skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Thermodynamically controlled preservation of organic carbon in floodplains

Abstract

Organic matter decomposition in soils and terrestrial sediments has a prominent role in the global carbon cycle. Carbon stocks in anoxic environments, such as wetlands and the subsurface of floodplains, are large and presumed to decompose slowly. The degree of microbial respiration in anoxic environments is typically thought to depend on the energetics of available terminal electron acceptors such as nitrate or sulfate; microbes couple the reduction of these compounds to the oxidation of organic carbon. But, it is also possible that the energetics of the organic carbon itself can determine whether it is decomposed. We examined water-soluble organic carbon by Fourier-transform ion-cyclotron-resonance mass spectrometry to compare the chemical composition and average nominal oxidation state of carbon—a metric reflecting whether microbial oxidation of organic matter is thermodynamically favourable—in anoxic (sulfidic) and oxic (non-sulfidic) floodplain sediments. We also observed distinct minima in the average nominal oxidation state of water-soluble carbon in sediments exhibiting anoxic, sulfate-reducing conditions, suggesting preservation of carbon compounds with nominal oxidation states below the threshold that makes microbial sulfate reduction thermodynamically favourable. Finally, we show that thermodynamic limitations constitute an important complement to other mechanisms of carbon preservation, such as enzymatic restrictions and mineral association, within anaerobic environments.

Authors:
 [1];  [2];  [3];  [2];  [4];  [2];  [5]
  1. SLAC National Accelerator Lab., Menlo Park, CA (United States). Stanford Synchrotron Radiation Lightsource; Stanford Univ., CA (United States). Earth System Science Dept.
  2. SLAC National Accelerator Lab., Menlo Park, CA (United States). Stanford Synchrotron Radiation Lightsource
  3. Pacific Northwest National Lab. (PNNL), Richland, WA (United States). Environmental Molecular Science Lab.
  4. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Climate and Ecosystem Sciences Division
  5. Stanford Univ., CA (United States). Earth System Science Dept.
Publication Date:
Research Org.:
SLAC National Accelerator Lab., Menlo Park, CA (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Biological and Environmental Research (BER) (SC-23)
OSTI Identifier:
1363868
Alternate Identifier(s):
OSTI ID: 1368457
Grant/Contract Number:
AC02-76SF00515; FG02-13ER65542; AC02-05CH11231
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Nature Geoscience
Additional Journal Information:
Journal Volume: 10; Journal Issue: 6; Journal ID: ISSN 1752-0894
Publisher:
Nature Publishing Group
Country of Publication:
United States
Language:
English
Subject:
58 GEOSCIENCES; carbon cycle; freshwater ecology

Citation Formats

Boye, Kristin, Noel, Vincent, Tfaily, Malak M., Bone, Sharon E., Williams, Kenneth H., Bargar, John R., and Fendorf, Scott. Thermodynamically controlled preservation of organic carbon in floodplains. United States: N. p., 2017. Web. doi:10.1038/ngeo2940.
Boye, Kristin, Noel, Vincent, Tfaily, Malak M., Bone, Sharon E., Williams, Kenneth H., Bargar, John R., & Fendorf, Scott. Thermodynamically controlled preservation of organic carbon in floodplains. United States. doi:10.1038/ngeo2940.
Boye, Kristin, Noel, Vincent, Tfaily, Malak M., Bone, Sharon E., Williams, Kenneth H., Bargar, John R., and Fendorf, Scott. Mon . "Thermodynamically controlled preservation of organic carbon in floodplains". United States. doi:10.1038/ngeo2940. https://www.osti.gov/servlets/purl/1363868.
@article{osti_1363868,
title = {Thermodynamically controlled preservation of organic carbon in floodplains},
author = {Boye, Kristin and Noel, Vincent and Tfaily, Malak M. and Bone, Sharon E. and Williams, Kenneth H. and Bargar, John R. and Fendorf, Scott},
abstractNote = {Organic matter decomposition in soils and terrestrial sediments has a prominent role in the global carbon cycle. Carbon stocks in anoxic environments, such as wetlands and the subsurface of floodplains, are large and presumed to decompose slowly. The degree of microbial respiration in anoxic environments is typically thought to depend on the energetics of available terminal electron acceptors such as nitrate or sulfate; microbes couple the reduction of these compounds to the oxidation of organic carbon. But, it is also possible that the energetics of the organic carbon itself can determine whether it is decomposed. We examined water-soluble organic carbon by Fourier-transform ion-cyclotron-resonance mass spectrometry to compare the chemical composition and average nominal oxidation state of carbon—a metric reflecting whether microbial oxidation of organic matter is thermodynamically favourable—in anoxic (sulfidic) and oxic (non-sulfidic) floodplain sediments. We also observed distinct minima in the average nominal oxidation state of water-soluble carbon in sediments exhibiting anoxic, sulfate-reducing conditions, suggesting preservation of carbon compounds with nominal oxidation states below the threshold that makes microbial sulfate reduction thermodynamically favourable. Finally, we show that thermodynamic limitations constitute an important complement to other mechanisms of carbon preservation, such as enzymatic restrictions and mineral association, within anaerobic environments.},
doi = {10.1038/ngeo2940},
journal = {Nature Geoscience},
number = 6,
volume = 10,
place = {United States},
year = {Mon May 01 00:00:00 EDT 2017},
month = {Mon May 01 00:00:00 EDT 2017}
}

Journal Article:
Free Publicly Available Full Text
Publisher's Version of Record

Citation Metrics:
Cited by: 7works
Citation information provided by
Web of Science

Save / Share:
  • We report the feasibility of the thermodynamically controlled synthesis of crystalline sp3-carbon networks. We show that there is a critical pressure below which decomposition of the carbon network is favored and above which the carbon network is stable. Based on advanced, highly accurate quantum mechanical calculations using the all-electron full-potential linearized augmented plane-wave method (FP-LAPW) and the Birch–Murnaghan equation of state, this critical pressure is 26.5 GPa (viz. table of contents graphic). Such pressures are experimentally readily accessible and afford thermodynamic control for suppression of decomposition reactions. The present results further suggest that a general pattern of pressure-directed control existsmore » for many isolobal conversions of sp2 to sp3 allotropes, relating not only to fluorocarbon chemistry but also extending to inorganic and solid-state materials science.« less
  • Active gas mixtures of iodine photodissociation lasers are used as an example to show that, in thermodynamically nonequilibrium media when the rates of the chemical reactions depend on the electromagnetic field intensity, stimulated light scattering by thermal waves excited as a result of the enthalpy of the thermodynamically nonequilibrium medium may be observed. A theoretical analysis is made of the scattered-light spectrum. It is found that the light is amplified at the anti-Stokes frequency and the stimulated scattering gain under conditions typical of iodine lasers for an active gas pressure mixture of approx. 0.5 atm may reach 100--400 cm/mW.
  • On the basis of a series of experimental studies from our laboratory, it is well established that metallocarbohedrenes, or Met-Cars for short, are a stable class of cluster materials. To account for their exceptional stability, we initially proposed a pentagonal dodecahedron structure. This cage-like structure is consistent with all the experimental findings. In general, there are two possible structures that can be developed in these metal-carbon systems, i.e., Met-Cars and cubes. Since only one structural pattern is generally observed for one particular cluster system, it has been suggested that their thermodynamical stabilities might be responsible for the selective formation ofmore » specific structures, e.g., Met-Cars or fcc structures. Herein, we present new experimental results on the system of Nb[sub m]C[sub n] under various conditions. It is shown that the experimental conditions are extremely critical for the formation of either Met-Cars or cubic structures, as predicted by Reddy and Khanma. Moreover, the new data show that the cubic structures do not develop on top of Met-Cars, but rather, they grow independently. The experiments were performed by using both time-of-flight and quadrupole mass spectrometer techniques coupled with a laser vaporization source. 23 refs., 1 fig.« less