As an alternative to the relatively complex and expensive spectroscopic methods, the redox properties of humic acids, determined by potentiometric titrations, have been used to evaluate the stability of soil organic C. The objective of the present study was to establish a Redox Index of C Stability (RICS) and to correlate it with some properties of the humic acids extracted from different modal soils in Brazil (distinct weathering stages or management) to facilitate system comparison. The RICS was efficient for […]

Soil organic matter is the largest carbon reservoir in natural systems. In such systems the carbon quality and stability can be estimated based on the increase of humified fractions which, among other factors, is related to the balance between losses and accumulations involving oxidation and reduction reactions of the soil organic matter. The objective of this study was to evaluate the electrochemistry of humic acids isolated from soils cultivated continually with sugar-cane, with or without pre-harvest burning and annual vinasse […]

According to the system conditions, humic acids act as oxidants or as reductants. In natural systems the electron flow is directly associated with humus content and quality. Electrode potential and oxidation capacity inform about the intensity and capacity of the redox systems. In previous studies it has been assumed that free radicals participate in humic acid redox reactions. In our study six humic acids isolated from composed organic residues were titrated with an oxidant (I2) in inert atmosphere and specified […]