Transactions on Ecology and the Environment vol 4, 997 WIT Press, www.witpress.com, ISSN 74-54 Environmental impact on the surface sediments of the bay and the gulf of Thessaloniki (Greece) according to the Geoaccumulation Index classification. Anagnostou Ch., Kaberi H. and Karageorgis A. National Centre for Marine Research, Agios Kosmas, 66 4 Elliniko, Athens, Greece. E-mail: ek@erato.fl.ariadne-t.gr Abstract The area under investigation is the gulf and the bay of Thessaloniki which comprise the northern part of Thermaikos gulf. During the last years the area is being loaded with heavy metals and organic pollutants coming from industrial and domestic discharges of Thessaloniki city. As a result of the anthropogenic activities, the seabed properties are changed and moreover the marine ecosystem is disturbed. The aim of the study was to determine the environmental impact on the surface sediments so that the extent of heavy metal pollution is quantified and the whole area could be characterized according to the geoaccumulation index (Igeo). For this purpose, thirty three sediment samples were collected from the bay and the gulf of Thessaloniki. The < urn sediment fraction of the samples was analysed for the heavy metal content (Zn, Cu, Ni, Cr, Pb, Cd, Fe and Mn). The geoaccumulation index was then calculated comparing the concentration of the respective elements to that of unpolluted sediments, the so called "background value". According to the Ig^ classification, the bay of Thessaloniki was characterized as moderately polluted to strongly polluted for the metals Zn, Cd, Pb and unpolluted to moderately polluted in Cu, Ni and Cr, while the gulf of Thessaloniki was characterized as an unpolluted to unpolluted to moderately polluted marine area. Introduction The area under investigation involves the bay and the gulf of Thessaloniki, which comprise the inner Thermaikos gulf. The southern border of the area is defined by the present outfall of Axios river, up to the cape Megalo Emvolo (Fig. ). Thessaloniki bay, that extends northerly of the line defined by the old outfall of Axios river (Paliomana) and the cape Mikro Emvolo, is a shallow embayment with a maximum depth of 9m. The gulf of Thessaloniki is a wider
Transactions on Ecology and the Environment vol 4, 997 WIT Press, www.witpress.com, ISSN 74-54 7 Water Pollution marine area, with a maximum depth of 9m. The major characteristic of both areas is the very shallow zone across the western coast, which is a result of Axios river supply. Figure : The area under investigation and the sampling stations In the last decades the domestic and industrial wastes of Thessaloniki city were totally discharged in the marine area of the bay. This anthropogenic influence caused certain changes of the seabed properties and furthermore disturbed the whole ecosystem. The aim of this study is to determine the environmental impact of heavy metal pollution on the surface sediments by characterising the area according to the geoaccumulation index (Igeo) classification. Materials and Methods Sediment sampling in the bay and the gulf of Thessaloniki was carried out in 995 with the R/V Aegaeo (Fig. ). Thirty three surface sediment samples were collected using a Mclntyre grab. Chemical analyses for the heavy metal determination were performed on the < im sediment fraction, because this fraction plays a very important role as a heavy metal carrier in the marine ecosystem. The <p.m sediment fraction was mechanically separated by settling.
Transactions on Ecology and the Environment vol 4, 997 WIT Press, www.witpress.com, ISSN 74-54 Water Pollution 77 For the total dilution of the sediments, the samples were successively attacked with concentrated nitric acid, hydrofluoric acid, aqua regia and perchloric acid in teflon bombs. The Zn, Cu, Ni, Cr, Pb, Fe and Mn concentrations of the diluted samples were measured by Atomic Absorption Spectrometry using a Varian SpectrAA plus model, whereas Cd concentrations were measured using a Perkin Elmer 4 model. The analytical procedure was tested by analysing simultaneously a reference sediment (SD-M- /TM IAEA - MONACO, No 8). For the better interpretation of the results, the geoaccumulation index [] was calculated according to the following mathematical formula: where is the measured concentration of the element "n" in the clay sediment fraction (< im) and Bn represents the geochemical background concentration of element "n" for the "average shale" referenced from Turekian and Wedepohl []. In this paper an effort is done to use as geochemical background the element concentrations determined in the deepest parts of sediment cores collected from the study area, the results of which are discussed below. The factor.5 is introduced to include possible variations of the background values due to lithogenic effects. Igeo value is a measure of heavy metal pollution and it is defined in the following scale: Igeo >5 4-5 -4 - - - < Igeo class 6 5 4 Designation of sediment quality Extremely polluted Strongly to extremely strongly polluted Strongly polluted Moderately to strongly polluted Moderately polluted Unpolluted to moderately polluted Unpolluted This classification is a methodological approach based on geochemical data which makes possible to map the study area and discriminate various sub-areas according to their pollution degree. In addition, it is possible to obtain a proper comparison between various marine areas in terms of their heavy metal quality []. Results and Discussion The sediments of the study area were homogeneous, in terms of their grain size properties, represented mainly by mud, sandy mud and sandy clay, sedimentary facies characteristic of deltaic systems with relatively high sedimentation rates. The input in the area of large amounts of industrial and domestic discharges from Thessaloniki city and the nearby industrial zone, has affected the
Transactions on Ecology and the Environment vol 4, 997 WIT Press, www.witpress.com, ISSN 74-54 7 Water Pollution sedimentation processes and the sediment composition as far as the metal content is concerned. Heavy metal concentrations in the < im sediment fraction along with the Ieo classes are shown in Table. Table. Heavy metal concentrations of the < xm grain size fraction of the surface sediments of the bay and the gulf of Thessaloniki, as well as the corresponding I** classes. Station TH-Sl TH-S TH-S TH-S4 TH-S5 TH-S6 TH-S7 TH-S8 TH-S9 TH-S TH-S TH-Sl TH-Sl TH-S4 TH-Sl 5 TH-Sl 6 TH-S7 TH-Sl 8 TH-S9 TH-S TH-S TH-S TH-S TH-S4 TH-S5 TH-S6 TH-S7 TH-S8 TH-S9 TH-S TH-S TH-S TH-S Average Shale () Local () Background Zn Igeo Cu y. Ni Igeo Cr Igeo Cd Hg g ' class ng g* class Hg g ' class ng g ' class ng g* 46 : > 84 44 : I 8 685 : i 98 4 :) 85 44 8 48 : I 74 6 : 86 : I 6 9 : I 64 468 : > 88 88 : I 65 6 : I 6 47 : I 67 4 5 5 5 56 55 5 49 5 6 6 5 98 46 47 77 5 96 48 57 4 46 96 49 89 45 66 I 5 4 59 I 7 7 49 95 45 5 4 () 54 5 5 8 5 8 8 7 7 6 8 98 4 49 9 9 4 9 9 9 4 54 4 55 7 88 7 5 6 4 7 48 7 4 8 46 55 47 4 6 68 5 6 68 9 46 7.69.69.47.7.88.45.7.8. 4.7.97 '.74..88.9..98.5.47.67.4.45.5.6.8.47.5.56.6.6.99.68.6,, Igeo class 4 4 4 Pb Igeo Fe jig g* class % 65 : > 5,87 4 : I 4,59 5 : > 5, 65 : I 5,9 49 5,57 58 5,4 55 5,7 49 4, 5 5,6 59 5,5 5 5,56 49 4,4 54 6,49 48 5,9 48 5,9 5 4,9 5 5,9 5 5,5 44 5, 49 6,4 48 6,7 46 4,8 44 6,4 48 6, 4 5,8 5 5, 45 5,88 49 5,8 4 5,45 4 5,68 59 6,5 66 6,7 5 5,98 4,7 5, Igeo class Mn Igeo pgg* class 797 64 98 474 89 45 6 79 85 55 85 6 9 78 74 749 9 965 756 856 456 8 469 899 987 878 9 67 94 567 5 96 8 () Turekian and Vedepohl [], values used for the Igeo calculation. () Metal concentrations determined in the deepest parts of sediment cores collected from the same area [4] are taken as background values. 85 7
Transactions on Ecology and the Environment vol 4, 997 WIT Press, www.witpress.com, ISSN 74-54 Water Pollution 7 Metal concentrations, especially those of Zn, Cd, Ni and Cr, were higher in this sediment fraction than in the <6^im one [4]. In addition to that, the larger portion of the metals is concentrated in the < LLm fraction showing the extended adsorption surface of the finer grains and also their role on transfering metal ions in the marine ecosystem (unpublished data). Chemical analyses revealed that the highest concentrations of Zn, Cu, Cd and Pb were observed in the bay of Thessaloniki with a southerly decreasing trend, while the elements Ni, Cr, Mn and Fe showed uniform distribution within the whole study area. As it is shown in the map of Fig., sampling stations TH-S till TH-S are geographically attributed to Thessaloniki bay, while stations TH-S till TH- S are located in the gulf of Thessaloniki. The highest concentration of Cu, Cd and Pb was observed in front of the city of Thessaloniki (station TH-S) as a result of domestic and industrial discharges from the city of Thessaloniki. The highest Zn concentration was determined in surface sediments near the old outfall of Axios river at the western part of the bay (station TH-S7) coming from inflow of polluted waters via the old bed of Axios river. Cr distribution seems to be influenced by anthropogenic inputs from the above mentioned pollution sources. As far as the other metals are concerned, Fe distribution is uniform within the study area, Ni concentrations tend to slightly increase from the bay to the gulf of Thessaloniki and Mn, the most sensitive element to redox changes, was found a bit lower near the city and the port of Thessaloniki, where anoxic conditions were also observed in the upper layer of the sediments in relation to their elevated organic matter content [5]. The differentiation observed from the metal concentrations in the < im sediment fraction between the bay and the gulf of Thessaloniki is clearly shown in the horizontal distribution of the I^ classes for Zn, Cu, Pb and Cd of Fig.. According to the Ig^ index classification, Thessaloniki bay could be characterised as moderately to strongly polluted by Zn, unpolluted to moderately polluted by Cu, moderately polluted to strongly polluted by Cd, moderately polluted by Pb, unpolluted to moderately polluted by Ni and Cr and unpolluted as far as Fe and Mn are concerned. In contrast, Thessaloniki gulf is characterised, according to the same classification, as an unpolluted to moderately polluted marine area for the metals Zn, Cd, Pb, Ni and Cr, whereas for Cu, Fe and Mn it is characterised as an unpolluted gulf. However, it should be noticed that there is another source of pollution at the southern border of Thessaloniki gulf, the present day outfall of Axios river which seems to supply the gulf with waters significantly enriched in heavy metals such as Zn, Cu, Cr, Pb and especially Cd. As a result, the area influenced by the input of polluted discharges from the river is characterised as moderately polluted in Zn, Cd, Cr and Pb, and unpolluted to moderately polluted in Cu and Ni. Another very important feature of the area under investigation is the significantly elevated Ni and Cr concentrations determined in the deepest parts
Transactions on Ecology and the Environment vol 4, 997 WIT Press, www.witpress.com, ISSN 74-54 74 Water Pollution (about cm) of sediment cores, collected during the same sampling cruises [4]. While the concentrations of the rest of the metals determined in the deep layers of the sediment cores are comparable to those of the average shale [], Ni and Cr concentrations are more than twice the average shale (table ). Considering these values as background values for the area, the Igeo index was recalculated. In this way, sediment samples are classified in the Igeo class, and the whole area is characterised as an unpolluted marine area for Ni and Cr. The fact that Ni and Cr, like Fe and Mn, are consistent with the background levels of the area shows that these metals are mostly subject to lithogenic influences. On the other hand, the conclusion that Zn, Cu, Cd and Pb are mainly of anthropogenic origin is also resulted from the statistical data processing, since there was a very strong correlation between Zn, Cu, Cd, Pb and organic carbon content [4]. Zn Igeo class Cu Igeo class Cd Igeo class Pb Igeo class Figure : Distribution of the Igeo classes for the metals Zn, Cu, Cd and Pb. 4 Conclusions Heavy metal concentrations were determined in the < im grain size fraction of a number of surface sediment samples collected from the bay and the gulf of Thessaloniki. In order to evaluate properly the results, the geoaccumulation index (Igeo) of the sediments was calculated. According to this index sediments were classified in Igeo classes which permitted the characterisation of the area in terms of metal pollution.
Transactions on Ecology and the Environment vol 4, 997 WIT Press, www.witpress.com, ISSN 74-54 Water Pollution 75 The horizontal distribution of the metals revealed that the main sources of waste discharges relatively rich in heavy metals are the city and the port of Thessaloniki, the nearby industrial zone, the old bed of Axios river and last but not least the present day outfall of Axios river. According to the Igeo classes, Thessaloniki bay is generally characterised as a moderately to strongly polluted area in Zn and especially Cd, unpolluted to moderately polluted in Cu, Pb, Ni and Cr, and unpolluted in Fe and Mn. On the other hand, Thessaloniki gulf is characterised as an unpolluted to moderately polluted marine area for the metals Zn, Cd, Pb, Ni and Cr, whereas for Cu, Fe and Mn it is characterised as an unpolluted gulf. Igeo was recalculated using as backgroung values the metal concentrations determined in the deepest core samples. With this approach, the whole area is characterised as unpolluted regarding Ni and Cr. The background values of metal concentrations, determined for the specific area of Thessaloniki bay and gulf, showed that Zn, Cu, Cd and Pb are mainly of anthropogenic origin, whereas elevated concentrations of Ni and Cr are the result of lithogenic influences. References. Muller G. Unseren Fluessen geht's wieder besser - Bild der Wissenschaft, 985,, 75-97.. Turekian K.K. & Wedepohl K.H. Distribution of the elements in some major units of the earth's crust. Bull. Geol Soc. Am., 96, 7, 75-9.. Anagnostou, Ch. & Kaberi H. An environmental quality approach of the sediments of Maliakos gulf (Central Greece) based on heavy metal levels (ed. L.C.Wrobel & P.Latinopoulos) Proceedings of the "* International Conference on Water Pollution: Modelling, Measuring and Prediction, Greece, 995. 4. NCMR, Study of the Thermaikos Gulf Marine Ecosystem. Technical Report, National Centre for Marine Research, Athens, 996. 5. Anagnostou Ch., Kaberi H. & A. Karageorgis, The effect of domestic and industrial discharges on the seabed quality of Thessaloniki bay and gulf, Proceedings of the "* International Conference on Environmental Pollution, Thessaliniki, Greece, 996.