Phytoremediation of mining areas: An overview of application in lead- and zinc-contaminated soils

Abstract

The metals concentration in soils is connected with natural and anthropogenic factors. Mine activities, in particular, entail the release of metals into the environment, a large proportion of which are accumulated in soil. Different approaches can be considered for soil remediation. Physical and chemical technologies are well known and extensively applied, but can alter soil and landscape characteristics and entail high costs due to the wide areas involved. Conversely, phytoremediation has been universally considered as a cost-effective technique that permit to restore biological activity and physical structure of soil. Lead and zinc are among the most common contaminants in soils originated by mineral exploitation; both phytoextraction and phytostabilization can be applied in this case. On the basis of experimental results, phytoextraction of heavily polluted soils may require decades to reduce the residual metal concentration to acceptable levels. Therefore, taking into account the characteristics of mine areas, in particular size and level of contamination, phytostabilization seems the most preferable technique, while phytoextraction could be applied in those areas surrounding mine sites when soil contamination is limited. The use of amendments could enhance the process by improving the soil properties and assisting the plant growth. The identification of the ideal candidate for phytoremediation must be tailored on the individual mine site. Recently, greater attention is addressed to apply native plant species, which demonstrated a better tolerance to local conditions, and are preferable in comparison to introduced or invasive species in order to reduce possible impacts on the ecosystem.