Radon and CO2 monitoring in Gallicano thermomineral spring

We present an automatic continuous monitoring station for radon gas (222Rn) in groundwater used to complement the study of earthquake related phenomena. Radon is a noble gas deriving from the 238U decay chain and it is considered a seismic precursor (Ghosh et al., 2009; Riggio and Santulin, 2015). The monitoring station has been operating since the end of 2016, measuring the radon concentration of a groundwater spring located in Gallicano, inside the Garfagnana seismic area of Tuscany in Central Italy. Along with the radon measurement, another monitoring station developed by the CNR-IGG (National Council of research, Institute of Geosciences and Earth Resources, Italy) performs a continuous measurement of several geochemical parameters of the groundwater, i.e. temperature, pH, redox potential, electrical conductivity, CO2 and CH4 concentration. This station is part of a larger CNR-IGG geochemical network that has been active in Tuscany for over ten years (Cioni et al., 2007) and sponsored by Tuscany Region in the within of own seismic risk reduction programs. The sampling site has been chosen on the basis of seismotectonic criteria (Pierotti et al., 2015). The radon station measures in situ the water radon concentrations every 6 hours and then transmits the data over the Internet. The radon measurement is performed by using gamma spectroscopy with a 2”x2” NaI(Tl) scintillation detector coupled to a multichannel analyzer. After the water sampling, enough time to achieve radioactive equilibrium between radon and its short decay progenies in the sample water is allowed to pass before the measurement. The detection limit is around 5 Bq/l. The purpose of this work is to combine the radon and CO2 concentration series of groundwater, searching for possible anomalies and correlations with seismic activities. Considering that CO2 is frequently a radon carrier in endogenous gases, the simultaneous measurement of both gases is expected to increase the probability of identifying earthquake-related geochemical and radioactive anomalies. The radon measurement is performed directly in water avoiding the temporal variations due to meteorological parameters and seasonal changes which affect the radon measurements in air. Moreover, a continuous measurement is directly associated with seismic activity, avoiding the uncertainties due to long time integration measurements. The first measurement results obtained from the two type of monitors (radon and CO2) will be shown in the paper