Long-Term Trends in Urban Atmospheric Polycyclic Aromatic Hydrocarbons and Nitropolycyclic Aromatic Hydrocarbons: China, Russia, and Korea from 1999 to 2014.

Total suspended particulate matter (TSP) was collected during the summer and winter in five cities in China (Shenyang, Beijing, and Shanghai), Russia (Vladivostok), and Korea (Busan) from 1997 to 2014. Nine polycyclic aromatic hydrocarbons (PAHs) with four to six rings, including pyrene (Pyr) and benzo[a]pyrene (BaP), were determined using high-performance liquid chromatography with fluorescence detection. Two nitropolycyclic aromatic hydrocarbons (NPAHs), 1-nitropyrene (1-NP) and 6-nitrobenzo[a]pyrene (6-NBaP), were also determined using high-performance liquid chromatography with online reduction/chemiluminescence detection. Two Chinese cities, Beijing and Shenyang, showed very high concentrations of total PAHs (ΣPAH) and total NPAHs (ΣNPAH) with a large seasonal difference (winter > summer), although the concentrations decreased over time. In both cities, maximum mean concentrations of ΣPAH over 200 ng m-3 were observed in the winter. In Beijing, an increase in the ΣPAH concentration was observed in the winter of 2010, which was after the 2008 Beijing Olympic Games. The [1-NP]/[Pyr] ratio, a diagnostic parameter for source, was smaller in the winter than in the summer over the monitoring period, suggesting a large contribution of coal heating systems in the winter. In Vladivostok, concentrations of ΣPAH and ΣNPAH were lower than in the above two Chinese cities. The [1-NP]/[Pyr] ratio was larger than in the above Chinese cities even in the winter, suggesting that the contribution of coal combustion facilities, such as power plants for heating, was not very large. In Shanghai and Busan, concentrations of ΣPAH and ΣNPAH were much lower than in the above three cities. At the beginning of the monitoring periods, the [1-NP]/[Pyr] ratios, which were as large as those of Japanese commercial cities, suggested a large contribution from automobiles. After that, the contribution of automobiles decreased gradually. However, BaP concentrations were still over 1 ng m-3 in all cities monitored in China, Russia, and Korea, suggesting that the urban air pollution of PAHs and NPAHs in these regions should not be ignored.