Abstract: Black carbon (BC) and brown carbon (BrC) are important light absorbers in the atmosphere. Recently, the contribution of atmospheric brown carbon to light absorption has become one of the research hotspots at home and abroad. During the 2014 Nanjing Youth Olympic Games, a real-time atmospheric observation was carried out using three-wavelength photoacoustic soot photometer (PASS-3), thermal denuder (TD), aerosol particle mass analyzer (APM), scanning mobility particle sizer (SMPS) and aerodynamic particle sizer (APS) at Nanjing Meteorological Bureau (32.06◦ N, 118.70◦ E) on Jiangxin Island of Nanjing, China. Based on Mie model and AAE method, the average light absorption coefficients of BrC at 405 and 532 nm were calculated to be (8.5±4.5) Mm−1 and (3.2±2.1) Mm−1, respectively, and the corresponding average light absorption contributions were (22.7±12.0)% and (13.6±9.2)%, indicating that the light absorption capacity of BrC is wavelength dependent. Furthermore, the sensitivity analysis of αBC with the change of refractive index in the core-shell model and external model was conducted. It is shown that in both models, αBC is the most sensitive to the imaginary part of the refractive index of BC core, followed by the real part of the refractive of BC core. While the difference is that in the external mixing model, the change of the real part of the refractive index of the non-light-absorption material does not affect the αBC.

Key words: brown carbon, black carbon aerosol, light absorption, absorption ?ngstrom exponent, sensitivity