洛阳市栾川县矿区周边土壤重金属污染特征、来源与生态风险评价

Evaluation of heavy metal pollution characteristics,sources and ecological risks of soil around mining areas in Luanchuan County,Luoyang City

为探究洛阳栾川县矿区周边土壤重金属污染特征与生态风险,采集并测定了研究区47个表层土壤(0-20 cm)样品Zn、Cu、Cd、Pb、Cr、Ni和As重金属元素含量,运用单因子指数(P_(i))、内梅罗综合指数法(P_(m))、地累积指数(I_(geo))、潜在生态风险指数(E_(r)^(i)和RI)、Tessier重金属五步提取法、主成分分析(PCA)等方法围绕重金属元素分布特征、污染程度、潜在生态风险、重金属形态和来源进行分析和讨论.结果表明,Cd和As的污染程度和生态风险最高(E_(r)^(i)>160),空间分布不均匀(CV>90.00%),为引起土壤环境风险的主要因子;其次是Pb、Cu、Zn;最低的是Cr和Ni,且其空间异质性较弱,迁移转化风险较低.不同的重金属在林地土壤、农田土壤和尾矿周边土壤中的富集程度和生态风险存在差异.结合E_(r)^(i)和RI值来看,林地土壤As和Cd潜在生态风险较高,E_(r)^(i)分别达到了643.35和536.10.从重金属形态分布来看,Cd和Pb有效态含量占比较高,分别为72.13%、86.84%;其次是Cu、Zn和As;林地土壤中Pb的碳酸盐结合态(43.82%)以及Cd可交换态(28.24%)和有机结合态(33.31%)明显高于农田和尾矿,发生迁移转化生态风险较高.主成分分析结果表明主成分PC1、PC2和PC3分别归因于矿业开采排放源、自然源、和混合源(自然淋溶、林业和农业活动、采矿).

To investigate the characteristics and ecological risks of heavy metal pollution in soils around mining areas in Luanchuan County,Luoyang City,47 surface soil(0-20 cm)samples in the study area were collected and measured for Zn,Cu,Cd,Pb,Cr,Ni and As,and single factor index(Pi),Nemero integrated index(Pm),ground accumulation index(Igeo),potential ecological risk index(E_(r)^(i)and RI),Tessier's five-step extraction,and principal component analysis(PCA)were used to portray and delineate the distribution characteristics,pollution level,potential ecological risk,heavy metal fractionations and source apportionment.The results showed that Cd and As had the highest pollution degree and ecological risk(E_(r)^(i)>160),with heterogeneous spatial distribution(CV>90.00%),and were the main factors causing soil environmental risk;followed by Pb,Cu,and Zn;the lowest were Cr and Ni,and their spatial heterogeneity was weak and the migration transformation risk was low.The degree of enrichment and ecological risk of the different heavy metals in woodland soils,agricultural soils and soils around tailings differed.Based on the calculation results of the E_(r)^(i)and RI,the potential ecological risk of forest soil As and Cd was high,while the Eri were 643.35 and 536.10,respectively.The heavy metal fractionation analysis showed that Cd and Pb have a higher content in the effective state,72.13%and 86.84%,respectively;followed by Cu,Zn and As;the carbonate bound state(43.82%)as well as the Cd exchangeable state(28.24%)and organic bound state(33.31%)of Pb in woodlands are significantly higher than the states in agricultural fields and tailing,with a higher ecological risk of migration transformation.The PCA results indicated that PC1,PC2 and PC3 were recognized as mining emission sources,natural sources,and mixed sources(natural leaching,forestry and agricultural activities,and mining),respectively.