Sun Yiming, Jones Kevin C, Sun Zongquan, Shen Jialun, Ma Fujun, Gu Qingbao
State Key Laboratory of Environmental Criteria and Risk Assessment, Chinese Research Academy of Environmental Sciences, Beijing 100012, China.
Lancaster Environnent Centre (LEC), Lancaster University, Lancaster LA1 4YQ, UK.
Sci Total Environ. 2023 Jan 1;854:158453. doi: 10.1016/j.scitotenv.2022.158453. Epub 2022 Sep 8.
As global warming intensifies, there will be increased uncertainty as to the environmental behavior and risks from heavy metals in industrial/legacy contaminated sites in permafrost regions. Bioavailability has been increasingly used for human health risk assessment of heavy metals in contaminated soils. Soil heavy metal bioavailability depends on soil physicochemical properties, and freeze-thaw affects soil physical, chemical and biological processes. However it is not clear whether freeze-thaw has an effect on the bioavailability of soil heavy metals. In this study, soils contaminated with Pb and As were collected from 10 industrial sites in northeast China. Extractability and bioavailability of soil Pb and As were determined by the Tessier sequential extraction method and four in vitro gastron-intestinal simulation methods under control and freeze-thaw treatments. The aims were: to compare the results of extraction and bioavailability from laboratory experiments which artificially simulate freeze-thaw conditions against control soils; to explore the correlation between bioavailability of Pb/As and soil properties. Freeze-thaw significantly decreased soil pH, and increased the soil weight surface area. Freeze-thaw decreased the percentage in the residual fraction, and increased the percentage of Pb and As in the exchangeable fraction, carbonate-bound fraction, Fe-Mn oxides-bound fraction and organic-bound fraction, relative to control soils. Freeze-thaw significantly increased Pb and As bioavailability compared to the controls. Pb and As released in the gastric phase of the four methods was significantly higher than that in the intestinal phase. Further analysis of correlations between Pb and As bioavailability and soil properties indicated that total concentrations of Al, Fe and Mn, particle size, and weight surface area significantly correlated to Pb and As bioavailability. Overall, this study demonstrated that freeze-thaw did influence the bioavailability of soil heavy metals. It suggests the freeze-thaw action should be comprehensively considered in the human risk assessment of soil pollutants in permafrost regions.
随着全球变暖加剧，关于多年冻土区工业/遗留污染场地中重金属的环境行为和风险的不确定性将会增加。生物可利用性已越来越多地用于污染土壤中重金属的人体健康风险评估。土壤重金属的生物可利用性取决于土壤的物理化学性质，而冻融作用会影响土壤的物理、化学和生物过程。然而，冻融是否会对土壤重金属的生物可利用性产生影响尚不清楚。在本研究中，从中国东北的10个工业场地采集了受铅和砷污染的土壤。通过Tessier连续提取法和四种体外胃肠模拟方法，在对照和冻融处理下测定了土壤铅和砷的提取率和生物可利用性。目的是：比较人工模拟冻融条件的实验室实验与对照土壤的提取结果和生物可利用性；探索铅/砷生物可利用性与土壤性质之间的相关性。冻融显著降低了土壤pH值，并增加了土壤重量表面积。与对照土壤相比，冻融降低了残渣态的百分比，增加了可交换态、碳酸盐结合态、铁锰氧化物结合态和有机结合态中铅和砷的百分比。与对照相比，冻融显著提高了铅和砷的生物可利用性。四种方法在胃相释放的铅和砷显著高于肠相。对铅和砷生物可利用性与土壤性质之间相关性的进一步分析表明，铝、铁和锰的总浓度、粒径和重量表面积与铅和砷的生物可利用性显著相关。总体而言，本研究表明冻融确实会影响土壤重金属的生物可利用性。这表明在多年冻土区土壤污染物的人体风险评估中应综合考虑冻融作用。
