Characterization of traffic-related particulate matter in an urban tunnel: Source apportionment of exhaust and non-exhaust particle number-size distribution emissions.

Vehicle exhaust is the dominant source of PM 2.5 in an urban tunnel, while non-exhaust emissions mainly influence PM 10 concentrations, especially resuspended road dust.

• Why it matters: Understanding the specific contributions of exhaust and non-exhaust sources to particulate matter is crucial for developing effective air pollution control strategies in metropolitan areas.
• What they did: Measurements of PM 2.5 and PM 10 were conducted at the Niayesh Tunnel in Tehran using high-volume air samplers and low-cost sensors across two seasons, with source apportionment performed via PMF on particle size distributions.
• The result: Vehicle exhaust significantly contributes to PM 2.5 levels, with emission factors higher during warm days, while non-exhaust sources, particularly resuspended road dust, mainly influence PM 10, highlighting the importance of including non-exhaust sources in pollution management.