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 SymposiumUrbino 17-20 September 2013

OutlineIntroduction- 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

Aerosols in the Arctic

Few Arctic local sources (but this is increasing)

Lifetime of days-weeks -> Transport to Arctic is main source

Arctic haze

Seasonal phenomenon (winter – early spring) when aerosol concentrations in the Arctic are very high

3 km North of Svalbard, 79oN

Joranger and Ottar, Geophys. Res. Lett., 1984Sharma et al. (2006)AMAP Technical Report No.4 (2011)

Reported trends of BC in the Arctic

Collaud Coen et al., 2013 (ACP)Absorption coefficient

– Barrow; -6.5 % yr-1 (2001–2010)“Surface BC (EBC) measurements at the three Arctic sites: overall decline of 40% in BC measurements in the Arctic from 1990 to 2009”

Sharma et al. 2013 (JGR)

Hirdmann et al, 2010 (ACP)EBC− Alert: -3.8 % yr-1 (1989-2008)− Barrow: not sig.(1998-2008)− Zeppelin: -9 % yr-1 (2002-2009)

Models prediction of ”BC” in the Arctic

Shindell et al. ACP (2008)

Models struggle to capture Arctic HazeProblems particularly severe for Black Carbon (BC)

Main objective of this studyTo provide a quantitative estimate of biomass burning BC (here: ECbb) in the European Arctic atmosphere by means of the biomass burning tracer levoglucosan

ECresidential wood burning ECwild and agricultural fires

ECbb at Zeppelin Observatory

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

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

Calculation of ECbb from the tracer levoglucosan• ECbb was calculated using

the following equations

TCbb = [Levo]×(TC/Levo)bb (1)

OCbb = TCbb×(OC/TC)bb (2)

ECbb = TCbb−OCbb (3)

1) Yttri et al. (2009/2011a); 2) Saarikoski et al. (2007)

... and the followoing emissions ratios

Residential wood burning1) Mean (SD)

(TC/Levo)bb 14.7 (3.7)

(OC/TC)bb 0.78 (0.04)

Wild/Agricultural fires2)

(TC/Levo)bb 48 (10)

(OC/TC)bb 0.85 (0.05)Equivalent Black Carbon (EBC) used a site specific α-value of 5.7 ± 2.3 m2 g-1 derived from concurrent measurements of EC and ap at the Zeppelin observatory

ResultsMarch 2008- March 2009

Winter WinterSummer

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c)

b)

ng m

-3

Levoglucosana)

100

200

300

400

ng m

-3

EBC mean

01 March 2008

01 April 2008

01 May 2008

01 June 2008

01 July 2008

01 August 2008

01 September 2008

01 October 2008

01 November 2008

01 December 2008

01 January 2009

01 February 2009

01 March 2009

0

10

20

30

40

50

ng m

-3

ECbb

A closer look at ECbb

• 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).

Pronounced seasonal variability of ECbb

= EC from wild and agricultural fires + EC from residential wood burning

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c)

b)

ng m

-3

Levoglucosana)

100

200

300

400

ng m

-3 EBC mean

01 March 2008

01 April 2008

01 May 2008

01 June 2008

01 July 2008

01 August 2008

01 September 2008

01 October 2008

01 November 2008

01 December 2008

01 January 2009

01 February 2009

01 March 2009

0

10

20

30

40

50

ng m

-3

ECbb

Results – ECbb relative to EBC

• 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.

Winter (Oct - May):

Mean ECbb to EBC: 8.8 ± 4.5%

Summer (May - Oct):

Mean ECbb to EBC: 6.1 ± 3.4%

FebMar

AprMay

JunJul

AugSep

OctNov

DecJan

Feb

0

2

4

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12

14

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18

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24

26

0

20

40

60

80

100

120

2009

ECbb

/EBC (%)

EC

bb to

EB

C (%

)

2008

EBC (ng m-3) EC

bb (ng m-3)

EC

bb a

nd E

CB

(ng

m-3)

0

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50

c)

b)

ng m

-3

ECbb

a)

*

0

10

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ng m

-3

Residential biomass burning

01 March 2008

01 April 2008

01 May 2008

01 June 2008

01 July 2008

01 August 2008

01 September 2008

01 October 2008

01 November 2008

01 December 2008

01 January 2009

01 February 2009

01 March 2009

0

10

20

30

40

50 GFED daily emission (wild + agricultural fires)

ng m

-3

Source region and sourcesModeled 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)

GAINS biofuelinventory

GFED for wild and agricultural fires

Source region and episodes

Distribution of the biomass burning emissions in the model: residential heating and wild and agricultural fires

Indicates that the residential wood burning source in Russia is underestimated in the emission inventory

0

10

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30

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50

c)

b)

ng m

-3

ECbb

a)

*

0

10

20

30

40

50

ng m

-3

Residential biomass burning

01 March 2008

01 April 2008

01 May 2008

01 June 2008

01 July 2008

01 August 2008

01 September 2008

01 October 2008

01 November 2008

01 December 2008

01 January 2009

01 February 2009

01 March 2009

0

10

20

30

40

50 GFED daily emission (wild + agricultural fires)

ng m

-3

Other sources of BC in the ArcticFlaring: Gas burnoff at Melkøya, 70 oN

Flaring seems to be a very important source of Arctic near-surface BC:

“we find that flaring contributes 42% to the annualmean BC surface concentrations in the Arctic. In March, flaring even accounts for 52% of all Arctic BC near the surface.”

Summary and outlookLarge 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-2 Over 10 years: 0.3 Wm-2

Thank you for your attention!

AcknowledgementsNorwegian Research Council through the IPY project PolarcatEuropean Union FP 7th under grant agreement no 282688 – ECLIPSE:

ECMWF and met.no granted access to ECMWF analysis data

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

02468

1012

c)

b)

ng

m-3

Levoglucosana)

100

200

300

400

ng m

-3

EBC mean

01 March 2008

01 April 2008

01 May 2008

01 June 2008

01 July 2008

01 August 2008

01 September 2008

01 October 2008

01 November 2008

01 December 2008

01 January 2009

01 February 2009

01 March 2009

0

10

20

30

40

50

ng m

-3

ECbb

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1012

c)

b)

ng m

-3

Levoglucosana)

100

200

300

400

ng m

-3

EBC mean

01 March 2008

01 April 2008

01 May 2008

01 June 2008

01 July 2008

01 August 2008

01 September 2008

01 October 2008

01 November 2008

01 December 2008

01 January 2009

01 February 2009

01 March 2009

0

10

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50

ng

m-3

ECbb

Calculations cont.

ECbb,rel = ECbb / EBC

= [LG] (TC/LG)bb (1 – (OC/TC)bb) / ap/α

• EBC was calclulated according to eq. 4, using a site specific α-value (5.7 ± 2.3) derived from concurrent measurements of EC and ap at 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:

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 × 106 molecules 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

Source region and sourcesEmission 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.

BC on snow

Decreased snow reflectivity (”albedo”)

Hole digged intoclean snow below

Polluted snow at Tryvann, ca 531 m.a.s.l Oslo,1974

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