ASSESSMENT AND SPECIATION OF CHROMIUM, NICKEL, LEAD AND CADMIUM IN THE SEDIMENTS OF THE RIVER NILE, EGYPT

Total (HNO3-digestible) Cr, Ni, Pb and Cd in the < 2 μm fraction of River Nile sediments varied in the range 169-5618, 62-124, 14-327 and 0.09-11.80 ppm, respectively. The results indicated increasing pollution of the river sediments proceeding from south to north. Speciation of metals showed that, on average, a high proportion of the total Cr, Ni and Pb is bound to organic material and sulphides (39.7, 38.7, and 49.4%, respectively), while Cd is bound to carbonate (22.5%). The results also showed that about 49.2, 46.1, 20.4 and 5.6% of the total Cr, Ni, Pb and Cd, respectively, are of lithogenous origin (residual fraction), while the remainder is of non-lithogenous origin (exchangeable + carbonate + easily reducible + moderately reducible + organic/sulphide). The geochemical distribution of metal into the different sedimentary phases showed that the sediments of the two branches of the Nile delta are highly polluted with Cr, Pb and Cd relative to those of the River Nile valley. © 1990.