Comprehensive mineralogical and physicochemical characterization of recent sapropels from Romanian saline lakes for potential use in pelotherapy

Claudiu Filip,Erika A Levei,Doriana M Buda,Dorin Dădârlat,Francisc V Dulf,Mihaela Aluaş,Adela Pintea,Vasile Muntean,Andreea Baricz,Adorján Cristea,Horia Leonard Banciu,Zsolt G Keresztes,Marin Șenilă,Carmen Tripon,Simona Cîntă Pînzaru,Adriana Vulpoi,Mircea Alexe

doi:10.1038/s41598-021-97904-1

Abstract

In this study we aimed to compare the mineralogical, thermal, physicochemical, and biological characteristics of recent organic carbon-rich sediments (‘sapropels’) from three geographically distant Romanian lakes (Tekirghiol and Amara, SE Romania, and Ursu, Central Romania) with distinct hydrogeochemical origins, presently used for pelotherapy. The investigated lakes were classified as inland brackish Na-Cl-sulfated type (Amara), coastal moderately saline and inland hypersaline Na-Cl types (Tekirghiol and Ursu, respectively). The settled organic matter is largely composed of photosynthetic pigments derived from autochthonous phytoplankton. Kerogen was identified in the sapropel of coastal Tekirghiol Lake suggesting its incipient maturation stage. The mineral composition was fairly similar in all sapropels and mainly consisted of quartz, calcite, and aragonite. Smectite, illite, mixed layer smectite/illite appeared as major clay components. Potentially toxic elements were found in low concentrations. The physical properties (i.e., specific heat, thermal conductivity and retentivity) and cation exchange capacity are comparable to other peloids used for therapy. This study is the first comprehensive multi-approached investigation of the geochemical nature of recent sapropels in Romanian saline lakes and thus contributes to expanding our knowledge on the origin and physicochemical qualities of organic matter-rich peloids with therapeutic uses.

Highlights

In this study we aimed to compare the mineralogical, thermal, physicochemical, and biological characteristics of recent organic carbon-rich sediments (‘sapropels’) from three geographically distant Romanian lakes (Tekirghiol and Amara, SE Romania, and Ursu, Central Romania) with distinct hydrogeochemical origins, presently used for pelotherapy
Knowledge of the therapeutic value of Romanian saline lakes extends over many centuries, as early as Dacian–Roman times[13] and numerous saline lakes of varying hydrogeochemical nature are found in the Transylvanian (Central Romania) and Dacian (South-Eastern) B asins[14]
The XRD analysis indicates that Amara and Tekirghiol sapropels are enriched in silicates, i.e., quartz (30.8% and 29.1% respectively), plagioclase-albite (10.1% and 8.9%), carbonates, mainly calcite (6.8%) and aragonite (13.1%) in Amara, and calcite (8.7%) in Tekirghiol (Fig. 2)

Summary

Introduction

In this study we aimed to compare the mineralogical, thermal, physicochemical, and biological characteristics of recent organic carbon-rich sediments (‘sapropels’) from three geographically distant Romanian lakes (Tekirghiol and Amara, SE Romania, and Ursu, Central Romania) with distinct hydrogeochemical origins, presently used for pelotherapy. This study is the first comprehensive multi-approached investigation of the geochemical nature of recent sapropels in Romanian saline lakes and contributes to expanding our knowledge on the origin and physicochemical qualities of organic matter-rich peloids with therapeutic uses. Maturated muds termed ‘peloids’ are composed of fine-grained minerals and/or organic matter derived from biological metabolic activity, mixed with sea water, salt water, or spring derived mineral-medicinal waters, and are widely used, in different cultures, for therapeutic p urposes[1,2,3,4,5,6,7]. Natural sapropels (and water) from these saline lakes have been used as treatment for musculoskeletal disorders, gynecological, endocrine, dermatological, and hepatobiliary d iseases[2,9]

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