ABSTRACT

The total amount of CO₂ released at Ischia Island has been estimated from soil gas flux measurements and from chemical composition of the gases released by fumaroles or dissolved in groundwaters. The preliminary results indicate an overall CO₂ output of about 15 kg s^-1 from the entire island (46 km²). The main contribution to the total output from diffuse soil degassing is about 14.8 kg s^-1, followed by dissolved CO₂ of about 0.3 kg s^-1. The contribution of fumaroles to the total output was found to be negligible (about 0.03 kg s^-1). Ischia's output, although being considerably less than that of open conduit volcanoes, is higher than many other volcanic systems, especially those related to volcanic arcs. The recent tensile tectonic regime of the area allows probably an easier upflow of CO₂ from the mantle sustaining the diffuse degassing of the island.