Articles | Volume 16, issue 21
https://doi.org/10.5194/acp-16-13379-2016
https://doi.org/10.5194/acp-16-13379-2016
Research article
 | 
31 Oct 2016
Research article |  | 31 Oct 2016

Airborne mercury species at the Råö background monitoring site in Sweden: distribution of mercury as an effect of long-range transport

Ingvar Wängberg, Michelle G. Nerentorp Mastromonaco, John Munthe, and Katarina Gårdfeldt

Abstract. Within the EU-funded project, Global Mercury Observation System (GMOS) airborne mercury has been monitored at the background Råö measurement site on the western coast of Sweden from mid-May 2012 to the beginning of July 2013 and from the beginning of February 2014 to the end of May 2015. The following mercury species/fractions were measured: gaseous elemental mercury (GEM), particulate bound mercury (PBM) and gaseous oxidised mercury (GOM) using the Tekran measurement system. The mercury concentrations measured at the Råö site were found to be low in comparison to other, comparable, European measurement sites. A back-trajectory analysis to study the origin of air masses reaching the Råö site was performed. Due to the remote location of the Råö measurement station it receives background air about 60 % of the time. However, elevated mercury concentrations arriving with air masses coming from the south-east are noticeable. GEM and PBM concentrations show a clear annual variation with the highest values occurring during winter, whereas the highest concentrations of GOM were obtained in spring and summer. An evaluation of the diurnal pattern of GOM, with peak concentrations at midday or in the early afternoon, which often is observed at remote places, shows that it is likely to be driven by local meteorology in a similar way to ozone. Evidence that a significant part of the GOM measured at the Råö site has been formed in free tropospheric air is presented.

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Short summary
Within the EU-funded project, Global Mercury Observation System (GMOS) airborne mercury has been monitored at the background Råö measurement site on the western coast of Sweden from May 2012 to the end of May 2015, the following mercury species/fractions were measured: gaseous elemental mercury (GEM), particulate bound mercury (PBM) and gaseous oxidised mercury (GOM). Evidence that a significant part of the GOM measured at the Råö site has been formed in the free tropospheric air is presented.
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