An inverse method to relate organic carbon reactivity to isotopecomposition from serial oxidation
Name
gmd-10-4321-2017.pdf
Size
3.78 MB
Format
Adobe PDF
Checksum (MD5)
967f7e072c2f4ea9529b27ea9fa7fe39
Author(s)
Galy, Valier V.
Hemingway, Jordon Dennis
Rosengard, Sarah Zhou
Rothman, Daniel H.
Alternative Title
Technical note: An inverse method to relate organic carbon reactivity to isotope composition from serial oxidation
Date Issued
November 2017
Journal
Biogeosciences Discussions
Publisher
Copernicus GmbH
Citation
Hemingway, Jordon D. et al. “An Inverse Method to Relate Organic Carbon Reactivity to Isotope Composition from Serial Oxidation.” Biogeosciences Discussions (August 2017): 1–27 © 2017 Author(s)
Version
Final published version
Abstract
Serial 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.
MIT Department
Massachusetts Institute of Technology. Department of Earth, Atmospheric, and Planetary Sciences
Woods Hole Oceanographic Institution
Terms of Use
Creative Commons Attribution 4.0 International License
Persistent DSpace Link
DOI of Published Version
https://doi.org/10.5194/BG-2017-344
