High-Resolution Molecular-Level Characterization of a Blanket Bog Peat Profile

To understand peatland carbon-cycling processes ultimately requires the ability to track changes occurring on the molecular-level. In this study, we profile a peat core taken from the world's largest blanket bog, Flow Country, Scotland, using physicochemical properties, ATR-FTIR, solid/liquid-state NMR, and solid/liquid-state FT-ICR-MS. Air-dried peat and labile and recalcitrant peat extracts, including pore water dissolved organic matter (PW-DOM), are analyzed and the merits of each technique are discussed. Solid-state NMR demonstrated changing distribution of compound classes with core depth and water table, the latter not picked up by IR. Liquid-state NMR and MS both demonstrated variations in molecular composition along the core depth in all phases and extracts. Contrary to previous reports, the composition of PW-DOM varied with depth. Major compounds, some previously unreported, identified by 1D/2D NMR occurred throughout the core, suggesting the existence of hot spots of microbial activity/compound accumulation. Offering complementary views, the techniques provided evidence of gradual molecular level changes with age, zonation due to the water table, and hot spots due to microbial activity. This study provides new insights into the molecular signatures of peat layers and establishes the foundation for examining peat function and health at the molecular-level.