Mixing characteristics of refractory black carbon aerosols at an urban site in Beijing

• Published in: Atmospheric chemistry and physics Vol. 20; no. 9; pp. 5771 - 5785
• Main Authors: Liu, Hang, Pan, Xiaole, Liu, Dantong, Liu, Xiaoyong, Chen, Xueshun, Tian, Yu, Sun, Yele, Fu, Pingqing, Wang, Zifa
• Format: Journal Article
• Language: English
• Published: Katlenburg-Lindau Copernicus GmbH 14-05-2020; Copernicus Publications
• Subjects: Aerosols; Air pollution; Atmospheric boundary layer; Black carbon; Black carbon aerosols; Calibration; Carbon; Climate change; Coatings; Core-shell structure; Diameters; Dimensions; Diurnal; Emissions; Fractal geometry; Global temperature changes; Growth rate; Influence; Laboratories; Lasers; Mass; Morphology; Particle mass; Particle size distribution; Photometers; Pollution; Protective coatings; Radiation (Physics); Roads & highways; Scattering cross sections; Size distribution; Solar radiation; Soot; Structures; Summer; Urban areas; Winds; Beijing China; United States > US; Asia; China
• ISSN: 1680-7324; 1680-7316; 1680-7324
• DOI: 10.5194/acp-20-5771-2020

Black carbon aerosols play an important role in climate change because they directly absorb solar radiation. In this study, the mixing state of refractory black carbon (rBC) at an urban site in Beijing in the early summer of 2018 was studied with a single-particle soot photometer (SP2) as well as a tandem observation system with a centrifugal particle mass analyzer (CPMA) and a differential mobility analyzer (DMA). The results demonstrated that the mass-equivalent size distribution of rBC exhibited an approximately lognormal distribution with a mass median diameter (MMD) of 171 nm. When the site experienced prevailing southerly winds, the MMD of rBC increased notably, by 19 %. During the observational period, the ratio of the diameter of rBC-containing particles (D.sub.p) to the rBC core (D.sub.c) was 1.20 on average for D.sub.c =180 nm, indicating that the majority of rBC particles were thinly coated. The D.sub.p /D.sub.c value exhibited a clear diurnal pattern, with a maximum at 14:00 LST and a D.sub.p growth rate of 2.3 nm h.sup.-1 ; higher O.sub.x conditions increased the coating growth rate.