CHARACTERIZATION OF NOM-COLLOID AGGREGATES IN SURFACE WATERS - COUPLING TRANSMISSION ELECTRON-MICROSCOPY STAINING TECHNIQUES AND MATHEMATICAL-MODELING

The role of inorganic colloids and natural organic macromolecules in a quatic and soil systems is essential for our understanding of contamin ant and nutrient transport. The submicron organic fraction, although i mportant in terms of total surface area, is poorly electron-dense and thus not susceptible to observation by transmission electron microscop y. Several staining techniques were therefore developed to enable the observation of the submicron aggregate fraction in natural waters. Lea d and silver based stains were especially successful in increasing the contrast of previously unobservable organic macromolecules. Computer simulations were developed for the interpretation of observed aggregat e structures in natural waters. Based on the TEM observations, modelli ng was employed to examine the formation kinetics and structural chara cteristics of aggregates under different physicochemical conditions. T he modelling results offered insight into the underlying mechanisms an d important factors influencing the aggregation processes.