渭干河-库车河绿洲土壤重金属分布特征与生态风险评价

随着工业发展和城市化进程的加剧,农用化学物质种类和数量不断增加,导致土壤受到不同程度的重金属污染,农田土壤重金属污染尤为严重。该文以新疆最典型的荒漠绿洲渭库绿洲为研究区,采集土壤样本57个,测定出土壤样本中砷(As)、汞(Hg)、铅(Pb)、铬(Cr)、锌(Zn)和铜(Cu)6种元素的含量,分别采用地统计空间分析法、地积累指数法(I_(geo))和潜在生态风险指数(RI)等方法,对研究区土壤重金属污染和潜在生态风险程度做出科学评价,并采用多因子分析方法对重金属的来源进行了讨论。1)研究区Hg、As、Cu、Cr、Pb和Zn 6种土壤重金属平均质量分数分别为2.41、0、37.64、25.25、39.78、15.01 mg/kg,平均含量均未超过国家二级标准,其中Pb的平均含量超过了新疆土壤重金属背景值,存在一定程度的重金属积累;2)由地积累指数法(I_(geo))和潜在生态风险指数(RI)分析得出,研究区土壤重金属的I_(geo)均值As(-4.59)Hg(-3.62)Cu(-1.92)Cr(-1.44)Zn(0.59)Pb(0.73),RI均值为22.26,整体上属于无污染水平,说明研究区域土壤重金属环境质量总体优良;3)通过综合相关性分析、主成分分析和聚类分析,研究区重金属的来源可以分为两类,Cu、Zn、Cr和Pb来源于成土母质等自然背景和人类农业生产活动;As和Hg来源于研究区域地形地貌、水文环境等自然背景。4)分析研究区域综合生态风险指数RI可知,研究区整体处于无污染水平,但各分区RI指数存在差异,其中西北部(NW)和东北部(NE)分区RI值相对较高,最高值出现在东北部(NE)分区上。该研究提出的分析方法能快速、客观反映绿洲土壤重金属污染特征以及来源,可为绿洲土壤环境质量评价和管理提供依科学依据。

Distribution of heavy metal pollution and assessment of its potential ecological risks in Ugan-Kuqa River Delta of Xinjiang

Abstract: As the progress of industrial development and urbanization, the quantities and types of agricultural chemicals have been increasing, which has led to heavy metal pollution in soil, and the pollution in agricultural soils was especially serious. In this paper, Ugan-Kuqa River oasis was selected to be study area. The amounts of As, Hg, Pb, Cr, Zn and Cu were determined from 57 soil samples collected in Ugan-Kuqa River oasis. The spatial analysis, geo-accumulation index, and potential ecological risk index were adopted to evaluate the pollution characteristics, pollution degree and potential ecological risks of heavy metal, and the multivariate statistical analysis was adopted for the discussion on heavy metal. The results showed that: 1) The contents of 6 kinds of heavy metals in soils, i.e. Hg, As, Cu, Cr, Pb and Zn, were different, and the average contents were 2.41, 0, 37.64, 25.25, 39.78 and 15.01 mg/kg, respectively; soil heavy metal contents were not higher than national standard level, but Pb content value was higher than the background value of soil in Xinjiang. There is a certain degree of heavy metal pollution in the study area. 2) Through the analysis of geo-accumulation index and potential ecological risk index, the results showed that the heavy metals for the geo-accumulation index value were sorted as As (-4.59) < Hg (-3.62) < Cu (-1.92) < Cr (-1.44) < Zn (0.59) < Pb (0.73), and the potential ecological risk index was 22.26, presenting the non-pollution level of soil heavy metal in research area. 3) By the correlation analysis, principal component analysis and cluster analysis, the sources of heavy metals could be classified 2 categories in the study area. The source of Cu, Zn, Cr and Pb might be from the combined influence of the soil parent material and human agricultural activities. As and Hg might be controlled by landform and hydrologic environment factors. 4) Although the ecological risk index of study area was non-pollution level, there was difference on ecological risk index for different regions; among them, the values of ecological risk index were higher in the areas north of west (NW), west of north (WN) and east of north (EN), and the highest value appeared in the area east of north (EN), which should be on alert. In this paper, the proposed method of analysis can reflect characteristics and source of soil heavy metal quickly and objectively in the oasis, and it can provide scientific basis for evaluation and management of soil environment quality in the oasis.