Nitrogen retention in the main channel and two transient storage zones during nutrient addition experiments

作者：Johnson Zachary C^*; Warwick John J; Schumer Rina

来源：Limnology and Oceanography, 2015, 60(1): 57-77.

DOI：10.1002/lno.10006

The main channel (MC), surface transient storage (STS), and hyporheic transient storage (HTS) zones provide unique habitats in streams. Most nutrient spiraling studies use models that aggregate the influence of the various transient storage zones on uptake and retention. This may explain contradictory results on drivers of nutrient cycling in streams. Here, a new two-storage zone transport model with Michaelis-Menten uptake kinetics was developed to quantify the relative role of the three stream compartments on the physical and biological transport of solutes and compared with a dynamic nutrient spiraling method (tracer additions for spiraling curve characterization). Both approaches are applied to coinjected conservative and reactive tracer tests in a stream with mean annual discharge >1.0 m(3) s(-1). The relative influence of the three stream compartments on in-stream uptake of NO3-N varied between reaches; each stream compartment dominated overall nitrate uptake in at least one subreach. HTS zones generally had greater influence on nitrate concentrations than STS zones because of longer residence times and faster uptake rates. However, a combination of geomorphology, MC-transient storage connectivity, residence time, compartment size, and uptake rate controls overall nutrient uptake capacity of a stream. Overall reach and compartment-specific uptake and uptake efficiency benefit from the upstream action of the transient storage zones during nutrient addition experiments, but STS and HTS contribute in different ways. Physical retention and biological uptake in STS zones contributed equally to overall reach uptake, but biological uptake in HTS zones overshadowed physical retention.

• 出版日期2015-1