Radon-calibrated emissions of CO2 from South Africa

Atmospheric CO2 and 222Rn have been monitored at Amsterdam Island since 1980. Data were selected in order to eliminate any local influence. Typical CO2 concentrations of the subantarctic marine atmosphere can be determined by selecting those values for which 222Rn radioactivity was particularly low: less than 1 pCi m-3. 222Rn concentrations higher than 2 pCi m-3 are mainly due to injections into the subantarctic atmosphere from the continental source of South Africa. The passage of air masses under continental influence also shows typical CO2 variations, well correlated with 222Rn variations. From the knowledge of the global continental fluxes of 222Rn, it has been possible to estimate CO2 fluxes into the atmosphere from South Africa. The mean CO2 flux corresponding to a 6-month period from May to October is about 5 millimole m-2 h-1. Continental CO2 emissions reach a maximum in August. (orig.)