低温工程性修复高浓度汞污染稻田土及底泥中汞形态变化研究

Transformation of Mercury Species in Hg-Contaminated Soil and Sediment during Low Temperature Engineering

为分析工程性低温热解技术对土壤和底泥中总汞及形态汞变化的影响,采集T1区(化工污染类型)稻田土、河道底泥及T2区(矿山冶炼类型)稻田土进行处理,并对处理前后土样总汞及形态汞浓度进行测定。结果表明,低温工程性修复高浓度汞污染土壤和底泥中总汞去除率可达70%以上,T1区稻田土、底泥及T2区稻田土中有机结合态汞分别降低84.2%、71.4%、92.2%,残渣态汞分别降低58.9%、69.4%、95.2%;不同污染形式所形成的汞污染状况不同,相较于T2区,T1区有机结合态高、残渣态低;热解后土壤露天放置相比于密封存储,有机结合态增高4.1%,残渣态降低4.3%,由于受到生态环境的影响,可能存在有机结合态向残渣态转化的趋势。以潜在生态危害指数法对土壤和底泥中总汞及生物有效态汞进行生态风险评价发现,低温热解修复效果表现为稻田土优于底泥。

In order to analyze the effects of engineering technology of low temperature pyrolysis on total mercury and mercury species in soil and sediment,samples from paddy soil in T1 area(chemical pollution type),river bottom sediment and the rice field in the T2 area(mineral smelting type)before and after remediation was collected for total mercury and mercury species concentration measurement.The results showed that more than 70%of total mercury have been removed from mercury-contaminated soil and sediment under low temperature engineering repair.Organic mercury in T1 paddy soil,sediment and T2 rice fields could be decreased for 84.2%,71.4%and 92.2%,respectively,and the residual state mercury could be removed of 58.9%,69.4%and 95.2%,respectively.The mercury pollution in different sediments are by different processes.Compared with the T2 zone,the T1 zone has a high organic mercury and low residual state mercury.After pyrolysis,the soil was placed in the open air condition could have 4.1%more organic mercury and 4.3%more residual state mercury than sealed storage condition.The organic mercury could be transformed to residual state mercury due to the influence of the ecological environment.The ecological risk assessment of total mercury and bioavailable mercury by potential ecological hazard index method showed that the low temperature pyrolysis repair performance of paddy soil is better than that of sediment.