Impact of HO2/RO2 ratio on highly oxygenated α-pinene photooxidation products and secondary organic aerosol formation potential

• DOI: 10.5194/egusphere-2023-2402
• Publication Date: 2023-10-26T10:42:56Z
• Authors: Yarê Baker; Sungah Kang; Hui Wang; Rongrong Wu; Jian Xu; Annika Zanders; Quanfu He; Thorsten Hohaus; Till Ziehm; Veronica Geretti; Thomas J. Bannan; Simon P. O'Meara; Aristeidis Voliotis; Mattias Hallquist; Gordon McFiggans; Sören R. Zorn; Andreas Wahner; Thomas Mentel
• Keywords: Chemistry; info:eu-repo/classification/ddc/550; 550; 13. Climate action; Physics; QC1-999; QD1-999

Abstract. Highly oxygenated molecules (HOM) from the atmospheric oxidation of biogenic volatile organic compounds are important contributors to secondary aerosol (SOA). Organic peroxy radicals (RO2) and hydroperoxy (HO2) key species influencing HOM product distribution. In laboratory studies experimental requirements often result in overemphasis RO2 cross-reactions compared reactions with HO2. We analyzed photochemical formation HOMs α-pinene their potential contribute SOA under high (≈1/1) low (≈1/100) HO2/RO2 conditions. As > 1 is prevalent daytime atmosphere, sufficiently crucial mimic conditions prevent biases by on distribution thus yield. Experiments were performed steady-state new, continuously stirred tank reactor SAPHIR-STAR at Forschungszentrum Jülich. The ratio was increased adding CO, while keeping OH concentration constant. determined HOM’s potential, considering fraction remaining gas phase after seeding (NH4)2SO4 aerosol. Increase led a reduction main driver being ≈60 % HOM-accretion products. also observed shift HOM-monomer functionalization carbonyl hydroperoxide groups. ≈30 HO2/RO2≈1/1. Particle observations measured an about according decrease mass Our study showed that too ratios atmosphere can lead overestimation yields.