Environ. Sci. Technol. 1990, 2 4 , 894-897
isolated in our fraction 3 would have occurred in the fraction in which Grimmer et al. isolated four- to seven-ring PAH compounds. We also cannot rule out the possibility that the Ames assay fails to detect the carcinogens that were detected in the bioassay used by Grimmer et al.
(8) Ball, J. C.; Young, W. C.; Salmeen, I. T. Mutat. Res. 1987, 192. 283-287. (9) Maron, D. M.; Ames, B. N. Mutat. Res. 1983,113,173-215. (lo)S h e e n , I. T.; Durisin, A. M. Mutat. Res. 1981,85,109-118. (11) IARC International Agency for Research on Cancer.
Literature Cited Claxton, L. D. Environ. Mutagen. 1983, 5, 609-631. Salmeen, I. T.; Pero, A. M.; Zator, R.; Schuetzle,D.; Riley, T. L. Environ. Sci. Technol. 1984, 18, 375-382. Pederson,T. C.; Siak, J.4. J. Appl. Tonicol. 1981, I , 61-66. Lofroth, G. Environ. Int. 1981,5, 255-261. Lewtas, J. Mutagenic Activity of Diesel Emissions; Lewtas, J., Ed.; Elsevier Science Publishing,Inc: Amsterdam, 1982;
46. (12) Bayona, J. M.; Markides, K. E.; Lee, M. L. Enuiron. Sci. Technol. 1988,22, 1440-1447. (13) Fu, P. P.; VonTungeln,L. S.; Chou, M. W. Carcinogenesis 1985,6, 753-757. (14) Rosenkranz, H. S.; Mermelstein,R. Mutat. Res. 1983,114, 217-267. (15) Grimmer, G.; Brune, H.; Deutsch-Wenzel, R.; Dettbarn, G.; Jacob, J.; Naujack, K. W.; Mohr, U.; Ernst, H. Cancer Lett. 1987, 37, 173-180.
pp 243-264.
Cooper, B. J.; Shore, P. R. Society of Automotive Engineers, 1989, PaDer No. 890494. McCk,-J.; Choi, E.; Yamasaki, E.; Ames, B. N. h o c . Natl. Acad. Sci. U.S.A. 1975, 72, 5135-5139.
Evaluations of Carcinogenic Risk to Humans. Diesel and Gasoline Engine Exhaust; IARC: Lyon, France, 1989; Vol.
Received for review October 17, 1989. Revised manuscript received January 26, 1990. Accepted February 15, 1990.
Atmospheric Chemistry of Gaseous Diethyl Sulfate Steven M. Japar, Timothy J. Wallington, Jean M. Andino, and James C. Ball
Research Staff, Ford Motor Company, Dearborn, Michigan 48121 The atmospheric reactivity of diethyl sulfate (DES) has been investigated. Upper limits to the rate constants (in cm3 molecule-' 5-l) for the homogeneous gas-phase reactions of DES with 03,NH3, and H20 have been determined by FTIR spectroscopy and are C3.4 X C1.4 X and 12.3 X respectively. The reactivity of DES toward OH radicals and C1 atoms has been determined by using relative rate techniques; rate constants for those reactions are (1.8 f 0.7) X and (1.1f 0.1) X lO-l', respectively. These rate constants correspond to atmospheric lifetimes ranging from 11 day with respect to reaction with water to >12 years with respect to ozone. With the possible exception of its reaction with water, these results indicate that the atmospheric fate of DES within an urban air parcel is not determined by its homogeneous gas-phase reactions with any of the atmospheric species studied. No evidence has been found for the formation of DES or related compounds during the ozonolysis of olefins in the presence of SO2 and ethanol. Introduction Diethyl sulfate (DES) has been shown to be carcinogenic in rats ( 1 , Z ) and is mutagenic in Salmonella typhimurium strain TAlOO (3). Because it is one of the most potent carcinogens of the class of simple alkylating sulfuric acid esters, it has been studied in order to investigate the relationship between chemical reactivity and carcinogenicity (2). Although DES has not been identified in the atmosphere, its methyl analogue, dimethyl sulfate (DMS), has been detected in the gas phase at ppb levels in Los Angeles air ( 4 ) and in power plant plumes (5,6). Since it has been speculated that the formation of DMS in the atmosphere involves the reaction of methanol with sulfuric acid aerosol (4-61, a concern has developed that centers on the possibility that atmospheric methanol levels may rise significantly with increasing use of methanol and methanolblended fuels for motor vehicles. Since ethanol and ethanol-blended fuels are used extensively in a number of areas, notably Brazil, and since their usage may increase 894
Environ. Sci. Technol., Vol. 24, No. 6, 1990
significantly in the United States in the future, a similar concern about atmospheric levels of DES may develop. We have recently completed a detailed study of the formation and reactivity of DMS in the atmosphere (7,8) in which it was shown (1)that DMS was not formed via homogeneous oxidation reactions involving methanol and SO2, (2) that it could be formed through a probable heterogeneous reaction of SO3with dimethyl ether, and (3) that its homogeneous gas-phase reactions with OH, C1, 03, and NH, were too slow to control its atmospheric fate. This report details a similar study of the atmospheric chemistry of DES. Experimental Procedures Experiments were carried out in a system consisting of a Mattson Instruments Inc. Sirius 100 FT-IR spectrometer interfaced to a 140-L, 2-m-long evacuable Pyrex chamber described previously (7-9). The Pyrex chamber was equipped with White-type multiple-reflection optics (path length set up to 34.2 m), and was surrounded by 22 UV fluorescent lamps (GTE F40BLB). The spectrometer was operated at a resolution of 0.25 cm-'. Infrared spectra were typically derived from 8 to 16 coadded interferograms. Reference spectra were acquired by filling the chamber with known concentrations of the appropriate compounds. We have used the relative rate technique to investigate the kinetics of the reaction of DES with C1 atoms and OH radicals in the evacuable chamber (7,8). C1 atoms were generated from the photolysis of C12by the black lights, while OH was formed through the photolysis of methyl nitrite (CH30NO)/N0 mixtures in air (10). Reaction mixtures consisting of a reference organic, DES, and C1, or CH,ONO/NO were introduced into the chamber by expansion of the gases from known volumes, diluted with synthetic air, and left to mix for at least 5 min. In the presence of C1 atoms (or OH radicals) there is competition between DES and the reference organic for the available reactive radicals via reactions 1 and 2, i.e., for C1 atoms C1 + DES products (1) C1 + reference organic products (2)
00 13-936X/90/0924-0894$02.50/0
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0 1990 American Chemical Society
0'25 0.20
r---
1.5 1
v
0.5
/
-
0.0
0.5
Ln [(Reference)+,/( -0.05
600
800
1000 1200 Wovenumber
1400
1600
Figure 1. Infrared spectrum of DES (10.6 mTorr, pathlength, 7.6 m) in the range from 700 to 1500 cm-'.
Providing that DES and the reference organics are lost solely by reactions 1and 2 and that neither is re-formed in any process, then it can be shown that [DES],, In-=[DES],
k1 [reference organic],, In k, [reference organic],
(3)
where [DES],, and [reference organic],, and [DES], and [reference organic], are the concentrations of DES and the reference organic at times toand t , respectively, and kl and k2 are the rate constants of reactions 1 and 2, respectively. The relative rate technique relies on the assumption that both the reactant and reference organics are removed solely by reaction with, for example, chlorine atoms. This assumption was tested by allowing the reactive mixtures to stand in the dark over the typical time periods used in this work. No dark reactions were observed. In addition, to test for the possible photolysis of the reactants, mixtures of the reactants in synthetic air were irradiated in the absence of C1, or CH,ONO. No photolysis of any of the reactants was observed. Methyl nitrite was generated by the dropwise addition of 50% H2S04to methanol saturated with sodium nitrite (11), as described previously (7). 0, was formed in a stream of O2 that had passed through a silent discharge and was introduced directly into the FTIR cell. C12 (Matheson Gas Products, high purity), and NH, (Matheson Gas Products, electronic grade) were used as received. The purity of the DES (Aldrich Chemical Co., 99+%) was found to be 196% by gas chromatography.
Results DES + Ozone, NH,, and H20. The reactions of DES with O,, NH,, and H20 were investigated in the evacuable reactor by FTIR spectroscopy. The behavior of DES was monitored by its characteristic infrared absorption in the 700-1500-cm-' region (Figure 1). In the absence of other reactants DES concentrations were stable in the reaction for more than 1 h. DES (2-14 mTorr) was mixed with either 0, (137 mTorr), NH3 (250 mTorr), or H20 (3.1 Torr) and left to stand in the chamber in the dark for 40 min, 30 min, and 17 h, respectively. In the first two cases no loss of DES (13.5% and 1 2 % , sensitivity dictated by spectral noise) was observed, thereby enabling the asand 9 years 51.0 dayy
1.1 X lo-"
