Polycyclic aromatic hydrocarbons in background air in central Europe – Seasonal levels and limitations for source apportionment

Positive matrix factorization (PMF) was applied on a large dataset of polycyclic aromatic hydrocarbon (PAH) concentrations determined in air at the central European background monitoring site Košetice, Czech Republic. The long-term (1996–2009) PAH median concentration in Košetice is about 6 times higher during winter than summer months. As the source apportionment of these pollutants is accompanied by concerns regarding the loss of the source signature during atmospheric transport, PMF was run on two winter PAH concentration data subsets stratified according to different ambient levels of oxidants. It is suggested, that the typical ambient air PAH pattern is largely preserved on a regional transport scale in winter in central Europe. However, the allocation of PMF model factors to particular PAH source categories (e.g., road traffic, residential wood combustion, residential and industrial coal combustion) could not be achieved due to (a) a high similarity of reference PAH profiles among each other and (b) variability in ambient reference PAH profiles. It is suggested, that the commonly studied set of EPA PAHs is not source category specific and thus not suitable for source apportionment. PAH source apportionment using more specific PAH and non-PAH markers is recommended.