Study On Remediation Of Pesticide-Contaminated Soil By Plant-Microorganism Combined Technology

With the development of modern agriculture,the pollutions that caused by the application of chemical fertilizers and pesticides have become more than serious,posing threats on human health and living environment.Bioremediation technology has received more and more attention on its remediation of contaminated soil,because of its safety,non-secondary pollutions and low cost.Carbofuran and chlorpyrifos as two common broad-spectrum insecticides,have been widely used in agricultural productions.Both carbofuran and chlorpyrifos have long half-lives,which are not easily degraded in the soil and the residues would do harm to crop and human health.Thus,repairing carbofuran and chlorpyrifos contaminated soil without delay.This paper focuses on degradation of polluted soil through three methods including microbial remediation,phytoremediation and combination of the two methods-which made by adsorption method and hope to provide a new way for the pesticide contaminated soils in-situ remediation.The main contents and results of this study are presented as follows:(1)The degradation results were studied in the pesticide contaminated soils with three white rot fungis-Phlebia.sp(C),Lenzites betulinus(Y),Iopex lacteus(W).The immobilization of white rot fungi on wheat straw was compared with that of white rot fungi in the free state.The result showed the degradation rate of free C and free bacteria C+Y could reach 50.59% and50.39%,respectively,in carbofuran-contaminated soil,and free C and free bacteria C+W could reach 47.97% and 53.17% in chlorpyrifos-contaminated soil.The highest degradation rate of immobilized C and immobilized C+Y could be reached up to 77.88% and 83.83% in carbofurancontaminated soil,and the highest degradation rate of immobilized C and immobilized C+W could reach up to 85.33% and 79.23% in chlorpyrifos-contaminated soil.Obviously,the immobilized method was significantly greater than free style(p<0.05).(2)A pot experiment was carried out to study the action of plants on the experimental pesticide contaminated soil,and the advantages of functional plants were screened.The capability of the six kinds of plants was compared by pot experiment,the degradation rate of sorghum and paddy were better in carbofuran-contaminated soil which reached 58.53% and53.78%,respectively.And in chlorpyrifos-contaminated soil,the highest degradation rates of paddy and ryegrass were 54.88% and 50.38%,respectively.Corn is a kind of good capabilityplant in the aspect of comprehensive degradation rate and biomass.(3)The method of plant-microorganism combined bioremediation was preliminarily pointed out and the basic conditional parameters were optimized by the pot experiments.When the using amount of immobilized was 3%,the removal effect was the best,however,there were no significant differences between the amount of 5% and 3%,even slightly lower.The result indicated that,after 30 d,compared with the single bioremediation in carbofuran-contaminated soil,the degradation rate was increased by 19.44% through corn-white rot fungi combined remediation,and by 17.46% using sorghum-white rot fungi combined remediation.After the uses of corn-white rot fungi,ryegrass-white rot fungi in chlorpyrifos-contaminated soil,the degradation rate was 17.76%,22.90% more improved than the single bioremediation.(4)The effect of the content of pesticide in soil on the combined remediation was mainly showed that there were significant differences in the number of microorganisms.Under the concentration of different pollutants,the combined bioremediation can be better to alleviate the impact of high pollution on microorganisms,more conducive to its pollution for continued degradationthe than the single bioremediation.Based upon the experimental results,the combined bioremediation is more suitable for use with high concentration(80~120mg/kg)of carbofuran and low concentration(40mg/kg)of chlorpyrifos.Although the plant concentration factors were very little,however,the special environment of its roots,microorganisms and soil is suitable for the functional microorganisms to propagate and grow with the pesticide as the main metabolic substrate.