The influence of the addition of isoprene on the volatility of particles formed from the photo-oxidation of anthropogenic–biogenic mixtures
<p>In this study, we investigate the influence of isoprene on the volatility of secondary organic aerosol (SOA) formed during the photo-oxidation of mixtures of anthropogenic and biogenic precursors. The SOA particle volatility was quantified using two independent experimental techniques (usin...
| Main Authors: | , , , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2022-10-01
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| Series: | Atmospheric Chemistry and Physics |
| Online Access: | https://acp.copernicus.org/articles/22/13677/2022/acp-22-13677-2022.pdf |
| Summary: | <p>In this study, we investigate the influence of isoprene on the volatility of
secondary organic aerosol (SOA) formed during the photo-oxidation of
mixtures of anthropogenic and biogenic precursors. The SOA particle
volatility was quantified using two independent experimental techniques
(using a thermal denuder and the Filter Inlet for Gas and Aerosols iodide high-resolution time-of-flight Chemical Ionisation Mass Spectrometer – FIGAERO-CIMS) in mixtures of <span class="inline-formula"><i>α</i></span>-pinene/isoprene, <span class="inline-formula"><i>o</i></span>-cresol/isoprene, and <span class="inline-formula"><i>α</i></span>-pinene/<span class="inline-formula"><i>o</i></span>-cresol/isoprene. Single-precursor experiments at various initial
concentrations and results from previous <span class="inline-formula"><i>α</i></span>-pinene/<span class="inline-formula"><i>o</i></span>-cresol
experiments were used as a reference. The oxidation of isoprene did not result in the formation of detectable SOA particle mass in single-precursor
experiments. However, isoprene-derived products were identified in the mixed
systems, likely due to the increase in the total absorptive mass. The
addition of isoprene resulted in mixture-dependent influence on the SOA
particle volatility. Isoprene made no major change to the volatility of
<span class="inline-formula"><i>α</i></span>-pinene SOA particles, though changes in the SOA particle composition were observed and the volatility was reasonably predicted based
on the additivity. Isoprene addition increased <span class="inline-formula"><i>o</i></span>-cresol SOA particle
volatility by <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">5</mn><mo>/</mo><mn mathvariant="normal">15</mn></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="37pt" height="14pt" class="svg-formula" dspmath="mathimg" md5hash="8fb514b05a689cc9c401220c86e61467"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-22-13677-2022-ie00001.svg" width="37pt" height="14pt" src="acp-22-13677-2022-ie00001.png"/></svg:svg></span></span> % of the total mass/signal,
respectively, indicating a potential to increase the overall volatility that
cannot be predicted based on the additivity. The addition of isoprene to the
<span class="inline-formula"><i>α</i></span>-pinene/<span class="inline-formula"><i>o</i></span>-cresol system (i.e. <span class="inline-formula"><i>α</i></span>-pinene/<span class="inline-formula"><i>o</i></span>-cresol/isoprene) resulted in slightly fewer volatile particles than those measured in the <span class="inline-formula"><i>α</i></span>-pinene/<span class="inline-formula"><i>o</i></span>-cresol systems. The measured volatility in the <span class="inline-formula"><i>α</i></span>-pinene/<span class="inline-formula"><i>o</i></span>-cresol/isoprene system had an <span class="inline-formula">∼6</span> % higher low volatile organic compound (LVOC) mass/signal compared to that predicted assuming additivity with a correspondingly lower semi-volatile organic compound (SVOC) fraction. This suggests that any effects that could increase the SOA volatility from the addition of isoprene are likely
outweighed by the formation of lower-volatility compounds in more complex anthropogenic–biogenic precursor mixtures. Detailed chemical composition measurements support the measured volatility distribution changes and showed
an abundance of unique-to-the-mixture products appearing in all the mixed
systems accounting for around 30 %–40 % of the total particle-phase signal. Our results demonstrate that the SOA particle volatility and its
prediction can be affected by the interactions of the oxidized products in mixed-precursor systems, and further mechanistic understanding is required to improve their representation in chemical transport models.</p> |
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| ISSN: | 1680-7316 1680-7324 |