Feedback mechanisms between snow and atmospheric mercury: Results and observations from field campaigns on the Antarctic plateau

Chemosphere ◽  
2018 ◽  
Vol 197 ◽  
pp. 306-317 ◽  
Author(s):  
Andrea Spolaor ◽  
Hélène Angot ◽  
Marco Roman ◽  
Aurélien Dommergue ◽  
Claudio Scarchilli ◽  
...  
Keyword(s):  
Atmospheric Mercury ◽  
Feedback Mechanisms ◽  
Antarctic Plateau ◽  
Field Campaigns ◽  
The Antarctic

scholarly journals New insights into the atmospheric mercury cycling in Central Antarctica and implications at a continental scale

2016 ◽  
Author(s):  
Hélène Angot ◽  
Olivier Magand ◽  
Detlev Helmig ◽  
Philippe Ricaud ◽  
Boris Quennehen ◽  
...  
Keyword(s):  
Chemical Exchange ◽  
Ambient Air ◽  
Oxidative Capacity ◽  
Atmospheric Mercury ◽  
Photochemical Reactions ◽  
Heterogeneous Reactions ◽  
Observation System ◽  
Antarctic Plateau ◽  
Continental Scale ◽  
The Antarctic

Abstract. Under the framework of the GMOS project (Global Mercury Observation System) atmospheric mercury monitoring has been implemented at Concordia Station on the high-altitude Antarctic plateau (75°06’ S, 123°20’ E, 3220 m above sea level). We report here the first year-round measurements of gaseous elemental mercury (Hg(0)) in the atmosphere and in snowpack interstitial air on the East Antarctic ice sheet. This unique dataset shows evidence of a continuous oxidation of atmospheric Hg(0) in summer (24-hour daylight) due to the high oxidative capacity of the Antarctic plateau atmosphere at this period of the year. Summertime Hg(0) concentrations exhibited a pronounced daily cycle in ambient air with maximal concentrations around midday. Photochemical reactions and chemical exchange at the air/snow interface were prominent, highlighting the role of the snowpack on the atmospheric mercury cycle. Our observations reveal a 20 to 30 % decrease of atmospheric Hg(0) concentrations from May to mid-August (winter, 24-h darkness). This phenomenon has never been observed elsewhere and likely results from a gas-phase oxidation and/or heterogeneous reactions. We also reveal the occurrence of multi-day to weeklong atmospheric Hg(0) depletion events in summer, not associated with depletions of ozone, and likely due to a stagnation of air masses above the plateau triggering an accumulation of oxidants within the shallow boundary layer. Our observations suggest that the inland atmospheric reservoir is depleted in Hg(0) in summer. Due to katabatic winds flowing out from the Antarctic plateau down the steep vertical drops along the coast and according to observations at coastal Antarctic stations, the striking reactivity observed on the plateau most likely influences the cycle of atmospheric mercury at a continental scale.

scholarly journals New insights into the atmospheric mercury cycling in central Antarctica and implications on a continental scale

2016 ◽  
Vol 16 (13) ◽  
pp. 8249-8264 ◽  
Author(s):  
Hélène Angot ◽  
Olivier Magand ◽  
Detlev Helmig ◽  
Philippe Ricaud ◽  
Boris Quennehen ◽  
...  
Keyword(s):  
Chemical Exchange ◽  
Ambient Air ◽  
Oxidative Capacity ◽  
Atmospheric Mercury ◽  
Photochemical Reactions ◽  
Observation System ◽  
Data Set ◽  
Antarctic Plateau ◽  
Continental Scale ◽  
The Antarctic

Abstract. Under the framework of the GMOS project (Global Mercury Observation System) atmospheric mercury monitoring has been implemented at Concordia Station on the high-altitude Antarctic plateau (75°06′ S, 123°20′ E, 3220 m above sea level). We report here the first year-round measurements of gaseous elemental mercury (Hg(0)) in the atmosphere and in snowpack interstitial air on the East Antarctic ice sheet. This unique data set shows evidence of an intense oxidation of atmospheric Hg(0) in summer (24-hour daylight) due to the high oxidative capacity of the Antarctic plateau atmosphere in this period of the year. Summertime Hg(0) concentrations exhibited a pronounced daily cycle in ambient air with maximal concentrations around midday. Photochemical reactions and chemical exchange at the air–snow interface were prominent, highlighting the role of the snowpack on the atmospheric mercury cycle. Our observations reveal a 20 to 30 % decrease of atmospheric Hg(0) concentrations from May to mid-August (winter, 24 h darkness). This phenomenon has not been reported elsewhere and possibly results from the dry deposition of Hg(0) onto the snowpack. We also reveal the occurrence of multi-day to weeklong atmospheric Hg(0) depletion events in summer, not associated with depletions of ozone, and likely due to a stagnation of air masses above the plateau triggering an accumulation of oxidants within the shallow boundary layer. Our observations suggest that the inland atmospheric reservoir is depleted in Hg(0) in summer. Due to katabatic winds flowing out from the Antarctic plateau down the steep vertical drops along the coast and according to observations at coastal Antarctic stations, the striking reactivity observed on the plateau most likely influences the cycle of atmospheric mercury on a continental scale.

scholarly journals Dynamic recycling of gaseous elemental mercury in the boundary layer of the Antarctic Plateau

2012 ◽  
Vol 12 (7) ◽  
pp. 18133-18161 ◽  
Author(s):  
A. Dommergue ◽  
M. Barret ◽  
J. Courteaud ◽  
P. Cristofanelli ◽  
C. P. Ferrari ◽  
...  
Keyword(s):  
Mixing Layer ◽  
Elemental Mercury ◽  
Atmospheric Mercury ◽  
Photochemical Reactions ◽  
Solar Irradiation ◽  
The Arctic ◽  
Gaseous Elemental Mercury ◽  
Antarctic Plateau ◽  
Mixing Ratios ◽  
The Antarctic

Abstract. Gaseous elemental mercury (Hg(0)) was investigated in the troposphere and in the interstitial air extracted from the snow at Dome Concordia station (alt. 3320 m) on the Antarctic Plateau during January 2009. Measurements showed evidence of a very dynamic and daily cycling of Hg(0) inside the mixing layer with a range of values from 0.2 ng m−3 up to 2.3 ng m−3. During low solar irradiation periods, fast Hg(0) oxidation processes in a confined layer were observed leading to an enrichment of the upper snow layers in divalent Hg. Unexpectedly high Hg(0) concentrations for such a remote place were measured under higher solar irradiation due to the reemission of Hg(0) by the snowpack via photochemical reactions. Hg(0) concentrations showed a negative correlation with ozone mixing ratios, which contrasts with atmospheric mercury depletion events observed during the Arctic spring. It remains unclear whether halogens are involved in Hg(0) oxidation. We suggest that snow surfaces may play a role in promoting the heterogeneous oxidation of Hg(0). The cycling of other oxidants should be investigated together with Hg in order to clarify the complex reactivity on the Antarctic Plateau.

scholarly journals Dynamic recycling of gaseous elemental mercury in the boundary layer of the Antarctic Plateau

2012 ◽  
Vol 12 (22) ◽  
pp. 11027-11036 ◽  
Author(s):  
A. Dommergue ◽  
M. Barret ◽  
J. Courteaud ◽  
P. Cristofanelli ◽  
C. P. Ferrari ◽  
...  
Keyword(s):  
Mixing Layer ◽  
Elemental Mercury ◽  
Atmospheric Mercury ◽  
Solar Irradiation ◽  
The Arctic ◽  
Gaseous Elemental Mercury ◽  
Antarctic Plateau ◽  
Mixing Ratios ◽  
The Antarctic ◽  
Snow Photochemistry

Abstract. Gaseous elemental mercury (Hg0) was investigated in the troposphere and in the interstitial air extracted from the snow at Dome Concordia station (alt. 3320 m) on the Antarctic Plateau during January 2009. Measurements and modeling studies showed evidence of a very dynamic and daily cycling of Hg0 inside the mixing layer with a range of values from 0.2 ng m−3 up to 2.3 ng m−3. During low solar irradiation periods, fast Hg0 oxidation processes in a confined layer were suspected. Unexpectedly high Hg0 concentrations for such a remote place were measured under higher solar irradiation due to snow photochemistry. We suggest that a daily cycling of reemission/oxidation occurs during summer within the mixing layer at Dome Concordia. Hg0 concentrations showed a negative correlation with ozone mixing ratios, which contrasts with atmospheric mercury depletion events observed during the Arctic spring. Unlike previous Antarctic studies, we think that atmospheric Hg0 removal may not be the result of advection processes. The daily and dramatic Hg0 losses could be a consequence of surface or snow induced oxidation pathways. It remains however unclear whether halogens are involved. The cycling of other oxidants should be investigated together with Hg species in order to clarify the complex reactivity on the Antarctic plateau.

scholarly journals The growth of sublimation crystals and surface hoar on the Antarctic plateau

2014 ◽  
Vol 8 (4) ◽  
pp. 1205-1215 ◽  
Author(s):  
J.-C. Gallet ◽  
F. Domine ◽  
J. Savarino ◽  
M. Dumont ◽  
E. Brun
Keyword(s):  
Energy Budget ◽  
Temperature Drop ◽  
Snow Surface ◽  
Surface Mass ◽  
Antarctic Plateau ◽  
Time Variations ◽  
Sunny Weather ◽  
Frost Flowers ◽  
Snow Model ◽  
The Antarctic

Abstract. On the Antarctic plateau, precipitation quantities are so low that the surface mass budget is for an important part determined by exchanges of water vapor between the snow surface and the atmosphere surface. At Dome C (75° S, 123° E), we have frequently observed the growth of crystals on the snow surface under calm sunny weather. Here we present the time variations of specific surface area (SSA) and density of these crystals. Using the detailed snow model Crocus, we conclude that the formation of these crystals was very likely due to the nighttime formation of surface hoar crystals and to the daytime formation of sublimation crystals. These latter crystals form by processes similar to those involved in the formation of frost flowers on young sea ice. The formation of these crystals impacts the albedo, mass and energy budget of the Antarctic plateau. In particular, the SSA variations of the surface layer can induce an instantaneous forcing at the snow surface up to −10 W m−2 at noon, resulting in a surface temperature drop of 0.45 K. This result confirms that snow SSA is a crucial variable to consider in the energy budget and climate of snow-covered surfaces.

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