Long-range transport of continental radon in subantarctic and antarctic areas

Gaseous Rn-222, a daughter product of U-238, is injected into the atmosphere from the surface of continents.Its atmospheric cycle is particularly simple since it disappears only by radioactive decay (half-life 3.8 days).Radon measurements obtained over more than 15 years in remote stations in Antarctic and Subantarctic areas generally give concentrations as low as 0. I to 2 pCi.m-'.However, we have shown the existence of sharp increases of concentrations reaching 3 to 30 pCi'rn-' called "radonic storms".Owing to the negligible degassing of radon from the sea surface, such peaks are accounted for by long-range transport from remote continents (mainly South Africa) over Southern Indian and Antarctic oceans, with transit times ranging from 1.5 to 7 days and very low dilution factors of the order of 3 to 7.This airmass transport is related to warm sectors of cyclonic systems passing over South Africa and around the Antarctic continent.* July 1980 calculated without the 3 days (28, 29, 30) during which the anticyclonic barrier was widely open.