Monitoring and treatment of combined radium in Iowa private wells

Unregulated private drinking water supplies, especially private wells, are likely to be disproportionately impacted by naturally-occurring radioactive material (NORM), which contaminates groundwater supplies across the United States. Well users are solely responsible for water treatment decisions, but data on well water quality is often limited. This research encompasses an investigation of two major NORM groundwater contaminants in private well water, radium-226 (226Ra) and radium-228 (228Ra). In the Upper Midwest, elevated 226Ra and 228Ra naturally occurs in groundwater, posing a possible health risk to private well users. This work encompasses one of the first high-resolution studies of the occurrence of 226Ra, 228Ra, and associated inorganic water quality parameters in private wells in Iowa. The purpose of this research is to gain an understanding of radium geochemistry in an often-overlooked water source affected by complex groundwater matrices. For the wells evaluated in this study, 53% (n = 50) measured below minimum detectable activity whereas 6.3% (n = 6) were found to contain Ra levels greater than the U.S. EPA Maximum Contaminant Level of 5 pCi/L. No associations with well depth, age, region, or water quality indicators (e.g., concentrations of other alkaline earth metals) were observed in samples with measurable activity. A resampling campaign during winter 2020 targeted 12 private wells from the 2019 survey that measured above detection for 226Ra and/or 228Ra to assess the efficacy of study participants’ in-home drinking water treatment devices at point-of-use. From a snapshot of paired indoor and outdoor samples, it was observed that water softeners and reverse osmosis reduced radium isotopes to non-detectable activity, yet other inorganic groundwater contaminants (As, Ba, and Li) persisted after treatment. This study demonstrates that Ra contamination is highly localized and occurs unpredictably in Iowa. Further, the efficacy of household water treatment technologies employed by well users merits additional assessment to ensure devices are adequately removing common inorganic groundwater contaminants. Management of radium and inorganic metal and metalloid pollutants in private well water requires knowledge of local water quality issues, regular testing at both hydrant and point-of-use, and routine evaluation and maintenance of in-home water treatment devices.