石河子垦区农田土壤重金属含量与风险评价

在石河子垦区北泉镇和桃花镇采集农田土壤样品130个，测定土壤Cu、Zn、Cr、Cd、Pb、As和Hg7种重金属含量，系统分析了土壤重金属的分布特征，并对该地区土壤重金属的累积污染现状和潜在生态风险进行评价。结果表明：石河子垦区农田土壤Cu、Zn、Cr、Cd、Pb、As和Hg的平均含量分别为33．34、102．64、58．77、0．46、13．72、18．89和0．036mg／kg，均超过新疆土壤背景值，其中Cd、Hg、Pb和As最为显著。7种重金属平均含量均低于国家《土壤环境质量标准》二级标准，但Cd和As的超标率分别达到了16．92％和9．23％。土壤中Cu—Zn—As、Cr-Cd—Pb有较强的同源性，而Hg具有强烈的异源特征。北泉镇农田土壤Hg平均含量明显高于桃花镇，而Cd、Cr和Pb则低于桃花镇。不同土地利用类型农田土壤重金属的平均含量总体差异较小。7种重金属元素均存在不同程度的累积，Cd和Hg的单因子污染指数较大，重金属综合污染指数平均为0．71，属尚清洁（警戒限）。样点中重金属多因子综合潜在生态风险指数处于低潜在生态风险的占27％，中等潜在生态风险占50％，较高潜在生态风险占23％；其中，土壤Cd的潜在生态风险指数最大，其次是Hg。

Assessment and Analysis of Heavy Metal Content in Farmland Soil in Shihezi Reclamation Area

The farmland soil in Beiquan and Taohua districts of Shihezi reclamation area were selected with 130 sampling points to evaluate the content and the distribution characteristics of seven heavy metals of Cu, Zn,Cr, Cd, Pb, As and Hg. The accumu- lation status and potential ecological risk of the heavy metals in soil of Shihezi were analyzed. The result showed that the average concentrations of the Cu,Zn,Cr,Cd,Pb,As and Hg in soil were 33.34,102. 64,58.77,0.46,13.72,18.89 and 0. 036 mg/kg. They were higher than background values of soil in Xiniiang,and among them,Cd, Hg,Pb and As showed a significant accumu- lation trend. The average concentrations of seven heavy metals in the farmland soil did not exceed the national standards Grade II ,but the exceeding standard rate of Cd and As reached 16.92% and 9.23% ,respectively. Cu-Zn-As and Cr-Cd-Pb had strong homology,but Hg had not similar source as the others. The average concentration of Hg in farmland soils of Beiquan was higher than that in Taohua,whi｜e the average concentrations of Cr,Cd,and Pb were lower than those in Taohua. In general,there were little difference for the average concentrations of heavy metals in soils under different land use types. The seven heavy metals in soil showed certain accumulation effects;especially Cd and Hg had the high pollution index. The average integrated pollution in- dex of Shihezi farmland soil was 0.71, belonging to the warning limit. About 27~ of the soil samples had low potential ecological risk, middle potential ecological risk accounted for 50%,and the higher potential ecological risk accounted for 23 %. Cd was the main factor of potential ecological risks and then was Hg.