Keywords: 
• littoral areas /
• Bohai Sea /
• Yellow Sea /
• PM₁₀ /
• spatiotemporal distribution

Abstract: Since PM₁₀ is one of the major indicators to assess atmospheric pollution, it is significant to explore the tempo-spatial changes in PM₁₀ for the air quality and human health. In the littoral zones of Bohai Sea and Yellow Sea, there are two municipalities and some industrial and agricultural provinces, therefore the spatiotemporal distribution and source characteristics of PM₁₀ are characterized by complexity and representativeness. In this study, the PM₁₀ samples were collected in 7 urban sites (i.e., Jinzhou, Beijing, Tianjin, Yantai, Qingdao, Lianyungang and Yancheng) and 3 corresponding rural sites for a period of 1 year. Meanwhile, the intensive sampling activities were conducted in January and July lasted for a total of 60 days in the sites at Jinzhou, Tianjin and Yantai. The results showed that the annual average of PM₁₀ concentrations in the whole littoral zone was (129 ±18) μg·m^-3. The minimum concentration of PM₁₀ in a single month was 15 μg·m^-3 at the rural site of Yancheng in July 2015; while the maximum concentration of PM₁₀ in a single month was 307 μg·m^-3 at the urban site of Beijing in March 2015. The concentrations of PM₁₀ in Yancheng (85 ±27 μg·m^-3 and 66 ±35 μg·m^-3 at urban and rural sites, respectively) were obviously lower than those at the other sampling sites. The concentrations of PM₁₀ in Beijing (140 ±68 μg·m^-3)and in Tianjin (169 ±60 μg·m^-3) situated in the mid-west part of Bohai littoral zone, were evidently greater than those in Jinzhou (125 ±41 μg·m^-3) and in Yantai (109 ±31 μg·m^-3) located in the east part of Bohai littoral zone. Moreover, the annual average concentration of PM₁₀ in the coastal zone of Yellow Sea (114 μg·m^-3) was apparent- ly lower than that in the coastal areas of Bohai Sea (136 μg·m^-3). Therefore, the spatial distribution of PM₁₀ con- centration exhibited the decreasing trend from the west to the east and from the north to the south. In addition, the annual averages of PM₁₀ concentrations in the urban and rural sites were (129 ±18) μg·m^-3 and (112 ±30) μg·m^-3, respectively. The levels of PM₁₀ in the rural sites during winter and spring were close to those in the urban sites with no significant differences, indicating that the air pollution in the local rural areas was considerably severe and thus more attention should be paid. The levels of PM₁₀ in the rural sites during summer and autumn were slightly lower than those in the urban sites. In view of two coastal zones, the seasonal feature of PM₁₀ concentration was higher in spring and winter, and lower in summer and autumn. Based on a multivariate regression model, the emis- sion source of PM₁₀ in the littoral areas of Bohai Sea and Yellow Sea was multiple. About 30% of the total varia- tions in the concentration of PM₁₀ could be attributed to the local wet precipitation, energy consumption per capita and sandstorm. The diurnal changes in concentration of PM₁₀ were not significant in the two zones. The concentra- tion PM₁₀ showed positive correlation with air temperature, and negative correlations with wind velocity and wet precipitation. In other words, PM2.5 concentration was affected by the combined meteorological factors.