Environmental dispersion in wetland flow

Effects of intertidal seagrass habitat fragmentation on turbulent diffusion and retention time of solutes

“…Solute dispersion within macrophyte canopies has been addressed in several studies with seaweeds (Escartín and Aubrey, 1995), seagrasses (Ackerman and Okubo, 1993;Worcester, 1995;Ackerman, 2002), saltmarshes (Serra et al, 2004;Lightbody and Nepf, 2006;Zeng et al, 2011) and artificial structures (Nepf et al, 1997;Nepf, 1999) revealing that (1) in a horizontal plane, the turbulent diffusion coefficient (K y ) comprises two components, a first one related to the turbulent mixing of flow and a second one due to the lateral movement of fluid at the scale of individual structures (i.e. mechanical diffusion) (Nepf, 1999); (2) when compared with non-vegetated areas, submersed canopies decrease, or not affect, turbulent mixing and consequently affecting K y values (Ackerman and Okubo, 1993;Worcester, 1995); and (3) mechanical diffusion contributes to higher K y values than those predicted by turbulent mixing (Nepf, 1999;Serra et al, 2004;Lightbody and Nepf, 2006).…”

Two-scale analysis for environmental dispersion in a two-layer wetland

“…Within the initial stage of the contaminant transport, which is characterized by the transverse-mixing time-scale H 2 =D Ã , where H is the depth of the channel and D Ã is the effective molecular diffusivity, the transverse mean concentration forms a skewed longitudinal distribution. In the latter stage, the vertical concentration difference decreases to a small fraction of its initial value, and the mean concentration tends to be in a Gaussian distribution, which is known as Taylor dispersion of the transport (Wu and Chen, 2014b;Zeng, 2010).…”

“…Chen and his collaborators Wu et al, 2011a;Zeng, 2010) provides a useful one-dimensional environmental dispersion model, which was based on the phase-average theory and the concept of Taylor dispersion (Taylor, 1953). By phase average the discontinuities of both velocity and concentration in space caused by the vegetation in wetlands are removed, and by Taylor dispersion concept the transport of the contaminant can be described by an effective diffusion equation under long-time evolution (Wu and Chen, 2014b;Zeng, 2010).…”

Taylor dispersion in a packed pipe with wall reaction: Based on the method of Gill’s series solution

“…For instance, groundwater flow in soils [12], chemical separation or purification of mixtures [13,14], extraction of energy from geothermal regions [15], and contaminant transport in wetlands [16][17][18][19][20][21][22][23], which cannot be described by the model of dispersion in a pure fluid flow. The model of dispersion in porous media with wall reaction is therefore highly in need.…”