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In London, the recent analysis of ambient measurements has shown that directly emitted (primary) nitrogen dioxide has increasehttp://bkstrm. Epnet. Com:8080/ai/images/save. GifSaved as a fraction of total nitrogen oxides from road transport sources. These increases appear to be mostly due to certain after-treatment devices, such as oxidation catalysts and particle filters fitted to diesel vehicles. This study uses a constrained simple chemical model to predict hourly concentrations of at a busy roadside site in central London to investigate the dependence of peak hourly concentrations of on the level of assumed primary emitted by road vehicles. The model performance is shown to be good across the full range of hourly and concentrations over seven years. Monte Carlo simulations are used to predict future hourly concentrations and the probability of exceeding the EU hourly limit value for by considering the model errors, uncertainties in future trends and the inter-annual variability of meteorology. It is shown that if the emission ratio of 22. 0% by volume, as calculated at the end of 2004, is sustained into the future, it is likely that the hourly EU limit value will not be met. However, the probability of not meeting the limit value in 2010 depends strongly on the meteorological year and varies from 16% to 88% depending on the year considered. This work shows that further increases in the ratio beyond those observed at the end of 2004 would considerably increase the probability of the EU hourly limit for being exceeded. Additionally, the analysis of road network emissions in London shows that many other roads are likely to be at risk from exceeding the hourly limit value. Further work is required to improve the quantification of in vehicle exhausts to determine the likely future risks of exceeding the hourly limit value in other European cities. [Copyright &y& Elsevier]

Abstract: Plans to build a third runway at London Heathrow (LHR) airport have been held back because of concerns that the development would lead to annual mean concentrations of nitrogen dioxide (NO2) in excess of the EU Directive limit value, which must be met by 2010. The dominant effect of other sources of NO x close to the airport, primarily from road traffic, makes it difficult to detect and quantify the contribution made by the airport to local NO x and NO2 concentrations. This work presents approaches that aim to detect and quantify the airport contribution to NO x concentrations for a network of seven measurement sites close to the airport. Two principal approaches are used. First, a graphical technique using bivariate polar plots that develops the idea of a pollution rose is used to help discriminate between different source types. The sampling uncertainties associated with the technique have been calculated through a randomised re-sampling approach. Second, the unique pattern of aircraft activity at LHR enables data filtering techniques to be used to statistically verify the presence of aircraft sources. It is shown that aircraft NO x sources can be detected to at least 2.6km from the airport, even though the airport contribution at that distance is very small. Using these approaches, estimates have been made of the airport contribution to long-term mean concentrations of NO x and NO2. At the airfield boundary we estimate that approximately 27% of the annual mean NO x and NO2 is due to airport operations. At background locations 2–3km downwind of the airport we estimate that the upper limit of the airport contribution to be less than 15% (<10μgm−3). This work also provides approaches that would help validate and refine dispersion modelling studies used for airport assessments. [Copyright &y& Elsevier]