HOW MUCH SALT PRECIPITATES FROM THE BRINES OF A HYPERSALINE LAKE - THE DEAD-SEA AS A CASE-STUDY

The actual density-salinity relation betaBAR = DELTArho/DELTAS of the post-1983 (supersaturated) Dead Sea brine is not a fixed thermodynamic constant as it would be in undersaturated brines, but rather a combination of two different thermodynamic constants. One of them, beta(NaCl), is the brine's expansion coefficient to sodium chloride and relates to the process of halite precipitation; and the other, beta, is the brine's expansion coefficient to total salts and relates to the dilution-evaporation process. For every particular period under study, the actual density-salinity relation betaBAR must be evaluated separately. The long-term betaBAR for the years 1983-1990, as estimated from climatological data, is about 3 sigmau kg/g, roughly 3.5 times larger than either beta or beta(NaCl). A new approach, based on the difference between beta(NaCl) and beta, is applied to the 1983-1990 density record; it reveals that salts precipitate from the Dead Sea brines at a rate of 1.9 X 10(-3) g/cm3 y, about 77% of which precipitate at the periphery of the lake, mostly at the southern tip, and only the remaining 23% in the interior of the lake.