Assessing the role of biogenic emissions and climate change on urban ozone formation: a modelling study in a Mediterranean city (Lecce, Italy)

Urban tropospheric ozone (O₃) is produced through complex photochemical reactions involving nitrogen oxides (NOₓ) and volatile organic compounds (VOCs) from both anthropogenic and biogenic sources, and its formation is strongly influenced by local meteorology, emission patterns and vegetation characteristics. This study investigates O₃ dynamics in an urban district of Lecce (Southern Italy), aiming to quantify the combined contribution of traffic emissions and biogenic VOCs (bVOCs), and to explore how vegetation characteristics and climate variability affect urban air quality.

The methodological framework integrates field observations, emission modelling and numerical simulations using the ADMS-Urban dispersion model. Traffic activity is characterised through video-based measurements of vehicle counts, speeds and fleet composition, while meteorological variables and pollutant concentrations are obtained from a local monitoring station for the baseline configuration, which also serves as a consistent reference for subsequent scenario analyses. Accordingly, bVOC emissions from dominant urban tree species are estimated as functions of temperature and photosynthetically active radiation using ERA5 reanalysis data, ensuring a coherent framework for both present conditions and future projections. The model simulates O₃ formation through a simplified photochemical scheme that accounts for both anthropogenic and biogenic precursors.

The baseline simulation for a representative summer period is validated against observed O₃ concentrations, showing a good ability to reproduce the main temporal variability and highlighting the contribution of bVOCs to peak ozone levels. Building on this baseline, ongoing work focuses on assessing the sensitivity of O₃ formation to alternative vegetation types with different ozone-forming potential and to future meteorological conditions derived from climate projections.

This integrated approach provides a robust framework for evaluating present and future air quality scenarios and supports the development of targeted mitigation strategies, including optimized urban greening and climate-adaptive planning, contributing to improved air quality management and resilience in Mediterranean cities.