Carbonaceous particles play a crucial role in atmospheric radiative forcing. However, our understanding of the behavior and sources of carbonaceous particles in remote regions remains limited. The Tibetan Plateau (TP) is a typical remote region that receives long-range transport of carbonaceous particles from severely polluted areas such as South Asia. Based on carbon isotopic compositions ( Delta 14 C/ delta 13 C) of water -insoluble particulate carbon (IPC) in total suspended particle (TSP), PM 2.5 , and precipitation samples collected during 2020 - 22 at the Nam Co Station, a remote site in the inner TP, the following results were achieved: First, fossil fuel contributions ( f fossil ) to IPC in TSP samples (28.60 +/- 9.52 %) were higher than that of precipitation samples (23.11 +/- 8.60 %), and it is estimated that the scavenging ratio of IPC from non -fossil fuel sources was around 2 times that from fossil fuel combustion during the monsoon season. The f fossil of IPC in both TSP and PM 2.5 samples peaked during the monsoon season. Because heavy precipitation during the monsoon season scavenges large amounts of long-range transported carbonaceous particles, the contribution of local emissions from the TP largely outweighs that from South Asia during this season. The results of the IPC source apportionment based on Delta 14 C and delta 13 C in PM 2.5 samples showed that the highest contribution of liquid fossil fuel combustion also occurred in the monsoon season, reflecting increased human activities (e.g., tourism) on the TP during this period. The results of this study highlight the longer lifetime of fossil fuel -sourced IPC in the atmosphere than that of non -fossil fuel sources in the inner TP and the importance of local emissions from the TP during the monsoon season. The findings provide new knowledge for model improvement and mitigation of carbonaceous particles.

Carbonaceous particles play a crucial role in atmospheric radiative forcing. However, our understanding of the behavior and sources of carbonaceous particles in remote regions remains limited. The Tibetan Plateau (TP) is a typical remote region that receives long-range transport of carbonaceous particles from severely polluted areas such as South Asia. Based on carbon isotopic compositions ( Delta 14 C/ delta 13 C) of water -insoluble particulate carbon (IPC) in total suspended particle (TSP), PM 2.5 , and precipitation samples collected during 2020 - 22 at the Nam Co Station, a remote site in the inner TP, the following results were achieved: First, fossil fuel contributions ( f fossil ) to IPC in TSP samples (28.60 +/- 9.52 %) were higher than that of precipitation samples (23.11 +/- 8.60 %), and it is estimated that the scavenging ratio of IPC from non -fossil fuel sources was around 2 times that from fossil fuel combustion during the monsoon season. The f fossil of IPC in both TSP and PM 2.5 samples peaked during the monsoon season. Because heavy precipitation during the monsoon season scavenges large amounts of long-range transported carbonaceous particles, the contribution of local emissions from the TP largely outweighs that from South Asia during this season. The results of the IPC source apportionment based on Delta 14 C and delta 13 C in PM 2.5 samples showed that the highest contribution of liquid fossil fuel combustion also occurred in the monsoon season, reflecting increased human activities (e.g., tourism) on the TP during this period. The results of this study highlight the longer lifetime of fossil fuel -sourced IPC in the atmosphere than that of non -fossil fuel sources in the inner TP and the importance of local emissions from the TP during the monsoon season. The findings provide new knowledge for model improvement and mitigation of carbonaceous particles.

The morphology, mixing state and hematite content of polluted mineral dust are not well accounted in the optical models and this leads to uncertainty in the radiative forcing estimation. In the present study, based on the morphological and mineralogical characterisation of polluted dust, the three-sphere, two-sphere and two-spheroid model shapes are considered. The optical properties of the above model shapes are computed using Discrete Dipole Approximation code. The single scattering albedo, omega(0), was found to vary depending on hematite content (0-6%) and model shape. For the two-sphere BC-mineral dust system, hematite was found to be a dominating absorber compared to that of black carbon as the R-BC/R-dust decreases. The omega(0) of the polluted dust system is larger if polluted dust is considered as pure dust spheroid (with 4% hematite) while smaller value is observed for Q(ext). Among all the systems, the omega(0) of BCBCD (two BC spheres attached to one dust sphere) system showed the maximum departure (40 and 35% for polluted dust with 0 and 6% hematite, respectively) from that of pure dust spheroid with 0 and 6% hematite. For the Asian region (pollution-prone zone), the modelled polluted dust optics will help to trace the optical and radiative properties of dust.