Mitigation of heavy metal contamination by organo-alkaline amendments and phytoremediation of abandoned mine sites

The research study investigates a remediation technique that combines phytoremediation with organo-alkaline amendments on a laboratory scale to address heavy metal contamination in waste from the Kettara mine in Marrakech, Morocco. The experiment involved pots filled with mine tailings mixed with various alkaline inorganic amendments (marble, snail shell, phosphate sludge), with and without organic amendments (sheep manure) in different combinations with <i>Tagetes erecta L.</i> (Aztec Marigold) culture. Key physicochemical parameters and trace metals (copper, lead, zinc) were measured in the tailings before and after treatment, and the metal content of the harvested plants was also analysed. The translocation factor (TF), bioconcentration factor (BCF), and enrichment coefficient (ECf) were evaluated. Results indicated that the initially extremely acidic pH of the tailings (1.23) was neutralised to 7.82 after treatment with alkaline inorganic amendments, enhancing plant viability in the pots. After rehabilitation, the concentrations of copper, zinc, and lead metals were significantly reduced, particularly with the combination of snail shell and phytoremediation, compared to mine tailings alone, which did not encourage any plant growth. Most extracted metals accumulate in the plant's roots, making <i>Tagetes erecta L.</i> (Aztec Marigold) a suitable candidate for phytostabilization of these contaminants.