The role of algae in fine sediment flocculation: In-situ and laboratory measurements

Journal article (2019)

Authors

Zhirui Deng East China Normal University
Qing He East China Normal Univeristy
Z. Safar Environmental Fluid Mechanics - CEG
C. Chassagne Environmental Fluid Mechanics - CEG
Research Group
Environmental Fluid Mechanics (CEG) (TU Delft)
Copyright: © 2019 Zhirui Deng, Qing He, Z. Safar, C. Chassagne
DOI
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https://doi.org/10.1016/j.margeo.2019.02.003
Yangtze Estuary Flocculation Algae Grain size distribution Floc size Tidal variation
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Published Date

2019

Language

English

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Faculty

Civil Engineering & Geosciences

Department

Hydraulic Engineering

Research Group

Environmental Fluid Mechanics

Abstract

The precise interactions between organic and inorganic particles in the context of flocculation is an on-going topic of research. The suspended particulate matter (SPM) found in estuaries is composed of both organic and inorganic particles with specific particle size distributions (PSD's). These PSD's are a function of the hydrodynamic conditions, suspended sediment concentration (SSC), organic matter composition, salinity and seasonal variations. A field campaign was carried out in August 2015 in the turbidity maximum zone of the Yangtze Estuary, where the SPM dynamics were recorded. The concentration of algae in the water column was indirectly measured through the chlorophyll-a concentration (CC). We show that there is a strong correlation between SSC and CC in the whole water column, for the whole tidal cycle. Additional flocculation experiments in the laboratory confirm that the largest observed flocs are predominantly organic-based, and that salinity alone could not induce the flocculation of the Yangtze mineral particles. A key parameter for the maximal floc size is the algae concentration to sediment concentration ratio. When this ratio is high, the D50 is high and vice-versa.