Summer-winter transitions in Antarctic ponds: III. Chemical

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TitleSummer-winter transitions in Antarctic ponds: III. Chemical changesAbstractObservations 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 H2S. 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. Copyright 2011 Antarctic Science Ltd.AcknowledgementsThis research was funded by the New Zealand Foundation for Research, Science and Technology (Contracts C01X0708 and C01X0306) and Antarctica New Zealand which provided logistic support. We are grateful to the editor and anonymous reviewers for suggestions that greatly improved the manuscript, to Drs Kevin Brown and Briar Wait for their contribution to the analysis of major ions, and to Dr Clive Howard-Williams for his ongoing support for this research.

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1st AuthorWebster-Brown, J.AuthorWebster-Brown, J.Hawes, I.Safi, K.Sorrell, B.Wilson, N.Year2012JournalAntarctic ScienceVolume24Number2Pages121-130DOI10.1017/S0954102011000721URLhttps://www.scopus.com/inward/recor.....8306a420350b5e1e903479b05Keywordsbrineconcentration (composition)hydrogen sulfideice free corridorpondprecipitation (chemistry)sodium chloridespeciation (chemistry)summertrace elementwater chemistrywinter, AntarcticaEast AntarcticaMcMurdo Ice Shelf, rank5Author Keywordsfreeze concentrationmajor ionMcMurdo Ice ShelfPHREEQC modellingtrace element

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TypeArticleCitationWebster-Brown, J., Hawes, I., Safi, K., Sorrell, B. and Wilson, N. (2012) Summer-winter transitions in Antarctic ponds: III. Chemical changes. Antarctic Science, 24(2): 121-130 doi:10.1017/S0954102011000721IdentifierWebster-Brown2012Relevancerank5

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Hawes, I.