An Integrated Observation Study On Spatial And Temporal Distribution Characteristics Of PM₁₀ In Urban Blocks Of Beijing

A study on spatial and temporal distribution and variety characteristics of PM₁0 mass concentration is carried out in this paper, which is from motor vehicle emissions in main streets and circular roads of urban district and suburb in Beijing, based on three field experiments and variational processing method by satellite MODIS AOD high resolution retrieval data.In order to get better understanding of spatial distribution characteristics of PM₁0 and discuss the effect of vehicle emissions in blocks of urban district and suburb, a point-to-face integrated research technique is developed. I.e. combination fixed point with ambulatory observation experiments and variational processing by MODIS AOD high resolution retrieval data and PM₁0 observation data on the ground.By means of this technique, some investigations are made in this study, which include spatial and temporal distribution characteristics of PM₁0 concentration from vehicle emissions and effect of vehicle emissions. It is also discussed that impacts of atmospheric dynamical and thermodynamic structure in the boundary layer , urban building communities distribution, urban heat island and mesoscale convergence and divergence secondary circulation forced by urban heat island. Results show that this technique is effective.Results of circular road experiment reveal that PM₁0 mass concentration in interior of the third circular road , north and east of urban district and suburb is lower, whereas that in exterior of the third circular road , south and west, and in the vicinity of highway and national road entrance is higher. Introducing MODIS AOD high resolution retrieval data, corrected by variational method, into the actual observation PM₁0 field on the ground can reflect the spatial distribution characteristics of PM₁0 to a certain extent, especially in exurb. Except middle and eastern part of the third southern circular road, PM₁0 mass concentration is lower in the most part of interior of the third circular road, especially in archaic building communities and landscape area for instance The Summer Palace and The Burning Of Imperial Palace and so on. Area of higher PM₁0 concentration are distributing along circular roads in exterior of the third circular road and suburb. And pollution of PM₁0 are more serious in southwest, southeast and northeast of suburb. PM₁0 concentration in the vicinity of highway and national road entrance is higher, and area of higher PM₁0 concentration in south highway and national road entrance is more than thatin north. Area of higher PM₁0 concentration corresponds to that of higher vehicle flux. This fact shows that influence of vehicle flux on PM₁0 concentration is serious. In the exurb, northeast of Fangshan district, northeast of Chaoyang district and part of Shunyi district, northwest of Haidian district and part of Changping district and north of Daxing district are badly polluted , Whereas northeast of Mentougou district and east of Fangshan district are lightly contaminated. The range and intensity of above contaminated area are steady relatively.The related results indicate that spatial distribution characteristics of urban heat island is correlative with urban buildings acreage and the density of urban middle and high layer building communities. Spatial distribution characteristics of urban regional scale heat island is asymmetric and polycentric, namely it is notable that the effect of urban heat island in dense area of urban middle and high layer building communities, especially in Haidian, Xicheng and Chaoyang districts. Whereas it is weak that intensity of urban heat island in landscape area in northwest of urban district for example The Summer Palace and The Burning Of Imperial Palace and middle axis in archaic urban district. Above research results can provide scientific bases for city development such as urban building communities layout and city planning.Effect of urban heat island can produce local secondary circulation and form regional convergence and divergence structure. Strong heat island is consisten...