孝义铝矿复垦土壤重金属污染潜在生态风险评价

Potential ecological risk assessment of heavy metals in the reclaimed soil of Xiaoyi Bauxite Mine

为了解和评估复垦区土壤重金属污染风险,采用Hakanson潜在生态风险指数(The Potential Ecological Risk Index)法,对孝义铝矿复垦3年后的土壤中7种(Cd、Cr、Cu、Pb、As、Ni和Zn)重金属质量分数和潜在生态风险进行评价。结果表明:复垦土壤中,主要超标重金属元素是Cd,7种元素均存在累积效应。污染源主要有复垦用土、农业生产和粉尘等外来影响;其中,Cd、Cr和As 3种元素具有伴随复合污染现象。Cd的污染指数最高,均值为11.54,处于很高的污染等级,污染指数均值顺序为Cd>Pb>As>Cr>Ni>Zn>Cu;重金属潜在生态风险指数RI为238.39,属于中等生态风险水平。表明孝义铝矿复垦土壤存在中等程度的污染风险,需要减少和控制复垦用土以外的其他染物源进入,降低土壤污染的风险。该研究为复垦土地的利用方式具有重要的现实指导价值,为矿区复垦和治理的措施体系提供科学依据。

Mineral is a key resource for social and economic development.However,environment issues from mining are more and more serious.Shanxi is a resource province,a lot of land were destructed during the mining,and should be reclaimed after mining.In order to understand the potential pollution characteristics and the pollution risk of heavy metals in reclaimed soil,the heavy metal elements Cd,Cr,Cu,Pb,As,Ni and Zn of reclaimed soils at Xiaoyi Bauxite Mine were analyzed.[Methods]On April in 2016,6 groups and 18 soil samples were collected from reclaimed land of in Xihedi village where corn was planted.Soil samples were passed 100 mesh sieves after natural air,drying.Then seven heavy mental elements were measured using inductively,coupled plasma spectrometer after digestion and decomposition by nitric acid,perchloric acid,hydrofluoric acid.Based on the heavy mental contents,pollution degree and potential ecological risk of heavy mental were evaluated using Hakanson ecological risk index.[Results]The mean content values of Cd,Cr,Cu,Pb,Ni and Zn were respectively 5.19,40.47,2.65,65.13,8.64,13.05 and 28.98 mg/kg.The Cd was higher than 0.45 mg/kg that is the national second standard,while others were lesser.Mainly pollution element was Cd,and all 7 element contents exceeded the background values,and exited accumulated effects.The main pollution resource was from reclaimed soil,agricultural actions,dust precipitation and other anthropogenic activities in the mine area.The contents of Cu,Pb,and Ni had higher difference than that of As,Cr,Zn and Cd at different sampling places.The contents of Cd,Cr,and As have significant correlations,and presented combined pollution.The mean pollution index of Cd,Cr,Cu,Pb,Ni and Zn were respectively 11.54,0.20,0.02,0.82,0.28,0.15 and 0.11,and as Cd>Pb>As>Cr>Ni>Zn>Cu.The Cd was at the highest pollution level,while other elements were in the lower.The comprehensive pollution index was 1.88,and at middle comprehensive pollution degree.The mean potential ecological risk index(RI)of Cd,Cr,Cu,Pb,Ni and Zn were respectively 230.87,0.40,0.13,4.07,1.44,1.45 and 0.03,and as Cd>Pb>Ni>As>Cr>Cu>Zn.The ecological risk index was 238.39,and at the medium ecological risk level.[Conclusions]The reclaimed soil in Xiaoyi Bauxite Mine is in medium grade pollution risk,and mainly pollution element was Cd.Element Cd,Cs and As have higher homology than other elements.We should pay enough attentions to control and cut down the input of pollution sources,reduce the risk of pollution,especially the input of Cd.Hakanson ecological risk index method could magnify the evaluation result,but it could increase the attention about pollution risk.