Mass Spectral Analysis of the Aged 1,3,5-Trimethylbenzene Secondary Organic Aerosol in the Presence of Ammonium Sulfate Seeds

Abstract

The ammonium sulfate ((NH 4 ) 2 SO 4 ) seed aerosols commonly found in the Chinese urban atmosphere could affect the formation and aging of secondary organic aerosols (SOA). Aging of aromatic SOA is performed using UV-irradiation of 1,3,5-trimethylbenzene (135-TMB)/CH 3 ONO/NO/air mixtures with high concentrations (~100 μg/m 3 ) of (NH 4 ) 2 SO 4 seeds in the laboratory chamber in this study. The particulate products of SOA were measured using an aerosol laser time-of-flight mass spectrometer (ALTOFMS) in real-time, and fuzzy c-means (FCM) was applied to the mass spectra organic species for clusters. Experimental results indicated that methylglyxoal, 2-methyl-4-oxo-2-pentenal, 4-methyl-1H-imidazole, 4-methyl-imidazole-2-acetaldehyde, and other imidazole derivative compounds are the principal products in the aged particles. Imidazole compounds that can absorb solar radiation effectively were newly detected in the aged 135-TMB SOA with high concentrations of (NH 4 ) 2 SO 4 seed aerosols. These would provide new information for discussing the 135-TMB SOA aging mechanism.

Effects of Inorganic Seed Aerosol on the Formation of Nitrogen-Containing Organic Compounds from Reaction of Ammonia with Photooxidation Products of Toluene

“…The reaction products were characterized by UV-visible spectroscopy, infrared spectroscopy and time-of-flight mass spectrometry. The series of characteristic mass spectral peaks C x H y N n + of imidazole nitrogen-containing organic compounds of aromatic SOA were obtained, and it was confirmed that imidazole nitrogen-containing compounds formed from the heterogeneous reaction of NH 3 and dicarbonyl components of aromatic SOA [22][23][24]. On this basis, this paper continues to study the effects of different ingredients, concentrations, humidity and acidity of seed aerosol on the formation of nitrogencontaining organic compounds formed from the reaction of NH 3 with the photooxidation products of toluene.…”

“…1. The mass spectrum peak with the highest peak intensity of m/z 41 (C 2 H 2 N + ), along with m/z 67 (C 3 H 3 N 2 + ) and 28 (CH 2 N + ) are the characteristic cracking peaks of the imidazole compounds, indicating that the nitrogen-containing imidazole organic compounds are the main reaction product [22][23][24]. In addition, in the mass spectrum, the fragment peak of m/z 18 corresponds to the ammonium ion (NH 4 + ), and m/z 44 is the fragment peak (COO + ) after the carboxyl group (-COOH) of the organic acid compound loses the hydrogen atom.…”

“…Since the formed NH 4 + is the weak acid, it cannot react with the condensed organic acid to form ammonium acid. According to the experimental results of Liu et al [7] and our group [23][24], the hydration of the dialdehyde compound and the reaction with NH 3 to form the tetraol and diimine products are important precursors for the formation of imidazole products. Since the reactivity of NH 4 + is less than that of NH 3 , the rate of NH 3 reaction with the condensed dialdehyde compound to form diimine is low, and the yield is small, resulting in the decrease of imidazole products.…”

“…The chemical composition of aerosol particles is gained from the ion peaks in the mass spectrum. Also, after the completion of the photoreaction, the products were collected with a 3% methanol solution for the UV-Vis spectrometric measurement as provided in our previous studies [23][24].…”

Enhanced secondary organic aerosol formation from the photo-oxidation of mixed anthropogenic volatile organic compounds

“…As an important contributor to SOA in urban areas, aromatic hydrocarbons are generally concerned about their kinetics (Atkinson and Arey, 2003;Calvert et al, 2002), reaction mechanisms (Tsiligiannis et al, 2019;J. Midey * et al, 2003;Huang et al, 2017c;Wang et al, 2020;Garmash et al, 2019), SOA yield (Cao and Jang, 2007;Kroll et al, 2007;Ng et al, 2007b;Huang et al, 2017b), ozone generation potential (Luo et al, 2019), and SOA physicochemical properties (optical properties, morphology, etc.) (Grosjean, 1981;Li et al, 2018;Li et al, 2017b;Phillips and Smith, 2014;Kim and Paulson, 2013;Huang et al, 2018).…”