Heterogeneity of Soil Organic Matter Challenges Scientists Attempting to Understand Carbon and Nutrient Cycling


Soils play an important role in the cycling of carbon and other nutrients with the atmosphere, and they are also known to contain a vast amount of carbon and are responsible for most emissions of greenhouse gases to the atmosphere. A key reservoir in soils for carbon and other nutrients is soil organic matter (SOM), which consists of a mixture of above and belowground plant litter and animal and microbial residues that are being decomposed. To understand the local, regional, and global cycling of carbon and other elements, it is important to attempt to characterize SOM. Researchers from the U.S. Department of Energy’s Idaho National Laboratory and Environmental Molecular Sciences Laboratory (EMSL) have, for the first time, done just that, comparing the molecular composition of SOM from different ecosystems using EMSL’s ultra-high resolution mass spectrometry. As expected, the SOM from these different ecosystems was heterogeneous; however, they also determined that by using different solvents (e.g., hexane and methanol), they could consistently extract specific, but different types of compounds from SOM. While the use of multiple solvents will result in the richest representation of the diverse molecular constituents from any SOM sample, other scientists will now know which selective solvent to use to extract specific molecular constituents from a particular type of SOM to answer specific science questions. This work clarifies the range of molecular constituents in SOM and sets the stage for enabling a greater understanding of carbon and nutrient cycling in soils.


Tfaily, M., R. K. Chu, N. Tolić, K. M. Roscioli, C. R. Anderton, L. Paša-Tolić, E. W. Robinson, and N. J. Hess. 2015. “Advanced Solvent Based Methods for Molecular Characterization of Soil Organic Matter by High-Resolution Mass Spectrometry,” Analytical Chemistry 87(10), 5206–15. DOI: 10.1021/acs.analchem.5b00116.