Investigating The Atmospheric Nucleation Mechanism Involving Organic Acids Based On Turbulent Flow Tube Experiment And Theoretical

Atmospheric aerosols have a great influence on health and climate patterns.In the past decades,although many experimental and theoretical works have been performed,the mechanism of secondary aerosols formation has not been well understood.Sulfuric acid(SA)has been identified to be an important precursor of aerosol nucleation through clustering with water(H2O),ammonia(NH3),methylamine(MA)and dimethylamine(DMA).However,the actual nucleation rate measured in the atmosphere is not be explained when the concentration of sulfuric acid in the range of 105-107 cm-3.It is hence suggested that other species are involved in nucleation,such as organic acids,aldehydes,amino acid and highly oxidized multifunctional organic molecules(HOMs).In this work,the nucleation mechanism of atmospheric aerosols participated by organic acids was studied by means of turbulent flow tube experiment and theoretical calculation.The contents of the paper are as follows as follows:1.A turbulent flow tube reaction system was designed and built.2.Using flow tube experiment and quantitative calculation,the nucleation mechanism of sulfuric acid(SA)-dimethylamine(DMA)involved succinic acid(SUA)were studied.The results show that succinic acid can promote the nucleation of sulfuric acid dimethylamine at 283k,and the promoting effect increases when the concentration of succinic acid increasing.Moreover,the promoting effect of succinic acid is more obvious at low sulfuric acid concentration.3.The nucleation mechanism of succinic acid in sulfuric acid-ammonia(NH3)was studied by theoretical calculation.The structure,thermodynamic parameters and formation rate of clusters were calculated.The results show that succinic acid can participate in the nucleation of sulfuric acid-ammonia.From the results of ACDC,the formation rate is lower than that of sulfuric acid-ammonia.The nucleation mechanism of succinic acid was determined through the nucleation path,in which SUA acted as an intermediary bridge for the formation of pure SA-NH3 clusters.4.The nucleation mechanism of malonic acid(MOA)in sulfuric acid dimethylamine was studied theoretically.It is found that SA,DMA and MOA molecules form rings through hydrogen bonds to form stable clusters.ACDC simulation shows that MOA can form new particles with SA-DMA system.Compared with the results of the CERN-CLOUD experiments,the formation rate of the SA-MOA-DMA system is between those of SA-DMA-W and SA-NH3-W systems at high concentration of DMA.In this work,organic acids are selected as nucleation precursors to clarify the mechanism of organic acids in the nucleation of sulfuric acid inorganic ammonia and sulfuric acid dimethylamine.It is of great significance to study the nucleation mechanism of atmospheric aerosols,which are organic acids involved,that is,identifying key precursors involved in nucleation,revealing the process of aerosol nucleation and transformation,and it is of great scientific significance for the study of multiple nucleation mechanism under the condition of China’s combined air pollution.