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Environmental Geochemistry of River Nile Bottom Sediments Between Aswan and Isna, Upper Egypt

2009; Linguagem: Inglês

2423-4400

Ahmed El-Kammar, Ali Boulemaredj, A. M. M. El-Badry,

Radioactivity and Radon Measurements

3 Abstract: The pollution of t he River N ile bottom sediment i s ind icative of wa ter a nd food-web quality in g eneral. About 60 samples were c ollected from the upper 50 cm of the Nile bot tom sediments between Aswan due south a nd Isna due north. The sampling considered the eastern and the western banks a s w ell as the middle of the Nile course. Collaborating analytical techniques have been employed to analyze group of environment-sensitive elements, including; Pb, Cd, Ni, Co, Cu, V, Zn, U, Th and Ra. Standard sequential extraction pro cedure was employed on polluted samples t o determine t he b ioavailability of the pollutants. The p resent study documents serious pollution by Cd in t he vi cinity of the p hosphate-shipping harbors at t he eastern and western banks o f S ibaiya area. T he average Cd content i n the study a rea (3.1 ppm) i s ab out 6 fold the maximum permissible li mit (MPL = 0.5 p pm) o f soil while the highest concentration (5.8 ppm) is more than 10 fold the MPL. C admium is more mobile in aquatic environments than most other heavy metals. The areas around Isna harbors and al ong Aswan dam show mark ed pollution by Pb which reaches 271ppm. The main reason for such Pb pollution is the fuel combustion from heavy traffic. However, there i s insignificant signature of pollution by o ther h eavy metals such as Ni, Co, Zn, V and Cu. The phosphorite mining and shipping area between Sibaiya and Mahamied exhibits marked pollution s ignature by ur anium (up to 8 p pm). Knowing t hat almost half of the urani um content in phosphorite is soluble in the hexavalent state, significant amount of uranium must have been d rained due no rth wi th N ile current . Radon and uranium have mutual distribution, while t horium is not. The sequential extraction data indicate that the insoluble fraction remains the main sink of zinc, copper a nd cobalt. Almost half the content of cadmium, lead and van adium occur s in a bi oavailable s tate; as exchangeable and carbonate-bound cations. Nickel mostly associates the iron oxy-hydroxides fraction. The unsupervised anthropogenic act ivities are the m ain causes of pollution i n t he N ile sedi ments. Routine program f or moni toring the abundance and di stribution of Cd, Pb and U in t he Nile wa ter, biota, sediments and f ood chain should be imposed.