Enriched Molecular-Level View of Saline Wetland Soil Carbon by Sensitivity-Enhanced Solid-State NMR

• Published in: Journal of the American Chemical Society Vol. 147; no. 1; pp. 519 - 531
• Main Authors: Zhao, Wancheng, Thomas, Elizabeth C., Debnath, Debkumar, Scott, Faith J., Mentink-Vigier, Frederic, White, John R., Cook, Robert L., Wang, Tuo
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 19.12.2024; American Chemical Society (ACS)
• Subjects: Aromatic compounds; biodiversity; Biopolymers; Carbohydrates; Carbon; carbon sequestration; climate; greenhouse gas emissions; herbaceous plants; highlands; nuclear magnetic resonance spectroscopy; sea level; soil carbon; soil organic matter; Soils; wetland soils; wetlands
• ISSN: 0002-7863; 1520-5126; 1520-5126
• DOI: 10.1021/jacs.4c11830

Soil organic matter (SOM) plays a major role in mitigating greenhouse gas emission and regulating earth’s climate, carbon cycle, and biodiversity. Wetland soils account for one-third of all SOM; however, globally, coastal wetland soils are eroding faster due to increasing sea-level rise. Our understanding of carbon sequestration dynamics in wetlands lags behind that of upland soils. Here, we employ solid-state nuclear magnetic resonance (ssNMR) to investigate the molecular-level structure of biopolymers in wetland soils spanning 11 centuries. High-resolution multidimensional spectra, enabled by dynamic nuclear polarization (DNP), demonstrate enduring preservation of molecular structures within herbaceous plant cores, notably condensing aromatic motifs and carbohydrates, even over a millennium, with the preserved cores constituting a decreasing minority among molecules from decomposition and repolymerization with depth and age. Such preserved cores occur alongside molecules from the decomposition of loosely packed parent biopolymers. These findings emphasize the relative vulnerability of coastal wetland SOM when exposed to oxygenated water due to geological and anthropogenic changes.