Mercury speciation in aquatic environment south eastern coast of the Mediterranean Sea, Egypt

Abstract

This study aims to describe distribution and speciation of Hg in coastal water, fish and sediments from the Western harbour (main harbour) in Egypt and has been studied in two surveys. The slightly high annual mean of total dissolved mercury TDHg value (1.81 μg/L) in the surface layer might reflect the highest average surface value (6.09 μg/L), selected at the outer part, due to the entering the water loaded by industrial pollutants from El Mex Bay to the harbour water. In addition to the internal activities as petroleum Quay (petroleum basin) and in front of Noubaria Canal outfall (5.13 and 5.32 μg/L respectively). On the other hand, the increased levels of mercury in suspension (particulate form) during the study period may be due to the effects of heavy winter rain over the highly industrialized area, also the surface input of mercury and its regeneration at the sediment/water interface in the Harbour. In the present study, the total and methyl mercury in the studied fish was exceeded the regulatory limit of the European Union for mercury concentration in fishes . The contamination of S. luridus species was higher than that of the other studied species due to its habitat, represented by small schools in very shallow water close to the bottom sediments, and its different approach in nutrition. The present study of surface sediments reveals that, there were probably an uncomplexed strong Hg-binding site available in the sediments, the major portion of mercury found in these sediments is in organo-chelated form followed by acid reducible form. Vis, mercury in residual fraction (mercury of natural origin) is the relatively low portion observed. Even though the percentage of the first three fractions of mercury is relatively high, absolute values of these mobile Hg fractions are quite high due to the high total mercury values.