Paul D. Capel

Pesticides in stream sediment and aquatic biota : distribution, trends, and governing factors

Introduction Purpose Previous Reviews Approach Characteristics of Studies Reviewed General Design Features Geographic Distribution Temporal Distribution Sampling Matrices Target Analytes Analytical Detection Limits National Distribution and Trends Pesticide Occurrence National Pesticide Use Geographic Distribution in Relation to Use Long-Term Trends Governing Processes Pesticide Sources Behavior and Fate of Pesticides in Bed Sediment Behavior and Fate of Pesticides in Aquatic Biota Analysis of Key Topics - Sources, Behavior, and Transport Effect of Land Use on Pesticide Contamination Pesticide Uptake and Accumulation by Aquatic Biota Seasonal Changes in Pesticide Residues Physical and Chemical Properties of Pesticides in Sediment and Aquatic Biota Composition of Total DDT as an Indicator of DDT Sources and Period of Use Analysis of Key Topics - Environmental Significance Effects of Pesticide Contaminants on Aquatic Organisms and Fish-Eating Wildlife Effects of Pesticide Contaminants in Aquatic Biota on Human Health Summary and Conclusion Appendix A: Table 2.1 Pesticides in bed sediment and aquatic biota from rivers and estuaries in the United States: National and multistate monitoring studies Appendix B: Table 2.2 Pesticides in bed sediment and aquatic biota from rivers in the United States: State and local monitoring studies Appendix C: Table 2.3 Pesticides in bed sediment and aquatic biota from rivers in the United States: Process and matrix distribution studies Appendix D: Common Names and Taxonomic Classifications of Aquatic Organisms Sampled in the Studies Reviewed Appendix E: Glossary of Common and Chemical Names of Pesticides References Index

Fate and transport of glyphosate and aminomethylphosphonic acid in surface waters of agricultural basins

BACKGROUND Glyphosate [N-(phosphonomethyl)glycine] is a herbicide used widely throughout the world in the production of many crops and is heavily used on soybeans, corn and cotton. Glyphosate is used in almost all agricultural areas of the United States, and the agricultural use of glyphosate has increased from less than 10 000 Mg in 1992 to more than 80 000 Mg in 2007. The greatest intensity of glyphosate use is in the midwestern United States, where applications are predominantly to genetically modified corn and soybeans. In spite of the increase in usage across the United States, the characterization of the transport of glyphosate and its degradate aminomethylphosphonic acid (AMPA) on a watershed scale is lacking. RESULTS Glyphosate and AMPA were frequently detected in the surface waters of four agricultural basins. The frequency and magnitude of detections varied across basins, and the load, as a percentage of use, ranged from 0.009 to 0.86% and could be related to three general characteristics: source strength, rainfall runoff and flow route. CONCLUSIONS Glyphosate use in a watershed results in some occurrence in surface water; however, the watersheds most at risk for the offsite transport of glyphosate are those with high application rates, rainfall that results in overland runoff and a flow route that does not include transport through the soil.

Atrazine, alachlor, and cyanazine in a large agricultural river system

Atrazine, alachlor, and cyanazine exhibited maximum concentrations of about 1000-6000 ng/L in the Minnesota River in 1990 and 1991, resulting from precipitation and runoff following the application period. Transport of these herbicides to the river occurs via overland flow or by infiltration to tile drainage networks. Suspended sediment, SO 4 2- , and Cl - concentrations were used as indicators of transport mechanisms. The atrazine metabolite, DEA, was present in the river throughout the year. The ratio of DEA to atrazine concentration was used to calculate an apparent first-order soil conversion rate of atrazine to DEA. Half lives of 21-58 d were calculated for 1990 and 1991, respectively

PCBQ: Computerized quantification of total PCB and congeners in environmental samples

Abstract Computerized methodologies for the quantification of total PCBs, PCB in Aroclor mixtures and individual PCB congeners in environmental samples are presented. The method for total PCBs is based on a multiple-linear regression analysis using data from capillary gas chromatography of Arocolor standards. PCB congeners were identified and their weight percentages determined in Aroclor mixtures by GC/MS. PCB congeners and total PCBs were accurately quantified in predetermined test data and environmental samples.

National, Holistic, Watershed-Scale Approach to Understand the Sources, Transport, and Fate of Agricultural Chemicals

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

Pesticides in rain in four agricultural watersheds in the United States.

Rainfall samples were collected during the 2003 and 2004 growing seasons at four agricultural locales across the USA in Maryland, Indiana, Nebraska, and California. The samples were analyzed for 21 insecticides, 18 herbicides, three fungicides, and 40 pesticide degradates. Data from all sites combined show that 7 of the 10 most frequently detected pesticides were herbicides, with atrazine (70%) and metolachlor (83%) detected at every site. Dacthal, acetochlor, simazine, alachlor, and pendimethalin were detected in more than 50% of the samples. Chlorpyrifos, carbaryl, and diazinon were the only insecticides among the 10 most frequently detected compounds. Of the remaining pesticide parent compounds, 18 were detected in fewer than 30% of the samples, and 13 were not detected. The most frequently detected degradates were deethylatrazine; the oxygen analogs (OAs) of the organophosphorus insecticides chlorpyrifos, diazinon, and malathion; and 1-napthol (degradate of carbaryl). Deethylatrazine was detected in nearly 70% of the samples collected in Maryland, Indiana, and Nebraska but was detected only once in California. The OAs of chlorpyrifos and diazinon were detected primarily in California. Degradates of the acetanilide herbicides were rarely detected in rain, indicating that they are not formed in the atmosphere or readily volatilized from soils. Herbicides accounted for 91 to 98% of the total pesticide mass deposited by rain except in California, where insecticides accounted for 61% in 2004. The mass of pesticides deposited by rainfall was estimated to be less than 2% of the total applied in these agricultural areas.

Occurrence and fate of the herbicide glyphosate and its degradate aminomethylphosphonic acid in the atmosphere

This is the first report on the ambient levels of glyphosate, the most widely used herbicide in the United States, and its major degradation product, aminomethylphosphonic acid (AMPA), in air and rain. Concurrent, weekly integrated air particle and rain samples were collected during two growing seasons in agricultural areas in Mississippi and Iowa. Rain was also collected in Indiana in a preliminary phase of the study. The frequency of glyphosate detection ranged from 60 to 100% in both air and rain. The concentrations of glyphosate ranged from <0.01 to 9.1 ng/m(3) and from <0.1 to 2.5 µg/L in air and rain samples, respectively. The frequency of detection and median and maximum concentrations of glyphosate in air were similar or greater to those of the other high-use herbicides observed in the Mississippi River basin, whereas its concentration in rain was greater than the other herbicides. It is not known what percentage of the applied glyphosate is introduced into the air, but it was estimated that up to 0.7% of application is removed from the air in rainfall. Glyphosate is efficiently removed from the air; it is estimated that an average of 97% of the glyphosate in the air is removed by a weekly rainfall ≥ 30 mm.

Pesticides in Mississippi air and rain: A comparison between 1995 and 2007

A variety of current-use pesticides were determined in weekly composite air and rain samples collected during the 1995 and 2007 growing seasons in the Mississippi Delta (MS, USA) agricultural region. Similar sampling and analytical methods allowed for direct comparison of results. Decreased overall pesticide use in 2007 relative to 1995 generally resulted in decreased detection frequencies in air and rain; observed concentration ranges were similar between years, however, even though the 1995 sampling site was 500 m from active fields whereas the 2007 sampling site was within 3 m of a field. Mean concentrations of detections were sometimes greater in 2007 than in 1995, but the median values were often lower. Seven compounds in 1995 and 5 in 2007 were detected in ≥50% of both air and rain samples. Atrazine, metolachlor, and propanil were detected in ≥50% of the air and rain samples in both years. Glyphosate and its degradation product, aminomethyl-phosphonic acid (AMPA), were detected in ≥75% of air and rain samples in 2007 but were not measured in 1995. The 1995 seasonal wet depositional flux was dominated by methyl parathion (88%) and was >4.5 times the 2007 flux. Total herbicide flux in 2007 was slightly greater than in 1995 and was dominated by glyphosate. Malathion, methyl parathion, and degradation products made up most of the 2007 nonherbicide flux.

Relationship between Chlorinated Hydrocarbons and Organic Carbon in Sediment and Porewater

Chlorinated hydrocarbons (PCBs and chlorinated pesticides) and organic carbon were measured in the bulk sediment, very fine, low density, sediment particles, porewater, and Hexagenia naiads of Lake Superior sediment to examine the distribution of the hydrophobic organic compounds and how this distribution is influenced by organic carbon. The porewater was divided into filtered and unfiltered fractions. The sediment fractions did not behave the same in their affinity to bind the chlorinated hydrocarbons, nor were all of the chlorinated hydrocarbons bound to the same extent. The affinity for most of the chlorinated hydrocarbons to the solids were in the order: larvae > fine particles > bulk sediment. The filtered porewater organic carbon (dissolved and/or colloidal) was about 1/2 to 2/3 as efficient as the bulk sediment organic carbon at binding these hydrophobic compounds. A three-phase (solid, porewater organic carbon, dissolved) competitive model estimates that < 10% of the chlorinated hydrocarbons in the porewater are dissolved. The remaining fraction is associated with the organic porewater colloids.

Quantifying watershed‐scale groundwater loading and in‐stream fate of nitrate using high‐frequency water quality data

We describe a new approach that couples hydrograph separation with high-frequency nitrate data to quantify time-variable groundwater and runoff loading of nitrate to streams, and the net in-stream fate of nitrate at the watershed scale. The approach was applied at three sites spanning gradients in watershed size and land use in the Chesapeake Bay watershed. Results indicate that 58–73% of the annual nitrate load to the streams was groundwater-discharged nitrate. Average annual first-order nitrate loss rate constants (k) were similar to those reported in both modeling and in-stream process-based studies, and were greater at the small streams (0.06 and 0.22 day−1) than at the large river (0.05 day−1), but 11% of the annual loads were retained/lost in the small streams, compared with 23% in the large river. Larger streambed area to water volume ratios in small streams results in greater loss rates, but shorter residence times in small streams result in a smaller fraction of nitrate loads being removed than in larger streams. A seasonal evaluation of k values suggests that nitrate was retained/lost at varying rates during the growing season. Consistent with previous studies, streamflow and nitrate concentrations were inversely related to k. This new approach for interpreting high-frequency nitrate data and the associated findings furthers our ability to understand, predict, and mitigate nitrate impacts on streams and receiving waters by providing insights into temporal nitrate dynamics that would be difficult to obtain using traditional field-based studies.