Bealey, Bill

Braban, Christine

Hall, Jane

Ilyinskaya, Evgenia

Kentisbeer, John

Loughlin, Sue

Roberts, Elin

Rowe, Ed

Vieno, Massimo

Witham, Claire

NERC Open Research Archive

Effusive Eruption Modelling project: Assessing UK impacts of trace species and sulphur depositionSee also NH2.1/AS3.19, 15:30–15:45 EGU2015-14100 UK hazard assessment for a Laki-type volcanic eruption: modelling results for sulphur dioxide and sulphate aerosol, Claire Witham• the potential UK impacts of a future eruption were assessed by characterising the source of a Laki-type eruption scenario and subsequently modelling the eruption with two CTM models over the European domain  • EMEP4UK (CEH) and NAME  (Met Office) models were run with 10 years meteorology and a repeating 5 week eruption scenario (resulting in 80 eruption scenarios under the 2003-2012 meteorology• Witham et al. (EGU2015-14100) present the results from the flight level and surface level modelling results for SO2 and SO42- concentrations• This poster presents EMEP4UK model results for:1) Proxies for surface concentrations of halogen acid and H2S 2) EMEP4UK model surface sulphur concentrations and deposition used to assess ecosystem impactsBackground to modelling Ecosystem impactsTrace species Acidity critical loads exceedance (as Average Accumulated Exceedance keq ha-1 year-1) for all habitats combined for (a) baseline; (b) average Laki-type scenario.  Modelled pH in 2005 for areas of UK dwarf shrub heath for (a) the baseline scenario; (b) the average Laki-type scenario.Summary Concentrations and critical levels exceedance• The annual mean SO2 concentrations are 2.02 μg m-3 (range 0.26- 38.2 μg m-3) for the baseline, and 2.23 μg m-3 (range 0.35- 38.5 μg m-3) for the average Laki-type scenario.• Exceedance of critical levels does not increase significantly.Sulphur deposition and critical loads exceedance Annual S deposition increases ~50%, similar to peak industrial S pollution in the 1970s. Sensitive ecosystem area exceeding their critical load doubles for that year: 22%-51%. Scotland has the greatest proportional increase in exceedance, with areas of dwarf shrubheath at most risk.Dynamic modelling Average soil pH drops only slightly but returns to near normal within 5 years. However,even a small drop in pH can result in damage when pH is already low, particularly todownstream freshwater natural systems and aquaculture. Impacts are likely be localised. Effects of concentrated, short-term peaks of S-deposition were not fully evaluated.• SO2, nitrogen oxides (NOx=NO+NO2) and ammonia (NH3) can contribute to acidification and adversely affect natural and semi-natural habitats.• sensitivity of habitats to acidification is assessed using “critical loads” a quantitative estimate of the exposure to one or more pollutants below which significant harmful effects on specified elements of the environment do not occur according to present knowledge” (Nilsson & Grennfelt,1988)• The amount of acid deposition that exceeds the critical load is called the “critical load exceedance” and indicates an ecosystem is at risk from potential harmful effects in the long term but is not a quantitative estimate of “damage” to the environment.• A “critical level” is the gaseous concentration of a pollutant (e.g., SO2) above which damage has been observed.  The excess pollutant concentration above the critical level is referred as the “critical level exceedance”0.00.51.01.52.0 SO2emitted (Tg)EDCB A0.010.1110HCl (g.m-3)110100 SO2 (g.m-3)110100 SO2-4(g.m-3)01/01/2005 01/04/2005 01/07/2005 01/10/2005 01/01/20061E-30.010.1110 ratio volcanic HCl/SO2 Shetland, Scotland, 20040.00.51.01.52.0 SO2emitted (Tg)EDCB A0.010.1110HCl (g.m-3)110100 SO2 (g.m-3)110100 SO2-4(g.m-3)01/01/2004 01/04/2004 01/07/2004 01/10/2004 01/01/20051E-30.010.1110 ratio volcanic HCl/SO2 Cromwell Road, London, 2005• HCl and HF emissions of the same magnitude as SO2, modelled as a soluble species, result inaverage concentrations at the UK surface mostly <1 µg m-3 with a 95th percentile <5 µg m-3.• Average modelled HCl concentrations are similar to normal UK coastal HCl concentrations• Even with conservatively high emission ratios the hourly human health limits for HF and HClare not exceeded in any of the simulations• H2S modelled as an insoluble species emitted in the ratio range of 0.04 - 0.3 µg m-3 does notexceed the relevant human health 24-hour limit of 150 µg m-3HCl and HF were modelled as a soluble tracer, Xsol using HNO3 solubility, dry & wet deposition  Two non-reactive tracer concentrations, Xinsol, low & Xinsol,high were put into the model runs. With Xinsol,low assessed as a proxy for H2S• Model run with the EmChem09 chemical mechanism 72 species & 137 reactions.• Anthropogenic emissions of NOx, NH3, SO2, primary PM2.5, primary PMcoarse, CO, & NMVOC• UK emissions from the National Atmospheric Emission Inventory (NAEI, http://naei.defra.gov.uk) at 1 km2 resolution, aggregated to 5 km x 5 km • For the outer domain emission estimates use the EMEP 50 km x 50 km resolution provided by CEIP (http://www.ceip.at/),  including emissions for Etna.• The volcanic emissions are injected in the appropriate level at (horizontal resolution 50 km2) emissions above the model vertical domain are injected in the highest level.• The land-based gridded emissions are distributed vertically according to a default distribution based upon the SNAP codes (Simpson et al., 2012). • Hourly temporal resolution was used to derive air quality and other detailed information• Each daily emission has a different vertical profile composed of five layers• different masses of SO2 are emitted into each layer. • Over the whole eruption ~24% SO2 is emitted into the stratosphere,~76% the troposphere. • eighty, non-overlapping, 6-week eruption periods in 2003-2012 were defined.Emission sourceEMEP4UK modellingThe model horizontal resolution scales down from 50 km x 50 km in the main EMEP ‘Greater European’ domain (which includes Iceland) to 5 km x 5 km for the domain covering the British Isles• HF and HCl are emitted in variable amounts from volcanic eruptions, perturbing both theatmospheric composition and adding to effects from sulphur species. H2S is also emitted.• Within a single eruption sequence the volatile ratios, HCl:SO2 and HF:SO2 are likely to behighly variable. However to initialise the model runs an estimate was made usingliterature appropriate for an Icelandic Laki-type eruption were assessed (11 studies,subset of a wider literature survey).• There are very few Icelandic H2S studies. The range of ratios covers 0.01 – 2.86, with theonly Icelandic measurement from Surtsey, Iceland with alkali-basalt reporting a H2S:SO2ratio of 0.04, Halmer et al. (2002).HCl:SO2 HF:SO2 H2S:SO2Range 0.03-1.69 0.03-0.34arithmetic mean 0.47 0.09geometric mean 0.31 0.05Selected value 1 0.3 0.04• Xsol:SO2 was set to 1:1 Xinsol, low:SO2 = 0.04 Xinsol,high =0.3 • It is emphasised that ratios selected were conservative to allow for a reasonable worst case scenario type assessment.Averaging period LevelHF 1 hour 0.2ppm/ 0.16mg/m3 (1)HCl 1 hour 0.5ppm/0.75mg/m3 (1)HBr 1 hour 0.2ppm/ 0.7mg/m3 (1)H2S 24 hour 150µg/m3 (2)(1) http://www.ivhhn.org/index.php?option=com_content&view=article&id=83(2) ; (2) http://archive.defra.gov.uk/environment/quality/air/airquality/publications/halogens/fullreport.pdfResultsHourly average (units: µg.m-3.)Xsol: Xsol:SO2=1Mean (upper panel);95th percentile (middle panel) maximum (lower panel)Hourly averageXinsol Xinsol:SO2 = 0.04Mean (upper panel);95th percentile (middle panel) maximum (lower panelExample site specific analysisSummaryResultsSO2 concentrations and S depositionEMEP4UK modelled sulphur deposition assuming moorland vegetation everywhere for (a) baseline scenario; (b) average Laki-type scenarioEMEP4UK modelled SO2 concentrations for (a) baseline scenario; (b) average Laki-type scenarioA: Volcano emissions (Tg); B: Modelled (purple squares) and measured average ambient (orange line) HClC: Modelled SO2: Baseline (continuous), eruption scenario (crosses)D: Modelled SO4: Baseline (continuous), eruption scenario (crosses)E: Ratio of HCl to SO2: eruption scenario emission ratio (purple line); eruption scenario-baseline (green crosses).Concentration statistics for the 10 year datasetThe emission scenarios considered do not capture the entire range of variability in the numerous aspects of such a Laki-type eruption and in-particular only one set of ratios has been simulated so the values given should be taken as guidance onlyThe Project Team acknowledge the help and assistance of representatives from Public Health England, Department of Health, Department for Transport and Department for Environment, Food and Rural Affairs in the definition of the parameters to be analysed and the relevant thresholds to be used. The Project Team would like to thank the members of the H55 Scientific Expert Advisory Group for their input and feedback on the report draft and for useful discussions at the meeting where these results were first presented. This work was funded by the Civil Contingencies Secretariat (Cabinet Office) and co-funded by NERC. Contacts: EME4UK modelling: mvi@ceh.ac.uk Halogen and trace species analysis: chri2@ceh.ac.uk Ecosystem impacts: jrha@ceh.ac.uk & ecro@ceh.ac.ukOverall project: Claire Witham claire.witham@metoffice.gov.ukMassimo Vieno, Christine Braban, Jane Hall, Sue Loughlin, Bill Bealey, Evgenia Ilyinskaya, John Kentisbeer, Elin Roberts, Ed Rowe Claire Witham Critical load exceedance and dynamic modellingSummary statistics of literature values Air quality metrics used for halogen acids and HBr in the UK• For 30 sites where Defra long term monthly average HCl, SO2& PM composition are measured (http://pollutantdeposition.defra.gov.uk/networks)• the daily average data from the model run was extracted. • 2 examples are shown below The results show that although an Icelandic plume will reach the UK and affect the atmospheric composition, in the scenario done trace species HCl and HF Xsol (modelled as HNO3) do not exceed air quality levels. 

Effusive eruption modelling project: assessing UK

impacts of trace species and sulphur deposition

http://nora.nerc.ac.uk/510683/1/volcano%20modelling%20poster_EGU_Braban.pdf

Effusive eruption modelling project: assessing UK impacts of trace species and sulphur deposition

Abstract

Similar works

Full text

Available Versions

NERC Open Research Archive