Atmospheric mercury speciation dynamics at the high-altitude Pic du Midi Observatory, southern France
Continuous measurements of atmospheric gaseous elemental mercury (GEM), particulate bound mercury (PBM) and gaseous oxidized mercury (GOM) at the high-altitude Pic du Midi Observatory (PDM Observatory, 2877 m a.s.l.) in southern France were made from November 2011 to November 2012. The mean GEM,...
| Main Authors: | , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2016-05-01
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| Series: | Atmospheric Chemistry and Physics |
| Online Access: | https://www.atmos-chem-phys.net/16/5623/2016/acp-16-5623-2016.pdf |
| Summary: | Continuous measurements of atmospheric gaseous elemental mercury
(GEM), particulate bound mercury (PBM) and gaseous oxidized mercury (GOM) at
the high-altitude Pic du Midi Observatory (PDM Observatory, 2877 m a.s.l.) in
southern France were made from November 2011 to November 2012. The mean GEM, PBM and
GOM concentrations were 1.86 ng m<sup>−3</sup>, 14 pg m<sup>−3</sup> and 27 pg m<sup>−3</sup>,
respectively and we observed 44 high PBM (peak PBM values of 33–98 pg m<sup>−3</sup>) and 61 high GOM (peak GOM values of 91–295 pg m<sup>−3</sup>) events.
The high PBM events occurred mainly in cold seasons (winter and spring)
whereas high GOM events were mainly observed in the warm seasons (summer and
autumn). In cold seasons the maximum air mass residence times (ARTs)
associated with high PBM events were observed in the upper troposphere over
North America. The ratios of high PBM ARTs to total ARTs over North America,
Europe, the Arctic region and Atlantic Ocean were all elevated in the cold
season compared to the warm season, indicating that the middle and upper
free troposphere of the Northern Hemisphere may be more enriched in PBM in
cold seasons. PBM concentrations and PBM ∕ GOM ratios during the high PBM
events were significantly anti-correlated with atmospheric aerosol
concentrations, air temperature and solar radiation, suggesting in situ
formation of PBM in the middle and upper troposphere. We identified two
distinct types of high GOM events with the GOM concentrations positively and
negatively correlated with atmospheric ozone concentrations, respectively.
High GOM events positively correlated with ozone were mainly related to air
masses from the upper troposphere over the Arctic region and middle
troposphere over the temperate North Atlantic Ocean, whereas high GOM events
anti-correlated with ozone were mainly related to air masses from the lower
free troposphere over the subtropical North Atlantic Ocean. The ARTs
analysis demonstrates that the lower and middle free troposphere over the
North Atlantic Ocean was the largest source region of atmospheric GOM at the
PDM Observatory. The ratios of high GOM ARTs to total ARTs over the
subtropical North Atlantic Ocean in summer were significantly higher than
those over the temperate and sub-arctic North Atlantic Ocean as well as that
over the North Atlantic Ocean in other seasons, indicating abundant in situ
oxidation of GEM to GOM in the lower free troposphere over the subtropical
North Atlantic Ocean in summer. |
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| ISSN: | 1680-7316 1680-7324 |