Study On The Real-time Evolution And Mixing State Of Aerosols Emitted From Residential Fuels Combustion

Domestic coal and biomass consumption amounts in China are considerable.Particulate matter?PM?emitted from residential coal and household biomass burning is a critical source of air pollution.It is also a factor which can threaten regional climate and human health.Researches on the physical and chemical characteristics of PM mostly focused on the mass concentration,while researches on the particle number concentration,which are key for assessing the health impacts,are relatively less.The types of solid fuels selected in former experiments are limited,and there is still a shortage of database for establishing the number concentration spectrum of residential solid fuels combustion emissions.Meanwhile,the studies on the particle number concentration are mostly concentrated in megacities or background stations,and there is a lack of researches on combustion source emission regions,such as rural or suburban sites.Therefore,indoor combustion simulation experiments and field atmospheric observation experiments were both conducted to explore the physical and chemical characteristics of particles emitted from solid fuels burning and to assess its impacts on atmospheric environment in typical regions and periods.In this study,by adopting SMPS,SPAMS and dilution system,size distribution,number concentration and chemical composition of solid fuels burning emissions were analyzed under different dilution ratios.Through aerosol number spectrum analysis,ART-2a,tracer ion classification and vector dot products,the particle number concentration,size distribution,chemical compositions and mixing state were obtained.With SMPS+E,the impacts of solid fuels burning emissions on atmospheric environment in typical regions and periods were deliberated by trajectory clustering analysis,potential source contribution function and concentration-weighted trajectory analysis.The main conclusions of this thesis are listed as follows.There are four burning stages for residential coal flaming burning.In the initial burning stage,the combustion temperature is low,total particle number concentration and particle size exhibited increasing trend.During the violent burning stage,it is characterized by high temperature and low total number concentration.For the stable burning stage,the temperature and total number concentration dropped,while particle size distribution shifts towards smaller size.The last one is the ember combustion stage and is similar to the former stage.The peak size is located in nucleation mode,but the temperature is lower and total number concentration is smaller,when compared with those for the stable burning stage.During the smoldering stage of honeycomb briquettes burning,there is no clear division of burning stages.The time evolution of domestic biomass burning resembles the residential coal combustion emissions,however,the duration of each stage is shorter.During the flaming stage of residential coal burning,the total particle number concentration shows a bimodal distribution.The first peak size is for 14.6²00 nm with the number concentration of 10⁹ cm^-3.The other peak value is 10³ cm^-3,and the peak size is for 0.8¹.4?m and 0.4¹.2?m for honeycomb briquettes and lump coal burning,respectively.For smoldering,the particle size distribution measured by SMPS holds a decreasing single-peak distribution,which is mainly concentrated in the nucleation mode with the concentration of 10⁹ cm^-3.By SPAMS,there is a unimodal distribution ranging from 0.7 to 1.2?m,and the concentration is 10³ cm^-3.Due to the variable origins,the concentration is 10⁸¹0⁹ cm^-3 for coal flaming,as the size was a unimodal distribution by SMPS.For honeycomb briquettes burning,dilution ratio as 100?DR100?was the best.For lump coal burning,there are two optical DRs,DR100?<57.3 nm?and DR60?>57.3nm?.For household biomass burning,the particle size distribution exhibits a single peak by SPAMS,while the particle number concentration ranges from 10⁴ to 10⁵ cm^-3.By SMPS,emissions from applewood,corn straw,pear wood and reed show the unimodal size distribution,with the number concentration of 10⁶¹0⁸ cm^-3.However,particles emitted from bamboo,cypress and pine show biomodal size distribution,peaking at40.0⁶1.5 nm and 140.7²50.3 nm,with the number concentration as 10⁶ cm^-3.Among the multiple DRs,DR20 is the best.There are mainly five particle classes from residential coal burning,including K-Rich particles,Metal particles,Carbonaceous particles,Na-K particles and Others.Honeycomb briquettes combustion emissions were dominated by K and M single particles.For lump coal burning,Carbonaceous single particles were the most abundant,followed by NaK particles.With variable DRs,the metal peak signal of honeycomb briquettes is stronger than that of lump coal.However,as for carbon peak signal,the trend is opposite.There are mainly four particle classes from household biomass burning,including K-Rich particles,Carbonaceous particles,Na-K particles and Others.For different biomass types burning,the Sulphur content was greatly different.The sulfate single particles emitted from apple wood,corn straw,pine and reed burning are higher than those from bamboo,cypress and pear wood burning.Under different particle sizes,the distributions of chemical compositions of particles emitted from honeycomb briquettes flaming were stable,while they are obviously different from those emitted from lump coal combustion.For honeycomb briquettes flaming or smoldering,the metal particle emission accounts for a high proportion.For the particles emitted from lump coal flaming,the carbonaceous particles dominate when the sizes are lower than 1.0?m,while the Na-K particles dominate when the sizes are greater than 1.0?m.What's more,the distribution of chemical compositions of single particles with different particle sizes from household biomass combustion is relatively stable,mainly C and K particles.For honeycomb briquettes flaming,dot product values of the EC,OC,K,NaK,and M single particles are high.For lump coal flaming,the EC and OC single particles have the highest similarity,followed by the OC and NaK particles.For honeycomb briquettes smoldering,except for NaK particles,the DP values of the carbonaceous particles and the remaining particles are higher.The similarity of biomass burning is higher than 0.7,the mixability is great.During the summer harvest period,due to the influence of biomass burning transportation,the concentration of submicron particulate matter in rural areas of North China Plain was mainly distributed at<300 nm,with an average total number concentration of 28371 cm^-3.During the sampling period,the particle size distribution of Nucleation mode,Atiken mode and Accumulation mode number are linear,multiphase and logarithmic distributed,respectively.Influenced by coal-fired heating in winter,the concentration of atmospheric submicron particulate matter in the southern suburbs of North China Plain mainly concentrated in the ultrafine particle size section of Nucleation mode and Atiken mode,showing a decreasing single peak distribution and an average concentration of particulate matter about 83174 cm^-3.What's more,the concentration of particulate matter in clean days and moderate polluted days shows single-peak distribution,while that in heavily polluted days exhibited decreasing single-peak distribution.And,the number concentration of nuclear modal particles increased evidently relative to those in clean and moderate polluted days.