| 1. |
- Abbatt, J. P. D., et al.
(författare)
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Halogen activation via interactions with environmental ice and snow in the polar lower troposphere and other regions
- 2012
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Ingår i: Atmospheric Chemistry and Physics. - : Copernicus GmbH. - 1680-7316 .- 1680-7324. ; 12:14, s. 6237-6271
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Tidskriftsartikel (refereegranskat)abstract
- The role of ice in the formation of chemically active halogens in the environment requires a full understanding because of its role in atmospheric chemistry, including controlling the regional atmospheric oxidizing capacity in specific situations. In particular, ice and snow are important for facilitating multiphase oxidative chemistry and as media upon which marine algae live. This paper reviews the nature of environmental ice substrates that participate in halogen chemistry, describes the reactions that occur on such substrates, presents the field evidence for ice-mediated halogen activation, summarizes our best understanding of ice-halogen activation mechanisms, and describes the current state of modeling these processes at different scales. Given the rapid pace of developments in the field, this paper largely addresses advances made in the past five years, with emphasis given to the polar boundary layer. The integrative nature of this field is highlighted in the presentation of work from the molecular to the regional scale, with a focus on understanding fundamental processes. This is essential for developing realistic parameterizations and descriptions of these processes for inclusion in larger scale models that are used to determine their regional and global impacts.
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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
(författare)
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Biogenic Halocarbons in Polar Sea Ice
- 2014
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Sea ice is to date a rather poorly investigated part of the cycling of volatile halogenated organic compounds, halocarbons. These compounds are natural sources of reactive iodine and bromine to the atmosphere, and are produced in the marine environment. The aim of this study was to determine the role of sea ice in terms of production and release of halocarbons to the atmosphere. Iodinated and brominated halocarbons were measured in polar sea ice as well as in snow, air, and seawater under the ice. Multiple samples were collected from the same location in order to cover variability. Studies were performed both in winter and summer, and seasonal variations were observed. Sea ice acted as a source of halocarbons both in winter and in summer. Biotic production was observed during summer, and depth distributions of halocarbons in the ice were related to ice algal biomass. Unexpectedly high concentrations of halocarbons were found at the surface of Antarctic winter sea ice. For bromoform (CHBr3) the concentration range was 0.2 - 20 nM in the top 10 cm of the ice. High concentrations were also found in the snow closest to the snow-ice interface. Our results suggest that an abiotic formation occurs in seasonal sea ice during polar night. This may lead to a winter accumulation of halocarbons in the marine boundary layer and enhance tropospheric ozone depletion in the polar spring.
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| 4. |
- 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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| 5. |
- Granfors, Anna, 1978, et al.
(författare)
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Contribution of sea ice in the Southern Ocean to the cycling of volatile halogenated organic compounds
- 2013
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Ingår i: Geophysical Research Letters. - : American Geophysical Union (AGU). - 0094-8276. ; 40:15, s. 3950-3955
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Tidskriftsartikel (refereegranskat)abstract
- The contribution of sea ice to the flux of biogenic volatile halogenated organic compounds to the atmosphere in the Southern Ocean is currently not known. To approach this question, we measured halocarbons in sea ice, sea ice brine, and surface water of the Amundsen and Ross Seas. Concentrations in sea ice of these compounds, normalized to seawater salinity, ranged from 0.2 to 810 pmol L-1. Salinity-normalized chlorophyll a concentrations in the ice ranged from 3.5 to 190 mu gL(-1). Our results suggest biological production of halocarbons in sea ice, with maxima of halogenated organics and chlorophyll a commonly found in the interior of the ice cores. Iodinated VHOCs were found to be more enriched in sea ice than brominated ones. Furthermore, depth distributions indicated a transport of halocarbons from sea ice to air and underlying water.
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| 6. |
- Granfors, Anna, 1978, et al.
(författare)
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Organic iodine in Antarctic sea ice: a comparison between winter in the Weddell Sea and summer in the Amundsen Sea
- 2014
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Ingår i: Journal of Geophysical Research - Biogeosciences. - 0148-0227 .- 2156-2202. ; 119:12, s. 2276-2291
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Tidskriftsartikel (refereegranskat)abstract
- Recent studies have recognized sea ice as a source of reactive iodine to the Antarctic boundary layer. Volatile iodinated compounds (iodocarbons) are released from sea ice, and they have been suggested to contribute to the formation of iodine oxide (IO), which takes part in tropospheric ozone destruction in the polar spring. We measured iodocarbons (CH3I, CH2ClI, CH2BrI and CH2I2) in sea ice, snow, brine and air during two expeditions to Antarctica, OSO 10/11 to the Amundsen Sea during austral summer, and ANT XXIX/6 to the Weddell Sea in austral winter. These are the first reported measurements of iodocarbons from the Antarctic winter. Iodocarbons were enriched in sea ice in relation to seawater in both summer and winter. During summer the positive relationship to Chl a biomass indicated a biological origin. We suggest that CH3I is formed biotically in sea ice during both summer and winter. For CH2ClI, CH2BrI and CH2I2 an additional abiotic source at the snow-ice interface in winter is suggested . Elevated air concentrations of CH3I and CH2ClI during winter indicate that they are enriched in lower troposphere and may take part in formation of IO at polar sunrise.
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| 7. |
- 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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