Analysis of environmental transport of suspended sediment particles in a tidal wetland flow under the effect of floating vegetation absorption

Abstract

Wetlands play an important role in maintaining many natural cycles and supporting a wide range of biodiversity. In the current world, the transport of solute in a wetland with vegetation is an essential issue in environmental, biological, geophysical, and concerned applications. Specially, floating vegetated wetland which is a buoyant platform enveloped by plants, playing a pivotal role in filtering and purifying water in aquatic ecosystems The main focus of the present research is to investigate the transport of sediment particles in a depth-dominated tidal floating vegetated wetland (FVW) flow. The characteristics of floating vegetation absorption and vegetation parameter in FVW are explained to explore the transport of sediment particles. This work’s model relies on an advection-diffusion equation, the solution of which discloses the concentration of settling particles in the water phase. Utilizing the method of moments, a set of moment equations is derived from the governing equation. The equations of moment are then solved using a finite difference implicit scheme. Further, the four moments and Hermite polynomial illustration is adopted to derive the vertical mean concentration distribution profile. The effective dispersivity and the concentration distributions of the sediment particles are illustrated for three different situations of fluid flow: steady, purely oscillatory, and periodic flow with non-zero-mean for all time. The effects of the vegetation factor, settling velocity, absorption due to floating vegetation, and other important factors on sediment transport in FVW are discussed for three different cases separately. Result shows as settling velocity (ω) increases, the influence of vegetation absorption (β) on dispersion coefficient diminishes in the steady state, and its effect on mean concentration becomes less pronounced due to the downward movement of particles. This is because vegetation absorption is stronger near the upper surface, but higher ω values lead to particle downward, reducing β′s impact. The results are described in the context of some real-world situations, as the free surface of a tidal wetland is naturally covered with plants; FVW serve as a natural water purification filter for polluted estuaries, contaminated crude oil wastewater, and so on. This study has potential to aid in water purification efforts as well as for the protection and conservation of coastal environments to limit sea level rise.