The Main Tree Species In Typical Areas Of Beijing Regulate The Air Quality And Ecological Function

This study mainly takes the typical tree species in four different areas of Beijing Changping Binhe Forest Park,Olympic Forest Park,Beijing University of Agricultural,Tongzhou Grand Canal Forest Park as the research object,and collects the leaves of different tree species every month in 2017.We detected the adsorption capacity of leaf area per unit to the particles of different sizes,and scanned the leaves by electron microscopy and atomic microscopy,and the surface micro-structure of the different leaves and the three-dimensional shape of the leaf surface were observed to explore the mechanism of particle adsorption on the leaves of different tree species.In July and August of 2018,under different rainfall conditions,the typical tree species leaves were collected before and after rainfall to measure the adsorption capacity to different particle sizes,while collecting rainwater,measured the content of particulate matter and water-soluble ions in rainwater,and explored the effect of rainfall on improving air quality of different tree species.In winter,we collected atmospheric particulate matter inside and outside the typical forest and used the atmospheric sampler to measure the weight of particles under unit volume and the content of water soluble ions in particles with different sizes.Through the above research,the following main conclusions were obtained:There are significant differences in the adsorption of atmospheric particulate matter in the leaf area of different tree species in time and space.On the whole,the amount of particulate matter adsorbed by leaves of different tree species in September and October is relatively large while the amount is the smallest in July.In different months,the adsorption amount of the particles with particle size of>10?m is much larger than that of the particles with particle size of 3-10?m and 0.2-3?m.There are significant differences in the content of adsorbed atmospheric particulate matter in the four areas of Changping Binhe Forest Park,Olympic Forest Park,Beijing University of Agricultural and Tongzhou Grand Canal Forest Park.The adsorption capacity of>10?m particle size in Tongzhou area and Changping area,Olympics There are significant differences in the adsorption capacities of the three areas of Forest Park and Beijing University of Agricultural.The adsorption capacity of 3-10?m particle size is not significantly different between Changping Forest Park and Tongzhou Grand Canal Forest Park,but it was significantly different from the adsorption amount of Olympic Forest Park and Beijing University of Agricultural.The adsorption amount of the 0.2-3?m particle size was not significantly different in the four regions.The differences in the adsorption of different particle size particles on the surface of plant leaves are mainly related to the microscopic morphology of the leaf surface.If there are a large number of pores with large opening degree,more fluff,deep gullies,more folds,rough The leaves of the tree species with large degree and obvious protrusions are easy to adsorb atmospheric particles,while the surface of the leaves is relatively smooth,and no obvious protrusions and depressions are harmful to the adsorption of particulate matter.The rainfall has a significant effect on the retention of leaf surface particles in the three species of Sophora japonica,Ginkgo biloba and Juniperus chinensis.The rainfall of different conditions has a greater scouring effect on the grain retention of>10?m particle size.The Sophora japonica of particulate matter of>10?m particle size is 5-7?g/cm² before and after rainfall.while the Ginkgo biloba of particulate matter before and after the rain was small,but the difference in the Juniperus chinensis of particulate matter per unit leaf area of the leaves before and after rainfall was the largest,and the leaching of the retention of particulate matter>10?m.The amount reaches 10-20?g/cm²,and under the Array rainfall,the flushing ratio of the large-sized particles reaches 80%.Rainfall has little effect on the retention of leaf waxy layer particles in three species of Sophora japonica,Ginkgo biloba and Juniperus chinensis.The difference of the retention of the waxy layer in the waxy layer between the Sophora japonica and the Ginkgo biloba was 4.5?g/cm².The difference of the retention of the leaf area in the leaf wax layer of the Juniperus chinensis was the largest before and after the rainfall,and the leaching of the retention of the particle size of>10?m.The amount reaches 10-20?g/cm ².Under different weather conditions,there are significant differences in the content of atmospheric particulates in the unit volume inside and outside the typical forest,and the contents of TSP,PM₁₀ and PM_2.5 have large differences.From December 30,2018 to January 3,2019,the content of atmospheric particulates in the inner and outer parts of the forest has little difference in unit volume,but the content of three kinds of particulate matter in the same place has a large difference.The variation of the three particle size particles in the unit volume content is consistent,all of which are TSP>PM₁₀>PM_2.5,and there are significant differences among the three particle sizes.And the anions in different particle sizes are mainly SO₄^2-,and the correlation between SO₄^2-concentration and small particle size is better.In general,the adsorption of atmospheric particulate matter by leaves of different tree species is obvious in spring and autumn,and the adsorption of particulate matter by evergreen coniferous species is much larger than that of broad-leaved forest.The adsorption capacity of trees is greater than that of shrubs,and the leaves are to some extent.It can reduce the amount of water-soluble ions in the atmosphere and can improve the air quality.In the future,when using plants to improve air quality,rational use of different tree species adsorption particles in time and space differences in planting will maximize the ecological effects of different landscapes.