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ACCENT Plus Symposium Urbino 17-20 September 2013

The importance of biomass burning as a source of BC in the European Arctic – Based on measurements at the Zeppelin Observatory, Svalbard. C. Lund Myhre, K.E. Yttri, S. Eckhardt, A. Stohl, M. Fiebig, C. Dye (NILU) J. Ström (ITM) Z. Klimont (IIASA). ACCENT Plus Symposium

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ACCENT Plus Symposium Urbino 17-20 September 2013

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  1. The importance of biomass burning as a source of BC in the European Arctic– Based on measurements at the Zeppelin Observatory, Svalbard C. Lund Myhre, K.E. Yttri, S. Eckhardt, A. Stohl, M. Fiebig, C. Dye (NILU) J. Ström (ITM) Z. Klimont (IIASA) ACCENT Plus Symposium Urbino 17-20 September 2013

  2. Outline • Introduction • On aerosols and “black carbon” in the Arctic • Aim of the study • Levoglucosan as a tracer for biomass burning • The Zeppelin Observatory • Results • The level and seasonal variation of • levoglucosan, equivalent black carbon (EBC) and ECbb at Svalbard • The relative contribution of ECbb to EBC • Discussions of source regions and sources • Outlook

  3. 3 km North of Svalbard, 79oN Aerosols in the Arctic Few Arctic local sources (but this is increasing) Lifetime of days-weeks -> Transport to Arctic is main source • Arctic haze • Seasonalphenomenon (winter – early spring) when aerosol concentrations in the Arctic areveryhigh • Sharma et al. (2006) • AMAP Technical Report No.4 (2011) Joranger and Ottar, Geophys. Res. Lett., 1984

  4. Reported trends of BC in the Arctic • CollaudCoen et al., 2013 (ACP) • Absorption coefficient • Barrow; -6.5 % yr-1 (2001–2010) • Hirdmann et al, 2010 (ACP) • EBC • Alert: -3.8 % yr-1 (1989-2008) • Barrow: not sig.(1998-2008) • Zeppelin: -9 % yr-1 (2002-2009) Sharma et al. 2013 (JGR) “Surface BC (EBC) measurements at the three Arctic sites: overall decline of 40% in BC measurements in the Arctic from 1990 to 2009”

  5. Models prediction of ”BC” in the Arctic Models struggle to capture Arctic Haze Problems particularly severe for Black Carbon (BC) • Shindell et al. ACP (2008)

  6. Main objective of this study To provide a quantitative estimate of biomass burning BC (here: ECbb) in the European Arctic atmosphere by means of the biomass burning tracer levoglucosan ECwild and agricultural fires • ECresidentialwood burning ECbb at Zeppelin Observatory

  7. The tracer levoglucosan for ECbb • Levoglucosan is a thermal degradation product of cellulose • High emission factor and a low vapour pressure • Stable over realistic transport time and conditions (?) • No emissions from fossil sources -> unique tracer of particulate matter emissions from biomass burning • Improve knowledge of fossil and non-fossil BC contribution in the Arctic

  8. The Zeppelin Observatory • A one year time series of levoglucosan with a 24 hr time resolution • 12th of March 2008 to 7th of March 2009, as part of POLARCAT (IPY) • Complemented with measurements from the ongoing measurement program • Aerosol absorption coefficient (σap) • Elemental carbon (EC) ECbb = EC from wild and agricultural fires + EC from residential wood burning Zeppelin Mountain, 478 m asl, close to the Ny-Ålesund settlement at Svalbard 78°54’N, 11°53’E

  9. Calculation of ECbb from the tracer levoglucosan • ECbb was calculated using the following equations ... and the followoing emissions ratios TCbb= [Levo]×(TC/Levo)bb (1) OCbb= TCbb×(OC/TC)bb (2) ECbb= TCbb−OCbb (3) Equivalent Black Carbon (EBC) used a site specific α-value of 5.7 ± 2.3 m2 g-1derived from concurrent measurements of EC and apat the Zeppelin observatory • 1)Yttri et al. (2009/2011a); 2) Saarikoski et al. (2007)

  10. ResultsMarch 2008- March 2009 Winter Summer Winter

  11. A closer look at ECbb • Pronounced seasonal variability ofECbb • = EC from wild and agricultural fires + EC from residential wood burning • Winter time mean (3.7±1.2 ng m-3) 5x higher than summer time mean (0.8±0.3 ng m-3) • Episodes much more frequent in winter compared to summer • Maximum 24 hour concentration observed in winter (34 ng m-3) was 5x higher than the maximum 24 hour concentration observed in summer • Due to possible degradation of levoglucosan by OH during transport, levels of ECbb are minimum estimates. We are working on estimating a range taking into account suggested degradation rates by Hoffmann et al. (2010, Environ. Sci. Technol).

  12. Results – ECbb relative to EBC • Winter (Oct - May): • Mean ECbbto EBC: 8.8 ± 4.5% • Summer (May - Oct): • Mean ECbbto EBC: 6.1 ± 3.4% • ECbb to EBC exceeded 10% for Aug-Oct, Dec and Jan as a low estimate. • Taking degradation of levoglucosan by OH into account • Preliminary results : 22% during winter as high estimate, and ca 10% during summer.

  13. Source region and sources Modeled concentration of ECbb using FLEXPART and a ECbb tracer subject to dry and wet deposition (Stohl et al, 2013) and the ECLIPSE emission data (Klimont et al. (2013) and available through the ECLIPSE website http://eclipse.nilu.no) • GAINSbiofuel • inventory • GFEDfor • wild and • agricultural fires

  14. Source region and episodes Indicates that the residential wood burning source in Russia is underestimated in the emission inventory Distribution of the biomass burning emissions in the model: residential heating and wild and agricultural fires

  15. Other sources of BC in the Arctic Flaring: Gas burnoff at Melkøya, 70 oN Flaring seems to be a veryimportantsourceof Arctic near-surface BC: “we find that flaring contributes 42% to the annual mean BC surface concentrations in the Arctic. In March, flaring even accounts for 52% of all Arctic BC near the surface.”

  16. Summary and outlook • Large seasonal variations in ECbb; highest concentrations during winter • Minimum estimates of ECbb: • Winter time mean 3.7±1.2 ng m-3 summer time mean 0.8±0.3 ng m-3 • The relative contribution of ECbb to EBC seem to be around 10 % in summer and 25% In winter, but this is still under analysis • Emissions from residential wood burning in Russia is significant, and seem to be underestimated in the emission inventories • Flaring is a strong source of absorbing aerosols in the Arctic, will likely increase! Annually averaged growth rate of CO2 from WMO GHG Bulletin - 2012 Annual increase of CO2: ca 2 ppm per year, ~0.03 Wm-2Over 10 years: 0.3 Wm-2

  17. Thank you for your attention! Acknowledgements Norwegian Research Council through the IPY project Polarcat European Union FP 7th under grant agreement no 282688 – ECLIPSE: ECMWF and met.no granted access to ECMWF analysis data

  18. Results - Levoglucosan • Winter time mean (1.0 ng m-3) 10 x higher than summer time mean (0.1 ng m-3) • Episodes much more frequent in winter (multiple) compared to summer (two) • Peak values up to 10 x the seasonal mean for both summer and winter • Maximum 24 hour concentration observed exceeded 10 ng m-3 • Winter time mean concentration was 1-2 orders of magnitude less compared to European rural areas and 2-3 orders of magnitude less than for European urban areas in winter • Levoglucosan levels observed at the Zeppelin Observatory should be considered conservative, as levoglucosan is likely subjected to degradation by OH during LRT

  19. Calculations cont. • EBC was calclulated according to eq. 4, using a sitespecificα-value (5.7 ± 2.3) derived from concurrent measurements of EC and apat the Zeppelin observatory (See eq. 5) • EBC = ap/ α (eq. 4) • α= ap/ EC(eq. 5) • calculation of the relative contribution of ECbb to EBC: ECbb,rel = ECbb / EBC = [LG] (TC/LG)bb (1 – (OC/TC)bb) / ap/α

  20. Results – Atmospheric life time of levoglucosan • Atmospheric sinks of levoglucosan discussed in the literature: • Depletion by OH [Hennigan et al. (2010); Hoffmann et al. (2010)] • Oligomerization (Holmes and Petrucci, 2007) • Suggested atmospheric life time based on chamber studies (Hennigan et al., 2010): • 0.7 – 2.2 days (exposed to typical summer time OH conc 1 × 106molecules cm−3) • Suggested τ1/2 in a combined experimental and model study by Hoffmann et al. (2010): • 12.7 – 83.2 hrs (depending on OH-concentration, rx rates, and in-cloud/non-cloud) • PRELIMINARY results from sensitivity runs (FLEXPART) in the current study: • Summer time degradation rates suggested by Hoffmann et al. (2010) appears much too high • Winter time degradation rates suggested by Hoffmann et al. (2010) appears not too far off • FLEXPART sensitivity runs suggest life time of approximately 10 days will reconstruct observed seasonal means of levoglucosan

  21. Source region and sources • Emission sensitivity: used the FLEXPART model to calculate the emission sensitivity of BC tracer aerosols for the summer and winter months. For each measurement 50000 particles were released and followed 30 days backward in time. Dry and wet scavenging is included.

  22. BC on snow Pollutedsnow at Tryvann, ca 531 m.a.s.l Oslo,1974 Hole diggedinto cleansnowbelow Decreasedsnowreflectivity (”albedo”)

  23. Bill Watterson, “The Complete Calvin and Hobbes”, 1994

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