Halogen chemistry and isotopic composition in McMurdo lake waters and pore fluids


As part of a collaborative investigation between researchers at Rice University, Arkansas State University, University of Rochester, and Ohio State University, lakes of the McMurdo Dry Valleys were sampled at discreet depth intervals during the 2005-2006 field season.  Sample splits were subsequently analyzed for chemical and isotopic composition of both gases and dissolved  ions, as well as dissolved organic carbon. In addition, cryogenic salts were sampled in the surrounding lake shores in order to determine the salt sources. Gravity cores were also obtained and the pore waters were collected by centrifuging the wet sediment.
Presented  in this file are the dissolved halogens :chloride, bromide, and total iodine in lake waters and pore waters. The isotopic composition of I-129 and Cl-36 are also presented for these same samples, as are the molar ratios of I-129/I-127, and Cl-36/Cl-37.   Alkalinity was also determined in order to subsequently investigate the relationship between the oxidation of organic matter and the release of iodine into the lake waters.

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 Waters were sampled by first drilling through the ice and then lowering a Go-Flo bottle to the indicated depths. Retrieved samples were then spit into separate containers for analysis. Following the sampling of water, a shallow gravity corer with plastic lining was  attached to steel cable  and lowered through the ice hole and down to the lake bottom. The corer was dropped the final 3 meters. Core recovery ranged from only a few centimeters to 25 centimeters. Once recovered, the sediments were stoppered and transported vertically to Crary Laboratory at McMurdo station. Sediment was separated along several intervals of each core and sediment and pore waters were separated by centrifugation.  
Chloride was determined through ion chromatography according to methods described in Welch, K.A., Lyons, W.B., Graham, E., Neumann, K., Thomas, J.M., and D. Mikesell. 1996. Determination of major element chemistry in terrestrial waters from Antarctica by ion chromatography. Journal of Chromatography A 739: 257-263. Kathy Welch carried out the chloride determinations at the Crary Laboratory, McMurdo Station.
Alkalinity was determined by titration of samples with hydrochloric acid at Crary Laboratory, McMurdo Station. The methods  used for alkalinity determinations are described in  Gieskes, J.M., Gamo, T.,Brumsack, H.,1991. Chemical Methods for Intersitital water analysis aboard JOIDES Resolution, ODP Tech. Note 15, Texas AandM University, 60 pp.
 Samples were diluted then analyzed for I-127 and Br-79 using ICP-MS. Replicate analyses were carried out at the ICP-MS facility of Cin-Ty Lee at Rice University, as well as the ICP-MS facility of Yasuyuki Muramatsu at  Gakushuin University, Tokyo. Methods for analysis are described in: Schnetger, B., and Muramatsu, Y., Determination of the halogens, with special reference to iodine, in geological and biological samples using pyrohydrolysis for preparation of inductively coupled plasma mass spectrometry and ion chromatography for measurement, Analyst, 121:1627-1631.
Chloride was extracted from the samples as purified AgCl. Likewise, iodine was extracted as purified AgI using methods described in Snyder, GT and  Fabryka-Martin, JT  (2007). 129-I and 36-Cl in dilute hydrocarbon waters: Marine-cosmogenic, in situ, and anthropogenic sources. In: G.T. Snyder and J.E. Moran (Eds.), special issue: "The halogens and their isotopes in marine and terrestrial aqueous systems", Applied Geochemistry, 22 , 692-704. The purified chloride and iodide targets were sent to PRIME Laboratory at Purdue University for AMS (accelerator mass spectrometry)  analysis of Cl-36 and I-129.

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This dataset was created Sept 30, 2008 by MCM-LTER information manager (Chris Gardner) after email discussion with PI Glen Snyder.

In 2016 metadata wsas completed (San Gil)

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This material is based upon work supported by the National Science Foundation under Grant No.0440686
Snyder, GT, Hubbard, A., Muramatsu, Y., Lu, H.-L. (2008) Radiogenic Halogen Isotopes in Cold Places: Deep Seeps or Recent Salt Dissolution? , GSA Annual meeting, Houston, Abstract 330-12.
Dowling, C., Leslie, D., Poreda, R., Darrah, T., Lyons, W.B., Snyder, G. (2007) Preliminary interpretations of the groundwater flow system of Wright Valley, Antarctica using stable isotopes and noble gas, GSA Denver Annual Meeting, October, 2007, abstract 177-1. 
Snyder, G T,  Dowling, C B, Poreda, R J  (2007) Redox controls on solute transfer between shallow sediments and bottom-waters: Chemical and isotopic evidence from two Antarctic Dry Valley Lakes, Eos Trans. AGU, 88(52), Fall Meet. Suppl.H14-D-07.
Lyons, WB, Dowling, C., Welch, KA, Snyder, G., Poreda, RJ, Doran, PT, Fountain, A. (2005) Dating water and solute additions in ice-covered Antarctic lakes, Goldschmidt Conference, Moscow, Idaho, Geochimica et Cosmochimica Acta 69 (2),305-323
Lyons, WB,  K.A. Welch, KA, Snyder, G,  Olesik, J, Graham, EY,  Marion, GM,  Poreda, RJ (2005). Halogen geochemistry of the McMurdo Dry Valleys lakes, Antarctica: Clues to the origin of solutes and lake evolution and age. Geochimica et Cosmochimica Acta, 69, 305-323.
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