5 research outputs found
Refining the conceptual model for radionuclide mobility in groundwater in the vicinity of a Hungarian granitic complex using geochemical modeling
Groundwater is an important freshwater resource, which can be affected by geogenic radionuclide contamination. To make decisions regarding the use and management of groundwater, understanding the controls of radionuclide mobility is critical. In the southern foreland of a granitic outcrop in Hungary, high gross alpha activity concentration was measured in drinking water wells, related probably to the presence of uranium. It has been suggested that understanding of the groundwater flow system may be a key aspect to understand uranium mobility in groundwater. The goal of the present work was to elucidate the conceptual model of radionuclide mobility in the study area, focusing in particular on the geochemical controls of uranium. For this purpose, water samples were collected and nuclide-specific measurements for 226Ra and radon isotopes were carried out, in addition to 234U+238U measurements, to increase the range of radionuclides and better understand their mobility. A geochemical modeling analysis involving redox-controlling kinetic reactions and a surface complexation model was developed to support the conceptual model. The results from the sampling indicate that excess of 234U+238U (3â753 mBq Lâ1) contribute to the natural radioactivity measured in drinking water to a large degree. 226Ra was measured in relatively low activity concentrations (<5â63 mBq Lâ1) with the exception of three specific wells. Notable radon activity concentration was measured in the springwaters from Velence Hills (1.01â3.14 Ă 105 mBq Lâ1) and in interrelation with the highest (285â695 mBq Lâ1) 226Ra activity concentrations. The geochemical model suggests that uranium distribution is sensitive to redox changes in the aquifer. Its mobility in groundwater depends on the residence time of groundwater compared to the reaction time controlling the consumption of oxidizing species. The longer the flow path from the recharge point to an observation point where U is measured, the more likely it is that reducing conditions will be found in the aquifer and the elemental concentration U will be low
Integration of a Shallow Soda Lake into the Groundwater Flow System by Using Hydraulic Evaluation and Environmental Tracers
Lake Velence is a shallow soda lake whose water level and water quality show a severely
deteriorating tendency in recent years. Until recently, the groundwater component in the lakeâs water
budget has not been taken into consideration. To integrate the lake into the groundwater flow system
at the regional scale, methods of âbasin hydraulicsâ were applied. In addition, 17 water samples
were collected for ÎŽ
2H and ÎŽ
18O, and for ÎŁU, 226Ra and 222Rn activity measurements to use these
parameters as environmental tracers of groundwater contribution. Groundwater mapping revealed
that groundwater recharges in Velence Hills and the local elevations south of the lake, whereas
discharge occurs by the lakeâs shoreline and along surface watercourses. The results indicated that
Lake Velence is the discharge point of local groundwater flow systems known to be more sensitive to
climate changes and anthropogenic activities (e.g., contamination, overexploitation). Groundwater
and lake water have similar uranium activity concentrations serving as another sign of groundwater
inflow into the lake. Therefore, it is necessary to consider both the groundwater component in
the lakeâs water management and its vulnerability regarding local and short-term changes in the
catchment area
Integration of a Shallow Soda Lake into the Groundwater Flow System by Using Hydraulic Evaluation and Environmental Tracers
Lake Velence is a shallow soda lake whose water level and water quality show a severely deteriorating tendency in recent years. Until recently, the groundwater component in the lake’s water budget has not been taken into consideration. To integrate the lake into the groundwater flow system at the regional scale, methods of “basin hydraulics” were applied. In addition, 17 water samples were collected for δ2H and δ18O, and for ΣU, 226Ra and 222Rn activity measurements to use these parameters as environmental tracers of groundwater contribution. Groundwater mapping revealed that groundwater recharges in Velence Hills and the local elevations south of the lake, whereas discharge occurs by the lake’s shoreline and along surface watercourses. The results indicated that Lake Velence is the discharge point of local groundwater flow systems known to be more sensitive to climate changes and anthropogenic activities (e.g., contamination, overexploitation). Groundwater and lake water have similar uranium activity concentrations serving as another sign of groundwater inflow into the lake. Therefore, it is necessary to consider both the groundwater component in the lake’s water management and its vulnerability regarding local and short-term changes in the catchment area
Natural Radioactivity in Drinking Water in the Surroundings of a Metamorphic Outcrop in Hungary: The Hydrogeological Answer to Practical Problems
Groundwater quality constantly evolves through rockâwater interactions, which can enrich groundwater with undesirable elements such as naturally occurring radionuclides. The aim of this study was to understand the cause of gross alpha activity exceeding the screening value of 0.1 Bq Lâ1 measured in groundwater-derived drinking water in the vicinity of a metamorphic outcrop in Hungary. As groundwater quality is strongly dependent on the properties of groundwater flow systems, environmental tracers (ÎŽ2H and ÎŽ18O composition, 226Ra, 222Rn, total U activity concentration, and 234U/238U ratio) and hydraulic evaluation were applied to understand groundwater dynamics. The collected groundwater samples had total U activities up to 540 mBq Lâ1, which translates into an indicative dose below the drinking water parametric value. However, in the presence of dissolved uranium, the ÎŽ2H (â52.6â(â83.4)) and ÎŽ18O (â7.17â(â11.96)) values led to the conclusion that local flow systems were sampled that are known to be most vulnerable to any changes in their recharge area. The results confirm that the groundwater flow system approach involving environmental tracers and hydraulic evaluation is a powerful tool for identifying the cause of natural radioactivity in groundwater-derived drinking water