Mediterranean Water properties

Mineral tanning was probably first practiced in ancient Mesopotamia and then spread to Egypt, the Middle East, and the Mediterranean Sea area (Levey 1958). Mineral-tanned leather is soft to handle, has a velvety texture, and is almost white, a color practically impossible to achieve by other tanning processes. It is, however, very sensitive to humidity and water under wet conditions the alum in the leather is hydrolyzed (decomposed by water), forming sulfuric acid, a very strong acid that attacks the leather and causes its rapid decay. Mineral-tanned leather that has been humid or wet for a more or less extended period of time loses some of its characteristic properties, such as softness, pliability, and strength, and becomes hard, horny, and brittle. 

Based on their molecular properties as well as the properties of the solvent, each inorganic or organic contaminant exhibits an adsorption isotherm that corresponds to one of the isotherm classifications just described. Figure 5.1 illustrates these isotherms for different organic contaminants, adsorbed either from water or hexane solution on kaolinite, attapulgite, montmorillonite, and a red Mediterranean soil (Yaron et al. 1996). These isotherms may be used to deduce the adsorption mechanism. 

Many studies have reported levels of NPs and related compounds in aquatic environments throughout Europe, North America and Japan. Values higher than 100 /xg/1 have been reported11,66. However, this range of concentration is unusual and most of the authors have reported values below 1 /xg/1 in surface waters, as discussed in recent reviews10,81. Due to their hydrophobic properties, NPs tend to be associated with sediments. The analysis of samples collected from the Great Lakes basin and the upper St Lawrence River yielded concentrations between 0.17 and 72 /jLg/g9,3 , whereas values between 6 and 69 /ig/g were found in sediments from the Mediterranean Sea near Barcelona15. In Japan, the concentrations of NPs were found... 

Experience gained during the last decade in the determination of CBs in off-shore surface and deep waters has shown that concentrations are extremely low, much lower than reported earlier (see Table 22-1). Concentrations reported for the Mediterranean Sea (Tolosa et al, 1997 Schulz-Bull et al., 1997), the North Sea Schulz-Bull et al., 1991) and the Baltic Sea Schulz-Bull et al., 1995) were well above those found in surface waters of the open ocean Iwata et al., 1993 Schulz-Bull et a/.,1998). In deep-ocean water Schulz et al., 1988 Petrick et al, 1996 Schulz-Bull et al, 1998) much lower concentrations were found than in surface waters. In North Atlantic Deep Water, values of individual CBs were found to be < 0.01 pg/L, yet concentrations in solution were higher than those in suspended material on an equal volume basis. It turns out that the distribution of CBs between solution and suspension is determined primarily by molecular properties (characterized by octanol/water distribution coefficients). However, biological processes disturb the establishment of equilibria. This phenomenon has been observed in river water, in estuarine and coastal waters and during biologically active periods in the surface layer of the open ocean. 

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