小分子有机碳对土壤中六氯苯厌氧降解及挥发的影响

Effect of Low-Molecular-Weight Organic Carbon on Anaerobic Degradation and Volatilization of Hexachlorobenzene in Soils

采用密封培养瓶装置,研究了红壤性水稻土和乌栅土在添加乙酸、葡萄糖、柠檬酸时六氯苯（HCB）的厌氧降解行为,同时分析了土壤pH变化、碳源转化过程中甲烷和二氧化碳的释放及六氯苯的挥发.结果表明,8周内红壤性水稻土中HCB减少了约20%-44%,加入乙酸抑制HCB的降解,表明低pH条件不利于脱氯反应,加入葡萄糖和柠檬酸在前期抑制后期则促进HCB的降解;乌栅土中HCB减少了约21%-23%,加入小分子有机质对其降解没有明显的效果;六氯苯降解的主要产物为五氯苯（PCB）,最终检测到红壤性水稻土中PCB为23-96μg/kg,乌栅土中为64-92μg/kg;HCB的降解与CH4和CO2的释放量在统计学上没有显著的相关性;2种土壤中,外加小分子有机碳均减少了HCB的挥发作用,且红壤性水稻土中HCB的挥发比乌栅土中更强,表明土壤有机质是影响HCB挥发的重要因子.

Batch incubation experiments in aid of anaerobic incubation flask were conducted to study the anaerobic degradation and volatilization of hexachlorobenzene （HCB）, the change of pH in soil, the emission of CH4 and CO2 , and the volatilization of HCB in the Hydragric Acrisol and Gleyi-Stagnic Anthrosol added with acetic acid, glucose and citric acid. Results showed that HCB was reduced by 20%-44% in Hydragric Acrisol during 8 weeks, and addition of acetic acid inhibited the dechlorination, indicating that dechlorination was impeded at low pH. Addition of glucose or citric acid decreased the dechlorination rate initially and then increased it. HCB was reduced by 21%-23% in GleyiStagnic Anthrosol, and there was no obvious effect by adding low-molecular-weight organic carbon. Th＇e main product of HCB anaerobic dechlorination was pentachlorobenzene （PCB） , which were 23-96 μg/kg and 64-92 μg/kg in Hydragric Acrisol and Gleyi-Stagnic Anthrosol respectively. Furthermore, the degradation of HCB had no statistically significant correlation with the productions of CH4 and CO2 . Addition of low-molecular-weight organic carbon reduced HCB volatilization, which was stronger in Hydragric Acrisol than in Gleyi-Stagnic Anthrosol, indicating that soil organic matter was an important factor in HCB volatilization.