The anaerobic degradation of endosulfan by indigenous microorganisms from low-oxygen soils and sediments

Indigenous mixed populations of anaerobic microorganisms from an irrigation tailwater drain and submerged agricultural chemical waste pit readily biod egraded the major isomer of endosulfan (endosulfan I). Endosulfan I was bio degraded to endosulfan diol, a low toxicity degradation product, in the pre sence of organic carbon sources under anaerobic, methanogenic conditions. W hile there was extensive degradation (> 85%) over the 30 days, there was no significant enhancement of degradation from enriched inocula. This study d emonstrates that endosulfan I has the potential to be biodegraded in sedime nts, in the absence of enriched microorganisms. This is of particular impor tance since such sediments are prevalent in cotton-growing areas and are ty pically contaminated with endosulfan residues. The importance of minimizing non-biological losses has also been highlighted as a critical issue in det ermining anaerobic biodegradation potential. Seals for such incubation vess els must be both oxygen and pollutant impermeable. Teflon-lined butyl rubbe r provides such a seal because of its resistance to the absorption of volat iles and in preventing volatilization. Moreover, including a 100 mM phospha te buffer in the anaerobic media has reduced non-biological losses from che mical hydrolysis, allowing biodegradation to be assessed. (C) 1999 Elsevier Science Ltd. All rights reserved.