Reducing Soil-Emitted Nitrous Acid as a Feasible Strategy for Tackling Ozone Pollution.

Severe ozone (O ₃ ) pollution has been a major air quality issue and affects environmental sustainability in China. Conventional mitigation strategies focusing on reducing volatile organic compounds and nitrogen oxides (NO _x ) remain complex and challenging. Here, through field flux measurements and laboratory simulations, we observe substantial nitrous acid (HONO) emissions ( F _HONO ) enhanced by nitrogen fertilizer application at an agricultural site. The observed F _HONO significantly improves model performance in predicting atmospheric HONO and leads to regional O ₃ increases by 37%. We also demonstrate the significant potential of nitrification inhibitors in reducing emissions of reactive nitrogen, including HONO and NO _x , by as much as 90%, as well as greenhouse gases like nitrous oxide by up to 60%. Our findings introduce a feasible concept for mitigating O ₃ pollution: reducing soil HONO emissions. Hence, this study has important implications for policy decisions related to the control of O ₃ pollution and climate change.