The measurement of radon 222 concentration in the soil is made on the gases collected from the soil at 1 metre depth by a low-flow intake pump and which are conveyed into a system of detection and evaluation of the radiations emitted by radon and its decay products. Two kinds of approaches were used which carry out the measurements by means of alpha-particles counters or beta-radiation counters, respectively. The study was performed in a hole dug in the basement of the Institute of Physics; the soil is the one typical of the Lombard plain. The measurements were performed during two yearly campaigns from 1993 through 1996. The study shows wide oscillations of radon concentration which occur every 24 and 12 hours. These
effects were noticed during the whole campaign. Radon concentration oscillations are compared with the pressure oscillations related to atmospheric tides
