| Autor: |
Koenig, Alkuin Maximilian, Magand, Olivier, Verreyken, Bert, Brioude, Jerome, Amelynck, Crist, Schoon, Niels, Colomb, Aurélie, Araujo, Beatriz Ferreira, Ramonet, Michel, Sha, Mahesh Kumar, Cammas, Jean-Pierre, Sonke, Jeroen E., Dommergue, Aurélien |
| Předmět: |
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| Zdroj: |
EGUsphere; 10/5/2022, p1-33, 33p |
| Abstrakt: |
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. [ABSTRACT FROM AUTHOR] |
| Databáze: |
Complementary Index |
| Externí odkaz: |
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