| Urban forest was an important component of urban ecological system, it provides many benefits to human ecological function for improve the urban environment. In recent years, with the deterioration of urban air particulate matter pollution in China, the system research of urban forest ability to reduce air particulate matter, which make great significance in different scales. At the landscape scale, this paper studied air PM2.5 and PM10 mass concentration in Nanchang and the relationship between meteorological factors,and the relationship between the traffic flow, and landscape patterns influence on the quality of PM2.5 and PM10 concentration. At the forest patch scale, we studied the different forest patch to attenuation of PM2.5 and PM10 mass concentration, and make the attenuation as the level, analyses the influence of forest canopy changes and microclimate factors to it.At leaf scales, the eight kinds of representative tree leaf in Nanchang, which were researched for capacity of retention PM2 5, PM10 and TSP. At the micro scale of leaf surface,leaf surfaces were observed to leaf surface microstructure, particle morphology characteristics, and it's distribution of the leaf surface,particulate matter composition and source apportionment. Quantitative research were combination of field observation and indoor control trials, which to explain the urban forest stand scale to trapped particulate matter, and reduce mass concentration, the mechanism of air PM2.5 and PM10 was made an exploration of new methods. This article aims to provide theoretical basis for the selection and configuration of urban forest system in Nanchang, and at improve urban forest configuration by the layout of urban forest ecological function, provide technical support by optimizing the structure of urban forest.(1) At the landscape scale research, we found that pollution situation of particulate has significantly improved from 2013 to 2015 in Nanchang, meteorological factors have significant effects on air particulate matter mass concentration, precipitation, relative humidity,wind speed can reduce PM2.5 and PM10 mass concentration,traffic flow can only significantly increase surrounding PM2.5 mass concentration,but not PM10. PM2 5 and PM10 mass concentration space distribution pattern in the city center is higher than rural, and PM2.5/PM10 ratio changes also follow this rule. Landscape pattern significantly correlated with atmospheric PM2.5 and PM10 mass concentration change, building land coverage and urban forest patches coverage correlation with PM2.5 and PM10 mass concentration, the most significant negative correlation, the correlation between showed typical landscape of source sink relationship in ecology, showing a classical sink-source landscape in ecology.(2) At the forest patch scale, we experiment to PMAC with forest patch of four seasons in 2015, found that the urban forest patches has ability to significantly reduced PM2.5 and PM10 mass concentration, forest patch can reduce PM2.5 and PM10 mass concentration to 6.00% and 6.39% all the year, respectively. The highest PM2.5AC and PM10AC is 7.35% and 8.42% in spring, the lowest PM2.5AC and PM10AC is 3.76% and 4.42% in winter. Coniferous forest reduction rate is the highest, PM2.5AC is 9.36% and PM10AC 10.51%, broad-leaved mixed forest reduction rate is the lowest, PM2.5AC is 3.96% and PM10AC 4.75%. The PMAC with urban forest patches has significantly negative correlation with humidity increase rate and negative ions increase rate, and positive correlation with LAI, negative correlation with DIFN. Total leaf area of forest patches is the most important factors to improve it s block ability for air PM2.5 and PM10.(3) At the tree leaf scale, we experiment to leaf retention ability of PM2 5, PM10 and TSP particles with eight tree leaves of four seasons in 2015, and found that different trees leaves retention PM2 5, PM10 and TSP particles have significant difference. As a whole,there was the law that retention ability showed evergreen conifer > evergreen broad leaved tree > deciduous trees, the retention capacity of pinus massoniana is the hightest and liquidambar weakest in all the trees. The retention ability of the tree leaves is also a significant seasonal difference, which spring is largest, then summer, fall, and winter is smallest.(4) At the leaf surface micro-scale, based on the SEM-EDX technology, as the research object, eight representative trees of South cities have been analyzed the form and shape on the leaf surface,typical particulate matters composition,size and shape on the leaf surface, and analyzed the possible source of particulate matter. Trees leaf surface retention particulate matter many to few with leaf structure is in turn: deep grooves/sunken > stoma/cell > trichome/vein > smooth leaf surface, retention on the leaf surface is mainly PM10 particles. Tree leaves trapped particulate matters mainly comes from natural sources, which composition of silicon, aluminum, calcium, potassium,magnesium. A few derived from anthropogenic sources,by fossil fuel combustion emission sulfur element and particle, retention particulate matter of leaves reflect the surrounding environment of particulate matter of air pollution sources. |
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