Background radiation measurements in the lower atmosphere before and after Chernobyl

The background radiation measurements in the lower atmosphere at different altitudes above sea level up to 1100 m and over the land were made at a temperate latitude (40°) in the Thessaloniki region, North Greece, before and after the Chernobyl accident (26 April 1986), using a portable γ-ray scintillation detector and a Cutie-pie survey meter with an ionization chamber. The average value of the total background radiation at ground level was 87 nGy h-1 (10.0 μR h-1, 25 cps), i.e. 60% from terrestrial radiation, 55 nGy h-1 (6.3 μR h-1, 15 cps) and 40% from cosmic radiation, 32 nGy h-1 (3.7 μR h-1, 10 cps), before the Chernobyl accident, while, after it, the total background radiation was doubled, due to the long-lived radioactive fallout suspended in the atmosphere and or deposited onto the ground.