Kinetics, SOA yields, and chemical composition of secondary organic aerosol from <i>β</i>-caryophyllene ozonolysis with and without nitrogen oxides between 213 and 313 K
<p><span class="inline-formula"><i>β</i></span>-caryophyllene (BCP) is one of the most important sesquiterpenes (SQTs) in the atmosphere, with a large potential contribution to secondary organic aerosol (SOA) formation mainly from reactions with ozone (O<sp...
| Main Authors: | , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2022-05-01
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| Series: | Atmospheric Chemistry and Physics |
| Online Access: | https://acp.copernicus.org/articles/22/6001/2022/acp-22-6001-2022.pdf |
| Summary: | <p><span class="inline-formula"><i>β</i></span>-caryophyllene (BCP) is one of the most important
sesquiterpenes (SQTs) in the atmosphere, with a large potential contribution
to secondary organic aerosol (SOA) formation mainly from reactions with
ozone (O<span class="inline-formula"><sub>3</sub></span>) and nitrate radicals (NO<span class="inline-formula"><sub>3</sub></span>). In this work, we study the
temperature dependence of the kinetics of BCP ozonolysis, SOA yields, and
SOA chemical composition in the dark and in the absence and presence of
nitrogen oxides including nitrate radicals (NO<span class="inline-formula"><sub>3</sub></span>). We cover a
temperature range of 213–313 K, representative of tropospheric
conditions. The oxidized components in both gas and particle phases were
characterized on a molecular level by a chemical ionization mass
spectrometer equipped with a filter inlet for gases and aerosols using
iodide as the reagent ion (FIGAERO-iodide-CIMS). The batch mode experiments
were conducted in the 84.5 m<span class="inline-formula"><sup>3</sup></span> aluminium simulation chamber AIDA at the
Karlsruhe Institute of Technology (KIT). In the absence of nitrogen oxides,
the temperature-dependent rate coefficient of the endocyclic double bond in
BCP reacting with ozone between 243–313 K is negatively correlated with
temperature, corresponding to the following Arrhenius equation: <span class="inline-formula"><i>k</i>=</span>
(1.6 <span class="inline-formula">±</span> 0.4) <span class="inline-formula">×</span> 10<span class="inline-formula"><sup>−15</sup></span> <span class="inline-formula">×</span> exp((559 <span class="inline-formula">±</span> 97)<span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M13" display="inline" overflow="scroll" dspmath="mathml"><mrow><mo>/</mo><mi>T</mi></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="14pt" height="14pt" class="svg-formula" dspmath="mathimg" md5hash="1817643d3376598401f9272685f497c2"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-22-6001-2022-ie00001.svg" width="14pt" height="14pt" src="acp-22-6001-2022-ie00001.png"/></svg:svg></span></span>).
The SOA yields increase from 16 <span class="inline-formula">±</span> 5 % to 37 <span class="inline-formula">±</span> 11 %, with
temperatures decreasing from 313 to 243 K at a total organic particle mass
of 10 <span class="inline-formula">µg</span> m<span class="inline-formula"><sup>−3</sup></span>. The variation in the ozonolysis temperature leads
to a substantial impact on the abundance of individual organic molecules. In
the absence of nitrogen oxides, monomers C<span class="inline-formula"><sub>14−15</sub></span>H<span class="inline-formula"><sub>22−24</sub></span>O<span class="inline-formula"><sub>3−7</sub></span>
(37.4 %), dimers C<span class="inline-formula"><sub>28−30</sub></span>H<span class="inline-formula"><sub>44−48</sub></span>O<span class="inline-formula"><sub>5−9</sub></span> (53.7 %), and
trimers C<span class="inline-formula"><sub>41−44</sub></span>H<span class="inline-formula"><sub>62−66</sub></span>O<span class="inline-formula"><sub>9−11</sub></span> (8.6 %) are abundant in the
particle phase at 213 K. At 313 K, we observed more oxidized monomers (mainly
C<span class="inline-formula"><sub>14−15</sub></span>H<span class="inline-formula"><sub>22−24</sub></span>O<span class="inline-formula"><sub>6−9</sub></span>, 67.5 %) and dimers (mainly
C<span class="inline-formula"><sub>27−29</sub></span>H<span class="inline-formula"><sub>42−44</sub></span>O<span class="inline-formula"><sub>9−11</sub></span>, 27.6 %), including highly oxidized
molecules (HOMs; C<span class="inline-formula"><sub>14</sub></span>H<span class="inline-formula"><sub>22</sub></span>O<span class="inline-formula"><sub>7,9</sub></span>, C<span class="inline-formula"><sub>15</sub></span>H<span class="inline-formula"><sub>22</sub></span>O<span class="inline-formula"><sub>7,9</sub></span>C<span class="inline-formula"><sub>15</sub></span>H<span class="inline-formula"><sub>24</sub></span>O<span class="inline-formula"><sub>7,9</sub></span>), which can be formed via hydrogen shift
mechanisms, but no significant trimers. In the presence of nitrogen oxides, the
organonitrate fraction increased from 3 % at 213 K to 12 % and 49 %
at 243 and 313 K, respectively. Most of the organonitrates were monomers
with C<span class="inline-formula"><sub>15</sub></span> skeletons and only one nitrate group. More highly oxygenated
organonitrates were observed at higher temperatures, with their
signal-weighted <span class="inline-formula">O:C</span> atomic ratio increasing from 0.41 to 0.51 from 213 to
313 K. New dimeric and trimeric organic species without nitrogen atoms
(C<span class="inline-formula"><sub>20</sub></span>, C<span class="inline-formula"><sub>35</sub></span>) were formed in the presence of nitrogen oxides at 298–313 K,
indicating potential new reaction pathways. Overall, our results show that
increasing temperatures lead to a relatively small decrease in the rate
coefficient of the endocyclic double bond in BCP reacting with ozone but to
a strong decrease in SOA yields. In contrast, the formation of HOMs and
organonitrates increases significantly with temperature.</p> |
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| ISSN: | 1680-7316 1680-7324 |