Physics and Biology as Likely Stream Bedfellows


Editors’ Highlights are summaries of recent papers by AGU’s journal editors.
Source: AGU Advances

Microbial communities in streambed sediments are thought to play a crucial role in the removal of nutrients and pollutants, but removal is a combination of both biological and physical processes.

Monofy et al. [2024] use the median grain size of a streambed and the stream’s depth, slope, and temperature to model how diffusivity of nitrate decays exponentially with streambed depth. The application of this model to a study of 72 headwater streams across the United States reveals that urban and agricultural steams have a diminished capacity for in-stream and in-bed mixing compared to reference streams. The results also demonstrate that nitrate removal occurs at a medium reaction rate of 0.5 hours for biological assimilation and 20 hours for denitrification. This modeling framework should catalyze new interdisciplinary collaboration on the role that streambed exchange plays in the removal of contaminants.

Conceptual (a) and mathematical model (b) for the rate of uptake of nutrients and other reactive contaminants in streams. In (b), the transport of nutrients is by turbulence in the stream (Step 1) coupled to nutrient transport into the streambed by exchange processes (Step 2) and biotic (or abiotic) reactions in the streambed (Step 3). The three steps are indicated by bold red numbers. The transport of nutrients into the streambed is modeled by an effective diffusivity that declines exponentially with depth into the sediment (c). Credit: Monofy et al. [2024], Figure 1

Citation: Monofy, A., Grant, S. B., Boano, F., Rippy, M. A., Gomez-Velez, J. D., Kaushal, S. S., et al. (2024). Toward a universal model of hyporheic exchange and nutrient cycling in streams. AGU Advances, 5, e2024AV001373. https://doi.org/10.1029/2024AV001373

—Eric Davidson, Editor, AGU Advances

Text © 2024. The authors. CC BY-NC-ND 3.0
Except where otherwise noted, images are subject to copyright. Any reuse without express permission from the copyright owner is prohibited.