Aqueous Saline Environments

Not all measures of salinity convey the same degree of salinity. For example, compare Orca Basin, the Great Salt Lake, the Dead Sea, and Basque Lake (Table 5.1). All four of these waters contain about the same salinity % [25.1-26.4% salt (wt/wt)]. Note, however, that Basque Lake has a much more favorable (for life) aw (0.919) compared with Orca Basin (0.774), Great Salt Lake (0.776), and, especially, the Dead Sea (0.690). The impact of salts on life depends on the anions and cations and their charges and molecular weight. Bacterial sulfate reduction occurs with salt concentrations up to 24% (Oren 1988), but chloride salt solutions at such concentrations deals much more harshly with life. Only the most halophilic organisms can live in the Dead Sea (Table 4.2). The Dead Sea was called dead because it was only in 1936 that life forms (e.g., bacteria, algae, yeast) were first isolated from this hypersaline water (Ventosa et al. 1999). 

Property Seawaterb Seawater at -20°C Orca Basin, Gulf of Mexico0 Great Salt Lake, USAd Dead Sea, Israel Don Juan Pond, Antarctica1 Basque Lake, Canadad Mono Lake, USAd Lake Magadi, Kenya  

1 pH values without parentheses are supersaturated with respect to calcite. pH values in parentheses are in equilibrium with calcite. 

For a pure CaCp solution, the FREZCHEM model predicts a eutectic temperature of —50.4°C with a CaCD molality of 3.99 mol kg-1 (Fig. 5.5) (Marion 1997), which is in reasonable agreement with literature values of —51 °C to —49.8°C and CaCD molalities of 3.90 to 4.32molkg 1 (Spencer et al. 1990). A pure NaCl-CaCF-EFO system more nearly matches the chemical behavior of DJP than does the pure CaCD-PFO system. The calculated eutectic temperature for a pure NaCl-CaCF-EFO system is —51.6°C, with a Ca concentration of 3.78 mol kg a Na concentration of 0.51 mol kg-1, and a Cl concentration of 8.07 mol kg 1, which is similar but not identical to the composition of DJP at the eutectic. The small differences between this pure system and DJP are due to the minor amounts of K and Mg present in DJP. The calculated eutectic temperature for DJP is —51.8°C the Ca concentration is 3.72mol kg the Na concentration is 0.50molkg 1 and the total Cl concentration is 8.08 mol kg which leaves a residual charge of 0.14 molc kg-1 consisting of K and Mg. Compared to pure CaCD, the eutectic for DJP is displaced to a lower Ca concentration and a lower temperature 

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Salinity affects microbial activity, in part, because it controls water availability. The higher the salinity, the more energy an organism must expend to maintain a favorable osmotic balance. Salts, of course, have effects on living organisms beyond water availability. For example, salts can be both a source of essential nutrients as well as a source of toxic heavy metals. Also, sulfate salts appear to be more favorable for life than chloride salts see the discussion in Sect. 5.1.2 (Aqueous Saline Environments). However, in this section on salinity, the focus will be on salinity as a control on water availability. 

The goal was to prepare an anchorable (polystyrene) product that, when exposed to an aqueous, saline environment, would result in exposure and swelling or other freedom of the hydrophilic spacer that would, in turn, allow the biologically active compound, heparin, to inhibit clotting and/or that could be used for fabrication of blood-contacting devices for the same purpose. These potential end uses were to be tested at a later date. 

An important process in which surfactants are removed from the aqueous environment is biodegradation. Whereas surfactant biodegradation in freshwater is in general quite fast, the degradation processes occur usually slower in saline waters [1,33] (see also Chapter 5.3). However, one study reported that the biodegradation of A9PE0 was faster in seawater than in freshwater in 50 days, primary biodegradation was 33-36% in pond water and 95% in seawater [34],... 

Wershaw RL (1986) A new model for humic materials and their interactions with hydrophobic organic chemicals in soil-water or in sediment-water systems. J Contam Hydrol 1 29-45 Whitehouse BG (1984) The effect of temperature and salinity on the aqueous solubility of polynuclear aromatic hydrocarbons. Mar Chem 14 319-332 Wolters A, Linnemann V, Herbst M, Klein M, Schaffer A, Vereecken H (2003) Pesticide volatihzation from soil Lysimeter measurements versus predictions of European registration models. J Environ Qual 32 1183-1193... 

In summary, we can conclude that at moderate salt concentrations typical for seawater ( 0.5 M), salinity will affect aqueous solubility (or the aqueous activity coefficient) by a factor of between less than 1.5 (small and/or polar compounds) and about 3 (large, nonpolar compounds, n-alkanals). Hence, in marine environments for many compounds, salting-out will not be a major factor in determining their partitioning behavior. Note, however, that in environments exhibiting much higher salt concentrations [e.g., in the Dead Sea (5 M) or in subsurface brines near oil fields], because of the exponential relationship (Eq. 5-28), salting-out will be substantial (see also Illustrative Example 5.4). 

In this chapter, we examine biogeochemical applications of the FREZCHEM model to Earth, Mars, and Europa, where cold aqueous environments played and continue to play a critical role in defining surficial geochemistry. Interpretations include the potential for life in these environments. These simulations cover applications to seawaters, saline lakes, regoliths, aerosols, and ice cores and covers. These examples are the proverbial tip of the iceberg in terms of the potential of this model to describe cold aqueous geochemical processes. At the end of the chapter, we discuss application limitations, cases where the underlying thermodynamic assumptions are at variance with real-world situations. 

Green-Pedersen, H., and N. Pind. 2000. Preparation, characterization, and sorption properties for Ni11 of iron oxyhydroxide-montmorillonite. Coll. Surf. A. 168 133-145. Green-Ruiz, C. 2009. Effect of salinity and temperature on the adsorption of Hg(II) from aqueous solutions by a Ca-montmorillonite. Environ. Technol. 30 63-68. 

There are several factors that can affect a given surfactant s performance in a reservoir environment. First, the effect of inorganic ions is significant. Most oil reservoirs have an aqueous phase of saline brine that may vary in concentration from 0.5% to upwards of 15% NaCl. Also, there are divalent ions, such as Ca" "" " and Mg "" " present in significant concentrations. Most of the experimentation, which serves as the basis for this paper, was conducted utilizing a brine of 3% NaCl with 100 ppm (mg/1) of Ca" "" ". This composition is typical of many natural reservoir brines, and those surfactants that will perform well with this brine will also do well in the majority of reservoirs. 

SRB are essentially ubiquitous in aqueous environments that contain organic carbon and sulfate (e.g., subsurface aquifers and lake sediments). Moreover, analysis of a key gene associated with sulfate reduction (dissimilatory sulfite reductase) indicates that microbial sulfate reduction is an ancient trait, suggesting that organisms may have contributed to sulfide mineral formation throughout much of Earth history (Wagner et al. 1998). SRB are tolerant to environmental extremes of heat (some are hyperthermophiles) and salinity (some are halophiles). 

Human breast adenocarcinoma MCF-7 cells were incubated for different time intervals with deuterated LIP and TATp-LIP at a Upid concentration of 2 mg ml" . After incubation, the cells were fixed in a phosphate-buffered formalin solution and subsequently washed and submerged in phosphate-buffered saline, to maintain the cell shape within the aqueous environment. 

Equation 7.69 needs further discussion, however. As we know, the allocation of surfactant in aqueous and oleic phases depends mainly on the salinity (type of microemulsion), not water/oil ratio. For example, in a type II(-) environment, almost all the surfactant is in the aqueous phase, regardless of WOR. Let us assume the surfactant concentration in the aqueous phase is C31, and the surfactant concentration in the oleic phase (C32) is KjCsi according to Eq. 7.69. Then the amount of surfactant in the aqueous phase is C31S1 = C3i(WOR/ (1-i-WOR), and the amount of surfactant in the oleic phase is KSC31S2 = KjCsi/ (1-i-WOR). Here, Si and S2 are the aqueous and oleic phase saturations, respectively. The total amount of surfactant in the system, C3, is... 

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