Unravelling the Correlation between the Optical Properties and Oxidative Potential of Atmospheric Fine Particulate Matter in the Tibetan Plateau

The Tibetan Plateau (TP), known as the “Third Pole” of the Earth, exhibits exceptional climate sensitivity, yet the climate and health effects of atmospheric fine particulate matter (PM 2.5 )a significant warming agentremain poorly characterized in the TP. In this study, we conducted parallel PM 2.5 sampling in the TP (Lhasa and Nyingchi) and Beijing. Comparative analysis revealed that PM 2.5 in the TP shows weaker light absorption but comparable inherent oxidative potential (OP) to urban Beijing, suggesting substantial aerosol toxicity in the pristine TP. This difference can be explained by considering the roles of organic carbon (OC) and metals. PM 2.5 in the TP contains both a greater proportion of OC and a higher degree of aging in its OC fraction, which not only influences light absorption and OP but also magnifies the effect of OC aging on these properties. Notably, in Nyingchi, a relatively pristine high-altitude region, the higher OC content demonstrates stronger OC-correlated light absorption and OP than Lhasa, where transition metals additionally contribute to OP. These findings provide valuable parameters for understanding optical properties and health effects in high-altitude areas, advance the optical–toxicity coupling relationship, and redefine our understanding of air pollution risks in high-altitude environments.