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Organic carbon burial with reactive iron across global environments
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  • Jack Longman,
  • Faust Johan,
  • Casey Bryce,
  • William B Homoky,
  • März Christian
Jack Longman
University of Oldenburg

Corresponding Author:jack.longman@uni-oldenburg.de

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Faust Johan
MARUM Center for Marine Environmental Sciences
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Casey Bryce
University of Bristol
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William B Homoky
University of Leeds
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März Christian
Leeds University
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Preservation of organic carbon (OC) in marine and terrestrial deposits is enhanced by bonding with reactive iron (FeR) phases. The association of OC with FeR (OC-FeR) provides physical protection and hinders microbiological degradation. Roughly 20% of all OC stored in unconsolidated marine sediments and 40% of all OC present in Quaternary terrestrial deposits is preserved as OC-FeR, but this value varies from 10 to 80% across depositional environments. In this work, we provide a new assessment of global OC-FeR burial rates in both marine and terrestrial environments, using published estimates of the fraction of OC associated with FeR, carbon burial, and probabilistic modelling. We estimate the marine OC-FeR sink at between 31 – 70 Mt C yr-1 (mean 52 Mt C yr-1), and the terrestrial OC-FeR sink at between 171 - 946 Mt C yr-1 (mean 472 Mt C yr-1). In marine environments, continental shelves (mean 17 Mt C yr-1) and deltaic/estuarine environments (mean 11 Mg C yr-1) are the primary locations of OC-FeR burial. On land, croplands (279 Mt C yr-1) and grasslands (121 Mt C yr-1) dominate the OC-FeR burial budget. Changes in the Earth system through geological time likely alter the OC-FeR pools, particularly in marine locations. For example, periods of intense explosive volcanism may lead to increased net OC-FeR burial in marine sediments. Our work highlights the importance of OC-FeR in marine carbon burial and demonstrates how OC-FeR burial rates may be an order of magnitude greater in terrestrial environments, those potentially most sensitive to anthropogenic impacts.