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 aquatic and soil systems is essential for our understanding of contaminant and nutrient transport. The submicron organic fraction, although important in terms of total surface area, is poorly electron-dense and thus not susceptible to observation by transmission electron microscopy. Several staining techniques were therefore developed to enable the observation of the submicron aggregate fraction in natural waters. Lead 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 aggregate structures in natural waters. Based on the TEM observations, modelling was employed to examine the formation kinetics and structural characteristics of aggregates under different physicochemical conditions. The modelling results offered insight into the underlying mechanisms and important factors influencing the aggregation processes.