Study On The Impact Of Endosulfan On Soil Microorganism And The Resistance Mechanism And Degradation Ability Of Microorganism

Organochlorine pesticides (OCPs) had been used widely in the world. But the use of OCPs was banned in most of the developed world from1973and in our country in the1980s, owing to their high toxicity and persistence. Although OCPs have been degraded naturally for more than twenty years, their residues in the environment is still high, while endosulfan is one of the most widespread and richest OPCs observing in the soil. Microorganisms have key functions in soil and affect nutrient cycling, carbon cycling and soil fertility. Besides they respond quickly to changes. Therefore microorganisms are generally considered important biotic indicators of soil health. Hence research about the impact of OPCs to soil microorganisms is significative to the safety evaluations of OPCs. Endosulfan, a kind of representative OPCs, was selected as objective to study its degradation rule and effect on soil microorganisms. A strain JZ-1resistant endosulfan was isolated from sludge that produced during the process of wastewater treatment in pesticide factory. The resistance mechanism and degradation ability of strain JZ-1were studied. The main results are as follows:(1) Endosulfan removed about50%after42days and its removal in soil fitted single first-order kinetics. The degradation of endosulfan was affected by its initial concentration. When the initial concentration of endosulfan was0.1mg/kg, its half-life time in soil was38.5days, while36.8days for1mg/kg endoulfan.(2) The exposure to endosulfan caused a short-lived inhibition on both fungal and bacterial quantity and this effect had a positive correlation with the concentration of endosulfan. A significant change in bacterial community structure was found after endosulfan application and this change were concentrtion and time regarding. Endosulfan also induced a change of fungal community structure, but this change was not observed until the endosulfan concentration exceeded a certain value. The main bacterial groups mainly belonged to four categories, they were Actinobacteria, Deinococcus-Thermus Gemmatimonadetes and Firmicutes. The main fungal groups were Ascomycota, Stramenopiles and Basidiomycota.(3) A strain JZ-1resistant endosulfan was isolated from sludge that contaminated by pesticide and it was belong to Serratia by molecular identification. Plasmid elimination and transformation experiments revealed that the endosulfan resistance of strain JZ-1primarily depended on the plasmids harbouring in its cells. Its ability of degrade endosulfan was weak. When adding external carbon source, the maximum degradation rate of endosulfan by JZ-1was31.02%after15days.