Vertical ozone formation mechanisms resulting from increased oxidation on the mountainside of Mount Tai, China

A study on Mount Taishan, China, reveals that vertical ozone (O3) formation mechanisms differ significantly between the mountainside and ground level. Unlike the VOC-limited regime observed at surface sites, the mountainside exhibits a NOx-limited regime due to lower NO levels, which restrict hydroxyl radical (OH) recycling reactions. This leads to earlier O3 peaks, higher concentrations of hydroperoxy radicals (HO2), and organic peroxy radicals (RO2). The arrival of fresh air masses rich in NO accelerates OH radical cycling, enhancing atmospheric oxidation and impacting surface O3 concentrations through vertical transport. Simulations indicate that considering vertical transport reduces the peak O3 production rate at the surface due to differences in O3 formation sensitivity vertically. This study underscores the significant sensitivity of O3 formation to NO within the boundary layer (BL) and highlights the potential impact of vertical in situ O3 formation on surface-level concentrations, particularly in cities with mountainous terrain.

Wu, W., Ge, Y., Wang, Y., Su, J., Wang, X., Zhou, B., & Chen, J. (2024). Vertical ozone formation mechanisms resulting from increased oxidation on the mountainside of Mount Tai, China. PNAS Nexus, 3(9). https://doi.org/10.1093/pnasnexus/pgae347