Characterization of agricultural nonpoint pollution: Pesticide migration in a West Tennessee watershed

Pesticide migration from agricultural fields may stress receiving stream ecosystems as well as contaminate ground water. Research was conducted on an 18-ha single-field watershed in west Tennessee to characterize the fate of atrazine during a 12-month period after pesticide application. Rainfall runoff and soil cores were sampled and analyzed for atrazine residues. Total loss of atrazine by runoff accounted for approximately 1.5% of the total atrazine applied. Concentrations as high as 0.25 mg/L were detected in the field discharge. By the fourth storm event after pesticide application, the atrazine concentration was below detection limits (0.1 μg/L). Atrazine loss in the upper 10 cm of soil followed a first-order decay trend, with only 1.88% of the initial concentration remaining 238 d after pesticide application. The mean half-life for atrazine in the upper 10 cm was approximately 21.5 d. Atrazine was detected in the 10- to 20-cm soil level after the first rainfall. Atrazine was not detected below 20 cm at any sampling date during the 238 d of the study.