Estimations of road vehicle primary NO\(_2\) exhaust emission fractions using monitoring data in London

research
vehicle emissions
NOx
Ambient monitoring data from London roadside sites are used to estimate the primary NO2 exhaust emission fraction from road vehicles, providing empirical evidence for the growing importance of direct NO2 emissions.
Authors

D.C. Carslaw

S.D. Beevers

Published

January 1, 2005

Estimations of road vehicle primary NO\(_2\) exhaust emission fractions using monitoring data in London

D.C. Carslaw, S.D. Beevers

Atmospheric Environment, 2005

Hourly mean concentration data for nitrogen oxides (NOX), nitrogen dioxide (NO2) and ozone (O3) have been used to derive a method for estimating the mean primary NO2 fraction from vehicle exhausts in London. A set of simple chemical equations has been used to explain the differences in NO2 concentrations between background and roadside site pairs and to estimate the proportion of NO2 that is likely to be derived from primary NO2 vehicle emissions and the NO2 formed through the reaction of nitric oxide (NO) with O3. The estimates ranged from 3.2 to 23.5 vol% with a median value of 10.6 vol% for the 43 measurement sites considered. A median primary NO2 fraction of 10.6% accounts for an average of 21% of the observed NO2 concentration at roadside sites.

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