ELECTRON-SPIN RESONANCE AS A GUIDE TO THE DEGREE OF HUMIFICATION OF PEATS

A novel approach was developed for assessing the degree of humification of peats at various stages of decomposition. The approach involves extraction of the peat with 0.5 M NaOH for 1 h, removal of the insoluble residue by centrifugation, and determination of the free radical content of the clear supernatant solution. Heights of ESR signals were found to be directly proportional to the degree of humification, as measured by solubility of the peat in dilute Na4P2O7solution (the Na4P2O7index). The free radicals that are involved in humification are substituted semiquinones, whose concentrations increase as humification advances. © 1979 The Williams & Wilkins Co.