改性生物炭负载零价铁对土壤中三氯乙烯的去除及微生物响应

Effects of Modified Biochar-Supported Zero-Valent Iron on the Removal of Trichloroethylene and Responses of Microbial Community in Soil

三氯乙烯是场地及地下水中广泛存在的典型有机污染物,生物炭基零价铁材料可用于去除地下水中三氯乙烯,然而其也会影响含水层土壤的微生物群落,进而改变三氯乙烯的归趋.通过限氧控温热解,NaOH和HNO_(3)改性处理,并采用球磨法合成了改性生物炭负载零价铁复合材料,研究了不同改性生物炭负载零价铁对模拟含水层土壤中三氯乙烯的去除及微生物群落的作用机制.结果表明,NaOH改性显著提高了复合材料的比表面积.NaOH改性和Fe/BC为1∶10的复合材料(BC_2处理组)对三氯乙烯的去除率最高,为90.01%.除BC_1处理组外,不同处理组均提高了土壤微生物的多样性,改变了微生物群落结构,其中芽孢杆菌属(Bacillus)、硫杆菌属(Thiobacillus)和假单胞菌属(Pseudomonas)可能是三氯乙烯的降解菌属.BC_2处理组增加了土壤中硫杆菌属和假单胞菌属的相对丰度,有利于三氯乙烯的降解.类诺卡氏菌属(Nocardioideas)、Thermincola、溶杆菌属(Lysobacter)、Gemmatimonas、Microvirga和假单胞菌属维持了微生物群落结构的稳定.微生物代谢通路预测分析结果表明BC_2处理组的异种生物降解与代谢基因丰度和折叠、分类与降解基因丰度均最高.说明NaOH改性复合材料可通过增加土壤降解菌丰度和促进降解基因的表达,提高土壤中三氯乙烯的去除,其可作为一种新型复合材料用于有机污染场地修复.

Trichloroethylene is a typical organic contaminant that has widely existed in industry sites and groundwater.Biochar-supported zero-valent iron material has been used to remove trichloroethylene in groundwater;however,it could affect the microbial communities in aquifer soil,leading to changes in the environmental behavior of trichloroethylene.In this study,biochar was prepared under oxygen-limited conditions and modified by NaOH and HNO_(3)agents.Then,a modified biochar-supported zero-valent iron composite(BC composites)was synthesized using ball milling technology.The effects of BC composites on the removal of trichloroethylene and the responses of the microbial community were investigated under the condition of simulated aquifer soil.The results showed that the specific surface areas of BC composites were increased after the modification with NaOH.The highest removal rate of trichloroethylene was observed in the BC_2 treatment,up to 90.01%.Except in the BC_1 treatment,the diversity and abundance of soil microorganisms were increased,and the microbial community structure was changed after the addition of different BC composites,in which Bacillus,Thiobacillus,and Pseudomonas might have been the potential degrading bacteria of trichloroethylene.The abundance of Thiobacillus and Pseudomonas increased under the BC_2 treatment,which was favorable to the removal of trichloroethylene.The stabilization of the microbial community structure was probably maintained by Nocardioideas,Thermincola,Lysobacter,Gemmatimonas,Microvirga,and Pseudomonas.According to the predictive analysis of microbial metabolic pathways,the abundance of xenobiotics biodegradation and metabolism genes and the folding,sorting,and degradation of genes were the highest under the BC_2 treatment.Thus,the NaOH-modified BC composite could prompt the removal of trichloroethylene in simulated aquifer soil,probably due to the increase in the abundance of soil-degrading bacteria and the expression of degradation genes,demonstrating that the NaOH-modified BC composite could be used for the remediation of the organic-contaminated industry sites as a new composite material.