2008 Joint Meeting of The Geological Society of America, Soil Science Society of America, American Society of Agronomy, Crop Science Society of America, Gulf Coast Association of Geological Societies with the Gulf Coast Section of SEPM

Paper No. 1
Presentation Time: 1:35 PM

Diel Cycling of as, Cu, Fe, Mn, and V In McMurdo Dry Valley, Antarctic Streams: Identifying Controls on Metal Geochemistry

FORTNER, Sarah K., School of Earth Sciences, Byrd Polar Research Center, The Ohio State University, 108 Scott Hall, Columbus, OH 43210, LYONS, W. Berry, School of Earth Sciences, Byrd Polar Research Center, The Ohio State University at Columbus, 108K Scott Hall, 1090 Carmack Rd, Columbus, OH 43210, MUNK, LeeAnn, Department of Geological Sciences, University of Alaska Anchorage, 3211 Providence Drive, Anchorage, AK 99508 and MCKNIGHT, Diane, Instarr, Univ of Colorado, 1560 30th Street, Campus Box 450, Boulder, CO 80309, fortner.27@osu.edu

We present data on dissolved (0.4 µm) and environmentally available, unfiltered-acidified, concentrations of As, Cu, Fe, Mn, and V within two McMurdo Dry Valley, Antarctic streams: Canada Stream and Andersen Creek. These streams both originate from Canada Glacier melt but differ in their geomorphology and biological composition. Flow and melt travel time controlled more than 33% of the diel variability observed in dissolved metal, major ion, and Si in these streams. Discharge (r2³ 0.56) significantly correlated (n= 24, µ=0.05) with the percentage of environmentally available metals that are adsorbed within each stream. Temperature also correlated with the amount of As and Cu adsorbed on particulate matter in Andersen Creek (r2= 0.83, 0.46) and Fe and Mn adsorbed in Canada Stream (r2=0.69, 0.49). Greater heterogeneity of environmentally available metal translated to greater heterogeneity in the amount of metal adsorbed. For example, environmentally available Cu concentrations in Canada Stream ranged from 2 to 88 nM with adsorbed Cu ranging from 13-88%, whereas Cu in Andersen Creek ranged from 1 to 5 nM with adsorbed Cu ranging from 88 to 99%. Silicate weathering controls approximately 20% of the chemical variability observed in both streams. In Andersen Creek increasing Si is associated with increasing Cu, Fe, and V with no relation to discharge.  However, in Canada Stream increasing Si is associated with decreasing discharge, Cu, Mn, and major cations. It is likely that in Andersen Creek Cu, Fe, and V are released via silicate weathering. Yet, metals are not released, and/or are adsorbed during silicate weathering within Canada Stream. This may be the result of greater hyporheic exchange, or biological activity occurring within Canada Stream. This study provides baseline data to understand hyporheic-groundwater controls on metal geochemistry and data illustrates the high rate of metal denudation from Antarctic Streams.