Monday, 29 January 2024: 9:45 AM
339 (The Baltimore Convention Center)
Tropospheric ozone (O3) is a phytotoxic air pollutant known to cause reductions in net photosynthesis and vegetation biomass, which poses a threat to critical carbon sinks and yields of major agricultural crops. The ambient concentrations that plants are exposed to are often used in risk assessments, but it is the uptake through plant stomata which delivers the phytotoxic dose. The cumulative stomatal uptake of O3 often correlates tightly with O3 induced losses in net photosynthesis and biomass. Furthermore, stomatal uptake represents a significant portion of dry deposition of O3 onto the land surface and can directly impact the tropospheric O3 budget. The dual significance of stomatal O3 flux as an indicator of the phytotoxic dose to vegetation and as a tropospheric O3 loss pathway warrants continued monitoring of O3 fluxes over agricultural fields and natural ecosystems. Here, we present O3 fluxes and the stomatal and non-stomatal components of O3 dry deposition over the growing season in a maize (Zea mays) agricultural field in central Illinois. We monitored O3 fluxes using the eddy covariance technique with 10 Hz measurements of wind velocity and O3 concentrations from two instruments based on UV-absorption. We partitioned the total O3 flux into stomatal and non-stomatal components. The stomatal component was estimated using CO2 and H2O fluxes with an inversion of the Penman-Monteith equation which describes ecosystem latent heat flux and a separate approach based on partitioning H2O and CO2 fluxes into their stomatal and non-stomatal components. We analyze how micrometeorological conditions and crop physiological activity impact diurnal and growing season O3 dry deposition and the cumulative growing season uptake of O3 by the maize field. Eddy covariance fluxes of O3 across tower networks can help monitor the cumulative uptake of O3 by natural ecosystems and agricultural fields along with providing relevant observations for testing O3 dry deposition schemes in air quality and chemical transport models.

