含磷基材固化/稳定化铅污染土的铅形态演化和浸出特性

LEAD SPECIATION EVOLUTION AND LEACHING CHARACTERISTICS OF LEAD CONTAMINATED SOIL SOLIDIFIED AND STABILIZED WITH PHOSPHORUS CONTAINING SUBSTRATE

采用过磷酸钙-水泥(SSPC)及水泥(OPC)固化稳定铅(Pb)重金属污染土。通过无侧限抗压强度(UCS)、毒性浸出(TCLP)试验研究了铅污染土固化体的力学和浸出特性,并通过形态提取(BCR)分析了固化体中铅赋存形态,结合重金属形态分布特征,运用风险评价编码法(RAC)评价了重金属的潜在风险程度。试验结果表明:过磷酸钙-水泥(SSPC)和水泥均可显著降低固化体中铅浸出特性,过磷酸钙-水泥(SSPC)固化体的浸出浓度远低于水泥固化体,当过磷酸钙添加量分别为5%和10%时,固化体中铅浸出浓度低于GB/T 5085. 3—2007《危险废物鉴别标准浸出毒性鉴别》。形态提取试验表明:水泥(OPC)和过磷酸钙-水泥(SSPC)均可促使Pb从活性态(弱酸提取态)向较稳定态(可还原态、残渣态)转化,但过磷酸钙-水泥(SPCC)固化体中残渣态Pb的含量较高。基于改进BCR法获得F1(弱酸态)的基础上,运用风险评价编码法评价了固化后污染土中铅的生态风险等级,对比未固化土,生态风险等级大幅降低。

Research about lead contaminated soil solidified and stabilized with calcium superphosphate-cement composite (SSPC) and cement (OPC) was carried out in this paper.Unconfined compressive strength (UCS) test and toxicity characteristic leaching procedure (TCLP) test were conducted to investigate the mechanical and leaching characteristics of the solidified body of lead contaminated soils, and the BCR test was used to analyze the occurrence form of lead in the solidified body, and then combining with morphological distribution characteristics of heavy metals, the potential risk degree of heavy metals was assessed by risk assessment coding (RAC) method.The test results showed that: both calcium superphosphate-cement (SSPC) and cement could significantly decrease the lead leaching in the solidified body, the leaching concentration of solidified body of calcium superphosphate-cement (SSPC) was far lower than that of cement, and when calcium superphosphate content was 5% and 10% respectively, the lead leaching concentration in the solidified body was far lower than limit value in Identification Standards for Hazardous Wastes (GB/T 5085.3-2007).The results of BCR test showed that: both cement (OPC) and calcium superphosphate-cement (SSPC) could promote the transformation of Pb from the active state (weak acid extraction state) to more stable state (reducible state and residual state), but the Pb content in the residual state of calcium superphosphate-cement (SSPC) solidified body was high.On the basis of obtaining F1 (weak acid state) by the improved BCR method, the ecological risk level of lead was evaluated by risk assessment coding (RAC) method, and compared with uncured soil, its ecological risk level was greatly reduced.