Kinetics of the reactions of OH with CO, NO, and NO<sub>2</sub> and of HO<sub>2</sub> with NO<sub>2</sub> in air at 1 atm pressure, room temperature, and tropospheric water vapour concentrations
<p>The termolecular reactions of hydroxyl radicals (<span class="inline-formula">OH</span>) with carbon monoxide (<span class="inline-formula">CO</span>), nitric oxide (<span class="inline-formula">NO</span>), and nitrogen diox...
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| Main Authors: | , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2025-03-01
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| Series: | Atmospheric Chemistry and Physics |
| Online Access: | https://acp.copernicus.org/articles/25/3481/2025/acp-25-3481-2025.pdf |
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| Summary: | <p>The termolecular reactions of hydroxyl radicals (<span class="inline-formula">OH</span>) with carbon monoxide (<span class="inline-formula">CO</span>), nitric oxide (<span class="inline-formula">NO</span>), and nitrogen dioxides (<span class="inline-formula">NO<sub>2</sub></span>) and the termolecular reaction of hydroperoxy radicals (<span class="inline-formula">HO<sub>2</sub></span>) with <span class="inline-formula">NO<sub>2</sub></span> greatly impact the atmospheric oxidation efficiency. Few studies have directly measured the pressure-dependent rate coefficients in air at 1 <span class="inline-formula">atm</span> pressure and water vapour as third-body collision partners. In this work, rate coefficients were measured with a high accuracy (<span class="inline-formula"><5</span> %) at 1 <span class="inline-formula">atm</span> pressure, at room temperature, and in humidified air using laser flash photolysis and detection of the radical decay by laser-induced fluorescence. The rate coefficients derived in dry air are <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M15" display="inline" overflow="scroll" dspmath="mathml"><mrow><mo>(</mo><mn mathvariant="normal">2.39</mn><mo>±</mo><mn mathvariant="normal">0.11</mn><mo>)</mo><mo>×</mo><msup><mn mathvariant="normal">10</mn><mrow><mo>-</mo><mn mathvariant="normal">13</mn></mrow></msup></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="101pt" height="15pt" class="svg-formula" dspmath="mathimg" md5hash="11f110e34de386442d86daf5914f1b5b"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-25-3481-2025-ie00001.svg" width="101pt" height="15pt" src="acp-25-3481-2025-ie00001.png"/></svg:svg></span></span> <span class="inline-formula">cm<sup>3</sup> s<sup>−1</sup></span> for the <span class="inline-formula">OH</span> reaction with <span class="inline-formula">CO</span>, <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M19" display="inline" overflow="scroll" dspmath="mathml"><mrow><mo>(</mo><mn mathvariant="normal">7.3</mn><mo>±</mo><mn mathvariant="normal">0.4</mn><mo>)</mo><mo>×</mo><msup><mn mathvariant="normal">10</mn><mrow><mo>-</mo><mn mathvariant="normal">12</mn></mrow></msup></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="89pt" height="15pt" class="svg-formula" dspmath="mathimg" md5hash="2e227973210dd155e6f3bacf2f3a22c9"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-25-3481-2025-ie00002.svg" width="89pt" height="15pt" src="acp-25-3481-2025-ie00002.png"/></svg:svg></span></span> <span class="inline-formula">cm<sup>3</sup> s<sup>−1</sup></span> for the <span class="inline-formula">OH</span> reaction with <span class="inline-formula">NO</span>, <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M23" display="inline" overflow="scroll" dspmath="mathml"><mrow><mo>(</mo><mn mathvariant="normal">1.23</mn><mo>±</mo><mn mathvariant="normal">0.04</mn><mo>)</mo><mo>×</mo><msup><mn mathvariant="normal">10</mn><mrow><mo>-</mo><mn mathvariant="normal">11</mn></mrow></msup></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="101pt" height="15pt" class="svg-formula" dspmath="mathimg" md5hash="d06c4a90661d2a63280fe6e6cf460bfc"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-25-3481-2025-ie00003.svg" width="101pt" height="15pt" src="acp-25-3481-2025-ie00003.png"/></svg:svg></span></span> <span class="inline-formula">cm<sup>3</sup> s<sup>−1</sup></span> for the <span class="inline-formula">OH</span> reaction with <span class="inline-formula">NO<sub>2</sub></span>, and <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M27" display="inline" overflow="scroll" dspmath="mathml"><mrow><mo>(</mo><mn mathvariant="normal">1.56</mn><mo>±</mo><mn mathvariant="normal">0.05</mn><mo>)</mo><mo>×</mo><msup><mn mathvariant="normal">10</mn><mrow><mo>-</mo><mn mathvariant="normal">12</mn></mrow></msup></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="101pt" height="15pt" class="svg-formula" dspmath="mathimg" md5hash="d68884290d6df8929a89c1c9b34a263e"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-25-3481-2025-ie00004.svg" width="101pt" height="15pt" src="acp-25-3481-2025-ie00004.png"/></svg:svg></span></span> <span class="inline-formula">cm<sup>3</sup> s<sup>−1</sup></span> for the <span class="inline-formula">HO<sub>2</sub></span> reaction with <span class="inline-formula">NO<sub>2</sub></span>. For the <span class="inline-formula">OH</span> reactions with <span class="inline-formula">CO</span> and <span class="inline-formula">NO</span>, no dependence on water vapour was observed for the range of water partial pressures tested (3 to 22 <span class="inline-formula">hPa</span>), and for <span class="inline-formula">NO<sub>2</sub></span>, only a weak increase of 3 % was measured, in agreement with the study by <span class="cit" id="xref_text.1"><a href="#bib1.bibx5">Amedro et al.</a> (<a href="#bib1.bibx5">2020</a>)</span>. For the rate coefficient of <span class="inline-formula">HO<sub>2</sub></span> with <span class="inline-formula">NO<sub>2</sub></span> an enhancement of up to 25 % was observed. This can be explained by a faster rate coefficient of the reaction of the <span class="inline-formula">HO<sub>2</sub></span>–water complex with <span class="inline-formula">NO<sub>2</sub></span> having a value of <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M40" display="inline" overflow="scroll" dspmath="mathml"><mrow><mo>(</mo><mn mathvariant="normal">3.4</mn><mo>±</mo><mn mathvariant="normal">1.1</mn><mo>)</mo><mo>×</mo><msup><mn mathvariant="normal">10</mn><mrow><mo>-</mo><mn mathvariant="normal">12</mn></mrow></msup></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="89pt" height="15pt" class="svg-formula" dspmath="mathimg" md5hash="618717defd8aa3503efae22097db1c11"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-25-3481-2025-ie00005.svg" width="89pt" height="15pt" src="acp-25-3481-2025-ie00005.png"/></svg:svg></span></span> <span class="inline-formula">cm<sup>3</sup> s<sup>−1</sup></span>.</p> |
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| ISSN: | 1680-7316 1680-7324 |