Sediment mobilization

Brannon and Patrick [129] reported on the transformation and fixation of arsenic V in anaerobic sediment, the long term release of natural and added arsenic, and sediment properties which affected the mobilization of arsenic V, arsenic III and organic arsenic. Arsenic in sediments was determined by extraction with various solvents according to conventional methods. Added arsenic was associated with iron and aluminium compounds. Addition of arsenic V prior to anaerobic incubation resulted in accumulation of arsenic III and organic arsenic in the interstitial water and the exchangeable phases of the anaerobic sediments. Mobilization of... 

This chapter focuses on the environmental implications of sediments mobilized in response to rain events. Three different aspects are discussed the role of suspended sediment in bacterial transport, temporal changes in sediment geochemistry, and... 

Salomons, W. Mook, W.G. (1977) Trace metal concentrations in estuarine sediments mobilization, mixing or precipitation. Netherlands Journal of Sea Research, 11, 119-29. 

Rantala, R.T.T. (1986) Sediment mobility and its contribution to trace metal cycling and retention in a macrotidal estuary. Water Science and Technology 18, 111-19. 

Song Y. and Muller G. (1999) Sediment—Water Interactions in Anoxic Freshwater Sediments Mobility of Heavy Metals and Nutrients. Springer-Verlag, Berlin-Heidelberg. 

Accumulation of heavy metals (HM) in different compartments of the biosphere, and their possible mobilization under changing environmental conditions induce a perturbation of the ecosystem and adverse health effects. Fast and correct estimating the environmentally relevant fonus of HM in soils, sediments, and sewage sludge is an urgent need for environmental monitoring and assessment. 

The behavior of elements (toxicity, bioavailability, and distribution) in the environment depends strongly on their chemical forms and type of binding and cannot be reliably predicted on the basis of the total concentration. In order to assess the mobility and reactivity of heavy metal (HM) species in solid samples (soils and sediments), batch sequential extraction procedures are used. HM are fractionated into operationally defined forms under the action of selective leaching reagents. 

Adsorption — An important physico-chemical phenomenon used in treatment of hazardous wastes or in predicting the behavior of hazardous materials in natural systems is adsorption. Adsorption is the concentration or accumulation of substances at a surface or interface between media. Hazardous materials are often removed from water or air by adsorption onto activated carbon. Adsorption of organic hazardous materials onto soils or sediments is an important factor affecting their mobility in the environment. Adsorption may be predicted by use of a number of equations most commonly relating the concentration of a chemical at the surface or interface to the concentration in air or in solution, at equilibrium. These equations may be solved graphically using laboratory data to plot "isotherms." The most common application of adsorption is for the removal of organic compounds from water by activated carbon. 

Research into the aquatic chemistry of plutonium has produced information showing how this radioelement is mobilized and transported in the environment. Field studies revealed that the sorption of plutonium onto sediments is an equilibrium process which influences the concentration in natural waters. This equilibrium process is modified by the oxidation state of the soluble plutonium and by the presence of dissolved organic carbon (DOC). Higher concentrations of fallout plutonium in natural waters are associated with higher DOC. Laboratory experiments confirm the correlation. In waters low in DOC oxidized plutonium, Pu(V), is the dominant oxidation state while reduced plutonium, Pu(III+IV), is more prevalent where high concentrations of DOC exist. Laboratory and field experiments have provided some information on the possible chemical processes which lead to changes in the oxidation state of plutonium and to its complexation by natural ligands. 

Lynn, D. C. and Bonatti, E. (1965). Mobility of manganese in diagenesis of deep-sea sediments. Marine Geol. 3,457-474. 

In soil and sediments, methyl parathion adsorbs to soil and is expected to display moderate mobility (EPA 1980c). The major degradation process of methyl parathion in soil is biodegradation by microbes (Badway and El-Dib 1984). Degradation by hydrolysis has been observed to occur at higher temperatures... 

Polychaete worms belonging to the genera Nereis and Scolecolepides have extensive metabolic potential. Nereis virens is able to metabolize PCBs (McElroy and Means 1988) and a nnmber of PAHs (McElroy 1990), while N. diversicolor and Scolecolepides viridis are able to metabolize benzo[a]pyrene (Driscoll and McElroy 1996). It is worth noting that apart from excretion of the toxicant, polar, and mnch more water-soluble metabolites such as the glycosides formed from pyrene by Porcellio sp. (Larsen et al. 1998) may be mobile in the interstitial water of the sediment phase. 

The predictable flux of °Thxs to the seafloor means that the flux of other components into marine sediments can be assessed by simply measuring their concentration relative to that of °Th (Fig. 5). This approach, termed °Thxs profiling, has seen widespread use in the last decade and has become a standard technique for measuring accumulation rates of many chemical species and sedimentary components. °Thxs provides possibly the best constraint on such accumulation rates for late Pleistocene sediments and is therefore an important tool. It is the best constrained of the constant flux proxies which include ofher chemical species such as Ti (Murray et al. 2000) and He (Marcantonio ef al. 1995). As wifh these other proxies, °Thxs is not mobilized during sediment dissolution because of its extreme insolubility so that °Thxs profiling assesses the final sedimentary burial flux, rather than the flux that initially arrives at the seafloor. 

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