DISTRIBUTION AND SPECIATION OF PHOSPHORUS IN SEDIMENTS

ABSTRACT

Phosphorus is essential for the normal functioning of organisms and ecosystems. In aquatic environments, excessive phosphorus is a key contributor to eutrophication. This study was aimed at assessing the distribution and speciation of phosphorus in sediments from the Ikpoba River in Benin City, Nigeria. Water and sediment samples were collected from November 2021 to January 2022 and analysed following standard procedures. The results showed that, for water samples, pH (6.96 - 8.18) and phosphorus (27 – 234 µg/L) were all within the permissible limits for drinking water prescribed by the WHO, while the temperature showed a trend that decreased in December and increased in January. For the phosphorus fractions in sediments, NaOH-P (94 – 439 µg P g^-1) concentrations were found to be higher than HCl-P (61 – 223 µg P g^-1), and IP (195 – 768 µg P g^-1) concentrations were higher than OP (76 – 390 µg P g^-1) across all months. The concentrations of TP in some of the samples were greater than some regional limits and pointed to contamination of the sediments, especially in the downstream sections of the river. There was an observed increasing trend in the concentrations of all fractions of phosphorus in the sediment samples for the dry season. It was then concluded that the overlying water was not contaminated by phosphorus, however, the sediments in some parts were contaminated. It was suggested that routine monitoring and assessment of the study area be implemented along with control of human activities which add phosphorus to the Ikpoba river.