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研究报告

Spatial distribution and pollution assessment of Pb in urban topsoil based on GIS:A case study of Yibin in Sichuan Province

摘要：基于ArcGIS地统计模块,对长江上游城市宜宾市的63个土壤样品进行了分析,探讨了城市土壤中重金属Pb的空间分布特征和污染状况.结果表明,城市土壤样品中Pb含量为20.3～223.9mg·kg^-1,平均含量为61.2mg·kg^-1,显著高于四川省土壤背景值,具有明显的累积效应(p=0);与四川省土壤基线值相比,宜宾市土壤中Pb含量的超标率为31.7%.地统计分析结果表明,宜宾市土壤中的Pb呈现中等程度的空间相关性,说明随机性因素(人类活动,如汽车尾气排放、工业排放等)和结构因素(指自然因素,如土壤性质、地形和气候等)对Pb的空间分布有较大的影响.Pb污染指数的克里格插值图可反映出Pb污染的空间格局,宜宾市土壤中Pb污染总体上接近中度污染水平(污染指数为1.98),其中,上江北、下江北地区Pb污染最为严重,翠屏区和南岸区表现出一定的Pb污染.总体上,工业区、交通区和商业区的Pb污染较为突出.

Abstract：To identify the concentration and spatial distribution of Pb in urban soils,63 soil samples were collected from Yibin and analyzed based on the extension geostatistical analysis of Geographical Information System (GIS). The concentration of Pb in the soils of Yibin ranged from 20.3 to 223.9 mg·kg^-1,with an average concentration of 61.2 mg·kg^-1 which is apparently higher than the background value of Sichuan Province (p=0). Moreover,compared with the soil baseline value of Sichuan Province,the concentration of Pb of all the sampled soils exceeded 31.7%. Geostatistical analysis showed that the spatial correlations of Pb belonged to the intermediate degree,which indicated that the concentration of Pb in the soils was influenced by the random factor (anthropologic activities such as vehicle exhaust and industrial emission) and structural factor (natural factors such as parent soil material,topography and climate).The map of the spatial distribution of Pb pollution index produced using ordinary kriging demonstrated that the Pb pollution risk in Shangjiangbei and Xiajiangbei District was close to the intermediate degree (1.98) and the soils in Cuiping and Nan'an District were contaminated by Pb to a certain degree,particularly in industrial areas,commercial areas and busy roads.