Distribution of carbonaceous aerosol during spring 2005 over the horqin sandland in northeastern china

The objective of this study was to characterize the elemental carbon and organic carbon (EC and OC, respectively) content of aerosol particles (PM2.5) collected at Tongliao, a site in the Horqin Sandland of northeastern China. During spring 2005, the PM2.5 mass concentration was 126±71 μg·m−3, with higher dust concentrations during five dust storms than on non-dusty days (255±77 vs. 106±44 μg·m−3). The average OC and EC concentrations in PM2.5 determined by a thermal/optical reflectance method were 15.7±7.3 μg·m−3 and 3.3±1.7 μg·m−3, respectively, and carbonaceous aerosol accounted for 9.9% of the PM2.5 mass during dust storms compared to 21.7% on normal days. The average ratios of OC to EC during dust storms were similar to those on non-dusty days, and the correlation coefficient between OC and EC was high, 0.86. The high OC/EC ratios, the distributions of eight carbon fractions, and the strong relationship between K with OC and EC indicate that rural biomass burning was the dominant contributor to the regional carbonaceous aerosol.