Activity concentrations of ²²⁶Ra, ²²⁸Ra, ²¹⁰Pb, ⁴⁰K and⁷Be and their temporal variations in surface air.

Activity concentrations of the long-lived natural radionuclides 226Ra, 228Ra, 210Pb, 40K and of 7Be in surface air were measured twice monthly at a semi-rural location 10 km north of Munich (FRG) for at least three years. For the time interval 1983-1985, all values were found to be distributed log-normally, with geometric means (in μBq m-3) of 1·2 for 226Ra, 0·5 for 228Ra, 580 for 210Pb, 12 for 40K and 3500 for 7Be. Reflecting their common origin, the activity concentrations of 226Ra and 40K are correlated with surface air dust concentrations (geometric mean 59 μg m-3). Seasonal variations of 210Pb and 7Be air activity concentrations are established for the time interval 1978-1985. The contribution of local soil activity to the air activity concentrations of these radionuclides and of natural uranium is discussed. Resuspension factors are found to be of the order of 10-9m-1