Table 2.

Some examples of primary constraint factors in mine tailings in relation to revegetation feasibility

Mine waste	Physical and hydraulic constraints	Chemical constraints	References
Base metal mine tailings	Fine particle size (e.g. mostly <100 µm), high bulk density and mechanical compaction, lack of aggregation and macropores, slow to very slow hydraulic conductivity and poor water infiltration	pH conditions: acidic (e.g. 2–3), near neutral (e.g. 6·5–7·5) or alkaline (>8) (depending on calcite/pyrite ratio)	Bell and Jones, 1987; Dold and Fontbote, 2001; Shu et al., 2005; Conesa et al., 2007a; Smuda et al., 2008; Huang et al., 2011b
		High levels of soluble salts (e.g. Mg, Na, sulfate, chloride)
		High levels of total concentrations of metals, metalloids, etc.
		High levels of soluble metals and metalloids depending on pH
		Low cation exchange capacity, low total and/or available nutrients (such as N, P, micronutrients at alkaline pH)
		Lack of organic matter
Gold mine – heap leach residue and tailings	Porous (heap leach residue, variable with tailings), dispersive (due to high sodicity)	High pH (>8·5)	Lottermoser, 2010
		High levels of cyanides (complexes with metals, such as Pb, Cu and Zn) in soluble and solid phases
		High levels of metals, metalloids
		High sodium levels and sodicity
		Deficiencies of micronutrients (Mn, Zn, Cu, etc.)
		Lack of organic matter
Bauxite residue mud	Small particle size (mainly silt and clay) and high bulk density, high compaction and low hydraulic conductivity, highly dispersive due to high sodicity.	High pH (10–12)	Wong and Ho, 1993; Courtney and Timpson, 2005b; Ippolito et al., 2005; Wehr and Menzies, 2005; Woodard et al., 2008; Harris, 2009
		High salinity (dominated by NaCl) and sodicity
		High levels of Na and low levels of exchangeable K
		Poor nitrogen retention capacity due to the high pH and low organic matter
		Low availability of micronutrients (e.g. Mn, Zn and B)