The presence of polycyclic aromatic hydrocarbons (PAHs) in the Yarlung Tsangpo River (YTR) poses substantial threats to both regional ecological security and human health. While it is imperative to accurately assess and pinpoint the risks and sources of PAHs in the YTR, a comprehensive understanding of their seasonal variations in composition and distribution is currently lacking. In a thorough investigation aimed at evaluating seasonal fluctuations, sources, potential hazards, and the impact of natural and anthropogenic factors on PAHs concentrations in the YTR, enlightening findings emerged. During the dry season, concentrations of the sum of 16 PAHs (Ʃ