Abstract
The levels of Cu, Zn, Cd, and Pb were determined in water, sediment, and aquatic plant samples taken from the Nile River and its branches at selected sites characterized by heavy industrialization and dense population. The results revealed that concentration factors in the sediments were, in most cases, much higher than in plants. Metals content in the plants collected from downstream wastewater discharge points was usually higher than that in the plants collected from sites upstream of these points. In laboratory scale models of the piston and completely mixed continuous flow hydraulic systems, Cu, Cd, and Pb removal by a test plant ( Eichhornia crassipes) was assessed. The results showed that the root of the test plant acted as a scavenger for the metals up to a certain capacity. The metals were taken up by different rates, the least of them was that of cadmium. In a batch system metals accumulation from waters of different compositions was investigated using the same test plant. The results are summarized in the following: (1) Cu, Zn, Cd, or Pb accumulation was a function of metal: plant root exposure ratio on dry weight basis. (2) The rates of metals accumulation from both the natural medium (Nile water) and the synthetic medium (mM NaHCO 3 solution) were quite close. (3) Metal accumulation was much lower in the presence of EDTA. (4) The presence of Ca 2+ and Mg 2+ in a concentration equivalent to that of EDTA did not eliminate the retarding effect of the latter on metal accumulation. (5) Metal translocation from the root to the shoot occurred at a low rate compared to metal accumulation by the root.
Published Version
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