Pollution Characteristics and Source Analysis of Polycyclic Aromatic Hydrocarbons in the Atmosphere of Southeast Tibet

To investigate the pollution, source, and transport characteristics of polycyclic aromatic hydrocarbons (PAHs) in the atmosphere of the southeast of Tibetan Plateau, a comprehensive analysis was carried out using 14 different PAHs from the total suspended particulate (TSP) matter and the atmospheric gaseous state in the Lulang area (29.77°N, 94.73°E) and combined with meteorological environment data from the same period. The results show that the variation ranges of PAHs mass concentration in TSP and gas phase are 0.22–5.05 ng m⁻³ and 0.83–63.75 ng m⁻³, respectively, with average values of 2.13 ng m⁻³ and 11.33 ng m⁻³. The primary source of pollution is the combustion of firewood and diesel, while other sources of pollution include the combustion of gasoline. PAHs are emitted by both local pollution and long-range transmission (LRT). In the four seasons, local pollution varies from source to source. Local pollution is serious in the winter and spring, and the source is in the southeast and due south. Pollution in the summer and autumn is primarily caused by local and LRT sources. The primary local source is mainly in the southeast, but LRT is dominant. The northwest air flow, westerly airflow, and southwest air flow all have an impact on the LRT. When pollution is serious, the dominant airflow is southwest, while the secondary dominant airflow is westerly. When the pollution is light, the dominant airflow is westerly or northwest, and the pollution transmitted by the northwest airflow is the least. The results of this study have contributed to a better knowledge of the changes and transport characteristics of PAHs in Southeast Tibet and a theoretical basis for the control of air pollution in this region and the improvement of plateau air quality.