焉耆盆地小麦地土壤重金属污染及生态风险

从新疆焉耆盆地采集35个小麦地土壤样品,测定其中As、Cd、Cr、Cu、Mn、Ni、Pb和Zn 8种重金属元素的含量,采用内梅罗污染指数(NPI)、潜在生态风险指数(RI)和生态风险预警指数(IER)对小麦地土壤重金属污染及生态风险进行评价。结果表明:焉耆盆地小麦地Cd含量平均值超出国家土壤环境质量二级标准的11.12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55.58、1.32、1.48、3.21倍和4.47倍。小麦地Cd、Pb和Zn呈现重度污染,Cr和Ni轻度污染,As和Cu轻微污染,Mn无污染;研究区NPI平均值为7.93(呈现重度污染状态),RI平均值为342.95(属于较强生态风险水平),IER平均值为5.68(属于重警级别),土壤RI和IER从研究区北向南部呈现逐渐增加趋势。小麦地Ni、Pb与Zn主要受到人为污染源的影响,Cu、Mn和Cr主要受到土壤地球化学特征的控制,As和Cd可能受人为污染和自然因素共同影响。综上认为,Cd是焉耆盆地小麦地主要的污染因子和生态风险因子,对研究区耕地Cd污染应予关注。

The soil heavy metal pollution and ecological risk assessment of wheat fields in Yanqi Basin

A total of 35 soil samples were collected from wheat fields in Yanqi Basin, Xinjiang, and determined the contents of eight heavy metal elements(As, Cd, Cr, Cu, Mn, Ni, Pb and Zn)by standard methods. The soil heavy metal pollution of wheat fields was analyzed based on Nemerow pollution index(NPI), potential ecological risk index(RI)and ecological risk warning index(IER). Results of the research indi-cated that:the average contents of Cd in wheat field soils of Yanqi Basin exceeded 11.12 times of the National Soil Environmental Quality Standard(GradeⅡ);The average contents of Cd, Cr, Ni, Pb and Zn exceeded 55.58, 1.32, 1.48, 3.21 times and 4.47 times of the back-ground values for irrigation soils in Xinjiang, respectively;Cd, Pb and Zn fell into high pollution level, whereas Cr and Ni fell into light pollu-tion level, As and Cu fell into slightly pollution level, and Mn fell into no pollution level for wheat field soils. The average value of NPI was 7.93, which showed a heavy pollution level;The average value of RI of soil was 342.95, which showed a highly ecological risk situation;The average value of IER of soil was 5.68, which showed a serious warning situation. The RI and IER of soil gradually increased from the northern parts to the southern parts of study area;Ni, Pb and Zn of wheat field were affected mainly by the human activities, whereas Cu, Mn and Cr were controlled mainly by the geochemical background of soils, and the main sources of As and Cd may be affected by the interaction of hu-man activities and natural factors. Cd was the main pollution factor and the main ecological risk factor of wheat fields in Yanqi Basin, the pollution risk of Cd should be a major concern in the study area.