Studies On Degradation Dynamics And Micro-biological Degradation Of Acetochlor In Soil Of Growing Tobacco

Acetochlor is the selective pre-emergence amide herbicides, and it’s mainly used for upland crops, such as soybean, corn, sugarcane, tobacco and so on, and it’s widely used to control annual graminaceous weeds and part of the small seeds broadleaf weeds all over the world, harmful effects for crop and aftercrop by acetochlor residual in the soil. In order to evaluate its degradation dynamics in the soil and effect of residues of acetochlor to succeeding crops, the degradation kinetics of acetochlor in soil of growing tobacco were studies in indoor controllable conditions by GC and GC/MS. And through high-pressure enrichment culture, a acetochlor degrading strain PR-2was isolated from sludge, and its identified by morphology and molecular biology. The result not only provided important guiding significance about reasonably application of acetochlor, but also, the result provided a scientific basis for evaluation environmental safety and its Environmental restoration. The main results were shown as follows:1. A method was established to analysis residue of acetochlor in soil and water based upon traditional methods. Soil and water samples were extracted with acetone and dichloromethane respectively, separated by capillary column and determined with gas chromatography-electron capture detector (GC-μECD). The result indicated the limit of detection of acetochlor was0.2x10-9, and the method detection limit (MDL) of acetochlor in the samples of soil and water were0.01mg/kg. Recoveries and RSD of the method at spiked concentrations between0.05mg/kg to0.5mg/kg were98.63%-109.37%,0.96%-1.84%for soil samples, and87.29%-94.68%,1.27%-2.05%for water samples. These results showed that the sensitivity and precision of methods accords with demands of residue analysis of pesticide. 2. The degradation dynamics of acetochlor in soil of growing tobacco were researched by laboratory conditions, effect degradation of acetochlor by soil types, soil microbial, soil moisture and so on facters were disscussed. The results showed that degradation dynamics of acetochlor in soil of growing tobacco accorded with the kinetic equation. The half life of acetochlor in Paddy soil and Latosolic red soil were5.1d, and7.92d, respectively, the microorganism is a dominant factor affecting degradation of acetochlor in soil, the degradation rate of acetochlor in sterilization soil lower than unpasteurized soil, it is bad for acetochlor to degrade in too high (90%) or too low (10%) soil moisture.3. Through high-pressure enrichment culture and separation one acetochlor highly effective degrading saccharomycetes PR-2were isolated from soil of acetochlor factory drain. The strains of PR-2morphological characteristics, physio-biochemical characteristics and molecular biology characteristics were researched and analyzed, the strain PR-2was preliminarily identified as Rhodotorula mucilaginosa.4. The main factors of affecting the growth and degradation ability of the strain PR-2were studies. The result indicates:the optimum culture condition of PR-2for degradate acetochlor is the acetochlor concentration25mg/L, the temperature was25℃, the pH was7, the inoculum amounts was5%and the carbon source was1%, acetochlor degradation rate was85%with in the optimum culture condition.