| 1. |
- Jaeger, Anna, et al.
(författare)
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Using recirculating flumes and a response surface model to investigate the role of hyporheic exchange and bacterial diversity on micropollutant half-lives
- 2019
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Ingår i: Environmental Science. - : Royal Society of Chemistry (RSC). - 2050-7887 .- 2050-7895. ; 21:12, s. 2093-2108
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Tidskriftsartikel (refereegranskat)abstract
- Enhancing the understanding of the fate of wastewater-derived organic micropollutants in rivers is crucial to improve risk assessment, regulatory decision making and river management. Hyporheic exchange and sediment bacterial diversity are two factors gaining increasing importance as drivers for micropollutant degradation, but are complex to study in field experiments and usually ignored in laboratory tests aimed to estimate environmental half-lives. Flume mesocosms are useful to investigate micropollutant degradation processes, bridging the gap between the field and batch experiments. However, few studies have used flumes in this context. We present a novel experimental setup using 20 recirculating flumes and a response surface model to study the influence of hyporheic exchange and sediment bacterial diversity on half-lives of the anti-epileptic drug carbamazepine (CBZ) and the artificial sweetener acesulfame (ACS). The effect of bedform-induced hyporheic exchange was tested by three treatment levels differing in number of bedforms (0, 3 and 6). Three levels of sediment bacterial diversity were obtained by diluting sediment from the River Erpe in Berlin, Germany, with sand (1 : 10, 1 : 1000 and 1 : 100 000). Our results show that ACS half-lives were significantly influenced by sediment dilution and number of bedforms. Half-lives of CBZ were higher than ACS, and were significantly affected only by the sediment dilution variable, and thus by bacterial diversity. Our results show that (1) the flume-setup is a useful tool to study the fate of micropollutants in rivers, and that (2) higher hyporheic exchange and bacterial diversity in the sediment can increase the degradation of micropollutants in rivers.
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| 2. |
- 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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| 3. |
- Mojarrad, Babak Brian, et al.
(författare)
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The Effect of Stream Discharge on Hyporheic Exchange
- 2019
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Ingår i: Water. - : MDPI. - 2073-4441. ; 11:7
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Tidskriftsartikel (refereegranskat)abstract
- Streambed morphology, streamflow dynamics, and the heterogeneity of streambed sediments critically controls the interaction between surface water and groundwater. The present study investigated the impact of different flow regimes on hyporheic exchange in a boreal stream in northern Sweden using experimental and numerical approaches. Low-, base-, and high-flow discharges were simulated by regulating the streamflow upstream in the study area, and temperature was used as the natural tracer to monitor the impact of the different flow discharges on hyporheic exchange fluxes in stretches of stream featuring gaining and losing conditions. A numerical model was developed using geomorphological and hydrological properties of the stream and was then used to perform a detailed analysis of the subsurface water flow. Additionally, the impact of heterogeneity in sediment permeability on hyporheic exchange fluxes was investigated. Both the experimental and modelling results show that temporally increasing flow resulted in a larger (deeper) extent of the hyporheic zone as well as longer hyporheic flow residence times. However, the result of the numerical analysis is strongly controlled by heterogeneity in sediment permeability. In particular, for homogeneous sediments, the fragmentation of upwelling length substantially varies with streamflow dynamics due to the contribution of deeper fluxes.
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| 4. |
- Sharma, Shikha, et al.
(författare)
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Emerging challenges in antimicrobial resistance : implications for pathogenic microorganisms, novel antibiotics, and their impact on sustainability
- 2024
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Ingår i: Frontiers in Microbiology. - 1664-302X. ; 15
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Forskningsöversikt (refereegranskat)abstract
- Overuse of antibiotics is accelerating the antimicrobial resistance among pathogenic microbes which is a growing public health challenge at the global level. Higher resistance causes severe infections, high complications, longer stays at hospitals and even increased mortality rates. Antimicrobial resistance (AMR) has a significant impact on national economies and their health systems, as it affects the productivity of patients or caregivers due to prolonged hospital stays with high economic costs. The main factor of AMR includes improper and excessive use of antimicrobials; lack of access to clean water, sanitation, and hygiene for humans and animals; poor infection prevention and control measures in hospitals; poor access to medicines and vaccines; lack of awareness and knowledge; and irregularities with legislation. AMR represents a global public health problem, for which epidemiological surveillance systems have been established, aiming to promote collaborations directed at the well-being of human and animal health and the balance of the ecosystem. MDR bacteria such as E. coli, Staphylococcus aureus, Pseudomonas aeruginosa, Enterococcus spp., Acinetobacter spp., and Klebsiella pneumonia can even cause death. These microorganisms use a variety of antibiotic resistance mechanisms, such as the development of drug-deactivating targets, alterations in antibiotic targets, or a decrease in intracellular antibiotic concentration, to render themselves resistant to numerous antibiotics. In context, the United Nations issued the Sustainable Development Goals (SDGs) in 2015 to serve as a worldwide blueprint for a better, more equal, and more sustainable existence on our planet. The SDGs place antimicrobial resistance (AMR) in the context of global public health and socioeconomic issues; also, the continued growth of AMR may hinder the achievement of numerous SDGs. In this review, we discuss the role of environmental pollution in the rise of AMR, different mechanisms underlying the antibiotic resistance, the threats posed by pathogenic microbes, novel antibiotics, strategies such as One Health to combat AMR, and the impact of resistance on sustainability and sustainable development goals.
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| 5. |
- Singh, Tanu, et al.
(författare)
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Effects of Successive Peak Flow Events on Hyporheic Exchange and Residence Times
- 2020
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Ingår i: Water resources research. - : AMER GEOPHYSICAL UNION. - 0043-1397 .- 1944-7973. ; 56:8
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Tidskriftsartikel (refereegranskat)abstract
- Hyporheic exchange is a crucial control of the type and rates of streambed biogeochemical processes, including metabolism, respiration, nutrient turnover, and the transformation of pollutants. Previous work has shown that increasing discharge during an individual peak flow event strengthens biogeochemical turnover by enhancing the exchange of water and dissolved solutes. However, due to the nonsteady nature of the exchange process, successive peak flow events do not exhibit proportional variations in residence time and turnover, and in some cases, can reduce the hyporheic zones' biogeochemical potential. Here, we used a process-based model to explore the role of successive peak flow events on the flow and transport characteristics of bedform-induced hyporheic exchange. We conducted a systematic analysis of the impacts of the events' magnitude, duration, and time between peaks in the hyporheic zone's fluxes, penetration, and residence times. The relative contribution of each event to the transport of solutes across the sediment-water interface was inferred from transport simulations of a conservative solute. In addition to temporal variations in the hyporheic flow field, our results demonstrate that the separation between two events determines the temporal evolution of residence time and that event time lags longer than the memory of the system result in successive events that can be treated independently. This study highlights the importance of discharge variability in the dynamics of hyporheic exchange and its potential implications for biogeochemical transformations and fate of contaminants along river corridors. Key Points Dynamic response of hyporheic exchange fluxes, residence times, and breakthrough curves to successive peak flow events is investigated Increased time lag between successive flow peaks cause higher temporal variability in mean residence times of hyporheic water Two events can be treated separately if the occurrence of subsequent event is longer than the memory of the system from the antecedent event.
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| 6. |
- Wu, Liwen, et al.
(författare)
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How daily groundwater table drawdown affects the diel rhythm of hyporheic exchange
- 2021
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Ingår i: Hydrology and Earth System Sciences. - : Copernicus GmbH. - 1027-5606 .- 1607-7938. ; 25:4, s. 1905-1921
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Tidskriftsartikel (refereegranskat)abstract
- Groundwater table dynamics extensively modify the volume of the hyporheic zone and the rate of hyporheic exchange processes. Understanding the effects of daily groundwater table fluctuations on the tightly coupled flow and heat transport within hyporheic zones is crucial for water resources management. With this aim in mind, a physically based model is used to explore hyporheic responses to varying groundwater table fluctuation scenarios. The effects of different timing and amplitude of groundwater table daily drawdowns under gaining and losing conditions are explored in hyporheic zones influenced by natural flood events and diel river temperature fluctuations. We find that both diel river temperature fluctuations and daily groundwater table drawdowns play important roles in determining the spatiotemporal variability of hyporheic exchange rates, temperature of exfiltrating hyporheic fluxes, mean residence times, and hyporheic denitrification potentials. Groundwater table dynamics present substantially distinct impacts on hyporheic exchange under gaining or losing conditions. The timing of groundwater table drawdown has a direct influence on hyporheic exchange rates and hyporheic buffering capacity on thermal disturbances. Consequently, the selection of aquifer pumping regimes has significant impacts on the dispersal of pollutants in the aquifer and thermal heterogeneity in the sediment.
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| 7. |
- Wu, Liwen, et al.
(författare)
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Impact of Dynamically Changing Discharge on Hyporheic Exchange Processes Under Gaining and Losing Groundwater Conditions
- 2018
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Ingår i: Water resources research. - : AMER GEOPHYSICAL UNION. - 0043-1397 .- 1944-7973. ; 54:12, s. 10076-10093
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Tidskriftsartikel (refereegranskat)abstract
- Channel discharge, geomorphological setting, and regional groundwater flow determine the spatiotemporal variability of bedform-induced hyporheic exchange and the emergence of biogeochemical hot spots and hot moments that it drives. Of particular interest, and significantly understudied, is the role that dynamically changing discharge has on the hyporheic exchange process and how regional groundwater flow modulates the effects of transience. In this study, we use a reduced-complexity model to systematically explore the bedform-induced hyporheic responses to dynamically changing discharge events in systems with different bedform geometries exposed to varying degrees of groundwater flow (under both upwelling and downwelling conditions). With this in mind, we define metrics to quantify the effects of transience: spatial extent of the hyporheic zone, net hyporheic flux, mean residence time, and denitrification efficiency. We find that regional groundwater flow and geomorphological settings greatly modulate the temporal evolution of bedform-induced hyporheic responses driven by a single-peak discharge event. Effects of transience diminish with increasing groundwater upwelling or downwelling fluxes, decreasing bedform aspect ratios, and decreasing channel slopes. Additionally, we notice that increasing discharge intensities can reduce the modulating impacts of regional groundwater flow on the effects of transience but hardly overcomes the geomorphological controls. These findings highlight the necessities of evaluating hyporheic exchange processes in a more comprehensive framework.
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| 8. |
- Wu, Liwen, et al.
(författare)
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Impact of Flow Alteration and Temperature Variability on Hyporheic Exchange
- 2020
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Ingår i: Water resources research. - : AMER GEOPHYSICAL UNION. - 0043-1397 .- 1944-7973. ; 56:3
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Tidskriftsartikel (refereegranskat)abstract
- Coupled groundwater flow and heat transport within hyporheic zones extensively affect water, energy, and solute exchange with surrounding sediments. The local and cumulative implications of this tightly coupled process strongly depend on characteristics of drivers (i.e., discharge and temperature of the water column) and modulators (i.e., hydraulic and thermal properties of the sediment). With this in mind, we perform a systematic numerical analysis of hyporheic responses to understand how the temporal variability of river discharge and temperature affect flow and heat transport within hyporheic zones. We identify typical time series of river discharge and temperature from gauging stations along the headwater region of Mississippi River Basin, which are characterized by different degrees of flow alteration, to drive a physics-based model of the hyporheic exchange process. Our modeling results indicate that coupled groundwater flow and heat transport significantly affects the dynamic response of hyporheic zones, resulting in substantial differences in exchange rates and characteristic time scales of hyporheic exchange processes. We also find that the hyporheic zone dampens river temperature fluctuations increasingly with higher frequency of temperature fluctuations. This dampening effect depends on the system transport time scale and characteristics of river discharge and temperature variability. Furthermore, our results reveal that the flow alteration reduces the potential of hyporheic zones to act as a temperature buffer and hinders denitrification within hyporheic zones. These results have significant implications for understanding the drivers of local variability in hyporheic exchange and the implications for the development of thermal refugia and ecosystem functioning in hyporheic zones.
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