Measurements of atmospheric 7Be properties using high-efficiency gamma spectroscopy

Two Be-7-related properties have been measured using a high-efficiency germanium gamma spectrometer (relative efficiency of 90%), namely, the activity median aerodynamic diameter (AMAD) of Be-7-associated atmospheric aerosols and the airborne Be-7 radioactivity. With time resolutions of about 1-3 d correlations between these Be-7-related properties and different meteorological parameters were identified. We found that AMAD is anti-correlated to Be-7 counts. It is correlated with the relative humidity (RH) and mean cloud cover with high confidence, but not with temperature. We also found that Be-7 radioactivity was correlated with the RH with a moderate confidence, but not with the mean cloud cover or temperature. Furthermore, wet precipitation present in the middle of the sampling period decreased the Be-7 activity and increased the AMAD, while wet precipitation before or at the beginning of the sampling period decreased both Be-7 activity and AMAD. Finally, after a cold front passed by, the AMAD decreased and the Be-7 activity increased. Possible explanations are also given. (C) 2002 Elsevier Science Ltd. All rights reserved.