HO<sub><i>x</i></sub> and NO<sub><i>x</i></sub> production in oxidation flow reactors via photolysis of isopropyl nitrite, isopropyl nitrite-d<sub>7</sub>, and 1,3-propyl dinitrite at <i>λ</i> = 254, 350, and 369 nm
oleh: A. T. Lambe, J. E. Krechmer, Z. Peng, J. R. Casar, A. J. Carrasquillo, J. D. Raff, J. L. Jimenez, D. R. Worsnop, D. R. Worsnop
| Format: | Article |
|---|---|
| Diterbitkan: | Copernicus Publications 2019-01-01 |
Deskripsi
<p>Oxidation flow reactors (OFRs) are an emerging technique for studying the formation and oxidative aging of organic aerosols and other applications. In these flow reactors, hydroxyl radicals (OH), hydroperoxyl radicals (<span class="inline-formula">HO<sub>2</sub></span>), and nitric oxide (NO) are typically produced in the following ways: photolysis of ozone (<span class="inline-formula">O<sub>3</sub></span>) at <span class="inline-formula"><i>λ</i>=25</span>4 nm, photolysis of <span class="inline-formula">H<sub>2</sub>O</span> at <span class="inline-formula"><i>λ</i>=185</span> nm, and via reactions of <span class="inline-formula">O(<sup>1</sup>D)</span> with <span class="inline-formula">H<sub>2</sub>O</span> and nitrous oxide <span class="inline-formula">(N<sub>2</sub>O)</span>; <span class="inline-formula">O(<sup>1</sup>D)</span> is formed via photolysis of <span class="inline-formula">O<sub>3</sub></span> at <span class="inline-formula"><i>λ</i>=254</span> nm and/or <span class="inline-formula">N<sub>2</sub>O</span> at <span class="inline-formula"><i>λ</i>=185</span> nm. Here, we adapt a complementary method that uses alkyl nitrite photolysis as a source of OH via its production of <span class="inline-formula">HO<sub>2</sub></span> and NO followed by the reaction NO <span class="inline-formula">+</span> <span class="inline-formula">HO<sub>2</sub></span> <span class="inline-formula">→</span> <span class="inline-formula">NO<sub>2</sub></span> <span class="inline-formula">+</span> OH. We present experimental and model characterization of the OH exposure and <span class="inline-formula">NO<sub><i>x</i></sub></span> levels generated via photolysis of <span class="inline-formula">C<sub>3</sub></span> alkyl nitrites (isopropyl nitrite, perdeuterated isopropyl nitrite, 1,3-propyl dinitrite) in the Potential Aerosol Mass (PAM) OFR as a function of photolysis wavelength (<span class="inline-formula"><i>λ</i>=254</span> to 369 nm) and organic nitrite concentration (0.5 to 20 ppm). We also apply this technique in conjunction with chemical ionization mass spectrometer measurements of multifunctional oxidation products generated following the exposure of <span class="inline-formula"><i>α</i></span>-Pinene to <span class="inline-formula">HO<sub><i>x</i></sub></span> and <span class="inline-formula">NO<sub><i>x</i></sub></span> obtained using both isopropyl nitrite and <span class="inline-formula">O<sub>3</sub></span> <span class="inline-formula">+</span> <span class="inline-formula">H<sub>2</sub>O</span> <span class="inline-formula">+</span> <span class="inline-formula">N<sub>2</sub>O</span> as the radical precursors.</p>