Analysis of hypersaline waters from Cojocna balneary resorts (Romania) using Raman spectroscopy techniques

Surface waters from hypersaline lakes of Cojocna Balneary Resort, Transylvania, Romania have been investigated in raw form, using Raman spectroscopy techniques. These lakes are usually exposed to high touristic influx mainly in summer months, due to their balneotherapeutic benefits. Therefore, chemical composition of waters and its variability is of high interest. Here we present spectroscopic characteristics of the lakes, obtained by Raman scattering techniques, probing several water samples collected in two consecutive years. Among the two lakes, Torok Lake showed 1.449 times higher sulfate concentration than the Great Lake in 2016 and 0.737 in 2017 respectively, according to the calculated ratio of the Raman band of sulfate at 979 cm-1 relative to water band. Chemical changes associated with the presence of different plankton species and their density fluctuations were reflected in changes in resonance Raman scattering signal of carotenoids during Artemia salina crustaceans blooming population in August, compared to July, in both years. Interestingly, the bloom appeared alternatively in two consecutive years and it is apparently correlated to lower sulfate level, as revealed by spectral data only. Raman data indicated the dynamic cycles in chemical composition of salt lakes. Such changes are certainly suitable for constant monitoring purpose of the balneotherapeutic salt water bodies via Raman spectroscopy. Both FT-Raman and dispersive Raman are suitable for this purpose. Fast analysis, without additional separation steps and chemicals consumption may provide information on the sulfate level and carotenoids. The results could be attractive for monitoring studies, or informative, for touristic purpose or aquaria hobby cultivars.