OMSAPC-78-1
II-A-3
Attachment II
An Assessment
of
The Potential Air Quality Impact
of
General Aviation Aircraft Emissions
Prepared by
Bruce C, Jordan
June 17, 1977
Office of Air Quality Planning and Standards
Environmental Protection Agency
Research Triangle Park, North Carolina, 27711
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OMSAPC-78-1
II-A-3
Attachment II
An Assessment
of
The Potential Air Quality Impact
of
General Aviation Aircraft Emissions
Prepared by
Bruce C. Jordan
June 17, 1977
Office of Air Quality Planning and Standards
Environmental Protection Agency
Research Triangle Park, North Carolina, 27711
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Table of Contents
List of Tables ii
List of Figures iii
INTRODUCTION 1
AIRCRAFT EMISSIONS 2
REVIEW OF HISTORICAL STUDIES AROUND AIRPORTS 3
Northern Research and Engineering Corporation Study ... 3
Environmental Protection Agency Study In Support of
Aircraft Emission Standards 9
Geomet Validation Study 13
Other Studies Using Geomet Model 19
Studies Conducted by Argonne National Laboratory .... 21
Studies Conducted by Systems Applications Incorporated . 23
OVERVIEW OF AIRCRAFT STUDIES 24
Comparison Between Emissions from General Aviation
Aircraft and Other Aircraft 25
Mathematical Model of CO Impact at Van Huys Airport . . 35
CONCLUSIONS 39
REFERENCES 41
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List of Tables
Table Title
1 Percentage of Total Emissions of Various
Air Pollutants from Aircraft Operations ... 4
2 Summary of Six Months of Air Quality
Observations at Washington National Airport . 17
3 Estimated Emissions by Various Aircraft
Operations During 1975 , 27
4 Estimated Emissions During 1974 from
General Aviation Aircraft Operations 29
5 1973 HC Emissions from Selected Sources
in Baltimore AQCR 34
11
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List of Figures
Title Page
NCL Isopleths at Los Angeles International:
Aircraft Sources 7
2 N02 Isopleths at Los Angeles International:
Total Emission Sources 8
3 Vicinity of Los Angeles International:
Percent Contribution by Aircraft to
Carbon Monoxide Levels 10
4 NO Isopleths in the Vicinity of Los Angeles
International: Aircraft Sources 1970 .... 11
5 NO Isopleths in the Vicinity of Los Angeles
International: Aircraft Sources 1980 .... 12
6 NO Isopleths in the Vicinity of Chicago-
O'nare International: Aircraft Sources
1980 H
7 Hydrocarbon Isopleths in the Vicinity of
Los Angeles International: Aircraft Sources
1980 15
8 Mean Annual Predicted Values of NO for
Salt Lake City 20
9 Estimated NO Isopleths in the Vicinity of
Los Angeles tnternational as the Result of
General Aviation Aircraft 1980 31
10 Maximum 1-Hour CO Concentrations as a
Function of Downv/ind Distance 37
11 Maximum 8-Hour CO Concentrations as a
Function of Downwind Distance 38
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INTRODUCTION
A number of studies have been conducted to assess the impact of
aircraft emission on air quality. Most of these studies have been
oriented toward the larger airports where the air traffic is heavily
dominated by transport (airline) type aircraft. An important segment of
the air transportation system is the group of aircraft-often referred to
as general aviation. This latter group includes a wide variety of
aircraft v/hich are used for business, training and pleasure flying.
Emission standards for general aviation aircraft were promulgated
in 1973 and will become effective in 1979. Therefore, it is prudent, at
this time, to review any new information which has developed since 1973
to determine if current emission standards are adequate to protect the
health and welfare of the general public or if any changes in these
standards are needed.
In this paper, an attempt is made to place into perspective the
emissions from general aviation aircraft, and their potential impact on
?>ir qualify. Tv/o approaches are used in this assessment. General
aviation aircraft emissions are compared on a national, regional and
local basis, with emissions from other categories of aircraft. Historical
studies are used to relate the potential impact of emissions from general
aviation aircraft to that noted from studies oriented around other types
of aircraft. Mathematical modeling of ? busy general aviation airport
is then used to more specifica.ly assess the impact of general aviation
aircraft on air quality in the vicinity of the airport.
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2
AIRCRAFT EMISSIONS
On a nationwide basis, aircraft are estimated* to contribute the
following percentages of the emission of various air pollutants:
Participates l.OOS
Carbon Monoxide 0.86%
Hydrocarbons 2M%
Nitrogen Oxides 0.725!
The above percentages are for all aircraft including transport
(airline, etc.), military, and general aviation. Similar percentages
for general aviation aircraft alone are shown below:
Particulatas 0,07%
Carbon Monoxide 0.2755
Hydrocarbons 0.20?,
Nitrogen Oxide 0.04&
The above figures are Indicative that on a nationwide basis, aircraft
contribute a relatively small percentage of the total emissions, and
that general aviation aircraft emissions constitute only a small portion
of the total aircraft emissions. With these small percentages, it is
not meaningful (or possible within the accuracy of any existing air
quality models) to discuss the impact of aircraft emissions from a
nationwide standpoint,
* National Emissions Data System (NEDS), Research Triangle Park, North
Carolina.
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3
Table 1 provides an estimate of the contribution of total emissions
by aircraft for several air pollutants in ten selected air quality
control regions (AQCR's). These ten regions provide a representative
sample of areas which experience a large amount of aircraft traffic.
The data displayed in Table 1 indicates that even on an AQCR basis,
aircraft emissions, especially those from general aviation aircraft,
constitute a very small percentage of the total emissions.
Thus, on both a national and an AQCR-wide basis, aircraft emissions
are relatively small compared to total emissions. Therefore, the most
significant air quality impacts of aircraft emissions must occur in more
localized areas where aircraft concentrations are higher. Such areas,
frequently called terminal areas, are found in the general vicinity of
airports.
REVIEW OF HISTORICAL STUDIES AROUND AIRPORTS
As stated in the introduction, a number of studies have been conducted
around major airports to assess the impact of aircraft emissions on air
quality. A review of the findings from these studias will be beneficial
in subsequent discussions on the impact of general aviation aircraft.
Northern Research and Engineering Corporation Study
One of the earliest comprehensive airport studies was performed in
1971 by the northern Research and Engineering Corporation^ for the
Environmental Protection Agency. During this study a mathematical
dispersion model was develor^d and utilized to study air quality impacts
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Table 1
Percentage of Total Emissions of
Various Air Pollutants from Aircraft Operations
Carbon Monoxide
AQCR
Los Angeles
San Francisco
NY-NJ-Conn
Chicago
St. Louis
Cincinnati
Baltimore
Bos to it
Houston
S.E. Wise.
All
Ai rcraf t
0.72%
0.87%
0.44%
0.39%
0.76%
o.m
0.592
0.582
1.15%
0.37%
General
Aviation
0.30%
0.39%
o.m
0.07%
o.m
0.06%
0.10%
0.21*
0.58%
0.15%
Hydrocarbons
All
Aircraft
1.30*
1 .60%
0.702
0.70%
1 .80%
0.40%
0.80%
0.84%
0.80%
0.302
General
Aviation
0.20%
0.30%
0.08%
0.05%
0.07%
0.142
0,043
0.13%
0.20%
0.05%
Nitrogen Oxides
Participates
All
Aircraft
0.81%
1.20%
0.50%
0.59%
0.45%
0.30%
0.73%
0.71%
0.65%
0.40%
General
Aviation
0.07%
0.10%
0.02%
0.06%
0.01%
0.03%
0.02%
0.02%
0.07%
0.03%
All
Aircraft
2.70%
2.10%
0.27%
0.14%
0.85%
0.05%
U.87%
0.67%
1.30%
0.12%
General
Aviation
0.33%
0.47%
0.08%
0.02%
0.03%
0.03%
0.05%
0.21%
0.30%
0.06%
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5
of several major airports; including Los Angeles International, Chicago
O'Hare, New York JFK, and Washington National. Also some limited modeling
was performed at two general aviation airports, Van Nuys in Los Angeles
and Tamiami in Florida. The model developed by Northern Engineering is
frequently referred to as the NREC model.
In the fJREC model, aircraft emissions were separated from other
sources located on or in the vicinity of the airport so that the impact
on air quality from aircraft emissiorc- could be assessed and compared to
the impact caused by other source Categories.
The NREC model had no capability to account for the reactive nature
of several of the pollutants emitted from aircraft and in the initial
study no attempt v/as made to verify the model through comparison with
monitoring data.
The general findings from the NREC study are perhaps best discussed
by the individual pollutants. For carbon monoxide, aircraft emissions
were calculated to be sufficiently high to cause violations of the
national CO standard in several locations. Most of these vio^tions
were found to occur on (or very near) the airport property. The calculated
concentrations of CO from aircraft emissions dispersed very rapidly in
areas surrounding the airport. Generally, at distances in excess of a
few kilometers from the airport, contributions of CO by aircraft emissions
were found to be less thar 10 percent of the national CO standards.
Although the NREC model did not have the capability to treat the
reactive pollutants, very high levels of nitrogen oxide (NO ) concentrations
A
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6
were estimated at several locations on the airport property such as near
the departure end of runways, stc. Assuming that a high percentage of
the NO was in the form of nitrogen dioxide (NCL), aircraft operations
X (..
were predicted to cause violations of the national M00 standard at
several locations on the airport property. Figures 'i .and 2 which have
been extracted from Reference 1, provide soms idea of how annual average
NCL levels were estimated to vary at points in the vicinity of Los
Angeles International Airport, and the contribution of aircraft emissions
to these concentrations.
As can be seen by comparing these two figures, aircraft emissions
were estimated to account for approximately 50 percent of the total NCU
near the ends of the runway, but only aboi:f. 10 percent of the NO,,
levels at locations near the airport fence line (except where the fence
line 1s near the end of the runway).
Concentrations of hydrocarbons were also calculated assuming no
reactivity. The results provided indications that during the early
morning hours (6:00 to 9:00 AM) high levels c-f hydrocarbon concentrations
from aircraft emissions could be expected to occur both on the aircraft
surface, and at distances considerably downwind of the airport property.
It is generally believed that hydrocarbons emitted during the early
morning hours are one of the primary pollutants that lead to ozone and
other photochemical oxidant formation during the afternoon hours.
Other pollutants viero also investigated, however since the purpose
of the present paper is to focus on general aviation aircraft, and the
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Note; Peak values of concentration
do not appear on the figure.
(numbers
!.E 1 - KO- ISOPLETHS AT LOS AHCEf-S IHTERaATlOMAti AIRCRAFT SOURCES
Annual ,ivr>rnne for 197fl
in Rpff»rf>nrp 1.
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Mote: Peak values of concentration
do not appear on the figure.
(numbers in pg/ra')
I SOPlETHS AT LOS AHCEIES 1»7£R»AT!0.'JAL; TOTAL EH I SSI ON. SOURCES
Annual average for 1970 as estimated in Reference 1.
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9
above three pollutants are of primary concern for this category of
aircraft, no discussion of other pollutants will be presented.
Environmental Protection Agency Study
In Support of Aircraft Emission Standards
Following the above work by NREC, the EPA conducted an analysis to
determine if emission standards on aircraft were needed. The results of
this study are contained in Reference 2. Briefly, the EPA found that at
some of the larger airports, CO emissions from aircraft could cause or
significantly contribute to violations of the CO standard at locations
where the general public could be exposed. While highest CO levels were
found on the airport property, the EPA estimated that aircraft emissions
could cause (or significantly contribute) to violations of the CO standard
in nearby residential areas. Figure 3 (from Reference 2) contains
isopleths of the percent contribution to CO levels by aircraft in the
vicinity of Los Angeles International Airport. This figure indicates
that under some conditions up to 70 percent of the CO in some residential
arsas near the airport could be attributed to aircraft emissions.
Monitoring data was used to show that in such areas violations of the 8-
hour CO standard could be expected to occur several times por year
unless CO omissions from aircraft were controlled.
The EPA study also concluded that at the larger airports, concentra-
tions of N02 as the result of aircraft emissions could contribute substan-
tially to HO,, levels in areas near the airport property. Figures 4 and
5 arc isopleths of predicted annual flO concentrations for 1970 and I(j80
X
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(as taken from Reference 2}
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13
around Los Angeles International Airport as estimated in the above EPA
study. Note that the isopleths are for NO concentrations while the air
3\
quality standard is for NCL. However, the above study indicated that
high levels of NO concentrations as a result of aircraft emissions
J\
extend well into the residential area around the airport. Projected
growth indicated a sharp increase in NO concentrations between 1970 and
X
1980. Similar conclusions were reached for other large airports as
shown in Figure 6.
The EPA study further found that hydrocarbons emitted by aircraft
at large airports could cause significant build up of this pollutant
during the earlier morning hours. This build up could lead to high
levels of photochemical oxidant later during the day after the air has
moved into areas where large numbers of people live or work. The 1980
projected average hydrocarbon concentrations during the 6:00 to 9:00 AM
time period on worst clays at Los Angeles International Airport are shown
on Figure 7.
Geomeb Validation Study
The NREC study was criticized for not having validation data to
support its conclusions. Since much of the above EPA study was based on
the IIREC results, it too was highly criticized. Consequently, in 1974,
Geomet, Incorporated, conducted a study-' to validate the NREC model.
This study was conducted using monitoring data collected during a six
r.;onth period at Washington National Airport.
Geomct found that the results of the NREC model did not correlate
very well with the monitoring data. The NREC model \vas found to general-
ly under predict emissions, in some cases by a factor of 10 or more. An
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( .s taken from Reference 2)
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I" T"F '/IC I'll TV Of Ct'.ICACQ-0"'j\!<^ l
Projoctctl Annual Avcrnve for t'JSO
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(as taken from Reference 2}
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16
improved version of the NREC model was developed by Geomet and was used
to demonstrate that reasonable correlation between airport dispersion
models and monitoring data could be obtained. The monitoring data
collected and used in the Geomet study is summarized in Table 2. Corres-
ponding locations of the monitoring sites are indicated on the insert of
the table.
From Table 2 it can be seen that violations of both the 1-hour (40
o o
ug/in ) and 8-hour (10 ug/m ) CO standard were recorded at several of the
monitoring sites. Unfortunately, the monitoring data cannot be dVferent-
iated into aircraft and other source category emissions. However, by
examining the monitoring site locations (see Table 2), it would appear
that the monitoring data tends to support the general findings of both
the NREC and EPA studies. That is, emissions from aircraft can cause
high levels of CO at locations on cue airport property. It is particularly
interesting that some of the highest recorded CO concentrations were
found in the ramp area where passengers embark and disembark. This is
probably due to a combination of the concentration of slow moving aircraft,
operation of ground power units, and operation of auxilary equipment
such as baggage tow trucks. Also it is interesting that both the peak
and highest mean CO levels were found in the maintenance area at the
southern end of the field. Finally, it would appear that monitoring
site number 3 (see Table 2) was somewhat isolated from sources other
than aircraft. The highest recorded value for this particular monitoring
site was 71 percent of the 8-hour CO standard and 27 percent of the
1-hour standard.
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18
For nitrogen dioxide, only three monitoring sites were used (sites
2, 3 and 6 on Table 2). As noted in Table 2, all three recorded mean
values in excess of 100 ug/m during the six month period (the ambient
o
standard is 100 ug/m annual average concentration). At least one of
these monitoring locations (site 2) could have been strongly influenced
by automobile traffic from a nearby heavily traveled highway.
Both the 1-hour and the 6:00 to 9:00 AM average concentration of
non-methane hydrocarbons were recorded at three monitoring sites (sites
2, 3 and 6 on Table 2). Very high levels of hydrocarbons were recorded
at all three monitoring sites with average concentrations between 6 and
9 AM ranging from 320 to 1187 ug/m . Although ozone levels were not
measured, the ratio of non-methane hydrocarbons to N0? indicates that
the atmosphere around the airport is quite conducive to the formation
of ozone.
The primary purpose of the Geomet study was to validate model
results, consequently little effort was expended to separate the impact
of aircraft emissions from that caused by other sources However, it is
interesting that Geomet does point out that except for a few occassions,
aircraft emissions appear to contribute a relatively small percentage to
the total air pollution around Washington National Airport, with the
majority of the burden being imposed by the surrounding major highways
and environ area sources (see page 6 of r. "erence 3).
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19
Other Studies Using Geomet Model
As mentioned above, the Geomet study conducted at Washington National
Airport lead to the development of a mathematical model frequently
referred to as the Geomet model. Versions of this model have been used
in several other studies, the bulk of which have been air quality assess-
ments associated v/ith the preparation of Environmental Impact Statements
(References 4, 5 and 6). One such analysis was performed to predict the
impact that a proposed expansion of Salt Lake City Airport would have on
future air quality (see Reference 4). This analysis revealed that with
the current levels of aircraft emissions, violations of the CO 8-hoi1;'
standard could be expected to occur as the result of emissions fror.'.
airport sources. These violations, however, would be co.vfined to the
immediate airport surroundings and the impact of CO emitted by airport
sources would have negligible impact on areas outside the airport.
Assuming that applicable aircraft emission standards for both aircraft
and other sourcjs were implemented, no violations of the CO standard
were projectrj to occur in 1985 even with the projected increase in
aircraft traffic.
Figure 8 provides a summary of the results of the Salt Lake City
Airport analysis for nitrogen oxide emissions. This figure is interest-
ing in that it provides a means of comparing the predicted impact on air
quality of a medium size airport to that previously found for a larger
airport. Also it provides a means of comparing, at various locations,
the contribution to predicted NO concentration levels by both aircraft
A
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52
airport
runways
PO
o
-.10
_ cs
KEY!
Station
N cn»bcr
...J
SLC
* SLCTA
Toul •
8 Me=o Annual PreJlncd ValaM of NOX jhowInE concibiitiotu foi airport source! (SLCIA) and r.oa-
jirjicrt KJUTCCS (S!XT), ar.J teals. In jiii^rogriMJ/C!:. CT. Contour Ui>« arc ilnvrn (or U -.Is.
{as taken from R^fercnne 1}
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21
and other sources of NO . Note that in the immediate vicinity of the
A
airport, calculated levels of NO are high and that aircraft emissions
A
account for a large portion of tht total concentrations. However, at
increasing distances from the airpo.-t property, the contribution to NO
A
concentrations by aircraft emissions diminishes very rapidly.
High concentration levels of hydrocarbons were also predicted to
occur in the near vicinity of the airport as the result of aircraft
emissions. However, substantial reductions in these concentration
levels were projected to occur by 1935 as the result of current aircraft
emission standards.
Another study (References 5 an! 6) involving the use of the Geomet
model was conducted for an airport proposed to locate in the vicinity of
Cleveland, Ohio. The conclusions reached were similar to those discussed
above, except that it v/as found that the location site of the airport
could significantly influence the air quality impacts, due to the histori-
cal prevailing wind patterns.
Studies Conducted by.
The Argonne National Laboratory has developed two mathematical
models for use in determining the impact of aircraft emissions on air
quality. Those models are referred to as the Airport Vicinity Air
Pollution (AVAP) model developed for the Federal Aviation Agency, and
the Air Quality Assessment H'del (AQAM) developed for the U.S. Air
Force. Validation studies for the above two models have been conducted
using monitoring data from Washington National Airport.
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22
Several studies have been conducted using the two Argonne developed
models. In two such studies using Washington National Airport (References
7 and 8), conclusions similar to those previously discussed were reached.
In addition, these Argonne studies noted that under certain conditions
the combining of pollutants from the airport and other sources (such as
from downtown Washington, D.C.) could cause violations of the national
air quality standards for CO, photochemical oxidant, MOp and TSP in
locations downwind of the airport. These studies expressed concern that
any future increases in emissions either from the airport or surrounding
areas could possibly lead to significant violations of the national air
quality standards, both on the airport property and in the outlying
areas.
One of the most extensive effort; to define and assess the impact
of aircraft emissions on air quality has been undertaken by the U.S. Air
Force. A summary of the results from this effort is contained in Reference
9. Briefly, ten air force bases were Modeled lo determine what impact
aircraft flights might have on air quality in neighborhoods aroirr! the
base. The findings from these studies tend to indicate that NO and CO
A.
emissions from air force aircraft have little to no effect on air quality
outside the base. Even within the base area-:, there were relatively few
areas where CO and MO concentrations were found to be excessively high
A
as the result of aircraft operations. On the other hand, the build up
of hydrocarbon concentrations during the early morning hours as a result
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23
of aircraft operations, was found to be sufficiently high to cause
concern over the potential for photochemical oxidant generation even in
areas considerably downwind of the base.
Studies Conducted by Systems Applications Incorporated
The previously discussed studies have all been severely handicapped
in that no capability existed to treat the reactive properties of the
hydrocarbon and nitrogen oxide emissions. Consequently, the results do
not adequately account for the potential of aircraft emissions to form
ozone and other photochemical cxidants.
In reference 10, Systems Applications Incorporated (SAI) attempted
to better define the potential role that jet aircraft emissions may play
in ozone formation. The SAI study found that the mixture of hydrocarbons
and nitrogen oxide emissions from aircraft vias quite different than that
from automobiles. The ratio of non-methane hydrocarbons to nitrogen
oxides emitted from aircraft tends to be relatively ! 'ih compared to
that from automobiles. In isolation from other emission sources air
containing jet exhaust was found not to be very conducive to the formation
of high levels of ozone (because of the high NMHC/tIO ratio). However,
A
under conditions where the air containing jet exhaust mixes with air
containing automobile exhaust, the net result is to make the air much
more conducive to ""orming ozone than would be the case where the air
contained only automobile e,\haiist. For this reason, the SAI study
indicates that around major airports, where there exists a high volume
of automobile traffic, emissions from jet engines can significantly
affect "he levels of ozone generated in the ambient air.
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24
OVERVIEW OF AIRCRAFT STUDIES
The purpose of the preceeding review was primarily to set the stage
for the discussion to follow. Therefore, it is prudent to briefly
summarize the findings from the historical airport studies. While t^ere
are many caveats which need to be placed on each individual airport
study, there appears to be some general agreements and conclusions that
all studies support. These include:
(1) Emissions from aircraft at major airports are sufficiVitly
high enough to cause the airport to be a local "hot spot" source of CO,
HC, and NO as well as other pollutants.
A
(2) Around major airports, r-0 emissions from aircrafts are high
enough to cause violations of the national CO standards. However, the
locations which experience CO violations will usually coincide very
closely with areas where the concentration of aircraft is high (i.e.,
parking ramps, departure/delay queues and the ends of runways). Also high
CO levels can be experienced when ventilation is poor, or where obstruc-
tions to natural dispersion (such as buildings, etc.) occur. The histori-
cal studies indicate that the CO from aircraft disperses very rapidly
and probably would not by itself cause violations o." the standard in
locations much beyond the airport perimeter. However, there may be
situations where CO from major airports could aggravate a local problem
in areas close to the airport.
(3) Some uncertainty exists over the potential impact NO emirsions
A
from aircraft have on both NOp and photochemical oxidant levels. There
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25
are good indications that aircraft emissions at major airports contribute
substantially to high NO- levels in areas near the ends of runways and
possibly at other points on the airport surface. Also some of the
studies have shown that aircraft emissions at major airports contribute
substantially to high NO concentrations in areas around the airport.
A
Other studies indicate that at medium size air terminals (such as tho
Salt Lake City Airport) NO emissions from aircraft have a relatively
A
srr:'l impact on NU concentrations in the immediate area adjacent to the
A
airport.
(4) There seems to be good agreement uetween all study efforts
that hydrocarbon emissions from aircraft at major and medium size air
terminals result in high levels of this pollutant beincj experienced both
on and off the airport property. These levels appear to be high enough
to cause violations of the photochemical oxidant standard in situations
where sources of NO may be present.
A
Comparison between Emissions from
General Aviation Alrcraft ancl Other Ai'\rcr_aft_
As previously stated, most of the historical studies have been
conducted around major airports where the air traffic is primarily
composed of transport type aircraft. While efforts to study the impacts
of smaller aircraft could be done using existing models, such efforts
v/ould be time consuming and require considerable expense and manpower.
This is because most existing models are data intensive, requiring
detailed emission inventories both for the aircraft and other sources
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26
around the airport. For major airports already modeled, general aviation
traffic is only a small portion of the total traffic and it is doubtful
that much could be learned by modeling the general aviation traffic
separately. Much can be learned, however, by comparing emissions from
general aviation aircraft and other types of aircraft and using this
comparison to quantitatively extrapolate the results from existing
studies to general aviation.
Reference 11 contains perhaps the most up to date compilation of
emissions from aircraft at several airports. In this reference, emissions
are appropriately accounted for by using distributions of the different
type aircraft normally operated at the individual airports. This includes
mixtures of jet transport, military, helicopters, business jet and other
general aviation aircraft.
Table 3 provides a breakdown of emission; from various aircraft
operating at three major airports; John F. Kennedy, Los Angeles Interna-
tional, and Chicago O'Hare. The emission data in Table 3 is divided
into three categories of aircraft. Transport (2, 3 and 4 jet-engine
airliners), general aviation and air taxi (actually the air taxi and
general aviation fleet contain similar type aircraft). Also shown in
Table 3 ?•• > emissions from auxiliary power units used by the transport
aircraft d<. 'ng ground operations. The emissions shown on the table are
annual value, and include all aircraft operations below 3,000 feet.
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27
Table 3
Estimated Emissions by Various Aircraft
Operations During 1975
(in tons per year)
Type Aircraft JFK LAX ORD
HC_
Transport 9082
Air Taxi 20
Gen. Aviation 26
APU 14
14
CO.
,513
54
161
394
NOV
— x
3141
3
5
315
HC
5739
37
133
15
CO
-
10,243
53
538
343
Mv
— x
3,349
7
45
346
HC.
6,799
91
45
16
CO
13,876
98
432
418
—x
4,562
14
9
429
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28
Two important points can be made from the data contained in Table
3. First, the magnitude of emissions from aircraft at these major air
terminals is far in excess of the level normally associated with a major
stationary source (a stationary source is normally considered major if
it emits 100 tons/year or more of any pollutant). Secondly, nearly all
the emissions . hown in Table 3 are from transport aircraft. Consequently,
the air quality impact of these emissions are primarily due to large jet
aircraft,
Table 4 provides aircraft emission data for five airports (two.
combined in San Oose because of their close proximity) which are heavily
dominated by general aviation traffic. The emission data shown in Table
4 are for general aviation aircraft operations only.
Van tluys Airport in California is the busiest general aviation
airport in the U.S. and ranks third in total operations among all
airports. For comparison purposes, the total number of aircraft operations
at Van Nuys in 1975 exceeded 588,000, while total operations at John F.
Kennedy during the same year v/ere approximately 335,000. General aviation.
accounts for over 90 percent of the total traffic at Van Nuys (VflY).
The 1974 HC, CO and NOV emissions from Van Nuys Airport as the result of
Js
general aviation tiaffic are shov/n below along with similar emissions
from transport aircraft (1975 emissions) operating at John F. Kennedy
(JFK), Los Angeles International (LAX), and Chicago O'Hare (ORD).
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29
Table 4
Estimated Emissions During 1974 from
General Aviation Aircraft Operations
(in tons per year)
Airport Percent of HC. CO NO
Total Traffic *
Van Huys 92 56 2488 10
Tamiami 91 35 1551 6
Phoenix 71 33 1448 6
Fairbanks 86 14 631 3
San Jose Municipal/ 84 64 2827 12
San Jose Reid
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30
Emissions (tons/year)
Ai.-port HC_ C0_ NOX
VNY 56 2488 10
JFK 9082 14513 3141
LAX 5739 10243 3349
ORD 6799 13876" 4562
Recall that even with the large magnitude of HC and NO emissions
A
from aircraft at the major airports, there has been some uncertainty in
assessing the impact such emissions have on air quality in areas around
the airport. Intuitively then, the magnitude of the HC and NO emissions
A
from general aviation aircraft at Van Muys Airport are so small that
there is little probability any of the existing models would show any
significant impact of such emissions on air quality in the area adjacent
to the airport.
As an illustration, consider Los Angeles International where, in
Reference 11, it is estimated that by 1980 NO emissions from general
X
co'.vition aircraft will be approximately 53 tons/year or about one percent
of the total NO emissions from aircraft. Recall that Figure 5 contained
X
estimated NO isopleths around Los Angelos International for 1980 as the
A
result of all aircraft traffic. Assuming that the isopleths are composed
of NO concentrations in direct proportion to the different type aircraft
A
operating at the Los Angeles Airport, similar isopleths can be constructed
for each type aircraft. Figure 9 contains estimated NO^ isopleths for
1980 at Los Angeles International as the result of general aviation
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P3&-:,
VafmTmf
\\^mf-\siSlitsVSir1-^' :i^i-^te^r,
(nunt-crs in/yg/m )
icure 9 Esti.-nated >WV Isopleths In Tin Vicinity of Los Angeles International
As The Result of fer/eral /wlation Aircraft
Annual Average for 1980
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32
traffic only. As can be seen, the MO concentrations from general
J\
aviation aircraft appear to be very small both on the airport property
and in the adjacent area.
The above illustration is not. entirely valid since general aviation
aircraft operations at Los Angeles International would not be uniformly
spread over the same area as emissions from transport aircraft. That
is, general aviation aircraft operations would tend to be confined to a
smaller area of the airport, and most such operations would be from a
single runway. Nevertheless, since the 1980 NO emissions from general
A
aviation aircraft at Los Angeles International are projected to be over
five times greater than similar emissions currently being experienced at
Van Muys, the illustration does indicate that NO emissions from general
A
aviation aircraft at Van Nuys probably have very small air quality
impacts.
The magnitude of carbon monoxide emissions at Van Nuys, although
considerably smaller than at JFK New York, Los Angeles International
and Chicago O'Hare, is sufficiently large enough to warrant further
assessment of the potential impact these emission may have on air quality.
This analysis will be presented in more detail later.
Hydrocarbon emissions from general aviation aircraft at Van Nuys
are considerably below 100 tons per year. Within the accuracy of existing
models, complete removal of these emissions would probably not significantly
alter projected air quality in the Van Nuys Airport area.
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33
While it cannot be shown with any degree of certainty that the HC
emissions at Van fluys (and other general aviation airports) have any
significant impacts on air quality, it must be remembered that a large
portion of the hydrocarbon emissions in an urban area come from relatively
small and diversely located sources. The additive impact on air quality
of these many small sources can be significant in some situations.
Nevertheless, except for a relatively few airport? which experience a
high volume of general aviation traffic, it appears that very small air
quality benefits can be expected from the exhaust emission control of HC
on general aviation aircrafts. Thus, a more appropriate measure of
whether or not such controls should be required is perhaps their cost-
effectiveness as compared to the cost-ef'ectiveness of controlling other
sources ,vith similar emission magnitudes. Table 5 provides a comparison
of the magnitude of HC emissions from several sources in the Baltimore
AQCR during 1973.
0
The HC emissions thus far discussed have all been from aircraft
engine exhaust. Very little work has been accomplished to date toward
estimating evaporative emissions from gasoline powered aircraft. However,
some rough calculations have indicated that the evaporative emissions
from such aircraft may be considerably higher than the HC emitted
through the exhaust. For example, the San Diego County Air Pollution
Control D strict recently estimated that HC evaporative emissions from
general aviation aircraft were over twelve times greater than froit,
exhaust (Reference 12). Also some rough hand calculations indicate that
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34
Table 5
1973 HC Emissions from
Selected Sources in Baltimore AQCR
Sources Tons of HC
Automobiles and Light Duty Trucks 86,200
Heavy Duty Trucks 16,000
Solvent Evaporative Loss 9,700
Gasoline Handling Loss 8,600
Solid Waste Disposal 3,950
Lawn and Garden Equipment 2,000
Vessels 1,300
Off Highway Vehicles 1,200
Locomotives 1,200
Woodburing Home Heaters 142
General Aviation Aircraft* 122
*Total HC emissions from all aircraft = 2,145 tons
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35
gasoline normally drained and poured on the ground during pre-flight
inspections, may result in several times more HC emissions than the
exhaust of general aviation aircraft. A1so, evaporation losses during
refueling may be significant.
The above findings, although preliminary at this time, indicate
that substantially more benefits may be gained through evaporation loss
control than from HC exhaust emission control.
Mathematical[Model of CO Impact at Van N'uys Airport
As previously noted, CO emissions from general aviation aircraft at
several airports exceeds 2000 tons per year. In Reference 11, such
emissions are predicted to sharply increase due to expected growth. For
example, even with the current emission standards, CO emissions at Van
fluys Airport are projected to increase to over 3700 tons per year by
1985. By comparison, this level is approximately the same as now being
experienced at Washington National Airport. Therefore, it is prudent to
further analyze the potential impact of these CO emissionr, from general
aviation aircraft.
The Office of Air Qua'ity Planning and Standards recently used a
nev;ly developed dispersion model to make the above assessment. The
findings of this study are contained in Reference 13 and will be briefly
suniii'iarued here.
Using Van Muys Airport (the busiest general aviation airport in the
country and the one having the highest CO emissions from general aviation
traffic), actual traffic counts were obtained during the month of August
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36
1976. From this data, the period of highest traffic was selected for
modeling. Aircraft activity at Van Nuys was divided into several categories
of aircraft and a distribution of various types of aircraft operating at
Van tluys was determined. Emission factors pertinent to these various
aircraft were developed.
The aircraft activity at Van Nuys was then modeled -using a dispersion
model designed for assessing the simultaneous impact of various point,
a.rea and line sources in a given area on a^r quality in that area. The
details of the model are contained in Reference 14.
Modeling of the airport consisted of dividing the aircraft activity
into various modes of operation such as taxi, parking, take off, approach,
etc. Emission factors for each mode of operation was determined for
each type aircraft modeled. Consequently, the impact of various types
of operations by the aircraft could be assessed.
Modeling was accomplished only for aircraft operations» thus providing
a means of determining the impact emissions from the aircraft would have
on CO air quality. The results of this modeling effort are summarized in
Figures 10 and 11. These figures present the predicted 1-hour and 8-hour
CO concentrations as a function of distance from the point of highest
concentrations calculated for several locations on the airport. The
results shown in Figures 10 and 11 are for a "worst-case" situation, that
is unfavorable meteorological conditions, a single runway in used (Van
Nuys utilizes two parallel runways) and high traffic causing substantial
departure delays.
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-37-
•^-~--r-- I—
1LJ.J/-/=jn:..ACt:A... SpURCE._ iji^L^.-1^
Figure 10 Maximum 1-Hour CO Concentrations as a Function of
Downwind Distance (assuming that all aircraft use Runway 1).
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-38-
'/'} ^-~t\(Ce>\ :
""8 -HOUR CO
0 O.Z.
DOVJMWIS4D
0.4 O.
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39
As can be seen from Figures 10 and 11, there are locations where
both the 1-hour and 8-hour CO standard is predicted to be violated by a
factor of over 2. These locations occur just downwind of the active
runway and taxi way. (The area sources 1 and 2 shown on the figures are
parking areas near the approach end of the active runv/ay.) However, as
can be seen from the figures, the CO concentration disperses very rapidly
as one moves away from the point of highest concentration. Thus, there
appears to be localized CO "hot spots" on the airport property where CO
levels are exceedingly high. The contribution of CO by aircraft at Van
Nuys appears to be no more than about 10 percent of the standard at
locations off the airport property. Similar calculations with both
runways in use show that the peak levels of CO near the "hot spots" are
reduced by about 25 percent, but that the impact outside the airport
property remains about the same as when a single runv/ay is in use. A
comparison with the results from the study involving 10 air force bases
previously discussed (Reference 9) shows good agreement with the results
found for the above Van Nuys study.
CONCLUSIONS
A review of the potential impact of general aviation aircraft
emissions indicates:
(1) The level of HC and NO emissions from these aircrafts
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40
(3) HC emissions from general aviation aircraft fall into a group
of sources which are not considered major, but which may eventually
require controls to insure the oxidant standard is met. The magnitude
of HC emissions from general aviation aircraft exhaust at the most
active general aviation airports indicate that relatively small air
quality benefits can be expected to be gained through control of these
emissions. There are some preliminary indications that substantially
more benefits can be gained through evaporative emission control,
(4) CO emissions are sufficiently high to cause excessive levels
of CO to be experienced at a few spots on the airport property. Maximum
contributions of CO emissions from general aviation traffic to areas
outside the airport are estimated not to exceed about 10 percent of the
national standards.
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References
1. Platt, M.> Baker, R. C., Bastress, E. K., Chng, K. M., and
Siegle, R. D., The Potential Impact of Aircraft Emissions Upon Air
Quality, Report Number 1167-1, Northern Research and Engineering
Corporation, December 29, 1971.
2. Aircraft Emissions: Impact on Air Quality and Feasibility of
Control, United States Environmental Protection Agency.
3. Thayer, S. D., Pelton, D. J., Stadsklev, G. H., and Weaver, B. D.,
Model Verification -Aircraft Emissions Impact on Air Quality, Geomet,
Incorporated, EPA-650/4-74-049, Project Officer D. Bruce Turner,
September 1974.
4. Thayer, S. D., "Impact on Air Quality of the Proposed Expansion
of the Salt Lake City International Airport," Environmental Impact
Statement, Geomet, Incorporated, March 29, 1974.
5. Cook, J. D., and Koch, R. C., "Air Quality Analysis of a Proposed
Cleveland Airport Lake Site," Final Report, Geomet, Incorporated,
August 1976.
C. Sawdey, E. R., and Thayer, S. D., "Evaluation of Air Quality
Impact for Alternative Cleveland Jetport Sites," Final Report,
Geomet, Incorporated, May 19, 1975.
7. Rote, 0. M., Wang, I. T., Wangen, L. E,, Hecht, R. W., Cirillo,
R. R., and Pratapas, J., "Airport Vicinity Air Pollution Study,"
Final Report, Argonne National Laboratory, Augu 1973.
8. Wangen, L. E., and Conloy, L. A., "Air Quality Assessment Model
applied to Washington National Airport," Argonne National Laboratory,
March 1975.
9. Naugle, D. F., Grems, III, G. C., and Daley, P. S., "Air Quality
Impact of Aircraft at Ton U.S. Air Force Bases," U.S. Air Force Civil
and Environmental Engineering Development Agency, Tyndall Air Force
Base, Florida 77-41.6.
10. Whitten, G. Z., and Hogo, H., Introductory Study ofthe Chemical
Bohavijor of Jet Emissions in PJiotocheinicajl Smog, Final Report, Systems
Ajjpl ication's",/Incorporated, May ID/fTi
11. Standards Development and Support Branch, "Technical Report:
Aircraft Emissions at Selected Airports 1972-1985," Draft Report
Office of Air and Waste Management, Environmental Protection Agency,
January 1977.
41
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12. Alberson, M., Mross, B., Evetovitch, H., Louthen, W., Anderson, G.,
and Save!, J., "San Diego Air Basin 1974 Emissions Inventory," Draft
Report, February 1977.
13. Source Receptor Analysis Branch, "Impact of General Aviation
Aircraft on Ambient CO Concentrations at Van Nuys Airport, California,"
Draft Report, Office of Air Quality Planning and Standards, Environ-
mental Protection Agency, April 1977.
14. Turner, 0. B., and Peterson, W, B., "A Gaussian-Plume Algorithm
for Point, Area and Line Sources," presentation at the Sixth NATO/
CCMS International Technical Meeting on Air Pollution -Modeling,
Battelle Institute, Frankfurt, Germany, September 1975.
42
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