U.S. Geological Survey Toxic Substances Hydrology Program--Proceedings of the Technical Meeting, Colorado Springs, Colorado, September 20-24, 1993, Water-Resources Investigations Report 94-4015

Atrazine Transport and Degradation in a Pristine Watershed: The Fate of Atrazine Deposited by Precipitation

Abstract

Atrazine used in agricultural areas is being transported atmospherically and deposited by precipitation onto pristine watersheds. The fate of atrazine was studied at Isle Royale National Park, an island park located in Lake Superior on the United States-Canadian border. Samples of rainfall, soil water, surface water, and soils were analyzed by combining solid-phase extraction (SPE) with enzyme-linked immunosorbent assay (ELISA). This SPE-ELISA combination enabled the field analysis of water samples in which the concentrations of atrazine were as small as 5 ng/L (nanograms per liter). The SPE-ELISA results were confirmed using gas chromatography/mass spectrometry (GC/MS) with isotope dilution. Maximum atrazine concentrations in rainfall occurred in late spring, approaching the U.S. Environmental Protection Agency Maximum Contaminant Level (MCL) for drinking water of 3.0 micrograms per liter. By mid-summer, rainfall concentrations of atrazine had decreased to less than 5 ng/L. Atrazine was found in small concentrations in water from all lakes that were sampled. Field data indicate that atrazine degrades rapidly in soil environments but more slowly in aquatic environments. This slow degradation rate in water has important implications for the quality of lakes in pristine areas receiving atrazine-contaminated rainfall because of the potential for accumulation of atrazine in the ecosystem.