Phytoremediation of Cd and Ni Contaminated Wastewaters by Miscanthus

Phytoremediation, the use of vegetation for the decontamination of different matrices, is not a very expensive strategy and has been presented as an approach to restore or attenuate and stabilize wastewaters. In this context, this research work aims to study the phytoremediation response of three Miscanthus genotypes (two species - Miscanthus sinensis and Miscanthus floridulus, and a hybrid – Miscanthus × giganteus) to nickel and cadmium contaminated waters (2,0 mg Ni.dm-3 and 0,2 mg Cd.dm-3). Results show that the irrigation with wastewaters contaminated with Ni and Cd did not affect the productivity of the studied Miscanthus genotypes and that M. x giganteus and M. floridulus were more productive than M. sinensis. However, M. x giganteus, but not M. sinensis and M. floridulus showed a trend to a lower yield due to Cd contamination. Biomass obtained with Cd and Ni contaminated waters presented higher Cd and Ni content than biomass from control pots. Miscanthus-soil systems accomplished 98-99% removal of Cd and M. x giganteus and M. sinensis, 96-98% removal of Ni from wastewaters. M. floridulus, however, showed less phytoremediation potential concerning Ni removal from wastewater: only 58% Ni was removed by the biofilter system. Yet, an accumulation of Ni and Cd were observed in the topsoil due to the irrigation with the contaminated wastewaters, thus showing that irrigation with wastewaters should be clearly controlled in order to avoid negative impacts on the environment.