Characteristic features of the major components of freshwater colloidal organic matter revealed by transmission electron and atomic force microscopy

Organic biopolymers such as humic substances and polysaccharides account fo r the majority of freshwater NOM. Their role in natural systems is largely dependent upon their supramolecular microscopic structure which cannot be d etermined by bulk chemical measurements alone. Microscopic techniques were developed so as to permit the systematic observation of several colloidal-s ized organic macromolecules with variable structures. This paper describes the characteristic structures of some reference compounds representative of the major organic components of natural waters. Polyacrylic acid, alginic acid and schizophyllan in addition to humic substances and polysaccharides isolated from natural freshwaters were examined by transmission electron mi croscopy (TEM) and atomic force microscopy (AFM). The techniques were optim ized for the observation of the aquatic biopolymers. Colloidal organic matt er isolated from natural freshwaters was also observed by TEM and AFM and c ompared with the standard images of colloidal organic matter. (C) 1999 Else vier Science B.V. All rights reserved.