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Formation and photochemical investigation of brown carbon by hydroxyacetone reactions with glycine and ammonium sulfate

机译：羟基丙酮与甘氨酸和硫酸铵反应生成棕褐色碳并进行光化学研究

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Increasing attention has been paid to atmospheric “brown carbon” (BrC) aerosols due to their effect on the earth's climate. Aqueous BrC aerosols were formed through aqueous reactions of hydroxyacetone (HA) with nitrogen compounds such as glycine (Gly) and/or ammonium sulfate (AS). When exposed to nitrogen compounds for several days, HA, as a type of aqueous carbonyl compound, becomes absorbent and fluorescent in the blue visible and near ultraviolet regions, which have been monitored by UV/vis and fluorescence spectroscopy. In this study, we quantified absorption and excitation-emission matrix (EEM) spectra in the formation of aqueous BrCs, which was generated from HA-Gly and HA-Gly-AS mixtures, respectively. The obtained data was used to determine the base-10 absorption coefficient ( α ), absorption Angstrom exponent (AAE), and effective quantum yield (QY). All of the related parameters provide further evidence for the formation of aqueous BrC. The absorbances of the as-obtained BrCs follow the order HA-Gly-AS > HA-Gly > HA-AS. In other words, HA-Gly-AS mixtures displayed the most intense absorbances, whereas HA-AS mixtures barely produced visible absorbance. It is reasonable to speculate that Gly promotes the formation of HA-Gly BrC mixtures. The experimental results are consistent with previous measurements reported by Powelson et al. BrCs from HA-Gly-AS and HA-Gly exhibit stronger fluorescence between 300 and 400 nm. Glycine plays a more important role in the formation of aqueous BrC than that of AS. Furthermore, we examined the mass absorption coefficient (MAC) by photolysis of aqueous BrCs, which resulted from the oxidation of HA-Gly and HA-Gly-AS mixtures by 5 mM H _(2) O _(2) . An effective photolysis time induced significant changes near-UV (300–400 nm) absorption intensity of HA-Gly and HA-Gly-AS mixtures. These results emphasize the dynamic nature of the corresponding atmospheric aqueous BrC. Overall, our study provides the optical properties of the corresponding atmospheric aqueous BrC and the H _(2) O _(2) oxidation photolysis process of the as-obtained BrC in detail, which may contribute to the understanding of the important effects of aqueous BrC for atmospheric chemistry and climate.
机译：由于大气中的“棕色碳”（BrC）气溶胶对地球气候的影响，因此越来越受到关注。通过羟基丙酮（HA）与氮化合物（例如甘氨酸（Gly）和/或硫酸铵（AS））的水性反应形成BrC气溶胶。当暴露于氮化合物中数天时，作为羰基水溶液的一种形式，HA在蓝色可见光和近紫外区域变成吸收剂和荧光剂，已通过UV / vis和荧光光谱法对其进行了监测。在这项研究中，我们量化了分别由HA-Gly和HA-Gly-AS混合物生成的BrCs水溶液形成过程中的吸收和激发发射矩阵（EEM）光谱。获得的数据用于确定以10为基的吸收系数（α），吸收埃指数（AAE）和有效量子产率（QY）。所有相关参数为形成BrC提供了进一步的证据。所获得的BrCs的吸光度遵循HA-Gly-AS> HA-Gly> HA-AS的顺序。换句话说，HA-Gly-AS混合物显示出最强的吸光度，而HA-AS混合物几乎不产生可见吸光度。有理由推测Gly会促进HA-Gly BrC混合物的形成。实验结果与Powelson等人先前报道的测量结果一致。 HA-Gly-AS和HA-Gly的BrC在300至400 nm之间显示较强的荧光。甘氨酸在水性BrC的形成中比AS扮演更重要的角色。此外，我们检查了由BrCs水溶液光解引起的质量吸收系数（MAC），这是由HA-Gly和HA-Gly-AS混合物被5 mM H _（2）O _（2）氧化引起的。有效的光解时间会引起HA-Gly和HA-Gly-AS混合物在近紫外线（300-400 nm）处的吸收强度发生显着变化。这些结果强调了相应的大气BrC水溶液的动力学性质。总体而言，我们的研究详细提供了相应的大气BrC的光学性质以及所获得的BrC的H _（2）O _（2）氧化光解过程，这可能有助于理解水溶液的重要作用。 BrC用于大气化学和气候。

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