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<p class="MsoNormal">Anita Anosike, Omar El Hajj, Chase K. Glenn, Samuel W. Hartness, Annabelle W. Hill, Nicholas S. Dewey, Jonathan Heeseung Choi, I. Jonathan Amster, Brandon Rotavera, and Rawad Saleh. Temperature dependence of secondary organic aerosol formation
in toluene-combustion emissions. <i>Aerosol Science and Technology</i>, 1–18. <a href="https://doi.org/10.1080/02786826.2026.2642843">
https://doi.org/10.1080/02786826.2026.2642843</a>, 2026. <o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><b>Abstract</b>. We investigated secondary organic aerosol (SOA) formation in toluene-combustion emissions for combustion temperatures ranging between 1000<span style="font-family:"Arial",sans-serif"> </span>K and 1300<span style="font-family:"Arial",sans-serif"> </span>K.
The experiments involved combusting a premixed toluene and air mixture in an atmospheric-pressure temperature-controlled reactor and then sending the emissions through an oxidation flow reactor (OFR) to simulate atmospheric aging with OH radicals. SOA production
dropped sharply with increasing temperature, with a reduction by a factor of <span style="font-family:"Cambria Math",serif">
∼</span>57 in SOA between 1000<span style="font-family:"Arial",sans-serif"> </span>K and 1300<span style="font-family:"Arial",sans-serif"> </span>K, consistent with previous studies that showed enhanced SOA formation during cold-start (low-temperature) operation
compared to hot-stabilized operation of gasoline vehicles. Chemical speciation analysis of the gaseous emissions (SOA precursors) and SOA particles demonstrated that SOA produced at 1000<span style="font-family:"Arial",sans-serif"> </span>K consisted of molecules
with higher O/C but less unsaturated and aromatic structures than SOA produced at 1200<span style="font-family:"Arial",sans-serif"> </span>K. These results indicate that SOA precursors at 1000<span style="font-family:"Arial",sans-serif"> </span>K were largely
comprised of simple aromatic species (mostly unburned toluene) that underwent OH-initiated abstraction followed by oxygen addition ring-opening reactions in the OFR, leading to the high O/C and loss of aromaticity. However, in addition to single-ring aromatics,
the SOA precursors at 1200<span style="font-family:"Arial",sans-serif"> </span>K likely featured large-molecular-size multi-ring aromatics that retained more of their aromatic structures after oxidation. Overall, the findings reported in this paper highlight
the importance of combustion temperature in determining the molecular distribution of the emitted SOA precursors and the consequent SOA formation potential, and provide fundamental reasoning for the high variability in SOA production for different operation
conditions of gasoline vehicles.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><a href="https://sites.google.com/site/pamwiki/publications-using-the-pam-oxidation-flow-reactor">PAM Wiki - Publications Using the PAM Oxidation Flow Reactor</a><o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New";color:black">Andrew Lambe, PhD, PMP<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New";color:black">Principal Scientist<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New";color:black">Center for Aerosol and Cloud Chemistry<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New";color:black">Aerodyne Research, Inc.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New";color:black">45 Manning Rd., Billerica, MA, 01821<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New";color:black">+1-978-663-9500 x 209<span style="mso-ligatures:none"><o:p></o:p></span></span></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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