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)
<p>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...
| Main Authors: | , , , , , , , , , , , , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2023-08-01
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| Series: | Atmospheric Chemistry and Physics |
| Online Access: | https://acp.copernicus.org/articles/23/8855/2023/acp-23-8855-2023.pdf |
| Summary: | <p>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 (<span class="inline-formula">49±23</span> %)
and secondary formation (<span class="inline-formula">51±23</span> %) accounted for comparable
fractions to the total particle-phase OON (pOON) but <span class="inline-formula">24±25</span> % and <span class="inline-formula">76±25</span> % 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<span class="inline-formula"><sub>3</sub></span>)
(49 %) oxidation pathways potentially dominated the secondary formation of
gOON. A high concentration of NO<span class="inline-formula"><sub>3</sub></span> radicals during the afternoon was
observed, demonstrating that the daytime NO<span class="inline-formula"><sub>3</sub></span> 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<span class="inline-formula"><sub><i>x</i></sub></span> ([O<span class="inline-formula"><sub><i>x</i></sub></span>] <span class="inline-formula">=</span> [O<span class="inline-formula"><sub>3</sub></span>] <span class="inline-formula">+</span> [NO<span class="inline-formula"><sub>2</sub></span>]) increased as a function of relative humidity and
aerosol surface area, indicating that heterogeneous reaction might be<span id="page8856"/> 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.</p> |
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| ISSN: | 1680-7316 1680-7324 |