博斯腾湖流域绿洲农田土壤重金属污染及潜在生态风险评价

Assessment of heavy metal pollution and its potential ecological risks of farmland soils of oasis in Bosten Lake Basin

新疆博斯腾湖流域绿洲采集195个农田土壤样品,测定其中As、Cd、Cr、Cu、Mn、Ni、Pb和Zn等8种重金属元素的含量,基于地统计法分析农田土壤重金属空间分布规律,采用污染负荷指数(PLI)和潜在生态风险指数(RI)评价农田土壤重金属污染和潜在生态风险程度,并对重金属的来源进行讨论。结果表明:(1)博斯腾湖流域农田土壤Cd、Cr、Cu、Ni、Pb和Zn含量平均值分别超出新疆土壤背景值的1.67倍、1.13倍、1.15倍、1.29倍、2.11倍和1.65倍。(2)农田土壤中8种重金属元素空间分布基本呈现岛状分布格局,各金属元素在部分区域出现高值区,表明研究区人类活动对农田土壤环境具有负面效应。(3)农田土壤Pb呈现中度污染,Cd、Cr、Cu、Ni和Zn轻度污染,Mn轻微污染,As无污染。农田土壤重金属污染负荷指数的平均值为1.09,呈现轻度污染态势。(4)各重金属元素单项生态风险指数平均值从大到小依次为:Cd、Ni、As、Cu、Pb、Cr、Zn。综合生态风险指数平均值为18.63,处于轻微生态风险态势。从生态风险程度的区域差异来看,各县生态风险指数从大到小依次为:和硕县、博湖县、焉耆县、和静县。(5)农田土壤Cr、Cu、Mn、Ni与Zn主要受到土壤地球化学成因的控制,As、Cd和Pb主要受到人类活动的影响。Cd与Pb是研究区主要的污染因子,研究区农田土壤中Cd与Pb污染必须关注。

A total of 195 soil samples of farmland were collected from oasis in the Bosten Lake Basin, Xinjiang, and the concentrations of eight heavy metal elements（As, Cd, Cr, Cu, Mn, Ni,Pb and Zn） were identified by standard methods. The spatial distribution of soil heavy metals in farmland was analyzed based on geostatistical analysis, while the pollution load index（PLI）and potential ecological risk index（RI） were employed to the assessment of the soil heavy metal pollution levels and potential ecological risk. Then the main sources of heavy metals were discussed. Results showed that：（1） The average value of the contents of Cd, Cr, Cu, Ni,Pb and Zn exceeded by 1.67, 1.13, 1.15, 1.29, 2.11 and 1.65 times of the soil background value of Xinjiang, respectively.（2） The spatial distribution of eight heavy metals showed an islandlike pattern, and all the heavy metal elements showed high value areas in some parts of the study area, indicating the negative effects of human activities on soil environment of farmlands.（3） Pb presented a moderate pollution, whereas Cd, Zn, Ni, Cu and Cr a light pollution, Mn a slight pollution and As no pollution for farmland soils. The average PLI value of the heavy metals was 1.09, which showed a slight pollution.（4） The average E value for each heavy metal element was ranked as： Cd Ni As Cu Pb Cr Zn. The average RI value was 18.63, which showed a slight ecological risk situation. In terms of regional differences, the ecological risk index was ranked as： Hoshut County Baghrash County Karashahar County Hejing County.（5） Cr, Cu, Mn, Ni and Zn contents were controlled mainly by the soil geochemical genesis and As, Cd and Pb were mainly affected by human activities. Cd and Pb were the main pollution sources of farmland soils, which should be given more attention.