Nitrate radical generation via continuous generation of dinitrogen pentoxide in a laminar flow reactor coupled to an oxidation flow reactor
<p>Oxidation flow reactors (OFRs) are an emerging tool for studying the formation and oxidative aging of organic aerosols and other applications. The majority of OFR studies to date have involved the generation of the hydroxyl radical (OH) to mimic daytime oxidative aging processes. In contras...
| Main Authors: | , , , , , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2020-05-01
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| Series: | Atmospheric Measurement Techniques |
| Online Access: | https://www.atmos-meas-tech.net/13/2397/2020/amt-13-2397-2020.pdf |
| Summary: | <p>Oxidation flow reactors (OFRs) are an emerging tool for studying the formation and oxidative aging of organic aerosols and other applications.
The majority of OFR studies to date have involved the generation of the hydroxyl radical (OH) to mimic daytime oxidative aging processes.
In contrast, the use of the nitrate radical (<span class="inline-formula">NO<sub>3</sub></span>) in modern OFRs to mimic nighttime oxidative aging processes has been limited due to the complexity of conventional techniques that are used to generate <span class="inline-formula">NO<sub>3</sub></span>.
Here, we present a new method that uses a laminar flow reactor (LFR) to continuously generate dinitrogen pentoxide (<span class="inline-formula">N<sub>2</sub>O<sub>5</sub></span>) in the gas phase at room temperature from the <span class="inline-formula">NO<sub>2</sub></span> + <span class="inline-formula">O<sub>3</sub></span> and <span class="inline-formula">NO<sub>2</sub></span> + <span class="inline-formula">NO<sub>3</sub></span> reactions.
The <span class="inline-formula">N<sub>2</sub>O<sub>5</sub></span> is then injected into a dark Potential Aerosol Mass (PAM) OFR and decomposes to generate <span class="inline-formula">NO<sub>3</sub></span>; hereafter, this method is referred to as “OFR-i<span class="inline-formula">N<sub>2</sub>O<sub>5</sub></span>” (where “i” stands for “injected”).
To assess the applicability of the OFR-i<span class="inline-formula">N<sub>2</sub>O<sub>5</sub></span> method towards different chemical systems, we present experimental and model characterization of the integrated <span class="inline-formula">NO<sub>3</sub></span> exposure, <span class="inline-formula">NO<sub>3</sub>:O<sub>3</sub></span>, <span class="inline-formula">NO<sub>2</sub>:NO<sub>3</sub></span>, and <span class="inline-formula">NO<sub>2</sub>:O<sub>2</sub></span> as a function of LFR and OFR conditions.
These parameters were used to investigate the fate of representative organic peroxy radicals (<span class="inline-formula">RO<sub>2</sub></span>) and aromatic alkyl radicals generated from volatile organic compound (VOC) <span class="inline-formula">+</span> <span class="inline-formula">NO<sub>3</sub></span> reactions, and VOCs that are reactive towards both <span class="inline-formula">O<sub>3</sub></span> and <span class="inline-formula">NO<sub>3</sub></span>.
Finally, we demonstrate the OFR-i<span class="inline-formula">N<sub>2</sub>O<sub>5</sub></span> method by generating and characterizing secondary organic aerosol from the <span class="inline-formula"><i>β</i></span>-pinene <span class="inline-formula">+</span> <span class="inline-formula">NO<sub>3</sub></span> reaction.</p> |
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| ISSN: | 1867-1381 1867-8548 |