Research On Micbioremediation Of Soil Contaminated By Organophosphorus Pesticide Dimethoate

Organophosphorus pesticide is an efficient, rapid and broad-spectrum pesticide. Studies have shown that: Organophosphorus pesticide is the main pesticide in soil. Residue of organophosphorus pesticide in soil is about 20% to 70% of general application. Therefore, removing organicphosphorus in soil is the important environmental problem which should be solved urgently. The methods of repairing pesticide-contaminated are physical, chemical and biological repair methods. Micbioremediation is a fast, secure, inexpensive and effective treatment method in contaminated soil. In this paper, using microbiological method to screen pesticide-resistant bacteria,using microbioremediation technology to remediated contaminated soil by phosphorus pesticide-dimethoate and reduced dimethoate content in polluted environment. I provided the theoretical foundation for microbioremediation which can be employed in organic phosphorus pesticide-contaminated soil and offered valuable strains for microbial remediation technology .The main research results are as followed:1. Using the traditional methods of microbiology, two bacteria and two fungi who can degradate organophosphorus pesticides dimethoate were separated from activated sludge in sewage treatment plants. Degradation rates of bacteria were 71.8% and 54.9%, degradation rates of fungi were 34.6% and 44.1%. Bacteria are Alcaligenes faecalis and Gemella morbillorum .2. In this paper, studied the biological characteristics of two bacteria and determinated their growth curve, pesticide tolerance, temperature and pH. When was cultured 16h, No.1 degradation rate is the highest about 77.2%, concentration of tolerance dimethoate is 6000ppm, the best culture temperature is 37℃, the optimum pH value is 8.0. Whenwas cultured 14h, No.2 degradation rate is the highest about 52.8%, concentration of tolerance dimethoate is 7000ppm, the best culture temperature is 37℃, the optimum pH value is 7.0.3. Used the two bacteria to remediation contaminated soil and determined converting enzyme and catalase activity of soil and content of pesticides in soil. The results showed that:①Polluted soil by dimethoate can inhibit converting enzyme and catalase activity, the two dimethoate-degrading bacteria can reduce inhibition of two types of Enzyme activity, the effect on the No.1 was better than the No.2;②I n low dimethoate concentration (50mg/kg) contaminated soil, after 5 days, dimethoate degradation rate of No.1 increased from 7.4% to 55.1%, dimethoate degradation rate of No.2 increased from 7.4% to 22.9%. After 30 days, No.1 degradation rate was as high as 86%, No.2 bacteria degradation rate was 73.2%; In high Rogor concentration (150mg/kg) contaminated soil, after 5 days, dimethoate degradation rate of No.1 was 24.3%, dimethoate degradation rate of No.2 was 18.3%. Dimethoate degradation rate of No.1 was 58.9%, dimethoate degradation rate of No.2 was 46%. In this experiment, two degrading bacteria reduced toxic action of soil which was polluted by organophosphorus pesticide.4. Studied the effects of dimethoate pollution on the growth and development, physiological and biochemical characteristics and absorption properties of cucumber. Detected bioremediation effect of organic phosphorus degrading bacteria in contaminated soil. The results showed that the plant height and growth rate of cucumber seedlings were lower than that of control in contaminated soil, CAT and POD activity was significantly higher than the control, they had weak root system and less fibrous roots,their growth potential and vitality were significantly less than control. Two organophosphorus pesticide-degrading bacteria can mitigate negative effect of Rogor. If the concentration of Rogor was high in the soil, the plant would residue large amount of pesticide. Though comparison of concentration, I knew residues as follows: root> stem> leaf in cucumber seedlings. After 4 weeks, total Rogor residues of cucumber seedling which grown in contaminated soil whose Rogor concentration was 100mg/kg was 56.27mg/kg in the first group, 7.26mg/kg in the second group, 23.95mg/kg in the third groud.The two organophosphorus pesticide-degrading bacteria can reduce dimethoate residue of cucumber plant.