Reply on RC1

Le résumé fourni par la source

Abstract. Atmospheric temperature and composition variations significantly influence secondary organic aerosol (SOA) formation and aging, and thus fine particulate matter levels and properties relevant for climate, air quality, and human health. However, the temperature dependence of SOA formation and aging from mixed volatile organic compounds (VOCs) remains insufficiently understood. Therefore, we investigated SOA formation from the oxidation of isoprene and α-pinene mixtures covering the range of tropospheric temperatures (213–313 K). We further examine the aging of the resulting SOA by gradually warming to mimic their atmospheric transport and diurnal aging processes. Notably, at 213 K, isoprene most strongly suppresses α-pinene dimer (C18–20) formation, with isoprene-α-pinene cross dimers appearing 3.5 times more frequently than at 273 K, while the suppression is not temperature-sensitive above 273 K. Upon subsequent warming, particles formed at different temperature ranges undergo distinct aging processes including aerosol evaporation and water uptake. Surprisingly, particles formed at higher temperatures are more oxidized yet more volatile than those formed at lower temperatures and subsequently warmed. Chemical transport modeling accounting for temperature-depended simultaneous oxidation of isoprene and α-pinene predicts higher SOA levels across Europe, aligning more closely with observations. These findings highlight the need to consider both temperature and the interaction of biogenic VOCs to accurately describe SOA formation, aging, and global burden.

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