Combined particle number size distributions and readily available gaseous concentration data were used to identify winter particle sources in the urban atmosphere of Prague, the capital of Czech Republic by applying bilinear Positive Matrix Factorization (PMF2). This study has identified and apportioned four major sources.
They are ozone-rich, (transported ozone/ozone precursors, mixed down from above boundary layer associated with high wind speed and temperature), NOx-rich (diesel emissions), traffic and local heating.