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. These results suggest that there is a wide range of primary NO2 emission fractions observed on different roads in London.

Atmospheric Environment 39 (2005) 167–177
Link to Journal: http://www.sciencedirect.com/science/journal/13522310