Study On Bioremediation Of HCHs In Contaminated Soil Of Chemical Field

HCH is one of the persistent organic pollutants(POPs),which is easy to accumulate in soil.Because of the large number and heavy pollution of chemical sites in China,the soil pollution in the original factory area of HCHs production enterprises has been stopped,and the contaminated site has attracted the attention of soil restoration workers.Microbial remediation is considered to be an effective method to eliminate HCHs in soil.The author tried to screen HCHs degrading bacteria from polluted soil,but after several rounds of acclimation,it was found that the degradation effect was not satisfactory.Therefore,High efficiency biodegradable bacteria agent was purchased to study the degradation offHCHs.In this study,soil bioremediation was carried out on a chemical contaminatedsiteinNanning.Thedegradation conditions of microorganism were optimized by indoor culture experiment,and then the in situ ectopic experiment was carried out in the chemical pollution factory.The dissipation of HCHs in soil of chemical field by exogenous microorganisms under two different oxygenation modes(forced ventilation andregular pile-turning)was studied.The metabolic activity,carbon source utilization and enzyme activity of soil microbial community were also studied in order to provide technical parameters and practical support for soil remediation engineering in chemical contaminated sites.The main contents of the study are as follows:(1)Methods and conditions for determination of HCHs in soil were established.Ultrasonic extraction and gas chromatographic detection methods were determined through comparing various methods and combining the pollution of HCHs in the soil on the site.The experimental results showed that the chromatographic peaks of four isomers of HCHs in soil samples were separated well.The recoveries of HCHs isomers were between 75.6%and 118.8%,and the relative deviations were 0.7%and 7.8%,respectively.The method is accurate and sensitive.(2)The effects of different dosage of bacteria and water content on the dissipationof HCHs in soil were studied by using indoor culture method.The results showed thatafter 14 days of culture,the content of HCHs in the soil was significantly decreased by adding exogenous bacteria compared with the soil without adding bacteria.The dissipation rates of HCHs were 24.8%and 29.6%respectively,when the dosage is 0.3%and 0.5%,but there was no significant difference between them.When the water content is 30%,the dissipation effect of HCHs is the best,and thedissipation rate is 27%.(3)Using biopiles to examine the dissipation effect of microbe to HCHsand changes of soil chemical indexes during remediationunder two different oxygenation modes of forced ventilation and regularpile-turningunder the action of exogenous bacteria in pilot scale.The results showed that the removal rates of total HCHs,a-HCH,?-HCH in the soil of forced ventilation reached 48%,61%and 35%respectively after 63 days of operation,and the dissipation rate of the regular pile-turninghas reached 71%,82%and 45%,respectively.The effect of regularpile-turning was better than that of forced ventilation.(4)The number of bacteria,the activities of catalase,urease and dehydrogenase in the two treatments were higher than those in 0 days at the pilot remediation.The activities of catalase,urease and dehydrogenase in the two treatments were higher than those in the 0 days.On the whole,regular pile-turning treatment is higher than forced ventilation treatment.The activity of three enzymes in the two treatments was negatively correlated with HCHs residues,and the activity of dehydrogenase was significantly correlated.(5)Under the action of exogenous microorganism,the microbial activity of both treatments was increased,and theregular pile-tumingwas higher than that of forced ventilation.The types of carbon sources preferentially used by microorganisms changed during remediation,but there was no significant difference between the two treatments.After the operation of the system,the preferred carbon sources for the two treatments were esters>amino acids>acids.The evenness index(E),richness index(S),dominance index(D)and McIntosh indexof the regular pile-turning treatment were all higher than those of the forced ventilation treatment,and the difference was significant.