222Radon as a Tracer of Atmospheric Motions: A Study in Milan

Atmospheric 222 Rn concentration was measured at ground level in Milan. The measurements were obtained using two different methods: a high-volume alpha particle detector giving a direct measurement of 222 Rn concentration, and the alpha activity released by radon progeny measured through the collection of atmospheric particulate. From the behaviour of the concentrations of this radioactive tracer it was possible to get data on the structure of the Planetary Boundary Layer. The changes in daily and weekly atmospheric radon levels are related to the stability or turbulence of the low troposphere. In particular, the analysis of data from sunny windless days indicates growth and dissolution of the inversion layer. Radon data can be used as the basis for the development of pollutant diffusion models and, in particular, could provide support to studies on ozone concentration in the Planetary Boundary Layer.