Mechanistic insights into chloroacetic acid production from atmospheric multiphase volatile organic compound–chlorine chemistry
<p>Chlorine-containing oxygenated volatile organic compounds (Cl-OVOCs) are indicators of atmospheric chlorine chemistry involving volatile organic compounds (VOCs). However, their formation mechanisms are insufficiently understood. Herein, a strong diel pattern of chloroacetic acid (<span...
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Copernicus Publications
2025-03-01
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| Series: | Atmospheric Chemistry and Physics |
| Online Access: | https://acp.copernicus.org/articles/25/3753/2025/acp-25-3753-2025.pdf |
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| author | M. Li M. Xia M. Xia C. Lin C. Lin Y. Jiang W. Sun Y. Wang Y. Zhang M. He T. Wang |
| author_facet | M. Li M. Xia M. Xia C. Lin C. Lin Y. Jiang W. Sun Y. Wang Y. Zhang M. He T. Wang |
| author_sort | M. Li |
| collection | DOAJ |
| description | <p>Chlorine-containing oxygenated volatile organic compounds (Cl-OVOCs) are indicators of atmospheric chlorine chemistry involving volatile organic compounds (VOCs). However, their formation mechanisms are insufficiently understood. Herein, a strong diel pattern of chloroacetic acid (<span class="inline-formula">C<sub>2</sub>H<sub>3</sub>O<sub>2</sub>Cl</span>) was observed with daytime peaks at 19 and 13 ppt (1 h averages) in 2020 and 2021, respectively, at a coastal site in southern China. Ethene was previously proposed as the primary precursor responsible for daytime <span class="inline-formula">C<sub>2</sub>H<sub>3</sub>O<sub>2</sub>Cl</span> levels, but a photochemical box model based on Master Chemical Mechanism (MCM) simulations indicates that ethene accounts for less than 1 %. Quantum chemical calculations suggest that other alkenes also can act as chloroacetic acid precursors. Using an updated gas-phase VOC–Cl chemistry model, we find that isoprene, the most abundant VOC at the sampling site, along with its oxidation products, accounts for 7 % of the observed <span class="inline-formula">C<sub>2</sub>H<sub>3</sub>O<sub>2</sub>Cl</span>. Moreover, the simulation with the updated MCM produces appreciable levels of other Cl-OVOCs, especially chloroacetaldehyde, a precursor of <span class="inline-formula">C<sub>2</sub>H<sub>3</sub>O<sub>2</sub>Cl</span>. We proposed the multiphase reaction of Cl-OVOCs to reconcile the overestimation of Cl-OVOCs and the underestimation of <span class="inline-formula">C<sub>2</sub>H<sub>3</sub>O<sub>2</sub>Cl</span> in our gas-phase model. The estimated reactive uptake coefficients for various Cl-OVOCs range from <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M6" display="inline" overflow="scroll" dspmath="mathml"><mrow><mn mathvariant="normal">3.63</mn><mo>×</mo><msup><mn mathvariant="normal">10</mn><mrow><mo>-</mo><mn mathvariant="normal">5</mn></mrow></msup></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="57pt" height="13pt" class="svg-formula" dspmath="mathimg" md5hash="cce2e488907f9c5af9bd4078433c43fe"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-25-3753-2025-ie00001.svg" width="57pt" height="13pt" src="acp-25-3753-2025-ie00001.png"/></svg:svg></span></span> to <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M7" display="inline" overflow="scroll" dspmath="mathml"><mrow><mn mathvariant="normal">2.34</mn><mo>×</mo><msup><mn mathvariant="normal">10</mn><mrow><mo>-</mo><mn mathvariant="normal">2</mn></mrow></msup></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="57pt" height="14pt" class="svg-formula" dspmath="mathimg" md5hash="4a89d9e21b2603b64d9d7047ed8eacca"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-25-3753-2025-ie00002.svg" width="57pt" height="14pt" src="acp-25-3753-2025-ie00002.png"/></svg:svg></span></span>, based on quantum chemical calculations and linear relationship modelling. The box model simulation with multiphase chemistry shows that the heterogeneous conversion of chloroacetaldehyde to <span class="inline-formula">C<sub>2</sub>H<sub>3</sub>O<sub>2</sub>Cl</span> can contribute 24 %–48 % of the observed levels. Our study thus proposes a formation mechanism of gaseous <span class="inline-formula">C<sub>2</sub>H<sub>3</sub>O<sub>2</sub>Cl</span> and highlights the potential importance of multiphase processes in atmospheric organic acid formation.</p> |
| format | Article |
| id | doaj-art-6958b67555da447ea0edd0ec0058f8d1 |
| institution | Kabale University |
| issn | 1680-7316 1680-7324 |
| language | English |
| publishDate | 2025-03-01 |
| publisher | Copernicus Publications |
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| series | Atmospheric Chemistry and Physics |
| spelling | doaj-art-6958b67555da447ea0edd0ec0058f8d12025-08-20T03:41:04ZengCopernicus PublicationsAtmospheric Chemistry and Physics1680-73161680-73242025-03-01253753376410.5194/acp-25-3753-2025Mechanistic insights into chloroacetic acid production from atmospheric multiphase volatile organic compound–chlorine chemistryM. Li0M. Xia1M. Xia2C. Lin3C. Lin4Y. Jiang5W. Sun6Y. Wang7Y. Zhang8M. He9T. Wang10Department of Civil and Environmental Engineering, The Hong Kong Polytechnic University, Hong Kong SAR 999077, ChinaInstitute for Atmospheric and Earth System Research/Physics, Faculty of Science, University of Helsinki, Helsinki 00014, FinlandAerosol and Haze Laboratory, Beijing Advanced Innovation Center for Soft Matter Science and Engineering, Beijing University of Chemical Technology, Beijing 100029, ChinaDepartment of Civil and Environmental Engineering, The Hong Kong Polytechnic University, Hong Kong SAR 999077, ChinaState Key Laboratory of Loess Science, Institute of Earth Environment, Chinese Academy of Sciences, Xi'an 710061, ChinaDepartment of Civil and Environmental Engineering, The Hong Kong Polytechnic University, Hong Kong SAR 999077, ChinaDepartment of Civil and Environmental Engineering, The Hong Kong Polytechnic University, Hong Kong SAR 999077, ChinaDepartment of Civil and Environmental Engineering, The Hong Kong Polytechnic University, Hong Kong SAR 999077, ChinaDepartment of Civil and Environmental Engineering, The Hong Kong Polytechnic University, Hong Kong SAR 999077, ChinaEnvironment Research Institute, Shandong University, Qingdao 266237, ChinaDepartment of Civil and Environmental Engineering, The Hong Kong Polytechnic University, Hong Kong SAR 999077, China<p>Chlorine-containing oxygenated volatile organic compounds (Cl-OVOCs) are indicators of atmospheric chlorine chemistry involving volatile organic compounds (VOCs). However, their formation mechanisms are insufficiently understood. Herein, a strong diel pattern of chloroacetic acid (<span class="inline-formula">C<sub>2</sub>H<sub>3</sub>O<sub>2</sub>Cl</span>) was observed with daytime peaks at 19 and 13 ppt (1 h averages) in 2020 and 2021, respectively, at a coastal site in southern China. Ethene was previously proposed as the primary precursor responsible for daytime <span class="inline-formula">C<sub>2</sub>H<sub>3</sub>O<sub>2</sub>Cl</span> levels, but a photochemical box model based on Master Chemical Mechanism (MCM) simulations indicates that ethene accounts for less than 1 %. Quantum chemical calculations suggest that other alkenes also can act as chloroacetic acid precursors. Using an updated gas-phase VOC–Cl chemistry model, we find that isoprene, the most abundant VOC at the sampling site, along with its oxidation products, accounts for 7 % of the observed <span class="inline-formula">C<sub>2</sub>H<sub>3</sub>O<sub>2</sub>Cl</span>. Moreover, the simulation with the updated MCM produces appreciable levels of other Cl-OVOCs, especially chloroacetaldehyde, a precursor of <span class="inline-formula">C<sub>2</sub>H<sub>3</sub>O<sub>2</sub>Cl</span>. We proposed the multiphase reaction of Cl-OVOCs to reconcile the overestimation of Cl-OVOCs and the underestimation of <span class="inline-formula">C<sub>2</sub>H<sub>3</sub>O<sub>2</sub>Cl</span> in our gas-phase model. The estimated reactive uptake coefficients for various Cl-OVOCs range from <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M6" display="inline" overflow="scroll" dspmath="mathml"><mrow><mn mathvariant="normal">3.63</mn><mo>×</mo><msup><mn mathvariant="normal">10</mn><mrow><mo>-</mo><mn mathvariant="normal">5</mn></mrow></msup></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="57pt" height="13pt" class="svg-formula" dspmath="mathimg" md5hash="cce2e488907f9c5af9bd4078433c43fe"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-25-3753-2025-ie00001.svg" width="57pt" height="13pt" src="acp-25-3753-2025-ie00001.png"/></svg:svg></span></span> to <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M7" display="inline" overflow="scroll" dspmath="mathml"><mrow><mn mathvariant="normal">2.34</mn><mo>×</mo><msup><mn mathvariant="normal">10</mn><mrow><mo>-</mo><mn mathvariant="normal">2</mn></mrow></msup></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="57pt" height="14pt" class="svg-formula" dspmath="mathimg" md5hash="4a89d9e21b2603b64d9d7047ed8eacca"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-25-3753-2025-ie00002.svg" width="57pt" height="14pt" src="acp-25-3753-2025-ie00002.png"/></svg:svg></span></span>, based on quantum chemical calculations and linear relationship modelling. The box model simulation with multiphase chemistry shows that the heterogeneous conversion of chloroacetaldehyde to <span class="inline-formula">C<sub>2</sub>H<sub>3</sub>O<sub>2</sub>Cl</span> can contribute 24 %–48 % of the observed levels. Our study thus proposes a formation mechanism of gaseous <span class="inline-formula">C<sub>2</sub>H<sub>3</sub>O<sub>2</sub>Cl</span> and highlights the potential importance of multiphase processes in atmospheric organic acid formation.</p>https://acp.copernicus.org/articles/25/3753/2025/acp-25-3753-2025.pdf |
| spellingShingle | M. Li M. Xia M. Xia C. Lin C. Lin Y. Jiang W. Sun Y. Wang Y. Zhang M. He T. Wang Mechanistic insights into chloroacetic acid production from atmospheric multiphase volatile organic compound–chlorine chemistry Atmospheric Chemistry and Physics |
| title | Mechanistic insights into chloroacetic acid production from atmospheric multiphase volatile organic compound–chlorine chemistry |
| title_full | Mechanistic insights into chloroacetic acid production from atmospheric multiphase volatile organic compound–chlorine chemistry |
| title_fullStr | Mechanistic insights into chloroacetic acid production from atmospheric multiphase volatile organic compound–chlorine chemistry |
| title_full_unstemmed | Mechanistic insights into chloroacetic acid production from atmospheric multiphase volatile organic compound–chlorine chemistry |
| title_short | Mechanistic insights into chloroacetic acid production from atmospheric multiphase volatile organic compound–chlorine chemistry |
| title_sort | mechanistic insights into chloroacetic acid production from atmospheric multiphase volatile organic compound chlorine chemistry |
| url | https://acp.copernicus.org/articles/25/3753/2025/acp-25-3753-2025.pdf |
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