| The pollution which caused by particulate matter especially the particulate matter smaller than 2.5 micrometers (PM2.5) does harm to our normal life and health seriously.lt becomes vital in most cities when it comes to environmental pollution. Taking the woodland of Beijing as the research background,the article includes comprehensive analysis of information collected from January 2013 to December 2014.Besides,Ⅰ select the Olympic Forest Park and the Beijing Forestry University as two monitoring points,and take method of Dustmate environment dust monitor and TH-150C intelligent flow total suspended particles sampler to detect concentration and sample. Moreover, Ⅰrecord the metecorological factors by the use of handheld Kestre14500 meteorological instrument, including temperature,relative humidity, wind speed, etc. By using the single-factor analysis and partial correlation analysis, the study consists of several parts such as the correlation of meteorological factors with PM2.5, the influence caused by woodland to EC and OC which are both ingredients of PM2.5 and how the concentration of PM2.5 varies along with the seasonal variation. The main conclusions of this article are as follows:(1)The concentration of PM2.5 decreases obviously when it rains.The heavier the rain falles,the more clearly the influence will be. However,the rain reduces the level temporarily which can’t change its changing regulations and the annual average concentration. Within a certain range, the concentration decreases with the wind speed and temperature increasing and increases obviously with relative humidity and atmospheric pressure increasing. The visibility and the concentration present exponential relationship. Under the influence of area pollution, the concentration will be influenced by wind direction and meteorological factors and their combination. Because of the influence of forest structure and composition,we can conclude that pinus tabuliformis are better than poplar trees when it comes to the ability to avoid adsorpting PM2.5 from the analysis of typical day concentration.(2)The organic carbon and the elemental carbon are the important parts of PM2.5 and the proportion of them will be different as a result of different polluteon sources.Both are positively related to the concentration of PM2.5 and the correlation between them is also different as a result of different polluteon sources. It is found that sampling points are contaminated by vehicle emissions and dust from the ground. We can find that the forest to avoid adsorpting EC is better than OC from the study on the changes of EC and OC concentrations in different positions of the same forest land. Different structures and compositions of forests play an important role in the composition of particulate matter.Besides, it is mixed forest have a better effect than pine forest,and effect of poplar forest is the least.(3)The efficiency to weaken PM2.5 will differ because of different seasons although growing in the same piece of land and deciduous species have larger changes than evergreen species in efficiency. The ability to avoid adsorpting PM2.5 will be different as a result of different seasons.It is found that the efficiency to avoid adsorpting PM2.5 can be ranked as follows:halosols deserts mixed forest> pine forest> poplar forest> grass irrigation mixed forest> arbor grass mixed forest> the grassland.In addition, the best width to weaken PM2.5 will differ because of different structures and composition types of forests. |
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