## 3 Results and Discussion
### Ambient Concentrations
The varied seasonal concentration of PAHs, identified in the present study, was also estimated to be affected by effects of cold ignition of vehicles in wintertime and photochemical decomposition in summertime, as it was reported in previously conducted studies. The sum of annual average concentration of alkanes appeared as 538 ng/m\({}^{3}\) in residential area and 1428 ng/m\({}^{3}\) on roads; the seasonal concentration thereof tended to show behaviors similar to seasonal variations of PAHs however the concentration in residential area appeared higher in summertime than that in wintertime. The sum of concentration of alkanes, observed in wintertime, appeared as 147 ng/m\({}^{3}\) in residential area and 841 ng/m\({}^{3}\) on roads; it appeared in residential area and on roads as 69 ng/m\({}^{3}\) and 66 ng/m\({}^{3}\), respectively, in summertime. Carbon Preference Index (CPI) signifies the ratio of concentrations of odd numbered alkanes to even numbered alkanes, wherein the C\({}_{\text{max}}\) is defined as the number of carbons of detected peak concentration, and it represents the input of anthropogenic sources [53]. The value of CPI close to 1 in the acceptance model implies the artificial emission of fossil fuels whereas the value over 2.0 represents the alkanes originated from biomass [53; 54; 55]. Hopanes and steranes are the ones of organic indicators of PM\({}_{2.5}\) which are mainly created from fossil fuels. Therefore, the hopanes and steranes, contained in the exhaust from vehicles or thermoelectric power plants wherein fossil fuels are used, are detected comparatively in higher level [10; 56; 57]. A total of 16 compounds of hopanes and steranes substances including 17\(\alpha\)(H)-22,29,30-trinorhopane, 17\(\beta\)(H)-21\(\alpha\)(H)-30-norhopane and 17\(\alpha\)(H)-21\(\beta\)(H)-hopane were analyzed as an ingredient of organic indicators of fossil fuels. Annual average concentration hopanes and steranes appeared in the subject area as 0.66 ng/m\({}^{3}\) in the residential area and 2.93 ng/m\({}^{3}\) on roads; the roads appeared with higher level of concentration. Levoglucosan is a substance of organic indicator resulted from the biomass burning. Annual average concentration of levoglucosan in the subject area of the present study appeared as 582.75 ng/m\({}^{3}\) (residential area) and 1007.25 ng/m\({}^{3}\) (roads), respectively. With regard to the seasonal concentrations of levoglucosan, the highest concentration of 1173 ng/m\({}^{3}\) appeared in residential area in autumn, while the highest concentration of 2834 ng/m\({}^{3}\) appeared on roads in wintertime. However, the ratio of levoglucosan/OC, employed for the acceptance model, appeared higher in wintertime regardless of the area of residence or roads; the ratio of levoglucosan /OC in wintertime appeared as 272.45 mg/g (residential area) and 247.29 mg/g (on roads), respectively. Further, the ratio of K\({}^{+}\)/EC, the one of indicator chemical components of biomass burning, also appeared with the highest level of 0.45 (annual average 0.18) in the residential area and 0.31 (annual average 0.12) on roads in wintertime. Therefore, the biomass burning in the subject area of the present study was identified to be increasing mainly in wintertime. The cholesterol, one of WSOC, is the one of organic indicator chemical components resulted from the burning of meats [24]. Previous study had employed the ratio of cholesterol to OC for the CMB model as an indicator material of burning of meats; the ratio of cholesterol/OC used in the previously conducted study was 0.0010 [58]. The annual average concentration of cholesterol appeared as 0.20 ng/m\({}^{3}\) in residential area and 3.86 ng/m\({}^{3}\) on roads, respectively, in the present study. The ratio of cholesterol/OC appeared commonly below 0.0000 in all four seasons in the residential area, whereas it appeared on roads as 0.0004 in spring and 0.0010 in wintertime.