FTIR-ATR Study On Hygroscopicity And Volatility Of Organic/Inorganic Mixed Aerosols

With the development of the economy,haze weather become norm because of suspended aerosols particles in the atmosphere,this have a considerable impact on climate change,visibility degration,the daily life and health of mankind.The formation and evolution of particles are important processes of haze formation,gas-to-particle conversion and gas-to-particle partitioning of volatile organic compounds（VOC）and semi-volatile organic compounds（SVOC）play an important role in the formation and aging process of aerosol particles.In this process,hygroscopicity and volatility are important physicochemical properties of particles,which are closely related to the chemical composition of particles and environmental humidity.Therefore,it is of great scientific significance to explore the formation and evolution of atmospheric particulates from the view of hygroscopicity and volatility.In this paper,Attenuated Totalinternal Reflectance Fourier Transform Infrared Spectroscopy（FTIR）is used to study the hygroscopicity and volatility expansion of organic and inorganic aerosol particles and the main conclusion as follow.（1）Study on the hygroscopicity of the mixed aerosols particles for glycine/salts nitrateFor the hygroscopicity of the mixed particles for pure glycine,pure sodium nitrate and glycine/sodium nitrate,the infrared spectra were collected by FTIR-ATR.Through the analysis of the infrared spectra and hygroscopic curves,it is found that pure glycine particles effloresce when the relative humidity（RH）is 64.5%and do not deliquesce on humidifying.The efflorescence and deliquescence point for pure Na NO₃ particles are 54%RH and 91.9%RH,respectively.In this work,pure glycine crystals exists inβ-form.For the internal mixed glycine/Na NO₃ particles,there exhibit various hygroscopicities and solid-aqueous phase transitions dependent upon the OIR.As OIR decreases,the ERH was delayed and the DRH advanced for Na NO₃ of mixed glycine/Na NO₃compared to pure Na NO₃ particles,and also the glycine exhibit the same trend.The addition of glycine can inhibit the crystallization of sodium nitrate with the decrease of OIR,while the addition of sodium nitrate promotes the crystallization of glycine.The infrared spectra and hygroscopic curves were investigated for Glycine/magnesium nitrate with OIRs of 1:3,1:1and 3:1.It is found that pure glycine exists inα-orγ-form in the mixed particles of Glycine/magnesium.When the OIRs are 1:3,1:1,glycine cannot crystallize.But OIR is 3:1,glycine effloresce at 68.5%RH and deliquesce at 85.2%RH.The addition of magnesium nitrate may changes the crystal structure of glycine.（2）Study on the volatility of reaction for the mixed aerosols particles for dicarboxylic salts/ammonium sulfateThe infrared spectra various time were collected by FTIR-ATR to investigate the reaction mechanism and volatility of internally mixed particles of sodium succinate/（NH₄）₂SO₄,sodium malonate/（NH₄）₂SO₄,sodium oxalate/（NH₄）₂SO₄ at1:1 molar ratio.The results shows that disodium succinate and disodium malonate can react with（NH₄）₂SO₄,respectively,resulting in the release of gaseous NH₃ and formation of succinic acid and malonic acid during the hydration process.Disodium oxalate can not react with（NH₄）₂SO₄.These reactions were attributed to the formation of low hygroscopicity organic acid and the evaporation of NH₃ into gas phase.With reaction time increases continuously,The reduction of the water,attributed to the the evaporation of itself and the volatilization of NH₃,which accelerates the crystallization rate of Na₂SO₄ drops.Similarly,the crystallization of Na₂SO₄ particles can result in the evaporation of water.the volatilization of NH₃speed up the evaporation of water.