Preprints
https://doi.org/10.5194/egusphere-2022-903
https://doi.org/10.5194/egusphere-2022-903
05 Oct 2022
 | 05 Oct 2022

Mercury in the Free Troposphere and Bidirectional Atmosphere-Vegetation Exchanges – Insights from Maïdo Mountain Observatory in the Southern Hemisphere Tropics

Alkuin Maximilian Koenig, Olivier Magand, Bert Verreyken, Jerome Brioude, Crist Amelynck , Niels Schoon, Aurélie Colomb, Beatriz Ferreira Araujo, Michel Ramonet, Mahesh Kumar Sha, Jean-Pierre Cammas, Jeroen E. Sonke, and Aurélien Dommergue

Abstract. Atmospheric mercury (Hg) observations in the lower free troposphere (LFT) can give important insights into Hg redox chemistry and can help constrain Hg background concentrations on a regional level. Relatively continuous sampling of LFT air, inaccessible to most ground-based stations, can be achieved at high-altitude observatories. However, such high-altitude observatories are rare, especially in the Southern Hemisphere (SH), and atmospheric Hg in the SH LFT is unconstrained. To fill this gap, we continuously measured gaseous elemental mercury (GEM; hourly) and reactive mercury (RM; integrated over ~6–14 days) for 9 months at Maïdo mountain observatory (2160 masl) on remote Réunion Island (21.1° S, 55.5° E) in the tropical Indian Ocean. GEM exhibits a marked diurnal variation characterized by a midday peak (mean: 0.95 ng m-3; SD: 0.08 ng m-3) and a nighttime low (mean: 0.78 ng m-3; SD: 0.11 ng m-3). We find that this diurnal variation is likely driven by the interplay of important GEM photo-reemission from the islands’ vegetated surface during daylight hours (8–22 ng m-2 h-1), boundary layer influences during the day, and predominant LFT influences at night. We estimate GEM in the LFT based on nighttime observations in particularly dry airmasses and find a notable seasonal variation, with LFT GEM being lowest from December to March (mean 0.66 ng m-3; SD: 0.07 ng m-3) and highest from September to November (mean: 0.79 ng m-3; SD: 0.09 ng m-3). Such a clear GEM seasonality contrasts the weak seasonal variation reported for the SH marine boundary layer, but goes in line with modeling results, highlighting the added value of continuous Hg observations in the LFT. Maïdo RM is 10.6 pg m-3 (SD: 5.9 pg m-3) on average, but RM in the cloud-free LFT might be about twice as high, as weekly-biweekly sampled RM observations are likely diluted by low-RM contributions from the boundary layer and clouds.

Journal article(s) based on this preprint

24 Jan 2023
Mercury in the free troposphere and bidirectional atmosphere–vegetation exchanges – insights from Maïdo mountain observatory in the Southern Hemisphere tropics
Alkuin M. Koenig, Olivier Magand, Bert Verreyken, Jerome Brioude, Crist Amelynck, Niels Schoon, Aurélie Colomb, Beatriz Ferreira Araujo, Michel Ramonet, Mahesh K. Sha, Jean-Pierre Cammas, Jeroen E. Sonke, and Aurélien Dommergue
Atmos. Chem. Phys., 23, 1309–1328, https://doi.org/10.5194/acp-23-1309-2023,https://doi.org/10.5194/acp-23-1309-2023, 2023
Short summary

Alkuin Maximilian Koenig et al.

Interactive discussion

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2022-903', Anonymous Referee #1, 13 Nov 2022
    • AC1: 'Authors' response to R1', Alkuin Koenig, 20 Dec 2022
  • RC2: 'Comment on egusphere-2022-903', Anonymous Referee #2, 29 Nov 2022
    • AC2: 'Authors' response to R2', Alkuin Koenig, 20 Dec 2022

Interactive discussion

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2022-903', Anonymous Referee #1, 13 Nov 2022
    • AC1: 'Authors' response to R1', Alkuin Koenig, 20 Dec 2022
  • RC2: 'Comment on egusphere-2022-903', Anonymous Referee #2, 29 Nov 2022
    • AC2: 'Authors' response to R2', Alkuin Koenig, 20 Dec 2022

Peer review completion

AR: Author's response | RR: Referee report | ED: Editor decision | EF: Editorial file upload
AR by Alkuin Koenig on behalf of the Authors (20 Dec 2022)  Author's response   Author's tracked changes   Manuscript 
ED: Publish as is (23 Dec 2022) by Leiming Zhang
AR by Alkuin Koenig on behalf of the Authors (09 Jan 2023)  Manuscript 

Journal article(s) based on this preprint

24 Jan 2023
Mercury in the free troposphere and bidirectional atmosphere–vegetation exchanges – insights from Maïdo mountain observatory in the Southern Hemisphere tropics
Alkuin M. Koenig, Olivier Magand, Bert Verreyken, Jerome Brioude, Crist Amelynck, Niels Schoon, Aurélie Colomb, Beatriz Ferreira Araujo, Michel Ramonet, Mahesh K. Sha, Jean-Pierre Cammas, Jeroen E. Sonke, and Aurélien Dommergue
Atmos. Chem. Phys., 23, 1309–1328, https://doi.org/10.5194/acp-23-1309-2023,https://doi.org/10.5194/acp-23-1309-2023, 2023
Short summary

Alkuin Maximilian Koenig et al.

Alkuin Maximilian Koenig et al.

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Short summary
The global distribution of mercury, a potent neurotoxin, depends on atmospheric transport, chemistry, and interactions between the earth’s surface and the air. Our understanding of these processes is still hampered by insufficient observations. Here, we present new data from a mountain observatory in the Southern Hemisphere. We give insights into mercury concentrations in air masses coming from aloft, and we show that tropical mountain vegetation may be a daytime source of mercury to the air.