The potential use of Piptatherum miliaceum for the phytomanagement of mine tailings in semiarid areas: Role of soil fertility and plant competition

Phytomanagement in terms of phytostabilisation has been proposed as a suitable technique to decrease the environmental risks of metal(loid) enriched mine tailings. Nevertheless, at these sites some issues must be solved to assure the long-term establishment of vegetation (e.g. salinity, low fertility, metal(loid) phytotoxicity, etc.) The objective of this study was to assess the effects of the addition of a municipal solid waste on a mine tailings soil and on the growth and metal(loid) accumulation of a grass plant species (Piptatherum miliaceum). In addition, the effects of intra-specific interactions were evaluated. A pot experiment was performed during 8 months, including two soil treatments: the mine soil and its combination with municipal solid wastes. For each treatment, pots without plants, pots with one plant, and pots with two plants were arranged. The addition of municipal solid wastes improved the soil fertility and plant growth in the mine soil, but also increased the mobile fractions of Zn, Pb, Cd, Mn and Ni. Plants in the amended treatments showed better nutritional status (higher P and K). Stable isotope δ15N was associated to the better nutritional status, while δ13C and δ18O indicated higher photosynthetic efficiency and stomatal conductance in amended treatments. Although the accumulation in leaves of most metal(loid)s decreased with the municipal waste application, the concentrations in both treatments did not exceed toxic limits for fodder. There was an effect of intra-specific competition in plant growth, probably due to lack of nutrients in the mining soil or limited pots volume in the treatments with municipal waste

Phytoremediation using native plants

The unprecedented growth in industrialization has significantly increased pollution in the environment causing public health concerns. The remediation of various contaminated environmental matrices presents a global challenge. Phytoremediation using native plants can serve a dual purpose of site remediation and ecological restoration. Native plants provide an ideal residence for microbial community in their rhizosphere with enzymatic ability to accumulate, stabilize, biodegrade or volatilize various inorganic and organic contaminants. A case study that compared a native plant, Chromolaena odorata, from crude oil-polluted land in Nigeria against a referenced plant, Medicago sativa, for polycyclic aromatic hydrocarbons (PAHs) remediation is presented in this chapter. It was observed that the native plant thrived, tolerated and degraded PAHs better than the reference plant but with no significant difference in PAH degradation. The use of plants is well suited to its natural contaminated area and solar-driven, prevents erosion and eliminates secondary airborne and waterborne waste but with some challenges. Phytoremediation using native species may be effective and efficient than its non-native counterparts, and it is ecologically safer, cheaper, aesthetically pleasing, socially acceptable and easier to cultivate. Native plants in phytoremediation can be further enhanced and improved using molecular techniques to optimize the harvest time, reduce growth duration and increase biomass production and root depth