![]() ![]() T.: 2001, ‘History of strong dust storms in beijing and ecological environmental change in nearby regions’, Journal of Desert Research 21(4), 402–407 (in Chinese).ĭuce, R. Although the very large particle specific surface area provided by dust storms would normally be conducive to heterogeneous reactions, the conversion rate from SO 2 to SO 4 2− was very low, because the relative humidity, less than 30%, was not high enough.Ĭheng, G. Crustal elements accounted for 60–70% of the chemical composition of PM 2.5, and sulfate and nitrate for much less, unlike the chemical composition of PM 2.5 on pollution days, which was primarily composed of sulfates, nitrates, and organic material. The PM 2.5 concentration was approximately 230 μg m −3, accounting for 28% of the total PM 10 mass concentration. ![]() Furthermore, during sand-dust storm periods, aerosols were created that consisted not only of many coarse particles, but also of a large quantity of fine particles. ![]() During the same period, the concentrations in urban areas were comparable to those in suburban areas, while the concentrations of gaseous pollutants, such as SO 2, NO x, NO 2, and O 3, remained at low levels, owing to strong winds. Ambient air monitoring and analysis of recent meteorological data from Beijing sand-dust storm periods revealed that PM 10 mass concentrations during dust storm events remained at 1500 μg m −3, which is five to ten times higher than during non-dust storm periods, for fourteen hours on both April 6 and 25, 2000. Floating dust, blowing sand, and dust storms, primarily from Mongolia, account for 71%, 20%, and 9% of sand-dust weather, respectively. In the Beijing area, March and April have the highest frequency of sand-dust weather. ![]()
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