Balloon-borne measurement of the aerosol size distribution from an Icelandic flood basalt eruption

• Published in: Earth and Planetary Science Letters
• Main Authors: Vignelles, D., Roberts, T. J., Carboni, E., Ilyinskaya, E., Pfeffer, M., Waldhauserova, P. D., Schmidt, A., Berthet, G., Jegou, F., Renard, J. B., Olafsson, H., Bergsson, B., Yeo, R., Reynisson, N. F., Grainger, R. G., Galle, Bo, Conde Jacobo, Alexander Vladimir, Arellano, Santiago, Lurton, T., Coute, B., Duverger, V.
• Language: unknown
• Published: 2016
• Subjects: Geophysical Engineering; Geochemistry; aerosol counter; volcano plume; in-situ measurement; balloon; Iceland; Holuhraun
• Online Access: https://doi.org/10.1016/j.epsl.2016.08.027; https://research.chalmers.se/en/publication/243683

We present in situ balloon-borne measurements of aerosols in a volcanic plume made during the Holuhraun eruption (Iceland) in January 2015. The balloon flight intercepted a young plume at 8 km distance downwind from the crater, where the plume is 15 min of age. The balloon carried a novel miniature optical particle counter LOAC (Light Optical Aerosol Counter) which measures particle number concentration and size distribution in the plume, alongside a meteorological payload. We discuss the possibility of calculating particle flux by combining LOAC data with measurements of sulfur dioxide flux by ground-based UV spectrometer (DOAS). The balloon passed through the plume at altitude range of 2.0-3.1 km above sea level (a.s.l.). The plume top height was determined as 2.7-3.1 km a.s.l., which is in good agreement with data from Infrared Atmospheric Sounding Interferometer (IASI) satellite. Two distinct plume layers were detected, a non condensed lower layer (300 m thickness) and a condensed upper layer (800 m thickness). The lower layer was characterized by a lognormal size distribution of fine particles (0.2 mu m diameter) and a secondary, coarser mode (2.3 mu m diameter), with a total particle number concentration of around 100 cm(-3) in the 0.2-100 mu m detection range. The upper layer was dominated by particle centered on 20 mu m in diameter as well as containing a finer mode (2 mu m diameter). The total particle number concentration in the upper plume layer was an order of magnitude higher than in the lower layer. We demonstrate that intercepting a volcanic plume with a meteorological balloon carrying LOAC is an efficient method to characterize volcanic aerosol properties. During future volcanic eruptions, balloon borne measurements could be carried out easily and rapidly over a large spatial area in order to better characterize the evolution of the particle size distribution and particle number concentrations in a volcanic plume.