An empirical approach for the prediction of daily mean PM 10 concentrations

Abstract

An empirical model has been devised to predict concentrations of PM 10 at background and roadside locations in London. Factors to calculate primary PM 10 and PM 2.5 concentrations are derived from annual mean NO X , PM 2.5 and PM 10 measurements across London and south east England. These factors are used to calculate daily means for the primary and non-primary PM 10 fractions for the London area. The model accurately predicts daily mean PM 10 and EU Directive Limit values across a range of sites from kerbside to rural. Predictions of future PM 10 can be made using the expected reductions in secondary PM 10 and site specific annual mean NO X predicted from emission inventories and dispersion modelling. The model suggests that the EU Directive Limit values will be exceeded close to many of London's busiest roads, and perhaps at central background sites should there be a repeat of 1996 meteorological conditions during 2005. A repeat of 1997 meteorology conditions during 2005 would lead to the EU Limit Value being exceeded alongside the busiest central London roads only. The model is applicable for London and south east England but the methodology could be applied elsewhere at a city or regional level. The model relies on the currently observed ratio between NO X and PM 10. This ratio has remained constant over the last 4 years but might change in the future. The NO X :PM 10 ratio derived from measurements and used in this model, implies that emission inventories might over estimate primary PM 10 by more than 50%.