A critical review on the occurrence and distribution of the uranium- and thorium-decay nuclides and their effect on the quality of groundwater

Survey of 226Ra/228Ra and inorganic constituents in Iowa private drinking water wells

“…One sample above 30 μg/L was collected from a well hydrant, whereas no information was provided for the remaining three private wells. 226 Ra and/or 228 Ra were not detected at any of these sites, but this finding may simply reflect well‐established differences in the geochemical environments that favor Ra and U mobility (Mathews et al, 2018; Porcelli & Swarzenski, 2003; Stackelberg et al, 2018; Szabo et al, 2012; Vengosh et al, 2022). Although elevated U concentrations in groundwater are generally not of concern in major aquifer systems throughout Iowa (Smith & Field, 2007), our analysis found U levels to be greatest in alluvial and buried sand and gravel wells, in addition to those wells for which we had insufficient information to assign an aquifer (Figure S9).…”

222Rn and 226Ra Concentrations in Spring Water and Their Dose Assessment Due to Ingestion Intake

“…In addition, according to Tricca et al [43], weathering of rocks is not a significant source of 222 Rn since this requires a high weathering rate. Some previous studies have reported that the occurrence of 222 Rn is primarily controlled by α-recoil of 222 Rn from the rock balanced by its decay [43][44][45]. Since it has recently been reported that grain size, distribution of Uranium in the rocks, and geological factors (e.g., faults and fracturing) of the aquifer are also important for the generation of 222 Rn in water [45][46][47], obtaining this information would lead to a more detailed discussion of the sources of 222 Rn in this study.…”

“…Some previous studies have reported that the occurrence of 222 Rn is primarily controlled by α-recoil of 222 Rn from the rock balanced by its decay [43][44][45]. Since it has recently been reported that grain size, distribution of Uranium in the rocks, and geological factors (e.g., faults and fracturing) of the aquifer are also important for the generation of 222 Rn in water [45][46][47], obtaining this information would lead to a more detailed discussion of the sources of 222 Rn in this study. Furthermore, it is also important to measure the chemical composition of the rock and water, as 226 Ra can be removed by adsorption reactions such as ion exchange at the rock-water boundary and coprecipitation reactions resulting in deposition of sulfate, etc.…”

Groundwater Quality and Health: Making the Invisible Visible

“…Both point and nonpoint source priority contaminants normally occur in unconfined and/or shallow confined aquifers, especially those sandy and silty ones with high and moderate hydraulic conductivities. Finally, priority of geogenic contaminants can be taken into account in the aquifers which contain elevated background concentrations and have favorable conditions for their release. ,, Taking arsenic as an example, its enrichment in groundwater normally occurs in the phreatic and confined aquifers in plain areas which contain elevated As in the sediments and favor the reductive release of As under reducing conditions. ,− …”

“…Geogenic substances are released from the aquifer matrix due to long-term water–rock interactions. ,, The types and concentrations of geogenic substances in groundwater depend on the sedimentogenesis and hydrobiogeochemistry of aquifer systems. , The geogenic substances of most concern include As, F, and I, and groundwater contamination by these substances has been a global problem which threatens the health of several hundreds of millions of people. ,,,,− In China, about 80 million people were influenced by using high F groundwater as the source of drinking water supply, and about 19.6 and 31 million people were exposed to high As and I groundwater, respectively . The high As groundwater in southeast Asia has attracted global concern because it has caused serious health problems among the local people. − Other geogenic substances such as U, Cr, Se, and ammonium in groundwater have been studied in recent years., − When the concentrations of geogenic substances exceed the safe levels recommended by the World Health Organization (WHO) or local governments, the groundwater is deemed to be harmful. Significant advancement has been made in recent decades in understanding the enrichment mechanism of geogenic substances in groundwater. ,,, More work is still needed to identify the toxicity and its association with the concentrations and speciation of geogenic substances in groundwater.…”