## 3 Results & Discussion  
### PAHs in PM\({}_{2.5}\)  
The one-second prevailing meteorological conditions, including wind speed, wind direction, temperature, and pressure, were determined using a professional weather station (PCE Instruments Ltd., Southampton, UK) to understand the source directions. Wind direction analysis showed that the sampling site had wind blowing from the east, indicating that the village was affected by emissions from the asphalt mix plant (Figure 1). The wind speed from December 2004 to December 2005 ranged from 0.0 m/sec to 8.0 m/s, with an annual average wind speed of 0.61 \(\pm\) 0.95 m/s. Wind direction histograms (wind rose) for the observation period were prepared, which were overlaid in the study area. The main wind directions were identified as easterly winds. This indicates that the wind blew predominantly from the source location. Table 1 shows the concentrations of various PAHs measured in the study area, capital city (KIST), and a Korean background location (BI) during the study period. We analyzed 13 species of PAHs to confirm the effects from the sources [35]. The concentration of \(\sum\)PAHs in the study area was 11.65 ng/m\({}^{3}\), which was about eight times higher than that at the background location and about five times higher than that in the capital city, which has the major emission sources of vehicles and heating. This suggests that there are facilities in the research area that emit high concentrations of PAHs. The concentration of each of the measured PAHs were, in decreasing order, Chry, Bbf, Fluo, BghiP, Phen, etc. ; it was confirmed that these five substances with the highest concentrations accounted for 60% of the total PAHs. The PAHs contained in the PM\({}_{2.5}\) were analyzed and are represented as time series concentrations in Figure 2. The results show that the \(\sum\)PAHs contained in PM\({}_{2.5}\) ranged from a minimum of 0.51 ng/m\({}^{3}\) to a maximum of 60.73 ng/m\({}^{3}\), with an average of 11.54 ng/m\({}^{3}\). Seasonal \(\sum\)PAHs were highest in winter (December-January), followed in order by spring (March-May), autumn (September-November), and summer (June-August). The higher concentrations of \(\sum\)PAHs in winter, autumn, and spring compared to summer may be due to meteorological conditions in the point source area. To identify emission sources of PAHs, diagnostic ratios for source analysis were performed. The diagnostic ratio method is widely used in the determination of PAH pollution sources, of which Anth/(Anth+Phen), Fluo/(Fluo+Pyre), BaA/(BaA+Chry), and Indeno/(Indeno+BghiP) are the most commonly used [36, 37, 38]. According to the summary analyses of previous studies; a BaA/(BaA+Chry) ratio of \(<\)0.2 indicates a petrogenic source, \(>\)0.35 indicates a vehicular emission, and a ratio between the two represents coal combustion [39]. An Anth/(Anth+Phen) ratio of \(<\)0.1 usually indicates a petrogenic source, whereas \(>\)0.1 indicates a source of combustion [40]. A Fluo/(Fluo+Pyre) ratio of \(<\)0.4 indicates a petrogenic source, \(>\)0.5 indicates a grass, wood, coal combustion, and a ratio between the two represents fossil fuel combustion [41]. Figure 3 shows the results of diagnostic ratios for source analysis for Anth/(Anth+Phen) vs. BaA/(BaA+Chry) and Anth/(Anth+Phen) vs. Fluo/(Fluo+Pyre). (BaA)/(BaA+Chr) ranged less than 0.2, and Anth/(Anth+Phen) ranged from 0.0 to 0.4. This indicates that the emission of PAHs in the study area is the condensation of complete and incomplete combustion of petrogenic sources [42]. (Fluo)/(Fluo+Pyre) was between 0.01 and 0.62, but most ratios were less than 0.4 during the study period. This indicates that the source of PAHs was fossil fuels from coal and petroleum [43]. These results show that the asphalt plant, the only petroleum raw material processing plant in the study area, dominates the PAHs concentration.