Primary Study On The Physical-chemical Properties Of Dust Aerosols Of The Typical Regions In The Northwest Of China

Using the Atmospheric Aerosol Optical Thickness (AOT) data from MODIS website, dust weather data from VSAT and daily air pollution index from State Environmental Protection Administration of China, the physical characteristic of aerosol were analyzed. Using the Report of Environmental Quality and rainwater data from 2004 to 2005, the chemical characteristic of aerosol were analyzed. The results indicated that:(1) There are four regional high value centers in the main inland regions of China: south Xinjiang Basin, Qinghai and Gansu, Midwest region of Inner Mongolia, Sichuan Basin, the lower reaches of Yangzi river and Yellow river. The aerosol optical thickness in the northern China is obviously higher than that in the southern China in spring. It has less difference than that in winter. In north of China, AOT changes evidently in the seasons, and it doesn't in south of China. In the area of more dust occurrences, the temporal and spatial distribution features of the dust weather occurred in China has the same step with the changes of AOT, and the atmospheric aerosol optical thickness has the better correlation with the dust weather in the area of more dust occurrences, vice versa. According to the results above, in the northern China, especially in droughty and desert regions, the atmospheric aerosol mainly comes from the sand which is come into being with the dust weather.(2) There are five regional high values in the main inland region of China: north of Xinjiang which center is Wulumuqi, east of the northwest which center is Lanzhou, Huabei region which center is Huhehaote, Sichuan Basin which center is Chongqing, Hunan and Hubei. Pollution index is the highest in winner, secondly is in spring, thirdly is in autumn, lastly is in summer. The distribution of large value has less difference in four seasons. There isn't evident difference in data between the south and the north in spring, summer, and autumn. In winter, the pollution index increases quickly, and the extent in the north is bigger than that in the south, so the pollution index in the north is evidently higher than that in the south.(3) The main contamination is inhalable particulate in most cities of China. Inthe north, especially in the northwest region, corresponding the region of more dust occurrences, AOT is high in spring and it is right the more dust occurrence season, too. There is less dust occurrence in the south, and AOT has no seasonal change. The change of pollution index, AOT and dust weather hasn't the same step in the north. Sichuan basin, Hubei and Hunan, have no dust weather, which are the high centers of pollution index and high AOT, too. It can be thought that the aerosol mainly comes from human activities.(4) Lanzhou and Yinchuan locate in the northwest which has more dust storms, so their pollution index are higher in March and April and the pollution is serious. The two cities belong to north cities, whose quantity of SO2 increases evidently after middle November when the heating is started. Yinchuan is nearer from desert than Lanzhou, but its pollution is less than that of Lanzhou. So it can be seen that human activities, geography environment and climate conditions play the most important roles.(5) In the period of observation, there is less acid rain occurrence, it can be considered that the alkalescent soil in Lanzhou goes into the atmosphere by turbulence through the atmospheric boundary layer. This alkalescent particle neutralize the acid components which makes less acid rain in Lanzhou.(6) The order of the content of anion in the rainwater is SO-*2' > NO3" > CT > F. The SO42" and NO3* are more than 80 percent. They are the main anions in the rainwater. The order of the content of cation in the rainwater is Ca2+ > NH/ > Na+ > Mg2+ > K+, and the role of calcium is important than ammonai's.(7) Through correlation analysis, it can be seen that HCO3" has the better correlation with Ca2+ and Mg2*. It means that HCO3" mainly be counteracted by dust particle, especially by soil particle. Except HCO3*, Ca2+has the better correlation with SO42". It can be thought that the ions mainly come from nature source. SO42" has better correlation with Ca2+ and NH4+, which shows that except for nature source, human is a important factor for component of rainwater ((NH4)2SO4 is mainly comes from human activities).(8) Weather process should be found before the rain. Dust weather may affect the component of rainwater. Wind speed is the another important factor which affect the atmospheric environment.