Field Processes and Applications-15 Comparison of Atrazine and Alachlor Sorption, Mineralization, and Degradation Potential in Surface and Aquifer Sediments

Atrazine and alachlor have been used for controlling weeds in crops. These herbicides and their degradation products also have been detected in surface and ground waters. The objective of this study was to determine atrazine and alachlor sorption and degradation potentials at four soil depths and in aquifer matrix materials. Sorption potentials decreased with sample depth but were similar between herbicides at each depth. Mineralization potential differed between herbicides with twice as much alachlor mineralized at each depth compared with atrazine. After 112-d incubation at 10 C, atrazine degradation products were not detected in sample extract, whereas alachlor degradation products were present in both soil and aquifer matrix samples. Alachlor degradation products detected in A-horizon soil included the ethanesulfonic acid (ESA) and oxanillic acid (OAA) forms of alachlor. In aquifer extracts, two degradation products were formed, one cochromatographing with OAA-alachlor and an unidentified product. The ESA degradation product of alachlor has been detected frequently in aquifers at higher concentrations than alachlor. Its presence may be due to transport through the soil profile since this product was not detected in incubated samples