A Simple, Affordable Way to Measure Diffuse Carbon Release at Volcanoes

Keeping tabs on carbon dioxide emitted from volcanoes can be valuable, both for forecasting potential eruptions and for determining how much deep carbon the volcano releases to the atmosphere. Some volcanoes, however, release more carbon dioxide as diffuse degassing along the flanks than through the main plume of the volcano. These volcanoes are difficult to study using a single monitoring station, complicating scientists’ attempts to monitor the “state and evolution” of volcanoes.

DCO members Matteo Lelli and Brunella Raco (both at the Institute of Geosciences and Earth Resources–CNR, Italy), in collaboration with West Systems S.r.l., have developed a new carbon dioxide monitoring device that is smaller, lighter, and cheaper than existing designs. It continuously measures diffuse carbon dioxide released from soil, as well several relevant environmental factors. The researchers described their successful test run of the instrument in a new paper in Applied Geochemistry [1]. Ultimately, they hope that the device will be used to set up monitoring networks that will yield more complete estimates of volcanic carbon release.

Lelli and Raco deployed their device in a quarry on Lipari, an island in Italy’s Aeolian archipelago in the Tyrrhenian Sea, which also includes active volcanoes Vulcano and Stromboli. While the most recent eruption of Lipari volcano occurred more than 1,400 years ago, it still emits carbon dioxide gas through soil and at nearby thermal springs that are popular with tourists. “We chose Lipari Island because it represents an active volcano in the quiescence stage, with fumaroles and strong carbon dioxide emissions that are related to active local tectonic structures,” said Lelli. “It’s a natural laboratory to test our device.”

They named their device the CO2-S-POT station, for “spot” as the point of measurement and “pot” for container that collects the gas. The device measures carbon dioxide at programmed time intervals using the accumulation chamber method, a technique first introduced for geochemical monitoring of volcanoes in late-1980s. It measures the increase in gas concentration inside a container placed on top of the soil. The instrument also detects air and soil temperature, atmospheric pressure, water content in the soil, and soil conductivity. Along with wind speed and rain, each of these factors influence how rapidly soil releases carbon dioxide.

After a field test consisting of three months of continuous operation without maintenance, the researchers retrieved a complete data set from the device.

Lelli and Raco also proposed a new approach for analyzing volcanic carbon dioxide emissions that takes into account environmental conditions. Their analysis of the collected data suggested that over short timescales, variations in carbon dioxide release can be attributed to measured environmental changes, such as waterlogged soils, but over long periods, these differences may be related to tectonic changes within the ”deep system.” By standardizing these analyses, data sets from different locations can be compared or compiled for global analyses.

Forecasting volcanic eruptions is a difficult task, but detailed, long-term volcano monitoring could improve researchers’ ability to recognize emissions trends that may occur before eruptions.

Forecasting volcanic eruptions is a difficult task, but detailed, long-term volcano monitoring could improve researchers’ ability to recognize emissions trends that may occur before eruptions. Additionally, smaller and more affordable monitoring stations could make it possible to observe emissions at more locations and to set up entire networks of devices. Thus far, logistical barriers, the expense of devices, and the need to maintain an instrument’s sensitivity, reproducibility, and detection limit over time, have hampered attempts to monitor carbon dioxide diffused from the soil.

“We dream of finding a way to set up a monitoring network on a volcano to improve volcano surveillance and to estimate the total amount of natural greenhouse gas emissions for use in climate change research,” said Raco.

In future work, Lelli and Raco together with West Systems S.r.l., plan to deploy the devices along with a meteorological station for measuring windy conditions. Their device had recorded some unusually high measurements over the course of four days, which statistically fell outside the norm of their three-month test drive. These extremes could represent natural variation of deep system, or could be due to unmonitored weather conditions, such as wind speed and direction. Only additional studies will clarify these measurements.

The development of the new monitoring device is part of DCO’s DECADE Initiative. Affiliated volcanologists are installing monitoring devices at 20 of the world’s 150 most actively degassing volcanoes, with the goal of providing a more efficient monitoring network and more accurate estimate of the global carbon dioxide release from volcanoes.

Matteo Lelli working with the CO2-S-POT station on the island of Lipari in the Tyrrhenian Sea, off the coast of southern Italy. Credit: Brunella Raco

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