CHARACTERIZING SURFACE WATER AND GROUNDWATER INTERACTIONS IN THE TRUCKEE RIVER SYSTEM USING ULTRA-TRACE CHEMISTRY

Characterizing surface water and groundwater is fundamental to better understanding hydrologic interactions in the Truckee River system. Here, we use ultra-trace chemistry to identify chemically unique characteristics of surface water and groundwater. Using low-flow ultra-clean sampling techniques from an array of piezometers, samples were collected from shallow and deeper piezometers (ranging from 2 m to 15 m depth) as well as co-located surface river water from the Truckee River. Samples were analyzed for a broad suite of elements at the Desert Research Institute’s Ultra-Trace Laboratory - including traditional major elements (e.g., Ca, Mg, Na), trace elements (e.g., Cr, Cu, Mn, V), and ultra-trace elements (e.g., rare earth elements (REE)). Ultra-trace elemental concentrations, often in the low ppt-ppq range, were above analytical detection limits, and method blanks indicate that contamination was minimal. Preliminary results indicate that chemically unique characteristics of surface water and groundwater can be identified via ultra-trace chemistry. For example, some elemental ratios varied by up to two orders of magnitude between different source waters, while elemental ratios from deeper groundwater samples exhibited relatively spatially and temporally conservative behavior.