| In recent years,haze has become an important part of global environmental pollution.Whether in a developed country or a developing country,haze pollution has posed a serious threat to transportation,human health,and economic development.Therefore,to achieve the scientific treatment of haze pollution has become one of the cutting edge scientific issues of common concern in chemistry,physics,atmosphere,mechanics and other disciplines.Many studies available have shown that haze aerosols are the main components which cause serious haze pollution.Similar to the particulate matter in dusty weather,haze aerosols can carry different charges and thereby generate a haze electric field in atmosphere just like sand electric fields.In this sence,to make the charge properties of haze aerosols clear can not only enable people to have a deeper understanding of the formation and evolution of haze,but also have important scientific significance for revealing the influence of charged haze aerosols on the propagation of electromagnetic waves(EMW)and seeking scientific and effective treatment methods for haze pollution.Studies on the charge properties of haze aerosols are mostly carried out in field.However,the complexity of field experimental conditions and the uncontrollability of environmental variables have severely restricted human to understand the nature and impact of haze aerosols.To this end,with the aerosol charge property monitoring system which self-developed by Lanzhou University,we conducted a series of quantitative laboratory experiments and long-time field observations,some general laws of charged nature on haze aerosols have been explored.Based on the analysis of a large amount of experimental data,we established a controllable laboratory experimental system and a macroscopic theoretical prediction model to study the energy attenuation of electromagnetic waves when they propagating in charged haze aerosols.The calculation results of the model are in good agreement with the experimental results.Finally,a movement model which quantitatively describes charged haze particles under the action of electric field force was proposed to discuss the feasibility of electrostatic haze removal scheme,and some significant results are given.1.In chapter two,we developed a quantitative measurement system to determine charge property of haze aerosol and conducted relevant laboratory experiments by control the condition variables.The results show that the charge polarity of primarily emitted haze aerosol is determined by the type of fuels and the charge quantity of haze aerosol is related to the flaming degree,the intenser the fuel combust,the larger charges the haze aerosol carries.In addition,approximately 60 % of airborne haze particles are charged,with positively charged,negatively charged and neutral particles coexisting.2.In chapter three,we find that the space charge density(SCD)and vertical electric field(Ez)increase exponentially with the increase of relative humidity(RH)when RH > 60%,which is two to three orders of magnitude larger than that the case of RH ≤ 60%.On this basis,a new classification standard for dust-haze and fog-haze events is proposed,i.e.,RH > 60% for fog-haze and RH ≤ 60 % for dust-haze.In dust-haze events,the SCD of atmosphere is dominated by the primarily emitted aerosol,so the polarity of SCD in dust-haze events can be used to identify the main pollution sources.During fog-haze events,the charged aerosol in atmosphere can form a space electric field and in turn inhibit the vertical transport of charged fog-haze aerosol,which may lead to the aggravation of pollution.3.In chapter four,we established a controllable laboratory experimental system to measure the attenuation coefficient of EMW when they propagating in charged haze aerosols.The system can quantitatively control the key variables such as concentration,charge and humidity.We found some new laws such as the attenuation coefficient of EMW is proportional to aerosol concentration,and increases linearly with the increase of aerosol moisture content and electric charge.In addition,we theoretically analyzed the laws above from two aspects.Firstly,we gave a general form of EMW attenuation coefficients which characterized by concentration,humidity and conductance factors according to the dimensional theory and experimental results.Then,based on the electromagnetic wave theory and the energy conservation law,we proposed a new method to determine the complex permittivity of haze aerosols.On this basis,by introducing a scale conversion coefficient and combining the electrical conductivity of a single particle on the microscopic level as well as the equivalent charge-to-mass ratio(ECTM)of charged haze aerosol on the macroscopic level,we proposed a prediction model to calculate the attenuation coefficient of EMW when they propagating in charged haze aerosol.The calculated results are in good agreement with the experimental results.By using this prediction model,we take 5G network deployment as an application background to discuss the seamless coverage of the network.When the moisture content of the haze aerosol is greater than 80%,the moisture and charge carried by the haze aerosol can reduce the coverage of the 3 cm wavelength electromagnetic wave signal by 80 % or the above.4.In chapter five,we proposed a numerical model to describe the movement of charged haze particles under the action of electric field force.The simulation results indicated that to apply an electric field in air can form a purified airspace near the surface,which implies that the electrostatic haze removal scheme is feasible in theory.Additionally,we found that the electrostatic haze eliminator designed and manufactured based on the principle of electrostatic adsorption have the disadvantages of incomplete adsorption and corona electrode contamination in haze event.In light of this,it is recommended to add a pre-adsorption zone before the corona electrode to make electrostatic haze eliminator work efficiently for a long time in haze days. |
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