## 3 Results
### Ratio Characteristic of Long-Range Transport Component  
Based on the chemical compositions of PM\({}_{2.5}\), AOD, S-5 P, RTWC, and the ERA wind field during the event period in this study, it can be concluded that a high concentration of PM\({}_{2.5}\) generated by long-range transport from the west of the study area had external effects. Thus, this study identified precursor components for long-range transport based on concentration differences between the event period and other periods. Chemical compounds that influenced the event period were selected based on concentrations measured during the event period and other periods. The analytical determination was the following: (1) a compound that was observed to show an increase in concentration during the event period; (2) a compound that affected SOA formation; and (3) a compound that satisfied the condition suggested by a previous study as an inert precursor of long-range transport. As a result, the indicators for long-distance tracking included gaseous materials (including CO and NH\({}_{3}\)) and PM\({}_{2.5}\) compositions (such as eBC, EC, WSOC, OC, NO\({}_{3}\)\({}^{-}\), SO\({}_{4}\)\({}^{-}\), and NH\({}_{4}\)\({}^{+}\)). Table 2 shows the results for the selected long-range indicators and PM\({}_{2.5}\). When results were compared between the event period and other periods, PM\({}_{2.5}\) and gaseous materials including CO and NH\({}_{3}\) were about 3.3 times, 1.5 times, and 2.7 times higher, respectively, during the event period. For PM\({}_{2.5}\) compositions, NO\({}_{3}\)\({}^{-}\), SO\({}_{4}\)\({}^{2-}\), and NH\({}_{4}\)\({}^{+}\) were increased by about 7.16 times, 2.9 times, and 4.7 times, respectively. These results confirmed that the PM\({}_{2.5}\) concentration increase during the event period was influenced by SOA from long-range transport. In addition, WSOC was influenced by SOA introduced by long-range transport because WSOC had about a 2 times increase during the event period and a dominant effect on SOA formation. Figure 6: The ratio of CO and CO\({}_{2}\) and the result of the residence time-weighted concentration (RTWC) model in the study area. Among the PM\({}_{2.5}\) components, eBC and EC were compared between the event period and other periods. eBC and EC are primarily derived from the combustion of fossil fuels and incomplete combustion of biomass. Regarding their analytical methods, EC can be determined using the thermo-optical method, and eBC can be determined using optical technology [48; 49]. In the case of eBC/EC with the NIOSH5040 protocol, PM\({}_{2.5}\) was generally in the range of 1.4\(\sim\)1.7. It might have a maximum difference of two times depending on particle size distribution, mixing status, and chemical compositions [50; 51; 52]. Except for the difference in analytical methods between eBC and EC, there are two examples that show differences between eBC and EC. The first is that brown carbon generated by biomass combustion increases eBC more than EC [53; 54]. The second is an underestimation of EC using char-OC, which is contained in samples. Previous studies have reported that methanol extraction of char-OC contained within filters can increase EC by more than two times [49; 55]. In other words, char-OC within filters can cause an underestimation of EC and an increase in the eBC/EC ratio. The measured ratio of eBC/EC in this study was 2.02 during other periods and 2.46 during the event period. Study areas specified by ratios of K\({}^{+}\)/K and K\({}^{+}\)/Cl had relatively low combusions of biomass. The orchard did not have any sources generating char-OC. Thus, the eBC/EC increase during the event period should be due to external influxes. To evaluate the above results more accurately, we analyzed correlations between CO and CO\({}_{2}\) and SOA formation indicators including SO\({}_{4}\)\({}^{2-}\), NO\({}_{3}\)\({}^{-}\), NH\({}_{4}\)\({}^{+}\) (SNA), eBC, and EC (Figure 7).