Degradation Of γ-HCH By Consortium And Biochar Supported Nanoscale Zero-valent Iron

y-HCH is an organochlorine pesticide,which is included in the POPs list due to its persistence and high harmness in the environment.It is difficult for the soil contaminated with high concentration of HCHs to be effectively degraded by indigenous microorganisms for a long time.The efficient degradation of HCHs can be achieved by building a collaborative system of chemical materials and microorganisms In this paper,we enriched and domesticated stable consortium from the contaminated soil,and prepared biochar-loaded nano-zero-valent iron material(NZVI@BC),and explored their degradation ofγ-HCH in solutions and soil microcosms.And analyze the changes in the microbial community structure in the soil.Firstly,enrichment and domestication of stable consortium.Among them,there are 5 types of bacteria:Clostridium sensu stricto 7,Sedimentibacter,Lysinibacillus,Georgia muralis,Anaerocolumna aminovalerica.There are 4 species of archaea,which are unclassified archaea,Bathyarchaeia,Methanothermobacter,and Thermoplasmata.The addition of 40 μg/mL rhamnolipid can improve the bioavailability and biodegradation rate.With lactate,acetate,and glucose as electron donors,the final degradation rates were 88.00%,86.92%and 70.11%respectively.When the concentration of lactate is 6 mM,the degradation rate of consortium reach to 87.96%.The addition of methanogens and sulfate-reducing bacteria inhibitors has a certain effect on the degradation of y-HCH in the microcosm.Tetrachlorocyclohexene is an intermediate product of y-HCH degraded by dielimination by consortium.Secondly,prepared the NZVI@BC material in which the biochar has a good adsorption effect on y-HCH,and the loaded NZVI further degrades pollutants.The dosage of NZVI@BC is 5 g/L when the pH is close to neutral,a higher degradation rate of y-HCH in the solution reaches to 85.25%.Theγ-HCH undergoes dehydrochlorination to produce the intermediate PCCH.The optimal conditions for the degradation of 20 mg/L y-HCH were obtained through orthogonal experiments:the dosage of NZVI@BC was 5 g/L,the initial pH was 7,and the dosage of consortium was 10%.The influence of three factors on the degradation rate is:NZVI@BC dosage>consortium dosage>initial pH.Thirdly,do some research on the degradation of y-HCH in the 63-day flooded culture period.The degradation rate of CK in the control group to y-HCH was extremely low at 2.02%.Degradation of γ-HCH in soil by consortium inoculation experimental group M,NZVI@BC group Fe,consortium combined NZVI@BC group M-NZVI@BC,and corresponding lactate groups M-Lac,NZVI@BC-Lac,M-NZVI@BC-Lac The rates were 94.48%,89.23%,95.13%,95.00%,92.33%,94.53%.The order of degradation rate from high to low is M-NZVI@BC>M-Lac>M-NZVI@BC-Lac>M>NZVI@BC-Lac>NZVI@BC.The final degradation rate between the groups is not much different,but the degradation process is different.The added lactic acid promotes the microbial degradation process in the first two weeks.Last,analyze the community structure of soil microorganism.After remediation,the order of bacterial abundance is NZVI@BC-Lac>M-Lac>M-NZVI@BC-Lac>CK,and the order of community diversity from high to low is CK>M-Lac>NZVI@BC-Lac>M-NZVI@BC-Lac.Compared with the control CK,the bacterial abundance becomes higher but the community diversity becomes lower,the dominant genus changes,the abundance of Firmicutes in the soil is greatly improved,and the proportion of genus Clostridium and Sedimentobacter increases;The order of archaeal abundance is NZVI@BC-Lac>M-Lac>M-NZVI@BC-Lac,and the order of community diversity is NZVI@BC-Lac>M-Lac>M-NZVI@BC-Lac.The content of archaea in CK in the blank group was low and the library was not successfully constructed and sequenced.In the three treatment groups,the phylum of Halophilic is absolutely dominant,and the main genera are Methanosarcina and Methanosphaera.