| 1. |
- Adyasari, D., et al.
(författare)
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Radon-222 as a groundwater discharge tracer to surface waters
- 2023
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Ingår i: Earth-Science Reviews. - : Elsevier BV. - 0012-8252. ; 238
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Tidskriftsartikel (refereegranskat)abstract
- The naturally occurring isotope radon-222 (222Rn) is widely employed as a tracer for groundwater discharge to lakes, lagoons, rivers, estuaries, and coastal oceans. However, owing to the highly diverse hydrogeological settings, limitations, and assumptions when applying the 222Rn mass balance, there is a clear need to create a uniform approach that will constrain the uncertainties in the reported groundwater fluxes. This review paper provides an overview of the 222Rn measurement techniques and discusses 222Rn mass balances and their application to various hydrological environments. We address the primary uncertainties faced when applying 222Rn mass balances including, (1) atmospheric evasion, (2) groundwater endmember, (3) offshore mixing loss, (4) steady-state assumptions, and (5) upscaling groundwater discharge from 222Rn measurements, and methods that can be applied to minimize these uncertainties. Finally, we provide guidelines and open-source scripts (i.e., R codes and FINIFLUX) that should assist future studies using 222Rn to quantify groundwater discharge to surface waters.
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| 2. |
- Knee, Karen, et al.
(författare)
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Submarine Groundwater Discharge: A Source of Nutrients, Metals, and Pollutants to the Coastal Ocean
- 2024
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Ingår i: Treatise on Estuarine and Coastal Science, 2nd Edition. - : Elsevier. ; , s. 123-163
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Bokkapitel (refereegranskat)abstract
- This chapter reviews the current knowledge on submarine groundwater discharge (SGD) and the associated fluxes of nutrients, trace metals, microbes, pharmaceuticals, and other terrestrial constituents to coastal waters. We review methods of estimating SGD, present flux estimates from different locations worldwide, and discuss how various hydrogeologic features such as topography, aquifer substrate, climate, waves, and tides affect SGD. We discuss the range of material concentrations and fluxes, their relationship to land use, and the chemical changes that nutrients and metals undergo during their seaward journey through the aquifer. Climate change is likely to affect both the quantity and the quality of SGD, and we review these effects. The chapter concludes with a discussion of active areas of SGD research, including expanding the geographic scope of SGD studies; characterizing and reducing the uncertainty associated with SGD measurements; understanding the behavior of nutrients, metals, and other pollutants in the subterranean estuary; and modeling SGD on a global scale.
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| 3. |
- Ljungberg, Wilma, 1998, et al.
(författare)
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Carbon Outwelling and Uptake Along a Tidal Glacier-Lagoon-Ocean Continuum
- 2024
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Ingår i: Journal of Geophysical Research (JGR): Biogeosciences. - 2169-8953 .- 2169-8961. ; 129:e2023JG007895
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Tidskriftsartikel (refereegranskat)abstract
- Tidewater glaciers are highly vulnerable to climate change due to warming from both atmospheric and seawater sources. Most tidewater glaciers are rapidly retreating, but little is known about how glacial melting modifies coastal biogeochemical cycles. Here, we investigate carbonate and nutrient dynamics and fluxes in an expanding proglacial tidal lagoon connected to Europe's largest glacier in Iceland (Vatnajökull). The lagoon N:P:Si ratios (2:1:30) imply a system deficient in nitrogen. The large variations in the freshwater endmembers highlighted the complexity of resolving sources and transformations. The lagoon acted as a sink of dissolved inorganic carbon (DIC). Floating chamber incubations revealed a CO2 uptake of 26±15mmolm−2d−1. Lagoon waters near the glacier had a 170% higher CO2 uptake than near the lagoon mouth, likely driven by primary production stimulated by nitrogen-rich bottom water upwelling. The lateral DIC and total alkalinity (TA) flux rates (outwelling) from the lagoon to the ocean were −1.5±0.1 (export to ocean) and 23±5mmolm−2d−1 (import into the lagoon) respectively. All samples were undersaturated with respect to aragonite due to glacial meltwater dilution of TA and CO2 uptake. This implies dilution of oceanic alkalinity, lowering the nearshore buffering capacity against ocean acidification.
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| 4. |
- McKenzie, Tristan, et al.
(författare)
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Metals in coastal groundwater systems under anthropogenic pressure: a synthesis of behavior, drivers, and emerging threats
- 2024
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Ingår i: Limnology And Oceanography Letters. - 2378-2242.
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Tidskriftsartikel (refereegranskat)abstract
- Submarine groundwater discharge (SGD) dynamically links land- and ocean-derived chemical constituents, such as metals, in the coastal ocean. While many metals are sediment-bound, changing environmental conditions, particularly along the coast, may lead to increased release of metals to their dissolved and more bioavailable form. Here, we review metal behavior, speciation, and drivers of mobilization in the coastal environment under anthropogenic influence. We also model global metal contamination risk to the coastal ocean via SGD considering anthropogenic and hydrogeologic pressures, where tropical regions with high population density, SGD, and acid sulfate soils (4% of the global coast) present the highest risk. Although most SGD studies focus on other analytes, such as nutrients, this review demonstrates the importance of considering SGD as a critical pathway for metals to reach the coastal ocean under rapidly changing environmental conditions.
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| 5. |
- McKenzie, Tristan, et al.
(författare)
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Submarine groundwater discharge: A previously undocumented source of contaminants of emerging concern to the coastal ocean (Sydney, Australia)
- 2020
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Ingår i: Marine Pollution Bulletin. - : Elsevier BV. - 0025-326X .- 1879-3363. ; 160:November
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Tidskriftsartikel (refereegranskat)abstract
- © 2020 The Authors Submarine groundwater discharge (SGD) is rarely considered as a pathway for contaminants of emerging concern (CECs). Here, we investigated SGD as a source of CECs in Sydney Harbour, Australia. CEC detection frequencies based on presence/absence of a specific compound were >90% for caffeine, carbamazepine, and dioxins, and overall ranged from 25 to 100% in five studied embayments. SGD rates estimated from radium isotopes explained >80% of observed CEC inventories for one or more compounds (caffeine, carbamazepine, dioxins, sulfamethoxazole, fluoroquinolones and ibuprofen) in four out of the five embayments. Radium-derived residence times imply mixing is also an important process for driving coastal inventories of these persistent chemicals. Two compounds (ibuprofen and dioxins) were in concentrations deemed a high risk to the ecosystem. Overall, we demonstrate that SGD can act as a vector for CECs negatively impacting coastal water quality.
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| 6. |
- McKenzie, Tristan, et al.
(författare)
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Traditional and novel time-series approaches reveal submarine groundwater discharge dynamics under baseline and extreme event conditions
- 2021
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Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 11:1
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Tidskriftsartikel (refereegranskat)abstract
- Groundwater is a vital resource for humans and groundwater dependent ecosystems. Coastal aquifers and submarine groundwater discharge (SGD), both influenced by terrestrial and marine forces, are increasingly affected by climate variations and sea-level rise. Despite this, coastal groundwater resources and discharge are frequently poorly constrained, limiting our understanding of aquifer responses to external forces. We apply traditional and novel time-series approaches using an SGD dataset of previously unpublished resolution and duration, to analyze the dependencies between precipitation, groundwater level, and SGD at a model site (Kiholo Bay, HawaiModified Letter Turned Commai). Our objectives include (1) determining the relative contribution of SGD drivers over tidal and seasonal periods, (2) establishing temporal relationships and thresholds of processes influencing SGD, and (3) evaluating the impacts of anomalous events, such as tropical storms, on SGD. This analysis reveals, for example, that precipitation is only a dominant influence during wet periods, and otherwise tides and waves dictate the dynamics of SGD. It also provides time lags between intense storm events and higher SGD rates, as well as thresholds for precipitation, wave height and tides affecting SGD. Overall, we demonstrate an approach for modeling a hydrological system while elucidating coastal aquifer and SGD response in unprecedented detail.
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| 7. |
- McKenzie, Tristan, et al.
(författare)
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Using Deep Learning to Model the Groundwater Tracer Radon in Coastal Waters
- 2023
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Ingår i: Water Resources Research. - 0043-1397 .- 1944-7973. ; 59:3
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Tidskriftsartikel (refereegranskat)abstract
- Submarine groundwater discharge (SGD) is an important driver of coastal biogeochemical budgets worldwide. Radon (222Rn) has been widely used as a natural geochemical tracer to quantify SGD, but field measurements are time consuming and costly. Here, we use deep learning to predict coastal seawater radon in SGD-impacted regions. We hypothesize that deep learning could resolve radon trends and enable preliminary insights with limited field observations of groundwater tracers. Two deep learning models were trained on global coastal seawater radon observations (n = 39,238) with widely available inputs (e.g., salinity, temperature, water depth). The first model used a one-dimensional convolutional neural network (1D-CNN-RNN) framework for site-specific gap filling and producing short-term future predictions. A second model applied a fully connected neural network (FCNN) framework to predict radon across geographically and hydrologically diverse settings. Both models can predict observed radon concentrations with r2 > 0.76. Specifically, the FCNN model offers a compelling development because synthetic radon tracer data sets can be obtained using only basic water quality and meteorological parameters. This opens opportunities to attain radon data from regions with large data gaps, such as the Global South and other remote locations, allowing for insights that can be used to predict SGD and plan field experiments. Overall, we demonstrate how field-based measurements combined with big-data approaches such as deep learning can be utilized to assess radon and potentially SGD beyond local scales.
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| 8. |
- Mora, C., et al.
(författare)
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Over half of known human pathogenic diseases can be aggravated by climate change
- 2022
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Ingår i: Nature Climate Change. - : Springer Science and Business Media LLC. - 1758-678X .- 1758-6798. ; 12, s. 869-875
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Tidskriftsartikel (refereegranskat)abstract
- It is relatively well accepted that climate change can affect human pathogenic diseases; however, the full extent of this risk remains poorly quantified. Here we carried out a systematic search for empirical examples about the impacts of ten climatic hazards sensitive to greenhouse gas (GHG) emissions on each known human pathogenic disease. We found that 58% (that is, 218 out of 375) of infectious diseases confronted by humanity worldwide have been at some point aggravated by climatic hazards; 16% were at times diminished. Empirical cases revealed 1,006 unique pathways in which climatic hazards, via different transmission types, led to pathogenic diseases. The human pathogenic diseases and transmission pathways aggravated by climatic hazards are too numerous for comprehensive societal adaptations, highlighting the urgent need to work at the source of the problem: reducing GHG emissions.
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| 9. |
- Wilson, Stephanie J., et al.
(författare)
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Global subterranean estuaries modify groundwater nutrient loading to the ocean
- 2024
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Ingår i: Limnology And Oceanography Letters. - 2378-2242.
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Tidskriftsartikel (refereegranskat)abstract
- Terrestrial groundwater travels through subterranean estuaries before reaching the sea. Groundwater-derived nutrients drive coastal water quality, primary production, and eutrophication. We determined how dissolved inorganic nitrogen (DIN), dissolved inorganic phosphorus (DIP), and dissolved organic nitrogen (DON) are transformed within subterranean estuaries and estimated submarine groundwater discharge (SGD) nutrient loads compiling > 10,000 groundwater samples from 216 sites worldwide. Nutrients exhibited complex, nonconservative behavior in subterranean estuaries. Fresh groundwater DIN and DIP are usually produced, and DON is consumed during transport. Median total SGD (saline and fresh) fluxes globally were 5.4, 2.6, and 0.18 Tmol yr−1 for DIN, DON, and DIP, respectively. Despite large natural variability, total SGD fluxes likely exceed global riverine nutrient export. Fresh SGD is a small source of new nutrients, but saline SGD is an important source of mostly recycled nutrients. Nutrients exported via SGD via subterranean estuaries are critical to coastal biogeochemistry and a significant nutrient source to the oceans.
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