| In this thesis, we carried out systematic investigation on the spatial and temproal variations of particulate matter concentrationin urban green space through taking the Haidian Park as main research object. The monitoring samples in experiment are arranged at different underlying surface, different functional areas and different direction with the Haidian Park center in the core. The experiment of those monitoring samples, meets the principle of universality, homogeneity and regularity. The spatial and temporal variations of particulate matter concentration in Haidian Park, the variation characteristics of particulate matter concentration in different functional areas and the horizontal gradient distribution rules of particulate matter concentration in different types of shelterbelts in urban park and the purification efficiency of the different types of shelterbelts in urban park are discussed. The main results obtained were as follows:1. The distribution of ambient particulate matter concentration in Haidian Park had significant spatial and temporal variation patterns.(1) The concentration of ambient particulate matter with different diameter in summer was higher than that in other seasons where it was lowest in spring.(2) The lowest concentration of the same ambient particulate matter appeared from13:00 to 15:00 in different seasons, while the highest concentration varied significantly.(3) The spatial variation of the ambient particulate matter concentration with the different diameter were the same.(4) The lowest value of ambient particulate matter concentration was located inside the Haidian Park.2. The variations of ambient particulate matter concentration in different functional areas of Haidian Park:(1) The concentration of TSP、PM10 had the lowest value in different functional areas compared to control area.(2) The trend of ambient particulate matter concentration was the same in different functional areas, the highest and lowest values of ambient particulate matter appeared at different times.(3) The relativelylower values of ambient particulate matter with different diameters in spring in different functional areas in Haidian Park.(4) The highest and lowest values of particulate matters with different diameter appeared most frequently at different functional areas.3. The horizontal gradient distribution of ambient particulate matter concentration in shelterbelts of Haidian Park and related purification efficiency:(1) For shelterbeltⅠ, the highest concentration values of TSP and PM10 were most frequent appeared at 0m; the highest concentration values of PM2.5 and PM1.0 were appeared at 0m during the daytime while they were appeared within the range of 30m~75m at night, for example, lowest value appeared at 210 m. For shelterbelt Ⅱ, the daytime concentration values of TSP and PM10 decreased as the increase of distance while their horizontal distribution showed the “V” shape change in the evening. The highest concentration values of PM2.5 and PM1.0 mainly appeared at the range of 0m~30m and the lowest values appeared at the range of 45m~75m. Moreover, for shelterbelt Ⅲ, the highest concentration values of TSP and PM10 appeared at the range of 15m~30m. The concentration of PM2.5 and PM1.0 had accumulation phenomenon in the range of 30m~45m and the lowest concentration value appeared at 135m~210m.(2) In terms of diurnal variation of purification efficiency of different types of shelterbelts in Haidian Park, the purification efficiency at 11:00am and 13:00 pm was high while it was low at 5:00 am、7:00 am、9:00 am.(3)From 15 m the both the shelterbelt Ⅰ and the shelterbelt Ⅱ had positive purification efficiency on ambient particulate matter with different diameters. The highest value of purification efficiency of the shelterbeltⅠand the shelterbelt Ⅱ appeared respectively at 210 m and 75 m. The protection forest of shelterbelt Ⅲ had negative purification efficiency in certain ranges.4. The spatial and temporal variations of ambient particulate matter concentration in Haidian Park under different weather conditions:(1) The changes of ambient particulate matter concentration was upward trend in four consecutive days after sunny and in four consecutive days after rain. The concentration value of ambient particulate matter with different diameters under the cloudy with overcast weather condition was remarkably higher than that in other weather conditions.(2) The spatial distribution patterns of high value region and low value region for TSP and PM10 concentration and that of PM2.5 and PM1.0 concentration were similar under the same weather condition; however, the spatial distribution patterns were different under different weather conditions.(3) In the same functional area, the value of particulate matter concentration under the cloudy with overcast weather condition was remarkably higher than that in other weather conditions. Under the same weather condition, the concentration in different functional areas was closely related to particles sizes.5. The proportion of fine particulate matter in Haidian Park:(1) The ratios of PM10/TSP、PM2.5/PM10 were significantly higher in summer; Furthermore, the ratio of PM1.0/PM2.5 was significantly higher in winter; in addition, the proportion of fine particulate matter had the lowest value in spring.(2) The proportion of fine particulate matter was higher on cloudy with overcast days and was much lower sunny after rain weather compared with other weather conditions.(3) The pollution in Haidian Park was mainly composed of particles was mainly due to 2.5~10μm diameter. The ratios of PM10/TSP was more than 50% in different season and different weather conditons. |
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