Preprints
https://doi.org/10.5194/egusphere-2024-343
https://doi.org/10.5194/egusphere-2024-343
18 Apr 2024
 | 18 Apr 2024
Status: this preprint is open for discussion and under review for Atmospheric Chemistry and Physics (ACP).

Assessing the Effectiveness of SO2, NOx, and NH3 Emission Reductions in Mitigating Winter PM2.5 in Taiwan Using CMAQ Model

Ping-Chieh Huang, Hui-Ming Hung, Hsin-Chih Lai, and Charles C.-K. Chou

Abstract. Taiwan experiences higher air pollution in winter when particulate matter (PM2.5) levels frequently surpass national standards. This study employs the Community Multiscale Air Quality model to assess the effectiveness of reducing NH3, NOx, and SO2 emissions on PM2.5 secondary inorganic species (i.e., SO­42-, NO3-, and NH4+). For sulfate, ~ 43.7 % is derived from the chemical reactions of local SO2 emission, emphasizing the substantial contribution of regional transported sulfate. In contrast, local NOx and NH3 emissions predominantly influence nitrate and ammonium. Reducing SO2 emissions decreases sulfate, thereby influencing NH3 partitioning and resulting in a decreased ammonium. Similarly, reducing NOx emissions lowers HNO3, impacting nitrate and ammonium concentrations due to changes in HNO3 and NH3 partitioning. A particularly significant finding is that NH3 emissions reduction decreases not only nitrate and ammonium but also sulfate by altering cloud droplet pH and SO2 oxidation processes. While SO2 reduction's PM2.5 impact is less than NOx and NH3, it emphasizes the complexity of regional sensitivities. Most of western Taiwan is NOx-sensitive, so reducing NOx emissions has a more substantial impact on lowering PM2.5. However, given the higher mass emissions of NOx than NH3 in Taiwan, NH3 has a more significant consequence in mitigating PM2.5 per unit mass emission reduction. The cost-effectiveness analysis suggests that NH3 reduction outperforms SO2 and NOx. Nevertheless, cost estimates vary due to methodological differences and regional emission sources. Overall, this study considers both efficiency and costs, highlighting NH3 emissions reduction as a promising strategy for PM2.5 mitigation in the studied Taiwan's environment.

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Ping-Chieh Huang, Hui-Ming Hung, Hsin-Chih Lai, and Charles C.-K. Chou

Status: open (until 30 May 2024)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2024-343', Anonymous Referee #2, 07 May 2024 reply
  • RC2: 'Comment on egusphere-2024-343', Anonymous Referee #1, 18 May 2024 reply
Ping-Chieh Huang, Hui-Ming Hung, Hsin-Chih Lai, and Charles C.-K. Chou

Data sets

CMAQ_dataset_2018_Dec Ping-Chieh Huang, Hui-Ming Hung, and Hsin-Chih Lai https://doi.org/10.5281/zenodo.10623526

Ping-Chieh Huang, Hui-Ming Hung, Hsin-Chih Lai, and Charles C.-K. Chou

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Short summary
Models were used to study ways to reduce PM pollution in Taiwan during winter. After considering various factors, such as physical processes and chemical reactions, we found that reducing NOx or NH3 emissions is more effective in mitigating PM2.5 than reducing SO2 emissions. When considering both efficiency and cost, reducing NH3 emissions seems to be a more suitable policy for the studied Taiwan's environment.