Evaluation of the Effect of Drilling Waste on the Soil: A Case Study of Otu-Jeremi, Nigeria

Abstract

Exploratory activities involving drilling generate waste. These wastes which consist of both liquid and solid have various chemical constituents, including heavy metals. This study evaluated the effect of heavy metals from drilling waste on the soil. Specifically, it investigated the contamination of soil resulting from heavy metals in Out-Jeremi where the Utorugun gas plant is conducting oil and gas exploration activities. Soil samples were collected from Otu-Jeremi community. Sample A (contaminated soil) was collected from the drilling site, and sample B (uncontaminated soil) was collected from a location 3km away from the drilling site. The two samples were examined for the heavy metals, pH, and electrical conductivity (E.C) using a pH meter and the APHA 145 method. The metals tested include Iron, Zinc, Copper, Chromium, Cadmium, and Lead using Flame Atomic Absorption Spectrophotometer with a met oxidation digestion method. The pH of samples A and B were 6.18 and 4.75 respectively. The soil samples were found to contain all the metals with Iron and lead having the highest concentration and the lowest concentrations in both samples respectively. The observed trend in the concentration was Fe>Zn>Cr>Cu>Cd>Ld in sample A, and Fe>Zn>Cu>Cr>Cd>Ld in sample B. Using the Department of Petroleum Resources (DPR) standard values as a basis for comparison, the metal concentrations of the two samples were evaluated. It found that all the metals in sample A except Cd were below the DPR target values. Nevertheless, this value of cadmium in sample A was not a threat as it was still less than the DPR’s Intervention values of 12mg/kg for cadmium.