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Isoprene versus Monoterpenes as Gas-Phase Organic Acid Precursors in the Atmosphere
ACS Earth and Space Chemistry ( IF 3.4 ) Pub Date : 2021-05-25 , DOI: 10.1021/acsearthspacechem.1c00093
Michael F. Link 1 , Patrick Brophy 1 , S. Ryan Fulgham 1 , Trey Murschell 1 , Delphine K. Farmer 1
Affiliation  

Gas-phase organic acids are ubiquitous throughout the atmosphere and are tracers for volatile organic compound oxidation, although their abundance and sources are poorly characterized. Several studies have pointed to the oxidation of isoprene and monoterpenes as major sources of formic and acetic acids. Here, we quantify >100 gas-phase organic acids produced from isoprene and α-pinene oxidation in a series of laboratory chamber experiments. Overall, gas-phase organic acids constitute 1–28% of the initial organic carbon reacted in the experiments. Isoprene is a precursor for detected organic acids in amounts at least 2–3× greater than α-pinene from OH oxidation. We compare laboratory observations with two summertime field sites—one dominated by isoprene emissions (Southern Oxidant and Aerosol Study—SOAS) and one by monoterpene emissions (Seasonal Particles in Forests Flux studY—SPiFFY). Daytime organic acid mixing ratios were 4× higher at SOAS than SPiFFY, likely because of the substantial isoprene OH oxidation. In contrast to SOAS, factor analysis reveals separate daytime and nighttime organic acid sources at SPiFFY not obviously originating from photochemical oxidation. When available, isoprene is likely a dominant precursor for gas-phase organic acids.

中文翻译:

异戊二烯与单萜作为大气中的气相有机酸前体

气相有机酸在整个大气中无处不在,是挥发性有机化合物氧化的示踪剂,尽管它们的丰度和来源尚不清楚。一些研究指出异戊二烯和单萜的氧化是甲酸和乙酸的主要来源。在这里,我们在一系列实验室室实验中量化了由异戊二烯和 α-蒎烯氧化产生的 >100 种气相有机酸。总体而言,气相有机酸占实验中反应的初始有机碳的 1-28%。异戊二烯是检测到的有机酸的前体,其含量至少比 OH 氧化产生的 α-蒎烯高 2–3 倍。我们将实验室观察结果与两个夏季现场站点进行了比较——一个以异戊二烯排放为主(南方氧化剂和气溶胶研究 - SOAS),一个以单萜排放为主(森林中的季节性粒子通量研究 - SPiFFY)。SOAS 的白天有机酸混合比比 SPiFFY 高 4 倍,这可能是因为大量的异戊二烯 OH 氧化。与 SOAS 不同的是,因子分析揭示了 SPiFFY 日间和夜间的有机酸来源不同,显然不是来自光化学氧化。如果可用,异戊二烯可能是气相有机酸的主要前体。因子分析揭示了 SPiFFY 日间和夜间不同的有机酸来源,并非明显来自光化学氧化。如果可用,异戊二烯可能是气相有机酸的主要前体。因子分析揭示了 SPiFFY 日间和夜间不同的有机酸来源,并非明显来自光化学氧化。如果可用,异戊二烯可能是气相有机酸的主要前体。
更新日期:2021-06-17
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