Screening rh1zosphere soil samples for the ability to mineralize elevated concentrations of atraz1ne and metolachlor

Rhizosphere soils from several plant species were tested for their ability to mineralize atrazine (2-chloro-4-ethylamino-6-isopropylamino-s-triazine) or metolachlor (2-chloro-A/-(2-ethyl-6-methylphenyl)-/V-(2-methoxy-1-methylethyl)acetamide) at concentrations typical of point-source contamination (50 ug/g). Rhizosphere soils were collected from the root zone of plants in areas with previous herbicide exposure. Several rhizosphere soils tested positive for ¹⁴C-atrazine mineralization (> 8.5%) including kochia (Kochia scoparia), lambsquarters (Chenopodium berlandieri), foxtail barley (Hordeum jubatum), witchgrass (Panicum capillare), catnip (Nepeta cataria), and musk thistle (Carduus nutans). None of the 15 rhizosphere samples tested was capable of significant (> 8.5%) ¹⁴C-metolachlor mineralization. The results on atrazine mineralization suggest that certain plants at pesticide-contaminated sites might be managed to facilitate microbial detoxication of unwanted organic compounds in soil.