Air Pollution
DYNAMIC
IRRADIATION
CHAMBER TESTS
OF
AUTOMOTIV
EXHAUST
U.S. DEPARTMENT OF HEALTH, EDUCATION, AND WELFARE
Public Health Service
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DYNAMIC IRRADIATION
CHAMBER TESTS OF
AUTOMOTIVE EXHAUST
Merrill W. Korth
Engineering Research and Development Section
Robert A. Taft Sanitary Engineering Center
U.S. DEPARTMENT OF HEALTH, EDUCATION, AND WELFARE
Public Health Service
Division of Air Pollution
Cincinnati 26, Ohio
November 1963
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The ENVIRONMENTAL HEALTH SERIES of reports was estab-
lished to report the results of scientific and engineering studies
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Public Health Service Publication No. 999-AP-5
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FOREWORD
The problem of vehicle exhaust as an air pollutant has been
under intensive study by government and private research
agencies for several years. Basic to these studies is the deter-
mination of the types of pollutants contained in vehicular exhaust,
the photochemical reactions that occur when exhaust is dis-
charged into the atmosphere, and the products responsible for
various air pollution effects.
Photochemical reactions are being studied in detail by the use
of 'smog1 chambers, in which vehicular exhaust diluted with
air is irradiated to simulate the effects of sunlight in the atmos-
phere. This report describes irradiation chamber tests con-
ducted by the Division of Air Pollution of the Public Health
Service. The work is performed by personnel of the Division's
Laboratory of Engineering and Physical Sciences at the Robert
A. Taft Sanitary Engineering Center.
Preliminary tests were conducted at the Center beginning in
February 1960. The dynamic irradiation tests described in
this report cover the period from November I960 to May 1961.
This work represents one of a series of irradiation studies
whose primary object is the determination of photochemical
reactions under a selected variety of laboratory conditions
representative of urban atmospheres. Future reports will
describe additional test projects, all of which are part of the
over-all Public Health Service program of research in environ-
mental health.
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CONTENTS
Page
ABSTRACT vii
SUMMARY 1
INTRODUCTION 1
TEST FACILITY AND PROCEDURES 2
Dynamometer System and Test Engine 3
Exhaust Transfer and Dilution System 4
Dilution-Air Purification System .... 6
Irradiation Chambers 7
Exposure Facilities 10
Analytical Procedures 1Z
TEST PARAMETERS 13
Exhaust Concentration 13
Average Irradiation Time 14
Fuel Content 14
Other Test Conditions 14
CHEMISTRY OF IRRADIATED EXHAUSTS 16
The NO - NO2 Reaction Process 16
NO — NO2 Photo-oxidation Reactions 16
NO2 — Free-Radical Reactions 16
CHEMICAL EFFECTS 18
NO2 18
Oxidant 21
Hydrocarbons 21
Formaldehyde 24
Other Aldehydes 25
BIOLOGICAL EFFECTS 26
Plants 26
Animals 28
Bacteria 28
SUMMARY OF RESULTS 29
REFERENCES 33
APPENDIX A: RAW DATA FOR IRRADIATION CHAMBER
REACTION PRODUCTS 35
APPENDIX B: COMPUTER PROGRAM FOR REDUCTION
OF OXIDES OF NITROGEN DATA 47
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ABSTRACT
As part of an intensive study by government and private
agencies the U. S. Public Health Service has built an irradiation
chamber facility for investigation of irradiated auto exhaust
under mixing conditions similar to those in the atmosphere.
The facility consists of a programmed continuous-cycling
chassis dynamometer, an exhaust dilution system, a dilution-
air purification system, two irradiation chambers, and ex-
posure facilities for evaluation of bacteria kill, plant damage,
and various effects on small animals.
Of the three variables studied during the first test series,
the exhaust concentration at the start of irradiation appeared
to produce the most significant effects. Fuel composition had
a lesser influence. Very little difference was noted in the
effects produced at two different average irradiation times.
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DYNAMIC IRRADIATION
CHAMBER TESTS OF
AUTOMOTIVE EXHAUST
SUMMARY
A dynamic irradiation chamber facility was designed and
built for investigations of irradiated auto exhaust under condi-
tions of continuous mixing. The facility consists of a pro-
grammed chassis dynamometer, an exhaust dilution system,
a dilution-air purification system, two irradiation chambers,
and various exposure facilities.
Three variables were considered in this first series of
tests: (1) initial exhaust concentration (approximately 13 ppm
carbon and 35 ppm carbon), (2) average irradiation time (85
and 120 minutes), and (3) fuel composition (14% and 23% olefins).
The effects of varying these test parameters were determined
by use of appropriate test criteria including NC>2 formation
rate, oxidant production, total hydrocarbon losses and reac-
tion of specific species, aldehyde production, plant damage,
and bacteria kill.
Of the three variables studied, the exhaust concentration
at the start of irradiation appeared to produce the most signi-
ficant effects. Fuel composition had a lesser influence on
some of the test criteria; very little difference was noted in the
effects produced at the two average irradiation times.
INTRODUCTION
Air masses over urban areas continually undergo varying
degrees of mixing of new pollutants with existing pollutants.
The degree of mixing depends on atmospheric turbulence and
the location and movement of parcels of air with respect to
pollutant sources. For study of the atmospheric photochemical
oxidation of dilute automotive exhaust under conditions that
simulate continuous uniform atmospheric mixing of new with
1
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2 IRRADIATION CHAMBER TESTS
old pollutants, a dynamic irradiation system has been developed.
In this dynamic system, dilute non-irradiated exhaust is con-
tinually introduced into the irradiation chamber and dilute irra-
diated exhaust is continually withdrawn.
TEST FACILITY AND PROCEDURES
The test facility used in this study consists of five major
components: an automatically cycled chassis dynamometer to
control the production of exhaust gases under simulated driving
conditions, a two-stage exhaust-transfer and dilution system
to dilute the raw exhaust gases to the specified concentrations,
a dilution-air purification system, dynamic irradiation chambers
for the irradiation of the dilute exhaust gases, and various ex-
posure facilities (Figure 1; See also Figures 2-5, 8, 9).
AUTOMOBILE
DYNAMOMETER
UNIT
PROPORTIONAL
STREAM
SPLITTER
EXHAUST DILUTION ASSEMBLY
(oY-J
[L)= i
=n ® ^
IL
N=— i rr
DILUTION-AIR
piiRiFir ATIDW i. «
00 V
IRRADIATION
CHAMBERS
TO EXPOSURE FACILITIES
AND CHEMICAL ANALYSIS
Figure I. Auto exhaust irradiation facility.
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facility and Procedures
DYNAMOMETER SYSTEM AND TEST ENGINE
To achieve reproducibility of engine operating conditions
and hence of exhaust composition for a 10-hour period (the nor-
mal period required for dynamic irradiation chamber runs), a
controlled hydraulic-type chassis dynamometer was used with
the test vehicle engine (Figure 2).
Figure 2. Dynamometer with test vehicle.
To assure that dynamometer operation would simulate actual
road conditions, the dynamometer was modified to allow simu-
lation not only of acceleration, uphill driving, and cruise, in
which the engine powers the vehicle (engine-load), but also of
deceleration and downhill driving, in which the inertia of the
vehicle drives the engine (engine-driven). The modification en-
tailed coupling a slave-engine assembly through an overrunning
clutch to the power absorption roll to allow contolled motoring
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IRRADIATION CHAMBER TESTS
for the engine-driven condition. Horsepower absorption, pre-
set on the dynamometer, established the engine-load conditions.
Deviations in dynamometer power absorption and slave-engine
power input are on the order of 1. 0%. To provide a continuous,
rapid, and reproducing cycle for the test vehicle, a program-
ming device for control of the output of the test vehicle engine
and the slave engine was necessary. The device that •was de-
veloped utilized a cam-operated servo mechanism, which con-
trolled throttle position for both the test vehicle engine and the
slave engine. Dynamometer horsepower absorption was pre-
set prior to each test run.
The test vehicle was a 1957 six-cylinder Chevrolet station
wagon. Measurements of engine speed, manifold vacuum, car-
buretor air flow, and throttle position, made on the test vehicle
during actual road operations, were used as the basis for es-
tablishing the power requirements for the programming cycle.
Time distribution for the programming cycle was based on the
frequency distribution of engine modes reported in earlier
studies. The programming cycle thus developed produced ex-
haust with a ratio of hydrocarbons to oxides of nitrogen of ap-
proximately 12:1 (hydrocarbons expressed as ppm total carbon).
Following is the sequence of engine conditions.
Vehicle Speed, Time, Manifold Vacuum, Power,
Condition . .
mph mm in. Hg np
Engine-load 18 2.2 18.3 2.0
Engine-driven 24 1. 1 23.5
Engine-load 38 2.2 15.5 9.5
Engine-driven 33 1. 1 24.5
Engine-load 36 2.2 16.0 8.0
Engine-driven 29 1.1 24.0
Idle mixture in the carburetor was adjusted daily to compensate
for the day-to-day variations in exhaust emissions. The ignition
system was checked weekly to assure peak condition of the spark
plugs and distributor points.
EXHAUST TRANSFER AND DILUTION SYSTEM
The exhaust gases generated by the vehicle on the dynamo-
meter were transferred to the irradiation chambers through the
dilution system by means of a proportional stream-splitter,
which separated a constant proportion (approximately 20%) of the
total exhaust flow (Figure 3). It was required that the sample
and waste gas streams discharge to equal pressure zones, and
that the pressure drop be identical through both the sample and
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Facility and Procedures 5
waste exhaust gas lines. Since the dilution-air system operated
at a positive pressure and since the waste portion of the auto
exhaust was discharged to atmosphere, it was necessary to pro-
vide a point of essentially atmospheric pressure for introduction
of the exhaust sample into the dilution-air system. This was
done by introducing the exhaust sample into the primary dilution
stage at a venturi throat held at atmospheric pressure.
SAMPLE TO
DILUTION SYSTEM
TO
SCAVENGE
SYSTEM
EXHAUST FROM
AUTOMOBILE
Figure 3. Proportional stream-splitter.
Dilution ratios of 400:1 to 1400:1 were used to establish the
hydrocarbon concentrations in the irradiation chamber at the
levels designated for irradiation studies. To meet these con-
ditions, the dilution system was constructed as a two-stage
unit, with each stage capable of operating at flow rates of 100
to 250 cubic feet per minute. For this series of tests, dilution
in the first stage was held constant at ratios of 19:1 to 21:1
while the second-stage dilution was maintained at 18:1 (for high
concentration of exhaust) and at 66:1 (for simulated atmospheric
concentrations).
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6 IRRADIATION CHAMBER TESTS
To prevent contamination of the dilute automotive exhaust
with unfiltered air, the dilution air was supplied under sufficient
positive pressure to move the gases through the dilution system,
the irradiation chamber, and the exposure facilities. Movement
of the exhaust gases at relatively low pressure into the first
stage of the dilution system, which was nominally at higher
pressure, and transfer of the required portion of the gases
from the first dilution stage to the second dilution stage were
accomplished by introducing the gas into zones of low pressure
created at venturi throats. Rapid mixing also was accomplished
by the high velocity and turbulence created by introduction at
each venturi throat.
DILUTION-AIR PURIFICATION SYSTEM
The dilution air, with which the exhaust sample is mixed
before it is introduced into the irradiation chamber, should be
as free as possible of contaminants that would interfere with
the photochemical reactions within the chamber. The tempera-
ture and humidity of this air should approximately duplicate
those conditions found in typical urban atmospheres.
To achieve these conditions, the dilution air was passed
through an air conditioning system, which included particulate
removal and charcoal filters, a cooling and dehumidifying
coil, a heating coil, and a humidifier (Figure 4).
PARTICIPATE
FILTER
CHARCOL
FILTER
OUTSIDE
AIR
FROM
FAN
Ji '
'RAIN —* HEATI
HEATING
COILS
TEMPERATURE
CONTROLLER
Figure 4. Dilution-air purification system
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Facility and Procedures
The particulate filter was a Cambridge Model ID-1000 ab-
solute filter with 1000-cfm capacity. This filter has an efficien-
cy of 99. 95% with 0. 3-micron particles. The charcoal filter
was a Barneby-Cheyney Model 7-FM cell charged with 45 pounds
of activated charcoal. Periodic sampling has shown that a rela-
tively constant hydrocarbon content of less than 2 ppm carbon,
which is essentially methane, remains in the clean air.
A 7-1/2-ton-capacity mechanical refrigeration system pro-
vided dehumidification and cooling. This system, together with
steam heating coils and a steam-heated humidifier, maintained
the diluting air at 75°F ± 3°F and 50% ± 5% relative humidity.
IRRADIATION CHAMBERS
Two 335-cubic-foot chambers were constructed for the dy-
namic irradiation facility. The chambers were designed to
operate as ideal dilution volumes into which the raw exhaust
gases, diluted to the designated concentration, were continu-
ously introduced as an equal quantity of irradiated gases was
withdrawn. The chambers were constructed of aluminum with
Mylar windows to allow for the irradiation of the dilute chamber
gases (Figure 5).
Figure 5. Irradiation chamber.
GPO 806—304—2
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« IRRADIATION CHAMBER TESTS
For this test series, rapid mixing, necessary for the dyna-
mic chamber to perform as an ideal dilution volume, \vas pro-
duced in each chamber by the jet action of two tube-axial fans,
which caused approximately 50% of the gas at the fan to be ac-
ct-lerated ahead and mixed, under turbulent conditions, within
the chamber. Since chamber operation approached the perform-
ance of an ideal dilution volume, any element of input gas
was rapidly and completely mixed into the entire chamber vol-
ume and any element of the output gas was representative of
the entire volume. Under such conditions the average irradia-
tion time for all molecules of gas in the chamber was equal to:
Ta I (1 e-kt) (1)
Where: Ta average irradiation time (exposure time)
k a
v
q chamber flow rate
v chamber volume
t time after irradiation begins
The exposure time is therefore determined only by the flow rate
through the chamber and the time since start of irradiation.
Irradiation of the gas within the chamber was supplied by
illumination from sources external to the chamber through
windows of 3-mil-thick Type D Mylar. The illumination was
provided by two banks of 70 fluorescent tubes each, mounted
in two cavity reflectors. The 96-inch T-8 tubes were operated
on T-1Z ballasts, which supplied a 25% overload to increase
the incident irradiation intensity. Two types of tubes, black
light and warm white deluxe, were used in equal proportions
to approximate solar radiation between the solar cut-off (about
Z900 angstroms) and 3700 angstroms. The choice of Mylar as
window material was a compromise among many factors, in-
cluding spectral transmission, strength, surface adsorption,
and diffusion. Strength and surface characteristics of the Mylar
were found to be adequate. As shown in Figure 6, the spectral
transmission curve for the Mylar is smooth, with a cut-off
point between 3100 and 3200 angstroms, which is somewhat
higher than the solar cut-off. The spectral distribution and
intensity in the near-ultraviolet range produced in the chamber,
as shown in Figure 7, approximated that of noonday sunlight^
below 3700 angstroms.
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IOO
800 2900 3000 3100 3200 3300 340O 350O 36OO 37OO 3800 390O 40OO
WAVE LENGTH, angstrom units
Figure 6. Spectral transmission curve for 3-mil Mylar.
1000
CHAMBER LIGHT
70 WHITE LAMPS
70 BLACK LAMPS
CAVITY REFLECTOR
"MYLAR CUTOFF"
25 % OVERLOAD
SUNLIGHT AND SKYLIGHT
3000
3200
3400
3600
3800 40OO
WAVE LENGTH, angstrom units
Figure 7. Light intensity.
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10 IRRADIATION CHAMBER TESTS
To minimize surface effects, the chamber was made as
large as possible within laboratory space limitations to reduce
the surface-to-volume ratio. The interior surface was com-
prised of approximately 168 square feet of Mylar and 132 square
feet of aluminum; the surface-to-volume ratio for Mylar was
0. 50 and for aluminum, 0. 39. These materials have been found
to have minimal effect on the major components present in the
exhaust gases or produced in the irradiated gases. -1
The diluted exhaust gases were continuously fed to the dyna-
mic chamber through the inlet port located at the rear of the
lower recirculating fan. Simultaneously the irradiated exhaust
gases were discharged through a distribution system to the
plant, bacteria, and animal exposure facilities and to a manifold
for chemical sampling and analysis.
EXPOSURE FACILITIES
Plant Exposures — Effluent from the irradiation chamber was
piped to a lighted plant exposure chamber about 16 cubic feet
in volume (Figure 8). The chamber was equipped with a system
of fluorescent lamps to maintain the sensitivity of the plants.
The light level was about 1000 foot-candles, high enough to keep
the stomates open. Potted plants grown under greenhouse con-
ditions were exposed. For most exposures two varieties of
tobacco, pinto bean at three stages of growth, and petunia •were
used.
Bacteria Exposures — A rotary impactor technique was used to
evaluate the effect-of irradiated exhaust on bacteria (Figure 9).
In this technique bacteria cultures of E. coli "were plated in
logarithmically increasing concentrations on a membrane filter
strip, which was attached to the outer surface of a 1-1/2 inch-
diameter metal cylinder. As the cylinder rotated at a constant
angular velocity, a thin line of irradiated exhaust gases im-
pinged on the surface of the membrane. After exposure, the
membranes were incubated, dried, and stained, and the degree
of kill was indicated by contrast between the color of the stained
living colonies and the lack of color of those areas where the
bacteria were killed.
Animal Exposures -- During a few runs investigations were
made of the effects of short-term exposure of animals to syn-
thetically produced smog. Rats and mice were exposed in
•whole-body chambers, and spontaneous running activity was
evaluated. Guinea pigs were exposed through face masks;
measurements included tidal volume, respiratory rate, and
pulmonary flow resistance. Animals were sacrificed for
various biochemical measurements. Most of the animal ex-
posures were made during special chamber runs and are not a
part of this test series.
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Figure 8. Plant exposure chamber.
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IRRADIATION CHAMBER TESTS
Figure 9. Bacteria exposure equipment.
ANALYTICAL PROCEDURES
Concentrations of chemical constituents were monitored in
(1) the raw exhaust from the automobile, (2) the exhaust-gas
mixture after dilution, and (3) the contents of the irradiation
chamber before and during irradiation. Carbon monoxide, car-
bon dioxide, and gross hydrocarbons (as hexane)were measured
in the raw exhaust gas by means of nondispersive infrared
analyzers, in which a raw exhaust sample was drawn through an
ice-bath condenser to remove interfering water vapor. The
total hydrocarbon concentration in both the nonirradiated and
irradiated exhaust gas mixture after dilution was measured
with a flame-ionization-type detector, which responds in ppm
total carbon atoms. NO and NO2 were measured by a continu-
ous-recording colorimetric instrument that uses a modified
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Parameters 13
Saltzman reagent. Because long response times are inherent
in the instrument, a computer program was used to convert
the instrument response to instantaneous values for NO and NO£.
Details of this procedure are given in Appendix B. Carbon
monoxide concentrations in the irradiated gases were measured
by means of a long-path nondispersive infrared analyzer. Oxi-
dant concentrations were measured by a continuous-recording
coulometric instrument (Mast) that uses a neutral potassium
iodide solution. Gas chromatography was used for detailed
analyses of hydrocarbons containing 2 to 5 carbon atoms.'*
Wet-chemical analytical methods were employed for measure-
ment of olefin, formaldehyde, and acrolein, ^ and for confirma-
tory measurements for NO and NO2- ^ A few mass-spectro-
graphic and infrared analyses were also made.
TEST PARAMETERS
Three variables that affect the photochemical reaction sys-
tem were studied in this test series.
EXHAUST CONCENTRATION
Effects of irradiation were evaluated under three conditions
of concentration:
1. 'Atmospheric' hydrocarbon levels of approximately
11-15 ppm carbon. These concentrations represent
ambient air levels during severe air pollution situations.
2. Concentrated hydrocarbon levels of approximately 32-
40 ppm carbon.
3. 'Equivalent1 atmospheric concentration levels achieved
by diluting the chamber contents produced during irra-
diation at concentrated levels.
Variations in chemical reaction were evaluated for conditions
1 and 2. Plant exposures were made and evaluated at conditions
1 and 3. Effects on bacteria were evaluated at all three condi-
tions.
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14 IRRADIATION CHAMBER TESTS
AVERAGE IRRADIATION TIME
Average irradiation times of 85 and 120 minutes were selec-
ted to represent equilibrium conditions in the chamber after an
extended period of irradiation. From the relationship previously
discussed (Equation 1), average irradiation periods of 85 and
120 minutes at equilibrium (t infinite) require flow volumes of
3. 9 and 2. 8 cubic feet per minute respectively. At these flow
volumes, for irradiation periods (i. e. time after irradiation
starts) of 1.5, 2. 0, and 2. 5 times the average irradiation time
selected, the actual average irradiation times are 78, 86, and
92 percent of the selected average irradiation time, respec-
tively.
FUEL CONTENT
Previous work indicated that the olefin content of fuels
could possibly influence the air pollution potential of irradiated
exhaust gases. For this reason two fuels were chosen for testing
in this series, one containing 14% olefins and one containing 23%
olefins. These fuels were obtained from special stocks pre-
pared by the Western Oil and Gas Association for automotive
exhaust research. Both fuels had approximately the same aro-
matic content: the low-olefin fuel, fuel 3, gave a bromine num-
ber of 30, and the higher-olefin fuel, fuel 5, gave a bromine
number of 50. The physical specifications of the fuels were
held approximately equal: both had research octane numbers of
100; ASTM distillation ranges varied by not more than 5% at
any point; Reid vapor pressures were 9. 3 and 9. 4; and API
gravities were 56. 0 and 56. 5. Physical and chemical proper-
ties of the fuels are shown in Table 1.
OTHER TEST CONDITIONS
Irradiation intensity in the region from 2900 to 3600 ang-
stroms was held at levels believed to approximate summer noon-
day sunlight in Southern California. All tests were conducted at
a constant volumetric ratio of hydrocarbon to oxides of nitrogen
of approximately 12:1 (hydrocarbon expressed as ppm carbon).
The reaction system used in this test series was dynamic
in that the introduction of the dilute nonirradiated exhaust gases
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Parameters
15
Table 1. PHYSICAL AND CHEMICAL, PROPERTIES OF TEST FUELS
Properties
API gravity, degrees
Reid vapor pressure, Ib/in. **
Distillation, °F
Initial
End point
Recovery, volume %
Sulfur (total), weight %
Sulfur (RSH), ppm
Gum (existent), mg/lOOml
Gum (accelerated, 4-hr), mg/lOOml
Bromine no. (electrometric), g/100 g
Tetraethyl lead, ml/ gal
Fluorescent indicator analysis
(as received), volume %
Saturates
Olefins
Aromatic s
Octane no.
Motor, F-2
Research, F-l
Fuel No. 3
56.0
9.3
92
406
98
0. 013
0. 0002
1. 1
1.4
31
0.53
47. 1
13.9
39.0
88.9
100. 1
Fuel No. 5
56.5
9.4
95
400
97.5
0.042
0.0004
2.3
3.2
49
1.38
38.8
22.9
38.3
87.8
100. 1
and the withdrawal of an equal quantity of irradiated exhaust
gases was continuous. In contrast, previous studies have
utilized a static system, °> ' in which a dilute mixture of exhaust
gases was charged to the chamber, the gases were irradiated,
and the effects were evaluated after a selected irradiation
period. The two techniques generally produce the same series
of reactions. The chief difference is that in the dynamic
system the incoming nonirradiated gases and the irradiated
gases present in the chamber approach kinetic chemical
equilibrium, whereas in the static system the chemical reaction
of the single charge is allowed to approach completion.
The extent of mixing of community atmospheres is both
complex and extremely variable. On the average it is probably
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!& IRRADIATION CHAMBER TESTS
greater than that which occurs in a static system and less than
O
the continuous, uniform mixing produced in the dynamic irradia-
tion chamber. Probably specific cases occur in which the
mixing actions of both static and dynamic systems are paralleled
in the atmosphere. Because of the intricate movements of
parcels of air, it is possible that mixing conditions much like
those produced in both systems could occur simultaneously at
different locations within a community. These two test condi-
tions represent extremes of mixing, and results obtained in
both series of chamber studies probably span the average
mixing conditions of the atmosphere.
CHEMISTRY OF IRRADIATED EXHAUSTS
THE NO NO2 REACTION PROCESS
The oxidation of NO to N©2 is one of the significant systems
in the photochemical reaction complex. Studies to date indicate
that this complex reaction system consists of two fundamental
reaction series: the NO NO-, photo-oxidation reactions and the
NO2 — free-radical reactions.
NO NO2 PHOTO-OXIDATION REACTIONS
Nitric oxide oxidizes to nitrogen dioxide in the presence of
organic compounds under ultraviolet radiation at a rate far high-
er than the thermal rate of oxidation of nitric oxide by molecular
oxygen. This rapid conversion of nitric oxide to nitrogen di-
oxide appears to require a chain reaction involving peroxyalkyl
(RO2) and peroxyacyl (RCOj) free radicals. These radicals
apparently are generated extremely rapidly by initial steps in-
volving atomic oxygen attack on hydrocarbon species or photoly-
sis of nitrogen dioxide.
Investigations of the photochemistry of model systems have
shown that many types of organic compounds can participate in
the photo -oxidation of nitric oxide to nitrogen dioxide and the for-
mation of ozone in the photochemical reaction complex. Olefins,
many aromatic hydrocarbons, some higher-molecular-weight
paraffins, and aldehydes already have been shown to participate.
Lower-molecular-weight paraffins (including methane, ethane,
propane, and the butanes), acetylene, and benzenes do not ap-
pear to participate to any marked degree in these reactions.
NO2 - FREE-RADICAL REACTIONS
The free-radical species that participate in the photo-oxida-
tion of nitric oxide also may react with nitrogen dioxide to form
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Chemistry
17
organic nitrogen compounds as the nitrogen dioxide concentration
increases during the irradiation. Alkyl nitrates and peroxyacyl
nitrates have been identified and measured as products in static
chamber experiments.
Under many of the experimental conditions used in this study
a substantial depletion of nitrogen dioxide was observed after the
nitrogen dioxide reached its maximum concentration. A limited
number of infrared measurements also indicated the presence
of alkyl nitrates and peroxyacyl nitrates. The presence of these
substances accounts for at least part of the decrease in the ni-
trogen dioxide during the irradiations.
Under dynamic irradiation conditions, photochemical reac-
tion begins when the irradiation is started (Figure 10, Table Al).
-120 -90 -60 -30 0 30 60 90 120 150 180 210 240 270 300 330
TIME, minutes
Figure 10. Chemical relationships for a typical chamber reaction.
It is postulated, as discussed above, that initially the NO-NO2
photo-oxidation reactions predominate. This results in a rapid
decrease in NO concentration, with a correspondingly rapid in-
crease in NO2 concentration. Some of the hydrocarbons present
also decrease significantly in this stage of the reaction. This
reaction continues, depending on the conditions of irradiation, for
30 to 120 minutes until the NO2 concentration reaches a maxi-
mum and the NO concentration approaches a minimum. At about
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18
IRRADIATION CHAMBER TESTS
this point the NO2 free-radical reactions become important,
and the NO2 concentration drops as the NO2 reacts with inter-
mediate exhaust reaction products. This condition continues un-
til equilibrium is approached between the NO NO2 photo-oxida-
tion reactions and the NO2 free-radical reaction. An increase
in the level of oxidant and other reaction products and a further
decrease in hydrocarbon concentration accompany the NO2
free-radical reactions. As similarly observed in the static ir-
radiation systems, ozone appears only when the NO2 reaches
peak concentration and the NO approaches its minimum equili-
brium concentration.
CHEMICAL EFFECTS
NO;
The rate of formation of NO2 is an important index for the
characterization of irradiated atmospheres because it is a mea-
sure of reactivity of the over-all system, readily obtained with
available monitoring instrumentation. Table 2 lists the average
and individual NO2 formation rates observed for all combina-
tions of the test variables. These data are pictured in Figure
11. It is apparent that within the scope of the study, initial ex-
haust concentration had the greatest effect on NO2 formation
rate. Fuel composition had a lesser effect; average irradiation
time (AIT) had little or no effect.
Table 2. NO2 FORMATION AND DISAPPEARANCE
Test conditions
Exhaust
level
Atm
Atm
Atm
Atm
Cone
Cone
Cone
Cone
Fuel
No.
3
3
5
5
3
3
5
5
AIT,
min
85
120
85
120
85
120
85
120
Average
actual exhaust
gas cone, ppm C
14.3
12.2
14.8
14.4
33.0
36.0
39.0
35.5
NO2 Formation rate,
pphm/min
Individual runs
1.76, 1.25, 1.50
1.45,1. 67
1.88,2.22
2. 10, 1.95
2.42,2.90
2. 61,2. 36
3. 59,3.80
2.68,2.74
Avg
1.5
1.5
2. 1
2.0
2.6
2.5
3.7
2.7
Average
NO2 disappearing,
%
41.5
60.5
60.0
63.0
27. 5
35.5
39.0
26.5
Comparing all runs made at atmospheric hydrocarbon levels
with those at concentrated levels shows a mean increase in aver-
age NO2 formation rate from 1. 8 (range 1. 25-2. 22) to 2. 9 pphm/
minute (range 2. 36-3. 80). Changing from a low (14%) to a high
(23%) olefin fuel caused an average increase from 2. 0 (range
1. 25-2. 9) to 2. 6 pphm/minute (range 1. 88-3. 80). Increasing
average irradiation time from 85 to 120 minutes caused a
-------
Chemical Effects
19
SHADED PLANE REPRESENTS
120-MINUTE AVERAGE
IRRADIATION TIME
UNSHADED PLANE
REPRESENTS 85-MINUTE
AVERAGE IRRADIATION
TIME.
FUEL 5 (23 % OLEFIN)
FUEL 3 (14% OLEFIN)
10 20 30 40 50
HYDROCARBON CONCENTRATION LEVEL, ppmC
Figure I I. NO2 formation rate as influenced by hydrocarbon
concentration, fuel type, and irradiation time.
decrease from 2.5 (range 1. Z5-3.80) to 2.2 (range 1. 45-2.74).
This decrease was the result of unusual test conditions; as will
be shown later essentially no change in NC>2 formation rate is
attributable to changes in average irradiation time. The aver-
age differences caused by changes in concentration and fuel
composition are both significant at the 1% level determined by
an analysis of variance.
As shown in Figure 11, the effects of increasing initial
hydrocarbon concentration and changing from fuel 3 to fuel 5
appear to be additive. This suggests that the initial olefin con-
centration may be the most important factor in determining the
NC>2 formation rate, since both concentration and fuel influence
olefin content. Table A2 gives the average concentration of
four-carbon and higher olefins at the start of irradiation for
each test situation. These data are plotted in Figure 12 against
NC>2 formation rate and show a good relationship between olefin
concentration at the start of irradiation and NC>2 formation rate.
Consideration of the importance of olefin concentration in
the initial exhaust mixture also helps explain the apparent de-
crease in NC>2 formation rate as the average irradiation time
(AIT) increased from 85 to 1ZO minutes in the concentrated
series with fuel 5 (Figure 11). Although the total hydrocarbon
concentrations were similar, the exhaust mixture for the runs
at 85 minutes AIT contained an average of 6. 57 |J.g/l of C^.+
olefins and that used in the runs at 120 AITaveraged 3. 82 p.g/1.
-------
20
IRRADIATION CHAMBER TESTS
8.0
o
+u*
z
O
O
Z
O
O
7.0 —
6.0
5.0
4.0
3.0
t 2.0
1.0
o 120 MIN AIT
• 85 MIN AIT
0 1.0 2.0 3.0 4.0 5.0 6.0
NO2 formation rate, pphm /min.
Figure 12. Relationship of olefin concentration to NO2 formation rate.
The apparent difference in NO£ formation rate (3. 7 vs Z. 7
pphm/min) is probably not due to changes in AIT but to initial
olefin concentration. Adjustment of these points to similar
olefin concentrations brings them into line and leads to the con-
clusion that AIT has no influence on NO? formation rate. The
experimental conditions that led to the low olefin levels for the
120-minute AIT cannot be explained.
-------
Chemical Effects 21
Analysis of the NOo free-radical reaction data does not
allow conclusions as detailed as for the NC>2 formation rate.
The rate of NC>2 disappearance cannot be established accurately,
since limitations in the instrumentation prevented the precise
determination of the time of peak NC>2 concentration. Therefore
the percentage of NO2 disappearing (defined as the percent de-
crease in NC>2 concentration from peak to equilibrium) has been
used as a measure of the NC>2 free-radical series of reactions
described earlier. Analysis of the data in Table 2 indicates
that NC>2 disappearance is greater for the atmospheric series
of tests than for the concentrated series. Average values drop
from 56% disappearance for the atmospheric series to 32% for
the concentrated series. This difference is significant at the
1% level. The differences caused by fuel composition (41 and
47%) and average irradiation time (42 and 46%) are not statisti-
cally significant.
OXIDANT
One of the principal reactions associated with the NO to NO2
photo-oxidation is the formation of oxidant (Figure 10). The
coulometric instrument used to monitor ozone is sensitive to
NO2 and other oxidants as well as to ozone. To secure a
better indication of ozone levels, corrections were made for the
principal interference, NO2- The corrected values for oxidant,
shown in Figure 13, are primarily ozone, although they include,
to a very limited degree, the response of other oxidants.
Two conclusions are apparent from the oxidant data: (1) av-
erage irradiation time has no influence on oxidant production
and (2) the higher initial hydrocarbon concentration level inhibits
the production of oxidant for as much as 1/2 hour at the begin-
ning of the irradiation. Although variations in oxidant level were
observed with changes in exhaust concentration and fuel composi-
tion, these followed no consistent pattern and provide no basis
for general conclusions. By contrast, reports of static irradia-
tion chamber tests" indicate that ozone formation increased with
exhaust concentration as a function of the one-half power of the
increase in hydrocarbon level. Additional work is needed to re-
solve the apparent difference between the results of static and
dynamic tests.
HYDROCARBONS
The disappearance of hydrocarbons during irradiation is in
accord with the NO2 free-radical reactions hypothesis, i. e.
the involvement of NO2 with intermediate hydrocarbon reaction
products. The disappearance of hydrocarbons also could be
the result of reactions involving ozone and oxygen atoms to form
oxygenated products. In all tests the reduction in organics as
-------
22 IRRADIATION CHAMBER TESTS
60
CURVE IRRADIATION
TIME
85
120
85
120
85
120
85
0
0 20 40 60 80 100 120 140 160 180 200 220 240 260 280
TIME, minutes
Figure 13. Oxidant concentrations corrected forNO2 response.
measured by the flame-ionization analyzer was not appreciable
until the NC>2 concentration peaked (Appendix A, Figures Al
through A8). At this point the reduction increased sharply and
continued until chamber equilibrium was reached. The over-all
reduction ranged from 15 to 20% for all test conditions.
A consistent difference was noted in the reactivity of the
various classes of hydrocarbons as measured by the percent
decrease in concentration of these individual species. These
reactivities were not influenced by changes in exhaust concen-
tration, fuel composition, or irradiation time, however.
Olefins were studied by both wet chemistry and gas chroma-
tography. Four-carbon and higher molecular weight olefins
were measured by a wet chemical procedure, the p-dimethyl-
aminobenzaldehyde method of Altshuller and Sleva. ^ Aroma-
tics and two- through five-carbon paraffins and olefins, acety-
lene and methyl acetylene were analyzed by gas chromato-
graphy.4' H
Measurements made for acetylene indicated no significant
reaction rate for this compound, but methyl acetylene appeared
to be slightly reactive. Tables AZ A5 give data on concentra-
-------
Chemical Effects
23
tion of four- and five-carbon paraffins for the various test con-
ditions. Table 3 summarizes losses of these paraffins during
irradiation. It appears that on the average four- and five-carbon
paraffins did not react at significant rates.
Table 3. PERCENT DECREASE FOR SPECIFIC HYDROCARBONS
Compound
Di olefin
Butadiene
Terminally bonded olefine
Butene-1, isobutene
Pentene-1
Z-Methylbutene
Avg
Internally bonded olefins
c-Butene-2
t-Butene-Z
c-Pentene-2
t-Pentene-2
2-Methylbutene-2
Avg
Paraffins
Isobutane
n-Butane
Isopentene
n-Pentene
Avg
Fuel No. 3
85
Atm
68
62
47
71
62
100a
100a
90
90
98
96
10
14
13
12
12
Min
Cone
62
60
55
67
61
100a
100a
86
81
87
85
4
5
6
8
6
120 Minb
Atm
73
75
67
77
73
100a
100*
100a
100a
100a
100a
13
3
10
10
9
Fuel No. 5
85
Atm
67
52
36
75
58
100a
100a
100a
100a
100a
100a
-4
3
-3
-3
-2
Min
Cone
67
71
57
88
71
100a
100*
96
95
93
95
4
-13
-5
-3
-4
120 Min
Atm
75
67
63
88
73
100a
100a
100a
100a
100a
100a
0
2
5
5
3
Cone
65
68
60
68
65
100a
100a
100a
100a
100a
100a
-5
-2
0
6
0
aValues after irradiation are below the limits of detection; although percent decrease is
approximate, it usually approaches 100 percent.
bNo values are given for concentrated levels, since data were inadequate for analysis.
Olefins — Although all olefins measured showed a significant
decrease in concentration during the test runs, the decrease
was not influenced by the test variables. The relative concen-
tration of the individual olefins at the start of irradiation was
dependent on fuel composition and did vary to some extent with
initial exhaust concentration. These data'are shown in Tables
A2 A5.
Individual four- and five-carbon olefins reacted at rates that
were dependent upon the location of the double bond (Table 3).
The terminal olefins showed an average decrease of approxi-
mately 65% after irradiation periods of 170 minutes for the 85-
minute AIT series and 240 minutes for the IZO-minute AIT
series. At the end of these same irradiation periods, all
internally bonded olefins showed almost complete reaction. The
final concentrations for internally bonded olefins were usually
below the limits of detection of the analytical methods. Bu-
tadiene-1, 3 behaved similarly to the terminally bonded olefins.
Decreases of 12% and 50% were found for ethylene and propylene,
respectively, in a few gas-chromatographic measurements
-------
24 IRRADIATION CHAMBER TESTS
of these compounds in the atmospheric series. Static irradiation
chamber tests9' 12 also show a high degree of reactivity for
terminally bonded olefins and essentially complete disappearance
of internally bonded olefins.
Aromatics — Aromatics were studied in a few runs by gas
chromatography. i1 The chromatographic column used did not
provide resolution for complete separation of benzene from other
reaction products. Work with the mass spectrometer, 13 con-
firmed by pure component studies, indicated that benzene is non-
reactive. All other aromatics studied showed some degree of
reactivity after an irradiation period equal to two times the av-
erage irradiation time. The results of three runs, all made
with fuel 3 in the concentrated series, are shown in Table 4.
These few tests indicated an average decrease of about 10% for
toluene and ethylbenzene, about 30% for xylene and the 3- and
4-ethyltoluenes, and about 50% for styrene.
Table 4. PERCENTAGE CHANGE IN AROMATIC HYDROCARBONSa
AITb
120
120
85
Avg
Toluene
5
-13
6
8
Ethyl -
Benzene
0
-17
-16
-11
m- and p-
Xylene
-21
-28
-27
-25
o-Xylene
-29
-29
-27
-28
Styrene
-40
-70
c
-55
3- and 4-
Ethyltoluene
-21
-39
c
-30
aPercent change after irradiation periods of 170 and 240 minutes for 85 and 120
minute AIT, respectively.
^Average irradiation time, minutes.
GConcentrations of these components too low to determine changes in composi-
tion.
These results indicate that the nature of substitution on the
benzene ring controls the reactivity rate. More detailed evalua-
tion of this possibility is not warranted by the limited experimen-
tal data available.
FORMALDEHYDE
Formation of formaldehyde in the irradiation system de-
pended primarily on initial exhaust concentration, as shown in
Figure 14. Increasing initial exhaust concentration by 2 to
2-1/2 times generally resulted in a proportional increase in
formaldehyde after 240 minutes of irradiation, although the ini-
tial formation rates appear about the same for each exhaust con-
centration. These average data also indicate that fuel composi-
tion may influence slightly the production of formaldehyde.
Average irradiation time did not appear to influence formalde-
hyde production.
GPO 8O6—304-3
-------
Chemical Effects
25
CURVE I IRRADIATION I FUEL I CONG. I
3 CONC
3 CONC
5 CONC
5 CONC
20 40 60
80 100 120 140 160 180 200 220 240 260 280
TIME, minutes
Figure 14. Formaldehyde concentrations.
OTHER ALDEHYDES
Aldehydes other than formaldehyde were measured in a
few runs and were found both in the nonirradiated and the irradi-
ated exhaust mixtures. Irradiation brought about a five-fold in-
crease in their concentration; that is, only about 20% of the
aldehyde came directly from the auto exhaust. Acrolein,
analyzed by the method of Cohen and Altshuller, 5 behaved gen-
erally like formaldehyde; the concentration was initially low,
increased during irradiation, and reached a maximum after
approximately two average irradiation times. In several analy-
ses a 25 to 30% decrease in acrolein concentrations, noted after
the maximum was reached, indicated further reaction of the
acrolein.
Aldehydes showed the same general relationships to initial
exhaust concentration and fuel composition as the NC>2 formation
rate — indicating a. dependency on initial olefin concentration.
This is not unexpected, since it is the attack of ozone and atomic
oxygen on the olefins and aromatics that produces aldehydes. In
this study, however, the aromatic content of the fuels was held
-------
26 IRRADIATION CHAMBER TESTS
constant. Increasing the concentration level of exhaust in the
chamber and changing from fuel 3 to fuel 5 both resulted in an
increase in the aldehydes produced. The reaction that produces
acrolein, primarily from the butadiene-1, 3 is typical of the
aldehyde-producing reactions:
CH2 = CH-CH=CH2 + (0)—*CH2 = CH-CHO + CH2O + other
products.
In two instances total aldehydes were also determined by the
3-methyl-Z-benzothiazolone hydrazone test described by Sawicki
et al. -^4 Table 5 shows the relationship between formaldehyde^
and total aldehydes for the tests with fuel 3 at concentrated
exhaust levels and 85-minute AIT. Approximately 60% of the
total aldehydes were formaldehyde in these runs.
Table 5. ALIPHATIC ALDEHYDE CONCENTRATION21 (ppm)
Run Total aldehydesb Formaldehyde0 % Formaldehyde
1 2.
1.
2 1.
1.
25
90
61
95
1. 11
1.28
0.96
1.02
49
67
60
52
Average 57
Concentration after equilibrium is attained.
bTotal aldehydes corrected for formaldehyde; absorptivity of
40 is used for all aldehydes other than formaldehyde.
°As determined by the chromotropic acid method. ^
BIOLOGICAL EFFECTS
PLANTS
Plants were exposed to two types of irradiated gases: (1)
directly to chamber gases irradiated at the atmospheric exhaust
levels, and (2) to chamber gases irradiated at the high exhaust
concentration, but diluted to atmospheric levels before plant
exposure. Exposures started within 15 minutes after the cham-
ber lights were turned on, and usually continued for 4 hours.
Following exposure, plants were returned to the greenhouse and
held for observation over a period of time.
-------
Biological Effects 27
Symptoms of severe injury were sometimes noticeable
within a few hours. Some injury patterns were not visible until
48 hours after exposure. The patterns of injury, including the
microscopic patterns observed with thin sections, varied with
species and age of tissue. Prior- and post-exposure culture
conditions had some effect on injury pattern.
Broad classes of injury patterns are thought to relate to
specific phytotoxicant classes. At this time, however, tech-
niques of exposure and classification of injury patterns have
not been developed sufficiently for formulation of a multiple-
class injury scale.
A number of general conclusions are possible concerning the
effect of the three variables on plant damage: (1) fuel 5 produced
a greater total injury than fuel 3 and also a different distribution
of type of injury, and (Z) higher exhaust concentrations at time of
irradiation also produced a different distribution of type of injury
than the atmospheric series, but tended to decrease the total in-
jury. (It should be noted that the higher exhaust concentrations
were diluted to atmospheric levels after irradiation and before
plant exposure. ) For reporting gross injury a scale of 0 (no in-
jury) to 4 (total injury of sensitive tissue) was used. The av-
erage index for all plants is shown in Table 6 for each fuel at
each irradiation time and concentration.
Table 6. AVERAGE GROSS PLANT INJURY3-
Irradiation
Irradiation concentration,
Fuel time, min PPm C
12-15
85 32-40c
3 „ 12-15
120 32-40C
12-15
32-40c
5 „ 12-15
120 32-40C
Plant injury
1. 0
0.4
0.5
0.2
2. 1
1.8
2. 2
1.0
aAverage of all plants exposed at each condition.
t>Scale: 0 (no injury) to 4 (total injury of sensitive
tissue).
cPlants exposed after dilution of exhaust to equivalent
atmospheric carbon levels.
-------
28
IRRADIATION CHAMBER TESTS
ANIMALS
Although animal exposures were made during only a few of
the irradiation chamber runs discussed in this report, the facil-
ities were used in special tests designed specifically for animal
studies. The conditions of these tests did not necessarily con-
form to those used for the chemical, plant, and bacteria studies
discussed in this report and are not a part of this test series.
These special investigations with small animals, which were
generally exploratory studies, are summarized in detail in a
report prepared by the Laboratory of Medical and Biological
Sciences, Division of Air Pollution.
16
BACTERIA
The effects of the irradiated gases on bacteria (E. coli) are
shown in Table 7.
Table 7. EFFECT OF CONCENTRATION ON BACTERIA KILL
Fuel No.
3
5
Irradiation
time, min
85
120
85
120
Irradiation
level
Atm
Cone
Atm
Cone
Atm
Cone
Atm
Cone
Bacteria kill, relative unitsa
Exposure at
irrad. level0
2.0
9.0
4.0
6.5
1.5
9.0
2.5
8.0
Exposure at
atm levelc
2.0
1.5b
4.0
1.0b
1. 5
2. Ob
2. 5
2.0b
aComplete kill equals 9; exponential scale.
^Exposure made at the concentration at which irradiation occurred.
cExposure made after dilution of the high-concentration exhaust to equiva-
lent atmospheric concentration levels.
The values for bacteria kill shown in Table 7 represent de-
gree of bacteria kill (rated on a scale of 1 through 9). They
were determined by visually estimating the area and distribution
of prepared culture strip affected by exposure to the irradiated
exhaust. Since the bacteria were plated on the test strip in con-
centrations that increased logarithmically, the degree of kill
given in Table 7 represents an exponential rather than a linear
kill scale.
Degree of bacteria kill was influenced only by exhaust con-
centration. No effect was observed for changes in fuel composi-
tion or average irradiation time. No difference in bacteria kill
was noted between exposure to gases irradiated at atmospheric
-------
Summary of Results 29
levels and gases irradiated at concentrated levels and diluted to
atmospheric levels.
SUMMARY OF RESULTS
Within the limits of experimental values selected for this
series of tests, the three major variables examined, (1) initial
exhaust composition, (2) fuel composition and (3) average irradi-
ation time can be ranked according to their influence on the
chemistry of the irradiation process, and biological effects of
reaction products. Concentration of exhaust at the start of ir-
radiation produced the greatest effect on the greatest number of
test parameters, including NC>2 formation rate, oxidant and for-
maldehyde production, plant damage, and bacterial kill. Chang-
ing fuel from number 3 (14% olefins) to number 5 (23% olefins)
also affected plant damage, NO2 formation rate, and possibly
formaldehyde production. Changing average irradiation time
from 85 to 120 minutes had essentially no effect on any of the
test parameters.
More detailed conclusions are appropriate for each of the
test parameters and are given below:
1. The NC>2 formation rate was increased significantly by
increases in both exhaust concentration and olefin con-
tent of the fuel. Average NO2 formation rate increased
from 1.8 to 2.9 pphm/min as the average initial exhaust
concentration increased from atmospheric levels (14
ppm C) to concentrated levels (36 ppm C). An average
increase from 2. 0 to 2. 6 pphm/min was observed in
going from fuel number 3 to fuel number 5. Increasing
average irradiation time from 85 to 120 minutes had no
effect on NC>2 formation rate. A good relationship was
observed between NO2 formation rate and initial olefin
concentration in the chamber.
2. The percentage of disappearance of NC>2 was decreased
significantly by increasing initial exhaust concentration.
Fuel composition and average irradiation time had no
effect.
3. Increasing exhaust concentration appeared to cause a
delay in initial oxidant production of approximately 30
minutes. The amount of oxidant (mostly ozone) pro-
duced was influenced by exhaust concentration and fuel
type, but no consistent pattern was apparent. Average
irradiation time had no apparent effect on oxidant pro-
duction.
-------
30
IRRADIATION CHAMBER TESTS
4. Reduction in organic concentration as measured by the
flame-ionization analyzer ranged from approximately
15 to 25%. The percentage decrease in the terminal
olefin varied between 35% and 88%, depending on the
specific hydrocarbon, and averaged about 65% decrease
in concentration with irradiation. All internally bonded
olefins reacted almost completely to form products.
Paraffins and acetylene were essentially unreactive.
The aromatic hydrocarbons disappeared through reac-
tion by amounts ranging from about 10% for toluene to
about 50% for styrene and appeared to depend on type of
substitution on the benzene ring. No consistent patterns
of influence of exhaust concentration, fuel type, or av-
erage irradiation time were observed for any group of
hydrocarbons.
5. Increasing initial exhaust concentration from 14 ppm
carbon to 36 ppm carbon resulted in proportional in-
creases in average formaldehyde concentrations of
from 50 pphm to 120 pphm at kinetic equilibrium.
6. In a few test runs analyses were made for both total
aldehydes and formaldehydes. Approximately 60% of
the total aldehydes appeared to be formaldehydes.
7. Most of the aldehyde present came from chamber reac-
tions. (About 20% originated in the auto exhaust. ) Gen-
erally aldehydes varied with exhaust concentration and
fuel type similarly to the NO£ formation rate — indica-
ting a dependency on initial olefin concentration. This
was as expected, since the attack of ozone and atomic
oxygen on olefins produces most of the aldehyde present.
8. Differences in extent and distribution of type of plant
damage were observed with changes in exhaust concen-
tration at irradiation and with fuel type. No effects
were attributable to changes in average irradiation
time. The high-olefin fuel generally gave a higher in-
jury index than did the low-olefin fuel. Plants exposed
to exhaust irradiated at 36 ppm carbon and diluted to the
14-ppm equivalent prior to plant exposure generally
gave a lower injury index than plants exposed to exhaust
irradiated at 14 ppm carbon.
9. The average degree of bacterial kill increased from 3
to 8 on an exponential scale as irradiated exhaust con-
centration increased from 14 to 36 ppm carbon. When
the concentrated irradiated mixture was diluted to at-
mospheric levels, the degree of kill decreased to a
value of about 2. Fuel composition and average irradi-
ation time had no apparent effect on degree of bacterial
kill.
-------
Summary of Results 31
In addition to the results enumerated above, this first
series of dynamic irradiation chamber investigations has demon-
strated the usefulness and versatility of the facility, permitted
development of reliable experimental and analytical techniques,
suggested possibilities for future investigations, and provided
the basis for their design. A second series of tests with the
dynamic irradiation chamber has been completed, and analysis
of data is now under way. These runs were designed to explore
in detail the effects of varying ratios of hydrocarbon to oxides
of nitrogen. Tests were run with a single fuel (similar to
fuel 3), 120-minute average irradiation time, and exhaust con-
centrations at atmospheric levels or below. A report is being
prepared on this second series. Additional test series -will
follow.
Investigations of the effect of raw and irradiated exhaust on
animals have been greatly expanded and transferred to a separate
facility since this first series of tests. The present study in-
volves nearly 3000 small animals and continuous exposures
over the life period of the animals to varying levels of raw and
irradiated exhaust.
-------
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-------
34 IRRADIATION CHAMBER TESTS
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of the American Chemical Society, Chicago, 111. , Sep-
tember 1961.
14. Sawicki, E. , Hauser, T. R. , Stanley, T.W., and Elbert,
W.C., "The 3-Methyl-2Benzothiazolone Hydrazone
Test, " Anal. Chem. , 33, 93(1961).
15. Altshuller, A. P. , Miller, D.L., and Sleva, S.F., "De-
termination of Formaldehyde in Gas Mixtures by the
Chromotropic Acid Method, " Anal. Chem. 33, (1961).
16. Murphy, S. J. , Leng, J.K., Ulrich, C.E., and Davis,
H. V. , "Effects on Experimental Animals of Brief Ex-
posure to Diluted Automobile Exhaust, " Submitted to
A.M. A. Arch, of Environmental Health, 1962.
-------
APPENDIX A
RAW DATA FOR IRRADIATION CHAMBER
REACTION PRODUCTS
-------
Table Al. CONCENTRATION VERSUS TIME AFTER IRRADIATION STARTED
(Mean values from two or more tests)
NO
(pphrn)
NO2
(pphm)
HC
(ppm)
Oxidant
(pphm)
Olefin
(pphm)
HCHO
(pphm)
3
3
5
Average
irrad.
85
1ZO
120
85
1EO
85
120
85
85
120
B5
120
85
120
85
31
85
120
85
120
Atmospheric levels
(11-15 ppm carbon)
62.3
79. 0
35. 0
2. 5
2. 0
14. 3
12.2
14. 4
0. 0
0. 0
0. 0
0. 0
16. 1
46. 0
13. 7
15. 0
0. 0
0. 0
27.3
21. 5
4.0
61.5
7 .0
6 .5
1 . 3
1 . 5
0. 5
2.0
2. 0
2. 0
12. 9a
35763-
15. 3a
21. 5
23. 0
32. 0
1.7
0.5
0. 5
52. 3
36. 5
36. 0
13. 2a
12. 1
24. 1
25.0
12. 5
IB. 8
5. 6
14. 9a
31.0a
31. 5a
54. Oa
40. 5a
90
1. 7
0. 5
0. 0
44. 5
38.0
31.5
31.0
12. 3
10.6
11.5*
33.5
31. 5
19. 0
19.5
3.3
10, 8a
39.7
36. 5a
58.5
43. 0
150
1. 3
2.0
0.0
43.0
31.0
29. 0
12.0
10. 2a
1 1. 1
33. 1
33. 5
19. 0
23.3
2.8*
7.3a
43. 3a
44. 5a
46. 5
240
Min
1. 0
0. 5
2.0
0.0
42. 3
28. 5
29. 0
12. 0
10.4
1 1. 3
36. 5
37. 5
26. 0
28.0
2. 7
6.2
46. 7
53. 0
54. Oa
Concentrated levels
(32-40 ppm carbon)
0
Min
214.5
195.8
216. 1
159- 4
14. 9
14.9
19. 7
18.2
33.0
35.5
0. 0
0. 0
0. 0
0. 0
45.
69.
39.
29. 0
33. 5
40. 0
30
Min
150. 0
159. 2
137. 1
102.7
83. 1
114. 9
101. 6
33. 0
36.0
35. 5
0. 0
0. 0
0.0
0. 0
41. 2*
61. Oa
54. 0
44. 0
50, 0
46. 5
60
Min
50. 8
73. 3
17. 3
30. 6
176. 1
182. 8
200. 1
31.5*
33.5
33.0
0. 0
2. 0
6. 5
3. 5
2S.5
25.5
89. Oa
60. 5
77. 0
68. 5
90
Min
22.3
38.9
16. 1
20. 3
173. 6
210.7
156.1
179,3
29.5
32.9
30.5
9.0
lb. 0
16. 3
20. 6*
20. 2a
97. Oa
68. 5
90. Oa
93.0
150
Min
16.9
16. 1
1 18.8
"151. 3 '
203.8
135.8
156, 2
27.8
31.1
29. i
21. 3
20.2
29. 8
27. 5
it. 4»
— mp-
103. 0
92. 55
112.5
107. 5
240
Min
16.9
20. 6
14.8
17. 1
148. 8
129.1
145. 1
28.0
50.8
29.0
23.4
32.5
32. B
32.8
15.0
12.2
113.5
116.5
137. 0
128. 0
Table A2. HYDROCARBON REACTIONS; CONCENTRATED SERIES - FUEL No. 3
Compound
Diolefin
Butadiene
Terminally bonded olefins
Butene-1, isobutene
Pentene-1
2-Methylbutene-l
Average
Internally bonded olefins
c-Butene-Z
t-Butene-2
c-Pentene-2
t-Pentene-2
2-Methylbutene,-2
Average
C4 + olefinsd
Paraffins'
Isobutane
n-Butane
leopentane
n-Pentane
Average
85-Min avg irradiation time
Concentration, ppma
Beforeb
U.047
0.094
0.031
0.049
0. 013
0. 015
0. 049
0.086
0. 101
3.78
0.027
0.222
0.313
0. 107
After0
0.018
0.038
0. 014
0. 016
0. 005>Ne
0. 005>N
~ 0.007
0. 016
0.013
1. 50
0. 026
0.212
0.294
0.098
% Decrease
62
60
55
67
61
> 62
> 67
~86
81
87
85
60
4
5
6
a
6
120-Min avg irradiation time
Concentration, ppma
Beforeb
0.026
0.052
0. 014
0.031
0.006
0.008
0. 021
0.042
0.068
3. 64
0.008
0. 087
After1
0. 021
0.045
0. 015
0. 017
0.005>N«
0, 005>N
0.005>N
0. 005>N
0. 009
0.8
0.022
0. 188
0.289
0. 106
% Decrease
19
13
0
45
>13
>37
>76
>88
87
-90*
78
^Chamber concentration before irradiation.
cChamber concentration after two average residence times.
^Olefins determined by wet chemical analysis (6); results in micrograms per liter.
^Values are less than stated value, which is limit of detection.
^Average value is estimated; actual value is not determinable because of limit of detection.
-------
Table A3. HYDROCARBON REACTIONS; CONCENTRATED SERIES - FUEL No. 5
Compound
Diolefin
Butadiene
Terminally bonded olefins
Pentene- 1
2-Methylbutene- 1
Average
Internally bonded olefins
C-Butene-2
t-Butene-2
C-Pentene-2
t-Pentene-2
2-Melhylbutene-2
Average
C4 * Olefmd
Paraffins
Isobutane
n-Butane
Isopentane
n-Pentane
Average
85 Mm
C
Before15
0. 072
0. 044
0. 110
0.029
0. 030
0.068
0. 127
0. 145
6.57 ,,g
0. 028
0. 189
0.409
0. 120
Afterc
0.024
0. 019
0.013
0. 005>Ne
0. 005>N
~ 0. 003
~0. 006
0. 010
2. 37
0. 027
0. 213
0.428
0. 123
on time
ppma
% Decrease
67
57
88
71
>83
>84
-96
~95
93
95
64
4
-13
5
3
4
120 Ml
C
Beforeb
0. 046
0. 045
0.076
0.024
0.024
0.054
0. 101
0. 093
3.82
0. 022
0. 165
0.316
0. 098
n avg irrac
oncentration,
Afterc
0. 016
0. 018
0. 024
0. 005>Ne
0. 005>N
0. 005>N
0. 005>N
0. 005 >N
0. 68
0.023
0. 169
0. 317
0. 092
la on clme
ppma
% Decrease
65
68
60
68
65
79
79
91
95
95
~65f
82
5
2
0
6
0
aAverage values for two or rnoi
^Chamber concentration before
dQlefins determined by wet che
^Average value is estimated, actual value
adiation.
al analysis (6); re
t dete
ults in micrograms per liter.
minable because of limit of detectn
Table A4. HYDROCARBON REACTIONS; ATMOSPHERIC SERIES - FUEL No. 5
Compound
Diolefin
Butadiene
Terminally bonded olefins
Butene-1, iaobutene
Pentene- 1
2-Methylbutene- 1
Average
Internally bonded olefins
c-Butene-2
t-Butene-2
c-Pentene-2
t-Pentene-2
2-Methylbutene-Z
Average
C4 t Olefind
Paraffins
Isobutane
n-Butane
leopentane
n-Pentane
Average
85-Min avg irradiation time
Concentration, ppma
Beforeb
0.030
0.040
0.022
0.073
0.016
0.016
0.045
0.085
0. 151
2.07 |ig
0.023
0. 154
0.232
0.072
Afterc
0.010
0.019
0.014
0. 018
0.001>Ne
0.001>N
0.001>N
0.001>N
0.001>N
0.40
0.024
0. 150
0.240
0.074
% Decrease
67
52
36
75
58
>94
>94
>98.
>99
>99.4
~99f
81
- 4
3
3
3
2
120-Min avg irradiation time
Concentration, ppma
Beforeb
0.024
0.036
0.019
0.052
0.014
0.014
0.035
0.068
0. 129
2.0ug
0.015
0. 110
0. 194
0.058
Afterc
0.006
0.012
0.007
0.006
0.001>N
0.001>N
0. OOJ>N
0.001>N
0. 001>N
0.26
0.015
0. 108
0. 184
0.055
% Decrease
75
67
63
88
73
> 93
> 93
> 97
> 99
> 99
~99£
87
0
2
5
5
3
aAverage values for two or more runs.
^Chamber concentration before irradiation.
^Chamber concentration after two average residence times.
^OlefinB determined by wet chemical analysis (6); results in micros
eValuee are less than stated value, which is limit of detection.
^Average value is estimated; actual value is not determinable becau
rams per liter.
ie of limit of detection.
-------
Table A5. HYDROCARBON REACTIONS; ATMOSPHERIC SEMES - FUEL No. 3
Compound
Diolefin
Butadiene
Terminally bonded olefms
Butene- 1 , isobutylene
Pentene-1
2-Methylbutene-l
Average
Internally bonded olefins
c-Butene-Z
t-Butene-2
c-Pentene-2
t-Pentene-2
2-Methylbutene-2
Average
C4 + Olefinsd
Paraffins
Isobutane
n- Butane
Isopentane
n-Pentane
Average
Co
Beforeb
0.025
0.042
0.017
0. 042
0. 006
0. 007
0.030
0. 050
0. 107
1.81 ^g
0. 020
0. 154
0. 191
0.066
avg irradiat
ncentration, p
Afterc
0. 008
0. 016
0.009
0. 012
0. 001>Ne
0. 001>N
0. 003
0. 005
0.002
0.40
0. 18
0. 132
0. 167
0.058
pma
% Decrease
68
62
47
71
62
>83
>86
90
90
98
96
78
10
14
13
12
12
Co
Before13
0.022
0. 040
0. 012
0. Olb
0.006
0. 007
0.019
0. 039
0. 078
1. 86 fig
0.015
0. 115
0. 143
0.051
ncentration,
Afterc
0.006
0.010
0.004
0.006
0. 001>Ne
0. 001>N
0. 001>N
0.001>N
0.001>N
0.41
0. 013
0. Ill
0. 128
0. 046
ppma
% Decrease
73
75
67
77
73
>83
>86
J95
>97
>99
>97f
78
13
3
10
10
9
stated
mated;
•mical analysis (6); results in micrograr
lue, which ie limit of detection.
:tual value is not deterrninable because <
if limit of detection.
-------
AVERAGE DATA FROM
TWO OR MORE RUNS
0 30 60 90 120 150 180 210 240 270
TIME, minutes
Figure Al. Test conditions: atmospheric level, 85-minute AIT, fuel no. 3
-------
a.
a.
Z
o
t—
at.
O
Z
o
o
a.
o.
O
t—
of
O
O
o
AVERAGE DATA FROM
TWO OR MORE RUNS
10
0 30 60 90 120 150 180 210 240 270
TIME, minutes
Figure A2. Test conditions: atmospheric level, 120-minute AIT, fuel no 3
GPO 806—304-4
-------
AVERAGE DATA FROM
TWO OR MORE RUNS
0 30 60 90 120 150 180 210 240 270
TIME, minutes
Figure A3. Test conditions: atmospheric level, 85-minute AIT, fuel no. 5
-------
20
AVERAGE DATA FROM
TWO OR MORE RUNS
0
30 60 90 120 150 180 210 240 270
TIME, minutes
Figure A4. Test conditions: atmospheric level, 120-minute AIT, fuel no. 5
-------
AVERAGE DATA FROM
TWO OR MORE RUNS
0 30 60 90 120 150 180 210 240 270
TIME, minutes
Figure A5. Test conditions: concentrated level, 85-minute AIT, fuel no. 3
-------
AVERAGE DATA FROM
TWO OR MORE RUNS
0 30 60 90 120 150 180 210 240 270
TIME, minutes
Figure A6. Test conditions: concentratedlevel, 120-minute AIT, fuel no. 3
-------
AVERAGE DATA FROM
TWO OR MORE RUNS
0 30 60 90 120 150 180 210 240 270
TIME, minutes
Figure A7. Test conditions:<;oncentr«ted level. 85-minute AIT, fuel no. 5
-------
AVERAGE DATA FROM
TWO OR MORE RUNS
30 60 90 120 150 ISO 210 240 270
TIME, minutes
Figure A8. Test conditionsrconcentratedlevel, 120-minute AIT, fuel no 5
-------
APPENDIX B
COMPUTER PROGRAM FOR REDUCTION OF
OXIDES OF NITROGEN DATA
-------
COMPUTER PROGRAM FOR REDUCTION OF
OXIDES OF NITROGEN DATA
The Borman colorimetric instrument used to measure nitric
oxide and nitrogen dioxide has a very slow time response. The
concentration indicated at any particular time is a value averaged
over a considerable period of time, since the deadtime is 4
minutes and the time constant ranges from 9 to 22 minutes over
the concentration range of interest. This large time constant
produces extreme "tailing" or "lagging" of the indicated concen-
tration behind the actual concentration of the gas being sampled.
For adjusting the observed concentration to true or instantaneous
concentrations at the designated times, a computational pro-
cedure was developed for the IBM 650 computer.
In general the operation of instruments and other dynamic
systems may be described as:
(Output Function) (Input Function) (System Function)
If the system function for a particular instrument can be
defined, it is possible to compute the input function from the
output function.
The system function for the Borman instrument was deter-
-kt
mined experimentally as being (1-e ) where "t" - time and "k"
is a constant for any given concentration.
Therefore: Output Input' (l-e~kt).
This equation was evaluated experimentally by observing the
response of the instrument as the concentration of NO or NO£
diluted in nitrogen was switched abruptly from zero to various
levels ranging from 0.25 to 2.0 ppm and from these levels back
to zero. Samples of NO and NO2 in nitrogen were prepared in
Mylar bags. This procedure introduces a step input to the in-
strument and produces an output from •which the exponent can be
determined and the equation validated.
On the basis of LaPlace transforms, the exponential (l-e~kt)
is equivalent to the differential expression:
\Ts + I/
Where T is the time constant function, f ( — ), and s is the dif-
ferential operator (d/dt). In this form the system function is
usually called the transfer function. If the output concentration
is termed Y and the input concentration is termed X, the equa-
tion becomes:
49
-------
50 IRRADIATION CHAMBER TESTS
Y X
\Ts + 1 j
which reduces to dy _
Y + T dT
This differential equation is solved by the computer to ad-
just the oxides of nitrogen data at 3-minute intervals. The time
constant function, T, is a variable that is dependent upon the
output concentration Y. This relationship, determined experi-
mentally as previously described, is stored in the computer.
The coefficients of this function must, of course, be determined
each time the instrument is modified or a different instrument is
used.
-------
COMPUTER PROGRAM
FOR
DATA REDUCTION
INPUT CONSTANTS
1) to
2) At
3) dtNO
4)
°l vmax
6) tits
INPUT FUNCTIONS
1) YNO f (t).
f (t),
2> YNO2
3) TNO+
4) TNO-
f (YNO)
f (YNO)
5) TNQ2+ f (YNOz)
7) PPM NQ = f (XNO)
8) PPM NQ = f (XNo2)
Univariate table, up to 200
points (Linear Interpolation)
Univariate table, up to 200
points (Linear Interpolation
Table or equation, whichever is
more convenient for computer
programmer. Equation con-
stants must be adjustable.
OUTPUT
DtL
4) PPMNO
5)
X
NO
Additional printout of constants
involved in curve fits, etc.
should be printed once for each
case.
7) XNO2
PROCEDURE
1) Read Program
2) Read Input
3) t =t0
4) YNQ = f (t), Tabular input function
5) Y-KJQ f (t), Tabular input function
51
-------
52 IRRADIATION CHAMBER TESTS
6) YNO+1 - YNO YNO - YNO-1
(^) _ tYNO+l tYNO tYNO tYNO-l
dt NO 2
7) YN02 +1 YN02 YN02 YN02-1
(^) tYN02+l tYN02 tYN02 tYN02-l
dt NO —
L 2
8) TNO+ = f (YNO)
9) TNO- f (YNO)
10) TN02 + = f (YN02)
11) TN02- f (YN02)
12) (Is dy negative?) Yes -14
(dt~ NO2 No -13
r-r, rp *- 1 K
13) TN02 - TN02+
14) TNO2 - TNO2-
15) (Is dy negative?) Yes -17
(dF NO No -16
^r *r * 18
16) 1NO ^-NO4"
17) TNO TNO-
18) XNQ YNQ + TNO
19)XNOz YNOz + TNQ2 |^dt.N02
20) PPMNO - f (XNO)
21)PPMN02 f (XNOz)
21A) tj^ t t^ts
22) tNO 'L dtNO
23) tNOz *L dtNO2
24) t - t + At
25) Is t >tmax. ? Yes-^26
No 4
26) Print Output
27) Go to i, read next case.
NOMENCLATURE
t0 Time that instrument was put on stream (minutes).
At Time increment at which output is to be printed
(minutes).
Deadtime for NO function.
Deadtime for NO2 function.
Last time value for input functions YNO and YNO
(minutes).
Chart indication for NO.
YNO+1 Chart indication for NO at next time point.
-------
Appendix B 53
^NO- 1 Chart indication for NO at preceding time point.
YNO2 Chart indication for NO2-
(^)
dt NO Average slope of YNQ function at this time point.
dy
(— ) -,„ Average slope of YJ^Q,, function at this time point.
T"NO+ Time constant for NO function for positive slopes.
TJSJQ- Time constant for NO function for negative slopes.
TJ^Q . Time constant for NO2 function for positive
slopes.
TJ^Q Time constant for NO2 function for negative
slopes.
TNO Time constant used for NO computation.
- Time constant used for NO2 computation.
XNO Adjusted NO chart indication.
XNO-, Adjusted NO2 chart indication.
PPM^O Parts per million NO.
PPMNo2 Parts per million NO2-
tj^jQ Time for NO function after deadtime correction.
" Time for NO2 function after deadtime correction.
- Time after t0 that lights were turned on.
-------
BLOCK DIAGRAM
START
1
.
READ
PROGRAM
,
READ
INPUT
'
t - t0
{First time
only)
YNO = i W
YN02 = f (t)
INPUT
<
l^ft * 'YNO*I - '*NO 'VNO-'YNO.I
^0+ = f (YNO)
TNO- = f (YNO)
TN02+ = f
TN02- = f
GPO 806-304-5
-------
BIBLIOGRAPHIC: Korth, Merrill W. DYNAMIC IRRADIATION
CHAMBER TESTS OF AUTOMOTIVE EXHAUSTS. PHS
Publ. No. 999-AP-5. 1963.54pp.
ABSTRACT: As part of an intensive study by government and
private agencies the U. S. Public Health Service has
built an irradiation chamber facility for investigation of
irradiated auto exhaust under mixing conditions similar
to those in the atmosphere. The facility consists of a
programmed continuous-cycling chassis dynamometer,
an exhaust dilution system, a dilution-air purification
system, two irradiation chambers, and exposure facili-
ties for evaluation of bacteria kill, plant damage, and
various effects on small animals..
Of the three variables studied during the first test
series, the exhaust concentration at the start of irradiation
appeared to produce the most significant effects. Fuel
composition had a lesser influence. Very little difference
was noted in the effects produced at two different average
irradiation times.
ACCESSION NO.
KEY WORDS:
Air Pollution
Auto Exhaust
Irradiation Chamber
Photochemistry
Vegetation
Bacteria Kill
BIBLIOGRAPHIC: Korth, Merrill W. DYNAMIC IRRADIATION
CHAMBER TESTS OF AUTOMOTIVE EXHAUSTS. PHS
Publ. No. 999-AP-5. 1963. 54 pp.
ABSTRACT: As part of an intensive study by government and
private agencies the U. S. Public Health Service has
built an irradiation chamber facility for investigation of
irradiated auto exhaust under mixing conditions similar
to those in the atmosphere. The facility consists of a
programmed continuous-eye ling chassis dynamometer,
an exhaust dilution system, a dilution-air purification
system, two irradiation chambers, and exposure facili-
ties for evaluation of bacteria kill, plant damage, and
various effects on small animals.
Of the three variables studied during the first test
series, the exhaust concentration at the start of irradiation
appeared to produce the most significant effects. Fuel
composition had a lesser influence. Very little difference
was noted in the effects produced at two different average
irradiation times.
ACCESSION NO.
KEY WORDS:
Air Pollution
Auto Exhaust
Irradiation Chamber
Photochemistry
Vegetation
Bacteria Kill
------- |