苏南典型工农业交错区土壤铅富集特征及源解析——基于PCA-PMF方法

为阐明长江三角洲典型工农业交错区土壤中Pb富集特征以及污染源贡献,以常熟地区典型水稻土为研究对象,分析了该地区表层土壤和土壤剖面中Pb、Cu、Zn、Cd以及主量元素等的含量及Pb形态分布.结果显示,研究区表层土壤发生了显著的Pb富集,土壤Pb平均含量超出了当地水稻土Pb背景值近一倍,地学统计分析反映表层土壤Pb处于轻度污染水平.外源铅在土壤中主要以铁锰氧化态和残渣态存在.相对于表层土壤,深层土壤(20~60cm)具有较高的碳酸盐结合态Pb占比和残渣态Pb占比,以及较低的腐殖酸结合态Pb占比和铁锰氧化态Pb占比.主成分分析法(PCA)和正定矩阵因子分析法(PMF)分析结果均显示表层土壤Pb主要来自4种污染源:约42.8%继承于岩石风化的自然产物、15.5%来自于含Pb汽油等化石燃料燃烧排放(通过大气沉降形式输送到土壤等方式)、21.6%来自于电镀等有色金属冶炼的工业活动和20.1%的可能为地表其它混合源.PCA-PMF源解析方法所得结果能较好地解析土壤中重金属来源.

Characteristics of lead enrichment in the soil from a typical peri-urban agricultural area of the southern Jiangsu and source appointment based on the PCA-PMF method

On the basis of chemical sequential extraction, statistics, principal component analysis (PCA) and positive matrix factorization (PMF), we identified the characteristics of Pb distribution, pollution and sources in cropland soils of Renyang district of Changshu city, a typical industry-based peri-urban area in China. Pb presented significantly enrichment in the topsoil, and the mean concentration of topsoil Pb exceeded approximately one time of the local background value. The exogenous Pb in the topsoil was mainly bound to Fe/Mn oxides and residual fractions. Compared to the topsoil, the deeper soils presented the higher proportions of Pb bound to carbonates and residual Pb, but the lower proportions of Pb bound to Fe/Mn oxides and Pb bound to humus acid, respectively. PCA and PMF revealed four primary factors with the following contribution rates to Pb in the soil: natural geologic process (42.8%), exhaust from vehicle (leaded petrol) and combustion of fossil fuel which were delivered by atmospheric deposition (15.5%), industrial emissions involved the nonferrous metals such as electroplating (21.6%), and other mixed sources in the terrestrial geochemical process (20.1%). The results of the PCA and PMF methods used for source apportionment of Pb were in good agreement.