Total (fumarolic + diffuse soil) CO₂ output from Furnas volcano

Area of Science:

• Volcanology and Geochemistry
• Environmental Science
• Earth Science

Background:

• Furnas volcano exhibits significant carbon dioxide (CO2) release through diffuse degassing and fumaroles.
• Previous studies characterized diffuse CO2 output but lacked data on fumarolic CO2 emissions.

Purpose of the Study:

• To quantify the total CO2 output from Furnas volcano by combining soil CO2 flux measurements with fumarolic CO2 flux measurements for the first time.
• To assess the relative contributions of diffuse soil degassing and fumarolic emissions to the volcano's CO2 budget.

Main Methods:

• Utilized a GasFinder 2.0 tunable diode laser for CO2 flux measurements.
• Conducted soil CO2 degassing surveys and fumarolic flux measurements at Furnas Lake and Furnas Village.
• Employed a portable Multi-GAS instrument to determine the CO2/H2S ratio for fumaroles.

Main Results:

• Fumaroles dominate CO2 output in main degassing areas, contributing approximately 50 tons/day, while soil diffuse CO2 contributes about 9.2 tons/day (~15%).
• Fumarolic emissions also release an estimated 0.25 tons/day of hydrogen sulfide (H2S).
• Diffuse soil CO2 from a wider, distal structure significantly contributes to the overall Furnas volcano CO2 budget, estimated at ~1030 tons/day.

Conclusions:

• Fumarolic emissions are the primary source of CO2 in localized degassing zones at Furnas volcano.
• Diffuse soil degassing, particularly from broader structures, plays a crucial role in the volcano's total carbon dioxide budget.
• Integrated measurements are essential for a comprehensive understanding of volcanic gas emissions.