First deployment of a drone-borne active AirCore in a volcanic plume at Mount Etna

Uncrewed Aircraft Systems (UAS) are by now established platforms for measurements in volcanic plumes. Trace gases of interest range from sulfur dioxide and halogenated substances to carbonaceous trace gases including carbon monoxide (CO) and carbon dioxide (CO₂). However, sophisticated measurement techniques for high-precision observations of trace gases often require instrumentation that cannot be used on board UAS due to the high weight and power consumption of the devices

Originally developed for stratospheric observations, air sampling with long coiled tubes in AirCores, has proven to be a light-weight sampling technique to probe parts of the atmosphere that are otherwise difficult to access. Trace gas analysis of sampled air is done post-flight, most commonly with fast high-precision optical methods, delivering high-quality and high-resolution trace gas mixing ratios. While balloon-borne AirCore setups perform so-called passive sampling, making use of natural pressure differences, in 2018, a team at Groningen University developed a UAS-deployable small active AirCore device collecting air with a small pump.

In July 2024, we deployed this AirCore setup on a UAS to probe the volcanic plume of Mt. Etna (Sicily, Italy), which was particularly active at the time of the measurements. This was to our knowledge the first time that the AirCore sampling technique was used to sample air inside a volcanic plume. The air sample was successfully analysed with cavity-ring down spectroscopy for CO, CO₂ and methane (CH₄). While CO and CO₂ mixing ratios were markedly enhanced in the plume and signals correlated well with SO₂ enhancements observed by an electro-chemical sensor, no significant enhancement of CH₄ was observed. The observed trace gas mixing ratios will be used in further studies to model the chemistry in the plume of Mt. Etna.