开都河下游绿洲耕地土壤重金属污染及潜在生态风险

Heavy metal pollution and potential ecological risks of farmland soils in oasis along the lower reaches of Kaidu River

开都河下游绿洲采集98个耕地土壤样品,测定其中As、Cd、Cr、Cu、Mn、Ni、Pb和Zn等8种重金属元素的含量.基于地统计法,污染负荷指数法和潜在生态风险指数法研究耕地土壤重金属污染和潜在生态风险,并对重金属的来源进行讨论.结果表明:(1)研究区Cd含量平均值超出《国家土壤环境质量标准》中Ⅱ级标准的11.08倍.Cd、Cr、Ni、Pb和Zn含量的平均值分别超出新疆灌耕土背景值的55.42、1.32、1.36、3.40和5.14倍.重金属元素空间分布各不相同,部分区域出现高值区,表明人类活动对耕地土壤环境具有负面效应.(2)研究区耕地土壤Cd呈现重度污染,Pb呈现中度污染,Cr、Cu、Ni和Zn呈现轻度污染,As和Mn呈现无污染态势.Cd是污染面积最大,污染程度最高的元素.研究区污染负荷指数PLI的平均值为1.68,呈现轻度污染.(3)各重金属元素单项生态风险指数(E)的平均值从大到小依次为:Cd、Ni、As、Cu、Pb、Cr与Zn.研究区综合生态风险指数(RI)的平均值为355.31,属于较强生态风险.(4)研究区耕地土壤As、Cd、Pb和Zn主要受到人类活动的影响,Cr、Cu、Mn和Ni主要受到土壤地球化学特征的控制.Cd是研究区耕地土壤主要的污染因子,对PLI和RI的贡献很大,耕地土壤中Cd污染必须关注.

A total of 98 farmland soil samples were collected from oasis along the lower reaches of Kaidu River, Xinjiang, and the contents of eight heavy metal elements （As, Cd, Cr, Cu, Mn, Ni, Pb and Zn） in the soil samples were determined by standard methods. The spatial distribution of heavy metal pollution level and its potential ecological risks were analyzed based on geostatistical analysis, pollution load index （PLI） and potential ecological risk index （RI）. The main sources of heavy metals were discussed. Results showed that the average value content of Cd in farmland soils of study area was 11.08 times the National Soil Environmental Quality Standard （GB15618-1995, Grade II）. The average contents of Cd, Cr, Ni, Pb and Zn were 55.42, 1.32, 1.36, 3.40 and 5.14 times the background values for irrigation soils in Xinjiang, respectively. Cd presented high pollution level, whereas Pb moderate pollution, Cr, Cu, Ni and Zn light pollution, and As, Mn no pollution level for farmland soils in study area. The average PLI of heavy metals in farmland soils was 1.68 and in the slight pollution level. The average E value for each heavy metal elements of farmland soils was ranked in the order of：Cd, Ni, As, Cu, Pb, Cr and Zn. The average RI value was 355.31, which showed a strong ecological risk situation. As, Cd, Pb and Zn of farmland soils were affected by the human activities in study area, whereas Cr, Cu, Mn and Ni were mainly controlled by the geochemical characteristics of soil. Cd was the main pollution factor of farmland soils that had strong influences on the pollution level and potential ecological risk situations of farmland soils in study area, therefore Cd pollution in farmland soils should be a major concern.