1725 Physicochemical and Microbiological Assessment of Oil-impacted Sediment in Ejama-Ebubu in Rvers State –a Case Study 1* Akani, N. P., 2 Braide, S. A. and Amadi, E. N. 1* Department of Applied and Environmental Biology, Rivers State University of Science and Technology, Port Harcourt, Rivers state, Nigeria.ss 2 Institute of Pollution Studies, Rivers State University of Science and Technology, Port Harcourt, Rivers State, Nigeria. Abstract Six physicochemical and microbiological properties were used to assess thirty-six year old spilled crude on marshy sediment in Ejama-Ebubu in Rivers State. Physicochemical properties included particle size, pH, total organic carbon, total hydrocarbon content, total nitrogen, available phosphorus, zinc, lead, cadmium nickel and chromium. Results of the study showed that the heavily impacted stations had higher mean values than the control station for all the parameters. The particle size of the sediment samples ranged between sandy to sandy- clay-loam at all the stations with the percentage sand being higher and ranged between 45.25% and 87.2%. The pH was acidic for all stations and ranged between 4.97(station 4) and 5.93 (station 5). It was also revealed that high levels of hydrocarbons between the range of 14.38ppm (control station 1) and 27,164.24ppm (station 4) were still found at the bottom sediment at all the 5 stations. The mean total organic carbon (TOC) ranged from 1.10% (station 1) to 56.86% (station 4). Total nitrogen levels were higher than the available phosphorus and ranged from 0.98mg/kg (station 4) to 6.90mg/kg (control station 1) and 1.23mg/kg (station 3) to 1.76mg/kg (station 5) respectively. Heavy metals showed higher levels of zinc at the heavily impacted station 4 with 104.47ppm while the lowest value 18.85ppm was observed at the control station 1. Nickel concentration ranged from 7.89(station 3) to 22.10ppm (station 4). Other metals, lead, cadmium and chromium had lower values. The persistent presence of hydrocarbons in the sediment samples coupled with low nutrient levels conclusively indicate that the environment is still stressed. Total heterotrophic bacteria ranged from 1.15 x 10 5 cfu/g(control station 1) to 3.03 x 10 5 cfu/g(station 3); percentage petroleum degrading bacteria, 1.52%(station 3) to 4.08%(station 5); total heterotrophic fungi,2.5 x 10 4 cfu/g (control station 1) to 7.12 x 10 4 cfu/g(station 3); and percentage petroleum degrading fungi from 0.53%(station 2) to 2.66%(station 4). The abundance of the microbial types was influenced by seasons and occurred more in the wet than dry season. *Corresponding author. Introduction Our history has been and continues to be shaped by major oil spills that exhibit long-term consequences associated with lagoons, estuaries and marshes. This is due to the persistence of oil or petroleum fractions in these low-energy environments (Vandermeulen, 1982). Increased petroleum exploration or related activities in the Niger Delta region of Nigeria has resulted in gross pollution of the environment (Gutnick and Rosenberg, 1977; Odokuma and Okpokwasili, 1992). These spills impact soil, freshwater, brackish water and marine environments (Okpokwasili and Odokuma, 1990; Nwachukwu and Ugoji, 1995; Amadi et al., 1996). The degree of ecological damage induced by an oil spill is determined by a number of factors as outlined by Awobajo (1981); and they include, amount of oil spilled, type of soil, its physical and chemical characteristics, meteorological and oceanographic conditions at the time of the spillage; turbidity, population/communities of organization impacted, control and oil spill clean-up methods employed. When oil gets transported through runoffs into the aquatic environment the heavy oils may eventually get carried into anaerobic bottom sediment; it will not be decomposed and may remain in place for many years (Vandermeulen, 1982). Oil in sediment is not attacked unless an oxygen source is available (Baker, 1978). Thus, a reducing environment such as near shores, swamps, marsh and bottom sediments preserve all original hydrocarbons with molecular weight greater than C 12 several years following an oil spill (Jordan and Payne, 1980).The number of documented long-term effects of oil spill in Nigeria is small hence this paper aims at using some physicochemical and microbiological properties to assess the long-term effects of a thirty- four (34) year old spill on sediment that occurred in Ejama-Ebubu in Rivers State of Nigeria. Materials and methods Description of study area The study area is the Ejama-Ebubu Community in Eleme Local Government Area of the Rivers State of Nigeria (Fig.1). The entire area lies Nigerian Journal of Microbiology, Vol. 22(1): 1725 – 1731 2008