Polyaromatic hydrocarbon distribution, source apportionment and ecological risks in the sediment of okpare river, olomu, delta State, Nigeria

A significant quantity of contaminants is produced primarily by anthropogenic activities degrades water quality. Toxic pollutants in aquatic systems can be stored in sediment, which may then impact aquatic life, humans who consume food from these systems, and the water column itself. This study examines the distribution, source apportionment, and ecological risks of Polyaromatic Hydrocarbon (PAHs) in the sediment of Okpare River, Olomu, Delta State, Nigeria. Samples were collected over 12 months, encompassing both the wet (May 2022 to October 2022) and dry seasons (November 2022 to April 2023). A total of eighty-four samples were obtained from seven sampling stations positioned 100 meters apart along the Okpare River, following standard methods and procedures. The sediment had mean values of Naphthalene (0.0005 mg/kg, 0.0018 mg/kg), Benz(a)anthracene (0.0067 mg/kg, 0.015 mg/kg), Benzo(a)pyrene (0.036 mg/kg, 0.027 mg/kg), Indeno (1,2,3-cd) pyrene (0.023 mg/kg and 0.028 mg/kg) and Benzo (g,h,i) perylene (0.026 mg/kg, 0.033 mg/kg) during the wet and dry seasons. PAHs (5 rings) were found in higher percentages in the sediments in both seasons. Diagnostic ratio results indicated that PAHs in the sediment may be attributed to both pyrogenic and petrogenic origins. Ecological risk assessment of PAHs in the sediment showed that the concentration of all the 16 priority PAHs were < ERL value. Although the are higher concentrations of 5rings PAHs in the sediment, they do not pose a significant ecological risk at present. Nevertheless, ongoing monitoring is essential to safeguard the health of the aquatic ecosystem and those dependent on it.