Numerical simulation of PM2.5 dispersion originated from vehicular traffic in urban environments: Situational validation of proposed biomonitoring method

Vehicular PM2.5 emissions pose a major urban air-quality challenge, particularly in dense street canyons. We developed a high-resolution CFD model (≈14.8 million cells) in ANSYS Fluent to simulate dispersion and deposition in a geo-referenced 3D domain representing a Prague roadway. The k–ω SST turbulence model, coupled with the Discrete Phase Model and energy equation, resolved airflow, heat–mass exchange, and particle trajectories. Vegetation was parameterized as an isotropic porous medium with calibrated Darcy–Forchheimer coefficients to capture canopy resistance and interception. Transient particle injections mimicking emissions from Euro 5 vehicles were applied under urban breeze and traffic-wake turbulence. Results identified hotspots linked to braking near signals and recirculation zones, with ≈65% of PM2.5 advected downstream and the rest deposited or intercepted, particularly by dense grasses. Model predictions of heavy-metal deposition agreed with biomonitoring using Calamagrostis epigejos. This integrated CFD–biomonitoring framework supports design of vegetation and traffic-flow interventions to improve air quality.