Abstract
The technics established for the study of Radon and Thoron daughters were applied to the determination of γ activity on particles of a radius below 2·10−6 cm at ground level. Long time samplings were used and the collections were measured with a γ multichannel spectrometer. Our experimental results allow us to verify that γ activity fixed on particles with radii below 2·10−6 cm represents an average of 16% of the total artificial radioactivity.DOI: 10.1111/j.2153-3490.1966.tb00276.x