KINETICS + THERMODYNAMICS OF
One fundamental challenge in geochemistry is the two to five orders of magnitude apparent discrepancy between field and laboratory reaction rates. Without resolving this discrepancy, we will not be able to simulate quantitatively geological or environmental processes. Our laboratory experiments described here complement the field component mentioned under "Hydrogeochemistry and Water Resources."
One fundamental challenge in geochemistry is the two to five orders of magnitude apparent discrepancy between field and laboratory reaction rates.
Through experiments and modeling, I have demonstrated that the coupling of precipitation and dissolution reactions partly explains the apparent discrepancy. A network of reactions operates in most multi-mineral geological systems, and their reaction rates are interlocked through mass balance and rate equations. In addition, research that my collaborators and I have carried out has innovatively applied non-conventional silicon stable isotopes—whose analysis has only recently become routine with the advent of MC-ICP-MS technology-to- kinetics studies. We show that Si isotope doping allows precise measurements at ambient temperatures and near neutral pH that were not possible before. Currently, we are using Si isotopes to study borosilicate glasses and a number of silicate minerals. We are also developing methods to use Ca, Mg, Fe isotopes in kinetics studies of carbonates, sulfides, and oxides. The newly available rate data will allow us to decipher the reaction mechanisms and rate equations, further resolving the apparent field-lab discrepancy.