Measurement of Salinity

Column A from Lyman and Flemming (1940) column B from Culkin and Cox (1966) column C from Riley and Tongadai (1967) and Morris and Riley (1966) column D update of earlier calculations of Millero (1982) using new dissociation constants for carbonic (Roy et al., 1993) and boric acids (Dickson, 1992, 1993). Atomic weights (appendix 1). The values of TA/Cl(%c) = 123.88 mol kg-1 (Millero, 1995) and B/Cl(%o) = 0.000232 (Uppstrom, 1974) were also used to determine total carbonate and borate. 

In 1978, the Joint Panel for Oceanographic Tables and Standards (JPOTS) decided that a new definition was needed for salinity that was based more on a salinity/conductivity ratio. 

This new relationship was termed the practical salinity scale and is based on a background paper by Lewis (1978). The practical salinity of a water sample is defined in terms of the conductivity ratio, F15, which is defined as follows  

More specifically, practical salinity is related to the ratio F15 by the following equation  

Therefore, a standard seawater sample with a salinity (5) of 35 (with no %o units needed) has a conductivity ratio of 1 at 15°C and 1 atmosphere, using a standard KC1 solution of 32.4356 g in a 1 kg mass of solution. Finally, recent applications of microwave remote sensing have been used to determine surface water of gradients of salinity in coastal regions, particularly in river plume regions (Goodberlet et al., 1997). 

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Electrical Conductivity This is often a convenient and accurate measurement of salinity or chlorinity. Here, too, there is considerable variation with temperature, so that simultaneous observation of temperature is essential. Figure 2.16 shows the relationship between conductivity and chlorinity at various temperatures. 

PSU (practical salinity units) are a unit of measurement of salinity, i.e. of the total amount of dissolved salts in water. If sea water has a salinity of 5 psu, 5 g of salt are dissolved in 1000 g of water. 

The following boxes present four case studies to illustrate how the introduction of reference materials has decreased the uncertainty of the chemical oceanographic measurement of salinity (Box 2.1), DOC (Box 2.2), and dissolved inorganic carbon (DIC) (Box 2.3). Box 2.4 illustrates the acute need for pigment reference materials, which are currently unavailable. 

Potential density is computed from measurements of salinity (5), in situ temperature (0, and pressure ip) using the equations provided in Table 3.4 to generate a value of p(5, t,p), which is then transformed into cr format using Eq. 3.5. As shown in Figure 3.4, 0-0 exhibits a much smaller range in values (20 to 30) than Although the vertical... 

Potassium chloride is the most important salt of potassium from the perspective of its abundant occurrence and apphcations. This salt, along with potassium sulfate, is used heavily in fertilizers as the primary source of potassium, an essential element for crops. Over 90% salt manufactured is consumed as fertilizer. Also, potassium chloride is a raw material for producing potassium metal and several important potassium salts including potassium nitrate, potassium hydroxide, and potassium sulfate. Other applications are in electrode cells photography buffer solutions and measurement of salinity in water. 

This diversity of measures of salinity is especially a problem in cross-disciplinary work, where alternative measures from other disciplines are often unfamiliar. The equations needed to convert from one measure to another are... 

Fig. 4.2. Alternative measures of salinity for pure NaCl solutions at 25 °C and 1 atm pressure. Reprinted from Marion et al. (2003b) with permission...

Figure 4.2 depicts several measures of salinity for pure NaCl solutions at 25 °C and 1.01 bar total pressure calculated using the FREZCHEM model and Eqs. 4.1 to 4.4. NaCl solutions were used in this example because this salt is often used as a background salt in physiological studies (Madigan and Oren, 1999 Kaye and Baross, 2000). For salts other than NaCl or at temperatures other than 25 °C, Eq. 4.1 to 4.4 must be relied upon to make conversions or see Marion (2007). 

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). 

For the continuous data, the alkalinity (CTA) was calculated from the continuous underway measurement of salinity by assuming a constant spe-... 

MEASURES OF SALINITY AND ALKALINITY 8.2a. The Residual Sodium Carbonate (RSC) Value... 

A general measures of salinity indicative of aggressiveness of ground and related to electrical conductivity or soil resistivity Undisturbed specimens required in sterilized containers... 

The earliest application of electrodeless conductivity measurements appears to have been for measurement of salinity at various ocean depths (1, 11, 45, ). Other early uses have also included determination of the equivalent conductances of salts at high concentrations (3, 34, 53) and the monitoring of nitric... 

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