Study on phytoextraction of heavy metal contaminated soil by fast-growth willow (Salix spp.)

Abstract

Environmental contamination by heavy metals is increasing worldwide, particularly in semi-arid developing countries due to rapid industrialization. In this study, we focused on phytoextraction of heavy metals by fast growing willow. The objectives of the study are to clarify the growth properties under heavy metal conditions and to evaluate the potential of willow for phytoextraction. Cultivation tests were carried out hydroponically and on an actual polluted field. Four clones of the willow were used. Although there was a slightly negative relationship between Cd content in the solution of culture media and dry weight on hydroponic tests, Cd seldom significantly prevented growth of the plants. Cd concentration (mg･kg^-1) and Cd content in the plant (mg･plant^-1) increased with Cd content in the culture medium. The KKD clone of willow (Salix petsusu) showed the best growth, even when compared with previous studies. On the actual polluted fields, Cd uptake derived from Cd content multiplied by plant weight was the greatest in the FXM clone, S. pseudolinearis, which showed almost the same performance as in a previous study. Cd was concentrated in litter before defoliation, thus litter collection will show better performance for Cd phytoextraction by fast growing willow.