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In this study, 30 PM 2.5 samples were collected from the atmosphere in Changchun City in the autumn of 2017. The concentration and composition characteristics of 17 polycyclic aromatic hydrocarbons (PAHs) in the samples were analyzed by gas chromatography mass spectrometry (GC-MS). The diagnostic ratio and principal component analysis method were used to determine the source of PAHs pollution. The health risk assessment was carried out by both calculating the equivalent carcinogenic concentration of benzo(a)pyrene and the lifetime risk of cancer. Results show that the average PM 2.5 concentration in autumn in Changchun is (50.84±12.23) μg·m -3 , and the content of organic carbon (OC) and elemental carbon (EC) are (17.07±5.64) μg·m -3 and (1.33±0.75) μg·m -3 , respectively, accounting for 37% of the total PM 2.5 . The total concentration of PAHs is (15.69±5.93) ng·m -3 , which was dominated by medium- to high-ring-number PAHs, accounting for 84.26% of total PAHs. The atmospheric PAHs in Changchun mainly originate from motor vehicle exhaust emissions (44.48%) > coal combustion (29.16%) > biomass burning (26.36%), local transportation (gasoline vehicles) emissions being the main source of pollution. The average carcinogenic concentration of benzo(a)pyrene is in the range of 1.55 ng·m -3 and 5.38 ng·m -3 , and the average carcinogenic equivalent concentration is (6.44±1.53) ng·m -3 , which is generally considered a slight pollution level. The ingestion of PAHs by breathing is the most harmful to the health of adult women, followed by adult males and children, however since the lifetime carcinogenic risk value of the entire population did not exceed 1×10 -6 , their health risks are considered to be at acceptable levels.

Many cities are located in the downstream areas of rivers. Rapid urbanization may result in drastic changes in the urban river ecosystem. Antibiotic resistant genes (ARGs) are considered to be emerging environmental pollutants, which may do harm to the health of humans and may pose a potential risk for urban ecological safety by the dissemination and enrichment of ARGs in urban rivers. In this study, a high-throughput quantitative PCR technique was used to investigate the diversity and abundance of ARGs at three sites in Lianjiang County and the estuary of the Aojiang River, Fujian Province. The results show the abundance of ARGs in the downstream urban area of Lianjiang County (3.9×10 10 copies·L -1 ) is significantly higher than upstream of the urban area and the estuary of the Aojiang River. A total of 129 ARGs are detected in the downstream urban area, which is higher than in the upstream and the estuary. The results also suggest that ARGs are persistent and not easy to reduce in the natural river following the occurrence of ARGs and indicated that the urban river is an important reservoir of ARGs.