PHYTOREMEDIATION OF HYDROCARBON POLLUTED SOIL USING KENAF (HIBISCUS CANNABINUS L.) PLANT
Contamination of existing and potential agricultural lands is a major problem associated with the processing and distribution of crude and refined petroleum products in many oil producing countries like Nigeria. Hydrocarbon contaminants in soil are potentially phytotoxic to plants and can interfere with plant establishment and growth as well as other potential land uses. Pollution control strategies involving physico-chemical methods are usually expensive and have often aggravated the problem rather than eliminate it. Phytoremediation is recently being favoured as a good option for the remediation of polluted sites and has proven to be a better alternative; hence there is the need to identify various plants especially native ones with potential for the phytoremediation of petroleum-polluted soils. The objectives of this study were to plant Kenaf (Hibiscus cannabinus L.) in a three media of simulated diesel polluted soil samples – soil amended with compost (Sample A), soil amended with fertilizer (Sample B) and unamended soil (Sample C); monitor the rate of reduction of TPH in the soil samples; determine pollutant concentrations in the plant parts and; and to identify the medium most suitable for the effective breakdown of hydrocarrbons in the contaminated soils. From an initial TPH concentration of 32387.68 ± 15.70 mg/kg, a Total Petroleum Hydrocarbon (TPH) reduction of 68.14 % was recorded in sample A while a reduction in TPH of 65.13 and 12.12 % were recorded in soil samples B and C respectively after 15 weeks of planting. Analysis of variance (ANOVA) carried out showed a significant different (P<0.05) in the TPH in the soil samples A (10319.53 ± 284.25 mg/kg), B (11293.85 ± 446.75 mg/kg) and C (28462.77 ± 90.95mg/kg) after 15 weeks of planting. Predictive models were developed using regression analysis to predict the TPH reduction in the three soil samples with time. A strong negative correlation (P<0.05) were observed (R2 for sample A = 0.9687, R2 for sample B = 0.9614 and R2 for sample C = 0.8600). Analysis of contaminant accumulation in the plant parts revealed that 405.45 ± 4.59, 126.85 ± 3.15 and 273.39 ± 4.32 mg/kg were recorded in the root, stem and leaf parts respectively. The results showed that a total of 57.44, 17.97 and 38.76 % of the contaminant were stored in the root, stem and leaf of Kenaf (Hibiscus cannabinus L.) plant. Generally, the plant showed no adverse growth effect, hence presents itself as a good candidate for phytoremediation of diesel contaminated soil samples amended with compost and fertilizer.