| 1. |
- Betterle, Andrea, et al.
(författare)
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Hyporheic exchange in recirculating flumes under heterogeneous bacterial and morphological conditions
- 2021
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Ingår i: Environmental Earth Sciences. - : Springer Science and Business Media LLC. - 1866-6280 .- 1866-6299. ; 80:6
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Tidskriftsartikel (refereegranskat)abstract
- Hyporheic exchange (HE) contributes to the biogeochemical turnover of macro- and micro-pollutants in rivers. However, the spatiotemporal complexity and variability of HE hinder understanding of its role in the overall functioning of riverine ecosystems. The present study focuses on investigating the role of bacterial diversity and sediment morphology on HE using a multi-flume experiment. A fully coupled surface–subsurface numerical model was used to highlight complex exchange patterns between surface water and the underlying flow field in the sediments. Under the experimental conditions, the surface water flow induced by bedforms has a prominent effect on both local trajectories and residence time distributions of hyporheic flow paths, whereas mean hyporheic retention times are mainly modulated by average surface flowrates. In case of complex bedform morphologies, the numerical model successfully reproduces the HE estimated by means of salt dilution tests. However, the 2D numerical representation of the system falls short in predicting HE in absence of bedforms, highlighting the intrinsic complexity of water circulation patterns in real scenarios. Finally, results show that higher bacterial diversities in the stream sediments can significantly reduce hyporheic fluxes. This work provides a framework to interpret micropollutants turnover in light of the underlying physical transport processes in the hyporheic zone. The study emphasizes the importance of better understanding the tradeoff between physically driven transport processes and bacterial dynamics in the hyporheic zone to quantify the fate of pollutants in streams and rivers.
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| 2. |
- Boehm, Michael, et al.
(författare)
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Changes in Renal Function in Patients With Atrial Fibrillation An Analysis From the RE-LY Trial
- 2015
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Ingår i: Journal of the American College of Cardiology. - : Elsevier BV. - 0735-1097 .- 1558-3597. ; 65:23, s. 2481-2493
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND Vitamin K-dependent factors protect against vascular and renovascular calcification, and vitamin K antagonists may be associated with a decreased glomerular filtration rate (GFR). OBJECTIVES This study analyzed changes in GFR during long-term treatment with warfarin or dabigatran etexilate (DE) in patients enrolled in the RE-LY (Randomized Evaluation of Long Term Anticoagulation Therapy) trial. METHODS Of the 18,113 patients in the RE-LY study randomized to receive DE (110 mg or 150 mg twice daily) or warfarin, 16,490 patients with atrial fibrillation had creatinine values measured at baseline and at least 1 follow-up visit. Changes in GFR for up to 30 months were evaluated. RESULTS GFR declined in all treatment groups. After an average of 30 months, the mean +/- SE decline in GFR was significantly greater with warfarin (-3.68 +/- 0.24 ml/min) compared with DE 110 mg (-2.57 +/- 0.24 ml/min; p = 0.0009 vs. warfarin) and DE 150 mg (-2.46 +/- 0.23 ml/min; p = 0.0002 vs. warfarin). A decrease in GFR >25% was less likely with DE 110 mg (hazard ratio: 0.81 [95% confidence interval: 0.69 to 0.96]; p = 0.017) or DE 150 mg (hazard ratio: 0.79 [95% confidence interval: 0.68 to 0.93]; p = 0.0056) than with warfarin in the observation period >18 months. Patients with poor international normalized ratio control (i.e., time in therapeutic range <65%) exhibited a faster decline in GFR. A more pronounced decline in GFR was associated with previous warfarin use and with the presence of diabetes. CONCLUSIONS Patients with atrial fibrillation receiving oral anticoagulation exhibited a decline in renal function that was greater in those taking warfarin versus DE, and it was amplified by diabetes and previous vitamin K antagonist use.
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| 3. |
- Böhm, Michael, et al.
(författare)
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Reply : Anticoagulant-Related Nephropathy
- 2015
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Ingår i: Journal of the American College of Cardiology. - : Elsevier BV. - 0735-1097 .- 1558-3597. ; 66:23, s. 2682-
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Tidskriftsartikel (refereegranskat)
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| 4. |
- Lewandowski, Jörg, et al.
(författare)
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Is the Hyporheic Zone Relevant beyond the Scientific Community?
- 2019
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Ingår i: Water. - : MDPI AG. - 2073-4441. ; 11:11
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Tidskriftsartikel (refereegranskat)abstract
- Rivers are important ecosystems under continuous anthropogenic stresses. The hyporheic zone is a ubiquitous, reactive interface between the main channel and its surrounding sediments along the river network. We elaborate on the main physical, biological, and biogeochemical drivers and processes within the hyporheic zone that have been studied by multiple scientific disciplines for almost half a century. These previous efforts have shown that the hyporheic zone is a modulator for most metabolic stream processes and serves as a refuge and habitat for a diverse range of aquatic organisms. It also exerts a major control on river water quality by increasing the contact time with reactive environments, which in turn results in retention and transformation of nutrients, trace organic compounds, fine suspended particles, and microplastics, among others. The paper showcases the critical importance of hyporheic zones, both from a scientific and an applied perspective, and their role in ecosystem services to answer the question of the manuscript title. It identifies major research gaps in our understanding of hyporheic processes. In conclusion, we highlight the potential of hyporheic restoration to efficiently manage and reactivate ecosystem functions and services in river corridors.
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| 5. |
- Thorslund, Josefin, 1988-
(författare)
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Hydrological spreading of metal pollution and wetlands as nature-based solutions
- 2017
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The quality of the Earth’s water resources have deteriorated due to human impacts. A key scientific challenge is to understand, quantify and predict the water-borne spreading of pollutants at relevant scales for freshwater management and water quality restoration programs. However, understanding the natural processes controlling large-scale hydrological transport of pollutants may be masked by river regulation schemes (in the form of dams and reservoirs), which are common in many large rivers. The main objective of this thesis is to increase the current knowledge regarding large-scale spreading of metals in hydrological systems. This objective is addressed through studying net impacts of mining (a main contributor to global metal pollution) on the spreading of metals in water systems and through investigating the mitigation opportunities of wetlands across the landscape. The main study region of this thesis is the Lake Baikal basin of Russia and Mongolia, which includes the large unregulated Selenga River and its delta-wetland areas. In addition, a set of global wetland sites are also studied. A multi-method approach is used in the four studies of this thesis. The methods include field-measurements, data synthesis, metal mass flow and water flow-path quantifications, as well as geochemical modelling. Results show that mining in the upstream part of the Lake Baikal basin is a significant contributor to riverine mass flows of several metals. The mass flows increased by an order of magnitude over the mining site. The observed speciation between dissolved (more bioavailable) and suspended (less bioavailable) phases could be well predicted for some metals (Fe, V, Pb and Zn) using a geochemical equilibrium model. However, the model failed to reproduce the speciation of other metals (Cr, Cu, Mn and Mo). In these cases, non-equilibrium processes may need to be considered, and adsorption databases may need to be developed, in order to make dependable predictions. Results also suggest that the concentration of dissolved organic carbon, which exhibits seasonal variability and long-term increasing trends due to climate change effects in the Arctic, can have a large impact on metal pollution transport. Further, observations showed that individual wetlands of the Selenga River delta locally retained between 77-99 % of incoming metal loads. However, a systematic analysis of current knowledge showed that large-scale net effects can differ considerably from the functions observed at individual wetlands on smaller scales. Along large-scale flow-paths, through which wetlands are connected with each other as well as with the larger landscape, key processes which can considerably contribute to such scale differences in function may occur. A survey of the current wetland research showed that relatively few studies have considered the larger scales at which key pollutant pressures and water quality changes take place. This thesis highlights the need for more research on large-scale wetland systems, which can aid in evaluating net pollution effects at landscape scales. This in turn can facilitate evaluations of how and when wetland systems may function as large-scale nature-based solutions.
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