The availability of metal toxicants in nature is commonly controlled by reactions at mineral surfaces. Surface spectroscopies cannot easily determine rates of these reactions in situ and geochemists have poor models for ranking reactivities of oxygens at the surface of clays and other minerals. This research will contribute to a better understanding of the kinetics of surface reactions by determining the rates of oxygen-exchange in a dissolved Keggin molecule [Al13O4(OH)24(H2O)127+(aq)] that has structural features in common with the surface of important soil minerals. The molecule consists of AlO6 octahedra that share edges and a single AlO4 tetrahedron. 17O-NMR methods will be employed to determine the exchange rates of terminal waters and one hydroxyl site in the dissolved complex. These rates will then be used to estimate the reactivity of similar sites at monoatomic steps on some rock and soil minerals. Some of these reactions are elementary; that is, they proceed as written on the molecular scale and can be used to test theoretical models of surface reactivities
