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| 2. |
- Krall, Lindsay, et al.
(author)
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Submarine groundwater discharge at Forsmark, Gulf of Bothnia, providedby Ra isotopes
- 2017
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In: Marine Chemistry. - Amsterdam : Elsevier. - 0304-4203 .- 1872-7581. ; 196, s. 162-172
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Journal article (peer-reviewed)abstract
- Submarine groundwater discharge (SGD) to the Gulf of Bothnia, Baltic Sea, has been believed to be insignificant from hydrological models, yet geochemical investigations of SGD in this basin are limited. In this study, 223Ra, 224Ra, 226Ra, and 228Ra have been complemented by stable δ18O and d2H isotopes to characterize and quantify SGD rates from the coast of Forsmark, Sweden to Öregrundsgrepen Strait (Gulf of Bothnia). In shallow bays, SGD has been traced using relations between Ra, d2H and d18O isotopes and salinity. Zonal SGD from deformation zones, expressed as hydraulically conductive fractures, overlain by the Börstilåsen esker, a strip of conductive gravel sediment, have been traced through offshore 224Raxs and 226Ra trends. On the basis of a 224Raxs mass balance, the SGD flow rate ranges from (5.5 ± 3.0) · 103 m3 d-1 to (950 ± 520) · 103 m3 d-1. These rates are up to two orders of magnitude higher than those determined from local hydrological models, which consider only the fresh component of SGD. From the divergence between the hydrological and 224Raxs models, it is inferred that the site is influenced by a component of recirculated seawater.
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| 3. |
- Olid, Carolina, 1981-, et al.
(author)
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Groundwater discharge as a driver of methane emissions from Arctic lakes
- 2022
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In: Nature Communications. - : Nature Publishing Group. - 2041-1723. ; 13:1
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Journal article (peer-reviewed)abstract
- Lateral CH4 inputs to Arctic lakes through groundwater discharge could be substantial and constitute an important pathway that links CH4 production in thawing permafrost to atmospheric emissions via lakes. Yet, groundwater CH4 inputs and associated drivers are hitherto poorly constrained because their dynamics and spatial variability are largely unknown. Here, we unravel the important role and drivers of groundwater discharge for CH4 emissions from Arctic lakes. Spatial patterns across lakes suggest groundwater inflows are primarily related to lake depth and wetland cover. Groundwater CH4 inputs to lakes are higher in summer than in autumn and are influenced by hydrological (groundwater recharge) and biological drivers (CH4 production). This information on the spatial and temporal patterns on groundwater discharge at high northern latitudes is critical for predicting lake CH4 emissions in the warming Arctic, as rising temperatures, increasing precipitation, and permafrost thawing may further exacerbate groundwater CH4 inputs to lakes.
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| 4. |
- Trezzi, Giada, et al.
(author)
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Assessing the role of submarine groundwater discharge as a source of Sr to the Mediterranean Sea
- 2017
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In: Geochimica et Cosmochimica Acta. - : Elsevier. - 0016-7037 .- 1872-9533. ; 200, s. 42-54
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Journal article (peer-reviewed)abstract
- Submarine groundwater discharge (SGD) has been identified as animportant source of Sr to the ocean and the SGD-driven Sr flux to theglobal ocean has been recently re-evaluated (Beck et al. 2013). However,the uncertainty of this value is still high because of the uncertaintiesrelated to the determination of SGD flow rates and the paucity of87Sr/86Sr data in SGD end-members. As carbonates have high Srconcentrations and are subjected to intense heightened weathering, theymight significantly influence the SGD input of Sr to the ocean. Here wepresent data on Sr concentrations and 87Sr/86Sr ratios in three carbonatedominated sites of the western area of the Mediterranean Sea, a semienclosedbasin characterized by abundant coastal carbonates. The87Sr/86Sr ratios in groundwater were lower compared to modern seawater (~0.70916), as expected for areas dominated by carbonate lithologies.Concentrations of Sr and 87Sr/86Sr ratios in groundwater showedconservative mixing in the studied subterranean estuaries. By using SGDflow rates reported in the literature for the study areas, a meteoricSGD-driven Sr flux of (0.12 - 2.1)·103 mol d-1 km-1 was calculated forthe region, with a fresh SGD end-member characterized by a Srconcentration of 27 - 30 μM and a 87Sr/86Sr ratio of 0.708020 - 0.707834.Integrating these Sr data with literature data (i.e. values of Srconcentration and 87Sr/86Sr ratio from other lithologies as well as SGDflow rates), we also calculated the fresh SGD-driven Sr flux to theentire Mediterranean Sea, obtaining a value of (0.34 - 0.83)·109 mol y-1,with a 87Sr/86Sr of 0.7086 - 0.7081. Thus, for the entire Mediterraneanbasin, SGD is globally a source of Sr less radiogenic compared toseawater. The SGD Sr flux to the Mediterranean Sea represents 5-6% of theSGD Sr flux to the global ocean and the Mediterranean SGD end-member hashigher Sr concentration (5.0 - 12 μM) than the global SGD end-member (2.9μM). This confirms the significant role of carbonate lithologies on SGDdrivenSr fluxes to seawater.The fresh SGD-driven Sr flux to the Mediterranean Sea is about 20 - 50%of the riverine Sr input and significantly higher than the input throughatmospheric dust deposition. Therefore SGD should be considered as animportant continental source of Sr to the basin.
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| 5. |
- Wilson, Stephanie J., et al.
(author)
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Global subterranean estuaries modify groundwater nutrient loading to the ocean
- 2024
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In: Limnology And Oceanography Letters. - 2378-2242.
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Journal article (peer-reviewed)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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