Application of source apportionment methods to identify emission sources with the help of ambient air quality measurements in six European cities

Abstract

The quantification of pollution sources' contributions is a crucial element for implementing the Directives on Air Quality (2008/50/EC and 2004/107/EC). Within the ICARUS project, the source apportionment of PM2.5 in six cities of Europe (Athens, Brno, Ljubljana, Madrid, Thessaloniki, and Stuttgart) was assessed using datasets of measurements made in two different seasons (summer and winter) and two modeling tools: the Lenschow approach and the Positive Matrix Factorization. In order to increase the reliability and robustness of the results, an inter-comparison exercise was carried out with two receptor models for the same datasets: the Principal Component Analysis and the Positive Matrix Factorization model run by a different institution. It was observed that the Lenschow approach does not show the same results as the receptor models and therefore cannot be used to design strategies for urban air quality planning but just as a qualitative method. The comparison of the receptor models led to the validation of the results. Five sources have been found to be the main sources of PM2.5 in all the participating cities, namely, traffic, secondary inorganic aerosols (nitrates and sulphates), resuspension of soil dust, heating systems (biomass burning and/or fuel oil combustion) and industry. Geographical and seasonal variations have been observed, especially for heating sources hence, air quality measures at a local scale should be designed for the abatement of air pollution.