Gerhard Lammel: “Trends and Advances in Atmospheric and Environmental Chemistry" Cloud chemistry: Ozone, acidity formation, dimethyl sulphide Atmospheric aerosol, its composition, surface and bulk particle reactions - humidity/supersaturation S (:=rh-1) is altitude (above cloud base)- dependent - 15% of the volume of the troposphere filled with clouds - liquid water content L = 0.1-2 10-6 Vwater/Vair = 0.1-2 g/m³ = (0.1-2) 10-3 L/m³ < 10% of total water content (10-40 g/m³!) - only 10% of clouds will rain out, while 90% will recycle aerosol particles - lifetime of clouds hours-days, of cloud droplets (D=5-50 µm) minutes - aqueous composition: dissolved (ci 10-6 - 10-3 M) + eventually nondissolved constituents, droplet-size dependent, ci(D) Cloudwater - introduction, significance Terminology: • Hydrometeors = cloud droplets + ice particles + rain droplets + snow flakes + graupel + ... • Wet deposition = rain + snow fall + rime • Wash-out = below-cloud scavenging + in-cloud scavenging of both gases and particles • in-cloud scavenging of gases = dissolution • Occult deposition = droplet deposition from clouds, fogs else than rain or snow fall some units: • 1 M = 1 mol/L • pH 7 ↔ cH3O+ = 10-7 M (Warneck, 1999) Henry coefficients Solubility increases with decreasing temperatures, e.g. 78, 63 and 53% of O2 at 0°C is soluble at 10, 20 and 30°C, respectively. Compilation of KH : • Warneck, Phys. Chem. Chem. Phys. 1 (1999) 5471-5483 • download from Rolf Sander’s webpage, MPI-C http://www.mpch-mainz.mpg.de/~sander/res/henry.html ...with diluted solutions (ideal behaviour). The in-cloud scavenged fraction of gaseous molecules is dependent on water solubility: i(g) = ni(aqu) / (ni(aqu) + n(g)) = ni(aqu) / [ni(aqu) + piVair/(RgT)] = = ni(aqu) / [ni(aqu) + Hi ni(aqu)Vair/(RgT nH2O)] = = [1 + HiMw/(Rg T L)]-1 with: Henry coefficient Hi [at] = pini(aqu)/nH2O = pi xi = pi/(ci/103/Mw), liquid water content L [g/m³] gas constant Rg = 8.206×10-5 m3 at/mol/K, Mw[g/mol], 103[cm3/L] (Warneck, 1986) Another, more common Henry coefficient: KH [M at-1] = 102 s/Mwp = (103/Mw) × H2O/H solubility s(T) [mg/L] = s(T0) × exp[- Hsol/Rg × (1/T-1/T0)] Sulfuric acid formation in the aqueous phase Dissolution of gases - thermodynamic equilibrium ... confusing: there are more common so-called ‚Henry coefficients‘: Air-water partitioning coefficient Kaw [ ] = Mwp/(105 RgTs) = 1/ (103 RgTKH) Henry coefficient H‘ [Pa m³/mol] = RgTKaw = 10-2/KH[M/at] Ozone is a source of radicals and H2O2 in cloudwater: (1a) O3 aqu + OHaqu O2 aqu + HO2 . aqu (1b) + HO2 . aqu 2 O2 aqu + OH. aqu (1c) + OH. aqu O2 aqu + HO2 . aqu (2a) HO2 . aqu + OH. aqu O2 aqu + H2O (2b) + HO2 . aqu O2 aqu + H2O2 (3b) H2O2 + h 2 OH. aqu Ozone reactions Tropospheric ozone and clouds Differences in solubility and chemical reactivity in the aqueous phase result in changed (overall) chemistry of the atmosphere. pH dependencies, e.g. O3 sink A6 (O3 + O2 - + H2O ) O3, OH, NOx overestimated when clouds are neglected (Lelieveld & Crutzen, 1990) Solubility of CO2 (g) ⇋ CO2 aqu + 20 kJ/mol (1) KH = cCO2 aqu / pCO2 = 3.4×10-7 mol/L/Pa (298 K) CO2 aqu + H2O ⇋ HCO3 - + H3O+ (2) KA1 = (cHCO3- cH3O+) / cCO2 aqu = 10-6.35 HCO3 - + H2O ⇋ CO3 2- + H3O+ (3) KA2 = (cCO3-- cH3O+) / cHCO3- = 10-10.33 Dissolved carbon dioxide Hydrogen ion CO2(aq) + H2O(aq) H2CO3(aq) H+ + HCO3 - Liquid water Dissolved carbonic acid Bicarbonate ion Hydrogen ion 2H+ + CO3 2- Carbonate ion Dissolved fraction is pH dependent, expressed as the effective Henry coeff. H*: KH CO2 * = (cCO2 aqu + cHCO3- + cCO3--) / p (mol/L/Pa) KH * = KH (1 + KA1 / cH3O+ + KA1KA2 / cH3O+ 2) pH of water in the atmosphere in equilibrium with CO2 (pCO2 = 36 Pa): (1) in (2): cHCO3- cH3O+ = KA1 KH pCO2 cHCO3- = cH3O+ cH3O+ = (KA1 KH pCO2)0.5 pH = - 0.5 (-pKA1 - log KH - log pCO2) pH = 0.5 (6.35 - log 3.4×10-7 - log 36) = 5.63 pH scale Courtesy: Jacobson during the day: NO2 + OH HNO3 fast: 9.2×10-12 cm³ molec-1 s-1 (Mollner et al., 2010) during night: NO2 + NO3 ⇌ N2O5 phase equilibria of N(-III), N(IV), N(V) species: NH3 ⇌ NH3 aqu. NO2 ⇌ NO2 aqu HNO3 ⇌ HNO3 aqu N2O5 ⇌ N2O5 aqu dissociation, hydration N(-III), N(V): NH3 aqu + H2O NH4 + aqu + OH- aqu HNO3 aqu + H2O H3O+ aqu + NO3 - aqu 2 NO2 + 3 H2O NO2 aqu + NO3 aqu + 2 H3O+ aqu; slow (Lee & Schwartz, 1981) N2O5 aqu + 3 H2O 2 H3O+ aqu + 2 NO3 - aqu Acidity formation in the troposphere: N Nitrogen compounds in the aqueous phase more phase equilibria of N(-III), N(V) species: HNO2 ⇌ HNO2 aqu KH = 50 M at-1 HNO4 ⇌ HNO4 aqu KH = 1.4×106 M at-1 dissociation, hydration N(-III), N(V): HNO2 aqu + H2O ⇌ H3O+ aqu + NO2 aqu KA = 0.6×10-5 M HNO4 aqu + H2O ⇌ H3O+ aqu + NO4 aqu KA = 1.0×10-5 M (Lammel et al., 1990) HNO4 aqu ⇌ HO2 . aqu + NO2 aqu KA = 4.6×10-10 M NO4 aqu O2 aqu + NO2 aqu k = 1.4×10-2 s-1 Crete, 2001-03 (Vrekoussis et al., 2006) HNO3 production: sources (1a) NO2 + .OH HNO3 (day) (1b) NO2 + NO3 . ⇌ N2O5 (night) (2b) dissolution + hydration: N2O5 +3 H2O 2 H3O+ aqu. +2 NO3 - aqu. Formation of sulfuric acid in the (A) gas-phase: (1) SO2 + OH. HOSO2 . (2) HOSO2 . + O2 SO3 + HO2 . (3) SO3 + 2 H2O H2SO4×H2O net: (1-3) SO2 + OH. + O2 + 2 H2O H2SO4×H2O + HO2 . Then very fast phase change by nucleation ( 3.1 Aer) and subsequent condensation Acids: formation reactions and cloud chemistry Sulfuric acid formation in the gas-phase Alkenes react readily with ozone: k 10-10 cm3 molec-1 s-1 (1) CH3CH=CH2 + O3 [primary ozonide] (2a) [primary ozonide] CH3CH(OO.)CH2O. 55% (3a) decomposition: CH3CH.OO. + HCHO (3b) + SO2 SO3 k 0.6×10-12 cm³/molec/s (estimate) (4b) SO3 + 2 H2O H2SO4×H2O additional gas-phase source for H2SO4! O OO CH3 Chemical mechanism modified, Hohenpeissenberg data set; Boy et al.., 2012 However, only 15% of S(VI) is formed in the gas-phase globally, 85% is formed (B) in cloud droplets and humid aerosol particles S(IV): = SO2 aqu.+ HSO3 - + SO3 2Phase equilibrium (Henry coeff., physical solubility of SO2): SO2 ⇋ SO2 aqu. KH (298K):= cSO2/pSO2 = 1.2×10-5 M/Pa Dissociation equilibria: SO2 aqu. + 2 H2O ⇋ HSO3 - + H3O+ KA1 (298K)= 1.7×10-2 M HSO3 . + H2O ⇋ SO3 2- + H3O+ KA2 (298K)= 6.5×10-8 M S(IV) phase equilibrium and reactions determined by Henry coeff. KH, pH, T For substances which interact with water to form ions via acid-base dissociation equilibria KH must be replaced by a modified coefficient KH*: (‚modified Henry coeff.‘): KH (298K)*:= cS(IV)/pSO2 = KH (1 + KA1/cH3O+ + KA1KA2/cH3O+²) = f(pH) S(IV): = SO2 aqu.+ HSO3 - + SO3 2Phase equilibrium (Henry coeff., physical solubility of SO2), subsequent dissociation: SO2 ⇋ SO2 aqu. ⇋ HSO3 - + H3O+ ⇋ SO3 2- + 2 H3O+ Sulfur dissolved bisulfite sulfite dioxide sulfur gas dioxide ... and S(VI) phase equilibrium and dissociation similarly: S(VI): = H2SO4 aqu. + HSO4 aqu + SO4 2- aqu Hydrogen ion H2SO4(aq) H+ + HSO4 - Dissolved sulfuric acid Bisulfate ion Hydrogen ion 2H+ + SO4 2- Sulfate ion H2SO4(g) Sulfuric acid gas Acid-base dissociation equilibrium (Warneck, 1999) Bulk aqueous phase chemistry Dissociated / undissociated species exist in ratios determined by acidity (pH) and the dissociation constant, KA. E.g. SO2 aqu.for pH < -log KA1= 1.7, SO3 2- for pH > -log KA2 = 7.1 and HSO3 - in between. S(IV) oxidation reactions (Graedel & Weschler, 1981; Warneck, 1999) (1) SO3 2aqu + HO2 . aqu SO4 2aqu + OH. aqu HO2 or HSO3 (2) + OH. aqu SO3 - . aqu + OH aqu SO5 - . aqu SO4 2- aqu (3a) HSO3 aqu + O3 aqu HSO4 aqu + H2O k3a = 3.2×105 M-1s-1 (3b) SO3 2aqu + O3 aqu SO4 2aqu + H2O k3b = 1.5×109 M-1s-1 (4) HSO3 aqu + H2O2 aqu HSO4 aqu + H2O k4 = 4.0×107 cH+ M-1s-1 (5) 2 HSO3 aqu + O2 aqu 2 HSO4 aqu “autoxidation“ reactions Oxidations are pH dependent, because in individual steps of the reactions of SO2 aqu, HSO3 - aqu and SO3 2aqu (which are present in pH-dependent fractions according to KS1, KS2) is H + aqu consumed or formed. for L = VH2O(l)/V = 3×10-6 (Seinfeld, Calvert) Acidity formation in the troposphere: sulfuric acid Aciditiy of precipitation and SO2 emissions • discovery of acid rain 1852 (Smith) • discovery of acidification of freshwater, Norway 1920 • effects on fishes, 1970 Tropospheric trace substances trends: pH, SO2 Rain water pH SO2 emissions Aerosol constituents McDonald Beach [nmol/m³] seasalt-S(VI)/Cl- = 0.051 Sulfuric acid: precursors other than anthropogenic SO2 Terminology: • NSSS = non-sea salt sulfate • DMS = dimethylsulfide, CH3SCH3 • MSA = methanesulfonate, CH3SO3 - (1) CH3SCH3 + OH CH3SCH2 . + H2O CH3SCH2 . + O2 + M CH3SCH2OO. + M (2) CH3SCH2OO. + NO CH3SCH2O. + NO2 (3a) CH3SCH2O. HCHO + CH3S. major (3b) + O2 CH3SCHO + HO2 . minor (4b) CH3SCHO + OH. CH3 . + COS + H2O (Gas-phase chemistry) Dimethylsulfide Formation of carbonyl sulfide in the marine boundary layer: CH3SCH3 CH3S. CH3S. S(IV) S(VI) Formation of SO2 dimethylsulfoxide dimethyl sulfone Hypothetical negative feedback mechanism in the marine boundary layer: CH3SCH3 emission more clouds less radiative flux less phytoplankton less CH3SCH3 emission (CLAW hypothesis; Charlson et al., 1987) Example: cSO2 = 2 nmol m-3, cH2O2 = 40 nmol m-3, T = 298 K (near Bermuda 1988) 1. Gas-phase: dcS(VI)/dt = 5.6×10-6 nmol m-3 s-1 2. Aqueous phase (L =3×10-8, pH=7): dcSO4--/dt = k4 pH2O2 KH H2O2 pSO2 K*H SO2 (M s-1) = (4×107× 10-7) × 40×10-9× 1×105× 2×10-9x3.4x105 K*H SO2 = KH SO2 × (1 + KA1 / cH+ + KA1KA2 / c2 H+) = = 3.4×105 M/atm dcS(VI)/dt = dcS(VI)/dt (M s-1) × L (L m-3) × 109 (nmol mol-1) = = 32×10-6 nmol m-3 s-1 Acidity formation in the troposphere: sulfuric acid Heterogeneous reactions in the gas/water droplet system In phase equilibrium Less selectivity than in the gas-phase (Graedel & Weschler, 1981) Reactivity of organics in the aqueous phase: Overview OH reactions Compilation of kaqu can be found in N, S chemistry: Warneck, Phys Chem Chem Phys 1 (1999) 5471-5483 Herrmann, Chem Rev 103 (2003) 4691-4716 HCx chemistry: Herrmann, Chem Rev 103 (2003) 4691-4716 [L/mol/s] 2000 2030 under CLE [mg N/m²/a] (Dentener et al., 2006) acid deposition, example NOy trends Impacts of atmospheric acidity in ecosystems [Tg/a] 2030 under MFR Impacts of atmospheric acidity: acidification of soils (Busch et al., 2001) plants, bacteria NO3 - + H+ ON Critical loads concept to protect ecosystems Wie müssen die Emissionen zurückgefahren werden, damit die Rezeptoren der Immissionen (Böden, Oberflächengewässer, Grundwasserleiter) nicht geschädigt werden ? Wieviel Schädigung ist hinnehmbar ? Mapping of critical loads „...below which harmful effects in ecosystem structure and function do not occur according to present knowledge“: Determines which loads of pollutants and combinations thereof will not cause adverse effects, do not exceed ecosystem resilience (PNEC). • + Protection of vulnerable areas is possible (protection of 95% of the area is common) • +Accounts for dynamics, mostly however based on steady state-assumption and therefore neglecting the very slow dynamics of the soils • - Scale problems when matching exposure (deposition model output) and vulnerabilities (mapped ecosystems) • - normative steps are not transparent • Integrated Assessment Modelling (IAM) under the auspices of the Convention on Long-range Transboundary Air Pollution (CLRTAP): Study various scenarios of emissions and related abatement costs + depositions and related exceedances of thresholds (Alcamo et al., 1987, besides others) Cycling of ammonia (following Manier) Gas-phase chemistry NH3 + OH. NH2 . + H2O k = 0.16×10-12 cm³/molec/s (1) NH2 . + O2 NO + H2O k1 < 6×10-21 cm³/molec/s (2) NH2 . + HO2 . NH3 + O2 k2 = 34×10-12 cm³/molec/s (3) NH2 . + NO N2 + H2O k3 = 17×10-12 cm³/molec/s (4) NH2 . + NO2 N2O + H2O k4 = 19×10-12 cm³/molec/s (5) NH2 . + O3 NH2O. + O2 k5 = 0.16×10-12 cm³/molec/s (6) NH2 . + RH too slow to be of any significance -dcNH3/dt = kOH (1) cNH3 = kOH (2) cOH cNH3; τOH = (kOH (1))-1 3 months for the global annual tropospheric mean (1.16×106 OH/cm3) 10 days inner tropics near ground ( 107 OH/cm3; Spivakovsky et al., 2000) -dcNH3/dt = kOH (1) cNH3 + kdep (1) cNH3 τair = (kOH (1) + kdep (1))-1 Global N cycle, fluxes (Tg/a) +80% 1890 (Hibbard et al., 2006) 1990 Ammonia budget dcNH3/dt = Fe - kOH (1) cNH3 - kdep (1) cNH3 Emission trends (kt) in the EU-25 (EEA, 2006) Ammonia trends Europe Future EU commitments EU scenarios Past emissions in Europe and adjacent seas (Mt/a) 1980 2004 NH3 7.64 5.74 -25 % SO2 54.3 15.1 -72 % NOx 25.7 20.2 -21 % NO3 -/SO4 2- and NH4 +/(SO4 2- + NO3 -) are increasing in depositions -4% -28% -6% -43% Deposition of nitrogen and sulphur compounds and their corresponding production of acidity in a nitrogen unsaturated plant-soil-system Deposited individual ion H+- Production [mol/mol] Deposited species H+-Produc- tion [mol/mol] H+ +1 [NH4]2SO4/ NH4NO3 +2 / 0 NH4 + +1 H2SO4/HNO3 +2 / 0 NO3 - -1 H2SO4/ NH4NO3 +2 / 0 SO4 2- 0 NH4HSO4/ HNO3 +2 / 0 Impacts of atmospheric acidity: acidification of soils (Busch et al., 2001) Critical loads concept to protect ecosystems Wie müssen die Emissionen zurückgefahren werden, damit die Rezeptoren der Immissionen (Böden, Oberflächengewässer, Grundwasserleiter) nicht geschädigt werden ? Wieviel Schädigung ist hinnehmbar ? • Mapping of critical loads „...below which harmful effects in ecosystem structure and function do not occur according to present knowledge“ • which loads of pollutants and combinations thereof will not cause adverse effects, do not exceed ecosystem resilience (PNEC) ? • + Protection of vulnerable areas is possible (protection of 95% of the area is common) • +Accounts for dynamics ( Sustainability), mostly however based on steady state-assumption and therefore neglecting the very slow dynamics of the soils • - Scale problems when matching exposure (deposition model output) and vulnerabilities (mapped ecosystems) • - normative steps are not transparent Aerosols = ? Aerosol processes Courtesy of: Fuzzi et al., 2006 Courtesy of: Cambra-López et al., 2010 Coagulation Sedimentation Diffusion Nucleation Evaporation Condensation Convection Other external forces Aerosol microphysical processes Atmospheric residence time τ = f(D): Atmospheric residence time / dry deposition Diameter ( m) Time to Fall 1 km Diameter ( m) Time to Fall 1 km 0.0005 9630 y 4 23 d 0.02 226 y 5 14.5 d 0.1 36 y 10 3.6 d 0.5 3.2 y 20 23 h 1 326 d 100 1.1 h 2 89 d 1000 4 m 3 41 d 5000 1.8 m Terminal velocity of all three particles = 0.22 cm s-1 Aerodynamic equivalent sphere Stokes’s equivalent sphereIrregular particle da = 8.6 m = 1 g cm-3 ds = 4.3 m = 4 g cm-3 de = 5.0 m = 4 g cm-3 χ = 1.36 The aerodynamic diameter is the diameter of the unit density sphere that has the same settling velocity as the particle Particle size – not trivial ! Mönkkönen et al., 2004 Nucleation events in polluted air Nucleation events: Reasons for occurrence of nucleation events unclear. No simple correlations, key factors unknown. Example: 3 different events on Hohenpeissenberg 1998- 2000 (Birmili et al., 2003). The nucleation rate is mostly 2nd order in H2SO4, in general 1st to 2nd. This suggests the prevalence of a bimolecular reaction (collision) of 2 clusters with each one H2SO4 molecule for formation of the critical cluster (Weber et al., 2006). Primary particle formation (nucleation) condensational growth n1 H2SO4 + n2 H2O + n3 NH3 (?) + RCOOH (??) critical cluster ultrafine particle Aerosol effects Atmospheric chemistry: • Chemistry of the ozone hole is heterogeneous chemistry on ice particles • Formation of acidity in the marine boundary layer is chemistry in the aqueous phase provided by humid sea salt particles Climate: • strong climate sensitivity to aerosols, direct and more so indirect Toxicology: • fine particles < 10 µm (PM10) reach the lung • consitutents are partly toxic Sulfate aerosols: cooling (Feichter & Lammel, 1999) Zonal & global mean temperature changes 1990- 1850: GHG, aerosols, GHG aerosols (Feichter et al., 2003) Optical and hygroscopic properties • Scattering (‚direct effect‘) + warming due to absorption (‚semi-direct effect‘): –1.2 W/m² (earth surface) • Clouds: increase optical thickness and albedo due to increased droplet number concentration: –1.5 0.5 W/m² (Lohmann & Feichter, 2001; Lohmann et al., 2001) (IPCC, 2001) Instead of +0.7°C global warming we had without anthropogenic aerosols +1.7°C Relevance of aerosols: Climate DUST STORMS PROVIDE VISIBLE EVIDENCE OF INTERCONTINENTAL TRANSPORT OF AEROSOLS Glen Canyon, AZ/USA Clear day April 16, 2001: Asian dust! satellite data satellite data Jacob, Heald et al., Harvard Univ., 2004 PROVEN PATHWAYS OF REGIONAL AND INTERCONTINENTAL TRANSPORT OF AEROSOLS Marx & McGowan, 2010 Main components – Trends Weekly filter samples, PM10, PM2.5 ’95-‘02 bzw. ’99-’02 (PM1) Spindler et al., 2004 0 10 20 30 40 50 60 30.12.94 30.12.95 30.12.96 30.12.97 30.12.98 30.12.99 30.12.00 30.12.01 30.12.02 Partikelmassenkonzentration[µg/m³] PM10 PM2.5 PM1 since 1999 Linear (PM10) Linear (PM2.5) Linear (PM1 since 1999) Aerosol sources (globally, TgE/a oder Tg/a) Precursors anthr. natural NOx 41 31 10 NH3 54 (40-70) 43 11 SO2 88 (67-130) 79 9 DMS 25 (12-42) 0 25 VOCs 236 (100-560) 109 127 (only terpenes) Primary Carbonaceous (OC) Biomass burning 54 (45-80) Fossil fuel burning 28 (10-30) biogenic 56 (0 – 90) Black carbon (soot) Biomass burning 5.7 (5-9) Fossil fuel burning 6.6 (6-8) Industrial dust 100 (40-130) Sea salt 3340 (1000-6000) Mineral dust 2150 (1000-3000) (Penner et al., in IPCC, 2001) (UBA) Aerosol concentrations, chemical composition in EuropeChemical composition Globally: Jaenicke: Aerosol physics and chemistry, Landolt-Börnstein, 1988 Europe: Putaud et al., EU-Report 2002 = van Dingenen et al., Atmos. Environ. 2004 Aerosol chemical composition Eur. Aer. Phenomenology (Putaud et al., 2002) Sources for aerosol inorganic ions, Los Angeles 24.-25.9.1996 (Mysliwiec & Kleeman, 2002) • Emission inventory (source distribution, characteristics) • Atmosphere model covering transport and transformations Particle growth downwind of NH3 sources: • plumes downwind < 300 m of open liquid manure pits and other more or less open sources (animal houses, feed stocks) • sub-µm size range: nCN = +(8-18)*103 cm-3 • super-µm size range: very significant around 2 µm, n1-4µm = 14-21 cm-3 • under humid conditions ((1) r.h. = 90%, T = 6-9 C; rh rhD((NH4)2SO4) and rh > rhD(NH4NO3)) growth rate 0.2-0.7 µm min-1 0,001 0,01 0,1 1 10 100 1000 10000 0,1 1 10 paticle diameter, D / µm dN/dlog(D)/cm -3 1 upwind 2 source 3 downwind 4 downwind strong temperature dependence of the N(V) phase equilibrium NH3 + HNO3 = NH4NO3: for rh < rhD: pNH3 * pHNO3 = 0.12 ppbv² (278 K), 2.0 ppbv² (288 K), 28 ppbv² (298 K) Humidity dependence: (Stelson & Seinfeld, 1982) Y = [NH4NO3]/{[NH4NO3] + 3 [NH4(SO4)2]} Ions volatile, and non-volatile: Winter 0.5 Cl- + 1.3 NO3 - + 0.5 SO4 2- + 0.5 Na+ + 2.3 NH4 + + 0.1 K+ + 0.05 Mg2+ + 0.33 Ca2+ - (0.9 NH4NO3 - 0.2 NH4Cl - 0.1 HCl) = Summer 0.2 Cl- + 0.4 NO3 - + 0.5 SO4 2- + 0.5 Na+ + 1.2 NH4 + + 0.1 K+ + 0.05 Mg2+ + 0.33 Ca2+ A large fraction of the organic carbon (OC, POM) is water soluble (WSOC) (...and, hence, suitable as cloud condensation nucleus (CCN)) Continental aerosol consists of (each 25-50%): • aliphatic polyols (mostly sugars) and polyethers (polyphenols) • low-molecular aliphatic and other multifunctional compounds, e.g. R(COOH)1-2 • unsaturated aliphatic and aromatic polyacids of various lipophilicity („humiclike“), M = 200-500 Da, sources: Oxidation of soot, acid catalyzed polymerisation of terpenes (Havers et al., 1998; Fuzzi et al., 2001; Krivacsy et al., 2001; Decesari et al., 2002; Gelencser et al., 2003; Puxbaum et al., 2003) Continental aerosol (Winkler, 1974) Aerosol sources, size segregated Air in Riverside, CA, 25.9.1996 (Kleeman et al., 1999) • Emission inventory (source distribution, characteristics) • Atmosphere model covering transport and transformations Source contributions to OC: urban Southern California, (Rogge et al., 1996; Schauer et al., 1996) Total fine part. OC emitt. 30 t/d Meat cooking 21% Road abrasion 16% Open fires 14% Vehicles without cat. converter 12% Diesel vehicles 6.2% Lacquing 4.8% Forest fires 2.9% Vehicles without cat. converter 2.9% Tobacco smoke 2.7% 0 2 4 6 8 10 12 14 16 18 20 W -L.A .1982 Rubidoux1982 Gentwinter1998 entsummer1998 winter1998-2000 summer1998-99 c(µg/m³) res id OC res unid OC el unres OC non-ex non-el OC EC identified organics Los Angeles 12% 50% 4% 6% 0% 2% 6% 20% n-alkanes fatty acis DCAs, oxoMCAs diterpenoic acids lignin pyrolysis products PAHs other aromatic polycarboxylic acids identified organics Gent / winter 23% 53% 3% 9% 5% 6% 1% 0% identified organics Gent / summer 35% 44% 9% 8% 0%0%4% 0% (Schauer et al, 1996; Kubátova et al., 2001) Ozonolysis of alkenes: Terpenes (Griffin et al., 1999ff; Iinuma et al., 2004) C14-1-en: Smog chamber UCR (Ziemann et al., 2000): C14-1-en + O3 SOA Secondary particle sources: SOA formation