Preprints
https://doi.org/10.5194/acp-2019-1012
https://doi.org/10.5194/acp-2019-1012
16 Dec 2019
 | 16 Dec 2019
Status: this preprint has been withdrawn by the authors.

The role of HONO in O3 formation and insight into its formation mechanism during the KORUS-AQ Campaign

Junsu Gil, Jeonghwan Kim, Meehye Lee, Gangwoong Lee, Dongsoo Lee, Jinsang Jung, Joonyeong An, Jinkyu Hong, Seogju Cho, Jeonghoon Lee, and Russell Long

Abstract. Photolysis of nitrous acid (HONO) has long been recognized as an early morning source of OH radicals in urban air, but the detailed mechanism of its formation is still unclear. During the Korea-US Air Quality (KORUS-AQ) campaign, HONO was measured using Quantum Cascade Tunable Diode Laser Absorption Spectroscopy (QC-TDLAS) at Olympic Park in Seoul from 17 May to 10 June, 2016. HONO concentrations ranged from 0.07 ppbv to 3.46 ppbv with an average of 0.93 ppbv. HONO remained high at night from 1 am to 5 am, during which the mean concentration was higher in high-O3 episodes (1.82 ppbv) than non-episode (1.20 ppbv). In the morning, OH budget due to HONO photolysis were higher by 50 % (0.95 pptv) during high-O3 episodes compared to non-episode. Diurnal variations of HOx and O3 simulated by the F0AM model demonstrated a difference of ~ 20 ppbv in daily maximum O3 between the two periods. The HONO concentration increased with relative humidity (RH) until 80 %, of which the highest HONO was associated with the top 10 % NOx, confirming that NOx is a crucial precursor of HONO and its formation is facilitated by humidity. The conversion ratio of NOx to HONO was estimated to be 0.86 × 10−2 h−1 at night and also increased with RH. As surrogate for the catalyst surface, the mass concentrations of black carbon (eBC) and the surface areas of particles smaller than 120 nm showed a tendency for RH similar to conversion ratio. Using an Artificial Neuron Network (ANN) model, HONO concentrations were successfully simulated with measured variables (r = 0.8 for the best suite), among which NOx, surface area, and RH were found to be main factors affecting ambient HONO concentrations with weigh values of 26.2 %, 11.9 %, and 10.6 %, respectively. This study demonstrates the coupling of HONO with HOx-VOCs-O3 cycle in Seoul Metropolitan Areas (SMA) and provides practical evidence for heterogeneous formation of HONO by employing the ANN model to atmospheric chemistry.

This preprint has been withdrawn.

Junsu Gil, Jeonghwan Kim, Meehye Lee, Gangwoong Lee, Dongsoo Lee, Jinsang Jung, Joonyeong An, Jinkyu Hong, Seogju Cho, Jeonghoon Lee, and Russell Long

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Interactive discussion

Status: closed
Status: closed
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment
Printer-friendly Version - Printer-friendly version Supplement - Supplement
Junsu Gil, Jeonghwan Kim, Meehye Lee, Gangwoong Lee, Dongsoo Lee, Jinsang Jung, Joonyeong An, Jinkyu Hong, Seogju Cho, Jeonghoon Lee, and Russell Long
Junsu Gil, Jeonghwan Kim, Meehye Lee, Gangwoong Lee, Dongsoo Lee, Jinsang Jung, Joonyeong An, Jinkyu Hong, Seogju Cho, Jeonghoon Lee, and Russell Long

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Latest update: 03 Mar 2024
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This preprint has been withdrawn.

Short summary
During the KORUS-AQ campaign, nitrous acid (HONO) concentrations in Seoul were higher in high-O3 episodes than non-episodes. The photochemical model simulation demonstrates the role of HONO in promoting O3 formation through OH production and subsequent VOCs oxidation. The ambient HONO concentrations were reasonably represented by an Artificial Neural Network model, highlighting NOx, surface area, and relative humidity as crucial parameters for HONO formation in Seoul under high NOx conditions.
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