广西废弃矿区土壤中Cd、Pb、As污染特征及环境质量评价研究

Pollution characteristics and environmental quality assessment of Cd-Pb-As in soil of abandoned mining area in Guangxi

文中对广西某废弃稀土矿区9个采样点0~20 cm(表层)和20~60 cm(深层)以及2个土壤剖面共38个土壤样品进行取样分析,采用地积累指数评价法和潜在生态风险指数评估模型评价了Cd、Pb、As三项重金属污染状况和潜在生态风险并应用相关性分析了重金属来源。结果显示:(1)表层和深层土壤中重金属元素Cd、Pb存在明显的重金属超标现象,尤其是Cd含量超标情况严重,在表层和深层土壤中,Cd的超标率均达到了100%,Pb的超标率分别达到了33.3%和22.2%,As含量正常处于未污染状态。(2)表层和深层土壤3种重金属元素的相关性分析显示,Cd和Pb的相关性不明显,As元素表现出极显著正相关;(3)污染评价显示,表层土壤重金属元素中Cd处于偏中度污染水平,Pb处于轻度污染水平,深层土壤中Cd、Pb均处于偏中度污染水平,表层和深层土壤中As元素均显示无污染。(4)As元素在矿区和非矿区0~100 cm剖面I_(geo)值均小于-1属于无污染等级。非矿区剖面土壤重金属Cd、Pb的污染程度整体上小于矿区Cd、Pb污染。在矿区范围内,Cd、Pb含量均表现出随着土壤深度增大先升高后降低,且在深度为40 cm处达到最高值,非矿区无明显变化规律。

In this paper,38 soil samples,from 9 sites of 0-20 cm(surface layer)and 20-60 cm(deep layer)and 2 soil profiles in an abandoned rare earth mining area in Guangxi,are collected and analyzed.The pollution status and potential ecological risk of Cd,Pb and As are evaluated by using the geo-accumulation index method and potential ecological risk index model.The result is shown as follows.(1)The heavy metal content of Cd and Pb in topsoil and deep soil exceeds the standard obviously,especially the content of Cd exceeds the standard seriously.The over-standard rate of Cd are both more than 100%and that of Pb is 33.3%and 22.2%,respectively.(2)The correlation analysis of the three heavy metal elements indicates that the correlation between Cd and Pb is not obvious,but the correlation between Cd and As is very significant.(3)The pollution assessment shows that heavy metal element Cd is at a moderate pollution level in the surface soil,Pb is at a mild pollution level,and Cd and Pb are both at a moderate pollution level in the deep soil,and As element shows no pollution in the surface and deep soil.(4)The Igeo values of As in 0-100 cm sections of the mining and non-mining area are less than-1,which belongs to non-pollution grade.The pollution degree of heavy metals of Cd and Pb in non-mining area is lower than that in mining area.In the range of mining area,the contents of Cd and Pb increase firstly and then decrease with the increase of soil depth,and reach the highest values at the depth of 40 cm,and there is no obvious change regularity of the contents of Cd and Pb in non-mining area.