Environ. Sci. Technol. 2001, 35, 3175-3181
An Isomer Prediction Model for PCNs, PCDD/Fs, and PCBs from Municipal Waste Incinerators F U K U Y A I I N O , ‡,† K E N T A R O T S U C H I Y A , §,† TAKASHI IMAGAWA,§ AND B R I A N K . G U L L E T T * ,‡ U.S. Environmental Protection Agency, National Risk Management Research Laboratory, Air Pollution Prevention and Control Division, Air Pollution Technology Branch, MD-65, 86 T.W. Alexander Drive, Research Triangle Park, North Carolina 27711, and National Institute for Resources and Environment, 16-3 Onogawa, Tsukuba, Ibaraki, 305-8569 Japan
Isomer patterns of polychlorinated naphthalenes (PCNs), polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated biphenyls (PCBs), and polychlorinated dibenzofurans (PCDFs) from municipal waste incinerators (MWIs) were predicted by a model based on symmetry numbers and preferential chlorination positions. Fly ash isomer patterns from five stoker and seven fluidized bed incinerators were compared to validate the prediction model. The isomer patterns of the highly chlorinated PCN homologues from stoker type incinerators were successfully predicted. The relative equilibrium concentrations of tetrachloronaphthalenes (TeCNs), calculated by an ab initio method, cannot explain the field isomer patterns. Formation pathways involving chlorophenol precursor condensation reactions should be examined to see whether these isomer patterns provide a better fit to the field PCDD data. The PCB isomer patterns were fit reasonably well, but this finding could merely be an artifact of the limited data and the large number of isomers. The prediction equations of PCDFs, revised from prior work to include a symmetry number for each isomer, represented the field data patterns for the higher chlorinated isomers very well. Successful prediction of isomer patterns for partial homologue ranges suggests that these patterns are determined by a mechanism governed by Cl-position-specific preferences.
Introduction The emission of polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), polychlorinated naphthalenes (PCNs), and polychlorinated biphenyls (PCBs) from municipal waste incinerators (MWIs) was reported by Olie et al. (1) and Eiceman et al. (2). Understanding the formation mechanisms of these pollutants based on their isomer patterns has been an important research topic (3-7), because isomer-specific information enables researchers to describe more detailed and molecular-based formation * Corresponding author phone: (919) 541-1534; fax: (919) 5410554; e-mail:
[email protected]. ‡ U.S. Environmental Protection Agency. § National Institute for Resources and Environment. † The present addresses are Research Center for Chemical Risk Management (F. Iino) and Research Institute of Energy Utilization (K. Tsuchiya), National Institute of Advanced Industrial Science and Technology, Onogawa 16-1, Tsukuba, Ibaraki 305-8569, Japan. 10.1021/es001857z CCC: $20.00 Published on Web 06/15/2001
2001 American Chemical Society
mechanisms than from homologue profiles only. A method has been attempted to model these isomer patterns by thermodynamic equilibrium (8), but it was not confirmed that the isomer patterns were thermodynamically controlled. Isomer pattern modeling for PCDD/Fs has been attempted by Wiesmu ¨ ller (9) by combining all possible chlorination and dechlorination reactions. This model met with some success, albeit only at explaining the PCDF isomer pattern. A model for PCDD isomers (5), derived from a superposition of thermodynamic stability and reactivity, gave a reasonable qualitative description of the typical PCDD 2,6-dichlorophenol condensation pattern, which is commonly observed in flue gas samples of MWIs (3), along with a 2,3-dichlorophenol condensation pattern. The PCDF isomer patterns of MWIs are generally consistent (10), whereas some fluidized bed incinerators have distinctive and more variable isomer patterns (11). Iino et al. (12) succeeded in predicting the consistent PCDF isomer pattern found in most MWIs based on a dechlorination mechanism (termed the “IIG model”). This model predicted field-observed patterns better than the equilibrium model. However, as with the Wiesmu ¨ ller model (9), their method (12) did not explain the PCDD isomer pattern. As with the PCDD/Fs, synthesis and identification of all 75 PCN congeners by gas chromatography and mass spectrometry (GC/MS) (13-21) have enabled a more complete evaluation of their 2,3,7,8-tetrachlorinated dibenzo-p-dioxin (TCDD)-like toxicity (14, 21). The establishment of analytical methods for PCNs also has revealed critical information necessary toward a better understanding of the formation behavior of PCNs in MWIs (7, 22, 23). Homologue profiles and isomer patterns of PCNs may provide some information on the PCDD/F formation mechanisms, since concentrations of PCNs in fly ash have strong correlations with those of both PCDDs and PCDFs (7). Imagawa and Takeuchi (7) also found two types of PCN isomer patterns from five stoker type incinerators and seven fluidized bed incinerators. Some of the seven fluidized bed incinerators showed the same isomer pattern as the stoker type incinerators. The fluidized bed incinerator isomer pattern of PCDFs and PCNs might be explained by their predominant formation from polycyclic aromatic hydrocarbons (PAHs) (24). However, still remaining to be answered is what controls the stoker PCN isomer patterns. PCBs are also known as persistent organic pollutants that are formed as combustion byproducts in MWIs (25, 26). Recently, 2,3,7,8-TCDD toxic equivalency factors (TEFs) were reevaluated for 12 congeners of the 209 PCBs (27). There have been few reports on the PCB isomer patterns from MWIs (28), because only the 12 so-called coplanar PCBs (Co-PCBs) are determined to have TEF values and are, therefore, of interest (29, 30). To understand the formation mechanisms of PCBs from MWIs, collection of field isomer patterns and a model to explain the observed isomer patterns, are necessary. In this paper, a slight modification of the previously reported (12) IIG model, showing the simplified model equations, was applied to predict PCDD/F, PCN, and PCB isomer patterns. The IIG model predictions of PCN field data were also compared to equilibrium model predictions. For this comparison, it was necessary to calculate Gibbs free energy of formation (∆Gf°T) values, since there are no reported PCN equilibrium concentrations available in the current literature.
Theoretical Backgrounds and Computational Methods The isomer pattern prediction equations for PCDD/Fs (described more fully in refs 12 and 31) assign the relative VOL. 35, NO. 15, 2001 / ENVIRONMENTAL SCIENCE & TECHNOLOGY
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FIGURE 1. Predicted H6CDD isomer pattern and the eight MWI sample data.
FIGURE 2. Predicted P5CDD isomer pattern and the eight MWI sample data. peak ratios of the four heptachlorodibenzofuran (H7CDF) isomers, termed a, b, c, and d, to the preference for loss of chlorine from the 9- or 1-, 8- or 2-, 7- or 3-, and 6- or 4-substitution positions, respectively, on an octachlorodibenzofuran (O8CDF) molecule. In this paper, we modify the previous theory to view the peak areas, a, b, c, and d, as the chlorination preference. In this revised IIG model, the equations of PCDFs, for example, can be formatted as follows:
1 w x y z a bcd σ
(1)
where σ is the symmetry number (the number of indistinguishable orientations of a molecule) for each isomer, 1/σ is discussed by Bishop and Laidler (32) and w, x, y, and z are the numbers of chlorine atoms removed from the 9- or 1-, 8- or 2-, 7- or 3-, and 6- or 4- positions on a PCDF molecule, respectively. Therefore, for example, the prediction equation of 3,4,6,7-T4CDF is 1/2a2b2. Note that eq 1 can be used to 3176
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derive relative intra-homologue concentrations either from chlorination of the monochlorodibenzofurans (M1CDFs) to the O8CDF or vice versa. Our approach, for simplicity, was to derive the equations from the O8CDF. The equations for the predicted intra-homologue relative concentrations were modified from those published previously (12) to reflect symmetry numbers in eq 1. While the equations and the values of a, b, c, and d changed from those previously reported for PCDD/Fs, the relative concentration values (now normalized by the sum of the revised equations) remain the same as in ref 12 and are shown in Appendix 1 and 2 in the Supporting Information. A similar approach was taken to derive expressions for PCN and PCB in this paper. The relative peak ratios of the two heptachloronaphthalenes (HpCNs), 1,2,3,4,5,6,7-HpCN (#73) and 1,2,3,4,5,6,8-HpCN (#74) are termed a and b, because each isomer has a symmetry number of 1. The values of a ) 0.829 and b ) 0.171 were taken from the relative abundance of each isomer in a representative MWI sample.
FIGURE 3. Predicted T4CDD isomer pattern and the seven MWI sample data.
TABLE 1. Calculated values of similarity, S, for PCNsa similarity values similarity values between equilibrium between prediction and samples TeCN and samples HxCN PeCN TeCN
Seq(A) Seq(B) Seq(C) Seq(D) Seq(E) Seq(F) Seq(G) Seq(H) Seq(I) Seq(J) Seq(K) Seq(L)
0.67 0.44 0.72 0.51 0.61 0.79 0.54 0.82 0.47 0.42 0.34 0.33
SIIG(A) SIIG(B) SIIG(C) SIIG(D) SIIG(E) SIIG(F) SIIG(G) SIIG(H) SIIG(I) SIIG(J) SIIG(K) SIIG(L)
0.94 0.94 0.89 0.96 0.88 0.93 0.93 0.85 0.88 0.93 0.64 0.62
0.87 0.88 0.86 0.89 0.86 0.82 0.81 0.54 0.63 0.74 0.30 0.35
0.81 0.45 0.82 0.73 0.70 0.73 0.71 0.53 0.59 0.61 0.43 0.47
a S (A): Similarity between equilibrium at 1073K and sampled data eq A. SIIG(A): similarity between prediction and sampled data A. A to C: Stoker type incinerators. D and E: mechanical batch stoker type incinerators. F to L: fluidized bed incinerators.
FIGURE 4. B3LYP/6-31G(d)-optimized 1,4,5,8-TeCN geometry (D2symmetry). The resulting equations, shown in Appendix 3 in the Supporting Information, predict the intra-homologue, relative isomer concentrations of hexachloronaphthalenes (HxCNs), pentachloronaphthalenes (PeCNs), and TeCNs. The same conceptual theory was also applied for PCBs as shown in Appendix 4 in the Supporting Information. Ab Initio Calculations. The relative energies of the 22 TeCN isomers were obtained by ab initio molecular orbital calculations using Gaussian 98 code (33). The G3(MP2)// B3LYP composite method (34), which is the Gaussian-3 (MP2) method (35) using B3LYP (36-38) hybrid-density functional geometries, frequencies, and zero-point energies, was employed to estimate enthalpies and ∆Gf°T at 298.15, 573, and 1073 K, respectively, for all 22 TeCN isomers. MP2 stands for second-order Møller-Presset perturbation theory (39). In the process of optimizing the geometry, which is necessary to calculate thermodynamic properties, it was found that 1,4,5,8-TeCN has a nonplanar structure. The illustration of the 1,4,5,8-TeCN molecule was printed by a
combination of two free software packages, MOLDA and PRAX, which can be downloaded from the Internet (40).
Results and Discussion PCDDs. The IIG-model-calculated isomer patterns of H6CDDs, P5CDDs, and T4CDDs (presented in order of elution from an SP-2331 column) are compared, in Figures 1, 2, and 3, respectively, with fly ash isomer patterns derived from Japanese field MWIs. The values of a for 1,2,3,4,6,7,8-H7CDD and b for 1,2,3,4,6,7,9-H7CDD used for the predicted results were 0.468 and 0.532, respectively, obtained from a H7CDD isomer pattern representative of these Japanese MWIs. The sampled PCDD isomer patterns are similar to those expected from a 2,6-dichlorophenol condensation mechanism (3). The IIGmodel predictions poorly predict the field-sampled isomer patterns, similar to results found by Wehrmeier et al. (5). The influence of precursor condensation pathways, from compounds such as chlorophenols (41) and chlorobenzenes, may have to be examined to see whether the condensation isomer pattern provides a better fit to the field PCDD isomer pattern. PCNs. The B3LYP/6-31G(d)-optimized geometry of 1,4,5,8TeCN (#46) is illustrated in Figure 4. Significant disruption VOL. 35, NO. 15, 2001 / ENVIRONMENTAL SCIENCE & TECHNOLOGY
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FIGURE 5. Relative concentrations of TeCNs in equilibrium at 298.15, 573, and 1073 K.
FIGURE 6. Predicted HxCN isomer pattern and the 12 MWI sample data. The predicted results were obtained with a ) 0.828 and b ) 0.172 in Table 1 which were calculated from a representative MWI sample. of the coplanar nature of the 1,4,5,8-TeCN (#46) isomer as well as OcCN (#75) was also concluded by Kalmykova et al. with infrared (IR) spectra (42). A more detail discussion is given in Appendix 5 in the Supporting Information. The calculated energies by the G3(MP2)//B3LYP composite method are shown in Appendix 6 (Supporting Information). The calculation procedures are detailed in the original G3 theory paper (43). The relative intra-homologue isomer concentrations in equilibrium at 298.15, 573, and 1073 K (Figure 5) were calculated based on the ∆Gf°T by the following equation:
[#i]T ) 3178
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exp(-∆Gi,j(T)/RT)
∑exp(-∆G
n,j(T)/RT)
(2)
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where ∆Gi,j is the difference in the total ∆G between isomer i (i ) 1...n) and j (the isomer which has the lowest value of ∆G is isomer j) and T is temperature. Rotational symmetries are already considered in the Gaussian 98 code, and so are neglected in this equation. At 298.15 and 573 K, 1,3,5,7-TeCN (#42) is the most stable because chlorine atoms are in the least crowded positions. The distortion of the 1,4,5,8-TeCN (#46) isomer makes it the most thermodynamically unstable at all three temperatures. At temperatures considered optimum for postcombustion formation of PCDD/Fs and PCNs via precursor condensation or de novo formation, 573 K, 1,3,5,7-TeCN (#42) therefore is the most prevalent TeCN isomer. At 1073 K, within the temperature range of combustion chamber outlets, the equilibrium isomer concentrations are more broadly distributed.
FIGURE 7. Predicted PeCN isomer pattern and the 12 MWI sample data.
FIGURE 8. Predicted TeCN isomer pattern and the 12 MWI sample data. The IIG-model-calculated isomer patterns of HxCNs, PeCNs, and TeCNs are compared with 12 field isomer patterns sampled from MWI fly ash in Japan in Figures 6, 7, and 8, respectively. Analytical procedures for the PCN isomers were described elsewhere (6, 21), as were the configuration details of the sampled MWIs (44). The MWIs (labeled A to C) are continuous stoker types, mechanical batch stoker types (D and E), and fluidized bed incinerators (F to L). In the HxCN and PeCN homologues, the predicted isomer patterns are fairly similar to the stoker type incinerator patterns (A to E) and to some of the fluidized bed incinerators (F and G). For MWIs H to L, 1,2,3,4,5,6-HxCN (#63) and coeluting 1,2,4,7,8- (#62) and 1,2,3,4,5-PeCNs (#49) showed remarkable differences from those in the stoker type patterns. Imagawa and Lee (44) pointed out that these isomers might be caused by preferentially oriented chlorination. In the TeCN homologue, the model prediction seems successful only for MWIs A and C. In particular, 1,3,6,7- (#44) and a coeluted peak of 2,3,6,7-/1,2,6,8-TeCNs (#48/40) are marginally predicted for all of the field samples.
As an evaluation method of the isomer distribution matching, Morita et al. (45) introduced a similarity value, S. In Table 1, the values of Seq(n) show the similarity between the predicted equilibrium concentrations of TeCNs at 1073 K and the field fly ash data for sample n (where n ) A to L). Likewise, the SIIG(n) values between the IIG-predicted isomer patterns in this paper and the nth MWI samples are shown in Table 1. The field samples that showed equilibrium similarity values, Seq(n), of more than 0.70, were only MWI C (0.72), F (0.79), and H (0.82). No consistent similarity values can be seen within the same category type of MWIs. Therefore, we conclude that the TeCN isomers emitted from MWIs cannot be explained by thermodynamic equilibrium isomer patterns. Similarity values with our model prediction, SIIG(n), of more than 0.81 clearly support the observation that the IIG-modelpredicted results for HxCNs and PeCNs matched well with all of the investigated stoker type incinerators (A to E) and some fluidized bed incinerators (F and G). In the TeCNs, the worst SIIG(n) is 0.45 for sample B, yet more than 0.70 for A VOL. 35, NO. 15, 2001 / ENVIRONMENTAL SCIENCE & TECHNOLOGY
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FIGURE 9. Predicted OcCB isomer pattern and the two MWI sample data. SIIG (X) and SIIG(Y) are 0.88 and 0.91, respectively. and C to G. The IIG-model prediction was not perfectly successful for the TeCNs. The tetrachlorodibenzofuran isomer patterns were more accurately predicted (12) than those of the TeCNs. Since the first chlorination of a naphthalene ring occurs more easily on an R (1-, 4-, 5-, 8-) position than on a β (2-, 3-, 6-, 7-) position, the prediction based on monochloronaphthalene (MoCN) isomer patterns could have more chlorine atoms on the R-positions, which is contradictory to those predicted based on the HpCN isomer patterns. Rogue behaviors of PCN and PCDF isomer patterns from some fluidized bed incinerators were reported by Imagawa and Takeuchi (7), and Weber and Hagenmaier (11), respectively. The fly ash samples from H to L can be classified in this more “extreme” fluidized bed incinerator pattern, as mentioned by Imagawa and Lee in their recent paper (44). The similarity values of SIIG(H) to SIIG(L) for PeCNs and TeCNs do not exceed the highest value of SIIG(J) for PeCN, or 0.74,
and so this suggests that other formation mechanisms may control PCN formation in fluidized bed incinerators H to L, such as direct formation from PAHs to specific PCN isomers (24). The main chemical structure difference of PCNs from PCDFs is the absence of oxygen atoms in the PCN structures, which may make PCNs more amenable to formation from PAHs under oxygen-scarce combustion conditions. This additional mechanism for PCNs may be why PCNs show two very distinctive isomer patterns (A to G and H to L) as opposed to PCDFs where the two pattern distinctions are less obvious. PCBs. Field isomer patterns for PCBs were measured from two stoker-type MWI samples taken in Japan from one emission gas sample (sample X) and one fly ash sample (sample Y). Both MWIs have a maximum capacity of 200 Mg/day of municipal solid waste and an electrostatic precipitator as a dust collector (29). The cleanup and analytical methods were described in detail elsewhere (28). With only two field isomer patterns, there are insufficient data to obtain statistically meaningful results related to model fitting. However, preliminary discussion based on the limited PCB isomer patterns may encourage further measurement and isomer-specific analysis of PCBs that will lead to an improved understanding of PCB formation mechanisms in MWIs. The prediction equations for octa- (OcCBs) to tetrachlorobiphenyls (TeCBs) by the IIG model were shown in Appendix 4 (Supporting Information) with the toxic congeners underlined. The nonortho, toxic congeners are IUPAC #77, #81, #126, and #169. The mono-ortho toxic congeners are #105, #114, #118, #123, #156, #157, #167, and #189. The orders of the congeners in Appendix 4 followed the elution order of a DB-5 column used for the isomer-specific analysis. Some isomers are coeluted, and the congeners with TEF values tend to elute later in each homologue due to their chemical structures. The IIG-model-predicted PCB isomer patterns (blank bars) of OcCBs and Hepta-CBs (HpCBs) are compared with the two field isomer patterns (filled bars, left: sample X, right: sample Y) and the similarity values, SIIG(X) and SIIG(Y), in Figures 9 and 10, respectively. The normalized Nona-CB (NoCB) peak height ratios of Sample Y were used, and the values were a ) 0.556 for #206, b ) 0.253 for #207, and c ) 0.192 for #208. The NoCB isomers of #206, #207, and #208 correspond to dechlorination at the 2- or 6-position, 3- or
FIGURE 10. Predicted HpCB isomer pattern and the two MWI sample data. SIIG(X) and SIIG(Y) are 0.88 and 0.84, respectively. 3180
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5-position, and 4-position from decachlorobiphenyl (DeCB, #209), respectively. The isomer patterns of OcCBs and HpCBs were reasonably well predicted with SIIG of more than 0.84. A prediction based on monochlorobiphenyl (MoCB) isomer patterns was also calculated by using three MoCB peak height ratios. The peak of 2-MoCB (#1) is the smallest in the mono-homologue (2-MoCB (#1)/3-MoCB (#2)/4-MoCB (#3) ) 1:2.5:3.2 in the average of the two samples), while the peak of #206 is the highest in the nona-homologue (#206/ #207/#208 ) 2.4:1.8:1). Because the MoCB is difficult to chlorinate in the ortho- (2- or 6-) position and the NoCB is easily dechlorinated from the ortho-position, the prediction results by using MoCBs and NoCBs turned out to be very similar. The ortho-positions of a PCB molecule are subject to strong steric effects, and it is reasonable to think that the ortho-positions have higher activation energies for chlorination than the other two positions. This steric effect was thermodynamically confirmed by Mulholland et al. (46). For example, the predominant peak of the #189 HpCB isomer (2,3,3′,4,4′,5,5′-HpCB) may be explained by this thermodynamic preference.
Acknowledgments The PCB field isomer patterns were provided by Mr. Takumi Takasuga, Shimadzu Techno-Research, Inc., Japan, and Prof. Shin-ichi Sakai, Kyoto University, Japan. The authors greatly appreciate the data contributed by the two researchers. We also greatly appreciate Prof. James Dunn, University of Arkansas, for his suggestions on the model. This research was supported in part by Dr. F. Iino’s appointment to the Postdoctoral Research Program at EPA’s National Risk Management Research Laboratory, administered by the Oak Ridge Institute for Science and Education through Interagency Agreement No. DW89938167 between the U.S. Department of Energy and the U.S. Environmental Protection Agency. This paper is dedicated to Dr. T. Imagawa who passed away on February 19, 2001 during the review process of this paper.
Supporting Information Available Predicted ratios of various isomers, detailed discussion on the ab initio calculation of the 1,4,5,8-TeCN molecule, and calculation results for G3(MP2)//B3LYP (Appendices 1-6). This material is available free of charge via the Internet at http://pubs.acs.org.
Literature Cited (1) Olie, K.; Vermeulen, P. L.; Hutzinger, O. Chemosphere 1977, 6, 455. (2) Eiceman, G. A.; Clement, R. E.; Karasek, F. W. Anal. Chem. 1979, 51, 2343. (3) Swerev, M.; Ballschmiter, K. Chemosphere 1989, 18, 609. (4) Luijk, R.; Akkerman, D. M.; Slot, P.; Olie, K.; Kapteijn, F. Environ. Sci. Technol. 1994, 28, 312. (5) Wehrmeier, A.; Lenoir, D.; Schramm, K. W.; Zimmermann, R.; Hahn, K.; Henkelmann, B.; Kettrup, A. Chemosphere 1998, 36, 2775. (6) Iino, F.; Imagawa, T.; Takeuchi, M.; Sadakata, M. Environ. Sci. Technol. 1999, 33(7), 1038. (7) Imagawa, T.; Takeuchi, M. Organohalogen Compd. 1995, 23, 487. (8) Addink, R.; Govers, H. A. J.; Olie, K. Environ. Sci. Technol. 1998, 32, 1888. (9) Wiesmu ¨ ller, T. Ph.D. Dissertation, University of Tu ¨ bingen, Federal Republic of Germany, 1990. (10) Schramm, K.-W.; Wehrmeier, A.; Lenoir, D.; Henkelmann, B.; Hahn, K.; Zimmermann, R.; Kettrup, A. Organohalogen Compd. 1996, 27, 196. (11) Weber, R.; Hagenmaier, H. Chemosphere 1999, 38, 2643. (12) Iino, F.; Imagawa, T.; Gullett, B. K. Environ. Sci. Technol.2000, 34(15), 3143. (13) Brinkman, U. A. Th.; Reymer, H. G. M. J. Chromatogr. 1976, 127, 203. (14) Hanberg, A.; Wærn, F.; Asplund, L.; Haglund, E.; Safe, S. Chemosphere 1990, 20, 1161.
(15) Williams, D. T.; Kennedy, B.; LeBel, G. L. Chemosphere 1993, 27 (5), 795. (16) Auger, P.; Malaiyandi, M.; Wightman, H.; Bensimon, C.; Williams, D. T. Environ. Sci. Technol. 1993, 27, 1673. (17) Imagawa, T.; Tanaka, T. Pollution Control 1988, 23, 277 (in Japanese). (18) Imagawa, T.; Tanaka, T.; Miyazaki, A. Pollution Control 1989, 24, 159 (in Japanese). (19) Imagawa, T.; Yamashita, N.; Miyazaki, A. J. Environ. Chem. 1993, 3, 221 (in Japanese). (20) Imagawa, T.; Yamashita, N. Chemosphere 1997, 35, 1195. (21) Kannan, K.; Imagawa, T.; Blankenship, A. L.; Giesy, J. P. Environ. Sci. Technol. 1998, 32, 2507. (22) Schneider, M.; Stieglitz, L.; Willand, R.; Zwick, G. Chemosphere 1998, 37, 2055. (23) Abad, E.; Caixach, J.; Rivera, J. Chemosphere 1999, 38, 109. (24) Weber, R.; Iino, F.; Imagawa, T.; Takeuchi, M.; Sakurai, T.; Sadakata, M. Organohalogen Compd. 1999, 41, 301. (25) Sakai, S.; Hiraoka, M.; Takeda, N.; Shiozaki, K. Chemosphere 1993, 27, 233. (26) Miyata, H.; Aozasa, O.; Mase, Y.; Ohta, S.; Khono, S.; Asada, S. Chemosphere 1994, 29, 2097. (27) Van den Berg, M.; Birnbaum, L.; Bosveld, B. T. C.; Brunstro¨m, B.; Cook, P.; Feeley, M.; Giesy, J. P.; Hanberg, A.; Hasegawa, R.; Kennedy, S. W.; Kubiak, T.; Larsen, J. C.; van Leeuwen, F. X. R.; Liem, A. K. D.; Nolt, C.; Peterson, R. E.; Poellinger, L.; Safe, S.; Schrenk, D.; Tillitt, D.; Tysklind, M.; Younes, M.; Waern, F.; Zacharewski, T. Environ. Health Perspect. 1998, 106 (12), 775. (28) Takasuga, T.; Inoue, T.; Ohi, E. J. Environ. Chem. 1995, 5(3), 647 (in Japanese). (29) Sakai, S.; Ukai, T.; Takatsuki, H.; Nakamura, K.; Kinoshita, S.; Takasuga, T. J. Mater. Cycles Waste Manag. 1999, 1, 62. (30) Fa¨ngmark, I.; Stro¨mberg, B.; Berge, N.; Rappe, C. Environ. Sci. Technol. 1994, 28, 624. (31) Iino, F.; Imagawa, T.; Gullett, B. K. Organohalogen Compd. 2000, 46, 114. (32) Bishop, D. M.; Laidler, K. J. J. Chem. Phys. 1965, 42(5), 1688. (33) Frisch, M. J.; Trucks, G. W.; Schlegel, H. B.; Scuseria, G. E.; Robb, M. A.; Cheeseman, J. R.; Zakrzewski, V. G.; Montgomery, J. A. Jr.; Stratmann, R. E.; Burant, J. C.; Dapprich, S.; Millam, J. M.; Daniels, A. D.; Kudin, K. N.; Strain, M. C.; Farkas, O.; Tomasi, J.; Barone, V.; Cossi, M.; Cammi, R.; Mennucci, B.; Pomelli, C.; Adamo, C.; Clifford, S.; Ochterski, J.; Petersson, G. A.; Ayala, P. Y.; Cui, Q.; Morokuma, K.; Malick, D. K.; Rabuck, A. D.; Raghavachari, K.; Foresman, J. B.; Cioslowski, J.; Ortiz, J. V.; Baboul, A. G.; Stefanov, B. B.; Liu, G.; Liashenko, A.; Piskorz, P.; Komaromi, I.; Gomperts, R.; Martin, R. L.; Fox, D. J.; Keith, T.; Al-Laham, M. A.; Peng, C. Y.; Nanayakkara, A.; Gonzalez, C.; Challacombe, M.; Gill, P. M. W.; Johnson, B.; Chen, W.; Wong, M. W.; Andres, J. L.; Gonzalez, C.; Head-Gordon, M.; Replogle, E. S.; Pople, J. A. Gaussian 98, Revision A.7, Gaussian, Inc., Pittsburgh, PA, 1998. (34) Baboul, A. G.; Curtiss, L. A.; Redfern, P. C.; Raghavachari, K. J. Chem. Phys. 1999, 110(16), 7650. (35) Curtiss, L. A.; Redfern, P. C.; Raghavachari, K.; Rassolov, V.; Pople, J. A. J. Chem. Phys. 1999, 110(10), 4703. (36) Becke, A. D. J. Chem. Phys. 1993, 98, 1372. (37) Becke, A. D. Phys. Rev. A 1988, 38(6), 3098. (38) Lee, C.; Yang, W.; Parr, R. G. Phys. Rev. B 1988, 37(2), 785. (39) Møller, C.; Plesset, M. S. Phys. Rev., 1934, 46, 618. (40) Yoshida, H. Molda Home Page. http://vbl01.chem.sci.hiroshimau.ac.jp/molda/molda.htm (accessed August 2000). (41) Mulholland, J. A.; Akki, U.; Yang, Y.; Ryu, J.-Y. Chemosphere 2001, 42, 719. (42) Kalmykova, G. O.; Kurmei, N. D.; Malykhina, N. N. Izv. Akad. Nauk S.S.S.R., Ser. Fiz. 1975, 39, 1925. (43) Curtiss, L. A.; Raghavachari, K.; Redfern, P. C.; Rassolov, V.; Pople, J. A. J. Chem. Phys. 1998, 109(18), 7764. (44) Imagawa, T.; Lee, C. W. Chemosphere 2001, 43(2), 223. (45) Morita, M.; Yasuhara, A.; Ito, H. Chemosphere 1987, 16, 1959. (46) Mulholland, J. A.; Sarofim, A. F.; Rutledge, G. C. J. Phys. Chem. 1993, 97, 6890.
Received for review November 8, 2000. Revised manuscript received April 30, 2001. Accepted May 7, 2001. ES001857Z VOL. 35, NO. 15, 2001 / ENVIRONMENTAL SCIENCE & TECHNOLOGY
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