A lagrangian case study of the evolution of aerosol composition from a boreal fire plume during the ARCTAS campaign

The University of Colorado Aerodyne High-Resolution Time-of-Flight Aerosol Mass Spectrometer (HR-ToF-AMS, Jayne et al., 2000; DeCarlo et al., 2006) was deployed aboard the NASA DC-8 research aircraft as part of the Arctic Research of the Composition of the Troposphere from Aircraft and Satellites (ARCTAS) campaign during the spring and summer of 2008. During the summer phase, operated out of Cold Lake, Alberta, the focus of research was investigating the composition and evolution of the outflow from large-scale boreal forest fires. The entrainment of such extensive plumes into zonal wind fields leads to inter-continental transport and thus their influence on climate and atmospheric chemistry is expected to have far-reaching impact. Analysis of the Lake McKay fire plume sampled by the DC-8 on July 1st, 2008, highlighted the fast oxidation of the biomass-burning organic aerosol during the first few hours of transport away from the source region. This analysis is now extended to further afield through a combination of trajectory and parcel analysis, satellite and in-situ observations. This allows periods to be positively identified for multiple interceptions of the Lake McKay fire plume by the DC-8, up to a week after the initial source observations. Model projections of anthropogenic plume transport are employed to evaluate the potential impact of polluted air-masses on the biomass-burning plume as is advected downwind. By combining these analyses with the in-situ high-resolution mass spectra acquired by the AMS aboard the DC-8, the nature and timescales of the evolution of the boreal fire aerosol, in particular the organic component, are investigated. Jayne, J.T. et al., Development of an Aerosol Mass Spectrometer for Size and Composition Analysis of Submicron Particles, Aerosol Sci. and Technol., 33, 49-70, 2000. DeCarlo, P.F et al., Field-Deployable, High-Resolution, Time-of-Flight Aerosol Mass Spectrometer, Anal. Chem., 78: 8281-8289, 2006.