Advancement in Research on Application of 13C NMR Techniques to Exploration of Chemical Structure of Soil Organic Matter
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Supported by the National Key Research and Development Program of China (No. 2016YFD0300802-01), the Key Research Program of Frontier Sciences, CAS (No. QYZDB-SSW-SYS022), the Youth Innovation Promotion Association CAS (No. 2016211) and the Excellent Young Talent Program of Northeast Institute of Geography and Agroecology, CAS

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    Abstract:

    The knowledge about chemical structure of soil organic matter (SOM) is crucial to accurate assessment of stability and function of SOM in the soil ecosystem. In the study on chemical structure of soil organic matter, the technology of solid-state 13C nuclear magnetic resonance (NMR) spectroscopy possesses a unique advantage of being capable of depicting chemical structure of nature soil organic matter, nondestructively and state-of-the-artly. Although extensive studies have been carried out on stability and molecular structure of SOM at a regional-climatic belt and ecosystem-community scale, little has been documented about chemical characteristics of SOM and its relationships with environmental factors at the global scale. This study presents a review on uses of the 13C NMR technology in determining chemical structures of organic carbons in bulk soil, soil aggregates, density fractions and humus components, and analyzes factors that alter the chemical structure of SOM. Organic carbons in bulk soils, regardless climate conditions, type of vegetation, land use pattern, soil type and content of organic carbon in the soil, were quite similar in chemical structure, all being the highest in O-alkyl C, which was followed by alkyl C, aromatic C, and carbonyl C in the end. It is widely accepted that soil organic carbon is mainly derived from plant residues, which are quite similar in chemical structure, so that soil organic carbons are similar in chemical structure, too. Differences in environment condition, soil property and microbial activity may cause some variations, but very minor, of the chemical structure of soil organic carbon, and the variations in soil particles and chemical components of the soil are quite significant. O-alkyl C abundance of the organic carbon is the highest in large-sized soil particles, while alkyl and carbonyl C are in small-sized or mineral associated particles. Chemical structure of organic carbon in silt-clayed particles and humic acid components vary quite sharply between soils different in type. Future researches should focus on quantitative analysis of SOM sources, contribution of soil microbes to the composition of SOM and stability of its structure and regulatory mechanisms, biophysico-chemical protection mechanisms of soil organic carbon stability, coupling mechanisms of spatial large-scaled environmental factors/soil ecological processes with microscopic scaled molecular structure of soil organic carbon, and interdisciplinary means and techniques to determine chemical structure of soil organic carbon.

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LI Na, SHENG Ming, YOU Mengyang, HAN Xiaozeng. Advancement in Research on Application of 13C NMR Techniques to Exploration of Chemical Structure of Soil Organic Matter[J]. Acta Pedologica Sinica,2019,56(4):796-812.

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History
  • Received:March 26,2018
  • Revised:August 31,2018
  • Adopted:September 14,2018
  • Online: April 10,2019
  • Published: