Mass transfer at the sediment/water interface for permeable sediments in an inland aquatic system

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Mass transfer at the sediment/water interface, e.g. dissolved oxygen uptake, phosphate release and so on, plays an important role for water quality and ecosystem in rivers, lakes, and reservoirs. Sedimentary oxygen demand (SOD) is the oxygen flux from water column over a sediment to the sediment surface, and has been studied for mainly impermeable organic sediments. SOD for sandy permeable sediment has not been investigated. This study considers a sandy permeable sediment. In impermeable sediments, molecular diffusion is a major mechanism for mass transfer. On the other hand, interstitial water motions caused by near-bed turbulence penetration has a significant effect on mass transfer for sandy permeable sediments. A model for pore water flow induced by pressure fluctuations at the sediment/water interface due to near-bed turbulent coherent motions has been developed. The model incorporates microbial oxygen uptake in the sediments. The proposed model quantifies SOD for not only impermeable organic sediments, but also sandy permeable sediments.