基于成土母质的矿产资源基地土壤重金属生态风险评价与来源解析

Ecological Risk Assessment and Source Apportionment of Heavy Metals in Mineral Resource Base Based on Soil Parent Materials

矿产资源基地具有资源经济与环境污染双重属性,阐明土壤重金属的空间分布特征、污染现状及其来源,有助于甄别“自然污染”和“人为污染”.以滦河流域滦平县红旗镇钒钛磁铁矿资源基地为研究对象,采用地累积指数、内梅罗指数和潜在生态风险指数评价土壤重金属污染特征,利用冗余分析(RDA)和正定矩阵因子分解法(PMF)解析土壤重金属污染来源.结果表明,矿产资源集中的中基性角闪岩类和片麻岩类变质岩母质的Cr、Cu和Ni含量平均值是其他成土母质的1~2倍,Pb和As含量平均值低于其他母质区.河道冲洪积母质Hg含量平均值最高,Cd在中基性片麻岩类变质岩母质、酸性流纹质火山岩母质和河道冲洪积母质中含量平均值较高.土壤重金属地累积污染程度(I_(geo))依次为:Cd>Cu>Pb>Ni>Zn>Cr>Hg>As.内梅罗综合污染指数(P_(N))变化范围为0.61~18.99,样点中10.00%和8.08%分别达到中度、重度污染,内梅罗单因子指数(P_(i))显示中基性角闪岩类和片麻岩类变质岩母岩区的Cu、Cd、Cr和Ni元素较高.潜在生态风险系数(E_(i))的大小顺序为:Hg(58.06)>Cd(39.72)>As(10.98)>Cu(6.56)>Pb(5.60)>Ni(5.43)>Cr(2.01)>Zn(1.10).表层土壤中84.27%的样点潜在生态风险指数(RI)≤150,整体属于轻微潜在生态风险等级.土壤重金属来源主要为成土母质风化自然源,其次为农业活动和交通运输混合源、矿业开发源,少量源于化石燃烧释放,贡献率分别为41.44%、31.83%、22.01%和4.73%.矿产资源基地的重金属污染风险具有多源性特点,并非完全来源于矿业开发.研究成果可为区域绿色矿业发展和生态环境保护提供科学依据.

Mineral resource bases have dual properties,e.g.,mineral resources and environmental pollution.The latter could be classified into natural and anthropogenic pollution based on identifying the spatial distribution characteristics and sources of heavy metals in the soil.The Hongqi vanadium titano-magnetite mineral resources base in Luanping County,Luanhe watershed,was taken as the research object.The geo-accumulation index(I_(geo)),Nemerow comprehensive pollution index(P_(N)),and potential ecological risk(E_(i))were utilized to assess the soil heavy metal pollution characteristics,and redundancy analysis(RDA)and positive determinate matrix factorization(PMF)were employed to identify sources of the soil heavy metals.The results revealed that the mean contents of Cr,Cu,and Ni in the parent material of medium-basic hornblende metamorphic rock and medium-basic gneisses metamorphic rock were 1-2 times that in other parent materials in the concentrated area of mineral resources.However,the mean contents of Pb and As were lower.Fluvial alluvial-proluvial parent materials had the highest mean content of Hg,and the mean content of Cd was higher in the parent materials of medium-basic gneisses metamorphic rocks,acid rhyolite volcanic rocks,and fluvial alluvial-proluvial facies.The I_(geo)decreased in the following order:Cd>Cu>Pb>Ni>Zn>Cr>Hg>As.P_(N) ranged from 0.61 to 18.99,and the sample proportion of moderate and severe pollution reached 10.00% and 8.08% respectively.P_(i) showed that the contents of Cu,Cd,Cr,and Ni were relatively higher in the parent material of intermediate-basic hornblende metamorphic rocks and intermediate-basic gneiss metamorphic rocks.E_(i) decreased in the order of Hg(58.06)>Cd(39.72)>As(10.98)>Cu(6.56)>Pb(5.60)>Ni(5.43)>Cr(2.01)>Zn(1.10).Samples whose RI was lower than 150 accounted for 84.27%,showing that the research area was predominantly at a slight potential ecological risk level.The sources of soil heavy metals were dominated by parent material weathering,followed by the mixed sources of agricultural activities and transportation,the exploitation of mining,and fossil burning,which accounted for 41.44%,31.83%,22.01%,and 4.73%,respectively.The risks of heavy metal pollution in the mineral resource base were characterized as multi-source instead of the single source from the mining industry.These research results provide the scientific basis for regional green mining development and eco-environmental protection.