This report presents the results of the June-July 1997 statewide pesticide survey of 64 streams and rivers across New York State, and discusses the methods used to collect and analyze the data. Detection rates for several pesticides are presented, and pesticide concentrations are discussed in relation to (1) Federal and State water-quality standards, (2) results of previous water-quality investigations in New York State, and (3) predominant land-use and pesticide-use patterns in the watersheds investigated.
Water samples were collected and filtered in accordance with methods described by Shelton (1994) and were analyzed for 47 pesticides through methods described by Zaugg and others (1995). Detection limits (technically known as Method Detection Limits) for pesticides analyzed ranged from 0.001 to 0.018 ug/L. Analyses of quality-assurance samples indicate that these laboratory results accurately represented concentrations in the streams. The laboratory methods used in this study resulted in low and (or) inconsistent recovery for five pesticides (carbaryl, carbofuran, deethylatrazine, terbacil, and azinphos-methyl). Thus concentrations reported for each of these compounds are considered estimates (Chris Lindley, U.S. Geological Survey, written commun., 1994). Detection rates are reported as a percentage of the total number of samples analyzed, and include samples in which concentrations were reported as being below the method detection limit. This reporting is common when a compound can be conclusively identified (Jeffrey W. Pritt, U.S. Geological Survey, written commun., 1994). These concentrations indicate the presence of pesticides in the sample; these concentrations are considered estimates. The data discussed in this report are available in Butch and others (1998) and on the Internet at http://ny.usgs.gov/htmls/pub/nypesticides/index.html. Each site was classified in one of five categories, depending on the predominant land use in the watershed. These categories were Forested, Urban/Residential, Orchard/Vineyard, Low row-crop agricultural and High row-crop agricultural. Watershed boundaries were overlain on mapping-data imagery generated from satellite data collected in 1994 (U.S. Geological Survey, 1997). Forested watersheds were defined as those in which forests and wetlands cover more than 88 percent of the watershed area. Urban/residential watersheds are those in which more than 13 percent of the land is urban (including residential, commercial and industrial land, parks, lawns, and golf courses). Low row-crop agricultural watersheds were those in which row crops occupy less than 20 percent of the land, and high row-crop watersheds are those in which more than 20 percent of the land is planted in row crops. The remote-sensing data were inadequate for delineation of orchards and vineyards. Therefore, these watersheds were not classified according to remote-sensing data, but through field reconnaissance, as having substantial orchard or vineyards.
Two insecticides-carbaryl and diazinon-were detected in 20 percent and 14 percent of the samples, respectively. These compounds were most often detected in streams draining areas in which these compounds are commonly applied-carbaryl in orchard/vineyard and urban/residential watersheds, and diazinon in urban/residential watersheds. The highest carbaryl concentrations were found in streams draining two types of watersheds-orchard/vineyard watersheds in western New York, and urban/residential watersheds in southeastern New York (including Long Island). The highest concentrations of diazinon were found in urban/residential watersheds in southeastern New York, including Long Island.
In general, concentrations of most pesticides detected in this statewide survey were low, and few exceeded 0.1 ug/L. The largest exceptions to this generalization were atrazine, metolachlor, cyanazine, and simazine; more than 10 percent of the streams contained these compounds in concentrations greater than 0.1 ug/L. Of the 47 pesticides studied, 22 were not detected in any sample (table 2).
The pesticide concentrations measured in this survey probably do not reflect maximum annual concentrations because most of the samples were collected during base-flow (low-flow) conditions. Previous sampling for pesticides in a small agricultural watershed in the Hudson River Basin during 1994-96 indicated that concentrations of pesticides are lower in base flow than in stormflow (Wall and Phillips, 1996a, 1997). Base flow consists mostly of ground water that discharges from the underlying aquifer to streams. Thus, the presence of pesticides in base flow samples suggests that these pesticides may be present in ground water.
The similarity of results from the 1997 survey to results from a 1994 survey of pesticides at 46 sites in the Hudson River Basin (Wall and Phillips, 1996b) indicates that most of these pesticides have been present in New York streams for at least 3 years. Both surveys used identical sample-collection and analytical methods; therefore, the results of the two surveys can be compared directly. The most commonly detected pesticides in both surveys were atrazine, metolachlor, and deethylatrazine. Other compounds that were commonly detected in both years were simazine, cyanazine, and alachlor. The most commonly detected insecticides in both years were carbaryl and diazinon.
The State criterion for protection of aquatic life (0.005 ug/L) for azinphos-methyl was exceeded at four sites (35, 36, 37, and 38). All of these sites are in western New York in orchard watersheds. The state criterion for protection of aquatic life (0.070 ug/L for diazinon ) was exceeded at three sites (sites 7, 35, and 64). Two of these sites are in urban/residential watersheds on Long Island or southeastern New York, and the other (site 35) is in an orchard/vineyard watershed in western New York. The State guideline for surface water and class GA ground water (0.50 ug/L for simazine) was exceeded at one site (site 40) . This site is in an orchard/vineyard watershed in western New York.
1. Use of low detection limits (for pesticides) allows detection of temporal trends and identification of streams that need protection to prevent concentrations of pesticides from increasing to levels that could threaten the water quality or the ecological health of a stream. Although detection limits close to the established water quality-criteria are suitable for compliance monitoring, they would provide less useful data than do low detection limits for early warning of increasing pesticide concentrations. Use of low detection limits over a long period can help indicate whether pesticide concentrations are increasing, decreasing, or remaining constant.
2. Low detection limits allow researchers to discern correlations between pesticide exposure and human health or ecological health. If detection limits were higher, most pesticide concentrations would be reported as below those limits and could not be used in statistical correlations between pesticide exposure and human health.
3. Low detection limits maximize the number of samples that can be used to relate pesticide concentrations to environmental factors. Large numbers of samples decrease the uncertainty in predicting pesticide contamination.
4. Low detection limits can increase the likelihood that pesticides not detected in analyses are truly absent from waters sampled.
Concentrations of only a few compounds exceeded applicable State water-quality standards, and no concentrations exceeded federal health advisory or maximum contaminant levels. New York State water-quality criteria were exceeded at 10 sites by four insecticides (azinphos-methyl, p,p'-DDE, diazinon, and dieldrin) and one herbicide (simazine).
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