Interpretation of the effects of anthropogenic chlorine on nitrate formation over northeast Asia during KORUS-AQ 2016

Hyun-Young Jo; Jaehyeoung Park; Gookyoung Heo; Hyo-Jung Lee; Wonbae Jeon; Jong-Min Kim; Saewung Kim; Jung-Kwon Kim; Yiming Liu; Pengfei Liu; Bingqing Zhang; Cheol-Hee Kim

doi:10.1016/j.scitotenv.2023.164920

Interpretation of the effects of anthropogenic chlorine on nitrate formation over northeast Asia during KORUS-AQ 2016

Sci Total Environ. 2023 Oct 10:894:164920. doi: 10.1016/j.scitotenv.2023.164920. Epub 2023 Jun 16.

Authors

Hyun-Young Jo¹, Jaehyeoung Park², Gookyoung Heo³, Hyo-Jung Lee², Wonbae Jeon², Jong-Min Kim², Saewung Kim⁴, Jung-Kwon Kim⁵, Yiming Liu⁶, Pengfei Liu⁷, Bingqing Zhang⁷, Cheol-Hee Kim⁸

Affiliations

¹ Institute of Environmental Studies, Pusan National University, Busan 46241, Republic of Korea.
² Department of Atmospheric Sciences, Pusan National University, Busan 46241, Republic of Korea.
³ National Air Emission Inventory and Research Center, Ministry of Environment, Cheongju 28166, Republic of Korea; Now at Environmental Satellite Center, National Institute of Environmental Research, Incheon 22689, Republic of Korea.
⁴ Department of Earth System Science, University of California, Irvine, Irvine, CA, USA.
⁵ Department of Environmental Engineering, Dong-Eui University, Busan 47340, Republic of Korea.
⁶ School of Atmospheric Sciences, Sun Yat-sen University, Zhuhai, China.
⁷ School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, GA 30332, USA.
⁸ Institute of Environmental Studies, Pusan National University, Busan 46241, Republic of Korea; Department of Atmospheric Sciences, Pusan National University, Busan 46241, Republic of Korea. Electronic address: chkim2@pusan.ac.kr.

PMID: 37331392
DOI: 10.1016/j.scitotenv.2023.164920

Abstract

The Weather Research and Forecasting-Community Multiscale Air Quality (WRF-CMAQ) model, implemented with anthropogenic chlorine (Cl) emissions, was evaluated against ground and NASA DC-8 aircraft measurements during the Korea-United States Air Quality (KORUS-AQ) 2016 campaign. The latest anthropogenic Cl emissions, including gaseous HCl and particulate chloride (pCl^-) emissions from the Anthropogenic Chlorine Emissions Inventory of China (ACEIC-2014) (over China) and a global emissions inventory (Zhang et al., 2022) (over outer China), were used to examine the impacts of Cl emissions and the role of nitryl chloride (ClNO₂) chemistry in N₂O₅ heterogeneous reactions on secondary nitrate (NO₃^-) formation across the Korean Peninsula. The model results against aircraft measurements clearly showed significant Cl- underestimations due mainly to the high gas-particle (G/P) partitioning ratios at aircraft measurement altitudes such as 700-850 hPa, but the ClNO₂ simulations were reasonable. Several simulations of CMAQ-based sensitivity experiments against ground measurements indicated that although addition of Cl emission did not significantly alter NO₃^- formation, the activated ClNO₂ chemistry with Cl emissions showed the best model performance with the reduced normalized mean bias (NMB) of 18.7 % compared to a value of 21.1 % for the Cl emissions-free case. In our model evaluation, ClNO₂ accumulated during the night but quickly produced Cl radical due to ClNO₂ photolysis at sunrise, which modulated other oxidation radicals (e.g., ozone [O₃] and hydrogen oxide radicals [HO_x]) in the early morning. In the morning hours (0800-1000 LST), the HO_x were the dominant oxidants, contributing 86.6 % of the total oxidation capacity (sum of major oxidants such as O₃ and HO_x species), while oxidability was enhanced by up to ∼6.4 % (increase in 1 h HO_x average of 2.89 × 10⁶ molecules·cm^-3) in the early morning mainly due to the changes in OH (+7.2 %), hydroperoxyl radical (HO₂)(+10.0 %), and O₃ (+4.2 %) over the Seoul Metropolitan Area, during the KORUS-AQ campaign. Our results improve understanding of the atmospheric changes in the PM_2.5 formation pathway caused by ClNO₂ chemistry and Cl emissions over northeast Asia.

Keywords: CMAQ modeling; Cl emission; ClNO(2) chemistry; N(2)O(5) heterogeneous chemistry; Particulate nitrate.