MINERAL DISSOLUTION KINETICS UNDER THE INFLUENCE OF MICROORGANISMS: A QUANTITATIVE EXPERIMENTAL APPROACH

The weathering of carbonates and alumino-silicates has been a primary focus of the geochemical community for years due to its importance in soil formation, groundwater pollution, waste management, geochemical cycles and carbon sequestration. Consequently, we have increased our understanding of the abiotic reaction kinetics of mineral dissolution even if some key issues are still unresolved. A new era began when the role of microbes in these geochemical processes began to be considered. However, consideration of microbial influences presents significant experimental challenges. While geochemists are accustomed to quantifying reaction rates and the parameters that determine reaction mechanisms, we have been confronted with the problem of developing strategies that allow in situ, real-time investigations with the capability of quantifying the ongoing processes. These techniques have to be non-invasive or at least non-destructive to the microorganisms interacting with the minerals. The introduction of vertical scanning interferometry (VSI) to the measurement of mineral (glass) surfaces and its capability of precisely quantifying surface-normal retreat (or advance) rates on a nanometer-scale (e.g., Luttge et al, 1999, 2002) provides a tool with large potential for the investigation of microbe-fluid-solid systems. By applying this technique, Luttge and Conrad (2002) have shown that at least under certain laboratory conditions a microorganism like Shewanella oneidensis MR-1 is capable of taking over the control of the dissolution reaction of calcite. Here we present new experimental results and a strategy that allows the quantification of microbe-mineral interactions in the presence of aqueous solutions.