The role of the iron oxyhydroxides and efflorescent sulfates in remediation by natural attenuation of mining contaminated systems

Abstract

[Excerpt] Acid mine drainage (AMD) is a common problem associated with the weathering of metal sulfide wastes in abandoned mining areas, which can be rich in toxic metals and metalloids. The formation of secondary mineral phases such as iron oxyhydroxides, oxyhydroxysulfates, and efflorescent sulfates may be a natural attenuation process in mining soils because these minerals can scavenge potentially toxic elements (PTE). Typically formed by the evaporation (efflorescent salts) or precipitation (ochreous iron-rich oxyhydroxides) these minerals could be highly soluble and reactive. Therefore, their inventory and characterization are particularly important for predicting the cycles of retention or accumulation zones of PTE and acidity in mining systems. [...]