Preliminary Study On Microorganism Coupling Chemical Oxidation For Remediation Of BaP Contaminated Soil

The remediation of organic contaminated soil is one of the most important environmental problems that urgently need to be solved in China.Microbial remediation technology coupling with in-situ chemical oxidation has great prospects for solving this situation.This technique uses oxidants to increase the bioavailability of organic contaminants to enhance the ability of microbes to degrade POPs.However,the effect of oxidants on microbial community structure and microbial activity is rarely documented.In this thesis,benzo[a]pyrene?BaP?was selected as a representative of POPs,and the effect of oxidants on BaP removal efficiency,microbial community structure and activity were investigated.Optimum oxidation conditions were trying to be found for cost-effectively repair and sustainable utilization of organic contaminated soil.The main results of this thesis are summarized below:?1?The optimum oxidation conditions for coupling technique to remediate BaP contaminated soil were clarified.20 mmol L^-1 sodium persulfate?PS?with activation ratio of 1:12?PS:Fe2+,c:c?and/or 10 mmol L^-1 potassium permanganate?PP?were the optimum oxidation conditions which have the best degradation efficiency of BaP.In these conditions,BaP could be released and oxidized into small-chain organic compounds?C<20?,such as short-chain hydrocarbons,carboxylic acids and esters,which improves the bioavailability of BaP,and promotes further degradation of indigenous microorganisms.After 60 days of coupling remediation with PS and PP,the degradation efficiency of BaP reached 98.4%and 80.9%,which was 27.2%and 9.7%higher than the control group,respectively.?2?Moderate oxidation with PS and PP can optimize soil microbial community structure and strengthen microbial activity.The soil respiration rate of 20 mmol L^-1 PS and 10 mmol L^-1 PP were 6.37 times and 1.64 times of the control group,and the enzyme activity were 1.71 times and 1.39 times of the control group,respectively.PS reduced the microbial community diversity in the original soil and the abundance of Bacillaceae which is a PAH-degrading bacterium.However,it increased the abundance of others PAH-degrading bacteria such as Alicyclobacillaceae and Xanthomonadaceae,and promoted the expression of PAH-degrading genes.PP had no significant effect on soil microbial diversity and the expression of PAH degradation gene.It also reduced the abundance of Bacillaceae while increased the abundance of Chitinophagaceae and Oxalobacteracea.