TY - JOUR

T1 - A simple method to model the reduced environment of lake bottom sapropel formation

AU - Gaskova, Olga L.

AU - Strakhovenko, Vera D.

AU - Ermolaeva, Nadezhda I.

AU - Zarubina, Eugene Yu

AU - Ovdina, Ekaterina A.

PY - 2017/7/1

Y1 - 2017/7/1

N2 - 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.

AB - 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.

KW - brackish lakes

KW - calcite

KW - mineral composition

KW - sapropel sediments

KW - silica

KW - thermodynamic calculations

KW - ACIDS

KW - SEDIMENTS

KW - RECONSTRUCTION

KW - DEPOSITION

KW - ORGANIC-MATTER

KW - EVOLUTION

KW - PRECIPITATION

KW - INHIBITION

KW - CHEMISTRY

KW - BASIN

UR - http://www.scopus.com/inward/record.url?scp=85020927087&partnerID=8YFLogxK

U2 - 10.1007/s00343-017-5345-9

DO - 10.1007/s00343-017-5345-9

M3 - Article

AN - SCOPUS:85020927087

VL - 35

SP - 956

EP - 966

JO - Chinese Journal of Oceanology and Limnology

JF - Chinese Journal of Oceanology and Limnology

SN - 0254-4059

IS - 4

ER -