Studies on Size Distribution and Mixing State of Black Carbon Aerosols in China

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Recent rapid growth of industrial activities in East Asia has been causing large increase in aerosols in this area. Atmospheric aerosols modify the radiation budget through scattering and absorption. Because black carbon (BC) aerosols (e.g., soot) efficiently absorb the solar radiation, they have been recognized one of the most important aerosol compounds the solar radiation, they have been recognized one of the mot important aerosol compounds for climate change.In the physical year of 2006, measurements of BC mass concentrations, size distribution, and mixing sate were in the Beijing region and Peal River Delta (PRD) region in China with Peking University Research Groups and some other international research groups. Aerosol chemical composition and some other parameters were also simultaneously measured.In the physical year of 2007, these data were precisely analyzed and interpreted from the viewpoint of emission sources, chemical production, transport processes, and removal processes using three-dimensional chemistry transport model. Observations show that BC concentrations in Beijing have a clear diurnal variation with a maximum during night. This feature was well reproduced by model calculations through diurnal variations, such as that in the boundary layer height. Although large day-to-day variations were found for secondary aerosols, such as inorganic aerosols, they were small for BC. Model calculations showed that BC concentrations were generally controlled by BC emissions within 100 km around Beijing within previous 24 hours. On the centrally, emissions as far as 500 km within previous 3 days were found to affect concentrations of secondary aerosols, such as sulfate through accumulations under stable synoptic-scale meteorological conditions.