Soil Quality Assessment of Crude Oil-Exposed Environments in Obama, Bayelsa State, Nigeria

Abstract

Soil is a living natural system whose healthy condition is essential for both economic and environmental sustainability. Therefore, this study evaluated soil quality parameters of some crude oil exposed soils in Obama oil flow stations in Bayelsa State, Nigeria, between 2022 and 2023. Thirteen (13) soil samples were collected each at two depths (0 – 15 cm and 15 – 30 cm) across wet and dry seasons, alongside control samples away from the stations. Physical observations indicated no marked differences in colour, texture, or permeability between exposed and control soils. Porosity declined with depth in both seasons. Soil pH remained strongly acidic during the wet season, but ranged from strongly acidic to moderately acidic in the dry season. Oxidation-reduction potential (ORP), total petroleum hydrocarbons (TPH), and total organic carbon in top-soils varied across sites and seasons.  Concentration of benzene, toluene, ethyl benzene and xylene (BTEX) were consistently low, generally < 0.001 mg kg^-1. Cation exchange capacity was very low in surface soils with slightly higher values in the dry season. Among anions, carbonate predominated across depths and seasons. Overall, results suggest that soils in the study area are not currently contaminated; however, periodic environmental monitoring remains essential to prevent the accumulation of hydrocarbons or other pollutants.