Quantification of Gas-Wall Partitioning in Teflon Environmental Chambers Using Rapid Bursts of Low-Volatility Oxidized Species Generated in Situ

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• 作者：Jordan E. Krechmer ; Demetrios Pagonis ; Paul J. Ziemann ; Jose L. Jimenez
• 刊名：Environmental Science & Technology
• 出版年：2016
• 出版时间：June 7, 2016
• 年：2016
• 卷：50
• 期：11
• 页码：5757-5765
• 全文大小：489K
• 年卷期：0
• ISSN：1520-5851

文摘

Partitioning of gas-phase organic compounds to the walls of Teflon environmental chambers is a recently reported phenomenon than can affect the yields of reaction products and secondary organic aerosol (SOA) measured in laboratory experiments. Reported time scales for reaching gas-wall partitioning (GWP) equilibrium (τ_GWE) differ by up to 3 orders of magnitude, however, leading to predicted effects that vary from substantial to negligible. A new technique is demonstrated here in which semi- and low-volatility oxidized organic compounds (saturation concentration c* < 100 μg m^–3) were photochemically generated in rapid bursts in situ in an 8 m³ environmental chamber, and then their decay in the absence of aerosol was measured using a high-resolution chemical ionization mass spectrometer (CIMS) equipped with an “inlet-less” NO₃^– ion source. Measured τ_GWE were 7–13 min (rel. std. dev. 33%) for all compounds. The fraction of each compound that partitioned to the walls at equilibrium follows absorptive partitioning theory with an equivalent wall mass concentration in the range 0.3–10 mg m^–3. Measurements using a CIMS equipped with a standard ion–molecule reaction region showed large biases due to the contact of compounds with walls. On the basis of these results, a set of parameters is proposed for modeling GWP in chamber experiments.