Behavior of DDT, Kepone, and Permethrin in Sediment-Water Systems under Different Oxidation-Reduction and pH Conditions

摘要

A study was conducted to determine the effects of pH and oxidation-reduction (redox) conditions of soil and sediment-water systems on the persistence of three insecticide compounds. Three pH levels, ranging from moderately acid to mildy alkaline, were studied for each compound. Four redox potential levels (-150, 50, 250, and 450 mv) were studied ranging from strongly reduced (anaerobic) to well oxidized (aerobic). The insecticide-substrate combinations included in the project were DDT in a Mobile Bay (Mobile AL) sediment material, Kepone in the sediment material of a tributary of the James River (Hopewell VA), and Permethrin in an Olivier soil material (Baton Rouge LA). Sample aliquots were removed from the laboratory microcosms to determine the recovery of the added compounds with time. A substantial redox potential effect was noted for DDT where recovery decreased from the spiking level of around 25 parts per million (ppm) to near 0 ppm within a few days at -150 mv (strongly reduced condition). A less rapid loss of DDT was noted at 50 mv (moderately reduced condition), but the pesticide appeared stable under better oxidized conditions during the 45-day incubations. The levels of Kepone recovered did not change appreciably during 56 days of incubation under any of the combinations of imposed pH and redox potential conditions. The recovery of Permethrin was affected by both pH and redox potential conditions over 25-day incubations. Unlike DDT, Permethrin was lost more rapidly under oxidizing conditions.