有机质的去除对磷酸盐稳定土壤铅的影响

为明确土壤有机质的去除对磷酸盐稳定化处理铅污染土壤反应效率的影响,通过马弗炉高温煅烧和双氧水氧化两种不同方法去除铅污染土壤中的有机质,分别在去除有机质前后的含铅污染土壤中添加7个不同P/Pb摩尔比的磷酸二氢钾进行稳定化试验,对稳定化处理后的土壤进行铅毒性浸出(TCLP)、有效磷含量和铅形态分布特征的分析。结果表明:经过马弗炉煅烧和双氧水氧化后土壤有机质的去除率分别为97.2%和11.3%,两种方法去除有机质后土壤中铅提取含量分别升高了43.4%和75.8%;当磷酸二氢钾的添加量达到P/Pb摩尔比为1.2时,去除有机质前后土壤中有效铅含量均降到1.0 mg·L^-1以下,原始土壤及用马弗炉和双氧水去除有机质的土壤中有效铅含量分别为0.4、0.8、0.5 mg·L^-1,有效磷含量分别为68.0、87.0、70.0 mg·kg^-1;原始土壤和去除有机质土壤中的铅以残渣态为主要赋存形态,去除有机质后土壤中有机结合态的铅减少。土壤有机质的去除能改变土壤中铅的生物有效性,影响铅污染土壤的稳定化效果,增大环境释放的风险。

Impact of Organic Matter Removal on Phosphate-Induced Pb Stabilization in Soil

Phosphate-containing materials are important stabilizers of soil Pb. However, soil organic matter may impact phosphate-induced Pb stabilization in soil. In the present study, the effect of soil organic matter on the Pb stabilization by phosphate was evaluated by comparing toxicity characteristic leaching procedure(TCLP), phosphate contents, and Pb fractionation of soils that were subjected to removal and non-removal of organic matter and then spiked with seven molar ratios of P/Pb. Soil organic matter was removed by two methods, i.e. muffle furnace calcination and hydrogen peroxide oxidation. Results indicated that the removal efficiencies of soil organic matters by muffle furnace and hydrogen peroxide were 97.2% and 11.3%, which in turn caused available Pb fractions increase by 43.4% and 75.8%, respectively. At 1.2 of P/Pb molar ratio, soil available Pb content was 0.4 mg·L^-1, 0.8 mg·L^-1, and 0.5 mg·L^-1, while available phosphorus content was 68.0 mg·kg^-1, 87.0 mg·kg^-1, and 70.0 mg·kg^-1 for non-organic matter removal, muffle furnace treatment and hydrogen peroxide treatment, respectively. The main chemical form of Pb was residual fraction in untreated and treated soils. Organically bound Pb reduced after the removal of organic matters. Removing soil organic matters could reduce the stabilization of Pb in contaminated soils, thus increasing the bioavailability and environmental risks of soil Pb.