Research Article
Assessment of Metal Pollution in Sediments along Sinop peninsula of the Black Sea 
,
Ebru Yesim Ozkan2 
,
Hasan Baha Büyükisik2 ,
Hasan Can Oztekin1 2 Ege University,Fisheries Faculty,Department of Hydrobiology, 35100 İzmir, Turkey
Author Correspondence author
International Journal of Marine Science, 2017, Vol. 7, No. 22 doi: 10.5376/ijms.2017.07.0022
Received: 04 May, 2017 Accepted: 01 Jun., 2017 Published: 09 Jun., 2017
Bat L., Ozkan E.Y., Büyükisik H.B., and Oztekin H.C., 2017, Assessment of metal pollution in sediments along Sinop peninsula of the Black Sea, International Journal of Marine Science, 7(22): 205-213 (doi: 10.5376/ijms.2017.07.0022)
The spatial distribution pattern and transportation of heavy metals in sediments (up to 10 cm) were studied along Sinop peninsula of the southern Black Sea. The influences of anthropogenic metals pollution in surface sediments of Sinop Peninsula in the Black Sea were assayed by using Igeo. Metal contents were significantly correlated each other. Heavy metal concentrations showed a significant relationship with Fe content, while most heavy metals were not enriched. The levels of most metals at all stations were lower than the contents indicated by the sediment quality.
Introduction
Coastal ecosystems are amongst the veriest prolific and vigorous ecosystems on marine environment. The development in seaside regions has rised the anthropogenic activities on the coastal ecosystems, with the inclusion of the disruption of many water system owing to increased supplies of land-based nutrients and other chemicals such as metals. Pollutants sustein to be entered into marine coastal ecosystem thanks to rivers, runoff and land-based hot spots, and so, heavy metal contamination is one of the important issues in the Black Sea. When heavy metals get into the sea environment eventually will settle into sediments withal organic matter (Bat and Raffaelli, 1998), and may influence the health of the ecosystem.These sediment-bonded metals may also be let into the water column again under variable conditions. Thus, the metal contents in sediment surface can emit the pollution level of the coastal water and geochemical behavior of the metals. In recent years, increasing quantities of heavy metals from rivers and anthropogenic activities have been discharged into the Black Sea, resulting in the continual deterioration of the water quality (Bat and Baki, 2014).
The Black Sea is the largest naturally anoxic water in the world (Jessen et al., 2017), with many rivers flowing into it. In the north-western side Dnieper, Southern Buh, Dniester, and Danube rivers are the main tributaries. The rivers running into the northern side of the Black Sea transport excessive silt and form deltas, sandbars, and lagoons throughout the usually low and sandy northern coast. In the southern side Sakarya, Kizilirmak and Yesilirmak are the biggest rivers. The southern coast is steep and rocky. The Black Sea has two layers of water of different densities. The very salty depth layer which originates in inflowing Mediterranean waters has very slow movement and covers hydrogen sulfide; it has no eukaryotic vita. The suface layer, much lesser saline flows in a counterclockwise direction around the sea.
The Black Sea coasts are impacted by anthropogenic pressures especially fast industrialization and development in the coastal regions resulting in pollution of marine sediments by persistent chemicals such as heavy metals (Bat and Özkan, 2015). Risk assessment of sediments was determined by these heavy metals, it is a highly effective analytical tool. Land based pollution combined with population growth, originate increasing pressures into the coastal environment of the Black Sea (Bakan and Büyükgüngör, 2000; Bat et al., 2009; Bat, 2014; Büyükgüngör et al., 2014), involving the degradation of coastal ecosystem.
Sinop Peninsula is located in the southern part of the Black Sea. Previous results showed showed that metals were not seriously polluted in Sinop coasts compared with levels observed in different region of the southern Black Sea (Bat et al., 2015; Bat and Özkan, 2015). However the rapid development of coastal cities in the Black Sea, increased quantities of chemicals draining into the rivers and the sea. Research on Sinop coasts sediments showed that As, Cr and Hg concentrations were estimated relatively higher enrichment values than other metals (Bat et al., 2015). It is suggested that this situation is alarming and needs urgent action (Bat et al., 2015).
In the present study, the content and distribution of heavy metals in surface sediments of Sinop Peninsula of the Black Sea were investigated. The main objectives of this study were: (1) to characterize the distribution and concentration of metals; (2) to assess the degree of pollution with these metals; and (3) to analyze the main factors affecting the concentration of the metals in sediments.
1 Materials and Methods
1.1 Study area
Sinop is the sharpest point toward the north, on the shore of the Black Sea coast of Turkey and extends between latitude of 41o59'40.51''N and longitude of 35o6'47.17''E. The sediment samples were collected four times between June and September in 2013 from three stations namely Karakum, Inner Harbor and Akliman. The sampling stations are shown in Figure 1. The water depth was 10 meters for all stations. The stations were chosen in ways to include hotspots of pollution around Sinop city such as domestic wastewater discharge points (Bat et al., 2001; Bat and Baki, 2014), touristic and fishing activities in coastal zone of Sinop Peninsula (Bat et al., 1999).
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Figure 1 Sampling area |
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1.2 Sample collection
Sample surface sediments (< 10 cm) were collected using core sampler with 10 cm in length with a diameter of 4 cm. After the collection of the cores, they were sliced at 2 cm intervals by using sediment extruding device. The sediment slices were stored in cleaned polyethylene bottles with ice to keep cold and transferred to the laboratory. They were frozen at -21ºC in a deep freezer until analyses for metals (Bat et al., 2015).
1.3 Analytical procedure
The heavy metal analysis (except for Hg) in all subsamples was performed using the 4 acid digestion and ultra-trace ICP-MS method by the ACME Analytical Laboratories Ltd. (Vancouver, Canada). Two stages of preparation, consisting of drying and screening, were performed on the sediment samples. Samples were dried at 60°C and were then 85% pulverized and passed through a 200 mesh sieve. Two 0.25 g subsamples were taken for digestion and were heated in HNO3-HClO4-HF to dryness. The residues were then dissolved in HCl and the solutions were analyzed using the ICP-MS method. The ultra-trace Aqua Regia digestion method for Hg analysis was also used by Acme Labs. Subsamples of 0.5 g were leached in hot (95°C) Aqua Regia and the average values of the samples were used.
1.4 Analysis of certified reference materials
Sediment samples were analyzed with the quality control. Blanks (analytical and method), duplicates and standard reference materials inserted in the sequences of client samples provide a measure of background noise, accuracy and precision. QA/QC protocol incorporates quartz sample-prep blank(s) carried through all stages of preparation and analysis as the first sample(s) in the job. A reagent blank to measure background and an aliquot of Certified Reference Material (STD OREAS24P) to monitor accuracy was used as a control for analytical methods.
The analytical concentrations of the metals were within the range of reference values, and the replicate analysis of samples showed that the variability of the analytical precision was always within the acceptable ranges.
1.5 Organic content
Total organic carbon was measured in surface sediment by drying the samples at 600°C for 4 h. Samples free of organic matter were also treated by using diluted HCl to remove calcium carbonates and the loss in weight was again determined, according to the method described by Buchanan (1984).
1.6 Statistical analysis
The data set has been subjected to correlation and factor analysis for elucidating the relationships between the heavy metals and geochemical characteristics. The geoaccumulation index is calculated to determine metals contamination in sediments of Sinop Peninsula as the following equations:
I geo= log2 [C sample / (1.5 x C background)]
In which, C sample is the measured concentration of samples; C background is the background concentration of sediments and factor 1.5 is the possible variations of background data due to anthropogenic impacts.
2 Results and Discussion
Levels of the metals in sediments from Sinop Peninsula are given in Table 1, Table 2 and Table 3. Higher amounts of some metals in sediments from Sinop Peninsula reflect that the sediments act as a settle and source for these metals. Sediment accumulation rates were around 1 ± 0.5 mm year−1 for the upper 10 cm of the oxic–hypoxic and the hypoxic-sulfidic zone in the Black Sea (Lichtschlag et al., 2015) and sediments are of fine-grain muddy composition with a brownish grayish fluff layer on top about 0.5 cm (Jessen et al., 2017). In general results showed that decreasing of the metal levels with increasing depth of the sediment. This can be explained that the deep layers are older age than those in the decomposition processes took place for a long time as compared with the layers above it (Al-Shamsi et al., 2016). The percentage of organic content in the sediment of Karakum, Akliman and Inner Harbor were 2.5-3, 0.85-1.16 and 0.93-1.31%, respectively.
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Table 1 Mean concentrations (ppm) of metals in sediments of Karakum of Sinop Peninsula in the Black Sea |
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Table 2 Mean concentrations (ppm) of metals in sediments of Akliman of Sinop Peninsula in the Black Sea |
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Table 3 Mean concentrations (ppm) of metals in sediments of Inner Harbor of Sinop Peninsula in the Black Sea |
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The normalization of metal concentrations to Al has become an important tool for evaluating elevated metal levels in natural waters due to anthropogenic activities. The effects of clay fraction are eliminated by keeping the entering of Al into the marine environment. Therefore, the preferred method for evaluating the heavy metal levels resulting from activities in natural waters is obtained by dividing each metal concentration by Al (Özkan and Büyükışık, 2012). The correlations of Al-normalized metals and other variables (P and Ca) are given in Figure 2 and Figure 3.
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Figure 2 The relationship between P and Al in Sinop Peninsula of the Black Sea |
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Figure 3 The relationship between Ca and Al in Sinop Peninsula of the Black Sea |
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SQGV are one of the most important and useful tools to save and assay marine ecosystem from adverse effects. The results compared to those determined by the recommended sediment quality guideline values (SQGV) (Simpson and Batley, 2016). In the present study, the results were compared with SQGV to get preliminary information about the metals concentration in surface sediments of Sinop Peninsula in the Black Sea. The levels of most metals at all stations were lower than the contents indicated by the sediment quality. For example SQGV and SQGV-high for Hg, Cd, Pb, Cr, Cu, Zn and As are 0.15-1.0, 1.5-10, 50-220, 80-370, 65-270, 200-410 and 20-70 mg/kg dry wt., respectively (Simpson and Batley, 2016).
The absence of any relationship between Al and Ca both in the Inner Harbor and Akliman suggests that calcium is derived from the sea. The fact that the reproduction of Emiliania huxleyii in Sinop increases in the spring and summer months (Türkoglu and Koray, 2004) explains this situation. On the other hand, the negative relationship between Ca and Al in Karakum (Figure 3; data points on the right) can be explained by the effect of dilution of Al on Ca.
Ca values greater than 20% at the Inner Harbor indicate that Coccolithophores reproduce were higher in the previous periods. About 15% of Ca values are located 0-4 cm depth of sediment. Al values in both Akliman and Inner Harbor are almost constant and the independent change of Ca from Al suggests that Ca is marine origin. The Ca values in Akliman and Karakum are less than 10%. The inverse relationship of high Al values ( > 6%) with Ca in Karakum suggests that terrestrial-derived Al dilutes the marine-origin Ca in the sediment. The values of Ca and Al are almost homogenous along the sediment column.
In general, Fe, Ti, Cu, Co and Al values in Karakum are higher than Akliman and Inner Harbor. However, there are strong positive correlations in all three stations. The values in Akliman are more homogeneous. It is likely that the north coast of the region is being sediment transported away by strong water movements. This similarity is also observed with stronger correlations between Fe / Co (R = 0.991), Fe / Al (R = 0.972) and Fe / Ti (R = 0.994). Whereas, Fe / Hg (R = 0.958) indicated a lower correlation coefficient (Figure 4). Correlation with Al-normalized is weak. Correlation with organic carbon-normalized is increased by some degree. This is due to the large sedimentation of erosion material and the transfer of some of the material by organic carbon. The higher values in Karakum may be attributed wider water catchment basins and the great flood deposits.
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Figure 4 The relationships of metal values against Fe (orange curves is the 95% confidence levels, blue curves is the prediction limits) Note: Ti/Fe R=0.994, Cu/Fe R=0.980, Al/Fe R=0.972, Co/Fe R=0.991, Hg/Fe R=0.958, Sr/Ca R=0.986, Co/Al R=0.971 |
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Ca and Sr are two welded components and are marine welded. The Ca and Sr ratios vary in relation to climates. The sediment has a value greater than 21% at 4-10 cm while it is 14-16% at the first 4 cm; this indicates that presence of predominant Coccolithophores reproduce in the past.
Müller (1969) has classified Igeo in relation to contamination levels into following classes; class 0, uncontaminated (Igeo ≤ 0), class 1 from uncontaminated to moderately contaminated (0 < Igeo< 1), class 1 moderately contaminated (1 < Igeo< 2), class 3 from moderately to strongly contaminated (2 < Igeo< 3), class 4 strongly contaminated (3 < Igeo< 4), class 5 from strongly to extremely contaminated (4 < Igeo< 5) and class 6, extremely contaminated (Igeo > 5). In the present study Igeo was calculated using geochemical background values for all stations of Sinop Peninsula (Figure 5, Figure 6 and Figure 7).
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Figure 5 Mean, median, 95% confidence levels, minimum, maximum values, and outliers of geoaccumulation index for 19 elements in the sediments of Akliman of Sinop Peninsula in the Black Sea |
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Figure 6 Mean, median, 95% confidence levels, minimum, maximum values, and outliers of geoaccumulation index for 19 elements in the sediments of Inner Harbor of Sinop Peninsula in the Black Sea |
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Figure 7 Mean, median, 95% confidence levels, minimum, maximum values, and outliers of geoaccumulation index for 19 elements in the sediments of Karakum of Sinop Peninsula in the Black Sea |
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Co showed extremely contaminated in all three stations. Co has close and strong relations with Fe and Ti. This explains why these dissolution-resistant elements decline directly from the water column into the sediment. According to the sedimentary rocks carbonates class, Igeo values indicate contamination, but may be natural enrichment from ultrabasic rocks, granite, olivine basalt mixtures (see Zr / Hf ratios, Zr and Y values). Igeo for Ca fell moderately to strongly contaminated can be autogenic (Emiliania huxleyii) (Türkoglu and Koray, 2004).
When the mean metal concentrations in the present study were compared with values of Bat and Ozkan (2015) in many parts of the Black Sea coast, they were generally lower than those locations that situated in large industrialized areas, river mouths, big ports and densely populated regions. Industrial and urban developments in Turkey as a developing country mostly occur in coastal areas (Bakan and Özkoç, 2007). Further, Sur et al. (2012) pointed out that the Turkish Black Sea coast is facing heavy metal pollution with high enrichment ratio. It is emphasized that the data on heavy metals in surface sediments in the Black Sea coasts are available but changeable since different methodologies that are not inter-comparable (Bat et al., 2015; Bat and Özkan, 2015).
3 Conclusions
It can be inferred from the present study the stations close to industrial and urban areas have more trace elements. The Igeo values suggest that surface sediments in Sinop Peninsula of the Black Sea varied from unpolluted to extremely contaminate. The present study recommended that risk of metal values can be evaluated by using indices not only by measuring of metals alone. Although some metal levels were found high in some stations at Sinop Peninsula, the most of them were not extremely contaminated in surface sediments and did not show an important risk to the local biota. It is being proposed that further studies and forthcoming monitoring would be helpful to assess long term effects of anthropogenic inputs on the Black Sea coast.
Authors’ contributions
LB designed and conducted the experiment; prepared the samples for metal analysis, evaluate data and finalized the manuscript. EYO contributed to the paper by processing the data and made figures and commented it. HBB performed critical review of the manuscript. HCO contributed to the paper by collecting samples and help to prepare them for metal analysis. All authors read and approved the final manuscript.
Acknowledgments
This work was supported in the Sinop University for Scientific Research Project; project number SÜF-1901-12-02. The project coordinator was LB.
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