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OAR Box 1846 

Prepped by Ollie Stewart 

Document Number: 

64) ll-J-7 

Docket Number: 

A-90-07 

Printed 11/18/2008 7:30:16 AM Sheet 64 of 93 
A -90-00 

H-:T-07 

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OJ 

DEVELOPMENT OF OZONE REACTIVITY SCALES 

FOR VOLATILE ORGANIC COMPOUNDS 

William P. L. Carter 

Statewide Air Pollution Research Center 

University of California 

Riverside, CA 92521 

MNS-90:scales 
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Abstract 

Model calculations of effects of over 140 types of volatile organic 

compounds (VOCs) on photochemical ozone formation in a set of 62 idealised 

airshed scenarios representing 12 different urban areas were employed to 

investigate alternative methods for developing VOC reactivity scales. 

Several methods for combining the widely^varying reactivities for the 

scenarios were used to derive various "aggregated base case" reactivity 

scales. The results varied depending on the aggregation method used and 

how ozone impacts were quantified. Since the main reason for this 

variability is the dependence of reactivities on N0X, a "maximum 

reactivity" scaie was derived by averaging reactivities when N0X inputs 

are adjusted so VOCs have cheir greatest impacc on ozone, and a "maximum 

ozone" reactivity scale was derived by adjusting N0X inputs to yield 

maximum ozone concentrations. These two scales had significant 

differences in relative reactivities. However, the maximum reactivity 

scaie correspondea reasonably well with the aggregated base case scaies 

where ozone impacts are quantified' Dy, integrated ozone concentration, or 

where the aggregation method takes into account the magnitude of the 

effect of the VOC on ozone. It is concluded that for che near term the 

maximum reactivity scale may be most appropriate for applications where a 

single VOC reactivity scale is applied to a wide variety of airsheds. 

Uncertainties in tne atmospheric chemical mechanisms for the VOCs affect 

these reactivity estimates, and qualitative rankings of mechanistic 

uncertainties are given for each VOC. 
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INTRODUCTION 

The formation of photochemical ozone continues to be an intractable 

problem in many urban areas. Ozone is not emitted directly into the 

atmosphere, it is formed oy the interactions of volatile organic compounds 

(VOCs) with oxides of nitrogen (N0X) in sunlight, and effective ozone 

control strategies must focus on both of tnese precursors. However, in 

urban areas where NO., sources are abundant and difficult to control, VOC 

control is the strategy receiving the most attention, at least for the 

near term. Since reduction of total VOC emissions from most of the major 

sources is difficult and costly, strategies involving changing the 

chemical nature of VOC emissions so that chey have less of a cendency co 

promote ozone formation, i.e., so that chey are less "reactive", are 

becoming increasingly attractive. Two examples of this is conversion of 

motor vehicles to alternative fuels such as methanol, and the substitution 

of currently used solvents with less reactive compounds. The development 

and assessmenc of such stracegies requires a means co quantify and compare 

the ozone formation reactivities of the many types of VOCs which can be 

emitted. 

There are a number of ways to quantify the reactivities of VOCs. 

Examples include the rate at which an organic reacts with hydroxyl 

radicals (the main atmospheric reaction pathway for most organics 

[Atkinson, 1989,1990]) (Darnall et al., 1976; ARB, 1989) and the amount of 

ozone the organic forms when irradiated in N0X - air mixtures in 

environmental chambers (Wilson and Doyle, 1970; Altshuller and Bufalini, 

1971; Laity et al., 1973). However, for most control strategy 

applications, which are concerned with the effects of incremental changes 

yy 
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in emissions into already polluted areas, the most useful measure of 

reactivity is "incremental reactivity". This is the change in ozone 

caused by the addition of the organic in a standard scenario representing 

an air pollution episode, normalized by the amount of organic added. 

Reactivity measured in this way takes into account not only the effects of 

all aspects of the organic's reaction mechanism, but also the effects of 

the environment into which it is emitted, which in general will influence 

how much ozone the emission of any organic would cause. 

The incremental reactivities of VOCs have been investigated 

experimentally (Carter and Atkinson, 1987) and in several computer 

modeling studies (Bufalini and Dodge, 1983; Dodge, 1984; Hough and 

Derwent, 1987; Carter 1989a, 1989b; Weir et al, 1988; Carter and Atkinson, 

1989). The results of these studies indicated that mechanistic and 

environmental factors are indeed important in affecting incremental 

reactivities of organic compounds. The most important single mechanistic 

factor affecting a VOCs reactivity is the rate at which it reacts in the 

atmosphere. However, the ocher aspects of its reaction mechanism is also 

important and cannot be ignored. The most important single environmental 

factor is the availability of N0X in the system, which is most 

conveniently measured by the ratio of total emissions of reactive organics 

(ROG) to N0X . In general, organic compounds are found to have the highest 

effects on ozone formation under relatively high N0X conditions (i.e., low 

ROG/NOv ratios), and to have much lower, in some cases even negative, 

reactivities under conditions where N0X is limited (high R0G/N0X 

ratios). This is because under relatively high N0X conditions the amount 

of ozone formed is determined by the levels of radicals formed from the 

reactions of the VOCs, while under lower N0X conditions the availability 
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of N0X, which must be present in order for ozone to be formed, limits 

ozone formation. Other aspects of the environment in which the VOC is 

emitted, such as nature of the other organics emitted into the airshed 

(Weir et al., 1988), the amount of dilution occurring (Carter and 

Atkinson, 1989), etc., can also be important in affecting VOC 

reactivities, though investigations of these aspects are limited. 

The dependence of VOC reactivities on environmental conditions 

presents problems to the development of a general VOC reactivity scale for 

the assessment of ozone control strategies involving VOC substitutions. 

The most scientifically justifiable approach would be not to use a general 

reactivity scale, but instead to carry out detailed model calculations on 

the effects of specific emissions substitution strategies on air quality 

in specific air pollution episodes. An example of this is the study of a 

number of methanol fuel substitution scenarios on an air pollution episode 

in the California South Coast Air Basin conducted by Russell et al., 

(1989). Such an approach has Che potential for giving the best available 

estimates of air quality impacts for the specific cases which are 

examined, though ic should be recognized that such complex model 

calculations are not without significant uncertainties. However, chis is 

extremely expensive and its results are applicable only to the particular 

air pollution episode and substitution scenarios which were examined. 

Because of this, this approach is probably not practical for the 

evaluation of the full range of VOC substitution options which need to be 

explored. 

The procedures described in this paper for assessing ozone impacts of 

VOC emissions are also based on airshed model calculations, but of a much 

more idealized type. Rather than estimating impacts of VOC emissions on 
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ozone formation in specific episodes (which are difficult to estimate 

because they are highly dependent on the specific conditions of the 

episodes and in most cases require highly complex multi-cell grid models 

for accurate representation), the procedure is based on estimating likely 

impacts of the VOCs on ozone under generalized sets of conditions. This 

is a simpler modeling problem than estimating reactivities for a specific 

set of conditions, since the set of model scenarios employed do not need 

to accurately represent the details of any particular air pollution 

episode; all that is necessary that the set of scenarios represents a 

realistic range of conditions which might affect reactivity. An 

appropriate set of idealized model scenarios should be sufficient for this 

purpose. 

Several approaches could be employed for deriving reactivity scales 

for generalized sets of conditions. The most obvious would be to 

determine the distribution of all airshed conditions where ozone formation 

is a problem, and then calculate the average reactivities for sets of 

scenarios representing chis difference. However, chis has several 

drawbacks. It would require a comprehensive analysis of the distribution 

of chemical conditions in airsheds which might affect VOC reactivities, 

which has not yet been carried out. Because reactivities (including 

relative reactivities) depend significantly on the relative availability 

of NOx in the system (Dodge, 1984; Carter and Atkinson, 1989), the 

reactivity scale would be particularly sensitive to the distribution of 

relative N0V levels which is assumed. This is highly uncertain (e.g., see 

Bauges, 1986). In addition, it would not be appropriate to include in the 

average those conditions where ozone formation is N0X limited, and where 

VOC control is therefore ineffective as an ozone control strategy. This 
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problem can to some extent be dealt with by using aggregation methods 

which give greater weights to reactivities in scenarios where VOC controls 

have the greatest effect on ozone. 

An alternative approach is to consider N0X availability separately 

from all other airshed characteristics which affecc reactivity. This can 

be done by deriving separate reactivity scales, where each represents a 

specified and consistent condition of N0X availability, but where each 

scale represencs aggregates, or averages, of other airshed conditions. 

For example, one sec of N0X condicions whicn could be used for deriving a 

reactivity scaie would be those where VOC emissions nave Che greatest 

effects on ozone formation; i.e., the N0;/ levels where VOCs have their 

maximum reactivities. This might be an appropriate Dasis for deriving a 

reactivity scale for concrol strategy purposes, since by definition it 

represents conditions where VOC control is tne mosc effective ozone 

concrol strategy (Weir et al., 1988). An alternative set of N0X 

conditions which might be appropriace for deriving a reactivity scale are 

those which resulc in formacion of maximum ozone concentrations. As shown 

previously (Carter and Atkinson, 1989), maximum ozone concentrations 

always occur at NO levels which are lower than chose where VOCs have 

cheir hignest incremental reactivities. For example,.for an idealized 

one-day scenario with conditions representing the Los Angeles basin, 

maximum VOC reactivities occur at a R0G/N0X ratio of approximately 6, 

while maximum ozone concentrations occur at a R0G/N0x ratio of 

approximately 8. 

It can be argued that maximum reactivity and maximum ozone conditions 

represent respectively the high and low limits for conditions of N0X 

availability which are appropriate for defining a VOC reactivity scale. 
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If N0X levels are significantly higher than those of maximum reactivity 

conditions, then ozone inhibition by the high N0X levels would prevent 

significant concentrations of ozone from being formed in single day 

episodes. If N0X levels are lower than those favorable for formation of 

maximum ozone concentrations, then ozone formation is NO -limited, and 

under those conditions it has been shown that changes in VOC emissions 

have only small effects on ozone (Carter and Atkinson, 1989), and thus VOC 

control would be an ineffective strategy for controlling ozone 

formation. 

In the sections below, the derivation of the several different 

aggregated reactivity scales are described, and their predictions of 

reactivities are summarized and compared. These scales are based on 

computer model calculations of incremental reactivities, in a variety of 

idealized single day ozone pollution scenarios, of che over 140 organic 

compounds represented in a recently-developed detailed reaction mechanism 

(Carter, 1990). The scenarios employea were basea on previously-developed 

EKMA models of o2 city-aays in 12 urban areas throughout the United States 

(Gery et al., 1987; Whitten, 1988) ana represent a wiae variety of 

conditions which might affect VOC reactivities. 
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METHODS 

Quantification of Ozone Reactivities 

In this work, the reactivity of a VOC with respect to ozone formation 

is measured by its "incremental reactivity". This is defined as the 

change in ozone caused by the addition of the VOC co a particular polluted 

airshed of interest (referred to as the "pollution scenario"), divided, by 

the amount of VOC added. 

Ozone Formed in Ozone Formed 

Pollution Scenario in an Idealized 

with VOC Added to - Pollution Scenario 

Incremental Emissions (Test Case) (Base Case) 

Reactivity = (I) 

of a VOC Amount of VOC Added to 

Emissions in Test Case 

To avoid dependence of the incremental reactivity on the amount of VOC 

added, the incremencal reactivity is defined as Che limit as the amount of 

VOC addea approacnes zero. This also permits incremental reactivities of 

mixtures VOCs to be calculaced by linear summations of those of their 

components. If the atmospheric chemical reaction mechanism for a VOC is 

known or can be estimated, its incremental reactivity for the conditions 

of a specific pollution scenario can be estimated by carrying out model 

calculations of amounts of additional ozone formation caused by adding the 

VOC to the emissions. 

Equation (I) is based on quantifying reactivity by the effect of the 

VOC on the total amount, or yield, of ozone which is ultimately formed 

from the VOC. Quantifying ozone by ozone yield, as opposed to ozone 

concentration or (as discussed below) ozone dose has the advantage that 
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incremental reactivities so derived are unitless quantities, reflecting 

just molecules of ozone formed per molecule of VOC emitted. If chemical 

effects are neglected, they are independent of the amount of dilution 

occurring or the length of time in the scenario. Inaeed, if differences 

in effects of reactivities on R0G/N0X ratios are taken into account, 

incremental reactivities have been shown to be remarkably insensitive to 

dilution, despite significant differences in maximum ozone concentrations 

which are formed (Carter ana Atkinson, 1989). For this reason:, reactivity 

quantified according to Equation (I) is considered co have Che best 

correspondence to the fundamental cnemical processes which occur on the 

molecular level. 

However, in cost-benefit analyses of effects of ozone exposure on 

populations or the environment, it is often the ozone concentrations 

integrated over time which is the quantity of interest. This is referred 

to as the "ozone dose" in this work. 

Ozone Dose = / [0^]dt 

To determine how reactivities based on ozone dose differed from those 

based on ozone yield, for comparative purposes "ozone dose reactivities" 

were calculated for representative VOCs. These are defined as follows. 

Ozone Dose in a Ozone Dose 

Pollution Scenario in an Idealized 

with VOC Added to - Pollution Scenario 

Ozone Dose Emissions (Test Case) (Base Case) 

Reactivity = HI ) 

of a VOC Amount of VOC Added to 

Emissions in Test Case 
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Again, the reactivity is defined as the limit of low added VOC in the test 

case. Note that reactivities defined in this manner cannot be expressed 

as unitless quantities, and tney are directly dependent on tne amount of 

time in the scenario. For this reason, ozone dose reactivities are thus 

not considered to De particularly meaningful in an absolute sense. 

However, ratios of ozone dose reactivities can provide a potentially 

useful basis for deriving relative reactivity scales. 

In the subsequent aiscussion, the term "reactivity" without 

qualifier, or "ozone yiela reactivity" will refer co reactivities defined 

using Equation (I). If ozone aose reactivity, i.e.. reactivity calculated 

using Equation (II), is being aiscussed, it is referenced explicitly as 

such. 

Chemical Mechanism Used for Representative VOC s 

The chemical mechanism used to represent the reactions of the base 

case ROG and NO. emissions, and to calculate the incremental reactivities 

A 

of the representative VOCs, was developed by the autnor and is documented 

in detail elsewhere (Carter 1990). This mechanism contains rate constant 

and proauct yield assignments for over 140 separate "detailed model 

species", making it the most detailed of all current state-of-the-art 

mechanisms in terras of the number of organic species which can be 

separately represented. Because of the number of different VOC species it 

can represent, it is particularly suitable for use in reactivity 

assessment calculations. 

This mechanism was tested against over 500 environmental chamber 

experiments (Carter et al., 1986; Lurmann et al., 1987; Carter, 1988; 

Carter and Lurmann, 1990a) and in most cases could simulate experimentally 

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observed ozone yields to within +30%. This is as good as presently can be 

expected with current mechanisms, given uncertainties in characterizations 

of chamber effects, combined with uncertainties in the mechanisms 

themselves (Carter et ai., 1986; Gery et al., 1988; Carter and Lurmann, 

1990a, 1990b). However, it should be recognized that for many VOCs the 

atmospheric reaction mechanism is highly uncertain, and the available 

environmental chamDer data are sufficient for testing mechanisms for only 

a relatively small subset of the VOCs whose reactivities are calculated. 

For most of the individual VOCs, the only aspect of the mechanism for 

which there are data are the rate constants for their initial reactions in 

the atmosphere; the mechanisms used for the reactions of the radicals 

subsequently formed, wnicn are responsible for ozone formation, are 

estimates based on analogies with the few compounds whose mechanisms are 

known in more detail. (Relative levels of uncertainty in the mechanisms 

of individual VOCs are summarized later in this paper). Nevertheless, the 

mechanism incorporates our best present estimates for the reaction 

mechanisms of the wide variety of VOCs which are emitted into the 

atmosphere. 

Pollution Scenarios Used for Reactivity Estimates 

Representative Pollution Episodes. In choosing a set of pollution 

scenarios to use for the estimation of VOC reactivities for an aggregated 

set of conditions, the objective is not that the scenarios necessarily 

represent in detail any particular air pollution episodes, but that they 

be sufficiently varied that they represent the distribution of chemical 

conditions in the atmosphere that might affect reactivity. Since a large 

number of simulations required in a comprehensive reactivity study, 

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scenarios must not be so complex that simulating them takes a large amount 

of computer time or that they require use of highly condensed 

photochemical mechanisms which are inappropriate for reactivity 

assessments of the wide variety of emitted VOCs. However, the scenarios 

also need to be sufficiently realistic that they the reactivities 

predicted for them would not be outside the range expected for conditions 

of real airsheds. 

The development of a comprehensive set of idealized pollution 

scenarios representing the true distribution of ozone pollution conditions 

requires an analysis of the range of conditions in airsheds where ozone 

formation is a problem. Such an analysis is beyond the scope of this 

study. Fortunately, an extensive set of idealized pollution scenarios has 

already been developed for the purpose of city-specific EKMA analyses 

(e.g., see Gipson et al., 1981; EPA, 1984) of ozone formation in various 

areas of the United States. The EKMA approach involves use of single-cell 

box models of one day urban ozone pollution episodes for the purpose of 

estimating the amount of ROG reauction needed co reduce ozone Co achieve 

the national air quality standard (Dodge, 1977). Although EKMA models use 

only a single cell formulation, and thus cannot represent realistic 

pollution episodes in great detail, they can represent dynamic injection 

of pollutants, time-varying changes of inversion heights with entrainment 

of pollutants from aloft as the inversion height increases throughout the 

day, and time-varying rates of photolysis reactions and temperatures. 

Thus, these models can represent a wiae range of chemical conditions which 

may affect predictions of effects of ROG control on ozone formation. 

These chemical conditions are the same as those affecting predictions of 

VOC reactivity. Therefore, at least extent they are suitable for their 

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intended purpose, the existing EKMA scenarios should also be suitable for 

use in reactivity assessment studies. 

The set of EKMA scenarios (or EKMA city-days) used as the starting 

point in this study were those which had been used by Gery et al. (1987) 

in their study of effects of changing UV radiation (due to stratospheric 

ozone depletion) on ozone formation in various urban areas, and those used 

by Whitten (1988) to study the effects of changes in ozone due to changes 

in vehicle fuel composition. These in turn were taken from EKMA analyses 

used as parts of State Implementation Plans for reducing ozone in various 

areas throughout the United States. The scenarios represented 62 episodes 

(city-days) in 12 different urban areas. [Five of che city-days from 

Whitten (1988) represented episodes which were also on the set from Gery 

et al. (1987), thougn the input conditions are sufficiently different that 

they are treated as separate scenarios for the purpose of this study.] 

The major characteristics of these city-days are listed in Table 1, which 

shows that a wide variety of conditions are represented. For example, the 

maximum calcuiatea ozone ranged from 76 ppb (well below che Federal ozone 

standard) up co almosc 0.37 ppm; che maximum inversion height ranged from 

400 to 3300 meters; and the initial plus emitted ROG pollutant input 

ranged from less than 2 to more than 50 raillimoles meter . 

No claim is made as to the accuracy of these model scenarios in 

simulating the episodes they are designed to represent, though clearly 

they were developed with an attempt to make their input data and 

predictions as consistent as possible with the available (though generally 

limited) data. However, even if they are not accurate in representing 

their particular episodes, they represent the modelers' best efforts to 

represent, as accurately as possible given the available data and the 

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limitations of the formulation of the EKMA model, the wide range of 

conditions occurring in urban areas throughout the United States. This 

variability, more than the accuracy of any particular scenario in 

representing a specific episode, makes them useful for the objectives of 

this study. 

The input data for these scenarios were provided to the author by 

Gery (1989) and Whitten (1989) in the form of input files to the OZIPM 

(Gipson, 1984; Hogo and Gery, 1988) computer program. Since the available 

versions of the OZIPM program are not compatible with the detailed 

mechanism used in this study, these inputs were converted for use in the 

software employed in this study. This involved some approximations to the 

representations used by the OZIPM program. For example, in the 

simulations reported here the photolysis rates were calculated using the 

ground level solar actinic fluxes given by Peterson (1976) for his "best 

estimate" surface albedos, which are somewhat different from those used by 

the OZIPM program. To partially correct for this, ail photolysis rates 

were adjusted upwards by a factor of 1.093 to yield the same N02 

photolysis rate as calculated by 0ZIPM4 for direct overhead sun. The 

effects of these differences on the model predictions should be minor. 

Perhaps more significantly, the city-specific EKMA scenarios used in 

this study were developed using various versions of the Carbon Bond gasphase chemical mechanism (see Gery et al., 1988 and references therein), 

which is different in some respects from the mechanism employed in this 

study. Although the latest Carbon Bond mechanism (Gery et al., 1988), 

like the mechanism used here (Carter, 1990), can be considered to 

represent the current state-of-the science, the Carbon Bond mechanism 

cannot be used for developing VOC reactivity scales involving large 

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P.17 

numbers of compounds because it is a condensed mechanism which does not 

provide for representation of differences between many individual VOCs of 

the same general type. However, despite the differences in the chemical 

mechanisms and the other modifications of the input files required to use 

different software systems to simulate the scenarios, the simulations of 

maximum ozone in the scenarios using the mechanism and software employed 

in this study were found not to be significantly different (agreeing to 

within + 10% or better) to those calculated using the Carbon Bond IV 

mechanism (Gery et al., 1988) and the OZIPP software and input files. They 

also were not significantly different from those reported by Gery et al. 

(1988) using an earlier version of Carbon Bond. 

In addition to these city-specific EKMA scenarios, for comparison 

purposes reactivities were also calculated for the three idealized EKMAtype scenarios used in our previous reactivity assessment studies (Carter 

and Atkinson, 1989). These were based on standard city-specific EKMA 

inputs for low (EKMA-1), medium (EKMA-2) and high (EKMA-3) dilution 

regions designed by Gipson and Freas (1983) for use in Regulatory Impact 

Analyses. As in our previous reactivity studies (Carter and Atkinson, 

1989), the ROG input was held constant at 12 millimoles meter , and the 

N0X input was varied to determine the dependencies of reactivities on the 

ROG/NOx ratio. - The major conditions of these scenarios are also 

summarized on Table 1. These scenarios were not used in deriving the 

aggregated reactivity scales, but selected results of reactivity 

calculations using them are included here for comparison with results of 

our previous studies. 

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Representation of Base Case ROG Compositions. The composition 

assumed for the base case ROG emissions has been shown to affect 

predictions of reactivity (Carter and Atkinson, 1989; Weir et al., 1988), 

and thus it is important that this be representee as accurately as 

possible. However, for most urDan areas the composition of the ROG 

emissions are highly uncertain, and no attempt was made to represent the 

city-specific ROG compositions in the development of the EKMA scenarios 

discussed above. Instead, like Gery et al. (1987) and Whitten (1988), a 

standard default representation of the ROG composition, which had been 

developed based on air quality data in a wide variety of areas (e.g., EPA, 

1984; Killus and Whitten, 1984; Lurmann et al., 1987; Jeffries et al., 

1989) was employed. The most recent and probably most comprehensive 

analysis of detailed VOC speciation data was carried out by Jeffries et 

al. (1989), who analyzed and summarized results of 860 ground level and 

160 aloft measurements made in various urban areas throughout the United 

States. (Of these, respectively 773 and 53 samples were considered to be 

usable for analysis.) Based on these data, they developed an "all-city 

average" ROG composition profile to represent typical ground level ROG 

emissions, and a separate "aloft" ROG profile to represent compositions of 

such species aloft. These compositions are considered to be appropriate 

for use airshed modeling of areas where reliable ROG speciation data are 

not available, and were thus used in all scenarios employed in this 

study. 

The all-city average and aloft ROG compositions reported by Jeffries 

et al. (1989) where given in terms of the lumped species used in the 

Carbon Bond IV (Gery et al, 1988) and the Lurmann et al. (1987) condensed 

mechanisms. These are somewhat different than those used in the mechanism 

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P.19 

employed in this study. The mechanism employed in this study uses 

variable lumped species whose mechanistic parameters are adjusted based on 

the compound or mixture they represent-(Carter, 1990). This requires 

knowledge of the detailed compositions of the mixture being represented. 

For use with this mechanism, the detailed compositions associated with 

all-city average and the aloft mixtures derived by Jeffries et al. (1989) 

were obtained from Jeffries (1988). The detailed compositions of these 

two surrogates are listed elsewhere (Carter and Lurmann, 1990b). 

It should be noted that the ground level measurements analyzed by 

Jeffries et al. (1989) did not include aldehyde measurements. In deriving 

the all-city average mixture, Jeffries et al. (1989) assumed 51 aldehyde 

composition assigned to the "allcity average" mixture is based on previous 

EPA-recommended EKMA defaults (e.g, EPA, 1984), whicn were derived based 

on highly scattered and uncertain data (see, for example, Lurmann et al., 

1987). This is an uncertainty which may affect results of reactivity 

calculations. The effect of this uncertainty, and on the variability base 

case ROG compositions in general, is being invescigaced, but is beyond the 

scope of the present paper. 

Derivation of Aggregated Base Case Reactivity Scales 

One approach for developing a generalized reactivity scale is to 

aggregate reactivities calculated for a representative distribution of air 

pollution episodes. If it is assumed that the pollution scenarios listed 

in Table 1 approximates the distribution of such airsheds, then they can 

be used to develop such an aggregated scale. Although the extent to which 

these scenarios approximate the true distribution of airshed conditions is 

unknown, it is instructive to see how an aggregated reactivity scale 

17 
developed using them compare with reactivity scales developed using other 

methods. 

Therefore, as part of this study, examples of aggregated reactivity 

scales were developed using the city-days listed in Table 1, without any 

of their input conditions being modified. Since the scenarios are 

essentially the same as used by Gery et al. (1987) and Whitten (1988) to 

represent base case conditions in their respective studies, they are 

referred to as the "base case" scenarios, and the scales derived from them 

as the "aggregated base case" scales. (This is to distinguish them from 

the scenarios where the N0X inputs were modified to represent "maximum 

reactivity" or "maximum ozone" conditions, as discussed below.) To avoid 

giving undue weight to those urban areas for which Gery et al., (1987) 

have many episodes, with one exception no more than two episodes were used 

from each urban area. A total of 21 episodes were used to derive the 

aggregated base case reactivity scales; the specific episodes used are 

indicated in footnotes to Table 1. 

For urban areas wich more Chan cwo episodes lisced on Table 1, the 

episodes chosen were those with the smallest and the largest change of 

ozone with respect to changing N0X emissions. The one exception is Tulsa, 

where the W-TL8 episode used by Whitten, (1988) had a significantly lower 

ROG/NO ratio than the representation of the same episode (G-TL8) used by 

Gery et al., (1987). Became of this difference, the W-TL8 was treated in 

effect as if it represented a different urban area, and thus three "Tulsa" 

episodes were used. On the other hand, only one "New York" episode was 

used, because the two were very similar. 

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Quantification of Reactivity for the Aggregated Base Case Scales. As 

discussed above, reactivity can be defined either in terms of effects of 

the VOCs on amounts of ozone formed, (Equation I) or on ozone doses 

(Equation II). For the Dase case scenarios, separate sets of reactivity 

scales were derived based on each of these two methods for quantifying 

ozone. The same sets of calculations and aggregation methods were 

employed in either case. 

Aggregation Methods. There are several ways that the reactivities 

for the 21 base case episodes can be aggregated to give a single 

reactivity scale. Since the reactivities of a given VOC varies widely in 

magnitude from scenario to scenario, it is considered to be more 

appropriate to aggregate on the basis of relative reactivities, rather 

than the widely varying absolute reactivities. The reactivity of the base 

case ROG mixture is chosen as the standard against which the reactivities 

of all other VOCs are compared in a given scenario. 

Given this, there are still at least two ways these relative 

reactivities can be aggregated. One way is simply to average, for each 

VOC, the ratios of reactivities for each of the episodes. This is 

referred to as the "average ratio" method. This has the advantage of 

simplicity, but the disadvantage that the scenarios where VOC reactivities 

are very low (i.e., where VOC control is an ineffective ozone reduction 

strategy) are given equal weight as episodes where VOCs have high 

reactivities, and thus where VOC control is much more effective. An 

alternative aggregation method is to plot, for each VOC, the reactivities 

of the VOC against the reactivities of the base case ROG mixture, and to 

use the slope of the least squares line, with intercept forced through 

zero, as the ratio of the reactivity of that VOC relative to the base case 

19 
P.22 

ROG mixture. (Examples of such plots are given in the Results section, 

below). This is referred to as the "line fit" method. This aggregation 

method has the advantage of giving greater weight to episodes where VOC 

reactivities are higher, while still taking into account, at least to some 

extent, the reactivities calculated for all the episodes. Both methods 

are used in this study. 

Derivation of the Maximum Reactivity and the Maximum Ozone Reactivity 

Scales 

The aggregated base case reactivity scales necessarily reflect the 

distribution of conditions in the specific set of scenarios used to derive 

chem, Chough relative contributions of different types of scenarios to the 

resulting scale can be varied by using differing aggregation approaches. 

An alternative approach is to derive reactivity scales which represent 

specific types of scenario conditions. Since, as discussed above, the 

most important scenario condition affecting reactivity is the availability 

of NO,., this was used as the basis for defining scenario conditions for 

deriving separate reactivity scales. For this purpose, "N0X availability" 

is measured by the effects of N0X on the reactivity characteristics in the 

scenarios, with one scale representing N0X conditions yielding maximum VOC 

reactivities, and another representing N0X conditions yielding maximum 

amounts of ozone formed. 

Note that in general R0G/N0x ratios yielding maximum VOC reactivities 

and maximum 02one formation can vary significantly from scenario to 

scenario, depending on other conditions (Carter and Atkinson, 1989; see 

also results below.) For example, since the rate at which N0X is consumed 

would increase with light intensity, a ROG/NOx ratio which is in the N0Xlimited regime at a high sunlight intensity may not be in that regime if 

20 
P.23 

the sunlight intensity were reduced. Therefore, the ROG/NO ratio itself 

is not considered adequate for quantifying N0X availability when a variety 

of scenarios are being considered. 

For the purpose of deriving these reactivity scales for each of the 

62 city-days-listed in Table 1, the total N0X emissions input was varied 

to determine the levels which yielded the highest VOC reactivities and the 

levels with highest maximum ozone concentrations. .The relative NO 

emissions schedules, levels of N0X aloft (in the few scenarios where this 

is applicable), the total ROG emissions input, and all other aspects of 

these scenarios were not varied. The incremental reactivity of the 

surrogate representing base case ROG emissions was used as the criterion 

to determine the N0X levels corresponding to maximum reactivity. 

(Incremental reactivities for toluene, formaldehyae, propene and CO were 

also calculated as a function of ROG/NOx ratio, and the ratios yielding 

highest reactivities for these compounds were similar, but not always 

exactly the same, to the ratio yielding the highest base' case ROG 

reactivity.) The scenarios or city-days with NO.,, levels adjusted to yielc 

the hignest caicuiatea reactivity of the base case ROG emissions are 

referred to in the subsequent discussion as che "maximum reactivity" 

scenarios, while chose with N0X levels yielding the highest calculated 

maximum ozone concentrations are referred co as the "maximum ozone" 

scenarios. The N0X inputs derived for each set of scenarios are given 

with the tabulations in the Results section. 

As indicated above, the other aspects of the scenarios were the same 

as used in the base case scenarios (i.e., were as indicated on Table 1.) 

Thus, in effect, the reactivity scales for maximum reactivity or maximum 

ozone N0X conditions represent aggregate averages over these other airshed 

21 
conditions. However, since these conditions in general have smaller 

effects on overall reactivities, the ranges of reactivities being 

aggregated should in principle be less, and thus the results should be 

less sensitive to the specific set of scenarios employed. 

Separate Estimates of React!vir.y r T o furthe r ^ ^ ^ 

range of variability of quantities which are being averaged for the 

various scenarios, and to examine in more detail how various environmental 

and mechanistic factors affect reactivity under given conditions of N0X 

availability, the two major components of VOC reactivity were considered 

separately in the derivation of the maximum reactivity and the maximum 

ozone reactivity scales. As discussed previously (Carter and Atkinson, 

1989), incremental reactivities can be thought of as being products of two 

factors, which we have designated as "kinetic" and "mechanistic" 

reactivities. The kinetic reactivity is defined the fraction of the 

emitted VOC which undergoes chemical reaction in the pollution scenario 

being considerea, 

Kinetic Fraction VOC Reacted 

Reactivity = Reacted = , 

VOC Emitted 

and the mechanistic reactivity is the amount of ozone formed relative to 

the amount of VOC which reacts in that scenario. 

Mechanistic Ozone Formed 

Reactivity = (IV) 

VOC Reacted 

22 
P.25 

The product of these two quantities then give the overall incremental 

reactivity. 

Incremental Kinetic Mechanistic 

Reactivity = Reactivity X Reactivity (V) 

Ozone Formed VOC Reacted Ozone Formed 

( ) = ( ) X ( ) 

VOC Emitted VOC Emitted VOC Reacted 

These two components of incremental reactivity, each of which are affected 

by different aspects both of the VOCs reaction mechanism and the 

conaitions of the airshed scenario, are more straightforward to estimate 

than overall incremental reactivity. Considering these two components of 

reactivity separately can also provide a basis for making reactivity 

estimates for VOCs whose atmospheric reactions are not represented in the 

chemical mechanisms used in current airshed models. 

Derivation of Kinetic Reactivities. The kinetic reactivity of a VOC 

is aefinea as the fraction of the emitted VOC which undergoes chemical 

reaction in the air pollution episode. It depenas on how rapidly the VOC 

reacts in the atmosphere and on conditions of the episodes such as overall 

light intensity and radical levels, but not on the other aspects of their 

reaction mechanism. For most types of emitted VOCs, reaction with 

hydroxyl radicals is the only significant process by which they react in 

the atmosphere. Thus, for these compounds, the kinetic reactivity depends 

only on the rate constant for the reaction of the compound with OH 

radicals, and the overall level of OH radicals in the pollution 

scenarios. In such cases, the kinetic reactivity, which has also been 

called the "OH reactivity", can be approximated by the following empirical 

relation (Carter and Atkinson, 1989): 

23 
P.26 

Kinetic Fraction . k0 H T • 

Reactivity = Reacted = ( i . e

 t0 H 

) (VI) 

where kOH is the VOCs rate constant for reaction with OH radicals, and 

IntOH is a scenario-dependent parameter which reflects primarily the 

overall integrated OH radical levels of the scenario. The OH radical rate 

constants are known for a wide variety of organic compounds (Atkinson, 

1986,1989), and methods exist for estimating them for most others 

(Atkinson, 1987). 

IntOH values appropriate for a given pollution scenario can be 

obtained by calculated ratios of amounts reacted to amounts emitted for 

species with varying OH radical rate constants, and deriving the value 

where these are fit by equation (VI). The IntOH values calculated for the 

individual maximum reactivity or maximum ozone scenarios can then be used 

to derive values which are appropriate for estimating kinetic reactivities 

appropriate for these two sets of conditions. 

Equation (VI) is based on assuming that the compound reacts 

significantly only with OH radicals and thus will underestimate the 

kinetic reactivities for compounds which react non-negligibly by other 

processes. The major examples of this are aldehydes and ketones, which 

react non-negligibly by photolysis, and alkenes, which also react nonnegligibly with" ozone. In the case of compounds which react with OH 

radicals so rapidly that they would be estimated to be completely consumed 

even if the other loss processes are ignored, the underestimation of 

kinetic reactivity caused by ignoring these other processes would be 

insignificant. This would be the case for propene and the higher alkenes, 

which Equation (VI) calculates to be at least 95} reacted under maximum 

reactivity conditions, and at least 999 reacted under maximum ozone 

24 
P.27 

conditions. However, for ethene, the ketones, and (in some cases) the 

aldehydes, the use of Equation (VI) would underestimate kinetic 

reactivities. Therefore, Equation (VI) is not used to estimate kinetic 

reactivities for these compounds; instead, the fractions reacted were 

calculated explicitly for various maximum reactivity and maximum ozone 

scenarios. The values obtained are then comDined to obtain estimates of 

kinetic reactivities for these compounds which are appropriate for the two 

sets of conditions. 

Calculation of Mechanistic Reactivities. Mechanistic reactivities 

measure the amount of ozone formed caused by the reaction of a given 

amount of the VOC, independently (to a first approximation at least) of 

' how rapidly the compound reacts. They are determined by the nature of the 

VOCs reaction mechanism, such as numbers of conversions of NO to N02 which 

occur during its oxidation process, whether the reactions enhance or 

inhibit radical or N0X levels, and the reactivities of the products they 

form. They are also strongly affected by the conditions of the scenario 

such as the V0C/N0x ratio and other aspects which affect the overall 

efficiency of ozone formation (Carter and Atkinson, 1989). Depending on 

the conditions of the scenario and the nature of the reaction mechanisms, 

mechanistic reactivities can range from negative values (indicating the 

VOC s reactions actually reduce overall ozone formation), to values as 

high as over 10 moles of ozone formed per mole carbon reacted (Carter and 

Atkinson, 1989). 

To obtain information necessary to derive comprehensive VOC 

reactivity scales for maximum ozone and for maximum reactivity conditions, 

mechanistic reactivities were calculated for all the VOC species which can 

be separately represented in the detailed photochemical mechanism (Carter, 

25 
P.28 

1990). The mechanistic reactivities of a voc in , 

a VUL m a given scenario can be 

calculated by computer model simulations of the \inr>- • 

ui cne VOCs incremental 

activity (uS i „ g Equatlon „ a „ d fractlon ^^ ^ <kinecic ^ ^ ^ 

reacted the scenario . , and dividing tne incremental reactmt y oy ^ ^ ^ 

For some VOCs, mechanistic reactivities were not calculated 

Erectly, but instead uere derlved fron mechanlst.o reactivr.t.es 

calculated for species for simplified a„c idealized reaction mechanisms. 

The methods for estimating reactivities based on idealized mechanism 

species, and the types of idealized species .„!„, „ 

species employed, are discussed 

elsewhere (Weir et al, 1988; Carter and Atkinson, 19 8 9 ) . Test 

calculacions showed that mechanistic reaori,,^ 

ecnanistic reaccivicies calculated this way were 

not significantly different from those calculated directly. 

Because of the large number of VOC species and scenarios, complete 

calculations of mechanistic reactivities uerp nor _. 

activities were not carried out for all the 

cases for those urban areas which had more than tun *„**-

ujut e tnan cwo scenarios. For those 

areas, mechanistic reactivities were caimiarart ?-

3 were calculated ror at least two selected 

scenarios, one of which had the highest and one of „hlCh had the lowest 

base case ROG reactivity. The tabulation of the results indicate the 

scenarios used. These should be sufficient to represent the variability 

of mechanistic reactivities ln the scenarios for an area. (To test this 

mechanistic reactivities for a small number of selected representative 

species were calculated for all the other maxima reactivity and maximum 

o*one scenarios., The results were then used to obtain, for each VOC 

represented in the detailed mechanism, mechanistic reactivities 

appropriate for maximum reactivity and for maximum ozone conditions. 

26 
P.29 

RESULTS AND DISCUSSION 

Calculated VOC Reactivities for Maximum Reactivity ann MOV< — Ozone Conditions ~"^~————— 

The results of the calculations for the maximum reactivity and the 

maximum ozone conditions are given on Tables 2 through 4. Tables 2 lists, 

for each of the 62 city-days and the three idealized EKMA scenarios, the 

R0G/N0X ratio found to give maximum VOC reactivities and selected 

reactivity results for the city-days at these N0X levels. These include 

the maximum ozone concentration, the reactivity of the base case ROG 

surrogate, the IntOH parameter, and the kinetic and mechanistic 

reactivities for selected representative species. Table 3 gives the 

corresponding results for the N0X conditions giving maximum ozone 

concentrations. Tables 2 and 3 also give the averages of the reactivity 

results for each of the 12 urban areas represented by the 62 city-days, 

and the overall averages of the averages for all the urban areas. 

The averaged kinetic and mechanistic reactivity results for maximum 

reactivity and maximum ozone conditions are summarized on Table 4. The 

averages were obtained by first calculating the average for each of the 12 

urban areas, and then averaging the averages for these areas, in a manner 

analogous to the representative results shown on Tables 2 and 3. For 

compounds which react only with OH radicals, estimated kinetic 

reactivities were derived using Equation (VI), using 

IntOH = 82 ppt-min for maximum reactivity conditions, and 

IntOH = 128 ppt-min for maximum ozone conditions. 

27 
P.30 

These were the averages of the average values for the 12 urban areas, 

taken from Tables 2 or 3. The mechanistic reactivities for compounds 

which react with species other than OH radicals were either averages of 

the values calculated explicitly, or assigned a value of unity based on 

assumption of essentially complete reaction. Footnotes to Table 4 

indicate how the estimated kinetic and mechanistic reactivities were 

derived for each of the individual VOCs. 

The estimated kinetic and mechanistic reactivities on Table 4 were 

then combined to obtained the aggregated incremental reactivity estimates 

for maximum reactivity or maximum ozone conditions. The incremental 

reactivities are given in units of both moles ozone formed per mole carbon 

VOC emitted, and grams ozone formed per gram VOC emitted. Note that in 

terms of relative reactivities, the choice of units can make a difference 

when considering reactivities of oxygenated compounds. For example, under 

maximum reactivity conditions, methanol has about the same reactivity as 

most branched C4-C6 alkanes when reactivity is measured on a per-carbonemitted basis, while it is less than half as reactive than those compounds 

when it is measured on a per-mass basis. Per-carbon units are perhaps of 

more fundamental chemical interest, and for that reason are the units we 

use for mechanistic reactivity results. However, per-mass units are 

probably more useful for control strategy purposes, since VOC emissions 

are generally measured and regulated on a mass basis. For that reason, 

reactivities measured on a per-mass basis are used when results are given 

comparing different reactivity scales. 

Comparison of Kinetic and Mechanistic Reactivities for Maximum Ozone 

and Maximum Reactivity Conditions. The representative data on Tables 2 

and 3 indicate that kinetic reactivities at N0X levels yielding maximum 

28 
P.31 

ozone concentrations are higher than those for N0X levels yielding maximum 

VOC reactivities. This is expected, since the reaction of OH radicals 

with N02 is an important radical terminating process, and N02 levels are 

higher under maximum reactivity conditions. On the other hand, the 

mechanistic reactivities for maximum ozone conditions are lower, by at 

least a factor of two, than the values which are observed under maximum 

reactivity conditions. Since (by definition) the incremental reactivities 

are higher under maximum reactivity conditions, it is clearly the 

mechanistic reactivities which are the more important in influencing how 

overall incremental reactivities vary with V0C/N0V. This is consistent 

with the results which have been presented previously (Carter and 

Atkinson, 1989). 

If the relative differences between the mechanistic reactivities 

under the two sets of conditions were the same for all types of VOCs, then 

the differences would have no practical significance in terms of 

developing VOC reactivity scales. However, this is not the case. Figure 

1 shows plots of mechanistic reactivities of the VOCs for maximum ozone 

conditions against those for maximum reactivity conditions. If the ratios 

of mechanistic reactivities for maximum ozone and maximum reactivity 

conditions were similar for all compounds, the points would all be on 

approximately the same line, with the slope being the ratio of mechanistic 

reactivities for the two sets of conditions. However, it can be seen that 

although compounds of similar types tend to fall on the same line, the 

lines are different for different classes of compounds. For example, the 

ratio of mechanistic reactivities for maximum ozone relative to maximum 

reactivity conditions are significantly lower for the carbonyl compounds 

and the aromatics (especially naphthalene and tetralin), and somewhat 

29 
P.32 

lower for the alkenes, than they are for the alkanes. 

However, it is the overall incremental reactivity, not the 

mechanistic reactivity, which is of direct relevance for VOC reactivity 

scales. For the most slowly reacting compounds, the higher radical levels 

in maximum ozone conditions relative to maximum reactivity conditions in 

part offsets the opposing effects of differences in mechanistic 

reactivity. For example, despite the factor of 2 difference in 

mechanistic reactivity, the incremental reactivity of methane in maximum 

ozone conditions is only -30/. lower than its reactivity in maximum 

reactivity conditions. On the other hand, for rapidly reacting compounds 

there is relatively little difference between kinetic reactivities (since 

the compounds are almost completely reacted in any case), and thus for the 

differences in incremental reactivity will be determined entirely by 

differences in mechanistic reactivities. 

Comparisons of overall reactivities for these two sets of conditions 

are shown on Figure 2, which gives plots of reactivities for maximum ozone 

conditions against reactivities for maximum reactivity conditions for the 

individual model species. The reactivities for CO, the alkanes, alcohols, 

ethers, glycols and the ketones have been multiplied by five, ten or 100 

so their magnitudes would be comparable to those for the aromatics, 

alkenes, and aldehydes. Figure 2 in general has the same features as 

indicated in Figure 1; under maximum ozone conditions the reactivities of 

the aromatics, oxygenates, and alkenes, relative to those for the alkanes 

and alcohols, are lower under maximum ozone conditions than they are under 

maximum reactivity conditions. This shows the importance in mechanistic 

reactivities in determining the dependence of overall reactivities on 

relative N0X levels. In addition, the differences between the relative 

30 
P.33 

incremental reactivities of the alkanes and the alkenes (as shown on 

Figure 2) are greater than one would expect from their differences in 

relative mechanistic reactivities as shown on Figure 1. This is because 

the higher radical levels of the maximum ozone conditions tend to decrease 

the differences in the reactivities for the relatively more slowly 

reacting alkanes to a greater extent than they do for the relatively 

rapidly reacting alkenes. This effect on alkane/alkene reactivity ratios 

is in the same direction as the effect of the ratio of their mechanistic 

reactivity, and thus enhances the differences in their relative 

reactivities between the two scales. 

To illustrate the effect of changing only the overall radical levels, 

and thus the kinetic reactivities, on the reactivity scales, Figure 3 

shows plots of incremental reactivities calculated using maximum ozone 

kinetic reactivities, against those using maximum reactivity kinetic 

reactivities, where both use maximum reactivity mechanistic 

reactivities. Consistent with the discussion above, the largest effect of 

overall radical levels is on the reactivities of the rapidly reacting 

compounds (e.g., alkenes and aldehydes), relative to those which react 

more slowly. However, the range of differences in reactivity when only 

the kinetic reactivities are varied is much less than the range of 

differences in overall reactivities, and is also less (especially for the 

aromatics) than when the mechanistic reactivities are varied (compare 

Figure 3 with Figures 2 and 1). 

Dependencies of Reactivities on Non-Nnir-Reiated Airshed Conditions. 

A study of the dependence of reactivity on non-NOx-related airshed 

conditions is complicated by the fact that most airshed conditions will 

affect the rate that N0X is consumed during the day, which in turn 

31 
P.34 

determines the level of N0X which defines the boundary between NOx-limited 

and VOC reactivity-sensitive conditions. .For example, increasing the 

light intensity, dilution, or the amount of radical-initiating species in 

the base case ROG mixture all increase radical levels in the scenario, 

which increases N0X consumption rate, and thus results in NO„-limiting 

conditions occurring at higher N0X levels. Thus the main reason for 

differences in reactivities calculated for different scenarios at the same 

ROG/NOx ratio is that the given ratio can correspond to different 

conditions of relative N0X availability in the different scenarios. 

Holding the ROG/NOx ratio fixed therefore does not assure consistent 

conditions of N0X availability. 

However, the derivation of separate reactivity scales for maximum 

reactivity or for maximum ozone conditions has the advantage that it tends 

to factor out, at least to some extent, effects on reactivities of 

variabilities of conditions N0X availability. This is because in the 

derivation of these scales the N0X inputs of each scenario are adjusted to 

yield consistent conditions of N0X availability. Therefore, if there is 

still variability in reactivities calculated among the various scenarios 

where conditions of relative N0X availability are held fixed, this would 

be due to effects of other, non-NOx-related airshed conditions. 

As shown on Table 1, there is considerable variability among.the 

scenarios in terms of amounts of dilution, total VOC inputs, integrated 

light intensity, amounts of pollutants entrained from aloft, and relative 

amounts of pollutants present initially or emitted during the day. Tables 

2 and 3 show that the variability in these conditions indeed cause 

variabilities in parameters which affect reactivities. This is also shown 

on Figure 4, which gives distribution plots for values of these parameters 

32 
calculated for selected city-days in each of the 12 urban areas. (The 

city-days selected for the maximum reactivity and for the maximum ozone 

conditions were those used to calculate the mechanistic reactivities for 

the model species. All the city-days are not shown on the distribution to 

avoid weighing unduly those urban areas which have the most city-days.) 

For comparison, Figure 4 also shows the distributions for the city-days 

with the base case N0X conditions, which used to derive the aggregated 

base case and ozone yield and ozone dose reactivity scales. 

As expected, adjusting the N0X levels to yield either maximum 

reactivity or maximum ozone conditions indeed results in much narrower 

distributions of reactivity parameters than is the case for the unadjusted 

(e.g., base case) scenarios. However, there is still a non-negligible 

variability of values even after N0X is adjusted. This shows that 

reactivities are indeed affected by the variability of the other, non-NOxrelated, airshed conditions. However, the comparison of the base case 

distributions with those for maximum reactivity or maximum ozone N0X 

conditions clearly indicate the over-riding importance of variabilities in 

N0X levels in affecting reactivities in various urban areas. 

In general, at least for the scenarios and urban areas used in this 

study, the urban-area-averaged reactivity oarameters tend to have a 

standard deviation on the order of +25%, though in some cases extreme 

values for certain individual scenarios can differ by a factor of 3 or 

more. The extent of variability for maximum reactivity and maximum ozone 

conditions tend to be similar. The exceptions to these generalizations 

are the mechanistic reactivities for the CQ + alkanes under all conditions, 

and the mechanistic reactivities of the aromatics (other than di- or trialkylbenzenes) under maximum ozone conditions, which tend to be low in 

33 
P.36 

magnitude and have high relative variabilities. In addition, the higher 

molecular weight alkenes tend to have higher variabilities in mechanistic 

reactivities (with standard deviations on the order of +30%) under maximum 

ozone conditions. 

The variability in the IntOH parameter, which reflects integrated OH 

radical levels and thus fractions of VOCs which react, is comparable to 

the variabilities in the mechanistic reactivities. Its variability yields 

a corresponding variability in the kinetic reactivities of the slowly 

reacting compounds, since from Equation (VI) fractions reacted become 

proportional to IntOH when the OH radical rate constant becomes 

sufficiently small. The variability in kinetic reactivities is 

significantly less for the more rapidly reacting compounds (including most 

of those which react with species other than OH radicals), since the 

fraction reacted approach the upper limited value of unity. Thus, for 

most reactive compounds,, it is the variability of mechanistic reactivity 

with airshed conditions which is the more important factor which is 

influencing variability, and thus uncertainties, of incremental 

reactivities for maximum ozone or maximum reactivity conditions. Figure 3 

gives an indication of the sensitivity of the reactivity scales to 

uncertainties in the IntOH parameter. The reactivities shown there show 

the effect of an approximately 601 increase in the IntOH parameter. 

These, results indicate the approximate magnitude of the sensitivity 

of the maximum reactivity or maximum ozone reactivity scales to the 

conditions which were varied in these scenarios. It should be recognized, 

however, that although they represent a wide range of conditions, not all 

potentially important aspects of airshed scenarios were varied. For 

example, they are all single box model scenarios, and it is not clear to 

34 
what extent reactivities may differ if more complex, gridded airshed 

scenarios were used. Perhaps more significantly in terms of direct 

chemical effects on reactivity, the same mixture of VOCs was used to 

represent base case ROG emissions for all scenarios. The "allcity 

average" mixture derived by Jeffries et al. (1989) was used because it 

represents our current best estimate as to actual VOC emissions in urban 

areas, and because data are insufficient to unambiguously derive separate 

mixtures for each the scenarios. However, the aldehyde fraction of this 

mixture is highly uncertain, and the composition of ROGs in emissions 

inventories is significantly different from those derived from analysis of 

air quality data. We have found that using emissions-derived ROG mixtures 

can result in non-negligibie differences in calculatea reactivities (Weir 

et al., 1988). These uncertainties are not reflected in the variabilities 

in the reactivities calculated in this study. 

In this regard, it should be noted that maximum reactivity scales 

previously derived and distributed by the author (Weir et al., 1988; 

Carter, 1989; Lowi and Carter, 1990) were based primarily on calculations 

using an emissions-derived mixture to represent base case ROG emissions. 

Therefore, the use of the measurement-based ROG mixture, which is now 

considered to be preferable to use of the highly uncertain emissions data, 

represents a departure from this previous work. This results in somewhat 

lower relative reactivities of formaldehyde and other radical-initiating 

species in the present maximum reactivity scale than was the case 

previously. The effects on reactivity of varying the composition of the 

base case ROG mixture is being investigated, and will be reported in a 

subsequent paper. 

35 
P.38 

Aggregated Base Case Ozone Reactivity Scales, and Comparison with the 

Maximum Reactivity and the Maximum Ozone Scales 

Table 5 summarizes the results of the calculations of aggregated 

relative reactivities for selected representative compounds for the 

selected base case scenarios. The base case reactivities are quantified 

both by ozone yield (as used for the maximum reactivity and maximum ozone 

scales), and by ozone dose. The reactivities of the VOCs are given 

relative to that of the base case ROG emissions, and they are aggregated 

either by calculating the average of the ratios for the various scenarios, 

or by plotting the reactivities of the VOC against the reactivities of the 

base case ROG surrogate, and calculating the aggregated ratio as the slope 

of the least squares line, forced through zero. Examples of these plots 

for representative VOCs are shown on Figure 5. Each point on these plots 

correspond to one of the city-days used to calculate the base case 

reactivity scale. The plots include lines whose slopes indicate the 

aggregated ratios derived using both methods, and also lines whose slopes 

show ratios of reactivities derived using the maximum reactivity and 

maximum ozone scales, discussed above. The ratios of maximum reactivities 

and maximum ozone reactivities are also included on Table 5, where they 

can be compared with the aggregated base case ratios. 

Comparison of Ozone Yield Reactivities. The data on Table 5 and 

Figure 5 indicate -that for some compounds the aggregation method can have 

a significant effect on the relative base case ozone yield reactivities. 

This sensitivity to the aggregation method is due to the sensitivity of 

reactivity ratios to the R0G/N0X ratio. The line fit aggregation is more 

sensitive to the scenarios with the higher reactivities, which in general 

reflect the lower N0X conditions characteristic of the maximum reactivity 

scale. The average ratio aggregation is equally sensitive to all 

36 
scenarios, including those with very low N0X levels and thus lower 

reactivity. 

Figure 6 shows a comparison of the aggregated base case ozone yield 

reactivities with the maximum reactivity and maximum ozone reactivity 

scales for all the model species. These indicate that the base case ozone 

yield reactivities aggregated using the line fit method correspond 

reasonably well to the maximum reactivity scale, while the base case yield 

reactivities aggregated using the average ratio method correspond better 

to the maximum ozone reactivities. This is expected, since the line fit 

aggregation method is most sensitive to scenarios near maximum reactivity 

conditions. On the other hand, the average R0G/N0X ratios for all the 

scenarios is closer to those for maximum ozone conditions, so the average 

ratio of reactivities, with all scenarios weighed equally, would be closer 

to maximum ozone reactivities. Note, however, that there are fewer cases 

of systematic differences among classes of compounds in the comparison 

between maximum reactivities and line fit base case reactivities than is 

the case for che comparison between maximum ozone reactivities and the 

average ratio. 

Comparison of Ozone Dose Reactivities. The data on Table 5- and 

Figure 5 also include results of the base case calculations where 

reactivity is quantified by ozone dose. Relative ozone dose reactivities 

tend to be less sensitive to the conditions of the base case scenarios 

than is the case for ozone yield reactivities. This is indicated by the 

standard deviations of the aggregated average reactivity ratios or slopes 

of fitted least squares lines given in Table 5, and also by the fact the 

aggregated ozone dose reactivities are much less sensitive to which 

aggregation method is employed. There are cases of variabilities of 

37 
P.40 

relative dose reactivities among the scenarios, particularly for the 

compounds with low or negative mechanistic reactivity, which have the most 

variable reactivities no matter how they are quantified or aggregated. 

However, for most compounds the scenario-to-scenario variability of 

relative dose reactivities is much less than is the case for ozone yield 

reactivities. 

Figure 7 shows a comparison of the aggregated base case ozone dose 

reactivities with the maximum reactivity and maximum ozone reactivity 

scales for all the model species. These indicate that the base case ozone 

dose reactivities aggregated using either method correspond reasonably 

well to the maximum reactivity scale, though there is more scatter when 

the average ratio method is employed. On the other hand, the dose 

reactivities correspond poorly with the maximum ozone reactivity scale. 

This is despite the fact that, for most of the base case scenarios, the 

N0X levels are closer to those of maximum ozone conditions than those 

yielding maximum VOC reactivities. 

These results suggest that the mechanistic factors that influence VOC 

reactivities under maximum reactivity conditions are the same as those 

which influence ozone dose reactivities under a much wider set of 

conditions. The major characteristic of maximum reactivity conditions is 

that ozone is not NOx-limited, and the final ozone yields are determined 

primarily by how rapidly ozone is formed. Aspects of VOCs reaction 

mechanisms which affect ozone formation rates, such as those involving 

initiating or inhibiting radical levels, therefore are the major factors 

affecting reactivity under those conditions (Carter and Atkinson, 1989). 

At lower N0X levels the availability of N0X becomes a more important 

factor affecting ozone yields, and at sufficiently low N0X the rate of 

38 
P.41 

ozone formation is ultimately not a major factor in affecting how much is 

ultimately formed. However, the ozone formation rate will affect the 

ozone dose under practically any set of conditions. Even in scenarios 

where ozone is ultimately N0X limited, VOCs causing more rapid ozone 

formation will result in earlier formation of ozone, and thus higher 

integrated ozone levels. Thus the good correspondence between relative 

ozone dose reactivities and maximum reactivities is not unexpected. 

Comparison of Incremental Reactivities with Reactivities Measured by the 

OH Radical Rate Constant 

For many VOCs, reaction with OH radicals is the major process 

affecting the rate at which chey react in the atmospnere, and thus the 

rate at which they can affect ozone formation. Because of this, it has 

been suggested that this rate constant can serve as a basis for a VOC 

reactivity scale (e.g. Darnall et al., 1976; ARB, 1989). This scale has 

the obvious disadvantage that it ignores other aspects of VOCs reaction 

mechanisms which affect ozone formation, and it also does not take into 

accounc the fact thac if cne compound reaccs sufficiencly rapidly, the 

amount of VOC which reacts in the atmosphere, and thus contributes to 

ozone formation, becomes independent of the rate at which it reacts. 

Since incremental reactivities take all of these factors into account, 

they clearly form a more Justifiable basis for deriving ozone reactivity 

scales for VOCs. However, the OH rate constant scale has the significant 

advantage that OH radical rate constants are known or can be estimated for 

most of the types of VOCs emitted into the atmosphere (Atkinson, 1989), 

and that it can be universally applied under all conditions. Thus, if it 

can be shown to give acceptable correlations with reactivities quantified 

using more comprehensive methods, its use might be appropriate for some 

39 
P.42 

types of applications. 

To show how well an OH radical reactivity scale would correlate with 

one based on incremental reactivities, Figure 8 shows plots of T=300K OH 

radical rate constants (kOH) against incremental reactivities in the 

maximum reactivity scale for all the VOCs represented in the model. Since 

the reactivities are quantified by ozone formed per mass of VOC, the OH 

radical rate constants are divided by their molecular weight to place them 

on a comparable basis. Plots of OH radical rate constants against maximum 

ozone reactivities or the aggregated relative reactivity scales look 

similar to Figure 8, and are not shown. 

Figure 8 shows that although there is a correlation between kOH and 

incremental reactivities for certain homologous classes of compounds, such 

as the alkenes and some of the aromatics, the correlation between 

different types of VOCs is extremely poor. In addition, for the 

homologous series of higher n-alkanes, three is a negative correlation 

between the kOH and incremental reactivity. Thus, although there are 

cases where the OH radical rate constant correlates reasonably well with 

reactivity, in general it does not appear to be a reliable predictor of 

the relative effect of the emissions of a VOC on ozone formation in the 

atmosphere. 

Uncertainties in Chemical Mechanisms 

The focus of this paper has been on the problems of developing a 

single reactivity scale given the variability of reactivities with 

environmental conditions. However, the dependencies of reactivities on 

environmental conditions is not the only significant source of uncertainty 

in the development of VOC reactivity scales. Uncertainties in our 

40 
knowledge and ability to model ozone formation from the gas-phase 

atmospheric reactions of VOCs ultimately limits the reliability of any VOC 

ozone reactivity scale based on model calculations. The relative 

importance of chemical mechanistic uncertainties varies significantly 

among VOCs, and thus the uncertainties in their calculated reactivities 

vary accordingly. Since this paper gives calculated reactivities for a 

wide variety of compounds, it is necessary to place these results in 

perspective by discussing and ranking the relative levels of uncertainty 

in the chemical mechanism used to calculate their reactivities. This must 

be taken into account when these or any other calculated reactivity scales 

are used in assessing effects of VOCs on ozone formation. 

There has in recent years been sufficient advances in our 

understanding in the gas-phase reactions involved in the formation of 

ozone in photochemical smog, that modeling these processes is becoming a 

viable approach for control strategy planning purposes. This has been 

made possible not only from the large body of fundamental kinetic and 

mechanistic data concerning the individual reactions (e.g., see Atkinson, 

1990, and references therein), but also from availability of environmental 

chamber experiments suitable for testing the predictions of these 

mechanisms. This has resulted in a convergence of the airshed model 

mechanisms developed by different groups in recent years, with differences 

in the predictions of the most recent mechanisms in simulations of ozone 

formation in mixtures representing polluted urban atmospheres being 

relatively small (Hough, 1988; Dodge, 1990). Indeed, many if not most 

airshed modelers now believe that it is uncertainties in the emissions 

data, rather than in the chemical mechanisms, which cause the major 

uncertainties limiting the reliability of predictions of current airshed 

41 
P.44 

models as they relate to chemical transformations. 

However, predicting relative ozone reactivities of the different 

individual VOCs is a more difficult problem than predicting ozone 

formation from the mixture of VOCs generally present in urban 

atmospheres. The latter has been the focus of much of the previous 

mechanism development work, where condensed mechanisms have been developed 

to efficiently represent realistic atmospheric mixtures, and have been 

tested against chamber experiments using such mixtures (e.g., Gery et al., 

1988; Carter and Lurmann, 1990b). The mechanism employed in this study 

differs from these in attempting to represent the reactions of a large 

number of the different types of individual VOCs (Carter, 1990). As 

discussed in its documentation (Carter, 1990), the level of knowledge upon 

which this mechanism is based varies considerably among the compounds it 

represents. This results in corresponding variabilities in the degree of 

uncertainty in predictions of reactivities of these compounds regardless 

of the types of scenarios or aggregation methods employed. 

The levels of uncertainty in the reaction mechanism obviously must be 

taken into account when using the results of model calculations of 

reactivities to assess ozone control strategies. To aid in such 

assessments, all the VOCs listed on Table 4 have been categorized in a 

six-class grouping according to the author's qualitative assessment of the 

level of our present knowledge of their atmospheric reaction mechanisms, 

and the availability of environmental chamber data suitable for testing 

these mechanisms. Thus, these should give a rough indication of the 

degree of uncertainty in their predictions of reactivities in any given 

scenario. These groupings are as follows: 

42 
Group 1: Compounds for which we believe we understand at least the most 

important of the fundamental processes by which the VOC promotes ozone 

formation, and whose mechanisms have been tested at least to some extent 

using environmental chamber data. Examples include n-butane, ethylene, 

formaldehyde and methanol. There are still some uncertainties for most of 

the compounds in this group, but new data are not expected to have major 

impacts on predictions of their reactivity. 

Group 2: Compounds for which we believe we understand the major reactions 

involving ozone formation reasonably well based on fundamental knowledge, 

but whose mechanisms have not been tested against chamber data. Examples 

include the C-\-C? alkanes and ethanol. 

Group 3: Compounds where there are major gaps in our knowledge in their 

mechanisms involved in ozone formation, but for which available 

environmental chamber data has allowed us to develop adjusted or 

parameterized mechanisms which can adequately simulate ozone formation and 

other observations in these experiments. Examples include several 

representative aromatic compounds, propene, 1-butene and 1-hexene. 

Group 4: Compounds which have uncertain mechanisms and for which there 

are only limited or unreliable chamber data available for testing or 

adjusting their mechanisms. Examples include several Ce+ alkanes, 

propionaldehyde, acetone, methylethyl ketone, and acetylene. In addition, 

this group is also used for isoprene and acrolein, for which there are 

probably enough chamber data to place the compound in Group 3* but for 

which the current mechanism does not have sufficient detail to simulate 

43 
these data as well as it could. [A more detailed isoprene mechanism, 

which should qualify for Group 3, is being developed (Carter and Atkinson, 

unpublished results), but has not yet been incorporated into the present 

mechanism.] 

Groups 5 and 6: Compounds whose mechanisms are uncertain and for which no 

adequate chamber data are available. Mechanisms for these have been 

estimated based on analogy or extrapolation from mechanisms developed for 

other compounds. Two categories are used to express the author's 

qualitative estimate concerning the relative degree of uncertainty in the 

estimated mechanism, with 6 being the most uncertain. Examples of 

compounds in the category 5 include the C^-C^ alcohols and the higher 

(C<CJ n-alkanes; examples in category 6 compounds listed on Table 4 

include the high molecular weight alkenes, methyl acetylene, higher 

molecular weight aromatics, and C^ * alkanes. 

As discussed above, reactivities of VOCs can be broken down into two 

components: their kinetic reactivity, which reflects how rapidly the VOC 

reacts, and their mechanistic reactivity, which reflects the amount of 

ozone formed once the VOC reacts. Since the rate constants for the major 

atmospheric consumption reactions have been measured for many VOCs 

(Atkinson, 1989 and references therein) and can be estimated for most 

others (Atkinson, 1987), the major uncertainties in the VOCs reaction 

mechanism are those which reflect their mechanistic reactivities. Thus 

the categorization above can be thought of as applying only to the 

mechanistic reactivity estimates, since this is almost always the most 

uncertain aspects of predictions of reactivity of a given VOC in a given 

scenario. 

44 
P.47 

If reactivities could be. measured directly in environmental chamber 

experiments, then such experiments could be used instead of model 

calculations to derive reactivity scales. However, as discussed 

previously (Carter and Atkinson, 1989), reactivities measured in chamber 

experiments are not the same as those in the atmosphere. This is because 

chamber effects impact the results of such experiments (Bufalini et al., 

1972,1977; Wu et al., 1976, Carter et al., 1979,1982,1986; Carter and 

Lurmann, 1990a), and because it is not practical to simultaneously 

duplicate all of the airshed conditions which might affect reactivity. On 

the other hand, chamber experiments are clearly useful to the development 

of the chemical mechanisms used in model calculations of reactivity, and 

provide the only practical means to test whether the mechanism has major 

errors or emissions which would invalidate its predictions of reactivity 

in model calculations. In addition, chamber experiments might be useful 

for the direct measurement of mechanistic reactivities of VOCs, which as 

indicated above is the most uncertain component in atmospheric reactivity 

estimates. The potential utility of chamber experiments for this purpose, 

which shows promise as a means to significantly reduce mechanistic 

uncertainties in reactivity scales, is under investigation in our 

laboratories. 

45 
P.48 

SUMMARY AND CONCLUSIONS 

A quantitative reactivity scale which compares the effects of 

different types of VOCs on ozone formation would be a useful tool for 

developing effective and flexible control strategies for ozone 

formation. However, the development of such a scale has a number of 

difficulties, which can be categorized into three major areas. The first 

concerns the fact that the gas-phase chemical mechanisms by which VOCs 

react in the atmosphere to form ozone are in many cases highly 

uncertain. This results in uncertainties in the model predictions of the 

reactivity of a VOC in any given scenario. The second concerns the fact 

that the effects of VOCs on ozone formation and their reactivities depend 

significantly on the environment in which they are emitted. This means 

that even if we are capable of reliably predicting the reactivity of a set 

of VOCs in a set of scenarios, it is not obvious how these results should 

be used in developing a single reactivity scale, or even whether a use of 

a single reactivity scale has any scientific or regulatory validity. The 

third problem concerns the fact that there are uncertainties in conditions 

of airsheds and episodes where unacceptable levels of ozone are formed. 

The uncertainties in conditions of a specific episode affect predictions 

of VOC reactivities for that episode, and uncertainties in distribution of 

conditions affect the development of appropriate methods for aggregating 

scenario-specific reactivities into a generalized reactivity scale. 

The focus of this paper has been primarily on the second of these 

three problems, that of deriving a single reactivity scale given that 

reactivities depend on environmental conditions. This has been studied by 

deriving reactivity scales using several different techniques, given a 

46 
P.49 

single chemical mechanism and a single set of representative airshed 

scenarios. The chemical mechanism employed may be uncertain for many 

VOCs, but it incorporates our current best estimate of their atmospheric 

reactions, and represents most of the major types of species which need to 

be incorporated in reactivity scales. The set of representative 

environmental scenarios employed may be even more uncertain, but they 

represent their developers' best estimate of the conditions of a wide 

variety of representative pollution episodes given the limitations in 

available data and the constraints of the simplified physical formulation 

of the city-specific EKMA model. This is considered to be sufficient for 

the purpose of evaluating methods for deriving reactivity scales. 

Differences in relative levels of N0X (usually measured by the 

ROG/NOx ratio) is the most important reason for differences of. VOC 

reactivities from scenario-tp-scenario. The maximum reactivity scale 

represents reactivities under the lowest ROG/NOx conditions which is 

appropriate for deriving an ozone reactivity scale because if ROG/NOx 

ratios were much lower, N0X inhibition would prevent significant amounts 

of ozone from being formed in a one-day episode. The maximum ozone 

reactivity scale represents the highest R0G/N0x conditions appropriate for 

VOC reactivity assessment because, if the ratios were any higher, ozone 

formation would be N0X limited. Under NOx-limited conditions VOC control 

is ineffective for reducing ozone, and thus VOC reactivities are 

irrelevant. Therefore comparison of relative reactivities calculated 

using these two scales give an appropriate indication of the maximum 

importance of uncertainties in the R0G/N0x ratio in reactivity 

predictions. 

47 
P-50 . 

Consistent with results of previous studies, it was found that the 

N0X conditions significantly affected both absolute and relative 

reactivities. Absolute reactivities are the most strongly affected, but 

differences in relative reactivities are more significant in practical VOC 

control strategy assessment applications. Relative reactivities among the 

same chemical class of VOC are not strongly affected by the ROG/NOx ratio, 

(at least when it is varied between the maximum reactivity and maximum 

ozone range), but relative reactivities of different chemical classes of 

r- VOCs can be quite different. In general, the ratios of reactivities of 

aromatics and alkenes relative to those of alkanes, CO and some alcohols 

are significantly lower under low N0X, maximum ozone conditions than under 

^relatively high N0X, maximum VOC reactivity conditions. This makes a 

difference, for example, in predictions of the ozone benefits of use of 

reformulated gasolines which reduce vehicle emissions of alkenes and 

aromatics relative to those of alkanes. The maximum ozone reactivity 

scale predicts much less benefit of use of such fuels than would the 

maximum reactivity scale. This has a practical effect in assessing the 

relative advantages of reformulated gasolines as opposed to methanol or 

other alternative fuels. 

Deriving reactivity scales by aggregating reactivities calculated for 

an appropriate distribution of actual ozone pollution episodes is an 

appealing approach because it can potentially be based on predictions of 

the most accurate models for conditions of those episodes. However, it is 

not currently practical for a number of reasons. In the first place, 

because of major uncertainties in emissions inventories and background and 

boundary pollutant levels, we may not have accurate models for any real 

pollution episodes, even those which have been the most extensively 

48 
studied and modeled. These uncertainties also make it difficult to 

determine an appropriate distribution of episodes to use for reactivity 

assessment purposes. In addition, accurate representation of conditions 

of "real world" episodes require complex gridded airshed models, which are 

expensive to run and have large input data requirements. Furthermore, 

because of present computer constraints, such models can calculate 

reactivities for only a limited number of compounds. Finally, even if one 

determined an appropriate distribution of episodes and could accurately 

model them, it is not immediately obvious what is the most appropriate way 

to aggregate the results for the various scenarios to yield a single 

scale. 

The results of this study indicate that the aggregation method can be 

important in affecting reactivity scales derived from scenarios 

representing a distribution of airshed conditions. If the reactivities 

are aggregated simply by averaging ratios of reactivities calculated for 

the individual scenarios, one obtains relative reactivities which are 

similar to those in the maximum ozone reactivity scale. On the other 

hand, if the reactivities are aggregated using a method which give greater 

weight to scenarios where VOCs have greater effects on ozone, such as by 

minimizing errors in predictions of absolute effects on ozone formation 

throughout the entire set (as is the case with the "line fit" method), the 

relative reactivities obtained are like those in the maximum reactivity 

scale. As indicated above, these two are in some cases significantly 

different in predictions of relative reactivity. 

The aggregation method appears to be less important if ozone impacts 

are quantified by integrated ozone concentration (ozone dose) rather than 

by the total yields of ozone formed. This is an encouraging result, 

49 
P.52 

because it suggests that a single reactivity scale may be applicable to 

measuring effects of VOCs on ozone exposure in a wide variety of 

airsheds. In addition, the relative reactivities in the aggregated ozone 

dose scales correspond reasonably well to those in the maximum reactivity 

scale. This is because integrated ozone concentrations, like ozone yields 

in high N0X maximum reactivity conditions, are both significantly affected, 

by ozone formation rates. This is the case even for scenarios where ozone 

formation is N0X limited, where the ultimate ozone yield is relatively 

insensitive to how rapidly ozone is formed. 

Based on these considerations, it is concluded that if one needs to 

use a single generalized reactivity scale for assessing effects of VOCs on 

ozone, a maximum reactivity scale is the most appropriate for this 

purpose, at least for the near term. It is not as sensitive to the 

distribution of airshed scenarios used to derive it as is the case for 

aggregated base case reactivity scales, and can be calculated using 

relatively simple airshed models without having to accurately simulate any 

particular air pollution episode. Although no single reactivity scale 

will perfectly represent all conditions, the maximum reactivity scale 

seems to give a reasonably close correspondence to relative ozone impacts 

of VOCs in a wide number of cases, particularly those where the impacts of 

VOCs are the largest. The present results also suggest that the maximum 

reactivity scale might give appropriate predictions of effects of VOCs 

changes on ozone exposure even in scenarios where they do not accurately 

predict effects on peak ozone levels. Although these conclusions are 

based on reactivities calculated for highly simplified and perhaps in some 

cases inaccurate scenarios, the scenarios employed are sufficiently varied 

that it is not unreasonable to expect that similar results would be 

50 
P.53 

obtained if more detailed and accurate scenarios were employed. 

However, it is clear that further research is needed to reduce the 

uncertainties in the derivation of VOC reactivity scales. The scenarios 

employed in this study may not represent the best currently available 

estimate of the distribution of ozone pollution conditions, and more work 

in this area is clearly needed. A systematic study of the effects of 

airshed conditions other than N0X availability on reactivity would aid in 

this effort. It would indicate which scenario characteristics are the 

most important to accurately represent when calculating maximum 

reactivity, and would assist in estimates of uncertainties in reactivity 

predictions caused by uncertainties in characterizing airshed 

conditions. This includes studies of the sensitivity of reactivity 

predictions on changes in composition of the base case ROG surrogate, 

which are presently underway in our laboratories, and which will be 

reported in a subsequent paper. In addition, the prediction that maximum 

reactivities will correspond reasonably well to effects of VOCs on ozone 

exposure needs to be tested using realistic, gridded airshed models. Such 

tests are presently underway, and preliminary results tend to support the 

general utility of the maximum reactivity scale (Russel, 1990). 

It should also be recognized that regardless of which approach or set 

of airshed conditions is used for developing a reactivity scale, the 

reactivities for many VOCs will be uncertain because of uncertainties in 

the chemical mechanism used to calculate them. Only for a limited number 

of VOCs are sufficient data available to test these mechanisms. Modeling 

studies may give us an indication of the magnitudes of the effects of 

these uncertainties, but will not reduce them. To reduce these 

uncertainties, experimental data are needed to test the mechanisms used to 

51 
P.54 

derive the reactivity factors, or at a minimum to test their predictions 

of maximum reactivity. We are currently investigating experimental 

approaches which can be used to reduce chemical uncertainties in VOC 

reactivity scales. 

52 
P.55 

Acknowledgements 

The author wishes to thank Drs. Michael W. Gery and Gary Z. Whitten 

for providing computer-readable input files for the scenarios employed in 

this study and Dr. Roger Atkinson, Mr. Bart Croes and Mr. Alvin Lowi, Jr. 

for helpful discussions. This work was supported primarily by the U.S. 

Environmental Protection agency through Cooperative Agreement No. 

R-814396-01-0. Additional support was provided by contracts with the 

California South Coast Air Quality Management District, the California Air 

Resources Board (Contract No. A932-094), and a consulting contract for the 

Western Liquid Gas Association. However, this paper has not been reviewed 

or approved by any of these agencies or organizations, and the opinions 

and conclusions given herein are entirely those of the author. 

53 
P.56 

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rr 

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A 

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BI 

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73 & tt 

•O m «-

o- o 

_ o • 

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3 " ~ 3 

«- s < 

rr A • 

• r» 

A X 

•n i A 

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3 wOQ 

BI 3 * 

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*— 3 

X 3 T! (TO 

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1 

1 A 

B 

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92 a w 

o — K a 

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rr 

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B 

s 

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"O I I 

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r> »- — o 

•»« i -i 

«-> i t» 

- ~ A 

^ o — 

• D W 

C I 

B) 

O" 
Table 

ID 

la] 

G-MA1 

G-MA2 

G-MA3 

G-MA1 

W-HA1 

G-MA5 

G-MA6 

G-MA7 

G-NA1 

G-NA2 

G-NA3 

G-NAl 

G-NA5 

G-NA6 

G-NA7 

G-NA8 

W-NA8 

G-NA9 

G-NY1 

G-NY2 

G-PH1 

G-PH2 

G-PHU 

G-PH5 

G-PH6 

G-PH7 

G-PH8 

1. Summary of the Ha 

City and Site 

Massachusetts 

Nashua 

Nashua 

Nashua 

Nashua 

Nashua 

Lexington 

Lexington 

Nashville 

Nashville 

Health Center 

Hendersonvl1ie 

Health Center 

Hendersonvl1le 

Health Center 

Hendersonvl1le 

Hendersonvl1le 

(Same as 

Hendersonvl1le 

New York 

Stratford 

Middletown 

Philadelphia 

(not given) 

(not given) 

Trenton 

(not given) 

(not given) 

Roxborough 

Roxborough 

MAY 

JUL 

AUG 

AUG 

|or 

Uat 

30. 

21. 

13, 

15, 

G-MA1) 

AUG 

JUN 

JUL 

JUL 

JUL 

JUL 

AUG 

AUG 

AUG 

AUG 

SEP 

16. 

29, 

10, 

2, 

25. 

25, 

1, 

1, 

10, 

10, 

11, 

C-NA8) 

SEP 

JUN 

JUN 

JUL 

JUL 

JUN 

JUN 

AUG 

JUN 

JUN 

12. 

21. 

21, 

13. 

19, 

15, 

16, 

19. 

27. 

27, 

Charac 

e 

1978 

1978 

1978 

1978 

1978 

1979 

1979 

1980 

1980 

1980 

1980 

1980 

1980 

1980 

1981 

1981 

i960 

1980 

1979 

1979 

1981 

1981 

1982 

1983 

1983 

terlstlcs 

Calc. 

max 0-> 

(ppb) 

127 

107 

117 

125 

131 

109 

113 

110 

88 

86 

97 

76 

87 

120 

131 

85 

137 

80 

218 

226 

233 

151 

151 

208 

131 

198 

173 

of the 

R0C/N0v 

Ib| 

6.1 

11.7 

6.3 

6.1 

6.1 

8.5 

6.0 

'7.1 

11.6 

191 

11.7 

18.9 

11.5 

10.6 

9. 1 

11.0 

11.0 

12.9 

12.8 

10.8 

6.8 

6.1 

8.3 

8.2 

8.0 

6.3 

5 7 

EKMA Sc 

Light 

Ic) 

210 

219 

238 

227 

227 

223 

255 

237 

230 

223 

223 

220 

220 

215 

215 

188 

181 

187 

238 

238 

236 

213 

211 

239 

210 

212 

212 

enarlos 

Inv. 

Used f 

Height 

(meters) 

lnlt. 

250 

250 

250 

250 

250 

250 

119 

360 

250 

250 

250 

250 

250 

250 

250 

250 

250 

250 

300 

300 

250 

250 

250 

250 

250 

250 

250 

Final 

571 

1850 

127 

580 

536 

893 

867 

1704 

1815 

1815 

1815 

18115 

1815 

18*15 

1815 

181)5 

1815 

1815 

1561 

1561 

1135 

871 

1682 

1211 

1659 

996 

996 

or Reactivity Assessment. 

2 

-- Input flux (m.mol/m ) 

(* input emitted)|d] --

--- IIC ---

5.15 (10J) 

3 1 2 (25*) 

5.00 (35») 

5.26 (38») 

5.13 (38*) 

3 05 (23%) 

1.60 (21?) 

371 (25*) 

2.81 ( 7») 

187 ( 9*) 

251 (23*) 

196 ( 9*) 

2.67 (23*) 

1 58 ( 91) 

6.00 (23*) 

1.11 (23*) 

1.11 (23*) 

3 13 (23X) 

3121 (28») 

32.11 (21*) 

18.23 (19*) 

50.23 (81*) 

16.37 (13») 

1135 (38») 

10.88 (15*) 

17.58 (17*) 

19.11 (52*) 

—

 NOx — 

0.99 

0.19 

0.85 

6.95 

0.95 

0.18 

0.88 

0.80 

0.59 

0.10 

0.57 

0.11 

0.59 

0.98 

1.31 

0.93 

0.93 

0.69 

2.78 

315 

2.89 

8.38 

3.02 

2.83 

1.72 

3.26 

3.60 

(65*) 

(32*) 

(59*) 

(61*) 

(61*) 

(30*) 

(52J) 

(58*) 

( 7») 

( 9*) 

(21») 

( 91) 

(21*) 

( 9*) 

(21») 

(21*) 

(21J) 

(21J) 

(16*) 

(53X) 

(56*) 

(85*) 

(58») 

(17*) 

(26») 

(61*) 

(65*) 

, -- Aloft 

-- HC --

(ppb) (*) 

10 ( 9*) 

10 (15*) 

10 ( 5*) 

10 ( 9*) 

80 (15*) 

10 (26*) 

10 (13») 

10 (37*) 

90 (67*) 

90 (76*) 

90 (69*) 

90 (75*) 

90 (69X) 

90 (56*) 

90 (19*) 

90 (57*) 

90 (57*) 

90 (65*) 

10 ( 6*) 

10 ( 6*) 

10 ( 7*) 

10 ( 2*) 

150 (35*) 

225 (38*) 

50 (21*) 

100 (15*) 

10 ( 6*) 

lej -

°3 (ppb) 

33 

81 

21 

56 

60 

60 

56 

63 

15 

35 

35 

13 

13 

12 

12 

1 

100 

6 

80 

80 

105 

32 

10 

10 

60 

65 

65 

Notes 

HI 

H 1 

HI 

HI 

H,gl 

Igl 

If) 

in 

! cont 1 nue<l) 
Table 1. (continued) - 3 

ID 

[a] 

G-WA1 

G-WA2 

G-WA3 

G-WA1 

W-WA1 

G-WA5 

W-CH1 

U-SL1 

W-LA1 

W-SF1 

N-SF2 

EKMA-1 

EKMA-2 

EKMA-3 

City and Site 

Washington 

Takoma 

Takoma 

Takoma 

Takoma 

(Same as 

Takoma 

Chicago 

Kenosha 

St. Louis 

(not given) 

Los Angeles 

Glendora 

San Francisco 

(not given) 

(not given) 

Dat 

. 

JUL 16, 

JUL 17, 

JUL 21, 

AUG 7, 

G-WA1) 

AUG 29, 

JUL 11, 

JUN 21, 

AUG 21, 

SEP 30, 

JUL 12, 

Standard EKMA Scenarios 

Los Angeles(k) 

Los Angelesfk) 

Los Angeles!k) 

June 21 

June 21 

June 21 

B 

1980 

1980 

1980 

1980 

1980 

1979 

1986 

1985 

1980 

1981 

Calc. 

max 0-s 

(ppbT 

117 

111 

138 

161 

167 

108 

178 

165 

367 

206 

210 

219 

111 

101 

ROG/NO. 

lb) 

7.9 

12.5 

7.9 

7.2 

6.9 

6.0 

7.1 

8.3 

8.8 

12.8 

10. 1 

10.2 

8.7 

8.6 

Light 

Ic) 

191 

190 

189 

198 

198 

163 

233 

215 

231 

175 

265 

251 

251 

251 

Inv. Height 

(meters) 

Init. 

160 

160 

160 

120 

120 

150 

250 

250 

250 

89 

89 

250 

250 

250 

Final 

2128 

2128 

2128 

1658 

1658 

2229 

880 

1700 

700 

100 

100 

600 

1500 

3500 

-- In 

(X 1 

.-. 

6.81 

6.68 

10.77 

16.22 

16.22 

16.61 

7.13 

13. 16 

21.87 

917 

6.22 

12.00 

12.00 

12.00 

put flux (m.mol/m ), 

iput em 

HC 

(28») 

(26*) 

(50*) 

(13*) 

(13*) 

(57*) 

(19*) 

(23*) 

(30») 

(71*) 

(71*) 

(33*) 

(33*) 

(33») 

ltted)|d) --

—

 NO x — 

1.26 

0.79 

1.77 

2.52 

2.52 

3.31 

1.35 

1.80 

2.70 

0.91 

0.78 

1.20 

1.50 

1.70 

(10*) 

(37*) 

(71*) 

(57*) 

(57*) 

(73*) 

(58*) 

(11*) 

(51*) 

(21*) 

(21J) 

(11*) 

(11*) 

(11*) 

Alort 

HC --

(ppb) (*) 

10 

10 

10 

10 

25 

10 

100 

30 

100 

250 

170 

20 

20 

20 

(32*) 

(32*) 

(23*) 

(11*) 

( 7*) 

(17*) 

(26*) 

(12*) 

( 8>) 

(26J) 

(26*) 

( 2*) 

( 8*) 

(18*) 

le) -

°3 (ppb) 

65 

65 

65 

56 

60 

65 

60 

50 

100 

61 

61 

70 

70 

70 

Notes 

If) 

ID 

ID 

ir) 

If) 

l.r.il 

ir.D 

Ul 

IJ] 

UJ 

Notes: 

(a] Scenarios with prefix "G-" from Gery et al. (1987); those with "W-" are from Whitten et al. (1988); and those with 

"EKMA-" are from Gipson and Freas (1983) modified as described by Carter and Atkinson (1989). See these references for 

more complete description of input data for these scenarios. 

(b] Tabulated Hydrocarbon/NO ls ratio of final hydrocarbon and N0_ concentration at the end of the simulation if no chemical 

reaction occurrs. Includes hydrocarbons and (where applicable) N0X entrained from aloft. 

(c] "Light" ls Integrated NOn photolysis rate for the simulation (it ls a unltless quantity). 

|dj Total Initial and emitted Hydrocarbon and NO input (excluding species entrained from aloft) are given in terms of 

effective numbers of moles (or moles carbon Tor HC) input into the cell per unit area. The value ln parentheses Is the 

percentage of the molar Input which ls present InitialIv. 
Table 2. 

Seen ID 

[a] 

Calculated RO 

Scenarios. 

ROG/ 

N0X 

Massachusetts 

Avg. 

S.Dev. 

• G-MA1 

G-MA2 

* G-MA3 

G-MAl 

W-MAl 

G-MA5 

G-MA6 

• G-MA7 

Nashville 

Avg. 

S.Dev. 

G-NA1 

• G-NA2 

G-NA3 

G-NA1 

G-NA5 

• G-NA6 

G-NA7 

G-NA8 

• H-NA8 

G-NA9 

5.0 

1.1 

6.0 

3.5 

7.0 

6.0 

6.0 

1.0 

l.o 

3-5 

6.1 

1.1 

6.0 

5.0 

5.0 

6.0 

6.0 

5.0 

6.0 

8.0 

6.0 

8.0 

Max. 

°3 (ppb) 

1 in. 

14. 

126. 

108. 

135. 

122. 

122. 

96. 

101. 

99. 

88. 

21. 

86. 

82. 

83. 

73. 

76. 

90. 

117. 

73. 

131. 

69. 

G/N0X Ratios and Selected 

Base ROG 

React'y 

(Og/ppraC) 

0.75 

0.09 

0.71 

0.78 

0.62 

0.67 

0.70 

0.80 

0.83 

0.89 

1.03 

0.22 

1.16 

1.17 

1.15 

1.27 

1.25 

1.03 

0.97 

0.86 

0.53 

0.93 

IntOH 

(ppt-

-rain) 

91. 

19. 

89. 

119. 

81. 

78. 

71. 

95. 

86. 

128. 

113. 

15. 

112. 

113-

107. 

126. 

122. 

92. 

121. 

101. 

100. 

106. 

Reactivi ty Resu] 

-Kinetic Reactivity-

(Fraction Reacted) 

HCHO 

0.91 

0.02 

0.92 

0.95 

0.91 

0.91 

0.91 

0.91 

0.95 

0.98 

0.97 

0.02 

0.98 

0.98 

0.98 

0.98 

0.98 

0.97 

0.98 

0.93 

0.91 

0.96 

Acetone 

0.017 

0.007 

0.015 

0.056 

0.012 

0.010 

0.038 

0.016 

0.016 

0.059 

0.055 

0.007 

0.067 

0.057 

0.051 

0.060 

0.059 

0.019 

0.059 

0.016 

0.016 

0.018 

Ethene 

0.71 

0.06 

0.69 

0.78 

0.69 

0.65 

0.63 

0.71 

0.69 

0.82 

0.76 

0.01 

0.83 

0.76 

0.75 

0.79 

0.78 

0.70 

0.80 

0.72 

0.73 

0.71 

Its for the Maximum VOC 

_ — • • 

Reactiv 

Mechanistic Reactivity 

(ppm O^ / 

CO 

0.91 

0.07 

0.88 

0.86 

0.80 

0.89 

0.88 

0.95 

1.00 

1.01 

0.91 

0.12 

0.85 

1.02 

1.05 

0.96 

0.98 

1.01 

0.82 

0.80 

0.71 

0.81 

n-C8 

0.22 

0.06 

0.20 

0.29 

0.15 

0.19 

0.15 

0.25 

0.26 

0.29 

0.27 

0.07 

0.31 

0.31 

0.31 

0.32 

0.31 

0.31 

0.27 

0.16 

0.19 

0.17 

ppmC VOC 

Toluene 

1.05 

0.09 

1.07 

0.91 

0.91 

1.02 

1.13 

1.10 

1.16 

1.10 

1.30 

0.25 

1.30 

1.15 

1.15 

1.51 

1.53 

1.38 

1.12 

1.23 

0.68 

1.28 

ity 

) Reacted) 

Propene 

2.25 

0.23 

2.25 

2.26 

1.81 

2.05 

2.15 

2.39 

2.50 

2.52 

3.01 

0.63 

3.33 

3.12 

3.36 

3.67 

3.61 

3.05 

2.78 

2.51 

1.58 

2.71 

(con 

HCHO 

1.23 

0.13 

1.50 

3.13 

3.96 

1.21 

1.80 

1.10 

1.61 

1.25 

1.50 

0.76 

1.78 

1.87 

1.86 

5.23 

5.20 

1.71 

1.29 

1.18 

2.61 

1.26 

tinued) 
Table 1. (continued) - 1 

|ej The values ln parentheses are the percentages of the total hydrocarbon present at the end of the simulation (assuming no 

chemical reaction) which are due to species entrained from aloft. 

|f) This scenario was used in the aggregated "base case" reactivity calculations. 

lgl These scenarios have 1 ppm NC" aloft. Aloft N0X contributes 2* of the total NO input in the base case simulation. 

|h) This scenario has 1 ppm N0X aloft. Aloft N0X contributes 5* of the total N0X input in the base case simulation. 

(i) These scenarios have 1 ppm N0X aloft. Aloft N0X contributes 5* of the total NO input in the base case simulation. 

|J) These scenarios were not used for deriving the reactivity scales, and are shown only for comparison with previous studies 

(Carter and Atkinson, 1989). The N0X inputs, ROG/NOx ratios, and maximum ozone yields shown are for maximum ozone 

conditions. 

|k] The latitude used for calculating photolysis rates was arbitrarily chosen to be that of Los Angeles. Otherwise, the 

scenarios are not necessarily designed to represent any particular city. 
Table 2. (continued) - 2 

Seen ID 

[a] 

New York 

Avg. 

S.Dev. 

• G-NY1 

• G-NY2 

Philadelph 

Avg. 

S.Dev. 

G-PH1 

• G-PH2 

• G-PH1 

• G-PH5 

G-PH6 

G-PH7 

G-PH8 

Phoenix 

Avg. 

S.Dev. 

• G-PX1 

• G-PX2 

• G-PX3 

G-PX1 

W-PX1 

G-PX5 

Seattle 

Avg. 

S.Dev. 

ROG/ 

N0X 

6.0 

0.0 

6.0 

6.0 

ia 

6.1 

0.8 

6.0 

8.0 

7.0 

6.0 

6.0 

6.0 

6.0 

6.7 

0.5 

6.0 

7.0 

7.0 

7.0 

6.0 

7.0 

7.3 

0.5 

Max. 

°3 (ppb) 

203. 

1. 

200. 

205. 

177. 

17. 

211. 

250. 

130. 

157. 

116. 

185. 

186. 

123. 

10. 

126. 

126. 

111. 

131. 

112. 

131. 

233. 

32. 

Base ROG 

React'y 

(O^/ppmC) 

0.63 

0.01 

0.63 

0.61 

0.62 

0.10 

0.61 

0.11 

0.62 

0.72 

0.61 

0.65 

0.61 

0.77 

0.11 

1.01 

0.76 

0.65 

0.66 

0.71 

0.78 

0.60 

0.07 

IntOH 

(ppt-

-min) 

82. 

8. 

77. 

88. 

80. 

12. 

100. 

59. 

79. 

78. 

85. 

79. 

78. 

85. 

21. 

120. 

100. 

72. 

68. 

66. 

88. 

72. 

2. 

-Kinetic Reactivity-

(Fraction Reacted) 

HCHO 

0.97 

0.00 

0.97 

0.97 

0.95 

0.03 

0.96 

0.89 

0.95 

0.96 

0.97 

0.95 

0.91 

0.91 

0.03 

0.98 

0.95 

0.92 

0.91 

0.92 

0.96 

0.93 

0.02 

Acetone 

0.017 

0.002 

0.015 

0.018 

0.013 

0.005 

0.019 

0.033 

0.011 

0.015 

0.011 

0.011 

0.013 

0.013 

0.009 

0.058 

0.017 

0.038 

0.036 

0.036 

0.013 

0.038 

0.001 

Ethene 

0.71 

0.03 

0.69 

0.73 

0.68 

0.05 

0.75 

0.58 

0.68 

0.68 

0.70 

0.69 

0.68 

0.67 

0.08 

0.79 

0.73 

0.63 

0.60 

0.59 

0.69 

0.65 

0.01 

_ — — — Mechanistic Reactivity 

(ppm 0, / 

CO 

0.82 

0.06 

0.86 

0.78 

0.83 

0.06 

0.81 

0.70 

0.83 

0.88 

0.86 

0.81 

0.86 

0.86 

0.01 

0.90 

0.80 

0.86 

0.87 

0.88 

0.81 

0.73 

0.01 

ppmC VOC 

n-C8 Toluene 

0.19 

0.00 

0.19 

0.19 

0.20 

0.03 

0.21 

0.11 

0.20 

0.22 

0.20 

0.21 

0.21 

0.18 

0.01 

0.26 

0.17 

0.17 

0.15 

0.16 

0.16 

0.11 

0.01 

0.87 

0.01 

0.87 

0.87 

0.89 

0.09 

0.80 

0.75 

0.92 

1.02 

0.89 

0.91 

0.93 

1.10 

0.08 

1.22 

1.01 

1.00 

1.08 

1.16 

1.09 

0.96 

0.10 

«• — ~~ _ 

Reacted) 

Propene 

1.81 

0.01 

1.83 

1.85 

1.86 

0.21 

1.85 

1.37 

1.89 

2.16 

1.86 

1.96 

1.95 

2.26 

0.36 

2.97 

2.19 

1.95 

2.03 

2.18 

2.21 

1.83 

0.21 

(con 

HCHO 

1.08 

0.01 

1.09 

1.07 

3.66 

0.36 

3.57 

2.89 

3.68 

3.85 

3-93 

3.81 

3.88 

1.19 

0.30 

5-01 

1.30 

1.25 

1.21 

1.55 

1.61 

3.72 

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Table 2. (continued) - 1 

Seen ID 

[a] 

• W-WA1 

• G-UA5 

Chicago 

• W-CH1 

St. Louis 

• W-SL1 

ROG/ 

NOx 

6.0 

6.0 

6.0 

1.0 

Los Angeles 

• H-LA1 6.0 

San Francj 

Avg. 

S.Dev. 

• W-SF1 

• W-SF2 

All Above 

Avg. 

S.Dev. 

LSCO 

9.0 

1.1 

10.0 

8.0 

Urban 

6.2 

1.2 

Max. 

°3 (ppb) 

115. 

108. 

157. 

91. 

287. 

193. 

35. 

168. 

217. 

Areas 

160. 

61. 

Base ROG 

React'y 

(O^/ppmC) 

0.81 

0.61 

0.80 

0.75 

0.63 

0.10 

0.15 

0.29 

0.51 

[b] 

0.71 

0.15 

IntOH 

(ppt-

-min) 

87. 

61. 

93. 

61. 

69. 

51. 

27. 

32. 

70. 

82. 

16. 

-Kinetic Reactivity-

(Fraction Reacted) 

HCHO Acetone Ethene 

0.91 

0.92 

0.97 

0.93 

0.91 

0.81 

0.15 

0.70 

0.91 

0.91 

0.01 

0.011 

0.031 

0.019 

0.011 

0.039 

0.028 

0.015 

0.018 

0.038 

0.011 

0.007 

0.69 

0.58 

0.73 

0.57 

0.67 

0.51 

0.17 

0.38 

0.63 

0.67 

0.07 

Mechanistic Reactivity 

(ppm Oo / ppmC VOC Reacted) 

CO n-C8 Toluene Propene HCHO 

0.90 

0.89 

0.82 

0.93 

0.79 

0.75 

0.03 

0.77 

0.73 

0.81 

0.07 

0.17 

0.19 

0.16 

0.21 

0.11 

0.11 

0.03 

0.12 

0.16 

0.19 

0.01 

1.17 

0.98 

1.05 

1.15 

1.01 

0.80 

0.01 

0.79 

0.80 

1.02 

0.13 

2.39 

1.90 

2.29 

2.11 

1.93 

1.18 

0.25 

1.31 

1.65 

2.13 

0.39 

5.22 

3.96 

5.00 

1.53 

1.11 

2.96 

0.11 

2.88 

3.03 

1.22 

0.51 

EKMA Scenarios [c] 

EKMA-1 

EKMA-2 

EKMA-3 

6.1 

6.5 

6.1 

166. 

126. 

91. 

0.61 

0.75 

0.76 

73. 

119-

156. 

0.91 

0.97 

0.98 

0.011 

0.056 

0.068 

0.65 

0.80 

0.87 

0.81 

0.80 

0.76 

0.19 

0.21 

0.31 

0.91 

0.85 

0.76 

1.87 

2.12 

2.12 

3.75 

3.83 

2.98 

Notes: 

[a] An "*" indicates this scenario was used to calculate mechanistic reactivities for all VOCs. 

[b] Averages of averages for each of the 12 urban areas. 

[c] Not used ln deriving the maximum reactivity sc 1 0 . Shown for comparison purposes only. 
Table 3. Calculated R0G/N0x Ratios and Selected Reactivity Results for the Maximum Ozone 

Concentration Scenarios. 

Seen ID 

[a] 

ROG/ 

N0X 

Massachusetts 

Avg. 

S.Dev. 

G-MA1 

• G-MA2 

• G-MA3 

G-MA1 

W-MA1 

G-MA5 

G-MA6 

G-MA7 

Nashville 

Avg. 

S.Dev. 

• G-NA1 

G-NA2 

G-NA3 

G-NA1 

G-NA5 

G-NA6 

G-NA7 

• G-NA8 

W-NA8 

G-NA9 

New York 

Avg. 

S.Dev. 

7.1 

2.0 

8.0 

5.0 

10.0 

8.0 

10.0 

6.0 

7.0 

5.0 

9.2 

1.7 

8.0 

8.0 

8.0 

10.0 

10.0 

8.0 

8.0 

12.0 

8.0 

12.0 

8.0 

0.0 

Max. 

°3 

(ppb) 

137. 

19. 

153. 

118. 

151. 

119. 

153. 

113. 

111. 

115. 

101. 

20. 

97. 

101. 

106. 

88. 

93. 

122. 

131. 

85. 

110. 

80. 

239. 

1. 

Base ROG 

React'y 

(OyppmC) 

0.29 

0.08 

0.28 

0.37 

0.17 

0.32 

0.18 

0.31 

0.29 

0.36 

0.11 

0.07 

0.53 

0.17 

0.18 

0.11 

0.11 

0.18 

0.19 

0.35 

0.29 

0.11 

0.20 

0.01 

IntOH 

(ppt-

-min) 

111. 

31. 

130. 

166. 

113. 

116. 

111. 

111. 

179. 

191. 

162. 

23-

181. 

179. 

177. 

180. 

180. 

168. 

165. 

131. 

120. 

137. 

121. 

11. 

-Kine 

(Fra 

HCHO 

0.97 

0.02 

0.95 

0.97 

0.98 

0.96 

0.96 

0.97 

1.00 

0.99 

0.99 

0.02 

0.99 

1.00 

1.00 

1.00 

1.00 

1.00 

0.99 

0.96 

0.96 

0.99 

0.99 

0.00 

tic Reactivityction Rez 

Acetone 

0.062 

0.011 

0.058 

0.071 

0.052 

0.052 

0.051 

0.062 

0.076 

0.079 

0.070 

0.010 

0.079 

0.078 

0.077 

0.078 

0.077 

0.071 

0.072 

0.056 

0.052 

0.058 

0.060 

0.003 

icted) 

Ethene 

0.83 

0.06 

0.80 

0.86 

0.78 

0.78 

0.76 

0.83 

0.90 

0.92 

0.86 

O.O'I 

0.89 

0.89 

0.89 

0.89 

0.89 

0.88 

0.88 

0.79 

0.78 

0.82 

0.83 

0.02 

— — — — Mechanistic Reactivity 

(ppm 0^ / 

CO 

0.17 

0.01 

0.17 

0.50 

0.11 

0.52 

0.11 

0.19 

0.13 

0.18 

0.17 

0.02 

0.50 

0.19 

0.18 

0.11 

0.11 

0.19 

0.50 

0.11 

0.19 

0.15 

0.15 

0.07 

n-C8 

0.11 

0.01 

0.10 

0.18 

0.06 

0.11 

0.01 

0.13 

0.09 

0.11 

0.16 

0.05 

0.20 

0.19 

0.19 

0.17 

0.16 

0.19 

0.19 

0.08 

0.13 

0.08 

0.11 

0.01 

ppmC VOC 

Toluene 

0.22 

0.08 

0.23 

0.26 

0.09 

0.30 

0.09 

0.27 

0.18 

0.30 

0.35 

0.06 

0.13 

0.31 

0.31 

0.33 

0.33 

0.31 

0.36 

0.36 

0.21 

0.10 

0.01 

0.02 

_ _ _ _ 

Reacted) 

Propene 

0.88 

0.21 

0.87 

1.12 

0.56 

0.96 

0.59 

1.05 

0.88 

1.01 

1.32 

0.19 

1.56 

1.12 

1.12 

1.31 

1.33 

1.11 

1.15 

1.10 

0.91 

1.26 

0.61 

0.03 

HCHO 

1.36 

0.21 

1.17 

1.11 

1.01 

1.76 

1.18 

1.32 

1.12 

1.56 

1.21 

0.21 

1.38 

1.06 

1.16 

0.86 

1.00 

1.36 

1.51 

1.21 

1.15 

1.36 

1.07 

0.07 

(continued) 
Table 3. (continued) - 3 

Seen ID 

[a] 

• G-NY1 

• G-NY2 

ROG/ 

N0X 

8.0 

8.0 

Philadelphia 

Avg. 

S.Dev. 

G-PH1 

G-PH2 

• G-PH1 

G-PH5 

G-PH6 

• G-PH7 

G-PH8 

Phoenix 

Avg. 

S.Dev. 

• G-PX1 

G-PX2 

G-PX3 

• G-PX1 

W-PX1 

G-PX5 

Seattle 

Avg. 

S.Dev. 

• G-PG1 

G-PG2 

8.9 

1.1 

8.0 

10.0 

10.0 

10.0 

8.0 

8.0 

8.0 

10.3 

0.8 

10.0 

10.0 

10.0 

12.0 

10.0 

10.0 

10.0 

0.0 

10.0 

10.0 

Max. 

°3 (ppb) 

238. 

239. 

215. 

59. 

239. 

310. 

157. 

207. 

131. 

231. 

231. 

152. 

16. 

117. 

111. 

130. 

175. 

162. 

155. 

291. 

27. 

319. 

320. 

Base ROG 

React*y 

(Og/ppmC) 

0.21 

0.19 

0.21 

0.01 

0.25 

0.21 

0.17 

0.21 

0.26 

0.27 

0.27 

0.31 

0.05 

0.37 

0.31 

0.29 

0.21 

0.32 

0.31 

0.21 

0.03 

0.20 

0.20 

IntOH 

(ppt-

-min) 

116. 

131. 

121. 

20. 

111. 

81. 

119. 

138. 

119. 

126. 

125. 

125. 

11. 

132. 

110. 

109. 

116. 

125. 

128. 

108. 

10. 

92. 

93. 

-Kinetic Reactivity-

(Fraction Reacted) 

HCHO 

0.99 

0.99 

0.98 

0.01 

0.98 

0.95 

0.99 

1.00 

0.99 

0.99 

0.99 

0.98 

0.01 

0.96 

0.98 

0.97 

0.98 

0.98 

0.99 

0.98 

0.02 

0.95 

0.96 

Acetone 

0.058 

0.062 

0.056 

0.008 

0.062 

0.010 

0.057 

0.061 

0.055 

0.059 

0.058 

0.055 

0.001 

0.058 

0.060 

0.019 

0.051 

0.055 

0.057 

0.050 

0.001 

0.011 

0.011 

Ethene 

0.82 

0.85 

0.81 

0.05 

0.81 

0.69 

0.81 

0.85 

0.81 

0.83 

0.82 

0.80 

0.03 

0.79 

0.83 

0.76 

0.77 

0.80 

0.82 

0.78 

0.03 

0.73 

0.73 

~ — ~- mm. Mechanistic Reactivity 

(ppm 0^ / 

CO 

0.50 

0.10 

0.17 

0.01 

0.15 

0.16 

0.15 

0.12 

0.51 

0.16 

0.18 

0.17 

0.01 

0.50 

0.13 

0.50 

0.11 

0.17 

0.19 ' 

0.10 

0.01 

0.10 

0.10 

ppmC VOC 

n-C8 Toluene 

0.12 

0.10 

0.11 

0.01 

0.12 

0.10 

0.09 

0.09 

0.11 

0.12 

0.12 

0.09 

0.01 

0.11 

0.10 

0.10 

0.07 

0.09 

o.io 

0.09 

0.00 

0.09 

0.09 

0.05 

0.03 

0.12 

0.07 

0.09 

0.22 

0.06 

0.03 

0.19 

0.15 

0.11 

0.22 

0.08 

0.32 

0.22 

0.25 

0.09 

0.23 

0.23 

0.11 

0.03 

0.13 

0.12 

___. 

) Reacted) 

Propene 

0.63 

0.58 

0.73 

0.10 

0.78 

0.69 

0.53 

0.69 

0.78 

0.83 

0.81 

0.91 

0.11 

1.12 

0.93 

0.90 

0.71 

0.98 

1.03 

0.76 

0.08 

0.61 

0.61 

(conl 

HCHO 

1.12 

1.02 

1.18 

0.26 

1.21 

1.36 

0.78 

0.81 

1.33 

1.39 

1.39 

1.18 

0.23 

1.70 

1.13 

1.53 

1.01 

1.57 

1.59 

1.25 

0.07 

1.17 

1.17 

iJnued) 
P.74 

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fD 

m 

rr 

3" 

fD 

3 

fD 

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o 

3 

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o 

rr 

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fD 

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O 

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(U 

OL 

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3 

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i—> 

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fD 

3 

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1 

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TJ 

fD 

3 

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a 

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3 

rt> 

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> - • 

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33 

rt> 

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f> 

rr 

**• 

< M -

rr 

«< i 

i 

i 

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i 

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3

1 

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3 

r*. 

CO 

cr 

M -

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o 

33 

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Table 3. (continued) 

Seen ID 

[a] 

Chicago 

• W-CH1 

St. Louis 

• W-SL1 

ROG/ 

N0X 

8.0 

8.0 

Los Angeles 

• W-LA1 8.0 

San Francj 

Avg. 

S.Dev. 

• W-SF1 

• W-SF2 

All Above 

Avg. 

S.Dev. 

I SCO 

13.0 

1.2 

16.0 

10.0 

Urban 

8.9 

1.6 

Max. 

°3 (ppb) 

179. 

165. 

367. 

230. 

11. 

220. 

210. 

Areas 

198. 

75. 

Base ROG 

React'y 

(03/ppmC) 

0.28 

0.33 

0.25 

0.20 

0.08 

0.11 

0.25 

[b] 

0.29 

0.07 

IntOH 

(ppt-

-min) 

122. 

177. 

103. 

70. 

27. 

50. 

89. 

128. 

28. 

-Kinetic Reactivity-

(Fraction Reacted) 

HCHO Acetone Ethene 

0.99 

0.98 

0.98 

0.89 

0.09 

0.82 

0.95 

0.98 

0.03 

0.058 

0.077 

0.050 

0.031 

0.015 

0.021 

0.015 

0.058 

0.011 

0.81 

0.88 

0.80 

0.60 

0.11 

0.51 

0.70 

0.81 

0.07 

Mechanl 

(ppm Oo / 

CO n-C8 

0.17 

0.38 

0.11 

0.18 

0.02 

0.17 

0.19 

0.16 

0.01 

0.08 

0.12 

0.08 

0.09 

0.03 

0.07 

0.11 

0.11 

0.02 

stic Reactivity 

ppmC VOC Reacted) 

Toluene Propene HCHO 

0.16 

0.16 

0.11 

0.17 

0.00 

0.17 

0.18 

0.18 

0.08 

0.88 

1.02 

0.77 

0.72 

0.19 

0.59 

0.85 

0.88 

0.19 

1.62 

1.27 

1.61 

1.21 

0.10 

1.17 

1.31 

1.35 

0.18 

EKMA Scenarios [c] 

EKMAEKMAEKMA1 

•2 

-3 

10 

8 

7 

0 

0 

0 

219. 

111. 

101. 

0 

0 

0 

.20 

.38 

.16 

112. 

175. 

230. 

0 

0 

0 

.99 

.99 

.99 

0.061 

0.071 

0.091 

0.85 

0.89 

0.91 

0.37 

0.19 

0.17 

0.09 

0.17 

0.21 

0 

0 

0 

.01 

.26 

31 

0.63 

1.10 

1.27 

0.98 

1.53 

1.29 

Notes: 

[a] An "*" indicates this scenario was used to calculate mechanistic reactivities for all VOCs. 

[b] Averages of averages for each of the 12 urban areas. 

[c] Not used in deriving the maximum reactivity scale. Shown for comparison purposes only. 
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Table 1. (continued) - 2 

Model 

Code 

(a) 

21-DM-C5 

3-ME-C6 

1-ME-C6 

BR-C7 

23-DM-C5 

IS0-C8 

1-ME-C7 

BR-C6 

BR-C9 

1-ET-C7 

BR-C10 

1-PR-C7 

BR-C11 

BR-C12 

BR-C13 

BR-C11 

BR-C15 

CYCC5 

HE-CYCC5 

CYC-C6 

CYCC6 

CYC-C7 

HE-CYCC6 

ET-CYCC6 

CYC-C8 

CYC-C9 

CYC-C10 

CYC-C11 

CYC-C12 

CYC-C13 

CYC-C11 

CYC-C15 

VOC Description 

2,1-Dimethyl Pentane 

3-Methyl Hexane 

1-Methyl Hexane 

Branched C7 Alkanes 

2,3-Dlaethyl Pentane 

Iso-Octane 

1-Methyl Heptane 

Branched CB Alkanes 

Branched C9 Alkanes 

IJ-Ethyl Heptane 

Branched CIO Alkanes 

31-Propyl Heptane 

Branched C U alkanes 

Branched C12 Alkanes 

Branched C13 Alkanes 

Branched C11 Alkanes 

Branched C15 Alkanes 

Cyclopentane 

Methylcyclopentane 

C6 Cycloalkanes 

Cyclohexane 

C7 Cycloalkanes 

Methy 1 cy c lohexane 

Ethylcyclohexane 

C8 Cycloalkanes 

C9 Cycloalkanes 

CIO Cycloalkanes 

C11 Cycloalkanes 

C12 Cycloalkanes 

C13 Cycloalkanes 

C11 Cycloalkanes 

C15 Cycloalkanes 

kOH 

IbJ 

(ppm ' 

min"') 

1.0E»1 

1.IE+1 

1.1E«1 

1.1E*1 

1.1E*1 

6.9E*3 

1.3E«1 

1.3E+1 

15E«1 

1.5E+1 

17E+1 

1.7E.1 

2.1E.1 

2.3E«1 

25E*1 

2.7E«1 

2.9E<1 

8.2E«3 

1.0E»1 

1.2E*1 

1.2E*1 

1.5E*»I 

1.5E«1 

1.8E*1 

1.8E+1 

2.1E*1 

2.3E*1 

2.6E*1 

2.9E*1 

31E»1 

33E*1 

35E»1 

Kinetic 

(Tract.. 

MaxRct 

0.56 

0.58 

0.58 

0.58 

0.5B 

0.13 

0.61 

0.61 

0.72 

0.72 

0.76 

0.76 

0.82 

0.85 

0.87 

0.89 

0.91 

0.19 

0.57 

0.61 

0.61 

0.71 

0.71 

0.77 

0.77 

0.81 

0.85 

0.88 

0.91 

0.92 

0.93 

0.91 

React. 

react) 

MaxOj 

0.72 

0.71 

0.71 

0.71 

0.71 

0.59 

0.80 

0.80 

0.86 

0.86 

0.89 

0.89 

0.93 

0.95 

0.96 

0.97 

O.98 

0.65 

0.71 

0.79 

0.79 

0.85 

0.85 

0.90 

0.90 

0.93 

0.95 

0.96 

0.98 

0.98 

0.99 

0.99 

Mech. React. 

(mol 0,/mol C) 

MaxRct 

0.57 

0.11 

0.11 

0.11 

0.19 

0.18 

0.33 

0.33 

0.28 

0.28 

0.23 

0.23 

0.26 

0.26 

0.19 

0.117 

0.132 

0.95 

0.87 

0.38 

0.38 

0.19 

0.19 

0.52 

0.52 

0.57 

0.15 

0.11 

0.39 

0.30 

0.28 

0.26 

MaxOj 

0.25 

0.21 

0.21 

0.21 

0.25 

0.20 

0.16 

0. 16 

0. 136 

0.136 

0. 112 

0.112 

0. 112 

0. Ill 

0. 108 

0.087 

0.078 

0.15 

0.13 

0.18 

0.18 

0.23 

0.23 

0.25 

0.25 

0.28 

0.23 

0.21 

0.20 

0.16 

0.138 

0.131 

Incremental 

(mol O^J 

HaxRct 

0.32 

0.25 

0.25 

0.25 

0.29 

0.21 

0.21 

0.?1 

0720 

0.20 

0.18 

0.18 

0.21 

0.22 

0. 17 

0.131 

0.120 

0.17 

0.50 

0.25 

0.25 

0.31 

0.31 

0.10 

0.10 

0.17 

0.38 

0.36 

0.35 

0.27 

0.26 

0.25 

'mol C) 

MaxOj 

0.18 

0.16 

0.16 

0.16 

0.19 

0.119 

0.128 

0.128 

0.117 

0.117 

0.100 

0.100 

0.132 

0.131 

0.101 

0.081 

0.076 

0.29 

0.32 

0.113 

0.113 

0.20 

0.20 

0.22 

0.22 

0.26 

0.22 

0.20 

0.20 

0.15 

0.136 

0.130 

Reactlvi 

(gm 03 / 

MaxRct 

1.07 

0.85 

0.85 

0.85 

0.96 

0.70 

0.72 

0.72 

0.68 

0.68 

0.60 

0.60 

0.72 

0.75 

0.57 

0.11 

0.11 

1.6 

1.7 

0.81 

0.81 

1.17 

1.17 

1.36 

1.36 

1.6 

1.31 

1.23 

1.20 

0.91 

0.88 

0.85 

ty De rlw. 

gm VOC) Codelc) 

Max03 KR MR 

0.61 

0.53 

0.53 

0.53 

0.63 

0.10 

0.13 

0.13 

0.39 

0.39 

0.31 

0.31 

0.15 

0.15 

0.35 

0.29 

0.26 

1.00 

1.08 

0.19 1 

0.19 1 

0.67 1 

0.67 1 

0.76 1 

0.76 1 

0.89 1 

0.71 1 

0.70 

0.68 

0.52 

0.17 

0.11 

1 2 

1 2 

1 2 

1 2 

1 2 

1 2 

1 2 

1 2 

1 2 

1 2 

1 2 

1 2 

1 2 

1 2 

2 

2 

2 

2 

2 

2 

2 

2 

2 

2 

2 

2 

2 

2 

2 

1 2 

1 2 

1 2 

Unc'ty 

Code 

Id] 

5 

5 

5 

5 

5 

5 

5 

5 

6 

6 

6 

6 

6 

6 

6 

6 

6 

5 

5 

5 

5 

5 

1 

5 

6 

6 

6 

6 

6 

6 

6 

6 

(continued) 
Table 1 . (continued) - 3 

Model 

Code 

[a] 

ETHENE 

PROPENE 

1-BUTENE 

1-PENTEN 

3M-1-BUT 

1-HEXENE 

C6-0LE1 

C7-0LE1 

C8-0LE1 

C9-0LE1 

C10-OLE1 

C11-OLE1 

C12-OLE1 

C13-OLE1 

C11-OLE1 

C15-OLE1 

1S0BUTEN 

2M-1-BUT 

T-2-BUTE 

C-2-BUTE 

2H-2-BUT 

C5-OLE2 

23M2-BUT 

C6-OLE2 

C7-0LE2 

C8-0LE2 

C9-OLE2 

C10-0LE2 

VOC Description 

Alkenes 

Ethene 

Propene 

1-Butene 

1-Pentene 

3-Methyl-1-Butene 

1-Hexene 

C6 Terminal Alkenes 

C7 Terminal Alkenes 

C8 Terminal Alkenes 

C9 Terminal Alkenes 

CIO Terminal Alkenes 

C11 Terminal Alkenes 

C12 Terminal Alkenes 

C13 Terminal Alkenes 

C11 Terminal Alkenes 

C15 Terminal Alkenes 

Isobutene 

2-Methyl-1-Butene 

trans-2-Butene 

cls-2-Butene 

2-Methyl-2-Butene 

C5 Internal Alkenes 

2,3-Dlmethy1-2-Butene 

C6 Internal Alkenes 

C7 Internal Alkenes 

C8 Internal Alkenes 

C9 Internal Alkenes 

CIO Internal Alkenes 

kOH 

lb] 

(PP"" 

min"') 

1.2E*1 

3.8E«1 

1.6E«1 

1.6E*1 

1.6E*1 

5.1E*1 

51E*1 

5.1E»1 

5.1E+1 

51E«1 

5.1E*1 

5.1E«1 

5.1E«1 

5.1E*1 

5.1E-.1 

5.1E*1 

7.5E*1 

8.BE+1 

9.2E+1 

8.2E*1 

1.3E*5 

9.2E»1 

1.6E*5 

92E*1 

9.2E*1 

9.2E+1 

9.2E«1 

9.2E*1 

Kinetic 

(fract. 

MaxRct 

0.67 

0.92 

0.95 

0.95 

0.95 

0.96 

0.96 

1.00 

1.00 

1.00 

1.00 

1.00 

1 .00 

1 .00 

1 .00 

1 .0(1 

1 .00 

1 .00 

1 .00 

1 .00 

1 .00 

1 .00 

1.00 

1.00 

1.00 

1.00 

1.00 

1 .00 

React. 

react) 

MaxO^ 

0.81 

0.97 

0.98 

0.98 

1.00 

1.00 

1.00 

1.00 

1.00 

1.00 

1.00 

1.00 

1.00 

1.00 

1.00 

1.00 

1 .00 

1.00 

1.00 

1.00 

1.00 

1.00 

1.00 

1.00 

1.00 

1.00 

1.00 

1.00 

Mech. React. 

(mol 0,/mol C) 

MaxRct 

2.3 

2. 1 

1.9 

1.31 

1.31 

0.91 

0.91 

0.70 

0.55 

0.16 

0.38 

0.31 

0.30 

0.27 

0.25 

0.23 

1.21 

1.09 

2. 1 

2. 1 

1.15 

1.8 

1.07 

1.5 

1.27 

1.07 

0.93 

0.82 

MaxO^ 

0.95 

0.85 

0.72 

0.19 

0.19 

0.31 

0.31 

0.26 

0.20 

0. 16 

0.137 

0.119 

0. 106 

0.095 

0.087 

0.081 

0.50 

0.15 

0.82 

0.82 

0.53 

0.67 

0.36 

0.56 

0.16 

0.38 

0.33 

0.29 

Incremental 

(mol 0,/mol C) 

MaxRct 

1.6 

1 9 

1.8 

1.21 

1.21 

0.87 

0.87 

0.70 

0.55 

0.16 

0.38 

0.31 

0.30 

0.27 

0.25 

0.23 

1.21 

1.09 

2. 1 . 

2.1 

1.15 

1.8 

1.07 

1.5 

1.27 

1.07 

0.93 

0.82 

Max03 

0.77 

0.83 

0.70 

0.18 

0.19 

0.31 

0.31 

0.26 

0.20 

0.16 

0.137 

0.119 

0.106 

0.095 

0.087 

0.081 

0.50 

0.15 

0.82 

0.82 

0.53 

0.67 

0.36 

0.56 

0.16 

0.38 

0.33 

0.29 

Reactlvl 

(gm O^/ 

MaxRct 

5.3 

6.6 

6.1 

1.2 

1.2 

3.0 

3.0 

2.1 

19 

1.6 

132 

115 

1.03 

0.93 

0.86 

0.80 

1.2 

3.7 

7.3 

7.3 

5.0 

6.2 

3.7 

5.3 

1.1 

3.6 

3.2 

2.8 

ty 

gm VOC) 

MaxO, 

2.6 

2.B 

2.1 

1.6 

1.7 

1.16 

1.16 

0.88 

0.68 

0.56 

0.17 

0.11 

0.36 

0.33 

0.30 

0.28 

1 7 

1.5 

2.8 

2.8 

1.8 

2.3 

1.22 

1.9 

1.6 

130 

1.13 

0.99 

Derlv. 

Code|c) 

KR MR 

2 1 

2 1 

2 1 

2 1 

3 3 

2,1 1 

3 3 

5 1 

5 1 

5 1 

5 1 

5 1 

5 1 

5 1 

5 1 

5 1 

1 1 

1 1 

1 1 

3 3 

1 1 

1 1 

1 1 

1 1 

5 1 

5 1 

5 1 

5 1 

Unc'ty 

Code 

Id] 

1 

3 

3 

5 

5 

3 

5 

6 

6 

6 

6 

6 

6 

6 

6 

6 

1 

5 

1 

1 

5 

5 

5 

6 

6 

6 

6 

6 

(continued) 
Table 1 . (continued) - 1 

Hodel 

Code 

M 

C11-0LE2 

C12-OLE2 

C13-OLE2 

C11-0LE2 

C15-0LE2 

13-BUTDE 

ISOPRENE 

CYC-PNTE 

CYC-HEXE 

A-PINENE 

B-PINENE 

BENZENE 

TOLUENE 

C2-BENZ 

N-C3-BEN 

1-C3-BEN 

S-C1-BEN 

C10-BEN1 

C11-BEN1 

C12-BEN1 

M-XYLENE 

O-XYLENE 

P-XYLENE 

C9-BEN2 

C10-BEN2 

C11-BEN2 

C12-BEN2 

VOC Description 

, 

C11 Internal Alkenes 

C12 Internal Alkenes 

C13 Internal Alkenes 

C11 Internal Alkenes 

C15 Internal Alkenes 

1,3-Butadlene 

Isoprene 

Cyclopentene 

Cyelohexene 

a-Plnene 

b-Plnene 

Aromatic Hydrocarbons 

Benzene 

Toluene 

Ethyl Benzene 

n-Propyl Benzene 

Isopropyl Benzene 

s-Butyl Benzene 

CIO Honoalkyl Benzenes 

C11 Honoalkyl Benzenes 

C12 Honoalkyl Benzenes 

m-Xylene 

o-Xylene 

p-Xylene 

C9 Dlalkyl* Benzenes 

CIO Dlalkyl Benzenes 

C11 Dlalkyl Benzenes 

C12 Dlalkyl Benzenes 

kOH 

[b] 

(ppm 

min'1) 

9.2E«1 

9.2E+1 

9.2E+1 

9.2E«1 

9.2E41 

9.7E+1 

1.5E*5 

97E*1 

9.8E4I 

7.8E*1 

1.1E«5 

19E*3 

8.7E«3 

1.0E«1 

8.8E43 

95E*3 

8.BE.3 

8.7E*3 

8.7E«3 

8.7E*3 

35E*1 

2.0E41 

2.1E+1 

35E»1 

35E»1 

3.5E*1 

35E*1 

Kinetic 

(fract. 

MaxRct 

1.00 

1.00 

1.00 

1.00 

1.00 

1.00 

1 .00 

1.00 

1.00 

1.00 

1.00 

0.113 

0.51 

0.57 

0.51 

0.51 

0.51 

0.51 

0.51 

0.51 

0.91 

0.81 

0.82 

0.91 

0.91 

0.91 

0.91 

React. 

react) 

Max03 

1.00 

1.00 

1.00 

1.00 

1.00 

1.00 

1.00 

1.00 

1.00 

1.00 

1.00 

0.21 

0.67 

0.71 

0.68 

0.71 

0.68 

0.67 

0.67 

0.67 

0.99 

0.92 

0.93 

0.99 

0.99 

0.99 

0.99 

Hech. 

(mol 0 

MaxRct 

0.73 

0.67 

0.61 

0.57 

0.53 

2.2 

1.8 

1.13 

0.91 

0.55 

0.55 

0.51 

1.00 

0.88 

0.78 

0.78 

0.70 

0.70 

0.61 

0.58 

1.8 

1.8 

1.8 

1.6 

1.11 

1.28 

1.18 

React.. 

j/mol C) 

Max03 

0.26 

0.21 

0.22 

0.20 

0.19 

0.85 

0.70 

0.10 

0.36 

0.21 

0.21 

0. Ill 

0.17 

0.115 

0.129 

0.129 

0.116 

0.116 

0.106 

0.097 

0.52 

0.52 

0.52 

0.16 

0.12 

0.38 

0.35 

ln 

(mol Oj 

MaxRct 

0.73 

0.67 

0.61 

0.57 

0.53 

2.2 

1.8 

1.13 

0.91 

0.55 

0.55 

0.077 

0.51 

0.50 

0.10 

0.12 

0.36 

0.36 

0.32 

0.30 

1 7 

1.12 

1.15 

1.18 

133 

1.21 

1.11 

cremental 

/mol C) 

MaxO? 

0.26 

0.21 

0.22 

0.20 

0.19 

0.85 

0.70 

0.10 

036 

0.21 

0.21 

0.021 

0.111 

0.107 

0.087 

0.091 

0.078 

0.078 

0.071 

0.065 

0.51 

0.18 

0.18 

0.16 

0.11 

0.37 

0.31 

Reactlvl 

(gm Oj/ 

MaxRct 

2.5 

2 3 

2.1 

1 9 

1.8 

7.7 

6.5 

1.0 

3 3 

1.9 

1.9 

0.28 

1.9 

1.8 

1.11 

1.5 

1.29 

1.28 

1.16 

1.06 

6.0 

5.2 

5.2 

5.3 

1.8 

1.3 

3.9 

ty 

gm VOC) 

MaxOj 

0.89 

0.81 

0.71 

0.69 

0.61 

3-0 

2.5 

1.11 

1.27 

0.71 

0.71 

0.088 

0.11 

0.39 

0.31 

0.33 

0.28 

0.28 

0.25 

0.23 

1 9 

1.7 

1.8 

1.6 

1.17 

133 

1.22 

Derlv 

Code] 

KR 

5 

5 

5 

5 

5 

1 

1 

1 

1 

5 

5 

1 

_ 

c] 

MR 

1 

1 

1 

1 

1 

1 

1 

1 

1 

1 

3 

1 

1 

3 

3 

3 

3 

3 

3 

3 

l 

3 

3 

3 

3 

3 

3 

Unc'ty 

Code 

Id] 

6 

6 

6 

6 

6 

6 

1 

6 

6 

1 

6 

3 

3 

5 

5 

5 

5 

6 

6 

6 

3 

3 

5 

6 

6 

6 

6 

(continued) 
Table 1. (continued) - 5 

Model VOC Description 

Code 

la] 

kOH 

l M - 1 

(PP* 

min"') 

Kinetic React. 

(Tract, react) 

MaxHct MaxOn 

Mech. React, 

(mol Oj/mol C) 

MaxRct MaxO-, 

Incremental Reactivity Derlv. Unc'ty 

(mol Oj/mol C) (gm O^/gm VOC) Code|c) Code 

_ | d ) 

MaxRct MaxO-, MaxRct MaxO-, KR MR 

135-TMB 1,3.5-Trimethyl Benzene 8.IE4I 1.00 

123-TMB 1,2.3-Trimethyl Benzene I.8E4I 0.98 

121-TMB 1,2,1-Trlmethyl Benzene I.8E4I 0.98 

C10-BEN3 CIO Trialkyl Benzenes 8.1E+1 

C11-BEN3 C11 Trialkyl Benzenes 8.IE4I 

C12-BEN3 C12 Trialkyl Benzenes 8.1E«1 

TETRALIN Tetralln 5.OE4I O.98 

NAPHTHAL Naphthalene 32E*1 0.93 

ME-NAPH Methyl Naphthalenes 7.6E4I 1.00 

23-DMN 2,3-Dlmethyl Naphthalene I.IE45 1.00 

.00 

.00 

.00 

1 .00 

1.00 

1.00 

1.00 

1.00 

1 .00 

1.00 

0.98 

1.00 

1.00 

2. 1 

2.1 

2. 1 

1.9 

1.7 

1.6 

0.20 

0.25 

0.61 

1.01 

0.67 

0.67 

0.67 

0.60 

0.51 

0.50 

030 

0120 

115 

0.27 

2.1 

2.1 

2.0 

1.9 

1.7 

1.6 

0.20. 

0.23' 

0.63 

1.01 

0.67 

0.66 

0.66 

0.60 

0.51 

0.50 

0.030 

0.0118 

0.115 

0.27 

7.5 

7.1 

7.1 

6.7 

0.73 

0.87 

2.1 

2.1 

2.1 

2.1 

1.9 

1.8 

0.109 

0.011 

0.51 

1.00 

Acetylene 

ACETYLEN Acetylene 

Alcohols 

1. 1E.3 0.090 0.137 1.11 0.53 0.099 0.073 0.37 0.27 

MEOH 

ETOH 

N-C3-0H 

I-C3-0H 

1-C1-0H 

N-C1-0H 

T-C1-0H 

ET-CLYCL 

PR-GLYCL 

FORMALD 

ACETALD 

PROPALD 

Methanol 

Ethanol 

n-Propyl Alcohol 

Isopropyl Alcohol 

Isobutyl Alcohol 

n-Butyl Alcohol 

t-Butyl Alcohol 

Ethylene Glycol 

Propylene Glycol 

Aldehydes 

Formaldehyde 

Acetaldehyde 

Propionaldehyde 

1.1E4 3 

1.8E43 

7.8E43 

7.6E43 

1.1E41 

1.2E«1 

1.7E*3 

1.1E+1 

1.8E*1 

1.1E»1 

2.3E*1 

2.9E>1 

0. 107 

0.33 

0.17 

0.17 

0.68 

0.63 

0. 127 

0.60 

0.76 

0.91 

0.83 

0.91 

0. 16 

0.16 

0.63 

0.62 

0.83 

0.79 

0.19 

0.76 

0.90 

0.98 

0.92 

0.95 

2.5 

1.01 

1. 17 

0.33 

0.11 

1.00 

0.89 

1.21 

0.63 

1.2 

2. 1 

2.0 

0.93 

0.3C 

0.10 

0.17 

0. 19 

0.37 

0.10 

0.18 

0.25 

1.30 

0.77 

0.70 

0.27 

0.31 

0.55 

0. 16 

0.28 

0.63 

0.113 

0.73 

0.18 

3-9 

1 7 

1.8 

0. 150 

0. 17 

0.25 

0. 105 

0. 16 

0.29 

0.077 

0.37 

0.23 

1.26 

0.70 

0.66 

0.10 

0.70 

1.33 

0 3 7 

0.72 

1.6 

0.29 

1 1 3 

0.92 

6.2 

3 8 

1.6 

0.22 

0.31 

0.60 

0.25 

0.11 

0.75 

0.20 

0.57 

0.13 

2.0 

1.5 

1.6 

2 

2 

2 

1 

1 

2 

2 

2 

2 

2 

2 

2 

1 

1 

1 

(coi 

1 

2 

5 

5 

5 

5 

5 

5 

5 

1 

3 

1 

11nued) 
oo 

Table 1. (continued) - 6 

Hodel 

Code 

(a) 

VOC Description 

?kOH 

lb] 

(ppm' 

Kinetic React. 

(Tract, react) 

Mech. React, 

(mol Oj/mol C) 

Incremental Reactivity 

(mol Oj/mol C) (gm Oj/gm VOC) 

min"') MaxRct MaxO, MaxRct MaxO;, MaxRct MaxO-, MaxRct MaxO-, 

Deriv. Unc'ty 

Code(c) Code 

|d] 

KR MR 

ACETONE 

MEK 

Ketones 

Acetone 

Cl Ketones 

3.1E*2 

1.7E*3 

0.011 

0. 16 

0.058 

0.22 

3.6 

1.8 

0.95 

0.53 

0.16 

0.29 

0.055 

0.117 

0.39 

0.76 

0.137 

0.31 

Aromatic Oxygenates 

BENZALD Benzaldehyde 1.9E+1 0.81 0.95 -0.20 -0.31 -0.17 -0.30 -0.51 -0.93 2 1 1 

PHENOL Phenol 39E*1 1.00 1.00 0.26 -0.17 0.26 -0.17 0.79 -0.51 1 1 5 

CRESOL Cresols 6.2E+1 1.00 1.00 0.51 -0.23 0.51 -0.23 1.6 -0.72 1 1 1 

Notes 

a. Detaled model species name used in the mechanism (Carter, 1990). 

to. Hydroxyl radical rate constant Tor T=300 K used in the mechanism (Carter, 1990). 

c. Codes for derivation of reactivities are as follows: 

Kinetic Reactivities (KR): 

1. Kinetic reactivity estimated using Equation (VI), and IntOH = 82 ppt-min Tor maximum reactivity or IntOH = 128 ppi-min Ioi 

maximum ozone conditions. ( \% 

2. Kinetic reactivity calculated explicitly Tor all scenarios, and average of averages Tor the 12 urban a^eas used. 

3. Kinetic reactivity assumed.to be the same as for compound listed above. 

1. Kinetic reactivity was calculated to be greated than 0.98. Compound assumed to be essentially completely reacted. 

5. C7* alkenes are assumed to be completely reacted.

 rl 

. Mechanistic Reactivities (MR): 

1. Mechanistic reactivity calculated directly Tor selected scenarios, and average of averages for the 12 urban areas used. 

2. Mechanistic calculated for "pure mechanism" species used to estimate the mechanistic reactivity as described 

by Carter and Atkinson (1989). Mechanistic reactivities for the "pure mechanism" species reacting with OH radical 

constants or 3.0E+3 and 3-0E+1 ppm"1 min" calculated as Indicated above ln note "d". The values Tor the OH radl 

constant of this species estimated by linear Interpolation IT the rate constant is between 3.0E+3 and 3.0E-.1 ppm* 

3. Per-molecule mechanistic reactivity ls assumed to be the same as the Bbove compound. 

1. Per-molecule mechanistic reactivity ls assumed to be the average of the compound listed above and that listed bei 

rate 

cal rate 

1 min"'. 
Table 5. 

VOC ID 

[a] 

CO 

HETHANE 

ETHANE 

PROPANE 

N-Cl 

N-C6 

N-C8 

ISO-C8 

N-C12. 

BR-C12 

N-C15 

ETHENE 

PROPENE 

T-2-BUTE 

ISOBUTEN 

1-HEXENE 

C10-OLE1 

i C10-OLE2 

BENZENE 

TOLUENE 

H-XYLENE 

135-TMB 

TETRALIN 

NAPHTHAL 

23-DMN 

Ratios of Reactivities of Selected VOCs Relative to the Reactlv 

ROG Surrogate, Derived from 

Maximum Ozone React! 

MaxRct 

0.017 

0.00*13 

0.062 

o.no 

0.27 

0.26 

0.17 

0.30 

0.081 

0.32 

0.061 

2.3 

2.8 

3.1 

1.8 

1.27 

0.56 

1.18 

0.120 

0.79 

2.5 

3.2 

0.31 

0.37 

1.6 

Max03 

0.036 

0.0079 

0.101 

0.21 

0.15 

0.17 

0.30 

0.13 

0.110 

0.18 

0.107 

2.8 

3.0 

3.0 

1.8 

1.23 

0.50 

1.06 

0.093 

0.13 

2.0 

2.5 

0.116 

0.017 

1.06 

the Aggregated Base Case, 

city Scales. 

- Reactivity Relative to 

Base Case Ozone Yi 

Avg. 

0.011 

0.0087 

0.115 

0.26 

0.17 

0.15 

0.19 

0.37 

0.025 

0.19 

0.0063 

3.2 

3.5 

3.3 

2.1 

1.15 

0.32 

1.00 

0.090 

0.23 

1.9 

2.6 

-0.0015 

-0.16 

0.93 

Ratio Line 

(61%) [b] 0.023 

(51*) 

(19*) 

(17*) 

(11*) 

(15*) 

(0.26) 

(29*) 

(0.35) 

(11*) 

(0.33) 

(37*) 

(25*) 

(18*) 

(56*) 

(12*) 

(0.59) 

(52J) 

(61*) 

(0.69) 

(12*) 

(30*) 

(0.57) 

(0.77) 

(0.87) 

0.0055 

0.077 

0.17 

0.32 

0.31 

0.18 

0.31 

0.097 

0.38 

0.078 

2.5 

3.1 

3.3 

1.9 

1.32 

0.51 

1.22 

0.111 

0.65 

2.1 

3.1 

0.23 

0.21 

1.18 

3ase Case 

eld 

Fit 

(11*) 

( 9*) 

(10*) 

( 8*) 

( 8*) 

( 8*) 

( 8*) 

( 5*) 

(13*) 

( 6*) 

(15*) 

( 1*) 

( 2*) 

( 1*) 

( 3*) 

( 2*) 

( 5*) 

( 3*) 

( 5*) 

( 9*) 

( 3*) 

( 1*) 

(15*) 

(22*) 

( 6*) 

ity of the Base Case 

the Maximum Reactj 

ROG Mixt 

B 

Avg. 

0.027 

0.0058 

0.072 

0.17 

0.30 

0.31 

0.126 

0.26 

-0.0031 

0.35 

-0.025 

2.6 

3.2 

1.0 

2.6 

0.98 

0.20 

1.13 

0.099 

0.51 

2.3 

3.6 

0.23 

0.110 

1.35 

ase Case 

Ration 

(19*) 

(10*) 

(33*) 

(35*) 

(29*) 

(35*) 

(77*) 

(16*) 

(0.16) 

(27*) 

(0.16) 

(26*) 

(16*) 

(21*) 

(39*) 

(15*) 

(0.18) 

(21*) 

(19*) 

(51*) 

(17*) 

(11*) , 

(73*) 

(0.27) 

(39*) 

Lvity, and the 

Ozone Dose 

Line 

0.020 

0.0015 

0.058 

0.137 

0.25 

0.25 

0.117 

0.25 

0.065 

0.32 

0.016 

2.3 

2.9 

3.6 

2.2 

1.20 

0.11 

1.25 

0.102 

0.68 

2.6 

3.6 

0.30 

0.30 

1.6 

Fit 

( 6*) 

( 1*) 

( 1*) 

( 1*) 

( 1*) 

( 1*) 

( 6*) 

( 2*) 

(15*) 

( 3*) 

(21*) 

( 2*) 

( 1*) 

( 2*) 

( 2*) 

( 2*) 

( 6*) 

( 3*) 

( 1*) 

( 3*) 

( 1*) 

( 2*) 

( 5*) 

( 8*) 

( 2*) 

(continued) 
Table 1. (continued) 

d. Mechanistic uncertainty codes: (See discussion ln text.) 

1. Least uncertain mechanism, and tested using environmental chamber data. 

2. Mechanism probably not uncertain, but no chamber data avalable to test it. 

3. Uncertain aspects of mechanism adjusted or parameterized to fit environmental chamber data. 

1. Mechanism uncertain, and only limited or uncertain chamber data available to test it, or mechanism not optimized to fit 

existing chamber data. 

5. Mechanism estimated, and no chamber data available to test it. 

6. Mechanism highly uncertain, and no chamber data available to test It. 
P.84 

FIGURE CAPTIONS 

Figure 1. Plots of Mechanistic Reactivities for the Model Species for 

Maximum Ozone Conditions Against Mechanistic Reactivities for 

Maximum Reactivity Conditions. (The lines show least 

squares fits, forced through zero, to the results for the 

alkanes or the aromatics). 

Figure 2. Plots of Incremental Reactivities for the Model Species for 

Maximum Ozone Conditions Against Incremental Reactivities for 

Maximum Reactivity Conditions. (The line shows the relative 

reactivity of the base case ROG mixture). 

Figure 3. Plots of Incremental Reactivities for the Model Species, 

Calculated using Kinetic Reactivities for Maximum Ozone 

Conditions and Mechanistic Reactivities for Maximum Reactivity 

Conditions, Against Incremental Reactivities for Maximum 

Reactivity Conditions. (The line shows the relative reactivity 

of the base case ROG surrogate). 

Figure 4. Distribution Plots of IntOH and Mechanistic Reactivities for 

Selected Species for Representative Maximum Reactivity, 

Maximum Ozone, and Base Case N0X Scenarios. 
Table 5. (continued) - 2 

VOC ID 

[a] 

ACETYLEN 

MEOH 

ETOH 

N-C1-OH 

FORMALD 

ACETALD 

ACETONE 

MEK 

CRESOL 

BENZALD 

MaxRct 

0.16 

0.17 

0.30 

0.69 

2.6 

1.6 

0.17 

0.32 

0.67 

-0.23 

Max03 

0.29 

0.21 

0.37 

0.80 

2.1 

1.6 

0.116 

0.33 

-0.77 

-1.00 

— Reactivity Relative to 

Base Case Ozone Yi 

Avg. 

0.32 

0.25 

0.37 

0.73 

2.5 

1.8 

0.117 

0.34 

-3.0 

-2.0 

Ratio Line 

(57*) 0.19 

(38*) 0.19 

(11*) 0.32 

(27*) 0.68 

(lot) 2.6 

(68*) 1.7 

(16*) 0.16 

(33*) 0.33 

(5.9) 0.082 

(2.5) -0.63 

Base Case 

eld 

Fit 

( 9%) 

( 5*) 

( 7*) 

( 5*) 

( 5*) 

( 1*) 

( 2*) 

( 1*) 

(0.30) 

(26*) 

Rfin Ml vf-nro 

Base Case 

Avg. 

0.21 

0.18 

0.24 

0.54 

3.6 

1.27 

0.133 

0.25 

-1.10 

-1.28 

Ratio 

(12*) 

(21*) 

(32*) 

(18%) 

(22%) 

(58*) 

(16*) 

(29*) 

(3.2) 

(1-30) 

Ozone Dose 

Line 

0. 16 

0.16 

0.21 

0.56 

3.4 

1.47 

0.15 

0.28 

0.37 

-0.53 

Fit 

( 5*) 

( 3*) 

( 4*) 

( 2*) 

( 2*) 

( 3*) 

( 2*) 

( 2*) 

(35*) 

(14*) 

[a] Detailed model species name used in the mechanism. See Table 4 for VOCs represented by 

this model species. 

[b] Quantities in parenthes are standard deviations of aggregated averages or line fit slopes. 

These are given as percentage unless standard deviation is greater than 90* of the average or 

the slope. 
-1— » 

> 

-*- » 

o D 

<D 

Ct 

o 

-*- > 

tn 

c 

o 

o 

Q) 

^ 

ro 

O 

X 

a 

X) 

<D 

-4-» 

O 

o OJ 

(Y. 

o O 

> 

O ppm 

^ 

^ 

o 

E 

Q_ 

Q_ 

z.u -

1.5-

1.0-

0.5-

0.0-

S 

. vj 

o 

D 

A 

A 

V 

X 

o 

-

9 

• 

Alkanes 

Alkenes 

Aromatics 

Acetylene y 

Aldehydes s^ 

Ketones ^y 

Alcohols y^ 

Aromatic Aldehydes yy ° 

CO / " v ^- ^ 

I .v^ D< ^ ^ 

1 T 

| 

IIIIII I 

/ Alkanes 

V 

^Aromatic s 

i l l l 

- . 5 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 

MaxRct Mechanistic Reactivity 

(ppm O3 / ppmC VOC Reacted) 

Figure 1. Plots of Mechanistic Reactivities for the Model Species for Maximum Ozone Conditions Against 

Mechanistic Reactivities for Maximum Reactivity Conditions. (The lines show least squares fits, 

forced through zero, to the results for the alkies or the aromatics). 

00 
P.87 

Figure 5. Plots of Reactivities of Selected VOCs against the Reactivity 

of the Base Case ROG Surrogate Calculated for the Base Case 

N 0X Scenarios. 

* = Reactivities for a city-day scenario. 

= Slope is maximum reactivity ratio. 

- — = Slope is maximum ozone reactivity ratio. 

- - - - = Least squares fit, forced through zero. 

= Slope is average of ratios. 

Figure 6. Plots of Relative Base Case Ozone Yield Reactivities Against 

Maximum Reactivities and Maximum Ozone Reactivities for All 

the Model Species. (Base case reactivities aggregated using 

both line fit and average ratio methods.) 

Figure 7. Plots of Relative Base Case Ozone Dose Reactivities Against 

Maximum Reactivities and Maximum Ozone Reactivities for All 

the Model Species. (Base case reactivities aggregated using 

both line fit and average ratio methods. The lines show the 

least squares fits, forced through zero, to the Data). 

Figure 8. Plots of OH Radical Rate Constants (Per Mass Basis) Against 

Reactivities in the Maximum Reactivity Scale. (The line shows 

the average kOH/maximum reactivity ratio for the base case ROG 

surrogate). 
or: 

o 

ct: 

X 

o 

QC 

*: 

ro 

O 

x o 

u 

o 

> 

E 

cn 

r o 

O 

E 

14-, 

12-

o 

o 

-

o 

V 

X 

• 

Alkanes X 5 

Alkenes 

Aromatics 

Acetylene X 10 

Alcohols X 5 

Aldehydes 

Ketones X 5 

Aromatic Oxygenates 

CO X 100 

r 

0 1 2 3 4 5 6/ 7 8 

MaxRct Reactivity (gm O3 / gm VOC) 

1 

9 

Figure 3. Plots of Incremental Reactivities for the Model Species, Calculated using Kinetic Reactivities 

for Maximum Ozone Conditions and Mechanistic Reactivities for Maximum Reactivity Conditions, 

Against Incremental Reactivities for Maximum R'' tivity Conditions. (The line shows the relative 

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oo 
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4 -

3 -

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A 

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x 

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© 

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1 

Alkanes X 5 

Alkenes 

Aromatic s 

Acetylene X 10 

Alcohols X 5 

Aldehydes 

Ketones X 5 

Aromatic Oxygenates 

CO X 100 

o 

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8 

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MaxRct Reactivity (gm O3 / gm VOC) 

Figure 2. Plots of Incremental Reactivities for the Model Species for Maximum Ozone Conditions Against 

Incremental Reactivities for Maximum Reactivity Conditions. (The line shows the relative 

reactivity of the base case ROG mixture). 
P.90 

(J 

O 

> 

Ozone Yield 

Reactivity 

n-Octane 

Ozone Dose 

Reactivity 

-rt 0.000 CJ 

o 

a> 

or Methanol 

Toluene 

0.030-

0.010-

-.010 

i—'— i 

0.00 0.0T 0.02 0.03 0.04 O.OS 0.0 0.2 0.4 0.6 0.8 

(gm O3 / gm VOC) (ppm-min O3 / gm VOC) 

Base ROG Reactivity 

Figure 5. Plots of Reactivities of Selected VOCs against the Reactivity 

of the Base Case ROG Surrogate Calculated for the Base Case NO 

Scenarios. * = Reactivities for a city-day 

scenario. • = Slope is maximum reactivity 

ratio. — — = Slope is maximum ozone reactivity ratio. 

= Least squares fit, forced through zero 

= Slope is average of ratios. 
P.91 

190-. 

Max Reactivity Max O3 Base Case 

IntOH 

Parameter 

Mechanistic 

Reactivity of 

n-Octane 

-.06 

6 4 8 12 16 0 4 8 1216. 0 4 I IZ 16 

Mechanistic 

Reactivity of 

Toluene 

Mechanistic 

Reactivity of 

Formaldehyde 

0 4 8 12 16 0 4 8 12 16 0 4 8 12 16 

Number of City—Days 

Figure 4. Distribution Plots of IntOH and Mechanistic Reactivities for 

Selected Species for Representative Maximum Reactivity, Maximum 

Ozone, and Base Case N0X Scenarios. 
01 

u 

o 

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VI 

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o 

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a: 

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» 

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m 

MaxRct Reactivity (gm O3 / gm VOC) Max03 Reactivity (gm O3 / gm VOC) 

Figure 7. Plots of Relative Base Case Ozone Dose Reactivities Against Maximum Reactivities and Maximum 

Ozone Reactivities for All the Model Species. (Base case reactivities aggregated using both line 

fit and average ratio methods. The lines show the least squares fits, forced through zero, to 
Base Case Relative Reactivities 

P.93 

(Average Ratio) (Une Rt) 

o»J 0»J 
o 

E 

E 

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c 

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Q. 

Q_ 

X 

O 

2500 -, 

2000 

1500-J 

1000-J 

500 H 

o 

D 

A 

A 

O 

V 

z 

• 

Alkanes X 5 

Alkenes 

Aromatics 

Acetylene X 10 

Alcohols X 5 

Aldehydes 

Ketones X 5 

Aromatic Oxygenates 

CO X 100 

a 

• • 

D 

oo 

a 

>o<>T 

a 

oo o 

o 

V 

0 1 2 

MaxRct Reactivity (gm O3 / gm VOC)