SEASONAL-VARIATION AND PARTITION OF TRACE-METALS (FE, ZN, CU, MN, CR,CD AND PB) IN SURFACE SEDIMENTS - RELATIONSHIP WITH PHYSICOCHEMICAL VARIABLES OF WATER FROM THE CALABAR RIVER, SOUTH EASTERN NIGERIA

The seasonal variation and partition of trace metals (Fe, Cu, Zn, Mn, Cd, Cr and Pb) in the surface sediments of the Calabar River are repor ted. Chemical partition of the metals in the sediments reveals that 2- 30% of the total metal load was contributed by the non-detrital (acid- soluble) fraction, while fine-grained host minerals/compounds are the main carriers of the detrital (acid-insoluble) fraction (70-98%). Usin g multivariate statistical analysis, the seasonal fluctuations in the distribution of some of the metals show significant influence by physi o-chemical changes (dissolved oxygen, pH, salinity and conductivity) i n the water column. Fe-Mn oxide grain coatings and sulphide materials have been identified as scavengers of some of the non-detrital and det rital trace metals in the sediments. On the basis of index of geoaccum ulation (I-geo) and comparison with previous studies, the Calabar Rive r surface sediments have been classified as unpolluted.