The Contribution of Highway Tunnels to Airborne Particle Concentrations in an Urban Area.
Skerker, Jennifer B.
- Over the past twenty years, the urban landscape of Boston, MA has been transformed as a result of the “Big Dig,” a multi-billion dollar project that replaced the aboveground Central Artery highway in Boston with an underground highway. With the completion of this project, the city of Boston has forty-five new public parks and plazas, and a 62% total reduction in vehicle-hours of travel on I-93 from ... read more1995 to 2003; however, there has not been much research on characterizing the extent to which vehicle-related air pollution patterns have changed. The purpose of this research is to better understand spatial and temporal, tunnel-related pollution patterns in Boston for particulate matter less than 2.5 microns in diameter (PM2.5) from the Central Artery/Tunnel (CA/T). Mobile pollution data through the CA/T and EPA stationary-site data in and around Boston were analyzed to understand PM2.5 spatial and temporal patterns. Modeling was completed in AERMOD, a steady state Gaussian dispersion model developed for industrial point sources. Measurements at EPA stationary-site monitors showed that PM2.5 concentrations were below the National Ambient Air Quality Standards, even in downtown Boston. About one-third of ambient PM2.5 concentrations may be attributed to local sources. Modeling results showed that 14 to 19% of PM2.5 concentrations may come from tunnel-related sources; however, this is highly dependent on the emission factor used. PM2.5 concentrations do not vary much seasonally or weekly. PM2.5 concentrations in the Boston area are greatest when winds are from the southwest. Although the local mobile component of PM2.5 is small compared to regional sources, it still impacts ambient PM2.5 concentrations in Boston.read less