Dynamics of heavy metal(loid)s in mine soils

Mine sites can be a potential threat to public health due to the risk of polluting nearby groundwater and soils. During the early mining period, mining companies had less strict remediation codes than those in place now, and waste material was customarily disposed in heaps (tailings) in the direct vicinity of the mine (Johnson et al. 2016; Pascaud et al. 2015). Once the ore was exhausted, companies either closed down or moved out, many of them leaving their mining waste behind. These abandoned wastes are considered among the worst environmental problems and a serious hazard to ecosystems and human health (Anawar 2015; Fields 2003; Hudson-Edwards et al. 2011). Tailing deposits generated from mining activities pose a potential risk for the soil and aquatic environments through the release of potentially toxic metal(loid)s occurring in a variety of minerals present in the tailings (Anawar 2015; Hudson-Edwards et al. 2011). Heavy metal(loid)s include both biologically essential (e.g., cobalt [Co], copper [Cu], chromium [Cr], manganese [Mn], and zinc [Zn]) and nonessential (e.g., arsenic [As], cadmium [Cd], lead [Pb], and mercury [Hg]) elements. The nonessential elements are highly toxic; however, at excessive concentrations, both groups are toxic to plants, animals, and/or humans (Adriano 2001; Alloway 1990)