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Structural Controls on the Geochemistry and Output of the Wells in the Olkaria Geothermal Field of the Kenyan Rift Valley

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International Journal of Geosciences 2016年第11期7卷 1299-1309页

作者： Ruth N. Wamalwa Christopher M. Nyamai Willis J. Ambusso josephat mulwa Aaron K. Waswa Kenya Electricity Generating Company—KenGen Naivasha Kenya Department of Geology University of Nairobi Nairobi Kenya School of Pure and Applied Sciences Kenyatta University Nairobi Kenya

The Olkaria geothermal field is located in the Kenya Rift valley, about 120 km from Nairobi. Geothermal activity is widespread in this rift with 14 major geothermal prospects being identified. Structures in the Greater Olkaria volcanic complex include: the ring structure, the Ol’Njorowa gorge, the ENE-WSW Olkaria fault and N-S, NNE-SSW, NW-SE and WNW-ESE trending faults. The faults are more prominent in the East, Northeast and West Olkaria fields but are scarce in the Olkaria Domes area, possibly due to the thick pyroclastics cover. The NW-SE and WNW- ESE faults are thought to be the oldest and are associated with the development of the rift. The most prominent of these faults is the Gorge Farm fault, which bounds the geothermal fields in the northeastern part and extends to the Olkaria Domes area. The most recent structures are the N-S and the NNE-SSW faults. The geochemistry and output of the wells cut by these faults have a distinct characteristic that is the N-S, NW-SE and WNW-ESE faults are characterized by wells that have high Cl contents, temperatures and are good producers whereas the NE-SW faults, the Ring Structure and the Ol’Njorowa gorge appear to carry cool dilute waters with less chloride concentration and thus low performing wells. Though the impacts of these faults are apparent, there exists a gap in knowledge on how wide is the impact of these faults on the chemistry and performance of the wells. This paper therefore seeks to bridge this gap by analysis of the chemical trends of both old wells and newly drilled ones to evaluate the impacts of individual faults and then using buffering technique of ArcGis estimate how far and wide the influence of the faults is. The data was obtained after the sampling and analysis of discharge fluids of wells located on six profiles along the structures cutting through the field. Steam samples were collected with a stainless steel Webre separator connected between the wellhead and an atmospheric silencer on the disc

关键词： Structural Controls Geochemistry Productivity Buffering Olkaria Geothermal Field Kenya

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Evaluation of the Factors Controlling Concentration of Non-Condensable Gases and Their Possible Impact on the Performance of Geothermal Systems: Case Study of Olkaria Wells in the Kenyan Rift Valley

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International Journal of Geosciences 2016年第3期7卷 257-279页

作者： Ruth N. Wamalwa Aaron K. Waswa Cristopher N. Nyamai josephat mulwa Wills J. Ambusso Kenya Electricity Generating Company—KenGen Naivasha Kenya Department of Geology University of Nairobi Nairobi Kenya School of Pure and Applied Sciences Kenyatta University Nairobi Kenya

The Olkaria geothermal field is located in the Kenyan Rift valley, about 120 km from Nairobi. Development of geothermal resources in the Olkaria area, a high temperature field, started in the early 1950s. In the subsequent years numerous expansions have been carried out with additional power plants being installed in Olkaria. These include a binary plant at Olkaria South West (Olkaria III) in 2000, a condensing plant at Olkaria North East (Olkaria II) in 2003, another binary plant at Olkaria North West (Oserian) in 2004 and finally condensing plants in the year 2014 within East production field (EPF) and Olkaria Domes (OD) areas. The total generation from this field is about 730 Mw. The study considered samples from 4 producing wells from 3 fields of the Olkaria geothermal area (OW-44 from the Olkaria East, OW-724A from the Olkaria North East, and OW-914 and OW-915 from the Olkaria Domes field). The chemical data were first analyzed using SOLVEQ. This helped in the determination of the equilibrium state of the system, the reservoir temperatures and the total moles to be run through CHILLER. The run CHILLER considered the processes that have been proven to be occurring in the Olkaria field i.e., boiling and condensing processes, fluid-fluid mixing rocks and titration resulting from water-rock interaction. The effects on gas evolution were evaluated based on the resulting recalculated gas pressures. The results indicate that the gas species are not in equilibrium with the mineral assemblages. The CHILLER evaluation shows boiling as the major process leading to the evolution of gases. OW-44 had the least gas concentrations, arising from the considered reservoir processes due to degassing, and near surface boiling, besides the removal of NH3, H2 and H2S are through the reaction with steam condensate. The gas breakout is most likely in OW-914 and least in OW-44. The study proposes different reservoir management strategies for the differen

关键词： Geothermal Energy Gases and Their Impact on Well Perfomance Olkaria Wells Kenyan Rift Valley

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Investigation of tropical coastal forest regeneration after farming and livestock grazing exclusion

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Journal of Forestry Research 2019年第5期30卷 1873-1884页

作者： Elly josephat Ligate Chengzhen Wu Can Chen College of Life Sciences Fujian Agriculture and Forestry UniversityFuzhou 350002People’s Republic of China Wuyi University Fuzhou 350002People’s Republic of China College of Forestry Fujian Agriculture and Forestry UniversityFuzhou 350002People’s Republic of China

It is critical to understand how forests regenerate after the exclusion of human induced disturbances because the regenerating species drive the renewal of resources and ecosystems,which in turn support human beings locally and *** study of forest regeneration was conducted in the tropical coastal forest ecosystems of Tanzania at Uzigua Forest Reserve(24,730 ha)in the Pwani *** collected data from adult trees in 47 sampling plots(25×25 m)randomly established in closed forest sites(control)and in sites disturbed by farming and livestock *** and seedling data were collected and analyzed in 2×2 m nested *** in the closed forest had higher mean basal area and volume for adult trees than those in sites disturbed by farming and livestock *** in sites disturbed by farming had the highest Shannon–Wiener index for seedlings and saplings,followed by closed forest and livestock grazed *** plots and farmed plots had higher Simpson’s index for seedlings and saplings than in grazed *** in farmed and livestock-grazed sites had a higher Simpson index for adult trees than in closed *** of seedlings and saplings was highest in closed forest sites,followed by farmed and livestock grazed *** disturbed by farming had higher equitability for adult trees than in livestock-grazed and closed ***,plots disturbed by farming and grazing had a higher importance value index for seedlings than in closed *** in closed forests had higher sapling importance values than in farmed and grazed ***,plots in closed forest had a higher importance value for adult trees than in farmed and grazed *** differences in tree species subcategories of regeneration across land-use indicates that farming and livestock grazing disturbances create heterogeneous microhabitats,which positively or negatively affects regeneration capacity of species after exclusion.

关键词： Coastal forests Disturbance Diversity Regeneration

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Evaluation of tropical coastal land cover and land use changes and their impacts on ecosystem service values

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Ecosystem Health and Sustainability 2018年第8期4卷 14-30页

作者： Elly josephat Ligate Can Chen Chengzhen Wu College of Life Sciences Fujian Agriculture and Forestry UniversityFuzhouFujianPR.China Department of Biosciences Sokoine University of AgricultureMorogoroTanzania College of Forestr Fyjian Agriculture and Forestry UniversityFuzhouP.R.China

Understanding about land cover and land use(LCLU)changes,as well as the associated impacts on ecosystem service values(ESV)is extremely important in the management of coastal ecosystems ***,this study assessed temporal LCLU changes,the underlying socio-economic drivers and dynamics of ESV in the coastal zone of *** LCLU data for 2000 and 2010 were from the Globe Land 30 mapping products at 30-meter spatial resolution developed by National Geomatics Center of China,while 2016 images were produced from Landsat *** of images was done from Landsat TM/ETM+for 2000,2010,and 2016 years complemented with MODIS and Normalized Difference Vegetation Index time series,and Chinese HJ *** categories and ecosystem service coefficients were used to compute ESV on each LCLU *** 2000 and 2016,farmland,shrub land,waterbody,and artificial surface expanded while forest,grazing land,and wetlands *** ESV increased on farmland,shrub land,and waterbody,while the decline was found on forest,grazing land,and *** ESV and the total population ratios declined from$80.4,63.8,and$46.0 million in 2000,2010,and 2016,*** positive correlation was on LCLU change and ESV,population and households in crop farming,livestock keeping,and bioenergy *** pressure and socioeconomic activities have amplified the degradation of the coastal *** not abetted,there is a danger of further impairments on these *** advise to regulate population and socioeconomic activities to avoid more negative impacts of coastal LCLU change.

关键词： Coastal ecosystems ecosystem service values land cover land use

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Invasion of <i>Cestrum aurantiacum</i>Lindl. in Kenya

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Journal of Environmental Protection 2018年第6期9卷 671-690页

作者： josephat Makokha Ministry of Environment and Forestry Kenya Forest Service Resources Elgeyo Marakwet County Cherangani Forest Station Kapcherop Kenya

Many forest ecosystems in Kenya are at risk from the invasion of exotic plant species that pose numerous threats like decreasing biodiversity, deteriorating ecosystem processes and degrading their services. They also affect human, other animal health and various angles of the general economy. Cestrum aurantiacum Lindl. is a species with invasive reputation having been reported with very high biological success rating and has been noted in parts of Kenya in proportions that raise concerns. It has negative effects on other plants and animal species function and diversity. These impacts have been recorded in Kenya and elsewhere in this review, I synthesized data from studies that have examined the taxonomy of Cestrum aurantiacum, how this species become part of the ecosystem in Kenya and its ecological and economic impacts. I sourced relevant articles from the internet using keywords relating to the taxonomy, impacts and reports of invasive species and narrowed to records from different parts of Kenya. In this review, I looked across twenty-seven studies, on Cestrum aurantiacum in Kenya and went ahead to review one hundred and thirteen other articles for expanded discussion. Species data in published articles from different parts of Kenya were used as georefences to model overall species distribution which was noted to lie between Mt Kenya, Mt Elgon-Nandi hills and Cherangani hills. It was clearly established that there are major adverse effects associated with species. First, it can change native ecosystem processes such as nutrient cycle or hydrology and contribute significant role on the decrease of native species. A primary risk of Cestrum aurantiacum is that when this species alters the biodiversity, ecosystems are transformed into new configurations with unpredictable consequences to humans and other wildlife in totality. Despite the few positive applications of cestrum species, these can’t compensate for the enormous detrimental consequences associated with the

关键词： Cestrum aurantiacum Lindl Invasive Species Kenya Ecosystem Impacts

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Performance of Experimental Bio-Digestion for Pathological and Biodegradable Waste Management at Mwananyamala Regional Referral Hospital Tanzania

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Journal of Environmental Protection 2020年第10期11卷 838-847页

作者： Anicetus Honest josephat Saria Ministry of Health Community Development Gender Elderly and Children Dodoma Tanzania Department of Environmental Studies The Open University of Tanzania Dar es Salaam Tanzania

The aim of the experimental trial was to evaluate the performance of the designed placenta and other pathological waste digester system on the effectiveness of digesting the placenta and its energy recovery (bio-gas) process in Mwananyamala Referral Hospital in Dar es Salaam. A 32 m3 digester is constructed in Mwananyamala Referral Hospital, one inlet of which is to attach to the toilet of maternity ward, where the placentas are flushed directly into the digester, while food waste is fed through another inlet. The slurry of the digester is sent to a sewer/septic tank to avoid further handling. Most fraction of the waste fed into the digester is food waste. In general with the amount of 25.6 ± 4.5 kg/day of placenta and 83.1 ± 14.7 kg/day of food waste, 2.5 m3/d gas was produced. The pH throughout the study period (that is of 18 weeks) was found to be consistent within the range of 6.3 to 8.0, while the pressure ranged from 5 kPa - 33 kPa. Average temperature within the digester was found to be 30.3°C. With all the favorable condition, gas production was consistent and hence the system has been successful in management of the pathological waste along with the production of gas as an alternative source of energy for the hospital.

关键词： Bio-Digester Biogas Placenta Hydraulic Retention Time

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Estimation of Different Categories of Healthcare Waste Generated at Two Different Hospital Categories in Four Hospitals in Dar es Salaam City

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Journal of Environmental Protection 2020年第10期11卷 872-888页

作者： Honest Anicetus josephat Saria Hussein Mohamed Ministry of Health Community Development Gender Elderly and Children Dodoma Tanzania Open University of Tanzania Department of Environmental Studies Dar es Salaam Tanzania Muhimbili University of Health and Allied Sciences Dar es Salaam Tanzania

This study aims to estimate the quantity of healthcare waste categorically generated in four different healthcare in Dar es Salaam city namely, Muhimbili National Hospital, Mwananyamala Regional Referral Hospital, Temeke Regional Referral Hospital and Ilala Regional Referral Hospital to evaluate the quantities of medical waste generated based on their level and capacity. Waste was collected in different categories of non-infectious, sharps, infectious, infectious plastics, and pathological waste which were measured daily for fourteen (14) consecutive days in all hospitals by using a weighting scale and observational checklist to document related waste management information and the assessment of the healthcare waste generation in each hospital. The average general healthcare waste generation rate per healthcare ranges from 298.9 kg/day to 1554.4 kg/day. The high fluctuation in general medical waste was established to be attributed to specialization difference between one hospital to the other, and the large number of in-patients and out patients between hospitals. The overall average sharps waste generation rate was established to range from 8.5 ± 2.7 - 13.9 ± 1.8 kg/day. Higher values of sharps waste generated observed at Muhimbili hospital are due to emergency cases referred to from other hospitals located within the city and from the surrounding districts and other regions of the country. The results from this study, raise alarm to hospital administrators, and other health stakeholders working in related fields to give special attention and priority in setting a related share in their budgets for proper management of medical waste in their health facilities.

关键词： Healthcare Dar es Salaam Infectious Waste Environmental Hazards Medical Waste Hospital Solid Waste

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Spectrum of Filamentous Fungi from Sputum of Tuberculosis Relapse and Retreatment Patients in Tuberculosis Reference Facilities

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Open Journal of Medical Microbiology 2020年第4期10卷 190-203页

作者： josephat Tonui Marianne Mureithi Walter Jaoko Christine Bii Department of Medical Microbiology School of Medicine University of Nairobi Nairobi Kenya Kenya Medical Research Institute Centre for Microbiology Research Mycology Unit Nairobi Kenya

Background: Fungal infections represent a significant cause of morbidity and mortality among immunocompromised individuals. Pulmonary fungal infection may be missed or misdiagnosed as tuberculosis (TB) hence complicating management of these patients. The current study reports the spectrum of filamentous fungi isolated from sputum of TB relapse and retreatment cases at selected reference facilities in Kenya. Methods: A total of 340 sputum samples collected during the period of June 2018 to June 2019 were subjected to mycological investigations. The samples were mucolysed and inoculated on sabourauds dextrose agar (SDA) and incubated at 30°C for 7 days and checked daily for fungal growth. Moulds were identified by macroscopic and microscopic morphological features and the species were confirmed by sequencing. Results: The diversity of fungi out of the 340 sputum samples analyzed was as follows;16% (n = 53) were positive for moulds with Aspergillus species being the predominant constituting 68 % (n = 36). Among the Aspergilli, A. flavus and A. niger were the most frequently isolated adding up to 23%, (n = 12) and 15% (n = 8) respectively. Additionally, Paecillomyces variotii (9%, n = 5), Scedosporium aspiospermum (6%, n = 3), Mucor racemosus (8%, n = 4) and Penicillium spp. (9%, n = 5) were also recovered. Conclusion: The isolated fungi represented potential respiratory pathogens that could be responsible for persistent TB like symptoms despite treatment that could be misdiagnosed as relapse requiring treatment. Fungal investigation of all presumptive TB relapse cases should be advocated before treatment. This will reduce unnecessary retreatment, delayed antifungal intervention and unwarranted morbidity and mortality associated with misdiagnosis.

关键词： Filamentous Fungi Tuberculosis Relapse Retreatment Spectrum

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Dynamic modelling and PFL-based trajectory tracking control for underactuated cable-driven truss-like manipulator

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Journal of Central South University 2021年第10期28卷 3127-3146页

作者： DING Shu-chen PENG Li QIAO Shang-ling LIU Rong-qiang josephat Bundi School of IoT Engineering Jiangnan UniversityWuxi 214122China State Key Laboratory of Robotics and System Harbin Institute of TechnologyHarbin 150001China Center for Control Theory and Guidance Technology Harbin Institute of TechnologyHarbin 150001China

In recent years,an innovative underactuated robot was developed,named as underactuated cable-driven trusslike manipulator(UCTM),to be suitable in aerospace ***,there has been strong consensus that the stabilization of planar underactuated manipulators without gravity is a great challenge since the system includes a second order nonholonomic constraint and most classical control methods are not suitable for this kind of ***,the complexity of the truss-like structure results in tremendous difficulty of computational complicacy and high nonlinearity during dynamic modelling in addition to controller *** is paramount to solve these difficulties for UCTM's future *** solve the above difficulties,this paper presents a dynamic modelling method for UCTM and a trajectory tracking control method based on partial feedback linearization(PFL)that fulfills the control goal of moving UCTM from its original position to a desired position by tracking a given trajectory of the joint *** achieve this,a model equivalent method is proposed to make UCTM equivalent with a three-link manipulator in the sense of dynamic *** the Lagrangian equation combined with complex vector method is proposed in the dynamic modelling process of UCTM,which simplifies the derivation *** on the established dynamic model,a coordinate transformation method is proposed to transform the control force matrix into the conventional form of an underactuated system,so that the control force can be separated from the unactuated *** PFL method in combination with the LQR control method is then proposed to realize the targets that the joint angles can track given desired *** experiments are conducted to verify the correctness and effectiveness of the proposed methods.

关键词： underactuated robot trajectory tracking control partial feedback linearization non-linear control

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坦桑尼亚Rungwe自然保护森林火灾对植物Morella salicifolia遗传多样性及遗传结构的影响

坦桑尼亚Rungwe自然保护森林火灾对植物Morella salicifolia遗传...

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作者： Josephine Karumuna josephat 中国科学院大学(中国科学院武汉植物园)

学位级别：硕士

火的历史可以追溯到志留纪时期,它极大地影响了全球生态系统的构成,尤其是对植物。火对生物多样性的影响,从群落,物种水平到整个生态系统,都已经得到了广泛的研究。生物遗传多样性及遗传结构是森林生态系统中生物多样性的重要组成部分,... 详细信息

火的历史可以追溯到志留纪时期,它极大地影响了全球生态系统的构成,尤其是对植物。火对生物多样性的影响,从群落,物种水平到整个生态系统,都已经得到了广泛的研究。生物遗传多样性及遗传结构是森林生态系统中生物多样性的重要组成部分,可评估其适应生物和非生物干扰能力的大小,然而,目前火对生物遗传多样性和结构的影响的研究仍十分有限。东非坦桑尼亚的野火发生率较高,并呈逐年上升趋势,但在坦桑尼亚几乎没有进行过森林火灾影响其森林生态系统的研究,尤其是对植物遗传多样性的影响研究更是少之又少。坦桑尼亚Rungwe自然森林保护区是整个坦桑尼亚发生山火事件最多的地区。而在坦桑尼亚大多数遭受山火的山区生态系统中,Morella salicifolia是已被记录为耐火物种,本研究选择Rungwe自然保护区内遭受山火及未经历山火的区域为对照研究区域,以该山区代表植物***为研究对象,基于本研究所开发的微卫星分子标记开展两对照区域不同斑块的遗传多样性及遗传分化模式研究。本研究首先在研究区域内选择五个实验样点,分别标记为高火频率(Bukanda和Ilundo站点),中等火灾频率(Ndengasombyo和Kabwe站点)和天然未燃烧过的森林(Kasemba站点),每个样点再选择不同的斑块(种群);然后,使用本研究所筛选的8对新开发的微卫星分子标记对来自总共17个代表种群的288个样本进行基因分型,评估其遗传多样性,观察并预期杂合性,等位基因数和有效等位基因数;此外,通过STRUCTURE聚类分析及邻接法建树,推断出种群之间的联系;最后,对可能存在的瓶颈效应进行评估。研究结果如下:(1)选择30对所开发的微卫星引物,对来自不同斑块的***样品进行基因分型,检验所选微卫星引物的多态性,结果显示所检验的30对微卫星引物中8对表现出稳定的扩增和高多态性,这8对引物后续被应用于研究不同火烧频率的居群的遗传多样性及遗传分化。(2)采用8对具多态性微卫星引物,我们对所有288个样本进行了遗传变异分析,发现所研究的种群具有高水平的遗传多样性(平均值He=0.655)和低的种群分化,这表明山火很可能未导致M salicifolia的遗传多样性降低。进一步对五个研究地点进行了比较分析,观察到具有较高遗传多样性的种群为Bukanda(He=0.696),Ilundo(He=0.66),Ndengasombyo(0.66)和Kabwe(0.64),而Kasemba地点的遗传多样性最低(He=0.62)。因此,火灾易发地区遗传多样性较高,表明山火可能促进了居群间的分化。(3)STRUCTURE分析将17个种群分成三个组,其中组1为高火频率的种群(种群1-5),而组2和3为轻度燃烧和未燃烧的种群的混合。同样地,UPGMA树状图将17个种群聚类成三个主要分支,经常发生火灾的区域形成比其他两个类别更加明显的分支,结果进一步支持森林火灾影响了*** 遗传结构的结论。最后在瓶颈效应分析未检测到瓶颈事件,三个类型的研究地区中等位基因频率的分布为L形,表明这些地区在近期居群是稳定的。BayesAss软件对植物在种群间迁移率估计发现了近期迁移事件,从Ndengasombyo 到 Kasemba(0.3172)的迁移率最高,从 Bukanda 到 Kasemba的迁移率最低(0.0073),这一结果显示了 Bukanda相较于其他居群具有较高的分化。本研究率先对山火频发的坦桑尼亚进行了山火对其植物遗传多样性的影响的究,相关的研究为进一步探讨坦桑尼亚山火对植物多样性的影响提供了案例。

关键词：森林火灾遗传多样性 Morella salicifolia 遗传结构 Myricacea

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