Browsing by Author "Mwaijengo, Grite"

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Assessment of liquid radioactive waste characteristics and management practices in nuclear medicine facilities in Tanzania
(Journal of Ecological Engineering, 2026) Kamaze, Didat; Jande, Yusufu; Amasi, Aloyce ; Mwaijengo, Grite
Residual liquids waste generated during nuclear medicine procedures may contain radioactive materials and toxic chemicals that pose potential risks to the environment and public health. This study assessed the physicochemical properties, radionuclide activity, heavy metal concentrations and Management practices of liquid radioactive waste generated at two major nuclear medicine facilities in Tanzania: Ocean Road Cancer Institute (ORCI) and Bugando Medical Centre (BMC). A cross-sectional study was conducted over eight days at ORCI and ten days at BMC. Approximately 735 mL of liquid waste was collected at each facility and combined into three composite samples per site. Radiation levels, physicochemical parameters, and heavy metal concentrations were measured using the APHA Standard Methods for the Examination of Water and Wastewater. Heavy metal contamination was evaluated using the Contamination Factor, Degree of Contamination, Pollution Load Index, Heavy Metal Pollution Index, and Metal Index. Results were compared against World Health Organization (WHO) guideline limits.Statistical differences between facilities were assessed using the Mann-Whitney U test, while radionuclide decay was modeled using exponential regression to estimate half-lives. The results indicated rapid radionuclide decay, with estimated half-lives of 0.62, 0.83, and 0.96 days for Tc-99m and Ga-68. Ambient radiation levels ranged from 0.15-0.75 µSv/h at ORCI and 0.38-0.85 µSv/h at BMC, with eleveted readings observed in generator storage areas, hot laboratories, and gamma camera rooms. No significant differences in radiation levels were observed between the two facilities (W = 11, p = 0.296). ORCI effluents were acidic (pH 3.84 ± 0.67) with higher conductivity and TDS, while BMC effluents were near neutral (pH 7.09 ± 0.21) and exibted higher salinity and turbidity.Concentrations of Cd , Ni , and Pb exceeded WHO limits at both sites, while Zn concentrations ware significantly higher at BMC (5.98 ± 0.072 mg/L) compared to ORCI (0.87 ± 0.012 mg/L, p < 0.001). In conclusion, radiological risks associated with liquid waste from nuclear medicine facilities appear to be adequetely controlled; however, chemical and heavy metal contamination remains a notable environmental concern. Radiological risks associated with liquid waste from routine monitoring, wastewater treatment practices, and strengthened regulatory oversight measures are recommended to mitigate these hazards.
Fish Diversity in Relation to Littoral Habitats in Three Basins of Lake Kivu (East Africa)
(MDPI, 2023-09-12) Kisekelwa, Tchalondawa; Alimasi, Wilondja; Mazambi, Lutete; Mwaijengo, Grite; Hyangya, Lwikitcha; Muzungu, Heri; Joyeuse, Mudagi; Lubala, Amani; Kubota, Musombwa; Wüest, Alfred; Muvundja, Amisi; Masilya, Mulungula
In total, 28 of the 29 fish species reported from the Lake Kivu basin occur in the littoral zone of the lake, but information about their structure, occurrence, and the habitats affecting their distribution is largely lacking. The lake’s inshore area is poorly heterogenous, with rock and macrophyte habitats representing the major habitats. The lack of heterogeneity in the habitats is probably an important factor influencing species richness, abundance, and the association between the species and habitats. We evaluated the fish diversity, abundance, and habitat parameters across 14 sites representing the major habitats of the lake, using data collected between April 2018 and October 2019. We calculated Hull and Jaccard indices and applied uni- and multivariate statistical approaches to the collected data. We identified 18 fish species in the lake. In the north, 17 species were found, with high abundance in rocky sites but low abundance in sandy habitats. In the south, 15 species were reported. We identified 12 species in the Ishungu Basin where the site with rock substrate had high abundance and 13 species in the Bukavu Basin with weak species richness and low abundance across degraded sites. Lamprichthys tanganicanus, a non-native species, was abundant in rocky (north) and macrophyte sites (south). Sand, rock, conductivity, depth, dissolved oxygen, and water transparency were significant parameters that could explain the fish distribution in the north while dissolved oxygen, vegetation cover, depth, and conductivity were significant in the south. A monitoring programme of the fish fauna in Lake Kivu is needed.
Fish predation affects invertebrate community structure of tropical temporary ponds, with downstream effects on phytoplankton that are obscured by pesticide pollution
(Elsevier Ltd., 2024-02-14) Kafula, Yusuph; Mataba, Gordian; Mwaijengo, Grite; Moyo, Francis; Munishi, Linus; Vanschoenwinkel, Bram; Brendonck, Luc; Thoré, Eli
Aquatic biota of tropical temporary ponds typically experience a wide range of stressors that can drive the structure and dynamics of natural communities. Particularly in regions with intense agricultural activity, aquatic biota may not only experience predation pressure but also stress from pesticides that inadvertently enter the ponds. We increasingly understand how these different sources of stress affect classic model taxa under controlled laboratory conditions, but how predators and pesticides may jointly affect pond invertebrate communities is still unclear, particularly for tropical systems. Here, we conducted an outdoor mesocosm experiment to study how fish predation combined with exposure to an environmentally relevant concentration of the commonly used insecticide cypermethrin (0.8 ng/L) affects the structure of invertebrate communities, and its potential effects on leaf litter decomposition and invertebrate grazing efficiency as measures of ecosystem functioning. A total of seven invertebrate taxa were recorded in the mesocosm communities. Fish predation effectively lowered the number of invertebrate taxa, with fish mesocosms being dominated by high densities of rotifers, associated with lower phytoplankton levels, but only when communities were not simultaneously exposed to cypermethrin. In contrast, cypermethrin exposure did not affect invertebrate community structure, and neither fish predation nor cypermethrin exposure affected our measures of ecosystem functioning. These findings suggest that predation by killifish can strongly affect invertebrate community structure of tropical temporary ponds, and that downstream effects on phytoplankton biomass can be mediated by exposure to cypermethrin. More broadly, we contend that a deeper understanding of (tropical) temporary pond ecology is necessary to effectively manage these increasingly polluted systems.
Keep your natural enemies close – native predators can maintain low mosquito densities in temporary ponds in a malaria expansion area in Northern Tanzania
(Elsevier, 2021-11-10) Mataba, Gordian; Kafula, Yusuph; Mwaijengo, Grite; Snoeks, Joren; Munishi, Linus; Brendonck, Luc; Vanschoenwinkel, Bram
Mosquitoes and the diseases they transmit are a global public health threat that affects most human populations. Mosquito abundances are strongly linked to the number of suitable larval habitats available. However, it is still not well understood how different land uses impact larval habitat quality in different parts of the world. We investigated links between land use practices and abundance of mosquito larvae in temporary ponds located in different land uses in a malaria expansion zone in Tanzania. Temporary ponds are often cited as important sources of mosquitoes but are also of substantial conservation concern being home to a unique fauna and flora. Often, they also have high socio-economic importance. Overall, encountered mosquito larval abundances were very low, both for the collected Anopheles gambiae s.l. and Culex quinquefasciatus. Although temporary ponds are important mosquito larval habitats in other parts of Africa, currently they are unlikely to be an important factor affecting the prevalence of mosquito borne diseases in the Manyara study region. Larval abundances in temporary ponds were higher in agricultural areas where more eutrophic conditions were found and minimal in residential areas. Overall, even though temporary ponds are often modified as rice paddies in the rainy season, they were in a good ecological condition and hosted a diverse assemblage of aquatic predators that likely prevented larval mosquitoes from reaching high densities. Maintaining this good condition by preventing pesticide and nutrient input as much as possible, can be important to prevent pond degradation that is likely to make these habitats more suitable for mosquitoes in the future.
Large branchiopod occurrence and community structure in relation to land-use types in temporary ponds of northern Tanzania
(Springer Nature Switzerland AG., 2023-02-14) Kafula, Yusuph; Mataba, Gordian; Mwaijengo, Grite; Lemmens, Pieter; Munishi, Linus; Moyo, Francis; Dube, Trevor; Vanschoenwinkel, Bram; Brendonck, Luc
Large branchiopods are a key component of the fauna of temporary ponds and play an important role in the functioning of these vulnerable ecosystems. Owing to the establishment of new settlements and agricultural expansion, temporary ponds in Tanzania are disappearing at an alarming rate whilst little is known about their diversity and ecology. We contrasted temporary ponds from a protected area with those in communal lands to detect associations between land-use types and large branchiopod community structure. Six large branchiopod species were collected, five of which have been previously reported from Southern Africa, whilst one turned out to be new to science: Streptocephalus manyarensis n.sp. Kafula and Brendonck (2023). The clam shrimp Cyzicus sp., fairy shrimps Streptocephalus lamellifer Thiele (1900) and S. bourquinii Hamer and Appleton (1993) were the most abundant and widely occurring. Variation in large branchiopod community structure was explained by the presence of Nothobranchius killifish and orthophosphate concentration. The large branchiopod community structure was different in settlement and protected areas. Our study on the occurrence and structure of large branchiopod communities in relation to land-use types serves as a base for formulation of guidelines and management tools to regulate land-use practices adjacent to temporary pond ecosystems.
Life cycle assessment and cost analysis of locally made solar powered cooler for vaccine storage
(Elsevier, 2025-04-15) Mbugano, Milton; Selemani, Juma; Kichonge, Baraka; Mwaijengo, Grite; Mwema, Mwema
Storing vaccines and perishable food in regions without access to the national grid presents significant chal- lenges. Solar power generation technologies have emerged as a viable alternative solution to address these issues. This study conducted a life cycle assessment (LCA) and cost analysis (CA) of the locally developed solar-powered cooler to assess its economic viability and potential environmental impacts. The cooler was designed to preserve vaccines and perishable foods for use, especially in areas with no electricity connectivity, as a cheaper alternative to electricity-powered coolers. The results of LCA show that battery manufacturing was a slightly higher contributor to environmental impacts across various indicators, with terrestrial ecotoxicity identified as the highest impact among other environmental impacts. Cost analysis results further revealed that a solar-powered cooler project demonstrated a positive economic outlook, with the unit manufacturing cost estimated at USD 2682. This quantitative analysis of life cycle and cost will help decision-makers comprehend both the economic aspects and environmental impacts throughout the life cycle of locally manufactured solar-powered coolers. Such insights will be instrumental in enhancing the sustainability of these products.
Life Cycle Assessment and Cost Analysis of Locally Made Solar Powered Cooler for Vaccine Storage.
(Elsevier, 2025-04-15) Mbugano, Milton; Selemani, Juma; Kichonge, Baraka; Mwaijengo, Grite; Mwema, Mwema
Storing vaccines and perishable food in regions without access to the national grid presents significant challenges. Solar power generation technologies have emerged as a viable alternative solution to address these issues. This study conducted a life cycle assessment (LCA) and cost analysis (CA) of the locally developed solar-powered cooler to assess its techno-economic viability and potential environmental impacts. The cooler was designed to preserve vaccines and perishable foods for use, especially in areas with no electricity connectivity, as a cheaper alternative to electricity-powered coolers. The results of LCA show that battery manufacturing was a slightly higher contributor to environmental impacts across various indicators, with terrestrial ecotoxicity identified as the highest impact among other environmental impacts. Cost analysis results further revealed that a solar-powered cooler project demonstrated a positive economic outlook, with the unit manufacturing cost estimated at USD 2682. This quantitative analysis of life cycle and cost will help decision-makers comprehend both the economic aspects and environmental impacts throughout the life cycle of locally manufactured solar-powered coolers. Such insights will be instrumental in enhancing the sustainability of these products.
Macroinvertebrates
(Elsevier, 2022-01-14) Dube, Trevor; Makaka, Caston; Mwaijengo, Grite; Mlambo, Musa; Brendonck, Luc
This chapter introduces the diversity and community composition of macroinvertebrates occurring in wetlands with emphasis on the permanent and temporary wetlands in the Afrotropical region of the world. The chapter explores factors shaping the composition of macroinvertebrate communities of the permanent and temporary habitats, and the structuring role of dispersal mechanisms. The diversity and composition of macroinvertebrates is contrasted between different regions of the world and between permanent and temporary wetland types. Furthermore, the role of macroinvertebrates as indicators of habitat quality, ecosystem functions, and services provided by macroinvertebrates in wetlands is explored. Finally, the threats to macroinvertebrates in wetlands are highlighted.
Multimedia assessment of heavy metal pollution and health risks in a riverine agro-mining landscape
(Springer Nature, 2025-01-05) Kadala, Charles; Rwiza, Mwemezi J; Mwaijengo, Grite; Sawe, Shovi; Mataba, Gordian
Heavy metal pollution in agro-mining zones threatens ecosystems and human health through bioaccumulation and food-chain transfer. This study assessed heavy metal pollution and associated health risks in the Likuyu River catchment by measuring concentrations of zinc (Zn), cadmium (Cd), nickel (Ni), copper (Cu), and lead (Pb). During the rainy season, samples of water, sediment, soil, and locally cultivated vegetables were systematically collected along a 22.7 km stretch of the river. Heavy metal concentrations were analyzed by flame atomic absorption spectroscopy (FAAS), providing a multi-media view of contamination and exposure pathways. Although water showed low ionic concentrations, Cd exceeded the WHO limit (0.01 mg/L). Sediments revealed elevated Zn at Site A (108.0 mg/kg) and Ni at Site E (35.97 mg/kg), with Ni surpassing the threshold effect concentration (TEC) of 22.7 mg/kg. However, overall sediment pollution was low: Zn enrichment was slight (CF = 1.14), and a negative Igeo with PLI < 1 indicated unpolluted conditions. Soil from Site D had Ni at 107.2 mg/kg, exceeding the Tanzania Bureau of Standards (TBS) limits, with CF = 1.58 and Igeo = + 0.07, indicating moderate pollution. Other sites showed CF < 1, negative Igeo, and low PLI, reflecting minimal contamination. Cowpea (Vigna unguiculata (L.) Walp.) and Napa cabbage (Brassica rapa subsp. pekinensis (Lour.) Hanelt) accumulated high levels of Ni and Pb, with Pb exceeding the Codex Alimentarius limits and Ni surpassing the European Food Safety Authority (EFSA) limits. Bioaccumulation was evident (BAF > 1), and health indices indicated noncarcinogenic (HI > 1) and carcinogenic risks (CR > 10⁻4), especially in cowpea (CR = 0.347). Elevated Ni and Pb in soils and vegetables indicated localized exposure risks, highlighting the need for targeted monitoring, informed vegetable selection, and coordinated mitigation in agro-mining areas.
Seasonal river connections modulate community structure in (sub) tropical temporary pools
(Elservier, 2025-12-01) Mwaijengo, Grite; Vanschoenwinkel, Bram; Brendonck, Luc
In natural river systems in arid and semi-arid lands, surrounding floodplains may contain temporary pools. Some of these may be mainly rain-filled (endorheic systems) while others may be partly rain-fed but connect to the flooding river during a good rainy season (river-connected pools). However, how seasonal river flooding affects the community structure in temporary floodplain pools is not well understood, particularly in the Afro-tropical region. Here, we studied the role of seasonal river connections in modulating water quality and benthic macroinvertebrate community structure and functional feeding groups in a set of endorheic versus river-connected temporary pools in a river-floodplain ecosystem in northeastern Tanzania. Benthic macroinvertebrate communities from the two habitats were significantly differentiated. Spatial species turnover (β-diversity) was higher in river-connected pools, but endorheic ones supported a higher taxon richness (alpha diversity). Benthic macroinvertebrate community dissimilarity between pools was largely determined by turnover rather than by nestedness. Hydrological connectivity was positively associated with electric conductivity and negatively associated with nutrient concentrations in the river-connected pools. In addition, the river facilitated fish dispersal, which likely excluded predation sensitive taxa such as the large branchiopod crustaceans Streptocephalus bourquinii and Streptocephalus wirminghausi. Taxon richness of collector- gatherers and scrapers was significantly different between pool types. Indicator species analysis revealed no specific fauna unique to river-connected pools. This study illustrates that land management schemes that aim to preserve temporary-pool biodiversity should strive to include both endorheic and river-connected pools to support high regional biodiversity, potentially with a priority for the more diverse endorheic systems
“Tree of life”: how baobab seed-derived biochar could lead to water safety for underprivileged communities through heavy metal (Fe) removal – SDG 6
(Royal science of chemistry, 2024-09-24) Mkelemi, Magdalena; Mwaijengo, Grite; Rwiza, Mwemezi
The abnormally gigantic baobab tree (Adansonia digitata) is often referred to as the “Tree of Life” due to its ability to provide food, water, shelter, and traditional medicine for both humans and animals in arid regions. This special tree is a landmark of Africa's savanna and has attracted the attention of the global research community. This study investigated the potential of biochar derived from baobab seeds for the removal of metallic ions from groundwater. The biochar, prepared at 700 °C, exhibited a unique surface morphology with deep voids and varied structures, suggesting increased surface area and favorable conditions for adsorption. SEM-EDX analyses confirmed the elemental composition, with carbon being the predominant element. Furthermore, XRD analysis indicated an amorphous structure, enhancing adsorption capacity for heavy metal ions. Additionally, BET analysis revealed a significant surface area (1386.704 m2 g−1 ) and well-defined pores, emphasizing the material's potential for metallic ion removal. The metallic ion of choice for this research was Fe because of its abundance in the study area and the community's need for affordable technology for discoloration of reddish-brown groundwater caused by Fe ion presence. In the batch mode equilibrium studies, the effect of pH, contact time, adsorbent particle size, adsorbent dose, solution temperature, and initial metal ion concentration was investigated. Optimal pH metallic ion removal occurred under neutral pH conditions, with higher removal efficiency observed at increased contact time (up to 120 min) and adsorbent doses. Adsorption isotherm modeling using Langmuir and Freundlich models indicated favorable adsorption, with the Freundlich model providing a slightly better fit. In conclusion, baobab seed-derived biochar demonstrated promising potential as an efficient and sustainable adsorbent for metal ion removal from groundwater. Further exploration, including the development of activated carbon and field applications, is recommended for a comprehensive understanding and practical optimization of this material's capabilities for metal ion removal.
Where does land use matter most? Contrasting land use effects on river quality at different spatial scales
(Elsevier, 2020-05-01) Mwaijengo, Grite; Msigwa, Anna; Njau, Karoli; Brendonck, Luc; Vanschoenwinkel, Bram
Understanding the influence of land-use activities on river quality has been a key focus of river monitoring programs worldwide. However, defining which land-use spatial scale is relevant remains elusive. In this study, therefore, we contrasted the influence of land use on river quality using three types of land-use estimators, namely circular buffers around a monitoring site, circular buffers upstream of the monitoring site and the entire watershed area upstream of the monitoring site. The land-use percentage compositions within the Usa-Kikuletwa River catchment in northeastern Tanzania were quantified using Landsat-8 satellite images with a maximum mapping resolution of 30 m. Redundancy analysis models and generalized linear models were used to evaluate the influence of land use on macroinvertebrate assemblages and physico-chemical water quality at different spatial scales in the dry and wet seasons. Overall, a substantial fraction of variation in physico-chemical water quality, macroinvertebrate taxon richness, Chao-1 and TARISS (Tanzania River Scoring System) score could be explained by land use of the entire watershed area upstream of the monitoring site in the dry and wet seasons. However, macroinvertebrate abundances showed strong links with more local land-use patterns within 100 m and 2 km radii. Circular buffers upstream of monitoring sites were more informative for macroinvertebrate assemblages than circular buffers around the monitoring sites. However, the latter did correlate well with physico-chemical water quality variables. Land-use variables correlated across spatial scales (i.e., 100 m up to 2 km radii), but not with the land use in the entire watershed area above the monitoring site. Our results indicate that physico-chemical water quality variables and macroinvertebrates may respond differently to land-uses at different scales. More importantly, our results illustrate that the choice regarding spatial land-use metrics can bias conclusions of environmental impact studies in river systems.