Environ. Sci. Technol. 1987, 21, 643-648 The Chemistry of Synthetic Dyes and Pigments; Luebs, H., Ed.; Reinhold: New York, 1955. The Chemistry of Synthetic Dyes;Venkatamaran, K., Ed.; Academic: New York, 1952; Vol. 2, pp 818-833. Bailey, P. S. Ozonation in Organic Chemistry; Academic: New York, 1982; Vol. 2. Toby, S.; Van de Burgt, L. J.; Toby, F. S. J. Phys. Chem.
(24) Moriconi, E. J.; Rakoczy, B.; O'Connor, W. F. J. Am. Chem. SOC.1961,83, 4618-4623. von Kortum, G.; Braun, W. Justus Liebig Ann. Chem. 1960, 632, 104-115.
Perkins, M. A. In The Chemistry of Synthetic Dyes and Pigments; Luebs, H. A., Ed.; Reinhold: New York, 1955; pp 335-369.
Kiel, E. G.; Heertjes, P. M. J. SOC. Dyers Colour. 1963,79(1), 21-27. Bauer, R. K.; et al. J. Phys. Chem. 1982,86, 3781-3789. Jiiger, T.; Hanus, V. J. Hyg. Epidemiol. Microbiol. Zmmunol. 1980, 24, 1-15. Saucy, D. A.; Cabaniss, G. E.; Linton, R. W. Anal. Chem. 1985,57, 876-879. Saunders, F. M.; Gould, J. P.; Southerland, C. R. Water Res. 1983,17, 1407-1419. Couper, M. Text. Res. J. 1951,21, 720-725. Lebensaft, W. W.; Salvin, V. S. Text. Chem. Color. 1972, 4, 182-186.
1985,89, 1982-1986.
Pryor, W. A.; Gleicher, G. J.; Church, D. F. J. Org. Chem. 1983,48,4198-4202.
Van Vaeck, L.; Van Cauwenberghe, K. Atmos. Environ. 1984,18, 323-328.
Particulate Polycyclic Organic Matter; National Academy of Sciences, National Academy: Washington, DC 1972. Particulate Polycyclic Hydrocarbons: Evaluation of Sources and Effects; National Academy of Sciences, Na-
tional Academy: Washington, DC, 1983. Wu, C. H.; Salmeen,I.; Niki, H. Environ. Sci. Technol. 1984, 18,603-607.
Butkovic, V.; et al. Enuiron. Sci. Technol. 1983,17,546-548. Grosjean, D.; Fung, K.; Harrison, J. Environ. Sci. Technol. 1983,17, 673-679. Moriconi, E. J.; Taranko, L. B. J . Org. Chem. 1963, 28, 2526-2529.
Received for review June 23,1986. Accepted January 28,1987. This work was supported by a contract with the Getty Conservation Institute, Marina del Rey, CA.
Photooxidation of Selected Polycyclic Aromatic Hydrocarbons and Pyrenequinones Coated on Glass Surfaces Vlrgil W. Cope* and Donald R. Kalkwarf Battelle Pacific Northwest Laboratory, Richland, Washington 99352 Reactions of ozone with perylene, pyrene, and benzo[alpyrene on glass surfaces exposed to simulated sunlight were studied. The ozonation rates of these hydrocarbons were increased only slightly by light intensities up to 1.3 kW/m2; however, the ozonation rates of the quinones, which result from pyrene ozonation, increased greatly. In the absence of ozone no photoreaction products of the three hydrocarbons could be detected. The photochemical ozonation rates of the pyrenequinones were proportional to their exposed surface area and to the concentration of ozone. The ozonation rate constant during exposure to simulated sunlight at 24 "C and [O,] = 6.2 X lo4 mol/m3 (0.16 ppm) was 8.2 X 10T4 s-l, which is about 15 times greater than the comparable rate constant for the dark reaction. Introduction
Polycyclic aromatic compounds (PACs) are commonly found on the surface of coal fly ash (1)and include both potential genotoxics ( 2 ) and substances that can be transformed to genotoxics by reaction in the atmosphere (3). The lifetime of PACs on fly ash surfaces has been estimated to range from minutes to days (4-7). Various chemical and physical processes have been proposed to account for the losses. Determination of the rates and products of these atmospheric reactions is important for assessing the environmental impact of the increasing use of coal for electric power production. Ozone has been identified as one of the most likely reactants with organic compounds in the atmosphere (8). *Address correspondence to this author at his present address:
Department of Chemistry, University of Michigan-Flint, Flint, MI 48502. 0013-936X/87/092 1-0643$01.50/0
It is continually replenished by natural processes, and its concentration is almost always measurable. Oxidation products of PACs have been identified in particulate samples taken from the atmosphere in various locations (9, 10). Polycylic aromatic hydrocarbons (PAHs) with benzylic carbons are rapidly oxidized in the dark (11). Some oxygen-containing PAH derivatives have also been determined to be mutagenic (12-14). Benzo[a]pyrene (BaP) coated on glass-fiber filters was reported to react with ozone-laden air to produce a mixture of benzo[a]pyrenequinones and benzo[a]pyrene 4,5-oxide, a direct-acting mutagen (6). In a study of nitration reactions, mutagenic nitro derivatives were found as products of the reaction of PAHs with NO2atmospheres (15). In an earlier paper, Kalkwarf and Cope have reported the rate law for reaction of ozone with pyrene coated on glass surfaces to form pyrenequinones and other products (4). Photochemical decay of PACs has been investigated by several groups (6,15-18). Films of BaP on alumina were found to be much less photoreactive than BaP in solution, whereas BaP on fly ash was not (11,19). Photooxidation of PACs has been invoked to explain sampling losses (20, 21), diurnal variation in mutagenicity of atmospheric particulates (22),and degradation of PAC spots on thinlayer chromatography (TLC) plates (16). Katz and coworkers found large changes in the half-lives of several PACs on cellulose TLC plates when exposed to ozone, simulated sunlight, or both (23). The possibility of photooxidation of BaP by ozone was considered by Tebbens (21),but no systematic study has been done. Pitts and co-workers proposed that 9-nitroanthracene undergoes photodegradation to a quinone (15). A photochemical reactor that mixed the fly ash by a rotating motion was designed by Korfmacher et al. (24). More recently a system designed by Daisey et al. used a fluidized bed in
0 1987 American Chemical Society
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solar simulator
-
0
Flgure 1. Apparatus for photochemical reactions of PAC films on glass.
a gas flow to provide uniform exposure of the fly ash surface to radiation (25). These systems create the possibility of losing PAC by sublimation, but no efforts were made to correct for it. Field studies have found that sublimation is not an important source of sampling loss for BaP (20,21),but other PACs may be partially lost from particulate samples in this way. The objectives of this study were to measure the ozonation rates of representative PACs coated on glass and to determine if these rates are affected by exposure to sunlight. Particular care has been taken to correct all data for sublimation of PACs during the reaction. In an earlier paper, we reported that ozone reacts rapidly with pyrene coated on glass surfaces to form pyrenequinones and other products ( 4 ) . Those reactions were carried out in the dark so that they could be clearly distinguished from possible reactions induced by exposure to sunlight. The photochemical decay of pyrene-1,6-quinone and pyrene-l,& quinone in measured concentrations of ozone, as well as in ozone-free air, was also studied. Experimental Section Approximately monomolecular layers of PAC on glass were exposed to ozone with the apparatus illustrated in Figure 1. The reaction flask was coated with PAC in a manner described previously ( 4 ) . Ozone was passed through the flask at concentrations of 0.051-0.161 ppm with a flow rate of 3 L/min. The ozone was produced by a commercial generator, Monitor Labs Model 8500, which purified the intake air supply to remove water vapor and residual ozone. The ozone concentration was measured with a Bendix Model 8002 ozone monitor. The simulated sunlight was produced by a solar simulator, Oriel Model 6720. The spectrum of the emitted radiation was adjusted to match sunlight, which strikes the earth at an angle of goo. The intensity was adjusted to the maximum striking the earth surface, 1.37 kW/m2, and was monitored with a pyranometer (Eppley, Model PSP). As depicted in Figure 1,the reaction flask was rotated in a water bath at 23 f 1"C to maintain a constant temperature. During the photolysis studies, the flask was rotated in the light beam so that the PACs would be exposed as uniformly as possible. Dark reactions were run with a heavy black cloth covering the flask to shield it from laboratory light. Sublimation rates of the PACs were measured while a stream of ozone-free air was passed through the same apparatus. After the desired reaction period, the flask was rinsed 3 times with 1-2 mL of methanol, the rinse solutions were 844
Environ. Sci. Technol., Vol. 21, No. 7, 1987
composited, and the composite solution was diluted to 5 mL. These solutions were analyzed by reversed-phase liquid chromatography with a C-18 Vydac 201TP analytical column on a Spectrophysics 8000 liquid chromatograph. The rate constants for the reaction of PAC were calculated from the slopes of plots showing the log of the fraction of PAC remaining as a function of time. In another method the reaction rates of ozone with PAC coated on glass were calculated as previously described (4). This method uses the change in ozone concentration between the inlet and outlet of the reaction flask. The effect of radiation on the reaction rate of ozone was determined by this method with the solar simulator on and with it off. The PACs used were of analytical reagent grade from Fluka. The solvents used were of high-performanceliquid chromatography (HPLC) grade from Burdick and Jackson. The pyrenequinones were synthesized by a modification of the procedure of Vollman (4,26,27). The pyrenic acid was prepared by the method of Fatiadi (28). The rate of production of O(lD) in the reaction flask wa8 calculated from eq 1,where PTis the total solar power in 4[0(lD)]/4t = PTfATXd(l - 10-aC"r/2)/109h~(1)
W m-2, f is the fraction of solar power in each wavelength interval, A is the cross-section area of the reaction flask in m2, T is the averge transmittance of Pyrex glass over each wavelength interval, X is the average wavelength of the interval in nm, 4 is the average quantum yield of O('D) for each interval in atoms per photon, a is the average absorptivity of O3 for the interval in atm-' cm-', C is the concentration of ozone in atm, r is the radius of the flask in cm, h is Planck's constant, and c is the speed of light. These quantities were calculated with the literature data for solar power (29),quantum yields for ozone photolysis (30),and absorptivities of ozone (31). Results Sublimation rates of the PACs in air were measured in order to have data for correcting PAC depletion rates measured in the presence of ozone and/or simulated radiation. When ozone-free air was passed through a reaction flask containing less than a monomolecular layer of PAC, the PAC depletion rate could be described by eq 2, -d(PAC)/dt = k,S (2)
where S represents the surface area of PAC exposed at any time t, (PAC) represents the moles of PAC remaining, and 112, is a constant. Since the PAC was distributed approx-
z
10
I
I
I 0
*e ReastiOn
30
ilme
I D
51
40
rn/nutes
Figure 2. Firstdrder rate plot for the sublimation of pyrene from glass: F = 3.0 L/min.
0
5
ozone
Table I. Rate Constants on Glass Surfaces
compound
sublimation rate constant.' k , s-l
photoreaction rate constantsb k,, s-l
1.1 x 10-4 pyrene
