Study On The Degradation Of Diazinon By Combing Cupriavidus Nantongensis X1~T And Irradiation Of Mercury Lamp

Diazinon is a kind of organophosphorus insecticide,which is often used for pest control in agriculture,animal husbandry and public health;its mechanism is to inhibit the activity of acetylcholinesterase in the target organism,so as to achieve the insecticidal effect.The ecological risks and health problems caused by long-term irrational use of diazine phosphorus have aroused wide concern.Diazinon degrades in the environment to produce a highly toxic substance called diazoxon.In this thesis,a strain of high efficiency degradation bacteria of organophosphorus pesticides,Cupriavidus nantongensis X1^T,was used as the research material,the kinetic data of degradation of diazinon by strain X1^T were obtained by optimizing the degradation conditions.The degradation path of diazinon under the action of strain X1^T was predicted by the comparison of standard substances.The ecotoxicity of diazinon and its metabolite was predicted by the ECOSAR software model.The degradation of diazinon and its metabolite under the exposure of natural light and high-pressure mercury lamp was investigated.The new combined process of Cupriavidus nantongensis X1^Tcombined with high-pressure mercury lamp can produce efficient step-by-step degradation of diazinon and its metabolite,which provides technical support for environmental remediation of diazinon pollution.The main results are as follows:1.The degradation of diazinon by Cupriavidus nantongensis X1^T was mainly affected by initial concentration,temperature,p H and inoculation amount.When the initial concentration was 100μmol/L,200μmol/L and 400μmol/L,the declination half-life of diazinon was 0.97 h,1.07 h and 2.21 h,respectively.With the increase of temperature,the degradation rate of diazinon by X1^T bacteria increased and then decreased,and the optimal degradation temperature was 30℃～37℃.With the increase of p H,the degradation rate of diazinon by strain X1^T also showed a trend of first increasing and then decreasing,and p H8was the best PH for degradation.With the increase of the initial inoculation amount,the degradation rate of diazinon gradually increased.When the inoculation amount reached 10%of the experimental system,the degradation rate did not change significantly with the continued increase of the inoculation amount.2.Strain X1^T degraded diazinon to 2-isopropyl-6-methyl-4-pyrimidinel（IMHP）by breaking the P-O bond,and did not produce highly toxic diazoxon in the degradation process.The ECOSAR model was used to predict the ecotoxicity of diazine phosphorus and its metabolites.The results showed that the 48 h LC₅₀ effects of diazinon and IMHP on Daphia were 6.8×10^-4 mg/L and 7.06 mg/L,respectively.The 96 h LC₅₀ of fish were 0.09 mg/L and14.8 mg/L,respectively.The semi-lethal dose of IMHP was 3～4 orders of magnitude higher than that of diazinon,indicating that the toxicity of IMHP was less than that of diazinon.The degradation of diazinon by strain X1^T was a detoxification process and beneficial to the environment.3.The photodegradation of diazinon and IMHP was investigated at 200μmol/L irradiation by high-pressure mercury lamp.The results showed that the degradation half-lives of diazinon and IMHP were 2.55 h and 23.74 min,respectively.Under optimal conditions,the half-life of strain X1^T was about 0.74 h for the degradation of 200μmol/L diazinon,which was faster than the photodegradation of diazinon.The photodegradation rate of IMHP was about 6.4 times that of diazinon.4.The rapid and stepwise degradation of diazinon can be achieved by combining strain X1^T with high-pressure mercury lamp.