Direct measurement of N<sub>2</sub>O<sub>5</sub> heterogeneous uptake coefficients on atmospheric aerosols in southwestern China and evaluation of current parameterizations
<p>The heterogeneous hydrolysis of dinitrogen pentoxide (N<span class="inline-formula"><sub>2</sub></span>O<span class="inline-formula"><sub>5</sub></span>) is a critical process in assessing NO<span class="inline-form...
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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/25/6395/2025/acp-25-6395-2025.pdf |
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| Summary: | <p>The heterogeneous hydrolysis of dinitrogen pentoxide (N<span class="inline-formula"><sub>2</sub></span>O<span class="inline-formula"><sub>5</sub></span>) is a critical process in assessing NO<span class="inline-formula"><sub><i>x</i></sub></span> fate and secondary pollutant formation. However, accurate quantification of the N<span class="inline-formula"><sub>2</sub></span>O<span class="inline-formula"><sub>5</sub></span> uptake coefficient (<span class="inline-formula"><i>γ</i></span> (N<span class="inline-formula"><sub>2</sub></span>O<span class="inline-formula"><sub>5</sub></span>)) in ambient conditions is a challenging problem that can cause unpredictable uncertainties in the predictions of air quality models. Here, the <span class="inline-formula"><i>γ</i></span> (N<span class="inline-formula"><sub>2</sub></span>O<span class="inline-formula"><sub>5</sub></span>) values were directly measured using an improved in situ aerosol flow tube system at a site located in a highland region in southwestern China to investigate influencing factors and the performance of current <span class="inline-formula"><i>γ</i></span> (N<span class="inline-formula"><sub>2</sub></span>O<span class="inline-formula"><sub>5</sub></span>) parameterizations under this typical environmental condition. The nocturnal mean <span class="inline-formula"><i>γ</i></span> (N<span class="inline-formula"><sub>2</sub></span>O<span class="inline-formula"><sub>5</sub></span>) value ranged from 0.0018 to 0.12 with an average of <span class="inline-formula">0.023±0.021</span>. The relationship between the measured <span class="inline-formula"><i>γ</i></span> (N<span class="inline-formula"><sub>2</sub></span>O<span class="inline-formula"><sub>5</sub></span>) and impacting factors was consistent with previous laboratory results, except for aerosol chloride. The aerosol water significantly promoted N<span class="inline-formula"><sub>2</sub></span>O<span class="inline-formula"><sub>5</sub></span> uptake, while particulate organics and nitrate showed suppression effects. We found that several parameterizations can capture the median of measured values, whereas none of the 10 parameterizations were able to reproduce the variabilities and showed poor correlations (<span class="inline-formula"><i>R</i><sup>2</sup>=0.00</span>–0.09). Elevated biases of predictions specifically occurred at high aerosol liquid water content (ALWC) (<span class="inline-formula">></span> 35 M) and low ALWC (<span class="inline-formula"><</span> 25 M) levels with an underestimation of <span class="inline-formula">−</span>37 % to <span class="inline-formula">−</span>1 % and an overestimation of 34 % to 189 %, respectively. Such differences between the measured and parameterized <span class="inline-formula"><i>γ</i></span> (N<span class="inline-formula"><sub>2</sub></span>O<span class="inline-formula"><sub>5</sub></span>) would lead to a biased estimation (<span class="inline-formula">−</span>77 % to 74 %) of the particulate nitrate production potential. Our findings suggest the need for more direct field quantifications of <span class="inline-formula"><i>γ</i></span> (N<span class="inline-formula"><sub>2</sub></span>O<span class="inline-formula"><sub>5</sub></span>) and laboratory measurements under extreme ALWC conditions to re-evaluate the response coefficients between <span class="inline-formula"><i>γ</i></span> (N<span class="inline-formula"><sub>2</sub></span>O<span class="inline-formula"><sub>5</sub></span>) and aerosol chemical compositions in parameterizations.</p> |
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| ISSN: | 1680-7316 1680-7324 |