The Studies On Phytoremediation Of Lead Tailing Leaching Liquid With Six Aquatic Plants And Their Tolerant Response

Six species of water plants, Iris pseudacorus L., Sagittaria sagittifolia L., Phragmites australis(Cav.) Trin. ex Steud, Eleocharis tuberosa S., Typha orientalis Pres. and Hydrocotyle vulgaris L. were selected as the materials to study the growth, physiological indexes and the phytoremediation of these species under the stress of Pb tailing leaching liquid(Pb L). The results are as follows:(1)The effects of Pb L on the growth, Pb accumulation and translocation of I. pseudacorus, S. sagittifolia, E. tuberosa, T. orientalis, P. Australis and H. vulgaris were studied by liquid culture. The results showed that analysis by synthesis of the plant height, root length,and the biomass of aboveground and underground parts of six species, S. sagittifolia, T. orientalis, P. australis and H. vulgaris were tolerant to higher portions of Pb L and the biomass of underground parts of them were not significantly different with the control(P<0.05). Pb contents of I. pseudacorus, S. sagittifolia, E. tuberosa and H. vulgaris were higher than other two species and the contents of Pb in aboveground parts were more than 60μg/g. The highest contents of Pb were found in the aboveground and underground parts of I. pseudacorus and the contents were 78.13μg/g, 115.63μg/g respectively. The values of translocation factors(TF) of Pb were lower than 1 and the TF of P. australis was highest. The results indicated that six species could be used to remediate the contaminated environment. I. pseudacorus and S. sagittifolia were desired species for the phytoremediation of Pb contaminated environment.(2)The effects of Pb L on the physiological indexes of six species were studied by liquid culture. Compared with control, S. sagittifolia and H. vulgaris’ s aboveground part and underground part of the electric conductivity were enhanced significantly. The MDA contents in aboveground and underground parts of E. tuberosa and H. vulgaris increased significantly. Pb L induced the activities of SOD and POD in the six species and the activities of S. sagittifolia were higher than other species. However, Pb L inhibited the production of As A and the contents of all species were lower than those of the control. The results indicated that six species have certain physiological tolerance to Pb L stress and SOD and POD in six aquatic species played an important role in resistance to Pb L stress.(3)The effects of different portions of Pb L on the leaf structure and the photosynthetic pigment contents were studied by liquid culture. Results showed that there was so little difference between 100% Pb L treatment and control and a large number of air hole cavities surrounding the main veins and the mesophyll cells were 4-6 layers in the leaves of S. sagittifolia. The leaf epidermal cells are arranged neatly and mesophyll cells of I. pseudacorus under Pb L treatment were 2 layer and no significant difference with control. There were a large number of chloroplasts in parenchyma cells in the leaf veins of I. pseudacorus of control, while, there were a little number of chloroplasts in parenchyma cells treated with Pb L. With the increase of Pb L portions, Chl.a, Chl.a, Cxc contents in two species decreased gradually as Pb L levels enhanced. Chl.a, Chl.a, Cxc contents of I. pseudacorus were 42%、45% and 51%, and S. sagittifolia were 53%、42% and 89%, respectively, of the control as treated with 100% Pb L. The results indicated that S. sagittifolia was more tolerant to Pb L than I. pseudacorus.(4)The effects of different portions of Pb L on the phytoremediation potential of I. pseudacorus and S. sagittifolia were researched by liquid culture. The results indicated the growth indexes of both species decreased gradually as the level of Pb L increased. Pb contents in the aboveground and underground parts of both species were gradually increased as Pb L portions increased and Pb contents in the aboveground parts of I. pseudacorus and S. sagittifolia were 149μg/g and 125μg/g, respectively. The TF values of both species were lower than 1. The cultivation of I. pseudacorus and S. sagittifolia on Pb concentration of the 100% Pb tailing leaching liquid medium were lower than original Pb tailing leaching liquid. After harvest, dissolved oxygen content and p H value of the cultivation liquids of S. sagittifolia were higher than in the liquids of cultivated I. pseudacorus. Electric conductivity values were markedly increased with the increase of concentration of Pb L and the electric conductivity value in 100% Pb L cultivated with I. pseudacorus was 4.4 times of the Pb L cultivated with S. sagittifolia. Results indicated that I. pseudacorus and S. sagittifolia have strong ability to adjust the DO, electric conductivity and p H of the solution for the growth, and these two species also accumulate a large amount Pb. Therefore, I. pseudacorus and S. sagittifolia could be used to the remediation of Pb L and Pb contaminated environment.