Presentation Slides for
Chapter 11, Part 2of
Fundamentals of Atmospheric Modeling 2nd Edition
Mark Z. JacobsonDepartment of Civil & Environmental Engineering
Stanford UniversityStanford, CA [email protected]
March 28, 2005
Alkene Reaction With Ozone
Ethene (11.89)
C C
H
H
H
H
+ O3
H2
C CH2
O O
O
Ethene Ethene molozonide
+37 %
Formaldehyde Criegee biradical
+63%
Formaldehyde Excited Criegee
biradical
C O
H
H
C O
H
H
C O
H
H
O
C O
H
H
O *
Alkene Reaction With Ozone
Criegee biradical reaction (11.90)
Excited criegee biradical decomposition (11.91)
FormaldehydeCriegee biradical
C O
H
H
C O
H
H
O
NO2
+ NO
Excited Criegee
biradical
C O
H
H
O *
C O
H
O*
60% CO + H2
O
21% CO2
+ H2
19%
+ O2
CO + OH + HO2
Excited formic
acid
H
Alkene Reaction With OzonePropene (11.92)
C CH2
H
H3
C
Propene
+ O3
CH CH2
O O
O
Propene molozonide
7.5 %
42.5%
18.5%
33.5%
Formaldehyde Methyl criegee biradical
+
Formaldehyde Excited methyl criegee
biradical
C O
H
H
C O
H3
C
H
O *
H3
C
C O
H3
C
H
C O
H3
C
H
Acetaldehyde
Acetaldehyde
Criegee biradical
Excited criegee
biradical
C O
H
H
O
C O
H
H
O *
+C O
H
H
C O
H3
C
H
O
+
+
Alkene Reaction With OzoneMethylcriegee biradical reaction (11.93)
Excited methylcriegee biradical decomposition (11.94)
Acetaldehyde
Methyl criegee
biradical
C O
H3
C
H
C O
H3
C
H
O
NO2
+ NO
Excited methyl criegee
biradical
C O
H3
C
H
O *
C O
H3
C
O*
16% CH4
+ CO2
64% CH3
+ CO + OH
20% CH3
O + HO2
+ CO
Excited acetic
acid
H
Alkene Reaction With NitrateEthene --> nitrated organic radicals (11.95)
Propene --> nitrated organic radicals (11.96)
C C
H
H
H
H
+ NO3
C CH2
H
H
O N
O
O
+ O2
C CH2
H
H
O N
O
O
O
Ethylperoxy nitrate
radical
Ethyl nitrate radical
C CH2
H
H
O N
O
O
O
Ethoxy nitrate radical
O
Ethene
NO2
+ NO
+ NO3
+ O2
NO2
+ NO
C C
H
H3
C
H
H
C CH2
H
H3
C
O N
O
O C CH2
H
H3
C
O N
O
O
O
Propylperoxy nitrate
radical
Propyl nitrate radical
C CH2
H
H3
C
O N
O
O
O
Propoxy nitrate radical
O
Propene
Aromatic Reaction With OHToluene oxidation (11.97)
CH3
H
OH
O
O
CH3
H
OH CH3
OH
H2
C O O
CH2
Toluene
o -Cresol
Benzylperoxy
radical
Toluene-hydroxyl-
radical adduct
Benzyl
radical
8%
92%
o -Hydroxytoluene
CH3
+ O2
+ O2
+ HO2
+ OH
H2
O
+ OH
Aromatic Reaction With OHBenzylperoxy radical reaction with NO (11.98)
CHH2
C
BenzaldehydeBenzoxy
radical
Benzyl nitrate
H2
C O O
Benzylperoxy
radical
H2
C O N
O
O
OO
NO2
+ NO + O2
HO2
+ NO
Aromatic Rxn With Hydroxyl Radical
Toluene-hydroxyl radical adduct reaction (11.99)
CH3
H
OH
Toluene-hydroxyl
radical adduct
CH3
H
OH
O
O
O
NO2
+ NO
Fate of CresolCresol --> methylphenylperoxy radical and nitrocresol (11.100)
CH3
OH
o -Cresol
CH3
O
Methylphenylperoxy
radical
O
+ OH, 2O2
2HO2
CH3
O
CH3
OH
m -Nitrocresol
+ NO2
N
O
Methylphenoxy
radical
+ OH
H2
O
O
Isoprene Reaction With OH(11.101)
Isoprene
H
C C
H2
CCH
2
CH3
CH C
C
H2
CH2
CH3
HO
O
O
CH C
C
H2
CH2
CH3
O
HO
O
H
C C
C
H2
C
H2
CH3
HOO
O
H
C C
H2
CC
H2
CH3
O
O
HO
H
C C
H2
CC
H2
CH3
OH
O
O
H
C C
C
H2
C
H2
CH3
O
OOH
(1)
16.4%
(2)
12.3%
(3)
12.3%
(4)
23.6%
(5)
21.2%
(6)
14.1%
Isoprene peroxy radicals
+ OH, O2
All six products convert NO to NO2
Fate of Isoprene ProductsMethacrolein production via second product (11.102)
Methylvinylketone production via fifth product (11.103)
CH C
C
H2
CH2
CH3
O
HO
O
H
C C
O CH2
CH3
Isoprene peroxy radical Methacrolein
+
Formaldehyde
C O
H
H
NO2
+ NO + O2
HO2
NO2
+ NO + O2
HO2
C O
H
H
H
C C
H2
CO
CH3
Isoprene peroxy radical Methylvinylketone
+
Formaldehyde
H
C C
H2
C C
H2
CH3
OH
O
O
Isoprene Reaction With Ozone(11.104)
Isoprene
+ O3H
C C
H2
C CH2
CH3
H
C C
OCH
2
CH3
Methylvinylketone
H
C C
H2
C O
CH3
H
C C
OCH
2
CH3
O
H
C C
H2
CO
CH3
O
+
+
+
+
Criegee biradical
Formaldehyde
Methacrolein
Ozonide product
Ozonide product Formaldehyde
Criegee biradical
C O
H
H
O
C O
H
H
O
C O
H
H
C O
H
H
Alcohol Reactions
Methanol oxidation by OH (36-h lifetime) (11.105)
H C
H
O
H
Methanol
H
H C O
H
H
H C
Formaldehyde
O
H
H
C O
H
H
Methoxy radical
85%
15%
+ OH
H2
O
+ O2
HO2
Alcohol Reactions
Ethanol oxidation by OH (10-h lifetime) (11.106)
C C
H
O
H
Ethanol
H C C O
H
H
C C
Acetaldehyde
O
H
H
C O
H
C
Ethoxy radical
5%
90%
H
H
H
H
H
H
H
H
H
H
H
H
5%
C C O
H
H
H
H
H
+ OH
H2
O
+ O2
HO2
Carbon Bond LumpingOrganic gases lumped into surrogate groups
PAR (paraffins) -- Single carbon atoms with a single-bond between them
OLE (olefins) -- Terminal carbon atom pair with a double-bond between the two atoms
ALD2 -- Non-terminal carbon atom pairs with a double bond attached to one of the carbons and terminal two-carbon carbonyl groups [C-C(=O)H]
KET -- Single carbon ketone groups (C=O)
TOL (toluene) -- 7-carbon aromatics
XYL (m-xylene) -- 8-carbon aromatics
ISOP (isoprene) -- Terpenes
UNR -- Unreactive
Carbon Bond Lumping
Table 11.7
H C
H
C
H
H
H
H
Ethane : 0.4 PAR + 1.6 UNR
n-Butane : 4 PAR H C
H
C
H
H
C
H
H
H
C
H
H
H
H3
C C
H
CH3
C
H2
C
CH3
CH3
CH32,2,4-Trimethylpentane : 8 PAR
Carbon Bond Lumping
Table 11.7
Trans-2-butene : 2 ALD2
Propene : 1 PAR + 1 OLE
Propionaldehyde : 1 PAR + 1 ALD2
H C
H
C
H
C
H
C
H
H
H
H
C CH2
H
H3
C
H
C CH2
OCH
3
Carbon Bond Lumping
Table 11.7
Benzaldehyde : 1 ALD2 + 5 UNR
1,2,3-Trimethylbenzene : 1 PAR + 1 XYL
CHO
CH2
H3
C
CH3
CH3
CH3
Ethylbenzene : 1 PAR + 1 TOL
Vertical Profile of Ozone
Fig. 11.30 2 4 6 8 10 12 14
0
10
20
30
40
Altitude (km)
O
3
(ppmv)
O
3
(molecules cm
-3
x 10
-12
)
Air (molecules cm
-3
x 5 x 10
-19
)
Alt
itud
e (k
m)
Column Abundance of Ozone
Fig. 11.4
Surface
Top of the atmosphere
293-Dobson Unit column of ozone= 293 x 2.7 x 10 16 molecules cm -2
= 2.93-mm column of air at 273 K and 1 atm
2.93-mm highcolumn of air
Stratosphereand above
Troposphere
Stratospheric ChemistryOzone mixing ratios
stratosphere ≈ 10 ppmv
free troposphere ≈ 40 ppbv
urban air ≈ 0.05 - 0.3 ppmv
Ozone production in the stratosphere
Oxygen photolysis (11.107-8)
O2
+ h ν λ < 175 nm(O1
D ) + O
O2
+ h ν 175 < λ < 245 nmO + O
Stratospheric Chemistry
Natural ozone formation (11.110)
(11.109)
Ozone photolysis (11.111)
(11.112)
O(
1
D ) O
M
O + O2
+ M O3
+ M
O3
+ h νO
2 + (O
1
D ) λ < 310 nm
O3
+ h ν O2
+ O λ > 310 nm
Natural Ozone Destruction by NOx
Nitrous oxide reaction: 10% of N2O destruction (11.113)
Nitrous oxide photolysis: 90% of N2O destruction (11.114)
N2
O + O(1
D )
64% 2NO
36% N2
+ O2
N2
O + h ν λ < 240 nmN2
+ (O1
D )
Natural Ozone Destruction by NOx
NO catalytically destroys ozone in upper stratosphere (11.115-7)
NO + O3
NO2
+ O2
NO2
+ O NO + O2
O + O3
2O2
Natural Ozone Destruction by HOx
Hydroxyl radical formation in stratosphere (11.115)
O(
1
D ) +
H2
O2OH
CH4
CH3
+ OH
H2
H + OH
Natural Ozone Destruction by HOx
OH catalytically destroys ozone in lower stratosphere (11.121-3)
OH + O3
HO2
+ O2
HO2
+ O3
OH + 2O2
2O3
3O2
Removal of HOx and NOx
(11.118)
(11.124)
(11.119)
Nitric acid and peroxynitric acid photolysis are slow
NO2
+ OH HNO3
M
M
HO2
+ NO2
HO2
NO2
HO2
+ OH H2
O + O2
Stratospheric Source of Water Vapor
(11.125)
CH4
+ OH CH3
+ H2
O
Changes in Monthly-Averaged Global Ozone From 1979-2001
Fig. 11.5
-10
-5
0
5
1980 1985 1990 1995 2000
Percent difference in global ozonefrom 1979 monthly average
Year
Mount Pinatubo
(June, 1991)
El Chichon
(April, 1982)
Per
cent
dif
fere
nce
in g
loba
l ozo
nefr
om 1
979
mon
thly
ave
rage
Variation with Latitude of October Zonally-Averaged Ozone in ‘79, ‘99, ‘00
Fig. 11.6
100
150
200
250
300
350
400
450
500
-90 -60 -30 0 30 60 90
Ozone (Dobson units)
Latitude (degrees)
October zonal average
1999
1979
2000Ozo
ne (
Dob
son
unit
s)
Variation with Altitude of CFCs and Other Chlorinated Compounds
Fig. 11.7
0 100 200 300 400 500 600
0
10
20
30
40
50
Altitude (km)
CFC-11
HCFC-22
CFC-12
CCl
4
(g)
Mixing ratio (pptv)
Tropopause
Alt
itud
e (k
m)
Variations With Altitude of CFCs and Other Chlorinated Compounds
Photolysis of chlorinated compounds above 20 km (11.126)
(11.127)
F C
Cl
Cl
Cl
+ h ν F C
Cl
Cl
+ Cl λ < 250 nm
F C
Cl
Cl
F
+ h ν F C
Cl
F
+ Cl λ < 230 nm
Natural Sources of Chlorine
Methyl chloride photolysis (11.130)
Methyl chloride scavenging by hydroxyl radical (11.128)
H C
H
Cl
H
+ h ν H C
H
H
+ Cl λ < 220 nm
H C
H
Cl
H
H C Cl
H
+ OH
H2
O
Chlorine Emission to Stratosphere
WMO (1994)
Chemical Percent emission to stratosphere
Anthropogenic sourcesCFC-12 (CF2Cl2) 28CFC-11 (CFCl3) 23Carbon tetrachloride (CCl4) 12Methyl chloroform(CH3CCl3)10CFC-113 (CFCl2CF2Cl) 6HCFC-22 (CF2ClH) 3
Natural sourcesMethyl chloride (CH3Cl) 15Hydrochloric acid (HCl) 3
Total 100
Ozone Destruction by Chlorine
Chlorine catalytic ozone destruction cycle (11.130)
(11.131)
(11.132)
Cl + O3
ClO + O2
ClO + O Cl + O2
O + O3
2O2
Only 1% of chlorine is typically active as Cl or ClO
Conversion of Active Chlorine to Reservoirs
Conversion of Cl and ClO (11.133)
(11.134)
CH4
HCl + CH3
HO2
HCl + O2
H2
HCl + H
H2
O2
HCl + HO2
Cl +
Cl O + NO2
Cl O
N
O
O
Chlorine
monoxide
Chlorine
nitrate
M
Conversion of Reservoirs to Active Chlorine
HCl reservoir leaks (11.135)
ClONO2 reservoir leaks
H + Clh ν
OH + Cl H2
O
O + Cl OH
+HCl
λ < 220 nm
Cl O
N
O
O
+ h ν + Cl O N
O
O
Chlorine
nitrate
Nitrate radical
λ < 400 nm
Ozone Destruction by Bromine
CH3Br = methyl bromide (produced biogenically in the oceans and anthropogenically as soil fumigant)
Photolysis of methyl above 20 km (11.137)
H C
H
Br
H
+ h ν H C
H
H
+ Br λ < 260 nm
Ozone Destruction by Bromine
Catalytic ozone destruction by bromine (11.138-40)
Br + O3
BrO + O2
BrO + O Br + O2
O + O3
2O2
Conversion of Active Bromine to Reservoirs
Conversion of Br and BrO (11.141)
(11.142)
HO2
HBr + O2
H2
O2
HBr + HO2
Br +
Br O + NO2
Br O
N
O
O
Bromine
monoxide
Bromine
nitrate
M
Conversion of Reservoirs to Active Bromine
HBr and BrONO2 reservoir leaks (11.143)
HBr + OH Br + H2
O
Br O
N
O
O
+ h ν +BrO N
O
O
Bromine
nitrate
Nitrate radical
λ < 390 nm
Change in Size of Antarctic Ozone Hole
Fig. 11.8
50
100
150
200
250
300
0
5
10
15
20
25
30
1980 1985 1990 1995 2000
Ozone minimum (DU)
Ozone-hole area (10
6
km
2
)
Year
Area of N. America
Area of Antarctic
continent
Ozo
ne m
inim
um (
Dob
son
unit
s)O
zone hole area (106 km
2)
Polar Stratospheric Cloud ReactionsType I Polar Stratospheric Clouds (PSCs)
nitric acid and water
temperature of formation < 195 K
diameter ≈ 0.01 - 3 m
number concentration ≈ 1 particle cm-3
Type II Polar Stratospheric Clouds
Water ice
temperature of formation < 187 K
diameter ≈ 1 - 100 m
number concentration ≈ 0.1 particle cm-3
Polar Stratospheric Cloud Reactions
Reactions on Polar Stratospheric Cloud Surfaces (11.145-9)
ClONO2
(g) + H2
O(a) HOCl(g) + HNO3
(a)
ClONO2
(g) + HCl (a) Cl2
(g) + HNO3
(a)
N2
O5
(g) + H2
O(a) 2HNO3
(a)
N2
O5
(g) + HCl(a) ClNO2
(g) + HNO3
(a)
HOCl (g) + HCl(a) Cl2
(g) + H2
O(a)
Surface Reaction Rates
First-order rate coefficient (s-1) (11.150)
Thermal speed of impinging gas (cm s-1) (11.151)
ks,q =14
v qγqa
v q =8kBTπM q
Reaction Probabilities
Table 11.9
Fractional loss of a species from the gas phase due to reaction with a particle surface. Accounts for diffusion of the gas to the surface and reaction with the surface.
Reaction ProbabilityReaction Type I PSC Type II PSC
ClONO2(g) + H2O(a) 0.001 0.3ClONO2(g) + HCl(a) 0.1 0.3N2O5(g) + H2O(a) 0.0003 0.01N2O5(g) + HCl(a) 0.003 0.03HOCl(g) + HCl(a) 0.1 0.3
Polar Ozone Destruction
Cl2 and HOCl photolysis in early spring (11.161-2)
Chlorine nitrite photolysis in early spring (11.163)
Cl2
+ h ν 2Cl λ < 450 nm
HOCl + h ν + Cl OH λ < 375 nm
ClNO2
+ h ν + Cl NO2
λ < 370 nm
Polar Ozone DestructionCatalytic ozone destruction by dimer mechanism (11.164-7)
Cl + O3
ClO + O2
2 x ( )
Cl2
O2
ClO + ClO
M
Cl2
O2
+ h ν λ < 360 nm + ClOO Cl
M
Cl + O2
ClOO
2O3
3O2
Polar Ozone DestructionA second catalytic cycle that involves bromine (11.169-72)
Cl + O3
ClO + O2
Br + O3
BrO + O2
BrO + ClO Br + Cl + O2
2O3
3O2
Conversion of Cl Reservoirs to Active Cl
Fig. 11.9
62%
HCl
37%
ClONO
2
1% Cl, ClO
Before PSC and photolysis
reactions
HCl
ClONO
2
Cl, ClO
After PSC and photolysis
reactions
Ozone Regeneration
Fig. 11.10
Change in globally-averaged ozone column abundance during two global model simulations in which all ozone was initially removed and chlorine was present and absent, respectively.
0
50
100
150
200
250
300
350
0 100 200 300 400
Avgerage global ozone column (Dobson units)
Day and date of simulation
10/1 1/7 4/17 7/26 11/4
No chlorine
With chlorine
Ave
rage
glo
bal o
zone
col
umn
(D
obso
n un
its)
Regeneration of Ozone Vertical ProfileTime-evolution of modeled profile of ozone (a) mixing ratio and (b)
number concentration at 34oN latitude, starting with zero ozone.
0 2 4 6 8 10
0
10
20
30
40
1 h
6 h
1 d
5 d
50 d
464 d
Ozone volume mixing ratio (ppmv)
Altitude (km)
Alt
itud
e (k
m)
Fig. 11.11
0 10 20 30 40 50 60
0
10
20
30
40
1 h
6 h
1 d
5 d
50 d
464 d
Ozone (10
11
molecules cm
-3
)
Altitude (km)
Alt
itud
e (k
m)
