Resuspension potential

An analysis of the contributions to the skin friction shows that the surface waves play the dominant role. The shear stress induced by bottom currents exceeds the low fluff threshold only occasionally, especially during inflow events of saline water through the narrow channels. Therefore, an estimation of the resuspension potential of bottom sediments may be based on waves only, as, for instance, done by Jonsson (2006). However, without bottom currents some events will be missing, and, more important, no conclusions about the transport paths are possible. 

In situ methods have potential use as an interim or emergency measure until dredging can be undertaken or as a primary remedial action where it is determined to be more cost-effective than removal. The biggest advantages are that they are much less costly than dredging, eliminate the need for dredged material management, and minimize the resuspension of contained sediments.15... 

Danesi et al.96 applied SIMS, in addition to X-ray fluorescence imaging, by using a microbeam (p-XRF) and scanning electron microscope equipped with an energy dispersive X-ray fluorescence analyzer (SEM-EDXRF) to characterize soil samples and to identify small DU particles collected in Kosovo locations where depleted uranium (DU) ammunition was employed during the 1999 Balkan conflict. Knowledge of DU particles is needed as a basis for the assessment of the potential environmental and health impacts of military use of DU, since it provides information on possible resuspension and inhalation. The measurements indicated spots where hundreds of thousands of particles may be present in a few mg of contaminated soil. The particle size distribution showed that most of the DU particles were < 5 pm in diameter and more than 50 % of the particles had a diameter of < 1.5 p.m.96... 

Resuspension of bottom sediments presents a potential problem for flux estimates. However, our results suggest minimal resuspension during stratification. As a part of a separate study, Hurley (unpublished data) measured pigment fluxes to the sediment surface. Sediment trap material was dominated by chlorophyll a and pheophorbide a (a grazing indicator). Surface sediments, however, were dominated by pheophytin a, a relatively stable chlorophyll degradation product. The lack of any substantial amounts of pheophytin in trap material suggested that if resuspension of particulates from the surface sediment was important, it was probably minimal. 

Copper, lead, cadmium and zinc have been found predominantly in potentially mobile forms by sequential extraction of material collected during road cleaning (Colandini et al, 1995). Cadmium and zinc were found to be more labile than lead and copper. A study of street dust and gully pot sediments confirmed this order of potential availability (Striebel and Gruber, 1997) and also suggested that lead levels in material of the types studied had decreased since the introduction of unleaded fuel in Germany. Lead has also been studied in street dusts from Brisbane, Australia. The element was found mainly in the carbonate phase and in the smaller particle size fraction (Al-Chalabi and Hawker, 1996) except where resuspension caused particle aggregation. 

Figure 2. Change in membrane potential during uptake and efflux of a neutral amino acid. Ehrlich cells incubated with amino isobutyric acid (AIB) show a transient increase in fluorescence (depolarization) followed by a return to control levels. Upon resuspension (arrow) in AIB-free medium (which results in loss of cellular AIB) fluorescence is decreased transiently (hyperpolarization) followed by a gradual return to baseline values. (From Laris et al. (1978), with permission.)...

The sample is aspirated and the beads washed (gentle resuspension and incubated at 4°C for 15 min with occasional agitation) with 1 mL of lysis buffer a minimum of three times. The isolated proteins are now ready to analyze. Potential approaches to optimize this protocol for the isolation of interacting proteins are discussed in Notes 3 and 4. 

Uranium may be transported to vegetation by air or by water. It can be deposited on the plants themselves by direct deposition or resuspension, or it can adhere to the outer membrane of the plant s root system with potential limited absorption. Similarly, uranium deposited on aquatic plants or water may be adsorbed or taken up from the water. The plants, aquatic or terrestrial, may be eaten directly by... 

Fanning, K. A., Carder, K. L., and Betzer, P. R. (1982). Sediment resuspension by coastal waters A potential mechanism for nutrient re-cycling on the ocean s margins. Deep Sea Res. 29,1223—1229. 

Pilskaln, C. H., ChurchiU, J., and Mayer, L. (1998). Resuspension of sediment by bottom trawling in the Gulf of Maine and potential geochemical consequences. Conserv. Biol. 12, 1223—1229. 

The frequency of occurrence plot given in the right panel of Fig. 19.13 confirms that the regions shallower than 30 m are potential erosion areas, where fluffy layers are washed off with a probability of 10% or more. Naturally, the erosion area is smaller and is affected with lower frequencies if the threshold for incident movement is higher, as for example 1.2 cm/s for the bed-load transport of fine sand, or 2 cm/s for its resuspension. 

One approach to increase certainty of data has been suggested e.g. by Suter (1983) the use of several lines of evidence in order to make a best-judgement weight of evidence decision. In this context, the application of different biotests with different endpoints, exposure routes and sensitivities towards contaminants could be regarded as different lines of evidence. If such a biotest battery, however, comprises e.g. sediment contact tests as well as elutriate tests, additional information could be drawn from the results on whether potential risks of contaminants are sediment-focused or could also affect organisms in tlie water column upon resuspension. 

Anoxic/oxidised samples. Changes of the forms of major, minor and trace constituents cannot be excluded when the sediment is transferred from its typical anoxic environment to chemical analysis via normal sample preparation. However, a comparison of extraction data from the original and oxidised samples could be used for worst-case considerations in respect of potential metal release during sediment resuspension, or subsequent to upland deposition of dredged material (Meyer et al., 1994). 

CTT stands for chemistry-toxicity test . These action levels are set by the Dutch authorities for the permit to relocate dredged material from Rotterdam harbour to the North Sea (Stronkhorst, 2003). The indication for resuspension was considered in dependence of the hydrological situation and was based on measurements of erosion potentials and observations of increased contaminated suspended matter downstream of the site. 

Anthropogenic (man-made) releases of plutonium are the primary sources of plutonium to the atmosphere. Atmospheric testing, fires involving plutonium-containing materials, and routine releases due to normal activities at processing and generating plants are all potential sources of airborne plutonium. Resuspension of plutonium sorbed to contaminated surface soils via fugitive dust emissions is an indirect pathway by which plutonium may be re-released into the atmosphere (Harley 1980). 

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