| Pesticide is one kind of necessary means of production in agriculture, however it is a harmful chemical substance. It will do harm to people's health and ecological environment owing to its unreasonable application. Before one kind of new pesticide is to extend, it is wholly essential to know its degradative tendency in environment and organism. It is also required to do risk assessment in environment and supply the pathway to control and decrease its environmental pollution. Imzapyr, which was discovered by American Cynamid Company, is a broad-spectrum postemergence herbicide containing with a long residual behaviour. It can control a broad-spectrum of annual and perennial grasses, sedges, broadleaf weeds, shrubs and deciduous trees. Now the species has been registered temporarily in China, but its environmental behaviors such as microbial and photolytic degradation kinetics et al in uncultivated land has not been reporting until now. In order to extend its use and registered forever, it is urgent to study now. Based on this, the research work in the thesis was done on the following: (1) the degradative behavior under different kinds of soil (2) Microbial and photolytic degradation kinetics (3) Screening the dominant degradation bacteria and their degradation kinetics.(4) Determination of microbial degradation and photolytic metabolites. The main results were summarized as following:An analytical method for determining residues of imazapyr in water, soil and weeds by HPLC was established, which used the mixture of methanol and ammonium hydrogen carbonate as extracting solution. The accuracy, sensitivity, precision for the method was satisfied to meet the quota requirements of pesticide residue.The degradative kinetic in four different kinds of soil which are powder soil, coast soil, yellow red loam soil, huangjin mud was studied respectively. The important factor, which influence degradative rate to imazapyr in soil, is organic matter content and pH values. Environmental factors also affect degradation rate, which will increase as temperature and moisture increased , Temperature effect coefficient(Q) varies from 1.08 to 1.42, which is not in accordance with Van't Hoff rule, and it is proved that the effect of temperature on degradative rate in soil is less than that in water.Degradative kinetic was also studied in sterilized and non-sterilized soil, and contribution rates of microbial degradation were also probed in different kinds of soil. The experimental results fully proved that microorganism in soil play a very important role to the fate of imazapyr.Two bacterial strains, which could degrade imazapyr herbicide in basal medium, were isolated from soil, collected from the land polluted by imazapyr, by a batch culture with imazapyr as a sole carbon, ZJX-5 and ZJX-9 were identified as pseudomonas fluorescenes biotype and bacillus cereu by means of VITEK-AMS. They both had so high decomposing ability that they can degrade over 70% imzapyr within two days, when fortified on the level of 50 or 100mg/L, It was also proved that degradation ability and resistence of the mixed bacterial strain to imazapyr are superior to their separated one, especially under high concentration.The effects of external circumstances on two bacterial strains were also studied, The fortified bacterial amount has remarkable influence on the degradation rate, which is proportional relations between them. On the contrary, the fortified concentration is opposite to degradative rate. Results showed that appropriately fortified concentration for degradation bacterial strain is 50~200mg/L.When surpassing the moderate concentration, the activity of bacterial strains can be severely inhibited. With the increasing of temperature, the degradation half-life decrease, especially at the range of 25~30 . The effect of pH value is the same as temperature, especially at the range of 5~10.The depth of soil which give the effection to photodegradation of pesticide was studied under simulated sunlight using four kinds of soil. T...
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