稀土尾矿区土壤重金属污染与优势植物累积特征

矿山废弃地不仅占用大量土地,而且还是严重的污染源,因此,矿山废弃地的生态恢复己成为一项紧迫而重要的研究课题。对广东省河源市和平县下车镇内的稀土矿区土壤的重金属污染情况进行调查,并对该区优势植物对重金属的富集特征进行分析,以期对稀土尾矿区的生态系统的恢复和重建提供理论依据。主要研究的3种植物分别是：马唐草（Digitaria sanguinalis）,香根草（Vetiveria zizanioides）,望江南（Cassia occidentalis）。采用原子吸收分光光度法测定稀土矿区废弃地土壤和植被中Mn、Pb、Zn的含量,并计算优势植物对重金属的生物富集系数BAC（Biological Accumulating Coefficient）和生物转移系数BTC（Biological Transfer Coefficient）。结果表明：研究区域的土壤中重金属含量Mn、Pb、Zn的平均含量均超出广东省土壤背景值和中国土壤背景值,土壤受Mn污染最严重,其次是Pb、Zn的污染。3种草本植物对于Pb的BAC和BTC均小于1,说明这3种植物对Pb的富集和运输能力都很弱。香根草对于Mn和Zn的BAC分别为0.9和0.4,小于1,BTC分别为3.7和1.1,大于1,说明香根草对Mn和Zn的富集能力不强,但吸收后的运输能力很强。马唐草和望江南2种植物对于Mn和Zn的BAC和BTC均大于1,说明它们对重金属Mn和Zn具有较强的吸收和转移能力,是Mn和Zn的超富集植物。马唐草覆盖率高,抗病虫能力强,可作为该矿区生态恢复的先锋植物,望江南可以间作种植。

Heavy metal contamination of soil and concentration of dominant plants in rare earth mine tailing area

The mining wastelands not only occupied vast land but also seriously polluted near environment. Therefore, ecological restoration of mine wastelands is an urgent and important research topic. A survey of the soils and analysis of dominant plants in rare earth mine tailing in Xiache Town, Heping County, Guangdong Province were conducted. Three main dominant plants Digitaria sanguinalis, Vetiveria zizanioides and Cassia occidentalis were found. The content of three heavy metals （Mn, Pb and Zn） in soil and 3 species of plants grown in rare earth mine tailing soil was measured with atomic absorption spectrophotometry. And the biological accumulating coefficient （BAC） and biological transfer coefficient （BTC） of these plants to heavy metals were further calculated. The results revealed that all the average contents of the three heavy metals in the soils of the mining area exceeded the background value in Guangdong Province and nationwide soil, showing that the soil of the rare earth mine tailing was seriously polluted by Mn, Pb and Zn. BAC and BTC of the three plants to Pb was less than 1, so these plants were not Pb hyperaccumulator. BAC of Vetiveria zizanioides to Mn and Zn was 0.9 and 0.4, and BTC of V. zizanioides to Mn and Zn was 3.7 and 1.1, respectively. BAC and BTC of Digitaria sanguinalis and Cassia occidentalis to Mn and Zn were all higher than 1, Showing that Digitaria sanguinalis and Cassia occidentalis could be used as pioneer plants for phytoremediation in rare earth mine tailing area.