湖南柿竹园矿区土壤重金属含量及植物吸收特征

Heavy metal concentrations in soils and plants around Shizhuyuan mining area of Hu′nan Province

矿区重金属污染十分严重,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。对我国湖南柿竹园有色金属矿区调查发现,该地区选矿厂的重金属污染问题普遍比尾砂库严重。选矿厂土壤砷、镉、铅、锌严重超标,尾砂库周围也受到不同程度的重金属污染。土壤重金属胁迫效应影响着植物物种分布,选矿厂物种分布较少,相比之下尾砂库的植物多样性较为丰富。柿竹园矿区植物对重金属的吸收表现为富集型(如蜈蚣草Pteris Vittata L .和苎麻Boehmerianivea (L .) Gaud.)、根部囤积型(如攀倒甑Patrinia villosa和木贼Equisetum hyemale)和规避型(如蔓出卷柏Selaginelladavidii Franch和芒草Miscanthus sinensis Andlerss)等3种类型。

Land contaminated by high levels of heavy metals in mining area is urgent to be remidiated. To find out the tolerant plants, which can adapt to the local climate and the soil conditions, is the premise of vegetation reconstruction. Field survey was carried out in the Shizhuyuan mining area of Hunan Province, which is the national largest nonferrous mine in China. Fifteen soil samples and 72 samples of 48 plants were collected during the field surveys at 5 contaminated sites, including the Caishan Smelter, the Caishan Tailing Pond, the Muchang New Tailing Pond, the Muchang Old Tailing Pond and the Bailutang Tailing Pond. The concentrations of heavy metals in soils and plants, including As, Cu, Cd, Pb, and Zn, were analyzed. The results showed that the soil pollution in the metal smelter was more severe than that in the tailing area. The concentrations of As, Cd, Pb and Zn in all the soil samples collected from smelter sites were dramatically higher than the national soil limitation values for the plant growth (30 mg/kg, 1 mg/kg, 400 mg/kg, 500 mg/kg and 500 mg/kg). The highest concentrations in the soil samples of the smelter sites were 11,299 mg/kg, 236 mg/kg, 29,702 mg/kg and 24,333 (mg/kg,) respectively. Same as the smelter sites, the soil samples taken from all of the tailing ponds contained high concentrations of As, Cd, Cu, Pb and Zn as well. The diversity of the plant species might be influenced by the heavy metal existence in the soils. Owing to the high level of the heavy metal content in the soil of the metal smelter, less species of plants were found in this area than the plants in the tailing ponds. There were totally 48 species among 16 families recorded in the metal smelter and the tailing ponds, of which 13 species botanically belonged to the Compositae, and were the dominant components of the tailings flora. Eight species belonged to Pteridaceae were naturally colonizing this area. The uptake of heavy metals by the plants can be classified into three types according to the metal concentrations in the plant shoots and roots: the accumulator, eg. Pteris vittata L. and Boehmeria nivea (L.) Gaud., which absorbed a large amount of heavy metals by the roots and transported to shoot; the root compartment, eg. Patrinia villosa and Equisetum hiemale, which also absorbed a large amount of heavy metals but mainly held in the roots; and the excluder, eg. Selaginella davidii Franch and Miscanthus sinensis Andlerss, which absorbed less heavy metals than the accumulators.