SULFUR-DIOXIDE, PARTICLE AND ELEMENTAL EMISSIONS FROM MOUNT ETNA, ITALY DURING JULY 1987

Sulphur dioxide emission rates were measured at Mount Etna, Italy duri ng July 1987 while the volcano was undergoing relatively 'quiet' activ ity. The SO2 flux averaged 930 +/- 587 (1sigma) Mg/d excluding 19 July when the flux was 3 200 +/- 1 730 (1sigma) Mg/d. Rising magma and/or an influx of less degassed magma could explain the increased SO2 flux. The high SO2 flux did not correlate with changes in observed volcanic activity. This suggests that SO2 monitoring may be useful as an indic ator of shallow magmatic activity, but not as a predictor of future er uptions of Mount Etna. Particles emitted from the two active craters, Bocca Nuova and southeast crater (SE), were composed of silicates, sul phates and dithionites. Chloride species were only observed in particl es from SE. Different eruptive styles probably produced the difference s in particle compositions emitted from each crater. Vapour-magma enri chment factors were calculated for many elements from both craters. Cl , Br and S were the most enriched elements in the sampled fumes. Simil ar enrichment factors at both craters suggest a common magma supply. C l, S and F have the largest elemental fluxes emitted from Mount Etna. During 'quiet' activity, the Cl flux represents 27% of the global anth ropogenic emissions, but its effect is limited to the local region due to atmospheric removal processes. Mount Etna also exhaled significant amounts of Zn, Br, Mo, F and Cu compared with regional anthropogenic emissions.