基于UNMIX模型和多元地统计模拟的土壤重金属的来源解析及空间预测

    Sources apportionment and spatial prediction of soil heavy metal pollution using UNMIX model and multivariate statistical simulation

    • 摘要: 为摸清江苏省太仓市土壤重金属来源和污染情况,开展土壤表层样品采集和重金属含量分析,选取新型受体(UNMIX)模型解析重金属的来源和贡献,并采用地累积指数和多元地统计技术,实现重金属污染的定量评价和空间预测。结果表明:1) As、Cd、Cr、Cu、Hg、Ni和Zn的含量较高,超过全国和江苏省土壤重金属背景值;Cd、Cu、Hg、Pb和Zn的富集程度较高,而As、Cr和Ni的富集系数正常,与自然基础水平相近。2) 8 种重金属元素呈现岛状的空间分布特征,并在部分区域存在高值区,表明人类活动对土壤环境具有负面效应。3) 土壤重金属受到交通-工业源、自然-农业源、工业-自然源和农业-工业源的综合影响,贡献率分别为35.18%、27.32%、20.26%和17.24%。其中Hg、Pb、Ni、Cu和Zn主要来源于交通-工业源,Cr、Zn和Cu主要源自自然-农业源,As和Ni主要为工业-自然源,Cd主要为农业-工业源。4) Cd、Hg和Ni,污染程度最高,60.38%以上的点位达到轻度污染及以上等级;As、Cu和Zn,污染居中;Cr和Pb的影响较低。5) Ni、Cd和Hg的污染面积最大,分别达到107.42、75.56和55.02 km2,且潜在污染空间成片分布。该研究作为土壤基础调查的核心,可为土壤环境管理和重金属污染修复提供科学依据。

       

      Abstract: This study aims to understand the sources and pollution of soil heavy metals. Taking Taicang City, Jiangsu Province as an example, the soil surface samples were collected to conduct the heavy metal content analysis. A novel receptor (UNMIX) model was selected to analyze the source and contribution of soil heavy metals. Geoaccumulation index and multivariate geostatistical techniques were used to quantitatively evaluate for the spatial prediction of heavy metal pollution. The results showed that: (1) The contents of As, Cd, Cr, Cu, Hg, Ni, and Zn were relatively high, exceeding the background values of soil heavy metals in the study area. The enrichment degree of Cd, Cu, Hg, Pb, and Zn was relatively high, while there were the normal enrichment coefficients of As, Cr, and Ni similar to the natural basic level. Except for Cr, the average content of the rest heavy metal elements exceeded the background values of soil heavy metals. The coefficients of variation for Cu and Zn were 0.60 and 0.64, respectively, indicating a high level of variation and a high skewness state. (2) The distribution trend of As and Pb gradually increased from west to east, with the highest content in Chengxiang and Ludu towns. The soil was mainly developed from basalt and metamorphic rocks, containing a certain amount of Ni element. There was the similar pattern of Cd, Cr, Cu, and Zn spatial distribution, where the high value areas were located in Shuangfeng Town and Chengxiang Town in the southwest. Overall, the high and low value areas of the eight heavy metal elements were distributed alternately with the island-like spatial feature, indicating the negative effects of human activities on the soil environment. (3) Soli heavy metals were comprehensively affected by transportation-industrial, natural-agricultural, industrial-natural, and agricultural-industrial sources, with the contribution rates of 35.18%, 27.32%, 20.26%, and 17.24%, respectively. Among them, Hg, Pb, Ni, Cu, and Zn were mainly from transportation-industrial sources, Cr, Zn, and Cu were from natural-agricultural sources, As and Ni were from industrial-natural sources, and Cd was from agricultural-industrial sources. (4) The ground accumulation index of Hg was ranked first among all elements with a mean of 1.12. A high degree of artificial accumulation of Hg was greatly influenced by non-natural factors. The elements with a ground accumulation index greater than 0 were Ni and Cd, with values of 0.68 and 0.42, respectively. The pollution levels of As, Cu, and Zn were in the middle. The soil condition was less affected by Cr and Pb. (5) The pollution areas of Ni, Cu, and Hg were the largest, reaching 107.42, 75.56, and 55.02 km2 respectively. The area of Cd pollution was 342 km2 (accounting for 8.6% of the total area) that distributed in industrial, tailings surrounding, and urban suburbs. The potential pollution space was distributed in patches, which should be given more attention. At the same time, it was also necessary to strictly prevent the expansion of Cr and Pb pollution space. This soil investigation can provide the scientific basis for the soil environmental management and heavy metal pollution remediation.

       

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