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Normalization to lithium for the assessment of metal contamination in coastal sediment cores from the Aegean Sea, Greece
Marine Environmental Research 52 (2001) 1±12 www.elsevier.com/locate/marenvrev
Normalization to lithium for the assessment of metal contamination in coastal sediment cores from the Aegean Sea, Greece M. Aloupi, M.O. Angelidis * Department of Environmental Studies, University of the Aegean, Karadoni 17, 81100 Mytilene, Greece Received 26 October 1999; received in revised form 23 June 2000; accepted 30 June 2000
Abstract Sediment cores from the harbour and the coastal zone of Mytilene, island of Lesvos, Greece, were used to study the metal contamination caused by the discharge of untreated urban euents into the sea. In the harbour, the upper layers were highly enriched in Cd, Cu, Pb and Zn, while no metal enrichment was recorded in the cores from the wider coastal zone. The metal data were normalized to Li (conservative element) to compensate for the natural textural and mineralogical variability. It was found that only the upper 18 cm of the core collected from the harbour of Mytilene could be reported as metal contaminated. Also, through the normalization procedure, it was found that the surface layers of coastal sediments assumed `clean' were enriched in Pb, probably as a result of atmospheric transportation of the metal from the nearby town. # 2001 Elsevier Science Ltd. All rights reserved. Keywords: Lithium; Normalization; Metal contamination; Aegean Sea; Sediment cores
1. Introduction The small towns on the coast of Mediterranean islands witnessed an important expansion and a seasonal population growth because of the rapid development of the tourism industry during the last decades. However, the urban infrastructure did not develop at the same rate and the town euents are still disposed of into the coastal marine environment without any treatment. In most cases the harbour is the place where sewage outfalls are located and harbour sediments are the ®nal * Corresponding author. Tel.: +30-251-36232; fax: +30-251-36262. E-mail address: [email protected] (M.O. Angelidis). 0141-1136/01/$ - see front matter # 2001 Elsevier Science Ltd. All rights reserved. PII: S0141-1136(00)00255-5
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deposition place of the euent-born pollutants. Urban euents may carry important metal loads (FoÈrstner & Wittmann, 1981), mostly in the colloidal and particulate fractions. In the marine environment, following ¯occulation and settling (Gibbs, 1983), the euent-born metals are ®nally accumulated into the harbour sediments thus creating important toxic metal deposits (Angelidis, 1995; Angelidis & Aloupi, 1995; Burgess & Scott, 1992; Gibbs, 1993). The impact of urban euents on metal distribution in the coastal environment of the relatively `unspoiled' islands of the Mediterranean Sea has not been investigated in depth. These islands (especially in the Aegean Sea) are popular holiday resorts with no serious pollution problems (lack of industrial activities, intensive agriculture or large urban clusters). However, the urban development in the islands constitutes a pollution source, which could aect the quality of the neighbouring marine coastal environment. In order to investigate the extent of metal contamination in such cases, a survey was conducted in the harbour and the wider marine coastal environment of Mytilene, island of Lesvos, Greece. The town has a population of 25 000 and its euents are discharged untreated into the sea through 25 sewage outfalls along the town coastline. Previous investigations revealed increased metal concentrations in the surface sediments of the harbour, while no signs of metal enhancements were detected in the sediments of the wider coastal zone (Angelidis, 1995; Angelidis & Aloupi, 1997). 2. Materials and methods Sediment cores were collected with a gravity corer from four locations including the harbour of Mytilene (cores A and B) and the wider area o the eastern coast of the island of Lesvos (cores C and D; Fig. 1). Both oshore sites were within 1 mile distance from the adjacent shore. To avoid contamination the corer was equipped with a plexiglass liner. After collection the cores were sealed with a polyethylene wrap and kept in refrigeration (4 C) until processed. In the laboratory, the upper 12 cm of the cores were sectioned every 2 cm and the deeper parts every 3 cm. The numbers 1, 2. . . were attributed to the sections from each core, from top to bottom, e.g. A1 corresponds to the upper 0±2 cm of the core A and D9 to the 18±21 cm section of core D. Thus, cores A, B, C, and D were divided to sections A1 to A12 (total length 30 cm), B1 to B9 (total length 21 cm), C1 to C6 (total length 12 cm) and D1 to D12 (total length 30 cm), respectively. In all sections of the cores, grain size distribution was measured by wet sieving and the following fractions were determined: silt+clay (<63 mm), sand (1 mm>x>63 mm) and gravel (>1 mm; Loring & Rantala, 1992). Organic carbon (OC), carbonate and metal contents were all determined in the <1 mm fraction. OC was determined by the Walkley±Black method, adopted and modi®ed by Jackson (1958) and carbonate content was measured using a method described by Loring and Rantala (1992). The total metal concentrations of the samples were determined after decomposition of 200 mg of dried ground sediment with 1 ml of aqua regia and 6 ml of hydro¯uoric acid (HF), in Savillex te¯on bombs heated in a microwave oven
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Fig. 1. Study area and sampling stations.
(Loring & Rantala, 1992). The metal determinations were performed using a PerkinElmer 5100ZL Atomic Absorption Spectrometer with Zeeman background correction. Al, Cu, Fe, Li, Mn and Zn were determined by ¯ame atomic absorption spectrometry, while Cd, Cr and Pb were determined by graphite furnace atomic absorption spectrometry with a mixture of 50 mg NH2H2PO4 and 3 mg Mg(NO3)2 as a matrix modi®er (Angelidis & Aloupi, 1997). The quality assurance of the analytical results was controlled with the use of Reference Materials certi®ed by National Research Council of Canada (BCSS-1 marine sediment, PACS-1 harbour sediment) and International Atomic Energy Agency (SDM2TM marine sediment). The metal data from the core sections were normalized to a conservative element, Li. Elements of natural origin which are structurally combined to one or more of the major ®ne-grained trace metal carriers are considered conservative. Several conservative elements have been used for normalization purposes: Al (Bertine & Goldberg, 1977; Bruland, Bertine, Koide, & Goldberg, 1974; Carral, Villares,
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Puente, & Carballeira, 1995; Hirst, 1962a, b; Sharma, Borole, & Zingde, 1994), Li (Loring, 1990), Cs (Ackerman, 1980), Sc (Ackerman, 1980; Grousset, Quetel, Thomas, Donard, Lawber, Quillard, & Monaco, 1995) and Fe (Blomqvist, Larsson, & Borg, 1992; Herut, Hornung, Krom, Kress, & Cohen, 1993; Piper, 1971). Normalization to OC has also been used in some cases (Horowitz, 1991). In the present study, OC was not considered as a reliable normalizer because of the diculty to assess undisturbed background concentrations. The presence of Poseidonia oceanica ®elds enhances the organic matter content in some oshore bottom sediments (stations 13±16, 24, 29, Fig. 1), whereas marine vegetation is absent from the rest of oshore and from harbour stations. The geochemical normalization, according to the literature, uses metal data from non-contaminated sediments of the study area to calculate the regression line of the metal on the normalizer and then tests the ratios metal/normalizer at other (possibly contaminated) stations. For the production of such a plot it is necessary to remove outlier values and to delineate a con®dence band of 95% of the regression line of the metal on the normalizer. Then, the data-points from the possibly contaminated areas have to be projected on the diagram. All points which are found inside the 95% con®dence band can be characterized as natural sediments, while all points above this area should be considered as contaminated sediments (Loring, 1990; Loring & Rantala, 1992). In the present study, the suitability of Li against Al, as a geochemical normalizer in the study area was tested. The data set used for the comparison included 13 samples of surface sediments from the wider coastal zone, located within 2 miles distance from the shoreline (Fig. 1, stations 13±18, 22±23, 25±29) (Aloupi & Angelidis, 2001). These sediments are considered to be representative of the local background and of the same origin with the harbour ones, as they are mainly formed from geological material transported from the eastern coast of Lesvos, the only adjacent land to the study area. They also have a great granulometric variability, as they vary from ®ne-grained material (87.8% silt+clay content, station 14) to sandy sediments (8.4% silt+clay content, station 28). This feature allows the relationship between normalizer and silt+clay content to be established, which is a prerequisite for the use of the normalizer as a proxy for the granulometric variability of the sediments. From the whole data set of oshore sediments, station 24 was excluded because of abnormally high values of OC and metals in the sandy sediments of the area. Table 1 shows the silt+clay content (on a gravel free basis), the OC content and the concentrations of metals in sur®cial coastal sediments of Mytilene. Regression of Al and Li on silt+clay content, as well as regression of metal concentrations on both Al and Li were performed, and the relative values of R2adj and statistical signi®cance (P) were compared. Table 2 summarizes R2adj and P values from the analysis of variance tables of the above regressions. From Table 2 it is clear that Li is more strongly correlated than Al with silt+clay ¯uctuations (R2adj for Li=0.977 and R2adj for Al=0.743). The very high value of R2adj for Li re¯ects the great ability of the element to normalize the metal concentrations in relation to the dierent texture of the sediments. It is also obvious (Table 2) that Li has stronger R2adj values for the regressions of metals. Therefore, Li is better
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Table 1 Silt+clay (S+C), organic carbon (OC) content and metal concentrations in surface sediments from Mytilene harbour and coastal area Stations
S+C (%)
OC (%)
Al (%)
Cd (mg/g)
Cr (mg/g)
Cu (mg/g)
Fe (%)
Li (mg/g)
Mn (mg/g)
Pb (mg/g)
Zn (mg/g)
13 14 15 16 17 18 22 23 24 25 26 27 28 29
64.80 87.80 75.96 41.42 42.00 35.45 31.09 16.64 16.49 10.59 35.90 38.08 8.36 63.99
3.39 2.86 3.35 2.97 1.41 1.55 0.71 0.35 3.33 0.27 1.09 1.06 0.35 2.24
4.75 5.34 5.24 3.65 4.45 3.94 3.74 2.79 4.43 2.83 3.88 4.08 3.61 3.83
0.131 0.085 0.082 0.119 0.076 0.062 0.044 0.053 0.061 0.059 0.074 0.044 0.030 0.080
122 132 120 86.5 81.8 97.5 59.8 67.1 99.0 40.0 74.4 68.4 54.2 99.0
27.3 23.4 30.5 24.0 16.7 20.4 9.91 6.07 22.0 6.17 14.0 11.0 5.34 17.8
2.40 2.70 2.75 1.65 1.74 1.74 1.34 1.12 2.63 1.15 1.77 1.36 0.80 2.04
27.0 37.1 31.8 19.9 21.8 19.4 15.2 11.7 34.0 12.3 20.6 18.8 9.74 28.4
280 300 302 222 229 261 224 260 323 226 260 183 171 273
44.2 39.8 42.5 39.0 34.5 37.1 24.2 20.7 23.2 29.7 34.4 36.7 27.8 37.5
69.1 73.1 72.9 76.7 45.8 55.0 33.7 23.0 71.0 29.8 41.9 32.3 12.9 53.0
Table 2 R2adj and probabilities from analysis of variance tables of regressions of Al and Li on silt+clay (S+C) content as well as of metals on Al and Li, in natural sediments from the coastal area of Mytilene (n=13) S+C
Cd
Cr
Cu
Fe
Mn
Pb
Zn
Al
R2adj
0.743 P<0.001
0.116 nsa
0.682 P<0.001
0.588 P<0.01
0.720 P<0.001
0.201 ns
0.535 P<0.01
0.435 P<0.01
Li
R2adj
0.977 P<0.001
0.296 P<0.05
0.830 P<0.001
0.663 P<0.001
0.928 P<0.001
0.543 P<0.01
0.591 P<0.01
0.656 P<0.001
a
ns, Non signi®cant (P>0.05).
suited to explain the natural variations in the metal concentrations. For example, Al cannot explain at all the natural ¯uctuations of the concentration of Cd and Mn (non-signi®cant correlations), whereas Li can normalize Mn concentrations but only to a limited degree for Cd concentrations. The low value of R2adj and the lower signi®cance level for Cd (Table 2) indicates that only 30% of its natural variability can be attributed to the textural and mineralogical variability of the sediments, suggesting the association of the metal with other geochemical substrates. The coexistence of both Al and Li in the lattice of clays re¯ects in their common ¯uctuation in relation to the content of silt+clay, as well as, in the regression of Li on Al (R2adj=0.727, P<0.001). Therefore, although both elements can be used as normalizers, Li appears to be better suited for the sediments of the study area than Al, which is the commonest normalizer mentioned in the literature. Li is a constituent of the ®ne-grained material of the sediments, such as primary micas and ferromagnesium minerals and secondary clay minerals (Loring, 1991). In non-contaminated sediments the ratio
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[Metal]/[Li] is relatively constant and a linear positive correlation exists between the concentrations of metal and the concentrations of Li. Since human activities will add anthropogenic metals but not Li to the marine environment, it is expected that contaminated sediments will present higher Metal/Li ratios. On the other hand, in most sedimentary environments, a linear relationship exists between Li concentrations and the percentage of ®ne-grained [silt+clay] content of the samples (Horowitz, 1991). Such a relationship allows the use of normalizer concentrations as a proxy for the granulometric variability of the sediments. Therefore, geochemical normalization to Li compensates for both granulometric and mineralogical variability of metal concentrations in sediments (Loring, 1990). Statistical analysis of data was performed with SPSS Ver. 7.5 for Windows software. 3. Results and discussion The content of the dierent sections of the cores in silt+clay, OC and carbonate is presented in Fig. 2a±c. In cores A, B and C the average percentage of ®ne-grained material was relatively high (55.578.09% in core A, 70.788.83% in core B and 63.045.66% in core C), whilst the sediments of core D had a coarser texture (only 34.698.06% of silt+clay and 49.807.03% of sand). The disturbance in the silt+clay content, which was recorded in core B at the depth of 6±10 cm, was attributed to the deposition of terrestrial material during the construction of the piers of the harbour. Similar patterns in core B were also found in the distribution of OC and metals (see below).
Fig. 2. Vertical pro®les of (a) silt+clay, (b) organic carbon and (c) carbonate contents in cores from the coastal area of Mytilene.
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Average OC concentrations are similar in cores A and B (3.210.47% and 3.18 0.40%, respectively) and re¯ect the deposition of euent-born organic matter in the harbour sediments. The ¯uctuation in OC concentrations with depth re¯ects changes in the activity of land-based pollution sources through time (but no data are available to further investigate the case). The higher OC in the deepest strata of core A are attributed to the discharge of euents of olive-oil re®neries in the past, which gradually ceased to operate during the last decade. In the cores from the coastal area outside the harbours (cores C and D), the concentrations of OC are lower and re¯ect non-polluted environments, with rapid oxidation of the organic material after deposition (Hedges & Keil, 1995; Wollast & Chou, 1998). Carbonate distribution in the cores is relatively stable in all locations, with the exception of core B, which at the depth of 6±10 cm shows a disturbance similar to that of grain-size at that depth. The total metal concentrations in cores A, B, C and D are presented in Fig. 3a±i. From the available data we can distinguish two kind of patterns: the pattern of anthropogenic metals (Cd, Cu, Pb, Zn) and the pattern of natural metals (Al, Fe, Li, Mn). The `anthropogenic' metals show a net increase in concentration in the upper parts of the harbour cores (A and B). This trend is more obvious in the pro®les of core A than of core B, because the sediments in core B have been disturbed by operations like dredging and input of foreign material transported to the place during the construction of docks (local Port Authority, personal communication). No dierences were found at dierent depths in the non-contaminated coastal zone cores (C and D). The higher concentrations in the upper layers of the sediments can be attributed to recent increases in metal discharges from sewer out¯alls related to urban activities (Aloupi, 1999). On the other hand, the `natural' metals have a relatively uniform distribution with depth in all cores, since their concentrations in coastal and harbour sediments are not aected by the discharge of town euents. The raw data are not sucient to quantify the intensity of contamination in the sediment layers of the harbour. To evaluate the natural levels of anthropogenic metals in the cores of the harbour and to indicate the depth where the metal concentrations exceed these natural levels, natural variability has to be considered by normalizing data to a conservative element. As mentioned in Section 2, the regression of each metal on Li in the natural sediment population was calculated using data from 13 stations at the wider coastal zone of Mytilene, o the harbours of the town. The diagrams produced from these data, as well as the projection of the core metal data on those diagrams, are presented in Figs. 4a±c and 5a±e. On the above diagrams two patterns are distinguished. For the `natural' metals (Al, Fe and Mn, Figs. 4a±c) data points are located within the limits of the 95% con®dence band of the regression line, for all (harbour and coastal zone) cores. On the other hand, all the anthropogenic metals (Cd, Cu, Pb and Zn, Fig. 5a±d) have increased Metal/Li ratios in the harbour cores, while the data points from the coastal zone cores are found within the 95% con®dence band, indicating no disturbance of natural concentrations. In the inner harbour (core A) the human in¯uence can be detected up to the depth of 18 cm for Cd and Cu (sections A1±A8) and
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Fig. 3. Vertical pro®les of metal concentrations in cores from the coastal area of Mytilene.
to the depth of 24 cm for Zn (sections A1±A10), while the sediment strata below these depths are considered as non-contaminated. Similarly, core B appears to be contaminated with Cd to the upper 6 cm (sections B1±B3) and with Cu and Zn to its full length.
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Fig. 4. Me:Li scatter plot (Me=Al, Fe, Mn) for core sediments of the coastal area of Mytilene. Solid line represents the regression line and dashed lines de®ne the 95% con®dence band for the surface sediments of the study area.
A similar but weaker anthropogenic in¯uence is also apparent for Cr (Fig. 5e). The normalization of the data showed enhanced Cr/Li ratios in the upper part of the inner harbour core (up to 10 cm depth, sections A1, A3±A5) and in almost the full length of the outer harbour core (sections B1, B3±B9). This ®nding suggests that part of Cr content in sediments of the harbour area can be attributed to anthropogenic sources. In the case of Pb, the upper parts of the cores A and B (Fig. 4c) appear to be contaminated, while the deeper sediment layers seem to be non-contaminated. However, the projection of the normalized metal concentrations from core C on the regression diagram, are below the con®dence band of the regression line which delineates the natural metal variability in the local sediments. This result indicates that Pb concentrations in the deeper layers of the core C are below the local natural background. The most probable explanation for such a result is that the natural background, as determined by the study of coastal surface sediments, has been overestimated. It is well known that Pb is transported through the atmosphere and is deposited in sediments of remote areas (Chester, 1990). So, the airborne Pb transport from the nearby town of Mytilene, as well as, from other remote unidenti®ed yet sources, may have been the reason for Pb deposition on the recent sediments of the coastal zone. Therefore, Pb concentrations in surface sediments may not be representative of the historical natural background. These results
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Fig. 5. Me:Li scatter plot (Me=Cd, Cu, Pb, Zn, Cr) for core sediments of the coastal area of Mytilene. Solid line represents the regression line and dashed lines de®ne the 95% con®dence band for the surface sediments of the study area.
underline the need for careful metal data interpretation during pollution studies in the coastal zone. 4. Conclusions The study of sediment cores collected from the harbour and the wider coastal zone of Mytilene showed that the ®ne-grained material, rich in OC and metals, which is transported by the town euents, is deposited to the sediments of the inner and outer
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harbour area, where calm hydrodynamic conditions prevail. Normalization to Li revealed that Cd, Cu, and Zn were highly enriched in the upper part of the inner and outer harbour cores. The deeper sediments of the harbour, as well as all the sediment layers of the wider coastal area, could be considered as non-contaminated. Cr had a similar behaviour, although its enhancement in the upper layers of the harbour sediments was less pronounced. In the case of Pb, normalization to Li showed that the assumed natural metal concentrations in the surface sediments of the marine coastal environment have been over-estimated. The probable cause may be atmospheric transportation of Pb from land based sources (urban) to the adjacent surface sediments.
References Ackerman, F. (1980). A procedure for correcting grain size eect in heavy metal analysis of estuarine and coastal sediments. Environment Technology Letters, 1, 518±527. Aloupi, M. (1999). Study of the in¯uence of urban discharges on the geochemistry of heavy metals in the marine coastal zone of Mytilene. PhD thesis, University of the Aegean, Greece (in Greek). Aloupi, M., & Angelidis, M. O. (2001). Geochemistry of natural and anthropogenic metals in the coastal sediments of the island of Lesvos, Aegean Sea. Environmental Pollution, 113, 211±219. Angelidis, M. O. (1995). The impact of urban euents on the coastal marine environment of Mediterranean islands. Water Science and Technology, 32(9±10), 85±94. Angelidis, M. O., & Aloupi, M. (1995). Metals in sediments of Rhodes harbor, Greece. Marine Pollution Bulletin, 31(4±12), 273±276. Angelidis, M. O., & Aloupi, M. (1997). Assessment of metal contamination in shallow coastal sediments around Mytilene, Greece. International Journal of Environmental Analytical Chemistry, 68, 281±293. Bertine, K. K., & Goldberg, E. D. (1977). History of heavy metal pollution in Southern California coastal zone. Environmental Science and Technology, 11, 201±207. Blomqvist, S., Larsson, U., & Borg, H. (1992). Heavy metal decrease in sediments of a Baltic Bay following tertiary sewage treatment. Marine Pollution Bulletin, 24, 258±266. Bruland, K. W., Bertine, K., Koide, M., & Goldberg, E. (1974). History of metal pollution in the Southern California coastal zone. Environmental Science and Technology, 8, 425±432. Burgess, R. M., & Scott, K. J. (1992). The signi®cance of in-place contaminated marine sediments on the water column: processes and eects. In G. A. Burton Jr., Sediments toxicity assessment (pp. 213±240). Boca Raton: Lewis Publishers. Carral, E., Villares, R., Puente, X., & Carballeira, A. (1995). In¯uence of watershed lithology on heavy metal levels in estuarine sediments and organisms in Galicia (North-West Spain). Marine Pollution Bulletin, 30, 604±608. Chester, R. (1990). Marine geochemistry. London: Unwin Hyman. FoÈrstner, U., & Wittmann, G. T. W. (1981). Heavy metals in the aquatic environment. Berlin: Springer Verlag. Gibbs, R. J. (1983). Coagulation rates of clay minerals and natural sediments. Journal of Sedimentary Petrology, 53, 1193±1203. Gibbs, R. J. (1993). Metals of the bottom muds in Townsville harbor, Australia. Environmental Pollution, 81, 297±300. Grousset, F. E., Quetel, C. R., Thomas, B., Donard, O. F. X., Lambert, C. E., Quillard, F., & Monaco, A. (1995). Anthropogenic vs. Lithogenic origins of trace elements (As, Cd, Pb, Rb, Sb, Sc, Sn, Zn) in water column particles: northwestern Mediterranean sea. Marine Chemistry, 48, 291±310. Hedges, J. I., & Keil, R. G. (1995). Sedimentary organic matter preservation: an assessment and speculative synthesis. Marine Chemistry, 49, 81±115.
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M. Aloupi, M.O. Angelidis / Marine Environmental Research 52 (2001) 1±12
Herut, B., Hornung, H., Krom, M. D., Kress, N., & Cohen, Y. (1993). Trace metals in shallow sediments from the Mediterranean coastal zone of Israel. Marine Pollution Bulletin, 26, 676±682. Hirst, D. M. (1962a). The geochemistry of modern sediments from the gulf of Paria Ð I. Geochimica et Cosmochima Acta, 26, 309±334. Hirst, D. M. (1962b). The geochemistry of modern sediments from the gulf of Paria Ð II. Geochimica et Cosmochima Acta, 26, 1147±1187. Horowitz, A. J. (1991). A primer on sediments Ð trace element chemistry (2nd ed.). Michigan: Lewis Publishers. Jackson, M. L. (1958). Soil chemical analysis. Englewood Clis, NJ: Prentice Hall. Loring, D. H. (1990). Lithium Ð a new approach for the granulometric normalization of trace metal data. Marine Chemistry, 29, 155±168. Loring, D. H. (1991). Normalization of heavy-metal data from estuarine and coastal sediments. ICES Journal of Marine Science, 48, 101±115. Loring, D. H., & Rantala, R. T. T. (1992). Manual for the geochemical analysis of marine sediments and suspended particulate matter. Earth Science Review, 32, 235±283. Piper, D. Z. (1971). The distribution of Co, Cr, Cu, Fe, Mn, Ni and Zn in Framvaren, A Norwegian anoxic Fjord. Geochimica Cosmochimica Acta, 35, 531±559. Sharma, P., Borole, D. V., & Zingde, M. D. (1994). 210Pb based trace element ¯uxes in the nearshore and estuarine sediments of Bombay India. Marine Chemistry, 47, 227±241. Wollast, R., & Chou, L. (1998). Distribution and ¯uxes of calcium carbonate along the continental margin in the gulf of Biscay. Aquatic Geochemistry, 4, 369±393.
Normalization to lithium for the assessment of metal contamination in coastal sediment cores from the Aegean Sea, Greece M. Aloupi, M.O. Angelidis * Department of Environmental Studies, University of the Aegean, Karadoni 17, 81100 Mytilene, Greece Received 26 October 1999; received in revised form 23 June 2000; accepted 30 June 2000
Abstract Sediment cores from the harbour and the coastal zone of Mytilene, island of Lesvos, Greece, were used to study the metal contamination caused by the discharge of untreated urban euents into the sea. In the harbour, the upper layers were highly enriched in Cd, Cu, Pb and Zn, while no metal enrichment was recorded in the cores from the wider coastal zone. The metal data were normalized to Li (conservative element) to compensate for the natural textural and mineralogical variability. It was found that only the upper 18 cm of the core collected from the harbour of Mytilene could be reported as metal contaminated. Also, through the normalization procedure, it was found that the surface layers of coastal sediments assumed `clean' were enriched in Pb, probably as a result of atmospheric transportation of the metal from the nearby town. # 2001 Elsevier Science Ltd. All rights reserved. Keywords: Lithium; Normalization; Metal contamination; Aegean Sea; Sediment cores
1. Introduction The small towns on the coast of Mediterranean islands witnessed an important expansion and a seasonal population growth because of the rapid development of the tourism industry during the last decades. However, the urban infrastructure did not develop at the same rate and the town euents are still disposed of into the coastal marine environment without any treatment. In most cases the harbour is the place where sewage outfalls are located and harbour sediments are the ®nal * Corresponding author. Tel.: +30-251-36232; fax: +30-251-36262. E-mail address: [email protected] (M.O. Angelidis). 0141-1136/01/$ - see front matter # 2001 Elsevier Science Ltd. All rights reserved. PII: S0141-1136(00)00255-5
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deposition place of the euent-born pollutants. Urban euents may carry important metal loads (FoÈrstner & Wittmann, 1981), mostly in the colloidal and particulate fractions. In the marine environment, following ¯occulation and settling (Gibbs, 1983), the euent-born metals are ®nally accumulated into the harbour sediments thus creating important toxic metal deposits (Angelidis, 1995; Angelidis & Aloupi, 1995; Burgess & Scott, 1992; Gibbs, 1993). The impact of urban euents on metal distribution in the coastal environment of the relatively `unspoiled' islands of the Mediterranean Sea has not been investigated in depth. These islands (especially in the Aegean Sea) are popular holiday resorts with no serious pollution problems (lack of industrial activities, intensive agriculture or large urban clusters). However, the urban development in the islands constitutes a pollution source, which could aect the quality of the neighbouring marine coastal environment. In order to investigate the extent of metal contamination in such cases, a survey was conducted in the harbour and the wider marine coastal environment of Mytilene, island of Lesvos, Greece. The town has a population of 25 000 and its euents are discharged untreated into the sea through 25 sewage outfalls along the town coastline. Previous investigations revealed increased metal concentrations in the surface sediments of the harbour, while no signs of metal enhancements were detected in the sediments of the wider coastal zone (Angelidis, 1995; Angelidis & Aloupi, 1997). 2. Materials and methods Sediment cores were collected with a gravity corer from four locations including the harbour of Mytilene (cores A and B) and the wider area o the eastern coast of the island of Lesvos (cores C and D; Fig. 1). Both oshore sites were within 1 mile distance from the adjacent shore. To avoid contamination the corer was equipped with a plexiglass liner. After collection the cores were sealed with a polyethylene wrap and kept in refrigeration (4 C) until processed. In the laboratory, the upper 12 cm of the cores were sectioned every 2 cm and the deeper parts every 3 cm. The numbers 1, 2. . . were attributed to the sections from each core, from top to bottom, e.g. A1 corresponds to the upper 0±2 cm of the core A and D9 to the 18±21 cm section of core D. Thus, cores A, B, C, and D were divided to sections A1 to A12 (total length 30 cm), B1 to B9 (total length 21 cm), C1 to C6 (total length 12 cm) and D1 to D12 (total length 30 cm), respectively. In all sections of the cores, grain size distribution was measured by wet sieving and the following fractions were determined: silt+clay (<63 mm), sand (1 mm>x>63 mm) and gravel (>1 mm; Loring & Rantala, 1992). Organic carbon (OC), carbonate and metal contents were all determined in the <1 mm fraction. OC was determined by the Walkley±Black method, adopted and modi®ed by Jackson (1958) and carbonate content was measured using a method described by Loring and Rantala (1992). The total metal concentrations of the samples were determined after decomposition of 200 mg of dried ground sediment with 1 ml of aqua regia and 6 ml of hydro¯uoric acid (HF), in Savillex te¯on bombs heated in a microwave oven
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Fig. 1. Study area and sampling stations.
(Loring & Rantala, 1992). The metal determinations were performed using a PerkinElmer 5100ZL Atomic Absorption Spectrometer with Zeeman background correction. Al, Cu, Fe, Li, Mn and Zn were determined by ¯ame atomic absorption spectrometry, while Cd, Cr and Pb were determined by graphite furnace atomic absorption spectrometry with a mixture of 50 mg NH2H2PO4 and 3 mg Mg(NO3)2 as a matrix modi®er (Angelidis & Aloupi, 1997). The quality assurance of the analytical results was controlled with the use of Reference Materials certi®ed by National Research Council of Canada (BCSS-1 marine sediment, PACS-1 harbour sediment) and International Atomic Energy Agency (SDM2TM marine sediment). The metal data from the core sections were normalized to a conservative element, Li. Elements of natural origin which are structurally combined to one or more of the major ®ne-grained trace metal carriers are considered conservative. Several conservative elements have been used for normalization purposes: Al (Bertine & Goldberg, 1977; Bruland, Bertine, Koide, & Goldberg, 1974; Carral, Villares,
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Puente, & Carballeira, 1995; Hirst, 1962a, b; Sharma, Borole, & Zingde, 1994), Li (Loring, 1990), Cs (Ackerman, 1980), Sc (Ackerman, 1980; Grousset, Quetel, Thomas, Donard, Lawber, Quillard, & Monaco, 1995) and Fe (Blomqvist, Larsson, & Borg, 1992; Herut, Hornung, Krom, Kress, & Cohen, 1993; Piper, 1971). Normalization to OC has also been used in some cases (Horowitz, 1991). In the present study, OC was not considered as a reliable normalizer because of the diculty to assess undisturbed background concentrations. The presence of Poseidonia oceanica ®elds enhances the organic matter content in some oshore bottom sediments (stations 13±16, 24, 29, Fig. 1), whereas marine vegetation is absent from the rest of oshore and from harbour stations. The geochemical normalization, according to the literature, uses metal data from non-contaminated sediments of the study area to calculate the regression line of the metal on the normalizer and then tests the ratios metal/normalizer at other (possibly contaminated) stations. For the production of such a plot it is necessary to remove outlier values and to delineate a con®dence band of 95% of the regression line of the metal on the normalizer. Then, the data-points from the possibly contaminated areas have to be projected on the diagram. All points which are found inside the 95% con®dence band can be characterized as natural sediments, while all points above this area should be considered as contaminated sediments (Loring, 1990; Loring & Rantala, 1992). In the present study, the suitability of Li against Al, as a geochemical normalizer in the study area was tested. The data set used for the comparison included 13 samples of surface sediments from the wider coastal zone, located within 2 miles distance from the shoreline (Fig. 1, stations 13±18, 22±23, 25±29) (Aloupi & Angelidis, 2001). These sediments are considered to be representative of the local background and of the same origin with the harbour ones, as they are mainly formed from geological material transported from the eastern coast of Lesvos, the only adjacent land to the study area. They also have a great granulometric variability, as they vary from ®ne-grained material (87.8% silt+clay content, station 14) to sandy sediments (8.4% silt+clay content, station 28). This feature allows the relationship between normalizer and silt+clay content to be established, which is a prerequisite for the use of the normalizer as a proxy for the granulometric variability of the sediments. From the whole data set of oshore sediments, station 24 was excluded because of abnormally high values of OC and metals in the sandy sediments of the area. Table 1 shows the silt+clay content (on a gravel free basis), the OC content and the concentrations of metals in sur®cial coastal sediments of Mytilene. Regression of Al and Li on silt+clay content, as well as regression of metal concentrations on both Al and Li were performed, and the relative values of R2adj and statistical signi®cance (P) were compared. Table 2 summarizes R2adj and P values from the analysis of variance tables of the above regressions. From Table 2 it is clear that Li is more strongly correlated than Al with silt+clay ¯uctuations (R2adj for Li=0.977 and R2adj for Al=0.743). The very high value of R2adj for Li re¯ects the great ability of the element to normalize the metal concentrations in relation to the dierent texture of the sediments. It is also obvious (Table 2) that Li has stronger R2adj values for the regressions of metals. Therefore, Li is better
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Table 1 Silt+clay (S+C), organic carbon (OC) content and metal concentrations in surface sediments from Mytilene harbour and coastal area Stations
S+C (%)
OC (%)
Al (%)
Cd (mg/g)
Cr (mg/g)
Cu (mg/g)
Fe (%)
Li (mg/g)
Mn (mg/g)
Pb (mg/g)
Zn (mg/g)
13 14 15 16 17 18 22 23 24 25 26 27 28 29
64.80 87.80 75.96 41.42 42.00 35.45 31.09 16.64 16.49 10.59 35.90 38.08 8.36 63.99
3.39 2.86 3.35 2.97 1.41 1.55 0.71 0.35 3.33 0.27 1.09 1.06 0.35 2.24
4.75 5.34 5.24 3.65 4.45 3.94 3.74 2.79 4.43 2.83 3.88 4.08 3.61 3.83
0.131 0.085 0.082 0.119 0.076 0.062 0.044 0.053 0.061 0.059 0.074 0.044 0.030 0.080
122 132 120 86.5 81.8 97.5 59.8 67.1 99.0 40.0 74.4 68.4 54.2 99.0
27.3 23.4 30.5 24.0 16.7 20.4 9.91 6.07 22.0 6.17 14.0 11.0 5.34 17.8
2.40 2.70 2.75 1.65 1.74 1.74 1.34 1.12 2.63 1.15 1.77 1.36 0.80 2.04
27.0 37.1 31.8 19.9 21.8 19.4 15.2 11.7 34.0 12.3 20.6 18.8 9.74 28.4
280 300 302 222 229 261 224 260 323 226 260 183 171 273
44.2 39.8 42.5 39.0 34.5 37.1 24.2 20.7 23.2 29.7 34.4 36.7 27.8 37.5
69.1 73.1 72.9 76.7 45.8 55.0 33.7 23.0 71.0 29.8 41.9 32.3 12.9 53.0
Table 2 R2adj and probabilities from analysis of variance tables of regressions of Al and Li on silt+clay (S+C) content as well as of metals on Al and Li, in natural sediments from the coastal area of Mytilene (n=13) S+C
Cd
Cr
Cu
Fe
Mn
Pb
Zn
Al
R2adj
0.743 P<0.001
0.116 nsa
0.682 P<0.001
0.588 P<0.01
0.720 P<0.001
0.201 ns
0.535 P<0.01
0.435 P<0.01
Li
R2adj
0.977 P<0.001
0.296 P<0.05
0.830 P<0.001
0.663 P<0.001
0.928 P<0.001
0.543 P<0.01
0.591 P<0.01
0.656 P<0.001
a
ns, Non signi®cant (P>0.05).
suited to explain the natural variations in the metal concentrations. For example, Al cannot explain at all the natural ¯uctuations of the concentration of Cd and Mn (non-signi®cant correlations), whereas Li can normalize Mn concentrations but only to a limited degree for Cd concentrations. The low value of R2adj and the lower signi®cance level for Cd (Table 2) indicates that only 30% of its natural variability can be attributed to the textural and mineralogical variability of the sediments, suggesting the association of the metal with other geochemical substrates. The coexistence of both Al and Li in the lattice of clays re¯ects in their common ¯uctuation in relation to the content of silt+clay, as well as, in the regression of Li on Al (R2adj=0.727, P<0.001). Therefore, although both elements can be used as normalizers, Li appears to be better suited for the sediments of the study area than Al, which is the commonest normalizer mentioned in the literature. Li is a constituent of the ®ne-grained material of the sediments, such as primary micas and ferromagnesium minerals and secondary clay minerals (Loring, 1991). In non-contaminated sediments the ratio
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[Metal]/[Li] is relatively constant and a linear positive correlation exists between the concentrations of metal and the concentrations of Li. Since human activities will add anthropogenic metals but not Li to the marine environment, it is expected that contaminated sediments will present higher Metal/Li ratios. On the other hand, in most sedimentary environments, a linear relationship exists between Li concentrations and the percentage of ®ne-grained [silt+clay] content of the samples (Horowitz, 1991). Such a relationship allows the use of normalizer concentrations as a proxy for the granulometric variability of the sediments. Therefore, geochemical normalization to Li compensates for both granulometric and mineralogical variability of metal concentrations in sediments (Loring, 1990). Statistical analysis of data was performed with SPSS Ver. 7.5 for Windows software. 3. Results and discussion The content of the dierent sections of the cores in silt+clay, OC and carbonate is presented in Fig. 2a±c. In cores A, B and C the average percentage of ®ne-grained material was relatively high (55.578.09% in core A, 70.788.83% in core B and 63.045.66% in core C), whilst the sediments of core D had a coarser texture (only 34.698.06% of silt+clay and 49.807.03% of sand). The disturbance in the silt+clay content, which was recorded in core B at the depth of 6±10 cm, was attributed to the deposition of terrestrial material during the construction of the piers of the harbour. Similar patterns in core B were also found in the distribution of OC and metals (see below).
Fig. 2. Vertical pro®les of (a) silt+clay, (b) organic carbon and (c) carbonate contents in cores from the coastal area of Mytilene.
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Average OC concentrations are similar in cores A and B (3.210.47% and 3.18 0.40%, respectively) and re¯ect the deposition of euent-born organic matter in the harbour sediments. The ¯uctuation in OC concentrations with depth re¯ects changes in the activity of land-based pollution sources through time (but no data are available to further investigate the case). The higher OC in the deepest strata of core A are attributed to the discharge of euents of olive-oil re®neries in the past, which gradually ceased to operate during the last decade. In the cores from the coastal area outside the harbours (cores C and D), the concentrations of OC are lower and re¯ect non-polluted environments, with rapid oxidation of the organic material after deposition (Hedges & Keil, 1995; Wollast & Chou, 1998). Carbonate distribution in the cores is relatively stable in all locations, with the exception of core B, which at the depth of 6±10 cm shows a disturbance similar to that of grain-size at that depth. The total metal concentrations in cores A, B, C and D are presented in Fig. 3a±i. From the available data we can distinguish two kind of patterns: the pattern of anthropogenic metals (Cd, Cu, Pb, Zn) and the pattern of natural metals (Al, Fe, Li, Mn). The `anthropogenic' metals show a net increase in concentration in the upper parts of the harbour cores (A and B). This trend is more obvious in the pro®les of core A than of core B, because the sediments in core B have been disturbed by operations like dredging and input of foreign material transported to the place during the construction of docks (local Port Authority, personal communication). No dierences were found at dierent depths in the non-contaminated coastal zone cores (C and D). The higher concentrations in the upper layers of the sediments can be attributed to recent increases in metal discharges from sewer out¯alls related to urban activities (Aloupi, 1999). On the other hand, the `natural' metals have a relatively uniform distribution with depth in all cores, since their concentrations in coastal and harbour sediments are not aected by the discharge of town euents. The raw data are not sucient to quantify the intensity of contamination in the sediment layers of the harbour. To evaluate the natural levels of anthropogenic metals in the cores of the harbour and to indicate the depth where the metal concentrations exceed these natural levels, natural variability has to be considered by normalizing data to a conservative element. As mentioned in Section 2, the regression of each metal on Li in the natural sediment population was calculated using data from 13 stations at the wider coastal zone of Mytilene, o the harbours of the town. The diagrams produced from these data, as well as the projection of the core metal data on those diagrams, are presented in Figs. 4a±c and 5a±e. On the above diagrams two patterns are distinguished. For the `natural' metals (Al, Fe and Mn, Figs. 4a±c) data points are located within the limits of the 95% con®dence band of the regression line, for all (harbour and coastal zone) cores. On the other hand, all the anthropogenic metals (Cd, Cu, Pb and Zn, Fig. 5a±d) have increased Metal/Li ratios in the harbour cores, while the data points from the coastal zone cores are found within the 95% con®dence band, indicating no disturbance of natural concentrations. In the inner harbour (core A) the human in¯uence can be detected up to the depth of 18 cm for Cd and Cu (sections A1±A8) and
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Fig. 3. Vertical pro®les of metal concentrations in cores from the coastal area of Mytilene.
to the depth of 24 cm for Zn (sections A1±A10), while the sediment strata below these depths are considered as non-contaminated. Similarly, core B appears to be contaminated with Cd to the upper 6 cm (sections B1±B3) and with Cu and Zn to its full length.
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Fig. 4. Me:Li scatter plot (Me=Al, Fe, Mn) for core sediments of the coastal area of Mytilene. Solid line represents the regression line and dashed lines de®ne the 95% con®dence band for the surface sediments of the study area.
A similar but weaker anthropogenic in¯uence is also apparent for Cr (Fig. 5e). The normalization of the data showed enhanced Cr/Li ratios in the upper part of the inner harbour core (up to 10 cm depth, sections A1, A3±A5) and in almost the full length of the outer harbour core (sections B1, B3±B9). This ®nding suggests that part of Cr content in sediments of the harbour area can be attributed to anthropogenic sources. In the case of Pb, the upper parts of the cores A and B (Fig. 4c) appear to be contaminated, while the deeper sediment layers seem to be non-contaminated. However, the projection of the normalized metal concentrations from core C on the regression diagram, are below the con®dence band of the regression line which delineates the natural metal variability in the local sediments. This result indicates that Pb concentrations in the deeper layers of the core C are below the local natural background. The most probable explanation for such a result is that the natural background, as determined by the study of coastal surface sediments, has been overestimated. It is well known that Pb is transported through the atmosphere and is deposited in sediments of remote areas (Chester, 1990). So, the airborne Pb transport from the nearby town of Mytilene, as well as, from other remote unidenti®ed yet sources, may have been the reason for Pb deposition on the recent sediments of the coastal zone. Therefore, Pb concentrations in surface sediments may not be representative of the historical natural background. These results
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Fig. 5. Me:Li scatter plot (Me=Cd, Cu, Pb, Zn, Cr) for core sediments of the coastal area of Mytilene. Solid line represents the regression line and dashed lines de®ne the 95% con®dence band for the surface sediments of the study area.
underline the need for careful metal data interpretation during pollution studies in the coastal zone. 4. Conclusions The study of sediment cores collected from the harbour and the wider coastal zone of Mytilene showed that the ®ne-grained material, rich in OC and metals, which is transported by the town euents, is deposited to the sediments of the inner and outer
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harbour area, where calm hydrodynamic conditions prevail. Normalization to Li revealed that Cd, Cu, and Zn were highly enriched in the upper part of the inner and outer harbour cores. The deeper sediments of the harbour, as well as all the sediment layers of the wider coastal area, could be considered as non-contaminated. Cr had a similar behaviour, although its enhancement in the upper layers of the harbour sediments was less pronounced. In the case of Pb, normalization to Li showed that the assumed natural metal concentrations in the surface sediments of the marine coastal environment have been over-estimated. The probable cause may be atmospheric transportation of Pb from land based sources (urban) to the adjacent surface sediments.
References Ackerman, F. (1980). A procedure for correcting grain size eect in heavy metal analysis of estuarine and coastal sediments. Environment Technology Letters, 1, 518±527. Aloupi, M. (1999). Study of the in¯uence of urban discharges on the geochemistry of heavy metals in the marine coastal zone of Mytilene. PhD thesis, University of the Aegean, Greece (in Greek). Aloupi, M., & Angelidis, M. O. (2001). Geochemistry of natural and anthropogenic metals in the coastal sediments of the island of Lesvos, Aegean Sea. Environmental Pollution, 113, 211±219. Angelidis, M. O. (1995). The impact of urban euents on the coastal marine environment of Mediterranean islands. Water Science and Technology, 32(9±10), 85±94. Angelidis, M. O., & Aloupi, M. (1995). Metals in sediments of Rhodes harbor, Greece. Marine Pollution Bulletin, 31(4±12), 273±276. Angelidis, M. O., & Aloupi, M. (1997). Assessment of metal contamination in shallow coastal sediments around Mytilene, Greece. International Journal of Environmental Analytical Chemistry, 68, 281±293. Bertine, K. K., & Goldberg, E. D. (1977). History of heavy metal pollution in Southern California coastal zone. Environmental Science and Technology, 11, 201±207. Blomqvist, S., Larsson, U., & Borg, H. (1992). Heavy metal decrease in sediments of a Baltic Bay following tertiary sewage treatment. Marine Pollution Bulletin, 24, 258±266. Bruland, K. W., Bertine, K., Koide, M., & Goldberg, E. (1974). History of metal pollution in the Southern California coastal zone. Environmental Science and Technology, 8, 425±432. Burgess, R. M., & Scott, K. J. (1992). The signi®cance of in-place contaminated marine sediments on the water column: processes and eects. In G. A. Burton Jr., Sediments toxicity assessment (pp. 213±240). Boca Raton: Lewis Publishers. Carral, E., Villares, R., Puente, X., & Carballeira, A. (1995). In¯uence of watershed lithology on heavy metal levels in estuarine sediments and organisms in Galicia (North-West Spain). Marine Pollution Bulletin, 30, 604±608. Chester, R. (1990). Marine geochemistry. London: Unwin Hyman. FoÈrstner, U., & Wittmann, G. T. W. (1981). Heavy metals in the aquatic environment. Berlin: Springer Verlag. Gibbs, R. J. (1983). Coagulation rates of clay minerals and natural sediments. Journal of Sedimentary Petrology, 53, 1193±1203. Gibbs, R. J. (1993). Metals of the bottom muds in Townsville harbor, Australia. Environmental Pollution, 81, 297±300. Grousset, F. E., Quetel, C. R., Thomas, B., Donard, O. F. X., Lambert, C. E., Quillard, F., & Monaco, A. (1995). Anthropogenic vs. Lithogenic origins of trace elements (As, Cd, Pb, Rb, Sb, Sc, Sn, Zn) in water column particles: northwestern Mediterranean sea. Marine Chemistry, 48, 291±310. Hedges, J. I., & Keil, R. G. (1995). Sedimentary organic matter preservation: an assessment and speculative synthesis. Marine Chemistry, 49, 81±115.
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M. Aloupi, M.O. Angelidis / Marine Environmental Research 52 (2001) 1±12
Herut, B., Hornung, H., Krom, M. D., Kress, N., & Cohen, Y. (1993). Trace metals in shallow sediments from the Mediterranean coastal zone of Israel. Marine Pollution Bulletin, 26, 676±682. Hirst, D. M. (1962a). The geochemistry of modern sediments from the gulf of Paria Ð I. Geochimica et Cosmochima Acta, 26, 309±334. Hirst, D. M. (1962b). The geochemistry of modern sediments from the gulf of Paria Ð II. Geochimica et Cosmochima Acta, 26, 1147±1187. Horowitz, A. J. (1991). A primer on sediments Ð trace element chemistry (2nd ed.). Michigan: Lewis Publishers. Jackson, M. L. (1958). Soil chemical analysis. Englewood Clis, NJ: Prentice Hall. Loring, D. H. (1990). Lithium Ð a new approach for the granulometric normalization of trace metal data. Marine Chemistry, 29, 155±168. Loring, D. H. (1991). Normalization of heavy-metal data from estuarine and coastal sediments. ICES Journal of Marine Science, 48, 101±115. Loring, D. H., & Rantala, R. T. T. (1992). Manual for the geochemical analysis of marine sediments and suspended particulate matter. Earth Science Review, 32, 235±283. Piper, D. Z. (1971). The distribution of Co, Cr, Cu, Fe, Mn, Ni and Zn in Framvaren, A Norwegian anoxic Fjord. Geochimica Cosmochimica Acta, 35, 531±559. Sharma, P., Borole, D. V., & Zingde, M. D. (1994). 210Pb based trace element ¯uxes in the nearshore and estuarine sediments of Bombay India. Marine Chemistry, 47, 227±241. Wollast, R., & Chou, L. (1998). Distribution and ¯uxes of calcium carbonate along the continental margin in the gulf of Biscay. Aquatic Geochemistry, 4, 369±393.