Evaporation line

Silver, with a thermal conductivity of 419 W/m°C is a somewhat better conductor of heat than copper, and this property is often utilised in the construction of heat exchangers, evaporator linings, etc. 

Crystallization takes place when the solute slowly comes out of solution as crystals, perhaps as the solvent evaporates. For example, salt crystals that form when water evaporates line the shores of the Great Salt Lake in Utah. In precipitation, a solute comes out of solution so rapidly that a single crystal does not have time to form. Instead, the solute forms a finely divided powder called a precipitate. Precipitation is often almost instantaneous (Fig. G.4). 

The net result of evaporative isotopic fractionation of lake water is a water mass that is not in isotopic equilibrium with its water sources. Therefore, the isotopic composition of a lake water should plot below the LM WL, as shown in Figure 2. The line that passes through the isotopic composition of a lake water and its volume-weighted input from precipitation and ground-water is referred to as an evaporation line. This line represents the isotopic evolution of lake water from its source waters. The slope of an evaporation line is a function of humidity, temperature, and the isotopic composition of atmospheric moisture above the lake the slope generally ranges from about 3.5 to 6.0 (23). 

As discussed previously, the isotopic composition of evaporating water bodies on plots of 8lsO versus 8D lie on evaporation lines. The intersection of any evaporation line with the LMWL corresponds to the average composition of water entering the lake. Geographically clustered lakes that meet the requirement of being at isotopic steady state should plot along the same... 

Figure 4. Isotopic compositions (bD versus b180) of four lakes in Vilas County, WI. The thick line is the local meteoric-water line (LMWL) determined from the data shown in Figure 2 the thin line is the evaporation line determined by the best-fit line for the four lakes shown here. Line segments plotted on the evaporation line represent specified ratios [GJ P/ calculated using eq 13.

Fig. 9.22 Isotopic composition of groundwaters south of Chott-el-Honda, Algeria. The shallow groundwaters lie on an evaporation line, and the degree of heavy isotope enrichment agrees with the salinity (the sample numbers are the same as in the previous figure). (From Gonfiantini et al., 1974.)...

On 6 0 versus 6 H plots, water that has evaporated from open surfaces (e.g., ponds and lakes), or mixed with evaporated water, plots below the MWL along a trajectory typically with a slope between 2 and 5 (Figure 4). The slope of the evaporation line and the isotopic evolution of the reservoir are strongly dependent upon the humidity under which evaporation occurs, as well as temperature and wind speed (Clark and Fritz, 1997), with lower slopes found in arid regions. 

USA). The precipitation samples define the LMWL (5D = 8.035 0 + 10.95), which is virtually identical to the GMWL. The lake samples plot along an evaporation line with a slope of 5.2 that intersects the LMWL at the eomposition of average local groundwater, with additional data (after Kendall et aL, 1995a). 

Figure 8 Distribution of Cl and Br in formation waters from the central Mississippi Salt Dome Basin relative to the evaporation line for seawater (SW, A-B) and mixing lines between Norphlet water (Norph. W) and meteoric (MW) and sea (SW) waters. Line E-F gives the trend when the mixture of meteoric and Norphlet waters dissolves halite with 70 ppm Br. Line C-D gives the trend where 50% of the Cl concentration in the mixture of meteoric and Norphlet waters is from dissolution of halite. Note that the samples from Coastal Texas and Louisiana (dashed field) plot in a different field (source Kharaka and Thordsen, 1992).

Local evaporation line The isotopic composition of surface waters within catchments or within the same climatic region commonly plot on lines with slopes ranging from about 4 to 7 in space, due to equilibrium and kinetic fractionation effects... 

Supersaturation can also be achieved by removing some of the solvent from the solution by evaporation. Line AB C represents such an operation carried out at constant temperature. Penetration beyond the supersolubility curve into the labile zone rarely happens, as the surface from which evaporation takes place is usually supersaturated to a greater degree than the bulk of the solution. 

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