Using measurements of nitrogen oxides to estimate the emission controls required to meet the uk nitrogen dioxide standard

Abstract

In this paper we introduce a new method of analysing the relationship between nitrogen dioxide (NO2) and oxides of nitrogen (NO(x)) concentrations using data from the UK National Air Quality Archive. The study includes analyses of measurements from two different types of site in London, a kerbside site: Cromwell Rd, and three background sites: Bridge Place, London Bloomsbury and West London, over several years (1991-7). The data in some years showed that hourly NO2 concentrations exceeded the UK Standard of 150 ppb. Data were binned, averaged, and polynomials fitted at each site. Analysis of the resulting polynomials was used to estimate reductions in NO(x) emission required to achieve the National Air Quality Strategy Objective. Examination of the empirical ratio NO2:NO(x) (the 'yield') gives an indication of the sensitivity of the NO2 to NO(x) controls and the amount of NO2 that would arise from modelled values of total oxides of nitrogen. The response of NO2 to emission changes is very non-linear, implying 30-45% controls on NO(x) may be required.