Drying-Induced Evaporation of Secondary Organic Aerosol during Summer

详细信息    查看全文

• 作者：Marwa M. H. El-Sayed ; Dziedzorm Amenumey ; Christopher J. Hennigan
• 刊名：Environmental Science & Technology
• 出版年：2016
• 出版时间：April 5, 2016
• 年：2016
• 卷：50
• 期：7
• 页码：3626-3633
• 全文大小：462K
• ISSN：1520-5851

文摘

This study characterized the effect of drying on the concentration of atmospheric secondary organic aerosol (SOA). Simultaneous measurements of water-soluble organic carbon in the gas (WSOC_g) and particle (WSOC_p) phases were carried out in Baltimore, MD during the summertime. To investigate the effect of drying on SOA, the WSOC_p measurement was alternated through an ambient channel (WSOC_p) and a “dried” channel (WSOC_p,dry) maintained at ∼35% relative humidity (RH). The average mass ratio between WSOC_p,dry and WSOC_p was 0.85, showing that significant evaporation of the organic aerosol occurred due to drying. The average amount of evaporated water-soluble organic matter (WSOM = WSOC × 1.95) was 0.6 μg m^–3; however, the maximum evaporated WSOM concentration exceeded 5 μg m^–3, demonstrating the importance of this phenomenon. The systematic difference between ambient and dry channels indicates a significant and persistent source of aqueous SOA formed through reversible uptake processes. The wide-ranging implications of the work are discussed, and include: new insight into atmospheric SOA formation; impacts on particle measurement techniques; a newly identified bias in PM_2.5 measurements using the EPA’s Federal Reference and Equivalent Methods (FRM and FEM); atmospheric model evaluations; and the challenge in relating ground-based measurements to remote sensing of aerosol properties.