The potential of willow for remediation of heavy metal polluted calcareous urban soils.

Growth performance and heavy metal uptake by willow (Salix viminalis) from strongly and moderately polluted calcareous soils were investigated in field and growth chamber trials to assess the suitability of willow for phytoremediation. Field uptakes were 2-10 times higher than growth chamber uptakes. Despite high concentrations of cadmium (>/=80 mg/kg) and zinc (>/=3000 mg/kg) in leaves of willow grown on strongly polluted soil with up to 18 mgCd/kg, 1400 mgCu/kg, 500 mgPb/kg and 3300 mgZn/kg, it is unsuited on strongly polluted soils because of poor growth. However, willow proved promising on moderately polluted soils (2.5 mgCd/kg and 400 mgZn/kg), where it extracted 0.13% of total Cd and 0.29% of the total Zn per year probably representing the most mobile fraction. Cu and Pb are strongly fixed in calcareous soils.