Variations Among 19 Wetland Plant Species in the Uptake and Tolerance of Cd, Pb and Zn from Metal Polluted Water

Variations among 19 wetland plant species in the tolerance and uptake of Cd, Pb and Zn from wastewater were investigated. The results showed that there were obvious differences among the plant species in metal tolerance. In metal polluted water, plant biomass was significantly reduced for three species, but was significantly increased for three other species. The variation among 19 plant species in plant biomass was 37.7 times for the control, and 45.3 times for metal treatment. The variation among the plant species was 61.6 times for metal quantity accumulations, but only 8.6 times for metal concentrations. Plant metal accumulations correlated positively and significantly with plant biomass (r = 0.6114, P<0.01), and also with plant metal concentrations (r = 0.5329, P<0.05). 15.4 % of the metals added to the water was removed by one harvest of the plants (aboveground part). The results indicated that plants could play important roles for removing metals in constructed wetland. Selection of plant species for use in constructed wetland will influence considerably the removal efficiency and the function duration of wetland. The first index of selecting plant species for the treatment of metal polluted wastewater is biomass, and the second index is metal concentration in plant.