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Seasonal Cycling of Mercury in the Antarctic Sea Ice Environment

Michelle Nerentorp (Institutionen för kemi- och bioteknik, Oorganisk miljökemi)
Göteborg : Chalmers University of Technology, 2014. - 48 s.
[Licentiatavhandling]

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.

Nyckelord: Kvicksilver, Antarktis, säsongsvariationer, deposition, vinter, havsis, snö



Denna post skapades 2014-10-29.
CPL Pubid: 204990

 

Institutioner (Chalmers)

Institutionen för kemi- och bioteknik, Oorganisk miljökemi (2005-2014)

Ämnesområden

Hållbar utveckling
Kemi

Chalmers infrastruktur

Examination

Datum: 2014-11-21
Tid: 13:00
Lokal: Seminarium 10:an, Kemivägen 4, plan 10 (forskarhus 1)
Opponent: Prof.Mattias Hallquist, Atmosfärskemi, Göteborgs Universitet

Ingår i serie

Licentiatuppsatser vid Institutionen för kemi- och bioteknik, Chalmers tekniska högskola 2014:23