EPA-450/3-78-023
June 1978
SEASONAL VARIATIONS
IN ORGANIC EMISSIONS
FOR SIGNIFICANT SOURCES
OF VOLATILE ORGANIC
COMPOUNDS
U.S. ENVIRONMENTAL PROTECTION AGENCY
Office of Air and Waste Management
Office of Air Quality Planning and Standards
Research Triangle Park, North Carolina 27711
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EP A-450 / 3-78-023
SEASONAL VARIATIONS IN ORGANIC
EMISSIONS FOR SIGNIFICANT SOURCES
OF VOLATILE ORGANIC COMPOUNDS
by
LoweU'G~ Wayne and-Clarence L. Boyd.
Pacif~c Environmental Servic~, Inc.
1930 14th Street
Santa Monica, California 90404
Contract No. 68-02-2583
Assignment No.6
EPA Project Officer:James H. Wilson, Jr. .
Prepared for
U.S. ENVIROl'l'MENTAL PROTECTION AGENCY
Office of Air and Waste ~anagement
Office of Air Quality Planning and Standards
Research Triangle Park, North. Carolina 27711
June 1978
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This report is issued by the Environmental Protection Agency to report.
technical data of interest to a limited number. of readers.. Copies are
available free of charge to Federal employees, :current contractors and
grantees, and nonprofit organizations - in limited quantities - from
the Library Services Office (MD-35), U.S. Environmental Protection Agency,
Research Triangle Park, North Carolina 27711; or, for a fee, from the
National Technical Information Service, 5285 Port Royal Road, Springfield,
Virginal 22161. .
. .
. .
This report was furnished to the Environmental Protection Agency by .
Pa~ific Environmental Services, ~nc., 1930 14th Street, Santa Monica,
California 90404. The. contents of this report are reproduced . .
herein as received from Pacific Environmental Services. The opinions,
findings, arid conclusions expressed are those of the author and not
necessarily those of the Environmental Protection Agency.. Mention of. .
company or product names is not to be considered .as an endorsement by the
Environmental Protection Agency. .
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.PUblicationNo~ EPA-45013-78-023
ii.
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TABLE OF CONTENTS
Section
Page
--
Executive Summary .o..oo..ooooo........oo..ooo..o..~........ iv
1.0 INTRODUCTI'ON 000....................................... 1-1
1.1 Background ....................................... 1-1
1.2 The Study Areas .".................................. 1-3
1.3 Data Sources 0.................................... 1-3
1.4 Findings and Conclusions ......................... 1-4
1.5 Organization of Report ...............~........... 1-7
2.0 ESTIMATION OF REACTIVE ORGANIC EMISSIONS .............. 2-1
2.1 General........................................... 2-1
2.2 Methane Correction for Organic Emissions ......... 2-1
3.0 SEASONAL VARIATION OF EMISSIONS BY SOURCE CATEGORY.... 3-1
3.1 General..............."........................... 3-1
3.2 Activity Rates ................................... 3-1
3.3 Effects of Temperature ........................... 3-3
3.3.1 Gasoline-Powered Vehicles ................. 3-4
3.3.2 Solvent Evaporation Loss .................. 3-9
3..3..3 . Pet.r.oleumJ?r.odu,ct Storage and Evaporation
Losses .................................... 3-10
3.3.4 Petroleum Refineries ...................... 3~13
3.3.5 Chemical Manufacturing .................... 3-13
3.3~6 Remaining Sources ..........~.............. 3-13
3.3.7 Summary of Temperature Correction Factors. 3-14
4.0 AREA STUDY RESULTS .................................... 4-1
4.1 Outline of Procedure ............................. 4-1 .
4.2 Tampa Bay Study Area ............................. 4-1
4.2.1 Total Organic Emissions ................... 4-2
4.2.2 Partition of Gasoline-Powered V~hicle
Emissions ................................~ 4-3
4.2.3 Petroleum Product Evaporation Losses ...~..,4-6
4.2.4 Correction Factors .................~...... 4-7'
4.2.5 Final Computations and Tabulations ........ 4-10
4.3 St. Louis Study Area ............'................. 4-10
4.3.1 Annual Organic Emissions .................. 4-10
4.3.2 Summer Activity Factors ................... 4-13
4.3.3 Temperature Adjustment Factors ............ 4-15
4.3.4 Final Computations and Tabulations ........ 4-15
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TABLE OF CONTENTS
Section Page
4.4 Buffalo Study Area ............................... 4-17
4.4.1 Annual Organic Emissions ..................4-17
.4.4.2 Summer Activity Factors ...................4-17
4.4.3 Temperature Adjustment Factors............ 4-19.
4.4.4 Final Computations and Tabulation ..~...... 4-19
5.0 DISCUSSION AND CONCLUSIONS ....................~....... 5-1
5.1 Partition of Vehicular Emissions ................. 5-1
5.2 Temperature'Variation in Stored Liquids .......~.~ 5~2
5.3 Effect of Economic Conditions ..........~......... 5-2
. ,
5.4 Interpretation of NEDS Categories ................5-3
"5.5 CQncl.usions .....................'..............~.. 5-4
:6.'0 ACKNOWLEDGEMENTS......... . .. . . . .. . . . . . . . . . . . . . .. . . . . . .. 6-1
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LIST OF TABLES
Page.
Significant Sources of Total Organic Emissions ........ 1-2
Emissions Estimates and Correction Factors ............ 1-5
Methane Content of Organic Emissions .................. 2-3
Methane Correction Factors by Source Category......... 2-4
Temperature Correction Terms for In-Transit Exhaust ... 3-7
Effects of Temperature and Other Factors on Emissions
of Organics in Petroleum Storage and Transport ........ 3-11
3-3 Temperature Correction Factors for Organic Emi.ssions .. 3-14
4-1 Total Organic Emissions, Tampa Bay Study Area ......... 4-4
4-2 Revised Organic Emissions, Tampa Bay Study Area ....... 4-5
4-3 Correction Factors for Tampa Bay...................... 4-11
4-4 Reactive Organic Emissions, Tampa Bay................. 4-12
4-5 Organic Emissions, St. Louis Study Area ...~........... 4-14
4-6 Emissions of Reactive Organics, Summer, St. Louis ..... 4-16
4-7 Organic Emissions, Buffalo Study Area .................. 4-18
4-8 Emissions of Reactive Organics, Summer, Buffalo ....... 4-20
Table
1-1
1-2
2-1
2-2
3-1
3-2
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EXECUTIVE SUMMARY
To investigate the magnitude of discrepancies between rates of
emi ss i on of vol at il e organi c compounds (VOC' s) determi ned on an
annual basis and those occurring during the summer season, PES
studied the significance of sources during the summer season for
three areas where oxidant air quality standards have been exceeded.
Reactive VOC's were estimated by correcting total VOC's for methane
content.
. A methodology for adapting annual VOC inventories to reflect
.summer emission patterns is outl ined.
Areas studied were Tampa Bay, Florida; St.. Louis, Missouri;..
and Buffalo, New York.. Basic data on emissions were provided by
output from the National Emissions Data System (NEDS) file. For
the Tampa Bay Area, more deta i1 ed data were ava il ab 1 e from a con-
current study directed toward the development of a detailed VOC
inventory for use in a photochemical air quality simulation model.
Estimated total. annual emissions were about 75,000 metric tons
. (MT) for Tampa Bay, 297,000 MT for St.Louis, and 120,000 MT for
Buffalo. Estimated methane emissions ranged from Ito 3 percent of .
the total. The indicated increase in rate of emissi.ons due to sum-
. .
. .
mer conditions was from 3 to 14 percent, applied to the estimated
annual non-methane emissions.
Corrections for methane and for summer conditions did not
appreciably change the order of importance of emission sourtecate-
. .
gories. In each area at least 80 percent of the organic emissions
came from three categories: gasoline-powered vehicles, solvent
evaporation loss~s, and petroleum product evaporation losses.-
The results show that the effect of changes in temperature is
the principal cause of increased VOC emissions in the summer.
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Seasonal variations due to changes in temperature may be small, as
in Tampa Bay, or very substantial, as in St. Louis. In Tampa Bay
the seasonal temperature variation is relatively small, and de-
creases in exhaust emissions partly offset increases in evaporative
emissions. In St. Louis the seasonal temperatures vary widely,
causing the increase in evaporative emissions to predominate in the
overall 14 percent summer increase. Humidity was not found to be a
factor in determining VOC emissions, nor did sunshine appear to
have any appre~;able effect.
Future improved controls on evaporative emissions could change
the relative importance of exhaust and evaporative effects and
shoul d tend to reduce the overall seasonal effect. Agai n, the
seasonal activity factor, which also affects the summer-to-annual
ratio, could be more important at other times and places than it
appears to be in the selected study areas. We may conclude that
the magnitude of seasonal variation of reactive organic emissions
is quite locale-specific. It may be of importance most especially
in places where seasonal variations in either temperature or
activity are 1 arg.e.
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1.0 INTRODUCTION
1.1 BACKGROUND
Emissions of organic compounds into the ambient atmosphere are
subject to regulation, primarily because vapors of these compounds
participate in chemical reactions. Chemical reactions cause con-
. tamination of the atmosphere with photochemical oxidants, often
leading to unacceptable air quality in both urban and rural loca-
tions. The objective of regulating reactive organic emissions is
to prevent the accumulation of photochemical oxidants to concen-
trations exceeding the National Ambient Air Quality Standards.
(NAAQS).
The highest observed concentrations of photochemical oxidants
occur during the summer season due to meteorological conditions
which are most conducive to oxidant formation in that season. To
implement oxidant air quality control by reduction of organic
emissions, therefore, it is necessary to promulgate control
measures which relate especially to those emissions which occur in
the summer months. Present organic emission inventories are
usua-Hy. camp-Hed. on. .an., annua-l ba.s.is-; thus. .they..may . not : accurately. .
reflect quantities of emissions which occur in the summer months.
To investigate the likely magnitude of discrepancies between
emission rates determined on an annual basis and those occurring
duri ng the. summer season, the Source Ana lys i s Sect ion, Air Manage-
ment Technology Branch, Office of Air Quality Planning and
Standards of the U.S. Environmental Protection Agency contracted
with PES. Under EPA Contract No. 68-02-2583, Task Order No.6, PES
was directed to determine the significant souces of reactive
organic emissions during the oxidant season, i.e., the quarter-
year, July through September, for three geographic areas where
violations of the air quality standard for oxidants have occured.
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Because only the nonmethane fraction of total organicemis-
sions is reactive and leads to the formation of oxidants, only
variations in nonmethane organics are relevant to the issue of
oxidant control. PES was therefore directed to determine
nonmethane fractions of the significant emissions wherever possi-
ble, and to determine the difference in inventories corresponding
to this correction. .
Present.EPA policy is that three other organic compounds (in
addition to methane) are of negligible photochemical reactivity and
should be exempt from regulation under State Implementation Plans.
These compounds are ethane, 1,1,1-trichloroethane, and trichloro-
trifl uoroethane (Freon 113). Therefore, ident ifyi ng the nonmethane
hydrocarbons with the reactive organic compounds is not strictly
correct. However, the latter two compounds constitute only a small
fraction of the total solvents used and are not expected to have
unusual seasonal distributions. At the same time, the principal
sources of ethane are the same as the principal sources of methane,
viz~, exhaust gases from internal combustion engines and from
combustion of natural gas. In such emissions, the ethane content
is usually. only 5 or 10 percent of the methane content.. Forthe
purpos~ of this report, therefore, emissions of these compounds are
considered to be negligible. . .
The most significant sources of total organic emissions, on an
annual basis, nationwide, were listed in the Task Assignment and
are shown in Table 1-1. For each of these source categories, PES
was directed to determine the effects of differences in ambient
temperature and activity level between the summer months and the
year as a whole, for each of the three chosen geographical areas.
Any additional sources which might be locally significant were to .
be i dent ifi ed, and other factors such as sunl i ght and humi dity were
to be investigated. .
1-2
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Table 1-1.
SIGNIFICANT SOURCES OF TOTAL ORGANIC EMISSIONSa
1.
2.
3.
4.
5.
6.
Gasoline-powered vehicles
Solvent evaporation loss
Petroleum product storage
Petroleum refineries
Open burning
Chemical manufacturing
Stationary fuel combustion
Carbon black production
Aircraft
Diesel-powered vehicles
and evaporation losses
7.
8.
9.
10.
a Listed in order of importance on an annual, nationwide
basis.
Finally, PES was directed to develop a preliminary outline of
a methodology for adapting annual inventories of organic emissions
to reflect the emissi~n patterns of the summer quarter.
1.2 STUDY AREAS
After consultation with the project officer, it was decided
that the geographical areas to be investigated would be:
. Tampa Bay, Florida: the air quality control region
compri sing Hi 11 sborough County and Pi ne 11 as County . This is'
a southern area having mild winters and fairly high summer
temperatures. (It was also subject of another PES study,
"Assessment of the Anthropogenic Hydrocarbon and Nitrogen
Oxide Emissions in the Tampa Bay Area," under EPA Contract
No. 68-02-2606, Task Order No.2).
.
St. Louis, Missouri: the area comprising the City and .
County of St. Louis and six adjoining counties, namely,
Madison, Monroe, St. Clair, Franklin, Jefferson, and St.
Charles. This area is part of the St. Louis Interstate Air
Quality Control Region. It is a midwestern location with
relatively severe winters and hot summers, and is a major
center of chemical industry.
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. Buffalo, New York: the area comprising Erie County and
Niagara County in "upstate" New York, having very severe
. winters but somewhat lower average summer temperature than
the other areas chosen. Buffalo, the major city. in the
area, has a rather substantial chemical industry.
1.3 DATA SOURCES
Basic data on emissions were provided by output from the
National Emissions Data System (NEDS) file. This information was
furnished in the form of County Emissions Reports for each of the.
counties in the selected areas, except that the City. of St. Louis
was the subj ect of one such report wh il e St. Lou is County, . ..
excl udi ng the city, accounted for another. . Thus, there were ei ght.
. such reports for the St. Louis area, two for the Tampa Bay area and
two for the Buffalo area.
Information regarding the methane content of emissions from
various source categories Was taken from the PES draft report. on.
emissons in the Tampa area, cited previously. Climatological
. .
information was obtained from the U.S. National Weather Service, or
from'the-Climati-c. Atlas' of-the- Un-;-ted- St.ates-..,. repri-nted-by--the- -
National Oceanic and Atmospheric Administration in 1977 (Ashevil~e,
N.e).
Information regarding the effect of temperature and other
factors on emission rates was principally abstracted from "Compila-.
tion of Air Pollutant Emission Factors," Publication No. AP-42 of
the USEPA. With specific reference to motor vehicle emission
factors, latest inf6rmation was obtained from "Mobile Source
Emission Factors, II an Interim Document of June 1977,. prepared and
. .
distributed by EPAOffice of Transportation and Land Use Policy
(OTLUP). This document has since been published in a final.
version, EPA-400j9-78-005, March 1978~
Information regarding the seasonal variation of motor vehicle
traffic and other activities causing organic emissions ~as obtained
1-4
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from a wide variety of sources, especially from personnel of EPA
Regions I, II, IV, and VII and of the states of Florida, Missouri~
and New York, (Ackno\'iledgementsare provided in Section 6.0).
1.4 FINDINGS AND CONCLUSIONS
Table 1-2 summarizes the estimated emissions totals for the
three study areas, as well as the corrections used to obtain the
estimated nonmethane emissions and the summer emission rates.
Estimated total annual emissions were about 75,000 metric tons (MT)
for Tampa Bay,* while for St. Louis* they were 297,000 MT and for
Buffalo* 120,000 MT. Estimated methane emissions amounted in each
case to about 1 to 3 percent of the total. The indicated increase
in rate of emissions due to summer conditions was from 2 to 14
. percent, applied to the estimated annual nonmethane emissions.
Detailed results ihdicated that the corrections for methane
emissions and for summer conditions of temperature and activity did
not appreciably change the order of importance of the emission
source categories from that found in the NEDS reports for annual
emtsstons;. In- each-- area.. at least 80- percent of the org-anic -
emissions came from the first three categories (gasoline-powered
vehicles, solvent evaporation losses, and petroleum product
evaporation losses).
In Tampa Bay, organic emissions from vessels were estimated at
about 5 percent of the total, making this the fourth most signifi-
cant source category in that study area. Although vessels were-
also significant sources in St. Louis and Buffalo, their quantita-
tive contribution was only one-half to one percent of total
emissions in those areas.
Humidity was not found to be a factor in reactive organic
emissions, nor was any evidence seen that sunshine causes signifi-
cant increases in emissions from storage tanks or other sources.
* The terms "Tampa Bay," "St. Loui s" and "Buffalo" herei nafter
refer to the respective study areas, as described in Section 1.2.
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Table 1-2.
EMISSIONS ESTIMATES AND CORREtTION FACTORS
:$;
Tampa Bay St. Laui s Buffalo.
Tatal annual ~rganic 74.7 297 120
emissians, 10 MT/yr
Methane emissians, as
percent af tatal 3.1 1.4 2.4
Me~hane-free emissians, 72.4 293 117
10 MT /yr
Ratio. af emissian
rates, summer/annual 1.03 1.14 - 1.08
Methane-free emissians,
summer, 103 MT/yr 74.8 333 127
Far example, emissian factars far hydracarbans fram matar vehicles
and fram starage tanks, as presented in AP-42 ("Campil at i an af Ai r
- Pallut-ant"Emi s's';-an"'Factars.!'),are.-g'iven';'-by.equat;.ans"wh.ich--depend- - -
an temperature and variaus ather factars, but do. nat depend an
humidity ar salar radiatian.
These results shaw that the effect af seasanal variatians in
- -
organicemissians due to. changes in temperature' may be small, as in
Tampa Bay, ar very substantial, as in St. Lauis. In Tampa Bay the
seasanal temperature variatian is relatively small, and decreases
in exhaust emissians partially offset increases in evaparative
emi ss i ans. In St. Lauis the seasanal temperatures vary widely, -
causing the evaparative increases to. predaminate in the 14 percent
- -
sunmer increase. -Future improved cantrals an evaparative emissians
relative impartanceaf exhaust and evaparative
the seasanal activity factar, which also. affects
cauldchange the
effects. Again,
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the summer-to-annual ratio, could be more important at other times
and places than it appears to be in the selected study areas. PES
therefore believes that it would not be wise to conclude, on the
basis of these results, that the seasonal variation of reactive
organic emissions is a reliably negligible effect.
1.5 ORGANIZATION OF REPORT
Calculations and other details .supporting these findings ar~
set forth in the ensuing sections of this report. Estimation of
reactive organic emissions by correcting total organic emissions
for methane content is discussed in Section 2.0. The seasonal
variation of emissions from various source categories is reviewed
in detail in Section 3.0. In Section 4.0, the methodology
developed for correcting total annual emissions inventories to
summer reactive emissions. inventories is first outlined, then
illustrated through application to three study areas.
Section 5.0 presents discussion bf the results and conclusions
derived therefrom, while Section 6.0 provides acknowledg~ents to
those' who' 'helped'. by' provid'i'ng' necessa'ry., informat i on for th.;s
project.
1-7
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2.0 ESTIMATION OF REACTIVE ORGANIC EMISSIONS
2.1
GENERAL
"Reactive organic emissions," for the purpose of this study,
are defined as all volatile organic compounds except methane.* In
order to estimate reactive organic emissions when total emissions
of volatile organic compounds are known, the fraction constituted
. by methane is estimated and subtracted from the total.
In the
fraction in
following section, information about the methane
emissions from various source categories is reviewed
for calculating reactive organic emissions (ROC) are
and factors
developed.
2.2 METHANE CORRECTION FOR ORGANIC EMISSIONS
Methane is a common constituent of emissions from combustion
of fuels, including exhaust gases from internal combustion engines.
It is a principal .constituent of natural gas and is, therefore,
particularly abundant in flue gases from combustion of natural gas.
It is not a constituent of organic solvents, nor does it occur in
emissions caused by evaporation of solvents. Emissions caused by
evaporation of hydrocarbons from crude oil may contain a small
proportion of methane.
*The nonmenclature of organic emissions in air pollution
parlance has been rather confusing for some years, but recently
changes have been proposed which may result in needed improve-
ments. Known, loosely,. as "hydrocarbons" (HC) from before
the inception of the USEPA, they have more recently been
referred to as "volatile organic compounds" (VOC). When a
method was developed to determine methane concentrations
separately, the difference between total VOCs and methane
became known as "nonmethane hydrocarbons" (NMHC). Since
methane is considered to be an unreactive organic compound (in
the sense of promoting or not promoting the chemical reactions
which occur in photochemical oxidant production), it is omitted
from the "reactive organic emissions," which are therefore
equivalent to the former NMHCs. Three other unreactive.
compounds of minor significance are discussed in Section 1-1.
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The composition of organic emissions from the types of sources
encountered in Tampa Bay was recently reviewed by PES as part of
the study, "Assessment of Anthropogenic Hydrocarbon and Nitrogen
Oxide Emissions in the Tampa Bay Area," EPAContract No.
68-02-2606, Task Order No.2. Table 2-1 presents the estimated
methane content of emissions from the sources condidered in that
study, except for vehicle exhaust emissions. The methane content
for a 1976 U.S. mix of all gasoline vehicles was derived from the
MOBILE-1 program (discussed below in Section 3.3.1). The program
calculates total and nonmethane hydrocarbon emissions, combining
both exhaust and evaporative into one figure. the evaporative
emissions are also given separately by vehicle class. By subtract-
ing the weighted sum of evaporative emissions, for all classes
- -
combined, from the total emissions, the exhaust emissions with and
without methane were calculated. The difference (methane content)
was 5.48 percent of the-total, rounded off to 5 percent for Table
2-1. (The calculation was made for 75°F, since there was little
variation with ambient temperature.)
Methane cQrrection factors for the source categories used in
this study, derived from the information in Table 2-1, are shown in
Table 2-2. Reactive organic emissions are estimated by multiplying
total organic emissions in any category by the appropriate correc~
- -
tion factor.
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Tab 1 e 2-1.
METHANE CONTENT OF ORGANIC EMISSIONS
Source of Emissions
Ai rcraft
Jet exhaust, kerosene fuel
Piston engine exhaust
Stationary fuel combustion
Coal
Fuel oil, distillate
Fuel oil, residual
Natural gas
Liquified petroleum gas (LPG)
Gasoline-powered vehicle
exhaust
Diesel-powered vehicle
exhaust (all) .
Light-duty equipment (gasoline)
Rail Locomotives (diesel)
Sma II craft. and boats ,. (gasol i.ne}. .
Ocean vessels (diesel fuel)
Ocean vessels (residual oil fuel)
Incineration of solid waste
Methane Content (C atom %)
5
9
15
11'
11
20
10
5
2
10
6
10.
6
11
34
Table 2.2.5-2, "Assessment of the Anthropogenic Hydro-
carbon and Nitrogen Oxide Emissions in the Tampa Bay"
Area," Draft Final Report, Pacific Environmental Servies,
Inc.
Source:
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Table 2-2. METHANE CORRECTION FACTORS BY SOURCE CATEGORY
Source Category Methane Correction Factor
1. Gasoline-powered vehicles
Exhaust emissions 0.95
Evaporative emissions 1.0
2. Solvent evaporation 1.0
3. Petro 1 eum product evaporation 1.0
4. Pet ro 1 eum refi neri es 1.0
5. Solid waste disposal .66
6. Manufacturing 1.0
7. . Stationary fuel combustion .85
8. Carbon black production .62
9. Ai rcraft .. .93 .
-
10. Diesel-powered vehicles .98
11. Vessels .91
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.1._---- -- ~
3.0 SEASONAL VARIATION OF EMISSIONS BY SOURCE CATEGORY
3. 1
GENERAL
Seasonal variations in emissions are due primarily to two
causes: seasonal changes in the rate of activities which yield
emissions, and seasonal changes in temperature which cause
differences in emission factors relating to organic emissions, .
independent of any changes in the basic activity rates.
3.2 ACTIVITY RATES
Considering first the effects of seasonal changes in activity
rates, it is clear that such changes should cause directly propor-
. .
tional changes in emissions, sn long as the operative emission
factors do not change with changes in activity; this is certainly
true for the great majority of souce types recognized as emitters,
and it has been assumed true for all souces in this study.
Vehicle transportation is normally the largest source of
organic emissions in urban areas. Seasonal variations can be
estimated either by traffic surveys or by monitoring the rates of
fuel usage for vehicle transportation. Traffic surveys commonly
show combined results for all vehicles used on streets and high-
ways and do not discriminate between gasoline- and diesel-powered
vehicles. However, the proportion of diesel-powered vehicles in
the urban vehicle population is normally small enough so that no
substantial error will be caused if the combined variations .are
taken to apply to gasoline-powered vehicles and diesel vehicles
severally. Off-highway vehicle use is not reflected in traffic
surveys.
The variation of gasoline consumption with season provides an
alternative index to rates of vehicle use. This index reflects
off-highway use of gasoline-powered vehicles, but does not include
diesel-powered vehicles either on or off streets and highways.
3-1
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Vehicle activity factors* for Tampa Bay were,in this study,
derived from traffic count information compiled monthly for several
years for 12 survey stations (these data had been supplied pre-
viously for the PES gridded emissions inventory project, mentioned
in Section 1.2). For St. Louis,monthly gasoline sales registered
by the State of Missouri were used. For Buffalo, the State of New
York provided gasoline consumption data for each of the two
counties involved (Erie and Niagara).
Activity factors for petroleum product evaporation were
assumed to be the. same as those for vehicle transportation~ This
assumption seems eminently appropriate for the emissions due to
service station operations. While it may be morequestionable'for
the activity of storage and transportation of petroleum products,
this source appears to be relatively'minor.
A substantial fraction of emitted organics is attributed to
solvent evaporation from area sources in the standard NEDS inven-
tory. Methodology for estimating this contribution is to assume a
per capita emission rate, currently 24 pounds per year; this is the
amount" 'requi'red' 'to" account". for-"the-' Mfferenee.;. nat i.ona~ly-, . between" ,
amounts of solvent manufactured and amounts accounted for in known
industrial and commercial uses.
It is quite posSible that the activity rates involved iri
various solvent-using processes may have appreciable seasonal
components. Unfortunately, no specific information to this effect
has come to light, so, there is at present no basis for estimating a
* For this study,the activity factor is defined as the ratio of
the average monthly activity rate for the 3-month period, July
through September, to the average monthly activity rate for an
entire year. ,An activity factor of 1.0 represents no change in
production in summer. ' ,
3-2
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summer activity factor for this source. Structural painting is
probably a somewhat seasonal activity, especially in the harsher
northern climate of Buffalo. However, the amount of solvent used
in this application appears to be only about one tenth of the total
solvent attributed to area sources. Lacking more specific informa-
tion, an activity factor of 1.0 has been assigned to this source.
Of the remaining source categories, only the emissions from
industry are of sufficient magnitude to require specific attention
as regards activity factors. Only in the St. Louis area did the
total organic emissions from all industry exceed 10 percent of the
total inventory. The only obvious basis for determining an .
industrial activity factor would be a seasonal index of either.
industrial production or industrial employment. Modification to
such an overall industrial activity factor might be needed if a
particular industry with a well-defined annual cycle of operations
happened to account for a large fraction of industrial organic
emissions. in a study area. However, this circumstance has not been
encounter.ed in the present study.
To- i nvesti'gate' th.;.s' po-i nt further, PES.. obta.i.ned.. NEDS po.i-nt.
source emission reports for Erie County, where the City of Buffalo
.is .located. These reports identified 21 industrial plants emitting
a total of 3,000 English tons of hydrocarbons per year. Of 66
point sources at the 21 plants, only one was reported to show any
seasonal variation at all; in that case, with total annual
emissions of 12 tons (11 metric tons), summer emissions were
reported to be 26 percent of the annual; this corresponds to an
activity factor of 1.04. These results suggest that seasonal
variation in emissions in industries emitting major amounts of
organics is. likely to be very minor; accordingly, an activity
factor of 1.0 has been assigned to these categories.
3-3
-------
The remaining source categories -- solid waste, stationary
fuel combustion, carbon black manufacture, aircraft, diesel
vehicles, and vessels -- together contributed less than 10 per-
cent of the estimated emissions in each study area. Since there is
no obvious reason to expect extreme seasonal fluctuations in these
activities, and since moderate variations would have only very
minor effects on the overall inventory, activity factors of 1.0
have been assigned to these categories also.
3.3 EFFECTS OF TEMP~RATURE
Emission rates for organics from various source categories
have different sensitivities to changes in temperature. Of the
major categories listed in Table 1-1~ it is reasonable to expect
gasoline-powered vehicles and petroleum product evaporation to be
most affected by summer temperatures. Solvent evaporation losses
, ,
are likely to be less affected because in many applications all
solvent used in evaporated, so that the quantity entering the'
.atmosphere is determined by the particular operation, independent
of temRerature.
The following sections discuss the principles applied in
estimating temperature,correction factors for emissions from
various source categories. .
3.3.1 GASOLINE-POWERED VEHICLES
Contaminants are emitted into the atmosphere from
gasoline~powered vehicles in three princip~l modes:
. In ~xhaust gases
. In vapors lost from the fuel tank and carburetor due to
heating and agitation
. In gases forced out of the motor through the crankcase
3-4
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Organics in the exhaust of vehicles in transit are sensitive
to temperature because such emissions are minimal after the engine
has achieved a steady operating temperature; when the vehicle is at
a low temperature when started, as in winter, the engine takes
longer to reach its steady operating temperature (that is, to "warm
Up") than when the vehicle is warmer on starting. Accordingly, an
increase in ambient temperature leads to reduced emissions of
organics from this mode of operation.
The use of an air conditioner on a vehicle has the opposite
effect, since with it the engine is more heavily loaded and.
consumes more fuel. The increased use of air conditioners at
higher ambient temperatures increases exhaust hydrocarbon
emissions. The theoretical maximum hydrocarbon increase (between
absence of air conditioner usage and presence of operating air
conditioners on all vehicles) is 13 percent. (For CO and NOx
emissions, this increase could theoretically reach a maximum of 18
percent. These figures are based on factors given in "Mobile
Source Emission Factors," March 1978).*
Emissions ffom the c~ankcase of vehictesin transttar~ not
known to be sensitive to temperature. According to OTLUP, emis-
sions from this source are much less important, quantitatively,
than they were 10 years ago, because more recent vehicle models
have generally incorporated crankcase ventilation systems. For
this reason, recently published emission factors combine crank-
case emissions with evaporative emissions. """
Emissions caused by evaporation of fuel carried in the vehicle
are sensitive to temperature, because the volatility of the fuel is
sensitive to temperature. Volatility is directly related to the
* Mobile Source Emission Factors, EPA-400/9-78-005, March 1978
3-5
-------
true vapor pressure of the gasoline,which increases by a factor of
about 1.2 for each 10°F of increased temperature.
A computer program "MOBILE-l", supplied on tape by EPA to PES,
was used to develop the temperature/exhaust hydrocarbon emission
relationship. There are nume~ous input variations to this program.
to permit its use in different situations. For our purposes most
. input factors used were "default II opti ons, based either on average
national data or on the conditions used in the Federal Test
Procedure for vehicle exhaust emissions. The route speed and
average speed in all three test modes was arbitrarily set at 30
mile~ per hour. It was assumed that there was no air conditioner
usage (for reasons discussed later), no extra vehicle loading, and
no trailer towing. The proportions of vehicle miles accumulated in
various test modes were taken from the earl ier Tampa Bay study
cited previouSly.
The program was run for a series of ambient. temperatures with
vehicle and mileage distributions for the calendar year 1976. The
national average weighted distribution of vehicle types available
in the. program- was" used-to"deve'lop..-the- tot.al emi-s-s-ion factors- for
total and nonmethane hydrocarbons for all gasoline vehicl.e types
combined~. (This also includes about 3 percent diesel vehi~les,
which has no importance in developing the temperature correction
. factors.) Evaporat i ve emi ss ions were not i ncl uded . in these totals,
which are reported in Table 3-1. . . .
The ratios of summer to annual emissions can be derived from
.this table by the use of the two corresponding average
temperatures. Thus the summer. adjustment factor.Fe(ts~~a) is
. defi ned as: .
Fe(ts,ta) = f(ts)/f(ta)
3-6
-------
Table 3-1. EXHAUST HYDROCARBON EMISSIONS AT
VARIOUS AMBIENT TEMPERATURES
Calculated by MOBILE-1 Computer Program for a Weighted
Combination of All Vehicle Types
Nonmethane
Ambient Hyd roca rbons Hyd roca rbons
of (gjmi) (gjmi)
o 6.67 6.28
5 6.43 6.06
10 6.22 5.86
15 6.02 5.67
20 5.83 5.50
25 5.67 5.34
30 . 5.51 5.20.
35 5.37 5.07
40 5.23 4.94
45 5.11 4.83
50 5.00 4.72
55 4.90 4.63
60 4.80 4.54
65 4.71 4.46
70 4.63 4.38
75 4.56 4.31
80 .4.49 4.25
85 4.42 4.19
90 4.37 4.13
95 4.31 4.08
100 4.26 4.03
105 4.21 3.99
110 4.17 3.95
. 3~7
-------
where ts is .the average summer dayt ime temperature, ta is the"
average annual daytime temperature, and f(ts) and f(ta) are
computer-derived exhaust nonmethane hydrocarbon factors interpo-
lated from Table 3-1.
The air conditioner usage factor deserves further comment.
There were no data available to us on the fraction of vehicles
equipped with air conditioners in the three study areas, nor on
their degree of usage, either annually or in summer. Therefore no
factor has been included for this effect. We suspect that the
effect may not be negligible, in many cases. Using national
av~rage data on fraction of equipped vehicles and some plausible
" "
guesses about degree of usage based on average temperatures, we can
roughly approximate what seasonal effects might be. The summer'
adjustment factor would be close to unity for Tampa Bay, where
temperatures vary little with season. In St. Louis, on the other
hand, where seasons are more extreme and summers are hot, the
factor could be well above unity; we estimate it as roughly 1.07.
Buffalo, which also has seasonal extremes, but cooler summers,
migbt. have a factor of abo~t 1.05.These estimates are not based
firmly enough for actual use, but they suggest the desirability of
obtaining air conditioner usage data whenever possible for inclu-
sion in these calculations.
The.MOBILE~1 program will also calculate a single emission
factor for crankcase and evaporative emissions. This apparently
" "
takes no account of the influence of ambient temperature. For the
purposes of this study," therefore, a different method was used.
. As a first approximation, the emission factor for organics
from crankcase and evaporative emissions can be taken to bean"
exponential functi.on of ambient temperature, proportional to the
gasoline volatility function. This leads to a factor of about 2
percent increase for each degree (Farenheit) of increasing
3-8
-------
temperature. Thus, the summer adjustment
evaporative emissions can be approximated
defined by
Fc(ts,ta) = exp [0.02(ts -ta)]
factor for crankcase and
as Fc(ts,ta),
(1 )
where ts .is the average summer daytime temperature, ta is the
average annual daytime temperature.
The temperature dependence of the net organic emissions from
light-duty vehicles is, of course, the resultant of the. effects of
exhaust and of crankcase and evaporative emissions, weighted in
terms of their relative importance. The factor Fe is less than
unlty when air conditioner usage is not considered. If air
conditioner usage were allowed for, Fe would increase (but
probably not above unity even in extreme cases). The factor Fc
is greater than unity. The two opposing factors tend to diminish
the sensitivity of the net emissions to changes in ambient
temperature. This is shown in the example calculations for the
three study areas; Sections 4.1 to 4.3
3.3.2 SOLVENT EVAPORATION LOSS
There seems to be no reason to believe that solvent
evaporation losses, generally, are .sensitive to changes in ambient
temperature~ Solvents are most commonly used in drycleaning and
degreasing and as vehicles in inks, paints, and other surface.
coating materials. In these applications the amount of organic
material which vaporizes is characteristic of the operation.
We therefore assume a temperature adjustment factor of 1.0 for
emissions in this category.
3.3.3 PETROLEUM PRODUCT STORAGE AND EVAPORATION LOSSES
This source category is . reported under two headings in NEDS
County Emission Reports, namely, IIPetroleum Storage and Transportll
3-9
-------
for industrial point sources and "Gasoline Station Evaporation
Loss" for miscellaneous area sources.
Petroleum storage and transport losses are reviewed in Section
. .
4.3 of "Compilation of Air Pollutant .Emission Factors." Various
types of sources of organic emissions and their dependence on
temperature, vapor pressure, and wind speed, as discussed in that
document, are listed here in Table 3-2.
In these expressions, ambient temperature does not enter
explicitly, but its variations exert their effects via the.
dependence of vapor pressure on temperature. As noted in Section
3.3.~, this effect amounts to 2 percent per degree Fahrenheit,
which can be applied directly to those terms which are proportional
to vapor pressure. On the other hand, the terms. in PI(14.7-P) have
a different temperature relation, which depends. on the magnitude .of
the vQPorpressure. For instance, if the vapor pressure is 11.8
psia, the denominator (14.7-P) is f6ur times as sensitive to
temperature as is the vapor pressure it self, and the sensitivity
. of the entire term, [P/14.7-P)]0.7, is about 7 percent per
degree; wliiT'e, i r P'is r; 4" ps i a, the sensttivity'.is..only.' ahout'3
percent per degree. . .
We must note, however, that these sensitivities are comp~ted
. .
. in terms of the temperature of the bulk liquid in the storage tank.
. .
Sensitivity to ambient air temperature will presumably be somewhat
smaller than this, in most cases, because the tank contents do not
rapidly reach ambient air temperature.
Another factor which tends to reduce the estimate of summer
. emissions is the customary practice of gasoline suppliers to market
less volatile gasoline in th~ hot season, in order to help prevent
problems with vehicle operation which are sometimes caused by
excessive volatility of the fuel.
3-10
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Table 3-2. EFFECTS OF TEMPERATURE AND OTHER FACTORS
ON EMISSIONS OF ORGANICS IN PETROlEUM'STORAGE AND TRANSPORT
I Emission Source Symbol Variation Terms
I
Breathing loss
(fixed-roof tanks) lB [P/(14.7-P)]O.68 ( T)O.SO
Working loss
(fixed-roof tanks) lW P
Standing loss
(floating-roof [P/(14.7-P)]O.7 vwO.7
tanks) lS
Withdrawa 1 loss
(float i ng- roof
tanks) lWD None
Fillin~ loss (variable
Vapor space systems) lV P
I ,
P = true vapor pressure, psia
T = average ambient temperature change from day to night, of
Vw = average wind velocity, miles per hour
Source: Compilation of Air Pollutant Emission Factors, AP-42,
Section 4.3
3-11
-------
In view of the imponderables involved in this estimate, it
seems prudent to assume that the petroleum storage and transport
emissions remain roughly proportional to gasoline vapor pressures
and therefore increase with temperature at about 2 percent per.
degree Fahrenheit.
Standing losses from floating roof tanks are also sensitive to
average wind velocity, increasing as wind velocity increases.
Since wind velocities in summer are likely to be relatively low,
. particularly on days with weather conducive to oxidant formation,
it is likely that this effect corresponds to a slight decrease in .
average emissions during the summer. Since it affects only one of
a number of comparable terms in regard to 'storage emi ss ions, we
assume it can safely be neglected in calculating the temperature
effect.
In regard to emissions from gasoline station evaporation
losses, the following equation is cited in "Compilation of Air
Pollutant Emission Factors," Section 4.4 (before Supplement 7,
since the latter provides no indication of relationship to
, ,
temperature):. ,
LO = 2.22exp(-0.02645 + 0.01155TOF - 0.01226Tv .
+ 0.00246TvPRVP)
(9 )
where
LO
TOF =
Tv
= vapor displacement loss, lb/l03 gal
average dispensed fuel temperature, of
= average temperature of vehicle tank vapor
displaced, of
Reid vapor pressure of gasoline pumped,
taken at storage temperature; psia
PRVP =
If the average Reid vapor pressure of gasoline were 10 psia and the
dispensed fuel were at ambient temperature, the implied sensitivity
of this emission source to ambient temperature would be about 2.4
3-12
-------
percent per degree. However, since most service stations keep
ga~oline in underground storage tanks where it is fairly well
insulated from the ambient air, the temperature sensitivity of
emissions from such stations could be as little as 1.2 percent per
degree. Since 'spillage constitutes a separate source of emissions
from gasoline service stations and is not sensitive to temperature,
we adopt the lower estimate (1.2 percent per aegree) as applying to
gasoline station evaporation losses.
3.3.4
PETROLEUM REFINERIES
We have no direct information as to the variation of petroleum
refinery emissions with temperature. Process emissions are likely
to be relatively constant throughout the year, depending mainly on
the throughput rate. Fugitive losses, however, seem likely to
increase in hot weather as pipes and exposed storage tanks and
, drums are heated by the sun. We assume a temperature sensitivity
of 0.5 percent per degree Fahrenheit. .
3-.3.5 ' CHEMIGAL. MANUFACTURING
We assume that most of the organic emissions from chemical
manufacturing are either process emissions or solvent evaporation
losses, both of which are basically independent of temperature.
We, therefore, assume zero temperature sensitivity, corresponding
to a temperature adjustment factor of 1.0 for these emissions.
3'.3.6
REMAINING SOURCES
Solid waste and incineration, stationary fuel combustion,
carbon black manufacturing, aircraft, diesel-powered vehicles, and
vessels all contribute relatively minor amounts of emissions to the
urban total. There is no obvious reason why any of them should be
3-13
-------
markedly sensitive to changes in temperature. We, therefore,
assume a temperature adjustment factor of 1.0 for each of these
categories.
3.3.7 SUMMARY OF TEMPERATURE CORRECTION FACTORS
The results of the computations discussed in Section 2.3 are
summarized in Table 3-3.
Table 3-3.
TEMPERATURE CORRECTION FACTORS FOR ORGANIC EMISSIONS
Sens it i vity, Correction Factor
Source Category % per of for 100 Increase
.1. Gasoline-powered vehicles
Exhaust emissions See note a
Crankcase.and I
evaporative +2.0 1.22
2. Solvent evaporation
losses o. 1.00
3; Petrol eum" product- 1 os.s" eS... . I
.. i
Storage and transport +2.0 1.22 I
Gasoline station I
evaporation I +1.2 1.13
4. Petroleum refinerie~ . + .5 1.05 I
I
, I
5. Solid waste disposal o. 1.00 j
6. Chemical manufacturing o. 1.00 I
7. Stationary fuel !
combustion o. 1.00
8. Carbon black production o. 1.00 I
9. Aircraft . o. 1.00 .
10. Diesel-powered vehicles o. 1.00
11. Vessels o. 1.00
a Exhaust emissions are to be corrected by direct application of
methodology explained in Section 3.3.1, using Table 3-1.
. 3-14
-------
4.0 AREA STUDY RESULTS
4.1 OUTLINE OR PROCEDURE
The PES approach to estimating ROC emissions consists,
basically, of the following steps:
1.
Retrieve County Emission Summaries for all counties in the
study area from NEDS, and tabulate HC emissions given
therein for each of the source categories listed in Table
1-1 and for any additional categories which appear to be
quantitatively important (contributing, for example, more
than 1 percent of total emissions). Convert the figures
to metric tons per year (MT/yr) if desired.
2.
Estimate what fraction of the ROC emissions from gasoline-
powered vehicles is attributable to exhaust emissions and
what fraction to evaporative emissions. This proportion
will vary, depending on the year of reference in the
study. Emissions data retrieved for this study were
assumed to represent 1976, and the fraction attributable
to exhaust was e'stimated at 0.65. (See Section 4.2.2)
3.
Ascertain emissions for petroleum storage and transport
and for gasoline station evaporative losses, as separate
parts of source category 3 (petroleum product storage and
evaporatio~ losses)..
4.
For each source category or subcategory, estimate
correction factors for methane exclusion, for seasonal
(summer) activity, and for temperature adjustment. (Where
no correction is needed or none is available, the
correction factor is 1.0, not zero). .
a.
For methane exclusion, determine or estimate the
typical methane content of the emissions in terms of
weight percent or in terms of carbon atoms percent
(not as mole percent or vapor volume percent). The
correction factor is (100 - percent methane)/100.
b.
For seasonal activity, estimate average monthly.
activity rate during summer and during the year and
take the quotient. For vehicle categories, the
activity rate index may be vehicle-miles as indicated
by traffic surveys or fuel consumption statistics for
4-1
-------
c.
the study area. For industrial categories, specific
industry production or employment figures may be used,
or more general statistics as to industrial employment
in the study area. For emissions at gasoline sta- .
tions, the same factor used for vehicle categories is
appropriate. For the remaining categories, unless one
of them proves to be an unusually large source,
activity fa~tors may be neglected..
For temperature adjustment, estimate the sensitivity
(St) of emissions in each category to changes in
temperature and determine, from local or national. .
.weather records, the average dail~ maximum temperature
in summer (ts) and year-round (t ). The tempera-
ture adjustment factor is exp[stfts-ta)/100J. ..
(St), given as percent per degree, is negative if . .
emlssions decrease when temperature increases. . (For
exhaust emissions from gasoline-powered vehicles, the
temperature adjustment may be estimated from tables of
emission factors or correction factors given as a .
function of temperature, as in Table 3-1. Evaporative
.emissions from vehicles, however, are treated in the
same manner as other source categories). .
Multiply the NEDS HC emissions for each category by all
three of the correction factors appropriate to that
category, obtaining a relative rate of emissions of . .
reactive organics for the sUlTlTler period, in units of tons.
or metric. tons..per-year.... Sum...the r:elat i-v.e. rates.:.for..a.U'
categories to obtain a relative total rate of organic.. .
emissions for the study area, again in tons or metric tons
per year. This is the desired result. .
The following sections illustrate this procedure as applied to.
the three study areas selected for this project.
5.
4.2 TAMPA BAY STUDY AREA
4.2.1 . TOTAL ORGANIC EMISSIONS
Emissions data for Tampa Bay were obtained from two sources,
. .
. .
the standard NED$. County Emissions Reports and, in addition, the
draft report, "Assessment of the Anthropogenic Hydrocarbon and
4-2
-------
Nitrogen Oxide Emissions in the Tampa Bay Area," prepared by PES
under EPA Contract No. 68-02-2606, Task Order No.2, March
1978.
Table 4-1 shows organic emission rates for each source
category extracted from the NEDS reports for the two counties. In
these NEDS inventories, motor vehicle emissions estimates were .
obtained using emission factors from Supplement 5 of AP-42 (prior
to changes introduced in Supplement 8). Also shown are the totals
for each county of all emissions in the categories listed, the
total for each county as given in the NEDS report, and (by
difference) the amounts of emissions in categories not included in
. . . .
the list. Other columns show the total area emissions in'each
category in short tons per year and metric tons per year, and the
percentage (by weight) of total emissions ,contributed by each
source category.
The PES survey of hydrocarbon emissions in the Tampa Bay Area
gave results differing from the NEDS data in two ways. The major
difference resulted from the. use of MOBILE-1 to calculate the
, , '
emissions from highway vehicles, which decreased the amount'"from
gasoline vehicles by 6,700 MT per year. Various other emissions
that had not been entered in ,the NEDS data base partially offset
this, so that the total increased from 71,400 to 74,700 MT per
year. Details of the revisions indicated by the PES survey are
. ,
given in Table 4-2. The storage-and-transport subcategory was
increased from zero to 6,100MT/yr by emissions calculated for
storage tanks, and industrial point sources of solvent evaporation,
entered as manufacturing rather than chemical manufacturing, came
to 2,700 MT/yr instead of zero. Aircraft emissions were estimated
lower than in the NEDS report, but emissions from vessels more than
made up the difference. Other categories increased were solid
waste disposal and stationary fuel combustion, which includes fuel
used in electric generating plants.
4-3
-------
Table 4-:-1. TOTAL ORGANIC EMISSIONS, TAMPA BAY STUDY AREA
,EmissionRates '
"
,H ill sborough Pine11as Total Percent,
Source Category tons/yr toris/yr tons/yr MT lyr of Total
1. Gasol.ine veh,i c 1 es 29,500 24,900 54,400 49,500 69
.2. Solvent evaporation 4,500 5,200 9,700 8 ,800 ' 12
3. Petroleum product
evaporation
a. Storage transport 0 0 0 0
b. Gaso 1 i ne 'stat ions' ,3,100 3,300 6,,400 5;800 8
4. Petrol euin refineries 0 0 0 0
"
5. Sol idw,aste disposal 400', ,400 400
6. Manufacturing 0 0 0 0
7. Stat i ohary fuel
combustiona 100,' 300, 400 400 1
8. Carbon black '
"
, product'i'on~ ' -" 0-- '0...'.- 0-- 0.,,'
9. Aircraft 2,400 ' ,300 2~700 2;400 3
10. Diesel vehicles' 800 ,900' ,1,700 1 ; 500, 2
11. Vessels ' 1,100 ,,300 1,400 1,300 2
Tota 1, this ,1 i st ' 41,900 35,200 77,100 70,100 '98
..
Total, NEDS 42,800 35,700 78 , 500 71,400 100
Rema~nder unlisted' 900 500, 1,400 " 1,300 2
a This includes fuel ,burned in generating electricity.
4-4
-------
Table 4-2.
REVISED ORGANIC EMISSIONS, TAMPA BAY AREA
NEDS PES
Estimate Estimate Percent
Source Category MT /yr MT/yr of Total
1. Gasoline vehicles 49,500 42,800 57
2. Solvent evaporation 8,800 8,800 12
3. Petroleum product
evaporation
a. Storage and transport 0 6,100 8
b. Gasoline stations 6,800 5,400 7
4. Petroleum refineries 0 0
5. Solid waste disposal 400 800 1
6. Manufacturinga 0 2,700 4
7. ~tationary fuel
combustion 400 800 . 1
8. Carbon black production 0 0
9-. A-irtra.ft .. 2,400~ 900- . 1-
10. Di esel fuel vehicles 1,500 1,500 2
11. Vessels 1,300 3,300 4
Remainder unlisted 1,300 1,600 2
Total 71 ,400 74,700
a This category has been broadened to include all recognizable
industrial solvent use emissions.
4-5
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4.2.2
PARTITION OF GASOLINE-POWERED VEHICLE EMISSIONS
The MOBILE-1 computer program calculations described in
Section 3.3.1 were also used to determine the proportions of
exhaust and evaporative gasoline vehicle emissions, since those
used to generate the NEDS estimates were not known. In Table 3-1
the exhaust reactive organic emissions are listed for various temp-
eratures. The evaporative emissions calculated in the same program
were invariant with temperature. The same vehicle type mixture
used for exhaust emissions was used to calculate the overall com-
bined evaporative emissions, 2.20 g/mi. The ratio of exhaust to
evaporative emissions then varies from 74/26 at O°F to 64/36 at .
110°F. Most of the change occurs in the lower part of the tempera-
. .
ture range, however. In the temperature ranges used in this study
a value of about 65/35 is suitable.
When these factors are applied to the total of 42,800 MT of
organic emissi'ons from gasoline-powered vehicles, subcategory
totals are calculated to be 27,900 MT attributable to exhaust
emissions, 14,900 to evaporation. (These numbers are carried to
. .
new lines as separte subcategorfes under category l~ gasonhe-
powered vehicles).
4.2.3 PETROLEUM PRODUCT EVAPORATION LOSSES
The NEDS listing for the study area indicated no emissions
attributable to evaporation frOm storage tanks and trucks used with
gasoline and other petroleum products. The PES survey, however,
did identify a substantial number of storage tanks and provided an
estimate of 900 MT of organic emissions annually from. this
subcategory.
A re-estimate of gasoline station evaporation losses by PES
yielded a reduction of 400 MT/yr in these emissions, as indicated
in Table 4-2.
..4-6
-------
4.2.4 CORRECTION FACTORS
4.2.4.1
Factors for Exclusion of Methane
The determination of reactive organic emissions requires
information on the methane content of the total organic emissions
(cf. Section 2.1). In the absence of specific information about
the composition of emissions in the study area, methane fraction~
as determined in other studies for comparable emissions are used,
taken from Table 2-1.
4.2.4.2 Summer Activity Factors
4.2.4.2.1
Vehicle Activity Factors
The seasonal aspect of vehicle activity in the Tampa Bay area
was investigated through review of traffic information, furnished
to PES originally by the Florida Department of Transportation for
use in the emissions survey project previously cited. Vehicle
counts were taken routinely at 12 selected stations representing
area traffic and were compiled monthly over a period of several
years. Using total monthly count as an index of vehicle activity,
we. est.imate" the:. factor. to. be.. approximate] y 0.98. Thi s factor is.
applied to both subcategories of source category 1, (gasoline- .
powered vehicles), and also to subcategory.3b (gasoline station
evaporation losses) and category 10 (diesel-powered vehicles).
4.2.4.2.2
Industrial Activity Factors
As explained in Section 3.2, most industrial sources of
organic emissions seem to have no marked seasonal variations in
activity. Since the PES survey provided no indications of such
variations occurring in the study area, an activity factor of 1.0
has been assigned for the industrial emissions category.
4-7
-------
4~2.4.2.3 Other Activity Factors
In the absence of any indications of marked seasonal varia-
tion, remaining activity factors have been assigned a value of 1.0.
4.2.4.3 Temperature Adjustment Factors
The temperature differential between summer and winter in
Florida is rather small in comparison with many other parts of the
United States, particularly inland areas such as St. Louis and.
Buffalo. Climatological data for the Tampa Bay area show that the
average daily maximum temperature for the summer quarter, ts' is
gO°F while the average for the entire year, ta' is 82°F. The
differential, ts - ta' is only 8°F.
4.2.4.3.1
Exhaust Emissions
By the procedure described in Section 3.3.1 and values inter-
polated from. Table 3-1, we find the correction factor for 82°F to.
gO°F for exhaust emissions to be 0.98.
4.2'. 4,. J~ 2. Veh-i'cle"EvapoY'at-i-ve." Emci.s s.f.ons..."' .
From Section 3.3.1, we apply Equation 1, which predicts the
temperature adjustment factor as
Fc(80,72) = exp(0.02 x 8), or 1.16.
4.2.4.3.3
Solvent Evaporation' Losses
As explained in Section 3.3.2, we use here an adjustment
factor of 1.0.
4.2.4.3.4
Petroleum Product Storage and Evaporation Losses
As shown in Section 3.3.3, it is reasonable to assu~e for this
type of emission the same sensitivity to temperature as for vehicle
evaporative emissions. We, therefore, assign a value of 1.16.
4:"8
-------
4.2.4.3.5 Gasoline Station Evaporation Losses
In accord with Section 3.3.3, we assign a sensitivity of 1.2
percent per degree, which leads to a factor equal to exp(O.012 x 8),
or 1.10.
4.2.4.3.6 Chemical Manufacturing
In accord with Section 3.3.5, we assign a temperature adjust-
ment factor of 1.0. (This category includes solvent losses from
other industries besides manufacture of chemicals.)
4.2.4.3.7 Remaining Sources
In accord with Section 3.3.6, all remaining sources receive a
temperature adjustment factor of 1.0.
4.2.4.4 Summary of Correction Factors
Table 4-3 presents a compilation of the correction factors for
Tampa Bay, as discussed in preceding sections.
4.2.5 FINAL COMPUTATIONS AND TABULATIONS
Table 4-4 shows the results of this procedure for the Tampa
Bay study area. Also shown, for ready comparison, are the annual
emissions of reactive organics, computed by combining the annual
emissions given in Table 4-2 with the methane correction factors
given in Table 4-3.
The comparison ~hows that the net effects of seasonal correc-
tions, for this study area, are rather small; total emission rates
in summer are larger than the annual rates, but only by 2,400 MT/yr
out of 72,400, approximately 3 percent. Exhaust emissions are,
about 4 percent lower in the summer, but automotive evaporation is
increased by about 14 percent, so that the net increase in
gasoline-powered vehicle emissions is 1,000 MT/yr, or about 2
percent. The order of importance of the various source categories
is unaffected by the seasonal corrections.
4-9
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Table 4-3. CORRECTION FACTORS FOR TAMPA BAY
Correction Factors
Source Category Methane Act i vi t.v Temp. Overall
1. G~soline-powered vehicles.
a. Exhaust emissions
(65%) 0.95 0.98 0.98 0.91
b~ Evaporative emissions
(35%) 1.00 .98 1.16 1.14
2. Solvent evaporative
losses 1.00 1.00 1.00 1.00
3. Petroleum product
evaporation
a. Storage and transport 1.00 1.00 1.00 1.00
b. Gasoline station
losses 1.00 .98 1.10 1.08
4. Petroleum refineries N/A N/A N/A N/A
5. Solid waste disposal .66 1.00 1.00 . .66
6. Manufacturing 1.00 1.00 1.00 1.00
7. Stationary fuel
combustion .85 . 1.00 1.00 .85
8. Carbon black production .62 1.00 1.00 .62
9. Aircraft .93 1.00 1.00 .93
10. Diesel-powered vehicles .94 .98 1.00 .92 .
11. Vessel s . .91 1.00 .1.00 .91
4-10
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Table 4-4.
REACTIVE ORGANIC EMISSIONS, TAMPA BAY
Emissions
Summer Annua 1
Source Category MT /yr % MT lv r %
1. Gasoline-powered vehicles 42,400 (61) 41,400 (61)
a. Exhaust emissions 25,400 37 26,500 39
b. Evaporative emissions 17,000 24 14,900 22
2. Solvent evaporative
losses 8,800 13 8,800 14
3. Petroleum product
evaporation
a. Storage and transport 7 , 100 1 6,100 1
b. Gasoline station
losses 5,800 9 5,400 8
4. Petroleum refineries 0 0 0 0
\
5. Solid waste disposal 500 1 500 1
6. Manufacturing 2,700 4 2,700 4
7. Stationary fuel '"
combustion 700 1 700 1
8. Carbon black production 0 0 0 0
9. Ai rcraft 800 1 800 1
10. Diesel~powered vehicles 1,400 2 1,400 2
11. Vessels 3,000 5 3,000 5
Remainder unlisted 1,600 2 1,600 2
Total 74,800 100 72,400 100
4-11
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r~--.
4.3 ST. LOUIS STUDY AREA
4.3.1 ANNUAL ORGANIC EMISSIONS
Emissions data for the St. Louis area were obtained from NEDS
Emissions Reports for seven counties and the City of St. Louis. .
Totals by source category are shown in Table 4-5, the total for all
categories coming to nearly 300,000 MT/yr. Emission rates for
reactive organics, also shown in Table 4-5, were calculated by
multiplying the total organic emissions entries by the correspond~
ing methane correction factors shown in Table 4-3; the difference
in totals ind.icates that methane emissions amounted to about 4,000
MT Iyr.
Some of the categories listed in table 4-5 are slightly.
different from those given for Tampa Bay in Tabl e 4-1. The changes
were made to make the category list cover all the emissions in the
NEDS list; thus, we refer to "petroleum industry" rather than
"petroleum refineries" and to "other industries" instead of "manu-
facturing." This allows miscellaneous small items shown in Table
4-1 as ~Remainder Unlisted" to be absorbed in the new categories.
The category, gasoline-powered vehicles, has .been
into subcategories ~ and ~ according to the same logic
Section 4.2.2. .
part i ti oned .
discusse.d in
4.3.2 SUMMER ACTIVITY FACTORS
Vehicle activity factors were estimated from monthly reports
of gasoline sales volume provided by the State of Missouri Depart-
. .
ment of Revenue. These reports dealt with sales throughout the
entire State of Missouri ; it is assumed that they provide a
reasonable estimate of seasonal traffic variation in the study
area. The factor thus derived was 1.04. It was applied to
category 3b, gasoline station evaporation losses, and category 10,
diesel-powered vehicles, as well as to exhaust emissions and
evaporative emissions from gasoline-powered vehicles.
4-12
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Table 4-5. ORGANIC EMISSIONS, ST. LOUIS STUDY AREA
Emission Rates. MT/vr %a
Source Cateqory Total Reactive
1. Gasoline-powered vehicles 121,700 (120,100) (41)
a. Exhaust emissions
(65%) (79,100) 77 , 500 26
b. Evaporative emissions
(35%) (42,600) 42,600 15
2. Solvent evaporative
losses 78,500 78,500 27
3. Petroleum product
evaporation
a. Storage and transport 33,600 33;600 11
b. Gasoline station
losses 11 ,300 11 ,300 4
4. Petroleum industry 11,400 11,400 4
5. Solid waste disposal 4,000 2,700 1
6. Other industries 23,200 23,200 8
7. Stat.ionary .fue,l, . ..
combustion 2,800 2,400 1
8. Carbon black production 0 0
9. Ai rcraft 2,800 2,600 1
10. Diesel-powered vehicles 4,200 3,900 1
11. Vessels 3, 100 2,800 1
Total 296,700 292,600 100
a Percent of total reactive emissions
4-13
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Because the specific NEDS point source reports which were
examined (Section 3.2) indicated no consistent increase or decrease
(in summer) of throughput or production in solvent-using or
petroleum-related industry, we have chosen to use activity factors
of 1.0 for all emission categories except those related to vehicle
use. We note, however, that fluctuations of 5 to 10 percent in
. manufacturing employment, generally, are not uncommon within a
given year. Some of this fluctuation may have a seasonal basis; in
particular, manufacturing tends to decline in winter in cold
cl imates.
4.3.3 TEMPERATURE ADJUSTMENT FACTORS
Climatological data for the St. Louis area show that the
average daily maximum temperature for the summer quarter, ts' is
86°F, while the average for the entire, ta' is 66°F; thus ts - ta
is 20°F.
Using Table 3-1 and proceeding as explained in Section
4.2.4.3.1, we find the correction term for vehicle exhaust
emiss ions.. for- these--temper.atures..to.. be-0..94......
The factor for evaporative emissions for gasoline-powered
vehicles and for petroleum product storage and evaporation losses.
is calculated by equation 1,.Section 3.3.1, as Fc (86,66) =
exp (0.02 x 20) = 1.49. Similarly, the factor for gasoline station
. evaporation losses is exp (0.012 x 20) or 1.27, and that for
petroleum industry is exp (0~005 x 20), or 1.10~
All other sources are assigned a temperature adjustment factor
of 1.0. .
4.3.4 FINAL COMPUTATIONS AND TABULATION
Table 4-6 summarizes the factors for activity and temperature
corrections and lists the estimated reactive organic emission rates
4-14
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for summer. These are obtained by multiplying the annual reactive
emission rates shown in Table 4-5 by both factors.
Comparison of results in Tables 4-5 and 4-6 shows that the
total rate of emissions in summer is about 41,000 MT/yr greater
than the annual rate of 293,000 MT/yr. A large share of the
increase is attributable to the increased estimate of petroleum
product storage and transport losses, which increases from 33,600
to 50,100 MT/yr. Evaporative emissions from automobiles also
increase by 23,000 MT/yr; this figure is sensitive not only to the
factor taken for temperature adjustment but also to the percentage
assumed to be evaporative, in partitioning the total emissions from
the gasoline-powered vehicles.
4.4 BUFFALO STUDY AREA
4.4.1 ANNUAL ORGANIC EMISSIONS
Emissions data from the Buffalo area were obtained from a NEDS
Emission Report for the Niagara Air Quality Control Region,
comprising the counties of Niagara and Erie, in New York. Totals by
source category. are shown.. in, Tab.le.4-7; the..total. for.all..
categories, including methane, is about 120,000MT/yr. Emission
rates for reactive organics, also shown in Table 4-7, were
calculated by multiplying the total organic emissions entries by
methane correction factors from Table 4-3. The total methane
correction is 2,900 MT/yr, slightly more than 2 percent of the
total.
Categories listed in Table 4-7 are the same as those listed in
Table 4-5; for discussion, refer to Section 4.3.1.
4.4.2 SUMMER ACTIVITY FACTORS
Vehicle activity factors were estimated from monthly reports
of gasoline sales volume for Erie and Niagara Counties, provided by
the Energy Office of the State of New York. These reports
4-15
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Table 4-6.
EMISSIONS OF REACTIVE ORGANICS) SUMMER) ST. LOUIS
I Emissions
Factors (Summer)
Source Category Activity Temp. MT/yr %
1. Gasoline-powered vehicles (139,000) (42)
a. Exhaust emissions 1.04 0.94 73,500 22
b. Evaporative emissions 1.04 1.49 66,000 20
2. Solvent evaporation I
I
losses 1.00 1.00 78,500 24
3. Petroleum product I
I
.1
evaporation I
a. Storage and transport 1.00 1.49 50,100 15
b. Gasoline station
losses 1.04 1.27 14,900 4
4. Petroleum refineries 1.00 1.10 12,500 4
5. Solid waste disposal 1.00 1.00 2,700 1
6. Manufacturing 1.00 1.00 23,200 7
7. Stationary fuel
combustion 1.00 1.00 2,400 1
8. Carbon black production N/A NII( '- 0 -, 1
9. Ai rcraft 1.00 1.00 2,600 1
10. Diesel-powered veh i c l.es 1.04 1.00 4,100 1
11. Vessels 1.00 1.00 2,800 ' 1
Total 333,300 . 100
4-16
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Table 4-7. ORGANIC EMISSIONS, BUFFALO STUDY AREA
Emission Rates. MT/yr
Source CateClOry Total Reactive %a
1. Gasoline-powered vehicles 50,900 (49,200) (42)
a. Exhaust '~mi5sions
(65%) (33,100) 31,400 26
b. Evaporative emissions
(35%) (17,800) 17 ; 800 15
2. Solvent evaporative
losses 49,100 49,100 42
3. Petroleum product
evaporation
a. Storage and transport 0 0
b. Gasoline station .1
losses 4,500 4,500 4
4. Petroleum industry 1,600 1,600 1
5. Solid waste disposal 2,300 1,500 1
6. Other industries 7,600 7,600 6
- 7.-- Stat.i-onary- fuel. -
combustion 1,300 1,100 1
8. Carbon black production N/A N/A N/A
9. . Ai rcraft 1,200 . 1,100 1
10. Diesel-powered vehicles 800 800 1
11. Vessels 900 800 1
Total 120,200 117,300 100b
a- Percent of total reactive emissions
b Slight discrepancies in the total may be caused by rounding
4-17
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i nd i cated that the rate ,of gasoline consumpt ion in summer ~as about
1.02 times the annual rate. This factor was applied to categories
, ,
la, 1b, 3b, and 10, all related to vehicle activity. Other cate-
gories were assigned activity factors of 1.0, following the
~easoning set forth in Section 4.3~2.
4.4.3 TEMPERATURE ADJUSTMENT FACTORS
, ,
Climatological data for the Buffaloar~ashow that the Bverage
daily maximum temperature for the summer quarted is 77°F while the
, '
, '
, '
,year-round average is 56°F, an incr~mentof 21°F. USing Table 3~1,
the correction factor for vehicle exhaust emissions is found to be "
0.93. This is smaller than the corresponding factor for St. Louis
(0.94; refer to Section 4.3.3) not only be~ause of the slightly,
, , '
larger temperature increment in Buffalo (21° versus 20°F) but also
because of the lower overall temperature~ 56° versus 66°F).
, ,The factor for ev aporat i ve emi ss ions of gaso 1 i ne- powered,
vehicles and for petroleum product storage and evaporation "losses' '
is 1.52; for gasoline stati.:>nevaporation losses, 1.29; and for '
, '
pet~oleum industry, 1.10. (Calculations are analogous to t~ose
expl ai ned in Sect ion 4~ 3.3. )
, '
All other sources are assigned a temperature adjustment factor
of 1.0.
'4.4.4 FINAL COMPUTATIONS AND TABULATION
Table 4.8 summarizes the factors for activity and temperature
corrections and 1 ists the estimated reactive organic emission rates
for summer. These are obtained by multiplying the annual reactive
organic emission rates shown in Table 4-7 by both factors.
Comparison of Tables 4-7 and 4~8 shows an increase in total
reactive organic emissions in the sunmer of about 10,000 MT/yr~
4-18
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Tab 1 e 4-8.
EMISSIONS OF REACTIVE ORGANICS, SUMMER, BUFFALO
Emissions
Factors (Summer)
Source CateQorv Activity Temp. MT /vr %
1. Gasoline-powered vehicles (57,400) (45)
a. Exhau5t emissions 1.02 0.93 29,800 23
b. Evaporative emissions 1.02 1.52 27,600 22
2. Solvent evaporation
losses 1.00 1.00 49,100 39
3. Petroleum product-
evaporation
a. Storage and transport 1.00 1.52 0 0
b. Gasoline station
1 asses - 1.02 1.29 5,900 5
4. Petroleum refineries 1.00 1.10 1 ~800 1
5. Solid waste disposal 1.00 1.00 1,500 1
6. Manufacturing 1.00 1.00 7,600 6
7. Stationary fuel
combustion 1.00 1.00 1,100 1 ,-
- 8". Carbon ~l~tk production -' NjA--' . N/A': .. N/A" - -
9. Aircraft 1.00 1.00 1,100 1
10. Diesel-powered vehicles 1.02 1.00 800 1
11. Vessels 1.00 1.00 800 1
Total 127,100 100a
.
a Slight discrepancies in the total may be due to rounding.
4-19
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This is only a 9 percent increase, compared to 14 percent for St.
Louis, and is largely due to evaporative emissions from gasoline
vehicles. It should be pointed out, however that in NEDS there are
no reported emisions for petroleum product storage and transport in
the Buffalo area. This category accounted for 11 percent of annual
emissions and 15 percent of estimated summer emissions for St.
Louis.
. 4-20
-------
"- ,
5.0 DISCUSSION AND CONCLUSIONS
The results described in Section 4.0 show that the effect of
summer conditions can be either an increase or a decrease in
emissions relative to the annual average, depending on the
particular circumstances of the region involved. It is clear,
also, that the results for a given region depend on what values are
assumed for various parameters required in the computations, and on
other assumptions having uncertain validity. Some of these
assumptions are reviewed in this section.
5.1
PARTITION OF VEHICULAR EMISSIONS
The differences in temperature sensitivity of various modes of
emission of organics from light-duty gasoline-powered vehicles were
described in Section 3.3.1. Since the emission factors for the
various modes are all composites, based on different values for
many different model-years and makes, the values of these emission
factors must be continually changing as the composition of the
vehicle population changes. Vehicle air conditioner usage also may
have a significant effect in some areas.
Vehicle air conditioner usage was not known but would probably
have negligible effect on Tampa Bay emissions. If our rough
estimate of an air conditioner usage factor of 1.07 were applied to
St. Louis exhaust emissions, it would increase the calculated total
reactive organic emissions in that city by 5,100 metric tons per
year, or less than 2 percent.
It appears that ~he uncertainty as to the correct partition of
vehicle emissions will contribute some uncertainty in the
determination of temperature corrections in any urban area subject"
to photochemical oxidant air pollution.
5-1
-------
5.2 TEMPERATURE VARIATION IN STORED LIQUIDS
As explained in Section 3.3, we have assumed that temperature
effects on storage and transport of petroleum products amount to
about 2 percent per degree (Fahrenheit), which is the same as the
temperature sensitivity of vapor pressure of petroleum products.
Nevertheless, some storage tanks may exhibit much higher tempera-
ture sensitivity (up to 7 percent per degree, at least), while
others may have less, because of different systems of vapor
control. Again, volatility isa function not of ambient
. temperature, but of the temperature of the stored liquid. We know
of no information on the actual seasonal variation in tank
temperatures through the year, but they may be expected to be at
. .'
least somewhat less than variations in ambient temperature. The
assumed sensitivity (2 percent per degree) may be reflected in
errors in the estimated emissions.
Thus, for St. Louis, a sensitivity of 3 percent per degree
would increase the summer emissions estimate by another 10,000 .
MT/yr; or 3 percent of the total reactive organic emissions.
5.3 EFFECT OF ECONOMIC CONDITIONS
Act i vity factors are based on the concept that emi ssi ons vary.
cyclically through the year in r~sponse to cyclic variations of the
activities that produce them. The cyclic hypothesis, however, is
an imperfect one in every instance; activity factors based on it.
will be found to vary from year-to-year, as the rate of such
activities is confounded with short-term fluctuations and long-term
. .
trends which have no detectable seasonal basis. If a gasoline
shortage should occur during the summer in an area with much summer
tourist travel, a substantial distortion of normal seasonal traffic
emissions might be encountered. Other economic disturbances can
cause reduced employment and reduced emissions in manufacturing
5-2
-------
industries. Thus, even an established seasonal pattern is not
necessarily a reliable tool for prediction of the seasonal effect
in any given year.
5.4
INTERPRETATION OF NEOS CATEGORIES
A problem which can introduce uncertainty into the estimation
of summer emissions arises from the fact that not all suppliers of
information to the NEOS data base have been completely consistent
in their assignment of particular source e~issions to the available
emissions categories. In the case of the Buffalo study area, no
emissions were reported in the category of losses from storage and
transport of petroleum compounds, although it seems hardly credible
that there should be no such facilities in an urban area as well
populated as the "Niagara Frontier.11 . On the.other hand, some 8,000
tons per year have been listed under "Other/not classified;" if
these were assumed to be storage and transport losses, the summer
emissions total for Buffalo would be increased by another 4,000
tons or about 3 percent of the organic emissions total. In the
particular case of Buffalo, this would raise the summer emissions
from-lOa- percent. to" 10.3-' percent. of"the.'annuaT'emtss.ions. .
Again, for Tampa Bay, the NEOS summaries reported no "gasoline
sta evap lossll under miscellaneous area sources, a category which
accounted for 11,000 MT/yr in St. Louis. In the Tampa Bay emis-
. .
sions survey, PES identified losses from gasoline service stations
in Tampa Bay, arriving at a total of 5,400 MT/yr. The NEOS sum-
maries do carry, however, under transportation area sources, an
. item of nearly 6,000 MT/yr titled IIgas handling evaporation 10ss,1I
which does not appear in the summaries for St. Louis and Buffalo.
Thus, care is needed in the interpretation and transcription
of the data presented in the NEOS summaries.
5-3
-------
5.5 CONCLUSIONS
The findings set forth in Section 4.0 show that emission rates
of reactive organics in urban areas in summer could be either
greater or less than the year-round average emission rates. In
general, emissions from gasoline-powered vehicle exhausts decrease
with increasing temperature, while evaporative emissions from
. .
vehicles, evaporation of petroleum products (in storage, transport,
and marketing), and perhaps petroleum refinery operations increase
with increasing temperature. The balance of these effects
determines whether the net effect in summer will be an increase or
a decrease.
On the whole, it may be expected that, in areas like Tampa
Bay, where motor vehicles generate a relatively large share of the
organic emissions, emissions will be very near the annual average
in summer. In more highly industrial locations such as St. Louis,
emissions are likely to be higher than average in summer~
Methane emissions in the areas studied were estimated to be
about 2 percent of the total organic emissions.
Corrections for seasonal variations in activities which'cause
organic emissions did not cause any significant alterations in the
order of relative importance of various emissions source
categories. In all the study areas investigated, at least 80
percent of the reactive organic emissions were generated by three
categories: . gasoline-powered vehicles, solvent evaporation from
area sources, and evaporation of petroleum products.
A methodology for estimati,ng summer emission rates of reactive
. .
organics has been outlined, and formulas and tables have been
presented for computing temperature corrections for emissions from
various source categories.
5-4
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6.0 ACKNOWLEDGEMENTS
PES wish~s to thank the following persons, who furnished
information essential to the completion of our assignment:
J. Courcier -- EPA,
J. Ulevicus -- EPA,
A. Camproni --. EPA,
Refion 1,
Region 1,
Region 1,
Boston, Massachusetts
Hartford, Massachusetts
Boston, Massachusetts
L. Heckman -- EPA, Region 2, New York, New York
M. Davis -- EPA, Region 2, New York, New York
D. Durst -- EPA, Region 7, Kansas City, Missouri
T. Gillard -- EPA, Region 7, Kansas City, Missouri
B. Bernaski, Department of Environmental Conservation,
New York, New York
Ansaldo, New York Department of Transportation, Albany,
New York
J. Edwards, New York State Energy Office, Albany, New York
T. Parks, State EPA, Boston, Massachusetts
Mrs. Chambers, Department of Revenue, St. Louis, Missouri
In addition, we wish to express our appreciation for the use
'of'information on T'ampa Bay'to R'.' McHenry'~" EPA. Region' 4.,~"
Atlanta, Georgia, project officer for Contract No. 68-02-2606,
Task Order No.2: "Assessment of the Anthropogenic Hydrocarbon
and Nitric Oxide Emissions in the Tampa Bay Area."
6-1
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TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
1. REPORT NO. EPA-450j3-78-023 12. 3. RECIPIENT'S ACCESSION NO.
4. TITLE AND SUBTITLE 5. REPORT DATE
Seasonal Variations in Organic Emissions for June 19.78
Significant Sources of Volatile Organic Com- 6. PERFORMING ORGANIZATION CODE
pounds
7. AUTHOR(S) 8. PERFORMING ORGANIZATION REPORT NO.
Lowell G. Wayne and Clarence L. Bovd
9. PERFORMING ORGANIZATION NAME AND ADDRESS 10. PROGRAM ELEMENT NO.
Pacific Environmental Services, Inc.
1930 14th Street 11. CONTRACT/GRANT NO.
Santa Monica, California 90404 68-02-2583
. Assignment No. 6
12. SPONSORING AGENCY NAME AND ADDRESS 13. TYPE OF REPORT AND PERIOD COVERED
U.S. Environmental Protection Agency Final Report
Office of Air and Waste Management 14. SPONSORING AGENCY CODE
Office of Air Quality Planning and Standards 200/4
Research Triangle Park, N.C. 27711
15. SUPPLEMENTARY NOTES
16. ABSTRACT
Discrepancies between rates of emission of VOC determined on an annual
basis and those occurring in summer were studied, using as example areas
Tampa Bay, St. Louis and Buffalo. Reactive VOC's were estimated by
correcting total VOC's for methane content. A methodology for
adapting VOC inventories to reflect summer emissiQn patterns is
outlined. The indicated increase in rate of emissions due to summer
conditions ranged from 3 to 14 percent, as applied to the estimated
annual non-methane emissions.
Corrections for methane and for summer conditions did not appreciably'
'change the 'order of import'ance' of' 'emiss:i:oIl"'source"dcategorie.s..- ,,' " ..,
The effect of temperature is the principal cause of increased VOC
emissions in summer. At least 80 percent of VOC's came from gasoline-
powered vehicles and from evaporation of solvents and petroleum
products.' Vehicle exhaust emissions, decrease as ambient temperature
increases, but this effect is not large enough to counterbalance the
enhanced gasoline losses from marketing and storage at summer tempera-
tures. Improved controls on evaporative emissions could change the
relative importance of exhaust and evaDorativp effect~
-
17. KEY WORDS AND DOCUMENT ANAL YSIS
a. DESCRIPTORS b.IDENTIFIERS/OPEN ENDED TERMS C. COSA TI Field/Group
Air pollution 7A
Emissions
Exhaust gases
Organic compounds
18. DISTRIBUTION STATEMENT 19. SECURITY CLASS (This R.?pol"t) 21. NO. OF PAGES
Unclassified 58
Release Unlimited 20. SECURITY CLASS (This page) 22. PRICE
pnclassified
EPA Form 2220-1 (Rev. 4-77)
PREVIOUS EDITION IS OBSOLETE
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