Carbonaceous aerosol composition over northern China in spring 2012.

The organic carbon (OC) and elemental carbon (EC) collected by eight-stage air samplers over northern China during spring 2012 were determined to characterize the spatial variations, size distributions, and sources of carbonaceous aerosols. OC and EC had high concentration levels and spatial heterogeneity. Higher carbonaceous aerosol loadings were found in urban areas, and high concentrations of OC and EC were found in eastern parts of northern China, including Beijing, Taiyuan in Shanxi Province, Yucheng in Shandong Province, Xianghe in Hebei Province, and Shenyang in Liaoning Province. Except the Cele site, OC and EC at all the sites showed a bimodal distribution, peaking in the size of 0.4-0.7 and 4.7-5.8 μm. Carbonaceous aerosols in the fine mode in the urban areas are mostly presented in smaller sizes than those in the rural/regional background areas. For most sites, mass median aerodynamic diameter (MMAD) values in the fine particles for OC were higher than those for EC with the addition of semi-volatile organics. Good correlations between OC and EC in all the cities (5 in North China and 1 in northeast China) may suggest the impact of anthropogenic emissions on carbonaceous aerosols in the above regions.