Colloid and solute dynamics in the extrusive critical zone - contributions to landscape chemical denudation

Abstract:

Colloidal dynamics are increasingly recognized as important contributors to the time and space variation in aqueous geochemistry of weathering systems. Whereas many studies separate "particulate" and "dissolved" components of hydrologic discharge using an arbitrary filtration cutoff (most commonly 450 nm), there is growing evidence of the importance of filterable colloids to critical zone weathering and the concentration-discharge relations of surface waters. Such impacts are manifest in the formation of structured soils, the accumulation of solid phase weathering products along deep hydrologic flow paths, and the growing relative prevalence of colloidal weathering products to hydrochemistry at high discharge and long water-rock contact times. For example, superimposed colloid enrichment and solute dilution trends with increasing discharge can lead to apparent chemostasis across the catchment hydrograph. Data from multiple experimental scales and field sites will be presented to make the case for a more rigorous quantitative assessment of colloidal contributions to geochemical reactions and fluxes in weathering systems.