Abstract: Objective：To study the concentrations of fine particulate matters and ultrafine particles and influenced factors during winter in an area of Beijing. Methods: Real-ime monitoring of particles’ mass and number concentrations were conducted in an area of Beijing from February 7^th to 27^th, 2013. At the same time, the meteorological data were also collected from the Beijing meteorological website. Differences of the particles’ mass and number concentrations during different periods were analyzed using Mann-hitney U test. Meanwhile, the influenced factors were also analyzed. Results: The mean concentrations of fine particulate matters and ultrafine particles were (157.2±142.8) μg/m³ and (25 018±9 309) particles/cm³, respectively. The particles’ number and mass concentrations in haze days were 1.27 times and 2.91 times higher than those in non-aze days, respectively. The mass concentrations of fine particulate matters in the self-onitoring site were higher than those in the nearest central monitoring sites, and the hourly-verage concentrations of particles were significantly consistent with those at the commuter times. Meanwhile, the setting off of fireworks/firecrackers during the Spring Festival could lead to short-term increases of the particles’ number and mass concentrations. When the wind speed was low and the related humidity was high, the concentrations of particulate matters were relatively high, and the mass concentrations of fine particulate matters were lagged about 1-2 d. Conclusion: The level of the particulate matters in this area was high. Heavy traffic, setting off of fireworks/firecrackers and meteorological factors may be some of the main factors affecting the concentrations of the particulate matters in this area. Among those factors, the effect of setting off of fireworks/firecrackers didn’t last long and the effect of the meteorological factors had a hysteresis effect.

Key words: Particulate matter, Air pollutants, Mass concentration, Beijing