Sediment resuspended

The existence of different fractions of particulate substrates in terms of then-specific hydrolysis rates is an important finding that originates from investigations of wastewater and resuspended sediments (Bjerre et al 1995 Bjerre et al., 1998a Vollertsen and Hvitved-Jacobsen, 1998 Tanaka and Hvitved-Jacobsen, 1998a). Typically, two to three fractions must be considered to interpret the hydrolysis when it occurs in wastewater of sewer systems (cf. Section 3.2.6). 

Vollertsen, J. and T. Hvitved-Jacobsen (1998), Aerobic microbial transformations of resuspended sediments in combined sewers — A conceptual model, Water Sci.Tech., 37(1), 69-76. 

A special device was used to collect artificially resuspended sediment. In this device, the sediment was placed in a tube with overlying water. An oscillating grid placed in the water above the sediment caused a steady state resuspension equilibrium, under the same conditions as typically generated by winds and currents in the lagoon. This overlying water was then filtered, and the resuspended material analysed. 

Where the waves and currents weaken, resuspended sediment settles back down to the seafloor. Given the small particle sizes of the suspended material (mostly 3 to 10 pm), redeposition can take many years. The resulting redistribution of sediments creates patches of clay, mud, and exposed rock on the continental margins. In other words, resuspension from waves and currents can cause some sediments to become reUct deposits. Hard bottoms can serve as good habitats for some members of the benthos as they promote the formation of coral reefs. For paleoceanographers, relict deposits are problematic because they represent gaps, or imconformities, in the sedimentary record. 

Nepheloid layer Deep and bottom waters that have high concentrations of resuspended sediment. 

The flux resulting from sediment resuspension is assumed to be proportional to the difference between the concentration on the resuspended sediment particles, Cssc, and the sorbed concentration, Csop, which the particles would have in equilibrium with the aqueous concentration in the water column, Cpp ... 

D. Resuspension and resettling of sedimentaiy particles (Box 23.2, Eq. 4). Remember that the parameter p,res is the resuspended sediment mass per unit area and time multiplied with the relative degree of equilibration between suspended particle and surrounding water. 

Assuming a bulk density of 1.05 g/cm3 and a dry weight fraction of 0.1 for the interface sediment, 0.38 mm of sediment would supply the observed 160-m water-column burden of resuspended phases, approximately half the basinwide average annual linear sedimentation. The corresponding amount of sediment was consistent with the mass of allochthonous components in the water column during the March-May spring mixing period (200-300 mg/m3). The quantity of resuspended P was calculated as the product of mass of resuspended sediment (g/m2) and phosphorus concentration in surface sediment (mg of P/g). For a 160-m water column, the amount was 48 mg of P/m2 (25 mg of P/m2 for the mean water-column depth of 85 m). The resuspended P flux (25 mg of P/m2) was also obtained from the product of resuspended Al (mg/m2) and the P Al ratio in bottom sediment. 

Ko, F.C., Baker, J.E., 1995. Partitioning of hydrophobic organic contaminants to resuspended sediments and plankton in the mesohaline Chesapeake Bay. Environ. Sci. Technol. 49, 171-188. 

Assessment of sediment stability serves to determine whether or not SQT studies need to be limited to superficial sediments (Chapman et al., 2002). Such assessments usually involve determining current flows required to resuspend sediments compared to worst case current flows or events such as 100-year storms at that site. 

A newly installed, i.e. a greatly stressed well, must stabilize for at least 24 hours after it has been developed in order to produce a representative sample in certain hydrogeological settings, stabilization time for new wells may exceed a week. After the well fills with fresh formation water, samples must be retrieved with a minimum exposure to air, with the least amount of resuspended sediment, and in a manner that prevents degassing. 

The particle velocity associated with the shallow water wave is elliptic ally with the major axis aligned parallel to the bottom and the minor axis perpendicular to it. The amplimde of the particle velocity decays with depth but remains finitely by close to the bottom where the minor axis of the particle motion approaches to zero. This implies that particle motions of shallow water waves are quite capable of resuspending sediments as well as to develop a turbulent bottom boundary layer. 

Tc-MAA is injected intravenously with the patient in supine position. Prior to injection, the syringe should be inverted repeatedly to resuspend sedimented macroaggregates they should be injected slowly over a period of at least 30 s to normalize different phases of the respiratory cycle (Wagner 1995). 

A very similar situation exists near the seafloor, where resuspended sediment particles scavenge " Th from the bottom water. The resulting depletion of " Th in the benthic nepheloid layer (BNL) is a measure of the intensity of the resuspension-sedi-mentation cycle on a timescale of weeks. The tracer thus shows whether a nepheloid layer is advected over large distances or sustained by local resuspension. 

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