A Computer Modelling Study of the Relationship between Urban Exposure to Nitrogen Dioxide and Motor Vehicle Exhaust Emissions During the Summer Months

Abstract

ABSTRACT The AERE Harwell photochemical column trajectory model was employed to investigate the complex relationship between motor vehicle nitric oxide (NO) emissions and the ground level distribution of nitrogen dioxide (NO2). The model describes the meteorology of the boundary layer, the height-dependent photochemical and chemical processes, the geographical distribution of the emissions into and the deposition from the column of air advected over London. During the daytime, the behaviour of NO2, NO and ozone (O3) was found to be largely determined by the photostationary state expression linking the NO+O3 reaction with the NO2 photolysis. During nighttime the NO2 distribution was determined by either the integrated NO emissions upwind or the atmosphere's limited capacity to oxidize NO to NO2, whichever was the smaller. The possible impact of doubling motor vehicle emissions was studied together with the impact of further future legislation to control motor vehicle NO emissions.