137Cs concentrations in Atlantic and western Antarctic surface waters:: results of the 7th Ukrainian Antarctic Expedition, 2002

The latitudinal distribution Of Cs-137 in the Atlantic-western Antarctic surface waters was studied during the 7th Ukrainian Antarctic Expedition in January-May 2002. The Cs-137 concentrations have also been measured in the upper ice of the coastal glacier Woozle Hill located near the Ukrainian Antarctic station "Akademik Vernadsky" (western Antarctica, 65 degrees 15' S-64 degrees 16' W). Comparison of these data with results of previous same-route expeditions SWEDARP (Swedish Antarctic Research Expedition, 1988/1989) and the French R/V "Jeanne d'Arc" (1992/1993), has shown practically parallel changes of Cs-137 surface concentrations between 40 degrees N and 20 degrees S, pointing to decrease of Cs-137 radioactivity at these latitudes with an apparent half-life of 10-15 years (12.5 +/- 2.1 years on average). This suggests that decrease of Cs-137 surface concentration within this latitude band is controlled, besides the radioactive decay Of Cs-137 (half-life = 30 years), by vertical mixing of the upper water masses. South of 20 degrees S, the Cs-137 concentrations in surface water have decreased more rapidly because of the influence of the less contaminated Antarctic waters. At 50-60 degrees S and near the Antarctic coast, the Cs-137 activity in 2002 was similar to those measured during the SWEDARP and "Jeanne d'Arc" expeditions, suggesting an additional input of Cs-137 to these waters from the melted ice from the adjacent glaciers. (c) 2005 Elsevier Ltd. All rights reserved.