CO2 budget from a 3D chemical tomography of a degassing volcanic lake (Lagoa das Furnas, São Miguel, Azores)

We here present a 3D mapping of the dissolved CO2 at Lagoa das Furnas (São Miguel Island, Azores) obtained with an infrared-based probe that measures the partial pressure of CO₂ gas dissolved in liquids, and a multi-parametric probe to measure pH, ORP, conductivity, dissolved O2, and temperature. We interpolated the dissolved CO2 at different depths and around the lake to calculate the total mass of CO2 dissolved as CO2 (aq) (109–176 tons). We identified different plumes of dissolved CO2 that spatially correspond to previously detected shallow anomalies of the diffusive CO2 degassing at the water-air (interface) and hydroacoustic signatures of the bubbling activity. Our result represents the first direct quantification of the total dissolved CO2 in a volcanic lake, opening new perspectives for volcanic lake monitoring and related hazard assessment.