Seasonal variation of sediment flocculation and the modeling thereof as function of biochemical factors

Abstract

The flocculation process and modelling of suspended sediment transport in estuarine regions is a hot topic in estuarine science[Winterwerp, 1999]. The flocculation is greatly influenced by biochemical parameters[De Lucas Pardo, 2014]. In this paper, we analyse the impact of algae on the processes of flocculation in the Yangtze Estuary, and we identify the mechanisms which are responsible for their changes. The amount of algae (phytoplankton biomass) is linked to the chlorophyll α concentration which we measured[Uncles et al., 1998]. The measurements were performed in the maximum turbidity zone. The seasonal variations of phytoplankton lead to changes in the flocculation dynamics and the composition of suspended particle matter. We recorded the floc size changes in the Yangtze Estuary and we found that: (1) the flocs are significantly influenced by tidal dynamics, as the floc size during slack water is larger than ebb tide and flood tide, (2) there is a correlation between the Chlorophyll concentration and sediment concentration, (3) the floc size is correlated to the algae-sediment mass ratio, (4) in winter, with high salinity and small river discharge, the region has a significant stratification and the floc size was smaller than the one in summer