Stochastic Assessment of Dissolution at Fluid‐Mineral Interfaces

• Published in: Geophysical research letters Vol. 51; no. 7
• Main Authors: Recalcati, Chiara, Siena, Martina, Riva, Monica, Bollani, Monica, Guadagnini, Alberto
• Format: Journal Article
• Language: English
• Published: Washington John Wiley & Sons, Inc 16.04.2024; Wiley
• Subjects: Atomic force microscopy; Calcite; Chemical precipitation; Chemical weathering; Contamination; Continuous flow; Crystal surfaces; Dissolution; dissolution rate; Dissolving; Evolution; Fluids; Fluxes; Groundwater; Groundwater pollution; Groundwater storage; Heterogeneity; Image acquisition; Imaging techniques; Interfaces; Microscopy; Minerals; mineral‐fluid interaction; Patchiness; Precipitation; Spatial heterogeneity; stochastic modeling; Storage capacity; Storage conditions; water; Weathering; Workflow
• ISSN: 0094-8276; 1944-8007
• DOI: 10.1029/2023GL108080

Chemical weathering associated with dissolution/precipitation at interfaces between minerals and flowing fluids is key for the evolution of geologic systems, including groundwater contamination and storage capacity. Relying on Atomic Force Microscopy (AFM) yields reaction rates at nanoscale resolutions. Challenges limiting our ability to quantify heterogeneity associated with these processes include establishing reliable platforms allowing AFM imaging of real‐time and in situ absolute material fluxes across mineral surfaces under continuous flow conditions to complement typically acquired surface topography images. We provide an experimental workflow and heterogeneous absolute rates at the nanoscale across the surface of a calcite crystal under dissolution. These high‐quality experimental observations are then interpreted through a stochastic approach. The latter is geared to embed diverse kinetic modes driving the degree of spatial heterogeneity of the reaction and corresponding to different mechanistic processes documented across the crystal surface. Plain Language Summary Quantification of basic processes underpinning precipitation/dissolution at mineral/fluid interfaces is key for realistic assessment of chemical weathering rates driving rock morphology, subsurface storage capacity and contamination. We provide direct observation of the complex mechanistic processes acting at nanoscales through an original experimental platform relying on Atomic Force Microscopy imaging to evaluate absolute material fluxes associated with dissolution of a mineral subject to reaction under continuous flow conditions. Dissolution is characterized at very high spatial resolutions (∼10 nm). This enables observing in real‐time and in situ mechanistic processes driving system evolution. The ensuing rich data set of absolute reaction rates displays a marked degree of spatial heterogeneity. The latter is then interpreted within a stochastic framework to yield a detailed mechanistic appraisal of mineral dissolution. Key Points A platform to evaluate absolute nanoscale topographic measurements of a crystal sample subject to dissolution/precipitation is designed The associated spatially heterogeneous fields of absolute material fluxes across the surface are evaluated Reaction rates are described through a stochastic framework encapsulating behaviors of surface features driving dissolution processes