Investigating Potential Causes of Intra-Urban Air Quality Variation via The Breathe Providence Network
By Adam Gendreau
It is estimated that 39% of Providence’s air pollution comes from traffic; however, the location and intensity of traffic flows may contribute to differences in air quality on a hyperlocal scale. Given Providence’s high density of highways (including being located on the I-95 corridor) and its history of neighborhood disruption caused by highway construction, it is worth investigating the short- and long-term effects of the transportation sector on air quality and environmental inequity. In order to do this, it is necessary to disentangle other local-scale influences, such as vegetation and building height, from the local traffic signal.
Adam’s research focused on concentrations of a common vehicle emission, carbon monoxide, at two specific monitors in Breathe Providence’s network: Zuccolo Recreation Center and United Way of RI. These two monitors are only 1 km apart from each other and are located an equal distance away from Route 6, a congested local highway. Despite geographic similarities, the Zuccolo Recreation and United Way sensors report noticeably different levels of carbon monoxide concentration during heavy commute times.
Street landscapes near Sensors 10 and 12 and respective wind patterns
Lastly, Adam attempted to investigate how much of the differences in carbon monoxide readings could be due to surrounding point source emissions. Adam found that Zuccolo is located near both Cathedral Art Metal Co. and Tercat Tool and Die Co., pollution sources that could be compounding the streetscape effects to result in higher concentrations.
By focusing on two specific monitors in such close proximity, Adam demonstrates how highly-local influences may impact residents’ exposure to pollution, even for people living comparable distances from major sources.
Two monitors and their relationship to Route 6
In an attempt to explain the reasons behind Zuccolo’s consistently higher values relative to United Way, Adam explored wind patterns, building heights, vegetation, and road widths. In his study of microclimate and road environments, Adam found that a high-density tree canopy and closely-packed multistory buildings can create a canyoning effect, trapping carbon monoxide at the street level.
Urban canyoning that takes place where Zuccolo is located could also be exacerbated by the orientation of the street, which runs perpendicular to the prevailing wind direction. As a result, there are fewer wind gusts circulating pollutants and preventing their accumulation in specific areas.
The orange circles are a 0.5 km radius around each site. Based on the National Emissions Inventory, Sensor 12 has 2 emission sites in that range, while Sensor 10 has 0.