International Equation Of State Research Articles

Impact of new SI on IAPWS International Equation of State for Water and Steam

Impact of new SI on IAPWS International Equation of State for Water and Steam

Algorithms for Density, Potential Temperature, Conservative Temperature, and the Freezing Temperature of Seawater

Abstract Algorithms are presented for density, potential temperature, conservative temperature, and the freezing temperature of seawater. The algorithms for potential temperature and density (in terms of potential temperature) are updates to routines recently published by McDougall et al., while the algorithms involving conservative temperature and the freezing temperatures of seawater are new. The McDougall et al. algorithms were based on the thermodynamic potential of Feistel and Hagen; the algorithms in this study are all based on the “new extended Gibbs thermodynamic potential of seawater” of Feistel. The algorithm for the computation of density in terms of salinity, pressure, and conservative temperature produces errors in density and in the corresponding thermal expansion coefficient of the same order as errors for the density equation using potential temperature, both being twice as accurate as the International Equation of State when compared with Feistel’s new equation of state. An inverse function relating potential temperature to conservative temperature is also provided. The difference between practical salinity and absolute salinity is discussed, and it is shown that the present practice of essentially ignoring the difference between these two different salinities is unlikely to cause significant errors in ocean models.

Densities of Huanghe River estuary and Bohai Bay waters

The densities of 36 water samples from the Huanghe River estuary and Bohai Bay were determined by a magnetic float densimeter under three temperatures from 15°C to 25°C. All the measured densities of samples were greater than that of the values calculated from the International Equation of State of Seawater. The differences between the measured and calculated densities increased with the decrease of salinities. The differences appeared exponentially correlated with [Ca2+]/s, [Mg2+]/s and [SO42−]/s, and had “s” type curve relationship with the alkalinity in all salinity range. But in the salinity ranging from 25.72 to 31.57, the relationships were all linear. The density difference can be estimated from the equation Δρ(103kg · m−3). It was the high alkalinity and [Ca2+]/s that resulted in the measured densities of seawaters being higher than the calculated densities in the Huanghe estuary and Bohai Bay.

The densities of Changjiang estuarine waters

In order to check the validity of the International Equation of State of Seawater set up by the UNESCO in 1980 for application to China coastal waters, the authors measured the relative density of Changjiang estuarine seawater and seawater solutions diluted with the Changjiang River water at one atmosphere from 5–35 salinity under 15–24°C with a high precision magnetic float densimeter designed by them. The average standard deviation of measured values was ±2.3×10−3 kgm−3. the statistical results showed that for all samples from the Changjiang estuary, the measured density with the densimeter was always higher than the density calculated by the UNESCO equation. The average differences, for dry season and flood season seawater samples were (+6.3±2.3)×10−3kgm−3 and (+8.1±2.3)×10−3kgm−3, respectively. The average difference between the measured and calculated (from the UNESCO equation) density increased linearly as salinity decreased and became +47.2×10−3 kgm−3 at the Changjiang River water salinity limit of around 0.134. A linear correlation was found between this average difference and the [Ca2+]/s ratio value. The experimental average values of [Ca2+]/s, [SO42−]/s, [Mg2+]/s, and [Sr2+]/s were 0.01183±1.0×10−4, 0.07698±1.7×10−4, 0.03743±8.1×10−5 and 2.26×10−4, respectively, at sample salinities of 30 to 35. The experimental value of [Ca2+]/s for the Wuhu Changjiang River water was 0.2597. The resulting densities of all samples were then fitted to an equation of the formd−dw=B1s1/2+B2s+B3s3/2+B4s2 wheredw is the density of SMOW andB1,B2,B3 andB4 are temperature-dependent parameters. The average standard deviation between calculated densities of this equation and experimental values was ±3.9×10−3 kgm−3.

Polynomial Approximation to the International Equation of State for Seawater

Polynomial Approximation to the International Equation of State for Seawater

The conductivity‐density‐salinity‐chlorinity relationships for estuarine waters1

The relative conductivity and density of estuarine waters formed by mixing “world” river water with standard seawater have been determined. The results are used to examine the conductivity‐density‐salinity‐chlorinity relationships of estuarine waters of known composition with seawater diluted with pure water (i.e. the new International Equation of State and Practical Salinity Scale). The maximum difference between the true salinity and the value derived from conductivity was 0.047 in dilute solutions; the maximum density difference between the measured and calculated values was 35 × 10−6 g·cm−3. These results are compared with measurements of waters from the St. Lawrence estuary.

Introduction of the practical salinity scale, 1978 and the new International equation of state of seawater, 1980 January 1982

Introduction of the practical salinity scale, 1978 and the new International equation of state of seawater, 1980 January 1982