Glutaric acid and adipic acid are dicarboxylic acids (DCAs) that are commonly found in atmospheric aerosols and cloud droplets. Within this study, the temperature-and pH-dependent rate constants of aqueous-phase OH radical reactions of these two DCAs were determined through the competition kinetics method. The following Arrhenius expressions were derived for the temperature dependency of the OH radical reaction with glutaric acid: k(T,(in units of L mol −1 s −1 ). Density functional theory (DFT) calculations were performed to calculate the energy barrier of the H atom abstraction. The calculation results show that the energy barriers at the C β -atoms of the two DCAs are much lower than those at the C α -atoms, indicating that the H atom abstractions predominantly occur at the C β -atoms. The increased •OH rate constant in the case of the deprotonated form can be explained by the reduction of energy barrier, which is predominately caused by the variation of the inductive effect of the carboxyl group. As an important sink in the atmosphere, the degradation of glutaric acid and adipic acid by •OH under atmospheric conditions can be accurately described by the Arrhenius expressions obtained.

Glycine, alanine, serine, and threonine are essential amino acids originating from biological activities. These substances can be emitted into the atmosphere directly. Within the present study, the aqueous phase reaction...

Secondary organic aerosol (SOA) is the main component of atmospheric particulate matter with wide implications for air quality, human health, and climate change. However, the formation mechanism of SOA has not been fully understood. Methylglyoxal (MGLY) and glyoxal (GLY) are ubiquitous dicarbonyls in the atmosphere and have been considered as important precursors for SOA formation, especially through the oligomerization in the atmospheric aqueous phase. In this paper, the oligomer formation mechanism through the self-oligomerization of MGLY and GLY, and especially their cross-reactions in the atmospheric aqueous phase were investigated by density functional theory (DFT) calculations. Carbenium ions play a key role in the oligomerization, and all of the reactions take place barrierless under acidic conditions. First-generation oligomers (dimers) lead to the formation of chain and cyclic (including five- and six-membered) oligomers, among which five-membered cyclic oligomers are the dominant products. The products identified and described by the energetics of their formation pathways are discussed in view of available experimental findings from the literature. Many of the products were actually measured and assigned. In addition, the diffusion rate constants (k D) of the nucleophilic addition were determined to estimate the formation rate of oligomers in the aqueous phase, and the calculated k D’s are in the range of 1.20–1.31 × 1010 L mol–1 s–1. All of these findings will help us to gain a better understanding of the oligomerization of the dicarbonyl compounds in the atmospheric aqueous aerosol particles, and thus to provide a scientific support toward controlling and reducing SOA formation.