146 research outputs found
FluvialSeds/isotopylog: Manuscript Submission Release
No full textThis release coincides with the submission of Hemingway and Henkes "A distributed activation energy model for clumped isotope bond reordering in carbonates" to EPS
Biomarker approaches for reconstructing terrestrial environmental change
No full textThe response of the terrestrial biosphere to warming remains one of the most poorly understood and quantified aspects of the climate system. One way to test the behavior of the Earth system in warm climate states is to examine the geological record. The abundance, distribution, and/or isotopic composition of source-specific organic molecules (biomarkers) have been used to reconstruct terrestrial paleoenvironmental change over a range of geological timescales. Here, we review new or recently improved biomarker approaches for reconstructing (a) physical climate variables (land temperature, rainfall), (b) ecosystem state variables (vegetation, fire regime), and (c) biogeochemical variables (soil residence time, methane cycling). This review encompasses a range of key compound classes (e.g., lipids, lignin, and carbohydrates). In each section, we explore the concept behind key biomarker approaches and discuss their successesas paleoenvironmental indicators. We emphasize that analyzing several biomarkers in tandem can provide unique insights into the Earth system. ▪ Biomarkers can be used to reconstruct terrestrial environmental change over a range of geological timescales. ▪ A multi-proxy biomarker approach provides novel insights into climate and the environment.</p
FluvialSeds/rampedpyrox: Biogeosciences companion code
No full text<p>This release is the version that accompanies Hemingway et al. (2017) "An inverse method to relate organic carbon reactivity to isotope composition from serial oxidation" Biogeosciences.</p>
FluvialSeds/isotopylog: Updated Manuscript Release
No full textThis version coincides with the release of Hemingway and Henkes (2021) Earth Planet. Sci. Lett., 566, 116962. It includes some practical updates over the previous version:
Ability to set calibration functions as lambda function at any point in the calculations. Previously, geologic history calculations required one of the pre-determined calibrations.
Inclusion of "I-CDES" reference frame as articulated in Bernasoni et al. (2021) Geochem. Geophys. Geosys., 22, e2020GC009588, which should be the "gold standard" for all clumped isotope measurements moving forward.
Inclusion of the Anderson et al. (2021) Geophys. Res. Lett., 48, e2020GL092069 unified temperature calibration (in I-CDES reference frame).
Also fixed minor bugs and nomenclature issues
Technical note: An inverse method to relate organic carbon reactivity to isotope composition from serial oxidation
Get PDFSerial oxidation coupled with stable carbon and radiocarbon analysis of sequentially evolved CO₂ is a promising method to characterize the relationship between organic carbon (OC) chemical composition, source, and residence time in the environment. However, observed decay profiles depend on experimental conditions and oxidation pathway. It is therefore necessary to properly assess serial oxidation kinetics before utilizing decay profiles as a measure of OC reactivity. We present a regularized inverse method to estimate the distribution of OC activation energy (E), a proxy for bond strength, using serial oxidation. Here, we apply this method to ramped temperature pyrolysis or oxidation (RPO) analysis but note that this approach is broadly applicable to any serial oxidation technique. RPO analysis directly compares thermal reactivity to isotope composition by determining the E range for OC decaying within each temperature interval over which CO₂ is collected. By analyzing a decarbonated test sample at multiple masses and oven ramp rates, we show that OC decay during RPO analysis follows a superposition of parallel first-order kinetics and that resulting E distributions are independent of experimental conditions. We therefore propose the E distribution as a novel proxy to describe OC thermal reactivity and suggest that E vs. isotope relationships can provide new insight into the compositional controls on OC source and residence time.National Science Foundation (U.S.) (Grant 2012126152)United States. National Aeronautics and Space Administration (Grant NNA13AA90A)National Science Foundation (U.S.) (Grant EAR-1338810
Understanding terrestrial organic carbon export : a time-series approach
Get PDFThesis: Ph. D., Joint Program in Chemical Oceanography (Massachusetts Institute of Technology, Department of Earth, Atmospheric, and Planetary Sciences; and the Woods Hole Oceanographic Institution), 2017.Cataloged from PDF version of thesis.Includes bibliographical references (pages 169-190).Terrestrial organic carbon (OC) erosion, remineralization, transport through river networks, and burial in marine sediments is a major pathway of the global carbon cycle. However, our ability to constrain these processes and fluxes is largely limited by (i) analytical capability and (ii) temporal sampling resolution. To address issue (i), here I discuss methodological advancements and data analysis techniques for the Ramped PyrOx serial oxidation isotope method developed at WHOI. Ramped-temperature pyrolysis/oxidation coupled with the stable carbon (¹²C, ¹³C) and radiocarbon (¹⁴C) analysis of evolved CO₂ is a promising tool for understanding and separating complex OC mixtures. To quantitatively investigate distributions of OC source, reservoir age, and chemical structure contained within a single sample, I developed a kinetic model linking RPO-derived activation energy, ¹³C composition, and radiocarbon content. This tool provides a novel method to fundamentally address the unknown relationship between OC remineralization rates and chemical structure in various environmental settings. To address issue (ii), I additionally present results from time-series sample sets collected on two end-member systems: the Congo River (Central Africa) and the LiWu River (Taiwan). For the Congo River, bulk and plant-wax-lipid ¹³C compositions indicate that a majority of particulate OC is consistently derived from downstream, C₃-dominated rainforest ecosystems. Furthermore, bulk radiocarbon content and microbial lipid molecular distributions are strongly correlated with discharge, suggesting that pre-aged, swamp-forest-derived soils are preferentially exported when northern hemisphere discharge is highest. Combined, these results provide insight into the relationship between hydrological processes and fluvial carbon export. Lastly, I examined the processes controlling carbon source and flux in a set of soils and time-series fluvial sediments from the LiWu River catchment located in Taiwan. A comparison between bedrock and soil OC content reveals that soils can contain significantly less carbon than the underlying bedrock, suggesting that this material is remineralized to CO₂ prior to soil formation. Both the presence of bacterial lipids and a shift toward lower activation energy of ¹⁴C-free OC contained in soil saprolite layers indicate that this process is microbially mediated and that microbial respiration of rock-derived OC likely represents a larger geochemical flux than previously thought. The results presented in this thesis therefore provide novel insight into the role of rivers in the global carbon cycle as well as their response to environmental perturbations.by Jordon Dennis HemingwayPh. D
Site visit report, Jackson County March 24 2023
No full textDocumentation of contacts with Criminal and Juvenile Justice service providers and recommendations on the issue of appointment of counsel for clients who qualify for state-funded representation.prepared by Jordon Huppert.This archived document is maintained by the State Library of Oregon as part of the Oregon Documents Depository Program. It is for informational purposes and may not be suitable for legal purposes.Mode of access: Internet from the Oregon Government Publications Collection.Text in English
(Tabel S1) Environmental parameters and bulk measurements from Congo River samples
No full text+ Data from Wang et al., 2013.
* Data from Hemingway et al., 2016
Table S6, Biomarker isotopic data of crenarchaeol (δ13C Cren.), bacteriohopanetetrol I (δ13C BHT-I), and bacteriohopanetetrol II (δ13C BHT-II) for ODP cores at sites 964 and 967
No full textStable-carbon isotope compositions for crenarchaeol, bacteriohopanetetrol I (BHT-I), and bacteriohopanetetrol II (BHT-II) for ODP cores at sites 964 and 967. All biomarkers were measured using a Thermo Scientific Delta V isotope ratio mass spectrometer at least in triplicate. For BHT-I and BHT-II, compounds were isolated using high-performance preparative liquid chromatography and individually analyzed by high-temperature gas-chromatography-IRMS following Hemingway et al. (2018). Crenarchaeol was isolated using high-pressure preparative chromatography and analyzed using a spooling-wire microcombustion interface on a Thermo Scientific Delta V isotope ratio mass spectrometer at least in quintuplicate following Polik et al. (2018).
This work was supported by the Gordon and Betty Moore Foundation
Site visit report, Klamath County March 23 2023
No full textDocumentation of Site Visit Klamath Falls to learn more about Klamath and Lake counties. In order to educate the agency on how our services are implemented. Information on issues particular to this jurisdiction that impact the public safety system.prepared by Jordon Huppert.This archived document is maintained by the State Library of Oregon as part of the Oregon Documents Depository Program. It is for informational purposes and may not be suitable for legal purposes.Mode of access: Internet from the Oregon Government Publications Collection.Text in English
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