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RESEARCH PRODUCT

The role of the aquifer in soil CO2 degassing in volcanic peripheral areas: A case study of Stromboli Island (Italy)

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Abstract The peripheral area of Stromboli Island, Italy, named “Scari”, was continuously studied between January 2009 and December 2010. Data on soil CO 2 flux and the partial pressure of CO 2 (pCO 2 ) in equilibrium with the thermal aquifer linked to the magmatic system are presented. Soil CO 2 fluxes range from 20 to 370 g m − 2  d − 1 and have been strongly affected by soil temperature variations. Soil CO 2 flux data were filtered with respect to the soil temperature and the calculated values, called “residuals”, were considered to detect changes induced by the magmatic system. The pCO 2 values change in a wide range from 0.03 to 0.6 (atm), showing rapid variations. The results of this study show that in the volcanic peripheral area, the degassing process of soil CO 2 is determined not only by the CO 2 released directly from the magma but also by gas–water interactions in the aquifer. The aquifer is able to dissolve the high amount of CO 2 discharged by the magmatic system. Moreover, the “residuals” of CO 2 flux diffused from the soil show a delay on the order of ~ 1 month with respect to the pCO 2 in equilibrium with the aquifer. The soil CO 2 flux is therefore not directly linked to the uprising of magmatic CO 2 but instead depends on the CO 2 discharged from the aquifer, which buffers and modulates the volatile changes released by the magmatic system.