Trace element and major ion concentrations and dynamics in glacier snow and melt: Eliot Glacier, Oregon Cascades

摘要

We present concentrations of environmentally available (unfiltered acidified 2% v/v HNO_3) As, Cu, Cd, Pb, V, Sr, and major ions including Ca~(2+), Cl~-, and SO_4~(2-) in a July 2005 and a March 2006 shallow snow profile from the lower Eliot Glacier, Mount Hood, Oregon, and its proglacial stream, Eliot Creek. Low enrichment factors (EF) with respect to crustal averages suggests that in fresh March 2006 snow environmentally available elements are derived primarily from lithogenic sources. Soluble salts occurred in lower and less variable concentrations in July 2005 snow than March 2006. Conversely, environmentally available trace elements occurred in greater and more variable concentrations in July 2005 than March 2006 snow. Unlike major solutes, particulate-associated trace elements are not readily eluted during the melt season. Additionally, elevated surface concentrations suggest that they are likely added throughout the year via dry deposition. In a 1-h stream sampling, ratios of dissolved (<0-45 μm) V : Cl~-, Sr: Cl~-, and Cu : Cl~- are enriched in the Eliot Stream with respect to their environmentally available trace element to Cl~- ratios in Eliot Glacier snow, suggesting chemical weathering additions in the stream waters. Dissolved Pb: Cl~- is depleted in the Eliot Stream with respect to the ratio of environmentally available Pb to Cl~- in snow, corresponding to greater adsorption onto particles at greater pH values.