IAVCEI 2013 Scientific Assembly - July 20 - 24, Kagoshima, Japan
Forecasting Volcanic Activity - Reading and translating the messages of nature for society

1P1_4F-O11

Room A6

Date/Time: July 21 15:45-16:00

Evolution in phase composition and morphology of volcanic aerosols during transport:
the Eyjafjallajoekull plume 2010
Bernard Grobety1 , Mario Meier1 , Cedric Botter1 , Konradin Weber2 , Andreas Vogel2 , Christian Fischer2
1

Dep. of Geosciences, University of Fribourg, Switzerland, 2 Lab. for Environmental Measurement
Techniques, University of Applied Sciences, Duesseldorf, Germany
E-mail: bernard.grobety@unifr.chTo assess the impacts of volcanic aerosol on the environment and anthropogenic activity, the physico-chemical
properties of the particles have to be known. Such information is usually drawn from samples taken on the groundor indirectly from remote sensing. Ground samples reflect only a deposited fraction of the aerosol. Remote sensing
allows to extract grain size distribution of an volcanic aerosol assuming monophasic, spherical aerosol particles.
Ash dispersal models are also based on same assumptions. Volcanic aerosols, however, are usually composedof more than one phase, each with a distinct density and preferred shape. In general, the main components areglass particles, phaenocrysts of minerals, which have crystallized before the eruption occurred, particles, which
are formed through resublimation of volatile components, and externally mixed particles composed of the previouscomponents. Particles of same size may have different travel distances because of differences in density and/orshape. During transport, therefore, not only the average size of particles but also the phase composition and themorphological character of a volcanic aerosol will change.
When assessing the societal and environmental impact of a volcanic plume these continuous physico-chemicalchanges will ultimately have to be taken into account. The eruption of Eyjafjallajoekull 2010 and the entrainmentof its plume into European airspace gave the possibility to sample a volcanic aerosol after several thousands ofkilometers of transport both in the air and on the ground. We compared the mineralogical composition and themorphology of particles of the following samples: 1) collected from an air filter of a piston- engined plane, which
entered the plume close to the crater, 2) resuspended particles sampled at 20 km from Eyjafjallajoekull, and 3)
taken from an airplane, which crossed the plume over the Dutch-German border. A clear change in mineralogy andmorphology could be observed. The airborne samples sampled in Europe are impoverished in phaenocrysts. This
reflects most probably the difference in density between the volcanic glass and the phaenocrysts. The aspect ratioof the particles evolves also during the transport. Particles with high aspect ratio are almost absent in the plumeover Europe. Possible explanation is the higher specific surface of such particles, which will enhance the tendencyof aggregation. The average physical properties of the aerosol thus changes with transport. The average hardnessof the aerosol, important to assess the mechanical impact on airplane components, decreases with transport.
Particles with high melting points e.g. olivine and pyroxene phaenocrysts are also decreasing in concentration withtransport.

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