Studies On The Physical Properties Of Carbonaceous Aerosols Based On New Design H/V/R-TDMA

Carbonaceous aerosol is one of the key components in atmospheric aerosol,which can produce multiple impacts on the radiative force,visibility and air quality.It also can change global climate and human health.Statistical analysis is performed on the physical properties of mono-ethanolamine(MEA)salts and soot based the experiments on new type of Tandem Differential Mobility Analyzer(TDMA).The thermal stability and hygroscopicity of MEA salts were presented,as well as the hygroseopicity and restructure transformation of soot aerosol particle coated with organic maters.Some results can be concluded as the following.In order to study the physical properties of aerosol particles from three differermt directions,including hygroscopicity properties,volatilization characteristics and coating reaction.A new type of TDMA called "H/V/R-TDMA" has been designed and self-built.Based on this system,the physical properties of carbonaceous aerosol could be measured.H/V/R-TDMA has been used to measure the thermodynamic properties of several representative MEA salts with mono-,di-,and tri-carboxylic acids and also with sulfuric acid,potentially the dominant forms of MEA in atmospheric particles.This study reports the synthesis of salts,measurements of their evaporation rates and calculation of their thermodynamic properties.The stability of MEA salts was found to depend strongly on the chemical nature of the acid counterpart.However,the stability of organic acid in aerosol phase is often complicated by the physical state of the chemical compounds.An Extended Aerosol Thermodynamics Model(E-AIM)has been introduced to compare the hygroscoicity data from measurements.Due to lack of the physical properties of MEA salts,the model results could not fit well with the experimental data.The saturation vapor pressures,vaporization enthalpies,and surface free energies obtained in this study can be used to evaluate the role of MEA in the aerosol and haze formation,helping to assess impacts of the MEA-based carbon capture technology on air quality and climate change.In another comprehensive study,/V/R-TDMA has been used to investigate the effect of coatings composed of tri-ethylene glycol(TEG),a proxy for oxidized organic aerosol(OOA)matter,on the structure and hygroscopicity of soot aggregates.Significant restructuring of soot aggregates was observed in the presence of sub-nanometer layers of TEG.The presence of TEG makes soot aggregates hygroscopic and further promotes their restructuring at higher relative humidity.Meanwhile,the effect of thin polycyclic aromatic hydrocarbons(PAH)coatings on the structure of soot aggregates also has been investigated.Soot aerosol from inverted diffusion burner was size classified,thermally denuded,coated with two different PAH.Contrary to the expectation,significant restructuring was observed in the presence of sub-nanometer layers of phenanthrene(PHE).This PAH remained in sub-cooled liquid state in thin films,whereby the liquid layer acted as a lubricant,reducing the force to initiate the restructuring.Thin layers of PAH of higher melting temperature(anthracene,ANT)remained solid because these chemicals induced lesser structural changes.These results suggest that some of the intrinsic PAH generated during incomplete combustion and small amounts of oxidized organic matter may induce significant restructuring of soot aggregates,even present in small quantities,altering the properties and atmospheric impact of combustion aerosols.