Interpreting noble-gas concentrations as proxies for salinity and temperature in the world’s largest soda lake (Lake Van, Turkey)

In this work we present noble-gas concentration profiles measured in the water column and in the sediment pore water of the Earth’s largest soda lake: Lake Van (eastern Anatolia, Turkey). The concentrations of noble gases (in particular Ar, Kr, and Xe) in the water body deviate significantly from the expected equilibrium concentrations calculated from the in situ temperature and salinity using existing solubility functions for seawater. The specific chemical composition of the water of the soda lake seems to be responsible for the observed deviations. Our measurements allow the identification and quantification of salinity factors that can be applied to correctly calculate the noble-gas equilibrium concentrations for the lake. These salinity factors provide a solid and robust empirical basis for the interpretation of noble-gas concentration signals measured in the sediment pore water of Lake Van in terms of palaeosalinity and palaeotemperature.

► We found apparent atmospheric noble-gas depletion in water column of Lake Van.
► This depletion is probably related to the specific soda water chemistry of the lake.
► The available solubility equations for seawater are adjusted with salinity factors.
► Adjusted solubilities are prerequisite for a correct interpretation of noble gases.
► This allows for temperature and salinity reconstruction using dissolved noble gases.