenolic metabolites. The interaction of these redox active metabolites should have major effects on the redox potential of the apoplast and subsequently affect the outcome of the plant tissue. To begin to understand the effects of these responses on the redox potential, two induced phenolics, acetovanillone (AV) and acetosyringone (AS) were studied in vitro with peroxidase and H2O2, all of which are present in the tobacco apoplast. While both phenolics were observed to be substrates for peroxidase, AV was found to react 10x faster than AS. The oxidation of AV resulted in an increase of the redox potential to a maximum of 0.35 V. The oxidation of AS resulted in an increase to a maximum of 0.55 V. Interestingly, the redox potential was not proportional to the oxidation of either phenolic. It was found that when present together, co-oxidation occurs with the faster acting AV as a catalyst to oxidize AS. This has an immediate effect on the redox potential. The rate of AS oxidation is dependent on the AV concentration and thus so is the redox potential reaching 4.5 V. The results suggest that these phenolics could play a role in the regulation of the apoplast redox potential during the early stages of stress.

The objective of this study was to corroborate, in pepper, the response of tobacco to induce apoplast phenolics upon bacterial inoculation. Leaves of Bell peppers (Capsicum annuum), 6–8 weeks old, were inoculated with bacteria and analyzed for apoplast phenolics after different periods of incubation. Pseudomonas syringae pv. tabacci, 108 cfu ml−1, induced numerous phenolics to accumulate in the leaf apoplast after 24 h. UPLC-UV chromatograms revealed about 15 UV-peaks, some containing several components. Using this bacterial isolate, it was found that all the fully developed leaves on a single plant had a similar phenolic response based on magnitude and composition of the phenolics. Between plants, the phenolic composition was also similar, although there was more variability. The magnitude of response was proportional to the bacterial concentration between 105-108 cfu ml−1. Plants inoculated with water or P. fluorescens, a saprophyte, had a negligible response. When pepper plants were inoculated with different bacterial pathogens, P. s. pv. tomato and pv. syringae, there were differences in the magnitude and composition of the phenolics after 24 h. A time course showed that phenolic accumulation was underway by 7 h and appeared to peak by 24 h. The bacterial induction of apoplast phenolics in pepper, described here, corroborates the similar response previously described for tobacco. The preliminary characterization by UPLC-UV/MS suggests the apoplast phenolics found in pepper are structurally different from those in tobacco. However, the similar timing and location of the responses in both plants would suggest that their roles in the plant bacterial interaction are also similar. Further investigation of the redox and bioactivity properties of these apoplast phenolics is needed.

There is growing concern about residual antibiotics and feed additives in the manure of treated animals because of the effects of these residues in the environment. Monensin is the most widely used ionophore coccidiostat in the U.S. The objective of this study was to determine the fate and effect of monensin during the anaerobic digestion of dairy manure. Duplicate plug flow field-scale digesters were operated using non-amended dairy manure and dairy manure amended with monensin to 1 and 10 mg/L for 56 days at 30°C at an organic loading rate of 1.4 kg VS/m3-d and 17-day hydraulic retention time. Results showed that monensin was reduced approximately 70% during anaerobic digestion. Methane production from digesters using manure amended with 1 mg/L monensin was comparable to that from digesters operated without added monensin. However, digesters using manure amended with 10 mg/L monensin yielded 75% less methane than digesters using manure without added monensin. These results suggest that anaerobic digestion is an effective treatment for reducing, but not eliminating, monensin in dairy manure. Monensin did not reduce methane production at concentrations expected in dairy manure at recommended dosage rates.

Urban streams are an integral part of the municipal water cycle and provide a point of discharge for wastewater treatment plant (WWTP) effluents, allowing additional attenuation through dilution and transformation processes, as well as a conduit for transporting contaminants to downstream water supplies. Domestic and commercial activities dispose of wastes down-the-drain, resulting in wastewater containing complex chemical mixtures that are only partially removed during treatment. A key issue associated with WWTP effluent discharge into streams is the potential to cause endocrine disruption in fish. This study provides a long-term (1999–2009) evaluation of the occurrence of alkylphenolic endocrine disrupting chemicals (EDCs) and other contaminants discharged from WWTPs into streams in the Great Lakes and Upper Mississippi River Regions (Indiana, Illinois, Michigan, Minnesota, and Ohio). The Greater Metropolitan Chicago Area Waterways, Illinois, were evaluated to determine contaminant concentrations in the major WWTP effluents and receiving streams, and assess the behavior of EDCs from their sources within the sewer collection system, through the major treatment unit processes at a WWTP, to their persistence and transport in the receiving stream. Water samples were analyzed for alkylphenolic EDCs and other contaminants, including 4-nonylphenol (NP), 4-nonylphenolpolyethoxylates (NPEO), 4-nonylphenolethoxycarboxylic acids (NPEC), 4- tert -octylphenol (OP), 4- tert -octylphenolpolyethoxylates (OPEO), bisphenol A, triclosan, ethylenediaminetetraacetic acid (EDTA), and trace elements. All of the compounds were detected in all of the WWTP effluents, with EDTA and NPEC having the greatest concentrations. The compounds also were detected in the WWTP effluent dominated rivers. Multiple fish species were collected from river and lake sites and analyzed for NP, NPEO, NPEC, OP, and OPEO. Whole-body fish tissue analysis indicated widespread occurrence of alkylphenolic compounds, with the highest concentrations occurring in streams with the greatest WWTP effluent content. Biomarkers of endocrine disruption in the fish indicated long-term exposure to estrogenic chemicals in the wastewater impacted urban waterways.

Benchtop bioreactors were run aerobically with activated sludge samples collected from a large municipal wastewater treatment plant (WWTP) to understand how increased hydraulic retention time (HRT), sludge retention time (SRT), and varying treatment temperatures (21°C and 30°C) impact concentrations of the endocrine disrupting antimicrobials triclosan (TCS), triclocarban (TCC), and their transformation products. Samples from the reactors were collected periodically over a 122-196h period and the solid and liquid fraction were separately quantitated for TCS, TCC, and methyltriclosan (MeTCS) and scanned qualitatively for six other transformation products. Results indicated that TCS, TCC and MeTCS were predominately associated with the solids fraction of the activated sludge with only nominal concentrations in the liquids fraction. TCS was degraded in the solids fraction, with increased rates at 30°C (-0.0224 ± 0.007h-1) when compared to reactors run at 21°C (- 0.0170 ± 0.003h-1). Conversely, TCC concentrations did not significantly change in solids samples from reactors run at 21°C, while an increase in reactor temperature to 30°C resulted in TCC degradation at an average rate of - 0.0158 ± 0.012h-1. Additionally, MeTCS formation in the solids fraction was observed in three out of four reactors run - indicating a notable transformation of TCS. Qualitative appearance of 2,4-dichlorophenol and 4-chloroanaline was observed in the liquids fraction of all reactor samples. The remaining four qualitatively scanned compounds were not detected. These experiments demonstrate that increased HRT, SRT, and temperature result in enhanced removal of TCS and TCC from wastewater during the activated sludge process. Furthermore, a substantial formation of TCS into MeTCS was observed.

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

Endosulfan (6,7,8, 9,10,10-hexachloro-1,5,5a,6,9,9a-hexahydro-6,9-methano-2,4,3-benzodioxathiepine-3-oxide) is a broad-spectrum, organochlorine insecticide used on numerous crops since the 1950s. It is has been identified as a persistent organic pollutant (POP) due to its persistence, bioaccumulation, long-range transport, and adverse effects to human health and aquatic ecosystems; it will be phased out in the United States in 2016. Endosulfan consists of two diastereomers, α and β; α-endosulfan exists as two asymmetrical, twist-chair enantiomers which interchange, while β-endosulfan has a symmetrical-chair conformation. β-Endosulfan has been shown to isomerize to α-endosulfan. Here we document the previously proposed isomerization mechanism using temperature-dependent Raman (TDR) spectroscopy. The bending frequencies in the fingerprint region were assigned to specific bonds. Changes in the signal intensity as a function of temperature were used to identify detailed ring movements and thus conversion of β to α. These movements cannot occur simultaneously nor symmetrically, precluding conversion of α-endosulfan to β-endosulfan.

This study analyzes the effect of liming on levels of triclocarban (TCC), triclosan (TCS), estrone (E1), and progesterone (P), two antimicrobial agents and two natural hormones, respectively. Factors studied include lime particle size, mixing time, and overall lime contact time. The study results suggest that coarse lime may be more active than fine lime due to less interaction with surrounding air. Both TCS and TCC concentrations were lower in coarse limed samples versus unlimed samples and the decrease was a function of time. A similar, but statistically insignificant trend in TCC and TCS levels was observed in fine lime samples with respect to unlimed samples. Liming was also found to decrease apparent E1 levels, with more notable decreases in samples amended with coarse lime. P-levels significantly increased after 1-day of contact time, stabilizing over the next 14 days of the study period. This increase and stabilization of P-levels was attributed to the pH and moisture-driven conversion of more chemically complex steroids into P.

Concerns about avian poisonings from anticoagulant rodenticides have traditionally focused on secondary poisoning of raptors exposed by feeding on contaminated mammalian prey. However, ground foraging songbirds can be directly poisoned from operational applications of the anticoagulant rodenticide Rozol® (0.005% chlorophacinone, active ingredient) applied as a grain bait, at black-tailed prairie dog Cynomys ludovicianus colonies. A dead western meadowlark Sturnella neglecta recovered from the study prairie dog colony displayed hemorrhaging in brain and pectoral muscle tissue, and it contained chlorophacinone residue concentrations of 0.59 and 0.49 µg/g (wet weight) in the liver and intestinal contents, respectively. Chlorophacinone residues from two Rozol-colored songbird droppings found at the study colony were 0.09 and 0.46 µg/g (wet weight). The timing of the meadowlark mortality and the occurrence of discolored droppings show that songbird exposure and poisoning can occur weeks after a Rozol application.

Nutrient inputs from urban encroachment and agricultural activities have been implicated in contributing to the environmental health decline and loss of organism diversity of South Florida ecosystems. Intensive agricultural pesticide use may also challenge these ecosystems. One possible mechanism is pesticide release to the atmosphere after application. The process is enhanced in this region due to the calcareous soils, frequent rainfall, and high humidity and temperatures. This study examined the atmospheric fate of the widely-used insecticide endosulfan. Air samples were collected over a five-year period (2001–2006) at a site within the agricultural community of Homestead, Florida and at sites located in nearby Biscayne and Everglades National Parks (NPs). Mean gas phase air concentrations of α-endosulfan were 17 ± 19 ng m−3 at Homestead, 2.3 ± 3.6 ng m−3 at Everglades NP, and 0.52 ± 0.69 ng m−3 at Biscayne NP. Endosulfan emissions from agricultural areas around Homestead appeared to influence air concentration observations at the NP sites. During an intensive sampling campaign, the highest total endosulfan concentrations at the NP sites were observed on days when air parcels were predicted to move from Homestead towards the sampling locations. The α-endosulfan fraction (α/(α + β)) was used to examine the contribution of pesticide drift versus volatilization to the overall residue level. The formulated product has an α fraction of approximately 0.7, whereas volatilization is predicted to have an α fraction of ≥0.9. The median α- fraction observed during periods of high agricultural activity at Homestead and Everglades NP was 0.84 and 0.88, respectively, and during periods of low agricultural activity the median at Homestead was 0.86, indicating contributions from drift. The median α fraction at Everglades NP was 1.0 during periods of low agricultural activity, while Biscayne NP was 1.0 year round indicating air concentrations are primarily influenced by regional volatilization.

The growing concern worldwide regarding the presence of emerging contaminants in biosolids calls for a better understanding of how different treatment technologies at water resource recovery facilities (WRRFs) can influence concentrations prior to biosolids land application. This study focuses on the influence of solids treatment via the Cambi Thermal Hydrolysis Process™ in conjunction with anaerobic digestion (TH-AD) on concentrations of triclosan (TCS), triclocarban (TCC), and their transformation products in biosolids and sludges. Concentrations of the target analytes in biosolids from the TH-AD process (Class A), sludges from the individual TH-AD treatment steps, and limed biosolids (Class B) from the same WRRF were compared. TCC concentrations were significantly lower in Class A biosolids than those in the Class B product - a removal that occurred during thermal hydrolysis. Concentrations of TCS, methyl triclosan, and 2,4-dichlorophenol, conversely, increased during anaerobic digestion, leading to significantly higher concentrations of these compounds in Class A biosolids when compared to Class B biosolids. Implementation of the TH-AD process had mixed effect on contaminant concentrations.

Culture medium from an isolate of the fungus Aspergillus candidus was extracted, fractionated and examined to discover compounds antagonistic to plant-parasitic nematodes that are important pathogens of agricultural crops. Column, thin layer and preparative chromatographies and spectral and elemental analyses, were used to isolate and identify two major constituents of an active fraction (Fraction F) obtained from the medium. Compound 1 was identified as 2-hydroxypropane-1, 2, 3-tricarboxylic acid (citric acid). Compound 2 was identified as 3-hydroxy-5-methoxy-3-(methoxycarbonyl)-5-oxopentanoic acid, an isomer of 1, 2-dimethyl citrate. Compound 1 and a citric acid standard, each tested at 50 mg mL(-1) in water, decreased hatch from eggs of the plant-parasitic nematode Meloidogyne incognita by more than 94%, and completely immobilized second-stage juveniles after 4-6 days exposure. Fraction F and Compounds 1 and 2 decreased the mobility of adults of the plant-parasitic nematode Ditylenchus destructor in vitro. Fraction F (25 mg mL(-1)) inhibited mobility >99% at 72 hrs. Compounds 1 and 2 (50 mg mL(-1)) each inhibited mobility more than 25% at 24 hr and more than 50% at 72 hr. This is the first assignment of nematode-antagonistic properties to specifically identified A. candidus metabolites.

Rye (Secale cereale L.) residue is known to suppress weeds in agronomic environments and to produce benzoxazinoid (BX) compounds which are phytotoxic. Experiments were conducted to determine the duration of indicator plant inhibition and BX soil concentrations in response to field incorporated or surface rye residue. Surface rye residue was highly inhibitory to lettuce (Lactuca sativa L.) and smooth pigweed (Amaranthus hybridus L.) throughout an experimental period of 4 weeks, whereas soil removed from beneath residue and assayed in pots had little phytotoxicity, suggesting that physical rather than chemical mechanisms were involved. Incorporated residue inhibited lettuce and pigweed for approximately 2 weeks after incorporation, which corresponded to the period when elevated BX levels were detected in soil, suggesting potential allelopathy. The most toxic BX compounds, APO, DIBOA, and DIMBOA, were present at relatively low levels, whereas the less toxic compounds, BOA and MBOA, and the non-toxic compounds, HBOA and HMBOA, were the predominant BX species in amended soils. When the benzoxazolinones BOA and MBOA were exogenously added to soils to maintain extractable levels of up to 10 μg g−1 soil (100–500 times higher than measured BX in field soils), no significant inhibition of pigweed plants was observed. This result indicated that the observed association between the duration of plant inhibition and BX from incorporated rye was not causal, and that other compounds released with similar dynamics were likely responsible. This approach provides a sound basis for demonstrating the presence of allelopathy in natural or managed ecosystems.

Aims: This study evaluated the effect of anaerobic digestion at 22, 38 and 55°C on odour, coliforms and chlortetracycline (CTC) in swine manure or monensin (MON) in cattle manure. Methods and Results: Swine or cattle were fed the respective growth promotant, manure was collected, and 2-l laboratory methane digesters were established at the various temperatures and sampled over 25 or 28 days. After 21 days, the concentration of CTC in the 22, 38 and 55°C swine digester slurries decreased 7, 80 and 98%, respectively. Coliforms in the 22°C digester slurries were still viable after 25 days; however, they were not detectable in the 38 and 55°C slurries after 3 and 1 days, respectively. After 28 days, the concentration of MON in the 22, 38 and 55°C cattle digester slurries decreased 3, 8 and 27%, respectively. Coliforms in the 22°C cattle digester slurries were still viable after 28 days; however, they were not detectable in the 38 and 55°C slurries after 14 and 1 days, respectively. Conclusions: These studies indicate that anaerobic digestion at 38 or 55°C may be an effective treatment to reduce coliforms and CTC; however, it is not an effective treatment to reduce MON. Significance and Impact of the Study: More studies are needed to determine which pharmaceuticals are susceptible to degradation by a specific manure treatment to prevent negative environmental consequences.

Phosphorous (P) is a major contributor to eutrophication of surface waters, yet a complete understanding of the P cycle remains elusive. Inositol hexa-kis phosphate (IHP) is the primary form of organic (PO) in the environment and has been implicated as an important sink in aquatic and terrestrial samples. IHP readily forms complexes in the environment due to the 12 acidic sites on the molecule. Quantification of IHP in environmental samples has typically relied on harsh extraction methods that limit understanding of IHP interactions with potential soil and aquatic complexation partners. The ability to quantify IHP in-situ at the pH of existing soils provides direct access to the role of IHP in the P cycle. Since it is itself a buffer, adjusting the pH correspondingly alters charged species of IHP present in soil. Density Functional Theory (DFT) calculations support the charged species assignments made based pKas associated with the IHP molecule. Raman spectroscopy was used to generate pH dependent spectra of inorganic (PI) and IHP as well as (PO) from IHP and (PI) in soil samples. Electro-spray ionization mass spectroscopy (ESI-MS) was used to quantify IHP-Iron complexes in two soil samples using a neutral aqueous extraction.

Excess nutrients and agrochemicals from non-point sources contribute to water quality impairment in the Chesapeake Bay watershed and their loading rates are related to land use, agricultural practices, hydrology, and pollutant fate and transport processes. In this study, monthly baseflow stream samples from 15 agricultural subwatersheds of the Choptank River in Maryland USA (2005 to 2007) were characterized for nutrients, herbicides, and herbicide transformation products. High-resolution digital maps of land use and forested wetlands were derived from remote sensing imagery. Examination of landscape metrics and water quality data, partitioned according to hydrogeomorphic class, provided insight into the fate, delivery, and transport mechanisms associated with agricultural pollutants. Mean Nitrate-N concentrations (4.9 mg/L) were correlated positively with percent agriculture (R2 = 0.56) and negatively with percent forest (R2 = 0.60). Concentrations were greater (p = 0.0001) in the well-drained upland (WDU) hydrogeomorphic region than in poorly drained upland (PDU), reflecting increased denitrification and reduced agricultural land use intensity in the PDU landscape due to the prevalence of hydric soils. Atrazine and metolachlor concentrations (mean 0.29 μg/L and 0.19 μg/L) were also greater (p = 0.0001) in WDU subwatersheds than in PDU subwatersheds. Springtime herbicide concentrations exhibited a strong, positive correlation (R2 = 0.90) with percent forest in the WDU subwatersheds but not in the PDU subwatersheds. In addition, forested riparian stream buffers in the WDU were more prevalent than in the PDU where forested patches are typically not located near streams, suggesting an alternative delivery mechanism whereby volatilized herbicides are captured by the riparian forest canopy and subsequently washed off during rainfall. Orthophosphate, CIAT (6-chloro-N-(1-methylethyl)-1,3,5-triazine-2,4-diamine), CEAT (6-chloro-N-ethyl-1,3,5-triazine-2,4-diamine), and MESA (2-[(2-ethyl-6-methylphenyl) (2-methoxy-1-methylethyl)amino]-2-oxoethanesulfonic acid) were also analyzed. These findings will assist efforts in targeting implementation of conservation practices to the most environmentally-critical areas within watersheds to achieve water quality improvements in a cost-effective manner.

Rye (Secale cereale L.) is a frequently used winter cover crop in many agronomic production systems in the United States. Our objective was to determine whether incorporating rye into soil while still green results in greater suppression of root-knot nematodes (Meloidogyne spp.) and Palmer amaranth (Amaranthus palmeri S. Wats.) compared to conventional cover crop management. Two similar experiments were conducted: one with peanut (Arachis hypogaea L.) and the other with cotton (Gossypium hirsutum L.). Both experiments were a split-plot design with tillage as the main plot (conventional, green manure, and strip) and cover crop as the subplot. The cover crop treatments were a weedy fallow and the rye cultivars Wrens Abruzzi, Wheeler, Oklon, and Elbon. Wrens Abruzzi produced the greatest amount of biomass, Oklon and Elbon intermediate, and Wheeler the least. Where there was substantial soil disturbance (e.g., conventional tillage and green manure), Palmer amaranth densities were low and not influenced by cover crop. In the strip tillage plots, however, all of the rye cultivars, except Wheeler, reduced establishment of the weed compared to winter fallow. Root galling from nematodes on cotton and peanut was influenced by tillage, but not by rye cover crop. Gall indices on cotton were greater in conventional tillage than in either strip tillage or green manure plots; whereas on peanut, they were greater in the strip tillage than in the conventional tillage or green manure plots. Neither tillage nor cover crop influenced yield except in 2008 in peanut, where yield was lower in strip tillage than in conventional or green manure plots.

Triclosan (5-chloro-2-[2,4-dichloro-phenoxy]-phenol (TCS) is an antimicrobial compound that is added to a wide variety of household and personal care products. The consumer use of these products releases TCS into urban wastewater and this compound ends up in the environment when agricultural land is fertilized with wastewater biosolids. This study examines the occurrence of TCS in biosolids and its fate in biosolid-treated soils. TCS levels in biosolids generated from one repeatedly-sampled wastewater treatment plant averaged 15.6 + or - 0.6 mg kg(-1) dry wt. (mean + or - standard error) with a slight increase from 2005 to 2007. Surface soil samples were collected from several farms in northern Virginia, US that had received no biosolids, one biosolid application or multiple biosolid applications since 1992. Farm soils that received one application presented TCS concentrations between 4.1 and 4.5 ng g(-1) dry wt. when time since application was over 16 months and between 23.6 and 66.6 ng g(-1) dry wt. for farms where sampling time after application was less than a year. Our results suggest that TCS content of biosolids are rapidly dissipated (estimated half-life of 107.4 d) when applied to agricultural fields. Statistical differences were found (p

The concentrations of nonylphenol (NP), octylphenol (OP), their ethoxylates (NP1-16EO and OP1-5EO respectively) and some of their carboxylated derivatives (NP1-2EC and OP1EC quantitatively; NP3-4EC and OP2EC qualitatively) were measured in water samples from the Back River, MD, a sub-estuary of the Chesapeake Bay that receives effluent from a large municipal wastewater treatment plant. The most abundant of the alkylphenolic compounds (APEs) were the carboxylates (APECs,95% of the APE-related compounds), followed by NP in September and October, and NP1-2EO in March. Ratios of the different compounds' concentrations provide evidence for the season dependency of two different degradation pathways. NP concentrations found in this study, 0.087-0.69 microg L(-1), were below acute toxicity thresholds, and below US EPA water quality criteria; although in March, concentrations were close to 40% of the chronic exposure limit for saltwater, 1.7 microg L(-1). A simple steady-state model of the Back River suggested that total NPE concentrations in the estuary varied in accordance with concentrations in the wastewater treatment plant effluent, especially in the case of the APECs. This model also suggested that in the fall sampling events, when rain occurred, APEOs present in particulate matter might have originated in the river's tributaries rather than the treatment plant.

The benzoxazinoid 2,4-dihydroxy-1,4-benzoxazin-3-one (DIBOA) is produced by rye (Secale cereale) and may contribute to plant-parasitic nematode suppression when rye plants are incorporated as a green manure. We investigated the fate of DIBOA in soil and DIBOA’s effects on nematode reproduction. Soil in plastic bags was treated with DIBOA at concentrations ranging from 1.1 to 18 m gg �1 dry soil, and with the root-knot nematode Meloidogyne incognita. Control soils were treated with water or with 0.31% methanol, with or without nematodes. DIBOA concentrations extracted from the soil were measured at selected times for 5 consecutive days. The soil from each bag was then placed into a pot in the greenhouse, and a cucumber seedling was transplanted into each pot. Five weeks later, only the highest DIBOA concentration, 18 m gg �1 soil, reduced nematode egg numbers. At 0 h, DIBOA measured in soil ranged from 19.68 to 35.51% of the initial DIBOA concentration, and was dependent on the concentration added to the soil. DIBOA half-life was from 18 to 22 h, and very little DIBOA was present in soil after 120 h. Identified breakdown products accounted for only 4% at maximum of the initially added DIBOA. The results of our study demonstrate that high soil concentrations of DIBOA are necessary to suppress M. incognita; DIBOA may not be a major factor in nematode suppression by a rye cover crop. Published by Elsevier Ltd.

This study focuses on the differential induction of extracellular phenolic amides that accumulate in potato cell suspensions during the first few hours of the interaction between these plant cells and either bacterial pathogens or pathogen-related elicitors. Using suspension cells of Solanum tuberosum we identified 4 hydroxycinnamic acid amides that accumulate in the extracellular environment. Treatment of the suspension cells with pathovars of the plant pathogens Pseudomonas syringae or Ralstonia solanacearum or with pathogen-related elicitors changed the composition of the extracellular phenolic amides within hours and the composition differed for each treatment. Some of the phenolic amides were sensitive to oxidative stress; when suspension cells were treated with bacterial strains or elicitors that triggered an oxidative burst, the phenolics were oxidized and depleted for the duration of the burst. Other critical parameters that affected the qualitative and quantitative makeup of these phenolic amides were plant cell age and density.

The Choptank River is an estuary, tributary of the Chesapeake Bay, and an ecosystem in decline due partly to excessive nutrient and sediment loads from agriculture. The Conservation Effects Assessment Project for the Choptank River watershed was established to evaluate the effectiveness of conservation practices on water quality within this watershed. Several measurement frameworks are being used to assess conservation practices. Nutrients (nitrogen and phosphorus) and herbicides (atrazine and metolachlor) are monitored within 15 small, agricultural subwatersheds and periodically in the lower portions of the river estuary. Initial results indicate that land use within these subwatersheds is a major determinant of nutrient concentration in streams. In addition, the 18O isotope signature of nitrate was used to provide a landscape assessment of denitrification processes in the presence of the variable land use. Herbicide concentrations were not correlated to land use, suggesting that herbicide delivery to the streams is influenced by other factors and/or processes. Remote sensing technologies have been used to scale point measurements of best management practice effectiveness from field to subwatershed and watershed scales. Optical satellite (SPOT-5) data and ground-level measurements have been shown to be effective for monitoring nutrient uptake by winter cover crops in fields with a wide range of management practices. Synthetic Aperture Radar (RADARSAT-1) data have been shown to detect and to characterize accurately the hydrology (hydroperiod) of forested wetlands at landscape and watershed scales. These multiple approaches are providing actual data for assessment of conservation practices and to help producers, natural resource managers, and policy makers maintain agricultural production while protecting this unique estuary.

Antibiotics and hormones are considered emerging environmental microcontaminants because of their potential adverse effects on ecosystems and human health. Available information on the source of these emerging contaminants in surface waters is very limited. The objectives of this study were to determine the occurrence of antibiotics and hormones in an agricultural watershed and to determine the seasonal variability of these contaminants. Water samples were collected from 15 subwatershed stations and 7 stations on the major receiving river, Choptank, Maryland, USA, over four different seasons (April, June, September and December). Antibiotics (sulfathiazole, sulfamerazine, sulfamethizole, sulfamethazine, sulfachloropyridazine, sulfamethoxazole, sulfadimethoxine, tetracycline, oxytetracycline, chlortetracycline and doxycycline) and hormones (estriol, estradiol, 17α-ethynylestradiol, estrone, testosterone and progesterone) as well as arsenic which is used as feed additive were determined in these water samples. In addition, the same antibiotics were analyzed in one set of sediment samples. This study indicated that agriculture may act as a source of antibiotic residues in the aquatic environment.

The removal of several hormones and antibiotics by nanofiltration membranes was studied in mixed solutions. The effects of solution chemistry, organic matter and salinity were investigated on the rejection of tetracycline's and sulfanamides and selected hormones and their adsorption on membranes. Tetracyclines were observed to have a high adsorptive affinity for the membrane. Almost 80% of chlorotetracycline was adsorbed on the membrane surface compared with 50% for doxcycline while the adsorption rates for hormones were lower than those obtained for tetracyclines. Addition of calcium, organic matter and salinity had an influence on the rejections. Rejection of sulfanamides was low compared to hormones and tetracyclines. Addition of antibiotics to hormone solution increased the hormone rejections while almost complete rejections were observed for tetracyclines.

Perchlorate has been detected in U.S. milk samples from many different states. Applying data from a recently reported 9-week experiment in which 16 Holstein dairy cows were administered perchlorate allowed us to derive an equation for the dose-response relationship between perchlorate concentrations in feed/drinking water and its appearance in milk. Examination of background concentrations of perchlorate in the total mixed ration (TMR) fed in addition to the variable dose supplied to treated cows as a ruminal infusate revealed that cows receive significant and variable exposure to perchlorate from the TMR. Weekly examination of the TMR disclosed that a change in ingredients midway through the experiment caused a significant (78%) change in TMR perchlorate concentration. Analyses of the ingredients comprising the TMR revealed that 41.9% of the perchlorate came from corn silage, 22.9% came from alfalfa hay and 11.7% was supplied by sudan grass. Finally, USDA Food and Nutrition Survey data on fluid milk consumption were used to predict potential human exposure from milk that contained concentrations of perchlorate observed in our previous dosing study. The study suggests that reducing perchlorate concentration in dairy feed may reduce perchlorate concentrations in milk as well as the potential to reduce human exposure to perchlorate in milk.

Manure composting is a well-described approach for stabilization of nutrients and reduction of pathogens and odors. Although composting studies have shown that thermophilic temperatures and aerobic conditions can increase removal rates of selected antibiotics, comparable information is lacking for many other compounds in untreated or composted manure. The objective of this study was to determine the relative effectiveness of composting conditions to reduce concentrations of four widely used ionophore feed supplements in dairy manure and poultry litter. Replicate aliquots of fresh poultry litter and dairy manure were amended with monensin, lasalocid, salinomycin, or amprolium to 10 mg kg−1 DW. Non-amended and amended dairy manure and poultry litter aliquots were incubated at 22, 45, 55, or 65 °C under moist, aerobic conditions. Residue concentrations were determined from aliquots removed after 1, 2, 4, 6, 8, and 12 weeks. Results suggest that the effectiveness of composting for contaminant reduction is compound and matrix specific. Composting temperatures were not any more effective than ambient temperature in increasing the rate or extent of monensin removal in either poultry litter or dairy manure. Composting was effective for lasalocid removal in poultry litter, but is likely to be too slow to be useful in practice (8–12 weeks at 65 °C for >90% residue removal). Composting was effective for amprolium removal from poultry litter and salinomycin in dairy manure but both required 4–6 weeks for >90% removal. However, composting did not increase the removal rates or salinomycin in poultry litter or the removal rates of lasalocid or amprolium in dairy manure.

Various chemical and biological measures were determined in carp ( Cyprinus carpio ) sampled from seven sites along the Cuyahoga River, Ohio; from the relatively pristine headwaters to the lower portion heavily polluted from various industrial, urban and wastewater treatment plants (WWTP). Levels of nonylphenol (NP), nonylphenol ethoxylates (NPEs; NP1EO, NP2EO) and total NPEs (NP plus the NPEs) in fish increased in a downstream direction, with maximal values observed below the discharge of the Akron WWTP. In female fish there were no significant differences between sites in GSI or levels of vitellogenin (VTG) and 17β-estradiol (E2). However, differences were observed between sites using measures of 11-ketotestosterone (11-KT) and the ratio E2/11-KT. In male fish the highest levels of VTG were observed downstream of the Akron WWTP and a significant correlation ( r = 85%) between levels of NP and VTG was demonstrated. No site differences were observed in the measures of GSI, E2, 11-KT or the E2/11-KT ratio in male fish. These data suggest that endocrine active chemicals, such as, NP and NPEs are impacting fish downstream of the Akron WWTP; however, further work is warranted to separate linkages to other possible chemical factors in the water.

Characterization of the effects of aircraft deicer and anti-icer fluid (ADAF) runoff on aquatic organisms in receiving streams is a complex issue because the identities of numerous toxic additives are proprietary and not publicly available. Most potentially toxic and endocrine disrupting effects caused by ADAF are due to the numerous additive package ingredients which vary among manufacturers and types of ADAF formulation. Toxicity investigations of nine ADAF formulations indicate that endpoint concentrations for formulations of different manufacturers are widely variable. Type IV ADAF (anti-icers) are more toxic than Type I (deicers) for the four organisms tested (Vibrio fischeri, Pimephales promelas, Ceriodaphnia dubia, and Selenastrum capricornutum). Acute toxicity endpoint concentrations ranged from 347 to 7700 mg/L as ADAF for Type IV and from 1550 to 45,100 mg/L for Type I formulations. Chronic endpoint concentrations ranged from 70 to 1300 mg/L for Type IV and from 37 to 18,400 mg/L for Type I formulations. Alkylphenol ethoxylates and tolyltriazoles are two known classes of additives. Nonylphenol, nonylphenol ethoxylates, octylphenol, octylphenol ethoxylates, and 4,5-methyl-1H-benzotriazoles were quantified in the nine ADAF formulations, and toxicity tests were conducted with nonylphenol ethoxylates and 4,5-methyl-1H-benzotriazoles. Toxicity units computed for glycol and these additives, with respect to toxicity of the ADAF formulations, indicate that a portion of ADAF toxicity can be explained by the known additives and glycols, but much of the toxicity is due to unidentified additives.

The fate of antibiotic residues in the manure of treated animals is of considerable concern because of the potential development of antibiotic-resistant bacteria in the environment and because of the effect of these residues on manure treatment systems. The objective of this study was to determine the fate and effect of oxytetracycline (OTC) during the anaerobic digestion of manure from medicated calves. Five beef calves were medicated for 5 days with 22 mg/kg/day of OTC. Manure samples collected from calves prior to and after medication were diluted five-fold with water, loaded into replicate 1.2 l anaerobic digesters and incubated at 35 °C. OTC levels in the manure slurry decreased from 9.8 ± 0.1 to 4.1 ± 0.1 mg/l in 64 days (59% removal) yielding a calculated value half-life for OTC of 56 days. Levels of the OTC epimer 4-epi-oxytetracycline increased gradually from 0.55 ± 0.03 mg/l at the start of experiment to 1.3 ± 0.1 mg/l on day 27 and then decreased to 0.84 ± 0.04 mg/l on day 64. Levels of two other OTC metabolites (α-apo-oxytetracycline and β-apo-oxytetracycline) decreased or remained unchanged during the anaerobic digestion process. Cumulative biogas production was 27% lower from digesters containing manure from medicated calves relative to that from digesters containing unmedicated manure. However, the presence of OTC did not show other negative effects on process stability as there were no significant differences in biogas methane content or in reductions of volatile solids and soluble organic carbon.

Snowbank samples were collected from snowbanks within a medium-sized airport for four years to characterize aircraft deicer and anti-icer (ADAF) components and toxicity. Concentrations of ADAF components varied with median glycol concentrations from individual sampling periods ranging from 65 to 5940 mg/L. Glycol content in snowbanks ranged from 0.17 to 11.4% of that applied to aircraft. Glycol, a freezing point depressant, was selectively removed during melt periods before snow and ice resulting in lower glycol concentrations after melt periods. Concentrations of ADAF components in airport runoff were similar during periods of snowmelt as compared to active ADAF application periods; however, due to the long duration of snowmelt events, greater masses of glycol were transported during snowmelt events. Alkylphenol ethoxylates (APEO), selected APEO degradation products, and 4- and 5-methyl-1H-benzotriazole were detected in snowbank samples and airport snowmelt. Concentrations of APEO parent products were greater in snowbank samples than in runoff samples. Relative abundance of APEO degradation products increased in the downstream direction from the snowbank to the outfalls and the receiving stream with respect to APEO parent compounds and glycol. Toxicity in Microtox assays remained in snowbanks after most glycol had been removed during melt periods. Increased toxicity in airport snowbanks as compared to other urban snowbanks was not explained by additional combustion or fuel contribution in airport snow. Organic markers suggest ADAF additives as a possible explanation for this increased toxicity. Results indicate that glycol cannot be used as a surrogate for fate and transport of other ADAF components.