Remediation of Polycyclic Aromatic Hydrocarbon (Pah) and Total Petroleum Hydrocarbon (Tph) With Megathyrsus Maximus: A Field Study

The study explored the field phytoremediation of hydrocarbon contaminated soils with selected native grasses. Greenhouse experiment for the selection and screening of four (4) native plants that was undertaken as pilot studies for the remediation of diesel contaminated soils. ‘‘The plant Megathyrsus maximus (Guinea grass) amended with poultry manure has proven a positive potential for use in the phytoremediation of diesel contaminated soils. The field studies was performed on an experimental/simulated site within the campus vicinity. Four different subplots were designed as the experimental plots for both contaminated soils and uncontaminated soils. All subplots were tilled and homogenized for experimental determination.Laboratory physiochemical tests on both the contaminated and uncontaminated soil samples were carried out to obtain the physical and chemical parameters of the soil samples. Gas Chromatograph-Mass Spectrometer (GC-MS) analysis was used to identify and quantify the volatile organic compounds (VOCs) present in the contaminated and uncontaminated soil samples. The laboratory tests revealed some microstructural changes within the soil structure due to hydrocarbon contamination. The liquid limit value for the uncontaminated subplot soil is 30.3% relative to 33.4% for the contaminated subplot soils, while the plastic limit value for the uncontaminated subplot soil is 15.2% relative to 18.4% for the contaminated subplot soils. There is a 10% increase in the moisture content of the contaminated subplot soil relative to the uncontaminated subplot. Phytoremediation parameters such as the soil pH, Electrical Conductivity (EC), CEC and Exchangeable bases all showed improved field remediation parameters after 16 weeks of the field study, indicating positive remediation activity. The Polycyclic Aromatic Hydrocarbon (PAH) and Total Petroleum Hydrocarbon (TPH) contaminants from the hydrocarbon contamination were degraded from the soil. PAH values were reduced to 3.77% in the contaminated subplot (contaminated soil with 20% diesel and 10% poultry manure), while TPH values were reduced to 20.45%. The plant Megathyrsus maximus (Guinea grass) revealed positive contaminant uptake with contribution from the roots, stems and leaves. 33% and 17% uptake of the TPH contaminants was obtained through the stem and leaves. Also, results showed 52% and 40% uptake of the PAH contaminants was obtained through the stem and leaves. Megathyrsus maximus (Guinea grass) recorded improved biomass development with enhanced bioremediation by the application of poultry manure.