Spatial Distribution of Diesel Transit Bus Emissions and Urban Populations: Implications of Coincidence and Scale on Exposure

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• 作者：Brian Gouge ; Francis J. Ries ; Hadi Dowlatabadi
• 刊名：Environmental Science & Technology
• 出版年：2010
• 出版时间：September 15, 2010
• 年：2010
• 卷：44
• 期：18
• 页码：7163-7168
• 全文大小：315K
• 年卷期：v.44,no.18(September 15, 2010)
• ISSN：1520-5851

文摘

Macroscale emissions modeling approaches have been widely applied in impact assessments of mobile source emissions. However, these approaches poorly characterize the spatial distribution of emissions and have been shown to underestimate emissions of some pollutants. To quantify the implications of these limitations on exposure assessments, CO, NO_X, and HC emissions from diesel transit buses were estimated at 50 m intervals along a bus rapid transit route using a microscale emissions modeling approach. The impacted population around the route was estimated using census, pedestrian count and transit ridership data. Emissions exhibited significant spatial variability. In intervals near major intersections and bus stops, emissions were 1.6−3.0 times higher than average. The coincidence of these emission hot spots and peaks in pedestrian populations resulted in a 20−40% increase in exposure compared to estimates that assumed homogeneous spatial distributions of emissions and/or populations along the route. An additional 19−30% increase in exposure resulted from the underestimate of CO and NO_X emissions by macroscale modeling approaches. The results of this study indicate that macroscale modeling approaches underestimate exposure due to poor characterization of the influence of vehicle activity on the spatial distribution of emissions and total emissions.