Alteration of reactive mineral surfaces by ground water

Two different investigations of shallow sandy aquifers inform our thinking about the role of reactive iron minerals in hydrogeological systems. Ground water in a number of settings has been described as having elevated concentrations of dissolved iron in anoxic portions of contaminant plumes (e.g. Baedecker et al., 1993; Lyngkilde and Christensen, 1992), and the coupling of microbial reduction of Fe(III) to the degradation of organic compounds links the study of the biogeochemistry of iron to our desire to understand processes influencing contaminated aquifers. Questions about the transport and fate of reactive constituents in ground water are linked to the study of iron through recognition of the importance of sorption processes on sesquioxide mineral surfaces common in sedimentary aquifers limiting the migration of metals, anions, and bacteria. We have been grappling with questions related to the stability of iron mineral phases in contaminated aquifers and the role of Fe(III)- bearing minerals and grain coatings as sorption substrates