Pollution Characteristics Of Air Particles In Main Urban Area Of Lanzhou City And Its Control Technology Using Dust Suppressant

With the rapid development of modern industry and economy,the air pollution problem is becoming more and more serious,which has become one of the main restricting factors of urban development.Atmospheric particulate matter is one of the main factors of urban air pollution.Atmospheric particulate matter is not only a pollutant itself,but also a carrier of other toxic and harmful pollutants due to its large surface area and strong adsorption,which plays an important environmental indicator role in the energy and material cycle among atmosphere,land surface and water.The research on atmospheric particulates has been widely concerned by scholars at home and abroad.Lanzhou City used to be one of the most polluted cities in China.In recent years,Gansu provincial government and Lanzhou municipal government have actively taken a number of effective measures to control air pollution in Lanzhou,and achieved good results.However,due to the impact of special geographical and climatic conditions and the harsh ecological environment in the desert areas of Northwest China,as well as the unreasonable influence of energy structure and industrial layout in Lanzhou,the situation of air pollution in Lanzhou is still serious,and atmospheric particulate matter is still the focus of air pollution control in Lanzhou City.Therefore,a systematic study on the spatial and temporal distribution characteristics,chemical components,possible sources and potential ecological risks of atmospheric particulates in Lanzhou City could provide theoretical basis and data support for the prevention and control of atmospheric particulate pollution in Lanzhou City.On this basis,the study on series of dust suppressants for air particle pollution control could provide specific technical support for the prevention and control of air pollution in Lanzhou City.The data of atmospheric particulate matters and meteorological factors over the years in Lanzhou City were collected,the spatial and temporal distribution of atmospheric particulate matters over the years,in different seasons,in different months and in one day were studied.The PM₁₀and PM_2.5samples at Lanzhou Institute of Biological Products(BPI),Lanzhou Railway Design Institute(RDI),Staff and Worker's Hospital(SWH),Lanyuan Hotel(LYH),Lanzhou University(LZU)were collected.The composition and content characteristics of five anions(F^-,Cl^-,NO₃^-,SO₃^2-,SO₄^2-),six cations(Li⁺,Na⁺,NH₄⁺,K⁺,Mg²⁺,Ca²⁺)and 10heavy metals(Cu,Cd,Pb,Fe,Mn,Sb,V,Co,As,Hg)in PM_2.5and PM₁₀were analyzed.The pollution level and potential ecological risk of heavy metals were evaluated.Through this study,the composition and content characteristics of PM_2.5and PM₁₀in the ambient air of Lanzhou City were mastered,so as to analyze and summarize the main sources of atmospheric particles in Lanzhou City,and provide scientific basis for the prevention and control of air pollution in Lanzhou City.Secondly,on the basis of the study on the characteristics of atmospheric particulate pollution in Lanzhou City,the specific measures of using series of dust suppressants to control the pollution sources of unorganized atmospheric particles were proposed.The main research results of this paper are as follows:(1)Atmospheric particulate pollution in Lanzhou is more serious in spring and winter,PM_2.5pollution is more serious in winter,and PM₁₀pollution is more serious in spring.The monthly distribution characteristics of PM_2.5and PM₁₀concentration are"U-shaped".The diurnal variation of PM_2.5and PM₁₀concentration is"bimodal".The spatial distribution of PM_2.5concentration was as follows:SWH>LYH=BPI>RDI>LZU;the spatial distribution of PM₁₀concentration was as follows:BPI>LYH>SWH>RDI>LZU.The average concentration ratio of PM_2.5to PM₁₀in Lanzhou City in winter is 0.75,which indicates that the contribution rate of large amount of fuel combustion in central heating to atmospheric particulate matter is high in winter,while it is less than 0.5 in spring,summer and autumn,which indicates that particulate matter mainly comes from construction,transportation,bulk material yard and other dust.(2)Multiple regression analysis was conducted with meteorological factors as independent variables and PM_2.5and PM₁₀concentrations as dependent variables.The results show that the concentrations of PM_2.5and PM₁₀are negatively correlated with wind speed and atmospheric pressure,and positively correlated with atmospheric temperature and humidity.In winter,the static wind rate is high and the inversion phenomenon is serious,which is not conducive to the diffusion of atmospheric particulate pollutants,which is one of the important reasons for the serious air pollution in Lanzhou in winter.To a certain extent,the atmospheric particulate matter in Lanzhou is mainly affected by urban emissions and other internal factors.(3)The water-soluble inorganic ions in atmospheric particulates in Lanzhou are mainly polluted in winter,and the high concentrations are mainly concentrated in Chengguan District and Xigu District.The overall order of water-soluble inorganic anion concentration is SO₄^2->NO₃^->Cl^->SO₃^2->F^-,and the overall trend of water-soluble inorganic cation concentration is Na⁺>Ca²⁺>K⁺>NH₄⁺>Mg²⁺>Li⁺.The water-soluble inorganic ions in atmospheric particulate matter in Lanzhou mainly come from the secondary pollution of fossil fuel and biomass combustion,followed by soil source.Soil source has a greater influence on PM₁₀than PM_2.5.(4)The concentrations of heavy metals in atmospheric particulates in Lanzhou were higher in winter and spring than those in summer and autumn,and there were ecological risks for Pb,Sb and Cd,but no risk for other heavy metals.The order of heavy metal concentrations in PM_2.5in Lanzhou City is Pb>V>Fe>As>Cu>Mn>Hg>Co=Cd>Sb.The order of heavy metal concentration in PM₁₀is Pb>Fe>V>As>Cu>Mn>Cd>Hg>Co>Sb.The heavy metals in PM₁₀mainly come from bare land surface,construction,traffic dust,agricultural and industrial emissions.Heavy metals in PM_2.5mainly come from industrial emissions and dust;heavy metals in PM₁₀mainly come from soil dust,industrial emissions and transportation emissions.(5)A series of dust suppressants are effective methods to solve the pollution of particulate matters from unorganized sources.The composite adhesive dust suppressant is suitable for the storage and transportation of bulk powder such as coal and mineral powder.The wind erosion rate of pulverized coal after spraying dust suppressant is less than 0.2%.The compound water absorbing and moisturizing dust suppressant is suitable for dust suppression of urban pavement road.Within 3 days after spraying the dust suppressant,the concentrations of PM₁₀and PM_2.5near the road surface are reduced by 20%and 13%respectively compared with the control road.The instant conjunctiva dust suppressant simplifies the preparation process of dust suppressant emulsion,and is suitable for various scale construction sites.The wind erosion rate was 0.14%when the wind speed was 20 m/s and the blowing time was 5 min.The compound sand fixing agent is suitable for local desertification land treatment,and does not affect plant growth.