Glycine-sulfuric Acid-ammonia Nucleation Mechanism And Hydration Promotion In The Atmosphere

Atmospheric aerosols have a tremendous influence on weather,the Earth's climate,and health quality.New particle formation(NPF)is a crucial source of atmospheric aerosols.Researchers generally believe that sulfuric acid(SA)is the important substance to participate in the nucleation process in the atmosphere.Ammonia(A)can effectively stabilize clusters by reducing the saturated vapor pressure of gaseous sulfuric acid.But Sulfuric acid-ammonia binary nucleation is not sufficient to explain the high nucleation rate events in the actual atmospheric environment.In recent years,the nucleation of amino acids can explain the high nucleation rate in some areas.The concentration of glycine(Gly)ranges from 106-109 molecules/cm~3 in the atmosphere.It is possible to enhance aerosol nucleation and the growth of nanoparticles.However,the nucleation mechanism of Gly clusters under various atmospheric conditions is still ambiguous.The content of this paper includes four chapters.The first chapter introduces the formation and source of atmospheric aerosols,and presents a systematic summary of the process of new particles participating in nucleation in recent experimental and theoretical researches,thereby the significance of the research was determined.The second chapter introduces the basic principles of quantum chemistry and the calculation methods used in this work.In the third and fourth Chapters,the effects of glycine on sulfuric acid-ammonia clusters and the hydration on glycine clusters are studied using quantum chemical theory combined with Atmospheric Cluster Dynamics Code.The main research contents and results are as follows:(1)At different temperatures and precursor concentrations,the formation mechanism of glycine in the sulfuric acid-ammonia binary system was investigated.The results show that Gly,with one carboxyl(-COOH)and one amine(-NH₂)group,can interact strongly with S A and A in two directions through hydrogen bonds or proton transfer.The enhancement R presents a positive dependence on[Gly]and a negative dependence on temperatures.The enhancement R of Gly decreases with the increase of[SA].Moreover,R firstly increases and then decreases with the increase of[A].The Gly-containing clusters can directly participate in the cluster formation and eventually leave the cluster by evaporation at low[Gly].The role of Gly is only a“transporter”to connect the smaller and larger clusters.But with the increase of[Gly],it could directly participate in the growth path and act as a“participator”in NPF.(2)At different temperatures and humidity,the interactions of glycine with sulfuric acid(SA),ammonia(A)and one to four water(H₂O)was investigated.The results show that the addition of H₂O molecules to the Gly·SA and Gly·SA·A clusters can promote the formation of intermolecular hydrogen bonding.And the carboxyl(COOH)group is easier to form hydrogen bonds than the amino(-NH₂)group in the process of interacting with nucleating precursors.The process of adding a cluster of(H₂O)_n more likely occurs in the atmosphere than gradually adding a single H₂O molecule.As the temperature increases,the proportion of the global minimum isomers decreases.Under the most relevant conditions of the troposphere,the total concentration in the hydrated clusters is mainly distributed in the monohydrate,that is,the monohydrate is more advantageous than the other hydrates.The results of this paper may lead to a better understanding of the properties of amino acid-containing organic aerosol under typical atmospheric conditions.It provides a reference information for a comprehensive understanding of the mechanisms of nucleation and growth in the real polluted environment of the atmosphere.