Empirical model for estimating vertical concentration profiles of re-suspended, sediment-associated contaminants

Abstract

Vertical distribution processes of sediment contaminants in water were studied by flume experiments. Experimental results show that settling velocity of sediment particles and turbulence characteristics are the major hydrodynamic factors impacting distribution of pollutants, especially near the bottom where particle diameter is similar in size to vortex structure. Sediment distribution was uniform along the distance, while contaminant distribution slightly lagged behind the sediment. The smaller the initial sediment concentration was, the more time it took to achieve a uniform concentration distribution for suspended sediment. A contaminants transportation equation was established depending on mass conservation equations. Two mathematical estimation models of pollutant distribution in the overlying water considering adsorption and desorption were devised based on vertical distribution of suspended sediment: equilibrium partition model and dynamic micro-diffusion model. The ratio of time scale between the sediment movement and sorption can be used as the index of the models. When this ratio was large, the equilibrium assumption was reasonable, but when it was small, it might require dynamic micro-diffusion model.

Characteristics and Pollution Contribution of the Internal Nitrogen Release From the Sediments in the Dahekou Reservoir in Inner Mongolia

“…The annual amount of total nitrogen released from the sediments in the reservoir was the largest in the wet season and the smallest in the dry season, which is consistent with the results reported by Liu et al (2006). Based on the comprehensive analysis of the water temperature, pH, DO, and the hydrodynamic conditions, the various physical, chemical, and biological reaction conditions (e.g., diffusion and organic matter degradation) during the wet season are conducive to promoting and accelerating the decomposition of the organic nitrogen in the sediments (Wang et al, 2013;Zhu et al, 2017), which leads to an increase in the amount released into the overlying water. The level period after the reservoir freezes is influenced by reservoir fisheries and power stations and by human activities, such as water disturbances.…”

Evaluating Regime Change of Sediment Transport in the Jingjiang River Reach, Yangtze River, China

“…In the non-equilibrium condition, the deviations of the vertical profiles of SSC from the local equilibrium state are different from those of the equilibrium state [9,10]. For hydraulic engineers, the vertical concentration profiles are essential for estimating erosion and deposition using the sediment balanced method, and also for estimating sediment-associated contaminants [11,12]. For geomorphologies, non-equilibrium suspended sediment transport (SST) is one of the key processes driving the channel evolution by erosion or deposition [13].…”