Factors influencing the degradation of soil-applied endosulfan isomers

The addition of isolated bacterial cells to contaminated soils causes an enhanced degradation of endosulfan isomers. Various factors, including the additional presence of carbon sources, pH, moisture content, concentration of endosulfan, and size of inoculum, influenced the degradation of endosulfan isomers. The degradation was faster in wet soils, as compared with the flooded soils, and was inhibited by the presence of additional carbon sources such as sodium acetate and sodium succinate. The degradation of endosulfan was not detectable at acidic pH and increased gradually to reach an optimal activity at pH 8.5. It chemically converts into endosulfan diol at higher pH values. The rate of biodegradation progressed with the increase in endosulfan concentration up to 5.0 mg g−1 soil, followed by an inhibitory effect at higher concentrations, reaching a total loss of biodegradative activity at 10 mg g−1 soil. The addition of 2×106 bacterial cells g−1 soil was optimal for endosulfan degradation and any further increase in inoculum size was of no additional advantage. Initial optimization of these factors is, therefore, essential for successful bioremediation.