Remediation Effects And Enzyme Effects Of Parathion Contaminated Soil

Parathion is a highly toxic organic phosphorus broad-spectrum insecticide,which was widely used in the control of rice borer,cotton bollworm,corn borer and other pests from the1960s to the end of the 1990s.The pesticide is difficult to degrade in the soil,and the large amount of parathion pesticides in the production site is toxic to the biochemical action of the soil,thereby causing serious harm to the soil ecological environment.Combined physical and chemical remediation is often used in soil contaminated by organophosphorus pesticides,especially the microwave-activated sodium persulfate synergistic remediation technology has a significant effect,but the changes in soil properties after remediation are less reported.For this reason,this paper studied the change of residual amount of parathion and the effect of three remediation methods（sodium persulfate,microwave,microwave-sodium persulfate oxidation synergistic remediation）in two soil types（red soil and coastal saline soil）by means of laboratory simulation and HPLC analysis.At the same time,the activity of soil FDA hydrolase was used as the biological activity monitoring index of soil parathion pollution.The change rule of the activity of fluorescein diacetate（FDA）hydrolase after three remediation methods were studied,and the influence of different remediation methods on the activity of soil FDA hydrolase was discussed by statistical analysis.The results provided a Technical support for evaluating the ecotoxicological effects of parathion remediation.The main conclusions are as follows:（1）The best conditions for the remediation of parathion contaminated soil with sodium persulfate are sodium persulfate 1 mol/L for 90 min,and the parathion in red soil and coastal saline soil will be reduced by less than 20%;after 100℃and 90 min microwave remediation,the removal rates of parathion in coastal saline soil and red soil reached 62.29%and 26.24%,and the restoration effect of coastal saline soil was better than that of red soil;after microwave-enhanced-sodium persulfate oxidation synergistic repair of parathion pollution,the optimal restoration conditions of red soil and coastal saline soil were sodium persulfate 1 mol L/L,temperature 100℃,time 90 min,and the repair rate reached 90%.The optimal conditions for parathion restoration were finally determined as sodium persulfate concentration of 1 mol/L,microwave temperature of 100°C,and restoration time of 90 min.（2）The removal rate of parathion in soil was fitted with the restoration time,and the time needed for 10%parathion removal was calculated.Among them,sodium persulfate restoration:9.89～256.23 min（red soil）and 23.72～536.97 min（coastal saline soil）;microwave restoration:0.81～95.84 min（red soil）and 0.18～129.45 min（coastal saline soil）;microwave enhanced-sodium persulfate oxidation Synergistic restoration:0.20～53.42 min（red soil）and 0.07～129.51 min（coastal saline soil）.It can be seen that compound restoration can quickly remove parathion residues in the soil in the shortest time.（3）After the remediation by the three technologies,the activity of soil FDA hydrolase decreased with the increase of sodium persulfate and microwave temperature and the prolongation of remediation time,all of which inhibited the activity of soil FDA hydrolase,especially the synergistic remediation by microwave enhancement and sodium persulfate oxidation.The range of FDA hydrolase activity was 0.46～36.77μg/g/h and 0.14～34.85μg/g/h in red soil and coastal saline soil after composite remediation,with a decrease of98.75%and 99.59%,respectively.The enzyme activity was close to 0 after composite remediation,indicating that the compound remediation caused serious damage to soil biological activity.（4）The relationship between soil FDA hydrolase activity and residual parathion was consistent with the partial inhibition model（y=c*（1+a*x）/（1+b*x））,which indicated that partial inhibition was the mechanism.The ecological dose values ED₁₀ of the three restoration methods were all lower than that before restoration.The critical values of parathion mild pollution after red soil and coastal saline restoration were 1.82 mg/kg and5.57 mg/kg,respectively.Microwave repair:10.88 mg/kg and 4.92 mg/kg;Combined remediation:0.12 mg/kg and 0.64 mg/kg,indicating that soil FDA hydrolase was more sensitive to parathion pollution in the three remediation technologies.（5）Analysis of variance was used to obtain the effects of remediation conditions and parathion on soil FDA hydrolase.The results showed that single or combined treatments had significant toxic effects on soil FDA hydrolase,and each remediation condition interacted with the concentration of parathion,and the inhibition effect on soil FDA hydrolase activity was strengthened.To sum up,three remediation methods of microwave strengthen visible-sodium persulfate oxidation synergy repair parathion can achieve quick fix,sodium persulfate as processing condition,the rise of temperature,time to repair,increased the removal rate of parathion in soil,but soil FDA hydrolytic enzyme activity decreased,soil enzyme activity was significantly suppressed,thus,The concentration of oxidant and temperature should be selected appropriately,and the remediation conditions should be adjusted according to different soil types to improve the remediation effect of contaminated soil.Finally,it provides an important basis for the remediation and efficient utilization of soil pollution,which has certain significance in theory and practice.