Study Of The Atmospheric Aerosol Nucleation Mechanism Involving Amines And Organic Acids

New particle formation(NPF)is an important source of atmospheric aerosol and cloud condensation,which directly or indirectly affects the balance of Earth’s radiation,the change of global climate and human health.However,due to the diversity of the global atmospheric environments and the limitations of the detection method,the detailed knowledge on the new particle formation is still unclear,especially the process of forming a critical nucleus by phase transformation.Thus,four methods including laboratory simulation,field observation,theoretical calculation and model simulation are implemented to study the mechanism of new particle formation.Among them,the application of theoretical calculation and laboratory simulation on revealing nucleation mechanism is very effective.In this work,we aim to investigate the contribution of amines and organic acids to new particle formation by theoretical calculation and laboratory simulation.For theoretical calculation,two parts will be presented as following:(1)on the properties and atmospheric implication of amine-hydration clusters.Dimethylamine-water clusters are favorable at low temperatures,but these clusters may be difficult to form because of the combined effect of Gibbs free energies with small negative values and the low relative concentration of dimethylamine in various atmospheric conditions,and this implies that dimethylamine-water clusters are difficult to form spontaneously in the atmosphere.;(2)interaction of oxalic acid with dimethylamine and its atmospheric implication.The stability of oxalic acid with dimethylamine by forming dicarboxylate aminium ion pair enhances the clusters,and may be involved in new particle formation.In terms of laboratory simulation,a new corona discharge ion source and a calibration source was developed for atmospheric pressure interface-time-of-flight mass spectrometer to measure both gaseous sulfuric acid concentration and the components of critical nucleus clusters.Nitrate core ions(NO3)were used as reagent ions and generated by discharging zero air followed by adding excess nitrogen dioxide to convert primary ions and hydroxyl radicals into NO3-and HNO3.The calibration system generates the sulfuric acid through the oxidation of SO2 by OH,which is produced by UV photolysis of water vapor.A numerical model calculates the sulfuric acid concentration at the outlet of the calibration source.By comparison of this concentration and the signals measure by mass spectrometer,a calibration factor is obtained.The corona discharge ion source has the advantages of low cost,simple but robust structure and easy to carry,it can be a powerful tool for field observation.Chemical ionization time-of-flight mass spectrometer can be effectively used for both field and laboratory studies of aerosol nucleation mechanism and chemical compositions.