First Evaluation of Metal Contamination and Phytoremediation Potential in Wastes from Mine Tailings Retreatment in Touissit, Morocco

Abstract Mining activities pose environmental challenges, particularly in the management of mine tailings. This study evaluates metal contamination in wastes generated during the retreatment of mine tailings for residual lead (Pb) recovery. Physicochemical and biological analyses were conducted on mine tailings (Mt), muddy wastes (Mw), and sandy wastes (Sw). Among the waste types, Mw exhibited the highest organic matter (7.4%) and clay content. The retreatment process led to shifts in metal concentrations, particularly for Pb, with total levels increasing in Mw (12.4 g·kg⁻¹). However, calcium chloride extraction indicated that Pb was more bioavailable in Sw (8.15 mg·kg⁻¹) than in Mw (5.88 mg·kg⁻¹). Sequential extraction analysis identified Mw as the most contaminated waste, displaying the highest exchangeable Pb (41.24%) and Cu (21.87%), while Zn mobility was similar in Mw (7.69%) and Sw (8.20%). The mobility factor (MF) further highlighted the environmental risks, with Mw exhibiting greater metal mobility. Enzymatic activity assessments indicated a decline in soil quality due to elevated metal concentrations. Plant surveys revealed that vegetation was primarily restricted to the clay-rich Mw, where species diversity was low and dominated by Asteraceae, Amaranthaceae, and Poaceae families. Metal analysis in rhizospheric soil and plant organs identified potential metal accumulators and hyperaccumulators. Bioaccumulation (BCF) and translocation (TF) factors highlighted distinct phytoremediation potentials, with Atractylis gummifera and Rhaponticum acaule emerging as promising hyperaccumulators. These findings provide valuable insights into metal speciation, soil contamination, and plant adaptation in newly generated wastes, supporting phytoremediation as a potential strategy for contaminant mitigation.