Volcanoes constitute an important source of aerosol. Here we report the size-resolved compositions of major water-soluble ions in particles collected in near-source emissions from three contrasting volcanoes (Solfatara, Vulcano and Stromboli, in Italy). Concentrations of soluble SO42- , Cl-, F-, NO3-, H+, K+, Na+, NH4+ , Ca2+ and Mg2+ were determined in 11 particle size bins from 0.069 to > 25.5 mum in diameter. Soluble ions were most concentrated in the emissions from Solfatara and Stromboli. At Solfatara the major ions were NH4+ and Cl-, tightly correlated in similar to0.8-1.5 mum diameter particles, strongly suggesting speciation as NH4Cl. At Stromboli enhanced levels of SO42-, H+, Na+; K+ and NH4+ were present in similar to0.5-1.5 mum diameter particles. Near-source soluble sulphate was observed in the plumes from Stromboli and Vulcano, with that from Stromboli in much higher concentration (0.94-2.14 compared with 0.07-0.13 mumol m(-3)). Comparing SO42- measurements from Vulcano to those from other volcanic systems suggests that near-source sulphate aerosol emissions scale with SO2 and contribute similar to0.03-0.05 Tg yr(-1) of sulphur to the atmosphere. Simple calculations suggest that all the particles containing these soluble ions will act as cloud condensation nuclei at typical atmospheric supersaturations. (C) 2004 Elsevier Ltd. All rights reserved.
- size distribution
- primary particles