Rapid gas measurements in volcanic plumes with UAVs: online and offline measurements of various trace gases with light UAVs

To protect people and infrastructures in the immediate vicinity of active volcanoes, monitoring the gas composition of the emitted plume is crucial. In order to react quickly to sudden changes in this composition, frequent measurements are key, as different ratios like the halogen/sulfur or the CO₂/SO₂ ratio can give hints on changing volcanic activity due to their different solubility in magma.   

However, monitoring the chemical composition of the volcanic plume is not an easy task, especially since stationary ground-based gas monitoring stations do not always measure the concentration in the plume, only under certain meteorological conditions, and remote sensing methods are not available for all gases of interest. In this case, human interaction is required to move the measurement equipment to the location of interest, which is close to the active vent. Not only does this pose a serious health risk, it is also burdensome, as the researcher must climb the volcano, take the measurements, climb back down, and analyze the results. This lengthy procedure can be sped up and facilitated by using lightweight drones to take the measurements. Sensors and various other instruments, such as miniaturized alkaline traps or impregnated syringe filters that employ an electrophilic addition to a double bond to selectively absorb halogen species in the oxidation states -1, ±0 and +1, can be mounted on the drone and controlled via a radio link to a ground station. The online results can then be used during the flight to locate the plume to ensure efficient sampling with the absorbers. The landing site of the drone is usually located far away from active vents, which significantly reduces health hazards and speeds up the process.

This poster presents such a drone with its advanced sensor system and absorbers for the determination and quantification of CO₂, SO₂, acidic gases and halogen species and its deployment during a measurement campaign on Etna in July 2022.