Sulfur isotope-based source apportionment and control mechanisms of PM2.5 sulfate in Seoul, South Korea during winter and early spring (2017-2020)

Giyoon Lee; Jinho Ahn; Seung-Myung Park; Jonghan Moon; Rokjin Park; Min Sub Sim; Hanna Choi; Jinsoo Park; Joon-Young Ahn

doi:10.1016/j.scitotenv.2023.167112

Sulfur isotope-based source apportionment and control mechanisms of PM_2.5 sulfate in Seoul, South Korea during winter and early spring (2017-2020)

Sci Total Environ. 2023 Dec 20:905:167112. doi: 10.1016/j.scitotenv.2023.167112. Epub 2023 Sep 17.

Authors

Giyoon Lee¹, Jinho Ahn², Seung-Myung Park³, Jonghan Moon¹, Rokjin Park¹, Min Sub Sim¹, Hanna Choi⁴, Jinsoo Park³, Joon-Young Ahn³

Affiliations

¹ School of Earth and Environmental Sciences, Seoul National University, Seoul 08826, South Korea.
² School of Earth and Environmental Sciences, Seoul National University, Seoul 08826, South Korea. Electronic address: jinhoahn@gmail.com.
³ Air Quality Research Division, National Institute of Environmental Research, Seo, Incheon 22689, South Korea.
⁴ Climate Change Response Division, Korea Institute of Geoscience and Mineral Resources, Gwahak-ro 124, Yuseong-gu, Daejeon 34132, South Korea.

PMID: 37717778
DOI: 10.1016/j.scitotenv.2023.167112

Abstract

High level of particulate matter (PM) concentrations are a major environmental concern in Seoul, South Korea, especially during winter and early spring. Sulfate is a major component of PM and induces severe environmental pollution, such as acid precipitation. Previous studies have used numerical models to constrain the relative contributions of domestic and trans-boundary sources to PM_2.5 sulfate concentration in South Korea. Because of the scarce measurement result of δ³⁴S for PM_2.5 sulfate in South Korea, poorly defined δ³⁴S value of domestic sulfur sources, and no application of sulfur isotope fractionation during sulfate formation in previous observation-based studies, source apportionment results conducted by model studies have not been corroborated from independent chemical observations. Here, we examined the δ³⁴S of PM_2.5 in Seoul and domestic sulfur sources, and considered the sulfur isotope fractionation for accurate source apportionment constraint. Accordingly, domestic and trans-boundary sulfur sources accounted for approximately (16-32) % and (68-84) % of the sulfate aerosols in Seoul, respectively, throughout the winter and early spring of 2017-2020. Air masses passing through north-eastern China had relatively low sulfate concentrations, enriched δ³⁴S, and a low domestic source contribution. Those passing through south-eastern China had relatively a high sulfate concentrations, depleted δ³⁴S, and high domestic source contribution. Furthermore, elevated PM_2.5 sulfate concentrations (>10 μg m^-3) were exclusively associated with a weak westerly wind speed of <3 m s^-1. From December 2019 to March 2020, Seoul experienced relatively low levels of PM_2.5 sulfate, which might be attributed to favorable weather conditions rather than the effects of COVID-19 containment measures. Our results demonstrate the potential use of δ³⁴S for accurate source apportionment and for identifying the crucial role of regional air mass transport and meteorological conditions in PM_2.5 sulfate concentration. Furthermore, the data provided can be essential for relevant studies and policy-making in East Asia.

Keywords: Backward air trajectory; COVID-19 lockdown; Fly ash; Particulate matter; Sulfate; δ(34)S-SO(4)(2−).