Random Rate Models for Age Dependence in Precipitation and Dissolution Rates

Several studies have demonstrated age dependence in the dissolution and precipitation rates of carbonates and silicates in aqueous solution. We propose a general random rate model for continuous dissolution and precipitation at mineral surfaces that may offer insight into the mechanisms responsible for this long term behavior. To place restrictions on the models, we then formulate inverse procedures that attempt to extract the intrinsic rate distributions from observed dissolution and precipitation time series. Because the inverse procedure is robust for noisy data, we can determine the applicability of the model itself via the success and failure of the inverse procedure. This work contributes an alternative to models that focus on the relationships between rates and concentrations that are currently being utilized to explore the age dependence, and the closely related disparity between laboratory and field measurements, of dissolution and precipitation rates. Understanding the long-time behavior of carbonates in this context is critical to predictions for geological sequestration of CO2.