Electron Spin Resonance and Scanning Electron Microscopy of Humic Substances

Humic substances isolated from an Inceptisol were studied with the help of electron spin resonance (ESR) and scanning electron microscopy (SEM). The most valuable information from the ESR data was that the fractions from humin were richer in free radicals than their corresponding counterparts obtained from the alkali-extractable portion thereby indicating the possible involvement of electron spins in “inorganic-humus” bonding. The notable SEM result was that the fulvic systems showed a better degree of ordered parallel orientation than the humic ones because of the higher content of ionising groups in the former.