**2.2 Analytical methods**

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

09/99 10/99 11/99 02/00 05/00 08/00

09/99 10/99 11/99 02/00 05/00 08/00

09/99 10/99 11/99 02/00 05/00 08/00

Fig. 2. Depth profile of salinity and temperature distribution along the water column of

20 25 30 35 40 S(psu)

20 25 30 35 40 S(psu)

20 25 30 35 40 S(psu)

0

20

40

60

80

100

0

20

40

60

80

100

0

20

40

60

80

100

5 8 11 14 17 20 23 T(degC)

5 8 11 14 17 20 23 T(degC)

5 8 11 14 17 20 23 T(degC)

some selected station from İzmit Bay (from Güven et al., 2000).

0

20

40

D(m)

60

80

100

0

20

40

D(m)

60

80

**7C**

100

0

20

40

D(m)

60

80

**30**

100

**R**

Samples for DO determinations were drawn first from the Niskin bottles of Rosette to prevent any biological activity and gas exchanges with the atmosphere. DO determination was carried out by Winkler method (Greenberg et al., 1985) on board from all the stations (Figure 1). The precision of method was estimated at 1.9 % .

Dissolved hydrogen sulfide (DHS) was measured only at stations where DO concentrations are lower than the detection limit of the method (0.03 mgl-1) (Figure 1), in all the sampling periods, except August and September 1999. DHS contents were measured by an iodometric titration method (Strickland and Parsons, 1972).

pH values measured along the water column at all stations with a WTW 526 pH-meter equipped with a temperature-compensation adjustment on board.

The water samples were filtered through 0.45 µm filters using metal clean tecniques (Bruland et al., 1979). The samples were stored in polyethylene bottles (LDPE) that were acid cleaned using methods described Patterson and Settle (1976). After collection, the samples were acidified to a pH between 1.5 and 2.0 using HNO3. Dissolved heavy metal concentrations (Fe, Mn, Pb, Cu and Cd) were measured by atomic absorption spectrophotometer (AAS) following preconcentration with ammonium 1 pyrrolidinedithiocarbamate (APDC) in an organic extraction (Bruland et al., 1985). The blanks for the metals analyzed were: Fe, 010 0.05 mg/l; Mn, 0.10 0.02 mg/l; Cu, 0.15 0.08; Cd, 0.05 0.03 mg/l; Pb, 0.20 0.30 mg/l.

The surface sediments total carbonate contents were determined by a gasometric-volumetric method (Loring Rantala, 1992). Total organic carbon (Corg) was analyzed by the Walkey-Blake method, which involves titration after a wet combustion of the sample (Gaudette, 1974; Loring Rantala, 1992). Al, Fe, Mn, Cu, Zn, Co and Cr contents were determined by atomic absorption spectrophotometer (AAS) after a "total" digestion, involving HNO3 + HClO4 + HF acid mixture.

The sequential selective extraction analyses were carried out using 1M Na-acetate (pH=5 adjusted by acetic acid) for the dissolution of carbonate phase, 0.04M hydroxylamine hydrochloride (HAHC) in 25% acetic acid for dissolving Fe-Mn-oxyhydroxides, 0.02M nitric acid + 30% hydrogen peroxide (pH=2) for extracting organic matter, and HNO3 + HClO4 + HF mixture for the total extraction of the residual (lithogenous) fraction (Tessier et al., 1979).


Table 1. Accuracy of ASS analyses used in this study, as determined by Analysis of AQCS (SL-1 and SL-7), IAEA405 and BCR (CRM 142) reference materials.

SL-1 and SL-7 are lake sediment and CRM 142 is a light sandy soil.

The Effect of Marmara (Izmit) Earthquake on the Chemical

0 2 4 6 8 10 12 14 16 DO(mg/L)

0 2 4 6 8 10 12 14 16 DO(mg/L)

**R**

<sup>200</sup> **2**

0

10

20

30

**16**

0 2 4 6 8 10 12 14 16 DO(mg/L)

**25** 0.0 0.1 0.2 0.3 0.4 0.5 DHS (mg/L)

Depth (m)

0

10

20

Depth (m)

İzmit Bay.

30

40

Depth (m)

Oceanography and Mangan Enrichment in the Lower Layer Water of Izmit Bay, Turkey 253

0 2 4 6 8 10 12 14 16 DO(mg/L)

0 2 4 6 8 10 12 14 16 DO(mg/L)

**17** 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 DHS (mg/L)

0 2 4 6 8 10 12 14 16 DO(mg/L)

**27** 0.0 0.2 0.4 0.6 0.8 1.0 1.2 DHS (mg/L)

Fig. 3. Vertical distribution of DO and DHS along the water column in various stations of

0 2 4 6 8 10 12 14 16 DO(mg/L)

**23** 0.0 0.1 0.2 0.3 0.4 0.5 DHS (mg/L)

0 2 4 6 8 10 12 14 16 DO(mg/L)

0 2 4 6 8 10 12 14 16 DO(mg/L)

> DO (mg/L) 09/1999 10/1999 12/1999 02/2000 05/2000 08/2000

> > DHS (mg/L) 10/1999 12/1999 02/2000 05/2000 08/2000

**30** 0.0 0.2 0.4 0.6 0.8 1.0 1.2 DHS (mg/L)

0

0

<sup>60</sup> **5C**

10

20

30

40

10

20

30

The precision of the "total" metal analyses and the different selective extraction steps is better than 10% and 15%, respectively, at 95% significance level. The accuracy of the analyses were checked by analyzing the AQCS (lake sediment SL-1 and SL-7), IAEA405 and BCR (light sandy soil CRM 142) reference materials (Table 1). The metal values were normalized to eliminate the grain-size effects using metal/Al ratios (e.g., Loring Rantala, 1992).
