In this study, impact of the COVID-19 outbreak on PM2.5 mass and its five chemical components (NH4 +, NO3 -, SO4 2-, OC, EC) in Busan was evaluated, and compared with that of Seoul. The study period over the recent three years was sub-divided into two periods: Pre-COVID (2018~2019) and COVID (2020) periods, and the differences in observed annual and monthly variations between the two periods were explored here. The results indicated that annual mean PM2.5 mass concentrations decreased during the COVID period by 16% in Seoul and 29% in Busan, and the satellite-observed annual average of aerosol optical depth (AOD) over the Korean Peninsula also decreased by approximately more than 10% compared with that of the Pre-COVID period. All of the five chemical components decreased but no particular changes were found in their fractions occupied during the COVID period. However, over the Lock-down period (2020-March), the sulfate fraction decreased in Seoul, mostly reflecting the recent Chinese trends of aerosol characteristics, whereas the nitrate fraction considerably decreased in Busan, which was attributable to the local emission changes and their variabilities in Busan. Other meteorological characteristics such as higher frequencies of easterly winds in the Busan area during the COVID period were also discussed in comparison with those in the Seoul area.

Abstract
1. 서 론
2. 자료 및 연구방법
3. 결과 및 고찰
    3.1. COVID 기간의 연평균, 월평균 농도 변화
    3.2. Lock-down 기간 (2020년 3월) COVID 영향분석
4. 결론
감사의 글
REFERENCES

• 박민준(부산대학교 지구환경시스템학부 대기과학전공) | Min-Jun Park (Atmospheric Sciences Major, Department of Earth Environmental System, Pusan National University)
• 김철희(부산대학교 지구환경시스템학부 대기과학전공, 부산대학교 환경연구원) | Cheol-Hee Kim (Atmospheric Sciences Major, Department of Earth Environmental System, Pusan National University, Institute of Environmental Studies, Pusan National University) Corresponding author