MACROMOLECULAR STRUCTURES OF HUMIC SUBSTANCES

Publisher Website
Google Scholar
Abstract
We investigated humic substances by surface pressure and viscosity measurements at different pHs and neutral salt concentrations to elucidate their macromolecular configurations. We observed that such configurations were not unique; they varied with the changes in the medium. The controlling parameters were sample concentration, pH of the system, and the ionic strength of the medium. Model macromolecular structures are proposed on the basis of our investigation and of data published in the literature. With the aid of these models, we were able to resolve the contradictions between the so-called rigid “spherocolloid” and flexible “linear molecule” concepts. Our work shows that humic and fulvic acids behave like rigid spherocolloids at high sample concentrations, low pH, or in the presence of sufficient amounts of neutral electrolytes, but they are flexible linear colloids at low sample concentrations, provided that the pH is not too low or that the ionic strength is relatively low, conditions that normally prevail in soils. We investigated humic substances by surface pressure and viscosity measurements at different pHs and neutral salt concentrations to elucidate their macromolecular configurations. We observed that such configurations were not unique; they varied with the changes in the medium. The controlling parameters were sample concentration, pH of the system, and the ionic strength of the medium. Model macromolecular structures are proposed on the basis of our investigation and of data published in the literature. With the aid of these models, we were able to resolve the contradictions between the so-called rigid “spherocolloid” and flexible “linear molecule” concepts. Our work shows that humic and fulvic acids behave like rigid spherocolloids at high sample concentrations, low pH, or in the presence of sufficient amounts of neutral electrolytes, but they are flexible linear colloids at low sample concentrations, provided that the pH is not too low or that the ionic strength is relatively low, conditions that normally prevail in soils. © Williams & Wilkins 1980. All Rights Reserved.

This publication has 2 references indexed in Scilit: