Preprints
https://doi.org/10.5194/acp-2020-1185
https://doi.org/10.5194/acp-2020-1185

  04 Feb 2021

04 Feb 2021

Review status: this preprint is currently under review for the journal ACP.

Impact of International Shipping Emissions on Ozone and PM2.5: The Important Role of HONO and ClNO2

Jianing Dai and Tao Wang Jianing Dai and Tao Wang
  • Department of Civil and Environmental Engineering, The Hong Kong Polytechnic University, Hong Kong, 999077, China

Abstract. Ocean-going ships emit large amounts of air pollutants such as nitrogen oxide (NOx) and particulate matter. Ship-released NOx can be converted to nitrous acid (HONO) and nitryl chloride (ClNO2), which produce hydroxyl (OH) and chlorine (Cl) radicals and recycle NOx, thus affecting the oxidative capacity and production of secondary pollutants. However, these effects have not been quantified in previous investigations of the impacts of ship emissions. In this study, a regional transport model (WRF–Chem) revised to incorporate the latest HONO and ClNO2 processes was used to investigate their effects on the concentrations of ROx (RO2+HO2+OH) radicals, O3, and fine particulate matter (PM2.5) in Asia during summer. The results show that the ship-derived HONO and ClNO2 increased the concentration of ROx radicals by approximately two to three times in the marine boundary layer. The enhanced radicals then increased the O3 and PM2.5 concentrations in marine areas, with the ship contributions increasing from 9 % to 21 % and from 7 % to 10 %, respectively. The largest ROx enhancement was simulated over the remote ocean with the ship contribution increasing from 29 % to 50 %, which led to increases in ship-contributed O3 and PM2.5 from 21 % to 38 % and from 13 % to 19 %, respectively. In coastal cities, the enhanced levels of radicals also increased the maximum O3 and averaged PM2.5 concentrations from 5 % to 11 % and from 4 % to 8 % to 4 % to 12 %, respectively. These findings indicate that modeling studies without considering HONO and ClNO2 can significantly underestimate the impact of ship emissions on radicals and secondary pollutants. It is therefore important that these nitrogen compounds be included in future models of the impact of ship emissions on air quality.

Jianing Dai and Tao Wang

Status: open (until 01 Apr 2021)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse

Jianing Dai and Tao Wang

Jianing Dai and Tao Wang

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Short summary
We used the WRF–Chem model with the latest HONO and ClNO2 processes to investigate their effects on the concentrations of ROx radicals, O3, and PM2.5 in Asia during summer. The results show that the ship-derived HONO and ClNO2 increased the ROx radicals concentration by two to three times and then increased the O3 and PM2.5 concentrations in marine areas. These findings indicate the importance of these nitrogen processes in the evaluation of the impact of ship emissions on air quality.
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