الفهرس 
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Abstract
Heavy metals are highly persistent and non-biodegradable contaminants that have been reported to cause toxic effect and bioaccumulation in food animals. As such heavy metals could reach hazardous levels with potential health risks to consumers through consumption of contaminated fish. Therefore, the present study was conducted to assess the heavy metals in aquaculture ponds of lake Mariut in Alexanderia and evaluation of the health risk from tilapia consumption.
The study came to the following results:
1. The mean Pb concentration in the muscles of Tilapia fish was 0.84±0.28 ppm, with highest mean concentration during September (1.18ppm), and the lowest 0.63ppm during April.
2. The highest concentration of Pb in fish muscles was 2.29 ppm, during June, in pond 1, and the lowest concentrations was 0.17 ppm, during June, in pond 3.
3. There was a significant difference in the concentration of Pb in muscles between the three ponds and between four months (p<0.05).
4. The mean Pb concentration in fish liver was 1.59±0.5 ppm, with highest concentration during September (2.04), and the lowest 0.96ppm during December.
5. The highest concentration of Pb in fish liver was 4.6 ppm during June in pond 1, and the lowest 0.41 ppm, during June, in pond 3.
6. There was no significant difference in the concentration of Pb in liver between the three ponds and between four months.
7. The mean Pb concentration in the gills of Tilapia fish was 2.84±0.6 ppm, with highest mean concentration during September (4.3ppm), which was significantly higher than the concentrations in the other months at p<0.01, and the lowest concentrations was 1.81ppm during December.
8. The highest concentration of Pb in fish gills was 4. 9 ppm, during September, in pond 2, and the lowest concentrations was 1.11 ppm, during April, in pond 3.
9. There was a significant difference in the concentration of Pb in gills between the three ponds and between four months (p<0.05).
10. The mean Pb concentration in water was 0.1±0.005 ppm, with highest mean concentration during June (0.28ppm), and the lowest 0.04ppm during September.
11. The highest concentration of Pb in water was 0. 8 ppm, during June, in pond 1, and the lowest concentrations was 0.01 ppm, during June, in pond 3.
12. There was no significant difference in the concentration of Pb in water between the three ponds and between four months.
13. The mean Pb concentration in sediment was 11.8±0.002 ppm, with highest concentration during December (14.1ppm), and the lowest 7.5 during September.
14. The highest concentration of Pb in sediment was 19.0 ppm, during December, in pond 1, and the lowest was 6.0 ppm, during September, in pond 2.
15. There was no significant difference in the concentration of Pb in sediment between the three ponds and between four months.
16. The mean Cd concentration in the muscles was 0.455±0.2ppm, with highest mean Cd concentration during December (1.57ppm), which was significantly higher than the concentrations in the other months at p<0.05, and the lowest concentrations was 0.21ppm during June.
17. The highest concentration of Cd in fish muscles was 3.76 ppm, during December, in pond 1, and the lowest was 0.16 ppm, during September, in pond 2.
18. There was no significant difference in the concentration of Cd in muscles between the three ponds.
19. The mean Cd concentration in the liver of Tilapia fish was 12.7±2.9ppm, with highest mean concentration of Cadmium in liver during December (35.2), which was significantly higher than the concentrations in the other months at p<0.05, and the lowest was 0.88ppm during September.
20. The highest concentration of Cd in fish liver was 43.5ppm, during December, in pond 2, and the lowest was 0.12ppm, during September, in pond 3.
21. There was no significant difference in the concentration of Cd in liver between the three ponds.
22. The mean Cd concentration in the gills of Tilapia fish was 1.2±0.3 ppm, with highest mean concentration of Cadmium in gills was during September (1.68ppm), and the lowest was 0.92ppm during June.
23. The highest concentration of Cd in fish gills was 4.06ppm, during September, in pond 1, and the lowest was 0.48ppm, during April, in pond 1.
24. There was no significant difference in the concentration of Cd in gills between the three ponds and between four months.
25. The mean Cd concentration in water was 0.023±0.0012ppm, with highest mean Cd concentration during September (0.043ppm), and the lowest 0.005ppm during April.
26. The highest concentration of Cd in water was 0.11ppm during September in pond 2, and the lowest concentrations was 0.004ppm, during April, in pond 3.
27. There was no significant difference in the concentration of Cd in water between the three ponds and between four months.
28. The mean Cd concentration in sediment was 1.015±0.001ppm, with highest mean Cd concentration in sediment during April (1.63ppm), which was significantly higher than the concentrations in the other months at p<0.05 and the lowest was 0.43ppm during September.
29. The highest concentration of Cd in sediment was 2.24ppm, during December, in pond 1, and the lowest was 0.30ppm, during June, in pond 3.
30. There was no significant difference in the concentration of Cd in sediment between the three ponds .
31. The mean Zn concentration in the muscles of Tilapia fish was 8.5±1.9ppm, with highest mean concentration during December (13.6ppm), and the lowest was 6.11ppm during June.
32. The highest concentration of Zn in fish muscles was 27.8ppm, during December, in pond 2, and the lowest concentrations was 4.46ppm, during September, in pond 3.
33. There was no significant difference in the concentration of Zn in muscles between the three ponds and between four months.
34. The mean Zn concentration in the liver of Tilapia fish was 18.7±2.1ppm, with highest concentration of Zinc during December (24.2), which was significantly higher than the concentrations in the other months at p<0.05 and the lowest was 13.3ppm during June.
35. The highest concentration of Zn in fish liver was29.9 ppm, during September, in pond 3, and the lowest concentrations was 9.5 ppm, during April, in pond 2.
36. There was no significant difference in the concentration of Zn in liver between the three ponds.
37. The mean Zn concentration in the gills of Tilapia fish was 19.3±2.6ppm, with highest mean concentration of Zinc in gills was during September (29.6ppm), which was significantly higher than the concentrations in the other months at p<0.05, and the lowest was 12.7ppm during April.
38. The highest concentration of Zn in fish gills was 31.8ppm, during September, in pond 3, and the lowest was 9.3ppm, during April, in pond 3.
39. There was a significant difference in the concentration of Zn in gills between the three ponds (p<0.05).
40. The mean Zn concentration in water was 0.11±0.0012ppm,with highest mean Zn concentration in water was during December (0.10ppm), which was significantly higher than the concentrations in the other months at p<0.05, and the lowest was 0.002ppm during April.
41. The highest concentration of Zn in water was 0.14ppm, during December, in pond 2, and the lowest was 0.001ppm, during April, in pond 1and 3.
42. There was no significant difference in the concentration of Zn in water between the three ponds.
43. The mean Zn concentration in sediment was 12.5±0.001ppm, with highest mean Zn concentration in sediment during April (15.06ppm), and the lowest was 9.3ppm during June.
44. The highest concentration of Zn in sediment was 18.2ppm, during April, in pond 2, and the lowest was 7.0ppm, during June, in pond 1.
45. There was no significant difference in the concentration of Zn in sediment between the three ponds and between four months.
46. The mean Cu concentration in the muscles of Tilapia fish was 0.76±0.3ppm,with highest mean concentration of Cu in muscle during September (1.67ppm), which was significantly higher than the concentrations in the other months at p<0.05, and the lowest was 0.066ppm during April.
47. The highest concentration of Cu in fish muscles was 1.83ppm, during September, in pond 1, and the lowest was 0.03 ppm, during April, in pond 3.
48. There was no significant difference in the concentration of Cu in muscles between the three ponds.
49. The mean Cu concentration in the liver of Tilapia fish was 2.1±0.42ppm, with highest concentration of Cu in liver was during September (7.94), which was significantly higher than the concentrations in the other months at p<0.05 and the lowest was 0.056 ppm during December.
50. The highest concentration of Cu in fish liver was 8.58 ppm, during September, in pond 3, and the lowest was 0.03ppm, during December, in pond 1.
51. There was no significant difference in the concentration of Cu in liver between the three ponds.
52. The mean Cu concentration in the gills of Tilapia fish was 1.15±0.39ppm,with highest mean concentration of Cu in gills was during September (4.02ppm), which was significantly higher than the concentrations in the other months at p<0.05, and the lowest was 0.13ppm during December.
53. The highest concentration of Cu in fish gills was 4.7ppm, during September, in pond1, and the lowest was 0.09 ppm, during December, in pond 3.
54. There was no significant difference in the concentration of Cu in gills between the three ponds.
55. The mean Cu concentration in water was 0.10±0.001ppm,with highest mean Cu concentration in water during June (0.05ppm), which was significantly higher than the concentrations in the other months at p<0.05 and the lowest was 0.001ppm during April.
56. The highest concentration of Cu in water was 0.05ppm, during June, in pond 1,2,3, and the lowest was 0.001ppm, during September, in pond 3 and during April, in pond 1.
57. There was no significant difference in the concentration of Cu in water between the three ponds.
58. The mean Cu concentration in sediment was 3.47±0.001ppm, with highest mean Cu concentration in sediment during June (4.9 ppm), and the lowest was 1.5ppm during September.
59. The highest concentration of Cu in sediment was 7.5 ppm, during April, in pond 3, and the lowest concentrations was 1.3 ppm, during September, in pond3.
60. There was no significant difference in the concentration of Cu in sediment between the three ponds and between four months.
61. The mean Ni concentration in the muscles of Tilapia fish was 0.43±0.12ppm,with highest mean Ni concentration in muscle during December (0.92ppm), which was significantly higher than the concentrations in the other months at p<0.05, and the lowest was 0.24 ppm during September.
62. The highest concentration of Ni in fish muscles was 1.15ppm, during December, in pond 1, and the lowest was 0.00 ppm, during September, in pond 3.
63. There was no significant difference in the concentration of Ni in muscles between the three ponds.
64. The mean Ni concentration in the liver of Tilapia fish was 1.062±0.36ppm, with highest Ni concentration in liver during December (1.51 ppm), and the lowest was 0.61 ppm during September.
65. The highest concentration of Ni in fish liver was 2.4ppm, during April, in pond 1, and the lowest was 0.18ppm, during September, in pond 3.
66. There was no significant difference in the concentration of Ni in liver between the three ponds and between four months.
67. The mean Ni concentration in the gills of fish was 1.06±0.24 ppm, with highest mean Ni concentration during December (1.55ppm), which was significantly higher than the concentrations in the other months at p<0.05, and the lowest was 0.66 ppm during April.
68. The highest concentration of Ni in fish gills was 1.92 ppm, during December, in pond 2, and the lowest concentrations was 0.5ppm, during April, in pond 3.
69. There was no significant difference in the concentration of Ni in gills between the three ponds.
70. The mean Ni concentration in water was 0.059±0.001 ppm, with highest mean Ni concentration during June (0.12ppm), and the lowest was 0.066 ppm during December.
71. The highest concentration of Ni in water was 0.15ppm, during June, in pond 3, and the lowest was 0.022 ppm, during April, in pond 2.
72. There was no significant difference in the concentration of Ni in water between the three ponds and between four months.
73. The mean Ni concentration in sediment was 4.46±0.001ppm, with highest mean Ni concentration during June (5.8 ppm), and the lowest was 3.6 ppm during September.
74. The highest concentration of Ni in sediment was 7.5 ppm, during june, in pond 2, and the lowest was 3.1 ppm, during September, in pond 1.
75. There was no significant difference in the concentration of Ni in sediment between the three ponds and between four months.
76. In case of Pb, 79.2% of fish exceeded the permissible limits of WHO/FAO and the Egyptian permissible limits.
77. In case of Cd, 95% of fish exceeded the permissible limits of WHO/FAO and the Egyptian permissible limits.
78. In case of Cu, 6.7% of fish exceeded the permissible limits of WHO (2006).
79. In case of Ni, 73.5% of fish exceeded the permissible limits of WHO (2006)
80. In pond 1 there was a significant strong positive relation between pb and cd, Zn and Cu (0.993, 0.973and 0.999, respectively), while pond 2 showed no relation between pb and cu. Pond 3 showed strong positive relation between Zn and Ni (0.928).
81. Pond 3 showed significant positive strong relation between Cu and Pb, Cd, and Zn (0.973, 0.930 and 0.941, respectively).
82. During September, Pond 1 and pond 2 showed a significant strong positive relation
84. During April in Tilapia fish muscles , showed significant strong positive relation between Cu and Cd (0.991), showed significant strong positive relation between Cd and Zn (0.997), Cd with Ni (0.977) and liver In pond 2 there was a significant strong positive relation between Cd and Zn (0.982).
85. During four months, there was a significant strong positive relation among the weight of fish and the concentration of Cd, Zn and Ni in liver.also, in gills there was significant strong positive relation among the weight of fish and the concentration of pb, Zn and Ni. But Ni showed a significant strong positive relation among the weight of fish and its concentration in all organs.
86. During four months, there were significant strong positive relations between heavy metals in water and sediment. there was a strong positive relation between Zn in water and Cu in water (0.590) at p< 0.05, between Pb concentration in muscles and Cd concentration in water (0.626).
87. The THQ values of Pb in Tilapia muscles ranged from 0.48 to I for citizen who eat tilapia fish five times a week, from 0.28 to 0.63for whose eat tilapia fish three times a week and from 0.09to 0.21 for people who consume tilapia fish once a week. During December and September the THQ of Cd was more than 1 (HQ>1).
88. The allowable fish consumption rate of Cd was between 0.02 to 0.128Kg/day, of Pb between 0.19 to 0.237Kg/day, and of Cu between 1.5 to 36 kg /day (the highest).