الفهرس 
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Abstract
Environmental contamination becoming a warningsign during the recent years due to increasing various types of environmental pollution and lack of limitation methods for prohibiting its rapid spreading all over the world.
Heavy metals considered one of the most dangerouscontaminants because of its great threatening on aquatic organisms specially fish which considered important protein containing food for human all over the world and consequently the rate of deleterious effect come over human through food chain in all living organisms specially human being.
from this point of view, this study carried out screening process for the five choosen fish farms (Abo Saleh, Abou Selim, El-Fashn, Ehnasia 1and Ehnasia2) and River Nile in Beni-Suef Governorate.
Samples had been taken from water, sediment and fish (Oreochromis niloticus) present in each place for measuring level of heavy metals (Pb, Cd, Zn and Cu) by using Atomic Absorption Spectrometry.
The results concerning Pb levels in muscle tissue was significantly increased in Ehnasia 2 farm when compared with permissible limitofWHO (2000). Concentrations of Pb in this study were inAbo Saleh, Abou Selim, El-Fashn, Ehnasia1, Ehnasia 2 and River Nile respectively(0.979±0.005, 2.301±1.046, 0.814±0.692, 2.347±0.789, 3.826±0.715 and 0.004±0.0003 ppm respectively).
Cdlevels in muscle tissue of five farms have higher levels than the permissible limits (0.05 ppm) according to WHO (2000).
Results were as follow: (0.135±0.006, 0.102±0.006, 0.143±0.004, 0.138±0.007, 0.095±0.009 and 0.042±0.001ppm) forAbo Saleh, Abou Selim, El-Fashn, Ehnasia 1, Ehnasia2 and River Nile respectively. Significant increase in Cd concentration was observed in (Abo Saleh farm, Abou Selim farm, El-Fashn farm and Ehnasia 1 farm) in comparison with permissible limits ofWHO (2000).
ZnandCu concentrations in muscles in all farms and River Nile have lower values than the permissible limits according to WHO (1993) and WHO (2000) which were(40 ppm) and (20 ppm) respectively.
Results also showed thatPb in water as follow: (3.048±0.368, 3.804±0.925, 2.079±0.462, 0.915±0.140, 2.370±0.075 and 0.001±0.0001 ppm) for Abo Saleh, Abou Selim, El-Fashn, Ehnasia 1, Ehnasia2 and River Nile respectively). The previous result indicated that all fish farms exceeded the permissible limits (0.05 ppm) according to WHO (2003). Results in the current studyindicated thatPb concentration was significantly increased in Abou Selim farm, Abo Saleh farm, El-Fashn farm andEhnasia2 farmwhen compared with permissible limit.
Cd levels in water were as follow: all the tested fish farms reported high levels ofCd over the permissible limits (0.003 ppm) according to WHO (2003). The highest levels of Cd were found in Ehnasia 1 (0.009±0.001 ppm) followed by Ehnasia2 (0.007±0.001 ppm), El-Fashn (0.005±0.001 ppm), Abo Saleh (0.004±0.001 ppm), Abou Selim(0.003±0.001 ppm) andRiver Nile (0.002±0.0004 ppm) in descending manner. Significant increase in Cd concentration was observed in (Ehnasia 1 and Ehnasia2 farm) in comparison with permissible limit.
Results showed significant difference in Zn concentration of all water samples compared to permissible limit. Our results as follow: (0.363±0.194, 0.179±0.041, 0.202±0.025, 0.231±0.038, 0.263±0.078 and 0.070±0.007 ppm) for Abo Saleh, Abou Selim, El-Fashn, Ehnasia 1, Ehnasia 2 and River Nile respectively).
Levels of Cu concentration in water were lower than the permissible limits (1 ppm) according to WHO (2003).It was (0.050±0.004, 0.065±0.004, 0.069±0.001, 0.076±0.004, 0.078±0.003 and 0.007±0.0004 ppm) for Abo Saleh, Abou Selim, El-Fashn , Ehnasia 1, Ehnasia 2 and River Nile respectively). There were significant differences in the mean values of Cu of all water samples in comparison with the permissible limit.
Cd concentrationin the sediment in Abo Saleh farm was (0.708±0.079 ppm) and Cu concentration in Ehnasia 1 was(44.607±10.221 ppm) they are the pronounced metals to be expressed which indicated that concentrations of Cd and Cu in these two farms exceed the permissible limit ofCanadian Council of Ministers of the Environment (2012)to Cd and Cuwhich were(0.6 mg/kg and 35.7 mg/kg respectively). While the other farms and River Nilehadlower concentrations of Cd and Cu in sediment samples than the permissible limits. Results in the current study indicated that Cd concentration in sediment sampleswas significantly increased in (Abou Selim farm , El-Fashn farm, Ehnasia 1 farm, Ehnasia2 farm and River Nile) when compared with permissible limit. Whiletherewere significant differences among the mean values of Cu from (Abo Saleh farm, Abou Selim farm and River Nile) compared to the permissible limit.
Pb and Zn concentrations in sediment samples showed significant difference in concentration of all farms and River Nile compared to permissible limit. Their concentrationswere lower than the permissible limits of Canadian Council of Ministers of the Environment (2012) (35 mg/kg and 123 mg/kg) respectively.
The main threats to human health from heavy metals are associated with exposure to Pb and Cd. These metals have been extensively studied and their effects on human health regularly reviewed by international agencies such as the WHO. Heavy metals have been used by humans for thousands of years. Although several adverse health effects of heavy metals have been known for a long time, exposure to heavy metals continues.
Pb and Cd are industrial pollutants which have strong negative effect on human and animal health. These metals are accumulated in the organism, in particularly in the liver and kidneys.So the concentrations of these metals must not exceed the permissible limitof the international organizations.