Effect of salt seed particle surface area, composition and phase on secondary organic aerosol mass yields in oxidation flow reactors
<p>Atmospheric particulate water is ubiquitous, affecting particle transport and uptake of gases. Yet, research on the effect of water on secondary organic aerosol (SOA) mass yields is not consistent. In this study, the SOA mass yields of an <span class="inline-formula"><i&g...
| Main Authors: | , , , , |
|---|---|
| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2019-03-01
|
| Series: | Atmospheric Chemistry and Physics |
| Online Access: | https://www.atmos-chem-phys.net/19/2701/2019/acp-19-2701-2019.pdf |
| Summary: | <p>Atmospheric particulate water is ubiquitous, affecting particle transport and
uptake of gases. Yet, research on the effect of water on secondary organic
aerosol (SOA) mass yields is not consistent. In this study, the SOA mass
yields of an <span class="inline-formula"><i>α</i></span>-pinene and m-xylene mixture, at a concentration of
60 <span class="inline-formula">µ</span>g m<span class="inline-formula"><sup>−3</sup></span>, were examined using an oxidation flow reactor
operated at a relative humidity (RH) of 60 % and a residence time of 160 s. Wet or dried
ammonium sulfate and ammonium nitrate seed particles were used. By varying
the amount of seed particle surface area, the underestimation of SOA
formation induced by the short residence time in flow reactors was confirmed.
Starting at a SOA mass concentration of <span class="inline-formula">∼5</span> <span class="inline-formula">µ</span>g m<span class="inline-formula"><sup>−3</sup></span>, the
maximum yield increased by a factor of <span class="inline-formula">∼2</span> with dry seed particles and on
average a factor of 3.2 with wet seed particles. Hence, wet particles increased
the SOA mass yield by <span class="inline-formula">∼60</span> % compared to the dry experiment. Maximum
yield in the reactor was achieved using a surface area concentration of <span class="inline-formula">∼1600</span> <span class="inline-formula">µ</span>m<span class="inline-formula"><sup>2</sup></span> cm<span class="inline-formula"><sup>−3</sup></span>. This corresponded to a condensational
lifetime of 20 s for low-volatility organics. The <span class="inline-formula">O:C</span> ratio of SOA on
wet ammonium sulfate was significantly higher than when using ammonium
nitrate or dry ammonium sulfate seed particles, probably due to differences
in heterogeneous chemistry.</p> |
|---|---|
| ISSN: | 1680-7316 1680-7324 |