Characteristics of PM10, SO2, NO(x) and O3 in ambient air during the dust storm period in Beijing.

In this study, the hourly variations of the mass concentrations of PM10, SO2, NO(x) and O3 at three sampling sites were observed in Beijing during dust storm occurrence period in April 2000. The PM2.5 samples were simultaneously collected. By comparing the hourly variations of the pollutant concentrations before, during and after dust storm event and haze pollution episode, the variation characteristics of the mass concentrations of PM10, SO2, NO(x) and O3 during dust storm events were presented. The results show that the mass concentration of PM10 reached 1500 microg m(-3) during dust storm events on April 6 and 25, 2000, which was 5-10 times that of the non-dust weather conditions, and this period of high mass concentration of PM10 lasted for about 14 h, and then the concentration level prior to the dust event was recovered in 6-h time period. Due to the strong wind, the concentrations of SO2, NO(x), NO2 and O3 during dust storm period were maintained at low levels, which was significantly different from those on non-dust storm and haze pollution conditions. A lot of coarse particles as well as a very large amount of fine particles were contained in the atmospheric particulates during dust storm period, and the concentration level of PM2.5 was comparable to that during haze pollution episode. During the dust storm period, the PM2.5 concentration was approximately 230 microg m(-3), accounting for 30% of the total PM10 mass concentration, was four times that of non-dust weather conditions, and the crustal elements constituted about 66.4% of the chemical composition of PM2.5 while sulfate and nitrate contributed much less, which was quite different from the chemical composition of PM2.5 primarily constituted by sulfate, nitrate and organics on haze pollution day.