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

Seasonal variability of non-refractory PM.sub.1 (NR-PM.sub.1) was studied at a rural background site (National Atmospheric Observatory Košetice - NAOK) in the Czech Republic to investigate the effect of regional and long-range atmospheric transport in central Europe. NR-PM.sub.1 measurements were p...

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Published in:Atmospheric chemistry and physics 2022-05, Vol.22 (9), p.5829
Main Authors: Pokorná, Petra, Zíková, NadÄžda, Vodicka, Petr, Lhotka, Radek, Mbengue, Saliou, Holubová Smejkalová, Adéla, Riffault, Véronique, Ondrácek, Jakub, Schwarz, Jaroslav, Zdímal, Vladimír
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Language:English
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Summary:Seasonal variability of non-refractory PM.sub.1 (NR-PM.sub.1) was studied at a rural background site (National Atmospheric Observatory KoÅ¡etice - NAOK) in the Czech Republic to investigate the effect of regional and long-range atmospheric transport in central Europe. NR-PM.sub.1 measurements were performed by compact time-of-flight aerosol mass spectrometry (C-ToF-AMS), and the chemically speciated mass size distributions, density, shape, and origin were discussed. Average PM.sub.1 concentrations, calculated as the sum of the NR-PM.sub.1 and the equivalent black carbon (eBC) concentrations measured by an aethalometer (AE), were 8.58 ± 3.70 µg m.sup.-3 in summer and 10.08 ± 8.04 µg m.sup.-3 in winter. Organics were dominant during both campaigns (summer/winter: 4.97 ± 2.92/4.55 ± 4.40 µg m.sup.-3 ), followed by SO42-in summer (1.68 ± 0.81/1.36 ± 1.38 µg m.sup.-3) and NO3- in winter (0.67 ± 0.38/2.03 ± 1.71 µg m.sup.-3). The accumulation mode dominated the average mass size distribution during both seasons, with larger particles of all species measured in winter (mode diameters: Org: 334/413 nm, NO3-: 377/501 nm, SO42-: 400/547 nm, and NH4+: 489/515 nm) indicating regional and long-range transport. However, since the winter aerosols were less oxidized than the summer aerosols (comparing fragments f.sub.44 and f.sub.43 ), the importance of local sources in the cold part of the year was still enough to be considered. Although aged continental air masses from the south-east (SE) were rare in summer (7 %), they were related to the highest concentrations of PM.sub.1, eBC, and all NR-PM.sub.1 species, especially SO42- and NH4+. In winter, slow continental air masses from the south-west (SW) (44 %) were linked to inversion conditions over central Europe and were associated with the highest concentrations among all NR-PM.sub.1 species as well as PM.sub.1 and eBC. Average PM.sub.1 material density (Ï.sub.m) corresponded to higher inorganic contents in both seasons (summer: â¼ 1.30 g cm.sup.-3 and winter: â¼ 1.40 g cm.sup.-3). During episodes of higher mass concentrations Ï.sub.m ranged from 1.30-1.40 g cm.sup.-3 in summer and from 1.30-1.50 g cm.sup.-3 in winter. The dynamic shape factors (Ï) decreased slightly with particle mobility diameter (D.sub.m) in both seasons. This study provides insights into the seasonal effects and air mass variability on aerosol particles, focusing on episodes of high mass and number concentrations measured at a central Eur
ISSN:1680-7316
1680-7324