Pollution Status of Sediment from a Remediated Crude Oil Produced Water Discharge Channel Using Various Indices

Abstract

The Forcados Terminal effluent discharged channel was remediated about twenty years ago with recommendation for periodic assessment of the organic and inorganic contaminants in the area. Forcados Terminal is in Delta State, Nigeria. This study was carried out to evaluate heavy metals pollution status of sediments in the remediated crude oil effluent discharge channel. A total of sixteen sediments samples were collected from ten sampling locations using grab sampling technique in October 2019 (wet season) and February 2020 (dry season). Heavy metals were determined in all the samples using atomic absorption spectrophotometry after digestion with aqua regia. The results showed that the concentrations of the sediment samples (mg/kg) ranged from <0.01-0.05, <0.01-0.91, <0.01-3.46, 13.2-45.3, 14.7-64.1, 5.56-105, 3.10-108, 0.14-5.86, 78.8-289, 28.2-254 and 3529-7773 for Hg, As, Cd, Pb, Cr, Ni, Cu, V, Mn, Zn and Fe. Hg and As were generally not detected in the sediments. On the average, the geoaccumulation index of Cd in the sediments falls into the moderately polluted category while the geoaccumulation index of all the other metals falls into the practically unpolluted category. On the average, the Contamination/Pollution index (CPI) value of Cd was > 1 which indicates that the sediments were polluted with Cd but the CPI values of other heavy metals were < 1 which indicates that these sediments were contaminated with the other heavy metals.