Concentration and speciation patterns of some heavy metals in streams sediments in an urban city in Nigeria

Download this article as: 

Concentration and distribution patterns of some heavy metals in stream sediments in Ibadan, a typical urban city in Nigeria were investigated. Stream sediments were collected from seven streams at 30 sampling sites within Ibadan metropolis and analysed for their total metal concentrating and speciation. The sediments were totally decomposed with hydrofluoric acid and Aqua regia for total metal concentration and subjected to sequential extraction for their speciation Pb, Zn, Ni, Co, Cd, and Cr were determined in this study using Atomic Absorption Spectrophotometer. The overall mean concentrations (ug/g dry weight of sample) and ranges were Pb(136.95±95.2,15.6-44.40), Zn(102±69, nd-240), Ni 137.0±11.50,4.17-14.20),Co(25.20±7.9,11.50-62.50), Cu(45.90±28. 3,6.89-134),Cd(2.57±0.37,1.4-3.8) and Cr 54.20±20.4,14.40-12.70) giving an order of Pb>Zn>Cu>Ni>Co>Cd. The mean concentrations of Pb and Zn were very high especially in areas with high population and traffic densities. Speciation studies revealed largely anthropogenic heavy metal enrichment for Pb, Zn, Cu and Cd and implicated refuse dumping and urban run-off water, transporting metals from land derived wastes as the source of the enrichment of the streams. Ni, Co and Cr were identified as being of geometrical origin. There were no significant difference among Ni, Co, Cd and Cr mean concentrations between the streams, indicating that they may be from the same source. Many of the metals showed significant correlation at P>0.05 levels.

heavy metals; metal concentration; speciations; contamination of stream sediments