Browsing by Author "Amasi, Aloyce"

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Assessing the Impacts of Land Use and Climate Changes on River Discharge towards Lake Victoria
(MDPI, 2023-05-08) James, Renatus; Amasi, Aloyce; Wynants, Maarten; Nobert, Joel; Mtei, Kelvin; Njau, Karoli
The Lake Victoria basin’s expanding population is heavily reliant on rainfall and river flow to meet their water needs, making them extremely vulnerable to changes in climate and land use. To develop adaptation and mitigation strategies to climate changes it is urgently necessary to evaluate the impacts of climate change on the quantity of water in the rivers that drain into Lake Victoria. In this study, the semi-distributed hydrological SWAT model was used to evaluate the impact of current land use and climate changes for the period of 1990–2019 and assess the probable future impacts of climate changes in the near future (2030–2060) on the Simiyu river discharge draining into Lake Victoria, Northern Tanzania. The General Circulation Model under RCPs 4.5, 6.0 and 8.5 predicted an increase in the annual average temperature of 1.4 ◦C in 2030 to 2 ◦C in 2060 and an average of 7.8% reduction in rainfall in the catchment. The simulated river discharge from the hydrological model under RCPs 4.5, 6.0 and 8.5 revealed a decreasing trend in annual average discharge by 1.6 m3/s from 5.66 m3/s in 2019 to 4.0 m3/s in 2060. The increase in evapotranspiration caused by the temperature increase is primarily responsible for the decrease in river discharge. The model also forecasts an increase in extreme discharge events, from a range between 32.1 and 232.8 m3/s in 1990–2019 to a range between 10.9 and 451.3 m3/s in the 2030–2060 period. The present combined impacts of climate and land use changes showed higher effects on peak discharge at different return periods (Q5 to Q100) with values of 213.7 m3/s (Q5), 310.2 m3/s (Q25) and 400.4 m3/s (Q100) compared to the contributions of climate-change-only scenario with peak discharges of 212.1 m3/s (Q5), 300.2 m3/s (Q25) and 390.2 m3/s (Q100), and land use change only with peak discharges of 295.5 m3/s (Q5), 207.1 m3/s Q25) and 367.3 m3/s (Q100). However, the contribution ratio of climate change was larger than for land use change. The SWAT model proved to be a useful tool for forecasting river discharge in complex semi-arid catchments draining towards Lake Victoria. These findings highlight the need for catchment-wide water management plans in the Lake Victoria Basin.
Assessment of Potentially Toxic Metals in Fish from Lake Manyara, Northern Tanzania
(Springer US, 2023-09) Sawe, Shovi; Amasi, Aloyce; Wynants, Maarten
Elemental tracer concentrations of copper, lead, nickel and zinc, were assessed in the muscles of Oreochromis amphimelas and Clarias gariepinus from Lake Manyara, Tanzania, to evaluate their safety to consumers, specifcally humans. Results revealed that no elemental concentrations exceeded the FAO permissible levels, indicating fsh from all sites are safe for human consumption. However, based on the highest found concentration of Pb, we recommend a maximum consumption of 2.2 kg of fsh from Lake Manyara per week. No signifcant diferences were observed in the metal concentrations between the two fsh species, suggesting there is no bioaccumulation in the food chain. Moreover, no signifcant diferences were found between fsh landing sites, indicating there are no regions in the lake with higher pollution. These fndings indicate that PTM concentrations have not increased to toxic levels due to increased mobilisation from the catchment. Continued monitoring of potential toxic metal concentrations in fsh is recommended due to endorheic nature of Lake Manyara and increasing anthropogenic activities in its catchment area.
Capacity building to strengthen nuclear security in the safety, operation and utilization of research reactors in Africa
(Egyptian Society of Nuclear Sciences and Applications (ESNSA), 2023-01-01) Amasi, Aloyce
Research reactors are indispensable for developing countries to benefit from the many quiet applications of nuclear science and technology, particularly in health services, food security, water resources, education and training and the development of nuclear technology. However, only eleven of the world's 220 operational research reactors are operational on the African continent. This means that only 3% of the world's nuclear research reactor capacity has access to 17.2% of the world's population in Africa. In this regard, there is a major gap in the nuclear power sector in Africa that needs to be filled for the economic development of developing countries, including the advent of micro and small modular reactors. Since research reactors encompass a wide range of facilities that involve different aspects and security considerations compared to other facilities in the nuclear industry, the nuclear security culture for personnel who work or are expected to work in nuclear reactors is essential for compliance with nuclear safety requirements. In this context, capacity building in the areas of security, operation and use of research reactors is important in order to strengthen the nuclear safety of this installation in developing countries. This paper addresses the need for human resource capacity building in Africa, particularly in Tanzania.
Drivers, Impacts and Mitigation of Increased Sedimentation in the Hydropower Reservoirs of East Africa
(MDPI, 2021-06-16) Amasi, Aloyce; Wynants, Maarten; Mahene, William; Mtei, Kelvin
Hydropower reservoirs are essential for the climate-neutral development of East Africa. Hydropower production, however, is threatened by human activities that lead to a decrease in water storage capacity of reservoirs. Land use/land cover and climatic changes are driving accelerated soil erosion in semi-arid East Africa, which ultimately increases reservoir sedimentation and decreases energy production. Sediment delivery dynamics at the catchment scale are complex, involving the interaction of multiple factors and processes on different spatial and temporal scales. A lack of under standing of these processes and their interactions may impede the efficiency of sediment mitigation and control strategies. A deep understanding of the processes of erosion and connectivity of the land to river channel, as well as storage of eroded material within hillslopes and floodplains, and sediment accumulation in the reservoirs supports selection of future dam locations and sustainable management of reservoirs. The sediment budget approach can provide such a holistic perspective by accounting for the various sediment sources, transport, sinks, and redistribution when the sediment is routed through that catchment. Constructing sediment budgets is challenging, but the potential for integrating a number of different techniques offers new opportunities to collect the required information. In East Africa, the spatial planning of dams is mainly dominated by political and financial motives, and impacts of land use and climate on the sediment transport dynamics are not adequately considered. Production of sediment budgets under different scenarios of land use and climate change should be an essential step when deciding the location and management strategies for dams. Selection of new hydroelectric reservoir sites must consider long-term scientific data on climate change, and the sediment budget components for sustainable land management planning, hydropower sustainability.
Evaluating Soil Carbon as a Proxy for Erosion Risk in the Spatio-Temporal Complex Hydropower Catchment in Upper Pangani, Northern Tanzania
(MDPI, 2021-10-15) Amasi, Aloyce; Wynants, Maarten; Kawala, Remigius; Sawe, Shovi; Blake, William; Mtei, Kelvin
Land use conversion is generally accompanied by large changes in soil organic carbon (SOC). SOC influences soil erodibility through its broad control on aggregate stability, soil structure and infiltration capacity. However, soil erodibility is also influenced by soil properties, clay mineral ogy and other human activities. This study aimed to evaluate soil organic carbon as proxy of soil erosion risk in the Nyumba ya Mungu (NYM) catchment in Northern Tanzania. Soil organic carbon (SOC) was measured by an AgroCares scanner from which the soil organic matter (SOM) was derived using the conversional van Bemmelen factor of 1.72. A regression analysis performed between the measured loss on ignition (LOI) values and SOM from the AgroScanner showed a strong positive correlation in all land use classes (LOIFL R 2 = 0.85, r = 0.93, p < 0.0001; LOICL R 2 = 0.86, r = 0.93, p = 0.0001; LOIGL R 2 = 0.68, r = 0.83, p = 0.003; LOIBS R 2 = 0.88, r = 0.94, p = 0.0001; LOIBL R 2 = 0.83, r = 0.91, p = 0.0002). This indicates that SOC from the soil scanner provided a good representation of the actual SOM present in soils. The study also revealed significant differences in the soil aggregate stability (WSA) and SOM stock between the different land use types in the Upper Pangani Basin. The WSA decreases approximately in the following order: grassland > forest land > bare land > cultivated > bush land. Land use change can thus potentially increase the susceptibility of soil to erosion risk when SOC is reduced. Since WSA was directly related to SOM, the study indicates that, where formal measurements are limited, this simple and inexpensive aggregate stability test can be used by farmers to monitor changes in their soils after management changes and to tentatively assess SOC and soil health.
Investigation of sediment source and delivery dynamics in an east African hydropower reservoir using sediment tracing technology
(NM-AIST, 2022-03) Amasi, Aloyce
This study aimed to reconstruct the sedimentation rates over time and identify the changing sources of sediment in a major hydropower reservoir in Tanzania, the Nyumba ya Mungu (NYM). The study also aimed to evaluate the soil carbon as a proxy for erosion risk in the catchment. Fallout 210Pb measurements were used to estimate age of sediment deposits and broad changes in sedimentation rates were reconstructed. Sedimentation peaks were cross referenced to geochemical profiles of allogenic and autogenic elemental constituents of the sediment column to confirm a causal link. Finally, geochemical fingerprinting of the sediment cores and potential sources were compared using a Bayesian mixing model (MixSIAR) to attribute the dominant riverine and land use sources to the reservoir. Reservoir sedimentation generally increased from 0.1 g cm−2 yr−1 in the lower sediment column to 1.7 g cm−2 yr−1 in the most recent deposits. These results correlated to changes in allogenic and autogenic tracers. The model outputs revealed that the Kikuletwa River with 60.3%, was the dominant contributing tributary to the total reservoir sediment and the Ruvu River 39.7%. However, downcore unmixing results indicated that the latest increases in sedimentation is moistly driven by an increased contribution from the Ruvu River. Cultivated land (CU) was shown to be the main land use source of riverine sediment, accounting for 38.4% and 44.6% in Kikuletwa and Ruvu rivers respectively. The “soil slake test” method for soil aggregate stability in water (WSA) indicated a significant decrease in soil aggregate stability in cultivated land in comparison to other land use types which indicates that the unsustainable land use changes can thus potentially increase the susceptibility of soils to erosion by water when soil organic matter (SOM) is reduced. This study has explicitly demonstrated that the integration of sediment tracing and -dating tools can be used for quantifying the dominant source of sediment infilling in East African hydropower reservoirs. The results underscore the necessity for catchment-wide management plans that target to limit soil erosion and reduce further impact to rivers and reservoirs to maintain and enhance food, water and energy security in Eastern Africa.
Novel use of portable gamma sensors to rapidly assess soil status and recovery in degraded East African agro-pastoral land
(Copernicus Publications, 2024-05-01) Blake, Will; Amasi, Aloyce; Kelly, Claire; Lewin, Shaun; Mkilema, Francis; Msale, Furaha; Mtei, Kelvin; Munishi, Linus; Nasseri, Mona; Ndakidemi, Patrick; Taylor, Alex
Soil resources in East African agro-pastoral lands are being rapidly depleted by erosion, threatening food, water and livelihood security. Here we explore the utility of innovation in portable gamma sensors to rapidly assess soil health via proxy measurement of soil organic matter (SOM) providing visual information that enables local communities to take action to mitigate land degradation before it reaches a critical tipping point. This study is grounded in the outcomes of an integrated, interdisciplinary approach to support co-design of land management policy tailored to the needs of specific communities and places. The work has shown that limitations to delivering socially acceptable and environmentally desirable solutions can be addressed by (1) closing fundamental gaps between the evidence bases of different disciplines and indigenous knowledge and (2) addressing, through participatory action, the implementation gap between science-based recommendations, policy makers and practitioners. Key adaptations implemented in the study region include new bylaws to enforce altered grazing regimes, grassland recovery and tree planting. Against this context, we report a first trial of a portable gamma spectrometer to rapidly assess spatial variability in soil health using total and radionuclide-specific gamma emissions from naturally occurring radioisotopes as a proxy for soil organic matter. A Medusa MS-700 portable gamma spectrometer was deployed on foot across a landscape of known variability in soil health status encompassing a spectrum of impact from severely gullied soil/subsoil, heavily grazed surface soil, recovered grazed soil (ca 3 years exclusion of livestock) and conservation agriculture plots. In-situ field results showed a clear gradient in raw total gamma count rate with sample areas in each zone at 1200 ± 100, 980 ± 70, 814 ± 60 and 720 ± 60 counts per second across the above four areas respectively. Correlations between radioisotope-specific gamma spectrometer data and organic matter (range 15 ± 2 to 30 ± 3 g kg-1 from degraded land to conservation agriculture) were evaluated to explore the dominant control on sensor response. Further comparisons are made to major and minor element geochemistry. Feedback from local Maasai community members who participated in the research further underpins the value of the sensor as a qualitative assessment tool e.g. using visual colour coding in the live data feed in the field. Quantitative comparison of sensor and laboratory data will permit development of protocols for airborne (drone) gamma spectrometry that offers community scale evaluation of grazing pressure on soil health to inform livestock future exclusion policy in common land prone to soil erosion.
The phosphorus negotiation game (P-Game): first evaluation of a serious game to support science-policy decision making played in more than 20 countries worldwide
(Springer Nature Link, 2025-01-02) Haneklaus, Nils; Kaggwa, Mary; Misihairabgwi, Jane; El-Magd, Sherif; Ahmadi, Naima; Brahim, Jamal; Amasi, Aloyce; Kovács, Andrea; Bartela, Łukasz; Bellefqih, Hajar; Beniazza, Redouane; Bernas, Jaroslav; Bilal, Essaid; Mtei, Kelvin
Environmental negotiations are complex, and conveying the interaction between science and policy in traditional teaching methods is challenging. To address this issue, innovative educational approaches like serious gaming and role-playing games have emerged. These methods allow students to actively explore the roles of different stakeholders in environmental decision-making and weigh for instance between sometimes conflicting UN Sustainable Development Goals or other dilemmas. In this work the phosphorus negotiation game (P-Game) is for the first time introduced. We present the initial quantitative and qualitative findings derived from engaging 788 students at various academic levels (Bachelor, Master, PhD, and Postdoc) across three continents and spanning 22 different countries. Quantitative results indicate that female participants and MSc students benefitted the most significantly from the P-Game, with their self-reported knowledge about phosphorus science and negotiation science/practice increasing by 71–93% (overall), 86–100% (females), and 73–106% (MSc students in general). Qualitative findings reveal that the P-Game can be smoothly conducted with students from diverse educational and cultural backgrounds. Moreover, students highly value their participation in the P-Game, which can be completed in just 2–3 h. This game not only encourages active engagement among participants but also provides valuable insights into the complex environmental issues associated with global phosphorus production. We strongly believe that the underlying methodology described here could also be used for other topics.
Radon Mass Exhalation Rates of Selected Building Materials in Tanzania
(Journal of Environment and Earth Science, 2015) Amasi, Aloyce; Mtei, Kelvin; Dinh, Chau; Jodlowski, Pawel
This study aimed at determining the mass radon exhalation rate of Tanzania Portland cements and their raw materials for assessment of the radiological hazards due to use of those materials in residential construction. The radon mass exhalation rate was measured by closed chamber coupled with the Pylon AB5  and varied from 0.3 to 13 %. The estimated indoor radon concentrations and annual effective dose for tightly closed standard room were within the safe limits of radon potential health hazards of 600 Bq m-3 for dwellings and 1500 Bq m-3 for workplaces recommended by International Commission on Radiological Protection (ICRP).
Rare earth elements and uranium in Minjingu phosphate fertilizer products: Plant food for thought
(ELSEVIER, 2024-08-01) Haneklaus, Nils; Mwalongo, Dennis; Lisuma, Jacob; Amasi, Aloyce; Mwimanzi, Jerome; Bituh, Tomislav; Ćirić, Jelena; Nowak, Jakub; Ryszko, Urszula; Rusek, Piotr; Maged, Ali; Bilal, Essaid; Bellefqih, Hajar; Qamouche, Khaoula; Brahim, Jamal; Beniazza, Redouane; Mazouz, Hamid; Merwe, Elizabet; Truter, Wayne; Kyomuhimbo, Hilda; Brink, Hendrik; Steiner, Gerald; Bertau, Martin; Soni, Raghav; Patwardhan, Ashwin; Ghosh, Pushpito; Kivevele, Thomas; Mtei, Kelvin; Wacławek, Stanisław
Minjingu phosphate ore is Tanzania's sole domestic supply of phosphorus (P). The ore contains medium to high concentrations of naturally occurring P2O5 (20–35 %) and relevant concentrations of uranium and rare earth elements (REEs) are also suspected to be present. Currently, neither uranium nor REEs are recovered. They either end up in mine tailings or are spread across agricultural soils with fertilizer products. This work provides a first systematic review of the uranium and REE concentrations that can be expected in the different layers of Minjingu phosphate ore, the way the ore is presently processed, as well as a discussion on alternative processing pathways with uranium/REE recovery. The study analyzed ten distinct Minjingu phosphate ore layers, four mine tailings, and five intermediate and final mineral fertilizer products from the Minjingu mine and processing plant located in northern Tanzania. The results confirm that the uranium concentrations and to a lesser degree, the REE concentrations are indeed elevated if compared to concentrations in other phosphate ores. The study does not identify a significant risk resulting from this. The development of techno-economic solutions for more comprehensive utilization of Minjingu ore is, however, strongly encouraged and suggestions on such processes are provided.
Reconstructing the Changes in Sedimentation and Source Provenance in East African Hydropower Reservoirs: A Case Study of Nyumba ya Mungu in Tanzania
(MDPI, 2021-08-08) Amasi, Aloyce; Wynants, Maarten; Kawalla, Remegius; Sawe, Shovi; Munishi, Linus; Blake, William; Mtei, Kelvin
This study aimed to reconstruct the sedimentation rates over time and identify the changing sources of sediment in a major hydropower reservoir in Tanzania, the Nyumba ya Mungu (NYM). Fallout 210Pb measurements were used to estimate age of sediment deposits and broad changes in sedimentation rates were reconstructed. Sedimentation peaks were cross referenced to geochemical profiles of allogenic and autogenic elemental constituents of the sediment column to confirm a causal link. Finally, geochemical fingerprinting of the sediment cores and potential sources were compared using a Bayesian mixing model (MixSIAR) to attribute the dominant riverine and land use sources to the reservoir together with changes through recent decades. Reservoir sedimentation generally increased from 0.1 g cm−2 yr−1 in the lower sediment column to 1.7 g cm−2 yr−1 in the most recent deposits. These results correlated to changes in allogenic and autogenic tracers. The model output pointed to one of two major tributaries, the Kikuletwa River with 60.3%, as the dominant source of sediment to the entire reservoir, while the other tributary, Ruvu River, contributed approximately 39.7%. However, downcore unmixing results indicated that the latest increases in sedimentation seem to be mainly driven by an increased contribution from the Ruvu River. Cultivated land (CU) was shown to be the main land use source of riverine sediment, accounting for 38.4% and 44.6% in Kikuletwa and Ruvu rivers respectively. This study explicitly demonstrated that the integration of sediment tracing and dating tools can be used for quantifying the dominant source of sediment infilling in East African hydropower reservoirs. The results underscore the necessity for catchmentwide management plans that target the reduction of both hillslope erosion reduction and the sediment connectivity from hillslope source areas to rivers and reservoirs, which will help to maintain and enhance food, water and energy security in Eastern Africa.
Tracing the dominant sources of sediment flowing towards Lake Victoria using geochemical tracers and a Bayesian mixing model
(Springer Nature, 2023-02-14) James, Renatus; Amasi, Aloyce; Wynants, Maarten; Nobert, Joel; Mtei, Kelvin; Njau, Karoli
Purpose Lake Victoria has been increasingly silting over the past decades, impacting water quality and loss of biodiversity. Sediment control strategies require information on the relative and absolute contributions of sediment from different sources. However, to date, there is no continuous monitoring of sediment flux or water quality in any of the tributaries, prohibiting an assessment of the scale of the problem. The aim of this study was to trace the dominant sources of riverine sediment using geochemical fingerprinting, thereby generating a knowledge base for improving land management and reducing sediment yields in Simiyu River catchment, one of the main contributing rivers to Lake Victoria. Materials and methods Geochemical tracer concentrations were analyzed in transported sediment from the main river and two tributaries (riverbed sediments) and from soils in five dominant land use types (agricultural land, bush land, forest land, channel banks, and main river banks). Dominant sources to the Simiyu main river sediment were attributed using the Bayesian MixSIAR model. Results and discussion The mixing model outputs showed that the Simiyu tributary was the dominant source of sediment to the Simiyu main river with 63.2%, while the Duma tributary accounted for 36.8%. Cultivated land was shown to be the main land use source of riverine sediment, accounting for 80.0% and 86.4% in Simiyu and Duma sub-tributaries, respectively, followed by channel banks with 9.0% in both sub-tributaries. Direct unmixing of the Simiyu main river sediment to the land use sources yielded 64.7% contribution of cultivated land and 26.5% of channel banks. Conclusion The demonstrated application of sediment source tracing provides an important pathway for quantifying the dominant sources of sediment in the rivers flowing towards Lake Victoria. Eroded soil from agricultural areas is the biggest contributor to transported sediment in the Simiyu River. This information is vital for the design of catchment wide man agement plans that should focus on reducing soil erosion and sediment delivery from farming areas to the river networks, ultimately supporting both food security and water quality in the Lake Victoria Basin.
Uranium Dissemination with Phosphate Fertilizers Globally: A Systematic Review with Focus on East Africa
(MDPI, 2024-01-09) Mwalongo, Dennis; Haneklaus, Nils; Lisuma, Jacob; Mpumi, Nelson; Amasi, Aloyce; Mwimanzi, Jerome; Chuma, Furaha; Kivevele, Thomas; Mtei, Kelvin
Growing concern has been expressed about uranium (U) accumulation in agricultural soils caused by the long-term application of mineral fertilizers. More than 80% of naturally occurring U transfers from phosphate rock (PR), the raw material used in mineral fertilizer production, to phosphorus (P) fertilizers. These fertilizers are then distributed on agricultural soils, where the U could accumulate over time and become a risk to the environment. The objective of this work was to review the reported content of U in P fertilizers, its potential dispersion in soils, and its uptake by plants in different countries in the world as reported in the literature. The articles for this systematic review were selected from the Scopus database published between 2003 and 2022. The preferred reporting items for systematic reviews and meta-analyses (PRISMA) protocol were used. A total of 54 articles were assessed based on the standard inclusion and exclusion criteria. U concentrations in P fertilizers, agricultural soil dissemination, and plant uptake for available data were obtained and assessed. In order to compare a set of related data from the collected articles, box and whisker plots showing the distribution of U in P fertilizers are presented by region. The results from the reviewed articles show that the U concentrations in P fertilizer were in the range of 0.1–653 mg kg−1. Interestingly, Minjingu P fertilizers from Tanzania, which are used in six East African countries, showed the highest U concentrations (159 to 653 mg kg−1, average 390 mg kg−1). The reported U concentrations for these fertilizers are, in fact, comparable to those of conventional low-grade uranium deposits mined in Namibia and elsewhere. Additionally, approximately 96% of the reviewed articles indicate that fertilized soil has higher U concentrations than non-fertilized soils, hinting at a measurable effect of mineral fertilizer use. The review recommends U extraction during mineral fertilizer production so that potential environmental risks can be reduced and U resources that would otherwise be lost can be recovered and used to substitute conventional U mining elsewhere.