Seasonal 7Be concentrations in near-surface air of Granada (Spain) in the period 1993–2001

Near-surface air samples for assessment of seasonal 7Be levels were taken weekly at Granada, Spain, (37o10′50′′N–3o35′44′′W, altitude 670 m) in the period 1993–2001. The 7Be levels measured reflect strong seasonal trends. Concentrations during autumn and/or winter showed a minimum (ca. 1.5 mBq/m3), and in each year a fallout maximum was found in summer (ca. 7.6 mBq/m3). Multiple regression of 7Be concentrations with temperature and rainfall, and with sunspot number explained about 71% of the variance in the 7Be data. The data reveal strong variations in the mean annual 7Be concentrations due to variations in the flux of cosmic galactic primary radiation caused by the 11-year sunspot cycle. A difference of a factor of 2.6 was found between the highest level (5.8 mBq/m3) obtained in 1996 (beginning of the solar cycle 23) and the lowest (2.6 mBq/m3) obtained in 2000 (maximum of the solar cycle 23).