Presentation Slides
for
Chapter 11, Part 2
of
Fundamentals of Atmospheric Modeling
2nd Edition
Mark Z. Jacobson
Department of Civil & Environmental Engineering
Stanford University
Stanford, CA 94305-4020
jacobson@stanford.edu
March 28, 2005
Alkene Reaction With Ozone
Ethene
(11.89)
H
C
37%
H
+ O3
C
H
H
O
O
H2 C
Ethene
O +
H
H
C
H
O
CH2
Ethene molozonide
Formaldehyde
H
C O +
63%
H
Formaldehyde
O
C O
H
Criegee biradical
H
O*
C O
H
Excited Criegee
biradical
Alkene Reaction With Ozone
Criegee biradical reaction
(11.90)
+ NO
H
C
O
O
H
C
H
Criegee biradical
NO2
O
H
Formaldehyde
Excited criegee biradical decomposition
(11.91)
60% CO + H2O
H
C
O
H
O*
H
Excited Criegee
biradical
C
H
O
21% CO2 + H2
O*
Excited formic
acid
+ O2
19%
CO + OH + HO2
Alkene Reaction With Ozone
Propene
(11.92)
H
H3C
C O +
7.5%
C O
H
O
H
Formaldehyde M ethyl criegee biradical
H
42.5%
O
H
C
O
CH2 + O3
H3C
Propene
H3C
O
CH CH2
Propene molozonide
H3C
C
O
+
H
C
O
O*
H
Excited methyl criegee
biradical
H3C
H
O
+
C O
C O
18.5%
H
H
Acetaldehyde
Criegee biradical
Formaldehyde
H3C
33.5%
H
C
O +
H
Acetaldehyde
C
O
O*
H
Excited criegee
biradical
Alkene Reaction With Ozone
Methylcriegee biradical reaction
+ NO
H3C
C
O
O
(11.93)
H3C
C
H
NO2
Methyl criegee
biradical
O
H
Acetaldehyde
Excited methylcriegee biradical decomposition
(11.94)
16% CH4 + CO2
H3C
C
O
H3C
O*
H
Excited methyl criegee
biradical
C
H
O
O*
Excited acetic
acid
64% CH3 + CO + OH
20% CH3O + HO2 + CO
Alkene Reaction With Nitrate
Ethene --> nitrated organic radicals
H
H + NO3
C
C
H
O
C
H
O
O
H
+ O2
N
CH2
O
H
Ethene
(11.95)
H
O
O
O
C
CH2
N
H
O
H
Ethylperoxy nitrate
radical
Ethyl nitrate radical
O
+ NO
NO2
H
C
H3C
C
H + NO
3H
H
Propene
O N
C
CH2
H3C
Propyl nitrate radical
C
CH2
N
O
Ethoxy nitrate radical
(11.96)
O
+ O2 H O
O
C
H3C
O
H
Propene --> nitrated organic radicals
O
O
O
O
CH2
N
+ NO
H
O
Propylperoxy nitrate
radical
O
C
NO2
O
O N
CH2
O
H3C
Propoxy nitrate radical
Aromatic Reaction With OH
Toluene oxidation
(11.97)
CH2
+ O2
+ OH
H2 C
O
O
Benzylperoxy
radical
8%
H2O
Benzyl
radical
O
O
CH3
CH3
H
OH
CH3
+ OH
Toluene
92%
H
OH
+ O2
Toluene-hydroxylradical adduct
CH3
OH
o-Hydroxytoluene
+ HO2
o-Cresol
Aromatic Reaction With OH
Benzylperoxy radical reaction with NO
(11.98)
H2C O
H2C O
O
O
+ NO
+ O2
NO2
HO2
+ NO
Benzoxy
radical
H2C O
Benzaldehyde
N
O
O
Benzylperoxy
radical
Benzyl nitrate
CH
Aromatic Rxn With Hydroxyl Radical
Toluene-hydroxyl radical adduct reaction
O
O
CH3
+ NO
H
O
CH3
H
OH
OH
NO2
Toluene-hydroxyl
radical adduct
(11.99)
Fate of Cresol
Cresol --> methylphenylperoxy radical and nitrocresol (11.100)
CH3
+ OH, 2O2
CH3
O
O
2HO2
Methylphenylperoxy
radical
OH
CH3
CH3
o-Cresol
+ OH
O
+ NO2
OH
N
H2O
Methylphenoxy
radical
m-Nitrocresol
O
O
Isoprene Reaction With OH
(11.101)
HO
(1) O
16.4%
H
C
H2C
CH3 + OH, O
2
C
CH2
Isoprene
O
O
(2)
12.3% HO
CH3
CH C
C
H2
CH2
HO CH
3
H
C C
(4)
O
H
C
2
C
O
23.6%
H2
O
O
CH3
CH C
C
H2
(3)
12.3% HO C
H2
CH3
C
O O
C
H2
H
C
(6)
14.1%
O
Isoprene peroxy radicals
All six products convert NO to NO2
O
CH3
C
H2C
CH2
H
C
O
(5)
21.2%
OH
C
H2
H
C
C
H2
CH3
C
C
H2
OH
Fate of Isoprene Products
Methacrolein production via second product
O
HO
O
CH3
+ NO
+ O2
H
C
CH C
C
H2
CH2
CH3
C
O
NO2
H
+
CH2
HO2
Isoprene peroxy radical
(11.102)
C
O
H
Formaldehyde
M ethacrolein
Methylvinylketone production via fifth product
(11.103)
O
H
C
H2C
O
CH3
C
C
H2
+ NO
+ O2
OH
Isoprene peroxy radical
H
C
H2C
NO2
HO2
CH3
C
H
+
O
M ethylvinylketone
C O
H
Formaldehyde
Isoprene Reaction With Ozone
(11.104)
H
C
CH3
C
H2C
O
H
CH3
H
C
H2C
CH3
C
+ O3
H
+
O
CH2
H
C
CH3
C
O O
Ozonide product
H
C
O O
C
O
H
H
C
Ozonide product
O
Formaldehyde
CH3
CH2
O
H
+
H2C
C
H
Criegee biradical
Methacrolein
CH2
Isoprene
C
O
H
Criegee biradical
Methylvinylketone
H
C
C
+
O
+
C
O
H
Formaldehyde
Alcohol Reactions
Methanol oxidation by OH (36-h lifetime)
85% H
H
C
O
H
M ethanol
O
H
+ OH
H
C
H
H
H
H2O
15% H
C O
H
M ethoxy radical
(11.105)
+ O2
O
H
HO2
C
H
Formaldehyde
Alcohol Reactions
Ethanol oxidation by OH (10-h lifetime)
(11.106)
H
5% H
H
H
H
C
C
H
H
Ethanol
C
C
H
H
O
H
O
H
+ OH
90% H
H2O
5% H
C
C O
H
H
H
H
C
C
H
H
H
H
H
HO2
O
Ethoxy radical
H
+ O2
C
O
C
H
H
Acetaldehyde
Carbon Bond Lumping
Organic 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
Ethane : 0.4 PAR + 1.6 UNR
n-Butane : 4 PAR
H
H
C
C H
H
H
H
H
H
H
C
C
C
C H
H
H
H
H
H
H
CH3
2,2,4-Trimethylpentane : 8 PAR
H3C
C
H
CH3
C C CH3
H2
CH3
Table 11.7
Carbon Bond Lumping
H
Trans-2-butene : 2 ALD2
H
C
C
H
H
H
H
C
C H
H
H
Propene : 1 PAR + 1 OLE
C
CH2
H3C
H
C
Propionaldehyde : 1 PAR + 1 ALD2
O
CH2
CH3
Table 11.7
Carbon Bond Lumping
O
CH
Benzaldehyde : 1 ALD2 + 5 UNR
H3C
CH2
Ethylbenzene : 1 PAR + 1 TOL
CH3
CH3
1,2,3-Trimethylbenzene : 1 PAR + 1 XYL
CH3
Table 11.7
Vertical Profile of Ozone
O (ppmv)
Altitude (km)
Altitude (km)
40
3
30
20
O (molecules cm
3
-3
x 10
-12
Air (molecules cm
-19
x 5 x 10 )
10
)
-3
0
0
2
4
6
8 10 12 14
Fig. 11.3
Column Abundance of Ozone
Fig. 11.4
Stratospheric Chemistry
Ozone 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
O(1D) + O
 < 175 nm
O2 + h
O + O
 < 245 nm
Stratospheric Chemistry
Natural ozone formation
(11.110)
M
O(1D)
O
(11.109)
O + O2 + M
Ozone photolysis
O3 + h
O3 + M
(11.111)
O2 + O(1D)
 < 310 nm
(11.112)
O3 + h
O2 + O
 > 310 nm
Natural Ozone Destruction by NOx
Nitrous oxide reaction: 10% of N2O destruction
(11.113)
64% 2NO
N2O + O(1D)
36% N2 + O2
Nitrous oxide photolysis: 90% of N2O destruction
N2O + h
N2 + O(1D)
(11.114)
 < 240 nm
Natural Ozone Destruction by NOx
NO catalytically destroys ozone in upper stratosphere (11.115-7)
NO + O3
NO2 + O
O + O3
NO2 + O2
NO + O2
2O2
Natural Ozone Destruction by HOx
Hydroxyl radical formation in stratosphere
O(1D) +
(11.115)
H2O
2OH
CH4
CH3 + OH
H2
H + OH
Natural Ozone Destruction by HOx
OH catalytically destroys ozone in lower stratosphere (11.121-3)
OH + O3
HO2 + O3
2O3
HO2 + O2
OH + 2O2
3O2
Removal of HOx and NOx
NO2 + OH
HO2 + NO2
HO2 + OH
M
M
HNO3
(11.118)
HO2NO2
(11.119)
H2O + O2
(11.124)
Nitric acid and peroxynitric acid photolysis are slow
Stratospheric Source of Water Vapor
(11.125)
CH4 + OH
CH3 + H2O
Percent difference in global ozone
from 1979 monthly average
from 1979 monthly average
Changes in Monthly-Averaged Global
Ozone From 1979-2001
5
El Chichon
(April, 1982)
M ount Pinatubo
(June, 1991)
0
-5
-10
1980
1985
1990
Year
1995
2000
Fig. 11.5
Ozone (Dobson units)
Ozone (Dobson units)
Variation with Latitude of October
Zonally-Averaged Ozone in ‘79, ‘99, ‘00
500
450
400
350
300
250
200
150
100
October zonal average
1979
2000
1999
-90
-60
-30
0
30
60
Latitude (degrees)
90
Fig. 11.6
Variation with Altitude of CFCs and
Other Chlorinated Compounds
HCFC-22
40
30
CFC-12
20
0
0
Tropopause
4
10
CCl (g)
Altitude (km)
Altitude (km)
50
CFC-11
100 200 300 400 500 600
Mixing ratio (pptv)
Fig. 11.7
Variations With Altitude of CFCs and
Other Chlorinated Compounds
Photolysis of chlorinated compounds above 20 km
Cl
F
C
(11.126)
Cl
Cl
+ h
F
Cl
C
+ Cl
 < 250 nm
Cl
(11.127)
Cl
F
C
F
Cl
Cl
+ h
F
C
F
+ Cl
 < 230 nm
Natural Sources of Chlorine
Methyl chloride photolysis
(11.130)
H
H
C
H
Cl
+ h
H
H
C
 < 220 nm
+ Cl
H
Methyl chloride scavenging by hydroxyl radical
H
H
C
H
+ OH
Cl
H2O
H
C
H
(11.128)
Cl
Chlorine Emission to Stratosphere
Chemical
Percent emission to stratosphere
Anthropogenic sources
CFC-12 (CF2Cl2)
CFC-11 (CFCl3)
Carbon tetrachloride (CCl4)
Methyl chloroform(CH3CCl3)
CFC-113 (CFCl2CF2Cl)
HCFC-22 (CF2ClH)
28
23
12
10
6
3
Natural sources
Methyl chloride (CH3Cl)
Hydrochloric acid (HCl)
15
3
Total
100
WMO (1994)
Ozone Destruction by Chlorine
Chlorine catalytic ozone destruction cycle
Cl + O3
(11.130)
ClO + O2
(11.131)
ClO + O
Cl + O2
(11.132)
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
Cl +
(11.133)
CH4
HCl + CH3
HO2
HCl + O2
H2
HCl + H
H2O2
HCl + HO2
(11.134)
Cl
O
Chlorine
monoxide
+ NO2
O
M
N
Cl
O
O
Chlorine
nitrate
Conversion of Reservoirs to Active
Chlorine
HCl reservoir leaks
HCl +
(11.135)
h
H + Cl
OH
Cl + H2O
O
Cl + OH
< 220 nm
ClONO2 reservoir leaks
O
N
Cl
O
O
Chlorine
nitrate
O
+ h
Cl +
O
 < 400 nm
N
O
Nitrate radical
Ozone Destruction by Bromine
CH3Br = methyl bromide (produced biogenically in the oceans
and anthropogenically as soil fumigant)
Photolysis of methyl above 20 km
H
H
C
H
(11.137)
H
Br
+ h
H
C
H
+ Br
 < 260 nm
Ozone Destruction by Bromine
Catalytic ozone destruction by bromine
Br + O3
BrO + O
O + O3
(11.138-40)
BrO + O2
Br + O2
2O2
Conversion of Active Bromine to
Reservoirs
Conversion of Br and BrO
(11.141)
HO2
HBr + O2
H2O2
HBr + HO2
Br +
(11.142)
Br
O
Bromine
monoxide
+ NO2
O
M
N
Br
O
O
Bromine
nitrate
Conversion of Reservoirs to Active
Bromine
HBr and BrONO2 reservoir leaks
(11.143)
Br + H2O
HBr + OH
O
O
+ h
N
Br
O
O
Bromine
nitrate
Br +
O
 < 390 nm
N
O
Nitrate radical
30
Area of N. America
250
200
25
Area of Antarctic
continent
150
100
50
1980
1985
1990 1995
Year
6 2) 2
Ozone hole area (106 km
)
km
Ozone minimum (Dobson units)
300
Ozone-hole area (10
Ozone minimum (DU)
Change in Size of Antarctic Ozone Hole
20
15
10
5
0
2000
Fig. 11.8
Polar Stratospheric Cloud Reactions
Type 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) + H2O(a)
HOCl(g) + HNO3(a)
ClONO2(g) + HCl(a)
Cl2(g) + HNO3(a)
N2O5(g) + H2O(a)
2HNO3(a)
N2O5(g) + HCl(a)
ClNO2(g) + HNO3(a)
HOCl(g) + HCl(a)
Cl2(g) + H2O(a)
Surface Reaction Rates
First-order rate coefficient (s-1)
(11.150)
1
k s,q  v q  q a
4
Thermal speed of impinging gas (cm s-1)
vq 
8k BT
Mq
(11.151)
Reaction Probabilities
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
Reaction Probability
Type I PSC Type II PSC
ClONO2(g) + H2O(a)
ClONO2(g) + HCl(a)
N2O5(g) + H2O(a)
N2O5(g) + HCl(a)
HOCl(g) + HCl(a)
0.001
0.1
0.0003
0.003
0.1
0.3
0.3
0.01
0.03
0.3
Table 11.9
Polar Ozone Destruction
Cl2 and HOCl photolysis in early spring
(11.161-2)
Cl2 + h
2Cl
 < 450 nm
HOCl + h
Cl + OH
 < 375 nm
Chlorine nitrite photolysis in early spring
ClNO2 + h
Cl + NO2
(11.163)
 < 370 nm
Polar Ozone Destruction
Catalytic ozone destruction by dimer mechanism
2 x ( Cl + O3
(11.164-7)
ClO + O2 )
M
Cl2O2
ClO + ClO
Cl2O2 + h
< 360 nm
ClOO + Cl
ClOO
2O3
M
Cl + O2
3O2
Polar Ozone Destruction
A second catalytic cycle that involves bromine
(11.169-72)
Cl + O3
ClO + O2
Br + O3
BrO + O2
BrO + ClO
2O3
Br + Cl + O2
3O2
Conversion of Cl Reservoirs to Active Cl
1% Cl, ClO
37%
ClONO 2
ClONO 2
HCl
62%
HCl
Before PSC and photolysis
reactions
Cl, ClO
After PSC and photolysis
reactions
Fig. 11.9
Ozone Regeneration
(Dobson
column
ozoneunits)
Average global
(Dobson units)
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.
350
300
No chlorine
250
200
150
With chlorine
100
50
0
0
10/1
100
200
300
1/7
4/17
7/26
Day and date of simulation
400
11/4
Fig. 11.10
Regeneration of Ozone Vertical Profile
Time-evolution of modeled profile of ozone (a) mixing ratio and (b)
number concentration at 34oN latitude, starting with zero ozone.
40
30
20
10
1h
6h
1d
5d
50 d
464 d
0
0
2
4
6
8
10
Ozone volume mixing ratio (ppmv)
Altitude (km)
Altitude (km)
Altitude (km)
Altitude (km)
40
30
20
1h
6h
1d
5d
50 d
464 d
10
0
0
10
20
Ozone (10
30
11
40
50
60
-3
molecules cm )
Fig. 11.11