Geochemistry and sources of fluoride and nitrate contamination of groundwater in six districts of the Dodoma region in Tanzania.
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Date
2023
Authors
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Publisher
Elsevier BV
Abstract
Fluoride (F−) and nitrate (NO3−) are common groundwater contaminants. In high concentrations, F− and NO3− cause skeletal fluorosis and methemoglobinemia in children respectively. Therefore protection of public health necessitates the evaluation of groundwater for F− and NO3− contamination. The goal of this study was to assess the geochemistry and spatial distribution of F− and NO3− in six districts in the Dodoma region. Results show that greater than 98% of samples were found to contain F− below 1.50 mgl−1 (WHO 2017). F− Levels exist in the gradient and concentrated to the north of the region. The highest and lowest levels of F− were found in Chemba district, and Mpwapwa district. In the Chemba district, values for F− are (max= 7.30 mgl−1, min = 0.11 mgl−1, mean and SD = 0.87±1.67). In the Mpwapwa district, values for F− are (max= 0.80 mgl−1, min = 0.06 mgl−1, mean and SD= 0.36±0.23). Positive correlation between F− and HCO3− / Ca2+ +Mg+2 and negative correlation between F− and TH, F− and Ca2++Mg2+, and F− and Ca2++Mg2+/Na++K+ suggests HCO3− promote dissolution of F containing rocks while Ca2++Mg2+ removes F− through precipitation reactions. Elevated levels of NO3− were found throughout the districts. The order of districts with NO3− levels above 45.0 mgl−1 was found to be Kongwa (94.74%) > Chemba (69.23%) > Dodoma urban (34.80%) > Chamwino (28.57%) > Mpwapwa (6.60%) and Kondoa (0.00%). Kongwa and Kondoa districts are located south and north of the region. The values in Kongwa are; (max= 196.8 mgl−1, min = 12.5 mgl−1, mean and SD= 137.02±48.47). Values in Kondoa are; (max= 28.00 mgl−1, min = 12.00 mgl−1, mean and SD= 19.97±4.61). Conclusions; groundwater in the Dodoma region safe for drinking with respect to F− and unsafe for drinking with respect to NO3− without remediation.
Description
Full-text. Available at: https://doi.org/10.1016/j.sciaf.2023.e01783
Keywords
Water quality, Pollution, Nitrate, Fluoride, Dodoma region, Central tanzania, Groundwater contamination
Citation
Banyikwa, A. T. (2023). Geochemistry and sources of fluoride and nitrate contamination of groundwater in six districts of the Dodoma region in Tanzania. Scientific African, 21, e01783.