Heavy Metal Contamination Indices for oil spilled Agricultural Soils in three Local Government Areas of River State, Nigeria

Abstract

Authors: Emeka Chima Ogoko, Kelle Henrietta Ijeoma & Enete Uchenna Oliver

This study evaluated the contamination indices of heavy metals in Agricultural soil contaminated with crude oil spills in three local
government areas (LGAs) within Rivers State, Nigeria (namely, Eleme, Ahoada and Oyigbo). Soil samples were taken at various depths (0-15cm, 15- 30cm and 30-45 cm) from the three LGAs. Concentrations of chromium, copper, iron, nickel and zinc ions were determined using atomic absorption spectrophotometry. Results obtained indicated that mean concentration of chromium ion
ranged from 10.53 -24.61mg/kg, copper ion ranged from 1.97-2.73mg/kg, iron ion ranged from 1329.58-1838.32 mg/kg. Nickel ion ranged from 1.07-3.03 mg/kg while mean zinc ion concentrations ranged from 0.38-3.99 mg/kg. The results also revealed that
mean concentrations of all the studied heavy metal ions were higher in oil spilled soil samples than those not exposed to spillage, indicating possible increase in soil heavy metal ions concentrations through oil spillage. Also, concentrations of heavy metal ions
were found to increase with soil depth and was attributed to natural processes. Calculated contamination factors indicated low to moderate contamination except Cr and Ni for Oyigbo samples whose CF values indicated moderate and considerable contamination. Pollution load index indicated low pollution levels for Ahoada and Oyigbo soil samples while that of Eleme was
polluted. The degree of contamination for all the heavy metals revealed low degree of contamination expect for nickel where it showed moderate degree of contamination. The ecological and the potential ecological risks were within the range of low
ecological risk pollution for soil samples at the spillage sites in the three Local Government Areas.