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Evaluation of the anthropogenic influx of metallic pollutants into Puck Bay, southern Baltic
PII: S0883-2927(97)00098-X
Applied Geochemistry, Vol. 13, pp. 293±304, 1998 # 1998 Elsevier Science Ltd All rights reserved. Printed in Great Britain 0883-2927/98 $19.00 + 0.00
Evaluation of the anthropogenic in¯ux of metallic pollutants into Puck Bay, southern Baltic P. Szefer*, A. Kusak and K. Szefer Department of Analytical Chemistry, Medical University of Gdansk, al. Gen. J. Hallera 107, 80-416 Gdansk, Poland
G. P. Glasby Department of Earth Sciences, University of Sheeld, Sheeld S3 7HP, U.K.
H. Jankowska and M. Wolowicz Institute of Oceanography, University of Gdansk, al. Marsz. J. Pilsudskiego 46, 81-378 Gdynia, Poland
A. A. Ali Faculty of Science, Arts and Education, University of Aden, P.O. Box 6014, Khormaksar, Aden, Yemen (Received 9 September 1995; accepted in revised form 20 May 1997) AbstractÐDistributions of 15 elements with depth in two sediment cores from Puck Bay in the Gulf of Gdansk show that Ag, Cd, Pb, Zn and possibly Cu and Ni are anthropogenically enriched in the sediments there. The concentrations of these elements decrease sharply with depth in the sediment column and the elements are preferentially enriched in the <2 mm size fraction of the sediment. The sequence of element enrichment depends on whether the enrichment factor (EF) and the anthropogenic factor (AF) are used to calculate the element enrichment. By contrast, the anthropogenic elements show no systematic decrease in concentration with depth in a sediment core taken from near the mouth of the Vistula River. This re¯ects the higher sedimentation rate there such that the entire upper 20 cm of the core was deposited during the major, post-war period of industrialization in Poland. In addition, these elements are enriched in the 2±63 mm fraction compared to the <2 mm fraction in these sediments. This suggests that the heavy metals are mainly adsorbed on Fe oxyhydroxide particles with diameters greater than 2 mm at the hydrological front where Vistula river water mixes with brackish Baltic water. It appears that heavy-metal pollution of sediments in parts of Puck Bay may be greater than that near the mouth of the Vistula River which may re¯ect, in part, the higher sedimentation rate near the mouth of the Vistula River. The mode of incorporation of heavy-metals into the sediments in the two areas may also be dierent. # 1998 Elsevier Science Ltd. All rights reserved
INTRODUCTION
Sediments and biota from Puck Bay in the Gulf of Gdansk are known to be signi®cantly contaminated by heavy metals (Szefer et al., 1994, 1995a, 1996) but little work has been carried out on the distribution of heavy metals with depth in sediment cores there (Szefer and Skwarzec, 1988). Furthermore, studies of heavy-metal pollution in sediments from Puck Bay have been carried out only at the reconnaissance level. In this study, we present data on the distribution of heavy metals with depth in two sediment cores from Puck Bay in order to assess the pollution load there more precisely. Heavy-metal data on one sediment core taken from near the mouth of the Vistula River in *Corresponding author. 293
the Gulf of Gdansk are also presented for comparison. Puck Bay forms the western part of the Gulf of Gdansk. It may be divided into two parts. The interior of the bay is a shallow area with an average depth of ca. 3 m (maximum of 9 m in the Kuznica Deep) and its extent is marked by the sandy barriers of Seagull Reef and by Hel Peninsula. The sediments are mainly ®ne sand and silty mud. The outer part of Puck Bay is a deeper basin with a maximum water depth of ca. 60 m. The sediments vary from coarse to ®ne sand in the shallower parts to silty clay and clay in the deeper parts (>30 m). Quartz, feldspar and plagioclase are the principal minerals present in the sediments. Quartz generally occurs in the range 30±40%. Secondary minerals include pyroxene, amphibole, garnet, pyrite, gypsum and calcite. Illite and chlorite are the principal
294
P. Szefer et al.
Fig. 1. Schematic map showing the locations of sediment cores 8, 25 and 38 in Puck Bay.
clay minerals with lesser amounts of kaolinite and smectite. The organic carbon content of the sediments varies mostly between 5±15% in ®ne-grained sediments. The Vistula is the dominant river draining into the Gulf of Gdansk (and therefore the principal source of pollution) but a number of rivers (Rewa and Kacza) discharge directly into Puck Bay. Accounts of various aspects of Puck Bay have been presented by Bolalek (1992a,b), Jankowska (1993), Korzeniewski (1993) and Plinski (1993) and the major characteristics of Gulf of Gdansk and Puck Bay have been summarized by Szefer et al. (1996).
METHODOLOGY
In this study, two sediment cores (No. 8 and No. 25) from the outer part of Puck Bay and one core from near the mouth of the Vistula River (No. 38) were taken during a cruise of R.V. Oceanograf II in 1991. The locations of the cores are shown in Fig. 1. Samples of sediment were taken at 5 cm intervals within the cores. Subsamples of the wet material were then washed through a polythene mesh with mesh sizes 63 and 2 mm and the excess water evaporated on a water bath at 808C to obtain a thick slurry. The material was dried at 1108C and weighed prior to digestion with concentrated HNO3 (65%), HF (40%) and HClO4 (70%) in volume ratios 7:7:1 (Szefer et al., 1995a). The dry residue was converted to chlorides by evaporation with concentrated HCl (36%) and dissolved in 1 M HCl. The concentrations of selected elements were measured by AAS using deuterium-background cor-
Fig. 2. The distribution of grain size in the surface sediments of the sediment cores 8, 25 and 38.
rection. The accuracy and precision of the method were satisfactory based on intercomparison with reference material (sediment sample code SD-N-1/2) from the IAEA in Monaco.
Anthropogenic in¯ux of metallic pollutants into Puck Bay
295
Fig. 3. The variation of organic carbon content with depth in the sediment cores 8, 25 and 38.
Bulk mineral composition was determined by Xray diraction using a DRON 1 X-ray diractractometer (Cu Ka, 4±678 2y) and clay mineral composition was determined on sedimented samples using a DRON 2 X-ray diractractometer (Cu Ka, 3±328 2y) using the procedures described by Brown (1980) and Brown and Brindley (1980). In order to evaluate the data in more detail, the enrichment factor (EF) and the anthropogenic factor (AF) for elements in the cores were calculated according to the formulae EF Cx =CAl s = Cx =CAl c where Cx and CAl refer to the concentrations of element x and Al in the surface sediments (s) and earth's crust (c), respectively. Aluminium is used here as the reference element and AF Cs =Cd where Cs and Cd refer to the concentrations of the
element in the surface sediments and sediments at depth in the sediment column. A fuller account of the calculation of the enrichment factor (EF) is given by Szefer et al. (1996).
RESULTS
The grain-size distribution in the surface sediments and the variation of organic C content with depth in the sediment column at each station are shown in Figs 2 and 3. The distributions of 15 elements with depth in the sediment cores are shown in Figs 4±6. The mineralogy of the bulk sediment is listed in Table 1. For cores 8 and 25, the element concentration data show that, in general, the maximum concentration of each element within a given sample is found in the ®nest fraction (<2 mm) of the sediment as is commonly observed (e.g. for sediments from
296
P. Szefer et al. Table 1. Mineralogy of bulk sediments from sediment cores 8, 25 and 38
Station No. 8 25 38
Essential minerals quartz
Clay
mineral
illite
kaolinite
chlorite
smectite
+++
++
+
+
+ +++
+
Accessory minerals
plagioclase, K-feldspar, low halite, pyrite quartz, plagioclase K-feldspar, garnet very low quartz K-feldspar, plagioclase, low calcite
Fig. 4Ðcaption opposite
contents
Anthropogenic in¯ux of metallic pollutants into Puck Bay
Fig. 4. Distribution of 15 elements with depth in each of the size fractions (<2, 2±63 and >63 mm) in sediment core 8.
297
298
P. Szefer et al.
Table 2. Enrichment factors (EF) for 14 elements for each of the size fractions (<2, 2±63 and >63 mm) in the surface sediments (0±5 cm) of sediment cores 8, 25 and 38 Station 8 <2 mm Na/Al Mg/Al K/Al Ca/Al Cr/Al Mn/Al Fe/Al Co/Al Ni/Al Cu/Al Zn/Al Ag/Al Cd/Al Pb/Al
2.5 0.2 1.7 0.1 1.2 0.7 0.9 1.1 2.5 1.7 11 300 14 21
Station 25
2±63 mm
>63 mm
0.3 0.1 1 0.8 0.7 0.5 0.8 1 1.2 1.2 6.6 18 16 6.3
0.5 0.2 0.8 0.5 0.4 0.4 0.6 0.6 1.6 0.5 2.3 8.3 3.8 2.9
<2 mm 1 0.2 1.1 0 1.4 0.2 0.6 0.5 1 1 4.3 200 17 11
the Vistula River, Helios Rybicka, 1992a,b). Exceptions are Ca in sediments from station 8 where the maximum concentration is found in the size class 2±63 mm. This presumably re¯ects the occurrence of calcareous organisms in this size fraction. Cadmium is also highest in this size fraction in sediments from station 8 and Pb is highest in the <63 mm size fraction in the basal sediments from station 25. In both cores, Cu, Zn, Ag, Cd and Pb show a decreasing concentration with depth in the sediment. The other elements show no such trend. By contrast, several elements (e.g. Ca, Fe, Cr, Co, Zn, Cd) are present in higher concentrations in the 2±63 mm than in the <2 mm size fraction of core 38 and there is no systematic decrease in the contents of Cu, Zn, Ag, Cd and Pb with depth in the sediment column in this core. Indeed, most elements show a maximum in their distribution with depth in this core increasing from the surface to the 5±15 cm interval before declining in the 15±20 cm depth interval. It is also seen that the concentrations of some elements (Fe, Cr, Co, Ni, Zn, Ag, Cd and Pb) are higher in the <2 mm fraction of the surface sediments of cores 8 and 25 than those in the <2 mm fraction of the surface sediments of core 38, although this relationship does not apply to the other size fractions. The enrichment factors (EF) for 15 elements for each of the size fractions (<2, 2±63 and >63 mm) in the surface sediments (0±5 cm) of all three cores are presented in Table 2. The anthropogenic factors (AF) have already been calculated for the elements (Cr, Cu, Zn, Ag, Cd and Pb) in the <2 mm size fraction in two cores (8 and 25) (Szefer et al., 1995b) but these data will not be repeated here. It will be noted that an AF could not be calculated for core 38 taken from near the mouth of the Vistula River since there is no systematic decrease in concentration of the anthropogenic elements with depth in the upper 20 cm of this core.
Station 38
2±63 mm
>63 mm
0.8 0.1 0.5 0.1 2.8 0.5 1.7 1.6 1.9 1.8 8.4 93 28 11
0.5 0.1 1.3 0.1 0.5 0.2 0.5 0.2 0.3 0.3 1.7 11 6.8 4
<2 mm
2±63 mm
>63 mm
0.6 0.1 0.5 0.3 0.5 0.8 1 0.6 1 1.2 9 42 27 7.3
1 0.1 1.3 0.1 0.4 0.5 0.4 0.3 0.4 0.3 2.4 4.1 4.7 2.4
12 0.2 3.7 0.2 2.9 1.5 1.6 1 2 4.3 14.6 360 16 24
DISCUSSION
These data show that the anthropogenic elements, Cu, Zn, Ag, Cd and Pb, are generally present in higher concentrations in sur®cial sediments from cores 8 and 25 than in core 38. This suggests that heavy-metal pollution of the sediments is greater in Puck Bay than near the mouth of the Vistula River. However, it may also re¯ect the higher rates of sedimentation (and therefore the greater dilution of pollutants) near the mouth of the Vistula River than in Puck Bay. The data also show a decrease in the concentrations of the anthropogenic elements with depth in the sediment column in cores 8 and 25 but not in sediments from core 38. The increase in heavy metals in the upper layers of cores 8 and 25 compared to the lower layers re¯ects the onset of industrialization and the resultant increase in heavymetal pollution, in Poland. By contrast, sediments from core 38 taken from near the mouth of the Vistula River have a much higher sedimentation rate than those from Puck Bay. Sedimentation rates for the upper layers of nearby sediments have be determined to be in the range 0.91±7.71 mm/year (Witkowski and Pempkowiak, 1995). Assuming the average of these two values for the upper layers of sediments for core 38, this implies that the sediments in the upper 20 cm of this core were deposited during the last 45 years or so (although this ®gure is subject to a wide margin of error). This corresponds to the period of heavy industrialization in the Vistula Basin (Szefer et al., 1996). In addition, this is a stormy area where extensive sediment resuspension takes place leading to mixing of the sediment. The maximum of many elements in the depth range 5±15 cm in this core may re¯ect the stagnation of the Polish economy after 1980 when industrial production declined. Szefer et al. (1995a) have already suggested that the anthropogenic elements, Cu, Zn, Ag, Cd and
Anthropogenic in¯ux of metallic pollutants into Puck Bay
299
Fig. 5Ðcaption overleaf
Pb, are most probably scavenged by Fe- and Mnoxyhydroxides at the hydrological front where mixing of the Vistula river water with brackish Baltic water takes place. The enrichment of several of
these elements in the 2±63 mm fraction compared to the <2 mm fraction in the sediments from core 38 may therefore possibly be explained by sorption of these elements on Fe- and Mn-oxyhydroxide par-
300
P. Szefer et al.
Fig. 5. Distribution of 15 elements with depth in each of the size fractions (<2, 2-63 and >63 mm) in sediment core 25.
Anthropogenic in¯ux of metallic pollutants into Puck Bay
Fig. 6Ðcaption overleaf
301
302
P. Szefer et al.
Fig. 6. Distribution of 15 elements with depth in each of the size fractions (<2, 2±63 and >63 mm) in sediment core 38.
Anthropogenic in¯ux of metallic pollutants into Puck Bay
ticles with diameters greater than 2 mm. This is supported by the fact that Fe is also enriched in the 2± 63 mm fraction compared to the <2 mm fraction in the sediments from this core and indicates that Feoxyhydroxide may be the dominant adsorbent. The increase in the Fe content in the 2±63 mm fraction of the sediment with depth may re¯ect the formation of iron sulphides within the sediment core. In order to assess the in¯uence of heavy-metal pollution in Puck Bay more precisely, enrichment factors (EF) were calculated for all three cores. From the data in Table 2, it is seen that Ni?, Cu?, Zn, Ag, Cd and Pb have EF values signi®cantly greater than unity and may therefore be considered to be dominantly anthropogenic in origin whereas all the other elements analyzed have EF values of about unity and may therefore be considered to be dominantly terrigenous in origin (except possibly Ca which may be partly biogenic in origin in some samples). This con®rms the previous ®ndings of Szefer and Skwarzec (1988) with the exception that Ag must be added to the list of anthropogenic elements. In addition, the enrichment factors are highest in the <2 mm fraction and decrease with increasing grain size. This con®rms that the anthropogenic elements are dominantly associated with the ®ne fraction of the sediment. The enrichment of these elements lies in the sequence Ag >> Cd r Pb>Zn >> Cu r Ni. Silver is therefore the most anthropogenically enriched element in these sediments and Cu and Ni appear to be only marginal for inclusion in this list. Silver is also characterized by concentrations much higher than background levels in the <2 mm fraction of the deeper sediments. These ®ndings re¯ect the fact that Poland has the highest abundance of silver deposits per unit area of any country (Singer, 1995). By contrast, a dierent pattern emerges when the anthropogenic factor (AF) is considered. Using this parameter, the enrichment of these elements lies in the sequence Cd >> Pb r Zn>Agr Cu>Cr. The dierence in these two sequence patterns may be attributed to the dierent methods of calculation of these two parameters. In the case of the enrichment factor, the enrichment of the element is normalized relative to Al in the sur®cial sediments whereas, in the case of the anthropogenic factor, the enrichment of the element is normalized relative the depth in the sediment core. The data may therefore indicate that the anthropogenic enrichment of Ag in the sediments has occurred over a longer time period than that of Pb and Zn such that the true background concentration of Ag at depth within the sediment was not available for these sediment cores.
303
CONCLUSIONS
The data presented here con®rm that heavy-metal pollution is a signi®cant factor in the sediments of Puck Bay and justi®es the continuing eort to study coastal pollution in the Baltic Sea. AcknowledgementsÐThis work was partly supported by grant No. 6 P202 034 06 to one of the authors (P. S.) from the Polish National Committee of Scienti®c Research (Komitet Badan Naukowych) in Warsaw as part of the LOICZ Programme. Editorial handling: R. Fuge.
REFERENCES Bolal/ ek J. (1992a) Ionic macroconstituents of the interstitial waters of Puck Bay Oceanologia 33, 131±158. Bolal/ ek J. (1992b) Phosphate at the water±sediment interface in Puck Bay Oceanologia 33, 159±182. Brown G. (1980) Associated minerals. In Crystal Structures of Clay Minerals and their X-ray Identi®cation, Vol. 5, pp. 361±410. Mineralogical Society Monograph. Brown G. and Brindley, G. W. (1980) X-ray diraction procedures of clay mineral identi®cation. In Crystal Structures of Clay Minerals and their X-ray Identi®cation, Vol. 5, pp. 305±359. Mineralogical Society Monograph. Helios Rybicka E. (1992a) Phase-speci®c bonding of heavy metals in sediments of the Vistula River, Poland. Appl. Geochem. 2 (Suppl. Issue), 45±48. Helios Rybicka E. (1992b) Heavy metal partitioning in polluted river and sea sediments: Clay mineral eects Miner. Petrogr. Acta 35-A, 297±305. Jankowska, H. (1993) The Bottom Deposits of Puck Bay. Marine Pollution (3), Scienti®c Committee on Oceanic Research, Polish Academy of Sciences, Gdansk, pp. 163±171. Korzeniewski, K. (1993) Puck Bay. Institute of Oceanography, University of Gdansk, 532 pp. (in Polish). Plinski, M. (1993) Ecological Problems of Puck Bay: Current Situation and Attempts at Recovery. University of Gdansk, Gdansk, 142 pp. (in Polish). Singer D. A. (1995) World class base and precious metal deposits: A quantitative analysis Econ. Geol. 90, 88±104. Szefer P. and Skwarzec B. (1988) Distribution and possible sources of some elements in the sediment cores of the southern Baltic Mar. Chem. 23, 109±129. Szefer, P., Szefer, K. and Styczynska-Jurewicz, E. (1994) Metallic elements in fauna and ¯ora of the inner Puck Bay. In Puck Bay Possibilities of Remediation, pp. 131± 143. Institute of Environmental Protection, Warsaw (in Polish). Szefer P., Glasby G. P., Pempkowiak J. and Kaliszan R. (1995a) Extraction studies of heavy-metal pollutants in sur®cial sediments from the southern Baltic Sea o Poland Chem. Geol. 120, 111±126. Szefer P., Kusak A., Szefer K., Jankowska H., Wolowicz M. and Ahmed Ali A. (1995b) Distribution of selected metals in sediment cores of Puck Bay, Baltic Sea Mar. Pollut. Bull. 30, 615±618. Szefer P., Glasby G. P., Szefer K., Pempkowiak J. and Kaliszan R. (1996) Heavy-metal pollution in sur®cial sediments from the southern Baltic Sea o Poland J. Environ. Sci. Health 31A, 2723±2754.
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Witkowski A. and Pempkowiak J. (1995) Reconstructing the development of human impact from diatoms and
210 Pb sediment dating (the Gulf of Gdansk-southern Baltic Sea) Geographia Polonica 65, 63±78.
Applied Geochemistry, Vol. 13, pp. 293±304, 1998 # 1998 Elsevier Science Ltd All rights reserved. Printed in Great Britain 0883-2927/98 $19.00 + 0.00
Evaluation of the anthropogenic in¯ux of metallic pollutants into Puck Bay, southern Baltic P. Szefer*, A. Kusak and K. Szefer Department of Analytical Chemistry, Medical University of Gdansk, al. Gen. J. Hallera 107, 80-416 Gdansk, Poland
G. P. Glasby Department of Earth Sciences, University of Sheeld, Sheeld S3 7HP, U.K.
H. Jankowska and M. Wolowicz Institute of Oceanography, University of Gdansk, al. Marsz. J. Pilsudskiego 46, 81-378 Gdynia, Poland
A. A. Ali Faculty of Science, Arts and Education, University of Aden, P.O. Box 6014, Khormaksar, Aden, Yemen (Received 9 September 1995; accepted in revised form 20 May 1997) AbstractÐDistributions of 15 elements with depth in two sediment cores from Puck Bay in the Gulf of Gdansk show that Ag, Cd, Pb, Zn and possibly Cu and Ni are anthropogenically enriched in the sediments there. The concentrations of these elements decrease sharply with depth in the sediment column and the elements are preferentially enriched in the <2 mm size fraction of the sediment. The sequence of element enrichment depends on whether the enrichment factor (EF) and the anthropogenic factor (AF) are used to calculate the element enrichment. By contrast, the anthropogenic elements show no systematic decrease in concentration with depth in a sediment core taken from near the mouth of the Vistula River. This re¯ects the higher sedimentation rate there such that the entire upper 20 cm of the core was deposited during the major, post-war period of industrialization in Poland. In addition, these elements are enriched in the 2±63 mm fraction compared to the <2 mm fraction in these sediments. This suggests that the heavy metals are mainly adsorbed on Fe oxyhydroxide particles with diameters greater than 2 mm at the hydrological front where Vistula river water mixes with brackish Baltic water. It appears that heavy-metal pollution of sediments in parts of Puck Bay may be greater than that near the mouth of the Vistula River which may re¯ect, in part, the higher sedimentation rate near the mouth of the Vistula River. The mode of incorporation of heavy-metals into the sediments in the two areas may also be dierent. # 1998 Elsevier Science Ltd. All rights reserved
INTRODUCTION
Sediments and biota from Puck Bay in the Gulf of Gdansk are known to be signi®cantly contaminated by heavy metals (Szefer et al., 1994, 1995a, 1996) but little work has been carried out on the distribution of heavy metals with depth in sediment cores there (Szefer and Skwarzec, 1988). Furthermore, studies of heavy-metal pollution in sediments from Puck Bay have been carried out only at the reconnaissance level. In this study, we present data on the distribution of heavy metals with depth in two sediment cores from Puck Bay in order to assess the pollution load there more precisely. Heavy-metal data on one sediment core taken from near the mouth of the Vistula River in *Corresponding author. 293
the Gulf of Gdansk are also presented for comparison. Puck Bay forms the western part of the Gulf of Gdansk. It may be divided into two parts. The interior of the bay is a shallow area with an average depth of ca. 3 m (maximum of 9 m in the Kuznica Deep) and its extent is marked by the sandy barriers of Seagull Reef and by Hel Peninsula. The sediments are mainly ®ne sand and silty mud. The outer part of Puck Bay is a deeper basin with a maximum water depth of ca. 60 m. The sediments vary from coarse to ®ne sand in the shallower parts to silty clay and clay in the deeper parts (>30 m). Quartz, feldspar and plagioclase are the principal minerals present in the sediments. Quartz generally occurs in the range 30±40%. Secondary minerals include pyroxene, amphibole, garnet, pyrite, gypsum and calcite. Illite and chlorite are the principal
294
P. Szefer et al.
Fig. 1. Schematic map showing the locations of sediment cores 8, 25 and 38 in Puck Bay.
clay minerals with lesser amounts of kaolinite and smectite. The organic carbon content of the sediments varies mostly between 5±15% in ®ne-grained sediments. The Vistula is the dominant river draining into the Gulf of Gdansk (and therefore the principal source of pollution) but a number of rivers (Rewa and Kacza) discharge directly into Puck Bay. Accounts of various aspects of Puck Bay have been presented by Bolalek (1992a,b), Jankowska (1993), Korzeniewski (1993) and Plinski (1993) and the major characteristics of Gulf of Gdansk and Puck Bay have been summarized by Szefer et al. (1996).
METHODOLOGY
In this study, two sediment cores (No. 8 and No. 25) from the outer part of Puck Bay and one core from near the mouth of the Vistula River (No. 38) were taken during a cruise of R.V. Oceanograf II in 1991. The locations of the cores are shown in Fig. 1. Samples of sediment were taken at 5 cm intervals within the cores. Subsamples of the wet material were then washed through a polythene mesh with mesh sizes 63 and 2 mm and the excess water evaporated on a water bath at 808C to obtain a thick slurry. The material was dried at 1108C and weighed prior to digestion with concentrated HNO3 (65%), HF (40%) and HClO4 (70%) in volume ratios 7:7:1 (Szefer et al., 1995a). The dry residue was converted to chlorides by evaporation with concentrated HCl (36%) and dissolved in 1 M HCl. The concentrations of selected elements were measured by AAS using deuterium-background cor-
Fig. 2. The distribution of grain size in the surface sediments of the sediment cores 8, 25 and 38.
rection. The accuracy and precision of the method were satisfactory based on intercomparison with reference material (sediment sample code SD-N-1/2) from the IAEA in Monaco.
Anthropogenic in¯ux of metallic pollutants into Puck Bay
295
Fig. 3. The variation of organic carbon content with depth in the sediment cores 8, 25 and 38.
Bulk mineral composition was determined by Xray diraction using a DRON 1 X-ray diractractometer (Cu Ka, 4±678 2y) and clay mineral composition was determined on sedimented samples using a DRON 2 X-ray diractractometer (Cu Ka, 3±328 2y) using the procedures described by Brown (1980) and Brown and Brindley (1980). In order to evaluate the data in more detail, the enrichment factor (EF) and the anthropogenic factor (AF) for elements in the cores were calculated according to the formulae EF Cx =CAl s = Cx =CAl c where Cx and CAl refer to the concentrations of element x and Al in the surface sediments (s) and earth's crust (c), respectively. Aluminium is used here as the reference element and AF Cs =Cd where Cs and Cd refer to the concentrations of the
element in the surface sediments and sediments at depth in the sediment column. A fuller account of the calculation of the enrichment factor (EF) is given by Szefer et al. (1996).
RESULTS
The grain-size distribution in the surface sediments and the variation of organic C content with depth in the sediment column at each station are shown in Figs 2 and 3. The distributions of 15 elements with depth in the sediment cores are shown in Figs 4±6. The mineralogy of the bulk sediment is listed in Table 1. For cores 8 and 25, the element concentration data show that, in general, the maximum concentration of each element within a given sample is found in the ®nest fraction (<2 mm) of the sediment as is commonly observed (e.g. for sediments from
296
P. Szefer et al. Table 1. Mineralogy of bulk sediments from sediment cores 8, 25 and 38
Station No. 8 25 38
Essential minerals quartz
Clay
mineral
illite
kaolinite
chlorite
smectite
+++
++
+
+
+ +++
+
Accessory minerals
plagioclase, K-feldspar, low halite, pyrite quartz, plagioclase K-feldspar, garnet very low quartz K-feldspar, plagioclase, low calcite
Fig. 4Ðcaption opposite
contents
Anthropogenic in¯ux of metallic pollutants into Puck Bay
Fig. 4. Distribution of 15 elements with depth in each of the size fractions (<2, 2±63 and >63 mm) in sediment core 8.
297
298
P. Szefer et al.
Table 2. Enrichment factors (EF) for 14 elements for each of the size fractions (<2, 2±63 and >63 mm) in the surface sediments (0±5 cm) of sediment cores 8, 25 and 38 Station 8 <2 mm Na/Al Mg/Al K/Al Ca/Al Cr/Al Mn/Al Fe/Al Co/Al Ni/Al Cu/Al Zn/Al Ag/Al Cd/Al Pb/Al
2.5 0.2 1.7 0.1 1.2 0.7 0.9 1.1 2.5 1.7 11 300 14 21
Station 25
2±63 mm
>63 mm
0.3 0.1 1 0.8 0.7 0.5 0.8 1 1.2 1.2 6.6 18 16 6.3
0.5 0.2 0.8 0.5 0.4 0.4 0.6 0.6 1.6 0.5 2.3 8.3 3.8 2.9
<2 mm 1 0.2 1.1 0 1.4 0.2 0.6 0.5 1 1 4.3 200 17 11
the Vistula River, Helios Rybicka, 1992a,b). Exceptions are Ca in sediments from station 8 where the maximum concentration is found in the size class 2±63 mm. This presumably re¯ects the occurrence of calcareous organisms in this size fraction. Cadmium is also highest in this size fraction in sediments from station 8 and Pb is highest in the <63 mm size fraction in the basal sediments from station 25. In both cores, Cu, Zn, Ag, Cd and Pb show a decreasing concentration with depth in the sediment. The other elements show no such trend. By contrast, several elements (e.g. Ca, Fe, Cr, Co, Zn, Cd) are present in higher concentrations in the 2±63 mm than in the <2 mm size fraction of core 38 and there is no systematic decrease in the contents of Cu, Zn, Ag, Cd and Pb with depth in the sediment column in this core. Indeed, most elements show a maximum in their distribution with depth in this core increasing from the surface to the 5±15 cm interval before declining in the 15±20 cm depth interval. It is also seen that the concentrations of some elements (Fe, Cr, Co, Ni, Zn, Ag, Cd and Pb) are higher in the <2 mm fraction of the surface sediments of cores 8 and 25 than those in the <2 mm fraction of the surface sediments of core 38, although this relationship does not apply to the other size fractions. The enrichment factors (EF) for 15 elements for each of the size fractions (<2, 2±63 and >63 mm) in the surface sediments (0±5 cm) of all three cores are presented in Table 2. The anthropogenic factors (AF) have already been calculated for the elements (Cr, Cu, Zn, Ag, Cd and Pb) in the <2 mm size fraction in two cores (8 and 25) (Szefer et al., 1995b) but these data will not be repeated here. It will be noted that an AF could not be calculated for core 38 taken from near the mouth of the Vistula River since there is no systematic decrease in concentration of the anthropogenic elements with depth in the upper 20 cm of this core.
Station 38
2±63 mm
>63 mm
0.8 0.1 0.5 0.1 2.8 0.5 1.7 1.6 1.9 1.8 8.4 93 28 11
0.5 0.1 1.3 0.1 0.5 0.2 0.5 0.2 0.3 0.3 1.7 11 6.8 4
<2 mm
2±63 mm
>63 mm
0.6 0.1 0.5 0.3 0.5 0.8 1 0.6 1 1.2 9 42 27 7.3
1 0.1 1.3 0.1 0.4 0.5 0.4 0.3 0.4 0.3 2.4 4.1 4.7 2.4
12 0.2 3.7 0.2 2.9 1.5 1.6 1 2 4.3 14.6 360 16 24
DISCUSSION
These data show that the anthropogenic elements, Cu, Zn, Ag, Cd and Pb, are generally present in higher concentrations in sur®cial sediments from cores 8 and 25 than in core 38. This suggests that heavy-metal pollution of the sediments is greater in Puck Bay than near the mouth of the Vistula River. However, it may also re¯ect the higher rates of sedimentation (and therefore the greater dilution of pollutants) near the mouth of the Vistula River than in Puck Bay. The data also show a decrease in the concentrations of the anthropogenic elements with depth in the sediment column in cores 8 and 25 but not in sediments from core 38. The increase in heavy metals in the upper layers of cores 8 and 25 compared to the lower layers re¯ects the onset of industrialization and the resultant increase in heavymetal pollution, in Poland. By contrast, sediments from core 38 taken from near the mouth of the Vistula River have a much higher sedimentation rate than those from Puck Bay. Sedimentation rates for the upper layers of nearby sediments have be determined to be in the range 0.91±7.71 mm/year (Witkowski and Pempkowiak, 1995). Assuming the average of these two values for the upper layers of sediments for core 38, this implies that the sediments in the upper 20 cm of this core were deposited during the last 45 years or so (although this ®gure is subject to a wide margin of error). This corresponds to the period of heavy industrialization in the Vistula Basin (Szefer et al., 1996). In addition, this is a stormy area where extensive sediment resuspension takes place leading to mixing of the sediment. The maximum of many elements in the depth range 5±15 cm in this core may re¯ect the stagnation of the Polish economy after 1980 when industrial production declined. Szefer et al. (1995a) have already suggested that the anthropogenic elements, Cu, Zn, Ag, Cd and
Anthropogenic in¯ux of metallic pollutants into Puck Bay
299
Fig. 5Ðcaption overleaf
Pb, are most probably scavenged by Fe- and Mnoxyhydroxides at the hydrological front where mixing of the Vistula river water with brackish Baltic water takes place. The enrichment of several of
these elements in the 2±63 mm fraction compared to the <2 mm fraction in the sediments from core 38 may therefore possibly be explained by sorption of these elements on Fe- and Mn-oxyhydroxide par-
300
P. Szefer et al.
Fig. 5. Distribution of 15 elements with depth in each of the size fractions (<2, 2-63 and >63 mm) in sediment core 25.
Anthropogenic in¯ux of metallic pollutants into Puck Bay
Fig. 6Ðcaption overleaf
301
302
P. Szefer et al.
Fig. 6. Distribution of 15 elements with depth in each of the size fractions (<2, 2±63 and >63 mm) in sediment core 38.
Anthropogenic in¯ux of metallic pollutants into Puck Bay
ticles with diameters greater than 2 mm. This is supported by the fact that Fe is also enriched in the 2± 63 mm fraction compared to the <2 mm fraction in the sediments from this core and indicates that Feoxyhydroxide may be the dominant adsorbent. The increase in the Fe content in the 2±63 mm fraction of the sediment with depth may re¯ect the formation of iron sulphides within the sediment core. In order to assess the in¯uence of heavy-metal pollution in Puck Bay more precisely, enrichment factors (EF) were calculated for all three cores. From the data in Table 2, it is seen that Ni?, Cu?, Zn, Ag, Cd and Pb have EF values signi®cantly greater than unity and may therefore be considered to be dominantly anthropogenic in origin whereas all the other elements analyzed have EF values of about unity and may therefore be considered to be dominantly terrigenous in origin (except possibly Ca which may be partly biogenic in origin in some samples). This con®rms the previous ®ndings of Szefer and Skwarzec (1988) with the exception that Ag must be added to the list of anthropogenic elements. In addition, the enrichment factors are highest in the <2 mm fraction and decrease with increasing grain size. This con®rms that the anthropogenic elements are dominantly associated with the ®ne fraction of the sediment. The enrichment of these elements lies in the sequence Ag >> Cd r Pb>Zn >> Cu r Ni. Silver is therefore the most anthropogenically enriched element in these sediments and Cu and Ni appear to be only marginal for inclusion in this list. Silver is also characterized by concentrations much higher than background levels in the <2 mm fraction of the deeper sediments. These ®ndings re¯ect the fact that Poland has the highest abundance of silver deposits per unit area of any country (Singer, 1995). By contrast, a dierent pattern emerges when the anthropogenic factor (AF) is considered. Using this parameter, the enrichment of these elements lies in the sequence Cd >> Pb r Zn>Agr Cu>Cr. The dierence in these two sequence patterns may be attributed to the dierent methods of calculation of these two parameters. In the case of the enrichment factor, the enrichment of the element is normalized relative to Al in the sur®cial sediments whereas, in the case of the anthropogenic factor, the enrichment of the element is normalized relative the depth in the sediment core. The data may therefore indicate that the anthropogenic enrichment of Ag in the sediments has occurred over a longer time period than that of Pb and Zn such that the true background concentration of Ag at depth within the sediment was not available for these sediment cores.
303
CONCLUSIONS
The data presented here con®rm that heavy-metal pollution is a signi®cant factor in the sediments of Puck Bay and justi®es the continuing eort to study coastal pollution in the Baltic Sea. AcknowledgementsÐThis work was partly supported by grant No. 6 P202 034 06 to one of the authors (P. S.) from the Polish National Committee of Scienti®c Research (Komitet Badan Naukowych) in Warsaw as part of the LOICZ Programme. Editorial handling: R. Fuge.
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