Chemical evolution of Mono Lake

In a second example, we consider the changing chemistry of Mono Lake, a saline alkaline lake that occupies a closed desert basin in California, USA, and why 

As it shrank, the lake became more saline. Salinity has almost doubled from 50 000 mg kg-1 in 1940 to about 90 000 mg kg-1 in recent years. The change in the lake s chemistry threatens to damage a unique ecosystem that supports large flocks of migratory waterfowl. 

Bischoff et al. (1991) attributed the occurrence of gaylussite to the lake s increase in Na+ content and pH since diversion began. Table 24.2 shows chemical analyses of lake water sampled at ten points in time from 1956 to 1988. We can use SPECE8 to calculate for each sample the saturation state of gaylussite. The procedure for the 1956 sample, for example, is 

In the calculation results, gaylussite appears increasingly saturated in the lake water as salinity increases irregularly over time. The calculations suggest that between about 1975 and 1980, as salinities reached about 75 000 to 80 000 mg kg-1, the mineral became supersaturated at summer temperatures. 

The solubility of gaylussite, however, varies strongly with temperature. Unlike calcite and aragonite, gaylussite grows less soluble (or more stable) as temperature 

In a second example, we consider the changing chemistry of Mono Lake, a saline alkaline lake that occupies a closed desert basin in California, USA, and why gaylussite [CaNa2(CO3)2-5H2O], a rare hydrated carbonate mineral, has begun to form there. The lake has shrunk dramatically since 1941, when the Los Angeles Department of Water and Power began to divert tributary streams to supply water for southern California. 

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Connell T. L. and Dreiss S. J. (1995) Chemical evolution of shallow groundwater along the northeast shore of Mono Lake, California. Water Resour. Res. 31, 3171-3182. 

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