Development of surface observation-based two-step emissions adjustment and its application on CO, NOx, and SO2 emissions in China and South Korea

Eunhye Kim; Hyun Cheol Kim; Byeong-Uk Kim; Jung-Hun Woo; Yang Liu; Soontae Kim

doi:10.1016/j.scitotenv.2023.167818

Development of surface observation-based two-step emissions adjustment and its application on CO, NO_x, and SO₂ emissions in China and South Korea

Sci Total Environ. 2024 Jan 10:907:167818. doi: 10.1016/j.scitotenv.2023.167818. Epub 2023 Oct 18.

Authors

Eunhye Kim¹, Hyun Cheol Kim², Byeong-Uk Kim³, Jung-Hun Woo⁴, Yang Liu⁵, Soontae Kim⁶

Affiliations

¹ Department of Environmental & Safety Engineering, Ajou University, Suwon 16499, South Korea; Gangarosa Department of Environmental Health, Rollins School of Public Health, Emory University, Atlanta, GA 30322, USA.
² Air Resources Laboratory, National Oceanic and Atmospheric Administration, College Park, MD 20740, USA; Cooperative Institute for Satellite Earth System Studies, University of Maryland, College Park, MD 20740, USA.
³ Georgia Environmental Protection Division, Atlanta, GA 30354, USA.
⁴ Department of Civil and Environmental Engineering, Konkuk University, Seoul 05029, South Korea.
⁵ Gangarosa Department of Environmental Health, Rollins School of Public Health, Emory University, Atlanta, GA 30322, USA.
⁶ Department of Environmental & Safety Engineering, Ajou University, Suwon 16499, South Korea; Gangarosa Department of Environmental Health, Rollins School of Public Health, Emory University, Atlanta, GA 30322, USA. Electronic address: soontaekim@ajou.ac.kr.

PMID: 37858815
DOI: 10.1016/j.scitotenv.2023.167818

Abstract

It is challenging to estimate local emission conditions of a downwind area solely based on concentrations in the downwind area. This is because air pollutants that have a long residence time in the atmosphere can be transported over long distances and influence air quality in downwind areas. In this study, a Two-step Emissions Adjustment (TEA) approach was developed to adjust downwind emissions of target air pollutants with surface observations, considering their long-range transported emission impacts from upwind areas calculated from air quality simulations. Using the TEA approach, CO, NO_x, and SO₂ emissions were adjusted in China and South Korea between 2016 and 2021 based on existing bottom-up emissions inventories. Simulations with the adjusted emissions showed that the 6-year average normalized mean biases of the monthly mean concentrations of CO, NO_x, and SO₂ improved to 0.3 %, -2 %, and 2 %, respectively, in China, and to 5 %, 7 %, and 4 %, respectively, in South Korea. When analyzing the emission trends, it was estimated that the annual emissions of CO, NO_x, and SO₂ in China decreased at a rate of 7.2 %, 4.5 %, and 10.6 % per year, respectively. The decrease rate of emissions for each of these pollutants was similar to that of ambient concentrations. When considering upwind emission impacts in the emissions adjustment, CO emissions increased by 1.3 %/year in South Korea, despite CO concentrations in the country decreasing during the study period. During the study period, NO_x and SO₂ emissions in South Korea decreased by 3.9 % and 0.5 %/year, respectively. Moreover, the TEA approach can account for drastic short-term emission changes (e.g., social distancing due to COVID-19). Therefore, the TEA approach can be used to adjust emissions and improve reproducibility of concentrations of air pollutants suitable for health studies for areas where upwind emission impacts are significant.

Keywords: Downwind; Emissions adjustment; Long-range transport; Surface observations; Transported impact.