In:
Biogeosciences, Copernicus GmbH, Vol. 15, No. 10 ( 2018-05-25), p. 3133-3142
Abstract:
Abstract. An
approach for nanoscale 3-D tomography of organic carbon (OC) and associated
mineral nanoparticles was developed to illustrate their spatial distribution
and boundary interplay, using synchrotron-based transmission X-ray microscopy
(TXM). The proposed 3-D tomography technique was first applied to in situ
observation of a laboratory-made consortium of black carbon (BC) and nanomineral
(TiO2, 15 nm), and its performance was evaluated using dual-scan
(absorption contrast and phase contrast) modes. This novel tool was then
successfully applied to a natural OC–mineral consortium from mountain
soil at a spatial resolution of 60 nm, showing the fine structure and
boundary of OC, the distribution of abundant nano-sized minerals, and the 3-D
organo-mineral association in situ. The stabilization of 3500-year-old
natural OC was mainly attributed to the physical protection of nano-sized
iron (Fe)-containing minerals (Fe oxyhydroxides including ferrihydrite, goethite,
and lepidocrocite), and the strong organo-mineral complexation. In situ
evidence revealed an abundance of mineral nanoparticles, in dense thin layers
or nano-aggregates/clusters, instead of crystalline clay-sized minerals on or
near OC surfaces. The key working minerals for C stabilization were reactive
short-range-order (SRO) mineral nanoparticles and poorly crystalline
submicron-sized clay minerals. Spectroscopic analyses demonstrated that the
studied OC was not merely in crisscross co-localization with reactive SRO
minerals; there could be a significant degree of binding between OC and the
minerals. The ubiquity and abundance of mineral nanoparticles on the OC
surface, and their heterogeneity in the natural environment may have been
severely underestimated by traditional research approaches. Our in situ
description of organo-mineral interplay at the nanoscale provides direct
evidence to substantiate the importance of mineral physical protection for
the long-term stabilization of OC. This high-resolution 3-D tomography
approach is a promising tool for generating new insight into the interior 3-D
structure of micro-aggregates, the in situ interplay between OC and minerals,
and the fate of mineral nanoparticles (including heavy metals) in natural
environments.
Type of Medium:
Online Resource
ISSN:
1726-4189
DOI:
10.5194/bg-15-3133-2018
DOI:
10.5194/bg-15-3133-2018-supplement
Language:
English
Publisher:
Copernicus GmbH
Publication Date:
2018
detail.hit.zdb_id:
2158181-2
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