Industrial dumping impact on oxygen and nitrogen fluxes in Abu Qir Bay, Southeastern Mediterranean Sea

Abstract

An input/output flux model was used for the technical assessment of the effects of the present as well as the proposed reduction in the discharge of a major wastewater (industrial and sewage) dumping site on the dissolved oxygen, and nitrogen regimes in the vicinity of the outfall. Existing data and field measurements were used to feed the model. During summer stratification characterized by maximum discharge, mass balance equations identified different fluxes of nitrogen and oxygen above and below the pycnocline layer, as well as in the top sediment layer of the receiving system. Parameters such as effluent discharge, atmospheric reaeration, organic matter decomposition, nitrification, photosynthesis/respiration, benthic nutrient regeneration, resuspension and particles deposition were used to represent the physical, chemical, and biological processes included in the model. Different scenarios for showing the impact of dumping on the receiving system were exercised. A 50% reduction in the amount of discharge keeps dissolved oxygen levels in the water column near saturation, accompanied by an increase in: 1) NH4+1 and NO3−1 concentrations below the pycnocline; and 2) a 16% increase in the productivity of the upper layer. Sediments appeared to be impacted with the discharge of oxygen demanding wastes, showing a 30-fold increase in organic content over baseline conditions.