Polar Nitrated Aromatic Compounds in Urban Fine Particulate Matter: A Focus on Formation via an Aqueous-Phase Radical Mechanism.
Environ Sci Technol
; 57(13): 5160-5168, 2023 04 04.
Article
en En
| MEDLINE
| ID: mdl-36940425
ABSTRACT
Polar nitrated aromatic compounds (pNACs) are key ambient brown carbon chromophores; however, their formation mechanisms, especially in the aqueous phase, remain unclear. We developed an advanced technique for pNACs and measured 1764 compounds in atmospheric fine particulate matter sampled in urban Beijing, China. Molecular formulas were derived for 433 compounds, of which 17 were confirmed using reference standards. Potential novel species with up to four aromatic rings and a maximum of five functional groups were found. Higher concentrations were detected in the heating season, with a median of 82.6 ng m-3 for Σ17pNACs. Non-negative matrix factorization analysis indicated that primary emissions particularly coal combustion were dominant in the heating season. While in the non-heating season, aqueous-phase nitration could generate abundant pNACs with the carboxyl group, which was confirmed by their significant association with the aerosol liquid water content. Aqueous-phase formation of 3- and 5-nitrosalicylic acids instead of their isomer of 4-hydroxy-3-nitrobenzoic acid suggests the existence of an intermediate where the intramolecular hydrogen bond favors kinetics-controlled NO2⢠nitration. This study provides not only a promising technique for the pNAC measurement but also evidence for their atmospheric aqueous-phase formation, facilitating further evaluation of pNACs' climatic effects.
Palabras clave
Texto completo:
1
Colección:
01-internacional
Banco de datos:
MEDLINE
Asunto principal:
Hidrocarburos Policíclicos Aromáticos
/
Contaminantes Atmosféricos
País/Región como asunto:
Asia
Idioma:
En
Revista:
Environ Sci Technol
Año:
2023
Tipo del documento:
Article