Character of organic matter in soils of temperate forest ecosystems: Do chlorophyll catabolites (phyllobilins) travel deep?
EMSL Project ID
51107
Abstract
Soil organic matter (SOM) is the largest reservoir of carbon (C) and nutrients, especially nitrogen (N), in terrestrial ecosystems. SOM is found throughout soil profiles, with content typically decreasing from surface to bedrock. Current theory accepts that organic matter in soils, and particularly in deep soil layers, consists of the remains of dead microorganisms (e.g., proteins). Our studies of the character of SOM (N and C XANES spectroscopy and biomolecule extraction methodologies) however suggest heterocyclic-N containing compounds accumulate at soil depths, likely as mineral-stabilized SOM. Based on our results, we posit the transport and reactivity of chlorophyll catabolites (i.e., phyllobilins) deposited at the soil surface comprise a large portion of SOM in deep soils of temperate forest ecosystems. Our hypothesis, if proven correct, would indeed represent a new paradigm in SOM dynamics. The proposed work utilizes soil depth profiles collected at three different landscape positions from the Susquehanna Shale Hills Critical Zone Observatory, in Pennsylvania. We propose a series of experiments that will advance knowledge and understanding of the character/structure of SOM that accumulates and persists in temperate forest ecosystems. Utilizing EMSL's advanced nuclear magnetic resonance (NMR), electron paramagnetic resonance (EPR), 21T Fourier transform ion cyclotron resonance mass spectrometry (21T FTICR-MS), and liquid chromatography in tandem with FTICR-MS (LC-UV/FTICR-MS) capabilities and scientific expertise, we will test our hypothesis and create new knowledge and understanding of SOM dynamics. Each technique provides unique information: NMR probes organic nitrogen and carbon functionalities; EPR yields information on organic matter nuclei associated with Fe and Mn, and degree of humification; 21T FTICR-MS is used in untargeted analyses to provide an indication of chemical diversity of C/H/N/S/P containing formulae; and LC-UV/FTICR-MS is used in target analyses to identify specific molecules of interest. The proposed work will be conducted in collaboration with Andrew Lipton, Eric Walter, and Rosalie Chu and Nicole Didonato, experts in advanced NMR, EPR, and FTICR-MS and LC-UV/FTICR-MS approaches at EMSL (respectively). A self-consistent interpretation of the various spectroscopic and spectrometric approaches is expected while an unequivocal interpretation could not be made from any individual technique. Consequently, the proposed experiments at EMSL are essential analytical approaches that will provide the ability to test our hypothesis and resolve the molecular structures of organic matter in complex environmental matrices such as soils.
Project Details
Project type
Exploratory Research
Start Date
2019-11-26
End Date
2021-09-30
Status
Closed
Released Data Link
Team
Principal Investigator
Team Members