POLYCHLORINATED

B I P H E N Y L S IN T H E S E D I M E N T S

OF

THE INNER OSLOFJORD

M. I. A B D U L L A H

and O. R I N G S T A D

Marine Chemisto, Section, Institute of Mar#le Biology and Lhnnology, University of Oslo, Oslo, Norway and N.J.

KVESETH

Dept Pharmacology and Toxicology, Veterinary College of Norwa),, Oslo, Norwa)'

(Received September 29, 1981; Revised March 1, 1982)

Abstract. Sediment cores (16)fronl the Inner Oslo0ord were analyzed for PCB's and DDT. Although localized high content of PCB's is observed, the data show even distribution of these compound - a consequence of removal by particulate and dctrital matter and the sedimentation of this material. Significant modification of the profiles of PCB's in the sedimentary column together with fractionation of the PCB's according to their chlorine content arc observed. The extent of these changes is shown to be related to the I+hysico-chcmical conditions in the sediments and hence the extent of biological mediation.

I. Introduction

The unique physical and chemical properties of PCB's render them ideal for a wide range of industrial applications with the inevitable release of these compounds to the environment. Since their discovery as environmental pollutants (Jensen, 1966), numerous studies have demonstrated their widespread occurrence, toxicity and persistence. Three main transport routes to the marine environment were postulated by Nisbet and Sarofim (1972): atmospheric transport, run-off and waste disposal, each being responsible for a certain type of PCB as dictated by their industrial application and mode of disposal. Global transport of PCB's via the atmosphere is demonstrated by their occurrence throughout the world oceans (Nisbet and Sarofim 1972; Harvey and Steinhaur, 1974). Transport to the sediment must be, with the exception of direct waste disposal, by processes confined within the sea. These are mainly assimilation and excretion by the biota, adsorption by particles and the sedimentation of particulate and detrital matter (Hiriazumi et al., 1979, Choi and Chen, 1976; Chiou et al., 1977). While attempts have been made to estimate the rates of transport and the proportions of manufactured PCB's transported to the marine environment (Goldberg, 1975), little is known of the role of marine sediments as sink for PCB's. Although previous work (Bokn et al., 1978) has suggested that Norwegian waters are relatively uncontaminated with PCB's when compared with other areas of Europe, PCB residues have been detected in marine organisms (Bjerk and Brevik, 1980). However, no information exists for the presence of PCB's in the sediments. We have examined the sediments of the Inner Oslol]ord, which is situated within the most densely populated and industrialized area in Norway, in an attempt to describe the distribution Water, Ah', and Soil Pollution 18 (1982) 485-497. 0049-6979/82/0184-0485501.95. Copyright 9 1982 b)' D. Reidel Publishing Co., Dordrecht. Holland, and Boston, U.S.A.

486

M. I. A B D U L L A H

ET AL.

of PCB's relative to known sources of domestic and industrial waste discharge and to elucidate the modes of dispersal throughout the area. The hydrographic regime in the Inner Oslofjord has been described by many authors (Braarud and Ruud, 1937; Gade, 1968). Briefly, the Inner fjord, maximum depth 154 m, is separated from the Outer fjord by a shallow sill of 20 m with consequent restriction of the water circulation and exchange to an annual exchange (often only partial) of the deep water and to the estuarine circulation within the water layer above the sill. This restriction, together with the resultant accumulation of organic matter, often leads to the production of anoxic conditions in the deep water of the Bunnefjord. In addition, the abundance of nutrients and the stability of the water has resulted in almost continuous high primary productivity throughout the period between March and October (Throndsen, 1978). Fresh water discharge into the Inner fjord is through few small rivers, the mean flow being 26 m 3 s - I (Eika, 1956). Domestic and industrial wastes, partially processed (but often not) are discharged mainly at Bekkelaget with other small outfalls around Oslo Harbour and Lysaker. 2. Material and Methods

Sediment cores between 30 and 50 cm in length were collected during the spring of 1980 (See Figure 1 for sampling positions) using a purpose-designed gravity corer. The corer was fitted with pre-ignited (at 500 ~ stainless steel coring tube (60 mm I.D. and 1 mm thickness). The corer was also fitted with a lid which sealed the top of the coring tubes before the core was hauled out of the sediments. This arrangement obviated the use of core catchers which can cause a great deal of disturbance to the sediments. This arrangement together with the choice of the coring tube dimension caused no detectable disturbance nor allowed any perculation of the interstitial water. Cores were kept at 4 ~ or frozen to -20 ~ (when treatment could not commence immediately). The cores were sectioned into 2 cm slices under nitrogen and immediately the pH and Eh were measured. Each section was then dried at 80 ~ for 24 h and the dried sediments were ground and homogenized. Organic C was determined on a subsample using the potassium dichromate sulphuric acid oxidation (Gaudette et al., 1974). The PCB's were determined on an aliquot of the dried sediments. Between 1 and 5 g were soxhlet-extracted for 3 h using 100 ml ofa 3 : 1 mixture of hexane and isopropanol (Holden, 1970). The extracts were washed three times with 50 ml portions o f 0 . 9 ~ NaCI solution. The organic phase was then dried by filtering through a bed of Na2SO4 and its volume reduced to 1 ml in a rotary evaporator. The extracts were shaken with 2 ml of concentrated H 2 S O 4 to break down lipids and non-persistent organics and, after allowing the phases to separate over a period of 1 h the organic phase was finally treated with an acid washed Cu-wire in order to reduce S containing compounds which would otherwise mask PCB's of low retention time (Ahling and Jensen, 1970). All reagent and glassware clean-up followed the usual procedure. Varian 1700 and 3700 gas chromatographs equipped with a 3H and 63Ni EC detectors respectively were used. A 6 ft glass column of 2 mm I.D. was packed with 4 ~ SF-96

POLYCHLORINATED BIPHENYLS IN THE SEDIMENTS OF THE INNER OSLOFJORD I

I

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Fig. 1. M a p of the Inner O s l o 0 o r d showin the locations of the core samples.

(80-100 mesh) on Chromosorb WHP. The temperature programs were as follows: Varian 1700: Injector, 205 ~ oven, 195 ~ detector 230 ~ Varian 3700: Injector, 240 ~ oven, 230 ~ detector 300 ~ The gas flow in both instruments was 30 ml min t.

488

M.I. ABDULLAH ET At..

Standardization was made using a 50-50 mixture of Aroclors 1254 and 1260 (Beezhold and Strout 1973). This mixture was found to be the most suitable standard for PCB's separated from the Oslofjord sediments. The mean of the peak height ratios for sample and standard using the six main peaks (retention time of 0.88, 1.15, 1.28, 1.51, 1.78, and 1.96 relative to DDT) was used for calculation. The method of Webb and McCall (1973) and their analytical values also was used taking into account all detected peaks in the extracts. The two methods showed agreement in assessing total PCB's within _+103{,. Saponification (10~ KOH in methanol) was carried out on the extract in order to check the identity of DDT and its metabolites and to determine the DDT residue by comparing the resultant chromatogram with that of the acid-only treated extract. PCB's values were corrected for ZDDT interference. The limits of detection of the method estimated to be 4 ng g-~. 3. Results

Chromatograms of PCB's separated from the Oslofjord sediments are shown in Figure 2. Apart frosm the differences in peak heights, no significant change in the

Core 0-

12 2cm

~

Core

~[

S

2 - 4 cm

I 5

10

Core

12

12 - 14 cm

Core 10-

5

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12 cm

ixture.

l0 i

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minutes

I

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Fig. 2. Typical chromatograms of PCB's extracted from the h m e r Oslot]ord sediments together with chronmtogram of the standard PCB mixture used.

I+OI/'(CI~LORINATI~D BIPIIF+NYI+S IN THE SEDIMI:iN'I'S OF r i l l i INNI-R OSI.OF.IORI)

489

TABLE I ( ,mccnlratiol'+ t)l"PCB and Z D D T (rig g ' ) and organic C ( ",, ) m sediment cores from the hmcr Osh',Oord. Concentrations arc in dr)', salt free sediments. I )cl'~th in ,cdinlctlt s

2 4 6 8 I11 t~1 12 12 14 1 4 - I(~ ,~

9 4 <, s

core I

core 2

PCB

ZDDT

1911 236 369 311 2118 111 65 32

3.1 9.7 18.2 19.1 7.5 7.3 63 11.2

ors, C.

PCB

ZDDT

9.8 111.9 10+4 8,7 7.11 5.7 4.6 4.1

2117 192 59 23 17 17 17 13

5.7 6.11 2.5 0.5 11.2 nd nd nd

core 5 <+

2 4 b 8 Ill 12 14

q t, x Ir 12 14

16

173 354 5811 4114 172 5e, 3q 14

2 4 6

8 I<~ 12 14 I(~

431 428 687 418 702 263 571 453

3 ) 20.8 II).11 19.1 l+,d nd nd

9.7 Ilk3 9.4 8.2 8.5 7.1 5.5 4.5

" 4 6 8 10 12 14 16

I<~ 12-

14 nd

=

62 4r 37 27 19 nd

PCB

7.1 5.5 3.4 2.9 2.4 2+0 1.8 1.6

152 148 102 32 17 20 14 15

179 425 197 129 153 185 1115 35

2511 225 391 223 331 486 978 924

S.6 4.9 ~.2 4+3 {~.3 5.3 6.1 6.9

97 85 87 59 26 15 18 13

4.4 13.3 I 1.2 7.9 17.2 46.4 42.11 7.8

8.7 7.2 3.5 2.3 2.4 3.4 2.7 1.5

3.5 2.8 2.6 2.6 2.4 2.2

411 411 29 42 45 nd

YDDT 9.1 9,9 5.4 1.8 11.6 11.5 nd nd

ors. C.

PCB

6.9 5.8 4.2 3.2 3.1 3.4 3.0 2.4

76 164 301 213 58 57 27 19

4511 652 357 149 81 20 nd

5.9 4.7 4.9 2.3 0.1 nd nd nd

3.7 3.1 3.3 2.7 1.8 1.7 1.6 1.6

47 14 II 16 tad

46.8 75.7 589 I Ill 16.6 3.6 lid

7.1 b.3 5.3 4.4 3.7 3.11 nd

2.7 2.6 2.4 2.5 2.6 1.9

70 411 10 nd

ors. C. 4.8 8.5 22.5 10.0 II.I 4.2 nd nd

10.8 10.8 8.4 6.1 3.8 3.1 3.1/ 2.3

81 56 32 19 8 4 6 2

22.1 12.4 12.2 nd nd nd nd nd

2.7 2.2 1.9 1.7 1.5 1.3 1.2 1.2

17.9 13.b 1,0 nd nd nd nd nd

4,7 3,6 2.6 2.2 2.2 2.1 1.8 1.8

31.5 274 55 2.5 3.6 nd

3.1 3.1 3.0 2.9 2.6 2.4 2.2 1.9

core 12 5.0 IL7 nd nd nd

3.7 2.6 1.7 1.4 1.3 nd

core 15 0.9 3.0 3.1] 3.3 4.1 nd

s

core 8

core 11

core 14 15.1 21k~l 7.2 72 2.5 nd

core 4

core 7

core ll}

core 13

4~ 9 4 <~

org. C.

corc h

core t) ~ 94 t, s1tl 12 14

core 3

198 131 38 23 17 16 17 16 core 16

rid 2.1 nd nd

2.7 1.9 1.8 1.7

179 334 73 274 39 15 84 7

Not dctcrlnhled.

composition can be detected between the top samples and those from 10 to 14 cm below. The analytical results for PCB's are listed in Table I together with those for D D T metabolites and organic C. It can be seen that the concentration of PCB in the sediment is highly variable throughout the Oord. The highest value found is 702 ng g- 1 at 8 to 10 cm in core 9 and the lowest value found in the upper 10 cm is 10 n g g - 1 in core 15.

490

t~4. {. A B D U L L A H

E T AL.

The profile of the PCB concentration in the sediment is also variable but two distinct patterns can be identified. Those observed in Bunnefjord (Figure 3, cores 1 and 4) where the sediments are generally reducing, showed a subsurface maximum and those elsewhere in Vestfjord (Figure 3, cores 10 and 12) showed PCB's to be the highest in the

2 l

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x

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16 Fig. 3. Profiles of PCB's (o) and organic C (x)in Bunne0ord (core 1 and 4) and Vestfjord (cores 10 and 12) sediments. Concentrations are in dry. saltfree sediment.

P O L Y C H L O R I N A T E D BIPttENYLS IN T H E S E D I M E N T S OF T H E INNER O SL O FJ O RD

491

sediment surface and decreasing with depth. The variation in the proportion of coumpounds with different chlorine numbers (5, 6, and 8 + 8) in the sediments is shown in Figure 4. In the sediment surface the 5-C1 compounds constitute about 30% of the total and that the 6-C1 compounds between 40 and 50~o. These proportions remain constant at stations in the Bunnefjord while at stations in Vestfjord an increase in the 5-C1 accompanied by a decrease in the 6-C1 is observed with sediment depth. The 7 + 8 CI compounds remain constant throughout the area. The ZDDT content is listed in Tables I and III. Except for core 7, where DDT predominates, only DDT metabolites (DDD, DDE) were detected in the sediments. As in the case of PCB's, cores 6, 7, 9, and 16 show significant contamination with EDDT

Core 1

Core 4

50 I

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6 e,-

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I0121416-

Fig. 4. Partition diagram (percentage) of: (A) 5-CI; (B) 6-CI and (C) (7 + 8)-C1 compounds in the sediments.

492

M . I. A B D U L L A I I

TABLE

ET A L .

II

Concentration of PCBs (ng g- i dry salt free wt) in the sediments from the Inner Oslofjord, together with reported ranges in other contaminated areas. Locality

Method of sampling

PCBs fl]eal]

Oslo0ord, Norway 0 - 4 cm depth 0 - 8 cm depth 0 - 12 cm depth Osaka Port area, Japan New York Bight, USA Clyde, Scotland Baltic Sea Mediterranean, Italian Coast Central North Sea, Norwegian depression Refs.: I. 2. 3. 4. 5. 6.

Ref. rallge

core 4 0 - 575 3 3 - 487 2 5 - 464 1220-3960 1-2200 30-289(I 5-3900

138 166 121 Unknown grab grab/core ( 0 - 2 cm)

1 2 3 4

2 8 - 770

5

14• 2 . 8 - 2 8 • 33.9

6

dredge ( 0 - 2 cm)

this work

N a k a m u r a and Kashimoto. 1979. West and Hatcher, 1980. Halcrow et al.. 1974. Oden and Ekstedt, 1976. Puccctti and Leoni, 1980. Edcr. 1976.

T A B L E 111 Calcukited a m o u n t s of PCBs and E D D T (rag) in tile sediments under 1 m 2. Station No.

Depth (rn)

I 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

153 102 129 117 65 66 35 55 23 82 55 60 81 101 125 130

PCB (mg) 2.56 2.79 2.12 2.47 2.37 7.24 10.07 1.59 15.55 3.18 0.78 3.00 1.52 1.95 1.13 6.83

ZDDT (rag) 0.15 0.07 0.I I 0.19 0.11 1. I 0 6.89 0.30 23.68 0.14 0.02 0.17 0.33 0.10 0.02 2.33

PCB/DDT

17.1 39.9 19.3 13.0 21.5" 6.6 1.5 5.3 0.7 22.7 39.0 17.6 4.6 19.5 56.5 2.9

POI.YCIII.ORIN;%|I!D BIPIH~NY|.SIN THE SEDIMENTSOF THE INNER OSI.OFJORD

493

due to the fact that these areas are the m a i n recipients o f domestic and industrial waste. Elsewhere, the level o f Z D D T

is generally low.

4. Discussion

Meaningful comparison with sediments from other areas is rather difficult to present because of the different sampling techniques employed. The majority of investigators have used grabs to obtain samples (see Table II). Because of the occurrence of PCB's mainly in the upper part of the sedimentary column (10 to 30 cm) (West and Hatcher, 1980; Halcrow et al., 1974), the steep gradient of PCB's and the different penetration of the grab into the sediments, the reported concentrations may not reflect the exact content in the sediment. The range and mean values found for the Oslofjord calculated for the uppermost 4, 8, and 12 cm of sediment are presented in Table II together with some values reported in the literature. These clearly show that the upper part of the PCB range found in these sediments to be lower than those reported from other areas. Table IIl shows the total PCB's calculated under 1 m 2 of sediments. Apart from the area under the direct influence of waste outfalls (stns 6, 7, 9, and 16), the remainder of the fjord shows a remarkably even distribution of these compounds. The range of values lies between ca 1 and 3.2 mg m -2 compared with 7.2, 10.1, 15.6, and 6.8 mg m -2 for stations 6, 7, 9, and 16 respectively. In other words the amounts of PCB's present in areas directly influenced by discharges are only between 4 and t0 times that recorded elsewhere in the fjord. Although a valid comparison cannot be made with other areas, concentration differences of 2 or 3 orders of magnitude have been reported for the Clyde (Halcrow et al., 1974), New York Bight (West and Hatcher, 1980), and Osaka port (Nakamura and Kashimoto, 1979). 4.1. TRANSPORT OF PSB'S An explanation of the general uniformity of PCB's levels lies in the special hydrographic regime, particulate chemistry and the biological productivity in the fjord. The association of PCB's with organic matter has been demonstrated by numerous studies (Choi and Chen, 1976; Chiou et aL, 1977; Kihlstrom and Berglund, 1978). The adsorption isotherms of PCB's established by Wildish et al. (1980), appears to be related to the organic C content of the sediment. These authors have shown that when calculated with respect to the organic C content, the adsorption data followed a single isotherm having a K value ( S = K C " ) of 50 to 100 times greater than that found for the total sediments. Further, adsorption of PCB's on phytoplankton and zooplankton material was also found by Hiraizumi et al. (1979) to be greater than that for muds and sands. Clearly, both adsorption onto organic detritus and uptake by the biota (Kihlstrom and Berglund, 1978; Chiou et al., 1977; Halcrow et al., 1974) constitute major transport mechanisms for PCB's to the sediments in areas not directly contaminated. In areas such as the Oslof]ord where the water is isolated and exchange through tides and currents is minimal (tidal range is ca 25 cm), the ensuing high productivity may be an important factor in scavenging water soluble PCB's and in the redistribution of these

494

M. I. ABDULLAH ET AL.

in the sedimentary province. Although atinospheric transport is a significant mode (Eisenreich et al., 1979), the relatively small area of the fjord precludes this. Atmospherically transported PCB's to the adjacent land mass and washed down by run-off are usually detected at the points of river discharges where such compounds have a more restricted and localized distribution. T A B L E IV Coefficients (r) of correlation between PCB's and organic C in the sediments of the Inner Oslot]ord. Sections 0 - 2 cm 2 - 4 cm 0 - 2 and 2 - 4 cm 0 - 2 and 2 - 4 cm, excluding cores 6, 7, 9 and 16 (Clyde sediments, UK.)

No. of samples 16 16 32 22 (ca. 25)

r 0.419 0.435 0.403 0.829 (0.85), Halcrow, et al. 1974.

The correlation of PCB's (Table IV) is not as good as those reported in other observations (Choi and Chen, 1976; Halcrow et al., 1974). The latter pertain to direct contamination and, therefore, primary association with organic matter. The lack of correlation in the Oslofjord is possibly due to post discharge (and post depositional) changes through biological utilization. When samples from directly contaminated areas are excluded (Table IV), better correlation, however, is obtained. This implies that PCB's presence in other areas is associated with the organic matter input to the sediments, that is, secondary association with the biota and detrital material. 4.2. VERTICALTRANSPORT OF PCB WITHIN THE SEDIMENTS An accurate interpretation of the profiles of PCB's in the sediments (Figure 3) is not feasible from the present data. Although the few PCB's profiles reported (West and Hatcher, 1980; Halcrow et al., 1974) have been assumed to be historically related to the use and discharge of PCB's, the possibility of remobilization, vertical transport or release to the overlying water by biological agencies has not been given much consideration. Furthermore, the recent introduction of PCB's to the environment and their incorporation with the sediments does not allow a meaningful assessment of their behavior during early diagenesis of the sediments. In the Inner Oslofjord two distinct types of profiles of PCB's in the sediments are encountered and are typically represented in Figure 3. Type A is commonly found at stations in Vestfjord and Type B found in Bunnefjord. In either area only minor variations are observed from station to station and these are related to levels and gradients. Thus, whatever the original and historically related profile may have been, significant modification of this can be deduced from the observed profiles. Of particular signification is the penetration depth of PCB's in the sediments being different in the two regions, that is, 10 to 14 cm in BunnOord and 6 to 8 cm in the

POLYCHLORINATED BIPHENYLS IN THE SEDIMENTS OF TFIE INNER OSI.OF.IORD

495

Vestfjord. Although penetration depth in a closed area such as the Inner Oslofjord is a function of sedimentation rate, the latter (about 1.5 mm yr- i, Strom, 1936) is not anticipated to vary so much as to account for the observed differences. Furthermore, the sedimentation rate in the Vestfjord which receives the greater part of run-off in the region is more likely to be the higher. Thus the difference in the penetration depth of PCB's may be partly explained by vertical transport resulting from bioperturbation. This is particularly relevant to the Inner Oslofjord in view of the absence of other forms of perturbation such as those produced by tides, currents and waves. The degree of bioperturbation in the upper part of the sediment and at the sediment/water interface is mainly controlled by the benthic community, its size and the prevailing species, which are dictated by the physicochemical description of the environment. The frequent anoxia encountered in Bunnefjord would restrict the benthic organisms to those opportunist species which can exist on the surface of the sediments (Gray, 1981) and which create little bioperturbation. Here, any remobilization of PCB's by uptake and release will be restricted to the upper few millimeters of the sediments and then only during periods where oxygen is present. On the other hand, the almost permanently oxic conditions in the Vestfjord has resulted in a diverse and well established benthic fauna where bioperturbation extends to few centimeters in the sediments and is limited only by the redox condition of the subsurface sediments. Thus here, vertical transport of the PCB's associated with assimilation of organic matter will be more pronounced. It may be concluded, therefore, that the profiles found in the Bunne0ord may approximately reflect the history of use and discharge of PCB's in the region. Thus the decrease of PCB's in the sediment surface is a result of the decline in the discharge of these compounds over the last 10 to 15 yr (Kveseth, 1980). A corollary of this is the role of benthic fauna in remobilizing persistent chemicals, such as PCB's, to the water and the redistribution and transfer through animal migration. In this respect KihlstrOm and Berglund (1978) estimated that approximately 10}0 of the annual input of PCB's to the Baltic is removed annually by fishing alone. 4.3.

POST

DEPOSITIONAL

FRACTIONATION

OF PCB'S

Except for hydroxylation, studies of biodegradation of PCB's has revealed no discernible change in their molecular structure under controlled or natural bioassimilation (Jensen and SundstrOm, 1974; Safe et al., 1980). Further, no transformation in the aquatic environment has been detected other than loss of C1 through photo-oxidation (Hutzinger and Roof, 1980). The integrity of PCB's under long burial periods and their survival during sedimentary diagenesis, however, remain unknown. We have attempted to elucidate the latter point from the observation by examining the ratio of the various isomers separated from different depths. No systematic or coherent picture can be presented as variations were inconsistent with the biological and geochemical regimes of the area. However, the differently chlorinated compounds show a more systematic change upon burial. The greatest change observed (Figure 4) is in the trend shown by the 5-C1 and 6-C1 compounds in sediments known to be mostly oxic or from shallow

496

M. I. A B D U L L X H

ET AI..

waters. Little or no change is observed in samples where anoxic conditions prevail. These changes cannot be considered to be related to changes in the composition of commercial PCB's in use since such changes would be reflected throughout the sedimentary province. A possible interpretation may be derived from the selectivity, metabolism and residence time of PCB's in the biota. It has been suggested that assimilation rates by biota are different for different PCB's (isomers and chlorine number) (Nisbet and Sarofim, 1972). Also it is probable that involvement of PCB's with the biota is also dependent on the class and species of the organisms. Thus, compounds assimilated by bacteria, for example, will to a certain extent be selected (Nisbet and Sarofim, 1972) and transfer along the food chain will magnify such selectivity. In areas where biological activity is limited, i.e., being mainly bacterial as in the Bunnefjord, the biotransference of PCB's will be more restricted than that found in permanently oxic environment where any fractionation of PCB's will be more pronounced. The observed distribution, (Figure 4) agrees generally with this postulation. Oxic sediments show pronounced increase in the 5-C1 and decreases in the 6-C1 compounds with depth (e.g. Stns. 12 and I0) while anoxic sediments (Stns. 1 and 4) consistently showed little variation in the two groups of compounds. There is a consensus in the literature which suggests that compounds with lower proportion of chlorine are more readily assimilated and released than more highly chlorinated ones. Such selectivity, together with differing adsorptive properties, may lead through several cycles of assimilation and release to different rates of vertical transport through bioperturbation. This is manifested in changes in the proportions of these compounds in the sediments. Although no attempt is made to interpret the ZDDT values for the sediments, generally, their distribution resembles that of the PCB's, that is, their transport within the f]ord is achieved through similar agencies to those involved with the PCB distribution. This interpretation is only a tentative one which is compatable with the biological and geochemical description of the sediments of the Inner Oslofjord and the distribution of PCB's therein. Information concerning the biochemical behavior of PCB's in sediments is seriously lacking. The present argument only highlights the complexity of PCB's involvement with the sedimentary components and suggests that the role of the biota is perhaps the most significant one in determining the distribution, residence and composition of PCB's held in the sediment.

5. Summary In restricted areas of the sea such as bays and fjords significant transport of PCB's to regions outside the domain of waste discharge may be achieved through association with the biota and sedimentation of organic matter. The history of use and discharge of PCB's as recorded in the sediment must be viewed cautiously as bioperturbation can cause both vertical transport and fractionation of these compounds during their burial.

POI,YCIII.ORINATI~D

BIPIII~NYI.S IN T I l E SEDIMENTS OF T Il t" INNI!R OSLOFJORD

497

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