Analysis of Formation Mechanisms and Inter-Provincial Transport of Ozone in South Korea

Ozone formation is driven by complex photochemical reactions, with inter-provincial transport exacerbating air quality in downwind region of South Korea. To identify transport pathways of ozone and its precursors and develop effective mitigation strategies, the WRF (v4.3) and CMAQ (v5.3.2) models were employed and integrated with the Process Analysis - Integrated Process Rates (PA-IPR) tool. Anthropogenic air pollutant emissions were based on the up-to-date national emission inventory (CAPSS 2021) in South Korea.

The PA-IPR tool was used to assess the ozone budget through the Index of Process Analysis (IPA), a dimensionless metric quantifying the relative contributions of chemical production (CHEM) and transport including advection (ADV) and diffusion (DIF). IPA analysis revealed an average value of 0.58 in Seoul, a major source region, and 1.47 in Gangwon-do, a downwind region from Seoul metropolitan area, highlighting distinct inter-provincial transport patterns. The IPA value increased when inter-regional transport was prominent, enabling case-specific analyses of ozone formation in downwind areas.

To develop effective ozone reduction policies, it is essential to quantify source-receptor relationships by assessing inter-regional contributions. For this purpose, the Integrated Source Apportionment Method (ISAM) was applied to analyze ozone transport from specific regions during April–May 2022. ISAM analysis was further utilized to assess inter-regional contributions during high-ozone episodes in downwind areas.

This work was supported by the National Research Foundation of Korea(NRF) grant funded by the Korea government(MSIT) (RS-2023-00219830, RS-2024-00356913).