Pesticide Compounds in Streamwater in the Delaware River Basin, December 1998–August 2001

Hickman, Edward

During 1998–2001, 533 samples of streamwater at 94 siteswere collected in the Delaware River Basin in Pennsylvania,New Jersey, New York, and Delaware as part of the U.S. GeologicalSurvey National Water-Quality Assessment Program.Of these samples, 531 samples were analyzed for dissolved concentrationsof 47 pesticide compounds (43 pesticides and 4 pesticidedegradation products); 70 samples were analyzed for anadditional 6 pesticide degradation products.Of the 47 pesticide compounds analyzed for in 531 samples,30 were detected. The most often detected compoundswere atrazine (90.2 percent of samples), metolachlor (86.1 percent),deethylatrazine (82.5 percent), and simazine (78.9 percent).Atrazine, metolachlor, and simazine are pesticides;deethylatrazine is a degradation product of atrazine.Relations between concentrations of pesticides in samplesfrom selected streamwater sites and characteristics of the subbasinsdraining to these sites were evaluated to determinewhether agricultural uses or nonagricultural uses appeared to bethe more important sources. Concentrations of atrazine, metolachlor,and pendimethalin appear to be attributable more toagricultural uses than to nonagricultural uses; concentrations ofprometon, diazinon, chlorpyrifos, tebuthiuron, trifluralin, andcarbaryl appear to be attributable more to nonagricultural uses.In general, pesticide concentrations during the growingseason (April–October) were greater than those during the nongrowingseason (November–March). For atrazine, metolachlor,and acetochlor, the greatest concentrations generally occurredduring May, June, and July.Concentrations of pesticide compounds rarely (in only 7out of 531 samples) exceeded drinking-water standards orguidelines, indicating that, when considered individually, thesecompounds present little hazard to the health of the publicthrough consumption of the streamwater. The combined effectsof more than one pesticide compound in streamwater were notconsidered.Diazinon appeared to be the pesticide compound mostlikely to adversely affect aquatic life in the streams of the DelawareRiver Basin; concentrations of diazinon exceeded guidelines(designed to protect aquatic life) in 19 samples, the mostof any pesticide compound. Concentrations of as many as 5compounds exceeded guidelines in 29 of 531 samples.

Pesticide Compounds in Streamwater in the Delaware River Basin, December 1998–August 2001

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