A combined gas- and particle-phase analysis of highly oxygenated organic molecules (HOMs) from <i>α</i>-pinene ozonolysis
<p>Highly oxygenated organic molecules (HOMs) are important for the formation of secondary organic aerosol (SOA), which poses serious health risks and exerts great influence on Earth's climate. However, the speciation of particle-phase HOMs and its relationship with gas-phase HOM formatio...
| Main Authors: | , , , , , , , |
|---|---|
| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2023-03-01
|
| Series: | Atmospheric Chemistry and Physics |
| Online Access: | https://acp.copernicus.org/articles/23/3707/2023/acp-23-3707-2023.pdf |
| Summary: | <p>Highly oxygenated organic molecules (HOMs) are important for the formation of secondary organic aerosol (SOA), which poses serious health risks and exerts great influence on Earth's climate. However, the speciation of particle-phase HOMs and its relationship with gas-phase HOM formation has been limited by the lack of suitable analytical techniques. Here, combining a novel particle evaporation inlet, the VIA (Vaporization Inlet for Aerosols), with a nitrate chemical ionization mass spectrometer (<span class="inline-formula">NO<sub>3</sub></span>-CIMS), gas- and particle-phase HOM products of <span class="inline-formula"><i>α</i></span>-pinene ozonolysis were studied under different conditions. Within the 50 min residence time of our Teflon chamber, we observed enhancement of <span class="inline-formula">C<sub>16</sub></span>–<span class="inline-formula">C<sub>19</sub></span> HOM dimers in particles compared to the HOMs that were condensing. In particular, gas-phase dimer formation was considerably suppressed in experiments with the addition of CO or NO, but dimers still made up a considerable fraction of the observed SOA. In addition to the generally shorter carbon skeletons of the particle-phase dimers (i.e., <span class="inline-formula">C<sub>16</sub></span>–<span class="inline-formula">C<sub>19</sub></span>) compared to the gas phase (<span class="inline-formula">C<sub>19</sub></span>–<span class="inline-formula">C<sub>20</sub></span>), average <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M11" display="inline" overflow="scroll" dspmath="mathml"><mrow><mrow class="chem"><mi mathvariant="normal">O</mi></mrow><mo>/</mo><mrow class="chem"><mi mathvariant="normal">C</mi></mrow></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="25pt" height="14pt" class="svg-formula" dspmath="mathimg" md5hash="60ed142825a1a501a71c21d96b08828b"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-23-3707-2023-ie00001.svg" width="25pt" height="14pt" src="acp-23-3707-2023-ie00001.png"/></svg:svg></span></span> ratios of the HOMs (especially in the dimer range) also decreased slightly in the particle phase. <span class="inline-formula">C<sub>17</sub>H<sub>26</sub>O<sub><i>z</i></sub></span> compounds, which have often been reported by previous offline measurements, dominate the particle-phase HOM mass spectra in <span class="inline-formula"><i>α</i></span>-pinene ozonolysis experiments. Our results indicate that these <span class="inline-formula">C<sub>17</sub></span> compounds might be related to
particle-phase processes within 1 h after HOM condensation. However,
the new VIA–<span class="inline-formula">NO<sub>3</sub></span>-CIMS system used in this work will require more
detailed characterization to better understand how the thermal desorption
and wall effects may modify the measured particle-phase HOM distributions.
Nevertheless, organic nitrate, for example, measured by this novel
VIA–<span class="inline-formula">NO<sub>3</sub></span>-CIMS system was consistent with the measurements of an Aerodyne aerosol mass spectrometer (AMS), showing the capability of this system as a promising technique for particle-phase HOM measurements. Taken together, we believe that this system is a promising technique for combined online gas- and particle-phase HOM measurements.</p> |
|---|---|
| ISSN: | 1680-7316 1680-7324 |