| Monitoring and characterization of atmospheric particulate matter(PM)has been an important area of research because of the far-reaching impact of PM on health,visibility,material damage and groundwater pollution.The long-term monitoring of coarse particulate matter was initiated at two motorways in Cologne(Germany)to validate projections of increased emissions of non-exhaust particulate matter in Europe.Beijing is another important research area for particle properties and variation trend.Using passive sampling technique,with the subsequent analysis of single particle characteristics,this thesis focus on particle mass concentration,size distribution,chemical composition,meteorological influence and source apportionment.Meanwhile,the calculation method of the converting between geometric diameter(dg)under the microscope and aerodynamic diameter(da)obtained by active sampling is given by case analysis.This provides the possibility for air pollution spatial distribution model to input the diameter parameter which presents the advantages of passive sampling.The results shows:(1)Motorway A 555 is surrounded by farm fields where the terrain is exposed to a free,largely undisturbed air flow while A 4 has disturbed and blocked air flow with traffic "stop and go" mode.The average coarse particle concentration of A 4 was 33% higher than that of A 555,and had a larger particle size than A 555.It can be seen that there are more particle load immission on "street canyon" motorway A 4 by different road environment and traffic condition.The speed of the traffic is closely related to the diameter and number of particles,and the average diameter of the particles decreases with the increase of the driving speed.The particles on both motorways contain the tire,brake,road wear particles and mineral dust.Tire wear is characterized by typical cylindrical,roundish or kidney shaped outline and the size range dominant in 10-40 ?m.Element Zn is the most important indicator.Brake wear particles have larger size range from nanometer to micrometer.The main trace elements are Cu,Fe,Cr and so on.Other natural mineral dusts like quartz,feldspar,clay mineral are considered from field or re-suspended from road surface.Precipitation and the temperature are the main factors for the particle concentration variation,while the maximum wind speed is not dominant bacause German climate combined with maritime moist air masses lead to a low-pressure system.So the wind speed influence can be ignored in wet weather periods.(2)The size distribution of total particulate matter at Beijing CUGB sampling site is dominated by 5-10 ?m size interval.In four seasons during eight-year measurement of CUGB coarse particles,spring has the highest mass concentration,followed by winter,autumn and summer.Back trajectory plot shows high mass concentration of particulate matter in spring comes from Russia,southern part of Mongolia Gobi area,eastern part of Kazakhstan desert area,and the western region of China's large area of the Gobi Desert,a wide range of arid and semi-arid Area in Inner Mongolia.The concentration of 2.5-80 ?m particles in the spring from 2005 to 2013 was positively correlated with the maximum wind speed and the average wind speed.On the contrary,it is negatively correlated with the average relative humidity,precipitation and average air pressure.Particle composition in Beijing is more complex compared to Germany,traffic wear particles containing Cr,Ni,Cu,Fe and other heavy metals,and the mineral particles are more vulcanized,revealing anthropogenic pollutions and a more diverse sources in Beijing.(3)In order to provide an aerodynamic diameter parameter to an existing particle spatial distribution model,the volume equivalent diameter obtained by passive sampling is needed to converted to aerodynamic equivalent diameter.In this thesis,according to the projected area under microscopy,geometric diameter,particle shape factor and particle density,a method of calculating the aerodynamic diameter of different types of particulate matter was summarized.Due to the reason that the shape factor(?)of most coarse particles is greater than 1 g/cm3,then the particle diameter is largely determined by the density of the particles.When the density is larger than 1 g/cm3,the aerodynamic diameter will be larger than the geometric diameter(da> dg),otherwise da <dg.Therefore,using of passive sampling to study the characteristics of particulate matter in the future can be reduced to about 1 ?m size range for analysis.That will be possible to compare with the active sampling. |
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