ated in this part of the program will be presented in future publications. Further Program Development
Literature Cited (1) Lundgren, D. A., “An Aerosol Sampler for Determination of Particle Concentration as a Function of Size and Time,” J . Air Pollut. Control Assoc. 17 ( 4 ) , (April 1967). (The Environmental
Research Corp. Multiday Impactor is of the Lundgren type.)
The data base provided by the collection and analysis of California’s aerosols lends itself to research efforts in numerous areas. Future work will concentrate on: Element-element correlations, which lead to characterization of sources Aerosol-to-gas pollutant correlations, which lead to information on gas pollutant sources Aerosol-to-visibility correlations, which lead to information on sources of visibility degradation By means of the a-scattering technique, analysis of very light elements (H-F) leads to subsequent presentation of total, and size-segreated mass values in the 0.1 20-pm size domain. As of July 1, 1975, the two-year research phase of the program ended, and the system was incorporated into the Air Resources Board monitoring effort a t the level of 10,000station-days of sampling per year. I t is our opinion t h a t the aerosol data generated by this program gain their greatest utility in their combination with data presently collected on gas pollutants, weather, and visibility at the same sites by existing ARB programs.
-
Acknowledgment Special appreciation is extended to the efforts of the late Dale Hutchison, who encouraged this program in its early stages. The support of the National Science Foundation was instrumental in developing the analytical system to a standard necessary to support such an effort. Donation of beam handling equipment to this effort by the U S . Navy is also gratefully acknowledged. The enthusiastic cooperation of the staff of the Crocker Nuclear Laboratory was essential to the performance of this work.
(2) Whitbv. K. T.. Husar. R. B.. Liu. B. Y. H.. J . Colloid Interface Sci., 39,177 (1972). ’ (3) Spumy, K. R., Lodge, J. P., Jr., “Collection Efficiency Tables for Membrane Filters”, National Center for Atmospheric ReI
,
search publication NCAR-TN/STR-77. (4) Cahill, T. A,, Feeney, P. J., “Contribution of Freeway Traffic
to Airborne Particulate Matter”, Final Report to the California Air Resources Board for Contract ARB-502, published as UC DavidCNL 169 (1973). (5) Wesolowski, J. J., John, W., Devor, W., Cahill, T. A., Feeney, P. J., Wolfe, G., Flocchini, R. G., “Collection Surfaces of Cascade Impactors”, to be presented at the X-ray Fluorescence Workshop, Research Triangle Park, North Carolina, January 26-28, 1976. (6) Flocchini, R. G., Feeney, P. J., Sommerville, R. J., Cahill, T. A,, Nucl. Instrum. Methods, 100, 397 (1972); Cahill, T. A,, “Cyclotron Analysis of Atmospheric Contaminants”, Final Report to the California Air Resources Board, published as UC Davis/ CNL 162 (1973). Cahill, T. A., in “New Uses for Ion Accelerator”, J. Ziegler, Editor, (1-721, Plenum Press (1975). (7) Camp, D. C., VanLehn, A. L., Rhodes, J. R., Pradzynski, A. H., “Intercomparison of Trace Element Determinations in Simulated and Real Air Particulate Samples”, J. X - r a y Spectrom. 4, 123 (1975). The ion-excited group was #15 in this study, while the X-ray fluorescence group was # 4 . (8) Cahill, T. A., Sommerville, R., Flocchini, R., “Nuclear Methods in Environmental Research, A.N.S. Topical Conference, “Elemental Analysis of Smog by Charged Particle Beams: Elastic Scattering and X-ray Fluorescence”, p 6, Columbia, Mo., 1971. (9) Harrison, J. F., Eldred, R. A., “Automatic Data Acquisition and Reduction for Elemental Analysis of Aerosol Samples”, “Advances in X-ray Analysis”, Vol. 17, pp 560-70, C. L. Grant, Ed., Plenum Press, New York, N.Y., 1973. Received for reuieu: Nouember 11, 1975. Accepted October I , 1975. Work supported in part by the California Air Resources Board, Research Contract 2-006, with analytical system development supported b y the Truce Contaminants Division of the National Science Foundation Program of Research Applied to National Needs.
NOTES
Photochemical Synthesis of Peroxyacyl Nitrates in Gas Phase via Chlorine-Aldehyde Reaction Bruce W. Gay, Jr.,* Richard C. Noonan, Joseph J. Bufalini, and Philip L. Hanst Environmental Protection Agency, Environmental Research Center, Research Triangle Park, N.C. 277 11
A new peroxyacyl nitrate synthesis in the gas phase has been developed. Molecular chlorine is photolyzed to yield chlorine atoms that abstract aldehydic hydrogen from the aldehyde. The acyl radical then adds oxygen and nitrogen dioxide to form the PAN. Any member of the PAN family can thus be produced from its parent aldehyde cleanly and in very high yield. The photooxidation of hydrocarbons in the presence of oxides of nitrogen leads to a number of interesting products. One of these is a strong oxidizing compound-peroxyacetyl nitrate (PAN). This compound is one of the principal nitrogen-containing products of photochemical smog. 82
Environmental Science & Technology
Studies have shown that PAN-type compounds can cause severe plant injury and are potent eye irritants ( I , 2). The PAN family of compounds was discovered in laboratory simulations of the chemical reactions in air polluted by auto exhaust ( 3 - 5 ) . In 1957, PAN was shown to be present in the Los Angeles atmosphere (6). During the six years that it took to characterize the molecular formula and molecular structure, the compound was first known as “compound X” and later as peroxyacetyl nitrite. Not until 1961 was the formula established as peroxyacetyl nitrate ( 7 ) . The acetyl, propionyl, and butyryl members of the peroxyacyl nitrate family were synthesized and reported during the first year or two after the family of compounds was discovered, but the corresponding benzoyl compound was not reported until 1968 (2). Prior to the present work there
have been many unsuccessful attempts to prepare the onecarbon member of the family, peroxyformyl nitrate. It has been assumed, and it is now confirmed, t h a t this lack of success was a result of the thermal instability of the formyl compound. A review of the work or PANs up to 1969 has been published by E. R. Stephens (8). An easy preparation of the PAN-type compounds has long been needed to provide samples for research and for calibration and testing of PAN-detection instruments. Such preparations had to be carried out in the user’s laboratory because gaseous PAN will slowly decompose in a vessel a t room temperature, and liquid PAN may explode. Four methods of preparation have been employed. These are: Photolysis of an olefin in the presence of oxides of nitrogen. This method was employed by Stephens et al. ( 3 ) in their work on the identification of “compound X.” Photolysis of di-acyl compounds and nitrogen dioxide in air. Diacetyl, diproprionyl, and dibutyryl were used to produce the corresponding PAN’S in 1956 ( 4 ) . Dark reaction of an aldehyde with NO2 and 0 3 . Since the aldehyde-ozone reaction is too slow to be important, it is assumed t h a t the aldehyde is attacked by either NO3 or N20.5. This technique has been used by Tuesday (9) for P A N and by Heuss and Glasson (2) for the production of peroxybenzoyl nitrate. Photolysis of a dilute gaseous mixture of alkyl nitrite and dry oxygen. This method was used by Stephens e t al. (10). In recent years this has been the most widely used method for the preparation of PAN samples for calibration of gas chromatographs. T h e new P A N synthesis method presented here suggested itself during a study of reactions of chlorine atoms with organic materials where the chlorine atoms were highly selective in the abstraction of hydrogen atoms. The hydrogen with the weakest bond strength is preferentially abstracted to form HCl. It was realized therefore t h a t chlorine atoms and aldehydes would react to yield the acyl-type free radicals that are the precursors of PANs. When these abstractions were carried out in the presence of NO2 and oxygen, the expected formation of PAN was confirmed. Any mem-
1600
14b0
l8bO
ber of the PAN family can thus be produced from its parent aldehyde cleanly and in very high yield. In the case of acetaldehyde, the reactions are:
C1.
hi
ec1
0 C1
0
II
+ CH -C-H
-*
0
CH,-C.
I1
+ 0.
-
0
I1
CH,-C-O-O
+
NO-
CH -C
11
+ HCl
0
I1
CH -C-0-0
-
0
II
CH --C-O-ONO
The reactions were carried out in a 690-1. borosilicate glass photochemical reaction cell (9.1 X 0.31 m) which contained long path infrared optics. A rapid scan Fourier Transform Spectrometer ( 1 1 ) was used for analysis of reactants and products with an infrared light path of 500 m. Surrounding the cell lengthwise are fluorescent blacklamps with energy maxima a t 3660 A. With forty-eight 40-W lamps, molecular chlorine was found to photodissociate with a half-life of about 2 min. This is similar to the rate of photodissociation of nitrogen dioxide in nitrogen under the same radiation conditions. For the formation of peroxyacetyl nitrate, 4 ppm of acetaldehyde, 4 ppm of NOa, and 2 pprn of C12 were introduced into the cell with tank air. The lamps were turned on, and rapid formation of PAN was observed. The infrared spectra of the initial acetaldehyde and nitrogen dioxide are shown in the upper trace of Figure 1. Chlorine, being a homonuclear diatomic molecule, does not show any bands. The spectra of the resultant peroxyacetyl nitrate and hydrogen chloride are shown in the lower trace of Figure 1. T h e conversion of aldehyde t o PAN was essentially complete after 20 min of irradiation. Only traces of such side products as CO, HCOOH, ” 0 3 , and CHrO were observed. In the absence of chlorine PAN forms a t a very slow rate. When 4 ppm of acetaldehyde and 1 ppm of nitrogen diox-
2800
30b0
m
I c
Figure 1. Upper spectrum at 500-m path length of 4 ppm acetaldehyde, 4 ppm NO2 in 760-torr air containing 2 ppm chlorine before irradiation. Lower spectrum of peroxyacetyl nitrate formed after irradiation
Volume 10, Number 1, January 1976
83
Figure 2. Upper spectrum at 500-m path length of 3 ppm propionaldehyde, 3.1 ppm NO2 in 760-torr air containing 1.6 ppm chlor,ine befoi’e ir. radiation. Lower spectrum of peroxypropionyl nitrate formed after irradiation
-1
B
I t
< -1
E
v)
1
2Zbo
1460
~
26b0
3060
Figure 3. Upper spectrum at 500-m path length of 3 ppm benzaldehyde, 3 4 ppm NO2 in 760-torr air containing 1 8 ppm chlorine be!for.e irradiation Lower spectrum of peroxybenzoyl nitrate formed after irradiation
I I
I
I
L
I
I
1-
1
--*
I
-1
L--
I I
4
I I
0
600 CM-’
I
1000
I
1400
0
I
I 1800
1
1 1
2200
I I I
2600
I
I I
3000
Figure 4. Ratioed spectra (50 sed10 sec irradiation time) at 357-m path length of 20 ppm formaldehyde, 20 ppm nitrogen, and 30 ppm chlorine in 760-torr oxygen 84
Environmental Science & Technology
Table I. Yields of Peroxyacyl Nitrates Figure
Identifying peak, crn-I Absorption, (IJI) Infrared absorptivities, ppm-’ M-’ * ( 8 ) Ppm formed Ppm initial aldehyde Yield
PAN 1
PPN 2
PBzN 3
930
1050
1810
26.5112 1.8 x 10-4
23.513.8
3.8 4.0
3.0
95
100%
5.3 x 10-4
3.0
27.8/1.8 6.9 x 10-4
3.4
3.0 1130/oa
a H i g h yield may be due to inaccuracy of benzaldehyde
measurement.
ide were photolyzed, only 0.15 ppm of P A N formed after 120 min of irradiation. With t h e addition of 0.8 ppm chlorine to t h e system, t h e P A N concentration increased from 0.15-1.55 ppm after only 4 min of irradiation. For t h e formation of peroxypropionyl nitrate, 3 ppm of propionaldehyde were reacted with 3.1 ppm of nitrogen dioxide and 1.6 ppm of molecular chlorine in air. T h e reactant and product spectra are shown in Figure 2 . Peroxybenzoyl nitrate was formed in like manner from 3 p p m of benzaldehyde, 3.4 pprn of nitrogen dioxide, and 1.8 pprn of chlorine. This case is recorded in Figure 3. Peroxyformyl nitrate ( P F N ) , t h e simplest homolog of t h e series and never before been synthesized, was apparently formed in t h e irradiation of formaldehyde, nitrogen dioxide, and chlorine in air, as indicated by a characteristic PAN-type bands a t 800, 1300, 1400, and 1740 cm-’. I t is under further study. Figure 4 shows t h e P F N spectrum from the irradiation of 20 ppm of formaldehyde, 20 ppm of nitrogen dioxide, and 30 ppm of chlorine in a n atmosphere of oxygen.
Since yields are very high (Table I), known concentrations of PANS can be prepared by this method without t h e use of infrared equipment. One prepares a known concentration of aldehyde with a slight excess of nitrogen dioxide and chlorine, photolyzes t h e mixture, and assumes t h e corresponding P A N member forms in stoichiometric yields. T h e chlorine-aldehyde-NO2 method of P A N preparation appears to be general in its application. I t produces high yields of PANS relatively free from organic side products, and it gives further confirmation to the generally accepted molecular structure of t h e PANs.
Literature Cited (1) Taylor, 0 . C., J . Air Pollut. Control Assoc., 19,347 (1969). (2) Heuss, J. M., Glasson, W. A,, Enuiron. Sci. Technol., 2, 1109
(1968). (3) Stephens, E. R., Hanst, P. L., Doerr, R. C., Scott, W. E., Ind. Eng. Chem., 48,1998 (1956). (4) Stephens, E. R., Scott, W. E., Hanst, P. L., Deorr, R. C., J . Air Pollut. Control Assoc., 6, 159 (1956). (5) Stephens, E. R., Hanst, P. L., Doerr, R. C., Scott, W. E., ibid., 8,333 (1959). (6) Scott, W. E., Stephens, E. R., Hanst, P. L., Doerr, R. C., Proc. Am. Petrol. Inst. (III),171 (1957). ( 7 ) Stephens, E. R., Darley, E. F., Taylor, 0. C., Scott, W. E., Intern. J . Air Water Pollut., 4, 79 (1961). (8) Stephens, E. R., “The Formation, Reactions, and Properties of Peroxy Acyl Nitrates (PANs) in Photochemical Air Pollution” in “Advances in Environmental Science and Technology,” Vol. 1. J. N. Pitts. and R. L. Metcalf. Eds.. DD 119-46. Wilev Interscience, New York, N.Y., 1969, (9) Tuesday, C. S., “The Atmospheric Photooxidation of Trans2-butene and Nitric Oxide.” in “Chemical Reactions in the Lower and Upper Atmosphere,” pp 1-49, Interscience, New York, N.Y., 1961. (10) Stephens, E. R., Burleson, F. R., Cardiff, E. A , , J Air Pollut Control Assoc , 15,87 (1965). (11) Hanst, P. L., Lefohn, A. S., Gay, B. W. Jr., Appl. Spectros, 27, 188 (1973). Received f o r reuiew March 3, 1975. Accepted August 11, 1975.
Means to Evaluate Performance of Stationary Source Test Methods William J. Mitchell and M. Rodney Midgett Quality Assurance Branch, Environmental Monitoring and Support Laboratory, Office of Research and Development, U.S. Environmental Protection Agency, Research Triangle Park, N.C. 277 1 1 Described are two sampling arrangements t h a t allow four independent stationary source sampling trains to sample simultaneously a t essentially t h e same point in t h e stack. Presented are t h e results obtained with these sampling arrangements during field tests using t h e E P A particulate sampling train.
Spatial and temporal variations in the velocity profile ( t h e distribution of t h e flow across t h e stack) a n d in t h e pollutant profile (the distribution of t h e pollutant concentration across t h e stack) frequently occur in t h e stacks of stationary sources. Since a shift in t h e velocity profile does not always produce an identical shift in the pollutant profile, t h e effect of these spatial and temporal variations on the sampling results must be minimized when sampling stationary sources. T o minimize the occurrence of temporal variations, t h e source is generally required t o operate at maximum rated capacity while it is being sampled. T h e
spatial variation is generally handled by dividing t h e stack into sections of equal area and sampling each area for an equal period of time (traversing). Traditionally, the within-laboratory and between-laboratory precision of test methods is determined through collaborative testing (round-robin testing). T h e collaborative test is designed so that t h e participants (collaborators) each make one or more measurements on identical samples using t h e same test method. Then, from a statistical analysis of t h e results, a n estimate is made of the within-laboratory and between-laboratory precision of the test method. This general technique has been used very widely for t h e validation of methods for t h e analysis of such items as water, drugs, food and agricultural products, fertilizers, coal, and ores. When a stationary source test method is collaboratively tested, the sampling, as well as t h e analytical aspects of t h e method, must be evaluated. However, t h e need t o traverse the stack while sampling creates a series of complex problems with no easy solutions. Paramount among these beVolume IO, Number l , January 1976
85
