Publication Type
Journal Article
Publication Date (Issue Year)
2026
Journal Name
Case Studies in Chemical and Environmental Engineering
Abstract
The increasing of tungsten (W) and tin (Sn) exploitation in some Rwandan mines requires an understanding of their distribution. It was also critical to assess the degradation of main and tertiary concentrates in soils, plants, and mining equipment. In this study, the concentration of elements, and the effect of contamination by W, Sn and other heavy metals (HMs) on soils and plants, as well as on the dump truck tyres were evaluated. The risks to humans, and the tyre composition degradation used at the mining sites, were also assessed. Metal compositions in the random samples collected at 50 m intervals from the Nyakabingo (W) and Musha (Sn) mines were analysed using x-ray fluorescence (XRF) and x-ray diffraction (XRD) approaches. The ecological and health risks contamination indices were used to assess the toxic effects of HMs: W, Sn, Pb, Zn, Cd, Cu, Ni, Mn, As and Cr. Some common metals were identified at higher mean concentrations by XRF in soils rich in W and Sn, notably Si˃ Fe˃ Al˃ Ce˃ Sr. These are along with K˃ Ca˃ Sn˃ Pb˃ Bi and K˃ Sn˃ Pb˃ Ca˃ Bi, which predominated among the 26 elements present in plants, according to the 45 elements identified from Nyakabingo and Musha, respectively. The XRD also identified the mineralogical phases and structure of about 5 composites in the Nyakabingo and about 3 compounds in the Musha. These are different from Urea, Cristobalite, Silvialite, Marialite, and Graphite, which were identified in tyre. Pearson's matrix revealed a positive link between soil concentrations of major elements in relation to uptaken elements in plants. The Sn was much taken-up by plants than W, with 16,800 mg/kgSn and 800 mg/kgW, and 8400 mg/kgSn and 1500 mg/kgW, respectively at the Musha and Nyakabingo mine sites. Other most uptaken elements by roots at these sites are Pb, Fe and Mn. The presence of K and Ca, W and Sn in the soil and plants at mines were reported in numerous previous studies, such as Gifurwe (W) mine site in Rwanda. Moreover, Fe was significant accumulated, particularly in tread tyre materials, while Si accelerate significantly the tyre wear. It was revealed that most of indices suggest serious risks and very strong contamination by HMs in soil and plants. The overall BCF˃1 also showed that most of the HMs were absorbed by plants. The second analysis revealed the presence of S, Sn and W, which may interact with ZnO, a key crosslinking agent in rubber vulcanization and disrupt the integrity of the standard composition of dump truck tyres. This compromises the structural integrity and durability of tyres at the mining site environment, and provides insights for hauling.
Keywords
Elemental concentration, Factors environmental, Heavy metals, Minerals soil, Truck tyre
Rsif Scholar Name
Gaspard Bizimungu
Thematic Area
Minerals, Mining and Materials Engineering
Africa Host University (AHU)
African University of Science and Technology (AUST), Nigeria
Recommended Citation
Bizimungu, G., Kolawole, S., & Afolayan, D. (2026). XRF and XRD approaches for evaluation of heavy metal contamination and physicochemical properties of soil and plants in tungsten and tin mining sites in Rwanda. Case Studies in Chemical and Environmental Engineering https://doi.org/10.1016/j.cscee.2026.101389