Calculation of sulphate and nitrate aerosol concentrations over Europe using a Lagrangian dispersion model

Abstract

The Met Office's Lagrangian dispersion model, NAME, has been extended to include the chemistry of nitrate aerosol in addition to that of sulphate aerosol formation. The model has been run over a regional scale for 1996 to predict both nitrate and sulphate aerosol. Import to the UK from Europe has been quantified. The model has been validated by comparison with available measurement data and results from the EMEP Eulerian model. Results are presented in the form of daily time series of aerosol at two rural sites and one urban site. Annual average maps of sulphur dioxide, nitrogen dioxide, sulphate aerosol, nitrate aerosol and nitric acid are presented and are found to exhibit a reasonable agreement with the exception of sulphur dioxide which over-predicts substantially. Annual average model sulphate aerosol for 1996 over-predicts compared with maps derived from 1995 measurement data; however, daily modelled values averaged over three UK sites for 1996 show a slight model under-prediction compared with 1996 observations. Annual average modelled nitrate aerosol compares well with maps derived from 1999/2000 measurement data. The model results indicate the maximum contribution to secondary inorganic aerosol in the UK is in the southeast, where the annual average contribution is 14 μg (PM 10) m −3 based on 1996 data. On average 30% of UK aerosol is imported from Europe in the summer and 25% in winter months.