BERYLLIUM-7 SURFACE CONCENTRATION EXTREMES IN EUROPE

Seasonal and spatial patterns of extremely high beryllium-7 surface concentration recorded over the 2001–2010 period across Europe are investigated. The beryllium-7 measurements for 14 sites are taken from the Radioactivity Environmental Monitoring Database. The maxima and minima in the annual cycle of the beryllium-7 surface concentration occur later in the year as the latitude of the measurement site decreases. Extremely high beryllium-7 surface concentrations are defined here as values greater than the 95th percentile in each measurement site. Most of the extremes occur over the March–August period. At least 10 % of the total number of extremes appear during autumn and winter, with an exception of Vienna, where all the extremes took place during spring and summer. The regional spread of extremes common to pairs of measurement sites points to an existence of three distinct regions in Europe: north of 55 °N, between 45 °N and 55 °N, and south of 45 °N. Although the beryllium-7 concentration records are significantly correlated across all the investigated sites, the strongest correlations are found within the identified regions.