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
<Mn+>
(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