An Investigation on the Environmental Impact of Petroleum Refinery Effluent on Soil Pollution

Waste oil represents a major challenge to soil quality and environmental sustainability. This study was conducted to determine the environmental impact of refinery effluent on the soil within the refinery site and surrounding area. Six different test sites were selected to measure soil pollutant concentrations according to their distance from the untreated effluent discharge lagoon. The study period lasted six months, as the testing work began in April and ended in September 2023. Standard methods were used to determine the physical, chemical, and biological pollutants of the soil, and soil pollution indices (PLI, CF, and I_geo) were adopted in determining soil quality. The results showed a clear effect of untreated wastewater on soil properties. The soil of the testing sites near the refinery appeared to be highly contaminated with organic pollutants (O&G, TOC, and phenol) and gradually decreased towards the city. The concentrations of heavy metals in the soil were less than the permissible limit of WHO at the various testing sites, with the exception of the concentrations of Cd and Pb. The Cd concentration was approximately 200% higher than the permissible limit, while the Pb concentration was close to the permissible limit or slightly more. Generally, the measured concentrations of these metals followed the order: Ni_geo) indicated that the soil was highly polluted with cadmium, while it did not indicate contamination with other heavy metals. The study recommends that in order to reduce pollution from refinery effluent, the responsible administration must implement waste drainage networks, establish a treatment plant for the untreated effluent, and also use modern technologies to reduce gaseous emissions and their deposits on the soil.