A New Carbon-Bond Mechanism For Air Quality Simulation Modeling


February 1982
A NEW CARBCN-BOND MECHANISM FOR
AIR QUALITY SIMULATION MODELING
Contract No. 68-02-3281
ENVIRONMENTAL SCIENCES RESEARCH LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
RESEARCH TRIANGLE PARK, NORTH CAROLINA 27711

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A NEW CARBON-BOND MECHANISM FOR
AIR QUALITY SIMULATION MODELING
by
J. P. Killus
G. Z. Whitten
Systems Applications, Incorporated
San Rafael, California 94903
Contract No. 68-02-3281
Project Officer
M. C. Dodge
Atmospheric Chemistry and Physics Division
Environmental Sciences Research Laboratory
Research Triangle Park, North Carolina 27711
ENVIRONMENTAL SCIENCES RESEARCH LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
RESEARCH TRIANGLE PARK, NORTH CAROLINA 27711

-------
DISCLAIMER
This report has been reviewed by the Environmental Sciences Research
Laboratory, U.S. Environmental Protection Agency, and approved for pub-
lication. Approval does not signify that the contents necessarily re-
flect the views and policies of the U.S. Environmental Protection Agency,
nor does mention of trade names or commercial products constitute
endorsement or recommendation for use.
ii

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ABSTRACT
R>
J^new generalized kinetic mechanism for photochemical smog, which
incorporates recent information on the atmospheric reactions of aromatic
hydrocarbons, has been developed. The mechanism,\labeled^the Carbon-Bond
Mechanism III (CBM-III), is the third lumped-parameter mechanism to be
designed in accordance with the carbon-bond reaction concept\in which carbon
atoms with similar bonding are treated similarly, regardless of the molecules
in which they occur. (The principal feature that distinguishes CBM-III from
previous Carbon-Bond Mechanisms is the updated aromatic hydrocarbon chemistry./
Because of the general nature of the CBM-III, it can be used to model the
entire atmospheric mix of ^hydrocarbons and is suitable for use in Air Quality
Simulation Models (AQSMs^/) Principal features of CBM-III include a separate
reaction scheme for ethylene; realistic photochemistry for aromatic
hydrocarbons and dicarbonyl compounds; and formation pathways for alkyl
nitrates and nitroaromatic compounds.
CBM-III was tested by comparing the predictions obtained with the
mechanism against smog chamber data of multi-component hydrocarbon/NOx
mixtures obtained in the indoor chamber facility at the University of
California, Riverside, and the outdoor chamber facility of the University of
North Carolina.
In addition to a discussion of the development and testing of the CBM-
III, information is also provided on the application of the mechanism for
urban air quality modeling. Instructions are given on how to partition the
emission and atmospheric hydrocarbon data into the various carbon-bond
groupings that are used in the CBM-III. Calculated bond groupings are given
for several types of hydrocarbon data (including data for several specific
urban areas).
m

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CONTENTS
Abstract		iii
Tables		vi
Abbreviations		viii
1.	Introduction		1
2.	Recommendations		3
3.	Formulation of the New Version of the Carbon-Bond
Mechanism		4
Elimination of the Peroxyformyl Radical		7
Products of the Ozone-Olefin Reactions		16
Explicit Treatment of the Olefin Hydroxyl
Addition Product		16
Inorganic Radical Sources		17
Carbonyl Photolysis and Oxidation		17
Alkyl Radical Chemistry		20
Aromatic Oxidation		23
Ring Opening		24
Pathways to Phenolic Hydrocarbons				25
4.	Using the Carbon-Bond Mechanism		27
Speciation of Emissions and Atmospheric
Concentrations Into Bond Categories		29
The Volumetric Equivalence Principle		30
Surrogate Carbonyl s		30
Sample Carbon-Bond Calculations		31
5.	Hydrocarbons in Urban Areas		45
Hydrocarbon Speciation for the Los Angeles Area		45
Hydrocarbon Speciation for Other Urban Areas		47
Carbonyl Compounds in Urban Air		53
Radical Sources and Hydrocarbon Reactivity		53
Emissions of Carbonyl Compounds			58
Summary of Urban Hydrocarbon Composition		60
6.	Summary		62
References		64
Appendices
A.	Validation Simulations for Carbon-Bond Mechanism III		68
B.	Molecular Weights and Bond Fractions of Common Molecules....	90
v

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TABLES
Number	Page
1	The Original Formulation of the Carbon-Bond Mechanism		5
2	Carbon-Bond Mechanism II		8
3	Carbon-Bond Mechanism III		12
4	Carbon-Bond Groupings		31
5	Carbon-Bond Concentrations Applied to Ambient Hydrocarbon
Measurements Reported by Kopczynski et al. (1972)		33
6	Los Angeles Ambient Measurements		39
7	Comparison of a Molecular Mechanism and the CBM as
Used in the OZIPM Program		41
8	Carbon-Bond Composition of Olefins		43
9	Hydrocarbon Emissions in the Los Angeles Basin by Carbon
Fraction in Categories Used in the SAI Urban Airshed Model..	46
10	Los Angeles Emissions Speciation for 1974
Emissions Inventory		48
11	Carbon-Bond Fractions of RHC for Emissions and Ambient
Measurements in the Los Angeles Area		48
12	Ratios of Pollutants to Sum of Hydrocarbons Less Cj to C3
Paraffins in Roadway Samples		49
13	Urban Hydrocarbon Composition Data		50
14	Statistical Summary of Hydrocarbon Data
for the Denver Area		51
15	Hydrocarbon Composition Data for Selected Sites
in the Eastern United States		54
vi

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16	Hydrocarbon Composition in Houston Air	
17	Range of Urban Hydrocarbon Composition (Normalized to RHC)....
vii

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LIST OF ABBREVIATIONS
ACO3	Peroxyacyl radical (two-carbon surrogate for RCO3)
APRC	Aromatic product carbon
ARO	Aromatic ring
ARPI	Aromatic oxidation intermediate product
CARB	Carbonyl bond
CBM	Carbon-Bond Mechanism
CRIG	Criegee intermediate (H2CO2)
CR02	Carbonyl peroxy which will produce DCRB
DCRB	Oicarbonyl compound
EKMA	Empirical Kinetics Modeling Approach
ETH	Ethylene or slow olefinic bond
GLY	Surrogate for dicarbonyl s
KET	Ketone
MCRG	Surrogate for RCH02 type Criegee intermediates
MEO2	Peroxy radical (one-carbon surrogate for RO2)
NMHC	Non-methane hydrocarbon
NPHN	Nitrophenol
NRAT	Organic nitrate
OLE	Olefinic bond
OPEN	Aromatics ring-opening intermediate
OZIPM	Same as OZIPP plus mechanism and other options
vi i i

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OZIPP Ozone Isopleth Plotting Package (computer program used in EKMA)
PAN	Peroxyacyl nitrate
PAR	Single or paraffinic bond
PHEN	Phenolic pathway surrogate in ARO oxidation
PHO	Phenoxy radical
General organic moiety (R = H, CH3, C2H3, etc.)
RAO2	Hydroxy peroxyl from OH + OLE
RARO	Aromatic radical
RB02	Hydroxyperoxyl from OH + ETH
RCO3	Peroxyacyl radical
RHC	Reactive hydrocarbons
RO	Alkoxyl radical
RO2	Peroxy radical
W	Carbonyl balancing unit
X	Carbon-mass balancing unit
ix

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SECTION 1
INTRODUCTION
The Carbon-Bond Mechanism (CBM) is a photochemical kinetic mechanism that
has been developed expressly to provide a reasonable compromise between
chemical realism and computational efficiency. The CBM is designed to meet
stringent validation standards in the simulation of laboratory smog-chamber
studies; however, it can also be easily applied to atmospheric studies using a
minimum number of assumptions.
The version of the Carbon-Bond Mechanism presented in this manual is the
product of two major revisions and is referred to as CBM-III. The original
Carbon-Bond Mechanism (CBM-I) is described in Whitten, Hogo, and Killus
(1980), and CBM-II is described in Whitten, Killus, and Hogo (1980). The
current version (CBM-III) differs from CBM-II principally in the structure of
the oxidation mechanism for aromatic hydrocarbons and in some modifications of
inorganic reaction-rate constants.
These three Carbon-Bond Mechanisms are so named because they treat the
carbon bond, rather than the molecule, as the principal unit of reaction.
This concept offers several important advantages. First, the CBM is carbon-
conservative. The olefinic bond group, for example, always contains two
carbon atoms that must be accounted for in its products. The paraffinic bond
contains one carbon atom, and the aromatic bonds, six. Thus we can eliminate
the cumbersome notion of "average molecular weight," which causes considerable
difficulty in the application of lumped molecular mechanisms. Furthermore,
use of the CBM allows precise calculation of carbon-mass balance in
simulations, whereas such calculations can only be approximated when other
mechanisms are used.
The second major advantage afforded by the CBM is a considerable
reduction in the range of reaction-rate constants that must be averaged for
the lumped hydrocarbon species. This is true for paraffins, for example, in
which iso-butane has a molecular reaction-rate constant with OH of
CBM-I treated aromatic bonds as a sum of three double-bonded carbon
atoms. This approximation was changed in the CBM-II.
1

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5000 ppm'^min"^, and iso-octane has a reaction rate of 11,500 ppnT*min~*.
These reactivity rates, normalized to the number of carbon atoms per molecule,
are 1250 ppm"^min"^ and 1440 ppnT^min"*, respectively. The relative
difference between these two figures is thus much smaller than the relative
difference between the molecular reaction rates.
Finally, because the CBM has been used for a wide variety of laboratory
and atmospheric applications, the validation data set is extensive. Past
performance has shown the CBM to be an eminently practical simulation tool.
Each update of the mechanism is carefully considered in the light of past
applications and current knowledge. The newer version of the CBM, therefore,
should yield results similar to those obtained in past applications in which
the older versions were used, but the recently modified CBM is more
representative of current knowledge of the explicit photochemistry of smog
formation.
2

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SECTION 2
RECOMMENDATIONS
When using the CBM, special attention should be given to the level of
carbonyls used in the inputs for emissions and air quality. Also, air
monitoring data should be used to verify both the carbonyl inputs and the
levels generated by the model using the CBM. Future validation studies for
any atmospheric kinetics mechanism should involve comparisons of measured and
simulated carbonyl levels.
Future versions of the CBM should include the correct chemistry for
natural hydrocarbon species such as isoprene and a-pinene. This improvement
will become possible as the explicit chemistry for these species becomes
available.
3

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SECTION 3
FORMULATION OF THE NEW VERSION OF THE CARBON-BOND MECHANISM
At the time the original CBM (shown in table 1) was formulated, it
represented a condensation of existing explicit mechanisms (primarily for
propylene and butane). It was also used to simulate a set of smog-chamber
experiments with a reasonable degree of success. Knowledge of smog chemistry
has expanded to include more molecules, however, and the amount of data
derived from smog-chamber experiments has increased. Therefore, we sought to
improve the Carbon-Bond Mechanism.
Periodic updating of generalized mechanisms like the CBM is preferable to
continuous updating. Changes in one reaction may require compensating changes
in other reactions to maintain the overall predictive accuracy of simulations
in which the mechanism is used. Consequently, after a reaction change, the
mechanism should be tested with an entire set of smog-chamber data to ensure
that no special problems have arisen that would make atmospheric applications
difficult. The cost of such testing makes it desirable to test the effects of
several changes at once. Documentation of any changes is also necessary to
keep all users of the mechanism informed.
For many applications (such as the use of the mechanism in a photo-
chemical dispersion model) major changes in the mechanism require extensive
program modification. Numerical changes in rate constants can be typically
accommodated by such programs, but changes in product yield may involve
modification of the steady-state approximations necessary for rapid solution
of the chemical equations.
The first update of the CBM (CBM-II), reported by Whitten et al. (1979),
reflected the following changes to the CBM formulation:
>	Eliminating the peroxyformyl radical (HCO3).
>	Updating the rate constants and excluding HONO and HOOH.
>	Including the reactions of intermediate Criegee species
formed from ozone-olefin reactions.
4

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TABLE 1. THE ORIGINAL FORMULATION OF THE CARBON-BOND MECHANISM
Rate Constant
Reaction	(ppm^min"1)
1	N02 + hu ~ NO + 0	*+
2	0 + 02 (+ M) 03 (+ M)	2.08 x 10"5
3	03 + NO ~ N02 + 02	25.2
4	0 + N02 ~ NO + 02	1.34 x 104
5	03 + N02 ~ N03 + 02	5 x 10"2
6	N03 + NO ~ N02 + N02	1.3 x 104
7	N03 + N02 + H20 ~ 2HN03	1.66 x 10-3§
8	NO + N02 + H20 ~ 2HN02	2.2 x 10"9§
**
t
3
3
9 HN02 + hu > NO + OH
10	N02 + OH* ~ HN03	9 x 10
11	NO + OH* HN02	9 x 10
12	CO + OH* + C02 + H02	2.06 x 102
On	«
13	OLE + 0H« -» HCHO + CH302	3.8 x 104
14	PAR + OH* CH302 + H20	1.3 x 103
15	ARO + OH* HCHO + CH302	8 x 103
16	OLE + 0 —<* HC(0)02 + CH302	5.3 x 103
0?
17	PAR + 0 CH^Oo + OH*	20
202
18	ARO + 0	* HC(0)02 + CH302	37
Oo
19	OLE + 03 S HC(0)02 + HCHO + OH*	0.01
(conti nued)
5

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TABLE 1
Rate Constant
Reaction	(ppm^min-1)
20
°o
ARO + 03 -» HC(0)02 + HCHO + 0H»
0.002
21
22
OLE + Oo -»• Ozonide
ZOy
HCHO + hu —» HC(0)O2 + HO2
0.005
t
23
HCHO + hu * CO + Ho
A ^
4 x
10-4*
24
9
HCHO + OH- —£ HC(0)02 + H20
1 X
10*
25
H02* + NO > 0H« + N02
2 x
103
26
CH3O2 + NO ~ N02 + HCHO + HOg
2 x
103
27
HC(0)02* + NO + no2 + co2 + ho2
2 x
»—»
0
CO
28
H202 + hu 0H» + OH*
t

29
H02 HO2 H2O2 O2
4 x
103
30
CH3O2 + H02 + H3COOH + o2
4 x
103
31
HC(0)02 + H02 - HC(0)00H + 02
1 X
104
32
HC(0)02 + N02 ~ PAN
50

33
PAN ~ HC(0)02 + N02
0.02*
34
ARO + NO3 ~ Products
50

35
ho2* + no2 ~ hno2
20

*	Units of min'l.
*	Light-dependent.
§ Units of ppnr^min"*.
** Rate constant is for the computer simulations of UCR smog-
chamber experiments.
(concluded)
6

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>	Including new surrogate species representing the addition
products of OH* to double bonds.
>	Including a new formulation for carbonyl photolysis and
oxidation.
>	Treating alkyl radicals in long-chain paraffins.
>	Treating ethylene as an explicit species.
>	Treating internal olefins as carbonyls.
>	Using a root-mean-square rate constant for the reactions
of OH., 0, and O3 with hydrocarbon mixtures.
>	Incorporating a new aromatic chemical reaction scheme.
The rate constants used in the aromatics chemistry were modified by
Whitten, Kill us, and Hogo (1980). The aromatics scheme developed in C8M-II
represented an interim treatment, occasioned by a rapid increase in our
understanding of aromatic hydrocarbon oxidation. The second update of the
CBM, discussed in this report, reformulates the aromatics chemistry to reflect
current understanding of the explicit chemistry of toluene and xylenes. This
revision also includes reactions that treat the oxidation of ketones to
dicarbonyl compounds. Each of these changes is discussed in the following
subsections.
The mechanism reported by Whitten, Killus, and Hogo (1980) (reflecting
the first update plus rate-constant changes for aromatics) is known as CBM-II
(see table 2); the new version of the Carbon-Bond Mechanism, shown in table 3,
is called CBM-111.
ELIMINATION OF THE PEROXYFORMYL RADICAL
At the time of the original formulation of the CBM, our explicit
mechanisms included the peroxyformyl radical (HCO3), which no longer appears
in our explicit chemistry. To account for this change, we introduced a new
species, ACO-j, which is a surrogate for RCO3 radicals (where R has one or more
carbon atoms). ACO3, which has two carbon atoms, is formed in the CBM from
the reaction of OH. with the species CARB, which represents only one carbon
atom. Thus some correction must be made to preserve carbon-mass balance. The
correction we used is suggested by a reaction of RCO3* in the explicit
mechanisms. In such mechanisms, RCO3* (R > CH3) can react with NO to produce
NOg, CO2, and RO^. The significance of that reaction is that it initiates the
oxidation of the carbon atom adjacent to the CO-j group in RCO3 without any
7

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TABLE 2. CARBON-BOND MECHANISM-11
Rate Constant	Activation
at 298K*	Energy
Reaction	(ppiWmin"1)	(K)
1
NO2 + hu -~ NO + 0
Experimental*

2
O+O2+M + O3 + M
2.1
X
10~5§
—
3
O3 + NO + NO2 + O2
23. <
)

1,450
4
O3 + NO2 NO3 + O2
00
•
X
10"2
2,450
5
0 + N02 NO + 02
1.34 x
; 104
—
6
O3 + OH •+¦ HO2 + O2
7.7
X
101
1,000
7
03 + H02 ~ OH + 202
5.0


1,525
8
no2 + oh + hno3
1.4
X
104
—
9
CO + OH ^5 H02 + C02
4.4
X
CM
O
tH

10
NO + NO + 02 > 2N02
7.1
X
•—»
O
1
O
—
11
N03 + NO - 2N02
CO
•
CM
X
104
—
12
no3 + no2 + h2o ~ 2HN03
311
X
k(N205 + H20)**
-10,600
13
H02 + NO > N02 + OH
1.2
X
104
--
14
HO2 + HOg +• H2O2 "*¦ O2
1.5
X
104
--
15
PAR + 0 -4 MEOo + OH
n
2 x
10
|1
2,100
16
17
2
PAR + OH -4 ME02 + H20
^2
OLE + 0 -4 ME02 + ACO3 + X
1.5
2.7
X
X
103
103
560
325
18
OLE + 0 + CARB + PAR
2.7
X
CO
0
H
325
(continued)
8

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TABLE 2
37
Rate Constant	Activation
at 298K*	Energy
Reaction	(ppm'^min-1)	(K)
°9	A
19	OLE + OH -*• RA02	4.2 x 104	-540
20	OLE + 03 ~ CARB + CRIG	8 x 10"3	1,900
21	OLE + 0-, ~ CARB + MCRG + X	8 x 10"3	1,900
°?	2
22	ETH + 0 -» ME02 + H02 + CO	6 x 10*	800
23	ETH + 0 ~ CARB + PAR	6 x 102	800
°2	A
24	ETH + OH —£ RB02	1.2 x 104	-382
25	ETH + 0, ~ CARB + CRIG	2.4 x 10-3	2,560
°2	3
26	ACOo + NO NOo + ME02 + C02	3.8 x 10J
°o	.
27	RBOo + NO-i NO? + 2 CARB + H0?	1.2 x 104
0
28	RA02 + NO N02 + 2 CARB + H02	1.2 x 104
29	ME02 + NO -£ N02 + CARB + ME02 + X	(1.2 x 104)(A-1)/At+
°9	a *
30	MEOo + NO -* NOo + CARB + H0?	(1.2 x 104)/A
.*~
J2 T nu	2	x r\\J<£
31	ME02 + NO ~ Nitrate	5 x 102
32	RB02 + 03 + 2 CARB + H02	+ 02	5.0
33	RA02 + 03 + 2 CARB + H02	+ 02	2 x 102
34	ME02 + 03 + CARB + H02 +	02	5.0
09	.
35	CARB + OH -* a(H02 + CO)	+ (1 - a)(AC03 + X) (2.4 - a) x 104
36	CARB + hu + CO + H2	akf*§§
0,
CARB + hu-£ (1 + a)H02 + (1 - a)(ME02 + X) + CO (fL+_L)kf
*tt
38 X + PAR >	1 x 105
(continued)
9

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TABLE 2
Reaction
Rate Constant
at 298K*
(ppm^min"1)
Activation
Energy
(K) •
39	AC03 + n02 * PAN
40	PAN » ACO3 + N02
41	ACO-j + H02 * Stable products
42	ME02 + H02 Stable products
43	CRIG + NO ~ N02 + CARB
44	CRIG + N02 ~ N03 + CARB
45	CRIG + CARB Ozonide
46	MCRG + NO ~ N02 + CARB + PAR
47	MCRG + N02 + N03 + CARB + PAR
48	MCRG + CARB ~ Ozonide
49
56
CRIG > CO + H20
50	CRIG Stable products
^2
51	CRIG -» 2H02 + C02
52	MCRG * Stable products
53	MCRG -» MEOo + OH + CO
°2
54	MCRG -» MEOo + HO? + C0?
°2
55	MCRG CARB + 2H0? + CO
°2
ARO + OH -i ARPI + ARPI + ARPI + HO,
0,
57	ARO + OH HOo + GLY + X
°2
58	ARO + OH -» OH + GLY + W
59	W + CARB ~
60	ARPI + NO NO + CARB + PAR
2 x 103
—
2.8 x 10_2+
12,500
4 x 103
—
4 x 103
—
1.2 x 104
—
8 x 103
—
2 x 103
—
1.2 x 104
—
8 x 103
--
2 x 103
—
6.7 x 102+
--
2.4 x 102+
—
9 x lO11
—
1.5 x 102t
—
3.4 x 102+
--
4.25 x 102+
--
8.5 x 101+
—
6 x 103
—
1.6 x 103
—
1.5 x 104
—
1.0 x 105

30
10
(continued)

-------
TABLE 2
Reaction
Rate Constant
at 298K*
(ppm~^min"^)
Activation
Energy
(K)
61 ARPI + NO -»¦ NO2 + Aerosol
62 ARPI + NO-:
CARB + CARB
63 ARPI + O3 -»¦ Aerosol
+
0,
64 GLY + OH + H02 + ARPI + ARPI + ARPI + CO
65 GLY -5- ME02 + H02 + ARPI + ARPI + ARPI
15
3.5 x 104
0.6
10'

CGLY
~~
The rate constants shown were those employed at UCR to model eleven experiments in
which mixes of seven hydrocarbons were used. For that study the default values
a = 0.5 and A = 1.3 were used.
* Units of min"l.
§ Units of ppnT^min-l.
k(N2O5 + H20) = 5 x 10"® ppm~lmin~l for UCR simulations.
A = A is the average number of R02-type radicals generated from a hydro-
carbon between attack by OH. and generation of H02.
§§ a is the fraction of total aldehydes that represents formaldehyde and
ketones, kf is the carbonyl photolysis rate constant.
kGLY - °'036 x k(N02 + hu)*
(concluded)
~ ~~
11

-------
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
TABLE 3. CARBON-BOND MECHANISM III
Rate Constant
at 298K
Reaction	(ppra"^min"^)
N02 -~ NO + 0
~

0 + (02) + (M) + 03
4.40 x
10'
NO + O3 -»¦ N02 + 02
26.6

N02 + O3 ->¦ NO3 + 02
0.048

N02 + 0 * NO + 02
1.3 x
104
OH + O3 ¦¥ HO2 + O2
100

HO2 + O3 * OH + 2O2
2.40

OH + N02 - HNO3
®2
OH + CO -4 ho2 + co2
1.60 x
440
10
NO + NO + (02) ~ N02 + N02
1.50 x
10
NO + N03 + N02 + N02
2.80 x
10'
N02 + N03 + H20 1. 2HN03
§

NO + H02 * N02 + OH
1.20 x
10'
HO2 + HO2 H2O2 + O2
1.50 x
10'
X + PAR >
°2
OH + PAR -4 ME02 + H20
®2
0 + OLE -4 ME02 + AC03 + X
105
1300
2700

0 + OLE + CARB + PAR
°2
OH + OLE -4 RA02
2700
3.70 x
10'
12

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20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
TABLE 3
Reaction
Rate Constant Activation
at 298K	Energy
(ppm-1mi n-1)	(K)
03 + OLE ~ CARB +	CRIG
Oo + OLE > CARB + MCRG + X
°2
0 + ETH -4 ME02 +	H02 + CO
0 + ETH -»¦ CARB + PAR
Oo
OH + ETH
RBO-
03 + ETH * CARB + CRIG
°2





aco3 -4
no2
+
meo2


°2
RBOo -4
no2
+
CARB
+
H02 + CARB
°2
RAOp -4
no2
+
CARB
+
H02 + CARB
°2
MEOo -4
no2
+
CARB
+
meo2 + X
°2
meo2 -4
no2
+
CARB
+
ho2
NO + ME02 ¦* NRAT
O3 + RB02 CARB + CARB + H02 + 02
O3 + RA02 + CARB + CARB + H02 + 02
OH + CARB - CR02 + X
°2
OH + CARB -4 HOo + CO
°2
OH + CARB -4 ACO3 + X
CARB -~ CO + H2
°2
CARB + (02) -4 2/3 (2H02 + CO)
1/3 (2ME02 + CO + 2X)
0.008

1900
0.008

1900
600

800
600

800
1.20 x
104
-382
0.0024

2560
1.04 x
104
0
1.20 x
104
0
1.20 x
104
0
3800

0
7700

0
500

0
5.0

0
200

0
500

0
7000

0
6000

0
(-0.001
Ki)*
0
(=0.002
\ *
Ki)
0
(continued)
13

-------
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
TABLE 3
Rate Constant Activation
at 298K	Energy
Reaction	(ppm'^-min"1)	(K)
no2 + aco3 * PAN
7000

0
PAN > ACO3 + N02
0.022

1.35 x 10
HO2 + ACO3 + Stable products
1.50 x
10*
0
HO2 + MEO2 Stable products
9000

0
NO + CRIG •> N02 + CARB
1.20 x
10*
0
N02 + CRIG + N03 + CARB
8000

0
CARB + CRIG + Ozonide
2000

0
NO + MCRG ~ N02 + CARB + PAR
1.20 x
104
0
N02 + MCRG + N03 + CARB + PAR
8000

0
CARB + MCRG + Ozonide
2000

0
CRIG * CO + H20
670**

0
CRIG -~ Stable products
240**

0
®2
CRIG -4 H02 + H02 + CO
_
90

0
MCRG + Stable products
150**

0
^2
MCRG -4 MEO? + OH + CO
340**

0
°2
MCRG -4 ME02 + H02
425**

0
®2
MCRG -4 CARB + H02 + CO + HOo
n
85**

0
2
OH + ARO -4 RARO + H20
°2
OH + ARO -4 HOo + OPEN
°2
NO + RARO -4 N02 + PHEN + H02
8000

600
1.45 x
104
400
4000

0
(continued)
14

-------
TABLE 3
Rate Constant Activation
at 298K	Energy
Reaction	(ppnrVin-1)	(K)
59
°2
OPEN + NO N02
+
DCRB + X + APRC
6000
0
60
u?
APRC -4 DCRB + CARB + CO
°2
APRC -4 CARB + CARB + CO + CO
104**
0
61
104**
0
62
PHEN + N03 + PHO
+
hno3
5000
0
63
PHO + N02 + NPHN


4000
0
64
PHO + H02 > PHEN


5.00 x 104
0
65
OPEN + 03 > DCRB
+
X + APRC
40
0
66
67
OH + PHEN -£ H02
°2
DCRB -4 1/2 (H02
1/2 (ME02
+
+
+
APRC + PAR + CARB
aco3 + CO)
H02 + 2C0)
3.00 x 104
(-0.04 Kx)*
0
0
68
69
PHEN + OH + PHO
°2
cro2 + NO -4 no2
+
H02 + DCRB
104
1.20 x 104
0
0
70
DCRB + OH ~ AC03


7000
0
71
hono > OH + NO


(-0.06 Kl)*
0
72
OH + NO * HONO


9770
0
73
03 ~ 0*0


(~io_3k1)*
0
74
01D 0


4.44 x 1010
0
75
0^ + H20 + OH +
OH
3.4 x 105
0
* Sunlight-dependent; units of min"*.
+ Units of ppnT^min"!.
§ Heterogeneous; pseudo third order. Equal to 591 x N205 + H20.
** Units of min"1.
15

-------
involvement of OH* or 0. Thus it corresponds, in the terms used in the CBM,
to the conversion of PAR (single or paraffinic bond) to ME02 (the surrogate
for RO^by a pathway not previously accounted for in the CBM. In the revised
Carbon-Bond Mechanism, ACO3 reacts with NO to produce NO2, CO2, and MEO2.
When this reaction is included in the CBM, one PAR must be subtracted to
account for the MEO2 formed (i.e., to maintain carbon-mass balance). We
accomplished this by means of a fictitious compound X. Whenever an extra
carbon atom appears on the right side of a chemical reaction, one X is
produced that immediately removes one PAR by means of the reaction PAR +
X+ , which is given a high rate constant. Typically, the appearance of X
accounts for the oxidation of a single-bonded carbon atom from the PAR pool by
pathways other than direct reaction with OH* (oxidation of paraffins by oxygen
atoms has been eliminated in the CBM-III). These other pathways were not
accounted for in the original formulation of the CBM.
In using the methodology just described, one may encounter difficulty if
X is produced when no saturated carbon atoms remain (i.e., [PAR] = 0). An
example of such a case would be one in which the formaldehyde concentration is
large compared with that of the paraffins and higher aldehydes. If it is
known a priori that such a case exists, the formation rate of ACO3 can simply
be set to a small number. However, it is unlikely that this situation will
occur in the atmosphere, where paraffinic hydrocarbons are abundant.
Tropospheric methane provides an equivalent minimum [PAR] level of 0.01 ppm.
In the application of complex atmospheric models, we have encountered
situations in which a flaw in the numerical transport algorithm artificially
reduced [PAR] to a low level (which was reduced to a negative number when the
"X chemistry" was employed). However, we do not consider this to be a
drawback in the treatment of chemistry. Indeed, in this instance the
chemistry subroutine helped to locate an error in the transport algorithm.
PRODUCTS OF THE 0Z0NE-0LEFIN REACTIONS
Because Criegee intermediates from the ozone-olefin reaction were added
to the explicit mechanisms, we included them in the Carbon-Bond Mechanism.
The Criegee intermediates are represented by the symbols CRIG for CH2O2 and
MCRG for CH3CH2O2, the two Criegee intermediates found in the explicit
mechanisms (see Whitten et al., 1979, and Dodge and Arnts, 1979).
EXPLICIT TREATMENT OF THE OLEFIN HYDROXYL ADDITION PRODUCT
The explicit chemistry of hydroxyl attack on olefins leads to the
formation of two aldehydes from the initial addition product, which in air is
a HORO2 radical. In CBM-I this radical was treated as a typical RO2 radical
16

-------
that produces but one aldehyde; the extra aldehyde was added along with the
RO2 as a product in the initial OH reaction. However, CBM-II and CBM-III
include a special reaction of the HORO2 addition product with O3. Hence, the
explicit treatment allows the formation of two aldehydes from the H0R02 or
reaction with O3. The O3 reaction is still under investigation, and future
versions of the CBM probably will not require this reaction.
INORGANIC RADICAL SOURCES
Although the chemistries of HONO and 0*0 (reactions 70 to 74) are
included in CBM-III, these reactions can be deleted from the mechanism for
most urban applications. The production and destruction of HONO is a
relatively unimportant cycle, and the steady-state concentration of HONO
during the day is very low. Small concentrations of HONO (1 to 2 ppb) have
been measured at night (Piatt et al., 1980), and the compound might be found
in small concentrations in emitted N0X. Although HONO is important in the
initiation phase of smog-chamber experiments, other radical sources (e.g.,
HCHO) have been measured at concentrations high enough to overshadow the
importance of HONO as a component of polluted air.
Ozone photolyzes to form O^-D, a fraction of which then reacts with water
to generate OH (reactions 72 to 74). We have found this reaction to be
important principally in application to rural areas, where the background
concentration of ozone is greater than 10 times the background of carbonyl
compounds. In urban applications 0*0 chemistry is relatively unimportant and
can often be omitted.
CARBONYL PHOTOLYSIS AND OXIDATION
A necessary part of the formulation of the Carbon-Bond Mechanism is the
condensation of the reactions of aldehydes and ketones into two types of
reactions, namely, photolysis and oxidation by hydroxyl radical.
In general, aldehydes larger than formaldehyde appear to photolyze as
follows:
RCHO + h0 -~ R'02- + HO^ + CO k^ = $kf .	(1)
The photolysis rate constant <|>kf is defined as follows:  is the average
quantum yield, and kf is the photolysis rate constant for formaldehyde
producing two radicals.
17

-------
In the photolysis of formaldehyde under a typical solar spectrum, two
reaction pathways occur at approximately equal rates:
HCHO + hu ~ H2 + CO	= kf ,	(2)
HCHO + hu + HO* + HO* + CO	k = k .	(3)
C	C	10 J t
Thus the total photolysis rate for formaldehyde is 2 x kf.
For simplicity, CBM-II treated ketone photolysis in the same manner as it
would formaldehyde. The lumped reaction set for carbonyl photolysis then
became
CARB + hu - H2 + CO	k = akf ,	(4)
CARB + hu -~ (1 + a)H0*	(5)
+ (1 - a)(ME02 + X) + CO	k(5) = (-2-^-1) kf
»
where
[formaldehyde] + [ketones]
a = 		,
[total carbonyls]
and
k^. = formaldehyde photolysis to radicals,
= formaldehyde photolysis to stable products
1/2 k^ = photolysis of higher aldehydes.
More realistically, ketone photolysis typically yields two peroxyalkyl
radicals:
KET + hu + RO^ + R02* + CO .	(5a)
Ketones can also yield peroxyacyl as a photolysis product:
18

-------
KET + hu -~ ROg + RCO^
(5b)
However, this is a minor formation pathway for peroxyacyl (hydroxyl attack on
higher aldehydes has much greater significance). Since RCO3 yields R0£ when
reduced by NO, equation (5a) is a good approximation of the overall process.
For the new lumped mechanism (CBM-III), we define CARB as the
concentration of carbonyls (i.e., the sum of the aldehyde and ketone
concentrations):
CARB + h0 ~ (H2 + CO) = CO + H2 ,	(6a)
CARB + hu > (HO^ + HO^ + CO) = 2H0^ + CO ,	(6b)
CARB + hu - (ME02 + 2X + MEO^ + CO) ,	(6c)
with the photolysis rate constants,
form , _ ,
CARB ' (1) = (6a)
[k(3)] form + (0.5 higher aldehydes)k^^
CARB	= k(6b)
[k^j] (0.5 higher aldehydes) + KET[k^5a^]
CARB	= k(6c)
Thus, the higher aldehyde photolysis pathway is halfway between formaldehyde
and ketones in product yield.
The second major reaction of aldehydes is oxidation	by hydroxyl radicals:
HO- + CO + H^O for formaldehyde	(7a)
RCHO + OH. +
ACOj + H^O for higher aldehydes	(7b)
19

-------
Ketone oxidation is more complex. For example, (MEK)
+°2
CH_C0CHoCH- + OH ~ CH,C0CH0*CH, + (H.O)
3 2 3	3 2 3 2
(8)
CH3C0CH02«CH3+ NO + N02 + CH3C0CH0CH3 ,	(9)
CH COCHOCH + 0 ~ HO + CH COCOCH (biacetyl, a highly
photolytic dicarbonyl (10)
compound).
A ketone oxidation pathway can easily be included in CBM-III because the
dicarbonyl compounds (DCRB) are already included as part of the new aromatics
chemistry.
CARB + OH * CR02 + X ,	(11)
CR02 + NO > N02 + H02 + DCRB .	(12)
Aldehyde oxidation pathways are the same for both CBM-II and CBM-III:
CARB + OH -»¦ H02 + CO + H20 ,	(13)
CARB + OH ~ AC03 + X + H20 ,	(14)
where X is the previously mentioned negative carbon species used to maintain
mass balance.
ALKYL RADICAL CHEMISTRY
The alkyl radical (RO*) chemistry used in our mechanisms was discussed in
detail by Whitten and Hogo (1977). In the propylene and butane explicit
mechanisms, only alkyl radicals with four or fewer carbon atoms are
important. The following reactions for the primary alkyl radicals are used in
these explicit mechanisms:
20

-------
°2	5 -1
CH3CH2CH(0.)CH3 + CH CH 0 + CH3CHO k = 1.0 x 10 min	, (15)
CH3CH2CH(0.)CH3 + 02 - CH3CH2C(0)CH3 + H0^	k =	1.43 ppm^min"1	, (16)
°2	6	,
CH3CH2CH2CH20. + H0CH2CH2CH2CH20^	k	=	2 x 10 min	, (17)
CH3CH2CH2CH20. + 02 * CH3CH2CH2CHO + H0^	k	=	3.3 ppm^min"1	, (18)
CH3CH2CH20. + 02 > CH3CH2CH0 + HOg	k	=	3.3 ppm^min"1	, (19)
CH3CH20. + 02 -»¦ CH3CH0 + HO^	k	=	3.3 ppm^min"1	, (20)
CH30. + 02 ¦+• HCHO + HO^	k	=	1.2 ppm *min *	. (21)
Alkylperoxyl radicals can thus react through a number of pathways that may
be represented as follows:
R0^ + NO -»¦ R0. + N02 ,	(22)
R0^ + NO -~ nitrates ,	(23)
RO. + °2 + aldehyde + HOj	» (24)
°2
RO. -»¦ HORO. (isomerization) ,	(25)
°2
RO. * R'O. + aldehyde	(decomposition) , (26)
RO^ + HO. -~ stable products	. (27)
21

-------
Reactions (25) and (26) occur in systems with carbon chains greater
than, or equal to, four (e.g., butane and 2,3-dimethylbutane). The
isomerization reaction chain (reaction 25) terminates when the a-hydroxyl
radical reacts with oxygen to form a carbonyl compound--i.e., reaction
(24). In the Carbon Bond Mechanism, we write reactions (22) and (24) as a
single step:
ME02 + NO -k N02 + CARB + HO^ .	(28)
We have condensed reactions (25) and (26) into the R0£ scheme as:
ME02 + NO ~ N02 + CARB + (ME02 + X) .	(29)
Reactions (23) and (27) translate directly into:
ME02 + NO +¦ nitrates ,	(30)
ME02 + HO. -»¦ stable products .	(31)
Reaction (29) condenses the alkyl isomerization and decomposition
processes, with the net effect that more than one R0£ radical is generated per
reaction of PAR with OH. The condensed reaction sequence lumps the hydroxy-
carbon group into the carbonyl category, an approximation whose validity
cannot be assessed without explicit data for the reactivity of hydroxy com-
pounds. However, isomerized hydroxy species have not yet been detected.
Since a slow reaction rate would allow the buildup of detectable concen-
trations of these species, a relatively high reaction rate for such compounds
is implied.
If we let "A" equal the number of R0£ radicals per alkyl oxidation, then
k(29) = k(28)
-------
k(28) + k(29) + k(30) = 12»000 ppin-1min_1
Therefore,
k/ort. = [12,000 - k,,rtJ
A - 1
(29) u '	(30) A
Empirically, nitrate formation observed in smog-chamber experiments
requires a reaction-rate constant for reaction (30) that falls within the
range of 250 ppm^min^to 1250 ppm^min-1, depending on the hydrocarbons
involved. For an intermediate urban mix of hydrocarbons, we recommend a
rate of 500 ppm"*min" . Long chain alkyl radicals tend to react according
to the pathways shown in reactions (29) and (30) more often than do
molecules having lower molecular weight. Insufficient information is
available to set these reaction-rate constants a priori; Carter et al.
(1979) suggested some values for individual peroxy radicals on the basis
of empirical fits to smog-chamber data.
For some hydrocarbons (e.g., 2,3-dimethylbutane) "A" can be as high
as 2. When calculations for butane are based on the detailed reaction
sequence, "A" is approximately 1.3. Calculations based on the ratio of
hydrocarbon consumed to the oxidation of NO in smog-chamber experiments
(Kopczynski, Kuntz, and Bufalini, 1975) yield a value for "A" of 1.5,
which we recommend as the default value for "A". Therefore, the nominal
rate constants for reactions (28), (29), and (30) are 7700, 3800, and 500,
respectively.
AROMATIC OXIDATION
We have devised an explicit mechanism for treating toluene oxidation
(Killus and Whitten, 1981) and have extended our work to include simula-
tion of m-xylene systems. Our studies indicate that aromatic hydrocarbon
oxidation differs from olefin and paraffin oxidation in several important
ways. Our simulation mechanisms show three major differences between
aromatic compounds and a compound such as propylene:
> A high photolysis rate of oxidation products: toluene
oxidation products, for example, photolyze at a rate twice
that which would result from a 100 percent yield of
formaldehyde from toluene decay. This high rate is
apparently caused by a fractional yield of methyl glyoxal,
23
-------
which photolyzes at a rate roughly 15 times that of
formaldehyde.
>	A low rate of peroxyl radical production: the ineffi-
ciency of toluene and other aromatic hydrocarbons in
effecting N0-to-N02 conversions has been observed by other
investigators (Kopczynski, Kuntz, and Bufalini, 1975).
Empirically, methyl glyoxal photolysis alone is nearly
sufficient to explain the number of N0-to-N02 conversions
observed in toluene oxidation. Thus, either the other
products of toluene decay are unreactive or there is a
mechanism in toluene oxidation that destroys peroxyl or
otherwise prevents the peroxyl radicals from reacting with
NO.
>	After the onset of ozone production, a powerful N0X sink
mechanism occurs that does not appear to consume hydrogen-
containing radicals. This sink probably involves NO3 and
can result in nitrophenols or dinitrate compounds.
The mechanism described herein contains the aforementioned features and is
based on a condensation of our explicit aromatics mechanisms.
RING OPENING
The initial step of the ring opening pathway can be easily treated with
three reactions:
ARO + OH + OPEN ,	(32)
OPEN + NO + N02 + H02 + DCRB + APRC ,	(33)
OPEN + 03 ~ H02 + DCRB + APRC .	(34)
These reactions are exactly analogous to reactions in our explicit
toluene mechanism. The lumped rate constant of initial OH attack depends on
the mix of hydrocarbons present.
The species DCRB represents photolyzable dicarbonyl species: methyl
glyoxal and biacetyl.
24
-------
The species APRC (aromatic product carbon) represents the remainder of
the aromatic molecule once the dicarbonyl species has been subtracted. In
toluene oxidation this would be either the compound cis-2-butenedial (CBO) or
two glyoxal molecules, depending on the degree of oxidation of the aromatic
molecule prior to ring opening. Since xylene has another methyl group
attached to the ring, the ultimate yield of methyl glyoxal is twice that of
toluene but depends on the xylene isomer.
We treat the secondary products represented by APRC in a simple way:
APRC + DCRB + GLY ,	(35)
APRC > GLY + GLY .	(36)
Thus far we have obtained the best results using a 50/50 split to
pathways (35) and (36) for experiments containing equal amounts of toluene and
xylene.
We have the following oxidation sequence for glyoxal:
(CH0)2 + OH H20 + HCO + CO ,	(37)
HCO. -~ H02 + CO .	(38)
This sequence is similar to that of formaldehyde oxidation except for the
extra yield of 1 molecule of CO. Therefore, we treat the production of
glyoxal in the carbon-bond units as
GLY = CARB + CO
PATHWAYS TO PHENOLIC HYDROCARBONS
In our toluene mechanism there are two pathways to phenolic hydrocar-
bons: (1) addition of OH to the aromatic ring, forming cresols, and (2)
hydration and nitrification of oxybenzoyl radicals. One example of the second
pathway is the terminating reactions of benzaldehyde (BZA) oxidation:
+0?
BZA + OH + peroxyl benzoyl (PBZ02) ,	(39)
PBZ02 + NO + N02 + oxybenzoyl (PBZO) ,	(40)
25
-------
+ wdt^r
PBZO + NO^	~ nitrophenol (NPHN) .	(41)
Phenolic hydrocarbons may serve as both radical sinks and N0X sinks in
our reaction scheme. N0X is lost from the system in the form of nitrophenols
and also when N03 is converted to nitric acid:
@r
OH
+ no3 + hno3 + i^ . (42)
Hydrogen abstraction from the paraffinic substituents on the aromatic
ring is treated in the single-bonded carbon portion of the Carbon-Bond
Mechanism. Similarly, the carbonyl portion of benzaldehyde is lumped together
with the carbonyl bonds, and peroxybenzoyl nitrate is lumped with other
PANS. The phenolic pathway of BZA oxidation is lumped with OH addition to the
aromatic ring:
ARO + OH ->• RARO (aromatic radical) ,	(43)
RARO + NO + N02 + H02 + PHEN .	(44)
The lumped species PHEN can then react with OH or N03 to form
nitrophenols:
PHEN + OH PH03 ,	(45)
PHEN + N03 ~ PHO + HN03 ,	(46)
PHO + N02 -»• NPHN .	(47)
Since nitrophenols have low vapor pressures, it is likely that they also
participate in aerosol formation.
The phenoxy radical can also react with H02:
PHO + H02 ~ PHEN + 02 .	(48)
This reaction can be an important radical sink in aromatic systems. We assume
that the reaction rate for this reaction is similar to that of OH + H02
(Baulch et al., 1980).
26
-------
SECTION 4
USING THE CARBON-BOND MECHANISM
In its current form, the Carbon-Bond Mechanism (CBM-III) treats the
reactions of six types of carbon atoms: (1) single-bonded carbon atoms, whose
principal constituent is paraffinic carbon molecules (hence the abbreviation
PAR), (2) relatively reactive double-bonded carbon (OLE), (3) slow double
bonds, which are almost exclusively ethylene (ETH), (4) reactive aromatic
rings (ARO), (5) carbonyl compounds such as aldehydes and ketones (CARB), and
(6) highly photolytic a-dicarbonyl compounds such as methyl glyoxal and
biacetyl (DCRB). Some other types of carbon atoms can also be treated within
this set. For instance, highly reactive internal double-bonded carbon atoms
were shown by Whitten, Kill us, and Hogo (1980) to be equivalent to two
carbonyls per double bond. Hence three levels of olefin reactivity can be
treated in the CBM (slow as ETH, relatively reactive terminal olefins as OLE,
and highly reactive internal olefins as 2 CARB per bond). Appendix B lists
the CBM fractions recommended for a variety of organics.
The use of the molecular bond rather than the whole molecule as the
principal unit may at first seem confusing to those whose experience is solely
with molecular reactions. However, several major advantages associated with
the bond-group-reaction principle make the conceptual effort involved
worthwhile.
The primary advantage is that the Carbon-Bond Mechanism does not require
the sometimes uncertain calculation of "average molecular weight." The carbon
number of each carbon-bond group is fixed:
27
-------
Carbon Number
Carbon-Bond Group	(carbon atoms)
PAR
ETH
OLE
ARO
CARB
DCRB
1
2
2
6
1	(plus 1 oxygen atom)
2	(plus 2 oxygen atoms)
In a lumped molecular mechanism, chemical reactions might be expected to
alter the average molecular weight of each species category. When this
phenomenon occurs, it is impossible to perform mass-balance calculations on
the reactive organic compounds remaining in the model simulation. The Carbon-
Bond Mechanism allows precise hydrocarbon-mass-balance calculations to be
made, thus facilitating the estimation of the importance of phenomena like
long-range smog precursor transport and day-to-day carry-over of pollutants.
Moreover, whereas most lumped molecular mechanisms do not conserve carbon, the
Carbon-Bond Mechanism conserves carbon and follows each hydrocarbon fraction
to its end products (generally CO or C02» but occasionally aerosol or
nonreactive hydrocarbons).
The range of reactivities of carbon bonds is generally less than that of
reactivities of molecules because larger molecules tend to react faster even
if each constituent atom is of similar reactivity. Thus the problem of rate-
constant averaging is reduced in the Carbon-Bond Mechanism.
The carbon-bond concept has an additional advantage over the molecular
concept because it offers a sensible method for dealing with the atmospheric
chemistry of many complex or unusual molecules. For example, the molecule
cinnamaldehyde (C5H5CH=CHCH0) might be treated as 1 ARO, 1 OLE, and 1 CARB
assuming that the double bond is about as reactive as propylene. The double
bond can also be treated as 1 ETH or 2 CARB, depending on the extent of its
reactivity compared with that of propylene. For mechanisms in which the
molecular concept is used, cinnamaldehyde can be described as an aromatic, an
olefin, or an aldehyde. In making a choice among the three possibilities, the
chemistry associated with the other two parts of the molecule is ignored,
whereas the CBM approach offers reasonable chemical pathways for all three
parts. Some surrogate mechanisms use a particular blend of propylene and
butane to provide a reasonable simulation fit to smog-chamber data in which
cinnamaldehyde is used. However, in the absence of smog-chamber data the
surrogate and molecular approaches require arbitrary decisions, whereas the
28
-------
carbon-bond approach provides a simple methodology for handling a large
variety of molecules. The current carbon-bond approach allows some
flexibility to adjust reactivity should smog-chamber data or other information
become available (as in the cinnamaldehyde example).
Another related advantage of the carbon-bond approach over the molecular
or surrogate approaches is optimization for simulating complex mixes rather
than single molecules. The current CBM is designed to be optimized for
simulating urban mixtures of hydrocarbons. If used for single-molecule smog-
chamber experiments, the CBM requires certain adjustments that are usually
straightforward. Molecular or surrogate mechanisms, on the other hand, are
inherently optimized to simulate smog-chamber experiments using only the
specific molecules that form the basis of the mechanisms. Thus, simulating
complex urban mixes with these mechanisms requires adjustments in both the
precursor definitions and the chemistry, and such adjustments are often
complicated.
Finally, the Carbon-Bond Mechanism in its present implementation (CBM-
III) has several features that enable us to recommend it over other available
mechanisms. For example, treating ethylene as a separate species is an
improvement over lumping all olefins together, because the behavior of olefins
varies greatly with changing olefinic composition. The treatment of aromatic
hydrocarbons in CBM-III is more chemically realistic than that in previous
mechanisms. However, a realistic treatment of ethylene and aromatic
hydrocarbons is not inherent in the carbon-bond concept. Molecular mechanisms
can also be designed with similar features; at the present time only the CBM-
III has been so designed.
SPEC IATION OF EMISSIONS AND ATMOSPHERIC CONCENTRATIONS INTO BOND CATEGORIES
Several important principles must be remembered in the application of the
Carbon-Bond Mechanism. First, all carbon must be accounted for. Thus, if one
adds up all of the carbon in each bond category of emissions, the sum should
equal the total carbon emitted. Although this principle appears simple and
obvious, there are practical complications. Emissions of solvents, for
example, are usually given in kilograms of emissions, but methyl alcohol
(H2COH) is a solvent in which most of the weight is represented by the oxygen
atom in the methanol molecule. Another example is the case of automobile
exhaust emissions, which are usually reported in gm/mi. of hydrocarbon as
methane—i.e., each carbon atom measured is assumed to have a molecular weight
of 16 gm/mole. Evaporative emissions, on the other hand, are reported as
straight mass, which means that a lower molecular weight is called for.
Accounting for all carbon is further complicated by the fact that the
procedures used to obtain automobile exhaust hydrocarbon estimates do not
respond efficiently to all reactive species. Aldehydes, for example, are not
often measured by standard procedures and must be added to the exhaust
emissions estimates.
29
-------
THE VOLUMETRIC EQUIVALENCE PRINCIPLE
The second important principle to remember when using the Carbon-Bond
Mechanism is that the volumetric concentrations (in ppm) of most species used
with the CBM are similar to both the volumetric measurements and the molar
concentrations used in other mechanisms. One ppm of aromatic hydrocarbon
bonds in the CBM is usually equivalent to 1 ppm of aromatic hydrocarbons in a
lumped mechanism.
We note two exceptions to the equivalence of speciation between the CBM
and molecular mechanisms. The major exception is the PAR species, which
includes not only the carbon in paraffinic molecules but also single-bonded
carbon in other molecules. A molecule of propylene, for example, contains one
single-bonded carbon in addition to the olefinic bond:
0LE»
PAR>


"1 ¦

H
H
1
H
1
1
1
1
C =
C
1
-C—H
1

1
1
H

1
¦
H


1
_
In other words, the CBM total reactive hydrocarbon (RHC) given in ppmC must
equal
(OLE x 2) + (ETH x 2) + (ARO x 6) + CARB
SURROGATE CARBONYLS
+ (DCRB x 2) + PAR = RHC (in ppmC)
A minor exception to the rule of equivalent speciation lies in the
relationship of CARB as a reaction product to other species. Some compounds,
especially internal olefins (e.g., trans-2-butene), react much more rapidly
than do terminal olefins like propylene. Thus, instead of creating a new
species with an atmospheric lifetime of only a few minutes, we chose to treat
* This is not true, however, for "surrogate mechanisms" in which all
hydrocarbons are assumed to be represented by some mixture of surrogate
hydrocarbons (e.g., propylene and butane). Comparison of speciation in
the CBM with that in a surrogate mechanism is obviously impossible.
30
-------
internal olefins as if they had already reacted (i.e., as if an internal
olefinic bond were already transformed to two carbonyls).
A similar approximation is used for cycloparaffins. No data exist for
the reactions and reactivity rates of these compounds; however, we believe
that they are more reactive than ordinary paraffinic hydrocarbons. At some
point in the reaction scheme the ring structure must break, yielding two
reactive sites instead of one. We therefore add one CARB group to the CBM
splits for cycloparaffins to account for the extra reactive site.
SAMPLE CARBON-BOND CALCULATIONS
In appendix B we present the name, molecular weight, carbon number, and
carbon-bond groupings for several compounds. This table can be referred to in
the preparation of emission inventories for the Carbon-Bond Mechanism.
To show how the CBM bond groupings can be obtained for a variety of user
objectives, we present several examples of such calculations. The first
example is presented as Table 4.
Example 1
TABLE 4. CARBON-BOND GROUPINGS
Hydrocarbon Concentrations

(ppm)
CBM Group/Molecule
Ethylene
1.051
1
ETH
Propylene
0.108
1
OLE + 1 PAR
Butane
1.13
4
PAR
trans-2-Butene 0.055
2
CARB + 2 PAR
2,3-Dimethylbutane 0.715
6
PAR
Toluene
0.121
1
AR0 + 1 PAR
m-Xylene
0.108
1
ARO + 2 PAR
Formaldehyde 0.03
1
CARB
(continued)
31
-------
Table 4
Carbon-Bond Calculations
ETH = 1 x 1.051 = 1.051
OLE = 1 x 0.108 = 0.108
ARO = (1 x 0.121) + (1 x 0.108) = 0.229
CARB = (2 x 0.055) + (1 x 0.03) = 0.14
PAR = (1 x 0.108) + (4 x 1.13) + (2 x 0.055)
+ (6 x 0.715) + (1 x 0.121) + (2 x 0.108) = 9.365
Source: University of California at Riverside Smog-Chamber
Experiment (EC-231)
Example 2
Example 2 calculates the carbon-bond concentrations that would be used
for the ambient hydrocarbon measurements reported by Kopczynski et al.
(1972). Gas chromatographic analysis (GCA) accounted for 90 percent of total
nonmethane hydrocarbons as identified by fiame ionization analysis (FIA).
Table 5(a) gives the carbon fraction allocated to each bond category for each
molecular species as calculated from the bond-splitting information in
appendix B. The calculated molar concentration for each bond group is also
given. Table 5(b) gives the sum of each bond category as well as the carbon
fraction for each bond category for the measured hydrocarbon mix. This
information could be directly input to 0ZIPM, a computer program designed to
generate EKMA-type isopleth diagrams with any kinetic mechanism.
Kopczynski et al. (1972) do not report carbonyl data for aldehydes or
ketones. The response of aldehydes and ketones to FIA and GCA is
inefficient. The carbon fraction shown for the CARB species in table 5(b)
consists exclusively of surrogate carbonyls—compounds such as internal
olefins (which form carbonyls rapidly); precise carbonyl data are lacking.
If the hydrocarbon splits in table 5(b) are used without correction for
probable carbonyl concentrations, underprediction of the reactivity of the
atmospheric mix results. Indeed, Kopczynski, Kuntz, and Bufalini (1975),
prepared a "simulated Los Angeles mix" on the basis of measured concentrations
in the 1972 study. They found that the simulated mix required the consumption
32
-------
Example 2
TABLE 5. CARBON-BOND CONCENTRATIONS APPLIED TO AMBIENT HYDROCARBON MEASUREMENTS REPORTED BY KOPCZYNSKI ET AL. (1972)
(a) Carbon-Bond Concentrations in ppb
Measured Hydrocarbon

Carbon
Fraction


Molar Concentrations
Olefina
ppbC
ETH OLE
ARO
PAR
CARB NR
ETH
OLE
ARO PAR
CARB NR
Ethylene
151
1.0



75.5



Propylene
60
0.67

0.33


20.0
20.0

1-Butene |
laobutene (
47
0.5

0.5


11.75
23.5

trans-2-Butene |
Methylacetylene|
12*


0.25
0.25 0.5


3.0
3.0 6.0
cis-2-Butene
8


0.5
0.5



4.0
1,3-Butadiene
11
0.5


0.5

2.75

5.5
1-Pentene
11
0.4

0.6


2.2
6.6

2-Methyl-1-butene
15
0.4

0.6


3.0
9.0

trana-2-Pentene
22


0.6
0.4


13.2
8.8
ci8-2-Pentene
10


0.6
0.4


6.0
4.0
2-Methyl-2-butene
29


0.6
0.4


17.4
11.6
1-Hexene
15
0.33

0.67


2.5
10.0

Unknown 7
Unknown 0*

0.33

0.67


1.5
6.0

Total
400




75.5
43.7
118.7
36.9 6.0
(continued)
-------
TABLE 5
(a) (continued)
Measured Hydrocarbon


Carbon Traction

Molar Concentrations

Aroniatics
ppbC
ETH
OLE ARO
PAR CARB NR
ETH
OLE ARO
PAR CARB
NR
Toluene
271

0.86
0.14

38.7
38.7

Ethylbenzene
67

0.75
0.25

8.4
16.75

p-Xylene
100

0.75
0.25

12.5
25.0

m-Xylens
215

0.75
0.25

26.9
53.75

o-Xylene
87

0.75
0.25

10.9
21.75

n-Propy lbenzerte
21

0.67
0.33

2.3
7.0

m-Ethyltoluene j
p-Ethyltoluene {
111

0.67
0.33

12.3
37.0

tert-Butylbenzene )
o-Ethyltoluene j
23

0.67
0.33

2.6
7.7

aec-Butylbenzene I
1,2,4-Trimethylbenzenej
137*

0.63
0.37

14.4
50.5

1,3,5-Trimethylbenzene
29

0.67
0.33




Isopropylbenzene j
Styrene j
76

0.7
0.22 0.074

8.9
17.0 5.6

Total
1137




137.9
275.15 5.6

(continued)
-------
TABLE 5
(a) (continued)
Measured Hydrocarbon 	Carbon Fraction	 	Molar Concentrations	
Paraffins	ppbC ETH OLE ARO PAR	CARB NR	ETH OLE ARO PAR CARB NR
Ethane	191	0.0	191.0
Propane	140	0.3	70.0	70.0
Isobutane	65	1.0	65.0
n-Butane	286	1.0	286.0
Isopentane	312	1.0	312.0
n-Pentane	171	1.0	171.0
Cyclopentane I	1J8«	091	Q Q9 125<6 nA
2-Methylpentane	I
3-Methylpentane	68	1.0	68.0
n-Hexane	82	1.0	82.0
2,4-Dimethylpentane	89	1.0	89.0
Cyclohexane	16	0.83	0.17 13.3 2.7
3-Methylhexan8	68	1.0	68.0
n-Heptane	40	1.0	40.0
Methylcyclohexane	49	0.86	0.14 42.1 6.9
Unknown 1	6	1.0	6.0
Unknown 2	11	1.0	11.0
Unknown 3	37	1.0	37.0
Unknown 4	28	1.0	28.0
Unknown 5	23	1.0	23.0
Unknown 6	80	1.0	80.0
(Acetylene)	160	0.0	160.0
Total	2060	1617.0 22.0
Assume 50/50 split.
* Assume molecular weight of 6.
(continued)
-------
TABLE 5
(b) Carbon-Bond Speciation Category
£ Molar
• Concentrations
Species	(ppb)	Carbon Fraction Normalized
ETH	75.5
OLE	43.7
ARO	137.9
PAR	2011.0
CARB	64.5
Non-Methane
Nonreactive	427.0
0.042
0.048
0.024
0.027
0.23
0.26
0.56
0.64
0.018
0.02
0.119

*
Gas chromatograph accounted for 3597 ppbC (3170 ppbC RHC + 427 ppbC nonreactive). Flame
ionization analysis (FIA): TNMHC = 4.0 ppmC (4000 ppb)
(c) Carbon-Bond Speciation Category Corrected for Unmeasured Hydrocarbons and
Unmeasured CarbonyIs
£ Molar
Concentrations	Carbon Fraction
Species	(ppb)	Normalized *
ETH	75.5 x -^2 = 04.0	0.044
4000
OLE	43.7 x r^j = 48.6	0.025
4000
ARO	137.9 x	= 153.4 0.24
PAR	2011.0 x -^£= 2236.3 0.58
CARB	64.5 +	0.11
S 4000
360*° X 3597 = 431*7
Unmeasured reactive hydrocarbon = (1 - PP^C GCA^ _ ^
4000 ppbC FIA
* Total reactive organic carbon = 3853.6 ppbC
§
Unmeasured carbonyl; see text
36
(concluded)
-------
of 2.3 moles of carbon per mole of NO oxidized to N02 in a smog chamber.
Kopczynski et al. (1972) found that samples of Los Angeles air required only
1.4 moles of carbon per mole of NO oxidized to NO2. Kopczynski, Kuntz, and
Bufalini (1975) suggested that other species, such as aldehydes, were
contributing to NO oxidation in Los Angeles.
From these data we can estimate the CARB concentration necessary to
replicate the oxidation reactivity observed by Kopczynski et al. (1972). If
we multiply the molar bond concentrations shown in table 5(b) by the OH
reaction-rate constant for each bond group, we obtain the production rate of
peroxyl radicals (which oxidize NO to NO2) from the measured hydrocarbons per
OH concentration in the air sample:
Compound
Bond
Concentration
(ppm)
OH Reaction-
Rate Constant
(ppm"*min~*)
Peroxyl
Radicals
per OH
Attack
Peroxyl
Production
Rate per OH
(min"l)
ETH
0.0755
12,000
2
1,812
OLE
0.0437
37,000
2
3,234
AR0
0.1379
20,500
2
5,654
PAR
2.011
1,300
2.5*
6,536
CARB
0.0645
14,000
2
1,806
(surro-



19,042
gate)




* The "A factor" of 1.5 gives 1.5 R0£ + 1 H0£ per OH attack
on a paraffinic bond.
The observed rate of peroxyl production was 2.3/1.4 = 1.64 times higher
in the Los Angeles air sample than in the surrogate mix. Compounds
unidentified by GCA for the Los Angeles air sample amounted to 10 percent of
the total. If we make the conservative assumption that the unidentified
compounds had the same reactivity as the identified mix, then the observed
rate becomes 2.07/1.4 = 1.48 times higher than the laboratory mix. This
adjustment for 10 percent unmeasured hydrocarbon raises all the calculated
bond concentrations by 10 percent and increases the peroxyl production rate to
21160. min"* per OH.
Given the observed "reactivity gap" of 0.48, we may estimate the
concentration of carbonyl compounds necessary to account for the additional
oxidation of NO to NO2:
37
-------
21160. x 0.48 _ = Q>36 ppm ^3g0 ppbj
14000 ppm"1 min 1 x 2
which is equal to 9 percent of the observed hydrocarbon concentration and
should be added to the carbon fractions shown in table 5(c).
Example 3
Example 3 also represents ambient sampling in the Los Angeles area
(Calvert, 1976). In this case, however, the measurements are reported in
molar units. To calculate CBM units from molar units, the appropriate bonds-
per-molecule factor (from appendix B) is multiplied by the molar
concentration.
Calvert (1976) stated that roughly 85 percent of total carbon atoms were
detected as individual species. Thus about 0.58 ppmC remain unaccounted for
in the analysis. If this excess carbon is reactive, we must make some
assumption regarding its composition. Normalizing to total RHC (see table
6[b]) is equivalent to assuming that the composition of the unidentified
carbon is similar to the average of that which was identified. This is what
we did in the previous example. Alternatively, if we assume that the
unidentified carbon is all paraffinic, the PAR fraction is then increased to
79 percent, and all other categories are reduced by 25 percent. Overall, the
normalized carbon fractionation of RHC as shown in table 6(b) is the most
conservative approach. However, it is important to bear in mind that only
"surrogate carbonyls" are represented in this speciation. The reactivity
calculations in example 2 indicate that this approach may underestimate the
carbonyl component. We discuss this problem more thoroughly in section 5.
Example 4
Example 4 (Table 7) shows the correspondence between a molecular
mechanism and the CBM as each would be used in the 0ZIPM program. In the
0ZIPM program two sets of numbers are input: the carbon number of each
species and the carbon fraction of emissions represented by that species. In
the case of the Carbon-Bond Mechanism, we also need to know the ethylene
fraction of the olefinic emissions, because the CBM splits out ethylene from
other olefins. This example is taken from a trajectory model study that uses
the RAPS data base for St. Louis (Jeffries, 1981, private communication). For
that study, ethylene was assumed to equal one-half of the olefinic emissions
(internal olefins were ignored). Given that ethylene represents one-half of
38
-------
Example 3
TABLE 6. LOS ANGELES AMBIENT MEASUREMENTS
(a) Reported in Molar Unite
Compound
[RH],ppm
Molar
Basis
NR
Bonds per Molecule x Concentration
OLE
ETH
PAR
ARO
CARS
CH4
2.01
2.01


C2H6
0.049
0.049


C2H4
0.043

0.043

C2H2
0.038
0.038


C3H8
0.037
0.0185

0.01B5
C3H6
0.0087

0.0087
0.0087
i80-c4Hio
0.012


0.048
n_C4H10
0.037


0.148
i-c,Ha
0.0015

0.0015
0.0030
iso-O^Hg
0.0030

0.0030
0.0060
lSO-C^H^
0.0443


0.02215
n_C5H12
0.0162


0.0810
Cyclo-CjH^
0.0026


0.0104
1"C5H10
0.004

0.004
0.016
2-Methylbutene
0.0008


0.0032
2,2-Dimethylbutene
0.0008


0.0032
2-Methylpent ane
0.0110


0.066
3-Methylpentane
0.0100


0.06
1-Hexene
0.0017

0.0017
0.0085
n-Hexane
0.0100


0.06
Cyclohexene
0.0107


0.0428
2,2,3-Trlmethy lbutane
0.0077


0.0539
C6H6
0.0082
0.0492


2-Methy lhexane
0.0069


0.0483
3-Methylhexane
0.0063


0.0441
0.0026
0.0016
0.0016
0.0214
(continued)
39
-------
TABLE 6
(a) (continued)
[RH],ppm
Molar 	Bonda per Molecule x Concentration	
Compound	Basis	NR OLE ETH PAR ARO CARB
1-Heptene
n"C7H16
Methylcyclohexane
2.2.3-	and 2,3,3-
Trlmethylpentane
2.2.4-Trimethylpentane
Toluene
1-Methylcyclohexene
2.2.5-Trimethylhexane
n-CgHi8
EtC6H5
p,m-Xylenes
o-Xylene
n-CgHjg
n-PrC6H5
aec-BuC6H5
n~C10H22
n~C11H24
n~C12H26
CO
0.0044
0.0043
0.0037
0.0019
0.0025
0.020
0.0047
0.0010
0.0021
0.0041
0.014
0.0060
0.0013
0.0010
0.0050
0.0011
0.0010
0.0003
1.91
0.0044
0.022
0.0301
0.0222
0.0152
0.02
0.02 0.02
0.0235
0.009
0.0168
0.0082 0.0041
0.028
0.012
0.0117
0.003
0.02
0.011
0.011
0.0036
0.014
0.006
0.001
0.005
0.0037
0.0094
0.001
Total
0.0233 0.043 1.2384 0.0501 0.040
(b) Total RHC Normalized

RHC

Carbon Fraction
Compound
(ppm)
ppmC
of RHC
OLE
0.0233
0.0466
0.0271
ETH
0.043
0.086
0.0501
PAR
1.2347
1.2347
0.719
ARO
0.0501
0.306
0.178
CARB
0.044
0.044
0.0256
Total

1.7173

40
(concluded)
-------
Example 4
TABLE 7. COMPARISON OF MOLECULAR MECHANISM AND THE CBM AS USED
IN THE OZIPM PROGRAM
	OZIPM INPUTS	
Average
Species Carbon Number	Carbon Fraction of Emissions
Olefin
3
0.193
Aromatic
8.1
0.142
Paraffin
6.0
0.601
Aldehyde
1
0.065
CARBON-BOND MECHANISM
Olefin	2	2/6 x 1/2 x 0.193 = 0.032
Ethylene	2	1/2 x 0.193 = 0.0965
Aromatic	6	6/8.1 x 0.142 = 0.105
Aldehyde	1	0.065 = 0.065
Paraffin	1	(2/3 x 1/2 x 0.193)
+ 2.1/8.1 x 0.142 + 0.601 = 0.70
* Ethylene = one-half of the carbon in the olefin category.
41
-------
the carbon in the olefin category, we can then calculate the average carbon
number for the remaining olefinic compounds:
total carbon
carbon number = 	
3 =
number of molecules
	0.193	
0.0965	0.0965
2 +	x
ethylene other olefins
| • 0.0965 + | • 0.0965 = 0.193
0.2895 = (0.193 - 0.14475) x
6 = x
Thus, one-half of the olefinic carbon is ethylene (0.0965 of the
total). Of the six carbon atom olefins remaining, one-third are olefinic
bonds (two carbons per olefinic bond; six carbons per molecule). Thus the
olefinic fraction is 2/6 x 1/2 x 0.193, or 0.032. The other calculations are
straightforward: 6/8.1 of the aromatic molecules are aromatic bonds; the
aldehydes do not change; and the remaining carbon is made up of PAR.
1 ppmC of emissions then equals:
0.032/2 ppm OLE
0.0965/2 ppm ETH
0.105/6 ppm AR0
0.065 ppm CARB
0.70 ppm PAR
We can also estimate olefin composition from the hydrocarbon data given
in examples 2 and 3. From table 8 we see that olefinic carbon is composed of
37 percent ETH, 21 percent OLE, 12 percent internal olefins as CARB, and 30
percent PAR. Similarly, from examples 2 and 3 we estimate that 1.1 percent of
primary paraffinic carbon can be placed in the CARB category because of the
cyclic paraffins that are included.
42
-------
TABLE 8. CARBON-BOND COMPOSITION OF OLEFINS
(Based on examples 2 and 3 in this chapter)
Species	Example 2 Example 3 Average
ETH	0.38	0.37	0.37
OLE	0.22	0.20	0.21
Internal olefin	0.09	0.15	0.12
(CARB)
PAR	(L31	(L28	0.30
Average carbon
number	2.9	2.8	2.86
43
-------
These data indicate an average carbon number of nearly three, which
agrees well with the estimate made on the basis of the RAPS emissions.
Ethylene, however, appears equal to 40 percent, rather than 50 percent, of
olefinic carbon.
If we use both the olefinic-composition factors in table 8 and the cyclic
paraffin carbonyl surrogate for the OZIPM inputs, the CBM carbon splits become
OLE = 0.193 x 0.21 = 0.0405,
ETH = 0.193 x 0.37 = 0.0714,
CARB = 0.065 + (0.193 x 0.12)
+(0.011 x 0.601) = 0.0948,
ARO = 0.142 x 6/8.1 = 0.105,
PAR = {0.193 x 0.3) + 2.1/8.1 x (0.142)
+ (0.601 x 0.989) = 0.689.
-------
SECTION 5
HYDROCARBONS IN URBAN AREAS
In this section we review available data regarding the composition of
hydrocarbons in polluted urban air. The study of ambient hydrocarbon
composition and the related subject of speciation of pollutant emissions is
important to the successful application of kinetic modeling of urban smog.
Any kinetic mechanism is liable to error if the various hydrocarbon
species that it treats are improperly specified. This problem does not
ordinarily arise in smog-chamber studies, because the experimenter has full
control over the introduction of hydrocarbons into the reaction vessel. Nor
does the speciation problem arise in the application of a surrogate mechanism
such as that used in EKMA, where all hydrocarbons are assumed to be
represented by a mixture of propylene and butane. The surrogate approach is
inflexible, however, because it does not allow for the differences that do
exist among hydrocarbon species.
Because a lumped-species mechanism like the Carbon-Bond Mechanism is more
flexible than a surrogate mechanism, there is greater potential for error. An
"assumed hydrocarbon speciation" can be supplied for the CBM to set exact
proportions for the emitted hydrocarbon species, thereby eliminating the
flexibility of the modeling exercise. Instead, we prefer to present
information about the probable composition of hydrocarbons within urban
areas. Such data allow the user to judge whether or not a particular
emissions inventory lies within the limits of variation for hydrocarbon
composition. At the end of this section, we provide a default hydrocarbon
composition profile, which can be used in the absence of data or when the
modeler suspects an error in the speciation data.
HYDROCARBON SPECIATION FOR THE LOS ANGELES AREA
Killus et al. (1980) prepared estimates of hydrocarbon composition for
the Los Angeles area on the basis of the work of Trijonis and Arledge
(1975). It should be noted that these estimates, shown in table 9, were
prepared prior to the adoption of the methodology in which internal olefins
and a fraction of cyclic paraffins are treated as carbonyl emissions. This
45
-------
TABLE 9. HYDROCARBON EMISSIONS IN THE LOS ANGELES BASIN BY CARBON FRACTION IN
CATEGORIES USED IN THE SAI URBAN AIRSHED MODEL
Source Category
Percentage
of Total
Hydrocarbon
Carbon Fraction
Nonreactive
Emissions Olefins Paraffins Ethylene Aromatics CarbonyIs Hydrocarbons
Land motor vehicles
Aircraft
Refineries
Other
Total hydrocarbons
from all sources
67.5
1.6
1.9
29.0
0.032
0.073
0.04
0.026
0.029
0.61
0.64
0.84
0.565
0.60
0.032
0.038
0.0
0.016
0.027
0.235
0.163
0.17
0.066
0.182
0.037
0.058
0.0
0.011
0.029
0.091
0.09
0.05
0.326
0.158
Normalized carbon
fraction emissions
excluding nonreac-
tive HC
Normalized carbon
fractions with
"surrogate"
carbonyls
0.034
0.71
0.032
0.22
0.034
0.024
0.70
0.032
0.22
0.055
Olefins excluding ethylene.
* Carbonyl emissions are estimates only (because they would not have been detected by the
measurement methods used); thus the sum of the weight fractions in this row is greater
than 1.
-------
"surrogate carbonyl" approximation tends to reduce slightly the olefinic and
paraffinic bond groups and to increase the carbonyl emissions. Internal
olefins represent between 10 and 15 percent of the carbon in olefin molecules,
which is 30 to 40 percent of OLE (as shown in section 4). Additional
surrogate carbonyls represent about 1 percent of the remaining emissions.
Table 9 also shows the principal effect of the "surrogate carbonyl"
approximation--the reduction of olefins to 0.024 of the RHC emissions and the
increase of carbonyls to 0.055 of RHC.
The Los Angeles inventory of volatile organic carbon emissions, as used
in the SAI Airshed Model, is presently undergoing review and modification
(Allen, 1981, private communication). The most recent emissions splits
(obtained by application of correction factors to the summation of the
emissions data file for the Airshed Model) are given in table 10.
Hydrocarbon speciation for the motor-vehicle emissions shown in table 10
is taken from measurements made by Black and High (1980) for an uncontrolled
automobile burning fuel that contains 22 percent aromatics (17 percent in
carbon-bond units). However, the average aromatic content measured by
Mayrsohn and Crabtree (1976) in a sample of Los Angeles gasolines was 37
percent (26 percent in carbon-bond units). Such speciation for gasoline
corresponds well with the measurements made by Kopczynski et al. (1972)
[described in example 2 in section 4] in which the aromatic-bond fraction was
greater than 20 percent. However, Calvert (1976) [example 3 in section 4]
reported hydrocarbon composition estimates in which the aromatic-bond fraction
was only 17 percent. The estimates made by Calvert were derived from typical
data from the LARPP study in Los Angeles. Thus, the range of emissions
estimates for the Los Angeles area is corroborated to some extent by
atmospheric measurements (see table 11).
HYDROCARBON SPECIATION FOR OTHER URBAN AREAS
Table 12 presents data regarding hydrocarbon speciation for several urban
areas (Kopczynski et al., 1975). Table 13 indicates the carbon-bond
composition for these samples, using the carbon-composition factors outlined
in example 4 in section 4. Note that CARB contains "surrogate carbonyl"
only. Actual carbonyl concentrations are likely to be higher than what is
indicated by these data.
Table 14 presents the data from a study performed by Ferman, Eisinger,
and Monson (1977) for the Denver area. The sampling site was 6 km northwest
of downtown Denver, and as the table indicates, the fractions for ethylene,
olefins, and aromatics are all two-thirds of those derived from the Kopczynski
et al. data for a Denver expressway. Surrogate carbonyl for the off-highway
data represents an even smaller fraction (relative to the expressway data)
47
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TABLE 10. LOS ANGELES EMISSIONS SPECIATION FOR 1974
EMISSIONS INVENTORY
Source	OLE PAR ETH ARO CARB
Land motor vehicles 0.1 0.59 0.124 0.19 0.046
All sources	0.049 0.705 0.090 0.154 0.046
Source: California ARB (1981).
TABLE 11. CARBON-BOND FRACTIONS OF RHC FOR EMISSIONS AND AMBIENT
	MEASUREMENTS IN THE LOS ANGELES AREA	
Estimate or Measurement	OLE PAR ETH ARO CARB
Emissions estimates for 1974
Kill us et al. (1980)
California ARB (1981)
Atmospheric measurements
Kopczynski et al. (1972)
Calvert (1976)
(LARPP—1974)
*	Calculated from excess reactivity over laboratory surrogate mix
(see Example 2 in section 4).
*	Surrogate CARB only; aldehydes and ketones not measured.
0.024
0.049
0.7
0.705
0.032
0.096
0.22
0.154
0.055
0.039
0.027
0.027
0.64
0.72
0.048
0.05
0.26
0.18
0.07
0.0261"
48
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TABLE 12. RATIOS OF POLLUTANTS TO SUM OF HYDROCARBONS LESS
Cx TO C3 PARAFFINS IN ROADWAY SAMPLES
Denver
Expressway	L.A.	Lincoln
St. Louis, 1972 Interchange Underpass Tunnel
Pollutant Highways Downtown 1971	1970	1970
C3 + paraffins	0.42	0.50	0.57	0.41	0.46
Olefins	0.23	0.19	0.15	0.13	0.22
Cg + aromatics	0.25	0.23	0.23	0.41	0.26
Acetylene	0.068	0.068	0.056	0.053	0.067
Carbon monoxide 5.0	5.1	4.0	3.2	4.5
Nitrogen oxides	0.13	0.22	0.16	0.14	0.40
Source: Kopczynski, Kuntz, and Bufalini (1975)
49
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TABLE 13. URBAN HYDROCARBON COMPOSITION DATA
(a) Carbon-Bond Splits for Data in Table 12
Site
ETH
From Olefins
OLE
CARB
PAR
From ARO
ARO
PAR
From PAR
PAR
CARB
Total
PAR
St. Louis
Highways	0.085 0.048 0.028 0.069 0.19 0.06 0.404 0.006 0.533
Downtown
Denver
Expressway
Los Angeles
Underpass
Lincoln Tunnel
0.07 0.04
0.023 0.057 0.15 0.04 0.493 0.007 0.59
0.056 0.0315 0.018 0.045 0.15 0.04 0.562 0.008 0.65
0.048 0.027 0.016 0.039 0.31 0.10 0.404 0.006 0.54
0.08 0.046 0.026 0.066 0.20 0.06 0.453 0.007 0.58
(b) Normalized to 100 Percent Carbon
Site
ETH
OLE
PAR
ARO CARB
St. Louis Highways
Downtown
Denver Expressway
0.094 0.053 0.59 0.21 0.038
0.076 0.044 0.64 0.16 0.033
0.059 0.033 0.68 0.16 0.027
Los Angeles Underpass 0.05 0.028 0.57 0.33 0.023
Lincoln Tunnel
0.085 0.049 0.62 0.21 0.035
50
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TABLE 14. STATISTICAL SUMMARY OF HYDROCARBON DATA FOR THE DENVER AREA*
(a) Hydrocarbon Concentrations
(ppbC)
Hydrocarbon
Average
99th
Percentile
Maximum
Ethane*
69
447
638
Ethylene
53
304
508
Acetylene*
59
344
530
Propane*
95
785
924
Propylene
25
146
243
Isobutane
58
557
857
n-Butane
123
685
979
Isopentane
111
600
999
n-Pentane
68
586
781
2-Methylpentane
53
424
652
3-Methylpentane
37
254
509
n-Hexane
55
321
535
2,2,3-Trimethyl butane
32
218
485
Cyclohexane
17
164
547
Benzene*
18
116
178
2-Methylhexane
34
198
441
3-Methylhexane
38
240
481
1-Heptene
20
135
301
n-Heptane
33
210
420
Methylcyclohexane
28
177
272
Toluene
64
338
520
1-Methy1cyclohexane
23
120
239
n-Octane
22
153
766
Ethylbenzene
15
80
115
m- and p-Xylene
47
260
372
o-Xylene
24
142
571
n-Nonane
19
116
334
sec-Butyl benzene
30
167
419
n-Decane
22
146
209
n-Undecane
14
84
120
Total
1112
7333

*	Based on >500 points for each compound. Compounds listed are the 30
with the highest average concentrations. Minimum concentrations for all
are less than 1 ppbC.
*	Nonreactive (propane 0.5 reactive).
(continued)
51
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TABLE 14
(b) Carbon-Bond Fractions for Denver Hydrocarbon Data
ETH	OLE	CARB ARO PAR
Average	0.0476 0.02 0.009 0.123 0.80
99th Percentile 0.0415 0.0185 0.0095 0.1025 0.83
(concluded)
52
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apparently because of the exclusion of trace compounds like internal
olefins. These data represent the least reactive mix of hydrocarbons in any
data set that we have analyzed. Use of fractions lower than these for
ethylene, olefins, and aromatics is not recommended. Because carbonyl
concentrations are usually unmeasured and conjectural, we present later in the
section some carbonyl emissions estimates.
Table 15 gives hydrocarbon-composition data for sites in the eastern
United States and the carbon-bond fractions calculated from these data. Since
no internal olefins were reported and only a small quantity of cyclic
paraffins was measured, no fraction of surrogate CARB is calculated. Note
also that the fraction of ethylene as carbon in olefin molecules varies from
0.33 to 0.49, with an average of 0.41. This figure is similar to the 0.37
fraction that we have used in the preceding examples.
The data in table 16 are derived from samples taken in September 1973 by
Lonneman and Bufalini (private communication) for the Houston, Texas, area.
The high ethylene fraction calculated for these samples represents the major
discrepancy between them and samples taken from other urban areas. The
ethylene concentrations observed were in some cases three to five times the
acetylene concentration, which indicates a large nonautomotive source of
ethylene in the Houston area. Other data gathered in Houston (Lonneman and
Bufalini, private corranunication; Siddiqi and Worley, 1975) show more common
ethylene fractions, with approximately a one-to-one ratio to acetylene.
CARBONYL COMPOUNDS IN URBAN AIR
In our discussion of hydrocarbon composition thus far, we have not
included carbonyl compounds per se. Because aldehydes and ketones require
special measurement techniques, they are not included in the available
composition data, and only "surrogate carbonyl" can be reported. However, the
photochemical reactivity observed in urban air pollution leads to the
conclusion that significant concentrations of carbonyl compounds do exist in
urban atmospheres, both as primary emissions and as secondary reaction
products.
In the following subsection we discuss the importance of carbonyl
compounds in the formation of smog, and we then examine some estimates of
carbonyls in emissions and ambient air.
RADICAL SOURCES AND HYDROCARBON REACTIVITY
Smog formation results from the catalytic oxidation of hydrocarbons by
hydroxyl radicals (OH). The concentration of hydroxyl radicals in the
53
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TABLE 15. HYDROCARBON COMPOSITION DATA FOR SELECTED SITES IN THE
EASTERN UNITED STATES
(a) Ratio* of Sum of Paraffins, Olefins, and Aromatics to
Acetylene at New York-New Jersey Station at All Times
Lincoln
Component
Bayonne
Linden
Manhattan
Brooklyn
Tunnel
I Paraffins
19.50
19.08
8.51
11.29
6.81
I C4 paraffins
5.34
5.24
1.97
2.47
1.41
I C5 paraffins
6.48
5.65
2.89
3.21
1.90
I Olefins
4.83
5.75
2.21
2.97
3.24
I C4 olefins
0.99
1.35
0.39
0.50
0.59
I Cg olefins
0.11
0.14
0.05
0.05
0.08
I Aromatics
12.77
11.70
6.74
11.3
3.87
Toluene
5.20
4.84
2.16
4.77
1.27
£ Cg aromatics
5.89
4.87
2.67
4.67
1.44
1 ^9 + C^g aromatics
1.68
1.99
1.91
1.86
1.16
Ethylene
1.83
1.91
1.08
1.28
1.33
Propylene
0.54
0.87
0.31
0.38
0.61
Average acetylene
concentration,
ppb carbon
15.9
21.7
43.7
32.1

Total
37.1
36.5
17.46
25.56
13.92
Source: Lonneman et al. (1974)
(continued)
54
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TABLE 15
(b) Average Ratios* of Hydrocarbon to Acetylene
in Lincoln Tunnel
Ratio of Component
to C2H2 and
Component	Standard Deviation
Ethylene
1.33
0.14
Isobutane
0.34
0.05
n-Butane
0.97
0.12
Propylene
0.61
0.07
Isopentane
1.25
0.14
Isobutylene
0.34
0.04
Butene-1


Sum of C4 olefins
0.60
0.07
n-Pentane
0.62
0.07
Sum of C5 olefins
0.53
0.08
Cyclopentane
0.76
0.08
2-Methylpentane


3-Methylpentane
0.34
0.04
n-Hexane
0.36
0.05
2,4-Dimethylpentane
0.34
0.04
2,2,4-Trimethylpentane
0.27
0.23
Toluene
1.27
0.23
Ethyl benzene
0.22
0.03
p-Xylene
0.25
0.03
m-Xylene
0.70
0.15
0-Xylene
0.28
0.04
Sum of Cg aromatics
1.44
0.25
3 & 4-Ethyl toluene
0.38
0.05
sec-Butyl benzene
0.40
0.06
1,2,4-Trimethyl benzene


Sum of paraffins
6.81
0.92
Sum of olefins*
3.24
0.32
Sum of aromatics
3.87
0.58
Total nonmethane hydrocarbons
13.9
1.5
Carbon monoxide
63.4
6.1
*	Ratios were calculated from component concentrations
in parts-per-bil1 ion carbon.
*	Average carbon number for olefins = 2.88	(continued)
Ethylene = £ olefin x 0.41.
55
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TABLE 15
(c) Carbon-Bond Fractions for Data Presented in Table 15(a) and (b)

Site
ETH
OLE
ARO PAR
CARB

Bayonne
0.049
0.0405
0.268 0.64


Linden
0.052
0.057
0.248 0.64
—

Manhattan
0.062
0.026
0.29 0.62
—

Brooklyn
0.0501
0.03
0.18 0.74
—

Lincoln Tunnel
0.0955
0.066
0.208 0.63
(concluded)

TABLE 16. COMPOSITION
OF HYDROCARBON IN HOUSTON
AIR


Fraction of
Carbon per Bond Category

Site
ETH
OLE PAR
ARO
Surrogate
CARB
Nonreactive
HOI
0.11
0.022 0.43
0.2
0.016
0.22

0.14
0.028 0.55
0.26
0.02
—
H05
0.107
0.057 0.57
0.16
0.026
0.08

0.12
0.062 0.62
0.17
0.0285

-------
atmosphere is small (about 10"^ ppm), but because they are rapidly destroyed,
a constant influx of such radicals is necessary to maintain the smog-formation
process. Most of the radicals necessary to generate smog are formed by the
photolysis of oxygenated hydrocarbons--e.g.:
+02
HCHO + hu -4 CO + H02 + H02
followed by
H02 + NO + N02 + OH
Since photolyzable oxygenates are intermediate products of the process of
hydrocarbon oxidation, the smog process is self-perpetuating; however, under
some circumstances, it is not self-starting. If a pure hydrocarbon of
relatively low reactivity were to be irradiated in an atmosphere free of
extraneous sources of radicals, the smog-formation process would never be
initiated. Urban air, however, contains numerous initial radical sources.
Some oxygenated hydrocarbons are formed in the combustion process, and others
are formed when extremely reactive hydrocarbons (like trans-2-butene) are
exposed to a background of trace ozone. This process represents one of the
sources of "surrogate carbonyl" used in the CBM. Inorganic radical sources
are also important in the formation of oxygenated hydrocarbons. Perhaps the
most important source for the troposphere is the photolysis of ozone:
0g + hv -~ Q*D + 02 ,
0*0 + H20 * OH + OH
This process dominates in clean air in which the concentration of hydrocarbons
and nitrogen oxides is low.
In urban or industrial areas where the concentration of nitrogen oxides
and nitrates is high, nitrous acid (HONO) photolysis can play an important
role in smog formation:
HONO + hv ~ H + NO
Nitrous acid, which has been observed in urban air, may be a minor component
of automobile exhaust. It can be formed in liquid water droplets (Schwartz
and White, 1981) or as part of the denitrification process in vegetation
(Anderson et al., 1978).
HONO has been detected in urban air at night near Riverside, California
(Piatt, et al., 1980) at concentrations of 3 percent to 6 percent of ambient
57
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N02.* Presumably, HONO is formed in heterogeneous reactions near the emissions
source of N0X, in this case automotive exhaust (the sample path in the
Riverside study included a section of a freeway). HONO has been observed in
direct sampling of auto exhaust under some conditions (Winer, 1981, private
communication).
Although total N0X was not reported in the study of Piatt et al., NO?
concentrations are typically one-third of total N0X in the Los Angeles and San
Gabriel basin area (LAAPCD, 1974, Hayes, private communication). This would
put emissions of HONO in the range of 1 to 2 percent of total N0X. In our
kinetic simulation studies (Whitten et al., 1979; Whitten, Killus, and Hogo,
1980), we have found that one-third of the equilibrium concentration of HONO
(calculated from the concentrations of NO, NO2, and water vapor) is generally
sufficient to explain initiation phenomena in smog-chamber experiments. For a
N02-to-N0x ratio of 0.33 and a water vapor concentration of 15,000 ppm, this
calculated concentration of HONO equals 1.9 percent—excel lent agreement with
the atmospheric measurements.
In modeling urban air, one might wish to include the effects of HONO by
including the species and specifying its emissions as approximately 2 percent
of N0X. However, as mentioned previously, for atmospheric studies the Carbon-
Bond Mechanism is usually implemented without the chemistry of HONO. Except
for the initiation effects discussed earlier, nitrous acid chemistry has a
negligible effect on the calculations.
We have devised a methodology to simulate the effects of HONO emissions
by specifying an emission of DCRB, the highly photolytic dicarbonyl species.
DCRB has a photolysis rate that is nearly as high as that of HONO. Since the
radical yield for DCRB photolysis is twice that of HONO, the emissions rate of
0CRB should be only 1 percent that of N0X, one-half the assumed HONO emissions
rate. Although DCRB emits peroxyl rather than hydroxyl radicals, the peroxyl
radicals are rapidly converted to OH by reaction with NO. The excess NO-to-
N02 conversions produced by this approach amount to only a few percent of
total N0X, and the discrepancy in carbon-mass balance is less than 1 percent.
EMISSIONS OF CARB0NYL COMPOUNDS
In addition to their role in the initiation of the smog process, carbonyl
compounds are also of major importance to smog chemistry, because a
significant fraction of hydrocarbon reactivity results from the oxidation of
carbonyl compounds by the hydroxyl radical. In section 4, when we compared
* The term "reactivity" has acquired a variety of meanings in smog
chemistry. In this context we define it as the oxidative production
of peroxyl radicals, a process which then effects a conversion of NO
to N02»
58
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the reactivity rate of an urban air sample with, that of a surrogate laboratory
smog mixture containing pure hydrocarbons, we found the reactivity rate for
the urban air sample to be about 40 percent greater than that of the
surrogate. Furthermore, since carbonyls are a principal reaction product of
hydrocarbons, a significant fraction of the peroxyl radicals formed in the
laboratory hydrocarbon mixture results from the oxidation of carbonyls.
The Carbon-Bond Mechanism is designed to treat explicitly the carbonyl
oxidation products of hydrocarbons. However, primary emissions make up a
significant fraction of carbonyl compounds, and unless the emissions inventory
of such compounds is reasonable, no mechanism, however well designed, will
produce acceptable results. Thus, the modeler must have an understanding of
the range of plausible values for the carbonyl composition of urban volatile
organic compounds.
Dimitriades and Wesson (1972) reviewed available information concerning
the relative levels of aldehydes and hydrocarbons found in automobile
exhaust. In tests performed by the U.S. Bureau of Mines (Sawicki, Stanley,
and Elbert, 1961; Dimitriades and Wesson, 1972), a mole fraction of total
aldehyde per mole of hydrocarbon was calculated to range from 0.06 to 0.09.
Other studies indicated greater variation, with mole fractions of aldehyde
ranging from 0.07 to 0.35 (Oberdorfer, 1967) and from 0.12 to 0.20 (Wadowski
and Weaver, 1970). Dimitriades and Wesson (1972) concluded that total
aldehyde levels in pre-1970 auto exhaust represented about 10 percent of total
hydrocarbon on a molar basis and 5 percent on a carbon basis (the aldehydes
being about 60 percent formaldehyde on a molar basis).
Altshuller and McPherson (1963) measured ambient concentrations of
formaldehyde and acrolein. Acrolein was found to make up 10 percent to 15
percent of the concentration of formaldehyde, thus indicating the probable
importance of carbonyl species other than simple aldehydes. Seizinger and
Dimitriades (1972) identified numerous carbonyl compounds in automobile
exhaust—notably acrolein, acetone, and the aromatic aldehydes. Although
Altshuller and McPherson (1963) did not report aldehydes as a fraction of
reactive hydrocarbon, the formaldehyde concentrations observed (0.01 to 0.115
ppm) were consistent with the 5 percent carbon fraction suggested by
Dimitriades and Wesson (1972).
In an analysis of monitoring data for the Los Angeles area (Scott
Research Laboratories, 1970), Killus et al. (1980) concluded that aldehyde
emissions were similar to olefin emissions when calculated on a molar basis.
If this assumption is made, the data given in this chapter indicate aldehyde
emissions that range from 0.034 to 0.074 as a fraction of emitted reactive
carbon.
59
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Data are very sparse for emissions from vehicles having pollution-control
devices. However, in a review of recent data, Bui on, Malko, and Taback (1978)
found no major differences in the formaldehyde emissions from controlled and
uncontrolled vehicles. Reported emission levels were fairly low in these
studies: approximately 2 to 3 percent of total RHC. Note that total aldehyde
emissions would be expected to be higher and total carbonyls higher still.
The preceding analysis provides an outline of plausible carbonyl
emissions in an urban emissions inventory. Formaldehyde emissions alone
account for perhaps 2 to 6 percent of the carbon emitted in automobile
exhaust; however, formaldehyde would account for only 1 to 4 percent of total
emitted reactive carbon, since other emission processes (e.g., evaporation)
seldom emit aldehydes per se.
Adding other aldehydes to formaldehyde increases our estimate of carbonyl
emissions by approximately 50 percent (since formaldehyde represents 60
percent of aldehyde emissions on a molar basis). The addition of other
carbonyl compounds (e.g., acetone, acrolein, and benzaldehyde) increases the
carbonyl emissions rate still further, to perhaps twice that of emitted
formaldehyde. Finally, surrogate carbonyl in the CBM accounts for perhaps 2
percent of emitted carbon.
In the CBM, carbonyl emissions as a fraction of total reactive carbon
emissions would be expected to represent a minimum of 5 percent, which is in
agreement with the assumptions used in other mechanisms (e.g., EKMA). Total
aldehyde emissions could be as high as 7 percent and total carbonyls as high
as 10 percent of reactive carbon (on the basis of reactivity differentials
between urban air and laboratory surrogate mixes) [see example 2, section
4]. With the onset of photochemical smog formation, the carbonyl fraction
increases because of oxidation of reactive hydrocarbons to aldehydes, ketones,
glyoxals, and so forth. This process eventually reaches a photochemical
equilibrium in which carbonyl carbon can represent as much as 25 percent of
reactive carbon.
SUMMARY OF URBAN HYDROCARBON COMPOSITION
In this section we have presented a variety of hydrocarbon-composition
data reported in carbon-bond units. Since the CBM allows for easy inventory
of emissions, ambient data, and modeled concentrations, the ranges of
composition data can be used to ascertain whether a particular modeling study
is employing a realistic hydrocarbon composition. Ranges are presented in
table 17, and a recommended composition is indicated for those studies in
which detailed species data are lacking.
60
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TABLE 17. RANGES OF URBAN HYDROCARBON COMPOSITION
(Fractions Normalized to RHC)

Carbon
Fraction
Compound
Range
Recommended
ETH
0.03 -~ 0.12
0.05
OLE
0.02 - 0.06
0.03
ARO
0.10 + 0.33
0.22
PAR
0.55 + 0.80
0.65
CARB*
0.03 - 0.11
0.05
* Includes surrogate carbonyl from internal
olefins and cyclic paraffins.
61
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SECTION 6
SUMMARY
The original publication of the Carbon-Bond Mechanism (CBM-1, given in
Whitten, Hogo, and Killus, 1980) introduced the concept of treating the
atmospheric chemistry of complex mixtures of organic molecules as if the
carbon atoms reacted more or less independently according to their local
bonding. Since that introduction, the mechanism has undergone two major
updates, and considerable experience with its use in atmospheric models has
shown that proper use of the mechanism is essential to produce good results.
This report presents the latest version of the Carbon-Bond Mechanism (CBM-III)
in section 1, followed by a guide to using virtually any version of the CBM in
section 2. In section 3, which also concerns the use of the CBM, specific
urban reactivities are illustrated and a recommended set of CBM fractions to
represent urban organics is developed for cases where data are lacking (table
17).
The latest CBM update, given in section 1, is mainly concerned with the
chemistry of aromatics. Dicarbonyl compounds and nitroaromatic compounds have
been shown to play a significant role in the smog chemistry of aromatics.
Reactions have therefore been introduced into CBM-III to account for similar
reactions identified in the detailed or explicit chemistry of aromatics,
especially toluene. The CBM update also includes changes in several rate
constants to reflect recent independent measurements and evaluations.
Finally, some minor changes in handling ketones have been introduced.
Section 2 explains how the CBM shows key advantages over other mechanisms
in actual use. For instance, the averaging of molecular weights is
eliminated; carbon conservation is automatic; reactivity averaging is often
done over a narrow range; molecules with various functional groups can be
handled in a straightforward manner; and the CBM concept tends to work best
for complex mixtures, although adjustments can be made to treat individual
hydrocarbons. Important principles relating to successful applications of the
CBM are also discussed. Some of these principles are the accounting of all
reactive carbon, the volumetric equivalence between CBM units and molecular
concentrations of certain species, and the surrogate nature of the CBM
carbonyl species. Examples of converting specific molecular information into
CBM speciation are then presented.
62
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Section 3 has been included to show how proper speciation can be
developed for several urban areas. Although the CBM has been formulated to
respond correctly to changes in reactivities, this sensitivity can lead to
incorrect results if the CBM is improperly utilized. In particular, the CBM
is very sensitive to carbonyl levels. A review of some available data is
presented. Finally, a set of CBM fractions representative of typical urban
reactivity is presented for use in the absence of speciation data. If
speciation data appear to give quite different CBM fractions than this
representative set, then the data should be checked to ensure that the
differences can be explained.
63
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REFERENCES
Altshuller, A. P., and S. P. McPherson (1963), "Spectrophotometryc
Analysis of Aldehydes in the Los Angeles Atmosphere," J. Air Pollut.
Control Assoc., Vol. 13, No. 3.
Anderson, G. E., et al. (1977), "Air Quality in the Denver Metropolitan
Region 1974-2000," EF77-222, EPA-908/1-77-002, U.S. Environmental
Protection Agency, Region VIII, Denver, Colorado.
Anderson, G. E., et al. (1978), "Process Influencing the Concentrations of
Nitrogen Oxides in the Lower Troposphere," EF78-31R3, Systems
Applications, Inc., San Rafael, California.
Baulch, D. L., et al. (1980), "Evaluated Kinetic and Photochemical Data
for Atmospheric Chemistry," reprint No. 159 from Journal of Physical
and Chemical Reference Data, Vol. 9, No. 2, pp. 295-471.
Black, F., and L. High (1980), "Passenger Car Hydrocarbon Emissions
Speciation," EPA-600/2-80/085, U.S. Environmental Protection Agency,
Environmental Sciences Research Laboratory, Research Triangle Park,
North Carolina.
Bulon, H. W., J. F. Malko, and H. J. Taback (1978), Volatile Organic
Compound (VOC) Species Data Manual, EPA-450/3-78-119, U.S.
Environmental Protection Agency, Research Triangle Park, North
Carolina.
Calvert, J. G. (1976), "Hydrocarbon Involvement in Photochemical Smog
Formation in Los Angeles Atmosphere," Environ. Sci. Techno!., Vol. 10,
No. 3, p. 257.
Carter, W.P.L., et al. (1979), "Computer Modeling of Smog Chamber Data:
Progress in Validation of a Detailed Mechanism for the Photooxidation
of Propene and n-Butane in Photochemical Smog," Int. J. Chem. Kinet.,
Vol. 11, pp. 45-103.
Davis et al. (1974), "Trace Gas Analysis of Power Plant Plumes via
Aircraft Measurement: 03, N0X, and S0X Chemistry," Science, Vol. 186,
pp. 733-736.
64
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Dimitriades, B., and T. C. Wesson (1972), "Reactivities of Exhaust
Aldehydes," Environ. Sci. Techno!., Vol. 22, No. 1, p. 33.
Dodge, M. C., and R. R. Arnts (1979), "A New Mechanism for the Reaction of
Ozone with Olefins," Int. J. Chem. Kinet., Vol. 11, pp. 399-410.
Ferman, M. A., R. S. Eisinger, and P. R. Monson (1977), "Characterization
of Denver Air Quality," EPA-600/9-77-001, Denver Air Pollution Study,
U.S. Environmental Protection Agency, Research Triangle Park, North
Carolina.
Gear, C. W. (1971), Numerical Initial Value Problems in Ordinary
Differential Equations (Prentice-Hall, Englewood Cliffs, New Jersey).
Hindmarsh, A. C. (1974), "GEAR: Ordinary Differential Equation System
Solver," Report UCID-30001, Rev. 3, Lawrence Livermore Laboratory,
Livermore, California.
Kill us, J. P., and G. Z. Whitten (1981), "A Mechanism Describing the
Photochemical Oxidation of Toluene in Smog," manuscript in review.
Killus, J. P., et al. (1980), "Continued Research in Mesoscale Air
Pollution Simulation Modeling—Vol. V," EF77-142R, Systems
Applications, Inc., San Rafael, California.
Kopczynski, S. L., R. L. Kuntz, and J. J. Bufalini (1975), "Reactivities
of Complex Hydrocarbon Mixtures," Environ. Sci. Techno!., Vol. 9, No.
7, p. 649.
Kopczynski, S. L., et al. (1975), "Gaseous Pollutants in St. Louis and
Other Cities," J. Air Pollut. Control Assoc., Vol. 25, No. 3, p. 251.
Kopczynski, S. L., et al. (1972), "Photochemistry of Atmospheric Samples
in Los Angeles," Environ. Sci. Technol., Vol. 6, No. 4, p. 342.
Lonneman, W. A., et al. (1974), "Hydrocarbon Composition of Urban Air
Pollution," J. Air Pollut. Control Assoc., Vol. 8, No. 3, p. 229.
Mayrsohn, H., and J. Crabtree (1976), "Source Reconciliation of
Atmospheric Hydrocarbons," Atmos. Environ., Vol. 10, pp. 137-143.
Miller et al. (1978), "Ozone Formation Related to Power Plant Emissions,"
Science, Vol. 202, p. 15.
65
-------
Oberdorfer, P. E. (1967), "The Determination of Aldehydes in Automobile
Exhaust Gas," SAE Paper 670123, Society of Automotive Engineers,
New York, New York.
Piatt et al. (1980), "Observations of HONO in an Urban Atmosphere by
Differential Optical Absorption," Nature, Vol. 285, p. 312.
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benzothiazolone Hydrazone Test," Anal. Chem., Vol. 38, No. 1,
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Schwartz, S. E., and W. H. White (1981), "Equilibrium Solubility of the
Nitrogen Oxides and Oxyacids in Aqueous Solution," BNL report 27102,
Brookhaven National Laboratory, Upton, New York.
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the Los Angeles Basin, Vol. III. El Monte Ground Data," National Air
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Lakeway, Texas.
Trijonis, J. C., and K. W. Arledge (1975), "Impact of Reactivity Criteria
on Organic Emission Control Strategies in the Metropolitan Los Angeles
AQCR," TRW, Incorporated, El Segundo, California.
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Parameters, Fuel Composition, and Control Devices on Aldehyde Exhaust
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66
-------
Whitten, G. Z., J. P. Killus, and H. Hogo (1980), "Modeling of Simulated
Photochemical Smog with Kinetic Mechanisms. Vol. 1. Final Report,"
EPA-600/3-80-028a, U.S. Environmental Protection Agency, Office of
Research and Development, Research Triangle Park, North Carolina.
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with Kinetic Mechanisms. Vol. 1. Interim Report," EPA-600/3-79-001a,
U.S. Environmental Protection Agency, Office of Research and
Development, Research Triangle Park, North Carolina.
67
-------
Appendix A
VALIDATION SIMULATIONS FOR CARBON-BOND MECHANISM III
UNIVERSITY OF CALIFORNIA AT RIVERSIDE—SEVEN COMPONENT RUNS
One of the requirements of a kinetic mechanism is that it respond
appropriately to changes in hydrocarbon composition. Three different
hydrocarbon mixtures containing varying amounts of olefins, paraffins, and
aromatics were used in the eleven modeling experiments performed at UCR
(see table A-l). As can be seen from the simulation results shown in
figures A-l through A-ll, CBM-III gives reasonable results for all three
mixtures of hydrocarbons.
Simulations more accurate than those we have presented can be
achieved by adapting CBM-III to the specific hydrocarbons in these
experiments rather than using the default values for various rate
constants. For example, the mixture of butane and 2,3-dimethylbutane in
the paraffin component has an average reaction rate with OH of
approximately 1100 ppm"^min"^, which is lower than the default value of
1300 ppm~lmin~l. Similarly, the default speciation of CARB in CBM-III is
one-half formaldehyde, one-quarter higher aldehydes, and one-quarter
ketones. The actual measured carbonyl compositions in these experiments
varied from these ratios.
The only variable factor for each experiment was the initial
concentration of H0N0 that was assumed to be formed when the chamber was
loaded with N0X. These concentrations are given in table A-l. Initial
H0N0 varies from 0 to 12 ppb. The maximum H0N0 used is 2.5 percent of
N0X, which is similar to the ratios of H0N0 to N02 that have been observed
in the atmosphere (Piatt et al., 1979).
68
-------

TABLE A-1.
INITIAL
CONDITIONS
AND REACTIVITY DATA
FOR SEVEN
HYDROCARBON/Nq, EXPERIMENTS








Concentration











(ppm)





EC Run No.
231
232
233
237
238
241
242
243
245
246
247
EPA Run No.
4
1
2
4
3
5
7
7A
6
1
8
Mix ture
B
A
A
B
B
B
C

C
A
c
Reactant











Ethene
1.051
0.258
0.260
0.875
0.982
0.484
2.014
1.939
2.055
0.253
1.025
Propene
0.108
0.051
0.051
0.100
0.093
0.045
0.109
0.109
0.104
0.049
0.054
trans-2-Butene
0.055
0.026
0.025
0.050
0.047
0.024
0.108
0.110
0.102
0.026
0.053
n-Butane
1.130
1.102
1.085
1.025
0.966
0.464
0.558
0.568
0.534
1.058
0.273
2,3-Dimethyl butane
0.715
0.612
0.648
0.463
0.420
0.211
0.203
0.084
0.185
0.538
0.080
Toluene
0.121
0.032
0.034
0.086
0.083
0.040
0.306
0.155
0.321
0.023
0.145
m-Xylene
0.108
0.029
0.033
0.091
0.084
0.044
0.306
0.154
0.317
0.023
0.145
Total HC (ppraC)
13.17
9.31
9.50
10.46
10.07
4.95
12.82
9.74
12.86
8.56
6.17
NO
0.440
0.469
0.096
0.377
0.718
0.379
0.377
0.386
0.743
0.386
0.380
NO-
0.052
0.024
0.007
0.106
0.234
0.110
0.125
0.114
0.259
0.122
0.125
NR<
0.492
0.492
0.103
0.483
0.952
0.469
0.503
0.502
0.992
0.506
0.505
HONO
0.006
0.004
0.004
0.008
0.010
0.008
0.010
0.010
0.020
0.012
0.010
HCHO
0.020
0.009
0.004
0.0
0.026
0.018
0.028
0.0
0.016
0.000
0.003
Reactivity











NO^ max (ppm)
0.357
0.333
0.071
0.368
0.663
0.351
0.400
0.394
0.752
0.366
0.369
at time (min)
75
150-165
30-45
60
120
135
30
30
60
135
60
0^ max (ppm)
0.623
—
0.330
0.655
0.692
—
0.682
0.716
0.892
0.574
0.657
at time (min)
225-255
—
240-345
240
435
—
105
135
180
570
210-240
6-hr 0^ (ppm)
0.540
0.305
0.325
0.584
0.674
0.408
0.418
0.711
0.635
0.374
—
PAN mac (ppm)
0.095
—
0.307
0.100
0.113
—
0.140
0.100
0.194
0.070
0.106
at time (min)
270-330
—
300
300
495
—
180
135-150
240
570
300
6-hr PAN (ppm)
0.092
0.040
0.036
0.098
0.084
0.047
0.111
0.100
0.162
0.041
—
Physical Parameters











(Averaqes)











Temperature (°F)
85.3
85.3
85.0
86.2
86.8
86.5
86.0
85.0
86.3
86.5
86.4
RH (%)
42.5
54.0
53.0
57.0
59.5
50.5
60.5
54.5
50.5
53.0
54.0
Radiometer (mv)
0.23
0.23
0.23
0.23
0.23
0.23
0.23
0.23
0.23
0.23
0.23
* In the Carbon-Bond Mechanism, internal olefins are treated as two carbonyl groups, i.e., their reaction times are asumed to be
instantaneously fast.
-------
N0
N02
o.eo
x
0.60

t 0.40
0.20
0.00
TIME (MINUTES)
PAN
0.12
0.09
P 0.06
u
0.03
0.00
50 100 150 200 250 300 350 400
TIME (MINUTES)
0LE
0.12
0.09
CB
t 0.06
u
U
0.03
0.00
TINE (MINUTES)
PAR §
CAR
9.40
x
8.30
E 7.20
u
6.10
5.00
350 400
TINE (HINUTES)
I Low concentrations include paraffins only; high concentrations include all
measured single-bonded carbon.
Figure A-l. Simulation results for EC-231.
70
-------
0.48 r
a.
a.
0.36 -
E 0.24 -
iu
o
0.12
0.00
0 50 100 150 200 250 300 350 400
TIME (MINUTES)
0.055
t—i—T
PAN ¦
i—i—r
0.044 -
0.033 -
0.022 -
u
z
at
u
0.011 -
0.000
0 50 100 150 200 250 300 350 400
TIME (MINUTES)
10.00
9.00
Z
a.
a.
8.00
x
m
*4
K
c
7.00
t-
z
ui
cj
6.00
5.00
TIME (MINUTES)
0LE
0.060
0.045
s
£ 0.030
cj
0.015
0.000
100 150 200 250 300 350 400
TINE (MINUTES)
S Paraffins only.
Figure A-2. Simulation results for EC-232.
71
-------
0.12
0.09
i= 0.06
u
0.09
0.00
50 100 150 200 250 300 350 400
TIME (MINUTES)
HCH0
0.48
0.36
fc 0.24
o
0.12
0.00
50 100 150 200 250 300 350 40
TIHE (HINUTES)
0.35
ETH
0.28
0.21
E 0.14 -
u
(B
o
0.07
0.00
100 150 200 250 300 350 400
TIME (HINUTES)
Figure A-2. (concluded)
72
-------
F 0.20
0.00
0 SO 100 150 200 250 300 350 400
T1HE (MINUTES)
0.100
0.075
»- 0.050
0.025
0.000
0 50 100 150 200 250 300 350 400
TINE (MINUTES)
0.080 -
0.045
0.030
0.015 -
0.000
0 SO 100 ISO 200 250 300 350 400
TIME (MINUTES)
10.00
9.00
6.00
7.00
o
ae
B
u
6.00
5.00
1 "1 1 T
PAR § ¦
h ¦—t—r
1
~ —.

-

K

_

m
1 1 1
1 1 1
-J.
0 50 100 150 200 250 300 350 400
TIME (MINUTES)
I Low concentrations include paraffins only; high concentrations include all
measured single-bonded carbon.
Figure A-3. Simulation results for EC-233.
73
-------
0.48
0.36
£ 0.24
b*
u
0.12
0 50 100 150 200 250 30G 350 400
TIME (MINUTES)
0.00
i i i i- r
HCHB ¦
1 1'
_

_ /
X
/ *
1
1 1 1 1 1
1 1
0 50 100 150 200 250 300 350 400
TIME (MINUTES!
0.35
0.26
a.
"0.21
z
m
E 0.14
LU
(J
X
m
u
0.07
°'0°0 50 100 150 200 250 300 350 400
TIME (MINUTES)
Figure A-3. (concluded)
74
-------
PAN
0.12
0.09
IB
U
CD
U
0.03
0.00
50 100 150 200 250 300 350 400
TIKE (MINUTES)
03
N0
N02
0.80
0.60
k 0.40
u
z
0.20
0.00
50 100 ISO 200 250 300 350 400
TIME (MINUTES)
CAR
7.40
6.80
a
t 6.20
u
5.60
5.00
TIME (MINUTES)
0LE
0.100
0.075
z
r 0.050
ui
o
0.025
0.000
TIME (MINUTES)
S Low concentrations Include paraffins only; high concentrations include all
measured single-bonded carbon.
Figure A-4. Simulation results for EC-237.
75
-------
1.25
N0
N02
1.00
z
a.
0.75
j= 0.50
u
0.25
0.00
70 140 210 280 350 420 490 560
TIHE (HINUTES)
PAN
0.16
0.12
E 0.08
u
u
0.04
0.00
TIHE (HINUTES)
0LE
0.100
0.075
£ 0.050
CJ
u
0.025
0.000
70 140 210 260 350 420 490 560
TIHE (HINUTES)
CAR
7.20
x
6.40
P 5.60
tu
u
o
4.80
4.00
TINE (HINUTES)
! Low concentrations include paraffins only; hi ah concentrations include all
measured single-bonded carbon.
Figure A-5. Simulation results for EC-238.
76
-------
0.75
0.60 ~
0.45 -
t 0.30 -
u
s
u
M*-*-*-H- \ | |
0.15
0 50 100 150 200 250 300 350 400
TINE (MINUTES)
0.060 -
0.045
•- 0.030
0.015
0.000
0 50 100 150 200 250 300 350 400
TINE (MINUTES)
0.040 -
0.036 -
a
at
0.024 -
hi
u
0.012 -
0.000
0 50 100 150 200 250 300 350 400
TINE (MINUTES)
4.50
—i—i—T
PAR § ¦
CAR ~
4.00 -
3.50 -
3.00 -
IU
2.50 -
+
2.00
I I I	I	I	I	L
0 50 100 150 200 250 300 350 400
TIME (MINUTES)
S Low concentrations Include paraffins only; high concentrations include all
measured single-bonded carbon.
Figure A-6. Simulation results for EC-241.
77
-------
0.60 — «
0.00

0 50 100 150 200 250 300 350 400
TIME (MINUTES)
0.16
Q.
O-
0.12
0.08
u
z
»
o
0.04
0.00
1—i—i—i—i—i—r
PAN *
J	I	' I I	L
0 50 100 150 200 250 300 350 400
TIME (MINUTES)
5.50
5.00
4.50
jjj 4.00
-------
0.80
0.60
B
ARB
t 0.40
0.20
0.00
50 100 150 200 250 300 350 400
TINE (MINUTES)
1.50
HCH0
1.20
0.90
a
t 0.60
0.30
0.00
50 100 150 200 250 300 350 400
TIME (MINUTES)
Figure A-7.
ETH
2.00
X
0_
CL
1.60
cc
1.20
h-
Z
IAJ
(J
z
CB
o
0.80
0.40
50 100 150 200 250 300 350 400
TIHE (MINUTES)
(concluded)
91 075T 11*
79
-------
PAN
0.12
0.09
0.06
u
z
0.03
0.00
TIHE {MINUTES)
N0
N02
0.80
0.60
0.40
0.20
0.00
TIHE (MINUTES)
PAR §
CRR
3.60
3.30
t 3.00
z
u
2.70
2.40
TINE (MINUTES)
0LE
0.12
0.09
0.06
0.03
0.00
TINE (MINUTES)
Low concentrations Include paraffins only; high concentrations include all
measured single-bonded carbon.
Figure A-8. Simulation results for EC-243.
80
-------
l.SO
N0
N02
1.20
0.90
a
t 0.60
u
z
(_>
0.30
^XxxxxxxxxX
0.00
50 100 150 200 250 300 350 400
TINE (HINUTES)
PAN
0.20
x
Q.
0.15
z
£ 0.10
u
z
u
0.05
0.00
50 100 150 200 250 300 350 400
TIME (MINUTES)
0LE
0.12
a.
0.09
E 0.06
u
0.03
0.00
50 100 150 200 250 300 350 400
TIME (HINUTES)
PAR
CAR
4.80
a.
4.20
-------
0.80 -
a.
a.
0.60 -
t 0.40 -
Ui
u
z
0.20
0.00
80 160 240 320 400 480 560 640
TIME (MINUTES)
0.100
0.075
i- 0.050
0.025
0.000
0 80 160 240 320 400 480 560 640
TIME (MINUTES)
0.060 -
0.045
0.030 -
UJ
u
0.015 -
0.000
0 BO 160 240 320 400 4B0 560 640
TIME (MINUTES)
7.80 -
o.
a.
7.00 -
E 6.20 -
u
z
s
o
5.40 -
4.60
PAR § ¦

0 60 160 240 320 400 480 560 640
TIME (MINUTES)
5 Paraffins only.
Figure A-10. Simulation results for EC-246.
82
-------
t—i—r
ARB ¦
i—r
0.08 -
0.06 -
£ 0.04 -
bJ
U
en
u
0.02 ~
0.00
J	I	I	I	I	I	L
0 80 160 240 320 400 480 560 640
TIME (MINUTES)
0.35
0.28
0.21
cc
ee
0.14
o
z
s
o
0.07
0.00
*
' ¦ '
0 80 160 240 320 400 480 560 640
TINE (MINUTES)
0.75
0.60
0.45
0.30
»
o
0.15
0.00
1 1 1 1 1
HCH0 ¦
1" ' 1 "
1
\
\
-
1
m
-/ m
f * «
-
' X
[

l I I 1 l
1 1
0 80 160 240 320 400 480 560 640
TIME (MINUTES)
Figure A-10. (concluded)
83
-------
h- 0.40

0.12 -
0.09 -
E 0.06 -
111
u
0 40 60 120 160 200 240 280 320
TINE (MINUTES)
0.03 ~
0 40 80 120 160 200 240 280 320
TINE (NINUTES)
0.060 -
0.045 -
0.030 -
u
z
0.015 -
0.000
0 40 60 120 160 200 240 2B0 320
TINE (NINUTES)
2.45
2.20 r
1.95 -
E 1.70 -
u
z
1.45 -
1.20
0 40 80 120 160 200 240 260 320
TINE (NINUTES)
S Low concentrations Include paraffins only; high concentrations include all
measured single-bonded carbon.
Figure A-11. Simulation results for EC-247.
84
-------
The chamber-dependent reactions used in these simulations are
O3 and NO2 loss to walls = 0.0016 min"1
= 0.0017 min"1
NO2 emission from walls = 0.1 ppb min"*
Photolysis rates are
-1
-4
kj =	0.3 min
kj7 =	2.7 x 10"4 min
^38 =	^ x m^n~^
k67 =	0.0135
k78 =	1 x 10*4 min"1.
UNIVERSITY OF NORTH CAROLINA OUTDOOR SMOG-CHAMBER EXPERIMENT
(URBAN MIX; TWO-DAY SIMULATION)
The UNC two-day, urban-mix experiment has been previously simulated
with CBM-I (Whitten, Hogo, and Killus, 1980). The hydrocarbon mix used
contained no aromatics (see table A-2). CBM-III gives results that are
comparable to those of CBM-I for mixtures containing olefins and paraffins
only (see figure A-12).
Rural North Carolina air is used in the UNC chamber experiments.
Background reactivity for the air and chamber is simulated by the
following reactions:
NO2 offgassing from walls: 5 x 10"^ x k^
Background reactivity: OH + MEO2	1000 ppm^min"1
H02 production 1.5 x 10"^ kj
These background reactivity reactions correspond to a hydrocarbon level of
about 0.3 ppmC of reactive hydrocarbon and 0.05 ppm formaldehyde. This
background reactivity is derived from UNC experiments performed with N0X
added but without added hydrocarbons. Both sides of the chamber were
assumed to have an initial condition of 7 ppb H0N0.
85
-------
TABLE A-2. SIMULATED URBAN HYDROCARBON MIXTURE
Relative
Concentration
Class/Compound	(ppm) (ppmC) Mole Fraction
Acetyl enic
Acetylene
Subtotal
Paraffins
Isopentane
n-Pentane
2-Methyl pentane
2,4-Dimethyl pentane
2,2,4-Trimethylene pentane
Subtotal
Average carbon number =5.7
Olefins
Butene-1
cis-2-Butene
2-Methyl-1-butene
2-Methyl-2-butene
Ethylene
Propylene
Subtotal
Average carbon number =2.7
Total
265	530	0.171
265	530	0.171
172	860	0.111
286	1430	0.184
85	510	0.055
69	483	0.044
76	608	0.049
688	3891	0.444
40	160	0.026
43	172	0.028
26	130	0.017
32	160	0.021
360	720	0.232
97	291	0.062
598	1633	0.385
1551	6,054	1.000
86
-------
0.625
	 Predicted 0
• Observed 0
Predicted NO
* Observed NO
0.500
X Observed NO.
Predicted NO.
~ *
0.375
k 0.250
* * **
u
0.125
o.occ
0 ISO 300 450 600 750 900 1050 1200 1350 1500 16S0 1600 1950 2100 2250 2400
TIME IHINUTESI	TIME (MINUTES)
(a) High Hydrocarbon (2.9 ppmC)
0.625
• Observed 0.
— Predicted NO
~ Observed NO
0.500
Predicted NO.
X Observed NO.
~ *
0.375
i= 0.250
u
0.125
0 n—' ' —	r~— ¦ ¦	* ¦	1 ¦ 1
0 150 300 450 600 750 900 1050 1200 1350 1500 1650 1600 1950 2100 2250 2400
TIME IHINUTESJ	TIME (MINUTES)
(b) Low Hydrocarbon (1.3 ppmC)
Figure A-12. Results of two-day University of North Carolina smog-chamber run.
87
-------
0.40
0.00
12 June
1—I—I—I—T
p- 0.20
fllrirr I ¦ 1
0 120 240 360 480 600 720 840 960
TIME (MINUTES)
0.40
0.30
cr
ae
0.20
bi
u
B
0.10
O.nn
13 June
1	1	1	1	1—T
		-C4*b.
J—J	I	I	J.	L
1140 1260 1380 1500 1620 1740 1860 1980 2100
TInE (MINUTES)
(c) High Hydrocarbon
0.40
0.30
0.20
u
z
0.10
0.00
g.ttl	1-
0.40 -
0.30 -
s
S 0.20H
0.10 -
13 June
T I I T
-CARB"
0 120 240 360 480 600 720 840 960
TIME (hlNUTES)
o.on
1140 1260 1380 1500 1620 1740 I860 1980 2100
TIHE IHINUTEbJ
(d) Low Hydrocarbon
Figure A-12. (continued)
38
-------
0.80
ac
H-
tn
en
in
0.60
0.40
0.20
0.00
12 June
1	1—
K 1NB2)
i T
0 120 240 360 480 600 720 840 960
TIME (MINUTES)
0.40
0.30
£ U. 20
0.10
1	1	f
K JN021
13 June
T
i i r
' me 1260 1J80 1500 1620 1740 I860 198C 210C
TIHE IMINUTtsl
(e) Photolysis Rate
Note: N02 data = NO2 + PAN
Figure A-12. (concluded)
75 81 10
89
-------
NO
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
Appendix B
MOLECULAR WEIGHTS AND BOND FRACTIONS
OF COMMON MOLECULES
TABLE B—1. MOLECULAR WEIGHTS OF MOLECULES
(ORDERED BY SAROAD CODE)
SRROAO	HClECULRR	CHEMICAL NfiME
CODE	HEIGHT
43002	86.00	UNKNOWN SPECIES
43105	86.17	ISOMERS OF MEXfiNE
43106	102.20	ISOMERS OF HEPTRNE
43107	114.23	ISOMERS OF OCTANE
43iee	128.25	ISOMERS OF NONRNE
43105	142.28	ISOMERS OF OECflNE
43110	155.30	ISOMERS OF UNDECRNE
43111	184.35	ISOMERS OF TRIDECRNE
43112	17e.33	ISOMERS OF DODECRNE
43113	lS6.3e	ISOMERS OF TETRROECRNE
43114	212.41	ISOMERS OF PENTRDECRNE
43115	9e.l9	C-7 CYCLOPRRRFFINS
43116	112.23	C-8 CTCLOPRRRFFINS
43117	126.26	C-9 CYCLOPRRRFFINS
4311B	114.23	MINERAL SPIRITS
43119	114.23	LRCTOL SPIRITS
43120	56.10	ISOMERS OF BUTENE
43121	7C.13	ISOMERS OF PENTENE
43122	72.15	ISOMERS OF PENTRNE
43123	135.24	TERPENES
43201	16.e4	METHANE
43202	30.27	ETHRNE
43203	28.05	ETHYLENE
43204	44.09	PROPANE
43205	42.eS	PROPYLENE
432ee	26. e<.	rcetylene
43207	42.CS	CYCLOPROPANE
43209	42.e6	PROPYNE
432CS	4C.C5	KETHYLRCETYLENE
43211	64.16	3-ME'hYL-l-PENrENE
43212	Se.12	N-BUTANE
43213	56.10	BUTENE
43214	58.12	1SOBUTRNE
43215	56.10	ISOBUTYLENE
43216	56.10	TRRNS-2-BUTENE
43217	56.10	CI5-2-BUTENE
43218	54.09	1.3-BUTROIENE
43219	54.09	ETHYLRCETYLENE
43220	72.15	N-PENTRNE
43221	72.15	ISOPE NTRNE
43223	7e.l4	3-METHYL-1-BUTENE
43224	70.13	1-PENTENf
(continued)
90
-------
EC I
NO.
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
S9
6e
6:
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
76
79
80
61
62
83
84
85
86
87
88
89
80
91
92
TABLE B-l
SBRORD	MOLECULAR	CHEMICAL NAME
CODE	WEIGHT
43225	70.13	2-METHYL-1-BUTENE
43226	70.13	TRANS-2-PENTENE
43227	70.13	CIS-2-PENTENE
43228	70.13	2-HETHYL-2-BUTENE
43229	86.17	2-METHrL PENTANE
43230	86.17	3-METHYL PENTANE
43231	86.17	HEXANE
43232	100.20	HEPTANE
43233	114.23	OCTANE
43234	64.16	2.3-D 1 METHYl-1 -B'-TENE
43235	128.25	NOt^NE
43236	142.28	N-DECANE"
43241	156.30	UNDECfi'.E
43242	70.14	CYClOPENTSSE
43245	84.16	1-hEXENE
43248	84.16	CYC.O^EX?\E
43255	170.33	N-DODECANE
43256	184.36	N-TRiOECAf,E
43258	86.17	2.3-DIKETnYLSJTSNE
43259	198.38	N-TETRSDECPNE
43260	212.41	N-PENTADECASE
43260	84.16	2-ETHYL-l-EJTENE
43261	98.18	METHYlCYClOHEX=\l
43262	84.16	KE~HYLCYCL2°ENTfi\E
43264	98.15	CYClOHEXCN™E
43265	40.06	PROPADIENE
43268	84.16	C-3-HEXENE
43269	84.16	2-METHYL-2-PENTENE
43270	84.16	3-KETHYL-T-2-PENTENE
43271	100.20	2.4-ClSETt-YLPE\TCNE
43272	82.14	HETHYLCYClOpENTENE
43273	82.14	CYCLOMEXENE
43274	100.20	2.3-DlMEThYLPENTR\E
43275	100.20	2-KETHYLhEXPNE
43276	114.22	2. 2.4-TR] "E^t LcE\~c\i
43277	114.22	2.4-D!KET-ruHE>e\E
43278	1 14.22	2.5-Dlf,ETf-Yt.hE>^,.E
43279	114.22	2.5.4-TRIl,E"h; lsE^=,.E
4328B	1 14.22	2.3.3-TRi vETn^eEN't^E
43281	226.44	HEXPDECANE
43282	240.46	HEPTAOECPNE
43283	254.49	0CTA3ECASE
43284	268.51	NONADECANE
43285	282.54	E1C0SANE
43286	296.57	HENE1COSANE
43287	310.59	DOCOSANE
43288	112.23	ETHYLCYCLOHEXANE
43289	84.16	C6 OLEFIN UNK
43290	112.23	C8 OLEFIN UNK
43291	86.17	2.2-OIMETHYLBJTRNE
(continued)
91
-------
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
TABLE B-l
SAROAD	MOLECULAR	CHEMICAL NAME
CODE	HEIGHT
43292	68.11	CYCLOPENTENE
43293	84.16	4-METHYL-T-2-PENTEME
43294	98.18	C7-0LEFIN UNKNOWN .
43295	100.20	3-METHYLHEXANE
43296	114.23	2.2.3-TRIMETHYLPENTANE
43297	114.23	4-METHYLHEPTfiNE
43298	114.23	3-METHYLHEPTRNE
43299	114.23	2.2.5-TRIMETHYlPENTRNE
433Ci	32.04	METHTL ALCOHOL
433C2	46.07	ETHYL ALCOHOL
4332c	6E.09	N-PROPYL ALCOHOL
433C4	60.09	ISOPROPYL ALCOHOL
455C;	74.12	N-BUTTL ALCOHOL
433Cc	74.12	1SOBUTYL ALCOHOL
433C5	118.17	BUTYL CELLOSOLVE
433C=	74.12	TERT-BUTYL ALCOHOL
433.e	76.11	METHYl CELLOSOLVE
432 i1	90.12	CELLOSOLVE
43312	112.23	1-T-2-C-4-TM-CYCL0PENTANE
43322	116.16	01 ACETONE ALCOHOL
43351	74.12	ETHYL ETHER
4335"	106.12	GLYCOL ETHER
4336E	62.07	GLYCOL
4335=	76.00	PROPYLENE GLYCOL
433"?	62.07	ETHYLENE GLYCOL
433=:	72.10	TETRAHYDROFJRAN
434C4	60.05	ACETIC ACID
43422	74.08	METHYL ACETATE
43433	88.10	ETHYL ACETATE
43434	102.13	PROPYL ACETATE
43425	1 16. 16	N-B'JTYL ACETATE
4343e	100.11	ETHYL ACRYLRTE
43443	132.00	CELLOSOLVE ACETATE
43444	104.00	ISOPROPYL ACETATE
4344:	140.00	METHYL PMYL ACETRTE
43445	116.16	I50BUTYL ACETATE
4345C	73.09	D1HETHYLF0RKRK1DE
4345;	144.21	IS06UTYL ISOBUTYRATE
43452	132.00	2-ETHOXYETHYL ACETATE
43522	30.03	FORMALDEHYDE
43502	44.05	RCETALDEHYDE
43524	58.08	PROPRIONALDEHYDE
43510	72.12	BUTYRALOEHYOE
43511	58.08	C3 ALDEHYDE
43512	86.14	C5 ALDEHYDE
43513	128.21	C8 ALDEHYDE
43551	58.08	ACETONE
43552	72.10	METHYL ETHYL KETONE
4355S	100.16	METHYL N-BUTYL KETONE
43560	100.16	METHYL ISOBUTYL KETONE
(continued)
92
81075T 6
-------
mu»
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
156
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
18E
181
182
183
184
185
186
187
188
189
190
191
192
TABLF B-l
SfiROflD	MOLECULAR	CHEMICAL NAME
CODE	WEIGHT
43601	44.05	ETHYLENE OXIDE
43602	58.08	PROPYLENE OXIOE
43702	41.05	RCETONITRILE
43704	53.06	RCRYLONITRILE
43721	45.09	ETHTLRMINE
43740	S9.ll	TRIMETHYL RHINE
43801	50.49	METHYL CHLORIDE
43801	112.56	CHLOROBENZENE
43802	64.94	DICHLOROMETHRNE
43803	119.39	CHLOROFORM
43804	153.84	CPRBON TETRACHLORIDE
43807	331.67	CRRBON TETRRBROMIDE
43811	137.37	TRICHLOROFLUOROMETHRNE
43812	64.52	ETHYL CHLORIDE
43813	98.97	1.1-DICHLORDETHRNE
43814	133.42	1.1.1-TRICHLOROETHRNE
43815	99.00	ETHYLENE DICHLORIDE
43817	165.85	PERCHLOROETHYLENE
43619	173.85	METHYLENE BROMIDE
43820	131.66	1.1.2-TR1CHL0R0ETHRNE
43821	187.38	TRICHLOROTRIFLUOROETHRNE
43822	92.00	TRIMETHYLFLUOROSILRNE
43823	120.92	DICHLORODIFLUOROMETHRNE
43824	131.40	TRICHLOROETHYLENE
43860	62.50	VINYL CHLORIDE
45101	114.23	NRPTHfi
45102	106.16	ISOMERS OF XYLENE
45103	134.21	DIMETHYLETHYLBENZENE
45104	120.19	ISOMERS OF ETHYLTOLUENE
45105	134.21	ISOMERS OF BUTYLBENZENE
45106	134.21	ISOMERS OF DIETHYLBENZENE
45107	120.19	ISOMERS OF TRIMETHYLBENZENE
45108	120.19	ISOMERS OF PROPYLBENZENE
45201	78.11	BENZENE
45202	92.13	TOLUENE
45203	106.16	ETHYLBENZENE
45204	106.16	O-XYLENE
45205	106.16	M-XYLENE
45206	106.16	P-XYLENE
45207	120.19	1.3.5-TR1METHYLBENZENE
45208	120.19	1.2.4-TRIMETH1LBENZENE
45209	120.19	N-PROPYLBENZENE
45211	120.19	O-ETHYLTOLUENE
45212	120.19	H-ETHYLTOLUENE
45215	134.21	TERT-BUTYLBENZENE
45216	134.21	5EC-BUTYLBENZENE
45220	104.14	5TYRENE
45221	118.15	fi-METHYLSTYRENE
45225	120.19	1.2.3-TRIMETHYLBENZENE
45232	134.21	TETRRMETHYLBENZENE
45233	148.23	TRI/TETRRRLKYL BENZENE
45234	134.21	ISOMERS OF METHYLPROP. BENZENE
45300	94.11	PHENOLS
45401	230.00	XYLENE BRSE RCIOS
46201	88.12	1.4-DIOXRNE
(concluded)
93
-------

TABLE
ro
•
BOND GROUPS
PER MOLECULE






(ORDERED BY SAROAD CODE)






SPECIES
PROFILES BY BONO GROUP



SPECIES
CHEMICAL NAME
OLE
PAR
ARO
CARB
ETH
UNREACTIVE
NO.







1
UNKNOWN SPECIES
0.10
4.00
0.25
0.32
0.16

2
ISOMERS OF HEXANE

6.00




3
ISOMERS OF HEP1ANE

7.00




4
ISOMERS OF OCTANE

8.00




5
ISOMERS OF NONANE

9.00




6
ISOMERS OF OECRNE

10.00




7
ISOMERS OF UNDECANE

11.00




8
ISOMERS OF TRIOECANE

13.00




9
ISOMERS OF OODECANE

12.00




10
ISOMERS OF TETRRDECANE

14.00




11
ISOMERS OF PENTADECANE

IS.00




12
C-7 CYCLOPARAFFINS

6.00

1.00


13
C-8 CYCLOPARAFFINS

7.00

1.00


14
C-9 CtCLOPnROFFINS

8.00

1.00


IS
MINERAL SPIRITS

7.00

1.00


16
LACTOL SPIRITS

8.00




17
ISOMERS OF BUTENE

2.00

2.00


18
ISOMERS OF PENTENE

3.00

2.00


19
ISOMERS OF PENTRNE

S.00




20
TERPENFS
1.00
9.00




?\
METHANE





1.00
22
ETHANE





2.00
23
ETHYLENE




1.00

24
PROPANE

I.S0



1.50
25
PROPYLENE
1.00
1.00




26
ACETYLENE





1.00
27
CYCLOPROPANE

2.00

1.00


20
PROPYNE

2.00



1.00
29
METHYLACETYLENE

1.50



1.50
30
3-METHYL-1-PENTENE

6.00




3t
N-BUTANE

4.00




32
BUTENE
1.00
2.00




33
ISOBUTANE

4.00




31
ISOBUTYLENE
1.00
2.00




35
TRAriS-2-BUTENE

2.00

2.00


36
CIS-/-BUTENE

2.00

2.00


37
1.3-ournoiEHE
1.00


2. na


38
ETHYI.fiCETYLCNE

4.00




39
N-PEN1ANE

S.00




40
ISOPENTANE

S 00




(continued)
-------
TABLE B-2
SPECIES PROFILES BY BOND CROUP
3PECIE9	CHEMICAL NOME	OLE	PAR	RRO	CURB	ETH	UNREACTIVE
NO.
41
3-HETHYL-l-BUTENE
1.00
3.00

42
l-PENTENE
1.00
3.00

13
2-NETHYL-l-BUTENE
1.00
3.00

44
TRRNS-2-PENTENE

3.00
2.00
15
CIS-2-PENTENE

3.00
2.00
46
2-HETHYL-2-BUTENE

3.00
2.00
47
2-NETHYL PENTRNE

6.00

18
3-METHYL PENTRNE

6.00

49
HEXONE

8.00

50
HEPTANE

7.00

SI
OCTANE

8.00

52
2.3-0IHETHYL-1-BUTENE
1.00
4.00

53
NONRNE

9.00

51
N-OECANE

10.00

55
UNOECANE

11.00

56
CYCLOPENTRNE

4.00
1.00
57
l-HEXENE
1.00
4.00

56
CYCLOHEXRNE

S.00
1.00
59
N-OOOECANE

12.00

60
N-TRIDECRNE

13.00

61
2.3-DIMETHYL0UTRNE

6.00'

62
N-TE1RADECANE

14.00

63
N-PENTAOECANE

15.00

64
2-ETHYL-l-BUTENE
1.00
4.00

65
HETHYLCYCLOHEXANE

8.00
1.00
66
METHYLCYCLOPENTRNE

S.00
1.00
67
CYCLOHEXANONE

4.00
2.00
68
PROPflDIENE

1.00
2.00
69
C-3-HE KENE
1.00
4.00

70
2-ME THYL-2-PENTENE

4.00
2.00
71
3-ME1HYL-T-2-PENTENE

4.00
2.0C
72
2.4-DIMETHYLPENTRNE

7.00

73
METHYLTYCLOPENTENE
1.00
4.00

71
CYCI OHFXENE
1.00
4.00

75
7.1 HIM iHYLPENTRNE

7.00

76
2-HLIHYLHEXRNE

7.00

77
2.2.1-TRI MEIHYLPENTRNE

8.00

78
2.1-DI MET MYLHEXANF

8.00

79
2.5-RIHETHYLHEXflNE

8.00

Rfl
2.1.1-TRI ME fHYLPFNTRNE

8.00

(continued)
-------
TABLE B-2


SPECIES PROFILE" BT
BOND GROUP



SPECIES
NO.
CHEMICAL NOME
OLE PAR
ARO
CURB
ETH
UNRERCT1VE
- , . t
01
2.3. 3-TRINETHYLPENTANE

B.00

82
HEXROECANE

16.00

83
HEPTRDECANE

17.00

64
OCTROECANE

18.00

85
NONROECANE

19.00

86
EICOSANE

20.00

87
HENEICOSANE

21.00

88
OOCOSflNE

22.00

89
ETHYLCYCLOHEXANE

7.00
1.00
90
C6 OLEFIN UNK
1.00
4.00

91
C8 OLEFIN UNK
1.00
6.00

92
2.2-0IHETHYL8UTANE

8.00

93
CYCLOPENTENE
1.00
3.00

94
4-HETHYL-T-2-PENTENE

4.00
2.00
95
C7-0LEFIN UNKNOHN
1.00
S.00

96
3-METHYLHEXRNE

7.00

97
2.2.3-TRIHEIHYLPENTANE

8.00

98
4-METHYLHEPTRNE

8.00

99
3-HETHYLHEPTANE

8.00

100
2> 2.5-TR1HE1HTLPENTANE

8.00

101
HETHYL ALCOHOL

1.00

102
ETHYL ALCOHOL

2.00

103
N-PROPYL ALCOHOL

3.00

104
1SOPROPYL ALCOHOL

3.00

105
N-BUTYL ALCOHOL

4.00

106
ISOBUTYL ALCOHOL

4.00

107
BUTYL CELL030LVE

S.00
1.00
106
TERT-8UTYL ALCOHOL

3.00
1.00
109
METHYL CELLOSOLVE

2.00
1.00
110
CELL030LVE

3.00
1.00
111
I-T-2-C-4-TH-CYCL0PENTBNE

7.00
1.00
112
OIACETONE ALCOHOL

5.00
1.00
113
ETHYL ETHFR

3.00
1.00
111
GLYCOL ETHER

1.00
1.00
IIS
GLYCOL

1.00
1.00
116
PROPYLENE GLYCOL

2.00
1.00
117
ETHYLFNE GLYCOL

1.00
1 .PC
116
TETRflHYOROFURRH

3.00
i.ho
119
ACETIC ncio

2.00

170
methyl acemTE



(continued)
-------
TABLE B-2
SPECIES PROFILES BT BOND GROUP
SPECIES	CHEMICAL NAME	OLE	PUR	PRO	CflRB	ETH	UNREACTIVE
NO.
121
ETHTL ACETATE

3.00
1.00


122
PROPYL HCETRTE

4.00
1.00


123
N-8UTYL ACETRTE

5.00
1.00


124
ethyl acrylate

3.00
2.00


125
CELLOSOLVE ACETATE

4.00
2.00


126
ISOPROPYL ACETRTE

5.00



127
METHYL RHYL RCETRTE

8.00



128
ISO0UTYL RCETRTE

6.00



129
0IMETHYLFORMRM10E




3.00
130
ISOBUTYL I50BUTYRATE

7.00
1.00


131
2-ETHOKYETHYL ACETATE

4.00
2.00


132
formaloehyde


1.00


133
RCE TALOEHYOE

1.00
1.00


1 34
PROPR1ONALOEHYDE

2. 00
1. 00


135
BUT YRALOEHYOE

3.00
1.00


136
C3 RLOEHYDE

2.00
1.00


137
C5 RLOEHYDE

4.00
1.00


I3B
C8 RLOEHYDE

7.00
1.00


1 in
ACETONE

2.00
1.00


1 "CI
METHYL ETHYL KETONE

3.00
1.00


HI
METHYL N-BUTYL KETONE

5.00
1.00


142
MFTHYI ISO0UTYL KFTONE

5.00
1.00


14^
ETHYI.f NT UXIPE

1.00


1.00
141
PROP/LTNE OXIDE

2.00


1.00
l 45
ACE TON!TRILE

1.00


1.00
I 46
ACRYLONITRILE
1.00
1.00



I 47
ETHYLAHINE

1.00


1.00
MB
TRIMETHYL AMINE

3.00



119
METHYL CHLORIDE




1.00
150
CHLOROBENZENE




e.00
151
DICHLOROMETHRNE




t.00
152
CHLOROFORM




1.00
153
CnROQII TETRACHLORIDE




1.00
154
CARBON TETRABROM1DE




1.00
155
TRICHLOROFLUOROHE THANE




1.00
156
ETHYL CHLORIDE




2.00
157
1.1-OICHLOROETHANE




2.00
158
1.1.1-TRICHLOROETHRNE




2.00
159
ETHYLFNE BICHLORIDE



1.00

160
PERCHI.nROEFHYLFNF




7.00
(continued)
-------
TABLE B-2



SPECIES
PROFILFS by
BONO CROUP




SPECIES
CHEHICRL NOME
OLE
PAR
RRO
CURB

ETH
UNRERCTIVE
NO.








161
METHYLENE BR0H10E






1.00
162
1. 1.2-IRICHLOROETHRNE






2.00
163
TRICHLOROTRIFLUOROE THflME






2.00
164
TRIMETHYLFLUOROS1 LflNE






3.00
165
OICHLOROOIFLUOROMETHANE






1.00
166
TR1CHL0R0ETHYLENE




1.1
10

167
VINYL CHLORIDE




1.1
90

160
NflPTHfl

0.00





1 R9
ISOMERS OF XYLENE

2.00
1.00




170
OINE THYLE THYLBENZENE

4.00
1.00




171
ISOMERS OF ETHYLTOLUENE

3.00
1.00




172
ISOMERS OF BUTYLBENZENE

4.00
1.00




173
ISOMERS OF 01E1HYL9ENHEKE

4.00
1.00




174
ISOMERS OF YR1 METHYLBENZENE

3.00
1.00




I7S
ISOMERS OF PROPYLBENZENE

3.00
1.00




176
BEN7FNE






6.00
177
IOLUENE

1.00
1.00




178
ETHYLBFNZENE

2.00
1.00




179
O-XYLENE

2.00
1. 00




IS0
M-XYLFNE

2.00
1.00




161
P-XYLENE

2.00
1.00




IH2
1.3.5-TRIMETHYLBENZENE

3.00
1 .00




103
1.2•4-IR1 METHYLBENZENE

3.00
1 .00




104
N-PROPYLBENZENE

3.00
1.00




185
0-E TMYLTOLUENE

3.00
1 .00




166
M-ETHYL10LUENE

3.00
1.00




107
TERT-BUT YLBF N7ENE

4.00
1.(10




1 00
5EC-BUTYLBENZENE

4.00
1.00




189
STYRENF

1.00
1.00
1.00



190
fl-METHYLSTYRENE

2.00
1.00
1.00



191
1.2.3-TRIMET HYLBENZENE

3.00
1.00




192
TElRnMI" THYLRFN7FNE

4.00
1.00




193
TRI/TFIPOni KYL BFNZENE

S.00
1.00




194
ISOMrRr- OF HE 1 HYlPRnP. BENZENE

4.00
1.00




195
PHcrmi "






6.00
196
xYLC»ir nnr.F nnos

2.00
1.00




197
1.4-oinxnnF
1.00
2.(10

2.00



(concluded)
-------
]
2
3
4
5
6
7
8
9
IB
11
12
13
14
15
16
17
16
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
35
37
38
39
40
41
42
43
44
45
46
47
46
49
50
TABLE B-3. MOLECULAR WEIGHT OF MOLECULES
(IN ALPHABETICAL ORDER)
SAROAO
MOLECULAR
CHEMICAL NAME
CODE
HEIGHT

43814
133.42
1.1.1-TRICHLOROETHANE
43820
131.66
1.1.2-TRICHLOROETHANE
43813
98.97
1.1-D1CHLOROETHRNE
45225
120.19
1.2.3-TRIMETHYLBENZENE
45208
120.19
1.2.4-TRIMETHYLBENZENE
45207
120.19
1.3.5-TRIMETHYLBENZENE
43218
54.09
1.3-BUTRDIENE
46201
88. 12
1.4-D10XANE
43245
84. 16
1-HEXENE
43224
70. 13
1-PENTENE
43312
112.23
1-T-2-C-4-TM-CYCL0PENTRNE
43295
114.23
2.2.3-TRIHETHYLPENTRNE
43276
114.22
2.2.4-TR]HETHYLPENTRNE
43299
114.23
2.2.5-TR1HETHYLPENTRNE
43291
86.17
2.2-DIMETHYLBUTRNE
43280
114.22
2.3.3-TR]HETHYLPENTRNE
43279
114.22
2.3.4-TRIHETHYLPENTRNE
43234
84. 16
2.3-0IMETHYL-1-BUTENE
43258
86. 17
2.3-D1METHYLBUTANE
43274
100.20
2.3-01METHYLPENTANE
43277
114.22
2.4-OIMETHYLHEXfiNE
43271
100.20
-2.4-D1METHYLPENTANE
43278
114.22
2.5-DIMETHTLHEXRNE
43452
132.00
2-ETHOXYEThYL RCETRTE
43250
84. 16
2-ETHYL-l-BUTENE
43229
86.17
2-METHYL PENTRNE
43225
70. 13
2-HETHYL-l-BUTENE
43228
70. 13
2-METHYL-2-BUTENE
43269
84. 16
2-HETHYL-2-PENTENE
43275
100.20
2-METHTLHEXflNE
43230
86. 17
3-METHYL PENTRNE
43223
70. 14
3-METHYL-l-BUTENE
4321 1
84. 16
3-METHYL-1-PENTENE
43270
84. 16
3-HETHYL-T-2-PENTENE
43298
114.23
3-METHYLHEPTANE
43295
100.20
3-METHYLHEXANE
43293
B4.16
4-METHYL-T-2-PENTENE
43297
114.23
4-HETHYLHEPTRNE
45221
118.15
r-methylstyrene
43503
44.05
RCETRLDEHYDE
43404
60.05
ACETIC ACID
43551
58.08
ACETONE .
43702
41.05
ACETONITRILE
43206
26.04
acetylene
43704
53.06
acrylonitrile
45201
78. 11
BENZENE
43213
56. 10
BUTENE
43308
118.17
BUTYL CELLOSOLVE
43510
72. 12
butyrrldehyde
43268
84. 16
C-3-HEXENE
(continued)
-------
NO
SI
52
53
54
55
56
57
56
53
60
61
62
63
64
65
66
6?
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
68
B9
90
91
92
93
94
95
86
97
98
TABLE B-3
SRRORD
HOLECULRR
CHEMICAL NRME
CODE
WEIGHT

43115"
98.19
C-7 CYCLOPRRRFFINS
43116
112.23
C-8 CTCLOPRRRFFINS
43117
126.26
C-9 CTCL0PRRRFFIN5
43511
58.08
C3 ALDEHYDE
43512
86.14
C5 ALDEHYOE
43289
84.16
C6 OLEFIN UNK
43294
98.18
C7-OLEFIN UNKNOWN
43513
128.21
C8 RLDEHYDE
43290
112.23
C8 OLEFIN UNK
43807
331.67
CARBON TETRRBROMIDE
43804
153.84
CRRBON TETRACHLORIDE
4331 1
90.12
CELLOSOLVE
43443
132.00
CELLOSOLVE ACETRTE
43801
112.56
chlorobenzene
43803
119.39
CHLOROFORM
43217
56. 10
CIS-2-BUTENE
43227
70.13
CIS-2-PENTENE
43248
84.16
CrCLOHEXRNE
43264
98.15
CrCLOHEXANONE
43273
62.14
CTCLOHEXENE
43242
70.14
CYCLOPENTRNE
43292
68.11
CYCLOPENTENE
43207
42.08
CYCLOPROPANE
43320
116.16
01 ACETONE ALCOHOL
43823
120.92
OICHLOROOIFLUOROMETHANE
43802
B4.94
dichloromethane
45103
134.21
DIMETHYLETHYLBENZENE
43450
73.09
dimethylformrmide
43287
310.59
OOCOSANE
43285
282.54
EICOSANE
43202
30.07
ETHRNE
43433
88.10
ethyl rcetrte
43438
100.11
ETHYL RCRYLRTE
43302
46.07
ethyl rlcohol
43812
64.52
ETHYL CHLORIDE
43351
74. 12
ETHYL ether
43219
54.09
ETHYLfiCETYLENE
43721
45.09
ETHYLAMINE
45203
106.16
ETHYLBEN2ENE
43288
112.23
ETHYLCYCLOHEXANE
43203
28.05
ETHYLENE
43815
99.00
ETHYLENE OICHLORIOE
43370
62.07
ETHYLENE GLYCOL
43601
44.05
ETHYLENE OXIDE
43502
30.03
FORMALDEHYDE
43368
62.07
GLYCOL
43367
106.12
GLYCOL ETHER
43286
296.57
HENEICOSANE
43282
240.46
HEPTAOECANE
43232
100.20
HEPTANE
(continued)
100
-------
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
TABLE B-3
SAROAD
CODE
MOLECULAR
WEIGHT

CHEMICAL NAME
43281
226.44
HEXRDECRNE

43231
86.17
HEXRNE


43214
58.12
1S0BUTRNE

43446
116.16
ISOBUTYL RCETRTE
43306
74.12
isobutyl RLCOHOL
43451
144.21
1SOBUTYL ISOBUTYRRTE
43215
56.10
ISOBUTYLENE
43120
56.10
ISOMERS
OF
BUTENE
45105
134.21
ISOMERS
OF
butylbenzene
43109
142.28
ISOMERS
OF
DECRNE
45106
134.21
ISOMERS
OF
DIETHYLBENZENE
43112
170.33
ISOMERS
OF
DODECRNE
45104
120.19
ISOMERS
OF
ETHYLTOLUENE
43106
100.20
ISOMERS
OF
HEPTANE
43105
86.17
ISOMERS
OF
HEXRNE
45234
134.21
ISOMERS
OF
METHYLPROP. BENZENE
43108
128.25
ISOMERS
OF
NONRNE
43107
114.23
ISOMERS
OF
OCTANE
43114
212.41
ISOMERS
OF
PENTADECANE
43122
72.15
ISOMERS
OF
PENTANE
43121
70.13
ISOMERS
OF
PENTENE
45108
120.19
ISOMERS
OF
PROPYLBENZENE
43113
198.38
ISOMERS
OF
TETRAOECRNE
43111
184.36
ISOMERS
OF
TRIOECANE
45107
120.19
ISOMERS
OF
TRIMETHYLBENZENE
43110
156.30
ISOMERS
OF
UNDECANE
45102
106.16
ISOMERS
OF
XYLENE
43221
72.15
ISOPENTRNE

43444
104.00
ISOPROPYL 1
RCETRTE
43304
60.09
ISOPROPYL 1
ALCOHOL
43119
114.23
LRCTOL
SPIRITS
45212
120.19
M-ETHYLTOLUENE
45205
106.16
M-XYLENE

43201
16.04
METHANE


43432
74.08
METHYL
ACETATE
43301
32.04
METHYL
ALCOHOL
43445
140.00
METHYL
AMYL RCETRTE
43310
76.11
METHYL
CELLOSOLVE
43801
50.49
METHYL
CHLORIDE
43552
72.10
METHYL
ETHYL KETONE
43560
100.16
METHYL
ISOBUTYL KETONE
43559
100.16
METHYL
N-BUTYL KETONE
43209
40.06
METHYLRCETYLENE
43261
98.18
METHYLCYCLOHEXRNE
43262
84.16
METHYLCYCLOPENTRNE
43272
82.14
METHYLCYCLOPENTENE
43819
173.85
METHYLENE 1
BROMIDE
43118
114.23
M1NERRL
SPIRITS
43212
58.12
N-BUTRNE

43435
116.16
N-BUTYL
RCETRTE
(continued)
101
-------
SPEC
NO
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
164
185
186
187
188
189
190
191
192
193
194
195
196
197
TABLE B-3
SAROAD
MOLECULAR
CHEMICAL NAME
CODF
HEIGHT

43305
74.12
N-BUTTL ALCOHOL
43238
142.28
N-DECANE
43255
170.33
N-OODECANE
43260
212.41
N-PENTADECANE
43220
72.15
N-PENTANE
43303
60.09
N-PROPYL ALCOHOL
45205
120.19
N-PROPYLBENZENE
43259
198.38
N-TETRADECANE
43258
184.36
N-TRIOECANE
45101
114.23
NAPTHA
43284
268.51
NONAOECANE
43235
128.25
NONANE
45211
120.19
O-ETHYLTOLUENE
45204
106.16
O-XYLENE
43283
254.49
OCTADECANE
43233
114.23
OCTANE
45206
106.16
P-XTLENE
43817
165.85
perchloroethylene
45300
94.11
PHENOLS
43265
40.06
PROPADIENE
43204
44.09
PROPANE
43504
58.08
PROPRIONALDEHYDE
43434
102.13
"PROPYL ACETATE
43205
42.08
propylene
43369
76.00
PROPYLENE GLYCOL
43602
58.08
PROPYLENE OXIDE
43208
40.06
PROPYNE
45216
134.21
SEC-BUTYLBENZENE
45220
104.14
STYRENE
43123
136.24
TERPENES
43309
74.12
TERT-BUTYL ALCOHOL
45215
134.21
TERT-BUTYLBENZENE
43390
72.10
TETRAHYDROFURAN
45232
134.21
TETRAMETHYLBENZENE
45202
92.13
TOLUENE
43216
56.10
TRANS-2-BUTENE
43226
70.13
TRAN5-2-PENTENE
45233
148.23
TRI/TETRAALKYL BENZENE
43824
131.40
TRICHLOROETHYLENE
43811
137.37
trichlorofluoromethane
43821
187.38
trichlorotrifluoroethane
43740
59.11
trimethyl amine
43822
92.00
trimethylfluorosilane
43241
156.30
UNDECANE
43000
86.00
UNKNOWN SPECIES
43860
62.50
VINYL CHLORIDE
45401
230.00
XYLENE BASE ACIDS
(concluded)
102
-------
TABLE B-4. BOND GROUPS PER MOLECULE
(IN ALPHABETICAL ORDER)


SPECIES
PROFILES BY BONO
GROUP


SPECIES
un.
CHEMICAL NAME
OLE
PAR
RRO
CRRB
ETH UNRERCTIVE
1
1.1. I-TRICHLOROETHRNE




2.00
2
1•1¦2-TRICHLOROETHRNE




2.00
3
1•1-DICHLOROETHRNE




2.00
4
1.2.3-TRI HETHYLBENZENE

3.00
1.00


5
1.2.4-TRIMETHYLBENZENE

3.00
1.00


6
i.3.s-trimethylben2ene

3.00
1.00


7
1.3-BUTROIENE
1.08


2.00

e
1.4-OIOXRNE
1.00
2.00

2.00

9
l-HEXENE
1.00
4.00



IB
l-PENTENE
1.00
3.00



11
I-T-2-C-4-TM-CTCLOPENTRNE

7.00

1.00

12
2.2.3-TRIHETHYLPEMTRNE

B. 00



13
2.2.4-TRIMETHYLPENTRNE

8.00



14
2.2.5-TRIMETHYLPENTRNE

6.00



15
2.2-0IMETHYL8UTHNE

6.00



16
2.3.3-IRIMEtHYLPEMtRNE

8.00



17
2.3.4-TRIMETHYLPENTRNE

a.00



18
2.3-01 METHYL-I-BUTENE
1.00
4.00



19
2.3-D I METHYLBUTONE

6.00



20
2.3-01METHYLPENTRNE

7.00



21
2.4-OIMETHYLHEXBNE

8.00



22
2.4-OIMETHYLPENTRNE

7.00



23
2.5-OIMETHYLHEXRNE

a.00



24
2-ETHOXYETHYL ACE1RTE

4.00

2.00

25
2-ETHYL-1-BUTENE
1.00
4.00



26
2-NE1HYL PENTRNE

6.00



27
2-HE THYL-1-BUTENE
1.00
3.00



28
2-HETHYL-2-BUTEME

3.00

2.00

29
2-NETHYL-2-PENTENE

4.00

2.00

30
2-METHYLHEXRNE

7.00



31
3-METHYL PENTRNE

6.00



32
3-HETHYL-l-BUTENE
1.00
3.00



33
3-METHYL-1-PENTENE

6.00



31
3-METHYL-T-2-PENTENE

4.00

2.00

3S
3-ME THYLHEPTHNE

a.00



36
3-METHYLHEXRNE

7.00



S7
4-METHYL-T-2-PENTENE

4.00

2.00

38
4-METHYLHEPTRNE

8.00



39
R-METHYLSIYRENE

2.00
1.00
1.00

40
RCETflLDEHYOE

1.00

1.00

(continued)
-------
TABLE B-4
SPECIES PROFILES BT BOND CROUP
SPECIES	CHEHICBL NRHE	OLE	PAR	ARO	CRRB	ETH	UNREACTIVE
MO.
41
ACETIC flCIO

2.00



42
ACETONE

2.00

1.00

43
RCETONITR1LE

1.00


1.00
44
ACETYLENE




1.00
45
ACRYL0N1TRILE
1.00
1.00



46
BENZENE




6.00
47
BUTENE
1.00
2.00



48
BUirL CELLOSOLVE

5.00

1.00

49
BUTYRALOEHYDE

3.00

1.00

50
C-3-HE XENE
1.00
4.00



51
C-7 CYCL0PARAFFIN3

6.00

1.00

52
C-8 CYCLOPARRFFIN3

7.00

1.00

53
C-9 CYCLOPARAFF1NS

8.00

1.00

54
C3 ALOEHYOE

2.00

1.00

55
C5 ALOEHYOE

4.00

1.00

56
C6 OLEFIN UNK
1.00
4.00



57
C7-0LEFIN UNKNOWN
1.00
S.00



58
CB RLOEHYOE

7.00

1.00

59
C0 OLEFIN UNK
1.00
6.00



60
CARBON TETRRBROMIDE




1.00
61
CARBON TETRACHLORIDE




1.00
62
CELLOSOLVE

3.00

1.00

63
CELLOSOLVE RCETATE

4.00

2.00

64
CHLOROBENZENE




6.00
65
CHLOROFORM




1.00
66
CIS-2-BUTENE

2.00

2.00

67
C1S-2-PENTENE

3.00

2.00

68
CYCLOHEXANE

5.00

1.00

69
CYCLOHEXANONE

4.00

2.00

70
CYCLOHEXENE
1.00
4.00



71
CYCLOPENTRNE

4.00

1.0B

72
CYCLOPENTENE
1.00
3.00



73
CYCLOPROPANE

2.00

1.00

74
OlflCETONE ALCOHOL

5.00

1.00

75
OICHLOROOIFLUOROHETHRNE




1.00
76
DICHLOROMETHANE




1.00
77
OIHETHTLETHTLBENZENE

4.00
1.00


78
o i methylformamide




3.00
79
OOCOSHNE

22.00



80
E 1COSANE

20.00



(continued)
-------
NO.
ei
82
63
84
65
as
87
88
S9
90
91
92
93
91
95
96
97
98
99
100
101
102
103
104
105
108
107
109
109
110
111
112
113
114
115
116
117
118
1 19
120
TABLE B-4
SPECIES PROFILES BY BONO CROUP
CHEMICAL NRHE	OLE	PRR	MO	CURB
ETHANE




ETHTL rcetbie

3.00

1.00
ethyl fiCRnnre

3.00

2.00
ETHTL ALCOHOL

2.00


ETHYL CHLORIDE




ETHTL ETHER

3.00

1.00
ETHTLRCE1TLEKE

4.00


ethtlrmine

1.00


ethtlbenzene

2.00
1.00

ethtlcyclohexrne

7.00

1.00
ethylene




ethtlene oichlorioe




ethylene glycol

1.00

1.00
ethylene oxide

1.00


formaldehyde



1.00
GLYCOL

1.00

1.00
GLYCOL ETHER

1.00

1.00
HENE1C05RNE

21.00


HEPTROECANE

17.00


heptbne

7.00


HEXROECRNE

16.00


HEXRNE

8.00


1SOBUTRNE

4.00


ISOBUTTL RCETRTE

8.00


ISOBUTYL RLCOHOL

4.00


ISOBUTYL 150BUTYRRTE

7.00

1.00
ISOBUTYLENE
1.00
2.00


ISOMERS OF aUTENE

2.00

2.00
ISOMERS OF BUTYLBENZEHE

4.00
1.00

I30HER3 OF OECRNE

10.00


ISOMERS OF OIETHYLBENZENE

4.00
1.00

ISOMERS OF OOOECRNE

12.00


ISOMERS OF ETHTLTOLUENE

3.00
1.00

ISOMERS Or HEPTANE

7.00


ISOMERS OF HEXRNE

8.013


ISUMEH5 OF METHYLPROP. BENZENE

4.00
1.00

ISOMERS OF NONRNE

9.00


ISOMERS OF OCTRNE

8.00


ISOMERS OF PENTAOECRNE

15.00


ISOMERS OF PENTRNE ..

5.00


-------
NO.
121
122
123
124
125
126
127
120
129
130
131
132
133
131
135
136
137
138
139
110
Ml
142
143
144
145
146
147
148
149
150
151
152
153
154
TABLE B-4
SPECIES PROFILES BY BONO GROUP
CHEMICAL NAME	OLE	PAR	RRO	CURB	ETH
ISOMERS OF PENTENE	3.00	2.00
ISOMERS OF PROPYLBENZENE	3.00	1.00
IS0HER9 OF TETRRDECRNE	14.00
ISOMERS OF TRIOECRNE	13.00
ISOMERS OF TRINETHYLBENZENE	3.00	1.00
ISOMERS OF UNDECRNE	11.00
ISOMERS OF XYLENE	2.00	1.00
ISOPENTRNE	5.00
ISOPROPYL RCETRTE	5.00
ISOPROPYL ALCOHOL	3.0B
LRCTOL SPIRITS	8.00
M-ETHYLTOLUENE	3.00	1.00
M-XYLENE	2.00	1.00
METHANE
METHfL ACETATE
METHYL RLCOHOL	1.00
METHYL RMYL RCETRTE	8.00
METHYL CELL050LVE	2.00	I-B0
METHYL CHLORIOE
METHYL ETHYL KETONE	3.00	1.00
METHYL ISOBUTYL KETONE	5.00'	1.00
METHYL N-BUTYL KETONE	5.00	1.00
METHYLACETYLENE	1.50
METHYLCYCLOHEXRNE	8.00	1.00
METHYLCYCLOPENTRNE	5.00	1.00
METHYLCYCLOPENTENE	1.00	4.00
METHYLENE BROMIDE
M1NERRL SPIRITS	7.00	1.00
N-BUTRNE	4.00
N-BUTYL RCETRTE	5.00	1.00
N-BUTYL RLCOHOL	4.00
N-OECRNE	10.00
N-DODECRNE	12.00
N-PENTRDECRNE
N-PENTRNE	5.00
N-PROPYL ALCOHOL	3.08
N-PROPYLBENZENE	3.00	1.00
N-TETRHOECHNE	14.00
N-TRIOECRNE
NflPTHR	8.00
-------
NO.
181
162
163
184
165
166
167
160
169
170
171
172
173
174
175
176
177
176
179
IBB
181
162
163
161
165
186
167
186
189
190
191
192
193
194
195
196
197
TABLE B-4
SPECIES PROFILES BY BONO CROUP
CHEHICRL NAME	OLE	PAR	RRO	CURB	ETH
NONADECflNE	19.00
NONRNE	9.00
O-ETMUOIUENE	3.00	1.00
O-XTLENE	2.00	1.00
OCTROECflNE	16.00
OCTANE	8.00
P-XYLENE	2.00	1.00
PERCHIDROETHYLENE
PHENOLS
PROPROIENE	1.00	2.00
PROPANE	1.50
PROPRIONRLOEHYOE	2.00	1.00
PROPYL fiCETRTE	4.00	1.00
PROPYLENE	1.00	1.00
PROPYLENE GLYCOL	2.00	I.0B
PROPYLENE OXIOE	2.00
PROPYNE	2.00
5EC-BUTYLBENIENE	4.00	1.00
STYRENE	1.00	1.00	1.00
TERRENES	1.00	8.00
TERT-eUTYL ALCOHOL	3.00	1.00
TERT-OUTYLBENZENE	4.00	1.00
TETRAHrDROFURflN	3.00	1.00
TETRAMETHTLBENZENE	4.00	1.00
TOLUENE	1.00	1.00
TRHNS-2-BUTENE	2.00	2.00
TRflNS-2-PENTENE	3.00	2.00
TRI/TETRRRLKYL BENZENE	5.00	1.00
TRICHLOROETHYLENE	1.00
TRICHLOROFLUORONE1HRNE
TRICHLOROTRlFLUOROETHflNE
TRIHETHYL RHINE	3.00
TRIHETHYLFLUOROSlLflNE
UNOECflNE	11.00
UNKNOHN SPECIES	0.10	4.00	0.25	0.32	0.16
VINYL CHLORIOE	1.00
XYLENE BASE ACIOS	2.00	1.00
-------
TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
1. REPORT NO.
2
3 RECIPIENT'S ACCESSION NO
4. TITLE AND SUBTITLE
A NEW CARBON-BOND MECHANISM FOR AIR QUALITY
SIMULATION MODELING
5 REPORT DATE
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
J. P. Klllus and 6. Z.
Whitten

8 PERFORMING ORGANIZATION REPORT NO.
9. PERFORMING ORGANIZATION NAME AND ADDRESS
Systems Applications. Inc.

10 PROGRAM ELEMENT NO.
CDWA1A/01-0301 (FY-82)
101 Lucas Valley Road
San Rafael, California
94903

11 CONTRACT/GRANT NO.
68-02-3281
12. SPONSORING AGENCY NAME AND ADDRESS
Environmental Sciences Research Laboratory-RTP, NC
Office of Research and Development
U.S. Environmental Protection Agency
Research Trianele Park. North CarnHna 27711
13. TYPE OF REPORT AND PERIOD COVERED
Interim 6/80 - 6/81
14. SPONSORING AGENCY CODE
FPA/#;nn/no
15. SUPPLEMENTARY NOTES
16. ABSTRACT
A new generalized kinetic mechanism for photochemical smog, which
incorporates recent information on the atmospheric reactions of aromatic hydro-
carbons, has been developed. The mechanism, labeled the Carbon-Bond Mechanism
III (CBM III), is the third lumped-parameter mechanism to be designed in accordance
with the carbon-bond reaction concept in which carbon atoms with similar bonding
are treated similarly, regardless of the molecules in which they occur. Because (
of the general nature of the CBM III, it can be used to model the entire atmospher
mix of hydrocarbons and is suitable for use in air quality simulation models.
Principal features of CBM III Include a separate reaction scheme for ethylene,
realistic photochemistry for aromatic hydrocarbons and dicarbonyl compounds, and
formation pathways for alkyl nitrates and nltroaromatic compounds. CBM III was
tested by comparing the predictions obtained with the mechanism against smog
chamber data of multi-component hydrocarbon/NO mixtures. In addition to a
discussion of the development and testing of tSe CBM III, information is also
provided on the application of the mechanism for urban air quality modeling.
17.
KEY WORDS ANO DOCUMENT ANALYSIS

a. DESCRIPTORS
b.IDENTIFIERS/OPEN ENDED TERMS
c. COSATI Field/Group



18. DISTRIBUTION STATEMENT
RELEASE TO PUBLIC
19 SECURITY CLASS (Thu Report)
UNCLASSIFIED
21. NO OF PACES
118
20 SECURITY CLASS (This page)
UNCLASSIFIED
22. PRICE
1
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108
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