Assessment of Metal Pollution around Sabal Drainage in River Nile and its Impacts on Bioaccumulation Level, Metals Correlation and Human Risk Hazard using Oreochromis niloticus as a Bioindicator

This work aimed to assess the impact of Sabal drains (northern part of El-Minufiyah governorate, Egypt) on the metals load of river Nile. Four sites were selected to monitor the partitioning of metals in the aquatic components: reference site (site1); 20Km before Sabal drainage (site2); Sabal site (site3) and 20Km after Sabal drainage (site4). The maximum means of aqueous metals were observed at site3 in the following order (mg/l): Fe (0.76) >Mn (0.325) >Zn(0.07) >Pb (0.064) >Cu (0.041) >Cd (0.0035), while the trend is slightly different in sediments (mg/kg): Fe (527.9) >Mn (102.7) >Zn (17.65) >Cu (11.4) >Pb (1.26)>Cd (0.07). Tissue-specific patterns of metal accumulation in Oreochromis niloticus were observed. As indicated by the calculated metal pollution index and bioaccumulation factor, the tissues of liver, kidneys and gills were observed to be strong bioaccumulators compared to muscular tissues. Regarding the correlation study in site3, the bioaccumulated metals in most tissues showed homogenous-correlation with aqueous metals (r>0.5) and diverse-correlations with respect to sedimentary metals. The calculated hazard index (HI) indicated that each metal had low HI but, the cumulative impacts of all metals represented a real threat to fish consumers especially at site3. Metals elevation was highly correlated with Sabal discharges and regulations for water and fish consumption have to be applied.