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

Radium is a naturally-occurring radioactive element found in Upper Midwest aquifers, yet exposure risks for unregulated water sources in this region are unknown. A survey of ^226/228Ra and other inorganic constituents in 94 private wells was conducted in 2019 across 10 Iowa counties. Within private wells, 53% measured below minimum detectable activity whereas 6.3% have ^226/228Ra levels above the United States Environmental Protection Agency Maximum Contaminant Level. ^226/228Ra occurrence was not associated with well-depth or chemical surrogates, but were generally consistent with the lithology and historical water quality trends for aquifers. In 2020, 11 of the ^226/228Ra-impacted wells were re-sampled to assess the efficacy of in-home water treatment. Water softeners reduced ^226/228Ra to non-detectable activities, but other inorganic constituents persisted and their removal required more advanced treatment. This study suggests that ^226/228Ra occurrence in private wells can reasonably be anticipated from public water supply data if reliable information is available to identify the source aquifer.