Assisted Phytostabilization of Acidic Polymetallic Mine Tailings Using Marble Waste and Native Plant Citrullus colocynthis: Effect on Soil, Plant, and Metal Uptake

Abstract

This study aimed to assess the effectiveness of the phytostabilization ability of the native Moroccan plant Citrullus colocynthis on the neutralization of soil acidity and stabilization of metallic trace elements (MTEs) assisted by marble waste. Mine tailings (MT) collected from an abandoned polymetallic site were mixed with powdered marble (PM) using different mixing ratios (%): (MTPM25), (MTPM50), (MTPM75), and agricultural soil (AS) acting as the control. Seeds of C. colocynthis were selected and planted under greenhouse conditions. Growth parameters were measured, and the metal concentrations in substrates and plant tissues were analyzed. The greenhouse results revealed that the growth parameters of C. colocynthis in the experimental treatments were significantly (p≤0.05) lower than those in agricultural soil. The growth of C. colocynthis significantly (p≤0.05) decreased as the ratio of powdered marble increased. The greatest increase in plant biomass was observed in the MTPM25, followed by MTPM50 and MTPM75. Some phytotoxic effects on plants were observed in MPTM­75. The concentrations of Zn, Cu, Pb, and Cd in C. colocynthis roots were significantly (p≤0.05) higher than those of shoots, with maximum values of 112.98 mg kg-1, 201.3 mg kg-1, 201.2 mg kg-1, and 40.03 mg kg-1, respectively. This is a typical characteristic of accumulator plants and maybe one of the tolerance mechanisms. Plants in the experimental treatments were characterized by TF<1 and BCF<1, which indicate that C. colocynthis could be useful for phytostabilization strategies. Our study demonstrates that the phytostabilization by C. colocynthis assisted by powdered marble could represent a successful and environmentally friendly strategy to remediate acidic polymetallic sites.