From Substrate to Surface: A Turbulence-Based Model for Gas Transfer Across Sediment-Water-Air Interfaces in Vegetated Streams

Chien Yung Tseng, Rafael O. Tinoco

Research output: Contribution to journalArticlepeer-review

Abstract

Dissolved Oxygen (DO) fluxes across the air-water and sediment-water interface (AWI and SWI) are two major processes that govern the amount of oxygen available to living organisms in aquatic ecosystems. Aquatic vegetation generates different scales of turbulence that change the flow structure and affect gas transfer mechanisms at AWI and SWI. A series of laboratory experiments with rigid cylinder arrays to mimic vegetation was conducted in a recirculating race-track flume with a lightweight sediment bed. 2D Planar Particle Image Velocimetry was used to characterize the flow field under different submergence ratios and array densities to access the effect of vegetation-generated turbulence on gas transfer. Gas transfer rate across AWI was determined by DO re-aeration curves. The effective diffusion coefficient for gas transfer flux across SWI was estimated by the difference between near-bed and near-surface DO concentrations. When sediment begins to mobilize, near-bed suspended sediment provides a negative buoyancy term that increases the critical Reynolds number for the surface gas transfer process according to a modified Surface Renewal model for vegetated flows. A new Reynolds number dependence model using near-bed turbulent kinetic energy as an indicator is proposed to provide a universal prediction for the interfacial flux across SWI in flows with aquatic vegetation. This study provides critical information and useful models for future studies on water quality management and ecosystem restoration in natural water environments such as lakes, rivers, and wetlands.

Original languageEnglish (US)
Article numbere2021WR030776
JournalWater Resources Research
Volume58
Issue number1
DOIs
StatePublished - Jan 2022
Externally publishedYes

Keywords

  • gas transfer
  • hyporheic exchange
  • surface renewal
  • suspended sediment
  • turbulence
  • vegetated flows

ASJC Scopus subject areas

  • Water Science and Technology

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