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Effects of inorganic seed aerosols on the particulate products of aged 1,3,5-trimethylbenzene secondary organic aerosol
AbstractInorganic aerosols such as (NH4)2SO4, NaNO3 and CaCl2 are commonly present in the Chinese urban atmosphere. They could significantly affect the formation and aging of ambient secondary organic aerosols (SOA), but the underlying mechanisms remain unknown. In this work we studied SOA formation from the photooxidation reaction of 1,3,5-trimethylbenzene (135-TMB) with 100 μg/m3 of the above three types of inorganic aerosols as seeds in a laboratory chamber. We focused on the aging products of SOA particles by exposing them to high levels of oxidizing hydroxyl radicals (OH). The particulate products of SOA were measured using an aerosol laser time-of-flight mass spectrometer (ALTOFMS) and Fuzzy C-Means (FCM) were applied to organic mass spectra for clustering. In the presence of (NH4)2SO4 seeds, 4-methyl-1H-imidazole, 4-methyl-imidazole-2-acetaldehyde and other imidazole derivative compounds formed from reactions of NH4+ with methylglyoxal were detected as new aged products. We also observed aromatic nitrogen-containing organic compounds as the major aged products in the presence of NaNO3 seeds as a consequence of reaction with OH and NO2 radicals, which were generated by UV irradiation of acidic aqueous nitrate, inducing nitration reactions with phenolic compounds. As CaCl2 has the strongest hygroscopic properties of the three salt particles tested, the greater water content on the surface of the aerosol may facilitate the condensing of more gas-phase organic acid products to the hygroscopic CaCl2 seeds, forming H+ ions that catalyze the heterogeneous reaction of aldehydes, products of photooxidation of 135-TMB, and forming high-molecular-weight (HMW) compounds. These results provide new insight into the aromatic SOA aging mechanisms.
Graphical abstract
HighlightsALTOFMS with FCM was used to measure the aged 135-TMB SOA in real time.Imidazoles were newly detected in aged 135-TMB SOA with (NH4)2SO4 seeds.NaNO3 seeds facilitate the formation of aromatic nitrogen-containing compounds.HMW products were the major products in aged 135-TMB SOA with CaCl2 seeds.
Effects of inorganic seed aerosols on the particulate products of aged 1,3,5-trimethylbenzene secondary organic aerosol
AbstractInorganic aerosols such as (NH4)2SO4, NaNO3 and CaCl2 are commonly present in the Chinese urban atmosphere. They could significantly affect the formation and aging of ambient secondary organic aerosols (SOA), but the underlying mechanisms remain unknown. In this work we studied SOA formation from the photooxidation reaction of 1,3,5-trimethylbenzene (135-TMB) with 100 μg/m3 of the above three types of inorganic aerosols as seeds in a laboratory chamber. We focused on the aging products of SOA particles by exposing them to high levels of oxidizing hydroxyl radicals (OH). The particulate products of SOA were measured using an aerosol laser time-of-flight mass spectrometer (ALTOFMS) and Fuzzy C-Means (FCM) were applied to organic mass spectra for clustering. In the presence of (NH4)2SO4 seeds, 4-methyl-1H-imidazole, 4-methyl-imidazole-2-acetaldehyde and other imidazole derivative compounds formed from reactions of NH4+ with methylglyoxal were detected as new aged products. We also observed aromatic nitrogen-containing organic compounds as the major aged products in the presence of NaNO3 seeds as a consequence of reaction with OH and NO2 radicals, which were generated by UV irradiation of acidic aqueous nitrate, inducing nitration reactions with phenolic compounds. As CaCl2 has the strongest hygroscopic properties of the three salt particles tested, the greater water content on the surface of the aerosol may facilitate the condensing of more gas-phase organic acid products to the hygroscopic CaCl2 seeds, forming H+ ions that catalyze the heterogeneous reaction of aldehydes, products of photooxidation of 135-TMB, and forming high-molecular-weight (HMW) compounds. These results provide new insight into the aromatic SOA aging mechanisms.
Graphical abstract
HighlightsALTOFMS with FCM was used to measure the aged 135-TMB SOA in real time.Imidazoles were newly detected in aged 135-TMB SOA with (NH4)2SO4 seeds.NaNO3 seeds facilitate the formation of aromatic nitrogen-containing compounds.HMW products were the major products in aged 135-TMB SOA with CaCl2 seeds.
Effects of inorganic seed aerosols on the particulate products of aged 1,3,5-trimethylbenzene secondary organic aerosol
Huang, Mingqiang (author) / Hao, Liqing (author) / Cai, Shunyou (author) / Gu, Xuejun (author) / Zhang, Weixiong (author) / Hu, Changjin (author) / Wang, Zhenya (author) / Fang, Li (author) / Zhang, Weijun (author)
Atmospheric Environment ; 152 ; 490-502
2017-01-04
13 pages
Article (Journal)
Electronic Resource
English