© by PSP Volume 16 – No 12a. 2007 Fresenius Environmental Bulletin 1544 WATER/SEDIMENT QUALITY ASSESSMENT AND SOD STUDIES IN KIZILIRMAK RIVER AT THE BLACK SEA COAST OF TURKEY Gülfem Bakan * and Hüseyin Cüce Ondokuz Mayıs University, Env. Eng. Dept., 55139 Kurupelit, Samsun, Turkey SUMMARY The high biological productivity in nutrient-enriched water means that the biochemical oxygen demand (BOD) and sediment oxygen demand (SOD) in the water column are high as dead material is broken down. The objective of this research included testing sediment oxygen demand pa- rameter measurements by laboratory techniques, determin- ing spatial distribution of sediment characteristics, and evaluating the relationship between SOD and depositional environment in the Kızılırmak River at the Black Sea coast of Turkey. SOD rates were dependent on the method; there- fore, care should be taken in comparing SOD data obtained by different methods. There is a need for a carefully re- searched standardized method for SOD determinations. In this study, SOD is investigated in laboratory experiments in which sediments are subjected to controlled conditions of two different techniques. According to both results of SOD measurement methods, mean SOD values were chang- ing in the range of 0.25 – 0.61 g O 2 / m 2 / day ; indicating that the river bed had a high sand and water content (av- erage 25.46% of wet weight) whereas low organic matter content (average 3.85% of dry weight) characteristics. Analyses of eight stations produced results that showed statistically significant differences between the two meth- ods (F (2.18)=16.610 P<0.01) when tested during the same time period, under the same conditions. In this study the measured field and laboratory data will be useful in under- standing the sediment/water quality of the water body and also provide parameters that may be used when developing numerical water quality models for the Kızılırmak River. KEYWORDS: sediment, dissolved oxygen, sediment oxygen demand, sediment/water interaction, water quality. INTRODUCTION Sediment chemistry is closely linked to the water qual- ity of the overlying water body. Many water-borne pollut- ant and nutrient species are predominately associated with particulate matter that can settle and become sediment. Oxy- gen demand in river, lake and coastal sediments is a key issue in determining water quality. Thus, it is important to quantify precisely and identify the processes responsible for sediment oxygen demand in shallow coastal environ- ments [1, 2]. Sediment oxygen demand (SOD) is a component of the dissolved oxygen (DO) balance of natural water bodies such as a river section, a lake or a reservoir. Other components are the biochemical oxygen demand (BOD), oxygen ex- change through the water surface (reaeration), photosyn- thesis and respiration of plants, respiration of animals, and chemical reduction or oxidation processes. Horizontal ad- vection and dispersion by the flow must also be considered [3]. The high biological productivity in nutrient-enriched water means that BOD and sediment oxygen demand in the water column are high as dead material is broken down. Thus, oxygen can be stripped out of the water column if the body of water is not well mixed. This can result in a series of ancillary problems with raw water quality, such as high manganese, iron, ammonia and hydrogen sulfide concen- trations, all of which are released from the sediment under reducing conditions. Sediment oxygen demand provides in- formation about the rate at which settled organic matter is remineralized and may serve as an integrative measure of sediment metabolism. SOD has been found to be an impor- tant sink for dissolved oxygen in a wide variety of surface waters. Moreover, since an increase in temperature will result in increased rates of bacterial respiration and bio- chemical reaction, higher SOD values are expected at higher temperature. Typically, the lowest SOD rates (0.5-1 g/ m 2 . day at 20 ºC) are observed for sediments with a high sand component and little organic matter, moderate rates (1 to 3 g/m 2 .day at 20 ºC) occur in silty sediments containing a moderate amount of organic matter, and the highest rates are found at sites polluted with organic sludge. Typical SOD