Beyond stomata: Interspecific heterogeneity and structural controls of urban ozone deposition

Abstract. Urban environments are critical ozone (O₃) hotspots where intense precursor emissions and high population densities escalate human exposure risks. Current deposition models typically rely on coarse land-use classifications, failing to capture the species-level heterogeneity at the city scale. We quantified O₃ dry deposition across 20 common tree species in a subtropical megacity using a modified micrometeorological gradient method to derive species-resolved resistance parameters. Field measurements identified substantial interspecific variation: daytime canopy concentration gradients peaked at 10.02 ± 0.86 ppb (Platanus acerifolia). While standardized stomatal conductance correlates with the inverted minimum stomatal resistance (1/R_{s, min}, R² = 0.36, P < 0.001), this relationship provides partial physiological support for the inferred resistance parameters. Sensitivity analysis showed that model-estimated deposition velocity was most sensitive to LAI, followed by wind speed and roughness length. Notably, a 20 % LAI increase reduced estimated deposition velocity by 17.55 % under the prescribed sensitivity experiments. These findings highlight species-level differences in O₃ deposition and the coupled roles of canopy structure, aerodynamic transport, and physiological regulation. The resulting resistance estimates provide observational constraints for species-resolved parameterization in atmospheric deposition models, although their transferability requires further validation.