Sediments mobile muds

Due to rapid and high sedimentation rates in the ETM, the accumulation of particles in the BBL can result in the formation of mobile and fluid muds. Fluid muds are defined as sediments suspended in concentrations of greater than 10 g L-1. 

The high vertical flux of particulates in river/estuarine plume regions commonly results in the accumulation of particles in the formation of a benthic boundary layer (BBL) and/or mobile and fluid muds (see chapter 6 for more details). The BBL is defined by Boudreau and Iprgensen (2001, p. 1) as those portions of sediment and water columns that are affected directly in the distribution of their properties and processes by the presence of... 

Amazon deltaic deposits are reworked extensively by tides and waves (Geyer et al. 1996, Kineke et al. 1996, Sternberg et al. 1996). Over 10% of the Amazon subaqueous delta is covered by fluid muds (suspended solid concentration > 10 g L O, which can be several meters thick in some places. These sediments and the water contained therein can be mobilized by changes in frontal dynamics or by fortnightly tidal cycles (Kineke et al. 1996, Geyer et al. 1996). Even in nonfluid mud areas, the sediment can be... 

Since the typical sedimentation rate is less than about a millimeter per year, the mean components of U and c represent averages over about 10 yr. Sediment deeper than h is here assumed to be part of the permanent mud deposit the fraction of this sediment that in fact may be mobilized by occasional very severe storms or bioturbation is neglected. The formation of the mud deposit occurs at a rate of - IVo and IVo is the velocity at which sand grains pass into the permanent deposit of marine mud and are removed from transport. 

Sound. For these reasons the transition zone was described using a onedimensional form of the mass-balance equation. The muddy floor of the Sound is blanketed with a layer of readily resuspendable agglomerates. This layer is about 1 cm thick. Any sand in this layer was assumed to be regularly set in motion by the currents, while sediment grains below this layer remained immobile. The formation of a permanent mud deposit occurs at the base of this layer at the rate of about 1 mm/year. This value was taken as the speed with which sand grains are removed from the zone of mobile sediment. 

AH contaminated dredge and other sediments are abundant and frequently not utilized or recycled for beneficial purposes. This work indicates that these sediments can be used, alone or mixed with clean sediments or other industrial materials (e.g., phosphogypsum and bauxite red mud ), for wetland creation or enhancement. It would seem that either or both marsh locations (interior vs. streamside) are appropriate, at least with respect to these AHs. The tradeoff involves time and potential offsite risks at streamside, the removal rates are twice as fast as and somewhat more complete than in the interior, but the action of the tides could mobilize contaminants to the estuary and beyond. The interior sediments will allow for less exchange of the pollutants with the estuarine water, but will take longer to depurate, particularly if the sediments become compacted. 

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