Remobilization metal

Price and Calvert could confirm this theory with the observation that Mn/Fe ratios in the manganese nodules are negatively correlated with the accumulation rates of the sediment. The slower the sedimentation, the more manganese-rich remobilized metal solution from the sediment contributes to the growth of the nodules. 

Phosphonates are often used in detergents as stabilizers for encymes and bleaching components in a concentration of <0.5%. Dates of acute aquatic toxicity of the most used substances HEDP, aminotrismethylenephosphonic acid (ATMP), and EDTMP are given in Table 14. In a concentration of <2 mg/L no remobilization of heavy metals from sediments was observed [207]. 

Heavy metals bound to bacteria-soil composites may not be as easily released to the environments as those sorbed by pure bacteria. Flemming et al. (1990) reported that the order of remobilization of heavy metals from bacteria-clay composites was Cr Ag < Cu. Chromium was veiy stable when sorbed by bacterial cell walls, clay, and bacterial wall-clay... 

Flemming CA, Ferris FG, Beveridge TJ, Bailey GW (1990) Remobilization of toxic heavy metals adsorbed to bacterial wall-clay composites. Appl Environ Microbiol 56 3191-3203... 

Saulnier, I. Mucci, A. 2000. Trace metal remobilization following the resuspension of estuarine sediments Saguenay Fjord, Canada. Applied Geochemistry, 15, 191-210. 

However, only the smallest part of soluble metals is involved in the biological cycle. Most of these are either lost to water runoff, or retained in the peat organic matter. The latter is the source of gradual remobilization but the whole mineralization may last up to 50 years or even more. The total accumulated retained amount of macro-or trace metals in organic matter of peat is tens and hundreds of time higher than the concentration of annually released soluble forms, which are available for plants. 

Due to their unique surface-active properties, surfactants possess the capacity to remobilize non-polar contaminants, such as polycyclic aromatic hydrocarbons or heavy metals, which have accumulated in... 

Sinking particles transport trace elements to the sediments. Once in the sediments, chemical reactions can resolubilize a significant fraction of the particulate metals. This process is termed diagenetic remobilization and is the subject of the next chapter. The resolubilized elements can diffuse across the sediment-water interface into the deep zone. 

The Fe-Mn oxides that form from the diagenetic remobilization of sedimentary metals accrete at fester rates, on the order of himdreds of millimeters per million years. 

Oxic Diagenesis Metals remobilized from sediments lying in the oxic zone. Remobilization likely occurs in anoxic microzones adjacent to nodules. Bioturbation is an important metal transport agent. Some nodules now found in oxic sediments were likely formed during times when the redox boundary was closer to the seafloor. 10-50 Todorokite (high Cu and Ni content) 32% 5-10 15-20... 

Suboxic Diagenesis Metals remobilized from reducing sediments. Upward diffusive transport through pore waters supplies metals to nodule bottoms. Accretion is episodic, occurring only when the depth of the redox boundary rises close to the sediment-water interface. 100-200 Todorokite/Birnessite (low Cu and Ni content) 48% 20-70 60-200... 

Nickel removed by coprecipitation can be remobilized by microbial action under anaerobic conditions (Francis and Dodge 1990). Remobilization results Ifom enzymatic reductive dissolution of iron with subsequent release of coprecipitated metals. A lowering of pH as a result of enzymatic reactions may indirectly enhance the dissolution of nickel. Experiments using mixed precipitates with goethite... 

Francis AJ, Dodge CJ. 1990. Anaerobic microbial remobilization of toxic metals coprecipitated with iron oxide. Environmental Science and Technology 24 373-378. 

Since the 1970s, there have been concerns about the environmental impact of poorly biodegradable cheiants such as EDTA and DTPA, as they could potentially remobilize toxic heavy metals, such as cadmium, mercury, and lead, from river sediments back into the water column [10]. More recent concern has focused on large-scale emissions from photographic laboratories, pulp and paper mills, metal treatment plants, and use of industrial detergents, as higher dosages of cheiants are more likely to cause a... 

The concentrations of heavy metals both in river water and in river sediment are strongly changed by deposition-remobilization processes. The deterministic modeling of the transition between both environmental compartments is severely limited by the complex chemical, physical, and biochemical processes. 

By applying methods of sequential leaching, direct chemical information can be obtained and a rough assessment of the remobilization potential of the sedimented heavy metals is possible. Because of the lack of specifity of the extraction procedures particular species cannot be identified (see also critical hints in [KHEBOIAN and BAUER,... 

In rivers and streams heavy metals are distributed between the water, colloidal material, suspended matter, and the sedimented phases. The assessment of the mechanisms of deposition and remobilization of heavy metals into and from the sediment is one task for research on the behavior of metals in river systems [IRGOLIC and MARTELL, 1985]. It was hitherto, usual to calculate enrichment factors, for instance the geoaccumulation index for sediments [MULLER, 1979 1981], to compare the properties of elements. Distribution coefficients of the metal in water and in sediment fractions were calculated for some rivers to find general aspects of the enrichment behavior of metals [FOR-STNER and MULLER, 1974]. In-situ analyses or laboratory experiments with natural material in combination with speciation techniques are another means of investigation [LANDNER, 1987 CALMANO et al., 1992], Such experiments manifest univariate dependencies for the metals and other components, for instance between different metals and nitrilotriacetic acid [FORSTNER and SALOMONS, 1991], but the interactions in natural systems are often more complex. 

The sampling and analytical conditions are described in detail in Section 8.2.1. For estimation of a medium water influence on the sediments the mean values of the water components over the investigation period of two years were used as the first (independent) data matrix the metal distribution coefficients were taken as the dependent data matrix. For description of deposition-remobilization effects a heavy metal distribution coefficient, DCh was defined as ... 

The strong dissolution effects on heavy metals of increasing phosphate concentrations in river water (Fig. 8-19) indicate the strong remobilization effects which result from complex formation. This tendency for complex formation with triphosphates is also described in the literature [GMELIN, 1965]. Increasing the concentration of phosphate in water from 0.38 to 0.68 mg L 1 increases the iron concentration by 648 pg L 1 in water in contact with sediment in which the iron concentration is 16220 mg kg ... 

---