Mount Etna fine ash: first data from investigation on surface area, reactivity and medical hazard

Mount Etna is the most active and largest volcano in Mediterranean area and is located on eastern Sicily (Italy). The recent activity of the volcano is characterized by paroxysmal events from the South-East Crater [1] consisting in lava fountains associated with flow emission and the formation of ash-plumes. We studied the possible respiratory health effects of the fine ashes erupted during the 2013 activity using leaching experiments with Gamble solution [2]. Etna volcanic ashes are mainly made of volcanic glass and subordinately by plagioclases and pyroxenes; cristobalite occasionally occurs due to the presence of quartz-rich xenoliths. However, the chemical characterization of the amorphous phases evidenced that surfaces of ash particles are widely modified by their interaction with the gas/aerosol of the plume [3]. The surface area of the sampled volcanic ashes was investigated by BET analysis finding values in the range 0.09 - 0.8 m2/g. Such values indicate low porosity of the ash particles. To investigate the effect of lung exposure to fine volcanic ash particles (<38 micron), leaching experiments in simulated lung fluid (Gamble solution) were carried out. The adopted ratio of ash to leaching solution was 1:100, and extraction time was 24 H. S, Si, Li, Ni, Cu and Tl were found in the leachates above detection limit only for grain size <38 micron. Zn, Ba, Fe and Al were found in meaningful amounts in all samples. As was found only in one sample. Leached amount of elements was normalized by BET surface area. Normalized leached elements were not found always dependent on BET surface area. Accordingly, the variability of BET total surface area and chemistry of leachate solutions are conceivably indicating an intrinsic dependence of sample properties and reactivity on location, actual wind, elapsed time from eruption. In further experiments, the leachate solutions will be used for cellular toxicity testing.