ATRAZINE MINERALIZATION POTENTIAL OF ALLUVIAL-AQUIFER SEDIMENTS UNDER AEROBIC CONDITIONS

Microorganisms in aerobic incubations of alluvial-aquifer sediment mineralized 9-14% of added [U-C-14]-D-glucose in 24 h, compared with < 0.1-1.5% of added [ethyl-2-C-14]atrazine and < 0.1% of added [U-ring-C-14]atrazine in 23 days. (CO2)-C-14 production from glucose and atrazine ethyl-2 carbon was greater in shallow sediment (< 6 m) than in deep sediment (> 17 m). Although first-order rate constants for (CO2)-C-14 production from the atrazine ethyl-2 carbon were low (< 4.5 x 10(-5)-5.4 x 10(-4) day-1), they may be significant in the time frame of groundwater flow. Laboratory-measured rate constants were similar to field-estimated rate constants [(3.2 +/- 1.4) x 10(-4) day-1] required to mineralize the atrazine ethyl carbon in groundwater prior to its discharge into an adjacent river. These results are consistent with the occurrence of detectable levels of deethylatrazine, but not atrazine, in groundwater from monitoring wells at the river.