Saturation state variation with temperature

Figure 4.2. The variation of total carbon dioxide (ICO2) and the saturation state of seawater with respect to calcite (Qc) with temperature for seawater with a total alkalinity of 2400 peq kg- seawater and in equilibrium with atmospheric CO2...

It should be kept in mind that, in spite of these major variations in the CO2-carbonic acid system, virtually all surface seawater is supersaturated with respect to calcite and aragonite. However, variations in the composition of surface waters can have a major influence on the depth at which deep seawater becomes undersaturated with respect to these minerals. The CO2 content of the water is the primary factor controlling its initial saturation state. The productivity and temperature of surface seawater also play major roles, in determining the types and amounts of biogenic carbonates that are produced. Later it will be shown that there is a definite relation between the saturation state of deep seawater, the rain rate of biogenic material and the accumulation of calcium carbonate in deep sea sediments. 

As previously mentioned, the primary processes responsible for variations in the deep sea C02-carbonic acid system are oxidative degradation of organic matter, dissolution of calcium carbonate, the chemistry of source waters and oceanic circulation patterns. Temperature and salinity variations in deep seawaters are small and of secondary importance compared to the major variations in pressure with depth. Our primary interest is in how these processes influence the saturation state of seawater and, consequently, the accumulation of CaC03 in deep sea sediments. Variations of alkalinity in deep sea waters are relatively small and contribute little to differences in the saturation state of deep seawater. 

Carbonate 1. Surface water nearly always supersaturated with respect to CaC03 (200-500%) favored by high pH values and moderate temperatures 2. Variation with depth saturation state with respect to CaC03 decreases as the result of lower temperature and pH. Under saturated in deep waters (e.g., below 200-300 m)... 

Variation of temperature introduces a difficulty in the use of percentage saturation as a measure of salt concentration, since the solubility of the salt will vary with temperature. Some data for ammonium sulfate are given by Taylor (1953). It would be preferable always to state the actual concentration of salt, for example as molarity. 

Figure 10.2 Variation with height of the properties of a mixture in the diffusion cloud chamber. Shown are the rnas.s densities of the carrier gas. ph, and the vapor,, the equilibrium vapor pressure, p, the partial pre.ssure of (he vapor, p, the temperature, 7/, and the saturation ratio, S. The highest temperature, vapor pressure, and gas density are at the chamber bottom, above the heated pool. The distributions with respect to chamber height are calculated by integrating expressions for the steady-state fluxes of heat and mass through the chamber...

The isobaric variation of enthalpy with temperature is shown in Figure 1.2. At low pressures in the gaseous state, when the gas behavior is essentially ideal, the enthalpy is almost independent of the pressure, so the isobars nearly superimpose on each other. The curves marked saturated liquid and saturated... 

Figure 6.2. (A) Variations in %N (which is proportional to C density) with precipitation along the 11 °C isotherm in the Great Plains of the United States. The humidity factor (NSQ, Niederschlag-Sattigungsdefizit from the German, or Meyer s quotient) is the total annual precipitation (mm) divided by the absolute saturation deficit of air (mm mercury). All soils were developed on loess deposits from the last glacial maximum. (B) Change in %N with precipitation along the 19 °C isotherm. Note that relative C density (estimated by assuming that the C/N ratio of SOM is fairly constant) is lower at higher mean annual temperature. Reprinted with permission from Jenny, H. (1941). Factors of Soil Formation, Dover Publications, New York.

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