Predicting pesticide emissions and downwind concentrations using correlations with estimated vapor pressures.

Pesticide emissions to air have been shown to correlate with compound vapor pressure values taken from the published literature. In the present study, emissions correlations based on vapor pressures derived from chemical property estimation methods are formulated and compared with correlations based on the literature data. Comparison was made by using the two types of correlations to estimate emission rates for five herbicides, a fungicide, and an insecticide, for which field-measured emission rates from treated soil, foliage, and water were available. In addition, downwind concentrations were estimated for two herbicides, three fungicides, four insecticides, and two fumigants, for which concentration measurements had been made near treated sources. The comparison results demonstrated that correlations based on vapor pressures derived from chemical property estimation methods were essentially equivalent to correlations based on literature data. The estimation approach for vapor pressures is a viable alternative to the inherently more subjective process of selecting literature values.

Accumulation of trifluoroacetate in seasonal wetlands in California.

Trifluoroacetate (TFA, CF3COO-) is a stable and mildly phytotoxic breakdown product of several fluorinated organic compounds including the hydro(chloro)fluorocarbons (HFC/HCFCs) that have largely replaced the stratospheric ozone-depleting chlorofluorocarbons (CFCs). TFA enters aquatic ecosystems primarily through precipitation and has the potential to accumulate in water bodies with little or no outflow to the point where toxic concentrations could be achieved. This study demonstrated that seasonal wetlands lacking outflow concentrated TFA as they evaporated during the dry season. In addition, the TFA within the pools was retained between years, which may result in long-term TFA accumulation. Since plants acquire TFA from their growing media, the plants exposed to high aqueous concentrations of TFA within the pools had elevated TFA concentrations with a median concentration of 279 ng/g dry weight in their tissues as compared to 33 ng/g for species growing outside the pools. The highest TFA concentrations in water, which occurred just prior to the pools drying up, were in the 2-10 micrograms/L range. These concentrations are approximately 190 or less than reported toxic concentrations for the most sensitive species tested, but our evidence suggests that these concentrations will increase with continued TFA deposition into the pools.

Extraction and analysis of trifluoroacetic Acid in environmental waters.

Trifluoroacetic acid (TFA), a mildly phytotoxic compound, is a stable atmospheric breakdown product of HFC-134a, HCFC-123, and HCFC-124. An extraction and analytical method has been developed for the routine analysis of low ppt levels of TFA in aqueous samples. TFA can be quantitatively recovered from most environmental waters by an extraction procedure using a commercial anion-exchange disk. In saline samples (conductivity >620 µS), where the presence of competing anions interfered with recovery, a liquid-liquid extraction cleanup was necessary. After extraction of TFA from water, the dried disk was placed in a headspace vial containing 10% sulfuric acid in methanol and the vial sealed and then vortexed for 30 s. The sulfuric acid-methanol solution extracts trifluoroacetate anion (TFA) from the anion-exchange matrix and, when heated, quantitatively converts it to the methyl ester, which is then analyzed by automated headspace gas chromatography using electron capture or mass spectrometry detection. Several environmental samples in addition to laboratory spike solutions were successfully extracted and analyzed with this technique. Recoveries averaged 108.2% for reagent water spiked at levels from 53 to 2110 ng/L with relative standard deviations ranging from 0.3 to 8.4%. The instrument's limit of detection for TFA standard was 3.3 ng. The limit of quantitation for the extraction and analytical technique was 36 ng/L. Three water samples can be prepared for automated analysis in 20 min using this technique.

An analytical method for trifluoroacetic Acid in water and air samples using headspace gas chromatographic determination of the methyl ester.

An analytical method has been developed for the determination of trace levels of trifluoroacetic acid (TFA), an atmospheric breakdown product of several of the hydrofluorocarbon (HFC) and hydrochlorofluorocarbon (HCFC) replacements for the chlorofluorocarbon (CFC) refrigerants, in water and air. TFA is derivatized to the volatile methyl trifluoroacetate (MTFA) and determined by automated headspace gas chromatography (HSGC) with electron-capture detection or manual HSGC using GC/MS in the selected ion monitoring (SIM) mode. The method is based on the reaction of an aqueous sample containing TFA with dimethyl sulfate (DMS) in concentrated sulfuric acid in a sealed headspace vial under conditions favoring distribution of MTFA to the vapor phase. Water samples are prepared by evaporative concentration, during which TFA is retained as the anion, followed by extraction with diethyl ether of the acidified sample and then back-extraction of TFA (as the anion) in aqueous bicarbonate solution. The extraction step is required for samples with a relatively high background of other salts and organic materials. Air samples are collected in sodium bicarbonate-glycerin-coated glass denuder tubes and prepared by rinsing the denuder contents with water to form an aqueous sample for derivatization and analysis. Recoveries of TFA from spiked water, with and without evaporative concentration, and from spiked air were quantitative, with estimated detection limits of 10 ng/mL (unconcentrated) and 25 pg/mL (concentrated 250 mL:1 mL) for water and 1 ng/m(3) (72 h at 5 L/min) for air. Several environmental air, fogwater, rainwater, and surface water samples were successfully analyzed; many showed the presence of TFA.

Comparison of extraction techniques, including supercritical fluid, high-pressure solvent, and soxhlet, for organophosphorus hydraulic fluids from soil.

The efficiencies of three extraction techniques for removal of nonpesticidal organophosphates from soil were determined. Traditional Soxhlet extraction was compared to supercritical fluid extraction (SFE) and a low solvent volume flow through technique referred to here as high-pressure solvent extraction (HPSE). SFE, optimized by varying parameters of temperature, pressure, and methanol polarity modifier, showed at least 90% efficiency in the extraction of OPs from both spiked and native soils. HPSE experiments showed efficient and consistent recoveries over a range of temperatures up to 200 °C and pressures up to 170 atm. Recovery of TCP from spiked soils with HPSE depends on the system variables of temperature and pressure, which dictate density and flow rate. HPSE provided extraction efficiencies comparable to those obtained with Soxhlet extraction and SFE but with substantial savings of time and cost.

Integration of immunochemical methods with other analytical techniques for pesticide residue determination.

The growing volume of literature concerning immunoassay analysis for trace levels of agrochemicals and other low molecular weight contaminants in various matrixes is indicative of the tremendous interest in and utility of this analytical technique. Most immunoassay methods described in the literature analyze compounds directly, for example, a herbicide in water, or involve solvent exchange of an organic sample extract or dilution of an aqueous-based sample to minimize the matrix effect. As immunoassay for small molecules becomes widely accepted and applied, new challenges involving more complex chemicals in more difficult matrixes arise. The integration of "classical" analytical chemistry with immunochemistry can provide new techniques and approaches useful in discovering the movement, mode of action, and ultimate impact of certain chemicals on humans and the environment.

Environmental activation of pesticides.

Spray drift from application sites, runoff from agricultural fields, leftover products from home use, and accidental spills have made pesticide contamination ubiquitous in the environment. As a pesticide moves through the environment, it may react through chemical and biotic processes such as hydrolysis, oxidation, or reduction, or be metabolized in microorganisms, animals, plants, and humans. Most reactions will be inactivations, forming degradation products less toxic or persistent than the parent compound. However, some reactions are activations, creating breakdown products equally or more toxic, persistent, or mobile than the parent and posing a greater threat to nontarget organisms and the environment. Examples are drawn from the major classes of pesticides including organochlorine compounds (DDT and aldrin), organophosphorus pesticides (malathion), carbamate pesticides (aldicarb), and fungicides to illustrate the various activation routes.

Determination of atrazine metabolites in human urine: development of a biomarker of exposure.

Enzyme-linked immunosorbent assays (ELISAs) are reported for the detection of atrazine and its principle metabolite in human urine. The ELISAs can be used with crude urine or following extraction and partial purification by methods described in this report. GC, MS, and HPLC techniques were used to confirm and complement the ELISA methods for qualitative and quantitative detection of urinary metabolites. A series of samples from workers applying this herbicide confirmed a mercapturic acid conjugate of atrazine as a major urinary metabolite. The mercapturate was found in concentrations at least 10 times that of any of the N-dealkylated products or the parent compound. Atrazine mercapturic acid was isolated from urine using affinity extraction based upon a polyclonal antibody for hydroxy-s-triazines and yielded products sufficiently pure for structure confirmation by MS/MS. In a pilot study monitoring applicators, a relationship between cumulative dermal and inhalation exposure and total amount of atrazine equivalents excreted over a 10-day period was observed. On the basis of these data, we propose that an ELISA for the mercapturate of atrazine could be developed as a useful marker of exposure.

A method for the trace analysis of naptalam (N-1-naphthylphthalamic acid) in water.

A method for the trace analysis of naptalam, N-1-naphthylphthalamic acid, in water is presented. Naptalam, a pre-emergent, broad-leaf, and grassy herbicide, is used with soybean, peanut, and vine crops. Tap and well water samples are extracted on a cyclohexyl solid phase extraction cartridge, eluted from the cartridge with methanol, and evaporated to dryness. The sample is esterified with diazoethane, evaporated to dryness, reconstituted with methanol, and converted to the stable N-1-naphthyl phthalimide in the gas chromatograph (GC) injector port for detection and quantitation using a nitrogen-phosphorus detector. Sample injection technique and injector port temperature are critical to high derivatization yields. Confirmation of conversion to N-1-naphthyl phthalimide was made by gas chromatograph/mass spectrometer (GC/MS). Spiking tests at levels of 3 to 100 micrograms/L showed good recovery.

Quantitative integration of the Salmonella microsuspension assay with supercritical fluid extraction of model airborne vapor-phase mutagens.

Vapor-phase mutagens are potentially a major class of toxic contaminants in ambient and indoor air. These compounds are not routinely analyzed due to a lack of an established integrated methodology to quantitatively trap, extract and test the compounds in a bioassay. In a previous report, we emphasized the trapping of volatile and semi-volatile mutagens and the extraction of these compounds using supercritical carbon dioxide (CO2). In the present study, we discuss the use of a bioassay for the quantitation of the model mutagens, ethylene dibromide(EDB) and 4-nitrobiphenyl (4-NB), trapped from an airstream. The compounds EDB and 4-NB were released into a controlled airstream, trapped on XAD-4 adsorbent, and were extracted using supercritical CO2. The extract was tested in a microsuspension modification of the Ames Salmonella/microsome test adapted for volatile compounds. Linear dose-response relationships were obtained for supercritical CO2-extracted EDB using tester strain TA100 (+/- S9) and for 4-NB using tester strains TA98 and TA100 (-S9). Standard dose-response curves with known amounts of the compounds were also determined for comparison with measured amounts of the model compounds collected in an airstream. The gas chromatographic (GC)- and bioassay-determined quantities of EDB and 4-NB were highly correlated, accurate and precise. For example, bioassay-determined EDB concentrations were within 10% of the GC-determined concentrations. Our results demonstrate that the integrated methodology for vapor-phase mutagens developed in this study would be useful for quantitative analysis of these and related airborne vapor-phase mutagenic compounds.

Determination of volatile and semivolatile mutagens in air using solid absorbents and supercritical fluid extraction.

Volatile toxicants may be present in emissions from mobile and stationary sources as well as in ambient air. Methods for collecting and concentrating volatiles from air samples have been developed. Solid-phase adsorbents were compared in their trapping efficiencies for dichloromethane (DCM), ethylene dibromide (EDB), 4-nitroblphenyl (4-NB), 2-nitrofluorene (2-NF), and fluoranthene (FI). Charcoal and Carbosieve were the most efficient media for retaining DCM, while XAD-4 was the best adsorbent for EDB and the aromatic compounds. Extraction of direct spikes of compounds from adsorbents using supercritical carbon dioxide resulted in greater than 90% recovery of EDB and 60-92% recovery of the aromatics. Integration of trapping and desorption methods with the Salmonella microsuspension bioassay was demonstrated with EDB and 4-NB recoveries from air; chemical analysis and bioassay gave comparable results (within 10%).

A multiresidue method by high performance liquid chromatography-based fractionation and gas chromatographic determination of trace levels of pesticides in air and water.

A multiresidue analytical method is described for pesticides, transformation products, and related toxicants based upon high performance liquid chromatographic (HPLC) fractionation of extracted residue on a Partisil silica gel normal phase column followed by selective-detector gas chromatographic (GC) determination of components in each fraction. The HPLC mobile phase gradient (hexane to methyl t-butyl ether) gave good chromatographic efficiency, resolution, reproducibility and recovery for 61 test compounds, and allowed for collection in four fractions spanning polarities from low polarity organochlorine compounds (fraction 1) to polar N-methylcarbamates and organophosphorus oxons (fraction 4). The multiresidue method was developed for use with air samples collected on XAD-4 and related trapping agents, and water samples extracted with methylene chloride. Detection limits estimated from spiking experiments were generally 0.3-1 ng/m3 for high-volume air samples, and 0.01-0.1 microgram/L for one-liter water samples. Applications were made to determination of pesticides in fogwater and air samples.

Solubilities of pesticide chemicals in water. Part I: Environmental physical chemistry.

It is hoped that this review of the equilibrium aqueous solution thermodynamics and environmental partitioning tendencies of chemicals will be valuable in elucidating the behavior of pesticide chemicals in the environment and in promoting the development of more reliable correlations between physical chemical measurements and environmental partitioning coefficients. Ultimately the success of both the thermodynamic and environmental interpretations depend on having reliable, critically reviewed data from both laboratory and the "field."

Pyrrolizidine alkaloids in an overwintering population of monarch butterflies (Danaus plexippus) in California.

California overwintering monarch butterflies contain both pyrrolizidine alkaloids (PAs) and theirN-oxides. Analysis of 76 individual monarchs by TLC, HPLC, GLC, and GC-MS has shown the presence of three types of PAs, the saturated diester sarracine, the saturated monoester 7-angelylplatynecine, and the unsaturated dialcohol retronecine. Monarchs arriving at the overwintering site in Santa Cruz, California, showed a wide variation in both the type and amount of PA present. Those sampled after a PA-containing plant (Senecio mikanioides) had bloomed at the site showed an altered PA profile. While the plant was found to contain sarracine and 7-angelylplatynecine, which are nontoxic to mammals, the monarchs showed an increase in retronecine levels, a toxic PA, after the plant bloom. Apparently monarchs utilize PA-containing plants both en route to their overwintering site and at the site, and potentially alter those PAs to forms toxic to mammals.