Sedimentary Record of Environmental Pollution in the Western Baltic Sea

German Mfilter, J. Dominik, and R. Reuther

Institut ftir Sedimentforschung der Universit/it, D-6900 Heidelberg

R. Malisch, E. Schulte, and L. Acker

Institut f/Jr Lebensmittelchemie der Universit~it, D-4400 Mtinster

G. Irion

Institut f~r Meeresgeologie und -Biologie Senckenberg, D-2940 Wilhelmshaven

The chronological development of environmental pol- lution in the Western Baltic Sea for the past hundred years was investigated in dated sediment cores. An artificial radionuclide (137Cs), nutrients, heavy met- als, chlorinated hydrocarbons (PCB, DDT, Lindane) and plasticizers (phthalate esters) show characteristic distribution patterns within the various cores. They can be related to the production and use of specific chemicals and goods, to emissions associated with the increased combustion of coal parallel to industrial- ization a n d - i n the case of 137Cs_ to emissions asso- ciated with atomic weapons tests in the high atmo- sphere. Characteristic trends in the general develop- ment of pollution may be superimposed by specific emissions from local sources.

The application of the concept that "sediments reflect the condition of an aquatic system" [1] to anthropo- genic pollution problems led to the discovery that numerous chemicals, which are pollutants themselves or are indicative of environmental pollution, are accu- mulated by sediments and so i l s - a process designated as "geoaccumulat ion" (Wagner, in [2]). This is true for all substances that have a certain affinity for sedi- ments and soils, i.e., those bound chemically or physi- cally to inorganic and/or organic particles or are themselves particles. Another prerequisite is that such substances are not easily dissolvable or degradable by microbial activity and/or diagenetic processes (which mainly effect the pH-Eh relationship) within the sediment. Heavy metals, artificial radionuclides, chlorinated hydrocarbons, phthalate esters, polycyclic aromatic hydrocarbons a n d - t o a lesser ex ten t -nu- trients, largely satisfy these two criteria. 21~ sedimentary cores permit the study of the historic record of such substances as are relevant

tO environmental pollution over the past hundred years. There are many investigations in which this method has been successfully applied in marine and limnic environments, but very few involve more than one group of contaminants studied simultaneously within the same sediment samples (i.e., heavy metals and polycyclic aromatic hydrocarbons [3]). The Baltic Sea has been described as one of the most severely polluted sea areas in the world and only re- cently has Leppfikosi [4] anew drawn attention to man's impact on the Baltic ecosystem. The present paper attempts to demonstrate how mul- tidisciplinary cooperation can lead to a better under- standing of the history of environmental pollution in a specific a r e a - t h e Western Baltic Sea. Only one or two examples from each group of con- taminants studied by the different research teams were selected for this report, which will soon be followed by a detailed monographic treatment of the subject. The groups and the selected examples are: 1. Artificial radionuclides derived from atomic tests in the high atmosphere or from atomic reactors: 137Cs"

2. Nutrients, not pollutants themselves, but indicators of eutrophication of an environment: P and N. 3. Heavy metals derived from burning of fossil fuels and from domestic and industrial sources: Zn and Pb. 4. Chlorinated hydrocarbons derived from their appli- cation in industry and pest control, a) polychlorinated biphenyls (PCB), b) pesticides: SDDT (p,p'-DDT, o,p'-DDT and their metabolites) and 7-benzene hexachloride (7-BHC, "Lindane "). 5. Di-(2-ethylhexyl)phthalate (DEHP) as example for phthalate esters, mainly used as plasticizers.

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Materials and Methods

Sampling

During June 1978, three sediment cores were collected aboard the research ship "Senckenberg" with a large box corer [5] from the Geltingen Bight " G B " (water depth 20 m), Eckernf6rde Bight " E B " (water depth 21 m) and from the Liibeck Bight " L B " (water depth 15 m) in the Western Baltic Sea (Fig. 1). With the exception of the uppermost oxidized brown- ish layer (thickness 1 3 ram), the sediment cores showed the typical black color indicating reducing condition and the presence of iron monosulfide. Im- mediately after their recovery, the cores were split into portions of 1 cm thickness, which were then placed in aluminum boxes and deep frozen.

Analytical Procedures

Grain size analysis was carried out applying Atterberg sedimentation and sieve analysis [6]. The mineralogy of the sediments was determined semi- quantitatively by X-ray methods. Special attention was paid to the determination of the different groups of clay minerals [7]. ~37Cs was measured directly by its 7-activity with a spectrometer (Ge-Li detector), maintaining a con- stant geometry of the samples. Total nitrogen was determined according to Kjeldahl's method (H2SO4 selenium reaction mixture) and total phosphorus colorimetrically (in HNO3-HC104). The quantities of heavy metals were measured with standard flame atomic absorption spectroscopy (AAS). Chlorinated hydrocarbons and phthalate esters were extracted with a mixture of acetone+hexane (1:1) in an ultrasonic device. The extracts were purified by column chromatography (AlzO3/Florisil/copper with a CH2C12-hexane mixture). This procedure was followed by a propylene carbon- ate cleanup from celite (separation of lipophilic sub- stances), a H2SO4 treatment (removal of oxidizable organic matter) and a subsequent Hg treatment (re- moval of native sulfur). Chlorinated hydrocarbons were determined by capil- lary GC (capillary coated with a SE 30/SE 52 mix- ture ; ECD), and the phthalate esters by capillary GC/ MS using the mass spectrometer as a specific detector at fixed mass (capillary deactivated with UCON 50 HB 5100 and then coated with SE 30; m/e=149). Details in analytical procedure will be given in a sepa- rate publication. The dating of sediments was carried out with the 21~ method [8, 9]. The determination of the 2~~ content was based on a-activity measurement of its daughter

21~ according to a procedure described elsewhere [10]. 2~~ excess values were plotted against cumula- tive weight of sediment deposited on the surface of 1 cm 2. Sedimentation rates were calculated from the slope of the best fit.

Results and Discussion

The results of our work are presented graphically in Fig. 2.

Sediment Composition (Reuther and MiHler)

The textural composition of the sediments is ex- pressed by its clay-silt-sand percentage. In all cores studied silt (fraction 2-63 gin) is the domi- nant size class, followed by clay (fraction < 2 gin) in cores EB and LB. Core GB differs from the other cores by a high percentage of particles of the sand size class (> 63 gin). From bottom to top no major changes or fluctuations in texture occur in cores LB and EB, whereas in core GB a triple partition of the core based on the sand/silt ratio can be ob- served. The qualitative mineralogical composition (not shown in Fig. 1) is very similar in all three cores; the muds are built up of clay minerals, quartz, feldspars, car- bonates and additional organic materials. In the finer- grained cores EB and LB the clay minerals (with predominant illite, followed by smectite, chlorite and kaolinite) are more abundant than in the quartz-rich coarse-grained sediments of core GB.

Radionuclides, 137Cs (Dominik)

The 137Cs distributions are fairly similar in all three cores. The highest activities occur in the depth interval 1-4 cm (cores GB, LB) or in the uppermost sample (0-1 cm, core LB). In all cores the 137Cs peak activity appears with a delay in comparison to the date of maximal atmospheric fallout (1962). This fact may suggest that a major fraction of 137Cs was transported with the soil material into the basin and only a minor fraction was immediately scavenged from the water column into the sediments. The first appearance of 137Cs in the sediments from cores GB and LB well before the expected date (1953) cannot exclusively be explained from a sediment mix- ing caused by bottom organism activity, since other constituents (PCB, DDT etc.) would then have been affected in the same manner. A diffusion of 137Cs into deeper layer seems to be an explanation for this phenomenon. The maximum 137Cs concentration in the uppermost

596 Naturwissenschaften 67, 595-600 (1980) �9 by Springer-Verlag 1980

90 30 ' 100 30 '

B a I t i S .....

sc, h,e.sw[g : i i : ' iA C e

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Fig. 1. Location of sedimentary cores investigated in this study. GB Geltingen Bight, EB Eckernf6rde Bight, LB L/.ibeck Bight. "A" designates coring station A in the Eckernf6rde Bight from a previous study [15]

layer o f core LB d e m a n d s special a t t en t ion since it c anno t be exc luded tha t sources o the r than a t m o - spher ic fa l lout (e.g., effluents f rom a tomic reactors) could be respons ib le for this unexpec ted increase.

In sed iment cores f rom the cent ra l and eas tern par t of the Baltic (Baltic P rope r and G u l f of F in land) 239pu/24~ d i s t r ibu t ion pa t te rns s imi lar to those for 137Cs in our GB and EB cores were repor ted [11].

Naturwissenschaften 67, 595 600 (1980) ,�9 by Springer-Verlag 1980 597

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Nutrients, P and N (Miiller)

In all cores the P concentrations begin to rise within the upper 4 cm of the core (representing the time after about 1965) until a maximum is reached in the uppermost 0-1 cm layer (GB, EB) or in the 1-2 cm layer (LB). When compared with the relative constant P concentrations in the deeper layers, the increase

is highest in core EB (1150~1860 ppm) and core GB (1250~1510 ppm). The N distribution pattern is similar to the P develop- ment. The fluctuations in the pre-1960 layers of core GB are however larger, possibly as a result of fluctua- tions in grain size. The increase of the P and N concentrations during the past 15 years clearly reflects the increasing eutro-

598 Naturwissenschaften 67, 595 600 (1980) �9 by Springer-Verlag 1980

phication of the Western Baltic Sea, which is caused by an increasing discharge of phosphates and N com- pounds (fertilizers, detergents) into the sea. According to [12] 308890 tons of nitrogen and 25825 of phos- phorus spill into the Baltic yearly, the respective fig- ures for the Western Baltic being 9910 and 4685 tons. Brandt [13] calculated that 50% of the P and N dis- charge from the Schleswig-Holstein drainage area into the Western Baltic are of anthropogenic origin. The P and N concentration patterns of our cores from the Baltic resemble very much those of dated sedimentary cores from Lake Constance [14], where the increase of the P and N concentrations dates back as early as 1950.

Heavy Metals, Zn and Pb (h'ion)

Core EB exhibits a "classical" Zn-evolution curve: From the pre-1880 values (105 ppm) the concentra- tion begins to climb after 1880 nearly steadily until it reaches a maximum (248 ppm) in the 1 2 cm layer. In core GB the development is somewhat different; from 54 ppm in the lowermost layer the Zn concentra- tion climbs to 20I ppm in the l l - i 2 c m layer ( ~ 1930). Above this layer it remains high and fluctu- ates between 146-179 ppm. In core LB the lowermost layer shows a Zn concentra- tion of 63 ppm which reaches 227 ppm in the 6 7 cm layer and then shows a sudden increase to 1150 ppm in the 5-6 cm layer (~1950). Above this maximum the concentrations fluctuate between 619ppm (3- 4 cm) and 319 ppm (0 1 cm). The Pb distribution pat- tern in core LB resembles exactly the Zn pattern. The maximum (1110 ppm) in the 5 6 cm layer differs by about a factor of 55 from the minimum (20 ppm) in pre-1880 layers of the core. In cores GB and EB again a general trend to increase from older to younger strata is observed, however, compared with Zn, the increments are much lower. An increase of zinc (and other heavy metals) similar to that in the sediments of the EB core has been recorded [15] from a 14C-dated sediment core collect- ed not far from the EB sampling site (marked " A " in Fig. 1). The authors observed a parallel develop- ment of heavy-metal concentrations with industrial growth as reflected in fossil-fuel consumption (especially of coal with much higher metal concentra- tions as in petroleum-derived products) within the last 130_+30 years. Mfiller et al. [3] found a similar parallel development not only with heavy metals but also with polycyclic aromatic hydrocarbons in cores from Lake Constance and assumed coal combustion to be the main source for both groups of pollutants. The very high Zn and Pb concentrations in the LB core cannot be explained as a "normal increase" from

non-point sources but are more likely a result of local pollution in the Lfibeck Bight. From the surface sedi- ments of the Gulf of Bothnia and the Central Baltic, Hallberg [16] reported Zn (129 and 274 ppm, resp.) and Pb concentrations (67 and 84 ppm, resp.) which are very similar to our findings in the GB and EB core.

Halogenated Hydrocarbons (Malisch, Schulte and Acker)

Polychlorinated biphenyls (PCB) resembling a Clo- phen A 60 pattern were first found to occur in sedi- ment layers deposited around 1940; their highest con- centrations occur in the EB core (possibly indicating a local source), being more than three times higher than in the other cores and remaining more or less constant since around 1950. In none of the cores a distinct decrease or increase towards the youngest sediment can be observed. Altogether 1 2 million tons of PCB have been pro- duced since 1929. The contamination of the environ- ment with PCB was first discovered by Jensen [17]. After their detection also in human milk and fat [18, 19] in 1973 the Organisation of Economic Coopera- tion and Development (OECD) recommended to stop the application of PCB in open systems. In Sweden similar restrictions had been planned on the use of PCB as early as in 1971. The first occurrence of PCB in our cores around 1940 indicates their relatively late general use in and around the area investigated. The recommendation of the OECD has not yet resulted in a decrease of its concentration in the youngest sediment layers, Kihlstr6m and Berglund [20] have even predicted an increase of the PCB contamination of the Baltic via atmospheric fallout (approx. 6 tons per year) which is supported by the fact that PCB levels in the fat of guillemot egg tissues analyzed annually between 1968 and 1975 still show increasing tendency [21]. On the other hand, PCB concentrations of fish from the Baltic did not change during the period from 1975-1979 [22]. ZDDT concentrations 1 gradually begin to develop directly above the 1940 date l i ne -p robab ly around 1945. In cores EB and LB the concentrations are about three times higher than in GB. Within Central Europe DDT was used in larger amounts predominantly as an insecticide after 1945 and was later totally banned in several European countries (e.g., in the F.R. Germany in 1973). The

1 Detailed information on p,p'-DDT, o,p'-DDT and their me- tabolites and on other BHC isomers will be given in the mono- graphic treatment.

Naturwissenschaften 67, 595 600 (1980) �9 by Springer-Verlag 1980 599

2;DDT distribution pattern in our cores therefore par- allels more or less the application of DDT in the researched region. In core LB a decrease can already be observed, in cores EB and GB no further increase in the youngest strata is indicated. Olsson [21] determined a steady decrease of DDE in the fat of guillemot egg tissues since 1970 and a considerable decrease of s in fish during the period 1975 1979 was found [22]. 7-Benzene hexachloride 1) (7-BHC, 7-hexachlorocyclo- hexane, "L indane" ) occurs for the first time in sedi- ments around 1950 and from that date the concentra- tion increases steadily until the youngest layer (0- 1 cm). The sharp increase of the Lindane concentra- tions is a result of the directed application of this chemical after the ban of "technical B H C " and other chlorinated insecticides.

Phthalate Esters (Malisch, Schulte and Acker)

Di-(2-ethylhexyl)phthalate (DEHP) was first found in traces in sediments deposited around 1950; since that time a steady increase is observed in all three cores with a maximum in the youngest layer (0-1 cm).

Phthalate esters are widely used as plasticizers and their application is closely related to the development of PVC production (commercially available since 1931). During the first two decades dibutylphthalate was more in use than DEHP; after World War II DEHP became the most common plasticizer. This change can clearly be demonstrated in the sediments (see the mongraphic treatment).~ In sea water of the Kiel Bight (Western Baltic), and other parts of the Baltic, Ehrhardt and Derenbach [23] reported "amazingly h i g h " phthalate ester con- centrations "exceeding those of chlorinated hydrocar- bon-type pesticides by a factor of approximately one hundred".

21~ Age Determination (Dominik)

In all cores studies the 21~ activity shows a loga- rithmic decrease with depth, except in the uppermost 2 3 cm interval where activity is nearly constant. This constant activity interval probably represents the ef- fect of bioturbation and results in a homogenization of the sediments. The observed 21~ distribution is interpreted in terms of a simple mixing model [24], assuming a mixing constant K--* oo. The following average rates of sedimentation have been deter- mined:

GB=0.092+0.007 g cm-~y -1 (~2.3 mm/y); EB=0 .103_+0 .005gcm-2y 1 ( ~ 3 . 2 m m / y ) ; LB =0.054+0.004 g cm-2y-1 ( ~ 1.6 mm/y).

The resulting time scales are shown in Fig. 2; details of age determination will be published in the mono- graphic treatment.

Conclusions

The investigation of dated sediment cores permits the establishment of a time scale for the beginning, the development, and the present trend of environmental pollution of the Western Baltic Sea with specific con- taminants. Background concentrations of heavy metals begin to rise already around 1880; the first occurrence of po- lychlorinated biphenyls dates back to 1940 and D DT was found to first appear in sediments deposited around 1945. D EH P (a phthalate ester) and Lindane occur some years later around 1950. The (back- ground) concentration of nutrients begins to climb around 1965 and indicates the change of the trophic level of the Western Baltic Sea since that time.

We express our thanks to the Senckenbergische Naturforschende Gesellschaft, Frankfurt/M, for providing us with their research vessel "Senckenberg", and to the Deutsche Forschungsgemein- schaft for financial support. The Institut ffir Umweltphysik, Hei- delberg University, kindly permitted us to use their facilities for

37Cs and 2aopb determinations; D. Godfrey gave us his assistance for the English version of the manuscript.

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Schweizerbart, New York London: Hafner 1967 7. Biscaye, P.E.: GeoL Soc. Am. Bull. 76, 803 (1965) 8. Krishnaswami, S., et al. : Earth Planet. Sci. Lett. l l , 407 (1971) 9. Koide, M., Burland, K., Goldberg, E.O.: Geochim. Cosmo-

chim. Acta 37, 1171 (1973) 10. Dominik, J., Mangini, A., Mtiller, G. : Sedimentology (in print) 11. Simola, K., et al.: Proc. 4th Int. Congr. Int. Radiat. Protect.

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chim. Acta 38, 823 (1974) 16. Hallberg, R.: Ambio 8, 265 (1979) 17. Jensen, S.: New Scient. 32, 612 (1966) 18. Acker, L., Schuite, E.: Dtsch. Lebensm. Rdsch. 66, 385 (1970) 19. A, cker, L., Schulte, E.: Naturwissenschaften 57, 497 (1970) 20. Kihlstr6m, J.E., Berglund, E.: Ambio 7, 175 (1978) 21. Olsson, M.: Finnish Mar. Res. 44, 227 (1978) 22. Luckas, B., Wetzel, H., Rechlin, O. : Nahrung 24, 405 (1980) 23. Ehrhardt, M., Derenbach, J.: Mar. Chem. 8, 339 (I980) 24. Robbins, J.A., in: The Biogeochemistry of Lead in the Environ-

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Received September 29, 1980

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