ATRAZINE, DEETHYLATRAZINE, AND DEISOPROPYLATRAZINE PERSISTENCE MEASURED IN GROUNDWATER IN-SITU UNDER LOW-OXYGEN CONDITIONS

The degradation of atrazine o-4-(ethylamino)-6-isopropylamino-1,3,5-tr iazine], deethylatrazine [DEA; amino-4-chloro-6-(isopropylamino)-1,3,5 -triazine], and deisopropylatrazine [DIA; 2-amino-4-chloro-6-(ethylami no)-1,3,5-triazine] was assessed under limited oxygen conditions using in situ microcosms. Denitrification was induced in a shallow sand and gravel aquifer to measure the potential for degradation of atrazine, DEA, and DIA under low-O-2 conditions. The dissolved oxygen content de creased from 7-8 mg/L to less than or equal to 1 mg/L within 4 days an d remained less than or similar to 3 mg/L for the remainder of the 45- day experiment. Atrazine, DEA, and DIA concentrations (normalized to t he bromide concentration at each sampling time to account for dilution ) did not show a significant decrease with time, indicating that these compounds are relatively stable under the low-O-2 conditions induced in the aquifer. Although removal of one alkyl group has been proposed as the rate-limiting step in atrazine degradation, no transformation o f either monodealkylated metabolite (DEA or DIA) was observed in this study.