1 research outputs found
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 2015โ2017, 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<sub><i>x</i></sub>, and particle
number EFs (R<sup>2</sup>:0.50โ0.75), with lower model performance
for CO and black carbon (BC) EFs (R<sup>2</sup>:0.28โ0.46).
NO<sub><i>x</i></sub> 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