Scientific Assessment of the Fate of Major Pollutants in the Lower Layer Based on Hydrodynamic Modeling of Bosphorus

This paper explores the role of the lower layer of Bosphorus in changes in the magnitude of major pollutants, namely, organic carbon and nitrogen components. The study was essentially designed to answer the following query: Does the lower layer function as a bioreactor? The evaluation benefited from the water quality model derived from extensive water quality data covering both layers and collected for the last 5 years, together with the flow regime determined by the hydrodynamic modeling of Bosphorus. It revealed a deficit of more than 15 t/day for total organic carbon and 60 t/day for ammonia nitrogen along with a nitrate nitrogen increase of around 11 t/day. These results, when evaluated in terms of microbial process stoichiometry, strongly suggested that the water body in the lower layer of Bosphorus exhibited all the characteristics of a bioreactor sustaining heterotrophic and autotrophic activities. Significant removals of organic carbon and nitrogen in the lower layer of Bosphorus should also be regarded as a decisive indication that treatment to sewage discharges in this zone could not be justified by either a scientific viewpoint or common sense.