| 61. |
- McDonough, L. K., et al.
(författare)
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Changes in global groundwater organic carbon driven by climate change and urbanization
- 2020
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Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 11:1
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Tidskriftsartikel (refereegranskat)abstract
- Climate change and urbanization can increase pressures on groundwater resources, but little is known about how groundwater quality will change. Here, we use a global synthesis (n = 9,404) to reveal the drivers of dissolved organic carbon (DOC), which is an important component of water chemistry and substrate for microorganisms that control biogeochemical reactions. Dissolved inorganic chemistry, local climate and land use explained ~ 31% of observed variability in groundwater DOC, whilst aquifer age explained an additional 16%. We identify a 19% increase in DOC associated with urban land cover. We predict major groundwater DOC increases following changes in precipitation and temperature in key areas relying on groundwater. Climate change and conversion of natural or agricultural areas to urban areas will decrease groundwater quality and increase water treatment costs, compounding existing constraints on groundwater resources. © 2020, The Author(s).
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| 62. |
- Pasquini, Luca, et al.
(författare)
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Magnesium- and intermetallic alloys-based hydrides for energy storage : modelling, synthesis and properties
- 2022
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Ingår i: Progress in Energy. - : Institute of Physics Publishing (IOPP). - 2516-1083. ; 4:3
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Forskningsöversikt (refereegranskat)abstract
- Hydrides based on magnesium and intermetallic compounds provide a viable solution to the challenge of energy storage from renewable sources, thanks to their ability to absorb and desorb hydrogen in a reversible way with a proper tuning of pressure and temperature conditions. Therefore, they are expected to play an important role in the clean energy transition and in the deployment of hydrogen as an efficient energy vector. This review, by experts of Task 40 'Energy Storage and Conversion based on Hydrogen' of the Hydrogen Technology Collaboration Programme of the International Energy Agency, reports on the latest activities of the working group 'Magnesium- and Intermetallic alloys-based Hydrides for Energy Storage'. The following topics are covered by the review: multiscale modelling of hydrides and hydrogen sorption mechanisms; synthesis and processing techniques; catalysts for hydrogen sorption in Mg; Mg-based nanostructures and new compounds; hydrides based on intermetallic TiFe alloys, high entropy alloys, Laves phases, and Pd-containing alloys. Finally, an outlook is presented on current worldwide investments and future research directions for hydrogen-based energy storage.
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| 63. |
- Rocha, C., et al.
(författare)
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A place for subterranean estuaries in the coastal zone
- 2021
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Ingår i: Estuarine Coastal and Shelf Science. - : Elsevier BV. - 0272-7714. ; 250
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Tidskriftsartikel (refereegranskat)abstract
- Willard S. Moore coined the term subterranean estuary (STE) as that part of the coastal aquifer 'where groundwater derived from land drainage measurably dilutes seawater that has invaded the aquifer through a free connection to the sea' more than two decades ago (Moore, 1999). In doing so, Moore was calling attention to the potential importance of this zone, long studied by terrestrial hydrologists, to marine systems. Since then, we have accumulated indisputable evidence of the importance of STEs and their associated submarine groundwater discharge (SGD) in coastal ecosystem function. Yet, subterranean estuaries are often not considered distinct systems in the land-ocean continuum either from an academic viewpoint or for developing integrative monitoring and management. This invisibility means that the impact of STEs on ecosystem state has been neglected when environmental assessments that aim to meet coastal water quality and ecosystem health targets are performed. It is possible that our current broad definition of STEs, as well as misuse and misunderstanding of terminology, partly explain their de-facto transparency to the wider coastal scientific community. Here, we argue for the inclusion of STEs as important, interconnected systems driving water quality, ecology, and biogeochemical cycles in nearby coastal ecosystems. To achieve broader recognition, we first need to address the perceived compartmentalization of surface and groundwater systems, as well as overcome a pigeon-holed approach to research often confined within narrow disciplinary boundaries. The establishment of open-water estuarine science over the last several decades shows that such obstacles are surmountable. A lack of awareness and recognition of STE functions impedes a holistic understanding of coastal ecosystems and slows down the development of cause-effect relationships for a science-based approach to ecosystem management.
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| 64. |
- Santos, Isaac R., et al.
(författare)
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Submarine groundwater discharge impacts on coastal nutrient biogeochemistry
- 2021
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Ingår i: Nature Reviews Earth & Environment. - : Springer Science and Business Media LLC. - 2662-138X. ; 2:5, s. 307-323
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Tidskriftsartikel (refereegranskat)abstract
- Submarine groundwater discharge (SGD) links terrestrial and marine systems, but has often been overlooked in coastal nutrient budgets because it is difficult to quantify. In this Review, we examine SGD nutrient fluxes in over 200 locations globally, explain their impact on biogeochemistry and discuss broader management implications. SGD nutrient fluxes exceed river inputs in similar to 60% of study sites, with median total SGD fluxes of 6.0 mmol m(-2) per day for dissolved inorganic nitrogen, 0.1 mmol m(-2) per day for dissolved inorganic phosphorus and 6.5 mmol m(-2) per day for dissolved silicate. SGD nitrogen input (mostly in the form of ammonium and dissolved organic nitrogen) often mitigates nitrogen limitation in coastal waters, since SGD tends to have high nitrogen concentrations relative to phosphorus (76% of studies showed N:P values above the Redfield ratio). It is notable that most investigations do not distinguish saline and fresh SGD, although they have different properties. Saline SGD is a ubiquitous, diffuse pathway releasing mostly recycled nutrients to global coastal waters, whereas fresh SGD is occasionally a local, point source of new nutrients. SGD-derived nutrient fluxes must be considered in water quality management plans, as these inputs can promote eutrophication if not properly managed.
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| 65. |
- Wadnerkar, P. D., et al.
(författare)
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Contrasting Radium-Derived Groundwater Exchange and Nutrient Lateral Fluxes in a Natural Mangrove Versus an Artificial Canal
- 2021
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Ingår i: Estuaries and Coasts. - : Springer Science and Business Media LLC. - 1559-2723 .- 1559-2731. ; 44
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Tidskriftsartikel (refereegranskat)abstract
- Artificial canals may function differently than the natural coastal wetlands, floodplains, and estuaries they often replace. Here, we assess the impact of canal estate development on saline groundwater exchange (tidal pumping) and associated nutrient fluxes. Time series observations of short-lived radium isotopes and dissolved nutrients were performed in a canal estate and a nearby mangrove creek in subtropical Australia. A mass balance model based on(223)Ra (1.3 +/- 0.4 and 3.4 +/- 0.9 cm day(-1)in the mangrove and canal, respectively) and(224)Ra (2.8 +/- 3.0 and 5.4 +/- 4.6 cm day(-1)) revealed tidally driven groundwater exchange rates were similar to 2-fold greater in the canal. Lateral fluxes of total dissolved nitrogen (TDN) from the nearby estuary into the canal estate were comparable with the mangrove creek (8.4 and 9.1 mmol m(-2) day(-1)in the mangrove and canal, respectively). Groundwater flows into the canal released similar to 5-fold more TDN than the mangrove. As expected, mangroves appear to be more efficient at retaining groundwater-derived nitrogen than vegetation-stripped, sandy canals. Overall, this study demonstrates that land reclamation for canal estate development not only drives losses of ecosystem services, but also modifies groundwater and related nutrient exchange with coastal surface waters.
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| 66. |
- Wang, F. M., et al.
(författare)
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Global blue carbon accumulation in tidal wetlands increases with climate change
- 2021
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Ingår i: National Science Review. - : Oxford University Press (OUP). - 2095-5138 .- 2053-714X. ; 8:9
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Tidskriftsartikel (refereegranskat)abstract
- Coastal tidal wetlands produce and accumulate significant amounts of organic carbon (C) that help to mitigate climate change. However, previous data limitations have prevented a robust evaluation of the global rates and mechanisms driving C accumulation. Here, we go beyond recent soil C stock estimates to reveal global tidal wetland C accumulation and predict changes under relative sea level rise, temperature and precipitation. We use data from literature study sites and our new observations spanning wide latitudinal gradients and 20 countries. Globally, tidal wetlands accumulate 53.65 (95%CI: 48.52-59.01) Tg C yr(-1), which is similar to 30% of the organic C buried on the ocean floor. Modeling based on current climatic drivers and under projected emissions scenarios revealed a net increase in the global C accumulation by 2100. This rapid increase is driven by sea level rise in tidal marshes, and higher temperature and precipitation in mangroves. Countries with large areas of coastal wetlands, like Indonesia and Mexico, are more susceptible to tidal wetland C losses under climate change, while regions such as Australia, Brazil, the USA and China will experience a significant C accumulation increase under all projected scenarios.
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| 67. |
- White, S. A., et al.
(författare)
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Natural attenuation of large anthropogenic nitrate loads in a subtropical stream revealed by delta N-15 and delta O-18
- 2021
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Ingår i: Journal of Hydrology. - : Elsevier BV. - 0022-1694. ; 598
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Tidskriftsartikel (refereegranskat)abstract
- Nitrogen pollution in subtropical waters is rapidly increasing due to land-use change, but specific sources, transformations, and attenuation rates remain understudied compared to cooler temperate catchments. Here, we quantify high-resolution nitrate (NO3--N) loads, sources and natural attenuation in a subtropical creek in Australia over contrasting hydrological conditions. We observed large creek NO3-N loads (ranging from 44 to 2938 mu mol m(-2) catchment d(-1)) exceeding the bottom-up estimates of nitrogen input to the catchment at the most upstream sites. Stable isotope natural abundances (delta N-15 and delta O-18 in NO3--N) and Bayesian analysis revealed that greywater was the dominant source accounting for similar to 55% of NO3--N in the upper creek, but fertilisers (similar to 29%) and rainfall (similar to 16%) were also relevant NO3--N sources. NO3--N loads at the most downstream site were only 0.2-9.7% of loads at the most upstream site. The resulting NO3--N attenuation efficiency (mainly via denitrification) was 52-84% of original upstream load per km of creek, depending on hydrological conditions. This large capacity to attenuate NO3--N during dry and first-flush events exceeds the attenuation found in temperate creeks subject to several decades of pollution in the northern hemisphere. During periods of high water flow and saturated soils, high NO3--N loads were exported downstream, turning the creek from a natural bioreactor to a system resembling a flow-through pipe. In spite of effective natural nitrogen attenuation providing a valuable ecosystem service, concentrations and loads remained well above expected for natural systems and water quality guidelines. Overall, our results highlight the need for modifying fertiliser use, capturing nitrogen on farms and reducing greywater nitrogen to prevent significant losses to subtropical waterways.
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| 68. |
- Woodrow, R. L., et al.
(författare)
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Nitrous oxide hot moments and cold spots in a subtropical estuary: Floods and mangroves
- 2022
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Ingår i: Estuarine, Coastal and Shelf Science. - : Elsevier BV. - 0272-7714. ; 264
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Tidskriftsartikel (refereegranskat)abstract
- Flood events can transport large nitrogen loads to the ocean in short periods with the potential to produce significant nitrous oxide (N2O) emissions along an estuarine gradient. Here, we evaluate temporal and spatial N2O air-water fluxes from both seasonal, and flood-event timescales in an urban subtropical estuary surrounded by mangroves (Coffs Creek, Australia). Overall, the estuary was a minor atmospheric source of N2O with emissions of 3.9 ± 1.2 μmol m−2 d−1. However, the mangrove-dominated lower estuary was a sink of N2O in the dry months (−5.4 ± 2.2 μmol m−2 d−1), then a source in the wet months (11.7 ± 1.6 μmol m−2 d−1) and also during an eight-day flood event (66.9 ± 9.8 μmol m−2 d−1). The flood event drove changes in estuary N2O dynamics, creating a ‘hot moment’ with the highest N2O emissions following the transport of nitrate + nitrite (NOX) from the modified catchment. The hot moment coincided with a 13-fold increase in mean daily N2O emissions and increased annual net emissions estimates to the atmosphere by 41%. In the mangrove-dominated creek sections, N2O was consumed in the dry conditions (cold spots). Seasonal variation was prominent in the attenuation and consumption of N2O in the mangrove dominated sections of the creek, while flood events potentially reduce natural creek NOX attenuation capacity and elevate N2O emissions. Without observation s in both seasonal and episodic rainfall timeframes, estuarine N2O studies in subtropical regions may underestimate N2O emissions and budgets. © 2021 Elsevier Ltd
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| 69. |
- Xin, P., et al.
(författare)
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Surface Water and Groundwater Interactions in Salt Marshes and Their Impact on Plant Ecology and Coastal Biogeochemistry
- 2022
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Ingår i: Reviews of Geophysics. - : American Geophysical Union (AGU). - 8755-1209 .- 1944-9208. ; 60:1
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Tidskriftsartikel (refereegranskat)abstract
- Salt marshes are highly productive intertidal wetlands providing important ecological services for maintaining coastal biodiversity, buffering against oceanic storms, and acting as efficient carbon sinks. However, about half of these wetlands have been lost globally due to human activities and climate change. Inundated periodically by tidal water, salt marshes are subjected to strong surface water and groundwater interactions, which affect marsh plant growth and biogeochemical exchange with coastal water. This paper reviews the state of knowledge and current approaches to quantifying marsh surface water and groundwater interactions with a focus on porewater flow and associated soil conditions in connection with plant zonation as well as carbon, nutrients, and greenhouse gas fluxes. Porewater flow and solute transport in salt marshes are primarily driven by tides with moderate regulation by rainfall, evapotranspiration and sea level rise. Tidal fluctuations play a key role in plant zonation through alteration of soil aeration and salt transport, and drive the export of significant fluxes of carbon and nutrients to coastal water. Despite recent progress, major knowledge gaps remain. Previous studies focused on flows in creek-perpendicular marsh sections and overlooked multi-scale 3D behaviors. Understanding of marsh ecological-hydrological links under combined influences of different forcing factors and boundary disturbances is lacking. Variations of surface water and groundwater temperatures affect porewater flow, soil conditions and biogeochemical exchanges, but the extent and underlying mechanisms remain unknown. We need to fill these knowledge gaps to advance understanding of salt marshes and thus enhance our ability to protect and restore them.
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| 70. |
- Xu, B. C., et al.
(författare)
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Closing the Global Marine Ra-226 Budget Reveals the Biological Pump as a Dominant Removal Flux in the Upper Ocean
- 2022
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Ingår i: Geophysical Research Letters. - : American Geophysical Union (AGU). - 0094-8276 .- 1944-8007. ; 49:12
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Tidskriftsartikel (refereegranskat)abstract
- Radium isotopes are powerful proxies in oceanography and hydrology. Radium mass balance models, including assessments of submarine groundwater discharge (SGD), often overlook particle scavenging (PS) as a pathway for dissolved radium removal from the world ocean. Here, we build a global ocean Ra-226 mass balance model and reevaluate the potential importance of PS. We find that PS is the major Ra-226 sink for the upper ocean, removing about 96% of the total input from various sources. Aside from vertical exchange with the lower ocean, SGD is the largest Ra-226 source into the upper ocean. The biological pump transfers particles to the deep ocean, resulting in a major but often overlooked impact on the global Ra-226 marine budget. Our findings suggest that radium mass balance models should consider PS in systems with high siliceous algae production and export fluxes and long water residence times to prevent underestimation of large-scale SGD fluxes.
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