南阳盆地东部山区土壤重金属分布特征及生态风险评价

Distribution Characteristics and Ecological Risk Assessment of Soil Heavy Metals in the Eastern Mountainous Area of the Nanyang Basin

通过分析南阳盆地东部山区表层土壤(0~20 cm)样品的As、Hg、Cd、Cr、Pb、Zn、Ni和Cu等8种重金属含量和pH值,对土壤重金属的空间分布特征、污染程度和生态风险进行研究,并对重金属的来源进行分析.结果表明,研究区内土壤Cd、Cu、Cr、Ni、Pb、Zn和As含量相比于土壤污染风险筛选值存在不同程度的超标.土壤重金属空间分布呈面状和岛状分布.含量高值区主要分布在研究区南部,且与矿区分布相吻合.除了少数样点的土壤以外,大部分样点未受到污染,Cd的污染最为严重.As、Cr、Pb、Zn、Ni和Cu在几乎全部地区的潜在生态风险系数为轻微风险等级,Cd和Hg的潜在生态风险系数为中等风险等级占比最高.研究区综合土壤重金属潜在很强和强生态风险指数占比较高,分别为58.93%和37.66%.土壤Hg、Cd和Pb主要受到矿产开采等人类活动的影响,As主要受到研究区地质背景的影响,Zn、Ni、Cr和Cu同时受到人类活动和地质背景的影响.研究区矿产资源的开采是造成土壤污染及生态风险的主要原因.

The spatial distribution,pollution degree,and ecological risk of heavy metals in the soil were studied by analyzing the contents of As,Hg,Cd,Cr,Pb,Zn,Ni,and Cu and pH values in surface soil samples of the eastern mountainous area of the Nanyang basin.The results showed that the contents of Cd,Cu,Cr,Ni,Pb,Zn,and As in the soil exceeded the screening value of soil pollution risk.The spatial distribution of soil heavy metals displayed regional-and island-shaped.The highest concentration of heavy metals was found in the south of the study area,where a mining area is located.Most of the samples had no pollution levels except some samples with high contents of Cd.For As,Cr,Pb,Zn,Ni,and Cu,the potential ecological risk of most samples were low,while Cd and Hg posed medium risk in most areas.The areas with high and relatively high ecological risk index accounted for 58.93%and 37.66%,respectively.Soil Hg,Cd,and Pb contents were related to anthropogenic activities such mineral mining.As derives from geological processes,while Zn,Ni,Cr,and Cu are both controlled by anthropogenic activities and geological processes.The mining of mineral resources is the main driving factor of soil heavy metal pollution and ecological risk in the study area.