177,159 research outputs found
The molecular composition of humus carbon: Recalcitrance and reactivity in soils
No full textSoil organic C (SOC) is the largest terrestrial reservoir in the biosphere, accounting for 1500–1770 Pg, as compared to C stocks of vegetation (450–
650 Pg) (IPCC, 2013). Although humus C represents from 60% to 80% of
SOC, its dynamics still remain poorly understood after nearly a century of
study, due to the multiplicity of factors that affect stabilization of humic matter. Industrial agricultural practices accelerate the decline of humus content
in soil, and, consequently, the reduction of soil fertility, biodiversity, and soil
structural stability (Fontaine et al., 2007; Reeves, 1997), while enhancing
greenhouse gases (GHG) emissions from soil (Smith et al., 2014). Because it
is the specific molecular composition of the soil Humeome that significantly
affects SOC storage dynamics (Woo et al., 2014), soil basal respiration (Fang
et al., 2005), and humus-plant relationships (Canellas and Olivares, 2014), a
rigorous identification of the molecular structure of the components of soil humus C is necessary, if any technological control of its content and dynamics
can ever be introduced
Molecular Characterization of Compost at Increasing Stages of Maturity. 2. Thermochemolysis-GC-MS and 13C-CPMAS-NMR Spectroscopy
No full textAdvanced CPMAS-13C NMR techniques for molecular characterization of size-separated fractions from a soil humic acid
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Sequestration of a biologically labile organic Carbon in soils by humified organic matter
No full textAmendments with humified compost effectively sequester organic carbon in agricultural soils
No full textSeparation of molecular constituents from a humic acid by solid-phase extraction following a transesterification reaction
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State of the art of CPMAS 13C-NMR spectroscopy applied to natural organic matter
No full textThe structural and conformational characteristics of humic carbon backbones were studied using NMR spectroscopy. Cross-polarized spectroscopy was used to investigate the composition of purified humic substances. High spin rate was obtained by reducing the size of rotors. Protons irradiation eliminated the heteronuclear dipolar interactions. It was found that the NMR signals were reduced due to the mobility of humic material inside the rotors
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