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Lookup NU author(s): David Banks
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Minewater is a subset of groundwater, subject to broadly similar hydrochemical processes. In “normal” groundwaters, access to oxidising species is poor and acid-base reactions tend to dominate over oxidation reactions. Acid-base reactions such as carbonate dissolution and silicate hydrolysis consume protons and carbon dioxide, and release alkalinity and base cations. In mines, the atmospheric environment is rapidly introduced to the deep reducing geosphere (or vice versa in the case of mine waste deposits). This carries the possibility of intense and rapid oxidation of sulphide minerals such as pyrite, to such an extent that these acid-generating redox reactions may dominate over acid-base “neutralisation” reactions and result in the phenomenon of “acid rock drainage” (ARD). In ARD, a negative correlation is typically observed between pH and concentrations of many metals and metalloids, base cations and sulphate. This correlation is due to (i) genetic co-variation – generation of protons, sulphate and metals in sulphide weathering reactions, (ii) pH-dependent solubility of many ARD-related metals and (iii) low pH intensifying carbonate dissolution and silicate hydrolysis to release aluminium, silica and base cations. This paper examines the reactions involved in ARD generation and neutralisation, and attempts to clarify key concepts such as pH, Eh, alkalinity, acidity and equilibrium constants.
Author(s): Banks D
Editor(s): Prokop, G., Younger, P.L., Roehl, K.E.
Publication type: Conference Proceedings (inc. Abstract)
Publication status: Published
Conference Name: 2nd IMAGE-TRAIN Advanced Study Course "Gorundwater Management in Mining Areas"
Year of Conference: 2003
Pages: 17-44
Publisher: Umweltbundesamt, Vienna
URL: http://www.umweltbundesamt.at/fileadmin/site/publikationen/CP035.pdf
Series Title: Umweltbundesamt, Vienna, Conference Papers
