Persistent organochlorine pollutants and metals residues in sediment and freshwater fish species cultured in a shallow lagoon, Egypt

Six freshwater fish species cultured in Lake Edku fish farm, one of the northern Nile Delta lakes in Egypt that receives input from numerous anthropogenic activities in addition to agriculture wastes through several huge drains, were collected for the detection and evaluation of residues of the persistent organochlorine (OC) pollutants polychlorinated biphenyls (PCBs), 1,1,1-trichloro-2,2-di(4-chlorophenyl)ethane (DDT), total cyclodienes (TC), hexachlorocyclohexanes (HCHs) and heavy metals (Cu, Cd and Pb) in their edible parts. In all fish and sediment samples, PCBs were found in higher concentrations than pesticides; the edible parts of Mugil capito, Tilapia galilaeus, Tilapia zilli and Clarias lazera had the highest PCBs (3.49, 0.83, 1.06 and 4.29 ng/g wet weight respectively), PCB 28 being most prevalent in Mugil capito and Clarias lazera with ratios 86 and 62%, respectively, of the total PCBs. PCB 180 was most prevalent in Tilapia zilli (about 56% of the total PCBs). In these four fish species OCs were found in the order: PCBs>DDTs>HCHs>TC. The other two species (Tilapia nilotica and Tilapia aureus) had the highest concentrations of pesticides (7.58 and 1.13 ng/g wet weight, respectively) with HCHs being most prevalent (96% and 74% of the total pesticides, respectively). OCs were found in the order: HCHs≫PCBs>DDTs>TC in the edible Tilapia nilotica , and in the order: PCBs>HCHs>DDTs>TC in the other species. The mean concentrations of PCBs and pesticides in sediments are 539.66±48.8 and 259.17±81.2 ng/g dry weight, respectively. Among the studied metals in the edible parts of the fish samples, about 67% of the samples contained marginally higher Pb content in the edible parts, above the European Community's legal limit. About 50% of the samples contained marginally higher Cd content (N.D to 0.88 μg/g) above the permissible level of Cd in fish edible parts; the Cu content ranged from 0.37–2.36 μg/g, with a marginally higher content in the fish but below the maximum permissible limits. As for the concentration of the studied metals in sediments of Edku lagoon, results showed that copper had the highest concentration (2.2±0.37 μg/g) in the lake sediment.