<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE article PUBLIC "-//NLM//DTD Journal Publishing DTD v3.0 20080202//EN" "https://jats.nlm.nih.gov/nlm-dtd/publishing/3.0/journalpublishing3.dtd">
<article xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink" article-type="research-article" dtd-version="3.0" xml:lang="en">
<front>
<journal-meta>
<journal-id journal-id-type="publisher">ACP</journal-id>
<journal-title-group>
<journal-title>Atmospheric Chemistry and Physics</journal-title>
<abbrev-journal-title abbrev-type="publisher">ACP</abbrev-journal-title>
<abbrev-journal-title abbrev-type="nlm-ta">Atmos. Chem. Phys.</abbrev-journal-title>
</journal-title-group>
<issn pub-type="epub">1680-7324</issn>
<publisher><publisher-name>Copernicus Publications</publisher-name>
<publisher-loc>Göttingen, Germany</publisher-loc>
</publisher>
</journal-meta>
<article-meta>
<article-id pub-id-type="doi">10.5194/acp-9-3163-2009</article-id>
<title-group>
<article-title>Spatio-temporal variability and principal components of the particle number size distribution in an urban atmosphere</article-title>
</title-group>
<contrib-group><contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Costabile</surname>
<given-names>F.</given-names>
</name>
<xref ref-type="aff" rid="aff1">
<sup>1</sup>
</xref>
<xref ref-type="aff" rid="aff2">
<sup>2</sup>
</xref>
</contrib>
<contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Birmili</surname>
<given-names>W.</given-names>
</name>
<xref ref-type="aff" rid="aff1">
<sup>1</sup>
</xref>
</contrib>
<contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Klose</surname>
<given-names>S.</given-names>
</name>
<xref ref-type="aff" rid="aff1">
<sup>1</sup>
</xref>
</contrib>
<contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Tuch</surname>
<given-names>T.</given-names>
</name>
<xref ref-type="aff" rid="aff1">
<sup>1</sup>
</xref>
<xref ref-type="aff" rid="aff3">
<sup>3</sup>
</xref>
</contrib>
<contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Wehner</surname>
<given-names>B.</given-names>
</name>
<xref ref-type="aff" rid="aff1">
<sup>1</sup>
</xref>
</contrib>
<contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Wiedensohler</surname>
<given-names>A.</given-names>
</name>
<xref ref-type="aff" rid="aff1">
<sup>1</sup>
</xref>
</contrib>
<contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Franck</surname>
<given-names>U.</given-names>
</name>
<xref ref-type="aff" rid="aff3">
<sup>3</sup>
</xref>
</contrib>
<contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>König</surname>
<given-names>K.</given-names>
</name>
<xref ref-type="aff" rid="aff1">
<sup>1</sup>
</xref>
</contrib>
<contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Sonntag</surname>
<given-names>A.</given-names>
</name>
<xref ref-type="aff" rid="aff1">
<sup>1</sup>
</xref>
</contrib>
</contrib-group><aff id="aff1">
<label>1</label>
<addr-line>Leibniz Institute for Tropospheric Research (IfT), Permoserstrasse 15, 04318 Leipzig, Germany</addr-line>
</aff>
<aff id="aff2">
<label>2</label>
<addr-line>National Research Council, Institute for Atmospheric Pollution (CNR), via Salaria km 29, 00016 Rome, Italy</addr-line>
</aff>
<aff id="aff3">
<label>3</label>
<addr-line>Helmholtz Center for Environmental Research (UfZ), Permoserstrasse 15, 04318 Leipzig, Germany</addr-line>
</aff>
<pub-date pub-type="epub">
<day>15</day>
<month>05</month>
<year>2009</year>
</pub-date>
<volume>9</volume>
<issue>9</issue>
<fpage>3163</fpage>
<lpage>3195</lpage>
<permissions>
<copyright-statement>Copyright: &#x000a9; 2009 F. Costabile et al.</copyright-statement>
<copyright-year>2009</copyright-year>
<license license-type="open-access">
<license-p>This work is licensed under the Creative Commons Attribution 3.0 Unported License. To view a copy of this licence, visit <ext-link ext-link-type="uri"  xlink:href="https://creativecommons.org/licenses/by/3.0/">https://creativecommons.org/licenses/by/3.0/</ext-link></license-p>
</license>
</permissions>
<self-uri xlink:href="https://acp.copernicus.org/articles/9/3163/2009/acp-9-3163-2009.html">This article is available from https://acp.copernicus.org/articles/9/3163/2009/acp-9-3163-2009.html</self-uri>
<self-uri xlink:href="https://acp.copernicus.org/articles/9/3163/2009/acp-9-3163-2009.pdf">The full text article is available as a PDF file from https://acp.copernicus.org/articles/9/3163/2009/acp-9-3163-2009.pdf</self-uri>
<abstract>
<p>A correct description of fine (diameter &lt;1 μm) and ultrafine (&lt;0.1 μm) aerosol
particles in urban areas is of interest for particle exposure assessment but also basic atmospheric
research. We examined the spatio-temporal variability of atmospheric aerosol particles (size range
3–800 nm) using concurrent number size distribution measurements at a maximum of eight
observation sites in and around Leipzig, a city in Central Europe. Two main experiments were
conducted with different time span and number of observation sites (2 years at 3 sites; 1 month at
8 sites). A general observation was that the particle number size distribution varied in time and
space in a complex fashion as a result of interaction between local and far-range sources, and the
meteorological conditions. To identify statistically independent factors in the urban aerosol,
different runs of principal component (PC) analysis were conducted encompassing aerosol, gas phase,
and meteorological parameters from the multiple sites. Several of the resulting PCs, outstanding
with respect to their temporal persistence and spatial coverage, could be associated with aerosol
particle modes: a first accumulation mode (&quot;droplet mode&quot;, 300–800 nm), considered to be the
result of liquid phase processes and far-range transport; a second accumulation mode (centered
around diameters 90–250 nm), considered to result from primary emissions as well as aging through
condensation and coagulation; an Aitken mode (30–200 nm) linked to urban traffic emissions in
addition to an urban and a rural Aitken mode; a nucleation mode (5–20 nm) linked to urban traffic
emissions; nucleation modes (3–20 nm) linked to photochemically induced particle formation; an
aged nucleation mode (10–50 nm). Additional PCs represented only local sources at a single site,
or infrequent phenomena. In summary, the analysis of size distributions of high time and size
resolution yielded a surprising wealth of statistical aerosol components occurring in the urban
atmosphere over one single city. A paradigm on the behaviour of sub-μm urban aerosol particles
is proposed, with recommendations how to efficiently monitor individual sub-fractions across an
entire city.</p>
</abstract>
<counts><page-count count="33"/></counts>
</article-meta>
</front>
<body/>
<back>
<ref-list>
<title>References</title>
<ref id="ref1">
<label>1</label><mixed-citation publication-type="other" xlink:type="simple"> Andronache, C.: Precipitation removal of ultrafine aerosol particles from the atmospheric boundary layer, J. Geophys. Res., 109, D16S07, https://doi.org/10.1029/2003JD004050, 2004. </mixed-citation>
</ref>
<ref id="ref2">
<label>2</label><mixed-citation publication-type="other" xlink:type="simple"> Alam, A., Shi, J. P., and Harrison, R. M.: Observations of new particle formation in urban air, J. Geophys. Res., 108(D3), 4093, https://doi.org/10.1029/2001JD001417, 2003. </mixed-citation>
</ref>
<ref id="ref3">
<label>3</label><mixed-citation publication-type="other" xlink:type="simple"> Birmili, W., Stratmann, F., and Wiedensohler, A.: Design of a DMA-based size spectrometer for a large particle size range and stable operation, J. Aerosol Sci., 30, 549–553, 1999. </mixed-citation>
</ref>
<ref id="ref4">
<label>4</label><mixed-citation publication-type="other" xlink:type="simple"> Birmili, W. and Wiedensohler, A.: New particle formation in the continental boundary layer: meteorological and gas phase parameter influence, Geophys. Res. Lett., 27, 3325–3328, 2000. </mixed-citation>
</ref>
<ref id="ref5">
<label>5</label><mixed-citation publication-type="other" xlink:type="simple"> Birmili, W., Wiedensohler, A., Heintzenberg, J., and Lehmann, K.: Atmospheric particle number size distribution in Central Europe: Statistical relations to air masses and meteorology, J. Geophys. Res., 106(D23), 32005–32018, 2001. </mixed-citation>
</ref>
<ref id="ref6">
<label>6</label><mixed-citation publication-type="other" xlink:type="simple"> Birmili, W., Berresheim, H., Plass-Dülmer, C., et~al.: The Hohenpeissenberg aerosol formation experiment (HAFEX): a long-term study including size-resolved aerosol, H&lt;sub&gt;2&lt;/sub&gt;SO&lt;sub&gt;4&lt;/sub&gt;, OH, and monoterpenes measurements, Atmos. Chem. Phys., 3, 361–376, 2003. </mixed-citation>
</ref>
<ref id="ref7">
<label>7</label><mixed-citation publication-type="other" xlink:type="simple"> Birmili, W., Alaviippola, B., Hinneburg, D., et al.: Dispersion of traffic-related exhaust particles near the Berlin urban motorway: estimation of fleet emission factors, Atmos. Chem. Phys., 9, 2355–2374, 2009. </mixed-citation>
</ref>
<ref id="ref8">
<label>8</label><mixed-citation publication-type="other" xlink:type="simple"> Brock, C. A., Trainer, M., Ryerson, T. B., et~al.: Particle growth in plumes of coal-fired power plants, J. Geophys. Res., 107(D12), 4155, https://doi.org/10.1029/2001JD001062, 2002. </mixed-citation>
</ref>
<ref id="ref9">
<label>9</label><mixed-citation publication-type="other" xlink:type="simple"> Bukowiecki, N., Kittelson, D. B., Watts, W. F., et~al.: Real-time characterization of ultrafine and accumulation mode particles in ambient combustion aerosols. J. Aerosol Sci. 33, 1139–1154, 2002. </mixed-citation>
</ref>
<ref id="ref10">
<label>10</label><mixed-citation publication-type="other" xlink:type="simple"> Bukowiecki, N., Dommen, J., Prévôt, A. S. H., Weingartner, E., and Baltensperger, U.: Fine and ultrafine particles in the Zürich (Switzerland) area measured with a mobile laboratory: an assessment of the seasonal and regional variation throughout a year, Atmos. Chem. Phys., 3, 1477–1494, 2003. </mixed-citation>
</ref>
<ref id="ref11">
<label>11</label><mixed-citation publication-type="other" xlink:type="simple"> Chan, T. W. and Mozurkewich, M.: Application of absolute principal component analysis to size distribution data: identification of particle origins, Atmos. Chem. Phys., 7, 887–897, 2007a. </mixed-citation>
</ref>
<ref id="ref12">
<label>12</label><mixed-citation publication-type="other" xlink:type="simple"> Chan, T W. and Mozurkewich, M.: Simplified representation of atmospheric aerosol size distributions using absolute principal component analysis, Atmos. Chem. Phys., 7, 875–886, 2007b. </mixed-citation>
</ref>
<ref id="ref13">
<label>13</label><mixed-citation publication-type="other" xlink:type="simple"> Charron, A., Birmili, W., and Harrison, R. M.: Factors influencing new particle formation at the rural site, Harwell, United Kingdom, J. Geohys. Res., 112, D14210, https://doi.org/10.1029/2007JD008425, 2007. </mixed-citation>
</ref>
<ref id="ref14">
<label>14</label><mixed-citation publication-type="other" xlink:type="simple"> Cubison, M. J., Ervens, B., Feingold, G., et~al.: The influence of chemical composition and mixing state of Los Angeles urban aerosol on CCN number and cloud properties, Atmos. Chem. Phys., 8, 5649–5667, 2008. </mixed-citation>
</ref>
<ref id="ref15">
<label>15</label><mixed-citation publication-type="other" xlink:type="simple"> Doyle, G. J.: Self-nucleation in the sulfuric acid-water system, J. Chem. Phys., 35, 795–799, 1961. </mixed-citation>
</ref>
<ref id="ref16">
<label>16</label><mixed-citation publication-type="other" xlink:type="simple">Drewnick, F., Jayne, J. T., Canagaratna, M. R., Worsnop, D. R., and Demerjian, K. L.: Measurement of ambient aerosol composition during the PMTACS-NY 2001 using an aerosol mass spectrometer. Part I: mass concentrations, Aerosol Sci. Technol., 38(S1), 92-103, 2004.</mixed-citation>
</ref>
<ref id="ref17">
<label>17</label><mixed-citation publication-type="other" xlink:type="simple"> Ebert, M., Weinbruch, S., Hoffmann, P., and Ortner, H M.: The chemical composition and complex refractive index of rural and urban influenced aerosols determined by individual particle analysis, Atmos. Environ., 38, 6531–6545, 2004. </mixed-citation>
</ref>
<ref id="ref18">
<label>18</label><mixed-citation publication-type="other" xlink:type="simple"> Eder, B K.: A principal component analysis of SO&lt;sub&gt;4&lt;/sub&gt; precipitation concentrations over the eastern United States, Atmos. Environ., 23, 2739–2750, 1989. </mixed-citation>
</ref>
<ref id="ref19">
<label>19</label><mixed-citation publication-type="other" xlink:type="simple"> Engler, C., Rose, D., Wehner, B., et~al.: Size distributions of non-volatile particle residuals (Dp&amp;lt;800 nm) at a rural site in Germany and relation to air mass origin, Atmos. Chem. Phys., 7, 5785–5802, 2007. </mixed-citation>
</ref>
<ref id="ref20">
<label>20</label><mixed-citation publication-type="other" xlink:type="simple"> Gnanadesikan, R.: Methods for statistical data analysis of multivariate observations, John Wiley and Sons, New York, USA, 311 pp., 1977. </mixed-citation>
</ref>
<ref id="ref21">
<label>21</label><mixed-citation publication-type="other" xlink:type="simple"> Gramotnev, G., Madl, P., Gramotnev, D. K., and Burchill, M. J.: Urban background aerosols: negative correlations of particle modes and fragmentation mechanism, Geophys. Res. Lett., 34, L11811, https://doi.org/10.1029/2006GL029109, 2007. </mixed-citation>
</ref>
<ref id="ref22">
<label>22</label><mixed-citation publication-type="other" xlink:type="simple"> Haywood, J. M. and Boucher, O.: Estimates of the direct and indirect radiative forcing due to tropospheric aerosols: A review, Rev. Geophys., 38, 513–543, 2000. </mixed-citation>
</ref>
<ref id="ref23">
<label>23</label><mixed-citation publication-type="other" xlink:type="simple"> HEI: Understanding the health effects of components of the particulate matter mix: progress and next steps, Tech. Rep 4, Health Effects Institute, Boston, MA, USA, 2002. </mixed-citation>
</ref>
<ref id="ref24">
<label>24</label><mixed-citation publication-type="other" xlink:type="simple"> Heintzenberg, J. Birmili, W., Wiedensohler, A., Nowak, A., and Tuch, T.: Structure, variability and persistence of the submicrometre marine aerosol, Tellus~B, 56(4), 357–367, 2004. </mixed-citation>
</ref>
<ref id="ref25">
<label>25</label><mixed-citation publication-type="other" xlink:type="simple"> Heintzenberg, J., Birmili, W., Theiss, D., and Kisilyakhov, Y.: The atmospheric aerosol over Siberia, as seen from the 300 m ZOTTO tower, Tellus~B, 60(2), 276–285, 2008. </mixed-citation>
</ref>
<ref id="ref26">
<label>26</label><mixed-citation publication-type="other" xlink:type="simple"> Hering, S. V. and Friedlander, S. K.: Origins of sulfur size distributions in the Los Angeles basin, Atmos. Environ., 16, 2647–2656, 1982. </mixed-citation>
</ref>
<ref id="ref27">
<label>27</label><mixed-citation publication-type="other" xlink:type="simple"> Hidy, G. M.: Summary of the California aerosol characterisation experiment, J. Air Poll. Control, 25, 1106–1114, 1975. </mixed-citation>
</ref>
<ref id="ref28">
<label>28</label><mixed-citation publication-type="other" xlink:type="simple"> Hinds, W. C.: Aerosol Technology, 2nd ed., John Wiley and Sons, New York, USA, 1999. </mixed-citation>
</ref>
<ref id="ref29">
<label>29</label><mixed-citation publication-type="other" xlink:type="simple"> Hoppel, W. A.: Determination of the aerosol size distribution from the mobility distribution of the charged fraction of aerosols, J. Aerosol Sci., 9, 41–54, 1978. </mixed-citation>
</ref>
<ref id="ref30">
<label>30</label><mixed-citation publication-type="other" xlink:type="simple"> Huang, S., Rahn, K. A., and Arimoto, R.: Testing and optimizing two factor-analysis techniques on aerosol at Narragansett, Rhode Island, Atmos. Environ., 33, 2169–2185, 1999. </mixed-citation>
</ref>
<ref id="ref31">
<label>31</label><mixed-citation publication-type="other" xlink:type="simple"> Hussein, T., Puustinen, A., Aalto, P., Mäkelä, J., Hämeri, K., and Kulmala, M.: Urban aerosol number size distributions, Atmos. Chem. Phys, 4, 391–411, 2004. </mixed-citation>
</ref>
<ref id="ref32">
<label>32</label><mixed-citation publication-type="other" xlink:type="simple"> Hussein, T., Hämeri, K., Aalto, P., Paatero, P., and Kulmala, M.: Modal structure and spatial-temporal variations of urban and suburban aerosols in Helsinki, Finland, Atmos. Environ., 39, 1655–1668, 2005. </mixed-citation>
</ref>
<ref id="ref33">
<label>33</label><mixed-citation publication-type="other" xlink:type="simple"> Imhof, D., Weingartner, E., Ordonez, C., et~al.: Real-world emission factors of fine and ultrafine aerosol particles for different traffic situations in Switzerland, Environ. Sci. Technol., 39, 8341–8350, 2005. </mixed-citation>
</ref>
<ref id="ref34">
<label>34</label><mixed-citation publication-type="other" xlink:type="simple"> Jaenicke, R.: Tropospheric aerosols. In: Hobbs, P V. Editor. Aerosol-cloud-climate interactions, Academic Press, San Diego, CA, USA, 1–31, 1993. </mixed-citation>
</ref>
<ref id="ref35">
<label>35</label><mixed-citation publication-type="other" xlink:type="simple"> Janhäll, S., Jonsson, A. M., Molnar, P., Svensson, E., and Hallquist, M.: Size resolved traffic emission factors of submicrometer particles, Atmos. Environ., 38, 4331–4340, 2004. </mixed-citation>
</ref>
<ref id="ref36">
<label>36</label><mixed-citation publication-type="other" xlink:type="simple"> Jimenez, J. L., Jayne, J. T., Shi, Q., et~al.: Ambient aerosol sampling with an Aerosol Mass Spectrometer, J. Geophys. Res., 108(D7), 8425, https://doi.org/10:1029/2001JD001213, 2003. </mixed-citation>
</ref>
<ref id="ref37">
<label>37</label><mixed-citation publication-type="other" xlink:type="simple"> John, W., Wall, S. M., Ondo, J. L., and Winklmayr, W.: Modes in the size distributions of atmospheric inorganic aerosol, Atmos. Environ. 24A, 2349–2359, 1990. </mixed-citation>
</ref>
<ref id="ref38">
<label>38</label><mixed-citation publication-type="other" xlink:type="simple"> John, W.: The characteristics of environmental and laboratory-generated aerosols, in: Aerosol measurement: Principles, techniques and applications, edited by: Willeke, K. and Baron, P. A., Van Nostrand Reinhold, New York, USA, 1993. </mixed-citation>
</ref>
<ref id="ref39">
<label>39</label><mixed-citation publication-type="other" xlink:type="simple"> Jobson, B. T., Parrish, D. D., Goldan, P., et~al.: Spatial and temporal variability of nonmethane hydrocarbon mixing ratios and their relation to photochemical lifetime, J. Geophys. Res., 103(D17), 22617–22628, 1998. </mixed-citation>
</ref>
<ref id="ref40">
<label>40</label><mixed-citation publication-type="other" xlink:type="simple"> Junge, C. E.: Residence time and variability of tropospheric trace gases, Tellus, 16, 477–488, 1974. </mixed-citation>
</ref>
<ref id="ref41">
<label>41</label><mixed-citation publication-type="other" xlink:type="simple"> Kerminen, V. M. and Wexler, A. S.: The occurrence of sulfuric acid-water nucleation in plumes: Urban environment, Tellus~B, 48, 65–82, 1996. </mixed-citation>
</ref>
<ref id="ref42">
<label>42</label><mixed-citation publication-type="other" xlink:type="simple"> Ketzel, M P., W&amp;aring;hlin, A., Kristensson, E., et~al.: Particle size distribution and particle mass measurements at urban, near-city and rural level in the Copenhagen area and Southern Sweden, Atmos. Chem. Phys., 4, 281–292, 2004. </mixed-citation>
</ref>
<ref id="ref43">
<label>43</label><mixed-citation publication-type="other" xlink:type="simple"> Kittelson, D.: Engines and nanoparticles: A review, J. Aerosol Sci., 29, 575–588, 1998. </mixed-citation>
</ref>
<ref id="ref44">
<label>44</label><mixed-citation publication-type="other" xlink:type="simple"> Kittelson, D., Johnson, J., Watts, W., et~al.: Diesel aerosol sampling in the atmosphere, SAE technical paper series, No. 2000-01-22212, 2000. </mixed-citation>
</ref>
<ref id="ref45">
<label>45</label><mixed-citation publication-type="other" xlink:type="simple"> Kittelson, D.B., Watts, W.F., Johnson, J.P.: Nanoparticle emissions on Minnesota highways, Atmos. Env., 38, 9–19, 2004. </mixed-citation>
</ref>
<ref id="ref46">
<label>46</label><mixed-citation publication-type="other" xlink:type="simple"> Kittelson, D. B., Watts, W. F., Johnson, J. P.: On-road and laboratory evaluation of combustion aerosols – Part 1: Summary of diesel engine results, J. Aerosol Sci., 37, 913–930, 2006. </mixed-citation>
</ref>
<ref id="ref47">
<label>47</label><mixed-citation publication-type="other" xlink:type="simple"> Klose, S., Birmili, W., Voigtländer, J., et~al.: Particle number emissions of motor traffic derived from street canyon measurements in a Central European city, Atmos. Chem. Phys. Discuss., 9, 3763–3809, 2009. </mixed-citation>
</ref>
<ref id="ref48">
<label>48</label><mixed-citation publication-type="other" xlink:type="simple"> Kulmala, M., Suni, T., Lehtinen, K. E. J., et~al.: A new feedback mechanism linking forests, aerosols, and climate, Atmos. Chem. Phys., 3, 6093–6107, 2003. </mixed-citation>
</ref>
<ref id="ref49">
<label>49</label><mixed-citation publication-type="other" xlink:type="simple"> Kulmala, M., Vehkamäki, H., Petäjä, T., et~al.: Formation and growth rates of ultrafine atmospheric particles: A review of observations, J. Aerosol Sci., 35, 143–176, 2004. </mixed-citation>
</ref>
<ref id="ref50">
<label>50</label><mixed-citation publication-type="other" xlink:type="simple"> Laaksonen, A., Hamed, A., Joutsensaari, J., et~al.: Cloud condensation nucleus production from nucleation events at a highly polluted region, Geophys. Res. Lett., 32, L06812, https://doi.org/10.1029/2004GL022092, 2005. </mixed-citation>
</ref>
<ref id="ref51">
<label>51</label><mixed-citation publication-type="other" xlink:type="simple"> Le Canut, P., Andreae, M. O., Harris, G. W., Wienhold, F. G., and Zenker, T.: Airborne studies of emissions from savanna fires in southern Africa – 1. Aerosol emissions measured with a laser optical particle counter, J. Geophys. Res., 101(D19), 23615–23630, 1996. </mixed-citation>
</ref>
<ref id="ref52">
<label>52</label><mixed-citation publication-type="other" xlink:type="simple"> Liu, S., Hu, M., Wu, Z., et~al.: Aerosol number size distribution and new particle formation at a rural/coastal site in Pearl River Delta (PRD) of China, Atmos. Env., 42, 6275–6283, 2008. </mixed-citation>
</ref>
<ref id="ref53">
<label>53</label><mixed-citation publication-type="other" xlink:type="simple"> Mäkelä, J. M., Koponen, I. K., Aalto, P., and Kulmala, M.: One-year data of submicron size modes of tropospheric background aerosol in Southern Finland, J. Aerosol Sci., 31(5), 595–611, 2000. </mixed-citation>
</ref>
<ref id="ref54">
<label>54</label><mixed-citation publication-type="other" xlink:type="simple"> McFiggans, G., Alfarra, M. R., Allan, J., et~al.: Simplification of the representation of the organic component of atmospheric particulates, Faraday Discuss., 130, 341–362, 2005. </mixed-citation>
</ref>
<ref id="ref55">
<label>55</label><mixed-citation publication-type="other" xlink:type="simple"> McMurry, P. H., Woo, K. S., Weber, R., Chen, D.-R., and Pui, D. Y. H.: Size distributions of 3 to 10 nm atmospheric particles: Implications for nucleation mechanisms. Phil. Trans. Roy. Soc., Lon., A358, 2625–2642, 2000. </mixed-citation>
</ref>
<ref id="ref56">
<label>56</label><mixed-citation publication-type="other" xlink:type="simple"> Mejia, J. F., Morawska, L., and Mengersen, K.: Spatial variation in particle number size distributions in a large metropolitan area, Atmos. Chem. Phys., 8, 1127–1138, 2008. </mixed-citation>
</ref>
<ref id="ref57">
<label>57</label><mixed-citation publication-type="other" xlink:type="simple"> Meng, Z. and Seinfield, J. H.: On the source of the submicrometer droplet mode of urban and regional aerosols, Aerosol Sci. Technol., 20, 253–265, 1994. </mixed-citation>
</ref>
<ref id="ref58">
<label>58</label><mixed-citation publication-type="other" xlink:type="simple">Meszaros, A.: On the size distribution of atmospheric aerosol particles of different composition, Atmos. Environ., 11, 1075&amp;ndash;1081, 1977.</mixed-citation>
</ref>
<ref id="ref59">
<label>59</label><mixed-citation publication-type="other" xlink:type="simple"> Mönkkönen, P., Koponen, I. K., Lehtinen, K. E. J., et~al.: Measurements in a highly polluted Asian mega city: observations of aerosol number size distribution, modal parameters and nucleation events, Atmos. Chem. Phys., 5, 57–66, 2005. </mixed-citation>
</ref>
<ref id="ref60">
<label>60</label><mixed-citation publication-type="other" xlink:type="simple"> Morawska, L., Thomas, S. Bofinger, N. D., Wainwright, D., and Neale, D.: Comprehensive characterisation of aerosols in a subtropical urban atmosphere: Particle size distribution and correlation with gaseous pollutants, Atmos. Environ., 32, 2467–2478, 1998. </mixed-citation>
</ref>
<ref id="ref61">
<label>61</label><mixed-citation publication-type="other" xlink:type="simple"> Morawska, L., Thomas, S., Jamriska, M., and Johnson, G.: The modality of particle size distributions of environmental aerosols, Atmos. Environ., 33, 4401–4411, 1999. </mixed-citation>
</ref>
<ref id="ref62">
<label>62</label><mixed-citation publication-type="other" xlink:type="simple"> Morawska, L., Keogh, D U., Thomas, S B., and Mengersen, K.: Modality in ambient particle size distributions and its potential as a basis for developing air quality regulation, Atmos. Environ., 42, 1617–1628, 2008. </mixed-citation>
</ref>
<ref id="ref63">
<label>63</label><mixed-citation publication-type="other" xlink:type="simple"> Morrison, D F.: Multivariate statistical methods, 2nd ed., McGraw-Hill, New York, USA, 415 pp., 1976. </mixed-citation>
</ref>
<ref id="ref64">
<label>64</label><mixed-citation publication-type="other" xlink:type="simple"> Mulaik, S. A.: The foundations of factor analysis, McGraw-Hill, New York, USA, 453 pp., 1972. </mixed-citation>
</ref>
<ref id="ref65">
<label>65</label><mixed-citation publication-type="other" xlink:type="simple"> Oberdörster, G.: Nanotoxicology: An emerging discipline evolving from studies of ultrafine particles, Env. Health Perspect., 113, 823–839, 2005. </mixed-citation>
</ref>
<ref id="ref66">
<label>66</label><mixed-citation publication-type="other" xlink:type="simple"> Ondov, J M. and Wexler, A S.: Where do particulate toxins reside? An improved paradigm for the structure and dynamics of the urban mid-Atlantic aerosol, Environ. Sci. Technol., 32, 2547–2555, 1998. </mixed-citation>
</ref>
<ref id="ref67">
<label>67</label><mixed-citation publication-type="other" xlink:type="simple"> Pohjola, M. A., Pirjola, L., Karppinen, A., et~al.: Evaluation and modelling of the size fractionated aerosol particle number concentration measurements nearby a major road in Helsinki – Part I: Modelling results within the LIPIKA project, Atmos. Chem. Phys., 7, 4065–4080, 2007. </mixed-citation>
</ref>
<ref id="ref68">
<label>68</label><mixed-citation publication-type="other" xlink:type="simple"> Pope, C. A., Burnett, R. T., Thun, M. J., et~al.: Lung cancer, cardiopulmonary mortality, and long-term exposure to fine particulate air pollution, J. Aerosol Med., 287, 1132–1141, 2002. </mixed-citation>
</ref>
<ref id="ref69">
<label>69</label><mixed-citation publication-type="other" xlink:type="simple"> Pugatshova, A., Reinart, A., and Tamm, E.: Features of the multimodal aerosol size distribution depending on the air mass origin in the Baltic region, Atmos. Environ., 41, 4408–4422, 2007. </mixed-citation>
</ref>
<ref id="ref70">
<label>70</label><mixed-citation publication-type="other" xlink:type="simple"> Puustinen, A., Hämeri, K., Pekkanen, J., et~al.: Spatial variation of particle number and mass over four European cities, Atmos. Environ., 41, 6622–6636, 2007. </mixed-citation>
</ref>
<ref id="ref71">
<label>71</label><mixed-citation publication-type="other" xlink:type="simple"> Ramanathan, V., Crutzen, P. J., Kiehl, J. T., and Rosenfeld, D.: Aerosol, climate, and the hydrological cycle, Science, 294, 2119–2124, 2001. </mixed-citation>
</ref>
<ref id="ref72">
<label>72</label><mixed-citation publication-type="other" xlink:type="simple"> Rönkkö, T., Virtanen, A., Kannosto, J., et~al.: Nucleation mode particles with a nonvolatile core in the exhaust of a heavy duty diesel vehicle, Environ. Sci. Technol., 41, 6384–6389, 2007. </mixed-citation>
</ref>
<ref id="ref73">
<label>73</label><mixed-citation publication-type="other" xlink:type="simple"> Schneider, J., Kirchner, U., Borrmann, S., Vogt, R., and Scheer, V.: In situ measurements of particle number concentration, chemically resolved size distributions and black carbon content of traffic-related emissions on German motorways, rural roads and in city traffic, Atmos. Environ., 42, 4257–4268, 2008. </mixed-citation>
</ref>
<ref id="ref74">
<label>74</label><mixed-citation publication-type="other" xlink:type="simple"> Seinfeld, J. H. and Pandis, S. P.: Atmospheric Chemistry and Physics, 2nd ed., John Wiley, New York, USA, 1232 pp., 2006. </mixed-citation>
</ref>
<ref id="ref75">
<label>75</label><mixed-citation publication-type="other" xlink:type="simple"> Sioutas, C., Delfino, R. J., and Singh, M.: Exposure assessment for atmospheric ultrafine particles (UFP) and implications in epidemiological research, Environ. Health Perspect. 113, 947–955, 2005. </mixed-citation>
</ref>
<ref id="ref76">
<label>76</label><mixed-citation publication-type="other" xlink:type="simple"> Stanier, C. O., Khlystov, A. Y., and Pandis, S. N.: Nucleation events during the Pittsburgh air quality study: description and relation to key meteorological, gas phase, and aerosol parameters. Aerosol Sci. Technol., 38, 253–264, 2004. </mixed-citation>
</ref>
<ref id="ref77">
<label>77</label><mixed-citation publication-type="other" xlink:type="simple"> Stolzenburg, M. R., McMurry, P. H., Sakurai, H., et~al.: Growth rates of freshly nucleated atmospheric particles in Atlanta, J. Geophys. Res., 110, D22S05, https://doi.org/10.1029/2005JD005935, 2005. </mixed-citation>
</ref>
<ref id="ref78">
<label>78</label><mixed-citation publication-type="other" xlink:type="simple"> Stott, P. A., Tett, S. F. B., Jones, G. S., et~al.: External control of 20$^th$ century temperature by natural and anthropogenic forcings, Science, 290, 2133–2137, 2000. </mixed-citation>
</ref>
<ref id="ref79">
<label>79</label><mixed-citation publication-type="other" xlink:type="simple"> Tuch, T. M., Herbarth, O., Franck, U., et~al.: Weak correlation of ultrafine aerosol particle concentrations $&lt;$800 nm between two sites within one city, J. Exp. Sci. Environ., 16, 486–490, 2006. </mixed-citation>
</ref>
<ref id="ref80">
<label>80</label><mixed-citation publication-type="other" xlink:type="simple"> Tunved, P., Ström, J., and Hansson, H. C.: An investigation of processes controlling the evolution of the boundary layer aerosol size distribution properties at the Swedish background station Aspvreten, Atmos. Chem. Phys., 4, 2581–2592, 2004. </mixed-citation>
</ref>
<ref id="ref81">
<label>81</label><mixed-citation publication-type="other" xlink:type="simple"> W&amp;aring;hlin, P., Palmgren, F., and van Dingenen, R.: Experimental studies of ultrafine particles in streets and the relationship to traffic, Atmos. Environ., 35(S1), 63–69, 2001. </mixed-citation>
</ref>
<ref id="ref82">
<label>82</label><mixed-citation publication-type="other" xlink:type="simple"> Wehner, B., Birmili, W., Gnauk, T., and Wiedensohler, A.: Particle number size distributions in a street canyon and their transformation into the urban background: Measurements and a simple model study, Atmos. Environ., 36, 2215–2223, 2002. </mixed-citation>
</ref>
<ref id="ref83">
<label>83</label><mixed-citation publication-type="other" xlink:type="simple"> Wehner, B. and Wiedensohler, A.: Long term measurements of submicrometer urban aerosols: statistical analysis for correlations with meteorological conditions and trace gases, Atmos. Chem. Phys., 3, 867–879, 2003.   </mixed-citation>
</ref>
<ref id="ref84">
<label>84</label><mixed-citation publication-type="other" xlink:type="simple"> Wehner, B., Siebert, H., Stratmann, F., et al.: Horizontal homogeinity and vertical extent of new particle formation events, Tellus~B, 59, 362–371, 2007. </mixed-citation>
</ref>
<ref id="ref85">
<label>85</label><mixed-citation publication-type="other" xlink:type="simple"> Whitby, K. T.: The physical characteristics of sulphur aerosols, Atmos. Environ., 12, 135–159, 1978. </mixed-citation>
</ref>
<ref id="ref86">
<label>86</label><mixed-citation publication-type="other" xlink:type="simple"> WHO: World Health Report 2002, Tech. Rep., World Health Organisation, Genova, Italy, 2002. </mixed-citation>
</ref>
<ref id="ref87">
<label>87</label><mixed-citation publication-type="other" xlink:type="simple"> Willeke, K. and Whitby, K. T.: Atmospheric aerosol: size distribution interpretation, J. Air Poll. Control Ass., 15(5), 529–535, 1975. </mixed-citation>
</ref>
<ref id="ref88">
<label>88</label><mixed-citation publication-type="other" xlink:type="simple"> Williams, P. I., Gallagher, M. W., Choularton, T. W., et~al.: Aerosol development and interaction in an urban plume, Aerosol Sci. Technol., 32, 120–126, 2000. </mixed-citation>
</ref>
<ref id="ref89">
<label>89</label><mixed-citation publication-type="other" xlink:type="simple"> Woo, K. S., Chen, D. R., Pui, D. Y. H., and McMurry, P. H.: Measurements of Atlanta aerosol size distributrions: observations of ultrafine particle events, Aerosol Sci. Technol., 34, 75–87, 2001. </mixed-citation>
</ref>
<ref id="ref90">
<label>90</label><mixed-citation publication-type="other" xlink:type="simple"> Yao, X. H., Lau, N. T., and Chan, C. K.: On the time-averaging of ultrafine particle number size spectra in vehicular plumes, Atmos. Chem. Phys., 6, 4801–4807, 2006. </mixed-citation>
</ref>
<ref id="ref91">
<label>91</label><mixed-citation publication-type="other" xlink:type="simple"> Zhang, K. M., Wexler, A. S., Zhu, Y. F., Hinds W. C., and Sioutas, C.: Evolution of particle number distribution near roadways. Part II: the Road-to-Ambient process, Atmos. Environ., 38, 6655–6665, 2004. </mixed-citation>
</ref>
<ref id="ref92">
<label>92</label><mixed-citation publication-type="other" xlink:type="simple"> Zhou, J., Swietlicki, E., Hansson, H. C., and Artaxo, P.: Aerosol particle size distribution and hygroscopic growth measured in the Amazon rain forest during, J. Geophys. Res., 107(D20), 8055, https://doi.org/10.1029/2000JD000203, 2002. </mixed-citation>
</ref>
<ref id="ref93">
<label>93</label><mixed-citation publication-type="other" xlink:type="simple"> Zhu, Y., Hinds, W. C, Kim, S., Shen, S., and Sioutas, C.: Study of ultrafine particles near a major highway with heavy-duty diesel traffic, Atmos. Env., 36, 4323–4335, 2002. </mixed-citation>
</ref>
</ref-list>
</back>
</article>