Decomposing the profile of PM in two low polluted German cities – Mapping of air mass residence time, focusing on potential long range transport impacts

• Four components of air pollution were identified by PCA in Karlsruhe and Potsdam.
• PMCOARSE production from secondary sources was indicated in Potsdam in warm period.
• Associations among slow moving air masses and increased PM10 levels were suggested.
• The residing areas of incoming air parcels are potential transboundary PM sources.

This paper aims to decompose the profile of particulates in Karlsruhe and Potsdam (Germany), focusing on the localization of PM potential transboundary sources. An air mass cluster analysis was implemented, followed by a study of air mass residence time on a grid of a 0.5° × 0.5° resolution. Particulate/gaseous daily air pollution and meteorological data were used to indicate PM local sources. Four Principal Component Analysis (PCA) components were produced: traffic, photochemical, industrial/domestic and particulate. PM2.5/PM10 ratio seasonal trends, indicated production of PMCOARSE (PM10–PM2.5) from secondary sources in Potsdam during warm period (WP). The residing areas of incoming slow moving air masses are potential transboundary PM sources. For Karlsruhe those areas were mainly around the city. An air mass residence time secondary peak was observed over Stuttgart. For Potsdam, areas with increased dwelling time of the arriving air parcels were detected particularly above E/SE Germany.