Seasonal analysis of organic aerosol composition resolves anthropogenic and biogenic sources at a rural background station in central Europe†

Organic aerosol (OA) has a significant impact on Earth's climate and human health, while its chemical composition remains largely unknown. A detailed analysis of the chemical composition of particulate matter (PM) can identify origins, sources and transformation pathways and reveal mitigation potential for the anthropogenic organic fraction. Here, we follow a top-down molecular resolution approach of source attribution of organic compounds in PM_2.5 at a rural background station in central Europe. One year of PM filters were measured using ultra-high-performance liquid chromatography coupled to electrospray ionisation high-resolution Orbitrap mass spectrometry. Non-target analysis detected over 6000 compounds, which hierarchical cluster analysis separated into a biogenic and an anthropogenic compound cluster. Compounds of the biogenic cluster make up a large part of SOA during summer, indicating strong local influence by the vegetation. Anthropogenic compounds are relatively enriched during colder conditions, with temporarily strong transport of air pollution. Concentration-weighted trajectories show the air mass origins of these pollution events and allow for an interpretation of potential sources.