大氣環(huán)境化學(xué)課件：大氣氣溶膠 (2)

1、大氣氣溶膠,大氣氣溶膠的重要性,空氣質(zhì)量 人體健康 能見(jiàn)度 氣候變化 云物理 大氣輻射 中小尺度動(dòng)力系統(tǒng)（城市氣象） 大氣化學(xué),Aerosols and Climate,Direct effect,Indirect effect,Scattering,Formation of CCN,Aerosol and Visibility,Aerosol and Visibility,氣溶膠的物理化學(xué)特征,化學(xué)成分 空間分布 物理特征 氣溶膠的形成,化學(xué)成分,Sulfate Nitrate Black Carbon Organic Carbon POC and SOC Mineral Dust Sea-

2、salt,垂直空間分布,SO2 sulfate,Stratospheric Background aerosols,OCS (1 year lifetime) Stratosphere OCS SO2 SO2 Sulfate Background aerosols (1-2 ug/m3) Volcanic aerosols (20-50 ug/m3),對(duì)流層空間分布,對(duì)流層空間分布,物理特征,數(shù)濃度,Nucleation mode,Accumulation Mode,Coarse Mode,0.03 0.3 3,um,物理特征,質(zhì)量濃度,Nucleation mode,Accumulation

3、 Mode,Coarse Mode,0.03 0.3 3,Log-normal distribution,Diameter,ln Dm = ln Dg + 3 N2g where Dm = mass weighted diameter Dg = geometric mean diameter Dm Dg,Dg,Dm,氣溶膠的形成,Sources of Particles:,Industrial,Biomass Burning,Sea-salt,Dust,氣溶膠的形成,氣溶膠的形成,Chemistry Nucleation Condensation Coagulation Hydrotropic

4、 growth Deposition,Aqueous Chemistry,SO2 H2SO4 (1) Gas-phase (30-40%) SO2 + OH H2SO4 (2) Aqueous-phase (60-70%) SO2(a) + H2O2(a) H2SO4(a) SO2(a) + O3(a) H2SO4(a),Nucleation,Homogeneous Nucleation Gas phase Particle phase Heterogeneous Nucleation Existing small particles (direct emission),Homogeneous

5、 Nucleation,Phase Transfer (Gas Particles) Gas vapor pressure P Ps Ps = Saturation Pressure Sulfate, SOC,Problem in Homogeneous Nucleation Theory,Number of particle,Vapor Pressure,103,Theory,Measurement,Progress on the problem,(1) Traditional theory,P Ps,Progress on the problem,(1) NH3 effects,P Ps,

6、Progress on the problem,(1) NH3 effects (Ps decrease),P Ps,Progress on the problem,(1) Organic Acid effects (Ps decrease),P Ps,Zhang et al., Science, 2004,Condensation,Ks, kd,Coagulation,Coagulation,M = (i-1),Hydrotropic growth,Hydrotropic growth,D,RH,80,Hydrotropic growth,Change the cross-section o

7、f scattering,Hydrotropic growth,Change the absorption of aerosols,Deposition,Dry deposition Wet deposition,Dry deposition,The flux (F) to the surface F = - Vd x C Vd = 1/(Ra + Rb + Rc) Ra is the aerodynamic resistance (meteorological conditions) Rb is the quasi-laminar sub-layer resistance (kinetic

8、viscosity of air) Rc is the total surface resistance (surface type),Wet deposition,Rain frequency and strength Solubility (hydrophilic aerosol only),氣溶膠大氣化學(xué),氣溶膠大氣化學(xué) Photolysis (J) Heterogeneous reactions,Tie et al., JGR 2005,Aerosols not only affect climate, but also chemistry,Photolysis rate J,Impo

9、rtant Photolysis (J),Ozone formation VOCs + OH RO2 RO2 + NO NO2 NO2 + hv NO + O (JNO2) O + O2 O3,Important Photolysis (J),OH formation O3 + hv O(1D) + O2 (JO3) O(1D) + H2O 2 OH,Important Photolysis (J),OH formation CH2O + hv H + HCO (JCH2O) H + O2 HO2 HO2 + NO OH + NO2,Important Photolysis (J),NOx i

10、n Remote region PAN + hv NO2 + Prod (JPAN),Important of PANTo transport NOx from source to remote region,PAN = CH3CO3NO2 CH3CO3 + NO2 PAN PAN + hv CH3CO3 + NO2 + CH3O2 + NO3,Impact of aerosol on J,J(i)= F x (i)(i),F = solar Flux,Impact of aerosols on JScattering,F0,F1,Impact of aerosols on JAbsorb,F

11、0,F1,Aerosols,Sulfate Scattering Nitrate Scattering OC Scattering (abs?) SOC Scattering Sea-salt Scattering Dust Weak absorption EC Strong absorption,Aerosol Parameters,Aerosol optical depth (AOD) Asymmetry parameter (g) Single albedo (),Aerosol optical depth,Asymmetry Parameter,Single Albedo,MODIS

12、AOD,Factors to affect the impact ofAerosols on radiative forcing,Mass of aerosol concentrations (AOD) Size of aerosols (AOD, g) Composition of aerosols (AOD, ) RH (AOD, , g) Shape of aerosols (AOD, , g) The vertical distribution of aerosol,Vertical distribution of scattering aerosols,Vertical distri

13、bution of scattering aerosols,Vertical distribution of absorption aerosols,Vertical distribution of absorption aerosols,Shape of aerosols,Composition of aerosols,EC (soot) = 0.46 Sulfate = 1.0 H2O = 1.0,External Mixing of aerosols, = Ai x Wi, = 0.46*0.1 + 1.0*0.9 = 0.946 = 0.46*0.2 + 1.0*0.8 = 0.892

14、,Fine particle optical properties: light scattering and absorption,Collaboration with MPI and IFT, Germany,Guangzhou urban, 2004,Internal Mixing of Aerosols,Heterogeneous ReactionsA B with ,N2O5 + sulfate 2HNO3,N2O5 + sulfate 2HNO3,HO2 + sulfate Products,NOx,CO, HCs, Aerosols,Emissions,大氣化學(xué)氣溶膠模式,NOx,CO, HCs, Aerosols,Mixing,Night PBL,Mixing in low PBL during night,NOx,CO, HCs, Aerosols,Mixing,Daytime PBL,Mixing in high PBL during day,NOx,CO, HCs, Aerosols,Mixing,Daytime PBL,Chemical