官厅水库周边土壤重金属空间变异特征及风险分析

Spacial Variation and Eco-Environmental Risk of Heavy Metals in Soil Surrounding Guanting Reservoir

在官厅水库周边2—10km范围内系统测定了8种重金属元素的含量，利用GIS技术和地统计分析方法，研究了重金属元素的空间变异特征及环境风险．结果表明，Cd是该区域主要的污染物，检测值（0．68±0．17）mg／kg相当于国家1级标准的3．4倍，40％的区域超过国家2级标准．土壤中7种重金属（Ni除外）的空间变异主要缘自于施肥、耕作及种植制度等人为活动引起的随机性因素，空间格局呈现西高东低，并呈洋河至怀来县区段污染最重的趋势．单因子污染指数和单因子生态危害系数Cd均显著高于其他重金属元素，复合污染指数呈库北高于库南，西部高于东部的空间趋势，复合生态风险指数南北向也有类似分布特征，东西向集中在怀来县、延庆县和中部北辛堡镇3个区域，说明高环境污染区将伴随高的生态风险，人口密集、工业化程度较高的城镇区域更容易引起生态危害．

Topsoil samples around the Guanting Reservoir ranging from 2 - 10kin were measured for heavy metals concentrations. GIS and geostatistical techniques were applied to analyze the special variation and eco-environmental risk of heavy metals. The results show that Cd is the major contamination in this area, 3.4 fold higher than the national background level, with a mean of 0.68 mg/kg and a standard deviation of 0.17. The area in which Cd concentration is higher than the second level of national standard accounts for about 40% of the whole study area. Spacial variation of heavy metals （except Ni） mainly is induced by the stochastic factors-mostly anthropogenic activities, e.g. fertilizer application, cultivation and planting modes, etc. The spatial pattern of heavy metals approximately declines in the W-N and N-S direction, with the highest value in the region between Yanghe River and Huailai County. The complex contamination index of heavy metals has the same distribution as their concentrations. However, the complex eco-risk index with higher value mainly occurs in vicinities of Huailai County, Yanqing County and Beixinpu town. It suggests that the town with higher population density and industrialization will induce both environmental pollution and ecological risk.