Abstract
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.
Highlights
Morocco has a long-standing history and an important role in the mining trade due to the diversity of its mineral resources [1]
The results showed that phosphate mine waste (PW) presented high concentrations of Cu (118.14 ± 33.71 mg kg−1) and Zn (96.09 ± 11.23 mg kg−1), followed by Ni (21.10 ± 2.48 mg kg−1) and Cd (11.13 ± 1.96 mg kg−1), whereas As presented the lowest value at 9.61 ± 1.22 mg kg−1
According to Kabata-Pendias and Pendias [41], Kabata-Pendias [42], and Kloke et al [43], the threshold limit concentrations values (TLVs) range from 100 to 150 mg kg−1 for Cu, 300 mg kg−1 for Zn, 50 mg kg−1 for Ni, and 20 mg kg−1 for As. The concentrations of these trace elements (Cu, Zn, Ni, and As) present in PW do not exceed the level of the environmental quality standards, except for the concentration of Cd, which exceeded the TLV (3 mg kg−1), which can be considered as a potential source of surrounding environment contamination [43]
Summary
Morocco has a long-standing history and an important role in the mining trade due to the diversity of its mineral resources [1]. During open-pit mining, millions of tons of waste are removed to access the phosphate rocks; they are generally stripped off and set aside in storage facilities, or are placed in disposal areas, and become exposed to atmospheric phenomena [5,6]. The accumulation of these waste rocks negatively affects the neighboring environment by disrupting the balance of the ecosystem, damaging the esthetics of the landscape, and is a potential threat of the local population’s health given the cadmium concentration occurring in this material [4,7,8]. Research conducted by Hakkou et al [7,13], Bossé et al [12], Ouakibi et al [6], and Knidiri et al [15] showed the feasibility of using such material from an operating phosphate mine in the Gantour sedimentary basin (Morocco) to control acid mine drainage generated by coarse tailings from the Kettara mine
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