湖南石门、冷水江、浏阳3个矿区的苎麻重金属含量及累积特征

对湖南省石门、冷水江、浏阳3个矿区土壤和苎麻体内重金属进行测定和分析。结果表明,石门雄黄矿区As污染严重,伴随Cd、Sb污染和轻微的Pb污染;冷水江锑矿区Sb为主要污染物,伴随Cd、As、Pb污染;浏阳七宝山矿区Cd污染严重,伴随Pb、Zn、Cu污染。15个采样点的苎麻群落生长繁茂,Sb和As在苎麻不同部位间的分布次序为叶片中含量最高,根茎中次之,其余重金属在部位间分布没有规律。所有采样点苎麻地上部的Cd含量比一般植物的Cd含量大2-10倍,As含量大9.9-147.5倍,Sb含量大1.2-338.4倍;Cd富集系数和转移系数最高值为2.07和3;As富集系数和转移系数最高值为1.04和12.42,Sb富集系数和转移系数最高值为1.91和9.04。3个矿区苎麻地上部生物量分别为3.47,14.3,15.7 t/hm²,地上部Cd、Pb、As、Sb、Zn和Cu的累积量分别高达0.11、1.17、0.72、7.97、6.71,1.69 kg/hm²,兼具一定的经济价值和观赏性,适合用作矿区重金属污染土壤的环境治理和修复。

Heavy metal concentrations and bioaccumulation of ramie(Boehmeria nivea) growing on 3 mining areas in Shimen,Lengshuijiang and Liuyang of Hunan Province

Metal mining and smelting have caused severe heavy metal pollution to the environment and have become a major threat to some local ecosystems in China. The eco-restoration is the first step for the seriously contaminated region. The plant species with high tolerance to heavy metals could be qualified for the eco-restoration. For the less contaminated land, culturing the economic crops is a candidate measure for safely reuse of the land, since economic crop could minimizes the potential hazard of bringing toxic metals into food chains, and with less uptake of contaminants safely utilization of the less contaminated region is the last step, and safely utilization of contaminated land. The application of these methods with the special species is a kind of phytoremediation techquies. The plant species with great biomass, high tolerance to heavy metal, and less uptake of contamninants have been explored as alternatives of phytoremediation in recent years. Ramie(Boehmeria nivea) is a promising plant species for the ecorestoration of mining land because it naturely distributed around many mine region in south China. Ramie has been cultivated for over 5 thousand years by Chinese people and thus also named "China grass". This species distributes from N19 to N39 in China. The aim of this study is to assess the potential of ramie for the phyto-remediating technique in the heavy metal polluted areas. Heavy metal concentrations in soil and ramie in 3 metal-contaminated sites of Hunan Provice(Shimen,Lengshuijiang and Liuyang) were measured. The results revealed that soil samples from realgar mine area(Shimen) were severely contaminated by As, accompanied with Cd, Sb and mild Pb contamination. Soil samples from antimony mine area(Lengshuijiang) were mainly contaminated by Sb, accompanied with Cd, As and Pb contamination. Soil samples from Qibao mountain area(Liuyang) were severely contaminated by Cd, acompanied with Pb, Zn and Cu contamination. The ramie communities are prosperous in the investigated areas. In these 3 sites, Cd, As, Sb concentration in ramie shoot were 2-10, 9.9-147.5, 1.2-338 times higher than that in other plant species respectively, while Pb, Zn and Cu concentrations in ramie shoot were not higher than those in other plant species because of lower concentrations in soil. And Sb, As concentrations in ramie leaves were higher than that in roots and stems. The distribution of other heavy metal elements among different parts of the plant did not show any regularity. Among these samples, the highest bioaccumulation factor(BF) and transfer factor(TF) of Cd were 2.07 and 3, those of Pb were 0.56 and 6.01, those of As were 1.04 and 12.42, those of Sb were 1.91 and 9.04, those of Zn were 0.19 and 1.40, and those of Cu were 0.06 and 0.98 respectively. The biomasses of ramie shoot from 3 metal-contaminated sites (Shimen,Lengshuijiang and Liuyang) reached 3.47,14.3 and 15.7 t/hm² respectively. The total accumulations of Cd, Pb, As, Sb, Zn and Cu in ramie shoot were up to 0.11, 1.17, 0.72, 7.97, 6.71 and 1.69 kg/hm^-2 respectively. Besides the above mentioned advantages, the ramie plant also has economic and aesthetic values and thus can be considered as a good candidate for phytoremediation of mining areas contaminated by multi heavy metals.