| Particulate matter (PM), especially, PM2.5causes harm directly to the health of people. How to use urban tree species or urban forest systems to control and prevent from atmospheric PM. On one hand, controlling the source emitting PM in order to minimize air pollution caused by PM is necessary. On the other hand, reasonable and highly effective methods for reduce available "in-the-air" PM accumulation must be defined. In order to optimise the effectiveness of particulate matter by reducing urban tree planting design, five commonly cultivated kinds of urban forest types were studied in Olympic park of Beijing city in2013year. Weighing method was used to collect PM2.5for PM2.5concentration and chemical composition analysis. TSP, PM10, PM2.5and PM1were measured by Air Dust-mate monitor. Chemical compositions of analyzed individual particles included carbonaceous and water-soluble inorganic ions. Particles on leaf surface and in-wax were used in water wash-off and chloroform wash-off methods.Results show that the urban forest systems are capable of storing and capturing dust from the air. The types of Shrub and Broadleaf tree have the ability to control particulate matter in the air most effectively at the stage when leaves are fully developed. During the leafless season, evergreen systems (for example coniferous types) and mixed tree systems (broad leaves and coniferous) are likely to be the most effective for preventing high aerosol PM2.5concentrations and have significant differences from other forest systems.The ability of year-PM concentration, absorption between no-tree system and with-tree systems shows Broadleaf treetype is highest (66.15%for TSP;35.32%for PM10), Conifertypeuptake is highest PM2.5(19.71%) and PM1(20.88%) compared to Control (no-tree). Grassland is mostly lower Control. And the ability of PM2.5concentration at four leaves growth stages shows high uptake for Conifer type up to:66.6%, followed closely by the Shrub and the Mixed tree type; with the Grassland lowest at33.6%. The concentration of PM2.5absorption between the models of urban forest at four leaves growth stages show Conifer are higher than the Control, and there is a significant difference with the remainder models.The PM concentrations suspend efficency of six urban forest types in year variation in descending order is Broadleaf tree> Mixed tree> Shrub> Conifer> Control> Grassland (with TSP); Broadleaf tree> Conifer> Shrub> Mixed tree> Control> Grassland (with PM10) and Conifer> Mixed tree> Broadleaf tree> Shrub> Control> Grassland (PM2.5and PM1). And the PM2.5capture efficency of six urban forest types at four growth stages of leaves is Conifer>Broadleaf tree>Shrub>Mixed tree> Grassland and Control.The year variation of the aerosol PM concentrations shows that PM concentrationsare highest in late spring, autumn and winter, and low in summer. The average for all urban forest types at the four stages of leaf growth and the different times of year studied, TSP, PM10, PM2.5and PM1capture in the morning and night air are high and low in the afternoon and evening.The experiment of this research does not show correlation of VOC, Cations, Anions and PM2.5concentration in the air clearly. Correlation analysis between VOC, OC, EC and PM2.5-mass showed:weak correlation between VOC and EC with increasing PM2.5-mass (R2=0.4364and R2=0.4422), and no significant correlation between OC, TC, NH4+, NO3-and PM2.5mass (R2=0.0646). There are correlation between the concentration of PM2.5and SO42-(R2=0.3181)/and Cl-(R2=0.3512), but no strong regression.Needle leaves and hairy-waxy leaves show their ability to deposit and capture PM content on the surface as well as in waxed layer. This project only focuses on the variation of PMs content at different seasons of a year. Necessary to replicate the experiment in subsequent studies or in further studies to be able to prove the result.Coniferous trees at different seasons show that PM content is highest in winter. Due to its long deposition process from previous months of the year, especially after rainy season. Small and rough needle leaves showan ability to capture large and coarst particles, but for fine particles, long and smooth needle leaves are more effective.Mixed tree urban forest type shows its effectiveness in capture PM concentration in comparison to monoculture forest type.The concentration of PM in air showed high correlation with humidity. In the morning, night or high humidity day, the aerosol PM concentration increases and varies in the same direction relative to humidity fluctuations.With haze pollution afterwards, the accumulation of TSP and PM10showed in Mixed tree and Shrub showed10is higher than in other models. But with PM2.5and PM1, Conifer showed the highest, followed by Broadleaf and Shrub systems. In Grassland and Control with favorable conditions, concentration of TSP, and PM10showed lower than remain forest types. |
PDF Full Text Request