Wild Plants for the Phytostabilization of Phosphate Mine Waste in Semi-Arid Environments: A Field Experiment

The management of mine waste has become an urgent issue, especially in semi-arid environments. In this context, and with an aim to inhibit the oxidation of the sulfide tailings of the abandoned mine of Kettara in Morocco, a store-and-release (SR) cover made of phosphate mine waste (PW) was implemented. In order to guarantee its long-term performance, phytostabilization by local wild plant species is currently the most effective and sustainable solution. This study aimed to assess the growth performance and phytostabilization efficiency of five local wild plant species to grow on the SR cover made of PW. A field experiment was conducted for two growing seasons (2018 and 2019), without amendments and with the minimum of human care. PW and the aboveground and belowground parts of the studied plant species were collected and analyzed for As, Cd, Cu, Ni, and Zn. The bioconcentration factor (BCF) and translocation factor (TF) were also calculated. Despite the hostile conditions of the mining environment, the five plant species showed promising growth performances as follows: Atriplex semibaccata > Vicia sativa > Launaea arborescens > Peganum harmala > Asparagus horridus. The five plants showed high accumulation capacity of the trace elements, with the highest concentrations in belowground tissue. Principal component analysis distinguished A. semibaccata as having a high concentration of Cu and As, while Asparagus horridus had higher concentrations of Cd and Zn. In contrast, P. harmala, V. sativa, and L. arborescens demonstrated affinity regarding Ni. According to the BCF (<1) and TF (<1), these plant species could be used as effective phytostabilizers of the studied trace elements. The present study showed that local wild plant species have a great potential for the phytostabilization of PW, and could ensure the long-term efficiency of SR cover.