Biological and Chemical Degradation of Atrazine in Three Oregon Soils

Abstract

Microbial degradation of 2-chloro-4-(ethylamino)-6-(isopropylamino)-s-triazine (atrazine) and 2-hydroxy-4-(ethylamino)-6-(isopropylamino)-s-triazine (hydroxyatrazine) was investigated in three Oregon soils. Hydrolysis of atrazine was determined by the presence of14C-hydroxyatrazine in methanol extracts. Respired14CO2from the14C-ethyl side chain of atrazine represented less than 10% of the added14C in the soils after 28 days. Degradation was dependent on soil type, atrazine concentration, and moisture content. The isopropyl and ring constituents of atrazine were subject to minimal attack. The hydroxyatrazine ring was attacked more readily than the atrazine ring. Hydroxyatrazine accounted for approximately 10% of the extracted14C from14C-atrazine-treated Parkdale-A, Parkdale-C, and Coker soils and 40% from the Woodburn soil. Hydrolysis was the dominant pathway of detoxification in the Woodburn soil, whereas detoxification of atrazine in Parkdale-A, Parkdale-C, and Coker soils was a combination of chemical hydrolysis and slow microbial degradation byN-dealkylation of the ethyl side chain constituent.