Summer–winter transitions in Antarctic ponds: III. Chemical changes
Abstract Observations were made of water column chemistry in four Na-Cl dominated ponds on the McMurdo Ice Shelf from the end of January to early April in 2008. During that time the ponds went from ice-free to predominantly frozen, with only a small volume of residual hypoxic, saline liquid trapped...
| Published in: | Antarctic Science |
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| Main Authors: | , , , , |
| Format: | Article in Journal/Newspaper |
| Language: | English |
| Published: |
Cambridge University Press (CUP)
2011
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| Subjects: | |
| Online Access: | http://dx.doi.org/10.1017/s0954102011000721 https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0954102011000721 |
| Summary: | Abstract Observations were made of water column chemistry in four Na-Cl dominated ponds on the McMurdo Ice Shelf from the end of January to early April in 2008. During that time the ponds went from ice-free to predominantly frozen, with only a small volume of residual hypoxic, saline liquid trapped at the base of each pond. Changes in the concentrations of inorganic solutes with time distinguished Na, Cl, Mg, K, SO 4 , As, U and Mn as ions and trace elements that behave mainly conservatively during freezing, from those which are affected by biological processes (removing HCO 3 ) and the precipitation of mineral phases such as calcite (removing Ca and more HCO 3 ). Dissolved Fe, Mo, Cu and Zn also show evidence of precipitation from the water column during freezing; geochemical speciation modelling predicts the formation of stable insoluble mineral phases such as Fe oxides and oxyhydroxides while conditions are oxic, and Fe-, Cu-, Mo- and Zn-sulphide minerals in the presence of H 2 S. Consequently, under winter conditions, residual liquid beneath the ice in such ponds is anticipated to be an anoxic Na-Cl brine with the capacity to develop high concentrations of toxic trace elements such as As and U. |
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