Mineral Formation in the Salton Sea.

The Salton Sea is a saline, closed basin lake 70 meters below MSL in the southern desert of California. It is the largest lake in California with a surface area of 945 km² and an annual inflow of 1,600 million m³. The inflow to the lake is predominately agricultural drainage water and tailwater from the Imperial and Coachella Valleys. The Sea is hypereutrophic and the high sulfate concentration results in hydrogen sulfide production and fish kills in the summer and fall. The salinity of the Sea is currently 52 g/L and rising, with an annual salt load of 4 million metric tons. We estimate between 0.7 – 0.9 M metric tons of calcite and gypsum are precipitating in the Sea each year, along with 7,000 tons of iron sulfide minerals. For comparison, the amount of calcite precipitating in the soils of the Imperial Valley has been estimated at 1.3 M tons. The coprecipitation of phosphate with the calcite controls the P concentration in the Sea. Hydrogen sulfide production rates, reoxidation rates in the water column, and atmospheric releases of H₂S have been measured.  The formation of alkalinity due to sulfate reduction is the main mechanism driving calcite precipitation in the Sea.