Acid/Base Account and Minesoils: A Review

Abstract

Generation of acidity from the oxidation of iron sulfides (FeS 2) is a common feature of geological materials exposed to the atmosphere by mining activities. Acid/base accounting (ABA) has been the primary method to evaluate the acid-or alkaline-potential of geological materials and to predict if weathering of these materials will have an adverse effect on terrestrial and aquatic environments. The ABA procedure has also been used to evaluate minesoils at different stages of weathering and, in some cases, to estimate lime requirements. Conflicting assessments of the methodology have been reported in the literature. The ABA is the fastest and easiest way to evaluate the acid-forming characteristics of overburden materials; however, accurate evaluations sometimes require that ABA data be examined in conjunction with additional sample information and results from other analytical procedures. The end use of ABA data, whether it be for minesoil evaluation or water quality prediction, will dictate the method's interpretive criteria. Reaction kinetics and stoichiometry may vary and are not clearly defined for all situations. There is an increasing awareness of the potential for interfering compounds, particularly siderite (FeC0 3), to be present in geological materials associated with coal mines. Hardrock mines, with possible mixed sulfide mineralogy, offer a challenge to the ABA, since acid generation may be caused by minerals other than pyrite. A combination of methods, static and kinetic, is appropriate to properly evaluate the presence of acid-forming materials.

Assessment of acid mine drainage formation using geochemical and static tests in Mutki (Bitlis, SE Turkey) mineralization area

“…The ABA is defined simply as the balance between the acid-production and acid-consumption properties of mine waste material (e.g., Smith et al, 1976;Skousen et al, 1987;Hossner and Brandt, 1997;Siddharth et al, 2002). It is used to make static measurements of acid mine drainage potential.…”