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<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>
</journal-title-group>
<issn pub-type="epub">1680-7324</issn>
<publisher><publisher-name>Copernicus GmbH</publisher-name>
<publisher-loc>Göttingen, Germany</publisher-loc>
</publisher>
</journal-meta>
<article-meta>
<article-id pub-id-type="doi">10.5194/acp-8-2243-2008</article-id>
<title-group>
<article-title>Properties of atmospheric humic-like substances &amp;ndash; water system</article-title>
</title-group>
<contrib-group><contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Salma</surname>
<given-names>I.</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>Ocskay</surname>
<given-names>R.</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>Láng</surname>
<given-names>G. G.</given-names>
</name>
<xref ref-type="aff" rid="aff1">
<sup>1</sup>
</xref>
</contrib>
</contrib-group><aff id="aff1">
<label>1</label>
<addr-line>Eötvös University, Institute of Chemistry, Budapest, Hungary</addr-line>
</aff>
<pub-date pub-type="epub">
<day>24</day>
<month>04</month>
<year>2008</year>
</pub-date>
<volume>8</volume>
<issue>8</issue>
<fpage>2243</fpage>
<lpage>2254</lpage>
<permissions>
<license xlink:type="simple">
<license-p>This is an open-access article ditributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.</license-p>
</license>
</permissions>
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<abstract>
<p>Urban-type PM&lt;sub&gt;2.5&lt;/sub&gt;-fraction aerosol samples were collected and samples of pure
atmospheric humic-like substances (HULIS) were isolated from them.
Atmospheric concentrations of organic carbon (OC), water soluble organic
carbon (WSOC) and HULIS were determined, and UV/Vis spectroscopic
properties, solubility and conductivity of HULIS in aqueous samples were
investigated. Atmospheric concentrations of OC and WSOC were 8.5 and 4.6 μg m&lt;sup&gt;&amp;minus;3&lt;/sup&gt;, respectively. Hydrophilic WSOC accounted for 39% of
WSOC, carbon in HULIS made up 47% of WSOC, and 14% of WSOC was
retained on the separation column by irreversible adsorption. Overall
average molecular mass and aromatic carbon abundance of HULIS were estimated
from molar absorptivity to be 556 Da and 12%, respectively. Both results
are substantially smaller than for standard reference fulvic acids, which
imply different mechanisms for the formation processes of atmospheric HULIS
and aquatic or terrestrial humic matter. HULIS were found to be water
soluble as ionic unimers with a saturation concentration of 2&amp;ndash;3 g l&lt;sup&gt;&amp;minus;1&lt;/sup&gt;.
Their solubility increased again with total HULIS concentration being above
approximately 4 g l&lt;sup&gt;&amp;minus;1&lt;/sup&gt;, which was most likely explained by the formation
of HULIS aggregates. Solubility increased linearly from approximately 5 up
to 20 g l&lt;sup&gt;&amp;minus;1&lt;/sup&gt; of dissolved HULIS concentration. The ionic dissolution was
confirmed by electrochemical conductivity in the investigated concentration
interval. Limiting molar conductivity was extrapolated and this was utilized
to determine the apparent dissociation degree of HULIS for different
concentrations. The dissociation degree was further applied to derive the
concentration dependence of the van&apos;t Hoff factor of HULIS. The van&apos;t Hoff
factor decreased monotonically with HULIS concentration; the decrease was
substantial for dilute solutions and the relationship became weak for rather
concentrated solutions.</p>
</abstract>
<counts><page-count count="12"/></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">Asa-Awuku, A., Sullivan, A. P., Hennigan, C. J., Weber, R. J., and Nenes, A.: Investigation of molar volume and surfactant characteristics of water-soluble organic compounds in biomass burning aerosol, Atmos. Chem. Phys., 8, 799&amp;ndash;812, 2008. </mixed-citation>
</ref>
<ref id="ref2">
<label>2</label><mixed-citation publication-type="other" xlink:type="simple">Baltensperger, U., Kalberer, M., Dommen, J., Paulsen, D., Alfarra, M.R., Coe, H., Fisseha, R., Gascho, A., Gysel, M., Nyeki, S., Sax, M., Steinbacher, M., Prevot, A. S. H., Sjögren, S., Weingartner, E., and Zenobi, R.: Secondary organic aerosols from anthropogenic and biogenic precursors, Faraday Discuss., 130, 265&amp;ndash;278, 2005. </mixed-citation>
</ref>
<ref id="ref3">
<label>3</label><mixed-citation publication-type="other" xlink:type="simple">Birch, M. E. and Cary, R. A.: Elemental carbon-based method for monitoring occupational exposures to particulate diesel exhaust, Aerosol Sci. Technol., 25, 221&amp;ndash;241, 1996. </mixed-citation>
</ref>
<ref id="ref4">
<label>4</label><mixed-citation publication-type="other" xlink:type="simple">Brown, T. L. and Rice, J. A.: Effect of experimental parameters on the ESI FT-ICR mass spectrum of fulvic acid, Anal. Chem., 72, 384&amp;ndash;390, 2000. </mixed-citation>
</ref>
<ref id="ref5">
<label>5</label><mixed-citation publication-type="other" xlink:type="simple">Cappiello, A., De Simoni, E., Fiorucci, C., Mangani, F., Palma, P., Trufelli, H., Decesari, S., Facchini, M. C., and Fuzzi, S.: Molecular characterization of water-soluble organic compounds in fogwater by ESIMS/MS, Environ. Sci. Technol., 37, 1229&amp;ndash;1240, 2003. </mixed-citation>
</ref>
<ref id="ref6">
<label>6</label><mixed-citation publication-type="other" xlink:type="simple">Chin, Y. P., Alken, G., and O&apos;Loughlin, E.: Molecular weight, polydispersity, and spectroscopic properties of aquatic humic substances, Environ. Sci. Technol., 28, 1853&amp;ndash;1858, 1994. </mixed-citation>
</ref>
<ref id="ref7">
<label>7</label><mixed-citation publication-type="other" xlink:type="simple">Decesari, S., Facchini, M. C., Fuzzi, S., and Tagliavini, E.: Characterization of water-soluble organic compounds in atmospheric aerosol: a new approach, J. Geophys. Res., D105, 1481&amp;ndash;1489, 2000. </mixed-citation>
</ref>
<ref id="ref8">
<label>8</label><mixed-citation publication-type="other" xlink:type="simple">Decesari, S., Facchini, M.C., Matta, E., Lettini, F., Mircea, M., Fuzzi, S., Tagliavini, E., and Putaud, J.-C.: Chemical features and seasonal variation of fine aerosol water-soluble organic compounds in the Po Valley, Italy, Atmos. Environ., 35, 3691&amp;ndash;3699, 2001. </mixed-citation>
</ref>
<ref id="ref9">
<label>9</label><mixed-citation publication-type="other" xlink:type="simple">Decesari, S., Facchini, M. C., Matta, E., Mircea, M., Fuzzi, S., Chughtai, A. R., and Smith, D. M.: Water soluble organic compounds formed by oxidation of soot, Atmos. Environ., 36, 1827&amp;ndash;1832, 2002. </mixed-citation>
</ref>
<ref id="ref10">
<label>10</label><mixed-citation publication-type="other" xlink:type="simple">Decesari, S., Fuzzi, S., Facchini, M. C., Mircea, M., Emblico, L., Cavalli, F., Maenhaut, W., Chi, X., Schkolnik, G., Falkovich, A., Rudich, Y., Claeys, M., Pashynska, V., Vas, G., Kourtchev, I., Vermeylen, R., Hoffer, A., Andreae, M. O., Tagliavini, E., Moretti, F., and Artaxo, P.: Characterization of the organic composition of aerosols from Rondônia, Brazil, during the LBA-SMOCC 2002 experiment and its representation through model compounds, Atmos. Chem. Phys., 6, 375&amp;ndash;402, 2006. </mixed-citation>
</ref>
<ref id="ref11">
<label>11</label><mixed-citation publication-type="other" xlink:type="simple">Dinar, E., Taraniuk, I., Graber, E. R., Katsman, S., Moise, T., Anttila, T., Mentel, T. F., and Rudich, Y.: Cloud condensation nuclei properties of model and atmospheric HULIS, Atmos. Chem. Phys., 6, 2465&amp;ndash;2482, 2006. </mixed-citation>
</ref>
<ref id="ref12">
<label>12</label><mixed-citation publication-type="other" xlink:type="simple">Dinar, E., Taraniuk, I., Graber, E. R., Anttila, T., Mentel, T. F., and Rudich, Y.: Hygroscopic growth of atmospheric and model humic-like substances, J. Geophys. Res., 112, D05211, doi:10.1029/2006JD007442, 2007. </mixed-citation>
</ref>
<ref id="ref13">
<label>13</label><mixed-citation publication-type="other" xlink:type="simple">Dinar, E., Riziq, A. A., Spindler, C., Erlick, C., Kiss, G., and Rudich, Y.: The complex refractive index of atmospheric and model humic-like substances (HULIS) retrieved by a cavity ring down aerosol spectrometer (CRD-AS), Faraday Discuss., 137, 279&amp;ndash;295, 2008. </mixed-citation>
</ref>
<ref id="ref14">
<label>14</label><mixed-citation publication-type="other" xlink:type="simple">Facchini, M. C., Mircea, M., Fuzzi, S., and Charlson, R. J.: Cloud albedo enhancement by surface-active organic solutes in growing droplets, Nature, 401, 257&amp;ndash;259, 1999. </mixed-citation>
</ref>
<ref id="ref15">
<label>15</label><mixed-citation publication-type="other" xlink:type="simple">Facchini, M. C., Decesari, S., Mircea, M., Fuzzi, S., and Loglio, G.: Surface tension of atmospheric wet aerosol and cloud/fog droplets in relation to their organic carbon content and chemical composition, Atmos. Environ., 34, 4853&amp;ndash;4857, 2000. </mixed-citation>
</ref>
<ref id="ref16">
<label>16</label><mixed-citation publication-type="other" xlink:type="simple">Fuzzi, S., Decesari, S., Facchini, M. C., Matta, E., Mircea, M., and Tagliavini, E.: A simplified model of the water soluble organic component of atmospheric aerosol, Geophys. Res. Lett., 20, 4079&amp;ndash;4082, 2001. </mixed-citation>
</ref>
<ref id="ref17">
<label>17</label><mixed-citation publication-type="other" xlink:type="simple">Fuzzi, S., Andreae, M. O., Huebert, B. J., Kulmala, M., Bond, T. C., Boy, M., Doherty, S. J., Guenther, A., Kanakidou, M., Kawamura, K., Kerminen, V.-M., Lohmann, U., Russell, L. M., and Pöschl, U.: Critical assessment of the current state of scientific knowledge, terminology, and research needs concerning the role of organic aerosols in the atmosphere, climate, and global change, Atmos. Chem. Phys., 6, 2017&amp;ndash;2038, 2006. </mixed-citation>
</ref>
<ref id="ref18">
<label>18</label><mixed-citation publication-type="other" xlink:type="simple">Gelencsér, A., Sallai, M., Krivácsy, Z., Kiss, G., and Mészáros, E.: Voltammetric evidence for the presence of humic-like substances in fog water, Atmos. Res., 54, 157&amp;ndash;165, 2000. </mixed-citation>
</ref>
<ref id="ref19">
<label>19</label><mixed-citation publication-type="other" xlink:type="simple">Gelencsér, A.: Carbonaceous Aerosol, Springer, Dordrecht, 2004. </mixed-citation>
</ref>
<ref id="ref20">
<label>20</label><mixed-citation publication-type="other" xlink:type="simple">Graber, E. R. and Rudich, Y.: Atmospheric HULIS: how humic-like are they? A comprehensive and critical review, Atmos. Chem. Phys., 5, 9801&amp;ndash;9860, 2006. </mixed-citation>
</ref>
<ref id="ref21">
<label>21</label><mixed-citation publication-type="other" xlink:type="simple">Graham, B., Mayol-Bracero, O. L., Guyon, P., Roberts, G. C., Decesari, S., Facchini, M. C., Artaxo, P., Maenhaut, W., Köll, P., and Andreae, M. O.: Water-soluble organic compounds in biomass burning aerosol over Amazonia, 1. Characterization by NMR and GC-MS, J. Geophys. Res., 107(D20), 8047, doi:10.1029/2001JD000336, 2002. </mixed-citation>
</ref>
<ref id="ref22">
<label>22</label><mixed-citation publication-type="other" xlink:type="simple">Gysel, M., Weingartner, E., Nyeki, S., Paulsen, D., Baltensperger, U., Galambos, I., and Kiss, G.: Hygroscopic properties of water-soluble matter and humic-like organics in atmospheric fine aerosol, Atmos. Chem. Phys., 4, 35&amp;ndash;50, 2004. </mixed-citation>
</ref>
<ref id="ref23">
<label>23</label><mixed-citation publication-type="other" xlink:type="simple">Havers, N., Burba, P., Lambert, J., and Klockow, D.: Spectroscopic characterisation of humic-like substances in airborne particulate matter, J. Atmos. Chem., 29, 45&amp;ndash;54, 1998. </mixed-citation>
</ref>
<ref id="ref24">
<label>24</label><mixed-citation publication-type="other" xlink:type="simple">Hantz, P., Partridge, J., Láng, G., Horvát, S., and Ujvári, M.: Ion-selective membranes involved in pattern-forming processes, J. Phys. Chem., B108, 18135&amp;ndash;18139, 2004. </mixed-citation>
</ref>
<ref id="ref25">
<label>25</label><mixed-citation publication-type="other" xlink:type="simple">Henning, S., Rosenørn, T., D&apos;Anna, B., Gola, A. A., Svenningsson, B., and Bilde, M.: Cloud droplet activation and surface tension of mixtures of slightly soluble organics and inorganic salt, Atmos. Chem. Phys., 5, 575&amp;ndash;582, 2005. </mixed-citation>
</ref>
<ref id="ref26">
<label>26</label><mixed-citation publication-type="other" xlink:type="simple">Kalberer, M., Paulsen, D., Sax, M., Steinbacher, M., Dommen, J., Prevot, A. S. H., Fisseha, R., Weingartner, E., Frankevich, V., Zenobi, R., and Baltensperger, U.: Identification of polymers as major components of atmospheric organic aerosols, Science, 303, 1659&amp;ndash;1662, 2004. </mixed-citation>
</ref>
<ref id="ref27">
<label>27</label><mixed-citation publication-type="other" xlink:type="simple">Kiss, G., Varga, B., Galambos, I., and Ganszky, I.: Characterization of water-soluble organic matter isolated from atmospheric fine aerosol, J. Geophys. Res., 107(D21), 8339, doi:10.1029/2001JD000603, 2002. </mixed-citation>
</ref>
<ref id="ref28">
<label>28</label><mixed-citation publication-type="other" xlink:type="simple">Kiss, G., Tombácz, E., Varga, B., Alsberg, T., and Persson, L.: Estimation of the average molecular weight of humic-like substances isolated from fine atmospheric aerosol, Atmos. Environ., 37, 3783&amp;ndash;3794, 2003. </mixed-citation>
</ref>
<ref id="ref29">
<label>29</label><mixed-citation publication-type="other" xlink:type="simple">Kiss, G., Tombácz, E., and Hansson, H.-C.: Surface tension effects of humic-like substances in the aqueous extract of troposphere fine aerosol, J. Atmos. Chem., 50, 279&amp;ndash;294, doi:10.1007/s10874&amp;ndash;005&amp;ndash;5079&amp;ndash;5, 2005. </mixed-citation>
</ref>
<ref id="ref30">
<label>30</label><mixed-citation publication-type="other" xlink:type="simple">Koehler, K. A., Kreidenweis, S. M., DeMott, P. J., Prenni, A. J., Carrico, C. M., Ervens, B., and Feingold, G.: Water activity and activation diameters from hygroscopicity data &amp;ndash; Part II: Application to organic species, Atmos. Chem. Phys., 6, 795&amp;ndash;809, 2006. </mixed-citation>
</ref>
<ref id="ref31">
<label>31</label><mixed-citation publication-type="other" xlink:type="simple">Krivácsy, Z., Kiss, G., Varga, B., Galambos, I., Sárvári, Z., Gelencsér, A., Molnár, A., Fuzzi, S., Facchini, M. C., Zappoli, S., Andracchio, A., Alsberg, T., Hansson, H.-C., and Persson, L.: Study of humic-like substances in fog and interstitial aerosol by size-exclusion chromatography and capillary electrophoresis, Atmos. Environ., 34, 4273&amp;ndash;4281, 2000. </mixed-citation>
</ref>
<ref id="ref32">
<label>32</label><mixed-citation publication-type="other" xlink:type="simple">Kujawinski, E. B., Hatcher, P. G., and Freitas, M. A.: High resolution Fourier transform ion cyclotron resonance mass spectrometry of humic and fulvic acids: Improvements and comparisons, Anal. Chem., 74, 413&amp;ndash;419, 2002. </mixed-citation>
</ref>
<ref id="ref33">
<label>33</label><mixed-citation publication-type="other" xlink:type="simple">Láng, G., Ujvári, M., and Inzelt, G.: Possible origin of the deviation from the expected impedance response of polymer film electrodes, Electrochim. Acta, 46, 4159&amp;ndash;4175, 2001. </mixed-citation>
</ref>
<ref id="ref34">
<label>34</label><mixed-citation publication-type="other" xlink:type="simple">Leenheer, J. A., Rostad, C. E., Gates, P. M., Furlong, E. T., and Ferrer, I.: Molecular resolution and fragmentation of fulvic acid by electrospray ionization/multistage tandem mass spectrometry, Anal. Chem., 73, 1461&amp;ndash;1471, 2001. </mixed-citation>
</ref>
<ref id="ref35">
<label>35</label><mixed-citation publication-type="other" xlink:type="simple">Limbeck, A., Kulmala, M., and Puxbaum, H.: Secondary organic aerosol formation in the atmosphere via heterogeneous reaction of gaseous isoprene on acidic particles, Geophys. Res. Lett., 30(19), 1996, doi:10.1029/2003GL017738, 2003. </mixed-citation>
</ref>
<ref id="ref36">
<label>36</label><mixed-citation publication-type="other" xlink:type="simple">Limbeck, A., Handler, M., Neuberger, B., Klatzer, B., and Puxbaum, H.: Carbon-specific analysis of humic-like substances in atmospheric aerosol and precipitation samples, Anal. Chem., 77, 7288&amp;ndash;7293, 2005. </mixed-citation>
</ref>
<ref id="ref37">
<label>37</label><mixed-citation publication-type="other" xlink:type="simple">Mayol-Bracero, O. L., Guyon, P., Graham, B., Roberts, G., Andreae, M. O., Decesari, S., Facchini, M. C., Fuzzi, S., and Artaxo, P.: Water-soluble organic compounds in biomass burning aerosols over Amazonia, 2. Apportionment of the chemical composition and importance of the polyacidic fraction, J. Geophys. Res., 107(D20), 8091, doi:10.1029/2001JD000522, 2002. </mixed-citation>
</ref>
<ref id="ref38">
<label>38</label><mixed-citation publication-type="other" xlink:type="simple">Mazurek, M. A., Masonjones, M. C., Masonjones, H. D., Salmon, L. G., Cass, G. R., Hallock, K. A., and Leach, M.: Visibility-reducing organic aerosols in the vicinity of Grand Canyon National Park: properties observed by high resolution gas chromatography, J. Geophys. Res., 102, 3779&amp;ndash;3793, 1997. </mixed-citation>
</ref>
<ref id="ref39">
<label>39</label><mixed-citation publication-type="other" xlink:type="simple">McFiggans, G., Artaxo, P., Baltensperger, U., Coe, H., Facchini, M.C., Feingold, G., Fuzzi, S., Gysel, M., Laaksonen, A., Lohmann, U., Mentel, T. F., Murphy, D. M., O&apos;Dowd, C.D., Snider, J. R., and Weingartner, E.: The effect of physical and chemical aerosol properties on warm cloud droplet activation, Atmos. Chem. Phys., 6, 2593&amp;ndash;2649, 2006. </mixed-citation>
</ref>
<ref id="ref40">
<label>40</label><mixed-citation publication-type="other" xlink:type="simple">Peuravuori, J. and Pihlaja, K.: Molecular size distribution and spectroscopic properties of aquatic humic substances, Anal. Chim. Acta, 337, 133&amp;ndash;149, 1997. </mixed-citation>
</ref>
<ref id="ref41">
<label>41</label><mixed-citation publication-type="other" xlink:type="simple">Puxbaum, H., Rendl, J., Allabashi, R., Otter, L., and Scholes M. C.: Mass balance of atmospheric aerosol in a South-African subtropical savanna (Nylsvley, May 1997), J. Geophys. Res., 105, 20697&amp;ndash;20706, 2000. </mixed-citation>
</ref>
<ref id="ref42">
<label>42</label><mixed-citation publication-type="other" xlink:type="simple">Puxbaum, H. and Tenze-Kunit, M.: Size distribution and seasonal variation of atmospheric cellulose, Atmos. Environ., 37, 3693&amp;ndash;3699, 2003. </mixed-citation>
</ref>
<ref id="ref43">
<label>43</label><mixed-citation publication-type="other" xlink:type="simple">Raymond, T. R. and Pandis, S. N.: Cloud activation of single-component organic aerosol particles, J. Geophys. Res., 107(D24), 4787, doi:10.1029/2002JD002159, 2002. </mixed-citation>
</ref>
<ref id="ref44">
<label>44</label><mixed-citation publication-type="other" xlink:type="simple">Rogge, W. F., Mazurek, M. A., Hildemann, L. M., and Cass, G. R.: Quantification of urban organic aerosols at a molecular level: Identification, abundance and seasonal variation, Atmos. Environ., 27A, 1309&amp;ndash;1330, 1993. </mixed-citation>
</ref>
<ref id="ref45">
<label>45</label><mixed-citation publication-type="other" xlink:type="simple">Schauer, J. J., Mader, B. T., DeMinter, J. T., Heidemann, G., Bae, M. S., Seinfeld, J. H., Flagan, R. C., Cary, R. A., Smith, D., Huebert, B. J., Bertram, T., Howell, S., Quinn, P., Bates, T., Turpin, B., Lim, H. J., Yu, J., and Yang, H.: ACE-Asia Intercomparison of a thermal optical method for the determination of particle-phase organic and elemental carbon, Environ. Sci. Technol., 37, 993&amp;ndash;1001, 2003. </mixed-citation>
</ref>
<ref id="ref46">
<label>46</label><mixed-citation publication-type="other" xlink:type="simple">Salma, I., Chi, X., and Maenhaut, W.: Elemental and organic carbon in urban canyon and background environments in Budapest, Hungary, Atmos. Environ., 38, 27&amp;ndash;36, 2004. </mixed-citation>
</ref>
<ref id="ref47">
<label>47</label><mixed-citation publication-type="other" xlink:type="simple">Salma, I., Ocskay, R., Varga, I., and Maenhaut, W.: Surface tension of atmospheric humic-like substances in connection with relaxation, dilution, and solution pH, J. Geophys. Res., 111, D23205, doi:10.1029/2005JD007015, 2006. </mixed-citation>
</ref>
<ref id="ref48">
<label>48</label><mixed-citation publication-type="other" xlink:type="simple">Salma, I. Ocskay, R., Chi, X., and Maenhaut, W.: Sampling artefacts, concentrations and chemical composition of fine water-soluble organic carbon and humic-like substances in a continental urban atmospheric environment, Atmos. Environ., 41, 4106&amp;ndash;4118, 2007. </mixed-citation>
</ref>
<ref id="ref49">
<label>49</label><mixed-citation publication-type="other" xlink:type="simple">Samburova, V., Zenobi, R., and Kalberer, M.: Characterization of high molecular weight compounds in urban atmospheric particles, Atmos. Chem. Phys., 5, 2163&amp;ndash;2170, 2005. </mixed-citation>
</ref>
<ref id="ref50">
<label>50</label><mixed-citation publication-type="other" xlink:type="simple">Samburova, V., Didenko, T., Kunenkov, E., Emmenegger, Ch., Zenobi, R., and Kalberer, M.: Functional group analysis of high-molecular weight compounds in the water-soluble fraction of organic aerosols, Atmos. Environ., 41, 4703&amp;ndash;4710, 2007. </mixed-citation>
</ref>
<ref id="ref51">
<label>51</label><mixed-citation publication-type="other" xlink:type="simple">Saxena, P. and Hildemann, L. M.: Water-soluble organics in atmospheric particles: A critical review of the literature and application of thermodynamics to identify candidate compounds, J. Atmos. Chem., 24, 57&amp;ndash;109, 1996. </mixed-citation>
</ref>
<ref id="ref52">
<label>52</label><mixed-citation publication-type="other" xlink:type="simple">Schäfer, A. I., Mauch, R., Waite, T. D., and Fane, A. G.: Charge effects in the fractionation of natural organics using ultrafiltration, Environ. Sci. Technol., 36, 2572&amp;ndash;2580, 2002. </mixed-citation>
</ref>
<ref id="ref53">
<label>53</label><mixed-citation publication-type="other" xlink:type="simple">Sullivan, A. P. and Weber, R. J.: Chemical characterization of the ambient organic aerosol soluble in water: 1. Isolation of hydrophobic and hydrophilic fractions with a XAD-8 resin, J. Geophys. Res., 111, D05314, doi:10.1029/2005JD006485, 2006a. </mixed-citation>
</ref>
<ref id="ref54">
<label>54</label><mixed-citation publication-type="other" xlink:type="simple">Sullivan, A. P. and Weber, R. J.: Chemical characterization of the ambient organic aerosol soluble in water: 2. Isolation of acid, neutral, and basic fractions by modified size-exclusion chromatography, J. Geophys. Res., 111, D05315, doi:10.1029/2005JD006486, 2006b. </mixed-citation>
</ref>
<ref id="ref55">
<label>55</label><mixed-citation publication-type="other" xlink:type="simple">Surratt, J. D., Kroll, J. H., Kleindienst, T. E., Edney, E. O., Claeys, M., Sorooshian, A., Ng, N. L., Offenberg, J. H., Lewandowski, M., Jaoui, M., and Seinfeld, J. H.: Evidence for organosulfates in secondary organic aerosol, Environ. Sci. Techn., 42, 517&amp;ndash;527, doi:10.1021/es062081q, 2007. </mixed-citation>
</ref>
<ref id="ref56">
<label>56</label><mixed-citation publication-type="other" xlink:type="simple">Svenningsson, B., Rissler, J., Swietlicki, E., Mircea, M., Bilde, M., Facchini,M. C., Decesari, S., Fuzzi, S., Zhou, J., Mønster, J., and Rosenørn, T.: Hygroscopic growth and critical supersaturations for mixed aerosol particles of inorganic and organic compounds of atmospheric relevance, Atmos. Chem. Phys., 6, 1937&amp;ndash;1952, 2006. </mixed-citation>
</ref>
<ref id="ref57">
<label>57</label><mixed-citation publication-type="other" xlink:type="simple">Szidat, S., Jenk, T. M., Gäggeler, H. W., Synal, H.-A., Fisseha, R., Baltensperger, U., Kalberer, M., Samburova, V., Reimann, S., and Hajdas, I.: Radiocarbon ($^14$C)-deduced biogenic and anthropogenic contributions to organic carbon (OC) of urban aerosols from Zürich, Switzerland, Atmos. Environ., 38, 4035&amp;ndash;4044, 2004. </mixed-citation>
</ref>
<ref id="ref58">
<label>58</label><mixed-citation publication-type="other" xlink:type="simple">Tabazadeh, A.: Organic aggregate formation in aerosols and its impact on the physicochemical properties of atmospheric particles, Atmos. Environ., 39, 5472&amp;ndash;5480, 2005. </mixed-citation>
</ref>
<ref id="ref59">
<label>59</label><mixed-citation publication-type="other" xlink:type="simple">Tagliavini, E., Moretti, F., Decesari, S., Facchini, M. C., Fuzzi, S., and Maenhaut, W.: Functional group analysis by H NMR/chemical derivatization for the characterization of organic aerosol from the SMOCC field campaign, Atmos. Chem. Phys., 6, 1003&amp;ndash;1019, 2005. </mixed-citation>
</ref>
<ref id="ref60">
<label>60</label><mixed-citation publication-type="other" xlink:type="simple">Taraniuk, I., Graber, E. R., Kostinski, A., and Rudich, Y.: Surface tension and diffusion coefficients of atmospheric and model humic like species (HULIS), Geophys. Res. Lett., 34, L16807, doi:16810.11029/12007GL029576, 2007. </mixed-citation>
</ref>
<ref id="ref61">
<label>61</label><mixed-citation publication-type="other" xlink:type="simple">Tombácz, E.: Colloidal properties of humic acids and spontaneous change of their colloidal state under variable solution conditions, Soil Sci., 164, 814&amp;ndash;824, 1999. </mixed-citation>
</ref>
<ref id="ref62">
<label>62</label><mixed-citation publication-type="other" xlink:type="simple">Traina, S. J., Novak, J., and Smeck, N. E.: An ultraviolet absorbance method of estimating the percent aromatic carbon content of humic acids, J. Environ. Qual., 19, 151&amp;ndash;153, 1990. </mixed-citation>
</ref>
<ref id="ref63">
<label>63</label><mixed-citation publication-type="other" xlink:type="simple">Varga, B., Kiss, G., Ganszky, I., Gelencsér, A., and Krivácsy, Z.: Isolation of water soluble organic matter from atmospheric aerosol, Talanta, 55, 561&amp;ndash;572, 2001. </mixed-citation>
</ref>
<ref id="ref64">
<label>64</label><mixed-citation publication-type="other" xlink:type="simple">Varga, Z., Kiss, G., and Hansson, H.-C.: Modelling the cloud condensation nucleus activity of organic acids on the basis of surface tension and osmolality measurements, Atmos. Chem. Phys., 7, 4601&amp;ndash;4611, 2007. </mixed-citation>
</ref>
<ref id="ref65">
<label>65</label><mixed-citation publication-type="other" xlink:type="simple">Wex, H., Hennig, T., Salma, I., Ocskay, R., Kiselev, A., Henning, S., Massling, A., Wiedensohler, A., and Stratmann, F.: Hygroscopic growth and measured and modeled critical supersaturations of an atmospheric HULIS sample, Geophys. Res. Lett., 34, L02818, doi:10.1029/2006GL028260, 2007. </mixed-citation>
</ref>
<ref id="ref66">
<label>66</label><mixed-citation publication-type="other" xlink:type="simple">Zappoli, S., Andracchio, A., Fuzzi, S., Facchini, M. C., Gelencsér, A., Kiss, G., Krivácsy, Z., Molnár, A., Mészáros, E., Hansson, H.-C., and Rosman, K.: Inorganic, organic and macromolecular components of fine aerosol in different areas of Europe in relation to their water solubility, Atmos. Environ., 33, 2733&amp;ndash;2743, 1999. </mixed-citation>
</ref>
<ref id="ref67">
<label>67</label><mixed-citation publication-type="other" xlink:type="simple">Ziese, M., Wex, H., Nilsson, E., Salma, I., Ocskay, R., Hennig, T., Massling, A., and Stratmann, F.: Hygroscopic growth and activation of HULIS particles: experimental data and a new iterative parameterization scheme for complex aerosol particles, Atmos. Chem. Phys., 8, 1855&amp;ndash;1866, 2008. </mixed-citation>
</ref>
</ref-list>
</back>
</article>