Black carbon (BC), an important light-absorbing aerosol component in the atmosphere, has significant impact on climate change and public health. The effects of BC on climate and public health have been well established, but uncertainties are large due to its characteristics including sources, size distribution, mixing state and coating composition. In order to have a more complete understanding of BC during winter episodes in 2018 in Beijing, this study combines several major online measurements simultaneously to investigate sources of BC using receptor model, mixing states, and coating composition of BC with high time resolution at an urban site in Beijing. The mixing state of refractory black carbon (rBC) was measured real-time using a single-particle soot photometer (SP2). The coating composition of BC was measured using a single particle aerosol mass spectrometry (SPAMS). The 7-wavelength Aethalometer (AE-33) along with other chemical components including elemental carbon and organic carbon by a Sunset instrument, multiple metals by the Xact, and ions by the IGAC are combined to identify sources of BC. The PMF source apportionment results showed that BC was mainly emitted from coal combustion, vehicle exhaust, and biomass burning in Beijing. From non-haze to haze episodes, the mass median diameter of rBC was increased, which might be due to the increased contribution of coal combustion. In addition, the ratio of the diameter of rBC particles to the diameter of core of BC was increased, which was due to enhanced secondary formation compared to non-haze periods. The result was consistent with the coating composition measured by SPAMS. During haze episodes, the fraction of BC particles which coated with sulfate, nitrate, and organic carbon was higher. This study presents a more complete and detailed examination of sources, mixing states, and coating composition of BC in Beijing, providing valuable and rich information for other studies which focus on studying health and climate effects of black carbon.
 

Black carbon, Mixing states and composition, Source apportionment, SP2, SPAMS, Beijing