Study of 7Be activity concentration in the air of northern Spain

Time series analysis techniques have been applied to the study of the 7 Be activity concentration in air, which was obtained by weekly collecting aerosols in filters in the north of Spain, and measuring them by gamma ray spectrometry. Between 2001 and 2009, a trend pattern is found. The cyclical component of this series is clearly influenced by the solar cycle (11 years period). Two kinds of seasonality were found in the time series: annual periodicity and variations with seasons of the year. The irregular component has also been studied but its contribution has been insignificant; one of its possible causes, rainfall, has been analysed and the conclusion is that the atmospheric concentration of Be-7 is unaffected by rainfall. The contribution of Be-7 presence in air to the total effective dose rate in air has also been studied, resulting negligible.