1. Real time 222 Rn measurements at Stromboli Island A. Lavagno 1, M. Laiolo 2, G. Gervino 3, C. Cigolini 2, D. Coppola 2 and C. Marino 3 1.- Dipartimento di Fisica, Politecnico di Torino, Italy 2.- Dipartimento di Scienze Mineralogiche e Petrologiche, Università di Torino 3.-Dipartimento di Fisica, Università di Torino, Italy The analysis of temporal and spatial variations of the soil gases flux across the soil-air interface is a useful tool to investigate geophysical process associated to volcanic activity. One of these gases is radon that has an unique properties: it appears in all the decay chains of the three main primordial radionuclides of the Earth crust such as 238 U, 235 U and 232 Th. Radon is a natural occurring noble element, chemically inert, constantly generated in the rock matrix and in the crustal material. Being monoatomic it could easily enter the rock pores and migrate to significant distances from the site of generation in a surprising short time. Radon is a component of the geothermal fluids, especially in the volcanic systems, measuring the variations of the radon flux, that are only induced by physical factors since it is not a reactive species, could give valuable information on dynamical transport process for geothermal fluid. 222 Rn isotope is an  emitter (E  =5.5 MeV) with half-life of 3.82 days, widely used as precursor of geological risks like earthquakes and volcanic eruptions, locating buried faults, exploring for uranium ores. In recent year it has been also used as a tracer in atmospheric research for the origin and trajectory of air masses [1]. 222 Rn emanates into the air-filled soil or rock pore space from where a fraction reaches the surface and escape to the atmosphere where it could be breathed and hence it has also been associated with lung cancer risk.. In active volcanoes like Stromboli Island, sharp variations on 222 Rn concentration may have a geological cause like magma injection, changes in the temperature and/or depth of hydrothermal system, the effect of stress in rocks induced by seismic events. But 222 Rn flux is also affected by environmental variables, namely atmospheric pressure and temperature, soil temperature, soil moisture and humidity. Hence the environmental modulation on the 222 Rn signal could mask variation related to volcanic activity reducing its potential as a precursor of geological risk. Since 2002 up to present days a network of field stations has been collected 222 Rn concentration data in the volcanic island of Stromboli. The in-soil radon concentration values are coupled to atmospheric pressure, soil temperature and soil humidity data. By continuously automatic measurements the role of the previous listed environmental parameters has been studied and quantified in order to disentangle the radon variation due to geological effects from the environmental ones. Radon measurements at the soil surface vs the temperature gradient from 5 m depth to the surface. The same behaviour of the two curves suggests a strong correlation Sketch of the 222 Rn real-time monitoring station placed at Stromboli volcano..All sensors are connected with the radio-modem placed near the radon detector inside the buried container, to be protected from atmospheric agents. The radio-moden is linked by the directional antenna to transmit the data to the control room at COA (Stromboli Obeservatory). a)Simplified structural map of Stromboli Island with the stations (dark grey triangles) and the Volcano Observatory of the National Civil Defense, where the transmitted data from real-time stations are stored, processed and visualized; b) Median 222 Rn concentration on the 21 sites of the network on the topographic DEM map has been obtained by means of a statistic elaboration. a) average radon concentration in the North side of Stromboli Volcano, b) measurement box with inside the radon detector and the read-out electronics, c) position of the two real-time station (full red circles), the full black square is the position of the Stromboli Observatory COA where the it is placed the control room. Both real time stations are on the same side of the volcano in order to ease the wireless communication. Time series for radon concentration (Bq/m 3 daily average), atmospheric pressure, soil temperature and cumulative rainfall. The radon Behaviour is in anti-phase with soil temperature curve, suggesting that temperature gradient between surface and in depth is the main cause of radon emanation References [1] J.M. Prospero and T.N. Carlson, Science 167 (1970) 974. [2] R. Bonetti et al., Nucl. Instr. and Meth. A 18 (1991) 321. [3] P. Kotrappa, J.C. Dempsey and L.R. Stieff, Rad. Prot. Dosim. 47 (1993) 461. [4] C. Cigolini et al., Geophys. Res. Lett. 32 (2005) L12308. [5] M. Grundel and J. Postendorfer, Rad. Prot. Dosim. 107 (2003) 287. [6] G. Gervino et al., Physica A 340 (2004) 402.