摘要
[研究目的]查清滇中中高山丘陵区土壤重金属地球化学特征及驱动机制,服务于高原特色农业发展和乡村振兴战略的实施.[研究方法]以滇中大姚县、姚安县和南华县为研究区,依据 1∶25万土地质量地球化学调查数据,采用地统计学分析土壤重金属来源、空间分布格局及驱动机制,建立滇中中高山丘陵区土壤重金属表生地球化学过程驱动模式.[研究结果]研究区表层土壤中Cd、Hg含量均值高于深层土壤背景值,Cr、Ni高于云南省土壤背景值,除As、Hg、Sb外的其他重金属显著高于全国土壤背景值,局部地区土壤可能存在As、Cd、Pb生态风险.构建的最小数据集的元素为As、Co、Cr、TFe、Ni、Pb、Sb、Sn、V、Zn,莫兰指数显示均具有显著的正空间自相关性.空间分布特征呈现变质岩和侵入岩重金属含量高、碎屑岩和第四系冲积物含量低的特点.多元统计分析与重金属空间分布特征表明Co、Cr、TFe、Mn、Ni、V主要来源于成土母质,As、Sb、Sn受原生地层与成矿地质背景影响较大,Cd、Pb、Zn主要受工矿活动等人类活动影响.[结论]重金属元素的分布与地层分布高度耦合,地质背景控制了表层土壤重金属的空间分布格局,不同土壤类型和土地利用类型土壤重金属含量显著差异.岩石风化作用驱动了重金属的垂向迁移和富集,重金属含量与高程呈显著的多项式线性拟合趋势,有机质和pH是不同高程区间控制重金属行为的主控因素.研究区强烈的表生地球化学作用重塑了重金属的宏观分布,受自身化学性质的制约以及环境条件(坡度、pH、有机质等)的影响在土壤中发生分配、迁移、富集,人类活动影响了局部重金属的分布格局.
Abstract
This paper is the result of environmental geological survey engineering.[Objective]The investigation of the geochemical behavior of heavy metals in the surface geochemical process has important guiding significance for the construction of life community of mountains,rivers,forests,fields,lakes and grasses.The purpose of this study is to investigate the geochemical behavior and driving mechanism of soil heavy metals in the middle-alpine hilly region of southwest China.It will serve the implementation of the strategy of plateau characteristic agricultural development and rural revitalization.[Methods]Based on 1∶250000 land quality geochemical survey data in Dayao County,Yao'an County and Nanhua County in central Yunnan Province,the source,spatial distribution pattern and driving mechanism of soil heavy metals were analyzed by geostatistics,and the driving model of soil epigenetic geochemical process of heavy metals was established in the middle-alpine hilly region of southwest China.[Results]The results showed that the average content of Cd and Hg in the surface soil in the study area was higher than the background value of the deep soil,Cr and Ni were higher than the background value of the soil in Yunnan province,and other heavy metals except As,Hg and Sb were significantly higher than the national background value of the soil,and local soil may have ecological risks of As,Cd and Pb.The elements of the constructed minimum dataset are As,Co,Cr,TFe,Ni,Pb,Sb,Sn,V and Zn,and the Moran index shows significant positive spatial autocorrelation.The spatial distribution features high content of heavy metals in metamorphic rocks and intrusive rocks,low content of clastic rocks and quaternary alluvium.Multivariate statistical analysis and spatial distribution characteristics of heavy metals show that Co,Cr,TFe,Mn,Ni and V mainly come from the parent material,As,Sb and Sn are greatly affected by the primary strata and metallogenic geological background,Cd,Pb and Zn are mainly affected by human activities such as industrial and mining activities.[Conclusions]The distribution of heavy metals is highly coupled with the ground distribution.The spatial distribution pattern of heavy metals in surface soil is controlled by geological background,and the content of heavy metals in soil varies significantly among different soil types and land use types.The vertical migration and enrichment of heavy metals are driven by rock weathering,and the heavy metal content and elevation show a significant polynomial linear fitting trend.Organic matter and pH are the main factors controlling the heavy metal behavior at different elevation intervals.Strong epigenetic geochemistry in the study area reshaped the macroscopic distribution of heavy metals.Restricted by their own chemical properties and influenced by environmental conditions(slope,pH,organic matter,etc.),distribution,migration and enrichment of heavy metals occurred in the soil.Human activities affected the distribution pattern of local heavy metals.
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