OS0
r---l
air was made to exhaust spontaneously from small door openings. It is interesting to note that when a value of the volume rate of outdoor air intake divided by the volume of the room becomes larger, the mixing factor becomes smaller. From these results, it seems no doubt that eq 3 or more generally eq 7 is an appropriate equation to estimate the concentration of indoor pollutants.
Literature Cited
Time ( m i n )
Figure 7. The same as Figure 6. Volume rate of outdoor air intake was 12 m3/min: (-) m = 1.0
perimental results with the mixing factor being -0.3. When the volume rate of outdoor air intake was 12 m3/min, the experimental result,s were in accord with eq 3 with the mixing factor being unity, as shown in Figure 7. The good mixing may be ascribed to the experimental condition that, in this case, mechanical exhausting of room air was not applied, but room
(1) Turk, A. ASHRAE J . 1963,5, 55. (2) Turk, A. ASTM Spec. Tech. Publ. 1968,433, 79. (3) Brief, R. S. Air Eng. 1960,2, 39. (4) Esmen, N. A. Enuiron. Sei. Technol. 1978,12, 337. (5) Hoegg, U. R. Enuiron. Health Perspect. 1972,2, 117. (6) Owen, D. F.; Rossano, A. T. ASHRAE Trans. 1969, 73, 93. ( 7 ) Bridge, D. P.; Corn, M. Enuiron. Res. 1972,5, 192. (8) Corn, M. “Environmental Tobacco Smoke Effects on Non-
Smoker”; report from workshop, Rylander, R. Ed.; University of Geneva, 1974; pp 21-36. (9) Dwight, H. B. “Tables of Integrals and Other Mathematical Data”; Macmillan: New York, 1961. (10) Olin, J. G.; Sem, G. J. Atmos. Enuiron. 1971,5, 653. (11) Sem, G. J.; Tsurubayashi, K. Am. Ind. Hyg. Assoc. J . 1975,36, 791. (12) Okada, T.; Matsunuma, K. J . Colloid Interface Sci. 1974, 48, 461. Receiued for review September 19, 1979. Accepted May 6,1980
Development of an Ozone River Associated with Synoptic Scale Episodes in the Eastern United States George T. Wolff”‘ and Paul J. Lioy2 Interstate Sanitation Commission, 10 Columbus Circle, New York, New York 10019 The spatial and temporal distributions of ozone in the eastern two-thirds of the United States during three July 1978 episodes are examined. In all three cases, a distinct area of high ozone concentrations was observed flowing northeastward in a “river”, extending from the southwest Gulf Coast to New England. The formation, size, and other characteristics of this “river” are discussed. Typical ozone episodes in the northeastern U S . are associated with high-pressure systems which originate in Canada and move southeastward into the Midwest en route to the Atlantic Ocean ( 1 ). As each system moves out of Canada, the air mass contains between 30 and 50 ppb of ozone (2,3).Then as it passes over industrialized and urbanized areas, additional ozone may be formed resulting from precursor emission oxidation and accumulation in the system (4, 5 ) . The highest ozone concentrations are usually found on the backside of the high-pressure system presumably because this sector has the longest residence time over areas of high precursor emission densities (4-6). Most of the above results were obtained from sites distributed in 19 states located in the midwestern and eastern U.S. (I, 2 , 4 , 5 ) .Frequently, however, high concentrations of
Present address, Environmental Science Department, General Motors Research Laboratories, Warren, MI 48090. * Present address, Institute of Environmental Medicine, New York University Medical Center, New York, NY 10016. 0013-936X/80/0914-1257$01.00/0
@ 1980 American Chemical Society
ozone appeared to extend beyond the 19-state area when influenced by southwesterly winds. This high ozone could not be accounted for by emissions in the study area, suggesting that ozone was being transported from areas to the southwest. Consequently, we have expanded the geographic boundaries of the study in an attempt to determine the possible sources of this extraregional ozone. In this note we will discuss the ozone patterns that developed during three such episodes by using data collected in 35 states encompassing all of the U.S. east of the Plains States (Figure 1).The three episodes examined occurred during July 1977 on the following dates: July 12-21, July 21-24, and July 26-30.
Results July 12-21 Episode. On July 12, a high-pressure system was formed in predominantly maritime tropical air over the Gulf of Mexico. This system affected the entire southeastern U.S. and extended from western Texas, northeastward through Illinois, and finally east to the Atlantic Ocean. By July 14 the southwesterly airflow pattern, which persisted until July 21, began to develop. Trajectories calculated from Heffter’s model (7) are shown in Figure 2a. Air parcels originating near the Texas-Louisiana area traveled northnortheastward to the lower Midwest and then eastward to the Atlantic Coast. The ozone concentration patterns found within this system are shown in Figure 2b-d. High ozone concentrations were associated with the return flow around the high-pressure system within an ozone river extending from Texas to southern New England parallel to the isobars. Volume 14, Number 10, October 1980 1257
The hydrocarbon emission densities for the area influenced by the high-pressure system are illustrated in Figure 3. The Texas and Louisiana Gulf Coast form an area of extremely high emission densities. By comparison, emission densities between this area and the central Midwest are much lower and the source points more diffuse. Consequently, it appears that much of the high ozone observed from Arkansas and Oklahoma to the lower Midwest may have originated from emissions along the Texas-Louisiana Gulf Coast. The ozone river, averaging -120-130 ppb, persisted for 1 week and extended northward from the Texas-Louisiana Gulf Coast to the northeastern Atlantic Coast. On almost every day, isolated areas of a few hundred square miles to one thousand square miles experienced higher ozone levels. In each case, the
Figure 1. Location of ozone monitoring sites.
a
b TRAJECTORIES
Number. R.1.r P.,C.I Po.ltlon a t 1300 E D 1 ,"I"
m
@# 80-99 I: 100.149
a 150-199
(0
on ~ h sGirm DO. I"
Ozone on 7/14/77
M
A. 6 Day Forward from Houston B. 6 Day Backward from N e w York C. 6 Day Backward from D C
2 200
1977
C
Flgure 2. (a) Air parcel trajectories during July 1258
wind speeds within areas of ozone greater than 150 ppb in concentration were significantly lower than areas within the broader band. For example, on July 16, an area which included the southern tip of Illinois, southeastern Missouri, western Kentucky, and most of Tennessee was affected by ozone concentrations of 178-198 ppb. Trajectory analysis indicated that when this air parcel passed over the Gulf Coast on July 13 and moved northward into the Tennessee area on July 15, it contained an average 0 3 concentration of -120 ppb. During the next 24 h, wind speeds diminished to less than 6 m/s and the ozone level increased. The wind speed increased to over 20 m/s by July 18, and the small area of high ozone appeared to have been dispersed and assimilated into the air mass. Similar 1-day incidents of 0 3 concentrations significantly higher than 120 ppb occurred in several other places during the episode. The greatest number of incidents was observed in the Washington D.C.-Baltimore MD area. Ozone concentrations in excess of 150 ppb occurred on July 15 and 16 and in excess of 200 ppb on July 17 and 19. On all of these occasions, the mean wind speed through the mixing layer was zoo
u
W ./’
../’
v
d
C Ozone on 7/24/77
m
BOUNDARY LA FROM 7/21 - 7 / Based on Fomard Trajectories From Houst and New Orleans
Flgure 4. (a-c) Ozone concentrations on July 22-24; (d) air parcel trajectories from Houston and New Orleans on July 21, 1977.
Volume 14, Number 10, October 1980
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Ozone on 7 / 2 8 / 7 7
U
...
Flgure 5.
Ozone concentration patterns on July 27 and 28, 1979.
phenom,enon can account for some of the high ozone which was observed being transported into the Northeast. During most of the final days of these episodes, maritime tropical air (as evidenced by elevated dew point and temperature measurements) was present. Previous analysis showed that the Midwestern and Eastern US.frequently experience the same ozone episodes. The data presented in this paper show an episode which simultaneously affected nearly two-thirds of the US., covering an area of -2 X 106 mi2 ( 5 X lo6 km2). The circulation around the high-pressure systems which caused these episodes traveled northward from the TexasLouisiana Gulf Coast to the Midwest and then eastward to the Northeast and the Middle Atlantic Coast. Ozone concentrations within this river averaged -120-130 ppb and were as high as 328 ppb in Connecticut. The first episode was a classic example of a prolonged elevated pollution episode associated with a stagnating highpressure system. The second two episodes, however, demonstrated that a stagnation in the Northeast is not necessary to produce elevated ozone concentrations. As a new high-pressure system rapidly moved from Canada on July 21, the prolonged ozone episode of July 12-20 terminated in the northern half of the study area but persisted over Texas, Oklahoma, Arkansas, and Louisiana until July 29. For the periods including July 23-24 and July 28-29, the high-pressure system followed the same route, and air containing elevated ozone levels was advected into the backside of each system and transported from the Gulf to New England. During July 22--24, ozone concentrations between 90 and 130 ppb traveled in excess of 2300 km in 48 h. Analysis of hydrocarbon emission density data suggests that the ozone river may originate in the high hydrocarbon emission density areas along the Gulf Coast between Corpus Cristi, Texas, and New Orleans, Louisiana. This area frequently experiences high temperature and ample sunshine which are conducive for ozone formation. The ozone produced is undoubtedly supplemented by emissions into the ozone river en route through the Mississippi and Ohio Valleys to the Northeast. In addition, recent evidence indicates that there is a stratospheric contribution of ozone on the backside of high-pressure systems (3,8, 9). This is based on measurements of a stratospheric air tracer, beryllium-7, which has been found to be the highest on the backside of high-pressure
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systems (3, 8 ) . Although the intrusion of stratospheric air occurs immediately behind the cold front, only rarely does it extend to the ground in the frontal zone (9).Instead, it appears that the intrusion reaches the midtroposphere, where it is advected in a clockwise circulation to the backside of the approaching high-pressure system. It is then brought to the surface during good mixing conditions (8) which are typical in humid maritime tropical air. This study has raised many qyestions regarding the relative importance of both anthropogenic and nonanthropogenic sources of ozone and its precursors along the ozone river. Unfortunately, these questions can only be answered after large regional scale models, which incorporate the complex chemistry and meteorology, are developed.
Acknowledgment We thank all of the states which made their surface ozone data available. In addition we are grateful to Richard Herrmann of General Motors Research Laboratories for performing the trajectory calculations. Literature Cited (1) Wolff, G. T.; P. J. Lioy; Wight, G. D. J. Environ. Sci. Health, Part A 1980,15, 183-99. (2) Wight, G. D.; Wolff, G. T.; Lioy, P. J.; Meyers, R. E.; Cederwall, R. T. Proceedings of the ASTM Symposium on Air Quality and Atmospheric Ozone, Boulder, CO, August 1977, pp 445-57. (3) Kelly, N. A.; Wolff, G. T.; Ferman, M. A.; Monson, P. R. Preprints of the 1979 Annual Meeting of the Air Pollution Control Association, Cincinnati, OH, June 1979, Paper No. 79-58.1. (4) Wolff, G. T.; Lioy, P. J.; Wight, G. D.; Meyers, R. E.; Cederwall, R. T. Atmos. Enuiron 1977,11, 797-802. (5) Wolff, G. T.; Lioy, P. J.; Wight, G. D. Proceedings of the MidAtlantic States APCA Conference on Hydrocarbon Control Feasibility, New York, April 1977, pp 98. (6) Vuckovich, F. M.; Bach, W. D.; Crussman, B. W.; King, W. J. Atmos. Enuiron. 1977,11, 967-83. (7) Heffter, J. L.; Taylor, A. D. NOAA Technical Memorandum; ERL ARL-50, U.S.Department of Commerce, Silver Spring, MD, 1975. (8) Wolff, G. T.; Ferman, M. A.; Monson, P. R. Geophys. Res. Lett. 1979,6, 637-41. (9) Johnson, W. B.; Viezee, W.; Cavanagh, L. A.; Ludwig, F. L.; Singh, H. B.; Danielsen, E. F. Preprints, 4th Symp. Turb. Diff. Air Pollut., American Meorological Society, Reno, NV, Jan 1979, pp 355-62. Received for review November 9,1979. Accepted M a y 16,1980
