高地球化学背景地区重金属污染分布特征及源解析研究

Distribution Characteristics and Enrichment Mechanisms of Heavy Metal Pollution in High Geochemical Background Areas

广西壮族自治区作为我国典型重金属高地球化学背景地区及有色金属重要产地,其土壤存在重金属污染问题。本研究结合随机森林模型、GIS技术和实地采样调查对广西不同地貌类型区域(峰丛喀斯特、峰林喀斯特、孤峰残山平原)中的土壤重金属含量特征及其富集特征进行综合分析对比,识别区域尺度高背景地区土壤重金属的地球化学特征。结果表明:在广西三种地貌类型中,土壤Cd、Hg、Pb、Zn的平均含量均高于广西背景值,其中Cd的平均含量为背景值的4.51倍,且样品中有27.2%的Cd、30.9%的Hg、65.5%的Pb和37.8%的Zn含量超出背景值。喀斯特地貌区的重金属高值区域与岩溶区高度重合,主要受到碳酸盐岩成土过程中的次生富集和金属氧化物吸附的影响。孤峰残山平原区域的重金属含量较低,未显示明显的高地球化学背景特征。研究区内人为工业活动和农业活动的复合作用对土壤中As和Cu的富集有显著贡献;采矿冶炼活动会对金属冶炼工业区周边土壤Cd、Zn有显著贡献;公路运输对附近土壤Hg的富集有显著贡献,铁路运输对土壤Cu的富集有显著贡献;城市活动对土壤Pb的富集有显著贡献。研究显示,广西地区土壤重金属污染具有明显的区域差异性,其中喀斯特地貌区域受高地球化学背景影响显著,重金属的富集主要由自然因素主导,但也受到多种人为活动的显著影响,尤其是在As、Cu、Cd、Zn、Hg和Pb等元素的分布上体现出复杂的成因机制。该研究不仅深化了对广西地区土壤重金属地球化学特征的理解,还为区域重金属污染防治提供了重要的科学依据。

As a region with a high geochemical background in heavy metals and a key source of non-ferrous metals in China,the Guangxi Zhuang Autonomous Region faces significant soil pollution challenges.In this study,we employed a random forest model,GIS technology,and field sampling surveys to comprehensively analyze and compare the heavy metal content in soil across different geomorphological types in Guangxi,including peaked karst,forest karst,and isolated peak residual mountain plains.Our findings reveal that the average concentrations of soil Cd,Hg,Pb and Zn were higher than Guangxi′s background values in all three landscape types.Notably,the average Cd concentration was 4.51 times the background value,with 27.2% of Cd,30.9% of Hg,65.5% of Pb,and 37.8% of Zn samples exceeding these values.High concentrations of heavy metals in the karst landscape areas significantly overlap with the karst regions,primarily due to secondary enrichment and the adsorption of metal oxides during carbonate rock soil formation.The Lone Peak Remnant Plain area exhibited lower heavy metal content without significant high geochemical background characteristics.The combined effects of human industrial and agricultural activities significantly contributed to the enrichment of As and Cu in the soil.Mining and smelting activities notably influenced Cd and Zn concentrations near industrial areas;road transport significantly contributed to Hg enrichment in nearby soils,while railway transport significantly influenced Cu enrichment;urban activities significantly contributed to Pb enrichment.This study highlights the pronounced regional variability of soil heavy metal pollution in Guangxi,where the karst landscape region is markedly influenced by high geochemical backgrounds.The enrichment of heavy metals is predominantly driven by natural factors,yet it is also significantly influenced by various anthropogenic activities,particularly affecting the distribution of elements such as As,Cu,Cd,Zn,Hg and Pb.This research not only enhances our understanding of the geochemical characteristics of soil heavy metals in Guangxi but also provides an essential scientific basis for the prevention and control of regional heavy metal pollution.