| 1. |
- 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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| 2. |
- Hagman, Johan, 1984, et al.
(författare)
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Do biofuels require more water than do fossil fuels? Life cycle-based assessment of jatropha oil production in rural Mozambique
- 2013
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Ingår i: Journal of Cleaner Production. - : Elsevier BV. - 0959-6526. ; 53, s. 176-185
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Tidskriftsartikel (refereegranskat)abstract
- Biofuels are advanced to replace fossil fuels in order to reduce emissions of greenhouse gases and other environmental impacts. Yet freshwater scarcity is another growing concern and increased production of biofuels may increase this problem. In order to assess whether biofuels truly have a higher water use than do fossil fuels, a life cycle assessment study of a low input jatropha plantation in northern Mozambique was conducted. In addition to different water use indicators, the fossil energy use and global warming potential were assessed for 1 MJ of jatropha oil. The analysis compares results for jatropha oil with fossil diesel, generally showing lower global warming potential and fossil energy use for jatropha oil. However, aspects related to land use may alter the global warming potential of jatropha oil. Regarding water use, the choice of the water use indicator strongly influences the results. Specifically the indication of (1) so-called green water flows, (2) formation of so-called blue water and (3) water scarcity show crucial influences on the comparison. Depending on these specific features, jatropha oil may have higher or lower water use than fossil diesel. A number of uncertainties, such as the jatropha oil yield, are also shown to have a considerable impact on the results.
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| 3. |
- 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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| 4. |
- 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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| 5. |
- 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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| 6. |
- Nerentorp, Michelle, 1986
(författare)
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Mercury cycling in the global marine environment
- 2016
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Mercury is a globally distributed contaminant that exists in the atmosphere in its elemental form as a stable monoatomic gas. Having a residence time of around one year in air allows it to be transported far from emission sources and end up in polar ecosystems. Gaseous elemental mercury (GEM) can in air be oxidized by photo-induced processes which produce water soluble oxidized forms of mercury which are more easily deposited. Deposited mercury can in the environment be transformed to organic and bio-accumulating compounds which are neurotoxic, making mercury a global concern. Deposited oxidized mercury into the sea can be reduced back to the elemental form (GEM) and be re-emitted to air. This re-evasion constitutes of around 30% of the total emissions of mercury to air and originates from both natural and anthropogenic sources. Models have estimated that the yearly mercury emission from global sea surfaces is between 2000 and 3000 tonnes. The mercury flux rate at the interphase between air and water depends on the Henry´s law constant, the concentration gradient and the gas transfer velocity. How to properly account for weather parameters such as wind speed, and how to accurately adjust the flux model to mercury (originally developed for CO2) has been debated in the literature and have resulted in diverse results of mercury flux rates. In this work, mercury has been measured in air and in seawater during several campaigns in Antarctica, the Mediterranean Sea, the west coast of Sweden, Northern Finland and in the Arctic. From measured concentrations of mercury, the mercury flux rates from the studied areas were calculated using the gas exchange model described in Johnson (2010). Large spatial and seasonal variations of measured mercury concentrations were found which resulted in similar variations in calculated flux rates. In Antarctica and the Arctic, high concentrations of mercury were also measured in the sea ice environment. Seasonal variations in mercury concentrations were found and a correlation between solar radiation and the photo-production of elemental mercury in sea ice was discovered. The sea ice was suggested to affect the global marine cycling of mercury in several ways: acting as a cap preventing elemental mercury to evade from sea surfaces in Polar Regions, acting as barrier against direct atmospheric deposition and being a significant reservoir of mercury. Climate change will likely affect the cycling of mercury in global marine environments due to an increase in temperature, leading to enhanced mercury evasion, and diminishing and melting sea ice causing an increased input of mercury into polar oceans. Results presented in this thesis bring new insights about how mercury is cycling in the global marine environment and the new collected mercury data from remote and inaccessible areas are valuable for future modeling. However, more research is needed to further understand and quantify the accumulation of mercury in vulnerable marine ecosystems.
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| 7. |
- 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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| 8. |
- 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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| 9. |
- Nerentorp, Michelle, 1986
(författare)
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Seasonal Cycling of Mercury in the Antarctic Sea Ice Environment
- 2014
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Mercury is a globally distributed contaminant that exists in the atmosphere as a stable monoatomic gas. Having almost a year’s residence time in the air allows it to reach remote polar regions. Deposited airborne mercury can be transformed in the environment to the organic and bio-accumulating compound methyl mercury. Methyl mercury is neurotoxic and affects land living and marine animals all over the world. Springtime atmospheric mercury depletion events, first discovered in 1995 in the Arctic, occur when the return of sunlight induces the formation of halogen radicals that oxidize tropospheric elemental mercury. These spring events occurring in polar regions increase the net deposition of mercury into polar marine ecosystems. Some studies have been performed on the fate of mercury deposited onto snowpack but the transportation and transformation of mercury through and within snow and sea ice are still not fully understood.This thesis is based on data from three oceanographic expeditions to Antarctica (winter, spring and summer). Here unique seasonal data are presented for mercury species in air and elemental and total mercury concentrations in snow, sea ice, sea water and brine. Results presented in this thesis show that atmospheric mercury depletion events also occur over sea ice areas in the middle of the dark winter period. The dark depletions lead to an increased net deposition of mercury onto surface snow. Results also show that when approaching warmer and more sunlit seasons, the reduction of deposited oxidized mercury increases and this leads to more re-emission of elemental mercury back into the atmosphere. Melting sea ice also increases the leaching of mercury in snow and ice via run-off and via brine channels to the sea water under the ice floes. In this thesis it is also shown that the amount of solar radiation and overlaying snowpack affect the concentrations of elemental mercury in sea ice. This indicates that photo-reduction of mercury occurs within sea ice and may be important for mercury transportation and transformation within the polar marine environment. The new discoveries bring new insights to the global mercury cycle and the fate of mercury in polar regions. However, more research is needed to further understand and quantify the accumulation of mercury in polar ecosystems.
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| 10. |
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