Atmos. Chem. Phys. Discuss., 9, 20979-21009, 2009
© Author(s) 2009. This work is distributed
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This discussion paper has been under review for the journal Atmospheric Chemistry and Physics (ACP). Please refer to the corresponding final paper in ACP.
Total gaseous mercury depletion events observed at Cape Point during 2007–2008
E.-G. Brunke1, C. Labuschagne1, R. Ebinghaus2, H. H. Kock2, and F. Slemr3
1South African Weather Service, P.O. Box 320, Stellenbosch, 7599, South Africa
2GKSS Research Centre, Institute for Coastal Research, 21502 Geesthacht, Germany
3Max Planck Institute for Chemistry, Atmospheric Chemistry Division, P.O. Box 3060, 55020 Mainz, Germany

Abstract. Gaseous mercury in the marine boundary layer has been measured with a 15 min temporal resolution at the Global Atmosphere Watch station Cape Point since March 2007. The most prominent features of the data until July 2008 are the frequent occurrences of pollution (PEs) and depletion events (DEs). Both types of events originate mostly within a short transport distance (up to about 100 km), which are embedded in air masses ranging from marine background to continental. The Hg/CO emission ratios observed during the PEs are within the range reported for biomass burning and industrial/urban emissions. The depletion of gaseous mercury during the DEs is almost quantitative in many cases and suggests a lifetime of elemental mercury as short as a few dozens of hours, which is in contrast to the commonly used estimate of approximately 1 year. The characteristics of the DE occurrence at Cape Point is neither similar to the halogen driven atmospheric mercury depletion events (AMDEs) observed in Polar Regions nor to the DEs reported for plumes of urban air. Additional measurements are necessary to reveal the chemical mechanism of the observed DEs and to assess its importance on larger scales.

Citation: Brunke, E.-G., Labuschagne, C., Ebinghaus, R., Kock, H. H., and Slemr, F.: Total gaseous mercury depletion events observed at Cape Point during 2007–2008, Atmos. Chem. Phys. Discuss., 9, 20979-21009, doi:10.5194/acpd-9-20979-2009, 2009.
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