DISTRIBUTION AND FALLOUT OF CS-137 AND OTHER RADIONUCLIDES OVER ANTARCTICA

This article aims to give a comprehensive view of the distribution pat terns for natural and artifical radionuclides over Antarctica. We focu s this study on Cs-137, Pb-210 and tritium. Applying various statistic al methods, we show that the deposition of radionuclides reveals a str uctured distribution, although local drift redistribution and the snow -surface roughness disturb the representativeness of samples and produ ce a ''noise'' effect. The deposition of Cs-137 over Antarctica (885 T Bq) represents 0.09% of the total deposition of this radionuclide in t he world and the correlation between Cs-137 fluxes and accumulation sh ows two sub-populations. For the stations with a mean annual temperatu re above -21 degrees C, a strong correlation is found, whereas the cor relation is lower for locations with temperatures below -21 degrees C. The flux of Pb-210 varies from 0.9 to 8.2 Bq m(-1) a(-1) with values strongly correlated with the accumulation and a well-defined spatial s tructure. The same mechanism governs the deposition of artificial and natural tritium but it clearly differs from that of other radionuclide s associated with particulate material. The ''dry fall-out'' accounts for between 60 and 80% of the total fall-out for the artificial radion uclides and around 40% for Pb-210. This difference is likely related t o a tropospheric fraction for Pb-210. Despite its isolated location, t he radioactive fall-out of artificial long-lived radionuclides over An tarctica has been ten times greater than for natural radionuclides.