Fundamental Time Scales Governing Organic Aerosol Multiphase Partitioning and Oxidative Aging

详细信息    查看全文

• 作者：Haofei Zhang ; David R. Worton ; Steve Shen ; Theodora Nah ; Gabriel Isaacman-VanWertz ; Kevin R. Wilson ; Allen H. Goldstein
• 刊名：Environmental Science & Technology
• 出版年：2015
• 出版时间：August 18, 2015
• 年：2015
• 卷：49
• 期：16
• 页码：9768-9777
• 全文大小：655K
• ISSN：1520-5851

文摘

Traditional descriptions of gas鈥損article partitioning of organic aerosols (OA) rely solely on thermodynamic properties (e.g., volatility). Under realistic conditions where phase partitioning is dynamic rather than static, the transformation of OA involves the interplay of multiphase partitioning with oxidative aging. A key challenge remains in quantifying the fundamental time scales for evaporation and oxidation of semivolatile OA. In this paper, we use isomer-resolved product measurements of a series of normal-alkanes (C₁₈, C₂₀, C₂₂, and C₂₄) to distinguish between gas-phase and heterogeneous oxidation products formed by reaction with hydroxyl radicals (OH). The product isomer distributions when combined with kinetics measurements of evaporation and oxidation enable a quantitative description of the multiphase time scales to be simulated using a single-particle kinetic model. Multiphase partitioning and oxidative transformation of semivolatile normal-alkanes under laboratory conditions is largely controlled by the particle phase state, since the time scales of heterogeneous oxidation and evaporation are found to occur on competing time scales (on the order of 10^鈥? h). This is in contrast to atmospheric conditions where heterogeneous oxidation time scales are expected to be much longer (on the order of 10² h), with gas-phase oxidation being the dominant process regardless of the evaporation kinetics. Our results demonstrate the dynamic nature of OA multiphase partitioning and oxidative aging and reveal that the fundamental time scales of these processes are crucial for reliably extending laboratory measurements of OA phase partitioning and aging to the atmosphere.