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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-7-4237-2007</article-id>
<title-group>
<article-title>Light induced conversion of nitrogen dioxide into nitrous acid on submicron humic acid aerosol</article-title>
</title-group>
<contrib-group><contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Stemmler</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>Ndour</surname>
<given-names>M.</given-names>
</name>
<xref ref-type="aff" rid="aff2">
<sup>2</sup>
</xref>
</contrib>
<contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Elshorbany</surname>
<given-names>Y.</given-names>
</name>
<xref ref-type="aff" rid="aff3">
<sup>3</sup>
</xref>
<xref ref-type="aff" rid="aff4">
<sup>4</sup>
</xref>
</contrib>
<contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Kleffmann</surname>
<given-names>J.</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>D&apos;Anna</surname>
<given-names>B.</given-names>
</name>
<xref ref-type="aff" rid="aff2">
<sup>2</sup>
</xref>
</contrib>
<contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>George</surname>
<given-names>C.</given-names>
</name>
<xref ref-type="aff" rid="aff2">
<sup>2</sup>
</xref>
</contrib>
<contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Bohn</surname>
<given-names>B.</given-names>
</name>
<xref ref-type="aff" rid="aff5">
<sup>5</sup>
</xref>
</contrib>
<contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Ammann</surname>
<given-names>M.</given-names>
</name>
<xref ref-type="aff" rid="aff1">
<sup>1</sup>
</xref>
</contrib>
</contrib-group><aff id="aff1">
<label>1</label>
<addr-line>Laboratory of Radio- and Environmental Chemistry, Paul Scherrer Institut, 5232 Villigen, Switzerland</addr-line>
</aff>
<aff id="aff2">
<label>2</label>
<addr-line>Université de Lyon, Université Lyon 1, CNRS, UMR5256, IRCELYON, Institut de recherches sur  la catalyse et l&apos;environnement de Lyon, Villeurbanne, 69626, France</addr-line>
</aff>
<aff id="aff3">
<label>3</label>
<addr-line>Physikalische Chemie/FB C, Bergische Universität Wuppertal, 42097 Wuppertal, Germany</addr-line>
</aff>
<aff id="aff4">
<label>4</label>
<addr-line>National Research Centre, Dokki, Giza, Egypt</addr-line>
</aff>
<aff id="aff5">
<label>5</label>
<addr-line>Institut für Chemie und Dynamik der Geosphäre 2: Troposphäre, Forschungszentrum Jülich, 52425 Jülich, Germany</addr-line>
</aff>
<pub-date pub-type="epub">
<day>20</day>
<month>08</month>
<year>2007</year>
</pub-date>
<volume>7</volume>
<issue>16</issue>
<fpage>4237</fpage>
<lpage>4248</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>
<self-uri xlink:href="http://www.atmos-chem-phys.net/7/4237/2007/acp-7-4237-2007.html">This article is available from http://www.atmos-chem-phys.net/7/4237/2007/acp-7-4237-2007.html</self-uri>
<self-uri xlink:href="http://www.atmos-chem-phys.net/7/4237/2007/acp-7-4237-2007.pdf">The full text article is available as a PDF file from http://www.atmos-chem-phys.net/7/4237/2007/acp-7-4237-2007.pdf</self-uri>
<abstract>
<p>The interactions of aerosols consisting of humic acids with gaseous nitrogen
dioxide (NO&lt;sub&gt;2&lt;/sub&gt;) were investigated under different light conditions in
aerosol flow tube experiments at ambient pressure and temperature. The
results show that NO&lt;sub&gt;2&lt;/sub&gt; is converted on the humic acid aerosol into
nitrous acid (HONO), which is released from the aerosol and can be detected
in the gas phase at the reactor exit. The formation of HONO on the humic
acid aerosol is strongly activated by light: In the dark, the HONO-formation
was below the detection limit, but it was increasing with the intensity of
the irradiation with visible light. Under simulated atmospheric conditions
with respect to the actinic flux, relative humidity and
NO&lt;sub&gt;2&lt;/sub&gt;-concentration, reactive uptake coefficients &amp;gamma;&lt;sub&gt;rxn&lt;/sub&gt; for the
NO&lt;sub&gt;2&lt;/sub&gt;&amp;rarr;HONO conversion on the aerosol between &amp;gamma;&lt;sub&gt;rxn&lt;/sub&gt;
&amp;lt;10&lt;sup&gt;&amp;minus;7&lt;/sup&gt; (in the dark) and &amp;gamma;&lt;sub&gt;rxn&lt;/sub&gt;=6&amp;times;10&lt;sup&gt;&amp;minus;6&lt;/sup&gt; were observed.
The observed uptake coefficients decreased with increasing
NO&lt;sub&gt;2&lt;/sub&gt;-concentration in the range from 2.7 to 280 ppb and were dependent
on the relative humidity (RH) with slightly reduced values at low humidity
(&amp;lt;20% RH) and high humidity (&amp;gt;60% RH). The measured uptake
coefficients for the NO&lt;sub&gt;2&lt;/sub&gt;&amp;rarr;HONO conversion are too low to
explain the HONO-formation rates observed near the ground in rural and urban
environments by the conversion of NO&lt;sub&gt;2&lt;/sub&gt;&amp;rarr;HONO on organic
aerosol surfaces, even if one would assume that all aerosols consist of
humic acid only. It is concluded that the processes leading to HONO formation on the Earth
surface will have a much larger impact on the HONO-formation in the
lowermost layer of the troposphere than humic materials potentially
occurring in airborne particles.</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"> Acker, K., Febo, A., Trick, S., Perrino, C., Bruno, P., Wiesen, P., Möller, D., Wieprecht, W., Auel, R., Giusto, M., Geyer, A., Platt, U., and Allegrini, I.: Nitrous acid in the urban area of Rome, Atmos. Environ., 40, 3123&amp;ndash;3133, 2006a. </mixed-citation>
</ref>
<ref id="ref2">
<label>2</label><mixed-citation publication-type="other" xlink:type="simple"> Acker, K., Möller, D., Wieprecht, W., Meixner, F. X., Bohn, B., Gilge, S., Plass-Dülmer, C., and Berresheim, H.: Strong daytime production of OH from HNO&lt;sub&gt;2&lt;/sub&gt; at a rural mountain site, Geophys. Res. Lett., 33, L02809, doi:10.1029/2005GL024643, 2006b. </mixed-citation>
</ref>
<ref id="ref3">
<label>3</label><mixed-citation publication-type="other" xlink:type="simple"> Alicke, B., Platt, U., and Stutz, J.: Impact of nitrous acid photolysis on the total hydroxyl radical budget during the Limitation of Oxidant Production/Pianura Padana Produzione di Ozono study in Milan, J. Geophys. Res., 107(D22), 8196, doi:10.1029/2000JD000075, 2002. </mixed-citation>
</ref>
<ref id="ref4">
<label>4</label><mixed-citation publication-type="other" xlink:type="simple"> Alicke, B., Geyer, A., Hofzumahaus, A., Holland, F., Konrad, S., Pätz, H.W., Schäfer, J., Stutz, J., Volz-Thomas, A., and Platt, U.: OH formation by HONO photolysis during the BERLIOZ experiment, J. Geophys. Res., 108(D4), 8247, doi:10.1029/2001JD000579, 2003. </mixed-citation>
</ref>
<ref id="ref5">
<label>5</label><mixed-citation publication-type="other" xlink:type="simple"> Ammann, M., Pöschl, U., and Rudich, Y.: Effects of reversible adsorption and Langmuir-Hinshelwood surface reactions on gas uptake by atmospheric particles, Phys. Chem. Chem. Phys., 5, 351&amp;ndash;356, 2003. </mixed-citation>
</ref>
<ref id="ref6">
<label>6</label><mixed-citation publication-type="other" xlink:type="simple"> Ammann, M., Rössler, E., Strekowski, R., and George, C.: Nitrogen dioxide multiphase chemistry: Uptake kinetics on aqueous solutions containing phenolic compounds, Phys. Chem. Chem. Phys., 7, 2513&amp;ndash;2518, 2005. </mixed-citation>
</ref>
<ref id="ref7">
<label>7</label><mixed-citation publication-type="other" xlink:type="simple"> Arens, F., Gutzwiller, L., Baltensperger, U., Gäggeler, H. W., and Ammann, M.: Heterogeneous reaction of NO&lt;sub&gt;2&lt;/sub&gt; on diesel soot particles, Environ. Sci. Technol., 35, 2191&amp;ndash;2199, 2001. </mixed-citation>
</ref>
<ref id="ref8">
<label>8</label><mixed-citation publication-type="other" xlink:type="simple"> Arens, F., Gutzwiller, L., Gäggeler, H. W., and Ammann, M.: The reaction of NO&lt;sub&gt;2&lt;/sub&gt; with solid anthrarobin (1,2,10-trihydroxy- anthracene), Phys. Chem. Chem. Phys., 4, 3684&amp;ndash;3690, 2002. </mixed-citation>
</ref>
<ref id="ref9">
<label>9</label><mixed-citation publication-type="other" xlink:type="simple"> Aumont, B., Chervier, F., and Laval, S.: Contribution of HONO sources to the NO&lt;sub&gt;x&lt;/sub&gt;/HO&lt;sub&gt;x&lt;/sub&gt;/O&lt;sub&gt;3&lt;/sub&gt; chemistry in the polluted boundary layer, Atmos. Environ., 37, 487&amp;ndash;498, 2003. </mixed-citation>
</ref>
<ref id="ref10">
<label>10</label><mixed-citation publication-type="other" xlink:type="simple"> Badger, C. L., George, I., Griffiths, P. T., Braban, C. F., Cox, R. A., and Abbatt, J. P. D.: Phase transitions and hygroscopic growth of aerosol particles containing humic acid and mixtures of humic acid and ammonium sulphate, Atmos. Chem. Phys., 6, 755&amp;ndash;768, 2006. </mixed-citation>
</ref>
<ref id="ref11">
<label>11</label><mixed-citation publication-type="other" xlink:type="simple"> Batjes, N. H.: Total carbon and nitrogen in the soils of the world, Eur. J. Soil Sci., 47, 151&amp;ndash;163, 1996. </mixed-citation>
</ref>
<ref id="ref12">
<label>12</label><mixed-citation publication-type="other" xlink:type="simple"> Behnke, W., George, C., Scheer, V., and Zetzsch, C.: Production and decay of ClNO&lt;sub&gt;2&lt;/sub&gt; from the reaction of gaseous N&lt;sub&gt;2&lt;/sub&gt;O$_5$ with NaCl solution: bulk and aerosol experiments, J. Geophys. Res., 102, 3795&amp;ndash;3804, 1997. </mixed-citation>
</ref>
<ref id="ref13">
<label>13</label><mixed-citation publication-type="other" xlink:type="simple"> Bongartz, A., Kames, J., Schurath, U., George, C., Mirabel, P., and Ponche, J.L.: Experimental-determination of HONO mass accommodation coefficients using 2 different techniques, J. Atmos. Chem., 18, 149&amp;ndash;169, 1994. </mixed-citation>
</ref>
<ref id="ref14">
<label>14</label><mixed-citation publication-type="other" xlink:type="simple"> Bröske, R., Kleffmann, J., and Wiesen, P.: Heterogeneous conversion of NO&lt;sub&gt;2&lt;/sub&gt; on secondary organic aerosol surfaces: A possible source of nitrous acid (HONO) in the atmosphere?, Atmos. Chem. Phys., 3, 469&amp;ndash;474, 2003. </mixed-citation>
</ref>
<ref id="ref15">
<label>15</label><mixed-citation publication-type="other" xlink:type="simple"> Cooney, D. O., Kim, S. S., and Davis, E. J.: Analyses of mass-transfer in hemodialyzers for laminar blood-flow and homogeneous dialysate, Chem. Eng. Sci., 29, 1731&amp;ndash;1738, 1974. </mixed-citation>
</ref>
<ref id="ref16">
<label>16</label><mixed-citation publication-type="other" xlink:type="simple"> Da Silva, G., Kennedy, E. M., and Dlugogorski, B. Z.: Ab initio procedure for aqueous-phase pKa calculation: The acidity of nitrous acid, J. Phys. Chem. A, 110, 11 371&amp;ndash;11 376, 2006. </mixed-citation>
</ref>
<ref id="ref17">
<label>17</label><mixed-citation publication-type="other" xlink:type="simple"> Dahmann, D., Riediger, G., Schlatter, J., Wiedensohler, A., Carli, S., Graff, A., Grosser, M., Hojgr, M., Horn, H. G., Jing, L., Matter, U., Monz, C., Mosimann, T., Stein, H., Wehner, B., and Wieser, U.: Intercomparison of mobility particle sizers (MPS), Gefahrstoffe Reinhaltung der Luft, 61, 423&amp;ndash;428, 2001. </mixed-citation>
</ref>
<ref id="ref18">
<label>18</label><mixed-citation publication-type="other" xlink:type="simple"> Finlayson-Pitts, B. J., Wingen, L. M., Sumner, A. L., Syomin, D., and Ramazan, K. A.: The heterogeneous hydrolysis of NO&lt;sub&gt;2&lt;/sub&gt; in laboratory systems and in outdoor and indoor atmospheres: An integrated mechanism, Phys. Chem. Chem. Phys., 5, 223&amp;ndash;242, 2003. </mixed-citation>
</ref>
<ref id="ref19">
<label>19</label><mixed-citation publication-type="other" xlink:type="simple"> Fitzer, E. and Fritz, W.: Technische Chemie: Einführung in die Chemische Reaktionstechnik, Springer-Verlag, Berlin, 1989. </mixed-citation>
</ref>
<ref id="ref20">
<label>20</label><mixed-citation publication-type="other" xlink:type="simple"> Gelencser, A., Hoffer, A., Kiss, G., Tombacz, E., Kurdi, R., and Bencze, L.: In-situ formation of light-absorbing organic matter in cloud water, J. Atmos. Chem. 45, 25&amp;ndash;33, 2003. </mixed-citation>
</ref>
<ref id="ref21">
<label>21</label><mixed-citation publication-type="other" xlink:type="simple"> George, C., Strekowski, R. S., Kleffmann, J., Stemmler, K., and Ammann, M.: Photoenhanced uptake of gaseous NO&lt;sub&gt;2&lt;/sub&gt; on solid organic compounds: A photochemical source of HONO?, Faraday Discuss., 130, 195&amp;ndash;210, 2005. </mixed-citation>
</ref>
<ref id="ref22">
<label>22</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., 6, 729&amp;ndash;753, 2006. </mixed-citation>
</ref>
<ref id="ref23">
<label>23</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="ref24">
<label>24</label><mixed-citation publication-type="other" xlink:type="simple"> Harrison, R. M., Peak, J. D., and Collins, G. M.: Tropospheric cycle of nitrous acid, J. Geophys. Res., 101, 14 429&amp;ndash;14 439, 1996. </mixed-citation>
</ref>
<ref id="ref25">
<label>25</label><mixed-citation publication-type="other" xlink:type="simple"> Heland, J., Kleffmann, J., Kurtenbach, R., and Wiesen, P.: A new instrument to measure gaseous nitrous acid (HONO) in the atmosphere, Environ. Sci. Technol., 35, 3207&amp;ndash;3212, 2001. </mixed-citation>
</ref>
<ref id="ref26">
<label>26</label><mixed-citation publication-type="other" xlink:type="simple"> Hofzumahaus, A., Kraus, A., and Müller, M.: Solar actinic flux spectroradiometry: a technique for measuring photolysis frequencies in the atmosphere, Appl. Opt., 38, 4443&amp;ndash;4460, 1999. </mixed-citation>
</ref>
<ref id="ref27">
<label>27</label><mixed-citation publication-type="other" xlink:type="simple"> Honrath, R. E., Lu, Y., Peterson, M. C., Dibb, J. E., Arsenault, M. A., Cullen, N. J., and Steffen, K.: Vertical fluxes of NO&lt;sub&gt;x&lt;/sub&gt;, HONO, and HNO&lt;sub&gt;3&lt;/sub&gt; above the snowpack at Summit, Greenland, Atmos. Environ., 36, 2629&amp;ndash;2640, 2002. </mixed-citation>
</ref>
<ref id="ref28">
<label>28</label><mixed-citation publication-type="other" xlink:type="simple"> Hueglin, C., Gehrig, R., Baltensperger, U., Gysel, M., Monn, C., and Vonmont, H.: Chemical characterisation of PM2.5, PM10 and coarse particles at urban, near-city and rural sites in Switzerland, Atmos. Environ., 39, 637&amp;ndash;651, 2005. </mixed-citation>
</ref>
<ref id="ref29">
<label>29</label><mixed-citation publication-type="other" xlink:type="simple"> IPCC: Climate Change 2001: The Scientific Basis. Chapter 3, Cambridge University Press, Cambridge, 2001. </mixed-citation>
</ref>
<ref id="ref30">
<label>30</label><mixed-citation publication-type="other" xlink:type="simple"> Jang, M. S., Czoschke, N. M., Lee, S., and Kamens, R. M.: Heterogeneous atmospheric aerosol production by acid-catalyzed particle-phase reactions, Science, 298, 814&amp;ndash;817, 2002. </mixed-citation>
</ref>
<ref id="ref31">
<label>31</label><mixed-citation publication-type="other" xlink:type="simple"> Janzen, H. H.: Carbon cycling in earth systems &amp;ndash; a soil science perspective, Agric. Ecosyst. Environ., 104, 399&amp;ndash;417, 2004. </mixed-citation>
</ref>
<ref id="ref32">
<label>32</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="ref33">
<label>33</label><mixed-citation publication-type="other" xlink:type="simple"> Kleffmann, J., Heland, J., Kurtenbach, R., Lörzer, J., and Wiesen, P.: A new instrument (LOPAP) for the detection of nitrous acid (HONO), Environ. Sci. Pollut. Res., 9 (special issue 4), 48&amp;ndash;54, 2002. </mixed-citation>
</ref>
<ref id="ref34">
<label>34</label><mixed-citation publication-type="other" xlink:type="simple"> Kleffmann, J., Kurtenbach, R., Lörzer, J., Wiesen, P., Kalthoff, N., Vogel, B., and Vogel, H.: Measured and simulated vertical profiles of nitrous acid &amp;ndash; Part I: Field measurements, Atmos. Environ., 37, 2949&amp;ndash;2955, 2003. </mixed-citation>
</ref>
<ref id="ref35">
<label>35</label><mixed-citation publication-type="other" xlink:type="simple"> Kleffmann, J., Gavriloaeiei, T., Hofzumahaus, A., Holland, F., Koppmann, R., Rupp, L., Schlosser, E., Siese, M., and Wahner, A.: Daytime formation of nitrous acid: A major source of OH radicals in a forest, Geophys. Res. Lett., 32, L05818, doi:10.1029/2005GL022524, 2005. </mixed-citation>
</ref>
<ref id="ref36">
<label>36</label><mixed-citation publication-type="other" xlink:type="simple"> Kleffmann, J., Lörzer, J. C., Wiesen, P., Kern, C., Trick, S., Volkamer, R., Rodenas, M., and Wirtz, K.: Intercomparison of the DOAS and LOPAP techniques for the detection of nitrous acid (HONO), Atmos. Environ., 40, 3640&amp;ndash;3652, 2006. </mixed-citation>
</ref>
<ref id="ref37">
<label>37</label><mixed-citation publication-type="other" xlink:type="simple"> Merienne, M. F., Jenouvrier, A., and Coquart, B.: The NO&lt;sub&gt;2&lt;/sub&gt; absorption-spectrum. 1. Absorption cross-sections at ambient-temperature in the 300&amp;ndash;500 nm Region, J. Atmos. Chem., 20, 281&amp;ndash;297, 1995. </mixed-citation>
</ref>
<ref id="ref38">
<label>38</label><mixed-citation publication-type="other" xlink:type="simple"> Murphy, D. M. and Fahey, D. W.: Mathematical treatment of the wall loss of a trace species in denuder and catalytic-converter tubes, Anal. Chem., 59, 2753&amp;ndash;2759, 1987. </mixed-citation>
</ref>
<ref id="ref39">
<label>39</label><mixed-citation publication-type="other" xlink:type="simple"> NCAR: Tropospheric Ultraviolet and Visible Radiation Model (TUV), National Center for Atmospheric Research, Boulder, CO, USA (http://cprm.acd.ucar.edu/Models/TUV/), 2006. </mixed-citation>
</ref>
<ref id="ref40">
<label>40</label><mixed-citation publication-type="other" xlink:type="simple"> Park, J.-Y. and Lee, Y.-N.: Solubility and decomposition kinetics of nitrous acid in aqueous solution, J. Phys. Chem., 92, 6294&amp;ndash;6302, 1988. </mixed-citation>
</ref>
<ref id="ref41">
<label>41</label><mixed-citation publication-type="other" xlink:type="simple"> Pöschl, U., Letzel, T., Schauer, C., and Niessner, R.: Interaction of ozone and water vapor with spark discharge soot aerosol particles coated with benzo[a]pyrene: O&lt;sub&gt;3&lt;/sub&gt; and H&lt;sub&gt;2&lt;/sub&gt;O adsorption, benzo[a]pyrene degradation, and atmospheric implications, J. Phys. Chem. A, 105, 4029&amp;ndash;4041, 2001. </mixed-citation>
</ref>
<ref id="ref42">
<label>42</label><mixed-citation publication-type="other" xlink:type="simple"> Putaud, J. P., Raes, F., Van Dingenen, R., Brüggemann, E., Facchini, M. C., Decesari, S., Fuzzi, S., Gehrig, R., Hueglin, C., Laj, P., Lorbeer, G., Maenhaut, W., Mihalopoulos, N., Müller, K., Querol, X., Rodriguez, S., Schneider, J., Spindler, G., ten Brink, H., Torseth, K., and Wiedensohler, A.: European aerosol phenomenology-2: chemical characteristics of particulate matter at kerbside, urban, rural and background sites in Europe, Atmos. Environ., 38, 2579&amp;ndash;2595, 2004. </mixed-citation>
</ref>
<ref id="ref43">
<label>43</label><mixed-citation publication-type="other" xlink:type="simple"> Ren, X. R., Harder, H., Martinez, M., Lesher, R. L., Oliger, A., Simpas, J. B., Brune, W. H., Schwab, J. J., Demerjian, K. L., He, Y., Zhou, X. L., and Gao, H. G.: OH and HO&lt;sub&gt;2&lt;/sub&gt; chemistry in the urban atmosphere of New York City, Atmos. Environ., 37, 3639&amp;ndash;3651, 2003. </mixed-citation>
</ref>
<ref id="ref44">
<label>44</label><mixed-citation publication-type="other" xlink:type="simple"> Ren, X. R., Brune, W. H., Mao, J. Q., Mitchell, M. J., Lesher, R. L., Simpas, J. B., Metcalf, A. R., Schwab, J. J., Cai, C. X., Li, Y. Q., Demerjian, K. L., Felton, H.D., Boynton, G., Adams, A., Perry, J., He, Y., Zhou, X. L., and Hou, J.: Behavior of OH and HO&lt;sub&gt;2&lt;/sub&gt; in the winter atmosphere in New York city, Atmos. Environ., 40, S252&amp;ndash;S263, 2006. </mixed-citation>
</ref>
<ref id="ref45">
<label>45</label><mixed-citation publication-type="other" xlink:type="simple"> Seinfeld, J. H. and Pandis, S. N.: Atmospheric chemistry and physics: From air pollution to climate change, Wiley Interscience, New York, 1997. </mixed-citation>
</ref>
<ref id="ref46">
<label>46</label><mixed-citation publication-type="other" xlink:type="simple"> Staffelbach, T., Neftel, A., and Horowitz, L. W.: Photochemical oxidant formation over southern Switzerland. 2. Model results, J. Geophys. Res., 102, 23 363&amp;ndash;23 373, 1997. </mixed-citation>
</ref>
<ref id="ref47">
<label>47</label><mixed-citation publication-type="other" xlink:type="simple"> Stemmler, K., Ammann, M., Donders, C., Kleffmann, J., and George, C.: Photosensitized reduction of nitrogen dioxide on humic acid as a source of nitrous acid, Nature, 440, 195&amp;ndash;198, 2006. </mixed-citation>
</ref>
<ref id="ref48">
<label>48</label><mixed-citation publication-type="other" xlink:type="simple"> Swift, R. S.: Sequestration of carbon by soil, Soil Sci., 166, 858&amp;ndash;871, 2001. </mixed-citation>
</ref>
<ref id="ref49">
<label>49</label><mixed-citation publication-type="other" xlink:type="simple"> Troe, J.: Are primary quantum yields of NO&lt;sub&gt;2&lt;/sub&gt; photolysis at $\lambda \le $398 nm smaller than unity?, Z. Phys. Chem. (Muenchen Ger.), 214, 573&amp;ndash;581, 2000. </mixed-citation>
</ref>
<ref id="ref50">
<label>50</label><mixed-citation publication-type="other" xlink:type="simple"> Vogel, B., Vogel, H., Kleffmann, J., and Kurtenbach, R.: Measured and simulated vertical profiles of nitrous acid &amp;ndash; Part II. Model simulations and indications for a photolytic source, Atmos. Environ., 37, 2957&amp;ndash;2966, 2003. </mixed-citation>
</ref>
<ref id="ref51">
<label>51</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&amp;ndash;879, 2003. </mixed-citation>
</ref>
<ref id="ref52">
<label>52</label><mixed-citation publication-type="other" xlink:type="simple"> Zhou, X. L., Beine, H. J., Honrath, R. E., Fuentes, J. D., Simpson, W., Shepson, P. B., and Bottenheim, J. W.: Snowpack photochemical production of HONO: a major source of OH in the Arctic boundary layer in springtime, Geophys. Res. Lett., 28(21), 4087&amp;ndash;4090, 2001. </mixed-citation>
</ref>
<ref id="ref53">
<label>53</label><mixed-citation publication-type="other" xlink:type="simple"> Zhou, X. L., Civerolo, K., Dai, H. P., Huang, G., Schwab, J., and Demerjian, K.: Summertime nitrous acid chemistry in the atmospheric boundary layer at a rural site in New York State, J. Geophys. Res., 107(D21), 4590, doi:10.1029/2001JD001539, 2002. </mixed-citation>
</ref>
<ref id="ref54">
<label>54</label><mixed-citation publication-type="other" xlink:type="simple"> Zhou, X. L., Gao, H. L., He, Y., Huang, G., Bertman, S. B., Civerolo, K., and Schwab, J.: Nitric acid photolysis on surfaces in low-NOx environments: Significant atmospheric implications, Geophys. Res. Lett., 30(23), 2217, doi:10.1029/2003GL018620, 2003. </mixed-citation>
</ref>
</ref-list>
</back>
</article>