Cadmium and lead uptake by Salix viminalis under modified Ca/Mg ratio.

The studies were focused on the influence of mutual changes in the ratio of calcium and magnesium in soil on the efficiency of cadmium and lead uptake and accumulation by Salix viminalis. In the environmental experiment the soil was modified according to the natural Ca/Mg ratio with the experimental groups 4:1 (physiological ratio), 20:1, and 1:10, and was characterized by the amounts of the most important elements (including heavy metals) and selected soil parameters. Efficiency of lead and cadmium accumulation was in the order of Ca/Mg ratios 1:10 > 4:1 > 20:1, and was higher in the shoots at 0.5 m height when compared to 0.1 m above the ground. Under Cd and Pb supplementation the level of both metals was 2-fold higher, while bioaccumulation factor values according to selected literature indicated weak accumulation. When the seasonal metal uptake was analysed (from April to October), the highest accumulation efficiency was observed in the first two periods (April to August) and was Ca/Mg ratio independent. Salix growth was restrained under 1:10 Ca/Mg ratio while it was stimulated under 20:1 ratio, which was opposite to the metal sorption. Summing up, increased calcium level in soil (20:1 Ca/Mg) resulted in limited sorption of heavy metals and stimulated biomass productivity. Under increased magnesium concentration (1:10 Ca/Mg) in relation to the natural 4:1 ratio the accumulation efficiency was the greatest but plant growth was inhibited.