Environ. Sci. Technol. 1992,26,1658-1662
due to its weave construction. The difference between the initial and resuspended sediment distributions for both filter types, even with the aforementioned pore clogging, filter disintegration, and sediment flocculation or coagulation, is statistically insignificant (ANOVA, a = 0.01). There is also no significant difference between the resuspended sediment distributions for the two filter types (ANOVA, cy = 0.01), indicating that the type of filter used to concentrate the sediment has a minimal influence on the resultant primary particle distribution, even with the differences in nominal pore sizes. The minimal influence of pore clogging on the grain-size distribution may be explained by the fact that there is a greater number of smaller particles than larger particles in the distribution. As it is the small sediment sizes which are most likely to be trapped by the pores of the filters, the impact of their loss to the distribution appears to be unimportant. The filtration of the 5 psi) may bind particles to the filters as well as suck particles through the filter, resulting in increased deviation from the actual primary grain-size distribution. The length of time required to complete the described technique is mostly dependent on the filtration rate, which is in turn highly dependent on the suspended sediment concentration. If a Millipore fibrous membrane filter type is used, it is recommended that the filters be prewashed to minimize filter disintegration and distribution distortion. Conclusions Often suspended primary grain-size distributions are required for sediment/contaminant transport studies. This parameter is, however, often difficult to quantify when suspended sediment concentrations are low. If this condition exists, the sediment must be concentrated for a more accurate determination of particle size. On the
basis of the results of this study, it can be concluded that concentrating predominantly fine inorganic sediments by filtering on and resuspending from both Millipore cellulose membrane (0.45 pm) and Nuclepore polycarbonate membrane (0.4 pm) type filters does not significantly alter the initial primary grain-size distributions. While some filter disintegration and pore clogging occurred, their influence on the primary grain-size distribution was minimal. Acknowledgments We thank R. Stephens for carrying out the size distribution measurements using the Malvern particle size analyzer and Dr.S. S. Rao, J. Marsalek, and M. Stone for their review of the manuscript. The comments of the three anonymous reviewers are also appreciated. Literature Cited (1) Allan, R. J. T h e Role of Particulate Matter in the Fate of
(2)
(3)
(4) (5)
(6) (7)
(8)
Contaminants in Aquatic Ecosystems; Inland Waters Directorate, Scientific Series No. 142; National Water Research Institute, Canada Centre for Inland Waters: Burlington, ON, Canada, 1986. Ongley, E. D.; Bynoe, M. C.; Percival, J. B. Can. J.Earth Sci. 1981,18, 1365-1379. Horowitz, A. J. In Chemical and Biological Characterization of Sludges, Sediments, Dredge Spoils and Drilling Muds; ASTM STP 976; Lichtenberg, J. J., Winter, J. A., Weber, C. I., Fradkin, L., Eds.; American Society for Testing and Materials: Philadelphia, PA, 1988; pp 102-113. Qualitative Analysis; Nuclepore Corp.: Pleasanton, CA, 1989. Millipore Catalog and Purchasing Guide; Millipore Products Division, Millipore Corp.: Bedford, MA, 1983. Bale, A. J.; Morris, A. W. Estuarine, Coastal Shelf Sci. 1987, 24, 253-263. Weiner, B. B. In Modern Methods of Particle Size Analysis; Barth, H. G., Ed.; John Wiley and Sons: New York, 1984; pp 135-172. Krishnappan, B. G.; Droppo, I. G.; Rao, S. S.; Ongley, E. D. Evaluation of a Filter-Fractionation Technique for Fine Sediments; NWRI Contribution 90-11; Canada Centre for Inland Waters, Burlington, ON, Canada, 1990.
Received for review February 25, 1992. Revised manuscript received M a y I , 1992. Accepted M a y 7,1992. T h e use of filter brand names does not imply a n endorsement of materials by Environment Canada.
Ozonation Byproducts: Identification of Bromohydrins from the Ozonation of Natural Waters with Enhanced Bromide Levels Joseph E. Cavanagh, Howard S. Weinberg," Avram Gold, R. Sangalah, Dean Marbury, and Wllllam H. Glare Department of Environmental Sciences and Engineering, University of North Carolina, Chapel Hill, North Carolina 27599
Timothy W. Collette, Susan D. Richardson, and Alfred D. Thruston, Jr. Environmental Research Laboratory, US. Environmental Protection Agency Athens, Georgia 306 13-7799
Introduction When ozone is used in the treatment of drinking water, it reacts with both inorganic and organic compounds to form byproducts (1). If bromide is present, it may be oxidized to hypobromous acid (21, which may then react with natural organic matter (NOM) to form brominated organic compounds (2,3). The formation of bromoform has been well documented (2, 4, 5 ) , and more recently, other byproducts, such as bromoacetic acids, bromopicrin, cyanogen bromide, bromoacetones, and bromate, have 1658 Environ. Sci. Technol., Vol. 26, No. 8, 1992
been identified (6-9). The purpose of this communication is to report the identification of bromohydrins, a new group of labile brominated organic byproducts from the ozonation of a natural water in the presence of enhanced levels of bromide. Experimental Section A sample of natural water was collected from University Lake, Orange County, NC, and used as received. The TOC of the water was 8.0 mg/L, pH 7, and the ambient bromide
0013-936X/92/0926-1658$03.0010
0 1992 American Chemical Society
and alkalinity levels were 0.03 and 25 mg/L (as CaCO,), respectively. Sodium bromide was Baker Analyzed reagent, purchased from J.T. Baker Chemical Co. Ammonium sulfate was ACS Reagent Grade from Fisher Scientific Co. 1,2-Dibromopropanewas purchased from Aldrich Chemical Co. Deionized, distilled water (DDW) came from a Corning Megapure water purifier LD-2A system. Ozonations were conducted in a semibatch, 70-L stainless steel reactor (IO),so that an absorbed ozone dose ratio of 1.0 mg of O,/mg of TOC was applied. Ozone was generated from breathing-quality air by a Union Carbide ozone generator (Model SG 4060). Applied and absorbed ozone were determined by the iodometric method (11). Two liters of lake water before or after ozonation was quenched of active bromine by the addition of ammonium sulfate and then extracted with 400 mL of either pentane (THM Grade, B&J Brand high-purity solvent, Baxter Scientific) or methyl tert-butyl ether (MTBE) (OmniSolv, MX0826-1 EM Science). The organic layer was separated from the water in a separatory funnel and then concentrated to 1mL with a gentle stream of nitrogen (ultrahigh purity 99.999%, Sunox Inc.). 1,2-Dibromopropane (DBP) was added as an internal standard to the concentrated extracts at a level of 50 ng/mL. A 30-m DB-5,l-pm film thickness capillary column (J&W Scientific) was used in all the analyses with the following gas chromatograph (GC) oven conditions: 50 "C for 4 min, 4 "C/min to 110 "C and held for 0.5 min, and then 10 "C/min to 250 "C. For routine monitoring of the organic bromides, a pentane microextraction method was used. A 40-mL headspace free sample of the water was taken in a glass vial with PTFE-lined screw cap, to which had been added 65 mg of ammonium sulfate. Vials were stored at 4 "C for no longer than 48 h prior to extraction by a procedure described by Krasner et al. (6). A 20-mL sample of the water was extracted in a 40-mL vial with 4.0 mL of pentane containing 50 ng/mL 1,2-dibromopropane internal standard and then the pentane layer was transferred to a minivial and analyzed by GC/ECD. The same chromatographic conditions were employed as before. For quan(I),a multipoint tification of 3-bromo-2-methyl-2-butanol calibration was carried out by spiking the neat compound into water along with bromoform, dibromoacetonitrile, and bromoacetone, using EPA-approved procedures (12). In this way, the absolute ECD response factors of the compounds were determined relative to the internal standard (DBP) and the relative ECD response factors of I vs the other compounds were determined. The levels of I in samples that had been analyzed before I had been identified were calculated retrospectively by comparison of the relative areas of I with bromoform, which had been previously quantified. Full-scan electron impact (EI) mass spectra were acquired on a Hewlett-Packard 5890 gas chromatograph interfaced to a VG 70-SEQ mass spectrometer at an electron energy of 70 eV and a 250 "C source temperature. Lowresolution and high-resolution experiments were performed at resolutions of lo00 and 8000, respectively. The magnet was scanned from 500 to 50 amu at 1s/decade. Chemical ionization (CI) mass spectra were acquired on a Finnigan 4515 quadrupole instrument using a Finnigan GC with a reagent gas mixture of 2% ammonia and 98% methane, a source temperature of 100 "C, and a resolution of 1000. Eight wavenumber (cm-') resolution Fourier transform infrared (FT-IR) spectra were acquired, with a useful range of 4000-700 cm-', on a Digilab Model FTS-60 infrared spectrometer interfaced to a Hewlett-Packard 5890 GC by a light-pipe-based interface equipped with a narrow-band
mercury-cadmium-telluride detector. Proton NMR spectra were obtained in CDC1, with a 400-MHz Varian Model XL-400 instrument with 5.299KHz spectral width, 2.832-9 acquisition time, and 15" pulse width. Chemical shift values were reported relative to tetramethylsilane. Synthesis of 3-Bromo-2-methyl-2-butanol.The procedure WBS adapted from a method described by Dalton et al. (13-15) and involves the bromination of 2-methyl2-butene with N-bromosuccinimide in wet dimethyl sulfoxide. To a 200-mL, round-bottomed flask equipped with a magnetic stir bar were added 1g of 2-methyl-2-butene (Chem Service Co.), 50 mL of dimethyl sulfoxide (reagent grade), 0.83 mL of deionized, distilled water, and 6 g of N-bromosuccinimide (Aldrich). The contents were stirred for 25 min, poured into 200 mL of ice water in a 500-mL separatory funnel, and extracted with 100 mL of diethyl ether (reagent grade). The ether was washed twice with 200 mL of DDW, dried over sodium sulfate, and evaporated on a rotary evaporator. The remaining liquid (orange-red color) was shown to be the desired product in relatively pure form by 400-MHz proton NMR: 1.28 and 1.30 (2 s, HOCCH,, 6 H), 1.65 (d, BrCCH,, J = 6.9 Hz, 3 H), 3.53 (br s, OH, 1H), 4.78 ppm (9, HCBr, J = 6.9 Hz, 1 H).
Results and Discussion The ozonation of natural water with elevated bromide ion concentration forms many neutral brominated organic byproducts. Figure 1 shows the total ion chromatogram (TIC) of the neutral MTBE extract of University Lake, NC, water with elevated bromide (8 mg/L). Essentially the same pattern of peaks was observed in pentane extracts. The asterisks on peaks in Figure 1 indicate compounds that are not present in samples before ozonation, nor are they present when water, pretreated to remove organics but containing the same level of bromide, undergoes the same degree of ozonation as did the natural water samples. These byproducts contain bromine as evidenced by their E1 mass spectra, which contain multiplets representative of the isotopic composition of bromine. An example of one such spectrum is shown in Figure 2A and represents the E1 mass spectrum of the peak with a retention time of 12:46 min (Figure 1). This compound gives the largest ion current response and is, therefore, an important component of the reaction mixture. The E1 mass spectrum contains a fragment ion at m/z 87 that does not show the characteristic doublet for bromine, indicating that the m/z 151/153 doublet ion is not the molecular ion. The base peak of the E1 mass spectrum appears at m/z 59. Although this peak can be indicative of the tertiary alcohol group (CH,),COH, this assignment could not be made based on the EI-MS data alone. In addition, for this compound, and for others marked with asterisks in Figure 1,no closely matching reference spectra were found. As a result, GC/CI-MS and GC/FT-IR methods were employed to establish the molecular structure. Negative chemical ionization with ammonia gave only Br- ions, and positive chemical ionization provided no useful information using methane, ammonia, and isobutane as reagent gases. However, a mixed-reagent gas, 2% ammonia in methane, successfully provided a CI spectrum for peak 12:46 (Figure 3A). On the basis of similar CI studies with alcohols (16), the doublet at m / z 166/168 is identified as the molecular ion [MI+, and the doublet at m / z 184/186 as the adduct of M with ammonium ion [M + NH4]+. The ions at m/z 149/151 are probably due to the loss of NHIOH (or the sequential loss of NH, and HzO) from [M + NH4]+. Envlron. Scl. Technol., Vol. 26, No. 8, 1992
1659
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Figure 1. Total ion chromatogram from the electron impact GC/MS analysis of MTBE extract of University Lake water with added bromide level of 8 mg/L, after ozonation (0,:TOC = 1.0). Asterisks indicate bromine-containingcompounds: double asterisks indicate both bromine- and hydroxy-containing compounds (from GC/FTIR or CI-MS pattern of [MI', [M NH,]', and ([M NH,]' - ",OH]).
+
The GC/FT-IR spectrum of peak 12:46 is shown in Figure 4A. The spectrum indicates that the compound is a saturated aliphatic alcohol. The doublet at 364413595 cm-l could be attributed to a diol, in which the two OH groups are in different environments, or to coeluting conformers of a hindered alcohol, in which one conformer exhibits intramolecular hydrogen bonding (17). The IR data, in concert with the information obtained from the CI-MS, permitted further interpretation of the EI-MS spectra. The fragment ion at mlz 59 was confirmed as the tertiary alcohol group, (CH,),COH. The fragment ion arising from the loss of this tertiary alcohol group from the molecular ion was also present at mlz 1071109. The doublet at mlz 151/153 was determined to be consistent with the loss of CH3 from the molecular ion, and the fragment at mlz 87, to the loss of Br from the molecular ion. The remaining prominent ions, mlz 69 and 71, are postulated to occur by loss of HzO from m/z 87 and by loss of HBr from mlz 151/ 153, respectively. High-resolution EI-MS supported all fragment ion assignments by providing the correct corresponding empirical formulas. On the basis of the data obtained from low- and high-resolution EI-MS, CI-MS, and FT-IR spectroscopy, compound 12:46 was assigned the structure 3-bromo-2-methyl-2-b~tanol (I): OH I CH,
-
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On the basis of this proposed structure, the band at 3595 cm-' in the FT-IR spectrum in Figure 4A is attributed to the O-H stretch of the conformer indicated in structure IA, in which the OH and Br can hydrogen bond, while the 1660 Environ. Sci. Technol., Voi. 26, No. 8, 1992
+
band at 3644 cm-l is attributed to a conformer generated by rotation about the single bond between the third and fourth carbons (for example, IB) (17,18). The remainder of the FT-IR spectrum is consistent with the proposed structure and contains the saturated, aliphatic CH stretching peaks between 2990 and 2850 cm-' and peaks for CH3deformation, OH deformation, and C-O stretching vibrations, which all fall between 1500 and 1000 cm-', but will not be interpreted here. The C-Br stretching peak is probably not observed, falling below the cutoff (700 cm-') of the detector used in these studies. The proposed structure was confirmed by comparison of its chromatographic retention time and infrared and mass spectra with those of a synthetic standard, 3bromo-2-methyl-2-butanol. The retention time of the standard was identical to that of peak 12:46. The mass and infrared spectra of the standard are shown for comparison in Figures 2B and 4B, respectively. Other compounds that have similar FT-IR spectra, indicating brominated alcohols, are denoted with double asterisks in Figure 1. These compounds exhibit molecular ions at the same mass-to-charge ratio by CI-MS, and show the same pattern of [MI+, [M + NH4]+,and ([M + NH41+ - ",OH]. However, the compounds show different E1 mass spectral fragmentation patterns, suggesting that they are isomers of I. In order to determine the source of these byproducts, aqueous bromine (hypobromous acid, 0.1 pM) was added directly to the same lake water, both unozonated and ozonated. The results show that the same brominated compounds are formed in both ozonated and unozonated waters, indicating that ozonation byproducts of the NOM are not necessarily precursors of these compounds. Also, the same group of compounds has been found by GC/ECD analysis of the extract of an ozonated sample of water from the Los Angeles Aqueduct Filtration Plant with added bromide.
.oo, 95 90 85
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These results, although preliminary, indicate the formation of a previously unreported group of brominated organic byproducts of ozonation of natural organic matter in water: bromohydrins. These compounds may also be formed during chlorination of natural waters but have not been reported because they have resisted identification by conventional methods employing only GC/EI-MS or are unstable under environmental conditions. Havlicek et al. (19) reported the formation of the chlorinated adducts of some of these same alcohols through chlorination of isolated humic material. This finding indicates that the
precursors of these byproducts are commonly occurring, arise from the natural product components of raw waters, and are not formed from the action of ozone on the NOM. In a separate paper, we will report on the levels of these compounds in ozonated lake water at various levels of bromide ion, hydronium ion (pH), and alkalinity and on the effect of temperature and quenching agents on their stability. There it will be shown that all of the bromohydrins are labile at 24 "C ( t l j z< 24 h) but are quite stable at 4 O C and that total organic bromide levels increase when ozonation is carried out at low pH (5, 7)and low alkalinity Environ. Sci. Technol., Vol. 26, No. 8, 1992
1661
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Literature Cited
i
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198 I
Flgure 3. Chemical ionization (2% ammonia in methane) mass spectrum of the peak eluting In Figure 1 at retention time of 12:46 min. (c 01
N
4000
3500
3000
2500
2000
'500
1000
Wovenumbers (cm- )
Flgure 4. (A, top trace) Vapor-phase infrared spectrum of the peak eluting in Figure 1 at retention time of 12:46 min. (6,bottom trace) Vapor-phase Infrared spectrum of 3-bromo-2-methyl-2-butanol (I).
values. Also, it will be shown that the levels of compound I in ozonated, bromide-containing water are much higher than those of the usually identified compounds, bromoform, dibromoacetonitrile,and the brominated acids (4-8), at least in the waters we have examined. For example, using the neat sample of I as the GC/ECD standard, we have found that ozonation of University Lake water with a bromide level of 0.43 mg of Br-/L at pH 7 results in the formation of 3.7 pg of I/L although none of the other brominated byproducts can be detected. At [Br-] = 0.82 mg/L, I is found at 255 pg/L while bromoform is only 2.3 pg/L. These bromide levels are not unrealistic for drinking water supplies in some parts of the world, and the results suggest that the potential health effects of this new group of compounds, as well as their levels in ozonated drinking water supplies, should be investigated. This study also demonstrates the power of GC/FT-IR as a complementary tool to GC/MS. Because of its dependence of functional group vibrations, infrared epectroscopy can be used effectively for compound class assignments of unknowns, as this work shows. In this work, GC/FT-IR, GC/EI-MS, and GC/CI-MS formed a pow-
1882 Environ. Sci. Technol., Vol. 26, No. 8, 1992
erful combination for study of a new group of compounds of potential environmental significance. (1) Rice, R. G. In Safe Drinking Water: T h e Impact of Chemicals on a Limited Resource; Rice, R. G., Ed.; Lewis Publishers: Alexandria, VA, 1985; pp 123-159. (2) Haag, W. R.; Hoigne, J. Enuiron. Sci. Technol. 1983, 17, 261-267. (3) Rook, J. J.; Gras, A. A.; van der Heijden, B. G.; de Wee, J. J . Enuiron. Sci. Health 1978, A13, 91-116. (4) Cooper, W. J.; Zika, R. G.; Steinhauer, M. S. Ozone: Sci. Eng. 1985, 7, 313-324. ( 5 ) Cooper, W. J.; Zika, R. G.; Steinhauer, M. S. J.-Am. Water Works Assoc. 1985, 77, 116-121. (6) Krasner, S. W.; Chinn, R.; Hwang, C. J.; Barrett, S. E. In Proceedings of the Water Quality Technology Conference, Nov 11-15,1990, San Diego, CA; American Water Works Association: Denver, CO, 1990. (7) Kuo, C.-Y.; Krasner, S. W.; Stalker, G. A.; Weinberg, H. S. In Proceedings of the Water Quality Technology Conference, Nov 11-15,1990, San Diego, C A American Water Works Association: Denver, CO, 1990. (8) Krasner, S. W.; Gramith, J. T.; Means, E. G.; Patania, N. L.; Najm, I. N.; Aieta, E. M. In Proceedings of the Annual Conference, June 23-27, 1991, Philadelphia, P A American Water Works Association: Denver, CO, 1991. (9) Amy, G. L.; Siddiqui, M. S. In Proceedings of the Annual Conference, June 23-27,19911 Philadelphia, PA; American Water Works Association: Denver, CO, 1991. (10) Glaze, W. H.; Kang, J. J.-Am. Water Works Assoc. 1988, 80,57-63. (11) Standard Methods for the Examination of Water and Wastewater, 17th ed.; American Public Health Association (APHA),American Water Works Association (AWWA),and Water Pollution Control Federation: Washington, DC, 1989. (12) U.S. Environmental Protection Agency. Trihalomethanes i n Drinking Water (Sampling,Analysis, Monitoring and Compliance);EPA 570/9-83-002;USEPA, U.S. Government Printing Office: Washington, DC, 1983. (13) Dalton, D. R.; Dutta, V. P.; Jones, D. C. J . Am. Chem. SOC. 1968,90, 5498-5501. (14) Dalton, D. R.; Dutta, V. P. J . Chem. SOC.B. 1971,85-89. (15) Langman, A. W.; Dalton, D. R.; Reingold, I. D.; Masamune, S. Org. Synth. 1980, 59, 16-20. (16) Rudewicz, P.; Munson, B. Anal. Chem. 1986,58,674-679. (17) Bellamy, L. J. The Infra-red Spectra of Complex Molecules; Methuen and Co.: London, 1954; p 89. (18) Welti, D. Infrared Vapor Spectra; Heyden and Son, Ltd.: London, 1970. (19) Havlicek, S. C.; Reuter, J. H.; Ingols, R. S.; Lupton, J. D.; Ghosal, M.; Ralls, J. W.; El-Barbary, I.; Strattan, L. W.; Cotruvo, J. H.; Trichilo, C. Abstracts of Papers, 177th National Meeting of the American Chemical Society, Honolulu, HI; American Chemical Society: Washington, DC, 1979.
Received for review October 24, 1991. Revised manuscript received April 15,1992. Accepted April 16,1992. UNC is grateful for the financial support of the American Water Works Association Research Foundation and the following water utilities: East Bay Municipal Utility District, Hackensack Water Co., Los Angeles Department of Water and Power, Metropolitan Water District of Southern California, and Portland Bureau of Water Works. Note: Mention of trade names or commercial products does not constitute endorsement or recommendation for use by the U S . Environmental Protection Agency.
