Variations of ²¹⁰Pb concentrations in surface air at Thessaloniki, Greece (40°N)

Aristotle University of Thessaloniki, Physics Department Nuclear Physics & Elementary Particle Physics Division Thessaloniki 54124 Greece

^* E-mail: anta@physics.auth.gr

Abstract

Atmospheric concentrations of ²¹⁰Pb 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 ²¹⁰Pb in surface air have been found to be 671 ± 213 μBq m⁻³. The highest values of monthly atmospheric concentrations of ²¹⁰Pb were observed in the autumn and the lowest in the spring period. The higher values of ²¹⁰Pb 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 ²¹⁰Pb 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 ²¹⁰Pb near ground-level air. The relative high values during summer are probably due to the higher ²²²Rn 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 ²¹⁰Pb whose origin is older air masses which entered into the free troposphere.