TY  - JOUR
AU  - Post, V. E. A.
AU  - Vassolo, S. I.
AU  - Tiberghien, C.
AU  - Baranyikwa, D.
AU  - Miburo, D.
PY  - 2017//
TI  - Weathering and evaporation controls on dissolved uranium concentrations in groundwater – A case study from northern Burundi
JO  - Science of The Total Environment
SP  - 281
EP  - 293
VL  - 607-608
KW  - Geochemical modelling
KW  - Hydrochemistry
KW  - Lake Tshohoha South
KW  - Public health
KW  - Radionuclides
KW  - Water supply
N2  - The potential use of groundwater for potable water supply can be severely compromised by natural contaminants such as uranium. The environmental mobility of uranium depends on a suite of factors including aquifer lithology, redox conditions, complexing agents, and hydrological processes. Uranium concentrations of up to 734μg/L are found in groundwater in northern Burundi, and the objective of the present study was to identify the causes for these elevated concentrations. Based on a comprehensive data set of groundwater chemistry, geology, and hydrological measurements, it was found that the highest dissolved uranium concentrations in groundwater occur near the shores of Lake Tshohoha South and other smaller lakes nearby. A model is proposed in which weathering and evapotranspiration during groundwater recharge, flow and discharge exert the dominant controls on the groundwater chemical composition. Results of PHREEQC simulations quantitatively confirm this conceptual model and show that uranium mobilization followed by evapo-concentration is the most likely explanation for the high dissolved uranium concentrations observed. The uranium source is the granitic sand, which was found to have a mean elemental uranium content of 14ppm, but the exact mobilization process could not be established. Uranium concentrations may further be controlled by adsorption, especially where calcium-uranyl‑carbonate complexes are present. Water and uranium mass balance calculations for Lake Tshohoha South are consistent with the inferred fluxes and show that high‑uranium groundwater represents only a minor fraction of the overall water input to the lake. These findings highlight that the evaporation effects that cause radionuclide concentrations to rise to harmful levels in groundwater discharge areas are not only confined to arid regions, and that this should be considered when selecting suitable locations for water supply wells.
SN  - 0048-9697
UR  - https://www.sciencedirect.com/science/article/pii/S0048969717317096
N1  - exported from refbase (http://www.uhydro.de/base/show.php?record=132), last updated on Fri, 26 Jan 2024 13:19:04 +0100
ID  - Post_etal2017
ER  -