Variation in airborne Cs-134, Cs-137, particulate I-131 and Be-7 maximum activities at high-altitude European locations after the arrival of Fukushima-labeled air masses

摘要

The Fukushima-labeled air mass arrival, and later the cesium-134 (Cs-134), cesium-137 (Cs-137) and particulate iodine-131 (hereafter noted I-131(p)) maximum levels were registered in Europe at different dates depending on the location. Most of those data were obtained at low-altitude sampling areas. Here, we compare the airborne levels registered at different high-altitude European locations (from 850 m to about 3500 m). The integrated Cs-137 activity concentration was not uniform with, regard to the altitude even after a long travel time/distance from Japan. Moreover, the relation of integrated Cs-137 vs. altitude showed a linear decrease up to an altitude of about 3000 m. A similar trend was noticed for I-131(p) (particulate fraction) while it increased above 3000 m. Comparison with Be-7 activity concentration showed that, as far as the high altitude location is concerned, the Cs-137 and Cs-134 maximum concentrations corresponded to the 7Be maximum, suggesting downdraft movements from high tropospheric or stratospheric layers to be responsible for (CS)-C-137,134 increase and peak values. This was also confirmed by high potential vorticity and low relative humidity registered during the peak values. (C) 2016 Elsevier Ltd. All rights reserved.