C5 species
BIGALK C5H12 Lumped >C3 alkane
ALKO2 C5H11O2 Lumped alkyl peroxy radical
ALKOOH C5H11OOH Lumped alkyl hydroperoxide
ISOP C5H8 Isoprene
ISOPO2 e.g., HOCH2C(OO)CH3CHCH2 Isoprene peroxy radical
ISOPOOH e.g., HOCH2C(OOH)CH3CHCH2 Isoprene hydroperoxide
HYDRALD e.g., HOCH2CCH3CHCHO Lumped unsaturated
Hydroxycarbonyl
XO2 e.g., HOCH2C(OO)CH3CH(OH)CHO HYDRALD peroxy radical
XOOH e.g., HOCH2C(OOH)CH3CH(OH)CHO HYDRALD hydroperoxide
BIGALD C5H6O2 Unsaturated dicarbonyl
ISOPNO3 e.g., CH2CHCCH3OOCH2ONO2 Peroxy radical from NO3 + ISOP
ONITR e.g., CH2CCH3CHONO2CH2OH Lumped isoprene nitrate
C7 species
TOLUENE C6H5(CH3) Lumped aromatic hydrocarbon
CRESOL e.g., C6H4(CH3)(OH) Phenols and cresols
TOLO2 C6H5(CH3OO) Aromatic peroxy radical
TOLOOH C6H5(CH3OOH) Aromatic hydroperoxide
XO2 C7H7O2 CRESOL peroxy radical
C10 species
TERPENE C10H16 Lumped monoterpenes, as α-pinene
TERPO2 C10H16(OH)(OO) Terpene peroxy radical
TERPOOH C10H16(OH)(OOH) Terpene hydroperoxide
D.1.3 Bulk Aerosols
Mechanism symbol Chemical formula Name
SO4 S(VI) ≡ SO42– + HSO4– + H2SO4(aq) Sulfate
NH4 NH4+ Ammonium
NO3A NO3– Ammonium nitrate
SOA Secondary organic aerosol
OC Organic carbon
EC Elemental carbon
D.2 Photolysis
The following table lists photolysis reactions of importance for the troposphere and the stratosphere. The photolysis frequency (often called J-value) for a given molecule A is calculated as a function of altitude z and solar zenith angle χ by spectral integration over all wavelengths λ of the product of (1) the solar actinic flux density qλ(λ;z,χ); (2) the absorption cross-section σA(λ) of the molecule; and (3) the quantum efficiency εA(λ):
The actinic flux at a given altitude and for a given solar zenith angle is calculated with a radiative transfer model; see Chapter 5. The photolysis products reported in the table are the ones used in the chemical mechanism above and assume in some cases fast reactions of the immediate photolysis products; for example, CCl4 + hν → CCl3 + Cl is given as CCl4 + hν → 4Cl. Values of the photolysis frequency J for different molecules, calculated by the TUV-5.1 model (Madronich, personal communication), are provided at sea level and at 25 km altitude for the following conditions: ozone column 300 DU, solar zenith angle 30°, surface albedo 5%, no clouds, no aerosol effects. They can be viewed as typical clear-sky daytime values. Some of the photolysis processes listed here are of importance for the upper stratosphere but negligible at lower altitudes, in which case the photolysis frequency is given as “0.0.” The symbol X e-Y stands for X × 10–Y.
D.2.1 Inorganic Species
Reaction J at sea level [s–1] J at 25 km [s–1]
Oxygen species
O2 + hν → 2O(3P) 0.0 1.5e-11
O3 + hν → O(1D) + O2 3.2e-05 1.3e-04
O3 + hν → O(3P) + O2 4.1e-04 4.9e-04
Hydrogen species
H2O + hν → OH + H 0.0 0.0
H2O + hν → H2 + O(1D) 0.0 0.0
H2O2 + hν → 2OH 7.4e-06 1.3e-05
Nitrogen species
N2O + hν → O(1D) + N2 0.0 2.8e-08
NO + hν → N + O 0.0 0.0
NO2 + hν → NO + O 9.3e-03 1.2e-02
N2O5 + hν → NO2 + NO3 4.3e-05 7.4e-05
HONO + hν → NO + OH 1.5e-03 2.2e-03
HNO3 + hν → NO2 + OH 6.0e-07 6.3e-06
NO3 + hν → NO2 + O 1.7e-01 1.8e-01
NO3 + hν → NO + O2 2.2e-02 2.4e-02
HO2NO2 + hν → OH + NO3 (20%) or NO2 + HO2 (80%) 6.6e-06 2.3e-05
Halogen species
Cl2 + hν → 2Cl 2.3e-03 3.6e-03
OClO + hν → O + ClO 8.2e-02 1.2e-01
ClOOCl + hν → 2 Cl 1.7e-03 2.9e-03
HOCl + hν → OH + Cl 2.7e-04 4.5e-04
HCl + hν → H + Cl 0.0 2.4e-08
ClONO2 + hν → Cl + NO3 3.9e-05 5.7e-05
ClONO2 + hν → ClO + NO2 7.7e-06 1.6e-05
BrCl + hν → Br + Cl 1.1e-02 1.4e-02
BrO + hν → Br + O 3.6e-02 6.0e-02
HOBr + hν → Br + OH 2.2e-03 3.1e-03
BrONO2 + hν → Br + NO3 4.0e-04 5.9e-04
BrONO2 + hν → BrO + NO2 9.8e-04 1.5e-03
CCl4 + hν → 4Cl 0.0 1.1e-06
CFCl3 + hν → 3Cl 0.0 5.9e-07
CF2Cl2 + hν → 2Cl 0.0 6.9e-08
CCl2FCClF2 + hν → 3Cl 0.0 9.6e-08
CF3Br + hv → Br 0.0 2.6e-07
CF2ClBr + hv → Br + Cl 0.0 2.5e-06
CH3Cl + hν → Cl + CH3O2 0.0 1.5e-08
CH3CCl3 + hv → 3Cl 0.0 8.8e-07
CHF2Cl + hν → Cl 0.0 1.7e-10
CH3Br + hv → Br + CH3O2 0.0 1.5e-06
D.2.2 Organic Species (Chemical Mechanism)
CH3OOH + hv → CH2O + H + OH
CH2O + hv → CO + 2H
CH2O + hv → CO + H2
CH4 + hv → H + CH3O2
CH4 + hv → 1.44 H2 + 0.18CH2O + 0.18O + 0.66 O H + 0.44 CO2 + 0.38 CO + 0.05 H2O
CH3 CHO + hv → CH3O2+CO + HO2
POOH + hv → CH3CHO + CH2O + HO2 + OH
CH3COOOH + hv → CH3O2+OH + CO2
PAN + hv → 0.6 CH3CO3 + 0.6 NO2 + 0.4 CH3O2 + 0.4 NO3 + 0.4 CO2
MPAN + hv → MCO3+NO2
MACR + hv → 0.67 HO2 + 0.33 MCO3 + 0.67 CH2O + 0.67 CH3CO3 + 0.33 OH + 0.67 CO
MVK + hv → 0.7 C3H6 + 0.7 CO + 0.3 CH3O2 + 0.3 CH3CO3
C2H5OOH + hv → CH3CHO + HO2 + OH
C3H7OOH + hv → 0.82 CH3COCH3+OH + HO2
ROOH + hv → CH3CO3+CH2O + OH
CH3COCH3 + hv → CH3CO3+CH3O2
CH3COCHO + hv → CH3CO3+CO + HO2
XOOH + hv → OH
ONITR + hv → HO2+CO + NO2+CH2O
ISOPOOH + hv → 0.402 MVK + 0.288 MACR + 0.69 CH2O + HO2
HYAC + hv → CH3CO3+HO2+CH2O
GLYALD + hv → 2 HO2+CO + CH2O
MEK + hv → CH3CO3+C2H5O2
BIGALD + hv → 0.45 CO + 0.13 GLYOXAL + 0.56 HO2 + 0.13 CH3CO3 + 0.18 CH3COCHOGLYOXAL + hv → 2 CO + 2 HO2
C5H11OOH + hv → 0.4 CH3CHO + 0.1 CH2O + 0.25 CH3COCH3 + 0.9 HO2 + 0.8 MEK + OH
MEKOOH + hv → OH + CH3CO3+CH3CHO
TOLOOH + hv → OH + 0.45 GLYOXAL + 0.45 CH3COCHO + 0.9 BIGALD
TERPOOH + hv → OH + 0.1 CH3COCH3+HO2 + MVK + MACR
D.2.3 Organic Species (Photolysis Frequencies)
Reaction J at sea level [s–1] J at 25 km [s–1]
CH3OOH + hv → CH3O + OH 5.4e-06 1.1e-05
CH2O + hv → HCO + H 3.3e-05 6.5e-05
CH2O + hv → CO + H2 3.8e-05 1.1e-04
CH4 + hv → products 0.0 0.0
CH3CHO + hv → CH3 + HCO 4.7e-06 5.4e-05
CH3COOOH + hv → CH3O2 + OH + CO2 7.4e-07 1.9e-06
PAN + hv → CH3CO3 + NO2 4.8e-07 4.1e-06
PAN + hv → CH3 + CO2 + NO3 2.1e-07 1.7e-06
MACR + hv → products 5.0e-06 8.1e-06
MVK + hv → products 4.1e-06 3.5e-05
C2H5OOH + hv → CH3CH2O + OH 5.4e-06 1.1e-05
HOCH2OOH + hv → HOCH2O + OH 4.5e-06 9.4e-06
C3H7OOH + hv → CH3CH(O)CH3 + OH 5.4e-06 1.1e-05
CH3COCH3 + hv → CH3CO + CH3 8.5e-07 1.0e-05
CH3COCHO + hv → CH3CO + HCO 1.4e-04 5.6e-04
CH3ONO2 + hv → NO2 + CH3O 8.5e-07 1.5e-05
HYAC + hv → CH3CO + CH2(OH) 9.1e-07 2.5e-06
HYAC + hv → CH2(OH)CO + CH3 9.1e-07 2.5e-06
GLYALD + hv → CH2OH+HCO 9.1e-06 2.5e-05
GLYALD + hv → CH3OH+CO 1.1e-06 3.1e-06
GLYALD + hv → CH2CHO+OH 7.7e-07 2.1e-06
MEK + hv → CH3CO + C2H5 6.1e-06 4.0e-05
C2H5CHO + hv → C2H5 + HCO 1.7e-05 8.
8e-05
GLYOXAL + hv → HCO + HCO 7.4e-05 1.1e-04
GLYOXAL + hv → H2 + 2 CO 1.6e-05 3.3e-05
GLYOXAL + hv → CH2O + CO 2.9e-05 5.6e-05
D.3 Gas-Phase Reactions
The following table lists the rate constants k for gas-phase reactions. In the case of two-body (bimolecular) reactions, written as X + Y → products, the temperature-dependent rate constant [cm3 s–1] is generally expressed as
where A [cm3 s–1] is the Arrhenius factor, B [K] the activation temperature equal to the activation energy Ea [J mol–1] divided by the gas constant R=8.3144 J K–1 mol–1, and T is the temperature [K]. The table also includes single-body (unimolecular) thermolysis reactions, written as X → products, with rate coefficients expressed in [s–1].
In the case of three-body (termolecular) reactions, written as X + Y + M → XY + M where M is an inert third body (typically N2 or O2), the pressure- and temperature-dependent coefficients k [cm3 s–1] are derived by the Troe formula
Here, [M] denotes the air number density [cm–3] and f = 0.6 if it is not otherwise specified in the tables below. The temperature dependence of coefficients k0 (low-pressure limit) and k∞ (high-pressure limit) is often expressed as C(T/300)–n where C and n are constants. For these types of reactions, the table provides the values of k0 [cm6 s–2] and k∞ [cm3 s–1]; only k0 is given when the low-pressure limit dominates throughout the atmosphere. The rate of the reverse reaction, XY + M → X + Y + M, is given as the rate of the forward reaction times an equilibrium constant.
D.3.1 Oxygen–Hydrogen–Nitrogen Chemistry
Oxygen reactions Rate constant
Two-body reactions
O + O3 → 2O2 8.0e-12 × exp(–2060/T)
O(1D) + N2 → O + N2 2.1e-11 × exp(115/T)
O(1D) + O2 → O + O2 3.2e-11 × exp(70/T)
O(1D) + H2O → 2OH 2.2e-10
O(1D) + H2 → HO2 + OH 1.1e-10
O(1D) + N2O → N2 + O2 4.9e-11
O(1D) + N2O → 2NO 6.7e-11
O(1D) + CH4 → CH3O2 + OH 1.1e-10
O(1D) + CH4 → CH2O + H + HO2 3.0e-11
O(1D) + CH4 → CH2O + H2 7.5e-12
O(1D) + HCN → OH 7.7e-11 × exp(100/T)
Three-body reactions
O + O + M → O2 + M k0 = 2.8e-34 × exp(720/T)
O + O2 + M → O3 + M k0 = 6.0e-34 × (T/300)–2.4
Hydrogen oxide reactions Rate constant
Two-body reactions
H + O3 → OH + O2 1.4e-10 × exp(–470/T)
H + HO2 → 2OH 7.2e-11
H + HO2 → H2 + O2 6.9e-12
H + HO2 → H2O + O 1.6e-12
OH + O → H + O2 2.2e-11 × exp(120/T)
OH + O3 → HO2 + O2 1.7e-12 × exp(–940/T)
OH + HO2 → H2O + O2 4.8e-11 × exp(250/T)
OH + OH → H2O + O 1.8e-12
OH + H2 → H2O + H 2.8e-12 × exp(–1800/T)
OH + H2O2 → H2O + HO2 1.8e-12
HO2 + O → OH + O2 3.0e-11 × exp(200/T)
HO2 + O3 → OH + 2O2 1.0e-14 × exp(–490/T)
HO2 + HO2 → H2O2 + O2 (kA+kB) + 1.4e-21 × [H2O] × exp(2200/T)
kA = 3.0e-13 × exp(460/T)
kB = 2.1e-33 × [M] × exp(920/T)
H2O2 + O → OH + HO2 1.4e-12 × exp(–2000/T)
Three-body reactions
H + O2 + M → HO2 + M k0 = 4.4e-32 × (T/300)–1.3
k∞ = 4.7e-11 × (T/300)–0.2
OH + OH + M → H2O2 + M k0 = 6.9e-31 × (T/300)–1.0
k∞ = 2.6e-11
Nitrogen oxide reactions Rate constant
Two-body reactions
N + O2 → NO + O 1.5e-11 × exp(–3600/T)
N + NO → N2 + O 2.1e-11 × exp(100/T)
N + NO2 → N2O + O 5.8e-12 × exp(220/T)
NO + HO2 → NO2 + OH 3.5e-12 × exp(250/T)
NO + O3 → NO2 + O2 3.0e-12 × exp(–1500/T)
NO2 + O → NO + O2 5.1e-12 × exp(210/T)
NO2 + O3 → NO3 + O2 1.2e-13 × exp(–2450/T)
HNO3 + OH → NO3 + H2O k = k0 + k3[M]/(1 + k3[M]/k2)with
k0 = 2.4e-14 × exp(460/T)
k2 = 2.7e-17 × exp(2199/T)
k3 = 6.5e-34 × exp(1335/T)
NO3 + NO → 2NO2 1.5e-11 × exp(170/T)
NO3 + O → NO2 + O2 1.0e-11
NO3 + OH → HO2 + NO2 2.2e-11
NO3 + HO2 → OH + NO2 + O2 3.5e-12
HO2NO2 + OH → H2O + NO2 + O2 1.3e-12 × exp(380/T)
Three-body and reverse reactions
NO + O + M → NO2 + M k0 = 9.0e-32 × (T/300)–1.5
k∞ = 3.0e-11
NO2 + O + M → NO3 + M k0 = 2.5e-31 × (T/300)–1.8
k∞ = 2.2e-11 × (T/300)–0.7
NO2 + NO3 + M → N2O5 + M k0 = 2.0e-30 × (T/300)–4.4
k∞ = 1.4e-12 × (T/300)–0.7
N2O5 + M → NO2 +NO3 + M kNO2+NO3 × 3.7e + 26 × exp(–11000/T)
NO2 + HO2 + M → HO2NO2 + M k0 = 2.0e-31 × (T/300)–3.4
k∞ = 2.9e-12 × (T/300)–1.1
HO2NO2 + M → HO2 + NO2 + M kHO2+NO2 × 4.8e + 26 × exp(–10900/T)
NO2 + OH + M → HNO3 +M k0 = 1.8e-30 × (T/300)–3.0
k∞ = 2.8e-11
D.3.2 Organic Chemistry
C-1 degradation (methane CH4) Rate constant
Two-body reactions
CH4 + OH → CH3O2 + H2O 2.5e-12 × exp(–1775/T)
CH3O2 + NO → CH2O + NO2 + HO2 2.8e-12 × exp(300/T)
CH3O2 + HO2 → CH3OOH + O2 4.1e-13 × exp(750/T)
CH3OOH + OH → CH3O2 + H2O 3.8e-12 × exp(200/T)
CH2O + NO3 → CO + HO2 + HNO3 6.0e-13 × exp(–2058/T)
CH2O + OH → CO + H2O + H 5.5e-12 × exp(125/T)
CH2O + O → HO2 + OH + CO 3.4e-11 × exp(–1600/T)
CH3O2 + CH3O2 → 2CH2O + 2HO2 5.0e-13 × exp(–424/T)
CH3O2 + CH3O2 → CH2O + CH3OH 1.9e-14 × exp(706/T)
CH3OH + OH → HO2 + CH2O 2.9e-12 × exp(–345/T)
CH3OOH + OH → 0.7 CH3O2 +0.3 OH +0.3 CH2O + H2O 3.8e-12 × exp(200/T)
CH2O + HO2 → HOCH2OO 9.7e-15 × exp(625/T)
HOCH2OO → CH2O + HO2 2.4e+12 × exp(–7000/T)
HOCH2OO + NO → HCOOH + NO2 + HO2 2.6e-12 × exp(265/T)
HOCH2OO + HO2 → HCOOH 7.5e-13 × exp(700/T)
HCOOH + OH → HO2 + CO2 + H2O 4.5e-13
CO + OH → CO2 + H 1.5e-13 × (1.0 + 6.e-7 p)
(p = air pressure in Pa)
C-2 degradation (acetylene C2H2, ethylene C2H4 and ethane C2H6 ) Rate constant
C2H2 + OH + M → 0.65 GLYOXAL + 0.65 OH + 0.35 HCOOH + 0.35 HO2 + 0.35 CO + M k0 = 5.5e-30
k∞ = 8.3e-13 × (T/300)2.0
GLYOXAL + OH → HO2 + CO + CO2 1.1e-11
C2H4 + O3 → CH2O + 0.12 HO2 + 0.5 CO + 0.12 OH + 0.5 HCOOH 1.2e-14 × exp(–2630/T)
C2H4 + OH + M → 0.75 EO2 + 0.5 CH2O + 0.25 HO2 + M k0 = 1.0e-28 × (T/300)–0.8
k∞ = 8.8e-12
EO2 + NO → EO + NO2 4.2e-12 × exp(180/T)
EO + O2 → GLYALD + HO2 1.0e-14
EO → 2 CH2O + HO2 1.6e+11 × exp(–4150/T)
GLYALD + OH → HO2 + 0.2 GLYOXAL + 0.8 CH2O + 0.8 CO2 1.0e-11
C2H6 + OH → C2H5O2 + H2O 8.7e-12 × exp(–1070/T)
C2H5O2 + NO → CH3CHO + HO2 + NO2 2.6e-12 × exp(365/T)
C2H5O2 + HO2 → C2H5OOH + O2 7.5e-13 × exp(700/T)
C2H5O2 + CH3O2 → 0.7 CH2O + 0.8 CH3CHO + HO2 + 0.3 CH3OH + 0.2 C2H5OH 2.0e-13
C2H5O2 + C2H5O2 → 1.6 CH3CHO + 1.2 HO2 + 0.4 C2H5OH 6.8e-14
C2H5OOH + OH → 0.5 C2H5O2 + 0.5 CH3CHO + 0.5 OH 3.8e-12 × exp(200/T)
CH3CHO + OH → CH3CO3 + H2O 5.6e-12 × exp(270/T)
CH3CHO + NO3 → CH3CO3 + HNO3 1.4e-12 × exp(–1900/T)
CH3CO3 + NO → CH3O2 + CO2 + NO2 8.1e-12 × exp(270/T)
CH3CO3 + HO2 → 0.75 CH3COOOH + 0.25 CH3COOH + 0.25 O3 4.3e-13 × exp(1040/T)
CH3CO3 + CH3O2 → 0.9 CH3O2 + CH2O + 0.9 HO2 + 0.9 CO2 + 0.1 CH3COOH 2.0e-12 × exp(500/T)
CH3CO3 + CH3CO3 → 2 CH3O2 + 2 CO2 2.5
e-12 × exp(500/T)
CH3COOH + OH → CH3O2 + CO2 + H2O 7.0e-13
CH3COOOH + OH → 0.5 CH3CO3 + 0.5 CH2O + 0.5 CO2 + H2O 1.0e-12
C2H5OH + OH → HO2 + CH3CHO 6.9e-12 × exp(–230/T)
CH3CO3 + NO2 + M → PAN + M k0 = 8.5e-29 × (T/300)–6.5
k∞= 1.1e-11 × (T/300)–1
PAN + M → CH3CO3 +NO2 + M kCH3CO3+NO2 × 1.1e+28 × exp(–14000/T)
PAN + OH → CH2O + NO3 4.0e-14
C-3 degradation (propene C3H6 and propane C3H8) Rate constant
C3H6 + OH + M → PO2 + M k0 = 8.0e-27 × (T/300)–3.5
k∞ = 3.0e-11
f = 0.5
C3H6 + O3 → 0.54 CH2O + 0.19 HO2 + 0.33 OH + 0.08 CH4 + 0.56 CO + 0.5 CH3CHO + 0.31 CH3O2 + 0.25 CH3COOH 6.5e-15 × exp(–1900/T)
C3H6 + NO3 → ONIT 4.6e-13 × exp(–1156/T)
PO2 + NO → CH3CHO + CH2O + HO2 + NO2 4.2e-12 × exp(180/T)
PO2 + HO2 → POOH + O2 7.5e-13 × exp(700/T)
POOH + OH → 0.5 PO2 + 0.5 OH + 0.5 HYAC + H2O 3.8e-12 × exp(200/T)
ROOH + OH → RO2 + H2O 3.8e-12 × exp(200/T)
HYAC + OH → CH3COCHO + HO2 3.0e-12
CH3COCHO + OH → CH3CO3 + CO + H2O 8.4e-13 × exp(830/T)
CH3COCHO + NO3 → HNO3 + CO + CH3CO3 1.4e-12 × exp(–1860/T)
ONIT + OH → NO2 + CH3COCHO 6.8e-13
C3H8 + OH → C3H7O2 + H2O 1.0e-11 × exp(–665/T)
C3H7O2 + NO → 0.82 CH3COCH3 + NO2 + HO2 + 0.27 CH3CHO 4.2e-12 × exp(180/T)
C3H7O2 + HO2 → C3H7OOH + O2 7.5e-13 × exp(700/T)
C3H7O2 + CH3O2 → CH2O + HO2 + 0.82 CH3COCH3 3.8e-13 × exp(–40/T)
C3H7OOH + OH → H2O + C3H7O2 3.8e-12 × exp(200/T)
CH3COCH3 + OH → RO2 + H2O 3.8e-11 × exp(–2000/T)+1.3e-13
RO2 + NO → CH3CO3 + CH2O + NO2 2.9e-12 × exp(300/T)
RO2 + HO2 → ROOH + O2 8.6e-13 × exp(700/T)
RO2 + CH3O2 → 0.3 CH3CO3 + 0.8 CH2O + 0.3 HO2 + 0.2 HYAC + 0.5 CH3COCHO + 0.5 CH3OH 7.1e-13 × exp(500/T)
C-4 degradation (lumped species BIGENE represented by butene C4H8) Rate constant
BIGENE + OH → ENEO2 5.4e-11
ENEO2 + NO → CH3CHO + 0.5 CH2O + 0.5 CH3COCH3 + HO2 + NO2 4.2e-12 × exp(180/T)
C-5 degradation (isoprene C5H8 and lumped species BIGALK represented by pentane C5H12) Rate constant
BIGALK + OH → ALKO2 3.5e-12
ALKO2 + NO → 0.4 CH3CHO + 0.1 CH2O + 0.25 CH3COCH3 + 0.9 HO2 + 0.8 MEK + 0.9 NO2 + 0.1 ONIT 4.2e-12 × exp(180/T)
Modeling of Atmospheric Chemistry Page 67