典型城市单元的土壤重金属溯源方法与实证研究

随着城市化进程的不断深入,土壤中重金属污染现状及其治理情况越来越受到重视,而查明污染源是有效治理污染的前提。源解析技术目前已广泛的应用于环境受体重金属来源解析实践中,总结了近年来土壤重金属成因分析的常用方法及原理,并提出了一种将多种方法相配合使用的方法体系。选取珠三角某市城郊农田作为研究对象,结果表明,Cd、Pb、Cu、Zn、As存在含量超过国家农用地筛选值的情况,其中Cd超标率高达60.1%。农业活动、工业生产、交通源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。正定矩阵因子分析法(PMF,Positive Matrix Factorization)模型模拟的Cd、Ni、Zn和Hg预测值与实测值线性拟合r~2均大于90%,其余元素r~2均大于60%,呈现出很好的相关性,满足研究需要。PMF模型和铅同位素比值法计算得到的交通及农业对土壤Pb累积的贡献率之和分别为86.0%和84.8%,PMF模型和物质流分析法计算得到的农业对土壤Cd的贡献率分别为86.7%和79.7%,结果均比较接近。结果表明正定矩阵因子法、同位素比值分析法,物质流分析法能很好的联用应用于土壤重金属源解析研究。

Source apportionment methods of soil heavy metals in typical urban units: an empirical study

With the deepening of urbanization, increasing attention has been paid to the status quo and control of heavy metal pollution in soil; however, identifying pollution sources is the premise of effective pollution control. Source analysis has been widely used to evaluate heavy metals in environmental receptors. In this paper, the common methods and principles of source analysis of soil heavy metals pollution in recent years are summarized, and a system combining various methods is proposed. A typical farmland in the Pearl River Delta was selected as a case area. The results indicated that (1) concentrations of Cd, Pb, Cu, Zn, and As in some soil samples were greater than the filter capacity of agricultural land according to the Soil Environmental Quality of China, especially cadmium, which reached 60.1%; and (2) the accumulation of heavy metals in soils was related to the overuse of fertilizers for industrial production, traffic pollution, and soil parent material. (3) The results of the correlation analysis implied that the r² values of Cd, Ni, Zn, and Hg were more than 90%, and the r² values of other heavy metals were more than 60%, which indicates that there were significant correlations between the values of the measured and predicted heavy metals. (4) The contribution rates of the sum of transportation and agriculture to soil Pb accumulation through the PMF model and Pb stable isotope ratio method were 86.0% and 84.8%, respectively. The contribution rates of agriculture to soil Cd through the PMF model and material flow analysis were 86.7% and 79.7%, respectively. (5) The results indicate that the positive matrix factor, isotope ratio analysis, and material flow analysis methods can be well combined to study the source of heavy metals in soil.