The Study On Residue Behavior Of Diazinon In Atractylodes And Soil

With the increasing demand for natural medicines, people are paying more attention to Chinese herbal medicine resources. Organophosphorus pesticides, as the most productive pesticides in china, are widely used in the cultivation of Chinese herbal medicines, which led to excessive pesticide residues-an obstacle of herbal medicines export. Therefore, study of pesticide environmental behaviors during the cultivation of herbel medicines are particularly important. In this paper, organophosphate pesticide diazinon was selected as a research subject, and the degradation and adsorption in cultivation soil and atractylodes were studied. The main findings are as follows:Results of field test showed that the dynamics of diazinon in atractylodes leaves followed the first order kinetics. The half-lives of diazinon were5.90d (Zhejiang) and5.12d (Hubei). The residues of diazinon were0.0022mg/kg～0.0025mg/kg (Zhejiang) and0.0021mg/kg～0.0058mg/kg (Hubei) in atractylodes rhizome after75days, respectively.According to the result of indoor tests, the dynamics of diazinon in dry atractylodes rhizome followed the first order kinetics. The half-lives were46.23d (10℃),24.29d (20℃) and18.27d (30℃). The half-lives of diazinon in different soils were Panan24.32d (10℃),12.10d (20℃) and8.64d (30℃). Tongxiang30.13d(10℃),16.82d (20℃) and9.65d (30℃). Hangzhou29.25d (10℃),17.26d (20℃) and10.13d (30℃). Qingyuan28.14d (10℃),14.79d (20℃) and10.88d (30℃). The degradation of diazinon was accelerated with temperature increasing and the half-lives were significantly different between diffrernt soils.The half-lives of diazinon in soils with different water-content were7.71d (submerged),12.10d (60%field capacity) and15.33d (dry), respectively. The dynamics of diazinon in unsterilized and sterilized soils showed that the half-lives were12.10d (unsterilized) and13.11d (sterilized). The hydrolysis dynamics of diazinon in water with diffrernt pH showed that half-lives of diazinon were10.25d (pH=5),117.46d (pH=7) and84.51d (pH=9), respectively.According to the result of adsorption behaviors test, the Kf of diazinon is5.70(Enshi soil) and4.87(Panan soil), showed that adsorption of diazinon was stronger in Enshi soil than in Panan soil. This may be caused by the organic carbon and clay content of Enshi soil is higher than Panan soil. Adsorption of diazinon belonged to physisorption in both Panan and Enshi soils with changes of free energy less than40kJ/mol.