Solid-state 13C nuclear magnetic resonance (NMR)
spectroscopy has become an important tool for examining the chemical structure
of natural organic materials and the chemical changes associated with
decomposition. In this paper, solid-state 13C NMR data
pertaining to changes in the chemical composition of a diverse range of
natural organic materials, including wood, peat, composts, forest litter
layers, and organic materials in surface layers of mineral soils, were
reviewed with the objective of deriving an index of the extent of
decomposition of such organic materials based on changes in chemical
composition. Chemical changes associated with the decomposition of wood varied
considerably and were dependent on a strong interaction between the species of
wood examined and the species composition of the microbial decomposer
community, making the derivation of a single general index applicable to wood
decomposition unlikely. For the remaining forms of natural organic residues,
decomposition was almost always associated with an increased content of alkyl
C and a decreased content of O-alkyl C. The concomitant increase and decrease
in alkyl and O-alkyl C contents, respectively, suggested that the ratio of
alkyl to O-alkyl carbon (A/O-A ratio) may provide a sensitive index of the
extent of decomposition. Contrary to the traditional view that humic
substances with an aromatic core accumulate as decomposition proceeds, changes
in the aromatic region were variable and suggested a relationship with the
activity of lignin-degrading fungi. The A/O-A ratio did appear to provide
a sensitive index of extent of decomposition provided that its use was
restricted to situations where the organic materials were derived from a
common starting material. In addition, the potential for adsorption of highly
decomposable materials on mineral soil surfaces and the impacts which such an
adsorption may have on bioavailability required consideration when the
A/O-A ratio was used to assess the extent of decomposition of organic
materials found in mineral soils.
The magnitude of future climate change could be moderated by immediately reducing the amount of CO entering the atmosphere as a result of energy generation and by adopting strategies that actively remove CO from it. Biogeochemical improvement of soils by adding crushed, fast-reacting silicate rocks to croplands is one such CO-removal strategy. This approach has the potential to improve crop production, increase protection from pests and diseases, and restore soil fertility and structure. Managed croplands worldwide are already equipped for frequent rock dust additions to soils, making rapid adoption at scale feasible, and the potential benefits could generate financial incentives for widespread adoption in the agricultural sector. However, there are still obstacles to be surmounted. Audited field-scale assessments of the efficacy of CO capture are urgently required together with detailed environmental monitoring. A cost-effective way to meet the rock requirements for CO removal must be found, possibly involving the recycling of silicate waste materials. Finally, issues of public perception, trust and acceptance must also be addressed.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.