Residue Analysis Of Organochlorine Pesticides And Preliminary Study Of DDT Degrading Strains

The residule and pollutant were attended by the whole world and the pesticides are yielded and used much in China.For this cause, the study of the residule and degradation of pesticides were significative.The soil pollution characters of organic chlorine pesticides (OCPs) around Chao-hu city were studied in this paper. Ultrasonic wave extraction, column chromatographic and gas chromatograph (electron capture detector GC-ECD) were used in this method to investigate the distribution of chlorine pesticides in soils of different types. Soil pollution and environment quality were also assessed. The DDT degrading-bacteria were isolated by enrichment culture way from soil exposed to pesticides and soil of pesticides production, and then researched on the bacteria in our laboratory conservation. And choose the strain degrading-bacteria for further study.First, The distribution and constitution of nineteen chlorine pesticides in16farmlands sites were studied. Seven pesticides including HCHs, DDTs, hexachlorobenzene, heptachlor, endosulfan, dieldrin and aldrosol were detected, which ranged from0.11-32.24ng/g. HCHs and DDTs were the main pollution accounting for95.05%of total pollution. The concentrations of them were1.39ng/L and7.87ng/L respectively. β-HCH was the main constitute of HCHs, concrete content order as β-HCH>α-HCH>δ-HCH>γ-HCH. β-HCH was strongly symmetrical, as a result of chemical and physical property more stable and difficult to degrade compared with other isomers. So other isomers would reform in the environment for β-HCH to achieve a more steady state.4,4’-DDE and4,4’-DDT were the main constitute of DDTs, accounting for above50%, which showed that DDTs was the main degenerate catabolism of DDE in the environment. Pollution resource showed HCHs residual α/γ value ranged from0.95-3.12,(DDD+DDE)/DDTs ratio>0.5, and the DDE/DDD ratio>1, which explained HCHs residue was the result of long-term degeneration of organic chlorine pesticides.Second, Five sampling sites including vegetable field, farmland were selected to compare the difference of distribution and content of OCPs. There was no significant difference between vegetable field and farmland. However, OCPs residual concentrations in vegetable field were higher than that in farmland. So soil type was an important factor affecting pesticides degrade.Third. OCPs residual concentration in farmland of Chao-hu city was lower compared with other parts of the world. The environmental pollution caused by organic chlorine pesticides and their potential risk to human health was small from the environmental quality assessment of this region.Fourth, The DDT degrading-bacteria were isolated by enrichment culture way from soil exposed to pesticides and soil of pesticides production, and then researched on the bacteria in our laboratory conservation. The high efficiently degrading strains (DX8) were isolated by selective enrichment, based on analysis of phenotype, physiological and biochemical characters, DX8was identified as Alcaligenes sp., we choose the strain DX8for further study.Fifth, The effects of carbon source, pH, temperature and DDT concentration on degradation was determined. The results showed that the biodegradation rates were the highest when the additional carbon source was0.5%, pH value was6.0, DDT concentration was10mg/L and cultivated temperature was30℃. The growth of bacteria increased with carbon source concentration increased, higher with pH from6.0to10.0, and the highest when temperature was30℃, DDT concentration was10mg/L. the removed amount of DDT increased with DDTconcentration.This research has reference valve for the distribution, transport and transformation characters of OCPs. It also facilitates to predicate OCPs transport transformation trends in Chao-hu river. The results of this paper would provide effective technical and method support for managerial decision. a strain of bacterium capable of highly degrading DDT was screened from the soil sample collected from a pesticide plant after taming and enrichment. Degrading-bacteria enrichment and isolation, characterization of biodegradation were studied systematically.