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Durham University

Department of Earth Sciences


Publication details for Prof. Claire Horwell

Martin, R S. Mather, T A., Pyle, D M., Power, M., Allen, A G., Aiuppa, A., Horwell, C J. & Ward, E P W. (2008). Composition-resolved size distributions of volcanic aerosols in the Mt. Etna plumes. Journal of Geophysical Research - Atmospheres 113: D17211.

Author(s) from Durham


Particle size distributions for soluble and insoluble species in Mt Etna’s summit plumes were
measured across an extended size range (10 nm < d < 100 ìm) using a combination of
techniques. Automated scanning electron microscopy (QEMSCAN) was used to chemically
analyze many thousands of insoluble particles (collected on pumped filters) allowing the
relationships between particle size, shape and composition to be investigated. The size
distribution of fine silicate particles (d < 10 ìm) was found to be lognormal, consistent with
formation by bursting of gas bubbles at the surface of the magma. The compositions of fine
silicate particles were found to vary between magmatic and nearly-pure silica; this is
consistent with depletion of metal ions by reactions in the acidic environment of the gas
plume and vent. Measurements of the size, shape and composition of fine silicate particles
may potentially offer insights into pre-, syn- and post- emission processes. The mass flux of
fine silicate particles from Mt Etna released during non-eruptive volcanic degassing in 2004
and 2005 was estimated to be ~7000 kg d-1. Analysis of particles in the range 0.1 < d/ìm <
100 by ion chromatography shows that there are persistent differences in the size distributions
of sulfate aerosols between the two main summit plumes. Analysis of particles in the range
0.01 ìm < d < 0.1 ìm by scanning transmission electron microscopy (STEM) shows that
there are significant levels of nanoparticles in the Mt Etna plumes although their compositions
remain uncertain.