**3.4 Metals**

### **3.4.1 Water column**

Iron concentrations range between <4 mg/l and 21 mg/l along the water column in İzmit Bay (Table 3). The highest values are measured after the Earthquake (October-1999). High dissolved Fe concentrations indicate reduction of Fe-oxides by bacteria during mineralization of organic carbon in the sediment and diffusion into bottom waters (Nealson, 1982; Lovley and Phillips, 1988; Nealson and Myers, 1990). Fe values are decrease in May and August 2000 where Fe limitation is thought to control phytoplankton productivity.

Manganese concentrations vary between <1 and 123 mg/l in water column of the Bay (Table 3). The values increased in lower layer water and near the sediment-water interface in eastern and central basins. This was attributable to the degradation of settling organic carbon (Nealson, 1982; Nealson and Saffarini, 1994; Nealson and Myers, 1990). Manganese oxides were reduced to dissolved Mn+2, which diffused from the sediment into the water column occurring the anoxic conditions. The lowest Mn values are obtained in December 1999 and February 2000. In these periods, oxygen-rich waters of Marmara Sea (Mediterranean originating) flow into the Bay. Thus, Mn-oxides are occurred and flocculated in water column with reoxidation of dissolved Mn in more oxygenated waters.

Lead concentrations range between <0.8 and 1.8 mg/l in the Bay waters (Table 3). The highest values are suggested that atmospheric and anthropogenic inputs.

Copper concentrations vary between <0.4 and 7.4 mg/l along the water column of the Bay (Table 3). The high values shows that Cu was mainly affected by redox reactions involving Mn and Fe in bottom waters of the eastern and central basins. The lowest Cu concentrations are measured in occurring the extreme phytoplankton blooms periods especially in these regions.

The Effect of Marmara (Izmit) Earthquake on the Chemical

40.80 October/1999

Oceanography and Mangan Enrichment in the Lower Layer Water of Izmit Bay, Turkey 263

29.20 29.30 29.40 29.50 29.60 29.70 29.80 29.90

Fig. 9. Spatial distribution of pH values in the lower layer of İzmit Bay.

29.20 29.30 29.40 29.50 29.60 29.70 29.80 29.90

7.00 7.10 7.20 7.30 7.40 7.50 7.60 7.70 7.80 7.90 8.00 8.10 8.20 8.30 8.40 8.50 8.60

pH

August/2000

29.20 29.30 29.40 29.50 29.60 29.70 29.80 29.90

May/2000

29.20 29.30 29.40 29.50 29.60 29.70 29.80 29.90

February/2000

29.20 29.30 29.40 29.50 29.60 29.70 29.80 29.90

December/1999

40.70

40.80

40.70

40.80

40.70

40.80

40.70

40.80

40.70

Fig. 8. Spatial distribution of pH values in the upper layer of İzmit Bay.

29.20 29.30 29.40 29.50 29.60 29.70 29.80 29.90

29.20 29.30 29.40 29.50 29.60 29.70 29.80 29.90

29.20 29.30 29.40 29.50 29.60 29.70 29.80 29.90

May/2000

29.20 29.30 29.40 29.50 29.60 29.70 29.80 29.90

29.20 29.30 29.40 29.50 29.60 29.70 29.80 29.90

Fig. 8. Spatial distribution of pH values in the upper layer of İzmit Bay.

7.40 7.50 7.60 7.70 7.80 7.90 8.00 8.10 8.20 8.30 8.40 8.50 8.60 8.70 8.80 8.90

pH

40.80 October/1999

40.80 December/1999

40.80 February/2000

40.80 August/2000

40.70

40.70

40.70

40.70

40.70

40.80

Fig. 9. Spatial distribution of pH values in the lower layer of İzmit Bay.

The Effect of Marmara (Izmit) Earthquake on the Chemical

(r=0.81, Table 4).

Element Al

Mn

CaCO3

(Table 5).

phases.

respectively) (Table5).

**3.4.2.2 Selective extraction analysis** 

geochemical phases were given in Table 6.

(%)

Fe (%)

Mn (µg/g)

Oceanography and Mangan Enrichment in the Lower Layer Water of Izmit Bay, Turkey 265

The Copper, Cobalt and Chromium concentrations are in general, below the shale average values of 50, 20 and 100 g/g (Krauskopf, 1979) (Table 3). The highest values in eastern basins surface sediments shows that the anthropogenic inputs from the industrialized regions in here. The Cu values show high correlation with the Corg content

> Zn (µg/g)

Al (%) 1 +0.22 -0.13 +0.17 +0.17 +0.39 +0.30 -0.57 +0.1 Fe (%) 1 -0.03 +0.37 +0.44 +0.14 +0.54 - 0.32 +0.22

(µg/g) 1 -0.28 -0.32 -0.12 +0.08 + 0.1 -0.20 Cu (µg/g) 1 +0.89 +0.55 +0.66 - 0.39 +0.81 Zn (µg/g) 1 +030 +0.61 -0.28 +0.78 Co (µg/g) 1 +0.39 -0.56 +0.46 Cr (µg/g) 1 -0.59 +0.55 Corg (%) 1 -0.1

(%) <sup>1</sup>

Zinc concentrations range between 84 g/g and 306 g/g and are above the shale average value of 4.7 % (Krauskopf, 1979) (Table 4). The high values seem to have been controlled mainly by the anthropogenic inputs from the eastern region similar to the other elements. This element shows a high correlation with the Corg and Cu contents (r=0.78, and 0.89

Al, Fe, Mn, Co and Cr values do not show any significant correlation with the Corg content

Sequential exraction analysis were performed to determined the anthropogenic and /or natural inputs on metal distributions in the bay surface sediments. Metal contents of the

The highest values of Al, Fe, Zn, Co, and Cr varied between 2.2 % with 10.9 %, 3.8 % with 5.4 %, 18 % with 98 %, 4 % with 9 %, and 12 % with 51 % in the residual phase, respectively. In contrast, the highest values of Cu and Mn ranged from 6 % to 26 % in organic phase and from 32 % to 276 % in the Fe-Mn oxyhydroxide phase, respectively. While Fe and Cr values were generally lower than the detection limit of the methods (<0.05 and 0.08 µgL-1) in the exchangeable and carbonate phases, Al contents were also detected in the organic and residual (lithogenous) phases. Zn and Mn showed the highest values in Fe-Mn-oxyhydroxide phase, but Cu those in the organic phase along the bay. In addition, Cu, Zn, Mn and Co levels were relatively high in all geochemical

Table 5. Corelation coefficient of matrix geochemical parameters of sediments.

Co (µg/g)

Cr (µg/g) CaCO3 (%)

Corg (%)

Cu (µg/g)


Table 3. Metal concentrations along the water column of the Izmit Bay (µg/l).

Cadmium concentrations are lower than the detection limit of the method (<0.01 mg/l) along the water column of the Bay (Table 3). Since the domestic and industrial waste-water system has been damaged by the earthquake, causing the extreme phytoplankton bloom (Okay et al., 2001). This element is incorporated into organic matter by phytoplankton during periods of primary production (Sunda and Huntsman, 1995). Therefore, the relatively low residence time could be the result of biological uptake.

#### **3.4.2 Surface sediments**

#### **3.4.2.1''Total'' metal distributions**

The Iron concentrations range between 2.4 % and 11.8 % and are generally above the shale average value of 4.7 % (Krauskopf, 1979) (Table 4). The highest values are measured in southern shelf and eastern basin of the İzmit Bay. The Fe distribution in the Bay sediments is controlled mainly by the riverine and anthropogenic inputs on this land-locked system.


a From Mason and Moore (1982, p.153)

Table 4. Range of metal concentrations of bulk surface sediments from different parts of the Marmara Sea

Manganese concentrations are in general, lower than the average abundance of this element in shale (<850 g/g). The values increase in western basin of the Bay. Here, Mn+2 form of this redox sensitive element derived from the early diagenesis of the sediments, is believed to have been oxidized and flocculated by the oxygen-rich lower layer waters of the Marmara Sea (Mediterranean originating).

The Copper, Cobalt and Chromium concentrations are in general, below the shale average values of 50, 20 and 100 g/g (Krauskopf, 1979) (Table 3). The highest values in eastern basins surface sediments shows that the anthropogenic inputs from the industrialized regions in here. The Cu values show high correlation with the Corg content (r=0.81, Table 4).


Table 5. Corelation coefficient of matrix geochemical parameters of sediments.

Zinc concentrations range between 84 g/g and 306 g/g and are above the shale average value of 4.7 % (Krauskopf, 1979) (Table 4). The high values seem to have been controlled mainly by the anthropogenic inputs from the eastern region similar to the other elements. This element shows a high correlation with the Corg and Cu contents (r=0.78, and 0.89 respectively) (Table5).

Al, Fe, Mn, Co and Cr values do not show any significant correlation with the Corg content (Table 5).

#### **3.4.2.2 Selective extraction analysis**

264 Earthquake Research and Analysis – Statistical Studies, Observations and Planning

Fe 7-15 <4-4 <4-13 <4 <4 Mn <1-4 1-7 2-4 4-12 <1-13 Pb <0.8-1 <0.8-0.9 0.9-1 <0.8-2 <0.8-1 Cu 0.5-0.7 0.5-0.9 0.4-0.8 <0.4-0.6 <0.4-0.8 Cd <0.1 <0.1 <0.1 <0.1 <0.1

Cadmium concentrations are lower than the detection limit of the method (<0.01 mg/l) along the water column of the Bay (Table 3). Since the domestic and industrial waste-water system has been damaged by the earthquake, causing the extreme phytoplankton bloom (Okay et al., 2001). This element is incorporated into organic matter by phytoplankton during periods of primary production (Sunda and Huntsman, 1995). Therefore, the

The Iron concentrations range between 2.4 % and 11.8 % and are generally above the shale average value of 4.7 % (Krauskopf, 1979) (Table 4). The highest values are measured in southern shelf and eastern basin of the İzmit Bay. The Fe distribution in the Bay sediments is controlled mainly by the riverine and anthropogenic inputs on this land-locked system.

Cu (µg/g) 50 11- 42 23 8.87 Zn (µg/g) 90 84 - 306 149 57 Fe (%) 4.7 4.6 - 7.1 6.1 0.6 Mn (µg/g) 850 139 - 494 327 89 Co (µg/g) 20 6 - 20 12 3.93 Cr (µg/g) 100 34 - 77 58 11 Al (%) 9.2 2.3 - 11.4 7.4 2.5 CaCO3 6.0a 13 -42 13.4 9.9 Corg (%) 0.8a 0.6 - 6.2 3.0 1.6

Table 4. Range of metal concentrations of bulk surface sediments from different parts of the

Manganese concentrations are in general, lower than the average abundance of this element in shale (<850 g/g). The values increase in western basin of the Bay. Here, Mn+2 form of this redox sensitive element derived from the early diagenesis of the sediments, is believed to have been oxidized and flocculated by the oxygen-rich lower layer waters of the Marmara

Gulf of Izmit min - max

February 2000

May 2000

> Gulf of Izmit mean - SD

August 2000

December 1999

Table 3. Metal concentrations along the water column of the Izmit Bay (µg/l).

relatively low residence time could be the result of biological uptake.

Element October

**3.4.2 Surface sediments** 

**3.4.2.1''Total'' metal distributions** 

Element Average shale

a From Mason and Moore (1982, p.153)

Sea (Mediterranean originating).

Marmara Sea

(Krauskopf, 1979)

1999

Sequential exraction analysis were performed to determined the anthropogenic and /or natural inputs on metal distributions in the bay surface sediments. Metal contents of the geochemical phases were given in Table 6.

The highest values of Al, Fe, Zn, Co, and Cr varied between 2.2 % with 10.9 %, 3.8 % with 5.4 %, 18 % with 98 %, 4 % with 9 %, and 12 % with 51 % in the residual phase, respectively. In contrast, the highest values of Cu and Mn ranged from 6 % to 26 % in organic phase and from 32 % to 276 % in the Fe-Mn oxyhydroxide phase, respectively. While Fe and Cr values were generally lower than the detection limit of the methods (<0.05 and 0.08 µgL-1) in the exchangeable and carbonate phases, Al contents were also detected in the organic and residual (lithogenous) phases. Zn and Mn showed the highest values in Fe-Mn-oxyhydroxide phase, but Cu those in the organic phase along the bay. In addition, Cu, Zn, Mn and Co levels were relatively high in all geochemical phases.

The Effect of Marmara (Izmit) Earthquake on the Chemical

the formation of DHS (Figure 9).

for the presence of DHS, by preventing the circulation.

(Morkoç, et al., 1988; Tuğrul et al., 1989; Morkoç et al., 1996).

Oceanography and Mangan Enrichment in the Lower Layer Water of Izmit Bay, Turkey 267

the Bay. Although no DHS data is available for the previous sampling period (August and September 1999), the establishment of this anoxic condition at the bottom might have started to develop earlier than October 1999. Earlier studies related to the ocenographic features of the Bay have never determined anoxic conditions in the water column

The Marmara Sea water flows as the upper layer into the Bay in December 1999 and the current system is towards the interior of the Bay, whereas the lower layer flows out of the Bay (Güven et al., 2000). The available DHS formation in the eastern and the central basins is reduced or completely disappears in this month by the outflow of the lower layer (Table 2). This current system becomes reversed in February 2000, entering the lower layer and out-flowing the upper layer. The significant increase of DO concentrations of the upper layer in February 2000 might possibly indicate the replenishment of water column in İzmit Bay with oxygenated waters. This is in agreement with the vertical and spatial distribution of DO concentrations in February (Figures 3 and 4b). The thickness of the upper layer increases to 25-30 m suggesting the entrance of waters into the Bay. DO content of the both the upper and the lower layer slightly decreases in May 2000, together with increasing alkalinity (Figures 4b, 7b, 8 and 9). The reducing DO content in this month might be related with the water influx enriched with nutrients into İzmit Bay from the Black Sea (via the Marmara Sea) that receives increasing amount of freshwater inflow during spring (Oğuz and Sur, 1986; Tuğrul and Polat, 1995). In August 2000, DO concentration of the water column is significantly reduced (Figures 4 and 6), suggesting the enhanced consumption of DO by decomposition of high organic materials that possibly from the subsequent death of blooming phytoplanktons. In the eastern basin, the lowest pH is found in this month, supporting the increasing decomposition processes and

The formation of DHS leading to anoxia at the lower layer of İzmit Bay occurs in the eastern basin where the depths are shallower than 30 m and also locally in the deep site of the central basin where circulation is restricted (Table 2). After the Earthquake, in the central and the eastern basins, the formation of DHS is resulted from the spreading petroleum from the refinery fire to the surface waters and accumulation of high amounts of organic load from the damaged wastewater systems, and resuspension of bottom sediments releasing the DHS in the anoxic part of the sediment column. This is in agreement with the low DO concentrations of the water column in İzmit Bay during August and September 1999 (Figures 4a, 7a). The removal of anoxia at the bottom of the eastern and the central basins occurred in December 1999 by the replacing of water layers with the oxygenated Marmara Sea waters. DHS exists in the lower layer consistently throughout the sampling period in station 17 (Table 2), however its thickness varies. The reduced bottom current velocities (Algan et al., 1999) and topographic restriction of this small depression might be the reasons

In August 2000, DHS forms again in the eastern basin in low concentrations (Table 2). This re-occurrence of DHS is related with the extreme phytoplankton bloom. A high amount of organic matter produced from their death consumes oxygen for decomposition in the sediment. High decomposition rates might have led the depletion of DO in the overlying water column and consequent formation of DHS. The seasonal circulation pattern and timing of blooms in İzmit Bay were not different than the present as indicated by the


Table 6. Metal distributions in different geochemical phases (%).
