Application of Vertical Electrical Soundings to Characterize Aquifer Potential in Ota, Southwestern Nigeria

A knowledge of hydrogeophysical parameters of aquifers is essential for groundwater resource assessment, development and management. Traditionally, these parameters are estimated using pumping test carried out in boreholes or wells; but this is often costly and time consuming. Surface geophysical measurements can provide a cost effective and efficient estimates of these parameters. In the present work, geoelectrical resistivity data has been used to characterize and evaluate the aquifer potential at Covenant University, Ota, southwestern Nigeria. Some thirty-five vertical electrical soundings (VESs) were conducted using Schlumberger array with a maximun half-current electrode spacing (AB/2) of 240 m. The geoelectrical parameters obtained were used to estimate longitudinal conductance and transverse resistance of the delineated aquifer. Both the longitudinal conductance and transverse resistance, which qualitatively reflects the hydraulic properties of the aquifer, indicate that the aquifer unit is characterized with high values of hydraulic parameters; consequently a good groundwater potential. Thus, groundwater resource development and management in the area can be effectively planned based on these parameters

Effect of Storage on Microbial and Sensory Qualities of Packaged Yam-Cassava “Poundo” Flour

Microbial load and Sensory quality of packaged yam-cassava poundo flour during storage were studied. Yam flour (YF) and cassava flour (CF) were mixed at different proportions to produce yam-cassava poundo flour and packaged using High Density Polyethylene (HDPE) and Polypropylene sack (PP) respectively.  The samples were HDPE 100%YF, HDPE 90%YF: 10%CF, HDPE 85%YF: 15%CF, HDPE 80%YF: 20%CF and 100%YF, 90%YF: 10%CF, 85%YF: 15%CF and 80%YF: 20%CF. The samples were stored at ambient temperature (32 ± 2oC) and relative humidity (76 ± 3%) for 24 weeks and were subjected to microbiological and sensory tests at 4 weeks interval. Results showed that the total plate count of sample (80% YF: 20%CF) packaged in HDPE was the lowest (4.9 x 104 cfu/g) while that of sample (100% YF) packaged in PP was the highest (9.4 x 104 cfu/g) at the end of the storage period. Fungal counts increased in all the packaged samples, as storage period increased. The lowest fungal counts (3.7 x 104sfu/g) were recorded in HDPE 80%YF: 20%CF, this is significantly different  (p<0.05) from the value obtained in PP 100% YF which was the highest fungal counts obtained (9.6 x 104sfu/g). A bacterial species (Bacillus subtilis) and two fungal species (Aspergillus niger and Fusarium solani) were isolated and enumerated. Data obtained from sensory test (colour, aroma, texture and overall acceptability) decreased throughout the storage period but 80%YF: 20%CF packaged in HDPE was more acceptable. The findings of this study indicate that yam-cassava poundo flour from the blend of 80%YF: 20%CF packaged in HDPE is less susceptible to microbes and more acceptable in terms of sensory qualities during a storage period of 24 weeks. &nbsp

Natural Radioactivity and Hazards in Soil Samples in Alade Community, Southwestern Nigeria

The concentrations of natural radionuclides in Alade community, Ado-Odo/Ota Local Government Area were determined using gamma ray spectrometer comprising a 7.6 cm x 7.6 cm Nal(TI) detector coupled to a multichannel analyser for spectral analysis. A total of 20 soil samples were collected from different locations in Alade community, Ado-Odo/Ota Local Government, Ogun state, Nigeria. Data were analysed using descriptive statistics. The activity concentration obtained were in ranges of 45.62 ± 2.53 Bq/kg to 665.25 ± 35.11 Bq/kg with mean value of 352.34 ± 18.67 Bq/kg for 40K, 2.32 ± 0.47 to 54.56 ± 6.20 Bq/kg with mean value of 19.86 ± 2.56 Bq/kg for 238U and 4.34 ± 0.28 Bq/kg to 23.10 ± 1.40 Bq/kg with mean value of 14.22 ± 0.87 Bq/kg for 232Th. The study evaluated radiation hazard indices, the mean values obtained were, 64.55 ± 5.05 Bq/kg for Radium equivalent activity (Raeq), 32.86 ± 2.53 nGyh-1 for Absorbed Dose Rate (D), 40.30 ± 3.10 µSvy-1 for Annual Effective Dose Equivalent (AEDE), 0.18 ± 0.01 for External Hazard Index (Hex) and 0.22 ± 0.02 for Internal Hazard Index (Hin). These calculated hazard indices were well below their permissible limit. The results obtained for the mean activity concentrations values from 20 soil samples from Alade community, revealed that 40K, 238U and 232Th values were below the United Nations Scientific Committee on the Effects of Atomic Radiation recommended international limits of 370Bq/kg and within the tolerance level indicating minimal radiological health burden on the Alade community and its environment

Experimental Evaluation of 3D Geoelectrical Resistivity Imaging using Orthogonal 2D Profiles

Numerical evaluation of 3D geoelectrical resistivity imaging was conducted using orthogonal set of 2D pseudo-sections generated over two synthetic models, horst and trough models. The models represent geological environment that simulates a typical weathered profile and refuse dump site in a crystalline basement complex, respectively. Different arrays including Wenner-alpha (WA), Wenner-beta (WB), Wenner-Schlumberger (WSC), dipole-dipole (DDP), pole-dipole (PDP), and pole-pole (PP) arrays were used for the data generation. The 2D apparent resistivity data were collated to 3D data set and then inverted using a full 3D inversion code. The effectiveness of the technique for 3D resistivity imaging as well as the imaging capabilities of the selected arrays is evaluated. The observed anomaly effect and normalized model sensitivities of the arrays indicate that DDP and PDP arrays are more sensitive to the 3D features, while WSC show moderate sensitivity to 3D features. Field example in which the technique was applied in a 3D geoelectrical resistivity imaging for engineering site investigation in the crystalline basement complex of southwestern Nigeria is also presented

Storm-time variation of the horizontal and vertical components of the geomagnetic fields and rate of induction at different latitudes

The paper presents the hourly mean variation of horizontal (H) and vertical (Z) components of the geomagnetic field and the rate of induction DH/DZ at different latitudes during magnetic storm of 20 March 2001 and 1 October 2001. The results of the analysis revealed that at high latitude stations greater than 60�, the reduction in DH component was noticed after the noon time while other stations less than 60� experienced reduction of H in the morning time during the geomagnetic storm. Large amplitude of DH and DZ were exhibited during the daytime over the equatorial zone, the amplitude decreases from mid latitudes to the dip equator during the nighttime. The daytime enhancement of DH at AAE, BAN and MBO suggest the presence of a strong eastward directed current which comes under the influence of electrojet. There were strong positive and negative correlations between ring current (DR) and horizontal component of the magnetic field DH. The effect of rate of induction is more significant at high latitudes than lower latitudes, during the geomagnetic storm. More enhancement in rate of induction occurred at nighttime than daytime. This result may be from other sources other than the ionosphere that is magnetospheric process significantly contributes toward the variation of induction

ECONOMIC RETURNS AND TECHNICAL EFFICIENCY IN CASSAVA-BASED FARMING SYSTEMS IN YEWA COMMUNITIES OF OGUN STATE, NIGERIA

This study analyzed the economic returns and technical efficiency in cassava-based farming systems in selected communities in the Yewa axis of Ogun State. Data were collected from 120 cassava farmers in a two-stage sampling technique. The data were analyzed using descriptive statistics, budgetary technique, and the stochastic frontier model. The study showed majority of the cassava farmers in the study area to be male, ageing, less formally educated but well experienced in farming. Result of the enterprise’s budgetary analysis showed that cassava sole-cropping generated a total gross margin (GM) of N236,051 and net farm income (NFI) of N233,862 as against the values of N474,084 and N470,168 respectively, for cassava intercrop program during the same production year. From the findings, sole cropping has total factor productivity (TFC) value of 0.46, producing more cassava yield from each unit of the input used than in intercrop program with a TFC value of 0.1.  Land and labour inputs were critical determinants of cassava output in the study area, while the involvement of younger folks in the cassava farming enterprise and attainment of higher education will significantly improve the technical efficiency of the cassava farmers. An average technical efficiency level of 79 percent was obtain for cassava production systems, implying a 21% gap for it to reach maximum production potentials. It was recommended that the policy formulation that will enhance access of the cassava farmers to more cultivable land, improved educational opportunities (through adult literacy education) and labour saving device/technology will assist to rapidly transform the cassava production systems in the study area. This will also help them increase their profitability and efficiency level in cassava production.     &nbsp

Distribution of radionuclides and assessment of risk exposure to the miners on a kaolin field

Mining of kaolin deposits are common in Nigeria without considering the background radiation in such environment and the health risks it might pose on the miners. In this study, in-situ measurements of the naturally occurring radionuclides were carried out with the aim of determining the distribution of these radionuclides on the mining field and estimation of the hazard indices exposure risks (γ- and α-radiation risks) to the miners. The study was achieved with the aid of gamma ray detector Super-Spec (RS-125) and global positioning system. The detector used has ability to measure activity concentrations of 238U, 232Th and 40K and gamma doses. For the purpose of this study, only the concentrations of the three radionuclides were considered. For each location, measurements were taken four times, while its mean value was estimated for better accuracy. In all, nineteen locations were occupied in order to cover the study area. Basic kriging method was adopted for the production of spatial distribution of these radionuclides and their corresponding γ- and α-radiation hazard indices. The mean values of 238U, 232Th and 40K are 46.7, 71.8 and 108.7 Bq kg-1 , respectively. When compared to the global standard, it was revealed that 238U and 232Th are greater than the global standard, while 40K fall below the permissible limit. The γ- and α-radiation exposure risks estimated revealed that the mean values of Iγ and Iα are 0.6 and 0.2 respectively. Though the estimated γ- and α-radiation indices showed that the kaolin field is safe for the miners, periodic check is required in order to monitor the rate at which these natural primordial radionuclides (238U and 232Th and their progenies) are being enhanced

Distribution of radionuclides and assessment of risk exposure to the miners on a kaolin field

Mining of kaolin deposits are common in Nigeria without considering the background radiation in such environment and the health risks it might pose on the miners. In this study, in-situ measurements of the naturally occurring radionuclides were carried out with the aim of determining the distribution of these radionuclides on the mining field and estimation of the hazard indices exposure risks (γ- and α-radiation risks) to the miners. The study was achieved with the aid of gamma ray detector Super-Spec (RS-125) and global positioning system. The detector used has ability to measure activity concentrations of 238U, 232Th and 40K and gamma doses. For the purpose of this study, only the concentrations of the three radionuclides were considered. For each location, measurements were taken four times, while its mean value was estimated for better accuracy. In all, nineteen locations were occupied in order to cover the study area. Basic kriging method was adopted for the production of spatial distribution of these radionuclides and their corresponding γ- and α-radiation hazard indices. The mean values of 238U, 232Th and 40K are 46.7, 71.8 and 108.7 Bq kg-1 , respectively. When compared to the global standard, it was revealed that 238U and 232Th are greater than the global standard, while 40K fall below the permissible limit. The γ- and α-radiation exposure risks estimated revealed that the mean values of Iγ and Iα are 0.6 and 0.2 respectively. Though the estimated γ- and α-radiation indices showed that the kaolin field is safe for the miners, periodic check is required in order to monitor the rate at which these natural primordial radionuclides (238U and 232Th and their progenies) are being enhanced

Radionuclide analysis of drinking water in selected secondary schools of Epe local government area, Lagos state, Nigeria

A total number of 20 water samples were collected from different locations, spreading over selected twenty public secondary schools in the Local government area of Epe in South Western, Nigeria. Ten well water samples were collected from selected rural school area and ten borehole water samples in urban schools area. The concentrations of natural radionuclides were determined using gamma ray spectrometer comprising a 7.6 cm x 7.6 cm Nal (TI) detector coupled to a multichannel analyser for spectral analysis. Data were analysed using descriptive statistics. The activity concentrations from boreholes and wells with depths ranging between 17.68 and 38.1 metres were randomly sampled and determined from 20 locations in public schools in Epe LGA. The activity concentration obtained were in the ranges of (38.3 – 292.8) Bq/L with mean value of 13.4 + 10.8 Bq/L for 40K, 1.2 – 36.7 Bq/L with mean value of 6 + 1.4 Bq/L for 238U and 1.2 – 11.7 Bq/L with mean value of 4.5 + 1.2) Bq/L for 232Th. The values obtained for the mean activity concentrations for the radionuclides from the 20 boreholes and well water samples in Epe, revealed that 40K, 238U and 232Th values were below the United Nations Scientific Committee on the Effects of Atomic Radiation recommended international limits of 370Bq/L and within the tolerance level indicating minimal radiological health burden.Keywords: Borehole water, Epe, Health hazard, Natural radionuclide, Secondary school, Well water