Beryllium-7 correlations in total deposition (dry and wet) measured in Serbia and Slovenia

Abstract

Beryllium-7 is a natural radionuclide whose specific activity at the surface strongly depends on transport history from the upper atmosphere where this isotope is produced. Since the major removal mechanism of beryllium-7 from the atmosphere is wet deposition, local meteorological factors also play an important role in its abundance at the surface. In this analysis we present the beryllium-7 correlations in total deposition (dry and wet) measured in three locations: Belgrade, the capital of Serbia; Ljubljana, the capital of Slovenia; and Krško, a town in eastern Slovenia where a nuclear power plants located. Air distance between Belgrade and Ljubljana is about 490 km, while Krško lies roughly between them, and is less than 80 km away from Ljubljana. The data in our analysis cover the 1995- 2015 period. The beryllium-7 specific activities were measured by standard gamma spectrometry at the Vinča Institute and Jožef Stefan Institute. A comparison of the three beryllium-7 records in total deposition shows some differences between the measurement sites. For example, the maximum beryllium-7 concentrations in Belgrade are noted in June, while in Ljubljana and Krško, the maximum is observed in August. However, in both cases, the minimum beryllium-7 concentrations occur five months after the maximum, i.e. in November in Vinča, and in February in Ljubljana and Krško. Further, the highest Pearson's linear correlation coefficient (r) is obtained for the LjubljanaKrško records (r=0.68). This strong linear correlation decreases down to a weak correlation of r=0.35 and r=0.30for the Belgrade-Ljubljana and Belgrade-Krško records, respectively.