Carbon Dioxide in Taal Volcanic Lake: A Simple Gasometer for Volcano Monitoring

Abstract

Abstract We report here an increase in the amount of carbon dioxide in Taal lake during the year preceding the January 2020 eruption. Starting in February 2019, the CO 2 emissions from the lake increased from background value (700 t day − 1 ) to a flux close to 2,400 t day −1 at the time of the eruption. We show that the lake acts as a highly sensitive gasometer where CO 2 (aq) reflects the balance between CO 2 supplied to the lake (by hot springs) and CO 2 lost by diffusion at air‐water interface. The lake waters are extremely enriched in dissolved carbon dioxide with pCO 2 values as high as 0.35 atm (350,000 ppmV) equivalent to a CO 2 (aq) of 9.32 mmol l −1 . The residence time of CO 2 in the lake is around 1 week which allows for fast detection of change in magma degassing and makes carbon dioxide a very promising tool for volcano monitoring.