广西锰矿区废弃地优势植物重金属含量及富集特征

Heavy Metal Concentrations of Dominant Plants and Bioaccumulation in Three Manganese Mine Wastelands, Guangxi

调查了广西全州、板苏、下雷3个锰矿区废弃地植物,并对20种主要优势植物及其土壤重金属含量进行了对比分析。结果表明,3锰矿区土壤中Mn、Cd是主要的污染因子。矿区植物体内的Mn含量较高;商陆、油茶表现出很强的Mn累积特征,是Mn污染土壤植物修复的理想物种;芦竹是矿渣堆、尾矿坝等严重污染区良好的恢复植物;五节芒、飞蓬对重金属有很强的耐性,在贫瘠、干旱环境下生长良好,可作为废弃地早期恢复的先锋种。优势植物对土壤重金属元素的富集能力普遍较低,部分植物对特定金属元素的转移能力较强。板苏矿区种植的玉米、木薯食用部分重金属含量不符合食品安全限量标准,因此不宜在废弃地恢复早期采用农业利用恢复模式。

Heavy metal contamination of metal-mined wasteland is an overlooked problem in China, and Guangxi, the largest Mn-ore mining region, has vast areas of minelands awaiting restoration. An extensive ecological survey and sampling were conducted on Quanzhou, Bansu and Xialei manganese mine wastelands in Guangxi. Soils and twenty dominant plants were determined for the heavy metal concentrations （Cu, Cr, Cd, pb, Zn and Mn ）. The results showed that Cd and Mn were the main contaminants of the minesoils. Among the three wastelands, Quanzhou minesoil was most seriously polluted by Mn. Heavy metal levels in the mineland plants were generally in the order of Mn〉Zn〉Cr〉 Cu〉Pb〉Cd, consistent with the trend of metal concentrations in minesoils. The Mn contents in the plant tissues were usually higher than normal. Phytolacca acinosa and Camellia sinensis exhibited very strong Mn accumulation characteristics, suitable for use in phytoremediation of manganese-contaminated soils;Arundo donax may be used as a good stabilizer for the loose slag dumps and tailings dams;Miscanthus floridulus and Erigeron acer are metal-tolerant grass species and resistant to drought and inadequacy of nutrients, thus can be used as pioneer plants for revegetation of manganese-mine wastelands. The dominant plants usually had low bioaceumulation of metals in tissues, but some species （e.g. Phytolacca acinosa） had very high transfer ability for particular metals （e.g. Cd, Cr and Mn）. The edible parts of corn and cassava grown in Bansu mineland failed tO satisfy the Maximum Allowable Levels for Food Safety Standards of China, thus agricultural utilization as a restoration prototype for reclaiming mine wasteland at early stage is not recommended.