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<front>
<journal-meta>
<journal-id journal-id-type="publisher">EGUsphere</journal-id>
<journal-title-group>
<journal-title>EGUsphere</journal-title>
<abbrev-journal-title abbrev-type="publisher">EGUsphere</abbrev-journal-title>
<abbrev-journal-title abbrev-type="nlm-ta">EGUsphere</abbrev-journal-title>
</journal-title-group>
<issn pub-type="epub"></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/egusphere-2026-2647</article-id>
<title-group>
<article-title>Reactivity Over Abundance: Unveiling the True Kinetic Drivers of Urban Ozone Using Process-Informed Machine Learning</article-title>
</title-group>
<contrib-group><contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Hu</surname>
<given-names>Qihua</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>Kim</surname>
<given-names>Hwajin</given-names>
<ext-link>https://orcid.org/0000-0001-6138-6443</ext-link>
</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>Gouw</surname>
<given-names>Joost de</given-names>
<ext-link>https://orcid.org/0000-0002-0385-1826</ext-link>
</name>
<xref ref-type="aff" rid="aff3">
<sup>3</sup>
</xref>
</contrib>
<contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Kwon</surname>
<given-names>Sujin</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>Park</surname>
<given-names>Yoojin</given-names>
</name>
<xref ref-type="aff" rid="aff4">
<sup>4</sup>
</xref>
</contrib>
<contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Lee</surname>
<given-names>Sojin</given-names>
<ext-link>https://orcid.org/0000-0002-9054-572X</ext-link>
</name>
<xref ref-type="aff" rid="aff5">
<sup>5</sup>
</xref>
</contrib>
</contrib-group><aff id="aff1">
<label>1</label>
<addr-line>Department of Environmental Health Sciences, Graduate School of Public Health, Seoul National University, 1  Gwanak-ro, Gwanak-gu, Seoul 08826, Republic of Korea</addr-line>
</aff>
<aff id="aff2">
<label>2</label>
<addr-line>Institute of Health and Environment, Seoul National University, 1 Gwanak, Gwanak-ro, Gwanak-gu, Seoul 08826,  Republic of Korea</addr-line>
</aff>
<aff id="aff3">
<label>3</label>
<addr-line>Department of Chemistry and Cooperative Institute for Research in Environmental Sciences (CIRES), University of  Colorado Boulder, Boulder, Colorado 80309, United States</addr-line>
</aff>
<aff id="aff4">
<label>4</label>
<addr-line>Hanwha Solutions Corporation, Jincheon plant, 27816, Republic of Korea</addr-line>
</aff>
<aff id="aff5">
<label>5</label>
<addr-line>The Seoul Institute, Seoul 06756, Republic of Korea</addr-line>
</aff>
<pub-date pub-type="epub">
<day>18</day>
<month>06</month>
<year>2026</year>
</pub-date>
<volume>2026</volume>
<fpage>1</fpage>
<lpage>17</lpage>
<permissions>
<copyright-statement>Copyright: &#x000a9; 2026 Qihua Hu 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://egusphere.copernicus.org/preprints/2026/egusphere-2026-2647/">This article is available from https://egusphere.copernicus.org/preprints/2026/egusphere-2026-2647/</self-uri>
<self-uri xlink:href="https://egusphere.copernicus.org/preprints/2026/egusphere-2026-2647/egusphere-2026-2647.pdf">The full text article is available as a PDF file from https://egusphere.copernicus.org/preprints/2026/egusphere-2026-2647/egusphere-2026-2647.pdf</self-uri>
<abstract>
<p>Ground-level ozone remains a persistent challenge in East Asian urban centers, where concentrations continue rising despite significant reductions in precursor emissions. Designing effective mitigation is complicated by the non-linear relationship between precursor abundance and reactivity. Standard data-driven approaches often suffer from &quot;survivor bias,&quot; systematically undervaluing highly reactive precursors that are rapidly depleted. We introduce a process-informed machine learning framework that uses net chemical consumption (&amp;Delta;VOC) rather than ambient concentrations to resolve this attribution failure. Applied to measurements from a NOₓ-saturated roadside site in Seoul, South Korea, the approach reveals a robust quantitative relationship between intrinsic hydroxyl radical reactivity (&lt;em&gt;k&lt;/em&gt;OH) and ozone formation sensitivity.&lt;/p&gt;
&lt;p&gt;Across a comprehensive suite of precursors&amp;mdash;including oxygenated VOCs (e.g., formaldehyde, acetone) and aromatics&amp;mdash;the framework identifies reactive aromatics (trimethylbenzenes, xylenes) and biogenics (isoprene, monoterpenes) as the dominant kinetic drivers. Whereas static metrics such as OFP rank precursors by stoichiometric capacity under idealized accumulated conditions, the process-informed framework shows that realized ozone production in fresh urban plumes is governed by kinetic turnover rather than abundance, with this kinetic selectivity further amplified during high-ozone episodes. These results indicate that mass-based VOC inventories and OFP-style rankings, when applied without kinetic context, can systematically misallocate control priorities in NOₓ-saturated urban regimes. Because the framework requires only sub-hourly co-located VOC and ozone observations and no prescribed mechanism, it offers a complementary empirical pathway in settings where explicit mechanism-based modeling is constrained by incomplete VOC speciation or unmeasured radical precursors.</p>
</abstract>
<counts><page-count count="17"/></counts>
<funding-group>
<award-group id="gs1">
<funding-source>Seoul National University</funding-source>
<award-id>900-20240101</award-id>
</award-group>
</funding-group>
</article-meta>
</front>
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