DOCTOR OF PHILOPHY
DEPARTMENT OF CHEMISTRY
2015/2016 SESSION
1. UNYIMADU, John Paul
Thesis: “Concentration of Organochlorine Pesticides and Polychlorinated Biphenyls along River Niger, Nigeria”.
Supervisor: Prof. O. Osibanjo
2. UMUNNA-JIKEMEL, Loretta Chkwudumebi
“Preparation and Characterisation of Magnetite/Raphiafarinifera Nanocomposite and its Evaluation for the Adsorption of some Divalent Metal ions from Aqueous Solutions”.
Supervisor: Prof. J. O. Babalola
3. OWOSO, Jokoade Omotayo
Thesis: “Environmental Impacts of E-Waste Management Activities on Heavy Metal Contamination of Selected Sites in Lagos, Nigeria”.
Supervisor: Prof. O. Osibanjo
4. SINDIKU, Omotayo Kabirat
Thesis: “Assessment of Brominated Flame Retardants, Dioxins and Furans in Electronic Waste in Ogun and Lagos States, Nigeria”.
Supervisor: Prof. O. Osibanjo
5. ETCHIE, Tunde Ogbemi
Thesis: “Chemical Characterisation of Tropospheric Particulate Matter and Prediction of Mortality Burden in Nagpur, Chennai, Delhi and Lagos Metropolises”.
Supervisors: Dr. G. O. Adewuyi and Prof. K. Krishnamurthi
6. APKOMIE, Godfrey Kovo
Thesis: “Comparative Study of Rice-Husk-Clay and Chemically Modified Clay as Adsorbents for Heavy Metals from Industrial Effluents”.
Supervisor: Dr. F. A. Dawodu
7. OLORUNTOBA, Kike Deborah
Thesis: “Assessment of Polybrominated Diphenyl Ethers Contamination in some Selected Dumpsites in Lagos and Abuja Metropolises, Nigeria”.
Supervisor: Prof. O. Osibanjo
8. AYODELE, Olubunmi Olumide
Thesis: “Gatalytic Conversion of Oil and Cake from Calophyllum inophyllum Linn. Seeds into Biodiesel and Gasoline”.
Supervisor: Dr. F. A. Dawodu
9. AJIBADE, Sunday Olugbenga
Thesis: “Synthesis and Characterisation of Quinoline Alkanoid Derivatives as Inhibitors of Mycobacterium Tuberculosis”.
Supervisors: Dr. I. A. Oladosu and Prof. Olapeju O. Aiyelaagbe
10. OJEZELE, Omolara Jemimah
Thesis: “Cypermethrin and Glyphosate Residues in Amaranthus Cruentus (Linn.) Thell., Top-Soils, Surface Water and Sediments from Selected Farm Settlements in Oyo State, Nigeria”.
Supervisors: Prof. P. C. Onianwa and Dr. A. R. Ipeaiyeda
11. ETCHIE, Ayotunde Titilayo
Thesis: “Assessment of Burden of Disease Attributable to Heavy Metals in Ibadan Municipal Water Supply using Modified Risk-Based Method”.
Supervisor: Dr. G. O. Adewuyi
12. OSOBAMIRO, Temitope Monsurat
Thesis: “Distribution and Transfer Factor of Heavy Metals in Soil-Crop System of Selected Agricultural Farm Settlements in Ogun State, Nigeria”.
Supervisor: Dr. G. O. Adewuyi
13. OBAJE, Monday Gabriel
Thesis: “Physico-chemical Characteristics of Effluents from Cement Plant and its impact on Surface Water and Sediments of Onyi River in Obajana, Kogi State, Nigeria”.
Supervisor: Dr. A. R. Ipeaiyeda
14. VAIKOSEN, Nicholas Edebi
Thesis: “Persistence and Accumulation of Organochlorine Pesticides in Selected Cocoa Farms in South-western Nigeria”.
Supervisors: Prof. Bamidele I. Olu-Owolabi and Prof. K. O. Adebowale
15. ISHOLA, Fatimah Temitayo
Thesis: “Chemical Composition of the Essential Oils of Five Fruit Trees and Non-Volatile Constituents of Theobromacacao L. Pod.-Husk”.
Supervisors: Prof. O. Ekundayo and Dr. Sherifat A. Aboaba
16. FABOYA, Oluwabamise Lekan
Thesis: “Occurrence and Distribution of Carbazoles in Sources Rocks and Crude Oils from Tertiary Niger Delta Basin, Nigeria”.
Supervisors: Prof. O. Ekundayo and Prof. O. O. Sonibare
NAME: OWOSO, Jokoade Omotayo
THESIS: ENVIRONMENTAL IMPACTS OF E-WASTE MANAGEMENT ACTIVITIES ON HEAVY METAL CONTAMINATION OF SELECTED SITES IN LAGOS, NIGERIA
SUPERVISOR: PROF. O. OSIBANJO
ABSTRACT
Crude processing and improper disposal of electrical and electronic waste (e-waste) in Nigeria have been a major concern. This is not unconnected with the release of hazardous substances such as heavy metals (HMs). Contamination of soil by HMs from anthropogenic activities in Lagos has been documented; but there is dearth of information on source apportionment due to e-waste management activities such as burning, dismantling, stockpiling and disposal. This study therefore, assessed the generation and management of End-of-Life (EoL) computing equipment, their HMs content and the environmental impacts of their release from different e-waste management activities.
Information on generation and management of EoL computing equipment was obtained by administering 650 structured questionnaires to computer importers, assemblers, marketers, users, repairers, e-waste collectors and scavengers. End-of-life computing equipment were collected from users, repairers and scavengers. They were dismantled into plastic casings (33), Cathode Ray Tubes (CRTs) (30), Printed Wiring Boards (PWBs) of computer monitors (30) and motherboards (22). Samples of soil (9), groundwater/leachate (2) and plant (2) were collected seasonally for 2 years at each of the five selected e-waste management activity sites where burning (Ojota and Solus), dismantling/disposal (Alaba), stockpiling (Olusosun) and dismantling/stockpiling (Ikorodu) were ongoing, and at the control site. The soil, groundwater/leachate, plant and computer component samples were prepared and analysed by standard procedures for Cd, Cr, Cu, Ni, Pb, Zn using atomic absorption spectrophotometer. Data were analysed by descriptive statistics and compared with Total Threshold Limit Concentrations (TTLCs) for hazardous waste, European Union (EU) limit for agriculture soil and World Health Organisation (WHO) recommended limits.
Estimated generation of e-waste from computing equipment was 166 tons/year. Copper and lead had the highest mean concentrations (mg/kg) in the PWBs of motherboards (162000±42000, 61500±20000), monitors (97000±44000, 33900±13000) and CRTs (8.29±23, 5120±3000). These values were above TTLC except Cu in CRT. The concentrations (mg/kg) range of Cu, Pb, Zn, Ni, Cr and Cd during dry season were 9.93-38800, 134-13800, 8.64-3600, 7.42-115, 10.8-93.4, 0.999-20.9 respectively. These were generally lower than those of wet season. Impact of e-waste management activities on soil metal concentrations followed the trend: burning>dismantling>stockpiling for Pb, Cu, Cd; while burning>stockpiling>dismantling was for Zn, Ni, Cr. Sequential extraction showed that Pb and Cu were predominant in Fe-Mn oxide and carbonate fractions. Levels (mg/kg) of Cu (34.3-106; 34.1-304) and Pb (2.5-526; 56.1-901) in plants in both seasons were generally above WHO limits. In most cases, heavy metals concentrations in water were within WHO limits.
E-waste management activities especially open burning is predominantly the major source of heavy metal contamination of the environment. Environmentally sound management of computer waste and remediation of e-waste contaminated sites are recommended.
Keywords: Printed wiring board, cathode ray tube, metal speciation, e-waste, end-of-life equipment.
Word count: 433
NAME: SINDIKU, Omotayo Kabirat
THESIS: ASSESSMENT OF BROMINATED FLAME RETARDANTS, DIOXINS AND FURANS IN ELECTRONIC WASTE IN OGUN AND LAGOS STATES, NIGERIA
SUPERVISOR: PROF. O. OSIBANJO
ABSTRACT
Electronic waste (e-waste) contains Persistent Organic Pollutants (POPs) such as brominated flame retardants (BFRs) which are toxic and bioaccumulate in the environment. Pollutants such as polybrominated dibenzo-p-dioxins and furans (PBDD/Fs) and polychlorinated dibenzo-p-dioxins and furans (PCDD/Fs) are released during indiscriminate disposal of e-waste. There is paucity of data on the levels of these pollutants in electronics imported to Nigeria. This study was designed to assess the levels of BFRs, dioxins and furans in e-waste imported into Nigeria.
A total of 382 plastic casings enclosing Cathode Ray Tubes (CRTs) of 158 televisions (TVs) and 224 computer monitors imported from three different regions were purposively collected from eight locations in Ogun and Lagos States. The samples were selected from waste storage sites, electronic workshops, dumpsites and dismantling sites. The labels on the TV and computer casings were examined for information on the year and region of production. The samples were dismantled and sorted into different parts. The plastic casings were pulverized and extracted using dissolution and precipitation method with tetrahydofuran and hexane solution. The extracts were cleaned up with multilayer silica and florisil column. The levels of BFRs {Tetrabromobisphenol-A (TBBP-A), Tribromophenoxyethane (TBPE), Octabromodiphenylether (OctaBDE) and Decabromodiphenylether (DecaBDE), polybrominated diphenylethers (PBDEs)}, PBDD/Fs and PCDD/Fs were determined by gas chromatography/mass spectrometer. Data were subjected to descriptive statistics and compared with European Union Threshold Limit (EUTL).
The year of manufacture was from 1981 to 2004 for TVs and 1987 to 2006 for computers. The distribution of samples based on the regions of origin for the TVs were 37.0 and 63.0 % from Asia and Europe, respectively. For computers, 33.0, 45.0 and 22.0 % were from America, Asia and Europe, respectively. The concentration (mg/kg) of BFRs (TBBP-A, TBPE, OctaBDE and DecaBDE) in TVs were in the range of 272-177000, 1650-366000, 994-290000 and 675-230000 while those of computers were 1090-165000, 2530-390000, 8690-50900 and 2740-54100, respectively. The concentrations range of PBDEs (mg/kg) in computers from America, Asia and Europe were 2-233000, 686-201000, and 247-94700 while those of TVs from Asia and Europe were 5-40500 and 1380-420000, respectively. These values were above the EUTL. The concentrations (ng/g) of PBDD/Fs in computer from America, Asia and Europe were in the range of 71-83800, 732-101000, and 209-1890 while that of TVs from Asia and Europe were 1220-127000 and 1030-349000, respectively. The concentrations (ng/g) of PCDD/Fs in computers from America, Asia and Europe were in the range of 0.8-22.7, 0.5-58.7 and 0.5-2.4 while those of TVs from Asia and Europe were 1.2-57.3 and 0.6-6.8, respectively. The PBDD/Fs levels according to region of manufacture follow the trend: Europe>Asia for TVs and Asia>America>Europe for computers. The levels of BFRs and PBDD/Fs in TVs were higher than that of computers.
End-of-life electronics imported to Nigeria from America, Asia, and Europe contained high levels of brominated flame retardants, dioxins and furans. Therefore, there is need for strict monitoring and proper management of electronic waste in Nigeria to protect the environment from the adverse effect of these pollutants.
Keywords: Persistent organic pollutants, Electronic waste, Cathode ray tubes, Dioxins, Furans.
Word Count: 491
5. ETCHIE, Tunde Ogbemi
Thesis: “Chemical Characterisation of Tropospheric Particulate Matter and Prediction of Mortality Burden in Nagpur, Chennai, Delhi and Lagos Metropolises”.
Supervisors: Dr. G. O. Adewuyi and Prof. K. Krishnamurthi
NAME: APKOMIE, Godfrey Kovo
THESIS: COMPARATIVE STUDY OF RICE-HUSK-CLAY AND CHEMICALLY MODIFIED CLAY AS ADSORBENTS FOR HEAVY METALS FROM INDUSTRIAL EFFLUENTS
SUPERVISOR: DR. F. A. DAWODU
ABSTRACT
Clays, used as low-cost adsorbents for the removal of Heavy Metals (HM) from Industrial Effluents (IE) have low Adsorption Capacity (AC). Efforts have been made to improve the AC of clays by acid and alkaline modifications, but these chemicals are expensive and noxious to the environment, therefore the need for other alternatives. Although rice-husk has high AC for HM, there is limited information on its use in the modification of clay. The aim of this study was to modify clay with rice-husk and to compare the AC for HM from IE with Chemically Modified Clay (CMC).
One thousand grams each of Unmodified-Montmorillonite-Clay (UMC) obtained from Ugwuoba, Enugu state, was treated with 1.5 M H2SO4 (150 °C; 3 h) and 0.5 M KOH (100 °C; 6 h) to obtain the Acid-Modified-Clay (AMC) and Alkaline-Modified-Clay (KMC), respectively. The Rice-Husk-Modified-Clay (RHMC) was prepared by the addition of 40% by weight of rice-husk to UMC (300 °C; 2 h). The physicochemical parameters of the adsorbents [Cation Exchange Capacity (CEC), pH point of zero charge (pHpzc), Specific Surface Area (SSA)] and IE [Chemical Oxygen Demand (COD), Biochemical Oxygen Demand (BOD)] were determined by standard methods. The adsorbents were characterised by Fourier-Transform-Infrared Spectrophotometer (FTIR), X-Ray-Diffraction (XRD) and Scanning Electron Microscope (SEM). The concentrations of HM (zinc, copper, manganese, cadmium, lead and nickel) in the IE were determined by Atomic Absorption Spectrophotometer (AAS). Batch method was employed for HM adsorption at varying conditions of pH, initial metal concentration, adsorbent dose, particle size, contact time, temperature and also for desorption. Data were fitted into isotherm, kinetic and thermodynamics and subjected to regression model, chi-square and descriptive statistics at α0.05.
The RHMC showed the highest CEC (97.17 Meq/100g) and SSA (55.1 m2/g), thus indicated enhanced surface properties. The pHpzc for UMC was 3.7, (AMC) 2.3, (RHMC) 3.3 and (KMC) 5.2, suggesting negative and positive surface charge above and below these pHpzc, respectively. The disappearance of the inner –OH stretching at 3697.6 cm-1, a sharp increase in montmorillonite peak, and increase in porosity of RHMC as revealed by FTIR, XRD and SEM respectively, showed successful modification. The concentration range (mg/L) of COD, BOD and HM for the IE were (189.3-368.1), (82.5-184.1) and (0.02-19.4), respectively. The AC of the adsorbents for HM was in the order: RHMC>AMC>KMC>UMC, while HM adsorption on the adsorbents followed the trend: zinc>copper>manganese>cadmium>lead≃nickel. Optimum RHMC adsorption was achieved at pH 6.5, adsorbent dose 0.1 g, particle size 100 µm and equilibrium time of 180 minutes. The R2 of 0.881-0.999 and chi-square of 0.017-1.262 showed that the Freundlich isotherm and Pseudo-second-order kinetic models gave best fit to the adsorption mechanism for all the adsorbents. Thermodynamics revealed a complex adsorption process and RHMC showed highest desorption (92%) and adsorption (80%) after three cycles of desorption experiment.
The rice-husk-clay had better adsorption and desorption potentials than the chemically modified clay, and can therefore be employed as an alternative low-cost adsorbent for heavy metals from industrial effluents.
Keywords: Montmorillonite, Chemically modified adsorbents, Rice husk, Rice-husk-clay
Word count: 478
NAME: OLORUNTOBA, Kike Deborah
THESIS: ASSESSMENT OF POLYBROMINATED DIPHENYL ETHERS CONTAMINATION IN SOME SELECTED DUMPSITES IN LAGOS AND ABUJA METROPOLISES, NIGERIA”.
SUPERVISOR: PROF. O. OSIBANJO
ABSTRACT
Polybrominated diphenylethers (PBDEs) are used as flame retardants in electronic equipment, textiles and plastics which are released into the environment through indiscriminate disposal of end-of-life products. The bioaccumulation and toxic effect of these chemicals on human, biota and environment have been of global concern. In Nigeria, there is dearth of information on levels of PBDEs in the environment. This study was designed to assess the levels of PBDEs in some environmental samples and animal products in selected dumpsites in Lagos and Abuja metropolises.
Electronic Waste Dumpsites (EWDs) and Municipal Waste Dumpsites (MWDs) from Lagos and Abuja were purposively selected. Samples were collected seasonally for two years from three EWDs and five MWDs in Lagos and two MWDs in Abuja. A total of 480 soil samples were collected from 10 sampling sites (four points per site at 0-15, 15-30 and 30-45cm depths) during dry and wet seasons using random sampling. Thirty-six samples each of water and sediments; 100 plant materials (spinach, pumpkin, tomatoes, sweet potatoes and forage); 56 each of free range chicken-eggs and cow-milk samples were collected. Control samples were collected about five Kilometres away from study sites. Soil, sediment, chicken-egg and plant samples were extracted separately with hexane:acetone (1:1) using Soxhlet Extractor, while water and cow-milk samples were extracted with dichloromethane using solvent partitioning. The extracts were cleaned-up in a silica column using hexane as eluting solvent. The levels of PBDEs were determined using gas chromatography. Data were analyzed using descriptive statistics, t-test atα0.05 and were compared with values from China and USA.
Concentrations of PBDEs (ng/g dry weight) in soils from EWDs at depth; 0-15, 15-30 and 30-45cm during dry/wet seasons for first and second year were: 157.3±16.5/176.0±19.8; 28.9±2.98/36.7±14.4; 1.5±0.1/3.0±1.3 and 242.4±25.1/285.0±36.4; 43.1±16.6/52.4±9.52; 4.5±1.9/5.2±2.4, respectively, indicating higher PBDEs concentrations during wet seasons but with no significant difference. Concentrations of PBDEs (ng/g dry weight) in soils at the three depths from MWDs in Lagos were199.2±27.3/309.1±41.2; 17.4±4.3/33.3±10.7; 1.0±0.9/8.3±5.6 and 341.0±68.6/585.0±47.0; 39.3±11.3/56.7±14.7); 8.1±6.9/19.6±1.9,respectively, while those for MWDs in Abuja were 124.2±32.8/253.0±18.3; 64.7±23.6/130.4±37.6; 8.5±4.0/17.9±10.3 and288.3±223.8/342.4±43.1; 63.6±19.0/120.1±24.4; 12.7±11.9/21.5±5.6, respectively. These levels indicated higher rate of PBDEs accumulation in Lagos compared to Abuja which could be attributed to industrial activity in Lagos. The PBDEs levels in water ranged from 0.2 to 23.4ng/mL and 51.4 to 85.8ng/g in sediments. Levels of PBDEs (ng/g dry weight) in plants ranged from 16.3 to 92.8 while the levels (ng/g lipid) ranged from 262.3 to 313.4 in chicken-eggs and 18.2 to 86.8 in cow-milk, suggesting bioaccumulation of PBDEs in biota. The levels of PBDEs in study sites were higher than those of the control. The range of PBDEs in EWDs and MWDs were comparable to those reported in USA but lower than those from China.
Environmental samples as well as animal products from the dumpsites in Lagos and Abuja were contaminated with polybrominated diphenylethers. Proper disposal management of end-of-life products containing polybrominated diphenylethers to reduce their levels in the environment is recommended.
Keywords: Flame retardants, bioaccumulation, Electronic waste dumpsites, chemical pollutants
Word count: 497
NAME: AYODELE, Olubunmi Olumide
THESIS: GATALYTIC CONVERSION OF OIL AND CAKE FROM CALOPHYLLUM INOPHYLLUM LINN. SEEDS INTO BIODIESEL AND GASOLINE
SUPERVISOR: DR. F. A. DAWODU
ABSTRACT
Biodiesel (mono alkyl esters of long chain fatty acids) from oil-bearing seeds is a promising alternative diesel fuel because of its favourable properties, environmental benefits and the fact that it is a renewable biological resource. Many studies have focused only on catalytic conversion of seed oil of few plants to biodiesel while no process has been able to utilise the cake for the production of gasoline. A process that can be used to convert the cake into gasoline may further enhance the economic potentials of seed oil of some plants. Therefore, this study was designed to produce biodiesel from seed oil of Calophyllum inophyllum Linn. and gasoline from the cake using less rigorous catalytic conversion process.
One kilogram of C. inophyllum seeds was pulverised, after which it was soxhlet extracted using n-hexane. The cake was later dried in an oven. The oil was esterified and transesterified in methanol using a biomass-derived catalyst to obtain biodiesel. The activity of biomass-derived catalyst was investigated in a batch reactor. The cake was thereafter hydrolysed using HCl as the catalyst to obtain Levulinic Acid (LA). The LA was dehydrated using Zeolite Socony Mobil-5 (ZSM-5 [Si=300]) to obtain Angelica Lactone (AL). The AL was then converted to AL-Dimers (ALD) and AL-Trimers (ALT) via C-C coupling reaction. The products were finally hydrodeoxygenated to gasoline in the presence of nickel supported on ZSM-5 (Ni/ZSM-5 [Si=40] or Ni/ZSM-5 [Si=300]) and nickel supported on Activated Carbon-Heteropoly Acid composite (Ni/Ac-HPA) catalyst. The physico-chemical parameters of the seed oil (oil yield, viscosity, acid value and fatty acid composition) were determined using standard methods, while the chemical composition of the gasoline was determined by Gas Chromatography-Mass Spectrometry (GC-MS). Data were analysed using descriptive statistics.
Esterification and transesterification of seed oil yielded 81.1 % and 78.3 % biodiesel respectively, which indicates a good method of producing biodiesel. The biomass-derived catalyst was active in the reactions achieving high yields within 5 hr. and its activity was related to higher SO3H acid density and surface area. Hydrolysis of the cake gave LA of 23.0 % while dehydration of LA yielded 97.0 % AL. The C-C coupling of the resultant AL yielded 64.0 % ALD and 34.0 % ALT over anhydrous K2CO3. Hydrodeoxygenation of mixture of ALD and ALT to gasoline over Ni/ZSM-5 (Si=40), Ni/ZSM-5 (Si=300), and Ni/Ac-HPA catalysts yielded 95.6 %, 91.7 % and 57.3 % hydrocarbons within C6 – C13, respectively. The oil yield, viscosity and acid value were 53.0 %, 21.2 mm2/g and 29.5 mgKOH/g, respectively; while oleic and linoleic acids were the dominant fatty acids. The major gasoline components were 2-methylhexane (C7H16), 1,2,4-trimethylcyclohexane (C9H18) and 1,2-dimethylcyclooctane (C10H20). The GC-MS also showed the presence of aromatics (propylbenzene [C9H12], p-xylene [C8H10]) and alkenes (2-methylpropene [C4H8], 2-heptene [C7H14]) which could be used as gasoline blend.
The oil and cake of Calophyllum inophyllum seeds were successfully converted to biodiesel and gasoline, respectively. The catalytic conversion process is practicable, and could therefore advance biorefinery operations in developing countries like Nigeria.
Keywords: Calophyllum inophyllum seed, Biodiesel production, Hydrodeoxygenation, Gasoline, Levulinic acid.
Word count: 492
NAME; AJIBADE, Sunday Olugbenga
THESIS: SYNTHESIS AND CHARACTERISATION OF QUINOLINE ALKANOID DERIVATIVES AS INHIBITORS OF MYCOBACTERIUM TUBERCULOSIS.
SUPERVISORS: DR. I. A. OLADOSU AND PROF. OLAPEJU O. AIYELAAGBE
ABSTRACT
Tuberculosis is treated by a combination of drugs and the current regime of drugs lack quinoline nucleus in their chemical structures despite the fact that quinoline alkaloids have been reported to possess diverse pharmacological activities. The use of this class of alkaloids as anti-tubercular drugs has not been established. Consequently, this study was designed to synthesise and characterise quinoline alkaloids and subsequently determine their inhibitory activities against Mycobacterium tuberculosis.
The quinoline alkaloids were synthesised by two routes. The first route entailed the reaction of para-substituted anilines with cinnamoyl chloride in the presence of phosphorus oxychloride to obtain chloro-quinoline derivatives. The chloro-quinolines were coupled with various substituted boronic acids by Suzuki cross-coupling reaction using microwave assisted synthetic method. The second route involved the introduction of nitro-substituent at the para-position through direct arylation of para-nitroquinolin-1-oxide with aryl halide in the presence of di-tert-butylmethylphosphonium tetrafluorate ligand and palladium catalyst. The synthesised compounds were purified using chromatotron chromatography and characterised by means of Infra-Red (IR) spectroscopy, Nuclear Magnetic Resonance (NMR) and elemental/combustion (CHN) analyses. The compounds were subjected to in-vitro anti-mycobacterial assay against ATCC35820 H37Rv strain of Mycobacterium tuberculosis using mycobacteria growth inhibition tube method. The assay was scored as either resistant or sensitive to the strain at specific Minimum Inhibitory Concentrations (MIC) (12.5, 25.0 and 50.0 µg/mL). Streptomycin, isoniazid, rifampicin and ethambutol were used as positive controls while dimethylsulphoxide was used as the negative control.
The first route yielded 34 compounds out of which nine were new. The new compounds were: 2-(4-tert-butylphenyl)-quinolin-6-ol, 2-(3,4-dimethoxyphenyl)-quinolin-6-ol, 4-Chloro-2-(3,4-dimethoxyphenyl)-quinoline, 6-Chloro-2-(3,4-dimethoxyphenyl)-quinoline, 4-(6-hydroxyquinolin2-yl)-benzaldehyde, 2-(4-mercaptophenyl)-quinolin-6-ol, 4-(6-chloroquinolin-2-yl)-bezenethiol, 2-(4-tert-butylphenyl)-4-chloro-6-methoxy-quinoline and 4-(quinoline-2-yl)-benzaldehyde. A new compound 2-(3,4-dimethoxy phenyl)-4-nitroquinoline was also synthesised through the second route. The 1H NMR spectrum of 2-(4-tert-butylphenyl)-quinolin-6-ol which is a representative example of the new compounds displayed resonance at δ 1.4, 7.1, 7.3, 7.5, 7.8, 7.9, 7.9 and 8.1 ppm for the methyl and aromatic protons. The 13C NMR spectrum similarly exhibited resonance for nineteen carbon atoms comprising three methyls at δ (30.3, 30.3, 30.3); nine methines at δ (108.1, 119.4, 121.9, 125.3, 125.3, 126.9, 126.9, 129.5, 135.6) and seven quaternary carbons at δ (34.1, 128.6, 136.7, 142.9, 152.0, 154.9, 155.6) ppm. The IR spectrum also showed absorptions for phenolic OH and aromatic (C=C) bonds at 3646 and 1607 cm-1. The CHN data for the compound were in agreement with the calculated values of C-82.2%; H-6.9%; N-5.09%; which correspond to the molecular formula C19H19NO. Seven quinoline derivatives exhibited better anti-mycobacterial activities than streptomycin which is a first line anti-tubercular drug. Two compounds: 2-(4-tert-butylphenyl)-quinolin-6-ol and 2-(4-mercaptophenyl)-quinolin-6-ol demonstrated the highest inhibition with an MIC value of 12.5 µg/mL while the other five compounds displayed activities between 25.0 and 50.0 µg/mL; an implication of anti-tubercular drug candidate.
New quinoline alkaloids possess novel structures which are different from the existing drugs and conferred potentials for anti-tubercular agents that require further development.
Keywords: Mycobacterium tuberculosis inhibition, 2-(4-tert-butylphenyl)-quinolin-6-ol, Chromatotron, Minimum inhibitory concentration.
Word count: 465
NAME: OJEZELE, Omolara Jemimah
THESIS: CYPERMETHRIN AND GLYPHOSATE RESIDUES IN AMARANTHUS CRUENTUS (LINN.) THELL., TOP-SOILS, SURFACE WATER AND SEDIMENTS FROM SELECTED FARM SETTLEMENTS IN OYO STATE, NIGERIA”.
SUPERVISORS: PROF. P. C. ONIANWA AND DR. A. R. IPEAIYEDA
ABSTRACT
Pesticides such as cypermethrin and glyphosate are widely used in agriculture to increase productivity, improve the quality and extend the storage life of food crops. However, these pesticides are toxic, persistent and bioaccumulate in the environment. Data on cypermethrin and glyphosate residues in environmental matrices including vegetables in developed world have been reported. There is paucity of information on human exposure risk of these pesticides residues in Nigeria. This study was therefore designed to determine pesticide residue concentrations in vegetable (Amaranthus cruentus), top-soils, surface water and sediments from selected farm settlements in Oyo State and also to assess human exposure risk to the vegetable consumption.
The farm settlements were located in Akufo, Ilora and Ogbomoso (representing three out of four agricultural zones of Oyo state) from where surface water, sediments, top-soils and vegetable were collected spanning September, 2010 to August, 2012. Composite top-soils (120) and vegetable (120) samples were purposively collected from each farm. Ninety-six samples each of surface water and sediments were collected over the same period from each settlement. Control samples were collected at about 10 km away from the farms. The pesticides were extracted from the samples using acetone and n-hexane (1:1) and cleaned-up by column chromatography. The extracts were analysed for cypermethrin and glyphosate using high performance liquid chromatography. Pesticide levels in vegetable and water samples were compared with European Union Maximum Residue Limits (EU-MRL) for organic contaminants. This standard limit was not available for top-soils and sediments. Acute Hazard Indices (AHI) of pesticide residues in vegetable samples were calculated for both adults and children using standard method recommended by WHO. Transfer factors (TF) of the pesticides from top-soil to vegetable were also calculated. Data were analysed using descriptive statistics and ANOVA at α0.05.
The concentrations of cypermethrin were 5.0±4.1, 15.0±8.7, 9.4±0.2 mg/kg in sediments; 5.4±2.1, 16.0±0.2, 6.1±0.7 mg/kg in top-soils; 12.0±9.2, 16.0±11.0, 5.1±1.7 mg/kg in vegetable and 0.73±0.28, 2.7±0.8, 0.7±0.4 mg/L in water for Akufo, Ilora and Ogbomoso farms, respectively. The corresponding glyphosate concentrations were 24.0±13.0, 36.0±15.0, 17.0±15.0 mg/kg; 29.0±16.0, 29.0±16.0, 24.0±22.0 mg/kg; 11.0±8.8, 8.7±5.8, 6.6±4.2 mg/kg and 22.0±16.0, 15.0±1.9, 11.0±0.9 mg/L in sediments, top-soils, vegetable and surface water, respectively. Cypermethrin and glyphosate concentrations exceeded EU-MRL of 0.1 and 0.7 mg/kg, respectively for vegetable and 0.0001 mg/L for water. The pesticide concentrations were significantly higher than the corresponding concentrations in the control sites. The TF for cypermethrin and glyphosate were 3.02 and 0.35 for Akufo; 1.15 and 0.30 for Ilora; 0.91 and 0.24 for Ogbomoso farms. The AHI of cypermethrin for adults (221.0 %, 276.0 %) and children (250.0 %, 310.0 %) for Akufo and Ilora farms, respectively were above 100 % (WHO limit) while those for Ogbomoso (adult-53.0 %, children-60.0 %) were less. The AHI of glyphosate for adults (21.0 %, 7.0 % and 5.0 %) and children (24.0 %, 8.0 % and 6.0 %) for Akufo, Ilora and Ogbomoso farms, respectively were below WHO limit.
Pesticide residues in all the farm settlements were above standard limits and therefore pose a health risk to populace and require intervention.
Keywords: Glyphosate cypermethrin bioaccumulation, Amaranthus cruentus, Transfer factor of pesticides, Hazard index
Word count: 491
NAME: ETCHIE, Ayotunde Titilayo
THESIS: ASSESSMENT OF BURDEN OF DISEASE ATTRIBUTABLE TO HEAVY METALS IN IBADAN MUNICIPAL WATER SUPPLY USING MODIFIED RISK-BASED METHOD”.
SUPERVISOR: DR. G. O. ADEWUYI
ABSTRACT
Disease Burden (DB) involvesthe overall impact of a pollutant on human health, taking into accountall risk factors: degree of exposure, toxicity, severity of their health effects and consumer-demography. Consequently, the WHOadvocatesthe assessment of DB of microbial and Chemical Pollutants (CPs) in drinking-water for informed decision-making on mitigation. Although, method for assessing DB of microorganisms has been documented, there is no precise method forCPsin drinking-water, consequently no report on DB of Heavy Metals (HMs) (most critical CPs) in Piped Municipal Water Supplies (PMWS).This study was designed to develop a Risk-Based Method (RBM)for assessing DB of CPs in drinking-water,subsequentlyDB ofHMsin Asejire and Eleyele PMWS. Influence of Seasonal Variation on Water Quality in the Distribution Systems (ISVWQDS) was examined while regression models were developed for easy prediction of DB of priority HMs.
The HMs (cadmium, chromium, cobalt, copper, iron, lead, manganese, nickel and zinc) were selected based on the WHO hazard identification protocol. Water samples (858) were obtained from feeding-rivers and dams (catchments) (120), Treatment Plants (TP) (90) and 72 consumer-taps (648) in 12 supply areas within Ibadan metropolis. Sampling was conducted bimonthly from April 2010 to December 2011. Concentrations of metals were determined by atomic absorption spectrophotometry. TheRBM was developed by harmonizing theUSEPA exposure assessment,carcinogenic and non-carcinogenic chemical products’life cycle assessment and microbial DB assessment methods, using the WHO framework. The DB(in Disability-Adjusted Life Years (DALYs)/person/year) was estimated forpriority HMs:those exceeding WHO limits;using the RBM. Monte Carlo Simulation Technique (MCST) was appliedin assessing theISVWQDS.The modelswere developed using locally-weighted-scatter-plot-smoothing and curvilinear regression. Uncertainty and spatio-temporal variability analyses were done by MCST. Models were validated by comparing cumulative density function curves of validation estimates with model-predictions at 95% confidence limit. Data were analysed using Principal Component Analysis-Multiple Linear Regression of the Absolute Principal Component Scores (PCA-MLR-APCS),Wilcoxon signed-rank test andMANOVA at p=0.05.
Average concentrations (mgL-1) of cadmium (0.01±0.01-0.08±0.03), cobalt (0.01±0.01-0.13±0.03), chromium (0.08±0.02-0.27±0.04), manganese (0.01±0.01-0.30±0.08) and lead (0.14±0.04-0.35±0.13) in consumer-taps from most supply areas exceeded WHO limits, whereas copper (0.01±0.01-0.08±0.02), iron (0.21±0.10-0.82±0.47),nickel (0.01±0.01-0.08±0.03) and zinc (0.19±0.05-0.71±0.26) were below limits. Metals’concentrationsvaried significantly (p<0.05) across sites (river>dam>consumer-taps>TP) and seasons (dry>wet). Patterns of metals’ loading from PCA-MLR-APCS suggested fouranthropogenicsources of pollution. Source attribution (0.98≤R2≤1) ranged from 60-100%.Estimated DB (DALYs/person/year) was highest for chromium (7.7×10-2±3.3×10-2), followed by cadmium (3.5×10-2±5.0×10-3), lead (1.6×10-3±1.2×10-5), manganese (1.3×10-4±7.3×10-5) and cobalt (5.7×10-5±8.5×10-6). The ISVWQDS was 9.7×10-3±8.0×10-3DALYs/person/year, exceeding WHO limit (1.0×10-6DALYs/person/year).The regression models take the form:
DB=β_1 C+β_2 C^2+β_3 C^3+ε
(where β=regression coefficient,C=concentrationand ε=residual) and were valid at 95% confidence limit.
Asuitable method for assessing disease burden of chemical pollutants in drinking-waterhas been developed.The application revealed highdisease burden that calls for mitigation of metals in Ibadan municipal water supplies.
Keywords: Disability Adjusted-Life Years (DALYs), Chemical pollutants, Asejire treatment plant,Cumulative Density Functions (CDF)
Word count: 471
NAME: OSOBAMIRO, TEMITOPE MONSURAT
THESIS: DISTRIBUTION AND TRANSFER FACTOR OF HEAVY METALS IN SOIL-CROP SYSTEM OF SELECTED AGRICULTURAL FARM SETTLEMENTS IN OGUN STATE, NIGERIA”.
SUPERVISOR: DR. G. O. ADEWUYI
ABSTRACT
Food Crops (FCs) grown on Heavy Metals (HMs) contaminated soils can bio-accumulate HMs thus becoming a threat to consumer’s health. There is dearth of information on HMs contamination and their transfer factor from soil to FCs grown in farm settlements in Ogun State. This study was designed to investigate HMs in soil, FCs and to establish transfer relationship from soil to crop in selected farm settlements in Ogun State.
Three farm settlements (Ago-Iwoye, Ajegunle and Sawonjo) were purposively selected. Samples (soils and Commonly Edible Crop Parts, CECP) from the settlements were randomly collected tri-monthly from November 2011 to September 2013. Soil samples in each settlement were collected from three depth 0-15, 15-30 and 30-45 cm, (n=144 each). A total of 432 samples of CECP comprising 144 each of Cassava Tuber (CT), Maize Cob (MC) and Oil Palm Seed (OPS) were also collected. Soil pH, Organic Matter (OM), Cation Exchange Capacity (CEC), Particle Size (PS) (sand, clay and silt) and soil speciation were carried out using standard analytical methods. Soil and CECP were digested using HNO3: HCIO4: H2SO4 (3:1:1) mixture. The HMs concentrations were determined by atomic absorption spectrophotometry and compared with standards. Mineralogical compositions of soil samples were determined using X-ray diffractometer. Data were analysed using multiple regression, extended Freundlich-type models and ANOVA at α0.05
The pH, CEC (cmol/kg) OM and PS (%) of soil samples were in the range: 5.84-6.39; 2.95-10.30; 1.46-2.49; 78.10-89.20 (sand), 5.70-10.20 (clay) and 4.20-11.80 (silt), respectively. Soil HMs (mg/kg) in all the sites were: Mn≤55.5; Fe≤3110.0; Pb≤37.1; Zn≤178.0; Cu≤18.8; Cd≤2.2 and Ni≤25.9 while USEPA limits were 80, not available, 300, 200, 50, 3 and 50, respectively. Levels of Fe, Pb and Zn varied significantly among farms. Average HM concentrations in CECP (mg/kg) (Mn≤19.0; Fe≤61.6; Pb≤2.17; Zn≤27.2; Cu≤6.03; Cd≤3.40 and Ni≤1.72) fall within WHO permissible limits except Cd. Highest levels of Ni, Cd and Fe, were found in maize from Ago-Iwoye, Ajegunle and Sawonjo farms, respectively while higher Zn and Mn were found in CT from Ago-Iwoye farm. Metal content in different soil fractions were in the range (%): soluble-exchangeable (0.60-1.80), surface-adsorbed (1.60-5.10), OM (3.70-17.90), Mn-oxide (8.10-27.90), poor crystalline Fe-oxide (11.40-25.40), crystalline Fe-oxide (13.20-28.50) and residual (24.10-52.80). These indicated that Fe-oxide and residual fractions had the highest HMs distribution accounting for low metal mobility. Clay minerals such as corensite, kaolinite, montmorillonite, smectite and chlorite were found in the soils. These enhanced soil adsorptive capacity for HMs thereby, inhibiting their transfer to plant. High level of Fe mineral such as hematite in the soils also inhibited HMs transfer. The extended Freundlich-type model showed better correlation (r ≤ 0.90) with available HMs in the soil when soil properties such as pH and CEC were included as variables.
Heavy metals in the soil and food crops were below permissible levels. The pH and cation exchange capacity were the major controlling factors of heavy metals transfer. A proper management of these parameters will therefore be useful in preventing heavy metals uptake in these farms.
Keywords: Soil physicochemical properties, Transfer factor, Freundlich-type model, Farm Settlements, Plant toxicity
Word count: 494
NAME: OBAJE, Monday Gabriel
THESIS: PHYSICO-CHEMICAL CHARACTERISTICS OF EFFLUENTS FROM CEMENT PLANT AND ITS IMPACT ON SURFACE WATER AND SEDIMENTS OF ONYI RIVER IN OBAJANA, KOGI STATE, NIGERIA.
SUPERVISOR: DR. A. R. IPEAIYEDA
ABSTRACT
Effluents from Obajana cement plant discharged into Onyi River in Kogi State is of environmental health significance due to its potential to impair the quality of the water bodies. Previous studies on the extent of contamination arising from the effluents discharged into the river are inadequate in scope and duration. Hence, there is need for frequent monitoring and assessment of effluents dischargedinto and effects on surface water quality of the river. This study was aimed at determining and monitoring the physicochemical characteristics of effluents from the cement plant to enable better assessment of its environmental impact on the receiving Onyi River for a period of one year.
Effluents from three locations along the effluent channel of Obajana cement plant were sampled. Surface water samples were collected monthly from five locations upstream of discharge point (control); one location at discharge point and five locations downstream at an equal distance from one location to another up to 1 km upstream and downstreambetween January and December, 2014. Sediment samples were also collected at each location of water and effluent samples. Thirty-six effluents, 132 surface water and 168 sediment samples were collected. Physicochemical characteristics of the effluents and water samples were determined using standard methods. Trace metal concentrations in the effluents, surface water and sediment samples were also determined according to APHA methods. Self-Purification Capacity-SPC and pollution status of the river were determined using recovery capacity expression and Prati indices, respectively. Data were compared with NESREA standard limit, analyzed using descriptive statistics and ANOVA at α0.05.
The values (mg/L) of total-alkalinity (87.0±33.0, 61.0±14.0, 70.0±16.0); total-hardness (27.0±13.0, 41.5±6.4, 55.0±12.0); Total-Suspended-Solids (TSS) (240.0±267.0, 116.0±6.0, 134.0±16.0); Total-Dissolved-Solids (TDS) (223.0±123.0, 94.0±13.0, 171.0±13.0);Dissolved-Oxygen (DO) (5.1±1.2, 8.6±0.7, 6.1±0.1); Chemical-Oxygen-Demand (COD) (63.0±43.0, 34.5±6.4, 44.0±1.4); Biochemical-Oxygen-Demand (BOD) (5.3±3.7, 3.7±1.1, 6.2±2.0); chloride (18.0±7.9, 9.8±3.7, 10.2±3.3);sulphate (3.8±1.9, 0.9±0.1, 1.8±0.3); phosphate (29.0±18.0, 25.4±5.0, 27.0±7.1); nitrate (141.0±106.0, 127.0±18.0, 133.0±33.0); Cr (0.07±0.01, 0.03±0.01, 0.04±0.01); Cu (0.02±0.01, 0.002±0.001, 0.003±0.002); Ni (0.01±0.01, 0.006±0.002, 0.007±0.002);Pb (0.03±0.03, 0.02±0.01, 0.02±0.01) and Zn (0.06±0.03, 0.04±0.02, 0.05±0.01) were obtained for effluents, upstream and downstream water, respectively. The downstream values were significantly higher than the corresponding upstreamexcept DO. The levels of TSS, phosphate, nitrate, COD and Cu for effluents exceeded NESREA limits. The concentrations (µg/g) of Co, Cd, Cr, Cu, Ni, Pb and Zn in sediments from effluents channel were 7.2±5.2, 2.8±0.7, 9.4±5.1, 3.9±6.7, 4.4±1.7, 31±8.9 and 29±13, respectively. These concentrations were lower than concentrations in downstream sediments and were within the Canadian sediment quality criteria. The river downstream was categorised as slightly polluted water, while upstream was in the class of non-polluted water based onPrati indices for classification of surface water quality. The SPC of the river was 12.1% (total-alkalinity), 19.7% (total-hardness), 0.6%(TDS), 15.2% (sulphate), 15.2% (phosphate),6.3% (DO), 11.0% (BOD) and 19.0% (COD).
The effluents quality from Obajana cement plant were not in compliance with effluent discharge guideline, hence contaminating the river and making it unfit for domestic use.Adequate treatment of the effluents prior to discharge is necessary.
Keywords: Cement industry effluent, Water quality, River and sediment pollution, Self-purification capacity.
Word count: 498
NAME: VAIKOSEN, NICHOLAS EDEBI
THESIS: PERSISTENCE AND ACCUMULATION OF ORGANOCHLORINE PESTICIDES IN SELECTED COCOA FARMS IN SOUTH-WESTERN NIGERIA.
SUPERVISORS: PROF. BAMIDELE I. OLU-OWOLABI AND PROF. K. O. ADEBOWALE
ABSTRACT
Organochlorine Pesticides (OCPs) are cyclic chlorinated hydrocarbons that are toxic and can bioaccumulate in the environment. Although, its usehas been prohibited in many countries including Nigeria; nevertheless they are still used extensively for pests control by cocoa (Theobroma cacaoL.) farmers in Nigeria. In addition, OCPs residual concentrations among other factors in cocoa bean influences their price in the World market. Therefore, this study was designed toassess the persistence of OCPs in cocoa plants, soil, surface water, and sediments in selected cocoa farms in Southwestern Nigeria.
The cocoa farms selected for this study were classified as; farms where OCPs have been used and discontinued for 15 years [Cocoa Research Institute of Nigeria, Ibadan [(CRIN (I&II)]; for 3–5 years (Sabo, Ondo); still in use [(Igba, Ondo) and (Sore-Bale, Ogun)]. Sampling was carried out during wet and dry seasons between November, 2009 and September, 2011. A total of 480 samples were randomly collected comprising: 120 soils [(0-15 and 15-30 cm), (CRIN I&II-48; Sore-Bale-24; Sabo-24; Igba-24)]; 60surface water (CRIN I&II-24; Sore-Bale-12; Sabo-12; Igba-12); 60 sediments (CRIN I&II-24; Sore-Bale-12; Sabo-12; Igba-12); 60 each of leaves, bark, pods and seeds (CRIN I&II-24; Sore-Bale-12; Sabo-12; Igba-12, per matrix)for analysis. Control samples were collected 5.0 km from CRIN I, where OCPs were not used. Terrestrial Field Dissipation (TFD) and adsorption-desorption studies for OCP were done by EPA/OECD methods using endosulfan (6,7,8,9,10,10-Hexachloro-1,5,5a,6,9a-hexahydro-6,9-methano,2,4,3-benzodioxathiepin-3-oxide). Extractions and clean-up of OCPs were done using standard analytical methods. TheOCPs were determined using Gas Chromatography-Mass Spectrophotometric (GC-MS) technique. Data were compared with WHO/FAO limits and analysed using correlation and descriptive statistics.
Nineteen OCPs were detected in all the matrices. Total (∑) OCPs in vegetation (µgg-1), soil (ngg-1) ranged from <0.001 to 12.67 and 11.48 to 1,166.71, respectively. Amongst the Hexachlorocyclohexanes (HCHs), β-isomer was most predominant in CRIN. Bioaccumulation factors ranged from 0.1 to 658.0 in CRIN. The ∑OCP0-15cm< ∑OCP15-30cm except in Sore-Bale and Igba, due to fresh input. Total Endosulfan was the most dominant, while α-/β-endosulfan and endosulfan sulfate/endosulfan ratios in Sore-Bale were >1.7 (0-15 cm) and <0.3 (15-30 cm), respectively. Total OCPs residues in surface water ranged from 0.10-1.39 µgL-1 and 0.06-1.35 µgL-1 for dry and wet seasons, respectively. Igba and CRIN exceeded the WHO/FAO limit (1.0 µgL-1). The ∑OCPs in sediments ranged from 0.88 to 9.85 µgg-1, with γ-HCH (lindane) >0.01µgg-1; these values exceeded consensus-based threshold effect concentrations and probable effect concentrations. The TFD studies, showed initial ∑endosulfan distribution trend as; leaves > bark > pods >seeds. Dissipation half-life ranged from 7.93 to 79.82 days. Adsorption rate constants for endosulfan sorption studies ranged from 6.91 to 11.52×10-3 min-1 for CRIN, Sore-Bale and Igba soils. The Freundlich adsorption constants for non-linear isotherm curve (≤0.5574) supports the mechanism of adsorption.
The presence of organochlorine pesticides in various matrices at Cocoa Research Institute of Nigeria and Sabo farms, established their persistence and accumulation. The pesticides were more adsorbed and persistent in the Cocoa Research Institute of Nigeria soil than other soils.
Keywords: Bioaccumulation of pesticides, Cocoa farm, Terrestrial field dissipation,
Adsorption-desorption
Word count: 494
NAME: ISHOLA, Fatimah Temitayo
THESIS: CHEMICAL COMPOSITION OF THE ESSENTIAL OILS OF FIVE FRUIT TREES AND NON-VOLATILE CONSTITUENTS OF THEOBROMACACAO L. POD.-HUSK.
SUPERVISORS: PROF. O. EKUNDAYO AND DR. SHERIFAT A. ABOABA
ABSTRACT
Essential Oils (EOs) are volatile secondary metabolites characterised by a strong odour and widely used for pharmacological and industrial applications. There is dearth of information on chemical compositions and bioactivities of EOs of some fruit trees in Nigeria. This study was therefore designed to extract and characterise the EOs from selected fruit trees, screen the EOs for bioactivity as well as to isolate and characterise non-volatile constituents from Theobroma cacao L. pod-husk due to its availability.
The plant samples (Carica papaya L., Theobroma cacao L., Persea americana M., Ananas comosus (L) Merr and Chrysophyllum albidum G. Don) were collected in Ibadan, identified and authenticated at the Herbarium of Forest Research Institute of Nigeria, Ibadan. Essential oils were extracted from the leaves, stem-barks, root-barks, fruits, peels, pod-husk and seeds of the plants using hydro-distillation method and analysed by Gas Chromatography (Flame Ionization Detector and Mass Spectrometry) techniques. The antibacterial activity of the EOs at 20 µg/mL was assayed on two Gram-positive and four Gram-negative bacteria using Microplate Alamar Blue Assay measured in UV/Visible spectrophotometer. The antioxidant activity of the EOs at 20 µg/mL was determined by radical scavenging procedure while insecticidal activity was evaluated by contact toxicity test using three grain pests. Pure compounds were isolated from methanol extract of T. cacao pod-husk by chromatographic techniques. The chemical structures of the compounds were elucidated using Infrared, Nuclear Magnetic Resonance and Mass Spectroscopic techniques. Data were analysed using descriptive statistics.
Twenty-seven EOs were obtained and their yield ranged from 0.1 to 1.2% (v/w). The major components in P. americana EOs were β-caryophyllene (12.7%; leaf), tetradecanal (31.8%; root-bark), globulol (25.4%; peel), (Z,Z)-4,15-octadecadien-1-ol acetate (21.8%; seed), tetradecanal (24.9%; stem-bark) and p-xylene (40.5%; fruit). Carica papaya EOs mainly comprised benzylisothiocyanate (89.1%; seed), octadecanol (62.5%; root), octadecanol (71.1%; stem), m-xylene (35.1%; stem-bark), heptadecanol (25.2%; fruit), phytol (21.8%; leaf), benzylisothiocyanate (71.5%; root-bark) and 9-hexadecen-1-ol (16.9%; peel). P-xylene (62.4%; fruit), p-xylene (29.9%; shoot) and tetradecanoic acid (8.6%; peel) dominated A. comosus EOs. The principal constituents in T. cacao EOs were hexadecanoic acid (78.7%; leaf), o-xylene (53.3%; seed), ledol (33.6%; pod-husk) and β-bisabolol (17.3%; stem-bark). The dominant compounds in C. albidum EOs were m-xylene (66.7%; seed), p-xylene (21.4%; seed-bark), ethylhexadecanoate (19.9%; leaf), hexadecanoic acid (14.7%; stem-bark), m-xylene (53.1%; root-bark) and hexadecanoic acid (14.7%; fruit-bark). The chemical constituents for twenty-one of the EOs of the fruit plants were obtained for the first time ever. Theobroma cacao leaf EO exhibited the highest inhibition against Gram-negative bacteria at 78.6%, while P. americana fruit and peel EOs showed the highest inhibition against Gram-positive bacteria at 69.9%. Persea americana fruit and seed EOs displayed the highest and lowest radical scavenging activity at 42.1 and 1.2%, respectively. The EOs showed activity between 0 to 20% in insecticidal assay. Column chromatography of the methanol extract of T. cacao pod-husk yielded three known triterpenes: 24-hydroxy-9,19-cycloanost-25-en-3-one, stigmast-5-en-3β-ol and ergosta-5α,8α-epidioxy-6,22-dien-3β-ol.
The EOs have antibacterial and antioxidant properties which is indicative of their potential as sources of pharmaceuticals.
Keywords: Fruit tree, Essential oils, Antibacterial activity, Triterpenes, Theobroma cacao L.
Word count: 488
NAME: FABOYA, OLUWABAMISE LEKAN
THESIS: OCCURRENCE AND DISTRIBUTION OF CARBAZOLES IN SOURCES ROCKS AND CRUDE OILS FROM TERTIARY NIGER DELTA BASIN, NIGERIA”.
SUPERVISORS: PROF. O. EKUNDAYO AND PROF. O. O. SONIBARE
ABSTRACT
The determination of hydrocarbon migration distance and charging direction is critical to the discovery of new and cost-effective hydrocarbon accumulation. However, there is dearth of information about migration processes in the Niger Delta basin. Isomers of carbazoles and benzocarbazoles have different partition coefficients between oil, water and mineral phase during migration which necessitated their use as migration markers. This study was designed to investigate the occurrence and distribution of carbazoles and benzocarbazoles in Niger Delta source rocks and crude oils in relation to source facies, thermal maturity and oil migration.
Seventy-three source rock from two wells and thirty-nine crude oil samples from thirty wells obtained from the northern and central parts of the Niger Delta Basin were analysed. The total organic carbon (TOC), genetic potential (GP), maximum temperature of hydrocarbon generation (Tmax) and production index (PI) of the rock samples were determined by Rock-Eval pyrolysis. The rock extracts obtained by Soxhlet extraction and crude oils were fractionated using column chromatography. Biomarkers distribution and isotope composition of the rock extracts and crude oils fractions were analysed by Gas Chromatography-Mass Spectrometry (GC-MS) and Elemental Analyzer-Isotope Ratio Mass Spectrometer (EA-IRMS), respectively. Biomarkers abundance was determined from integrated peak areas. The oil migration directions and distances were determined based on the plot of carbazoles concentrations on a scale map. Data were analysed using descriptive statistics and linear regression analysis.
The TOC and GP of the source rocks ranged from 0.7 to 19.4 wt% (4.3±1.3) and 0.9 to 81.9 mg/g (11.4±5.6), respectively. These mean values exceeded the minimum threshold value of 0.5 wt% TOC and 2.0 mg/g GP required for potential petroleum source rocks. Source diagnostic parameters derived from biomarker distribution showed that the rocks were formed from similar organic matter of mainly type III kerogens. The Tmax (413 to 438 oC), PI (0.02 to 0.24) and other maturity parameters from the biomarkers distribution indicated immature to early maturity stage for the source rock. The biomarkers and carbon isotope composition of oils from the same field in the Niger Delta showed that they were formed from source rocks of similar organic matter and thermal maturity. Carbazoles and benzocarbazoles distribution were found to be maturity dependent in the rocks with R2 values of 0.8 and 0.6, respectively. The carbazoles were in high abundance (1671.6 to 7901.5 μg/g) in the oils, while benzocarbazoles were present in low concentrations (0.0 to 96.0 μg/g) and below the detection limit in many of the oils. Carbazoles (C0–C2) abundances in the source rocks and oils were dominated by C2-carbazoles. The total concentrations of carbazoles decrease from 7901.5 to 1671.6 μg/g in the longest migrated oil. The variation in carbazoles distribution and abundance among the oils resulted from migration induced fractionation effect. The maximum migration distances of 1 to 37 km were estimated for the oils.
The abundance and distribution of carbazoles in oils from similar source facies and thermal maturities could be used to determine the hydrocarbon migration direction and distances in the Niger Delta basin.
Keywords: Hydrocarbon migration, Oil biomarkers, Carbazoles, Benzocarbazoles.
Word count: 496
NAME: IBEJI, COLLINS UGOCHUKWU
THESIS: COMPUTATIONAL STUDY ON POLYMERS OF UNSUBSTITUTED AND SOME SUBSTITUTED PYRROLES.
SUPERVISORS: PROF. B. B. ADELEKE AND DR. I. A. ADEJORO
ABSTRACT
Conjugated polymers which interact with biological systems have attracted much interest due to their high conductivity, stability and electronic properties. Substituted polymers of 3-methyl pyrrole-4-carboxylic acid (MPC) have been synthesised and used as components of biosensor, while unsubstituted polypyrroles were not effective for such application. However the mechanism of interaction, nature, the relative importance of dynamic and static electron correlation of polymers are not completely understood. This research was designed to study the molecular properties of substituted and unsubstittued pyrrole polymers with a view to understanding what make polymers of substituted pyrroles suitable components of biosensors.
Structures of unsubstituted Pyrrole (Py); substituted pyrroles which include 3-methyl-pyrrole-4-carboxylic acid (MPCa), 3-methyl-pyrrole-4-carboxamide (MPCam), 3-methyl-pyrrole-4-sulfonic acid (MPSO3H), 3-methyl-pyrrole-1-carboxylic acid, (MPCb), 3-methyl-pyrrole-4-carbothioic acid (MPCOSH), 3-methyl-pyrrole-4-carbaldehyde (MPCHO) and their polymers were subjected to quantum mechanical calculations. The molecular properties investigated were Energy gap (Eg), Koopman’s reactivity descriptors, Fukui function, Lowest Unoccupied Molecular Orbital (LUMO), Highest Occupied Molecular Orbital (HOMO) and thermodynamic properties. These were calculated using restricted hybrid density functional theory with Becke three, Lee Yang and Parr at 6-31G(d) basis set. The calculated Eg were extrapolated to polymer through second order-degree polynomial fit equation. Spin-flip time density functional theory and coupled cluster single and double method with 6-311++G(d,p) basis set were used to calculate Coupled Cluster operator (T1) diagnostic and Vertical Singlet-Triplet (VST) gap. All calculations were carried out using quantum mechanical softwares.
The calculated Eg of the polymers decreased with increasing chain length and the nature of substituent. The order of Eg was MPCHO > Py > MPCb > MPCa > MPCam > MPSO3H > MPCOSH, with MPCOSH having the lowest value of 1.7 eV. Substituted polypyrroles except MPCHO have stronger electron-electron interactions since electron-electron interaction is more when the Eg is low (between 1.0 and 3.0 eV). Koopman’s reactivity descriptors were within the range of -3.9 to 2.4 eV (chemical potential), 1.5 to 2.1 eV (chemical hardness) and 1.4 to 4.4 eV (electrophilicity index). Fukui function revealed a high electron density around the substituted functional groups and the LUMO and HOMO were extended over the C-C and C=C bonds. Thermodynamic parameters were enthalpy change (-4361.1 to -1045.7 kJmol-), entropy change (540.3 to 952.2 Jmol-1K-1) and free energy change (ΔG0f) (-4361.2 to -1045.8 kJmol-1) indicating spontaneous formation of the polymers. The T1 diagnostic of unsubstituted polypyrroles ranged from 0.0015 to 0.0013, while substituted polypyrroles ranged from 0.030 to 0.065. The T1 < 0.02 indicated that unsubstituted polypyrrole had dynamic correlation with single reference (closed shell), while T1 > 0.02 showed that substituted polypyrroles possessed static electron correlation with multireference (open shell) nature. The VST gap of unsubstituted polypyrroles ranged from 3.0 to 4.8 eV, while substituted polypyrroles ranged from 3.1 to 5.3 eV. The VST gap > 0 revealed that all studied systems have a singlet ground state.
Generally, the presence of substituents on polypyrrole decreased the energy gaps which led to the enhancement of their molecular properties. Their interactions with proteins make them suitable components of biosensors.
Keywords: Conjugated polymers, Substituted and unsubstituted polypyrrole, Quantum mechanical calculations, Energy gap.
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