Carbon dioxide circulation and diffuse degassing within the Roman volcanic province (Colli Albani, Italy). IAVCEI General Assembly, Pucon, Chile Novembre 2004.The 2002-2003 submarine gas eruption at Panarea (Aeolian Islands, Italy): study of the seafloor and implications for volcanic hazard assessment.

The Colli Albani is a quiescent Quaternary volcano located nearby the city of Roma, characterized by moderate seismic activity, ground deformation, and by a remarkable CO2 degassing through the soil that, at some locations, induces significant health hazard. The circulation and ascent of deep seated CO2 in the Colli Albani region has been simulated by applying a two-phase, two-component heat and fluid flow model (TOUGH2), describing the circulation of water and carbon dioxide through an heterogeneous porous medium. The model accounts for phase changes, and for CO2 dissolution in liquid water, with the associated latent heat and dissolution enthalpy effects. All the available geological, geophysical, geochemical and hydrogeological information available for the Colli Albani region have been implemented into the model to provide a reliable description of the underground rock sequence, with the most relevant porous domains, and to define initial and boundary conditions for the simulation. Simulations are performed to evaluate conditions favoring the ascent and exsolution of carbon dioxide from the carbonatic basement up to the shallow volcanic series hosting the water table. Structural highs in the carbonatic basement, regions of enhanced vertical permeability, or periods of increased CO2 supply from depth are all features going to affect shallow CO2 degassing that will be taken into account by the simulations. Early results show that overall fluid circulation and surface CO2 emissions are highly affected by the physical properties of the carbonatic basement, and its thickness.