The reactions of water and hydrated cations and anions at mineral-water interfaces control many aspects of the natural environment, including the composition of natural waters, the sequestration and release of contaminants and nutrients, and the chemical weathering of minerals. We will discuss recent ambient-pressure XPS results on the initial reaction of water with environmentally important metal oxide surfaces [alpha-Fe2O3(0001) and Fe3O4(001)] as well as the interaction of these surfaces with environmentally important contaminant ions such as As(III) as studied by EXAFS spectroscopy and XPS. Particle size is another variable that affects chemical reactivity and this effect will be illustrated by results from a recent study of Zn(II) adsorption on ferrihydrite nanoparticles. In order to approach the complexity of natural systems, we will also present new synchrotron-based long period x-ray standing wave fluorescent yield (LP-XSW-FY) spectroscopy results on the competition between Zn(II) and Pb(II) for functional groups in thin films of microbial biofilm, humic acid, and polyacrylic acid and reactive sites on the alpha-Al2O3 (1-102) and (0001) and alpha-Fe2O3 (0001) surfaces on which these thin films have been deposited. Such �dirty� surfaces are the rule rather than the exception in many natural aquatic and soil environments, yet are typically neglected in laboratory studies of sorption reactions. We will conclude with perspectives on important problems remaining to be addressed in mineral-water interface chemistry.

Factors controlling chemical reactions at environmental interfaces

246th National Meeting (2013)

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