A comparative and experimental study of the reactivity with nitrate radical of two terpenes: <i>α</i>-terpinene and <i>γ</i>-terpinene
<p>Biogenic volatile organic compounds (BVOCs) are intensely emitted by forests and crops into the atmosphere. During the night, they react very rapidly with the nitrate radical (<span class="inline-formula">NO<sub>3</sub></span>), leading to the formation of...
| Main Authors: | , , , , , |
|---|---|
| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2020-12-01
|
| Series: | Atmospheric Chemistry and Physics |
| Online Access: | https://acp.copernicus.org/articles/20/15167/2020/acp-20-15167-2020.pdf |
| Summary: | <p>Biogenic volatile organic compounds (BVOCs) are intensely
emitted by forests and crops into the atmosphere. During the night, they
react very rapidly with the nitrate radical (<span class="inline-formula">NO<sub>3</sub></span>), leading to the
formation of a variety of functionalized products including organic nitrates
and to large amounts of secondary organic aerosols (SOAs). Organic nitrates
(ONs) have been shown not only to play a key role in the transport of reactive
nitrogen and consequently in the ozone budget but also to be important
components of the total organic-aerosol mass, while SOAs are known to play a direct
and indirect role in the climate. However, the reactivity of BVOCs with
<span class="inline-formula">NO<sub>3</sub></span> remains poorly studied. The aim of this work is to provide new
kinetic and mechanistic data for two monoterpenes (<span class="inline-formula">C<sub>10</sub>H<sub>16</sub></span>),
<span class="inline-formula"><i>α</i></span>- and <span class="inline-formula"><i>γ</i></span>-terpinene, through experiments in simulation
chambers. These two compounds, which have very similar chemical structures,
have been chosen in order not only to overcome the lack of experimental data but also to
highlight the influence of the chemical structure on the reactivity.</p>
<p>Rate constants have been measured using both relative and absolute methods.
They were found to be <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M9" display="inline" overflow="scroll" dspmath="mathml"><mrow><mo>(</mo><mn mathvariant="normal">1.2</mn><mo>±</mo><mn mathvariant="normal">0.5</mn><mo>)</mo><mo>×</mo><msup><mn mathvariant="normal">10</mn><mrow><mo>-</mo><mn mathvariant="normal">10</mn></mrow></msup></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="89pt" height="15pt" class="svg-formula" dspmath="mathimg" md5hash="e7da5de7f6d22f350852b4d8faf07c17"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-20-15167-2020-ie00001.svg" width="89pt" height="15pt" src="acp-20-15167-2020-ie00001.png"/></svg:svg></span></span> and (<span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M10" display="inline" overflow="scroll" dspmath="mathml"><mrow><mn mathvariant="normal">2.9</mn><mo>±</mo><mn mathvariant="normal">1.1</mn><mo>)</mo><mo>×</mo><msup><mn mathvariant="normal">10</mn><mrow><mo>-</mo><mn mathvariant="normal">11</mn></mrow></msup></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="85pt" height="15pt" class="svg-formula" dspmath="mathimg" md5hash="12768fc4778aa761021ecc4c03fcad0a"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-20-15167-2020-ie00002.svg" width="85pt" height="15pt" src="acp-20-15167-2020-ie00002.png"/></svg:svg></span></span> cm<span class="inline-formula"><sup>3</sup></span> molecule<span class="inline-formula"><sup>−1</sup></span> s<span class="inline-formula"><sup>−1</sup></span> for <span class="inline-formula"><i>α</i></span>- and <span class="inline-formula"><i>γ</i></span>-terpinene respectively. Mechanistic studies have
also been conducted in order to identify and quantify the main reaction
products. Total organic nitrate and SOA yields have been determined. While
organic nitrate formation yields appear to be similar, SOA yields exhibit
large differences with <span class="inline-formula"><i>γ</i></span>-terpinene being a much more efficient
precursor of aerosols. In order to provide explanations for this difference, chemical analysis of the gas-phase products was performed at the molecular scale. Detected products allowed for proposing chemical mechanisms and providing explanations through peroxy and alkoxy reaction pathways.</p> |
|---|---|
| ISSN: | 1680-7316 1680-7324 |