In this paper we present the variation of 7 Be concentration in the surface air of Thessaloniki, Greece (40 • 62 N,22 • 95 E) over the year 2009, a year of a deep solar minimum, and, as a consequence, a year of maximum concentration of 7 Be in surface air. The mean annual activity concentration of 7 Be for the year 2009 was 6.0 mBq m −3 . The relative variability of 7 Be surface concentration related to the solar cycle was calculated to be deviated by about 20% from maximum to mean. A positive correlation (R = 0.97) was revealed between the activity of 7 Be and the temperature T ( • C), confirming that the increased rate of vertical transport within the troposphere, especially during warmer months, that make descend air masses enriched in 7 Be down to the surface layer. The anticorrelation (R = −0.65) with RH% is due to intense condensation during high relative humidity conditions, which results in increased aerosol particle sizes and as a consequence in higher scavenging rate of aerosols and lower concentration of 7 Be in the atmosphere. The influence of precipitation on the 7 Be atmospheric concentration variability was approximately 10%, with greater the influence of rainfall events of low precipitation rate e.g. drizzling. *

Atmospheric concentrations of 210 Pb were measured over the year 2009 in ground level air at Thessaloniki, Northern Greece (40 • 62 N, 22• 95 E). The mean activity concentrations of 210 Pb in surface air have been found to be 671 ± 213 μBq m −3 . The highest values of monthly atmospheric concentrations of 210 Pb were observed in the autumn and the lowest in the spring period. The higher values of 210 Pb during autumn were attributed to frequent inversion conditions of the surface layers, resulting in an enrichment of radon and its decay products in surface air. The lower values during the winter months might be due to the low emanation of radon from the frozen or snow-covered soil. The minima of 210 Pb concentrations during spring might reflect on higher washout during this period, which results in less emanation of radon from saturated with water soil, resulting in less production of 210 Pb near ground-level air. The relative high values during summer are probably due to the higher 222 Rn exhalation from the ground and due to the higher air mixing within the troposphere, which has as a result to carry down to the surface layer 210 Pb whose origin is older air masses which entered into the free troposphere. *

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