## 3 Results and Discussion  
### Chemical Components in PM\({}_{2.5}\)  
Table 1 presents the concentrations of chemical components analyzed in this study. Figure 3 illustrates the temporal concentrations of wind speed, temperature, and relative humidity; OC; ionic compounds; K\({}^{+}\) and K; levoglucan and mannosan; BC\({}_{880}\); and BrC\({}_{370}\) observed at 3 h intervals throughout the study period. Figure 3f shows the contributions to the light absorption coefficients of BC and BrC at 370 nm. Meteorological variables such as temperature, relative humidity, precipitation, wind direction, wind speed, mixing height, and atmospheric boundary layer play an essential role in influencing the levels of and variations in atmospheric constituents due to their impact on air pollution [31]. For this study, temperature, relative humidity, and wind speed data were obtained from the Meteorological Data Open Portal ([[https://data.kma.go.kr/cmmn/main.do](https://data.kma.go.kr/cmmn/main.do)]([https://data.kma.go.kr/cmmn/main.do](https://data.kma.go.kr/cmmn/main.do)) accessed on 1 May 2024), as shown in Figure 3a. The average values for temperature, relative humidity, and wind speed were 3.1 \({}^{\circ}\)C, 70.1%, and 4.2 m s\({}^{-1}\), respectively. The average concentration of PM\({}_{2.5}\) was 21.27 ug m\({}^{-3}\), with the highest value recorded at 9:00 am on 19 February, coinciding with elevated levels of the secondary inorganic ions. According to previous studies, PM\({}_{2.5}\) occurring in winter was analyzed to have NO\({}_{3}\)\({}^{-}\) and NH\({}_{4}\)\({}^{+}\) as its main ionic components, appearing as a result of fuel combustion for heating and vehicle emissions due to cold weather [22; 32]. In this study, the average concentrations of NO\({}_{3}\)\({}^{-}\), NH\({}_{4}\)\({}^{+}\), and SO\({}_{4}\)\({}^{2-}\) were 6.6, 4.4, and 2.9 ug m\({}^{-3}\), respectively. Atmospheric NO\({}_{3}\)\({}^{-}\) is known to be associated with NH\({}_{3}\), sea salt, or soil dust particles (heterogeneous reactions) and favors the formation of NH\({}_{4}\)NO\({}_{3}\) under high-humidity and low-temperature conditions. During the measurement period, a strong correlation coefficient of determination (r\({}^{2}\) = 0.78) was observed between the observed NO\({}_{3}\)\({}^{-}\) and NH\({}_{4}\)\({}^{+}\) concentrations, while a weak correlation (r\({}^{2}\) = 0.19) was observed between NH\({}_{4}\)\({}^{+}\) and SO\({}_{4}\)\({}^{2-}\). These results indicate that NH\({}_{4}\)\({}^{+}\) in the atmosphere may have contributed to PM\({}_{2.5}\) concentrations by forming NH\({}_{4}\)NO\({}_{3}\). The average concentrations of OC and EC were 6.1 and 0.5 ug m\({}^{-3}\), respectively, exhibiting a correlation coefficient of 0.62. Ref. [33] reported OC/EC ratios of 4.2 and 14.5 for residential wood combustion and wildfires, respectively. Figure 4 depicts the diurnal variations in the average hourly concentrations of EC and BrC\({}_{880}\). In addition, the figure includes scatterplots illustrating pairwise correlations between EC and BrC\({}_{880}\). A discernible decline is observed in both EC and BrC\({}_{880}\) during the morning and afternoon periods, attributed to anthropogenic sources such as traffic emissions. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Compounds** & **Unit** & **Average \(\pm\) S.D (\({}^{\text{th}}\))** & **Range** \\ \hline PM\({}_{2.5}\) mass & ug/m\({}^{3}\) & 21.3 \(\pm\) 6.6 & 7.9–37.2 \\ \hline OC & ug/m\({}^{3}\) & 6.1 \(\pm\) 2.8 & 2.0–18.0 \\ EC & ug/m\({}^{3}\) & 0.5 \(\pm\) 0.2 & 0.2–1.2 \\ \hline NO\({}_{3}\)\({}^{-}\) & ug/m\({}^{3}\) & 6.6 \(\pm\) 5.0 & 0.5–21.9 \\ SO\({}_{4}\)\({}^{2-}\) & ug/m\({}^{3}\) & 2.9 \(\pm\) 1.3 & 1.0–9.8 \\ NH\({}_{4}\)\({}^{+}\) & ug/m\({}^{3}\) & 4.4 \(\pm\) 2.4 & 1.0–13.2 \\ K\({}^{*}\) & ug/m\({}^{3}\) & 0.2 \(\pm\) 0.1 & 0.1–0.4 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Overall average results of major chemical compounds in PM\({}_{2.5}\) in this study. Figure 2: DTT-OP reduction rate results by quinone concentration.