Soil organic matter extraction using water at high temperature and elevated pressure (ASE) as compared to conventional methods

Large amounts of soil organic matter can be extracted when using salt solut ions or organic solvents, but these extracts do not represent the organic m atter soluble under natural conditions. The objective of our study was to e valuate the usefulness of water at high-temperature and elevated pressure f or soil organic matter extraction. Soil samples were extracted with water a t different temperatures under high pressure (10 MPa), using an Accelerated Solvent Extractor (ASE). These extracts were compared to extracts obtained by conventional methods using distilled water, NaOH and Na4P2O7 solutions. Yields of ASE extracts were up to twenty-fold higher than those of convent ional water extracts. UV spectra as well as H-1 and C-13 NMR spectra reveal ed high similarity between conventional water extracts and ASE extracts up to 150 degrees C. At higher temperatures, ASE extracts were enriched in aro matic and depleted in O-alkyl-C structures, strongly resembling the NaOH an d Na4P2O7 extracts.