Energy Solution

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Human Exposure and Associated Risks Due to Natural Radioactivity and Heavy Metals In Ortum, West Pokot County, Kenya
(Kenyatta University, 2021) Wanjala, Felix Omonya
The background radiation in air, the activity concentration of selected radionuclides in soil and rock samples, the radon and thoron concentration in selected mud houses and elemental concentration of heavy metals in soil and water samples from Ortum, West Pokot County in Kenya was determined in this study. Ortum was chosen due to the presence of granitic and silicon rocks which are associated with high levels of background radiation. The activity concentration of 238U, 232Th and 40K in soil was determined using the High Purity Germanium detector (HPGe) and the average values were 40 ± 3 Bq/kg, 56 ± 4 Bq/kg and 425 ± 19 Bq/kg respectively which is within the world average range. The activity concentration of 238U and 232Th in soil samples reduced with increasing depth while that of 40K increased slightly with increase in depth. The average activity concentration of 238U, 232Th, and 40K in soil samples was higher than in the rock samples implying that the soils originate from other regions. The average outdoor absorbed dose rate in air at 1 m above the ground was found to be 112 ± 30 nGy/h which is almost double the world average value of 60 nGy/h. The average Raeq was 153 ± 49 Bq/kg which is less than the limit of 300 Bq/kg and the external hazard indices (Hex) and the internal hazard index (Hin) were 0.41 ± 0.13 and 0.52 ± 0.16 respectively which is below the limit values of unity (>1). This implies that soil and rocks in Ortum poses low radiological risk and they can therefore, be used for construction of houses, industrial and agricultural purposes. The average radon and thoron concentration in mud houses was determined using RADUET detector and found to be 40 ± 19 Bq/m3 and 54 ± 30 Bq/m3 respectively which is below the ICRP recommended lower and upper limit of 100 Bq/m3 and 300 Bq/m3 respectively. The elemental concentration of Ni, Cu, Zn, Pb, K, Ca, Fe, Ti, Mn, Rb, Sr, Zr and Nb in soil was determined using the Energy dispersive X-Ray Fluorescence Spectrometer (EDXRF) and found to be below the WHO recommended limits. The mean concentration of trace elements Pb, Zn and Cu in soil samples reduced with increasing depth while that of Ni increased with increasing depth. The Geoaccumulation Index (Igeo), Potential Ecological Risk Index (Ei) and synthesized potential ecological risk index (Er) were evaluated and found to be -0.40, 4.92 and 19.69 respectively. The results show that soil from Ortum is moderately polluted and the risk associated with exposure to heavy metals in soil is low. The concentration of Ni, Cu, Pb, Zn, Ag, Al, As, Ba, Ca, Cd, Co, Cr, Fe, K, Mg, Mn, Mo, Na and Se in water samples was determine using Agilent-5100 Inductively Coupled Plasma-Optical Emission Spectrometry (ICP-OES). The elemental concentrations in water samples from the two rivers was found to be lower than the WHO permissible limits, except for calcium (Ca) which was higher than the permissible levels in borehole water. Hence, water from rivers in Ortum is unpolluted and fit for use except for borehole water which has high calcium levels. The lifetime cancer risk due to background radiation (LTCRBR) and elemental pollution in water (LTCREP) was found to be 1.47 x 10-3 and 1.92 x 10-6 respectively which is within the recommended safe limits. The lifetime cancer risk due to exposure to background radiation evaluated using RESRAD programme for a resident farmer in Ortum was found to be 0.011 or 1.1%. This implies that cancer risk due to exposure to background radiation in Ortum is low.
Oil and Gas Exploration and Sustainable Environmental Management in Oil Block 13t South Lokichar Basin, Turkana County, Kenya
(Kenyatta University, 2020) Mugendi, Kariuki David
Commercial oil and gas was discovered in Kenya in 2012. Few academic studies have been done on the effects of the mentioned discovery to the environment.The oil and gas resources are expected to transform the economic wellbeing of the locals and the nation at large.However,land degradation, environmental pollution and socio-economic problems have always ensued oil and gas exporation ventures globally.This study aimed at determining the effects of oil and gas exploration on biophysical and socio-economic environments in Oil Block 13T South Lokichar Basin,Turkana South-subcounty and come up with sustainable environmental management strategies in the oil fields.The specific objectives were to review,constitutional,policy,legal and institutional framework governing environmental management in the backdrop of oil and gas exploration in Kenya and determination of oil and gas exploration effects on biophysical and socio-economic environments in the study area.The study adopted an exploratory mixed method research design.Purposive non-probability sampling was applied in determining the study area,sampling the boreholes,sampling the drill cutting samples and sampling the key informants.Probability sampling was used in identifying the manyattas,households and the villages for conducting focused group discussions.Questionnaires,documents review, photography,observation,landsat satellite imageries acquisition and analysis,laboratory analysis using XRF and AAS machines, for drill cuttings and water samples respectively to determine the levels of physicochemical properties were the data collection methods used.The questionnaires were coded into the Statistical Package for Social Sciences version 20.0 software and Excel 10.0.Descriptive and inferential statistics were used in data analysis.The study identified several gaps in the existing environmental policy and legal framework in relation to the oil fields environmental management coupled with poor enforcement of the laws by the relevant agencies.In addition, the study observed a decline in NDVI from 1 to 0.4329 for the rainy season and 0.4107 to 0.1217 jfor the dry season between 2006 and 2017 with a p-value of 0.0091< 0.05 on paired T-test implying a significant change on vegetation cover.The area under forest, shrubland and grassland had significantly reduced at 90% confidence interval with a,value of,0.0718,0.0738 and 0.0609.The drill cuttings whose levels of detected heavy metals concetration for Manganese(Mn),Copper(Cu),Nickel(Ni),Iron(Fe),Calcium(Ca),Lead(Pb),were;1.58,0.21,0.05,70.4,62.57,4.58 respectively were incorrectly being managed onsite.Mn, Feand Pb concentration levels in the drill cuttings were above the WHO and USEPA recommended standards for the reserve pit.The levels of Fe,Ni,Turbidity and Total Dissolved Solids of the sampled water from the study area,were all above the prescribed WHO standards.The study noted improved socio-economic characteristics, physical and social infrastructures in the study area.70% of the respondents felt that water provision, health facilities, education facilities, employment opportunities had improved since oil and gas exploration began with a Cohen kappa coefficient of agreement of 0.608.However,challenges such as population influx,land displacement,lack of adequate engagement of the locals, gender inequalities with a Cronbach’s Alpha of reliability of 0.735, health challenges of the locals and increased number of conflicts cases since 2012 with a statistical p-value of 0.005< 0.05 were noted.The study recommends enforcement of the existing environmental legislations and development of oil specific environmental laws,adoption of advanced oil drilling and drill waste management technologies, as well as participatory environmental management approach in the oil fields.
Positron-Impact Excitation of the Lowest Autoionizing State in Rubidium Atom using Distorted Wave Method
(2014-05) Marucha, Alex Magembe
Many calculations on atomic collisions and scattering processes have been performed on electron impact excitation of the lowest autoionizing state of rubidium, but not much attempt has been made with positron impact which is of equally fundamental importance and is receiving attention nowadays with the availability of improved positron beam experiments. So, in this study, total cross-sections, differential cross-sections, lambda parameter, R parameter and the alignment parameter for positron impact excitation of the lowest autoionizing state of rubidium have been calculated using Distorted Wave method. The wave functions used are the Roothan Hatree Fock double zeta and multi zeta wave functions due to Clementi and Roetti. Variations in distortion potential have been made such that the static potential of the initial state of rubidium atom is used as the initial channel distortion potential and a linear combination of static potentials of the initial and final states as the final channel distortion potential to check its effect on cross- sections. Numerical calculations have been done using a modified DWBA1 FORTRAN computer program which was originally made for hydrogen atom. The results for positron impact excitation of the lowest autoionizing state of rubidium have been analyzed and compared with experimental and theoretical results for positron and electron impact excitation of the same state available in literature. From the comparison of the results, it is seen that in general the electron impact excitation cross section results are higher than the positron impact excitation cross section especially near excitation threshold energy. This can be attributed to the exchange process which takes place in the case of electron impact and not in the case of positron impact and also due to larger interaction between the projectile and the target in case of electron impact than in case of positron impact. It is also found from the alignment parameter results that the integral cross section results for m=0 level are larger compared to m=1 level for impact energies up to about 500 eV beyond which integral cross-sections for the magnetic sublevel m=1 become greater. The lambda parameter indicates that more particles are scattered towards m=0 for electron impact compared to positron impact excitation near threshold energy. R parameter results have been calculated to account for phases of scattered amplitudes in the collision process
Quantifying Greenhouse Gas Emissions and Carbon Stocks in Maize-Soybean Cropping Systems in Siaya County, Kenya
(Kenyatta University, 2020) Karanja, Anne Njeri
As climate change continues to threaten ecosystems’ functions, agriculture remains one of the major source of greenhouse gas (GHG) emissions that are responsible for global warming. The major GHG in agriculture are; carbon dioxide (CO2), nitrous oxide (N2O) and methane (CH4). Unfortunately, agriculture is also one of the most affected sectors by climate change. There is therefore need to reduce emissions by adopting agricultural practices with mitigation potential. This is by enhancing soil carbon sequestration to offset emissions, or reducing emissions while safeguarding crop yields. However, little is still known about GHG quantities and intensities that major cropping systems in Kenya emmit. Site specific studies on GHG emissions to establish interventions for mitigation of climate change and enhanced crop production is therefore of essence. The objective of this study was to examine the effect of reduced tillage, crop residue retention and use of controlled release urea (CRU) in maize-soybean cropping systems on GHG emissions, soil N mineralization, organic carbon stocks and yields. Field measurements were carried out in a 13 year old researcher-managed trial in Siaya county, Kenya between March 2016 and January 2017. Four treatment combinations: ZT M-S NU (reduced tilage+maize soybean rotation+normal urea), ZT M-S CRU (reduced tillage+maize soybean rotation+controlled release urea), ZT M/S (reduced tillage+maize soybean intercrop without urea), CT M-S NU (Conventional tillage+maize soybean rotation+normal urea) were tested. The treatments were laid out in a randomized complete block design. DAYCENT model was used to simulate soil carbon, N2O emissions and maize yields. Results showed that daily fluxes of N2O ranged between -0.5-26 g ha-1 d-1 and -2-10 g ha-1 d-1 in the long and short rainy seasons respectively. Cumulatively, N2O emissions were between 0.2 - 0.7 kg ha-1 and 0.2 - 0.4 kg ha-1 in the long and short rainy seasons respectively. In the long rainy season, ZT M-S CRU had significantly higher N2O fluxes than the other treatments (P=0.05). In the short rainy season there were no significant effects of treatment on N2O emissions. In the long rainy season, CO2 daily fluxes were between 9 to 42 kg ha-1 while the cumulative emissions ranged between 2.5 to 2.8 t ha -1. In the short rainy season daily CO2 fluxes ranged between 6 to 30 kg ha-1 while cumulative emissions were 1.8- 2.5 t ha -1. There was no significant effect of treatment on CO2 emissions. Methane emissions were largely negative, and did not differ significantly among treatments. Yield was significantly low for ZT M/S but N2O emission intensities were not significantly different among treatments. DAYCENT simulated soil carbon and maize yield within the same ranges observed by measurement. N2O emissions by DAYCENT were higher during the peak of the seasons, but were comparable with observed measurements later in the seasons. Even though the long rainy season had higher N2O and CO2 emissions, the difference was not significant. These results indicate that emissions in the study area were low.These results further indicate that the current soil management practices in Siaya County influence GHG emissions, and the higher emissions observed with ZT M-S CRU in the long rainy season calls for further investigations of the effect of CRU on N2O emissions. The lower emission intensity shown by ZT M/S despite having lower yield points to the need of evaluating cropping systems for climate change mitigation and adaptation. These results indicated that DAYCENT model can be used to simulate soil carbon and yield but not N2O emissions in the study area.
Relativistic Distorted Wave Approach to Electron Impact Excitation of Heavy Rare Gases Using a Complex Potential
(Kenyatta University, 2022) Marucha, Alex Magembe
Data on excitation of rare gases is important in the study of plasma displays, lighting and lasers.From literature, both relativistic and non-relativistic computations performed on electron impact excitation of low-lying states of rare gases often fail to give satisfactory agreement with available experimental data mostly at low impact energies and at intermediate scattering angles. With this in view, in the present study, we have applied relativistic effects in a fully-relativistic distorted-wave approach to excitation of the lowest lying resonance states of argon, krypton and xenon gases, by modifying the electron-atom interaction distortion potential in such a way that the complex part, the absorption potential, and the real part, which includes an energy dependent polarization potential, exchange and electrostatic potentials, form the complex distortion potential used in calculating radial wavefunctions. The atomic wavefunctions are constructed in the multi-configuration Dirac-Fock approach by modifying the general-purpose relativistic atomic structure code GRASP for numerical procedures. In this study, the WKB approximation is used to compute the free continuum electron wavefunctions which are then used in computing scattering cross sections and angular parameters using our program RDWBA1. Present results from this study predict that use of a complex distortion potential in the relativistic approach to excitation of argon, krypton and xenon generally lowers integral cross sections as impact energies of the incident electron increases, compared to those obtained using real distortion potentials only. For argon, the effect of the absorption potential, which accounts for loss of flux into other open scattering channels is more visible at electron impact energies above 50 eV, while for krypton, absorption becomes more dominant above 100 eV. For xenon, which is the heaviest of the three, absorption in the distortion potential generally has minimal effect on cross sections at impact energies below 50 eV then significantly improves these results when compared with experiments as kinetic energy of the electron increases. Furthermore, for all the rare gases under investigation, it is the energy dependent polarization potential adopted, that plays a major role in improving shapes of cross-sections at low and near threshold impact energies, where available distorted-wave methods fail to give satisfactory results when compared to experiments. We have also obtained angular correlation parameters lambda to predict the magnetic sublevel responsible for most excitations, and Stokes parameters to predict the polarization of the emitted photon during atomic decay. Cross section results obtained from this study are in good agreement with experiments at all impact energies under investigation, therefore it will be interesting to see how these cross sections vary when this present approach is used to investigate excitation of the metastable states of rare gases with both electron and positron impact.
Simulating Pressure Distribution of a Horizontal Well in an oil Reservoir Subject to Single Edged and Bottom Constant Pressure
(Kenyatta University, 2022-12) Mutisya, Mutili Peter
In this study the pressure distribution in an oil reservoir with a horizontal well is investigated. A horizontal well with single-edged and constant bottom pressure is outlined. A reservoir bounded with two constant pressure boundaries, like an edge and bottom water, requires that the production engineer should adhere diligently to a production schedule, developed by a reservoir engineer, for clean oil production to be possible. This means that arbitrary production practices through selection of production rates could lead to production of these external fluids. This can mar the economics of the project. Production schedules or plans show acceptable rates, well design and production time that can guarantee only clean oil production. In this study, pressure behaviour of a horizontal well drilled and completed in a reservoir subject to with simultaneous single-edged and bottom water drives is investigated in detail. All possible flow periods or patterns that can be exhibited by the well are determined. Fluid flow in oil reservoirs in real time is governed by a heterogenous diffusivity equation, which describes reservoir pressure as a function of reservoir, fluid and wellbore properties. To solve this unsteady state problem, Green’s functions were deployed to represent the boundaries of the reservoir selected for study. The Green’s functions selected are for flow from start of transient to late time, when all the external boundaries are felt. Newman product rule was used to derive a dimensionless pressure expression for the reservoir system oil flow. The source of pressure transient was production throughout. All the resulting integrals were performed numerically. MATLAB programming was used to plot the curves by applying spline functions interpolation. Influence of reservoir, fluid and wellbore properties on reservoir pressure was investigated in real time. To assist interpretation, dimensionless pressure derivatives were also computed. Near wellbore problems, like skin and wellbore storage, which affect well performance only at very early time, were not considered in the study. From the results, 𝑃𝐷 and 𝑃𝐷 ′ vary directly with ℎ𝐷 and inversely as 𝐿𝐷. The 𝑃𝐷 ′ gradually reduces to zero when 𝑃𝐷 begins to exhibit a constant trend. 𝑃𝐷 ′ vary inversely with ℎ𝐷 and 𝑦𝑒𝐷 at all flow times. The number of flow periods varies with reservoir size, well length and production time. The time at which the 𝑃𝐷 ′ starts to exhibit a downward trend is the external fluid breakthrough time. The breakthrough time is affected by well design. Longer wells exhibit delayed breakthrough time because of lower pressure drawdown associated with increased well length. If production rate is sustained for any particular well design, the well will completely water-out. Finally, infinite conductivity 𝑥𝐷 = 0.732 and uniform flux condition do not really affect 𝑃𝐷 and 𝑃𝐷 ′ at early time.

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