HR: 0830h
AN: V21C-0532    [PDF]
TI: Monitoring Volcanic Plumes By Passive Samplers: Data From Mt. Etna And Stromboli Volcanoes
AU: Aiuppa, A
EM: aiuppa@pa.ingv.it
AF: Dipartimento CFTA, Universit… di Palermo, Via Archirafi 36, Palermo, Ita 90123 Italy
AU: * Federico, C
EM: federico@pa.ingv.it
AF: INGV - Sezione di Palermo, Via Ugo La Malfa 153, Palermo, Ita 90146 Italy
AU: Valenza, M
AF: Dipartimento CFTA, Universit… di Palermo, Via Archirafi 36, Palermo, Ita 90123 Italy
AB: Diffusive samplers are of common use in environmental monitoring for the collection of air gaseous volatiles, basing on molecular diffusion and the use of a specific adsorbent support. Here, we present the very first determinations of hydrofluoric, hydrochloric acids and sulfur dioxide in the volcanic plume of both Mount Etna and Stromboli volcanoes, in the attempt of highlighting the potentiality of passive samplers in volcano monitoring. On Mt. Etna, diffusive samplers were used during the powerful October 2002-February 2003 eruption. Data from diffusive samplers fairly matched results of direct measurements in the plume, obtained through the filter packs method (Aiuppa et al., 2002). Also, they allowed acquiring a continuous record of the chemical composition of the eruptive plume from a "safe" distance of ~1 km from the vents, thus considerably decreasing the risks involved in the direct sampling. The clear time decrease of sulfur dioxide concentrations and SO2/HCl ratios we observed from mid December (2600 gúm-3 and 8.2, respectively) to early February (350 gúm-3 and 1.5, respectively) allowed us to track the progressive exhausting of volatile degassing and to forecast the imminent ending of the eruption. Diffusive samplers were used on Stromboli volcano during the last stages of 2002-03 eruption, from May to August 2003. A few determinations carried out a few days before the April 5 paroxysm highlighted S/Cl ratios as high as 8 and low Cl/F ratios, which we interpret as due to shallow degassing of a fresh gas-rich magma batch. Since then, a progressive trend of decrease of S/Cl ratio was observed, from 3.5 to 1. Highest values correspond to the reestablishment of explosive activity at summit craters, after almost two months of continuous and quiet lava emission from 600-m vents on Sciara del Fuoco, seldom interrupted by sporadic explosions. After then, S/Cl ratios present a progressive drop to very low values (~1). This finding could be attributed to the decline of S-rich magma feeding from depth and/or a decrease of SO2 mass output, which probably allowed the background S/Cl ratio (marine spray?) to prevail.
DE: 1000 GEOCHEMISTRY (New field, replaces Rock Chemistry)
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2003 Fall Meeting