湘西花垣矿区主要植物种类及优势植物重金属蓄积特征

矿区重金属污染严重,寻找和发现适合当地气候与土壤条件的重金属耐性植物是矿区植被恢复和污染土壤修复的前提.通过对湘西花垣县锰矿、铅锌矿区植被调查,共记录到高等植物76种,隶属69属,39科.对两矿区的主要优势植物及其土壤重金属含量进行了测定、分析,结果表明,两矿区土壤Pb、Zn、Cd含量均超过国家土壤环境质量二级标准阈值,对矿区土壤造成了污染.主要优势植物均能适应矿区土壤重金属元素较高的环境,对重金属具有一定的耐性,但不同植物对重金属的吸收和蓄积特征不同,油茶、芒萁吸收的重金属主要分布在地上部分,属于金属富集型植物,适于修复湘西矿区重金属污染中等且使用价值较高的污染土壤;灰白毛莓、山莓、毛萼莓、魁蒿、蕨吸收的重金属主要累积在根部,属于根部囤积型植物;芒草、白茅、箬竹、飞龙掌血根、茎、叶重金属含量均较低,属于重金属规避型植物.这2种类型的植物适合种植在湘西矿区重金属污染严重、使用价值相对较低、面积较大的矿山废弃地.

Bioaccumulation of Heavy Metals by the Dominant Plants Growing in Huayuan Manganese and Lead/Zinc Mineland, Xiangxi

Heavy metal pollution is a major environmental problem of mine wasteland. Finding out the tolerant plants, which can adapt to the local climate and the soil conditions, is the premise of vegetation restoration. An extensive vegetation survey and sampling were conducted in Huayuan Mn and Pb/Zn mineland, 76 species belonging to 69 genera and 39 families were recorded. The main dominant species and their associated soils were determined for heavy metal concentrations. The results showed that soil Pb, Zn and Cd levels exceeded the threshold levels of Class II of China Environmental Quality Standard for Soils, which suggested minesoils might be polluted by the three elements. The main dominant plants can adapt to the unfavorable edaphic conditions of mineland and were tolerant to heavy metals. There were great variations of metal uptake and accumulation among different plant species. They were classified into three types according to the metal concentrations in the plant shoots and roots: the accumulator, e.g. Camellia oleifera and Dicranopteris dichotoma, absorbed a large amount of heavy metals by the roots and transported to the shoots, which can be used to clean up the soils containing light to moderate toxic metal concentration and with high-value; the root compartment, e.g. Rubus tephrodes, R. corchorifolius, R. chroosepalus, Artemisia princeps and Pteridium aquilinum also absorbed a large amount of heavy metals but held in the roots; and the excluder, e.g. Miscanthus sinensis, Imperata cylindrica, Indocalamus tessellatus and Toddalia asiatica, absorbed less heavy metals than the accumulators. The root compartment and the excluder were more suitable for remediation of the mine wastelands with high heavy metal concentration, low-value and extensive area.