[Characteristic comparative study of particulate matters in Beijing before and during the Olympics]

Two city ecosystem research stations were selected for continuous monitoring of atmospheric fine particulate matter (PM2.5) concentration from June to September 2008, when the Beijing Olympic Games was held. The relationship between meteorological factors, artificial control management measures and PM2.5 dynamic characteristics were analyzed. The results showed that the daily average concentration of PM2.5 at RCEES Station, which is near the 5th North Ring, was 0.067 mg x m(-3) during the study period, and the particle concentration during the Olympic Games was 0.060 mg x m(-3), which was decreased by about 26% compared with the content before the Olympic Games (0.081 mg x m(-3)). As for JX Station located in the 2th South Ring, its daily average concentration of PM2.5 was 0.078 mg x m(-3). Similar to RCEES Station, PM2.5 average content during the Olympic Games (0.069 mg x m(-3)) was 27% lower compared with the content before the Olympic Games (0.095 mg x m(-3)). Two peaks could be found when daily distribution of PM2.5 was displayed, one appeared between 08:00 and 10:00 (the average content for RCEES and JX were 0.068 and 0.089 mg x m(-3), respectively), and the other appeared at 20:00-22:00, which could be attributed to traffic emission and road dust pollution, especially the emission from the growing number of cars in rush hours. Meteorological condition during the whole period was typical in summer in Beijing with both high temperature and humidity. Correlation analysis revealed that the concentrations of PM2.5 had a positive correlation with the air temperature (P < 0.01), while it had no significant relationship with wind speed, relative humidity or precipitation (P > 0.05). Our monitoring results suggested that the artificial air pollution control strategies were effective measures for air pollution control during 2008 Beijing Olympic Game.