Attenuation of Power Station Plumes as Determined by Instrumented Aircraft N. Thomas Stephens’ and Roy 0. McCaldin2 Department of Environmental Engineering, University of Florida, Gainesville, Fla. 32601
This paper summarizes a series of investigations into the transport, diffusion, and pollutant characteristics in power station plumes as determined by instrumented aircraft. The specific objectives were to examine SOz and particle concentrations up to a point where they could n o longer be distinguished from background values, to compare findings with expected dispersion characteristics, and to test a method for evaluating SO2 decay rates in the plume. Pollutant concentration profiles and SO2half-life determinations were made in very stable plumes at distances up to SO km downwind from the source.
S
ince combustion products from fossil-fuel electric power generation are one of the major atmospheric emission sources of sulfur dioxide, and can be a substantial source of dust and oxides of nitrogen as well, these sources have been investigated for many years. Meteorological studies dealt with the effects of tall stacks (Smith, 1966; Stone and Clarke, 1967), the height of plume rise above the stack (Carson and Moses, 1967; Carpenter et al., 1967), the dispersion of pollutants as they travel downwind, and the expected ground level concentrations that occur under differing weather conditions (Montgomery and Corn, 1967; Turner, 1969). These studies generally dealt with time-average plumes-Le., they were concerned with the average pollutant concentration that may be expected over a 20 to 30-min period. In addition to dispersion studies, there have been numerous inquiries into the chemical reactions that occur in plumes, principally the conpersion of SO2 to its acid and salt forms (Gartrell et al., 1964; Berger et al., 1968; Martin and Barber, 1966). The wide range of findings reported (from almost none to 3 0 z conversion per hour of SO1 to SO,), and the lack of information on plume behavior at relatively great distances prompted this inquiry. The lack of definitive data on the reactions of sulfur dioxide in polluted atmospheric regimes may be related to the inherent difficulties in sampling and analysis techniques. Emission conditions are quite variable with respect t o quantity and composition, and the influence of atmospheric factors such as turbulence, temperature, humidity, and sunlight further complicates attempts to delineate the decay function. Although environmental constraints and analytical limitations imposed by in-situ measurements are severe, it is precisely in this actual environment where data are needed. Thus, this paper summarizes a series of investigations into
Present address, Department of Civil Engineering, Virginia Polytechnic Institute and State University, Blacksburg, Va. 24061. Present address, Pima County Health Department, Tucson, Ariz. 85701.
the transport, diffusion, and pollutant characteristics in power station plumes as determined by a n instrumented aircraft. The specific objectives were to examine SO2 and particle concentrations up to a point where they could no longer be distinguished from background values, to compare findings with expected dispersion characteristics, and to test a method for evaluating SO2decay rates in the plume. Method Plume studies were conducted primarily at Florida Power Corp.’s Crystal River station, located on the flat Gulf Coast plain SO miles north of Tampa, about 2 miles inland from the coast. The plant, at the time of this work, used pulverized coal brought by barge from West Virginia. A single 500-ft discharge stack served the plant which had a 375 MW capacity. Florida Power Corp. generously furnished wind speed and direction data from a wind vane mounted 75 f t above the power station. They also furnished coal analyses and hourly fuel burning rates. A single engine aircraft (Cessna 182) was appropriately instrumented and used for airborne plume sampling. Sample air was obtained by inserting a 0.5-in. i.d. rubber tube through the fresh air duct in the wing and into the cabin. This inlet protruded about 2 in. in front of the leading edge of the wing just to the right of the cockpit, and out of the propeller slip stream. R a m air then traveled about 5 ft through the collector tubing to a series ofinverted Y’s,several of which were open to the cabin to vent excess air. Others channeled air to the sampling instrument intakes. Particle concentration was determined with a Bausch & Lomb 40-1 dust counter. In the counter, sample air flows in a narrow stream through a sensing zone and then to a meter and pump. In the sensing zone, a n intense white light is transmitted a t a right angle to the airstream. If no particles are present, the light goes to a trap, and no signal is generated. If a particle is present, the light is scattered by the particle and is then detected by a photocell which is positioned out of the path of the unscattered light. The resulting electrical signal is proportional to the particle optical characteristics and size. By use of appropriate electrical circuitry, the signals are classified into amplitude ranges, and particles larger than a preselected size classification recorded on a strip chart with respect to time. These data in turn were related to ground location by recording aircraft position a t the time of sampling. Sulfur dioxide samples were obtained with a modified Smith-Greenburg impinger utilizing the West-Gaeke (Interbranch Chemical Advisory Committee, 1965) sampling and analytical procedures. Impinger sampling times varied between 0.5 and 2 min, depending upon SO2 concentrations and plume geometry. A continuous strip chart record of SOz concentration was also generated by use of a Sign-X Laboratories (Essex, Conn.) electroconductivity analyzer with a n instrument time constant on the order of 2 sec. This rapid response feature made it especially suitable for airborne work. Threshold sensitivity Volume 5, Number 7, July 1971
615
Crystal River Power Stofion
x 20
‘ 0
4
8 I2 16 20 Temperature. “C
24
40
Relative
60
f
0 Kilometers 15
L-1’
Figure 2. Typical sampling pattern in Crystal River power station plume
80
Humidity, %
Longitudinal axial transverse downwind and upwind from the source followed by cross-sectioning patterns at 5, 11, 29, and 35 km downwind
Figure 1. Temperature and relative humidity profiles Temperature soundings obtained during enroute ascent from Gainesville, Fla., to Crystal River power station on 12/19/68, 1/2/69,1/3/69
A Particlwr05~ 0 SO, Sign-X 0 S O p Impinqer
60
in constant background conditions was about 0.01 to 0.02 ppm; however, under actual plume measurement conditions, a value of 0.05 ppm would be required to be distinguishable from background interferences, Provisions were made for selective scrubbing of SOz to measure remaining background interference, with COzbeing the most likely interfering species in the plume. Auxiliary measurements included altitude, air speed, wet and dry bulb temperatures, and location of aircraft when readings were being taken. Electric power was supplied by the aircraft generator to an inverter and then to the instruments. Data collection flights started at sunrise for maximum early-morning atmospheric stability. Plume height and vertical dimensions were determined by flying parallel to the plume and aligning the aircraft with the plume top and the distant horizon and then noting the altitude. The plume base was determined in a similar manner. Plume direction was determined by sighting the aircraft along the plume and noting the compass heading. Two principal patterns were flown. One was to fly longitudinally down the center line, the other was to fly a series of cross sections at increasingly greater distances downwind. Data are reported for flights made on Dec. 19, 1968, and Jan. 2 and 3, 1969. Meteorological conditions during these flights were characterized by a high-pressure area over the southeastern U. S., with generally fair cool weather prevailing. Cloud cover ranged from none to scattered clouds. Strong inversion conditions prevailed on all three days, as evidenced by the vertical temperature profiles (Figure 1). Also illustrated (Figure 1) are the relative humidity profiles for each of the three days. Average winds varied from 5.8 to 7.2 mjsec from the southeast and east. The combined conditions resulted in very cohesive plume configurations over the Gulf of Mexico during the January flights, with less stable transport over the flat coastal terrain during the December flight. Figure 2 shows the flight sampling patterns. First, the plume altitude and direction were visually determined by aligning the aircraft with the plume upwind from the stack. A sampling sequence consisting of a combination of longitudinal center 616 Environmental Science & Technology
50
40 E
B O’, 20
10
‘0
10
20
30
40
M
60
70
80
Dirtonce, km
Figure 3. SO2 and particulate center line concentrations obtained by longitudinal axial traverse (1/3/69) Emission source strength varied from 1400 to 1900 g/sec SO?,based on coal analysis and consumption figures. Plume altitude range: 150 to 250 m above sea level. Average wind speed: 7.2 mkec
line traverses and cross-sectional traverses at fixed geographic locations was chosen to yield the maximum data before inversion breakup occurred. Background concentration measurements were made outside the plume boundaries between traverses. Wind speeds at plume elevations were estimated from wind vane measurements taken from the power plant tower. These were corroborated by calculating the wind speed at plume height based on measured time and airspeed between fixed ground reference points. Results Figure 3 shows the particulate and SOz concentrations found along the plume center line. The data are recorded concentrations uncorrected for wind speed and emission strength variations. Normalizing corrections for changes in coal consumption rate and estimated average wind speed changes would tend to smooth out the major plateaus. Minor fluctuations in concentration are attributable to varying plume concentrations in discontinuous emission “puffs,” which persist in the diffusing plume (Figure 4). Of
Figure 4. Crystal River power station plume 0730,1/3/69
"h
0
1.0
0 0
1 10
1 20
3u
0
o o
0
0.1
'- $
Figure 5. Calculated and experimental concentration profiles (1/3/69)
I
1
I
t
1
I
30
40
50
60
70
80
Distance. hm
particular interest is the high (1 ppm) concentration observed approximately 75 km (47 miles) downwind. Verified by a simultaneous high particulate concentration, it was apparently due to some anomalous transport mechanism, since power plant records indicated no emission strength variation at the time of release. Peak values plotted represent maximum points taken from the strip-chart records, while averages represent mean values over a 5-sec interval. In addition to the electroconductivity SO2 measurements, three 30-sec time-averaged impinger SO? samples are shown by horizontal bars. These data are compared with predicted axial downwind concentrations in Figure 5. A Gaussian distribution was assumed for the predictiye calculations, with values for the vertical and horizontal standard deviation derived from actual plume spread measurements. As shown in Table I, these values are similar to the 10min time-averaged values for Class F (very stable) meteorological conditions (Turner, 1969). On the data collection flight of January 2 (Figure Z), four sets of cross sections were flown at 5,11,29, and 35 km downwind. A replica from each of these sets is shown in Figure 6.
The similarity of response for both the SO?and particle concentration becomes apparent, especially with respect to the bimodal peak found at 5 km. Based on a known cross-sectioning speed, the plume widths are easily calculated, and Table I shows the degree of agreement between the measured plume width and the time-averaged values predicted for stable conditions. It should be noted that the predicted plume widths are for a 10-min time average, and the measured values are for an instantaneous plume. For a relatively stable plume, as this was observed to be, the two values should be rather similar. In addition to the plume traverses described in detail, there were a number of additional data gathering flights. Table I1 shows the relation between measured and predicted plume widths measured on some of these flights. Figure 6 illustrates the problem of distinguishing plume concentrations from background values. For the SOz curve, the background value of approximately 0.1 ppm can be explained as CO?interference, and the remaining peak value of 0.15 ppm SO? can readily be detected from the background. The particle background value in this case is about 1.4 particles
Table 11. Measured vs. Predicted Plume Widths Table I. Horizontal Plume Spread Distance from Plume width, m source, km Predicted0 Measured 5 600 450 11 1200 750 29 2800 2700 35 3360 3150 e by
from Turner (1969). Width taken as 4 ~ .
Date
Most Distance probable from stability source, H ~ ~ ~ , Eclasse sT km
12/18/68 12/19/69 l / 1/69 1/ 3/69
1800 0730 0800 0730
D E B F
11 17 15 11
l'hme width, m , PreMeadicted sured 2400 2600 880 1200
900 2000 400 700
Turner (1969). Volume 5, Number 7, July 1971 617
I
30 t 36 Porticulofes/cin3 2.0 pprn SO,
40k
1
20
Figure 6. Cross-sectional plume traces at 5, 11, 29, and 35 km downwind from the source (1/3/69)
2 0.5 plcrn3, and here again the peak cross-sectional value of approximately 3.6 particles per cm3 above background is readily detectable. This illustrated the benefits of working in a n isolated location that is free of other pollution sources which could add to background values. Also of considerable interest in this series of plume studies is the distance of travel of detectable concentrations of pollutants from various sources. While the concentration experienced by a downwind receptor depends on many factors, the concentrations found in the plume are indicative of the magnitude and duration of the eventual ground level concentrations. In certain situations, for example when damage to vegetation occurs, short-term exposure to a high-level concentration may be more significant than long-term exposure to a low-average concentration (Air Quality Criteria for Sulfur Oxides, 1969). A tabulation of maximum or average SOn concentrations recorded at various distances downwind from two coal-fired power plants and a copper smelter is shown in Table 111.
Date
Wind speed, mjsec
1/ 3/69 l / 3/69 l / 2/69 10/22/68 10/22/68 91 5/68
7 7 6 8 8 4
9/17/68 9/17/68 9/19/68 9/19/68 9/21/68
3 3 3 3 3
9/23/68 9/23/68
6 6
It is evident that, under stable atmospheric conditions, SO2 may be transported relatively great distances at appreciable concentrations. In certain cases, apparent anomalies were encountered. On Sept. 17, 1968, concentrations of 6 to 7 ppm were found 1 3 and 24 km from the copper smelter, while 2 pprn was recorded near the source. Unfortunately, no emission data were available from the copper smelter, and these higher concentrations could have resulted from higher emission factors a t release time, Poor mixing in large “cells” may also have played a role in producing these high concentrations. On Jan. 3, 1969, SOnand particulate matter from the Crystal River Plant were tracked and recorded 70 km from the source a t concentrations equivalent to those found a t 20 and 50 km. In this case, the emission factors were known, and were apparently not responsible for the anomaly. The average concentration of both particulate and SOe was recorded by independent instrumentation systems (Figure 3). The concentration profile is indicative of the extremely limited mixing
Table 111. Distance of Transport and Detection SO2 emission Distance Concentration, ppm rate, g/sec detected, km Max Ava Crystal River, Fla. Power station plume 1400 82 0.2 ... 1400 73 1.o ... 1400 77 0.1 ... 1400 77 , . . 0.4 1400 68 ... 0.5 1400 40 ... 0.2 Douglas, Ariz. Copper smelter plume unknown 24 ... 6.0 unknown 32 ... 2.0 unknown 6 , . . 8.0 unknown 15 ... 3.0 unknown 20 ... 2.0 Four Corners, N.M. Power station plume unknown 24 ... 0.5 unknown 29 ... 0.3
Methodb A A A B B B C C C C C
C C
a One to two minute average during cross-sectional traverse of plume. A, electroconductivity method (Sign-X). Minimum detectable: 0.01 ppm (under flight conditions it is more likely 0.05 ppm). B, jmpjnger method (colorimetric analysis). Minimum detectable: 0.005 ppm for 24-hr sample (at flight sampling times estimate more likely 0.1 pprn). C, impinger method (color comparator analysis). Minimum detectable: estimated 0.2 ppm.
618 Environmental Science & Technology
and dilution capability of atmospheric processes in highly stable conditions. Thus, SO2 concentrations greater than 1.0 ppm have been detected over 70 km from their source. This is 50 times the background or minimum detectable value, which, under these circumstances, was the same. Detectable concentrations of SOzhave been routinely followed 50 to 80 km under conditions of atmospheric stability. Particulates have been tracked comparable distances. Sulfur Dioxide Decay To assess the decay of sulfur dioxide in the plume, it was necessary to differentiate between a decrease in concentration due to atmospheric dispersion processes and a decrease in concentration due to oxidation or other chemical or physical decay factors. The method selected for this determination was developed to avoid the problems of sampling extremely small concentrations of potentially complex reactant products in a material balance approach. I t was also designed to avoid problems associated with the inability to sample at precise locations within the plume. The technique consists of a comparative ratio of sulfur dioxide concentration to a conservative tracer concentration. The tracer consists of submicron-sized particulate matter, which is continuously emitted from the stack. These particles, in the case of a pulverized coal-fired boiler operated at high temperatures, consist mainly of mineral ash in the form of glassy spheres. Because of their small size, the particulates tend to diffuse as a gas and remain airborne for considerable lengths of time, subject to settling velocity of the particles. Settling velocities and agglomeration rates of 0.3 to 1.0-p particles were computed as an indication of suitability as a conservative tracer. Agglomeration rates calculated by the Wytlaw-Gray formula (Greene and Lane, 1964) for aerosols containing on the order of I O 4 particles per cm3 were less than 1 % in 3 hr. Since the particle concentrations encountered in this current study were in the range of 10 to IO2 particles per cm3, agglomeration rates should be even less. Terminal settling velocities may be calculated based on Stoke's law applying Cunningham's correction factor. A 0.4-p diameter particle of unit density will have settled about 10 cm in a plume 4-hr old. The particulate matter should thus serve as a conservative tracer, and was considered as such in the decay rate studies. Some uncertainty in this consideration exists, as explained in the next section. If the SO2 were also conservative, the ratio of particulates/S02 would approximate a constant as the plume ages and diffuses. If the SO1 demonstrates a measurable decay rate, then the ratio of particulates/SOz would increase as the plume ages. The most significant SOz decay data were obtained on Jan. 2 and 3, 1969, when extremely stable atmospheric conditions existed, and on Dec. 19,1968, when a slightly less stable regime existed. Figure 7 shows data from the three days listed. Values of the particulate/S02 ratio are plotted on the logarithmic ordinate, with plume age (in minutes) on the linear abscissa. (Plume age was determined by dividing the total distance from the source by the average wind speed.) The particulate/SOn ratio consisted of the number of particles per cm3 of air sampled with a diameter equal to or greater than the selected size range divided by the grams of SO2per cm3.
IO"
, A 12/19/68
01/02/69 0 01/03/69
; 0
1010
(z
'4
-
0 0
0
0
80
0
b
.
0 .
On
O O Q O 0
*
0
om
0
0
/
I
I
I
l
0"
-
~
!
0
0
O0
I
'
A 30-40%R/H
I
0
0 00 0
l
~
ii l
I
/
Figure 7. Sulfur dioxide decay rates in three relative humidity ranges (12/19/68,1/2/69,1/3/69)
Curve A shows data from two longitudinal axial traverses made on Jan. 3, 1969. Distance tracked over the Gulf of Mexico was 80 km. Ratio data were obtained for plume ages from 20 to 180 min. Relative humidity in the plume ranged from 43 to 30% during this time. The relative humidity range is accounted for in part by the higher plume humidity early in the dilution process, and in part by the change in relative humidity encountered when tracking the plume center line at different altitudes in the downwind traverse. Curve B is plotted from data taken from two similar traverses made on Jan. 2, 1969. Distance tracked over the Gulf of Mexico was 77 km. Ratio data were obtained for plume ages from 70 to 210 min. Relative humidity in the plume during this time ranged from 40 to 56%. The ratio data indicate an increasing SO2decay rate with time. Curve C shows the results of ratio computations from a series of cross-sectional traverses at 5, 17, and 28 km downwind on Dec. 19, 1968. Plume age varied from 20 to 90 min. Relative humidity in the plume ranged from 78 to 80%. The data again indicate an increasing particulate to SOz ratio, but at an even faster rate than for Jan. 2, 1969. Half-life determinations, the time required for the decay of one-half of the sulfur dioxide, indicated that the reaction obeyed a first-order rate equation. SO2loss rates varied from a negligible value at low relative humidity (35% range) to a half-life of approximately 140 min as medium relative humidity (50% range), and 70 min at high relative humidity (80z range). Rate constants independent of meteorological diffusion and transport parameters were determined from data as follows : Assuming that:
and C,
=
AIQ,exp-kt
(2)
where A1 constant = [ l / ( ~ u U u z ) ] uy,uz ; are assumed identical for both particulate and gas distributions. Volume 5, Number 7, July 1971 619
Table IV. Reaction Rate Constants Date 1/3/69 1/2/69 12/19/68
Date 8/19/60 81 2/60 9130168 to 1/9/69
Rel. humidity, 30-40 40-55 78-80
(no. of particles/g SO2)
SOn half-life, min
0
0.80 x 1010 0.83 X 1O1O 0.98 X 1Olo
No apparent decay 144 70
4.7 9.9
x x
10-3 10-3
Table V. Percentage Oxidation of SO2in Power Plant Plumes SOn oxidation Investigator Plume age, min Re]. humidity, rate, min-’ Gartrell 23 +95 0.35 et al. 108 +95 0.51 Gartrell 5 92 0.0 et al. 15 73 0.0 Dennis 1-80 36-52 ... et al.
axial concentration of particulate matter at time, t axial concentration SOzat time, t = particulate emission rate U = average wind speed uu, uz = standard deviations of plume concentration distribution in the horizontal and vertical dimensions, respectively Qs = SOpemission rate exp-kt = the SOz decay function C, C, Q,
Then,
Q,!Qs
k , min-1
= =
c,/c, = ___ Qsexp-kt Qp
and,
(3)
(4)
where k = rate constant, min-1; and t = time, min. A plot of semilog paper of the ratio (C,/C,) vs. t [plume age), yields k values and ( Q p / Q s )values from slope and intercept calculations as shown in Table IV. These data tend to support and add detail to the conclusion of Gartrell et al. [1964), based on SOs, acid aerosol, and SOs samples in power plant plumes within 10 miles of the source, that relative humidity in the plume and ambient air is the controlling factor in the oxidation of Son. Data from this current study summarized in Table IV suggest that available moisture is a major factor in the decay of sulfur dioxide in plumes of this type. Other possible variables such as sunlight and catalysts should have been similar on each of these flights since all were conducted just after sunup at the same emission source. Data reported by Gartrell et al. (1964), on percentage oxidation of SOz in power plant plumes, are presented in Table V. Only data representative of extreme values are listed for comparative purposes. Also shown in Table V are data reported by Dennis et al. (1969), on the SO2 decay rate in power plant plumes. The decay rate is a composite rate based on a number of different experiments. Discussion These investigations have shown the degree of agreement between experimental measured and predicted plume dimensions under conditions of considerable stability. 620 Environmental Science & Technolog)
min-1 ... . . I
... 7.67 X 10-3
SOn half-life,
min ...
...
... -50
In addition, a ratio technique has been utilized to make estimates of SOs half-life in the plumes. A major uncertainty remains in these techniques because of a problem not originally anticipated. Lundgren and Cooper (1968) showed experimentally that light-scatter particle counters, as used in this investigation, are humidity dependent-i.e., the particle count for a given abundance of aerosols will increase with increasing humidity. This phenomenon could explain the difference in particles/SO* ratios as reported in Figure 7. Thus, for the moment, findings by this technique are not confirmed. A means for solving this problem is to take comparison impaction or filter samples of particulates and relate these values to the light-scatter values. Another possibility is to use heating coils on the particle sampler inlet or mix sample air with dry dilution air, so that the relative humidity of the inlet will be low and not a cause for concern. Acknowledgment The authors thank the Florida Power Corp. for their assistance by furnishing weather records, fuel composition, and fuel use data. Literature Cited “Air Quality Criteria for Sulfur Oxides,” NAPCA Publication no. AP-50, 1969. Berger, A. W., Dennis, R., Lull, D., Billings, C. E., “Reactions of Sulfur Oxides in Stack Plumes,” APCA Paper no. 68-20, 61st Annual Meeting of the Air Pollution Control Association, St. Paul, Minn., June 23-27, 1968. Carpenter, S. B., Frizzola, J. A,, Smith, M. E., Leavitt, J. M., Thomas, F. W., “Report on Full-Scale Study of Plume Rise at Large Electric Generating Stations,” preprint. Presented at the 60th Annual Meeting, Air Pollution Control Association, Cleveland, Ohio, June 11-16, 1967. Carson, J. E., Moses, H., “The Validity of Currently Popular Plume Rise Formulas,” Mawson, C. A., Ed., Proceedings of the USAEC Meteorological Information Meeting held at Chalk River Nuclear Lab, Sept. 11-14, 1967. Dennis, R., Billings C. E., Record, F. A., Warneck, P., Arin, M. L., “Measurements of Sulfur Dioxide Losses from Stack Plumes,” APCA Paper no. 69-156, 62nd Annual Meeting of the Air Pollution Control Association, New York City, June 26, 1969. Gartrell, F. E., Thomas, F. W., Carpenter, F. W., “Full-Scale Study of Dispersion of Stack Gases,” a summary report by Tennessee Valley Authority and U.S. Public Health
Service, Chattanooga, Tenn., August 1964. Greene, H. L., Lane, W. R., “Particulate Clouds: Dusts, Smokes, and Mists,” E. and F. N. Spon Ltd., London, 1964, pp 138-41. Interbranch Chemical Advisory Committee, “Selected Methods for the Measurement of Air Pollutants,” PHS Publication no. 999-AP-11, 1965. Lundgren, D. A., Cooper, D. W., “Effect of Humidity on Light-Scattering Methods of Measuring Particle Concentration,’’ APCA Paper no. 68-107, 61st Annual Meeting of the Air Pollution Control Association, St. Paul, Minn., June 23-27, 1968. Martin, A., Barber, F. W., J. Inst. Fuel 39,294-307 (1966).
Montgomery, T. L., Corn, M., J . Air Pollut. Contr. Ass. 17 (S), 512-17 (1967). Smith, M. E., “Reduction of Ambient Air Concentrations of Pollutants by Dispersion From High Stacks,” Proceedings of the Third National Conference on Air Pollution, PHS Publication no. 1649, Dec. 12-14, 1966, pp 151-60. Stone, G. N., Clarke, A. J., Combustion 39, 41-9 (1967). Turner, D. B., “Workbook of Atmospheric Dispersion Estimates,’’ Public Health Service, Cincinnati, Ohio, National Air Pollution Control Administration, PHS Publication no. 999-AP-26,1969. Receiced for review May 21, 1970. Accepted December 28, 1970.
Effect of Peroxyacetyl Nitrate (PAN) in vivo on Tobacco Leaf Polysaccharide Synthetic Pathway Enzymes Lawrence Ordin, Morris J. Garber, Juanita I. Kindinger, Sherry A. Whitrnore, L. Carl Greve, and 0. Clifton Taylor Departments of Biochemistry, Statistics, Horticultural Science, and Statewide Air Pollution Research Center, University of California, Riverside, Calif. 92502
m Tobacco plants were exposed to 1 ppm of peroxyacetyl
nitrate (PAN) for 1 hr. Subsequent exposure of the plants to light caused leaf-cell collapse, which was noted after 24 hr. Assay of the leaves at that time showed a strong inactivation of alkali-soluble glucan, cellulose, and lipid synthetases, no effect on phosphoglucomutase, and a stimulation of UDP glucose pyrophosphorylase. Assay of the leaves a t the end of the gassing period showed no effect of the PAN except for relatively decreased alkali-soluble glucan and cellulose synthetase activities. Plants placed in a dark chamber a t that time showed no subsequent lethal effects. It was concluded that PAN treatment of potentially sensitive green plant tissue can cause a nonlethal, and probably reversible, decrease of cellulose synthetase (and of growth).
G
rowth and cell-wall metabolism, particularly cellulose synthesis, measured as incorporation of 4C from 14C-glucose, was inhibited by peroxyacetyl nitrate (PAN) treatment of oat coleoptile sections (Ordin, 1962; Ordin et al., 1970). Wall metabolism and growth of oat coleoptile sections responded to auxin similarly, Even in nongrowing coleoptiles (auxin omitted), wall metabolism was decreased by a PAN pretreatment. Pretreatment of oat coleoptile sections with PAN inhibited P-glucan synthetases such as cellulose synthetase (Ordin and Hall, 1967). Phosphoglucomutase was also inhibited by PAN pretreatments; UDP glucose pyrophosphorylase, however, was not inhibited (Hall and Ordin, 1967). Glucan synthetase level corresponded with growth rate of coleoptiles (Hall and Ordin, 1968). The inhibitory pattern induced by PAN for P-glucan synthetase was similar to the pattern of growth rate reduction in oat coleoptiles as shown by unpublished work in this laboratory. The question arises: Will PAN treatment of growing green leaves lead to inhibition
of wall glucan synthetases and of other enzymes on the pathway of glucan synthesis without necessarily producing lethal consequences ? Ozonated hexenes suppressed linear growth, fresh and dry weight and leaf area of beans without symptoms of visible injury (Todd and Garber, 1958). Height increase of pea plants was temporarily arrested by such treatments. Low concentrations of NO? suppressed pinto beans and tomato growth without producing necrosis (Taylor and Eaton, 1966). As indicated in published work (Taylor, 1969), long-term plant growth effects by PAN (without lethal symptoms) have not been studied. Tobacco leaves displayed a sensitivity to Los Angeles ambient air, which varied according to the physiological stage of development of the leaf (Glater et al., 1962). The gradient from tip to base of the tobacco leaf is a gradient from senescent to young tissues with leaf expansion occurring primarily by cell expansion in the second and third leaves (Avery, 1933). Taylor (1967) has shown that tobacco leaves display a sensitivity to PAN which varies according t o physiological stage of development in the leaf itself-i.e., similar to Glater’s finding. This response was measured by cell collapse visible to the naked eye. Damage was found in leaves which were still expanding. Decreased photosynthesis could cause decreased growth. It was reported, however, that PAN did not cause photosynthesis to decline until water-soaked areas became visible (Dugger et al., 1963; Taylor, 1969). We will show below that nonlethal inhibition of glucan synthetase can occur in sensitive tobacco leaves. Materials and Methods Plant Growth Condition and Selection. Tobacco plants, Nicotiana tabacuni L. var. Bel W-3, were grown in a mixture of peat moss and pearlite (1-to-1) in natural light in carbonfiltered air in a greenhouse. Temperatures were 27 ’ to 32 “C for day and 21 ‘C for night. Plants were watered once a day; Volume 5, Number 7, July 1971 621
