铝矿复垦土壤重金属含量变化及污染风险评价

目的]对孝义铝矿复垦区土壤重金属含量和污染状况进行研究,为了解和评价矿区复垦土壤重金属污染风险提供科学依据。方法]采用ICP-MS测定土壤中Cd,Cr,Cu,Pb,As,Ni等6种重金属元素含量,分析各含量随复垦年限的变化特征,并用单因子标识指数和内梅罗综合标识指数法对重金属的污染程度进行评价。结果](1)Cd含量均值为5.19mg/kg,是国家二级标准0.3mg/kg的约10倍,其余5种元素含量均低于国家二级标准。随着复垦年限的延长,Cd含量在0—15cm土层处逐渐降低,在15—30cm土层处逐渐增加。(2)Cd的单项因子污染指数在所有样点均达到5级严重污染水平,其它元素均属清洁水平。内梅罗综合污染指数12.08~13.14,均值12.43,是5级重污染指数的3~4倍,属严重污染水平。(3)复垦用土中6种重金属含量均超过国家2级标准,是复垦土地重金属主要的来源。结论]复垦区土壤由于复垦用土及后期的施肥和粉尘沉降等所致已被Cd污染,在矿区复垦中,应当严格控制复垦用土的质量。

Contents and Pollution Risk Assessment of Heavy Mentals in Reclaimed Soil

Objective] The contents and pollution state of heavy mentals of soil in Xiaoyi bauxite mine of Shanxi Province were studied to provide scientific basis for the understanding and evaluating the risk of heavy metal pollution in reclaimed soil in mining area. Methods] The contents of Cd, Cr, Cu, Pb, As and Ni by ICP-MS were measured, and their changes along different reclaimed years were analyzed. Single factor index and Nemerow comprehensive index methods were used to evaluate the potential pollution degree and risk. Results] (1) The mean value of Cd was 5.19 mg/kg, exceeding the 0.3 mg/kg of national stand by 17 times. Other elements was not exceed the national stand and no pollution risk was observed. With the extension of reclamation time, the content of Cd increased at 0-15 cm and decreased at 15-30 cm layer. (2) The single pollution index of Cd is the highest of all sampling plots, was assessed at 5th level severe pollution. Other 5 elements are lower, and are at 1st degree of safe level. The Nemerow comprehensive index ranged from 12.08 to 13.14, with an average of 12.43, at severe pollution level, and it exceeds the 5th degree by 3~4 times. (3) Soil which was used to reclaim is the mainly pollution resource, the contents of 6 heavy mental elements exceeded the national stand. Conclusion] The soil in reclamation area have been polluted by Cd sourced from reclaimed soil, manure and dust. When considering reclaimed mine, the quality of soil which will be used to reclaim should be protected strictly.