Enhancing SO<sub>3</sub> hydrolysis and nucleation: the role of formic sulfuric anhydride
<p>Although the nucleation route driven by sulfuric acid (H<span class="inline-formula"><sub>2</sub></span>SO<span class="inline-formula"><sub>4</sub></span>) and ammonia (NH<span class="inline-formula"><sub...
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| Main Authors: | , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2025-06-01
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| Series: | Atmospheric Chemistry and Physics |
| Online Access: | https://acp.copernicus.org/articles/25/5695/2025/acp-25-5695-2025.pdf |
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| Summary: | <p>Although the nucleation route driven by sulfuric acid (H<span class="inline-formula"><sub>2</sub></span>SO<span class="inline-formula"><sub>4</sub></span>) and ammonia (NH<span class="inline-formula"><sub>3</sub></span>) primarily dominates new particle formation (NPF) in the atmosphere, exploring the role of other trace species in the H<span class="inline-formula"><sub>2</sub></span>SO<span class="inline-formula"><sub>4</sub></span>–NH<span class="inline-formula"><sub>3</sub></span> system is crucial for a more comprehensive insight into NPF processes. Formic sulfuric anhydride (FSA) has been observed in the atmospheric environment and is found in abundance in atmospheric fine particles. Nevertheless, its effect on SO<span class="inline-formula"><sub>3</sub></span> hydrolysis and NPF remains poorly understood. Here, we studied the enhancing effect of FSA on gaseous and interfacial SO<span class="inline-formula"><sub>3</sub></span> hydrolysis as well as its impact on H<span class="inline-formula"><sub>2</sub></span>SO<span class="inline-formula"><sub>4</sub></span>–NH<span class="inline-formula"><sub>3</sub></span>-driven NPF occurring through quantum chemical calculations, Atmospheric Cluster Dynamics Code (ACDC) kinetics combined with Born–Oppenheimer molecular dynamics (BOMD). Gaseous-phase findings indicate that FSA-catalyzed SO<span class="inline-formula"><sub>3</sub></span> hydrolysis is nearly barrierless. At an [FSA] <span class="inline-formula">=</span> 10<span class="inline-formula"><sup>7</sup></span> molecules cm<span class="inline-formula"><sup>−3</sup></span>, this reaction competes effectively with SO<span class="inline-formula"><sub>3</sub></span> hydrolysis in the presence of HNO<span class="inline-formula"><sub>3</sub></span> (10<span class="inline-formula"><sup>9</sup></span> molecules cm<span class="inline-formula"><sup>−3</sup></span>), HCOOH (10<span class="inline-formula"><sup>8</sup></span> molecules cm<span class="inline-formula"><sup>−3</sup></span>) and H<span class="inline-formula"><sub>2</sub></span>SO<span class="inline-formula"><sub>4</sub></span> (10<span class="inline-formula"><sup>6</sup></span> molecules cm<span class="inline-formula"><sup>−3</sup></span>) in the range of 280.0–320.0 K. At the gas–liquid nanodroplet interface, BOMD simulations reveal that FSA-mediated SO<span class="inline-formula"><sub>3</sub></span> hydrolysis follows a stepwise mechanism, completing within a few picoseconds. Notably, FSA enhances the formation rate of H<span class="inline-formula"><sub>2</sub></span>SO<span class="inline-formula"><sub>4</sub></span>–NH<span class="inline-formula"><sub>3</sub></span> clusters by over 10<span class="inline-formula"><sup>5</sup></span> times in regions with relatively high [FSA] at elevated temperatures. Additionally, the interfacial FSA<span class="inline-formula"><sup>−</sup></span> ion has the ability to appeal precursor species for particle formation from the gaseous phase to the water nanodroplet interface, thereby facilitating particle growth. These results present new insights into both the pathways of H<span class="inline-formula"><sub>2</sub></span>SO<span class="inline-formula"><sub>4</sub></span> formation and aerosol particle growth in the polluted boundary layer.</p> |
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| ISSN: | 1680-7316 1680-7324 |