Movement and degradation of [14C]atrazine in undisturbed soil columns

Abstract

The movement and degradation of [¹⁴C]‐atrazine were studied in undisturbed soil columns (15 × 60 cm) taken manually from a field with no previous pesticide history. The experiment was conducted indoors under controlled temperature conditions. Three weeks after application of [¹⁴C]‐atrazine (2.2 kg a.i. per hectare) to the soil surface, the columns were leached at weekly intervals for 12 weeks. Approximately 1.2% of the applied ¹⁴C was recovered in the leachate over the 12‐week period, which corresponds to an atrazine (plus degradation products) concentration of 7.6 μg/L. On completion of the last leaching event, the columns were cut into 10‐cm increments and analyzed for [¹⁴C]‐atrazine and degradation products. Seventy‐seven percent of the ¹⁴C applied to soil columns remained in the upper 10 cm and included primarily atrazine (9%) and soil‐bound residues (57%). Deethylatrazine was the predominant degradation product in the top 10 cm (3.6%). Other degradation products were found in the top 10 cm at relative concentrations of deisopropylatra‐zine > hydroxyatrazine > didealkylatrazine > deethylhydroxyatrazine > deisopropylhydroxyatra‐zine. Uncharacterized polar metabolites in the top 10 cm accounted for 6% of the applied ¹⁴C. Atrazine, deethylatrazine, and deisopropylatrazine were found at all depths. In addition, didealkylatrazine was detected to the 50‐cm depth, hydroxyatrazine to the 30‐cm depth, and deethylhydroxyatrazine to the 20‐cm depth.