武河人工湿地沉积物中镉砷累积和空间分布特征及其生态风险评价

Accumulation and Spatial Distribution Characteristics of Cd and As in Sediments from Wuhe Artificial Wetland and Their Ecological Risk Assessment

本文研究采用四酸消解法(HCI-HNO3-HF-HCIO4)和Tessier五步法对样品进行处理,测定了武河人工湿地沉积物中Cd、As两种重金属元素的总量及赋存形态,分析了Cd、As的累积及空间分布特征,并对其污染程度和潜在生态风险进行了评价,结果表明:表层沉积物中Cd、As的平均含量分别为3.18 mg·kg-1、35.41 mg·kg-1,分别超出环境背景值238%、18.03%,具有明显的累积效应;Cd、As主要以残渣态形式存在,其平均含量分别为82.59%、76.31%;湿地Cd、As的Igeo平均值分布为1.62、0.44,说明Cd、As除自然的土壤来源外,还叠加了工农业污染的影响;空间分布特征分析表明,Cd、As质量分数、Igeo、RI最大值均出现在南涑河流域来水处;潜在生态风险评价表明湿地沉积物中潜在生态危害指数RI为501.20,属III较强生态危害。

This paper used four acid digestion methods（HCI-HNO3-HF-HCIO4） and the Tessier five-step method to examine the content and special characteristics of the elements Cd and As in samples. The accumulation and spatial characteristics were also analyzed. Further measures included ecol-accumulation index and potential ecological risk index, for a comprehensive ecological risk and pollution level assessment. The results showed that the average content were 3.18 mg·kg-1for Cd and 35.41 mg·kg-1 for As. The content was 238%,18.03% respectively, which was higher than the environment background values, with a significant cumulative effect. Heavy metals at the study site mainly existed in residual state, and the average contents were 82.59% for Cd and 76.31% for As. Among all sampling points, the Igeo of Cd was 1.62 and that of As was 0.44. Which indicated that in addition to natural sources of Cd and As in the soil, there might also be an overlay effect from industrial and agricultural pollution. Spatial analysis showed that the maximum of the content, Igeo and RI appeared in the South Su River. The overall potential ecological risk index（RI） had a mean of 501.20, which indicated a III strong ecological harm to the wetland.