Doctor of Philosophy (Ph.D.) Theses and Dissertations
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- ItemOpen AccessAssessment of ecosystem services of Ikogosi warm spring, Ikogosi and Olumirin waterfall, Erin- Ijesa, Southwest, Nigeria.(Department of Ecology and Enivronmental studies, Faculty of science,Obafemi Awolowo University., 2023) Olusola, Johnson AdedejiThis study profiled the ecosystem services offered by Ikogosi Warm Spring and Olumirin Waterfall, valued the ecosystem services and benefits offered by Ikogosi Warm Spring and Olumirin Waterfall and compared ecosystem services offered between and within the study areas. The study also developed support tools for the management and sustenance of Ikogosi Warm Spring and Olumirin Waterfall. These were with a view to providing a database on the services and benefits offered by these ecosystems and give information on the drivers of ecosystem degradation that have been eroding these values The study was conducted in two phases: field survey and laboratory investigation. Soil and water samples were collected using standard methods to determine their physicochemical parameters. Ecosystem services were evaluated using the carbon tax and industrial oxygen price methods for carbon sequestration and oxygen regulatory services. The market valuation method was used to determine water provisioning services. Travel cost methods were used to estimate cultural benefits. The total ecosystem services of the study areas in monetary terms were calculated by adding carbon sequestration and oxygen potential, water storage capacity, water purification, nutrient cycling, erosion prevention, water consumption, and recreational values. The ecosystem service values of the two sites were then compared. A participatory framework approach was used to develop support tools for managing and sustaining resources of the study areas. Pearson correlation was used to find relationship between the variables while qualitative data was analysed using a thematic approach. The study identified four ecosystem services in the study areas. The total ecosystem services estimated in 2022 was US$132.19 million. Ikogosi Warm Spring contributedUS$ 78.37 million, while the contribution of Olumirin Waterfall was US$ 53.82 million. The contributions of individual ecosystem services at Ikogosi Warm Spring were carbon sequestration (43.8%) >water regulation (29.93%)> water purification (15.96%) > oxygen potential (6.93%), >nutrient recycling (3.23%) > erosion prevention (0.09%). For Olumirin waterfall, the level of contributions of individual ecosystem services was carbon sequestration (39.94%) >water regulation (39.01%) >oxygen potential (13.98%) >water purification (2.75%) > erosion prevention (0.11%). Soil chemical characteristics of the study areas were total nitrogen 8.40 g/kg (Ikogosi Warm Spring), 7.00 g/kg (Olumirin Waterfalls); organic matter 58.00 g/kg (Ikogosi Warm Spring), 26.00 g/kg (Olumirin Waterfalls); available phosphorus 0.80 mg/kg (Ikogosi Warm Spring) and 0.54 m/kg (Olumirin Waterfalls). The water alkalinity was 0.15 mg /l (Ikogosi Warm Spring), 2.40 mg/l (Olumirin Waterfalls); total dissolved solids 0.03 mg/l (Ikogosi Warm Spring), 171.60 mg /l (Olumirin Waterfalls); total hardness 1.13 mg/l (Ikogosi Warm Spring), 0.95 mg/l (Olumirin Waterfalls); turbidity 10.81 (NTU) (Ikogosi Warm Spring), 0.80 NTU (Olumirin Waterfalls) and electrical conductivity 12.06 (μS/cm) (Ikogosi Warm Spring), 1.10 (μS/cm) (Olumirin Waterfalls), Ca2+ (3.44) (mg/l) (Ikogosi Warm Spring), 0.10 (mg/l) (Olumirin Waterfalls); Mg2+ (1.23) (mg/l) (Ikogosi Warm Spring), 0.25 (mg/l) (Olumirin Waterfalls) and dissolved oxygen, 0.25 (mg/l) (Ikogosi Warm Spring), 0.05 (mg/l) (Olumirin Waterfalls) . All the water samples results were below the permissible limits. Focus Group Discussion (FGD) and in-depth interviews from the study showed the negligence of local communities in the sustenance and management of tourist destinations. This study concluded that land use and deforestation were the drivers of ecosystem degradation in the study areas.
- ItemOpen AccessBioaccumulation and oxidative stress impact of toxic heavy metals and polycyclic aromatic hydrocarbons on selected mosses in Nigeria(Department of Botany, Faculty of Science, Obafemi Awolowo University., 2023) Olasoji, Kehide OlayemiThis study investigated the bioaccumulation of heavy metals and polycyclic aromatic hydrocarbons in Philonotis hastata (Duby) Wijk & Margad and Barbula lambarenensis P. de la Varde, and also determined the impact of oxidative stress on chlorophyll content and anatomical features of the mosses. These were with a view to providing detailed information on the bioaccumulation potential of the selected mosses as well as the antioxidant response of these mosses to oxidative stress. The moss species were collected in industrial areas in Ile-Ife, Ibadan and Ikeja while the control samples were collected at Obafemi Awolowo University, Ile-Ife. The concentrations of heavy metals and polycyclic aromatic hydrocarbons (PAHs) in moss samples were determined using standard method. Estimation of chlorophyll content (chlorophyll a, chlorophyll b and total chlorophyll) were determined using standard procedure. Stress biomarkers (hydrogen peroxide (H2O2) and proline contents), non enzymatic antioxidant activity (ascorbate, total glutathione, lipid peroxidation and carotenoids) and enzymatic antioxidant activity (superoxide dismutase, catalase and ascorbate peroxidase) were determined following standard procedures. General anatomical features of the stem and leaves of the mosses were studied and photomicrographs of the slides were taken. Data were analyzed using one-way Analysis of Variance (ANOVA) and Duncan Multiple Range Test (DMRT) were used for separation of mean using SAS software, 2001. The concentrations of heavy metals in moss samples in the study locations ranged from: Cu (1.200 – 2.330 µg/g), Zn (0.855 – 1.370 µg/g), Fe (0.525 – 1.050 µg/g), Mn (0.027 – 0.052 µg/g), Cr (0.016 – 0.057 µg/g), Cd (0.018 – 0.045 µg/g), Pb (0.007 – 0.020 µg/g), As (0.010 – 0.018 µg/g). The results revealed that the heavy metal concentrations in the studied moss samples followed the trend: Cu>Zn>Fe>Mn>Cr>Cd>Pb>As. The study showed that copper, zinc and iron were the most accumulated heavy metals while lead and arsenic were the least accumulated heavy metals in all the sampling locations. Moss samples from control sites have the lowest concentration of metals in all the sampling locations. There is significant difference in the accumulation of heavy metals in the mosses with respect to the different locations in the study area. The concentrations of 19 PAHs varied from 0.02 to 3.81 mg/L in P. hastata and from 0.02 to 5.92 mg/L in B. lambarenensis in all the locations. The PAHs were not detected in the moss samples from control sites. Naphthalene and 3-methylcholanthrene were detected in all the study areas except for control sites. There was a significant decrease in chlorophyll a, chlorophyll b and total chlorophyll contents of the selected mosses when compared to chlorophyll contents of mosses from control sites. The selected mosses exhibited significant variations in the antioxidant response to oxidative stress in polluted sites and control sites. The anatomical studies of the stem and leaves of the selected mosses showed there is no feasible effect of pollutants bioaccumulation on micromorphological features of the moss species obtained from polluted sites when compared to moss species from the control sites. The study concluded that accumulation of heavy metals and polycyclic aromatic hydrocarbons in the selected mosses from industrial areas induces oxidative stress and causes reduction in their chlorophyll contents. The antioxidant response of these mosses indicated that the selected moss species were tolerant to oxidative stress.
- ItemOpen AccessStructure and sediment thickness mapping of eastern dahomey (Benin) basin, southwest Nigeria.(Department of Geology, Faculty of Science. Obafemi Awolowo University., 2022) OKUNUBI, Michael Olajide.This study acquired, processed and interpreted satellite gravity and aeromagnetic data over the Eastern Dahomey Basin, Southwest Nigeria, for lineaments and sediment thicknesses and validated the results with existing well information and results. This was with a view to providing information on the basin’s structural setting, geometry and geotectonics required for the development of its natural resources. Free-air and Bouguer anomaly data of the study area were downloaded from International Centre for Global Earth Models website. High resolution airborne magnetic data covering nineteen magnetic sheets were acquired from the Nigerian Geological Survey Agency, Abuja. The Bouguer anomaly data were separated into Regional Bouguer Anomaly (RGBA) and Residual Bouguer Anomaly (RSBA) data by upward continuation. The Total Magnetic Intensity (TMI) map was corrected for diurnal variation and offset and Reduced to the Equator (RTE). The RTE map was separated into Regional Magnetic Anomaly (RGMA) and Residual Magnetic Anomaly (RSMA) maps. Both the RSBA and RSMA maps were subjected to Total Horizontal Derivative, Analytical Signal and Euler Deconvolution filters and interpreted for lineaments. Sediment thicknesses were generated from Spectral Analysis of RSBA and RSMA data, constrained by existing well data. The gravity and magnetic lineaments and sediment thicknesses were integrated into composite lineament and sediment thickness maps. The composite maps were used to assess prospects for hydrocarbon, geothermal and groundwater resource development within the basin. Fifty deep seated (1,000-6,500 m) steeply to gently dipping lineaments (suspected to be faults) with lengths varying from 9,400 – 111,500 m and primary orientations in the NS, NE-SW, NW-SE directions with subsidiary E-W direction, were delineated. Composed sediment thicknesses ranged from 20-9,000 m with thicknesses of 20-300 m in the northern flank (Zone A); 500-3,100 m in the central region (Zone B) and 2,500-9,000 m in the southern flank (Zone C). Sediment thickness variations delineated series of basement structures including the earlier mapped Afowo Graben, Ojo Platform, Orimedu Graben, a newly identified horst structure, the Ise Graben and the Okitipupa Ridge, in that order, with onshore and lateral extensions and sediment thicknesses respectively of 20,000-25,000, 48,000 and 3,500-6,600 m; 8,700-11,600, 30,800 and 3,100-5,000 m; 8,800-11,200, 37,500 and 3,800-7,200 m; 3,800-6,700, 28,000 and 2,000-3,500 m; 6,300-12,100, 42,100 and 4,200-7,400 m; 35,900, over 44,500-57,000 and 1,100-3,100 m. The Ondo Basin (western flank of Niger Delta Basin and eastern flank of Zone C) had sediment thicknesses of between 3,500-9,000 m. The identified structures (graben, horst and ridge) had their edges defined by E-W and N-S bounding lineaments with some cross cutting the structures including several delineated subbasins and basement depressions, typical of a rift-like basin. Sediment thicknesses are well over the threshold of 4000 m for crude oil prospection in the southern flank (ZoneC) and over the threshold of 1,500 m for geothermal prospection in parts of the central region (Zone B) and the southern flank (Zone C) with large storativity and transmissivity for hydrocarbon, geothermal water and groundwater. The study concluded that the Eastern Dahomey Basin has the requisite structural setting and sediment thicknesses for prospective hydrocarbon, geothermal and groundwater development.
- ItemOpen AccessAntibiotic susceptibility and molecular analysis of staphylicoccus aureus from nasal samples of west african dwarf goats (Capra hircus) in Osun State, Nigeria.(Department of Microbiology, Faculty of Sciences, Obafemi Awolowo University., 2022) TAIWO, Fadekemi FunmilayoThis study isolated and identified Staphylococcus aureus from the anterior nares of West African Dwarf (WAD) goat in Osun State, Nigeria, determined the antibiotic susceptibility pattern of S. aureus isolates and identified methicillin-resistant S. aureus (MRSA) isolates and Panton Valentine Leukocidin gene. It also investigated the population structure of S. aureus from the nasal samples of the WAD goats. These were with a view to providing information on the prevalence, antibiotic susceptibility pattern, and clonal nature of S. aureus from the nasal samples of WAD goats.
- ItemOpen AccessSynthesis, characterisation and antimicrobial activity of mental (11) complexes of (E)-N'-(4-phenylbutan 2-ylidene) isonicotinohydrazones and their mixed ligand complexes.(Department of Chemistry, Faculty of Science. Obafemi Awolowo University., 2022) OGUNSAKIN, Olanike Esther.This study synthesised hydrazide-hydrazone metal(II) complexes, its derivatives, along with the mixed ligand complexes with N,N’-chelating ligands, characterised the synthesised compounds and their metal complexes, carried out an in silico studies of the ligands and their metal complexes and also determined the antimicrobial activity the synthesised compounds and their metal complexes. These were with a view to establishing the geometry and antimicrobial activity compounds against some selected strains of microorganisms. The ligands (E)-N´-(4-Phenylbutan-2-ylidene) isonicotinohydrazone(L1) and (Z)-3-hydroxy-N´-(4-phenylbutan-2-ylidene)-2-naphthohydrazone(L2) were synthesized by adding ethanolic solution of isonicotinic acid hydrazide and 3,2-napthoic hydrazide on ethanolic solution of 4-phenyl-butan-2-one in the ratio of 1:1 and then refluxed at 80 oC for 6 hours. Metal complexes of the ligands were synthesized by reacting ethanolic solution of the chloride salts of the metal with ethanoic solution of the ligands in the ratio 1:2 and the mixture stirred for one hour, precipitates formed were washed with ethanol and dried over calcium chloride in a desiccator. The mixed ligand complexes of these ligands were carried out by reacting ethanoic solution of metal chloride salts to a stirring ethanolic solution of the hydrazide-hydrazone as the primary ligand and then adding ethanolic solution of N,N'-chelating ligand as the secondary ligand in 1:1 molar ratio. These compounds were characterised using physicochemical parameters, infra-red and uv-visible spectroscopy, elemental analysis, conductivity and magnetic susceptibility measurements. Antimicrobial screening of the compounds was investigated against two Gram-positive bacteria and two Gram-negative bacteria using the cup-plate agar diffusion and the microbroth dilution techniques to determine the minimum inhibitory concentration and minimum bactericidal concentration. The molecular docking studies were carried out using the Molegro Virtual Docker to predict the most probable kind of interactions, binding affinity and ligand orientation of these compounds at the active site of the selected proteins. The complexes displayed varying colours ranging from green to yellow with high melting points. The infra-red spectra of the ligands displayed medium bands in the range of 1588-1599 cm-1 C=N for the synthesised hydrazones and 3188,3286 cm-1 for the NH2 of the hydrazide, which shifted to a higher or lower frequency on chelation. The appearance of new weak bands at 543-659 cm-1 and 418-545 cm-1 assignable to M-O and M-N bonds indicated coordination of the ligands to metal ions. The electronic spectra of the complexes revealed intraligand transitions from π-π* and n-π*. There were d-d transitions in the visible region of the spectra, proving a strong interaction between the ligands and its complexes. The observed molar conductivities were within the range 169.21 - 172.00 Ω-1cm2mol-1 and 84.21 - 99.17 Ω-1cm2mol-1 suggesting 1:2 and 1:1 electrolytic ratio of the complexes except for [Fe(ISH)2(H2O)2]Cl3 with conductivity value of 314.19 Ω-1cm2mol-1 suggesting a 1:3. Magnetic moments studies indicated an octahedral geometry for these complexes. That is, the synthesised metal complexes displayed six coordinate geometries, while the in silico studies also revealed that these compounds exhibited a good interaction with the target proteins. The study concluded that the novel (E)-N´-(4-Phenylbutan-2-ylidene) isonicotinohydrazones, its derivatives and their mixed ligand complexes synthesised interacted in silico with target proteins and had antimicrobial activity comparable with streptomycin, hence, they could serve as precursor for drug synthesis.