Properties of Seawater

Engineering and technical properties of seawater and certain aqueous electrolyte solutions... 

This can be demonstrated by considering the high pressure PVT properties of seawater. For seawater solutions the values of K , A and Bata given temperature are given by (127). 

Jenkinson IR (1993) Bulk-phase viscoelastic properties of seawater. Oceanol Acta, 16 317-334 Jenkinson IR, Biddanda BA (1995) Bulk-phase viscoelastic properties of seawater relationship with plankton components. J Plankton Res 17 2251-2274 Jenkinson IR, Wyatt T, Malej T (1998) How viscoelastic effects of colloidal biopolymers modify rheological properties of seawater. In Emri I, Cvelbar R (eds) Proceedings of the 5th European Rheology Conference, Portoroz, Slovenia, September 6-11, 1998, Progress and Trends in Rheology 5 57-58... 

Seawater contains about 3.5% salts, in which the content of sodium chloride is about 80%. The concentration of dissolved salts as well as temperature and pressure influence the physical properties of seawater. The total salt concentration is usually called salinity . Salinity is generally measured by the electrical conductivity or determination of chloride content. At present, salinity(S) is defined as S = 1.80655 Cl (Cl is the concentration of chloride in seawater) [5]. Dissolved oxygen and silica are usually measured as additional parameters to characterize seawater. The concentrations of nitrogen and phosphorus are the indices of nutrients and measure the fertility and production of the oceans. 

From an oceanographic perspective, the fundamental properties of seawater are temperature, salinity and pressure i.e., depth dependent). Together, these parameters control the density of the water, which in turn determines the buoyancy of the water and pressure gradients. Small density differences integrated over oceanic scales cause considerable pressure gradients and result in currents. 

Below the thermocline, the temperature changes only little with depth. The temperature is a non-conservative property of seawater because adiabatic compression causes a slight increase in the in situ temperature measured at depth. For instance in the Mindanao Trench in the Pacific Ocean, the temperature at 8500 and 10,000 m is 2.23 and 2.48 °C, respectively. The term potential temperature is defined to be the temperature that the water parcel would have if raised adiabatically to the ocean surface. For the examples above, the potential temperatures are 1.22 and 1.16 °C, respectively. Potential temperature of seawater is a conservative index. 

Jenkinson, I. R., andBiddanda, B. A. (1995). Bulk-phase viscoelastic properties of seawater relationship with plankton components. J. Plankton Res. 17(12), 2251—2274. 

Since the salinity is related to the total salts in a given sample of seawater, it can be used to express the changes in the physical chemical properties of seawater as a function of composition. In essence, one treats seawater as a sea salt similar to an individual salt such as NaCl. Most of the early physical-chemical properties of seawater were made on diluted or evaporated seawater of a known chlorinity (19.374 or 5 = 35.000). By multiplying the values of Cl by... 

Equations are available for the pressure-volume-temperature PVT) properties of seawater as a function of salinity (0-40), temperature (—2 °C to 40 °C), and pressure (0-1,000 bar)... 

The PVT properties of seawater have been fitted to equations of the form (Wirth, 1940)... 

The measurements of the solubility of Fe(III) in seawater point out the importance of how low concentrations of natural organic material can affect the speciation and solubility of metals in seawater. This organic material does not have an effect on the physical and chemical properties of seawater and the activity of the major components of seawater, but can change the reactivity of most trace metals in the oceans. These effects are discussed in more detail in other chapters. 

The difficulties encountered in establishing activity coefficients also relate to the problem of defining pH in seawater. Accurate assessment of the thermodynamic properties of seawater depends on measurements of pH. Essentially, three pH scales are possible. 

If all the relevant equilibrium constants are known, together with the amounts of the ions present, the proportions of the various ions associated with each ion pair can be calculated. The results of such an analysis for seawater (Table 1) show that ion pairing is common. A full analysis of the properties of seawater requires that these species are taken into account. 

Fofonoff, N.P, Millard, R.C., 1983. Algorithms for computation of fundamental properties of seawater. Unesco technical papers in marine science 44. 

Describe how properties of seawater illustrate the two characteristics that define mixtures. 

The temperature and salinity of each measurement are given in the table. Salinity is a standardized measure of the concentration of dissolved salts, as explained in the table Properties of Seawater in Section 14. Salinity values in the open oceans at mid-latitude typically fall between 34 and 36. 

In addition to the dependence on temperature and pressure, the physical properties of seawater vary with the concentration of the dissolved constituents. A convenient parameter for describing the composition is the salinity, S, which is defined in terms of the electrical conductivity of the seawater sample. The defining equation for the practical salinity is ... 

The first table below gives several properties of seawater as a function of temperature for a salinity of 35. The second and third give density and electrical conductivity as a function of salinity at several temperatures, and the fourth lists typical concentrations of the main constituents of seawater as a function of salinity. The final table gives the freezing point as a function of salinity and pressure. 

Properties of Seawater as a Function of Temperature at Salinity S = 35 and Normal Atmospheric Pressure... 

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