EEPS Colloquium: Jennifer Druhan

 

Intentional efforts by the critical zone (CZ) community have recently advanced the use of numerical reactive transport models (RTMs) to accurately simulate multi-component, rate-dependent ensembles of chemically reactive pathways between water and minerals to produce soils and solutes contemporaneously in natural systems. Challenges in the adaptation of these frameworks persist, as individual solutes are geochemically coupled, yet serve a variety of individual purposes (e.g., ecosystem nutrition, pedogenesis), such that their storage within catchments varies uniquely and dynamically over seasons and years. Here, we consider a set of recent advancement in adaptation of RTMs to offer a robust and predictive description of these mechanisms. First, we describe a new multi-component RTM allowing solid phase deposition of exogenous dust in an otherwise actively uplifting and eroding watershed. The result is the first process-based estimate of the capacity for external mass additions to impact the internal chemical weathering rates of a natural environment. Second, we describe a new reactive transport framework embedding water-rock reactivity, plant water demand, and the capacity for plants to extract solutes along with this water. We show that the water and nutrient demands of ecosystems, coupled with the capacity to recycle elements to the soil surface, allow plants to modulate the rate and depth of pedogenesis. Finally, the vast majority of studies seeking to link discharge to solute concentrations have been based on representations of fluid age distributions in watersheds that are time-invariant. Here we offer the first merging of a model featuring time-variant fluid age distributions with a geochemical model for isotopically fractionating weathering reactions.