Summer PM1 measured at a rural background site in Central Europe
Authors: Pokorná Petra , Zíková Naděžda , Lhotka Radek , Vodička Petr , Petit Jean-Eudes , Mbengue Saliou , Holubová Šmejkalová Adéla , Ondráček Jakub , Schwarz Jaroslav , Ždímal Vladimír 
Published: March 2021

&lt;p&gt;This work aims to assess the summer PM&lt;sub&gt;1&lt;/sub&gt; based on particle size distribution, density and origin. An intensive sampling campaign was conducted in July 2019 at the National Atmospheric Observatory Ko&amp;#353;etice (NAOK) in the Czech Republic.&lt;/p&gt;&lt;p&gt;5-min integrals of particle number concentration (PNC) and particle number size distribution (PNSD) data were recorded by a Scanning Mobility Particle Sizer (size range 10 &amp;#8211; 800 nm, SMPS, IFT TROPOS, Leipzig, with CPC 3772, TSI USA) and size-resolved PM chemical composition was measured by a Compact Time of Flight Aerosol Mass Spectrometer (C-ToF-AMS, Aerodyne, USA). 1-min PM&lt;sub&gt;1 &lt;/sub&gt;black carbon (BC) concentrations by aethalometer (AE33, Magee Scientific, USA) and 4-h PM&lt;sub&gt;2.5 &lt;/sub&gt;organic and elemental carbon (OC/EC) concentrations (Sunset Laboratory Inc., USA) were measured.&amp;#160; Also 12-h PM&lt;sub&gt;1&lt;/sub&gt; samples by a sequential Leckel LVS-3 (Sven Leckel Ingenieurb&amp;#252;ro, Germany) for a subsequent chemical analysis (water-soluble ions, monosaccharides, anhydrides, and saccharides) were collected. Additionally, 10-min average SO&lt;sub&gt;2&lt;/sub&gt;, NO&lt;sub&gt;2&lt;/sub&gt;, NO&lt;sub&gt;x&lt;/sub&gt; and CO concentrations along with the values of meteorological parameters were recorded. To determine the origin of non-refractory PM&lt;sub&gt;1&lt;/sub&gt; (NR-PM&lt;sub&gt;1&lt;/sub&gt;) species (Org, NO&lt;sub&gt;3&lt;/sub&gt;&lt;sup&gt;-&lt;/sup&gt;, SO&lt;sub&gt;4&lt;/sub&gt;&lt;sup&gt;2-&lt;/sup&gt;, NH&lt;sub&gt;4&lt;/sub&gt;&lt;sup&gt;+&lt;/sup&gt;) the back trajectories describing the air mass origin were clustered using the Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) model [1]. Last, but not least, the multi-time factor analysis model [2] with modifications was applied on combined dataset (on-line and off-line measurements) to refine the analysis results with respect to the organic aerosol factors as well as organic aerosol sources and their origin.&lt;/p&gt;&lt;p&gt;The campaigns was characterized by prevailing westerly winds with average wind speed of 3.0&amp;#177;1.5 m s&lt;sup&gt;-1&lt;/sup&gt;, average temperature of 18.5&amp;#177;4.7 &amp;#176;C and negligible precipitation. The average PM&lt;sub&gt;1&lt;/sub&gt; (NR-PM&lt;sub&gt;1&lt;/sub&gt; and eBC) measured concentration was 8.5&amp;#177;3.5 &amp;#181;g m&lt;sup&gt;-3&lt;/sup&gt; (12h PM&lt;sub&gt;1&lt;/sub&gt; 10.1&amp;#177;6.4 &amp;#181;g m&lt;sup&gt;-3&lt;/sup&gt;). Based on the PNC predominated particles in the size range 25 &amp;#8211; 80 nm (N25 &amp;#8211; 50 and N50 &amp;#8211; 80), also called the Aitken mode, typical for rural background stations and originates from the aging of the particles generated during new particle formation events [3]. NR-PM&lt;sub&gt;1&lt;/sub&gt; was composed primarily by organics (58%) and sulphate (22%) in the accumulation mode (Org mode diameter 300 nm and SO&lt;sub&gt;4&lt;/sub&gt;&lt;sup&gt;2-&lt;/sup&gt; mode diameter 385 nm) with average particle density ~ 1.4 g m&lt;sup&gt;-3&lt;/sup&gt;. This result in combination with the cluster analysis points to the regional origin of the particles from southeast (Austria-Hungary-Slovakia). Six Org factors (primary organic aerosol (POA) &amp;#8211; fungal origin, biomass burning organic aerosol (BBOA) &amp;#8211; related secondary aerosol (SA), semivolatile aerosol &amp;#8211; nitrate-rich, secondary organic aerosol (SOA) &amp;#8211; oxalate-rich, semivolatile aerosol &amp;#8211; microbial origin, primary traffic and biomass organic aerosol (OA)) based on combined data were resolved by multi-time factor analysis model. Modelling of combined dataset provided insides into processes involved in SOA formation and sources.&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;&lt;p&gt;[1] Rolph, G., et al., (2017) Environ. Modell. Software 95, 210&amp;#8211;228.&lt;/p&gt;&lt;p&gt;[2] Zhou, L., et al., (2004) Atmos. Environ. 38, 4909&amp;#8211;4920.&lt;/p&gt;&lt;p&gt;[3] Costabile, F., et al., (2009) Atmos. Chem. Phys. 9, 3163&amp;#8211;3195.&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;&lt;p&gt;This work was supported by the GACR under grant P209/19/06110Y and by the MEYS of the Czech Republic under grant ACTRIS-CZ LM2018122 and ACTRIS-CZ RI (CZ.02.1.01/0.0/0.0/16_013/0001315).&lt;/p&gt;