RAPID MINERALIZATION OF THE HERBICIDE ATRAZINE IN ALLUVIAL SEDIMENTS AND ENRICHMENT CULTURES

The fate of atrazine in sediment sampled from two agricultural watersh eds in the Great Lakes basin of southern Ontario was studied in labora tory flask incubations of sediment slurry and enrichment cultures. Atr azine at an initial concentration of 10 mg/L disappeared within 15 d i n sediment slurries incubated aerobically at 30 degrees C. Because atr azine concentrations were stable in similarly incubated autoclaved slu rry and the lag preceding atrazine degradation was abolished by repeat ed atrazine additions, it was concluded that the herbicide was biodegr aded. Rapid atrazine degradation was found in concentrated suspended p articulates and surface (0 to 10 cm) sediments, but not in sediments t aken from a depth of 20 cm. Atrazine was not degraded under anaerobic or denitrifying conditions. Sediment and enrichment cultures converted [U-ring-C-14]-labeled atrazine to hydrophilic metabolites, tentativel y identified as cyanuric acid and urea, and then to carbon dioxide.