| In recent years, heavy metal pollution of soils has become a widespread problem. It originates from continuous exploitation of mineral resources, electronic waste, sewage sludge, and wide usage of fertilizers, herbicides and pesticides. An alternative and widely-used approach with great advantages over traditional methods is phytoremediation of soil heavy metals, which is cost-effective and ecologically friendly. It is important to choose the right phytoremediation strategy for each polluted area. Phytoremediation includes both phytoextraction (removal of metals from soil through hyperaccumulators) and phytostabilization (accumulation of metals into root tissue or precipitation in the root zone). In this study, plant species growing on lead-zinc mine tailing and their corresponding non-mining ecotypes were investigated for their potential phytostabilization of lead. The differences of accumulative ability and effective of physical and chemical charateristics of two ecotypes were analysed under pot experiment. The main results are as follow:1. Land contaminated by high level of heavy metals in mining area is urgent to be remediated. To find out the accumulator and tolerant plants is the premise of vegetation reconstruction. A field survey on soils and plants growing at the tailing in the Sanhe lead-zinc mining area was carried out. The concentrations of Pb and Zn in soil and 22 plant species which belong to 15 families were analyzed. The results showed that the soils have been polluted in varying degrees, and the highest concentration in the soil samples were dramatically higher than the national soil limitation values for plant growth. Among the tested plants, none of them can be hyperaccumulator and most of them were plant of exclusion. Especially for Athyrium wardii and Cyperus rotundus which can accumulate high Pb and Zn in roots (11086.7mg kg-1 and 7626.8mg kg-1; 4634.6 mg kg-1 and 5908.2 mg kg-1, respectively) and transfer few up to the shoots. Furthermore, those plants had strong tolerance to heavy metal contamination, which indicated that they could be useful for harnessing and rehabilitating contaminated soils by heavy metals in the future.2. Screening out plants that are hyper-tolerant to certain heavy metals plays a fundamental role in remediation of mine tailing. In this study, nine dominant plant species growing on lead-zinc mine tailing and their corresponding non-mining ecotypes were investigated for their potential phytostabilization of lead. Lead concentration in roots of these plants was higher than in shoots, and the highest concentrations of lead were found in A. wardii (L1):15542 and 10720 mg kg-1 in the early growth stage (May) and vigorous growth stage (August), respectively, which were 426 and 455 times higher than those of the non-mining ecotypes. Because of poor lead translocation ability, lead accumulation in roots reached as high as 42 mg per plant. Available lead in the rhizosphere soils of Athyrium wardii was 310 mg kg-1, which was 17 times higher than that of the non-rhizosphere soil. Lead concentrations of roots for the 9 mining ecotypes were positively correlated with available lead in the rhizosphere soils, whereas a negative correlation was observed in the non-mining ecotypes. These results suggest that A. wardii was the most promising candidate among the tested species for lead accumulation in roots, and it could be used for phytostabilization in lead-polluted soils.3. Lead (Pb) pollution poses great threats to human health and can trigger serious environmental consequences. Phytoremediation has been considered an environmentally-friendly means of removing Pb from an affected area. The A. wardii, a new plant with potential for phytostabilization of Pb, has been found by a survey of plant species in a mine tailing of lead-zinc in Yingjing county of Sichuan province in China. Thus the growth, Pb concentration and some physiological and biochemical characteristics of mining ecotypes (ME) and the non-mining ecotypes (NME) were analyzed and discussed by pot experiments of A. wardii with different concentrations of Pb(NO3)2 in tested soil during four weeks. The results show that the A. wardii is of a higher tolerance to excessive levels of Pb in the soils. There was a significant decrease (P<0.05) in shoot biomass under Pb treatments in both ecotypes, and the shoot biomass of ME was 1.5 times higher than that of NME. On the condition of 800 mg Pb kg-1 treatment, the concentration of Pb in shoots and roots of the ME was most high, and was 3.5 and 3.0 times higher than those of the NME, respectively. The chlorophyll a and chlorophyll b in the leaves of both ecotypes decreased with increasing Pb concentration. The trend of lipid peroxidation and membrane damage of the ME and NME gradually increased, but declined markedly at the highest Pb treatment of ME. The activities of superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT) were most high at the Pb concentration of 600 or 800 mg Pb kg-1 of ME, and then decreased. The higher tolerance to Pb displayed in the ME was due to greater shoot biomass, root concentration, chlorophyll content and activities of antioxidant enzymes than those of the NME. The ME also was of lower lipid peroxidation products and membrane permeability. Therefore, the mining ecotype of A. wardii has potential phytostabilization of Pb contaminated soils.
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