Dry Deposition of Ozone to a Maize Crop Canopy – Implications for Crop Ozone Response and Productivity

Tropospheric ozone (O₃) is a greenhouse gas and phytotoxic air pollutant that weakens vegetation carbon assimilation, with cascading impacts on the global carbon and water cycles. Although the dry deposition of O₃ to the land surface constitutes a substantial sink of tropospheric O₃, uptake into leaf stomata creates oxidative stress, reducing the yields of major agricultural crops and posing a threat to food security. A mechanistic understanding of the coupling between O₃ air pollution and crop response is needed, as O₃ uptake does not always coincide with exposure. However, direct measurements of O₃ deposition over crop fields are extremely sparse. Here, we will present eddy covariance fluxes of O₃ monitored over a maize (Zea mays) field in central Illinois during the 2023 growing season. We partition the total O₃ flux into stomatal and non-stomatal components using site meteorology and fluxes of carbon dioxide and water vapor and discuss how crop physiological activity impacts stomatal O₃ uptake. Our results highlight the importance of such observations for testing O₃ dry deposition schemes in models and motivates the need for more sustained monitoring of O₃ fluxes over agricultural sites.