Quantitative bioassays for monitoring the dissipation of atrazine in soil

Abstract

A simple bioassay technique was used to study the residual activity of atrazine [2-chloro-4-(ethylamino)-6-(isopropylamino)-s-triazine] applied at 0.25 kg ai ha⁻¹ at different depths in a sandy clay loam (22% clay; 0.31% organic C) soil. Oats (Avena sativa L. cv. SWK001) was planted on treated and untreated plots and soil samples for glasshouse bioassay were taken from different soil layers (0–100, 100–200, 200–300 and 300–400 mm) −1, 0, 1, 30, 60, 90 and 120 days after atrazine application. The phytotoxic atrazine residues remaining in each soil layer were estimated by means of logarithmic dose-response curves. Bioassays for dose-response curves were conducted in parallel with the assays of soil samples collected in the field. It was estimated that 55% of the amount applied in the field was present in the 200–300-mm soil layer on day 30 after application. At days 60, 90 and 120 the percentages remaining in the 200–300-mm soil layer were 2.8%, 1.7% and 2.7%, respectively. Estimates on day 120 indicated that 2.2% of the amount applied remained in the topsoil layer and 5.6% in the 300–400-mm layer. There was generally good correlation between indoor and outdoor results, as well as between visual and measured (fresh and dry mass) assessments of damage in the field. The bioassay technique could be convenient for estimating atrazine residues in the soil profile, especially to predict the potential for damage to sensitive follow-up crops.

Keywords:

• Atrazine
• bioassay
• leaching
• persistence