| In this paper, the Polygonum capitatum Buch taked from copper mining sites at Baofeng (BF) and Liwu (LW) in Sichuan province was used to as material. We study growing response and accumulating characteristics of Polygonum capitatum Buch under single copper (Cu), lead (Pb) and cadmium (Cd) pollution. And block test was adopted to study the capability of remediating the polluted soil to providing scientific basis and the basic information for local ecological restoration. The result showed that:(1) The Polygonum capitatum Buch from the two sites could grow normally and did not show visible toxicity symptoms in leaves (withering and yellow spots) when Cu concentration was less than 2000 mg kg-1 under Cu treatment (0-2000 mg kg-1). The roots, plant heights, biomasses were decreased by the increasing Cu concentration in soil. The highest concentrations of Cu in the two sites were 1087.26 mg kg-1 and 746 mg kg-1 at the Cu level of 2000 mg kg-1 and 1000 mg kg-1, respectively. Furthermore, Cu accumulations in the two places reached maximum values of 0.387 mg and 0.886 mg when the Cu concentration in soil was 750 mg kg-1, respectively. Both of the BCFs and TFs were lower than 1.0, but most of the shoot concentrations were close to the threshold value for a Cu-hyperaccumulator.(2)The Polygonum capitatum Buch from two sites grew similarly under Pb treatment (0-2000 mg kg-1), and its growth was effected slightly when Pb concentration in soil was more than 1500 mg kg-1. Its root length, plant height and biomass peaked when Pb concentration in soil was 750 mg kg-1. In addition, all of them from LW were higher than that of BF. The root, shoot concentration and shoot accumulation were increased with the increasing Pb concentration in soil (P<0.01). The Pb concentration in shoot exceeded 1000 mg kg-1 when the Pb concentration was more than 1000 and 500 mg kg-1 from the two sites. The largest Pb concentrations of these areas were 2694.33mg kg-1 and 2783.03 mg kg-1. The highest shoot accumulations of Pb in the BF and LW were 1.102 mg and 5.323 mg, respectively, when the Pb concentrations reached 2000 mg kg-1. The BCFs in shoot from the LW were larger than 1.0, but most of them from the BF were not. All of these indicated that this plant had great tolerance to absorb and accumulate of Pb. (3) The Polygonum capitatum Buch from the two sites were damaged deeply with the increasing concentration under Cd treatment (0-200 mg kg-1) and the plants became death when the Cd concentration was higher than 150 mg kg-1.The root lengths, plan heights and biomasses were decreasing by the increasing Cd concentration in soil and these from LW were all higer than that from BF. The root and shoot contents of the plants from BF and LW increased with Cd concentration in soil increasing. When soil Cd concentrations were higher than 25 mg kg-1 and 175 mg kg-1, the shoot contents from BF and LW were all higher than 100 mg kg-1 and the maximum were 138.97 mg kg-1 and 328.82 mg kg-1 respectively. Cd accumulations in shoot from BF and LW peaked at 0.0794 mg and 0.0583 mg when Cd concentration in soil was 25 mg kg-1 and 50 mg kg-1, which were BCFs and TFs in the two places were higher than 1 except TFs from LW, which indicated that Polygonum capitatum Buch had basic characteristics of hyper-accumulator and could govern the Cd polluted soil.(4) The field plot experiment showed that the order of the Cu, Pb and Cd concentration in Polygonum capitatum Buch is root>leaf>stem>follower, and the three heavy metals concentration in shoots were increased with the increase of the three heavy metals concentration in soil with the highest concentration of 498.82 mg kg-1,19.37 mg kg-1,472 mg kg-1 respectively. The maximum values of BCFs and TFs in the shoot of the Cu,Pb and Cd were 0.52,0.93,1.06 and 0.36,0.82,0.78, respectively, which suggested that the plant has a relatively strong ability of absorbtion and translocation. The Polygonum capitatum Buch were harvested 4 times in one year. In this way, the 10.096 kg ha-1 of Cu, 0.364 kg ha-1 of Pb and 0.168 kg ha-1 of Cd in soil were removed in one year, which showed that the effect of remediation is good.(5) In summary, The Polygonum capitatum Buch from two sites had a strong uptake and accumulation of Cu,Pb and Cd, which had well restoration to the mine soil. Therefore, The Polygonum capitatum Buch has good potential and value in treatment of Cu/Pb/Cd contaminated soil. |
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