title: Towards a mechanistic understanding of carbon stabilization in manganese oxides.
abstract: Minerals stabilize organic carbon (OC) in sediments, thereby directly affecting global climate at multiple scales, but how they do it is far from understood. Here we show that manganese oxide (Mn oxide) in a water treatment works filter bed traps dissolved OC as coatings build up in layers around clean sand grains at 3%w/wC. Using spectroscopic and thermogravimetric methods, we identify two main OC fractions. One is thermally refractory (>550 °C) and the other is thermally more labile (<550 °C). We postulate that the thermal stability of the trapped OC is due to carboxylate groups within it bonding to Mn oxide surfaces coupled with physical entrapment within the layers. We identify a significant difference in the nature of the surface-bound OC and bulk OC . We speculate that polymerization reactions may be occurring at depth within the layers. We also propose that these processes must be considered in future studies of OC in natural systems.
authors.affiliation: School of Engineering and Computing Sciences, Durham University, South Road, Durham DH1 3LE, UK.
authors.forename: Karen
authors.initials: K
authors.lastname: Johnson
authors.affiliation: School of Civil Engineering and Geosciences, Devonshire Walk, Newcastle University, Newcastle upon Tyne NE1 3RE, UK.
authors.forename: Graham
authors.initials: G
authors.lastname: Purvis
authors.affiliation: School of Agriculture, Food and Rural Development, Newcastle University, Newcastle upon Tyne NE1 7RU, UK.
authors.forename: Elisa
authors.initials: E
authors.lastname: Lopez-Capel
authors.affiliation: Earth Surface Science Institute, School of Earth and Environmental Sciences, University of Leeds, Leeds LS2 9JT, UK.
authors.forename: Caroline
authors.initials: C
authors.lastname: Peacock
authors.affiliation: School of Civil Engineering and Geosciences, Devonshire Walk, Newcastle University, Newcastle upon Tyne NE1 3RE, UK.
authors.forename: Neil
authors.initials: N
authors.lastname: Gray
authors.affiliation: School of Civil Engineering and Geosciences, Devonshire Walk, Newcastle University, Newcastle upon Tyne NE1 3RE, UK.
authors.forename: Thomas
authors.initials: T
authors.lastname: Wagner
authors.affiliation: School of Civil Engineering and Geosciences, Devonshire Walk, Newcastle University, Newcastle upon Tyne NE1 3RE, UK.
authors.forename: Christian
authors.initials: C
authors.lastname: März
authors.affiliation: Department of Physics, Durham University, South Road, Durham DH1 3LE, UK.
authors.forename: Leon
authors.initials: L
authors.lastname: Bowen
authors.affiliation: Experimental Techniques Centre, Institute of Materials and Manufacturing, Brunel University, Uxbridge UB8 3PH, UK.
authors.forename: Jesus
authors.identifier: http://orcid.org/0000-0002-2046-1010
authors.initials: J
authors.lastname: Ojeda
authors.affiliation: School of Engineering and Computing Sciences, Durham University, South Road, Durham DH1 3LE, UK.
authors.forename: Nina
authors.initials: N
authors.lastname: Finlay
authors.affiliation: School of Engineering and Computing Sciences, Durham University, South Road, Durham DH1 3LE, UK.
authors.forename: Steve
authors.initials: S
authors.lastname: Robertson
authors.affiliation: Department of Earth Sciences, Durham University, South Road, Durham DH1 3LE, UK.
authors.forename: Fred
authors.initials: F
authors.lastname: Worrall
authors.affiliation: Department of Earth Sciences, Durham University, South Road, Durham DH1 3LE, UK.
authors.forename: Chris
authors.initials: C
authors.lastname: Greenwell