典型农业区农田土壤重金属潜在生态风险评价

采用野外采样和室内分析相结合的方法,以典型农业区山东禹城的农田表层土壤(0-20 cm)为研究对象,分析了土壤中重金属Cr、Ni、Pb、As、Hg、Cd、Cu和Zn的含量,探讨了土壤中重金属的含量与不同人类活动的关系并进行了潜在生态风险评估.结果显示,8种重金属的含量均超过黄河下游潮土区的背景值.潜在生态风险评估表明,当地的农田土壤Cr、Ni、Pb、As、Cu、zn有轻度的生态风险,Hg和Cd存在较大的生态风险.城市化进程、畜禽养殖和污灌是造成十壤Cd高生态风险的主要因素,城市化进程和污灌也是造成土壤Hg高生态风险的主要因素.禹城各区域土壤受8种重金属的综合潜在生态风险程度大小依次为城郊农田>污灌农田>典型施肥农田>井灌农田>引黄灌农田,不同人类活动区域土壤Cd生态风险和8种重金属的综合潜在生态风险存在显著差异.

Assessment of the Potential Ecological Risk of Heavy Metals in the Farmland Soils in Yucheng City,Shandong Province

Heavy metal pollutions in the soil of farmland are regarded as serious threats to rural environment in China. Human activities, such as intensive livestock, sewage irrigation, large amounts of agrochemicals input and the rapid urbanization are proved to be the main sources of the heavy metals. Yucheng City is located in Huang-Huai-Hai plain, the largest alluvial plain and important agricultural area in China. The concentrations of Cr, Ni, Pb, As, Hg, Cd, Cu and Zn in the topsoil(0～20 cm) of the farmland in Yucheng City were analyzed, and their relations with different human activities were discussed. The potential ecological risks of these heavy metals were assessed. Furthermore, the heavy metal concentrations in wheat grown in the sampled soils were also collected and analyzed to compare those in soils. The results showed that the concentrations of the eight heavy metals in all of the soil samples were far lower than those critical values of the National Soil Quality Standard (Grade Ⅱ) except Cd, while they were all higher than that of the backgrounds in the soils of the alluvial plain of the lower Yellow River. The rapid urbanization, sewage irrigation and long-time typical manure usage were responsible for the high value of heavy metals in soils. The potential ecological risks of Cr、Ni、Pb、As、Cu、Zn were at a lower level while that of Hg and Cd were at a higher level. The higher e-cological risk of soil Cd was mainly derived from the rapid urbanization, intensive livestock and sewage irrigation. And that of soil Hg was located in the suburb of Yucheng City and the area irrigated with sewage from Tuhai River. The potential ecological hazard index of the eight heavy metals in soils followed the sequence as suburban farmland>farmland irrigated with sewage>farmland with typical manure used>farm-land irrigated with groundwater>farmland irrigated with the Yellow River. Hg and Cd concentrations in some wheat samples were as high as or even higher than that of critical values of the National Standard (GB2715-2005).