Assessment of Oil and Grease, Total Petroleum Hydrocarbons and Some Heavy Metals in Surface and Groundwater within the Vicinity of Nnpc Oil Depot in Apata, Ibadan Metropolis, Nigeria

The present study discusses an assessment of oil, grease, total petroleum hydrocarbons (TPH) and some heavy metals in surface and ground water within and around the Nigeria National Petroleum Corporation (NNPC) depot, in Apata, Ibadan metropolis in other to assess the pollution status of the water. Samples were collected randomly within and around the depot. Control samples were taken from Awba dam and Obafemi Awolowo hall of residence, within the University of Ibadan. TPH, oil and grease were analyzed gravimetrically while the levels of heavy metals were determined by atomic absorption spectrophotometry (AAS) The results revealed the presence of oil and grease in both surface and ground water with a value ranging from 59.74±4.92 to 67.35±2.21, and 10.48+1.21 to 34.94+5.04 mg/l compared to control sample with a value of, 37.21±4.77 and 12.17±0.78 mg/l respectively. Conversely, high values of TPH were recorded for both surface and groundwater in the studied area ranging from, 20.34±1.79 to 27.40±5.32 and 2.67±0.80 to 13.03±2.21mg/l respectively as against the control of 13.18±2.41 and 1.58±0.22 mg/l. The level of heavy metals concentration recorded in both surface and groundwater samples of studied sites were ranged from 0.162±0.015 to 0.195±0.011mg/l Pb, 0.279±0.088 to 0.315±0.085mg/l Cd, 5.063±0.377 to 5.096±0.373mg/l Zn, 0.103±0.0207 to 0.133±0.036mg/l Ni, 8.744±0.112 to 10.307±0.387mg/l Cu and 0.052±0.006 to 0.059±0.013mg/l Cr for surface water respectively while groundwater contained as much as 0.046±0.016 to 0.156±0.023mg/l Pb, 0.016±0.004 to 0.045±0.003mg/l Cd, 1.560±0.061mg/l to 2.972±0.136mg/l Zn, 0.015±0.006 to 0.315±0.037mg/l Ni, 2.256±0.121 to 4.820±0.288mg/l Cu and 0.0033±0.013 to 0.073±0.009mg/l Cr. A statistically significant difference at p<0.05 was found to exist between the concentrations of oil and grease, TPH and the analyzed metals collected from the sites and the control sites. Based on this study, the human and environmental risk to TPH, oil and grease, Pb, Cr, Ni, Cu, Cd and Zn in surface and ground water are high for now, as the concentrations were higher than those of the control sites and the recommended permissible limit of the World Health Organization (WHO), European and Union (EU). It is therefore recommended among others that primary treatment plant be install in all NNPC depot for the uptake of these toxicants which may pose treat to human health on bioaccumulation.