Comparison of temporal features of sulphate and nitrate at urban and rural sites in Spain and the UK

► Aerosol nitrate and sulphate patterns are compared seasonally in Madrid and London. ► Results show the dominant processes affecting their formation and evolution. ► Weekly analysis show weekend reductions for nitrate in summer and sulphate in winter. ► Daily evolution of nitrate is heavily influenced by meteorological factors. ► Strong differences seen emphasises the need to study cities individually.