Polycyclic aromatic hydrocarbons (PAHs) and nitro-PAHs (NPAHs) in PM_2.5 samples were collected at a roadside monitoring station in Kanazawa, Japan, in every season from 2017 to 2018. Nine PAHs and five NPAHs were determined using high-performance liquid chromatography with fluorescence detection and chemiluminescence detection, respectively. The mean concentrations of PAHs and NPAHs were highest in winter and lowest in summer. Fluoranthene and pyrene were the dominant PAHs and 1-nitropyrene was the dominant NPAH in all seasons, and these compounds were mainly emitted by diesel vehicles. The concentration ratio of benzo(a)pyrene (BaP) to benzo(ghi)perylene (BgPe) ((BaP)/(BgPe)) and of indeno(1,2,3-cd)pyrene (IDP) to the sum of IDP and benzo(ghi)perylene (BgPe) ((IDP)/((IDP)+(BgPe0) might still be useful indicators for identifying traffic emission sources today. Moreover, our results showed that the carcinogenic risk in all seasons was below the acceptable limit set by the WHO.

Particulate matter (PM) was collected in three different areas, SY-1, SY-2, and SY-3, in Shenyang, China, during the warm and cold seasons from 2012 to 2014. SY-1 was located beside a thermal power plant, far from the central area. SY-2 was near a coal heating boiler on the main road, close to the central area. SY-3 was on the main road, without fixed emission sources. Nine PM-bound polycyclic aromatic hydrocarbons (PAHs) were analyzed. The results showed that the mean concentration of total PAHs was higher in the cold season (92.6–316 ng m⁻³) than in the warm season (18.4–32.2 ng m⁻³). Five- and six-ring PAHs occupied a large percentage at all sites in the warm season, and four-ring PAHs were the dominant components in the cold season. Several diagnostic PAH ratios indicated that the main sources of PAHs in Shenyang in the warm and cold seasons were not only coal burning but also vehicle emission. In this study, we suggest that a benzo[a]pyrene/benzo[ghi]perylene ratio ([BaP]/[BgPe]) of 0.6 was a useful indicator to speculate the relative significance of coal burning and vehicle exhaust. Although the Shenyang government has undertaken actions to address air pollution, the PM and PAH concentrations did not decrease significantly compared to those in our previous studies. The cancer risk calculated from the BaP equivalent total concentration at all three sites in the warm and cold seasons exceeded the acceptable limit established by the US EPA.

Background: Background sites are mainly affected by long-range-transported air pollutants, resulting in potential adverse effects on local atmospheric environments. A 4–5 year observational study was conducted to illustrate the air pollution profile at the Kanazawa University Wajima air monitoring station (KUWAMS), an ideal remote background site in Japan. Methods: Nine polycyclic aromatic hydrocarbons (PAHs) in the particulate phase and various air pollutants were continuously monitored for 4–5 years. Diagnostic ratios of PAHs and back-trajectory analysis were applied to trace the possible sources of the air pollutants collected at the sampling site. Results: The atmospheric concentration of PAHs in the atmosphere at the site decreased from 2014 to 2019, benefit from the predominant air pollution control policy in China and Japan. Common air pollutants including sulfur dioxide (SO₂), nitrogen oxides (NO_x), ozone, methane (CH₄), and non-methane hydrocarbon (NMHC) were detected in low concentrations from 2016 to 2019, while ozone (O₃) and particulate matter (PM_2.5, PM with a diameter less than 2.5 μm) were present in high levels that exceeded the Japanese standards. Most air pollutants peaked in spring and showed evident diurnal variations in spring and summer. Conclusions: This is the first study to clarify the atmospheric behaviors of multiple air pollutants at a background site in Japan. Significant external air pollutant impact and unneglectable air pollution were demonstrated at KUWAMS, indicating the importance of studying atmospheric pollution at remote sites.