Liu Guannan, Wang Juan, Zhang Erxi, Hou Jing, Liu Xinhui
State Key Laboratory of Water Environment Simulation, School of Environment, Beijing Normal University, Beijing, 100875, People's Republic of China.
Institute of Mineral Resources, Chinese Academy of Geological Sciences, Beijing, 100037, People's Republic of China.
Environ Sci Pollut Res Int. 2016 May;23(9):8709-20. doi: 10.1007/s11356-016-6114-6. Epub 2016 Jan 23.
Heavy metal contamination of soils has been a long-standing environmental problem in many parts of the world, and poses enormous threats to ecosystem and human health. Speciation of heavy metals in soils is crucial to assessing environmental risks from contaminated soils. In this study, total concentrations and speciation of As, Cd, Cr, Cu, Mn, Ni, Pb, and Zn were measured for agricultural soils near mines along the Diaojiang River in Guangxi Zhuang Autonomy Region, China. The sources of heavy metals in soils also were identified to assess their effect on speciation distribution of soil heavy metals. Furthermore, the speciation distribution of Cd and Zn, main soil heavy metal pollutants, in dry land and paddy soils were compared. Results showed that there were two severely polluted regions near mine area reaching alarming pollution level. As, Cd, Pb, and Zn were more affected by mining activities, showing very strong pollution level in soils. The mean percentage of exchangeable and carbonate fraction was highest and up to 46.8 % for Cd, indicating a high environmental risk. Greater bioavailable fractions of As, Cd, Cu, Mn, Pb, and Zn were found in soils heavily polluted by mining activities, whereas Cr and Ni as geogenic elements in the stable residual fraction. In addition, in the dry land soils, reducible fraction proportion of Cd was higher than that in the paddy soils, whereas exchangeable and carbonate fraction of Cd was lower than that in the paddy soils. Oxidizable fraction of Zn was higher in the paddy soils than that in the dry land soils. The results indicate that the sources of soil heavy metals and land types affect heavy metal speciation in the soil and are significant for environmental risk assessment of soil heavy metal pollutions.
土壤重金属污染一直是世界许多地区长期存在的环境问题，对生态系统和人类健康构成巨大威胁。土壤中重金属的形态对于评估受污染土壤的环境风险至关重要。本研究测定了中国广西壮族自治区刁江沿岸矿区附近农业土壤中砷、镉、铬、铜、锰、镍、铅和锌的总浓度及形态。还确定了土壤中重金属的来源，以评估其对土壤重金属形态分布的影响。此外，比较了旱地和水田土壤中主要土壤重金属污染物镉和锌的形态分布。结果表明，矿区附近有两个严重污染区域，达到了令人担忧的污染水平。砷、镉、铅和锌受采矿活动影响更大，在土壤中呈现出非常高的污染水平。镉的交换态和碳酸盐态平均百分比最高，可达46.8%，表明环境风险较高。在受采矿活动严重污染的土壤中，砷、镉、铜、锰、铅和锌的生物可利用态比例更高，而铬和镍作为地质成因元素则存在于稳定的残留态中。此外，旱地土壤中镉的可还原态比例高于水田土壤，而镉的交换态和碳酸盐态则低于水田土壤。水田土壤中锌的氧化态比例高于旱地土壤。结果表明，土壤重金属来源和土地类型影响土壤中重金属形态，对土壤重金属污染的环境风险评估具有重要意义。
