Hydrochemical evolution of Na-SO4-Cl groundwaters in a cold, semi-arid region of southern Siberia |
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Authors: | V P Parnachev D Banks A Y Berezovsky D Garbe-Schönberg |
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Institution: | Department of Dynamic Geology, Tomsk State University, Lenina prospekt 36, Tomsk, 634050 Russia, RU Norges Geologiske Unders?kelse, Postboks 3006 Lade, N-7002 Trondheim, Norway, NO Geologisch-Pal?ontologisches Institut und Museum, Christian-Albrechts-Universit?t zu Kiel, Olshausenstra?e 40–60, D-24118 Kiel, Germany, DE
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Abstract: | The Shira region of Khakassia in southern Siberia exhibits many features governing the evolution of groundwater and surface-water
chemistry that are common to other cold, semi-arid areas of the world: (1) a continental climate, (2) location in a rain shadow,
(3) low density of surface-water drainage, (4) occurrence of saline lakes, and (5) occurrence of palaeo- and modern evaporite
mineralisation. In lowland areas of Shira, the more saline groundwaters and lake waters have a sodium-sulphate (-chloride)
composition. Results of thermodynamic modelling suggest that these evolve by a combination of silicate weathering and gypsum
and halite dissolution, coupled with carbonate precipitation to remove calcium and bicarbonate ions. An approximately 1:1
sodium:sulphate ratio occurs even in groundwaters from non-evaporite-bearing aquifers. This may indicate the formation of
secondary sodium sulphate evaporites (in or near saline lakes or in soil profiles where the water table is shallow), which
are subsequently distributed throughout the study area by atmospheric transport. Several urban groundwaters are characterised
by very high nitrate concentrations, conceivably derived from sewage/latrine leakage.
Received, June 1998 /Revised, May 1999, August 1999 /Accepted, August 1999 |
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Keywords: | groundwater quality hydrochemical modelling salinisation Siberia semi-arid regions |
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