Natural and induced cadmium-accumulation in poplar and willow: Implications for phytoremediation

Potentially poplars and willows may be used for the in situ decontamination of soils polluted with Cd, such as pasturelands fertilised with Cd-rich superphosphate fertiliser. Poplar (Kawa and Argyle) and willow (Tangoio) clones were grown in soils containing a range (0.6-60.6 mug g(-1) dry soil) of Cd concentrations. The willow clone accumulated significantly more Cd (9-167 mug g(-1) dry matter) than the two poplar clones (6-75 mug g(-1)), which themselves were not significantly different. Poplar trees (Beaupre) sampled in situ from a contaminated site near the town of Auby, Northern France, were also found to accumulate significant quantities (up to 209 mug g(-1)) of Cd. The addition of chelating agents (0.5 and 2 g kg(-1) EDTA, 0.5 g kg(-1) DTPA and 0.5 g kg(-1)NTA) to poplar (Kawa) clones caused a temporary increase in uptake of Cd. However, two of the chelating agents (2 g kg(-1) EDTA and 0.5 g kg(-1) NTA) also resulted in a significant reduction in growth, as well as abscission of leaves. If the results obtained in these pot experiments can be realised in the field, then a single crop of willows could remove over 100 years worth of fertiliser-induced Cd contamination from pasturelands.