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Oxygen Transfer at the Sediment/Water Interface for Sediment Bed With Rough Surface
Author(s) -
Higashino Makoto
Publication year - 2018
Publication title -
journal of geophysical research: biogeosciences
Language(s) - English
Resource type - Journals
eISSN - 2169-8961
pISSN - 2169-8953
DOI - 10.1029/2018jg004602
Subject(s) - surface finish , sediment , surface roughness , hydraulic roughness , oxygen , limiting oxygen concentration , turbulence , shear (geology) , shear velocity , water flow , chemistry , soil science , materials science , geology , mechanics , composite material , geomorphology , physics , organic chemistry
Abstract A model of sediment oxygen demand (SOD) for a sediment bed with a rough surface was presented. The equivalent sand roughness commonly used in hydraulics was chosen to express the size of roughness elements, and SOD was expressed as a function of the intensity of near‐bed turbulence described by the shear velocity; microbial oxygen uptake rate, that is, the maximum oxidation rate; and roughness height. The modeling results show that bed roughness enhances oxygen transfer from the water column to the sediment surface. The effects of bed roughness on SOD depend on both the shear velocity and microbial oxygen uptake rate. At low microbial oxygen uptake rate, SOD approaches a constant value rapidly as the shear velocity increases. Bed roughness barely influences SOD regardless of the shear velocity because SOD can substantially be sediment side limiting . The roughness height plays an important role in determining SOD at high microbial oxygen uptake rate, because SOD can be controlled by oxygen transfer from the water column to the sediment surface, that is, transfer limiting . Increasing roughness height makes the oxygen transfer rate from flowing water to the sediment surface faster as well as increasing shear velocity, resulting in raised SOD. The proposed mode can substantially reproduce the experimental SOD for rough bed.