While due to improved filtering techniques the coarse dust emission in Europe has been reduced considerably, the very fine grained (< 10 µm) and more dangerous dust emission stayed constant or has even increased. Because of their small size as well as their shape, dust particles may be particularly harmful to the human respiratory system. High concentrations of some minerals themselves (asbestos, quartz etc.) or the high heavy metal content as well as carcinogenic organic compounds (PAH's) frequently adsorbed in them have noxious effects.
The most important natural and manmade particle sources in urban environments are materials eroded by wind (soils, construction materials), as well as industrial and traffic emissions. Speculation about their sources has mostly been on the basis of chemical information only. Very little is known about their mineral and organic phases. In order to interpret the physical properties of the particles, their environmental behaviour and the health risks they may pose in future, the combined information of chemistry and mineralogy is essential.
The very fine-grained particulates have been collected on "low blank" cellulose nitrate and glassfibre filters in a high-volume sampler (Stroehlein) or in a cascade impactor (CMI). The mineralogical composition was analysed by x-ray diffraction, FTIR and SEM. The trace element and Pb-isotope composition was obtained by dissolving parts of the filters and subsequent analysis with ICP-MS. Glassfibre filters were extracted with supercritical CO2 and the PAH were analysed with GC-MS.
The solid phase composition of the dust samples is of gypsum, organic matter (+soot), calcite, dolomite, quartz, mica and chlorite. The considerable enrichment in As, Cd, Pb and Zn, compared with the mean crustal composition, as well as the lead isotope-ratios (207/206) indicate a fair mixture of emissions from heating and gasoline combustion during winter and a dominance of the latter during summer. The PAH-pattern support the conclusions drawn from the heavy metal analysis.