资源环境科技发展态势分析平台

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 CO₂ 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 CO₂ supplied to the lake (by hot springs) and CO₂ lost by diffusion at air‐water interface. The lake waters are extremely enriched in dissolved carbon dioxide with pCO₂ 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 CO₂ in the lake is around one week which allows for fast detection of change in magma degassing and makes carbon dioxide a very promising tool for volcano monitoring.