ARSENIC AND OTHER HEAVY METALS IN SURFACE WATER AND SHALLOW GROUNDWATER IN SALT LAKE AND UTAH VALLEYS, UTAH

A recent study (Ferreira 2013) examined concentrations of fluvial As and the transition metals normally associated with As in Provo and American Fork Rivers, which flow westward across the Wasatch Range and heavily-populated Utah Valley to drain into Utah Lake. Within Utah Valley average fluvial As for Provo River (As = 0.342 mg/L) and American Fork River (As = 0.152 mg/L) exceeded the EPA standards for freshwater streams for acute exposure (As = 0.340 mg/L) and chronic exposure (As = 0.150 mg/L), respectively, which are not unusual for rivers affected by mine tailings. The objective of this study is to determine whether elevated levels of As and other heavy metals also occur in shallow groundwater in Salt Lake and Utah Valleys. The objective is being addressed by analyzing water samples from the “backyard wells” in Salt Lake and Utah Valleys, shallow (depths < 10 m), hand-dug wells, some of which date back to pioneer days, which many residents maintain as their “emergency water supply” or for watering lawns and gardens. Since nearly all backyard wells are unregistered, they are being sought through conversations with water departments, historical societies, real estate listings, and local residents. Water and sediment samples are also being collected from American Fork River, Hobble Creek, Provo River and Spanish Fork River, which drain into Utah Lake, and Bear River and Weber River, which drain into Great Salt Lake. Samples are being analyzed for nitrate, phosphate and sulfate using the Hach DR-2700 Spectrophotometer, while the PerkinElmer Optima 8000 ICP-OES is being used to measure for As, the transition elements Co, Cu, Cr, Fe, Mn, Ni and Zn, and other associated elements Ag, Cd, Pb and Ti. Stable isotopes of water are being measured in order to assign groundwater samples to watersheds of origin. Preliminary results indicate that shallow groundwater As in the American Fork watershed is much lower (mean As = 0.0022 mg/L) than fluvial As and that there is an excellent negative correlation (R² = 0.83) between groundwater As and Ti. It is suggested that TiO₂, which may originate in the Cottonwood Stock in the American Fork watershed, may play a role in the demobilization of groundwater As. Further results will be reported at the meeting.