Environ. Sci. Technol. 1996, 30, 2984-2992
Formation and Spectroscopic Investigation of Two Hexachlorobornanes from Six Environmentally Relevant Toxaphene Components by Reductive Dechlorination in Soil under Anaerobic Conditions† GERDA FINGERLING,‡ NORBERT HERTKORN,§ AND H A R U N P A R L A R * ,| Department of Analytical Chemistry, University of Kassel, D-34109 Kassel, Germany, Institute of Ecological Chemistry, GSF, D-85356 Freising-Attaching, Germany, and Department of Chemical Technical Analysis and Chemical Food Technology, TU Munich, D-85350 Freising-Weihenstephan, Germany
Six pure polychlorinated bornanes isolated from technical toxaphene, namely, Parlar 32 (toxicant B), Parlar 42a (toxicant A1), Parlar 42b (toxicant A2), Parlar 49a, Parlar 56, and Parlar 59, as well as the technical mixture were investigated as to their fate in a loamy silt under anaerobic conditions by laboratory studies taking 4 or 6 months. All test substances shared the geminal dichloro group in the C-2 position and, additionally, one chlorine atom each in the C-5endo and C-6exo positions, respectively. Reductive dechlorination was the major reaction leading to a sequential removal of a chlorine atom from each geminal dichloro group. Generally, in the first step of transformation, all six compounds lost a chlorine atom from the geminal dichloro group in the C-2 position, preferentially from the endo-position. The dechlorination rate was in the order of nonachlorobornanes > octachlorobornanes > heptachlorobornanes. While the two monodechlorination products formed from Parlar 32 underwent no further transformation, those products with additional geminal dichloro groups lost further chlorine atoms from exactly these groups. Finally, all six compounds formed two very stable end-metabolites in different ratios, which have been isolated and identified as 2-exo,5endo,6-exo,8c,9b,10a- and 2-endo,5-endo,6-exo, 8c,9b,10a-hexachlorobornane. Additionally, one of these end-metabolites was identified as the major product of the degradation of technical toxaphene after 6 months.
2984
9
ENVIRONMENTAL SCIENCE & TECHNOLOGY / VOL. 30, NO. 10, 1996
Introduction Toxaphene is a complex mixture of more than 200 polychlorinated C10-terpenes, primarily bornane derivatives with 6-11 chlorine atoms. Formerly, it has been one of the most thoroughly used organochlorine insecticides in many parts of the world. More than 106 t have been applied from 1947 to 1985 especially for cotton pest control as well as on soya beans, vegetables, and small grains (1-4). Due to its persistence in the environment, its extreme accumulationsespecially in the aquatic food chainsand its toxicity to higher animals, toxaphene has been banned or restricted in many countries since the 1980s, but it is still used in developing countries (1). Despite reduced emission, toxaphene continues to be a major organochlorine pesticide contaminant in the biosphere (2). One of the major problems in toxicity evaluation is the diversity of toxic components in the complex mixture of technical toxaphene, whose exact composition is still not known (3). However, it is known that the various toxaphene components are differently transformed in the environment; while some congeners are highly persistent, others are rapidly degraded (1). This implies that the biological recalcitrance of the individual toxaphene component is obviously related to number and, especially, position of the chlorine substituents. Under environmental conditions, the half-life of toxaphene in well-aerated soils is 10-14 years (5, 6), although soil factors such as temperature, microbial activity, air, and moisture have a direct as well as an indirect effect on its persistence. However, when toxaphene-spiked soil is subjected to a reducing environment the complex mixture is rapidly transformed. The most important reaction is reductive dechlorination, including a two-electron transfer with the release of a chlorine ion and its replacement by hydrogen. The exact mechanism is still not known, but the participation of transition metal-containing coenzymes has been stated by several investigators (7, 9). Generally, aerobic soil microorganisms often fail to metabolize higher halogenated compounds such as polychlorinated bornane derivatives. While the lower chlorinated bornane derivatives, like trichlorobornanes, can be oxidized by the microbial enzymatic systems, the higher chlorinated components cannot (9). Hence, anaerobic conditions are necessary for the initial step in the transformation of polychlorinated compounds. Several investigators have examined the degradation of toxaphene under anaerobic conditions. Laboratory studies indicated that reductive dechlorination of toxaphene occurred with iron(II)protoporphyrin as well as in anoxic salt marsh sediments (10, 11). Furthermore, it was demonstrated in sewage sludge, in an anaerobic silt loam, and in irrigation drainage ditch sediments, all of which favored the formation of lower chlorinated products (12-16). †
Dedicated to Prof. Dr. H.-D. Scharf on the occasion of his 65th birthday. * Author to whom correspondence should be addressed. ‡ University of Kassel. § Institute of Ecological Chemistry. | TU Munich.
S0013-936X(95)00957-6 CCC: $12.00
1996 American Chemical Society
However, no metabolite was isolated for structure identification. Studies dealing especially with the microbial degradation of isolated toxaphene components under anaerobic conditions are limited. Only the transformation of 2,2,5-endo,6-exo,8,9,10-heptachlorobornane (Tox B) in sewage sludge has been investigated (12). In this paper, we report on the degradation of six toxaphene components as well as technical toxaphene by reductive dechlorination in a loamy silt under anaerobic conditions. The structure of the resulting metabolites have been investigated by HRGC-MS, HRGC-FTIR, 1H-NMR, and X-ray analysis.
Experimental Section Materials. The toxaphene components 2,2,5-endo,6-exo, 8c,9b,10a-heptachlorobornane (Parlar 32); 2,2,5-endo,6exo,8b,8c,9c,10a-octachlorobornane (Parlar 42a); 2,2,5endo,6-exo,8c,9b,9c,10a-octachlorobornane (Parlar 42b); 2,2,5-endo,6-exo,8c,9b,10a,10b-octachlorobornane (Parlar 49a); 2,2,5-endo,6-exo,8b,8c,9c,10a,10c-nonachlorobornane (Parlar 56); and 2,2,5-endo,6-exo,8c,9b,9c,10a,10bnonachlorobornane (Parlar 59) were isolated from technical toxaphene as previously described (17, 18). Technical toxaphene was obtained from Ehrenstorfer, Germany. The soil, a loamy silt (pH 6.7, 1.8% organic carbon) was collected from a field in the surroundings of Kassel. It had been chosen because of its lack of any detectable organochlorine contaminants. The soil was air-dried and passed through a 2-mm sieve prior to use. Incubation of Toxaphene Components with Soil and Sample Preparation. Incubation with soil was done with portions of 80 g of soil each placed in a 200-mL Erlenmeyer flask and fortified with 1 mL of acetone containing 400 µg of the toxaphene component. After adding 150 mL of sterile, distilled water to each flask, the flasks were shaken, and the solved O2 was removed with a stream of nitrogen for 30 min. Then the flasks were tightly capped with Teflon-coated stoppers and kept in the dark at ∼30 °C. Two samples were prepared in this way for each component. Furthermore, two blanks were prepared. In the case of technical toxaphene, the total of 800 µg (10 µg/g of soil) was added to the soil. One series of the spiked soil samples was sterilized by autoclaving (121 °C, 15 psi) for two 1-h periods at intervals of 24 h before adding the compounds. Anaerobic conditions were checked by measurements of redox potentials (EH) with combination platinum/calomel electrodes. The redox potentials were greater than -0.20 V. Gas production was observed but was not further investigated. Samples for analysis were taken weekly during the first two months and for the rest of the timesa total of 4 and 6 months, respectivelysin intervals of 2 weeks. The flasks were shaken and then opened under a stream of N2, and 10-mL aliquots of the suspension were taken. Each sample was acidified with H2SO4 to pH ca. 1 and extracted with a mixture of 5 mL of petroleum ether (45-65 °C)/ acetone (1:1) in an ultrasonic bath for 30 min. The petroleum ether layer was separated, and the aqueous medium was reextracted twice with 2 × 5 mL of petroleum ether (45-65 °C). Finally, the organic phases were combined, dried over sodium sulfate, and concentrated under a gentle stream of N2 to ca. 1 mL. These petroleum ether extracts were directly used for GC analysis. With the help of measurements of blanks, carried out parallel to the samples, possible contaminations could be excluded.
Gas Chromatography. All routine analyses were carried out on a Varian 3400 gas chrornatograph (injection, splitless/split 230 °C); column 30 m DB-5, fused silica, i.d. 0.25 mm; thickness 0.32 µm; EC detector 280 °C; carrier gas, N2, 1 mL/min; temperature program (column): 120 °C (0 min)-20 °C/min-200 °C (0 min)-5 °C/min-230 °C (1 min)-1.5 °C/min-250 °C (15 min). Isolation of Major Metabolites. The isolation of the major metabolites formed from all six compounds was carried out by liquid chromatography. For that purpose, all samples were combined, and the solvent was reduced to ca. 1 mL and afterwards applied to a silica gel column (column 100 × 1.2 cm, 50 g of silica gel 60, 70-230 mesh; mobile phase: petroleum ether, 45-65 °C; flow rate ca. 1.5 mL; retention volume ca. 500 mL). Besides other metabolites, two hexachlorobornanes were isolated with a purity of more than 98%. During slow evaporation of the solvent, one of them crystallized as colorless needles. Mass Spectrometry. The MS experiments were carried out using a HP 5890/5988A GC/MS system (column: 25 m HP-5, i.d. 0.2 mm, film thickness 0.33 µm; carrier gas He, 1 mL/min; temperature program: 140 °C (3 min) to 250 °C (20 min) with 4 °C/min, splitless (0.5 min)/split injection; injection block and transfer line 280 °C). The temperature of the ion source was 100 °C for ECNI/MS, with CH4 as the moderating gas. The emission current was ca. 200 µA. EI measurements were performed at 70 eV and 200 °C ion source temperature (mass range: m/z 40-500). FTIR Spectroscopy. An HP 5890/5965 GC/FTIR system was used to record the IR spectra (column: HP-5, i.d. 0.32 mm, film thickness 0.52 µm; carrier gas: He, 1 mL/min); temperature program: 140 °C (3 min) to 250 °C (20 min) with 4 °C/min; transfer lines: 250 °C; light pipe: 280 °C). 1H-NMR Spectroscopy. Proton NMR spectra were recorded with a Bruker AC 400 spectrometer (400.13 MHz) at 303 K in CDCl3 (δ ) 7.25 ppm) using a 5-mm broadband inverse geometry probe (90°: 8.5 µs). DQF-COSY, NOE difference spectra (mixing time: 1 s) and phase-sensitive NOFSY spectra (mixing time: 450 ms) were performed using Bruker standard software, employing 90-deg pulses (8.5 µs). X-ray Analysis. The X-ray measurements were taken with an Enraf-Nonius CAD4 V 5.0 four-circle diffractometer with a MoKR radiation of λ ) 71.073 pm (graphite monochromator). A total of 2639 reflections were collected in the 2θ range of 3-25°.
Results and Discussion Figure 1 presents the six toxaphene congeners investigated in an anaerobic, loamy silt. All of them are rather labile under these conditions. Preferentially, they were transformed by reductive dechlorination. No degradation of any component occurred in autoclaved soil controls, which indicates that degradation is mediated primarily by microorganisms. This has also been found by other investigators (13, 16, 20). All compounds are sucessively dechlorinated by reductive removal of one chlorine atom from each geminal dichloro group, beginning with that in the C-2 position, which is the most labile. The dechlorination rate depends on the chlorination stage (nonachlorobornanes > octachlorobornanes > heptachlorobornanes). In most cases, the chlorine atome in the C-2endo position was removed, indicating stereoselective degradation. The two products derived from Parlar 32, which are formed in a ratio of 1:2.8
VOL. 30, NO. 10, 1996 / ENVIRONMENTAL SCIENCE & TECHNOLOGY
9
2985
FIGURE 1. HRGC/ECD chromatogram of technical toxaphene. I-V are the investigated congeners; II includes two coeluting isomers (IIa and IIb).
2986
9
ENVIRONMENTAL SCIENCE & TECHNOLOGY / VOL. 30, NO. 10, 1996
FIGURE 2. ECNIMS spectra of 2-exo,5-endo,6-exo,8c,9b,10a- and 2-endo,5-endo,6-exo,8c,9b,10a-hexachlorobornane.
(endo/exo), are both lacking a further geminal dichloro group and therefore stable enough not to be further degraded under these experimental conditions. Contrary to this, all higher chlorinated bornane derivatives with geminal dichloro groups except the one at the six-membered ring are further dechlorinated so that no exact product ratio can be
determined for the first step. Nevertheless, the exo-product also seems to be the preferred one here. That the first loss of chlorine really takes place in the C-2 position is shown by the fact that no Parlar 32 can be found as intermediate during dechlorination of other components, which would inevitably be the case if dechlorination started at C-8, C-9,
VOL. 30, NO. 10, 1996 / ENVIRONMENTAL SCIENCE & TECHNOLOGY
9
2987
FIGURE 3. EIMS spectra of 2-exo,5-endo,6-exo,8c,9b,10a- and 2-endo,5-endo,6-exo,8c,9b,10a-hexachlorobornane.
or C-10. The successive loss of a chlorine atom from geminal dichloro groups in these positions by secondary reactions could be seen from the signals of the CHCl2 fragments (m/z 83) in the EIMS spectra, which became significantly smaller with decreasing chlorination grade. The final degradation products of all six components are two hexachlorobornanes, one with the remaining chlorine atom in the C-2endo position and the other with this atom in the C-2exo position; they are formed in varying ratios being 1:3 (endo/exo) in the case of Parlar 42, 1:4.8 in the case of Parlar 49a, 1:95 in the case of Parlar 59, and 1:98 in the case of Parlar 56. Obviously, the ratio depends on the number of geminal dichloro groups in the parent molecule; with increasing number an increasing preference of the exo-isomer can be seen. Both products seem to be dead-end-metabolites under these experimental conditions. A comparison of retention times and mass spectra proved the concurrence of the final metabolites of all tested congeners. Therefore, all samples could be combined to allow the isolation of both metabolites giving enough material for 1H-NMR and, in the case of the exo-isomer, for crystallization and X-ray analysis. Mass Spectrometric Investigation of Two Hexachlorobornanes. ECNI and EI mass spectra of both metabolites can be seen in Figures 2 and 3. The parent peak m/z 342 in the ECNI spectra shows the presence of hexachlorobornane derivatives. The M- ion signal of the endo-isomer is rather strong, while that of the exo-isomer is far less intense, which is not typical for hexachlorobornanes where, normally, M- signals are favored (21) as compared to the stronger fragmentation of higher chlorinated bornanes.
2988
9
ENVIRONMENTAL SCIENCE & TECHNOLOGY / VOL. 30, NO. 10, 1996
With the exo-isomer, the loss of Cl- in the ECNI modus is increased, so that here the base peak constitutes the [M-CI]ion with m/z 307. On the other hand, the spectrum of the endo-isomer shows an unusually strong HCI cleavage; the ions M-, [M - CI]-, and [M - HCI]- appear in a ratio of 1:1:1. The EIMS spectra differ only slightly, being typical of bornane derivatives without dichloromethyl groups. The lack of this group can be deduced from the absence of the fragment m/z 83, which otherwise would be recorded with rather high intensity and, in the presence of two of this group, would generally form the base peak (22, 24). Presumably, the CHCl2 groups are split off as positive ions, and the remaining neutral skeleton as well as further fragmentation products cannot be detected. In both cases, the base peak corresponds to the very stable, monochlorosubstituted tropylium cation (m/z 125), which is generally strong in all spectra of bornane derivatives. However, the EIMS spectrum of the endo-isomer shows an intense signal at m/z 244, which is very small in that of the exo-isomer. This ion cluster originates from Retro-Diels-Alder fragmentation (RDA) following the elimination of HCl, whose appearance could be expected already from the strong HCl elimination under ECNI modus. Judging from the fragment C2H3Cl (m/z 62) obtained by the RDA reaction, the elimination of HCl must have taken place between C-5 and C-6. In accordance to this, the neutral fragment should contain C-2 and C-3. This result confirms the rule that HCl elimination will occur preferentially between those vicinal ring carbon atoms that are substituted with the highest number of chloro atoms.
FIGURE 4. 1H-NMR spectra of 2-exo,5-endo,6-exo,8c,9b,10a- and 2-endo,5-endo,6-exo,8c,9b,10a-hexachlorobornane. TABLE 1 1H-NMR Data
of 2-exo,5-endo,6-exo,8c,9b,10aand 2-endo,5-endo,6-exo,8c,9b,10a-Hexachlorobornane chemical shifts (ppm), coupling constants (Hz) in parentheses 2-endo
protons
H-2endo H-2exo 4.97 dd H-3endo 2.44 dd H-3exo 2.54 dddd H-4 H-5exo H-6endo H-8a H-8b H-9a H-9c H-10b H-10c
FIGURE 5. Molecular structure of (1S,2R,4R,5R,6R)-2-exo,5-endo,6exo,8c,9b,10a-hexachlorobornane. 1H-NMR Spectroscopic Investigations.
Figure 4 shows the 1H-NMR spectra of the two metabolites. In each case, 12 protons are registered revealing an empirical formula of C10H12Cl6, which is in accordance with the MS data. While the signals are distinctly separated in the case of the endoisomer, six protons overlap between 4.15 and 4.45 ppm in the case of the exo-isomer. Therefore, an definite spectral assignment required two dimensional NMR experiments. COSY spectra established, like NOESY spectra, geminal
2.60 4.58 4.85 3.71 4.43 4.43 4.13 3.60 4.34
dd ddd d dd d dd d d d
(10.7; 4.7) (14.9; 4.7) (14.9; 10.7; 4.5; 2.0) (4.5; 4.5) (4.5; 4.5; 2.0) (4.5) (12.2; 2.2) (12.2) (12.1; 2.2) (12.1) (12.4) (12.4)
2-exo 4.28 dd
(9.0; 4.7)
3.0 dd 2.19 dddd
(15.5; 9.0) (15.5; 4.7; 4.6; 2.1) (4.6; 4.6) (4.6; 4.3; 2.1) (4.3) (12.1; 1.2) (12.1) (12.1; 1.2) (12.1) (11.9) (11.9)
2.68 4.57 3.99 4.27 4.18 4.33 4.23 3.94 4.18
dd ddd d dd d dd d d d
proton pairs and furthermore hydrogen connectivities within the six-membered ring (H-2,3,4,5,6) while NOESY spectra revealed interactions between spatially close exo protons and the protons of the CH2Cl substituents at C-7. The presence of three CH2Cl groups in each metabolite is confirmed by appearance of the respective six chloromethyl protons with the typical geminal coupling constants of ca. 12 Hz. Two of them are spatially close, and longrange couplings of 2.2 Hz correlating protons at 3.71 and 4.43 ppm in the endo-isomer and of 1.2 Hz correlating
VOL. 30, NO. 10, 1996 / ENVIRONMENTAL SCIENCE & TECHNOLOGY
9
2989
FIGURE 6. HRGC/ECD chromatograms of technical toxaphene before (above) and after degradation in soil under anaerobic conditions (below).
protons at 4.27 and 4.33 ppm in the exo-isomer indicate a substitution of a single carbon atom with two CH2Cl groups each. The remaining CH2Cl group displays geminal couplings of 11.9 Hz (exo-isomer: 3.94 and 4.18 ppm) and 12.5 Hz (endo-isomer: 3.60 and 4.34 ppm), respectively. As no other coupling of these protons are observed, the CH2Cl groups must be isolated, indicating a location of two CH2Cl substituents in C-7 and another at a bridgehead position.
2990
9
ENVIRONMENTAL SCIENCE & TECHNOLOGY / VOL. 30, NO. 10, 1996
Of ring protons, six signals each are present (Table 1). As all parent compounds lack chlorine only in the C-3 position, the rather large coupling constants of 14.9 and 15.5 Hz (endo- and exo- isomer), which are characteristic of geminal ring-protons, can belong only to the protons in the C-3 position. Generally, ring protons of bornanes in exo-orientation are shifted to lower δ-values by about 0.4 ppm as compared to those in endo-orientation (18).
Besides, according to Karplus, the coupling constants of vicinal protons are small for a dihedral angle of Φ ≈ 90° and large for Φ ) 0° or 180° and, in the last case, larger for 180° than for 0°. H-2endo (4.28 ppm) interacts with H-3endo with a vicinal cis-coupling constant of 9.0 Hz and with H-3exo with a vicinal trans-coupling of 4.7 Hz, whereas the constants are 4.7 Hz for the H-2exo (4.97 ppm) interaction with H-3endo and 10.7 Hz for that with H-3endo. Similar relations have been found with other bornane derivatives (22, 23). As for the protons H-4 and H-5exo, the δ-values are almost the same for both isomers, while there is a significant difference between the δ-values of H-6endo. X-ray Analysis. The structure of the exo-isomer could be confirmed by X-ray analysis too. Figure 5 shows the molecular structure (1S,2R,4R,5R,6R)-2-exo,5-endo,6-exo, 8c,9b,10a-hexachlorobornane. The crystallographic data are summarized as follows: C10H12Cl6, formula wt ) 444.90, monoclinic space group Cc, a ) 823.5(5) pm, b ) 1277.1(8) pm, c ) 1276.7(7) pm, R ) 90°, β ) 93.22(5)°, γ ) 90°, z ) 4, density (calculated) 1.69 g cm-3. One important result of the X-ray analysis was that the structure originated from only one enantiomer of the chiral hexachlorobornane. The absolute structure of this enantiomer could be settled. Unfortunately, the isolated amount was too small for chiroptic investigations, and GC separation with chiral columns is still going on. Therefore, whether enantioselective degradation has taken place in addition to the stereoselective one cannot be decided at present. Enantioselective degradation has been demonstrated for several chiral organochloro compounds (25-27), whereas the loss of one enantiomer by total degradation seems rather improbable; until now, only one case has been reported (28). Nevertheless, it may be that a separation occurred during crystallization as has been observed in rare cases (29). Palmer et al. (30) also reported separation of chiral 2,2,5-endo,6-exo,8,9,10-heptachlorobornane (Tox B) into its antipodes during crystallization. Perhaps this unusual process is more frequent with chiral chlorobornanes. This can be settled only by additional X-ray investigations. All these results show the geminal dichloro group in the C-2 position of the six-membered ring of chlorobornanes to be the most labile under anaerobic conditions. Therefore, all toxaphene components possessing this group should be rapidly transformed in anaerobic soils. The same seems to be true for other experimental conditions, as has been found with Parlar 32 (12). During photodegradation, too, chlorine loss takes place exactly from the geminal dichloro group in C-2 position (31, 32). As toxaphene is synthesized by photoinduced chlorination of camphene, preferentially under the formation of a geminal dichloro group in the 2-position as the primary step, a high percentage of components containing this group should be produced. This could explain the low stability of higher chlorinated toxaphene congeners, which can be derived from the shift of the GC peak pattern to shorter retention times after anaerobic degradation, as has been observed by several investigators. Geminal dichloro groups in other positions, being labile also, obviously contribute to this effect. The common dead-end-metabolite of all pure parent congeners (2-exo,5-endo,6-exo,8c,9b,10a-hexachlorobornane) was formed also after 6 months of degradation of technical toxaphene. The partial degradation of the technical mixture under anaerobic conditions results in a characteristic shift of the GC peak pattern to shorter
retention times. During the first 2 months, no significant reduction in peak number could be observed, only after ca. 4 months the peak pattern gradually became more simple together with an accumulation of certain degradation products. After 6 months, finally, only few products could be detected (Figure 6), with 2-exo,5-endo,6-exo,8c,9b,10ahexachlorobornane as the major one, whereas the portion of 2-endo,5 endo,6-exo,8c,9b,10a-hexachlorobornane was very small and could be identified only by comparison of GC/ECD retention times. Analogous to the single congeners, degradation of the higher chlorinated components preferentially leads to the exo-isomer. As in technical toxaphene, octa- and nonachlorobornanes dominate; this degradation path prevails here as well. In sediments from toxaphene-treated lakes, hexachlorobornanes and heptachloro compounds were also found to be the dominant transformation products (33), although none of the metabolites could be isolated and have its structure determined. The situation differed in marine mammals where mainly an octa- and a nonachlorobornane derivative have been found (34, 35). Here, the majority of components must have been either totally degraded or eliminated, while only these highly chlorinated, persistent compounds could accumulate (36). Contrary to this, liver oil samples contained small amounts of the same hexachlorobornanes formed by successive dechlorination (37), indicating the occurrence of reductive dechlorination in mammals also. As has been shown, polychlorinated bornane derivatives, which amount to 75% of technical toxaphene, are partially dechlorinated under anaerobic conditions, mainly by reductive dechlorination. Where the loss of chlorine takes place depends on the individual substitution of the congener. Generally, all geminal dichloro groups are labile, but most of all those at the C-2 atom, as the first reaction step involves the elimination of chlorine exactly in this position. The higher the total number of chlorine, the higher is the degradation rate. The same mechanism probably applies to technical toxaphene. Here also chlorine from geminal ring dichloro groups is preferentially eliminated, followed by reductive dechlorination of other dichloro groups. The continuous decrease in chlorine content can be seen in the GC peak pattern, whereas the change in intensity of the CHCI2+ ion peak (m/z 83) in the EIMS spectra shows the loss of one chlorine atom each with successive reduction of the dichloro groups. The favored formation of 2-exo,5-endo,6-exo,8c,9b,10a-hexachlorobornane from technical toxaphene suggests that most of the bornane derivatives in technical toxaphene possess the same chloro substitution at the ring, thus being precursors for this final metabolite.
Literature Cited (1) Saleh, M. A. Rev. Environ. Contam. Toxicol. 1991, 118, 1-85. (2) Korte, F.; Scheunert, I.; Parlar, H. Pure Appl. Chem. 1979, 51, 1583-1601. (3) Parlar, H. Chem. Tech. Lab. 1991, 39, 26-35. (4) Bidleman, T. F.; Zaranski, M. T.; Walla, M. D. In Toxic Contamination in Large Lakes, Vol. I; Schmidtke, N. W., Ed.; Lewis Publishers, Chelsea, MI, 1998; pp 257-284. (5) Nash, R. G.; Woolson, E. A. Science 1967, 157, 924-927. (6) Menzie, C. M. Annu. Rev. Entomol. 1972, 17, 199. (7) Mohn, W. W.; Tiedje, J. M. Microbiol. Rev. 1992, 56, 482-507. (8) Vogel, T. M.; Criddle, C. S.; McCarty, P. L. Environ. Sci. Technol. 1987, 21, 722-736.
VOL. 30, NO. 10, 1996 / ENVIRONMENTAL SCIENCE & TECHNOLOGY
9
2991
(9) Esaac, E. G.; Matsumura, F. Pharmacol. Ther. 1980, 9, 1-26. (10) Khalifa, S.; Holmstead, R. L.; Casida, J. C. J. Agric. Food Chem. 1976, 24, 277-282. (11) Williams, R. R.; Bidleman, T. F. J. Agric. Food Chem. 1978, 26, 280-282. (12) Saleh, M. A.; Casida, J. C. J. Agric. Food Chem. 1978, 26, 593-590. (13) Parr, J. F.; Smith, S. Soil Sci. 1976, 121, 52-57. (14) Seiber, J. N.; Madden, C. S.; McChesney, M. M.; Winterlin, W. L. J. Agric. Food Chem. 1979, 27, 284-290. (15) Murthy, N. B. K.; Lusby, W. L.; Oliver, J. E.; Kearney, P. C. J. Nucl. Agric. Biol. 1984, 13, 16-17. (16) Mirsatari, S. G.; McChesney, M. M.; Craigmill, A. C.; Winterlin, W. L.; Seiber, J. N. J. Environ. Sci. Health 1987, B22, 663-690. (17) Hainzl, D.; Burhenne, J.; Parlar, H. Chemosphere 1993, 27, 18571863. (18) Hainzl, D.; Burhenne, J.; Barlas, H.; Parlar, H. Fresenius J. Anal. Chem. 1995, 351, 271-285. (19) Kallenborn, R.; Oehme, M.; Vetter, W.; Parlar, H. Chemosphere 1994, 28, 89-98. (20) Kuhn, E. P.; Suflita, J. M. In Reactions and Movement of Organic Chemicals in Soils; Sawhney, B. L., Brown, K., Eds.; SSSA Special Publication No. 22; SSSA: Madison, WI, 1989; pp 111-180. (21) Swackhamer, D. L.; Charles, M. J.; Hites, R. A. Anal. Chem. 1987, 59, 913-917. (22) Hainzl, D. Thesis, University of Kassel, GFR, 1994. (23) Burhenne, J. Thesis, University of Kassel, GFR, 1993. (24) Fingerling, G. M. Thesis, University of Kassel, GFR, 1995.
2992
9
ENVIRONMENTAL SCIENCE & TECHNOLOGY / VOL. 30, NO. 10, 1996
(25) Hu ¨ hnerfuss, H.; Faller, J.; Kallenborn, R.; Ko¨nig, W. A.; Ludwig, P.; Pfaffenberger, B.; Oehme, M.; Rimkus, G. Chirality 1993, 5, 393-399. (26) Buser, H.-R.; Mu ¨ ller, M. D. Environ. Sci. Technol. 1995, 29, 664672. (27) Falconer, R. L.; Bidleman, T. F.; Gregor, D. J.; Semkin, R.; Teixeira, C. Environ. Sci. Technol. 1995, 29, 1297-1320. (28) Ludwig, P.; Gunkel, W.; Hu ¨ hnerfuss, H. Chemosphere 1992, 24, 1423-1429. (29) Secor, R. M. Chem. Rev. 1963, 63, 297-309. (30) Palmer, K. J.; Wong, R. Y.; Lundin, R. E.; Khalifa, S.; Casida, J. E. J. Am. Chem. Soc. 1975, 97, 408-413. (31) Parlar, H.; Korte, F. Chemosphere 1983, 12, 927-934. (32) Parlar, H. Chemosphere 1988, 17, 2141-2150. (33) Miskimmin, B. M.; Muir, D. C. G.; Schindler, D. W.; Stern, G. A.; Grift, N. P. Environ. Sci. Technol. 1995, 29, 2490-2495. (34) Bidleman, T. F.; Walla, M. D.; Muir. D. C. G.; Stern. G. A. Environ. Sci. Technol. 1993, 12, 701-709. (35) Stern, G. A.; Muir, D. C. G.; Ford, C. A.; Grift, N. P.; Dewailly, E.; Bidleman, T. F.; Walla, M. D. Environ. Sci. Technol. 1992, 26, 1838-1840. (36) Muir, D. C. G.; de Boer, J. Chemosphere 1993, 27, 1827-1834. (37) Fingerling, G. M. University of Kassel, unpublished results.
Received for review December 29, 1995. Accepted May 28, 1996.X ES950957F X
Abstract published in Advance ACS Abstracts, August 1, 1996.
