The ratio of aerosol optical absorption coefficients to sulfur concentrations, as an indicator of smoke from forest fires when sampling in polar regions

Analyses of aerosol composition data from seven National Park Service locations in Alaska were performed. All of the sampling sites in Alaska experience aerosol pollution from long distance and regional sources. One of the most important regional sources of particles in the area is wood smoke from forest fires. The Denali National Park aerosol data and the corresponding meteorological data made it possible to identify samples of background (long-range-transported) aerosol, which are likely to be without contamination from local and regional sources. Background values of optical absorption (BABS) and sulfur concentration for this site are well correlated and in ranges of 2 × 10−7−50 × 10−7 m−1 and 10–350 ng m−3, respectively. Positive matrix factorization method was used for obtaining information about possible sources of aerosol in the remote locations. Seasonal variations with maxima during the winter-spring season and minima in summer were observed for the sulfur concentration but not for BABS. Seasonal variations were always higher for the more northerly locations. The influence of emissions from regional sources on the BABS values was higher than for sulfur concentrations. The ratios of optical absorption coefficient to sulfur concentration were used to characterize the relative influence of regional pollution sources on the measured particle compositions.