Over 2 billion people and the instream flows of numerous aquatic systems depend on snowmelt. However, climate change is decreasing the amount of snowpack and stressing surface water resources. Further, urbanization and increasing human population is creating a growing demand for drinking water and stressing the quantity and quality of instream flows. The environmental occurrence and bioaccumulation of pharmaceuticals and other contaminants of emerging concern (CECs) are increasingly reported in the peer-reviewed literature. However, seasonal instream dynamics including occurrence and bioaccumulation across trophic positions are rarely studied, particularly in semiarid streams with flows influenced by seasonal snowmelt and municipal effluent discharges. We selected East Canyon Creek, located in Park City, Utah, USA, because it experiences yearly snowmelt and thus has higher flows in spring, which dilutes reclaimed wastewater discharge, but experiences lower and increasingly effluent-influenced flows during summer and fall months. We examined longitudinal gradients of select pharmaceuticals and other CECs in surface waters upstream and at incremental distances downstream (0.15, 1.44, and 13 miles) from the effluent discharge. This gradient was then sampled during spring, summer and fall to determine whether contaminant levels responded to seasonally variable instream flows. A secondary objective was to examine the spatio-temporal bioaccumulation of select pharmaceuticals in multiple trophic positions (e.g., periphyton, invertebrates, fish) along this incremental gradient downstream from the discharge during spring, summer, and fall. Stable isotopes analysis identified trophic positions within functional food chains, and spatio-temporal trophic magnification factors (TMFs) were determined. During the spring sampling event the lowest instream CEC concentrations were observed. Decreased concentrations of target analytes were generally observed with distance downstream of the effluent discharge, though the magnitude of attenuation varied among analytes. Bioaccumulation of target analytes generally decreased with distance from discharge; seasonal instream flows responding to snowmelt altered concentration of target analytes. TMF results suggest bioaccumulation of moderately lipophilic CECs (log K<sub>ow</sub> &lt;5) appears influenced to a greater extent by water exposure than diet.

Spatio-temporal occurrence, bioaccumulation, and trophic transfer of select contaminants of emerging concern in a semi-arid river influenced by snowmelt

253rd National Meeting (2017)

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