Abstract. Saturated aldehydes, e.g. 2-methylbutanal (2MB, CH₃CH₂CH(CH₃)C(O)H), are emitted into the atmosphere by several biogenic sources. The first step in the daytime atmospheric degradation of 2MB involves gas-phase reactions initiated by hydroxyl (OH) radicals, chlorine (Cl) atoms and/or sunlight. In this work, we report the rate coefficients for the gas-phase reaction of 2MB with OH (k_OH) and Cl (k_Cl) together with the photolysis rate coefficient (J) in the ultraviolet solar actinic region in Valencia (Spain) at different times of the day. The temperature dependence of k_OH was described in the 263–353 K range by the following Arrhenius expression: k_OH(T)=(8.88±0.41)×10^-12 exp[(331±14)/T] cm³ molecule^-1 s^-1. At 298 K, the reported k_OH and k_Cl are (2.68±0.07)×10^-11 cm³ molecule^-1 s^-1 and (2.16±0.16)×10^-11 cm³ molecule^-1 s^-1. Identification and quantification of the gaseous products of the Cl-reaction and those from the photodissociation of 2MB were carried out in a smog chamber by different techniques (Fourier transform infrared spectroscopy, proton transfer time-of-flight mass spectrometry, and gas chromatography coupled to mass spectrometry). The formation and size distribution of secondary organic aerosols formed in the Cl-reaction was monitored by a fast mobility particle sizer spectrometer. A discussion on the relative importance of the first step in the daytime atmospheric degradation of 2MB is presented together with the impact of the degradation products in marine atmospheres.

中文翻译：

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2-甲基丁醛白天对流层损失的评价

摘要。饱和醛，例如2-甲基丁醛(2MB, CH ₃ CH ₂ CH(CH ₃ )C(O)H)，通过多种生物源排放到大气中。2MB 白天大气降解的第一步涉及由羟基 (OH) 自由基、氯 (Cl) 原子和/或阳光引发的气相反应。在这项工作中，我们报告了 2MB 与 OH ( k _OH ) 和 Cl ( k _Cl )的气相反应的速率系数以及巴伦西亚（西班牙）紫外线太阳光化区的光解速率系数 ( J )一天中的不同时间。k _OH的温度依赖性在 263–353 K 范围内由以下阿伦尼乌斯表达式描述：k _OH (T)=(8.88±0.41)×10 ^-12 exp[(331±14)/T] cm ³分子^-1 s ^-1。在 298 K 时，报道的k _OH和k _Cl为 (2.68±0.07)×10 ^-11 cm ³分子^-1 s ^-1和 (2.16±0.16)×10 ^-11 cm ³分子^-1 s ^-1. 在烟雾室中，通过不同的技术（傅里叶变换红外光谱、质子转移飞行时间质谱和气相色谱耦合到质谱）。Cl-反应中形成的二次有机气溶胶的形成和尺寸分布由快速迁移率粒度仪光谱仪监测。讨论了白天大气降解 2MB 中第一步的相对重要性以及降解产物在海洋大气中的影响。