English Abstract In 1989 airborne particles were daily sampled, using a
sampling-period of 24 hours. After 5 days decay of the short-lived
daughters of radon and thoron gross-alpha, gross-beta and gross-gamma
activities were measured. The yearly average of gross-alpha activity was
0.04 mBq/m3, of gross-beta activity 0.18 mBq/m3, and of gross-gamma
activity 0.19 mBq/m3. These mean levels are quite similar to those of
1988. Applying gamma-spectroscopy no artificial radionuclides could be
detected in airborne particles. Only the natural activationproduct Be-7 was
detectable. The yearly average was 1.2 mBq/m3 and the contribution to the
gross-gamma activity was estimated at approximately 0.12 mBq/m3. The major
contributions to gross-alpha and gross-beta activity in airborne particles
are most likely explained by natural Po-210 resp.
Pb-210/Bi-210.
