基于正定矩阵因子分析模型的城郊农田土壤重金属源解析

Source appointment of heavy metals in suburban farmland soils based on positive matrix factorization

选取南京城郊农田为研究对象,通过正定矩阵因子分析法(PMF)探究表层土壤重金属主要来源,将预测值和实测值进行线性拟合,讨论该方法的准确性,并利用Pb稳定同位素比值结果进行对比分析,进一步验证该方法的可行性.结果表明,农田表层土壤Cd、As、Hg、Pb、Cu、Zn和Cr的平均含量远远超过背景值,部分土壤样点Cd和Cu超过国家土壤环境质量标准的二级标准.常年大量施用肥料等农业投入品进行高强度农业活动、周边工业生产、交通污染和自然母质均对研究区土壤重金属的累积产生一定的贡献.PMF模型模拟的Cd、Hg和Cr预测值与实测值线性拟合r2均大于90%,其余元素r2均大于70%,呈现很好的相关性,满足研究需要.PMF模型和Pb稳定同位素比值法计算大气降尘对土壤Pb累积的贡献率分别为32.1%和36.8%,结果比较接近,表明PMF模型可以很好地应用于土壤重金属源解析研究.

A typical suburban farmland of Nanjing city was selected as a case area. Positive matrix factorization （PMF） model was applied to identify the main sources of heavy metals in the topsoils. Correlation between measured and predicted heavy metals were analyzed by Linear Regression in order to investigate the accuracy and feasibility of PMF model. The results were also compared with those obtained through Pb stable isotopic technique, which could further verify the PMF ones. The results indicated that： （1） Mean values of Cd, As, Hg, Pb, Cu, Zn, and Cr in farmland topsoils were greater than their respective soil background values in Nanjing. Concentrations of Cd and Cu in some soil samples were greater than the Grade II of the Standard according to the Soil Environmental Quality of China. （2） Accumulation of the heavy metals in soils were related to the overuse of fertilizers for agricultural production for several years, surrounding industrial production, traffic pollution, and soil parent material. （3） The results of the correlation analysis implied that r2values of Cd, Hg and Cr were more than 90%, besides the rZvalues of other heavy metals were more than 70%, which showed that there were significant correlation between the values of the measured and predicted heavy metals. （4） The contribution of atmospheric deposition to heavy metal accumulation in the soils through PMF model and Pb stable isotopic technique were 32.1% and 36.8%, respectively, which firmly verified that PMF model can be effectively applied to source apportionment of heavy metals in the soils.