Method and apparatus for detection of the remote origin fraction of radon present in a measuring site

A method of detecting a fraction of remote origin of 222Rn present in a measuring site (Z) for monitoring dynamic phenomena inside land crust, comprising the following steps:

• a) analyzing the measuring site (Z) in order to determine a typical ratio between 222Rn of local origin and 220Rn of local origin, said typical ratio being proportional to a ratio between an emission coefficient ε222Rn of said 222Rn of local origin and an emission coefficient ε220Rn of said 220Rn of local origin, said ε222Rn and ε220Rn being measured on ground samples collected from the measuring site (Z);
• b) measuring, at predetermined time intervals, alpha spectroscopy in the measuring site (Z) using a measuring chamber (2);
• c) elaborating said alpha spectroscopy in order to find total concentration of said 222Rn and total concentration of said 220Rn present in the measuring site (Z);
• d) determining concentration of said 222Rn of local origin by multiplying said total concentration of said 220Rn with said typical ratio;
• and
• e) subtracting said concentration of said 222Rn of local origin from said total concentration of said 222Rn to obtain a concentration of said fraction of remote origin of said 222Rn.