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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-2026-3066</article-id>
<title-group>
<article-title>Eddy covariance measurements of nitrogen dioxide exchange at a grazed savanna grassland in South Africa</article-title>
</title-group>
<contrib-group><contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Hamilton</surname>
<given-names>Tamryn</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>Jaars</surname>
<given-names>Kerneels</given-names>
<ext-link>https://orcid.org/0000-0001-6723-5646</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>van Zyl</surname>
<given-names>Pieter G.</given-names>
<ext-link>https://orcid.org/0000-0003-1470-3359</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>Aurela</surname>
<given-names>Mika</given-names>
<ext-link>https://orcid.org/0000-0002-4046-7225</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>Adon</surname>
<given-names>Marcellin</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>Beukes</surname>
<given-names>Johan P.</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>Josipovic</surname>
<given-names>Miroslav</given-names>
<ext-link>https://orcid.org/0000-0002-5133-4559</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>Feig</surname>
<given-names>Gregor T.</given-names>
</name>
<xref ref-type="aff" rid="aff5">
<sup>5</sup>
</xref>
<xref ref-type="aff" rid="aff6">
<sup>6</sup>
</xref>
</contrib>
<contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Kulmala</surname>
<given-names>Markku</given-names>
<ext-link>https://orcid.org/0000-0003-3464-7825</ext-link>
</name>
<xref ref-type="aff" rid="aff7">
<sup>7</sup>
</xref>
</contrib>
<contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Laakso</surname>
<given-names>Lauri</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>Vakkari</surname>
<given-names>Ville</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-group><aff id="aff1">
<label>1</label>
<addr-line>Atmospheric Chemistry Research Group, Chemical Resource Beneficiation, North-West University, Potchefstroom, South  Africa</addr-line>
</aff>
<aff id="aff2">
<label>2</label>
<addr-line>Department of Chemistry and Polymer Science, Stellenbosch University, Stellenbosch, South Africa</addr-line>
</aff>
<aff id="aff3">
<label>3</label>
<addr-line>Finnish Meteorological Institute, Helsinki, Finland</addr-line>
</aff>
<aff id="aff4">
<label>4</label>
<addr-line>Laboratoire des Sciences et Technologie de l’Environnement (LSTE), Université Jean Lorougnon Guédé, Daloa, Côte d’Ivoire</addr-line>
</aff>
<aff id="aff5">
<label>5</label>
<addr-line>South African Environmental Observation Network, Pretoria, South Africa</addr-line>
</aff>
<aff id="aff6">
<label>6</label>
<addr-line>Department of Geography, Geoinformatics and Meteorology, University of Pretoria, Pretoria, South Africa</addr-line>
</aff>
<aff id="aff7">
<label>7</label>
<addr-line>Institute for Atmospheric and Earth System Research, University of Helsinki, Helsinki, Finland</addr-line>
</aff>
<pub-date pub-type="epub">
<day>11</day>
<month>06</month>
<year>2026</year>
</pub-date>
<volume>2026</volume>
<fpage>1</fpage>
<lpage>39</lpage>
<permissions>
<copyright-statement>Copyright: &#x000a9; 2026 Tamryn Hamilton 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-2026-3066/">This article is available from https://egusphere.copernicus.org/preprints/2026/egusphere-2026-3066/</self-uri>
<self-uri xlink:href="https://egusphere.copernicus.org/preprints/2026/egusphere-2026-3066/egusphere-2026-3066.pdf">The full text article is available as a PDF file from https://egusphere.copernicus.org/preprints/2026/egusphere-2026-3066/egusphere-2026-3066.pdf</self-uri>
<abstract>
<p>&lt;span&gt;South Africa is a global hotspot for anthropogenic atmospheric NO&lt;sub&gt;2&lt;/sub&gt;, where emissions from the industrialised Mpumalanga Highveld influence air quality across the southern African region. In the atmosphere, NO&lt;sub&gt;2&lt;/sub&gt; is a key player in oxidative chemistry and contributes to particulate nitrate formation and the biogeochemical nitrogen cycle through deposition. At the same time, various ecosystem processes act as sources and sinks of NO and NO&lt;sub&gt;2&lt;/sub&gt;. The net result of these factors implies differences in the ecosystem scale flux of NO&lt;sub&gt;2&lt;/sub&gt;. Here we perform the first-ever high-resolution NO&lt;sub&gt;2&lt;/sub&gt; measurements with a quantum cascade laser (QCL) instrument in a grazed African savannah landscape from 2015 to 2020. Micrometeorological eddy covariance measurements were used to quantify the NO&lt;sub&gt;2&lt;/sub&gt; flux and explore temporal trends at diurnal, monthly, seasonal and interannual scales. Our findings highlight the variability of NO&lt;sub&gt;2&lt;/sub&gt; flux within this system, with notable interannual change observed at both monthly and hourly scales. Seasonal differences in NO&lt;sub&gt;2&lt;/sub&gt; flux and deposition velocity were strongly linked to the rainfall season, with negligible differences between dry season months. Diurnal flux trends peaked during daylight hours, with consistently low NO&lt;sub&gt;2&lt;/sub&gt; flux during nighttime. These findings contribute to our understanding of near-surface atmospheric NO&lt;sub&gt;2&lt;/sub&gt; dynamics in arid landscapes and, for the first time, can be used to estimate ecosystem-scale compensation point of NO&lt;sub&gt;2&lt;/sub&gt;. &lt;/span&gt;</p>
</abstract>
<counts><page-count count="39"/></counts>
<funding-group>
<award-group id="gs1">
<funding-source>National Research Foundation</funding-source>
<award-id>MND200520523132</award-id>
<award-id>PMDS230502100985</award-id>
</award-group>
</funding-group>
</article-meta>
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