Understanding summertime H<sub>2</sub>O<sub>2</sub> chemistry in the North China Plain through observations and modeling studies
<p>Hydrogen peroxide (H<span class="inline-formula"><sub>2</sub></span>O<span class="inline-formula"><sub>2</sub></span>) is a key atmospheric oxidant, crucial for oxidation capacity and sulfate production. However, its chemis...
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| Main Authors: | , , , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2025-07-01
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| Series: | Atmospheric Chemistry and Physics |
| Online Access: | https://acp.copernicus.org/articles/25/6991/2025/acp-25-6991-2025.pdf |
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| Summary: | <p>Hydrogen peroxide (H<span class="inline-formula"><sub>2</sub></span>O<span class="inline-formula"><sub>2</sub></span>) is a key atmospheric oxidant, crucial for oxidation capacity and sulfate production. However, its chemistry remains understudied compared to ozone (O<span class="inline-formula"><sub>3</sub></span>), limiting our understanding of photochemical pollution. In summer 2016, atmospheric peroxides and trace gases were measured at a rural site in the North China Plain. H<span class="inline-formula"><sub>2</sub></span>O<span class="inline-formula"><sub>2</sub></span> was the dominant peroxide (0.62 <span class="inline-formula">±</span> 0.80 ppb), constituting 69 % of total peroxides. It exhibited diurnal variation similar to peroxyacetyl nitrate (PAN) and O<span class="inline-formula"><sub>3</sub></span>, indicating photochemical production. The <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M12" display="inline" overflow="scroll" dspmath="mathml"><mrow class="chem"><msub><mi mathvariant="normal">O</mi><mn mathvariant="normal">3</mn></msub><mspace width="0.125em" linebreak="nobreak"/><mo>/</mo><mspace linebreak="nobreak" width="0.125em"/><msub><mi mathvariant="normal">H</mi><mn mathvariant="normal">2</mn></msub><msub><mi mathvariant="normal">O</mi><mn mathvariant="normal">2</mn></msub></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="50pt" height="14pt" class="svg-formula" dspmath="mathimg" md5hash="06902578fea60196e9a44a2af6762aaa"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-25-6991-2025-ie00001.svg" width="50pt" height="14pt" src="acp-25-6991-2025-ie00001.png"/></svg:svg></span></span> ratio was higher on high-particle days, suggesting that H<span class="inline-formula"><sub>2</sub></span>O<span class="inline-formula"><sub>2</sub></span> uptake by particles reduces its concentration. A box model with default gas-phase chemistry overestimated H<span class="inline-formula"><sub>2</sub></span>O<span class="inline-formula"><sub>2</sub></span> by a factor of 2.7, and including particle uptake of H<span class="inline-formula"><sub>2</sub></span>O<span class="inline-formula"><sub>2</sub></span> (uptake coefficient of 6 <span class="inline-formula">×</span> 10<span class="inline-formula"><sup>−4</sup></span>) improved agreement with observations, although we note that this value carries some uncertainty related to the assumed HO<span class="inline-formula"><sub>2</sub></span> uptake coefficient.</p>
<p>HO<span class="inline-formula"><sub>2</sub></span> recombination contributed 91 % of H<span class="inline-formula"><sub>2</sub></span>O<span class="inline-formula"><sub>2</sub></span> production, with a peak rate of 1 ppb h<span class="inline-formula"><sup>−1</sup></span>. Major removal pathways included particle uptake (69 %), dry deposition (25 %), OH reaction (4 %), and photolysis (2 %). Relative incremental reactivity (RIR) analysis showed that reducing NO<span class="inline-formula"><sub><i>x</i></sub></span>, PM<span class="inline-formula"><sub>2.5</sub></span>, and alkanes increased H<span class="inline-formula"><sub>2</sub></span>O<span class="inline-formula"><sub>2</sub></span>, while reducing alkenes, aromatics, CO, and HONO decreased it, with alkenes having the strongest effect. <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M30" display="inline" overflow="scroll" dspmath="mathml"><mrow class="chem"><msub><mi mathvariant="normal">H</mi><mn mathvariant="normal">2</mn></msub><msub><mi mathvariant="normal">O</mi><mn mathvariant="normal">2</mn></msub><mspace linebreak="nobreak" width="0.125em"/><mo>/</mo><mspace width="0.125em" linebreak="nobreak"/><msub><mi mathvariant="normal">NO</mi><mi>z</mi></msub></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="58pt" height="14pt" class="svg-formula" dspmath="mathimg" md5hash="a9182d24475047cf51b4132e8d78eed3"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-25-6991-2025-ie00002.svg" width="58pt" height="14pt" src="acp-25-6991-2025-ie00002.png"/></svg:svg></span></span> ratios (<span class="inline-formula"><i>></i>0.15</span> in 82 % of cases) indicated that O<span class="inline-formula"><sub>3</sub></span> formation was in a transition and NO<span class="inline-formula"><sub><i>x</i></sub></span>-sensitive regime, emphasizing the need for further volatile organic compound (VOC) and NO<span class="inline-formula"><sub><i>x</i></sub></span> reductions to mitigate both H<span class="inline-formula"><sub>2</sub></span>O<span class="inline-formula"><sub>2</sub></span> and O<span class="inline-formula"><sub>3</sub></span> pollution. These findings improve our understanding of H<span class="inline-formula"><sub>2</sub></span>O<span class="inline-formula"><sub>2</sub></span> chemistry and provide insights into the mitigation of photochemical pollution in rural North China.</p> |
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| ISSN: | 1680-7316 1680-7324 |