Environmental impact of some chemical pollutants on Lake Manzala

Abstract

Environmental pollution problems in Lake Manzala and its main drains evaluated by measuring the levels of some chemical pollutants in terms of organochlorine insecticides, polychlorinated biphenyls, petroleum hydrocarbons and some trace metals in fish and sediment samples. Lindane, HCB, DDT and its metabolites were detected in all fish samples. The highest concentration of DDTs was 101.45 ng/g wet weight. PCBs as Aroclor 1254 were found in the range between 3.58 and 43.38 ng/g wet weight. Results of this study demonstrated that fish samples collected from Lake Manzala are contaminated with low levels of chlorinated hydrocarbons, the percentage of FAO/WHO acceptable daily intake (ADI) is below 1% and that public is not at risk from fish consumption, even if totally dependent upon fish as a protein source. Petroleum hydrocarbons and some trace metals (TMs) were detected in Clarius angullaris (catfish), Tilapia (bolta) and A. angilla (eelfish) species. The total hydrocarbons concentration ranged between 15.6 and 146.7 mug/g wet weight. Residue levels of TMs are relatively low except Zn and Cu were found at highest values of 97 and 28.8 mug/g wet weight, respectively. According to the present study the major environmental impacts on Lake Manzala are due to direct discharge of untreated wastewater, discharge of irrigation water from drainage canals and land reclamation. These problems have contributed to a significant deterioration of water quality and disappearance of several important species of fish.