Stable carbon isotope measurements of atmospheric organic acids in Los Angeles, California
Stable carbon isotope measurements of atmospheric organic acids in Los Angeles, California
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DOI：
10.1029/95gl01359
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发表时间：
1995-06
影响因子：
5.2
通讯作者：
H. Sakugawa;I. Kaplan
中科院分区：
文献类型：
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作者：
H. Sakugawa;I. Kaplan
大气中的有机酸是城市烟雾和霾中普遍存在的成分，也存在于农村和大部分无人居住地区（例如亚马逊雨林盆地）的大气中。我们在这里通过测量稳定碳同位素比（例如 13C/12C(δ13C)）报告洛杉矶大气有机酸的来源特征。该研究是通过使用离子色谱排除（ICE）分离甲酸和乙酸并从大气雨样品中分离毫克量的单独有机酸来进行的。使用甲酸和乙酸的真实参考样品确定，ICE 分离后仅发生可忽略不计的 δ13C 值同位素分馏。 1991 年至 1992 年间，在洛杉矶收集雨水，分离甲酸和乙酸用于同位素测量。本文提出的结果表明，乙酸 (-20.5‰) 和甲酸 (-30.1‰) 的平均 δ13C 值之间存在显着同位素差异。我们从这些结果中得出结论，甲酸源自直接排放的甲酸与大气中二次氧化过程形成的酸（最有可能来自醛）的混合，而乙酸仅源自直接源排放。
Atmospheric organic acids are ubiquitous constituents of urban smog and haze and are also present in the atmospheres of rural and largely uninhabited areas (e.g., the Amazon Rain Forest Basin). We report here source characterization of atmospheric organic acids in Los Angeles by measurements of their stable carbon isotopic ratios, e.g., 13C/12C(δ13C). The study was performed by separating formic and acetic acids using ion chromatography exclusion (ICE) and isolating milligram quantities of individual organic acids from atmospheric rain samples. Authentic reference samples of formic and acetic acids were used to determine that only a negligible isotope fractionation of δ13C value occurs after the ICE separation. During 1991–1992, rainwaters were collected in Los Angeles to isolate formic and acetic acids for the isotope measurements. Results presented in this paper demonstrate a significant isotopic difference between the mean δ13C value for acetic acid (−20.5‰) and formic acid (−30.1‰). We conclude from these results that the formic acid is derived from mixing of formic acid from direct emissions with the acid formed by secondary oxidation processes in the atmosphere, most probably from aldehydes, whereas acetic acid originates only from direct source emissions.