Characteristics and source distribution of air pollution in winter in Qingdao, eastern China

To characterize air pollution and determine its source distribution in Qingdao, Shandong Province, we analyzed hourly national air quality monitoring network data of normal pollutants at nine sites from 1 November 2015 to 31 January 2016. The average hourly concentrations of particulate matter <2.5 μm (PM_2.5) and <10 μm (PM₁₀), SO₂, NO₂, 8-h O₃, and CO in Qingdao were 83, 129, 39, 41, and 41 μg m^-3, and 1.243 mg m^-3, respectively. During the polluted period, 19-26 December 2015, 29 December 2015 to 4 January 2016, and 14-17 January 2016, the mean 24-h PM_2.5 concentration was 168 μg m^-3 with maximum of 311 μg m^-3. PM_2.5 was the main pollutant to contribute to the pollution during the above time. Heavier pollution and higher contributions of secondary formation to PM_2.5 concentration were observed in December and January. Pollution pathways and source distribution were investigated using the HYbrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) model and potential source contribution function (PSCF) and concentration weighted trajectory (CWT) analyses. A cluster from the west, originating in Shanxi, southern Hebei, and west Shandong Provinces, accounted for 44.1% of the total air masses, had a mean PM_2.5 concentration of 134.9 μg m^-3 and 73.9% trajectories polluted. This area contributed the most to PM_2.5 and PM₁₀ levels, >160 and 300 μg m^-3, respectively. In addition, primary crustal aerosols from desert of Inner Mongolia, and coarse and fine marine aerosols from the Yellow Sea contributed to ambient PM. The ambient pollutant concentrations in Qingdao in winter could be attributed to local primary emissions (e.g., coal combustion, vehicular, domestic and industrial emissions), secondary formation, and long distance transmission of emissions.