Transitions from Functionalization to Fragmentation Reactions of Laboratory Secondary Organic Aerosol (SOA) Generated from the OH Oxidation of Alkane Precursors

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• 作者：Andrew T. Lambe ; Timothy B. Onasch ; David R. Croasdale ; Justin P. Wright ; Alexander T. Martin ; Jonathan P. Franklin ; Paola Massoli ; Jesse H. Kroll ; Manjula R. Canagaratna ; William H. Brune ; Douglas R. Worsnop ; Paul Davidovits
• 刊名：Environmental Science & Technology (ES&T)
• 出版年：2012
• 出版时间：May 15, 2012
• 年：2012
• 卷：46
• 期：10
• 页码：5430-5437
• 全文大小：402K
• 年卷期：v.46,no.10(May 15, 2012)
• ISSN：1520-5851

文摘

Functionalization (oxygen addition) and fragmentation (carbon loss) reactions governing secondary organic aerosol (SOA) formation from the OH oxidation of alkane precursors were studied in a flow reactor in the absence of NO_x. SOA precursors were n-decane (n-C₁₀), n-pentadecane (n-C₁₅), n-heptadecane (n-C₁₇), tricyclo[5.2.1.0^2,6]decane (JP-10), and vapors of diesel fuel and Southern Louisiana crude oil. Aerosol mass spectra were measured with a high-resolution time-of-flight aerosol mass spectrometer, from which normalized SOA yields, hydrogen-to-carbon (H/C) and oxygen-to-carbon (O/C) ratios, and C_xH_y⁺, C_xH_yO⁺, and C_xH_yO₂⁺ ion abundances were extracted as a function of OH exposure. Normalized SOA yield curves exhibited an increase followed by a decrease as a function of OH exposure, with maximum yields at O/C ratios ranging from 0.29 to 0.74. The decrease in SOA yield correlates with an increase in oxygen content and decrease in carbon content, consistent with transitions from functionalization to fragmentation. For a subset of alkane precursors (n-C₁₀, n-C₁₅, and JP-10), maximum SOA yields were estimated to be 0.39, 0.69, and 1.1. In addition, maximum SOA yields correspond with a maximum in the C_xH_yO⁺ relative abundance. Measured correlations between OH exposure, O/C ratio, and H/C ratio may enable identification of alkane precursor contributions to ambient SOA.