基于多种方法的区域农业土壤重金属污染成因分析研究

Identifying the Source of Soil Heavy Metal Pollution in Regional Agricultural Area Based on Multiple Methods

土壤重金属污染问题日益突出,分析土壤重金属污染成因与来源对污染预防及风险管控具有重要的指导意义。选择珠江三角洲地区某农业土壤集中分布区域,综合采用相关分析、土壤剖面元素分布、同位素比值、主成分分析和正定矩阵因子分析等多种方法,开展了土壤重金属污染特征分析与源解析。结果表明,研究区表层土壤累积程度最高的重金属为Hg,其次为Cd和Zn,其平均含量分别为珠江三角洲区域土壤背景值的3.22、1.29和1.09倍,As、Pb、Cr、Ni、和Cu平均含量均低于区域背景值。土壤中Hg含量仅与Pb呈极显著正相关,两者呈现较强的同源性,在高含量分布区土壤剖面垂直方向的表层聚集特征明显,呈外源输入为主的特征。主成分分析与稳定性同位素比值法相结合能够进一步对研究区的主要污染元素Hg与Pb进行来源识别,土壤中Hg和Pb的累积与工业、交通等人为活动输入高度相关。采用正定矩阵因子分析法对重金属来源进行定量解析,结果表明,研究区土壤中Hg和Pb的累积主要来自于工业生产活动等人为源;土壤Cr和Ni主要为自然地质背景来源;Cd、Cu、Zn和As除自然地质背景来源外,还受到流域上游物质迁移沉积作用的影响。综合采用多种源解析方法开展区域农业土壤污染成因分析,能够通过方法间的相互结合与印证来提高分析结果的合理性和可靠性。

The problem of soil heavy metal pollution is becoming increasingly serious.Identifying the sources of soil heavy metal pollution has important guiding roles for pollution prevention and risk control.In this study,a concentrated distribution area of agricultural soils in the Pearl River Delta was selected to study the pollution characteristics and sources of heavy metals in soils by multiple methods including correlation analysis,elements distribution in soil profile,isotope ratio,principal component analysis and positive matrix factorization(PMF).The results show that the highest cumulative element in surface soil was Mercury(Hg),followed by Cadmium(Cd)and Zinc(Zn),and their average concentrations were 3.22,1.29 and 1.09 times of the regional soil background values of the Pearl River Delta,respectively.The average concentrations of Arsenic(As),Lead(Pb),Chromium(Cr),Nickel(Ni),and Copper(Cu)were lower than the regional background values.The concentration of Hg in soil was only significantly positively correlated only with Pb,showing that Hg and Pb had the same sources.The obvious characteristics of surface layer aggregation of Hg and Pb in soil profile indicate the exogenous input.The combination of principal component analysis and stable isotope ratio can further identify the sources of Hg and Pb,which was highly correlated with the input of human activities such as industry and transportation.The results of PMF show that the accumulation of Hg and Pb in the soils of the study area was mainly caused by artificial sources such as industrial activities,and Cr and Ni in the soils were mainly from natural geological background,and Cd,Cu,Zn and As were greatly affected by both material migration and deposition from the upper drainage basin and natural geological background.When analyzing the cause of regional agricultural soil pollution,the rationality and reliability of the analytical results can be improved by the mutual verification of the combination using of different methods.