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

Abstract

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.

Mercury isotope evidence for Arctic summertime re-emission of mercury from the cryosphere

“…The absolute Δ 200 Hg difference between Hg II and Hg 0 is small however, and at the limit of atmospheric Hg II isotope analytical uncertainty. In addition, while membranes collect more Hg II than denuder-based methods in the Arctic 67 , there is a possibility that over a 1-week sampling period some gaseous or particulate Hg II was lost from the membranes, leading to unpredictable minor bias in Hg II Δ 200 Hg (but not Hg 0 Δ 200 Hg).…”

Determining sources of reactive mercury compounds in Reno, Nevada, United States

“…Thus, GOM and PBM have a greater impact on ecosystems. The automated instrument (Tekran 1130/ 1135/2537) used for ~20 years to determine atmospheric Hg concentrations does not accurately measure GOM and PBM (Gustin et al, 2013;Gustin et al, 2019;Luippold et al, 2020aLuippold et al, 2020bOsterwalder et al, 2021;Dunham-Cheatham et al, 2023). Because of the lack of accurate RM measurements by the Tekran system, alternative measurement systems have been developed.…”

Observations of the chemistry and concentrations of reactive Hg at locations with different ambient air chemistry

“…GEM is ubiquitous in the atmosphere, with terrestrial background concentrations in Northern and Southern Hemisphere ranging from 1.5 to 1.7, and 1.0 to 1.3 ng m -3 , respectively (Sprovieri et al, 2016). Remote Southern Hemisphere ocean locations exhibited concentrations for Amsterdam Island and Cape Point of ~1.0 ng m -3 (Jiskra et al, 2018;Angot et al, 2014;Li et al, 2023;Slemr et al, 2015 and, while in the Northern Hemisphere observations at Svalbard, Norway were 1.4 ng m -3 (Osterwalder et al, 2021).…”