The shifting of secondary inorganic aerosol formation mechanisms during haze aggravation: the decisive role of aerosol liquid water
<p>Although many considerable efforts have been done to reveal the driving factors on haze aggravation, however, the roles of aerosol liquid water (ALW) in secondary inorganic aerosol (SIA) formation were mainly focused on the condition of aerosol liquid water content (ALWC) <span class=&qu...
| Main Authors: | , , , , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2023-02-01
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| Series: | Atmospheric Chemistry and Physics |
| Online Access: | https://acp.copernicus.org/articles/23/2365/2023/acp-23-2365-2023.pdf |
| Summary: | <p>Although many considerable efforts have been done to reveal the driving
factors on haze aggravation, however, the roles of aerosol liquid water (ALW) in secondary inorganic aerosol (SIA) formation were mainly focused on the condition of aerosol liquid water content (ALWC) <span class="inline-formula"><</span> 100 <span class="inline-formula">µ</span>g m<span class="inline-formula"><sup>−3</sup></span>. Based on the in situ high-resolution field observations, this work studied the decisive roles and the shifting of secondary inorganic aerosol formation mechanisms during haze aggravation, revealing the different roles of ALWC on a broader scale (<span class="inline-formula">∼500</span> <span class="inline-formula">µ</span>g m<span class="inline-formula"><sup>−3</sup></span>) in nitrate and sulfate formation induced by aqueous chemistry in the ammonia-rich atmosphere. The results showed that chemical domains of perturbation gas limiting the generation of secondary particulate matter presented obvious shifts from a <span class="inline-formula">HNO<sub>3</sub></span>-sensitive to a <span class="inline-formula">HNO<sub>3</sub></span>- and <span class="inline-formula">NH<sub>3</sub></span>-co-sensitive regime with the haze aggravation, indicating the powerful driving effects of ammonia in the ammonia-rich atmosphere. When ALWC <span class="inline-formula"><</span> 75 <span class="inline-formula">µ</span>g m<span class="inline-formula"><sup>−3</sup></span>, the sulfate generation was preferentially triggered by the high ammonia utilization and then accelerated by nitrogen oxide oxidation from clean to moderate pollution stages, characterized by nitrogen oxidation ratio (NOR) <span class="inline-formula"><</span> 0.3, sulfur oxidation ratio (SOR) <span class="inline-formula"><</span> 0.4, ammonia transition ratio (NTR) <span class="inline-formula"><</span> 0.7 and the moral ratio of <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M16" display="inline" overflow="scroll" dspmath="mathml"><mrow><mrow class="chem"><msubsup><mi mathvariant="normal">NO</mi><mn mathvariant="normal">3</mn><mo>-</mo></msubsup><mo>/</mo><msubsup><mi mathvariant="normal">SO</mi><mn mathvariant="normal">4</mn><mrow><mn mathvariant="normal">2</mn><mo>-</mo></mrow></msubsup></mrow><mo>=</mo><mn mathvariant="normal">2</mn><mo>:</mo><mn mathvariant="normal">1</mn></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="90pt" height="17pt" class="svg-formula" dspmath="mathimg" md5hash="4f934f2b78299b885908646ed902d934"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-23-2365-2023-ie00001.svg" width="90pt" height="17pt" src="acp-23-2365-2023-ie00001.png"/></svg:svg></span></span>. When ALWC <span class="inline-formula">></span> 75 <span class="inline-formula">µ</span>g m<span class="inline-formula"><sup>−3</sup></span>, the aqueous-phase chemistry reaction of <span class="inline-formula">SO<sub>2</sub></span> and <span class="inline-formula">NH<sub>3</sub></span> in ALW became the prerequisite for SIA formation driven by Henry's law in the ammonia-rich atmosphere during heavy and serious stages, characterized by high SOR (0.5–0.9), NOR (0.3–0.5) and NTR (<span class="inline-formula">>0.7</span>), as well as the high moral ratio of <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M23" display="inline" overflow="scroll" dspmath="mathml"><mrow><mrow class="chem"><msubsup><mi mathvariant="normal">NO</mi><mn mathvariant="normal">3</mn><mo>-</mo></msubsup><mo>/</mo><msubsup><mi mathvariant="normal">SO</mi><mn mathvariant="normal">4</mn><mrow><mn mathvariant="normal">2</mn><mo>-</mo></mrow></msubsup></mrow><mo>=</mo><mn mathvariant="normal">1</mn><mo>:</mo><mn mathvariant="normal">1</mn></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="90pt" height="17pt" class="svg-formula" dspmath="mathimg" md5hash="a4275230ebd894edd1a417cc5f147057"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-23-2365-2023-ie00002.svg" width="90pt" height="17pt" src="acp-23-2365-2023-ie00002.png"/></svg:svg></span></span>. A positive feedback of sulfate on nitrate production was also observed in this work due to the shift in ammonia partitioning induced by the ALWC variation during haze aggravation. It implies the target controlling of haze should not simply focus on <span class="inline-formula">SO<sub>2</sub></span> and <span class="inline-formula">NO<sub>2</sub></span>, but more attention should be paid to gaseous precursors (e.g., <span class="inline-formula">SO<sub>2</sub></span>, <span class="inline-formula">NO<sub>2</sub></span>, <span class="inline-formula">NH<sub>3</sub></span>) and aerosol chemical constitution during different haze stages.</p> |
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| ISSN: | 1680-7316 1680-7324 |