MOVEMENT AND DEGRADATION OF [C-14] ATRAZINE IN UNDISTURBED SOIL COLUMNS

The movement and degradation of [C-14] -atrazine were studied in undisturbed soil columns (15 x 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 [C-14]-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 C-14 was recovered in the leachate over the 12-week period, which corresponds to an atrazine (plus degradation products) concentration of 7.6 mug/L. On completion of the last leaching event, the columns were cut into 10-cm increments and analyzed for [C-14]-atrazine and degradation products. Seventy-seven percent of the C-14 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 deisopropylatrazine > hydroxyatrazine > didealkylatrazine > deethylhydroxyatrazine > deisopropylhydroxyatrazine. Uncharacterized polar metabolites in the top 10 cm accounted for 6% of the applied C-14. 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.