Alterations in Selected Soil Nutrients Impacted by Oil Spill in Ahoada, Rivers State of Nigeria

Alterations in selected macro- and micro- nutrients’ profile due to petroleum spill contamination of Edeoha soil in Ahoada East of the Niger Delta was investigated. Oil spill-impacted soil samples were randomly collected from depths of 0-15 cm and 15-30 cm from each sampling spot to make a total of 10 composite samples. The macronutrients analysed were nitrogen, phosphorus, and potassium while the micronutrients were cobalt, copper, iron, nickel, and zinc. Nitrogen was determined using the Kjeldahl method, phosphorus through the Olsen’s sodium bicarbonate procedure, and potassium via ammonium acetate extraction route prior the use of a flame photometer (DR fp6430). The micronutrients were determined using atomic absorption spectrophotometer (DR 390 AAS). Results showed a mean pH of 5.99, below EGASPIN recommended soil pH range. Nitrogen (700 - 1,380 mg/kg) and iron (1,760 - 2,193 mg/kg) concentrations exceeded agronomic limits while the mean contents of Cobalt (1.338 mg/kg), copper (0.959 mg/kg), phosphorus (0.22 mg/kg), and potassium (33.01 mg/kg) were below optimal ranges. Zinc (1.20 to 2.92 mg/kg) is slightly within acceptable range whereas Nickel (0.48 to 2.10 mg/kg) is far below USEPA toxicity geometric mean level of 13 ± 2.31 mg/kg. The soil acidic condition coupled with imbalance in soil nutrients would result to an impending deleterious effect on cropping activities. To restore soil health, boost food security and supply, an acid soil management strategy with the application of the deficient soil nutrient-fertilizers on the oil spill-impacted study site, is recommended as an integral part of the soil remediation and amendment process.