In a greenhouse experiment, plant growth and copper (Cu) and zinc (Zn) uptake by four Salix cultivars grown in Cu and Zn contaminated soils collected from a mining area in Finland were tested to assess their suitability for phytoextraction. The cultivars displayed tolerance to heavily contaminated soils throughout the experiment. After uptake, total mean Cu concentrations in the leaves, shoots and roots in all cultivars and treatments ranged from 163 to 474 mg kg-1 and mean Zn concentrations ranged from 776 to 1823 mg kg-1. Lime and wood ash addition increased dry biomass growth (25-43%), chlorophyll fluorescence (Fv/Fm) values (3-6%), the translocation factor (TF) (15-60% for Cu; 10-25% for Zn), the bio-concentration factor (BCF) (40-85% for Cu; 70-120% for Zn), and metal uptake (55-70% for Cu; 50-65% for Zn) compared to unamended treatment across all cultivars. The results revealed that Salix cultivars have the potential to take up and accumulate significant amounts of Cu and Zn. Cultivar Klara (Salix viminalis × S. schwerinii × S. dasyclados) was found to be the most effective cultivar for phytoextraction since it displayed greater dry biomass production, Fv/Fm, TF, BCF values and uptake percentage rates of Cu and Zn compared to the other three cultivars. This study indicates that further research is needed to clarify the wider phytoextraction capabilities of different Salix cultivars.
Keywords: Copper; Salix; phytoextraction; zinc.