Radon and its progenies variation in the urban polluted atmosphere of the Mediterranean city of Thessaloniki, Greece.

Radon and Rn progenies' concentrations were determined in the urban polluted atmosphere of Thessaloniki's city center using two experimental procedures: (i) filter with 0.8-μm porosity measured using α-counting technique determining the radon equilibrium equivalent concentration (C), which varies from 2.6 to 8.9 Bq m, and (ii) filter with 0.3-μm porosity measured in the laboratory using γ-spectrometry determining Pb activity concentration 1.3-7.5 Bq m and Bi activity 3.1-11.5 Bq m. Strong daily correlation with the relative humidity is presented, in association to an inverse correlation with the temperature gradient. Radon and its daughter's concentration correlate well smoke particles' content because radon is trapped inside them due to their high effective porosity, and so the Rn daughter collection in the filter increases. Gas pollutants have similar daily distribution with the radon activity, while SO levels are correlated the best with Pb and Bi concentrations, as Pb is more chemically associated to sulfuric complex ions than nitric formation in presence of vapors. The lower Pb/ Bi activity ratio appeared during the highest temperature gradient and amount of vapors, smoke, and gases giving rise to high formation of ultrafine aerosol particles. The ultrafine aerosol creation boosts Pb recoil effect taken place during Po α-decay, so Pb nuclei become free starting the clustering process yet again having ingrowth coefficient ~ 0.1 nm s regarding accumulation mode aerosols.