222Rn-calibrated mercury fluxes from terrestrial surface of southern Africa F. Slemr1, E.-G. Brunke2, S. Whittlestone3, W. Zahorowski3, R. Ebinghaus4, H. H. Kock4, and C. Labuschagne2 1Max-Planck-Institut für Chemie, Hahn-Meitner-Weg 1, 55128 Mainz, Germany 2South African Weather Service c/o CSIR, P.O. Box 320, Stellenbosch 7599, South Africa 3ANSTO Environment, PMB 1, Menai, NSW 2234, Australia 4Helmholtz-Zentrum Geesthacht, Institute of Coastal Research, Max-Planck-Strasse, 21502 Geesthacht, Germany
Abstract. Gaseous elemental mercury (GEM) and 222Rn, a radioactive gas of
primarily terrestrial origin with a half-life of 3.8 days, have been
measured simultaneously at Cape Point, South Africa, since March 2007.
Between March 2007 and December 2011, altogether 191 events with high
222Rn concentrations were identified. GEM correlated with 222Rn in
94 of the events and was constant during almost all the remaining events
without significant correlation. The average GEM / 222Rn flux ratio of
all events including the non-significant ones was −0.0001 with a standard
error of ±0.0030 pg mBq−1. Weighted with the event duration, the
average GEM / 222Rn flux ratio was −0.0048 ± 0.0011 pg mBq−1.
With an emission rate of 1.1 222Rn atoms cm−2 s−1 and a
correction for the transport time, this flux ratio corresponds to a radon-calibrated
flux of about −0.54 ng GEM m−2 h−1 with a standard
error of ±0.13 ng GEM m−2 h−1 (n = 191). With wet
deposition, which is not included in this estimate, the terrestrial surface
of southern Africa seems to be a net mercury sink of about
−1.55 ng m−2 h−1. The additional contribution of an unknown but presumably
significant deposition of reactive gaseous mercury would further increase
Citation: Slemr, F., Brunke, E.-G., Whittlestone, S., Zahorowski, W., Ebinghaus, R., Kock, H. H., and Labuschagne, C.: 222Rn-calibrated mercury fluxes from terrestrial surface of southern Africa, Atmos. Chem. Phys., 13, 6421-6428, doi:10.5194/acp-13-6421-2013, 2013.