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- Title
Observations and Modeling of Gaseous Nitrated Phenols in Urban Beijing: Insights From Seasonal Comparison and Budget Analysis.
- Authors
Xia, Men; Chen, Xin; Ma, Wei; Guo, Yishuo; Yin, Rujing; Zhan, Junlei; Zhang, Yusheng; Wang, Zongcheng; Zheng, Feixue; Xie, Jiali; Wang, Yuzheng; Hua, Chenjie; Liu, Yongchun; Yan, Chao; Kulmala, Markku
- Abstract
Nitrated phenols (NPs) are critical components of brown carbon with climate effects and threaten human health and ecosystems. Early studies mainly focus on particulate NPs, while the sources and impacts of gas‐phase NPs remain less known. This study observed 17 kinds of gaseous NPs in urban Beijing during winter and summer by nitrate‐based long‐time‐of‐flight chemical ionization mass spectrometer (NO3−‐LToF‐CIMS). NPs have an apparent seasonal variation and various diurnal patterns among different species. Source apportionment indicates that secondary productions are the major sources of NPs, besides minor contributions from coal burning and regional industrial emissions. As shown by the observation and box modeling, NO3‐initiated nocturnal oxidation and OH‐driven photochemistry are the secondary sources of NPs. In both seasons, photolysis constitutes the dominating removal pathway of NPs. We determined the observation‐constrained photolysis frequency of typical NPs (i.e., C6H5NO3, C7H7NO3, C6H4N2O5, and C7H6N2O5), ranging from 1.75% to 7.5% of jNO2. Budget analysis reveals that benzaldehyde produced by styrene oxidation is a critical but overlooked precursor of C6H5NO3, and xylene is an essential precursor for C7H7NO3. Modeling results further show that the photolysis of total NPs produces significant amounts of HONO in summer, making noticeable contributions to atmospheric oxidation capacity. This study contributes to a better understanding of the budget of gaseous NPs in the urban atmosphere and provides insights into mitigating NPs‐induced secondary pollution. Plain Language Summary: Nitrated phenol is the oxidation product of aromatics (e.g., benzene and toluene) in the air, appearing as gas and particles. Previous studies mainly investigated its particulate form, while this work studies the gaseous counterpart by combining field campaigns and computer simulations. Air samples were continuously collected and analyzed by a state‐of‐the‐art instrument to obtain the concentration of gaseous nitrated phenols (NPs) in Beijing, China. The speciation, time series, and diurnal patterns of NPs are presented here. Together with supporting measurements, we found that NPs are mainly produced by chemical reactions among aromatics and airborne radicals (i.e., OH and NO3) and are mostly destroyed by sunlight. The decomposition of NPs can produce nitrous acid which is a critical source of OH radicals. These processes have implications for air quality, climate change, and the welfare of ecosystems, and the above impact should be significant in other human‐affected regions beyond Beijing due to the widespread anthropogenic emissions of aromatics and nitrogen oxides. Key Points: Gas‐phase nitrated phenols (NPs) were observed and modeled in winter and summer in Beijing, ChinaNPs mainly originate from secondary productions via oxidation by OH and NO3 radicals and are removed mostly by photolysisNPs constitute a significant source of nitrous acid with implications for atmospheric oxidative capacity
- Subjects
BEIJING (China); BUDGET; PHENOLS; PHENOL; EMISSIONS (Air pollution); NITROUS acid; CARBONACEOUS aerosols; NITROGEN oxides
- Publication
Journal of Geophysical Research. Atmospheres, 2023, Vol 128, Issue 22, p1
- ISSN
2169-897X
- Publication type
Article
- DOI
10.1029/2023JD039551