Both source apportionment services are based on the chemical transport model LOTOS-EUROS and the emission knowledge developed at TNO. Information on intercontinental transport and forest fire emissions are taken from the Copernicus Atmospheric Monitoring Service. Modelled source specific PM concentrations representing urban background conditions are uploaded daily before noon. For questions or more detailed information on this source apportionment service, please contact our colleagues of the TOPAS team through the email address topas@tno.nl and describe your intended use of the information of TOPAS.