[Characteristics and Source Apportionment of Black Carbon Over the Eastern Tibetan Plateau]

As the most important absorbing aerosol, black carbon (BC) can affect radiation, clouds, and surface snow cover over the Tibetan Plateau. In this study, the BC mass concentrations were measured using a seven-channel aethalometer (AE-33) in Litang County over the eastern Tibetan Plateau from July 5 to September 5, 2017. The aethalometer model, potential source contribution function (PSCF), and concentration-weighted trajectory (CWT) models were used to analyze the variation characteristics, potential sources, and affecting areas of BC. The results showed that the mass concentration of ρ(BC) in Litang ranged from 0.4 to 4699.8 ng·m^-3, with an average value of 816.4 ng·m^-3, accounting for 5.96% of PM_2.5. The average mass concentrations of ρ(BC_liquid) and ρ(BC_solid) in Litang were 486.1 ng·m^-3 and 398.5 ng·m^-3, respectively, with a C of 0.51. The ρ(BC) mass concentration was mainly distributed from 0-2000 ng·m^-3, which accounted for 92.5% of the total observation period. The diurnal variation in BC, BC_liquid, and BC_solid showed a bimodal distribution, with the peaks appearing at 08:00 and 20:00, respectively. The first peak was mainly related to traffic sources and incomplete combustion of carbonaceous materials, whereas the second peak was mainly related to incomplete combustion of carbonaceous materials. The potential sources and affecting areas of PM_2.5 and BC were different. Imports from abroad had a greater impact on the concentrations of PM_2.5 and BC in Litang, and the affecting areas were mainly transmitted to the northeast in China. The high-value centers were mainly concentrated in the surrounding areas of Litang.