9628023 Hochella The proposed research continues long-standing research committed to rethinking, and sometimes reformulating, perceptions of how mineral surfaces communicate with their geologic environment. The specific objectives are: (1) To show that sophisticated mineral surface investigations can be performed on natural mineral surfaces instead of only surfaces created by fracture. (2) To probe electronic structure of different sites on unreacted hematite, pyrite, and pyrrhotite surfaces at the atomic level. (3) To probe the electronic structure of reaction products on these surfaces at the atomic level. (4) To characterize complex surface reaction sequences, and to specifically define "reactive surface area" for a given reaction on a given mineral surface. (5) To incorporate newly identified fundamental reaction mechanisms and processes into kinetic models that describe macroscopic observables. The methods that will be employed include: experimental ultra-high vacuum scanning tunneling microscopy and spectroscopy, calculation of tunneling images and spectra at the ab initio level, ultra-violet and x-ray photoelectron spectroscopy, low energy electron diffraction, scanning force microscopy and standard wet chemistry techniques. The significance of the proposed research is in its ability to determine fundamental reaction parameters and mechanisms.
