scholarly journals A generalizable box model for kinetic clumped isotope effects in the CaCO3 -DIC-H2O system

2021 ◽  
Author(s):  
James Watkins ◽  
Laurent Devriendt
Keyword(s):  
Isotope Effects ◽  
Box Model ◽  
Clumped Isotope

scholarly journals Clumped isotope effects during OH and Cl oxidation of methane

2017 ◽  
Vol 196 ◽  
pp. 307-325 ◽  
Author(s):  
Andrew R. Whitehill ◽  
Lars Magnus T. Joelsson ◽  
Johan A. Schmidt ◽  
David T. Wang ◽  
Matthew S. Johnson ◽  
...  
Keyword(s):  
Isotope Effects ◽  
Oxidation Of Methane ◽  
Clumped Isotope

scholarly journals Clumped isotope effects of thermogenic methane formation: insights from pyrolysis of hydrocarbons

2021 ◽  
Author(s):  
Guannan Dong ◽  
Hao Xie ◽  
Michael Formolo ◽  
Michael Lawson ◽  
Alex Sessions ◽  
...  
Keyword(s):  
Isotope Effects ◽  
Methane Formation ◽  
Clumped Isotope ◽  
Thermogenic Methane

scholarly journals Equilibrium clumped-isotope effects in doubly substituted isotopologues of ethane

2017 ◽  
Vol 197 ◽  
pp. 14-26 ◽  
Author(s):  
Michael A. Webb ◽  
Yimin Wang ◽  
Bastiaan J. Braams ◽  
Joel M. Bowman ◽  
Thomas F. Miller
Keyword(s):  
Isotope Effects ◽  
Clumped Isotope

scholarly journals Kinetic isotope effects of <sup>12</sup>CH<sub>3</sub>D  + OH and <sup>13</sup>CH<sub>3</sub>D  + OH from 278 to 313 K

2016 ◽  
Vol 16 (7) ◽  
pp. 4439-4449 ◽  
Author(s):  
L. M. T. Joelsson ◽  
J. A. Schmidt ◽  
E. J. K. Nilsson ◽  
T. Blunier ◽  
D. W. T. Griffith ◽  
...  
Keyword(s):  
Isotope Effects ◽  
Kinetic Isotope Effects ◽  
State Theory ◽  
Atmospheric Methane ◽  
Isotopic Signatures ◽  
Budget Analysis ◽  
Kinetic Isotope ◽  
Methane Budget ◽  
Source Signal ◽  
Clumped Isotope

Abstract. Methane is the second most important long-lived greenhouse gas and plays a central role in the chemistry of the Earth's atmosphere. Nonetheless there are significant uncertainties in its source budget. Analysis of the isotopic composition of atmospheric methane, including the doubly substituted species 13CH3D, offers new insight into the methane budget as the sources and sinks have distinct isotopic signatures. The most important sink of atmospheric methane is oxidation by OH in the troposphere, which accounts for around 84 % of all methane removal. Here we present experimentally derived methane + OH kinetic isotope effects and their temperature dependence over the range of 278 to 313 K for CH3D and 13CH3D; the latter is reported here for the first time. We find kCH4/kCH3D = 1.31 ± 0.01 and kCH4/k13CH3D = 1.34 ± 0.03 at room temperature, implying that the methane + OH kinetic isotope effect is multiplicative such that (kCH4/k13CH4)(kCH4/kCH3D) = kCH4/k13CH3D, within the experimental uncertainty, given the literature value of kCH4/k13CH4 = 1.0039 ± 0.0002. In addition, the kinetic isotope effects were characterized using transition state theory with tunneling corrections. Good agreement between the experimental, quantum chemical, and available literature values was obtained. Based on the results we conclude that the OH reaction (the main sink of methane) at steady state can produce an atmospheric clumped isotope signal (Δ(13CH3D) = ln([CH4][13CH3D]/[13CH4][CH3D])) of 0.02 ± 0.02. This implies that the bulk tropospheric Δ(13CH3D) reflects the source signal with relatively small adjustment due to the sink signal (i.e., mainly OH oxidation).

Clumped isotope constraints on equilibrium carbonate formation and kinetic isotope effects in freezing soils

2018 ◽  
Vol 235 ◽  
pp. 402-430 ◽  
Author(s):  
Landon K. Burgener ◽  
Katharine W. Huntington ◽  
Ronald Sletten ◽  
James M. Watkins ◽  
Jay Quade ◽  
...  
Keyword(s):  
Isotope Effects ◽  
Kinetic Isotope Effects ◽  
Carbonate Formation ◽  
Kinetic Isotope ◽  
Clumped Isotope

Farmed calcite δ18O, δ13C, and Δ47 at Ascunsă cave, Romania

2021 ◽  
Author(s):  
Virgil Dragusin ◽  
Vasile Ersek ◽  
Alvaro Fernandez ◽  
Roxana Ionete ◽  
Andreea Iordache ◽  
...  
Keyword(s):  
Air Temperature ◽  
Saturation Index ◽  
Isotope Effects ◽  
Monitoring Program ◽  
Drip Water ◽  
Water Ph ◽  
Calcite Saturation ◽  
Calcite Deposition ◽  
Clumped Isotope ◽  
Kinetic Fractionation

&lt;p&gt;Ascuns&amp;#259; cave (Romania) is the subject of a monitoring program since 2012. While the cave air temperature was very stable around 7&amp;#176;C for most of the time, it experienced in 2019 a 3&amp;#176;C rise, and remained high until the present.&lt;/p&gt;&lt;p&gt;We present here &amp;#948;&lt;sup&gt;18&lt;/sup&gt;O, &amp;#948;&lt;sup&gt;13&lt;/sup&gt;C, and clumped isotope results from calcite farmed at two drip points inside the cave (POM X and POM 2). POM X has a slower drip rate than POM 2 and deposits calcite more continuously. Calcite deposition has been shown to depend on cave air CO&lt;sub&gt;2&lt;/sub&gt; concentration, which controls the drip water pH and, further, the calcite saturation index.&lt;/p&gt;&lt;p&gt;In 2019, &amp;#948;&lt;sup&gt;18&lt;/sup&gt;O values at both sites quickly shifted to lower values as a response to the increase in temperature. At POM X, values were situated between approximately -7.2&amp;#8240; and -7.6&amp;#8240; before this transition, whereas in 2019 they shifted to -7.8&amp;#8240; - -8.0&amp;#8240;. At POM 2, where values were generally lower, they shifted from -7.5&amp;#8240; to -7.8&amp;#8240; to -8.0&amp;#8240;.&lt;/p&gt;&lt;p&gt;Clumped isotope temperature estimates mostly agree, within measurement error, with measured cave temperature. This agreement is notable given that strong offsets are commonly observed in mid-latitude caves, reflecting kinetic fractionation effects. However, intervals with deviations from cave temperature are also observed, suggesting variations in isotopic disequilibrium conditions with time.&lt;/p&gt;&lt;p&gt;Here we will discuss these isotope changes in relation to cave air temperature and CO&lt;sub&gt;2&lt;/sub&gt; concentration, drip water isotope values and elemental chemistry, as well as in relation to drip rates, in order to improve our understanding of calcite precipitation and isotope effects in caves.&lt;/p&gt;

Three-Box Model of Sexual Orientation: A Challenge to Categorical Conceptualizations

2007 ◽  
Author(s):  
Joel T. Nadler ◽  
Tyrel J. Starks ◽  
Lynda M. Sagrestano ◽  
Paul D. Sarvela
Keyword(s):  
Sexual Orientation ◽  
Box Model
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