Literature Cited (1) Herron. J. T.. Huie, R. E., Hodgeson, J. A., Eds, NBS Spec. Publ. (U.S.)1979, No. 557. (2) Dimitriades, B.; Wesson, T. C. J. Air Pollut. Control Assoc. 1977,
22,33. (3) Demerjian, K. L.; Kerr, J. A.; Calvert, J. G. Adu. Enuiron. Sci. Technol. 1974,4,1. (4) Cox, R. A.; Derwent, R. G.; Holt, P. M.; Kerr, J. A. J . Chem. Soc., Faraday Trans. I 1976,72,2061. (5) Carter, W. P. L.; Lloyd, A. C.; Sprung, J. L.; Pitts, J. N., Jr. Int. J . Chem. Kinet. 1979,1I, 45. (6) Derwent, R. G.; Hov, 0. “Computer Modelling Studies of Photochemical Air Pollution Formation in North West Europe”; U.K. Atomic Energy Authority, AERE-R9434,1979. (7) Cox, R. A.; Derwent, R. G.; Williams, M. R. Enuiron. Sci. Technol. 1980,14,57. (8) Cox. R. A.: Sheuuard. D. Nature (London)1980.284,330. (9) Cox, R. A.J. P h o c h e m . 1974,3,175. (10) Niki, H.; Maker, P. D.; Savage, C. M.; Breitenbach, L. P. J. Phys. Chem. 1978,82,135. (11) Atkinson, R.: Darnall, K. R.; Lloyd, A. C.; Winer, A. M.; Pitts, J. N., Jr. Adu. Photochem. 1979,II; 375. (12) Herron, J. T.; Penzhorn, R. D. J . Phys. Chem. 1969,73,191. (13) Morris, E. D., Jr.; Niki, H. J . Chem. Phys. 1971,55,1991. (14) Atkinson, R.; Pitts, J. N., Jr. J . Chem. Phys. 1978,68,3581. (15) Niki, H.; Maker, P. D.; Savage, C. M.; Breitenbach, L. P. J. Phys. Chem. 1978,82,132.
(16) Stief. L. J.: Nava. D. F.: Pavne. W. A.: Michael, J. V. J . Chem. Phys. 1980,73,2254. (17) Morris. E. D.. Jr.: Stedman. D. H.: Niki. H. J . Am Chem Soc. 1971,93,3570. (18) Morris, E. D., Jr.; Niki, H. J . Phys. Chem 1971, 75, 3640. (19) Gaffney, J. S.; Levine, S. Z. Int. J . Chem. Kinet. 1979, 11, 1197. (20) Kerr, J. A.; Trotman-Dickenson, A. F. In “Handbook of Chemistry and Physics”, 60th ed.; CRC Press: Boca Raton, FL, 1980;pp F231-2. (21) Baldwin, R. R.; Cleugh, C. J.; Plaistowe, J. C.; Walker, R. W. J . Chem. Soc., Faraday Trans. 1 1979,75,1433. (22) Singleton, D. L.; Irwin, R. S.; Cvetanovii., R. J. Can. J. Chem. 1977,55,3321. (23) Birrell, R. N.; Trotman-Dickenson, A. F. J . Chem. Soc. 1960, 2059. (24) Kerr, J. A,; Parsonage, M. J. “Evaluated Kinetic Data on Gas Phase Hydrogen Transfer Reactions of Methyl Radicals”; Butterworths: London, 1976. (25) Darnall, K. R.; Lloyd, A. C.; Winer, A. M.; Pitts, J. N., Jr. Enuiron. Sei. Technol. 1972,10,692. (26) Dimitriades, B. “Proceedings of the Solvent Reactivity Conference”; U.S. Environmental Protection Agency: Research Triangle Park, NC, Nov 1974;EPA-650/3-74-010, Received for review December 15,1980. Accepted March 11,1981.
NOTES
Allocation of Vehicular Emissions of Carbon Monoxide in El Paso, Texas, and Ciudad Juarez, Chihuahua Howard G. Applegate Department of Civil Engineering, University of Texas at El Paso, El Paso, Texas 79968
Some of the CO measured in the city of El Paso, Texas, has its origin either on federally owned land or in Mexico. Neither the city nor the state has jurisdiction over these two areas. Unless CO emissions from these areas are lowered, El Paso cannot come into compliance with federal standards.
Introduction The Environmental Protection Agency has declared El Paso, Texas, to be a nonattainment area in regard to carbon monoxide (CO). Local air pollution authorities believe some of the CO measured within El Paso is emitted from vehicles and in areas over which they have no control. This paper reports on the allocation of vehicular emissions of CO within the El Paso-Cd. Juarez (EPJAZ) airshed for 1977. For this study, the following broad categories were set up: local emissions-CO emitted by vehicles registered in and driving the streets of El Paso; federal-CO emitted by vehicles waiting to pass through customs on the international bridges and vehicles registered in and driving on Fort Bliss; foreign-CO emitted from vehicles registered in and driving the streets of Cd. Juarez. Methods
All CO measurements in El Paso were made by the Texas Air Control Board using EPA-approved methodology. All traffic data in El Paso were gathered by the Texas Department of Highways. Light-duty gasoline vehicles (LDGVs) are those passenger cars registered in El Paso by the Texas Department of Motor Vehicles as of March 1,1977; heavy-duty diesel vehicles (HDDVs) are commercial trucks, farm trucks, combination trucks, and buses registered on the same date. Total 0013-936X/81/0915-0963$01.25/0
vehicle miles traveled in El Paso were obtained from the Texas Department of Highways. The assumption was made that, since LDGVs constituted 81%of the total vehicles, they drove 81%of the total mileage. The number of vehicles crossing the international bridges between El Paso and Cd. Juarez was obtained from the U.S. Customs. They listed “freight carrier vehicles” and “other ground vehicles” in the report. For this study, the first were assumed to be HDDVs and the latter to be LDGVs. It was further assumed that the vehicles were warmed up and the average waiting time to pass through customs was 20 min. The total number of vehicles registered on Fort Bliss in 1977 was obtained from the post’s environmental office. It was assumed, in order to have a conservative estimate, that all were LDGVs. Officials from Fort Bliss estimated that the average vehicle traveled 5.49 mi day-l on the post in 1977. It proved impossible to obtain reliable figures on vehicle registration or miles traveled in Cd. Juarez. For this study, earlier published data were used to calculate that Cd. Juarez had 26 087 vehicles in 1977 (I,2). Further, it was assumed that the distribution between HDDVs and LDGVs was the same as in El Paso for the same year. This should give a conservative estimate of CO emissions since the percentage of HDDVs is probably much greater. A further conservative estimate was made that the mileage distribution between HDDVs and LDGVs was similar to that in El Paso. Buses, notorious polluters along the ent,ire border, are greater in number in Cd. Juarez and are driven more miles per day than in El Paso. Finally, it was assumed that the age distribution of vehicles in Cd. Juarez was the same as in El Paso. Since the tax on cars less than 5 yr old imported into Mexico is 100%of the purchase price, this estimate is very conservative. In addition, the quality of gasoline and diesel fuel in Cd. Juarez is lower than
@ 1981 American Chemical Society
Volume
15, Number 8, August 1981 963
Table 1. CO Concentration in El Paso, 1977 site
hours
6
12
site
hours
6
12
a
0000
0001
0002
0003
0004
0005
0006
0007
0008
0009
0010
1.20a
1.00
0.78
0.61
0.58
0.80
2.00
2.89
2.73
2.09
1.80
1.73
0.27’ 0.52’
0.18 0.43
0.17 0.41
0.08 0.28
0.03 0.18
0.12 0.35
0.91 0.95
0.54 0.73
0.94
0.32
0.10
1.08
0.97
0.56
0.31
0.28
1.04a
0.77
0.59
0.43
0.36
0.44
0.78
1.61
0.99
0.52
0.32
0.20
0011
0.22b
0.18
0.09
0.08
0.03
0.02
0.12
0.34
0.37
0.09
0.04
0.01
0.47c
0.42
0.31
0.29
0.19
0.17
0.35
0.59
0.61
0.31
0.20
0.12
0012
0013
0014
0015
0016
0017
0018
0019
0020
0021
0022
0023
1.63a 0.07’ 0.27’ 0.14a 0.01’ 0.1lc
1.56 0.04 0.20 0.13 0.01 0.11
1.66 0.04 0.20 0.11 0.00 0.09
2.01 0.11 0.34 0.15 0.01 0.10
2.69 0.18 0.43 0.32 0.15 0.38
2.81 2.00 1.41 0.45 0.17 0.41
2.52 1.69 1.30 1.07 0.64 0.80
2.54 0.90 0.95 1.74 0.67 0.82
2.49 0.52 0.72 2.03 0.63 0.79
2.39 0.56 0.75 1.95 0.38 0.62
2.09 0.55 0.74 1.76 0.30 0.55
1.58 0.46 0.68 1.39 0.31 0.56
Mean concentration(ppm), throughout row. Variance, throughout row. Standard deviation, throughout row.
Table II. CO Emissions from Local Sources, 1977 no. of heavy-duty dlesei vehicles
vehlcle miles traveled
CO, kg
total pre-1974
46 089 24 105
418918714 219 093 441
7 690 180
1974-1 977
21 984
199 823 273
5 395 228
no. of light-duty gasoline vehlcles
total
vehlcle mlles traveled
194 842
pre-1968
CO, kg
1 785 908 098
25914
237 525 777
16 223 0 12
1968-1974
112619
1975- 1977
56 302
1 032 254 881 516 127440
32 103 127 9 599 970
Table 111. CO Emissions from Federal Sources, 1977 Bridge Crossing no. of heavy-duty diesel vehlcles
total
92 433
pre-1974
48 342 44091
1975-1977
1276 582
no. of light-duty gasollne vehlcles
11 055 888
total pre-1968
1470 446
482 894
1968- 1974
6 390 361
1 626 985
1975-1977
3 195 181
346 986 Fort Bliss
no. of Ilght-duty gasoline vehlcles
vehlcie mlles traveled
50891
101 977931
1968-1974
14 707 29415
29 470 622 58 943 248
1975- 1977
6 769
13 564 061
total pre-1968
CO, kg
2 012 843 1833 136 252 296
Table IV. CO Emissions from Foreign Sources, 1977 no. of heavy-duty diesel vehicles
vehlcle mlles traveled
4 957 2 593 2 364
45 341 579 23 7 13 646 21 627 933
no. of Ilght-duty gasoline vehlcles
vehlcle miles traveled
total pre-1968
21 130 2810
1968-1974
12 213 6 107
193 298313 25 708 576 111726425
total pre-1974 1975- 1977
1974-1977
964
Environmental Science & Technology
55 863 2 12
CO, kg
832 349 583 954 CO, kg
1 755 988 3 474 692 1 039 056
1 1
Table V. CO Emissions in the El Paso-Cd. Juarez Area
=I
f
i
area
local federal foreign
CO emitted, kg
%
71 011 517
a3
6 557 ooa 7 685 947
a 9
total = a5 254 472
o+-mn~
i i
t i
o i
im
i i
iv
ii
i i
*
Discussion a1 m i i s
Mmuni
Figure 1. CO concentrations (dashed line) and traffic flow on Interstate 10 west (smooth line) and east (dotted line); dimensions are parts per million for CO and X 10 000 for vehicular traffic.
that used in El Paso. This would lead to poorer combustion with greater emissions of carbon monoxide. The kilograms of CO emitted from all of these vehicles were calculated by using an EPA formula (3).
Results Mean CO concentrations, variances, and standard deviations per hour for 1977 are given in Table I. Calculated CO emissions from local sources are given in Table 11, from federal sources in Table 111, and from foreign sources in Table IV.
Data from Table 11-IV are summarized in Table V. It can be seen that 17% of the CO emitted from vehicles within EPJAZ (and presumably monitored by the Texas Air Control Board) is from areas over which neither the city of El Paso nor the state of Texas has any jurisdiction. In view of the conservative estimates made of federal and foreign emissions, this 17% is probably a low estimate. No CO measurements have ever been made in Cd. Juarez. There is evidence that CO emitted in that city has been measured in El Paso. The mean hourly CO concentrations at CAMS 6 and traffic on Interstate 10 (-50 m from the sampling site) for January 1977 are shown in Figure 1.At 0800 and 17:OO hours both traffic counts arid CO concentrations peak. However, a t 22:OO hours there is a peak in CO concentrations without a similar rise in traffic counts. Figure 2 shows the mean hourly CO concentrations for
A
Figure 2. Hourly CO concentrations and resultant wind directions and speeds at CAMS 6 (dashed line) and CAMS 12 (solid line),
Figure 3. Hourly GO concentrations and resultant wind directions and speeds at CAMS 6 (dashed line) and CAMS 12 (solid line). Volume 15, Number 8, August 1981 965
CAMS 6 and 12 sites for January 1977 together with resultant wind speed and direction. (Resultant wind speed and direction, obtained from the Texas Air Control Board, are the hourly vectors of 1-s readings taken every 5 min). When these data were plotted for each month of 1977, similar figures were obtained for 9 of the 1 2 months, Le., peaks a t 08:OO and 20:OO hours for both stations, a peak of CAMS 6 for 16:OO hours and with CAMS 12 always having lower concentrations of CO than CAMS 6. The three atypical months, May, September, and October, have the peaks of the other nine months, but CAMS 12 has higher CO concentrations in the late evening than CAMS 6 (Figure 3). During January, a typical month, from 17:OO to 23:OO hours, winds at CAMS 6 were from 23' to 157" (NE to SE) 30% of the time and from 203' to 292' (SW to NW) 62% of the time; a t CAMS 12 they were from 23' to 157' 33% of the time and from 203' to 292' 40% of the time. In September, an atypical month, winds at CAMS 6 changed little-35% from 23' to 157' and 54%from 203' to 292'. However, a t CAMS 12,28%of the winds were from 23' to 157' and 49% from 203' to 292'. In January, the ratio of west: east winds during the 17:OO and 23:OO hours was 2.0:1.2; in September, the ratio was 1.51.7. These ratios and carbon monoxide concentrations are typical of all of the months which we have studied since 1975. CAMS 6 is located directly north of downtown Cd. Juarez and -1.8 km from the border. CAMS 12 is located directly east of downtown Cd. Juarez and -0.5 km from the border. During most of the year, CO from downtown Cd. Juarez is measured
a t CAMS 6; when the winds shift so as to blow more from the west, the CO from downtown Cd. Juarez is measured at CAMS 12. Conclusion The cities of El Paso and Cd. Juarez share a common airshed. Previous studies have shown that heavy metals from a local smelter crisscross the border. Parts of El Paso are farther south than the northern parts of Cd. Juarez. This means that whatever is put into the air of either city may end up in the air of the other city. International cooperation is needed if both cities are to meet the air standards of their respective countries. Acknowledgment
I thank Sabino Gomez, Regional Director, Texas Air Control Board, and Raul Munoz, Director, El Paso Environmental Unit, for furnishing data and fruitful discussions. Literature Cited (I) Barajas Weber, L. H. In "Air Pollution Along the United
States-Mexico Border"; Applegate and Bath, Eds.; Texas Western Press; El Paso, TX, 1974;pp 50-7. (2) Dominguez C., C. A. In "Air Pollution Along the United StatesMexico Border; Applegate and Bath, Eds.; Texas Western Press; El Paso, TX, 1974; pp 140-54. (3) Environmental Protection Agency "Mobile Source Emission Factors"; Final Document, EPA-400/9-78-005. Received f o r review September 15, 1980. Accepted March 23, 1981.
Rate of Reaction of Hydrogen Sulfide-Carbonyl Sulfide Mixtures with Fully Calcined Dolomite Vivek S. Kamath and Thomas W. Petrie' Department of Thermal and Environmental Engineering, Southern Illinois University at Carbondale, Carbondale, Illinois 62901
Kinetic data are obtained by a gravimetric technique for rates of reaction of calcium oxide in fully calcined dolomite with hydrogen sulfide and hydrogen sulfide-carbonyl sulfide mixtures. The data are presented as values for a factor K defined by d[CaO] = -K[CaO] dt. At 600,700, and 800 'C with [H2S] from 0.5% to 5.0% by volume and [H2S]/[COS] = 20 for mixtures, expressions for K show apparent rate constants and the dependence on sulfurous gas concentration. For example, at 700 'C, K = 1.43 X 10-4[H2S]1.06s-l and K = 1.70 X 10-4[H2S COS]l.oos-l. Since the data show first-order dependence on calcium oxide, K's for H2S alone as the sulfurous gas and H2S-COS mixtures can be obtained for the same sample, free from scatter due to variations from sample to sample. Addition of values for K from runs with H2S as the only sulfurous gas and runs with COS as the only sulfurous gas are compared to measurements with actual mixtures. K's for the mixtures are -30% higher than the sum of the appropriate separate values.
+
Introduction Schemes for high-temperature desulfurization of raw coal gas seek removal of hydrogen sulfide and carbonyl sulfide. Many results are available for the kinetics of H2S removal, starting with the data for half-calcined and fully calcined dolomites obtained at the City University of New York ( I ) . 966
Environmental Science & Technology
-
Data for COS removal by calcined calcium carbonate were obtained by Yang and Chen ( 2 ) .Since hydrogen sulfide and carbonyl sulfide occur together in coal gas, data for mixtures are a valuable extension of the available results. We have experience with the gravimetric technique used in much research on high-temperature desulfurization. Our apparatus and technique are described in detail elsewhere ( 3 ) . To study H2S-COS mixtures, we added COS to H2S and other gases to maintain a molar ratio of [H2S]/[COS]equal to 20 and a total reaction gas flow rate of 500 SCCM. This total flow rate was selected to provide enough sulfurous gas atoms to the volume of solid removal agent so that the reaction is not dominated by gas film resistance. A few runs with 1000 SCCM of reaction gases through the apparatus showed no effect of flow rate. Besides the sulfurous gases, the reaction gas mixture contained 20% by volume of hydrogen and 30% by volume of carbon monoxide to prevent dissociation of H2S and COS, respectively. Dissociation effects were checked a t various volume percentages of hydrogen and carbon monoxide by comparative gas chromatography on inlet and exit gas streams in the absence of the solid-gas reaction. Nitrogen comprised the rest of the gas mixture. All gases were obtained from gas cylinders. The solid removal agent was dolomite supplied by the Pfizer Corp. from their quarry in Gibsonville, OH. Calcium-to-
0013-936X/81/0915-0966$01.25/0 @ 1981 American Chemical Society
