Measurement report: Effects of NO x and seed aerosol on highly oxygenated organic molecules (HOMs) from cyclohexene ozonolysis

摘要: Abstract. Cyclohexene ( C6H10 ) is commonly used as a proxy for biogenic monoterpenes, when studying their oxidation mechanisms and secondary organic aerosol (SOA) formation. The ozonolysis of cyclohexene has been shown to be effective at producing highly oxygenated molecules (HOMs), group known important in the formation SOA. Here, we provide an in-depth look how fate broad range observed HOMs changed with perturbations from NOx seed particles. were produced chamber measured chemical ionisation mass spectrometer (CIMS) using nitrate NO 3 - reagent ion. As high-resolution CIMS instruments spectra numerous ion signals wealth information that can hard manage, employed primarily statistical approach data analysis. To utilise many individual HOM possible, each compound was assigned parameter describing quality signal. These parameters then weights or determine inclusion given signal further analyses. Under unperturbed conditions, peaks chamber, including C6H8O9 largest C12H20O9 “dimer” product. With addition nitric oxide (NO) into spectrum considerably, expected. Dimer product decreased overall, but increase dimers functionalities seen, result NO3 radical oxidation. response monomer varied, while nitrate-containing monomers increased, non-nitrate either increased decreased, depending on molecules. condensation sink, which markedly all low-volatility compounds. Larger seen have higher affinity condensation, more detailed analysis showed uptake controlled mainly by number oxygen atoms molecule. Nitrates required content condense similar rates HOMs. We also tested two existing elemental-composition-based parameterisations ability reproduce our system. Both predicted volatilities than observed, most likely due enhancing models would suggest.