Study On Phytoremediation Of Eutrophic Waters And Removal Of Heavy Metal Copper By Vetiveria Zizanioides

The study investigated the remediation effect of eutrophic water by Vetiveria zizanioides under different nutritional environment, the absorption effect of heavy metal copper by Vetiveria zizanioides under different Cu2+concentrations, and the effect of polyaspartic acid (PASP) on the removal of N,P and the absorption of heavy metal copper.Vetiveria zizanioides had a good ability to adapt to high concentration of N, P. Vetiveria zizanioides grew well in different eutrophic waters. There was a positive correlation between fresh weight growth rate of plant, the content of N,P within the tissue of Vetiveria zizanioides and water eutrophication level. On the basis of mechanism study on nitrogen and phosphorus removal, it was found the NH4+-N was removed mainly by nitrification of microbe in waters, not by the adsorption of plant; Vetiveria zizanioides provided a good living environment for the nitrifying bacteria, and thus it provided favorable conditions for the removal of NO2--N. NO3--N was removed mainly by the assimilation of Vetiveria zizanioides, and TP was removed mainly by the interaction of Vetiveria zizanioides absorption, microbial transformation and phosphorus sorption and settlement.NH4+-N would be absorpted by Vetiveria zizanioides at first priority, because the maximum absorption rate (Vmax) and affinity (1/Km) of NH4+-N were higher than those of NO3---N.PASP could promote the growth of Vetiveria zizanioides and enhance photosynthesis of plants. The removal of TN was enhanced remarkably at 10 mg·L-1 of PASP. The removal of TP was considerably enhanced by PASP under different concentrations.Vetiveria zizanioides had better tolerance to heavy metal copper. With the increase of Cu2+concentration, the content of chlorophyll within the tissue of Vetiveria zizanioides decreased, and the content of malonic dialdehyde was higher than that of control group, indicating that Vetiveria zizanioides had been poisoned to some extent. The content of copper in leaves and roots of Vetiveria zizanioides had a positive correlation with the concentration of Cu2+in solution, and copper mainly concentrated in the roots of Vetiveria zizanioides. The Cu2+absorption of Vetiveria zizanioides was the process of fast sorption-release-slow metabolism absorption. PASP could promote the growth of Vetiveria zizanioides at low Cu2+ concentration, and alleviate the damage of Cu2+to the Vetiveria zizanioides tissue to some extent. After adding PASP, the copper content of the Vetiveria zizanioides roots increased a little, but the copper content of the Vetiveria zizanioides leaves had no significant change.