High crop yield losses induced by potential HONO sources - A modelling study in the North China Plain

Nitrous acid (HONO) is a major source of hydroxyl radicals in the troposphere through its photolysis, and can significantly influence ozone (O₃) levels, thereby causing considerable crop yield losses. Previous studies have assessed relative crop yield losses by using exposure-response equations with observed or simulated O₃, however, the contribution of enhanced O₃ due to potential HONO sources to the crop yield losses has never been quantified. In this study, for the first time, we evaluated the crop yield losses caused by potential HONO sources in the North China Plain (NCP), which is one of the major grain-producing areas in China suffering from heavy O₃ pollution, by using the Weather Research and Forecasting/Chemistry (WRF-Chem) model during the wheat and maize growing seasons of 2016. HONO simulations were significantly improved after including six potential HONO sources in the WRF-Chem model. The potential HONO sources produced a daily maximum 8-h O₃ enhancement of 8.1/8.2 ppb during the wheat/maize growing seasons, respectively, and led to ~11.4%/3.3% relative yield losses for wheat/maize, respectively, corresponding to approximately US$3.78/0.66 billion losses, respectively, in NCP in 2016. The above results suggest that potential HONO sources play a significant role in O₃ formation and could induce high crop yield losses globally.