of Antarctica

• Main Authors: Gideon M. Henderson A, Brenda L. Hall B, Andrew Smith A, Laura F. Robinson A
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Published: 2005
• Subjects: Antarctic; McMurdo Dry Valleys; Antarc*; Antarctica
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.434.9017; http://www.earth.ox.ac.uk/~gideonh/pdffiles/Lake 48.pdf

The ( 234 U / 238 U) ratio in surface waters is generally higher than secular equilibrium due to nuclide recoil during alpha-decay of 238 U. The size of the deviation from secular equilibrium contains information about the environment in which the water is found. This potential tool for environmental reconstruction has previously been studied in rivers, groundwater, and sediment pore-water. Here we conduct a first assessment of the controls on ( 234 U / 238 U) in lakewaters. Thirty-three waters from glacial melt, streams, and lakes of the McMurdo Dry Valleys (Antarctica) were analysed for U concentration and isotope ratio. Glacial melt has a low U concentration and a ( 234 U / 238 U) identical to seawater, suggesting that U in Antarctic ice is largely sourced from sea-salt aerosols. Stream waters have higher U concentration (0.009 to 1.282 ppb) and ( 234 U / 238 U) (1.280 to 1.832) due to chemical weathering of sediment in stream channels and 234 U recoil from this sediment. Average ( 234 U / 238 U) is 1.502, close to the average of observations from other surface waters worldwide. The absence of groundwaters in the Dry Valleys indicates that reasonably high ( 234 U / 238 U) ratios do not require groundwater sources of U, so care should be taken before using high ( 234 U / 238 U) as an indicator of groundwater inputs to stream waters. Lakewaters have U concentrations ranging from 0.027 to 46 ppb (i.e. up to 14 times the