²²²Rn calibrated mercury fluxes from terrestrial surfaces of southern Africa derived from observations at Cape Point, South Africa

¹ Max-Planck-Institut für Chemie, P.O.Box 3060, D-55020 Mainz, GERMANY
² South African Weather Service c/o CSIR, P.O.Box 320, Stellenbosch 7599, SOUTH AFRICA
³ ANSTO Environment, PMB 1, Menai, NSW 2234, AUSTRALIA
⁴ Helmholtz-Zentrum Geesthacht, Institute of Coastal Research, Max-Planck-Strasse, D-21502 Geesthacht, GERMANY

^a franz.slemr@mpic.de
^b ernst.brunke@weathersa.co.za
^c wza@ansto.gov.au
^d ralf.ebinghaus@hzg.de
^e hans.kock@hzg.de
^f casper.labuschagne@weathersa.co.za

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 2009 altogether 59 events with high ²²²Rn concentrations were identified. GEM correlated with ²²²Rn in 41 of the events and was constant during the remaining events without significant correlation. The average GEM/²²²Rn emission ratio of all events was −0.0047 ± 0.0054 pg mBq⁻¹, with ± 0.0054 being the standard error of the average. With an emission rate of 1.1 ²²²Rn atoms cm⁻² s⁻¹ and a correction for the transport duration, this emission ratio corresponds to a radon calibrated flux of about −0.53 ± 0.62 ng m⁻² h⁻¹ which is statistically not distinguishable from zero. With wet deposition, which is not included in this estimate, the terrestrial surface of southern Africa appears to be a net mercury sink.