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DOI	10.5194/acp-19-7649-2019
	The formation of nitro-aromatic compounds under high NOx and anthropogenic VOC conditions in urban Beijing; China
	Wang Y.; Hu M.; Wang Y.; Zheng J.; Shang D.; Yang Y.; Liu Y.; Li X.; Tang R.; Zhu W.; Du Z.; Wu Y.; Guo S.; Wu Z.; Lou S.; Hallquist M.; Yu J.
发表日期	2019
ISSN	16807316
起始页码	7649
结束页码	7665
卷号	19 期号:11
英文摘要	Nitro-aromatic compounds (NACs), as important contributors to the light absorption by brown carbon, have been widely observed in various ambient atmospheres; however, their formation in the urban atmosphere was little studied. In this work, we report an intensive field study of NACs in summer 2016 at an urban Beijing site, characterized by both high-NOx and anthropogenic VOC dominated conditions. We investigated the factors that influence NAC formation (e.g., NO2, VOC precursors, RH and photolysis) through quantification of eight NACs, along with major components in fine particulate matter, selected volatile organic compounds, and gases. The average total concentration of the quantified NACs was 6.63 ngm-3, higher than those reported in other summertime studies (0.14-6.44 ngm-3). 4-Nitrophenol (4NP, 32.4 %) and 4-nitrocatechol (4NC, 28.5 %) were the top two most abundant NACs, followed by methyl-nitrocatechol (MNC), methyl-nitrophenol (MNP), and dimethyl-nitrophenol (DMNP). The oxidation of toluene and benzene in the presence of NOx was found to be a more dominant source of NACs than primary biomass burning emissions. The NO2 concentration level was found to be an important factor influencing the secondary formation of NACs. A transition from low-to high-NOx regimes coincided with a shift from organic-to inorganic-dominated oxidation products. The transition thresholds were NO2×20 ppb for daytime and NO2×25 ppb for nighttime conditions. Under low-NOx conditions, NACs increased with NO2, while the NO-3 concentrations and .NO-3/=NACs ratios were lower, implying organic-dominated products. Under high-NOx conditions, NAC concentrations did not further increase with NO2, while the NO-3 concentrations and .NO-3/=NACs ratios showed increasing trends, signaling a shift from organic-to inorganic-dominated products. Nighttime enhancements were observed for 3M4NC and 4M5NC, while daytime enhancements were noted for 4NP, 2M4NP, and DMNP, indicating different formation pathways for these two groups of NACs. Our analysis suggested that the aqueous-phase oxidation was likely the major formation pathway of 4M5NC and 3M5NC, while photo-oxidation of toluene and benzene in the presence of NO2 could be more important for the formation of nitrophenol and its derivatives. Using the (3M4NCC4M5NC) = 4NP ratios as an indicator of the relative contribution of aqueous-phase and gas-phase oxidation pathways to NAC formation, we observed that the relative contribution of aqueous-phase pathways increased at elevated ambient RH and remained constant at RH>30 %. We also found that the concentrations of VOC precursors (e.g., toluene and benzene) and aerosol surface area acted as im-portant factors in promoting NAC formation, and photolysis as an important loss pathway for nitrophenols. © Author(s) 2019.
语种	英语
scopus关键词	anthropogenic source; aromatic hydrocarbon; concentration (composition); formation mechanism; nitrogen oxides; urban atmosphere; volatile organic compound; Beijing [Beijing (ADS)]; Beijing [China]; China
来源期刊	Atmospheric Chemistry and Physics
文献类型	期刊论文
条目标识符	http://gcip.llas.ac.cn/handle/2XKMVOVA/144346
作者单位	State Key Joint Laboratory of Environmental Simulation and Pollution Control, College of Environmental Sciences and Engineering, Peking University, Beijing, 100871, China; Department of Chemistry and Molecular Biology, University of Gothenburg, Gothenburg, Sweden; Environmental Science Programs, Hong Kong University of Science and Technology, Hong Kong, Hong Kong; Department of Chemistry, Hong Kong University of Science and Technology, Hong Kong, Hong Kong; Beijing Innovation Center for Engineering Sciences and Advanced Technology, Peking University, Beijing, 100871, China; Shanghai Academy of Environmental Sciences, Shanghai, 200233, China
推荐引用方式 GB/T 7714	Wang Y.,Hu M.,Wang Y.,et al. The formation of nitro-aromatic compounds under high NOx and anthropogenic VOC conditions in urban Beijing; China[J],2019,19(11).
APA	Wang Y..,Hu M..,Wang Y..,Zheng J..,Shang D..,...&Yu J..(2019).The formation of nitro-aromatic compounds under high NOx and anthropogenic VOC conditions in urban Beijing; China.Atmospheric Chemistry and Physics,19(11).
MLA	Wang Y.,et al."The formation of nitro-aromatic compounds under high NOx and anthropogenic VOC conditions in urban Beijing; China".Atmospheric Chemistry and Physics 19.11(2019).