| 1. |
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| 2. |
- Fransson, Agneta, 1964, et al.
(författare)
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CO2-system development in young sea ice and CO2 gas exchange at the ice/air interface mediated by brine and frost flowers in Kongsfjorden, Spitsbergen
- 2015
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Ingår i: Annals of Glaciology. - 0260-3055. ; 56:69, s. 245-257
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Tidskriftsartikel (refereegranskat)abstract
- In March and April 2010, we investigated the development of young landfast sea ice in Kongsfjorden, Spitsbergen, Svalbard. We sampled the vertical column, including sea ice, brine, frost flowers and sea water, to determine the CO2 system, nutrients, salinity and bacterial and ice algae production during a 13 day interval of ice growth. Apart from the changes due to salinity and brine rejection, the sea-ice concentrations of total inorganic carbon (C T), total alkalinity (A T), CO2 and carbonate ions (CO3 2–) in melted ice were influenced by dissolution of calcium carbonate (CaCO3) precipitates (25–55 μmol kg–1) and played the largest role in the changes to the CO2 system. The C T values were also influenced by CO2 gas flux, bacterial carbon production and primary production, which had a small impact on the C T. The only exception was the uppermost ice layer. In the top 0.05 m of the ice, there was a CO2 loss of ∼20 μmol kg–1 melted ice (1 mmol m–2) from the ice to the atmosphere. Frost flowers on newly formed sea ice were important in promoting ice–air CO2 gas flux, causing a CO2 loss to the atmosphere of 140–800 μmol kg–1 d–1 melted frost flowers (7–40 mmol m–2 d–1).
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| 3. |
- Granfors, Anna, 1978, et al.
(författare)
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Biogenic halocarbons in young Arctic sea ice and frost flowers
- 2013
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Ingår i: Marine Chemistry. - : Elsevier BV. - 0304-4203. ; 155, s. 124-134
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Tidskriftsartikel (refereegranskat)abstract
- The fate of halocarbons, naturally produced volatile halogenated organic compounds, in young Arctic sea ice was studied to better understand the role of sea ice in halocarbon cycling. In early spring, halocarbons were measured in sea ice frozen in core holes, during 12 days of formation and freezing. In order to understand which factors govern halocarbon concentration and distribution, salinity, temperature and biological parameters were monitored in the growing sea ice. It was found that sea ice participates in the cycling of halocarbons between sea and air. Sea ice concentrations and distributions of these compounds were influenced by production in the ice, where ice-inhabiting microorganisms caused local increases in halocarbon concentrations. Moreover, the halocarbon ice concentration decrease/change with time did not follow ice salinity, suggesting that additional removal processes caused sea ice to be a source of halogens to overlying air. The net production rate of bromoform in the surface of newly frozen ice was estimated to 14 pmol L−1 d−1 and the maximum removal rate was 18 pmol L−1 d−1. In addition frost flowers on newly formed sea ice were identified as contributors of halocarbons to the atmosphere with halocarbon concentrations in the same order of magnitude as in sea ice brine
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| 4. |
- Gårdfeldt, Katarina, 1959, et al.
(författare)
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A kinetic study on the Abiotic Methylation of Divalent Mercury in the Aqueous phase
- 2003
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Ingår i: Science of the Total Environment. - 0048-9697 .- 1879-1026. ; 304:1-3, s. 127-136
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Tidskriftsartikel (refereegranskat)abstract
- The mechanism and kinetics of the formation of methylmercury from an experimental solution containing divalent mercury and acetic acid has been investigated. The experiments were performed in a 2-dm3 Teflon reactor. The organic mercury was measured with time resolutions varying between minutes and hours, after derivatisation, gas chromatography separation and Cold vapour atomic fluorescence detection. (GC)-CVAFS. CVAFS technique was used for determination of inorganic mercury in the aqueous phase using an automated mercury analyser. The experiments were carried out in concentrations relevant for natural waters. Our result shows that the reaction proceeds via mercury acetate complexes. A first order reaction coefficient has been calculated at various pH values, and was found to be (9.0±0.9)×10−7 s−1 at pH 3.6–3.7. The rate was not found to be enhanced by UV-light when taking into account the photolytical degradation of methylmercury. The reaction rate at various pH values, the influences of some other relevant reaction parameters, and implications for atmospheric and terrestrial waters are discussed.
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| 5. |
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| 6. |
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| 7. |
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| 8. |
- Gårdfeldt, Katarina, 1959, et al.
(författare)
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Evasion of Mercury from coastal and open waters of the Atlantic ocean and the Mediterranean sea
- 2003
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Ingår i: Atmospheric Environment. - 1352-2310 .- 1873-2844. ; 37:Suppl 1
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Tidskriftsartikel (refereegranskat)abstract
- Dissolved gaseous mercury (DGM) was measured in coastal Atlantic seawater and in the Mediterranean Sea. The Atlantic measurements were performed during September 1999 at the Mace Head Atmospheric Research Station, situated on the Irish west coast. The measurements in the Mediterranean Sea were made along a 6000 km cruise path from 14 July to 9 August 2000 in the framework of the Med-Oceanor project. Total gaseous mercury (TGM) concentrations in air were continuously measured with a 5 min time resolution using an automated mercury analyser (Tekran 2537A) during both expeditions. Paired TGM and DGM samples from all campaigns showed that the surface water was supersaturated with elemental mercury. The mercury evasion was estimated using a gas exchange model (J. Geophys. Res. 97 (1992) 7373), which uses salinity, wind speed and water temperature as independent parameters. The predicted average mercury evasion from the coastal Atlantic water was 2.7 ng m−2 h−1 implying that the concentration of TGM in the Atlantic air is enhanced by mercury evasion from the sea. Measurements in different regions of the Mediterranean Sea showed spatial variations in DGM concentrations. The highest DGM concentration (90 pg l−1) was observed at a location in the Strait of Sicily (37°16N 11°52E). The mercury evasion in the eastern sector of the Mediterranean Sea (area: 32–36°N, 17–28°E) was generally higher (7.9 ng m−2 h−1) than that observed in the Tyrrhenian Sea (4.2 ng m−2 h−1) or in the western sector (2.5 ng m−2 h−1) (areas: 38–42°N, 8–13°E and 38–41°N, 7–8°E, respectively). Estimations of mercury evasion were also made at Mediterranean coastal sites using a dynamic chamber technique. In addition, a newly developed method making continuous in situ DGM measurements possible was tested.
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| 9. |
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| 10. |
- Gårdfeldt, Katarina, 1959, et al.
(författare)
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Oxidation of atomic mercury by hydroxyl radicals and photoinduced decomposition of methylmercury species in the aqueous phase
- 2001
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Ingår i: Atmospheric Environment. - 1352-2310 .- 1873-2844. ; 35:17, s. 3039-3047
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Tidskriftsartikel (refereegranskat)abstract
- The rate constant for Hg0+.OH, kHg0+.OH=(2.4±0.3)×109 M−1 s−1, in the aqueous phase was determined using a relative rate technique with methyl mercury as reference compound. The .OH initiated mercury reaction proceeds via the molecular Hg(I) radical which is oxidised to Hg(II) by dissolved O2. The reaction can be of importance under certain atmospheric circumstances, such as when the aqueous phase capacity of forming OH radicals is significant and the gas phase concentration of ozone drops. The same end product, i.e. Hg(II) was observed from the photodegradation of methylmercury hydroxide. In this case, molecular Hg(I) radicals are again likely to be formed after photodegradation of the Hg–C bond with subsequent oxidation. A lifetime of 230 h of methylmercury at outdoor conditions was estimated due to this reaction. The action of .OH on methylmercury species also involves breaking of organometallic bonds and formation of Hg(II). Speciation of these reaction products from methylmercury is important for the estimation of biogeochemical cycling of mercury.
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| 11. |
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| 12. |
- Munthe, John, et al.
(författare)
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Distribution of atmospheric mercury species in Northern Europe: Final results from the MOE-project
- 2003
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Ingår i: Atmospheric Environment. - 1352-2310 .- 1873-2844. ; 37:Suppl 1
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Tidskriftsartikel (refereegranskat)abstract
- The mercury species over Europe (MOE) project was aimed at identifying sources, occurrence and atmospheric behaviour of atmospheric Hg species. Within MOE, emission measurements, ambient air measurements, process and regional-scale modelling and laboratory measurements were conducted. In this work, a summary of some of the main results is given. From the emission measurements, information on stack gas concentrations and emission factors for five coal fired power plants and three waste incinerators are presented. Results from field measurements of mercury species in ambient air at five locations in Northern Europe are presented. Examples from regional-scale atmospheric modelling are also given. The results emphasise the importance of information on Hg species for instance in emission inventories and measurement data from background sites. Furthermore, the importance of considering the role of the global cycling of mercury in future control strategies is emphasised
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| 13. |
- Nerentorp, Michelle, 1986, et al.
(författare)
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Antarctic winter mercury and ozone depletion events over sea ice
- 2016
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Ingår i: Atmospheric Environment. - : Elsevier BV. - 1352-2310 .- 1873-2844. ; 129, s. 125-132
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Tidskriftsartikel (refereegranskat)abstract
- During atmospheric mercury and ozone depletion events in the springtime in polar regions gaseous elemental mercury and ozone undergo rapid declines. Mercury is quicldy transformed into oxidation products, which are subsequently removed by deposition. Here we show that such events also occur during Antarctic winter over sea ice areas, leading to additional deposition of mercury. Over four months in the Weddell Sea we measured gaseous elemental, oxidized, and particulate-bound mercury, as well as ozone in the troposphere and total and elemental mercury concentrations in snow, demonstrating a series of depletion and deposition events between July and September. The winter depletions in July were characterized by stronger correlations between mercury and ozone and larger formation of particulate-bound mercury in air compared to later spring events. It appears that light at large solar zenith angles is sufficient to initiate the photolytic formation of halogen radicals. We also propose a dark mechanism that could explain observed events in air masses coming from dark regions. Br-2 that could be the main actor in dark conditions was possibly formed in high concentrations in the marine boundary layer in the dark. These high concentrations may also have caused the formation of high concentrations of CHBr3 and CH2I2 in the top layers of the Antarctic sea ice observed during winter. These new findings show that the extent of depletion events is larger than previously believed and that winter depletions result in additional deposition of mercury that could be transferred to marine and terrestrial ecosystems.
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| 14. |
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| 15. |
- Sommar, Jonas, 1969, et al.
(författare)
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A kinetic study of the gas-phase reaction between the hydroxylradical and atomic mercury
- 2001
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Ingår i: Atmos.Environ. - 1352-2310 .- 1873-2844. ; 35:17, s. 3049-3054
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Tidskriftsartikel (refereegranskat)abstract
- The atom is the dominating species of mercury in the atmosphere. Its oxidation processes are of great interest since it is mainly oxidised mercury that undergoes deposition and thereby spreads into the ecosystems and becomes bioaccumulated. The kinetics of the gas-phase reaction between atomic mercury and hydroxyl radical has been determined at room temperature and atmospheric pressure of air by relative rate technique. OH radicals were produced by photolysis employing methyl nitrite. By using cyclohexane as the reference compound, the rate coefficient obtained was k(Hg0+·OH)=(8.7±2.8)×10−14 cm3 s−1 leading to natural lifetimes of mercury at global mean conditions of 4–7 month due to this reaction.
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| 16. |
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| 17. |
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| 18. |
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| 19. |
- Andersson, Maria, et al.
(författare)
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Air-sea exchange of volatile mercury in the North Atlantic Ocean
- 2011
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Ingår i: Marine Chemistry. - : Elsevier BV. - 0304-4203. ; 125:1-4, s. 1-7
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Tidskriftsartikel (refereegranskat)abstract
- Part of the Beringia 2005 expedition covered the North Atlantic Ocean. During this passage, dissolved gaseous mercury (DGHg) in seawater and atmospheric concentrations of total gaseous mercury (TGHg), carbon monoxide (CO), and ozone (O-3) were measured continuously at high resolution. In addition, meteorological parameters such as wind speed and water temperature were measured continuously by the ship's meteorological instrumentation. The DGHg concentration was measured using a continuous equilibrium system where the elemental mercury in the sea water was equilibrated with a stream of gas. The DGHg concentration was calculated using DGHg=Hg-eq/k(H), where Hg-eq is the concentration of elemental mercury in the equilibrated air and k(H), is the dimensionless Henry's law constant. The degree of saturation was determined directly from the measurements S = Hg-eq/TGHg. The water sampled had an average DGHg concentration of 58 +/- 10 fM and the average TGHg concentration was determined to 1.7 +/- 0.1 ng m(-3). The water sampled was under- and super-saturated with respect to elemental mercury covering a large range of saturation of 70 to 230% resulting in an average degree of saturation of 150 +/- 30%. Therefore, both evasion and deposition of elemental mercury were observed in the sampled water. In the light of the average flux, 2.1 +/- 1.8 pmol m(-2) h(-1), it is concluded that mostly evasion occured during the sampling period. (C) 2011 Elsevier B.V. All rights reserved.
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| 20. |
- Andersson, Maria, 1980, et al.
(författare)
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Enhanced concentrations of dissolved gaseous mercury in the surface waters of the Arctic Ocean
- 2008
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Ingår i: Marine Chemistry. - : Elsevier BV. - 0304-4203. ; 110:3-4, s. 190-194
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Tidskriftsartikel (refereegranskat)abstract
- During an almost three months long expedition in the Arctic Ocean, the Beringia 2005, dissolved gaseous mercury (DGM) was measured continuously in the surface water. The DGM concentration was measured using an equilibrium system, i.e. the DGM in the water phase equilibrated with a stream of gas and the gas was thereafter analysed with respect to its mercury content. The DGM concentrations were calculated using the following equation, DGM = Hg eq / k H' where Hg eq is the equilibrated concentration of elemental mercury in the gas phase and k H' is the dimensionless Henry's law constant at desired temperature and salinity. During the expedition several features were observed. For example, enhanced DGM concentration was measured underneath the ice which may indicate that the sea ice acted as a barrier for evasion of mercury from the Arctic Ocean to the atmosphere. Furthermore, elevated DGM concentrations were observed in water that might have originated from river discharge. The gas-exchange of mercury between the ocean and the atmosphere was calculated in the open water and both deposition and evasion were observed. The measurements showed significantly enhanced DGM concentrations, compared to more southern latitudes. © 2008 Elsevier B.V. All rights reserved.
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| 21. |
- Andersson, Maria, 1980, et al.
(författare)
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Seasonal and daily variation of mercury evasion at coastal and off shore sites from the Mediterranean Sea
- 2007
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Ingår i: Marine Chemistry. - : Elsevier BV. - 0304-4203. ; 104:3-4, s. 214-226
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Tidskriftsartikel (refereegranskat)abstract
- Dissolved gaseous mercury (DGM) was measured continuously using two newly developed techniques and a manual technique. The continuous techniques were based on the equilibrium between the aqueous and gaseous phase (DGM = Hg-extr / H', Hg-extr is the measured mercury concentration in the gas phase, H' is the Henry's Law coefficient at the desired temperature). In order to calculate the annual mercury evasion from the Mediterranean Sea, diurnal and seasonal measurements of DGM, total gaseous mercury in air (TGM), water temperature and wind speed were performed. During August 2003, March-April 2004 and October-November 2004 measurements of these parameters were conducted on board the RV Urania. The continuous measurements of DGM showed a diurnal variation in concentration, at both coastal and off shore sites, with higher concentrations during daytime than nighttime. The concentration difference could be as large as 130 fM between day and night. The degree of saturation was calculated directly from the measurements, S = Hg-extr / TGM and was found to vary between the different seasons. The highest average degree of saturation (850%) and the largest variation in saturation (600-1150%) was observed during the summer. The spring showed the lowest variation (260-360%) and the lowest average degree of saturation (320%). The autumn also showed a large variation in saturation (500-1070%) but a lower average (740%) compared to the summer cruise. This might be explained by the temperature difference between the different seasons, since that parameter varied the most. The flux from the sea surface was calculated using the gas exchange model developed by Nightingale et al. [Nightingale, P.D., Malin, G., Law, C.S., Watson, A.J., Liss, P. S., Liddicoat, M.I., Boutin, J., Upstill-Goddard, R. C., 2000. In situ evaluation of air-sea gas exchange parameterization using novel conservative and volatile tracers. Global Biogeochemical Cycles, 14(l):373-387]. The evasion varied between the different seasons with the highest evasion during the autumn, 24.6 pmol m(-2) h(-1). The summer value was estimated to 22.3 pmol m(-2) h(-1) and the spring to 7.6 pmol m(-2) h(-1). Using this data the yearly evasion from the Mediterranean Sea surface was estimated to 77 tons. (C) 2006 Elsevier B.V. All rights reserved.
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| 22. |
- Angot, H., et al.
(författare)
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Chemical cycling and deposition of atmospheric mercury in polar regions: review of recent measurements and comparison with models
- 2016
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Ingår i: Atmospheric Chemistry and Physics. - : Copernicus GmbH. - 1680-7316 .- 1680-7324. ; 16:16, s. 10735-10763
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Tidskriftsartikel (refereegranskat)abstract
- Mercury (Hg) is a worldwide contaminant that can cause adverse health effects to wildlife and humans. While atmospheric modeling traces the link from emissions to deposition of Hg onto environmental surfaces, large uncertainties arise from our incomplete understanding of atmospheric processes (oxidation pathways, deposition, and re-emission). Atmospheric Hg reactivity is exacerbated in high latitudes and there is still much to be learned from polar regions in terms of atmospheric processes. This paper provides a synthesis of the atmospheric Hg monitoring data available in recent years (2011-2015) in the Arctic and in Antarctica along with a comparison of these observations with numerical simulations using four cutting-edge global models. The cycle of atmospheric Hg in the Arctic and in Antarctica presents both similarities and differences. Coastal sites in the two regions are both influenced by springtime atmospheric Hg depletion events and by summertime snowpack re-emission and oceanic evasion of Hg. The cycle of atmospheric Hg differs between the two regions primarily because of their different geography. While Arctic sites are significantly influenced by northern hemispheric Hg emissions especially in winter, coastal Antarctic sites are significantly influenced by the reactivity observed on the East Antarctic ice sheet due to katabatic winds. Based on the comparison of multi-model simulations with observations, this paper discusses whether the processes that affect atmospheric Hg seasonality and inter-annual variability are appropriately represented in the models and identifies research gaps in our understanding of the atmospheric Hg cycling in high latitudes.
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| 23. |
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| 24. |
- Gårdfeldt, Katarina, 1959, et al.
(författare)
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SWEDARCTIC Arctic Ocean 2016: Expedition Report
- 2017
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Key words: Nyckelord [sv]geophysical mapping, seismic reflection, seismic refraction, water column imaging, physical oceanography, heavy metals, mercury, microplastics, trace gases, biogeochemistry, dredging, sediment coring, sediment properties, meteorology, atmospheric boundary-layer, surface fluxes, ice management, ice thickness, polar on stage
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| 25. |
- Hoglind, Hanna, et al.
(författare)
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Ship-based measurements of atmospheric mercury concentrations over the Baltic Sea
- 2018
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Ingår i: Atmosphere. - : MDPI AG. - 2073-4433. ; 9:2
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Tidskriftsartikel (refereegranskat)abstract
- Mercury is a toxic pollutant emitted from both natural sources and through human activities. A global interest in atmospheric mercury has risen ever since the discovery of the Minamata disease in 1956. Properties of gaseous elemental mercury enable long range transport, which can cause pollution even in pristine environments. Gaseous elemental mercury (GEM) was measured from winter 2016 to spring 2017 over the Baltic Sea. A Tekran 2357A mercury analyser was installed aboard the research and icebreaking vessel Oden for the purpose of continuous measurements of gaseous mercury in ambient air. Measurements were performed during a campaign along the Swedish east coast and in the Bothnian Bay near Lulea during the icebreaking season. Data was evaluated from Gothenburg using plotting software, and back trajectories for air masses were calculated. The GEM average of 1.36 ± 0.054 ng/m 3 during winter and 1.29 ± 0.140 ng/m 3 during spring was calculated as well as a total average of 1.36 ± 0.16 ng/m 3 . Back trajectories showed a possible correlation of anthropogenic sources elevating the mercury background level in some areas. There were also indications of depleted air, i.e., air with lower concentrations than average, being transported from the Arctic to northern Sweden, resulting in a drop in GEM levels.
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| 26. |
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| 27. |
- Jonsson, Sofi, et al.
(författare)
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Distribution of total mercury and methylated mercury species in Central Arctic Ocean water and ice
- 2022
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Ingår i: Marine Chemistry. - : Elsevier BV. - 0304-4203 .- 1872-7581. ; 242
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Tidskriftsartikel (refereegranskat)abstract
- The central Arctic Ocean remains largely unexplored when it comes to the presence and cycling of mercury and its methylated forms including mono- and dimethylmercury (MMeHg and DMeHg, respectively). In this study, we quantified total Hg (HgT) and methylated Hg species in seawater, ice cores, snow, brine, and water from melt ponds collected during the SWEDARCTIC 2016 expedition to the Amerasian and Eurasian side of the Lomonosov Ridge. In the water column, concentrations of HgT, MMeHg and DMeHg ranged from 0.089 to 1.5 pM, <25 to 520 fM and from <1.6 to 160 fM, respectively. HgT was enriched in surface waters while MMeHg and DMeHg were low at the surface (i.e. in the polar mixed layer) and enriched at a water depth of around 200–400 m. A 1:2 ratio of DMeHg to MMeHg was observed in the water column suggesting a lower ratio in the central parts of the Arctic Ocean than what has previously been reported from other parts of the Arctic Ocean. At the ice stations, average HgT ranged from 0.97 ± 1.2 pM in the ice cores to 27 ± 17 pM in melt pond waters and average MeHgT (total MeHg) from 28 ± 15 fM in brine to 130 ± 18 fM in melt pond water. The HgT observed in melt ponds and brine was an order of magnitude greater than HgT observed in surface waters and HgT in the upper part of the ice-cores was ~4–8 times higher HgT in comparison to lower layers. Our study suggests that ice may act as a source of HgT to surface waters but not to be a likely source of the methylated Hg forms. Unlike elemental Hg, DMeHg did not enrich in surface waters covered by ice. Concentrations of DMeHg observed in the ice cores and other samples collected from the ice stations were low, suggesting ice to not act as a source of DMeHg to the atmosphere nor to surface waters.
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| 28. |
- Kanhai, La Daana K., et al.
(författare)
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Deep sea sediments of the Arctic Central Basin: A potential sink for microplastics
- 2019
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Ingår i: Deep-Sea Research Part I: Oceanographic Research Papers. - : Elsevier BV. - 0967-0637 .- 1879-0119. ; 145, s. 137-142
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Tidskriftsartikel (refereegranskat)abstract
- Deep sea sediments have emerged as a potential sink for microplastics in the marine environment. The discovery of microplastics in various environmental compartments of the Arctic Central Basin (ACB) suggested that these contaminants were potentially being transported to the deep-sea realm of this oceanic basin. For the first time, the present study conducted a preliminary assessment to determine whether microplastics were present in surficial sediments from the ACB. Gravity and piston corers were used to retrieve sediments from depths of 855-4353 m at 11 sites in the ACB during the Arctic Ocean 2016 (AO16) expedition. Surficial sediments from the various cores were subjected to density flotation with sodium tungstate dihydrate solution (Na2WO4 center dot 2H(2)O, density 1.4 g cm(-3)). Potential microplastics were isolated and analysed by Fourier Transform Infrared (FT-IR) spectroscopy. Of the surficial samples, 7 of the 11 samples contained synthetic polymers which included polyester (n = 3), polystyrene (n = 2), polyacrylonitrile (n = 1), polypropylene (n = 1), polyvinyl chloride (n = 1) and polyamide (n = 1). Fibres (n = 5) and fragments (n = 4) were recorded in the samples. In order to avoid mis-interpretation, these findings musi be taken in the context that (i) sampling equipment did not guarantee retrieval of undisturbed surficial sediments, (ii) low sample volumes were analysed (similar to 10 g per site), (iii) replicate sediment samples per site was not possible, (iv) no air contamination checks were included during sampling and, (v) particles < 100 mu m were automatically excluded from analysis. While the present study provides preliminary indication that microplastics may be accumulating in the deep-sea realm of the ACB, further work is necessary to assess microplastic abundance, distribution and composition in surficial sediments of the ACB.
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| 29. |
- Kanhai, La Daana K., et al.
(författare)
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Microplastics in sea ice and seawater beneath ice floes from the Arctic Ocean
- 2020
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Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322 .- 2045-2322. ; 10:1
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Tidskriftsartikel (refereegranskat)abstract
- Within the past decade, an alarm was raised about microplastics in the remote and seemingly pristine Arctic Ocean. To gain further insight about the issue, microplastic abundance, distribution and composition in sea ice cores (n = 25) and waters underlying ice floes (n = 22) were assessed in the Arctic Central Basin (ACB). Potential microplastics were visually isolated and subsequently analysed using Fourier Transform Infrared (FT-IR) Spectroscopy. Microplastic abundance in surface waters underlying ice floes (0-18 particles m-3) were orders of magnitude lower than microplastic concentrations in sea ice cores (2-17 particles L-1). No consistent pattern was apparent in the vertical distribution of microplastics within sea ice cores. Backward drift trajectories estimated that cores possibly originated from the Siberian shelves, western Arctic and central Arctic. Knowledge about microplastics in environmental compartments of the Arctic Ocean is important in assessing the potential threats posed by microplastics to polar organisms.
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| 30. |
- Kanhai, L. D. K., et al.
(författare)
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Microplastics in sub-surface waters of the Arctic Central Basin
- 2018
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Ingår i: Marine Pollution Bulletin. - : Elsevier BV. - 0025-326X .- 1879-3363. ; 130, s. 8-18
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Tidskriftsartikel (refereegranskat)abstract
- Polar oceans, though remote in location, are not immune to the accumulation of plastic debris. The present study, investigated for the first time, the abundance, distribution and composition of microplastics in sub-surface waters of the Arctic Central Basin. Microplastic sampling was carried out using the bow water system of icebreaker Oden (single depth: 8.5 m) and CTD rosette sampler (multiple depths: 8–4369 m). Potential microplastics were isolated and analysed using Fourier Transform Infrared Spectroscopy (FT-IR). Bow water sampling revealed that the median microplastic abundance in near surface waters of the Polar Mixed Layer (PML) was 0.7 particles m−3. Regarding the vertical distribution of microplastics in the ACB, microplastic abundance (particles m−3) in the different water masses was as follows: Polar Mixed Layer (0–375) > Deep and bottom waters (0–104) > Atlantic water (0–95) > Halocline i.e. Atlantic or Pacific (0–83). © 2018 Elsevier Ltd
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| 31. |
- Nerentorp, Michelle, 1986, et al.
(författare)
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Comparison of two measurement methods of dissolved gaseous mercury concentrations and estimations of supersaturation grade and mercury fluxes during a research campaign at the Mediterranean Sea
- 2013
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Ingår i: E3S Web of Conferences. - : EDP Sciences. - 2555-0403 .- 2267-1242. ; 1
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Konferensbidrag (refereegranskat)abstract
- Dissolved gaseous mercury (DGM) concentrations and gaseous elemental mercury (GEM) concentrations were measured during an oceanographic campaign in the Mediterranean Sea. The DGM concentrations were measured using two different methods, a manual-and an automated method. The manual method was used to obtain DGM depth profiles at several stations throughout the campaign. The automated device measured DGM concentrations continuously at a depth of 4 m. Gaseous elemental mercury (GEM) concentrations in air were measured continuously at the bridge deck. The objectives were to achieve DGM depth profiles, compare the manual-and automated DGM measurement methods, to calculate the supersaturation grades of the sea and the evasional fluxes from the sea surface. Depth profiles of the four measured stations show no diurnal variations. The manual-and the automated method show good compliance. Supersaturation grades are high due to high DGM values and low GEM concentrations. Fluxes of Hg from the sea surface are more dependent on the wind speed than on the supersaturation grade according to the flux models used.
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| 32. |
- Nerentorp, Michelle, 1986, et al.
(författare)
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Mercury flux over West Antarctic Seas during winter, spring and summer
- 2017
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Ingår i: Marine Chemistry. - : Elsevier BV. - 0304-4203 .- 1872-7581. ; 193, s. 44-54
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Tidskriftsartikel (refereegranskat)abstract
- For the first time elemental mercury in air and surface seawater was measured continuously in the remote seas of western Antarctica. A major contributor to atmospheric emissions of the toxic and globally dispersed pollutant mercury is the re-evasion from water surfaces, due to a supersaturation of dissolved gaseous mercury (DGM) in surface water. In this study the degree of saturation and mercury flux at the air-sea surface interface have been estimated from continuous measurements of gaseous elemental mercury (GEM) or total gaseous mercury (TGM) in air, DGM in surface water and meteorological parameters. The measurements were performed during winter and spring (2013) in the Weddell Sea and during summer (2010/2011) in the Bellingshausen, Amundsen and Ross Seas, and show spatial and seasonal variations. The average DGM concentration in surface water in open sea was highest during spring (12 +/- 7pg L-1) and lowest during summer (7 +/- 6.8 pg L-1), resulting in a net evasion of mercury during spring (1.1 +/- 1.6 ng m(-2)h(-1)) and a net deposition during summer (-0.2 +/- 1.3 ng m(-2)h(-1)). In open sea, higher average concentrations of GEM (or TGM) and DGM were found close to the Drake Passage compared to in the Bellingshausen and Weddell Seas. Emission sources from the South American continent, identified with back trajectories, were suggested to explain the observed variations. The yearly mercury evasion from open sea surfaces in the Southern Ocean was estimated to 30 ( -450-1700) tons, using the average (and min and max) flux rates obtained in this study. Higher DGM was measured under sea ice (19-62 pg L-1 compared to in open sea due to a capsuling effect, resulting in a theoretical prevented evasion of 520 (0-3400) tons per year. Diminishing sea ice and higher water temperatures in polar regions could result in increased mercury evasion to the atmosphere. However, the contribution of the Southern Ocean to the global modeled annual emissions of mercury from sea surfaces would probably only be a few percent.
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| 33. |
- Nerentorp, Michelle, 1986, et al.
(författare)
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Seasonal and spatial evasion of mercury from the western Mediterranean Sea
- 2017
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Ingår i: Marine Chemistry. - : Elsevier BV. - 0304-4203. ; 193, s. 34-43
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Tidskriftsartikel (refereegranskat)abstract
- Continuous measurements of gaseous elemental mercury (GEM) in air and dissolved gaseous mercury (DGM) in surface seawater were performed during two oceanographic campaigns (Fenice 2011 (25/10-11/11) and Fenice 2012 (11-29/8)), carried out in the Tyrrhenian Sea (Fenice 211), western Mediterranean Sea and the Atlantic Ocean (Fenice 2012) as part of the GMOS project (Global Mercury Observation System). Measured GEM and DGM were used to estimate the air-sea exchange of elemental mercury by using a two-thin film gas exchange model. Measured GEM concentrations showed significantly higher values in fall (1.7 +/- 0.4 ng m(-3)) compared to summer (1.5 +/- 03 ng m(-3), p
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| 34. |
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| 35. |
- Nerentorp, Michelle, 1986, et al.
(författare)
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Speciation of mercury in the waters of the Weddell, Amundsen and Ross Seas (Southern Ocean)
- 2017
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Ingår i: Marine Chemistry. - : Elsevier BV. - 0304-4203 .- 1872-7581. ; 193, s. 20-33
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Tidskriftsartikel (refereegranskat)abstract
- Despite the distance from large anthropogenic emission sources, toxic mercury is transported via the atmosphere and oceans to the Southern Ocean. Seawater samples were collected at selected stations and were analysed for total mercury (HgT) (8 stations), dissolved gaseous mercury (DGM) (62 stations) and methylmercury (12 stations) during winter (Weddell Sea), spring (Weddell Sea) and summer (Amundsen and Ross Seas) in the Southern Ocean. The HgT distribution in water columns was found to not vary significantly with depth. In the Weddell Sea the average column concentration was higher in spring (2.6 +/- 1.3 pM, 2 stations) than in winter (2.0 +/- 1.0 pM, 6 stations). We hypothesize that the seasonal HgT increase is due to atmospheric deposition of particulate Hg(II) formed during atmospheric mercury depletion events (AMDEs), as well as the addition of inorganic mercury species from melting sea ice and snow. Furthermore, HgT concentrations found in this study were significantly higher than previously measured in the Southern Ocean (Cossa et al., 2011), which was hypothesized to be due to seasonal variations in atmospheric deposition. The average water column DGM concentration in the Weddell Sea was 454 +/- 254 fM in winter and 384 +/- 239 fM in spring. The lowest average DGM concentration was found in summer in the Amundsen and Ross Seas (299 +/- 137 fM). The highest observed concentration in winter was hypothesized to be caused by the larger sea ice coverage, which is known to reduce the evasion of Hg(0) from the sea surface. The average monomethylmercury (MMHg) concentration in the Weddell Sea was 60 +/- 30 fM in winter (6 stations) and 95 +/- 85 fM in spring (2 stations), showing no significant seasonal difference. In the Amundsen and Ross Seas the summer average concentration of MeHg (MMHg and dimethylmercury; DMHg) was 135 +/- 189 fM (4 stations). The highest MeHg concentration was found in modified circumpolar deep water, which is known to have high primary production. 2017 Elsevier B.V. All rights reserved.
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| 36. |
- Polyakov,, et al.
(författare)
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Borealization of the Arctic Ocean in Response to Anomalous Advection From Sub-Arctic Seas
- 2020
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Ingår i: Frontiers in Marine Science. - : Frontiers Media SA. - 2296-7745. ; 7
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Tidskriftsartikel (refereegranskat)abstract
- An important yet still not well documented aspect of recent changes in the Arctic Ocean is associated with the advection of anomalous sub-Arctic Atlantic- and Pacific-origin waters and biota into the polar basins, a process which we refer to as borealization. Using a 37-year archive of observations (1981-2017) we demonstrate dramatically contrasting regional responses to atlantification (that part of borealization related to progression of anomalies from the Atlantic sector of sub-Arctic seas into the Arctic Ocean) and pacification (the counterpart of atlantification associated with influx of anomalous Pacific waters). Particularly, we show strong salinification of the upper Eurasian Basin since 2000, with attendant reductions in stratification, and potentially altered nutrient fluxes and primary production. These changes are closely related to upstream conditions. In contrast, pacification is strongly manifested in the Amerasian Basin by the anomalous influx of Pacific waters, creating conditions favorable for increased heat and freshwater content in the Beaufort Gyre halocline and expansion of Pacific species into the Arctic interior. Here, changes in the upper (overlying) layers are driven by local Arctic atmospheric processes resulting in stronger wind/ice/ocean coupling, increased convergence within the Beaufort Gyre, a thickening of the fresh surface layer, and a deepening of the nutricline and deep chlorophyll maximum. Thus, a divergent (Eurasian Basin) gyre responds altogether differently than does a convergent (Amerasian Basin) gyre to climate forcing. Available geochemical data indicate a general decrease in nutrient concentrations Arctic-wide, except in the northern portions of the Makarov and Amundsen Basins and northern Chukchi Sea and Canada Basin. Thus, changes in the circulation pathways of specific water masses, as well as the utilization of nutrients in upstream regions, may control the availability of nutrients in the Arctic Ocean. Model-based evaluation of the trajectory of the Arctic climate system into the future suggests that Arctic borealization will continue under scenarios of global warming. Results from this synthesis further our understanding of the Arctic Ocean's complex and sometimes non-intuitive Arctic response to climate forcing by identifying new feedbacks in the atmosphere-ice-ocean system in which borealization plays a key role.
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| 37. |
- Snoeijs-Leijonmalm, Pauline, et al.
(författare)
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A deep scattering layer under the North Pole pack ice
- 2021
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Ingår i: Progress in Oceanography. - : Elsevier BV. - 0079-6611 .- 1873-4472. ; 194
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Tidskriftsartikel (refereegranskat)abstract
- The 3.3 million km marine ecosystem around the North Pole, defined as the Central Arctic Ocean (CAO), is a blind spot on the map of the world's fish stocks. The CAO essentially comprises the permanently ice-covered deep basins and ridges outside the continental shelves, and is only accessible by ice-breakers. Traditional trawling for assessing fish stocks is impossible under the thick pack ice, and coherent hydroacoustic surveys are unachievable due to ice-breaking noise. Consequently, nothing is known about the existence of any pelagic fish stocks in the CAO, although juveniles of Boreogadus saida richly occur at the surface associated with the sea ice and ice-associated Arctogadus glacialis has been reported as well. We here present a first indication of a possible mesopelagic fish stock in the CAO. We had the opportunity to analyse a geophysical hydroacoustic data set with 13 time windows of usable acoustic data over a transect from 84.4 °N in the Nansen Basin, across the North Pole (90.0 °N), to 82.4 °N in the Canada Basin. We discovered a deep scattering layer (DSL), suggesting the presence of zooplankton and fish, at 300–600 m of depth in the Atlantic water layer of the CAO. Maximum possible fish abundance and biomass was very low; values of ca. 2,000 individuals km and ca. 50 kg km were calculated for the DSL in the North-Pole area according to a model assuming that all acoustic backscatter represents 15-cm long B. saida and/or A. glacialis. The true abundance and biomass of fish is even lower than this, but cannot be quantified from this dataset due to possible backscatter originating from pneumatophores of physonect siphonophores that are known to occur in the area. Further studies on the DSL of the CAO should include sampling and identification of the backscattering organisms. From our study we can conclude that if the central Arctic DSL contains fish, their biomass is currently too low for any sustainable fishery.
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| 38. |
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| 39. |
- Steffen, A., et al.
(författare)
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A synthesis of atmospheric mercury depletion event chemistry in the atmosphere and snow
- 2008
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Ingår i: Atmospheric Chemistry and Physics. - : Copernicus GmbH. - 1680-7316 .- 1680-7324. ; 8:6, s. 1445-1482
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Tidskriftsartikel (refereegranskat)abstract
- It was discovered in 1995 that, during the spring time, unexpectedly low concentrations of gaseous elemental mercury (GEM) occurred in the Arctic air. This was surprising for a pollutant known to have a long residence time in the atmosphere; however conditions appeared to exist in the Arctic that promoted this depletion of mercury (Hg). This phenomenon is termed atmospheric mercury depletion events (AMDEs) and its discovery has revolutionized our understanding of the cycling of Hg in Polar Regions while stimulating a significant amount of research to understand its impact to this fragile ecosystem. Shortly after the discovery was made in Canada, AMDEs were confirmed to occur throughout the Arctic, sub-Artic and Antarctic coasts. It is now known that, through a series of photochemically initiated reactions involving halogens, GEM is converted to a more reactive species and is subsequently associated to particles in the air and/or deposited to the polar environment. AMDEs are a means by which Hg is transferred from the atmosphere to the environment that was previously unknown. In this article we review Hg research taken place in Polar Regions pertaining to AMDEs, the methods used to collect Hg in different environmental media, research results of the current understanding of AMDEs from field, laboratory and modeling work, how Hg cycles around the environment after AMDEs, gaps in our current knowledge and the future impacts that AMDEs may have on polar environments. The research presented has shown that while considerable improvements in methodology to measure Hg have been made but the main limitation remains knowing the speciation of Hg in the various media. The processes that drive AMDEs and how they occur are discussed. As well, the role that the snow pack and the sea ice play in the cycling of Hg is presented. It has been found that deposition of Hg from AMDEs occurs at marine coasts and not far inland and that a fraction of the deposited Hg does not remain in the same form in the snow. Kinetic studies undertaken have demonstrated that bromine is the major oxidant depleting Hg in the atmosphere. Modeling results demonstrate that there is a significant deposition of Hg to Polar Regions as a result of AMDEs. Models have also shown that Hg is readily transported to the Arctic from source regions, at times during springtime when this environment is actively transforming Hg from the atmosphere to the snow and ice surfaces. The presence of significant amounts of methyl Hg in snow in the Arctic surrounding AMDEs is important because this species is the link between the environment and impacts to wildlife and humans. Further, much work on methylation and demethylation processes has occurred but these processes are not yet fully understood. Recent changes in the climate and sea ice cover in Polar Regions are likely to have strong effects on the cycling of Hg in this environment; however more research is needed to understand Hg processes in order to formulate meaningful predictions of these changes.
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| 40. |
- Stranne, Christian, et al.
(författare)
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Acoustic mapping of mixed layer depth
- 2018
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Ingår i: Ocean Science. - : Copernicus GmbH. - 1812-0784 .- 1812-0792. ; 14:3, s. 503-514
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Tidskriftsartikel (refereegranskat)abstract
- The ocean surface mixed layer is a nearly universal feature of the world oceans. Variations in the depth of the mixed layer (MLD) influences the exchange of heat, fresh water (through evaporation), and gases between the atmosphere and the ocean and constitutes one of the major factors controlling ocean primary production as it affects the vertical distribution of biological and chemical components in near-surface waters. Direct observations of the MLD are traditionally made by means of conductivity, temperature, and depth (CTD) casts. However, CTD instrument deployment limits the observation of temporal and spatial variability in the MLD. Here, we present an alternative method in which acoustic mapping of the MLD is done remotely by means of commercially available ship-mounted echo sounders. The method is shown to be highly accurate when the MLD is well defined and biological scattering does not dominate the acoustic returns. These prerequisites are often met in the open ocean and it is shown that the method is successful in 95% of data collected in the central Arctic Ocean. The primary advantages of acoustically mapping the MLD over CTD measurements are (1) considerably higher temporal and horizontal resolutions and (2) potentially larger spatial coverage.
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| 41. |
- Stranne, Christian, et al.
(författare)
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Acoustic Mapping of Thermohaline Staircases in the Arctic Ocean
- 2017
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Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 7
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Tidskriftsartikel (refereegranskat)abstract
- Although there is enough heat contained in inflowing warm Atlantic Ocean water to melt all Arctic sea ice within a few years, a cold halocline limits upward heat transport from the Atlantic water. The amount of heat that penetrates the halocline to reach the sea ice is not well known, but vertical heat transport through the halocline layer can significantly increase in the presence of double diffusive convection. Such convection can occur when salinity and temperature gradients share the same sign, often resulting in the formation of thermohaline staircases. Staircase structures in the Arctic Ocean have been previously identified and the associated double diffusive convection has been suggested to influence the Arctic Ocean in general and the fate of the Arctic sea ice cover in particular. A central challenge to understanding the role of double diffusive convection in vertical heat transport is one of observation. Here, we use broadband echo sounders to characterize Arctic thermohaline staircases at their full vertical and horizontal resolution over large spatial areas (100 s of kms). In doing so, we offer new insight into the mechanism of thermohaline staircase evolution and scale, and hence fluxes, with implications for understanding ocean mixing processes and ocean-sea ice interactions.
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| 42. |
- Wängberg, Ingvar, et al.
(författare)
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Airborne mercury species at the Råö background monitoring site in Sweden: distribution of mercury as an effect of long-range transport
- 2016
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Ingår i: Atmospheric Chemistry And Physics. - : Copernicus GmbH. - 1680-7316 .- 1680-7324. ; 16, s. 13379–13387-
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Tidskriftsartikel (refereegranskat)abstract
- Within the EU-funded project, Global Mercury Observation System (GMOS) airborne mercury has been monitored at the background Råö measurement site on the western coast of Sweden from mid-May 2012 to the beginning of July 2013 and from the beginning of February 2014 to the end of May 2015. The following mercury species/fractions were measured: gaseous elemental mercury (GEM), particulate bound mercury (PBM) and gaseous oxidised mercury (GOM) using the Tekran measurement system. The mercury concentrations measured at the Råö site were found to be low in comparison to other, comparable, European measurement sites. A back-trajectory analysis to study the origin of air masses reaching the Råö site was performed. Due to the remote location of the Råö measurement station it receives background air about 60 % of the time. However, elevated mercury concentrations arriving with air masses coming from the south-east are noticeable. GEM and PBM concentrations show a clear annual variation with the highest values occurring during winter, whereas the highest concentrations of GOM were obtained in spring and summer. An evaluation of the diurnal pattern of GOM, with peak concentrations at midday or in the early afternoon, which often is observed at remote places, shows that it is likely to be driven by local meteorology in a similar way to ozone. Evidence that a significant part of the GOM measured at the Råö site has been formed in free tropospheric air is presented.
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