Seasonal changes in physico-chemical parameters and nutrient load of river sediments in Ibadan City, Nigeria

Seasonal variations in ecological parameters exert a profound effect on the distribution and
population density of both animal and plant species (Odum, 1971). The productivity in terms
of planktonic biomass in freshwater bodies is regulated by various physico-chemical factors
viz., temperature, transparency, pH, total hardness, nitrates, phosphates etc. A field study
was conducted (October 2003 and March 2004) to develop a data-base on seasonal changes
of physico-chemical parameters and nutrient load of the river sediment in Ibadan metropolis.
Quantitative samples of sediments were collected during dry and rainy seasons from 11
stations and analyzed for various physico-chemical parameters and nutrient load. All (except
dissolved oxygen) physico-chemical parameters assessed in this study were higher than the
recommended standard (EPA, 2002). The nutrient load of pore water of Ibadan river system
sediments during rainy and dry seasons was found in the range of: phosphate (2.23-16.2 ppm
and 0.35-2.8 ppm respectively); nitrate (0.22 to 0.9 ppm and 0.47-3.3 ppm respectively);
Nitrite (0.2-0.42 ppm and 0.03-0.3 ppm respectively); Total nitrogen (0.13-0.9ppm and 0.47-
3.4 ppm respectively) and sulphate (70-99.4 ppm and 26.6-120 ppm respectively). The levels
of parameters downstream were significantly elevated than the corresponding levels
upstream. This result suggests that the water quality of Ibadan river system is adversely
affected and impaired by the discharge of domestic, agricultural and industrial wastes, which
is the usual practice in Ibadan. The data generated from this study will guide potential
remediation and other management decisions.