TY - JOUR

T1 - Hydrological control of water quality – Modelling base cation weathering and dynamics across heterogeneous boreal catchments

AU - Jutebring Sterte, Elin

AU - Lidman, Fredrik

AU - Balbarini, Nicola

AU - Lindborg, Emma

AU - Sjöberg, Ylva

AU - Selroos, Jan Olof

AU - Laudon, Hjalmar

N1 - Funding Information: The authors are thankful to the funding by Svensk K?rnbr?nslehantering AB (SKB), DHI Sweden AB for software access and expert consultation, and the crew of the Krycklan Catchment Study (KCS) funded by SITES (VR) for advice and data collection. KCS is funded by the Swedish University of Agricultural Sciences, Swedish Research Council (as part of the SITES network and project funds), Formas, Knut and Alice Wallenberg Foundation through Branch-Point and Future Siliviculture, Kempe Foundations, and SKB. Several individuals have also helped with the creation of this work. Funding Information: The authors are thankful to the funding by Svensk Kärnbränslehantering AB (SKB), DHI Sweden AB for software access and expert consultation, and the crew of the Krycklan Catchment Study (KCS) funded by SITES (VR) for advice and data collection. KCS is funded by the Swedish University of Agricultural Sciences , Swedish Research Council (as part of the SITES network and project funds), Formas , Knut and Alice Wallenberg Foundation through Branch-Point and Future Siliviculture, Kempe Foundations , and SKB . Several individuals have also helped with the creation of this work. Publisher Copyright: © 2021 The Authors

PY - 2021/12/10

Y1 - 2021/12/10

N2 - Linking biogeochemical processes to water flow paths and solute travel times is important for understanding internal catchment functioning and control of water quality. Base cation weathering is a process closely linked to key factors affecting catchment functioning, including water pathways, soil contact time, and catchment characteristics, particularly in silicate-dominated areas. However, common process-based weathering models are often calibrated and applied for individual soil profiles, which can cause problems when trying to extrapolate results to catchment scale and assess consequences for stream water and groundwater quality. Therefore, in this work, base cation export was instead modelled using a fully calibrated 3D hydrological model (Mike SHE) of a boreal catchment, which was expanded by adding a relatively simple but still reasonably flexible and versatile weathering module including the base cations Na, K, Mg, and Ca. The results were evaluated using a comprehensive dataset of water chemistry from groundwater and stream water in 14 nested sub-catchments, representing different catchment sizes and catchment characteristics. The strongest correlations with annual and seasonal observations were found for Ca (r = 0.89-0.93, p < 0.05), Mg (r = 0.90-0.95, p < 0.05), and Na (r = 0.80-0.89, p < 0.05). These strong correlations suggest that catchment hydrology and landscape properties primarily control weathering rates and stream dynamics of these solutes. Furthermore, catchment export of Mg, Ca, and K was strongly connected to travel times of discharging stream water (r = 0.78-0.83). Conversely, increasing Na export was linked to a reduced areal proportion of mires (r = -0.79). The results suggest that a significant part (~45%) of the catchment stream export came from deep-soil weathering sources (>2.5 m). These results have implications for terrestrial and aquatic water quality assessments. If deep soils are present, focusing mainly on the shallow soil could lead to misrepresentation of base cation availability and the acidification sensitivity of groundwater and water recipients such as streams and lakes.

AB - Linking biogeochemical processes to water flow paths and solute travel times is important for understanding internal catchment functioning and control of water quality. Base cation weathering is a process closely linked to key factors affecting catchment functioning, including water pathways, soil contact time, and catchment characteristics, particularly in silicate-dominated areas. However, common process-based weathering models are often calibrated and applied for individual soil profiles, which can cause problems when trying to extrapolate results to catchment scale and assess consequences for stream water and groundwater quality. Therefore, in this work, base cation export was instead modelled using a fully calibrated 3D hydrological model (Mike SHE) of a boreal catchment, which was expanded by adding a relatively simple but still reasonably flexible and versatile weathering module including the base cations Na, K, Mg, and Ca. The results were evaluated using a comprehensive dataset of water chemistry from groundwater and stream water in 14 nested sub-catchments, representing different catchment sizes and catchment characteristics. The strongest correlations with annual and seasonal observations were found for Ca (r = 0.89-0.93, p < 0.05), Mg (r = 0.90-0.95, p < 0.05), and Na (r = 0.80-0.89, p < 0.05). These strong correlations suggest that catchment hydrology and landscape properties primarily control weathering rates and stream dynamics of these solutes. Furthermore, catchment export of Mg, Ca, and K was strongly connected to travel times of discharging stream water (r = 0.78-0.83). Conversely, increasing Na export was linked to a reduced areal proportion of mires (r = -0.79). The results suggest that a significant part (~45%) of the catchment stream export came from deep-soil weathering sources (>2.5 m). These results have implications for terrestrial and aquatic water quality assessments. If deep soils are present, focusing mainly on the shallow soil could lead to misrepresentation of base cation availability and the acidification sensitivity of groundwater and water recipients such as streams and lakes.

KW - Calcium

KW - Export

KW - Magnesium

KW - Potassium

KW - Sodium

KW - Travel time

U2 - 10.1016/j.scitotenv.2021.149101

DO - 10.1016/j.scitotenv.2021.149101

M3 - Journal article

C2 - 34388880

AN - SCOPUS:85112485053

VL - 799

JO - Science of the Total Environment

JF - Science of the Total Environment

SN - 0048-9697

M1 - 149101

ER -