Sapropel
Spa & Balneology Terms
Also: sapropel, lake mud, lake sediment, gyttja
Organic-rich sediment deposited on the bottom of freshwater lakes. Used therapeutically in Latvia, Russia, and other Eastern European countries. Differs from peat in formation: sapropel forms underwater in lakes, while peat forms in bogs from surface plants.
Comparison with Peat
Sapropel has different humic substance composition than peat — typically lower humic acid content but may be richer in specific lipids and amino acids depending on the lake biology. The two are sometimes used interchangeably in Baltic balneological literature, but they are distinct materials with different therapeutic profiles.