STABLE HYDROGEN AND OXYGEN ISOTOPES IN TAP WATERS FROM PROVO AND OREM (UTAH, USA)

To assess the spatial and seasonal variability in the stable isotope composition of domestic waters from Provo and Orem (Utah, USA), we collected 308 samples of tap water and analyzed them for their δ²H and δ¹⁸O. Samples were collected at ~80 households in ~20 different neighborhoods in the fall and winter of 2017, and in the spring and summer of 2018. To investigate the major source(s) of domestic water for the two cities, we also compared the tap water compositions with those of the major local rivers, Utah Lake, local meteoric precipitation, and 111 groundwater wells obtained in a study conducted in 2014-2016.

Tap water δ²H and δ¹⁸O show low spatial and temporal variability, suggesting a single, isotopically homogeneous domestic water source for the neighborhoods throughout the year. Average (±1 sd) tap water δ²H and δ¹⁸O (vs. V-SMOW) in the fall (δ²H=-119.6±1.2‰; δ¹⁸O=-16.25±0.37‰), winter (δ²H=-119.6±1.2‰; δ¹⁸O=-16.34±0.26‰), spring (δ²H=-119.8±0.8‰; δ¹⁸O=-16.25±0.43‰), and summer (δ²H=-120.1±1.6‰; δ¹⁸O=-16.19±0.34‰) are all indistinguishable or similar to each other and to the average values of the Provo River (δ²H=-118.8±0.9‰; δ¹⁸O=-16.07±0.32‰). In turn, the average δ-values of the Provo River are similar to those of the groundwater wells (δ²H=-123.0±4.7‰; δ¹⁸O=-16.33±0.87‰) and cold-season (i.e., December-March) meteoric precipitation (δ²H=-122.8±28.6‰; δ¹⁸O=-16.13±3.23‰). These observations indicate that snowmelt-fed groundwater is the major water source for the Provo River and that the river and/or the groundwater wells are the major source of domestic water for the Provo and Orem neighborhoods. In addition, tap water δ²H and δ¹⁸O plot on or close to the local meteoric water line, suggesting no evaporative loss in the water reservoirs and in the distribution lines. By establishing a connection between tap (drinking) waters and local environmental waters, the results of this study have implications for forensic applications of human tissue provenance and geolocation.