2017/08/28 by Ågot K. Watne, Jonathan Westerlund, Watne, Ågot K. +7
Earth and Planetary Sciences · Environmental Science · #Air Quality Monitoring and Forecasting #Air Quality and Health Impacts #Atmospheric and Oceanic Physics (physics.ao-ph) #Atmospheric chemistry and aerosols #FOS: Physical sciences
paper · pdf · doi:10.48550/arxiv.1708.08243
openalex publication_date 2017/08/28 · openalex created_date 2022/09/24 · openalex updated_date 2026/07/28
The behaviour of secondary organic aerosols (SOA) in the atmosphere is highly\ndependent on their thermal properties. Here we investigate the volatility of\nSOA formed from alpha-pinene, beta-pinene and limonene upon ozone- and\nOH-induced oxidation, and the effect of OH-induced ageing on the initially\nproduced SOA. For all three terpenes, the ozone-induced SOA was less volatile\nthan the OH-induced SOA. The thermal properties of the SOA were described using\nthree parameters extracted from the volatility measurements: the temperature at\nwhich 50 per cent of the volume has evaporated (TVFR0.5), which is used as a\ngeneral volatility indicator; a slope factor (SVFR), which describes the\nvolatility distribution; and TVFR0.1, which measures the volatility of the\nleast volatile particle fraction. Limonene-derived SOA generally had higher\nTVFR0.5 values and shallower slopes than SOA derived from alpha- and\nbeta-pinene. This was especially true for the ozone-induced SOA, partially\nbecause the ozonolysis of limonene has a strong tendency to cause SOA formation\nand to produce extremely low volatility VOCs (ELVOCs). Ageing by OH exposure\ndid not reduce TVFR0.5 for any of the studied terpenes but did increase the\nbreadth of the volatility distribution by increasing the aerosols heterogeneity\nand contents of substances with different vapour pressures, also leading to\nincreases in TVFR0.1. This stands in contrast to previously reported results\nfrom smog chamber experiments, in which TVFR0.5 always increased with ageing.\nThese results demonstrate that there are two opposing processes that influence\nthe evolution of SOAs thermal properties as they age, and that results from\nboth flow reactors and static chambers are needed to fully understand the\ntemporal evolution of atmospheric SOA thermal properties.\n