Daily Variation of Air Pollutants Near an Elevated Highway System

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I-81 is an elevated viaduct and goes through the heart of Syracuse, with local businesses and communities located underneath it. The safety limit of the viaduct is ending, and the NY Department of Transportation (DOT) is looking for recommendations to rebuild the roadway using its current elevated design or lower the highway to ground level creating a community grid. People living below I-81 are concerned about increases in air pollution if I-81 is lowered. With no knowledge of current air quality levels in this community, assessing how lowering the highway would impact the neighborhood is impossible. We began an air quality monitoring campaign to measure pollutant levels simultaneously near the highway and on the ground below. Models generated by the DOT suggest traffic levels will not change if the highway is lowered. By monitoring air quality at highway and ground levels, results will offer a glimpse of potential air quality problems that could arise. To assess daily variation in traffic-related particulate matter (PM) near this highway, a site adjacent to I-81 was selected. Two high-volume cascade impactors were placed at ground and highway levels of a building to collect daily PM samples for two weeks over two seasons. Two real-time PM monitors measured PM number concentration with elevation. For fine PM at the rooftop location, the average number of particles was 1.2 times higher with a maximum of 10 times higher. Three days in summer had exceptionally high vehicle flow and had PM concentrations ranging from 4.5 to 10 times higher at highway level. Results from gravimetric analyses agreed with measured number concentrations. This data shows particle count and PM concentration are variable with elevation and suggests that vehicle emissions may be more influential at highway level, implying air quality may be affected if the community grid option is pursued.