Influence of Pollutants on the Bottom Sediment of Sewage Receiving Asa River, Ilorin, Nigeria

Abstract

The aim of this study was to evaluate the sediment quality in the Asa River environment, in order to identify areas where sediment contamination could cause ecosystem degradation. Samples were obtained from three different locations and sediment are characterized for grain sizes, total organic matter, total recovery metals such as, lead, nickel, zinc, iron, arsenic, chromium, copper and cadmium. The sampling and processes of analyzed samples were carried out using the analytical methods as described by American Public Health Association (APHA) and sampling were done for a total period of twenty-four months (Between April, 2011 and March, 2013). Sediment sample from sampling site A had very low concentration of metal compared to sites B and C. High anthropogenic metal contamination was identified at sampling site B while metal concentration was found to be lower at sampling site C. This increased level of metals at sampling sites B and C could be due to an inappropriate use of waters at these two sites and, this contamination could possibly also be toxic for the resident species in case of re - suspension due to overturning. Statistically, there were significance correlations in the concentrations of heavy metals between the three sampling sites and the two seasons of the year. The level of all heavy metals analyzed was relatively higher than the permissible limits as recommended by World Health Organization, Environmental Standards and Regulations Enforcement Agency, and National Industrial Standard. Of all the metals examined, iron, copper and cadmium were found to be the most abundant in Asa River and its tributaries. Therefore, unregulated deposition of anthropogenic wastes into this river should be discouraged.