Investigating air toxics exposure from vehicular emissions at a US border crossing using fast building-aware atmospheric dispersion modeling (QUIC) and continuous measurements

Motor vehicle traffic in urban settings is associated with numerous environmental impacts including air pollution, traffic delays and congestion. These environmental impacts are also linked to adverse health consequences, including cardiovascular disease, hypertension, respiratory illness, and premature mortality. The Peace Bridge in Buffalo, New York is the third busiest U.S. border crossing with average daily traffic of 5,000 heavy-duty diesel trucks and 20,000 passenger cars. The associated plaza on the U.S. side is a complex of roads, custom inspection areas, passport control and duty-free shopping, where vehicles are frequently idling. In a series of winter and summer field campaigns, air pollutants including ultrafine particle (UFP) counts and particle-bound polycyclic aromatic hydrocarbons (pPAHs) were measured at three fixed locations and with portable instruments along established routes in an approximately 1 square kilometer residential neighborhood adjacent to the bridge complex. The objectives of this study are to identify areas of the local community that are most likely to be impacted by traffic-induced air pollution and to explore further the transport mechanism of traffic related particulate matters under various meteorological conditions.

The Quick Urban and Industrial Complex (QUIC) model developed by Los Alamos National Laboratory can incorporate building configurations, roadway elevations, and various meteorological conditions. The model is being used to investigate the effects of street geometry, local structures and wind speed and direction on the transport of pollutants from the bridge and associated plaza into the nearby residential neighborhood. The model can also be used to simulate the impact of weather and traffic conditions that were not present, or only occurred transiently during the field campaigns. In addition, using different emission factors for local streets, the nearby interstate highway, the bridge and the plaza, in the model is useful for exploring the relative impacts of these sources.

A preliminary comparison of modeling results with concentration surfaces generated from field measurements for prevailing wind conditions shows that modeling results capture the spatial variability associated with the bridge and local roads. Modeled and measured results demonstrate that border crossing vehicles elevate the concentrations of mobile source related emissions downwind to distances of 300 m to 600 m.