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, TJ, Carboni, E, Ilyinskaya, E, Pfeffer, M, Dagsson Waldhauserova, P, Schmidt, A, Berthet, G, Jegou, F, Renard, J-B, Olafsson, H, Bergsson, B, Yeo, R, Fannar Reynisson, N, Grainger, RG, Galle, B, Conde, V, Arellano, S, Lurton, T, Coute, B, Duverger, V
• Format: Article in Journal/Newspaper
• Language: English
• Published: Elsevier 2016
• Subjects: Holuhraun; Iceland
• Online Access: https://eprints.whiterose.ac.uk/103843/; https://eprints.whiterose.ac.uk/103843/1/VIGNELLES_Holuhraun_20160811.docx; https://eprints.whiterose.ac.uk/103843/3/VIGNELLES_Holuhraun_suppl_20160811.docx; https://doi.org/10.1016/j.epsl.2016.08.027

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 minutes 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 μm diameter) and a secondary, coarser mode (2.3 μm diameter), with a total particle number concentration of around 100 cm-3 in the 0.2-100 μm detection range. The upper layer was dominated by particle centered on 20 μm in diameter as well as containing a finer mode (2 μm 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.