C-13 AND N-15 NMR-SPECTROSCOPY AS A TOOL IN SOIL ORGANIC-MATTER STUDIES

Nuclear magnetic resonance (NMR) is a valuable tool for the characteri zation of soil organic matter and humification processes in soils. Thi s review highlights soil organic matter studies based mainly on solid- state C-13 and N-15 NMR spectroscopy and some emerging applications, t hat may provide significant progress in our knowledge on soil organic matter. A major advantage of Nmr spectroscopy is that it can be used a s a non-invasive method for solid soil samples or soil fractions. Alth ough resolution is limited, one can obtain an overview on the organic matter structures present in the soil sample. Application of C-13 and N-15 NMR to soils has, for a long time, been confined to the study of bulk soils or humic extracts for structural characterization. The tran sformations of soil organic C and N are now being investigated after a ddition of C-13- and N-15-labelled parent materials to the soil and fo llowing their evolution in different C and N pools. With labelling tec hniques it is also possible to study the interaction of organic pollut ants with soil organic matter. Contamination of a soil with man-made a dditives, such as soot or brown coal dust, can also be detected in soi ls or individual soil fractions. (C) 1997 Elsevier Science B.V.