Comparison of Hourly PM(2.5) Observations Between Urban and Suburban Areas in Beijing, China

Hourly PM(2.5) observations collected at 12 stations over a 1-year period are used to identify variations between urban and suburban areas in Beijing. The data demonstrates a unique monthly variation form, as compared with other major cities. Urban areas suffer higher PM(2.5) concentration (about 92 μg/m(3)) than suburban areas (about 77 μg/m(3)), and the average PM(2.5) concentration in cold season (about 105 μg/m(3)) is higher than warm season (about 78 μg/m(3)). Hourly PM(2.5) observations exhibit distinct seasonal, diurnal and day-of-week variations. The diurnal variation of PM(2.5) is observed with higher concentration at night and lower value at daytime, and the cumulative growth of nighttime (22:00 p.m. in winter) PM(2.5) concentration maybe due to the atmospheric stability. Moreover, annual average PM(2.5) concentrations are about 18 μg/m(3) higher on weekends than weekdays, consistent with driving restrictions on weekdays. Additionally, the nighttime peak in weekdays (21:00 p.m.) is one hour later than weekends (20:00 p.m.) which also shows the evidence of human activity. These observed facts indicate that the variations of PM(2.5) concentration between urban and suburban areas in Beijing are influenced by complex meteorological factors and human activities.