Salinity increase

Evaporite deposition is a much more episodic process and thus difficult to quantify. Because seawater is significantly undersaturated with respect to common evaporitic minerals, like gypsum and halite, evaporites are only formed when restricted circulation develops in an ocean basin in which evaporation exceeds precipitation. A geologically recent example is the Mediterranean Sea of 5-6 Myr ago. At this time excess evaporation exceeded the supply of ocean water through shallow inlet(s) from the Atlantic Ocean. As salinity increased, first CaS04, then NaCl precipitated. Over time, salt deposits 2-3 km thick formed. This thickness represents about 40 desiccations of the entire... 

Weggler-Beaton K., McLaughlin M.J., Graham R.D. Salinity increased cadmium uptke by wheat and Swiss chard from soil amended with biosolids. Aust J Soil Res 2000 38 37 15. 

The river Ebro is characterized by high water conductivity mainly because of its geology. The abundance of gypsum is mainly responsible for the salinity increase of the river water mostly due to the inputs of chlorides and sulfates in the Ebro... 

In the calculation results, gaylussite appears increasingly saturated in the lake water as salinity increases irregularly over time. The calculations suggest that between about 1975 and 1980, as salinities reached about 75 000 to 80 000 mg kg-1, the mineral became supersaturated at summer temperatures. 

Fig. 7.3 Decreasing evaporation rate of salt water compared with fresh water as salinity increases. Adapted from (Leaney and Christen 2000)...

The study sites in the Chesapeake Bay are shown in Figure 2. Depth profiles were obtained at both the North and South Basin locations, where the water column was oxic throughout and had a fairly constant 02 concentration of 5 mg/L. The surface-water temperature, approximately 10 °C, remained constant at the South Basin throughout the water column while decreasing in the North Basin to slightly less than 9 °C in the lower 18 m of the water column. At both locations the surface water (approximately the top 10 m) was relatively fresh, with a saltwater wedge at the bottom. The surface-water salinity increased from the North Basin (10.6%o) to the South Basin (12.3%0). 

Changes in the electrophilicity of the acceptor enormously affects the rate of exchange (69), This trend is illustrated by Fig. 4, which shows the rates of transmethylation of some methylmetals toward chloromercury species in certain cases there is a 107-fold dimunition of rate constant as salinity increases. This strongly suggests that the frequent salinity gradients found in natural waters will markedly influence the rates of naturally occurring transmethylations (vide infra). 

Salts can affect sorption of organic compounds by displacing cations from the soil ion exchange matrix, by changing the activity of the sorbate in solution, and by changing the charge density associated with the soil sorption surface (Hamaker and Thompson, 1972). Salt effects are most important for basic sorbates in the cation state, where an increase in salinity can significantly lower the sorption coefficient. Salt effects are least important for neutral compounds, which may show either increases or decreases in sorption as salinity increases. 

Figure 3.22 documents the role of salinity as an inhibitor of COoFHoO formation. At 275 K, the equilibrium carbon dioxide gas pressures for pure water, 10.0 wt.% NaCl (1.901m) and 15.2 wt.% NaCl (3.067 m), are approximately 15, 25, and 39 bars. As salinity increases, aw decreases, and P(g) must increase to satisfy the solubility product (Eq. 3.36). 

Temperature as well as salinity and other compositional variables have a profound influence on the viscosity of aqueous solutions and many aspects of life. As temperature declines and salinity increases, viscosity increases, diffusion rates decline, metabolic rates decline, motility of motile microorganisms and feeding rates decline, life spans may increase, and rates of evolution decline. All other things being equal, aqueous systems and planets allowing only cryogenic life will have less evolved life than chemical systems and planets that have permitted life to occur for substantial periods at higher temperatures. 

The Black Sea mussel Mytilus galloprovincialis is one more bivalve mollusk species that invaded the Sea of Azov at the end of the 1950s at the salinity increase. Before the Don River runoff was regulated, only single mussel specimens were encountered later, when the salinity increased, mussels obtained optimal conditions for their development and started to spread over the entire area of the basin [34], Presently, mussels also play an important role in the benthic biocoenoses of the Sea of Azov. 

Volovik SP, Dakhno VD (1983) On species composition of the Azov ichthyofauna in conditions of salinity increasing. Abstract on results of research of AzNIIRKH for 25 years. AzNIIRKH, Rostov-on-Don (in Russian)... 

The only study of the interannual variability of the T,S characteristics of the Black Sea waters at depths from 500 to 2000 m published to date [32] suggests the vertical and horizontal homogeneity of the deep temperature variations with standard deviations of 0.01-0.03 °C. The standard deviations of the interannual salinity variations decrease with depth from 0.2-0.3 psu at a depth of 500 m to 0.02-0.03 psu at depths of 1500-2000 m. At all the levels, statistically significant quadratic trends dominate with temperature and salinity maximums confined approximately to 1980. The mean rates of the salinity increase (decrease) before (after) 1980 comprised 0.0025 psu year-1. Against the background of the quadratic trends, 6.5-year and 20-year periodicities were recognized. 

The T,S structure of the Black Sea waters consists of a few characteristic layers with different thicknesses top-down the upper mixed layer, the seasonal pycnocline (thermocline) the cold intermediate layer, the main pycnocline (halocline) the isothermal intermediate layer the thickest deep layer with a slow temperature and salinity increase with depth and the near-bottom mixed layer. 

Salinity—increasing the salinity decreases the oxygen solubility (negligible for fresh waters)... 

Answer 9.7 The HC03 concentration decreases as a function of salinity increase. The deeper waters reflect, by their elevated chlorine concentration, that the wells tapped seawater, and this is supported by the lower HC03 concentrations. 

The ODN adsorption onto cationic polystyrene latexes as a function of NaCl concentration and at acidic pH was investigated [24] and found to be slightly influenced by the salinity as given in Fig. 5. At acidic pH, the adsorbed amount of ODN decreased markedly as the salinity increases, compared to the adsorption at basic pH. For such a highly charged colloidal system, the effect of salt was attributed to the reduction in the attractive electrostatic interaction. 

At any given matrix potential, m, under a constant gravitational potential, g, as salinity increases, w decreases. This is because osmotic potential, is directly related to total dissolved solids (TDS). The relationship between osmotic potential and TDS can be expressed by... 

The density of the water controls the deepwater circulation. If the density of a water body increases, it has a tendency to sink. Subsequently, it will spread out over a horizon of uniform circulatory system is also known as thermohaline circulation. As shown in Figure 5 of the ocean conveyor belt, the densest oceanic waters are formed in Polar Regions due to the relatively low temperatures and the salinity increase that results from ice formation. Antarctic Bottom Water (ABW) is generated in the Weddell Sea and flows northward into the South Atlantic. North Atlantic Deep Water (NADW)... 

A component can undergo considerable physico-chemical speciation alterations in an estuary. With respect to dissolved constituents, the composition and concentration of available ligands changes. Depending upon the initial pH of the riverine water, OH may become markedly more important down the estuary. Similarly, chlorocomplexes for metals such as Cd, Hg and Zn become more prevalent as the salinity increases. Conversely, the competitive influence of seawater derived Ca and Mg for organic material decreases the relative importance of humic complexation for Mn and Zn. 

Sea water contains a much lower concentration of dissolved organic matter than river water. More than half of this dissolved organic load is of a humic nature. These dissolved organic acids tend to flocculate as the salinity increases (10). Hair and Bassett (11) have observed an increase in the particulate humic acid load of an estuary as one approaches the sea. Although no studies of the distribution of humic materials throughout an estuarine system have been performed, it would appear that estuaries and their sediments in particular, act as a major sink for the dissolved and particulate humic materials. Nissenbaum and Kaplan (12) have observed that terrestrial humic materials are not deposited at great distances from shore in the marine system. A study of the flux of particulate carbon through the Chesapeake Bay comes to a similar conclusion (13). 

The control of fluoride concentration by fluorite (CaF2) saturation is likely in some waters. Fluorite solubility has been shown to be a complex function of temperature, salinity, and major ion chemistry (Holland and Malinin, 1979 Richardson and Holland, 1979). Hitchon (1995) found that lower salinity waters of the Alberta Basin are generally undersaturated with respect to fluorite, and that there is a gradual increase in fluoride to CaF2 saturation as temperature and salinity increase. 

In contrast, ions such as bicarbonate show a gradual decrease, from a surface value of 250mgL to <10mgL , as salinity increases. Sulfate increases to a maximum level of —1,000 mg and tends to decrease in the more sahne fluids. These characteristics indicate solubihty control by a sparingly soluble mineral phase (calcite and gypsum, respectively). 

The S04 concentration in sediments affects S04 reduction only when concentrations are quite low. The reduction of SOl in marine sediments appears to be zero-order with respect to S04 to concentrations of 2 mM (Boudreau and Westrich, 1984 Goldhaber and Kaplan, 1974). In freshwaters, SO concentrations must be much lower before they limit SO reduction (Bak and Pfennig, 1991 Lovley and Klug, 1983b Sinke et al., 1992). Because freshwater contains very little sot compared to seawater, the importance of SO4 reduction in sediments increases in an estuary as the salinity increases (Capone and Kiene, 1988). Therefore, the vertical extent of the SO4 reduction zone increases substantially as more SO4 becomes available, while the metha-nogenic zone is pushed deeper into the sediment and its contribution to carbon mineralization decreases in importance. 

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