Anaerobic Biodegradation of Pesticides

With the exception of those used in paddy rice, pesticides are typically applied to oxic environments but may be transported to anoxic environments through leaching, surface runoff, or eroded sediments. Pesticides are often applied to sites subject to transient flooding, eventually causing soil to become anoxic as oxygen consumptions rates exceed supply rates. This is largely due to decreased gas diffusion as pore space becomes saturated. Pesticide degradation occurs in each of the major anaerobic redox regimes, including aerobic, nitrate-reducing, iron-reducing, sulfate-reducing, and methanogenic environments. The ecology of microorganisms involved in anaerobic degradation of pesticides was poorly described until recently. Pesticide degraders (especially anaerobes) can be difficult to isolate; however, molecular biology tools allow examination of microorganisms involved in pesticide degradation without the need for isolation. In some cases, pesticide biodegradation has proved more rapid in aerobic environments, while certain substances are more labile under anaerobic conditions.