A Study of Size Distributions of Carbonaceous Species in Ambient Particles in Baoding, China

Atmospheric particulate matter (PM) pollution is serious in Baoding, an industrial city in North China. Carbonaceous aerosols are key components of particles of various sizes. Total carbonaceous aerosols (TCA) account for (49±20)%, (45±19)%, and (19±7)% of PM1.1, PM2.1, and PM2.1-9.0, respectively. The spectral distribution and the amount of enrichment in particulate matter concentration show seasonal variations. During autumn and winter, organic carbon (OC) concentrations in fine particulate matter were 44.0±38.3 and 78.5±30.2 μg m^-3 and elemental carbon (EC) concentrations in fine particulate matter were 3.5±1.6 and 8.5±6.8 μg m^-3, respectively. The geometric mean diameter (GMD) of OC and EC in the whole size range was found to be centered in fine particles. The GMD of the coarse mode (≥2.1 μm) was found to be larger in spring and summer and smaller in autumn and winter. However, the GMD of the coarse mode for EC showed the opposite tendency. The average OC/EC ratios in particles with a diameter less than 0.4 μm were 5.2 in spring, 3.5 in summer, 4.1 in autumn, and 5.4 in winter, respectively. The main origin of the particles below 0.4 μm was local vehicular exhaust, while the carbonaceous particles in other size modes mainly came from combustion of coal and burning of biomass.