## 1 Introduction  
Black carbon (BC) and brown carbon (BrC) absorb light, significantly impacting the Earth's radiative forcing [1]. BC is emitted only through the incomplete combustion of fossil fuels in biomass burning (BB) processes. In contrast, BrC is emitted through primary sources and formed through secondary oxidation processes of volatile organic compounds [2, 3]. Currently, BrC is receiving significant attention due to its potential impact on the Earth's radiative balance, atmospheric chemical reactions, and human health [4, 5, 6, 7]. BB is primarily recognized as a significant primary source of BrC, and the optical absorption characteristics of BrC are greatly influenced by fuel types and combustion conditions [8, 9]. BrC strongly absorbs solar radiation and thereby affects Earth's climate [1, 10]. BrC absorbs light more strongly within the ultraviolet range (300-400 nm), impacting the Earth's radiative forcing. Currently, it is necessary to investigate the contribution of specific emission sources to BrC absorption and to study the relationship between specific emission sources and BrC. The combustion of biomass and fossil fuels emits substantial amounts of gaseous and particulate pollutants on both local and global scales. BB is a worldwide phenomenon and includes agricultural resulting burning, illegal burning, wildfires, and residential wood burning for cooking and heating purposes [11]. BB activities are intense, and the contribution of BrC to light absorption ranges from 20 to 50%. Therefore, it is necessary to investigate the characteristics of BrC light absorption in regions with concentrated BB activities. BB emits various gases, including volatile organic compounds (VOCs) and particulate matter containing BC, BrC, and organic matter (OM), making it a significant source of greenhouse gases [12; 13]. Due to its significance as a source of diverse pollutants, it has received considerable attention in recent years. However, there are significant challenges in identifying and quantifying BB emissions in the atmosphere and assessing their environmental impacts. Satellite observations, such as Moderate-Resolution Imaging Spectroradiometer (MODIS) active fire detection, are commonly used to capture their spatial occurrence in open fields [14]. However, these methods have limitations in detecting emissions from residential fuel combustion, which dominates in certain regions, resulting in underestimation. For this reason, various chemical tracers have wide use in identifying BB sources. Several organic molecular markers, such as levoglucasan, mannosan, and galactosan, have been employed recently. Among these BB tracers, levoglucasan is the most suitable as it exhibits high availability and chemical stability under various environmental conditions [15]. Wood combustion emissions in Europe contribute approximately 60% to primary pyrogenic organic carbon (OC) based on conversion factors derived from levoglucasan [16]. According to previous studies, particulate matter (PM) poses numerous health risks, including cardiovascular diseases, mental disorders, carcinogenic diseases, and respiratory problems [17]. Moreover, PM interacts with cells and macrophages to generate reactive oxygen species (ROS) that can alter cellular redox state. Recently, several studies have used oxidative potential (OP) as an indicator to evaluate the impact of PM toxicity, defined as the ability of PM to generate ROS [18; 19; 20; 21]. OP integrates various physicochemical properties of PM, including size, surface area, and chemical composition, to assess its effects on human health. The dithiothreitol (DTT) assay, a non-cellular chemical reaction using DTT for biological reducing agents, is one of the methods used to estimate OP [18; 21]. This study aimed to evaluate the optical absorption coefficient of BrC by measuring PM\({}_{2.5}\) and BC concentrations during the winter season at Mokpo University located in Muan-gun, Jeonnam, Republic of Korea. In addition, this study aims to provide an outlook on levoglucasan as a tracer for BB.