Articles | Volume 16, issue 17
Atmos. Chem. Phys., 16, 11415–11431, 2016
Atmos. Chem. Phys., 16, 11415–11431, 2016

Research article 14 Sep 2016

Research article | 14 Sep 2016

Impacts of the 2014–2015 Holuhraun eruption on the UK atmosphere

Marsailidh M. Twigg1, Evgenia Ilyinskaya2,a, Sonya Beccaceci3, David C. Green4, Matthew R. Jones1, Ben Langford1, Sarah R. Leeson1, Justin J. N. Lingard5, Gloria M. Pereira6, Heather Carter6, Jan Poskitt6, Andreas Richter7, Stuart Ritchie3, Ivan Simmons1, Ron I. Smith1, Y. Sim Tang1, Netty Van Dijk1, Keith Vincent5, Eiko Nemitz1, Massimo Vieno1, and Christine F. Braban1 Marsailidh M. Twigg et al.
  • 1NERC Centre for Ecology and Hydrology, Bush Estate, Penicuik, EH26 0QB, UK
  • 2NERC British Geological Survey, Murchison House, W Mains Rd, Edinburgh, EH9 3LA, UK
  • 3Environment Division, National Physical Laboratory, Teddington, London, UK
  • 4Environmental Research Group, King's College London, Franklin-Wilkins Building, 150 Stamford Street, London, SE1 9NH, UK
  • 5Ricardo Energy & Environment, The Gemini Building, Fermi Avenue, Harwell, Didcot, OX11 0QR, UK
  • 6NERC Centre for Ecology and Hydrology, Lancaster Environment Centre, Library Avenue, Bailrigg, Lancaster, LA1 4AP, UK
  • 7Institute of Environmental Physics, University of Bremen, Otto-Hahn-Allee, 28359 Bremen, Germany
  • anow at: School of Earth and Environment, University of Leeds, Leeds, LS2 9JT, UK

Abstract. Volcanic emissions, specifically from Iceland, pose a pan-European risk and are on the UK National Risk Register due to potential impacts on aviation, public health, agriculture, the environment and the economy, from both effusive and explosive activity. During the 2014–2015 fissure eruption at Holuhraun in Iceland, the UK atmosphere was significantly perturbed. This study focuses one major incursion in September 2014, affecting the surface concentrations of both aerosols and gases across the UK, with sites in Scotland experiencing the highest sulfur dioxide (SO2) concentrations. The perturbation event observed was confirmed to originate from the fissure eruption using satellite data from GOME2B and the chemical transport model, EMEP4UK, which was used to establish the spatial distribution of the plume over the UK during the event of interest. At the two UK European Monitoring and Evaluation Program (EMEP) supersite observatories (Auchencorth Moss, SE Scotland, and Harwell, SE England) significant alterations in sulfate (SO42−) content of PM10 and PM2.5 during this event, concurrently with evidence of an increase in ultrafine aerosol most likely due to nucleation and growth of aerosol within the plume, were observed. At Auchencorth Moss, higher hydrochloric acid (HCl) concentrations during the September event (max  =  1.21 µg m−3, cf. annual average 0.12 µg m−3 in 2013), were assessed to be due to acid displacement of chloride (Cl) from sea salt (NaCl) to form HCl gas rather than due to primary emissions of HCl from Holuhraun. The gas and aerosol partitioning at Auchencorth Moss of inorganic species by thermodynamic modelling confirmed the observed partitioning of HCl. Using the data from the chemical thermodynamic model, ISORROPIA-II, there is evidence that the background aerosol, which is typically basic at this site, became acidic with an estimated pH of 3.8 during the peak of the event.

Volcano plume episodes were periodically observed by the majority of the UK air quality monitoring networks during the first 4 months of the eruption (August–December 2014), at both hourly and monthly resolution. In the low-resolution networks, which provide monthly SO2 averages, concentrations were found to be significantly elevated at remote “clean” sites in NE Scotland and SW England, with record-high SO2 concentrations for some sites in September 2014. For sites which are regularly influenced by anthropogenic emissions, taking into account the underlying trends, the eruption led to statistically unremarkable SO2 concentrations (return probabilities  > 0.1, ∼ 10 months). However, for a few sites, SO2 concentrations were clearly much higher than has been previously observed (return probability < 0.005,  > 3000 months). The Holuhraun Icelandic eruption has resulted in a unique study providing direct evidence of atmospheric chemistry perturbation of both gases and aerosols in the UK background atmosphere. The measurements can be used to both challenge and verify existing atmospheric chemistry of volcano plumes, especially those originating from effusive eruptions, which have been underexplored due to limited observations available in the literature. If all European data sets were collated this would allow improved model verification and risk assessments for future volcanic eruptions of this type.

Short summary
This study integrates high and low resolution temporal measurements to assess the impact of the Holuhraun effusive eruption in 2014 across the UK. Measurements, modelling and satellite analysis provides details on the transport and chemistry of both gases and particulates during this unique event. The results of the study can be used verify existing atmospheric chemistry models of volcano plumes in order to carry improved risk assessments for future volcanic eruptions.
Final-revised paper