An empirical approach for the prediction of annual mean nitrogen dioxide concentrations in London

Annual mean limits for NO2 concentrations have been set in the European Uni on, which will be most challenging to meet in large urban conurbations. in this paper, we discuss techniques that have been developed to predict curre nt and future NO2 concentrations in London, utilising ambient data. Hourly average NOx (NO + NO2) and NO2 concentrations are used to calculate NO, fre quency distributions. By defining relationships between the annual mean NO, and NO, at different sites, it is possible to investigate different NO, re duction strategies. The application of the frequency distribution approach to monitoring sites in London shows that given the likely change in emissio ns by 2005, it is unlikely that much of central and inner London will meet the objective. The approaches used suggest that meeting the objective in ce ntral London will be the most challenging for policy makers requiring NO, c oncentrations as low as 30 ppb, compared with values closer to 36-40 ppb fo r outer London. Predictions for 2005 indicate that concentrations of NO2 up to 6 ppb in excess of the objective are likely in central London. (C) 2001 Elsevier Science Ltd. All rights reserved.