Sediments in rivers can contribute to the concentration of phosphorus and nitrogen in overlying water which affect aquatic life adversely at excessive concentrations. This study examined the various forms of phosphorus and nitrogen in sediments of Ogun River, the major river in the city of Abeokuta.Total phosphorus and total nitrogen concentrations ranged from 820-2740 ?g P g-1and 840-1960 ?g N g-1 respectively. Inorganic phosphorus was the major component of phosphorus in the sediments. Exchangeable phosphorus, aluminium-bound phosphorus, iron-bound phosphorus, reductant phosphorus, and calcium-bound phosphorus were the inorganic phosphorus fractions obtained by sequential extraction using appropriate extractants. Exchangeable phosphorus was least present while calcium-bound phosphorus was predominantly present at all the sampling sites, showing that the sediments in the river were apatitic in nature. Inorganic nitrogen forms: nitrate-nitrogen, nitrite-nitrogen and ammonium-nitrogen were obtained and nitrate-nitrogen was found to be the most dominant form of inorganic nitrogen at all the sampling sites. The results from this study suggest that Ogun River, Abeokuta, contained phosphorus and nitrogen which were traceable to anthropogenic activities from residential homes, farmlands, and an abattoir found close to the river. These elements have the potential of increasing algal bloom in the river.

Keywords: Sediments contamination, Phosphorus speciation, Nitrogen speciation, Ogun River