Multiproxy Record of Late Pleistocene–Holocene Climate and Vegetation Changes from a Peat Bog in Patagonia

2001 ◽  
Vol 55 (2) ◽  
pp. 168-178 ◽  
Author(s):  
Elise Pendall ◽  
Vera Markgraf ◽  
James W. C. White ◽  
Mark Dreier ◽  
Ray Kenny
Keyword(s):  
Late Pleistocene ◽  
Hydrogen Isotope ◽  
Deterministic Model ◽  
Isotope Composition ◽  
Ice Core ◽  
Isotope Analysis ◽  
Tierra Del Fuego ◽  
Vegetation Changes ◽  
Peat Core ◽  
Stable Hydrogen Isotope

AbstractPollen assemblage changes and stable hydrogen isotope analysis of mosses (Sphagnum magellanicum and Drepanocladus s.l.) from a bog in Tierra del Fuego, Argentina, provided independent proxies for reconstructing changes in effective moisture and temperature over the past 16,000 cal yr B.P. A deterministic model was used to reconstruct the stable hydrogen isotope composition of meteoric water from the D/H ratios of bog mosses over the last 16,000 years. Abrupt changes in temperature, as recorded in D/H ratios of moss cellulose, were accompanied by synchronous changes in vegetation composition during the late Pleistocene and early and middle Holocene, when moisture levels were lower than today. In contrast, temperature variability during the late Holocene was not accompanied by comparable vegetation changes. In particular, grass pollen (Poaceae) increased during periodic cold spells between 15,000 and 11,000 cal yr B.P., but a cold spell of similar magnitude ca. 2000 cal yr B.P. did not appear to affect vegetation. During the late Pleistocene, the isotopic record from the peat core shows variations similar to the D/H ratios in the Antarctic Taylor Dome ice core. However, the timing of the changes in the Harberton record is more in line with the timing of other Southern Hemisphere records.

scholarly journals Mass spectrometric measurement of hydrogen isotope fractionation for the reactions of chloromethane with OH and Cl

2018 ◽  
Author(s):  
Frank Keppler ◽  
Enno Bahlmann ◽  
Markus Greule ◽  
Heinz Friedrich Schöler ◽  
Julian Wittmer ◽  
...  
Keyword(s):  
Hydrogen Isotope ◽  
Isotope Fractionation ◽  
Isotope Effects ◽  
Isotope Analysis ◽  
Isotope Ratio Mass Spectrometry ◽  
Detailed Knowledge ◽  
Mass Spectrometric Measurement ◽  
Isotopic Analyses ◽  
Chlorine Radicals ◽  
Stable Hydrogen Isotope

Abstract. Chloromethane (CH3Cl) is an important provider of chlorine to the stratosphere but yet lacks detailed knowledge of its budget. Stable isotope analysis is potentially a powerful tool to constrain CH3Cl flux estimates. The largest degree of isotope fractionation is expected to occur for deuterium in CH3Cl in the hydrogen abstraction reactions with its main sink reactant tropospheric OH and its minor sink reactant Cl atoms. We determined the isotope fractionation by stable hydrogen isotope analysis of the fraction of CH3Cl remaining after reaction with hydroxyl and chlorine radicals in a 3.5 m3 Teflon smog-chamber at 293 ± 1 K. We measured the increasing stable hydrogen isotope values of the unreacted CH3Cl using compound specific thermal conversion isotope ratio mass spectrometry. The isotope fractionations of CH3Cl for the reactions with hydroxyl and chlorine radicals were found to be −242 ± 7 mUr (or ‰) and −280 ± 11 mUr, respectively. For comparison, we performed similar experiments using methane (CH4) as the target compound with OH and obtained a fractionation constant of −205 ± 6 mUr which is in good agreement with values previously reported. The observed large kinetic isotope effects are helpful when employing isotopic analyses of CH3Cl in the atmosphere to improve our knowledge of its atmospheric budget.

scholarly journals Using stable isotopes to estimate migratory connectivity for a patchily distributed, wetland-associated Neotropical migrant

The Condor ◽  
2019 ◽  
Vol 121 (4) ◽  
Author(s):  
Jessie Reese ◽  
Catherine Viverette ◽  
Christopher M Tonra ◽  
Nicholas J Bayly ◽  
Than J Boves ◽  
...  
Keyword(s):  
Hydrogen Isotope ◽  
Isotope Analysis ◽  
Distribution Model ◽  
Migratory Connectivity ◽  
Calibration Equation ◽  
Abundance Data ◽  
Assignment Model ◽  
Breeding Distribution ◽  
Stable Hydrogen Isotope ◽  
Species Specific

Abstract Estimates of migratory connectivity are needed for full annual cycle population models of migratory bird species experiencing rapid declines in abundance. One technique to determine migratory connectivity is through stable isotope analysis. This low-resolution method may be influenced by how data are calibrated between isotopes measured in precipitation and those measured in feathers, and can be informed by incorporating relative abundance into the assignment model. eBird abundance maps are a new tool combining citizen science data into a predictive species distribution model. In the Prothonotary Warbler (Protonotaria citrea), a wetland-associated songbird with a patchy breeding distribution, we sought to use stable-hydrogen isotope analysis informed by a species-specific calibration equation and eBird abundance data to determine the strength of migratory connectivity. We developed a species-specific calibration equation using known-origin samples from the breeding grounds and found that stable-hydrogen isotope values measured in precipitation explained 50% of the variation in stable-hydrogen isotope values among feathers. We found that the assignment model incorporating eBird abundance data correctly identified the true origins of 66% of individuals, and that the average assignment area (as a measure of precision) was 64% of the breeding distribution. These results represented a 7% increase in precision and a 3% decrease in accuracy when compared to a model that was not informed by abundance. Based on these models, wintering populations from 6 countries represented a mix of likely breeding origins, suggesting low migratory connectivity for Prothonotary Warblers. We found evidence that wintering latitude was related to likely breeding origin, with individuals at western wintering locations more likely to have southern breeding origins, but this relationship was weak. These results corroborate studies using archival light-level geolocators and high-resolution genetic markers, which also demonstrated weak migratory connectivity in this species. For patchily distributed species, eBird abundance data may not provide a useful increase in precision and accuracy for isotope assignments.

Using Stable Hydrogen Isotope Analysis of Feathers to Delineate Origins of Harvested Sandhill Cranes in the Central Flyway of North America

Waterbirds ◽  
2006 ◽  
Vol 29 (2) ◽  
pp. 137-147 ◽  
Author(s):  
Keith A. Hobson ◽  
Steven Van Wilgenburg ◽  
Leonard I. Wassenaar ◽  
Helen Hands ◽  
William P. Johnson ◽  
...  
Keyword(s):  
North America ◽  
Hydrogen Isotope ◽  
Isotope Analysis ◽  
Stable Hydrogen Isotope ◽  
Sandhill Cranes ◽  
Central Flyway

scholarly journals Oxygen isotope mass balance of atmospheric nitrate at Dome C, East Antarctica, during the OPALE campaign

2016 ◽  
Vol 16 (4) ◽  
pp. 2659-2673 ◽  
Author(s):  
Joël Savarino ◽  
William C. Vicars ◽  
Michel Legrand ◽  
Suzanne Preunkert ◽  
Bruno Jourdain ◽  
...  
Keyword(s):  
Oxygen Isotope ◽  
Transfer Functions ◽  
Isotope Composition ◽  
Surface Ozone ◽  
Ice Core ◽  
Isotope Analysis ◽  
Austral Summer ◽  
Direct Observations ◽  
Atmospheric Nitrate ◽  
Stable Oxygen

Abstract. Variations in the stable oxygen isotope composition of atmospheric nitrate act as novel tools for studying oxidative processes taking place in the troposphere. They provide both qualitative and quantitative constraints on the pathways determining the fate of atmospheric nitrogen oxides (NO + NO2 = NOx). The unique and distinctive 17O excess (Δ17O = δ17O − 0.52 × δ18O) of ozone, which is transferred to NOx via oxidation, is a particularly useful isotopic fingerprint in studies of NOx transformations. Constraining the propagation of 17O excess within the NOx cycle is critical in polar areas, where there exists the possibility of extending atmospheric investigations to the glacial–interglacial timescale using deep ice core records of nitrate. Here we present measurements of the comprehensive isotopic composition of atmospheric nitrate collected at Dome C (East Antarctic Plateau) during the austral summer of 2011/2012. Nitrate isotope analysis has been here combined for the first time with key precursors involved in nitrate production (NOx, O3, OH, HO2, RO2, etc.) and direct observations of the transferrable Δ17O of surface ozone, which was measured at Dome C throughout 2012 using our recently developed analytical approach. Assuming that nitrate is mainly produced in Antarctica in summer through the OH + NO2 pathway and using concurrent measurements of OH and NO2, we calculated a Δ17O signature for nitrate on the order of (21–22 ± 3) ‰. These values are lower than the measured values that ranged between 27 and 31 ‰. This discrepancy between expected and observed Δ17O(NO3−) values suggests the existence of an unknown process that contributes significantly to the atmospheric nitrate budget over this East Antarctic region. However, systematic errors or false isotopic balance transfer functions are not totally excluded.

scholarly journals Mass spectrometric measurement of hydrogen isotope fractionation for the reactions of chloromethane with OH and Cl

2018 ◽  
Vol 18 (9) ◽  
pp. 6625-6635 ◽  
Author(s):  
Frank Keppler ◽  
Enno Bahlmann ◽  
Markus Greule ◽  
Heinz Friedrich Schöler ◽  
Julian Wittmer ◽  
...  
Keyword(s):  
Hydrogen Isotope ◽  
Isotope Fractionation ◽  
Isotope Effects ◽  
Isotope Analysis ◽  
Isotope Ratio Mass Spectrometry ◽  
Detailed Knowledge ◽  
Mass Spectrometric Measurement ◽  
Isotopic Analyses ◽  
Chlorine Radicals ◽  
Stable Hydrogen Isotope

Abstract. Chloromethane (CH3Cl) is an important provider of chlorine to the stratosphere but detailed knowledge of its budget is missing. Stable isotope analysis is a potentially powerful tool to constrain CH3Cl flux estimates. The largest degree of isotope fractionation is expected to occur for deuterium in CH3Cl in the hydrogen abstraction reactions with its main sink reactant tropospheric OH and its minor sink reactant Cl atoms. We determined the isotope fractionation by stable hydrogen isotope analysis of the fraction of CH3Cl remaining after reaction with hydroxyl and chlorine radicals in a 3.5 m3 Teflon smog chamber at 293 ± 1 K. We measured the stable hydrogen isotope values of the unreacted CH3Cl using compound-specific thermal conversion isotope ratio mass spectrometry. The isotope fractionations of CH3Cl for the reactions with hydroxyl and chlorine radicals were found to be -264±45 and -280±11 ‰, respectively. For comparison, we performed similar experiments using methane (CH4) as the target compound with OH and obtained a fractionation constant of -205±6 ‰ which is in good agreement with values previously reported. The observed large kinetic isotope effects are helpful when employing isotopic analyses of CH3Cl in the atmosphere to improve our knowledge of its atmospheric budget.

New method for hydrogen isotope analysis of non-structural carbohydrates

2020 ◽  
Author(s):  
Philipp Schuler ◽  
Jobin Joseph ◽  
Marc-Andre Cormier ◽  
Roland A. Werner ◽  
Matthias Saurer ◽  
...  
Keyword(s):  
Hydrogen Isotope ◽  
Isotope Composition ◽  
Isotope Analysis ◽  
Stable Isotope Composition ◽  
Safety Issues ◽  
Nitrate Ester ◽  
Exchangeable Hydrogen ◽  
Sample Amount ◽  
Hydrogen Isotope Ratios ◽  
Living Organisms

<p>Analysing stable isotope composition of biologic components can be a powerful tool to reconstruct past environmental conditions, physiological responses, and to trace metabolic pathways. The analysis of the carbon-bound non-exchangeable hydrogen isotope ratios (δ<sup>2</sup>H<sub>NE</sub>) in carbohydrates can be challenging, partly due to the exchangeability of oxygen-bound hydrogen in the same molecule with those in water or vapour. To eliminate such sample alterations, carbohydrates have been nitrated to substitute exchangeable hydrogen with nitrate ester. However, the nitration of carbohydrates is time consuming, needs high sample amount, has several safety issues, and the nitrated products of short-chained carbohydrates are instable. δ<sup>2</sup>H<sub>NE</sub> of sugars derived from living organisms or directly from the environment are thus still limited and not widespread available. Here we optimized recent δ<sup>2</sup>H<sub>NE</sub> methods, with the focus on plant-derived non-structural carbohydrates such as starch, sugars, and sugar alcohols. The exchangeable hydrogen is replaced via equilibration with water vapour of a known isotopic composition to calculate δ<sup>2</sup>H<sub>NE</sub>. In this presentation, we will explain the new δ<sup>2</sup>H<sub>NE</sub> method, discuss precision, accuracy, as well as referencing strategies, and give a first outlook for future applications in plant and environmental sciences.</p>

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