Seasonal Variations of Sediment and Water Quality Correlated to Land-Based Pollution Sources in the Middle of the Black Sea Coast, Turkey

Levent Bat<sup>1</sup>; Oylum Gökkurt Baki<sup>2</sup>

Seasonal Variations of Sediment and Water Quality Correlated to Land-Based Pollution Sources in the Middle of the Black Sea Coast, Turkey

Levent Bat¹

, Oylum Gökkurt Baki²

1. Sinop University, Fisheries Faculty, Department of Hydrobiology TR57000 Sinop, Turkey
2. Sinop University, Vocational School of Environmental Health Program TR57000 Sinop, Turkey

Author

Correspondence author
International Journal of Marine Science, 2014, Vol. 4, No. 12 doi: 10.5376/ijms.2014.04.0012
Received: 24 Nov., 2013 Accepted: 29 Dec., 2013 Published: 05 Feb., 2014

This is an open access article published under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Preferred citation for this article:

Bat and Baki, 2014, Seasonal Variations of Sediment and Water Quality Correlated to Land-Based Pollution Sources in the Middle of the Black Sea Coast, Turkey, International Journal of Marine Science, Vol.4, No.12: 108-118 (doi: 10.5376/ijms.2014.04.0012)

Abstract

The environmental pollution parameters were analyzed at the surface sediment and water samples collected from the untreated discharge basin of Sinop coasts of the Black Sea. On the sediment samples, redox potential, water content, organic matter content and porosity percentages and pH analyses and on the water samples, DO, salinity, BOD₅, TSS, T (℃), pH, conductivity, NO₂-N, NO₃-N, silicate and organic matter analyses were measured. Water content (%) and porosity (%) of the surface sediment were found in the ranges of 62.9 to 0.1 and 58.9 % to 0.76, respectively. As the pH values of the sediment samples varied in the ranges of 7.23 to 9.4, its organic matter content varied in the ranges of 2.6 to 0.11 %. Results indicated that, there was a domestic pollution at the sediment layer of some sampling stations and water according to some physico-chemical parameters at class 2-slightly/moderately polluted water, or very polluted class 4 water class. According to the Environment Law-Water Pollution Control Legislation, Land-Based Water Quality Classification, generally, it has polluted water and the origin of this pollution is mainly domestic. The pollution loads of the water body also appeared at where were discharged untreated water, sediment layer and water content, especially with its high organic matter content.

Keywords

Surface sediment; Wastewater; Land-based pollution; Sinop Coasts; Black Sea

1 Introduction

The Black Sea is located between the latitudes, 40°55′ and 46°42′ and the longitudes 27°27′ and 41°42′E. It is a semi-closed inland basin from the oceans surrounded by the countries of Russia, Romania, Bulgaria, Ukraine, Georgia and Turkey. The Black Sea is connected to the Mediterranean through the narrow and shallow Bosphorus strait which is 32 m deep and total length of 31 km, to the South and connected with the Sea of Azov through the shallow Kerch strait to the North (Özsoy et al., 1986; Balkas et al., 1990). The Black Sea has historically been one of the most biologically productive regions in the world (Bat et al., 2011; Bat et al., 2013a). The oceanography of the Black Sea has been relatively well studied and documented in the literature. The same, however, cannot be said for documentation of the levels of marine pollution and the regions that are affected by various activities, especially in coastal areas (Balkas et al., 1990; Bat et al., 2012a; Bat et al., 2013b). The Black Sea receives large quantities of unregulated and unplanned fresh water with drawl for irrigation purposes, hydro and thermal generation and the use of coastal areas for permanent human settlements, and the many untreated industrial and agricultural wastes drain into the sea via rivers (Bat et al., 2013c). This variety of activities has had detrimental effects on the health of the Black Sea (Akdoğan, 1991; Bat et al., 2012b).

Sinop is located on the southern coast of the Black Sea, Turkey. There were 8 stations for water samples monthly and 7 stations for sediment and benthic samples seasonally. The stations determined according to discharge points and potential discharge points and clean areas in coastal marine environment. The samples collected from these areas where Dis Liman and Iç Liman of Sinop Peninsula at the Black Sea coast of Turkey (Figures 1 and 2.).

Figure 1 Map of the study area showing the sampling stations

Figure 2 Sampling station 2 in Dis Liman of Sinop Peninsula and domestic discharge point

2 Methodology

Sediment samples collected four times and water samples were collected monthly in 2006–2007. The 4 sampling stations were chosen in a way to include hotspots of pollution around Sinop city such as domestic wastewater discharge areas and in this study 3 stations were chosen in way clean areas. Descriptions of coastal sampling sites are given in Table 1.

Table 1 General description of coastal sediment sampling sites

2.1 Sediment sampling

Surface sediment samples were collected at 7 sites monthly in 2006–2007. At each site, three surface sediment (0-5 cm) samples were collected by scraping the surface layer by using a hand dredge sampler. The sediment samples were kept in separately labeled pre-cleaned polyethylene bags and kept in an ice box. As soon as the field work was finished, the samples were transferred into the laboratory and preserved at -21℃ for future analysis. The samples of 15–20 g for water content assessment were dried by using an air-circulating oven at 105℃ for 48 h. Concentration of organic carbon (TOC) was measured in surface sediment by drying the samples at 600℃ for 4h. 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).

In sediment samples, the porosity values are calculated with water density and sediment density. Redox potential (Eh) was also measured using an electrode which was pushed stepwise down into an undisturbed sediment core a 4 cm depth which provide a better estimate of the sediment conditions (Pearson and Stanley, 1979) and the readings were corrected for hydrogen reference by adding +198 mv to the meter reading (Pearson and Stanley, 1979). The electrode was allowed to equilibrate for 2 min before each reading (Jørgensen, 1977).

2.2 Water sampling

Water samples were taken from surface of the sea (less than 1 m). Physico-chemical properties of wastewater were determined according to the standards of the American Public Health Association (APHA 2005). Temperature, pH, TSS, salinity and dissolved oxygen of surface water were determined at the collection sites using a HORIBA Multi-parameter meter for pH/temperature/ORP/dissolved oxygen. Nitrite and nitrate were determined using a UV visible spectrophotometer (Thermo Spectronic, Heλios). For the analysis of BOD, water samples were diluted, then the samples were placed into 250 ml narrow neck glass bottles and left in an incubator at 20℃ without light for five days. Dissolved oxygen of the diluted samples and control (dilution water) was measured at the beginning and end of the analysis (APHA 2005).

Calculations of the results were as follows:

BOD (mg/L) = [A*(C－D)/B] + D

A = total volume after dilution (mL)

B = volume of undiluted sample (mL)

C = oxygen consumption of diluted sample after 5 days (mg/L)

D = oxygen consumption of dilution water after 5 days (mg/L)

3 Results and Discussion

3.1 Summer

The percentage of organic matter is a parameter that shows especially indicate the organic matter loads in sediment. The organic matter loads are usually originating from domestic discharges. The level of organic content in the sediment of site 4 was maximal (2.18%) as compared to all other sites. The lowest value of organic matter is determined in station 8 with 0.32% (Figure 3A).

Figure 3 A) Organic content (%) and water content (%) B) Porosity (%) and water content (%) C) Organic content (%) and redox potential (Eh) comparison in sediment in summer.

The porosity values are given in Figure 4. It can be said that % water content and % porosity data are parallel to each other (Figure 3B).

Figure 4 A) Organic content (%) and water content (%) B) Porosity (%) and water content (%) C) Organic content (%) and redox potential (Eh) comparison in sediment in autumn.

The redox potential (Eh) of the sediments ranged from -45mV to -145mV, indicating oxygen deficiency sediment in all stations except station 7 where redox value was +11mV (Figure 3C).

3.2 Autumn

In autumn, it can be said that in surface sediment, the organic matter content is accumulate in the areas which are the % water content and water depth is high in sediment (Figures 4A and B). The redox potential (Eh) of the sediments ranged from -152 and -52 mV (Figure 4C). In station 2, the domestic wastewater is always discharge in marine coastal areas without any treatment. The sediment samples aren’t black but, it can be feel that the sulfide smells during the analyses easily.

3.3 Winter

The highest value of organic matter content (6.5%) is determined in station 4 in winter in sediment samples. The lowest value of organic matter is determined in station 3 with 0.11% (Figure 5A). Water content and porosity values (%) are partly parallel to each other (Figure 5B).

The maximum redox potential (Eh) was 203 mV. The other redox potential values of the sediments ranged from -125mV to -32mV (Figure 5C). In station 4, both water and sediment samples had organic pollution in winter. In this station, sediment samples had bad smell, dark color and insufficient oxygen. Moreover there was no Mollusca fauna, indicating that coastal zone was affected from pollution of land-based sources (Figure 6).

Figure 5 A) Organic content (%) and water content (%) B) Porosity (%) and water content (%) C) Organic content (%) and redox potential (Eh) comparison in sediment in winter.

Figure 6 Station 4 in winter

Sediment structure of station 4 was small pieces, in clay form, dark color and bad smell, indicating sulfide and high organic matter. On the other hand sediment was not oxygenated.

3.4 Spring

The highest value of organic content is determined in station 4 with 0.69 % whereas the lowest value (0.15%) of organic matter is determined in station 3 (Figure 7A). Water content and porosity values (%) are parallel to each other (Figure 7B). The highest redox potential (Eh) was 191 mV at station 7. The other redox potential values of the sediments ranged from-98mV to -81mV (Figure 7C). Station 4 was the lowest value. The domestic wastewater is discharged in this coastal area without any treatment.

Figure 7 A) Organic content (%) and water content (%) B) Porosity (%) and water content (%) C) Organic content (%) and redox potential (Eh) comparison in sediment in spring.

The pH values of the sediment samples varied in the range of 7.23 to 9.40, its organic matter varied in the range of 0.11 to 2.6 percent indicates that there was a domestic and agricultural pollution accumulation at the sediment layer of Sinop coasts. Furthermore on the water samples which were collected parallel to the sediment sampling stations in the same period, BOD₅, TSS, T (℃), pH, NO₂-N, NO₃-N, organic matter, dissolved oxygen, salinity, conductivity and silicate analyses were also performed (Tables 2, 3 and 4). According to these analytical results, it can be concluded that Sinop domestic discharge points has polluted water for NO₂-N, NO₃-N and TSS parameters at class 2 or even if very polluted class 4 water class (Gökkurt et al., 2007).

Table 2 pH values of sediment samples (X ± S_X)

Table 3 Redox potential (Eh) values of sediment samples(X ± S_X)

Table 4 Minimum and maximum values of physico-chemical parameters from Sinop Peninsula of the Black Sea coast, Turkey between 2006 and 2007.

According to the Environment Law-Water Pollution Control Legislation, Land-Based Water Quality Classification (Turkish Environmental Regulation, 2004), generally, it has polluted water and the origin of this pollution is mainly domestic (see Tables 5 and 6). The pollution load of the water body also appeared at the sediment layer, especially with its high organic matter content. In sediment samples, redox potential values were usually determined negative and this result showed in discharged points (Table 3). These results verified with organic matter values and water samples.

Table 5 Turkish Environmental Regulation (2004), Quality Criteria of Inland Water Sources according to be Classes

Table 6 Turkish Environmental Regulation (2004), Quality Criteria of Recreational Coasts and Marine Water

Other researchers have reported high organic content (5.61 %) in Samsun Mert Stream (Bakan and Senel, 2000). The high organic matter content in the Samsun Mert Stream sediments is mainly due to agricultural and domestic discharges. In our study, organic matter was 2.6 % with fine grain, wet clay form bad smell and dark color in station 4. This is probably a result of the sulfide and organic matter concentrations. The results of the present study are similar to those reported by Bat and Culha (2001). Organic content in sediment found between 1,2 % and 3,4 % in Sinop inner on 2001.

Especially in shallow water, the turbidity is reason of decreasing oxygen and according to accumulation of organic matter the increasing of oxygen consumption. This situation result was high turbidity, muddy sand and bad smell (Özel, 1992).

The research area of Sinop peninsula coasts, affected with intensive land-based pollution and organic matter discharge originating from domestic discharge.

The dissolved oxygen (DO) level in Sinop Peninsula of the Black Sea wastewater ranged from 2.2-8.9 mg/L in 2006 and 2007, compared with 5.17-6.48 mg/L in 1999 (Bat et al., 1999). Many factors determine DO levels in wastewater including surface water temperature, which has an inverse relationship with DO, photosynthesis by green algae, salinity, organic matter and pollution. Organic waste and other nutrient inputs from sewage and industrial discharges, agricultural and urban runoff can decrease DO levels. High nutrient inputs usually lead to algal blooms. In the present case, the DO levels of station 2 (2.2 mg/L) were considered not suitable for aquatic life. It is concluded that Sinop coasts may be face with big danger because of untreated domestic discharges.

The temperatures recorded at sample locations ranged from 9.3-30.8℃. The water temperatures of Sinop coast were within Water Pollution Control Regulations of 2872 the Official Gazette Environment Law (<25°C) for water (Table 5) Class II/III/IV for all stations maximum values; therefore, the treated wastewater released from waste water treatment plant is in need of further purification. The levels of biological oxygen demand in the wastewater of Sinop coast of the Black sea ranged from 0.033-4.86 mg/L. The BOD increase correlated with increase of population in the city which increased the quantity of biodegradable matter from the domestic waste in summer. Unpolluted natural water should have a BOD of 4 mg/L or less; however, the BOD in the water of Sinop coast exceeded (only station 5) the standard limit set by Turkish Environmental Regulations (2004).

Conductivity was in range of 25.7-29.6 mSiemens/cm, while TSS ranged from 11-820 mg/L, above the standard maximum of 30 mg/L set by the Turkish Environmental Regulation (2004), for General Quality Criteria of Marine Water for TSS (Table 6).

The mean pH levels of the water of Sinop coast in 2006-2007 ranged from 6.43-9.49, the values slightly above the standards maximum 9 set by the Turkish Environmental Regulation (2004), for General Quality Criteria of Marine Water for pH levels (Table 6).

Nowadays the Black Sea is face with environmental pollution. In the Black Sea coast of Turkey, some cities use the sewerage system directly but most of the small settlement areas used septic tanks. On the other hand, present sewerage systems show also variety such as combined or separate system. Ordu, Giresun city centres have separate sewerage systems where Sinop, Trabzon and Zonguldak have combined systems but only Samsun city centre have both combined and separate sewerage system (Bakan et al., 1996).Many industrial untreated industrial and agricultural wastes drain into the sea (Bat et al., 2009).Domestic discharge is the greatest source of organic matter discharged into coasts. Bat et al. (2009) pointed out that many towns and cities situated on the coast, however, sewage is discharged untreated in the Black Sea coast of Turkey. Organic matter is an important pollutant, as it is a source of food for many benthic invertebrates in the marine ecosystem (Bat et al., 2007).

In conclusion the results of the present study indicated that in terms of sediment and water pollution of Sinop coasts of the Black Sea is not dangerous for marine habitat. However, especially hotspots are beginning to pollution in locally. Agricultural practices should be improved to reduce fertilizer loading and consequent runoff from agricultural lands and domestic discharge should be treated specially in station 2.

Acknowledgments

Suggestions from two anonymous reviewers are greatly appreciated.

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