CONCENTRATION MEASUREMENTS OF 7Be AT GROUND LEVEL AIR AT PALERMO, ITALY- COMPARISON WITH SOLAR ACTIVITY OVER A PERIOD OF 21 YEARS

Air activity concentrations of 7Be in Palermo determined for the period January 1995–December 2002 by -ray spectrometric analysis of particulate samples collected on paper filter by a high-volume sampler (~900 m3 h-1) are reported. The temporal behaviour of 7Be concentration presents the same characteristics already observed in the measurements carried out over the previous 13-year (1982–1994) investigated period. The mean value of 5.06 mBq m-3 obtained from the analysis of the 4636 particulate samples collected from 1982 to 2002 can be considered a representative value of 7Be air concentration at ground level in our geographical zone. The comparison of long-term variation in the 7Be concentrations with the cyclic solar activity—extended to the whole period of 21 years—confirms the inverse correlation between the two quantities.