Biological and Chemical Degradation of Atrazine in Three Oregon Soils

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 of 14 C-hydroxyatrazine in methanol extracts. Respired 14 CO 2 from the 14 C-ethyl side chain of atrazine represented less than 10% of the added 14 C 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 extracted 14 C from 14 C-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 by N -dealkylation of the ethyl side chain constituent.