| Frequent haze weather has become the most serious social public event in China at present,and haze is caused by a large number of fine dry dust particles floating evenly in the air,making the general visibility of air with horizontal visibility less than ten kilometers.Urban haze phenomenon is closely related to urban microclimate.Changes in thermal environment and wind environment are the main differences of urban microclimate.Both of them directly affect the distribution of suspended particulate matter in urban space.The micro wind speed near the ground is the driving force of haze.Factors,near-surface inversion structure is the thermal factor for the formation of haze,and the city's underlying surface is precisely the main factor in the change of urban micro-climate.The city's underlying surface is the total amount of land that can be used within the city.It mainly consists of forest land,grassland,farmland,waters,bare land,and hardened ground.The rapid development of urbanization in China results in changes in the type of urban underlying surface,which in turn affects the health of the urban environment.With microclimate.The spatial structure of the city and the atmosphere itself have special interaction and influence.Urban planning plays an important role in the development of urban spatial structure.At the same time,it also has the obligation to work hard to improve the atmospheric environment of the city.The city's underlying surface is a rigid process by changing the city's microclimate and thus affecting the city's atmospheric environment.Urban planning is an elastic process by configuring urban land resources to create a healthy living environment,and the urban underlying surface and urban land resources are closely related.The influence of air pollution from city underlays is of great significance for rational allocation of urban land resources.According to the research data of pollutants in large cities and mega cities in China,PM2.5 particles are the “starters” that cause haze.The root cause of PM2.5 particle diffusion in urban areas is the urban microclimate.The formation of urban microclimate is caused by different types of urban underlying surfaces.Based on this,the paper studies the relationship between the urban underlay surface and the vertical distribution of PM2.5,finds out that urban smog can be mitigated by regulating the urban spatial composition model and optimizing the urban microclimate,and provides a theory for the planning and construction of ecological city.Based on and design measures.The study revealed that:(1)The distribution of PM2.5 concentration in Xi'an was highest in winter,followed by spring,lower in autumn than in spring,and lowest in summer;(2)the highest concentration of PM2.5 in Xi'an was about 250 m away from the ground;(3)The real-time data of the Guangyuntan monitoring station in Xi'an is compared with the real-time data of the Side PakTM AM520 monitoring instrument,and the coefficient between the two is about 0.68;(3)The PM2.5 concentration in Xi'an is between 8 o'clock and 17 o'clock.The time change law was as follows: increase first and then decrease,the PM2.5 concentration at 8 o'clock was not consistent at different heights,and the highest concentration was at 11 o'clock.PM2.5 concentrations at 14 o'clock and 17 o'clock were relatively stable at different altitudes,and PM2 at 17 o'clock.5 The lowest concentration;(4)The influence of the lower surface of the urban water system on the concentration of PM2.5 varies between 40 m and 70 m.The impact of the park's green mat on the concentration of PM2.5 is less than 40 m.Hard paving The change in concentration of PM2.5 with the ground mats affects the height of about 70 m or more.And from the perspective of urban planning put forward relevant recommendations,such as improving the layout of the group,the construction of urban ventilation corridors,scientific planning of the architectural pattern,and improving the city's underlying surface. |
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