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

By extending the method of Stedman (1998), daily data of atmospheric concentrations of gravimetric PM10, black smoke (BS) and sulphate aerosol (SA) from national networks were analysed to determine the trends in time of the contribution of different sources of particulate matter to total PM10 measured in central Edinburgh. Since BS is an indicator of combustion-related primary sources of particulate matter, the quantity obtained by subtraction of daily BS from daily PM10 is indicative of the contribution to total PM10 from other primary sources and from secondary aerosol. This PM10-BS statistic was regressed on SA, since SA is an indicator of variation in secondary aerosol source. For Edinburgh, SA is a considerably better indicator of PM10-BS during summer than winter (reflecting the much greater photochemical generation of secondary aerosol in summer) and there is evidence that the contribution of other secondary aerosol (presumably nitrate aerosol) has increased relative to SA between 1992 and 1997. The concentration of non-combustion primary particulate material (marine aerosol, suspended dust) to PM10 in Edinburgh has not changed over this period but is about twice that calculated as the U.K. national average. The increasing input to PM10 from secondary aerosol sources at regional rather than urban scale has important implications for ensuring local air quality compliance. The method should have general applicability to other locations