Depositional fluxes and other physical characteristics of atmospheric beryllium-7 in the temperate zones (40°N) with a dry (precipitation-free) climate

Abstract

Abstract Atmospheric depositional fluxes of 7Be were measured over a 3-year period (January 1987–April 1990) in Thessaloniki, Greece (40°38′N, 22°58′E). Total precipitation accumulation during 1987, 1988 and 1989 was 65.0, 46.2 and 32.6 cm, respectively, reflecting a relatively dry (precipitation-free) climate. The volume-weighted concentrations of 7Be in rainwater ranged between 0.1 and 5.2 Bq l −1 (average 0.6 Bq l −1). The annual total deposition fluxes of 7Be in 1987, 1988 and 1989 were 841, 510 and 483 Bq m−2, respectively, while the average concentrations of 7Be in the atmosphere in the corresponding periods were 6.3, 5.7 and 4.2 mBq m−3, showing a decreasing trend with time. On an annual average, the washout (scavenging) ratio for 7Be was 144 and the resuspension factor was 2.5 × 10−4 m−1, the latter is too high. The annual average total deposition velocity for 7Be was estimated to be 0.4 cm s−1. The air-to-vegetation transfer rate estimate for 7Be is 5150 m3 kg−1. Seasonal variations of 7Be concentration depend considerably on the local meteorological conditions, mainly the rainfalls.