The Role Played By The Environmental Factors On Diffuse Soil Degassing At Stromboli Volcano

Abstract

Geochemical surveys and continuous measurements of several gas species in volcanic areas are useful to identify changes in volcanic activity as well as in deep magmatic processes. Diffuse soil degassing in volcanic areas releases high amount of gases and its monitoring monitoring can be helpful for the mitigation of risk and volcano surveillance. At Stromboli, previous surveys permitted us to recognize the zones surrounding the crater where diffuse degassing is active. Here we present the first results of the in-soil [222Rn] and CO2 flux continuous monitoring started in April 2007 in one of these zones. Measurements of the CO2 flux and in-soil 222Rn concentration have been acquired simultaneously with the main environmental parameters (soil and air temperature, atmospheric pressure, soil humidity, wind direction and velocity). A multivariate statistical analysis has been applied on the entire acquired dataset, in order to outline the role of each environmental parameter in controlling the variation of in-soil degassing. Results show the key role played by the environmental factors in the process of soil gas transfer from depth to the surface. A good correlation has been found between 222Rn and CO2 flux, confirming the role of the latter as carrier of other gas species. Our results stress the importance of the collection of environmental parameters in the geochemical monitoring aimed at the identification of the processes modulating soil diffuse degassing in volcanic areas. Furthermore, the simultaneous acquisition of several gas species can provide valuable information on the state of the volcano activity and its capability to release gas from its fracture network.