Measurements of 220Rn and 222Rn and CO2 emissions in soil and fumarole gases on Mt. Etna volcano (Italy):: Implications for gas transport and shallow ground fracture

Measurements of Rn-220 and Rn-222 activity and of CO2 flux in soil and fumaroles were carried out on Mount Etna volcano in 2005-2006, both in its summit area and along active faults on its flanks. We observe an empirical relationship between (Rn-220/Rn-222) and CO2 efflux. The higher the flux of CO2, the lower the ratio between Rn-220 and Rn-222. Deep sources of gas are characterized by high Rn-222 activity and high CO2 efflux, whereas shallow sources are indicated by high Rn-220 activity and relatively low CO2 efflux. Excess Rn-220 highlights sites of ongoing shallow rock fracturing that could be affected by collapse, as in the case of the rim of an active vent. Depletion both in Rn-220 and in CO2 seems to be representative of residual degassing along recently active eruptive vents.