Erlandsson, Martin
- Stockholm University
Abstract
The permeability architecture of the critical zone exerts a major influence on the hydrogeochemistry of the critical zone. Water flow path dynamics drive the spatiotemporal pattern of geochemical evolution and resulting streamflow concentration-discharge (C-Q) relation, but these flow paths are complex and difficult to map quantitatively. Here we couple a new integrated flow and particle tracking transport model with a general reversible Transition State Theory style dissolution rate law to explore theoretically how C-Q relations and concentration in the critical zone respond to decline in saturated hydraulic conductivity (K-s) with soil depth. We do this for a range of flow rates and mineral reaction kinetics. Our results show that for minerals with a high ratio of equilibrium concentration (C-eq) to intrinsic weathering rate (R-max), vertical heterogeneity in K-s enhances the gradient of weathering-derived solute concentration in the critical zone and strengthens the inverse stream C-Q relation. As C-eq/R-max decreases, the spatial distribution of concentration in the critical zone becomes more uniform for a wide range of flow rates, and stream C-Q relation approaches chemostatic behavior, regardless of the degree of vertical heterogeneity in K-s. These findings suggest that the transport-controlled mechanisms in the hillslope can lead to chemostatic C-Q relations in the stream while the hillslope surface reaction-controlled mechanisms are associated with an inverse stream C-Q relation. In addition, as C-eq/R-max decreases, the concentration in the critical zone and stream become less dependent on groundwater age (or transit time).
Keywords
chemical weathering; conductivity profile; stream C-Q relation; saturated-unsaturated flow and transport; transit time
Published in
Water Resources Research
2017, volume: 53, number: 1, pages: 942-960
Publisher: AMER GEOPHYSICAL UNION
SLU Authors
Bishop, Kevin
- Department of Aquatic Sciences and Assessment, Swedish University of Agricultural Sciences
- Uppsala University
- Department of Aquatic Sciences and Assessment, Swedish University of Agricultural Sciences
Associated SLU-program
SLU Future Forests
UKÄ Subject classification
Oceanography, Hydrology, Water Resources
Publication identifier
- DOI: https://doi.org/10.1002/2016WR019448
Permanent link to this page (URI)
https://res.slu.se/id/publ/94040