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 su perphosphate fertiliser. Poplar (Kawa and Argyle) and willow (Tangoio) clon es 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 (9-16 7 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, w ere also found to accumulate significant quantities (up to 209 mug g(-1)) o f 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 inc rease in uptake of Cd. However, two of the chelating agents (2 g kg(-1) EDT A 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 expe riments can be realised in the field, then a single crop of willows could r emove over 100 years worth of fertiliser-induced Cd contamination from past urelands.