藉由热力学观念讨论GAS-PHASE

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1、Ch9.ThermodynamicsofAerosolsCONTENTS9.1ThermodynamicsPrinciples9.2AerosolLiquidWaterContent9.3EquilibriumVaporPressureOveraCurvedSurface:TheKelvinEffect9.4ThermodynamicsofAtmosphericAerosolSystemsCONTENTS9.1ThermodynamicsPrinciples9.1.1InternalEnergyandChemicalPotential9.1.2TheG

2、ibbsFreeEnergy9.1.3ConditionsforChemicalEquilibrium9.1.4ChemicalPotentialsofIdealGasesandIdealGasMixtures9.1.5ChemicalPotentialofSolutions9.1.6TheEquilibriumConstantChemicalPotential藉由熱力學觀念討論Gas-Phase、AqueousPhase、SolidPhase三相平衡SOLID=LIQUIDChemicalPotential=f(T,P,ni)ni:themole

3、sofspeciesi9.1ThermodynamicsPrinciples9.1.3ConditionsforChemicalEquilibrium自發性反應趨向減少Gibbsfreeenergy之方向進行CONTENTS9.2AerosolLiquidWaterContent9.2.1ChemicalPotentialofWaterinAtmosphericParticles9.2.2TemperatureDependenceoftheDRH9.2.3DeliquescenceofMulticomponentAerosols9.2.4Crystal

4、lizationofSingleandMulticomponentSaltsDRH(deliquescencerelativehumidity)LowRHaerosolsolidDeliquescence：當RH開始增加至DRH時，氣膠內特定組成會開始吸收水分，藉以維持其其熱力學平衡關係，因而變為水相。每一物種之DRH並不相同。Crystallization：當RH下降時，其水分會揮發形成結晶，但此RH與DRH並不相同。例如(NH4)2SO4,fig9.49.2AerosolLiquidWaterContent9.2AerosolLiquidWate

5、rContent9.2AerosolLiquidWaterContentDRH、Deliquescence、Crystallization：與G相關DeliquescenceandCrystallizationDeliquescence當RHDRH，Liquid之Gibbsfreeenergy較低，因而致使(NH4)2SO4以Liquid存在當RH=DRH，兩者之Gibbsfreeenergy相同，因而致使Solid會開始吸收水分Gibbsf

6、reeenergy變化圖Crystallization當RH下降至DRH時，水分並不會在此時揮發。RH持續下降，使氣膠成為超飽和溶液。帶其達到臨界超飽和(CriticalSupersaturation)後，即發生再結晶現象Gibbsfreeenergy變化圖9.2.1ChemicalPotentialofWaterinAtmosphericParticlesWaterVapor(atmosphere):theorderofgramsperm3ofair.H2Oconcentrationintheaerosolislessthan1mg/m3ofair

7、氣膠相內水之濃度變化並不會影響大氣中水蒸氣之濃度氣膠熱力學模式計算時，可將ambientRH視為一常數9.2.1ChemicalPotentialofWaterinAtmosphericParticlesWaterActivityPw:thewatervaporpressure(inatm)w:thewateractivityinsolution純水平衡w=1，pw=pw0(T,saturationvaporpressure)(9.61)、(9.62)可得9.2.1ChemicalPotentialofWaterinAtmosphericPar

8、ticlesWaterActivity由於Pw/Pw0即為相對濕度(0~1)之定義大氣氣膠中之