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<front>
<journal-meta>
<journal-id journal-id-type="publisher">ARD</journal-id>
<journal-title-group>
<journal-title>Aerosol Research Discussions</journal-title>
<abbrev-journal-title abbrev-type="publisher">ARD</abbrev-journal-title>
<abbrev-journal-title abbrev-type="nlm-ta">Aerosol Research Discuss.</abbrev-journal-title>
</journal-title-group>
<issn pub-type="epub">2940-3405</issn>
<publisher><publisher-name></publisher-name>
<publisher-loc>Göttingen, Germany</publisher-loc>
</publisher>
</journal-meta>
<article-meta>
<article-id pub-id-type="doi">10.5194/ar-2026-28</article-id>
<title-group>
<article-title>Contributions of Fine and Coarse Particles to Light Absorption at an Urban Traffic Site during Street Dust Season</article-title>
</title-group>
<contrib-group><contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Barreira</surname>
<given-names>Luis M. F.</given-names>
<ext-link>https://orcid.org/0000-0003-0196-2140</ext-link>
</name>
<xref ref-type="aff" rid="aff1">
<sup>1</sup>
</xref>
</contrib>
<contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Li</surname>
<given-names>Delun</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>Hoivala</surname>
<given-names>Jussi</given-names>
<ext-link>https://orcid.org/0009-0005-1031-3574</ext-link>
</name>
<xref ref-type="aff" rid="aff2">
<sup>2</sup>
</xref>
</contrib>
<contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Aurela</surname>
<given-names>Minna</given-names>
<ext-link>https://orcid.org/0000-0001-7561-2974</ext-link>
</name>
<xref ref-type="aff" rid="aff1">
<sup>1</sup>
</xref>
</contrib>
<contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Virkkula</surname>
<given-names>Aki</given-names>
<ext-link>https://orcid.org/0000-0003-4874-7552</ext-link>
</name>
<xref ref-type="aff" rid="aff1">
<sup>1</sup>
</xref>
</contrib>
<contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Niemi</surname>
<given-names>Jarkko V.</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>Manninen</surname>
<given-names>Hanna E.</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>Rönkkö</surname>
<given-names>Topi</given-names>
<ext-link>https://orcid.org/0000-0002-1555-3367</ext-link>
</name>
<xref ref-type="aff" rid="aff2">
<sup>2</sup>
</xref>
</contrib>
<contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Timonen</surname>
<given-names>Hilkka</given-names>
<ext-link>https://orcid.org/0000-0002-7987-7985</ext-link>
</name>
<xref ref-type="aff" rid="aff1">
<sup>1</sup>
</xref>
</contrib>
<contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Saarikoski</surname>
<given-names>Sanna</given-names>
</name>
<xref ref-type="aff" rid="aff1">
<sup>1</sup>
</xref>
</contrib>
</contrib-group><aff id="aff1">
<label>1</label>
<addr-line>Atmospheric Composition Research, Finnish Meteorological Institute, 00101, Helsinki, Finland</addr-line>
</aff>
<aff id="aff2">
<label>2</label>
<addr-line>Aerosol Physics Laboratory, Physics Unit, Faculty of Engineering and Natural Sciences, Tampere University, 33014,  Tampere, Finland</addr-line>
</aff>
<aff id="aff3">
<label>3</label>
<addr-line>Helsinki Region Environmental Services Authority, 00066, Helsinki, Finland</addr-line>
</aff>
<pub-date pub-type="epub">
<day>24</day>
<month>07</month>
<year>2026</year>
</pub-date>
<volume>2026</volume>
<fpage>1</fpage>
<lpage>28</lpage>
<permissions>
<copyright-statement>Copyright: &#x000a9; 2026 Luis M. F. Barreira et al.</copyright-statement>
<copyright-year>2026</copyright-year>
<license license-type="open-access">
<license-p>This work is licensed under the Creative Commons Attribution 4.0 International License. To view a copy of this licence, visit <ext-link ext-link-type="uri"  xlink:href="https://creativecommons.org/licenses/by/4.0/">https://creativecommons.org/licenses/by/4.0/</ext-link></license-p>
</license>
</permissions>
<self-uri xlink:href="https://ar.copernicus.org/preprints/ar-2026-28/">This article is available from https://ar.copernicus.org/preprints/ar-2026-28/</self-uri>
<self-uri xlink:href="https://ar.copernicus.org/preprints/ar-2026-28/ar-2026-28.pdf">The full text article is available as a PDF file from https://ar.copernicus.org/preprints/ar-2026-28/ar-2026-28.pdf</self-uri>
<abstract>
<p>Light absorption by urban aerosols is dominated by fine particles (particulate matter &amp;le;2.5 &amp;micro;m; PM&lt;sub&gt;2.5&lt;/sub&gt;), particularly from traffic exhaust and residential combustion. However, coarse particles (2.5&amp;ndash;10 &amp;micro;m; PM&lt;sub&gt;2.5&amp;ndash;10&lt;/sub&gt;) can also contribute during spring street dust events in northern countries. This study investigated size-resolved optical properties and chemical composition of PM in an urban street canyon during spring. Hourly PM₁₀ concentrations averaged 27.1 &amp;micro;g m⁻&amp;sup3;, while PM&lt;sub&gt;2.5&lt;/sub&gt; and PM&lt;sub&gt;1&lt;/sub&gt; (&amp;le;1 &amp;micro;m) concentrations averaged 7.1 and 4.3 &amp;micro;g m⁻&amp;sup3;, respectively. Light absorption across PM₁, PM₂.₅, and PM₇.₂ fractions was dominated by submicron particles, predominantly at short wavelengths, while coarse particles enhanced absorption during dust-resuspension events. Equivalent black carbon (eBC) showed strong size dependence, with PM&lt;sub&gt;1&lt;/sub&gt; capturing most combustion-derived BC despite low campaign-mean concentrations (0.49 &amp;micro;g m⁻&amp;sup3;). Relative to PM₁, hourly eBC increased by 14 % in PM&lt;sub&gt;2.5&lt;/sub&gt; and 41 % in PM&lt;sub&gt;7.2&lt;/sub&gt;. Absorption &amp;Aring;ngstr&amp;ouml;m exponent analysis revealed size- and source-dependent spectra differences, with stronger wavelength dependence during high PM&lt;sub&gt;10&lt;/sub&gt; dust events and values closer to unity under traffic-exhaust-dominated conditions. The inclusion of coarse particles complicated the interpretation of the AAE&lt;sub&gt;470/950&lt;/sub&gt; and related biomass burning contribution estimates. Elemental analysis revealed elevated concentrations of Si, Fe, and Al in coarse PM, suggesting contributions from crustal material and/or non-exhaust emissions that may also influence optical properties. These findings demonstrate that quantification and source identification of urban aerosol light absorption requires consideration of the selected particle size cut-off.</p>
</abstract>
<counts><page-count count="28"/></counts>
<funding-group>
<award-group id="gs1">
<funding-source>Business Finland</funding-source>
<award-id>8308/31/2022</award-id>
</award-group>
<award-group id="gs2">
<funding-source>HORIZON EUROPE Climate, Energy and Mobility</funding-source>
<award-id>101096133</award-id>
</award-group>
<award-group id="gs3">
<funding-source>Business Finland</funding-source>
<award-id>3971/31/2025</award-id>
<award-id>3973/31/2025</award-id>
</award-group>
<award-group id="gs4">
<funding-source>Research Council of Finland</funding-source>
<award-id>337552</award-id>
<award-id>337551</award-id>
</award-group>
</funding-group>
</article-meta>
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