Reach-Scale Cation Exchange Controls on Major Ion Chemistry of an Antarctic Glacial Meltwater Stream

Abstract

Abstract. The McMurdo dry valleys of Antarctica represent the largest of the ice-free areas on the Antarctic continent, containing glaciers, meltwater streams, and closed basin lakes. Previous geochemical studies of dry valley streams and lakes have addressed chemical weathering reactions of hyporheic substrate and geochemical evolution of dry valley surface waters. We examine cation transport and exchange reactions during a stream tracer experiment in a dry valley glacial meltwater stream. , Li + and K + were taken up in downstream transport and Na + was released. Simulations of conservative and reactive (firstorder uptake or generation) solute transport were made with the OTIS (one-dimensional solute transport with inflow and storage) model. Among the four experimental reaches of Green Creek, solute transport simulations reveal that Li + was removed from stream water in all four reaches, K + was released in two reaches, taken up in one reach, and Na + was released in all four reaches. Hyporheic sediments appear to be variable with uptake of Li + in two reaches, uptake of K + in one reach, release of K + in two reaches, and uptake of Na + in one reach. Mass balances of the conservative and reactive simulations show that from 1.05 to 2.19 moles of Li + was adsorbed per reach, but less than 0.3 moles of K + and less than 0.9 moles of Na + were released per reach. This suggests that either (1) exchange of another ion which was not analyzed in this experiment or (2) that both ion exchange and sorption control inorganic solute transport. The elevated cation concentrations introduced during the experiment are typical of initial flows in each flow season, which flush accumulated dry salts from the streambed. We propose that the bed sediments (which compose the hyporheic zone) modulate the flushing of these salts during initial flows each season, due to ion exchange and sorption reactions.

Hyporheic zone influences on concentration‐discharge relationships in a headwater sandstone stream

“…In contrast, chemodynamic solute export has been associated with catchments where the connectivity between solute storage zones and the receiving stream is spatially and temporally variable [Musolff et al, 2015]. Intermittent mobilization of highly reactive or strongly sorbed solutes also exhibit chemodynamic trends when physiochemical thresholds are surpassed in systems [Gooseff et al, 2004;Thompson et al, 2011;Musolff et al, 2015].…”

Seasonal hydrological and suspended sediment transport dynamics in proglacial streams, James Ross Island, Antarctica

“…Previous studies on proglacial fluvial sediment transport in Antarctica have almost exclusively focussed on solute load (Gooseff et al, 2004;Barker et al, 2013;Fortner et al, 2013). Suspended sediment transport was included into the complex study of proglacial zone of the Wanda Glacier on King George Island (Rosa et al, 2014).…”

Trickle or treat: The dynamics of nutrient export from polar glaciers

“…We found differences in the dynamics of nutrient export to downstream environments under changing discharge regimes. The concentrations of most solutes in proglacial stream water are controlled primarily by chemical weathering of the highly permeable, unconsolidated sediments found in the channel margins and hyporheic zone (Gooseff et al, 2004) including carbonate and silicate weathering, and by salt dissolution (Lyons et al, 1998;Maurice et al, 2002;Fortner et al, 2005). Weathering takes place where source material is supplied directly to the channel by aeolian transport, atmospheric deposition (Fortner et al, 2005(Fortner et al, , 2013 and/or bed/bank erosion.…”