| [Object] Phorate is a high effective, broad-spectrum organic phosphorous insecticides and acaricide which was widely used in cotton cultivation in Xinjiang. For its long term and widespread used, soil contamination is in high risk, this study were conducted on the Influence of phorate on t soil microbes activities, the dgradation and residual dynamics of Phorate in soil, and phorate-biodegradation.[Methods] Influence of phorate on the quantities of soil microbes, microbial Biomass C. N, enzyme activities and the dgradation and residual dynamics of Phorate in soil under the simulating experiment and the pot culture experiment were studied. phorate-degrading stains were isolated by enrichment culture.[Results] 1) Phorate slightly decreased the number of fungi and actinomyces at early stage after phorate was applied to soil and then recovered quickly to the levels of antitheses. Bacteria were restrained significantly after the application of phorate. The number of bacteria in rhizosphere soil was higher than that in bulk soil, and the R/S was between 1.52-2.68. The number of fungi and actinomycetes was relatively stable as phorate applied, and the rhizosphere effect was so strong as compare to bacteria in this study.2) In the simulating experiment, the activity of the soil sucrase, soil protease and alkaline phosphatase in soil were all be inhibited remarkably when soil was treated with phorate. However, the activity of urease was inhibited at early stage, and then stimulated and recovered.3) In pot culture experiment, phorate remarkably stimulated the activities of soil protease, and alkaline phosphatase in rhizophere and non-rhizosphere soil, the activity of soil sucrase in soil was restrained first, then recovered, the activity of soil urease was stimulated first, then was inhibited in tomato rhizophere soil. The activities of soil urease were restrained in tomato non-rhizosphere soil when phorate was added to soil at low dosage,while the activity of soil urease was stimulated in tomato non-rhizosphere soil,when Phorate was added to soil at high dosage. Generally, soil enzyme activities in rhizosphere were higher than those in non-rhizosphere soil.4) Soil microbial biomass C, microbial N, SMB/SOC and SMB/TN were all lower than CK when phorate was added in soil.5) A method for determination of phorate residues in soil was performed by GC-FPD. With methylene chloride, phorate residues in soil was extracted ultrasonically. the recoveries rates were in the ranges of 81.3%-102.2%with a relative standard deviation of 5.3%-7.8%.The results showed that the distilled method, detected method and conditions were suitable for this experiment, and the accurate data could be acquired and could be used to detect phorate.6) The degradation of phorate in soil followed the first-order function. The half-life of phorate in soil under laboratory condition was measured to be 8.6d,8.2d and 7.6d, at levels of 2.0mg/kg,8mg/kg and 20mg/kg, respectively, the half-life of phorate in soil reduced with the concentration phorate. The residues were found to be 0.153 mg/kg,0.471 mg/kg and 0.839 mg/kg,30 days after application of phorate at dosage of 2.0mg/kg,8mg/kg and 20mg/kg, respectively, the degradation rate was over 90%.7) Under condition of 30℃and PH 7, both XT1 and XT2 could degrade 500mg/L phorate by more than 83%within 5days.8) Two phorate-degrading stains were isolated by enrichment culture from cotton land. Based on its morphological, physiological and biochemical properties, as well as 16S rDNA sequence analysis resules, the strain XT2 was tentatively indenifited as Providencia sp.[Conclusion] The microbial community structure was changed and the microbial activities were reduced when phorate was added to soil. The degradation rate of phorate was more fast in soil in arid area and the half-life was lower than lOdays. Two phorate-degrading stains XT1 and XT2 which could degrade 500mg/L phorate by more than 83%within 5days, were isolated by enrichment culture. |
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