“New” Reactive Nitrogen Chemistry Reshapes the Relationship of Ozone to Its Precursors

Tropospheric ozone pollution has been a major environmental issue, and mitigation of this persistent problem requires a comprehensive understanding of the sensitivity of ozone to its precursors, i.e., nitrogen oxides (NOx) and volatile organic compounds (VOCs). Recent studies have proposed several "new" reactive nitrogen chemical processes, including additional sources of nitrous acid, heterogeneous uptake of dinitrogen pentoxide, and production of nitryl chloride. These processes significantly affect the budgets of radicals and NOx and hence the formation of ozone. In present study, we aim to investigate to what extent these processes alter the relationships between ozone and its precursors. A revised Weather Research and Forecasting model coupled with Chemistry incorporating the "new" nitrogen chemistry was adopted to simulate the ozone sensitivity regime in China in summer. The results showed that nitrogen chemistry changed the ozone sensitivity regime for approximately 40% of the simulated area with human influence, mostly from VOC-sensitive or NOx-sensitive regimes to mixed-sensitive regime. The nitrogen chemistry changed the isopleth plots of the ozone peak values for major cities, suggesting a different strategy for controlling ozone pollution. This study underscores the need to consider unconventional nitrogen chemistry in air quality models used in the design of ozone control strategies.