Epr of micronutrients-humic substances complexes extracted from a brazilian soil
1991
NETO, LADISLAU MARTIN | NASCIMENTO, OTACIRO R. | TALAMONI, JOSE | POPPI, NILVA R.
The technique of electron paramagnetic resonance was used to examine the formation of micronutrients-humic substances complexes extracted from a Brazilian soil. Results indicate that there are two types of copper (II) complexes, one with oxygen and another with nitrogen atoms, in humic acids while in fulvic acids only the copper complexed with oxygen was detected. The iron (III) complex signal with g = 4.3 was observed in both humic acid and fulvic acid. The concentration of free radicals (semiquinone) detected in humic acids (10 spins/g) was bigger than in fulvic acids (10 spins/g) due to a greater humification degree confirmed by elementary analysis and E4/E6 ratio measurements.
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