Using archive data to investigate trends in the sources and composition ofurban PM10 particulate matter: Application to Edinburgh (UK) between 1992 and 1997

By extending the method of Stedman (1998), daily data of atmospheric concen trations of gravimetric PM10, black smoke (BS) and sulphate aerosol (SA) fr om national networks were analysed to determine the trends in time of the c ontribution of different sources of particulate matter to total PM10 measur ed in central Edinburgh. Since BS is an indicator of combustion-related pri mary sources of particulate matter, the quantity obtained by subtraction of daily BS from daily PM10 is indicative of the contribution to total PM10 f rom other primary sources and from secondary aerosol. This PM10-BS statisti c was regressed on SA, since SA is an indicator of variation in secondary a erosol source. For Edinburgh, SA is a considerably better indicator of PM10 -BS during summer than winter (reflecting the much greater photochemical ge neration of secondary aerosol in summer) and there is evidence that the con tribution of other secondary aerosol (presumably nitrate aerosol) has incre ased relative to SA between 1992 and 1997. The concentration of non-combust ion primary particulate material (marine aerosol, suspended dust) to PM10 i n Edinburgh has not changed over this period but is about twice that calcul ated as the U.K. national average. The increasing input to PM10 from second ary aerosol sources at regional rather than urban scale has important impli cations for ensuring local air quality compliance. The method should have g eneral applicability to other locations.