大型垃圾焚烧厂周边土壤重金属含量水平、空间分布、来源及潜在生态风险评价

摘要

s:The contents of nine selected heavy metals (Cd, Pb, Hg, As, Cr, Cu, Ni, Zn, Co) were determined in the top soils surrounding a large municipal solid waste incinerator (MSWI) in the east of Pearl River Delta. Based on the analyses, the spatial distribution, possible sources and potential ecological risk of the metals were studied. The contents of Cd, Pb, Hg, As, Cr, Cu, Ni, Zn, Co in the top soils were (0.183±0.07) mg·kg-1, (34.8±18.7) mg·kg-1, (0.081±0.028) mg·kg-1, (11.5±9.1) mg·kg-1, (31.5±19.1) mg·kg-1, (17.6±12.3) mg·kg-1, (7.13±4.20) mg·kg-1, (82.4±44.2) mg·kg-1, (3.37±3.08) mg·kg-1, respectively. The mean contents of Hg and Zn were 1 and 2 times higher than their respective background values of Guangdong Province, respectively. Accompanied with Pearson's correlation, hierarchical cluster and principle component analysis, four groups of heavy metals with different spatial distribution were identified: Cr, Ni, Cu, Co originated from lithological sources, Pb, As, Zn were affected by both lithological and human sources (e.g. industrial, agricultural and traffic sources), Cd showed certain spatial correlation with the MSWI, and Hg was strongly related to the MSWI. The range of the potential ecological risk index (RI) of top soil is 51~269.79, of which 52.33% and 18.30% were from Hg and Cd, respectivley. The above results indicated that the unique pollution characteristics of Hg deserve serious attention in pollution monitoring in soils surrounding solid waste incinerator.%通过采集珠三角东部某市大型垃圾焚烧厂周边表层土壤样品，分析了各样品中 Cd、Pb、Hg、As、Cr、Cu、Ni、Zn和Co等9种重金属含量，研究了重金属的含量水平、空间分布、来源及潜在生态风险。结果表明，研究范围内表层土壤重金属含量分别为Cd(0.183±0.07) mg·kg-1、Pb(34.8±18.7) mg·kg-1、Hg(0.081±0.028) mg·kg-1、As(11.5±9.1) mg·kg-1、Cr(31.5±19.1) mg·kg-1、Cu(17.6±12.3) mg·kg-1、Ni(7.13±4.20) mg·kg-1、Zn(82.4±44.2) mg·kg-1、Co(3.37±3.08) mg·kg-1。其中，Hg和Zn的含量分别超出广东省土壤历史背景值1倍和2倍，其余重金属含量与背景值相差不大。综合空间分布特征分析、相关性分析、聚类分析和主成分分析的结果，可以将9种重金属分为4类。Cr、Ni、Cu、Co的分布特征极为相似，且相互之间有极显著相关性，结合聚类分析和主成分分析结果，其来源主要为土壤母质。As、Zn、Pb的空间分布特征具有一定相似性，但相关性分析和聚类分析显示元素间联系不紧密，结合主成分分析结果，其来源与土壤母质和多种人类活动污染有关。Cd 和 Hg的空间分布特征均显示这两种重金属与垃圾焚烧厂存在联系，Cd 与垃圾焚烧厂存在一定联系，而 Hg 与垃圾焚烧厂存在较强联系。潜在生态风险评价结果显示，该研究区域土壤重金属生态风险不高，多种重金属的综合潜在生态风险指数（RI）的范围为51~269.79，Hg和Cd对RI的贡献率相对较大，分别为52.33%和18.30%。研究表明，垃圾焚烧厂周边表层土壤Hg具有独特的环境污染特征，在垃圾焚烧厂周边的土壤重金属污染调查中，Hg污染应受到重点关注。