Understanding the environmental impacts of large fissure eruptions:Aerosol and gas emissions from the 2014–2015 Holuhraun eruption (Iceland)

• Published in: Earth and Planetary Science Letters
• Main Authors: Ilyinskaya, Evgenia, Schmidt, Anja, Mather, Tamsin A., Pope, Francis D., Witham, Claire, Baxter, Peter, Jóhannsson, Thorsteinn, Pfeffer, Melissa, Barsotti, Sara, Singh, Ajit, Sanderson, Paul, Bergsson, Baldur, McCormick Kilbride, Brendan, Donovan, Amy, Peters, Nial, Oppenheimer, Clive, Edmonds, Marie
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2017
• Subjects: air quality; environment; Iceland; volcanic emissions; volcanic eruption; volcanic plume; Reykjavík
• Online Access: https://research.manchester.ac.uk/en/publications/81413f96-de34-46ef-93b7-936a1177f0be; https://doi.org/10.1016/j.epsl.2017.05.025

The 2014–2015 Holuhraun eruption in Iceland, emitted ∼11 Tg of SO 2 into the troposphere over 6 months, and caused one of the most intense and widespread volcanogenic air pollution events in centuries. This study provides a number of source terms for characterisation of plumes in large fissure eruptions, in Iceland and elsewhere. We characterised the chemistry of aerosol particle matter (PM) and gas in the Holuhraun plume, and its evolution as the plume dispersed, both via measurements and modelling. The plume was sampled at the eruptive vent, and in two populated areas in Iceland. The plume caused repeated air pollution events, exceeding hourly air quality standards (350 μg/m 3 ) for SO 2 on 88 occasions in Reykjahlíð town (100 km distance), and 34 occasions in Reykjavík capital area (250 km distance). Average daily concentration of volcanogenic PM sulphate exceeded 5 μg/m 3 on 30 days in Reykjavík capital area, which is the maximum concentration measured during non-eruptive background interval. There are currently no established air quality standards for sulphate. Combining the results from direct sampling and dispersion modelling, we identified two types of plume impacting the downwind populated areas. The first type was characterised by high concentrations of both SO 2 and S-bearing PM, with a high S gas /S PM mass ratio (SO 2(g) /SO 4 2− (PM) > 10). The second type had a low S gas /S PM ratio (<10). We suggest that this second type was a mature plume where sulphur had undergone significant gas-to-aerosol conversion in the atmosphere. Both types of plume were rich in fine aerosol (predominantly PM 1 and PM 2.5 ), sulphate (on average ∼90% of the PM mass) and various trace species, including heavy metals. The fine size of the volcanic PM mass (75–80% in PM 2.5 ), and the high environmental lability of its chemical components have potential adverse implications for environmental and health impacts. However, only the dispersion of volcanic SO 2 was forecast in public warnings and operationally monitored ...