FORMATION AND MOVEMENT OF C-14 ATRAZINE DEGRADATION PRODUCTS IN A SANDY LOAM SOIL UNDER FIELD CONDITIONS

Formation and distribution of C-14-atrazine degradation products in th e top 120 cm of soil were determined over 16 mo under field conditions in an Estherville sandy loam. After 16 mo, 78% of applied C-14 was st ill present in the soil. By 2 mo after treatment (MAT), C-14 had moved to the 30- to 40-cm depth; however, movement to depths greater than 4 0 cm was not observed. Greater than 98% of the C-14 remaining in the s oil profile after 16 mo was in the top 20 cm. Twenty-seven percent of the C-14 applied was atrazine 16 MAT. Atrazine was the predominant C-1 4-compound in soil below 10 cm. Hydroxyatrazine (HA) was the major deg radation product in the top 10 cm of soil. The proportion of C-14 as H A in the top 10 cm increased from 15% 2 MAT to 37% 16 MAT. Deethylatra zine (DEA) was the predominant degradation product at the 10- to 30-cm depth and accounted for up to 23% of the C-14 present in the 10- to 2 0-cm depth. Deisopropylatrazine (DIA) accounted for less than 6% of th e radioactivity recovered at any soil depth. The proportion of DEA and DIA increased while the proportion of HA decreased as soil depth incr eased, indicating that DEA and DIA are more mobile in soil than HA. De tection of HA at depths greater than 10 cm appears to be due to in sit u degradation of atrazine previously moved to that soil depth. The lar ge amount of C-14 remaining in the soil 16 MAT suggests that a large p ool of atrazine and its degradation products are present in the soil f or an extended period following application and have the potential to contaminate ground water.