Fly ash and lime-stabilized biosolid mixtures for mine spoil reclamation

Mining operations result in point source contamination, releasing high levels of trace elements in soils. Under such circumstances, soils are degraded and their ecological functions (nutrient cycling, water storage, microbial habitat, plant growth support, etc.) impaired. Soil contamination with trace elements affects soil quality and threatens the surrounding ecosystem, as surface and groundwater resources, flora and fauna, human health, and even air quality can be impacted (Fig. 10.1). Mining involves one of the greatest alterations of the landscape through human activity and acts, particularly with metals and in reserves-rich regions, as a major driver of anthropogenic land use and land surface change (Murguía, 2015; Sonter et al., 2014). Several thousands of historic and currently operating mines are scattered throughout the earth, with further estimates of around 0.4 × 106 km2 of land area disturbed by mining activities (Wijesekara et al., 2016a). Unfortunately, most of these areas have never been suitably reclaimed, thereby contributing to severe environmental consequences (Murguía, 2015; Wijesekara et al., 2016a). Mine spoils are waste materials from underground mining, quarries, or opencast excavations. Therefore, mine spoils are often considered as drastically disturbed, nutritionally, and microbiologically depleted habitats that need urgent restoration (Wijesekara et al., 2016a). Mine tailings represent a major component of mine spoils; “mine tailings” is a generic term, which refers to a range of matrices such as mixtures of crushed rock and processing fluids from mills, washeries, or concentrators that remain after the extraction of economic metals, minerals, mineral fuels, or coal from the mine resource. Generation and land disposal of waste materials such as mine tailings, oxidized wastes, fireclay, and mudstone are the main causes of land disturbance (Kossoff et al., 2014; Wijesekara et al., 2016a). Extraction of metals from sulfide minerals usually results in large amounts of tailings, which often contain potentially hazardous substances such as heavy metals in elevated concentration, causing contamination of soil, ground, and surface waters (Evangelou and Zhang, 1995). Heavy metal contamination has been one serious environmental problem in the vicinity of mine sites because of the discharge and dispersion of mine waste materials into the ecosystems (Bech et al., 2016; Wahsha et al., 2012)