Temporal-spatial variations, source identification and ecological risks of nutrients and dissolved metals in seawater of the Southeastern Mediterranean Sea, Egypt

Abstract

ABSTRACTThe Egyptian Mediterranean coastal zone suffers from several types of pollutants, due to different inputs from industrial, sewage effluents, shipping activities, spillage and coastal activities. In the present study, the nitrogen, phosphorus compounds and dissolved metals (Cd, Cr, Cu, Fe, Mn, Ni, Pb and Zn) concentrations in the Egyptian Mediterranean seawater were investigated during 2012 to 2015. The aim of the study was to understand the temporal and spatial variations of the determined parameters and their ecological risk along the Egyptian Mediterranean seawater. The relative dominance of metals was in the following decreasing order: Fe>Zn>Mn>Cu>Pb>Cr>Ni>Cd in 2012, Fe>Zn>Pb>Cu>Ni>Cr>Mn>Cd in 2013, Fe>Cu>Zn>Ni>Cr>Mn>Pb>Cd in 2014 and Fe>Ni>Cr>Cu>Zn>Pb>Mn>Cd in 2015. Relatively high levels of Cu, Cr, Cd, Ni, Zn and Pb were detected in El-Mex bay which is one of the most important industrial and trade regions of Alexandria city. While, higher mean values of Fe and Mn were registered in El Burg and El Dekhaila, respectively. El-Dekheila harbor is considered as a part of El-Mex bay which is subjected to several sources of wastewater and the degree of water contamination of the harbor depends on seawater circulation in the bay. The contamination by metals in seawater samples were assessed using metal pollution index, enrichment and contamination factors. Descriptive statistical analysis showed that terrestrial inputs via Nile River and sewages may be the main sources for the dissolved metals and nutrients contamination.