Chemically speciated mass size distribution, particle density, shape and origin of non-refractory PM<sub>1</sub> measured at a rural background site in central Europe

Abstract. Seasonal variability of non-refractory PM1 (NR-PM1) was studied at a rural background site (National Atmospheric Observatory Košetice – NAOK) in the Czech Republic to investigate effect regional and long-range atmospheric transport central Europe. NR-PM1 measurements were performed by compact time-of-flight aerosol mass spectrometry (C-ToF-AMS), chemically speciated size distributions, density, shape, origin discussed. Average concentrations, calculated as sum equivalent black carbon (eBC) concentrations measured an aethalometer (AE), 8.58 ± 3.70 µg m−3 summer 10.08 8.04 winter. Organics dominant during both campaigns (summer/winter: 4.97 2.92/4.55 4.40 m−3), followed SO42-in (1.68 0.81/1.36 1.38 m−3) NO3- winter (0.67 0.38/2.03 1.71 m−3). The accumulation mode dominated average distribution seasons, with larger particles all species (mode diameters: Org: 334/413 nm, NO3-: 377/501 SO42-: 400/547 NH4+: 489/515 nm) indicating transport. However, since aerosols less oxidized than (comparing fragments f44 f43), importance local sources cold part year still enough be considered. Although aged continental air masses from south-east (SE) rare (7 %), they related highest PM1, eBC, species, especially SO42- NH4+. In winter, slow south-west (SW) (44 %) linked inversion conditions over Europe associated among well eBC. material density (ρm) corresponded higher inorganic contents seasons (summer: ∼ 1.30 g cm−3 winter: 1.40 cm−3). During episodes ρm ranged 1.30–1.40 1.30–1.50 dynamic shape factors (χ) decreased slightly particle mobility diameter (Dm) seasons. This study provides insights into seasonal effects on particles, focusing high number European site.