Reach-scale predictions of the fate and transport of contaminants of emerging concern at Fourmile Creek in Ankeny, Iowa

Contaminants of emerging concern (CECs) are an unregulated suite of constituents frequently detected in environmental waters, which possess the potential to cause a host of reproductive and developmental problems in humans and wildlife. Degradation pathways of several CECs are well-characterized in idealized laboratory settings, but CEC fate and transport in complex field settings is poorly understood. In the present study I use a multi-tracer solute injection to study and quantify physical transport and photodegradation in a wastewater effluent-impacted stream in Ankeny, Iowa, USA. Conservative tracers are used to quantify physical transport processes in the stream. Use of photolytic fluorescent tracers allows for isolation of the relative contribution of photodegradation within the system. Field data were used to calibrate a one-dimensional transport model for tracers, and forward modeling was then used to predict the transport of sulfamethoxazole, an antibiotic in the effluent which is susceptible to photolysis. Results of this study demonstrate that accurate predictions of reactive CECs at the scale of stream reaches can be made using the fate and transport model based on field tracer studies. This work validates a conceptual framework that can be used to couple field tracer and laboratory CEC studies to accurately predict the transport and fate of CECs at the scale of stream reaches.