An adequate knowledge of the chemical nature and structure of humic substances (HSs) is fundamental to better understanding of the effects of these organic systems on the biological dynamics of natural ecosystems. However, despite the great number of investigations devoted to this subject, there still is no definitive answer to the question, which is due to the chemical complexity of HSs [1-4]. Whereas many studies founded on the macromolecular chemical behavior of HSs in solution have proposed that they fundamentally consist of complex mixtures of different macromolecules whose physicochemical properties are qualitatively similar [3], other recent studies, normally based on the HPSEC technique, propose that these systems are supramolecular assemblies of relatively small molecules [4]. Because of these different results, an interesting debate about the macromolecular or supramolecular nature of HSs is underway in the literature [2].