Dynamic release process of pollutants during suspended sediment transport in aquatic system |
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Authors: | Hong-wei Zhu Dao-zeng Wang Peng-da Cheng |
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Institution: | 1. Shanghai Institute of Applied Mathematics and Mechanics, Shanghai Key Laboratory of Mechanics in Energy Engineering, Shanghai University, Shanghai, 200072, P. R. China
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Abstract: | Pollutants release is highly consistent with suspended sediment concentration (SSC) in water column, especially during re-suspension and transport events. The present research focuses on pollutant dynamic release from re-suspended sediment, especially the vertical distribution relationship between them. The sediment erosion experiments on a series of uniform flow are conducted in a circulate flume. Reactive tracer (phosphorus) is used as the contaminant in fine-grained sediments to identify the release characteristic length and time. Experimental results show that the flow condition near-bed depends on the sediment surface roughness. The region with high turbulent intensities corresponds to a high concentration sediment layer. In addition, the SSC decreases with the distance, water depth, and particle grain size. The sediment in a smaller grain size takes much more time to reach equilibrium concentration. Total phosphorus (TP) concentration changes along the water depth as SSC in the initial re-suspension stage, appearing in two obvious concentration regimes: the upper low-concentration layer and the high-concentration near-bottom layer. This layered phenomenon remains for about 3 hours until SSC distribution tends to be uniform. Longitudinal desorption plays an important role in long-way transport to reduce the amount of suspended sediment in water column. |
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Keywords: | sediment pollutant turbulence surface roughness grain size vertical distribution longitudinal desorption |
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