Determination of the Physicochemical Parameters and Pollution Indices in Soils of Obodo Community in Delta State, Nigeria

Oil and gas activities are one of the environmental concerns in the crude oil-rich areas of the Niger Delta. This study aimed to determine the physicochemical level and some pollution indices in the soils of the Obodo community in Delta State to ascertain if there is an anthropogenic influence on the soil quality. Soil samples were collected from 14 sampling stations and 2 control stations during the wet and dry seasons from two soil depths (topsoil, 0 - 15cm) and (subsoil, 15-30cm) according to standard methods and procedures. The study results revealed elevated concentrations of total hydrocarbon content, polyaromatic hydrocarbon, total petroleum hydrocarbon and sulphate with mean values of 138.45 mg/kg  (topsoil) and 147.66 mg/kg (subsoil); 52.62 mg/kg  (topsoil) and 30.01 mg/kg (subsoil); 229.95 mg/kg  (topsoil) and 160.33 mg/kg (subsoil); 54.89 mg/kg  (topsoil) and 44.88 mg/kg (subsoil) during the wet season respectively; and mean values of 172.94 mg/kg  (topsoil) and 151.46 mg/kg (subsoil); 11.11 mg/kg  (topsoil) and 10.25 mg/kg (subsoil); 19.63 mg/kg  (topsoil) and 17.99 mg/kg (subsoil); 22.57 mg/kg  (topsoil) and 19.95 mg/kg (subsoil) during the dry season respectively. The high concentrations observed in this study indicates anthropogenic influence that may be due to oil spillage, emission from vehicle exhaust, incomplete combustion of coal, and the use of inorganic fertilizer. The results of the index of geo-accumulation and contamination factor showed that the levels of heavy metals were those of unpolluted soil except for the cadmium concentration observed in the topsoil of the study area, which showed moderate pollution during the wet season. The low pH values and a higher percentage of sand in the soil infer that the low heavy metals concentration observed in this study may be due to cations leaching down the aquifer which requires further studies to examine the groundwater quality.