الفهرس 
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Abstract
As a result of industrial activities, the aquatic ecosystem has been increasingly contaminated by heavy metals. This posses great stresses to aquatic organisms in particular and to the whole ecosystem in general. Investigation of heavy metal concentrations in fish and water compartment of the environment are an important aspect of the control of environmental pollution to counteract the human activities which progressively increase
heavy metal concentration in the aquatic system.
100 fish samples, 50 water samples and 50 weed samples were collected from five regions at Assiut governorate (Abu-Tig, Assiut, Manqabad, Bany-Qurra and Dairut), five samples from Oreochromis niloticus, Clarias lazera, water and aquatic weeds from each examined region in winter and in summer. Fish, water and weed samples were digested and subjected to chemical analysis for determination of lead, copper, mercury and cadmium by using specific ion electrodes.
Lead concentrations in water of the different examined areas were 1.940, 0.810, 0.810, 0.314 and 0.790 ppm in winter and 0.220, 0.270, 0.313, 0.222 and 0.200 ppm in summer at Abu-Tig, Assiut, Manqabad, Bany-Qurra and Dairut respectively. Abu-Tig and Assiut areas registered the highest concentration in winter and Manqabad and Assiut in summer. The examined water samples were above the permissible limit of WHO which is 0.10 ppm or united states environmental protection agency (US EPA) which is 0.05 ppm. The highest concentration of copper in water samples collected from Manqabad and Bany-Qurra were 0.42 and 0.088 ppm in winter and 0.522 and 0.39 ppm in summer. The examined water samples showed values less than the permissible limits adopted by
US EAP which is 1.0 ppm. 18.700 and 12.400 ppb were the highest concentrations of mercury in water samples collected from Assiut and Bany-Qurra in winter and 24.800 and 15.600 ppb in Bany-Qurra and Dairut in summer. The examined water samples showed values more than the permissible limits adopted by US
EPA which is 2 ppb. The highest concentration of cadmium in water at Bany-Qurra and Manqabad (0.009 and 0.007 ppm) in winter and Dairut and Manqabad (0.012 and 0.015 ppm) in summer. Water samples showed cadmium values less than the permissible limit (0.01 ppm) except water samples collected from Manqabad and Dairut in summer which reached to 0.015 and 0.012 ppm respectively.
Lead showed its highest concentration in weeds at Assiut and Bany-Qurra which reached 4.92 and 1.120 ppm respectively in winter and 6.070 and 2.540 ppm respectively at Dairut and Bany-Qurra in summer. The highest concentration of copper in weeds were 4.872 and 2.52 ppm in winter and 3.55 and 1.512 ppm in summer respectively at
Manqabad and Bany-Qurra areas.
Mercury showed its highest concentration in weeds at Assiut and Bany-Qurra which reached 0.710 and 0.610 ppb in winter and Dairut and Bany-Qurra which reached 0.240 ppb for each in summer.
The highest concentration of cadmium in weeds was 0.918 ppm at Assiut in winter and 0.70 ppm at Manqabad in summer.
The highest concentrations of lead in fish samples were 6.700 and 3.880 ppm in kidney and liver followed by 3.000 and 1.780 ppm M. bone and muscles respectively. The examined muscle samples for lead showed values less than the permissible limit which is 2.62 ppm. The highest concentration of copper in fish samples were 70.72 and 53.53 ppm respectively in kidney and liver followed by 33.156 and 15.93 ppm respectively in bone and muscle. Muscle samples collected from Assiut, Manqabad and Bany-Qurra exceed the permissible limit of WHO which is 10 ppm.
The highest concentration of mercury in fish samples were 90.8 and 39.900 ppb in kidney and liver followed by 24.00 and 23.700 ppb in muscle and bone respectively. The examined muscle samples for mercury showed values less than the permissible limit which is 0.5 ppm. Cadmium showed its highest concentration in liver and kidney which reached 3.090 and 2.450 ppm followed by 0.658 and 0.820 ppm in muscle and bone. All muscle samples showed cadmium values less than the permissible limit of WHO which is 0.5 ppm.
The correlation between the examined elements in fish, water and aquatic weeds were also one of our goals in this study. Lead concentrations showed that there was a highly significant correlation between concentration in fish and water as well as in water and weeds, while there was no significant correlation between its concentration in fish and weeds. Copper levels showed that there was a highly significant correlation between fish and water, fish and weed and water and weed concentrations. Mercury levels proved that there was a significant correlation between fish and weeds as well as water and weed concentrations, while there was no significant correlation between fish and water. In case of cadmium there was a significant correlation between fish and water as well as water and weed concentrations, while there was no significant correlation between fish and weeds.