Phytoremediation Potential of Populus deltoides W. Bartram ex Marshall in Post-mining Watershed

Heavy metal (HM) contamination in mining-impacted watersheds poses a serious environmental challenge and necessitates effective and sustainable remediation strategies. This study evaluated the phytoremediation potential of Populus deltoides W. Bartram ex Marshall (P. deltoides) in a post-mining watershed in Tongling, Anhui Province, China, with a focus on the accumulation characteristics of Cd, Zn, Cu, Pb, and As. The results showed that the soils were heavily contaminated by HMs, particularly Cd, Pb, and As, while Cd exhibited pronounced spatial heterogeneity among sampling sites. HM concentrations in P. deltoides tissues decreased in the order of leaves > bark > roots > stems > branches, and Zn showed the highest overall concentration among the investigated metals. Bioconcentration factor (BCF) analysis indicated a strong enrichment capacity for Cd in leaves (BCF up to 10.01), limited uptake of Zn and Cu, and negligible accumulation of Pb and As. Over a 5-year rotation period, the mean HM accumulation per tree was highest for Zn (10.21 g tree⁻¹), followed by Cd (0.30 g tree⁻¹). According to the remediation cycle (RC) model, reducing soil Cd contamination by one pollution grade in lightly to moderately contaminated areas required up to 7.45 RCs, whereas achieving background levels required 10.41 RCs. Remediation of Zn-contaminated soils required even longer periods. Overall, these findings suggest that P. deltoides is a promising species for the long-term management of Cd- and Zn-contaminated soils through combined phytoextraction and phytostabilization, providing practical support for ecological restoration and environmental management in mining-affected watersheds.