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The Influence of Distant Fires on the Chemical Properties of Arctic Aerosol During the Spring of 2008

A. M. Middlebrook (1), R. Bahreini (1,2), J. Brioude (1,2), C. A. Brock (1), J. A. Cozic (1,2), J. A. de Gouw (1,2), K. D. Froyd (1,2), J. S. Holloway (1,2), D. A. Lack (1,2), S. M. Lance (1,2), D. M. Murphy (1), T. B. Ryerson (1), J. P. Schwarz (1,2), J.

(1) CIRES, (2) NOAA ESRL CSD, (3)now at Droplet Measurement Technologies, Boulder, CO

Investigating Arctic aerosol chemical properties and sources was a primary component of the spring 2008 Aerosol, Radiation, and Cloud Processes affecting Arctic Climate (ARCPAC) airborne field study above Alaska and the nearby Arctic Ocean. Size-resolved, non-refractory (NR) aerosol composition was measured on a 10-second basis and with high sensitivity aboard the NOAA WP-3D aircraft using an Aerodyne Compact Time-of-Flight Aerosol Mass Spectrometer (C-ToF AMS). Other onboard measurements included aerosol black carbon, single particle aerosol mass spectra, aerosol size distributions, and aerosol extinction as well as carbon monoxide (CO), sulfur dioxide, ozone, and volatile organic compounds.

The aerosol chemical composition was highly variable as a function of altitude, in some cases within a few 100s of meters, with generally higher organic mass fractions at higher altitudes. Long-range transport of biomass burning pollutants (CO, acetonitrile, and aerosols) from large fires in the Lake Baikal (Russia) and Kazakhstan regions was observed at these altitudes and contributed to the highest measured aerosol concentrations during this study. The biomass burning organic material was highly oxidized, as measured by the m/z 44 to organic mass ratio. The peak at m/z 60, considered to be an AMS marker for biomass burning, was enhanced in these plumes along with the single particle biomass burning marker of potassium. Furthermore, these markers of biomass burning particles were observed when the sulfate mass fraction was higher and with lower aerosol mass concentrations. This indicates that biomass burning was an important source of the organic mass in background Arctic aerosol during the study period.