The elemental composition, infrared spectrum, and proton titration curve were determined for (i) the fulvic acid fraction of a Domino soil which had received applications of composted sewage sludge for three years in a field experiment, and (ii) a commercially available fulvic acid extracted from a spodosol. Data showed that the Domino fulvic acid more resembled a typical sludge‐derived fulvic acid than a fulvic acid extracted from natural soil organic matter. The distinguishing features of the Domino fulvic acid which led to this conclusion were: (i) a high total sulfur (S) content and the presence of sulfonyl groups, (ii) a significant content of anionic surfactants and S‐containing amino acids, (iii) a low glucosamine/galactosamine ratio, and (iv) more than two classes of acidic functional groups. However, the Domino fulvic acid had a much larger content of carboxyl and other acidic functional groups than a typical sludge‐derived fulvic acid, evidently because of partial oxidation of the sludge in the Domino soil.
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Sposito et al. (1982) studied this question.