Abstract

Alternating marine inflow and continental outflow make southern Sweden a suitable region for investigating natural and anthropogenic contributions to background particulate matter (PM). However, interpreting dust and marine aerosol sources remains challenging because their source signatures often overlap during atmospheric transport. This study investigated aerosol sources at the Vavihill and Hyltemossa background stations using source apportionment, elemental analysis, transport modelling, reanalysis data, and particle-resolved microscopy. At Vavihill, filter samples provided elemental composition, while TEOM measurements provided PM10 and PM2.5 mass concentrations. The combined data were analysed using Positive Matrix Factorization (PMF). At Hyltemossa, online XACT elemental measurements were combined with FIDAS coarse PM observations to evaluate coarse PM source contributions. HYSPLIT backward trajectories, CAMS diagnostics, and SEM/EDX analysis supported the interpretation of selected dust-related episodes and particle mixing states. The analysis identified mineral- and marine-related aerosols, regional pollution, and mixed combustion particles as important components of background PM. Mineral-associated contributions increased markedly during spring, accounting for 39% of the measured coarse PM at Vavihill and 29% at Hyltemossa. In contrast, marine aerosol made its largest contribution to measured coarse PM during winter, accounting for 48% at Vavihill and 40% at Hyltemossa. The mineral-related factor reflected multiple source regions and transport pathways rather than a single recurring dust source. At both sites, mineral, marine, and anthropogenic components frequently co-occurred and underwent atmospheric processing and mixing. Together, these results highlight the chemically heterogeneous and seasonally variable nature of background PM in southern Sweden.

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