Interaction of atrazine with soil microorganisms: population changes and accumulation.

A loam soil treated with atrazine at rates of 10, 30, and 100 microgram/g soil resulted in increased populations of actinomycetes, bacteria, and fungi over those in non-treated soil. The increases were in proportion to the amount of atrazine and persisted for at least 2 months. Living actinomycete amd fungal mycelia were incubated for 48 h in distilled water, nutrient broth, or soil containing 5 microgram/ml (g) of the herbicide. Actinomycete and fungal mycelia accumulated atrazine from water to concentrations up to 87-fold and 132-fold, respectively, over that in the ambient medium. The maximum accumulation from soil by actinomycete mycelia was 26-fold and by fungal mycelia 13-fold. Fungi accumulated little or no atrazine from a nutrient medium whereas actinomycetes accumulated up to 13-fold. Dead mycelia usually did not accumulate atrazine in excess of the ambient concentration. Mycelium of Sclerotium rolfsii growing in a nutrient medium containing 20 microgram atrazine/ml accumulated 157 microgram/g wet weight after 8 days. Sclerotia subsequently produced after transfer of similar mats to soil contained 550 microgram/g wet weight.