The source and longevity of sulphur in an Icelandic flood basalt eruption plume

Lead Research Organisation: NERC British Geological Survey
Department Name: Earth Hazards & Observatories

Abstract

For the first time in the modern age we have the opportunity to study at first hand the environmental impact of a flood basalt (>1 km3 fissure eruption). Flood basalt eruptions are one of the most hazardous volcanic scenarios in Iceland and have had enormous societal and economic consequences across the northern hemisphere. A flood basalt eruption was included in the UK National Risk Register in 2012 as one of the highest priority risks.

The Holuhraun eruption reached the flood basalt size sometime after 20 October 2014. It is now the largest flood basalt in Iceland since the Laki eruption in 1783-84, which caused the deaths of >20% of the Icelandic population by environmental pollution and famine and likely increased European levels of mortality through air pollution by sulfur-bearing gas and aerosol. The pollution from Holuhraun has been intensifying over the last few weeks, reaching a "Dangerous" level for the first time in Iceland on 26 October (as defined by the World Health Organisation). During 18-22 September, SO2 fluxes reached 45 kt/day, a rate of outgassing rarely observed during sustained eruptions, suggesting that the sulfur loading per kg of erupted magma (we estimate >0.35 wt%) exceeds both that of other recent eruptions in Iceland and perhaps also other historic basaltic eruptions globally, raising questions regarding the origin of these prodigious quantities of sulfur. A lack of data concerning conversion rates of SO2 gas into aerosol, the residence times of aerosol in the plume and the dependence of these on meteorological factors is limiting our confidence in the ability of atmospheric models to forecast gas and aerosol concentrations in the near- and far-field from Icelandic flood basalt eruptions.

Preliminary study of the erupted products highlights two extraordinary features: (1) matrix glasses contain up to 1000 ppm sulfur (<100 ppm is expected for degassed melt) and are extremely heterogeneous and (2) abundant sulfide liquid globules in the matrix glass are "caught in the act" of breaking down on quenching, suggesting that sulfur is not only supplied by the melt, but also by the breakdown of sulfide liquid during degassing. These observations highlight a previously overlooked but potentially very large reservoir of sulfur that leaves little petrological record. These results might go some way towards understanding the extremely high sulfur yield of this eruption and have implications for assessing the environmental impact.

This project combines the expertise of a large group of researchers to understand better the sulfur and chalcophile metal budget of the Holuhraun eruption. We will follow the formation of sulfide liquids, through to their breakdown on degassing, to the outgassing of SO2 gas and conversion to aerosol. The entire pathway is not well understood, particularly given complexities related to the rapid magma ascent rates postulated for the Holuhraun magmas and the lack of ash in the plume, both of which we hypothesise impose kinetic constraints on sulfur processing in different parts of the system. We will carry out detailed petrological, geochemical measurements of lavas and plume chemistry to understand the sulfur budget and to feed into models of plume chemistry and dispersion, which are essential for hazard monitoring.

Planned Impact

The proposed project focuses on the ongoing volcanic eruption at Holuhraun in central Iceland and the associated air pollution effects. There is a very limited understanding of what controls the sulphur output, how the plume evolves geochemically downwind, how the SO2 converts to aerosols and the size distribution of potentially hazardous aerosol particles containing a range of metals.

WHO will benefit from this research and HOW:

A. Icelandic Civil Protection (NCIP) is responsible for disseminating hazard information and mitigation advice to the general public and if needed, ordering evacuations. A better understanding of the plume composition and hence health implications and forecasting the plume dispersion via modelling is of direct benefit to this group. They work closely with the Icelandic Environment Agency who also issue advice to the public.

B. Icelandic Meteorological Office (IMO) is the state volcano monitoring agency. IMO are responsible for the gas plume dispersion modelling over Iceland. This project will directly benefit IMO because a better characterisation of the emitted gas flux will enable more accurate modelling of plume dispersion (for NCIP and the public) and will further the understanding of the geochemical budget of the eruption. IMO will also benefit from a better source and process characterisation to establish scenarios for eruption evolution.

C. UK Civil Contingencies Secretariat (CCS) is responsible for volcanic risks to the UK arising from fissure eruptions such as this one. They work closely with the Government Office for Science. This project will enhance understanding of these risks which are updated regularly in the National Risk Register. Specifically the CCS need better data at source and improved understanding of eruptive and atmospheric processes in order to effectively forecast and provide early warnings to other key UK stakeholders during such eruptions.

D. UK Meteorological Office (UKMO) forecasts air quality and aviation hazards in the UK over the UK and liaising (as London Volcanic Ash Advisory Centre) with other European agencies. UKMO will benefit from a better understanding of the rates of formation and growth of aerosols. The NAME forecast model now includes a chemistry component and we will compare and evaluate NAME's ability to simulate the Holuhraun plume chemistry with respect to a global aerosol model and observations.

E. People living in Iceland, the UK and the rest of Europe will benefit directly from a more informed hazard assessment and risk mitigation strategy to deal with air quality arising from Icelandic eruptions in general: not just Holuhraun but future eruptions also.

F. Academic beneficiaries: We will present at UK and international conferences in both geosciences and atmospheric science disciplines to ensure the research is made available and has wide impact.

G. Other volcano observatories (e.g. USGS Hawaii Volcano Observatory) dealing with volcanic air pollution issues will benefit from our findings.

H. We will also interact with the global Disaster Risk Reduction sector (through UNISDR) and provide evidence for how science can contribute to better understanding and reduction of risk.

I. Aviation stakeholders, including UK Department for transport, CAA, and Volcanic Ash Advisory Group (note: VAAG focuses not only on ash but also on gas and aerosol), who lead work on assessing the impact of volcanic aerosol metals on air frames and engines.

Publications

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Gettelman A (2015) Icelandic volcanic emissions and climate in Nature Geoscience

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Hartley M (2018) Melt inclusion constraints on petrogenesis of the 2014-2015 Holuhraun eruption, Iceland in Contributions to Mineralogy and Petrology

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Twigg M (2016) Impacts of the 2014-2015 Holuhraun eruption on the UK atmosphere in Atmospheric Chemistry and Physics

 
Description The 2014 -2015 Holuhraun eruption in Iceland produced about 1.6 km3 of lava, making it the largest eruption in Iceland in more than 200 years. Over the course of the eruption, the daily volcanic sulfur dioxide (SO2) emissions exceeded daily SO2 emissions from all anthropogenic sources in Europe in 2010 by at least a factor of 3.

The first publication which presents some of our key findings (Schmidt et al. 2015, doi:10.1002/2015JD023638) discussed surface air quality observations from across Northern Europ etogether with satellite remote sensing data and model simulations of volcanic SO2 for September 2014. We show that volcanic SO2 was transported in the lowermost troposphere over long distances and detected by air quality monitoring stations up to 2750 km away from the source.

A publication in prep is presenting a comprehensive dataset which characterises the chemistry of aerosol and gas in the Holuhraun plume, and the changes which occurred as the plume aged. The plume was sampled at the eruptive vent, and in two populated areas in Iceland located at different distances downwind of the volcano: Reykjahlíð town (100 km), and Reykjavík capital area (250 km). The dataset comprises a detailed analysis of major and trace species in the volcanic plume, including size-resolved chemistry of the aerosol phase. We also present a time series of volcanic air pollutants (SO2, PM2.5 and sulphate aerosol) in the populated areas.
We discovered that there were two types of volcanic plume detected in the populated areas that exceeded air quality limits in different ways. The first type, a 'young' plume had high concentrations of both SO2 and sulphate. The second type, an 'aged' plume, where sulphur had undergone complete or near-complete gas-to-aerosol conversion. We show that a tropospheric plume from a large fissure eruption has the potential to have a continued environmental and health impact on a timescale of days (as a minimum) after emission. We recommend that pollution forecasting during future eruptive events should account for aged plumes in addition to the routinely forecasted young plumes, in Iceland and further afield, especially during larger fissure eruptions, such as a 'Laki-type' eruption scenario included in the UK National Risk Register.

The objective to measure pre-eruptive volatile contents of Holuhraun magma, including sulfur, was also met. These results are also being prepared for publication.
Exploitation Route The results will be passed on to the Icelandic Meteorological Office (the Iceland volcano observatory), the national health authorities in Iceland, and the UK Civil Contingency Secretariat. It is expected that they will allow better assessments of environmental and health hazards associated with volcanic eruptions, in particular in Iceland.
Sectors Agriculture, Food and Drink,Environment,Healthcare,Leisure Activities, including Sports, Recreation and Tourism

 
Description This project and its findings were discussed at a table top exercise on the impacts of large magnitude eruptions in Iceland on London. The exercise was attended by many government departments and officials as well as practitioners. The project and its findings have also been discussed at Air Quality expert group meetings in Scotland.
First Year Of Impact 2017
Sector Environment
Impact Types Societal,Policy & public services

 
Description Royal Society Research Grant
Amount £10,000 (GBP)
Organisation The Royal Society 
Sector Academic/University
Country United Kingdom
Start 04/2016 
End 04/2017
 
Description STFC Diamond Light Source
Amount £72,000 (GBP)
Funding ID EE13522 
Organisation Diamond Light Source 
Sector Academic/University
Country United Kingdom
Start 04/2016 
End 04/2017
 
Description Unseen but not unfelt: resilience to persistent volcanic emissions (UNRESP). Case study from Masaya volcano, Nicaragua
Amount £170,100 (GBP)
Funding ID NE/P015271/1 
Organisation Natural Environment Research Council 
Sector Public
Country United Kingdom
Start 11/2016 
End 07/2017
 
Description Volcanic plume understanding and forecasting: Integrating remote-sensing, in-situ observations and models (V-PLUS)
Amount £1,500,000 (GBP)
Funding ID NE/S00436X/1 
Organisation Natural Environment Research Council 
Sector Public
Country United Kingdom
Start 03/2019 
End 08/2022
 
Description British Science Festival 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Public/other audiences
Results and Impact Talk title "Volcanoes and air pollution" at The British Science Festival 2018, Europe's longest standing science Festival. Featuring a diverse programme of over a hundred talks, debates, performances and activities
Year(s) Of Engagement Activity 2018
URL https://www.britishsciencefestival.org/app/uploads/2018/08/G1492_BSA_BSF18_PROG_09B.pdf
 
Description EGU 2015 press conference 
Form Of Engagement Activity A press release, press conference or response to a media enquiry/interview
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Public/other audiences
Results and Impact Press conference held during European Geophysical Union Assembly in Vienna 2015 on "Bardarbunga eruption gas emissions". Modelling results from our project showing impact of this eruption on Europe were presented at the press conference. See e.g. the link below to BBC news item
Year(s) Of Engagement Activity 2015
URL http://www.bbc.co.uk/news/science-environment-32321005
 
Description Morgunbladid newspaper interview (Iceland) 
Form Of Engagement Activity A press release, press conference or response to a media enquiry/interview
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Public/other audiences
Results and Impact Interview taken with Evgenia Ilyinskaya during our fieldwork at the volcano eruption site in Holuhraun, Iceland. The fieldwork was a core part of NERC grant NE/M021130/1. The interview was done by Iceland's largest newspaper, Morgunbladid and briefly covered the progress of our fieldwork
Year(s) Of Engagement Activity 2015
URL http://www.mbl.is/frettir/innlent/2015/01/22/setja_upp_maela_i_haettulegu_gasskyi/
 
Description NI Science Festival, Dippy Talks series 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Public/other audiences
Results and Impact NI Science Festival, Dippy In Depth | Air. Talk title "Volcanoes and air pollution"
Year(s) Of Engagement Activity 2018
URL https://nisciencefestival.com/event.php?e=19
 
Description RUV TV news interview (Iceland) 
Form Of Engagement Activity A press release, press conference or response to a media enquiry/interview
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Public/other audiences
Results and Impact TV interview taken with Evgenia Ilyinskaya immediately after our fieldwork at the volcano eruption site in Holuhraun, Iceland. This was a follow up after the midday radio news interview the same day, and was broadcast on the primetime evening news. The fieldwork was a core part of NERC grant NE/M021130/1. The interview was done by Icelandic National Broadcasting Service and covered the purpose and progress of project.
Year(s) Of Engagement Activity 2015
URL http://www.ruv.is/frett/rannsaka-gas-vid-holuhraun
 
Description RUV radio interview (Iceland) 
Form Of Engagement Activity A press release, press conference or response to a media enquiry/interview
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Public/other audiences
Results and Impact Radio interview taken with Evgenia Ilyinskaya immediately after our fieldwork at the volcano eruption site in Holuhraun, Iceland. The fieldwork was a core part of NERC grant NE/M021130/1. The interview was done by Icelandic National Broadcasting Service and covered the purpose and progress of project. It was broadcast on the lunchtime news.
Year(s) Of Engagement Activity 2015
URL http://www.ruv.is/frett/rannsaka-gastegundir-fra-holuhrauni