The important contribution of secondary formation and biomass burning to oxidized organic nitrogen (OON) in a polluted urban area: insights from in situ measurements of a chemical ionization mass spectrometer (CIMS)
Year: 2023
Type: article
Abstract: To investigate the sources and formation mechanism of oxidized organic nitrogen (OON), field measurements of OON were conducted using an iodide-adduct chemical ionization mass spectrometer equipped with a Filter Inlet for Gases and AEROsols (FIGAERO-CIMS) during fall of 2018 in the megacity of Guangzhou, China. Using levoglucosan as a tracer of biomass burning emissions, the results show that biomass burning (49±23 %) and secondary formation (51±23 %) accounted for comparable fractions to the total particle-phase OON (pOON) but 24±25 % and 76±25 % to the gas-phase OON (gOON), respectively, signifying the important contribution of biomass burning to pOON and secondary formation to gOON in this urban area. Calculations of production rates of gOON indicated that hydroxyl radical (42 %) and nitrate radical (NO 3 ) (49 %) oxidation pathways potentially dominated the secondary formation of gOON. A high concentration of NO 3 radicals during the afternoon was observed, demonstrating that the daytime NO 3 oxidation might be more important than the previous recognition. Monoterpenes, found to be major precursors of secondary gOON, were mainly from anthropogenic emissions in this urban area. The ratio of secondary pOON to O x ([O x ] = [O 3 ] + [NO 2 ]) increased as a function of relative humidity and aerosol surface area, indicating that heterogeneous reaction might be an important formation pathway for secondary pOON. Finally, the highly oxidized gOON and pOON with 6 to 11 oxygen atoms were observed, highlighting the complex secondary reaction processes of OON in the ambient air. Overall, our results improve the understanding of the sources and dynamic variation of OON in the urban atmosphere.
Institutions: Chinese Academy of Sciences, Guangzhou Institute of Geochemistry, University of Chinese Academy of Sciences, State Key Laboratory of Organic Geochemistry, Guangdong Provincial Academy of Environmental Science, Jinan University, Guangdong-Hongkong-Macau Joint Laboratory of Collaborative Innovation for Environmental Quality, Qilu University of Technology, Peking University
Language: English
Subfield: Atmospheric Science
Field: Earth and Planetary Sciences
Domain: Physical Sciences
Open Access status: gold
Estimated APC paid: $1,725
OpenAlex ID: W4385897071