10th International Aerosol Conference September 2 - September 7, 2018 America's Center Convention Complex St. Louis, Missouri, USA
Abstract View
Radiative Absorption by Light Absorbing Carbon: Uncertainty, Seasonal and Spatial Variation in a Typical Polluted City in Yangtze River Delta
DONG CHEN, Yu Zhao, Ritao Lyu, Jie Zhang, Nanjing University
Abstract Number: 737 Working Group: Aerosol Chemistry
Abstract One of the major challenges in understanding radiative forcing by aerosols is to accurately monitor and assess the light absorbing components and their contributions to climate forcing in the present-day atmosphere. In this study, the optical properties of light absorbing carbon (LAC) in aerosols, including its temporal and spatial variations were studied at suburban (NJU), urban (PAES) and industrial (NUIST) sites in Nanjing, a typical polluted city in Yangtze River Delta (YRD). It was found that the application of constant values for multiple scattering factor could not well represent the actual absorption characteristics of aerosols in Nanjing. The relative deviation between calculated and measured absorption coefficients of BC was up to 56 ± 34%. An improved method that applied local multiple scattering correction factors could reduce the uncertainty to less than 5%. Distinct seasonal variation exhibited in the mass absorption efficiency (MAEBrC,365) of brown carbon (BrC) at NJU. BrC from secondary sources had a stronger absorption ability than that from primary emissions such as diesel vehicles in winter. MAEBrC,365 in autumn when the SOA precursors were dominated by anthropogenic volatile organic compounds (VOCs) was 1.9 times higher than that in summer when biogenic VOCs were the main secondary organic aerosol (SOA) precursors. At industrial site, BrC was mainly formed by aged secondary organic carbon (SOC) and had a stronger light absorbing ability than that at other two sites. The results of simultaneous observation at NJU and PAES indicated that formation of fresh BrC enhanced the optical absorption of BC but reduced that of BrC. This study indicates the necessity of measurement of local multiple scattering factor for evaluation of BC absorption and implies possible ways to alleviate the light absorption effect of LAC.