Groundwater resources in the East African Rift Valley: Understanding the geogenic contamination and water quality challenges in Tanzania

Fluoride accumulation in coffee seeds and associated health risks: a case study from Meru District, Tanzania

This study assessed fluoride accumulation in coffee seeds and its potential public health implications in Meru District, Tanzania-a region characterized by naturally high soil fluoride due to volcanic activity. Coffee seeds and water samples were systematically collected from three distinct areas (Meru Lowland, Tengeru, and Meru Highland) and brewed using both local and distilled water. Fluoride concentrations in the brewed coffee were determined using the SPADNS method, and health risks were evaluated through calculations of Estimated Daily Fluoride Intake (EDFI) and Hazard Quotient (HQ). Results revealed that fluoride levels in coffee infusions increased with both altitude and the fluoride content of the brewing water, with the highest concentrations observed in samples brewed with Meru Highland water. A population exposure assessment indicated that a notable proportion of the local community might exceed the recommended fluoride intake, thereby elevating the risk of dental and skeletal fluorosis. These findings underscore the need for targeted public health interventions, such as the promotion of low-fluoride water for coffee preparation. The study provides a comprehensive framework for understanding the soil-water-plant nexus and highlights the importance of mitigating fluoride exposure in regions with high environmental fluoride.

Methodological inconsistencies and variations in environmental pollution reports: A case study of the mining-affected Geita region, Tanzania

Various studies report pollutant levels in the environment to raise awareness and call for government intervention to protect the environment and public health. However, inconsistent findings across studies complicate environmental actions and policy-making processes in many countries. Geita region in Tanzania is one of the areas with a high focus on metal pollution problems emanating from artisanal, small-scale, and industrial mining operations. This article presents a review of environmental studies conducted in the region as a case study to show the impacts of inconsistent methodological approaches resulting to varying pollutant levels of heavy metals (Hg, As, Pb, Zn and Ni) in soil, sediment, rice and water. The diversity of metal pollutant concentrations is caused by varying sample treatment methods, which result from a lack of standardised analytical methods for various pollutants within the country. For example, two different studies reported different total mercury (THg) concentrations in soil samples near the Geita gold mine: 1.89 mg/kg and 0.0625 mg/kg. Similarly, arsenic (As) levels were reported as 126.1 mg/kg and 5.5 mg/kg, while lead (Pb) concentrations varied between 23.46 mg/kg, 2.58 mg/kg, and 17.99 mg/kg in different studies of the same area. Classical analytical instruments were used in the analyses, including Atomic Absorption Spectroscopy (AAS), Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES), Energy Dispersive X-ray Fluorescence (EDXRF), and Cold Vapour Atomic Fluorescence Spectrometry (CV-AFS). However, there have been diverse sample pre-treatment methods, including sample drying techniques, sample digestion, and chemical mixture ratios, that contribute to the differences in results. Although sampling seasons and weather conditions were not reported by the different authors, they likely contributed to the observed variations. To address these discrepancies, this review suggests establishing standardised analytical methods for different pollutants to ensure uniform procedures and comparable results in the country. This standardisation would aid in effective decision-making and policy formulation to manage environmental and health risks in mining-affected and other polluted areas.

Hydrogeochemical characterization and assessment of factors controlling groundwater salinity in the Chamwino granitic complex, central Tanzania

Chamwino district, central Tanzania is a semi-arid granitic complex province, where groundwater is the major source of water for domestic and other uses. However, groundwater in the area is affected by salinity, thus, lowering the availability of potable water for various uses, decrease in crop production, taste less, wastage of soap, and abnormal pain. Due to this, this study sought to characterize groundwater using hydrogeochemical facies and signatures in order to identify the factors influencing the distribution of salt water in the Chamwino Granitic Complex. A total of 141 groundwater samples were collected from wells spatially distributed within the study area from January 2023 to April 2023, (a season of relatively low rainfall). All samples were subjected to in situ analyses of physicochemical parameters pH, temperature (T), total dissolved solids (TDS), electrical conductivity (EC), and salinity using a multi-parameter water analyzer and analyses of major ions (Ca2+, Mg2+, K+, Na+, Cl-, SO42-, HCO3-, and NO3-). The study revealed that the dominant cations in the groundwater are Na+ > Ca2+ > Mg2+, and the anions are Cl- > HCO3- > SO42. Five geological formations (granodiorite, tonalitic orthogenesis, migmatite, tonalite, and alluvium) were identified, and each is characterized by its unique groundwater facie. In the areas that are dominated with granodiorite, the major hydrogeochemical facies were Ca-HCO3, Na-Cl, Ca-Na-HCO3, Ca-Mg-Cl, and Ca-Cl water types; tonalitic orthogenesis was dominated by Ca-HCO3, Na-Cl, Ca-Mg-Cl, and Ca-Cl water types; migmatite was dominated by Ca-HCO3, Na-Cl, Ca-Mg-Cl, and Ca-Cl water types; tonalite was dominated by Na-Cl, Ca-Mg-Cl, and Ca-Cl water types; and alluvium was dominated by Na-Cl and Ca-Mg-Cl and Ca-Cl water types. The common hydrogeochemical facies in all five geological units are Na-Cl, Ca-Mg-Cl, and Ca-Cl water types. It is revealed that the groundwater in the study area is alkaline in nature and slightly saline with salinity level between 0.2 mg/L (fresh water) and 2.8 mg/L (brackish water) with mean 1.07 mg/L (of 141 samples). The factors controlling groundwater salinity distribution are mainly rock-water interaction and ion exchange reactions. Groundwater salinity in the study area is largely attributed to the abundance of Na+, Ca2+, Cl- and SO42-. Abundance of Na+ and Ca2+ is the results of both, weathering of feldspar minerals particularly plagioclase (Na-Ca feldspars) which are the major mineral in granites, and evaporation crystallization cycles of evaporates in semi-arid areas such as Chamwino. Also, such evaporation crystallization cycles account for the abundance of Cl- and SO42- especially in areas dominated by alluvium. However, anthropogenic activities as evidenced by elevated nitrate up to 212.6 mg/L in congested areas are also likely to contribute in area) to the elevated Cl- and SO42-. In other geological units such as tonalitic orthogneiss, migmatite and granodiorite, there was an ostensible mixing of saline water with fresh water from local recharge as indicated by the abundance of HCO3- ions. Nonetheless, the hydrogeochemical characterization of groundwater in the Chamwino granitic complex suggests that there is little possibility for groundwater to evolve to a carbonate water type (fresh water) because the groundwater salinity is mainly geogenic, unless artificial recharge through rainwater harvesting is applied.

Determination of aquifer hydraulic parameters and groundwater protective capacity in parts of Nsukwa clan, Nigeria

The goal of this study is to determine aquifer parameters and groundwater protective capacity in parts of the Nsukwa clan using geoelectric and pumping test methods. Seventeen vertical electrical soundings were acquired to determine the geoelectric properties, while two wells were drilled to determine the lithology and the aquifer parameters of the area. The result showed that the lithology comprised lateritic topsoil and sand, fine sand, medium sand, and coarse sand, respectively. Geoelectric data interpretation using Win Resist software revealed a close correlation with the well record. Geoelectric data analysis indicated that prolific aquifer can be sourced within the third and fourth layers, located within 24.2-43.8 m and comprised medium to coarse sand. The aquifer resistivity ranged from 703.1 to 26,367.7 Ωm. The Dar Zarrouk parameters, such as transverse resistance (R) and longitudinal conductance (S), were applied to determine the aquifer transmissivity (T) and hydraulic conductivity (K). The computed T and K from geoelectric sounding ranged from 11.37 to 34.79 m2/day, with a mean value of 18.51 m2/day and 0.8243 m/day, respectively, while the T and K values from the pumping test are 18.58 m2/day and 0.8251 m/day, respectively. S and R values ranged from 0.001179 to 0.0131619 Ω-1 and 2434 to 102,090 Ωm2, respectively, revealing a poor aquifer protective capacity and moderate yield. The storativity and storage coefficient of the aquifer values of 0.0023 and 0.072 m2/min, respectively, revealed a confined aquifer capable of providing sufficient water to the people. These findings showed moderate aquifer potential with poor protective capacity; thus, adequate aquifer protective strategies are recommended.

Geogenic contaminants and groundwater quality around Lake Victoria goldfields in northwestern Tanzania

Geogenic contamination of groundwater is frequently associated with gold mining activities and related to drinking water quality problems worldwide. In Tanzania, elevated levels of trace elements (TEs) have been reported in drinking water sources within the Lake Victoria Basin, posing a serious health risk to communities. The present study aims to assess the groundwater quality with a focus on the concentration levels of geogenic contaminants in groundwater around the Lake Victoria goldfields in Geita and Mara districts. The water samples were collected from community drinking water sources and were analysed for physiochemical parameters (pH, EC, Eh), major ions, and trace elements. The analysed major ions included Na⁺, K⁺, Ca²⁺, Mg²⁺, SO₄^2-, HCO₃^- and Cl^- whereas the trace elements were As, Al, Li, Ba, B, Ti, V, U, Zr, Sr, Si, Mn Mo, Fe, Ni, Zn, Cr, Pb, Cd, and V. The present study revealed that the concentration levels of the major ions were mostly within the World Health Organization (WHO) drinking water standards in the following order of their relative abundance; for cations, Ca²⁺∼Na⁺>Mg²⁺>K⁺ and for anions was HCO₃^- > SO₄^2- > NO₃^-, Cl^- > PO₄^3-. Statistical and geochemical modelling software such as 'R Studio', IBM SPSS, geochemical workbench, visual MINTEQ were used to understand the groundwater chemistry and evaluate its suitability for drinking purpose. The concentration of As in groundwater sources varies between below detection limit (bdl) and 300 μg/L, with highest levels in streams followed by shallow wells and boreholes. In approximately 48% of the analysed samples, As concentration exceeded the WHO drinking water guideline and Tanzania Bureau of Standards (TBS) guideline for drinking water value of 10 μg/L. The concentration of the analyzed TEs and mean values of physicochemical parameters were below the guideline limits based on WHO and TBS standards. The Canadian Council of Ministries of the Environment Water Quality Index (CCME WQI) shows that the overall water quality is acceptable with minimum threats of deviation from natural conditions. We recommend further geochemical exploration and the periodic risk assessment of groundwater in mining areas where high levels of As were recorded.