Assessment of heavy metals levels in water, sediment and fish in cage fish culture at Damietta branch of the river Nile uri icon

abstract

  • The present study aimed to gain detailed information on the distribution of some heavy metals (Cu, Pb, Zn, Fe and Cd) among the major components of the aquatic ecosystem (water, sediment and fish â??Oreochromis niloticusâ?�) of Damietta district at the area of El- Bostan. Such information is needed to identify the effect of fish cages on the aquatic ecosystem. Water and sediment samples were collected from three sites, as the following: before the cages area (Be), at the cages area (Ca) and after the cages area (Af). Fish samples were collected from the studied cages. All samples were collected monthly for one year period from April 2004 to March 2005. Heavy metal analyses were carried out by using furnace atomic absorbance spectrophotometer (Unicam ®, 969). Pearson correlation coefficients were calculated between heavy metals in both fish and water in the cages site. The lowest concentrations of the water heavy metals were recorded in spring and summer times, while winter and autumn showed the highest water heavy metal concentrations. Average concentrations of Cu, Zn and Fe in water were below the maximum acceptable levels recommended by FAO. On the other hand, average Pb and Cd concentrations in water from the three test sites were 0.314 and 0.025 ppm for (Be), 0.323 and 0.030 ppm for (Ca) and 0.365 and 0.026 ppm for (Af) respectively which were higher than FAO levels, indicating that fish cages are not the source of these metals. Concentrations of all studied heavy metals of the sediments in the (Ca) site were significantly higher than that in the (Be) and (Af) sites due to the adsorption capacity of organic matter. On the other hand, annual average of most sediment heavy metals, especially Pb, in the (Be) site were higher than that in the (Af) site, which means that the release of heavy metals from the power station located before the cages site could be the main source of heavy metals accumulated around and under cages. The mean concentrations of Cu, Fe and Cd in the fish samples of the present study were lower than the maximum permissible concentrations proposed by FAO. However, mean levels of Pb and Zn were higher than limits given for fish. Thus, fish in the cages area accumulates Pb with levels exceeding the maximum permissible level (about 4 times). This could represent a significant health risk for humans consuming diets of fish. The flow of industrial effluents discharged to the Nile River accumulates more toxic heavy metals in the fish flesh reared in this area than those caused directly or indirectly by cages

publication date

  • 2008