珠江三角洲冲积平原土壤重金属元素含量和来源解析

Occurrence and source identification of heavy metals in the alluvial soils of Pearl River Delta region, south China

利用全国地球化学基准计划在珠江三角洲地区的22个点位上采集的44件冲积平原土壤样品,分析了As、Cd、Cr、Cu、Hg、Ni、Pb、Zn等8个重金属元素的含量特征,并利用多元统计分析方法和铅同位素示踪技术研究了重金属元素的来源.结果表明,珠三角地区冲积平原土壤8个重金属元素含量均高于全国土壤背景值,Hg在表层土壤中显著富集,As、Cd、Cu、Pb、Zn在表层土壤的含量略高于深层土壤中含量,Cr、Ni在表层土壤和深层土壤中含量相当.因子分析结果显示,土壤Cu、Cr、Ni主要受地质背景控制,Zn、Cd的高含量既与地质背景有关,也受人类活动影响,As、Pb、Hg的异常则受人为活动影响较严重.富集因子法得出8个重金属元素受人类活动影响程度大小排序为:Hg>As>Cd>Cu>Pb>Zn>Cr>Ni,当深层土壤某元素有外源输入时,会导致其富集因子偏低.铅同位素示踪结果显示,表层土壤铅含量与^(206)Pb/^(207)Pb呈显著的负相关关系,根据二元混合模型推测表层土壤中有超过30%的外源铅输入.综合来看,珠三角地区冲积平原土壤Hg、Cd、As、Pb受到较为严重的人为污染.

Forty-four alluvial samples were collected at 22locations in the Pearl River Delta to study the distribution and sources of 8heavy metals with factor analysis,enrichment factor and lead isotopic tracing methods.The study showed that the concentrations of all heavy metals were enriched relative to the background value of soil of China and Guangdong Province.The concentrations of Cr and Ni were similar in top and deep soils,while the concentration of As,Cu,Zn,Cd,Pb in top soils were slightly elevated to deep soils,while the concentration of Hg was significantly enriched in the top soils.Factor analysis indicated that the concentration of Cu,Cr,Ni was mainly controlled by the natural conditions,and the anomalies of As,Pb,Hg were caused by anthropogenic contamination.In some cases,the high concentrations of Cd and Zn were controlled by both geological background and anthropogenic contamination.The results of enrichment factor analysis indicated that the pollution levels of 8heavy metals were Hg>As>Cd>Cu>Pb>Zn>Cr>Ni.The enrichment factor values would be low if the elements were enriched in deep soils.The scatter plot showed there was significantly negative correlation between Pb concentration and 206Pb/207Pb ratio.A binary comprehensive model show that at least 30%Pb in the top soils were derived from anthropogenic contamination.In conclusion,the study found that enhanced levels of Hg,Cd,As,Pb were due to contamination.