Residues Of Organochlorine Pesticides In Vegetable Soil And Screen Of Acetamiprid-degrading Bacterium

Organochlorine pesticides are the most typical persistent organic pollutants (POPs). The twelve persistent organic pollutants listed as priority pollutants in Stockholm Convention on Persistent Organic Pollutants(POPs Convention) are all organic chlorine compounds.China is the largest user and producer of OCPs in the world. Hunan province has long hisrory in vegetable planting. Soil samples of vegetab- le soil were collected from seven sites in northeast of Hunan province in March 2006.This paper studied concentrations and pollution characteristics of OCPs, and pollution source. The main original conclusions of this work are as follows:(1)Eleven organochlorine pesticides wre detected in all these considered samples, concentrations in turn:∑DDTs>∑HCHs>Heptachlor epoxide>γ-chlordane >Diedrin> Aldrin. Concentration of OCP were in the rang of 29.19～77.46μg/kg.(2)The DDTs and HCHs were the main components and with a range of 0.15～16.80μg·kg-1 for HCHs and 6.05～57.91μg·kg-1 for DDTs, respectively, which was much lower than the standard values of HJ332-2006; but higher than the corresponding target values in the Dutch List.(3)The concentrations of DDTs are higher than HCHs. Compared to the referece data, the residual levels of DDTs,HCHs in soil was more slight.(4) The ratio ofα-HCH/γ-HCH were above 1.0, DDT /(DDE+DDD) were less than 1.0 in the great mass of regions which indicated that Lindane and DDTs might come from the old usage ,but there might be input into environment recently in Yueyang and Hengyang regions.(5) Aldrin, dieldrin,γ-chlordane and heptachlor epoxide were found with different degree in all the samples.They might come from the old usage.(6)With a simple risk assessment, concentration of DDT was above the maximum peimissible concentration for soils which is based on the bioaccumulation in terrestrial food webs.In this study, two degrading bacteriums were isolated by enrichment culture and screening, and named as strain AC2 and AC3. Their growth characteristics and degrading abilities wre also investigated. The main results are as follows:(1)Based on the phenotype, physiological and biochemical characteristics, and the phylogenetic analysis of 16S rDNA sequence, the strain AC2 was identified as Salmonella sp. and Bordetella parapertussis. (2)Effects of different initial acetamiprid concentration, total inocula biomass amount,incubation temperatures,initial pH,carbon source and nitrogen source were investigated to determine the optimal biodegradation conditions. The most suitable condition of Strain Salmonella sp.for its growth was 37℃, pH7.0, initial acetamiprid 150mg/L,10% total inocula biomass amount. Addition of extra carbon source, such as glucose and sucrose;addition of extra nitrogen source, such as beef extract could greatly enhance the growth. And the most suitable condition of Strain Bordetella parapertussis. for its growth was 37℃, pH7.0, initial acetamiprid 300mg/L, total inocula biomass amount 10%. Addition of extra carbon source, such as glucose and citric acid, addition of extra nitrogen source, such as beef extract and yeast extract could greatly enhance the growth.(3)The optimum conditions for acetamiprid degradation by strain Salmonella sp. were with total inocula biomass 10%, pH 7.0, 37℃.Addition of extra carbon source glucose could stimulated acetamiprid degradation. Bordetella parapertussis.could degradate 400mg/L under the condition of pH 7.0, 37℃, addition of extra nitrogen source, such as beef extract and yeast extract.