Phytostabilization of store‐and‐release cover made with phosphate mine wastes in arid and semiarid climate using wild local plants

Abstract

AbstractTo limit the generation of acid mine drainage at the Kettara abandoned mine (KAM) located 35 km North‐North West of Marrakech, Morocco, a store‐and‐release (SR) system was constructed. The SR system made of two materials, the cover constituted by phosphate waste (PW) rock and lower layer was the coarse‐grained tailings of KAM. The lower layer restricted water in the interface and the stocked water during wet periods by the PW layer is released during dry ones. The objective of this study is to assess the phytostabilization ability of SR cover using local plants. Seeds of five wild local plants: Atriplex semibaccata R. Br., Peganum harmala L., Asparagus horridus L., Launaea arborescens (Batt.) Murb., and Vicia sativa L., were selected and planted. Pots experiment of phosphate mine wastes (PW) and PW amended with different ratios of compost and commercial peat. These pot experiments were performed in greenhouse conditions. The germination and growth parameters studied were germination percentage (GP), mean germination time (MGT), speed of germination (SG), epigeal height, and hypogeal length evolution. Cd, Ni, As, Cu, and Zn concentrations in substrates and in plant fractions were analyzed. The results obtained using 100% PW (PW100) as the highest GP (87.50%) were obtained for A. semibaccata R. Br., followed by V. sativa L. with GP (25.00%). The uppermost MGT results showed that A. semibaccata R. Br. (MGT = 4.39) and L. arborescens (Batt.) Murb. (MGT = 1.91), were the most suitable for the phosphate mine wastes. Concerning SG, the values obtained were 19.07 and 5.11, for A. semibaccata R. Br., and L. arborescens (Batt.) Murb., respectively. Regarding the epigeal and hypogeal length, respectively, the best values were obtained for A. semibaccata R. Br., and V. sativa L., with 40.70 cm and 13.73 cm for epigeal length and 20.97 cm and 82.67 cm for hypogeal length. The results obtained with different ratios of amendments showed that the application of 10% compost and 20% organic fertilizer, showed significantly higher germination index, hypogeal, and epigeal growth for A. semibaccata R. Br., V. sativa L., and L. arborescens (Batt.) Murb. The concentrations of the studied trace elements in selected plant fractions does not exceed domestic animal metal toxicity limits in any trial. The concentrations of these trace elements in plant hypogeal fractions were significantly (p < .05) higher than those of epigeal fractions. The transfer and bio‐concentration factors were <1 in all selected plants. According to these results, we can affirm that A. semibaccata R. Br., as a key species and that V. sativa L. and L. arborescens (Batt.) Murb. are also good candidates for the phytostabilization necessary for the SR cover.