Mass concentrations and temporal profiles of PM10, PM2.5 and PM1 near major urban roads in Beijing

Mass concentrations of PM10, PM2.5 and PM1 were measured near major roads in Beijing during six periods: summer and winter of 2001, winter of 2007, and periods before, during and after the 2008 Beijing Olympic Games. Since the control efforts for motor vehicles helped offset the increase of emissions from the rapid growth of vehicles, the averaged PM2.5 concentrations at roadsides during the sampling period between 2001 and 2008 fluctuated over a relatively small range. With the implementation of temporary traffic control measures during the Olympics, a clear "V" shaped curve showing the concentrations of particulate matter and other gaseous air pollutants at roadsides over time was identified. The average concentrations of PM10, PM2.5, CO and NO decreased by 31.2%, 46.3%, 32.3% and 35.4%, respectively, from June to August; this was followed by a rebound of all air pollutants in December 2008. Daily PM10 concentrations near major roads exceeded the National Ambient Air Quality Standard (Grade II) for 61.2% of the days in the non-Olympic periods, while only for 12.5% during the Olympics. The mean ratio of PM2.5/ PM10 near major roads remained relatively stable at 0.55 (+/- 0.108) on non-Olympic days. The ratio decreased to 0.48 (+/- 0.099) during the Olympics due to a greater decline in fine particles than in coarse-mode PM. The ratios PM1/ PM2.5 fluctuated over a wide range and were statistically different from each other during the sampling periods. The average ratios of PM1/PM2.5 on non-Olympic days were 0.71.