Strategies of cadmium and copper uptake and translocation in different plant species growing near an E-waste dismantling site at Wenling, China

This study aimed to explore the interactions between cadmium (Cd) and copper (Cu) during uptake and translocation in plants growing in soil polluted with heavy metals derived from electronic waste (E-waste). We collected the roots, stems, leaves, and root-surrounding soils of ten dominant plant species growing in farmland near an E-waste dismantling site, and analyzed their Cd and Cu concentrations. Among the ten plant species, Echinochloa crus-galli (L.) P. Beauv., Cucurbita moschata (Duch. ex Lam.) Duch. ex Poiret, Phragmites australis (Cav.) Trin. ex Steud., and Benincasa hispida (Thunb.) Cogn. accumulated Cd (2.40-4.56 mg kg(-1)) and Cu (19.60-35.21 mg kg(-1)) in the roots. In Polygonum hydropiper L. and Sesbania cannabina (Retz.) Poir., the Cd (0.50-0.81 mg kg(-1)) and Cu (11.04-15.55 mg kg(-1)) concentrations were similar among the three organs. Glycine max (L.) Merr. accumulated more Cu in the roots (16.42 mg kg(-1)) than in the stems (5.61 mg kg(-1)) and leaves (7.75 mg kg(-1)), and accumulated Cd at similar levels in the three organs (0.65-0.99 mg kg(-1)). Sesamum indicum L., Bidens pilosa L., and Solidago decurrens Lour. accumulated Cd at similar levels among the three organs (0.16-3.34 mg kg(-1)) and accumulated less Cu in the stems (6.89-8.28 mg kg(-1)) than in the roots (12.61-21.63 mg kg(-1)) and leaves (12.93-22.38 mg kg(-1)). S. indicum had a stronger capacity to accumulate and translocate Cd and Cu according to transfer coefficient and translocation factor. The concentrations of Cd and Cu in soils were significantly positively correlated with those in the roots (p<0.01) but not those in the stems and leaves. We detected significantly positive correlations between Cd and Cu concentrations in the roots and leaves (p<0.01) but not in the stems. These results suggest that there is a synergetic strategy of Cd and Cu transport from soils to the roots and from the roots to the leaves, while the stems may not be the key organ controlling Cd and Cu transport in plants. These findings have important implications for the phytoremediation of soils contaminated with Cd and Cu, the mechanisms of plant Cd and Cu transport, and the food safety of agricultural products.