| 1. |
- Jutebring Sterte, Elin, et al.
(författare)
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Hydrological control of water quality – Modelling base cation weathering and dynamics across heterogeneous boreal catchments
- 2021
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Ingår i: Science of the Total Environment. - : Elsevier BV. - 0048-9697 .- 1879-1026. ; 799, s. 149101-149101
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 2. |
- Logue, Jürg Brendan, et al.
(författare)
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Experimental insights into the importance of aquatic bacterial community composition to the degradation of dissolved organic matter
- 2016
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Ingår i: The ISME Journal. - : Springer Science and Business Media LLC. - 1751-7362 .- 1751-7370. ; 10:3, s. 533-545
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Tidskriftsartikel (refereegranskat)abstract
- Bacteria play a central role in the cycling of carbon, yet our understanding of the relationship between the taxonomic composition and the degradation of dissolved organic matter (DOM) is still poor. In this experimental study, we were able to demonstrate a direct link between community composition and ecosystem functioning in that differently structured aquatic bacterial communities differed in their degradation of terrestrially derived DOM. Although the same amount of carbon was processed, both the temporal pattern of degradation and the compounds degraded differed among communities. We, moreover, uncovered that low-molecular-weight carbon was available to all communities for utilisation, whereas the ability to degrade carbon of greater molecular weight was a trait less widely distributed. Finally, whereas the degradation of either low-or high-molecular-weight carbon was not restricted to a single phylogenetic clade, our results illustrate that bacterial taxa of similar phylogenetic classification differed substantially in their association with the degradation of DOM compounds. Applying techniques that capture the diversity and complexity of both bacterial communities and DOM, our study provides new insight into how the structure of bacterial communities may affect processes of biogeochemical significance.
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| 3. |
- Oni, Stephen, et al.
(författare)
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Soil temperature responses to climate change along a gradient of upland–riparian transect in boreal forest
- 2017
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Ingår i: Climatic Change. - : Springer Netherlands. - 0165-0009 .- 1573-1480. ; 143:1-2, s. 27-41
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Tidskriftsartikel (refereegranskat)abstract
- There is growing evidence of climate change impacts on northern ecosystems. While most climate change studies base their assessments on air temperature, spatial variation of soil temperature responses have not been fully examined as a metric of climate change. Here we examined spatial variations of soil temperature responses to an ensemble of regional climate model (RCM) projections at multiple depths in upland and riparian zones in the Swedish boreal forest. Modeling showed a stronger influence of air temperature on riparian soil temperature than was simulated for upland soils. The RCM ensemble projected a warming range of 4.7–6.0 °C in riparian and 4.3–5.7 °C in upland soils. However, soils were slightly colder in the riparian zone during winter. While the historical record showed that upland soils are about 0.4 °C warmer than the riparian soils, this may be reversed in the future as model projections showed that on an annual basis, riparian soils might be slightly warmer by 0.2 to 0.4 °C than upland soils. However, upland soils could warm up earlier (April) compared to riparian soils (May).
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| 4. |
- Wörman, Anders, et al.
(författare)
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Fragmentation of the Hyporheic Zone Due to Regional Groundwater Circulation
- 2019
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Ingår i: Water resources research. - : American Geophysical Union (AGU). - 0043-1397 .- 1944-7973. ; 55:2, s. 1-21
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Tidskriftsartikel (refereegranskat)abstract
- By use of numerical modeling and field observations, this work quantified the effects of catchment-scale upwelling groundwater on the hyporheic (below stream) fluxes over a wide range of spatial scales. A groundwater flow model was developed that specifically accounted for the hydrostatic and dynamic head fluctuations induced by the streambed topography. Although the magnitudes and relative importance of these streambed-induced fluxes were found to be highly sensitive to site-specific hydromorphological properties, we showed that streambed topographic structures exert a predominant control on the magnitude of hyporheic exchange fluxes in a Swedish boreal catchment. The magnitude of the exchange intensity evaluated at the streambed interface was found to be dominated by the streambed-induced hydraulic head across stream order. However, the catchment-scale groundwater flow field substantially affected the distribution of groundwater discharge points and thus decreased the fragmentation of the hyporheic zone, specifically by shifting the cumulative density function toward larger areas of coherent upwelling at the streambed interface. This work highlights the spectrum of spatial scales affecting the surface water-groundwater exchange patterns and resolves the roles of key mechanisms in controlling the fragmentation of the hyporheic zone.
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