Distribution and fall-out of Cs-137 and other radionuclides over Antarctica

This article aims to give a comprehensive view of the distribution patterns for natural and artifical radionuclides over Antarctica. We focus this study on 137Cs, 210Pb and tritium. Applying various statistical methods, we show that the deposition of radionuclides reveals a structured distribution, although local drift redistribution and the snow-surface roughness disturb the representativeness of samples and produce a "noise" effect. The deposition of 137Cs over Antarctica (885 TBq) represents 0.09% of the total deposition of this radionuclide in the world and the correlation between 137Cs fluxes and accumulation shows two sub-populations. For the stations with a mean annual temperature above -21°C, a strong correlation is found, whereas the correlation is lower for locations with temperatures below -21°C. The flux of 210Pb varies from 0.9 to 8.2 Bq m -1a -1 with values strongly correlated with the accumulation and a well-defined spatial structure. The same mechanism governs the deposition of artificial and natural tritium but it clearly differs from that of other radionuclides associated with particulate material. The "dry fall-out" accounts for between 60 and 80% of the total fall-out for the artificial radionuclides and around 40% for 210Pb. This difference is likely related to a tropospheric fraction for 210Pb. Despite its isolated location, the radioactive fall-out of artificial long-lived radionuclides over Antarctica has been ten times greater than for natural radionuclides.