1. Sources and Sinks of Carbonaceous Aerosols in the Arctic in Spring
Qiaoqiao Wang, Daniel J. Jacob, Jenny A. Fisher, Jingqiu Mao, Philippe Le Sager, Eric M. Leibensperger, Claire C. Carouge, Yutaka Kondo, Jose-Luis Jimenez, Michael J. Cubison, Steven G. Howell, Steffen Freitag, Antony D. Clarke, Cameron S. McNaughton, Rodney Weber, Eric Apel and
The ARCTAS Science Team
Research funded by the NASA Tropospheric Chemistry Program

2. Aerosol composition during ARCTAS
April 1-21, 2008
Organic matter accounts for % of fine aerosol mass
Median black carbon concentration of 55 ng m-3 ( 2-5%)

3. GEOS-CHEM
GEOS-CHEM
Chemical transport model (2˚x2.5˚ with 72 vertical levels)
Emission: FLAMBE for Biomass burning with hourly resolution, Bond et al.[2007] for anthropogenic emission
SOA: from reversible partitioning of semivolatile products of biogenic VOCs oxidation

4. Wet deposition in GEOS-CHEM
Large scale precipitation
Cloud updraft scavenging
Anvil precipitation
CCN
In-cloud IN
Below-cloud
entrainment
Washout:
Re-evaporation
detrainment
1.2-day time scale for conversion from hydrophobic to hydrophilic
Water-soluble compounds for CCN and water-insoluble BC for IN
Use scavenging coefficient for accumulation aerosol mode instead of the bulk parameterization for the whole aerosol size range

5. Simulations vs. Observations
Model (red) vs. observations (black)
model source attribution OC BC
Dominance of biomass burning for OC
Dominance of anthropogenic emission from all continents contributing comparably for BC near the surface

6. Carbonaceous Aerosol in the Arctic in April 2008OC BC
BC_Anthropogenic
BC_Biomass burning
Alaska is not representative of the Arctic in terms of fire influence
Fire plumes are superimposed on a well-mixed background

7. Total deposition of OC and BC onto snow in April
Anthropogenic OC
Biomass burning OC
Anthropogenic BC
Biomass burning BC OC
Uniformity of deposition in the Arctic

8. Seasonal variation in source contributions
Deposition in the Arctic ( monthly average, Gg) OC BC
Contributions of biomass burning to deposition in Arctic increase from 2% to 63% for BC and from 9% to 89% for OC from Jan. to Apr.
71% of OC and 33% of BC is from biomass burning in terms of total deposition in Jan-Apr.

9. Conclusions
OC in ARCTAS originated mainly from Russian biomass burning
Dominance of anthropogenic contribution from all continents contributing comparably to BC near surface in ARCTAS
Sources of OC and BC deposited onto snow are similar to those in the atmosphere
Contributions of biomass burning to deposition in the arctic increase from 2% to 63% for BC and from 9% to 89% for OC from Jan. to Apr.