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show an EF consistently greater than 1was methidathion. For this compound, KAWwas estimated from literature values of vapor pressure and solubility and may have been in error. Temperature effects play an important but poorly known role in the air/water distribution of pesticides and may reduce the measured EF by a factor of 2-4 in the present experiment. Even though there were high concentrations and high EF for the water phase, the largest proportion of all the compounds in all events was in the interstitial air phase, either vapor or adsorbed to aerosol particles. The distribution between air and droplet phases for each pesticide covered a broad range from one event to the next. The proportion associated with droplet-phase particles was small, averaging 0.71. On the other hand, the strong decrease of coprostanol vs coprostanone found in moderately polluted samples (characteristic coprostanol concentration on the order of micrograms per gram or below) indicates that coprostanone should also be quantitatively determined for sewage monitoring. In this respect, it has been observed that the 5@/(5P+ 5a) cholestan-3P-01ratio is modified by direct inputs of 5a(H)-cholestan-3P-o1in cases of high algal productivity. The usefulness of that ratio is precluded in these situations. However, the 5@/(5P+ 5a) cholestan3-one ratio is not significantly affected, affording an alternative parameter for the reliable identification of sewage pollution in this type of depositional environment. Registry No. 5P-Cholestan-3P-ol,360-68-9;5P-cholestan-3a-01, 5a-cholestan-3@-01,80-97-7; 516-92-7;cholest-5-en-3@-01,57-88-5; 24-ethyl-5~-cholest-3~-ol,33947-19-2; 24-ethylcholest-5-en-3P-01, 19044-06-5; 24-ethyl-5a-cholestan-3/3-01, 19044-02-1; 50-choles362
tan-a-one, 601-53-6; 5a-cholestan-3-one, 566-88-1; 24-ethyl-50cholestan-3-one, 83603-22-9; 24-ethyl-5a-cholestan-3-one, 81571-54-2.
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Wun, C. K.; Walker, R. W.; Litsky, W. Water Res. 1976, 10, 955-959. Goodfellow, R. M.; Cardoso, J.; Eglinton, G.; Dawson, J. P.; Best, G. A. Mar. Pollut. Bull. 1977, 8 , 272-276. Hatcher, P. G.; Keister, L. E.; McGillivary, P. A. Bull. Enuiron. Contam. Toxicol. 1977, 17, 491-498. Hatcher, P. G.; McGillivary, P. A. Environ. Sci. Technol. 1979, 13, 1225-1229. McCalley, D. V.; Cooke, M.; Nickless, G. Bull. Enuiron. Contam. Toxicol. 1980, 25, 374-381. McCalley, D. V.; Cooke, M.; Nickless, G. Water Res. 1981, 15, 1019-1025. Wade, T. L.; Oertel, G. F.; Brown, R. C. Can. J. Fish. Aquat. S C ~1983, . 40, 34-40. Brown, R. C.; Wade, T. L. Water Res. 1984,18,621-632. Pierce, R. H.; Brown, R. C. Bull. Enuiron. Contam. Toxicol. 1984, 32, 75-79. Readman, J. W.; Preston, M. R.; Mantoura, R. F. C. Mar. Pollut. Bull. 1986, 17, 298-308. Eganhouse, R. P.; Olaguer, D. P.; Gould, B. R.; Phinney, C. S. Mar. Enuiron. Res. 1988,25, 1-22. Bjorkhem, I.; Gustafsson, J. A.; Wrange, 0.Eur. J. Biochem. 1973,37, 143-147. Eyssen, H. J.; Parmentier, G. G.; Compernolle, F. C.; de Pauw, G.; Piessens-Denef, M. Eur. J . Biochem. 1973, 36, 411-421. Parmentier, G.; Eyssen, H. Biochim. Biophys. Acta 1974, 348, 279-284. Rosenfeld, R. S.;Fukushima, D. K.; Hellman, L.; Gallagher, T. F. J . Biol. Chem. 1954,211, 301-311. Walker, R. W.; Wun, Ch.; K. Litsky, W. CRC Crit. Reu. Enuiron. Control 1982, 12, 91-112. Vivian, C. M. G. Sci. Total Enuiron. 1986, 53, 5-40. Bartlett, P. D. Mar. Pollut. Bull. 1987, 18, 27-29. Gaskell, S. J.; Eglinton, G. Nature 1975, 254, 209-211. Taylor, C. D.; Smith, S. 0.; Gagosian, R. B. Geochim. Cosmochim. Acta 1981,45, 2161-2168. Robinson, N.; Cranwell, P. A,; Finley, R. J.; Eglinton, G. Org. Geochem. 1984,6, 143-152. Boudou, J. P.; Trichet, J.; Robinson, N.; Brassell, S. C. Org. Geochem. 1986,10, 705-709. Robinson, N.; Cranwell, P. A.; Eglinton, G.; Brassell, S. C.; Sharp, C. L.; Gophen, M.; Pollingher, U. Org. Geochem. 1986, 10, 733-742. Nishimura, M. Geochim. Cosmochim. Acta 1982, 46, 423-432. Edmunds, K. L. H.; Brassell, S. C.; Eglinton, G. In Advances in Organic Geochemistry 1979; Douglas, A. G., Maxwell, J. R., Eds.; Pergamon: Oxford, 1980; pp 427-434. Pocklington, R.; Leonard, J. D.; Crewe, N. F. Oceanolog. Acta 1987, 10, 83-89. Dougan, J.; Tan, L. J . Chromatogr. 1973, 86, 107-116. Gomez-Belinchh, J. I.; Grimalt, J. 0.;AlbaigBs, J. Environ. Sci. Technol. 1988, 22, 677-685. Aceves, M.; Grimalt, J. 0,;AlbaigBs, J.; Broto, F.; Comellas, L.; Gassiot, M. J . Chromatogr. 1988, 436, 503-509. van Graas, G.; Baas, J. M. A,; van de Graaf, B.; de Leeuw, J. W. Geochim. Cosmochim. Acta 1982, 46, 2399-2402. Nishimura, M.; Koyama, T. Geochim. Cosmochim. Acta 1977. 41, 379-385. Smith, A. G.; Goodfellow, R.; Goad, L. J. Biochem. J . 1972, 128, 1371-1372. Nishimura, M.; Koyama, T. Chem. Geol. 1976,17,229-239. Robinson, N.; Eglinton, G.; Brassell, S. C.; Cranwell, P. A. Nature 1984, 308, 439-441. Grimalt, J.; Albaigbs, J. Mar. Geol., in press. Ramos, I.; Fuentes, M.; Mederos, R.; Grimalt, J. 0.;Albaigbs, J. Mar. Pollut. Bull. 1989, 20, 262-268.
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Gagosian, R.; Smith, S. 0.;Nigrelli, G. E. Geochim. Cosmochim. Acta 1982,46,1163-1172. Lefebvre, G.; Germain, P.; Schneider, F. Bull. SOC. Chim. Fr. 1980,1-2, 11-96-11-97, Stohs, S. J.; Haggerty, J. A. Phytochemistry 1973, 12, 2869-2872.
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Received for review March 20,1989. Accepted November 9,1989. Financial support from EROS-2000 Project is gratefully acknowledged. We thank J.I. Gomez-Belinchon, R. Llop, and M. Valls for technical assistance.
Oxidation of Aniline and Other Primary Aromatic Amines by Manganese Dioxide Shonali Laha and Rlchard G. Luthy" Department of Civil Engineering, Carnegie Mellon University, Pittsburgh, Pennsylvania 152 13 This investigation evaluated the redox reaction between a manganese dioxide, 6-Mn02, and anilines and other aromatic reductants in aqueous suspensions at pH values ranging from 3.7 to 6.5. The reaction with manganese dioxide may represent a pathway for transformation of aniline and other primary aromatic amines in acidic mineralogical and soil/water environments in the absence of oxygen and substantial microbial activity. The reaction rate with aniline is pH-dependent, increasing with decreasing pH, and first order with respect to 6-Mn02and organic solute. Aniline and p-toluidine are demonstrated to be 2-equiv reductants, as is believed to be the case for the other aromatic solutes considered in this study, including the substituted anilines, and hydroquinone and catechol and their alkyl substituents. Ring-bound nitrogen-containing aromatic solutes (methylimidazole,quinoline, and 5,5-dimethylhydantoin) were unreactive with manganese dioxide at pH 6.4. The order of the reactivity of para-substituted anilines was methoxy >> methyl > chloro > carboxy >> nitro; the relative reactivity of these compounds correlated with the solute's half-wave potential and Hammett constant. The principal oxidation products of aniline and p-toluidine with manganese dioxide at pH 4 were azobenzene and 4,4'-dimethylazobenzene, respectively, which agreed with a postulated oxidative-coupling reaction mechanism. The abiotic redox reactions of primary aromatic amines and azo compounds may result in various respective oxidative-coupling and reductive-decoupling reactions. These processes may be significant with regard to the persistance and transformation of these classes of organic contaminants in environmental systems.
Introduction The purpose of this investigation was to assess the rate of the redox reaction between a manganese dioxide, 6Mn02(s),and various aromatic reductants including several nitrogen-containing compounds. The initial rate and order of the reaction with respect to the reductant was determined as well as the effects of manganese dioxide concentration and pH. The principal reaction products, under acidic conditions, resulting from the oxidation of aniline and p-toluidine were determined. In natural waters, Mn(II1) and Mn(1V) are usually present in the form of sparingly soluble oxides and hydroxides, whereas Mn(I1) is the soluble phase. In soil/ sediment environments, manganese oxide is believed to be among the strongest oxidizing agents that may be encountered in the absence of molecular oxygen. Manganese oxide can be reduced and dissolved by organic compounds, increasing the mobility of manganese and its availability to organisms ( 1 , 2 ) . These oxidative processes involving manganese oxides may constitute an important abiotic degradative pathway for organic compounds in subsurface 00 13-936X/90/0924-0363$02.50/0
environments. Earlier studies by Stone and Morgan (2) demonstrated some features of the reductive dissolution reaction between manganese oxide and organic solutes and some of the factors that influence the rate of the reaction. Stone (3) considered the reductive dissolution of manganese(III/IV) oxides by substituted phenols. Those investigations were performed with various manganese oxide suspensions, one of which was primarily the mineral-phase feitknechtite, P-MnOOH(s), with some amount of manganite, y-MnOOH(s). In this study, a hydrous manganese dioxide suspension was prepared according to Murray (4), for which his stoichiometric and X-ray diffraction analyses indicated that this synthetic manganese dioxide is structurally similar to the naturally occurring mineral birnessite, 6-Mn02(s). The organic reductants investigated in this study were aniline and various substituted anilines, hydroquinone and catechol and some of their alkyl substituents, and several ring-substituted nitrogen-containing aromatics. Figure 1 shows the structures of the compounds discussed in this study. Anilines and other aromatic amines may originate as environmental contaminants from the use of pesticides and herbicides, as well as from chemical manufacturing residues, and from byproducts of energy technologies. Along with phenol, aniline is listed as a high-priority compound in the study of pollutants from coal-conversion process wastes (5). Aniline residues are formed in the soil as a result of microbial and plant metabolism of phenylurea, acylanilide, phenylcarbamate, and nitroaniline herbicides (6). Chlorinated anilines such as 2,4,5-trichloroaniline, 4-chloroaniline, 3,4-dichloroaniline, and 2,6-diethylaniline may be released as degradation products and intermediates of various phenylurea and phenylcarbamate pesticides (7, 36). Aniline derivatives occur as intermediates in dye-stuff manufacture and this constitutes another possible source of environmental aniline contamination. A number of substituted anilines may be carcinogenic (8). Aniline and toluidine, i.e., methylaniline, and other aromatic amines are generally toxic and can induce various adverse physiological responses (8, 9). For these reasons it is of considerable interest to explore the physical, chemical, and microbial transformations that may alter the toxicity, mobility, and bioavailability of aniline and related compounds in the environment. Aniline and other aromatic amines are subject to complex environmental transformations. Lyons, Katz, and Bartha (6, 10, 11) performed studies on the microbial pathways for aniline elimination from aquatic environments, from which they concluded that biodegradation may be the most significant mechanism for the removal of aniline from pond water. Hwang and Lee (7) concluded that photochemical processes were primarily responsible for mineralization of 2,4,5-trichloroaniline in surface water
@ 1990 American Chemical Society
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