الفهرس 
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Abstract
The present investigation was conducted in Brullus and Edku Lakes and Nile River as a reference site. This investigation was carried out to assess wastewater pollution and accumulation of detergents residues; Linear Alkylbenzene Sulphonate (LAS) in water, sediments, and muscles of Nile Tilapia, Oreochromis niloticus from autumn 2019 to summer 2020, and estimated detergents residues’ pollution and their impacts on fish. Aim : Determination of detergents residues; Linear Alkylbenzene Sulphonate (LAS) in each of water, sediment, and fish samples sampled from different studied ecosystems. Ecotoxicological investigation by studying the impact of detergents residues on hematological, biochemical, ecological parameters and histopathological examination of Nile Tilapia, Oreochromis niloticus in study sites seasonally. Methodology : Water Sampling: Five sites were selected along Brullus, Edku and Damietta Branch of Nile River at 50 cm depth were seasonally collected from each site in one-liter polyethylene bottles at the seasonal intervals from autumn 2019 to summer 2020. Collected samples were immediately placed in icebox and transferred to the Environmental Sciences Laboratory and kept in a refrigerator at 4°C until conducting the intended analyses. Linear Alkylbenzene Sulphonate (LAS) in Water Samples : Determination of anionic surfactants (AS) by improved spectrophotometric method using methylene blue (MB), as cationic dye. The method based on the reaction between linear alkylbenzene sulphonate (LAS), as anionic surfactants, and methylene blue (MB), as cationic dye, to form associated ion-pair (LAS-MB ion pair) in water with 1:1 molar ratio which can be easily extracted to the organic phase (chloroform, CHCl3). Linear Alkylbenzene Sulphonate (LAS) in Sediment Samples: Linear Alkylbenzene Sulfonate was assayed by reversed phase high performance liquid chromatography (RP-HPLC). LAS standard1000 ppm 120 mL Amber Glass was used in the present study (RICCA Chemical Company, Texas), with standard solution (by mass) 3.4%, 8.8%, 7.3% and 5.1% for the homologues C10, C11, C12 and C13, respectively. Concentration of LAS in sediments is the sum of homologues C10, C11, C12 and C13. The resulting treatments were characterized by the following nominal initial concentrations of LAS (µgKg-1). Results : It was clear that there was a very high significant difference of LAS concentration in water between different study stations and increased its concentrations in the investigated stations of both Brullus and Edku Lakes compared to that in Nile River may be due to continuous discharge of sewage and domestic wastes to the water surface. As well as there was a very high significant difference in LAS concentration in all investigated stations between different seasons, decreased concentrations of LAS in hot seasons than colder seasons suggested because elevated temperature and oxygen depletion induce microbial activity which accelerates LAS degradation. The obtained results showed a decreased concentration of LAS in sediments in hot seasons than colder seasons may be due to decreased concentrations of LAS in the water column in hot seasons and a very high significant difference of LAS concentration in sediments between different study stations and increased its concentrations in the investigated stations of both Brullus and Edku Lakes compared to that in Nile River leading to sorption of a considerable fraction of LAS to sediment because this surfactant has a high adsorption capacity, so sediment acts as a sink for LAS. Conclusion : The data showed very high significant decreases in Hb content, Ht, RBC counts, and platelets counts in fish with detergent- concentration gradient which may be due to exposure to detergents causing inhibition of erythrocyte production or damage and bleeding. While very high significant increases in WBC count with increased detergent concentration exposure due to induction of the fish defense mechanism to counteract the stress of toxicants.