A simple method to model the reduced environment of lake bottom sapropel formation

Olga L. Gaskova, Vera D. Strakhovenko, Nadezhda I. Ermolaeva, Eugene Yu Zarubina, Ekaterina A. Ovdina

Research output: Contribution to journalArticlepeer-review

6 Citations (Scopus)

Abstract

The Kambala and Barchin brackish lakes (Baraba steppe, southern West Siberia) contain an organic-rich sapropel layer that was formed in oxygen-depleted waters. We measured the bulk sediment elemental composition, the water chemistry and determined the mineralogical composition and predominant biota species (Diatoms and Cyanobacteria in phytoplankton community respectively) in the lakes. The result indicates that the first lake has a siliceous type of sapropel and the second a carbonaceous one. A computer thermodynamic model was developed for chemical interaction in water-bottom sediment systems of the Kambala and Barchin Lakes. The surface sodium bicarbonate waters are supersaturated with respect to calcite, magnesite (or low Mg-calcite), quartz and chlorite with minor strontianite, apatite and goethite (pH 8.9–9.3, Eh 0.3 V). Nevertheless, it is shown that during sapropel deposition, deep silt waters should be anoxic (Eh<0 V). The virtual component CH2O has been used to create an anoxic environment suitable for pyrite formation due to the biotic community impact and abiotic reduction. Thermodynamic calculation has shown that silt water is not necessarily euxinic (anoxic and sulfidic). Depending on Eh, sulfate sulfur can dominate in solution, causing the formation of gypsum together with pyrite. An attempt was made to find a reason for solution supersaturation with respect to Ca and Mg ions due to their complexation with humic acids.

Original languageEnglish
Pages (from-to)956-966
Number of pages11
JournalChinese Journal of Oceanology and Limnology
Volume35
Issue number4
DOIs
Publication statusPublished - 1 Jul 2017

Keywords

  • brackish lakes
  • calcite
  • mineral composition
  • sapropel sediments
  • silica
  • thermodynamic calculations
  • ACIDS
  • SEDIMENTS
  • RECONSTRUCTION
  • DEPOSITION
  • ORGANIC-MATTER
  • EVOLUTION
  • PRECIPITATION
  • INHIBITION
  • CHEMISTRY
  • BASIN

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