434 / 2024-03-16 15:24:22

Influence of mineral compositions of sediment particles on dissolved oxygen consumption in the sediment-laden flow

Fine sediment; Dissolved oxygen; Cohesive mineral; Montmorillonite; Yellow River basin

Subtheme 7: Sediment Regulation and Management > Topic 4: Sediments and Environment

The dissolved oxygen content is critical to the self-purification capacity of water and the survival of aquatic organisms in natural water flow. And the dissolved oxygen consumption caused by biochemical reaction is one of the important indicators in river ecological environment assessment frequently. In the analysis of BOD degradation capacity of natural sediment-laden flow, the influence of sediment mineral compositions was often ignored, which would cause the underestimation of river degradation capacity. In order to clarify the quantitative relationship between the BOD degradation process and the content of cohesive and non-cohesive minerals in the sediment particles, a series of laboratory experiments and theoretical analysis were carried out in the sediment-laden flow. The experimental results show that the BOD temporal hydrographs of the coarse and fine sediment composed of non-cohesive minerals present the convex-shape curves during the degradation process. Meanwhile, the BOD temporal hydrographs of cohesive minerals present the concave-shape curves. The reasons for the different trends of the curves were studied from the perspectives of the turbulence characteristics of the sediment-laden flow and the microstructures of the sediment mineral composition. Based on the experimental study and theoretical analysis, the cohesive mineral composition, especially the montmorillonite, would reduce the degradation rate of BOD, which was due to the binding effect of smaller particle size with larger specific surface area and the hysteresis effect of special layered structure.