| 1. |
- Luyssaert, S, et al.
(författare)
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The European land and inland water CO2, CO, CH4 and N2O balance between 2001 and 2005
- 2012
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Ingår i: Biogeosciences. - : European Geosciences Union (EGU) / Copernicus Publications. - 1726-4170 .- 1726-4189. ; 9:8, s. 3357-3380
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Tidskriftsartikel (refereegranskat)abstract
- Globally, terrestrial ecosystems have absorbed about 30% of anthropogenic greenhouse gas emissions over the period 2000-2007 and inter-hemispheric gradients indicate that a significant fraction of terrestrial carbon sequestration must be north of the Equator. We present a compilation of the CO2, CO, CH4 and N2O balances of Europe following a dual constraint approach in which (1) a land-based balance derived mainly from ecosystem carbon inventories and (2) a land-based balance derived from flux measurements are compared to (3) the atmospheric data-based balance derived from inversions constrained by measurements of atmospheric GHG (greenhouse gas) concentrations. Good agreement between the GHG balances based on fluxes (1294 +/- 545 Tg C in CO2-eq yr(-1)), inventories (1299 +/- 200 Tg C in CO2-eq yr(-1)) and inversions (1210 +/- 405 Tg C in CO2-eq yr(-1)) increases our confidence that the processes underlying the European GHG budget are well understood and reasonably sampled. However, the uncertainty remains large and largely lacks formal estimates. Given that European net land to atmosphere exchanges are determined by a few dominant fluxes, the uncertainty of these key components needs to be formally estimated before efforts could be made to reduce the overall uncertainty. The net land-to-atmosphere flux is a net source for CO2, CO, CH4 and N2O, because the anthropogenic emissions by far exceed the biogenic sink strength. The dual-constraint approach confirmed that the European biogenic sink removes as much as 205 +/- 72 Tg C yr(-1) from fossil fuel burning from the atmosphere. However, This C is being sequestered in both terrestrial and inland aquatic ecosystems. If the C-cost for ecosystem management is taken into account, the net uptake of ecosystems is estimated to decrease by 45% but still indicates substantial C-sequestration. However, when the balance is extended from CO2 towards the main GHGs, C-uptake by terrestrial and aquatic ecosystems is offset by emissions of non-CO2 GHGs. As such, the European ecosystems are unlikely to contribute to mitigating the effects of climate change.
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| 2. |
- 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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| 3. |
- Taniguchi, M., et al.
(författare)
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Submarine Groundwater Discharge: Updates on Its Measurement Techniques, Geophysical Drivers, Magnitudes, and Effects
- 2019
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Ingår i: Frontiers in Environmental Science. - : Frontiers Media SA. - 2296-665X. ; 7
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Tidskriftsartikel (refereegranskat)abstract
- The number of studies concerning Submarine Groundwater Discharge (SGD) grew quickly as we entered the twenty-first century. Many hydrological and oceanographic processes that drive and influence SGD were identified and characterized during this period. These processes included tidal effects on SGD, water and solute fluxes, biogeochemical transformations through the subterranean estuary, and material transport via SGD from land to sea. Here we compile and summarize the significant progress in SGD assessment methodologies, considering both the terrestrial and marine driving forces, and local as well as global evaluations of groundwater discharge with an emphasis on investigations published over the past decade. Our treatment presents the state-of-the-art progress of SGD studies from geophysical, geochemical, bio-ecological, economic, and cultural perspectives. We identify and summarize remaining research questions, make recommendations for future research directions, and discuss potential future challenges, including impacts of climate change on SGD and improved estimates of the global magnitude of SGD.
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| 4. |
- Arevalo-Martinez, D. L., et al.
(författare)
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Ideas and perspectives: Land-ocean connectivity through groundwater
- 2023
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Ingår i: Biogeosciences. - : Copernicus GmbH. - 1726-4170 .- 1726-4189. ; 20:3, s. 647-662
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Tidskriftsartikel (refereegranskat)abstract
- For millennia, humans have gravitated towards coastlines for theirresource potential and as geopolitical centres for global trade. A basicrequirement ensuring water security for coastal communities relies on adelicate balance between the supply and demand of potable water. Theinteraction between freshwater and saltwater in coastal settings is,therefore, complicated by both natural and human-driven environmentalchanges at the land-sea interface. In particular, ongoing sea-level rise,warming and deoxygenation might exacerbate such perturbations. In thiscontext, an improved understanding of the nature and variability ofgroundwater fluxes across the land-sea continuum is timely yet remains outof reach. The flow of terrestrial groundwater across the coastal transitionzone and the extent of freshened groundwater below the present-dayseafloor are receiving increased attention in marine and coastal sciencesbecause they likely represent a significant yet highly uncertain componentof (bio)geochemical budgets and because of the emerging interest in thepotential use of offshore freshened groundwater as a resource. At the sametime, "reverse" groundwater flux from offshore to onshore is of prevalentsocio-economic interest, as terrestrial groundwater resources arecontinuously pressured by over-pumping and seawater intrusion in many coastalregions worldwide. An accurate assessment of the land-ocean connectivitythrough groundwater and its potential responses to future anthropogenicactivities and climate change will require a multidisciplinary approachcombining the expertise of geophysicists, hydrogeologists, (bio)geochemistsand modellers. Such joint activities will lay the scientific basis forbetter understanding the role of groundwater in societally relevant issuessuch as climate change, pollution and the environmental status of thecoastal oceans within the framework of the United Nations SustainableDevelopment Goals. Here, we present our perspectives on future researchdirections to better understand land-ocean connectivity through groundwater,including the spatial distributions of the essential hydrogeologicalparameters, highlighting technical and scientific developments and brieflydiscussing the societal relevance of that connectivity in rapidly changing coastal oceans.
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| 5. |
- Hajati, Mithra Christin, et al.
(författare)
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Modeling Catchment-Scale Nitrogen Losses Across a Land-Use Gradient in the Subtropics
- 2020
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Ingår i: Frontiers in Earth Science. - : Frontiers Media SA. - 2296-6463. ; 8
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Tidskriftsartikel (refereegranskat)abstract
- © Copyright © 2020 Hajati, White, Moosdorf and Santos. Changing land use in subtropical and tropical catchments to farmland can result in higher nitrogen (N) loss to aquatic ecosystems. Here, we developed a lumped water and N balance model to estimate regional N losses to creeks at catchment scale within understudied subtropical catchments in Australia. The conceptual water balance model CoCa-RFSGD was extended by the nitrogen mass balance in top and subsoil by adding nitrogen cycle transformation estimates depending on meteorological, soil, and land-use properties. The model estimates the impact of pristine and agricultural land use on catchment-wide water quality using only low-order creek samples as water quality measurements of nitrate and nitrite (NOx) with increased model performance with increased agricultural coverage. The model revealed that an agricultural proportion of 3% in the study site drove a 3.5-fold increase of N losses to creeks and a 6.7-fold increase of N losses to the atmosphere compared to catchments without agriculture. Agricultural land use lost 92 kg-N ha−1, 85% of which evaded to the atmosphere and 15% was discharged via surface waters. A change from forest to cleared land may increase the total denitrification potential of a catchment. Overall, our lumped model provides a simple but effective tool to upscale local aquatic water quality measurements to the catchment scale, allowing for assessment of changing land use on aquatic N loads in areas with limited data availability.
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