CONCENTRATION-DISCHARGE RELATIONSHIPS REVEAL TRENDS IN GEOGENIC CONTAMINANT INPUT TO THE UPPER PROVO RIVER, UTAH, USA

Mountain streams experience seasonal fluctuations in chemistry during spring runoff, with certain elements exhibiting concentration, dilution, or chemostatic trends in response to increasing river discharge. To evaluate water chemistry in response to spring runoff in the upper Provo River, Utah, we analyzed trace element concentrations over a five-year period (2014-2018). Concentrations of La, Pb, Cu, Al, and Be increased by as much as 20-fold during spring runoff relative to baseflow conditions. These elements were found in elevated concentrations in soil water and ephemeral streams, suggesting that they are sourced during the activation of shallow soil flow paths during the snowmelt period. The soil, which is a combination of local bedrock and atmospheric dust, is an important geogenic source of trace metals to the river. Increased concentrations of these contaminants during peak discharge can be attributed to increased contact with and flow through this dust-laden soil column. Our findings suggest that soil water interactions play a critical role in seasonal solute contributions and biogeochemical cycling and may be also be a primary source of solutes to mountain watersheds.