TCLP法评价铅锌尾矿库土壤重金属污染:浸提剂的选择及其与重金属形态的关系

分析测定河北省涞源县某铅锌矿区污染土壤的重金属(Zn, Pb, Mn, Ni, Cr, Cd)含量, 基于美国法定重金属污染评价方法(toxicity characteristic leaching procedure, TCLP)对土壤重金属污染状况及生态环境风险进行评价, 并对TCLP浸提剂进行比较筛选, 探究TCLP浸提量与重金属化学形态的相关性。比较两种TCLP浸提剂发现, 浸提剂B (用试剂水稀释17.25 mL的冰醋酸至1 L, 配制后溶液pH值为2.64 ± 0.05)比浸提剂 A (加5.7 mL冰醋酸至500 mL 试剂水中, 再加入64.3 mL 1 mol/L氢氧化钠溶液, 稀释至1 L, 配制后溶液pH应为4.93 ± 0.05)能更有效地提取土壤中的重金属, 并且两者之间存在一定的正相关性, TCLP浸提液中的重金属质量分数与重金属的可交换态、碳酸盐结合态存在一定的关系。

Assessment of Heavy Metal Contaminated Soils from the Lead-Zinc Mine by Toxicity Characteristic Leaching Procedure

The contents of heavy metals (Zn, Pb, Mn, Ni, Cr and Cd) in soils samples taken from the Laiyuan lead-zinc mine in Hebei Province were analyzed. The toxicity characteristic leaching procedure (TCLP) developed by US EPA was employed to evaluate the pollution status and assess the environmental risk. Extraction reagents used in the TCLP experiments were investigated, and the relationship was examined between the concentrations of heavy metals by TCLP extraction and those of their chemical different speciation. The experimental results indicate that TCLP agent B (17.25 mL of glacial acetic acid is diluted to 1 L with distilled water, and the solution pH was 2.64 ± 0.05) is more effective than method TCLP agent A (5.7 mL of glacial acetic acid and 64.3 mL sodium hydroxide were diluted to 1 L with distilled water, and the solution pH was 4.93±0.05) in extracting heavy metals from the polluted soils. A positive correlation has been found between the concentrations of heavy metals extracted by TCLP agent A and those by TCLP agent B. The contents of available heavy metals by agent B are correlated with the total contents of enchangeable and carbonate-bound species.