基于生物可给性的某冶炼厂土壤重金属健康风险评价

为科学评价重金属污染场地的人体健康风险,以某冶炼厂土壤为研究对象,采用PBET(Physiologically-Based Extraction Test)和IVG(In-Vitro gastrointestinal)两种方法测定了As、Cd、Cu、Pb、Zn的生物可给性,并对比了只考虑重金属总量与基于生物可给性的人体健康风险.结果表明,场地土壤As、Cd、Pb的平均含量分别高达7063,691,3811mg/kg,严重超过国家环境质量标准.在PBET和IVG测试中,5种重金属的平均生物可给性介于1.81%~44.8%与1.78%~30.1%之间.As是PBET中生物可给性最高的重金属元素,而在IVG中Cd的生物可给性最高;含磷矿物的存在使Pb的生物可给性最低.提取液pH值及组成组分与重金属元素间的化学行为是造成两种方法结果差异的主要原因.在模型假设的条件下,土壤原有重金属的总危险商与总致癌系数为27.2与2.95×10^-3.考虑生物可给性使二者降低了59.9%~84.4%与55.6%~79.4%,且两个系数大小均呈现PBET胃液>PBET胃肠液>IVG胃液>IVG胃肠液的规律.调整后可以认为Pb不再具有健康风险,Cd仅具有致癌风险,只有As同时具有非致癌风险与致癌风险.尽管考虑重金属生物可给性后场地仍具有不可忽视的人体健康风险,但经过调整后能更准确地识别重金属的危害程度,避免场地的过度修复.

Human health risk assessment of heavy metals in soil from a smelting plant based on bioaccessibility

In order to scientifically evaluate the risks of heavy metal-contaminated soil to human health, the bioaccessibility of As, Cd, Cu, Pb and Zn in the soil of a smelting plant was tested by PBET and IVG, and the bioaccessibility-based health risks were compared with the ones based on total amount of heavy metals. The results showed that the average contents of As, Cd and Pb were up to 7063, 691 and 3811mg/kg, respectively, which seriously exceeded the Chinese environmental standard. In PBET and IVG tests, the average bioaccessibility of the 5 heavy metals ranged from 1.81% to 44.8% and 1.78% to 30.1%, respectively. As was the highest bioaccessible heavy metal in PBET test, while it was Cd in IVG test. Pb showed the lowest bioaccessibility because of phosphorous minerals. The above differences could be attributed to the pH and components of extracting solutions, which had chemical interaction with heavy metals. Under the hypotheses in the model, the total hazardous quotient and total carcinogenic risk were 27.2 and 2.95×10^-3. Based on bioaccessibility, the two coefficients could be reduced by 59.9%~84.4% and 55.6%~79.4%, respectively, following the order: PBET gastric solution > PBET intestinal solution > IVG gastric solution > IVG intestinal solution in these two coefficients. It also could be considered that Pb no longer had health risk, Cd had carcinogenic risk, and only As had both non-carcinogenic risk and carcinogenic risk. Although there is still a nonnegligible human health risk in this site, the hazardous levels of heavy metals can be identified and excessive site remediation should be avoided after considering the bioaccessibility of heavy metals.