Ozone air quality during the 2008 Beijing Olympics: effectiveness of emission restrictions

A series of aggressive measures was launched by the Chinese government to reduce pollutant emissions from Beijing and surrounding areas during the Olympic Games. Observations at Miyun, a rural site 100 km downwind of the Beijing urban center, show significant decreases in concentrations of O ₃, CO, NO _y, and SO ₂ during August 2008, relative to August 2006–2007. The mean daytime mixing ratio of O ₃ was lower by about 15 ppbv, reduced to 50 ppbv, in August 2008. The relative reductions in daytime SO ₂, CO, and NO _y were 61%, 25%, and 21%, respectively. Changes in SO ₂ and in species correlations from 2007 to 2008 indicate that emissions of SO ₂, CO, and NO _x were reduced at least by 60%, 32%, and 36%, respectively, during the Olympics. Analysis of meteorological conditions and interpretation of observations using a chemical transport model suggest that although the day-to-day variability in ozone is driven mostly by meteorology, the reduction in emissions of ozone precursors associated with the Olympic Games had a significant contribution to the observed decrease in O ₃ during August 2008, accounting for 80% of the O ₃ reduction for the month as a whole and 45% during the Olympics Period (8–24 August). The model predicts that emission restrictions such as those implemented during the Olympics can affect O ₃ far beyond the Beijing urban area, resulting in reductions in boundary layer O ₃ of 2–10 ppbv over a large region of the North China Plain and Northeastern China.