Phytoremediation Potential of Senna fistula L. in the Decontamination of Crude Oil-Polluted Soil

Abstract

Crude oil contaminated soil could be treated using physicochemical, thermal or biological managements. However, the objective of this paper is to assess the phytoremediation potential of Senna fistula L in the decontamination of crude oil-polluted soil in a greenhouse located at Wilberforce Island, Niger Delta Area, Nigeria using appropriate standard methods. This study examined the survivability of Senna fistula in soil contaminated with crude oil with a view to ascertain its potential in bioremediation. Experiments to assess the germination and growth rates of S. fistula were conducted in a greenhouse, using soil contaminated with varying concentrations of crude oil (25%, 50%, 75% and 100%). Germination rate and growth parameters (number of leaves, nodulation, plant girth and height) were ascertained in accordance with scientific methods. Equally, the physicochemical properties of the soil (organic matter, pH, calcium, magnesium, sodium, phosphorous, potassium and nitrogen) were determined in accordance with scientific methods. Results revealed that at 0% 25%, 50%, 75% and 100% crude oil in soil the corresponding germination rates for S. fistula were 26%, 22%, 22%, 15% and 14% in that order. The mean heights of the plant 16 weeks after planting, were 52.30cm, 34.50cm, 26.50cm, 25.40cm and 20.80cm; mean girths 0.40mm, 0.35mm, 0.35mm, 0.25mm and 0.20mm; number of nodules 8, 2, 0, 0 and 0 and number of leaves 13.00, 8.00, 8.00, 7.00 and 4.00, 0% for 0%, 25%, 50%, 75% and 100% crude oil concentrations, in that order. Organic matter in the contaminated soil was in the range of 4.15%-4.73%; pH, 3.34-4.25; N, 0.30-0.41%; P, 6.15- 6.38 mg/kg; Na, 2.05-2.81 mg/kg; Ca, 12.85-14.50 mg/kg, and Mg, 1.45-1.91 mg/kg. An inverse proportionality was observed between measured parameters and crude oil concentrations. However, the germination efficiency and the relative growth rate of the plant evinced survivability under crude oil chemical stress and its fittingness for use in soil remediation in the Niger Delta.