United States
Environmental Protection
Agency
Environmental Sciences Research
Laboratory
Research Triangle Park NC 27711
EPA-600/3-79-016
February 1979
Research and Development
&EPA
Oxidant
Formation in the
Generation of
Ozone
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RESEARCH REPORTING SERIES
Research reports of the Office of Research and Development, U.S. Environmental
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EPA-600/3-79-016
February 1979
OXIDANT FORMATION IN THE GENERATION OF OZONE
by
Bruce W. Gay, Jr.
George R. Namie
Joseph J. Bufalini
Atmospheric Chemistry and Physics Division
Environmental Sciences Research Laboratory
Research Triangle Park, North Carolina 27711
ENVIRONMENTAL SCIENCES RESEARCH LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
RESEARCH TRIANGLE PARK, NORTH CAROLINA 27711
-------
DISCLAIMER
This report has been reviewed by the Environmental Sciences Research
Laboratory, U.S. Environmental Protection Agency, and approved for
publication. Mention of trade names or commercial products does not
constitute endorsement or recommendation for use.
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ABSTRACT
Ozone samples generated by UV photolysis and silent electric discharge
upon air or oxygen were examined to determine if other oxidants were formed.
Chemical and physical methods (IR and UV spectroscopy) failed to show the
presence of such oxidants. Absence of such oxidants was also indicated by
the excellent agreement between analytical results from UV photometry and
gas phase titration. Ozone measurements by the colorimetric 1 percent
neutral buffered potassium iodide method were biased 10-30 percent positive
compared to UV photometry. A colorimetric method employing a solution
of cyclohexene-dimethanol and ferrous ammonium sulfate (CHD), which is
claimed to measure singlet oxygen and/or other oxidants along with ozone,
proved to have a different stoichiometry in the presence and absence of
oxygen. These latter results were interpreted to mean that the high response
of CHD to ozonized air/oxygen streams does not indicate the presence of non-
ozone oxidants; rather, it reflects a greater-than-stoichiometric response
of the CHD reagent to ozone.
iii
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CONTENTS
Abstract iii
Figures v
1. Introduction 1
2. Conclusions 2
3. Experimental Procedures 3
4. Results 6
5. Discussion 9
References 13
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FIGURES
Number Page
1 Comparison of Colorimetric and UV Photometric 15
Determinations of Ozone
2 Comparison of Gas Phase Titration and UV Photometric 16
Ozone Determinations
3 Infrared Spectrum of Ozone 17
vi
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SECTION 1
INTRODUCTION
Recently, researchers at the Texas Air Control Board (TACB) used a
modified ferrous ammonium sulfate-thiocyanate method containing 3-cyclo-
hexene-l,l-dimethanol to measure ozone generated by UV photolysis or silent
electric discharge of air (1). This method combined two different techni-
ques for measuring oxidants, the olefin-singlet oxygen reaction in which a
peroxide is formed (2) and the ferrous ammonium sulfate-thiocyanate techni-
que (3). The TACB investigators found high values of oxidant when the
cyclohexene-dimethanol-ferrous ammonium sulfate-thiocyanate method (CHD) was
compared to the neutral buffered potassium iodide (NBKI) method for measuring
ozone/oxidants generated by UV photolysis or silent electric discharge. The
conclusion reached by the TACB investigators was that singlet oxygen and/or
other oxidants are formed in the generation of ozone samples. Also, TACB
claimed that the additional oxidant, tentatively identified as electronically
excited singlet oxygen, was not measured by other standard methods such as
NBKI. They speculated that singlet oxygen may be responsible for the effects
observed in clinical health effects studies (4). The primary national am-
bient air quality standard for ozone is based on the evidence collected
during these health studies. The TACB contends that the evidence may be
invalid since other oxidants besides ozone were present during the health
studies.
The objective of the experiments described in this report was to
determine if any other oxidants are formed in the generation of ozone sam-
ples.
-------
SECTION 2
CONCLUSIONS
The results of this study indicate:
1. The generation of ozone standards produces insignificant concen-
trations of singlet oxygen and no other oxidant species can be
detected by a variety of measurement techniques.
2. Good agreement in ozone measurements was observed between UV
photometric, gas phase titration, and NBKI methods. The NBKI
method is biased in a positive direction as observed by other
investigators.
3. Measurements of ozone in oxygen or air by the CHD method were
always substantially (approximately 100%) higher than the NBKI
method. In the absence of oxygen, ozone concentrations determined
by the CHD method were lower than values determined by UV or
NBKI methods.
4. The CHD method did not detect other oxidants.
5. The results of this work disagrees with the Texas Air Control
Board (TACB) position that the CHD method is detecting other
oxidants in air "ozonized" by UV irradiation or silent electric
discharge. Rather they indicate the CHD method is not applicable
to analysis of ozone and/or other oxidants in air because of a
variable stoichiometry of the reagent-ozone reaction in the
presence of oxygen.
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SECTION 3
EXPERIMENTAL PROCEDURES
Ozone was prepared by exposing tank air or tank oxygen flowing through
a quartz tube to the ultraviolet radiation from a mercury lamp (5). Ozone
was also produced by flowing tank air or oxygen through a silent electrical
discharge apparatus operated at 15,000 volts. The ultraviolet ozone genera-
tion system was connected to a manifold and mixing chamber system which was
all glass except for a small amount of Teflon connecting tubing. Through
a port upstream of the mixing chambers nitric oxide could be added. Down-
stream of the mixing chambers were sampling ports from which simultaneous
measurements could be made. The flow of air passing through the generator
and manifold system was controlled with a needle valve. Ozone produced by
each of the two generation methods was also collected and sampled from
300 liter 5 mil Teflon bags.
The tank air used was low in humidity and contained less than 0.1 ppmC
hydrocarbon. Two types of tank oxygen were used; one contained less than
0.2 ppmC as methane, the other contained approximately 1.4 ppmC as methane.
Both oxygens were very low in relative humidity. In some experiments the
air was first humidified by bubbling through distilled water in an impinger
bubbler. At room temperature a relative humidity in the resulting air
stream of 47% was measured on a Hygrodynamics modeled No. 15-3050 hygrometer.
Ozone in nitrogen was prepared as follows: The output from the silent
electric discharge ozone generator was passed through a glass freeze out
trap immersed in liquid oxygen. Ozone having a higher boiling point than
oxygen condensed out as a dark blue liquid at liquid oxygen temperatures.
When sufficient liquid ozone had condensed, about 0.25 ml, the ozonator and
oxygen stream were turned off. Tank nitrogen was then allowed to flow
through the freeze-out trap at liquid oxygen temperatures. Any oxygen in
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the trap was displaced leaving ozone in nitrogen. The contents of the trap
containing liquid ozone and nitrogen were transferred to an evacuated 43
liter tank by withdrawing the trap from the liquid oxygen and allowing a
stream of nitrogen to carry the vaporizing ozone into the tank. The 43
liter tank and fittings were constructed of stainless steel and had been
previously cleaned and conditioned with ozone in oxygen. After four trap-
pings of ozone were tranferred, the 43 liter tank was pressurized to 60 psi
with tank nitrogen. Samples of ozone in nitrogen or oxygen were prepared
by metering the ozone mixture from the tank into the manifold-mixing chamber
system and greatly diluting with tank nitrogen or oxygen.
Wet chemical analyses of ozone were carried out using the 1 percent
neutral buffered-potassium iodide (NBKI) (6), a modified ferrous ammonium
sulfate-thiocyanate method (FAST) (7), and the cyclohexene-dimethanol-
ferrous ammonium sulfate-thiocyanate method (CHD) developed by the Texas
Air Control Board (1). The NBKI method was standardized using a volu-
metrically diluted standard iodine solution. The absorbing reagent used
in the CHD method was similar to that of the FAST method with the exception
of added 3-cyclohexene-l, 1-dimethanol. The FAST reagent was prepared by
diluting 0.25 gm of ferrous ammonium sulfate and 2.5 ml of 6N H_SO, with
water to 500 ml. To make the CHD reagent 2.5 gm 3-cyclohexene-l,
1-dimethanol was added to the above FAST reagent solution. To develop a
color, two ml of thiocyanate reagent (5 gm ammonium thiocyanate in 100 ml
water) were added to 10 ml of each of the absorbing solutions. The FAST
and CHD methods were standardized with ferric ammonium sulfate standards.
A plot of absorption versus ferric iron concentration for both methods
gave nearly identical lines having a molar absorption coefficient of about
5800 liter/mole cm. Samples were collected in 10 ml absorbing reagent at
a flow rate of 0.51 1/min. The same midget impinger bubblers were used for
each individual method throughout the experiments. Colorimetric measure-
ments of resulting solutions were made using matched one cm cells in a Gary
14 spectrophotometer. The absorption of the NBKI solutions were read
o
immediately after sampling at a wavelength of 3520 A. The FAST and CHD
o
solutions were read 10 minutes after sampling at a wavelength of 4800 A.
-------
Ozone concentrations were determined with a modified (8) Dasibi model
1003-AH instrument which measures the absorption of ozone in the ultraviolet
spectra region. The ultraviolet absorption of ozone samples were also
examined in a laboratory built UV system. The system consisted of a
deuterium lamp, a long path multi-pass optical glass cell, associated input
and output optics, scanning monochrometer, and detector. This system was
used to scan the ultraviolet region of the spectrum looking for unusual
absorptions due to oxidants other than ozone. Ozone generated in air or
oxygen was also examined by long path Fourier transform infrared spectro-
scopy to determine oxidants other than ozone which might be present. This
IR equipment has been described elsewhere (9).
Ozone generated in dry or humidified air or oxygen was examined for
peroxides by bubbling through distilled water to absorb any peroxides. The
resulting solution was analyzed with a newly developed method.for hydrogen
peroxide. This method measures the chemiluminescence produced in the
reaction between luminol, a catalyst and peroxide in a basic solution (10).
Using an impinger bubbler with 10 ml water, samples were collected at a
flow rate of 0.5 1/min.
In the gas phase titration of ozone a Bendix NO chemiluminescent
X
analyzer was used to measure the nitrogen dioxide produced in the reaction
of ozone with nitric oxide. In the titration experiments nitric oxide from
a cylinder containing 49.3 ppm NO in nitrogen was metered into the ozone
air stream.
Formaldehyde samples used to test interference in the CHD method were
prepared by heating alpha-polyoxymethylene and diluting with tank air. The
chromotropic acid method was used to determine the concentration of the
formaldehyde sample (11).
Nitric oxide and N0~ samples were prepared using tank air and labora-
tory grade chemicals. Nitric acid vapor was prepared by vaporizing ACS
certified concentrated nitric acid and diluting with tank air.
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SECTION 4
RESULTS
Simultaneous measurements of ozone generated at various concentrations
in an air stream are shown in Figure 1. A typical comparison of ozone con-
centrations measured by gas phase titration and UV photometry is shown in
Figure 2. The slope of the curve is approximately unity indicating an
excellent agreement between the two methods. Ozone concentrations measured
by the CHD method were nearly 100 percent higher than measurements made
by NBKI, UV photometric or gas phase titration methods. In these experi-
ments ozone values obtained with the NBKI method were higher by approximately
10 percent when compared to UV photometry.
Ozone was also generated in the two types of tank oxygen available,
one contained less than 0.2 ppm and the other contained approximately 1.4
ppm carbon as methane. When tank oxygen was substituted for tank air, the
ozone generator was adjusted to produce the same ozone concentration as
was produced in tank air as measured by UV photometry. The resulting
values of ozone concentration in the oxygen system as measured by the CHD
and NBKI methods were essentially unchanged from results using tank air,
i.e., NBKI values were 10 percent higher and CHD values 100 percent higher.
In other experiments tank air and tank oxygen were humidified to 47
percent by bubbling through distilled water in a glass impinger bubbler.
Ozone, generated by the UV photolysis of the humidified air or oxygen was
determined by UV photometry, NBKI, and CHD methods. The results were
essentially the same as those shown in Figure 1.
Ozone prepared in nitrogen was slowly metered out of the stainless
steel tank into a glass manifold system and greatly diluted with tank
nitrogen (N?) or tank oxygen. The results of three samples so prepared
in nitrogen are listed in Table 1.
6
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TABLE 1. OZONE MEASUREMENTS IN NITROGEN, [0,]
J ppm
METHODS
UV Photometry
0.600 ppm
0.800 ppm
1.730 ppm
NBKI
0.719 ppm
1.005 ppm
2.211 ppm
CHD
0.381 ppm
0.383 ppm
0.493 ppm
Ozone in nitrogen at a concentration of 0.816 ppm as determined by UV photo-
metry resulted in a concentration of 0.357 ppm by CHD and 0.09 ppm by FAST
methods. In another experiment tank nitrogen was replaced with tank oxygen
as a diluent gas in the system. UV photometric measurements indicated
0.811 ppm ozone in this sample while NBKI measurements indicated 1.011 ppm
and CHD 1.708 ppm.
Ozone in oxygen was stored in a 300 liter Teflon bag and sampled over a
period of 4 hours. These experiments were performed in order to establish;
(1) the stability of ozone in Teflon bags and (2) note if other oxidants
i.e. other than ozone, would be detected because of different stabilities of
these oxidants upon standing. The ozone in this experiment was generated by
silent electrical discharge in tank oxygen containing approximately 1.4 ppm
carbon as methane. The results of this experiment are shown in Table 2.
TABLE 2. MEASURED [00] FROM TEFLON BAG
3 ppm
Time
0
45 min
260 min
UV
1.155 ppm
1.014 ppm
0.360 ppm
METHOD
NBKI
1.267 ppm
1.193 ppm
0.410 ppm
CHD
2.161 ppm
2.064 ppm
0.736 ppm
CHD/UV
1.871
2.035
2.044
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A high concentration of ozone was generated by slowly flowing dry tank
oxygen through a silent electrical discharge apparatus. A concentration of
43 ppm ozone was achieved by diluting to one atmosphere the output of the
ozone generator with tank oxygen into an evacuated 690 liter infrared absorp-
tion cell. Shown in Figure 3 is the infrared spectrum of this sample between
the spectral region of 700-3400 cm at a path length of 216 meters. The
main absorption band at 1050 cm is off scale at this path length with such
a high concentration. The first overtone of the 1050 cm absorption band
is seen in the 2100 cm region. Absorption bands of lesser intensity are
observed at 720, 1120, and 3050 cm regions. Absorption bands due to
atmospheric water (1250-2010) and carbon dioxide (2250-2400) are also
observed. These were caused by absorption in the optical path exterior to
the absorption cell.
The ultraviolet absorption spectrum of ozone generated by silent
o
electrical discharge in oxygen was observed over the 2000 to 3600 A spectral
region in a 18.3 meter multipass absorption cell. The spectrum did not
exhibit any unusual absorption associated with species other than ozone.
Humidified oxygen used as a blank and ozone generated in humidified
oxygen were bubbled through distilled water to absorb peroxides. The
resulting aqueous solutions were analyzed for peroxides by measuring the
chemiluminescence developed in the reaction with luminol. The blank
solution resulted in a chemiluminescence response equivalent to 2.8 ppb
H_0- and the ozone sample equivalent to 4 ppb H_CL.
Using the CHD method, no increases in absorbance above that of the
blank were observed after 5 liters of each of the following compounds in
air were bubbled through the CHD absorbing solution: 0.36 ppm CH?0, 1 ppm
NO, 0.54 ppm N02, about 1 ppm HNO.J.
-------
SECTION 5
DISCUSSION
SINGLET OXYGEN - O
It was claimed by the TACB that singlet oxygen 02 ( A g) is also formed
in the generation of ozone at concentrations equal to or greater than that
of ozone. Two electronically excited singlet molecular oxygen species, 0~
11 +
( A g) and 0« (Eg), can be produced by the absorption of light by 0_ .
02 + hv -> 02 (•''A g) ^ 12,700 A (1)
02 + hv -»• 02 ("4 g+) -v 7600 A (2)
Singlet oxygen can also be produced by electronic energy transfer from
electronically excited N09 molecules formed by absorption of light of
^ o
wavelengths greater than 4000 A,
N02* + 02 -> N02 + 02 (XA g) (3)
o
and by ozone photolysis in the wavelength range 2000-3200 A (12) . Ozone
generated by UV photolysis from the 184.9 nm line of a mercury lamp will
also be dissociated to singlet oxygen by the photolysis of ozone at 253.7
nm. Based upon steady state approximations the concentration of singlet
oxygen formed in a photochemical ozone generator is estimated to be about
7% of ozone (13) . The principal decay mode of singlet oxygen is by
collisional deactivation with ground state oxygen.
02 (XA g) + 02 (3E g) ^ 202 (3Z g) (4)
The rate of this reaction is very fast with a rate constant of k = 2.2 x
_•! Q O I-!
10 cm mole S (14).
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In calibration experiments the output of an ozone generator is trans-
ported through glass tubing to a manifold-mixing chamber system and
through glass or Teflon lines to the absorbing reagent. Typical residence
times between the generator and absorbing reagent are 5-15 seconds. Once
the ozonized air leaves the generator at slightly above atmospheric pressure,
the singlet oxygen decay can be described mathematically in the following
way since molecular oxygen in reaction (4) above is in large excess when
compared to the singlet oxygen concentration.
§ = e-k[02]t
Cl
where C = singlet oxygen concentration at any time t
C. = initial singlet oxygen concentration
18
Using an [0 ] = 5 x 10 molecules per cubic centimeter for a 20% oxygen
system and the rate constant of the reaction, the above expression becomes:
C -11 t
Ve
With a steady state singlet oxygen concentration in the ozone generator of
7 percent of the ozone concentration one can calculate the ratio of singlet
oxygen to ozone at any point in time downstream using the above expression.
After one second the singlet oxygen to ozone ratio would be 1.1 x 10 ;
-24
after 5 seconds the ratio would be 1.3 x 10 . Thus the concentration of
singlet oxygen reaching the absorbing reagent would be insignificant.
HYDROGEN PEROXIDE - H 0-
Experiments were carried out under conditions which would be most
favorable for peroxide formation, such as, humidifying the air or oxygen
stream prior to generating ozone. High concentrations of ozone were
generated and its infrared spectrum was studied. The resulting infrared
spectrum was not significantly different from that shown in Figure 3 where
only a small amount of water vapor was present. If hydrogen peroxide or other
peroxides were formed at substantial concentrations (concentrations 1/10 less
than ozone) the infrared spectrum would exhibit prominent absorption in the
10
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1250 cm" region of the spectrum. These absorptions are definitely absent.
The infrared spectrum is relatively clean and all absorption bands present
are accounted for.
Tests for hydrogen peroxide and other peroxides were conducted by
bubbling the ozone sample through water to trap the peroxide. The
resulting solutions were analyzed using a chemiluminescent method which can
detect sub ppb quantities of peroxide. A maximum value of less than 2 ppb
peroxide equivalents were observed for solutions through which 15 liters
of sample were bubbled. This concentration is an insignificant amount and
might be due to instrument variability.
OTHER OXIDANTS - Ozonides - Unstable Species
Other oxidizing species could be ozonides (15-17) formed in the
reaction of ozone with olefinic compounds in the gas stream. Unlike the
experiments conducted by the TACB in which employed filtered room air, the
experiments carried out in this study used tank air or oxygen essentially
free of hydrocarbons, except for one tank of oxygen which contained methane.
Air free of hydrocarbons is a necessity in the generation of ozone
standards (5). The formation of ozonides was not observed in the infrared
spectrum even when oxygen containing 1.4 ppmC as methane was used. It
should also be pointed out that both H-O- and organic peroxides do react
with NBKI solution (18). However, as stated above, no H.0? was observed
in our studies and, the organic peroxides could not exist as very high
concentrations since the organic carbon concentration was very low.
Using a Teflon bag as a static reactor, ozone samples were allowed to
stand and decay. These experiments would detect the presence of reactive
species if their lifetimes are either longer or shorter than that of ozone.
Data shown in Table 2 indicate that the ratio of CHD to UV values remained
nearly constant at about 2 over 260 minutes. The constant ratio indicates
that either the reactive species have the same lifetime as ozone or that no
other reactive species are present. The latter is the more reasonable con-
clusion since all other experiments had shown that no other oxidants are
present and it is doubtful that two compounds have exactly the same lifetime
under these experimental conditions.
11
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Long path ultraviolet spectroscopy failed to show any unknown absorb-
ances due to species other than ozone in the generation of ozone standards.
Although the values and calculations are not reported in this text, ozone
concentrations measured by long path infrared and long path ultraviolet
spectroscopy were in excellent agreement.
CYCLOHEXENE-DIMETHANOL (CHD) METHOD
The CHD method used by TACB is essentially the FAST method in which
3-cyclohexene-l,l-dimethanol has been added. The olefinic compound
3-cyclohexene-l,l-dimethanol had been added to presumably react with
singlet oxygen or other oxidants to form peroxides that oxidize the ferrous
ammonium sulfate reagent. The reaction of singlet oxygen with an olefinic
compound has been shown to produce a peroxide. Peroxides are particularly
responsive to the ferrous ammonium sulfate absorbing reagent. However,
singlet oxygen exists only at very low concentrations and cannot be
responsible for the increased response of the CHD reagent.
Because all experimental results failed to indicate the presence of
oxidants other than ozone, additional experiments were carried out to
determine why the CHD method had an increased sensitivity to ozone. As
a method of examining the stoichiometry of the CHD method, ozone samples
were prepared in nitrogen. The results from Table 1 show that in the
absence of oxygen, ozone concentrations determined by the CHD method were
substantially lower. The UV photometric, NBKI, and FAST methods were
unaffected by the absence of oxygen. These differences in CHD results when
ozone is measured in nitrogen as compared to oxygen clearly point to a
serious problem of the variability of stiochiometry. Others have observed
a difference in the stoichiometry of olefin-ozone reactions in the presence
and absence of oxygen (19). Although we do not know the exact number of
sequence of reactions operative in the CHD method, the presence of oxygen
apparently affects the ozone-cyclohexene-dimethanol reaction stoichiometry.
Thus, the presence of molecular oxygen gives rise to more than one peroxide
for every ozone molecule consumed. This increase in peroxide formation
would be responsible for the increased oxidation of the ferrous ammonium
sulfate reagent which given rise to the higher values obtained using the
CHD method.
12
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REFERENCES
1. Payne, J.S., Demonstration of Presence of "Singlet Oxygen" in Ozone
Generator Output. Presented before public hearing on proposed revisions
to the National Ambient Air Quality Standards for photochemical oxidants.
. Dallas, Texas, August 22, 1978.
2. Winner, A.M., K.D. Bayes. The Decay of 0- (a'A) in Flow Experiments.
J. Phys. Chem., 70, 302-304, 1966.
3. Cohen, I.R., J.J. Bufalini. Further Observations on the Ferrous
Ammonium Thiocyanate Reagent for Ozone. Environ. Sci. Technol., 1,
1014, 1967.
4. Texas Air Control Board, Executive Director, Bill Stewart. Presented
at EPA Public Hearing on Proposed Revisions to the National Ambient
Air Quality Standards for Photochemical Oxidants. Dallas, Texas,
August 22, 1978.
5. Hodgeson, J.A., R.K. Stevens, and B.E. Martin. A Stable Ozone Source
Applicable as a Secondary Standard for Calibration of Atmospheric
Monitors, pp. 149-158. In J. Scales, Ed. Air Quality Instrumentation.
Vol. 1 Selected Papers from International Symposia Presented by the
Instrument Society of America. Pittsburgh: Instrument Society of
America, 1972.
6. Saltzman, B.E. "Determination of Oxidants (Including Ozone): Neutral
Buffered-Potassium Iodide Method," pp. D1-D5 in "Selected Methods for
the Measurement of Air Pollutants" USHEW, PHS, No. 99-AP-ll, May 1965.
7. Todd, G.W. Modification of Ferrous Thiocyanate Colorimetric Method
for Determination of Some Atmospheric Oxidants. Anal. Chem. 27,
1490-1492, 1955.
8. Paur, R.J., M. Beard. Modification of Dasibi Ozone Monitors, EPA
memorandum, August 27, 1975.
9. Gay, Jr., B.W., P.L. Hanst, J.J. Bufalini and R.C. Noonan. Atmospheric
Oxidation of Chlorinated Ethylenes. Environ. Sci. Technol, 10, 58-67,
1976.
10. Kok, G.L., T.P. Holler, M.B., Lopez, H.A. Nachtrieb, and M. Yuan.
Chemiluminescent Method for Determination of Hydrogen Peroxide in the
Ambient Atmosphere. Environ. Sci. Technol. 12, 1972-1976, September 1978.
13
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11. Altshuller, A.P., D.L. Miller, and S.F. Sleva. Determination of
Formaldehyde in Gas Mixtures by Chromotropic Acid Method. Anal. Chem.
33, 622-625, 1961.
12. Kummler, R.H., M.H. Batner, and T. Baurer. The Hartley Photolysis of
Ozone as a Source of Singlet Oxygen in Polluted Atmospheres. Environ.
Sci. Technol., 3:248, 1969.
13. The National Research Council. Committee on Medical and Biologic
Effects of Environmental Pollutants. Ozone and Other Photochemical
Oxidants. Washington, DC, National Academy of Sciences, 1977, p. 254.
14. Hampson, R.F. Kr., Garvin, D. Reaction Rate and Photochemical Data for
Atmospheric Chemistry - 1977, NBS Special Publication 513, May 1978.
15. Leighton, P.A. Photochemistry of Air Pollution. In Physical Chemistry
Monograph series, Vol. IX, Academic Press, New York, 1961.
16. Niki, H., P.D. Maker, C.M. Savage, L.P. Breitenbach. Fourier Transform
IR Spectroscopic Observations of Propylene Ozonide in the gas Phase
Reaction of Ozone-Cis-2-butene-Formaldehydei Chem. Phys. Lett. 46,
273-280, 1977.
17. Martinez, R.I., R.E. Huie and J.T. Herron. Mass Spectrometric
Detection of Dioxirane, I^COO, and Its decomposition Products, H2, and
CO from the Reaction of Ozone with ethylene. Chem. Phys. Lett., 51,
457-459, 1977.
18. Cohen, I.R., T.C. Purcell and A.P. Altshuller. Analysis of the Oxidant
in Photooxidation Reactions. Environ. Sci. Technol. 1, 247-252, 1967.
19. Wei, Y.K. and R.J. Cvetanovic. A study of the Vapor Phase Reaction of
Ozone with Olefins in the Presence and Absence of Molecular Oxygen.
Canadian J. of Chem., Vol. 41, 913-925, 1963.
14
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COMPARISON OF COLORIMETRIC AND UV PHOTOMETRIC
DETERMINATIONS OF OZONE
OZONE (BYUV PHOTOMETRY), ppm
15
-------
COMPARISON OF GAS PHASE TITRATION AND UV PHOTOMETRIC
OZONE DETERMINATIONS
0.7
0.6
CL
a
§ 0.5
CC
p 0.4
LU
CO
0.3
CO
HI
O
N
O
0.2
0.1
0.1 0.2 0.3 0.4 0.5 0.6
OZONE (BY UV PHOTOMETRY), ppm
0.7
16
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SPECTRUM OF OZONE (43 ppm) PRODUCED BY SILENT ELECTRICAL DISCHARGE IN OXYGEN,
PATHLENGTH 216 meters, 760 torr
I
I
OZONE OZONE
z
LU
\-
z
z
g
CO
WATER ABSORPTION
CARBON
OZONE DIOXIDE
' OZONE
700
1100
1500
1900 2300
WAVELENGTH, cm'1
2700
3100
3400
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TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
'•RKra8-/3-79-016 ;
2.
4. TITLE AND SUBTITLE
OXIDANT FORMATION IN THE GENERATION OF OZ
7. AUTHORISI, _ _ .,
Bruce W. Gay, Jr., George
Joseph J. Bufalini
R. Namie, and
9. PERFORMING ORGANIZATION NAME AND ADDRESS
Environmental Sciences Research Laborator
Office of Research and Development
U.S. Environmental Protection Agency
Research Triangle Park, NOrth Carolina 2
12. SPONSORING AGENCY NAME AND ADDRESS
Environmental Sciences Research Laborator
Office of Research and Development
U.S. Environmental Protection Agency
Research Triangle Park, North Carolina 2
3. RECIPIENT'S ACCESSION>NO.
5. REPORT DATE
February 1979
J"11 6. PERFORMING ORGANIZATION CODE
8. PERFORMING ORGANIZATION REPORT NO.
10. PROGRAM ELEMENT NO.
y-RTP, NC 1AA603A
11. CONTRACT/GRANT NO.
7711
13. TYPE OF REPORT AND PERIOD COVERED
y-RTP, NC In-house
14. SPONSORING AGENCY CODE
7m EPA/600/09
15. SUPPLEMENTARY NOTES
16. ABSTRACT
Ozone samples generated by UV photolysis and silent electric discharge
upon air or oxygen were examined to determine if other oxidants were formed.
Chemical and physical methods (IR and UV spectroscopy) failed to show the
presence of such oxidants. Absence of such oxidants was also indicated by
the excellent agreement between analytical results from UV photometry and
gas phase titration. Ozone measurements by the colorimetric 1 percent
neutral buffered potassium iodide method were biased 10-30 percent positive
compared to UV photometry. A colorimetric method employing a solution
of cyclohexene-dlmethanol and ferrous ammonium sulf ate (CHD) , which is claimed
to measure singlet oxygen and/or other oxidants along with ozone, proved to
have a different stoichiometry in the presence and absence of oxygen, these
latter results were interpreted to mean that that the high response of CHD
to ozonized air/oxygen streams does not indicate the presence of non-ozone
oxidants; rather, it reflects a greater-than-stoichiometric response of the
CHD reagent to ozone.
17.
KEY WORDS AND DOCUMENT ANALYSIS
a. DESCRIPTORS
* Air pollution
* Ozone
Oxidizers
* Chemical analysis
18. DISTRIBUTION STATEMENT
RELEASE TO PUBLIC
b.lDENTIFIERS/OPEN ENDED TERMS
19. SECURITY CLASS (This Report)
UNCLASSIFIED
20. SECURITY CLASS (This page)
UNCLASSIFIED
c. COSATI Field/Group
13B
07B
11G
07D
21. NO. OF PAGES
24
22. PRICE
EPA Form 2220-1 (9-73)
18
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