Hydrogen in the gas plume of an open-vent volcano, Mount Etna, Italy

A groundbreaking study reveals that Mount Etna, Italy's iconic volcano, emits hydrogen (H₂) at concentrations of 1–3 parts per million (ppm) above ambient levels. Using an upgraded MultiGAS system equipped with a specialized electrochemical sensor, researchers measured H₂-SO₂ and H₂-H₂O plume ratios during field surveys on the summit. These findings suggest that Etna's passive gas emissions likely reflect equilibrium conditions in the magma system at temperatures between 750°C and 950°C, near the nickel-nickel oxide (NNO) mineral buffer redox state. The study also estimates a time-averaged H₂ flux of approximately 0.65 gigagrams per year, indicating that volcanogenic hydrogen contributes marginally to the global atmospheric budget. Additionally, the positive correlation between H₂-SO₂, H₂-H₂O, and CO₂-SO₂ ratios implies that H₂ is partially supplied by deeply rising CO₂-rich gas bubbles moving through a CO₂-depleted shallow conduit magma.

Aiuppa, A., Shinohara, H., Tamburello, G., Giudice, G., Liuzzo, M., & Moretti, R. (2011). Hydrogen in the gas plume of an open-vent volcano, Mount Etna, Italy. Journal of Geophysical Research, 116(B10). https://doi.org/10.1029/2011jb008461