Document 1Qene49VYLMJ46pe5wBr0BOVa
j.*hi,
carbon tctrachioridc,495(1969). n brains and bodies of (1966). Jmium, and lead. Ann.
bilization of DDT by
lobcnzcne in Japanese production, and tissue
and gross development
1).
20,1974
mr s >
1975
LABORATORY MODEL ECOSYSTEM STUDIES OF THE DEGRADATION AND FATE OF RADIOLABELED TRI-, TETRA-, AND PENTACIILOROBIPHENYL COMPARED WITH DDE
'
Robert l. Metcalf, James r. Sanborn, ro Yung lu and DONALD NYE
Department of Entomology and Environmental Studies Institute, University of Illinois
and Illinois Natural History Survey, Urbana-Champaign Urbana, Illinois 61801
tt 1
.
Radiolabeled tri-, tetra-, and pcnlachlorobiphenyls (PCB)and DDE were studied in a laboratory model ecosystem for degradation pathways, and biomagnification in alga, snail, mosquito, and fish. Trichlorobipheny! was degraded in all the organ isms of the model ecosystem much more rapidly than tetrachloro- and pentachlorobiphenyl. Pcntachlorobiphcnyl was approximately as persistent as DDE. There was a linear relationship between lipid/water partition and ecological magni fication and between water solubility and ecological magnification. No evidence of conversion of DDE to PCB was detected.
The laboratory model ecosvslem Dreviousiv described (Metcall et al. 1971) has been employed for the estimation of the environmental fate of DDT and a number of its analogues (Kapoor et al. 1970, 1972, 1973) and for study of aldrin, dieldrin, endrin, mirex, lindane, and hexachlorobenzcnc (Metcalf el al. 1973a). The methodology de veloped has yielded useful information about (1) tire degradation pathways of the various xenobiotics, (2) the toxic effects of the compounds and their degradation products, (3) their comparative bionragnification and food chain concentration, and (4) their comparative biodegradability; all in organisms of five phyla linked in several food drains. This information has proved of value in characterizing the potential environ mental pollutant effects of candidate insecticides (Kapoor etal. 1973, Coats cl al. 1973) and of plasticizers (Metcalf el al. 1973b). In this paper wc report the application of these techniques to a belter understanding of tire comparative environmental properties of trichloro-, tetrachloro-, and pcntaclilorobiplienyl (I'Cll's), and of dichlorodjphcnyldichtorocthylcno (DDE) the persistent DDT degradation product.
Methods and materials
The laboratory model ecosystem evaluation was carried out in a small glass aquarium with a sloping terrestrial-aquatic interface of pure white sand exactly as previously de scribed (Metcalf cl al. 1971). The **C radio-labeled compounds were applied quantita tively from acetone solution at 5.0 mg (or ca. one kg per ha) to Sorghum vulgare seedlings grown in tire terrestrial portion. Tire treated leaves were consumed by fourth instar salt
Archive! of Environment*! Conummaikm
end Toxicology, Vol. 3. No. 2. 1975 O 1975 by Springer-Vcriag New York Inc.
151
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152 R. L. Metcalf rr o/.
marsh caterpillar larvae Estigmene acrca, whose activities and fecal products contaminated the aquatic portion of the system.
The radiolabeled products were transferred through several food chains, e.g., alga (Oedogonium cardiacum) -* snail (Physa)\ plankton -* water flea (Daphnia magna) -* mosquito (Culex pipiens quinqucfascialus) -* fish (Gambusia affmis). After 33 days in an environmental chamber at 26C and a 12-lir photoperiod at 5,000 foot candles simulated daylight, the organisms were extracted with acetonitrile and the 14C-radiolabeled com pounds evaluated by TLC on silica gel containing fluorescent marker (E. Merck GF-254) and radioautography on no-screen x-ray film. Liquid scintillation counting of the individual components was done in cocktail D (5 g PPO and 100 g naphthalene in dioxane to make one liter) and counts were corrected to dpm by using channels ratio quenching correction. The residues, after extraction, were counted by total combustion to ,4C02 by the Schbnigcr oxygen flask technique (Kelly er al. 1961) to determine the unextractablc radioactivity. Whenever possible, the identity of individual components on the TLC plates was determined by cochromatography with known standards and by extraction and mass spectrometry.
Radiolabeled compounds. The individual 14C-labeled PCB's were obtained from Mallinkrodt.St. Louis, Missouri. They were: 2,5,2'-trichIorobiphenyI (2,5-dichlorophenylring-UL-l4C), 9.91 mCi per mmole with>98% radiopurity and 41.5%Cl, and a principal constituent of Aroclor 1242 (Webb and McCall 1972); 2,5,2',5,-letrachlorobiphenyl (ring-UL-14C),9.87 mCi per mmole with > 98% radiopurity and 48.7% Cl, and a principal constituent of Aroclor 1248 (Webb and McCall 1972); and 2,4,5,2',5'-pcntacIilorobipher.y! (2,,5,-di':h,Arrvphf*nyl-nno.lfl,Mf;'). 9.87 mCi per mmole with ? 9B'/o raaiopurity and 54.4% Cl, a principal constituent of Aroclor 1254 (Webb and McCall 1972).
4C labeled 2,2-Ws-(p-chlorophenyl)-l ,1-dichlorocthylene (DDE) was prepared from ,4C-ring-UL p,p-DDT obtained from the Radiochemical Centre, Amersham, England, 5.48 mCi per mmole, by dehydrochlorinating with 1.0 M alcoholic KOH, and purifying on a silicic acid column with hexane elution to 99% radiopurity.
Results PCD'*. The movement of l4C radioactivity fiom Sorghum plants into the water phase of the model ecosystem is shown in Figuic 1. All thicv chloiinatcd biphenyls readied a maximum concentration in water at about seven days after treatment and (he levels of contamination declined as the LCD's were taken up by the organisms of the system. I he levels of the chloiinatcd hiphcnyls in (lie water phase (Table I) wete in the ppl> range, below the water solubility of the compounds as determined by radiotracer technique (Table II).
Radioautographs of the extracts from the components of the model system after TLC are shown in Figure 2. The data in Table 1 represent the quantitative distribution of the l*C in the spots on the TLC plates. The results for the three PCB's are also expressed in
DSW 029385
STLCOPCB4013347
products contaminated
food chains, e.g., alga i (Daphnia magna) -* b). After 33 days in an foot candles simulated *4C-radio!abeied comker (E. Merck CE-254) ition counting of the naphthalene in dioxane bannels ratio quenching combustion to '"'COj etermine the unextractjal components on the tom standards and by
t were obtained from tyi (2,5-dichlorophenyl13% Cl, and a principal 'y-tetrachlorobiphcnyl i8.7% Cl, and a principal ;* rr VrC"' --v*----------- Die wttn > y&7' radio*ebb and McCall 1972).
DE) was prepared from re, Amersham, England, alic KOH, and purifying
ints into the water phase tied biphenyls readied a atment and the levels of iiisms of the system. The ) were in the ppb range,
radiotracer technique
! model system after TLC Hative distribution of the CB's arc also expressed in
iu'imwi Hi I
Degradation of Polychlorinated Biphenyls Compared with DDE
153
Tabic 11 in terms of ecological magnification (E.M.) (ppm in organism/ppm in water) and of biodcgradability index (B.l.) (ppm polar degradation products/ppm nonpolar products). The E.M. values for the parent compounds increased substantially with the number of chlorine atoms, from trichlorobiphcnyl (41.5% Cl) to tctracldorobiphcnyl (48.7% Cl) to pentachlorobiphcnyl (54.4% Cl). Conversely the B.l. values decreased with increasing degree of chlorine. This consistent and regular behavior gives added confidence that these parameters are ecologically significant (see Kapoor et at. 1973) and must be a function of the number of C-H bonds available for hydroxylation by microsomal oxida
tions in the various organisms. The spots of low Rf value (0.02-0.06), Figure 2, arc presumably hydroxylated PCB compounds and the polar radioactivity (Rf 0.0) is thought to consist of conjugates of these compounds. Wallnofere/n/. (1973) have found 4-ch!oro4'-hydroxybiphenyl as a metabolite of 4-chlorobiphcnyl from soil fungus, Rhizopus japonicus. Yoshimura and Yammamoto (1973) have reported the 5-hydroxylatcd deriva
tive as the major and the 3-hydroxylated derivative as the minor excretion product of 2,4,3',4'-tetraclilorobiphenyl in the rat. Hutzinger et al. (1972) have shown that rat and
pigeon could hydroxylate 2,5,2',5'-teUach)orobiphenyl but they could not detect hydroxylated metabolites in brook trout. However, the amounts of polar material in Gambusia (Figure 2, Table I) suggest that tliis fish is able to slowly hydroxylate this tetrachlorobiphenyl.
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OSW 029386
STLCOPCB4013348
Table 1. Distribution of chlorinated biphenyls and their degradation products in the model ecosystem
11,0
Chlorinated biphenyl equivalents (ppm)
Ocdogonium (alga)
Physa (snail)
Culex
Cambusia
(mosquito)
(fish)
I. 2,5,2'-trichlorobiphenyl total 1 4C
Unknown 1 (Rr 0.66)
trichiorobiplienyl (Rf 0.56)
Unknown 11 (Rf 0.23)'
Unknown HI (Rf 0.10)
Unknown IV (Rf 0.06)
Unknown V (Rf 0.04)
Unknown VI (Rf 0.03)
Polar (Rf 0.0) Unextractable
0.03845
0.00015 0.00020 0.00005
0.00055 0.00040 0.00040 0.02265 0.01405
23.2155 15.9575
1.4630 0.0520
_ 0.0685 0.5185 5.1560
31.2015
18.9720 1.1590 0.6480
0.9735 0.5460 0.2205 0.4410 3.9315 4.3100
2.7030
1.1995
0.1630 + _
_ _ _
0.4795 0.8610
3.2055
0.2085 1.2800 0.1595
--
-- __
_
0.9985 0.5590
11. 2,512',S'-tetrachloro biphenyl total 14C
trnrhlotobiphenyi /i>. n afial
Unknown I (Rr 0.23)
Unknown 11 (Rf 0.04)
Polar (Rf 0.0) Unextractable
0.02065
n nniTO
0.00005
0.00155 0.01225 0.00560
23.6845
21.5975
0.3220
0.1030 0.3275 1.3345
53.7465
4 /.j/n
0.7560
0.4360 3.9850 1.2420
14.5335 i *.6745 0.1070
0.9670 0.7850
15.5685 l*T4 . r r\ 0.0890
0.8545 0.3900
III.2,5,2',4',5'-pcnta-
chlorobiphenyl
total14C pentachloro-
biplicnyl
(Rf 0.55)
Unknown I
(Rf 0.46)
Unknown II
(Rf 0.39)
Unknown HI
(Rf 0.21)
Unknown IV
(Rf 0.04)
.
Unknown V
(Rf 0.02)
Polar (Rf 0.0)
Unextractable
0.04340
0.00985
0.00020 0.00015 0.00030 0.00385 0.02055 0.00850
62.4660
53.8440 0.6850 0.5080 0.1425 _
0.2570 1.6265 5.4330
TLC with hexane (Skellysolve B,bp 60-68C).
633.0165 181.4565 127.6945
587.3545 170.8480
8.6210
2.4070
2.2490
1.3195
1.9365
0.5000
7.4965 16.5550 8.3040
1.0520
_
_ 2.6745 3.1555
1 19.7060
2.5380
0.5810
0.3285 _
0.7450 2.3610 1.4350
154
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Table n. Ecological magnificatior. {EM.) and Biodegradability index (B.l.) ofPCB's and DDE compared with water solubility and partition coefficient
H20 solubility
Chemical
(ppb)
tri-CI-PCB '
16
tetra-Cl-PCB
16
penta-Cl-PCB
19
DDE
. 1J
Partition coefficient
7,803 8,126
16,037 18,893
Ecological magnification (E.M.)
Aiga
Snail Mosquito Fish
7,315
5,795
815 6,400
17,997 39,439 10,562 11,863
5,464
59,629
17,345
12,152
11,251 36,342 59,390 12,037
BiodegMdability index (B.l.)
Alga
Snail Mosquito Fish
0.30
0.17
0.3 5
0.60
0.015
0.082
0.076
0.060
0.029
0.027
0.0134 0.019
0.069
0.049
0.033
0.050
----- ------ /i- "'NntoUMfuo&ji
156 R. L. Metcalf et al.
The pentachlorobipheny! with B.I. values of 0.019 to 0.027 in fish and snail is very comparable in mode! ecosystem behavior to DDT, B.I. 0.015 and 0.044 (Kapoor et al. 1973) and this suggests that the two compounds should behave similarly in the environ ment (Risebrough et al. 1968). Properties of the tctrachlorobiphenyl were similar to those of the pcntachlorobiphcnyl (Figure 2) but the trichlorobiphenyl was much more degradable. A prominent degradative product (Rf 0.66) is stored in alga, snail, and mosquito larva in much greater quantities than the parent compound. This compound is less polar (higher Rf) in the hexane solvent than any oT the three PCB isomers. As shown in Table 1 it is magnified to very high values, 106.382X in alga and 126.480X in snail, is stored in lipids, and is highly persistent. Its presence in high amounts in alga and in the snail and mosquito which are alga feeders suggests that it might be formed by photo chemical processes during photosynthesis in the alga. This compound forms slowly and no traces of it were visible In three-day uptake studies of trichlorobiphenyl by alga, snail, daphnia, mosquito or fish (Metcalf and Lu 1973) although it appeared in alga in
Cl * Cl
Cl
Cl
*
Cl
Cl et
Fig. 2A. Radioaulogram of TLCplate con taining extracts of water and organisms treated with 2,5,2,-trichlorobiphenyl. A (alga), F (fish), M (mosquito larva), S (snail) and STD ( 4C-radiolabclcd com pound).
Fig. 2B. Radioautograni of TLC plate con taining extracts of water and organisms treated with 2,5,2',5,-tctrachlorohiplH-nyl. A (alga), F (fish), M (mosquito larva), S
(snail) and STD (* 4C-radioiabclcd com pound).
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029389
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STLCOPCB4013351
fish and snail is very 0.044 (Kapoor et al. .rtilarly in the environhenyl were similar to henyl was much more led in alga, snail, snd
[and. This compound is *CB isomers. As shown id 126,4BOX in snail, is junts in alga and in the
( be formed by photoaund forms slowly and
jhlorobipltcnyl by alga, a it appeared in alga in
' ; ! I ]
j i ; j
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Cl
Degradation of Polychlorinated Biphenyls Compared with DDE
157
14-day studies. To data wc have been unsuccessful in identifying the unknown by mass spectrometry.
DDE. This compound has been implicated as a possible environmental precursor of PCB isomers through pholoxidation reactions involving radical rearrangements to 3,6-dichlorofluorcnonc intermediates (Plimmer et al. 1970, Pcakall and Lincer 1970, Moilanen and Crosby 1973). Although such rearrangements could logically produce, 4,4'-dichlorobiphenyl, it is difficult to see how trichloro- and tetrachlorobiphcnyls could be formed as suggested by Mauglt (1973). Moreover, Kcrncr et al. (1972) could delect only ius-(p-chlorophenyl)-chloiocthylenc (DDMU) after ultraviolet irradiation of DDE. Because of the ecological importance of these possible rearrangements wc have reinvesti gated the behavior of DDE in the model ecosystem (Metcalf et al. 1971) to determine if any PCB-Iike products could be formed under the simulated daylight of the model ecosystem (5000 foot candles) in an environmental chamber. The radioautograph show-
Cl
*
Cl
Ct Ct
Cl
%
hyil.
llograttt of Tl.Cplate con . of water and organisms ,2 ,5'-tetrachlorobiphenyl. h), M (mosquito iarva), S 0 f,4C-radiolabeled com-
A F M STD S H20 H20
hyd.
Fig. 2C. Rndionutogrmn of TLC plate con taining extracts of water and organisms treated with 2,4,5,2,,5,-pentachlorobiphenyl. A (alga), F (fish), M (mosquito larva), S (snail) and STD (14C-radiolabcled compound).
Fig. 2D. Radioautogram of Tl.C plate con taining extracts of water and organisms treated with DDE. A (alga), F (fish), M (mosquito latva), S (snail) and STD (* 4C-radiolabcled compound).
............... rrrrvr*-*"' 'm.WWHIWWMIlt mw
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STLCOPCB4013352
---------- du
158 R. L. Metcalf n al.
ing the fate of pure DDE is presented in Figure 2. When the extracts of water and organisms were developed on TLC plates with Skcltysolvc B (hexane fraction) there was no trace of any 1 4C labeled compounds with Rr values between 0.05 and 0.47 (DDE) or of any less polar materials with higher Rr values. Under these conditions, as shown in
Figure 2, trichlorobiphcnyl has Rf 0.43, tetrachlorobiphcnyi Rf 0.50, and pentachlorobiplienyl Rf 0.53. Detection levels with the techniques used arc approximately 0.1 tig
(e.g., spot at alga origin in DDE, Figure 2) or about 0.00002% of the total 1 aC applied. Thus under the model ecosystem conditions thcic is no evidence of formation of PCB isomers from DDE.
, DDE is extremely stable in the tissues of the living organisms of the model ecosystem and is stored as approximately 92, 93, 95, and 97% of the total 14C in snail, alga, fish, and mosquito larva. The percent of unextractable 14C in these organisms ranged from 0.10 to 0.93 (Table 111). The B.l. value for DDE in fish was 0.049 and the E.M. value 12,037 (compared with 0.032 and 27,358 found by Metcalf et al. (1971). From these values it is apparent that DDE is a more stable environmental pollutant than 2,4,5,2',5'pentachlorobiphenyl (Table 1) which was stored in the organisms at 86 to 94% of the total radioactivity, with from 1.12 to 8.67% of unextractable 14C, and had a B.l. of 0.019 and an E.M. of 12,152 in fish.
It is of interest that Sodergren (1973) using a model aquatic ecosystem found no major metabolic changes in DDE occurring in passage through a food chain into fish, although similar experiments with a polychlorinated biphenyl mixture (Clophcn A) showed that the lower fractions with low chlorine content were degraded when trans ported through the food chain, as was 2,5,2-trichlorobiphenyl in out experiments. How ever, ir. go; studies (Figure 2, T?b!" ril) thp water phase rontained several nolar radio-
Table III. Distribution of DDE and degradation products ' in the model ecosystem
H20
DDF equivalents (ppm)
Oedogonium J'hysa
(alga)
(snail)
Culex (mosquito)
Gambusia (fish)
Total >4C
0.00384
DDE (Rf 0.49")
0.00062
Unknown 1 (Rf 0.05) 0.00009
l'olar (Rf 0.0)
0.00223
Unextractable
0.0009
7.4720 6.9759 0.4881 0.0080
38.1958 22.5325
0.8035 1.1612 0.3616
24.8588 36.8223
1.2448 0.1087
7.8653 7.4632
0.3746 0.027S
TLC with hexane (Skellysolve B, bp 60-68C).
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DSW 029391
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STLCOPCB4013353
xtracts of wafer and te fraction) there was >5 and 0.47 (DDE) or nditions, as shown in 0, and pcntachlorobiipproximatciy 0.1 ng the total 14C applied, of formation' of PCB
f the model ecosystem i4C in snail, alga, fish, organisms ranged from 49 and the E.M. value el. (1971). From these liutant than 2,4,5,2',5'n$ at 86 to 94% of the |4C, and had a B.I. of
ic ecosystem found no t food chain into fish, I mixture (Clophen A) t degraded when trans1 our experiments. How-
several polar radio-
products
ppm)
" Culex (mosquito)
Oambu.de
(fish)
24.R5B8 36.8223
7.8653 7.4632
1.2448 0.1087
0.3746 0.0275
Degradation of Polychlorinated Biphenyls Compared with DDE
159
labeled degradation products. These were resolved on silica gel into at least 11 distinct compounds using a solvent of bcn7.ene:dioxnne:acetic acid (90:30:1) and we arc presently attempting to identify the pathway of DDE degradation in the environment.
Biomass Recovery. To determine the relative availability of the various organisms of the model ecosystem as reservoirs for the bioaccumulation of the micropollutants studied, the total amounts of ,4C-labeled products recovered from tire principal organisms of the model ecosystems treated with Iri-, tetra-, and pentachloro-PCB's, and DDE were evaluated as shown in Table IV. The evaluations were made on the basis of total re covery of the applied pollutant, recovery of the maximum amount of pollutant in water (Figure 1) for each of the four principal organisms, aJga, snail, mosquito, and fish; and biomass recovery (four organisms) of the total amount of pollutant lost from water (Figure 1). The figures of Table IV are very revealing in terms of the biodegradability of the various compounds. The highest recoveries of the 14C lost from solution were ob tained from the organisms with DDE, 65.8%, and pentachlorobiphcnyl, 57.2% With letrachlorobiphenyl recoveries of 8.7% were still substantial, but with triclilorobiphenyl (recovery 0.45%) the compound was nearly completely degraded and excreted.
Table IV. Biomass recovery of chlorinated biphenyls, and DDE from organisms of model ecosystem
' % Recovery
Alga
Snail
Mosquito
Fish
trtchiurobtphenyi
,4C in solution
0.18
0.015
total 4C
JD.033
0.0028
' (biomass) of ,4C lost from solution ---- 0.45
0.0017 0.00032
' tetrach lorob iph enyl
,4C in solution
3.33
1.04
0.23
total '4C
0.28
0.088
0.019
(biomass) of * 4C lost from solution ---- 8.7
pen tachlorobiph enyl
4Cin solution
4.57
19.0
2.32
total '4C
0.74
3.06
0.37
(biomass) of 14C lost from solution -- -57.2
,4C in solution
22.4
4.03
total 4C
0.24
0.044
(biomass) of 14 C lost from solution ---65.8
DDE 2.25 0.055
0.12 0.021
1.91 0.16
11.8 1.90
20.2 0.22
ppwVUili. ,'W' n/imyi
DSW 029392
STLCOPCB4013354
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Th^iriiTiii I faft J
160 R. L. Metcalf a at.
Degradation in Salt Marsh Caterpillar. This animal was chosen, after considerable study, as tire dispersing agent for the model ecosystem because it was able to ingest a large variety of organic compounds without apparent injury (Metcalf er al. 1973). The effects of passage of tire PCB isomers through the insect are of interest as representing the first stage in the biodegradation of these compounds. Figure 3 shows radio autographs of TLC plates of extracts of feces and body homogenates from larvae feeding on about 30 pg of > 4C PCB incorporated in a synthetic diet. Figure 3 and the quantitative
tri-CI
totra-CI
pcnta-CI
Fig. 3. Radioautogram of TLC plate containing extracts of bodies and feces of salt marsh caterpillar larvae fed ,4C-!abcled 2,5,2 -tri-, 2,5,2`,5'-tetra-1 and 2,4,5,2',5'-pentach)orobiphenyls. B (body homogenate), and F (fecal excreta).
vU*a' K.'t
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STLCOPCB4013355
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in, after considerable t was able to ingest a
loir etol. 1973). The jutrest as representing
jfgurc 3 shows radio'tes from larvae feeding
3 and the quantitative
1 j
j j
, j
.t*Ct IPJ^W
4
ii \- 5
MXlics and feces of salt marsh ,and J^.S^.S'-pcntachioro-
Degradation of Polychlorinated Biphenyls Compared with DDE
161
evaluation of the radioactivity in the various spots shown in Table V demonstrate con clusively the mucli greater degradability of the trichJorobiphcnyl over the tctrachlorobiphenyl and pcntachlorobiphcnyl. With the trichloro-compound the caterpillar feces con tained 91% of the recovered 14C, with the remainder in the body homogenate, while with the telrachloro- and pentacldorobiphcnyis, tiie feces contained 21% and 24% of the radioactivity. The unknown (Rf 0.05) found in fcccs after tricldorobiphcnyi is probably the principal hydroxyiated degradation product leading to the very large amount of polar radioactivity. Whereas only low levels of triclilorobiphenyi were retained in the salt marsh caterpillar body, with tctrachloro- and penlachlorobiphenyl the major portion of 14C was retained in the insect body.
Tabic V. Metabolism of ,AC radiolabeled compounds by salt marsh caterpillar*
Body
Feces
A. 2,5,2'-trichlorobiphenyl total l4C(%) Unknown 1 (Rf 0.53*) trichlorobiphenyl (Rf 0.43) Unknown 11 (Rf 0.31) Unknown 111 (Rf 0.13) Unknown IV (Rr 0.05) Unknown V (Rf 0.02) Polar (Rf 0.0)
B. 2,5,2 ,5 -tctracftiorooipiienyi tuiol : 'C (%)
tetrachlorobiphenyl (Rf 0.50*)
Unknown 1 (Rf 0.41)
Unknown 11 (Rf 0.05)
.
Unknown HI (Rf 0.03)
Polar (R( 0.0)
C. 2,5,2',4',5,-pentachiorobiphenyl total ,4C(%) pcntachlorobiphcnyl (Rf 0.S3*) Unknown I (Rf 0.46) Unknown 11 (Rf 0.39) Unknown HI (Rf 0.03) Polar (It, 0.0)
D. 2,2-6ri-(/r-clilorophcnyl)-l,l-dichlorocthylcnc (DDE)
total 14C (%)
DDE (Rf 0.49*)
.
Polar (Rf 0.0)
TLC with hexane (Skeliysolve B, bp 60-68C).
8.66 0.64 5.84 0.27 0.05 ' 0.10 0.11 1.65
78.68 75.60
0.99 0.13 trace 1.96
75.86 74.00
0.74 0.62 0.08 0.42
80.59 76.88
3.71
91.34 8.91 0.37 0.12 4.67 0.92
76.35
71 32 ID.UO
1.36 0.20 4.64
24.14 20.70
0.74 0.56 0.08 2.06
19.41 19.37 0.04
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162 R. L. Metcalf el al.
DDE passed through the salt marsh caterpillar largely unchanged with 81% of the total radioactivity recovered retained in the body homogenate and 19% in the fecal excreta (Table V).
Ecological Magnification. The uptake and concentration of organic compounds by living organisms either directly or through food chains appears to be a function of two important factors, their high lipid solubility and low water solubility, /.<?., a large lipid/ water partition coefficient; and their resistance to degradation by enzymatic processes, especially the multifunction oxidase enzymes (Metcalf et al. 1973). Hamclink et al. (1971) have suggested that the water Insolubility of highly lipid-soluble compounds pro vides the driving force in producing lipid storage, through a series of simple partitionings from water to lipids. We have correlated the E.M. values for the FCB's and DDE from the fish of the model ecosystems with both water solubility (Table U) in Figure 4, and with the octanol/water partition value (Table 11) in Figure 5. Because the values for the BCD's and DDE fall closely together, the relationships have been extended using values for aniline, anisolc, benzoic acid, chlorobenzene, and nitrobenzene taken from other model ecosystem studies (Lu and Metcalf 1974). For the limited number of compounds Included, the correlation between physical properties arid biomagnification is excellent. The regression equation for log water solubility vs log E.M. (Figure 4) was:
y = 4.4806-0.4732 X :
n = 9,
r=-0.9677
1 c
Fig. 4. Plot of log E.M. (ecological magnification) for fish vs. log water solubility (ppb).
1 F C R G
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anged with 81% of the e and 19% in the fecal
organic compounds by to be a function of two bliity, l.e.. a large lipid/ by enzymatic processes, 1973). Hamclink et al. soluble compounds pro:s of simple partitionings >CB's and DDE from the H) in Figure 4, and with ause the values for the n extended using values lzene taken from other J number of compounds ignification is excellent, e 4) was:
>677
I .
Degradation of Polychlorinated Biphenyls Compared with DDIZ
163
Tlic regression equation for log partition coefficient (Hansch's tt) vs. log E.M. (Figure 5)
y = -0.7504 + 1.1587 X :
n = 9,
r = 0.9771
Thus for the organic compounds studied, the properties of water solubility and octanol/watcr partition coefficient appear to provide a realistic estimate of the biological magnification found in living organisms.
i
>JC Kelli '
aniline 6.0 7.0 8.0
water solubility (ppb).
Fig. 5. Plot of log E.M. (ecological magnification) for fish vs. log octanol/wuter partilion
coefficient.
.
Acknowledgment
This research was supported in part by. research giants from the U. S. Department of Interior, Office of Water Resources Research through the University of Illinois Water Resources Center Project B-050, Illinois; the National Science Foundation Grant GI 39843X,,thc U. S. Environmental Protection Agency Grant R802022 and Grant R800736, and tire Bureau of Veterinary Medicine, Food and Drug Administration, Contract FDA 72-116.
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References
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t
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DSW 029397
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STLCOPCB4013359
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ft VlnfcH-*"--*
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Manuscript received March 18, 1974; accepted May 14, 1974
i.
.
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DSW 029398
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