Sand-Dust Activity Over Beijing-Tianjin-Hebei Region And Its Impact On Urban Atmospheric Environment

The Beijing-Tianjin-Hebei region(BTH) has been suffering hazards of sand storms for a long time. With the sharp increase of atmospheric particulate and dustfall caused by frequent sand-dust weather in winters and springs, atmosphere visibility will be degrading. The transportation safety and normal production and lives of people are severely threatened. Currently, only few investigation has been conducting on overall characteristics of sand-dust in BTH and little is known about the impact of the sand-dust on the environment of this region. Under the background of coordinative development of BTH, the sand-dust activity in spring and its impact on urban atmospheric environment in BTH were investigated with the combined measures including field observation, data statistics and model analysis. The obtained results are described as follows:1.Sand-dust routines in the geological history. 220 ka B.P., there was a strong hydro-dynamism and a relatively weak wind power in BTH. The frequency of the sand-dust weather was low and it was really weak. 220 to 160 ka B.P., the wind power dominated this area. Sand-dust activity was active and the sand-dust weather was relatively frequent. 160 to 80 ka B.P., the hydro-dynamism gradually became stronger while the wind power was getting weaker, volatile decrease of the frequency of the sand-dust activity was observed.2.Characteristics of modern sand-dust activity. The blowing sand dominates the sand-dust weather in BTH, then comes the floating dust and the sand storms the last.In spatial distribution the sand-dust activity gradually reduces eastwards. According to the region difference of the sand-dust weather, BTH may be generally divided into 4type regions of sand-dust activity. The sand-dust weather in the duration of 1980 to2012 was in a declining trend. Spring is the special season of sand-dust weather.3.Influence from kinds of elements on sand-dust activity. The wind speed factor is positively correlated with the inter-annual and annual variance of frequency of sand-dust weather. The humidity factor has only a certain annual relevance with it.The main reasons of annual variance of sand-dust weather in BTH are the circular changes of global climate and the annual fluctuation of atmospheric circulation factors. Due to the rich dust source on the ground of this area, the northwest and south central part of BTH become the high-incidence area of the dust weather. Apart from the influence of the dust moving eastwards and southwards from the up wind, the rich local dust source also has a close relation with the frequent dust activities in Beijing.In despite of strong wind in the east coastal area, the sand-dust weather seldom appears here because of shortage of sand matter on the ground.4.Relation between sand-dust and urban atmospheric pollution. The sand-dust activity of BTH has certain inter-annual and annual relevance and space coincidence with the atmospheric pollution. Sand-dust has much more impact on the atmospheric environment to those city located close to the northwest dust source, such as Beijig and Tianjin, than those city located far away from the the northwest dust source, such as Shijiazhuang. Almost all of its activities always pollute the atmosphere of this region. In recent years, the atmospheric pollution in BTH caused by sand-dust activities has a negative trend and accounts for a small part in the total atmospheric pollution in this region. However, it still makes up a high percentage in the total atmospheric pollution in springs. Therefore, the control targeting on bare sand source in spring is a significant measure for improvement of spring atmospheric environment.5.Contributions of sand-dust to urban atmospheric dustfall in spring. More than97% of urban atmospheric dustfall in spring comes from soil wind dust, dust from burning or smelting, vehicle exhaust and road dust, cement dust and coal ash. Soil wind dust of Shijiazhuang City, accounted for 34.23 % of the total dustfall of this city in spring in 2014, is the most dominant part compared with other dustfall in spring.Also it is a major source of atmospheric dust fall of Beijing City in spring,respectively accounting for 20.88 % and 30.07 % of the total dustfall in the urban area and suburban area. In all dustfall sources, its amount ranks for the third in the urban area and the first in the suburban area. There is a close relevance between the days of sand-dust occurring and the dustfall amount in terms of inter-annual changes. With agreat contribution to the atmospheric dustfall of BTH in spring and a significant influence on urban atmospheric environment, the sand-dust transported with a long or short distance can seriously pollute the atmospheric particulates in spring.6.Suggestions for sand-dust pollution control. First, the sand source control project of Beijing-Tianjin should be implemented further. Main measures include conservation tillage, returning farmland to soil’s original ecology instead of returning farmland to forest or grassland, enhancement of grazing exclosure and paying more subsidies to farmers. Second, local sand-dust sources control should be strengthened.Such as comprehensive administration to the dry-river around the city, reduction of bare farmland in spring and restoration of mining wasteland and strict control of fugitive dust from urban construction.