Evidence for salt diffusion from sediments contributing to increasing salinity in the Salton Sea, California

Geochemical investigations of interstitial waters from the Salton Sea, CA reveal evidence of concentrated brines in the sediments underlying the lake's two basins. The brines are likely caused by the gradual dissolution of evaporite deposits. The chemical composition of the brine in the northern basin is dominated by magnesium and sulfate and differs from the southern basin where the dominant components are sodium and chloride. Sediment depth distributions of major ions and porosity indicate diffusion of salts from the sediments into the overlying waters in both basins. Benthic fluxes have been calculated for the four most abundant ions: magnesium, sodium, sulfate and chloride. For the northern basin we calculate diffusive fluxes of 3.7 x 10 super(-2), 8.2 x 10 super(-2), 44 x 10 super(-2), and 5.4 x 10 super(-2) g cm super(-2) yr super(-1) for magnesium, sodium, sulfate and chloride, respectively. For the southern basin we calculate diffusive fluxes of 0.9 x 10 super(-2), 9.7 x 10 super(-2), 6.9 x 10 super(-2), and 25 x 10 super(-2) g cm super(-2) yr super(-1) for these same ions. By scaling up our results we estimate the salinity flux from the sediment to the water column to be between 3.6 x 10 super(4) and 3.6 x 10 super(5)metric tons per year, equivalent to 1-10% of the riverine input. These results are important for developing strategies to combat rising salinity in the Salton Sea, CA.