China CDC Key Laboratory of Environment and Population Health, National Institute of Environmental Health, Chinese Center for Disease Control and Prevention, Beijing, 100021, China; State Key Laboratory of Environmental Criteria and Risk Assessment, Chinese Research Academy of Environmental Sciences, Beijing 100012, China.
Lancaster Environment Centre (LEC), Lancaster University, Lancaster LA1 4YQ, UK.
J Hazard Mater. 2024 Feb 15;464:132980. doi: 10.1016/j.jhazmat.2023.132980. Epub 2023 Nov 10.
Arsenic is a metalloid with carcinogenic properties and has been classified as a Category I carcinogen by the International Agency for Research on Cancer (IARC). Freeze-thaw processes affect the migration and transformation of soil heavy metals, as well as adsorption/desorption and redox reactions. However, there is limited research directly addressing the impact of freeze-thaw processes on the bioavailability of soil heavy metals. In this study, we focused on As and selected As-contaminated soil samples from three types of legacy sites in heavy industrial areas. Under controlled freeze-thaw experimental conditions, we utilized both in vivo and in vitro bioavailability measurement methods to investigate whether and how freeze-thaw processes affect the bioavailability of soil As. The results of this study showed that freeze-thaw processes reduced soil pH (P < 0.05), CEC, SOM, and particle size, with decreases of 0.33, 1.2 cmol/kg, 5.2 g/kg, and 54 µm, respectively. It also increased weight specific surface area (BET) (P < 0.05), with an increase of 300 m/kg. Freeze-thaw processes increased the proportions of exchangeable (P < 0.05), carbonate-bound, and iron-manganese oxide-bound As (P < 0.05), but reduced the proportions of organic-bound and residual As (P < 0.05). Freeze-thaw processes significantly increased the relative bioavailability and bioaccessibility of As, with increases of 32 ± 9.6% and 13 ± 0.23%, respectively. Soil pH, SOM, BET and electronic conductivity (EC) were identified as factors which could contribute to the increased bioavailability of As due to freeze-thaw processes. These results provide new insights and evidence for refining the assessment of human health risks associated with heavy metal contamination in polluted soils.
砷是一种类金属，具有致癌特性，已被国际癌症研究机构（IARC）归类为 I 类致癌物。冻融过程会影响土壤重金属的迁移转化，以及吸附/解吸和氧化还原反应。然而，目前直接研究冻融过程对土壤重金属生物有效性影响的研究较少。本研究以砷为重点，选择了来自重工业区三种遗留场地的砷污染土壤样品。在受控的冻融实验条件下，我们利用体内和体外生物有效性测量方法，研究了冻融过程是否以及如何影响土壤砷的生物有效性。研究结果表明，冻融过程降低了土壤 pH 值（P < 0.05）、阳离子交换量（CEC）、土壤有机质（SOM）和粒径，分别降低了 0.33、1.2 cmol/kg、5.2 g/kg 和 54 µm。它还增加了重量比表面积（BET）（P < 0.05），增加了 300 m/kg。冻融过程增加了可交换态（P < 0.05）、碳酸盐结合态和铁锰氧化物结合态砷的比例，但降低了有机结合态和残渣态砷的比例（P < 0.05）。冻融过程显著增加了砷的相对生物有效性和生物可利用性，分别增加了 32 ± 9.6%和 13 ± 0.23%。土壤 pH 值、SOM、BET 和电导率（EC）被确定为由于冻融过程导致砷生物有效性增加的因素。这些结果为完善污染土壤重金属污染相关的人体健康风险评估提供了新的见解和证据。
