Salinity and ionic composition of the shallow astatic soda pans in the Carpathian Basin

We investigated the chemical characteristics of the astatic soda pans in the Carpathian Basin based on comprehensive new and archive data. Analysed parameters were salinity and ionic composition. The most frequent type of soda waters was the basic alkaline type (Na-HCO3) that represented more than half of the natural soda pans. Besides 11 subtypes occurred. The second and third most frequent types were the chloride (13%) and sulphate subtypes (11%), with the secondary dominance of these anions. The other subtypes meant <4% of the pans. Magnesium sometimes occurred as a secondary dominant cation beside sodium. Until now, this subtype of soda waters has not been published in any part of the world, because of the general rule of soda lake formation (depending on low levels of magnesium and calcium). We found a regionally constant correction factor [Salinity (mg.L-1) = 0.8 x E1.Cond. (mu S.cm(-1))] for confidentially estimating salinity from electrical conductivity in these habitats. Salinity varied between sub- (0.5-3 g.L-1) and hypersaline (>50 g.L-1) ranges, with its mean value (similar to 4 g.L-1) in the hyposaline range (3-20 g.L-1). The basic alkaline type had random geographical distribution, while the other subtypes were restricted to certain regions of the Basin. The high number of subtypes reflects the high chemical diversity of alkaline soda pans in the relatively small territory of the Carpathian Basin.