Evaluation
of levels and spatial characteristics of dissolved nutrients and heavy metals
in the river bed sediment within a basin are critical to understanding the
extent of land-use impact on the river systems. Surface river bed sediments
across eight rivers in the Ogun-Osun River Basin in Nigeria were collected and
analyzed for Total N, ,
Total P, Total organic carbon, Cd, Hg, Pb, Zn, Cu, Fe, Mn and Cr. Pollution Load Index (PLI), Accumulation Factor
(AF) and Hierarchical Clustering Analysis (HCA) were used to identify the
impact of the pollutants and also define the spatial variation across the
basin. The pollution load indices of heavy metals were moderately high ranging
from 0.41 - 0.60, while AFs were 0.43 - 2.00 and 0.61 - 1.29 for heavy metals
and nutrients from upstream to downstream in the rivers systems, respectively.
The HCA identified 7 distinct spatial patterns describing pollutant input from
the land-use in the basin. Although, heavy metals contents were low in relation
to the background values, and the potential for redistribution and secondary
pollution was high hence, there was need to impose checks on the activities
across agricultural, urban and grazing land-uses that had impact negatively on
the river systems in the basin.