Water regime and variations in hydrochemical characteristics of the soda Salt Lake Khilganta (Southeastern Transbaikalia)

Abstract

Hydrochemical and biogeochemical processes in Lake Khilganta were studied during more than ten years. The lake was shown to pass through periods of wetting and drying. This is accompanied by considerable changes in water chemistry and microbiological processes. During the passage from a wet to a dry period, lake water mineralization increases from 40 to 260 g/l and pH decreases from 9.9 to 7.1. At the same time, the isotope composition of organic matter carbon in bottom deposits becomes lighter (from −15.6 to −30.6‰), as well as that of carbon in carbonates (from +4.1 to −8.6‰), due to the lower rate of photosynthetic processes in lake bacterial mats. The order of salt precipitation during the passage from a wet to a dry period and the mechanism of maintaining water pH are considered. A possible similarity between the modern processes in Lake Khilganta and the processes in analogous Pre-Cambrian water bodies is discussed, and the hypothesis regarding the possibility of wider development of soda water bodies at early stages of Earth’s history is considered.