Fate of Springtime Atmospheric Reactive Mercury: Concentrations and Deposition at Zeppelin, Svalbard

Mid-latitude atmospheric elemental mercury (Hg) emissions undergo extensive oxidation to reactive Hg (RM) compounds during Arctic polar sunrise, resulting in enhanced atmospheric deposition that impacts Arctic marine wildlife and humans. It has been difficult to estimate RM dry deposition, because R...

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Bibliographic Details
Main Authors: Osterwalder, Stefan, Dunham-Cheatham, Sarrah M., Ferreira Araujo, Beatriz, Magand, Olivier, Thomas, Jennie L., Baladima, Foteini, Pfaffhuber, Katrine Aspmo, Berg, Torunn, Zhang, Lei, Huang, Jiaoyan, Dommergue, Aurélien, Sonke, Jeroen E., Sexauer Gustin, Mae
Format: Article in Journal/Newspaper
Language:English
Published: American Chemical Society 2021
Subjects:
Aerohead
Arctic
Pollution
RMAS
Speciation
Thermal desorption
Svalbard
Arctic pollution
Sea ice
Online Access:https://hdl.handle.net/20.500.11850/512564
https://doi.org/10.3929/ethz-b-000512564
Description
Summary:Mid-latitude atmospheric elemental mercury (Hg) emissions undergo extensive oxidation to reactive Hg (RM) compounds during Arctic polar sunrise, resulting in enhanced atmospheric deposition that impacts Arctic marine wildlife and humans. It has been difficult to estimate RM dry deposition, because RM concentrations, compounds, and their deposition velocities are ill-defined. Here, we investigate RM concentrations sampled with membrane-based methods and find these to exceed denuder-based RM detection by 5 times at the Zeppelin Observatory on Svalbard (March 26–July 24, 2019). Measured dry deposition of gaseous oxidized Hg was about half of the modeled RM deposition, demonstrating that particulate-bound Hg was an important component of dry deposition. Using thermal membrane desorption, RM chemistry was found to be dominated by Hg–Cl/Br (51%) and Hg–N (45%) compounds. Back-trajectory analysis indicated that Hg–Br/Cl compounds were predominantly advected from within the marine boundary layer (sea ice exposure), while Hg–N originated from the free troposphere. Weekly average RM compound-specific dry deposition velocities ranged from 0.12 to 0.49 cm s–1, with a net RM dry deposition of 1.9 μg m–2 (1.5–2.5 μg m–2; 95% confidence interval) that exceeds the mean annual Hg wet deposition flux in Svalbard. Overall, we find that springtime atmospheric RM deposition has been underestimated in the Arctic marine environment. ISSN:2472-3452

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