## 1 Introduction  
Carbonaceous aerosols, which are a major component of fine particulate matter (PM\({}_{2.5}\)) in urban atmospheres, influence air quality and visibility impairment and also affect adverse human health [1; 2; 3; 4; 5; 6]. Carbonaceous components are typically classified into organic and elemental carbon (OC and EC). OC is produced from not only primary emission sources (primary OC), but also from the atmospheric transformation processes of volatile organic species in the air (secondary OC). Organic aerosols (OAs) generally scatter incoming solar radiation, but a certain type of OA, brown carbon (BrC), absorbs radiation in near-ultraviolet (UV) wavelengths [7]. BrC aerosols exhibit a strong spectral dependence, with increasing absorption in the near UV range and weak absorption at infrared wavelengths. On the other hand, EC is directly emitted in the particle phase from incomplete combustion of fossil and biomass fuels [4; 6; 8]. EC strongly absorbs solar radiation, with weak spectral dependence [7]. Due to the importance of OC and EC in the atmosphere, information about the carbonaceous components of PM\({}_{2.5}\), such as concentrations, emission sources, absorption properties, etc., is essential to examining the causes of pollution, identifying their sources, estimating their source contributions, and better understanding the factors related to global climate change [6; 9; 10; 11; 12; 13]. Another important species that significantly contributes to PM\({}_{2.5}\) is water-soluble inorganic components, such as NO\({}_{3}\)-, SO\({}_{4}\)\({}^{2-}\), and NH\({}_{4}\)+. Secondary NO\({}_{3}\)- and SO\({}_{4}\)\({}^{2-}\) are formed through gas-phase oxidation and the heterogeneous reactions of gaseous NO\({}_{2}\) and SO\({}_{2}\)[14]. In urban environments, where vehicle emissions are important, haze pollution that leads to increases in the PM\({}_{2.5}\) concentration is directly linked to increases in the concentration of secondary inorganic components as well as carbonaceous particles [15; 16; 17; 18; 19; 20; 21; 22; 23; 24; 25; 26]. Moreover, meteorological conditions, such as low wind speed, high relative humidity (RH), high surface pressure, and shallow boundary layers, play an important role in increasing PM\({}_{2.5}\) pollution [27; 28; 29; 30; 31; 32; 33; 34]. The characteristics of PM\({}_{2.5}\) pollution vary with the season, location, and weather conditions [2; 12; 15; 24; 26; 27; 33; 34]. For example, during summer, when the formation of oxidants such as OH-, O\({}_{3}\), and H\({}_{2}\)O\({}_{2}\) is strongly activated, the secondary formation of particulate SO\({}_{4}\)\({}^{2-}\) accelerates, resulting in high PM\({}_{2.5}\) pollution [15; 26; 35]. Secondary OAs (SOAs) also contribute to high PM\({}_{2.5}\) formation in the summertime [2; 15]. On the other hand, during winter, when meteorological conditions such as air stagnation and high RH often occur, both the accumulation of primary particle pollutants (e.g., carbonaceous particles) and enhanced formation of secondary ionic species through the heterogeneous oxidation of SO\({}_{2}\), NO\({}_{2}\), and NH\({}_{3}\) play important roles in the formation of haze pollution [21; 25; 26; 27; 33; 34; 35; 36; 37; 38; 28; 39]. Therefore, since the major chemical composition of PM\({}_{2.5}\), and thus PM pollution, change greatly with the season and location, the seasonal causes of high PM\({}_{2.5}\) episodes need to be explored. Traffic emissions from the roadside are a significant part of urban pollution and are an important contributor of volatile organic compounds, nitrogen oxides, and carbonaceous particles in urban environments, contributing significantly to increases in the PM\({}_{2.5}\) concentration. Carbonaceous particles are especially crucial causes of PM\({}_{2.5}\) concentration increases in the vicinity of a roadway; measuring them is vital to estimating the contribution of traffic emission sources to PM\({}_{2.5}\)[10; 11; 12; 13; 40].