Rights statement: An edited version of this paper was published by AGU. Copyright 2017 American Geophysical Union. Ameli, A. A., K. Beven, M. Erlandsson, I. F. Creed, J. J. McDonnell and K. Bishop (2017), Primary weathering rates, water transit times, and concentration-discharge relations: A theoretical analysis for the critical zone, Water Resour. Res., 53, 942–960, doi:10.1002/2016WR019448. To view the published open abstract, go to http://dx.doi.org and enter the DOI.
Accepted author manuscript, 1.45 MB, PDF document
Available under license: CC BY-NC: Creative Commons Attribution-NonCommercial 4.0 International License
Rights statement: C 2016. American Geophysical Union. All Rights Reserved.
Final published version, 2.39 MB, PDF document
Available under license: CC BY: Creative Commons Attribution 4.0 International License
Final published version
Research output: Contribution to Journal/Magazine › Journal article › peer-review
Research output: Contribution to Journal/Magazine › Journal article › peer-review
}
TY - JOUR
T1 - Primary weathering rates, water transit times, and concentration-discharge relations
T2 - a theoretical analysis for the critical zone
AU - Ameli, Ali A.
AU - Beven, Keith
AU - Erlandsson, Martin
AU - Creed, Irena F.
AU - McDonnell, Jeffrey J.
AU - Bishop, Kevin
N1 - An edited version of this paper was published by AGU. Copyright 2017 American Geophysical Union. Ameli, A. A., K. Beven, M. Erlandsson, I. F. Creed, J. J. McDonnell and K. Bishop (2017), Primary weathering rates, water transit times, and concentration-discharge relations: A theoretical analysis for the critical zone, Water Resour. Res., 53, 942–960, doi:10.1002/2016WR019448. To view the published open abstract, go to http://dx.doi.org and enter the DOI.
PY - 2017/1
Y1 - 2017/1
N2 - 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).
AB - 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).
KW - chemical weathering
KW - conductivity profile
KW - stream C-Q relation
KW - saturated-unsaturated flow and transport
KW - transit time
KW - ENVIRONMENTAL SYSTEMS
KW - RUNOFF CHEMISTRY
KW - SUBSURFACE FLOW
KW - RESIDENCE TIME
KW - STORM RUNOFF
KW - MID-WALES
KW - CATCHMENT
KW - DISSOLUTION
KW - MODEL
KW - TRANSPORT
U2 - 10.1002/2016WR019448
DO - 10.1002/2016WR019448
M3 - Journal article
VL - 53
SP - 942
EP - 960
JO - Water Resources Research
JF - Water Resources Research
SN - 0043-1397
IS - 1
ER -