Near-Road Air Pollutant Measurements: Accounting for Inter-Site Variability Using Emission Factors

A daily integrated emission factor (EF) method was applied to data from three near-road monitoring sites to identify variables that impact traffic related pollutant concentrations in the near-road environment. The sites were operated for 20 months in 2015–2017, with each site differing in terms of d...

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Bibliographic Details
Published in:Environmental science & technology 2018-08, Vol.52 (16), p.9495-9504
Main Authors: Wang, Jonathan M, Jeong, Cheol-Heon, Hilker, Nathan, Shairsingh, Kerolyn K, Healy, Robert M, Sofowote, Uwayemi, Debosz, Jerzy, Su, Yushan, McGaughey, Michiyo, Doerksen, Geoff, Munoz, Tony, White, Luc, Herod, Dennis, Evans, Greg J
Format: Article
Language:English
Subjects:
Air pollution
Air pollution measurements
Ambient temperature
Annual variations
Black carbon
Composition
Dilution
Dispersion
Emission
Emission measurements
Emissions
Environmental impact
Exhaust pipes
Genetic transformation
Meteorology
Pollutants
Pollution monitoring
Regression models
Roads
Seasonal variations
Subtraction
Variability
Variables
Vehicles
Velocity
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Summary:A daily integrated emission factor (EF) method was applied to data from three near-road monitoring sites to identify variables that impact traffic related pollutant concentrations in the near-road environment. The sites were operated for 20 months in 2015–2017, with each site differing in terms of design, local meteorology, and fleet compositions. Measurement distance from the roadway and local meteorology were found to affect pollutant concentrations irrespective of background subtraction. However, using emission factors mostly accounted for the effects of dilution and dispersion, allowing intersite differences in emissions to be resolved. A multiple linear regression model that included predictor variables such as fraction of larger vehicles (>7.6 m in length; i.e., heavy-duty vehicles), vehicle speed, and ambient temperature accounted for intersite variability of the fleet average NO, NO x , and particle number EFs (R2:0.50–0.75), with lower model performance for CO and black carbon (BC) EFs (R2:0.28–0.46). NO x and BC EFs were affected more than CO and particle number EFs by the fraction of larger vehicles, which also resulted in measurable weekday/weekend differences. Pollutant EFs also varied with ambient temperature and because there were little seasonal changes in fleet composition, this was attributed to changes in fuel composition and/or post-tailpipe transformation of pollutants.
ISSN:0013-936X
1520-5851
DOI:10.1021/acs.est.8b01914