ASSESSMENT OF A TRACER ADDITION TECHNIQUE FOR QUANTIFYING STREAM NUTRIENT UPTAKE

Stream tracer addition is frequently used to quantify nutrient uptake metrics. An approach Tracer Additions for Spiraling Curve Characterization (TASCC) was recently developed and has been suggested as a quick and easy technique for quantifying nutrient uptake kinetics from ambient to saturation. We developed a one-dimensional solute transport model with transient storage to simulate nutrient uptake in rivers and used this model to evaluate the sensitivity of the TASCC technique. The model was run with varying the hydrogeomorphologic and uptake parameters to simulate a pulse bromide and nitrate addition under a suite of environmental conditions. The simulated breakthrough curves of bromide and nitrate downstream were used to run TASCC analysis as if they were measured at a field experiment. Nitrate uptake metrics estimated by the TASCC deviated from the correct value estimated from the model and these differences varied with the hydrogeomorphologic and uptake parameters. Our results suggest that despite its advantages, the TASCC technique should be used with caution under certain environmental settings.