日照市土壤重金属来源解析及环境风险评价

Sources Identification and Hazardous Risk Delineation of Heavy Metals Contamination in Rizhao City

选择日照市的东港区和岚山区为研究区，采集了445个0-20cm表层土壤样品，并测定了10种重金属元素的含量；采用多元统计和地统计分析，揭示了研究区土壤重金属污染的主要来源以及与土地利用、成土母质之间的关系，绘制了重金属的环境风险概率的空间分布图。结果表明：①As、Co、Cr和cu的平均值低于山东省东部地区土壤背景值，Cd、Hg、Mn、Ni、Pb和zn的平均值高于背景值，尤其是Cd、Hg的含量分别为背景值的1．85和1．38倍，土壤中重金属累积较为明显。②10种元素可被辩识出4个主成分（PCs），PCI（Co、Cr、Mn、Ni和Zn）和PC3（As、Cu）为自然源因子，PC2（Cd、Pb）为工农业及交通源因子，PC4（Hg）为工业源因子；其中Pb、zn在PCI和PC3上均有较大载荷，受地质背景和人类活动的共同控制。⑧Cd、Hg含量在不同的覆被类型有显著差异，在城镇建设用地的含量最高；Co、Cr、Cu、Mn和Ni在花岗岩和变质岩母质的含量高，与冲积与海积物母质有较大差异。④来自于同一主成分的元素及元素组合的环境风险空间格局与相应主成分插值结果基本一致，所有重金属综合环境风险的高值区在西部和东部呈点状分布，主要是由西部的高地质背景和东部的强烈人为干扰的综合作用造成的。

A total of 445 surface soils samples were collected at the nodes of a 2 ~ 2 km grid from Rizhao City and analyzed for 10 heavy metals （As, Cd, Co, Cr, Cu, Hg, Mn, Ni, Pb and Zn）. Sources of heavy metals pollutant and the differences of contents among various land use types and parent material were revealed by multivariate analysis; meanwhile, spatial distribution of hazardous risk from heavy metals contamination was given by geostatistics based on GIS. The results are shown as follows. （1） The mean concentrations of As, Co, Cr and Cu were lower than the background values （BV） in eastern Shandong Province, respectively; but those of Cd, Hg, Mn, Ni, Pb and Zn exceeded the BV, especially for Cd and Hg （1.85 and 1.38 times of BV, respectively）, indicating distinct accumulations of some heavy metals in soils of Rizhao City. （2） A total of I0 heavy metals could be classified as 4 Principal Components （PCs）, including PC1 （Co, Cr, Mn, Ni and Zn）, PC2 （Cd, Pb）, PC3 （As, Cu）, and PC4 （Hg）. PC1 and PC3 were the factors dominated by natural sources, PC2 represented the factors from industrial, agricultural and traffic sources, and PC4 was contributed by industrial sources. Pb and Zn with a high load in different PCs might originate from the mixed sources including anthropogenic and natural sources. （3） There were significant differences in Cd and Hg contents among various land cover types with the highest level in urban areas. The concentrations of Co, Cr, Cu, Mn and Ni in the soils from weathered granite and metamorphic rock were all higher than those in the soils from alluvial and marine deposits. （4） The single element, elements integration and the corresponding PC presented similar spatial patterns of hazardous risk. The high risk regions with comprehensive assessment on all elements were located in densely-populated urban areas and western study area, which was attributed to the higher geological background in the western part and strong human interference in the eastern part.