Browsing by Author "Haneklaus, Nils"

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Age-Stratified Spatial Radiological Risk Assessment of 226Ra 232Th and 40K in Water Surrounding the Geita Gold Mine in Tanzania
(MDPI, 2025-09-26) Mwimanzi, Jerome; Haneklaus, Nils; Lolila, Farida; Marwa, Janeth; Rwiza, Mwemezi; Mtei, Kelvin
Long-term ingestion of water contaminated with naturally occurring radioactive material (NORM) may pose health risks. Water around the Geita Gold Mine in Tanzania was assessed by high-purity germanium gamma spectrometry to quantify the activity concentrations of 226Ra, 232Th, and 40K, and computed age-stratified ingestion doses and risk indices were determined. The average activity concentrations were 57 mBq L−1 for 226Ra and 5026 mBq L−1 for 40K, while the activity concentrations of 232Th were below the detection limit in all samples. The estimated adult fatal cancer risk ranged from 0.9 × 10−6 to 3.1 × 10−6 (mean 2.0 × 10−6). The excess lifetime hereditary effect ranged from 2.0 × 10−6 to 7.3 × 10−6 for males (average 4.5 × 10−6 ± 1.5 × 10−6) and 2.1 × 10−6 to 7.7 × 10−6 for females (average 4.8 × 10−6 ± 1.6 × 10−6). One-way ANOVA and Pearson correlations indicated significant spatial variation in activities and indices across sites and age groups. Under current conditions, waters appear to be radiologically safe. However, mine-adjacent hotspots warrant targeted surveillance. The obtained results provide a baseline for sound monitoring approaches at the Geita Gold Mine and other mines showing similar activity profiles.
Bacterial Diversity Dynamics in Sandy Loam Soils in Tanzania Under Varying Fertilizer-Derived Uranium Concentrations
(Microorganisms, 2025-08-13) Mwalongo, Dennis; Lisuma, Jacob; Haneklaus, Nils; Maged, Ali; Brink, Hendrik; Carvalho, Fernando; Wacławek, Stanisław; Mpumi, Nelson; Amasi, Aloyce; Mwimanzi, Jerome; Chuma, Furaha; Kivevele, Thomas; Mtei, Kelvin
The presence of radiotoxic uranium (U) in mineral fertilizers is of global concern. A pilot study was conducted in Tabora (Tanzania) to determine the release of U from three brands of phosphate fertilizers and its impact on soil bacteria. The experiment used three types of fertilizer: Minjingu Powder (MP), Nafaka Plus (NP), a mixed and granulated fertilizer made from Minjingu Phosphate Rock (MPR), and YaraMila Cereal (YC) fertilizer. There was also a control treatment that was not fertilized (NF). Alpha diversity and the R tool were used to analyze bacterial diversity in four samples within an average sequencing depth of 74,466 reads, using metrics like ASVs, Shannon index, and Chao1. The results showed that the number of amplicon sequence variants (ASVs) in the DNA from soil bacteria decreased, specifically to 400 ASVs, in the NP treatment, which was in line with the higher U concentration (3.93 mg kg−1) in the soils. In contrast, the MP fertilizer treatment, associated with a lower U concentration (3.06 mg kg−1) in soils, exhibited an increase in ASVs within the DNA of soil bacteria, reaching 795; the highest ASV value (822) was observed in the NF treatment. Higher amounts of U in the soil plots seemed to have resulted in more types of bacteria, with the Actinobacteriota phylum being the most common in all of the treatments. The NP (3.93 mg kg−3 U concentration) and MP (3.06 mg kg−3 U concentration) treatments were the only ones that showed Halobacteriota and Crenarchaeota phyla. Nonetheless, bacterial diversity may also account for the alterations in soil phosphorus and nitrogen following fertilizer application. The YaraMila Cereal treatment did not seem to be linked to any particular bacterial phylum. This means that in this study it did not have any measurable effect on the soil bacteria species compared to the MP and NP treatments
Bacterial Diversity Dynamics in Sandy Loam Soils in Tanzania Under Varying Fertilizer-Derived Uranium Concentrations
(MDPI, 2025-08-13) Mwalongo, Dennis; Lisuma, Jacob; Haneklaus, Nils; Maged, Ali; Brink, Hendrik; Carvalho, Fernando; Wacławek, Stanisław; Mpumi, Nelson; Amasi, Aloyce; Mwimanzi, Jerome; Chuma, Furaha; Kivevele, Thomas; Mtei, Kelvin
The presence of radiotoxic uranium (U) in mineral fertilizers is of global concern. A pilot study was conducted in Tabora (Tanzania) to determine the release of U from three brands of phosphate fertilizers and its impact on soil bacteria. The experiment used three types of fertilizer: Minjingu Powder (MP), Nafaka Plus (NP), a mixed and granulated fertilizer made from Minjingu Phosphate Rock (MPR), and YaraMila Cereal (YC) fertilizer. There was also a control treatment that was not fertilized (NF). Alpha diversity and the R tool were used to analyze bacterial diversity in four samples within an average sequencing depth of 74,466 reads, using metrics like ASVs, Shannon index, and Chao1. The results showed that the number of amplicon sequence variants (ASVs) in the DNA from soil bacteria decreased, specifically to 400 ASVs, in the NP treatment, which was in line with the higher U concentration (3.93 mg kg−1) in the soils. In contrast, the MP fertilizer treatment, associated with a lower U concentration (3.06 mg kg−1) in soils, exhibited an increase in ASVs within the DNA of soil bacteria, reaching 795; the highest ASV value (822) was observed in the NF treatment. Higher amounts of U in the soil plots seemed to have resulted in more types of bacteria, with the Actinobacteriota phylum being the most common in all of the treatments. The NP (3.93 mg kg−3 U concentration) and MP (3.06 mg kg−3 U concentration) treatments were the only ones that showed Halobacteriota and Crenarchaeota phyla. Nonetheless, bacterial diversity may also account for the alterations in soil phosphorus and nitrogen following fertilizer application. The YaraMila Cereal treatment did not seem to be linked to any particular bacterial phylum. This means that in this study it did not have any measurable effect on the soil bacteria species compared to the MP and NP treatments.
Influence of phosphate fertilizers on the radioactivity of agricultural soils and tobacco plants in Kenya, Tanzania, and Uganda
(Springer Berlin Heidelberg, 2023-06-20) Mwalongo, Dennis; Haneklaus, Nils; Carvalho, Fernando; Lisuma, Jacob; Kivevele, Thomas; Mtei, Kelvin
Three brands of NPK fertilizers that contain variable concentrations of natural radioactivity are commonly used in tobacco plantations in Kenya, Tanzania, and Uganda. Tobacco plants are known for hyper-accumulation of natural radionuclides, particularly 238U. This study investigated if the elevated radioactivity in phosphate fertilizers could enhance radioactivity in soils and tobacco plant leaves. The 232Th, 238U, and 40K radionuclide levels in NPK-fertilized soils and tobacco leaves were measured using gamma-ray spectroscopy. The research included a one-year reference experiment with tobacco growing in plots, a ten-year semi-controlled experiment in well-managed tobacco farms, and a field survey of radioactivity in soils and tobacco leaves at three traditional tobacco fields in Migori (Kenya), Urambo (Tanzania), and Kanungu (Uganda). The findings demonstrated that soils and tobacco leaves exposed to NPK fertilizers with increased radioactivity had activity concentrations of 232 Th, 238 U, and 40 K that were considerably higher (at all sites) than in the control samples (with no use of NPK fertilizers). As the continued application of NPK fertilizers raises concentrations of 232Th, 238U, and 40K in agricultural soils, the study assessed radiological risks for humans from exposure to agricultural soils enriched with phosphate fertilizers, and it was found to be below the exposure limit of 1 mSvy-1 suggested by the International Commission on Radiological Protection (ICRP). However, tobacco consumers, both by snuffing and smoking, may face significant radiological risks, as the snuffing and smoking resulted in effective doses that were 2.41 to 6.53 and 1.14 to 2.45 times greater than the average yearly dose that the general public receives from inhalation of natural radionuclides (United Nations Scientific Committee on Atomic Radiations estimates). Furthermore, the results indicate that the lifetime excess cancer risk for tobacco snuffers and smokers ranged from 5 × 10 -5 to 24.48 × 10 -3 and 2.0 × 10 -5 to 9.18 × 10 -3 , respectively. The influence of phosphorus-derived fertilizer containing relatively high natural radioactivity, potential human radiation exposure, and radiological risk due to gamma radionuclides is estimated and discussed. The results reveal that applying phosphate fertilizers enhances natural radioactivity in soil and is subsequently influenced by soil to tobacco plant uptake. Therefore, the study recommends that countries use fertilizers with lower radionuclide content to conserve soil quality and reduce gamma-emitting radionuclides in tobacco plants.
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.
Radioactivity distribution in soil, rock and tailings at the Geita Gold Mine in Tanzania
(Elsevier, 2025-04-30) Mwimanzi, Jerome; Haneklaus, Nils; Bituh, Tomislav; Brink Hendrik; Katarzyna Kiegiel; Lolila, Farida; Marwa, Janeth; Rwiza, Mwemezi; Mtei, Kelvin
This study evaluated the activity concentrations of natural radionuclides in soil, waste rocks and tailings from the Geita gold mining site in Tanzania using high-resolution gamma spectroscopy. A total of 41 samples: 31 soil, 5 waste rock, and 5 tailing samples were collected around the mine to assess their radiological hazards. The average activity concentrations in soil were 54, 45 and 279 Bq kg-1 for 226Ra, 232Th and 40K. In contrast, tailings exhibited higher activity concentrations of 70, 36 Bq kg-1 for 226Ra and 232Th, and significantly elevated levels of 877 Bq kg-1 for 40K, while waste rocks showed intermediate values, with 66, 73 and 660 Bq kg-1 for 226Ra, 232Th and 40K respectively. Radiological hazard indices were calculated to quantify potential risks. In soil, the radium equivalent activity (Raeq) averaged 139 Bq kg-1, the annual effective dose equivalent (AEDE) was 78 μSv y-1, the annual gonadal dose equivalent (AGDE) reached 430 μSv y-1, and the excess lifetime cancer risk (ELCR) was 0.27 × 10-1. Tailings showed a Raeq of 189 Bq kg-1, AEDE of 111 μSv y-1, AGDE of 678 μSv y-1, and ELCR of 0.39 × 10- 1, while waste rocks exhibited a Raeq of 200 Bq kg-1, AEDE of 108 μSv y-1, AGDE of 642 μSv y-1, and ELCR of 0.37 × 10-3. Notably, the ELCR values for tailings and waste rocks exceeded the global average of 0.29 × 10-3, rendering them unsuitable for use as building materials. The absorbed dose rates were 69 nGy h-1 for soil, 91 nGy h-1 for tailings, and 88 nGy h-1 for waste rocks. One-way ANOVA revealed significant differences (p < 0.05) among the matrices. These findings underscore the need for targeted waste management and remediation strategies to mitigate radiological health risks in the investigated mining area as well as other areas with similar characteristics
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.
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.
Uranium in phosphate rocks and mineral fertilizers applied to agricultural soils in East Africa
(Springer Link, 2022-12-11) Mwalongo, Dennis; Haneklaus, Nils; Lisuma, Jacob; Kivevele, Thomas; Mtei, Kelvin
Phosphate rock, pre-concentrated phosphate ore, is the primary raw material for the production of mineral phosphate fertilizer. Phosphate rock is among the fifth most mined materials on earth, and it is also mined and processed to fertilizers in East Africa. Phosphate ore can contain relevant heavy metal impurities such as toxic cadmium and radiotoxic uranium. Prolonged use of phosphate rock powder as a fertilizer and application of mineral fertilizers derived from phosphate rock on agricultural soils can lead to an accumulation of heavy metals that can then pose an environmental risk. This work assesses the uranium concentrations in four major phosphate rocks originating from East Africa and four mineral phosphate fertilizers commonly used in the region. The concentration measurements were performed using energy-dispersive X-ray fluorescence spectrometry. The results showed that the uranium concentration in phosphate rock ranged from as low as 10.7 mg kg−1 (Mrima Hill deposit, Kenya) to as high as 631.6 mg kg−1 (Matongo deposit, Burundi), while the concentrations in phosphate fertilizers ranged from 107.9 for an imported fertilizer to 281.0 mg kg−1 for a local fertilizer produced from Minjingu phosphate rock in Tanzania. In this context, it is noteworthy that the naturally occurring concentration of uranium in the earth crust is between 1.4 and 2.7 mg kg−1 and uranium mines in Namibia commercially process ores with uranium concentrations as low as 100–400 mg kg−1. This study thus confirms that East African phosphate rock, and as a result the phosphate fertilizer produced from it can contain relatively high uranium concentrations. Options to recover this uranium are discussed, and it is recommended that public–private partnerships are established that could develop economically competitive technologies to recover uranium during phosphate rock processing at the deposits with the highest uranium concentrations.