上海宝山区农业用地土壤重金属空间分异规律及分布特征研究

SPATIAL VARIABILITY AND DISTRIBUTION OF HEAVY METALS IN SOIL OF BAOSHAN DISTRICT

利用地理信息系统(GIS)和地统计分析方法对宝山区农业用地土壤重金属(As,Cd,Cr,Hg,Pb)空间分异规律和分布特征进行研究.结果表明,区内农业用地土壤中5种重金属均表现为中等空间变异性;在全局趋势上,Cd为一次全局趋势,其余重金属元素都表现为二次趋势;5种元素在空间上均存在明显的方向效应;Cr,Hg和Pb具有强烈的空间相关性,As和Cd具有中等强度的空间相关性;5种重金属的空间变程由大到小分别为Hg,Pb,Cr,As和Cd.土壤重金属As,Cd,Cr,Hg和Pb平均含量分别为7.31mg.kg-1、0.24 mg.kg-1、107.89 mg.kg-1、0.15 mg.kg-1和38.54 mg.kg-1,分别是上海土壤背景值的0.80,1.81,1.44,1.43和1.51倍.宝山区南部农业用地土壤重金属污染程度普遍高于北部.从宝山区各镇农业用地土壤重金属污染看,Cr和Pb普遍污染严重,而基本不存在As污染.同期降尘污染调查表明,降尘重金属是本区土壤重金属污染的最重要来源.

Geographical information system（GIS） combined with geostatistics method was applied to reveal the spatial variability of heavy metals including As, Cd, Cr, Hg and Pb in soils of Baoshan district, Shanghai city. All heavy metal elements displayed modest spatial variability. For the global trend, Cd is a single function, and the other four heavy metal elements are dual funtions. All heavy metal elements have obvious directional effect. Cr, Hg and Pb have strong spatial correlation, whereas As and Cd have moderate spatial correlation. The spatial variation of all heavy metal elements is in the order of Hg, Pb, Cr, As and Cd. The average content of As, Cd, Cr, Hg and Pb are 7. 31, 0. 24, 107. 89, 0. 15 and 38.54 mg · kg-1 respectively, which are 0. 80, 1.44, 1.43 and 1.51 times that of the soil background value for Shanghai. The pollution level of agricultural soil in the southern area of baoshan is worse than the northern area. For the pollution level of heavy metals in every town, Cr and Pb pollution is serious, but As is not an issue. In the dustfall survey same period , heavy metals in the dusffall are the most important sources for soil in Baoshan district.