Contribution des Sondes Aérologiques Motorisées à l’Etude de la Physico-Chimie des Panaches Volcaniques

Our knowledge of the physico-chemical properties of volcanic plumes remains at an embryonic state, mainly because of the prohibitive cost of measurements made from aircraft, which alone can provide samples representative of the total aerosol and gaseous emission from a volcanic source. The authors show that a small Remotely Piloted Vehicle (R.P.V.), similar in design to the one they used for some probative flights over Mt. Etna, may be of great use in this field. They can, for instance, insure frequent measurement of the SO₂/HCl ratio in volcanic emanations close to active craters at times when the eruptive vents themselves cannot be sampled directly. In June 1978, we were thus able to measure a mean ratio of SO₂/HCl (7.6) in the Mt. Etna volcanic plume. In addition, a correlation spectrometer was in operation during the airborne sampling and allowed us to obtain order of magnitude values for the Mt. Etna discharge in water vapour (170000 tons/day), sulphur dioxide (1700 t/d), hydrochloric acid (340 t/d) and hydrofluoric acid (40 t/d). Widespread use of such R.P.V’s would insure the collection of a great deal of physicochemical data from volcanic plumes, data which are presently lacking and which could extensively enhance the efficiency of chemical methods of volcano surveillance.