Elemental composition and sources of fine and ultrafine ambient particles in Erfurt, Germany

We present the first results of a source apportionment for the urban aerosol in Erfurt, Germany, for the period 1995–1998. The analysis is based on data of particle number concentrations (0.01–2.5 μm; mean 1.8×104 cm−3, continuous), the concentration of the ambient gases SO2, NO, NO2 and CO (continuous), particle mass less than 2.5 μm (PM2.5) and less than 10 μm (PM10) (Harvard Impactor sampling, mean PM2.5 26.3 μg/m3, mean PM10 38.2 μg/m3) and the size fractionated concentrations of 19 elements (impactor sampling 0.05–1.62 μm, PIXE analysis). We determined: (a) the correlations between (i) the 1- and 24-h average concentrations of the gaseous pollutants and the particle number as well as the particle mass concentration and (ii) between the 24-h elemental concentrations; (b) Crustal Enrichment Factors for the PIXE elements using Si as reference element; and (c) the diurnal pattern of the measured pollutants on weekdays and on weekends. The highly correlated PIXE elements Si, Al, Ti and Ca having low enrichment factors were identified as soil elements. The strong correlation of particle number concentrations with NO, which is considered to be typically emitted by traffic, and the striking similarity of their diurnal variation suggest that a sizable fraction of the particle number concentration is associated with emission from vehicles. Besides NO and particle number concentrations other pollutants such as NO2, CO as well as the elements Zn and Cu were strongly correlated and appear to reflect motor vehicle traffic. Sulfur could be a tracer for coal combustion, however, it was not correlated with any of the quoted elements. Highly correlated elements V and Ni have similar enrichment factors and are considered as tracers for oil combustion.