摘要
以喀斯特山区燃煤型电厂周边不同方向的土壤及农作物为研究对象，探讨了火电厂周边随距电厂水平方向、垂直剖面土壤中8种重金属总量及污染分布特征，并分析了土壤中重金属元素之间及其与pH、有机质的相关性。结果表明，与贵州省土壤背景值相比，土壤样品中除了Cd和Cr之外，其它元素均有不同程度的超标现象，以Hg元素的超标最为严重；土壤中大多数重金属元素主要以残渣态为主，而Cd主要以酸可提取态和可还原态存在，容易发生环境迁移；土壤剖面中重金属含量均表现为20-50 cm土层大于0-20 cm，土壤重金属在次表层出现富集现象。相关分析表明，除了Zn以外，其它元素间的相关关系较高，pH与土壤Hg、As、Cu元素之间存在正相关关系，有机质与As、Ni之间也存在着显著正相关，电厂不同方向上的pH变化与8种重金属含量变化的差异相一致。采用内梅罗综合污染指数法进行环境污染评价，发现电厂周围土壤中的重金属含量具有方向性，不同方向上的污染程度表现为正北〉西南〉东北〉东南〉西北〉正东。对比农业土壤采样点，森林土壤中的Hg、Pb和Ni含量明显较低，推测森林植被可能对电厂重金属的沉降有一定的减缓作用；电厂周边研究区内卷心菜的Hg、Pb、Ni元素的超标最为严重，而卷心菜对Cd元素的富集能力明显高于其它重金属。
Eight heavy metals （Hg, As, Pb, Cd, Cr, Cu, Zn and Ni） in soil and crop samples from different directions around the coal-fired power plant located in karst mountainous area were designed as the research object. The total concentrations and distribution characteristics of soil heavy metals in the horizontal and vertical distributions were also discussed, and the correlation between eight metals and pH and organic matter in soils were analyzed as well. The results showed that the majority contents of other elements in soils exceeded the permissible limit, while Cd and Cr were below the safe limit compared with soil background values of Guizhou province, and the pollution of Hg is most serious. The majority of the heavy metals are primarily kept in residual fractions, while Cd existed mainly in acid soluble and reducible factions. The concentrations of heavy metals in the 20-50 cm soil horizon were higher than those in the 0-20 cm soil horizon. In other words, these metals are inclined to accumulate in sub-surface soil. The results of correlation analysis showed that the correlations among seven heavy metals under study were significantly positive except for Zn. There are some positive correlations among pH and Hg, As and Cu of soil organic matter was positively related to As and Ni. The variation of soil pH values from different directions along this power plant were in agreement with those of eight heavy metals concentrations. The environmental pollution of heavy metals was evaluated by using Nemerow comprehensive pollution index method. Meanwhile, the pollution level in different directions was in the following order： north 〉 westsouth 〉 eastnorth 〉 eastsouth 〉 westnorth 〉 east. In addition, comparing with agricultural soil sampling sites, Hg, Pb and Ni contents in forest soils are significantly lower. It is speculated that forest vegetation may alleviative the deposition of these metals. In study region,Brassica oleracea Linnaeus var.capitata Linnaeus was main polluted by Hg, Pb, Ni and Cd, and it is also foundBrassica oleracea Linnaeus var. capitata Linnaeus presented a higher accumulating ability to Cd in comparison with other heavy metals under study.
出处
《生态环境学报》
CSCD
北大核心
2016年第5期893-902,共10页
Ecology and Environmental Sciences
基金
国家自然科学基金项目(21407031)
关键词
燃煤型电厂
重金属
土壤
污染特征
喀斯特山区
coal-fired power plant
heavy metals
soil
pollution characteristics
karst mountainous area
