Deuterium Content of Deuterium Depleted Water: 1st Trial

2012-07-20T21:24:18Z (GMT) by Anthony Salvagno Scott Jasechko
<p>Introduction by Anthony:</p> <p>Here we present some initial findings regarding the nature of deuterium exchange of deuterium depleted water with its environment. Deuterium depleted water experiments involving living organisms are extremely sensitive to deuterium exchange, which is the process of water molecules swapping hydrogens with deuterium atoms. DDW purchased from Sigma is purported to have</p> <p>Because of this, deuterium exchange over time needs to be better understood. Here we present some initial findings that may help to determine this process.</p> <p>We analyzed two samples of deuterium depleted water. One sample was dated January 7, 2012, the other February 16, 2012 which indicate the day the bottles of water were initially opened (exposed to atmosphere). Both samples were stored in a desiccator since the opening date. The samples were analyzed on July 19, 2012.</p> <p>Contained in this fileset you will find the raw (.csv file) and slightly analyzed data (see below). There is also a notation calculator which converts from the machines per mille notation to the pure ratio (which can be easily converted to part per million) and a .pdf that explains per mille notation.</p> <p>Methods and Data by Scott:</p> <p>We measured the 18O/16O and2H/1H ratios of water in two samples of deuterium-depleted water (DDW) using a cavity ring down spectrometer (Picarro). <br><br>Results are presented in ["HDGS71...calib.xlsx"]. January and February 2012 samples have similar stable oxygen and hydrogen isotope compositions, at roughly δ18O values near -535‰, and δD values close to -1000‰ relative to standard mean ocean water (SMOW; de Wit et al., 1980; Baertschi and Macklin, 1976) which is approximately 1/6420 or 155.76ppm. The δD value of -1000 per mille corresponds to a 2H/1H ratio of zero (within analytical error), suggesting that these waters contain near zero amounts of deuterium. It should be noted at this point that the spectrometer used in these measurements is calibrated to measure natural waters that range in δD values from ~-500 to ~+100, so the instrument is not suited to measure the extremely low deuterium abundances expected in these waters.<br><br>The oxygen isotope composition of these water samples contains roughly half the concentration of 18O when compared to modern oceans (18O/16O of 0.00092 compared to 0.002005 in SMOW). In δD-δ18O space these waters are shown to lie well “above” the global meteoric water line (Craig, 1961) – a rather unique feature that only occurs under special conditions of moisture recycling in nature (ex. Gat et al., 1994).</p>