ACCUMULATION OF SOME TRACE METALS IN TILAPIA FISH, WATER AND SEDIMENT IN MOD NEAR THE CENTER OF Al-NASSIRIYIA CITY

The present study was conducted to investigate the concentration and distribution of four trace metals (Cd, Pb, Cu and Zn) in different tissues (gills, liver, kidney, ovaries and muscle) of Oreochromis aureus collected from main outfall drain (MOD) during summer 2015, and in water (dissolved and particulate) phases also (exchangeable and residual) phases of sediment. Sediment texture and Total Organic Carbon (TOC%) were measured in the sediment of the study area as a percentage.

Distribution of studied metals showed that, station 1 generally was polluted more than station 2 and 3, which may be attributed to the impact of pollution sources in this station among them domestic sewage effluents without treatment from the residual region near the mentioned. In sediment, trace metals was recorded higher concentrations in the residual phase compared to exchangeable phase with exception for Cd and Pb at all stations during the study period.

The mean concentrations of Cd, Pb, Cu and Zn in dissolved phase of water were 0.03, 0.46, 0.08 and 11.54 µg/l respectively, whereas their concentrations in particulate phase were 9.84, 22.11, 17.37 and 63.75 µg/g dry weight respectively. For sediment, the mean concentrations of these metals in the exchangeable and residual phases were as follows: Cd (4.40, 0.05), Pb (27, 1.64), Cu (5.54, 9.02) and Zn (2.65, 17.46) µg/g dry weight respectively.

In the fish tissues, the mean concentrations were oscillated for the studied tissues. These concentrations appeared in tissues (liver, gills, kidney, ovary and muscle) of Oreochromis aureus as follows: Cd (0.13, 0.15, 1.53, 0.06 and 0.02), Pb (10.23, 14.19, 13.01, 0.7 and 2.31) Cu (20.01, 15.61, 10.41, 9.10, and 16.00), and Zn (35.12, 25.01, 18.20, 70.71 and 20.11) µg/g dry weight respectively.

Results showed a difference in concentrations of studied metal in different tissues of fish. The tissues of same species showed differences in concentration of studied metals. According to the results of this study, the consumption of MOD fish can be safe for human health in spite of possible contamination with trace metals.