Sources, size distribution, and downwind grounding of aerosols from Mount Etna

The number concentrations and size distributions of aerosol particles >0.3 μ diameter were measured at the summit of Mount Etna and up to 10 km downwind from the degassing vents during July and August 2004. Aerosol number concentrations reached in excess of 9 × 106 L-1 at summit vents, compared to 4-8 × 104 L-1 in background air. Number concentrations of intermediate size particles were higher in emissions from the Northeast crater compared to other summit crater vents, and chemical composition measurements showed that Northeast crater aerosols contained a higher mineral cation content compared to those from Voragine or Bocca Nuova, attributed to Strombolian or gas puffing activity withi…