Rapid summertime photochemical VOC consumption and ozone production at Lhasa and Yangbajain on the Tibetan Plateau.

Quantitatively evaluating the initial sources and photochemical activities of volatile organic compounds (VOCs) provides valuable insights into photochemical pollution on the vulnerable Tibetan Plateau (TP). In this study, we conducted intensive measurements of VOCs in the urban (Lhasa) and background (Yangbajain) regions on the TP in summer 2022. The mean observed VOC concentrations were 8.1 ± 5.7 ppbv at Lhasa and 5.5 ± 3.4 ppbv at Yangbajain, but the initial values were 26.3% and 34.9% higher, respectively. The photochemically consumed VOCs reached up to 5.3 ppbv h-1 at Lhasa and 4.7 ppbv h-1 at Yangbajain, exhibiting positively synchronous variations with daytime ozone (O3) enhancement. Neglecting photochemical loss in source apportionment substantially underestimated the contributions of burning emissions, biogenic emissions, and solvent usage on the TP. Maximum O3 formation potential and OH reactivity were primarily driven by initial alkenes and biogenic VOCs. Net O3 production rates on the TP substantially exceed typical values reported in low-altitude areas. These findings underscore the necessity of targeted emission control measures and sustainable development strategies to mitigate environmental and public health risks from photochemical hazards in developing yet vulnerable high‑altitude regions worldwide.